JPS60642B2 - optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to optical devices for displaying, recording and reproducing information using laser light, such as laser printers, laser facsimile terminals, and laser COM (Computer Output).
The present invention relates to an optical scanning device that is applied to a laser recording unit or a laser display such as a putM C rofdm).

A conventional optical apparatus for laser recording or display is shown in FIG.

3-1 is a laser beam, and 2 is a rotating polygon mirror which rotates in the direction of the arrow and scans the laser beam 3-2 in the direction 6.

1 is a light receiving section for recording, displaying, and reproducing information;
One surface of the rotating polygon mirror forms one scanning line in the x direction on the light receiving section.

For scanning in the y direction with the light receiving section 1, by moving the light receiving section 1 at a constant speed in the direction of the arrow 7, the entire surface of the light receiving section 1 can be optically scanned. The light receiving section 1 may be made of paper or a photosensitive material, or may be a display surface coated with poppy or light material. Reference numeral 5 denotes an optical modulator, which modulates the intensity of the laser beam 3 to enable laser recording or display with an arbitrary intensity distribution on the light receiving section 1.

By the way, if the angle between the normal line of each surface of the rotating polygon mirror and the rotation axis of the rotating polygon mirror is not constant, ``if there is so-called tilting of the surface of the rotating polygon mirror,'' in the laser recording or display on the photoreceptor, The unevenness of the optical scanning pitch in the y direction as shown in FIG.

For example, if the distance between the rotating polygon mirror and the photoreceptor is 60 degrees, and the allowable optical scanning pitch unevenness on photoreceptor 1 is 0.025 degrees, then the distance is 2 × 10-6 radians or more. It is necessary to have a rotational polygon mirror with a tilting accuracy of .

However, this accuracy is close to the limit of machining accuracy, and even if it could be achieved, it would be expensive. The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a laser recording and display device that enables high-quality laser recording and display with small optical scanning pitch unevenness.

In order to achieve the above object, the optical scanning device of the present invention includes a laser light source, a rotating polygon mirror that deflects and scans the laser light from the laser light source, and a rotating polygon mirror that receives the deflected light and temporarily stores information. Or, in an optical scanning device that uses a photoconductor with a flat scanning surface for permanent recording and a focusing lens that guides the light deflected onto the photoconductor, the cross-sectional shape of the laser beam that enters the distortion correction optical system section. is characterized by having a rectangular shape that is long in the direction in which the light is deflected and scanned and short in the direction of the rotation axis of the rotating polygon mirror, and the direction in which the light is deflected and scanned is formed between the photoreceptor and the distortion correction optical system section. A cylindrical lens with no curvature is used to correct the tilt of the rotating polygon mirror.

The present invention will be explained in detail below using examples.

FIG. 2 shows an embodiment of the optical scanning device of the present invention. This embodiment shows a case where the optical scanning device of the present invention is applied to a laser recording and display device. 3-1 is a laser beam, 3-4 is a modulated laser beam modulated by a modulator 5, and 8 and 9 are cylindrical lenses each having a focal length f, .

The laser beam 3-3 emitted from the cylindrical lens 9 is a parallel beam having a cross-sectional shape as shown in FIG. A rotating polygon mirror 2 deflects and scans the laser beams 3 and 3.

Reference numeral 11 denotes a lens as a distortion correction optical system section, which is known as an f8 lens.

The fo lens is a rotating polygon mirror with a deflection angle, and the photoreceptor 12
The above linearity, that is, if the coordinate x is taken as shown in FIG. 2, the laser beam has the function of narrowing down the laser beam to a minute spot at the position of x=f8 (f is a constant). Reference numeral 10 denotes a cylindrical lens with a focal length f3, which has a width sufficient to scan the photoreceptor 12, and has no curvature in the light scanning direction.

Reference numeral 12 denotes a drum-shaped photoreceptor, and the portion scanned by light is flat.

In electrophotography, materials coated with Se, CdS, etc. are used. The photoreceptor 12 is rotating as shown in FIG. 2, and by working simultaneously with the light deflection of the rotating polygon mirror,
Information can be recorded on the entire surface of the photoreceptor. If a printing process known as electrophotography is used, that is, a charging device, a developing device, a transfer device, an IJ cleaning device, etc. are placed around the photoconductor, the information recorded on the entire surface of the photoconductor can be printed on paper. It is also possible to take a photo. By the way, when the laser beam incident on the photoreceptor 12 is narrowed down to a fine spot on the photoreceptor 12, for example, on the 0.1 side, the horizontal length d2 of the cross-sectional shape of the laser beam shown in FIG. Considering the diffraction phenomenon of laser light,
If fa lens focal length is f, then d2 is 4s fd2=-
Mountain - Light×〇.・It is necessary to

However, the input is the wavelength of light, and the unit is ribs. For example, if input is 0,4416×10-4 (willow) and f is 600 (kite), then d2=3.37 (rib).

The length d shown in FIG. 3 is set to such a length that even if the light passes through the fo lens, the light remains almost parallel.

That is, it is necessary to make the length such that the light convergence property of the f8 lens and the divergence caused by the diffraction phenomenon are balanced.
Therefore, it is necessary to select d, which satisfies the following equation. = Crocodile therefore d, = Mu△L entry = 0.4416-10-4 (skin), f = 600 (rib)
Then, d,=0.581 (kite).

The focal length f3 of the cylindrical lens 10 is F3 sardine board determined by Hirotoshi.

・Narrow down your focus to one bright spot.

Therefore, by narrowing down the aperture using the f8 lens and narrowing down the cylindrical lens, it is possible to narrow down the light spot to a nearly circular light spot of approximately 0.1 square inches. Furthermore, by selecting f3, which is shorter than f3, and adjusting the distance between the cylindrical lens and the photoreceptor, the narrowing shape of the light spot on the photoreceptor by the cylindrical lens can be arbitrarily adjusted to some extent. Therefore, by providing a means for adjusting this distance, the recording density in the y direction on the photoreceptor can be adjusted as desired. FIG. 4 is an explanatory diagram showing a case where a tilt error occurs in the rotating polygon mirror in the laser recording apparatus of the present invention shown in FIG. The laser beam 3-5 emitted from the rotating polygon mirror passes through the f-resist lens 11 and the cylindrical lens 10, and then forms an image near the origin of the y-coordinate on the photoreceptor 12.

If the laser beam is emitted in a direction that makes an angle with the optical axis as shown in Fig. 4, 3-6, due to a surface tilt error of the rotating polygon mirror, and if there is no 10 cylindrical lens (focal length f3), the iron wire As shown in , the laser beam is irradiated near the position y=fJ on the photoconductor 12, but if the cylindrical lens 20 is placed at a position substantially away from the top of the photoconductor, the laser beam is irradiated near the position y=f3. You can narrow it down.

By the way, since f3 is smaller than f, the surface tilt error of the rotating polygon mirror is significantly corrected. In Figure 2, an f8 lens was used as the distortion correction optical system, but a parabolic mirror was used as the f8 lens.
It is also effective to use it instead of a lens.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a conventional laser recording device. 2 to 4 are explanatory diagrams of the present invention. grandchild 7
Zutsutomu-no-zu Inferior Zutsutomu-zu

Claims (1)

[Claims] 1. A rotating polygon mirror that deflects and scans laser light from a laser light source, a photoreceptor having a flat scanning surface that receives the deflected laser light and records information temporarily or permanently, and the photoreceptor. In an optical scanning device that uses an optical system that guides the deflected light upward and focuses the laser light to a position on the photoreceptor that is proportional to the deflection angle of the deflected light, the laser light is incident on the rotating polygon mirror. The laser beam has a shape that is long in the scanning direction and short in the direction perpendicular to the scanning direction, is a substantially parallel beam, and has a curvature in the direction perpendicular to the scanning direction between the photoreceptor and the optical system. A cylindrical lens is placed at a position approximately equal to the focal length of the cylindrical lens from the photoconductor, and the laser beam deflected by the rotating polygon mirror is focused into a minute spot on the recording medium by the optical system and cylindrical lens. An optical scanning device characterized by: