JPH08340155A - Optical scanning device - Google Patents

Abstract

PURPOSE: To provide an optical scanning device, which can obtain easily a high-quality level image having little image noise, by a method wherein extra reflected light is reduced and a side lobe, which causes the image noise, is reduced. CONSTITUTION: A stop member 2 is arranged between a light source 1 and a collimator lens 3 so that the unnecessary part of a laser beam emitted from the light source 1 is shielded by the stop member 2 and is made incident in the collimator lens 3.

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 for scanning a light beam emitted from a light source onto a surface to be scanned to form an image.

[0002]

2. Description of the Related Art Conventionally, in an optical scanning device such as a laser beam printer, image information is written by optically scanning the surface to be scanned with laser light that has been optically modulated. For example, in FIG. 4, Japanese Patent Laid-Open No. 6-43372.
The main part of a conventional optical scanning device as described in Japanese Patent Laid-Open Publication No. 2003-242242 is schematically shown.

In FIG. 4, reference numeral 101 is a light source unit such as a semiconductor laser. The laser light emitted from the light source unit 101 is divergent light and becomes a substantially parallel light flux when passing through the collimator lens 102. Further, the laser light passing through the collimator lens 102 passes through the cylindrical lens 103 having a refractive power only in the sub-scanning direction and is converged only in the sub-scanning direction.

Further, the laser light focused in the sub-scanning direction by the cylindrical lens 103 is used as the diaphragm member 10.
The light beam diameter is changed at the opening of No. 4, and the light is deflected and reflected by the deflection reflection surface 105d of the optical deflector 105. The laser light deflected and reflected by the light deflector 105 passes through the image forming optical system 106, so that its scanning linearity is corrected and the photosensitive drum 1
An image is formed on the 07 surface, and the surface of the photoconductor drum 107 is optically scanned by a substantially uniform linear motion.

Further, in FIG. 4, reference numeral P indicates a deflective reflection surface 1.
The position of the reflecting surface of 05d is shown, and the light beam is focused on this reflecting surface position P substantially in the sub-scan section as described above. Here, the reflection surface position P and the photosensitive drum 10
The image forming optical system 106 and the image forming optical system 106 are in a substantially optically conjugate positional relationship. Accordingly, even if the deflecting / reflecting surface is tilted in the sub-scanning section and there is so-called surface tilt, the light beam is formed on the same scanning line on the surface of the photosensitive drum 107.

In the prior art shown in FIGS. 4 and 5, the light beam that has passed through the collimator lens 102 and the cylindrical lens 103 has its luminous flux diameter changed at the opening of the diaphragm member 104, and the optical deflector 105 is used. Since the deflecting / reflecting surface 105d is deflected and reflected, the following problems occur when the light beam enters the collimator lens 102.

That is, depending on the accuracy of the laser chip which is the light source, the incident angle when the light beam emitted from the light source section 101 enters the collimator lens 102 may vary, and as a result, it is essentially unnecessary. Similar light beams may enter the collimator lens 102 as well as useful light beams. And the unnecessary rays are shown in FIG.
As shown in FIG. 2, the light is reflected in the lens barrel 108 supporting the collimator lens 102 and passes through the diaphragm member 104,
Further, the light is deflected by the light deflecting surface 105d, and the image forming optical system 1
After passing through 06, the surface to be scanned 107 is scanned and becomes a side lobe. Such side lobes often cause noise in image information and often adversely affect the final image.

[Problems to be Solved by the Invention]

In the present invention, unnecessary rays of the light beam diverging from the light source are prevented from entering the collimator lens to reduce side lobes that cause noise in the image information and to provide a high-quality image with less noise. It is an object of the present invention to provide an optical scanning device that can easily obtain

[0009]

The optical scanning device of the present invention comprises:
The collimator lens converts the light beam diverged from the light source into a parallel light beam, which is deflected by a rotary deflector, and then the imaging optical system is caused to scan the surface to be scanned with the parallel light beam as a spot shape. In the optical scanning device, a diaphragm member that blocks an unnecessary portion of the divergent light from the light source is arranged between the light source and the collimator lens.

[0010]

According to such an optical scanning device, since the laser light emitted from the light source passes through the diaphragm member and then enters the collimator lens, unnecessary light rays are removed by the diaphragm member in advance, and then the collimator lens. Since the light is incident on the side lobes, side lobes that cause image information are reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 3A and 3B show an optical scanning device according to an embodiment of the present invention. FIG. 3A is a plan view with a cover removed, and FIG. 3B is a side sectional view of FIG.

In FIG. 3, reference numeral 11 denotes a semiconductor laser unit as a laser light generating means. In this semiconductor laser unit 11, only a laser chip and a useful portion of the laser light emitted from this laser chip are provided. A diaphragm member for passing the laser light and a collimator lens for collimating the laser light are incorporated. This point will be described later. Laser unit 11
The parallel light emitted thereby is converged by the cylindrical lens 4 on the mirror surface of the optical deflector 5 as the polarization scanning means. The optical deflector 5 is rotated by an optical deflector drive motor (not shown).

The converged laser light has a constant velocity linear motion in the main scanning direction through the image forming optical system 6 having a structure described later, and pitch unevenness is corrected in the sub scanning direction. When the laser light emitted from the imaging optical system 6 arrives at a position immediately before the start end position of the image recording area of the image recording medium (not shown), the fixed mirror 1
4, 15 and the non-focused beam reflected by the timing adjusting mirror 16 and reflected by the timing adjusting mirror 16 is, for example, a Pin photo (a kind of photodiode) as a photoelectric conversion element forming a photodetector. 1
It is directed to 7a, becomes a condensed beam at the position of the Pin photo 17a, and is received by the Pin photo 17a.

The Pin photo 17a is exposed inside the chassis 18, and a circuit board (not shown) is electrically connected to the Pin photo 17a. The circuit board is fixed on the outside of the chassis 18 with its surface facing downward.

When the laser light reflected by the timing adjusting mirror 16 is received by the Pin photo 17a, a so-called synchronizing signal is emitted, and after a predetermined time elapses with reference to this signal generating time, the semiconductor laser records. The modulation drive is started by the information signal. In this way, scanning is started from the start position of the image recording medium with the beam modulated by the synchronization signal.

The essential parts of the above embodiment will be described in detail below. FIG. 1 is a schematic view of a main part of an optical scanning device according to an embodiment of the present invention. Semiconductor laser unit 11 described above
First, the laser diode (hereinafter LD
1) is provided, and laser light is emitted from this LD1. A useful light beam of the laser light diverged from the LD 1, that is, a part of the laser light passes through the opening of the diaphragm member 2 and becomes a parallel light flux by the collimator lens 3 as described later.

The laser light which has become a parallel light beam is further incident on the cylindrical lens 4. Since the cylindrical lens 4 is set to have a refracting power only in the sub-scanning direction, the laser light of the parallel light flux passing through the cylindrical lens 4 is converged in the sub-scanning direction to form a linear shape, It is incident on the light deflection surface 5d of the deflector 5.

The laser light deflected by the deflector 5 passes through an image forming optical system 6 including a toric lens 6a and an image forming lens 6b. Since the image forming optical system 6 comprises the deflection position P of the optical deflector 5 and the f-θ system on the surface of the photosensitive drum 7, the scanning linearity of the laser beam is corrected, and the corrected laser beam is corrected. The light forms an image on the surface of the photoconductor drum 7 and optically scans the surface of the photoconductor drum 7 with a substantially uniform linear motion.

The process until the laser light emitted from the laser diode (LD) 1 passes through the collimator lens 3 will be described with reference to FIG. The diaphragm member 2 and the collimator lens 3 are fixed at predetermined positions inside a substantially cylindrical lens barrel 8, and the diaphragm member 2 is arranged between the LD 1 and the collimator lens 3. Unnecessary light rays of the laser light diverging from LD1 are blocked by the diaphragm member 2,
Only useful rays of the more divergent laser light pass through the aperture of the diaphragm member 2. Then, only the useful light beam that has passed through the diaphragm member 2 passes through the collimator lens 3 to be a parallel light beam.

According to the embodiment having the above-described structure, unnecessary portions of the laser light emitted from the LD 1 are blocked by the diaphragm member 2 so that only useful laser light enters the collimator lens 3. Therefore, the amount of light incident on the collimator lens 3 itself becomes unnecessarily small, so that the amount of extra reflected light is reduced and side lobes that cause image information are reduced.

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, in the above embodiment, an example in which the optical scanning device is applied to a laser beam printer is described, but the invention is not limited to the laser beam printer, and other devices can be used. Is similarly applicable.

[0022]

As described above, according to the optical scanning apparatus of the present invention, a diaphragm member cuts off a part of the laser light emitted from the light source, removes unnecessary light rays, and makes them enter the collimator lens. As a result, the amount of light entering the collimator lens itself is reduced, and the excess reflected light is reduced to reduce the side lobes that cause noise in the image information, making it easy to produce high-quality images with little noise. Therefore, the reliability of the optical scanning device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a main part of an optical scanning device according to an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part of the optical scanning device according to the present invention.

FIG. 3 is an overall view of an optical scanning device according to an embodiment of the same, FIG. 3A is a plan view with a cover removed,
(B) is a side sectional view of (a).

FIG. 4 is a schematic perspective view of a main part of a conventional optical scanning device.

5 is a partially enlarged side view showing a light source portion of the conventional device shown in FIG.

[Explanation of reference numerals] 1 laser diode 2 diaphragm member 3 collimator lens 4 cylindrical lens 5 optical deflector 6 imaging optical system 7 photoconductor drum

Claims (1)

[Claims] 1. A light beam emitted from a light source is converted into a parallel light beam by a collimator lens, the parallel light beam is deflected by a rotary deflector, and then the parallel light beam is made into a spot shape on a surface to be scanned through an imaging optical system. In the optical scanning device for scanning, a diaphragm member for blocking an unnecessary portion of the divergent light from the light source is arranged between the light source and the collimator lens.