JP6198101B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus.

    As an image forming apparatus such as a copying machine, a printer, or a facsimile, a latent image is formed on a latent image carrier by irradiating the latent image carrier with writing light according to image information by deflecting scanning. An image obtained by developing an image is known (for example, Patent Document 1). An optical scanning device described in Patent Document 1 includes a first light source, a second light source arranged in a sub-scanning direction with respect to the first light source, a first light flux emitted from the first light source, and a second light source. And a rotary deflector for deflecting each of the emitted second light beams. The first light beam incident on the rotary deflector is deflected and scanned at a constant angular velocity, and is incident on the upper scanning lens of the two scanning lenses provided in the sub-scanning direction so as to overlap with the first latent image. Corrections are made to scan at an equal speed on the carrier. The first light beam incident on the rotary deflector is deflected and scanned at a constant angular velocity, and is incident on the lower scanning lens among the two scanning lenses provided in the sub-scanning direction so as to be the second latent image. Corrections are made to scan at an equal speed on the carrier.

  In the optical scanning device described in Patent Document 1, an upper scanning lens is stacked on a lower scanning lens and is housed in an optical housing. The optical scanning device described in Patent Document 1 having such a configuration has the following problems. That is, there is a problem that the optical characteristics such as the spot diameter are deteriorated on the first latent image carrier of the first light beam incident on the upper scanning lens arranged so as to be superimposed on the lower scanning lens.

  As a result of intensive studies by the present applicants on the cause of the above problem, the following has been found. In other words, the upper scanning lens attached to the lower scanning lens overlaps the tolerance of the scanning lens mounting portion of the optical housing with the outer tolerance of the lower scanning lens. Thus, it has been found that since the outer tolerance of the lower scanning lens is accumulated, the positional accuracy of the upper scanning lens is deteriorated, and the optical characteristics of the first light flux on the first latent image carrier are deteriorated.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical scanning device and an image forming apparatus capable of suppressing deterioration of optical characteristics on each irradiated body.

In order to achieve the above object, the invention of claim 1 is directed to a rotating deflector that optically scans a first light beam and a second light beam, and a first light beam deflected and scanned at an equiangular velocity by the rotating deflector. The first scanning lens that corrects scanning so as to scan at a constant speed on the first irradiated body, and the second light flux that has been deflected and scanned at a constant angular speed by the rotary deflector are moved at a constant speed on the second irradiated body. An optical scanning device comprising: a second scanning lens that corrects to perform scanning automatically; and an optical housing that houses the first scanning lens and the second scanning lens side by side in the rotational axis direction of the rotary deflector. The optical housing has the first scanning lens attached to the top surface and the second scanning lens on the bottom surface when the first scanning lens and the second scanning lens are viewed from a direction orthogonal to the rotational axis direction of the rotary deflector. The scanning lens is attached A scanning lens mounting portion and a deflector mounting portion to which the rotary deflector is mounted, and an end portion on the rotational deflector side of the scanning lens mounting portion is an end portion on the scanning lens side of the deflector mounting portion. It is characterized by being located on the scanning lens side .

  According to the present invention, since the first scanning lens and the second scanning lens are attached to the optical housing, the following effects can be obtained. That is, unlike the optical scanning device described in Patent Document 1 in which one scanning lens is overlapped with the other scanning lens and attached to the optical housing, the positional accuracy is deteriorated due to the outer dimension tolerance of the other scanning lens of the one scanning lens. It can be lost. Thereby, the deterioration of the optical characteristics on each irradiated body can be suppressed.

1 is a schematic diagram illustrating a main configuration of a color printer according to an embodiment. The schematic diagram which shows the layout of the optical system of a Bk-C unit. The schematic diagram which shows the layout of the incident optical system of a Bk-C unit. The schematic diagram which shows the layout of the scanning optical system of a Bk-C unit. The schematic diagram which shows the structure of the deflector seen from the rotating shaft direction of the polygon mirror. (A) is a perspective view around the deflector when the upper polygon mirror is optically scanning the surface of the photosensitive drum, and (b) is a lower polygon mirror that optically scans the surface of the photosensitive drum. FIG. The top view which shows a deflector periphery. X1-X1 sectional drawing of FIG. Sectional view around a deflector of a conventional optical scanning device The figure explaining the case where the communication port is not provided.

Hereinafter, an embodiment of a color printer as an image forming apparatus using an optical scanning device according to the present invention will be described.
FIG. 1 is a schematic diagram illustrating a main configuration of a color printer 500 according to the present embodiment.
The color printer 500 is a tandem multicolor printer that can form a full color image by superimposing four color toner images of black, cyan, magenta, and yellow. The color printer 500 includes an optical scanning device 100 and four photosensitive drums 501, 502, 503, and 504. In addition, four cleaning units 605Y, 605M, 605C, and 605Bk and four charging devices 602Y, 602M, 602C, and 602Bk are provided. Further, four developing devices 604Y, 604M, 604C, and 604Bk including developing rollers 603Y, 603M, 603C, and 603Bk are also provided. Further, an intermediate transfer belt 606 that is an intermediate transfer member, a secondary transfer roller 613, a fixing device 610, a paper feed roller 608, a pair of registration rollers 609, a paper discharge roller 612, a paper discharge tray 611, and the like are also provided.

  The photosensitive drum 501, the cleaning unit 605Y, the charging device 602Y, the developing roller 603Y, and the developing device 604Y constitute an image station (hereinafter referred to as “Y station”) that forms a yellow image. The photosensitive drum 502, the cleaning unit 605M, the charging device 602M, the developing roller 603M, and the developing device 604M constitute an image station (hereinafter referred to as “M station”) that forms a magenta image. The photosensitive drum 503, the cleaning unit 605C, the charging device 602C, the developing roller 603C, and the developing device 604C constitute an image station (hereinafter referred to as “C station”) that forms a cyan image. The photosensitive drum 504, the cleaning unit 605Bk, the charging device 602Bk, the developing roller 603Bk, and the developing device 604Bk constitute an image station (hereinafter referred to as “K station”) that forms a black image.

  Each of the photosensitive drums 501, 502, 503, and 504 has a photosensitive layer on its peripheral surface, and is driven to rotate in the direction of the arrow in FIG. 1 by a rotating mechanism (not shown). Each charging device 602Y, 602M, 602C, 602Bk uniformly charges the surface of the corresponding photosensitive drum 501, 502, 503, 504.

  The optical scanning apparatus 100 exposes and scans the yellow photosensitive drum 501 and the magenta photosensitive drum 502 by exposure, and the cyan photosensitive drum 503 and the black photosensitive drum 504 by exposure scanning Bk-C. It consists of unit 100B. The optical scanning device 100 irradiates scanning light with lighting control based on image information using the corresponding photosensitive drum surface as a scanning surface, and forms an electrostatic latent image on the photosensitive drum surface. The electrostatic latent image formed here is conveyed to the developing area facing the developing roller of the developing devices 604Y, 604M, 604C, and 604Bk as the photosensitive drums 501, 502, 503, and 504 rotate.

  Each developing device 604Y, 604M, 604C, 604Bk is provided with a developing roller for carrying charged toner. A predetermined developing bias is applied to the developing roller, and the toner on the developing roller adheres to the electrostatic latent image on the photosensitive drum by the action of the developing electric field formed thereby. As a result, an image (hereinafter referred to as “toner image”) with toner attached thereto is formed on the photosensitive drums 501, 502, 503, and 504.

  The toner image formed in this way is conveyed to a primary transfer region facing the intermediate transfer belt 606 as the photosensitive drums 501, 502, 503, and 504 rotate. The yellow, magenta, cyan, and black toner images on the photosensitive drums 501, 502, 503, and 504 are sequentially primarily transferred onto the intermediate transfer belt 606 at the timing of overlapping each other. As a result, a multicolor image is formed on the intermediate transfer belt 606. Each of the cleaning units 605Y, 605M, 605C, and 605Bk removes transfer residual toner that remains without being transferred to the surface of the corresponding photosensitive drum 501, 502, 503, or 504.

  On the other hand, the recording paper 510 as a recording material is conveyed to the registration roller pair 609 one by one by the paper feeding roller 608. The registration roller pair 609 sends the recording paper 510 to the secondary transfer area where the intermediate transfer belt 606 and the secondary transfer roller 613 face each other at a predetermined timing. In this secondary transfer area, the multicolor toner image on the intermediate transfer belt 606 is secondarily transferred to the recording paper 510. The recording paper 510 on which the multicolor toner image is transferred is then sent to the fixing device 610. The fixing device 610 fixes the toner image on the recording paper 510 to the recording paper with heat and pressure. The fixed recording paper 510 is discharged onto a paper discharge tray 611 via a paper discharge roller 612.

FIG. 2 is a schematic diagram showing the layout of the optical system of the Bk-C unit 100B, and FIG. 3 is a schematic diagram showing the layout of the incident optical system of the Bk-C unit 100B.
The incident optical system is converted into circularly polarized light by a light source 1 that emits laser light with linearly polarized light, a quarter wavelength plate 2 that converts laser light emitted from the light source 1 into circularly polarized light, and a quarter wavelength plate 2. A collimating lens 3 for converting the laser light into parallel light. Further, an ND filter 4 as a light amount changing element for adjusting the light amount, and a polarization beam splitter (PBS) 5 for dividing the circularly polarized laser light into S-polarized light and P-polarized light and splitting it into two optical paths are provided. ing. In addition, quarter wavelength plates 6a and 6b are provided for converting the polarization characteristics of the laser beams L1 and L2 split into two into linearly polarized light and circularly polarized light. Cylindrical lenses 7 a and 7 b are also provided for imaging the laser beams L 1 and L 2 converted into circularly polarized light on the mirror surfaces of the two polygon mirrors 10 a and 10 b mounted on the deflector 10. The cylindrical lenses 7a and 7b have a function of condensing the laser light converted into circularly polarized light only in the sub-scanning direction.

  The laser beams L1 and L2 formed in a predetermined laser profile by such an incident optical system are imaged on the mirror surfaces of the polygon mirrors 10a and 10b of the deflector 10, respectively. The deflector 10 stably drives the polygon mirrors 10a and 10b integrally at a predetermined rotation number around a rotation axis parallel to the sub-scanning direction. When the laser beams L1 and L2 are incident on the mirror surfaces of the polygon mirrors 10a and 10b rotating in this way, the laser beams L1 and L2 are scanned in the main scanning direction as shown in FIG.

FIG. 4 is a schematic diagram showing the layout of the scanning optical system of the Bk-C unit 100B.
The scanning optical system includes fθ lenses 11a and 11b that change the equiangular motion of the laser light scanned by the polygon mirrors 10a and 10b into a constant linear motion, and a first mirror that guides the laser light to the photosensitive member as the scanning object. 12a, 12b and second mirrors 14a, 14b. Further, long lenses 13a and 13b for correcting the surface tilt of the polygon mirrors 10a and 10b, and dustproof glasses 15a and 15b for preventing the entry of dust and the like into the optical housing are provided.

  The laser beam L1 scanned on the mirror surface of the upper polygon mirror 10a passes through the fθ lens 11a, the first mirror 12a, the long lens 13a, and the second mirror 14a, passes through the dust-proof glass 15a, and the surface of the photosensitive drum 504. At a constant speed. The laser beam L2 scanned on the mirror surface of the lower polygon mirror 10b passes through the fθ lens 11b, the first mirror 12b, the long lens 13b, and the second mirror 14a, passes through the dust-proof glass 15a, and passes through the photosensitive drum 503. Is scanned at a constant speed on the surface.

  Further, as shown in FIG. 2, the Bk-C unit 100B includes a synchronization sensor 17 for determining the main scanning writing timing, and a synchronization cylindrical lens 16 for condensing the laser light on the synchronization sensor 17 with high accuracy. It has.

  The incident optical system, scanning optical system, synchronization sensor 17, and synchronization cylindrical lens 16 are mounted on the optical housing 20a of the Bk-C unit 100B, and characteristics as an optical scanning device are ensured.

  The laser light scanned by the deflector 10 passes through the fθ lenses 11 a and 11 b, is collected by the synchronization cylindrical lens 16, and then enters the synchronization sensor 17. When the synchronization sensor 17 detects the light beam, a synchronization signal is output. Then, the laser light based on the image data is output from the light source 1 in synchronization, and the laser light based on the image data is scanned on the photosensitive drums 503 and 504 via the scanning optical system. As a result, a latent image is formed on the photosensitive drums 503 and 504.

  The laser light L0 emitted from the light source 1 is converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 2. Thus, when the laser beam L0 having the circular polarization characteristic reaches the polarization separation surface of the polarization beam splitter 5 shown in FIG. 11, the polarization component of the circular polarization and the rotation axis direction of the polygon mirrors 10a and 10b Only the orthogonal component (s-polarized component) is transmitted through the polarization separation surface. Then, the laser beam L2 having only the s-polarized component goes to the lower polygon mirror 10b. On the other hand, of the circularly polarized light components, a component parallel to the rotation axis direction of the polygon mirrors 10a and 10b (p-polarized light component) is reflected by the polarization separation surface. Since the laser light incident on the polarization separation surface is circularly polarized, the ratio of the s-polarized component to the p-polarized component is 1: 1. Thereafter, the laser beam L1 having only the p-polarized component is reflected by the reflecting surface of the polarization beam splitter 5 and travels toward the upper polygon mirror 10a. At this point, the two separated laser beams L1 and L2 have different polarization characteristics, but after that, the laser beams L1 and L2 are again transmitted by the quarter-wave plates 6a and 6b. Converted to circularly polarized light.

FIG. 5 is a schematic diagram showing the configuration of the deflector 10 as seen from the rotation axis direction of the polygon mirrors 10a and 10b.
In the deflector 10, the two polygon mirrors 10a and 10b have an integral shape and are assembled on the motor substrate 10C. Each of the polygon mirrors 10a and 10b has four mirror surfaces, and the mirror surface of the upper polygon mirror 10a and the mirror surface of the lower polygon mirror 10b are arranged so as to be shifted by an angle θ in the rotation direction. In the present embodiment, θ = 45 °.

  As shown in FIG. 6A, when the laser beam L1 scans the surface of the photosensitive drum 504 with the upper polygon mirror 10a, the laser beam L2 scans the surface of the light shielding member 18 with the lower polygon mirror 10b. To do. As shown in FIG. 6B, when the laser beam L2 scans the surface of the photosensitive drum 503 with the lower polygon mirror 10b, the laser beam L1 is applied to the surface of the light shielding member 18 with the upper polygon mirror 10a. Scan.

FIG. 7 is a plan view showing the periphery of the deflector, and FIG. 8 is a cross-sectional view taken along the line X1-X1 of FIG.
In the following description, for the sake of convenience, the rotation axis direction of the polygon mirrors 10a and 10b will be described as the Z direction, the longitudinal direction of the fθ lenses 11a and 11b as the Y direction, and the direction orthogonal to both will be described as the X direction.
As shown in FIGS. 7 and 8, the optical housing includes a deflector mounting portion 21 to which the deflector 10 is mounted and a scanning lens mounting surface portion 22 to which the fθ lenses 11a and 11b are mounted. As shown in FIG. 7, the scanning lens mounting surface portion 22 has a plate shape orthogonal to the Z direction.

  As shown in FIG. 8, the first fθ lens 11a on which the upper laser beam L1 as the first light beam is incident is attached to the upper surface of the scanning lens attachment surface portion 22 of the optical housing 20a. The second fθ lens 11 b on which the lower laser beam L 2 that is the second light beam is incident is attached to the lower surface of the scanning lens attachment surface portion 22. The second fθ lens 11b is mounted directly below the first fθ lens 11a with the scanning lens mounting surface portion 21 interposed therebetween.

  Cylindrical lenses 7 a and 7 b are also attached to the scanning lens attachment surface portion 22. The first cylindrical lens 7 a on which the upper laser beam L 1 is incident is attached to the upper surface of the scanning lens attachment surface portion 22. Further, the second cylindrical lens 7 b on which the lower laser beam L <b> 2 is incident is attached to the lower surface of the scanning lens attachment surface portion 22. Further, the second cylindrical lens 7b is attached directly below the first f cylindrical lens with the scanning lens attachment surface portion 21 interposed therebetween.

  As shown in FIG. 8, the center position in the Z-axis direction of the scanning lens mounting surface 22 is configured to be the same height as the intermediate position A between the upper polygon mirror 10a and the lower polygon mirror 10b.

FIG. 9 is a cross-sectional view around the deflector 10 of the conventional optical scanning device.
As shown in FIG. 9, in the conventional optical scanning device, the second fθ lens 11b is attached to the upper surface of the scanning lens attachment surface portion 22, and the first fθ lens 11a is overlaid and fixed on the second fθ lens 11b. With this configuration, the outer dimension tolerance in the Z direction of the second fθ lens 11b is accumulated on the first fθ lens 11a in the Z direction of the scanning lens mounting surface portion 22. For this reason, the upper stage laser beam L1 does not pass through the center B in the Z direction of the first fθ lens 11a but passes through the upper side in the figure from the center B. As a result, in some cases, the upper laser beam L1 may pass outside the effective range in which the predetermined optical characteristics of the first fθ lens 11a are obtained. As a result, optical scanning with desired optical characteristics cannot be performed on the photosensitive drum 504 on which the upper laser beam L1 optically scans, and an abnormal image such as density unevenness may occur.

  It has also been conventionally known that the upper laser beam L1 and the lower laser beam are converted into equal speeds with a single fθ lens having two thicknesses. However, in this case, a thick lens forming technique is required, and it is extremely difficult to provide uniform optical characteristics in the scanning direction. As a result, the internal refractive index is different between the upper optical path and the lower optical path, and there is a problem that the beam spot diameter is different between the photosensitive drum 503 and the photosensitive drum 504. Further, the transmittance is also different between the upper optical path and the lower optical path, and there is a problem that the light amount is different between the photosensitive drum 503 and the photosensitive drum 504.

  On the other hand, in the present embodiment, as shown in FIG. 8, the only factor that deteriorates the positional accuracy of the fθ lenses 11 a and 11 b in the Z direction is the tolerance in the Z direction of the scanning lens mounting surface portion 22. As a result, both the first fθ lens 11a and the second fθ lens 11b can be accurately attached in the Z direction. As a result, both the upper laser beam L1 and the lower laser beam L2 can pass through the effective range of the fθ lens, and both the photosensitive drums 503 and 504 can perform optical scanning with desired optical characteristics. Thereby, both the photosensitive drums 503 and 504 can form a good latent image.

  Further, as shown in FIG. 9, the first cylindrical lens 7a is attached so as to overlap the second cylindrical lens 7b. For this reason, the positional accuracy in the Z direction of the first cylindrical lens 7a is deteriorated, and there is a possibility that the first laser light L1 cannot be focused on a desired position of the upper polygon mirror 10a. However, in the present embodiment, as shown in FIG. 8, each cylindrical lens 7a, 7b is attached to the scanning lens attachment surface portion 22, and therefore, the deterioration factor of the Z-direction position accuracy of each cylindrical lens 7a, 7b is caused by scanning. Only the lens mounting surface portion 22 is provided. Therefore, both the first and second cylindrical lenses 7a and 7b can focus the laser beams L1 and L2 on desired positions of the polygon mirrors 10a and 10b. Thereby, both the photosensitive drums 503 and 504 can form a good latent image.

  In the present embodiment, as shown in FIG. 8, the center position in the Z-axis direction of the scanning lens mounting surface portion 22 is the same as the intermediate position A between the upper polygon mirror 10a and the lower polygon mirror 10b and the same height in the Z-axis direction. It has become. Thus, the same first fθ lens 11a and second fθ lens 11b can be used. That is, when the center position in the Z-axis direction of the scanning lens mounting surface portion 22 is not the same height as the intermediate position A between the upper polygon mirror 10a and the lower polygon mirror 10b and the Z-axis direction, the laser beams L1 and L2 are fθ lenses. In order to transmit the central portion of 11a in the Z direction, it is necessary to change the length of each fθ lens in the Z direction. On the other hand, by setting the center position in the Z-axis direction of the scanning lens mounting surface portion 22 to the same position as the intermediate position A between the upper polygon mirror 10a and the lower polygon mirror 10b and the Z-axis direction, each laser beam can be obtained with the same fθ lens. L1 and L2 can be transmitted through the central portion of the fθ lens in the Z direction. Since the same fθ lens can be used in this way, component management costs and the like can be reduced, and an inexpensive optical scanning device can be provided. Further, the same first cylindrical lens 7a and second cylindrical lens 7b can be used. Thereby, component management cost etc. can further be reduced and an inexpensive optical scanning device can be provided.

  Further, since the deflector 10 rotates at a high speed, the bearing portion 10d of the deflector 10 generates heat due to friction with the rotation shaft. Further, when the deflector 10 is driven, the motor substrate 10C generates heat due to the current flowing through the motor substrate 10C.

  In the conventional configuration shown in FIG. 9, the air heated by the bearing 10d and the motor substrate 10C rises in the optical housing 20a, and the temperature of the upper side of the optical housing becomes higher than that of the lower side. Therefore, as shown in FIG. 9, when the fθ lenses 11a and 11b are provided so as to overlap each other, the temperature of the upper first fθ lens 11a becomes higher than that of the lower second fθ lens 11b. As a result, the upper first fθ lens 11a differs from the lower second fθ lens 11b in thermal expansion, and adverse effects such as color misregistration occur.

  Further, as shown in FIG. 10, when the scanning lens mounting portion 22 does not have the communication port 23, much of the air heated by the bearing portion 10 d and the motor substrate 10 </ b> C is directed to the lower side of the scanning lens mounting portion 2. Flows in. Accordingly, the temperature of the second fθ lens 11b becomes higher than that of the first fθ lens 11a, and the second fθ lens 11b expands more thermally than the first fθ lens 11a. As a result, adverse effects such as color misregistration may occur.

  In contrast, in the present embodiment, as shown in FIGS. 7 and 8, a communication port 23 is provided on the deflector side of the scanning lens mounting portion 22. As a result, as shown in FIG. 8, part of the air heated by the bearing portion 10 d of the deflector 10 and the motor substrate 10 </ b> C flows through the communication port 23 to the upper side of the scanning lens mounting portion 22. As a result, the temperatures of the first fθ lens 11a and the second fθ lens 11b can be made substantially the same. As a result, the thermal expansion of the fθ lenses 11a and 11b can be made substantially the same, and color misregistration can be suppressed.

  Moreover, in this embodiment, although the deflector 10 is not sealed, the same effect can be acquired by providing the said communicating port 23 also in the structure sealed with soundproof glass etc. That is, in the configuration in which the deflector 10 is sealed, heat is released from the soundproof glass. At this time, the amount of heat released from the lower side of the scanning lens mounting portion 22 provided with the motor substrate 10C and the bearing portion 10d, which are heat sources, is larger than that of the upper side. Accordingly, when the communication port 23 is not provided, the temperature on the lower side of the scanning lens mounting portion 22 is higher than that on the upper side. As a result, also in this case, if the communication port 23 is not provided, the second fθ lens 11b is thermally expanded more than the first fθ lens 11a. On the other hand, by providing the communication port 23, part of the heat released from the soundproof glass moves to the upper side through the communication port 23. Thereby, the temperature of the 1st f (theta) lens 11a and the 2nd f (theta) lens 11b can be made substantially the same. As a result, the thermal expansion of the fθ lenses 11a and 11b can be made substantially the same, and color misregistration can be suppressed.

  In the above description, the embodiment in which the present invention is applied to the optical scanning device that optically scans the photosensitive drums 503 and 504 with one light source has been described. However, the present invention can also be applied to an optical scanning device in which two light sources are provided, one of the light sources scans the photosensitive drum 503, and the other light source scans the photosensitive drum 504.

What has been described above is an example, and the present invention has a specific effect for each of the following aspects.
(Aspect 1)
A rotary deflector such as a deflector 10 that optically scans the first light flux and the second light flux, and a first light flux that is deflected and scanned at an equiangular velocity by the rotary deflector is irradiated on a first subject such as a photosensitive drum 504. A first scanning lens such as a first fθ lens 11a that is corrected so as to scan at a constant speed on the body, and a second light beam that is deflected and scanned at a constant angular speed by a rotary deflector are applied to a second object such as a photosensitive drum 503. An optical housing that houses a second scanning lens such as the first fθ lens 11b that corrects scanning so as to scan at an equal speed on the irradiation body, and the first scanning lens and the second scanning lens side by side in the direction of the rotation axis of the rotary deflector. In the optical scanning device 100 including 20a, the first scanning lens and the second scanning lens are attached to the optical housing 20a.
By providing such a configuration, as described in the embodiment, the first scanning lens such as the first fθ lens 11a and the second scanning lens such as the second fθ lens 11b are attached in a stacked manner to the conventional configuration shown in FIG. In comparison, it is possible to suppress the deterioration of the optical characteristics on each irradiated body.

(Aspect 2)
In the aspect 1, the optical housing 20a is a first scanning lens such as the first fθ lens 11a and a second scanning lens such as the second fθ lens 11b viewed from a direction orthogonal to the rotation axis direction of the rotary deflector such as the deflector 10. In some cases, the first scanning lens is attached to the upper surface and the scanning lens attaching portion 22 is attached to the lower surface on the second scanning lens.
With this configuration, the first scanning lens such as the first fθ lens 11a and the second scanning lens such as the second fθ lens 11b can be attached to the optical housing with a simple configuration.

(Aspect 3)
In the aspect 2, the space on the first scanning lens mounting side and the second scanning lens between the rotary deflector such as the deflector 10 and the first and second scanning lenses such as the first and second fθ lenses 11a and 11b. The optical housing 20a is provided with a communication portion 23 that communicates with the space on the mounting side.
With this configuration, as described in the embodiment, the temperature of the first scanning lens such as the first fθ lens 11a and the temperature of the second scanning lens such as the second fθ lens 11b can be made substantially the same. it can. As a result, the thermal expansion of each scanning lens can be made substantially the same, and color misregistration can be suppressed.

(Aspect 4)
In (Aspect 2) or (Aspect 3), the rotating deflector such as the deflector 10 rotates with the first rotating polygon mirror such as the upper polygon mirror 10a that deflects and scans the first light beam, and the first rotating polygon mirror. A second rotating polygon mirror such as a lower polygon mirror that is arranged side by side in the direction of the rotation axis of the deflector and deflects and scans the second light beam, and scans when viewed from a direction orthogonal to the direction of the rotation axis of the rotation deflector. The center position of the lens mounting portion 22 is set to the same height as the intermediate position between the first rotating polygon mirror and the second rotating polygon mirror.
With this configuration, as described in the embodiment, the first scanning lens such as the first fθ lens 11a and the second scanning lens such as the second fθ lens 11b can be made the same scanning lens.

(Aspect 5)
In addition, the optical scanning device scans the photosensitive member with scanning light according to the image information to form a latent image on the photosensitive member, and finally the image obtained by developing the latent image is transferred onto the recording material. In the image forming apparatus for forming an image on the recording material, any one of (Aspect 1) to (Aspect 4) is used as the optical scanning device.
With such a configuration, a high-quality image can be formed.

7a: first cylindrical lens 7b: second cylindrical lens 10: deflector 10a: upper polygon mirror 10b: lower polygon mirror 10c: motor substrate 10d bearing 11a: first fθ lens 11b: second fθ lens 20a: optical housing 21: deflection Device mounting portion 22: Scanning lens mounting portion 23: Communication port 100: Optical scanning device 501, 502, 503, 504: Photosensitive drum L1: Upper laser beam L2: Lower laser beam

Japanese Patent No. 4675709

Claims (3)

A rotary deflector that optically scans the first light flux and the second light flux;
A first scanning lens that corrects the first light beam deflected and scanned at a constant angular velocity by the rotary deflector so as to scan at a constant velocity on the first irradiated body;
A second scanning lens that corrects the second luminous flux deflected and scanned at a constant angular velocity by the rotary deflector so as to scan at a constant velocity on the second irradiated body;
An optical scanning device comprising: an optical housing that houses the first scanning lens and the second scanning lens side by side in a rotational axis direction of the rotary deflector;
The optical housing has the first scanning lens attached to the top surface and the second scanning lens on the bottom surface when the first scanning lens and the second scanning lens are viewed from a direction orthogonal to the rotational axis direction of the rotary deflector. A scanning lens mounting portion to which a scanning lens is mounted; and a deflector mounting portion to which the rotary deflector is mounted;
An optical scanning device characterized in that an end of the scanning lens mounting portion on the rotary deflector side is positioned closer to a scanning lens than an end of the deflector mounting portion on the scanning lens side . The optical scanning device according to claim 1 .
The rotary deflector is arranged side by side in a rotation axis direction of the first rotary polygon mirror that deflects and scans the first light beam, and the first rotary polygon mirror and the rotary deflector, and deflects and scans the second light beam. A two-turn polygon mirror,
When viewed from a direction orthogonal to the rotation axis direction of the rotary deflector, the center position of the scanning lens mounting portion is the same height as the intermediate position between the first rotary polygon mirror and the second rotary polygon mirror. An optical scanning device characterized by that. The photosensitive member is scanned with scanning light according to the image information to form a latent image on the photosensitive member, and the latent image is developed to finally transfer the image onto the recording material. In an image forming apparatus for forming an image on the recording material,
An image forming apparatus using the optical scanning device according to claim 1 or 2 as the optical scanning device.

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