JPH0713094A - Optical scanner - Google Patents

Abstract

PURPOSE:To provide an optical scanner capable of correcting deformation caused by the dynamic distortion of the reflecting surface of a mirror rotation type light deflector and realizing high-accurate recording or reading. CONSTITUTION:A laser beam L outputted from a laser diode 14 is guided to a concave cylindrical lens 18 through a collimator lens 16 and diffused in a main-scanning direction (direction shown by an arrow X). Thereafter, it is reflected and deflected on the reflecting surface 24 of a rotary scanning mirror 20 formed to be concave in a major axis direction. Besides, it is guided to a film F through a scanning lens 22. In such a case, the reflecting surface 24 becomes plane in the major axis direction by centrifugal force generated by rotation. Besides, the concave deformation in a minor axis direction caused in accordance with the dynamic distortion of the reflecting surface 24 in the major axis direction is canceled by the lens 18. As a result, the beam L is guided to the film F without receiving the effect of the dynamic distortion of the reflecting surface 24. Thus, an image is accurately recorded.

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 capable of correcting a deformation of a beam shape on a scanned object due to a dynamic distortion of a reflecting surface caused by a deflection operation of a mirror rotation type optical deflector. .

[0002]

2. Description of the Related Art Laser beam printers for deflecting a laser beam at a high speed to record an image on an object to be scanned such as a film are used in various fields. in this case,
As shown in FIG. 7, the reflection surface 2 is set at an inclination angle of about 45 ° with respect to the incident direction of the laser beam L.
There is a rotary scanning mirror (mirror rotation type optical deflector) 4 which is configured to deflect and scan the laser beam L on the object to be scanned by rotating at a high speed in the direction of arrow A.

[0003]

However, in the case of the rotary scanning mirror 4, when the reflecting surface 2 is rotated at a high speed,
The reflecting surface 2 is deformed by the dynamic distortion, and the beam spot shape on the object to be scanned is distorted. That is, the reflecting surface 2 is deformed into a convex shape as shown in FIG. 8A with respect to the long axis direction (α direction) by the centrifugal force generated by the rotation, while the reflection surface 2 is deformed in the long axis direction (α direction). As shown in FIG. 8B, it deforms into a concave shape in the minor axis direction (β direction). As a result, for example, when an image is recorded on a film or the like using the laser beam, the image becomes blurry or unclear.

The present invention has been made to solve the above-mentioned inconvenience, and the reflecting surface of the mirror rotation type optical deflector has a predetermined curved surface shape which becomes a flat surface during rotation, or
By refracting or reflecting the light beam so as to cancel the dynamic distortion of the reflecting surface that has become a curved surface shape by rotation,
An object of the present invention is to provide an optical scanning device capable of recording or reading highly accurate images and the like.

[0005]

To achieve the above object, the present invention provides a light beam generating means and a light beam output from the light beam generating means which is deflected by a rotating reflecting surface to be scanned. Mirror rotation type optical deflector to guide on the body,
A beam disposed between the light beam generating means and the mirror rotation type optical deflector for refracting or reflecting the light beam in accordance with the surface shape due to the dynamic distortion of the reflecting surface generated at a predetermined rotation speed. And a correction unit.

Further, according to the present invention, a light beam generating means and a mirror rotation type optical deflector for deflecting the light beam outputted from the light beam generating means by a rotating reflecting surface and guiding the light beam onto the object to be scanned. It is characterized in that the reflecting surface is set to have a curved surface shape which becomes a flat surface due to dynamic strain generated at a predetermined rotation speed.

[0007]

In the optical scanning device according to the present invention, when the mirror rotary type optical deflector rotates at a predetermined rotational speed, its reflecting surface is curved due to dynamic distortion. Therefore, the light beam condensed or diverged corresponding to the curved surface shape of the reflecting surface is guided to the reflecting surface via the beam correcting means for refracting or reflecting the light, and the light beam deflected by the reflecting surface is By canceling the influence of the curvature of the reflecting surface and guiding it to the object to be scanned, the beam spot shape of the light beam on the object to be scanned is made constant.

Further, in the optical scanning device according to the present invention, the reflecting surface of the mirror rotation type optical deflector is formed in advance into a curved surface shape in consideration of deformation due to dynamic distortion so that it becomes a planar shape when rotated at a predetermined rotation speed. By doing so, the beam spot shape of the light beam on the scanned object is made constant.

[0009]

1 shows the construction of an embodiment of an optical scanning device according to the present invention. In the apparatus shown in the drawing, a recording surface is stretched in a flat shape, and a sheet-like film F which is sub-scanned and conveyed by a roller 11 in a direction of an arrow Y is scanned with a modulated laser beam L to generate image information. Is a so-called planar scanning image recording apparatus 10 for recording.

This plane scanning type image recording apparatus 10 includes a laser diode 14 (light beam generating means) which outputs a laser beam L modulated by a driver 12 based on an image signal, and a collimator which makes the laser beam L parallel light. The lens 16, a concave cylindrical lens 18 (beam correcting means) that diverges the laser beam L only in the main scanning direction of the film F (arrow X direction), and rotates at high speed in the direction of arrow A to rotate the laser beam L. Rotating scanning mirror 20 for scanning in the main scanning direction (direction of arrow X) of film F
(Mirror rotation type optical deflector) and a scanning lens 22 composed of an fθ lens disposed between the rotary scanning mirror 20 and the film F.

In this case, the reflecting surface 2 of the rotary scanning mirror 20.
As shown in FIG. 2, 4 is formed in a concave shape in the major axis direction (α direction). As shown in FIG. 3A, the amount of deformation cancels the dynamic strain (shown by a dotted line) in the major axis direction (α direction) that occurs when the rotary scanning mirror 20 rotates at a predetermined rotation speed (shown by a solid line). ) Is set. Further, the curvature of the surface of the concave cylindrical lens 18 is, as shown in FIG. 3B, a dynamic distortion (indicated by a dotted line) in the minor axis direction (β direction) caused by deformation of the rotary scanning mirror 20 in the major axis direction (α direction). ) Is set to the amount to offset.

The plane scanning type image recording apparatus 10 of this embodiment.
Is basically constructed as described above. Next, its operation and effect will be explained.

The laser diode 14 is a laser beam L which is modulated based on the image signal supplied to the driver 12.
Is output. The laser beam L is collimated by the collimator lens 16 and then diverged by a predetermined amount in the main scanning direction (arrow X direction) by the concave cylindrical lens 18 to enter the reflecting surface 24 of the rotary scanning mirror 20. The rotary scanning mirror 20 is rotating at a high speed in the direction of arrow A, and the laser beam L reflected and deflected by the reflecting surface 24 thereof is guided onto the film F via the scanning lens 22. In this case, the laser beam L main-scans the film F, which is sub-scanned and conveyed in the arrow Y direction by the roller 11, in the arrow X direction to record an image two-dimensionally.

Here, in the rotary scanning mirror 20, as shown in FIGS. 2 and 3A, the reflecting surface 24 of the laser beam L is formed in a concave shape with respect to the long axis direction (α direction) when stopped, and has a predetermined shape. It is set to become a plane when rotated at a rotation speed. Therefore, the laser beam L reflected by the reflecting surface 24 is guided to the film F in a desired state without any deformation of the shape in the major axis direction (α direction). On the other hand, the minor axis direction of the reflecting surface 24 of the rotary scanning mirror 20 (β
3B is deformed as shown in FIG. 3B along with the deformation in the major axis direction (α direction). However, the influence of the deformation is canceled by the concave cylindrical lens 18 in the preceding stage, so that the laser beam L Is guided to the film F without any deformation even in the minor axis direction (β direction). As a result, the laser beam L is reflected by the reflecting surface 2 of the rotary scanning mirror 20.
It is possible to scan the film F in a state in which the influence of the dynamic distortion of No. 4 is canceled, and record a highly accurate image.

In the above-described embodiment, the concave cylindrical lens 18 formed concave in the main scanning direction (arrow X direction) and the reflecting surface 24 concave in the major axis direction (α direction). By using the rotary scanning mirror 20 formed in the above, the deformations of the beam spot shapes of the laser beam L in the short axis direction and the long axis direction are offset. On the other hand, as shown in FIG. 4, the rotary scanning mirror 28 is formed so that the reflecting surface 26 is flat in the major axis direction (α direction) and is convex in the minor axis direction (β direction). , And between the collimator lens 16 shown in FIG. 1 and the rotary scanning mirror 28 on which the reflecting surface 26 is formed as described above, a convex surface having condensing characteristics in the sub-scanning direction (arrow Y direction). By disposing the cylindrical lens, it is possible to cancel the dynamic distortion of the reflecting surface 26 during rotation and perform highly accurate image recording in the same manner.

Further, as shown in FIG. 7, a rotary scanning mirror 4 whose reflection surface 2 is a plane is used, and between the rotary scanning mirror 4 and the collimator lens 16 shown in FIG. Direction) and a convex cylindrical lens having a converging characteristic in the sub-scanning direction (arrow Y direction) are arranged. Dynamic distortion of the reflecting surface 2 is generated by these lenses. You may make it offset.

Further, instead of diverging the laser beam L in the main scanning direction (arrow X direction) by using the beam correcting means composed of the concave cylindrical lens 18, as shown in FIG. 5, a collimator lens 16 and a rotary scanning mirror 20 are provided. A convex cylindrical mirror 29 for diverging the laser beam L by reflection may be disposed between the two to cancel the dynamic distortion of the rotary scanning mirror 20. Also in this case, similarly to the above-described embodiment, when the rotary scanning mirror 28 having the reflecting surface 26 shown in FIG. 4 is used, it has a light-condensing characteristic in the sub-scanning direction (arrow Y direction). By disposing the concave cylindrical mirror described above, it is possible to cancel the dynamic distortion. Further, a cylindrical mirror that is convex in the main scanning direction (arrow X direction) and concave in the sub scanning direction (arrow Y direction) is used for the rotary scanning mirror 4 having the planar reflecting surface 2 shown in FIG. It is possible to cancel the dynamic strain.

Further, as shown in FIG. 6, the longitudinal direction (α
Direction), the reflecting surface 30 is formed as a concave surface, and
A collimator lens 16 shown in FIG. 1 is used by using a rotary scanning mirror 32 which is formed to have a convex surface with respect to the minor axis direction (β direction), and the reflecting surface 30 becomes a flat surface when rotated at a predetermined rotation speed. By guiding the transmitted laser beam L directly to the reflecting surface 30 without passing through the beam correcting means such as the concave cylindrical lens 18 or the like, the reflecting surface 3
It is also possible to cancel the dynamic distortion at the time of rotation of 0 and perform highly accurate image recording.

Furthermore, in the above-described embodiment, the planar scanning type image recording apparatus 10 has been described as an application target, but for the cylindrical inner surface scanning type image recording apparatus in which the scanning surface of the laser beam L is set to a curved surface. Of course, it is applicable.

[0020]

As described above, according to the present invention, the dynamic distortion of the reflecting surface due to the operation of the mirror rotation type optical deflector is corrected,
The shape of the beam spot on the object to be scanned can be made constant at all times. This enables highly accurate recording or reading using the light beam. Further, by making the reflecting surface and / or the beam correcting means have a shape corresponding to the dynamic distortion generated at a predetermined rotation speed, the recording or reading accuracy is maintained even when the mirror rotation type optical deflector is operated at a high speed. Therefore, it is possible to work at high speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a planar scanning type image recording apparatus which is an embodiment of an optical scanning apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a rotary scanning mirror in the plane scanning image recording apparatus shown in FIG.

3A is an explanatory diagram of a deformation amount in a major axis direction of the rotary scanning mirror shown in FIG. 2, and FIG. 3B is an explanatory diagram of a deformation amount in a minor axis direction of the rotary scanning mirror shown in FIG.

FIG. 4 is an explanatory view of another embodiment of the rotary scanning mirror in the plane scanning type image recording apparatus shown in FIG.

FIG. 5 is a configuration diagram of a plane scanning image recording apparatus which is another embodiment of the optical scanning apparatus according to the present invention.

FIG. 6 is an explanatory view of another embodiment of the rotary scanning mirror in the plane scanning type image recording apparatus shown in FIG. 1 or FIG.

FIG. 7 is an explanatory diagram of a rotary scanning mirror according to a conventional technique.

8A is an explanatory diagram of a major axis direction deformation amount of a reflecting surface of the rotary scanning mirror shown in FIG. 7, and FIG. 8B is a minor axis direction deformation amount of a reflecting surface of the rotary scanning mirror shown in FIG. FIG.

[Explanation of symbols]

10 ... Planar scanning image recording device 14 ... Laser diode 18 ... Concave cylindrical lens 20, 28, 3
2 ... Rotating scanning mirror 24, 26, 30 ... Reflecting surface

Claims (4)

[Claims] 1. A light beam generating means, a mirror rotation type light deflector for deflecting the light beam output from the light beam generating means by a rotating reflecting surface and guiding the light beam onto an object to be scanned, and the light beam generating means. A beam correction means that is disposed between the mirror rotation type optical deflector and refracts or reflects the light beam in accordance with the surface shape due to the dynamic distortion of the reflection surface generated at a predetermined rotation speed. An optical scanning device comprising: 2. The apparatus according to claim 1, wherein the mirror rotation type optical deflector comprises a rotating mirror having the reflecting surface inclined with respect to the incident direction of the light beam.
The optical beam scanning device, wherein the beam correction means comprises a cylindrical lens that diverges or condenses the light beam in accordance with the surface shape due to the dynamic distortion of the reflecting surface. 3. The apparatus according to claim 1, wherein the mirror rotation type optical deflector comprises a rotating mirror in which the reflecting surface is set to be inclined with respect to an incident direction of a light beam,
The optical scanning device, wherein the beam correction means comprises a cylindrical mirror that diverges or condenses the light beam in accordance with the surface shape due to the dynamic distortion of the reflecting surface. 4. A mirror rotation type optical deflector for deflecting a light beam output from the light beam generating means by a rotating reflecting surface and guiding the light beam onto an object to be scanned. An optical scanning device, wherein the surface is set to a curved surface shape that becomes a flat surface due to a dynamic strain generated at a predetermined rotation speed.