JP2011123444A - Exposure device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress unevenness in density in a sub scanning direction. <P>SOLUTION: An exposure device (ROS) includes a light amount storing means (C11) which is set according to the unevenness in density in respective plurality of divided regions (A0 to A31) regarding the plurality of divided regions (A0 to A31) where the surface is virtually divided along the sub scanning direction of image carriers (PRy to PRk) with reference positions (P0) set in image carriers (PRy to PRk) as references and stores light amount information that specifies the light amount for a light source (1) in a front end position in the sub scanning direction in the respective divided regions (A0 to A31) and light amount variation information which is the variation amount for the light amount in the divided regions and a light source control means (C12) for changing the light amount in the respective divided regions (A0 to A31) by controlling the light source (1) based on the reference position (P0), the light amount information and the light amount variation information that are stored to the light amount storing means (C11). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an image forming apparatus.

  In a conventional electrophotographic image forming apparatus, the techniques described in the following Patent Documents 1 and 2 are known for an exposure apparatus that exposes an image carrier.

  Japanese Patent Application Laid-Open No. 2005-7697 as Patent Document 1 discloses that in order to correct density unevenness in the sub-scanning direction of the photoconductor, the surface of the photoconductor (16) has 16 belt-like regions along the sub-scanning direction. The photoconductor reference position set in one place on the photoconductor (16) is detected by the photoconductor reference position detection sensor (30) once per rotation of the photoconductor (16), and the photoconductor is detected. A technique is described in which the light quantity of a semiconductor laser (LD) is corrected for each of the 16 regions with the body reference position as a reference.

  Japanese Patent Application Laid-Open No. 2005-262477 as Patent Document 2 describes, in an exposure apparatus, due to a difference in each laser beam of a surface emitting laser that irradiates a plurality of laser beams, an uneven charging of an optical system, a photosensitive drum, dirt, and the like. A technique for storing correction coefficients in the main scanning direction and the sub-scanning direction with respect to the reference light amount is described in order to reduce the amount of correction data when correcting the light amount unevenness in the main scanning direction and the sub-scanning direction.

Japanese Patent Laying-Open No. 2005-7697 (“0021”, “0031” to “0041”, “0051” to “0064”, FIGS. 1 to 3 and FIGS. 8 to 10) Japanese Patent Laying-Open No. 2005-262477 (“0004” to “0019”)

  An object of the present invention is to suppress density unevenness in an image caused by controlling a light amount change for correcting density unevenness of an image carrier.

In order to solve the technical problem, an exposure apparatus according to claim 1 comprises:
A light source that emits light that forms a latent image with respect to the exposure position of the image carrier;
With respect to a plurality of divided regions obtained by virtually dividing the surface along the sub-scanning direction of the image carrier with reference to a reference position set in advance along the sub-scanning direction of the image carrier, in each divided region A light amount that is set according to density unevenness and that stores light amount information that identifies the light amount of the light source at the front end position in the sub-scanning direction of each divided region and light amount change information that is a change amount of the light amount in the divided region Storage means;
Light source control means for controlling the light source based on the light quantity information and the light quantity change information stored in the light quantity storage means to change the light quantity in each divided region,
When the light source control unit receives a light amount change instruction, the light source control unit changes the light amount from the front end of the divided region in the sub-scanning direction when a latent image is not formed by the light source.

According to a second aspect of the present invention, in the exposure apparatus according to the first aspect,
The light amount storage means for storing the light amount information and the light amount change information set for each of a plurality of preset exposure conditions;
When there is a change in the exposure condition, control of the light source based on the light quantity information corresponding to the changed exposure condition and the light quantity change information from the front end in the sub-scanning direction of the divided area approaching the exposure position The light source control means for performing
It is provided with.

The invention described in claim 3 is the exposure apparatus according to claim 2,
First light source control means for controlling the light source using the light quantity information and the light quantity change information before the change of the exposure condition, and the light quantity information and the light quantity change information after the change of the exposure condition are used. And second light source control means for controlling the light source, and switching between the first light source control means and the second light source control means in accordance with a change in the exposure condition. means,
It is provided with.

The invention according to claim 4 is the exposure apparatus according to claim 2 or 3,
One light source for sequentially irradiating the surface of the image carrier with light forming images of different colors;
As the exposure condition, the light quantity storage means in which the respective colors formed on the surface of the image carrier are set;
It is provided with.

According to a fifth aspect of the present invention, in the exposure apparatus according to any one of the first to fourth aspects,
The light source control means for controlling the light source using the light amount value as the limit value when the light amount value exceeds the limit value based on limit information that specifies a preset limit value of the light amount,
It is provided with.

In order to solve the technical problem, an image forming apparatus according to a sixth aspect of the present invention provides:
A rotating image carrier;
An exposure apparatus according to any one of claims 1 to 5, wherein a latent image is formed on the surface of the image carrier.
A developing device for developing the latent image on the surface of the image carrier into a visible image;
A transfer device for transferring a visible image on the surface of the image carrier to a medium;
A fixing device for fixing a visible image on the surface of the medium;
It is provided with.

According to the first and sixth aspects of the present invention, the light quantity change for correcting the density unevenness of the image carrier is controlled based on the light quantity change information as compared with the case where the light quantity in each divided region is not changed. Can suppress density unevenness in the image.
According to the second aspect of the present invention, productivity can be improved as compared with the case where the light amount information and the light amount change information are controlled based on the reference position.
According to invention of Claim 3, productivity can be improved compared with the case where it does not have the structure of this invention.
According to the fourth aspect of the present invention, when an image of a plurality of colors is exposed with one exposure apparatus, the amount of light corresponding to the color can be set.
According to the fifth aspect of the present invention, it is possible to reliably detect the light serving as a reference for the start of scanning, compared to the case where no limit value is provided.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is an enlarged explanatory view of a main part of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is an overall explanatory view of the exposure apparatus according to the first embodiment. FIG. 4 is an explanatory diagram of a main part of the control unit according to the first embodiment. FIG. 5 is an explanatory diagram of a divided area according to the first embodiment. FIG. 6 is an explanatory diagram of an example of the light amount control of the first embodiment, FIG. 6A is an explanatory diagram of a change history of the light amount, FIG. 6B is an explanatory diagram of a history of changing from the Nth region to the N + 1th region, and FIG. It is explanatory drawing in the case of carrying out 1 step | paragraph correction | amendment of light quantity. FIG. 7 is a flowchart of the area head detection process according to the first embodiment. FIG. 8 is a flowchart of the parameter setting process according to the first embodiment. FIG. 9 is a flowchart of the light amount correction process according to the first embodiment. FIG. 10 is an explanatory diagram of an example of light amount control according to the first embodiment. FIG. 11 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the second embodiment, and corresponds to FIG. 4 according to the first embodiment. FIG. 12 is a flowchart of the parameter setting process according to the second embodiment and corresponds to FIG. 8 according to the first embodiment. FIG. 13 is a flowchart of the light amount correction process according to the second embodiment and corresponds to FIG. 9 according to the first embodiment. FIG. 14 is a flowchart of the control switching process according to the second embodiment. FIG. 15 is an explanatory diagram of an example of the light amount control of the second embodiment. The reference position, the inter-image area, the light amount setting value by the first light source control unit, and the light amount setting value by the second light source control unit. It is explanatory drawing of the relationship between and the output which actually controls light quantity. FIG. 16 is an overall explanatory view of an image forming apparatus according to Embodiment 3 of the present invention. FIG. 17 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the third embodiment, and corresponds to FIG. 4 according to the first embodiment. FIG. 18 is an explanatory diagram of the light amount setting value, FIG. 18A is an explanatory diagram of parameters of the third embodiment, and FIG. 18B is an explanatory diagram of parameters of a modified example of the third embodiment. FIG. 19 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the fourth embodiment, and corresponds to FIG. 4 according to the first embodiment. FIG. 20 is a flowchart of parameter setting processing according to the fourth embodiment, and corresponds to FIG. 8 according to the first embodiment. FIG. 21 is a flowchart of the light amount correction process according to the fourth embodiment and corresponds to FIG. 13 according to the second embodiment. FIG. 22 is an explanatory diagram of an example of light amount control according to the fourth embodiment. FIG. 23 is a block diagram illustrating functions of the control unit of the image forming apparatus according to the fifth embodiment, and corresponds to FIG. 4 according to the first embodiment. FIG. 24 is an explanatory diagram of an example of light amount control according to the fifth embodiment.

Next, examples as specific examples of embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The directions indicated by Z and -Z or the indicated side are defined as front, rear, right, left, upper, lower, or front, rear, right, left, upper, and lower, respectively.
In the figure, “•” in “○” means an arrow pointing from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a copying machine U as an example of an image forming apparatus includes an automatic document feeder U1 and an apparatus body U2 that supports the automatic document feeder U1 and has a transparent document reading surface PG at the upper end.
The automatic document feeder U1 includes a document feeding unit TG1 that accommodates a plurality of documents Gi to be copied, and a document feeding position that is fed from the document feeding unit TG1 and passes through a document reading position on the document reading surface PG. A document discharge section TG2 from which the document Gi is discharged.
The apparatus main body U2 includes an operation unit UI through which a user inputs an operation command signal for starting an image forming operation, an exposure optical system A, and the like.

Reflected light from a document conveyed on the document reading surface PG by the automatic document feeder U1 or a document manually placed on the document reading surface PG is passed through the exposure optical system A by the solid-state image sensor CCD. It is converted into electrical signals of red: R, green: G, blue: B.
The RGB electrical signals input from the solid-state imaging device CCD are converted into image information to be exposed in black: K, yellow: Y, magenta: M, cyan: C in the control unit C and temporarily stored. At a preset time, the image information is processed into image information for exposure and output to the latent image forming circuit DL.
When the original image is a single color image, so-called monochrome, image information of only black: K is input to the latent image forming circuit DL.

Further, when image information to be exposed is transmitted from a terminal PC such as a personal computer as an example of an image information transmitting apparatus connected to the copying machine U, the control unit C causes image information for exposure, that is, a latent image. The image information for formation is converted and output to the latent image forming circuit DL.
The latent image forming circuit DL has latent image forming circuits (not shown) for the respective colors Y, M, C, and K, and a latent image forming device driving signal corresponding to input image information is set at a preset time. The image is output to a latent image forming apparatus ROS as an example of an exposure apparatus.

Visible image forming devices Uy, Um, Uc, Uk arranged above the latent image forming device ROS are respectively visible images of yellow: Y, magenta: M, cyan: C, and black: K. This is an apparatus for forming a toner image as an example.
The latent image forming device ROS emits latent image writing lights Ly, Lm, Lc, and Lk. The latent image writing lights Ly to Lk are incident on rotating photoreceptors PRy, PRm, PRc, and PRk, respectively, as an example of an image carrier.
The Y-color visible image forming device Uy includes a photoreceptor PRy, a charger CRy, a developing device Gy, and an image carrier cleaning device CLy, and the visible image forming devices Um, Uc, Uk are all. It is configured in the same manner as the Y-color visible image forming device Uy.

FIG. 2 is an enlarged explanatory view of a main part of the image forming apparatus according to the first embodiment of the present invention.
1 and 2, the photoconductors PRy, PRm, PRc, and PRk are charged by their respective chargers CRy, CRm, CRc, and CRk, and then image writing positions Q1y, Q1m, as an example of exposure positions. In Q1c and Q1k, an electrostatic latent image is formed on the surface by the latent image writing lights Ly to Lk. The electrostatic latent images on the surfaces of the photoconductors PRy, PRm, PRc, and PRk are developed in the developing regions Q2y, Q2m, Q2c, and Q2k as developing roller R0y as an example of a developer holding member of the developing devices Gy, Gm, Gc, and Gk. , R0m, R0c, and R0k are developed into a toner image as an example of a visible image.
The developed toner image is conveyed to primary transfer regions Q3y, Q3m, Q3c, and Q3k that are in contact with an intermediate transfer belt B as an example of an intermediate transfer member. The primary transfer units T1y, T1m, T1c, and T1k disposed on the back side of the intermediate transfer belt B in the primary transfer regions Q3y, Q3m, Q3c, and Q3k are preliminarily supplied from the power supply circuit E controlled by the control unit C. At the set time, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied.

The toner images on the photoconductors PRy to PRk are primarily transferred to an intermediate transfer belt B as an example of an intermediate transfer body by the primary transfer units T1y, T1m, T1c, and T1k. Residues and deposits on the surface of the photoreceptors PRy, PRm, PRc, and PRk after the primary transfer are cleaned by the photoreceptor cleaners CLy, CLm, CLc, and CLk. The cleaned surfaces of the photoreceptors PRy, PRm, PRc, and PRk are recharged by the chargers CRy, CRm, CRc, and CRk.
In FIG. 2, in the first embodiment, a reference position sensor SN <b> 1 as an example of a reference position detection member is disposed to face each of the photoconductors PRy to PRk.

  Above the photoconductors PRy to PRk, a belt module BM as an example of an intermediate transfer device is disposed. The belt module BM includes the intermediate transfer belt B, a belt drive roll Rd as an example of an intermediate transfer member drive member, a tension roll Rt as an example of a tension applying member, a walking roll Rw as an example of a meandering prevention member, and a driven It includes an idler roll Rf as an example of a member, a backup roll T2a as an example of a secondary transfer counter member, and the primary transfer units T1y, T1m, T1c, and T1k. The intermediate transfer belt B is rotatably supported by the rolls Rd, Rt, Rw, Rf, and T2a.

A secondary transfer roll T2b as an example of a secondary transfer member is disposed facing the surface of the intermediate transfer belt B in contact with the backup roll T2a. The backup roll T2a and the secondary transfer roll T2b constitute a secondary transfer device T2. Further, a secondary transfer region Q4 is formed by a region where the secondary transfer roll T2b and the intermediate transfer belt B face each other.
The single-color or multi-color toner images transferred on the intermediate transfer belt B by the primary transfer units T1y, T1m, T1c, and T1k in the primary transfer regions Q3y, Q3m, Q3c, and Q3k It is conveyed to the secondary transfer area Q4.
The primary transfer units T1y to T1k, the intermediate transfer belt B, the secondary transfer unit T2, and the like constitute a transfer device T1 + T2 + B of Example 1 that transfers an image formed on the photoconductors PRy to PRk to a medium.

  Below the visible image forming devices Uy to Uk, a pair of left and right guide rails GR as an example of a guide member is provided, and the guide rail GR has a sheet feed as an example of a sheet feeding unit. The trays TR1 to TR3 are supported so as to be able to enter and exit in the front-rear direction. A recording sheet S as an example of a medium accommodated in the paper feed trays TR1 to TR3 is taken out by a pickup roll Rp as an example of a medium take-out member, and separated one by one by a separating roll Rs as an example of a medium separating member. The The recording sheet S is transported along a sheet transport path SH, which is an example of a medium transport path, by a plurality of transport rolls Ra, which is an example of a medium transport member, and is disposed upstream of the secondary transfer region Q4 in the sheet transport direction. Is sent to a registration roll Rr as an example of the transport time adjusting member. A sheet conveying device SH + Ra + Rr is configured by the sheet conveying path SH, the sheet conveying roll Ra, the registration roll Rr, and the like.

The registration roll Rr conveys the recording sheet S to the secondary transfer area Q4 in time for the toner image formed on the intermediate transfer belt B to be conveyed to the secondary transfer area Q4. When the recording sheet S passes through the secondary transfer region Q4, the backup roll T2a is grounded, and the secondary transfer unit T2b is supplied with a polarity opposite to the charged polarity of the toner from the power supply circuit E controlled by the control unit C. A secondary transfer voltage is applied. At this time, the toner image on the intermediate transfer belt B is transferred to the recording sheet S by the secondary transfer device T2.
The intermediate transfer belt B after the secondary transfer is cleaned by a belt cleaner CLb as an example of an intermediate transfer body cleaner.

The recording sheet S on which the toner image is secondarily transferred has a fixing region Q5 which is a contact region of a heating roll Fh as an example of a heating fixing member of the fixing device F and a pressure roll Fp as an example of a pressure fixing member. And heated and fixed when passing through the fixing region Q5. The heat-fixed recording sheet S is discharged from a discharge roller Rh as an example of a medium discharge member to a discharge tray TRh as an example of a medium discharge unit.
A release agent for improving the releasability of the recording sheet S from the heating roll Fh is applied to the surface of the heating roll Fh by a release agent coating device Fa.

  Above the belt module BM, developer cartridges Ky, Km, Kc, and Kk as an example of developer storage containers that store yellow: Y, magenta: M, cyan: C, and black: K developers are arranged. Has been. Developers stored in the developer cartridges Ky, Km, Kc, Kk are replenished to the developing devices Gy, Gm, Gc, Gk according to the consumption of the developer in the developing devices Gy, Gm, Gc, Gk. Is done. In Example 1, the developer contained in the developing devices Gy to Gk is constituted by a two-component developer including a magnetic carrier and a toner to which an external additive is applied. Then, toner is supplied to the developing devices Gy to Gk from the developer cartridges Ky to Kk.

(Explanation of exposure apparatus)
FIG. 3 is an overall explanatory view of the exposure apparatus according to the first embodiment.
In FIG. 3, the latent image forming apparatus ROS according to the first embodiment of the present invention includes a laser diode 1 for each of Y, M, C, and K as an example of a light source. Although the laser diode 1 is exemplified as the light source, the present invention is not limited to this, but a VCSEL (Vertical Cavity Surface Emitting LASER) in which light emitting elements are two-dimensionally arranged in the main scanning direction and the sub-scanning direction, a vertical cavity surface emitting laser. It is also possible to employ a surface emitting laser such as
The laser beam 2 output from the laser array 1 is irradiated to a rotary polygon mirror that rotates at a preset rotation speed, a so-called polygon mirror 6, via a collimator lens 3 and a cylindrical lens 4 as an example of a condensing optical system. Is done.

The laser beam 2 reflected by the polygon mirror 6 is irradiated onto the surfaces of the photoconductors PRy to PRk via a toroidal lens 7 and a scanning lens 8 as an example of an irradiation optical system, a so-called fθ lens 8 and a reflecting mirror (not shown). . Therefore, in the laser diode 1 according to the first embodiment, the pixel 9 is formed by one lighting, and the scanning line 10 is formed when scanning is performed in the main scanning direction on one surface of the polygon mirror 6.
Note that the laser beam 2 is incident on the photodetector 12 via the reflecting mirror 11 immediately before or immediately after the scanning of the scanning line group 9 at positions separated in the main scanning direction of the photoconductors PRy to PRk. The transition to the next scan is detected. That is, a so-called SOS: Start of Scan signal is output.

(Description of control unit C)
FIG. 4 is an explanatory diagram of a main part of the control unit according to the first embodiment.
In FIG. 4, the control unit C stores an input / output interface for performing input / output of signals to / from the outside, adjustment of input / output signal levels, etc .: I / O, a program and information for performing necessary processing, and the like. Read only memory: ROM, random access memory for temporarily storing necessary data: RAM, central processing unit for processing according to the program stored in the ROM: CPU, small information having an oscillator, etc. The processing unit is constituted by a so-called microcomputer, and various functions can be realized by executing a program stored in the ROM.

(Signal input element connected to control unit C)
The control unit C is supplied with output signals such as the next signal output elements UI and SN1.
UI: Operation Unit The operation unit UI includes a display unit UI1, a copy start key UI2 as an example of a copy start input unit, a copy number input key UI3 as an example of a copy number input unit, and the like.

FIG. 5 is an explanatory diagram of a divided area according to the first embodiment.
SN1: Reference position sensor Each reference position sensor SN1 detects a reference position P0 set in advance along the sub-scanning direction of the photoconductors PRy to PRk. In FIG. 5, in Example 1, in each of the photoconductors PRy to PRk, the surface is virtually divided into a plurality of divided regions A0 to A31 along the sub-scanning direction of the photoconductors PRy to PRk, that is, the rotation direction of the surface. Thus, the reference position P0 is set at the front end of the first divided area A0 in the sub-scanning direction, that is, the position of the upstream end of the surface in the direction of rotation. In Example 1, the detected member 21 is supported at each reference position P0 of each of the photoconductors PRy to PRk, and the reference position P0 is detected by detecting the detected member 21 by the reference position sensor SN1. In the first embodiment, the divided area is set to a band-shaped area divided into 32 areas A0 to A31. However, the number of areas can be arbitrarily changed according to the design, specifications, and the like.

(Controlled element connected to control unit C)
The control unit C outputs a control signal for the next controlled element.
DL: Laser drive circuit The laser drive circuit DL drives the latent image forming device ROS to form electrostatic latent images on the surfaces of the photoconductors PRy to PRk.
D0: main motor drive circuit The main motor drive circuit D0 as an example of the main drive source drive circuit drives the main motor M0 to drive the photoconductors PRy to PRk and the developing devices Gy to Gk through gears (not shown). The developing roller, the heating roller Fh, the conveying roller Ra, the registration roller Rr, and the like are driven to rotate.

E: Power supply circuit The power supply circuit E has the following power supply circuit.
E1y to E1k: Developing power supply circuit The developing power supply circuits E1y to E1k apply a developing voltage to the developing rollers of the developing devices Gy to Gk.
E2y to E2k: Charging power supply circuit The charging power supply circuits E2y to E2k apply a charging voltage to the chargers CRy to CRk.
E3y to E3k: primary transfer power supply circuit The primary transfer power supply circuits E3y to E3k apply a primary transfer voltage to the primary transfer rollers T1y to T1k.
E4: Secondary transfer power supply circuit The secondary transfer power supply circuit E4 applies a secondary transfer voltage to the secondary transfer roller T2b.
E5: Fixing Power Supply Circuit The fixing power supply circuit E5 supplies heating power to the heating roller Fh.

(Function of the controller C)
The controller C has function realization means that is a program that realizes a function of executing a process according to an output signal from each signal output element and outputting a control signal to each control element. Next, function realizing means for realizing various functions of the controller C will be described.
C1: Main motor rotation control means A main motor rotation control means C1, which is an example of a main drive source control means, controls the main motor drive circuit D0 so that the photosensitive members PRy to PRk, the developing rollers of the developing devices Gy to Gk, Controls the rotation of the fixing device F or the like.

C2: Power supply circuit control means The power supply circuit control means C2 includes the following means C2a to C2e, and controls the power supply circuit E to control the developing voltage, charging voltage, transfer voltage, and heater of the heating roller Fh. Control on / off, etc.
C2ay to C2ak: Development voltage control means The development voltage control means C2ak to C2ak control the development voltage applied to the development rollers of the development devices Gy to Gk by controlling the operations of the development power supply circuits E1y to E1k.
C2by to C2bk: Charging voltage control means The charging voltage control means C2by to C2bk controls the operation of the charging power supply circuits E2y to E2k to control the charging voltage applied to the chargers CRy to CRk.

C2cy to C2ck: primary transfer voltage control means The primary transfer voltage control means C2cy to C2ck controls the operation of the primary transfer power supply circuits E3y to E3k to control the transfer voltage applied to the primary transfer rollers T1y to T1k.
C2d: Secondary transfer voltage control means The secondary transfer voltage control means C2d controls the operation of the secondary transfer power supply circuit E4 to control the secondary transfer voltage applied to the secondary transfer roller T2b.
C2e: Fixing power supply control means The fixing power supply control means C2e controls the operation of the fixing power supply circuit E5, controls the heater of the heating roller Fh on / off, and controls the fixing temperature.
C3: Job Control Unit The job control unit C3, which is an example of the image forming operation control unit, responds to an input from the copy start key UI2 or the terminal PC, and the latent image forming device ROS, the photoconductors PRy to PRk, and the transfer rollers T1y to By controlling the operations of T1k, T2, fixing device F, etc., a job which is an image forming operation is executed.

C4: Exposure condition setting means The exposure condition setting means C4 sets the exposure conditions in the latent image forming apparatus ROS for each color. The exposure condition setting means C4 according to the first embodiment includes information related to exposure such as resolution, character image or photographic image included in information from the terminal PC, medium conveyance speed according to the type of medium used, and an operation unit. Based on information such as resolution set in the UI, exposure conditions such as an arrangement angle when a halftone dot in which a plurality of pixels are arranged, a so-called screen angle, and a screen line number which is a pixel density are set. Set. For example, in the case of a photographic image, the screen resolution is set to 150 [lines / inch] for the low resolution and low speed conveyance speed, and the screen is set for the character image, the high resolution setting and the high speed conveyance speed. It is possible to set the number of lines to 200 [lines / inch]. In the first embodiment, as an example, the exposure condition is set to change in order to change the amount of light every time the number of continuously printed sheets exceeds 100 [sheets]. Note that the exposure condition setting unit C4 according to the first embodiment determines and sets the exposure condition for each page when a plurality of pages of images are printed.

C5: Exposure condition storage means The exposure condition storage means C5 stores the exposure conditions set by the exposure condition setting means C4.
C6: Exposure condition change determining means The exposure condition change determining means C6 determines whether or not the exposure condition set by the exposure condition setting means C4 is changed between the previous page and the next page.
C7: Reference position detection means The reference position detection means C7 determines whether or not the reference position P0 has passed the image writing positions Q1y to Q1k for each of the photoconductors PRy to PRk based on the output result of the reference position sensor SN1. Determine. In the first embodiment, the reference position P0 is determined from the distance from the reference position sensor SN1 to the image writing positions Q1y to Q1k, the rotational speed of the photoconductors PRy to PRk, and the output of the reference position sensor SN1. It is determined whether or not it has passed through the insertion positions Q1y to Q1k.

C8: Area start detection means The area start detection means C8 as an example of the front end position detection means includes an area determination time storage means C8A as an example of the front end determination time storage means, and a discrimination time timing timer TM1 as an example of a time measurement means. And front signal output means C8B as an example of the area front edge signal output means, and the front ends of the divided areas A1 to A31 in the sub-scanning direction, that is, the areas A1 to A31, for each of the photoconductors PRy to PRk. It is detected whether or not the front end, that is, the head of the image has passed the image writing positions Q1y to Q1k.
C8A: Area discriminating time storage means The area discriminating time storage means C8A stores an area discriminating time t1 for discriminating whether or not the head has reached the image writing positions Q1y to Q1k. In the area determination time t1 of the first embodiment, when n is a positive number from 0 to 31, the photosensitive body PRy from when the front end of each divided area An passes until the front end of the next divided area An + 1 passes. It is set based on the rotation time of PRk.

TM1: Discrimination time clock timer The discrimination time clock timer TM1 measures whether or not the region discrimination time t1 has elapsed. The discrimination time counting timer TM1 of the first embodiment starts measuring the region discrimination time t1 when the SOS signal at the front end of each divided region An is output, but is not limited to the time when the SOS signal is output. It is also possible to start measurement based on the time and signal.
C8B: Leading signal output means When the leading time t1 elapses and the front end of the next divided area An + 1 passes, the leading signal output means C8B outputs a signal for notifying that the leading has passed.
C9: Area Number Storage Unit The area number storage unit C9 stores an area number n that identifies the divided area An that the current head has passed.
C10: Area number update means When the head signal is output, the area number update means C10 updates the area number n stored in the area number storage means C9 to a value obtained by adding 1. That is, n = n + 1 is calculated.

FIG. 6 is an explanatory diagram of an example of the light amount control of the first embodiment, FIG. 6A is an explanatory diagram of a change history of the light amount, FIG. 6B is an explanatory diagram of a history of changing from the Nth region to the N + 1th region, and FIG. It is explanatory drawing in the case of carrying out 1 step | paragraph correction | amendment of light quantity.
C11: Light quantity storage means The light quantity storage means C11 is set according to the density unevenness in each divided area A0 to A31, and the light quantity of each laser diode 1 at the front end position in the sub-scanning direction of each divided area A0 to A31. A starting light amount value V0 to V31 as an example of light amount information to be specified and correction amounts H0 to H31 as an example of light amount change information that is a change amount of the light amount in the divided areas A0 to A31 are stored. As shown in FIG. 6, in the first embodiment, start light amount values V0 to V31 determined in advance by experiments or the like are stored, and the correction value Hn of the divided region An is the start light amount value Vn and the next divided region An + 1. Is set to a value obtained by dividing the difference from the starting light quantity value Vn + 1 by 6. That is, in each divided area An, the start light quantity value Vn is corrected six times so that the start light quantity value Vn + 1 of the next divided area An + 1 is gradually set. The number of corrections is not limited to six, and can be arbitrarily changed according to design, specifications, and the like. In addition, the light amount storage unit C11 according to the first embodiment stores a start light amount value Vn and a correction amount Hn for each of the exposure conditions.

C12: Light source control means The light source control means C12 includes start light quantity value acquisition means C12A, correction amount acquisition means C12B, acquisition information update means C12C, light quantity setting means C12D, light quantity setting value storage means C12E, and correction period storage. Means C12F, a correction period timing timer TM2 as an example of a correction period timing means, a light quantity correction means C12G, a limit value storage means C12H, a limit determination means C12J, a control light quantity setting means C12K, and a control light quantity output means C12L And have. Then, the light source control means C12 controls each laser diode 1 based on the reference position P0, the start light quantity value Vn and the correction value Hn stored in the light quantity storage means C11, and sets the light quantity in each divided area An. Change. That is, in the latent image forming apparatus ROS according to the first embodiment, a latent image is formed by the laser beams Ly to Lk having the changed and set light amounts.

C12A: Start light amount value acquisition unit A start light amount value acquisition unit C12A as an example of a light amount information acquisition unit acquires a start light amount value Vn corresponding to an exposure condition from the light amount storage unit C11.
C12B: Correction Amount Acquisition Unit An amount correction amount acquisition unit C12B as an example of the light amount change information acquisition unit acquires a correction amount Hn corresponding to the exposure condition from the light amount storage unit C11.

C12C: Acquisition Information Update Unit The acquisition information update unit C12C includes an inter image determination unit C12C1 as an example of an inter-image region determination unit, and updates the information acquired by each of the acquisition units C12A and C12B. The acquisition information updating unit C12C according to the first embodiment corresponds to the changed exposure condition from the front end in the sub-scanning direction of the divided area An that approaches the image writing positions Q1y to Q1k when the exposure condition is changed. The information is reacquired and updated from the light amount storage means C11 so as to be changed to the start light amount value Vn and the correction amount Hn. In the first embodiment, the image writing positions Q1y to Q1k are set in the area between the previous page and the next page, that is, in the so-called inter-image area, by the inter-image area determination unit C12C1. When it reaches, the parameter including the start light amount value Vn and the correction light amount Hn is updated and changed.

C12D: Light quantity setting means The light quantity setting means C12D sets the light quantity of each laser diode 1 when forming a latent image, based on the parameters acquired by the start light quantity value acquisition means each acquisition means C12A. The light amount setting unit C12D according to the first embodiment sets the corresponding start light amount value Vn to the light amount setting value Va every time the tip of each divided region An passes.
C12E: Light quantity setting value storage means The light quantity setting value storage means C12E stores the light quantity setting value Va set by the light quantity setting means C12D.

C12F: Correction Period Storage Unit The correction period storage unit C12F stores a correction period t2 for correcting the light amount setting value Va. In FIG. 6, in the first embodiment, the correction period t <b> 2 corresponds to performing six stepwise corrections until the head of the next divided area An + 1 reaches after the head of the divided area An has passed. A value obtained by dividing the period t1 by 6 is set.
TM2: Correction period timing timer The correction period timing timer TM2 counts whether or not the correction period t2 has elapsed. The correction period clock timer TM2 of the first embodiment starts measurement of the correction period t2 when the SOS signal at the front end of each divided region An is output, but is not limited to the output of the SOS signal. It is also possible to start measurement based on the time and signal.

C12G: Light quantity correction means The light quantity correction means C12G has a light quantity setting value Va with a correction value Hn each time a correction period t2 which is a correction period elapses after the start light quantity value Vn is set by the light quantity setting means C12D. Correct. That is, Va = Va + Hn is calculated, and the set value Va stored in the light amount set value storage means C12E is updated.
C12H: Limit value storage means As shown in FIG. 6, the limit value storage means C12H as an example of limit information storage means stores an upper limit value storage means C12H1 for storing the upper limit value VH of the light amount and a lower limit value VL of the light amount. Lower limit value storage means C12H2, and stores an upper limit value VH and a lower limit value VL as an example of limit information.

C12J: Limit determination unit The limit determination unit C12J determines whether or not the set value Va stored in the light amount set value storage unit C12E is within the range of the lower limit value VL to the upper limit value VH.
C12K: Control light quantity setting means The control light quantity setting means C12K sets a control value of the light quantity for controlling the laser diode 1 of each color of the latent image forming apparatus ROS. The control light amount setting unit C12K according to the first embodiment sets the set value Va as a control value when the light amount setting value Va is within the range of the lower limit value VL to the upper limit value VH. When the set value Va is larger than the upper limit value VH, the upper limit value VH is set as the control value. When the set value Va is smaller than the lower limit value VL, the lower limit value VL is set as the control value.
C12L: Control light quantity output means The control light quantity output means C12L outputs the control value of the light quantity set by the control light quantity setting means C12K to the laser drive circuit DL, and causes the laser diode 1 to emit light with the control value.

(Explanation of flowchart of Example 1)
Next, a processing flow of the image forming apparatus U according to the first exemplary embodiment of the present invention will be described with reference to a flowchart, that is, a so-called flowchart.
In the following description, since the same processing is executed for each color of Y, M, C, and K, only one color processing will be described, and description of other color processing will be omitted. .

(Description of area head detection processing)
FIG. 7 is a flowchart of the area head detection process according to the first embodiment.
7 is performed according to a program stored in the ROM of the control unit C. This process is executed in a multitasking manner in parallel with other various processes of the copying machine U.
The flowchart shown in FIG. 7 is started when the power is turned on.

In ST1 of FIG. 7, it is determined whether or not a job that is an image forming operation is started. If yes (Y), the process proceeds to ST2. If no (N), ST1 is repeated.
In ST2, it is determined whether or not the reference position P0 is detected, that is, whether or not the reference position P0 has reached the image writing positions Q1y to Q1k. If yes (Y), the process proceeds to ST3. If no (N), the process proceeds to ST6.
In ST3, the area number n is set to 0. That is, n = 0 is set. Then, the process proceeds to ST4.
In ST4, it is determined whether or not an SOS signal is output. If yes (Y), the process proceeds to ST5, and if no (N), ST4 is repeated.
In ST5, the region discrimination time t1 is input to the discrimination time clock timer TM1 to start timing. Then, the process returns to ST2.

In ST6, it is determined whether or not the determination time counting timer TM1 has expired, that is, whether or not the region determination time t1 has elapsed. If yes (Y), the process proceeds to ST7. If no (N), the process proceeds to ST9.
In ST7, it is determined whether or not an SOS signal is output. If yes (Y), the process proceeds to ST8, and if no (N), ST7 is repeated.
In ST8, the following processes (1) and (2) are executed, and the process proceeds to ST5.
(1) Add 1 to the area number n. That is, n = n + 1 is set.
(2) The updated area number n and the head signal are output.
In ST9, it is determined whether or not the job is finished. If yes (Y), the process returns to ST1, and if no (N), the process returns to ST2.

(Explanation of parameter setting process)
FIG. 8 is a flowchart of the parameter setting process according to the first embodiment.
The process of each ST: step in the flowchart of FIG. 8 is performed according to a program stored in the ROM of the control unit C. This process is executed in a multitasking manner in parallel with other various processes of the copying machine U.
The flowchart shown in FIG. 8 is started when the power is turned on.

In ST11 of FIG. 8, it is determined whether or not a job that is an image forming operation is started. If yes (Y), the process proceeds to ST12. If no (N), ST11 is repeated.
In ST12, parameters corresponding to the exposure conditions of the image of the first page to be printed, that is, start light amount values V0 to V31 and correction values H0 to H31 are acquired. Then, the process proceeds to ST13.
In ST13, it is determined whether or not the exposure conditions of the current page and the next page are the same. If no (N), the process proceeds to ST14, and if yes (Y), the process proceeds to ST17.

In ST14, it is determined whether or not the image writing areas Q1y to Q1k have entered the inter image area from the print area of the current page. If yes (Y), the process proceeds to ST15, and if no (N), ST14 is repeated.
In ST15, it is determined whether or not a head signal has been output in the region head detection process of FIG. If yes (Y), the process proceeds to ST16, and if no (N), ST15 is repeated.
In ST16, parameters corresponding to the exposure conditions for the next page are acquired and updated. Then, the process returns to ST13.
In ST17, it is determined whether or not the job is finished. If no (N), the process returns to ST13, and if yes (Y), the process returns to ST11.

(Explanation of light intensity correction process)
FIG. 9 is a flowchart of the light amount correction process according to the first embodiment.
9 is performed according to a program stored in the ROM of the control unit C. This process is executed in a multitasking manner in parallel with other various processes of the copying machine U.
The flowchart shown in FIG. 9 is started when the power is turned on.

In ST21 of FIG. 9, it is determined whether or not a job that is an image forming operation is started. If yes (Y), the process proceeds to ST22, and if no (N), ST21 is repeated.
In ST22, it is determined whether or not the reference position P0 has been detected. If yes (Y), the process proceeds to ST23, and, if no (N), the process proceeds to ST31.
In ST23, the starting light amount value V0 of the 0th divided area A0 is set from the acquired parameters as the light amount setting value Va. That is, Va = V0. Then, the process proceeds to ST24.
In ST24, it is determined whether or not an SOS signal is output. If yes (Y), the process proceeds to ST25, and if no (N), ST24 is repeated.
In ST25, the correction period t2 is set in the correction period timekeeping timer TM2, and time measurement is started. Then, the process proceeds to ST26.

In ST26, it is determined whether or not the light intensity setting value Va is greater than or equal to the upper limit value VH. If yes (Y), the process proceeds to ST27, and, if no (N), the process proceeds to ST28.
In ST27, the upper limit value VH is output as the light quantity control value. Then, the process proceeds to ST22.
In ST28, it is determined whether or not the light intensity setting value Va is less than or equal to the lower limit value VL. If yes (Y), the process proceeds to ST29, and, if no (N), the process proceeds to ST30.
In ST29, the lower limit VL is output as the light quantity control value. Then, the process proceeds to ST22.
In ST30, the set value Va is output as the light amount control value. Then, the process proceeds to ST22.

In ST31, it is determined whether or not a head signal is output. If yes (Y), the process proceeds to ST32. If no (N), the process proceeds to ST33.
In ST32, the starting light amount value Vn of the nth divided region An is set from the acquired parameters as the light amount setting value Va. That is, Va = Vn is set. Then, the process proceeds to ST24.
In ST33, it is determined whether or not the correction period clock timer TM2 has expired, that is, whether or not the correction period t2 has elapsed. If yes (Y), the process proceeds to ST34, and, if no (N), the process proceeds to ST35.

In ST34, the light quantity setting value Va is corrected using the correction amount Hn of the divided area An of the current area number n from the acquired parameters. That is, Va = Va + Hn. Then, the process proceeds to ST24.
In ST35, it is determined whether or not the job is finished. If no (N), the process returns to ST22, and if yes (Y), the process returns to ST21.

(Operation of Example 1)
FIG. 10 is an explanatory diagram of an example of light amount control according to the first embodiment.
In the copying machine U of the first embodiment having the above-described configuration, image information read by the exposure optical system A or transmitted from the terminal PC is subjected to image processing to image information for exposure by the latent image forming device ROS, and a laser diode 1 emits light and a latent image is formed.
6 and 10, in the copying machine U according to the first embodiment, when an image is formed on the recording sheets S1 and S2, the light quantity is set with reference to the reference position P0, and the latent image forming apparatus uses the set light quantity. The ROS laser diode 1 emits light to form a latent image.

It is difficult to make the surface distribution completely uniform in the manufacturing process of the photoconductors PRy to PRk, and uneven sensitivity occurs in the sub-scanning direction. In addition, unevenness in sensitivity also occurs due to attachment errors of the photoconductors PRy to PRk to the apparatus main body U2 and wear over time. At this time, in the conventional technique as shown in Patent Document 1, the light amount is controlled stepwise with respect to the sensitivity unevenness in the sub-scanning direction, and a large light amount step is generated at the boundary between the divided regions. Therefore, in the written image, there is a possibility that a level difference, that is, density unevenness occurs in the density of the image.
On the other hand, in the first embodiment, even within each divided region An, the correction amount Hn is finely corrected, and as a whole, the light amount is changed pseudo-continuously. Therefore, the occurrence of density unevenness across the switching of the divided areas is reduced. Further, in the prior art, the parameter amount, that is, the number of control values of the light amount increases in order to continuously change the light amount so that the step is not conspicuous. In the first embodiment, the correction is made with the start light amount value Vn and the correction. Only the value Hn is sufficient, and the parameter amount is small. That is, in the prior art, it is necessary to store all the values corresponding to Vn, Vn + Hn, Vn + 2 × Hn, Vn + 3 × Hn,..., But in Example 1, only the starting light amount value Vn and the correction value Hn are stored. That's it.

  In FIG. 10, when the exposure condition is changed between the preceding recording sheet S1 and the succeeding recording sheet S2, for example, when the preceding sheet S1 is a character image and the succeeding sheet S2 is a photographic image, In the conventional configuration as described in Document 1, the parameter is changed when the reference position P0 arrives. If the parameters are changed during printing of each image, a change in shading, that is, density unevenness occurs in the middle of the image. Therefore, in the prior art, the reference position P0 needs to be an inter-image area in order to prevent density unevenness from occurring. However, in this case, unless the length of the inter image area in the sub-scanning direction is equal to or longer than one rotation of the photoconductors PRy to PRk, the parameter cannot be switched at the reference position P0 in the inter image area, which is long. It is necessary to secure an inter-image area. Therefore, the conventional technique has a problem that it is difficult to improve productivity, which is the number of printed sheets per unit time.

On the other hand, in the first embodiment, when the exposure condition for the next page is different, the parameter is changed at the head of the divided area An of the inter-image area. Therefore, the parameter is not changed in the middle of the image, and the inter-image area may be set to the length of the divided area An, that is, the length of 1/32 round or more in the first embodiment. The inter-image area can be shortened, and productivity can be improved.
In particular, when performing continuous printing of several hundred to several thousand sheets, the temperature of the photoconductors PRy to PRk may increase during printing, and the sensitivity of the photoconductors PRy to PRk may change. There is a problem that the density unevenness becomes conspicuous between the eyes and the 1000th page, and it is necessary to change the light quantity parameter for every fixed number of sheets. In the first embodiment, the parameter is changed every 100 sheets, and density unevenness is reduced as compared with the case where the parameter is not corrected during continuous printing.

In addition, if the parameter is changed, the timing for adding the correction value Hn or the timing for setting the start light quantity value Vn at the beginning of the divided area An overlaps with the parameter rewriting timing. Correction is performed with only some parameters being changed. Further, the end position of the divided area An, that is, the area determination time t1 may be changed in the middle of the change in the image forming speed. In some cases, the starting light amount value Va set as a parameter or the setting value Va being corrected exceeds the upper limit value VH or the lower limit value VL. In these cases, the light amount setting value Va may be an unexpected numerical value different from the target numerical value to be controlled, and may exceed the upper limit value VH or the lower limit value VL. Here, when the light is emitted with the light amount equal to or higher than the upper limit value VH, there is a problem that the laser diode 1 is loaded and the life is shortened. When the light amount is emitted with the light amount equal to or lower than the lower limit value VL, There is a possibility that the laser beam 2 cannot be detected and the SOS signal is not output.
In contrast, in the first embodiment, when the light intensity setting value Va is equal to or higher than the upper limit value VH or lower than the lower limit value VL, the upper limit value VH and the lower limit value VL are used without using the setting value Va. Control. Therefore, in the first embodiment, it is possible to reliably output the SOS signal from the photodetector 12 while extending the life of the laser diode 1 as compared with the case where the upper limit value VH and the lower limit value VL are not used. .

FIG. 11 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the second embodiment, and corresponds to FIG. 4 according to the first embodiment.
In the description of the second embodiment, components corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
The second embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.

(Description of Control Unit of Example 2)
In FIG. 11, the light source control means C12 ′ of the copying machine U according to the second embodiment includes a first light source control means C121, a second light source control means C122, and a control switching means C123. The first light source control means C121 has the following means C121A, C121B, C121C in place of the acquired information update means C12C in the light source control means C12 of the first embodiment, and the light source control means of the first embodiment. Each means C12A, C12B, C12D to C12L is the same as C12. Similarly to the first light source control unit C121, the second light source control unit C122 also includes the units C122A, C122B, C122C, and the same units C12A, C12B, C12D as the light source control unit C12 of the first embodiment. ~ C12L. The units C122A to C122C of the second light source control unit are the same as the units C121A to C121C of the first light source control unit, and thus detailed description thereof is omitted.

C121A: Acquisition Information Update Unit The acquisition information update unit C121A updates the information acquired by each acquisition unit C12A, C12B. The acquisition information update unit C121A of the second embodiment updates parameters when there is a change in exposure conditions and the first light source control unit C121 is not used for controlling the laser diode 1. In addition, in the acquisition information update unit C121A of the second embodiment, when the start of the first divided area An is reached after the acquisition time t3 for acquiring the parameter has passed, the acquired information is updated, that is, with the acquired information. The calculation of the set value Va of the light quantity is started. Therefore, the correction of the set value Va is not performed until the calculation of the light amount set value Va is resumed after the acquisition of the parameter corresponding to the exposure condition on the next page is started, and the value of the set value Va is not changed. , The value at the start of parameter acquisition is held.

C121B: Acquisition Time Storage Unit The acquisition time storage unit C121B stores acquisition time t3 for acquiring parameters, so-called access time. The acquisition time t3 of the second embodiment is set to a time during which the parameters after changing the exposure conditions can be sufficiently acquired according to the circuit configuration, the CPU processing speed, the communication speed between the circuits and elements, and the like.
C121C: Acquisition time timing means The acquisition time timing means C121C measures the acquisition time t3 when there is a change in exposure conditions.

C123: Control switching unit The control switching unit C123 includes an output setting unit C123A, an output storage unit C123B, an inter-image determination unit C123C, and an output change determination unit C123D, and is a unit that controls the light amount of the laser diode 1. , Switching between the first light source control means C121 and the second light source control means C122.
C123A: Output Setting Unit The output setting unit C123A uses either the light amount control signal from the first light source control unit C121 or the light amount control signal from the second light source control unit C122 as an actual control signal for the laser diode 1. Set whether to output as. In the output setting unit C123A of the second embodiment, a setting is made so that the light amount control signal from the first light source control unit C121 is output immediately after the start of the job, and thereafter, the exposure condition is changed. In addition, in the inter-image area, when the head of the divided area An is approaching, a setting is made to switch from one light source control means C121, C122 used so far to the other light source control means C122, C121.

C123B: Output Storage Unit The output storage unit C123B stores the light source control units C121 and C122 that are currently being output and are set by the output setting unit C123A.
C123C: Inter-image discriminating means The inter-image discriminating means C123C determines whether or not the image writing positions Q1y to Q1k have reached an area between the print area of the previous page and the print area of the next page, so-called inter-image area. Is determined.
C123D: Output Change Determination Unit The output change determination unit C123D determines whether it is time to change from one of the first light source control unit C121 and the second light source control unit C122 to the other. The output change determination unit C123D according to the first exemplary embodiment determines that it is time to change the light source control unit when the head of the divided area An is approaching in the inter-image area when the exposure condition is changed.

(Explanation of flowchart of Example 2)
Next, a processing flow of the image forming apparatus U according to the second exemplary embodiment of the present invention will be described with reference to a flowchart. In the following description, processes similar to those in the first embodiment are denoted by the same ST numbers as those in the first embodiment, and detailed description thereof is omitted.
In the second embodiment, the area head detection process is the same as that in FIG. 7 of the first embodiment, and thus illustration and detailed description thereof are omitted.
(Explanation of parameter setting process)
FIG. 12 is a flowchart of the parameter setting process according to the second embodiment and corresponds to FIG. 8 according to the first embodiment.
In the parameter setting process shown in FIG. 12, since the same process is executed in parallel in each of the first light source control unit C121 and the second light source control unit C122, in FIG. The parameter setting process in the light source control unit C121 will be described, and the illustration and detailed description of the process in the second light source control unit C122 will be omitted.

In FIG. 12, processes ST11 to ST13 similar to those in the first embodiment are performed. If yes (Y) in ST13, the process proceeds to ST17 similar to the first embodiment, and if no (N), the process proceeds to ST41.
In ST41, it is determined whether or not the first light source control means C121 is currently in use, that is, whether or not the control signal from the first light source control means C121 is used to control the laser diode 1. If no (N), the process proceeds to ST42, and if yes (Y), the process returns to ST13.
In ST42, the following processes (1) and (2) are executed, and the process proceeds to ST43.
(1) Acquisition of parameters corresponding to the exposure conditions for the next page is started.
(2) Start timing of acquisition time t3.
In ST43, it is determined whether or not the acquisition time t3 has elapsed. If yes (Y), the process proceeds to ST44, and if no (N), ST43 is repeated.
In ST44, the parameters, that is, the starting light amount value Vn and the correction amount Hn are updated to the acquired parameters. Then, the process returns to ST13.

(Explanation of light intensity correction process)
FIG. 13 is a flowchart of the light amount correction process according to the second embodiment and corresponds to FIG. 9 according to the first embodiment.
In the light amount correction process shown in FIG. 13, since the same process is executed in parallel in each of the first light source control means C121 and the second light source control means C122, in FIG. The parameter setting process in the light source control unit C121 will be described, and the illustration and detailed description of the process in the second light source control unit C122 will be omitted.

In FIG. 13, the same processes ST21 to ST34 as in the first embodiment are performed, and if NO (N) in ST34, the process proceeds to ST51.
In ST51, it is determined whether or not parameter acquisition in ST42 of FIG. 12 is started. If yes (Y), the process proceeds to ST52, and, if no (N), the process returns to ST22.
In ST52, it is determined whether or not the parameter update in ST44 of FIG. If no (N), ST52 is repeated, and if yes (Y), the process returns to ST22.

(Description of control switching process)
FIG. 14 is a flowchart of the control switching process according to the second embodiment.
In ST61 of FIG. 14, it is determined whether or not a job that is an image forming operation is started. If yes (Y), the process proceeds to ST62, and if no (N), ST61 is repeated.
In ST62, the first light source control means C121 is set to the control means that uses it. Then, the process proceeds to ST63.
In ST63, it is determined whether or not the exposure conditions of the current page and the next page are the same. If no (N), the process proceeds to ST64, and if yes (Y), the process proceeds to ST67.

In ST64, it is determined whether or not the image writing areas Q1y to Q1k have entered the inter image area from the print area of the current page. If yes (Y), the process proceeds to ST65, and if no (N), ST64 is repeated.
In ST65, it is determined whether or not a head signal has been output in the region head detection process. If yes (Y), the process proceeds to ST66, and if no (N), ST65 is repeated.
In ST66, the currently used control means C121, C122 is switched to the currently unused control means C122, C121. Then, the process returns to ST63.
In ST67, it is determined whether or not the job is finished. If no (N), the process returns to ST63, and if yes (Y), the process returns to ST61.

(Operation of Example 2)
FIG. 15 is an explanatory diagram of an example of the light amount control of the second embodiment. The reference position, the inter-image area, the light amount setting value by the first light source control unit, and the light amount setting value by the second light source control unit. It is explanatory drawing of the relationship between and the output which actually controls light quantity.
In the copying machine U according to the second embodiment having the above-described configuration, when there is a change in the exposure condition, as shown in ST41 to ST44 in FIG. Is updated. For example, as shown in FIG. 15, in the first recording sheet S1, during exposure using the signal of the first light source control means C121, the second light source control means C122 side is sufficient for parameter acquisition. The parameter is updated over the acquisition time t3. That is, in the configuration of the first embodiment, if the parameter update is not in time due to the access speed or the like, the calculation and control of the set value Va is adversely affected. However, in the second embodiment, the unused side is sufficient. The parameter is reliably updated over a long acquisition time t3.

During parameter updating, as shown in ST51 and ST52 of FIG. 13, the setting value Va of ST23, ST31, and ST33 is set not to be performed, and as shown in FIG. The value Va is held at a constant value. Therefore, the load on the CPU is reduced as compared with the case where the set value Va is calculated during the update.
Then, when the inter-image area is reached and the head of the divided area An is reached, the second light source control means C122 is switched to, as shown in FIG. 15, the latent image of the latent image with the light quantity corresponding to the next page S2. Writing is performed. Further, when the exposure condition is changed on the next page S3, the parameter is updated on the side of the first light source control means C121 that is not in use, and in the next inter-image area, the beginning of the divided area An. Is switched to the first light source control means C121.
In addition, the second embodiment has the same operation as the first embodiment.

FIG. 16 is an overall explanatory view of an image forming apparatus according to Embodiment 3 of the present invention.
Next, the third embodiment will be described. In the description of the third embodiment, the same reference numerals are given to the components corresponding to the components of the first embodiment, and the detailed description thereof will be omitted.
The third embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.

In FIG. 16, the copying machine U of the third embodiment is configured by a so-called tandem type image forming apparatus in that it is configured by an image forming apparatus having a rotary, so-called rotary type developing device G. And different. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
Therefore, in the copying machine U according to the third embodiment, four latent images Y, M, C, and K are sequentially written on one photoconductor PR by one latent image forming apparatus. In the developing device G in which the four developing devices Gy, Gm, Gc, and Gk of Y, M, C, and K are rotatably supported around the rotation axis GA, the developing devices Gy to Gk are sequentially arranged on the photoconductor PR. The latent image on the photosensitive member PR is developed by moving to the developing region Q2 facing the surface.

(Description of Control Unit of Example 3)
FIG. 17 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the third embodiment, and corresponds to FIG. 4 according to the first embodiment.
In FIG. 17, the copying machine U according to the third embodiment includes an exposure condition determination unit C4 ″ and a light amount storage unit C11 ″ instead of the exposure condition determination unit C4 and the light amount storage unit C11 according to the first embodiment.
C4 ″: Exposure condition determining means The exposure condition determining means C4 ″ sets the exposure conditions in the latent image forming apparatus ROS for each color. The exposure condition setting means C4 ″ of the third embodiment includes a change in color as the exposure condition in addition to the resolution and the like.

FIG. 18 is an explanatory diagram of the light amount setting value, FIG. 18A is an explanatory diagram of parameters of the third embodiment, and FIG. 18B is an explanatory diagram of parameters of a modified example of the third embodiment.
C11 ″: Light quantity storage means The light quantity storage means C11 ″ stores parameters such as a start light quantity value Vn and a correction quantity Hn according to the exposure conditions. In FIG. 18A, in Y, M, C, and K, the developed density fluctuates depending on the characteristics of the developer used, but the density unevenness in the sub-scanning direction is affected by the unevenness of the surface of the photoconductor PR. The waveform of the change in the set value Va tends to have the same tendency. Accordingly, in FIG. 18A, the parameters Y, M, C, and K are set to α × Vn and α × Hn, for example, when the magnification of the parameter M is α with respect to the parameters Vn and Hn of Y. ing. Similarly, when β and γ are magnifications, the C parameter is set to β × Vn and β × Hn, and the K parameter is set to γ × Vn and γ × Hn. Note that the method is not limited to the method of multiplying the magnifications α to γ as shown in FIG. 18A. For example, as shown in FIG. 18B, the Y, M, C, and K waveforms are set to be the same and moved in parallel. However, the present invention is not limited to this, and it is also possible to set individual parameters for Y, M, C, and K according to experiments and the like.

(Operation of Example 3)
In the copying machine U according to the third embodiment having the above-described configuration, the Y, M, C, and K images are written between the Y, M, C, and K images even in the configuration in which the single latent image forming apparatus ROS writes the images. Color unevenness and density unevenness are reduced.

FIG. 19 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the fourth embodiment, and corresponds to FIG. 4 according to the first embodiment.
In the description of the fourth embodiment, components corresponding to those of the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.
The fourth embodiment is different from the first and second embodiments in the following points, but is configured in the same manner as the first and second embodiments in other points.

(Description of Control Unit of Example 4)
In FIG. 19, the light source control means C212 of the copier U of the fourth embodiment has the following means C13 to C19 in place of the means C12A to C12C of the first embodiment. Therefore, in the fourth embodiment, unlike the configuration having the two light source control means C121 and C122 as in the second embodiment, the control is performed by one light source control means C212 as in the first embodiment.
C13: Inter-image discriminating means The inter-image discriminating means C13 determines whether or not the image writing positions Q1y to Q1k have reached a so-called inter-image area between the print area of the previous page and the print area of the next page. Is determined.

C14: Start light quantity value acquisition means The start light quantity value acquisition means C14 as an example of the light quantity information acquisition means acquires the start light quantity value Vn corresponding to the exposure condition from the light quantity storage means C11. Note that the start light amount value acquisition unit C14 according to the fourth exemplary embodiment starts acquisition of the start light amount value Vn when a head signal is output after reaching the inter image area.
C15: Correction Amount Acquisition Unit An amount correction amount acquisition unit C15 as an example of a light amount change information acquisition unit acquires a correction amount Hn corresponding to the exposure condition from the light amount storage unit C11. The correction amount acquisition unit C15 of the fourth embodiment starts acquiring the correction amount Hn when the head signal is output when the inter-image area is reached.

C16: Acquisition Information Update Unit The acquisition information update unit C16 updates information acquired by the acquisition units C14 and C15. The acquired information update unit C16 of the fourth embodiment stores the light amount when there is a change in the exposure condition and there is a change in the exposure condition, and when the head signal is output when reaching the inter-image area. The parameters are updated while being acquired from the means C11 by the acquisition means C14 and C15. In addition, in the acquisition information update unit C16 of the fourth embodiment, when the acquisition time t3 for acquiring the parameter has elapsed and the head of the first divided area An has reached, as in the acquisition information update unit C121A of the second embodiment. Then, the calculation of the light quantity setting value Va by the light quantity setting means C12D and the light quantity correction means C12G with the updated information is resumed. Therefore, the correction of the set value Va is not performed until the calculation of the light amount set value Va is resumed after the acquisition of the parameter corresponding to the exposure condition on the next page is started, and the value of the set value Va is not changed. , The value at the start of parameter acquisition is held.

C17: Acquisition Time Storage Unit The acquisition time storage unit C17 stores acquisition time t3 for acquiring parameters, so-called access time, as with the acquisition time storage unit C121B of the second embodiment. The acquisition time t3 of the fourth embodiment is set to a time during which the parameters after changing the exposure conditions can be sufficiently acquired according to the circuit configuration, the CPU processing speed, the communication speed between the circuits and elements, and the like. In particular, in the fourth embodiment, the acquisition time t3 is set to a time shorter than the time during which the inter image area passes.
C18: Acquisition time timing means The acquisition time timing means C18 measures the acquisition time t3 when there is a change in exposure conditions, as in the acquisition time timing means C121C of the second embodiment.
C19: Acquisition Completion Determination Unit The acquisition completion determination unit C19 determines whether the parameter acquisition and update have been completed. The acquisition completion determination unit C19 according to the fourth embodiment completes the parameter acquisition / update process when the acquisition time t3 has elapsed after the start of parameter acquisition / update and the next head signal is output. Is determined.

(Explanation of flowchart of Example 4)
Next, a processing flow of the image forming apparatus U according to the fourth exemplary embodiment of the present invention will be described with reference to a flowchart. In the fourth embodiment, the area head detection process is the same as that in FIG. 7 of the first embodiment, and thus illustration and detailed description thereof are omitted.
(Explanation of parameter setting process)
FIG. 20 is a flowchart of parameter setting processing according to the fourth embodiment, and corresponds to FIG. 8 according to the first embodiment.
In the parameter setting process shown in FIG. 20, the same processes as those in FIG. 8 of the first embodiment are denoted by the same ST numbers, and detailed description thereof is omitted.

In FIG. 20, the same processes ST11 to ST15 and ST17 as those in the first embodiment are performed. If YES in ST15, the process proceeds to ST71.
In ST71, the following processes (1) and (2) are executed, and the process proceeds to ST72.
(1) Start acquisition and update of parameters corresponding to the exposure conditions of the next page.
(2) Start timing of acquisition time t3.
In ST72, it is determined whether or not the acquisition time t3 has elapsed. If yes (Y), the process proceeds to ST73, and if no (N), ST72 is repeated.
In ST73, it is determined whether or not a head signal has been output in the region head detection process of FIG. If yes (Y), the process proceeds to ST74, and if no (N), ST73 is repeated.
In ST74, a signal for notifying completion of parameter acquisition and update is output. Then, the process returns to ST13.

(Explanation of light intensity correction process)
FIG. 21 is a flowchart of the light amount correction process according to the fourth embodiment and corresponds to FIG. 13 according to the second embodiment.
In the parameter setting process shown in FIG. 21, the same processes as those in FIG. 13 of the second embodiment are denoted by the same ST numbers, and detailed description thereof is omitted.
In FIG. 21, in the light amount correction process of the fourth embodiment, the following process ST52 ′ is executed instead of ST52 of the second embodiment.
In ST52 ′ of FIG. 21, it is determined whether or not a signal notifying that parameter acquisition and update has been completed is output. If yes (Y), the process proceeds to ST32. If no (N), the process returns to ST22.

(Operation of Example 4)
FIG. 22 is an explanatory diagram of an example of light amount control according to the fourth embodiment.
In the image forming apparatus according to the fourth embodiment having the above-described configuration, acquisition and updating of parameters are performed in the inter-image area over an acquisition period t3. In other words, as in the first embodiment, a sufficient time is required for a case where the CPU processing speed and the information communication speed with the CPU, that is, the so-called access speed are secured such that parameter acquisition and updating can be executed without delay. The parameter is acquired and updated over t3. Therefore, it is possible to adopt a CPU or the like that is less expensive than the first embodiment, and it is possible to reduce the price.
In the fourth embodiment, the value of the setting value Va is held at a constant value while the CPU is accessing, and the load on the CPU is reduced compared to the case where the setting value Va is calculated during the update. The setting value Va is reduced to an unexpected value.

FIG. 23 is a block diagram illustrating functions of the control unit of the image forming apparatus according to the fifth embodiment, and corresponds to FIG. 4 according to the first embodiment.
In the description of the fifth embodiment, components corresponding to the components of the first, second, and fourth embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.
Although the fifth embodiment is different from the first, second, and fourth embodiments in the following points, the fifth embodiment is configured in the same manner as the first, second, and fourth embodiments.

(Description of Control Unit of Example 5)
In FIG. 23, the light source control means C212 ′ of the copier U of the fifth embodiment has the following acquisition information update means C16 ′ instead of the acquisition information update means C16 of the fourth embodiment. Accordingly, in the fifth embodiment, unlike the configuration having the two light source control units C121 and C122 as in the second embodiment, the configuration is such that control is performed by one light source control unit C212 as in the first and fourth embodiments. Yes.

C16 ′: Acquisition Information Update Unit The acquisition information update unit C16 ′ updates the information acquired by the acquisition units C14 and C15. The acquisition information update unit C16 ′ according to the fifth exemplary embodiment is configured to change the light amount when the exposure condition is changed and the exposure condition is changed, and the head signal is output after reaching the inter-image area. The parameters are updated while being acquired from the storage means C11 by the acquisition means C14 and C15. The acquisition information update unit C16 ′ of the fifth embodiment, unlike the acquisition information update unit C16 of the fourth embodiment, calculates the light amount setting value Va by the light amount setting unit C12D and the light amount correction unit C12G even during parameter acquisition and update. Let it run. Therefore, the calculation of the light amount setting value Va is continued even during the parameter acquisition, and since the drawing is not actually performed because of the inter-image area, the setting value Va is calculated and corrected.

  In the fifth embodiment, the area head detection process and the light amount correction process are the same as those in FIGS. 7 and 9 of the first embodiment, and the parameter setting process is the same as that in FIG. 20 of the fourth embodiment. The detailed explanation is omitted. In the fifth embodiment, the parameter setting process ST74 shown in FIG. 20 of the fourth embodiment is unnecessary as a process and can be omitted.

(Operation of Example 5)
FIG. 24 is an explanatory diagram of an example of light amount control according to the fifth embodiment.
In the image forming apparatus according to the fifth embodiment having the above-described configuration, as in the case of the working collar 4, the acquisition and update of parameters are performed in the inter-image area over the acquisition period t3. In other words, as in the first embodiment, a sufficient time is required for a case where the CPU processing speed and the information communication speed with the CPU, that is, the so-called access speed are secured such that parameter acquisition and updating can be executed without delay. The parameter is acquired and updated over t3. Therefore, it is possible to adopt a CPU or the like that is less expensive than the first embodiment, and it is possible to reduce the price.
In the fifth embodiment, while the CPU is accessing, the calculation of the set value Va is continued. However, the set value Va does not become the upper limit value VH or the lower limit value VL, and the set value Va falls between the upper limit value VH and the lower limit value. Deviation from the range of the value VL is prevented, and unexpected numerical values are reduced.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Modification examples (H01) to (H05) of the present invention are exemplified below.
(H01) In the above-described embodiment, the copying machine U as an example of the image forming apparatus is illustrated. However, the present invention is not limited to this. It is also possible to do.
(H02) In the above embodiment, the copying machine U has exemplified the configuration in which four color developers are used. However, the present invention is not limited to this. For example, a single color image forming apparatus, five or more colors, or three colors or less. The present invention can also be applied to a multicolor image forming apparatus.

(H03) In the above-described embodiment, specific numerical values such as the screen angle and the number of screen lines are not limited to the exemplified values, and can be arbitrarily changed according to the design, use, and the like.
(H04) In the above-described embodiment, the configuration in which the two light source control units C121 and C122 are switched is illustrated, but the present invention is not limited to this, and a configuration in which three or more units are switched is also possible.
(H05) In the above embodiment, it is desirable to provide the upper limit value VH and the lower limit value VL, but either one or both may be omitted.

1 ... light source,
2 ... light,
A0 to A31 ... divided regions,
C11, C11 "... light quantity storage means,
C12, C12 ', C12 "... light source control means,
C121 ... First light source control means,
C122 ... second light source control means,
F: Fixing device,
G, Gy, Gm, Gc, Gk ... developing device,
H0 to H31 ... Light quantity change information,
P0: Reference position,
PR, PRy, PRm, PRc, PRk ... Image carrier,
Q1, Q1y, Q1m, Q1c, Q1k ... exposure position,
ROS ... exposure device,
SN1 ... reference detection member,
S ... medium
T1 + T2 + B ... transfer device,
U: Image forming apparatus,
V0-V31 ... light quantity information,
VH, VL: Limit values.

Claims (6)

A light source that emits light that forms a latent image with respect to the exposure position of the image carrier;
With respect to a plurality of divided regions obtained by virtually dividing the surface along the sub-scanning direction of the image carrier with reference to a reference position set in advance along the sub-scanning direction of the image carrier, in each divided region A light amount that is set according to density unevenness and that stores light amount information that identifies the light amount of the light source at the front end position in the sub-scanning direction of each divided region and light amount change information that is a change amount of the light amount in the divided region Storage means;
Light source control means for controlling the light source based on the light quantity information and the light quantity change information stored in the light quantity storage means to change the light quantity in each divided region,
When the light source control unit receives an instruction to change the amount of light, the light source changes the amount of light from the front end in the sub-scanning direction of the divided region when a latent image is not formed by the light source. The light amount storage means for storing the light amount information and the light amount change information set for each of a plurality of preset exposure conditions;
When there is a change in the exposure condition, control of the light source based on the light quantity information corresponding to the changed exposure condition and the light quantity change information from the front end in the sub-scanning direction of the divided area approaching the exposure position The light source control means for performing
The exposure apparatus according to claim 1, further comprising: First light source control means for controlling the light source using the light quantity information and the light quantity change information before the change of the exposure condition, and the light quantity information and the light quantity change information after the change of the exposure condition are used. And second light source control means for controlling the light source, and switching between the first light source control means and the second light source control means in accordance with a change in the exposure condition. means,
The exposure apparatus according to claim 2, further comprising: One light source for sequentially irradiating the surface of the image carrier with light forming images of different colors;
As the exposure condition, the light quantity storage means in which the respective colors formed on the surface of the image carrier are set;
The exposure apparatus according to claim 2 or 3, further comprising: The light source control means for controlling the light source using the light amount value as the limit value when the light amount value exceeds the limit value based on limit information that specifies a preset limit value of the light amount,
The exposure apparatus according to claim 1, further comprising: A rotating image carrier;
An exposure apparatus according to any one of claims 1 to 5, wherein a latent image is formed on the surface of the image carrier.
A developing device for developing the latent image on the surface of the image carrier into a visible image;
A transfer device for transferring a visible image on the surface of the image carrier to a medium;
A fixing device for fixing a visible image on the surface of the medium;
An image forming apparatus comprising:

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