JPH0542682A - Ink jet recording apparatus - Google Patents

Abstract

(57) [Summary] [Object] In an inkjet printing apparatus in the form of a copying machine, a process of obtaining correction data for correcting drive conditions of respective printing elements of a printhead so as to prevent density unevenness from occurring. The test pattern formed by the recording head can be correctly read by the reader unit of the copying apparatus. [Structure] Based on the density data obtained by reading the test pattern by the CCD 5 provided in the reader unit, the recording medium on which the test pattern is formed is correctly placed on the reader unit, or the recording medium is shifted in the main / sub scanning direction of the CCD 5. It is judged whether or not it is placed, and if it is not in such a normal placement state, this is an error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, when an image is recorded by an ink jet head having a large number of ink ejection ports, unevenness in density occurs due to variations in ink ejection amount between the ejection ports peculiar to the head, and unevenness. There was a problem of degrading quality. In order to deal with such a problem, data relating to the density unevenness of each head is measured at the time of manufacturing the inkjet head, and the correction data for correcting the image data to be recorded is written in the ROM according to the driving conditions of the head and the image processing. The method of incorporating it in the product was adopted. However, this method is not sufficient for the density unevenness of the inkjet head due to the change over time, and in practice, the head has been replaced regularly, or maintenance or density unevenness correction data has been corrected.

[0003]

However, in the above-mentioned conventional example, since the periodical maintenance is required, the maintenance cost and the time required for correcting the density unevenness correction data are long, and there is a strong demand for improvement.

The present invention has been made in view of the above-mentioned conventional example, and corrects and records the input image information based on the image correction information created by reading the image pattern recorded by the recording head. An object of the present invention is to provide an inkjet recording apparatus that has high reliability when creating or updating image correction information.

[0005]

To this end, an ink jet recording apparatus of the present invention is a recording head having a plurality of ink ejection ports, and the recording head referred to at the time of recording and the identification information of the recording head. In an ink jet recording apparatus that performs recording using the recording head provided with a unit that stores unique first uneven density correction data, the identification information and the uneven density correction data are read out and stored in association with each other. First storage means, density unevenness correction data creating means for creating second density unevenness correction data using the first density unevenness correction data read from the first storage means, and the created first density unevenness correction data creating means. No. 2 density unevenness correction data and second storage means for storing the identification information corresponding to the first density unevenness correction data as a set; Means for reading the identification information and the first density unevenness correction data at a predetermined timing and storing them in the first storage means, and the identification information read from the second storage means and the first storage means. The print head identification information thus obtained is compared, and if the two match, the second density unevenness correction data read from the second storage means is used during printing to drive the print head. The first density unevenness correction data read from the first storage means is used at the time of printing to drive the print head.

The present invention is also an ink jet recording apparatus for forming an image by using a recording head having a plurality of ink ejection ports, which is used to eject ink from the plurality of ejection ports. In an inkjet recording apparatus including a correction unit that corrects at least one image processing condition of a plurality of elements that generate energy to suppress uneven density during image formation, a predetermined test pattern is formed by the recording head. A unit for forming on the recording medium, a reading unit for reading the test pattern, a density unevenness correction data creating unit for creating data for the correction by using the read result, and a data for the correction. In producing the recording medium, the recording medium on which the test pattern is formed has a regular reading position with respect to the reading means. Characterized in that comprises a determining means for determining whether to have.

Furthermore, the present invention is an ink jet recording apparatus for forming an image using a recording head having a plurality of ink ejection ports, which is used to eject ink from the plurality of ejection ports. In an inkjet recording apparatus including a correction unit that corrects at least one image processing condition of a plurality of elements that generate energy to suppress uneven density during image formation, a predetermined test pattern is formed by the recording head. Means for forming on a recording medium, reading means for reading the test pattern, density unevenness correction data creating means for creating data for the correction using the reading result, and the test pattern from the reading result Is provided in a normal state, and a determining means for determining whether or not is formed in a normal state.

In addition, according to the present invention, in an ink jet recording apparatus using a recording head having a plurality of ink ejection ports for storing identification information and unique density unevenness correction data, when the recording head is mounted, A means for reading out the identification information and the density unevenness correction data from the recording head and storing the read data in the first storage area and the density unevenness correction data in the first storage area are changed to the first storage area.
Means for storing the identification information in the second storage area together with the identification information in the second storage area, and comparing the identification information in the first storage area and the identification information in the second storage area at a predetermined timing. If the two match, the density unevenness correction data in the second storage area is used for recording, and if they do not match, the density unevenness correction data in the first storage area is used. It is characterized by doing.

[0009]

According to the present invention, even if the attached ink jet recording head changes over time and density unevenness occurs as a result, it is possible to appropriately suppress the occurrence of density unevenness by correcting the density unevenness correction data. This makes it possible to always maintain high quality images.

By selecting the first or second density unevenness correction data on the basis of the printhead identification information, the density unevenness correction process is performed when the printhead is replaced or after the same head is replaced. The reliability of can be improved.

Further, when the recording medium on which the test pattern is formed is not properly positioned with respect to the reading means (reader) when the density unevenness correction data is created or updated (deviation in the main and sub-scanning directions, oblique placement, etc.). Since this is detected, it is possible to correctly recognize the occurrence state of density unevenness by performing appropriate replacement.

Furthermore, by making it possible to judge whether or not the test pattern is formed in a normal state (non-ejection, etc.), it is possible to prevent the creation of inappropriate correction data using an abnormal test pattern. it can.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

<Color Copying Machine (FIG. 1)> FIG. 1 is a diagram showing a sectional shape of a color copying machine using the ink jet recording apparatus of this embodiment.

This color copying machine includes an image reading and image processing section (hereinafter referred to as a reader section 24) and a printer section 4.
4 and 4. The reader unit 24 is R, G, or B.
The CCD line sensor 5 (see FIG. 2) having a color filter scans the document 2 placed on the document glass 1 to read an image, and the read image is processed by an image processing circuit to be printed by the printer unit 44. 4 for cyan (C), magenta (M), yellow (Y), and black (Bk)
An image is recorded on a paper or other recording medium (hereinafter also referred to as recording paper) by a color inkjet head.

The details of the operation will be described below.

The reader unit 24 comprises members or portions 1 to 23, and the printer unit 44 comprises members or portions 25 to 43. Further, in this example, the upper left side of FIG. 1 is the front surface facing the operator.

The printer unit 44 includes an ink jet head (recording head) 32 for recording by ejecting ink, and the recording head 32 has, for example, 63.5 micron pitch discharge ports in the vertical direction (sub-scanning direction described later). 128
They are arranged side by side and are configured to record a width of 8.128 mm. Therefore, when recording on the recording paper, the conveyance of the recording paper (conveyance in the sub-scanning direction) is temporarily stopped, and in this state the recording head 32 is moved in the direction orthogonal to the drawing to record the necessary distance with a width of 8.128. After that, the operation of feeding the recording paper by 8.128 mm and stopping it, and recording the next 8.128 mm width is repeated. This recording direction is called the main scanning direction, and the paper feed direction is called the sub-scanning direction. In the configuration of this embodiment, the main scanning direction is orthogonal to FIG. 1 and the sub scanning direction is the left and right direction in FIG.

The reader unit 24 repeats the operation of reading the original 2 with a width of 8.128 mm corresponding to the printer unit 44, but the reading direction is the main scanning direction and the moving direction for the next reading is the sub direction. This is called the scanning direction. In the configuration of this embodiment, the main scanning direction is the left-right direction in FIG. 1 and the sub-scanning direction is the orthogonal direction in FIG.

The operation of the reader section 24 will be described below.

A document 2 on the platen glass 1 is illuminated by a lamp 3 on a main scanning carriage 7, and its image is passed through a lens array 4 to a light receiving element 5 (CCD line sensor).
Be led to. The main scanning carriage 7 is fitted on a main scanning rail 8 on the sub scanning unit 9 and is slidable. Further, the main scanning carriage 7 is connected to the main scanning belt 17 by an engaging member (not shown), and is rotated in the horizontal direction in FIG. 1 by the rotation of the main scanning motor 16 to perform the main scanning operation.

The sub-scanning unit 9 is fitted on a sub-scanning rail 11 fixed to the optical frame 10 and is slidable. Further, since the sub-scanning unit 9 is connected to the sub-scanning belt 18 by an engagement member (not shown), the sub-scanning motor 19 rotates to move in the orthogonal direction in FIG. 1 to perform the sub-scanning operation.

In this way, the image signal read by the CCD 5 is transmitted to the sub-scanning unit 9 by the flexible signal cable 13 which can be curved in a loop. The signal cable 13 is held on the main scanning carriage 7 at one end by the gripping portion 14, and the other end is fixed to the bottom surface 20 of the sub-scanning unit by the member 21 so that the sub-scanning unit 9 and the printer unit 44 are connected. It is connected to a sub-scanning signal cable 23 that connects to the electrical unit 26. Here, the signal cable 13 follows the movement of the main scanning carriage 9, and the sub-scanning signal cable 23 follows the movement of the sub-scanning unit 9.

The operation of the printer section 44 will be described below.

The recording papers fed out one by one from the recording paper cassette 25 by a paper feed roller 27 driven by a power source (not shown) are recorded by a recording head 32 between two pairs of rollers 28, 29 and 30, 31. To be recorded. The recording head 32 is configured integrally with the ink tank 33, and is detachably mounted on the printer main scanning carriage 34. The printer main scanning carriage 34 is fitted to the printer main scanning rail 35 and is slidable.

Further, since the printer main scanning carriage 34 is connected to the main scanning belt 36 by an engaging member (not shown), the main scanning motor 37 rotates to move in the direction orthogonal to FIG. Take action.

The printer main scanning carriage 34 has an arm portion 38, to which a printer signal cable 39 for transmitting a signal to the recording head 32 is fixed. The other end of the printer signal cable 39 is fixed to the printer middle plate 40 by a member 41, and is further coupled to the electrical unit 26. The printer signal cable 39 follows the movement of the printer main scanning carriage 34, and is not in contact with the upper optical frame 10.

The sub-scanning of the printer unit 44 is performed by the roller pair 2.
8.29, 30, and 31 are rotated by a power source (not shown), and the recording paper is conveyed by 8.128 mm each. 42 is a bottom plate of the printer unit 44, 45 is an exterior plate, 46 is a pressure bonding plate for pressure bonding an original to the original glass 1, 1009 is a paper ejection port, 47 is a paper ejection tray, and 48 is an electrical component of the operation unit.

FIG. 2 is a diagram showing details of the CCD line sensor 5 of this embodiment. Since the line sensor 5 is provided with 498 light receiving cells in a line and one pixel is composed of three pixels of R, G, and B, 166 pixels can be read substantially. Of these, the effective number of pixels is 144 pixels, and the pixel width composed of this number of pixels is approximately 9 mm.

<Structure of Recording Head (FIGS. 3 to 9)> FIG. 3 is a view showing the outer appearance of the ink jet cartridge in the printer section 44 of the color copying machine of this embodiment. FIG. 4 is a diagram showing details of the printed board 85 shown in FIG.

In FIG. 4, reference numeral 851 denotes a printed circuit board, and 8
Reference numeral 52 is an aluminum heat dissipation plate, 853 is a heater board composed of heating elements and a diode matrix, and 854 is a storage means for storing density unevenness information in advance, which may be a nonvolatile memory such as an EEPROM or any other suitable form. A contact electrode 855 serves as a joint with the main body. The ejection port group arranged in a line is not shown here.

In this way, the ink jet recording head 3
An EEPROM 854 for storing density unevenness information peculiar to each recording head is mounted on a printed circuit board 851 including two heating elements and a drive controller. And this EE
The PROM 854 measures density unevenness of individual heads during head production, and corrects density unevenness data or density unevenness corresponding to each discharge opening or several discharge openings as a unit based on the measured data. The data for is recorded.

By doing so, when the recording head 32 is attached to the main body device, the main body device reads out information relating to density unevenness from the recording head 32, and performs predetermined control for improving density unevenness based on this information. .. As a result, it is possible to secure good image quality.

FIGS. 5 (a) and 5 (b) are diagrams showing a circuit configuration example of a main part on the printed board 851 of FIG. Here, the inside of the dashed-dotted line is the circuit configuration inside the heater board 853, and this heater board 853 has an N × M matrix structure of a circuit in which a heating element 857 and a diode 856 for preventing current sneak are connected in series. It is configured. That is, these heat generating elements 857 are driven in time division for each block as shown in FIG. 6, and the control of the supply amount of the drive energy is performed by changing the pulse width (T) applied to the segment (Seg) side. It is realized by controlling.

FIG. 5B is a diagram showing an example of the EEPROM 854 in FIG. 4, in which density unevenness information relating to the present embodiment is stored. This density unevenness information is output to the main body side device by serial communication in response to a request signal (address signal) D1 from the main body device side.

In order to facilitate understanding of this embodiment,
First, the basic factors that cause uneven density will be described.

FIG. 7A is an enlarged view showing a recording state of the ideal recording head 32. Reference numeral 61 denotes an ink ejection port, and when recording is performed by the recording head 32, ink spots 60 having a uniform drop diameter (droplet diameter) are aligned and arranged on the paper. In addition, in the same figure, the case of so-called full discharge (state in which all discharge ports are ON) is shown, but for example, 50%
Even in the case of halftone such as output, uneven density does not occur.

On the other hand, in the case shown in FIG. 7B, the drop 6 of the second and (n-2) th discharge ports is
The diameters of 2, 63 are smaller than the others, and the (n-2) th and (n-1) th are recorded at positions displaced from the ideal landing center. That is, the (n−2) th drop 63 is recorded in the upper right of the center and in the lower left of the center of the (n−1) th drop 64.

As a result of recording in this way, FIG.
Area A shown in (b) appears as thin lines, and B
In the area as well, the (n-1) th and (n-2) th center-to-center distances are larger than the average distance l ₀ between the drops, and as a result, appear as thinner lines than other areas. On the other hand, C
In the area, the (n-1) th and nth center-to-center distances are narrower than the average distance l ₀ , and therefore appear as darker lines than in other areas.

As described above, the density unevenness mainly appears due to the variation in the drop diameter and the deviation from the center position (this is generally called "wobble"). However, such density unevenness occurs. A specific example of a method of correcting the drop diameter variation, which is one of the factors, will be described.

FIG. 8 is a diagram showing the relationship between the drive energy used to eject ink applied to the heater (heating element) 853 of the ejection port of the recording head 32 and the drop diameter of the ink ejected at that time. is there. As can be seen from the characteristic curve of FIG. 8, the drop diameter shows a tendency to increase with increasing energy in a certain drive energy range, and after that, the drop diameter becomes almost flat. However,
It can be seen that there is a large difference in the values of these drop diameters with respect to the driving energy between the case of a discharge port having a large diameter and the case of a discharge port having a small diameter.

Here, in order to make the sizes of the drop diameters uniform among the discharge ports having different diameters, referring to FIG. 8, for example, in order to control the drop diameters to the same value of l ₀ , the discharge port having a small diameter is used. It is understood that the drive energy of the large-diameter discharge port may be E ₁ (E ₂ > E ₁ ), while the drive energy of E ₂ is E ₂ . With such a method, an appropriate drive energy is obtained corresponding to the actual size of the drop diameter of each ejection port, and the value of the drive energy or the identification information corresponding to the value of the drive energy is shown in FIG. By writing the data in the volatile memory (EEPROM) 854, it is possible to eliminate at least the density unevenness due to the difference in the drop diameter between the ejection ports.

In the case where variably controlling the driving energy for each ejection port increases the circuit scale on the main body side, matrix driving is performed as shown in FIG. 5A, for example. In the case of the recording head 32, each block is set as the minimum unit (in FIG. 5A, each common terminal COM
1 to COMN are set as the minimum unit), average values of drop diameters of these outlets are obtained, and drive energy based on the average value is written in the nonvolatile memory 854 in the same manner as described above. As a result, it is possible to perform density unevenness control on a block-by-block basis and realize simplification in terms of circuitry.
It should be noted that control pulse width, drive voltage, drive current, and the like are conceivable as the identification information of the drive energy described above.

Next, a means for dealing with the above-mentioned "wrinkle" which is another cause of uneven density will be described.

The main reason for this “wobble” is that the ejection direction of the ink ejected from the ejection port is deflected due to the limit of the processing accuracy of the ejection port, and this deflection is properly corrected. It is practically difficult to do. Therefore, as a specific method for solving the density unevenness due to the “wobble”, instead of distinguishing the drop diameter and the “wobble” described above, the image density in a certain area stored by this recording head is used. Detect before product shipment. Then, a method of storing control data based on the detected value in the non-volatile memory 854 and controlling the amount of ink ejected into the area is adopted.

For example, as shown in FIG. 9A, 50% halftone recording by an ideal recording head has "variation" or "wobble" of the drop diameter as shown in FIG. 9B. In order to make density unevenness inconspicuous in printing by the printhead, the following is done. That is, by bringing the total dot area in the area within the broken line a shown in FIG. 9B closer to the total dot area of the area a in FIG. 9A, recording having the characteristics shown in FIG. Even when recording with the head, the user can perceive the same density as that shown in FIG. 9A with the naked eye.

By performing the same operation for the area b in FIG. 9B, the density unevenness is actually eliminated. Such density correction control is performed by the reader unit 2 as described below.
It is realized in the image processing of No. 4.

Note that FIG. 9B shows a model of the processing result of the density correction control in order to simplify the description, and α and β indicate correction dots. Further, as a method generally known as an image binarization process described below, a dither method, an error diffusion method, an average density method and the like are known. However, these methods are not the gist of the present invention, and thus the description thereof will be omitted.

<Structure of Control System, etc. (FIGS. 10 to 18)> In the density correction processing of the embodiment of the present invention, for example, in the flow of signal processing of the reader unit 24 as shown in FIG. It can be carried out as a process.

In FIG. 10, the image sensitivity read from the CCD sensor 5, which is one of the solid-state image pickup devices, has its sensor sensitivity corrected by the shading correction circuit 91, and L
In the OG conversion circuit 92, the three primary colors of light R (red), G (green), and B (blue) to the color (printing color) of the three primary colors C
Converted to (cyan), M (magenta), and Y (yellow). Next, the C, M, Y signals are extracted by using the Bk (black) part as a common component, or by extracting a part of the common component as a part of the black component and performing head shading as C, M, Y, Bk signals. It is input to the circuit 94. In the head shading circuit, γ correction (density correction) is performed as described later according to the characteristics of the nozzles of the corresponding head when the image signal read by the CCD is recorded by the printer unit, and the correction data is stored in the γ conversion circuit 95. Supplied. γ
The conversion circuit 95 has, for example, as shown in FIG. 11, a function of several steps for calculating output data with respect to input data, and has an appropriate relationship depending on the density balance of each color and the user's preference of tint. To be selected. The curve function is determined according to the characteristics of ink and the characteristics of recording paper. Further, the output of the γ conversion circuit is sent to the binarization processing circuit. In this embodiment, the average concentration dependent method (MD method) is adopted. The output of the binarization circuit is sent to the printer section and recorded by the head. In FIG. 10, the head shading circuit (γ
Although the correction circuit) 94 is placed in front of the γ conversion circuit 95 and the γ conversion is performed after the γ correction, this may be reversed.

Reference numeral 97 in FIG. 10 is a density unevenness measuring section. In the present embodiment, the electrical configuration block of the portion 100 including the head shading circuit (γ correction circuit) 94 and the density unevenness measuring section 97 is shown in FIG. It is composed.

In FIG. 12, reference numeral 150 is a control unit,
In this embodiment, the gate array is used as described later with reference to FIGS. Reference numeral 151 denotes a CPU, which sets registers in the control unit 150, writes the γ correction table number to the RAM 152 via the control unit 150, and RAM.
The density unevenness data is read from 152, and the calculation described later with reference to FIGS. 37 and 39 is performed based on the read data. Reference numeral 152 denotes a RAM, which is internally assigned such that the lower address is used as an area for temporarily storing the data for capturing density unevenness and the upper address is used as a storage area for the density correction table number. Reference numeral 126 denotes a ROM that stores a γ correction table, and 64 types of γ correction tables are prepared for each color as shown in FIG.

FIG. 14 further shows a portion 100 in FIG.
The functional block diagram of the above is shown, and the portions 97 and 94 surrounded by the one-dot chain line are the density unevenness measuring unit 97 and the head shading circuit (γ correction circuit) 94, respectively.

First, in the density unevenness measuring section 97, L
From the data converted into the three primary colors by the OG converter 92, the color signal for which the density unevenness is being measured is selected and latched in the latch circuit 131. The latched image signals are added by the adder 132, and the addition result is averaged by the averaging circuit 133.
Is averaged by. The data thus averaged is stored in the temporary memory 134. Here, the data added by the adder 132 is the density of a plurality of dots recorded by each ejection port, and the sampling number can be selected from several types.

The original is set on the original table so that the arrangement direction of the discharge ports of the basic pattern for measuring the density unevenness (50% of halftone etc.) and the arrangement direction of the CCD line sensor 5 are at right angles, and the CCD line sensor 5 is set. When the scanning is performed with the scanning line, the resolution of the recording head 32 and the CCD line sensor 5
When the resolutions are the same, the density data of the number of pixels corresponding to the number of light receiving elements of the CCD 5 can be obtained by sampling the CCD 5 once. If the resolution of the CCD 5 is higher than that of the recording head 32, C
It is necessary to calculate the density of one pixel recorded from the data of a plurality of light receiving elements of CD5.

The average density data of each discharge port is calculated by the calculation unit 13
5 (CPU 151) performs arithmetic processing, and the correction table shown in FIG. 15 is assigned to each ejection port. The correction table number thus obtained is the correction R in FIG.
Stored in AM 136.

In this embodiment, the memory 134 for temporarily storing the read density unevenness and the γ correction memory 136 are one RA.
It is shared by M152. FIG. 15 shows the internal allocation.

Further, the EPROM 126 stores the 64 types of γ correction curves shown in FIG. 16 in the layout of FIG.

Next, a specific example of the γ correction process will be described.

The γ correction circuit 94 has a large number of correction functions (64 types # 0 to # 63 in this example) as shown in FIG. For example, the function indicated by # 32 is a straight line with an inclination of 45 ° and outputs an input signal as it is as an output signal. On the other hand, in the functions of # 31 and below, the input signal is multiplied by a constant smaller than 1 and output. If this function is made to correspond to, for example, a high density portion of the recording head 32, the input image data will be corrected to a density lower than the actual density. On the other hand, in the functions indicated by # 33 and above, by multiplying the input data by a coefficient larger than 1, the input image is corrected to be darker than it actually is. Therefore, in this case, it is effective for the thin density portion of the recording head 32.

Further, this correction table is shown in FIG. 17 depending on the ink bleeding rate determined by the relationship between the ink and the paper and the binarization method in FIG. 10, for example, the error diffusion method or the density storage method.
Try to take a curve like.

In general, the rate of increase in density when dots are printed on a blank sheet is higher than when dots are stacked in a state where dots already exist. Further, at high duty, the dots have already overlapped each other, so that the density unevenness becomes less noticeable. Therefore, the correction rate is highest near the halftone (80H), and decreases toward both ends. Also, at low duty, there is a sufficient distance between dots, so that correction is unnecessary. This is because, when the correction is applied, the difference between the ejection port that ejects the ink and the ejection port that does not eject the ink is conspicuous and the lines become conspicuous.

In this way, in this embodiment, each of the ejection ports of the recording head 32 is made to correspond to one function of the plurality of characteristics shown in FIG. That is, the identification number of the correction function as shown in FIG. 17 is recorded in the nonvolatile memory 854 of FIG. 4 from the beginning so as to correspond to each ejection port. Then, by referring to these identification numbers, the image signal is γ-corrected by the γ-correction circuit 94 corresponding to each ejection port, and the correction result is sent to the binarization processing circuit 96 via the γ-conversion circuit 95. .. The binarization circuit 96 has a function of finally converting the multi-valued information (shown by 8 bits in FIG. 17) of each pixel into a binary value of “1” or “0”, and as described above. Binarization is performed using various dither methods, error diffusion methods, average density preservation methods, etc. In the present embodiment, as an example, the average density storage method is adopted, and the output result as shown in FIG. 7B can be obtained by the printer unit 44 as a binary output of the processing result.

FIG. 18 is a block diagram showing a detailed circuit configuration example of the γ correction circuit 94 of FIG.

Here, 120 is a counter and 121 is a decoder, which is a RAM 122 in the subsequent stage according to the color signals T1 and T2.
Any one of .about.125 is selected. Reference numerals 122 to 125 denote RAMs (random access memories) that store color conversion data corresponding to each color. However, in the present invention, as shown in FIG. 14, the γ correction RAM (122 to 12
5) and the RAM 134 for temporarily storing density data described later are shared. Reference numeral 126 is a γ correction ROM (read only memory), which stores the γ correction table data shown in FIG.

The color signals T1 and T2 supplied from the BK generation / UCR circuit 93 are "00", "01", "10",
It is a 2-bit signal in which a combination of "11" is possible,
In order to perform color identification of image data, the above 2-bit contents correspond to Y, M, C, and Bk in that order. In the counter 120 to which the signal T2 of the lower bit of the 2-bit color signal is input, the output of the decoder 121 is Bk (C
S-EK) counts up at the rising edge of the signal T2. In other words, the counter 120 is + at the end of the C signal.
Will be 1. Since one set of Y, M, C, and Bk means one pixel information, the counter 120 counts up in pixel units. The output of the counter 120 is connected to the address input terminals of the four RAMs 122 to 125.

The contents of the non-volatile memory 854 in each recording head are initially transferred and written in the RAMs 122 to 125 in advance via the CPU 151 (see FIG. 14) which is the central processing unit. The output of the decoder 121 is sequentially RAMs 122 to 1 in synchronization with the color signals T1 and T2.
The contents of the accessed RAM are selectively output and input as the upper address of the γ correction ROM 126.

That is, the output of the counter 120 indicates the ejection port number of the recording head 32 corresponding to the image data at that time, and the gamma correction curve of the ejection port is set at a location where the ejection number of the RAMs 122 to 125 is used as an address. The numbers (numbers # 0 to # 63 of the characteristic curve in FIG. 17) are recorded. Therefore, the γ-correction ROM 126 discriminates the table number at the upper address and Bk generation / UCR at the lower address.
The image data output from the circuit 93 is directly captured, the input image data is corrected according to one function selected from the γ correction curves in FIG. 17, and the next γ conversion circuit 95 is used.
I am giving it to.

<Variable recording (FIGS. 19 to 21)> Here,
The operation of the γ correction circuit during zooming of this example will be described.

FIG. 19 shows the relationship between the reading by the scanner and the recording by the printer in the reduction mode in this embodiment. In the figure, the case of 50% reduction is shown for the sake of simplicity.

In this case, the information read by the CCD 5 with the 128 sensors thins out the information of the original 2 by half, and the printer section prints with 64 ejection ports. In the present embodiment, as shown in the figure, for the first scan of the CCD, recording is performed from the first ejection port of the head 32 to the 64th ejection port (first group) in the printer section, and the second scanning of the CCD is performed. On the other hand, from the 65th outlet to the 128th outlet (second
Group) to record. Hereinafter, the first for the third scan
Records will be made for the second group and the fourth group. So in reduced mode,
Recording is performed by alternately using the halves of the heads. Therefore, in the printer unit 44, when the recording paper is fed, the recording paper is conveyed by 8.128 mm each. However, the printer main scanning carriage 34 scans the same area (that is, a width of 8.128 mm) of the recording paper twice each.

As can be understood from the above description, since the discharge outlets used are alternately switched in the reduction mode, the initial value of the control nozzle counter 120 shown in FIG. 18 is set to "0" when recording in the first group. , And when recording in the second group, set to 64 (actually CPU 1 in FIG.
35 does this). Here, as already mentioned, CC
D5 has 166 sensors, which is used for the binarization algorithm when the image processing is performed by band processing as in the case of the present embodiment shown in FIG. It is necessary to perform the connection processing in (between (n + 1)). Therefore, the image processing unit of the scanner unit actually processes 128 + α pixels in each band, and the head shading circuit 94 (FIG. 13) is no exception.

FIG. 20 shows the RAM 152 of this embodiment (see FIG.
4, FIG. 15) shows the data contents of the HS data (density correction table number) storage area. The HS data from ejection port No. 1 to 128 is written from address 1800H, and the data from ejection port No. 1 is written again from address 1880H. This is because the HS data is written so as to be adapted to the connection processing in the present embodiment as shown on the right side of the figure. Specifically, the connection portion (the portion indicated by the dotted arrow) is the printer main scanning carriage 34 for the next time.
Is determined by which ejection port is used for recording.

In this embodiment, as described with reference to FIG.
Since the first group and the second group are alternately used at the time of reduction, as a result, H at the same size (including enlargement) and at the time of reduction
The S table configuration is the same as that shown in FIG. 20, which can be dealt with by changing the access area as shown on the right side of the figure. However, for example, when only 64 ejection ports of the first group are used at the time of reduction, the HS data table in the RAM 152 may be written again from the address 1840H as shown in FIG. Good. Therefore, in this case, the HS data area of the RAM 152 may be selectively rewritten and used according to the contents as shown in FIG. 20 or FIG. In this case, a memory area for saving the contents of FIGS. 20 and 21 may be provided. Even if printing is performed with an arbitrary number of continuous ejection ports, R
This can be handled by appropriately rewriting the HS data of AM152.

In the above-described embodiment, the case where the image reading device and the ink jet recording device are connected as a copying machine and the density correction processing is performed in the image reading device has been described, but the present invention is not limited to this, and the color VTR is not limited thereto. The present invention can also be applied to an ink jet recording apparatus of a type in which R, G, B signals are input from an apparatus or the like, or a facsimile machine. In this case, the γ correction circuit 94 for density unevenness correction described above is used for signal processing in the ink jet recording apparatus. It is provided in the system.

<Operation Sequence> Next, FIG. 22 showing an example of the external configuration of the device of the present example, FIG. 23 showing a schematic control procedure of the device of the present example, FIG. 24 showing step S1 in FIG. 23, and the same step. An outline of the operation of the apparatus of this example will be described with reference to FIGS. 25, 26, 27A and 27B, which are specific procedures of S2, S4, S6 and S7.

In step S1 of FIG. 23, after the power is turned on by the main power switch 1008 of FIG. 22, so-called temperature adjustment for keeping the temperature of the head at 25 ° C. for printing is started, and then the recording head mounted on the apparatus. 24 (data in the nonvolatile memory of the recording head stores a head-specific identification number (ID) and a γ correction table number for each nozzle) of the printer unit shown in FIG. Copies together with ID to SRAM (HS data buffer). This processing is always performed when there is a possibility that the user has replaced the head, such as when the power is turned on or immediately after the head replacement door (1010 in FIG. 22) of the apparatus is opened and closed.

In the SRAM of the printer unit, at the end, R
The HS data obtained by the HS processing is stored and backed up by a battery together with the above-mentioned HS data buffer. Since the HS data buffer and the RHS data buffer store the ID and γ correction data for each of the four color heads of cyan, magenta, yellow, and black, the γ correction data of different heads are not used by mistake. It is like this.

Thereafter, in step S2, the HS data is transferred to the γ correction memory. At this time, since the latest HS data of the mounting head is used, the following judgment is made.

That is, as shown in step S8 of FIG. 25, the cyan head ID and RH copied when the power is turned on.
The head IDs of the S data buffers are compared, and if they match, it means that the head has been subjected to RHS processing in the past and the result remains in the RAM.
RHS-processed HS data is used for recording (step S9). Since the data in the non-volatile memory of the head is never rewritten, the RHS-processed HS data is guaranteed to be newer than the initial HS data of the recording head. The ID of each head is compared with the head ID of the RHS data buffer, and if they do not match, R
Since the data in the HS data buffer cannot be used for the current head because it belongs to another head, the data in the HS data buffer copied from the head is transferred to the γ correction memory (step S10). .. Then, for other colors (magenta, yellow, and black), the processing of S11, S12, and S13 including the same procedure as S8 to S10 is performed.

After the HS data corresponding to the head has been transferred to the γ correction memory, the apparatus operation unit (FIG. 22) which is a command to perform the copying operation in step S4 of FIG. 23, which is the main purpose of the apparatus.
Reference numeral 1004) of the COPY key (reference numeral 1005 in the figure)
And the like, and the input determination process of the door switch (not shown) provided on the head replacement door is performed (step S3 in FIG. 23).

Next, the outline of the copying operation shown in step S4 of FIG. 23 will be described.

FIG. 26 shows an example of the copying operation procedure.
It is activated in response to the operation of the PY key 1005. First, in step S4-1, it is determined whether the reduction mode is the same size / enlargement mode. If it is in the reduction mode, the process proceeds to step S4-2, while switching the access area so that the HS data (table number) corresponding to the group selected in one scan is read as described in FIG. Make a record. Alternatively, as described with reference to FIG. 21, recording is performed after rewriting to the HS data corresponding to the use group (rewriting from the state of FIG. 20 to the state of FIG. 21). On the other hand, in the case of the normal size / enlargement mode, FIG.
As described above, the recording operation is performed after switching so that the area in the mode is accessed because all the ejection ports are involved in recording in one scan, or after rewriting to the state of FIG. Is executed (step S4-3).

Next, step S6 of FIG. 23 is a process when the door for head replacement is opened.
The process shown in is performed. That is, when the door is opened, the above-mentioned door switch is turned off, and after the detection in step S3, the processing in step S6 is performed. As shown in FIG. 27A, this is done by stopping all drive motors in the apparatus (step S6-1), turning off the halogen lamp of the reading system, and shutting off the head drive power (step S6).
-2) is a process for the purpose of ensuring the safety of the user by stopping the electric current flowing in the head part which the user can touch and the physical movement of the head part by performing the above-mentioned 2). .. After the door opening process is performed, input of other keys is prohibited and the display LED of the operation unit (reference numeral of FIG. 22 is displayed until the door switch is turned on, that is, the door is closed in step S3 of FIG. 23. 100
An error message is displayed in 7) (step S6-3), the user is notified of the door open state, and the loop state is entered.

On the other hand, when the door is closed, the door shut process in step S7 is performed. The process will be described with reference to FIG. 27B. This is to restart the temperature control of the head to prepare for printing when detecting that the door is closed (step S7-1) and stop the error display. This is the processing for returning to the normal display (the number of copies, etc.) (step S7-2).

Note that the apparatus of the present invention performs processing of keys other than the keys on the operation unit already described, but since they are not directly related to the present invention, description and description thereof are omitted in FIG.

The RHS (Read) of step S5 of FIG.
er Head Shading) operation, which is the most important operation in this example, is an operation for correcting unevenness in density using an apparatus reading system. As described above, this process eliminates the uneven density caused by the aging of the recording head.
This is a process in which a certain printed pattern is read by the reading system of the apparatus, and the HS data is updated from the obtained data so as to correct the density unevenness.

This is the end of the description of the operation outline of the apparatus of this example.

<RHS Operation> In the present embodiment, the apparatus itself has means for correcting unevenness in density which occurs due to a change with time of the head. That is, when unevenness occurs, the unevenness measurement pattern shown in FIG. 28 is first printed by the operation procedure described later. This is read by the CCD 5 of the scanner itself to perform the unevenness measurement process.

As shown in FIG. 28, the original is set on the original plate in such a manner that the nozzle direction of the basic pattern for measuring the density unevenness (halftone 50%, etc.) and the arrangement direction of the CCD line sensor 5 are at right angles. CCD line sensor 5
When the scanning is performed with, the resolution of the recording head 32 and the C
If the resolution of the CD line sensor 5 is the same, one C
By sampling the CD5, density data of a number of pixels corresponding to the number of light receiving elements of the CCD5 can be obtained. When the resolution of the CCD 5 is higher than that of the recording head 32, it is necessary to calculate the density of one pixel recorded from the data of a plurality of light receiving elements of the CCD 5.

The average density data of each nozzle is stored in the CPU 13.
5, the correction table as shown in FIG. 17 is assigned to each nozzle. The correction table number thus obtained is the γ correction RAM 1 in FIG.
This is newly stored in 36 and the γ correction data is updated. However, as described above, in this example, RA
The M134 and the RAM 136 are shared by one RAM 152.

Next, FIG. 29 shows a specific control flow of RHS.
Follow along. The processing is roughly classified into printing of the uneven reading pattern, reading by the reading system of the same pattern, and HS data calculation.

By pressing the RHS key (reference numeral 1006 in FIG. 22) on the operation section of the apparatus, the uneven read pattern is first printed. This corresponds to the head recovery operation shown in step S14 of FIG. 29 and S15. In step S14, removal of ink adhered to the recording head, removal of bubbles by sucking ink from the ejection port, and cooling of the head heater are performed in a series of operations, and unevenness reading pattern printing in the RHS operation is performed in the best state. This is a highly desirable preparatory action for tightening.

In step S15, the unevenness reading pattern shown in FIG. 28 is printed out. As described above, the print pattern has a total of 16 blocks in which halftone with a density of 50% is printed in four blocks of each color in the vertical direction in the figure. The pattern is printed at a predetermined position on the recording paper. This physical position is set so as to be convenient for error detection when reading a pattern to be described later. In addition, each block is made by printing 3 lines. The 1st and 3rd lines discharge from only the 16 discharge ports at the lower end and the upper end of the 128 discharge ports, and the 2nd line from all 128 discharge ports. By performing ejection, a halftone printing block having a printing width of 160 ejection ports in total is formed. The reason for recording each block with a width of 160 ejection ports is as follows.

As shown in FIG. 30, when a recording head 32 having 128 ejection ports is used, when the pattern recorded by the recording head 32 is read by the CCD sensor 5 or the like, the background of the recording paper is read. The density data An tends to lag due to the influence of the color (for example, white). Therefore, if each block is recorded with only 128 ejection ports, the reliability of the density data of the end ejection ports may be lost.
Therefore, in this embodiment, printing is performed with 160 ejection ports, density data above a certain threshold is treated as valid data, and the center of the valid data is regarded as the central ejection port, and from that point (the number of ejection ports)
The data at points separated by / 2 (64 in this case) corresponded to the first ejection port and the 128th ejection port, respectively.

The reason why both end patterns are printed with 16 ejection openings is that the capacity of the irregular data temporary storage RAM 152 is saved, and in the case of a small main body (A4 machine etc.), the repeated pattern shown in FIG. 28 is processed by the scanner. This is so that it can be done.

After the printing of the reading pattern is completed, the RHS key 1006 is displayed as shown in step S16 of FIG.
Wait for pressing. The user can print the recording sheet 2 shown in FIG.
The pattern is placed downward on the document table 1 and the four blocks of the same color are arranged in line in the main scanning direction of the CCD sensor 5.
After that, when the RHS key 1006 is pressed, the process proceeds to step S17 in FIG.

From step S17 to step S28, it is an uneven reading and HS data calculation part. In step S17, the shading process of the CCD sensor 5 is performed using the reference white plate 1002 of FIG. 22, and the uneven read pattern reading is performed in step S18. One line here refers to one main scan of the CCD sensor that reads four blocks of a certain color at a time. Therefore, the black pattern for four blocks is stored in the memory by the one-line reading in step S18. The read data (density data) of each of the four blocks is printed at a specified position on the recording paper so that it will be stored in a specified area of the memory. The arrangement on the memory and the size of the data are as shown in FIG. Specifically, one block from the read data storage area 0000H to 01FFH, similarly 0200H to 03FFH, 0400H to 05FFH, 0600H.
From 0 to 07FFH, data is stored for each block.

Next, in step S19, error detection is performed on the read data stored in the memory. In the RHS of this example, the user needs to put the recording medium on which the print sample (test pattern) is formed on the reader, so it is strongly desirable to take into account the user's erroneous operation, so that the series of operations is correct. Try to check as closely as possible whether it is done or not. Further, even if the user's operation is correct, there is a possibility that if the reader reads inappropriate data, unless the processing is stopped, an inappropriate operation is performed and the unevenness is increased. Therefore, in the RHS of this example, the following error detection (step S
19) is performed and appropriate processing is performed for each.

First, as a possible error that the printed sample does not take the proper reading position, there is a case where the user shifts the printed sample with respect to the reading area of the reader. For example, the print sample of FIG. 28 should originally be placed on the document table 1 as shown in FIG. 31A, but if it is displaced in the main scanning direction of the reader as shown in FIG. Data is 1 as in (c)
There are not enough blocks or halfway. Further, if there is a deviation in the sub-scanning direction of the reader as shown in FIG. 31 (d), the data of "0" is read, and as shown in FIG. 32 (d), it is read as low density data, or in the worst case it is different. Color data is read. Further, if the print sample is placed with an inclination as shown in FIG. 31 (b), the data of the nozzles adjacent to the adjacent nozzles will come into the area corresponding to each ejection port as shown in FIG. 32 (b). I will end up. Correct correction will not be possible in any of these cases, so
It should be detected as an error and the read data should be rejected.

In order to do this, in this embodiment the reader is
When scanning, if there is no print area above a certain threshold at an appropriate position (address), it is an error. Here, the print area refers to a place where a value equal to or more than a predetermined absolute value for each color continues, but if a blank page is read and 0 is included in the data at this time, the print area is not recognized. Further, as another error detection method, when the width of the print area is larger than a certain threshold, this is detected as an oblique placement, and this is also an error in which the print sample does not take the regular reading position (FIG. 32 (b)). ).

The above method prevents writing of erroneous RHS data due to misalignment of print samples. Such error detection corresponds to an erroneous placement of the print sample by the user, and is not limited to the case where the print sample is simply misplaced as described above, and also corresponds to reverse placement, upside-down placement, and the like. In this case, the error can be read again by placing the print sample again and pressing the RHS button again.

However, even if the user puts the print sample in the correct position, if the state of the head itself is unstable, the discharge port may suddenly become non-discharge, and the print sample is in the reading stage. Should be considered abnormal.
Generally, as shown in FIG. 33C, when only one ejection port is not ejected, the area does not drop to the same level of density as the blank area. Therefore, in the present embodiment, a threshold for non-ejection detection is separately provided, and it is determined that non-ejection occurs when the data in the print area is lower than this threshold. At this time,
If there is a discharge failure in all four of the four print patterns of 8, this is a complete discharge failure, but if there is no discharge failure in other than one area, use only the remaining area for calculation. Alternatively, the printing may be started again as an RHS error. Further, even if there is a non-ejection in all four areas, if it is possible to cover with the printing of the nozzles on both sides, the calculation processing may be performed as it is, or only that color is not performed and another color Only SRA
M may be rewritten. Further, the above-mentioned print area threshold may be provided at a slightly higher position and may be detected at the same time without specially providing a non-ejection threshold. In any case, it is R
Strongly desirable for HS.

In this embodiment, the error detection as described above is performed to prevent erroneous data from being written in the SRAM, and it is protected to always store the most appropriate data in the SRAM.

Next, how and in what order such error processing is performed will be specifically described with reference to FIG. When the data for one block of one color is read, the value is first processed by the print position abnormality detection (detection of deviation in the main scanning direction or the sub scanning direction) (step S19-1). The shape of the data is normally as shown in FIG. Here, the horizontal axis represents the reader address, and the vertical axis represents the density. As described above, the range above a certain density level is set as the print area. Here, it is confirmed whether the address X1 of the density exceeding the threshold for the first time is within the allowable range. .. If the print start position starts at X from the beginning of reading by the reader, it is checked whether X1 is within X ± Δx. If this rising condition is not satisfied, it is judged as an error when it is detected, an error is displayed (step S20 in FIG. 29), and step S
Return to 16. Upon seeing this, the user re-places the print sample and starts reading again when the RHS button is pressed again.

When the above error detection of the print position abnormality is cleared, the obtained data is processed by the print width abnormality detection (oblique placement detection) (step S19-2). Since the print pattern has only a fixed width, when a sample is printed using a total of 160 discharge ports as in the present embodiment, the density data at the position of X1 + 160 ± Δx is Must fall below threshold (X2). If this is not satisfied, it is determined that there is a possibility of oblique placement, as described above, and the same display as the above error is displayed (step S21 in FIG. 29), the process returns to step S16, and the RHS is performed again.
Wait until the button is pressed.

The data for which the above two error detections have been cleared is processed by the non-ejection detection which is the last error detection (step S19-3). Here, the density data in the range from X1 to X2 determined as the print area is taken out pixel by pixel, and it is checked whether the density data is below the threshold for non-ejection. If there is a place where ejection failure is judged even at one place, an error is made at that point and an error display is carried out (step S22 in FIG. 29). However, since the error this time is an error at the printing stage, when the RHS button is pressed again (step S23 in FIG. 29), step S1
4, the RHS will start from the initial state.

Now, the data which has cleared the error detection successfully is inputted to the arithmetic circuit according to FIG. As shown in this figure, the calculation is the density ratio calculation process (step S2
4) and 1 line correction table number calculation processing (step S25). In the density ratio calculation, the ratio between the print density and the average density of each ejection port is calculated. Further, in the calculation of the 1-line correction table number, it is determined which of the 64 types of correction tables prepared in advance should be given to each ejection port having the above-mentioned density ratio. As described above, the changed output signal is written for each print input signal in each table. That is, for a nozzle with a low density, it is sufficient to select a table in which the output signal is always converted into a high value with respect to the input signal. Conversely, for a nozzle with a high density, the output signal is always You should choose a table that outputs lower than the input signal.

Here, from the fact that the data is actually input in the form as shown in FIG. 33 (a) from the error detection, FIG.
Will be explained in sequence. First, the rising positions X1 and X2 at both ends are averaged to obtain the center value of the print area.
It is determined that this is the central portion of the ejection port array, that is, between the 64th and 65th ejection ports. Therefore, the data at the positions 64 pixels before and after the central portion are the densities of the 1st and 128th ejection ports. As a result, the print density n (i) including the joints at both ends is obtained at each ejection port. However, it is very dangerous to use the density data of the area having only the width of one pixel as the density data of the ejection port as it is. This is because, as shown in FIG. 36, it is certain that one pixel of the reading area includes the density of the dots ejected from the ejection ports on both sides, and it does not matter whether the ejection port is slightly left or right. This is because it is unavoidable to rely on it. Furthermore, it is desirable to take into consideration that the density unevenness seen by the human eye is influenced according to the surrounding situation including the pixel of interest. Therefore, in this embodiment, before the density of each ejection port is determined, the
As shown in FIG. 7, the average value of the density data (A _i−1 , A _i , A _{i + 1} ) of three pixels including the pixel and the pixels on both sides is sequentially obtained, and the average value is obtained as the ejection port density ave (i). I am trying.

Furthermore, from ave (1) to ave (12
The average value AVE up to 8) is calculated and used as the average density of all the ejection ports. Next, the ratio to this average density is obtained for all ejection ports. It is important to note here that the obtained value d (i) is the reciprocal of the value for each ejection port density. That is, d (i) = AVE / ave
(I). For low density ones, it is necessary to make a correction with a large slope to increase the density, and conversely for high density ones, a correction with a small slope to give a low density must be made. For later calculation processing,
It is convenient to find the reciprocal number in this way.
Thus, the density ratio calculation ends when 128 density ratios d (i) are obtained, and the data is used for calculation of the one-line correction table.

Here, first, the density ratio d (i) obtained by the current unevenness reading and the density ratio D up to the previous time are compared.
Multiplication with (i) D (i) = d (i) × D (i) is performed.
As a result of making such corrections in the arithmetic processing, as a result, all the past d (i) are included while being multiplied. The density unevenness changes gradually, and it is meaningful to add the data up to that point to the arithmetic processing for correction. Next, the table is determined, and the determination formula at this time is T (i) = (D (i) −1) × 100 + 32, where table number T (i). As described above, 64 correction tables are prepared, and the inclination is gradually increased / decreased with the table number # 32 as the center.

Here, the relationship between the correction table and the above equation will be described again in detail with reference to FIG. In FIG. 17, the table number # 32 is a straight line having a slope 1 in which the input value and the output value are always equal. This is a table to be taken by the ejection ports for obtaining the average density of 128 ejection ports. The remaining curve above and below it is 50% density equal to the printed sample.
At (80H), there is a table centered on # 32 in 1% steps. Therefore, T obtained by the above equation
In the case of (i), the signal value conversion that always matches the density ratio is performed on the input signal of 80H. In this way, the calculation of the 1-line correction table number ends when 128 T (i) have been obtained.

When the uneven reading for one line, that is, one color, and the calculation of the HS data (γ correction table number) in which the unevenness is corrected from the data are completed as described above, the heads for four lines, that is, four colors are printed at step S26. Then, it is checked whether the same processing is completed, and when the HS data for four colors is calculated, the γ correction memory is updated in the next step S27. The γ correction memory stores the latest HS data (γ correction table number) until the RHS process is performed, and replaces it with the calculated latest HS data.

Subsequently, in step S28, the HS data in the RHS data buffer of the backup memory of the printer section is replaced with the latest HS data.

With the above, the description of the control flow of the RHS processing is completed.

As is apparent from the above, in this embodiment, when the head is replaced with a new head, the EEPRO in the head is changed.
The HS data (γ correction data) of M is written in the SRAM 136, and the data of the SRAM 136 is updated according to the above-mentioned operation with respect to the subsequent change with time. Therefore, in this embodiment, the latest HS data is stored in the RA in the printer control unit so that the updated data is stored even when the power is turned off.
It is transferred to M (not shown) and this RAM is backed up by a battery.

Incidentally, in the density ratio calculation of step S25 in FIG. 29, as shown in FIG.
Instead of obtaining the moving average of the pixels, it can be performed as follows.

FIG. 38 shows a procedure for explaining the density ratio calculation according to another embodiment. First, step S3.
The processing of 1 is performed by the adder 132 and the averaging circuit 1 shown in FIG.
And 33.

The average value data obtained in step S31 is subjected to a moving average with respect to the adjacent ejection ports in step S32. In this example, as shown in FIG. 39, this is to weight the proximity ejection ports and calculate the density average value of the recorded image densities. For example, A in FIG. 39 (a)
If you want to obtain the density of pixel data corresponding to ₀ ,
Obtain the density data (A _{-4 to} A ₄ ) of 8 pixels before and after that,
As shown in FIG. 39 (b), their weighted averages are taken. This takes into account that the density unevenness seen by the human eye is influenced by the surrounding situation including the pixel of interest. In this way, in step S23, the average D of all the ejection ports is obtained from the moving average value D _n (n is the ejection port number) corresponding to each ejection port thus obtained. Next, in step S34, the reciprocal 1 / α _n ¹ (= D _n / D) of the density ratio with respect to the average value D of each ejection port of the recording head 32 is obtained. The reason for taking the reciprocal here is that the discharge port having a lower density than the average value D,
That is, for a discharge port with (D _n / D) <1,
The correction curve shown in FIG. 17 having a slope of (D _n / D)> 1 is selected, the input of the γ correction circuit 94 is multiplied by D / D _n and output, and the density is controlled to be higher than the actual output. This is because.

On the contrary, for nozzles having a high density with respect to the average value D, the density is controlled to be D / D _n (<1) times lower than the actual value and output.

In step S35, a multiplication value α _n of the reciprocal α _n ¹ of the density ratio obtained in the current density unevenness measurement and α _n ⁰ up to the previous time is obtained. That is, when the basic pattern for density unevenness measurement is recorded with the correction coefficient α _n ⁰ , this time the density ratio becomes D _n / D (= 1 / α _n ¹ ), and as a result, correction of α _n ¹ must be added. It means that it is no longer. Therefore, along with aging, twice as 3 times ... that, the correction coefficient alpha _n If we repeated these operations
Changes to α _n = α _n ⁰ · α _n ¹ · α _n ² · α _n ³ ... From the α _n thus obtained, the table number can be calculated, that is, the correction curve can be selected in the process of step S25 of FIG.

<Structure of Control Unit 150> As one of the features of this embodiment, as described above, the RAMs 122 to 125 for storing the γ correction table numbers of the γ correction circuit of FIG. 18 and the density unevenness measuring unit of FIG. It is shared with the block density unevenness data temporary storage RAM 134. The internal allocation of the RAM 134 is shown in FIG. In addition, the unevenness processing circuit 1 of FIG.
The electrical configuration of 00 is as shown in FIG. 12, and the control unit 150 is configured by the gate array as described above.

40 to 43 are block diagrams of the control unit 150, and show that the symbols C1 to C4 in the respective drawings are connected to the portions having the same symbols in the other drawings.

There are three types of operation modes: a CPU mode in which the CPU accesses the SRAM, a copy mode in which the head shading function is performed, and a head shading mode (HS mode) in which unevenness of the head is read.

First, the HS mode will be described. As described above, in order to measure the current density unevenness first, a pattern for density measurement as shown in FIG. 28 is printed by the binarization processing circuit 96 of FIG.
The data is printed by inputting the data to the printer 4, and the density is sampled by the CCD line sensor 5 shown in FIG.
Modified 3 line printing is performed in order to save the memory area of the RAM 152 (see FIG. 12). That is, only the central line is printed by using all 128 ejection ports, and the front and back lines are printed by only 16 ejection ports. By doing this,
The RAM area for storing patterns 1 to 4 can be saved. That is, one pattern can be accommodated within 512 bytes. The relationship between the pattern and the RAM address is shown on the right side of FIG. 28 (see also FIG. 15).

WINDOW 161 and ADD shown in FIG.
The calculation result is stored in the SRAM via the ER 162 and DIVIDER 163, and this portion is an average value circuit. That is, 128 pieces of data for calculating the density of a dot ejected by a certain ejection port (this set number can be changed by changing the set value of the register corresponding to the sampling number in the register group 160 in FIG. 40). ) Is calculated (the state is already schematically shown in FIG. 30). This average value is the VE signal (video en)
It is the average of the predetermined sampling data within the (able) period. Here, the VE signal period is one scanning period of the CCD 5. In the WINDOW circuit 161, as shown in FIG. 42, the data input range of the CCD 5 (BVE signal: block
The video capture area is instructed to the video enable). The density average value data corresponding to each ejection port determined in this way is temporarily stored in the RAM address shown in FIG. 15. This address is generated by the selector 167 in FIG. 43 selecting the HS mode. It is checked whether the average value data thus obtained is suitable for performing density unevenness calculation. For example, if the non-ejection portion as shown in FIG. 33C is generated in the pattern of each color, the pattern is removed from the calculation target. The average value data thus obtained is calculated by the CPU according to the procedure described in FIG.
Finally, the density correction table number corresponding to each nozzle is obtained. Next, the CPU stores the obtained table number in the SRAM 15
Write to 2. At this time, the CPU switches the control unit to the CPU mode. In this example, as shown in FIG. 15, the density table number is selected in the final area of the SRAM address.

Next, the CPU mode will be described. Figure 4
3 in the CPU mode, SR is selected by the selector 167.
The lower 10 bits of the AM152 address bus is the CPU
Connected to address bus. The upper 3 bits are for this controller
Given by register. SRAM152 data bar
In the case of writing and reading, the CPU
Signal generated from the read signal WRN and the read signal RDN
(S in FIG. 41 WEN 1 and S OEN).

Next, the copy mode will be described. In the copy mode, the address bus of the SRAM 152 is connected to the nozzle correspondence counter 166 by the selector 167, and C
The area is counted up in synchronization with the read pixel signal of CD5 and the density correction table number storage area in FIG. 15 is accessed. In FIG. 42, upper addresses 1T and 2T are head color discrimination signals. As a result, the SRAM 152 outputs the density correction table number corresponding to each ejection port, and this output becomes the table ROM 126 (the upper address in FIG. 12).
The contents of the table ROM have 64 types of tables for each color as shown in FIG. That is, the SRAM 15
The output of 2 specifies the table number. Further, the 8-bit image signal becomes the lower address of the table ROM 126,
It becomes the data value of the horizontal axis of FIG. As a result, table R
It is output to the data bus of OM126. Table ROM
The output of 126 is sent to the binarization processing circuit in the subsequent stage shown in FIG.

SRAM 1 in each mode described above
The configuration of the address bus 52 is summarized in FIG.

In this example, the control unit 150 shown in FIG. 12 is composed of a gate array. Further, since the density correction table number in the SRAM 152 needs to be stored even when the power is turned off, the SRAM has a battery backup in this example. However, the density correction table number in the EEPROM 854 shown in FIG. It may be updated anew. In this case, since the head always has the latest HS data, such as when several heads are prepared for the same machine, the head temperature reaches an abnormally high temperature during continuous printing, for example. In such a case, it is possible to immediately restart image output without density unevenness by replacing the head.

Further, even when the head is mounted on another apparatus main body, it is possible to realize image output without density unevenness.

(Others) In particular, the present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, especially in the ink jet recording system. The present invention provides excellent effects in a recording head and a recording apparatus of the type in which the thermal energy causes a change in ink state. This is because such a system can achieve high density recording and high definition recording.

Regarding its typical structure and principle, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal as a result
This is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection openings to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333, U.S. Pat. No. 44, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The configuration using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in Japanese Patent Laid-Open No. 59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus or the electrical connection to the main body of the apparatus or the ink from the main body of the apparatus by being mounted on the main body of the apparatus. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add ejection recovery means of the recording head, preliminary auxiliary means and the like because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping means, a cleaning means, a pressure or suction means for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type or number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but may be either integrally formed of the recording heads or a combination of a plurality of them. The present invention is also very effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet method, it is common to adjust the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. At times, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy for changing the state of the ink from the solid state to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in a standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP 54-56847 A or JP 60-7.
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

[0140]

As described above, according to the present invention,
Even if the attached inkjet recording head changes over time and density unevenness occurs as a result, it is possible to appropriately suppress the occurrence of density unevenness by correcting the density unevenness correction data, and always obtain a high-quality image. Can be maintained.

By selecting the first or second density unevenness correction data based on the printhead identification information, processing for density unevenness correction to be performed at the time of replacement of the printhead or for the same head thereafter. The reliability of can be improved.

When the recording medium on which the test pattern is formed is not properly positioned with respect to the reading means (reader) when the density unevenness correction data is created or updated (deviation in the main and sub-scanning directions, oblique placement, etc.). Since this is detected, it is possible to correctly recognize the occurrence state of density unevenness by performing appropriate replacement.

Furthermore, by making it possible to judge whether or not the test pattern is formed in a normal state (non-ejection, etc.), it is possible to prevent the creation of inappropriate correction data using an abnormal test pattern. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a color copying machine using an ink jet recording apparatus as an embodiment of the ink jet recording apparatus of the present invention.

FIG. 2 is an explanatory diagram for explaining a configuration of a CCD line sensor used in the color copying machine.

FIG. 3 is an external perspective view showing an example of an inkjet recording head applicable to the present invention.

FIG. 4 is a perspective view showing a configuration example of the substrate.

5A and 5B are respectively a circuit diagram and a circuit diagram of an EEPROM showing a circuit configuration of a heater board in the print head of the present example.

6 is a timing diagram of drive signals of the circuit of FIG. 5 (a).

7A and 7B are explanatory diagrams showing a relationship between ejection ports of a recording head and recorded dots, FIG. 7A is an ideal state, and FIG. 7B is a diagram showing actual recording dot states. is there.

FIG. 8 is a characteristic diagram showing the relationship between drive energy for ejecting ink applied to the heating elements of the recording head and the drop diameter of ejected ink.

9A and 9B are diagrams showing a 50% halftone recording result by an ideal recording head and a halftone recording result after density correction processing by an actual recording head, respectively. It is a figure.

FIG. 10 is a block diagram showing a configuration of an image processing circuit of this embodiment.

11 is a characteristic diagram showing a relationship between an input signal and an output signal of the γ conversion circuit of FIG.

12 is a block diagram showing an outline of an electrical configuration of a density unevenness control circuit in FIG.

13 is an explanatory diagram for explaining the internal allocation of the head shading table of the ROM in FIG.

14 is a functional block diagram showing details of a density unevenness measuring unit and a head shading circuit in FIG.

15 is an explanatory diagram showing internal allocation of RAM in FIG. 12;

16 is a characteristic diagram showing an example of a relationship between an input signal and an output signal of the γ correction circuit in FIG.

FIG. 17 is a characteristic diagram showing another example of the relationship between the input signal and the output signal.

18 is a block diagram showing a circuit configuration example of the γ correction circuit in FIG.

FIG. 19 is an explanatory diagram illustrating a relationship between reading by the scanner unit and recording by the printer unit in the reduction mode.

FIG. 20 is an explanatory diagram showing the relationship between the details of the HS data storage area in FIG. 15 and the usage area during scaling.

FIG. 21 is an explanatory diagram showing a method of storing HS data when only the first to 64th discharge ports are used at the time of scaling.

FIG. 22 is a schematic perspective view showing an external configuration example of a color copying machine according to an embodiment.

FIG. 23 is a general flowchart showing an outline of the overall control procedure of the color copying machine according to the embodiment.

FIG. 24 is an explanatory diagram illustrating an HS data storage area.

FIG. 25 is a flowchart showing an example of the HS data reading processing procedure in FIG. 23.

FIG. 26 is a flowchart showing an example of a copying operation procedure in FIG. 23.

27 (a) and 27 (b) are flowcharts showing an example of a processing procedure at the time of door opening and door shut in FIG. 23, respectively.

FIG. 28 is an explanatory diagram illustrating an unevenness measurement pattern and a reading method.

FIG. 29 is a flowchart showing an example of a processing procedure at the time of RHS operation in FIG. 23.

FIG. 30 is an explanatory diagram showing a relationship between a density unevenness measurement pattern and a CCD line sensor.

31A to 31D are explanatory views showing various states in which a recording sheet on which a test pattern is recorded can be placed on a reader.

32 (a)-(d) are shown in FIG.
It is explanatory drawing of the read state of the test pattern corresponding to the mounting state of (d), and the content of the read density data.

FIGS. 33A to 33C are explanatory views for explaining a means for detecting an error from the density data read by the reader.

FIG. 34 is a flowchart showing an example of an error detection processing procedure in FIG. 29.

FIG. 35 is an explanatory diagram for explaining allocation of density data read by a reader to each ejection port.

FIG. 36 is an explanatory diagram of a dot formation state in the test pattern.

FIG. 37 is an explanatory diagram of moving average calculation for obtaining density data for each ejection port.

FIG. 38 is a flowchart showing another example of the density ratio calculation process in FIG. 29.

FIG. 39 is an explanatory diagram of moving average calculation in the processing.

FIG. 40 is a block diagram illustrating a detailed configuration example of a control unit in FIG.

FIG. 41 is a block diagram of the same.

FIG. 42 is a block diagram of the same.

FIG. 43 is a block diagram of the same.

FIG. 44 is an SRAM in each control mode of the control unit
3 is an explanatory diagram of an address selector of FIG.

[Explanation of symbols]

 1 Document Plate 2 Document 5 CCD Run Sensor 7 Main Scanning Carriage 9 Sub Scanning Unit 24 Reader Section 32 Recording Head 34 Printer Main Scanning Carriage 44 Printer Section 85 Print Board 91 Shading Correction Circuit 92 LOG Conversion Circuit 93 Bk Generation / UCR Circuit 94 Head Shading Circuit (γ correction circuit) 95 γ conversion circuit 96 Binarization processing circuit 97 Density unevenness measurement unit 100 Density unevenness control unit 126 EPROM 130 Color signal selection unit 131 Latch circuit 132 Adder 133 Averaging circuit 134 Data temporary storage unit 135, 151 arithmetic unit (CPU) 136,152 RAM 150 control unit 854 EEPROM

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B41J 2/07 H04N 1/034 9070-5C 1/23 101 A 9186-5C 8703-2C B41J 3 / 04 101 A 9012-2C 104 H (72) Inventor Norifumi Koitabashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (16)

[Claims] 1. A recording head having a plurality of ink ejection ports, which stores identification information of the recording head and first density unevenness correction data specific to the recording head, which is referred to during recording. In an ink jet recording apparatus for performing recording using the recording head provided with, a first storage unit that reads out the identification information and the density unevenness correction data and stores them in association with each other; Density unevenness correction data creating means for creating second density unevenness correction data using the read first density unevenness correction data, the created second density unevenness correction data, and the first density unevenness correction data
Second storage means for storing the identification information corresponding to the density unevenness correction data as a set, and the identification information and the first density unevenness correction data are read from the mounted recording head at a predetermined timing. Means for storing in the first storage means, the identification information read from the second storage means, and the first information
Comparing the printhead identification information stored in the storage means of
If they match, the second density unevenness correction data read from the second storage means is used during printing to drive the printhead, and if they do not match, the first read out from the first storage means. An ink jet recording apparatus comprising: a unit for driving a recording head by using density unevenness correction data during recording. 2. The ink jet recording apparatus according to claim 1, wherein the predetermined timing is when the power is turned on. 3. The predetermined timing is when a door provided to open the inside of the apparatus to receive the replacement work of the recording head is opened and closed while the apparatus power is on. Inkjet recording device. 4. The ink jet recording apparatus according to claim 1, further comprising a battery that backs up the first and second storage means. 5. The ink jet recording apparatus according to claim 1, wherein the second uneven density correction data is stored in the second storage means only by the uneven density creating means. .. 6. The density unevenness correction data creating means further corrects the second density unevenness correction data to newly create second density unevenness correction data, and updates the contents of the second storage means. 6. The inkjet recording apparatus according to claim 1, further comprising: 7. A means for repeatedly recording a predetermined test pattern on a recording medium a plurality of times to create the second density unevenness correction data, a means for reading the test pattern, and a plurality of the read plural patterns. For each of the test patterns, the density or density ratio is obtained for each of the plurality of ink discharge ports, and the average value of the density or density ratio between the plurality of test patterns is calculated as the density or density ratio for each of the plurality of ink discharge ports. 7. The ink jet recording apparatus according to claim 1, further comprising means for determining. 8. An ink jet recording apparatus for forming an image using a recording head having a plurality of ink ejection ports, wherein energy used to eject ink from the plurality of ejection ports is generated. In an inkjet recording apparatus including a correction unit that corrects at least one image processing condition of a plurality of elements to suppress density unevenness during image formation, a predetermined test pattern is recorded on a recording medium by the recording head. Means for forming, reading means for reading the test pattern, density unevenness correction data creating means for creating data for the correction using the read result, and creating data for the correction, Whether the recording medium on which the test pattern is formed is in a normal reading position with respect to the reading means. An ink jet recording apparatus, characterized in that it comprises a determining means for determining. 9. The determination unit is configured to detect a predetermined amount of deviation between the position of the end of the test pattern detected by the reading unit and the position of the end when the test pattern is formed. 9. The ink jet recording apparatus according to claim 8, wherein the reading position is determined to be defective when the value exceeds the limit. 10. The reading means reads the width when the difference between the width of the test pattern detected by the reading means and the original width of the test pattern formation exceeds a predetermined value. The inkjet recording apparatus according to claim 8, wherein the position is determined to be defective. 11. An ink jet recording apparatus for forming an image using a recording head having a plurality of ink ejection ports, wherein energy used to eject ink from the plurality of ejection ports is generated. In an inkjet recording apparatus including a correction unit that corrects at least one image processing condition of a plurality of elements to suppress density unevenness during image formation, a predetermined test pattern is recorded on a recording medium by the recording head. A means for forming, a reading means for reading the test pattern, a density unevenness correction data creating means for creating data for the correction using the reading result, and a normal state of the test pattern from the reading result. And an ink jet recording apparatus characterized by comprising a judgment means for judging whether or not . 12. The determination means determines that the test pattern read by the reading means is not formed in the normal state when there is a density lower than a predetermined absolute density in the test pattern. The inkjet recording device according to claim 11. 13. A storage unit for storing the created density unevenness correction data, wherein the density unevenness correction data creation unit updates the contents of the storage unit every time the creation is performed, and uses the correction unit. The inkjet recording apparatus according to claim 8, wherein the inkjet recording apparatus is provided. 14. The test pattern is repeatedly formed on a storage medium a plurality of times, and the density nonuniformity correction data creating means is arranged for each of the plurality of ink ejection openings for each of the plurality of test patterns read by the reading means. And a means for determining a density or a density ratio and determining an average value of the density or the density ratio among the plurality of test patterns as a density or a density ratio for each of the plurality of ink ejection ports. Claims 9 to 13
The inkjet recording device according to any one of 1. 15. An ink jet recording apparatus using a recording head having a plurality of ink ejection ports for storing identification information and unique density unevenness correction data, the identification being performed from the recording head when the recording head is mounted. Reading information and the density unevenness correction data,
Means for storing in the first storage area, and the density unevenness correction data in the first storage area is changed to a second storage area together with the identification information in the first storage area.
Means for storing the identification information in the first storage area and the identification information in the second storage area at a predetermined timing, and if the two match, the second information is stored. The ink jet recording apparatus is characterized in that the density unevenness correction data in the storage area is used at the time of recording, and if they do not match, the density unevenness correction data in the first storage area is used. 16. The ink jet recording head has an electrothermal conversion element used as an element for causing film boiling of ink to eject the ink, as the element. Inkjet recording apparatus according to the item.