JP4904904B2 - Laser scanning optical device - Google Patents

Description

  The present invention relates to a laser scanning optical apparatus, and more particularly to a laser scanning optical apparatus for forming an image (electrostatic latent image) on a photoreceptor in an image forming apparatus such as a printer using electrophotography.

  Conventionally, in a laser scanning optical device mounted on a tandem type color printer, laser beams emitted from light sources for black and three primary colors (yellow, magenta, cyan) are concentrated on the reflecting surface of a polygon mirror. For example, Patent Document 1 discloses a single-sided deflection method in which light is incident and scanned on the photosensitive member with the reflected light. In the optical device described in Patent Document 1, a plurality of light sources are held on the bottom surface of a housing (housing of the optical device).

  By the way, it is also known that a plurality of light sources are held on the wall surface of the casing by a single-sided deflection method. As shown in FIG. , 62 are attached at different heights, and are incident on the optical axis A of the polygon mirror 56 through the composite member 55 at an angle of ± α, ± β (hereinafter referred to as oblique incidence), and the optical path is sub-scanned. A photoconductor (not shown) is scanned in the direction Z.

However, in the laser scanning optical device shown in FIG. 2, the semiconductor lasers 50 a to 50 d are held by the housing wall surfaces 61 and 62, so that the semiconductor lasers 50 a to 50 d vibrate in the direction in which the wall surfaces 61 and 62 fall. In response to (the polygon mirror 56 becomes a vibration source), the laser beam having a large oblique incident angle is more strongly affected than the small laser beam. Specifically, the semiconductor laser 50a having the oblique incident angle + β is held at the highest position, and is most strongly affected by the vibration of the wall surfaces 61 and 62, causing color misregistration and pitch unevenness in the image, thereby degrading the image quality. Had problems.
JP 2001-91873 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a laser scanning optical device that can suppress the influence as much as possible even if vibration is generated on a wall surface of a casing and can improve image quality.

In order to achieve the above object, the present invention provides:
Laser that guides the laser light emitted from each of the four light sources to the deflector via the first optical system, and guides the laser light deflected by the deflector onto the photosensitive member via the second optical system. In a scanning optical device,
Said first optical system, the four laser beams emitted from the four light sources,-beta relative to the optical axis to each of the deflectors,-.alpha., + alpha, so that the angle of + beta, And incident so as to intersect the deflection surface of the deflector ,
Each of the four light sources is held on the wall of the housing, and a light source that emits laser light incident at an angle of −β and a light source that emits laser light incident at an angle of + β are incident at an angle of −α. The height from the bottom of the housing is lower than the light source that emits laser light and the light source that emits laser light incident at an angle of + α,
α and β satisfy the relationship 0 <α <β,
It is characterized by.

According to the laser scanning optical apparatus according to the present invention, a light source for emitting a laser beam incident at an angle larger than the optical axis passes through a position away from the housing bottom to the deflector (± beta), small angle ( Because the height from the bottom of the housing is lower than the light source that emits laser light that is incident at ± α), laser light with a large oblique incidence angle that is easily affected by vibration of the housing wall is affected. The image quality is improved.

  Embodiments of a laser scanning optical apparatus according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a main part of an embodiment of a laser scanning optical apparatus according to the present invention. This laser scanning optical device is mounted on a tandem type color printer for forming an electrostatic latent image on a photoreceptor, and roughly includes a housing 20, semiconductor lasers 10a, 10b, 10c, 10d as light sources, The polygon mirror 16, the composite member 15 (first optical system) for guiding the laser beams 11a, 11b, 11c, and 11d emitted from the semiconductor lasers 10a to 10d to the polygon mirror 16, and the laser beam 11a deflected by the polygon mirror 16 To 11d on the photosensitive member. Note that the second optical system has a known configuration having an fθ function and the like, and illustration and detailed description thereof are omitted.

  The housing 20 holds the polygon mirror 16, the semiconductor lasers 10a to 10d, the second optical system, and the like, and is formed of a resin molded product. In addition, it may be comprised with the metal plate and the metal plate may be used for one part.

  The semiconductor lasers 10a to 10d are for forming a black image, and for forming images of each color of yellow, magenta, and cyan. As shown in FIG. 22 is attached. 1C and 1D schematically show the height from the bottom surface 23. 1C and 1D show the wall surfaces 21 and 22 as an integral unit.

  As shown in FIG. 1 (B), the combining member 15 has the optical path of the laser beams 11a, 11b, 11c, and 11d emitted from the semiconductor lasers 10a to 10d on the cross section in the sub-scanning direction Z. It has a function of bending three-dimensionally so that the angles with respect to the optical axis A are obliquely incident at ± α and ± β, respectively.

  Here, the present embodiment and the conventional example shown in FIG. 2 will be compared with respect to the structure for attaching the semiconductor lasers 10a to 10d to the wall surfaces 21 and 22. In the conventional example, the semiconductor laser 50a having an oblique incident angle + β passing above the optical axis A is disposed closest to the polygon mirror 56 as a vibration source and at the highest position, and the influence of the vibration of the wall surfaces 61 and 62 is affected. Strongly received. However, in the present embodiment, the semiconductor laser 10a having the oblique incident angle + β is disposed lower than the other semiconductor lasers 10b and 10c and at the same height as the semiconductor laser 10d. The variation of the oblique incident angle + β is suppressed without much influence. As a result, it is possible to eliminate problems that cause color misregistration and pitch unevenness in the image, and improve image quality.

  That is, when any one of the semiconductor lasers 10a and 10d having a large oblique incident angle is disposed at a position closest to the polygon mirror 16, the semiconductor laser 10a or 10d is disposed in a housing than the semiconductor lasers 10b and 10c having a small oblique incident angle. What is necessary is just to arrange | position the height from the bottom face 23 low. In other words, the semiconductor laser 10a that emits laser light 11a that passes through a position farther from the bottom surface 23 of the optical axis A and enters the polygon mirror 16 at a large oblique incident angle + β is separated from the bottom surface 23 of the housing. It is only necessary that it is not arranged at the highest position in height.

  The laser scanning optical apparatus according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  For example, the configuration of the combining member 15 that is the first optical system is arbitrary, and can be configured using a half mirror or a prism. Further, the four semiconductor lasers 10a to 10d do not necessarily need to be incident obliquely at a vertically symmetrical angle with respect to the optical axis A.

1 shows an embodiment of a laser scanning optical device according to the present invention, (A) is a plan view, (B) is a side view showing an oblique incident angle on a polygon mirror, and (C) and (D) are holding a semiconductor laser. It is an elevation view showing the height. 1 shows a conventional laser scanning optical device, (A) is a plan view, (B) is a side view showing an oblique incidence angle to a polygon mirror, and (C) and (D) are elevations showing a holding height of a semiconductor laser. FIG.

Explanation of symbols

10a to 10d ... Semiconductor laser 11a to 11d ... Laser light 15 ... Synthetic member (first optical system)
16. Polygon mirror (deflector)
20 ... Housing
21, 22 ... Wall 23 ... Bottom A ... Optical axis Z ... Sub-scanning direction

Claims (2)

Laser that guides the laser light emitted from each of the four light sources to the deflector via the first optical system, and guides the laser light deflected by the deflector onto the photosensitive member via the second optical system. In a scanning optical device,
Said first optical system, the four laser beams emitted from the four light sources,-beta relative to the optical axis to each of the deflectors,-.alpha., + alpha, so that the angle of + beta, And incident so as to intersect the deflection surface of the deflector ,
Each of the four light sources is held on the wall of the housing, and a light source that emits laser light incident at an angle of −β and a light source that emits laser light incident at an angle of + β are incident at an angle of −α. The height from the bottom of the housing is lower than the light source that emits laser light and the light source that emits laser light incident at an angle of + α,
α and β satisfy the relationship 0 <α <β,
A laser scanning optical device. The angle of + β is an angle located on the opposite side to the bottom surface of the housing with respect to the optical axis of the deflector, and a light source that emits laser light incident at an angle of + β is the light source among the four light sources. 2. The laser scanning optical apparatus according to claim 1, wherein the laser scanning optical apparatus is disposed at a position closest to the deflector.

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