JP2007121345A - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

The present invention simplifies the configuration of a BD sensor and the optical path setting for the BD sensor, and further reduces the number of optical parts such as mirrors for setting the optical path, thereby reducing the size of the apparatus by using common parts. To do.
Each folding mirror 210, 208, 205 for YMC is provided with a reflection region 217 and a transmission region 216, and reflects the light beam in the image region on the optical path toward the photosensitive drum, and also in the non-image region. The synchronous detection beam is transmitted toward the optical path toward the BD sensor. The K mirror 204 reflects the K light beam, and the synchronous detection beam in the non-image area for K is condensed on the BD sensor together with the synchronous detection beams transmitted through the folding mirrors 210, 208, and 205. The
[Selection] Figure 7

Description

  The present invention relates to an optical scanning device and an image forming apparatus including the optical scanning device, and more particularly to an optical scanning device used in an electrophotographic image forming apparatus such as a digital copying machine, a printer, or a facsimile. .

  Image forming apparatuses such as digital copying machines, laser printers, and facsimiles have become widespread. In such an image forming apparatus, an optical scanning device that scans a laser beam is used. When an image is formed by the image forming apparatus, the photosensitive member is charged by the charging device, and then writing according to image information is performed by the optical scanning device to form an electrostatic latent image on the photosensitive drum. Then, the electrostatic latent image on the photosensitive drum is visualized with toner supplied from the developing device. The toner image visualized on the photosensitive drum is transferred onto a recording sheet by a transfer device, and further fixed on the recording sheet by a fixing device, whereby a desired image can be obtained.

  Also, in color image forming apparatuses such as digital copying machines and laser printers, tandem type apparatuses in which a plurality of photosensitive drums are arranged in tandem have been put into practical use as their speed increases. Here, for example, four photosensitive drums are arranged in the conveyance direction of the recording paper, and these photosensitive members are simultaneously exposed by a scanning optical system corresponding to each of these photosensitive drums to form a latent image. The image is developed with a developing device using developers of different colors such as yellow, magenta, cyan, and black. Then, these visualized toner images are sequentially superimposed and transferred onto the same recording paper to obtain a color image.

  The tandem method of simultaneously exposing a plurality of photoconductors is advantageous for high-speed printing because it can output both color and monochrome at the same speed as a method of sequentially forming an image for each color with a single photoconductor. On the other hand, a scanning optical system corresponding to a plurality of photosensitive drums is required, and there is a tendency that an apparatus for exposing the photosensitive member is increased in size. Another problem is to prevent color misregistration when a toner image visualized on each photoconductor is transferred onto a recording sheet.

  In the optical scanning device that performs optical scanning on the photosensitive drum as described above, the main scanning direction is detected by detecting the light beam before (or after) the main scanning of the light beam on the photosensitive drum. A BD (Beam Detect) sensor for generating a reference signal for writing is installed.

  Regarding the configuration of the BD sensor provided for the optical scanning signal, for example, in Patent Document 1, a small and low-cost color image that improves the exchangeability of the image carrier (photosensitive member) and enables accurate scanning position measurement. A forming apparatus is disclosed. Here, the photosensitive member is provided corresponding to the light beams emitted from a plurality of light sources that emit light beams. A latent image is formed on the photoconductor by scanning exposure with light beams emitted from a plurality of light sources. A plurality of beam synchronization sensors and PSDs for detecting the main scanning position and sub-scanning position of the light beam are arranged on a single substrate, and the beam synchronization sensor on the substrate is arranged away from the photosensitive member by a pickup mirror. And guiding the light beam to the PSD.

Patent Document 2 discloses a high-accuracy scanning optical system that prevents the occurrence of color misregistration for each color by independently controlling the light emission timings of a plurality of independent laser light emitters according to the output signal of a single BD element. An apparatus is disclosed. Here, a single rotating polygon mirror, a plurality of independent laser emitters, and a single BD element for detecting the emission timing are provided in a single optical box. The BD element is held at a position where the scanning light from the laser emitter can be detected alternately. The light emission timings of a plurality of independent laser emitters are independently controlled by the output signal of this single BD element, thereby preventing the occurrence of color misregistration for each color.
JP 2000-180746 A JP 2005-17680 A

  As described above, the tandem type optical scanning apparatus has a plurality of laser light emitting units corresponding to colors such as yellow, magenta, cyan, and black, for example, and the light beams emitted from the respective laser light emitting units are each photosensitive. Scanning is performed on the body drum. In order to control the writing position of the light beam on these photosensitive drums, for example, a BD sensor for detecting the light beam at the beginning of writing of scanning light onto the photosensitive drum corresponding to black is provided, and the detection result of the BD sensor Therefore, a method of controlling the writing start position of the photosensitive drum corresponding to other yellow, magenta, and cyan is adopted.

  However, since the light beams for scanning the plurality of photosensitive drums for each color are independent beams, the BD sensor used for controlling the writing reference position in the main scanning direction on the photosensitive drum is originally each light beam. It is desirable to be able to detect the write start timing for the beam.

  In order to detect the scanning light to the plurality of photosensitive drums in this way, in Patent Document 1, a synchronization sensor and PSD for detecting a plurality of light beams are arranged on the substrate and arranged away from the photosensitive member. A light beam is guided to the beam synchronization sensor and the PSD using a pickup mirror. Similarly, in Patent Document 2, a reflection mirror is arranged to guide the light beam to the BD element arranged away from the photosensitive member. In such a configuration, a configuration in which the light beam is guided to a BD sensor (synchronous sensor) disposed at a position distant from the photosensitive member is required, resulting in an increase in the number of components and an increase in the size of the apparatus.

  As described above, in the tandem method in which a plurality of photoconductors are simultaneously exposed, an apparatus for exposing each photoconductor drum tends to increase in size, and downsizing becomes an issue. In this case, the above-described BD sensor is no exception, and it is required to simplify the configuration of the BD sensor that receives a plurality of light beams, the setting of the optical path thereof, and the like, and rationalize parts such as a mirror. At this time, by standardizing the parts to be used as much as possible and not requiring parts with various standards, an effect of reducing the number of parts can be obtained, and the manufacturing process and cost can be rationalized.

  The present invention has been made in view of the above-described circumstances. The configuration of the BD sensor for detecting the scanning light to the plurality of photosensitive drums and the setting of the optical path to the BD sensor are simplified, and the components to be used are further shared. Accordingly, it is an object of the present invention to provide an optical scanning device that reduces the number of optical components such as an optical path setting mirror and the like and realizes downsizing of the device.

  In order to solve the above problems, a first technical means includes a light source, a polygon mirror that uses a plurality of light beams emitted from the light source as scanning light, and a plurality of light beams that are converted into scanning light by the polygon mirror. An optical system that emits light toward the photosensitive member, and writes a latent image for image formation on the photosensitive member by scanning light onto the photosensitive member. The optical system has one light beam detecting means for detecting a light beam in order to control the writing start position of the latent image in the scanning direction, and the optical system folds back the optical path of one of the plurality of light beams. There are a plurality of mirrors, and a part of the folding mirror transmits the detection light beam incident on the light beam detecting means and separates it from the folding optical path of the light beam for image formation. Noso The detection light beam, respectively, is obtained by further comprising a focusing optical system that focuses on one of the light beam detecting means.

  A second technical means is the same as the first technical means, wherein a plurality of folding mirrors having a function of transmitting the detection light beam are provided, and the plurality of folding mirrors scan the transmission region in which the detection light beam is transmitted. Are of the same width and are arranged at different positions in the scanning direction according to the optical path of the detection light beam.

  According to a third technical means, in the second technical means, the plurality of light beams are four light beams that are scanned to draw yellow, magenta, cyan, and black images, respectively. The folding mirror having the function of transmitting the beam is characterized in that it is three folding mirrors that act on the light beams for drawing yellow, magenta, and cyan images, respectively.

  According to a fourth technical means, in the first technical means, a plurality of folding mirrors having a function of transmitting the detection light beam are provided, and a part of the folding mirrors includes a detection light beam. The widths of the transmission regions to be transmitted are the same in the scanning direction, and are arranged at different positions in the scanning direction according to the optical path of the detection light beam.

  According to a fifth technical means, in the third technical means, the plurality of light beams are four light beams that are scanned to draw yellow, magenta, cyan, and black images, respectively. The folding mirrors having the same width in the scanning direction of the transmission region that transmits the beam are two folding mirrors that act on the light beams for drawing magenta and cyan images, respectively.

  The sixth technical means emits a light source, a polygon mirror that uses a plurality of light beams emitted from the light source as scanning light, and a plurality of light beams that are scanned by the polygon mirror toward a plurality of photosensitive members, respectively. In an optical scanning device comprising an optical system and writing a latent image for image formation on the photosensitive member by scanning light on the photosensitive member, the optical scanning device starts writing a latent image in the main scanning direction on the photosensitive member. The optical system includes a plurality of folding mirrors that fold back the optical path of any one of the plurality of light beams, and the folding mirror. A part of the light source has a notch that passes through the detection light beam incident on the light beam detection means without acting, and the optical path of the detection light beam that has passed through the notch is folded back of the light beam for image formation. Separated from the road, the optical scanning device is to each of the detection light beam of the plurality of light beams, and further comprising a focusing optical system that focuses on one of the light beam detecting means.

  A seventh technical means according to any one of the first to sixth technical means is characterized in that the plurality of folding mirrors having the transmission region or the notch have the same length in the scanning direction. It is.

  The eighth technical means includes a photoconductor and the optical scanning device according to any one of the first to seventh technical means, and the optical scanning device forms a latent image on the photoconductor to visualize the latent image. Thus, the image forming apparatus is characterized in that image formation is performed.

  According to the present invention, the configuration of the BD sensor for detecting the scanning light to the plurality of photosensitive drums and the setting of the optical path to the BD sensor are simplified, and the parts to be used are further shared, so that the mirror for setting the optical path is obtained. Accordingly, it is possible to provide an optical scanning device that reduces the number of optical components and the like and realizes downsizing of the device, and an image forming apparatus including the optical scanning device.

  FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus in which the optical scanning device of the present invention is used. The image forming apparatus forms multicolor and single color images on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside. As shown in the figure, an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 8, a paper discharge tray 9, and the like are provided. Configured.

  Note that image data handled in the image forming apparatus corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four developing devices 2, photosensitive drums 3, charging devices 5, and cleaner units 4 are provided to form four types of latent images corresponding to the respective colors, and are respectively provided in black, cyan, magenta, and yellow. These are set to form four image stations.

  The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. As shown in FIG. 1, in addition to a contact type roller type or brush type charger, a charger type charging unit is used. A vessel may be used.

  The exposure unit 1 corresponds to an optical scanning apparatus according to the present invention, and is configured as a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror as shown in FIG. The exposure unit 1 includes a polygon mirror 201 that scans a laser beam, and optical elements such as a lens and a mirror for guiding the light beam reflected by the polygon mirror 201 to the photosensitive drum 3. The configuration of the optical scanning device constituting the exposure unit 1 will be specifically described later. In addition, the exposure unit 1 may use a technique such as an EL or LED writing head in which other light emitting elements are arranged in an array.

  The exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toner of four colors (KCMY). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 6 disposed above the photosensitive drum 3 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt tension mechanism 63, an intermediate transfer belt driven roller 64, an intermediate transfer roller 65, and An intermediate transfer belt cleaning unit 66 is provided. Four intermediate transfer rollers 65 are provided corresponding to the respective colors for KCMY.

  The intermediate transfer belt drive roller 62, the intermediate transfer belt tension mechanism 63, the intermediate transfer belt driven roller 64, and the intermediate transfer roller 65 stretch the intermediate transfer belt 61 and rotate it in the direction of arrow M. Each intermediate transfer roller 65 is rotatably supported by an intermediate transfer roller mounting portion of the intermediate transfer belt tension mechanism 63 of the intermediate transfer belt unit 6, and the toner image on the photosensitive drum 3 is transferred onto the intermediate transfer belt 61. Provides transfer bias for transfer.

  The intermediate transfer belt 61 is provided in contact with each photosensitive drum 3. A function of forming a color toner image (multicolor toner image) on the intermediate transfer belt 61 by sequentially superimposing and transferring the toner images of the respective colors formed on the photosensitive drum 3 onto the intermediate transfer belt 61. have. The intermediate transfer belt 61 is formed endlessly using a film having a thickness of about 100 μm to 150 μm.

  The transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 61 is performed by an intermediate transfer roller 65 that is in contact with the back side of the intermediate transfer belt 61. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 65 in order to transfer the toner image. The intermediate transfer roller 65 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller shape is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic images visualized on the respective photosensitive drums 3 according to the respective hues are stacked on the intermediate transfer belt 61. As described above, the laminated image information is transferred onto the sheet by the transfer roller 10 disposed at a contact position between the sheet and the intermediate transfer belt 61 described later by the rotation of the intermediate transfer belt 61.

  At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed against each other at a predetermined nip, and a voltage for transferring the toner onto the sheet is applied to the transfer roller 10 (the polarity opposite to the toner charging polarity (−)). (+) High voltage). Further, in order to obtain the nip constantly, the transfer roller 10 uses either the transfer roller 10 or the intermediate transfer belt drive roller 62 as a hard material (metal, etc.) and the other as a soft material (elasticity, such as an elastic roller). A rubber roller, a foaming resin roller, or the like) is used.

  Further, as described above, the toner adhered to the intermediate transfer belt 61 by contacting the photosensitive drum 3 or the toner remaining on the intermediate transfer belt 61 without being transferred onto the sheet by the transfer roller 10 is used in the next step. Therefore, the intermediate transfer belt cleaning unit 66 is configured to remove and collect the toner. The intermediate transfer belt cleaning unit 66 includes a cleaning blade as a cleaning member that contacts the intermediate transfer belt 61, for example, and the intermediate transfer belt 61 that contacts the cleaning blade is supported by an intermediate transfer belt driven roller 64 from the back side. ing.

  The paper feed cassette 8 is a tray for storing sheets (recording paper) used for image formation, and is provided below the exposure unit 1 of the image forming apparatus. A paper discharge tray 9 provided at the upper part of the image forming apparatus is a tray for collecting printed sheets face down.

  In addition, the image forming apparatus is provided with a substantially vertical sheet conveyance path S for sending the sheets of the sheet feeding cassette 8 to the sheet discharge tray 9 via the transfer roller 10 and the fixing unit 7. In the vicinity of the paper transport path S from the paper feed cassette 8 to the paper discharge tray 9, a pickup roller 11, a plurality of transport rollers 12a to 12e, a registration roller 13, a transfer roller 10, a fixing unit 7, and the like are arranged.

  The conveyance rollers 12 a to 12 e are small rollers for promoting and assisting the conveyance of the sheet, and a plurality of the conveyance rollers 12 a to 12 e are provided along the sheet conveyance path S. The pickup roller 11 is provided near the end of the paper feed cassette 8 and picks up sheets one by one from the paper feed cassette 8 and supplies them to the paper transport path S.

  Further, the registration roller 13 temporarily holds the sheet being conveyed through the sheet conveyance path S. The sheet has a function of conveying the sheet to the transfer roller 10 at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72, and the heat roller 71 and the pressure roller 72 rotate with the sheet interposed therebetween. The heat roller 71 is set so as to reach a predetermined fixing temperature by a control unit based on a signal from a temperature detector (not shown), and the toner is thermocompression bonded to the sheet together with the pressure roller 72. It has the function of fusing, mixing, and pressing the transferred multicolor toner image and thermally fixing the sheet.

  Next, the sheet conveyance path will be described in detail. As described above, the image forming apparatus is provided with the paper feed cassette 8 that stores sheets in advance. In order to feed sheets from the sheet feeding cassette 8, pickup rollers 11 are arranged so as to guide the sheets one by one to the conveyance path S.

  The sheet conveyed from the sheet feeding cassette 8 is conveyed to the registration roller 13 by the conveying roller 12a in the sheet conveying path S, and conveyed to the transfer roller 10 at a timing when the leading edge of the sheet and the leading edge of the image information on the intermediate transfer belt 61 are aligned. The image information is written on the sheet. Thereafter, the sheet passes through the fixing unit 7 so that the unfixed toner on the sheet is melted and fixed by heat, and then discharged onto the sheet discharge tray 9 through the conveyance roller 12c disposed.

  The above-mentioned conveyance path is for a single-sided printing request for a sheet. On the other hand, when a double-sided printing request is made, the trailing edge of the sheet that has finished single-sided printing and has passed through the fixing unit 7 as described above. When chucked by the final transport roller 12c, the transport roller 12c rotates backward to guide the sheet to the transport rollers 12d and 12e. Then, after printing is performed on the back side of the sheet through the registration roller 13, the sheet is discharged to the discharge tray 9.

Next, an embodiment of the optical scanning device of the present invention will be specifically described.
The optical scanning device of this embodiment has a plurality of photosensitive drums 3 as described above, and each photosensitive drum 3 is simultaneously scanned and exposed by a plurality of light beams, and each photosensitive drum 3 has a different color. The present invention can be applied to a tandem image forming apparatus that forms an image and forms a color image by superimposing the images of the respective colors on the same transfer medium.

As described above, the image forming apparatus includes a photosensitive drum for black (K) image formation, a photosensitive drum for cyan (C) image formation, a photosensitive drum for magenta (M) image formation, and yellow (Y ) Photosensitive drums for image formation are arranged at substantially equal intervals. The tandem image forming apparatus forms images of the respective colors at the same time, so that the time required for forming a color image can be greatly shortened.
In the following description, black, cyan, magenta, and yellow are represented by K, C, M, and Y, respectively.

  The optical scanning device according to the present invention for exposing the photosensitive drum 3 includes a unitary primary optical system (incident optical system) and a secondary optical system (exit optical system). The primary optical system includes four semiconductor lasers that respectively emit KCMY light beams, and optical elements such as mirrors and lenses that guide these light beams to the polygon mirror 201 (rotating polygon mirror) of the secondary optical system. ing. The secondary optical system includes the polygon mirror 201 that scans a laser beam on a photosensitive drum 3 that is a scanning target, and a lens and mirror for guiding the light beam reflected by the polygon mirror 201 to the photosensitive drum 3. And the like, and a BD sensor for detecting a light beam. The BD sensor corresponds to the light beam detecting means of the present invention that detects a light beam for controlling the latent image writing start position in the main scanning direction on the photosensitive drum 3. Further, the polygon mirror 201 employs a configuration shared by each color.

  FIG. 2 is a plan view showing a configuration example of a primary optical system unit of the optical scanning device of the present invention, and FIG. 3 is a schematic perspective view of the primary optical system unit of FIG. 2 and 3, 100 is a primary optical system unit, 101 is a laser diode, 102 is a collimator lens, 103 is an aperture, 104 is a laser drive substrate, 105 is a laser holder, 106 is a lens holder, 107 is a lens barrel, 108 is a mounting screw, 110 is a first mirror, 111 is a second mirror, 112 is a cylindrical lens, 113 is a third mirror, and 120 is a substrate on which optical elements of the primary optical system are arranged.

  Each of the laser diodes 101 for K, C, M, and Y is driven by a laser drive circuit (not shown) as light source drive means. Various control signals output from the control unit of the image forming apparatus and image data supplied from the image processing unit are input to the laser driving circuit, and light emission of each laser diode 101 is controlled according to these control signals and image data. .

  K, C, M, and Y collimator lenses 102 are disposed on the laser emission side of each laser diode 101, respectively. The light beam output from each laser diode 101 is substantially elliptical diffused light, and is converted into parallel light by a collimator lens 102 provided for each color. After each color collimator lens 102, an aperture (slit) 103 having a predetermined gap is arranged to regulate the diameter of the light beam. In this specification, parallel light refers to a state in which the diameter of the light beam does not change even when the beam travels, and is distinguished from a state in which the optical axes of a plurality of beams are parallel to each other.

  Each laser diode 101 is attached to a laser holder 105. The laser holder 105 is attached to the back side of the lens holder 106 that is integrally formed on the substrate of the primary optical system. A lens barrel 107 in which the collimator lens 102 and the aperture 103 are arranged is attached to the front side of the lens holder 106. The light beam emitted from the laser diode 101 is emitted to the front outside of the lens barrel 107 through the collimator lens 102 and the aperture 103.

  The light beam emitted from the lens barrel 107 of the K laser diode 101 is directed to the second mirror 111 through the K collimator lens 102 and the K aperture 103. The light beam emitted from the lens barrel 107 of the C, M, Y laser diode 101 enters the first mirror 110 through the C, M, Y collimator lens 102 and the aperture 103, respectively. The first mirror 110 includes three mirrors that individually reflect the C, M, and Y light beams, and the light beams for the respective colors reflected by these mirrors travel in the traveling direction of the K light beam. , And enters the second mirror 111.

  The laser diodes 101 of the respective colors are arranged at different heights in the sub scanning direction (direction perpendicular to the substrate surface). The difference in height is set to about 2 mm, for example. The first mirror 110 is disposed at a position where only the light beam emitted from the corresponding laser diode 101 can be reflected. Further, the three mirrors (for C, M, and Y) constituting the first mirror 110 are arranged at positions overlapping the light beam emitted from the K laser diode 101 when viewed from the main scanning direction.

  With the configuration as described above, the K light beam emitted from the K laser diode 101 and the C, M, and Y light beams reflected by the first mirror 110 all coincide in the main scanning direction, There is a deviation (level difference) in the sub-scanning direction, and the optical axes of the respective light beams are incident on the second mirror 111 in parallel with each other. Here, the light beam for each color emitted from each collimator lens 102 is parallel light whose diameter does not change even when the light beam travels.

  The second mirror 111 causes the incident light beams for K, C, M, and Y colors to enter the cylindrical lens 112. The cylindrical lens 112 is arranged to focus the incident light beam for each color in the sub-scanning direction. Then, the light beam for each color emitted from the cylindrical lens 112 is reflected by the third mirror 113 and enters the reflecting surface of the polygon mirror 201.

  Here, the cylindrical lens 112 has a lens power in the sub-scanning direction, and the light beam converges near the reflecting surface of the polygon mirror 201 in the sub-scanning direction according to the optical path length from the cylindrical lens 112 to the polygon mirror 201. It is set to be. That is, the light beams for the respective colors incident on the cylindrical lens 112 as parallel lights are almost converged on the reflection surface of the polygon mirror 201 in the sub-scanning direction. At the same time, the light beams for the respective colors incident on the cylindrical lens 112 with their optical axes parallel to each other converge at substantially the same position on the surface of the polygon mirror 201 in the sub-scanning direction.

  Since this cylindrical lens 112 does not have lens power in the main scanning direction, the incident light beam for each color is emitted as parallel light as it is in the main scanning direction and is incident on the reflecting surface of the polygon mirror 201. To do. Usually, parallel light is incident on the polygon mirror 201 in the main scanning direction. Converging light in the main scanning direction is not preferable because a negative field curvature is generated by an fθ lens described later. Further, the sub-scanning direction is converged on the surface of the reflecting surface in order to correct the surface tilt of the reflecting surface. For example, the position of the light beam incident on the reflection surface of the polygon mirror 201 in the sub-scanning direction is near the center in the height direction of the reflection surface.

  In the optical scanning device of this embodiment, four light beams for KCMY are deflected by one polygon mirror 201 of the secondary optical system. In this case, it is necessary to be able to separate the four light beams after passing through the polygon mirror 201 and to prevent the light beams for each color from shifting in the main scanning direction. For this reason, the four light beams emitted from the cylindrical lens 112 of the primary optical system are incident on the polygon mirror 201 from the same direction in the main scanning direction to the same position, and the angular difference in the sub-scanning direction. It is set so as to be incident at substantially the same position from a certain direction. In these optical path settings, the arrangement of the laser diodes 101 having a difference in height in the sub-scanning direction makes the light beams for the respective colors coincide in the main scanning direction and has a predetermined height difference in the sub-scanning direction. It is realized by going forward. Thereby, the light beam for each color can be separated by the scanning optical system.

  Also, with the above configuration, since the light beams for each color are parallel light and their optical axes are parallel to each other on the optical path from the collimator lens 102 for each color of the primary optical system to the cylindrical lens 112, the collimator lens 102. To the cylindrical lens 112 can be freely set.

  FIG. 4 is a diagram showing a configuration example of the secondary optical system of the optical scanning device. FIG. 4A is a configuration diagram of the interior of the housing of the secondary optical system unit as viewed from above, and the interior of the housing 223 as viewed from the side. FIG. 4B shows a schematic configuration of the photosensitive member. 4, 200 is a secondary optical system unit, 201 is a polygon mirror, 202 is a first fθ lens, 203 is a second fθ lens, 204 is a K mirror, 205 is a first mirror for C, and 206 is a second mirror for C. , 207 is a third mirror for C, 208 is a first mirror for M, 209 is a second mirror for M, 210 is a first mirror for Y, 211 is a second mirror for Y, 212 is a third mirror for Y, 213 Is a BD sensor lens, 214 is a BD sensor, 220 is a cylindrical lens for each color, 221a and 221b are fixing shafts, 222 is an installation position of the primary optical system unit, 223 is a housing, and 224 is a frame for holding the cylindrical lens. It is.

  The optical path shown in FIG. 4B indicates the optical path of the light beam including the effective image area that scans the photosensitive drum 3 among the light beams that are scanned along with the rotation of the polygon mirror 201. The arrangement of the BD sensor and the optical path of the detection light beam according to the present invention will be described later.

  The polygon mirror 201 has a plurality of (for example, seven) reflecting surfaces in the rotation direction, and is driven to rotate by a polygon motor (not shown). The polygon motor is installed in a recess on the back side of the casing 223 where the polygon mirror 201 is installed, and a lid for sealing the recess is provided. The polygon motor is provided with fins for heat dissipation. The light beams of the respective colors emitted from the laser diode 101 of the primary optical system and reflected by the third mirror 113 are reflected by the reflecting surface of the polygon mirror 201 of the secondary optical system, and then the photosensitive member through the respective optical elements. The drum 3 is scanned.

As described above, each laser beam incident on the polygon mirror 201 with an angle difference in the sub-scanning direction maintains the angle difference and passes through the scanning optical system including the first fθ lens 202 and the second fθ lens 203. It will be separated later.
The first fθ lens 202 has lens power in the main scanning direction. Thereby, in the main scanning direction, the light beam of the parallel light emitted from the polygon mirror 201 is converged so as to have a predetermined beam diameter on the surface of the photosensitive drum 3. The first fθ lens 202 has a function of converting a light beam that moves at a constant angular velocity in the main scanning direction by a constant angular velocity movement of the polygon mirror 201 so as to move on the scanning line on the photosensitive drum 3 at a constant linear velocity. Have.

  The second fθ lens 203 has a lens power mainly in the sub-scanning direction. As a result, the diffused light beam emitted from the polygon mirror 201 is converted into parallel light in the sub-scanning direction. The second fθ lens 203 also has lens power in the main scanning direction, and complements the functions of the first fθ lens 202 so that the beam diameter can be controlled and the beam linear velocity movement can be executed with high accuracy.

  The first fθ lens 202 and the second fθ lens 203 are made of resin. In order to form an aspherical shape for obtaining desired characteristics of the fθ lens, it is preferable to use a resin material for the fθ lens. In particular, since the second fθ lens 203 has lens power in both the main scanning direction and the sub-scanning direction, in order to obtain a complicated aspherical shape that realizes this, it can be manufactured using a resin material. preferable. As the resin material, an optimum material is selected in consideration of characteristics such as transparency, moldability, photoelastic modulus, heat resistance, hygroscopicity, mechanical strength, and cost.

  Of the four light beams for each color separated by the polygon mirror 201 and passed through the first and second fθ lenses 202 and 203, the K light beam passes through the first and second fθ lenses 202 and 203. The light is reflected by the K mirror 204, passes through the K cylindrical lens 220, and enters the photosensitive drum 3 (K). Drawing is performed in the scanning area on the photosensitive drum 3.

The separated Y light beam is reflected by the Y first to third mirrors 210, 211, and 212, passes through the Y cylindrical lens 220, and enters the photosensitive drum 3 (Y). Similarly, the separated C light beam is reflected by the C first to third mirrors 205, 206, and 207, passes through the C cylindrical lens 220, and enters the photosensitive drum 3 (C). The separated light beam for M is reflected by the first and second mirrors 208 and 209 for M and enters the photosensitive drum 3 (M) through the cylindrical lens 220 for M.
The above optical path is the optical path of the beam in the image area that scans the photosensitive drum 3, and the light beam (detection light beam) to the BD sensor is an optical path separated from the light beam in the image area for each color. proceed. A specific example of the optical path to the BD sensor will be described later.

  In the secondary optical system, the cylindrical lens 220 for each color has lens power in the sub-scanning direction. Thereby, in the sub-scanning direction, the light beam incident as parallel light is converged on the photosensitive drum 3 so as to have a predetermined beam diameter. In the main scanning direction, the light beam that has been converged by the first fθ lens 202 is converged on the photosensitive drum 3 as it is. The cylindrical lens 220 is formed using a resin. The long cylindrical lens 220 that covers the entire scanning width as in the optical scanning device is preferably a resin lens.

  The light beams of the respective colors emitted from the cylindrical lens 220 expose the charged photosensitive drum 3 according to the image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 3. Then, the electrostatic latent images formed on the respective photosensitive drums 3 are visualized by the developing unit by the KCMY toner.

Next, an example of setting the installation position of the BD sensor and the optical path of the light beam incident on the BD sensor according to the present invention will be described.
Of the light beams reflected by the polygon mirror 201 and traveling toward the photosensitive drum 3, a light beam used for image formation on the photosensitive drum 3, that is, a light beam for scanning the main scanning line is referred to as a main scanning beam. To do. Here, a spatial region that passes when the main scanning beam scans is an image region, and a region other than the image region is a non-image region.

  When the light beam scans the photosensitive drum 3, the light beam periodically scans the main scanning line. At this time, since the photoconductive drum 3 is rotating, the photoconductive drum 3 is scanned at a different place every predetermined period. Each time the light beam is scanned, the writing start position of the scanning line needs to be the same. In order to detect the writing start position of the scanning line, the optical scanning device is provided with a synchronization detecting device. The synchronization detection device has a BD sensor (synchronization detection sensor) for detecting the light beam in the non-image area as a synchronization detection beam, and a BD sensor lens that focuses the synchronization detection beam on the BD sensor. The synchronous detection beam corresponds to the detection beam of the present invention, and the BD sensor lens and an optical system such as a mirror for guiding the synchronous detection beam to the lens correspond to the condensing optical system of the present invention.

  FIG. 5 is a diagram for explaining the installation position of the BD sensor and the optical path of the light beam incident on the BD sensor in the optical scanning device, in which 213 is a BD sensor lens, and 214 is a BD sensor. As shown in FIG. 4, the light beam including the image area for scanning the KCMY photosensitive drum 3 is folded back by a mirror (folding mirror) provided for each optical path so as to be directed to the photosensitive drum 3. Is set. On the other hand, the synchronization detection beam in the non-image area is separated from the light beam in the image area and is incident on one BD sensor 214.

The light beam for each color of KCMY emitted from the polygon mirror 201 passes through the first and second fθ lenses 202 and 203, and the light beam in the image area travels on the optical path described with reference to FIG. 3 is scanned.
The synchronous detection beam in the non-image area passes through the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C and travels straight. In the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C, in the region where the synchronous detection beam is incident, a transparent glass substrate is exposed without forming a reflecting surface. As a result, the light beam in the image area is reflected toward a predetermined optical path, and the synchronous detection beam is transmitted through the folding mirrors 210, 208, and 205 as they are. Specific configuration examples of these folding mirrors will be described later.

Then, the Y, M, and C synchronous detection beams and all the K light beams are incident on the K mirror 204 and reflected toward the upper K photosensitive drum 3. Then, the light beam in the K image region is directly incident on the K cylindrical lens 220 to expose the K photosensitive drum 3.
On the other hand, the synchronous detection beam for the non-image area for K and the synchronous detection beams for Y, M, and C reflected by the K mirror 204 are arranged in the non-image area of the K light beam. The light enters the lens 213 and is focused on the BD sensor 214. The BD sensor lens 213 collects the light beam, improves the detection level of the light beam in the BD sensor 214, and even when the position of the beam spot is deviated from the optical axis of the BD sensor lens 213. , The direction of the light beam is changed toward the optical axis of the BD sensor lens 213, and the detection surface of the BD sensor 214 is irradiated with the light beam with high accuracy.

Thus, the light beam for each color of KCMY is guided to the photoconductive drum 3 for each color, and the synchronous detection beam for the non-image area is guided to one BD sensor 214.
The BD sensor 214 outputs a sensor signal corresponding to the amount of received light. Then, a control unit (for example, an LSU controller described later) of the optical scanning device generates a synchronization signal (BD signal) for determining an image writing start position based on a sensor signal from the BD sensor 214. Specifically, a BD signal is generated when the amount of light received by the BD sensor 214 is at least greater than the amount of light necessary for the laser beam to expose the photosensitive drum 3 to form an electrostatic latent image. The BD signal is used as a scanning start reference signal in the main scanning direction, and the writing start position of each line in the main scanning direction is synchronized based on this signal.

  Further, the synchronization detection device outputs an error signal when the BD sensor 214 cannot detect the light beam. In an image forming apparatus incorporating an optical scanning device, the operation of the device is stopped, and a predetermined service code is displayed on the display screen, for example, so that the user is informed of a defect in the writing start position in the scanning direction.

  In the present embodiment, the synchronous detection beam in the plurality of light beams for KCMY is collected and detected on one BD sensor 214, so that it is not necessary to provide the BD sensor 214 for each color, and the optical path setting can be rationalized. Miniaturization of the scanning device can be realized.

FIG. 6 is a diagram for explaining another example of the installation position of the BD sensor and the optical path of the light beam incident on the BD sensor in the optical scanning device. In FIG. 6, reference numeral 215 denotes a mirror for returning the synchronous detection beam (synchronous mirror). ).
If the BD sensor 214 is disposed on the optical path of the light beam directed toward the photosensitive drum 3, a simple configuration is preferable. However, in the case where the BD sensor 214 cannot be disposed directly on the optical path toward the photosensitive drum 3 due to the space limitation of the non-image area portion or the like, for example, a synchronous mirror 215 as shown in FIG. Can be configured to guide the light beam to the BD sensor 214. Also in this case, the number of synchronous mirrors 215 is increased, and the rationalization effect by sharing the BD sensor 214 and the folding mirrors (the first mirror 210 for Y, the first mirror 208 for M, the first mirror for C) which will be described later. The effect of reducing the number of parts by the separation structure of the light beam and the synchronous detection beam in the image area in one mirror 205) can also be obtained in this embodiment.

FIG. 7 is a main part perspective view for explaining a configuration example of a folding mirror that separates the light beam in the image region and the synchronization detection beam in the non-image region. In FIG. 7, reference numeral 216 denotes a transmission region provided in each folding mirror, and 217 denotes a reflection region.
As described above, the folding mirrors of the first mirror for Y 210, the first mirror for M 208, and the first mirror for C 205 reflect the light beam in the image area on the optical path toward the photosensitive drum 3, and A function of transmitting the synchronous detection beam in the non-image area toward the optical path toward the BD sensor 214 is provided.

In order to realize such a function, each of the folding mirrors 210, 208, and 205 is provided with a reflection region 217 that reflects the light beam in the image region and a transmission region 216 that transmits the light beam in the non-image region. .
Each of the folding mirrors 210, 208, and 205 can create a reflective surface by providing a metal vapor deposition film on the surface of a glass substrate formed into a plate shape. That is, in this example, a region where metal deposition is performed on the surface of the glass substrate and a region where metal deposition is not performed by masking are formed, and the region where the metal deposition film is formed is the reflective region 217, and the region where metal deposition is not performed. Is defined as the transmission region 216.

  The transmissive region 216 is formed in the non-image region on the writing side in the main scanning direction in order to detect the light beam by the BD sensor 214. When synchronization detection is performed on the writing end side in the main scanning direction, a transmission area 216 is appropriately provided in the corresponding non-image area on the writing end side. In this embodiment, the synchronous detection beam is detected on the writing start side in the main scanning direction.

  Moreover, the formation method of the reflective region 217 and the transmissive region 216 is not limited to the above-described metal vapor deposition by masking, and a known method can be appropriately applied. For example, a technique may be employed in which a glass substrate is coated with a paint having a metallic luster on a portion where the reflection region 217 is formed, or a reflection sheet having a resin film as a substrate is laminated on the glass substrate. .

  FIG. 8 is a diagram for explaining the optical path of the synchronous detection beam in the non-image region in more detail, and schematically shows the main part of the optical system and the optical path of the light beam. As described above, in the optical scanning device of this embodiment, the four light beams for KCMY are deflected by the single polygon mirror 201 of the secondary optical system. At this time, the four light beams emitted from the polygon mirror 201 travel with a height difference in the sub-scanning direction. For this reason, each of the folding mirrors (the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C) is configured so that the image region light of the corresponding light beam can be separated and reflected. They are arranged with a height difference in the scanning direction.

Therefore, the light beams that pass through the transmission regions 216 of the folding mirrors 210, 208, and 205 differ depending on the folding mirrors.
That is, as shown in FIG. 8, the first Y mirror 210 acts on the Y light beam that passes through the lowest side in the sub-scanning direction among the four light beams of KCMY. Therefore, in the first Y mirror 210, only the synchronous detection beam in the non-image region of the Y light beam is transmitted, and the light beams for other colors (MCK) pass above the first Y mirror 210. To do. The image area light (dotted line) reflected by the reflection area 217 of the first Y mirror 210 is directed to the Y photosensitive drum 3.

  In the transmission region 216 of the M first mirror 208, the Y synchronization detection beam that has passed through the Y first mirror 210 and the M non-image region synchronization detection beam are transmitted, and other colors (CK ) Light beam passes above the M first mirror 208. The image area light (dotted line) reflected by the reflection area 217 of the M first mirror 208 is directed to the M photoconductor drum 3.

  Similarly, in the transmission region 216 of the first C mirror 205, the synchronization detection beams for Y and M that have passed through the first mirror 210 for Y and the first mirror 208 for M and the non-image region for C are synchronized. The light beam for the other color (K) passes above the first mirror 205 for C. The image area light (dotted line) reflected by the reflection area 217 of the C first mirror 205 is directed to the C photosensitive drum 3.

The K mirror 204 reflects the K light beam and the YMC synchronous detection beam. Therefore, the K mirror 204 is not provided with a transmission region 216 unlike other mirrors (the first mirror 210 for Y, the first mirror 208 for M, the first mirror 205 for C), and the surface on the optical path is All are reflective surfaces.
Then, the synchronous detection beam of the non-image area for each color of KCYM reflected by the K mirror is incident on the BD sensor lens 213 and is condensed on the BD sensor 214.

  FIG. 9 is a diagram for explaining a configuration example of a transmission region and a reflection region set in a mirror for folding. In the example of FIG. 9, the three folding mirrors that form the transmission region 216, that is, the first mirror for Y 210, the first mirror for M 208, and the first mirror for C 205 are transmitted according to the passing position of the synchronous detection beam. The widths 216 are configured to be different from each other.

  Here, glass substrates having the same width are used for the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C, and the glass substrates are arranged at the same position in the main scanning direction. So that In this case, the scanning light for each color of KCMY reflected by the polygon mirror 201 (not shown) has different scanning widths at the positions of the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C. The scanning width becomes wider from Y to K. Therefore, the passing position of the synchronous detection beam in the non-image area for each color also changes from the inside to the outside in the width direction of each folding mirror as it goes from Y to K.

  In the embodiment of FIG. 9, the transmission region 216 is formed on the optical path of the synchronous detection beam according to the above conditions. Accordingly, in the case of FIG. 9, the width of the transmission region 216 is different in the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C, and the width of the transmission region 216 of the first mirror for Y 210 is different. Next, the width of the transmission region 216 of the first mirror for M 208 is widest, and the width of the transmission region 216 of the first mirror for C 205 is the narrowest.

  In this embodiment, although the passing positions of the synchronous detection beams are different, the above-described folding mirrors (the first mirror 210 for Y, the first mirror 208 for M, and the first mirror for C) are formed using the same standard glass substrate. 1 mirror 205) can be formed, so that rational component design can be performed without increasing the standard of the glass substrate.

  FIG. 10 is a diagram for explaining another configuration example of the transmission region and the reflection region set in the mirror for folding. In the example of FIG. 10, glass substrates having the same width are used for the three mirrors forming the transmission region 216, that is, the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C, In addition, the transmission region 216 has the same width and is a common part, and the installation positions of the folding mirrors 210, 208, and 205 are shifted in the main scanning direction according to the passage position of the synchronous detection beam.

  In the present embodiment, the widths of the transmission region 216 and the reflection region 217 in each of the mirrors (the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C) are the same. The standards for the folding mirrors 210, 208, and 205 can be made common, and rational component design can be performed without increasing the standards for the folding mirrors.

  FIG. 11 is a diagram for explaining still another configuration example of the transmission region and the reflection region set in the mirror for folding. Also in this example, glass substrates having the same width are used for the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C. In each of the folding mirrors 210, 208, and 205, for the first mirror for M 208 and the first mirror for C 205, the widths of the transmission region 216 and the reflection region 217 are the same, and for the first mirror for Y 210 The width of the transmission region 216 is made wider than the other folding mirrors.

  For example, as shown in FIG. 10, the standards of the three folding mirrors 210, 208, and 205 are standardized, and the installation positions of the folding mirrors 210, 208, and 205 are shifted in the main scanning direction according to the optical path for each color. In this case, the position of the end portion (in this example, the writing end side of main scanning) opposite to the side where the transmissive region 216 is formed is different in each of the folding mirrors 210, 208, and 205. In particular, in the first Y mirror 210 where the synchronous detection beam passes the innermost side in the main scanning direction, the end portion on the writing end side protrudes to the most writing end side compared to the other M and C folding mirrors 208 and 205. The space of the optical scanning device is required.

  In the example of FIG. 11, the width of the transmission region 216 of the first Y mirror 210 closest to the polygon mirror 201 is made wider than the width of the transmission region 216 of the first mirror for M 208 and the first mirror for C 205, The installation position of the first Y mirror 210 is set so as not to deviate greatly in the main scanning direction as compared with the other mirrors. Here, the first mirror for M 208 and the first mirror for C 205 can be created as a common folding mirror, and the spatial constraints of the optical scanning device can be flexibly dealt with.

  FIG. 12 is a view for explaining a support structure for fixing and supporting the folding mirror. FIG. 12A is a schematic side view of the folding mirror fixedly supported by the supporting member. A schematic perspective view of the folding mirror is shown in FIG. In FIG. 12, 218 is a leaf spring, 219 is an adjusting screw, and 225 is a support portion of the optical scanning device on which a folding mirror is installed.

  The folding mirror (the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C) includes a support part on the housing or frame of the optical scanning device as shown in FIG. 225 is fixedly supported by using a support member by a leaf spring 218. The leaf spring 218 is installed so as to press the folding mirrors 210, 208, and 205 against the support portion 225.

  An adjustment screw 219 is provided on the back side of each of the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C, and the adjustment screw 219 is moved forward and backward. Thus, the angle of the reflecting surface of each of the folding mirrors 210, 208, and 205 can be adjusted.

  The folding mirrors 210, 208, and 205 need to be configured to be pressed against the support portion 225 serving as a reference surface by using the leaf spring 218. When such a configuration is not adopted, the reflection angle is accurately set. It cannot be specified. For example, it is difficult to fix and support each folding mirror 210, 208, 205 without affecting the reflection area by using only the back surface and the upper and lower surfaces of the reflecting surface of the folding mirror 210, 208, 205.

In the embodiment of the present invention, the transmissive region 216 as described above is formed in each folding mirror (the first mirror 210 for Y, the first mirror 208 for M, and the first mirror 205 for C). The leaf spring 218 is installed so as to fix and support the transmission region 216 at the end of each folding mirror 210, 208, 205 as shown in FIG.
By holding the folding mirrors 210, 208, and 205 on the end side of the transmission region 216, the distance D between the position of the synchronous detection beam incident on the BD sensor 214 and the end portion of the image region can be set as shortest as possible. The most reasonable folding mirror fixed support structure can be obtained.

It is a figure for demonstrating the problem at the time of comprising so that a synchronous detection beam may pass the outer side of a folding mirror. For example, when the synchronous detection beam is configured to pass outside the folding mirror as shown in FIG. 13 without forming the transmission region 216 in the folding mirrors 210, 208, and 205, the synchronous detection beam and the light beam in the image region are used. It is necessary to arrange a leaf spring 218 as a support member between the two. In this case, the distance D between the position of the synchronous detection beam incident on the BD sensor 214 and the end of the image area becomes long, the scanning width in the main scanning direction becomes long, and the apparatus becomes large. Further, at this time, the scanning width is increased, so that the scanning speed is lowered and the productivity of image formation is deteriorated.
Therefore, as in the present embodiment, the folding mirrors 210, 208, and 205 are provided with the transmission region 216, and the folding mirror is fixedly supported at the end of the transmission region 216, thereby reducing the size and productivity of the optical scanning device. From this, a rational mirror fixed support structure can be obtained.

FIG. 14 is a schematic perspective view for explaining another configuration example of the folding mirror, in which 226 is a notch. In each of the above-described embodiments, the transmission region 216 for transmitting the synchronization detection beam to each of the folding mirrors 210, 208, and 205 is formed, but in this embodiment, in each of the folding mirrors 210, 208, and 205, A notch 226 is provided in a portion of the non-image area where the synchronous detection beam passes. In this case, for example, a notch 226 is formed when a glass substrate constituting each of the folding mirrors 210, 208, and 205 is formed, and a notch is formed on the glass substrate by forming a reflective surface by metal deposition. Folding mirrors 210, 208, and 205 having 226 can be obtained.
The folding mirrors 210, 208, and 205 having the notches 226 prevent the synchronous detection beam from passing through the glass substrate, so that, for example, slight reflection on the glass substrate surface and stray light can be prevented.

FIG. 15 is a block diagram illustrating a configuration example of a control system of the optical scanning device.
The LSU controller 301 receives an image data signal output from an image memory or the like of the image processing unit 402 of the image forming apparatus, and a laser driver circuit in accordance with the scanning start timing sent from the main body control unit 401 of the image forming apparatus. (LD Driver) 302 and the laser diode (LD) 101 is turned on.
The LSU controller 301 controls the reference rotation operation of the polygon motor 303 that drives the polygon mirror so as to meet the specifications in the main scanning direction of the image forming apparatus. Further, the BD sensor 214 that detects the writing start position in the main scanning direction detects the timing of the main scanning by receiving the light beam, and outputs an error signal to the main body control unit 401 if there is an error. The LSU controller 301 is configured by an ASIC (application specific integrated circuit).

1 is a diagram illustrating a configuration example of an image forming apparatus in which an optical scanning device of the present invention is used. It is a top view which shows the structural example of the primary optical system unit of the optical scanning apparatus of this invention. FIG. 3 is a schematic perspective view of the primary optical system unit in FIG. 2. It is a figure which shows the structural example of the secondary optical system of an optical scanning device. It is a figure for demonstrating the installation position of the BD sensor in an optical scanner, and the optical path of the light beam made to inject into a BD sensor. It is a figure for demonstrating the other position of the installation position of the BD sensor in an optical scanning device, and the other example of the optical path of the light beam which injects into a BD sensor. It is a principal part perspective view for demonstrating the structural example of the folding mirror which isolate | separates the light beam of an image area | region, and the synchronous detection beam of a non-image area | region. It is a figure for demonstrating in more detail the optical path of the synchronous detection beam of a non-image area | region. It is a figure for demonstrating the structural example of the transmissive area | region and reflection area | region set to the mirror for folding | turning. It is a figure for demonstrating the other structural example of the permeation | transmission area | region and reflection area | region set to the mirror for a return | turnback. It is a figure for demonstrating the further another structural example of the transmissive area | region and reflection area | region set to the mirror for folding | turning. It is a figure for demonstrating the support structure for fixedly supporting a folding mirror. It is a figure for demonstrating a problem when it comprises so that a synchronous detection beam may pass the outer side of a folding mirror. It is a perspective schematic diagram for demonstrating the other structural example of a folding mirror. It is a block diagram explaining the structural example of the control system of an optical scanning device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exposure unit, 2 ... Developing device, 3 ... Photosensitive drum, 4 ... Cleaner unit, 5 ... Charger, 6 ... Intermediate transfer belt unit, 7 ... Fixing unit, 8 ... Paper feed cassette, 9 ... Paper discharge tray, DESCRIPTION OF SYMBOLS 10 ... Transfer roller, 11 ... Pick-up roller, 12a, 12c, 12d, 12e ... Conveyance roller, 13 ... Registration roller, 61 ... Intermediate transfer belt, 62 ... Intermediate transfer belt drive roller, 63 ... Intermediate transfer belt tension mechanism, 64 ... Intermediate transfer belt driven roller, 65 ... Intermediate transfer roller, 66 ... Intermediate transfer belt cleaning unit, 71 ... Heat roller, 72 ... Pressure roller, 100 ... Primary optical system unit, 101 ... Laser diode, 102 ... Collimator lens, 103 ... Aperture, 104 ... Laser drive substrate, 105 ... Laser holder, 106 ... Lens holder 107: barrel, 108: mounting screw, 110: first mirror, 111: second mirror, 112: cylindrical lens, 113: third mirror, 120: substrate, 200: secondary optical system unit, 201: polygon mirror, 202: 1st fθ lens, 203: 2nd fθ lens, 204: mirror for K, 205: 1st mirror for C, 206 ... 2nd mirror for C, 207 ... 3rd mirror for C, 208 ... 1st mirror for M, 209 ... M second mirror, 210 ... Y first mirror, 211 ... Y second mirror, 212 ... Y third mirror, 213 ... BD sensor lens, 214 ... BD sensor, 215 ... mirror (synchronous detection mirror) 216 ... Transmission area, 217 ... Reflection area, 218 ... Leaf spring, 219 ... Adjustment screw, 220 ... Cylindrical lens, 221a, 221b ... Fixing shaft 222: Installation position of the primary optical system unit, 223 ... Case, 224 ... Frame for holding the cylindrical lens, 225 ... Support portion, 226 ... Notch, 301 ... LSU controller, 302 ... Laser driver circuit (LD Driver), 303: Polygon motor 401: Main body control unit 402: Image processing unit

Claims (8)

A light source, a polygon mirror that uses a plurality of light beams emitted from the light source as scanning light, and an optical system that emits the light beams scanned by the polygon mirror toward a plurality of photoconductors, respectively. In the optical scanning device in which a latent image for image formation is written on the photosensitive member by scanning light on the photosensitive member,
The optical scanning device has one light beam detecting means for detecting a light beam in order to control the writing start position of the latent image in the main scanning direction on the photosensitive member,
The optical system has a plurality of folding mirrors that fold the optical path of any one of the plurality of light beams,
A part of the folding mirror transmits a detection light beam incident on the light beam detecting means and separates it from the folding optical path of the image forming light beam,
The optical scanning device further includes a condensing optical system for condensing the detection light beams of the plurality of light beams on the one light beam detecting means. The optical scanning device according to claim 1, wherein a plurality of the folding mirrors having a function of transmitting the detection light beam are provided,
The plurality of folding mirrors have the same width in the scanning direction of the transmission regions that transmit the detection light beam, and are arranged at different positions in the scanning direction according to the optical path of the detection light beam. An optical scanning device.   3. The optical scanning device according to claim 2, wherein the plurality of light beams are four light beams that are scanned to draw yellow, magenta, cyan, and black images, respectively. An optical scanning device characterized in that the folding mirror having a function of transmitting light is three folding mirrors respectively acting on the light beams for drawing the yellow, magenta, and cyan images. The optical scanning device according to claim 1, wherein a plurality of the folding mirrors having a function of transmitting the detection light beam are provided,
Among the plurality of folding mirrors, some of the folding mirrors have the same width in the scanning direction of the transmission region that transmits the detection light beam, and is mutually in the scanning direction according to the optical path of the detection light beam. An optical scanning device characterized by being arranged at different positions.   4. The optical scanning device according to claim 3, wherein the plurality of light beams are four light beams that are scanned to draw yellow, magenta, cyan, and black images, respectively. An optical scanning device characterized in that the folding mirrors having the same width in the scanning direction of the transmission region that transmits light are two folding mirrors that act on the light beams for drawing the magenta and cyan images, respectively. . A light source, a polygon mirror that uses a plurality of light beams emitted from the light source as scanning light, and an optical system that emits the light beams scanned by the polygon mirror toward a plurality of photoconductors, respectively. In the optical scanning device in which a latent image for image formation is written on the photosensitive member by scanning light on the photosensitive member,
The optical scanning device has one light beam detecting means for detecting a light beam in order to control the writing start position of the latent image in the main scanning direction on the photosensitive member,
The optical system has a plurality of folding mirrors that fold the optical path of any one of the plurality of light beams,
A part of the folding mirror has a cutout that allows the detection light beam incident on the light beam detection means to pass therethrough, and an optical path of the detection light beam that has passed through the cutout is formed in the image formation. Separating from the folded light path of the light beam for
The optical scanning device further includes a condensing optical system that condenses the detection light beams of the plurality of light beams onto the one light beam detection unit.   7. The optical scanning device according to claim 1, wherein the plurality of folding mirrors having the transmission region or the notch have the same length in the scanning direction. apparatus.   An image is formed by forming the latent image on the photosensitive member by the optical scanning device and visualizing the latent image, comprising the photosensitive member and the optical scanning device according to any one of claims 1 to 7. An image forming apparatus for performing formation.

Images