Polygonal mirror, deflection device, optical scanning device, and image forming device

Abstract

To provide a technique advantageous for reducing the individual differences between polygon mirrors.SOLUTION: A polygon mirror has: a substrate that has a plurality of side faces, a first surface adjacent to the plurality of side faces, and a second surface adjacent to the plurality of side faces and on a side opposite to the first surface; and a film that is formed on the plurality of side faces and formed extending from above the plurality of side faces to above the first surface and above the second surface. The film has a first area formed on the first surface along the plurality of side faces, and a second area formed on the second surface along the plurality of side faces. A first volume of the first area and a second volume of the second area are different from each other.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a polygon mirror, a deflection device, an optical scanning device, and an image forming device. [Background technology]

[0002] An optical scanning device used in an image forming device such as a laser beam printer reflects a light beam such as a laser beam by a polygon mirror and performs optical scanning by rotating the polygon mirror at high speed. The scanning light thus obtained is focused on the surface of a rotating photosensitive drum to form an electrostatic latent image. Next, an image is formed by transferring a toner image formed by a developing device from the electrostatic latent image on the surface of the photosensitive drum to a recording material.

[0003] Patent Document 1 describes a deflection scanning device used in such an image forming apparatus. In the device described in Patent Document 1, the rotating polygon mirror has a center hole that is an axial hole into which a shaft integrally connected to a rotor constituting a motor is inserted. The rotating polygon mirror is pressed against the rotor by a pressure spring that is a pressing means attached to the upper end of the shaft, and is integrally connected thereto. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-096872 Summary of the Invention [Problem to be solved by the invention]

[0005] Polygonal mirrors include those that warp upward, those that warp downward, and those that do not warp, and individual differences can occur.

[0006] Therefore, an object of the present invention is to provide a technique that is advantageous in reducing the individual differences between polygon mirrors, and to provide a technique that is advantageous in improving the quality of deflection devices, optical scanning devices, and image forming devices that use polygon mirrors. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a polygonal mirror comprising a base having a plurality of side surfaces, a first surface adjacent to the plurality of side surfaces, and a second surface adjacent to the plurality of side surfaces and opposite the first surface, and a film formed on the plurality of side surfaces and extending from above the plurality of side surfaces to above the first surface and above the second surface, wherein the film has a first region formed on the first surface along the plurality of side surfaces and a second region formed on the second surface along the plurality of side surfaces, and a first volume of the first region and a second volume of the second region are different from each other.

[0008] According to another aspect of the present invention, there is provided a polygonal mirror comprising a base having a plurality of side surfaces, a first surface adjacent to the plurality of side surfaces, and a second surface adjacent to the plurality of side surfaces and opposite the first surface, and a film formed on the plurality of side surfaces and extending from above the plurality of side surfaces to either above the first surface or above the second surface.

[0009] According to yet another aspect of the present invention, there is provided a deflection device comprising: the above-mentioned polygon mirror; a drive unit that rotates the polygon mirror about an axis passing through the center of the first surface and the center of the second surface; and a fixing unit that fixes the polygon mirror with the second surface facing the drive unit to the drive unit.

[0010] According to yet another aspect of the present invention, there is provided an optical scanning device comprising the above-mentioned deflection device which deflects a light beam to scan a surface to be scanned in a main scanning direction, and an imaging optical system which guides the light beam deflected by the deflection device to the surface to be scanned. According to yet another aspect of the present invention, there is provided an image forming apparatus comprising the above-mentioned optical scanning device, a developing unit which develops an electrostatic latent image formed on the scanned surface by the optical scanning device into a toner image, a transfer unit which transfers the developed toner image to a transfer material, and a fixing unit which fixes the transferred toner image to the transfer material.

[0011] According to yet another aspect of the present invention, there is provided an image forming apparatus comprising the above-mentioned optical scanning device and a printer controller that converts a signal output from an external device into image data and inputs the image data to the optical scanning device. Effect of the Invention

[0012] According to the present invention, it is possible to provide a technique that is advantageous in reducing individual differences between polygon mirrors, and also to provide a technique that is advantageous in improving the quality of deflection devices, optical scanning devices, and image forming devices that use polygon mirrors. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic main-scanning sectional view of an optical scanning device including a polygon mirror according to a first embodiment of the present invention. [Diagram 2] 1 is a schematic configuration diagram of a deflection device in an optical scanning device according to a first embodiment of the present invention. [Diagram 3] 1 is a perspective view of a polygon mirror according to a first embodiment of the present invention. [Figure 4] 1 is a schematic configuration diagram of an example of a film forming apparatus for forming a multilayer film on a polygon mirror according to a first embodiment of the present invention. [Diagram 5] 3 is a cross-sectional view showing the direction in which deposition particles are incident on the polygon mirror according to the first embodiment of the present invention. FIG. [Figure 6] 1 is a cross-sectional view showing a layer structure of a multilayer film in a polygon mirror according to a first embodiment of the present invention. [Figure 7] FIG. 1 is a diagram showing the results of a study on an embodiment of the present invention. [Figure 8] FIG. 11 is a sub-scanning sectional view of a main part of an image forming apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0015] [First embodiment] A polygonal mirror, a deflection device, and an optical scanning device according to a first embodiment of the present invention will be described with reference to Figures 1 to 5. The polygonal mirror can also be called a polygon mirror.

[0016] 1 shows a schematic main-scanning cross-sectional view of an optical scanning device 100 according to the first embodiment. The optical scanning device 100 includes a light source 1, an aperture 2, an anamorphic collimator lens 3, a deflection device 50, and a scanning lens 6. The optical scanning device 100 also includes a mirror (not shown).

[0017] The light source 1 is composed of a semiconductor laser having a light emitting point. The diaphragm 2 is an aperture diaphragm having an elliptical opening, and regulates the width of the light beam emitted from the light source 1 in the main scanning direction and the sub-scanning direction. The anamorphic collimator lens 3 converts the light beam that passes through the diaphragm 2 into a weakly convergent light beam in the main scanning direction and a convergent light beam in the sub-scanning direction. In other words, the anamorphic collimator lens 3 is composed of an anamorphic lens that has different powers in the main scanning cross section and the sub-scanning cross section. The anamorphic collimator lens 3 is formed, for example, from a plastic mold.

[0018] As described above, in the optical scanning device 100, the diaphragm 2 and the anamorphic collimator lens 3 form the incident optical system 75.

[0019] The deflection device 50 has a polygon mirror 5 (described later) which is a four-faceted polygon mirror with a circumscribed circle diameter of 20 mm in the optical scanning device 100. The deflection device 50 rotates the polygon mirror 5, which is a deflector, at a constant speed in the direction of arrow R by a driving means such as a motor (not shown), thereby deflecting and scanning the light beam that has passed through the incident optical system 75.

[0020] The scanning lens 6 is an fθ lens having approximately fθ characteristics, and a spot is formed in an image area of ​​the scanned surface 7 by guiding the light beam deflected by the deflection device 50 onto the scanned surface 7. The scanning lens 6 establishes an approximately conjugate relationship between the deflection surface (reflection surface) 5a of the polygon mirror 5 or its vicinity and the scanned surface 7 or its vicinity in the sub-scanning cross section. This allows the deflection device 50 to correct the inclination of the deflection surface 5a of the polygon mirror 5. In the optical scanning device 100, the scanning lens 6 forms an imaging optical system 85.

[0021] With the above configuration, in the optical scanning device 100, when the light beam emitted from the light source 1 after being optically modulated in accordance with image information passes through the diaphragm 2, the width of the light beam in the main scanning direction and the sub-scanning direction is restricted by the opening of the diaphragm 2. Then, the light beam that has passed through the diaphragm 2 is converted by the anamorphic collimator lens 3 into a light beam having different degrees of convergence in the main scanning cross section and the sub-scanning cross section. Furthermore, the light beam is condensed so that an image of a substantially focal line (a line image long in the main scanning direction) is formed on the deflection surface 5a of the polygon mirror 5 in the deflection device 50.

[0022] The light beam reflected and deflected by the deflecting surface 5a of the polygon mirror 5 is focused into a spot on the scanned surface 7 by the scanning lens 6, and the scanned surface 7 is optically scanned at a substantially constant speed in the main scanning direction by rotating the polygon mirror 5 in the direction of the arrow R. As a result, an image is recorded on a photosensitive drum surface serving as a recording medium, which is disposed at the position of the scanned surface 7.

[0023] When optically scanning the surface 7 to be scanned, it is necessary to determine the timing of starting scanning on the surface 7 to be scanned. For this reason, in the optical scanning device 100, a light beam reflected and deflected in a predetermined direction by the deflection device 50 is guided to a BD sensor (not shown) by a BD (Beam Detect) lens (not shown). Then, a control unit (not shown) detects an output signal from the BD sensor to obtain a synchronization signal (BD signal), and uses the synchronization signal to determine the timing of emitting light from the light emitting point of the light source 1 for starting scanning in recording an image on the surface 7 to be scanned.

[0024] Next, the deflection device 50 in the optical scanning device 100 according to this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic configuration diagram of the deflection device 50 in the optical scanning device 100 according to this embodiment, and shows a ZX cross section that is a cross section along the Z direction that is the sub-scanning direction including the optical axis.

[0025] 2, the optical scanning device 100 includes, as described above, a deflection device 50, a scanning lens 6, a light source 1 (see FIG. 1), a collimator lens such as an anamorphic collimator lens 3 (see FIG. 1), etc. These elements constituting the optical scanning device 100 are disposed in a housing (not shown).

[0026] The deflection device 50 is a polygon motor unit, and includes a polygon mirror (polygonal mirror) 5, a rotating shaft 504, a rotor 505, a stator 506, a substrate 507, a bearing device 508, and a pressure spring 509 which is an elastic member for fixing the polygon mirror 5 in place.

[0027] The rotor 505 is integrally connected to a rotating shaft 504 that runs along the Z direction and passes through its center. The rotating shaft 504 is supported by a bearing device 508 so as to be rotatable about a central axis that runs along the Z direction. The rotor 505 is a rotating part that rotates around the rotating shaft 504 as the center of rotation. The bearing device 508 is attached to a substrate 507 and is integrated with the substrate 507. The polygon mirror 5 is attached and fixed to the rotor 505 by a pressure spring 509, as described below.

[0028] The stator 506 is attached and fixed to the outer periphery of the bearing device 508 so as to face the rotor 505. The stator 506 and the rotor 505 constitute a drive motor 516. The drive motor 516 is a drive unit that rotates the polygon mirror 5. When a current is supplied to the stator 506, the drive motor 516 is driven. The polygon mirror 5 receives a rotational force due to a magnetic force or the like generated between the rotor 505 and the stator 506 in the driven drive motor 516, and rotates together with the rotor 505 around the rotation axis 504.

[0029] The polygon mirror 5 is formed in a polyhedral outer shape having a plurality of the above-mentioned deflection surfaces 5a. That is, the base 503 of the polygon mirror 5 has a plurality of side surfaces 510, an upper surface 514 adjacent to the plurality of side surfaces 510, and a lower surface 515 adjacent to the plurality of side surfaces 510 and opposite to the upper surface 514. Note that one of the upper surface 514 and the lower surface 515 can be referred to as a first surface, and the other can be referred to as a second surface.

[0030] Specifically, the base 503 of the polygon mirror 5 is formed, for example, of a regular prism having a plurality of side surfaces 510, an upper surface 514, and a lower surface 515. In this case, the upper surface 514 and the lower surface 515 are parallel regular polygonal bottom surfaces of the regular prism facing each other in the Z direction. Also, the plurality of side surfaces 510 are a plurality of rectangular side surfaces of the regular prism.

[0031] The base 503 of the polygon mirror 5 is made of resin, such as cycloolefin resin, polycarbonate resin, acrylic resin, etc. The base 503 is not limited to being made of a resin material, and may be made of other materials, such as a metal material or a glass material, or may be made of a reflector that reflects light.

[0032] The polygon mirror 5 according to this embodiment has a base 503 formed into a flattened regular square prism that is a hexahedron by resin molding, and has four rectangular side surfaces 510. The outer shape of the base 503 is not limited to a hexahedron, and may be a polyhedron other than a hexahedron, such as a regular prism such as a regular pentagonal prism or a regular hexagonal prism. The number of side surfaces 510 may be a number other than four depending on the outer shape of the base 503. The outer shape of the base 503 is not limited to a polyhedron itself, and may be a shape that is a partially modified polyhedron or a shape other than a polyhedron, as long as it has a plurality of side surfaces 510 circumferentially around the center of rotation.

[0033] A multilayer film 511 is formed on the multiple side surfaces 510 by using a vacuum deposition method, a sputtering method, or the like. The multilayer film 511 is a reflective film that reflects laser light, which is light emitted from the light source 1. The multilayer film 511 is formed on each side surface 510, and is formed across the multiple side surfaces 510, the upper surface 514, and the lower surface 515. A reflective layer 521, which will be described later, included in the multilayer film 511 has a reflective surface that functions as the above-mentioned deflection surface 5a that reflects the light emitted from the light source 1. In addition, when the base 503 of the polygon mirror 5 is composed of a reflector, the side surface 510 can function as a reflective surface. In this case, instead of the multilayer film 511 including the reflective layer 521, a protective film that does not have a reflective function can be formed asymmetrically in the same manner as the multilayer film 511. In this way, in the polygon mirror 5, the multilayer film 511 formed on the side surface 510 or the side surface 510 of the base 503, which is a reflector, can form the reflective surface of the polygon mirror 5.

[0034] The base 503 of the polygon mirror 5 has a central hole 512 serving as the center of rotation for fitting the rotation shaft 504. The central hole 512 penetrates the base 503 in the Z direction so as to connect between the center of the upper surface 514 and the center of the lower surface 515. The rotation shaft 504, which is an axis passing through the center of the upper surface 514 and the center of the lower surface 515 and serves as the center of rotation, is inserted and fitted into the central hole 512.

[0035] Furthermore, the base 503 of the polygon mirror 5 includes, on an upper surface 514, an area 513 that is pressurized by a pressure spring 509 attached to the upper end of the rotating shaft 504. The polygon mirror 5 is fixed by being pressed to the rotor 505 in a circumferential area 513 centered on the central hole 512 by the pressure spring 509 attached to the rotating shaft 504 fitted into the central hole 512, and is integrally joined with the rotating shaft 504 and the rotor 505.

[0036] In this way, with the lower surface 515 facing the rotor 505 of the drive motor 516, the polygon mirror 5 is fixed to the rotor 505 by applying pressure to an area 513 of the upper surface 514 by the pressure spring 509, which is a fixing part. The polygon mirror 5 can also be fixed to the rotor 505 by using an elastic member instead of the pressure spring 509 as a fixing part, or can be fixed to the rotor 505 by an appropriate fixing method using a member other than an elastic member as a fixing part.

[0037] The laser light emitted from the light source 1 is focused in the sub-scanning direction by an anamorphic collimator lens 3 or the like and limited to a predetermined beam diameter. The laser light is deflected by a polygon mirror 5 that is driven to rotate around a rotation axis 504 along the Z direction by a deflection device 50, passes through a scanning lens 6, and is then focused on a scanned surface 7 of an image carrier (not shown) and scanned in the Y-axis direction to form an electrostatic latent image.

[0038] Next, the polygon mirror 5 used in the optical scanning device 100 according to this embodiment will be described in detail with reference to Fig. 3. Fig. 3(a) is a perspective view of the polygon mirror 5 looking down from above, and Fig. 3(b) is a perspective view looking up from below. The polygon mirror 5 shown in Fig. 3 has a base 503 with an outer shape of a regular quadrangular prism, and has square upper and lower surfaces 514 and 515, and four rectangular side surfaces 510.

[0039] As shown in FIG. 3(a), the multilayer film 511 is formed across from the side surface 510 to the top surface 514. The multilayer film 511 has a first region 517 formed on the top surface 514. The first region 517 of the multilayer film 511 is formed on the periphery of the top surface 514 along the multiple side surfaces 510 at a certain distance from the side surfaces 510. If the volume of the first region 517 of the multilayer film 511 is V1, the volume V1 is determined by the film thickness of the multilayer film 511 in the first region 517, the lengths L11 to L14 from the four side surfaces 510 to the inner ends of the first region 517, and the shape of the base 503 of the polygon mirror 5.

[0040] On the upper surface 514, a region 513 pressurized by the pressing spring 509 is formed in a circular shape around the central hole 512. Although the region 513 pressurized by the pressing spring 509 is provided on the same surface as the upper surface 514 in FIG. 3(a), the region 513 pressurized does not necessarily have to be provided on the same surface as the upper surface 514. The region 513 pressurized may be formed to have a step between it and the upper surface 514. By forming a step between the region 513 pressurized and the upper surface 514, the region 513 pressurized can be easily seen, and the risk of accidentally scratching the polygon mirror 5 during transportation or installation can be reduced. The region 513 pressurized may be formed discretely on the same circumference. By forming the region 513 discretely, the area of ​​the region 513 pressurized, which requires precision, is reduced, and the risk of scratching the polygon mirror 5 can be further reduced.

[0041] As shown in FIG. 3(b), the multilayer film 511 is formed across from above the side surface 510 to above the lower surface 515. The multilayer film 511 has a second region 518 formed on the lower surface 515. The second region 518 of the multilayer film 511 is formed on the periphery of the lower surface 515 along the multiple side surfaces 510 at a certain distance from the side surface 510. If the volume of the second region 518 of the multilayer film 511 is V2, the volume V2 is determined by the film thickness of the multilayer film 511 in the second region 518, the lengths L21 to L24 from the four side surfaces 510 to the inner ends of the second region 518, and the shape of the base 503 of the polygon mirror 5.

[0042] Multilayer film 511 is configured such that volume V1 of first region 517 and volume V2 of second region 518 are different from each other. By configuring multilayer film 511 in this manner, polygon mirror 5 can be made to be more likely to warp toward either upper surface 514 or lower surface 515. This makes it possible to reduce individual differences in polygon mirror 5. According to this embodiment, individual differences in polygon mirror 5 can be reduced, and therefore variation in the reflection characteristics of polygon mirror 5 can be reduced.

[0043] Furthermore, in this embodiment, it is possible to reduce the plane tilt of the reflecting surface that occurs when the polygon mirror 5 is pressurized and fixed to the rotor 505 by using the compressive stress or tensile stress of the multilayer film 511. The plane tilt of the reflecting surface can occur due to deformation when the polygon mirror 5 is fixed to the rotor 505 as follows.

[0044] That is, since the polygon mirror 5 is fixed by being pressed against the rotor 505 by the pressure spring 509, if the polygon mirror 5 is fixed without forming the multilayer film 511, deformation that is one of the causes of the tilt of the reflecting surface may occur. If the tilt of the reflecting surface becomes large, the light reflected by the reflecting surface is misaligned, and for example, when the optical scanning device 100 is used in an image forming apparatus such as a printer as described later, the light beam is incident obliquely on the surface of the photosensitive drum, causing a defocus. As a result of the defocus, the spot of the light beam becomes larger, causing deterioration of the image.

[0045] On the other hand, in this embodiment, the multilayer film 511 has compressive stress or tensile stress. Therefore, by configuring the multilayer film 511 so that the volumes V1 and V2 are different from each other, the resultant force of the force acting on the upper surface 514 and the force acting on the lower surface 515 can be directed in the opposite direction to the force that generates deformation that is one of the causes of the face tilt that occurs when the multilayer film 511 is pressed and fixed to the rotor 505. Therefore, according to this embodiment, the face tilt of the reflecting surface of the polygon mirror 5 can be reduced. By reducing the face tilt of the reflecting surface, the quality of the deflection device 50, the optical scanning device 100, and the image forming device 104 that use the polygon mirror (polygon mirror 5) can be improved.

[0046] In recent years, it has been considered to reduce manufacturing costs by making polygon mirror 5 from a resin material instead of the conventional metal. Since resin often has a smaller Young's modulus than metal, when attaching a resin polygon mirror 5 to rotor 505, the deformation that is a cause of the face tilt of the reflecting surface caused in polygon mirror 5 by pressure from pressure spring 509 may be larger than that of a conventional metal polygon mirror. According to this embodiment, even in the case of such a resin polygon mirror 5, the face tilt of the reflecting surface can be reduced.

[0047] In addition, in this embodiment, the individual differences of the polygon mirrors 5 are reduced as described above, thereby reducing the variation in the reflection characteristics of the polygon mirrors 5. That is, if the volumes V1 and V2 are equal to each other, the polygon mirrors 5 will be warped in a manner that is convex toward the upper surface 514, convex toward the lower surface 515, and unwarped, and individual differences will easily occur among the polygon mirrors 5. In contrast, in this embodiment, the volumes V1 and V2 are different from each other, so that the polygon mirrors 5 are easily warped toward one of the upper surface 514 and the lower surface 515, thereby reducing the individual differences among the polygon mirrors 5 and reducing the variation in the reflection characteristics. Furthermore, the volumes V1 and V2 are different from each other, so that the upper surface 514 and the lower surface 515 can be easily distinguished from each other. This improves the manufacturability, maintainability, and the like of the deflection device 50 in which the polygon mirror 5 is used.

[0048] The magnitude relationship between the volume V1 and the volume V2 can be determined according to the type of the multilayer film 511. Specifically, when the multilayer film 511 has a compressive stress, the multilayer film 511 can be configured so that the volume V1 of the first region 517 is larger than the volume V2 of the second region 518. On the other hand, when the multilayer film 511 has a tensile stress, the multilayer film 511 can be configured so that the volume V2 of the second region 518 is larger than the volume V1 of the first region 517. With these configurations, it is possible to reduce individual differences in the polygon mirror 5. In addition, it is possible to reduce the surface tilt of the reflecting surface that occurs when the polygon mirror 5 is pressurized and fixed to the rotor 505.

[0049] For example, when the multilayer film 511 has compressive stress and the volume V2 is larger than the volume V1, it is preferable that the volumes V1 and V2 satisfy the following formula (1), as described below, and it is more preferable that the volumes V1 and V2 satisfy the following formula (2). 1 <V2 / V1<2.4 (1) 1 <V2 / V1<1.94 (2)

[0050] The multilayer film 511 can be configured to have compressive stress or tensile stress as necessary by appropriately selecting the materials and film formation methods of the individual films that make up the multilayer film 511, such as the adhesion layer 520, the reflective layer 521, and the protective layer 522, as described below.

[0051] The multilayer film 511 does not necessarily have both the first region 517 and the second region 518, and may have at least one of the first region 517 and the second region 518. Therefore, the multilayer film 511 may be formed on the multiple side surfaces 510 and may be formed over either the multiple side surfaces 510 or the upper surface 514 or the lower surface 515. The multilayer film 511 may extend from the multiple side surfaces 510 to only one of the upper surface 514 and the lower surface 515. In this case, a surface other than the multiple side surfaces 510, the upper surface 514, or the lower surface 515 may be provided and the multilayer film 511 may be provided on that surface. That is, even when one of the volume V1 and the volume V2 is zero, the individual difference of the polygon mirror 5 can be reduced as described above, and the surface tilt of the reflecting surface can also be reduced.

[0052] Next, a film forming apparatus for forming the multilayer film 511 of the polygon mirror 5 according to this embodiment will be described with reference to Fig. 4. Fig. 4(a) is a schematic diagram showing a vacuum deposition apparatus as an example of the film forming apparatus according to this embodiment. Fig. 4(b) is an enlarged cross-sectional view showing a state in which the substrate 503 on which the multilayer film 511 is to be formed is placed on the rotation axis part 307.

[0053] As shown in FIG. 4( a ), a vacuum deposition apparatus 300 includes a film formation chamber 301 , an exhaust system 302 , a revolution part 304 , a drive mechanism 305 , a gear 306 , a rotation axis part 307 , a crucible 308 , an ion gun 309 , and a quartz film thickness sensor 310 .

[0054] The film formation chamber 301 is configured so that the inside can be maintained in a vacuum state, and a multilayer film 511 is formed on a substrate 503 inside the film formation chamber 301. The exhaust system 302 includes a vacuum pump and the like, and is installed so as to be able to exhaust the film formation chamber 301. The vacuum deposition apparatus 300 also has an Ar introduction line (not shown) for introducing oxygen gas into the film formation chamber 301, and an oxygen introduction line (not shown) for introducing oxygen gas into the film formation chamber 301.

[0055] In the film forming chamber 301, an orbital part 304 capable of revolving around an orbital axis 303 along the vertical direction is disposed. The orbital part 304 has an annular shape centered around the orbital axis 303. The orbital part 304 is driven by a drive mechanism 305 via a gear 306 to perform the orbital drive. In addition, in the film forming chamber 301, an ion gun 309 that performs ion assist during film formation by deposition is disposed below the orbital axis 303 of the orbital part 304. In addition, a quartz film thickness sensor 310 that measures the film thickness of the multilayer film 511 to be formed is disposed near the center lower side of the orbital part 304. In addition, in the film forming chamber 301, a crucible 308 in which a deposition material is placed is disposed on the side of the ion gun 309.

[0056] The substrates 503 on which the multilayer film 511 is to be formed are arranged in a stacked manner on the rotation shaft part 307 so that the rotation shaft part 307 passes through the central hole 512. The rotation shaft part 307 is installed on the revolution part 304 in a state in which the substrates 503 are stacked, and the substrates 503 are rotated by a driving mechanism (not shown). The substrates 503 arranged on the rotation shaft part 307 do not necessarily have to be multiple, and may be one. The rotation shaft part 307 is arranged inclined toward the revolution shaft 303 at an angle Sθ with respect to the horizontal direction. The substrates 503 are rotated and revolved by the revolution part 304 and the rotation around the rotation shaft part 307, and the multilayer film 511 is formed on the substrates 503. The substrates 503 are arranged at a height SL from the crucible 308 in which the deposition material for the multilayer film 511 is placed. The crucible 308 is positioned at a horizontal distance OFS from the orbital axis 303 .

[0057] As shown in Fig. 4(b), a plurality of bases 503 are arranged at intervals of gap G via spacers 311 so that upper surfaces 514 face upward in the axial direction of the rotation shaft part 307 inclined at angle Sθ. Note that, although the gap G is formed using the spacers 311 in Fig. 4(b), the gap G may be formed by providing a step in the base 503. Providing a step eliminates the need for the spacers 311, and therefore the number of parts can be reduced.

[0058] Next, the formation of the multilayer film 511 on the side surface 510, upper surface 514, and lower surface 515 of the base 503 of the polygon mirror 5 will be described with reference to Fig. 5. Fig. 5(a) is a cross-sectional view showing a state in which the multilayer film 511 is formed on the base 503 above the crucible 308. Fig. 5(b) is a cross-sectional view showing a state in which the multilayer film 511 is formed on the base 503 above and on the opposite side of the crucible 308.

[0059] The crucible 308 is disposed at a position spaced a distance OFS horizontally from the revolution axis 303. For this reason, as shown in Fig. 5(a), when a multilayer film 511 is formed on the substrate 503 above the crucible 308, the multilayer film 511 is formed on the side surface 510 and the bottom surface 515. On the other hand, as shown in Fig. 5(b), when a film is formed on the substrate 503 on the opposite side to the top of the crucible 308, the multilayer film 511 is formed on the side surface 510 and the top surface 514.

[0060] An incidence angle Zθ1 of the deposition particles incident on the upper surface 514 is larger than an incidence angle Zθ2 of the deposition particles incident on the lower surface 515. Therefore, lengths L11 to L14 of a first region 517 of the multilayer film 511 formed on the upper surface 514 are longer than lengths L21 to L24 of a second region 518 of the multilayer film 511 formed on the lower surface 515. In addition, since the incidence angle Zθ1 is larger than the incidence angle Zθ2, in the multilayer film 511, the film thickness of the first region 517 is smaller than the film thickness of the second region 518.

[0061] By adjusting the angle Sθ, distance OFS, height SL, and gap G described above that determine the incidence angles Zθ1 and Zθ2, the multilayer film 511 can be formed so that the lengths and film thicknesses of the first region 517 and the second region 518 of the multilayer film 511 are desired. Therefore, the volume V1 of the first region 517 obtained from the length and film thickness of the first region 517, and the volume V2 of the second region 518 obtained from the length and film thickness of the second region 518 can also be set to desired values.

[0062] In this embodiment, the case has been described where the base 503 is disposed in the axial direction of the rotation shaft part 307 so that the upper surface 514 faces upward, thereby making the length of the film formation region on the upper surface 514 longer than the length of the film formation region on the lower surface 515. Conversely, the length of the film formation region on the lower surface 515 can also be made longer than the length of the film formation region on the upper surface 514. In this case, the base 503 may be disposed in the axial direction of the rotation shaft part 307 so that the lower surface 515 faces upward.

[0063] Next, the layer structure of the multilayer film 511 formed using the above-mentioned vacuum deposition apparatus 300 will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing the layer structure of the multilayer film 511. Note that the multilayer film 511 can also be formed using other deposition apparatuses such as a sputtering apparatus, in addition to the vacuum deposition apparatus 300.

[0064] As shown in FIG. 6, the multilayer film 511 is continuously formed on the side surface 510, the peripheral portion of the upper surface 514, and the peripheral portion of the lower surface 515 of the base 503 of the polygon mirror 5. The multilayer film 511 has a layer structure in which an adhesive layer 520, a reflective layer 521, and a protective layer 522 are sequentially laminated from the side of the side surface 510, the upper surface 514, and the lower surface 515 toward the outside. The adhesive layer 520 is a layer that enhances the adhesiveness between the base 503 and the reflective layer 521. The reflective layer 521 is a layer that reflects the laser light that is the light emitted from the light source 1. The protective layer 522 is a layer that protects the reflective layer 521 from corrosion, damage, and the like.

[0065] The adhesion layer 520 and the protection layer 522 are each formed of, for example, a dielectric material. Specifically, the material of the adhesion layer 520 and the protection layer 522 is selected from, for example, silicon oxide, magnesium fluoride, magnesium oxide, aluminum oxide, tantalum oxide, titanium oxide, zirconium oxide, niobium oxide, or a mixture thereof. The adhesion layer 520 and the protection layer 522 may be formed of the same material or may be formed of different materials. The reflective layer 521 is formed of, for example, a metal material. Specifically, the material of the reflective layer 521 is selected from, for example, aluminum, copper, silver, gold, or an alloy thereof.

[0066] As shown in FIG. 6, the reflective layer 521 is preferably formed covered with the adhesive layer 520 and the protective layer 522. By forming the reflective layer 521 in this manner, it is possible to suppress or prevent moisture contained in the air or moisture absorbed by the substrate 503 from reaching the reflective layer 521, and to improve the durability of the reflective layer 521. Such a layer structure of the multilayer film 511 can be realized by forming the multilayer film 511 with a film forming pressure of the adhesive layer 520 and the protective layer 522 higher than that of the reflective layer 521. By increasing the film forming pressure of the adhesive layer 520 and the protective layer 522 to scatter the deposition particles when forming each of them, the reflective layer 521 is formed so as to be covered with the adhesive layer 520 and the protective layer 522.

[0067] 6 shows a case where the protective layer 522 is formed on the surface of the adhesive layer 520, but the protective layer 522 may be formed so as to cover the adhesive layer 520 as well. If the reflective layer 521, which is a metal layer, is formed on the base 503 via the adhesive layer 520 so as not to come into contact with the base 503, the durability of the reflective layer 521 is improved, and therefore the protective layer 522 may be formed so as to cover the adhesive layer 520.

[0068] Furthermore, the number of layers in each of the adhesive layer 520 and the protective layer 522 does not need to be limited to one. Each of the adhesive layer 520 and the protective layer 522 may be formed as a multi-layer film having two or more layers.

[0069] The materials and the number of layers of the adhesive layer 520 and the protective layer 522 can be selected from the viewpoints of the material of the reflective layer 521, the film stress and durability of the dielectric material, and the like.

[0070] Next, the operation of the vacuum deposition apparatus 300 when forming the multilayer film 511 will be described. First, in the film formation chamber 301, the rotation axis part 307 on which the substrates 503 are stacked and arranged is attached to the revolution part 304 and set. Granular material is placed in the crucible 308 as the deposition material. The crucibles 308 are installed in a necessary number in an electron gun crucible exchange mechanism (not shown) according to the materials constituting the adhesion layer 520, the reflection layer 521, and the protection layer 522. The electron gun crucible exchange mechanism mounts a plurality of crucibles 308 exchangeably on the electron gun according to the materials of each layer. In addition, a quartz crystal film thickness sensor 310 for monitoring the film thickness is placed near the revolution part 304.

[0071] Next, the inside of the film forming chamber 301 is evacuated to, for example, 2×10 -3 The chamber is evacuated without heating to a high vacuum region of approximately Pa. After the inside of the film formation chamber 301 has been brought into a high vacuum state in this manner, oxygen, Ar as an inert gas, or both are introduced into the ion gun 309, and the ion gun 309 is caused to discharge.

[0072] In parallel with the discharge of the ion gun 309, the deposition material in the crucible 308 is preheated by the electron gun. When the ion gun 309 reaches a stable state, oxygen is introduced into the film formation chamber 301. Furthermore, the revolution of the revolving part 304 and the rotation of the base body 503 by the rotation axis part 307 are started. During the formation of the adhesion layer 520, the reflective layer 521, and the protective layer 522, the revolution of the revolving part 304 and the rotation of the base body 503 are continued.

[0073] The vacuum pressure in the film forming chamber 301 is, for example, 1×10 -2 ~3×10 -2 When the pressure reaches about Pa, a shutter (not shown) is opened. In this manner, the crucible 308 containing the material for the adhesion layer 520 is used to perform ion-assisted deposition using oxygen ions while heating the material in the crucible 308 with an electron gun, thereby forming the adhesion layer 520.

[0074] After the adhesion layer 520 is formed, the introduction of oxygen or Ar gas is stopped. In addition, the crucible 308 containing the material for the adhesion layer 520 is replaced with the crucible 308 containing the material for the reflective layer 521 by the electron gun crucible replacement mechanism. Next, the inside of the film formation chamber 301 is filled with 9×10 -3 The pressure is reduced to below 1 Pa, and the crucible 308 containing the material for the reflective layer 521 is used to deposit the reflective layer 521 while heating the material in the crucible 308 with an electron gun. At this time, oxygen is not introduced.

[0075] After the reflective layer 521 is formed, the crucible 308 containing the material for the reflective layer 521 is replaced with the crucible 308 containing the material for the protective layer 522 by the electron gun crucible replacement mechanism. The protective layer 522 and the adhesive layer 520 may be layers of the same material or layers of different materials. Therefore, the same crucible 308 as the crucible 308 used for forming the adhesive layer 520 may be used for forming the protective layer 522, or a different crucible 308 may be used. Next, the protective layer 522 is formed by performing film formation similar to that for forming the adhesive layer 520.

[0076] In order to uniformize the characteristics of the multilayer film 511 obtained on each of the multiple side surfaces 510 of the base 503, it is preferable to deposit the multilayer film 511 while revolving the revolving part 304 at a speed of about 5 to 15 rpm. In addition, it is preferable that the rotation speed of the base 503 is at least twice the revolution speed of the revolving part 304.

[0077] Although the above-mentioned vacuum deposition apparatus 300 is configured to perform deposition using an electron gun, deposition may also be performed using resistance heating. For example, when forming a SiO film, it is preferable to use resistance heating. Heating using an electron gun or resistance heating can be used depending on the material.

[0078] [Example 1] An example of the first embodiment will be described below. The vacuum deposition apparatus used was a vacuum deposition apparatus manufactured by Shincron Co., Ltd. The basic specifications are as follows:

[0079] Vacuum chamber: Inner diameter φ850mm, can rotate at 3 to 15 rpm Evaporation source: 10kW electron gun Ion gun: End-hole type ion gun Film thickness control: Deposition rate control and film thickness control using a quartz crystal film thickness gauge Inlet gas: Oxygen and Argon (inside the ion gun), Oxygen (inside the vacuum chamber)

[0080] The geometric arrangement conditions were set as follows: Sθ: 20° OFS: 270mm SL: 650mm G: 0.2mm Arrangement of the base body 503: Arranged in the direction of the rotation axis so that the upper surface 514 faces upward. Size of base 503: 15mm x 15mm

[0081] In the case of base 503 of this embodiment, when upper surface 514 is pressed and fixed using spring 509 without forming multilayer film 511, deformation occurs in the direction from lower surface 515 to upper surface 514. In order to suppress this deformation, base 503 is arranged in the rotation axis direction so that upper surface 514 faces upward.

[0082] Under the above conditions, a multilayer film 511 was formed by deposition on the four side surfaces of a hexahedral base body 503 formed by molding a cycloolefin resin (COP resin). Table 1 shows the film material and film thickness of the multilayer film 511, and the general film formation conditions.

[0083] [Table 1]

[0084] As a result of film formation under the above conditions, in this embodiment, a polygon mirror 5 was obtained in which the average value of lengths L11 to L14 of the first region 517 on the upper surface 514 was approximately 0.7 mm, and the average value of lengths L21 to L24 of the second region 518 on the lower surface 515 was 0.4 mm. In this case, the film thicknesses of the multilayer film 511 were 120 nm and 290 nm in the first region 517 and the second region 518, respectively, and the volume V1 of the first region 517 was 0.0049 mm. 3 , the volume V2 of the second region 518 is 0.0070 mm 3 It was.

[0085] In this embodiment, Ta2O5 was used for the fourth layer, which is a high refractive index layer included in the protective layer 522. TiO2, ZrO2, Ta2O5, or a mixture of these can be used as the high refractive index material. In vacuum deposition, the film stress of Ta2O5 generates a compressive stress from a weak tensile stress, but in ion-assisted deposition, it is possible to generate a strong compressive stress. Therefore, Ta2O5 was used because it has the advantage that the compressive stress of the multilayer film is enhanced compared to when other materials are used as the high refractive index material.

[0086] In this embodiment, SiO2 was used for the third and fifth layers, which are low refractive index layers included in the adhesive layer 520 and the protective layer 522. SiO2 can generate compressive stress by ion-assisted deposition, similar to Ta2O5.

[0087] The combination of the adhesion layer 520 and the protective layer 522 is not limited to SiO2 and Ta2O5. SiO (silicon monoxide) may be used instead of SiO2 (silicon dioxide). Since SiO generates compressive stress even in vacuum deposition without ion assistance, a combination of SiO and Ta2O5 by ion assistance deposition may be used. SiO2 and SiO can be collectively called silicon oxide.

[0088] Also, materials other than Ta2O5, such as TiO2 or ZrO2, can be used as the high refractive index material. TiO2 or ZrO2 exhibits tensile stress even when formed by ion-assisted deposition, but the tensile stress of TiO2 or ZrO2 can be alleviated by combining it with SiO, which exhibits compressive stress. Therefore, even when TiO2 or ZrO2 is used, the film stress of the multilayer film 511 becomes compressive stress. The same applies when SiO2 formed by ion-assisted deposition is used instead of SiO. Whether or not to use ion-assisted deposition can be determined by taking into consideration the film stress of the material. If ion-assisted deposition is not used, the running costs of the device can be reduced.

[0089] A mixed material may also be used for the adhesion layer 520 and the protective layer 522. As the material for each layer, at least one material is selected from, for example, silicon oxide, magnesium fluoride, magnesium oxide, aluminum oxide, tantalum oxide, titanium oxide, zirconium oxide, and niobium oxide, taking into consideration the film stress.

[0090] Furthermore, the number of layers in the multilayer film 511 is not limited to five, and may be determined according to the film stress, and may be three layers. The three-layer film has the advantage of being able to reduce material costs. In the case of three layers, it is preferable to use SiO or SiO2 by ion-assisted deposition, which can provide a stronger compressive stress, as the material for the adhesion layer 520 and the protective layer 522.

[0091] The multilayer film 511 formed in this example exhibited compressive stress. In this example, the volume V1 of the first region 517 was 0.0049 mm 3 , the volume V2 of the second region 518 is 0.0070 mm 3 Since V2>V1, the compressive stress generated in second region 518 was large. Therefore, the resultant force of the forces acting on upper surface 514 and lower surface 515 was directed in the opposite direction to the force that generates the deformation when the polygon mirror 5 is pressed and fixed, and the tilt of the reflecting surface of polygon mirror 5 could be reduced.

[0092] [Example 2] In this example, a case where a different geometric arrangement from Example 1 is adopted is shown. The vapor deposition apparatus used in this example is a vacuum vapor deposition apparatus manufactured by Synchron Corporation, Ltd., the same as in Example 1. The basic specifications are the same as in Example 1.

[0093] The geometric arrangement conditions and the like were set as follows. Sθ: 15° OFS: 285 mm SL: 500 mm G: 0.2 mm Arrangement of the substrate 503: Arranged in the direction of the rotation axis so that the upper surface 514 faces upward Size of the substrate 503: 15 mm × 15 mm

[0094] In this example, film formation similar to that in Table 1 of Example 1 was performed with the above arrangement. As a result, in this example, the average value of the lengths L11 to L14 of the first region 517 of the upper surface 514 was 0.36 mm, and the average value of the lengths L21 to L24 of the second region 518 of the lower surface 515 was 0.44 m, and the polygon mirror 5 was obtained. At this time, the film thicknesses of the multilayer film 511 were 170 nm and 280 nm in the first region 517 and the second region 518, respectively, and the volume V1 of the first region 517 was 0.0036 mm 3 , and the volume V2 of the second region 518 was 0.0070 mm 3 . Also, the multilayer film 511 exhibited compressive stress as in Example 1.

[0095] FIG. 7 is a graph showing the results of examining the tilting occurring in the polygon mirror 5 obtained by forming the multilayer film 511 with the vapor deposition apparatuses of Example 1 and Example 2, respectively. In the polygon mirror 5 of Example 1, V2 / V1 was 1.43, and in the polygon mirror 5 of Example 2, it was 1.94. From the results of FIG. 7, it can be seen that if the volume V2 is larger than the volume V1, the tilting of the polygon mirror 5 is improved as compared with the case where the multilayer film 511 is not formed. Also, it can be seen that preferably within the range of 1 < V2 / V1 < 2.4, more preferably within the range of 1 < V2 / V1 < 1.94, an effect of improving the tilting can be obtained.

[0096] [Example 3] In this embodiment, the multilayer film 511 has a tensile stress instead of a compressive stress. The deposition apparatus used in this embodiment is a vacuum deposition apparatus manufactured by Shincron Co., Ltd., similar to that in the first embodiment. The basic specifications are similar to those in the first embodiment.

[0097] The geometric arrangement conditions were set as follows: Sθ: 20° OFS: 270mm SL: 650mm G: 0.2mm Arrangement of the base body 503: Arranged in the direction of the rotation axis so that the lower surface 515 faces upward. Size of base 503: 15mm x 15mm Table 2 shows the film material and film thickness of the multilayer film 511, and outlines the film formation conditions.

[0098] [Table 2]

[0099] MgF2, which is used as the material for the fifth layer in this embodiment, exhibits strong tensile stress even in ion-assisted deposition. Therefore, even if a layer of SiO2 by ion-assisted deposition, which has compressive stress, is used, the multilayer film 511 as a whole exhibits tensile stress. In order to make the resultant force of the force acting on the upper surface 514 and the force acting on the lower surface 515 opposite to the force that generates deformation when pressed and fixed, the base 503 is arranged in the direction of the rotation axis so that the lower surface 515 faces upward. Note that MgF2 has a smaller refractive index than SiO2, and therefore has the advantage of being able to increase the reflectance of the multilayer film 511.

[0100] As a result of film formation under the above conditions, a polygon mirror 5 was obtained in which the average value of the lengths L11 to L14 of the film formation region on the upper surface 514 was 0.4 mm, and the average value of the lengths L21 to L24 of the film formation region on the lower surface 515 was 0.7 mm. In this case, the film thicknesses of the multilayer film 511 were 290 nm and 120 nm, respectively, and the volume V1 of the first region was 0.0070 mm. 3 , the volume of the second region V2 is 0.0049 mm 3 It was.

[0101] In the substrate 503 of this embodiment, when the upper surface 514 was pressed and fixed using the spring 509 without the multilayer film 511 being formed, the deformation that occurred was in the direction from the lower surface 515 to the upper surface 514, as in the first embodiment.

[0102] Multilayer film 511 formed in this embodiment exhibited tensile stress. In this embodiment, since volume V1 of first region 517 was larger than volume V2 of second region 518 (V1>V2), the tensile stress generated in first region 517 was large. Therefore, in this embodiment, the resultant force of the force acting on upper surface 514 and the force acting on lower surface 515 was in the opposite direction to the force that generates deformation when pressed and fixed, and the face tilt of the reflecting surface of polygon mirror 5 could be reduced.

[0103] In the substrate 503 shown in Examples 1 to 3, the deformation occurring when the substrate is pressed and fixed is in the direction from the lower surface 515 to the upper surface 514, so in Examples 1 and 2, the substrate is arranged in the direction of the rotation axis so that the upper surface 514 faces upward. In Example 3, the substrate is arranged in the direction of the rotation axis so that the lower surface 515 faces upward. It is also possible that the deformation occurring when the substrate is pressed and fixed will be in the opposite direction to these. In this case, the substrate 503 may be arranged in the opposite direction to the direction of the rotation axis and the multilayer film 511 may be formed. This makes it possible to obtain the same effects as those obtained in Examples 1 to 3.

[0104] [Second embodiment] The optical scanning device 100 according to the first embodiment can be used as an optical scanning unit in an image forming apparatus. In this embodiment, an image forming apparatus in which the optical scanning device 100 according to the first embodiment is used as an optical scanning unit will be described with reference to FIG.

[0105] [Monochrome image forming device] FIG. 8A is a sub-scanning sectional view of a main part of a monochrome image forming apparatus 104 in which the optical scanning device 100 according to the first embodiment is mounted as an optical scanning unit.

[0106] Code data Dc output from an external device 117 such as a personal computer is input to the monochrome image forming device 104. This code data Dc is converted into image data (dot data) Di by a printer controller 111 in the image forming device 104. This image data Di is input to the optical scanning device 100. Then, a light beam 103 modulated according to the image data is emitted from the optical scanning device 100, and the photosensitive surface of the photosensitive drum 101 is scanned in the main scanning direction by this light beam 103.

[0107] The photosensitive drum 101, which is an electrostatic latent image carrier (photosensitive body), is rotated clockwise by a motor 115. With this rotation, the photosensitive surface of the photosensitive drum 101 moves in a sub-scanning direction perpendicular to the main scanning direction relative to the light beam 103. A charging roller 102 that uniformly charges the surface of the photosensitive drum 101 is provided above the photosensitive drum 101 so as to come into contact with the surface. The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with a light beam 103 scanned by the optical scanning device 100.

[0108] As described above, the light beam 103 is modulated based on the image data Di, and an electrostatic latent image is formed on the surface of the photosensitive drum 101 by irradiating the photosensitive drum 101 with the light beam 103. This electrostatic latent image is developed into a toner image by a developing device 107 disposed so as to come into contact with the photosensitive drum 101 further downstream in the rotation direction of the photosensitive drum 101 than the irradiation position of the light beam 103.

[0109] The toner image developed by the developing unit 107 is transferred onto a sheet of paper 112, which is a transfer material, by a transfer roller (transfer unit) 108 disposed below the photosensitive drum 101 so as to face the photosensitive drum 101. The sheets of paper 112 are stored in a paper cassette 109 in front of the photosensitive drum 101 (on the right side in FIG. 8(a)), but can also be fed manually. A paper feed roller 110 is disposed at the end of the paper cassette 109, which feeds the sheets of paper 112 in the paper cassette 109 into the transport path.

[0110] The paper 112 onto which the unfixed toner image has been transferred in the above manner is further transported to a fixing device 150 behind the photosensitive drum 101 (on the left side in FIG. 8(a)). The fixing device 150 is composed of a fixing roller 113 having an internal fixing heater (not shown) and a pressure roller 114 arranged so as to be in pressure contact with the fixing roller 113. The paper 112 transported from the transfer section is heated while being pressed at the pressure contact portion between the fixing roller 113 and the pressure roller 114, whereby the unfixed toner image on the paper 112 is fixed. Furthermore, a paper discharge roller 116 is arranged behind the fixing device 150, and the fixed paper 112 is discharged to the outside of the monochrome image forming apparatus 104.

[0111] The printer controller 111 not only converts data, but also controls the motor 115 and other components in the monochrome image forming device 104, the deflection device 50 in the optical scanning device 100, and the like.

[0112] [Color image forming equipment] FIG. 8B is a sub-scanning sectional view of a main part of an image forming apparatus 60 in which the optical scanning device 100 according to the first embodiment is mounted as optical scanning devices 61 to 64. As shown in FIG.

[0113] The image forming apparatus 60 is a tandem type color image forming apparatus in which four optical scanning devices are arranged in parallel, and each of them records image information on a photosensitive drum surface serving as an image carrier. The image forming apparatus 60 includes optical scanning devices 61, 62, 63, and 64, which are the optical scanning device 100 according to the first embodiment, and photosensitive drums 81, 82, 83, and 84 serving as image carriers. The image forming apparatus 60 also includes developing devices 31, 32, 33, and 34, a conveyor belt 51, a printer controller 53, and a fixing device 54.

[0114] To the image forming apparatus 60, R (red), G (green), and B (blue) color signals (code data) are input from an external device 52 such as a personal computer. These color signals are converted into C (cyan), M (magenta), Y (yellow), and K (black) image data by a printer controller 53 in the apparatus. These image data are input to optical scanning devices 61, 62, 63, and 64 as image signals and image information. Then, from these optical scanning devices 61, 62, 63, and 64, light beams 71, 72, 73, and 74 modulated according to the image data of each color are emitted. The photosensitive surfaces of photosensitive drums 81, 82, 83, and 84 are scanned in the main scanning direction by these light beams.

[0115] In image forming apparatus 60, for example, a C (cyan) image signal is input to optical scanning device 61, an M (magenta) image signal is input to optical scanning device 62, a Y (yellow) image signal is input to optical scanning device 63, and a K (black) image signal is input to optical scanning device 64. Then, the image signals are recorded in parallel on the photosensitive surfaces of photosensitive drums 81, 82, 83, and 84, respectively, to print a color image at high speed.

[0116] As described above, the image forming apparatus 60 uses light beams based on image data from the four optical scanning devices 61, 62, 63, and 64 to form electrostatic latent images of each color on the photosensitive surfaces of the corresponding photosensitive drums 81, 82, 83, and 84. Thereafter, the electrostatic latent images of each color are developed into toner images of each color by developing devices 31, 32, 33, and 34, and the developed toner images of each color are multi-transferred by a transfer device onto a transfer material conveyed by a conveyor belt 51. The transferred toner images are then fixed by a fixing device 54, forming a single full-color image.

[0117] Furthermore, for example, a color image reading device equipped with a CCD sensor may be used as the external device 52. In this case, the color image reading device and the color image forming device 60 constitute a color digital copying machine.

[0118] Furthermore, the image forming apparatus 60 is not limited to a configuration of four optical scanning devices and four photosensitive drums. For example, the image forming apparatus 60 may be configured with only one optical scanning device and one photosensitive drum. The image forming apparatus 60 may also be configured with two, three, five or more optical scanning devices and one photosensitive drum.

[0119] In the above, the image forming devices 60 and 104 are printers, but the image forming device is not limited to these. The image forming device may be a printer, or may be, for example, a display having a scanning mechanism including an optical scanning device 100 and a display controller. In the display, the scanning mechanism including the optical scanning device 100 forms an image by projecting a laser beam corresponding to image data while scanning it in the main scanning direction and the sub-scanning direction under the control of the display controller. The optical scanning device 100 in the scanning mechanism can scan the laser beam in the main scanning direction. [Explanation of symbols]

[0120] 5: Polygon mirror 50: Deflection device 100: Optical scanning device 503: Base 504: Rotation axis 505:Rotor 506:Stator 509: Presser spring 510: Side 511: Multilayer film 512: Center hole 513: Pressurized area 514:Top surface 515: Bottom surface 516: Drive motor 517: First Area 518: Second Area 520: Adhesion layer 521: Reflective layer 522: Protective layer

Claims

1. a substrate having a plurality of side surfaces, a first surface adjacent to the plurality of side surfaces, and a second surface adjacent to the plurality of side surfaces and opposite the first surface; a film having stress formed on the plurality of side surfaces and extending from the plurality of side surfaces to the first surface and the second surface; having The membrane comprises: a first region formed on the first surface along the plurality of side surfaces; a second region formed on the second surface along the plurality of side surfaces; and having The first volume of the first region and the second volume of the second region are different from each other. A polygonal mirror characterized by:

2. a substrate having a plurality of side surfaces, a first surface adjacent to the plurality of side surfaces, and a second surface adjacent to the plurality of side surfaces and opposite the first surface; a film having a stress formed on the plurality of side surfaces and formed across only one of the first surface and the second surface among the plurality of side surfaces and the first surface and the second surface; A polygonal mirror comprising:

3. The film is a multi-layer film.

3. A polygonal mirror according to claim 1 or 2.

4. The multilayer film includes a reflective layer that reflects light, an adhesive layer formed between the substrate and the reflective layer, and a protective layer formed on the reflective layer.

4. The polygonal mirror according to claim 3.

5. 5. The polygonal mirror according to claim 4, wherein the reflective layer is covered with the adhesive layer and the protective layer.

6. The adhesion layer is a layer of silicon oxide.

6. A polygonal mirror according to claim 4 or 5.

7. The protective layer comprises a layer of silicon oxide.

7. A polygonal mirror according to claim 4, wherein the polygonal mirror is a polygonal mirror.

8. The protective layer comprises a layer of magnesium fluoride.

8. A polygonal mirror according to claim 4, wherein the polygonal mirror is a polygonal mirror.

9. The substrate is made of resin.

9. A polygonal mirror according to claim 1, wherein the polygonal mirror is a polygonal mirror.

10. A polygonal mirror according to any one of claims 1 to 9; a drive unit that rotates the polygon mirror about an axis that passes through a center of the first surface and a center of the second surface; a fixing part that fixes the polygon mirror to the driving part with the second surface facing the driving part; A deflection device comprising:

11. The fixing unit applies pressure to the first surface to fix the polygon mirror to the driving unit.

11. Deflection device according to claim 10.

12. A polygonal mirror according to claim 1; a drive unit that rotates the polygon mirror about an axis that passes through a center of the first surface and a center of the second surface; a fixing part that fixes the polygon mirror to the driving part with the second surface facing the driving part; having the membrane has a compressive stress; The second volume is greater than the first volume.

13. A deflection device comprising:

13. 13. The deflection device according to claim 12, wherein, when the first volume is V1 and the second volume is V2, V1 and V2 satisfy the following formula: V1=V2+V2. 1<V2 / V1<2.4

14. A polygonal mirror according to claim 1; a drive unit that rotates the polygon mirror about an axis that passes through a center of the first surface and a center of the second surface; a fixing part that fixes the polygon mirror to the driving part with the second surface facing the driving part; having the membrane has a tensile stress; The first volume is greater than the second volume.

13. A deflection device comprising:

15. a deflection device according to any one of claims 10 to 14, which deflects a light beam to scan a surface to be scanned in a main scanning direction; an imaging optical system that guides the light beam deflected by the deflection device to the surface to be scanned;

16. 16. An image forming apparatus comprising: an optical scanning device according to claim 15; a developing unit which develops an electrostatic latent image formed on the scanned surface by the optical scanning device into a toner image; a transfer unit which transfers the developed toner image onto a transfer material; and a fixing unit which fixes the transferred toner image onto the transfer material.

17. 16. An image forming apparatus comprising: the optical scanning device according to claim 15; and a printer controller for converting a signal output from an external device into image data and inputting the image data to the optical scanning device.

Images