JP7404103B2 - Optical scanning device and image forming device - Google Patents

Description

Embodiments of the present invention relate to an optical scanning device and an image forming device.

An electrophotographic image forming apparatus forms an electrostatic latent image on an image plane by scanning a beam. Such an image forming apparatus includes an optical scanning device that scans a beam. The optical scanning device includes a photodetector that detects the beam for synchronization. In order to properly make the beam incident on the photodetector, it is necessary to correct the optical path of the beam and give it a predetermined focusing characteristic. However, there are restrictions on the arrangement of lenses for this purpose, which leads to an increase in the size of the optical scanning device and the image forming device.

Japanese Patent Application Publication No. 2004-280056

A problem to be solved by the embodiments of the present invention is to provide an optical scanning device and an image forming device that can be made smaller than conventional ones.

The optical scanning device of the embodiment includes a first light source, a second light source, a deflector, a first imaging element, a second imaging element, a third imaging element, a first optical surface, and a second optical surface. The optical surface includes an optical surface, a third optical surface, a fourth optical surface, and a light detection section. The first light source emits a first light beam. The second light source emits a second light beam having an opening angle with respect to the first light beam in the main scanning direction. The deflector deflects the first light beam and the second light beam in a second direction different from the first direction and the first direction at positions shifted in the sub-scanning direction on the same surface. The first imaging element imparts predetermined optical characteristics to the first light beam and the second light beam deflected in the first direction and the second direction. The second imaging element guides the first light beam deflected in the first direction onto the surface to be scanned. The third imaging element guides the second light beam deflected in the first direction onto the scanned surface. The first optical surface converges the first light beam deflected in the second direction. The second optical surface converges the second light beam deflected in the second direction. The third optical surface guides the first light beam deflected in the second direction to the photodetector. A fourth optical surface that is not parallel to the third optical surface guides the second light beam deflected in the second direction to the photodetector. The photodetector detects the incident first light beam and the second light beam.

1 is a diagram illustrating an example of a schematic configuration of an image forming apparatus according to an embodiment. 2 is a diagram illustrating an example of a schematic configuration of an image forming section in FIG. 1. FIG. FIG. 2 is a block diagram showing an example of a main circuit configuration of the image forming apparatus in FIG. 1. FIG. 2 is a diagram showing an example of the optical scanning device in FIG. 1. FIG. FIG. 2 is a plan view of an example of the optical system of the optical scanning device in FIG. 1; FIG. 6 is a partially enlarged view of a main part of FIG. 5; FIG. 7 is a side view of the structure shown in FIG. 6; FIG. 6 is a side view of the optical path correction element in FIG. 5; FIG. 6 is a perspective view of the optical path correction element in FIG. 5; FIG. 6 is a diagram for explaining correction of beam optical path deviation. The figure which shows the comparative example when a conventional lens is used. 6 is a diagram showing a modification of the optical path correction element in FIG. 5. FIG. 6 is a diagram showing a modification of the optical path correction element in FIG. 5. FIG. 6 is a diagram showing a modification of the optical path correction element in FIG. 5. FIG.

An image forming apparatus according to an embodiment will be described below with reference to the drawings. Note that in each of the drawings used to describe the embodiments below, the scale of each part may be changed as appropriate. Further, each drawing used in the description of the embodiments below may omit the configuration for the sake of explanation.

FIG. 1 is a diagram illustrating an example of a schematic configuration of an image forming apparatus 100 according to an embodiment.
The image forming apparatus 100 is a device with a printing function, such as an MFP (multifunction peripheral), a copy machine, a printer, or a facsimile. However, in the following explanation, it is assumed that the image forming apparatus 100 is an MFP. The image forming apparatus 100 includes, for example, a printing function, a scanning function, a copying function, an erasing function, a facsimile function, and the like. The printing function is a function of forming an image on the image forming medium P using a recording material such as toner. The image forming medium P is, for example, a sheet of paper. The scan function is a function of reading an image from a document on which an image is formed. The copy function is a function that prints an image read from a document or the like using a scan function onto an image forming medium P using a print function. The decoloring function is a function to decolor an image formed on the image forming medium P using a decolorable recording material. Image forming apparatus 100 includes, for example, a printer 101, a scanner 102, and an operation panel 103.

The printer 101 is a device that has a printing function. The printer 101 includes, for example, a paper feed tray 111, a manual feed tray 112, a paper feed roller 113, a toner cartridge 114, an image forming section 115, an optical scanning device 116, a transfer belt 117, a secondary transfer roller 118, a fixing section 119, and a double-sided It includes a unit 120 and a paper discharge tray 121.

The paper feed tray 111 accommodates an image forming medium P used for printing.
The manual feed tray 112 is a stand for manually feeding the image forming medium P.
The paper feed roller 113 is rotated by the action of a motor to carry out the image forming medium P accommodated in the paper feed tray 111 or the manual feed tray 112 from the paper feed tray 111 or the manual feed tray 112.

The toner cartridge 114 stores recording materials such as toner to be supplied to the image forming section 115. Image forming apparatus 100 includes a plurality of toner cartridges 114. For example, as shown in FIG. 1, the image forming apparatus 100 includes four toner cartridges 114: a toner cartridge 114C, a toner cartridge 114M, a toner cartridge 114Y, and a toner cartridge 114K. The toner cartridge 114C, toner cartridge 114M, toner cartridge 114Y, and toner cartridge 114K each store recording materials corresponding to each color of CMYK (cyan, magenta, yellow, and key). That is, the toner cartridge 114C stores cyan (C) recording material. The toner cartridge 114M stores magenta (M) recording material. The toner cartridge 114Y stores yellow (Y) recording material. The toner cartridge 114K stores black (K) recording material. Note that the colors of the recording materials stored in the toner cartridge 114 are not limited to CMYK, but may be other colors. Further, the recording material stored in the toner cartridge 114 may be a special recording material. For example, the toner cartridge 114 stores a color erasable recording material that disappears and becomes invisible at a temperature higher than a predetermined temperature.

Image forming apparatus 100 includes a plurality of image forming sections 115. For example, as shown in FIG. 1, the image forming apparatus 100 includes four image forming sections 115: an image forming section 115C, an image forming section 115M, an image forming section 115Y, and an image forming section 115K. The image forming section 115C, the image forming section 115M, the image forming section 115Y, and the image forming section 115K each form an image using recording materials corresponding to each color of CMYK. That is, the image forming unit 115C forms a cyan image. The image forming unit 115M forms a magenta image. The image forming unit 115Y forms a yellow image. The image forming unit 115K forms a black image.

The image forming unit 115 will be further explained using FIG. 2. FIG. 2 is a schematic diagram showing an example of a schematic configuration of the image forming section 115. The image forming section 115 includes, for example, a photosensitive drum 1151, a charging unit 1152, a developing unit 1153, a primary transfer roller 1154, a cleaner 1155, and a static elimination lamp 1156.

The photosensitive drum 1151 is hit by the beam B irradiated from the optical scanning device 116 . As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 1151.
The charging unit 1152 charges the surface of the photoreceptor drum 1151 with a predetermined positive charge.

The developing unit 1153 uses the recording material D supplied from the toner cartridge 114 to develop the electrostatic latent image on the surface of the photoreceptor drum 1151. As a result, an image is formed on the surface of the photoreceptor drum 1151 using the recording material D.

The primary transfer roller 1154 is arranged at a position facing the photosensitive drum 1151 with the transfer belt 117 in between. The primary transfer roller 1154 generates a transfer voltage between it and the photoreceptor drum 1151. Thereby, the primary transfer roller 1154 transfers the image formed on the surface of the photoreceptor drum 1151 onto the transfer belt 117 that is in contact with the photoreceptor drum 1151 (primary transfer).

The cleaner 1155 removes the recording material D remaining on the surface of the photoreceptor drum 1151.
The charge removal lamp 1156 removes the charge remaining on the surface of the photoreceptor drum 1151.

The optical scanning device 116 is also called an LSU (laser scanning unit). The optical scanning device 116 controls the beam B according to the input image data under the control of the processor 141 to form an electrostatic latent image on the surface of the photoreceptor drum 1151 of each image forming section 115. The image data input here is, for example, image data read from a document or the like by the scanner 102. Alternatively, the image data input here is image data transmitted from another device or the like and received by the image forming apparatus 100.

Note that the beam B that the optical scanning device 116 irradiates on the image forming section 115Y is referred to as beam BY, the beam B that irradiates the image forming section 115M as beam BM, the beam B that irradiates the image forming section 115C as beam BC, and the beam B that irradiates the image forming section 115K. The beam B that is irradiated to the area is referred to as beam BK. Therefore, the optical scanning device 116 controls the beam BY according to the Y (yellow) component of the image data. The optical scanning device 116 controls the beam BM according to the M (magenta) component of the image data. The optical scanning device 116 controls the beam BC according to the C (cyan) component of the image data. The optical scanning device 116 controls the beam BK according to the K (key) component of the image data. The optical scanning device 116 will be further described later.

The transfer belt 117 is, for example, an endless belt, and is rotatable by the action of rollers. The transfer belt 117 rotates to convey images transferred from each image forming unit 115 to the position of the secondary transfer roller 108 .

The secondary transfer roller 108 includes two rollers facing each other. The secondary transfer roller 108 transfers the image formed on the transfer belt 117 onto the image forming medium P that passes between the secondary transfer rollers 108 (secondary transfer).

The fixing unit 119 applies heat and pressure to the image forming medium P onto which the image has been transferred. As a result, the image transferred onto the image forming medium P is fixed. The fixing unit 119 includes a heating unit 1191 and a pressure roller 1192 that face each other.

The heating unit 1191 is, for example, a roller equipped with a heat source for heating the heating unit 1191. The heat source is, for example, a heater. The roller heated by the heat source heats the image forming medium P.
Alternatively, the heating section 1191 may include an endless belt suspended between a plurality of rollers. For example, the heating unit 1191 includes a plate-shaped heat source, an endless belt, a belt conveyance roller, a tension roller, and a press roller. The endless belt is, for example, a film-like member. A belt conveyance roller drives an endless belt. Tension rollers provide tension to the endless belt. The press roller has an elastic layer formed on its surface. The heat generating portion side of the plate-shaped heat source contacts the inner side of the endless belt and is pressed toward the press roller, thereby forming a fixing nip of a predetermined width between the plate-shaped heat source and the press roller. Because the plate-shaped heat source heats the device while forming a nip region, the responsiveness during energization is higher than in the case of a heating method using a halogen lamp.

The pressure roller 1192 presses the image forming medium P passing between the pressure roller 1192 and the heating section 1191.

The duplex unit 120 puts the image forming medium P into a state where printing is possible on the back side. For example, the duplex unit 120 reverses the image forming medium P by switching back the image forming medium P using a roller or the like.
The paper ejection tray 121 is a platform on which the image forming medium P after printing is ejected.

The scanner 102 is a device with a scanning function. The scanner 102 is an optical reduction type scanner that includes an imaging element such as a CCD (charge-coupled device) image sensor. Alternatively, the scanner 102 is of a contact image sensor (CIS) type that includes an image sensor such as a complementary metal-oxide-semiconductor (CMOS) image sensor. Alternatively, the scanner 102 may be of any other known type. A scanner 102 reads an image from a document or the like. The scanner 102 includes a reading module 131 and a document feeder 132.

The reading module 131 converts the incident light into a digital signal using an image sensor. Thereby, the reading module 131 reads an image from the front surface of the document.

The document feeder 132 is also called, for example, an ADF (auto document feeder). The document feeder 132 sequentially conveys documents placed on a document tray. The image of the conveyed document is read by the scanner 102. Further, the document feeding device 132 may include a scanner for reading an image from the back side of the document. Note that the surface on which the image is read by the scanner 102 is the front surface.

The operation panel 103 includes a man-machine interface for inputting and outputting between the image forming apparatus 100 and an operator of the image forming apparatus 100. The operation panel 103 includes, for example, a touch panel 1031 and an input device 1032.

The touch panel 1031 is a stack of a display such as a liquid crystal display or an organic EL display, and a pointing device for touch input. The display included in the touch panel 1031 functions as a display device that displays a screen for notifying the operator of the image forming apparatus 100 of various information. Furthermore, the touch panel 1031 functions as an input device that receives touch operations by the operator.

Input device 1032 accepts operations by the operator of image forming apparatus 100 . Input device 1032 is, for example, a keyboard, keypad, touch pad, or the like.

Next, the main circuit configuration of the image forming apparatus 100 will be described using FIG. 3. FIG. 3 is a block diagram showing an example of the main circuit configuration of the image forming apparatus 100. The image forming apparatus 100 includes, for example, a processor 141, a ROM (read-only memory) 122, a RAM (random-access memory) 123, an auxiliary storage device 144, a communication interface 145, a printer 101, a scanner 102, and an operation panel 103. . A bus 146 or the like connects these parts.

The processor 141 corresponds to a central part of a computer that performs processing such as computation and control necessary for the operation of the image forming apparatus 100. The processor 141 controls each unit to realize various functions of the image forming apparatus 100 based on programs such as system software, application software, and firmware stored in the ROM 142 or the auxiliary storage device 144. Note that part or all of the program may be incorporated into the circuit of the processor 141. The processor 141 is, for example, a CPU (central processing unit), an MPU (micro processing unit), an SoC (system on a chip), a DSP (digital signal processor), a GPU (graphics processing unit), an ASIC (application specific integrated circuit), These include a PLD (programmable logic device) or an FPGA (field-programmable gate array). Alternatively, processor 141 is a combination of more than one of these.

The ROM 142 corresponds to the main storage of a computer in which the processor 141 is the core. The ROM 142 is a nonvolatile memory used exclusively for reading data. The ROM 142 stores, for example, firmware among the above programs. Further, the ROM 142 stores data or various setting values used by the processor 141 to perform various processes.

The RAM 143 corresponds to the main storage of a computer in which the processor 141 is the core. The RAM 143 is a memory used for reading and writing data. The RAM 143 is used as a so-called work area for storing data temporarily used by the processor 141 in performing various processes. The RAM 143 is, for example, a volatile memory.

The auxiliary storage device 144 corresponds to an auxiliary storage device of a computer in which the processor 141 is the core. The auxiliary storage device 144 is, for example, an EEPROM (electric erasable programmable read-only memory), an HDD (hard disk drive), or a flash memory. The auxiliary storage device 144 stores, for example, system software and application software among the above programs. Further, the auxiliary storage device 144 stores data used by the processor 141 to perform various processes, data generated by processing by the processor 141, various setting values, and the like. Note that the image forming apparatus 100 may include an interface into which a storage medium such as a memory card or a USB (universal serial bus) memory can be inserted as the auxiliary storage device 144. The interface reads and writes information to the storage medium.

Communication interface 145 is an interface through which image forming apparatus 100 communicates via a network or the like.

The bus 146 includes a control bus, an address bus, a data bus, and the like, and transmits signals exchanged between each part of the image forming apparatus 100.

The optical scanning device 116 will be further explained below using FIGS. 4 to 7 and the like. FIG. 4 is a diagram showing an example of the optical scanning device 116. FIG. 5 is a plan view of an example of the optical system of the optical scanning device 116. FIG. 6 is a partially enlarged view of the main part of FIG. 5. FIG. 7 is a side view of the structure of FIG. 6. The optical scanning device 116 includes, for example, a polygon mirror 151, a motor 152, a light source 153, and a plurality of optical elements.

The polygon mirror 151 is a regular polygonal columnar mirror (deflector) in which each side is a reflective surface 1511 that reflects laser. The polygon mirror 151 shown in FIGS. 4 to 7 is, for example, a regular heptagonal prism-shaped mirror having seven side surfaces (reflecting surfaces 1511). The reflective surface 1511 of the polygon mirror 151 is continuous along the rotation direction CCW of the polygon mirror 151 (counterclockwise direction in FIG. 5), and constitutes the outer peripheral surface of the polygon mirror 151. The polygon mirror 151 is rotatable about a rotation axis parallel to each reflective surface 1511. Further, the rotation axis of the polygon mirror 151 is orthogonal to the rotation axis of each photoreceptor drum 1151. It is assumed that the paper surface of FIG. 6 is a plane perpendicular to the rotation axis of the polygon mirror 151.

The motor 152 rotates the polygon mirror 151 in the rotation direction CCW at a predetermined speed. For example, the rotation axis of the motor 152 and the rotation axis of the polygon mirror 151 are coaxial. However, the rotation axis of the motor 152 and the rotation axis of the polygon mirror 151 do not have to be coaxial.

The light source 153 emits a beam B such as a laser beam. The light source 153 includes, for example, a plurality of laser diodes. That is, beam B is a multi-beam consisting of beams emitted from a plurality of laser diodes. Note that the plurality of laser diodes have a distance in the main scanning direction. Therefore, each beam included in beam B also has a distance in the main scanning direction. The optical scanning device 116 includes, for example, four light sources 153: a light source 153C, a light source 153M, a light source 153Y, and a light source 153K. For example, the light source 153Y emits the beam BY corresponding to the Y component, the light source 153M emits the beam BM corresponding to the M component, the light source 153C emits the beam BC corresponding to the C component, and the light source 153K emits the beam BC corresponding to the K component. A corresponding beam BK is emitted.

The optical scanning device 116 irradiates each beam B onto the surface of each photoreceptor drum 1151 through an optical path formed by a predetermined scanning optical system provided for each beam B. The scanning optical system includes multiple optical elements. For example, as shown in FIGS. 4 and 5, the optical scanning device 116 has two beams B as one set, and one set of scanning optical systems is arranged on the left and right sides of the polygon mirror 151. In other words, as shown in FIGS. 4 and 5, the optical scanning device 116 includes two scanning optical systems 161 and 161, each including a plurality of optical elements on both sides (left and right sides in the figure) of a single polygon mirror 151. It has a scanning optical system 162. Note that the polygon mirror 151 is included in each of the scanning optical system 161 and the scanning optical system 162. That is, the polygon mirrors 151 included in each of the scanning optical system 161 and the scanning optical system 162 are the same polygon mirror 151.

The scanning optical system 161 on the left side of the figure includes a scanning optical system that scans the beam BY and a scanning optical system that scans the beam BM. The scanning optical system 161 reflects the beam BY emitted from the light source 153Y and the beam BM emitted from the light source 153M on the same reflective surface 1511 of the polygon mirror 151 rotating in the rotational direction CCW. Thereby, the beam BY and the beam BM are deflected in the main scanning direction along the rotation direction CCW, and scan the surfaces of the two photoreceptor drums 1151Y and 1151M, respectively. The scanning optical system 161 includes a polygon mirror 151, a light source 153Y, a light source 153M, a pre-deflection optical system 170Y, a pre-deflection optical system 170M, and a post-deflection optical system 180YM. Note that the pre-deflection optical system 170Y is an optical system for beam BY. Further, the pre-deflection optical system 170M is an optical system for the beam BM. Furthermore, the post-deflection optical system 180YM is an optical system for beam BY and beam BM.
Note that, as an example, one of the beams BY and the beam BM is an example of a first luminous flux, and the other is an example of a second luminous flux. Further, the light source 133Y or the light source 133M that emits the first light beam is a first light source. The light source 133Y or the light source 133M that emits the second light beam is a second light source.

Note that here, the direction in which each beam B is deflected (scanned) by the polygon mirror 151 serving as a deflector (the circumferential direction of the polygon mirror 151) is defined as a "main scanning direction." Further, a direction perpendicular to the main scanning direction and perpendicular to the optical axis direction of the beam B is defined as a "sub-scanning direction" of the beam B. In FIGS. 5 and 6, the rotation axis direction of the polygon mirror 151 is the sub-scanning direction. In FIGS. 5 and 6, the direction perpendicular to the rotation axis direction of the polygon mirror 151 and perpendicular to the optical axis direction of the beam B is the main scanning direction of the beam B.

The scanning optical system 162 on the right side of the figure includes a scanning optical system that scans the beam BC and a scanning optical system that scans the beam BK. The scanning optical system 162 reflects the beam BC emitted from the light source 153C and the BK emitted from the light source 153K on the same reflecting surface 1511 of the polygon mirror 151 rotating in the rotational direction CCW. Thereby, the beam BC and the beam BK are deflected in the main scanning direction along the rotational direction CCW, and scan the surfaces of the two photoreceptor drums 1151C and 1151K, respectively. The scanning optical system 162 includes a polygon mirror 151, a light source 153C, a light source 153K, a pre-deflection optical system 170C, a pre-deflection optical system 170K, and a post-deflection optical system 180CK. Note that the pre-deflection optical system 170C is an optical system for the beam BC. Further, the pre-deflection optical system 170K is an optical system for beam BK. Furthermore, the post-deflection optical system 180CK is an optical system for beam BC and beam BK.
Note that, as an example, one of the beams BC and the beam BK is an example of a first luminous flux, and the other is an example of a second luminous flux. Further, the light source 133C or the light source 133K that emits the first light beam is a first light source. The light source 133C or the light source 133K that emits the second light beam is a second light source.

Here, the polygon mirror 151, the light source 153, and the pre-deflection optical system 170 will be further explained using the scanning optical system 161 on the left side of the figure as an example. The polygon mirror 151 rotates while reflecting two beams B, the beam BY emitted from the light source 153Y and the beam BM emitted from the light source 153M, on the same reflective surface 1511. Thereby, the reflected beam B is deflected and scans a range including the surface of the photoreceptor drum and the scanning position AA. Among these directions, the direction in which the beam B incident on the surface of the photoreceptor drum is deflected is the first direction. Further, the direction in which the beam B incident on the scanning position AA is deflected is the second direction. In addition, the beam B deflected by the polygon mirror 151 moves along two image planes arranged at predetermined positions, that is, the surfaces of the corresponding photoreceptor drum 1151Y and photoreceptor drum 1151M at a predetermined linear velocity in the main scanning direction ( scanning in the direction of the rotation axis of the photoreceptor drum 1151). At this time, the image forming apparatus 100 rotates the photoreceptor drum 1151Y and the photoreceptor drum 1151M in the sub-scanning direction. As a result, an electrostatic latent image corresponding to the Y component is formed on the surface of the photoreceptor drum 1151Y. Further, an electrostatic latent image corresponding to the M component is formed on the surface of the photoreceptor drum 1151M.

As shown in FIGS. 5 and 6, the light source 153Y and the light source 153M of the scanning optical system 161 are arranged at different angular positions when viewed from the front side of the paper. In other words, the two light sources 153Y and 153M are arranged such that the directions in which the beams BY and BM enter the reflective surface 1511 have an opening angle θ. In other words, the two light sources 153Y and 153M are arranged such that the beams BY and BM have an opening angle θ in the main scanning direction. As a result, the beam BY and the beam BM are incident on the reflective surface 1511 of the polygon mirror 151 at angles θ different from each other. Further, of the two light sources 153, the light source 153Y is located upstream of the light source 153M along the rotation direction CCW of the polygon mirror 151. On the other hand, the light source 153M is located downstream from the light source 153Y along the rotation direction CCW. Further, the light source 153M and the light source 153Y are arranged such that their emission surfaces face the reflective surface 1511 of the polygon mirror 151. Therefore, beam BY and beam BM are incident on polygon mirror 151 without being reflected by the mirror.

Further, as shown in FIG. 7, the two light sources 153Y and 153M are located at slightly shifted positions in the sub-scanning direction. For example, light source 153M is located higher than light source 153Y. When this is seen in FIGS. 5 and 6, the light source 153M is located closer to the front of the paper than the light source 153Y. Further, the optical axes (light beam traveling direction) of the pre-deflection optical system 170Y and the pre-deflection optical system 170M are orthogonal to the rotation axis 131b of the polygon mirror 151. Therefore, the beams BY and BM emitted from the light sources 153Y and 153M are incident on the same reflecting surface 1511 at positions slightly shifted in the sub-scanning direction.

The scanning optical system 161 includes pre-deflection optical systems 170 on each optical path between the light source 153 and the polygon mirror 151. That is, the scanning optical system 161 includes two pre-deflection optical systems 170, a pre-deflection optical system 170Y and a pre-deflection optical system 170M. The pre-deflection optical system 170Y is arranged on the optical path between the light source 153Y and the polygon mirror 151. The pre-deflection optical system 170M is arranged on the optical path between the light source 153M and the polygon mirror 151. Each pre-deflection optical system 170 includes a collimator lens 171, an aperture 172, and a cylinder lens 173. The pre-deflection optical system 170Y includes a collimator lens 171Y, an aperture 172Y, and a cylinder lens 173Y. Further, the pre-deflection optical system 170M includes a collimator lens 171M, an aperture 172M, and a cylinder lens 173M. Note that the collimator lens 171Y and the collimator lens 171M are the collimator lenses 171. Further, the aperture 172Y and the aperture 172M are the aperture 172. The cylinder lens 173Y and the cylinder lens 173M are the cylinder lenses 173.

The collimator lens 171 gives a predetermined convergence to the beam B emitted from the light source 153. Collimator lens 171 converts beam B into parallel light.

The aperture 172 shapes the beam B that has passed through the collimator lens 171 in the main scanning and sub-scanning directions. For example, the aperture 172 shapes the width of the beam B in the main scanning direction and the sub-scanning direction to a predetermined width.

The cylinder lens 173 provides a predetermined convergence in the sub-scanning direction to the beam B that has passed through the aperture 172. As a result, the width of the beam B that has passed through the cylinder lens 173 in the sub-scanning direction becomes narrower as it approaches the reflective surface 1511. Therefore, the plurality of beams B can be incident on the same reflecting surface 1511 at positions shifted in the sub-scanning direction so as not to overlap.

Furthermore, the polygon mirror 151, light source 153, and pre-deflection optical system 170 of the scanning optical system 162 on the right side of the figure will also be explained. The polygon mirror 151 rotates while reflecting two beams B, the beam BC emitted from the light source 153C and the beam BK emitted from the light source 153K, on the same reflective surface 1511. As a result, the reflected beam B is deflected and scans a range including the surface of the photoreceptor drum and the scanning position AB. Among these directions, the direction in which the beam B incident on the surface of the photoreceptor drum is deflected is the first direction. Furthermore, the direction in which the beam B incident on the scanning position AB is deflected is the second direction. Furthermore, the beam B deflected by the polygon mirror 151 moves along the surfaces of two image planes disposed at predetermined positions, that is, the surfaces of the corresponding photoreceptor drums 1151C and 1151K, at a predetermined linear velocity in the main scanning direction ( scanning in the direction of the rotation axis of the photoreceptor drum 1151). At this time, the image forming apparatus 100 rotates the photoreceptor drum 1151C and the photoreceptor drum 1151K in the sub-scanning direction. As a result, an electrostatic latent image corresponding to the C component is formed on the surface of the photoreceptor drum 1151C. Further, an electrostatic latent image corresponding to the K component is formed on the surface of the photoreceptor drum 1151K.

The two light sources 153C and 153K of the scanning optical system 162 are arranged at different angular positions when viewed from the front side of the paper in FIGS. 5 and 6, similarly to the light sources 153Y and 153M of the scanning optical system 161 described above. . That is, the two light sources 153C and 153K are arranged so that the directions in which the beams BC and BK enter the reflective surface 1511 have an opening angle θ. In other words, the two light sources 153C and 153K are arranged such that beam BC and beam BK have an opening angle θ in the main scanning direction. As a result, the beam BC and the beam BK are incident on the reflective surface 1511 of the polygon mirror 151 at angles θ different from each other. Further, of the two light sources, the light source 153C is located downstream of the light source 153K along the rotation direction CCW of the polygon mirror 151. On the other hand, the light source 153K is located upstream of the light source 153C along the rotation direction CCW. Further, the light source 153C and the light source 153K are arranged such that their emission surfaces face the reflective surface 1511 of the polygon mirror 151. Therefore, beam BC and beam BK are incident on polygon mirror 151 without being reflected by the mirror.

Further, the light source 153C and the light source 153K are located at slightly shifted positions in the sub-scanning direction. For example, the light source 153C is located at a higher position than the light source 153K. Therefore, the beams BC and BK emitted from the light sources 153C and 153K are incident on the same reflecting surface 1511 at positions slightly shifted in the sub-scanning direction.

The scanning optical system 162 includes pre-deflection optical systems 170 on each optical path between the light source 153 and the polygon mirror 151. That is, the scanning optical system 162 includes two pre-deflection optical systems 170: a pre-deflection optical system 170C and a pre-deflection optical system 170K. The pre-deflection optical system 170C is arranged on the optical path between the light source 153C and the polygon mirror 151. The pre-deflection optical system 170K is arranged on the optical path between the light source 153K and the polygon mirror 151. The pre-deflection optical system 170C includes a collimator lens 171C, an aperture 172C, and a cylinder lens 173C. Further, the pre-deflection optical system 170K includes a collimator lens 171K, an aperture 172K, and a cylinder lens 173K. Note that the collimator lens 171C and the collimator lens 171K are the collimator lenses 171. Further, the diaphragm 172C and the diaphragm 172K are the diaphragm 172. The cylinder lens 173C and the cylinder lens 173K are cylinder lenses 173. As described above, the scanning optical system 162 includes the same components as the scanning optical system 161.

Next, the post-deflection optical system 180 will be explained. The post-deflection optical system 180 guides the beam B reflected by the reflective surface 1511 to the surface of the photoreceptor drum 1151. The optical scanning device 116 includes two post-deflection optical systems 180: a post-deflection optical system 180YM and a post-deflection optical system 180CK. The post-deflection optical system 180 includes an fθ lens 181, an fθ lens 182, a photodetector 183, a folding mirror 184, an optical path correction element 185, and a folding mirror 186 to a folding mirror 188.

The fθ lens 181 and the fθ lens 182 are a pair of imaging lenses that optimize the shape and position of the beam B deflected (scanned) by the polygon mirror 151 on the image plane.
One fθ lens 181 on the upstream side near the polygon mirror 151 is provided for one post-deflection optical system 180. That is, the fθ lens 181 is on the optical path of a set of two beams B. Then, one set of two beams B passes through the same fθ lens 181. For example, the fθ lens 181YM is located at a certain position on the optical path of the beam BY and on the optical path of the beam BM. Then, the beam BY and the beam BM pass through the fθ lens 181YM.
Note that the fθ lens 181 is an example of a first imaging element that provides predetermined optical characteristics to the first light beam and the second light beam.

In FIG. 5, one fθ lens 182 on the downstream side near the photosensitive drum 1151 is shown for each post-deflection optical system 180. However, as shown in FIG. 6, one fθ lens 182 is independently provided in the optical path of each beam B. The fθ lens 182YM shown in FIG. 5 is a combination of the fθ lens 182Y and the fθ lens 182M shown in FIG. 6. The fθ lens 182CK shown in FIG. 5 is a combination of the fθ lens 182C and the fθ lens 182K shown in FIG. 6. Note that the fθ lens 182Y, the fθ lens 182M, the fθ lens 182C, and the fθ lens 182K are the fθ lenses 182. Each beam B passes through an fθ lens 182 on its respective optical path. The fθ lenses 182 are each located near a third cover glass 193, which will be described later.
Note that one of the fθ lenses 182Y and the fθ lens 182M is a second imaging element that guides the first light flux onto the scanned surface, and the other is a third imaging element that guides the second light flux onto the scanned surface. It is a child. Furthermore, one of the fθ lens 182C and the fθ lens 182K is a second imaging element, and the other is a third imaging element.

The photodetector 183 is located upstream of the scanning start portion of beam B (scanning position AA and scanning position AB). Note that the beam B is reflected by the folding mirror 184 and folded back. However, in FIG. 5, in order to make it easier to understand that the scan position AA and the scan position AB are upstream of the scan start part, the beam B is also shown with a broken line without being folded back. Further, in FIG. 5, the photodetector 183 and the optical path correction element 185, on which the beam B drawn without being folded is incident, are also shown with broken lines. A photodetector 183 is provided to align the horizontal synchronization of beam B. Note that the beam B incident on the photodetector 183 passes through the fθ lens 181 but does not pass through the fθ lens 182. The optical scanning device 116 includes one photodetector 183 for one post-deflection optical system 180. The post-deflection optical system 180YM includes a photodetector 183YM. The post-deflection optical system 180CK includes a photodetector 183CK. Photodetector 183YM detects incident beam BY and beam BM. Photodetector 183CK detects incident beam BC and beam BK. Photodetector 183 is an example of a photodetector.

The folding mirror 184 is on the optical path from the fθ lens 181 to the photodetector 183. The folding mirror 184 reflects the beam B and returns it toward the photodetector 183. However, in FIG. 5, the optical path of the beam B, the photodetector 183, the folding mirror 184, and the optical path correction element 185 on the optical path are shown expanded on a plane. The optical scanning device 116 includes, for example, one folding mirror 184 for one post-deflection optical system 180. The post-deflection optical system 180YM includes a folding mirror 184YM. The post-deflection optical system 180CK includes a folding mirror 184CK. The folding mirror 184YM reflects the beam BY and the beam BM. A folding mirror 184 reflects beam BC and beam BK.

The optical path correction element 185 is a lens located on the optical path between the folding mirror 184 and the photodetector 183. The optical path correction element 185 guides the beam B reflected by the folding mirror 184 onto the detection surface of the photodetector 183. Therefore, both the beam BY and the beam BM are reflected by the polygon mirror 151, pass through the fθ lens 181YM, the folding mirror 184YM, and the optical path correction element 185YM, and enter the photodetector 183YM. That is, after being reflected by the polygon mirror 151, the beam BY and the beam BM pass through a common optical element (lens and mirror) and enter a common photodetector 183YM. In addition, both the beam BC and the beam BK are reflected by the polygon mirror 151, and then pass through the fθ lens 181CK, the folding mirror 184CK, and the optical path correction element 185CK, and enter the photodetector 183CK. That is, after being reflected by the polygon mirror 151, the beam BY and the beam BM pass through a common optical element (lens and mirror) and enter a common photodetector 183CK. In this way, by using a common optical element for the plurality of beams B, the number of optical elements can be reduced.
The optical scanning device 116 includes one optical path correction element 185 for one post-deflection optical system 180. The post-deflection optical system 180YM includes an optical path correction element 185YM. The post-deflection optical system 180CK includes an optical path correction element 185CK. Optical path correction element 185YM guides beam BY and beam BM onto the detection surface of photodetector 183YM. Optical path correction element 185 guides beam BC and beam BK onto the detection surface of photodetector 183CK.

The folding mirrors 186 to 188 are a plurality of mirrors that reflect the beam B that has passed through the fθ lens 181 and thereby fold it back toward the surface of each photoreceptor drum 1151. The optical scanning device 116 includes two folding mirrors 186, a folding mirror 186YM and a folding mirror 186CK. The optical scanning device 116 includes four folding mirrors 187: a folding mirror 187Y, a folding mirror 187M, a folding mirror 187C, and a folding mirror 187K. The optical scanning device 116 includes two folding mirrors 188, a folding mirror 188Y and a folding mirror 188K. Note that in FIG. 5, the folding mirrors 186 to 188 are not illustrated.

The optical scanning device 116 also includes a first cover glass 191, a second cover glass, and a third cover glass 193.

The first cover glass 191 is located between the pre-deflection optical system 170 and the polygon mirror 151. The second cover glass 192 is between the polygon mirror 151 and the post-deflection optical system 180. The first cover glass 191 and the second cover glass 192 are provided to prevent wind noise when the polygon mirror 151 rotates. The first cover glass 191 prevents the wind noise from leaking from the entrance of the beam B. The second cover glass 192 prevents the wind noise from leaking from the exit of the beam B.

The third cover glass 193 is between the fθ lens 182 and the photosensitive drum 1151. The third cover glass 193 covers the exit from which the beam B exits in the housing of the optical scanning device 116 .

Note that, as described above, in the optical scanning device 116, the scanning optical system 161 and the scanning optical system 162 are arranged on the left and right sides with the polygon mirror 151 in the center. Therefore, in the optical scanning device 116, when the polygon mirror 151 is rotated in a certain direction, the scanning direction of the photosensitive drum 1151 by the scanning optical system 161 and the scanning direction of the photosensitive drum 1151 by the scanning optical system 162 are reversed. . Here, in FIG. 5, it is assumed that the side where the light source 153Y, light source 153M, light source 153C, and light source 153K are drawn around the polygon mirror 151 (the upper side of the paper) is the plus side, and the opposite side (the lower side of the paper) is the minus side. Assume. In this case, the scanning optical system 161 scans the image plane from the plus side indicated by arrow S to the minus side. On the other hand, the scanning optical system 162 scans the image plane from the minus side shown by arrow T to the plus side.

The optical path correction element 185 will be further explained using FIGS. 8 and 9.
FIG. 8 is a side view of the optical path correction element 185. Note that the vertical direction in FIG. 8 is the sub-scanning direction. Further, the direction perpendicular to the paper surface of FIG. 8 is the main scanning direction. FIG. 9 is a perspective view of the optical path correction element 185 in FIG. 8. Note that FIGS. 8 and 9 show the optical path correction element 185YM for the beam BY and the beam BM. The optical path correction element 185CK for beam BC and beam BK also has the same shape as the optical path correction element 185YM, so the optical path correction element 185 will be explained using the optical path correction element 185YM.

As shown in FIGS. 8 and 9, the optical path correction element 185 is, for example, a straight column whose height direction coincides with the main scanning direction. Further, the optical path correction element 185 is a straight columnar body including four side surfaces: a cylindrical surface 18511, a prism surface 18512, a cylindrical surface 18513, and a prism surface 18514. However, the shape of the optical path correction element 185 shown in FIGS. 8 and 9 is an example, and the optical path correction element 185 may have any other shape except for the portion through which the beam B passes.

The cylindrical surface 18511 has the shape of a curved surface obtained by cutting out a part of the side surface of a cylinder. That is, the cylindrical surface 18511 has a curvature in the sub-scanning direction and a curvature of 0 in the main-scanning direction. Note that other cylindrical surfaces to be described below similarly have curvature in the sub-scanning direction and zero curvature in the main-scanning direction. Therefore, a cross section of the cylindrical surface 18511 taken along a plane perpendicular to the main scanning direction is a circular arc. The cylindrical surface 18511 functions as a cylindrical lens that converges the beam BY in the sub-scanning direction. Further, FIG. 8 shows an optical axis 18515 of the cylindrical surface 18511.

Prism surface 18512 is a flat surface. That is, the prism surface 18512 has a curvature of 0 in the sub-scanning direction and a curvature in the main scanning direction. Note that the curvature in the sub-scanning direction and the curvature in the main scanning direction of other prism surfaces described below are also 0. Prism surface 18512 refracts and changes the direction of beam BY.
The beam BY enters the optical path correction element 185YM from the cylindrical surface 18511 and exits from the prism surface 18512. Thereby, the beam BY is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

The cylindrical surface 18513 has the shape of a curved surface obtained by cutting out a part of the side surface of a cylinder. That is, the cylindrical surface 18513 is a surface that has a curvature in the sub-scanning direction and a curvature of 0 in the main scanning direction. The cylindrical surface 18513 functions as a cylindrical convex lens that converges the beam BM in the sub-scanning direction. Further, FIG. 8 shows an optical axis 18516 of the cylindrical surface 18513.
Note that one of the cylindrical surfaces 18511 and 18513 is a first optical surface, and the other is a second optical surface.

Prism surface 18514 is a plane. Prism surface 18514 refracts beam BM to change its direction.
Note that one of the prism surfaces 18512 and 18514 is a third optical surface, and the other is a fourth optical surface. As described above, the optical path correction element 185 is an example of the fourth imaging element.
The beam BM enters the optical path correction element 185YM from the cylindrical surface 18513 and exits from the prism surface 18514. Thereby, the beam BM is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

The cylindrical surface 18511 and the cylindrical surface 18513 have different optical axes. Thereby, it is easy to set the focal length of the optical path correction element 185 to an appropriate value regardless of the arrangement position of the optical path correction element 185.
Further, prism surface 18512 and prism surface 18514 are not parallel. Thereby, the optical path correction element 185 can bend the beam BM and the beam BY in different directions. Therefore, the optical path correction element 185 can bend the beam BM and the beam BY in an appropriate direction regardless of the arrangement position.

As shown in FIG. 5, the optical path of the beam B that is folded back by the folding mirror 184 intersects with the optical path of the beam B that passes through the fθ lens 182, for example. Therefore, in such a case, it is not possible to arrange optical elements within the intersecting range. When there are restrictions on the arrangement of optical elements in this way, in the conventional optical element, the optical path from the folding mirror 184 to the photodetector 183 becomes long, leading to an increase in the size of the optical scanning device and the image forming device. On the other hand, if the optical path correction element 185 of the embodiment is used, the beam B can be converged with appropriate power and bent in an appropriate direction even if there are restrictions on the arrangement position. Therefore, the optical scanning device 116 and the image forming device 100 using the optical path correction element 185 of the embodiment can be made smaller than conventional ones.

Note that, in the optical path correction element 185, it is preferable that a portion including the cylindrical surface 18511 and the prism surface 18512 and a portion including the cylindrical surface 18513 and the prism surface 18514 are not separated but are integrated. Since the two parts of the optical path correction element 185 are integrated, it is possible to prevent the two parts from being misaligned or twisted.

FIG. 10 is a diagram for explaining correction of optical path deviation of beam B. In addition to the beam BM, FIG. 10 shows a beam BMb and a beam BMc. Beam BMb and beam BMc indicate beam BM when the optical path is shifted in the sub-scanning direction. As shown in FIG. 10, it can be seen that the optical path correction element 185 converges the beams BMb and BMc at the same position as the beam BM whose optical paths are not shifted, even when the optical paths are shifted. In addition to the beam BY, FIG. 10 also shows a beam BYb and a beam BYc. Beam BYb and beam BYc indicate beam BY when the optical path is shifted in the sub-scanning direction. As shown in FIG. 10, it can be seen that the optical path correction element 185 converges at the same position as the beam BY whose optical path is not shifted even when the optical path of the beam BYb and beam BYc is shifted.

FIG. 11 is a diagram showing a comparative example in which a conventional lens 200 is used in place of the optical path correction element 185YM. Lens 200 is a general cylindrical lens and includes a cylindrical surface 201 and a prism surface 202. As shown in FIG. 11, the conventional lens 200 cannot achieve both optical path correction and convergence if there are restrictions on the optical arrangement. For example, in the lens 200 of the comparative example shown in FIG. 11, the optical path can be corrected, but the convergence position of the light beam exists between the photodetector and the optical path correction element. In this case, the beam spot enters the photodetector with a large beam spot diameter, which may cause detection problems.

Other shapes of the optical path correction element 185 will be explained using FIGS. 12 to 14. 12 to 14 are plan views of modified examples of the optical path correction element 185 viewed from the side.
FIG. 12 shows an optical path correction element 1852YM as a modification of the optical path correction element 185YM. The optical path correction element 1852YM is a straight column including four side surfaces: a prism surface 18521, a cylindrical surface 18522, a prism surface 18523, and a cylindrical surface 18524.

Prism surface 18521 is a plane. Prism surface 18521 refracts and changes the direction of beam BY.

The cylindrical surface 18522 has the shape of a curved surface obtained by cutting out a part of the side surface of a cylinder. That is, the cylindrical surface 18522 is a surface that has a curvature in the sub-scanning direction and a curvature of 0 in the main scanning direction. The cylindrical surface 18522 functions as a cylindrical lens that converges the beam BY in the sub-scanning direction. Further, FIG. 12 shows an optical axis 18525 of the cylindrical surface 18522.
The beam BY enters the optical path correction element 1852YM from the prism surface 18521 and exits from the cylindrical surface 18522. Thereby, the beam BM is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

Prism surface 18523 is a plane. The prism surface 18523 refracts the beam BM to change its direction.
Note that one of the prism surfaces 18521 and 18523 is a third optical surface, and the other is a fourth optical surface.

The cylindrical surface 18524 has the shape of a curved surface obtained by cutting out a part of the side surface of a cylinder. That is, the cylindrical surface 18524 is a surface that has a curvature in the sub-scanning direction and a curvature of 0 in the main scanning direction. The cylindrical surface 18524 functions as a cylindrical lens that converges the beam BM in the sub-scanning direction. Further, FIG. 12 shows an optical axis 18526 of the cylindrical surface 18524.
Note that one of the cylindrical surfaces 18522 and 18524 is a first optical surface, and the other is a second optical surface.
The beam BM enters the optical path correction element 1852YM from the prism surface 18523 and exits from the cylindrical surface 18524. Thereby, the beam BM is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

Prism surface 18521 and prism surface 18523 are not parallel. Thereby, the optical path correction element 1852 can bend the beam BM and the beam BY in different directions. Therefore, the optical path correction element 1852 can bend the beam BM and the beam BY in an appropriate direction regardless of the arrangement position.
Further, the cylindrical surface 18522 and the cylindrical surface 18524 have different optical axes. This makes it easy to set the focal length of the optical path correction element 1852 to an appropriate value regardless of the position where the optical path correction element 1852 is placed.

FIG. 13 shows an optical path correction element 1853YM as a modification of the optical path correction element 185YM. The optical path correction element 1853YM is a straight column including three side surfaces: a cylindrical surface 18531, a prism surface 18532, and a prism surface 18533.

The cylindrical surface 18531 has the shape of a curved surface obtained by cutting out a part of the side surface of a cylinder. That is, the cylindrical surface 18531 is a surface that has a curvature in the sub-scanning direction and a curvature of 0 in the main scanning direction. The cylindrical surface 18531 functions as a cylindrical lens that converges the beam BY in the sub-scanning direction. Further, FIG. 13 shows an optical axis 18534 of the cylindrical surface 18531.
Note that the cylindrical surface 18531 is a first optical surface and a second optical surface.

Prism surface 18532 is a plane. Prism surface 18532 refracts and changes the direction of beam BY.
The beam BY enters the optical path correction element 1853YM from the cylindrical surface 18531 and exits from the prism surface 18532. Thereby, the beam BY is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

Prism surface 18533 is a plane. The prism surface 18533 refracts the beam BM to change its direction.
Note that one of the prism surfaces 18532 and 18533 is a third optical surface, and the other is a fourth optical surface.
The beam BM enters the optical path correction element 1853YM from the cylindrical surface 18531 and exits from the prism surface 18533. Thereby, the beam BM is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

Prism surface 18532 and prism surface 18533 are not parallel. Thereby, the optical path correction element 1853 can bend the beam BM and the beam BY in different directions. Therefore, the optical path correction element 1853 can bend the beam BM and the beam BY in an appropriate direction regardless of the arrangement position.

FIG. 14 shows an optical path correction element 1854YM as a modification of the optical path correction element 185YM. The optical path correction element 1854YM is a straight column including three side surfaces: a prism surface 18541, a cylindrical surface 18542, and a prism surface 18543.

Prism surface 18541 is a plane. Prism surface 18541 refracts and changes the direction of beam BY.

The cylindrical surface 18542 has the shape of a curved surface obtained by cutting out a part of the side surface of a cylinder. That is, the cylindrical surface 18542 is a surface that has a curvature in the sub-scanning direction and a curvature of 0 in the main scanning direction. The cylindrical surface 18542 functions as a cylindrical lens that converges the beam BM and the beam BY in the sub-scanning direction. Further, FIG. 14 shows an optical axis 18544 of the cylindrical surface 18542.
Note that the cylindrical surface 18542 is a first optical surface and a second optical surface.
The beam BY enters the optical path correction element 1852YM from the prism surface 18541 and exits from the cylindrical surface 18542. Thereby, the beam BY is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

Prism surface 18543 is a plane. The prism surface 18543 refracts the beam BM to change its direction.
Note that one of the prism surfaces 18541 and 18543 is a third optical surface, and the other is a fourth optical surface.
The beam BM enters the optical path correction element 1854YM from the prism surface 18543 and exits from the cylindrical surface 18542. Thereby, the beam BM is guided to the detection surface of the photodetector 183YM and converged on the detection surface.

Prism surface 18541 and prism surface 18543 are not parallel. Thereby, the optical path correction element 1854 can bend the beam BM and the beam BY in different directions. Therefore, the optical path correction element 1854 can bend the beam BM and the beam BY in an appropriate direction regardless of the arrangement position.

The above embodiment can also be modified as follows.
The optical path correction element 185 may be a lens using an aspherical surface instead of a cylindrical surface. For example, an aspherical surface α is used in place of the cylindrical surface 18511 of the optical path correction element 185 shown in FIG. 8, and an aspherical surface β is used in place of the cylindrical surface 18513. In this case, the cross section of the aspherical surface α and the aspherical surface β taken along a plane perpendicular to the main scanning direction is, for example, a parabola, a hyperbola, or an elliptical arc. Alternatively, the cross section may be a higher-order curve such as a quartic curve.
Note that, from the viewpoint of cost, it is preferable that the optical path correction element 185 uses a cylindrical surface.

The optical path correction element 185 does not need to have a curvature of 0 in the main scanning direction.

The optical scanning device of the embodiment may be realized using a plurality of optical elements having similar optical characteristics instead of one optical element in the above embodiment. Further, the optical scanning device of the embodiment may be realized using one optical element having similar optical characteristics instead of the plurality of optical elements in the above embodiment.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

100... Image forming device, 101... Printer, 115, 115C, 115K, 115M, 115Y... Image forming section, 116... Optical scanning device, 117... Transfer belt, 118... Secondary transfer roller, 119... ... Fixing unit, 151 ... Polygon mirror, 153 ... Light source, 161, 162 ... Scanning optical system, 170 ... Pre-deflection optical system, 171 ... Collimator lens, 172 ... Aperture, 173 ... Cylinder lens, 180... Post-deflection optical system, 181, 182... fθ lens, 183... Photodetector, 184, 186, 187, 188... Returning mirror, 185... Optical path correction element, 1511... Reflecting surface, 18511, 18513. ...optical axis

Claims (5)

a first light source that emits a first luminous flux;
a second light source that emits a second light beam having an opening angle with respect to the first light beam in the main scanning direction;
a deflector that deflects the first light flux and the second light flux in a second direction different from the first direction and the first direction at a position shifted in the sub-scanning direction on the same surface;
a first imaging element that imparts predetermined optical characteristics to the first light beam and the second light beam deflected in the first direction and the second direction;
a second imaging element that guides the first light beam deflected in the first direction onto a scanned surface;
a third imaging element that guides the second light beam deflected in the first direction onto the scanned surface;
a first optical surface that converges the first light beam deflected in the second direction;
a second optical surface that converges the second light beam deflected in the second direction;
a third optical surface that guides the first light beam deflected in the second direction to a photodetector;
a fourth optical surface that is not parallel to the third optical surface and guides the second light beam deflected in the second direction to a photodetector;
An optical scanning device comprising: the photodetector that detects the incident first light beam and the second light beam. The optical scanning device according to claim 1, further comprising a fourth imaging element including the first optical surface, the second optical surface, the third optical surface, and the fourth optical surface. The optical scanning device according to claim 1 or 2, wherein the second optical surface has a different optical axis from the first optical surface. the first light source and the second light source face the deflector;
The optical scanning device according to any one of claims 1 to 3, wherein the first light beam and the second light beam pass through a common optical element from the deflector to the photodetector. a first light source that emits a first luminous flux;
a second light source that emits a second light beam having an opening angle with respect to the first light beam in the main scanning direction;
a deflector that deflects the first light flux and the second light flux in a second direction different from the first direction and the first direction at a position shifted in the sub-scanning direction on the same surface;
a first imaging element that imparts predetermined optical characteristics to the first light beam and the second light beam deflected in the first direction and the second direction;
a second imaging element that guides the first light beam deflected in the first direction onto a scanned surface;
a third imaging element that guides the second light beam deflected in the first direction onto the scanned surface;
a first optical surface that converges the first light beam deflected in the second direction;
a second optical surface that converges the second light beam deflected in the second direction;
a third optical surface that guides the first light beam deflected in the second direction to a photodetector;
a fourth optical surface that is not parallel to the third optical surface and guides the second light beam deflected in the second direction to a photodetector;
the light detection unit that detects the incident first light flux and the second light flux;
An image forming apparatus comprising: an image forming section that transfers an electrostatic latent image formed by the first light beam and the second light beam guided onto a scanned surface onto a medium as an image.