JP2021009242A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can prevent a reduction in the accuracy of image data of a test pattern caused by image reading means, and can calculate a correction value with high accuracy.SOLUTION: In an image forming apparatus comprising: image forming means; image reading means; test pattern forming means that controls the image forming means to form a test pattern on a recording medium; acquisition means that reads the test pattern on the recording medium with the image reading means to acquire the image data of the test pattern; and correction value calculation means that calculates a predetermined correction value for optimizing an image based on the image data of the test pattern, a reading operation is performed by the image reading means before the test pattern is formed on the recording medium.SELECTED DRAWING: Figure 17

Description

The present invention relates to an image forming apparatus.

Conventionally, an image forming means, an image reading means, a test pattern forming means for controlling the image forming means to form a test pattern on a recording medium, and a test pattern of the recording medium are read by the image reading means to obtain a test pattern. An image forming apparatus including an acquisition means for acquiring image data and a correction value calculation means for calculating a predetermined correction value for optimizing an image based on the image data of a test pattern is known.

Patent Document 1 describes an image forming apparatus that calculates an exposure correction value, which is a correction value, based on the image density of a test pattern read by an image reading means. Based on the calculated exposure compensation value, the drive of each LED element of the LED array as a latent image forming means is controlled, and the direction of the LED elements is the main scanning direction which is the direction orthogonal to the transport direction of the recording medium. The image is optimized by suppressing density unevenness.

However, due to the image reading means, the image data of the test pattern cannot be acquired with high accuracy, and there is a possibility that the correction value with high accuracy cannot be calculated.

In order to solve the above-mentioned problems, the present invention uses an image forming means, an image reading means, a test pattern forming means for controlling the image forming means to form a test pattern on a recording medium, and the image reading means. An acquisition means for reading the test pattern of the recording medium to acquire image data of the test pattern, and a correction value calculation means for calculating a predetermined correction value for optimizing an image based on the image data of the test pattern. The image forming apparatus provided with the above is characterized in that the reading operation of the image reading means is performed before the test pattern is formed on the recording medium.

According to the present invention, it is possible to suppress a decrease in accuracy of the image data of the test pattern caused by the image reading means, and it is possible to calculate a highly accurate correction value.

The schematic block diagram which shows the image forming apparatus which concerns on embodiment. An enlarged configuration diagram showing an enlarged view of the photoconductor and its surrounding configuration in the image forming apparatus. An enlarged configuration diagram showing the internal configuration of the image reading unit from the side. The block diagram which shows a part of the electric circuit of density unevenness correction control in a main scanning direction. The control flow diagram of the density unevenness acquisition control in the main scanning direction. (A) is a graph showing an example of the first light amount correction value, and (b) is a graph showing the light amount distribution in the main scanning direction when each LED element is controlled based on the first light amount correction value. The figure which shows an example of the test pattern formed on the recording sheet. The control flow diagram of the image formation processing of this embodiment. (A) is a graph showing an example of density data stored in the storage unit, and (b) is density data (solid line), density mean value (broken line), and second light amount correction value (dashed line). And the graph showing. (A) is a graph illustrating the relationship between the first light amount correction value (broken line), the second light amount correction value (dashed line), and the third light amount correction value (solid line), and (b) is the third light amount correction value (solid line). A graph showing the density of a test pattern when a latent image of the test pattern is formed based on the correction value. The figure which shows the state which the initial screen (home screen) is displayed on the display part of the operation display part. The figure which shows the state which the setting screen is displayed on the display part of the operation display part. The figure which shows the state which the image adjustment inquiry screen is displayed on the display part of the operation display part. The figure which shows the state which the pop-up screen prompting to set the recording sheet which formed the test pattern in the display part of the operation display part is displayed in the image reading part. The schematic diagram which shows the state which the contact glass of an image reading part is dirty. Density data obtained from the read data obtained by reading the portion of the broken line T1 shown in FIG. The control flow diagram of the density unevenness acquisition control in the main scanning direction which performs a reading operation before forming a test pattern. The figure explaining an example of setting of the test pattern formation position. A calculation flow chart for calculating the second light intensity correction value. A perspective view showing an image forming apparatus and a reading plate included in the image forming apparatus. (A) is a diagram showing a state in which the C color test pattern overlaps with the dirt on the contact glass. (B) is a diagram showing a state in which the formation positions of the test patterns are set so that the four-color test patterns do not overlap with the stains on the contact glass.

Hereinafter, an electrophotographic image forming apparatus for forming an image by an electrophotographic method to which the present invention is applied will be described.

First, the basic configuration of the image forming apparatus according to the embodiment will be described. FIG. 1 is a schematic configuration diagram showing an image forming apparatus 200 according to an embodiment. In the figure, the image forming apparatus 200 includes a photoconductor 1 as a latent image carrier, a plurality of paper feed cassettes 100 as recording medium mounting means detachably and detachably attached to a main body housing 50, and the like. ing. Inside each paper cassette 100, a plurality of recording media S are housed in a bundle of sheets.

The recording sheet S in the paper feed cassette 100 is sent out from the cassette by the rotational drive of the feed roller 35 described later, passes through the separation nip described later, and then reaches the feed path 42. After that, it is sandwiched between the transport nips of the pair of feed relay rollers 41, and is transported in the feed path 42 from the upstream side to the downstream side in the transport direction. A pair of resist rollers 49 are arranged near the end of the supply path 42. The recording sheet S is temporarily suspended with its tip abutting against the resist nip of the resist roller 49. At the time of the abutting, the skew of the recording sheet S is corrected.

The resist roller 49 starts rotational driving at a timing when the recording sheet S can be superimposed on the toner image on the surface of the photoconductor 1 by the transfer nip described later, and sends the recording sheet S toward the transfer nip. At this time, the feed / relay relay roller 41 starts the rotary drive at the same time, and resumes the transport of the recording sheet S which has been temporarily stopped.

In addition, the main body housing 50 holds a manual feeding unit 26 including a manual feeding tray 27 as a recording medium mounting means, a manual feeding roller 28, and a separation pad 29. The recording sheet S manually fed to the manual feed tray 27 of the manual paper feed unit 26 is fed out from the manual feed tray 27 by the rotational drive of the manual feed feed roller 28. Then, after passing through the separation nip due to the contact between the manual feed roller 28 and the separation pad 29, the paper enters the region on the upstream side of the resist roller pair 11 in the paper feed path 20. Then, similarly to the recording sheet S sent out from the paper feed cassette 100, it is sent to the transfer nip after passing through the resist roller pair 11.

An image reading unit 60, which is an image reading means, is attached to the upper part of the main body housing 50. Further, an automatic document transfer device 61 is attached to the image reading unit 60. The automatic document transfer device 61 separates the documents one by one from the document bundle placed on the document tray 61a and automatically feeds the documents to the contact glass on the image reading unit 60. The image reading unit 60 reads the document conveyed on the contact glass by the automatic document conveying device 61.

FIG. 2 is an enlarged configuration diagram showing an enlarged view of the photoconductor 1 and its surrounding configuration in the image forming apparatus 200. Around the drum-shaped photoconductor 1 that is rotationally driven in the counterclockwise direction in the figure, a recovery screw 3, a cleaning blade 2, a charging roller 4, a latent image writing device 7 as a latent image forming means, and a developing means as a developing means. A device 8, a transfer roller 10 as a transfer means, and the like are arranged. The charging roller 4 provided with the conductive rubber roller portion rotates while in contact with the photoconductor 1 to form a charging nip. A charging bias output from the power supply is applied to the charging roller 4. As a result, in the charging nip, an electric discharge is generated between the surface of the photoconductor 1 and the surface of the charging roller 4, so that the surface of the photoconductor 1 is uniformly charged.

The latent image writing device 7 includes an LED array, and image data input from a personal computer or image data of a document read by an image reading unit 60 on a uniformly charged surface of the photoconductor 1. Light irradiation with LED light based on is performed. Of the uniformly charged background portion of the photoconductor 1, the region irradiated with light attenuates the potential. As a result, an electrostatic latent image is formed on the surface of the photoconductor 1.

The electrostatic latent image passes through the developing region facing the developing device 8 as the photoconductor 1 is rotationally driven. The developing apparatus 8 has a circulating transport section and a developing section, and the circulating transport section contains a developer containing toner and a magnetic carrier. The circulation transport unit includes a first screw 8b for transporting the developer for supplying to the developing roller 8a, which will be described later, and a second screw 8c for transporting the developer in an independent space located directly below the first screw 8b. doing. Further, it also has an inclined screw 8d for transferring the developing agent from the second screw 8c to the first screw 8b. The developing rollers 8a, the first screw 8b, and the second screw 8c are arranged in a posture parallel to each other. On the other hand, the inclined screw 8d is arranged in an inclined posture from them.

The first screw 8b conveys the developer from the back side to the front side in the direction orthogonal to the paper surface in the figure as it is driven to rotate. At this time, a part of the developing agent is supplied to the developing rollers 8a arranged to face each other. The developer conveyed by the first screw 8b to the vicinity of the front end in the direction orthogonal to the paper surface in the figure is dropped onto the second screw 8c.

The second screw 8c receives the used developer from the developing roller 8a, and conveys the received developer from the back side to the front side in the direction orthogonal to the paper surface in the figure along with its own rotational drive. .. The developer conveyed by the second screw 8c to the vicinity of the front end in the direction orthogonal to the paper surface in the figure is delivered to the inclined screw 8d. Then, along with the rotational drive of the inclined screw 8d, it is conveyed from the front side to the back side in the direction orthogonal to the paper surface in the figure, and then becomes the first screw 8b near the end portion on the back side in the same direction. Delivered.

The developing roller 8a includes a rotatable developing sleeve made of a tubular non-magnetic member, and a magnet roller fixed in the sleeve so as not to rotate with the developing sleeve. Then, a part of the developing agent conveyed by the first screw 8b is pumped up on the surface of the developing sleeve by the magnetic force generated by the magnet roller. The layer thickness of the developer carried on the surface of the developing sleeve is regulated as it passes around the surface of the developing sleeve and at the opposite position between the sleeve and the doctor grade. After that, it moves while rubbing against the surface of the photoconductor 1 in the developing region facing the photoconductor 1.

A development bias having the same polarity as the background potential of the toner or the photoconductor 1 is applied to the development sleeve. The absolute value of this development bias is larger than the absolute value of the latent image potential and smaller than the absolute value of the background potential. Therefore, in the developing region, a developing potential that electrostatically moves the toner from the sleeve side to the latent image side acts between the electrostatic latent image of the photoconductor 1 and the developing sleeve. On the other hand, between the background portion of the photoconductor 1 and the developing sleeve, a background potential that electrostatically moves the toner from the background portion side to the sleeve side acts. As a result, in the developing region, toner is selectively adhered to the electrostatic latent image of the photoconductor 1, and the electrostatic latent image is developed.

The developer that has passed through the developing region enters the facing region between the sleeve and the second screw 8c as the developing sleeve rotates. In this facing region, a repulsive magnetic field is formed by two magnetic poles having different polarities among the plurality of magnetic poles provided in the magnet roller. The developer that has entered the opposite region is separated from the surface of the developing sleeve by the action of the repulsive magnetic field and is collected on the second screw 8c.

The developer conveyed by the inclined screw 8d contains the developer recovered from the developing roller 8a, and the developer contributes to the development in the developing region, so that the toner concentration is lowered. The developing device 8 includes a toner concentration sensor that detects the toner concentration of the developer conveyed by the inclined screw 8d. Based on the detection result by the toner concentration sensor, a replenishment operation for replenishing the developer conveyed by the inclined screw 8d is executed as necessary.

A toner cartridge 9 is arranged above the developing device 8. In the toner cartridge 9, the toner contained therein is agitated by an agitator 9b fixed to the rotating shaft member 9a. Then, the toner replenishment member 9c is rotationally driven in response to the replenishment operation signal output from the main body control unit 52 (see FIG. 4), so that the amount of toner corresponding to the rotational drive amount is supplied to the first screw of the developing device 8. Replenish 8b.

The toner image formed on the photoconductor 1 by the development enters the transfer nip where the photoconductor 1 and the transfer roller 10 serving as the transfer means come into contact with each other as the photoconductor 1 rotates. A charging bias having a polarity opposite to the latent image potential of the photoconductor 1 is applied to the transfer roller 10, whereby a transfer electric field is formed in the transfer nip.

As described above, the resist roller 49 feeds the recording sheet S toward the transfer nip at a timing when it can be superimposed on the toner image on the photoconductor 1 in the transfer nip. The toner image on the photoconductor 1 is transferred to the recording sheet S which is brought into close contact with the toner image by the transfer nip by the action of the transfer electric field and the nip pressure.

The transfer residual toner that has not been transferred to the recording sheet S adheres to the surface of the photoconductor 1 after passing through the transfer nip. The transfer residual toner is scraped off from the surface of the photoconductor 1 by the cleaning blade 2 in contact with the photoconductor 1, and then sent to the outside of the unit casing by the recovery screw 3. The transfer residual toner discharged from the unit casing is sent to the waste toner bottle by the waste toner transfer device.

The surface of the photoconductor 1 cleaned by the cleaning blade 2 is statically removed by the static elimination means, and then uniformly charged again by the charging roller 4. Foreign substances such as toner additives and toner that cannot be completely removed by the cleaning blade 2 adhere to the charging roller 4 that is in contact with the surface of the photoconductor 1. This foreign matter is transferred to the cleaning roller 5 that is in contact with the charging roller 4, and then scraped off from the surface of the cleaning roller 5 by the scraper 6 that is in contact with the cleaning roller 5. The scraped foreign matter falls on the recovery screw 3 described above.

In FIG. 1, the recording sheet S that has passed through the transfer nip where the photoconductor 1 and the transfer roller 10 come into contact with each other is sent to the fixing device 44. The fixing device 44 forms a fixing nip by contact between the fixing roller 44a containing a heat generating source such as a halogen lamp and the pressure roller 44b pressed toward the fixing roller 44a. A toner image is fixed on the surface of the recording sheet S sandwiched between the fixing nips by the action of heating or pressurizing. After that, the recording sheet S that has passed through the fixing device 44 passes through the paper ejection path 45, is sandwiched between the paper ejection nips of the paper ejection roller 46, and is ejected to the outside of the machine by the paper ejection roller 46. The discharged recording sheet S is stacked on a stack portion 51 provided on the upper surface of the main body housing 50.

FIG. 3 is an enlarged configuration diagram showing the internal configuration of the image reading unit 60 from the side thereof.
As shown in the figure, a movable first traveling body 162 (see arrow X1 in the figure) and a movable second traveling body 163 (see arrow X2 in the figure) are provided in the housing of the image reading unit 60. ing. The first traveling body 162 includes a first mirror 162a. The second traveling body 163 includes a second mirror 163a and a third mirror 163b.

A lighting device 165 and an imaging device 164 are provided in the housing of the image reading unit 60. The lighting devices 165 are arranged on both sides of the image pickup device 164 in the main scanning direction (direction orthogonal to the paper surface). The image pickup device 164 includes an imaging lens 164a and an image pickup element 164b such as a CCD image sensor.

Each illuminating device 165 includes a light source 165a, an integrated lens 165d, an illuminating lens 165c, a condenser lens 165e, and a parabolic mirror 165b. The light source 165a is an LED array and irradiates a light beam toward the parabolic mirror 165b. The luminous flux emitted toward the parabolic mirror 165b is reflected by the parabolic mirror 165b toward the condenser lens 165e.

The condensing lens 165e is a lens that divides the light beam from the light source 165a in the main scanning direction and condenses the light beam in order to allow the illumination lens 165c to transmit the entire light beam, and the cylinder lenses are arranged side by side in the main scanning direction. It is an array.

The illumination lens 165c is a lens for irradiating the light beam emitted from the light source 165a with respect to the illumination target surface of the document D set on the contact glass 161 in the main scanning direction, and is a cylinder lens like the condenser lens 165e. It consists of an array.

The integrated lens 165d is a lens for superimposing a luminous flux divided by an illumination lens 165c and a condenser lens 165e on an illumination target surface of a document D, and is a normal lens having an optical axis axially symmetric.

The light flux of the light source 165a that has passed through the integrated lens 165d is reflected by the third mirror 163b, the second mirror 163a, and the first mirror 162a, and is applied to the illuminated surface of the document D.

When reading the image of the document D placed on the contact glass 161, the first traveling body 162 and the second traveling body 163 are moved from the left side to the right side in the drawing. Then, in the process of moving the first traveling body 162 and the second traveling body 163 from the left side to the right side in the drawing, the light emitted from the light source 165a is reflected by the document D placed on the contact glass, and a plurality of light sources D are reflected. The image of the document D is read by the image pickup device 164b via a reflection mirror, an imaging lens 164a, or the like.

The image sensor 164b photoelectrically converts the reflected light image of the imaged document D and outputs an analog image signal which is a scanned image. The analog image signal output from the image sensor 164b is converted into a digital image signal by an analog / digital converter, and each image processing (binarization, multivalued, gradation) is performed on a circuit board equipped with an image processing circuit. Processing, scaling processing, editing processing, etc.) are performed.

In the figure, G indicates deposits such as dust and dirt adhering to the mirror, and the dashed arrow F in the figure indicates flare light among the light diffusely reflected by the deposit G adhering to the mirror. It shows the path of the light incident on the element 164b.

In the present embodiment, the latent image writing device 7 includes an LED array, and each LED element of the LED array is turned on based on the image data and the image data of the document read by the image reading unit 60 to be exposed to light. An electrostatic latent image is formed on the surface of the body 1. In the LED array, the shape, characteristics, etc. of each LED element may vary, the arrangement of the LED chips may be slightly misaligned, or the optical characteristics of the lens array may change periodically or aperiodically. Therefore, even if the same driving power is applied to each LED element, the amount of emitted light is not the same. As a result, the image formed on the recording sheet S has density unevenness in a direction orthogonal to the transport direction of the recording sheet S (hereinafter, referred to as a main scanning direction). As described above, if there is density unevenness in the main scanning direction, vertical stripes, vertical bands, etc. extending in the transport direction of the recording sheet S (hereinafter referred to as the sub-scanning direction) are generated, and the image quality is deteriorated.

Therefore, the light amount of each LED element is measured in advance using a predetermined device, and the first light amount correction value for correcting the drive power applied to each LED element is obtained so that each LED element has the same amount of emitted light. Remember. Then, by controlling the LED array based on the first light amount correction value, it is possible to suppress density unevenness in the main scanning direction caused by the LED array.

However, when the density unevenness in the main scanning direction is caused not only by the LED array but also by an image forming engine such as the photoconductor 1, the charging roller 4, the developing device 8, the transfer roller 10, and the fixing device 44. There is. Therefore, in the present embodiment, in order to eliminate the density unevenness in the main scanning direction caused by the image drawing engine, the LED array is controlled based on the first light amount correction value to record the test pattern. The test pattern formed on the recording sheet S is read by the image reading unit 60. Next, based on the read data read by the image reading unit 60, the density unevenness in the main scanning direction caused by the image drawing engine is obtained. Next, a second light amount correction value for correcting the emitted light amount (applied power) of each LED element is calculated based on the obtained density unevenness in the main scanning direction. Then, based on the first light amount correction value that suppresses the density unevenness in the main scanning direction caused by the LED array 74 and the second light amount correction value that suppresses the density unevenness in the main scanning direction caused by the image drawing engine. Then, the third light intensity correction value is calculated. At the time of image formation, by controlling the LED array and writing a latent image on the photoconductor 1 based on this third light amount correction value, the density unevenness in the main scanning direction caused by the LED array and the image drawing engine are caused. It is possible to form a good image in which both density unevenness in the main scanning direction due to the LED is suppressed.

FIG. 4 is a block diagram showing a part of an electric circuit for density unevenness correction control in the main scanning direction.
As shown in FIG. 4, the LED array 74 included in the latent image writing device 7 includes a plurality of LED elements 74b arranged side by side in the main scanning direction, and an IC (Integrated Circuit) driver for driving each LED element 74b. The 74a has a ROM (Read Only Memory) 74c that stores a first light amount correction value for correcting variations in the amount of light emitted from the LED array 74.

The main body control unit 52, which controls the entire image forming apparatus 200, has image density data in the main scanning direction as image data based on the reading data of the test pattern formed on the recording sheet S read by the image reading unit 60. Based on the image density acquisition unit 86 as the acquisition means for acquiring the image density, the storage unit 87 that stores the image density data acquired by the image density acquisition unit 86, and the image density data stored in the storage unit 87, each LED element It has a light amount correction value calculation unit 88 as a correction value calculation means for calculating a second light amount correction value for correcting a light emission amount.

Further, the main body control unit 52 includes a first light amount correction value acquisition unit 85 that acquires the first light amount correction value from the LED array 74, a first light amount correction value acquired by the first light amount correction value acquisition unit 85, and a light amount. A calculation unit 82 is also provided as a correction value calculation means for calculating the third light amount correction value used at the time of image formation based on the second light amount correction value calculated by the correction value calculation unit 88. Further, the main body control unit 52 has a correction value transfer unit 83 that transfers the third light amount correction value calculated by the calculation unit 82 to the LED array 74 at the time of image formation. Further, the main body control unit 52 controls an image forming engine such as the photoconductor 1, the charging roller 4, the developing device 8, the transfer roller 10, and the fixing device 44 to form an image on the recording sheet S. The image forming processing unit 84 It has. The image forming processing unit 84 functions as a test pattern forming means for forming a test pattern on the recording sheet S.

In addition, the main body control unit 52 also has a stain position specifying unit 90 that specifies the position of the stain on the contact glass from the image density data acquired by performing a reading operation before reading the test pattern.

FIG. 5 is a control flow diagram of density unevenness acquisition control in the main scanning direction.
First, the first light amount correction value acquisition unit 85 of the main body control unit 52 acquires the first light amount correction value stored in the ROM 74c of the LED array 74 (S1). As described above, the first light amount correction value is obtained by measuring the light amount of each LED element of the LED array 74 in advance using a predetermined device, and each LED element 74b so that each LED element has the same amount of emitted light. This is data for correcting the drive power applied to the LED.

Next, the main body control unit 52 transfers the acquired first light amount correction value to the IC driver 74a of the LED array 74 by the correction value transfer unit 83 (S2). Further, the image forming processing unit 84 transmits a control signal to each device constituting the image forming engine to execute the image forming process for forming the test pattern (S3). When the IC driver 74a of the LED array 74 receives the control signal and the test pattern data from the image forming processing unit 84, the IC driver 74a controls each LED element 74b based on the first light amount correction value received from the correction value transfer unit 83. , A latent image of the test pattern is formed on the surface of the photoconductor 1.

FIG. 6A is a graph showing an example of the first light amount correction value, and FIG. 6B is a light amount in the main scanning direction when each LED element 74b is controlled based on the first light amount correction value. It is a graph which shows the distribution.
As shown in FIG. 6A, the portion where the light amount correction value is large in the main scanning direction is the portion where the amount of emitted light is small. Therefore, the light amount correction value (driving power) is increased at such a location, and the light amount is set as the reference light amount. On the other hand, a place where the light amount correction value (correction drive power) is small is a place where the amount of emitted light is large. Therefore, the light amount correction value (correction drive power) is reduced at such a location, and the light amount is set as the reference light amount. As a result, as shown in FIG. 6B, the amount of emitted light can be made substantially uniform in the main scanning direction.

After that, the latent image of the test pattern is developed by the developing device 8, transferred to a predetermined position on the recording sheet S by the transfer roller 10, and fixed on the recording sheet S by the fixing device 44. Then, when the recording sheet S on which the test pattern is formed is ejected and printing is completed (Yes in S4), the process proceeds to the acquisition process of the density data of the test pattern (S5).

FIG. 7 is a diagram showing an example of a test pattern 171 formed on the recording sheet S.
As shown in FIG. 7, the test pattern 171 is a halftone image uniform in all of the sub-scanning direction (conveying direction) and the main scanning direction (direction orthogonal to the conveying direction) of the recording sheet S. By using a halftone image as the test pattern, it is possible to satisfactorily detect both a part brighter than the specified brightness (the image density is lighter) and a part darker than the specified brightness (the image density is darker), which is preferable. .. Further, the length of the recording sheet forming the test pattern in the main scanning direction is preferably set to the maximum size (3/4 or more) in the main scanning direction that can be formed by the image forming apparatus 200. Further, it is preferable that the test pattern 171 formed on the recording sheet is fully formed in the main scanning direction so that there is no margin. As a result, the correction can be applied to the end in the main scanning direction as well.

If the test pattern 171 formed on the recording sheet has density unevenness in the main scanning direction, vertical stripes, vertical bands, etc. extending in the sub-scanning direction are generated. The test pattern 171 is a latent image formed by controlling each LED element 74b based on the first light intensity correction value shown in FIG. 6A, and is shown in FIG. 6B. As described above, the amount of light emitted from each LED element 74b to the surface of the photoconductor is substantially uniform in the main scanning direction. Therefore, in the main scanning direction, the surface of the photoconductor is attenuated substantially uniformly to a certain potential, so that the density unevenness in the main scanning direction of the test pattern is mainly caused by a factor different from that of the LED array 74. ..

After printing the test pattern 171 on the recording sheet S, the main body control unit 52 sets the recording sheet S on which the test pattern 171 is formed on the operation display unit 89 of the image forming apparatus 200 or the like in the image reading unit 60, and sets the test pattern. Instructs the reading of 171. When the operator sets the recording sheet S on which the test pattern 171 is formed in the image reading unit 60 and starts reading the image based on the instruction of the operation display unit, the image density acquisition unit 86 of the main body control unit 52 starts reading the image. , Image density data in the main scanning direction, which is image density information, is acquired (S5). Then, the acquired image density data is stored in the storage unit 87 (S6).

As an example of the method of acquiring the image density data in the image density acquisition unit 86, as shown in FIG. 7, the test pattern 171 is divided into a plurality of areas 1 to n having a predetermined area (Xdot × Ydot), and the area 1 Examples thereof include a method of obtaining an average concentration every ~ n.

For example, when Xdot = 1dot and the density data in the main scanning direction of the A4 size recording sheet S is acquired at a resolution of 600 dpi, image density data for an area of 210 mm × (600 dpi / 25.4 mm) ≈4960 can be obtained. Be done. When the image density data is represented by 8 bits (0-255), a storage capacity of 4960 × 8 bits = 4.96 kByte is required. If Xdot = 2dot or 4dot, the required storage capacity is 1/2 or 1/4, and the storage unit 87 (see FIG. 4) can be constructed at low cost. However, if the Xdot is made too large, the density of a wide area is averaged, so that the accuracy of the density information is lowered. The value of Xdot and the resolution of the image density data may be appropriately determined according to the image forming apparatus. For example, the value of Xdot may be determined after grasping whether the density unevenness in the main scanning direction is dominated by the high-frequency density unevenness or the low-frequency density unevenness.

On the other hand, since the Ydot values in each area 1 to n do not affect the storage capacity, the Ydot value is the density unevenness in the sub-scanning direction (conveyance direction) in the target image forming apparatus (one rotation cycle of the photoconductor 1, transfer). By taking into account periodic density unevenness caused by one rotation cycle of the roller 10 and one rotation cycle of the developing roller 8a, or non-periodic density unevenness), the density detection result may be set so as not to cause a large difference. Good. However, if the value of Ydot is too large, it takes time to acquire the density data. Therefore, it is preferable to determine the value of Ydot in consideration of the balance between the required accuracy and the data acquisition time (processing capacity).

The density unevenness acquisition control in the main scanning direction shown in FIG. 5 is performed at an arbitrary timing by a user or a serviceman, at a timing when members constituting an image drawing engine such as the photoconductor 1 and the latent image writing device 7 are replaced, and image formation. This is done when the power is turned on to the device. By performing this every time the power is turned on, there is an advantage that an image having no density unevenness can always be output in the main scanning direction. On the other hand, in the density unevenness acquisition control of the present embodiment, the user sets the recording sheet S on which the test pattern 171 is formed in the image reading unit 60 and causes the user to read the test pattern 171. Therefore, some users find it bothersome to carry out each time the power is turned on. Therefore, it is preferable that the user can set not to perform the density unevenness acquisition control at the time of turning on the power.

FIG. 8 is a control flow diagram of the image forming process of the present embodiment.
As shown in FIG. 8, when the main body control unit 52 receives the image formation start signal, first, the density data stored in the storage unit 87 is read out, and based on the density data read out by the light intensity correction value calculation unit 88. , The second light amount correction value is calculated (S11).

FIG. 9 (a) is a graph showing an example of the density data stored in the storage unit 87, and FIG. 9 (b) shows the density data (solid line), the density average value (broken line), and the second light amount correction. It is a graph which showed the value (dashed line). The density average value shown in FIG. 9B shows the average value of the image density indicated by the image density data.
Due to factors other than the LED array, density unevenness occurs in the main scanning direction as shown in FIG. 9A. The density unevenness in the main scanning direction is the density unevenness in the main scanning direction mainly due to the image forming engine (photoreceptor 1, charging roller 4, developing device 8, transfer roller 10 and fixing device 44).

As shown in FIG. 9B, the second light amount correction value is calculated based on the image density average value (the average value of the image density of the test pattern) and the image density at each position in the main scanning direction indicated by the image density data. To. As shown in FIG. 9B, the position where the image density shown by the broken line in the figure is light (bright) is corrected so that the amount of emitted light of the LED element 74b corresponding to the position is large, and is darker than the average density. The (dark) position is corrected so that the amount of emitted light of the LED element corresponding to the position is reduced. Specifically, for a position where the density is lower (brighter) than the average density, a correction value for increasing the drive power applied to the LED element 74b corresponding to that position is obtained, and the density is darker (darker) than the average density. For the position, a correction value for reducing the driving power applied to the LED element 74b corresponding to the position is obtained.

After the light amount correction value calculation unit 88 calculates the second light amount correction value in this way, the calculation unit 82 calculates the third light amount correction value used for image formation (S12 in FIG. 8). Specifically, the third light amount correction is based on the second light amount correction value calculated by the light amount correction value calculation unit 88 and the first light amount correction value acquired from the LED array 74 by the first light amount correction value acquisition unit 85. Calculate the value. Then, the calculated third light amount correction value is transferred (S13) to the IC driver 74a of the LED array 74 by the correction value transfer unit 83. After the correction value transfer unit 83 transfers the data to the IC driver 74a of the LED array 74, an image formation process is performed based on the image data (S14). In this image forming process, the IC driver 74a forms a latent image on the surface of the photoconductor based on the third light amount correction value transferred from the correction value transfer unit 83 and the image data.

FIG. 10A is a graph illustrating the relationship between the first light amount correction value (broken line), the second light amount correction value (dashed line), and the third light amount correction value (solid line), and FIG. 10B is a graph. It is a graph which shows the density of the test pattern when the latent image of the test pattern is formed based on the 3rd light quantity correction value.
As shown in FIG. 10A, the third light amount correction value is calculated by adding the first light amount correction value and the second light amount correction value. The calculation method of the third light amount correction value is not limited to this, and may be appropriately determined by the calculation method of the first light amount correction value and the second light amount correction value.

The third light amount correction value is the first light amount correction value that corrects the density unevenness in the main scanning direction caused by the LED array 74 and the second light amount correction value that corrects the density unevenness in the main scanning direction mainly due to the image formation engine. It is calculated based on the light intensity correction value. Therefore, the image formed based on the third light amount correction value is an image in which the density unevenness in the main scanning direction caused by the LED array 74 and the image forming engine is suppressed. Therefore, the image in which the latent image is formed with the corrected light amount based on the third light amount correction value becomes an image having a uniform density distribution in the main scanning direction as shown in FIG. 10B, and has vertical streaks and vertical streaks. A high-quality image without vertical bands can be obtained.

In the present embodiment, in the density unevenness acquisition control in the main scanning direction shown in FIG. 5 above, the density unevenness in the main scanning direction of the test pattern 171 is acquired and ended, but the second light amount correction value You may go to the calculation. When the calculation of the second light amount correction value is performed, the second light amount correction value is stored in the storage unit 87. Further, in the density unevenness acquisition control in the main scanning direction, the third light amount correction value may be calculated. When the calculation of the third light amount correction value is performed, the third light amount correction value is stored in the storage unit 87. Further, in this case, at the time of image formation, it is not necessary to acquire the first light amount correction value from the LED array, and the third light amount correction value stored in the storage unit 87 is transmitted to the IC driver 74a of the LED array 74. ..

Further, based on the detection result of the test pattern 171, it is determined whether or not the correction of the density unevenness in the main scanning direction is necessary, and if it is determined that the correction of the density unevenness in the main scanning direction is not necessary, image formation is performed. At times, the LED array 74 may be controlled based on the first light amount correction value without calculating the third light amount correction value.

In addition, when the user or the service person looks at the image output after correcting the density unevenness in the main scanning direction and determines that the density unevenness in the main scanning direction is not improved or deteriorated, the third step is taken. The user or the service person may be able to set so that the light amount correction value is not calculated. When the user or the serviceman sets not to calculate the third light amount correction value, for example, the density data stored in the storage unit 87 is deleted, and the LED array 74 is controlled based on the first light amount correction value. To do.

Further, the test pattern 171 was formed without using the first light amount correction value, and the main scanning direction density unevenness caused by the LED array 74 and the main scanning direction density unevenness caused by other than the LED array were superimposed. The density unevenness in the main scanning direction is acquired from the read data. Then, the third light amount correction value is calculated based on the main scanning direction density unevenness in which the main scanning direction density unevenness caused by the LED array 74 and the main scanning direction density unevenness caused by other than the LED array are superimposed. May be good.

However, after suppressing the density unevenness in the main scanning direction caused by the LED array 74 with the first light amount correction value, the test pattern 171 is formed, and the density from the test pattern 171 in the main scanning direction mainly due to other than the LED array is formed. It is preferable to acquire unevenness. This is because when the test pattern 171 is formed without using the first light amount correction value, the density unevenness in the main scanning direction of the test pattern 171 is other than the density unevenness in the main scanning direction caused by the LED array 74 and the LED array. The density unevenness in the main scanning direction due to the above is superimposed. As a result, for example, when the portion where the density becomes high due to the LED array 74 and the portion where the density becomes high due to a factor other than the LED array overlap, the upper limit of the density may be reached. Specifically, for example, a test pattern is formed with an image density of 255 gradations of halftones (127 gradations), and is darkened (dense density) by 70 gradations due to the LED array 74. , When a part that is darkened by 70 gradations (dense density) overlaps with a factor other than the LED array 74, the part that is originally darkened by 140 gradations (dense density) is the upper limit value (gradation value 0). Is reached, and only 127 gradations can be detected. Therefore, even if the light amount of each LED element is corrected by the correction data calculated based on the image density data of the test pattern, the density unevenness remains.

On the other hand, as in the present embodiment, by forming the test pattern 171 after suppressing the density unevenness in the main scanning direction caused by the LED array 74 with the first light amount correction value, the main scanning direction of the test pattern 171 is formed. It is possible to suppress the unevenness of the density of the LED, and it is possible to suppress the occurrence of problems such as the concentration reaching the upper limit value. This has the advantage that density unevenness in the main scanning direction can be satisfactorily suppressed.

Further, each LED element 74b may be controlled based on the third light amount correction value to form a latent image of the test pattern on the surface of the photoconductor 1. In this case, a new third light amount correction value is calculated from the third light amount correction value used for forming the test pattern and the second light amount correction value calculated from the density data, and stored in the storage unit 87.

The density unevenness acquisition control in the main scanning direction shown in FIG. 5 above can be performed at an arbitrary timing by the user operating the operation display unit.
FIG. 11 is a diagram showing a state in which the initial screen (home screen) is displayed on the display unit 89a of the operation display unit 89.
As shown in FIG. 11, the operation display unit 89 includes a display unit 89a including a liquid crystal display (LCD) and the like, and an operation unit 89b having a numeric keypad and a start button. The display unit 89a has a touch panel function, and can detect the contact position of the user together with various displays. Further, the operation unit 89b may be a GUI component displayed on the touch panel.

When performing the density unevenness acquisition control in the main scanning direction, the user first presses the GUI component C1 of the "setting" displayed on the display unit 89a. Then, as shown in FIG. 12, the screen displayed on the display unit 89a is switched from the initial screen to the setting screen. Next, when the user presses the GUI component C2 of the "image adjustment" displayed on the display unit 89a, the screen of the display unit 89a is switched to the image adjustment inquiry screen as shown in FIG. Then, when the user presses the GUI component C3 of the "density unevenness correction" of the image adjustment inquiry screen displayed on the display unit 89a, the density unevenness acquisition control in the main scanning direction shown in FIG. 5 is started.

Further, when the recording sheet on which the test pattern is formed is ejected from the apparatus, as shown in FIG. 14, a pop-up screen prompting the image reading unit 60 to set the recording sheet on which the test pattern is formed is displayed. .. It should be noted that the recording sheet on which the test pattern is formed is set in the image reading unit 60 by voice, or the warning lamp is turned on so that the recording sheet in which the test pattern is formed is set in the image reading unit 60. May be urged to.

When the user determines that it is necessary to correct the density unevenness by looking at the test pattern, the user sets the recording sheet in which the test pattern is formed in the image reading unit 60 in the image reading unit 60, and clicks "Reading start" on the pop-up screen. Press the GUI component to start loading the test pattern. On the other hand, if it is determined that the correction of the density unevenness is not necessary by looking at the test pattern, the GUI component of "Cancel" on the pop-up screen is pressed to stop the acquisition of the density unevenness.

FIG. 15 is a schematic view showing a state in which the contact glass 161 of the image reading unit 60 is dirty.
When the original D in which the correction fluid is not completely dried is set on the contact glass 161, a part of the correction fluid applied to the original D adheres to the contact glass 161 as an adhering matter and is shown on the contact glass 161 as shown in FIG. Dirt Y may occur.

FIG. 16 is density data obtained from the read data obtained by reading the portion of the broken line T1 shown in FIG.
The density data shown in FIG. 16 is density data obtained from the reading data obtained by performing the reading operation with the pressure plate closed without placing the recording sheet on the contact glass 161. This density data shows the density (brightness) of each position in the main scanning direction of the region shown by the broken line T1 in FIG. 15, and the density at each position in each main scanning direction is the density of the broken line T1 in FIG. 15 at each position in the main scanning direction. It is an average value of the density of each pixel in the sub-scanning direction of the region indicated by. The density in each pixel is an average value of RGB.

Since the background, that is, the pressure plate is white, the density corresponding to the portion other than the portion to which the dirt Y is attached is uniformly bright. On the other hand, it can be seen that the density corresponding to the portion where the dirt Y is attached is dark.

When the recording sheet on which the test pattern is formed is set on the contact glass 161 and a part of the test pattern overlaps with the stain Y, the image density data in the main scanning direction obtained by reading the test pattern is used. Concentration unevenness due to dirt Y is also included. As a result, the second light amount correction value is calculated based on the density data including the density unevenness due to the stain Y, and the second light amount correction value calculated from the calculated second light amount correction value and the first light amount correction value is calculated. When the image is formed with the three light intensity correction values, the following density unevenness occurs in the formed image. That is. This is density unevenness in which the density corresponding to the position of the stain in the main scanning direction becomes thinner (brighter) than the specified density.

Further, as shown in FIG. 3, in the image reading unit 60 having the same optical system as the optical system of the illumination light and the optical system of the reading light reflected from the document, an optical component (third mirror) is used. When deposits such as dust and dirt adhere to the 163b, the second mirror 163a, and the first mirror 162a), the illumination light is diffusely reflected by the deposits, and a part of the diffusely reflected light is indicated by the dashed arrow F in the figure. As shown in the above, there is a possibility that the flare light is directly incident on the image pickup element 164b (in the example shown in FIG. 3, deposits G such as dust adhere to the first mirror 162a and the third mirror 163b. An example of flare light is shown). The part where the flare light is incident becomes brighter than the other parts.

There is a possibility that the density unevenness caused by this flare light is included in the image density data obtained by reading the test pattern. As a result, the second light amount correction value is calculated based on the density data including the density unevenness due to the flare light, and the second light amount correction value calculated from the calculated second light amount correction value and the first light amount correction value is calculated. When the image is formed with the three light intensity correction values, the following density unevenness occurs in the formed image. That is. This is density unevenness in which the density corresponding to the position where the flare light is incident in the main scanning direction becomes darker (darker) than the specified density.

A lighting device 165 is provided on the first traveling body 162, and the light emitted from the lighting device 165 is emitted from the illuminated target surface of the document D without passing through optical components (third mirror 163b, second mirror 163a, first mirror 162a). The flare light is less likely to occur in the image reading unit 60 having a configuration in which light is irradiated to the mirror. However, the read light, which is the reflected light from the document, may be incident on the adhered substances such as dust and dirt adhering to the optical components (third mirror 163b, second mirror 163a, first mirror 162a) and diffusely reflected. When the read light is incident on the deposit and diffusely reflected, the read light incident on the image sensor 164b is reduced and becomes darker than other parts.

The image density data obtained by reading the test pattern includes density unevenness due to a decrease in the reading light caused by deposits attached to the optical components (third mirror 163b, second mirror 163a, first mirror 162a). Then, when the image is formed with the third light amount correction value calculated as described above, the following density unevenness occurs in the formed image. That is. This is density unevenness in which the density corresponding to the position where the read light is lowered in the main scanning direction becomes thinner (brighter) than the specified density.

If the density unevenness caused by the image reading unit 60 is included in the image density data obtained by reading the test pattern, the accuracy of the calculated third light amount correction value is lowered and the image density unevenness is not improved. There is a risk.

Therefore, in the present embodiment, before forming the test pattern (before the image forming process of S3 in FIG. 5), the reading operation of the image reading unit 60 is performed to acquire the reading data, and based on the acquired reading data. The formation position of the test pattern 171 is set. In addition, the density unevenness in the main scanning direction of the image reading unit due to factors such as the adhesion of deposits to the optical components at the test pattern formation position should be acquired from the scanned data, and the acquired density unevenness data should be used as the light amount correction value calculation value. I made it. Hereinafter, a specific description will be given.

FIG. 17 is a control flow diagram of density unevenness acquisition control in the main scanning direction in which a reading operation is performed before forming a test pattern.
When the user presses the GUI component C3 of the "density unevenness correction" of the image adjustment inquiry screen displayed on the display unit 89a shown in FIG. 13, the image reading unit 60 is driven to start the reading operation and the pressure plate can be read ( S21). The read data obtained by reading the pressure plate is sent to the image density acquisition unit 86 of the main body control unit 52, and the main scanning direction image density data of the image reading unit 60 is acquired (S22).

Next, the main scanning direction image density data of the image reading unit 60 at each position in the sub-scanning direction acquired by the image density acquisition unit 86 is sent to the stain position specifying unit 90, and the stain position specifying unit 90 is in each of the sub-scanning directions. The dirty position of the contact glass 161 is specified based on the image density data in the main scanning direction at the position (S23). Specifically, based on the image density data in the main scanning direction at each position in the sub-scanning direction, it is examined whether or not there is a portion where the image density is darker (darker) than a certain threshold with respect to the average image density. .. If there is a part where the density is darker (darker) than a certain threshold with respect to the average image density, the position of the image density data in the sub-scanning direction and the density above a certain threshold with respect to the average image density are The dirty position of the contact glass 161 is specified from the position in the main scanning direction of the darkened (darkened) portion.

In this way, when the dirt position specifying unit 90 identifies the dirt position of the contact glass 161, the dirt position specifying part 90 sets the test pattern on the contact glass 161 when the recording sheet on which the test pattern is formed is set on the contact glass 161. It is examined whether or not the formation position of the test pattern can be set so as not to overlap with the deposit (S24).

FIG. 18 is a diagram illustrating an example of setting a test pattern forming position.
E1 to E2 shown in the figure are test pattern forming ranges in which a test pattern can be formed on a recording sheet, E1 is set at a position slightly distant from the front end side of the recording sheet to the rear end side, and E2 is , It is set at a position slightly away from the rear end of the recording sheet to the tip side. This is an example, and E1 may be set at the front end of the recording sheet and E2 may be set at the rear end of the recording sheet.

The dirt position specifying unit 90 calculates the distance β1 in the sub-scanning direction from E1 to the tip of the first dirt Y1, and then the sub-scanning direction from the rear end of the first dirt Y1 to the tip of the next dirt Y2. The distance β2 of is calculated. In this way, the distance between the stains in the sub-scanning direction is calculated, and finally, the distance in the sub-scanning direction from the rear end of the last stain Y3 to E2 is calculated. In the example of FIG. 18, dirt is attached to the contact glass 161 at three places, and a total of four distances β1 to β4 in the sub-scanning direction are calculated.

Then, when the maximum sub-scanning distance (β2 in the example of FIG. 18) among these calculated sub-scanning distances is shorter than the sub-scanning direction length α of the test pattern (β2 ≦ α), the sub-scanning direction No matter where the test pattern is formed, the test pattern overlaps with dirt. Therefore, it is determined that the test pattern cannot be formed (No in S24), the density unevenness acquisition control in the main scanning direction is stopped, and the display unit 89a is contacted. An indication is given to instruct the glass 161 to be cleaned (S33).

On the other hand, when the maximum sub-scanning distance (β2 in the example of FIG. 18) is longer than the sub-scanning direction length α of the test pattern (β2> α), it is determined that the test pattern can be formed (Yes in S24). , The center of the region (in the example of FIG. 18 from the rear end of the first stain to the tip of the second stain) is set as the test pattern forming position (S25). This method of setting the test pattern formation position is an example, and the test pattern formation position may be set by any other method.

For example, first, the dirt position specifying unit 90 checks whether or not the test pattern overlaps with the dirt on the contact glass 161 at the test pattern initial formation position shown in FIG. 7. When there is no overlapping dirt, the initial formation position is set to the test pattern formation position. On the other hand, when it is determined that the stain on the contact glass 161 and the test pattern overlap at the initial formation position, the distance from the front end of the test pattern at the initial formation position to the rear end of the overlapping stain is calculated. Next, the formed position of the test pattern by the calculated distance is shifted to the rear end side. Check if there is overlapping dirt at the shifted position. If there are overlapping stains. In the same manner as described above, the distance between the tip of the test pattern at the shifted position and the rear end of the dirt overlapping at the shifted position is calculated, and the test pattern forming position is shifted again by the calculated distance. In this way, the test pattern formation position is shifted to search for the test pattern formation position. Then, when the rear end of the test pattern reaches the rear end of the recording sheet, it may be determined that the test pattern cannot be formed.

After setting the test pattern forming position, the stain position specifying unit 90 stores the main scanning direction density data of the sub-scanning direction position corresponding to the test pattern forming position in the storage unit 87 as the image density data of the image reading unit (S26). ).

When the dirt position specifying unit 90 is set to the test pattern forming position, the process proceeds to the test pattern forming operation. First, similarly to the control flow shown in FIG. 5, the first light amount correction value acquisition unit 85 acquires the first light amount correction value (S27), and the acquired first light amount correction value is LED by the correction value transfer unit 83. Transfer to the IC driver 74a of the array 74 (S28).

Further, the dirt position specifying unit 90 transmits the set test pattern forming position information to the image forming processing unit 84. The image formation processing unit 84 controls the timing of transmitting the control signal to the IC driver 74a of the LED array 74 based on the set test pattern formation position information, and adjusts the lighting timing of the LED array 74. As a result, a test pattern can be formed at a set position.

When the recording sheet S on which the test pattern is formed is ejected and printing is completed (Yes in S30), the recording sheet S on which the test pattern 171 is formed is set in the image reading unit 60 and reading of the image is started. Then, the image density acquisition unit 86 of the main body control unit 52 acquires the image density data in the main scanning direction of the test pattern (S31), and stores the acquired image density data of the test pattern in the storage unit 87 (S32).

FIG. 19 is a calculation flow diagram for calculating the second light intensity correction value.
When calculating the second light amount correction value, first, the image density data in the main scanning direction of the image reading unit corresponding to the test pattern forming position stored in the storage unit 87 and the density data in the main scanning direction of the test pattern are used. Is read (S41, S42). Then, the calculation image density data for calculating the second light amount correction value is calculated based on the image density data in the main scanning direction of the read image reading unit and the density data in the main scanning direction of the test pattern ( S43).

The density data in the main scanning direction of the test pattern includes an image of dust or dust adhering to the optical components (third mirror 163b, second mirror 163a, first mirror 162a) of the image reading unit 60 described above. The density unevenness caused by the reading unit is included. Therefore, the image density data of the image reading unit 60 is subtracted from the density data in the main scanning direction of the test pattern, and the image reading unit 60 removes the cause of density unevenness from the density data in the main scanning direction of the test pattern. In this way, the image density data for calculation calculated by subtracting the image density data of the image reading unit 60 from the density data in the main scanning direction of the test pattern is obtained by the image forming engine (photoreceptor 1, charging roller 4, developing device). 8. The data is the density unevenness in the main scanning direction mainly due to the transfer roller 10 and the fixing device44).

Then, based on the calculation image density data, the second light amount correction value is calculated in the same manner as described above (S44). As a result, the light amount correction value capable of eliminating the density unevenness in the main scanning direction mainly due to the image forming engine (photoreceptor 1, charging roller 4, developing device 8, transfer roller 10 and fixing device 44) is accurately calculated. be able to. Therefore, it is possible to satisfactorily suppress the image density unevenness in the main scanning direction of the image formed by the light amount corrected by the third light amount correction value calculated from the first light amount correction value and the second light amount correction value.

In the present embodiment, the pressure plate is read in the reading operation before the test pattern is formed, but the recording sheet before the test pattern is formed is set in the image reading unit, and the recording sheet before the test pattern is formed is set. The surface on which the test pattern of is formed may be read. According to this, the read data read by the reading operation before forming the test pattern includes not only the dirt on the contact glass but also the dirt on the recording sheet, and does not overlap with not only the dirt on the contact glass but also the dirt on the recording sheet. As described above, the formation position of the test pattern can be set. As a result, the second light amount correction value can be calculated more accurately. Further, in the reading operation before the test pattern formation, the recording sheet before the set test pattern is formed is a blank sheet. Therefore, the density unevenness caused by dust, dust, or other deposits attached to the optical components (third mirror 163b, second mirror 163a, first mirror 162a) of the image reading unit 60 from the reading data read from this recording sheet. Information can also be obtained without problems.

Further, by reading the recording sheet, it is possible to prevent the read data from containing dirt on the pressure plate.

When the recording sheet before this test pattern is formed is set in the image reading unit, when the user presses the GUI component C3 of "density unevenness correction" on the image adjustment inquiry screen, the display unit is used to form the test pattern. A display instructing the image reading unit to set the recording sheet and a display instructing the start of the reading operation by pressing the start button after setting are performed. Then, when the test pattern formation position can be set after the reading operation, a display instructing the display unit to set the recording sheet set in the image reading unit in the bypass tray and an image by pressing the start button after the setting are performed. A display is displayed instructing to start the forming operation.

Further, as shown in FIG. 20, a reading plate 53 such as a reading member to be set during the reading operation before forming the test pattern is bundled with the image forming apparatus 200, and the reading plate 53 is set during the reading operation before forming the test pattern. The reading operation may be performed. White or gray (intermediate color) can be used for the reading plate 53. The gray color has an advantage that the density unevenness in the main scanning direction due to the flare light can be detected more sensitively than the white color.
Further, by reading the reading plate 53, it is possible to prevent the reading data from including dirt on the pressure plate.

The reading operation before forming the test pattern does not have to be performed each time the density unevenness in the main scanning direction is acquired. For example, during normal density unevenness correction, a test pattern is formed without performing a reading operation. Then, the density unevenness is aggravated by the normal correction of the density unevenness, or the improvement of the density unevenness is dissatisfied. Therefore, when the density unevenness is corrected again, the reading operation before forming the test pattern is performed. You may do so.

In the above, the image forming apparatus is monochrome, but a full-color image is printed on a recording sheet using four toners of Bk (black) color, C (cyan) color, M (magenta) color, and Y (yellow) color. It can also be applied to a full-color image forming apparatus to be formed. In the full-color image forming apparatus, four image-forming portions including a cleaning blade 2, a charging roller 4, a latent image writing device 7, and a developing device 8 are provided around the photoconductor 1, and four latent image writing devices are provided. A light amount correction value is calculated for each of the LED arrays of the built-in device 7 to correct the light amount. In this full-color image forming apparatus, a Bk color test pattern, a C color test pattern, an M color test pattern, and a Y color test pattern are formed on a recording sheet at predetermined intervals in the sub-scanning direction. Image density data in the main scanning directions of four colors is acquired by controlling the density unevenness acquisition in the main scanning direction.

FIG. 21A is a diagram showing a state in which the C color test pattern 171C of the four color test patterns 171Bk, 171C, 171M, and 171Y formed on the recording sheet overlaps the dirt Y of the contact glass 161. is there. FIG. 21B is a diagram showing a state in which the formation positions of the test patterns are set so that the four-color test patterns 171Bk, 171C, 171M, and 171Y do not overlap with the stains on the contact glass 161.

As shown in FIG. 21 (a), when the C color test pattern 171C overlaps the dirt Y of the contact glass 161, the image density data in the main scanning direction obtained by reading the C color test pattern 171C is obtained. , The stain Y is included, the second light amount correction value cannot be calculated accurately for the C color, and the density unevenness remains only for the C color. As a result, the tint of the color image at a predetermined portion (the portion corresponding to the stain Y) in the main scanning direction may be different from that of other portions.

Therefore, even in a full-color image forming apparatus. A reading operation is performed before forming the test pattern, image density data of the image reading unit 60 is acquired, and a stain position of the contact glass is specified based on the acquired image density data of the image reading unit 60. Then, the test pattern formation position of each color is set based on the specified dirt position of the contact glass.

First, the dirt position specifying unit 90 of the main body control unit 52 confirms whether there is a test pattern that overlaps with the dirt on the contact glass based on the dirt position on the contact glass. If there are overlapping test patterns, the formation position of the test patterns determined to be overlapping is shifted to the front end side or the rear end side based on the position in the overlapping sub-scanning direction.

In the example shown in FIG. 21, as shown in FIG. 21 (a), the position where the C color test pattern 171C overlaps with the dirt Y is the rear end side (lower side in the figure), so that the C color test pattern 171C Shift the formation position to the tip side (upper side in the figure). By shifting the formation position of the C-color test pattern 171C to the tip side (upper side in the figure), as shown in FIG. 21 (b), the C-color test pattern 171C does not overlap with the stain Y on the contact glass. it can.

For example, when the test pattern is shifted to a position where it does not overlap with the stain Y, if the interval between the test patterns is less than the predetermined lower limit value, the two test patterns (in FIG. 21B, the C color The test pattern 171C and the Bk color test pattern 171Bk) are shifted.

As a result, the second light amount correction value can be calculated accurately for each color, and the density unevenness in each color main scanning direction can be satisfactorily suppressed. As a result, it is possible to suppress the change in color in the main scanning direction.

Further, in the above description, the formation position of the test pattern is set based on the position of the specified stain so that the test pattern does not overlap with the stain of the contact glass 161. However, the formation position of the test pattern is the specified stain position. The storage unit 87 may not save the portion of the image density data in the main scanning direction including the deposits for calculating the second light amount correction value.

In this case, after the image density acquisition unit 86 acquires the image density data of the test pattern, the image density acquisition unit determines whether or not there is a portion where the image density data contains stains based on the specified stain position. To judge. As a result of the determination, when there is a portion where the image density data contains stains, the image density data in the main scanning direction of the portion containing the stain is deleted and stored in the storage unit 87. Even in this way, when the second light amount correction value is calculated based on the main scanning direction image density data stored in the storage unit 87 by the light amount correction value calculation unit 88, the contact glass is not contaminated. The scanning direction image density data can be used, and the decrease in accuracy of the second light amount correction value can be suppressed.

What has been described above is an example, and each of the following aspects produces a unique effect.
(Aspect 1)
Image forming means (in this embodiment, composed of a photoconductor 1, a charging roller 4, a latent image writing device 7, a developing device 8, a transfer roller 10, a fixing device 44, etc.) and an image reading means such as an image reading unit 60. Then, the test pattern forming means such as the image forming processing unit 84 that controls the image forming means to form a test pattern on the recording medium and the image reading means read the test pattern of the recording medium to acquire the image data of the test pattern. A correction value calculation means (the present embodiment) including an acquisition means such as an image density acquisition unit 86 and a correction value calculation means for calculating a predetermined correction value for optimizing an image based on image data of a test pattern. Then, in the image forming apparatus having the light amount correction value calculation unit 88 and the calculation unit 82 and the like), the reading operation of the image reading means is performed before forming the test pattern on the recording medium.
Adhesives such as dust may adhere to the contact glass of the image reading means. When the recording medium on which the test pattern is formed is set on the contact glass, the test pattern formed on the recording medium may overlap with the deposits. In this way, when the test pattern of the recording medium is read by the image reading means in a state where the deposit and the test pattern are overlapped, the deposit is included in the image data of the test pattern as dirt on the image reading means. As a result, correct image data cannot be acquired, and the correction value may not be calculated accurately.
Therefore, in the first aspect, before forming the test pattern, the image reading means is read and the read data is acquired. When the deposit is attached to the contact glass, the deposit is read by the reading operation of the image reading means before forming the test pattern, and the position of the deposit can be specified from the read data. Therefore, the test pattern is formed on the recording medium by avoiding the position of the deposits specified from the read data, or the data of the part containing the stain of the image reading means is deleted from the acquired image data of the test pattern. It is possible to prevent the image data used for calculating the correction value from including stains on the image reading means. As a result, a highly accurate correction value can be calculated.

(Aspect 2)
In the first aspect, setting means such as a stain position specifying unit 90 for setting the position of the test pattern to be formed on the recording medium is provided based on the reading data acquired in the reading operation before forming the test pattern on the recording medium.
According to this, as described in the embodiment, when a recording medium such as a recording sheet on which a test pattern is formed is set in an image reading means such as an image reading unit 60, the contact glass of the image reading means becomes dirty. It is possible to prevent the test patterns from overlapping. As a result, it is possible to prevent the contact glass from being contaminated in the image data of the test pattern, and it is possible to suppress a decrease in the calculation accuracy of the correction value.

(Aspect 3)
In the first or second aspect, the user is instructed to maintain the image reading means based on the reading data acquired in the reading operation before forming the test pattern on the recording medium.
According to this, as described in the embodiment, it is possible to grasp the dirt on the contact glass based on the read data. Therefore, if the contact glass is heavily soiled based on the read data and there is a risk that the image data of the test pattern obtained by reading the test pattern with an image reading means will be affected by the stain, a user such as cleaning the contact glass may use it. It is possible to instruct the maintenance of the image reading means.
As a result, it is possible to prevent the contact glass from being contaminated in the image data of the test pattern obtained by reading the test pattern with the image reading means.

(Aspect 4)
In any one of aspects 1 to 3, the acquisition means forms a test pattern on the recording medium or stops forming the test pattern based on the read data acquired in the reading operation before forming the test pattern on the recording medium. To do.
According to this, as described in the embodiment, the contact glass is severely soiled based on the read data, and the image data of the test pattern acquired by reading the test pattern by the image reading means may be affected by the stain. At some point, the formation of test patterns on the recording medium can be stopped.
As a result, it is possible to prevent the contact glass from being contaminated in the image data of the test pattern obtained by reading the test pattern with the image reading means.

(Aspect 5)
In any one of aspects 1 to 4, the reading data acquired in the reading operation before forming the test pattern on the recording medium is the reading data obtained by reading a reading member such as a reading plate 53 included in the image forming apparatus. is there.
According to this, as described in the embodiment, it is possible to prevent the read data from including the stain on the pressure plate.

(Aspect 6)
In any one of aspects 1 to 4, the read data acquired in the reading operation before forming the test pattern on the recording medium is the read data obtained by reading the recording medium on which the test pattern is formed.
According to this, as described in the embodiment, it is possible to prevent the read data from including the stain on the pressure plate. Further, the read data includes stains on the recording medium on which the test pattern is formed, and the position of the stains on the recording medium can be avoided to form the test pattern. As a result, it is possible to prevent the image data of the test pattern obtained by reading the test pattern by the image reading means from including the stain on the recording medium.

(Aspect 7)
In any one of aspects 1 to 6, the image forming means is a latent image forming means such as a latent image writing device 7 that exposes the surface of the latent image carrier to form a latent image on the latent image carrier, and the latent image. A developing means such as a developing apparatus 8 for developing and a transfer means such as a transfer roller 10 for transferring an image developed by the developing means to a recording medium conveyed by the conveying means are provided, and the correction value calculating means reads. The exposure correction value for correcting the amount of light for exposure is calculated based on the image data of the test pattern.
According to this, as described in the embodiment, it is possible to calculate the exposure amount correction value with high accuracy, and it is possible to satisfactorily suppress the image density unevenness in the main scanning direction.

1: Photoreceptor 4: Charging roller 7: Latent image writing device 8: Developing device 52: Main body control unit 53: Reading plate 60: Image reading unit 61: Automatic document transporting device 61a: Document tray 74: LED array 74a: IC Driver 74b: LED element 74c: ROM
82: Calculation unit 83: Correction value transfer unit 84: Image formation processing unit 85: First light amount correction value acquisition unit 86: Image density acquisition unit 87: Storage unit 88: Light amount correction value calculation unit 89: Operation display unit 89a: Display Part 89b: Operation part 90: Dirt position specifying part 161: Contact glass 171: Test pattern 200: Image forming apparatus

Japanese Unexamined Patent Publication No. 2018-132723

Claims (7)

Image forming means and
Image reading means and
A test pattern forming means that controls the image forming means to form a test pattern on a recording medium,
An acquisition means for reading the test pattern of the recording medium by the image reading means and acquiring image data of the test pattern, and
In an image forming apparatus provided with a correction value calculating means for calculating a predetermined correction value for optimizing an image based on the image data of the test pattern.
An image forming apparatus, characterized in that a reading operation of the image reading means is performed before forming the test pattern on the recording medium. In the image forming apparatus according to claim 1,
Image formation characterized by comprising a setting means for setting the position of the test pattern to be formed on the recording medium based on the read data acquired in the reading operation before forming the test pattern on the recording medium. apparatus. In the image forming apparatus according to claim 1 or 2.
An image forming apparatus comprising instructing maintenance of the image reading means based on the reading data acquired in the reading operation before forming the test pattern on the recording medium. In the image forming apparatus according to any one of claims 1 to 3.
An image forming apparatus characterized in that the formation of the test pattern is stopped based on the read data acquired in the reading operation before the test pattern is formed on the recording medium. In the image forming apparatus according to any one of claims 1 to 4.
An image forming apparatus, characterized in that the reading data acquired in the reading operation before forming the test pattern on the recording medium is the reading data obtained by reading the reading member included in the image forming apparatus. In the image forming apparatus according to any one of claims 1 to 4.
An image forming apparatus, characterized in that the read data acquired in the reading operation before forming the test pattern on the recording medium is the read data obtained by reading the recording medium on which the test pattern is formed. In the image forming apparatus according to any one of claims 1 to 6.
The image forming means was developed by a latent image forming means for exposing the surface of the latent image carrier to form a latent image on the latent image carrier, a developing means for developing the latent image, and the developing means. A transfer means for transferring an image to a recording medium conveyed by the transfer means is provided.
The image forming apparatus is characterized in that the correction value calculating means calculates an exposure correction value for correcting the amount of light of the exposure based on the read image data of the test pattern.