JPH0542685A - Recording apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] In a recording apparatus that performs recording with a plurality of recording colors by using a recording head having a plurality of recording elements, it is possible to eliminate density unevenness of each recording color with a simple configuration. When a test pattern is read by a reading device, the density level is read differently for each recording color as shown in (A). Therefore, the density unevenness is corrected based on the data in which the density level of the read data is the same as shown in (B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device.

[0002]

2. Description of the Related Art For example, in an ink jet recording head having a plurality of ink ejection ports, it is conventionally known that ejection characteristics vary among the plurality of ejection ports. This is often caused by variations in the shape of the ejection ports during the manufacturing process of the printhead, and such variations cause variations in the ink ejection amount, and some ejection ports may have different ejection directions. It causes twisting. As a result,
There is a problem that unevenness in density occurs in a recorded image, which deteriorates image quality.

In order to deal with such a problem, data relating to the density unevenness of each print head is measured at the time of manufacturing the print head, and the print head is driven in accordance with the driving conditions and image processing.
A method of writing correction data for correcting recorded data in a ROM and mounting the correction data on a product has been adopted.

However, the above method is insufficient for the density unevenness due to the change of the printhead over time, and in practice, it is necessary to periodically replace the printhead or correct the density unevenness correction data at the time of maintenance. I was trying.

However, there has been a problem that when the recording head is replaced or the periodical maintenance is performed, the maintenance cost and time required therefor become enormous.

On the other hand, a predetermined image pattern is recorded, the recorded image pattern is optically read by means such as CCD, and the print data is corrected for each ejection port of the print head based on the read result. However, there has been proposed a configuration for eliminating uneven density.

[0007]

However, when the above-described density unevenness correction is performed in a printing apparatus that prints with a plurality of inks of different colors, the density level of read data is generally different for each color. Is.
Therefore, the degree of density unevenness appearing in the read data differs for each color. Therefore, if the same correction is performed for each color based on the read data, the degree of correction is different, and uneven density may not be completely eliminated for some colors.

On the other hand, it is conceivable to make the correction mode different for each color, but in this case, there is a problem that the structure for this correction becomes complicated.

The problem described above is not limited to the ink jet type recording apparatus, but is common to a recording apparatus having a recording head having a plurality of recording elements and recording with a plurality of recording colors. An example of such a recording device is a thermal transfer recording device.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a recording apparatus for recording with a plurality of recording colors, which has a simple structure and has uneven density of each recording color. It is an object of the present invention to provide a recording device capable of solving the above problem.

[0011]

Therefore, according to the present invention,
In a recording apparatus for recording with a plurality of recording colors by using a recording head having a plurality of recording elements, a reading unit for reading an image recorded by the recording head, and a density level of data read by the reading unit. On the basis of the data changed by the density changing means and the density changing means, and the density printed by each of the plurality of printing elements in the print head is corrected. And a means for correcting unevenness in density.

[0012]

With the above arrangement, the density level of the read data can be changed according to the recording color. Therefore, when the uneven density correction process is performed based on the read data, the density level is made the same between the recording colors. be able to. As a result, the density unevenness of each recording color is faithfully reflected in the read data which is the basis of the density unevenness correction.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a side sectional view of a color copying machine using an ink jet recording apparatus according to an embodiment of the present invention.

The color copying machine is roughly divided into an image reading and image processing section (hereinafter referred to as a reader section 24) and a printer section 44. The reader unit 24 scans the document 2 placed on the document glass 1 by the CCD line sensor 5 having filters of three colors of R, G, and B, and reads an image. The read data thus read is subjected to a predetermined process by the image processing circuit to be recorded data used in the printer section 44. Based on the print data, the printer unit 44 prints an image on the print paper with four print heads corresponding to four colors of cyan (C), magenta (M), yellow (Y), and black (Bk). To do.

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. In this configuration, the upper left side of FIG. 1 is the front surface of the device.

The printer section 44 is provided with four ink jet recording heads 32 for ejecting ink for recording. Each recording head 32 has, for example, six ink ejection ports.
In the vertical direction at the 3.5 μm pitch (in the sub-scanning direction, as shown in FIG.
By arranging 128 in the middle (left and right direction), a width of 8.128 mm can be recorded by one main scan. When recording on the recording paper, the conveyance (paper feeding) of the recording paper is stopped, the main scanning of the recording head 32 is performed, and
After recording with a width of 8 mm, the recording paper is then
Paper is fed by 8 mm, and the next main scan is 8.128.
The operation of recording the millimeter width is repeated.

In the structure of the present embodiment, the main scanning direction of the recording head is the direction perpendicular to the plane of FIG. 1, and the sub-scanning direction is the horizontal direction of the drawing.

The reader unit 24 repeats reading the original 2 with a reading line having a width of 8.128 mm corresponding to the printer unit 44. The moving direction of the reading head for this reading is the main scanning direction. The direction in which the head moves to the next reading line is called the sub-scanning direction. In this configuration, the main scanning direction is the left-right direction of FIG. 1, and the sub-scanning direction is that of FIG.
The direction perpendicular to the plane of.

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

The original image of the original 2 on the original table glass 1 is
Sequential reading is performed by the following main scanning and sub-scanning of the reading head. That is, on the main scanning carriage 7,
A read head including the lens array 4 and the light receiving element 5 is configured. The original image is illuminated by the lamp 3, and the light reflected by the original 2 enters the light receiving element 5 (CCD) through the lens array 4. The main scanning carriage 7 is fitted to a main scanning rail 8 provided on the sub scanning unit 9,
It is slidable. Further, the main scanning carriage 7 is connected to the main scanning belt 17 by an engaging member (not shown).
It can be moved in the horizontal direction in FIG. 1 by rotation of the main scanning motor 16. Along with this movement, the lamp 3 irradiates the document to perform main scanning for reading.

The sub-scanning unit 9 is fitted to a sub-scanning rail 11 fixed to the optical frame 10 and slidably provided. Further, since the sub-scanning unit 9 is connected to the sub-scanning belt 18 by an engagement member (not shown), the sub-scanning operation can be performed by the rotation of the sub-scanning motor 19.

The read data received by the CCD 5 and converted into an electric signal is transmitted to the printer section 44 via the loop-shaped signal cable 13. That is, the signal cable 1
3 is held on the main scanning carriage 7 near one end thereof by a gripper 14, and the other end is fixed to a bottom surface 20 of the sub-scanning unit 9 by a member 21.
It is connected to the sub-scanning signal cable 23 connected to the electrical unit 26 of the printer unit 44. 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 the paper feed roller 27 driven by a power source (not shown) are two roller pairs 28, 29 and 3.
While being conveyed between 0 and 31, recording is performed by main scanning of four recording heads 32 corresponding to each ink. The four recording heads 32 are arranged in the main scanning direction, so that only one is shown in FIG. Each recording head 32
Is configured integrally with the ink tank 33, and the carriage 34
It is detachably attached on top. These recording heads 32 are
An electrothermal converter is provided in an ink path communicating with each of the ejection ports, and thermal energy generated by the electrothermal converter generates bubbles in the ink, and the ink is ejected as the bubbles are generated. The carriage 34 slidably engages with the printer main scanning rail 35. Further, the carriage 34 is connected to the main scanning belt 36 by an engagement member (not shown), so that main scanning can be performed by rotation of the main scanning motor 37.

An arm portion 38 is provided on the carriage 34, and one end of a printer signal cable 39 for transmitting a drive signal thereof to the recording head 32 is fixed to the arm portion 38. The other end of the printer signal cable 39 is fixed to the printer middle plate 40 by a member 41 and is also connected to the electrical unit 26. The wiring of the printer signal cable 39 follows the movement of the carriage 34 and is configured not to contact the upper optical frame 10.

The sub-scanning of the printer section 44 is performed by the roller pair 28.
29, 30 and 31 are rotated by a power source (not shown), and the recording paper is fed by 8.128 mm. 42 is a bottom plate of the printer unit 44, 45 is an exterior plate,
Reference numeral 46 is a document pressure plate, 47 is a paper discharge tray, and 48 is an electric component of the operation unit.

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

FIG. 2A is an enlarged schematic view showing a recording state by the ideal recording head 32. Reference numeral 61 denotes an ink ejection port, and when recording is performed by the recording head 32, ink dots 60 having a uniform diameter are formed on the recording paper. In such a case, uneven density does not occur. In addition,
Although the same drawing shows the case of so-called full discharge (state where all discharge ports are ON), density unevenness does not occur even in the case of halftone such as 50% output.

On the other hand, in the case shown in FIG. 2B, the dots 6 of the second and (n-2) th ejection ports are
The diameters of 2, 63 are smaller than the average, and dots are formed at positions deviated from the center for the (n-2) th and (n-1) th. That is, the (n−2) th dot 63 is formed in the upper right of the center and in the lower left of the center of the (n−1) th dot 64.

As a result of such recording, 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 dot-to-dot average distance l ₀ , and as a result, appear as thinner stripes in other areas. On the other hand, in the C area, the distance between the centers of the (n-1) th and nth dots is narrower than the average distance l ₀ , so that the area appears as a darker line than the other areas.

As described above, the uneven density appears mainly due to the variation of the dot diameter and the deviation from the center position (this is generally referred to as "wobble").

The density unevenness correction processing in the printing apparatus described above will be described below.

As described above, the density unevenness is caused by the variation in the shape of the ejection port or the ink path or the variation in the heat generation characteristic of the electrothermal converter, which occurs in the manufacturing process of the recording head, and the recording operation is performed. In some cases, this may be due to variations in ejection characteristics caused by changes over time. Although variations in ejection characteristics that occur during the manufacturing process can be corrected by inspection at the time of shipping, etc., it is difficult to take measures against those that occur due to changes over time, as described above. It is considered that the variations in the ejection characteristics due to changes over time are caused by variations in the deterioration of the ejection ports and the like, changes in the ink head pressure, and the intrusion of dust into the ejection ports, but they have not been sufficiently explained. is the current situation.

As for the density unevenness caused by such a change with time, the apparatus itself detects the density unevenness generated there and resets a new correction curve, as described above.

(First Embodiment) FIG. 3 is a block diagram showing a process of image processing in which density unevenness correction processing (referred to as head shading) according to the first embodiment of the present invention is performed.

In FIG. 3, the read data read by the CCD sensor 5 is amplified by the amplifier 200 and converted into an 8-bit digital image signal by the A / D converter 201. Reference voltages RT and RB of the A / D converter 201 are microcomputers (CP not shown)
U). For example, as shown in FIG. 4, the reference voltage is changed from RT, RB to R
By changing to T ', RB', a minute value of the input voltage can be converted into an 8-bit value, so that the dynamic range can be expanded.

The A / D converted image signal is corrected by the white correction circuit 202 for the white signal, and the black correction circuit 2
At 03, the black signal is corrected.

Then, in the LOG conversion circuit 204, three primary colors of light R (red), G (green), B (blue) to three primary colors (recording color) of C (cyan), M (magenta),
Converted to Y (yellow). Next, the UCR circuit 205
In the C, M, Y signals, the Bk (black) portion is extracted as a common component, or a part of the common component is extracted as a black component, and the C, M, Y, Bk signals are extracted as head shading circuit 206. Entered in.

In the head shading circuit 206, 4
Γ correction (density correction) is performed on the image signal corresponding to each ejection port according to the ejection characteristics of each ejection port of each recording head. The head shading circuit 206 includes an SRAM and an EPROM as will be described later.
The table number stored in the SRAM is referred to according to the ejection port corresponding to the data input to the SRAM, and then the EPROM corrects the data by the γ correction curve corresponding to the table number. The next γ conversion circuit 207 has a function of several steps for calculating output data with respect to the data input to this circuit, and it is suitable for each recording color depending on the density balance and the user's preference of hue. The function is set. This function is also set according to the characteristics of ink and the characteristics of recording paper.

The output of the γ conversion circuit 207 is sent to the binarization processing circuit 208. The binarization processing of this embodiment uses the average density preservation method (MD method). The output of the binarization circuit 208 is sent to the print head drive circuit 32A of the printer unit 44, and the print head 32 prints based on this output data.

Further, in FIG. 3, a density unevenness measuring circuit 209 calculates density data of each ejection port based on the data from the LOG conversion circuit 204. Details of the shading circuit 206 and the density unevenness measuring circuit 209 are shown in FIG. FIG. 6 shows a specific circuit example for realizing the block of FIG. That is, the density unevenness temporary storage memory 134 and the γ correction memory 136 shown in FIG.
It is shared by AM152. Also, EPRO
In M126, 64 types of γ correction curves shown in FIG. 7 are stored. Further, the arithmetic circuit 135 shown in FIG. 5 is configured by the CPU 151 shown in FIG.

FIG. 8 is a flow chart of the density unevenness correction processing according to the first embodiment of the present invention.

For example, when the user determines that density unevenness has occurred in the recorded image, the user presses the density unevenness correction button in the operation unit (not shown) (step S1). In response to this, the printer unit 44 prints out a pattern for density unevenness measurement as shown in FIG. 9 (step S2).

Next, as shown in FIG. 9, the user makes the main scan of the CCD 5 perpendicular to the direction in which the recording head 32 moves with respect to the recording sample of this test pattern, as shown in FIG. And place it on the document table (step S3). Then, the density unevenness correction button is pressed again (step S4).

In response to this, the CPU sets the reference voltage of the A / D converter corresponding to the color to be read (step S5). That is, when A / D conversion is performed while the reference voltage of the A / D conversion circuit 201 is in the normal reading, that is, the reference voltage is constant, FIG.
As shown in (A), even if a pattern recorded with the same density is read, the density level of the read data differs depending on the recording color. Even if the degree of density unevenness (density change width) of each recording color is the same, for example, in the case of yellow (Y), the density level of read data is relatively low, so the degree of density unevenness is higher than that of other colors. Read small. Therefore, in the case of the configuration in which the same density unevenness correction algorithm is used for each color, in the case of yellow,
The degree of correction decreases. As a result, the uneven density is not completely eliminated, and the uneven density of yellow is prominent in the case of a color mixture with another color in the recorded image.

Therefore, the reference voltage of the A / D conversion circuit 201 is changed in accordance with the recording color so that the density unevenness is equalized for all recording colors (FIG. 10 (B)). As a result, the density unevenness correction algorithm for each recording color can be made equal, and the circuit configuration for the density unevenness correction processing can be simplified.

After setting the above reference, step S6
Then, the operation for the shading correction of the CCD 5, that is, the reading from the CCD is first performed with the lamp off, the black correction value is determined so that the value of each pixel becomes the black level, and then the lamp is turned on. Then, after reading the white plate and performing the operation of determining the white correction value, the main scanning of the CCD 5 is performed,
First, the black test pattern is read (step S
7. From then on, cyan, magenta, and yellow are sequentially performed from the second time onward).

Regarding the result of this reading, each circuit 200
After the processings of up to 204 are performed, the processing by the density unevenness measuring circuit 209 is performed and stored in the SRAM 136 (step S8). That is, in step S8, the circuits 131, 132, 133, 134, and 135 shown in FIG. 5 obtain an average value of the number of samplings of the read data corresponding to each ejection port, and store the result in the SRAM 136.

Next, a moving average Dn of three pixels including one pixel before and after the read pixel corresponding to each element of the CCD 5 is obtained for each ejection port (step S9). The average in this case may be, for example, an average of a total of 9 pixels including 4 pixels before and after, and each pixel may be weighted. Then, the average value of the three-pixel average obtained in step S9 is obtained (step S10). Furthermore, the ratio α _n between the average of each three pixels obtained in step S9 and the value obtained in step S10
[%] (N is a discharge port number, 1 or more and 128 or less) is obtained (step S11). Steps S9 to S1 described above
The processes up to 1 are performed for the test patterns 1 to 4 shown in FIG. 9 (step S12).

Next, the average value α of α _n in each pattern
_{n (ave)} is calculated (step S13), and a new correction table number Ti + 1 is calculated as follows from the _calculated α _{n (ave)} and the current density correction table number Ti (step S1).
4).

[0053]

## EQU00001 ## Ti + 1 (n) = Ti (n) + (. Alpha.n _(ave) -100) (1) The newly obtained table number Ti + 1 (n) is stored in SRAM1.
It writes in 36 (step S15).

The processing from steps S5 to S15 described above is performed for each color (step S16). When reading the test pattern, the filter outputs of green, red, green, and blue, which have complementary colors to each other, are sampled corresponding to the patterns of black, cyan, magenta, and yellow (however, for black, It is possible other than green).

As is apparent from the above, in the present embodiment, the table data in the SRAM 136 is updated by the above processing in order to deal with the occurrence of density unevenness due to the change with time of the head.

In this case, the updated data is turned off.
In this embodiment, the latest shading data is transferred to a RAM (not shown) in the printer control section so that the RAM is backed up by a battery so that the RAM can be stored at any time.

In the above embodiment, the reference voltage of the A / D conversion circuit is set by the CPU according to the ink color before reading the test pattern. However, the reference voltage is read at the normal reference voltage, and the density and It is also possible to perform a feedback method using prescan in which a variation in read data is detected, a reference voltage is set based on the variation, and then the pattern is read again.

(Second Embodiment) In the first embodiment described above, the reference voltage of the A / D conversion circuit is set according to the recording color so that the density level of the read data is the same between the recording colors. As a result, the actual density unevenness is reflected equally in the read data of each recording color.

On the other hand, in the present example, the black correction circuit 203 shown in FIG. 3 performs black correction according to the recording color to make the density levels of the read data equal.

The second embodiment of the present invention will be described below.

FIG. 11 is a diagram for explaining the black correction according to this example.

In the CCD 5, not all the elements output "0" due to variations in manufacturing the respective light receiving elements even if a black original is read. Therefore, by reading the black shading correction plate painted in black, or by performing the reading operation by turning off the original illumination lamp, the black reading value is sampled (in the present embodiment, turned off and is sampled), and Store in memory.

When performing normal recording, the black correction circuit 203
Then, the stored black read value is subtracted from the read data of the original, and the correction value is multiplied to perform black correction. That is, from the read data shown in FIG.
The black correction data (solid line) shown in FIG. 11B that was sampled earlier is subtracted to obtain the data (solid line) shown in FIG. 11C.

Here, if the black correction data having relatively high brightness shown by the broken line in FIG. 11B is obtained by sampling the black shading plate which is not completely black,
When black correction is performed using this data, the brightness of the input data can be lowered (the density can be increased) as indicated by the broken line in FIG.

As described above in the first embodiment, when the density level is low such as yellow (Y), the stored data (sampling data) in the black correction of yellow (Y) is relatively bright. By setting a high value, it is possible to align the density levels of the read data of each recording color.

FIG. 12 shows a flowchart of the density unevenness correction processing according to this embodiment. In the process of this example, the first process shown in FIG.
Only step S105 differs from the processing of the embodiment. Therefore, the process of step S105 will be described.
The description of the processing of other steps is omitted.

In step S105, the black shading plate corresponding to the recording color to be read at that time is read and black data is sampled. That is, if, for example, data sampled by turning off the original illumination lamp is used as black data commonly for each recording color as usual, the same density as shown in FIG. 10A is obtained as described in the first embodiment. Even if the pattern recorded in step 1 is read, the density level of the read data differs depending on the recording color. For example, in the case of yellow (Y), the density level of the read data is relatively low, and therefore the degree of density unevenness is read smaller than in other colors. For this reason, if the same density unevenness correction algorithm is applied to each color, the degree of correction for yellow becomes smaller. As a result, yellow becomes uneven when mixed with other colors.

Therefore, in the black correction process, the density level is increased in accordance with each recording color so that the actual density unevenness is reflected equally in the density level after black correction for each recording color. Therefore, the black shading plate for black data sampling is made different according to the recording color. As a result, the subsequent density unevenness correction can be similarly performed for each recording color.

The black shading plate for each recording color of the present embodiment does not have its own plate, but the black shading plate for each color is provided next to the white shading correction unit in the CCD operation area outside the original glass. The color is applied, and the CCD is moved below the part where the desired color is applied to perform sampling. Also,
Since the sampling method at this time is a well-known technique,
Detailed description is omitted.

In each of the above embodiments, a copying machine equipped with a document reading device has been described as an example. However, a printing device equipped with a reading device capable of reading a recorded test pattern and recording with a plurality of recording colors. If so, it is obvious that the present invention can be applied.

Further, although the ink jet type recording apparatus has been described in the above example, the present invention can be applied to, for example, a thermal transfer type recording apparatus. In any case, the present invention can be applied to an apparatus that has a plurality of recording elements and performs recording with a plurality of recording colors.

(Others) In particular, the present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating heat 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. Nos. 4,723,129 and 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 ink jet from the main body of the apparatus is electrically connected to the main body of the apparatus by being attached to the main body. 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 the ejection recovery means of the recording head, the preliminary auxiliary means, etc. 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 and 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.

In addition, as the form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function are provided. It may be in a form or the like.

[0081]

As is apparent from the above description, according to the present invention, the density level of read data can be changed according to the recording color. Therefore, when the uneven density correction processing is performed based on the read data, the recording color is corrected. This concentration level can be the same between. As a result, the density unevenness of each recording color is
It is faithfully reflected in the read data that is the basis of density unevenness correction.

As a result, it is possible to satisfactorily carry out density unevenness correction in the case of recording with a plurality of recording colors with a simple structure.

[Brief description of drawings]

FIG. 1 is a sectional view of a copying machine according to an embodiment of the present invention.

FIGS. 2A and 2B are schematic diagrams for explaining uneven density.

FIG. 3 is a block diagram of an image processing circuit according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining a change in output with respect to a change in reference voltage in the A / D conversion circuit.

5 is a block diagram showing details of a head shading circuit and a density unevenness measuring circuit shown in FIG.

FIG. 6 is a block diagram of a circuit that realizes the configuration shown in FIG.

7 is a conceptual diagram showing the contents of a γ correction table shown in FIG.

FIG. 8 is a flowchart of density unevenness correction processing according to the first embodiment of the present invention.

FIG. 9 is a schematic diagram of a test pattern according to an example of the present invention.

10 (A) and 10 (B) are diagrams for explaining the equalization of the density level of read data of each recording color according to the embodiment of the present invention.

11A, 11B, and 11C are diagrams for explaining the influence of black correction data on the black correction processing.

FIG. 12 is a flowchart of uneven density correction processing according to the second embodiment of the present invention.

[Explanation of symbols]

 5 CCD line sensor 32 recording head 32A recording head drive circuit 126 γ correction table 130 color signal selection unit 131 latch circuit 132 adder 133 averaging circuit 134 data temporary storage circuit (RAM) 135 arithmetic circuit 136 γ correction circuit (SRAM) 150 Control unit 151 CPU 152 RAM 200 Amplifier 201 A / D conversion circuit 202 White correction circuit 203 Black correction circuit 204 LOG conversion circuit 205 UCR circuit 206 Head shading circuit 207 γ conversion circuit 208 Binarization processing circuit 209 Density unevenness measurement circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B41J 2/08 H04N 1/23 101 C 9186-5C 9012-2C B41J 3/04 103 X 9012-2C 104 G (72) Inventor Miyuki Matsubara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Norifumi Koitabashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A recording apparatus for recording with a plurality of recording colors by using a recording head having a plurality of recording elements, a reading unit for reading an image recorded by the recording head, and a reading unit for reading the image. Density changing means for changing the density level of the data according to each of the plurality of recording colors, and based on the data changed by the density changing means,
A recording apparatus comprising: a density unevenness correcting unit for correcting the density recorded by each of a plurality of recording elements in the recording head. 2. The density changing means changes the density of the read data by changing reference data used for processing the read data when converting the read data into print data of the print head. The recording apparatus according to claim 1, wherein the level is changed. 3. The density changing means has a CPU, and the C
The recording apparatus according to claim 2, wherein the PU changes the reference data of an A / D conversion circuit for converting the read data into a digital signal. 4. The recording apparatus according to claim 2, wherein the density changing unit changes black data when performing black correction processing on the read data. 5. The recording apparatus according to claim 4, wherein the density changing unit changes the black data by changing a black shading plate read for black data sampling according to a recording color. 6. The recording element has an ejection port for ejecting ink and a bubble for the ink by generating heat energy, and ejects the ink from the ejection port based on the generation of the bubble. The recording apparatus according to claim 1, further comprising an electrothermal converter.