Image forming apparatus

Abstract

The present invention provides an image forming apparatus that uses two optical scanning devices per color and can reduce density differences that occur when divided image data is joined together on a photoreceptor. [Solution] The present invention provides an optical writing device in which a plurality of optical writing means are arranged in a row in the main scanning direction on an image carrier, and a latent image is formed by irradiating a plurality of divided regions on the image carrier in the main scanning direction with an optical beam corresponding to the image data; a division means for dividing the image data for each optical writing means; a correction means for correcting the amount of light from the optical writing means based on a correction value; a correction pattern output unit for outputting a correction pattern in a coupling portion where two adjacent optical writing means can irradiate with an optical beam; and a feedback unit for feeding back the correction value that corrects the density difference of the correction pattern to the correction means.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] In an image forming apparatus in which two optical scanning devices (an example of light writing means) per color are arranged side by side in the scanning direction, the image width can be increased and the printing speed can also be improved. And in the said image forming apparatus, the technique of reducing the magnification deviation of the boundary part and maintaining the image connection state of the boundary part by scanning two optical scanning devices in the direction of separating from each other has been developed.

[0003] Patent Document 1 discloses a technique for setting a delay amount of image data based on a comparison result of scanning timings between optical scanning means for the purpose of correcting a positional deviation occurring in the sub-scanning direction between a plurality of image regions when a plurality of regions are optically scanned by connecting them in the main scanning direction by a plurality of deflection devices rotating asynchronously.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above technique, in an image forming apparatus using two optical scanning devices per color, when connecting divided image data on a photoreceptor, since the two optical scanning devices are independent optical systems, the light amount cannot be made uniform, and there is a light amount difference between the optical scanning devices especially at the coupling part. Although each of the two optical scanning devices is manufactured to have the same light amount, it does not become exactly the same due to optical characteristics. However, even a slight density difference occurring on the paper surface is highly sensitive to the human eye and is perceived as a density step.

[0005] The present invention has been made in view of the above, and an object thereof is to provide an image forming apparatus capable of reducing a density step occurring on a paper surface when connecting divided image data on a photoreceptor in an image forming apparatus using two optical scanning devices per color.

Means for Solving the Problems

[0006] To solve the above-mentioned problems and achieve the objective, the present invention provides an optical writing device in which a plurality of optical writing means are arranged in the main scanning direction, wherein a scanning area on the image carrier is divided into a plurality of divided areas in the main scanning direction, and a latent image is formed by irradiating each of the optical writing means with a light beam; a division means for dividing the image data for each of the optical writing means; a correction means for correcting the amount of light from the light beam irradiated from the optical writing means based on a correction value; a correction pattern output unit that outputs a correction pattern from each of the two adjacent optical writing means in a coupling portion where light beams can be irradiated by the two adjacent optical writing means; and a feedback unit that feeds back the correction value to the correction means to correct the density difference of the correction patterns output by the two adjacent optical writing means in the coupling portion. [Effects of the Invention]

[0007] According to the present invention, in an image forming apparatus using two optical scanning devices per color, it is possible to reduce the density difference that occurs on the paper surface when the divided image data is joined together on the photoreceptor. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a schematic configuration of a laser printer as an example of an image forming apparatus according to this embodiment. [Figure 2] Figure 2 shows an example of the basic configuration of the optical beam scanning device (writing unit) of the laser printer according to this embodiment. [Figure 3] Figure 3 shows an example of the configuration of the optical beam scanning apparatus according to this embodiment. [Figure 4] Figure 4 is a diagram illustrating an example of image data division processing when using two light beam scanning devices for one color in the laser printer according to this embodiment. [Figure 5] Figure 5 is a block diagram showing an example of the functional configuration related to density calculation and correction in the laser printer according to this embodiment. [Figure 6] Figure 6 is a diagram illustrating an example of automatic density correction in a laser printer according to this embodiment. [Figure 7] Figure 7 is a diagram illustrating an example of automatic density correction in a laser printer according to this embodiment. [Figure 8] Figure 8 is a diagram illustrating an example of automatic density correction in a laser printer according to this embodiment. [Figure 9] Figure 9 is a diagram illustrating an example of automatic density correction in a laser printer according to this embodiment. [Figure 10] Figure 10 is a diagram illustrating an example of manual density correction in a laser printer according to this embodiment. [Figure 11] Figure 11 is a diagram illustrating an example of manual density correction in a laser printer according to this embodiment. [Figure 12] Figure 12 is a flowchart showing an example of the automatic density correction flow in a laser printer according to this embodiment. [Figure 13] Figure 13 is a flowchart showing an example of the manual density correction process in a laser printer according to this embodiment. [Modes for carrying out the invention]

[0009] An embodiment of the image forming apparatus will be described in detail below with reference to the attached drawings.

[0010] Figure 1 is a diagram showing a schematic configuration of a laser printer as an example of an image forming apparatus according to this embodiment. As shown in Figure 1, the laser printer includes an image forming unit. The laser printer also includes an image processing unit that performs necessary image processing on print data, a paper feeding unit that supplies printing paper (recording paper) to the image forming unit, a paper discharge unit that discharges the recording paper (printing paper) that has been image-formed in the image forming unit and fixed in the fuser unit to the output tray, a data receiving unit that receives print data from an external device (personal computer, scanner, etc.), and an operation display unit that has operation keys for setting various operating modes of the laser printer and a display that shows various information.

[0011] In the image forming section, a charger 102, a static eliminator 103, a light beam scanning device 104, a developing unit 105, a transfer roller 106, a cleaning unit 108, and the like are arranged around the rotating photoreceptor 101.

[0012] In the image forming unit, the photoreceptor 101 is uniformly charged by the charger 102, and then a light beam modulated based on image data is irradiated onto the photoreceptor 101 from the light beam scanning device 104 to form an electrostatic latent image on the photoreceptor 101. Next, the image forming unit applies toner (developer) to the photoreceptor 101 using the developing unit 105 to form a toner image as a developer image. Then, the image forming unit uses the transfer roller 106 to transfer the toner image on the photoreceptor 101 onto the intermediate transfer belt 110, and transfers it to the printing paper, which is the recording medium, fed from the paper feeding unit through the paper feeding path between the intermediate transfer belt 110 and the secondary transfer roller 107. A density sensor 109 is positioned opposite the intermediate transfer belt 110, and this density sensor 109 can measure the toner density of the toner image transferred to the intermediate transfer belt 110 and change the amount of toner applied. Next, the image forming unit transports the printing paper on which the toner image has been transferred to the fuser unit.

[0013] The fixing unit includes a heating roller that is rotationally driven and heated to a predetermined fixing temperature, a pressure roller that abuts against the heating roller and rotates together with the heating roller, a heating heater that heats the heating roller to the predetermined fixing temperature, and the like. Then, the fixing unit forms an image by conveying the printed paper onto which the toner image has been transferred while heating and pressing it with the heating roller and the pressure roller, and fixing the toner image onto the paper.

[0014] Further, after the image forming unit cleans the residual toner on the photoreceptor 101 that has completed the transfer of the toner image with the cleaning unit 108, it discharges the charge with the discharger 103, and then uniformly charges it with the charger 102, and performs image formation again. In the present embodiment, the image forming unit is a full-color image forming apparatus of four colors (K: black, C: cyan, M: magenta, Y: yellow), but it can also be applied to a monochrome image forming apparatus that forms only one color image.

[0015] FIG. 2 is a diagram showing an example of the basic configuration of a light beam scanning device (writing unit) included in the laser printer according to the present embodiment. FIG. 3 is a diagram showing an example of the configuration of the light beam scanning device according to the present embodiment. In FIG. 2, the dashed arrow indicates the light beam. The light beam scanning device 104 includes an LD (laser diode) 201 as a light source that emits a light beam, a polygon mirror 202 that rotates at an angular velocity corresponding to the image density of the laser printer, an fθ lens 207, a synchronous mirror 208, a synchronous lens 209, and a synchronous detection sensor 203.

[0016] The light beam emitted from the LD 201 is reflected by the polygon mirror 202, passes through the fθ lens 207, reaches the reflection mirror and is reflected, and forms an image on the photoreceptor 101. The incident position (reflection position) of the light beam on the reflection mirror moves in the scanning direction indicated by the arrow as the polygon mirror 202 rotates, and the imaging position on the photoreceptor 101 moves in the scanning direction indicated by the arrow. The scanning direction of the arrow is the direction of the generatrix of the cylinder that is the shape of the photoreceptor 101, and is the main scanning direction of the image.

[0017] A part of the light beam transmitted through the fθ lens 207 also enters a synchronization mirror 208 disposed in proximity to a position outside the image formation region on the scanning line of the light beam on the photoreceptor 101. The synchronization mirror 208 reflects the incident light beam to the synchronization detection sensor 203.

[0018] The synchronization detection sensor 203 has, for example, a PD (photodiode), and generates a synchronization signal which is a pulse output when a light beam is incident. The image writing control unit 205 controls the rotation of the polygon mirror 202 based on the synchronization signal, and sets an effective scanning period which is a period for writing an image on the photoreceptor 101.

[0019] Also, the light beam emitted from the LD 201 enters the PD 204 provided inside the light source, and the light source control unit 206 can perform feedback control of the light quantity by detecting the PD voltage output from the PD 204.

[0020] In the present embodiment, the light beam scanning device 104 has a configuration in which two light beam scanning devices 104-1 and 104-2 are arranged side by side in the scanning direction. The laser printer divides the image data into two, sends the divided image data to the respective light beam scanning devices 104-1 and 104-2, and scans the light beam so that the divided image data is joined on the photoreceptor 101. The region A (hereinafter also referred to as the joining portion) in FIG. 3 becomes a region where image data can be written by both the light beam scanning device 104-1 and the light beam scanning device 104-2. That is, the light beam scanning devices 104-1 and 104-2 are arranged side by side in the scanning direction, and are an example of a light writing means for forming an image (an example of a latent image) by irradiating a light beam corresponding to the image data on the photoreceptor 101 (an example of an image carrier). Further, the light beam scanning device 104 is an example of a light writing device for forming a latent image by irradiating a light beam on the divided regions by the respective light beam scanning devices 104-1 and 104-2. Here, the divided region is a region obtained by dividing the scanning region in the main scanning direction on the photoreceptor 101.

[0021] Figure 4 is a diagram illustrating an example of image data division processing when using two light beam scanning devices for one color in a laser printer according to this embodiment. In this embodiment, the laser printer divides the image data into two lines at a division unit 401, sends the divided image data to the image writing control unit 205-1 and the image writing control unit 205-2, and irradiates the photoreceptor 101 with light beams from the LD201-1 and LD201-2 of the respective light beam scanning devices 104-1 and 104-2, writing the divided image data onto the photoreceptor 101. In other words, the division unit 401 is an example of a division means that divides the image data for each light beam scanning device 104-1 and 104-2.

[0022] When the laser printer divides image data, it sends image data to both the image writing control unit 205-1 and the image writing control unit 205-2 for at least the width corresponding to the joining portion A at the boundary of the multiple divided regions. This division section 401 is one of the functions of the image processing unit 503 (see Figure 5). That is, at the boundary of the multiple divided regions, a joining portion A is secured where light beams are irradiated by two adjacent light beam scanning devices 104-1 and 104-2. The joining portion A may overlap by a certain distance only at the respective ends of the multiple divided regions.

[0023] However, the two optical beam scanning devices 104-1 and 104-2 each have their own optical characteristics, and the light intensity at the combined portion A of the scanning regions of the two optical beam scanning devices 104-1 and 104-2 is not the same. Although light intensity correction is performed to match the shading characteristics of each optical beam scanning device measured during the manufacturing of the optical beam scanning devices 104-1 and 104-2, the combined portion A will output a small difference in light intensity as a clear step in the image. To reduce the light intensity step, light intensity correction of the combined portion will be necessary after installation in the actual device.

[0024] Figure 5 is a block diagram showing an example of the functional configuration related to density calculation and correction in a laser printer according to this embodiment. The laser printer has an engine board that controls electrical operation, and the engine board is equipped with a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 502 that stores control programs and correction patterns, an image processing unit 503, and a density calculation unit 504.

[0025] The CPU 501 executes a control program stored in the ROM 502 to perform image formation and density correction. Following the control program, the CPU 501 operates the image processing unit 503 to transmit image data to the light beam scanning device 104 and scans the photoreceptor 101 with the light beam.

[0026] As explained in the image forming unit shown in Figure 1, the image forming unit deposits the toner image formed on the photoreceptor 101, which has been scanned by the light beam, onto the intermediate transfer belt 110. At this time, the analog output of the density sensor 109, which is positioned opposite the intermediate transfer belt, is sent to the density calculation unit 504, where the density calculation unit 504 calculates the density level. Based on the calculation result of the density level, if there is a change in the density level, the CPU 501 changes the light intensity setting of the light beam scanning devices 104-1 and 104-2. In other words, the CPU 501 functions as an example of a correction means that corrects the light intensity of the light beam irradiated from the light beam scanning devices 104-1 and 104-2 based on a correction value.

[0027] Furthermore, CPU 501 is an example of a correction pattern output unit that outputs a correction pattern to the combined portion A using two adjacent optical beam scanning devices 104-1 and 104-2. Here, the combined portion A is a region secured at the boundary of multiple divided regions and irradiated with optical beams by two adjacent optical beam scanning devices 104-1 and 104-2. Here, the correction pattern may be a pattern in which the outputs of the two adjacent optical beam scanning devices 104-1 and 104-2 are arranged left and right (in the main scanning direction), or a pattern in which the outputs of the two adjacent optical beam scanning devices 104-1 and 104-2 are arranged alternately vertically (in the sub-scanning direction, which is an example of a direction perpendicular to the main scanning direction). Furthermore, the correction pattern may include multiple correction patterns that change the image density (for example, the amount of light from the optical beams irradiated from each of the optical beam scanning devices 104-1 and 104-2), or it may be a correction pattern of a single intermediate density.

[0028] The density calculation unit 504 is an example of a feedback unit that feeds back a correction value to the CPU 501 to correct the density difference between the correction patterns output by the two adjacent optical beam scanning devices 104-1 and 104-2 in the coupling section A. In this embodiment, the density sensor 109 functions as an example of a sensor that detects the density of the correction pattern. The density calculation unit 504 then feeds back a correction value to the CPU 501 based on the density of the correction pattern detected by the density sensor 109. As a result, the CPU 501 changes the correction value to correct the density difference in the coupling section A (i.e., the difference between the light intensity of optical beam scanning device 104-1 and the light intensity of optical beam scanning device 104-2). At that time, the CPU 501 may correct the light intensity of one of the optical beam scanning devices 104-1 and 104-2. Alternatively, the CPU 501 may correct the light intensity of both optical beam scanning devices 104-1 and 104-2.

[0029] Furthermore, the laser printer is equipped with an operation unit 505 for user interface, from which manual density correction can be scanned. In this case, the operation unit 505 may also feed back the operator's visual confirmation result of the density on the recording medium such as paper on which the correction pattern has been printed as the correction value to the CPU 501.

[0030] Here, an example of automatic density correction in a laser printer according to this embodiment will be described. In this embodiment, the laser printer needs to output a correction pattern to the joint area, read the joint area on the intermediate transfer belt with a density sensor 109, and correct the density of the joint area by feeding this back.

[0031] Figures 6-9 illustrate an example of automatic density correction in a laser printer according to this embodiment. In Figure 9, the vertical axis represents density, and the horizontal axis represents pixel density. Automatic density correction is performed based on the number of pages printed since the last correction, without operator intervention. For example, automatic density correction is performed before printing 100 pages after the last correction. This number (e.g., 100 pages) is pre-defined and incorporated into the software control stored in ROM 502.

[0032] As shown in Figure 6, the CPU 501 outputs a correction pattern at the coupling point in each of the two optical beam scanning units 104-1 and 104-2. The correction pattern may be a square that is easy for the density sensor 109 to read, and may also be an intermediate tone pattern with gradation that changes density, and is larger than the reading width of the density sensor 109.

[0033] The CPU 501 reads the correction pattern with the density sensor 109 and corrects the shading curve. The shading curve is drawn in the light intensity area. The light intensity can be set for each light intensity area, and there are 64 such areas in the optical scanning area in the main scanning direction. If the optical scanning area in the main scanning direction is 325 mm and 2400 dpi, one light intensity area will be 480 dots, and the light intensity will be varied in increments of 480 dots to draw the shading curve.

[0034] As shown in Figure 7, the CPU 501 may correct the density by correcting the light intensity of either one of the light beam scanning devices 104-1 or 104-2 so that the density of the combined portion A matches. Alternatively, as shown in Figure 8, the CPU 501 may calculate the average value of the densities of the two light beam scanning devices 104-1 and 104-2, and then correct the density by correcting the light intensity of both light beam scanning devices 104-1 and 104-2 based on this average value so that the density of the combined portion A matches.

[0035] Performing density correction based on the average value (corrected value) of the density (measured value) of both units of the two optical beam scanning devices 104-1 and 104-2 reduces the density step per unit. However, as shown in Figure 9, both units of the optical beam scanning devices 104-1 and 104-2 will deviate from the target light quantity (ideal value) due to the optical characteristics adjusted in the process. If only one of the two optical beam scanning devices 104-1 or 104-2 is used, the deviation from the target light quantity due to the optical characteristics adjusted in the process is limited to half the area. The shading curve is an approximate curve that takes into account the shading curve of the optical characteristics from the target value at the joint and the target value at the right or left end.

[0036] The correction pattern is a square, which is easy for the operator to visually confirm, and may also be a halftone pattern with gradation by varying the density. By outputting multiple halftone patterns, density steps at multiple densities can be detected, and the detection results can be used to determine a light intensity setting value that enables reduction of steps across a wide range of densities. This halftone pattern has gradation through a dot matrix-like arrangement (arrangement and number of printed pixels per predetermined area composed of multiple pixels). The multiple halftone patterns are patterns with gradation in 10 steps, in 10% increments, from density: 100% to density: 0%. This makes it possible to measure the optimal value for reducing density steps at multiple pixel densities (number of printed pixels per predetermined area), and to set an optimal value that can reduce density steps regardless of pixel density.

[0037] Figures 10 and 11 illustrate an example of manual density correction in a laser printer according to this embodiment. In manual density correction, as shown in Figures 10 and 11, a correction pattern (manual correction pattern) is output to the combined area, and the operator must visually check the density on the paper where the correction pattern has been output and provide feedback to correct the combined area. Manual density correction is initiated when the operator operates an execution command from the control unit 505.

[0038] The correction pattern is a square that is easy for the operator to visually confirm, and may also be a halftone pattern with gradation by changing the density. By outputting multiple halftone patterns, density steps at multiple densities can be detected, and based on the detection results, it is possible to determine a light intensity setting value that enables reduction of steps across a wide range of densities.

[0039] The halftone pattern can be given gradation by a dot matrix-like arrangement with a constant light intensity. Alternatively, the halftone pattern can also be given gradation by changing the light intensity. Multiple halftone patterns are made up of patterns with 10 steps of gradation from density: 100% to density: 0%, in 10% increments. As shown in Figure 11, the CPU 501 may output the halftone pattern with the left and right light beam scanning devices 104-1 and 104-2 arranged horizontally. Alternatively, as shown in Figure 10, the CPU 501 may output the halftone pattern with the left and right light beam scanning devices 104-1 and 104-2 alternating vertically. If the operator visually recognizes that the pattern created by one unit is darker or lighter, they can input a light intensity correction from the control unit 505, and the CPU 501 will perform the light intensity correction.

[0040] Figure 12 is a flowchart showing an example of the automatic density correction flow in a laser printer according to this embodiment. Automatic density correction is determined when a print job is generated, and it is decided whether or not to perform density correction.

[0041] When an image forming device such as a laser printer detects the occurrence of a print job, the printing operation starts (step S101). Then, under normal circumstances (if the number of jobs since the last density correction is not a) (step S102: No), the CPU 501 starts image formation (step S103). After that, the CPU 501 finishes image formation and transitions to a standby state (step S104).

[0042] Before image formation begins, the CPU 501 reads the number of jobs since the last density correction stored in the ROM 502, and if the number of jobs is the specified a (step S102: Yes), it starts automatic density correction (step S105). In this embodiment, the CPU 501 performs automatic density correction when the number of jobs since the last density correction is a, but it may also perform automatic density correction based on temperature conditions, such as whether the temperature inside the image forming apparatus is above a specified temperature b.

[0043] When automatic density correction is started, the CPU 501 creates a correction pattern on the photoreceptor 101 based on the correction pattern stored in the ROM 502, and transfers the created correction pattern to the intermediate transfer belt 110 (step S106). Next, the CPU 501 acquires the toner density of the correction pattern created on the intermediate transfer belt 110 using the density sensor 109 (step S107).

[0044] Next, the CPU 501 performs a density correction calculation based on the acquired toner density (step S108). Furthermore, the CPU 501 changes the light intensity parameter of the image processing unit 503 based on the density correction calculation result, and then changes the light intensity of the light beam emitted from the light beam scanning device 104, and then finishes (step S109). After that, the process proceeds to step S103.

[0045] Figure 13 is a flowchart showing an example of the manual density correction process in a laser printer according to this embodiment. Manual density correction is performed by an operator through the user interface (operation unit 505) of an image forming apparatus such as a laser printer (step S201). When manual density correction is started, the CPU 501 creates a correction pattern for the photoreceptor 101 based on the correction pattern stored in the ROM 502.

[0046] The correction pattern created on the photoreceptor 101 is transferred to the paper via the intermediate transfer belt 110 and the secondary transfer roller 107, and fixed onto the paper by the fixing device. After that, the paper with the corrected pattern fixed on it is discharged from the image forming apparatus (step S202). The operator visually checks the correction pattern formed on the paper (step S203). Based on the result of the visual check of the correction pattern, the operator changes the light intensity of one or both light beam scanning devices 104 by making a predetermined input to the operation unit 505 (step S204). The series of processes from steps S202 to S204 are repeated until the operator determines that there is no need for density correction and inputs the operation to the operation unit 505 to end the density correction (step S205).

[0047] Thus, according to the image forming apparatus of this embodiment, a correction pattern is output to the joined portion, the joined portion is read by a single density sensor 109 on the intermediate transfer belt 110, and the density of the joined portion can be corrected by feeding this back. Therefore, in an image forming apparatus using two light beam scanning devices 104-1 and 104-2 per color, the density difference that occurs on the paper surface when the divided image data is joined together on the photoreceptor 101 can be reduced.

[0048] Examples of the present invention are as follows: <1> A light writing device is provided, comprising: a plurality of light writing means arranged in the main scanning direction, which form a latent image by irradiating an image carrier with a light beam corresponding to the image data; a scanning area on the image carrier is divided into a plurality of divided areas in the main scanning direction; and a latent image is formed by irradiating each of the light writing means with a light beam to the divided area; A division means for dividing the image data for each optical writing means, A correction means for correcting the amount of light emitted from the light writing means based on a correction value, In a coupling portion where a light beam can be irradiated by two adjacent light writing means, a correction pattern output unit outputs a correction pattern by each of the two adjacent light writing means, A feedback unit that feeds back to the correction means a correction value that corrects the density difference of the correction patterns output by two adjacent optical writing means at the coupling portion, An image forming apparatus equipped with the following features. <2> The system includes a sensor for detecting the density of the correction pattern, The feedback unit feeds back the correction value to the correction means based on the density of the respective correction patterns output by the two adjacent optical writing means detected by the sensor. <1> The image forming apparatus described above. <3> The system includes an operation unit that feeds back the results of the operator's visual confirmation of the density on the paper on which the correction pattern has been output as the correction value to the correction means. <1> The image forming apparatus described above. <4> The correction means corrects the light intensity of one of the two adjacent optical writing means. <1> from <3> An image forming apparatus as described in any one of the following. <5> The correction means corrects the light intensity of both of the multiple optical writing means. <1> from <3> An image forming apparatus as described in any one of the following. <6> The correction pattern is a pattern that aligns the outputs of two adjacent optical writing means in the main scanning direction. <1> from <5> An image forming apparatus as described in any one of the following. <7> The correction pattern is a pattern in which the outputs of two adjacent optical writing means are aligned in a direction perpendicular to the main scanning direction. <1> from <5> An image forming apparatus as described in any one of the following. <8> The correction pattern includes a plurality of correction turns in which the image density is changed. <1> from <7> An image forming apparatus as described in any one of the following. [Explanation of symbols]

[0049] 101 Photoreceptor 102 Charger 103 Static eliminator 104 Optical beam scanning device 105 Developing Unit 106 Transfer Roller 107 Secondary transfer roller 108 Cleaning Unit 109 Concentration Sensor 201 LD 202 Polygon Mirror 203 Synchronization detection sensor 204 PD 205 Image Writing Control Unit 206 Light source control unit 401 Split section 501 CPU 502 ROM 503 Image Processing Unit 504 Concentration calculation section 505 Operation section [Prior art documents] [Patent Documents]

[0050] [Patent Document 1] Japanese Patent Publication No. 2008-040098

Claims

1. A light writing device is provided, comprising: a plurality of light writing means arranged in the main scanning direction, which form a latent image by irradiating an image carrier with a light beam corresponding to the image data; a scanning area on the image carrier is divided into a plurality of divided areas in the main scanning direction; and a latent image is formed by irradiating each of the light writing means with a light beam to the divided area; A division means for dividing the image data for each optical writing means, A correction means for correcting the amount of light emitted from the light writing means based on a correction value, In a coupling portion where a light beam can be irradiated by two adjacent light writing means, a correction pattern output unit outputs a correction pattern by each of the two adjacent light writing means, A feedback unit that feeds back to the correction means a correction value which corrects the density difference of the correction patterns output by two adjacent optical writing means at the coupling portion, An image forming apparatus equipped with the following features.

2. The system includes a sensor for detecting the density of the correction pattern, The image forming apparatus according to claim 1, wherein the feedback unit feeds back the correction value to the correction means based on the density of each of the correction patterns output by two adjacent optical writing means detected by the sensor.

3. The image forming apparatus according to claim 1, further comprising an operation unit that feeds back to the correction means the result of an operator's visual confirmation of the density on the paper on which the correction pattern has been output as the correction value.

4. The image forming apparatus according to any one of claims 1 to 3, wherein the correction means corrects the light intensity of one of the two adjacent optical writing means.

5. The image forming apparatus according to any one of claims 1 to 3, wherein the correction means corrects the light intensity of both of the plurality of optical writing means.

6. The image forming apparatus according to any one of claims 1 to 3, wherein the correction pattern is a pattern that aligns the outputs of two adjacent optical writing means in the main scanning direction.

7. The image forming apparatus according to any one of claims 1 to 3, wherein the correction pattern is a pattern in which the outputs of two adjacent optical writing means are arranged in a direction perpendicular to the main scanning direction.

8. The image forming apparatus according to any one of claims 1 to 3, wherein the correction pattern includes a plurality of correction turns in which the image density is changed.

Images