JPH09318894A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of a scanning optical device and also to miniaturize the device. SOLUTION: A half mirror 14, a scanning lens 15 and a reflection mirror are arranged in a direction that a laser beam L2 deflected by a polygon mirror 12 advances, and a rotating drum is arranged in the reflecting direction of the reflection mirror. A photodetecting lens 16 for detecting a horizontal synchronizing signal and a horizontal synchronizing signal detector 17 are arranged in the advancing direction of the laser beam L3 reflected by the mirror 14. The mirror 14 has width by which the laser beam L2 for forming an image is transmitted and also inclines the reflected light L3, so that the light L3 is prevented from being returned to the mirror 12.

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 used in a laser printer, a laser facsimile, etc., which deflects a laser beam from a laser light source by a polygon mirror and forms an image on a photosensitive member by a scanning lens. .

[0002]

2. Description of the Related Art A conventional scanning optical device of this type is constructed, for example, as shown in FIG. That is, inside the optical box 1, the laser light emitted from the laser unit 2 is linearly focused on the reflection surface 4 a of the polygon mirror 4 by the cylindrical lens 3 and deflected and scanned by the rotation of the polygon mirror 4. Most of the laser light deflected and scanned by the polygon mirror 4 is used as image forming laser light, passes through the central area A of the scanning lens 5, is reflected by the folding mirror 6, and is exposed by a rotating drum (not shown). Incident on the body. The laser light incident on the photoconductor forms a two-dimensional electrostatic latent image by the main scanning by the rotation of the polygon mirror 4 and the sub-scanning by the rotation of the rotating drum in the direction orthogonal to the main scanning direction.

On the other hand, a part of the laser light deflected by the polygon mirror 4 is used as a laser light for detecting a horizontal synchronizing signal, passes through a region B at one end of the scanning lens 5, and then is reflected by a light detecting mirror 7. The light enters the horizontal sync signal detector 8 having a photoelectric conversion element built therein. Here, the laser light deflected by the polygon mirror 4 is either parallel light or light parallel to the sub-scanning direction and diffused in the main scanning direction, which is peculiar to an optical system having a tilt correction function. The laser light has a large diameter.

[0004]

However, the above-mentioned prior art has the following problems. (1) Since it is necessary to provide the scanning lens 5 with a region A for transmitting a laser beam for image formation and a region B for transmitting a laser beam for horizontal synchronization signal detection, the longitudinal direction of the scanning lens 5 becomes large. At the same time, the cost of the scanning lens 5 increases.

(2) A photo-detecting mirror 7 behind the scanning lens 5
And the horizontal synchronization signal detector 8 are arranged, the scanning lens 5
Therefore, it becomes difficult to reduce the distance between the folding mirrors 6.

(3) Since the diameter of the laser beam deflected by the polygon mirror 4 is large, the rise of the voltage / current of the photoelectric conversion element of the horizontal synchronizing signal detector 8 becomes slow, and the accuracy of the horizontal synchronizing signal is improved. Becomes difficult.

(4) Since the diameter of the laser beam deflected by the polygon mirror 4 is large, the laser beam is correctly incident on the horizontal synchronizing signal detector 8 and the rising and falling edges of the laser beam are detected to obtain an accurate synchronizing signal. In order to obtain the above, it is necessary to widen the width of the light detection mirror 7 in the scanning direction of the laser light. On the other hand, when the width is narrowed, it becomes difficult to adjust the photodetection mirror 7 so that the laser light is properly incident on the horizontal sync signal detector 8.

(5) Since the diameter of the laser light at the position of the light detection mirror 7 is also large, there is a risk that the laser light for image formation will be cut off. Therefore, the timing of the image writing signal and the timing of obtaining the horizontal synchronizing signal should be sufficiently separated.
In other words, it is necessary to make the distance between the reflection points of the laser light for image recording and the laser light for horizontal synchronization signal sufficiently large.
The polygon mirror 4 becomes large.

An object of the present invention is to solve the above-mentioned problems and to provide a small-sized and inexpensive scanning optical device which improves the accuracy of horizontal synchronization.

[0010]

To achieve the above object, a scanning optical device according to the present invention is a scanning optical device in which a light beam from a light source is deflected onto a surface to be scanned by a deflecting means and an image is formed by an image forming means. In the apparatus, a half mirror that transmits at least an image forming light beam of the light beams from the deflecting means is arranged between the deflecting means and the image forming means, and the light beam reflected by the half mirror is arranged. In the traveling direction of, the light collecting means and the light detecting means for detecting the horizontal synchronizing signal are provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a plan view of an embodiment,
FIG. 2 is a side view, and the laser unit 11 that emits laser light modulated by an image signal is attached to an optical box (not shown). A polygon mirror 12 that deflects the laser light L1 is arranged in the traveling direction of the laser light L1 from the laser unit 11.
Is held by a drive motor 13 having a circuit board 13a,
It is designed to rotate at high speed. The length of the reflecting surface 12a of the polygon mirror 12 is set so as to reflect the laser light L2 for image formation and the laser light L3 for the horizontal synchronizing signal, and the distance between the reflection points of these laser lights L2 and L3. Are so close that the laser light L3 for the horizontal synchronizing signal does not affect the laser light L2 for image formation.

Further, in the traveling direction of the laser beams L2 and L3 deflected by the polygon mirror 12, the half mirror 1
4, a scanning lens 15, a folding mirror (not shown), and a rotating drum (not shown) having a photoconductor are arranged. Then, on the circuit board 13a of the drive motor 13 in the direction of reflection from one end of the half mirror 14, a light detection lens 16 and a horizontal synchronization signal detector 17 are provided. The half mirror 14 is arranged so as not to return the reflected light to the polygon mirror 12 as shown in FIG.

The size of the half mirror 14 in the longitudinal direction is
The size is such that at least the laser light L2 for image formation is transmitted, and the ratio of the transmitted light and the reflected light by the half mirror 14 is set to half or a desired ratio depending on the coating composition.

In this embodiment having such a configuration, the laser beam L1 emitted from the laser unit 11 is driven by the drive motor 13 to rotate the polygonal mirror 12 at high speed.
Deflected and scanned by the
It becomes L2, passes through the half mirror 14 and the scanning lens 15, is further folded by the folding mirror, and is incident on the rotary drum. The laser beam L2 incident on the rotating drum forms a spot image on the photoconductor by the main scanning of the polygon mirror 12 and the sub-scanning of the rotating drum. On the other hand, a part of the laser light L3 deflected and scanned by the polygon mirror 12 is reflected by the half mirror 14, is converged by the photodetection lens 16, and is detected by the horizontal synchronization signal detector 17.

In this embodiment, since the half mirror 14 for detecting the horizontal synchronizing signal is arranged between the polygon mirror 12 and the scanning lens 15, the length of the scanning lens 15 in the longitudinal direction is necessary for image formation. The area can be shortened, and the distance between the polygon mirror 12 and the scanning lens 15 and the distance between the scanning lens 15 and the folding mirror can be narrowed, and the overall size can be reduced.

Since the laser light L3 for generating the horizontal synchronizing signal is separated in advance from the laser light L2 used for image formation, a minute interval that does not match the timing of obtaining the horizontal synchronizing signal and the timing of writing the image Can be approached. Therefore, downsizing and cost reduction of the polygon mirror 12 can be realized.

Due to the miniaturization of the polygon mirror 12,
Wind loss and inertial force during rotation of the polygon mirror 12 can be reduced, and rise time of the polygon mirror 12, noise of the polygon mirror 12, power consumption of the drive motor 13 and the like can be reduced.

Further, laser light is emitted by the half mirror 14.
Since L3 can be accurately incident on the photodetection lens 16 and the horizontal sync signal detector 17, horizontal sync can be performed with high accuracy and the width of the photodetection mirror can be widened as in the conventional case. It becomes unnecessary to adjust the reflection direction of the light detection mirror.

If a plastic lens is used for the scanning lens 15, the scanning lens 15 can be downsized, so that the scanning lens 1 can be manufactured by molding equipment of the same scale.
It is possible to increase the number of 5s from the conventional 4s to 8s, and a significant cost reduction can be realized.

The horizontal sync signal detector 17 is provided on the circuit board 13a of the drive motor 13 to share the circuit board. However, if the overall arrangement is not balanced, the horizontal sync signal detector 17 is exclusively used. Another circuit board may be provided.

[0021]

As described above, in the scanning optical device according to the present invention, a half mirror for transmitting a light beam for image formation is arranged between the deflecting means and the image forming means, and the light beam reflected by the half mirror is arranged. Since the light converging means for detecting the horizontal synchronizing signal and the light detecting means are provided in the traveling direction of the image forming means, the longitudinal direction of the image forming means can be made large enough to allow the light beam for image formation to pass therethrough. It is possible to narrow the distance behind the image means, and it is possible to realize miniaturization and cost reduction.

Further, since the laser light for the horizontal synchronizing signal can be accurately incident on the light detecting means by the half mirror, the reflection points of the laser light for the image forming and the horizontal synchronizing signal on the deflecting surface of the deflecting means can be defined. It is possible to bring them closer to each other, and it is possible to downsize the deflecting means. Therefore,
The rise time and noise of the deflecting unit can be reduced by reducing the windage loss and the inertial force of the deflecting unit.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment.

FIG. 2 is a side view.

FIG. 3 is a perspective view of a conventional example.

[Explanation of symbols]

 11 Laser Unit 12 Polygon Mirror 13 Drive Motor 13a Circuit Board 14 Half Mirror 15 Scan Lens 16 Photo Detection Lens 17 Horizontal Sync Signal Detector

Claims (2)

[Claims] 1. A scanning optical device in which a light beam from a light source is deflected onto a surface to be scanned by a deflecting means and an image is formed by an image forming means, wherein the deflecting means is provided between the deflecting means and the image forming means. A half mirror that transmits at least the light beam for image formation among the light beams of (1), and a converging means and a light detecting means for detecting a horizontal synchronizing signal are provided in the traveling direction of the light beam reflected by the half mirror. A scanning optical device characterized by being provided. 2. The scanning optical device according to claim 1, wherein the light detection unit shares a drive circuit board of the deflection unit.