Image forming apparatus, light emission control method and program

Abstract

To provide an image formation device, a light-emission control method and a program which correct inclination for each light source at each main scanning position, and can reduce occurrence of irregular pitches.SOLUTION: An image formation device includes: an image formation part 10 for scanning an image carrier (photoreceptor 200) with a plurality of rays of light emitted from a plurality of light sources in a main scanning direction, and forming an image; a modulation part (control part 20) for modulating frequencies of each of the light sources according to main scanning intervals at a plurality of main scanning positions; a light-emission control part (control part 20) for controlling light-emission timings of each of the light sources on the basis of a modulation result; and a storage part 30 for storing main scanning intervals measured by a first measurement part for measuring the main scanning intervals, and a second measurement part arranged corresponding to the plurality of main scanning positions in a manufacturing process. The modulation part modulates frequencies of each of the light sources on the basis of a frequency modulation rate calculated based on a main scanning interval stored in the storage part 30 and a main scanning interval measured by the first measurement part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a light emission control method, and a program. [Background technology]

[0002] 2. Description of the Related Art Conventionally, image forming apparatuses such as laser printers and digital copiers are equipped with an image writing unit that scans a photosensitive member using a semiconductor laser emitted from a light source.

[0003] In recent years, there has been a demand for higher speed and density in image recording in image forming devices. Images are formed by writing multiple lines of an image onto a photosensitive member in a single scan using laser beams emitted from multiple light sources. This image formation is repeated in the sub-scanning direction to form one page of image. In configurations using multiple light sources, an increase in ambient temperature or other factors can cause each light source to shift in the main scanning direction from its designed position, resulting in changes in the inclination (main scanning interval) of each light source. This can result in pitch unevenness in the output image.

[0004] Therefore, a configuration has been disclosed in which the main scanning interval (main scanning pitch) is corrected by adjusting the light emission start timing for each light source (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-105895 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even with the configuration described in Patent Document 1, the inclination for each light source at each main scanning position on the photosensitive body (each position in the main scanning direction) changes depending on the lens accuracy of the fθ lens and the mechanical adjustment accuracy, so the main scanning magnification changes for each light source, making the main scanning pitch correction ineffective, and as a result, there is a problem in that pitch unevenness occurs in the output image.

[0007] An object of the present invention is to provide an image forming apparatus, a light emission control method, and a program that can correct the inclination of each light source at each main scanning position and reduce the occurrence of pitch unevenness. [Means for solving the problem]

[0008] The invention described in claim 1 has been made to achieve the above object, In the image forming apparatus, an image forming unit that scans a plurality of light beams emitted from a plurality of light sources in a main scanning direction on an image carrier to form an image; a modulation unit that applies frequency modulation to each light source in accordance with main scanning intervals at a plurality of main scanning positions of the plurality of light beams; a light emission control unit that controls the light emission timing of each of the light sources based on a result of modulation by the modulation unit; a first measurement unit that measures the main scanning interval; a storage unit that stores the main scanning intervals measured by a second measurement unit that is arranged to correspond to the plurality of main scanning positions in a production process; and an image formation control unit that causes the image forming unit to form a chart for calculating the main scanning interval; an acquisition unit that acquires density information of the chart formed by the image forming unit; a calculation unit that calculates the main scanning interval based on the density information; Equipped with The modulation unit When a change in the main scanning interval is detected based on the calculation result by the calculation unit, The frequency modulation rate of each of the light sources is calculated based on the main scanning interval stored in the storage unit and the main scanning interval measured by the first measurement unit, and frequency modulation is applied to each of the light sources based on the calculated frequency modulation rate.

[0009] The invention described in claim 2 is the image forming apparatus described in claim 1, The first measurement unit is characterized in that it is disposed near an irradiation start position and an irradiation end position outside an image area.

[0010] The invention described in claim 3 is the image forming apparatus described in claim 1 or 2, A detection unit is provided to detect environmental changes within the device, When the detection unit detects an environmental change of a predetermined level or greater, the modulation unit calculates a frequency modulation rate for each of the light sources based on the main scanning interval stored in the memory unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate.

[0012] Claim 4 The invention described in claims 1 to 3 In the image forming apparatus according to any one of the above items, The modulation unit is characterized in that, after a predetermined time has elapsed, it calculates a frequency modulation rate of each of the light sources based on the main scanning interval stored in the memory unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate.

[0013] Claim 5 The invention described in A light emission control method for an image forming apparatus including an image forming unit that forms an image by scanning a plurality of light beams emitted from a plurality of light sources in a main scanning direction on an image carrier according to image data, a first measurement unit that measures main scanning intervals at a plurality of main scanning positions of the plurality of light beams, and a storage unit that stores the main scanning intervals measured by a second measurement unit that is disposed so as to correspond to the plurality of main scanning positions in a production process, a modulation step of applying frequency modulation to each light source in accordance with main scanning intervals at a plurality of main scanning positions of the plurality of light beams; a light emission control step of controlling the light emission timing of each of the light sources based on a modulation result obtained by the modulation step; an image formation control step of causing the image forming unit to form a chart for calculating the main scanning interval; an acquisition step of acquiring density information of the chart formed by the image forming unit; a calculation step of calculating the main scanning interval based on the density information; Including, The modulating step When a change in the main scanning interval is detected based on the calculation result in the calculation step, The frequency modulation rate of each of the light sources is calculated based on the main scanning interval stored in the storage unit and the main scanning interval measured by the first measurement unit, and frequency modulation is applied to each of the light sources based on the calculated frequency modulation rate.

[0014] Claim 6 The invention described in a computer for an image forming apparatus, the computer comprising: an image forming unit that scans an image carrier in a main scanning direction with a plurality of light beams emitted from a plurality of light sources according to image data to form an image; a first measuring unit that measures main scanning intervals at a plurality of main scanning positions of the plurality of light beams; and a storage unit that stores the main scanning intervals measured by a second measuring unit that is arranged to correspond to the plurality of main scanning positions in a production process; a modulation unit that applies frequency modulation to each light source in accordance with main scanning intervals at a plurality of main scanning positions of the plurality of light beams; a light emission control unit that controls the light emission timing of each of the light sources based on the modulation result by the modulation unit; an image formation control unit that causes the image forming unit to form a chart for calculating the main scanning interval; an acquisition unit that acquires density information of the chart formed by the image forming unit; a calculation unit that calculates the main scanning interval based on the density information; It functions as The modulation unit When a change in the main scanning interval is detected based on the calculation result by the calculation unit, The program calculates a frequency modulation rate of each of the light sources based on the main scanning interval stored in the storage unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate. [Effects of the Invention]

[0015] According to the present invention, the inclination for each light source at each main scanning position can be corrected, thereby reducing the occurrence of pitch unevenness. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram showing a control structure of the image forming apparatus according to the present embodiment. [Figure 3] FIG. 2 is a diagram illustrating a schematic configuration of an image writing unit. [Figure 4] 10A and 10B are diagrams showing an example of the light emission timing of each light source when straight lines are printed at three locations on the leading edge, center, and trailing edge of a sheet in the main scanning direction. [Figure 5] 10A and 10B are diagrams illustrating an example of how the print position gradually shifts when straight lines are printed at three locations on the paper, namely the leading edge, center, and trailing edge in the main scanning direction. [Figure 6] FIG. 10 is a diagram showing an example of a configuration for measuring the inclination of each light source at a plurality of main scanning positions using a photodiode during the production process. [Figure 7] 7 is a diagram showing an example of the timing of receiving light in each photodiode when measuring the tilt of each light source in the configuration of FIG. 6. FIG. [Figure 8] FIG. 10 is a diagram showing an example of data measured in a production process before a change and data measured in an actual machine after the start of operation after a change; [Figure 9] 4 is a flowchart showing the operation of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0018] The image forming apparatus 1000 according to this embodiment is used, for example, as a laser printer or a digital copier, and is configured to include an image forming unit 10, a control unit 20, a memory unit 30, a camera 40, an operation panel 50, and an environment detection unit 60, as shown in FIGS. 1 and 2.

[0019] The image forming unit 10 is configured to include a plurality of image writing units 100, each provided for one of the colors cyan, magenta, yellow, and black; a photosensitive body (image carrier) 200, such as a photosensitive drum, provided corresponding to the image writing unit 100; a charging unit 210 that charges the photosensitive body 200; a developing unit 220 that supplies developer to the photosensitive body 200 irradiated with light, thereby visualizing the electrostatic latent image into a developer image; an intermediate transfer belt 300; a transfer roller 400 that transfers the developer image onto paper P; and a fixing unit 500 that fixes the developer image transferred by the transfer roller 400 onto paper P.

[0020] Image forming unit 10 forms an image by irradiating (scanning) multiple laser beams (light rays) emitted from multiple light sources 1 (see FIG. 3) onto photoreceptor 200 in the main scanning direction according to image data. Specifically, image forming unit 10 first forms a toner image on photoreceptor 200, which has been photosensitized by laser beams irradiated from image writing unit 100, and transfers the toner image onto intermediate transfer belt 300. Next, image forming unit 10 presses the toner image transferred onto intermediate transfer belt 300 onto paper P using transfer roller 400, and then fixes the toner image onto paper P by heating and pressurizing paper P using fixing unit 500. Then, image forming unit 10 performs image formation processing by transporting paper P using paper discharge rollers (not shown) and discharging it onto a tray (not shown).

[0021] 3, the image writing unit 100 irradiates the photoreceptor 200, which has been charged by the charging unit 210, with laser light L to photosensitize the photoreceptor 200 (forming an electrostatic latent image on the photoreceptor 200). The image writing unit 100 includes a light source 1 that emits laser light L, a deflector 2 that deflects the laser light L emitted from the light source 1, an fθ lens 3 that focuses the laser light L deflected by the deflector 2 on the photoreceptor 200, a first reflecting mirror 4 that reflects the laser light L that has passed through the fθ lens 3 toward the photoreceptor 200, a second reflecting mirror 5 that reflects a portion of the laser light L deflected by the deflector 2, and a light receiving unit 6 that receives the laser light L reflected by the second reflecting mirror 5.

[0022] The light source 1 is a laser diode (LD) that emits laser light L. The laser light L emitted from the light source 1 is irradiated onto the deflector 2. Note that, in the example shown in FIG. 3, for the sake of convenience of explanation, only one light source 1 is shown, but in this embodiment, a plurality of light sources 1 are arranged at equal intervals in the main scanning direction, and these plurality of light sources 1 constitute a light source unit 11. Note that a light source unit 11 is provided for each color.

[0023] The deflector 2 includes a polygonal prism-shaped polygon mirror with mirrored side surfaces, and a motor that applies a rotational force to the polygon mirror to rotate it. The deflector 2 deflects the laser light L emitted from the light source 1 in a direction corresponding to the rotation. The deflector 2 then irradiates the deflected laser light L onto the peripheral surface of the photoconductor 200 via an fθ lens 3. At this time, the deflector 2 irradiates the laser light L at different positions in the longitudinal direction of the photoconductor 200 depending on the rotation position, thereby enabling the laser light L to scan in the main scanning direction (the longitudinal direction of the photoconductor 200 in FIG. 3).

[0024] The fθ lens 3 focuses the laser light L deflected by the deflector 2 onto the photosensitive member 200 to form an image. The first reflecting mirror 4 reflects the laser light L that has passed through the fθ lens 3 toward the photosensitive member 200 .

[0025] The second reflecting mirror 5 is positioned near the irradiation start position and irradiation end position outside the image area, and reflects a portion of the laser light L that has been deflected by the deflector 2 and passed through the fθ lens 3, and causes the reflected laser light L to enter the light receiving unit 6. Similar to the second reflecting mirror 5, the light receiving unit 6 is arranged near the irradiation start position and irradiation end position outside the image area, and detects the laser light L reflected by the second reflecting mirror 5. The light receiving unit 6 includes an SOS board 61 arranged near the irradiation start position outside the image area, and an EOS board 62 arranged near the irradiation end position outside the image area. Each board (SOS board 61, EOS board 62) is provided with a pair of photodiodes PD11, PD12. The photodiodes PD11, PD12 function as a first measurement unit of the present invention that measures the main scanning interval at each main scanning position.

[0026] The control unit 20 is configured to include a CPU, RAM, etc. The CPU reads various processing programs stored in a storage device such as the storage unit 30, loads them into the RAM, and performs centralized control of the operations of each unit of the image forming apparatus 1000 in accordance with the loaded programs. For example, the control unit 20 adjusts the timing of the writing position on the photosensitive element 200 based on a detection signal detected by the light receiving unit 6, which detects the laser light L reflected by the second reflecting mirror 5 located near the irradiation end position. Furthermore, the control unit 20 applies frequency modulation to each light source 1 in accordance with the main scanning intervals (inclinations) of the plurality of light beams at the plurality of main scanning positions. That is, the control unit 20 functions as a modulation unit of the present invention. Furthermore, based on the modulation result, the control unit 20 controls the light emission timing of each light source 1. That is, the control unit 20 functions as a light emission control unit of the present invention.

[0027] The storage unit 30 stores programs that can be read by the control unit 20, files used when the programs are executed, etc. As the storage unit 30, a large-capacity memory such as a hard disk can be used. For example, the storage unit 30 stores main scanning intervals measured by photodiodes PD1 and PD2 (second measurement unit: see FIG. 6) arranged to correspond to a plurality of main scanning positions in the production process. The storage unit 30 may also store the frequency modulation rate of each light source 1 calculated based on the main scanning intervals measured by the photodiodes PD1 and PD2.

[0028] The camera 40 acquires density information of the image (chart) formed by the image forming unit 10. That is, the camera 40 functions as an acquisition unit of the present invention. Note that instead of the camera 40, a sensor such as a photodiode may be used to irradiate the image formed by the image forming unit 10 with light, receive the reflected light, and acquire density information of the image based on the amount of the received reflected light, etc.

[0029] The operation panel 50 is configured to include a display unit 51 that displays various information to the user, and an operation unit 52 that accepts operation inputs from the user. The display unit 51 is configured with a color liquid crystal display or the like, and displays operation screens and the like (various setting screens, various buttons, operation status of each function, etc.) according to a display control signal input from the control unit 20. The operation unit 52 is configured to include a touch panel provided on the screen of the display unit 51 and various hard keys arranged around the screen of the display unit 51. When a button displayed on the screen is pressed with a finger, a touch pen, or the like, the operation unit 52 detects the X and Y coordinates of the pressed point of force as a voltage value and outputs an operation signal associated with the detected position to the control unit 20. Note that the touch panel is not limited to a pressure-sensitive type and may be, for example, an electrostatic type or an optical type. Furthermore, when a hard key is pressed, the operation unit 52 outputs an operation signal associated with the pressed key to the control unit 20. A user can operate the operation unit 52 to perform settings related to image formation, such as image quality settings, magnification settings, application settings, output settings, and paper settings, as well as paper transport instructions and stop operations for the device.

[0030] The environment detection unit (detection unit) 60 is, for example, a temperature and humidity sensor, and detects environmental information (environmental changes) such as the temperature and humidity inside the device.

[0031] In this embodiment, as shown in Fig. 4(A), four light sources 1 (LD1 to LD4) are arranged at equal intervals in the main scanning direction. In this embodiment, the light source unit 11 includes a plurality (four) of light sources 1 (LD1 to LD4). Note that the number of light sources 1 constituting the light source unit 11 is not limited to four, and may be any number as long as it is plural. As shown in FIG. 4B, when printing straight lines at three locations on the paper P—the leading edge, center, and trailing edge in the main scanning direction—the light emission of each light source 1 (LD1 to LD4) constituting the light source unit 11 is repeatedly controlled in the sub-scanning direction with the light emission timing shown in FIG. 4A. In the example shown in FIG. 4A, the light sources 1 are controlled to emit light in order, starting with the light source 1 at the trailing edge in the main scanning direction (i.e., in the order LD4 → LD3 → LD2 → LD1). Note that the symbol X2 in the figure indicates the distance between adjacent light sources 1 in the main scanning direction and the light emission time of each light source 1. In other words, each light source 1 is controlled to emit light (scan) for a time corresponding to the distance between adjacent light sources 1. Also, the symbol X1 in the figure indicates the distance between the light source 1 (LD1) at the leading edge in the main scanning direction and the light source 1 (LD4) at the trailing edge in the main scanning direction and indicates the time difference between the timing when the light source 1 (LD4) at the trailing edge in the main scanning direction starts emitting light and the timing when the light source 1 (LD1) at the leading edge in the main scanning direction starts emitting light.

[0032] In the configuration of the image forming apparatus 1000 according to this embodiment, the main scanning interval (tilt) for each light source 1 at the main scanning position changes depending on the lens accuracy of the fθ lens and the mechanical adjustment accuracy. Therefore, when printing a straight line at three locations in the main scanning direction of the paper P, namely the leading edge, center, and trailing edge, as shown in FIG. 5, even if the leading edge is straight, the printing position may shift at the center or trailing edge, and the line may no longer be straight, as shown in FIG. Therefore, in this embodiment, in order to suppress the occurrence of pitch unevenness as described above, the frequency modulation rate is calculated based on the main scanning interval (main scanning interval measured in the production process) stored in the memory unit 30 and the main scanning interval measured by the light receiving unit 6 (photodiodes PD11, PD12), and frequency modulation is applied to each light source 1 based on the calculated frequency modulation rate (the frequency modulation rate of each light source 1 is changed), and the light emission timing of each light source 1 is controlled based on the modulation result.

[0033] One example of a method for measuring the inclination (main scanning interval) of each light source 1 at a plurality of main scanning positions in the production process is a method using a sensor (photodiode). Specifically, as shown in FIG. 6, multiple sensor substrates 70 are fixedly arranged so as to correspond to the leading, center, and trailing ends in the main scanning direction as viewed from the image writing unit 100, and the tilt (main scanning interval) of each light source 1 at each main scanning position is measured. Each sensor substrate 70 is provided with a pair of photodiodes PD1 and PD2. The photodiodes PD1 and PD2 function as a second measurement unit of the present invention. In the example shown in FIG. 6, the sensor substrates 70 are arranged so as to correspond to the leading, center, and trailing ends in the main scanning direction, but this is not limiting, and more sensor substrates 70 can be arranged to match each position in the main scanning direction. Here, the time from when light emitted from the light source 1 (LD4) on the trailing edge in the main scanning direction enters the photodiode PD1 on the leading edge in the main scanning direction until it enters the photodiode PD2 on the trailing edge in the main scanning direction is defined as A (see FIG. 7A), and the time from when light emitted from the light source 1 (LD4) on the trailing edge in the main scanning direction enters the photodiode PD1 on the leading edge in the main scanning direction until the light emitted from the light source 1 (LD1) on the leading edge in the main scanning direction enters the photodiode PD2 on the trailing edge in the main scanning direction is defined as B (see FIG. 7B). The slope (main scanning distance) X1 between LD1 and LD4 can be calculated using the following formula (1). The slope (main scanning distance) X2 between adjacent LDs can be calculated using the following formula (2). X1=BA …(1) X2=X1 / 3 …(2) The main scanning interval of each light source 1 measured by the second measurement unit (photodiodes PD1, PD2) in the production process is stored in the storage unit 30.

[0034] In the examples shown in Figures 6 and 7 above, a method is described in which a pair of photodiodes PD1 and PD2 is used to measure the main scanning interval of each light source 1 during the production process. However, when measuring the main scanning interval of each light source 1 in an actual machine after operation has begun, the measurement can also be performed in a similar manner to the above, using a pair of photodiodes PD11 and PD12 provided on each board (SOS board 61, EOS board 62) that makes up the light receiving unit 6.

[0035] In this embodiment, the control unit 20 compares the data measured by the actual machine after operation has started with the data measured in advance in the production process (data stored in the memory unit 30) for the irradiation start position and irradiation end position outside the image area, and calculates correction values for areas that cannot be measured by the actual machine after operation has started (main scanning positions other than the irradiation start position and irradiation end position). Figure 8 shows an example of data measured in the production process before the change and data measured on the actual machine after the start of operation after the change. In the graph shown in Figure 8, the X axis is the sensor position (distance from the position of the board placed at the irradiation start position), and the Y axis is the main scanning interval (the amount of deviation between LD1 and LD4). Note that symbol L1 in the figure is the measurement data before the change, and symbol L2 in the figure is the measurement data after the change. Also, symbol C1 in the figure is the measurement data at the irradiation start position (SOS board 61), and symbol C2 in the figure is the measurement data at the irradiation end position (EOS board 62). Specifically, first, the coordinates of the measurement data before the change are (X(n), Y(n)), and the coordinates of the measurement data after the change are (X'(n), Y'(n)). In this embodiment, a configuration in which measurements are taken at six main scanning positions (a configuration in which six substrates are arranged in the production process) is exemplified. n is the position (order) of the substrate, and 1 to 6 is input depending on the position of the substrate. The irradiation start position (SOS substrate 61) is n=1, and the irradiation end position (EOS substrate 62) is n=6. The correction characteristic A(n) before the change at each main scanning position is calculated using the following formula (3). A(n)=(Y(n)-Y(n-1)) / (X(n)-X(n-1))…(3) The correction value A'(n) after the change at each main scanning position is calculated using the following formula (4). A'(n)=(Y'(6)-Y(6)) / (Y'(1)-Y(1)) ×A(n)…(4) This correction value A'(n) is used as the frequency modulation rate of each light source 1 at each main scanning position.

[0036] The operation of the image forming apparatus 1000 according to this embodiment will be described below with reference to the flowchart of FIG.

[0037] First, the control unit 20 reads out the data stored in the storage unit 30 (step S101).

[0038] Next, the control unit 20 determines whether the data read out in step S101 is a correction value (the frequency modulation rate of each light source 1) (step S102). If the control unit 20 determines that the data read out in step S101 is a correction value (step S102: YES), the process proceeds to step S104. On the other hand, if the control unit 20 determines that the data read out in step S101 is not a correction value (i.e., a measurement value (main scanning interval measured by the second measurement unit (photodiodes PD1, PD2))) (step S102: NO), it proceeds to the next step S103.

[0039] In step S103, the control unit 20 calculates a correction value at each main scanning position based on the data (measured values) read out in step S101.

[0040] In step S104, the control unit 20 applies frequency modulation to each light source 1 based on the correction value read out in step S101 or the correction value calculated in step S103.

[0041] Next, the control unit 20 determines whether a predetermined condition is satisfied (step S105). Here, the predetermined condition refers to a condition that may cause a change in the main scanning interval of each light source 1, such as a condition in which the environment detection unit 60 detects an environmental change (temperature change) of a predetermined level or more, or a condition in which a predetermined time has passed since the frequency modulation in step S104. Here, an environmental change (temperature change) of a predetermined level or more refers to, for example, a change to a degree that may cause deformation of the optical system. Furthermore, the predetermined time refers to a period of time that may cause deterioration of the optical system. If the control unit 20 determines that a predetermined condition is met (for example, a predetermined or greater environmental change has been detected, or a predetermined time has passed) (step S105: YES), the control unit 20 proceeds to the next step S106. On the other hand, if the control unit 20 determines that the predetermined conditions are not met (for example, an environmental change of a predetermined magnitude or more has not been detected, or a predetermined time has not elapsed) (step S105: NO), it repeats the processing of step S105 until it determines that the predetermined conditions are met.

[0042] In step S106, the control unit 20 acquires the measurement value (main scanning interval) measured by the first measurement unit (photodiodes PD11 and PD12).

[0043] Next, the control unit 20 calculates a correction value at each main scanning position (step S107) based on the measurement values acquired in step S106 and the measurement values stored in the storage unit 30. Specifically, the control unit 20 calculates the correction value A'(n) at each main scanning position using the above equations (3) and (4). Thereafter, the control unit 20 proceeds to step S104, and applies frequency modulation to each light source 1 based on the correction value calculated in step S107.

[0044] As described above, the image forming apparatus 1000 according to this embodiment includes an image forming unit 10 that scans multiple light beams (laser light L) emitted from multiple light sources 1 in the main scanning direction on an image carrier (photoconductor 200) in accordance with image data to form an image, a modulation unit (controller 20) that applies frequency modulation to each light source 1 in accordance with the main scanning intervals of the multiple light beams at multiple main scanning positions, an emission control unit (controller 20) that controls the light emission timing of each light source 1 based on the modulation results from the modulation unit, a first measurement unit (photodiodes PD11 and PD12) that measures the main scanning intervals, and a storage unit 30 that stores the main scanning intervals measured by a second measurement unit (photodiodes PD1 and PD2) arranged to correspond to multiple main scanning positions during a production process. The modulation unit calculates a frequency modulation rate for each light source 1 based on the main scanning intervals stored in the storage unit 30 and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each light source 1 based on the calculated frequency modulation rate. Therefore, according to the image forming apparatus 1000 of this embodiment, the tilt of each light source 1 at each main scanning position can be corrected, thereby reducing the occurrence of pitch unevenness. In particular, since it is possible to respond to changes over time that occur in the actual device, it is possible to reduce the occurrence of pitch unevenness even in the actual device after it has been used.

[0045] Furthermore, according to the image forming apparatus 1000 of this embodiment, the first measurement unit is disposed near the irradiation start position and irradiation end position outside the image area. Therefore, according to the image forming apparatus 1000 of this embodiment, the main scanning interval can be measured using a measuring unit positioned so as not to interfere with irradiation of the image area, thereby reducing the occurrence of pitch unevenness while performing image formation as usual.

[0046] Furthermore, the image forming apparatus 1000 according to this embodiment includes a detection unit (environment detection unit 60) that detects an environmental change within the apparatus. When the detection unit detects an environmental change of a predetermined level or more, the modulation unit calculates a frequency modulation rate for each light source 1 based on the main scanning interval stored in the storage unit 30 and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each light source 1 based on the calculated frequency modulation rate. Therefore, according to the image forming apparatus 1000 of this embodiment, frequency modulation can be applied to each light source 1 when there is a risk of deformation of the optical system, so that the tilt of each light source 1 at each main scanning position can be corrected at a more appropriate timing.

[0047] Furthermore, according to the image forming apparatus 1000 of this embodiment, when a predetermined time has elapsed, the modulation unit calculates the frequency modulation rate of each light source 1 based on the main scanning interval stored in the memory unit 30 and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each light source 1 based on the calculated frequency modulation rate. Therefore, according to the image forming apparatus 1000 of this embodiment, frequency modulation can be applied to each light source 1 when there is a risk of deterioration of the optical system, so that the inclination of each light source 1 at each main scanning position can be corrected at a more appropriate timing.

[0048] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above embodiments and can be modified within the scope of the present invention.

[0049] For example, in the above embodiment, when a predetermined condition is met, such as when a predetermined or greater environmental change (temperature change) is detected or when a predetermined time has passed, a correction value at each main scanning position is calculated based on the measurement values measured by the first measurement unit (photodiodes PD11, PD12) and the measurement values stored in memory unit 30. However, this is not limiting. For example, the main scanning interval may be calculated based on density information of an image (chart) used to calculate the main scanning interval, and when a fluctuation in the main scanning interval is detected based on the calculation result, a correction value at each main scanning position may be calculated based on the measurement values measured by photodiodes PD11, PD12 and the measurement values stored in memory unit 30. Specifically, first, the control unit 20 causes the image forming unit 10 to form an image (chart) for calculating the main scanning interval. That is, the control unit 20 functions as the image formation control unit of the present invention. Next, the control unit 20 calculates the main scanning intervals at multiple main scanning positions of each light source 1 based on density information of the image (chart) acquired by the acquisition unit (camera 40). That is, the control unit 20 functions as the calculation unit of the present invention. Next, when the control unit 20 detects a variation in the main scanning interval based on the calculation results, it calculates a correction value at each main scanning position based on the measurement values measured by the photodiodes PD11 and PD12 and the measurement values stored in the memory unit 30. As described above, the apparatus is equipped with an image formation control unit (control unit 20) that causes the image forming unit 10 to form a chart for calculating the main scanning interval, an acquisition unit (camera 40) that acquires density information of the chart formed by the image forming unit 10, and a calculation unit (control unit 20) that calculates the main scanning interval based on the density information, and when the modulation unit detects a fluctuation in the main scanning interval based on the calculation result by the calculation unit, it calculates the frequency modulation rate of each light source 1 based on the main scanning interval stored in the memory unit 30 and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each light source 1 based on the calculated frequency modulation rate, so that when a fluctuation in the main scanning interval is actually detected, frequency modulation can be applied to each light source 1, and the inclination of each light source 1 at each main scanning position can be corrected at a more appropriate timing.

[0050] In the above embodiment, the photodiodes PD1 and PD2 are used as an example of a method for measuring the main scanning intervals of the light sources 1 at multiple main scanning positions in the production process, but the present invention is not limited to this. For example, a camera (CCD camera) may be used instead of the photodiodes PD1 and PD2.

[0051] Furthermore, in the above embodiment, a configuration has been described in which the light receiving unit 6 detects the laser light L reflected by the second reflecting mirror 5, but the present invention is not limited to this. For example, the second reflecting mirror 5 may not be provided, and the light receiving unit 6 may be located at the position of the second reflecting mirror 5. Furthermore, the light receiving unit 6 does not necessarily have to be located inside the image writing unit 100, and may be located outside the image writing unit 100 as long as it is capable of detecting the laser light L at the start and end of irradiation.

[0052] In addition, the detailed configuration and operation of each device constituting the image forming apparatus can be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0053] 1000 Image forming device 10 Image forming unit 100 Image writing unit 11 Light source section 1 light source 2 deflector 3 fθ lenses 4. First reflecting mirror 5 Second reflecting mirror 6 Light receiving part 61 SOS board 62 EOS board PD11, PD12 Photodiodes (first measurement section) 200 Photosensitive body (image carrier) 210 Charging section 220 Development unit 300 Intermediate transfer belt 400 Transfer Roller 500 Fixing unit 20 control unit (modulation unit, light emission control unit, image formation control unit, calculation unit) 30 Storage section 40 Camera (acquisition unit) 50 Operation Panel 51 Display section 52 Operation section 60 Environmental detection unit (detection unit) 70 Sensor board PD1, PD2 Photodiodes (second measurement section) L Laser light (ray)

Claims

1. an image forming unit that scans a plurality of light beams emitted from a plurality of light sources in a main scanning direction on an image carrier to form an image; a modulation unit that applies frequency modulation to each light source in accordance with main scanning intervals at a plurality of main scanning positions of the plurality of light beams; a light emission control unit that controls the light emission timing of each of the light sources based on a result of modulation by the modulation unit; a first measuring unit that measures the main scanning interval; a storage unit that stores the main scanning intervals measured by a second measurement unit that is arranged to correspond to the plurality of main scanning positions in a production process; an image formation control unit that causes the image forming unit to form a chart for calculating the main scanning interval; an acquisition unit that acquires density information of the chart formed by the image forming unit; a calculation unit that calculates the main scanning interval based on the density information; Equipped with an image forming apparatus characterized in that, when a fluctuation in the main scanning interval is detected based on the calculation result by the calculation unit, the modulation unit calculates a frequency modulation rate of each of the light sources based on the main scanning interval stored in the memory unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate.

2. 2. The image forming apparatus according to claim 1, wherein the first measuring unit is disposed near an irradiation start position and an irradiation end position outside an image area.

3. A detection unit is provided to detect environmental changes within the device, 3. The image forming apparatus according to claim 1, wherein when the detection unit detects an environmental change of a predetermined magnitude or greater, the modulation unit calculates a frequency modulation rate for each of the light sources based on the main scanning interval stored in the memory unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate.

4. The image forming apparatus according to any one of claims 1 to 3, characterized in that, when a predetermined time has elapsed, the modulation unit calculates a frequency modulation rate of each of the light sources based on the main scanning interval stored in the memory unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate.

5. A light emission control method for an image forming apparatus including an image forming unit that forms an image by scanning a plurality of light beams emitted from a plurality of light sources in a main scanning direction on an image carrier according to image data, a first measurement unit that measures main scanning intervals at a plurality of main scanning positions of the plurality of light beams, and a storage unit that stores the main scanning intervals measured by a second measurement unit that is disposed in a production process so as to correspond to the plurality of main scanning positions, a modulation step of applying frequency modulation to each light source in accordance with main scanning intervals at a plurality of main scanning positions of the plurality of light beams; a light emission control step of controlling the light emission timing of each of the light sources based on a modulation result obtained by the modulation step; an image formation control step of causing the image forming unit to form a chart for calculating the main scanning interval; an acquisition step of acquiring density information of the chart formed by the image forming unit; a calculation step of calculating the main scanning interval based on the density information; Including, a modulation step of calculating a frequency modulation rate of each of the light sources based on the main scanning interval stored in the memory unit and the main scanning interval measured by the first measurement unit when a fluctuation in the main scanning interval is detected based on the calculation result of the calculation step, and applying frequency modulation to each of the light sources based on the calculated frequency modulation rate;

6. a computer for an image forming apparatus, comprising: an image forming unit that forms an image by scanning a plurality of light beams emitted from a plurality of light sources in a main scanning direction on an image carrier in accordance with image data; a first measuring unit that measures main scanning intervals at a plurality of main scanning positions of the plurality of light beams; and a storage unit that stores the main scanning intervals measured by a second measuring unit that is disposed so as to correspond to the plurality of main scanning positions in a production process; a modulation unit that applies frequency modulation to each light source in accordance with main scanning intervals at a plurality of main scanning positions of the plurality of light beams; a light emission control unit that controls the light emission timing of each of the light sources based on the modulation result by the modulation unit; an image formation control unit that causes the image forming unit to form a chart for calculating the main scanning interval; an acquisition unit that acquires density information of the chart formed by the image forming unit; a calculation unit that calculates the main scanning interval based on the density information; It functions as the modulation unit, when detecting a fluctuation in the main scanning interval based on the calculation result by the calculation unit, calculates a frequency modulation rate of each of the light sources based on the main scanning interval stored in the storage unit and the main scanning interval measured by the first measurement unit, and applies frequency modulation to each of the light sources based on the calculated frequency modulation rate.

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