JPH07281117A - Optical deflector - Google Patents

Abstract

PURPOSE:To facilitate working of a rotary polyhedral mirror and to decrease restrictions on packaging by making the light from a light source incident on the end face of the rotary polyhedral mirror and making the reflected light from the end face incident on the deflection surface of the rotary polyhedral mirror via the mirror. CONSTITUTION:The light from a semiconductor laser unit 2 is made incident on the end face A of the rotary polyhedral mirror 1 and the reflected light from the end face A is made incident on the deflection surface D of the rotary polyhedral mirror 1 via first and second stationary mirrors B, C and, therefore, even if the rotary polyhedral mirror 1 inclines by theta, the deflection surface D eventually inclines similarly by theta and, consequently, the correction of a plane tilt is executed with good accuracy. The light beam reflected from the end face of the rotary polyhedral mirror 1 inclines by 2theta and the incident light beam on the deflection surface of the rotary polyhedral mirror 1 inclines by 2theta as well if the axis of rotation of the rotary polyhedral mirror 1 is assumed to have the theta face tilt. Since the deflection surface of the rotary polyhedral mirror 1 inclines by theta, the light beam reflected by the plane of polarization is paralleled with the light beam in the case of the absence of the plane tilt. The light beam moved in parallel is image at the same point on an image recording medium via an ftheta lens, etc., and the correction of the plane tilt is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector.

[0002]

2. Description of the Related Art Conventionally, there is known an apparatus for recording image information such as characters and figures on an image recording medium such as a photoconductor by deflecting a laser beam by a rotating polygon mirror (polygon mirror) and scanning the image information. ing. In this device, the rotary polygon mirror as the optical deflector may be tilted due to processing, assembling accuracy, etc. When such tilting occurs,
Since the focused spot on the image recording medium is displaced, it is necessary to correct the positional deviation of the light beam focused on the image recording medium.

As this correction method, a method of making correction using an fθ lens or the like in a scanning image forming optical system is widely known, but in recent years, f of this scanning image forming optical system is corrected.
Proposals for making corrections with a scanning optical system by omitting the θ lens are disclosed in, for example, Japanese Patent Application Laid-Open No. 61-70522 and Japanese Patent Application Laid-Open No. 2-1119.
No. 13, for example.

The optical deflector described in Japanese Patent Laid-Open No. 61-70522 uses a rotary draft polygon, and corrects the positional deviation of the light beam due to the surface tilt of the polygon due to double reflection of an infinite conjugate light beam. The optical deflector disclosed in Japanese Patent Laid-Open No. 2-111913 is provided with a right-angled prism for a rotating polygon mirror, a light beam is incident on the rotating polygon mirror, and reflected light from the prism is reflected at the right angle. The light incident on the prism is incident on the rotating polygonal mirror again, and the light reflected by the prism is focused on the image recording medium via the fθ lens. This is to correct the positional deviation of the light beam.

[0005]

However, the above-mentioned proposed devices have the following problems. That is,
In the device described in JP-A-61-70522,
There is a problem that it is very difficult to process a polygonal body having a draft.

Further, in the apparatus described in Japanese Patent Laid-Open No. 2-111913, since the right angle prism is also scanned as the rotary polygon mirror rotates, the width of the prism must be increased, There is a problem that the restrictions on implementation become large.

Furthermore, in the devices described in both of the above publications, since the incident angle of the light beam on the deflecting surface is not a right angle, the light beam reflected from the deflecting surface is twisted when the rotating polygon mirror rotates. There is also a problem in that it becomes difficult to perform linear scanning.

Therefore, it is a first object of the present invention to provide an optical deflector in which the processing of a rotary polygon mirror is facilitated and the restrictions on mounting are reduced.

A second object of the present invention is to provide, in addition to the above-mentioned first object, an optical deflecting device capable of excellent linear scanning.

[0010]

In order to achieve the first object, a light deflector according to a first aspect of the present invention makes light from a light source incident on an end face of a rotary polygon mirror and reflects light reflected from the end face. It is incident on the deflecting surface of the rotary polygon mirror via a mirror.

In order to achieve the above-mentioned second object, the optical deflecting device of claim 2 is characterized in that, in addition to claim 1, the optical beam from the mirror and the deflecting surface of the rotary polygon mirror for reflecting this optical beam are provided. The mirrors are arranged so that the rotating polygon mirror including the light beam forms an angle of about 90 ° in the axial cross section.

In order to achieve the second object, the optical deflecting device of claim 3 is the same as that of claim 1 except that the end face of the rotary polygon mirror and the deflecting surface form approximately 90 °, and the mirror rotates. A first mirror that reflects the light beam reflected from the end face of the polygon mirror; and a second mirror that reflects the light beam reflected by the first mirror to the deflection surface of the rotating polygon mirror,
When the angle between the end face of the rotary polygon mirror and the incident light is α and the angle between the first mirror and the second mirror is β, β =
To satisfy (180 ° -α) / 2, the first and second
The mirror is placed.

[0013]

According to the optical deflecting device of the present invention, for example, when the rotation axis of the rotary polygon mirror is tilted by the θ plane, the light beam reflected from the end face of the rotary polygon mirror is tilted by 2θ and passes through the mirror. The light beam incident on the deflecting surface of the rotary polygon mirror is also inclined by 2θ, but the deflecting surface of the rotary polygon mirror is also θ.
Since it is tilted, the light beam reflected by the deflecting surface becomes parallel to the light beam when the surface is not tilted. Therefore, the parallel-moved light beam is imaged at the same point on the image recording medium via, for example, the fθ lens, and the surface tilt is corrected. As such a rotary polygon mirror, a general rotary polygon mirror can be used, and therefore its processing is facilitated. Further, since the reflected light from the end face of the rotary polygon mirror is incident on the mirror, the mirror is not scanned even when the rotary polygon mirror rotates, and therefore the mirror is a small-sized one capable of covering the thickness of the light beam. However, the restrictions on implementation are reduced.

According to the optical deflecting device of the second and third aspects, the light beam from the mirror and the deflecting surface of the rotary polygon mirror that reflects the light beam are arranged in the axial direction of the rotary polygon mirror including the light beam. Since the cross section forms approximately 90 °, the light beam reflected from the deflection surface is not twisted when the rotary polygon mirror is rotated, and good linear scanning is performed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a vertical sectional view of an optical deflecting device showing an embodiment of the present invention, and FIG. 2 is a plan view of the same optical deflecting device.

The optical deflecting device of the present embodiment is a general hexahedral rotating polygonal mirror in which the end face A and the deflecting face D form approximately 90 ° and which rotates about the rotary shaft 1a. The rotary polygon mirror 1 whose end face A is a mirror surface, for example, a semiconductor laser unit 2 as a light source that emits light toward the end face A at an incident angle (90 ° -α), and is reflected by the end face A. And a second fixed mirror C for reflecting the light beam reflected by the first fixed mirror B to the deflection surface D of the rotary polygon mirror 1. There is.

When the angle between the first fixed mirror B and the second fixed mirror C is β, the first fixed mirror B and the second fixed mirror C are β = (180 ° -α ) / 2
Are arranged so as to satisfy. Here, in the present embodiment, α = 45 ° and β = 67.5 °.

Therefore, the light beam emitted from the semiconductor laser unit 2 is incident on the end face A of the rotary polygon mirror 1 at an incident angle (9
Incident at 0 ° -α) and reflected at the end face A (90 ° -α)
Reflected by the first fixed mirror B and the second fixed mirror C
To the deflecting surface D of the rotary polygon mirror 1. At this time, the light beam from the second fixed mirror C and the deflecting surface D that reflects the light beam form approximately 90 ° in the axial cross section of the rotary polygon mirror 1 including the light beam (see FIG. 1). .

Then, the light beam F reflected by the deflecting surface D escapes in the direction E as shown in FIG.
The image is collected on the image recording medium via the θ lens and the like, and the image recording medium is scanned as the rotary polygon mirror 1 rotates.

Here, it is assumed that the rotary polygon mirror 1 is tilted by the θ plane as shown by the alternate long and short dash line in FIG. 3 for some reason. Then, the light beam reflected from the end surface A of the rotary polygon mirror 1 is inclined by 2θ, and the light beam incident on the deflection surface D of the rotary polygon mirror 1 through the first and second fixed mirrors B and C is also 2 degrees.
θ will be inclined. However, since the deflecting surface D of the rotary polygon mirror 1 is also inclined by θ as shown by the alternate long and short dash line, the light beam G reflected by the deflecting surface D is different from the light beam F when it is not tilted. Become parallel.

Therefore, the parallel-moved light beam G is
An image is formed at the same point on the image recording medium through the fθ lens, and the surface tilt is corrected.

As described above, in this embodiment, the light from the semiconductor laser unit 2 is incident on the end face A of the rotary polygon mirror 1, and the reflected light from this end face A is reflected by the first and second fixed mirrors B, Since the light is incident on the deflecting surface D of the rotary polygon mirror 1 via C, even if the rotary polygon mirror 1 is tilted by θ, the deflecting surface D is also tilted by θ, so that the surface tilt correction can be accurately performed. It is like this. For this rotary polygon mirror 1,
Since a general rotary polygon mirror is used, its processing can be easily performed. As a method therefor, there is a method of attaching a glass prism to the surface, for example.

Further, since the reflected light from the end face A of the rotary polygon mirror 1 is made incident on the first fixed mirror B, even if the rotary polygon mirror 1 rotates, the first fixed mirror B is rotated. Is no longer scanned (of course, the second fixed mirror C is also not scanned). Therefore, the first and second fixed mirrors B and C can be made small so as to cover the thickness of the light beam, and mounting restrictions can be reduced. .

Furthermore, the end surface A of the rotary polygon mirror 1 and the deflection surface D form an angle of approximately 90 °, and β = (180 ° -α) /
Since the first and second fixed mirrors B and C are arranged so as to satisfy 2, the light beam from the second fixed mirror C and the deflection surface D of the rotary polygon mirror 1 that reflects this light beam are However, in the axial cross section of the rotary polygon mirror 1 including the light beam, the angle becomes approximately 90 °. Therefore, the light beam reflected from the deflection surface D is not twisted when the rotary polygon mirror 1 is rotated, and good linear scanning can be performed.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say, for example, although the rotary polygon mirror 1 is a hexahedron in the above embodiment, it is not limited to a hexahedron.

The optical deflector of the present invention is applicable to both pre-object type and post-object type.

[0027]

As described above, according to the optical deflecting device of the first aspect, for example, when the rotation axis of the rotary polygon mirror is tilted by the θ plane, the number of light beams reflected from the end face of the rotary polygon mirror is 2.
The light beam incident on the deflecting surface of the rotary polygon mirror through the mirror is inclined by θ, but the deflecting surface of the rotating polygon mirror is also inclined by θ, so that the light beam reflected by the deflecting surface is It becomes parallel to the light beam when it is not tilted. Therefore, the translated light beam is, for example, fθ.
An image is formed at the same point on the image recording medium via a lens,
The trouble is corrected. As such a rotary polygon mirror, a general rotary polygon mirror can be used, so that the processing can be facilitated. Further, since the reflected light from the end face of the rotary polygon mirror is incident on the mirror, the mirror is not scanned even if the rotary polygon mirror rotates.
Therefore, the mirror can be made into a small size capable of covering the thickness of the light beam, and restrictions on mounting can be reduced.

According to the optical deflecting device of the second and third aspects, the light beam from the mirror and the deflecting surface of the rotary polygon mirror that reflects the light beam are arranged in the axial direction of the rotary polygon mirror including the light beam. Since the cross section is approximately 90 °, the light beam reflected from the deflecting surface is not twisted when the rotary polygon mirror is rotated, and therefore good linear scanning can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an optical deflecting device showing an embodiment of the present invention.

FIG. 2 is a plan view of the above optical deflecting device.

FIG. 3 is a diagram illustrating a principle of correcting a beam position shift due to a surface tilt of a rotating polygon mirror.

[Explanation of symbols]

 1 rotating polygon mirror 2 light source A end face of rotating polygon mirror B first mirror C second mirror D deflection surface of rotating polygon mirror

Claims (3)

[Claims] 1. An optical deflector in which light from a light source is incident on an end face of a rotary polygon mirror and reflected light from the end face is incident on a deflecting surface of the rotary polygon mirror via a mirror. 2. The optical deflector according to claim 1, wherein the light beam from the mirror and the deflection surface of the rotary polygon mirror that reflects the light beam are substantially in the axial cross section of the rotary polygon mirror including the light beam. An optical deflector in which mirrors are arranged so as to form 90 °. 3. The optical deflector according to claim 1, wherein an end face of the rotary polygon mirror and a deflection surface form an angle of about 90 °, and the mirror reflects the light beam reflected from the end face of the rotary polygon mirror. And a second mirror that reflects the light beam reflected by the first mirror to the deflecting surface of the rotating polygon mirror. The angle between the end surface of the rotating polygon mirror and the incident light is α, An optical deflecting device in which the first and second mirrors are arranged so that β = (180 ° −α) / 2 is satisfied, where β is the angle formed by the first mirror and the second mirror. .