JP2007334203A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the positional accuracy of a beam waist in a main scanning direction by correcting the shape error of a scanning lens without demanding a rigorous shape accuracy of the scanning lens. <P>SOLUTION: First scanning lenses 5 are selected from one and the same cavity for manufacturing the first scanning lenses, the averaged deviation of the optical characteristic (position of beam waist in main scanning direction) of every cavity for manufacturing the scanning lenses 5 is grasped, and light source units composed of respective combinations of a light source 1 and a coupling lens 2 which optimize the focusing state to correct the average deviation are preliminarily prepared for respective cavities. The positional deviation of the beam waist in the main scanning direction of the first scanning lenses 5 due to the shape accuracy for respective cavities is corrected by the combination. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical scanning device and an image forming apparatus used for a laser printer, a copying machine, a facsimile machine, and the like.

  In recent years, in order to increase the recording speed onto a transfer medium such as a color digital copying machine or a color laser printer, it has a plurality of scanned surfaces, and images of different colors are formed on the scanned surfaces. A so-called tandem type color image forming apparatus that forms a color image by sequentially transferring the image onto a transfer medium has been widely known.

  Here, the tandem full-color image forming apparatus will be briefly described. Four photosensitive media corresponding to the cyan (C), magenta (M), yellow (Y), and black (Bk) colors are arranged along the conveyance surface of the intermediate transfer belt. It shall be. The four scanned surfaces are optically scanned by the optical scanning device. The optical scanning device has four light sources that are driven by image signals corresponding to C, M, Y, and Bk colors, respectively, and scans the surface of each scanned surface with a light beam corresponding to each color. The images are formed on the plurality of scanned surfaces corresponding to the respective colors. Each image is developed with a corresponding color toner, and each toner image is transferred onto the intermediate transfer belt to form a full-color image. This full-color image is transferred and fixed on one transfer sheet.

  In a tandem type color image forming apparatus, for example, as disclosed in Patent Document 1, a scanning optical system is arranged on the left and right with a single deflector interposed therebetween, and light scanning is performed on a photoconductor as four scanned surfaces. There has been proposed an optical scanning device for performing the above.

  In addition, since the tandem color image forming apparatus performs optical scanning on the photoconductor which is the four scanned surfaces, the scanning optical system of the optical scanning apparatus improves the imaging performance and eliminates color misregistration and the like, and the scanning direction. It is necessary to obtain the beam waist position accuracy and the scanning lens shape accuracy.

On the other hand, in Patent Documents 2 to 4, in order to reduce dot position deviation in the scanning direction and form a color image without color deviation, a resin lens used for the scanning optical system is produced by the same cavity. A color image forming apparatus is disclosed in which the accuracy of parts is improved and the beam waist position shift is reduced.
JP 2002-090672 A JP 2000-187173 A Japanese Patent Laid-Open No. 2003-262813 Japanese Patent Laid-Open No. 2004-213029

  In the tandem color image forming apparatus having such a configuration, the resin scanning lens used in the scanning optical system is selected from the same cavity to improve the accuracy. The diameter of the beam spot to be scanned has also been reduced, and correction of part errors produced in the same cavity has become strict.

  In order to solve such a problem, the present invention provides a light source unit of an optical scanning device composed of a plurality of scanning optical systems used in a tandem color image forming apparatus or the like, among a plurality of scanning lenses constituting the scanning optical system. By selecting the same type of scanning lens from the same cavity and adjusting the condensing state of the light source unit in consideration of the shape accuracy of each cavity, the amount of error in the shape of each cavity for producing the scanning lens is corrected. It is an object of the present invention to provide an optical scanning device and an image forming apparatus that can improve the beam waist position accuracy in the main scanning direction without particularly stricting the shape accuracy of the scanning lens.

  In order to achieve the above object, an optical scanning device according to claim 1 of the present invention includes a plurality of light sources, a coupling optical system for coupling light beams emitted from the plurality of light sources, and a coupling optical system. A linear image optical system that converts a light beam from the light into a line image that is long in the main scanning direction, a deflecting unit that deflects a plurality of light beams emitted from the line image optical system by a deflecting reflecting surface having a common rotation axis, and deflected by the deflecting unit In an optical scanning device comprising a plurality of scanning optical systems for guiding a plurality of light beams onto different surfaces to be scanned, at least one of a plurality of types of scanning lenses used in the plurality of scanning optical systems is made by molding a plurality of resins with a resin. The light source unit consisting of the light source and the coupling optical system, selected from the same cavity, runs differently because the condensing state is different for each cavity for producing the scanning lens. Can loosen the surface accuracy and surface accuracy tolerance of the lens, it can be corrected in the main scanning direction of the beam waist position shift due to the shape accuracy using a scanning lens and the light source unit in accordance with the cavity.

  The optical scanning device according to claims 2 and 3 is the optical scanning device according to claim 1, wherein each of the plurality of scanning optical systems includes a plurality of scanning lenses, and at least a scanning lens having a large power in the main scanning direction. By selecting from the same cavity, and by giving a symbol to the scanning lens that can identify a plurality of cavities produced by molding, the cavity of the scanning lens having at least a large power in the main scanning direction is made the same. The beam waist position deviation in the main scanning direction can be corrected by using the light source unit corresponding to the cavity, and an error in assembling can be eliminated by the identification code of the cavity.

  In addition, the image forming apparatus according to claim 4 can obtain a stable beam spot diameter by using the optical scanning device according to any one of claims 1 to 3, and can form a good image. An image forming apparatus that performs the above can be realized.

  According to the present invention, the average deviation of the optical characteristics is grasped for each cavity of the resin scanning lens, and the combination of the light source unit that optimizes the light collection state for each cavity is used, thereby making the resin scanning The main scanning beam waist position deviation due to the shape accuracy of each lens cavity can be corrected, the surface accuracy of the scanning lens is not tightened, and the surface accuracy tolerance can be relaxed, improving yield and reducing costs, and reducing environmental impact The effect that it can also contribute to reduction is produced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a front view and FIG. 1B is a side view showing a schematic configuration of an optical scanning device according to Embodiment 1 of the present invention. In FIGS. 1A and 1B, 1 is a light source comprising a semiconductor laser, an LD array, etc., 2 is a coupling lens, 3 is a cylindrical lens, 4 is a deflector, 5 is a first scanning lens made of resin, 6 Is a resin-made second scanning lens, and 7 is a photosensitive medium, which is a surface to be scanned that is imaged by scanning lines. In FIGS. 1A and 1B, illustration of an aperture, dustproof glass, and the like disposed between the deflector 4 and the first scanning lens 5 is omitted.

  The first embodiment will be described with reference to FIGS. 1 (a) and 1 (b). As shown in FIG. 1A, the light beam emitted from the light source 1 is coupled into a substantially parallel light beam by the coupling lens 2, enters the cylindrical lens 3, and is condensed into a substantially linear shape that is long in the main scanning corresponding direction. However, the light enters the deflector 4. A light beam deflected by the deflector 4 passes through the first scanning lens 5 and the second scanning lens 6 to form a scanning optical system that forms an image on the scanned surface 7.

  As described above, in the scanning optical system, the scanning optical system of each station corresponding to, for example, four colors of C (cyan), M (magenta), Y (yellow), and Bk (black) is applied to the scanned surface 7 of each color. An image is formed to form a color image.

  The deflecting surface of the deflector 4 may be a common deflecting surface, or may be composed of two upper and lower deflecting surfaces. As shown in FIG. Each of the first scanning lens 5 and the second scanning lens 6 is made of a scanning optical system and is made of resin.

  Furthermore, a scanning lens made of an aspherical surface is being advanced to reduce the beam spot diameter, and a resin-made scanning lens has become mainstream in order to reduce the cost of the scanning lens. As an advantage of producing by resin molding, a plurality of molds can be formed by using a metal mold, which is advantageous for cost reduction.

  However, in the case of multiple molding, the surface accuracy of the scanning lens in each cavity of the mold is not necessarily constant due to the influence of the surface accuracy of the metal piece for creating the mirror surface, the temperature distribution of the mold, etc. In the case of the optical scanning device used in the tandem type image forming apparatus as shown in FIGS. 1A and 1B, the beam waist position shift amount on the scanned surface 7 differs for each station. Further, since the beam spot diameter has been reduced for the above-described high image quality, the smaller the beam spot diameter, the smaller the depth and the allowable deviation of the beam waist position (focus position). Get smaller.

  For example, when the first scanning lens 5 and the second scanning lens 6 made of resin are each made by four molding, when the first scanning lens 5 and the second scanning lens 6 are combined with random cavities, Each scanning optical system of the four stations has different optical characteristics.

  As the same type of scanning lens used in the optical scanning device, each of the first scanning lens 5 and the second scanning lens 6 is composed of four of the same cavity, so that the scanning optical system of the four stations separates the cavities. The optical characteristics are more uniform than those used in the above. Here, “uniform” means that the beam waist position deviations in the main scanning direction are equal, and indicates that the variation from station to station is reduced.

  Naturally, as an optical element other than the scanning lens, the optical characteristics of the four sets of scanning optical systems are not exactly the same due to surface accuracy error of the folding mirror, but as a factor of beam waist position deviation in the main scanning direction. Since the contribution of the surface accuracy error of the scanning lens is large, the optical characteristics of the scanning optical system can be made substantially the same.

  In addition, the first scanning lens 5 and the second scanning lens 6 are configured by selecting a cavity for producing the first scanning lens 5 having a strong power in the main scanning direction from the same cavity, thereby performing the main scanning of each station. The beam waist position shift in the direction can be shifted to the same extent in substantially the same direction.

  As an adjustment in the optical scanning device for correcting another beam waist position, it is conceivable to adjust the coupling lens 2 in the direction of the optical axis. However, the adjustment of the distance between the light source 1 and the coupling lens 2 is micron. Since adjustment at the level is required, adjustment within the optical scanning device is difficult, and a long assembling time is required.

  Therefore, in the present invention, the above-described resin-made scanning lens is selected from the same cavity, and the average deviation of the optical characteristics (main scanning beam waist position) for each cavity in which the first scanning lens 5 is manufactured is grasped. In addition, by preparing a light source unit including a light source 1 and a coupling lens 2 optimized in a condensing state so as to correct the average deviation for each cavity, the first scanning lens 5 is provided. The beam waist position deviation in the main scanning direction due to the shape accuracy of each cavity was corrected.

  For example, if the radius of curvature of the first scanning lens 5 tends to increase and the main scanning beam waist position shifts to the plus side, the light source unit is made to be focused light with respect to the designed parallel light beam. A light source unit that optimizes the light collection state so as to be corrected by the above is prepared for each cavity in advance, and the beam waist position deviation in the main scanning direction due to the shape accuracy is corrected.

  In this way, the beam waist position in the main scanning direction can be aligned on the scanned surface 7 without making the surface accuracy of the first scanning lens 5 strict. Moreover, since the light source unit is preliminarily adjusted in the light condensing state, adjustment in the optical scanning device is not necessary, and assembly time can be shortened. Furthermore, since the surface accuracy tolerance of the resin scanning lens itself can be relaxed, the yield can be improved and the cost can be reduced, and the environmental load can be reduced.

  When the resin first scanning lens 5 is a four-piece mold, four types of light sources 1 corresponding to the four cavities are prepared. Here, if a light source unit corresponding to each cavity is prepared, in the case of a four-station tandem optical system, the cavities of the four resin-made first scanning lenses 5 are randomly attached to the cavities. A corresponding light source unit may be used. In this case, however, the assembly of the optical scanning device is confused, and the possibility that the light source unit corresponding to the cavity of the resin-made first scanning lens 5 is mistakenly assembled is increased. Therefore, it is desirable to unify the cavities of the first scanning lens 5 made of resin in the optical scanning device.

  Of course, it is possible to increase the accuracy by repeating the metal piece processing and reduce the difference between the cavities, but it is difficult to implement because the time and cost of the metal piece processing increase.

  In the first embodiment, both the first and second scanning lenses 5 and 6 in the scanning optical system are resin lenses, but one may be made of glass, and at least one is resin. The present invention can be applied to a case where a plurality of resin lenses are manufactured by molding by using a lens.

  FIG. 2 is a front view showing a schematic configuration of the optical scanning device in another example of the first embodiment. The configuration of the optical scanning device shown in FIG. 1A is that of the light source 1 and the coupling lens 2. The operation is the same as that described above, except that a multi-beam is provided with a plurality of light source units.

  In addition, a resin scanning lens manufactured by multiple molding is given a symbol that identifies the manufactured cavity, and it is identified when combined with the light source unit. Can be eliminated.

  FIG. 3 is a diagram showing a schematic configuration of an image forming apparatus using the optical scanning device according to the second embodiment of the present invention.

  According to the image forming apparatus shown in FIG. 3, each color photoconductor having the surface to be scanned 7 rotates at a substantially constant speed in the clockwise direction indicated by the arrow in the figure to form a full color image. The surface of the photosensitive member is uniformly charged by the charging unit 10 and is exposed and scanned by the optical scanning device on the surface to be scanned 7 to write an electrostatic latent image. Further, the toner image visualized as a toner image by the developing unit 11 and visualized on the plurality of scanned surfaces 7 by the transfer unit 12 is sequentially transferred and superimposed on the intermediate transfer belt 13 so as to be formed as one image. A full color image is formed. This full-color image is transferred onto the transfer sheet S by another transfer unit 14 and fixed by the fixing unit 15 to complete image formation, and is discharged outside the apparatus.

  The surface to be scanned 7 is removed by the cleaning means 16 from the toner and paper dust remaining without being completely transferred. Thereafter, it is charged again by the charging means 10.

  In such an image forming apparatus, by using the optical scanning device described above, a stable beam spot diameter can be obtained, and an image forming apparatus that can perform good image formation can be realized.

  The optical scanning device and the image forming apparatus according to the present invention grasp the average deviation of the optical characteristics for each cavity of the resin scanning lens and combine it with the light source unit that optimizes the light collection state for each cavity. By using it, the main scanning beam waist displacement due to the shape accuracy of each cavity of the resin scanning lens can be corrected, the surface accuracy of the scanning lens is not tightened, and the surface accuracy tolerance can be relaxed, improving the yield of the apparatus. It is possible to reduce the cost and contribute to reducing the environmental load, and is useful as an apparatus used for a laser printer, a copying machine, a facsimile machine, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS (a) which shows schematic structure of the optical scanning device in Embodiment 1 of this invention is a front view, (b) is a side view The front view which shows the other structure of the optical scanning device in this Embodiment 1. FIG. FIG. 5 is a diagram illustrating a schematic configuration of an image forming apparatus using an optical scanning device according to a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Coupling lens 3 Cylindrical lens 4 Deflector 5 1st scanning lens 6 2nd scanning lens 7 To-be-scanned surface 10 Charging means 11 Developing means 12, 14 Transfer means 13 Intermediate transfer belt 15 Fixing means 16 Cleaning means

Claims (4)

A plurality of light sources, a coupling optical system that couples light beams emitted from the plurality of light sources, a line image optical system that converts a light beam from the coupling optical system into a line image that is long in a main scanning direction, and the line image An optical scanning device comprising a deflecting unit for deflecting a plurality of light beams emitted from an optical system by a deflecting reflecting surface having a common rotation axis, and a plurality of scanning optical systems for guiding the plurality of light beams deflected by the deflecting unit onto different scanned surfaces In
A light source comprising at least one of a plurality of types of scanning lenses used in the plurality of scanning optical systems selected from the same cavity formed by molding a plurality of resins with a resin, and comprising the light source and the coupling optical system An optical scanning device characterized in that the unit has a different light collection state for each cavity for producing the scanning lens.   2. The optical scanning device according to claim 1, wherein each of the plurality of scanning optical systems includes a plurality of scanning lenses, and scanning lenses having at least a large power in the main scanning direction are selected from the same cavity.   The optical scanning device according to claim 1, wherein a symbol that makes it possible to identify a plurality of cavities produced by molding is added to the scanning lens.   An image forming apparatus using the optical scanning device according to claim 1.

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