Light emission control device and image forming device

Abstract

To provide a light emission control device and an image forming device which can correct variation in quantity of emitted light with a simpler structure.SOLUTION: A light emission control device 100 comprises a driver circuit 73 and a control circuit 74. The driver circuit 73 drives a light emission module 71 with a quantity of emitted light corresponding to a reference voltage Vs1 inputted from the outside. The control circuit 74 controls the driver circuit 73 by outputting the reference voltage Vs1 to the driver circuit 73. The control circuit 74 adjusts the reference voltage Vs1, on the basis of output of an optical sensor 72 for generating a BD signal Si2 that is a synchronization signal in a main scanning direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] As related technologies, a light emission control device (laser control device) that controls the amount of light emitted from a light emitting module (semiconductor laser) used as a light source for writing image information, and an image forming device equipped with this light emission control device are known (see, for example, Patent Document 1).

[0003] In this image forming device, a light beam (laser beam) emitted from a light emitting module is deflected by a polarizer and irradiated onto a photosensitive member (photosensitive drum). The surface of the photosensitive member is first uniformly charged by a charger, and the photosensitive member rotates as the imaging spot repeatedly scans the axial direction of the photosensitive member, thereby scanning the entire image forming area on the photosensitive member.

[0004] This light-emitting control device includes a variable resistor, and the variable resistor is used to correct variations in the amount of light emitted by the light-emitting modules. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-305882 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the configuration of the related art described above, it is necessary to adjust the variable resistors individually, which requires a lot of man-hours, and the inclusion of variable resistors makes the configuration complicated, which also hinders cost reduction.

[0007] An object of the present invention is to provide a light emission control device and an image forming apparatus that can correct variations in the amount of emitted light with a simpler configuration. [Means for solving the problem]

[0008] A light-emitting control device according to one aspect of the present invention includes a driver circuit and a control circuit. The driver circuit drives a light-emitting module with an amount of light emission corresponding to an externally input reference voltage. The control circuit outputs the reference voltage to the driver circuit to control the driver circuit. The control circuit adjusts the reference voltage based on the output of an optical sensor for generating a BD signal, which is a synchronization signal in the main scanning direction.

[0009] An image forming apparatus according to another aspect of the present invention includes the light emission control device, the light emitting module, and an image carrier on which an electrostatic latent image is formed by light output from the light emitting module. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a light emission control device and an image forming apparatus that can correct variations in the amount of emitted light with a simpler configuration. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram of the image forming unit of the image forming apparatus according to the first embodiment. [Figure 3] FIG. 3 is a schematic diagram of an optical scanning device of the image forming apparatus according to the first embodiment. [Figure 4] FIG. 4 is a schematic plan view of the optical scanning device of the image forming apparatus according to the first embodiment. [Figure 5] FIG. 5 is a schematic perspective view of the optical scanning device of the image forming apparatus according to the first embodiment. [Figure 6] FIG. 6 is a block diagram showing a schematic configuration of the optical scanning device according to the first embodiment. [Figure 7]FIG. 7 is a graph showing an example of the relationship between the reference voltage and the pulse width of the BD signal in the optical scanning device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description will discuss preferred embodiments of the present invention with reference to the accompanying drawings. The preferred embodiments are merely examples of the present invention and are not intended to limit the technical scope of the present invention.

[0013] (Embodiment 1) [1] Overall configuration of image forming device First, with reference to FIG. 1, the overall configuration of an image forming apparatus 10 according to this embodiment will be described.

[0014] For ease of explanation, the vertical direction in the installed state (the state shown in FIG. 1) in which image forming apparatus 10 can be used is defined as the up-down direction D1. Also, the left side of image forming apparatus 10 in the plane of the drawing shown in FIG. 1 is defined as the front (front face), and the front-to-back direction D2 is defined. Also, the left-to-right direction D3 is defined based on the front face of image forming apparatus 10 in the installed state.

[0015] The image forming apparatus 10 according to the present embodiment is, for example, a multifunction peripheral having multiple functions, such as a scanning function for acquiring image data from an original, a printing function for forming an image based on the image data, a facsimile function, and a copy function. The image forming apparatus 10 may be a printer, a facsimile machine, a copy machine, or the like, as long as it has the function of forming an image.

[0016] 1, the image forming apparatus 10 includes an automatic document feeder 1, an image reading unit 2, an image forming unit 3, an optical scanning device 4, a paper feed unit 5, and an operation display unit 6. In other words, the optical scanning device 4 according to this embodiment, together with the image forming unit 3, etc., constitutes the image forming apparatus 10. The automatic document feeder 1 is an ADF (Auto Document Feeder), and will be referred to as "ADF1" in the following description.

[0017] The ADF 1 transports an original document whose image is to be read by the image reading unit 2. The ADF 1 includes an original document setting unit, a plurality of transport rollers, an original document holder, and a paper discharge unit.

[0018] The image reading unit 2 reads an image from a document and outputs image data corresponding to the read image. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, a CCD (Charge Coupled Device), and the like.

[0019] The image forming unit 3 realizes a printing function by forming a color or monochrome image on a sheet using an electrophotographic method. The image forming unit 3 forms an image on a sheet based on image data output from the image reading unit 2. The image forming unit 3 also forms an image on a sheet based on image data input from an information processing device external to the image forming apparatus 10, such as a personal computer.

[0020] The paper feed unit 5 supplies sheets to the image forming unit 3. The paper feed unit 5 includes a paper feed cassette, a manual feed tray, a sheet transport path, and a plurality of transport rollers. The image forming unit 3 forms an image on the sheet supplied from the paper feed unit 5.

[0021] The operation display unit 6 is a user interface in the image forming apparatus 10. The operation display unit 6 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit, and an operation unit such as a switch or a touch panel that inputs various information to the control unit in response to user operations.

[0022] The image forming apparatus 10 further includes a control unit, a storage unit, a communication unit, etc. The control unit controls the image forming apparatus 10 in an integrated manner. The control unit is primarily composed of a computer system having one or more processors and one or more memories. In the image forming apparatus 10, the functions of the control unit are realized by the one or more processors executing programs. The programs may be pre-recorded in memory, provided via a telecommunications line such as the Internet, or provided by being recorded on a non-transitory recording medium readable by a computer system, such as a memory card or an optical disk. The storage unit includes one or more non-volatile memories and pre-stores information such as control programs for causing the control unit to execute various processes. The communication unit is an interface that performs data communication between the image forming apparatus 10 and external devices connected via a communication network, such as the Internet or a LAN (Local Area Network).

[0023] [2] Image forming unit configuration Next, the configuration of the image forming unit 3 will be described in more detail with reference to FIGS.

[0024] As shown in FIG. 1, the image forming section 3 has four image forming units 31 to 34, an intermediate transfer device 36, a secondary transfer roller 37, a fixing device 38, and a paper discharge tray 39.

[0025] Image forming unit 31 forms a Y (yellow) toner image. As shown in Fig. 2, image forming unit 31 includes photosensitive drum 311, charging roller 312, developing device 313 including developing roller 313A, primary transfer roller 314, and drum cleaning unit 315. Image forming unit 31 also includes toner container 316 (see Fig. 1).

[0026] Image forming unit 32 forms a C (cyan) toner image. As shown in Fig. 2, image forming unit 32 includes a photosensitive drum 321, a charging roller 322, a developing device 323 including a developing roller 323A, a primary transfer roller 324, and a drum cleaning unit 325. Image forming unit 32 further includes a toner container 326 (see Fig. 1).

[0027] Image forming unit 33 forms a magenta (M) toner image. As shown in Fig. 2, image forming unit 33 includes a photosensitive drum 331, a charging roller 332, a developing device 333 including a developing roller 333A, a primary transfer roller 334, and a drum cleaning unit 335. Image forming unit 33 further includes a toner container 336 (see Fig. 1).

[0028] The image forming unit 34 forms a K (black) toner image. As shown in Fig. 2, the image forming unit 34 includes a photosensitive drum 341, a charging roller 342, a developing device 343 including a developing roller 343A, a primary transfer roller 344, and a drum cleaning unit 345. The image forming unit 34 further includes a toner container 346 (see Fig. 1).

[0029] In this way, the multiple (four in this example) image forming units 31 to 34 correspond to the four colors of Y (yellow), C (cyan), M (magenta), and K (black), respectively, and basically have a common configuration. Therefore, hereinafter, unless otherwise specified, the configuration described for image forming unit 34 also has the same configuration for the other image forming units 31 to 33.

[0030] An electrostatic latent image is formed on the photosensitive drum 341. The photosensitive drum 341 is rotatably supported about a rotation axis extending in the left-right direction D3 by a unit housing that houses the photosensitive drum 341, charging roller 342, and drum cleaning unit 345. The photosensitive drum 341 receives a driving force supplied from a motor, for example, and rotates in a rotation direction D5 shown in FIG.

[0031] The charging roller 342 positively charges the surface (outer circumferential surface) of the photosensitive drum 341. Specifically, the charging roller 342 is electrically connected to a power supply circuit, and receives a high voltage from the power supply circuit to charge the surface of the photosensitive drum 341. However, the charging roller 342 is not limited to a configuration that charges the surface of the photosensitive drum 341 positively, and may also charge the surface of the photosensitive drum 341 negatively.

[0032] The surface of the photosensitive drum 341, which has been charged by the charging roller 342, is irradiated with a light beam B4 (see FIG. 3) based on image data from the optical scanning device 4. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 341. That is, in this embodiment, the photosensitive drum 341 is an example of an "image carrier" on which an electrostatic latent image is formed by the light beam B4 output from the optical scanning device 4.

[0033] The developing device 343 develops the electrostatic latent image formed on the surface of the photosensitive drum 341. For example, the developing device 343 includes a case, a pair of stirring members, a magnet roller, and a developing roller 343A. The case rotatably supports the pair of stirring members, the magnet roller, and the developing roller 343A around a rotation axis extending in the left-right direction D3. The case also contains K (black) toner and carrier. The pair of stirring members stir the toner and carrier contained in the case to charge the toner. In this embodiment, the toner is positively charged. However, the charged polarity of the toner is not limited to positive and may be negative. The magnet roller picks up the toner and carrier stirred by the pair of stirring members and supplies the toner to the surface (outer circumferential surface) of the developing roller 343A.

[0034] The developing roller 343A uses charged toner to develop the electrostatic latent image formed on the photosensitive drum 341. Specifically, a high-voltage developing bias is applied between the developing roller 343A and the photosensitive drum 341 by a power supply circuit, thereby forming a developing electric field, and the charged toner moves from the developing roller 343A to the photosensitive drum 341. As a result, a toner image is formed on the surface of the photosensitive drum 341.

[0035] The primary transfer roller 344 transfers the toner image formed on the surface of the photosensitive drum 341 by the developing device 343 onto the outer circumferential surface of the intermediate transfer belt 361 (see FIG. 2). Specifically, a high-voltage transfer bias is applied between the photosensitive drum 341 and the primary transfer roller 344 by a power supply circuit, thereby forming a transfer electric field, and the charged toner moves from the photosensitive drum 341 to the intermediate transfer belt 361. As a result, a toner image is formed (transferred) on the outer circumferential surface of the intermediate transfer belt 361.

[0036] Drum cleaning unit 345 cleans the surface of photosensitive drum 341 after the toner image has been transferred by primary transfer roller 344. For example, drum cleaning unit 345 has a blade-shaped cleaning member and a transport member. The cleaning member comes into contact with the surface of photosensitive drum 341 to remove toner adhering to the surface. The transport member transports the toner removed by the cleaning member to a toner storage container.

[0037] The toner container 346 supplies toner to the case of the developing device 343. In the image forming unit 34 that forms a K (black) toner image, the toner container 346 supplies K (black) toner.

[0038] The toner images of each color formed by each of the multiple (four in this example) image forming units 31 to 34 are transferred in layers onto the outer circumferential surface of the intermediate transfer belt 361. As a result, a color image (toner image) is formed on the outer circumferential surface of the intermediate transfer belt 361.

[0039] 2, the intermediate transfer device 36 includes an intermediate transfer belt 361, a drive roller 362, a tension roller 363, a belt cleaning unit 364, and a density detection unit 365. The intermediate transfer device 36 uses the intermediate transfer belt 361 to transport the toner images formed by the image forming units 31 to 34 to a transfer position P1 (see FIG. 2) where the toner images are transferred by a secondary transfer roller 37.

[0040] The intermediate transfer belt 361 is an endless belt onto which the toner images of each color are transferred from the photosensitive drums 311, 321, 331, and 341. As shown in FIG. 2, the intermediate transfer belt 361 is looped around a drive roller 362 and a tension roller 363, which are spaced apart from each other in the front-to-rear direction D2 of the image forming apparatus 10. The drive roller 362 rotates by receiving a driving force supplied from a motor. This causes the intermediate transfer belt 361 to rotate in a rotation direction D4 shown in FIG. 2. The toner images transferred onto the outer peripheral surface of the intermediate transfer belt 361 are transported to a transfer position P1 by the secondary transfer roller 37 as the intermediate transfer belt 361 rotates. A belt cleaning unit 364 cleans the outer peripheral surface of the intermediate transfer belt 361 after the toner images have been transferred at the transfer position P1.

[0041] The secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 onto a sheet supplied by the paper feed unit 5. As shown in FIG. 2, the secondary transfer roller 37 is disposed opposite the tension roller 363 across the intermediate transfer belt 361, so as to be in contact with the outer peripheral surface of the intermediate transfer belt 361. The secondary transfer roller 37 is pressed toward the tension roller 363 by a biasing member. The secondary transfer roller 37 is electrically connected to a power supply circuit, and when high voltage is applied from the power supply circuit, the secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 onto a sheet passing through transfer position P1 where the secondary transfer roller 37 and the intermediate transfer belt 361 come into contact.

[0042] The fixing device 38 fuses and fixes the toner image transferred to the sheet by the secondary transfer roller 37 to the sheet. For example, the fixing device 38 includes a fixing roller and a pressure roller. The fixing roller is arranged to be in contact with the pressure roller, and heats the toner image transferred to the sheet to fix it to the sheet. The pressure roller applies pressure to the sheet passing through the contact area formed between the fixing roller and the pressure roller.

[0043] The sheet on which the image has been formed is discharged to the discharge tray 39.

[0044] [3] Optical scanning device configuration Next, the configuration of the optical scanning device 4 will be described in more detail with reference to FIGS.

[0045] The optical scanning device 4 forms an electrostatic latent image on each of the photosensitive drums 311, 321, 331, and 341 of the four image forming units 31 to 34. To this end, the optical scanning device 4 outputs light beams B1, B2, B3, and B4 corresponding to the photosensitive drums 311, 321, 331, and 341, respectively, as shown in FIG. 3. The light beam B1 is irradiated onto the photosensitive drum 311 in response to input image data of Y (yellow), forming an electrostatic latent image on the photosensitive drum 311, which is an image carrier. The light beam B2 is irradiated onto the photosensitive drum 321 in response to input image data of C (cyan), forming an electrostatic latent image on the photosensitive drum 321, which is an image carrier. The light beam B3 is irradiated onto the photosensitive drum 331 in response to input image data of M (magenta), forming an electrostatic latent image on the photosensitive drum 331, which is an image carrier. The light beam B4 is irradiated onto the photosensitive drum 341 in accordance with input image data of K (black), and forms an electrostatic latent image on the photosensitive drum 341, which is an image carrier.

[0046] In this way, the optical scanning device 4 is configured to be able to output (irradiate) a plurality (four in this case) of light beams B1 to B4 for forming electrostatic latent images to a plurality (four in this case) of image forming units 31 to 34 corresponding to a plurality of colors (four in this case). In this embodiment, the plurality (four in this case) of light beams B1 to B4, which have different optical paths, are output from a single optical scanning device 4.

[0047] In this embodiment, as shown in FIG. 3, the optical scanning device 4 includes a substrate unit 7, a deflector 41, a mirror 42, and a scanning lens 43. FIG. 3 schematically illustrates the configuration of each component, and does not accurately illustrate the shape and positional relationship of each component. The deflector 41, the mirror 42, and the scanning lens 43 are housed in a case 400 of the main unit 40. As shown in FIGS. 4 and 5, the substrate unit 7 is attached to the outer surface of the main unit 40 (strictly speaking, the case 400 of the main unit 40). That is, the optical scanning device 4 roughly includes the main unit 40 including the deflector 41, the mirror 42, and the scanning lens 43, and the substrate unit 7 attached to the main unit 40.

[0048] The board unit 7 has a board 70 and a light emitting module 71, and irradiates light from the light emitting module 71 onto the deflector 41. In the example of FIGS. 4 and 5, the board unit 7 is attached to the left side of the main unit 40, which is substantially rectangular in plan view (top view). The board unit 7 irradiates light into the case 400 through a light entrance hole formed in the case 400 of the main unit 40. The board unit 7 is detachably attached to the main unit 40 using fixing means such as screws. Therefore, for example, by removing the board unit 7 from the main unit 40, maintenance and replacement of just the board unit 7 are possible.

[0049] In this embodiment, the substrate unit 7 has a semiconductor laser as the light-emitting module 71, which outputs laser light. The substrate unit 7 has a plurality of (four in this example) light-emitting modules 71, and each of these light-emitting modules 71 outputs laser light for forming an electrostatic latent image corresponding to each of the colors Y (yellow), C (cyan), M (magenta), and K (black).

[0050] Furthermore, the board unit 7 has an optical sensor 72 in addition to the board 70 and the light-emitting module 71. The optical sensor 72 is a synchronization detection sensor (BD sensor) that detects the scanning light emitted from the light-emitting module 71 and outputs a reference signal that determines the timing of writing an image based on image data based on the timing of detecting the scanning light. In other words, the timing of writing an electrostatic latent image onto the photosensitive drums 311, 321, 331, and 341 is determined by the timing at which the optical sensor 72 receives (detects) the scanning light.

[0051] Here, the scanning light detected by optical sensor 72 is not direct light from light-emitting module 71, but light emitted from light-emitting module 71 and scanned (deflected) by deflector 41 of main unit 40. More specifically, main unit 40 includes a synchronous detection mirror, and the scanning light that is scanned by deflector 41 and travels along an optical path outside the effective scanning range (the range where image data is actually written) is reflected by the synchronous detection mirror and enters optical sensor 72. Therefore, scanning light enters optical sensor 72 of board unit 7 from inside case 400 of main unit 40 through a light extraction hole formed in case 400. The light extraction hole may be integrated with the light entrance hole.

[0052] In the present embodiment, the deflector 41 is, as an example, a polygon mirror scanner, and includes a polygon mirror 411 and a scanner motor 412, as shown in FIG. 3 . That is, the deflector 41 rotates the polygon mirror 411 using the scanner motor 412, thereby scanning the light from the substrate unit 7 in the main scanning direction along the rotation axis direction (left-right direction D3) of the photosensitive drums 311, 321, 331, and 341. However, the deflector 41 is not limited to a polygon scanner, and may be, for example, an acousto-optical element, a hologram scanner, a galvanometer mirror, or a micromirror scanner using MEMS (Micro Electro Mechanical Systems) technology. The deflector 41 may also be integrated with the substrate unit 7.

[0053] The mirror 42 reflects the light from the deflector 41. The scanning lens 43 includes an fθ lens, etc. As a result, in the optical scanning device 4, the light from the substrate unit 7 passes through the deflector 41, the mirror 42, and the scanning lens, and is output toward the image forming units 31 to 34. Here, the optical scanning device 4 is capable of outputting a plurality of (four in this case) light beams B1 to B4, and forms electrostatic latent images corresponding to each color by scanning each of the light beams B1 to B4 in the main scanning direction.

[0054] In other words, of the light from light-emitting module 71, the scanning light that is deflected by deflector 41 and travels along an optical path outside the effective scanning range is reflected by the synchronous detection mirror and enters optical sensor 72, while the light that travels along an optical path within the effective scanning range is output as light rays B1 to B4. In other words, light rays B1 to B4 that are irradiated onto and expose photosensitive drums 311, 321, 331, and 341 are scanning light, but are different from the scanning light detected by optical sensor 72.

[0055] [4] Configuration of the light-emitting control device Next, the configuration of the light emission control device 100 in the optical scanning device 4 will be described with reference to FIGS.

[0056] 6, the optical scanning device 4 includes a light-emitting control device 100 in addition to a light-emitting module 71 and an optical sensor 72. The light-emitting control device 100 controls the light-emitting state of the light-emitting module 71. The optical scanning device 4 further includes optical elements such as a collimator lens, an aperture, and a mirror.

[0057] The optical scanning device 4 according to this embodiment, together with the image forming unit 3 including the photosensitive drums 311, 321, 331, and 341 as image carriers, constitutes an image forming apparatus 10. In other words, the image forming apparatus 10 according to this embodiment includes the light-emitting control device 100, the light-emitting module 71, and the image carriers (photosensitive drums 311, 321, 331, and 341) on which an electrostatic latent image is formed by the light beam output from the light-emitting module 71.

[0058] Four light-emitting modules 71 are provided for one main unit 40 in order to form electrostatic latent images corresponding to the colors Y (yellow), C (cyan), M (magenta), and K (black). Since the four light-emitting modules 71 have a common configuration, the following description will use one light-emitting module 71 as an example to explain the configuration of the light-emitting module 71, unless otherwise specified.

[0059] The light emitting module 71 includes a light emitting element LD1 and a monitoring photodiode PD1. The light emitting element LD1 is configured as a semiconductor laser (LD: Laser Diode) that generates laser oscillation by passing a current through a semiconductor. The light emitting element LD1 and the photodiode PD1 are housed in a single package.

[0060] Only one optical sensor 72 is provided for each main unit 40. The optical sensor 72 has a light receiving section, and detects light (scanning light) at the light receiving section. The optical sensor 72 is configured with a photoelectric conversion element that outputs a BD signal Si2 in response to the light (scanning light) incident on the light receiving section. The optical sensor 72 is, for example, a photodiode, a phototransistor, or a photo IC (Integrated Circuit).

[0061] As shown in FIG. 6, the light emission control device 100 includes a driver circuit 73 and a control circuit 74.

[0062] The driver circuit 73 drives the light-emitting module 71. That is, the driver circuit 73 causes the light-emitting module 71 to emit light by passing a current through the light-emitting module 71. In this embodiment, four driver circuits 73 are provided for one main unit 40 in order to drive the four light-emitting modules 71. That is, the four driver circuits 73 are associated one-to-one with the four light-emitting modules 71, and each drive the corresponding light-emitting module 71. FIG. 6 shows only one driver circuit 73 corresponding to one light-emitting module 71.

[0063] Here, the driver circuit 73 changes the amount of light emitted by the light-emitting module 71 in accordance with an externally input reference voltage Vs1. Specifically, the driver circuit 73 drives the light-emitting module 71 so that the amount of light emitted by the light-emitting module 71 increases as the reference voltage Vs1 input to the driver circuit 73 increases. As an example, in this embodiment, the reference voltage Vs1 and the amount of light emitted by the light-emitting module 71 are assumed to have a linear relationship so that the amount of light emitted by the light-emitting module 71 increases in proportion to the reference voltage Vs1.

[0064] Only one control circuit 74 is provided for each main unit 40. The control circuit 74 controls multiple (four in this example) driver circuits 73. The control circuit 74 is electrically connected to each driver circuit 73 by conductive wiring (signal lines) formed on the substrate 70. The control circuit 74 controls each driver circuit 73 individually using a control signal Si1 such as LVDS (Low Voltage Differential Signaling), for example.

[0065] Furthermore, the control circuit 74 is electrically connected to the optical sensor 72 by conductive wiring (signal line) formed on the substrate 70. The control circuit 74 receives a BD signal Si2 from the optical sensor 72.

[0066] The control circuit 74 outputs a control signal Si1 to the driver circuit 73 in synchronization with the BD signal Si2, thereby controlling the light-emitting state (on / off) of the light-emitting module 71. That is, the optical sensor 72 outputs a BD signal Si2 that determines the timing of writing an image based on image data, based on the timing of detecting the scanning light, and the control circuit 74 determines the light-emitting timing of the light-emitting module 71 based on this BD signal Si2.

[0067] In addition, the control circuit 74 controls the amount of light emitted by the light-emitting module 71 by outputting a reference voltage Vs1 to the driver circuit 73. In other words, the amount of light emitted by the light-emitting module 71 is determined by the reference voltage Vs1 output from the control circuit 74.

[0068] The driver circuit 73 and the control circuit 74 are each realized by an integrated circuit (IC). The multiple (four in this case) light-emitting modules 71, the optical sensor 72, the multiple (four in this case) driver circuits 73, and the control circuit 74 are all mounted on one (single) substrate 70.

[0069] In this embodiment, the same number of light-emitting modules 71 and driver circuits 73 (four in this example) are mounted on the substrate 70, but this is not limiting. For example, if one driver circuit 73 drives two light-emitting modules 71, four light-emitting modules 71 and two driver circuits 73 will be mounted on the substrate 70.

[0070] Meanwhile, as related art, there are known light emission control devices (laser control devices) that control the amount of light emitted from a light emitting module (semiconductor laser) used as a light source for writing image information, and image forming devices equipped with such light emission control devices.

[0071] In this image forming device, a light beam (laser beam) emitted from a light emitting module is deflected by a polarizer and irradiated onto a photosensitive member (photosensitive drum). The surface of the photosensitive member is first uniformly charged by a charger, and the photosensitive member rotates as the imaging spot repeatedly scans the axial direction of the photosensitive member, thereby scanning the entire image forming area on the photosensitive member.

[0072] This light-emitting control device includes a variable resistor, and the variable resistor is used to correct variations in the amount of light emitted by the light-emitting modules.

[0073] However, in the configuration of the related art described above, it is necessary to adjust the variable resistors individually, which requires a lot of man-hours, and the inclusion of variable resistors makes the configuration complicated, which also hinders cost reduction.

[0074] In contrast to this, the light-emitting control device 100 according to this embodiment has a configuration described below that makes it possible to correct variations in the amount of emitted light with a simpler configuration.

[0075] That is, the light-emitting control device 100 according to this embodiment includes a driver circuit 73 and a control circuit 74. The driver circuit 73 drives the light-emitting module 71 with an amount of light emission corresponding to a reference voltage Vs1 input from outside. The control circuit 74 outputs the reference voltage Vs1 to the driver circuit 73 to control the driver circuit 73. The control circuit 74 adjusts the reference voltage Vs1 based on the output of an optical sensor 72 for generating a BD signal Si2, which is a synchronization signal in the main scanning direction.

[0076] According to this configuration, the control circuit 74 can adjust the amount of light emitted by the light-emitting module 71 by adjusting the reference voltage Vs1. Therefore, a variable resistor is not required to adjust the amount of light emitted, eliminating the need for adjusting the variable resistor. Furthermore, eliminating the variable resistor simplifies the configuration and facilitates cost reduction. Furthermore, since the control circuit 74 adjusts the reference voltage Vs1 based on the output of the optical sensor 72 that generates the BD signal Si2, it is possible to determine the reference voltage Vs1 that results in the desired amount of light emitted, without the need for a separate optical sensor. As a result, it is possible to provide a light-emitting control device 100 and an image forming apparatus 10 that can correct variations in the amount of light emitted with a simpler configuration.

[0077] More specifically, the control circuit 74 determines the reference voltage Vs1 by the operation described below so that the light emitting module 71 emits a desired amount of light.

[0078] First, as a premise, the pulse width of the BD signal Si2 basically changes depending on the amount of light received by the optical sensor 72. As an example in this embodiment, if the amount of light emitted by the light-emitting module 71 is equal to or less than a predetermined amount of light, the pulse width of the BD signal Si2 output from the optical sensor 72 increases (widens) as the amount of light received increases.

[0079] 7, the pulse width of the BD signal Si2 varies depending on the reference voltage Vs1 that determines the amount of light emitted by the light-emitting module 71. FIG. 7 shows characteristics G1 and G2 for two light-emitting modules 71 that have different amounts of light emitted relative to the same reference voltage Vs1. The characteristic G1 is the pulse width characteristic of the BD signal Si2 relative to the reference voltage Vs1 for the first light-emitting module 71, which has a relatively large amount of light emitted. The characteristic G2 is the pulse width characteristic of the BD signal Si2 relative to the reference voltage Vs1 for the second light-emitting module 71, which has a relatively small amount of light emitted. Therefore, for the same value of the reference voltage Vs1, the pulse width of the BD signal Si2 is larger in the characteristic G1 than in the characteristic G2.

[0080] Here, the pulse width of the BD signal Si2 saturates at a value w1 when the light-emitting module 71 emits a predetermined amount of light. That is, in either characteristic G1 or G2, when the reference voltage Vs1 is gradually increased, the pulse width of the BD signal Si2 becomes substantially constant after a certain value w1. The region below this value w1 is a "linear region" in which the reference voltage Vs1 and the pulse width of the BD signal Si2 have a linear relationship, and in this linear region, the reference voltage Vs1 and the pulse width of the BD signal Si2 are substantially proportional to each other.

[0081] The light emission control device 100 according to this embodiment has, as its operation modes, an emitted light amount adjustment mode for adjusting the amount of light emitted by the light emitting module 71, and a normal mode for using the image forming device 10.

[0082] In the light emission amount adjustment mode, the control circuit 74 varies the magnitude of the reference voltage Vs1 applied (output) to the driver circuit 73, and measures the pulse width of the BD signal Si2 at multiple reference voltages Vs1. At this time, the control circuit 74 determines the rate of change of the pulse width of the BD signal Si2 with respect to the reference voltage Vs1 in a region (linear region) where the pulse width of the BD signal Si2 is equal to or less than a value w1.

[0083] The control circuit 74 then predicts, as the target voltage v1, the reference voltage Vs1 at which the emitted light intensity of the first light-emitting module 71 will reach the target light intensity (the position indicated by "Th1" in FIG. 7) from the rate of change (the slope of characteristic G1) of the pulse width of the BD signal Si2 relative to the reference voltage Vs1 obtained for the first light-emitting module 71. Similarly, the control circuit 74 predicts, as the target voltage v2, the reference voltage Vs1 at which the emitted light intensity of the second light-emitting module 71 will reach the target light intensity (the position indicated by "Th1" in FIG. 7) from the rate of change (the slope of characteristic G2) of the pulse width of the BD signal Si2 relative to the reference voltage Vs1 obtained for the second light-emitting module 71.

[0084] This allows the control circuit 74 to determine the reference voltage Vs1 (target voltage v1) when the light intensity of the first light-emitting module 71 becomes the target light intensity, and the reference voltage Vs1 (target voltage v2) when the light intensity of the second light-emitting module 71 becomes the target light intensity.

[0085] In the normal mode, the control circuit 74 adjusts the reference voltage Vs1 to the target voltage v1 for the first light-emitting module 71, and adjusts the reference voltage Vs1 to the target voltage v2 for the second light-emitting module 71. As a result, the emitted light intensity of both the first and second light-emitting modules 71 becomes the target light intensity, and variations in the emitted light intensity are corrected.

[0086] As described above, the control circuit 74 adjusts the reference voltage Vs1 based on the output of the optical sensor 72 (the pulse width of the BD signal Si2) when the reference voltage Vs1 changes. This allows the control circuit 74 to identify the reference voltage Vs1 when the desired amount of emitted light is achieved, based on the change in the output of the optical sensor 72 (the pulse width of the BD signal Si2) when the reference voltage Vs1 is changed.

[0087] Here, the control circuit 74 adjusts the reference voltage Vs1 based on the output of the optical sensor 72 (the pulse width of the BD signal Si2) when the reference voltage Vs1 changes in a linear region where the reference voltage Vs1 and the output of the optical sensor 72 (the pulse width of the BD signal Si2) are linearly related. This allows the control circuit 74 to utilize linearity to adjust the reference voltage Vs1 even in the portion where the output of the optical sensor 72 (the pulse width of the BD signal Si2) is saturated.

[0088] Furthermore, the control circuit 74 determines the reference voltage Vs1 at which the amount of light emitted by the light-emitting module 71 becomes the target amount of light as the target voltages v1 and v2 based on the output of the optical sensor 72 (the pulse width of the BD signal Si2), and adjusts the reference voltage Vs1 to the target voltages v1 and v2. This allows the control circuit 74 to adjust the reference voltage Vs1 to adjust the amount of light emitted by the light-emitting module 71 to the target amount of light.

[0089] [5] Variation The multiple components included in the image forming apparatus 10 may be distributed across multiple housings. For example, the image reading unit 2 and the image forming unit 3 may be provided in separate housings.

[0090] In addition, in the first embodiment, four light-emitting modules 71 are provided to form electrostatic latent images corresponding to the colors Y, C, M, and K, but this configuration is not limiting. For example, two or more light-emitting modules 71 may be provided for each color.

[0091] Furthermore, in the first embodiment, only one optical scanning device 4 (main unit 40 and board unit 7) is provided for the four image forming units 31 to 34 corresponding to the four colors, but this configuration is not limited to this. For example, one optical scanning device 4 (main unit 40 and board unit 7) may be provided for one, two, or three image forming units corresponding to one, two, or three colors. For example, if an optical scanning device 4 is provided for each image forming unit of each color, four optical scanning devices 4 (main unit 40 and board unit 7) will be provided for the four image forming units 31 to 34.

[0092] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0093] <Appendix 1> a driver circuit that drives the light-emitting module with an amount of light emitted according to an externally input reference voltage; a control circuit that outputs the reference voltage to the driver circuit to control the driver circuit, the control circuit adjusts the reference voltage based on the output of an optical sensor for generating a BD signal, which is a synchronization signal in the main scanning direction; Light emitting control device.

[0094] <Appendix 2> the control circuit adjusts the reference voltage based on an output of the optical sensor as the reference voltage changes. 2. The light-emitting control device according to claim 1.

[0095] <Appendix 3> the control circuit adjusts the reference voltage based on the output of the optical sensor when the reference voltage changes in a linear region where the reference voltage and the output of the optical sensor have a linear relationship. 3. The light-emitting control device according to claim 2.

[0096] <Appendix 4> the control circuit determines, based on the output of the optical sensor, the reference voltage when the amount of light emitted by the light-emitting module becomes a target amount of light, as a target voltage, and adjusts the reference voltage to the target voltage. 4. The light-emitting control device according to any one of claims 1 to 3.

[0097] <Appendix 5> A light-emitting control device according to any one of Supplementary Notes 1 to 4, the light emitting module; an image carrier on which an electrostatic latent image is formed by the light beam output from the light emitting module; Image forming device. [Explanation of symbols]

[0098] 10 Image forming device 71 Light-emitting module 72 Optical Sensor 73 Driver Circuit 74 Control Circuit 100 Light-emitting control device 311, 321, 331, 341 Photosensitive drum (image carrier) Si2 BD signal v1,v2 target voltage Vs1 reference voltage

Claims

1. a driver circuit that drives the light-emitting module with an amount of light emitted according to an externally input reference voltage; a control circuit that outputs the reference voltage to the driver circuit to control the driver circuit, the control circuit adjusts the reference voltage based on an output of an optical sensor for generating a BD signal, which is a synchronization signal in the main scanning direction; Light emitting control device.

2. the control circuit adjusts the reference voltage based on an output of the optical sensor as the reference voltage changes. The light emission control device according to claim 1 .

3. the control circuit adjusts the reference voltage based on the output of the optical sensor when the reference voltage changes in a linear region where the reference voltage and the output of the optical sensor have a linear relationship. The light emission control device according to claim 2 .

4. the control circuit determines, based on the output of the optical sensor, the reference voltage when the amount of light emitted by the light-emitting module becomes a target amount of light, as a target voltage, and adjusts the reference voltage to the target voltage. The light emission control device according to any one of claims 1 to 3.

5. A light-emitting control device according to any one of claims 1 to 3, the light emitting module; an image carrier on which an electrostatic latent image is formed by the light beam output from the light emitting module; Image forming device.

Images