JP2008112041A5 - - Google Patents

Description

Scanning optical apparatus and image forming apparatus

  The present invention relates to a scanning optical device that performs optical writing scanning with respect to a plurality of photoconductors using a single rotating polygonal mirror, and an image forming apparatus such as an electrophotographic copying machine and the printer having the scanning optical device.

  A scanning optical device used in an image forming apparatus such as a laser beam printer or a digital copying machine has an optical deflector composed of, for example, a rotating polygon mirror (polygon mirror), and a light source according to an image signal by the optical deflector. The light beam modulated and emitted from the means is periodically deflected. Then, the deflected light beam is imaged in a spot shape on a photosensitive recording medium (photosensitive drum) surface by an imaging optical system (scanning optical means) having fθ characteristics, and the surface is optically scanned to form an image. We are recording.

  In recent years, various so-called multi-beam scanning optical devices have been proposed in order to increase the number of light beams that simultaneously perform optical scanning on a surface to be scanned due to the demand for higher speed.

  In the case of a multi-beam scanning optical device that simultaneously scans a plurality of light beams, it is necessary to make the imaging spot interval in the main scanning direction of each scanning line on the photosensitive drum surface, which is the scanning surface, uniform. The imaging spot interval of the scanning lines by a plurality of light beams on the surface to be scanned in one scan must be uniform over the entire image height.

  1) For example, when a different inclination or curvature occurs for each scanning line, and the imaging spot interval of the scanning line changes for each image height and becomes non-uniform, a good image cannot be obtained.

  2) In addition, even if the image spot spacing in the main scanning direction of the scanning lines is uniform at all image heights, if the scanning line spacing in the sub-scanning direction matches the desired resolution, the photosensitive drum is desired. It is rotating at a constant angular velocity according to the resolution of the. As a result, pitch unevenness occurs and a good image cannot be obtained. That is, the scanning line interval in one scanning and the scanning line interval between each scanning of the mirrors of the rotary polygon mirror are different, and pitch unevenness occurs in the sub-scanning direction.

  The problem 2) can be solved by adjusting the arrangement of light sources having a plurality of light emitting portions (light emitting points). That is, it can be corrected by adjusting the arrangement of the light sources so that the scanning line interval on the photosensitive drum surface, which is the surface to be scanned, becomes a desired value. For example, in the case of using a light source that emits two light beams separated from the light emitting unit, the distance of each light emitting unit with respect to the optical axis in the sub-scan section is rotated by rotating the light source around the optical axis of the incident optical means. It can be placed at a desired distance, thereby making the desired adjustment.

  However, regarding the problem 1), if there is a processing error of each optical element, deflection means, etc., a processing error of an optical box in which the optical element is assembled, or an assembly error of the scanning optical device, an image of the scanning line is formed by the image height Spot spot non-uniformity occurs.

  A light source that generates a multi-beam cannot be shortened by a certain distance (about 90 μm) due to the influence of thermal crosstalk or the like at present. Further, when the light source is rotated by a desired angle about the optical axis by the adjustment, for example, the two light emitting units are arranged with a certain interval in the main scanning section. Accordingly, the two light beams emitted from the aperture stop are incident on the subsequent deflecting means, scanning optical means, and the like at a relative angle. The two light beams incident on the scanning optical means are incident on positions separated from each other in the main scanning section, and the incident angles are also different. Further, since the light emitting portion is disposed at a position away from the optical axis even in the sub-scanning section, it enters the scanning optical means with a certain angle.

  Here, if there is a processing error of each optical element or the like, an assembly error of the scanning optical device, etc., the difference between the incident position and incident angle of the two light beams becomes large, and an optical path length difference occurs. At this time, since the powers of the incident surfaces of the two light beams are also different, the refraction angles of the two light beams in the sub-scanning section are also different, and an imaging spot interval error of the scanning line occurs for each image height.

  In particular, in recent years, when the configuration in which the shape of the scanning optical means in the main scanning direction is aspherical or the curvature radius in the sub-scanning direction is changed as the distance from the optical axis is increased for higher definition, the optical path length of the two light beams is increased. The difference and the power difference at the incident surface are also larger. For this reason, an imaging spot interval error of the scanning line becomes remarkable.

  As a means for correcting such an imaging spot interval error of the scanning line, an aperture stop for restricting the light beam width in the main scanning direction is arranged on the deflecting means side, and the incident light beams incident on the deflecting means and the scanning optical means are incident. Japanese Patent Application Laid-Open No. H10-228688 proposes a scanning optical device that suppresses the angular difference. The closer the aperture stop is to the deflecting means, the smaller the exit angle difference between a plurality of light beams exiting the aperture stop. As a result, it is possible to reduce the difference between the incident positions and the incident angles of a plurality of light beams incident on the scanning optical means, and it is possible to suppress the imaging spot interval error of the scanning lines.

  However, if an aperture stop that restricts the light beam width in the main scanning direction is arranged in the vicinity of the deflecting means, the distance between the aperture stop and the optical elements constituting the scanning optical means is reduced, and the spatial margin is reduced. In recent years, due to the demand for miniaturization of the scanning optical device, the scanning angle is widened, and the optical element is arranged in the vicinity of the deflecting means. In this case, the spatial margin is further reduced.

  Here, when the BD light beam (synchronous detection light beam) is taken in the same direction as the incident optical unit with respect to the optical axis of the scanning optical unit and on the scanning optical unit side with respect to the optical axis of the incident optical unit, The BD light flux is kicked by the diaphragm, and the amount of light guided to the BD sensor is reduced. As a result, the accuracy of the output of the BD signal from the BD sensor may be reduced, or all the synchronous detection light beams may be kicked, and the light beams may not be guided to the BD sensor, and the BD signal may not be obtained at all. .

  Therefore, even when the aperture stop is arranged in the vicinity of the deflecting means, in order to ensure the BD light beam without being kicked by the aperture stop, the BD light beam is opposite to the incident optical means with respect to the optical axis of the scanning optical means. Patent Document 2 discloses that a part of a light beam passing through the region is used.

  A tandem type apparatus is known as a color image forming apparatus. This apparatus has an independent image carrier (hereinafter referred to as a photosensitive drum) for each color of yellow, magenta, cyan, and black. Each of the photosensitive drums is exposed to laser light to form an electrostatic latent image, the electrostatic latent image is developed with each color toner, and the resulting toner images are superimposed on a sheet-like recording medium to form a color image. obtain.

  In such an apparatus, the following scanning optical apparatus is known as means for exposing a laser beam to each photosensitive drum in order to reduce cost and size. That is, a scanning type in which a rotary polygon mirror as a deflection scanning unit is shared by a plurality of light sources, and laser light from a plurality of light sources is simultaneously deflected and scanned by a single rotary polygon mirror and irradiated to a plurality of photosensitive drums. It is an optical device.

In such an apparatus, a plurality of light sources, a rotating polygon mirror, and a plurality of laser beams that are symmetrically arranged in two directions around the rotating polygon mirror and that are polarized and scanned by the rotating polygon mirror are respectively scanned. There is known a configuration in which an imaging optical system that guides and forms an image on a surface is arranged in one casing.
JP-A-5-34613 JP 2001-021819 A

  As in Patent Document 2, if a part of the light beam passing through the region opposite to the incident optical means is used with respect to the optical axis of the scanning optical means, the synchronous detection light beam is scanned by the rotating polygon mirror. When the incident optical system is arranged on the writing side, the light beam for synchronization detection becomes the light beam after scanning. For this reason, since the writing start position accuracy is deteriorated, it is necessary to arrange the incident optical system on the writing end side.

  However, in a small-sized color scanning optical apparatus that performs deflection scanning in two directions using one conventional rotary polygon mirror, the optical axis centers in the main scanning direction in the two directions that are deflected and scanned are made to coincide with each other. One of the incident optical systems must be arranged on the writing side and the other on the writing end side. For this reason, there is a problem that the aperture stop cannot be arranged in the vicinity of the deflecting means, the imaging spot interval in the main scanning direction of each scanning line becomes non-uniform, and the image quality deteriorates.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-density, high-accuracy scanning optical device by reducing the number of parts of the device and reducing the size, and reducing jitter. It is to be.

  It is another object of the present invention to provide a scanning optical device that is compact and low in cost and has uniform imaging spot intervals in the main scanning direction of each scanning line.

  Another object of the present invention is to provide an image forming apparatus with high image quality and high speed.

To achieve the above object, a typical configuration of a scanning optical device according to the present invention is as follows:
Multiple light sources;
A rotating polygon mirror that deflects and scans the light beams emitted from the plurality of light sources in both directions with a rotation axis interposed therebetween;
An optical system that forms an image of the light beam emitted from the light source on the reflecting surface of the rotary polygon mirror ;
Imaging means for imaging the light beams deflected and scanned by the rotary polygon mirror onto separate photosensitive members;
In the scanning optical device, comprising: a synchronization detection unit that detects a light beam scanned by the rotary polygon mirror and outputs a synchronization signal for synchronizing a scanning start position in the main scanning direction of each of the plurality of light beams.
Before SL is disposed between the optical science system and the rotary polygon mirror, and is disposed to span the part of the scanning line of the light beam scanned by the rotary polygon mirror, the light beam incident on the rotary polygonal mirror has an aperture stop member having an aperture stop for regulating the aperture stop member is characterized by having a reflecting surface to fold the light beam deflected by the rotary polygon mirror toward the synchronous detection means.

  An image forming apparatus that includes a plurality of photoconductors and an exposure unit for the photoconductors and executes image formation, wherein the exposure unit is the above-described scanning optical device.

  According to the scanning optical device of the present invention, even if the aperture stop member is disposed in the vicinity of the rotary polygon mirror, a sufficient amount of light is incident on the synchronization detection unit without kicking the light beam toward the synchronization detection unit by the aperture stop member. can do. As a result, the apparatus can be made low-cost and compact, and the imaging spot interval in the main scanning direction of each scanning line can be made uniform.

  Further, it is possible to provide an image forming apparatus with high image quality and high speed using this scanning optical apparatus.

[Example]
(1) Image Forming Unit FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus equipped with a scanning optical device according to the present invention. FIG. 2 is a partially enlarged view of FIG. 1. In an image forming apparatus that has a plurality of photoconductors and an exposure unit for the photoconductor and executes image formation, ri.

The image forming apparatus 100 of this example is a tandem type color image forming apparatus (color printer) using a transfer type electrophotographic process, and includes a plurality of photoconductors and an exposure unit for the photoconductors, An image forming apparatus that executes image formation. A full-color image can be formed and output on a recording material by performing an image forming operation according to electrical image information input from an external host device 300 that is communicably connected to the control circuit unit 200. The external host device 300 is a personal computer, an image reader, a counterpart facsimile, or the like. The control circuit unit 200 exchanges various signals with the external host device 300. In addition, image sequence control is performed by exchanging signals with various image forming devices.

  In the printer 100, four image forming units (image forming units) 81Bk, 81C, 81M, and 81Y that respectively form a black toner image, a cyan toner image, a magenta toner image, and a yellow toner image are arranged in a line at regular intervals. Has been.

  Each of the image forming units 81 (Bk, C, M, and Y) is an electrophotographic image forming mechanism having the same configuration, and is provided with drum-type photoreceptors (hereinafter referred to as drums) 82a, 82b, 82c, and 82d. ing. Around each drum 82 (a to d), there are primary chargers 83a, 83b, 83c, and 83d, developing devices 84a, 84b, 84c, and 84d, primary transfer rollers 85a, 85b, 85c, and 85d, a drum cleaner device 86a, 86b, 86c and 86d are arranged.

  In this example, each of the drums 82 (a to d) is a negatively charged OPC photoconductor, has a photoconductive layer on an aluminum drum base, and a clockwise direction indicated by an arrow by a driving device (not shown). Are rotated at a predetermined process speed. Each drum 82 (a to d) is uniformly charged to a predetermined negative potential by applying a predetermined charging bias to each primary charger 83 (a to d).

  Each of the developing devices 84a, 84b, 84c, and 84d contains black toner, cyan toner, magenta toner, and yellow toner, respectively.

  Below each image forming unit 81 (Bk, C, M, Y), a scanning optical device 50 for each drum 82 (ad) is installed. The scanning optical device 50 is a laser scanner, and includes a semiconductor laser, a collimator lens, a cylindrical lens, a polygon mirror, an fθ lens, a folding mirror, and the like as a light source that emits light that is modulated in accordance with given image information. Yes. The scanning optical device 50 will be described in detail in the next item (2).

  In the image forming unit 81Bk, the laser beam modulated in accordance with the image information of the black component image of the full-color image is exposed as scanning light E1 from the scanning optical device 50 to the primary charged rotary drum 82a. Thus, an electrostatic latent image is formed. The latent image is developed as a black toner image by the developing device 84a.

  In the image forming unit 81C, the laser beam modulated in accordance with the image information of the cyan component image of the full-color image is exposed as scanning light E2 from the scanning optical device 50 to the primary charged rotary drum 82b. Thus, an electrostatic latent image is formed. The latent image is developed as a cyan toner image by the developing device 84b.

  In the image forming unit 81M, the laser beam modulated according to the image information of the magenta component image of the full-color image is exposed as the scanning light E3 from the scanning optical device 50 to the rotary drum 82c that is primarily charged. An electrostatic latent image is formed. The latent image is developed as a magenta toner image by the developing device 84c.

  In the image forming unit 81Y, the laser beam modulated in accordance with the image information of the yellow component image of the full-color image is exposed as scanning light E4 from the scanning optical device 50 to the rotary drum 82d that is primarily charged. As a result, an electrostatic latent image is formed. The latent image is developed as a yellow toner image by the developing device 84d.

  Above each image forming portion 81 (Bk, C, M, Y), an endless intermediate transfer belt (hereinafter referred to as a belt) 87 is disposed. The belt 87 is stretched between a pair of belt conveyance rollers 88 and 89, and is driven to rotate at a predetermined process speed in a counterclockwise direction indicated by an arrow by a driving device (not shown). The belt 87 is made of a dielectric resin such as a polycarbonate, a polyethylene terephthalate resin film, a polyvinylidene fluoride resin film, or the like.

  The upper surface of each drum 82 (ad) of each image forming unit 81 (Bk, C, M, Y) is opposed to the lower surface of the descending belt portion of the belt 87. Each primary transfer roller 85 (ad) is disposed inside the belt 87 and is in contact with the upper surface of each corresponding drum 82 (ad) across the descending belt portion. The contact portions between the drums 82 (a to d) and the belt 87 are primary transfer nip portions T1a, T1b, T1c, and T1d, respectively.

  A secondary transfer roller 90 is brought into contact with the belt conveying roller 88 with the belt 87 interposed therebetween. A contact portion between the belt 87 and the secondary transfer roller 90 is a secondary transfer nip portion T2.

  When a print start signal is input, the control circuit 200 forms each image forming unit 81 (Bk, C, M, Y) based on the color separation image information of the color image input from the external host device 300. Make it work. As a result, black, cyan, magenta, and yellow color toner images are formed on the respective drums 82 (a to d) that rotate in the respective image forming units at a predetermined control timing. The electrophotographic image forming principle and process for forming a toner image on each drum 82 (a to d) are well-known and will not be described.

  The toner images formed on the surfaces of the drums 82 (a to d) of the image forming units 81 (Bk, C, M, and Y) rotate at the primary transfer nip portions T1 (a to d), respectively. The images are sequentially superimposed and transferred onto the outer surface of the belt 87. During the primary transfer, a predetermined transfer bias is applied to each primary transfer roller 85 (ad). As a result, an unfixed full-color toner image is synthesized and formed on the surface of the belt 87 by superimposing the four color toner images.

  Each drum cleaner 86 (ad) includes a cleaning blade or the like for removing residual toner remaining on each drum 82 (ad) after the primary transfer from the drum surface.

  On the other hand, at a predetermined paper feed timing, a paper feed roller 93 of a paper feed cassette 92 in which a recording material (transfer paper) that is a sheet-like recording medium is stacked and driven is driven. As a result, the recording materials stacked and stored in the paper feed cassette 92 are separated and fed one by one and conveyed to the registration roller pair 94 through the vertical conveyance path.

  The registration roller pair 94 stops rotating at that time, and receives the leading edge of the recording material at the nip portion to correct the skew of the recording material. The registration roller pair 94 has the leading end of the recording material at the nip T2 in accordance with the timing at which the leading end of the full-color toner image synthesized and formed on the rotating belt 87 reaches the secondary transfer nip T2. The recording material is conveyed in a timing manner so as to reach the recording material. As a result, at the secondary transfer nip T2, the full-color toner images on the belt 87 are secondarily transferred sequentially onto the surface of the recording material. A predetermined transfer bias is applied to the secondary transfer roller 90 during the secondary transfer.

  The recording material that has exited the secondary transfer nip T2 is separated from the surface of the belt 87, guided by a longitudinal guide, and introduced into the fixing device 95. By the fixing device 95, the above-described toner images of a plurality of colors are melted and mixed by heat and pressure and fixed as fixed images on the surface of the recording material. The recording material exiting the fixing device 95 is conveyed and discharged as a full-color image formed product onto a paper discharge tray 98 through a pair of transport rollers 96 and a pair of paper discharge rollers 97.

  The transfer residual toner remaining on the belt 87 after the secondary transfer is removed by a belt cleaning device 91 disposed on the belt conveyance roller 89 outside the belt 87.

  Reference numeral 71 denotes a registration detection sensor (hereinafter referred to as a registration sensor) which is a color registration amount detection unit, which detects a registration error pattern of each color formed on the belt 87 to detect a color registration amount, and feeds back to the control circuit unit 200. To do. By detecting the amount of color misregistration by the registration sensor 71, the color misregistration due to the top margin and the side margin electrically corrects the writing timing of the image data, and the image clock frequency is slightly changed even for the color misregistration due to the magnification factor. Thus, the magnification is matched.

(2) Scanning optical device 50
FIG. 3 is a plan view showing the configuration of the main part inside the scanning optical apparatus. 4A is a diagram of the first incident optical system, and FIG. 4B is a diagram of the second incident optical system. FIG. 5 is an explanatory diagram regarding adjustment of the collimator lens. FIG. 6 is a partial perspective view regarding attachment of the laser holder portion. FIG. 7 is a front view of the laser holder portion, and FIG. 8 is an explanatory diagram of adjustment between multi-beam pitches. 9 is a perspective view of the first aperture stop, and FIG. 10 is a perspective view of the second aperture stop.

  Here, in the following description, the main scanning direction is conventionally a drum longitudinal direction (a drum axis direction, which is a direction in which the scanning optical system of the scanning optical device 50 optically scans the drums 82 (a to d)). Drum busbar direction), or a direction corresponding to this direction. The sub-scanning direction is a drum rotation direction or a direction corresponding to this direction.

The scanning optical device 50 includes first incident optical systems 5 to 8 that allow the light beams emitted from the first and second semiconductor lasers 2 and 3 as a plurality of light sources to enter the polygon mirror 10.

In addition, second incident optical systems 15 to 18 that allow the light beams emitted from the third and fourth semiconductor lasers 12 and 13 as a plurality of light sources to enter the polygon mirror 10 are provided.

(2-1) First incident optical systems 5 to 8
The first and second semiconductor lasers 2 and 3 are semiconductor lasers (multi-beam lasers) each having two light emitting points in one housing (package). In this embodiment, the first semiconductor laser 2 is a light source that scans and exposes the drum 82a of the image forming unit Bk, and the second semiconductor laser 3 is a light source that scans and exposes the drum 82b of the image forming unit C.

As shown in FIG. 4A, the two semiconductor lasers 2 and 3 are press-fitted and held in two lens barrel holders 1a and 1b provided in a first laser holder (housing) 1, respectively (package )) .

  Reference numeral 4 denotes an electric circuit board mounted on the laser holder 1, which is electrically connected to the first and second semiconductor lasers 2 and 3, and is provided with a laser driving circuit.

  As shown in FIG. 8, each of the semiconductor lasers 2 and 3 has two light emitting points 2a and 2b and 3a and 3b, respectively, so that the interval between the laser beams when scanning the drums 82a and 82b is almost a predetermined value. The lens barrel holding portions 1a and 1b are press-fitted while being inclined in the same direction by an angle α °.

  Further, as shown in FIG. 4A, the lens barrel holding portions 1a and 1b are provided with the optical axes inclined so that the optical paths of the semiconductor lasers 2 and 3 intersect each other with a predetermined angle θ in the sub-scanning direction. A part of the outer shape of the lens barrel is integrated. For this reason, it is possible to keep the distance between the first and second semiconductor lasers 2 and 3 close to each other.

  At the tip of the lens barrel holding portions 1a and 1b, there are bonded portions of collimator lenses 5 and 6 as a first optical system for converting the light beams emitted from the first and second semiconductor lasers 2 and 3 into substantially parallel light beams. 1e and 1f are provided at two locations in the main scanning direction.

Because the collimator lens 5, 6 is to adjust the irradiation position and focus the laser in a state such, that securely holds the collimator lens 5 at three points of the adjustment chucking unit 51a, 51b, 51c in FIG. 5 (a) Adjustment is performed in the X, Y, and Z directions while detecting the optical characteristics of the light. When the position is determined, the ultraviolet curable adhesive is irradiated with ultraviolet rays and bonded and fixed to the bonding portion 1e. The adjustment of the collimator lens 6 is also performed in the same manner as in the case of the collimator lens 5 of (a) by rotating the laser holder 1 180 degrees as shown in (b). Bonded and fixed.

  As described above, since the adhesion portions 1e and 1f of the collimator lenses 5 and 6 are provided in the main scanning direction, three axes are provided with respect to the laser holder 1 having the lens barrel integrated with the collimator lenses 5 and 6 in proximity. Direction adjustment and adhesion are possible.

  Reference numeral 40 denotes an optical case for storing each optical component of the scanning optical device 50, and a circular fitting hole 40a for positioning the laser holder 1 is formed on the side wall of the optical case 40 as shown in FIG. Is provided. The laser holder 1 can be attached to the side wall of the optical case 40 by fitting the circular fitting portion 1m provided at the center of the lens barrel holding portions 1a and 1b of the laser holder 1 into the fitting hole portion 40a. I have to.

  By fitting the circular fitting hole 40a and the circular fitting portion 1m, the laser holder 1 can be rotated by pushing the adjustment groove 1n with an eccentric cam or the like around the fitting portion 1m. When the laser holder 1 is rotated, the pitches of the two light emitting points 2a, 2b and 3a, 3b of the first and second semiconductor lasers 2, 3 are respectively small while the movement amount of the semiconductor lasers 2, 3 is very small. The interval (interval in the sub-scanning direction) P changes (FIG. 8).

  As described above, the first and second semiconductor lasers 2 and 3 have two light emitting points 2a and 2b and 3a and 3b so that the interval between the laser beams when scanning the drums 82a and 82b is substantially a predetermined value. Is tilted by a predetermined angle α and is press-fitted into the lens barrel holding portions 1 a and 1 b of the laser holder 1. However, in reality, it has a certain relative angle due to an error at the time of press-fitting. In addition, a gap in the interval between the laser beams occurs due to an attachment error of the laser holder 1 or an inclination of the optical component for each optical path. Therefore, it is necessary to rotate the laser holder 1 by a small angle to adjust the pitch P between the light emitting points 2 a and 2 b of the first semiconductor laser 2 and the pitch P between the light emitting points 3 a and 3 b of the second semiconductor laser 3. There is.

  However, a single laser holder 1 holds the first and second semiconductor lasers 2 and 3 which are multi-beam lasers. For this reason, the interval between the laser beams when the light beams of the first and second semiconductor lasers 2 and 3 scan the respective drums 82a and 82b may not be adjusted to a predetermined value.

  In such a case, the distance between the laser beams in the first and second semiconductor lasers 2 and 3 is substantially equal to the predetermined value so as to be within the scanning line pitch standard defined by several μm or less. Adjust to an error amount. As described above, the first and second semiconductor lasers 2 and 3 have the two light emitting points 2a and 2b and 3a and 3b inclined in the same direction by a predetermined angle α, respectively, in the lens barrel holding portion 1a of the laser holder 1. And 1b. As a result, when the laser holder 1 is rotated in the direction B in FIGS. 7 and 8, the pitch between the light emitting points 2a and 2b of the first semiconductor laser 2 is changed as shown in FIGS. P2 is P2a, and the pitch P3 between the light emitting points 3a and 3b of the second semiconductor laser 3 is P3a. That is, both the first and second semiconductor lasers 2 and 3 have a small pitch between the light emitting points. On the contrary, when the laser holder 1 is rotated in the C direction, the pitch P2 between the light emitting points 2a and 2b of the first semiconductor laser 2 is P2b, as shown in FIG. The pitch P3 between the light emitting points 3a and 3b of the second semiconductor laser 3 is P3b. That is, both the first and second semiconductor lasers 2 and 3 have a large pitch between the light emitting points.

  When adjusting the pitch, a CCD camera or the like is placed at a position corresponding to the drum surface to be scanned. Then, the spot interval of each laser beam by the two light emitting points 2a and 2b of the first semiconductor laser 2 and the spot interval of each laser beam by the two light emitting points 3a and 3b of the second semiconductor laser 3 are simultaneously measured. And do it.

  When the spot interval is larger than the predetermined value in both the first and second semiconductor lasers 2 and 3, the laser holder 1 is rotated in the B direction. Thereafter, when the spot interval between the first and second semiconductor lasers 2 and 3 is larger than a predetermined value and the other is smaller than the predetermined value, the respective spots of the first and second semiconductor lasers 2 and 3 are used. The adjustment is finished at a position where the interval P becomes a deviation amount from a substantially equivalent predetermined value.

  On the contrary, when the spot interval P is smaller than the predetermined value in both the first and second semiconductor lasers 2 and 3, the laser holder 1 is rotated in the C direction. Thereafter, when the spot interval between the first and second semiconductor lasers 2 and 3 is larger than a predetermined value and the other is smaller than the predetermined value, the respective spots of the first and second semiconductor lasers 2 and 3 are used. The adjustment is finished at a position where the interval P becomes a deviation amount from a substantially equivalent predetermined value.

  If the spot distance between the first and second semiconductor lasers 2 and 3 is deviated from a predetermined value within the scanning line pitch standard from the beginning, the adjustment can be omitted.

  In this way, fine adjustment of the pitch P between the two light emitting points 2a, 2b and 3a, 3b of the first and second semiconductor lasers 2, 3 can be performed simultaneously.

  As a result, the time required for the adjustment can be shortened and the working efficiency can be improved as compared with the case where the first and second semiconductor lasers 2 and 3 are individually adjusted.

  Since the laser holder 1 is attached to the optical case 40 after the laser holder 1 is adjusted, the positional relationship with each optical component stored in the optical case 40 can be assured with high accuracy.

  Reference numeral 7 denotes a cylindrical lens as a second optical system having a predetermined refractive power only in the sub-scanning direction. The lens 7 forms the light beam emitted from the first and second semiconductor lasers 2 and 3 on the deflection surface of the polygon mirror 10 as a substantially line image (line image elongated in the main scanning direction). Lens portions 7a and 7b corresponding to the emitted light beams of both semiconductor lasers are integrally formed.

Reference numeral 8 denotes a first aperture stop member, which is disposed between the cylindrical lens 7 as the second optical system and the polygon mirror 10. As shown in FIG. 9, the aperture stop member 8 is arranged so as to cover a part of the stop portion corresponding to the first and second semiconductor lasers 2 and 3 (on the scanning line of the light beam scanned by the polygon mirror 10). is, an aperture stop for regulating the light beam incident on the polygon mirror 10) 8a-8b are provided, and the light beam emitted from the semiconductor laser 2 and 3 was molded into a desired optimum beam shape.

  A reflective mirror surface 8c is provided on the surface of the aperture stop member 8 on the polygon mirror 10 side, and reflects the scanning light of the polygon mirror 10 as shown in FIG. And it has the synchronous detection means (BD sensor) 28 * 29 which detects the reflected light beam (BD light beam) LBD, and outputs the synchronizing signal of the main scanning direction of a light beam. That is, the reflecting mirror surface 8c of the aperture stop member 8 reflects the scanning light of the polygon mirror 10 and folds it back as a BD light beam LBD toward the BD sensors 28 and 29. This BD light beam LBD crosses the optical path of the scanning lights E1 and E2 between the polygon mirror 10 and a first imaging lens 21 on the first imaging means side described later, passes through the BD lens 9, and is a BD sensor. 28 and 29 receive light.

  The aperture stop member 8 is formed of an aluminum plate, and the reflecting mirror surface 8c is deposited on the aluminum plate.

  The BD sensors 28 and 29 are synchronization detection means corresponding to the first and second semiconductor lasers 2 and 3, and detect the light beam reflected by the polygon mirror 10 and output a synchronization signal in the main scanning direction. The timing of the scanning start position at the image edge is adjusted. The BD lens 9 forms an image of the light beam reflected by the polygon mirror 10 on the light receiving surfaces of the BD sensors 28 and 29 described above.

  Since the scanning light of the polygon mirror 10 is folded back toward the BD sensors 28 and 29 on the reflecting mirror surface 8c of the aperture stop member 8, the BD light beam traveling toward the BD sensor is not kicked by the aperture stop member 8 and a sufficient amount of light is obtained. Can be incident on the BD sensors 28 and 29. For this reason, the aperture stop member 8 can be disposed in the vicinity of the polygon mirror 10.

  In other words, even if the aperture stop member 8 is disposed in the vicinity of the polygon mirror 10, a sufficient amount of light can be incident on the BD sensors 28 and 29 without being kicked by the aperture stop member 8 with respect to the BD sensors 28 and 29. it can. For this reason, jitter can be reduced and high density and high accuracy can be achieved.

  Further, the aperture stop member 8 can be disposed in the vicinity of the polygon mirror 10 by having the semiconductor laser have a plurality of light emitting points and deflecting and scanning the light beams emitted from the plurality of light emitting points simultaneously by the polygon mirror 10 onto the same drum. . Therefore, a high quality image can be obtained by making the imaging spot interval in the main scanning direction uniform.

  Further, the scanning light of the polygon mirror 10 is reflected as a BD light beam by the reflecting mirror surface 8c of the aperture stop member 8, and intersects the optical path of the scanning light E1 and E2 between the polygon mirror 10 and the first imaging lens 21. In this way, it is folded back toward the BD sensor 28/29. As a result, the degree of freedom of arrangement of the BD lens 9 and the BD sensors 28 and 29 is increased, and the BD lens 9 and the BD sensors 28 and 29 can be arranged in a compact manner while sufficiently securing the optical path length of the BD light flux. That is, the aperture stop member 8 can be disposed closer to the polygon mirror 10, and the image formation spot interval in the main scanning direction is made uniform, and a high quality image can be obtained.

  In addition, since the aperture portions 8a and 8b corresponding to the first and second semiconductor lasers 2 and 3 are provided in the aperture diaphragm member 8 of the same member, the distance between the apertures of the aperture portions 8a and 8b can be reduced. Thus, the aperture stop member 8 can be disposed close to the polygon mirror 10. That is, since it is possible to reduce the distance between the holes of the plurality of aperture stops, the aperture stop member 8 can be disposed closer to the polygon mirror 10, and the imaging spot interval in the main scanning direction is made uniform, A scanning optical device capable of obtaining a high-quality image can be provided.

  When the aperture is a common opening corresponding to the first and second semiconductor lasers 2 and 3, the laser light emitted from the plurality of semiconductor lasers 2 and 3 is sub-scanned in the common opening. Cross at. Therefore, if the incident angle θ (FIG. 4) in the sub-scanning direction is large, the sub-scanning interval on the deflection surface of the polygon mirror 10 is widened, and the thickness of the polygon mirror 10 is required. If the incident angle θ in the sub-scanning direction is small, the distance between the first and second semiconductor lasers 2 and 3 in the sub-scanning direction is widened, so that the incident optical path length becomes long. Therefore, in order to provide a compact scanning optical device by reducing the thickness of the polygon mirror 10, the aperture portions 8a and 8b corresponding to the semiconductor lasers 2 and 3 are provided in the aperture stop member 8 of the same member. Becomes important.

(2-2) Second incident optical systems 15 to 18
Similarly to the first and second semiconductor lasers 12 and 13, the third and fourth semiconductor lasers 12 and 13 are semiconductor lasers (multi-beams) each having two light emitting points in one casing (package). Laser). In the present embodiment, the third semiconductor laser 12 is a light source that scans and exposes the drum 82c of the image forming unit M, and the fourth semiconductor laser 13 is a light source that scans and exposes the drum 82d of the image forming unit Y.

  The two semiconductor lasers 12 and 13 are press-fitted and held in the two lens barrel holding portions 11a and 11b provided in the second laser holder 11 as shown in FIG. 4B. The second laser holder 11 is the same component as the first laser holder 1.

  Reference numeral 14 denotes an electric circuit board mounted on the laser holder 11, which is electrically connected to the third and fourth semiconductor lasers 12 and 13, and is provided with a laser driving circuit.

  The lens barrel holders 11a and 11b are provided with their optical axes inclined so that the optical paths of the third and fourth semiconductor lasers 12 and 13 intersect each other with a predetermined angle θ in the sub-scanning direction. A part of the outer shape is integrated.

  At the tips of the lens barrel holding portions 11a and 11b, there are bonded portions of collimator lenses 15 and 16 as a first optical system for converting the light beams emitted from the third and fourth semiconductor lasers 12 and 13 into substantially parallel light beams. 11e and 11f are provided at two locations in the main scanning direction. The collimator lenses 15 and 16 are adjusted to the irradiation position and focus in the same manner as the collimator lenses 5 and 6 on the first incident optical system side described above (FIG. 5), and are fixedly bonded to the bonding portions 11e and 11f. Is done.

  The positioning and adjustment of the second laser holder 11 with respect to the optical case 40 are performed in the same manner as the first laser holder 1 described above (FIG. 8).

  For this reason, fine adjustment of the pitch P between the two light emitting points 12a, 12b and 13a, 13b of the third and fourth semiconductor lasers 12, 13 can be simultaneously performed. Thereby, the positional relationship between the semiconductor lasers 12 and 13 and the optical components stored in the optical case 40 can be assured with high accuracy.

  Reference numeral 17 denotes a cylindrical lens as a second optical system having a predetermined refractive power only in the sub-scanning direction. The lens 17 forms the light beam emitted from the third and fourth semiconductor lasers 12 and 13 on the deflection surface of the polygon mirror 10 as a substantially linear image (a linear image extending in the main scanning direction). Lens portions 17a and 17b corresponding to the emitted light beams of both semiconductor lasers are integrally formed.

  Reference numeral 18 denotes a second aperture stop member, which is disposed between the cylindrical lens 17 as the second optical system and the polygon mirror 10. As shown in FIG. 10, the aperture stop member 18 is provided with stop portions 18a and 18b corresponding to the third and fourth semiconductor lasers 12 and 13, so that the light beams emitted from the respective semiconductor lasers 12 and 13 are transmitted in a desired manner. It is molded into an optimal beam shape.

  In FIG. 3, reference numerals 38 and 39 denote BD sensors which are synchronization detection means corresponding to the semiconductor lasers 12 and 13, respectively, by detecting the light beam reflected by the polygon mirror 10 and outputting a synchronization signal in the main scanning direction. The timing of the scanning start position at the edge of the image is adjusted. Reference numeral 19 denotes a BD lens, which focuses the light beam reflected by the polygon mirror 10 on the light receiving surfaces of the BD sensors 38 and 39 described above.

  Since the BD sensors 38 and 39 are provided on the side opposite to the incident optical system with respect to the polygon mirror 10, the BD light beam LBD directed toward the BD sensors 38 and 39 is not kicked by the aperture stop member 18 and a sufficient amount of light is supplied to the BD. The light can enter the sensors 38 and 39. For this reason, the aperture stop member 18 can be disposed in the vicinity of the polygon mirror 10.

(2-3) Polygon mirror 10 and first and second imaging means The polygon mirror 10 which is a rotating polygon mirror is rotated at a constant speed by a motor (not shown). A light beam incident from the first and second semiconductor lasers 2 and 3 through the first incident optical systems 5 to 8 and a second incident optical system 15 from the third and fourth semiconductor lasers 12 and 13 are provided. The light beam incident through ˜18 is deflected and scanned in both directions with the rotation axis 10a of the polygon mirror 10 interposed therebetween.

The first imaging means 21 to 26 corresponding to the first incident optical systems 5 to 8 and the second incident optical systems 15 to 18 are disposed on one side with respect to the polygon mirror 10 and on the opposite side to 180 °. Second imaging means 31 to 36 corresponding to the above are disposed. The first image forming means 21 to 26 and the second image forming means 31 to 36 are image forming means for forming an image of the light beams deflected and scanned by the polygon mirror 10 on different photoconductors.

  Then, the light beam emitted from the first semiconductor laser 2 and deflected and scanned by the polygon mirror 10 is scanned into the drum 82a of the image forming unit Bk by the imaging means 21, 22, and 24 as shown in FIG. Imaged as E1.

  The light beam emitted from the second semiconductor laser 3 and deflected and scanned by the polygon mirror 10 is imaged on the drum 82b of the image forming unit C as the scanning light E2 by the imaging means 21, 25, 23, and 26. .

  The light beam emitted from the third semiconductor laser 12 and deflected and scanned by the polygon mirror 10 is imaged as scanning light E3 on the drum 82c of the image forming unit M by the imaging means 31, 35, 33, and 36. .

  The light beam emitted from the fourth semiconductor laser 13 and deflected and scanned by the polygon mirror 10 is imaged as scanning light E4 on the drum 82d of the image forming unit Y by the imaging means 31, 32, and 34.

  In the first image forming means 21 to 26, reference numeral 21 denotes a first image forming lens, which is an fθ lens for performing constant-speed scanning of laser light and spot image formation on the drum together with the second image forming lenses 22 and 23. . The first imaging lens 21 is composed of a cylinder lens because the light beams emitted from the first and second semiconductor lasers 2 and 3 are incident at different angles. This range 21 includes a second imaging lens 22 arranged for the light flux of the first semiconductor laser 2 and a second imaging lens 23 arranged for the light flux of the semiconductor laser 3 in the sub-scanning direction. Make an image. Reference numerals 24 to 26 denote folding mirrors that reflect the light beam in a predetermined direction, and reference numeral 24 denotes a final folding mirror arranged with respect to the light beam of the first semiconductor laser 2. Reference numeral 25 denotes a separation folding mirror disposed with respect to the light flux of the second semiconductor laser 3. Reference numeral 26 denotes a final folding mirror arranged with respect to the light flux of the second semiconductor laser 3. As described above, the separation folding mirror 25 and the final folding mirror 26 reflect the light flux of the second semiconductor laser 3 a plurality of times, so that the same light flux as that of the first semiconductor laser 2 can be used by effectively utilizing a small space. Can be optical path length.

  The second imaging means 31 to 36 are the same as the first imaging means 21 to 26, and the first imaging lenses 31 and 2 corresponding to the third and fourth semiconductor lasers 12 and 13 are used. Imaging lenses 32 and 33. Further, the final folding mirror 34 disposed with respect to the light flux of the fourth semiconductor laser 13, the separation folding mirror 35 disposed with respect to the light flux of the third semiconductor laser 12, and the light flux of the third semiconductor laser 12. A final folding mirror 36 arranged with respect thereto is arranged. In this way, the separation folding mirror 35 and the final folding mirror 36 reflect the light flux of the third semiconductor laser 12 a plurality of times, so that the same light flux as that of the fourth semiconductor laser 13 can be used by effectively utilizing a small space. Can be optical path length. For this reason, it is possible to make the scanning optical device 50 compact.

  Reference numeral 41 (FIG. 2) denotes an upper lid that is attached to the optical case 40 to seal the scanning optical device 50 and prevent entry of dust, toner, and the like into the scanning optical device 50. The upper lid 41 is provided with slit-like openings at positions corresponding to the respective drums 82a, 82b, 82c, and 82d, and dust-proof glasses 43a, 43b, 43c, and 43d, which are transparent members, are attached thereto. Therefore, it is possible to expose the scanning lights E1, E2, E3, and E4 to the drums 82a, 82b, 82c, and 82d through the dust-proof glasses 43a, 43b, 43c, and 43d, and dust in the scanning optical device 50. And toner can be prevented from entering.

(2-4) Scanning Exposure to Each Drum Next, the light beams emitted from the first to fourth semiconductor lasers 2, 3, 12, and 13 are scanned onto the corresponding drums 82a, 82b, 82c, and 82d. The flow until exposure is performed as E1, E2, E3, and E4 will be described.

  The light beams emitted from the first and second semiconductor lasers 2 and 3 are converted into substantially parallel light beams by the collimator lenses 6 and 7 and enter the lens portions 8 a and 8 b of the cylindrical lens 8. The light beam incident on the cylindrical lens 8 is transmitted as it is in the main scanning section, and converges in the sub-scanning section and forms an almost linear image on the same surface of the polygon mirror 10. At this time, the light is incident obliquely with an angle θ (FIG. 4) in the sub-scanning direction. The aperture portions 8a and 8b of the aperture stop member 8 limit the size of the beam cross-section of the light beams emitted from the first and second semiconductor lasers 2 and 3, thereby forming a desired optimum beam shape. Yes.

  The light beams emitted from the first and second semiconductor lasers 2 and 3 are reflected at an angle θ in the sub-scanning direction while being deflected and scanned as the polygon mirror 10 rotates. The light beam reflected from the polygon mirror 10 is reflected by the reflecting mirror surface 8c of the aperture stop member 8 and intersects the optical path of the scanning lights E1 and E2 between the polygon mirror 10 and the first imaging lens 21 so as to cross the BD lens 9. Is received by the BD sensors 28 and 29.

  The BD sensor 28 detects all the light beams of the multi-beams respectively emitted from the first semiconductor laser 2 and outputs a synchronization signal, and the image ends of the light-emitting points 2a and 2b of the multi-beams by the first semiconductor laser 2 are detected. The timing of the scanning start position in the unit is adjusted.

  The BD sensor 29 detects all the light beams of the multi-beams respectively emitted from the second semiconductor laser 3 and outputs a synchronization signal, and the image ends of the light emission points 3a and 3b of the multi-beams by the second semiconductor laser 3 are detected. The timing of the scanning start position in the unit is adjusted.

  The light beams emitted from the first and second semiconductor lasers 2 and 3 with the timing adjusted pass through the first imaging lens 21 while being deflected and scanned by the polygon mirror 10.

  Thereafter, the light beam emitted from the first semiconductor laser 2 passes through the second imaging lens 22, is reflected by the final folding mirror 24, passes through the dust-proof glass 43a, and passes through the drum 82a of the image forming unit Bk. The scanning light E1 is exposed.

  On the other hand, the light beam emitted from the second semiconductor laser 3 is reflected downward by the separation folding mirror 25, then passes through the second imaging lens 23 and is reflected by the final folding mirror 26. Then, the light passes through the dust-proof glass 43b and is exposed on the drum 82b of the image forming unit C as multi-beam scanning light E2.

  Here, the multi-beam scanning lights E1 and E2 are used to adjust the pitch between the light-emitting points 2a and 2b and 3a and 3b of the multi-beams by the first and second semiconductor lasers 2 and 3, respectively. This is possible by rotating. As a result, each of the two laser beams can be scanned on the drums 82a and 82b with a substantially predetermined interval in the sub-scanning direction. Further, since the aperture stop member 8 is disposed in the vicinity of the polygon mirror 10, the multi-beam emission points 2a, 2b and 3a, 3b of the first and second semiconductor lasers 2, 3 are connected in the main scanning direction. The image spot interval can be made uniform.

  The light beams emitted from the third and fourth semiconductor lasers 12 and 13 are converted into substantially parallel light beams by the collimator lenses 15 and 16 and are incident on the lens portions 17 a and 17 b of the cylindrical lens 17. The light beam incident on the cylindrical lens 17 is transmitted as it is in the main scanning section, converges in the sub-scanning section, and forms an almost linear image on the same surface of the polygon mirror 10. At this time, the light is incident obliquely with an angle θ (FIG. 4) in the sub-scanning direction. The aperture portions 18a and 18b of the aperture stop member 18 limit the size of the beam cross section of the light beams emitted from the third and fourth semiconductor lasers 12 and 13, thereby forming a desired optimum beam shape. .

  The light beams emitted from the third and fourth semiconductor lasers 12 and 13 are reflected at an angle θ in the sub-scanning direction while being deflected and scanned as the polygon mirror 10 rotates. The light beam reflected from the polygon mirror 10 passes through the BD lens 19 and is received by the BD sensors 38 and 39.

  The BD sensor 38 detects all the light beams of the multi-beams respectively emitted from the third semiconductor laser 12 and outputs a synchronization signal, and the image ends of the light emission points 12a and 12b of the multi-beams by the third semiconductor laser 12 are detected. The timing of the scanning start position in the unit is adjusted.

  The BD sensor 39 detects all the light beams of the multi-beams respectively emitted from the fourth semiconductor laser 13 and outputs a synchronization signal, and the image ends of the light emission points 13a and 13b of the multi-beams by the fourth semiconductor laser 13 are output. The timing of the scanning start position in the unit is adjusted.

  The light beams emitted from the third and fourth semiconductor lasers 12 and 13 after the timing adjustment pass through the first imaging lens 31 while being deflected and scanned by the polygon mirror 10.

  Thereafter, the light beam emitted from the third semiconductor laser 12 is reflected downward by the separation folding mirror 35, then passes through the second imaging lens 33 and is reflected by the final folding mirror 36. Then, the light passes through the dust-proof glass 43c and is exposed to the drum 82c of the image forming unit M as the multi-beam scanning light E3.

  On the other hand, the light beam emitted from the fourth semiconductor laser 13 passes through the second imaging lens 32, is reflected by the final folding mirror 34, passes through the dustproof glass 43d, and passes through the dust-proof glass 43d to the drum 82d of the image forming unit Y. It is exposed as scanning light E4.

  The multi-beam scanning lights E3 and E4 rotate the second laser holder 11 to adjust the pitch between the light-emitting points 12a and 12b and 13a and 13b of the multi-beams by the third and fourth semiconductor lasers 12 and 13. This is possible. As a result, each of the two laser beams can be scanned on the drums 82c and 82d with a substantially predetermined interval in the sub-scanning direction. Further, since the aperture stop member 18 is disposed in the vicinity of the polygon mirror 10, the connection of the light emission points 12a, 12b and 13a, 13b of the multi-beams by the third and fourth semiconductor lasers 12 and 13 in the main scanning direction. The image spot interval can be made uniform.

  Scanning beams E1, E2, E3, and E4 scan the drums 82a, 82b, 82c, and 82d with two laser beams each having a substantially predetermined interval in the sub-scanning direction. The color misregistration is electrically corrected. Therefore, a high-quality image with little pitch unevenness and color misregistration can be obtained on the discharged recording material.

  As described above, a single polygon mirror 10 simultaneously deflects and scans laser beams emitted from a plurality of semiconductor lasers 2, 3, 12, and 13 and irradiates a plurality of drums 82a, 82b, 82c, and 82d. To perform exposure. Therefore, the number of parts is reduced, and the scanning optical device 50 can be reduced in cost and size.

  In addition, since the scanning light of the polygon mirror 10 is turned back toward the BD sensors 28 and 29 on the reflecting mirror surface 8c of the aperture stop member 8, the BD light beam directed toward the BD sensor is not kicked by the aperture stop member, and sufficient. The amount of light can be incident on the BD sensors 28 and 29. For this reason, the aperture stop member 8 can be disposed in the vicinity of the polygon mirror 10. At this time, the BD light beam turned back by the reflecting mirror surface 8c of the aperture stop member 8 intersects the optical path of the scanning lights E1 and E2 between the polygon mirror 10 and the first imaging lens 21. As a result, the degree of freedom of arrangement of the BD lens 9 and the BD sensors 28 and 29 is increased, and the BD lens 9 and the BD sensors 28 and 29 can be arranged in a compact manner while sufficiently securing the optical path length of the BD light flux. The aperture stop member 8 can be disposed closer to the polygon mirror 10. For this reason, it is possible to provide a scanning optical device in which the imaging spot interval in the main scanning direction is made uniform and a high-quality image can be obtained.

  From the above, the color printer 100 can be reduced in cost and size, and the image quality can be improved.

  Here, as shown in FIG. 11, the laser beams emitted from the plurality of semiconductor lasers 2 and 3 are separated by X at the deflection point of the polygon mirror 10 and intersected in the sub-scanning direction after the deflection scanning. Thereby, the distance between the holes of the aperture portions 8a and 8b corresponding to the respective semiconductor lasers 2 and 3 of the aperture stop member 8 can be separated.

  When the narrowed portions 8a and 8b are formed as an integral part, it is desirable that the distance between the holes of the narrowed portions 8a and 8b be about 1.5 mm or more due to processing restrictions. Therefore, as shown in FIG. 4, the aperture stop member 8 can be arranged closer to the polygon mirror 10 than the case where the laser beams emitted from the plurality of semiconductor lasers 2 and 3 intersect at the deflection point of the polygon mirror 10 in the sub-scanning direction. . Thereby, the imaging spot interval in the main scanning direction can be made more uniform. Although FIG. 11 shows the first incident optical systems 5 to 8, the same applies to the second incident optical systems 15 to 18.

  In the scanning optical device that scans the light beam on the left and right sides of the polygon mirror 10 as in the above embodiment, the aperture stop member 8 is provided with a mirror surface 8c, and the BD light beam is reflected by the mirror surface 8c. Thereby, separation from the BD light beam is performed, and the aperture stop member 8 can be brought close to the polygon mirror 10 without the BD light beam being kicked. For this reason, jitter can be reduced and high density and high accuracy can be achieved. Since the BD light beam reflected on the mirror surface 8c of the aperture stop member 8 intersects the scanning optical path between the polygon mirror 10 and the imaging lens 21 closest to the polygon mirror 10, the degree of freedom of arrangement of the BD sensors 28 and 29 increases. As a result, the optical path length of the BD light beam can be sufficiently secured and arranged compactly, and the aperture stop member 8 can be brought closer to the polygon mirror 10. For this reason, compactness and higher density and higher accuracy can be achieved.

  When the aperture stop member 18 is also provided with a reflecting mirror surface, the BD sensors 28 and 29 detect the light beams after scanning of the scanning lights E3 and E4. Since the writing position cannot be determined by detecting the light beam after scanning, the writing position for scanning on the next polygon surface is actually determined after BD detection, and the reflectance and angle error on each reflecting surface of the polygon mirror, or A position shift corresponding to a change in the rotation period of the motor driving the polygon mirror occurs, and the writing position system deteriorates. For this reason, the second incident optical systems 15 to 18 are configured to perform BD detection before scanning (writing side).

  In the present embodiment, as the scanning optical device 50, laser light emitted from a plurality of semiconductor lasers 2, 3, 12, 13 in different housings is incident on one side of the polygon mirror 10, and 4 4 The method of exposing the two drums 82 (a to d) has been described. In addition, a system in which a laser beam emitted from a semiconductor laser in one housing is incident on both sides of one polygon mirror and two drums are exposed may be used, and the embodiment does not limit the present invention.

  Further, the laser beams emitted from a plurality of semiconductor lasers in different housings are arranged so as to intersect in the sub-scanning direction, but a plurality of laser light beams are parallel to the polygon mirror 10 without intersecting in the sub-scanning direction. The structure which injects may be sufficient.

  In addition, since all the drums are multi-beams that scan two laser beams at a predetermined interval in the sub-scanning direction, a semiconductor laser having a plurality of light emitting points in one housing is held by the light source of the laser holder. Used in the department. However, for a single color that is frequently used, for example, for black, a semiconductor laser having a plurality of light emitting points in one housing is used, and when using a single color, writing is performed at high speed with a multi-beam. For the remaining colors, a semiconductor laser having one light emitting point in one housing may be used to write at a normal speed in the color mode.

Schematic configuration diagram of an example of an image forming apparatus equipped with a scanning optical device according to the present invention Partial enlarged view of FIG. The top view which shows the structure of the principal part inside a scanning optical apparatus. (A) is a sectional view of the first incident optical system, and (b) is a sectional view of the second incident optical system. Explanatory drawing about adjustment of collimator lens Partial perspective view regarding attachment of laser holder Front view of the laser holder Illustration of multi-beam pitch adjustment The perspective view of the 1st aperture stop part Perspective view of second aperture stop Sectional view of an incident optical system according to another embodiment

  1 · 11: Laser holder, 2 · 3 · 12 · 13: Semiconductor laser, 4 · 14: Electric circuit board, 5 · 6: Collimator lens (first optical system), 7 · 17: Cylindrical lens, 8 · 18: Aperture stop member, 10: polygon mirror (rotating polygon mirror), 28, 29, 38, 39: BD sensor, 40: optical case, 50: scanning optical device, 81Bk, 81C, 81M, 81Y: image forming unit, 82a 82b 82c 82d: photosensitive drum

Claims (5)

Multiple light sources;
A rotating polygon mirror that deflects and scans the light beams emitted from the plurality of light sources in both directions with a rotation axis interposed therebetween;
An optical system that forms an image of the light beam emitted from the light source on the reflecting surface of the rotary polygon mirror ;
Imaging means for imaging the light beams deflected and scanned by the rotary polygon mirror onto separate photosensitive members;
In the scanning optical device, comprising: a synchronization detection unit that detects a light beam scanned by the rotary polygon mirror and outputs a synchronization signal for synchronizing a scanning start position in the main scanning direction of each of the plurality of light beams.
Before SL is disposed between the optical science system and the rotary polygon mirror, and is disposed to span the part of the scanning line of the light beam scanned by the rotary polygon mirror, the light beam incident on the rotary polygonal mirror it has an aperture stop member having an aperture stop for regulating the aperture stop member is scanning optical apparatus characterized by having a reflecting surface for folding the light beam deflected by the rotary polygon mirror toward the synchronous detection means.   2. The scanning optical apparatus according to claim 1, wherein the light source has a plurality of light emitting points, and the light beams emitted from the light emitting points simultaneously by the rotating polygon mirror are deflected and scanned onto the same photosensitive member. .   A light beam that is turned back toward the synchronization detection unit by a reflecting surface provided on the aperture stop member is deflected and scanned by the photoconductor between the rotary polygon mirror and the imaging unit closest to the rotary polygon mirror. The scanning optical apparatus according to claim 1, wherein the scanning optical apparatus crosses an optical path.   The plurality of light sources are a plurality of light sources packaged in different housings in which emitted light beams intersect each other at a predetermined angle in the sub-scanning direction, and each of the plurality of light sources is provided on the aperture stop member. The scanning optical device according to claim 1, further comprising a plurality of aperture stops provided corresponding to the housing. In an image forming apparatus that includes a plurality of photoconductors and an exposure unit for the photoconductor and executes image formation.
5. The image forming apparatus according to claim 1, wherein the exposure unit is the scanning optical apparatus according to claim 1.