JPH0511211A - Optical scanning device - Google Patents

Abstract

PURPOSE:To excellently make an optical scan on an object surface while reducing the size of the whole device by using an optical deflector where plural refracting members are annularly arranged and a light source means which is arranged inside the annulation. CONSTITUTION:The optical deflector 2 which has the refracting members annularly arranged at equal intervals is mounted rotatably on a driving means 3 and the light source means 1 is arranged in the annulation of the optical deflector 2; and luminous flux emitted by the light source means 1 is made incident on the refracting members and optically deflected luminous flux is guided onto the scanned surface 7, which is scanned. Those refracting members are prisms or lenses. The laser light which is optically modulated and emitted from the light source means 1 is made incident on one of the refracting members of the optical deflector 2, refracted and deflected and made incident on a scanning lens 6, and converged by the scanning lens 6 and made incident on the scanned surface 7. In this case, the optical deflector 2 is rotated by the driving means 3 around an axis 4 of rotation to optically scan the scanned surface 7 as shown by an arrow 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an electrophotographic process for forming an image by optically scanning a surface to be scanned which is an image bearing member such as a photosensitive member or an electrostatic recording member. The present invention relates to an optical scanning device suitable for an apparatus such as a laser beam printer, a color laser beam printer, and a multi-color laser beam printer having the above.

[0002]

2. Description of the Related Art Conventionally, in an optical scanning device such as a laser beam printer, writing of image information is performed by optically scanning the surface of an image carrier with a light beam modulated.

FIG. 4 is a schematic view of a main part of a conventional optical scanning device. In the figure, a light beam emitted from a light source unit 1 such as a semiconductor laser is collimated by a collimator lens 42a into a parallel light beam, which is condensed by a cylindrical lens 42b having a refracting power only in the sub-scanning direction. The light is linearly incident on the deflecting / reflecting surface 44a of the container 44. The collimator lens 42a and the cylindrical lens 42b form an imaging optical system 42. The light beam reflected and deflected by the deflecting / reflecting surface 44a is covered by a lens 47a having a negative refracting power, which is a spherical surface that constitutes the scanning lens 47, and a lens 47b having two toric surfaces having different refracting powers. The light is guided on the scanning surface 49 to form a spot. Then, the optical deflector 44 is rotated around the rotation shaft 43 by the motor 4
5, the deflection scanning surface on the scan surface 49 is optically scanned in the direction of arrow 48 by rotating in the direction of arrow 46.

[0004]

In the conventional optical scanning device, a rotating polygon mirror is used as an optical deflector to deflect and reflect a light beam. For this reason, a certain space is required between the optical deflector and the light source means for arranging each optical element such as a collimator lens and a cylindrical lens. Therefore, there is a problem that the entire optical scanning device becomes large.

The present invention provides an optical scanning device in which the entire device is miniaturized by using an optical deflector in which a plurality of refracting members such as prisms and lenses are annularly arranged instead of a rotating polygon mirror as the optical deflector. With the goal.

[0006]

The optical scanning device of the present invention comprises:
An optical deflector in which a plurality of refracting members are annularly arranged at equal intervals is rotatably mounted on a driving means, a light source means is disposed inside the annular shape of the optical deflector, and a light beam emitted from the light source means is It is characterized in that the light beam deflected and deflected by the refraction member is guided to the surface to be scanned and optically scanned by making the light beam incident on the refraction member and rotating the light deflector.

[0007]

Embodiment 1 FIG. 1 is a perspective view of an essential part of Embodiment 1 of the present invention, and FIG.
3 is an enlarged explanatory view of a part of FIG. 1, and FIG. 3 is a schematic sectional view of a part of FIG.

In FIG. 1, reference numeral 1 denotes a light source means, which is composed of a semiconductor laser or the like, and emits a laser light flux which is optically modulated based on image information. Reference numeral 2 is a rotatable optical deflector.
The optical deflector 2 has six refracting members 2a, 2b, ... 2f each having a spherical surface on one side (inner surface, 2a1) and a flat surface on the other surface (outer surface, 2a2) in a central portion. It is composed of rotating regular hexahedrons arranged at equal intervals so that a predetermined space 5 is formed. O is the annular center of the optical deflector 2. Here, each spherical surface 2 inside the refracting members 2a, 2b, ... 2f
.. 2f1 are composed of radii of curvature centered on the point O.

The light emitting point 1a of the light source means 1 is set so that the light source means 1 is directly arranged in the space 5 or is guided in a space such as a mirror to be positioned in the space 5. In the figure, the semiconductor laser is arranged directly in the space 5 so that the light emitting point 1 a is located in a part of the space 5.

Reference numeral 3 denotes a driving means, which is composed of a motor or the like, and rotates the optical deflector 2 at a constant speed in the direction of the arrow 4a with the annular center O as the rotation axis 4. A scanning lens 6 is composed of two lenses 6a and 6b having negative and positive refracting powers, and collects the light beam from the optical deflector 2 and guides it to the surface 7 to be scanned. Scanned surface 7
Consists of a photosensitive drum.

In this embodiment, light is modulated from the light source means 1,
The emitted laser light is reflected by one refracting member (2
It is incident on a), is refracted and deflected, and is incident on the scanning lens 6.
Then, it is condensed by the scanning lens 6 and is incident on the surface 7 to be scanned. Then, the optical deflector 2 is rotated about the rotary shaft 4 by the driving means 3 so that the surface to be scanned 7 is optically scanned in the direction of arrow 8.

In the present embodiment, one refracting member of the optical deflector 2 acts as a prism on the incident light flux, and emits the incident light flux based on the law of refraction (nsini = sini '). Therefore, in the present embodiment, the rotation angle θA of the optical deflector 2 is
And the scanning angle (deflection angle) θB of the light beam have a non-linear relationship.

On the other hand, the optical deflector 2 rotates at a constant speed. Therefore, the optical scanning speed on the surface 7 to be scanned is not constant, and for example, the optical scanning speed becomes faster in the peripheral portion of the scanning range than in the central portion. The unevenness of the optical scanning speed on the surface 7 to be scanned at this time is due to the unevenness of the dot (pixel) interval on the scanning line 8,
That is, it causes distortion of the image and unevenness of the exposure amount, that is, uneven density, which causes deterioration of the image quality.

Therefore, in this embodiment, the relationship between the optical scanning speed on the surface to be scanned and the incident angle (angle θB) of the light beam on the surface to be scanned is obtained in advance at the time of design. When the image information is written, the image clock frequency is changed according to the dot positions so that the dot intervals are uniform based on the design data. This corrects the image distortion.

Further, the density unevenness of the image is corrected by controlling the light emission amount from the semiconductor laser according to the dot position so that the exposure amount becomes uniform, for example.

In this embodiment, the optical deflector 2 is operated as described above.
Of the image distortion and density unevenness due to the non-uniformity of the optical scanning speed on the surface 7 to be scanned, which is caused by the non-linear relationship between the rotation angle θA of the light beam and the deflection angle θB of the light beam deflected and refracted by the optical deflector 2. However, good images are recorded.

In the present embodiment, the six refracting members (2a, 2b to 2f) forming the optical deflector may be formed of a triangular prism whose inner and outer surfaces are flat.
Alternatively, the inner and outer surfaces may be formed of a lens having a spherical surface or an aspherical surface having different curvatures. The optical deflector is not limited to the rotating regular hexahedron but may be any polygon.

[0018]

According to the present invention, as described above, by using the optical deflector in which a plurality of refracting members are annularly arranged and the light source means disposed inside the annular member, the size of the entire device can be reduced while the device is covered. It is possible to achieve an optical scanning device capable of excellently performing optical scanning on the scanning surface.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory view of a main part of the optical deflector shown in FIG.

FIG. 3 is a schematic cross-sectional view of a portion of FIG.

FIG. 4 is a schematic view of a main part of a conventional optical scanning device.

[Explanation of symbols]

1 light source means 2 Optical deflector 2a, 2b, ... 2f Refractive member 3 drive means 4 rotation axes 6 scanning lens 7 Scanned surface

Claims (2)

[Claims] 1. An optical deflector in which a plurality of refracting members are annularly arranged at equal intervals is rotatably mounted on a drive means, and a light source means is disposed inside the annular light deflector. The emitted light beam is made incident on the refracting member and the optical deflector is rotated, so that the light beam refracted and deflected by the refracting member is guided to the surface to be scanned for optical scanning. Optical scanning device. 2. The optical scanning device according to claim 1, wherein the refraction member is a prism or a lens.