JP2010120199A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which uses an imaging optical system and suppresses degradation of an image quality, and to provide an image forming method. <P>SOLUTION: In an exposure head, the imaging optical system and the light emitting elements imaged to a latent image carrier by the imaging optical system are arranged in a first direction and a second direction. A screen module 25 set in an image processing part 23 performs screen processing of image data, and a CPU 21 adjusts a light amount of the light emitting elements by screen processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method configured to prevent image quality deterioration when screen processing image data using an imaging optical system.

  In an electrophotographic image forming apparatus, a latent image is formed on an image carrier (photoreceptor) using an exposure head in which two or more light emitting elements and an imaging optical system for imaging light from the light emitting elements are arranged. Those of the construction to be formed are known. As this imaging optical system, a technique using a lens (ML) having a negative optical magnification has been developed. Patent Document 1 describes a line head using ML as an imaging optical system and an image forming apparatus using the line head.

Japanese Patent Laid-Open No. 2008-049792

  In an image forming apparatus using a lens array (MLA) composed of ML, unevenness in the amount of light is caused due to temperature unevenness between MLs caused by the number of light emitting elements in the ML and the light emission time. For this reason, when the image data is screen-processed, as shown in the explanatory diagram of FIG. 14, unevenness in density occurs in the printed image 16 due to unevenness in the amount of light, and the image quality deteriorates. Patent Document 1 has a problem that it does not describe how to deal with such a case.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an image forming apparatus and an image in which image quality deterioration is prevented when image data is screened using an imaging optical system. It is to provide a forming method.

The image forming apparatus of the present invention that achieves the above object provides:
A latent image carrier;
An imaging optical system, a light emitting element that emits light imaged on the latent image carrier by the imaging optical system, and a first direction and a second direction orthogonal or substantially orthogonal to the first direction; An exposure head having a substrate on which the light emitting element is disposed;
A screen processing unit for screen processing image data;
A control unit for adjusting the light amount of the light emitting element by the screen processing unit;
It is characterized by having.

  In the image forming apparatus of the present invention, the control unit predicts the temperature of the substrate based on a light emission count value of the light emitting element.

  The image forming apparatus of the present invention sets an offset value to be applied when screen processing is performed on the image data based on the predicted substrate temperature.

  In the image forming apparatus of the present invention, screen adjustment data is set in the screen processing unit corresponding to the light emission count value of the light emitting element.

  In the image forming apparatus of the present invention, the screen adjustment data is added to a gradation value of one pixel of the image data, and compared with screen data corresponding to the pixel set in the screen processing unit, Determine whether screen data is on or off.

  In the image forming apparatus of the present invention, the imaging optical system is an inverted system.

The image forming method of the present invention comprises:
A latent image carrier;
An imaging optical system, a light emitting element that emits light imaged on the latent image carrier by the imaging optical system, and a first direction and a second direction orthogonal or substantially orthogonal to the first direction; An exposure head having a substrate on which the light emitting element is disposed,
Counting the number of light emission per unit time of a light emitting element that emits light imaged by the imaging optical system;
A step of decreasing the count value when the light emitting element emitting light imaged by the imaging optical system is turned off, and a step of increasing the count value when the light emitting element emits light;
Predicting the temperature of the substrate based on the count value;
Adjusting the light amount of the light emitting element by a screen according to the temperature of the substrate;
It is characterized by having.

The image forming method of the present invention includes
The step of adjusting the light amount of the light emitting element with a screen,
Adding a gradation value of one pixel of image data and screen adjustment data;
Comparing the screen data corresponding to the pixel set in the screen processing unit and determining whether the screen data is on or off;
The image forming method according to claim 7, comprising:

  An embodiment of the present invention will be described with reference to the drawings. 11 and 12 are explanatory diagrams showing the prerequisite technology of the present invention. FIG. 11 shows an arrangement relationship between a lens (ML) having a negative optical magnification and a light emitting element (dot). In FIG. 10, two or more light emitting elements 2 are arranged in ML4 in the axial direction (X direction, first direction) of the photoconductor and the rotation direction (Y direction, second direction) of the photoconductor. These light emitting elements form a latent image on the photoreceptor. In the embodiment of the present invention, the X direction may be described as a first direction, and the Y direction may be described as a second direction.

  For the sake of convenience, the light emitting elements 2 are numbered “1 to N”. A dot row 3a of “2, 4,... N” is formed from the left side to the right side in the X direction by the first light emitting element row in the Y direction. Hereinafter, dot rows 3b, 3c, and 3d are formed by two or more light emitting element rows arranged in the Y direction. A dot row 3d of “1, 3,...” Is formed by the fourth light emitting element row shown in the Y direction. Here, two or more lenses (ML) 4 are arranged in the X direction to constitute a microlens array (MLA). In addition, a lens array (MLA) can be configured by arranging two or more lenses (ML) in the X direction and the Y direction. Here, the dot “2, N” is a dot at the X-direction end of the micro lens (ML).

  FIG. 12 is an explanatory diagram of an exposure head using a lens array (MLA). When the number of light emitting elements (number of dots) for forming a one-line latent image in the axial direction of the photoconductor increases, a long MLA (lens array) is required in the axial direction of the photoconductor. In such a case, it is possible to form a long MLA head by connecting a plurality of MLAs having a certain length. FIG. 12 (a) shows a schematic overall configuration, and FIG. 12 (b) schematically shows a part of FIG. 12 (a). FIG. 12A shows a long MLA head (exposure head) 10, and 5 n is a part of the long MLA head. FIG.12 (b) is a figure which expands and shows 5n of MLA.

In FIG. 12B, the exposure head has two or more light emitting elements 2 arranged on a substrate 1. 3
Is a light emitting element group composed of two or more light emitting elements arranged on one lens 4a. In the light emitting element group 3, two or more light emitting elements are arranged in the axial direction X of the photoreceptor and the rotation direction Y of the photoreceptor. Reference numeral 4 denotes a lens (ML), and two or more lenses are arranged in the axial direction (main scanning direction) X of the photoconductor and the rotation direction (sub-scanning direction) Y of the photoconductor to constitute a lens array (MLA). . L of the lens 4a is the width of one row of light emitting elements arranged in the X direction within one lens, dp is the distance between the light emitting elements (dots), and P is the distance between the adjacent lenses 4a and 4b in the Y direction. The distance between the first dots in the X direction is shown.

Here, in the embodiment of the present invention, terms are used as follows.
The original image is a printed image before screen processing. Further, regarding the arrangement of light emitting elements in one lens (ML) in the MLA, the number of light emitting elements in the direction Y (second direction) and the direction X (first direction) in one lens may be arbitrary. . By such light emitting elements arranged in the ML, latent image dots are formed on the photosensitive member (latent image carrier). Here, one light emitting element corresponds to one latent image dot.

  Screen processing is a technique for expressing halftones by binary values of on / off of color materials. When a screen table is used, the data value of the screen table indicates a color material on / off threshold. For example, when the gradation value of the original image, that is, the print image before screen processing is 80, dots whose screen table value is 80 or less are turned on, and dots that are 81 or more are turned off.

  The density unevenness for each ML is caused by unevenness in the amount of light generated from the temperature unevenness for each ML. Therefore, in the embodiment of the present invention, a growth adjustment table (screen adjustment data) for controlling the degree of growth of screen dots is provided for each ML, and the temperature in the ML (the temperature of the substrate due to light emission of the light emitting element) is predicted. Thus, the data in the growth adjustment table is determined, and the density difference for each ML is reduced by changing the degree of dot growth for each ML during screen processing.

In the embodiment of the present invention, the screen processing is performed as follows. (1) Information on the number of dots and the number of redundant dots for each ML is obtained from the MLA head.
(2) A growth adjustment table (screen adjustment data) for adjusting the degree of screen growth is prepared separately from the screen table. The data in the growth adjustment table is used for the purpose of adjusting the degree of dot growth in each ML. (3) Based on the information of (1), it is determined which ML the dot to be screened is, and using the corresponding ML data in the growth adjustment table of (2), the dot for each ML Change the degree of growth and screen.

  FIG. 3 is a characteristic diagram showing the relationship between the number of light emitting elements in the ML and the temperature. As shown in FIG. 3, if the temperature in the printing system is constant, the temperature in the ML increases when the light emitting element in the ML emits light, and decreases when the temperature is turned off. The following methods can be considered for grasping the temperature in the ML. (1) A method of measuring with a temperature sensor, (2) A method of analyzing the number of times of light emission of each ML light emitting element from screen-processed data transmitted to the MLA head, and (3) The number of light emissions per unit time of the light emitting elements in the ML. Is a method of predicting the temperature in the ML by counting.

As an example, a method of predicting the temperature in the ML by counting the number of light emission of the light emitting elements in the ML per unit time will be described with reference to the flowchart of FIG.
S1: After the counter is initialized, the count process for each ML is started.
S2: The presence or absence of light emission in the ML is counted at the light emission time interval of the light emitting elements for one pixel.
S3: When all the light emitting elements in the ML are turned off, the count value is decreased.
S4: When even one of the light emitting elements in the ML emits light, the count value is increased.

  If counting is performed in units of one light emitting element, the accuracy increases, but the processing time increases. Therefore, this process is performed for each ML, and the count value is stored in the memory in the head controller. The counter may be realized by either S / W or H / W, and is installed at a place other than the place where the output dots to the MLA head are determined.

  FIG. 4 is an explanatory diagram showing a specific example of the present invention. In this example, the number of dots in ML is 10, the number of ML is 10, the number of gradations is 256 (0-255), and the sizes of the original image and the screen table are 5 × 5. 4, MLA 5n is provided with ML1 (4a) to ML6 (4f)... In the first direction (X direction) and the second direction (Y direction).

  FIG. 5 is an explanatory diagram showing an example of creating a screen growth adjustment table. FIG. 5 will be described. FIG. 5A shows the data storage position corresponding to the MLA in the growth adjustment table. FIG. 5B shows a state in which the count value on the memory in the head controller is initialized. FIG. 5C shows the number of times counting is started according to the light emission count processing flow for each ML described in FIG.

In the light emission time interval of the light emitting elements for one pixel, the count value is incremented by 1 when any one of the light emitting elements in the ML emits light, and the count value is set to 1 when all the light emitting elements in the ML are turned off. Decrease. As an example, if the lower limit value of the counter is 0, (count value <0), the count value = 0, the upper limit value is 5000, and if (count value> 5000), the count value = 5000. .

  FIG. 6 is a characteristic diagram showing the relationship between the number of light emitting elements in the ML and the screen offset value. FIG. 6 shows a situation in which the screen offset value is set stepwise according to the predicted temperature in each ML described in FIG. 5C, that is, the light emission count value. When printing is completed for a predetermined number of times, data in the growth adjustment table is determined from the relationship between the predicted temperature in the ML and the amount of light that changes, and is stored in the memory of the image processing unit. Since the data in the growth adjustment table is used by adding to the threshold value in the screen table, it is an offset value indicating the degree of screen growth. This value is obtained from the characteristic diagram showing the relationship between the number of light emission in the ML and the screen offset value described in FIG.

  FIG. 7 is an explanatory diagram showing the screen growth adjustment table 13. In FIG. 7, data is set such that 20 for ML1 and 8 for ML2 are associated with the data storage positions of each ML shown in FIG. The data of the screen growth adjustment table 13 is set in correspondence with the light emission count value of the light emitting elements in each ML.

  FIG. 8 is an explanatory diagram showing an embodiment of the present invention. 8A shows the screen table 11, FIG. 8B shows the growth adjustment table 13, and FIG. 8C shows the situation where the screen-processed image data is output to the light emitting elements in the MLA 5n. In the example of FIG. 8, the screen table is used in common. In the growth adjustment table, offset values for dot growth corresponding to ML 1, 2, 3,... Are stored. At the time of screen processing, an ML offset value (screen adjustment data) corresponding to threshold data in the screen table is added to the gradation value of one pixel and processed.

  The size of the screen table in the first direction (X direction) is independent of the number of pixels in the ML. In the above example, the screen table width and the number of pixels in the ML are both 5, but the data to be screened based on the information on the number of dots of each ML and the number of redundant dots obtained from the MLA head is in which ML. It can be applied to the case where the screen table width (the number of elements in the X direction) and the number of pixels in the ML are different by determining whether or not it is.

  FIG. 9 is an explanatory diagram showing an embodiment of the present invention corresponding to the arrangement of the light emitting elements of the MLA 5n described in FIG. FIG. 9A shows data 12 of the gradation value (64) of the original image. FIG. 9B shows the growth adjustment table 13. FIG. 9C shows a screen applied to screen processing of image data. Reference numeral 12a represents an original image of interest (tone value 64), 13a represents an ML1 offset value (20), and 11a represents a screen threshold (60) corresponding to the original image of interest.

FIG. 10 is an explanatory diagram showing screen processing for the example of FIG. The screen processing procedure will be described. The screen data indicates a threshold value and is used as follows.
Output is 0 when (original image data) + (growth adjustment table data) <(screen data).
Output 255 if (original image data) + (growth adjustment table data) ≧ (screen data).

Example 1: Since the upper left pixel of the original image in FIG. 9A is a pixel of ML1,
Original image data: 64, screen data: 170, growth adjustment table data: 20,
(Original image data) + (growth table data) = 64 + 20 = 84,
(Screen data) = 170,
It becomes. In this example,
(Original image data) + (Growth table data) <(Screen data),
Therefore, the output is “0”.

Example 2: Since the pixel 12a in FIG. 9A is a pixel of ML1, original image data: 64, screen data (11a): 60, growth adjustment table data: 20,
Because
(Original image data) + (Growth table data) ≧ (Screen data). The output is “255”.

  FIG. 10A shows an example of the output data 14a using the growth adjustment table, and FIG. 10B shows the output data 14b when the growth adjustment table is not used. The shaded portion 15a in FIG. 10A and the shaded portion 15b in FIG. 10B are portions where the output is “255”.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG.
In the configuration of FIG. 1, an image forming unit (printer driver) is provided in a host computer (PC) 20. Similarly, a memory for storing solid information such as MLA pitch deviation is provided in the host computer (PC) 20.

  As described above, in the configuration of FIG. 1, the host computer (PC) 20 is provided with the memory (second storage means) 22 for storing the MLA solid information. An image forming unit (printer driver) 23 is provided in the host computer (PC) 20. The image forming unit (printer driver) 23 is provided with a color conversion module 24, a screen processing module 25, and a page memory 26 for storing print image data. Although not shown, a table memory having table data for the color conversion module and a table memory having table data for the screen processing module are provided.

The main controller (MC) 31 is provided with a memory 32, but the memory 32 does not store MLA solid information (ML pitch or the like). For example, the page memory function can be provided in the memory 32 instead of the image forming unit (printer driver) 23 of the host computer (PC) 20. The engine unit (EG) 36 is provided with memories 38C to 38K (first storage means) for storing ML or MLA individual information. The image scan and density measurement unit is provided in the engine unit (EG) 36. In the configuration of FIG. 1, the image scan and density measurement unit is provided in a device other than the engine unit (EG) 36, for example, the main controller (MC) 31. be able to.

  1 includes a printer engine unit including a main controller (MC) 31, an engine controller (EC) 33, a head controller (HC) 34, an engine unit (EG) 36, and MLA heads 37C, 37M, 37Y, and 37K. It includes a PC (printer driver) 20 that forms a print image and requests printing. The page memory 26 that stores the print image data of FIG. 1 may be provided in the main controller (MC) 31.

  1 may be a print server. Further, the image processing unit 26 in FIG. 1 may be printer driver software or accelerator hardware. In the memories 38C, 38M, 38Y, and 38K in each MLA head, ML and MLA individual information are stored. However, the individual information of ML and MLA is not limited to the memories 38C to 38K of the MLA heads 37C, 37M, 37Y, and 37K. For example, the head controller (HC) 34, the engine controller (EC) 33, etc. It can be stored in any module in the unit 30.

  As described above, in the configuration of FIG. 1, since the printer driver can grasp individual differences between ML and MLA, the same printer driver can be used for models having various print heads. Therefore, the configuration of the printer engine unit is simplified and the cost can be reduced. In addition, since color conversion processing and screen processing can be performed on data close to the original image to be printed, more accurate correction can be performed, so that deterioration in image quality can be prevented.

  The head controller (HC) 34 is provided with a head control module 35 and a memory 32a. The memory 32a can store the growth adjustment data for each ML described with reference to the screen table and FIG. The head control module 35 transmits print data to the four color MLA heads 37C, 37M, 37Y, and 37K of C, M, Y, and K. The engine controller (EC) 33 controls the head control module 35 and the engine unit (EG) 36. The engine unit (EG) 36 is provided with an image scan and density measurement unit 36 a that scans an image and measures density.

  Next, referring to FIG. 1, the data flow of each part will be described. (1) The host computer (PC) 20 transmits a print command to the main controller (MC) 31 and sets head data (Da). (2) The main controller (MC) 31 transmits the head data setting to the engine controller (EC) 33 (Db). (3) The engine controller (EC) 33 transmits the head data setting to the head controller (HC) 34 (Dc). (4) The head controller (HC) 34 transmits the head data setting to each MLA head (Dd).

  (5) Each MLA head transmits head information to the head controller (HC) 34 (De). (6) The engine controller (EC) 33 acquires head information from the head controller (HC) 34 (Df). (7) The main controller (MC) 31 acquires head information from the engine controller (EC) 33 (Dg). (8) The host computer (PC) 20 acquires status information and head information from the main controller (MC) 31 (Dh).

The solid state information of ML or the solid state information of MLA is stored in the memory 22. The ML or MLA solid information is as follows: (1) Number of MLAs: the interval between MLA joints linked by this information is grasped. (2) Number of microlenses for each MLA {number of microlenses in the axial direction (row direction) of the photoconductor, rotation direction (column direction) of the photoconductor}: Based on information on the number of microlenses in the MLA Know the number of dots in between. (3) Number of light emitting elements for each microlens (number in the row direction and column direction): The number of dots in the microlens is grasped based on the information on the number of light emitting elements in the row direction and the number of light emitting elements in the column direction. (4) Number of redundant dots between each microlens: This information is used to grasp the number of redundant dots and the location of the redundant dots.

  (5) Number of effective dots for each microlens: The number of dots that can be emitted by each microlens is determined from this information. (6) Variation in light emission amount for each light emitting element: Based on this information, variation in light emission amount in one microlens is grasped. (7) Light emission amount variation for each microlens: This information is used to grasp the light emission amount variation within one MLA. (8) Pitch interval between microlenses: This information is used to grasp the pitch interval error between microlenses. (9) Tilt amount for each microlens: This information is used to grasp the difference between the screen coordinate system and the actual print coordinate system.

  Next, the process of FIG. 1 will be described. The ML for each MLA head and the individual information of the MLA are stored in the memories 38C, 38M, 38Y, and 38K in advance. When the printer 30 is connected to the host computer (PC) 20, the individual information of ML and MLA is transmitted from the memory 38C, 38M, 38Y, 38K of the printer 30 to the PC 20 and stored in the memory 22 on the PC 20. When the user requests printing, the PC 20 transmits the ML stored in the memory 22 and the individual information of the MLA to the image processing unit 23, and the image processing unit 23 generates a print image.

  The image processing unit 23 transmits a print command to the main controller (MC) 31 and print data (Video Data) stored in the page memory 26 via the main controller (MC) 31 to the head controller (HC) 34. (Di). The engine controller (EC) 33 controls printing by the engine unit (EG) 36, and the head controller (HC) 34 transmits print data to the MLA heads 37C, 37M, 37Y, and 37K.

  Next, usage examples of individual information of ML and MLA will be described. The printer driver (image processing unit) 23 performs image processing (color conversion processing, screen processing) suitable for the head based on the individual information received from the printer 30. In this image processing, for example, the following processing is performed based on information on the presence / absence of redundant dots. (1) Change the screen table. (2) Change the screen processing method. Further, (3) the number of microlenses for each MLA {the number of photoconductors in the axial direction (row direction), the rotation direction of the photoconductor (column direction)}, the number of effective dots for each microlens, and between the microlenses The screen table or the screen processing method is changed based on the pitch interval and the tilt amount for each microlens.

  It is assumed that a printed image formed on the photoconductor has two or more lines printed in the rotation direction of the photoconductor. In this case, the density distribution of the print image that scans the print image in which the MLA is turned on for each row is measured, and the dot position of the print image is measured. Next, the measurement result of the dot position of the printed image is reflected on the screen table. This process includes a change of the color conversion parameter value, a change of the screen table or the parameter value of the screen process.

The above processing is repeated for the number of MLA rows. With the apparatus having such a function, the CPU 21 in FIG. 1 creates a screen table. Further, the temperature of the substrate in the ML is predicted based on the ML light emitting element count as described in the flowchart of FIG. The offset value is set by such processing. Further, the screen processing for the image data is executed by the screen growth adjustment data as described with reference to FIG. By such processing, it is possible to prevent image quality deterioration due to temperature rise in the ML.

  In the configuration of FIG. 1, the main controller (MC) 31 is provided with a memory 32 for storing solid information such as MLA redundant dots corresponding to each color. The memory 32 for storing such MLA solid information is provided in all the exposure heads. The number of times of light emission of the light emitting element is counted, and information is transmitted to the main controller. The main controller stores the information in the memory as MLA information. Further, the head controller 34 is provided with a memory 32a, which can store screen adjustment data.

  In the embodiment of the present invention, a tandem color printer that exposes four photoconductors with four line heads, simultaneously forms four color images, and transfers them onto one endless intermediate transfer belt (intermediate transfer medium). The target is a line head used in (image forming apparatus). FIG. 13 is a vertical side view showing an example of a tandem image forming apparatus using an organic EL element as a light emitting element. In this image forming apparatus, four line heads 101K, 101C, 101M, and 101Y having the same configuration are exposed to four corresponding photosensitive members (image carriers) 41K, 41C, 41M, and 41Y having the same configuration. They are arranged at each position.

  As shown in FIG. 13, this image forming apparatus is provided with a driving roller 51, a driven roller 52, and a tension roller 53, and an intermediate transfer belt that is circulated and driven by the tension roller 53 in the direction indicated by the arrow (counterclockwise). 50. Photosensitive members 41K, 41C, 41M, and 41Y are arranged at predetermined intervals with respect to the intermediate transfer belt 50. K, C, M, and Y added after the reference sign mean black, cyan, magenta, and yellow, respectively. The photoconductors 41 </ b> K to 41 </ b> Y are driven to rotate in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50. Around each photoconductor 41 (K, C, M, Y), a charging unit 42 (K, C, M, Y) and an exposure head 101 (K, C, M, Y) are provided.

  Further, a developing device 44 (K, C, M, Y) that applies a toner as a developer to the electrostatic latent image formed by the exposure head 101 (K, C, M, Y) to form a visible image; The primary transfer roller 45 (K, C, M, Y) and the cleaning device 46 (K, C, M, Y) are included. The emission energy peak wavelength of each line head 101 (K, C, M, Y) and the sensitivity peak wavelength of the photoconductor 41 (K, C, M, Y) are set to substantially coincide.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). The toner image, which is sequentially primary transferred onto the transfer belt 50 and sequentially superposed on the intermediate transfer belt 50 to become a full color, is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 66, and serves as a fixing unit. The toner is fixed on the recording medium P by passing through the fixing roller pair 61, and is discharged onto a paper discharge tray 68 formed in the upper part of the apparatus by a paper discharge roller pair 62.

  63 is a paper feed cassette in which a large number of recording media P are stacked and held, 64 is a pickup roller for feeding the recording media P from the paper feed cassette 63 one by one, and 67 is a secondary transfer portion of the secondary transfer roller 66. A pair of gate rollers for defining the supply timing of the recording medium P to the medium, 66 is a secondary transfer roller as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50, and 69 is an intermediate after the secondary transfer. This is a cleaning blade that removes toner remaining on the surface of the transfer belt 50.

When the light source is an organic EL (OPH = OLED Printer Head), the OPH is remarkably deteriorated due to the light emission time of the element, leading to a decrease in the amount of light. If the amount of light is insufficient, the charge on the photoconductor will be insufficient,
The toner is not loaded, resulting in a print result with insufficient density or missing colors. Also in this case, the local light shortage can be reduced by the screen processing according to the present invention.

  As described above, the image forming apparatus and the image forming method in which the deterioration of the image quality of the present invention is suppressed have been described based on the principle and the embodiments. However, the present invention is not limited to these embodiments and can be variously modified.

It is a block diagram which shows embodiment of this invention. It is a flowchart which shows embodiment of this invention. It is a characteristic view which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is a characteristic view which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. 1 is a schematic cross-sectional view showing an overall configuration of an embodiment of an image forming apparatus using an electrophotographic process of the present invention. It is explanatory drawing which shows the premise technique of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Light emitting element, 3 ... Light emitting element group (spot group), 4 ... Lens (ML), 5n ... Lens array (MLA), 6 ... Latent image Spot, 11 ... screen table (screen data), 12 ... original image data, 13 ... screen growth adjustment data, 14a, 14b ... screen output data, 20 ... host computer (PC) , 23... Printer driver (image processing unit), 24... Color conversion module, 25... Screen processing module, 30... Image forming unit (printer), 31. 32, 32a ... Memory, 33 ... Engine controller (EC), 34 ... Head controller (HC), 35 ... Head control module, 6 ... Engine (EG), 37C, 37M, 37Y, 37K ... MLA head, 41 (Y, M, C, K) ... Photoconductor, 50 ... Intermediate transfer medium, 101 (Y , M, C, K) ... exposure head, P ... recording medium, Y, M, C, K ... image forming station

Claims (8)

A latent image carrier;
An imaging optical system, a light emitting element that emits light imaged on the latent image carrier by the imaging optical system, and a first direction and a second direction orthogonal or substantially orthogonal to the first direction; An exposure head having a substrate on which the light emitting element is disposed;
A screen processing unit for screen processing image data;
A control unit for adjusting the light amount of the light emitting element by the screen processing unit;
An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein the controller predicts the temperature of the substrate based on a light emission count value of the light emitting element. The image forming apparatus according to claim 2, wherein an offset value applied when screen processing is performed on the image data is set based on the predicted substrate temperature. The image forming apparatus according to claim 2, wherein screen adjustment data is set in the screen processing unit in correspondence with a light emission count value of the light emitting element. The screen adjustment data is added to a gradation value of one pixel of the image data and compared with screen data corresponding to the pixel set in the screen processing unit to determine whether the screen data is on or off. Item 5. The image forming apparatus according to Item 4. The image forming apparatus according to claim 1, wherein the imaging optical system is an inverted system. A latent image carrier;
An imaging optical system, a light emitting element that emits light imaged on the latent image carrier by the imaging optical system, and a first direction and a second direction orthogonal or substantially orthogonal to the first direction; An exposure head having a substrate on which the light emitting element is disposed,
Counting the number of light emission per unit time of a light emitting element that emits light imaged by the imaging optical system;
A step of decreasing the count value when the light emitting element emitting light imaged by the imaging optical system is turned off, and a step of increasing the count value when the light emitting element emits light;
Predicting the temperature of the substrate based on the count value;
Adjusting the light amount of the light emitting element by a screen according to the temperature of the substrate;
An image forming method comprising: The step of adjusting the light amount of the light emitting element with a screen,
Adding a gradation value of one pixel of image data and screen adjustment data;
Comparing the screen data corresponding to the pixel set in the screen processing unit and determining whether the screen data is on or off;
The image forming method according to claim 7, comprising:

Images