JP4661479B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

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

  In an electrophotographic full-color image forming apparatus, a plurality of color toner images are superimposed to form a full-color image. Therefore, if the toner images of the respective colors are not accurately positioned, so-called color misregistration occurs.

  One cause of this color misregistration is that the scanning lines (BOW (Y) to BOW (M)) of the light beam that scans on the photoconductor are bowed with different curvatures as shown in FIG. Some are due to bending (BOW). Therefore, as shown in FIG. 15B, so-called BOW correction is performed to correct the color misregistration by correcting and aligning the curvature of the scanning lines (BOW (Y) to BOW (M)) in the sub-scanning direction. ing.

  The following methods have been proposed as conventional techniques for bow correction.

  (1) A method of correcting by curving in the sub-scanning direction by pushing the long cylinder lens with an adjusting screw. (For example, refer to Patent Document 1).

  (2) A method of correcting the curve by correcting the curvature of the lens by pressing a central portion with an adjustment screw screwed onto the support plate, and a plastic lens is integrally provided with a curve correction means. (For example, refer to Patent Document 2).

(3) A method of correcting by curving the mirror by pushing the center while pressing force is applied to both ends of the mirror (see, for example, Patent Document 3).
JP 05-34612 A Japanese Patent Laid-Open No. 10-268217 Japanese Patent Laid-Open No. 08-146325

  However, in any of the above methods (1) to (3), as shown in FIG. 5, both ends of the lens and the mirror are supported and the central portion is pressed and curved. When curved in this way, as shown in FIG. 8, stress concentrates on the pressing portion 872, and the curve is tightly localized around the pressing portion 872, and does not curve into an arc shape having a single center of curvature. .

  Therefore, as shown in FIG. 9, there is a difference between the dotted line B indicating the scanning line on the photoconductor corrected by bending and the solid line K indicating the desired scanning line (the scanning line desired to be corrected, FIG. 15B). Occurs. For this reason, it is difficult to accurately match the color registration (color shift correction).

  The present invention has been made to solve the above-described problem, and an object thereof is to appropriately correct the curvature of a scanning line of a light beam on a scanned object.

  In order to achieve the above object, an optical scanning device according to claim 1 includes a deflector for deflecting and scanning a laser beam emitted from a light source, an image of the deflected laser beam and an object to be scanned at a substantially constant speed. A scanning optical system that scans the upper side; a correction optical element that forms part of the scanning optical system and has power in the sub-scanning direction; and a bending adjustment unit that curves the correction optical element in the sub-scanning direction. The curvature adjusting means is elastically deformed by an external force, and the correction optical element is connected to the correction optical element via an elastic member that distributes the external force to a plurality of action portions arranged in the main scanning direction and transmits the force to the correction optical element. It is characterized by bending in the scanning direction and acting force in the main scanning direction in the plurality of acting portions.

  According to the optical scanning device of the first aspect, the external force (pressing force or pulling force) is applied to be elastically deformed, and the applied external force is applied to the plurality of acting portions arranged in the main scanning direction. The correction optical element is curved in the sub-scanning direction via an elastic member that is dispersed in the direction and transmitted to the correction optical element, so that stress is not concentrated locally. Further, local deformation is suppressed by acting force in the main scanning direction, and the correction optical element is curved in a shape close to an arc shape having a single center of curvature in the sub scanning direction.

  Therefore, it is possible to appropriately correct the curvature of the scanning line of the light beam that scans the scanned object in the main scanning direction. Further, since it is elastically deformed, adjustment sensitivity can be lowered, and finer adjustment than before can be achieved.

  The optical scanning device according to claim 2 is provided with the same deflector for deflecting and scanning beams emitted from a plurality of laser light sources, a scanning lens common to the plurality of beams, and provided for each of the plurality of beams in the sub-scanning direction. A correction optical element having power and a curve adjusting means for bending the correction optical element in the sub-scanning direction. The curve adjustment means is elastically deformed by an external force, and the external force is used as a main component of the correction optical element. The correction optical element is curved in the sub-scanning direction via an elastic member that is distributed and transmitted to a plurality of acting portions arranged in the scanning direction, and an acting force acts in the main scanning direction in the plurality of acting portions. It is a feature.

  According to another aspect of the present invention, a plurality of beams are incident on the same deflector and, after passing through a common scanning lens, are separated and scanned on different photoconductors. Here, since the incident angle at the deflector is different for each laser beam, a different amount of scanning line curvature occurs. Therefore, a correction optical system having power in the sub-scanning direction is provided for each beam, and the correction optical system is curved to make the scanning line curve of each laser beam the same. In addition, due to the elastic deformation, the deforming portion is slightly deformed in the main scanning direction by the elastic deformation, and the correcting optical element is moved in the sub scanning direction. Curved closer to a circular arc shape with a single center of curvature.

  According to a third aspect of the present invention, there is provided the optical scanning device according to the first or second aspect, wherein the elastic member is integrated with the correction optical element.

  According to a third aspect of the present invention, the elastic member is integrated with the correction optical element. That is, the action part for transmitting the dispersed force is connected to the correction optical element and integrated.

  Therefore, all the force applied to the action part is used for bending the correction optical element. Therefore, it is possible to reduce the variation in the curved shape due to the variation in the contact state between the elastic member and the correction optical element.

  The optical scanning device according to claim 4 is the configuration according to any one of claims 1 to 3, wherein the correction optical element includes a correction optical element body that corrects the light beam and the correction optical element. It consists of a frame provided around the main body, and the action portion of the elastic member is characterized in that an external force is distributed and transmitted to the frame.

  In the optical scanning device according to claim 4, the correction optical element includes a correction optical element body and a frame body provided around the correction optical element body, and the frame body is bent through an elastic member. The entire correction optical element is curved. Therefore, since the local deformation of the action part is alleviated by the frame, it is possible to avoid the local deformation of the beam passage part of the optical element.

  According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the arrangement position of the elastic member is outside the support portion that supports the correction optical element. It is characterized by being.

  The optical scanning device according to claim 5, wherein the elastic member is disposed outside the support portion that supports the correction optical element, whereby the scanning line of the light beam that scans the scanning target in the main scanning direction. Can be corrected to an asymmetrical arc shape.

  According to a sixth aspect of the present invention, in the configuration according to any one of the first to fifth aspects, the correction optical element is a resin toroidal lens.

  The optical scanning device according to claim 6 uses a resin toroidal lens as the correction optical element. A resin used as a resin lens, for example, a polyolefin resin, is a material that is easily bent at a Young's modulus of 1/20 to 1/40 compared to optical glass. A curved shape that is closer to an arc shape can be realized by bending and applying an acting force in the main scanning direction.

  Also, the convex portion or the apex portion of the concave portion in the main scanning direction of the resin toroidal lens tends to deteriorate the surface accuracy during die processing. The beam diameter on the object to be scanned changes greatly. However, a plurality of action portions of the elastic member are provided, and the change in the beam diameter is almost eliminated by shifting the action portions in the main scanning direction from the convex portion or the concave vertex.

  The toroidal lens is a lens made of surfaces having different vertical and horizontal curvatures, such as a via barrel, and can improve the spot diameter uniformity on the surface to be scanned.

  As described above, according to the present invention, there is an effect of appropriately correcting the curvature of the scanning line of the light beam on the scanned object.

  An embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, an optical scanning device 10 provided in a color laser printer includes four photoconductors 12Y, 12M, 12C, and 12K as laser beams, and laser beam groups LY, LM, A latent image is formed by irradiating LC and LK. The latent images formed on the photoconductors 12Y, 12M, 12C, and 12K are developed with yellow (Y), magenta (M), cyan (C), and black (K) toners, respectively. Then, the toner on each photoconductor is transferred to a transfer belt (not shown). At this time, the toners of the respective colors are superimposed to form a full-color image and transferred to a recording medium such as plain paper.

  The optical scanning device 10 includes a light source 14, a pre-deflection optical system 16, a polygon mirror 18 as a deflection unit, and a scanning optical system 20, and includes four laser beam groups LY, LM, LC, The laser beam LY is emitted and the laser beam groups LY, LM, LC, and LK are separated in the scanning optical system and image-scanned on the four photoconductors 12Y, 12M, 12C, and 12K. The deflection scanning direction by the rotation of the polygon mirror 18 of the optical scanning device is called a main scanning direction, and the direction orthogonal to the deflection scanning direction is called a sub-scanning direction. That is, in the photoconductors 12Y, 12M, 12C, and 12K, a direction corresponding to the axial direction is referred to as a main scanning direction, and a direction corresponding to the rotation direction is referred to as a sub-scanning direction.

  The light source 14 is a surface emitting laser beam array in which a total of 32 light emitting points P of 8 columns × 4 rows are arranged two-dimensionally in the main scanning direction and the sub-scanning direction, and the laser beam group in order from the top row. LK, LC, LM, and LY are emitted, and the photosensitive members 12K, 12C, 12M, and 12Y are scanned with eight laser beams, respectively.

  In the sub-scanning direction of the light source 14, four groups of light-emitting point groups PK, PC, PM, and PY each composed of eight light-emitting points P are arranged in the sub-scanning direction. Each light-emitting point group is composed of eight light-emitting points P that are linearly arranged with an inclination with respect to the main scanning direction and the sub-scanning direction.

  As shown in FIGS. 1 and 2, the pre-deflection optical system 16 includes a coupling lens 22, an aperture 24, and a cylinder lens 26 that are common to the four laser beam groups LY, LM, LC, and LK. Yes. The coupling lens 22 is provided facing the light source 14 and has a focal length of 23.3 mm. The aperture 24 is provided at the rear focal position of the coupling lens 22. The cylinder lens 26 is provided with the front focal position aligned with the opening 24A of the aperture 24, and the focal length is 97.86 mm. The cylinder lens 26 has no power in the main scanning direction and has positive power in the sub-scanning direction.

  The laser beam groups LK, LC, LM, and LY emitted from the light source 14 are condensed by the coupling lens 22 and pass through the aperture 24A of the aperture 24 while being truncated, and the principal ray is made to pass in the sub scanning direction by the cylinder lens 26. The light enters the deflecting surface 18A of the polygon mirror 18 in parallel or converged. Here, the aperture 24 was set to have an opening width that narrows the beam diameter to 50 μm in order to ensure a sufficient depth of focus.

  As a result, the imaging magnification in the sub-scanning direction of the pre-deflection optical system is 4.2 times, and the pitch of the laser beams in each laser beam group on the deflection surface 18A of the polygon mirror 18 is 21 μm. The laser beam groups LY, LM, LC, and LK are imaged with the pitch in the sub-scanning direction enlarged to 0.693 mm. For this reason, the laser beam groups LY, LM, LC, and LK are easily separated later in the scanning optical system 20.

  Further, the laser beam groups LY, LM, LC, and LK are incident on the deflecting surface 18A with the principal ray parallel or focused. For this reason, the distance to the crossing position of each laser beam group LY, LM, LC, LK in the scanning optical system 20 to be described later can be shortened, and the distance to the separating means can be shortened. it can.

  The polygon mirror 18 has six deflecting surfaces 18A and rotates at a speed of about 30,000 revolutions per minute, and moves the scanning line to each of the photoconductors 12Y, 12M, 12C, and 12K at a speed of 254 mm per second. .

  The scanning optical system 20 includes an aspherical lens 28 as a first scanning optical system through which the laser beam groups LK, LC, LM, and LY pass, a plane mirror group 30 as a separating unit, and each laser beam group LY, It is composed of toroidal lenses 32Y, 32M, 32C, and 32K as the second scanning optical system provided for each of LM, LC, and LK. The aspherical lens 28 and the toroidal lenses 32Y, 32M, 32C, 32K all have positive power.

  The aspherical lens 28 is provided in the optical path of the laser beam groups LY, LM, LC, and LK deflected by the polygon mirror 18 and has a focal length of 60 mm in the sub-scanning direction. Further, the distance from the deflection surface 18A is also about 60 mm. As a result, the laser beam groups LY, LM, LC, and LK intersect at the rear focal position of the aspherical lens 28 and enter the plane mirror group 30. Each laser beam becomes substantially parallel light.

  Here, the aspherical lens 28 is formed by plastic shaping so that the cross-sectional shape in the sub-scanning direction becomes an aspherical shape, and the laser beam group LY passing through a position away from the optical axis of the aspherical lens 28, The LK aberration is corrected, and the imaging magnifications of the laser beam groups LY, LM, LC, and LK in the sub-scanning direction are made substantially the same. The aspheric lens 28 is configured to have an fθ characteristic in the main scanning direction in cooperation with plastic toroidal lenses 32Y, 32M, 32C, and 32K.

  The cross-sectional shape of the aspherical lens 28 in the sub-scanning direction is an aspherical shape. However, the shape is not limited to this and is a wave shape optimized for the position where each laser beam group LY, LM, LC, LK passes. Any non-circular arc shape that can correct the aberrations of the laser beam groups LY, LM, LC, and LK may be used.

  The plane mirror group 30 includes first plane mirrors 34Y, 34M, 34C, and 34K provided for the laser beam groups LY, LM, LC, and LK, and second plane mirrors 36Y, 36M, 36C, and 36K. Has been.

  The first plane mirrors 34Y, 34M, 34C, and 34K negatively absorb the laser beam groups incident on the plane mirror group 30 after the optical axes of the laser beam groups LY, LM, LC, and LK are diffused by the aspheric lens 28. Reflect in the direction of. Further, the second plane mirrors 36Y, 36M, 36C, and 36K respectively apply the laser beam groups LY, LM, LC, and LK reflected by the first plane mirrors 34Y, 34M, 34C, and 34K to the respective photoreceptors 12Y, 12M, and 12C. , Reflected toward 12K.

  The first plane mirrors 34Y, 34M, 34C, 34K are arranged at a position 300 mm away from the aspherical lens 28, and the intervals in the sub-scanning direction of the laser beam groups LY, LM, LC, LK at this position are as follows. Since it is 2.8 mm, a sufficient space for arranging the first plane mirrors 34Y, 34M, 34C, 34K can be secured.

  Thus, since the mechanism for separating the laser beam groups LY, LM, LC, and LK is configured by combining a plurality of inexpensive plane mirrors, the manufacturing cost can be reduced. The plane mirror group 30 is provided with two plane mirrors for each laser beam group LY, LM, LC, and LK, and each laser beam group LY, LM, LC, and LK is folded twice. Therefore, the laser beam groups LY, LM, LC, and LK are incident on the photoreceptors 12Y, 12M, 12C, and 12K without reversing the order in the sub-scanning direction and the writing order.

  The toroidal lenses 32Y, 32M, 32C and 32K respectively transfer the laser beam groups LY, LM, LC and LK reflected by the second plane mirrors 36Y, 36M, 36C and 36K to the photoreceptors 12Y, 12M, 12C and 12K. Focusing is performed at an interval of 10.58 μm in the sub-scanning direction. Thereby, a latent image is formed on each of the photoconductors 12Y, 12M, 12C, and 12K by 2400 scanning lines per inch. At this time, the toroidal lenses 32Y, 32M, 32C, and 32K correct the beam position variation due to the tilt of the deflecting surface 18A, and prevent image quality deterioration due to pitch unevenness. The positions of the toroidal lenses 32Y, 32M, 32C, and 32K are adjusted so that the imaging magnifications from the light source 14 to the photoconductors 12Y, 12M, 12C, and 12K are substantially the same, and the focal length is set. .

  The toroidal lenses 32Y, 32M, 32C, and 32K can adjust the distance and inclination with respect to each scanning target (photosensitive members 12Y, 12M, 12C, and 12K) by a known adjusting unit. For this reason, it is possible to adjust the attitude of the scanning line on each scanning object, the imaging magnification, and the beam waist position for each of the laser beam groups LY, LM, LC, and LK. Further, the curve in the sub-scanning direction can be corrected for the curve of the scanning line on each scanning target, so-called BOW correction (see FIG. 15). In this embodiment, the laser beams LY to LK deflected by the polygon mirror 18 are incident on different positions in the sub-scanning direction of the aspherical lens 28, so that each laser beam LY to LK generates a different amount of BOW. Therefore, BOW correction for making the BOW of each laser beam the same is an important function in order to keep the color registration below a predetermined value. The bow correction will be described in detail later.

  Next, the toroidal lenses 32Y, 32M, 32C, and 32K will be described in detail. Since the toroidal lenses 32Y, 32M, 32C, and 32K have the same structure, they are described as the toroidal lens 32 without distinguishing each color.

  As shown in FIG. 3, the toroidal lens 32 includes a lens body 52 and a frame body 54 provided around the lens body 52. On the upper surface of the frame body 54, an elastic portion 60 having a bridge shape (a U-shaped cross section) is formed. The elastic portion 60 includes a pair of plate-like abutment portions 61 and 62 erected from the upper surface of the frame body 54. The pair of abutment portions 61 and 62 are arranged along the depth direction orthogonal to the longitudinal direction (main scanning direction) of the toroidal lens 32, and the center between the pair of abutment portions 61 and 62 is the center in the longitudinal direction of the toroidal lens 32. It almost coincides with the position. A plate-like bridge girder part 64 is formed between the upper parts of the pair of abutment parts 61 and 62.

  The lens body 52, the frame body 54, and the elastic portion 60 (the abutment portions 61 and 62, the bridge girder portion 64) are all made by integrally molding plastic.

  The toroidal lens 32 is supported so that both ends are indicated by arrows S. In the present embodiment, as shown in FIG. 6, the lower end of the toroidal lens 32 is placed on the projection 84 and the upper end is supported by a spring member 82 made of sheet metal or the like. Both ends are supported by the support structure 80 that suppresses the portion.

  Moreover, as shown in FIG. 3, an external force is applied to the upper surface of the bridge girder part 64 of the elastic part 60, and it presses in a subscanning direction. As a configuration for applying this external force, in this embodiment, as shown in FIG. 4, a screw 72 is screwed into a fixing portion 70 provided in a housing (not shown) or the like above the toroidal lens 32. The screw 72 is configured to press the bridge girder 64 by tightening.

  As shown in FIG. 7, by pressing the upper surface of the bridge girder part 64 of the elastic part 60 with the screw 72 in the sub-scanning direction, the bridge girder part 64 of the elastic part 60 is elastically deformed and bent by the elasticity of plastic, and The pressing force is distributed and transmitted in the sub-scanning direction to the boundary portions 61A and 62A of the abutment portions 61 and 62 with the frame 54. Then, the frame body 54 is pressed while the force that separates the boundary portions 61A and 62A from each other in the main scanning direction is applied, and the toroidal lens 32 is curved. Since the curvature of the frame body 54 is smaller than the curvature of the bridge girder portion 64, the abutment portions 61 and 62 have a divergent shape with a slightly wider portion between the lower ends (boundary portions 61A and 62A) between the upper ends (C shape). The acting force that separates in the main scanning direction acts to relieve the compression in the vicinity of the acting part by applying stress in the sub-scanning direction, and approaches a circular arc shape by making the curved shape more gradual.

  Further, a frame body 54 is formed around the lens body 52, and an elastic portion 60 is formed on the frame body 54. Compared with a configuration in which the lens body 52 itself is directly curved, the curved body 54 having a quadrangular prism shape as a whole is curved into an arc shape closer to an arc shape having a single center of curvature.

  Next, the operation of this embodiment will be described.

  The scanning lines (BOW (Y) to BOW (M)) of the laser beam groups LY, LM, LC, and LK that scan the photoconductors 12Y, 12M, 12C, and 12K shown in FIG. The bow-curved state (BOW) with different curvatures in each direction is corrected by BOW as shown in FIG. 15B, and the scanning lines (BOW (Y) to BOW (M)) are aligned. Corrects color misregistration. Specifically, by tightening the screws 72 shown in FIG. 4, the toroidal lenses 32Y, 32M, 32C, and 32K are pressed and curved to perform BOW correction. FIG. 15 shows each laser beam group LY, LM, LC, LK as one light beam for easy understanding.

  As shown in FIGS. 5 and 8, when the central portion is directly pressed and curved as in the prior art, the stress concentrates on the pressing portion 872, and the bending is locally tight with the pressing portion 872 as the center. Therefore, it does not curve into an arc shape having a single center of curvature. For this reason, the contour line T in FIG. 5 showing the internal stress distribution (= internal birefringence distribution diagram) is also locally curved and does not have a shape close to an arc shape having a single center of curvature.

  Therefore, as shown in FIG. 9, the dotted line B indicating the shape of the scanning lines (BOW (Y) to BOW (M)) on the photoconductors 12Y, 12M, 12C, and 12K is locally curved, and is desired. Does not coincide with a solid line K indicating a scanning line (a scanning line desired to be obtained by correction (FIG. 15B) and a shape substantially similar to an arc shape having a single center of curvature). This makes it difficult to accurately match the color registration. (Color shift cannot be corrected accurately).

  Further, stress concentrates on the pressing portion 872, and the toroidal lens 832 may be broken. Furthermore, the center portion of the toroidal lens mainly hits a convex or concave apex, and the movement of the grinding tool is reversed during die processing, so that the surface accuracy tends to deteriorate. Therefore, when the apex portion and the pressing portion 832 substantially match (or are very close to each other), as shown by the dotted line B in FIG. (In FIG. 10, the horizontal axis represents the position in the main scanning direction on the photosensitive member, and the vertical axis represents the beam diameter).

  On the other hand, in this embodiment, as shown in FIG. 7, the bridge girder part 64 is elastically deformed by the pressing force applied to the bridge girder part 64, and the pressing force is a boundary portion 61A, 62A with the frame body 54 of the abutment parts 61, 62. The frame body 54 is transmitted while being distributed in the main scanning direction, and a force is applied to the boundary portions 61A and 62A to move away from each other in the main scanning direction.

  Therefore, the toroidal lens 32 of the present embodiment is curved in an arc shape that is substantially close to an arc shape having a single center of curvature without locally curving around the pressed portion as in the prior art.

  Here, in the present embodiment, the principle of bending into an arc shape by applying an acting force to a plurality of acting parts in the main scanning direction will be described.

  As shown in FIG. 17B, when an acting force F1 is applied to the correction optical element 32 having a beam shape in the vertical direction at the center, a compressive stress P is generated in the longitudinal direction of the applied side, and the opposite side is tensile. Stress Q is generated. For this reason, especially in a resin with a small Young's modulus, the deformation of the portion to which the acting force is applied is large, and it deforms into a so-called V-shape.

  Further, as shown in FIG. 17C, even if the acting force F1 is applied in the vertical direction at a plurality of locations, the compressive stress P generated in the acting portion is not relieved, so that the acting force F1 is dispersed, but the acting portion The deformation of is not mitigated.

  On the other hand, in the configuration of FIG. 17A, which is the present embodiment, the vertical acting force F1 is applied to a plurality of locations, and the direction against the compressive stress P caused by the applied force in the vertical direction, that is, main scanning. By generating the acting force F2 also in the longitudinal direction, which is the direction, the deformation of the acting portion can be relaxed and deformed over the entire correction optical element, so that the curved shape is closer to an arc.

  For this reason, the contour line T in FIG. 6 showing the internal stress distribution (= internal birefringence distribution diagram) is not locally curved, and has an arc shape substantially similar to an arc shape having a single center of curvature.

  Therefore, the scanning lines (BOW (Y) to BOW (M)) on the photoconductors 12Y, 12M, 12C, and 12K are the desired scanning lines shown in FIG. 9 (scanning lines to be obtained by correction (FIG. 15B)). ) And an arc shape having a single center of curvature). Therefore, it is possible to make the color registrations substantially coincide with each other accurately. (Color shift can be corrected accurately).

  Further, since the stress is distributed and applied, there is no possibility that the toroidal lens 32 is broken. Furthermore, since the elastic part 60 is elastically deformed, adjustment sensitivity can be lowered, and finer adjustment than before can be performed.

  Further, since the shape of the projection in the main scanning direction or the apex portion (in the present embodiment, the center portion) of the convex portion or the concave portion is separated from the boundary portions 61A and 62A between the frame bodies 54 of the abutments 61 and 62, FIG. As shown by the solid line A, the beam diameter hardly changes. Therefore, image quality defects are also prevented.

  In addition, this invention is not limited to said embodiment.

  For example, in the above-described embodiment, the elastic portion 60 is formed at the central portion of the toroidal lens 32 (while supporting the toroidal lens 32), but is not limited thereto. For example, like the toroidal lens 232 of the first modification shown in FIG. 11, the elastic portion 260 is formed at one end portion, and the other end portion and the central portion are supported as indicated by an arrow S. There may be. Note that with such a configuration, it is possible to bend into a left-right asymmetric shape.

  For example, in the above-described embodiment, the toroidal lens 32 is bent by pressing the elastic portion 60, but the toroidal lens 32 may be bent by pulling the elastic portion 60. In this case, since a force is applied to the boundary portions 61A and 62A so as to approach each other, the acting portion can relieve the tensile stress, so that a curved shape close to an arc can be obtained.

  Further, for example, in the above embodiment, the lens main body 52, the frame body 54, and the elastic portion 60 are integrally molded, but the present invention is not limited to this. The lens body 52 and the frame body 54 may be separate bodies.

  Further, unlike the toroidal lens 332 of the second modification shown in FIG. 12, the elastic member 360 and the frame body 354 are not integrally molded, and the contact surface 360A and the frame body 354 are joined by an adhesive or welding. It may be a configuration. Alternatively, as in the toroidal lens 432 of the third modification shown in FIG. 13, the abutment tip 460A of the elastic member 460 may be press-fitted into a hole 454A provided in the frame 454. Alternatively, although not shown, the elastic member and the frame may be screwed.

  Alternatively, unlike the toroidal lens 532 of the fourth modified example shown in FIG. 16, the end surface 560A of the abutment of the elastic member 560 and the frame body 554 are not joined, and the elastic member as shown in FIG. The configuration may be such that the position of the contact portion 554A of the front end surface 560A and the frame body 554 is shifted due to elastic deformation caused by pressing the 560. In this embodiment, the acting force generated in the main scanning direction can be controlled by setting the friction coefficient of the contact portion 554A between the tip surface 560A and the frame 554 to a predetermined value.

  Further, for example, in the above embodiment, the elastic portion 60 has a bridge shape (the cross section is a U shape), but is not limited thereto. For example, a tunnel-shaped elastic portion 660 having a semicircular cross section may be used like a toroidal lens 632 of the fifth modification shown in FIG.

  For example, in the above-described embodiment, the present invention is applied to the toroidal lenses 32Y, 32M, 32C, and 32K, but the present invention is not limited to this. For example, the present invention may be applied to other lenses such as the cylinder lens 26. Alternatively, the present invention may be applied to a mirror such as the plane mirror group 30 instead of the lens.

  For example, the present embodiment is applied to a scanning device that scans a plurality of photoconductors after deflecting and scanning a plurality of beams with a single deflector, but the present invention is not limited to this. .

  For example, as shown in FIG. 18, the present invention can also be applied to a full-color printer having an optical scanning device for each of a plurality of photoconductors. In this case, since the plurality of optical scanning devices can have the same configuration, the designed scanning line curve can be the same, but a difference occurs in each scanning line curve due to manufacturing variations or adjustment variations. Therefore, the present invention is effective. In order to make the scanning line curve between the optical scanning devices the same, by adjusting the three correction optical elements 32Y, 32M, and 32C among the four optical scanning devices, the scanning line curve can be made the same as that of the optical scanning device 10C. Good.

  Further, it is effective to apply the present invention and perform BOW correction in order to achieve high image quality even in a single color printer, not a full color printer.

1 is a perspective view showing an optical scanning device according to an embodiment of the present invention. It is the schematic which shows the optical scanning device of one Embodiment of this invention. It is a perspective view which shows the toroidal lens of the optical scanning device of one Embodiment of this invention. It is a figure explaining an example of the mechanism which presses the elastic part of the toroidal lens of the optical scanning device of one embodiment of the present invention. It is a figure which shows the toroidal lens of the conventional optical scanning apparatus, and demonstrates the state of internal stress distribution (= internal birefringence distribution map) by pressing the center part and curving the toroidal lens. FIG. 5 shows a toroidal lens of an optical scanning device according to an embodiment of the present invention, and is a diagram illustrating a state of an internal stress distribution (= internal birefringence distribution diagram) caused by pressing the elastic portion to curve the toroidal lens. is there. (A) is an enlarged view near the elastic member in a state where the toroidal lens of the optical scanning device of one embodiment of the present invention is not curved, and (B) is pressed through the elastic part and the toroidal lens is curved. It is an enlarged view which shows the state which carried out. (A) is an enlarged view of a state where the toroidal lens of the conventional optical scanning device is not curved, and (B) is an enlarged view showing a state where the center portion is pressed and the toroidal lens is curved. It is a schematic diagram which shows the dotted line B which shows the scanning line which curved and corrected the toroidal lens of the conventional optical scanning apparatus, and the continuous line K which shows the desired scanning line (scanning line to obtain by correction | amendment). The vertical axis represents the beam diameter, the horizontal axis represents the position in the main scanning direction on the photoconductor, and the solid line A represents the change in spot diameter due to the curvature of the toroidal lens of the optical scanning device of one embodiment of the present invention. Dotted line B is a schematic diagram showing a change in spot diameter due to the curvature of the toroidal lens of the conventional optical scanning device. It is a figure which shows the toroidal lens of a 1st modification. It is a figure which shows the toroidal lens of a 2nd modification. It is a figure which shows the toroidal lens of a 3rd modification. It is a figure which shows the toroidal lens of a 5th modification. (A) is a figure which shows the scanning line before BOW correction | amendment, (B) is a figure which shows the scanning line after BOW correction | amendment. It is a figure which shows the toroidal lens of a 4th modification. (A) It is a figure explaining the effect | action of this invention. (B), (C) is a figure explaining the deformation | transformation in a prior art example. It is the figure which applied this invention to the scanning device of a different structure.

Explanation of symbols

10 optical scanning device 12Y photoconductor (scanned body)
12M photoconductor (scanned body)
12C photoconductor (scanned body)
12K photoconductor (scanned body)
32Y toroidal lens 32M toroidal lens 32C toroidal lens 32K toroidal lens 52 Lens body (correction optical element body)
54 Frame 60 Elastic member (elastic part)
61A boundary part (action part)
62A boundary part (action part)
560A Tip surface (action part)
LY laser beam group (light beam)
LM laser beam group (light beam)
LC laser beam group (light beam)
LK laser beam group (light beam)

Claims (6)

A deflector that deflects the laser beam emitted from the light source, a scanning optical system that forms an image of the deflected laser beam and scans the object to be scanned at a substantially constant speed, and forms part of the scanning optical system, A correction optical element having power in the sub-scanning direction, and a curve adjusting means for bending the correction optical element in the sub-scanning direction,
The bending adjustment means includes
While being elastically deformed by an external force, the correction optical element is curved in the sub-scanning direction via an elastic member that distributes the external force to a plurality of action portions arranged in the main scanning direction and transmits the force to the correction optical element. An optical scanning device characterized in that an acting force acts in a main scanning direction in the plurality of acting portions. A single deflector for deflecting and scanning beams emitted from a plurality of laser light sources, a scanning lens common to the plurality of beams, a correction optical element provided for each of the plurality of beams and having power in the sub-scanning direction, and the correction Bending adjustment means for bending the optical element in the sub-scanning direction,
The bending adjustment means includes
While elastically deforming by an external force, the correction optical element is curved in the sub-scanning direction via an elastic member that distributes and transmits the external force to a plurality of action portions arranged in the main scanning direction of the correction optical element, and An optical scanning device characterized in that an acting force acts in a main scanning direction in the plurality of acting portions.   The optical scanning device according to claim 1, wherein the elastic member is integrated with the correction optical element. The correction optical element comprises a correction optical element main body for correcting the light beam and a frame provided around the correction optical element main body.
4. The optical scanning device according to claim 1, wherein the action portion of the elastic member distributes and transmits the external force to the frame body. 5.   5. The optical scanning apparatus according to claim 1, wherein the elastic member is disposed outside a support portion that supports the correction optical element. 6.   The optical scanning device according to claim 1, wherein the correction optical element is a resin toroidal lens.

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