JPH05224148A - Optical scanning device - Google Patents

Abstract

PURPOSE:To reduce the man-hour for adjusting a lens group and to reduce a cost-up caused due to the increase of lenses by using a rotary unifacial mirror instead of a rotary polygon mirror. CONSTITUTION:The device is constituted of a light source 1, a lens a2, collimated beams of light 3, the rotary unifacial mirror 4, a lens b5 and a scanning surface 6, laser beam 11 from the light source 1 is formed to become the collimated beams of light 3 through the lens 2, and then, deflected by the rotary unifacial mirror 4 having a reflection surface for the collimated beams of light 3 at least on one side of the mirror 4, and then, an image is formed as a spot on the scanning surface 6 through the lens b5 provided with an ftheta characteristic performance. Thus, the number of man-power for adjusting the position of the lens is drastically reduced, and also, the cost is reduced according to the reduced number of lenses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device,
In particular, it relates to a scanning optical device which operates with a laser beam.

[0002]

2. Description of the Related Art In a conventional scanning optical apparatus, a laser beam from a light source is caused to perform main scanning on a scanning surface by a mechanical optical deflector such as a galvanometer mirror or a rotary polygon mirror, and in the direction perpendicular to the main scanning direction. A general method is to perform a sub-scan by relatively moving the laser beam and the scanning surface.

In this type of scanning optical system, especially in the rotary polygon mirror system, it is technically difficult to make each reflecting surface parallel to the rotation axis, and the scanning line corresponding to the tilt of each surface. Uneven pitch occurs.

Therefore, a first lens group for forming a line image in the scanning direction in the vicinity of the reflecting surface is arranged between the light source and the rotary polygon mirror, and this line image and the scanning surface are conjugated in the sub-scanning direction. By arranging the second lens group having the fθ characteristic function between the rotary polygon mirror and the scanning surface so as to be in a relationship, it is possible to prevent the unevenness of the scanning line pitch due to the surface tilt.

That is, in the case of such a polyhedron, the tilt angle of each surface is different due to a processing error, and therefore, when correction is necessary, f becomes long with one lens, which cannot be practically used, and the number of lenses is increased. Will increase.

If the number of faces of the mirror is increased, the number of revolutions may be reduced, and the number of revolutions may be reduced by using 4 to 6-sided polygons (Max 15000 rpm).

The above-described conventional scanning optical device will be specifically described with reference to the drawings.

FIG. 3 is a sectional view of the conventional scanning optical device in the main scanning direction, and FIG. 4 is a sectional view of the scanning optical device in FIG. 3 in the sub scanning direction.

3 and 4, the conventional scanning optical device includes a light source 1, a first lens group 7, and a rotary polygon mirror 8.
And a second lens group 9, a scanning surface 6, a line image 10, and a laser beam 11.

Here, in order to correct the tilt of the laser beam 11 from the light source 1, the line image 1 is formed near the reflecting surface of the rotary polygon mirror 8.
The line image 10 and the scanning surface 6 are made to have a conjugate relationship by the second lens group 9 in order to shape them to 0 and to include the fθ characteristic function.

In the above description, collimated light is present in the main scanning plane, but is condensed in the sub-scanning plane to form a line image 10.

[0012]

In the above-described conventional scanning optical device, since it is necessary to have the fθ characteristic function and the surface tilt correction function of the rotary polygon mirror, a plurality of both the first lens group and the second lens group are provided. Since it is composed of the lens of No. 1, the adjustment man-hour of the first lens group is increased, and the rotation speed is relatively low (Max1).
In the scanning optical device used at 5000 rpm),
For example, in FIGS. 3 and 4, the number of man-hours for adjusting the lens position of the second lens of the first lens group 7, the material cost, and the like increase, which results in a cost increase.

An object of the present invention is to solve the above-mentioned drawbacks by using a rotary polygonal mirror as a rotary single-sided mirror, and the first lens group and the second lens group can each be composed of one lens, There is no need for tilt correction, and the number of man-hours required for lens position adjustment for maintaining the conjugate relationship between the line image and the scanning surface can be greatly reduced, and the number of rotations of the rotating single-sided mirror is 15,
In the case of about 000 rpm or less, a rotating body equivalent to a rotary polygon mirror can be used, and further, since the number of lenses can be reduced by at least two, it is an object of the present invention to provide a scanning optical device capable of significantly reducing the cost. ..

[0014]

A scanning optical apparatus according to the present invention is arranged between a light source, a rotary polygon mirror, and a light source and the rotary polygon mirror, and forms a line image in the vicinity of the reflecting surface of the rotary polygon mirror. In a scanning optical device composed of one lens group and a second lens group which is arranged between the rotary polygon mirror and the scanning surface and connects the line image and the scanning surface in a conjugate relationship, the rotary polygon mirror is rotated. It's a face mirror.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a sectional view in the main scanning direction of a scanning optical device according to an embodiment of the present invention, and FIG. 2 is a sectional view in the sub scanning direction of the scanning optical device in FIG.

Referring to FIGS. 1 and 2, the scanning optical device of this embodiment includes a light source 1, a lens a2, a collimated light beam 3, and a collimated light beam 3.
It is composed of a rotating single-sided mirror 4, a lens b5, and a scanning surface 6.

Here, the laser beam 11 from the light source 1
Is shaped into the collimated light 3 by the lens a2, is deflected by the rotating single-sided mirror 4 having the reflecting surface of the collimated light 3 on at least one side, and has the function of fθ characteristic b.
At 5, an image is formed as a spot on the scanning surface 6.

With the above arrangement, the scanning optical device of this embodiment does not require the correction of the surface tilt of the rotating single-sided mirror 4, and the laser beam 11 is used as the first lens for the laser beam 11 unlike the conventional scanning optical device. It is not necessary for the group 7 to form the line image 10 near the reflecting surface of the rotary polygon mirror 8 and for the second lens group 9 to make the line image 10 and the scanning surface 6 in a conjugate relationship.

That is, as described in the section of the prior art, in the case of a polyhedron, the tilt angle of each surface is different depending on the processing error, so when correction is necessary, f becomes long with one lens, and it becomes practical. The above cannot be used and the first lens group 7 and the second lens group 9 are used, but in the case of this embodiment,
The lens a2 and the lens b5 are sufficient.

[0021]

As described above, in the scanning optical device of the present invention, the rotating polygon mirror is a rotating single-sided mirror.
The first lens group and the second lens group can each be composed of one lens, there is no need to perform tilt recorrection, and the man-hours required for lens position adjustment to maintain the conjugate relationship between the line image and the scanning surface are greatly increased. There is an effect that can be reduced to.

Further, the rotation number of the rotating single-sided mirror is 15,0.
In the case of about 00 rpm or less, a rotating body equivalent to a rotary polygon mirror can be used, and further, the number of lenses is at least 2.
Since the number of sheets can be reduced, there is an effect that the cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a scanning optical device according to an exemplary embodiment of the present invention in a main scanning direction.

2 is a sectional view of the scanning optical device of FIG. 1 in a sub-scanning direction.

FIG. 3 is a sectional view of a conventional scanning optical device in the main scanning direction.

4 is a cross-sectional view of the scanning optical device of FIG. 3 in the sub-scanning direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 lens a 3 collimated light 4 rotating single-sided mirror 5 lens b 6 scanning surface 7 first lens group 8 rotating polygon mirror 9 second lens group 10 line image 11 laser beam

Claims (1)

[Claims] 1. A light source, a rotary polygonal mirror, a first lens group which is arranged between the light source and the rotary polygonal mirror and forms a line image in the vicinity of a reflecting surface of the rotary polygonal mirror, and the rotary polygonal surface. In a scanning optical device that is arranged between a mirror and a scanning surface and is composed of a second lens group that connects the line image and the scanning surface in a conjugate relationship, the rotating polygon mirror is a rotating single-sided mirror. A scanning optical device.