JP2006350065A - Scanning optical system, optical scanning device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning optical system, an optical scanning device and, an image forming apparatus, which adjust a curved scanning line like a quadratic curved line or a curve scanning line like a three-dimensional function in a small number of adjusting steps. <P>SOLUTION: The scanning optical system condenses a beam deflected by a deflector to the proximity of a scanning surface, and the optical system is characterized in that: the scanning optical system comprises at least one scanning lens 4; the lens 4 includes a means 10 to correct a quadratic component in a curved scanning line, and a means 11 to correct a component of a curved scanning line like an odd-number function of three or more dimensions; the means 10 to correct a quadratic component in a curved scanning line presses an almost center of at least one scanning line, in a direction almost perpendicular to the scanning plane; and the correcting means 11 presses at an end in the longitudinal direction of the scanning lens 4, in a deflector side or a scanning plane side of the scanning lens 4, in a direction perpendicular to the scanning plane to twist the lens 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a scanning optical system used in a laser printer, a digital copying machine, a facsimile, and the like, an optical scanning device, and an image forming apparatus such as the laser printer having the optical scanning device and digital copying.

  In recent years, with the increase in image quality and density of color laser printers and digital color copying apparatuses, the problem of color misregistration required for optical scanning apparatuses has become an issue to be solved. In order to solve this problem, there has been proposed a technical means for adjusting the scanning line curve by pressing the central portion in the longitudinal direction of a long lens as a scanning lens in the sub-scanning direction (see, for example, Patent Document 1). . However, with this conventional technical means, it is possible to adjust the scan line curve of a quadratic curve, but it is not possible to adjust the scan line curve of a higher order component.

  In addition, technical means has also been proposed that can adjust higher-order components of scanning line bending by providing adjusting means, for example, three screws, along the main scanning direction of the long lens (for example, Patent Document 2). reference). However, according to the invention described in Patent Document 2, in the mass-produced image forming apparatus, providing the adjustment process at each of the three long lenses has a problem that the adjustment process becomes complicated and the cost increases.

  The inventor of the present invention has invented an adjusting device that can adjust a scanning line curve such as a quartic function, for example, an M-shaped or W-shaped scanning line, by adjusting means such as two male screws. However, according to the present invention, it has been found that there is a problem that it is not possible to adjust a scanning line curve of a cubic function (odd function), for example, an S-shaped scanning line curve.

JP 9-33846 A JP 2002-182145 A

  The present invention has been made in view of the above-described problems of the prior art, and adjusts not only a quadratic scanning line curve but also a cubic (odd function) scanning line curve with fewer adjustment steps. An object of the present invention is to provide a scanning optical system, an optical scanning device, and an image forming apparatus.

  According to the present invention, as in the first aspect of the invention, in the scanning optical system for condensing the light beam deflected by the optical deflector in the vicinity of the surface to be scanned, the scanning optical system comprises at least one scanning lens, It is most preferable that at least one scanning lens has a means for correcting a quadratic function component of the scanning line curve and a means for correcting an odd function line curve component of a cubic function or higher. Main features.

The means for correcting the quadratic function component of the scanning line bending is a means for pressing the substantially center of at least one scanning lens in a direction substantially perpendicular to the scanning plane as in the invention of claim 2. Good.
Further, the correcting means presses the optical deflector side or the scanned surface side of the scanning lens in a direction substantially perpendicular to the scanning surface at the end in the longitudinal direction of the scanning lens as in the invention described in claim 3. By doing so, it is preferable to twist the scanning lens.
The at least one scanning lens may be configured to be capable of adjusting the inclination of the scanning line by being rotatably provided with the lower surface or the upper surface at the center as a fulcrum, as in the fourth aspect of the invention.

According to a fifth aspect of the present invention, there is provided an optical deflector that deflects a light beam from a light source, and a scanning optical system that causes the light beam deflected by the optical deflector to converge on the surface to be scanned and scan the surface to be scanned. A scanning apparatus includes the scanning optical system according to any one of claims 1 to 4 as the scanning optical system.
According to a sixth aspect of the present invention, the optical scanning device may include a plurality of scanning optical systems.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus for forming an image by executing an electrophotographic process, wherein the optical scanning device according to the fifth or sixth aspect is used as an apparatus for performing an exposure process in the electrophotographic process. It is used.

  According to the first to fourth aspects of the invention, it is possible to adjust not only the scanning curve of a quadratic curve but also the scanning curve of a cubic function (odd function) with fewer adjustment steps. By reducing the adjustment process time, it is possible to reduce the scanning line bending while reducing the cost. In addition, the cost can be reduced by reducing the number of parts and reducing the accuracy of the receiving portion of the scanning lens.

  According to the fifth aspect of the present invention, it is possible to provide an optical scanning device with a small image distortion by reducing the scanning line bending.

  According to the sixth aspect of the invention, in the tandem scanning optical system composed of a plurality of scanning optical systems, the scanning line bending of each scanning optical system can be reduced, so that the tandem scanning optical system is used as a color image forming apparatus. When applied, it is possible to provide an optical scanning device capable of obtaining a color image with small color misregistration.

  According to the seventh aspect of the invention, an image forming apparatus capable of outputting a high-quality image can be provided by using the optical scanning device according to the fifth or sixth aspect, and if used in a color laser printer or the like. An image forming apparatus free from color misregistration can be provided.

Embodiments of a scanning optical system, an optical scanning device, and an image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration example of a scanning optical system and an optical scanning device according to the present invention. The configuration example of the scanning optical system and the optical scanning device shown in FIG. 1 is configured as a so-called tandem scanning optical system having a plurality of scanning optical systems, more specifically, four scanning optical systems. Reference numerals 1-1 to 1-4 denote light source units. These light source units include, for example, a light source composed of a semiconductor laser and a coupling lens that narrows down the laser light emitted from the light source. Reference numerals 1a-1 to 1a-4 denote cylindrical lenses, 2 denotes an optical deflector composed of a polygon mirror, 3-1 to 3-4 denote first scanning lenses constituting a scanning optical system, and 4-1 to 4- Reference numeral 4 denotes a second scanning lens constituting the scanning optical system, and reference numerals 5-1 to 5-4 denote a surface to be scanned which is the surface of the drum-shaped photosensitive member. Since the configuration and operation of each scanning optical system are the same, the following description will be made using a symbol in which one scanning optical system is represented by omitting the symbol “−”. In other words, reference numeral 1 denotes a light source unit, 1a denotes a cylindrical lens, 3 denotes a first scanning lens, 4 denotes a second scanning lens, and 5 denotes a surface to be scanned.

  The light beam emitted from the light source of the light source unit 1 is coupled into a substantially parallel light beam by the coupling lens included in the light source unit 1 and enters the cylindrical lens 1a. The light beam is converged only in the sub-scanning corresponding direction by the cylindrical lens 1a, and is converged in a substantially linear shape in the main scanning corresponding direction, and is incident on the deflecting / reflecting surface of the optical deflector 2. The polygon mirror constituting the optical deflector 2 is rotationally driven at a high speed at a constant speed, thereby deflecting and reflecting the light beam at each deflection reflection surface. The deflected light beam passes through the first scanning lens 3 and the second scanning lens 4, is reflected by an appropriate mirror, is guided to the scanned surface 5, and forms an image as a light spot on the reflected surface 5. Scanning optics composed of the first scanning lens 3 and the second scanning lens 4 so that the spot of the light beam deflected at a constant angular velocity by the rotational driving of the polygon mirror is scanned on the surface to be scanned 5 at a constant speed. System characteristics are defined. The equiangular velocity optical scanning direction is the main scanning direction, and the direction along the rotation center axis direction of the surface to be scanned 5 made of the drum-type photosensitive member is the main scanning direction. Adjustment is made by adjusting the scanning lens so that the scanning line in the main scanning direction due to the light spot is not bent.

  Here, the conventional scanning line curve adjustment will be described. FIG. 2 shows the prior art. For example, in the case of the scanning optical system having the configuration shown in FIG. 1, the scanning line bending is adjusted by pressing substantially the center in the longitudinal direction of the second scanning lens 4 which is a long lens in the sub-scanning direction. More specifically, the lower surfaces of both end portions in the longitudinal direction of the outer peripheral portion 41 of the second scanning lens 4 are placed on the support base 42, and the second scanning lens 4 is pressed from above by pressing substantially the center in the longitudinal direction. The scanning lens 4 is adjusted by bending in the sub-scanning direction. However, in this conventional method, when a S-shaped scanning line curve having a cubic function as shown in FIG. 4A is generated, the scanning line curve cannot be adjusted.

Further, in the invention described in Patent Document 2, the higher-order component of the scanning line curve can be adjusted by providing three adjusting means made of a female screw along the main scanning direction of the long lens. However, the provision of three adjustment steps in the mass production process of the scanning optical system has a problem of high cost.
In the embodiment of the scanning optical system according to the present invention, such a conventional problem can be solved.

  FIG. 3 shows Example 1 of the scanning optical system according to the present invention. In this example, a scanning line bending adjustment mechanism is incorporated in the second scanning lens 4 of the optical scanning device shown in FIG. FIG. 3A is a view as seen from the optical axis direction, and FIG. 3B is a sub-scan sectional view at the substantially center in the longitudinal direction of the scanning lens 4. The lower surfaces of both ends of the scanning lens 4 in the longitudinal direction are placed on protrusions formed on the housing 50, and the bent portions of both ends of the sheet metal 20 made of a material such as iron are placed on the upper surfaces of both ends of the scanning lens 4 in the longitudinal direction. The scanning lens 4 is sandwiched between the protruding portion of the housing 50 and the bent portions of the metal plate 20. The upper ends of the longitudinal ends of the sheet metal 20 are covered with the bent upper ends of the leaf springs 30 and 31 fixed to the housing 50, and the leaf springs 30 and 31 press the both ends of the sheet metal 20 from the top to the bottom. The scanning lens 4 is fixed to the housing 50 together with the sheet metal 20.

  One first adjusting screw 10 as a correcting means is screwed into the longitudinal center portion of the sheet metal 20 from the top to the bottom, and the tip of the first adjusting screw 10 is on the upper surface of the longitudinal center portion of the scanning lens 4. It is in contact. Between the lower surface of the scanning lens 4 and the housing 50, there is a gap corresponding to the protruding height of the protruding portion except for the protruding portion of the housing 50, and a plate spring 40 is disposed in the gap, and the scanning lens. The leaf spring 40 is pushed upward by the elasticity of the central portion in the longitudinal direction 4. As shown in FIG. 3B, the first adjusting screw 10 is in contact with the center of the length of the scanning lens 4 in the optical axis direction. When the screwing amount of the adjusting screw 10 is adjusted, the scanning lens 4 is moved in the vertical direction, that is, the scanning plane. On the other hand, the amount of bow-like bending in a direction substantially perpendicular to the vertical direction is adjusted, and the scanning line bending can be adjusted. Further, the second adjustment screw 11 as a correction means is screwed into the metal plate 20 through the bent upper end portion of the plate spring 31 from above, and the tip of the second adjustment screw 11 comes into contact with the upper surface of the scanning lens 4. Yes. As shown in FIG. 3C, the contact position of the second adjustment screw 11 with the scanning lens 4 is biased to one side, for example, the front side of the length of the scanning lens 4 in the optical axis direction. 11 is adjusted, the amount of inclination of the scanning lens 4 in the front-rear direction of the optical axis, and hence the amount of twist of the scanning lens 4 can be adjusted. The first adjustment screw 10 is a means for correcting a quadratic function component of scanning line bending. The second adjusting screw 11 is a means for correcting an odd-numbered scanning line curve component that is a cubic function or higher, and as described above, the position of contact with the scanning lens 4 is set in the optical axis direction of the scanning lens 4. The scanning lens is biased to one side of the length, that is, the optical deflector side or the surface to be scanned of the scanning lens 4 and the optical deflector side or the surface to be scanned is pressed in a direction substantially perpendicular to the scanning surface. 4 is twisted.

  Next, a method for adjusting the scanning line bending by the first and second adjusting screws 10 and 11 will be described. First, by adjusting the screwing amount of the first adjusting screw 10, the central portion in the longitudinal direction of the scanning lens 4 is moved in the sub-scanning direction, and the second-order curve scanning line bending on the surface to be scanned is adjusted. Next, the first adjustment screw 10 is fixed, and the tightening degree of the second adjustment screw 11 is finely adjusted. By adjusting the second adjusting screw 11, the amount of twist of the scanning lens 4 is adjusted as described above, and the amount of cubic line-like scanning line bending on the surface to be scanned can be adjusted to be smaller. When the S-shaped scanning line curve having a cubic function as shown in FIG. 4A is generated, the S-shaped scanning line curve having the cubic function is adjusted by adjusting the second adjusting screw 11. By adjusting, the scanning line bending can be reduced as shown in FIG.

  In this way, the degree of tightening of the two screws 10 and 11 as the scanning line bending correction means is adjusted, and the scanning lens 4 is kinked to adjust the cubic function component of the scanning line bending. . This is because, for example, when the flatness of the receiving portions at both ends of the metal plate 20 supporting the scanning lens 4 or the receiving portions at both ends of the housing 50 is shifted, the scanning lens 4 is kinked, and the S-shaped. Since scanning line bending occurs, this scanning line bending is adjusted. Strict management of the flatness of the receiving portions at both ends of the sheet metal 20 and the receiving portions at both ends of the housing 50 can reduce the bending of the scanning line, but this greatly increases the manufacturing cost. In that respect, according to the above embodiment, the accuracy of the receiving portions at both ends of the sheet metal 20 and the receiving portions at both ends of the housing 50 can be relaxed, so that a predetermined performance can be obtained while increasing manufacturing efficiency. Manufacturing cost can be reduced.

  Next, a second embodiment shown in FIG. 6 will be described. In FIG. 6, the scanning lens 4 is sandwiched between leaf springs 22, 23 bent in a U-shape with the projections of the sheet metal 21 in contact with the upper surfaces of both longitudinal ends, and integrated with the sheet metal 21. Has been. The housing 51 has a protrusion at a position corresponding to the longitudinal center of the scanning lens 4, and the lower surface of the scanning lens 4 is in contact with the protrusion. The sheet metal 21 is fixed to the ceiling portion of the housing 51 via the leaf springs 24 and 25. Reference numeral 32 denotes a stepping motor. For example, the lead screw provided on the output shaft of the stepping motor 32 is screwed into the screw hole of the sheet metal 21. By controlling the rotation of the stepping motor 32, the sheet metal in FIG. The left end portion of 21 is moved up and down in the sub-scanning direction, and the inclination of the scanning lens 4 is adjusted with the projection of the housing 51 as a fulcrum. In other words, not only the scanning line bending but also the scanning line inclination can be adjusted.

  Similarly to the first embodiment, this embodiment also includes a first adjusting screw 10 and a second adjusting screw 11, and these adjusting screws 10 and 11 are the first adjusting screw 10 in the first embodiment. And the same function as the second adjustment screw 11. However, in the case of the second embodiment, as shown in FIG. 6B, the central portion in the longitudinal direction of the scanning lens 4 is sandwiched with the sheet metal 21 by U-shaped plate springs 26 and 27 from the front and rear in the optical axis direction. They are fixed to each other. 6A, the right end portion of the scanning lens 4 is pressed by the second adjustment screw 11 shown in FIG. 6C, and the scanning lens 4 is kinked. The amount of kinking is adjusted by the second adjustment screw 11. Thus, the scanning line curve is finely adjusted.

  In the case of the second embodiment shown in FIG. 6 as well, it is a premise that the sheet metal 21 is higher in rigidity than the scanning lens 4. The adjustment method is the same as the adjustment method of the first embodiment shown in FIG. 3, wherein the first adjustment screw 10 adjusts the scanning curve of the quadratic curve, and the second adjustment screw 11 distorts the scan lens 4. It is possible to adjust the scanning line bending component generated by a cubic function (odd function). In addition, the inclination of the scanning line can be adjusted by controlling the rotation of the stepping motor 32.

  FIG. 5 shows a simulation result of the scanning optical system according to the present invention. In this simulation, the curve A before adjustment is a result of simulation in a state in which the scanning lens 4 is intentionally bent. Next, a curve B represents the result of adjusting the tilt component and the scanning curve curve like a quadratic curve by the first adjusting screw 10 and the stepping motor 32. Next, the scanning line curve is adjusted by twisting the scanning lens 4 by tightening the second adjusting screw 11. As is apparent from the simulation results, the scan line bend is greatly improved by adjusting the tilt component and the scan line bend in the form of a quadratic curve as compared with those before the adjustment, and scanning is performed by tightening the second adjustment screw 11. It can be seen that the scan line curve is improved more satisfactorily by adjusting the scan line curve like a cubic function by twisting the lens 4.

As shown in FIG. 6C, the scanning lens receiving portion on one side of the sheet metal 21 into which the second adjustment screw 11 is screwed is slightly inclined in the optical axis direction so that the scanning lens 4 is twisted in advance. Is attached. In this way, the kinking adjustment range of the scanning lens 4 can be increased. It is assumed that the sheet metal 21 has sufficiently high rigidity compared to the scanning lens 4. The scanning lens 4 is made of resin, for example.
In the embodiments shown in FIGS. 1, 3, and 6, the scanning optical system is composed of a first scanning lens and a second scanning lens, and an adjustment screw as scanning line bending correction means is provided in the second scanning lens. However, the correction means may be provided in the first scanning lens. When the scanning optical system is composed of one scanning lens, the correction means is provided for the one scanning lens. In short, at least one scanning lens has means for correcting the quadratic function component of the scanning line curve, and means for correcting the odd line function component of the cubic function or higher. It only has to be.

In the example of the optical scanning device shown in FIG. 1, by employing a scanning optical system having an adjustment mechanism as shown in FIG. 3 or FIG. 6, an optical scanning device with less scanning line bending can be obtained.
In addition, by using an optical scanning apparatus that employs a scanning optical system having an adjustment mechanism as shown in FIG. 3 or 6 in the image forming apparatus, a high-definition and high-quality image can be formed. In particular, an optical scanning device provided with a scanning optical system according to the above embodiment in a color-compatible image forming apparatus that forms an image with image signals for a plurality of colors and superimposes these images to obtain a color image. By adopting, it is possible to obtain a high-quality color image with little color misregistration.

  The image forming apparatus referred to here is, for example, an image forming apparatus that forms an image by executing an electrophotographic process. The electrophotographic process consists of a charging device that uniformly charges the photosensitive member that is the surface to be scanned as described above, an exposure device that forms an electrostatic latent image by exposing in accordance with an image signal, and the electrostatic latent image is converted into toner. A developing device for developing the toner image, a transfer device for transferring the toner image onto a transfer medium such as transfer paper, a fixing device for fixing the toner image on the transfer medium, and a cleaning device for removing residual toner after transfer. By employing an optical scanning device employing a scanning optical system having an adjustment mechanism as shown in FIG. 3 or FIG. 6 as the exposure device, an image forming apparatus capable of obtaining the above-described effects can be obtained. Can do. Since an image forming apparatus that forms an image by executing an electrophotographic process is well known, illustration is omitted.

1 shows an embodiment of an optical scanning device according to the present invention, where (a) is a plan view seen from a main scanning correspondence direction, and (b) is a side view seen from a sub-scanning correspondence direction. It is a front view which shows the general adjustment method of the scanning lens in a scanning optical system. 1 shows a first embodiment of a scanning optical system according to the present invention, where (a) is a front view, (b) is a cross-sectional view taken along line aa ′ in (a), and (c) is (a). It is sectional drawing in alignment with line bb 'in the inside. FIG. 4 is a characteristic diagram showing an example of scanning line bending, where (a) shows a cubic function-like S-shaped scanning line bending, and (b) shows a scanning line bending after adjusting the scanning line bending in (a) above. Indicates. It is a characteristic diagram which compares and shows the state of a scanning line bend before a scan line bend adjustment, after a tilt and a quadratic curve component adjustment, and after a twist adjustment. 2 shows a second embodiment of the scanning optical system according to the present invention, in which (a) is a front view, (b) is a sectional view taken along line aa ′ in (a), and (c) is (a). It is sectional drawing in alignment with line bb 'in the inside.

Explanation of symbols

2 Optical deflector 4 Scan lens 10 First adjustment screw 11 Second adjustment screw

Claims (7)

In the scanning optical system that focuses the light beam deflected by the optical deflector in the vicinity of the surface to be scanned,
The scanning optical system comprises at least one scanning lens, and at least one scanning lens has means for correcting a quadratic function component of scanning line bending, and is an odd function having a cubic function or higher. A scanning optical system comprising means for correcting a scanning line bending component. 2. The scanning optical system according to claim 1, wherein means for correcting a quadratic function component of scanning line bending is means for pressing substantially the center of at least one scanning lens in a direction substantially perpendicular to the scanning plane. A scanning optical system. 3. The scanning optical system according to claim 1, wherein the correcting means presses the optical deflector side or the scanned surface side of the scanning lens in a direction substantially perpendicular to the scanning surface at an end portion in the longitudinal direction of the scanning lens. A scanning optical system characterized in that the scanning lens is twisted. 4. The scanning optical system according to claim 1, wherein at least one scanning lens is provided so as to be rotatable about a central lower surface or upper surface as a fulcrum, so that the inclination of the scanning line can be adjusted. A scanning optical system. An optical scanning device comprising: an optical deflector that deflects a light beam from a light source; and a scanning optical system that causes the light beam deflected by the optical deflector to converge on the scanned surface and scan the scanned surface. An optical scanning apparatus comprising the scanning optical system according to claim 1. 6. The optical scanning device according to claim 5, wherein the optical scanning device includes a plurality of scanning optical systems. 7. An image forming apparatus for forming an image by executing an electrophotographic process, wherein the optical scanning device according to claim 5 or 6 is used as an apparatus for performing an exposure process in the electrophotographic process. Forming equipment.

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