JPH0440164A - image forming device - Google Patents

Abstract

PURPOSE:To protect a reading means from trouble such as ink mist or the like, for example, to be generated in the reading means by providing a protecting means having transmissivity for the optical path part at least in the reading means, and cleaning the transmissive part at least. CONSTITUTION:In order to prevent a light source 218, which is composed of a photodetector 232, lamp 123 and filter 220 arranged in a read sensor 217, from getting dirty by the ink mist, the photodetector 232, lamp 233 filter 220 are respectively held in enclosures 245a and 246a and in the optical path parts of those enclosures, transmissive members such as glass windows 245b and 246b are provided, for example. By the glass windows and cleaning means as protecting members, an optical system can be prevented from getting dirty by the ink mist, particles of paper or water drop, etc., in the machine, and a density nonuniformity reading unit can be prevented from being degraded with the passage of time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image using a recording head having a plurality of recording elements arranged.

In particular, the present invention relates to an apparatus equipped with a mechanism for automatically adjusting the printing characteristics of a recording head of an inkjet recording apparatus, and is particularly effective for an apparatus that forms a color image with high gradation by overlapping ink droplets.

[Background technology 1] With the spread of copying machines, information processing equipment such as word processors, computers, and even communication equipment, digital images are being created using recording heads based on inkjet methods, thermal transfer methods, etc. as image forming (recording) devices for these devices. Things that record are rapidly becoming popular. In such a recording apparatus, in order to improve the recording speed, it is common to use a recording head (hereinafter referred to as a multihead in this section) formed by an integrated arrangement of a plurality of recording elements.

For example, inkjet recording heads are generally so-called multi-nozzle heads that integrate multiple ink ejection ports and liquid channels, and thermal transfer and thermal heads also typically integrate multiple heaters. be.

However, it is difficult to uniformly manufacture multi-head recording elements due to variations in characteristics due to the manufacturing process and variations in characteristics of head constituent materials, etc., and the characteristics of each recording element may vary to some extent. In the multi-nozzle head described above, variations occur in the shapes of the discharge ports, liquid paths, etc., and variations occur in the shapes and resistances of the heaters in the thermal head as well. Such non-uniformity in characteristics between printing elements manifests itself as non-uniformity in the size and density of dots printed by each printing element, resulting in uneven density in the printed image.

To solve this problem, various methods have been proposed to obtain a uniform image by visually detecting density unevenness or visually inspecting the adjusted image and manually correcting the signals given to each recording element. .

For example, in a multi-head 330 in which recording elements 31 are lined up as shown in FIG. 20A, input signals to each recording element are
If uneven density as shown in Fig. 20C is visually detected when the density is made uniform as shown in Fig. 0B, the input signal is corrected as shown in Fig. 200, and a large input signal is applied to the recording element in the area of low density. It is known as a general manual correction to apply a small input signal to the recording element in a high density area.

In the case of a recording method that can modulate the dot diameter or dot density, it is known that gradation recording is achieved by modulating the dot diameter recorded by each recording element according to the input. In an inkjet recording head using a jet method, the drive voltage or pulse width applied to each ejection energy generating element such as a piezo element or an electrothermal transducer element is controlled according to the input signal, and in the case of a thermal head, the drive voltage or pulse width applied to each heater is controlled depending on the input signal. It is considered possible to make the dot diameter or dot density uniform by each recording element and to make the density distribution uniform as shown in FIG. 20E by utilizing modulation. Also, if it is impossible or difficult to modulate the driving voltage or pulse width, or if it is difficult to adjust the concentration over a wide range even if they are modulated,
For example, when one pixel is composed of multiple dots,
The number of dots to be recorded can be modulated according to the input signal, so that a large number of dots can be recorded in areas with low density, and a small number of dots can be recorded in areas with high density. In addition, when one pixel is composed of one dot, an inkjet recording device also calculates the number of ink ejections per pixel (
The dot diameter can also be changed by modulating the number of implantations. With these, the concentration distribution can be made uniform as shown in FIG. 20E.

Japanese Unexamined Patent Application Publication No. 57-41965 filed by the applicant of the present application states that a color image is automatically read by an optical sensor,
It is disclosed that a correction signal is applied to each color inkjet recording head to form a desired color image. This publication discloses basic automatic adjustment and provides important technical disclosures. However, as the practical application progresses, various problems will become apparent in order to apply it to various device configurations, but this publication does not recognize the technical problems of the present invention.

On the other hand, for methods other than the concentration detection method, JP-A-60-20666
Publication No. 0, U.S. Pat.
There is known a device that automatically reads the landing position of a droplet and corrects it so that the droplet lands at an accurate position, as disclosed in Japanese Patent No. 27728. Although these methods are common as automatic adjustment techniques, there is no recognition of the technical problem of the present invention.

[Problems to be Solved by the Invention] In order to deal with this problem, a density unevenness reading unit is provided in the image forming apparatus, and the density unevenness reading section is periodically read in the recording element arrangement range and density unevenness correction data is generated. It is effective to recreate it.

According to this, even if the density unevenness distribution of the head changes, the correction data is re-created accordingly, making it possible to always maintain a uniform image without unevenness.

On the other hand, when the recording head and the reading means are provided in the same device, the recording head may have an undesirable effect on the reading means.

For example, in the case of an inkjet recording apparatus, there is a risk that ink mist, water droplets, etc. generated from the recording head may adhere to the reading sensor, light source, etc. of the reading means, reducing the reading accuracy and making it impossible to perform accurate correction. In addition, there is generally a risk that paper dust from the recording paper and other dust may adhere to the reading unit.

An object of the present invention is to provide an image forming apparatus that can perform accurate and stable reading operations without increasing the size of the apparatus.

[Means for Solving the Problems] For this purpose, the image forming apparatus of the present invention includes a print head in which a plurality of print elements are arranged in order to form an image on a print medium, and a test pattern formed by the print head. A reading means for reading the information, a correction means for correcting the recording head driving conditions based on the reading result, and the reading means are protected from contamination, and at least a light-transmitting member is placed in the optical path of the reading means. and a cleaning means for cleaning the light-transmitting member.

The present invention also provides a reading means for reading a test pattern formed by the print head in an image forming apparatus that uses a print head in which a plurality of print elements are arranged and forms an image by scanning a print medium with the print head. a correction means for correcting the recording head driving conditions based on the reading result and a protection means for protecting the reading means from contamination and having a light-transmitting member disposed at least in the optical path thereof; The present invention is characterized by comprising a cleaning means for cleaning the optical member.

[Function] As explained above, according to the present invention, the reading means is provided with a protection means (at least the optical path portion thereof is translucent),
Since at least the light-transmitting part is cleaned, the reading means can be protected for a long period of time from inconveniences that may occur in the reading means, such as ink mist, thereby enabling accurate reading and, by extension, accurate unevenness correction.

The light-transmitting protection means of the present invention prevents mist and paper dust from entering the specific optical reading means, prevents deterioration of its properties and life, and solves problems specific to inkjet. (stains on the translucent property itself,
(This can be solved by cleaning by a service person), but even this point alone makes it difficult to use conventional inkjet equipment! has an advantage over

In other words, since the optical reading mechanism is protected, it is possible to prevent dew condensation and ink mist from entering the mechanism, making it possible to detect the test pattern more accurately.

Based on this configuration, the present invention can further achieve longer life and maintenance-free operation.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail in the following steps with reference to the drawings.

(1) Mechanical configuration of the device (Figures 1 to 5) (2) Control system (Figures 6 to 8) (3) Sequence of unevenness correction (Figures 9 to 16) (4)
)Other embodiments (Figs. 17 to 19) (5) Others (1) Mechanical configuration of the device, etc. Fig. 1A schematically shows an inkjet recording device in the form of a serial printer according to an embodiment of the present invention. Recording heads 201C, 201M, 201Y, 2018
Inks of cyan, magenta, yellow, and black colors are supplied from an ink tank (not shown) through an ink tube. Then, the recording head 201C,
The ink supplied to 201M, 201Y, and 2018 is driven by a print head driver or the like in response to a print signal corresponding to print information from the main control unit, which will be described later with reference to FIG. A droplet is ejected and recorded onto the recording medium 202.

The conveyance motor 208 is a drive source for intermittently feeding the recording medium 202, and includes a feed roller 204 and a conveyance roller 205.
The main scanning motor 206 that drives the main scanning carriage 20
3 in the directions of arrows A and B through the main scanning belt 210.

In this embodiment, since accurate paper feeding control is required, pulse motors are used for the paper feeding motor 208 and the main scanning motor 206.

When the recording medium 202 reaches the feeding roller 205, the feeding roller clutch 211 and the conveyance motor 208 are turned on.
The recording medium 202 is conveyed on a platen 207 until it reaches a conveyance roller 204 . The recording medium 202 is a platen 207
It is detected by a detection sensor 212 provided above, and the sensor information is used for position control, jam control, etc. When the recording medium 202 reaches the conveying roller 204, the feeding roller clutch 211. The conveyance motor 208 is turned off, and a suction operation (not shown) is performed from inside the platen 207 to bring the recording medium 202 into close contact with the platen 207 on the image recording area. Prior to the image recording operation on the recording medium 202, the home position sensor 2
The scanning carriage 203 is moved to position 09, and then forward scanning is performed in the direction of arrow A, and cyan, cyan, and
Recording head 2 for magenta, yellow, and black ink
Ejection image recording is performed from 010 to 2018.

After recording the image for a predetermined length, the scanning carriage 20
3, and conversely, start a return scan in the direction of arrow B.
The scanning carriage 203 is returned to the position of the home position sensor 209. During the backward scan, the recording heads 2010~
The transport motor 20 feeds the paper by the length recorded in 2018.
By driving the conveyance roller 204 by arrow C
Do it in the direction of.

In this embodiment, the recording heads 2010 to 2018 are inkjet recording heads of the type that form bubbles using heat and eject ink droplets with the pressure of the bubbles, and each has 256 ejection openings assembled into four inkjet recording heads. I am using it.

The scanning carriage 203 is the home position sensor 209
When the recording head 1 stops at the home position detected by , the recovery device 290 performs a recovery operation of the recording head 1 . This is a process for stable recording operation, and the recording head 2
In order to prevent unevenness at the start of ejection caused by changes in the viscosity of the ink remaining in the ejection port of 01, the pause time,
Temperature inside the device.

Depending on pre-programmed conditions such as dispensing time,
This is a process in which the recovery device 290 performs a suction operation for the recording head 201, a preliminary ink ejection operation, and the like.

By repeating the operations described above, an image is recorded on the entire surface of the recording medium.

In the figure, reference numeral 214 denotes a density unevenness reading unit that reads a test pattern printed on the recording medium 202 by applying a uniform image signal to each recording head 201C to 2018K by a control circuit 215, and outputs a reading signal. In this example, it is fixed to the main scanning belt 210 via a holder 244, and the reading operation is performed on the platen 207. Therefore, when the recording head and reading unit move, they are interlocked.

In this example, the recording medium 202 on which the test pattern has been recorded is illuminated by a light source 218, and the sensors 217C and 217M read the recording density of the test pattern recorded on the recording paper by each recording head.

217Y and 2178K, and the read signal of the test pattern recording by each recording head read by each reading sensor is converted into a digital signal by the A/D converter 236, and then the read signal is temporarily stored in the RAM 219. It is.

247 is the reading unit 214 described with reference to FIG. 1B.
This is a cleaning means for cleaning the light-transmitting protection means, and in this example, it is in the form of a blade that engages with the protection means and cleans its surface every time the reading unit moves during recording or other movement of the carriage. It is. Therefore, the surface of the protection means is kept clean from ink mist, paper dust, and the like by the movement of the carriage during recording or the like. In addition, this means 247 may include such a blade,
It may take any suitable form and cleaning mode. For example, in order to reliably remove ink mist and other substances that have solidified on the surface of the protective means, an ink solvent or other cleaning liquid may be applied to the surface of the protective means during reading to soften the solidified ink and facilitate removal of other contaminants. It may also be possible to wipe it off with a blade or the like after cleaning.

FIG. 1B is a side sectional view showing a configuration example of a reading unit according to a first embodiment of the present invention. Reading unit 21
4 is connected to the main scanning belt 210 via the holder 244, so it repeats reciprocation in the main scanning direction together with the carriage 203 during normal printing. Reading sensor 217
(Sensors 217C to 2178k are collectively shown) In order to prevent the light source 218, which is composed of the light receiving element 232, the lamp 233, and the filter 220, from being contaminated by ink mist, the light receiving element 232 and the lamp 233. The filters 220 are held in housings 245a and 246a, respectively, and light-transmitting members such as glass windows 245b and 246b are provided in the optical path portions of these housings.

By using the glass window as a protective member and the cleaning means described above, it is possible to prevent the optical system from being contaminated by ink mist, paper powder, water droplets, etc. inside the machine, and to prevent the density unevenness reading unit from deteriorating over time.

FIG. 2 is a schematic diagram for explaining the reading section of this example. In order to improve the reading accuracy of the density unevenness of the test pattern by the recording head recorded on the recording medium 202, the illumination light source 18 is placed on the recording medium side. Color filter 220R, 2
20G and 220BL are provided, and R, G, and BL are provided for the C, M, and Y test patterns recorded on the recording medium 202.
It is designed to emit light. And like this C
, M, and Y, each reading sensor 217C, 2
It is not necessary to make the spectral sensitivities of 17M, 217Y, and 2178 different for each color of the test pattern, and density unevenness of each color can be read while using a sensor with the same spectral sensitivity for each sensor.

The image signal read in this way is sent to the image forming section,
This will be used to correct the driving conditions of the recording head, as will be described later.

In the present invention, the meaning of adjusting to prevent density unevenness during image formation is to equalize the image density of droplets from the plurality of liquid ejection ports of the printhead within the printhead itself, or to make adjustments for each of the printheads. In order to make the image density uniform, or to obtain the desired color by mixing multiple liquids, or to obtain the desired density, it is necessary to Including one, and preferably including satisfying more than one of these.

As for the density uniformity correction means for this purpose, it is preferable that the reference print giving the correction conditions is automatically read and the correction conditions are automatically determined, and a manual adjustment device for fine adjustment and user adjustment is added to this. It's not something I refuse to do.

The purpose of correction determined by the correction conditions may be not only optimal printing conditions, but also adjustments to a predetermined range including tolerance ranges, or a standard density that changes depending on the desired image (anything that is included in the purpose of correction is acceptable). It is applicable.

As an example, a case will be described in which density unevenness correction is performed for a multihead having N recording elements, in which the print output of each element is converged to an average density value as a correction purpose.

Assume that the density distribution when printing is performed by driving each element (1 to N) with a certain uniform image signal S is as shown in FIG. 3.

First, the density OD+ to ODN of the portion corresponding to each recording element is measured, and the average density plane: ΣOD, . . . /N for the purpose of correction is determined. This average density is not limited to each element, and may be determined by a method of integrating the amount of reflected light to obtain an average value, or by a known method.

If the relationship between the value of the image signal and the output density of a certain element or group of elements is as shown in Fig. 4, the signal actually given to this element or group of elements will correct the signal S to achieve the target density OD. It is only necessary to determine the correction coefficient α that brings about
A correction signal S obtained by correcting the signal S to αxS=(00100,) x S may be applied to this element or group in accordance with the input signal S. Specifically, the fifth
This is executed by performing table conversion as shown in the figure. Fifth
In the figure, straight line A is a straight line with a slope of 1.0, and is a table that outputs all input signals without converting them, but straight line B is a straight line with a slope of α = 0D10D, and for input signal S This is a table for converting the output signal into α・S.Therefore, this table determines the correction coefficient α for each table as shown in the straight line B in FIG. 5 for the image signal corresponding to the n-th recording element. If the head is driven after conversion, each density of the portion recorded by N recording elements will be O.
It becomes equal to D. If such processing is performed on all the recording elements, density unevenness will be corrected and a uniform image will be obtained. That is, by obtaining data in advance about what kind of table conversion should be performed on the image signal corresponding to which recording element, it is possible to correct unevenness.

It goes without saying that this objective correction may be performed by comparing the densities of each nozzle group (in units of 3 to 5 nozzles) and may be used as an approximate uniformization process.

Although it is possible to correct density unevenness using this method, density unevenness may occur later depending on the usage conditions of the device or changes in the environment, or due to changes in the density unevenness situation before correction or changes over time in the correction circuit. Therefore, in order to deal with such a situation, it is necessary to change the amount of correction of the input signal. The possible cause of this is that as the inkjet recording head is used, the density distribution may change due to deposits from the ink adhering to the vicinity of the ink ejection ports or foreign matter from the outside adhering to the inkjet recording head. . This can also be predicted from the fact that in a thermal head, each heater may deteriorate or change in quality, resulting in a change in the concentration distribution. In such a case, for example, the initial input correction amount set at the time of manufacturing will no longer be sufficient to correct the density unevenness, so the problem with long-term use is that the density unevenness will gradually become more noticeable as the product is used. This becomes an issue that needs to be solved.

By the way, the distance between the reading unit and the recording medium on which the test pattern is recorded varies depending on the reading accuracy, but it is desirable to keep it constant. In this example, since the reading unit scans over the platen 207, it is necessary to maintain the distance. can do.

Further, the reflected light from the recording medium is incident on each reading sensor, and this incident light is made into a predetermined range of light on the test pattern by arranging an appropriate aperture member in front of each sensor. Then, the average of the unevenness in that range will be detected. According to the inventors' experiments, the aperture diameter is 0.
．． A thickness of about 2 to 1 mm was good. Then, by performing unevenness correction according to the detection results, it becomes possible to obtain a uniform image.

(2) Configuration of control system Next, the control system of the apparatus of this example, which is constructed by combining the above-mentioned parts, will be explained.

FIG. 6 shows an example of the configuration of the control system, where H is a host device that supplies image data and various commands related to recording to the device in this example, and has a computer, image league, or other form. . Reference numeral 1 denotes a CPU which constitutes the main control section of the apparatus of this example, has the form of a microcomputer, and controls each section according to processing procedures etc. to be described later. 102 is a ROM that stores programs and other fixed data corresponding to the processing procedure, and 219 is an RA that has a temporary storage area for image data and an area used for work in various control processes.
It is M.

Reference numeral 106 denotes an instruction input unit for inputting an online switch with the host device, inputting a command to start recording, inputting a command to record a test pattern for correcting density unevenness, and inputting information on the type of recording medium. Sensors 108 detect the presence or absence of a recording medium, its conveyance state, the presence or absence of a remaining amount of ink, and other operating states. Reference numeral 110 denotes a display unit, which is used to notify the operating status and setting status of the device, and whether or not an abnormality has occurred. 111 is for image data related to recording,
This is an image processing unit that performs logarithmic conversion, masking, OCR, and color balance adjustment.

112 is the recording head 201 (superior head 201Y, 2
01M.

This is a head driver for driving the ink ejection energy generating elements of 201G and 2018K). Reference numeral 113 denotes a temperature adjustment unit for adjusting the temperature of the recording head 201, and specifically, it can include, for example, a heating heater and a cooling fan disposed for the head 1.

111 is a drive mechanism of the recovery device; 115 is a mechanism including a motor 206 for scanning the recording head and reading unit; and 116 is a motor 20 that drives the recording medium transport system.
8 drive unit.

FIG. 7 shows in detail the system for correcting density unevenness among the above configurations. Here, 121C.

121M, 121Y and 1218 have image processing unit 1
These are cyan, magenta, yellow, and black image signals processed in step 11, respectively. 122C, 12
2M, 122Y and 1228 are unevenness correction tables for each color, which can be provided in the area of the ROM 102. 123G, 123M, 123Y and 1238 are image signals after the correction.
0C to 1308 are gradation correction tables for each color, 131
C knee 1318 uses dither method, error diffusion method, etc. 2
This is a digitizing circuit, and the binarized signal is supplied to each color head IC to IBK via a driver 112 (not shown in FIG. 7).

126G, 126M, 126Y and 1268 are each color signal read by the reading unit 214 through each color filter shown in FIGS.
The signal is input to the D converter 236. 119 is a RAM area that temporarily stores the digital output signal;
Nine areas can be used. 128G, 128
M, 128Y, and 1288 are correction data calculated by the CPU 101 based on the stored signals.

129C to 1298 are nonuniformity correction RAMs for each color, and the area of the RAM 219 can be used. and,
The output unevenness correction signals 130C to 130 for each color
8, unevenness correction tables 122G-122, respectively.
8K, and converted into image signals 121C to 1218 to correct unevenness in the heads 201C to 2018.

FIG. 8 shows an example of an unevenness correction table, and in this example, y=
o, the slope from 7ox to Y = 1.30X is 0. O
There are 61 corrected straight lines that differ by l, and the corrected straight lines are switched according to unevenness correction signals 130C to 1308K. For example, when a signal from a pixel to be recorded using an ejection port with a large dot diameter is input, a correction straight line with a small slope is selected.
Conversely, when the dot diameter is small, the image signal is corrected by selecting a correction straight line with a large slope.

The unevenness correction RAMs 129C to 1298 store correction straight line selection signals necessary for correcting unevenness of each head. That is, it stores unevenness correction signals having 61 types of values from 0 to 60 for the number of ejection ports, and outputs unevenness correction signals 130C to 1308K in synchronization with the input image signal. Then, the signals 123C to 1238, whose unevenness has been corrected by the γ straight line selected by the unevenness correction signal, are input to the gradation correction tables 130C to 1308K,
Here, the gradation characteristics of each head are corrected and output. The signals are then binarized by binarization circuits 131C to 1318K and sent to heads 2010 to 20 via head drivers.
A color image is formed by driving 18K.

(3) Sequence of unevenness correction With the above configuration, in this example, the following processing is performed to enable more accurate unevenness correction.

By performing unevenness correction processing, the drive energy (for example, drive duty) of the ejection energy generating element corresponding to the ejection port in the high density part of the head is reduced, and conversely, the ejection energy generating element corresponding to the ejection port in the light part of the head is reduced. Increase drive energy. As a result, the recording head density unevenness is corrected and a uniform image is obtained, but if the density unevenness pattern of the head changes as it is used, the unevenness correction signal used becomes inappropriate and unevenness appears on the image. occurs. In such a case, the next procedure is started by operating the unevenness correction signal rewriting mode instruction switch provided in the instruction input section 106 to instruct to rewrite the unevenness correction data.

FIG. 9 shows an example of an unevenness correction processing procedure according to this example.

When this procedure is started, first, in step S1, input of the type of recording medium is accepted. To do this, for example, a message "Please input the type of recording paper currently being used" is displayed on the display section 110 such as a liquid crystal panel.Seeing this, the operator enters the instruction input section 106. Specify the type of recording medium currently being used using the provided switch. In step S3, a judgment is made based on this, and if the input recording paper type is not optimal for detecting density unevenness, such as an OHP sheet or trace coated paper, a message is displayed on the display unit 11Q in step S5. , for example, displays a message such as "Please use the specified paper." As a result, if the specified paper is replaced with the specified paper type and the specified paper type is input, or if the input recording medium type is If it is specified, proceed to the following steps.

In this embodiment, the type of recording medium is input again each time the mode is entered into the unevenness correction data rewriting mode, and based on the input, it is determined whether or not to rewrite the unevenness correction data. However, information about the type of recording medium being used is usually already specified at the time of recording. For example, since the color tone of the printed output often differs depending on the type of recording medium, it is known that image processing such as masking coefficients is changed depending on the type of recording medium used.

Therefore, in a modification of this embodiment, the type of recording medium used during normal recording is input, the optimal image processing is performed accordingly, and when entering the unevenness correction data rewriting mode, the type of recording medium used during normal recording is input. It is determined whether or not to rewrite the unevenness correction data depending on the type of recording medium being used. Therefore, there is an advantage that there is no need to input the type of recording medium again.

Further, in the present embodiment, it was necessary to specify the recording medium by pressing a switch, but this is not necessary in yet another modification of the present embodiment.

FIG. 1θ shows a recording medium 2' used in the example, where 20 is a recorded unevenness correction pattern of each color, 25
is a recording medium identification mark, and an identification mark with a density corresponding to the type of recording medium is provided in the leading edge margin of the recording medium. When reading the density unevenness, the density is read by the density unevenness reading unit 214 before reading the unevenness correction pattern.
so that it can be read with

Then, if it is determined that the paper is the designated paper, rewriting of the unevenness correction data will begin. If not, a display will be displayed to prompt the user to change the recording medium to the designated paper, and the work of rewriting the unevenness correction data will be prohibited. .

By doing this, it is possible to save the effort of inputting the type of recording medium.

In yet another modification of this embodiment, similar effects are obtained without using identification marks. For this purpose, a sensor unit for detecting the type of recording medium can be provided separately from the density unevenness reading unit 214. In this sensor, an ultraviolet lamp is used as the lamp, and a sensor sensitive to the ultraviolet region is used as the sensor. Then, the type of recording medium is determined from the amount of light reflected from the margin itself of the recording medium. In general, coated paper for inkjet recording often has fluorescent agents added to it to make it look whiter. Therefore, if an ultraviolet lamp is used as the lamp, it is possible to determine the type of recording medium from the reflected light. can. That is, when the amount of reflected light is large, it can be determined that the paper has a thick coating layer, when it is medium, it is determined that the paper has a thin coating layer, and when it is rare, it can be determined that the paper is an OHP film.

Then, only when it is determined that the paper has a lot of reflected light and is suitable for detecting density unevenness, the density unevenness is read and the unevenness correction data is rewritten. Otherwise, the same display as above is displayed and this is confirmed. Can be prohibited. As a result, the same effect as described above can be obtained without the need for the operator to input the type of recording medium or to provide an identification mark.

Note that in this example, the test pattern is recorded only when the recording medium is a specific one, but by appropriately determining the range for averaging unevenness during reading, it is possible to correspond to various recording media. You can also do that.

Referring again to FIG. 9, if the recording medium is suitable for unevenness correction processing, the process proceeds to step S7 and temperature adjustment is performed.
This is due to the following reasons.

In an inkjet recording apparatus, the recording head is usually maintained within a predetermined temperature range (for example, about 40° C., which is the first temperature adjustment standard) in order to suppress fluctuations in image density, stabilize ejection, and the like. Therefore, for example, when this procedure is started and a test pattern is recorded, recording will be performed with the recording head temperature at 40°C, which is the first temperature adjustment standard, as shown in area a of Fig. 18. . On the other hand, when actually recording images continuously, the temperature of the head increases as shown in area b in Figure 11, and recording is performed at a maximum of 50°C, which is the second temperature adjustment standard. There is also.

By the way, from the experimental results, as shown in Figure 12A,
It is known that the degree of unevenness in density (OD value) changes depending on the temperature of the recording head. Therefore, in this case, as shown in Figure 12B, when unevenness correction is performed for 40°C, , it is possible to obtain a uniform image without unevenness when the head temperature is 40°C.
Images at 50° C. may still be uneven.

Therefore, in the apparatus of this example, during normal recording or during recording standby, the temperature control section 1 adjusts the temperature of the recording head 1.
13 (heater and fan) as appropriate.
As shown in FIG. 1, the temperature of the recording head is maintained within a predetermined temperature range (approximately 40° C.). On the other hand, in the density unevenness correction process, the set temperature is raised to 45°C, that is, the temperature adjustment standard is raised when printing a test pattern compared to the temperature adjustment standard for normal recording, and the heater and fan are adjusted appropriately. After the head temperature is raised to around 45° C. by turning on/off, a test pattern for checking density unevenness is recorded, and density unevenness correction is performed based on this. As shown in FIG. 11C, by stabilizing the recording operation of the recording head by adjusting the temperature, for example, by forming a test pattern at a head temperature of 45° C. and correcting density unevenness based on this. As shown in FIG. 2, it becomes possible to perform density unevenness correction almost uniformly over the entire temperature control range.

In addition, in this example, test patterns are created when the head temperature is 40°C, which is the first temperature adjustment standard in this example, and when the head temperature is 50°C, which is the maximum temperature increase during recording (second temperature adjustment standard). is printed, the density unevenness of these two types of test patterns is detected, and the density unevenness (first and second
The correction may be performed based on the average value of the density data (density data).

In addition, in order to shorten the overall time required to correct density unevenness, the head temperature is adjusted from 40°C to 45°C, for example.
In addition to the temperature adjustment heater, there is also a temperature control element (
It is also possible to shorten the time required to correct density unevenness by applying an electric pulse to the electrothermal transducer (electrothermal transducer) to the extent that no ink is ejected, thereby shortening the time required to raise the head temperature.

Note that in order to lower the head temperature to the normal recording state (from 45°C to 40°C) after recording a test pattern for density unevenness correction as described below and performing correction, the fan must be driven and the recovery device 220 By performing ink refresh using , it is possible to shorten the time it takes to reach a printable state.

Furthermore, it goes without saying that the temperature adjustment during test pattern recording can be appropriately determined in relation to the temperature adjustment range during normal recording.

Referring again to FIG. 9, in this example, a discharge stabilization operation is executed in step S9. This means that if the print head does not have normal ejection characteristics due to ink thickening, dust or air bubbles, and if you perform the density unevenness correction process, the faithful head characteristics (density unevenness) will be corrected.
This is because there is a risk that it will not be possible to recognize the

During the ejection stabilization process, the recording heads 2010 to 20
18 and the recovery device 290 may be arranged to face each other, and the above-described suction process may be performed to forcibly discharge ink from the ejection port. Further, the ejection orifice forming surface may be cleaned by contacting the ink absorber that can be disposed in the cap unit with the ejection orifice forming surface, or by blowing air, wiping, or the like. It is also possible to perform preliminary ejection by driving the print head in the same way as during normal printing.

However, the driving energy during preliminary ejection does not necessarily have to be the same as that during recording. That is, a process similar to the so-called ejection recovery operation performed in an inkjet recording apparatus may be performed.

In addition, instead of or after the above processing,
A pattern for ejection stabilization can also be recorded on the recording medium. After that, a test pattern or the like for correcting density unevenness may be recorded.

Figure 13 shows examples of recording of these patterns. In the figure, ■ is a pattern for stabilizing ejection, and ■ is an inspection image pattern for inspecting the presence or absence of ejection failure (in the figure, while scanning the print head, The pattern is formed by sequentially driving from the ejection ports of 1) and 2) is a test pattern for detecting density unevenness. The pattern used here for ejection stabilization was one with a printing ratio of 100% duty, which was performed by driving all ejection ports of all recording heads. By recording this stable ejection pattern, the temperature of the head is stabilized, and the ink supply system is also in a steady state, creating conditions for normal printing, and whether there is any ejection failure during actual printing. It becomes possible to accurately grasp the density unevenness.

By the way, in this example, if the recordable width of the recording head 201 is set to be slightly larger than the image recording width in preparation for registration adjustment between each head, the recording width at the time of test pattern placement will be larger than the normal image recording width. It is preferable to do so. Therefore, in such a case, it is important to inspect the width of the ejection port array range (preferably, a test pattern of that width is recorded).

FIG. 14 shows an example of the configuration of a circuit for performing such an operation, in which 141 is a selector for selecting the ejection opening range to be used in the recording head, and 143 and 145 store image data and test patterns to be recorded, respectively. memory,
A counter 145 is used to cause the selector 141 to select the ejection port range to be used during actual recording operation.

When the discharge stabilization process as described above is completed, step S
In this example, a predetermined test pattern is recorded by the recording heads 2010 to 2018K, and the density unevenness is read from the test pattern.The operation at the time of recording the test pattern or reading the density unevenness in this example is described using the timing chart in FIG. I will explain.

FIG. 15 is a timing chart showing the operation of the apparatus of this embodiment. At timing a in the figure, the density unevenness correction processing procedure is started, and after the above-mentioned processing, the recording medium 202 is moved to the image recording area at timing b. After being transported, the main scanning motor is driven at timing C, and at timings d, e, f.
, cyan in g.

Magenta, yellow, and black recording heads 201C
, 201M, 201Y, and 2018 are driven to record a test pattern onto the recording medium 202.

This test pattern is used for reading density unevenness, and at this time, all unevenness correction tables are set as straight lines with an inclination of 1.0, and no unevenness correction is performed. The pattern may be a uniform halftone, and the printing ratio may be about 30 to 75%.

By the way, when a test pattern is recorded on the recording medium 202 by each recording head in this way, depending on the type of recording medium, the ink recorded from each recording head may not be absorbed instantly and may not be recorded on the recording medium 2. The density unevenness of the test pattern may not stabilize immediately.

Therefore, in this embodiment, the density unevenness reading unit 214 is prevented from reading the density unevenness of the test pattern until the condition of the density unevenness of the test pattern recorded by each recording head has stabilized. In order to do this, after the recording head finishes recording the test pattern,
The recording paper is stopped without being conveyed for a predetermined time t ((step 513 in FIG. 9). Then, after the condition of the density unevenness of the test pattern becomes stable, the recording medium is conveyed at timing i. When the test pattern reaches the scanning range of the reading unit 214, it stops, and at timing j
After that, the reading sensor is driven to read the reading unit 214.
The density unevenness of the test pattern of each color is read using the following method.

According to experiments by the inventors, a printing head with a resolution of 400 dpi has a printing ratio of 5 on coated paper for inkjet recording.
When a test pattern was recorded at 0%, the above-mentioned recording paper stop time of approximately 3 to 10 degrees was sufficient.

FIG. 16 is a timing chart showing another example of the operation of the device of this example. In this operation example, the recording medium 202
Conveying speed Vl when conveying with respect to the recording position
On the other hand, at time g') when the test pattern recording by the recording head is about to end, the paper conveyance speed v2 when conveying the recording medium to the density unevenness reading unit 14 is decelerated.
+>Vi, and this also provides the same effect as in FIG. 15.

In these examples, since the scanning range of the recording head and the scanning range of the reading unit in FIG. 1 are different on the platen, a fixing stabilization time is provided for conveyance of the recording medium.
The scanning of the reading unit may be stopped for a predetermined period of time. Furthermore, this is effective when the scanning range of the recording head and the scanning range of the reading unit match. However, if fixing stability up to reading is not a problem, the above processing is unnecessary.

After fixing stabilization as described above, step S15 in FIG.
An uneven reading process will be performed at the step. That is, each unevenness is read from the test pattern recorded for each color, and the unevenness correction data for each head is rewritten. At this time, the glass windows 245b and 246b engage with the blade 247 as the carriage moves during recording, and the surfaces thereof are wiped clean, so that there is no reduction in accuracy during reading.

In other words, according to this example, reading is performed with high accuracy even if no special cleaning procedure is provided. The means for applying such a cleaning fluid during the carriage movement can also be configured to engage the glass window, but it is also possible to carry out such cleaning only during reading. If the processing is performed using the standby time for fixing stabilization, etc., it is possible to avoid increasing the overall processing time for unevenness correction.

(Hereafter, blank space) Based on the above, unevenness correction is performed in step S17 in FIG. In other words, from the signal obtained by reading the density unevenness,
Signals corresponding to the number of ejection ports are sampled and these are used as data corresponding to each ejection port.

Assuming that these are R,,R,,...R, (N is the number of discharge ports), once these are stored in the RAM 119, the CP
The following calculation is performed in Ul0I.

These data are converted into a concentration signal by performing an operation such that C11=-log(R-/Ro) (R is a constant such that R0≧R1; 15n≦N).

Then the average concentration C=Σ　C1,/N Calculate by calculation.

Subsequently, how much the density corresponding to each ejection port deviates from the average density is calculated as follows.

ΔCl1=C/C1 Next, (ΔC). The signal correction amount (ΔS) □ according to ΔS
It is determined by n = A x ΔCl+.

Here, A is a coefficient determined by the gradation characteristics of the head.

Next, a selection signal for a correction straight line to be selected according to ΔSゎ is obtained, and unevenness correction signals having 61 types of values from "0" to "60" are stored in unevenness correction RAMs 129C to 1298 for the number of ejection ports.
Let K memorize it. Using the unevenness correction data created in this manner, a different γ straight line is selected for each ejection port, density unevenness is corrected, and the unevenness correction data is rewritten.

Then, through the determination step S19 in FIG. 19, a test pattern is recorded by each recording head again using this correction data, and the test pattern of each recording head is read again by the density unevenness reading unit 14 to calculate density unevenness correction data. After repeating this operation several times,
The density unevenness correction operation is ended.

In this way, test pattern recording of each recording head, reading by the density unevenness reading unit 14, and calculation of density unevenness correction data can be repeatedly performed multiple times or more automatically in one process for one recording medium. As a result, it is possible to improve the density unevenness correction accuracy of each recording head and shorten the correction time as a whole, even for recording heads whose density unevenness cannot be sufficiently corrected even with a single density unevenness correction operation. become able to.

In the embodiment of the present invention described above, at least when printing for density inspection such as a test pattern, if one pixel is composed of a plurality of dots, the printing duty, that is, the printing setting, is determined by recording within the number of constituent dots. This can be done by modulating the number of dots. In this case, the printing duty is not 100% (preferably less than 75% or more than 25%), but optimally it is preferable to form a test pattern with a printing duty of 50%. This is because it is optimal for the method used to obtain the recording head, and even minute density changes can be obtained that are suitable for the printing characteristics of the recording head.

However, the above printing ratio can also be set by modulating the drive voltage and/or drive pulse width, or the number of ink strikes per dot, and these also apply when one pixel is composed of one dot. It is possible. That is, it goes without saying that the present invention can be applied to any type of modulation in which the printing ratio is set.

In addition, although the above embodiment of the present invention is an optimal embodiment in which the obtained correction processing is performed for each ejection energy generating element, in practice, considering the convergence state of the density uniformization processing and the processing time, it is necessary to It is preferable to perform a process to apply a common correction to a plurality of adjacent ejection energy generating elements. The optimal configuration from this point of view is preferably such that the multiple ejection energy generating elements of the print head apply a common correction to each block drive group including a plurality of elements.

This block drive itself may be a well-known or publicly known method or a unique block drive method, but it is important to provide drive conditions that can implement the corrected uniform density after determining density unevenness according to the present invention. Needless to say, this is a prerequisite.

Further, the data related to the test pattern may be provided by a host device having the configuration shown in FIG. 7, or may be provided by the configuration shown in FIG. You can also do this.

As described above, in this example, the density unevenness reading unit is installed on the carriage or a member that moves in conjunction with the carriage, so the test pattern reading operation can be performed on the platen that regulates the recording surface to be flat. This makes it possible to keep the recording medium flat and keep the distance between the reading unit and the recording medium constant, and also to accurately perform sub-scanning of the recording medium, making it possible to read the density accurately. Further, since there is no need for a special configuration for maintaining the above-mentioned distance for reading in terms of the device configuration, the device can be made smaller. Furthermore, since the recording head and the reading unit are kept at a predetermined distance, the reading sensor can be protected from inconveniences that may occur when the two come close to each other, such as the influence of ink mist or heat.

Furthermore, by using a monocular sensor instead of using a line sensor such as a CCD, by accurately feeding the recording medium, and by moving the reading unit, density detection can be easily performed over the print width, and the line sensor can be used. The sensor is cheaper than when using a conventional method, there is no need for shading correction, and a simple light source can be used.
There is also less deterioration in accuracy when the sensor or light source becomes dirty.

In addition, there is no need to eject the recording medium in its printed state outside the machine (as it is read, so there are fewer sources of error in concentration detection during reading, and combined with the highly accurate reading position accuracy, highly accurate concentration pressure detection is achieved. can.

(4) Other embodiments FIG. 17 shows a schematic diagram of another embodiment, in which each recording head 2
Similar to the above, a test pattern recorded on the recording medium 202 by applying a uniform image signal to 01C, 201M, 201Y, and 2018K is read and a read signal is output. In this example, the density unevenness reading unit 21
4 is composed of a line-shaped reading sensor 232 and a light source 233. Also, hold these in the holder 244.
The structure of fixing to the main scanning belt 210 via the main scanning belt 210 or appropriate modification thereof is the same as that described with reference to FIG. 1, and the same effects can be obtained. Furthermore, since one reading sensor is sufficient, the device configuration can also be downsized.

In addition, as shown in FIG. 18, the reading line sensor 232
On the reading surface side of the recording medium 202, R, G,
Color filters 234R for each color of BL.

234G and 234BL are provided to improve the reading accuracy of the reading sensor 232 for each color of the print pattern.

However, in this example, although the unevenness reading sensor 232 is a single one, the reading output of the sensor changes depending on the color. For example, when using a commonly used sensor whose spectral sensitivity is close to the visual sensitivity, the read output density is the thickest for BK and decreases in the order of C, M, and Y.For example, BK:C:M:Y The output ratio is 1:0.
8:0.75:0.25.

If the density unevenness correction amount is determined from the ratio between the in-head average density and the density of the ejection port of interest, this difference in output does not pose a problem. For example, suppose the output for C is three times the output for BH. The average density in the head IBK is OD□, the density at the target ejection port is 0DsK,..., the average density in the head IC is 00. , the density of the target ejection port of head IC is 00. , suppose that.

If the unevenness of the ejection port of interest in the head IBK is the same as that of the head IC, the sensor output will be 0Dc=+
X 0DIIXI Den = K+ X ODmxn
It is. At this time, the correction value of C becomes equal to BK. Therefore, the output difference between each color is not a problem.

However, when determining the density unevenness correction amount from the absolute value of the density of the ejection port of interest or the difference between the average density and the density of the ejection port of interest, the difference in sensor output between each color becomes a problem.

For example, when calculating the correction value from the difference between the average density and the target ejection port density, ODc 0Dcll=L (ODmx - 0DIKn)
This value is 1 times larger for C than for BK. Based on this value, correction data for the ejection port of interest is obtained, but there is a problem that the final correction amount is different for BK and C, even though the density unevenness of the head is the same. Occur.

Therefore, in this embodiment, the ratio of sensor outputs between each color is determined in advance, and the CPU
This problem is solved by multiplying the sensor output by the reciprocal of this ratio by i and performing unevenness correction based on it.

For example, the output ratio of BK, C, M, Y is 1:+:Km
: When it becomes Ks, the output when reading BK is “
Multiply by 1”, for C, multiply by 1/, for M, multiply by 1
/ is multiplied by 2, and in the case of Y, multiplied by 17.

This way, for example in the example above, 1/KIX
(ODc-ODcn) J/ni+ (KIX (ODll
K −0DaKn))”0Dsx ODmx.

Therefore, optimal correction can be performed without being affected by the sensor output ratio between each color.

Note that such correction of the sensor output is not performed by calculation by CPUl0I (it can also be performed in the previous stage).

For example, if the A/D converter 127 is configured with 8 bits, the output value of each color is divided into 8 bits of the dynamic range.
It must be converted into digital data within the width (
This is effective in preventing the resolution of read data of each color from decreasing.

That is, for example, as shown in FIG. 18, amplifiers 235C, 235M, and 235Y amplify the read signals of each color.
.
It becomes possible to set the read signal width at the time of /D conversion to be narrow as a whole. Therefore, the resolution of the read data within 8 bits can be increased, and the reading accuracy can be further improved.

Note that the present invention is not limited to the example described above (appropriate modifications are possible. For example, each recording head 201G,
When the carriage carrying 201M, 201Y, and 2018K is scanned in the A and B directions to record a test pattern on the recording medium 202, each time the carriage 203 is scanned, a test pattern is recorded by the recording head of one color. After recording is performed and the reading line sensor 232 reads the test pattern recorded on the recording medium 202, the carriage 203 is scanned again, and the next recording head is caused to record the test pattern on the recording medium 202. You can also.

In other words, by reading the test pattern recorded on the recording medium by each recording head for each color as in this embodiment, the capacity of the RAM 219 for storing the read data of the test pattern can be left unused. , the device configuration can be made smaller.

Further, in each of the embodiments described above, the present invention has been applied to an image forming apparatus in the form of a serial printer, but the present invention is applicable to an apparatus in the form of a line printer, for example, ink ejection ports extending over a range corresponding to the width of a recording medium. Of course, the present invention can also be applied to an inkjet recording apparatus equipped with a so-called full multi-type recording head formed by arranging the recording heads.

Furthermore, regarding the configuration of the reading system, it is of course not limited to the upper side in terms of the type, size, and relative scanning of the reading sensor with respect to the test pattern. It may be a monocular sensor that reads the information, or it may be one in which reading elements such as CCDs are arranged over a range corresponding to the arrangement range of the recording elements. In the latter case, it is preferable that a plurality of reading elements react to one ejection port and the average value of the read values is associated with one ejection port.

In addition, the structure of the means for protecting the light source, sensor, etc. from contamination by ink mist etc. does not necessarily consist of separate casings and windows combined with the casings as described above.
However, an appropriate configuration can be adopted. For example, a lamp (at least its light emitting part), a sensor (at least its light receiving part).

It is also possible to provide a light-transmitting protective means for each filter (at least its transparent part) and to clean it all at once.
In addition, if contamination of any component is not a problem, protective measures for that component may be omitted; alternatively, the entire reading unit may be housed in an integrated housing, and protective measures such as a single glass window may be used. may be provided.

(5) Others The present invention can be applied to image forming apparatuses using various recording methods in which density unevenness is a problem (for example, thermal printers, etc.), but when applied to inkjet recording methods, it is proposed by Canon This brings about excellent effects in bubble jet type recording devices. According to this method, recording density can be increased,
This is because since high definition can be achieved, prevention of density unevenness becomes more effective.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. The electrothermal converter that is
By applying a single drive signal that corresponds to the recorded information and causes a rapid temperature rise exceeding nucleate boiling, the electrothermal transducer generates thermal energy, causing film boiling on the heat-active surface of the recording head. This is effective because it can cause bubbles in the liquid (ink) that correspond one-to-one to this drive signal.The growth and contraction of these bubbles causes the liquid (ink) to flow through the ejection opening. is ejected to form at least one droplet.If this drive signal is in the form of a pulse, the growth and contraction of bubbles is performed immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved. More preferably, this pulse-shaped drive signal is
U.S. Pat. No. 4,463,359, U.S. Pat. No. 4,345,26
Those described in Specification No. 2 are suitable.

Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

The configuration of the recording head includes, in addition to the combination configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. The present invention also includes configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the wafer is placed in a bending region. In addition, Japanese Patent Application Laid-Open No. 1989-5 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 9-23670 and Japanese Patent Application Laid-Open No. 1987-59 which discloses a configuration in which an opening for absorbing pressure waves of thermal energy corresponds to a discharge part.
The effects of the present invention are also effective even with a configuration based on the publication of No. 138461. That is, regardless of the form of the recording head, according to the present invention, recording can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head in which the recording apparatus has a length corresponding to the maximum width of a recording medium that the recording head can record. Such a recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally.

In addition, in serial type devices, there is a recording head fixed to the device body, or a replaceable chip that is attached to the device body to enable electrical connection with the device body and supply of ink from the device body. The present invention is also effective when using a cartridge-type recording head or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself.

Furthermore, the effects of the present invention can be further stabilized by adding preliminary auxiliary means, etc., in addition to the recovery means for the recording head, which is provided as a configuration of the recording apparatus.
This is preferable. Specifically, these include a capping means for the recording head, a cleaning means, a preheating means using an electrothermal transducer or a heating element separate from this, or a combination thereof, and a discharge method other than recording. It is also effective to perform a preliminary ejection mode to perform stable printing.

In addition, regarding the type and number of recording heads installed, for example, in addition to one type that corresponds to single-color ink, there is also a plurality of recording heads that correspond to multiple inks with different recording colors and densities. In other words, for example, the recording mode of the recording apparatus is not limited to a recording mode for only mainstream colors such as black, but the recording head may be configured integrally or by a combination of multiple heads. The present invention is also extremely effective for devices equipped with at least one of , multiple colors of different colors, or full colors by mixing colors.

Additionally, in the embodiments of the present invention described above,
Although ink is described as a liquid, it is an ink that solidifies at room temperature or below, but softens or liquefies at room temperature, or in an inkjet method, the ink itself is
Generally, the temperature is adjusted within the range of 0°C or more and 70'C or less so that the viscosity of the ink is within the stable ejection range, so the ink is in a liquid state when the recording signal is applied. Good to have. In addition, the temperature increase caused by thermal energy can be actively prevented by using it as energy for changing the state of the ink from a solid state to a liquid state, or
Or, in order to prevent ink evaporation, ink that solidifies when left unused is used, and in either case, the ink is liquefied by applying thermal energy according to the recording signal, and the liquid ink is ejected, or the recording medium The present invention is also applicable to the case where an ink that is liquefied only by thermal energy is used, such as an ink that begins to solidify by the time it reaches . The ink for such cases is disclosed in Japanese Patent Application Laid-Open No. 54-56847 or Japanese Patent Application Laid-Open No. 60-7126.
As described in Japanese Patent No. 0, the porous sheet may be held as a liquid or solid in the recesses or through-holes of the porous sheet, facing the electrothermal converter. In the present invention, the most effective method for the above-mentioned nuclear ink is the one that implements the above-mentioned film boiling method.

In addition, image forming apparatuses may take the form of image output terminals for information processing equipment such as computers, copying machines combined with leagues, etc., and even facsimile machines with transmitting and receiving functions. It may be. Particularly in devices such as copying machines and facsimile machines that are equipped with image reading means (league) as a document reading system, it can also be used as a reading means for reading density unevenness in recorded images.

Although the above embodiments show various configurations that address a number of technical issues, all of the above configurations are not essential to the present invention, and the designed device configuration and the setting of the desired concentration uniformity level are This indicates that it is more preferable to perform any required configuration using one or more of the above configurations.

[Effects of the Invention] As explained above, according to the present invention, the reading means is provided with a protection means whose optical path portion is transparent,
Since at least the light-transmitting portion is cleaned, the reading means can be protected from inconveniences that may occur in the reading means, such as ink mist, thereby enabling accurate reading and, by extension, accurate unevenness correction.

[Brief explanation of the drawing]

FIG. 1A is a schematic perspective view of an inkjet recording device according to an embodiment of the image forming apparatus of the present invention, FIG. 1B is a side sectional view showing an example of the structure of the reading unit and protection means, and FIG. 2 is the reading unit. FIGS. 3 to 5 are explanatory diagrams for explaining the mode of density unevenness correction in a multi-nozzle head. FIG. 6 is a block diagram showing an example of the configuration of a control system of an inkjet recording apparatus according to this example. 7 is a block diagram showing the system for correcting density unevenness in detail, FIG. 8 is an explanatory diagram for explaining the unevenness correction table used in this example, and FIG. 9 is an unevenness correction process according to this example. A flowchart showing an example of the procedure; Figure 1O is a schematic diagram showing a state in which an identification mark is attached to a recording medium in order to correct density unevenness depending on the type of recording medium; Figure 11 explains temperature changes in the recording head. Figures 12A, 12B, and 12C are explanatory diagrams for explaining how to perform stable density unevenness correction regardless of temperature. Figure 13 is a pattern for stabilizing ejection. , an explanatory diagram showing an example in which an ejection failure detection pattern and a test pattern for density unevenness correction are recorded on a recording medium, FIG. 15 and 16 are timing charts showing two examples of the operation of this example device from recording a test pattern to reading density unevenness, and FIG. FIG. 18 is a schematic perspective view of an inkjet recording apparatus according to another embodiment of the present invention; FIG. 19A and 19B are explanatory diagrams of the mode of correction, and FIGS. 20A to 20E are explanatory diagrams for explaining general density unevenness correction in a multi-nozzle head. 101...cpu. 102...ROM. 106... Instruction input section, 113... Head temperature adjustment section, 219... RAM, 122C, 122M, 122Y, 1228k...
Unevenness correction table, 236... A/D converter, 129C, 129M, 129Y, 1298k...
Unevenness correction RAM. 235G, 235M, 235Y, 235G...
Amplifier, 201.201G, 201M, 201Y,
2018k... Recording head, 202... Recording medium, 203... Carriage, 206... Motor, 210... Main scanning belt, 214... Reading unit, 217G, 217M, 217Y, 2178k...
- Sensor, 218... Light source, 220... Filter, 232... Light receiving element, 233... Lamp, 245a, 246a... Housing, 245b, 246b... Glass window, 247... Cleaning means. Fig. 1B Fig. Fig. Fig. \n Fig. ti Fig. Erotic 4tLt Fig. 12A Erotic position Fig. 12c To scy +7 do nttll No. To Figure 19A Fan 1. Dochidoguchi No. No. 19 B-Zha Igu Sugaya-ha Ichiman-ha Mai-ha

Claims (1)

[Scope of Claims] 1) A recording head in which a plurality of recording elements are arranged to form an image on a recording medium, a reading means for reading a test pattern formed by the recording head, and a method based on the result of the reading. a correction means for correcting the recording head driving condition and a protection means for protecting the reading means from contamination and having a light-transmitting member disposed at least in an optical path thereof; and a cleaning means for cleaning the light-transmissive member. An image forming apparatus comprising: 2) The recording head has a configuration in which the recording medium is scanned in a predetermined direction when forming the image, and the reading means is provided on a member that is driven in conjunction with the scanning,
2. The image forming apparatus according to claim 1, wherein the cleaning means includes a member that engages with and cleans the translucent member during the scanning. 3) The image forming apparatus according to claim 1 or 2, wherein a plurality of recording heads are provided corresponding to recording materials of different colors in order to perform multicolor recording. 4) The recording head has the form of an inkjet recording head, and the inkjet recording head is characterized in that the recording element includes an electrothermal conversion element used to cause film boiling in the ink to eject the ink. The image forming apparatus according to any one of claims 1 to 3. 5) In an image forming apparatus that forms an image by scanning a recording medium with a recording head having a plurality of recording elements arranged therein, a reading means for reading a test pattern formed by the recording head; a correction means for correcting the recording head drive conditions based on the results of the above and a protection means for protecting the reading means from contamination and having a light-transmitting member disposed at least in an optical path thereof; An image forming apparatus comprising a cleaning means for cleaning. 6) The recording head has a configuration in which the recording medium is scanned in a predetermined direction when forming the image, and the reading means is provided on a member that is driven in conjunction with the scanning,
6. The image forming apparatus according to claim 5, wherein the cleaning means includes a member that engages with and cleans the translucent member during the scanning. 7) The recording head has the form of an inkjet recording head, and the inkjet recording head is characterized in that the recording element includes an electrothermal transducer used to cause film boiling in the ink to eject the ink. The image forming apparatus according to claim 5 or 6.