Optical scanner and image forming apparatus

Abstract

To provide an optical scanner that prevents an optical scanner from erroneously detecting scanning light, and an image forming apparatus.SOLUTION: An optical scanner comprises a substrate 70, a light-emitting module 71, a driver circuit 73, a control circuit 74, and an optical sensor 72. The substrate 70 has a first surface 701 on one side and a second surface 702 on the other side in a thickness direction. The light-emitting module 71 is mounted on the substrate 70, and outputs light toward the first surface 701. The driver circuit 73 is mounted on the substrate 70, and drives the light-emitting module 71. The control circuit 74 is mounted on the substrate 70, and controls the driver circuit 73. The optical sensor 72 is mounted on the substrate 70, and receives scanning light B0 emitted from the light-emitting module 71 as a light source from the side of the first surface 701. The substrate 70 has, on the second surface 702, a connection pad 704 for electrically connecting the optical sensor 72 thereto.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an optical scanning device and an image forming apparatus. [Background technology]

[0002] As a related art, an optical scanning device is known which is used in an image forming apparatus and scans and exposes the peripheral surface of a photosensitive member (photosensitive drum) with scanning light (laser light) to form an electrostatic latent image on the peripheral surface of the photosensitive member (see, for example, Patent Document 1). This optical scanning device includes a light emitting module (laser light source) mounted on a substrate (circuit board), and the light emitted from the light emitting module is reflected by a polygon mirror to scan the scanning light along the main scanning direction.

[0003] This optical scanning device further includes an optical sensor (BD sensor) that detects the deflected light beam, and synchronizes the write timing, which is the timing at which irradiation of the deflected light beam onto the peripheral surface of the photosensitive member, begins for the main scanning line. In the optical scanning device according to the related art, the light emitting module and the optical sensor are mounted on the same surface of the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-72946 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration of the related art, the light (scanning light) from the light-emitting module may be reflected by the connection pads for joining the optical sensor on the substrate, by the joining members such as solder that join the optical sensor to the substrate, or by the terminals of the optical sensor, which may cause stray light. The occurrence of stray light may lead to false detection by the optical sensor.

[0006] An object of the present invention is to provide an optical scanning device and an image forming apparatus in which erroneous detection by an optical sensor is unlikely to occur. [Means for solving the problem]

[0007] An optical scanning device according to one aspect of the present invention includes a substrate, a light-emitting module, a driver circuit, a control circuit, and an optical sensor. The substrate has a first surface and a second surface on both sides in a thickness direction. The light-emitting module is mounted on the substrate and outputs light to the first surface side. The driver circuit is mounted on the substrate and drives the light-emitting module. The control circuit is mounted on the substrate and controls the driver circuit. The optical sensor is mounted on the substrate and receives scanning light emitted from the light-emitting module as a light source from the first surface side. The substrate has connection pads on the second surface that electrically connect the optical sensor.

[0008] An image forming apparatus according to another aspect of the present invention includes the optical scanning device described above, and an image carrier on which an electrostatic latent image is formed by a light beam output from the optical scanning device. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an optical scanning device and an image forming apparatus in which erroneous detection by an optical sensor is unlikely to occur. [Brief explanation of the drawings]

[0010] [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 schematic view of the substrate unit according to the first embodiment as viewed from the first surface side. [Figure 7] FIG. 7 is a schematic view of the substrate unit according to the first embodiment as viewed from the second surface side. [Figure 8] FIG. 8 is a schematic cross-sectional view taken along line AA in FIG. 6, showing a main part of the substrate unit according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] (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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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).

[0022] [2] Image forming unit configuration Next, the configuration of the image forming unit 3 will be described in more detail with reference to FIGS.

[0023] 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.

[0024] 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).

[0025] 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).

[0026] 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).

[0027] 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).

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] The sheet on which the image has been formed is discharged to the discharge tray 39.

[0043] [3] Optical scanning device configuration Next, the configuration of the optical scanning device 4 will be described in more detail with reference to FIGS.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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).

[0049] 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 B0 (see FIG. 8) 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 B0. 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 of receiving (detecting) the scanning light B0 by the optical sensor 72.

[0050] Here, the scanning light B0 detected by the optical sensor 72 is not direct light from the light-emitting module 71, but light emitted from the light-emitting module 71 and scanned (deflected) by the deflector 41 of the main unit 40. More specifically, the main unit 40 includes a synchronous detection mirror, and the scanning light B0 that is scanned by the 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 the optical sensor 72. Therefore, the scanning light B0 enters the optical sensor 72 of the board unit 7 from inside the case 400 of the main unit 40 through a light extraction hole formed in the case 400. The light extraction hole may be integrated with the light entrance hole.

[0051] 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.

[0052] 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.

[0053] In other words, of the light from light-emitting module 71, scanning light B0 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 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 scanning light B0 that is detected by optical sensor 72.

[0054] [4] Circuit board unit configuration Next, the configuration of the substrate unit 7 in the optical scanning device 4 will be described in more detail with reference to Figures 6 to 8. Figure 8 is a schematic cross-sectional view taken along line AA in Figure 6.

[0055] 6 and 7, the board unit 7 includes a board 70, a plurality of light-emitting modules 71, an optical sensor 72, a plurality of driver circuits 73, and a control circuit 74. The board unit 7 is a part of the optical scanning device 4, so in other words, the optical scanning device 4 includes the board 70, a plurality of light-emitting modules 71, an optical sensor 72, a plurality of driver circuits 73, and a control circuit 74. The board unit 7 further includes a signal processing circuit that performs signal processing on the output of the optical sensor 72, and optical elements such as a collimator lens, an aperture, and a mirror.

[0056] The substrate 70 is a member on which various electronic components can be mounted, and is a printed wiring board having an electrically insulating substrate main body and conductive wiring formed on or inside the substrate main body. The substrate 70 includes not only printed wiring boards literally formed in a plate shape, but also three-dimensionally molded substrates, such as three-dimensionally molded substrates. Here, as an example, the substrate 70 is a rectangular plate-shaped printed wiring board having a length in the front-rear direction D2 and having wiring formed on at least one surface. The surfaces (surfaces) on both sides of the thickness direction (left-right direction D3) of the substrate 70 are respectively referred to as a first surface 701 (see FIG. 6 ) and a second surface 702 (see FIG. 7 ). That is, the substrate 70 has a first surface 701 and a second surface 702. Here, in the left-right direction D3, which is the thickness direction of the substrate 70, the surface facing the main unit 40 (right side) is the first surface 701, and the surface facing the opposite side (left side) from the main unit 40 is the second surface 702.

[0057] 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.

[0058] Only one optical sensor 72 is provided for each main unit 40. The optical sensor 72 has a light receiving section 720, which detects light (scanning light B0). The optical sensor 72 is configured with a photoelectric conversion element that outputs an electrical signal in response to the light (scanning light B0) incident on the light receiving section 720. The optical sensor 72 is, for example, a photodiode, a phototransistor, or a photo IC (Integrated Circuit).

[0059] 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 driver circuit drives its corresponding light-emitting module 71.

[0060] 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 such as LVDS (Low Voltage Differential Signaling), for example.

[0061] Meanwhile, as a related art, there is known an optical scanning device used in an image forming apparatus that scans and exposes the peripheral surface of a photosensitive member (photosensitive drum) with scanning light (laser light) to form an electrostatic latent image on the peripheral surface of the photosensitive member. This optical scanning device includes a light emitting module (laser light source) mounted on a substrate (circuit board), and reflects light emitted from the light emitting module by a polygon mirror to scan the scanning light along the main scanning direction.

[0062] This optical scanning device further includes an optical sensor (BD sensor) that detects the deflected light beam, and synchronizes the write timing, which is the timing at which irradiation of the deflected light beam onto the peripheral surface of the photosensitive member, begins for the main scanning line. In the optical scanning device according to the related art, the light emitting module and the optical sensor are mounted on the same surface of the substrate.

[0063] However, in the configuration of the related art, the light (scanning light) from the light-emitting module may be reflected by the connection pads for joining the optical sensor on the substrate, by the joining members such as solder that join the optical sensor to the substrate, or by the terminals of the optical sensor, which may cause stray light. The occurrence of stray light may lead to false detection by the optical sensor.

[0064] In contrast, the optical scanning device 4 according to this embodiment has a configuration described below that makes it less likely for the optical sensor 72 to make erroneous detections due to stray light.

[0065] That is, the optical scanning device 4 according to this embodiment includes a substrate 70, a light-emitting module 71, a driver circuit 73, a control circuit 74, and an optical sensor 72. The substrate 70 has a first surface 701 and a second surface 702 on both sides in the thickness direction. The light-emitting module 71 is mounted on the substrate 70 and outputs light to the first surface 701 side. The driver circuit 73 is mounted on the substrate 70 and drives the light-emitting module 71. The control circuit 74 is mounted on the substrate 70 and controls the driver circuit 73. The optical sensor 72 is mounted on the substrate 70 and receives scanning light B0 emitted from the light-emitting module 71 as a light source from the first surface 701 side. The substrate 70 has connection pads 704 (see FIG. 7 ) on the second surface 702 to electrically connect the optical sensor 72. In other words, the optical sensor 72 is mounted on the second surface 702 of the substrate 70, which is opposite the first surface 701 from which light from the light-emitting module 71 is output.

[0066] According to this configuration, the light-emitting module 71, driver circuit 73, control circuit 74, and optical sensor 72 are all mounted on the same substrate 70, thereby reducing the number of substrates 70 included in the optical scanning device 4. Furthermore, signals such as LVDS output from the control circuit 74 to the driver circuit 73 can also be transmitted using wiring formed on the substrate 70. Therefore, compared to using wiring (harness) that runs outside the substrate 70, such as a flexible flat cable (FFC) or discrete wires, for the signals output from the control circuit 74 to the driver circuit 73, the wiring length can be kept relatively short, thereby reducing unnecessary radiation from the signal line (wiring). Furthermore, by orienting the mounting surface of the optical sensor 72 in the opposite direction to the light emission direction from the light-emitting module 71, the generation of stray light caused by reflection of light from the light-emitting module 71 (scanning light B0) on the connection pad 704, a joining member X1 (see FIG. 8 ) such as solder that joins the optical sensor 72 to the substrate 70, or a terminal 722 of the optical sensor 72 (see FIG. 7 ) can be reduced. As a result, it is possible to provide the optical scanning device 4 and the image forming apparatus 10 in which the optical sensor 72 is less likely to make erroneous detections due to stray light.

[0067] The configuration of the substrate unit 7 will be described in more detail below.

[0068] The substrate 70 has a through-hole 703 formed therein, penetrating from the first surface 701 to the second surface 702. That is, the substrate 70 has the through-hole 703 penetrating the substrate 70 in the thickness direction (left-right direction D3). The through-hole 703 is a hole that enables the scanning light B0 incident on the substrate 70 from the first surface 701 side to be detected by the optical sensor 72 located on the second surface 702 side. That is, the scanning light B0 from the first surface 701 side is incident on the optical sensor 72 on the second surface 702 side through the through-hole 703. Here, as an example, the through-hole 703 has a substantially square shape in a plan view, that is, the opening surface is substantially square.

[0069] Electronic components included in the board unit 7, such as the light-emitting module 71 and the optical sensor 72, are mounted on the board 70. Integrated circuits (ICs) constituting the driver circuit 73, the control circuit 74, and the signal processing circuit, etc., are also mounted on the board 70. In this disclosure, "mounting" refers to mechanical and electrical connection to the board 70. More specifically, "mounting" of a component on the board 70 is achieved by mechanically and electrically connecting the terminals of the component to wiring formed on the board 70 using a bonding material (solder or conductive paste such as silver paste). As an example, the light-emitting module 71 is mounted on the board 70 using insertion mount technology (IMT). That is, the light-emitting module 71 is mounted on the surface (mounting surface) of the board 70 with multiple terminals 712 inserted into mounting holes in the board 70 from the surface (mounting surface) side of the board 70. Meanwhile, the optical sensor 72 is mounted on the board 70 using surface mount technology (SMT). That is, the optical sensor 72 is mounted on the surface (mounting surface) of the substrate 70 with the plurality of terminals 722 facing the surface (mounting surface) of the substrate 70. However, this is not limiting, and for example, the light-emitting module 71 may be mounted on the substrate 70 by surface mounting technology.

[0070] The light emitting module 71 uses a semiconductor laser (LD: Laser Diode) that generates laser oscillation by passing a current through a semiconductor. In this embodiment, the light emitting module 71 has a metal package 711 formed in a substantially cylindrical shape and a plurality of terminals 712 (see FIG. 8). The light emitting module 71 accommodates a light emitting element that serves as the main body of the semiconductor laser, a photodiode (PD: Photo Diode) for monitoring, and the like within the package 711. A light emitting port for extracting light beam B10 (see FIG. 8) is formed in the center of the surface of the package 711. The plurality of terminals 712 protrude from the back surface of the package 711 (the surface opposite the light emitting port).

[0071] The light emitting module 71 is a "component with leads" that is inserted and mounted on the substrate 70. Here, the light emitting module 71 is mounted on the substrate 70 with a plurality of terminals (lead terminals) 712 inserted into the substrate 70 from the first surface 701 side. Therefore, as shown in FIG. 8 , the light emitting module 71 is mounted in an orientation where the package 711 is located on the first surface 701 side and where light ray B10 is output toward the first surface 701 side (to the right) along the normal direction of the first surface 701. The plurality of terminals 712 are solder-bonded to wiring on the substrate 70 on the opposite side of the substrate 70 from the package 711, i.e., on the second surface 702 side.

[0072] Here, the light-emitting module 71 has a multi-beam structure capable of outputting multiple light beams B10. That is, the light-emitting module 71 has two or more light-emitting elements made of semiconductor lasers in the package 711, and can cause these multiple light-emitting elements to emit light individually. In this way, by making the light-emitting module 71 multi-beam, the optical scanning device 4 can achieve both high speed and high resolution in forming an electrostatic latent image. In particular, with a multi-beam structure, the effect of suppressing unnecessary radiation from the signal line is extremely significant. However, it is not essential that the light-emitting module 71 has a multi-beam structure.

[0073] More specifically, as shown in FIG. 6, the four light-emitting modules 71 are arranged in a straight line. Furthermore, in this embodiment, the distance between adjacent light-emitting modules 71 is uniform. However, it is not essential that the four light-emitting modules 71 are arranged in a straight line. The four light-emitting modules 71 may be arranged, for example, in an arc shape, a free-form curve, a zigzag shape, or the like. Furthermore, it is not essential that the distance between adjacent light-emitting modules 71 is uniform.

[0074] 6, in this embodiment, the four light-emitting modules 71 are arranged with their positions shifted in the vertical direction D1 so that they are gradually positioned lower from the left (front) to the right (rear) in the figure. This allows the optical paths of the light from the multiple light-emitting modules 71 to be shifted in the vertical direction D1, and makes it possible to avoid interference of light from the multiple light-emitting modules 71.

[0075] The optical sensor 72 has a resin package 721 that is substantially square in a plan view, and a plurality of terminals 722. The optical sensor 72 accommodates a light receiving element (photoelectric conversion element) that forms the main body of the optical sensor 72 within the package 721. A light receiving unit 720 is disposed on a portion of the surface of the package 721, and the optical sensor 72 detects light (scanning light B0) that is incident on the light receiving unit 720. The plurality of terminals 722 protrude laterally (in the front-to-rear direction D2 in FIG. 8 ) from a portion of the side surface of the package 721 that is adjacent to the back surface of the package 721 (the surface opposite the light receiving unit 720).

[0076] The optical sensor 72 is a "surface-mounted component" that is surface-mounted on the substrate 70. The optical sensor 72 is mounted on the substrate 70 with the light-receiving unit 720 facing the substrate 70 and at least a portion of the package 721 inserted into the through-hole 703 from the second surface 702 side. That is, the optical sensor 72 has the light-receiving unit 720 and is mounted on the second surface 702 side of the substrate 70. The optical sensor 72 receives the scanning light B0 that enters the through-hole 703 from the first surface 701 side with the light-receiving unit 720. Specifically, as shown in FIG. 8 , the optical sensor 72 is mounted on the second surface 702 side of the substrate 70 with the light-receiving unit 720 facing the same direction as the first surface 701 of the substrate 70. The light-receiving unit 720 of the optical sensor 72 is visible from the first surface 701 side through the through-hole 703, that is, exposed on the first surface 701 side. Therefore, the optical sensor 72 is able to receive the scanning light B0 incident on the through-hole 703 from the first surface 701 side (right side) at the light receiving unit 720. The multiple terminals 722 are solder-bonded to connection pads 704 provided on the second surface 702 of the substrate 70 around the through-hole 703 on the second surface 702 side. The connection pads 704 are part of the conductive wiring formed on the second surface 702 of the substrate 70.

[0077] Here, the light receiving section 720 of the optical sensor 72 has a length in a direction perpendicular to the scanning direction of the scanning light B0. In other words, the optical sensor 72 is arranged so that the longitudinal direction of the light receiving section 720 coincides with the direction perpendicular to the scanning direction of the scanning light B0. As an example, the dimension of the light receiving section 720 in the longitudinal direction (direction perpendicular to the scanning direction) is about 3 mm, and the dimension of the light receiving section 720 in the lateral direction (scanning direction) is about 0.5 mm.

[0078] The "scanning direction" of the scanning light B0 in this disclosure refers to the scanning direction of the scanning light B0 irradiated onto the substrate unit 7, and is different from the main scanning direction (the main scanning direction along the rotational axis direction of the photosensitive drums 311, 321, 331, and 341). In other words, the scanning direction of the scanning light B0 may be the same as or different from the main scanning direction. As an example, in this embodiment, as shown in FIG. 8, the scanning direction of the scanning light B0 is the direction along the longitudinal direction of the substrate 70, that is, the front-rear direction D2.

[0079] As described above, in this embodiment, the substrate 70 has a through-hole 703 that penetrates from the first surface 701 to the second surface 702. The optical sensor 72 is mounted on the second surface 702 side of the substrate 70, and receives the scanning light B0 that enters the through-hole 703 from the first surface 701 side. This allows the optical sensor 72 to receive the scanning light B0 that enters from the first surface 701 side, while also allowing its terminal 722 to be connected to the connection pad 704 on the second surface 702 side of the substrate 70.

[0080] Each driver circuit 73 is implemented as an integrated circuit (IC). Each driver circuit 73 has a resin package that is approximately square in plan view and houses a semiconductor chip. Each driver circuit 73 has multiple terminals (lead terminals) on the back surface of the package.

[0081] In this embodiment, each light-emitting module 71 has a multi-beam structure capable of outputting multiple light beams, and therefore the driver circuit 73 can individually drive two or more (four in this case) light-emitting elements included in one light-emitting module 71. The driver circuit 73 operates in response to control signals from the control circuit 74, and drives the multiple light-emitting modules 71.

[0082] The control circuit 74 is realized by an integrated circuit (IC). The control circuit 74 has a resin package that is approximately square in plan view and houses a semiconductor chip inside the package. The control circuit 74 has multiple terminals (lead terminals) on the back surface of the package.

[0083] The driver circuit 73 and the control circuit 74 are both "surface-mounted components" that are surface-mounted on the substrate 70. Here, the driver circuit 73 and the control circuit 74 are mounted on the second surface 702 of the substrate 70 with the back surface (terminals) of the package facing the substrate 70. In other words, the driver circuit 73 and the control circuit 74 are solder-bonded to connection pads provided on the second surface 702, which is one surface of the substrate 70 in the thickness direction.

[0084] In short, in this embodiment, the multiple driver circuits 73 and the control circuit 74 are surface-mounted on the second surface 702 of the substrate 70, which is the same surface as the optical sensor 72, as shown in Fig. 7. As shown in Fig. 7, the control circuit 74 is electrically connected to each driver circuit 73 by multiple wirings 741. The multiple wirings 741 are conductive wirings formed on the second surface 702 of the substrate 70. Fig. 7 shows only the wirings 741 that connect some of the driver circuits 73 and the control circuit 74, and does not show the other wirings.

[0085] 7, the four driver circuits 73 are arranged such that two driver circuits 73 are located on each side of an imaginary straight line along which the four light emitting modules 71 are lined up, in the vertical direction D1. Furthermore, as shown in FIG. 7, the two driver circuits 73 located above or below the four light emitting modules 71 are lined up diagonally along the line direction of the four light emitting modules 71. In other words, the driver circuit 73 located on the left side (rear) in the drawing is shifted in position in the vertical direction D1 so as to be located lower than the driver circuit 73 located on the right side (front).

[0086] This allows the wiring length between the driver circuit 73 and the corresponding light-emitting module 71 to be as short as possible, improving the responsiveness of the control of the light-emitting module 71 by the driver circuit 73. However, it is sufficient that the multiple light-emitting modules 71 and the multiple driver circuits 73 are approximately symmetrical, and the multiple light-emitting modules 71 and the multiple driver circuits 73 can be said to be symmetrical when they deviate from their symmetrical positions by an amount of deviation equivalent to the tolerance.

[0087] Here, 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) board 70. That is, at least multiple light-emitting modules 71 and multiple driver circuits 73 are mounted on the board 70 so as to correspond to the multiple colors of scanning light B0. With this configuration, the light-emitting modules 71 and driver circuits 73 for outputting the multiple colors of scanning light B0 can be integrated onto one board 70, making it easy to miniaturize the optical scanning device 4. Furthermore, in an optical scanning device 4 provided with light-emitting modules 71 for multiple colors, the effect of suppressing unwanted radiation from the signal lines is extremely significant.

[0088] 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.

[0089] 6, in this embodiment, the light-emitting module 71 serving as the light source of the scanning light B0 is located below the optical sensor 72 that receives the scanning light B0 in the vertical direction (up-down direction D1) of the substrate 70. Specifically, the upper end position of the front light-emitting module 71 (the left end in FIG. 6) that is located at the top among the multiple (four) light-emitting modules 71 is located a distance L1 below the center of the optical sensor 72.

[0090] Here, the photosensitive drums 311, 321, 331, and 341 are located above the optical scanning device 4 (see FIG. 1). Deflecting the light beam B10 in the opposite direction (i.e., downward) from the photosensitive drums 311, 321, 331, and 341 to make the scanning light B0 incident on the optical sensor 72 may lead to stray light, which may ultimately lead to erroneous detection by the optical sensor 72. In this embodiment, the optical sensor 72 is located on the same side (upper side) as the photosensitive drums 311, 321, 331, and 341 in the up-down direction D1 when viewed from the light-emitting module 71, and therefore it is possible to suppress such stray light.

[0091] [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.

[0092] 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.

[0093] 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.

[0094] [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.

[0095] <Appendix 1> a substrate having a first surface and a second surface on both sides in a thickness direction; a light emitting module mounted on the substrate and outputting light to the first surface side; a driver circuit mounted on the substrate and configured to drive the light emitting module; a control circuit mounted on the substrate and controlling the driver circuit; an optical sensor mounted on the substrate and configured to receive scanning light emitted from the light-emitting module as a light source from the first surface side; the substrate has connection pads on the second surface for electrically connecting the optical sensor; Optical scanning device.

[0096] <Appendix 2> the substrate has a through hole that penetrates from the first surface to the second surface, the optical sensor is mounted on the second surface side of the substrate and receives the scanning light incident on the through hole from the first surface side. 2. The optical scanning device according to claim 1.

[0097] <Appendix 3> the light-emitting module as a light source of the scanning light is located below the optical sensor that receives the scanning light in the vertical direction of the board; 3. The optical scanning device according to claim 1 or 2.

[0098] <Appendix 4> a plurality of the light-emitting modules and a plurality of the driver circuits are mounted on the substrate so as to correspond to scanning lights of a plurality of colors; 4. The optical scanning device according to any one of claims 1 to 3.

[0099] <Appendix 5> The light-emitting module has a multi-beam structure having two or more light-emitting elements; 5. The optical scanning device according to any one of Supplementary notes 1 to 4.

[0100] <Appendix 6> An optical scanning device according to any one of Supplementary Notes 1 to 5; an image carrier on which an electrostatic latent image is formed by the light beam output from the optical scanning device; Image forming device. [Explanation of symbols]

[0101] 4 Optical scanning device 10 Image forming device 70 boards 71 Light-emitting module 72 Optical Sensor 73 Driver Circuit 74 Control Circuit 311, 321, 331, 341 Photosensitive drum (image carrier) 701 Page 1 702 2nd page 703 Through hole 704 connection pad B0 scanning light D3 Left-right direction (thickness direction)

Claims

1. a substrate having a first surface and a second surface on both sides in a thickness direction; a light emitting module mounted on the substrate and configured to output light to the first surface side; a driver circuit mounted on the substrate and configured to drive the light emitting module; a control circuit mounted on the substrate and controlling the driver circuit; an optical sensor mounted on the substrate and configured to receive scanning light emitted from the light-emitting module as a light source from the first surface side; the substrate has connection pads on the second surface for electrically connecting the optical sensor; Optical scanning device.

2. the substrate has a through hole that penetrates from the first surface to the second surface, the optical sensor is mounted on the second surface side of the substrate and receives the scanning light incident on the through hole from the first surface side; 2. The optical scanning device according to claim 1.

3. the light-emitting module as a light source of the scanning light is located below the optical sensor that receives the scanning light in the vertical direction of the board; 3. The optical scanning device according to claim 1 or 2.

4. a plurality of the light-emitting modules and a plurality of the driver circuits are mounted on the substrate so as to correspond to scanning lights of a plurality of colors; 3. The optical scanning device according to claim 1 or 2.

5. The light-emitting module has a multi-beam structure having two or more light-emitting elements.

3. The optical scanning device according to claim 1 or 2.

6. The optical scanning device according to claim 1 or 2; an image carrier on which an electrostatic latent image is formed by the light beam output from the optical scanning device; Image forming device.

Images