JP2006154377A - Scanning optical apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and accurately position an fθ lens 6 without spoiling the optical characteristic of the fθ lens 6. <P>SOLUTION: In a scanning optical apparatus 100 in which a light source 1, a rotating polygon mirror 5 which deflects and scans a scanning luminous flux L emitted from the light source 1, the fθ lens 6 which focuses the luminous flux deflected with the rotating polygon mirror 5 are disposed in a housing member 7. The apparatus is characterized by that a marking 10 is given on the face of the fθ lens 6 opposing to the housing member 7 and the fθ lens 6 is positioned by detecting the marking 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a scanning optical apparatus that forms an electrostatic latent image by scanning a laser beam, and an electrophotographic apparatus such as an LBP, a digital copying machine, or a digital FAX that forms an image using the scanning optical apparatus. .

  Conventionally, in a scanning optical device used in an image forming apparatus such as a laser beam printer or a digital copying machine, the scanning lens is positioned in the scanning direction by arranging a positioning pin in an optical box as a device housing. (For example, see Patent Document 1). Specifically, as shown in FIG. 1 of Patent Document 1, it is performed by fitting a central protrusion provided at a substantially central portion of a scanning lens between positioning pins provided in an optical box. It was.

JP-A-11-72733 (FIG. 1)

  However, the positioning has the following problems.

  The scanning lens as described above is integrally formed of plastic. However, since the central protrusion has a shape protruding in the emission direction from the lens outer shape, the portion is partially thick. For this reason, in the process of taking out the scanning lens from the mold or the process of cooling, the scanning lens may be distorted and the optical characteristics may be impaired.

  Further, since the center projection and the positioning pin of the optical box are fitted, there is a fitting backlash. In particular, in a tandem color image forming apparatus that forms a color image using a plurality of image carriers, there is a possibility that color shift may occur due to the movement of the lens due to this loose fit.

  An object of the present invention is to easily and accurately position a scanning lens without impairing the optical characteristics of the scanning lens.

  A typical configuration according to the present invention for achieving the object includes a light source, a deflector that deflects and scans a light beam emitted from the light source, and a scanning lens that forms an image of the light beam deflected by the deflector. In the scanning optical device disposed in the device housing, a marking is formed on a surface of the scanning lens facing the device housing, and the scanning lens is positioned by detecting the marking. Features.

  With this configuration, it is not necessary to form a large member such as a positioning projection on the scanning lens, and the optical characteristics are not greatly affected. Further, if positioning is performed by detecting the marking and the scanning lens is integrally provided in the apparatus housing, it is possible to fix without looseness as compared with the case where the scanning lens is provided with a pin or the like. Thereby, positioning can be performed with high accuracy. Further, it is easy because positioning can be performed only by detecting the marking. Further, the number of members is not increased.

  Accordingly, the scanning lens can be easily and accurately positioned without impairing the optical characteristics of the scanning lens.

  The present embodiment will be described with reference to the drawings. In the description, after describing the outline of the image forming apparatus and the scanning optical apparatus, the positioning of the scanning lens, which is a characteristic part of the invention, will be described.

(Image forming device)
First, the overall configuration of the image forming apparatus will be described. FIG. 5 is a schematic explanatory diagram of the image forming apparatus. The image forming apparatus will be described by taking a monochromatic laser beam printer as an example. However, the present invention is not limited to this, and a tandem color image forming apparatus that forms a color image using a plurality of image carriers can also be used.

  As shown in FIG. 5, the image forming apparatus 30 includes a scanning optical device 100 that emits a laser beam (light beam) L, and a photosensitive drum that forms an electrostatic latent image using the scanning light beam L emitted from the scanning optical device 100. (Image carrier) 32. Around the photosensitive drum 32, a primary charger 33 that uniformly charges the photosensitive drum 32 before the electrostatic latent image is formed, and development is performed by supplying a developer to the electrostatic latent image. And a developing unit 34 for forming a toner image, and a transfer charging roller 35 for transferring the toner image to the transferred transfer material 36. A fixing device 37 for fixing the transferred toner image on the transfer material 36 and a discharge roller for discharging the transfer material 36 to the outside of the apparatus on the downstream side of the photosensitive drum 32 in the conveyance direction of the transfer material 36. 38 is arranged.

  With this configuration, image formation is performed as follows. A laser beam L optically modulated based on the image information is emitted from the scanning optical device 100. Since the surface of the photosensitive drum 32 is uniformly charged by the primary charger 33 in advance, an electrostatic latent image is formed on the surface of the photosensitive drum 32 by the emitted scanning light beam L.

  The electrostatic latent image is visualized as a toner image by the developing device 34. Thereafter, the toner image formed on the surface of the photosensitive drum 32 is attracted to the transfer material 36 by the voltage applied to the transfer charging roller 35 in order, thereby transferring the toner image. The toner image transferred onto the transfer material 36 is fixed by being pressurized and heated by a fixing device 37. Finally, the transfer material 36 is conveyed out of the apparatus by the discharge roller 38 and the image formation is completed.

(Scanning optical device)
The scanning optical device 100 of this embodiment will be described. FIG. 1 is a perspective view of the scanning optical device, and FIG. 2 is a top view of the scanning optical device.

  As shown in FIGS. 1 and 2, the light source unit from which the light beam of the scanning optical device 100 is emitted includes a light source 1 that generates the light beam, a collimator lens 2 that makes the light beam emitted from the light source 1 parallel light, A diaphragm 3 and a cylindrical lens 4 having refractive power only in the sub-scanning direction are sequentially arranged. A rotating polygon mirror (deflector) 5 for deflecting and scanning the light beam is disposed at the tip of the emitted light beam. Further, an fθ lens (scanning lens) 6 (6a, 6b) that has an fθ characteristic and forms an image on the photosensitive drum 32 is disposed at a point where the light beam is deflected and scanned.

  With the above configuration, the divergent light beam emitted from the light source 1 is made into a substantially parallel light beam by the collimator lens 2, the light amount of the light beam is adjusted by the diaphragm 3, and is incident on the cylindrical lens 4.

  The parallel light beam incident on the cylindrical lens 4 is emitted as a light beam that is converged only in the sub-scanning section in the state of a substantially parallel light beam in the main scanning section, and is formed as a line image on the reflecting surface 5a of the rotary polygon mirror 5. Image. The light beam deflected and scanned by the rotation of the rotary polygon mirror 5 passes through the fθ lens 6 and forms an image on the imaging surface of the photosensitive drum 32.

  A point image (spot) imaged on the imaging surface is scanned on the photosensitive drum 32 in the arrow B direction by rotating the rotary polygon mirror 5 in the arrow A direction. An electrostatic latent image is formed on the photosensitive drum 32 with such main scanning and sub-scanning by rotating the photosensitive drum 32 around its rotation axis. The fθ lens 6 described above is fixed to a housing member (apparatus housing) 7.

(Fθ lens positioning)
A structure for accurately positioning the fθ lens 6 with respect to the housing member 7 will be described. 2 is a top view of the scanning optical device 100, FIG. 3 is a sectional view of the fθ lens 6 (a sectional view taken along the line CC in FIG. 2), and FIG. 4 is a perspective view of the fθ lens 6 viewed from below.

  The fθ lens 6 is a plastic lens that is inexpensive and easy to process. A marking 10 indicating the center of the fθ lens in the scanning direction (arrow D direction) is provided at the center of the lower surface 9 of the fθ lens 6 on the side disposed on the housing member 7.

  The housing member 7 is provided with an opening 11 at a position facing the marking 10 attached to the fθ lens 6. Accordingly, the marking 10 of the fθ lens 6 can be recognized from the outside of the housing member 7 below the opening 11.

  With this configuration, the fθ lens 6 is positioned as follows. First, the fθ lens 6 is installed at an initial position on the housing member 7. Then, the fθ lens 6 is moved in the main scanning direction by a moving means (not shown).

  At this time, the mark detection means 12 for recognizing the fθ lens 6 from the outside of the housing member 7 is arranged outside the opening 11. For this reason, when the fθ lens 6 moves from the initial position on the housing member 7 and the marking 10 of the fθ lens 6 reaches a desired position, the mark detection means 12 indicates that the fθ lens 6 has moved to the desired position. Recognize

  When the mark detection means 12 recognizes that the fθ lens 6 has moved to a desired position, the movement of the fθ lens 6 is stopped and the positioning is performed by fixing it to the housing member 7. Here, the fixing means is fixed by a known method such as adhesion. By doing so, the fθ lens 6 can be accurately positioned with respect to the housing member 7.

  The mark detection means 12 may be a means for directly reading the marking 10 such as a CCD camera, or a means for reading using a reflective photosensor.

  The marking 10 of the fθ lens 6 will be described with reference to FIG. The marking 10 of the present embodiment is provided at the center of the fθ lens 6 in the main scanning direction. The size is such that it can be detected by the mark detection means 12. Specifically, it has a convex shape or a concave shape with a depth and width of about 0.5 mm, and is integrally formed with the fθ lens 6.

  The conventional central protrusion shape was about 3 mm wide, 2 mm thick, and 3 mm in protrusion. For this reason, compared with the conventional center protrusion, the marking 10 is considerably small, and the influence on the optical characteristics of the fθ lens 6 can be greatly suppressed.

  In addition, although the marking 10 of this embodiment is integrally molded with the fθ lens 6, it is not limited to this. For example, the fθ lens 6 may be provided as a print.

  As described above, a marking is provided at the center of the fθ lens 6 in the main scanning direction, and an opening is provided in the housing member at a position facing the marking, so that the position of the fθ lens in the main scanning direction can be adjusted from the outside of the housing member. It is possible to detect and fix the fθ lens 6 at a predetermined position.

  This eliminates the need for a central projection as in the prior art, so that when the fθ lens is formed, the fθ lens is not distorted and optical characteristics are not impaired in the step of removing from the mold or the step of cooling. Further, since the positioning is not performed by fitting to the positioning pins as in the prior art, there is no fitting play and positioning with high accuracy is possible.

  Further, it is easy because positioning can be performed only by detecting the marking. Furthermore, since it is a method of forming only the scanning lens and the apparatus housing without using pins or the like, the number of members is not increased.

  If the marking is provided at the end of the fθ lens in the main scanning direction, the mark detection position differs for each fθ lens. Here, if the marking is provided at the center of any fθ lens, the versatility is increased without changing the position of the detection means. For this reason, the position where the marking is provided is preferably the center of the fθ lens.

The perspective view of a scanning optical apparatus. The top view of a scanning optical apparatus. Sectional drawing of f (theta) lens (CC sectional drawing of FIG. 2). The perspective view which looked at the f (theta) lens from the lower side. 1 is a schematic explanatory diagram of an image forming apparatus.

Explanation of symbols

L ... Scanning light beam 1 ... Light source 5 ... Rotating polygon mirror (deflector)
6 ... fθ lens (scanning lens)
7: Housing member (device housing)
9 ... Bottom
10 ... Marking
11… opening
12 ... Mark detection means (detection means)
30 Image forming apparatus
32… Photoreceptor drum (image carrier)
100 ... Scanning optical device

Claims (5)

In a scanning optical device in which a light source, a deflector that deflects and scans a light beam emitted from the light source, and a scanning lens that forms an image of the light beam deflected by the deflector are disposed in an apparatus housing.
A scanning optical device, wherein a marking is formed on a surface of the scanning lens facing the device casing, and the scanning lens is positioned by detecting the marking. The scanning optical according to claim 1, wherein an opening for detecting the marking from the outside is formed in the apparatus housing at a position facing the marking formed on the scanning lens. apparatus. The scanning optical apparatus according to claim 2, further comprising a detection unit that detects the marking through the opening. The scanning optical device according to claim 1, wherein the marking is formed at a substantially central portion of the scanning lens in the main scanning direction. In an image forming apparatus comprising: an image carrier; and a scanning optical device for scanning the light beam with respect to the image carrier to form an electrostatic latent image.
5. The image forming apparatus according to claim 1, wherein the scanning optical apparatus is a scanning optical apparatus according to claim 1.

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