JPH07111511B2 - Laser scanning optical system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output device such as a laser printer, and more particularly to a laser scanning optical system for performing highly accurate scanning.

[Conventional technology]

A laser printer is known as a device that outputs a high-quality image at high speed. In this laser printer, a laser beam is deflected by a laser scanning optical system using an optical scanner such as a rotating polygon mirror, and the deflected laser beam scans the photoconductor to form a latent image on the photoconductor. . Then, after developing this latent image, it is transferred onto a sheet to obtain an output image.

FIG. 2 shows a schematic explanatory view of a laser scanning optical system in a conventional example.

In the figure, 1 is a semiconductor laser. Semiconductor laser 1
The laser light 2 from the laser light is collimated by the collimator lens 3. The laser light 2 from the collimator lens 3 is
The rotary polygon mirror scanner 4 is irradiated, and the laser beam 2 is deflected according to the rotation of the rotary polygon mirror scanner 4.

The laser light 2 from the rotary polygon mirror scanner 4 receives the fθ lens 5
An image is formed on the image forming surface 6 via, and the image forming surface 6 is scanned according to the rotation of the rotary polygon mirror scanner 4. The image plane 6 is, for example, the surface of a drum-shaped photoconductor having a rotation axis along the scanning direction of the laser light 2, and the scanning of the laser light 2 in the rotation axis direction by the rotary polygon mirror scanner 4, that is, the main surface. A two-dimensional image is formed on the image plane 6 by scanning and sub-scanning by rotation of the drum.

[Problems to be solved by the invention]

In the conventional laser scanning optical system, the above optical system is housed in the housing, but heat is generated from the semiconductor laser 1, the drive motor (not shown) and the like included in the rotary polygon mirror scanner 4. Therefore, a temperature difference occurs in the housing. Therefore, air convection occurs in the optical path from the semiconductor laser 1 to the image plane 6 and fluctuations of the laser light 2 occur. For example, in FIG. 2, if the fluctuation occurs like the laser beam 2a, the irradiation position of the image plane 6 is the original irradiation position.
Displacement from 20 to the irradiation position 20a appears as a deviation of the scanning position. Further, the laser beam 2 is deviated from the original optical path and f
Since the light enters the θ lens 5, there is a drawback that the image forming performance of the fθ lens 5 is deteriorated and the image quality is deteriorated.

An object of the present invention is to eliminate the above-mentioned drawbacks, prevent convection of air in the optical path, eliminate fluctuations of laser light, and perform scanning with laser light with high accuracy.

[Means for solving problems]

In order to achieve the above-mentioned object, the laser scanning optical system of the present invention encloses at least a part of an optical path between a light source and an image forming surface on which the laser light from the light source forms an image in an airtight state. Is provided with a cover whose transparent surface is a transparent member.

Further, the cover is provided without including the light source.

[Action]

According to the present invention, the air in the cover is separated from the other portions, so that the convection of air in the device does not affect the optical path of the laser light. That is, there is no air convection in the cover, and the laser light does not fluctuate.

Further, when the cover is provided without including the light source, there is no heat source in the cover, so that convection does not occur in the cover.

〔Example〕

Hereinafter, features of the present invention will be specifically described based on embodiments with reference to the drawings. The same parts as those in the conventional example are designated by the same reference numerals.

FIG. 1 is a plan view showing the outline of an embodiment of the present invention.

In the figure, A indicates a laser scanning optical system as a whole. In the laser scanning optical system A, the laser light 2 emitted from the semiconductor laser 1 is collimated by the collimator lens 3 and is deflected by the rotary polygon mirror scanner 4.
Further, scanning is performed while forming an image on the image forming surface 6 by the fθ lens 5.
The laser scanning optical system A is the same as the laser scanning optical system A.
It is assumed that the device is stored in the housing (not shown) of the device to which the above is applied.

Here, in this embodiment, in order to prevent the fluctuation of the laser light 2, the semiconductor laser 1 and the rotary polygon mirror scanner 4 which are heat sources are removed, and most of the entire optical path is covered by the covers 7 and 8. Convection is prevented from occurring in the enclosed optical path.

That is, in the optical path from the laser beam 2 emitted from the semiconductor laser 1 to the rotary polygon mirror scanner 4 after passing through the collimator lens 3, the upper, lower, left and right surfaces of the optical path are covered with a cover 7 having no air permeability. Transparent cover glasses 7a and 7b are arranged at both ends of the cover 7 in an airtight state. The cover 7 is provided so that its front end is close to the semiconductor laser 1 and its rear end is close to the rotary polygon mirror scanner 4. The cover glasses 7a and 7b are used for the laser light 2 in the optical path.
The material and shape shall not have any influence on the straight transmission of.

In the optical path from the rotary polygon mirror scanner 4 to the image forming surface 6, the laser light 2 is deflected by the rotary polygon mirror scanner 4, and the rotary polygon mirror scanner 4 is rotated in the arrow direction to form an image. Since the laser beam 2 scans the surface 6 in the order of 2b, 2c, 2d, the optical path of the laser beam 2 is expanded to the end. Therefore, the part in this optical path is
A fan-shaped cover 8 is provided so as to surround the enlarged optical path.

The front end of the cover 8 is arranged at a position close to the rotary polygon mirror scanner 4, and a cover glass 8a is provided at this front end. A cover 8 covers the upper, lower, left and right surfaces of the optical path so as to surround the fθ lens 5 and the enlarged optical path, and the rear end portion of the cover 7 is extended to a position close to the image forming surface 6, and the rear end is formed. A cover glass 8b is provided on the part.

As described above, in this embodiment, since most of the optical path is surrounded by the covers 7 and 8, the convection of air in the device does not affect the optical paths of the laser beams of the covers 7 and 8. . Therefore, the laser light 2 does not fluctuate due to the convection of air in the device. In addition, laser light 2 which is a heat source
Since the rotary polygon mirror scanner 4 is provided outside the covers 7 and 8 and the covers 7 and 8 are provided, a heat source does not exist in the cover and convection does not occur in the cover.

In the above-described embodiment, the covers 7 and 8 are hermetically sealed by the cover glasses 7a, 7b, 8a, and 8b, but the air near the optical path of the laser light can be separated from the air where convection exists. It does not have to be completely airtight as long as it is one. For example, the cover glass 7a, 7b, 8a, 8b may not be provided, and the optical path may be surrounded only by the covers 7 and 8, and even in this case, it has been confirmed that it is sufficient to prevent air convection. .

As the light source, a semiconductor laser is preferable from the viewpoint that the device can be downsized because direct modulation is possible.
The present invention is not limited to this, and a gas laser such as a He-Ne laser may be used. However, in this case, when it is necessary to modulate the laser light, it is necessary to provide an external modulator between the light source and the collimator lens.

The laser scanning optical system described above can be applied to a device that requires scanning with laser light, for example, a laser printer. In this case, since scanning on the surface of the photoconductor is accurately performed, high-quality output without disturbance is obtained. An image is obtained.

〔The invention's effect〕

As described above, according to the present invention, since the periphery of the optical path of the laser light is surrounded by the cover, convection does not occur in the air in the optical path, and fluctuations of the laser light can be prevented. Therefore,
Scanning on the image plane of the laser light such as the surface of the photoconductor becomes accurate and a high quality image can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an outline of an embodiment of the present invention, and FIG. 2 is a plan view showing an outline of a laser scanning optical system in a conventional example. 1: Semiconductor laser, 2, 2a: Laser light 3: Collimating lens, 4: Rotating polygon mirror scanner 5: fθ lens, 6: Image plane 7,8: Cover, 7a, 7b, 8a, 8b: Gover glass A: Laser Scanning optics

Claims (2)

[Claims] 1. A cover in which at least a part of an optical path between a light source and an image forming surface on which laser light from the light source is formed is surrounded in an airtight state, and a surface through which the laser light passes is a transparent member. A laser scanning optical system characterized by being provided. 2. The laser scanning optical system according to claim 1, wherein the cover is provided without including the light source.