JPH0439046A - Image forming device - Google Patents

Abstract

PURPOSE:To conduct an irregularities correction processing in a black box system for a user by a method wherein an exclusive paper discharge part for discharging a recording medium with a test pattern recorded thereon and an exclusive containing part for containing a recording medium used for a test pattern recording are shielded in a device case or the like. CONSTITUTION:After a pattern generated by a test pattern generation part is recorded on a recording medium 2 by recording heads 1Bk, 1Y, 1M, and 1C, the pattern is optically read by a reading unit 14. Correction data are arithmetically found from the read data and stored in a correction data storage part as new correction data. The unnecessary recording medium 2 the pattern of which has been read already is discharged in a discharge box 49 while being guided along a movable guide 45. The discharge box 49 detachable from a device is made of an opaque material and disposed inside the device shielded by a device case or the like. In this manner, a user cannot visually recognize that a recording medium and a recording material are used for a density irregularities correction processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] 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 Art 1] With the spread of information processing equipment such as copying machines, word processors, and computers, as well as communication equipment, digital image forming (distribution) devices using inkjet methods, thermal transfer methods, etc. are used as image forming (distribution) devices for these devices. Devices that record images 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 in which multiple ink ejection openings and liquid channels are integrated, and thermal transfer type and thermal type thermal heads also generally have multiple heaters integrated in them. .

However, it is difficult to uniformly manufacture multi-head recording elements due to variations in characteristics due to the manufacturing process, variations in characteristics of head constituent materials, etc., and a certain degree of variation occurs in the characteristics of each recording element. For example, in the multi-nozzle head described above, variations occur in the shapes of ejection ports, liquid paths, etc., and in thermal heads, variations occur in the shapes, resistances, etc. of heaters. 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. 32A, an input signal to each recording element is input to a third
If density unevenness as shown in Fig. 32C is visually detected when the density is made uniform as shown in Fig. 2B, the input signal is corrected as shown in Fig. 32D, 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 system capable of modulating the dot diameter or dot density, it is known to achieve gradation recording by modulating the dot diameter recorded by each recording element in accordance with the input. For example, in an inkjet recording head using a piezo method or a bubble jet method, the drive voltage or pulse width applied to each piezo element or an ejection energy generating element such as an electrothermal conversion element is determined, and in the case of a thermal head, the drive voltage or pulse width is applied to each heater. 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. 32E by utilizing modulation of the dots according to the input signal. 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 human input signal, and a large number of dots can be recorded for low density areas, and a small number of dots can be recorded for high density areas. 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. 32E.

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 five basic automatic adjustments 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 the above-mentioned apparatus, for example, the user presses a key to instruct density unevenness correction at a desired point in time (at a point in time when the unevenness of the recorded density becomes noticeable). Density unevenness correction processing is performed by recording a test pattern, reading the pattern, and rewriting correction data. At this time, in the simplest configuration, the recording medium and its conveyance system for recording the test pattern are the same as those provided for the original image formation.

However, as mentioned above, if the above-mentioned density unevenness correction process is performed using the recording medium transport system and recording medium that are originally provided for recording images based on image information, the test pattern Because the recorded recording medium is ejected to a paper ejection unit such as a paper ejection tray, the user is worried that the purchased recording medium and recording agents such as ink and toner will be used for purposes other than the original image formation and will be wasted. It's easy to think that there is. Particularly, in image forming apparatuses that use recording methods that require high running costs, users may feel uncomfortable.

The present invention has been made in order to solve the problems associated with such density unevenness correction processing, and its purpose is to provide a dedicated ejector for ejecting a recording medium on which a test pattern has been recorded. A dedicated storage section for storing the paper section and the recording medium used for recording test patterns is provided. By shielding these sections with the case of the device, etc., and preventing the user's consent, density unevenness correction processing can be easily performed by the user. An object of the present invention is to provide an image forming apparatus that performs image forming in a black box manner.

[Means for Solving the Problems] To this end, the present invention provides a recording head in which a plurality of recording elements are arranged in order to form an image on a recording medium, and a recording head that records a predetermined test pattern on the recording medium by the recording head. a reading means for reading a test pattern formed on a recording medium by the recording head based on the signal generating means; and a correction for correcting the recording head driving conditions based on the result of the reading. a paper feed unit that stores a recording medium on which the test pattern is recorded; and a discharge unit that discharges the recording medium on which the test pattern is recorded, the recording medium having an image other than the test pattern recorded thereon; The present invention is characterized by comprising a discharge section different from a medium discharge section, and a conveying means for conveying the recording medium in the paper feed section to a recording position by the recording head, a reading position by the reading means, and to the discharge section. do.

[Function] According to the above configuration, by providing the ejecting section exclusively for the recording medium for recording the test pattern, the user can, for example, press a key to instruct density unevenness correction processing at a desired time. The recording of the test pattern is started, and then the pattern is read and the recording medium is ejected from the user's OFF state. Effective correction can be performed without causing any discomfort.

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

(1) Overview and mechanical configuration of the device (Figure 1 and Figure 2) 2 Reading system (Figures 3 to 12) 3 Control system (Figures 13 to 15) 4 Sequence of unevenness correction (Figure 16) Figure ~ Figure 25) 5)
Other Embodiments (FIGS. 26 to 31) 6 Others (1) Mechanical Structure and Overview of the Apparatus FIG. 1 shows a schematic structure of an inkjet recording apparatus according to an embodiment of the present invention.

Here, Ic, IM, IY, and IBK are print heads corresponding to cyan, magenta, yellow, and black inks, respectively, and the width in the printing medium conveyance direction, in this example, the short side of an A3 size printing medium. 400dp over the range corresponding to the length (297mm >
This is a full-line head with discharge ports arranged at a density of i (dots/inch). 3 are these recording heads Ic
- This is a head holder that holds the IBM in one piece, and can be moved by the head holder moving mechanism 5 in six directions toward the recording position in the figure and in the B direction away from the recording position.

The head holder moving mechanism 5 includes a drive source such as a motor, a transmission mechanism that transmits the drive force to the head holder 3, and a drive source such as a motor.
It has a guide member etc. that guides the movement of the head holder 3, and by appropriately moving the head holder 3 in directions A and B, the ejection ports of the recording heads IC to IBK face the recording medium at a predetermined interval. The head holder 3 can be set at a recording position, a retracted position for receiving the intrusion of a cap unit, which will be described next, a position for capping each head, and the like.

Reference numeral 7 denotes an ink supply/circulation system unit, which includes a supply path for supplying each color ink to each recording head, a circulation path for refreshing the ink, and an appropriate pump. Furthermore, by driving the pump during the ejection recovery process described below, it is possible to pressurize the ink supply path and forcibly discharge ink from each recording head.

9 is a cap unit, which includes a recording head IC1IM,
Caps 9C, 9M, 9Y, and 98, which can face or be joined to IY and IBK, respectively, and are made of an elastic material such as rubber to improve adhesion during joining, are used to store ink (waste) received from the recording head during ejection recovery processing. The printer has an absorber for absorbing ink (ink), and a waste ink path for introducing waste ink into a waste ink tank (not shown). 1
1 is a cap unit moving mechanism, which includes a motor, a transmission mechanism, a guide member, etc., and moves the cap unit 9 to C in the figure.
By appropriately moving the cap unit 9 in the direction and the direction D, the cap unit 9 can be set at a position directly below the head holder 3 in the retracted position and at a position where it does not obstruct the descent of the head holder 3 during recording.

During the ejection recovery process, the head unit 3 is raised in the direction B to a position where the cap unit 9 is not blocked from entering, and the cap unit 9 is placed in the space created by this.
The cap unit 9 is set at a position where the corresponding head and cap face each other. In this state, or in a state in which the head holder 3 is lowered and the ejection port forming portion of the recording head and the cap face each other at a predetermined interval or are joined, the pump etc. of the ink supply/circulation system unit 7 is driven. As a result, the ink can be forcibly discharged and causes of ejection failure such as dust, air bubbles, and thickened ink can be removed, thereby stabilizing the ink ejection condition during recording.

Furthermore, in the above state, the print head may be driven in the same manner as during printing to perform ink ejection (preliminary ejection), thereby eliminating the cause of ejection failure.

Note that when recording ends or is interrupted, the head may be capped to protect the ejection ports from drying.

Reference numeral 38 denotes a cassette containing recording media 2 such as paper, OHP film, etc. The recording media 2 accommodated here are separated and fed one by one by a pickup roller 39 rotating in the F direction. 40 is the fed recording medium 2
This is a conveyor belt that conveys the image in the E direction with respect to the recording positions of the recording heads IC to IBK, and is wound between the rollers 41. In addition, in order to increase the adhesion of the recording medium 2 to the belt 40 to ensure smooth conveyance and to obtain an appropriate distance between the head and the recording medium (head gap),
A member such as means for performing electrostatic adsorption or air adsorption, or a recording medium holding roller may be provided.

42 is a discharge roller for discharging the recorded recording medium 2, 43 is a tray for loading recording media on which recording has been performed based on normal image information, and 49 is a record on which a test pattern has been recorded. This is an ejection box for storing media. The discharge box is formed of an opaque member and is provided inside the device. A movable guide 45 is located between the ejection roller 42, the paper ejection tray 43, and the paper ejection box 49, and is used to switch the ejection path of the recording medium 2.

14 is a density unevenness reading unit, and a recording head Ic
- It is arranged between the recording position by IBK and the ejection roller 42, facing the recording surface of the recording medium 2, and reads a test pattern formed on the recording medium 2 during processing for density uniformity correction, etc. 15 is a mechanism for scanning the reading unit, which will be described later with reference to FIG. Reference numeral 16 indicates various parts related to conveyance of the recording medium 2, namely, a feeding roller 39, a roller 41 . Discharge roller 42. This is a drive unit for driving the movable guide 45 and the like.

When the user desires to correct density unevenness, for example, when density unevenness becomes noticeable due to changes in the recording head over time, the user presses a key (not shown) instructing density unevenness correction processing. This starts the density unevenness correction process.

That is, with this start, the recording medium 2 is transferred from the paper cassette 38 to the conveyor belt 4 by the pickup roller 39.
0, and conveyance of the recording medium 2 is started. At the same time, a pattern generated by a test pattern generation section (not shown) is generated by the recording head IBk.

IY, IM, l(1:) are recorded on the recording medium 2. This recorded test pattern is optically read by the reading unit 14, correction data is calculated from this read data, and correction data (not shown) is read. It is stored in the storage unit as new correction data.After the pattern has been read, the unnecessary recording medium 2 is guided to the ejection box 49 by the movable guide 45 which has been switched to the state shown by the solid line in FIG. 1A. The discharge box 49 can be configured to be detachable from the device.

In this way, by constructing the ejection box for storing the recording medium on which the test pattern is recorded from an opaque member and disposing it inside the device that is shielded by the device case (not shown) or the like, It is possible to make it impossible for the user to visually recognize that the recording medium and recording materials such as ink are used for density unevenness correction processing. Thereby, it is possible to avoid unnecessary discomfort to the user due to the recording medium being used for purposes other than the intended purpose of image formation.

FIG. 1B is a schematic configuration diagram of an inkjet recording apparatus according to a second embodiment of the present invention, and the same elements as in FIG. 1A are denoted by the same reference numerals, and the explanation thereof will be omitted.

In the figure, 50 is a cassette dedicated to the recording medium on which the test pattern is recorded. When the correction process is started, the dedicated recording medium is supplied from this cassette 50, and is ejected to the ejection box 49 in the same manner as described above. be done. The cassette 50 and the ejection poxle 49 are also normally made of an opaque material so as not to be visually recognized by the user, and are disposed inside the apparatus. Moreover, both of these structures can be configured to be detachable from the apparatus.

The area of the recording medium required to record the test pattern is
In general, it is much smaller than the area of the recording medium originally required for recording the image (in most cases, a standard size such as A4.84),
If a recording medium of a special size and a dedicated cassette are provided for the recording medium on which the test pattern is recorded, the correction process can be performed with less waste of the recording medium.

FIG. 1C is a schematic configuration diagram of an inkjet recording apparatus according to a third embodiment of the present invention, and the same elements as in FIG. 1A are given the same numbers and their explanations are omitted.

In the figure, reference numeral 51 denotes a correction cartridge in which a cassette for storing a recording medium on which a test pattern is recorded and an ejection box for the recording medium on which a test pattern is recorded are integrally constructed of the same opaque member. It has a removable structure.

By integrating the storage cassette and ejection box into a cartridge, it is possible to easily replace the recording medium for correction processing even if it runs out.Furthermore, since it is not possible to see what is inside, the user is not required to record the recording medium. It doesn't make you feel like you're consuming the medium.

In addition, in any of the above embodiments, the discharge box,
In the storage cassette or correction cartridge,
A configuration that allows service personnel to replenish, eject, or replace recording media; for example, the number of storage media that can be stored corresponds to the timing of regular maintenance processing by service personnel; or If the structure is such that recording media can be exchanged,
Density unevenness correction processing will become more of a black box for users.

Furthermore, in each of the above embodiments, the process from the paper feeding section to the paper ejection section of the recording medium, that is, the process of recording by the recording head and reading by the reading unit, is also visible to the user because these components are inside the device. It is now impossible to do so.

FIG. 2 shows the recording head 1 (recording head IC, IM).

An ink system consisting of an ink supply/circulation system unit 7 is schematically shown.

In the recording head, 1a is a common liquid chamber to which an ink tube from an ink supply source is connected, and also communicates with an ink discharge port 1b via a liquid path. An ejection energy generating element such as an electrothermal conversion element is disposed in each liquid path, and ink is ejected from the corresponding ejection port in response to energization of the element.

An ink tank 701 serves as an ink supply source, and is connected to the common liquid chamber 1a of the recording head 1 via ink paths 703 and 705. 707 is a pump provided in the middle of the ink path 703, and 71f) is a valve provided in the middle of the ink path 705.

By configuring the ink system in this way, the pump 70
By appropriately switching the operating state of 7 and the opening/closing state of the valve 710, the ink system can be set to each of the following modes.

(2) Print mode Ink necessary for recording is supplied from the ink tank 701 side to the head l. Note that since this embodiment is applied to an on-demand type inkjet printer, no pressure is applied to the ink during recording, and therefore the pump 56 is not driven. Also, assume that the valve 710 is opened.

In this mode, ink is supplied to the head 1 via the ink path 705 in response to ink ejection from the head 1 .

■Circulation mode This mode is used to circulate ink to supply ink to each head during the initial use of the device, or to remove air bubbles in the heads or supply channels and refresh the ink inside them at the same time. This is set when the inkjet printer is left unused for a long time.

In this mode, the valve 710 is opened and the pump 56 is operated, so that ink flows back into the ink tank 701 via the ink tank 701, the ink path 703, the head l, and the ink path 705.

■Pressure mode When the ink inside the ejection port of the head 1 thickens, or when the ejection port or liquid path becomes clogged, pressure is applied to the ink and the ink is pushed out from the ejection port 1b to remove the ink. This is the removal mode.

In this mode, the valve 710 is closed, the pump 707 is operated, and ink is supplied from the ink tank 701 to the print head 1 via the ink path 703.

(2) Reading system FIG. 3 shows an example of the configuration of the reading unit and its scanning mechanism in this embodiment.

A flat recording medium guide section (indicated by reference numeral 17 in FIG. 2A) serving as a platen is placed below the scanning section of the reading head 60, and the recording medium 2 is conveyed onto this guide section, and the recording medium 2 is conveyed onto this guide section. The image formed on the recording medium is read by the reading head 60 at the position. Note that the position of the reading head 60 shown in FIG.
This is the home position of 0. This home position is desirably located at a position laterally away from the recording medium transport range. This is because each reading device is away from dangers such as water droplets adhering to it due to ink evaporation.

In FIG. 3, 60 is a reading head which slides on a pair of guide rails 61, 61' to read the image. The reading head 60 includes a light source 62 for illuminating the original, and a lens 63 for forming an image of the original onto a group of photoelectric conversion elements such as a CCD.
It is composed of etc. 64 is a flexible conducting wire bundle that supplies power to the light source 62 and the photoelectric conversion element and transmits image signals and the like from the photoelectric conversion element.

The reading head 60 is fixed to a driving force transmitting section 65 such as a wire for main scanning (G, H directions) in a direction intersecting the recording medium conveyance direction. Main scanning direction driving force transmission section 6
5 is suspended between pulleys 6B and 66 degrees, and is moved by the rotation of a main scanning pulse motor 67. As the pulse motor 67 rotates in the direction of the arrow {circle around (2)}, the reading head 60 moves in the direction of the arrow G and reads row information of an image perpendicular to the main scanning direction G with the number of bits corresponding to the photoelectric conversion element group.

After a predetermined width of the image has been read, the main scanning pulse motor 67 rotates in the direction opposite to the arrow I. As a result, the reading head 60 moves in the H direction and returns to the initial position. Note that E+8.68° is a support member.

If only one main scan is performed to read the density unevenness, the reading operation is completed above, but if the density unevenness is read for each of multiple colors, or if one color is read multiple times and averaged. When taking a value, for a certain color or after one main scan G,
The recording medium 2 is conveyed in the E direction by the conveyor belt 4° or the ejection roller 42 and moves a predetermined distance (a distance d equal to the pitch between each color pattern or the read image width in one main scan in the G direction), Stop. Here, main scanning G is started again. Then, by repeating the main scanning G, the return H1 in the main scanning direction, and the movement of the recording medium (sub-scanning), it is possible to read the density unevenness of each color pattern or a plurality of times for one color. Note that in this process, instead of conveying the recording medium 2, the reading unit may perform sub-scanning. Further, if the sensor is a full-line sensor, a mechanism related to main scanning becomes unnecessary.

The image signal read in this way is sent to the image forming section and is used to correct the driving conditions of the recording head as 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 applied 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 standard density that changes depending on the desired image, and all of the purposes included in the purpose of correction are applicable. It is possible.

As an example, a case will be described in which density unevenness is corrected for a multi-head with N arranged 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. 33. First, the density OD of the portion corresponding to each recording element, ~OD,
Measure and correct the average density 00=Σ00n/N
seek. 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 a certain group of elements is as shown in FIG. What is necessary is to determine the correction coefficient α that brings about this. That is, a correction signal S obtained by correcting the signal S to αxS=(0010D,)XS may be applied to this element or group in accordance with the input signal S. Specifically, the 35th
This is executed by performing table conversion as shown in the figure. Third
In Figure 5, 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).
Straight line B is a straight line with a slope of a=0010D, and is a table for converting an input signal S into an output signal α·S. Therefore, the correction coefficient α for each table as shown by the straight line B in FIG. 35 for the image signal corresponding to the n-th recording element. If the head is driven after table conversion is performed, each density of the portion recorded by N recording elements becomes equal to OD. If such processing is performed on all recording elements, density unevenness will be corrected and a uniform image will be obtained. That is, if data indicating what kind of table conversion should be performed on the image signal corresponding to which recording element is obtained in advance, it becomes 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 be predicted from the fact that the five heaters in the thermal head may deteriorate or change in quality, causing the concentration distribution to change. In such a case, for example, the initial input correction amount set at the time of manufacturing may no longer be sufficient to correct density unevenness (therefore, the problem with long-term use is that density unevenness gradually becomes noticeable as it is used). becomes a problem to be solved.

Incidentally, the distance between the reading unit and the recording medium on which the test pattern is recorded varies depending on the reading accuracy, but is preferably kept constant. Therefore, in order to maintain this spacing, configurations as shown in FIGS. 4 to 6 can be adopted.

FIG. 4 schematically shows one example, in which a housing 76 in which the reading unit 14 and its scanning mechanism 15 are housed is provided with presser rollers 78a78b that engage with the recording medium 2. Since these rollers 78a and 78b rotate in the recording medium conveyance direction, there is no problem in conveying the recording medium. As a result, the recording medium 2 is prevented from floating, and the housing 76 is displaced according to the thickness of the recording medium 2, so that the above-mentioned interval is kept constant.

In FIG. 4, 74 is a lens for converting the emitted light from the light source 62 into parallel light, 73 is a sensor having a photoelectric conversion element group, 63 is a lens for converging reflected light, and 77 is an aperture with an aperture of d0. It is a filter with

Then, by a scanning mechanism as shown in Fig. 3, these lenses,
The sensor, light source, filter, etc. are scanned within the housing 76 in the G and H directions (directions perpendicular to the drawing in FIG. 4).

The reflected light from the recording medium enters the sensor 73 via the lens 63 and the filter 77 having an aperture d0.

This incident light is light in a range d on the test pattern, and therefore, the average of the unevenness in that range is detected. According to experiments by the inventors, the opening 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.

Note that if the reading unit itself including the lens, sensor, light source, etc. can be displaced in the vertical direction in FIG. 3 with respect to the scanning mechanism 15, a roller as a holding member may be provided on the reading unit itself. In this case, if the rollers have a caster structure, conveyance of the recording medium and movement of the reading unit can be carried out smoothly. Further, in the case of a configuration in which reading is performed while moving the recording medium, reading can be performed while reducing the load on the rollers by making the scanning direction diagonal.

FIG. 5 shows another configuration example for maintaining a constant distance between the reading unit and the recording medium, and in this example, a holding member 80 made of transparent plastic or the like is provided at the bottom of the housing.

In this example, the housing 76 that houses the reading unit and the scanning mechanism is first removed from the platen 17.
When the recording medium 2 on which the test pattern has been recorded comes under the reading unit, the housing is lowered and the recording medium 2 is held down with the transparent plastic 8o. Then, by scanning the reading head 6o, density unevenness is detected in the process. However, in this case, it is preferable that the image is completely fixed.

Such a configuration also prevents paper from floating and allows accurate reading. Furthermore, the transparent plastic 8o covering the lower part of the casing has the effect of preventing the light source 62, sensor 73, etc. from getting dirty.

FIG. 6 shows yet another configuration example for maintaining the distance between the reading unit and the recording medium. In FIG. 6, the housing 76 is fixed in the vertical direction, but a cylindrical roller 81 made of transparent plastic or the like is rotatable about a shaft 82.

The recording medium 2 is held by the transparent roller 8I, and density unevenness can be read from inside the transparent roller 81 while paper floating is prevented. According to this example as well, density unevenness can be accurately detected.

In addition to the embodiments described above, the main body of the apparatus has recording medium holding means on each of the upstream side and the downstream side.

The above-described high-precision reading is also possible with a device configured to read the recording medium between the downstream clamping means.

By the way, in order to rewrite the unevenness correction data when recording a color image with a head of three colors (cyan (C), magenta (M), and yellow fY), or four colors including black (8K), In this case, it is highly desirable to record a test pattern for correction with each head, read the unevenness, and rewrite the unevenness correction data for each head.

At that time, when reading the unevenness of C, M, Y, especially Y, when white light is irradiated onto the Y test pattern and the reflected light is received without a filter, the amount of light received by the sensor 73 is as shown in Fig. 78. As shown in curve A, the dynamic range is narrow and uneven (the difference in optical density is small, 0.02 to 0.15
degree) is difficult to accurately read. So the 7th B
As shown in the figure, when using light that has passed through an L (blue) filter, the overall amount of received light decreases, but the dynamic range expands and the accuracy of reading unevenness increases, as shown by curve B in Figure 7A. become. If R (red) and G (green) filters are used for C and M, respectively,
The same is true.

FIG. 8 shows an example of a configuration for switching such color filters. Here, 79 is a color filter switching section, and the shaft 7
Rotating around 9A, R filter 77R, G filter 77G, and BL filter 77 are placed on the optical path to sensor 73.
Aperture (no filter) 778K for BL or BK,
When reading the test pattern of each color, it is possible to selectively position it as appropriate. Note that the diameter of each filter or opening is do as described above.

By doing so, it becomes possible to accurately correct unevenness for each color using a single unevenness reading sensor 73 and light source 62.

Note that the filter is located at a distance from the light source 62 to the sensor 73.
It can be anywhere on the optical path. Furthermore, in order to correct the amount of received light that decreases by the amount that passes through the filter, the amount of emitted light from the lamp light source is increased by the amount of the decrease, thereby widening the dynamic range as shown in FIG. 7C. Further, as will be described later, multiplication by an appropriate constant or signal amplification may be performed depending on the color.

Furthermore, instead of switching the color filters as described above, it is also possible to switch the light sources.

Figure 9 shows an example of its configuration, with R, G, and B
Four light sources 62R, 6 with L and white spectral characteristics
The configuration is such that 2G, 62BL, and 62W can be switched in the same way as the upper side. This also provides the same effect as above.

By the way, it is also possible to integrate the above-described mechanism for preventing floating of the recording medium 2 and the structure for expanding the dynamic range according to the color.

FIG. 10 shows a configuration example for this purpose. Here, 85 is a transparent roller for pressing that is divided into four parts in the circumferential direction, of which 85A is a colorless and transparent part, 85R is a part forming a red filter, and 85G is a green part. The part forming the filter, 8
5BL is a part forming a blue filter. 848 on the recording medium 2 is a test pattern produced by the black head IBK, 84C is a test pattern produced by the cyan head IC, 84M is a test pattern produced by the magenta head IM, and 84Y is a test pattern produced by the yellow head IY.

The reading unit 14, which can enter inside the transparent roller 85, is supported by a support rod 15', and the support rod 15' is movable in the direction of the arrow.

When reading unevenness in the test pattern 848 using the black head IBK, rotate the roller 85 and
The unit 14 enters and moves while holding down the recording medium at the portion . Similarly, when reading the test pattern 84C of the cyan head IC, read it at the position 85R, for the test pattern 84M of the magenta head LM at the position 85G, and for the test pattern 84Y of the yellow head IY at the position 85BL. Set to press the recording medium with .

As described above, according to this example, density unevenness of each color head can be read with high precision through the filter, and paper floating can be prevented, so that accurate reading is possible.

Next, scanning of the reading head in the configuration shown in FIG. 3 will be described.

As described above, the recording medium on which the test pattern has been recorded is conveyed to the reading unit 14, which is disposed on the recording surface side of the recording medium 2 downstream of the recording head in the conveyance direction. Thereafter, the pulse motor 67 in FIG. 3 is driven, and the reading unit 14, that is, the reading head 60 fixed to the driving force transmission part 65, such as a wire or a timing belt, connected to the pulse motor moves in the G direction in FIG. The test pattern recorded on the recording medium 2 is read by the reading sensor 73 while being main scanned.

In this embodiment, when the pulse motor 67 is driven by a control circuit to be described later to transport the reading unit 14, the pulse motor 67 is driven at a frequency different from the resonant frequency of the reading unit transport system. ing.

That is, when the pulse motor 67 is driven to transport the reading unit transport system, the resonance frequencies fω, fω2, . At fω3..., the vibration of the reading unit conveyance system becomes extremely large. Therefore, when the reading unit 14 is conveyed at a resonant frequency where such a system vibrates, as shown in FIG. 12A, even if the recording density of the test pattern recorded on the recording medium 2 is uniform, However, as shown in FIG. 12B, the conveyance speed ■ω of the reading unit 14 may change. In such a case, as a result, the read output from the reading unit 14 has an output characteristic with pitch unevenness as shown by ω in FIG. 12c, and the recording density of the test pattern recorded on the recording medium 2 cannot be read correctly.

Therefore, in this embodiment, in order to cope with such a case, the reading unit 14 is driven at a frequency f1 other than the resonance frequency of the reading unit transport system, and the test pattern is read at a constant reading speed V. It becomes possible to accurately read the recorded density of the test pattern without being affected by the vibrations of the transport system.

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

FIG. 13 shows an example of the configuration of the control system. Here, H is a host device that supplies image data and various commands related to recording to the device in this example, and is a host device that supplies a computer, image league, and other forms of information. have 1 is a CPU that forms the main control section of the device of this example, and has the form of a microcomputer;
Each part is controlled according to the processing procedure described later. 102 is a ROM that stores a program corresponding to the processing procedure, predetermined test pattern image data and other fixed data;
Reference numeral 104 denotes a RAM having a temporary storage area for image data and an area used for work in various control processes.

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. [08] Sensors 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. 110 is a display section;
It is used to notify the operating status and setting status of the device, as well as the presence or absence of an abnormality. An image processing unit 111 performs logarithmic conversion, masking, UCR, and color balance adjustment on image data related to recording.

112 is the recording head 1 (the above heads IY, IM,
This is a head driver for driving ink ejection energy generating elements (Ic and IBK shown collectively).

Reference numeral 113 denotes a temperature adjustment unit for adjusting the temperature of the recording head l, and specifically, it can include, for example, a heating heater and a cooling fan disposed for the head l. Reference numeral 114 designates a drive unit for the color filter switching unit 79 described with reference to FIG. 8, and reference numeral 11B designates a drive unit for each motor that drives the recording medium transport system.

FIG. 14 shows in detail the system for correcting density unevenness among the above configurations. Here, 121G.

121M, 121Y and 1218 have image processing unit 1
These are image signals of cyan, 5 magenta, yellow, and black processed in step 11, respectively. 122c, 122
M 122Y and 1228 are unevenness correction tables for each credit, which can be provided in the ROM 102 area. 123C, 123M, 123Y and 123BK are image signals after the correction. 130c
~1308 is a gradation correction table for each credit, 1310~
1318 is a binarization circuit using a dither method, an error diffusion method, etc., and the binarized signal is supplied to each color head IC to IBK via a driver 112 (not shown in FIG. 14). .

126G, 126M, 126Y and 1268 are color signals read by the reading unit 14 through the color filters and apertures shown in FIG. 8, and are input to the A/D converter 127. 119 is a RAM area for temporarily storing the digital output signal, and the area of RAM 104 can be used. 128C, 12111
M, 128Y and 1288 are correction data calculated by CPUl0I based on the stored signals.
129C to 1298 are non-uniformity correction RAMs for each credit, and the area of RAMI 04 can be used. Then, the unevenness correction signals 130C to 13 of each credit which are the outputs are
08, unevenness correction tables 1220 to 12, respectively.
28K, and is converted into image signals 121c to 1218 so as to correct the unevenness of the heads IC to IBK.

FIG. 15 shows an example of an unevenness correction table, and in this example, Y
= 0.70X to Y=1.30X Mano kind is 0.
There are 61 corrected straight lines that differ by 0.01, and the corrected straight lines are switched according to the unevenness correction signals 130C to 1308K. For example, when a pixel signal to be recorded by an ejection port with a large dot diameter is input, a correction straight line with a small slope is selected, and conversely, when an ejection port with a small dot diameter is used, a correction straight line with a large slope is selected to correct the image signal. to correct.

The unevenness correction RAMs 129C to 1298 store correction straight line selection signals necessary to correct 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 tone correction tables 1306 to 130BK,
Here, the gradation characteristics of each head are corrected and output. The signals are then binarized by binarization circuits 131C to 1318K, and a color image is formed by driving heads IC to IBK via a head driver.

(The following is a blank space) (4) Sequence of unevenness correction With the above configuration, in this example, the following processing is performed to perform unevenness correction more accurately.

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. 16 shows an example of the unevenness correction processing procedure according to this example.

When this procedure is started, first, in step Sl, input of the type of recording medium is accepted. In this case, for example, the cassette 38° shown in FIGS. 1A to 1C, the cassette 50
Alternatively, when the cartridge 51 is installed, the type of recording medium is simultaneously input automatically, for example, by a switch provided on the cassette or the like. In step S3, a determination is made based on this, and if the input recording paper type is not optimal for density unevenness detection, such as an OHP sheet or trace coated paper, then in step S5, the display unit 11. 0, for example, displaying a message such as "Please use the specified paper", such a display can be made by printing a test pattern on the recording medium for the original recording, as in the embodiment shown in Figure 1A. It is effective when used for As a result, if the paper is replaced with the designated paper and the designated paper type is input, or if the input recording medium type is the designated one from the beginning, the process proceeds to the following procedure.

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 this embodiment, the recording medium is designated by a switch such as a cassette, but this is not necessary in yet another modification of this embodiment.

FIG. 17 shows a recording medium 2' used in this example. Here, 20 is a recorded unevenness correction pattern, 25 is a recording medium identification mark, and the identification mark is provided at the leading end margin of the recording medium with a density corresponding to the type of the recording medium. and,
When reading the density unevenness, the density is read by the density unevenness reading unit 14 before reading the unevenness correction pattern.

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 14.The configuration of this sensor is almost the same as that shown in FIG. 8, but the lamp is an ultraviolet lamp, and the sensor is Use one that is sensitive to ultraviolet light. 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 IP film. And there is a lot of reflected light,
Only when it is determined that the specified paper is suitable for density unevenness detection, the density unevenness is read and the unevenness correction data is rewritten, and in other cases, the same display as above is displayed and this can be prohibited. As a result, the operator does not have to input the type of recording medium or provide an identification mark.
The same effect as above can be obtained.

Referring again to FIG. 16, if the recording medium is suitable for unevenness correction processing, the process proceeds to step S7 and temperature adjustment is performed for the following reason.

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 18, 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 19A,
It is known that the magnitude of density (00 value) unevenness changes depending on the temperature of the recording head. Therefore, in this case, as shown in FIG. 19B, if unevenness correction is performed for 40°C, a uniform image without unevenness can be obtained when the head temperature is 40°C.
Images at 50° C. may still be uneven.

Therefore, in the apparatus of this embodiment, the temperature control section 1 adjusts the temperature of the recording head 1 during normal recording or during recording.
13 Turn on/off (heater and fan) as appropriate,
As shown in FIG. 18, 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. 19C, 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. Thus, it becomes possible to perform density unevenness correction more or less 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 heater for temperature adjustment, it is necessary to apply electric pulses to the recording element (electrothermal conversion element) to the extent that ink is not ejected, shorten the time to raise the head temperature, and correct density unevenness. It is also possible to shorten the time.

In addition, in order to lower the head temperature to the normal recording state (from 45 degrees Celsius to 40 degrees Celsius) after recording a test pattern for density unevenness correction as described below and performing the correction, you must drive the fan and turn on the ink described above. By performing circulation, the time required to reach a recordable state can be shortened.

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. 16, in this example, a discharge stabilization operation is executed in step S9. This increases the viscosity of the ink,
If the recording head does not have normal ejection characteristics due to the incorporation of dust or air bubbles, if density unevenness correction processing is performed as is, it will not be possible to recognize the faithful characteristics of the head (a degree unevenness). This is because there is a risk.

During the ejection stabilization process, the recording heads IC to IBK and the cap unit 9 can be placed facing each other, and the above-mentioned pressurization mode can be set to forcibly eject ink from the ejection ports. Further, the ejection port forming surface may be cleaned by bringing an ink absorber that can be disposed in the cap unit into contact with the ejection port 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 manner as during normal printing. However, the drive energy during preliminary ejection is not necessarily the same as that during recording (or may be). In other words, the same process as 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 20 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 conveying the recording medium, 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 print 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 an apparatus as in this example in which the recording head 1 is a fully multi-type one and the recordable width is slightly larger than the image recording width in preparation for registration adjustment, the recording width when recording the test pattern is It is preferable to make the image recording width larger than the normal image recording width. For example, the maximum recording paper size is A3, and the normal image recording width is approximately 293 mm, taking into account left and right margins, compared to 297 ml, which is the length of the short side of A3 or the long piece of A4, Further, consider a case where the recordable width of the recording head is 295 mm. This is to electrically adjust the range of the ejection ports to be used and to correct errors in the relative positional relationship between the mechanical heads and the recording medium.

Therefore, in this case, it is important to inspect the width of 295 mm, which is the ejection port arrangement range (preferably, a test pattern with a length of 295 mm is recorded).

FIG. 21 shows an example of the configuration of a circuit for performing such an operation, in which 141 is a selector for selecting the range of ejection ports 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 head Ic-IBK, and the density unevenness is read from the test pattern. I will explain.

FIG. 22 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 2 is moved to the image recording area at timing b. After being transported, timing C
The main scanning motor is driven at timings d, e, f, g.
cyan, magenta, yellow, and black recording head ICs.

The IM, IY, and IBK drivers are driven to record a test pattern onto the recording medium 2. 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 can be a uniform halftone, and the printing ratio is 30~30.
It may be about 75%.

By the way, when a test pattern is recorded on the recording medium 2 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 of the test pattern is not read by the density unevenness reading unit 14 until the state of the density unevenness of the test pattern recorded by each recording head has stabilized. 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. 16). Then, after the density unevenness of the test pattern becomes stable, the recording medium is transported at timing i, and stopped when pattern C reaches the reading device, and at timing j, the reading sensor 17 is driven to read the recording medium. The unit 14 reads the density unevenness of the 0 color test pattern. Thereafter, the density unevenness of each color of M, Y, and 8 is read in the same manner at timing kβ1m.

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 seconds was sufficient.

FIG. 23 is a timing chart showing another example of the operation of the device of this example. In this operation example, with respect to the conveying speed Vl when conveying the recording medium 2 to the recording position, the recording of the test pattern by the recording head is not completed at time g'), and the recording medium is conveyed to the density unevenness reading unit 14. The actual paper conveyance speed V is decelerated so that v+>v
m, and by this, the 22nd
The same effect as shown in the figure can be obtained.

After fixing stabilization as described above, step S1 in FIG.
In step 5, uneven reading processing is performed. That is, each unevenness is read from the test pattern recorded for each color, and the unevenness correction data for each head is rewritten.

However, in this example, although the unevenness reading sensor 73 is a single sensor, the reading output of the sensor generally changes depending on the color. For example, when using a sensor whose spectral sensitivity is close to the visual sensitivity, as is commonly used, the read output density is the thickest for B and decreases in the order of C, M, and Y. For example, BK:C:M :Y 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, assume that the output for C is one times the output for BK. The average density in head IBK is OD, the density at the target ejection port is 0DllKn,
The average density within the head IC is ODC, and the density of the target ejection port of the 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 0DIII, Dcn = K+ X 0Daxn
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 ODc,, =X+(ODgx 0DIXn
), and this value for C is three times that for BK. Based on this value, correction data for the target ejection port is calculated, but even though the density unevenness of the heads is the same,
A problem arises in that the final correction amount is different for BK and C.

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 t and performing unevenness correction based on it.

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

In this way, for example, in the above example, +X to l/
(ODc−ODcj”l/ni+ (K+X (ODmx
ODagn)1=ODmK-0DSK.

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. 24, amplifiers 135G, 135M, 135 amplify the read signal of each color.
Y, 1358K are provided, and the sensor output values of the read signals of each color as shown in Fig. 25A are adjusted to be almost equal as shown in Fig. 25B, so that the read signal when the read signal is A/D converted. The overall width can be set narrowly. Therefore, the resolution of read data within 8 bits can be increased, and reading accuracy can be further improved.

Based on the above, unevenness correction is performed in step S17 in FIG. That is, from the signals 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 R1, Ri,...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 C,=log(R-/Ro) (R, is a constant such that R0≧R; l≦n≦N).

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

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

ΔC,=C/Cn Next, the signal correction amount (ΔS) according to (ΔC). Δ5
It is determined by ll=A X△C1.

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

Next, a selection signal for the correction straight line to be selected according to ΔSo is obtained, and unevenness correction signals having 61 types of values from "0" to "60" are stored in the 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. 16, 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%, but preferably 75% or less and 25% or more, and optimally, it is preferable to form the test pattern with a printing duty of 50%. This is because it is most suitable for a method of optically obtaining reflection density, and allows minute changes in density to be obtained as appropriate to the print 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.

Furthermore, the data related to the test pattern may be provided from the host device for the configuration shown in FIG.
4. The test pattern data may be provided by the configuration shown in FIG. 4 or by a test pattern data generating means integrated with the recording head 1.

(5) Other Embodiments The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the present invention. In the following, embodiments in which the present invention is applied to a serial printer will be mainly described. It goes without saying that the same control system and processing procedure as described above can be employed in the following examples as well. Further, although the cassette, ejection box, and cartridge shown in FIGS. 1A to 1C are not explained in the following examples, it goes without saying that they can be provided with similar configurations.

FIG. 26 shows a schematic diagram of an embodiment of an inkjet recording device in the form of a serial printer, in which the recording head 2
01C, 201M, 201Y, and 201tlK are supplied with cyan, magenta, yellow, and black inks from ink tanks (not shown) via ink tubes. And a recording head 201C.

The ink supplied to 201M, 201Y, and 201BK is driven by a print head driver or the like in response to a print signal according to print information from the main control unit, which is almost the same as shown in 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 conveying 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 from a predetermined position, cyan, cyan,
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.
8 by driving the conveyance roller 204 to move the arrow C.
Do it in the direction of.

In this embodiment, the recording heads 201C to 2018 are inkjet recording heads that form bubbles using heat and eject ink droplets using 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 recording head 1, the recovery device 220 performs a recovery operation of the recording head 1.
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 220 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 214 in the figure is a control circuit 215 that gives a uniform image signal to each of the recording heads 201C to 2018K to print on the recording medium 202. This is a density unevenness reading unit that reads a test pattern and outputs a reading signal, and is installed outside the image recording area. It is arranged so as to face the recording surface side of the recording medium in the direction of the lower sheet discharge side. Then, as described above, the recording medium 202 on which the test pattern is recorded is illuminated by the light source 218, and the recording density of the test pattern recorded on the recording paper by each recording head is read by the sensors 217G, 217M, 217Y, and 2178K. After the read signal of the test pattern recorded by each recording head read by each read sensor is converted into a digital signal by the A/D converter 236, the read signal is temporarily stored in the RAM 219.

FIG. 27 is a schematic diagram for explaining the reading section of this example.
In order to improve the accuracy of reading the density unevenness of the test pattern recorded on the recording medium 202 by the recording head,
A color filter 220R is provided on the recording medium side of the illumination light source 18.
220G and 220BL are provided, and R, G, and B are used for the C, M, and Y test patterns recorded on the recording medium 202.
, L light is irradiated. By irradiating the test patterns of each color of C, M, and Y with light of the complementary color in this way, each reading sensor 217C
, 217M, 217Y, and 2178 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.

Note that a holding member as described above may be provided to this configuration to prevent the paper from floating during reading.

FIG. 28 shows a schematic diagram of another embodiment in which the present invention is applied to a device in the form of a serial printer, in which each recording head 2
Similar to the above, a test pattern recorded on the recording medium 202 by applying uniform image signals to 01C, 201M, 201Y, and 2018K is read and a read signal is output. In this example, the uneven density reading unit 214 provided outside the image recording area is composed of a linear reading sensor 232 and a light source 233.

In other words, as in this example, the density unevenness reading unit 214 is arranged so as to face the recording surface side of the recording medium in the paper ejection direction below the recording head with respect to the conveyance direction of the recording medium 202 (direction of arrow C). If a holding member similar to that described above is provided, it becomes easy to maintain a constant distance between the recording medium 202 and the reading sensor 232 when reading a test pattern recorded on the recording medium 202, and Since only one reading sensor is sufficient, the device configuration can also be downsized.

In addition, as shown in FIG. 29, the reading line sensor 232
On the reading surface side of the recording medium 202, R, G,
Color filters 234R, 234G, 2 for each color of B and L
34B, the reading accuracy of the reading sensor 232 for each color of the print pattern can be improved. Then, as described in FIGS. 24 and 25, the read signals of each color from the read sensor 232 are sent to the amplifier 2350.
By amplifying by ~2358K, the resolution of the read data can be increased and the reading accuracy can be further improved.

FIG. 30 shows still another embodiment in which the present invention is applied to a serial printer type device. In this example,
Each recording head 201G, 201M, 201Y201
When the carriage carrying BK is scanned in the A and B directions to record the test pattern distribution on the recording medium 20, the test pattern is recorded by the recording head of one color each time the carriage 203 is scanned once. After 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 records the test pattern on the recording medium 202.

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 that stores the read data of the test pattern can be reduced to , the device configuration can be made smaller.

After the situation has calmed down, the test pattern recording sheet 213 is conveyed to the uneven density reading section.

(The following is a blank space.) Fig. 31 shows an outline of another embodiment in which the present invention is applied to a device in the form of a serial printer. A case is shown in which the density unevenness correction section 237 consisting of a pattern reading section is provided outside the image recording area.

Also in this embodiment, after the test pattern is recorded by each recording head on the test pattern recording sheet 231 of the test pattern recording section, the density unevenness of the test pattern becomes stable (6). The 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, the invention can be applied to the bubble jet method proposed by Canon. This provides excellent effects in 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
Generating thermal energy in the electrothermal transducer and producing film boiling on the thermally active surface of the recording head by applying at least one drive signal that corresponds to recorded information and provides a rapid temperature rise above nucleate boiling. As a result, bubbles in the liquid (ink) can be formed in a one-to-one correspondence with this drive signal, which is effective. The growth and contraction of this bubble causes the liquid (ink) to be ejected through the ejection opening to form a small droplet (at least one droplet).If this drive signal is in the form of a pulse, the growth and contraction of the bubble will occur immediately and appropriately. Because you will be exposed to
Particularly responsive liquid (ink) ejection can be achieved,
More preferred. This pulse-shaped drive signal is described in U.S. Pat. Nos. 4,463,359 and 4,345,262.
Those described in the specification 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. 59-1987 which discloses a configuration compatible with an open discharge part that absorbs pressure waves of thermal energy.
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, in a full-line type (full multi-type) recording head that has a length corresponding to the maximum width of a recording medium that can be recorded by a recording device, there are configurations in which multiple recording heads can be combined to meet the length, or they can be formed in one piece. The recording head may be configured as a single recording head.

In addition, even for serial types, there are recording heads that are fixed to the device body, or replaceable recording heads that are installed on the device body to enable electrical connection with the device body and supply of ink from the device body. chip type recording head,
Alternatively, the present invention is also effective when using a cartridge type recording head in which an ink tank is integrally provided in the recording head itself.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order 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. It may be something that can be done. That is, for example, the recording mode of the recording apparatus is not limited to a recording mode for only a mainstream color such as black, but may also be a recording mode in which the recording head is configured integrally or in a combination of multiple colors, The present invention is also extremely effective for devices equipped with at least one full color by color mixture.

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 even if the ink is in a liquid state when the recording signal is applied. Bye. In addition, the temperature increase caused by thermal energy can be actively prevented by using the energy to change the state of the ink from a solid state to a liquid state, or ink that solidifies when left standing is used to prevent ink evaporation. In any case, the ink is liquefied by applying thermal energy in accordance with the recording signal, and the liquid ink is ejected, or the ink has already begun to solidify by the time it reaches the recording medium. The present invention is also applicable when using ink that is liquefied only by energy. The ink used in this case is
Publication No. 4-56847 or JP-A-60-71260
As described in the above publication, the porous sheet may be held in a liquid or solid state 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, the image forming apparatus may take the form of an image output terminal for information processing equipment such as a computer, a copying device combined with a reader, etc., or a facsimile device 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.

[Effect of the Invention 1] As is clear from the above description, according to the present invention, by providing an ejection section dedicated to the recording medium for recording test patterns, the user can, for example, correct density unevenness at a desired time. Recording of a test pattern is started by pressing a key that instructs processing, and the operation of reading the pattern and ejecting the recording medium appears to the user as a black box. It becomes possible to perform effective correction without causing unnecessary discomfort such as wasted time.

[Brief explanation of the drawing]

1A to 1C are schematic configuration diagrams of image forming apparatuses according to embodiments of the present invention, and FIG. 2 is a schematic diagram for explaining its ink system. FIG. 3 is a reading unit in the second ffi and its scanning mechanism. FIGS. 4, 5, and 6 are schematic side views showing examples of the word structure of a portion for maintaining the distance between the reading unit and the recording medium, and FIGS. Figures 7B and 7C are explanatory diagrams for explaining how the dynamic range of the amount of light received by the sensor is expanded according to the color, and Figures 8, 9, and 1O are diagrams showing how the density unevenness of the test pattern is adjusted to that color. FIG. 11 is an explanatory diagram for explaining the mode of scanning drive of the reading unit according to the present example. FIGS. 12A, 12B, and 12c are An explanatory diagram for explaining fluctuations in read values according to fluctuations in the scanning speed of the reading unit, FIG. 13 is a block diagram showing an example of the configuration of the control system of the inkjet recording apparatus according to this example, and FIG. 14 shows the density FIG. 15 is an explanatory diagram for explaining the unevenness correction table used in this example; FIG. 16 is a flowchart showing an example of the unevenness correction processing procedure according to this example; FIG. 17 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, FIG. 18 is an explanatory diagram for explaining temperature changes in the recording head, and FIG. 19A 19B and 19C are explanatory diagrams for explaining a mode of stably correcting density unevenness regardless of temperature, and FIG. 20 shows a pattern for stabilizing ejection, a pattern for detecting ejection failure, FIG. 21 is an explanatory diagram showing an example in which a test pattern for density unevenness correction is recorded on a recording medium. FIG. FIG. 22 and FIG. 23 are timing charts showing two examples of the operation of this example device from recording a test pattern to reading density unevenness. FIG. 24 shows the output of the unevenness reading sensor according to color. FIG. 25A and FIG. 25B are explanatory diagrams illustrating the mode of correction, and FIG. 26 shows an example in which the present invention is applied to a serial printer type device. FIG. 27 is a schematic diagram showing the reading system unit; FIG. 28 is a schematic diagram showing another embodiment in which the present invention is applied to a serial printer type device; FIG. 29 is a schematic diagram of the reading system unit. , FIG. 30, and FIG. 31 are schematic diagrams showing two further embodiments in which the present invention is applied to a serial printer type device. 32A to 32E, FIG. 33, FIG. 34, and FIG. 35 are explanatory views for explaining the mode of density unevenness correction in a multi-nozzle head. 1, Ic, IM, IY, IBk, 201C, 201M,
201Y, 2018k... Recording head, 2.202... Recording medium, 3... Head holder, 5... Head holder moving mechanism, 7... Ink supply/circulation system unit, 9... Cap Unit, 11... Cap unit moving mechanism, 14, 214.
...reading unit, 15...reading unit scanning mechanism, 16...recording medium conveyance system drive section, 17...platen, 40...conveyance belt, 41...roller, 42...discharge roller , 43... Paper ejection tray, 45... Movable guide, 49... Ejection box, 50... Storage cassette, 51... Cartridge, 60... Reading head, 62... Light source, 63 .74... Lens, 73, 217... Reading sensor, 76... Housing, 77R, 77G, 77BL... Color filter, 78a
, 78b...Press roller, 80...Press member, 81.85...Transparent roller, 1oi.cpu. 102...ROM. 104...RAM. 106... Instruction input section, 113... Head temperature adjustment section, 114... Color filter switching drive section, 119219.
...RAM. 122C, 122M, 122Y, 1228k...
Unevenness correction table, 127, 236...A/D converter, 129G, 129M, 129Y, 1298k...
・Unevenness correction RAM, 135c, 135M, 135Y
, 1358, 235C, 235M, 235Y,
235G...Amplifier, 220...Recovery device. Fig. 7A Fig. 7B Fig. 0.5 10 1.5 Gradation Befun (Y) light intensity Fig. 70 fω (f + fω2 Pulse 7-Rich tb mounting U, fω3 f (H2) Fig. Fig. 12A Fig. 128 Fig. 12C Fig. 15 Fig. 16 Fig. 17 Fig. ■ ■ ■ Fig. 19A Figure 198 Figure 19c Figure 258 Bath Figure 33 Ukiha Figure 34 Figure 35

Claims (1)

[Scope of Claims] 1) A recording head having a plurality of recording elements arranged to form an image on a recording medium, and a signal generating means for causing the recording head to record a predetermined test pattern on the recording medium. , reading means for reading the test pattern formed on the recording medium by the recording head based on the signal generating means; correction means for correcting the recording head driving conditions based on the reading result; and the test pattern is a paper feed section that stores a recording medium to be recorded; and an ejection section that ejects the recording medium on which the test pattern is recorded, which is different from the ejection section for the recording medium on which images other than the test pattern are recorded. An image forming apparatus comprising: a discharge section; and a conveying means for conveying the recording medium in the paper feeding section to a recording position by the recording head, a reading position by the reading means, and the discharge section. 2) The discharge section is located inside the image forming apparatus,
The image forming apparatus according to claim 1, wherein the image forming apparatus is shielded from the outside. 3) The image forming apparatus according to claim 2, wherein the discharge section is made of an opaque member. 4) The image forming apparatus according to claim 3, wherein the discharge section is configured to be detachable from the image forming apparatus. 5) The paper feeding unit is located inside the image forming apparatus,
The image forming apparatus according to claim 1, wherein the image forming apparatus is shielded from the outside. 6) The image forming apparatus according to claim 1, wherein the paper feeding section is made of an opaque member. 7) The image forming apparatus according to claim 1, wherein the paper feeding section is configured to be detachably attached to the image forming apparatus. 8) The image forming apparatus according to claim 1, wherein the paper discharge section and the paper feed section are integrally constructed. 9) Image formation according to any one of claims 1 to 8, characterized in that a plurality of recording heads are provided corresponding to recording materials of different colors in order to perform multicolor recording. Device. 10) 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 that is used to cause film boiling in the ink to eject the ink. The image forming apparatus according to any one of claims 1 to 9. 11) In an image forming apparatus that forms an image on a recording medium using a recording head in which a plurality of recording elements are arranged, a signal generating means for causing the recording head to record a predetermined test pattern on the recording medium; reading means for reading a test pattern formed on a recording medium by a recording head based on the signal generating means; a correction means for correcting the recording head drive condition based on the reading result; a paper feed unit that stores a recording medium with the test pattern recorded thereon, and an output unit that discharges the recording medium on which the test pattern is recorded, which is different from the output unit for the recording medium on which images other than the test pattern are recorded. An image forming apparatus comprising: a conveying means for conveying a recording medium in the paper feeding section to a recording position by the recording head, a reading position by the reading means, and to the ejecting section. 12) 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 element used for causing film boiling in the ink to eject the ink. The image forming apparatus according to claim 11.