JPH07113969A - Laser optical device - Google Patents

Abstract

PURPOSE:To obtain good image quality free from unequal pitches by obviating the generation of abnormal vibrations by the strain of the laser optical device generated at the time of building the laser optical device into a writing device and lessening the movement of the optical axis by the strain of the laser optical device. CONSTITUTION:This laser optical device consists of an optical base plate 1 installed with a light source unit 3, imaging optical systems 4, 6 and a deflector 5 and a fixing part 2 for fixing this optical base plate 1 to the writing device. A material harder than the material of the fixing part 2 is applied to the material constituting the optical base plate 1. Further, the Young's modulus of the material constituting the fixing part 2 is set larger than 0.2X10<10>N/m<2> and smaller than 7.5X10<10>N/m<2>. The Young's modulus of the material constituting the fixing part 2 is set smaller than the Young's modulus of the optical base plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a laser optical device, and more particularly to a technique for reducing scanning pitch unevenness by reducing movement of an optical axis due to deformation of an optical substrate.

[0002]

2. Description of the Related Art A laser optical device generally includes a laser light source unit, a first image forming optical system for converging a light beam emitted from the laser light source, a deflector polygon mirror and its drive motor, and a reflection by the polygon mirror. A unit in which a second image forming optical system for forming an image of light on the surface of the medium to be scanned is installed with its positional relationship strictly determined is fixed to a mounting surface of a writing device, and emitted from the laser light source. The light flux is controlled to form an image on the surface of the medium to be scanned of the writing device,
By irradiating the intensity of the separately controlled laser light source light in the main scanning direction by the rotation of the polygon mirror, main scanning exposure is performed, and the medium to be scanned is sub-scanned by moving in a direction orthogonal to the main scanning direction. It is the most important part of a writing device that forms a two-dimensional image on the surface of a medium to be scanned.

In order for the above two-dimensional image to be formed correctly, the main scanning is required to have good linearity, and the sub-scanning is required to have a uniform moving speed and be stable. In addition to vibrations and uneven rotation of the polygon mirror, various measures have been taken, and in addition, the movement of the medium to be scanned in the sub-scan has been devised to eliminate the uneven movement speed.

However, in order to assemble the laser optical device and the mechanism for moving the medium to be scanned in the sub-scan as an integrated structure, there is a technical problem that it is large and complicated and the processing accuracy cannot be secured. However, the laser optical device is not assembled as a single unit, but is separately assembled as a separate unit and then attached to the writing device to match the moving mechanism of the separately scanned medium.

The problem that occurs there is that an abnormal condition occurs after the unit is assembled and the operation is started due to an easily checkable event of assembling each unit to determine the relative position and an unreasonable distortion when assembling each unit. It is a phenomenon that cannot be easily checked as vibration that causes non-negligible harm.The latter is greatly related to the pitch unevenness of the sub-scanning as a writing device, and the parts in the laser optical device due to excessive distortion are There is also a problem that the relative position changes and the scanning light cannot be emitted correctly, and a countermeasure is required.

[0006]

In view of the drawbacks of the prior art, the distortion generated when the laser optical device is incorporated in the writing device does not cause abnormal vibration of the laser optical device, and the movement of the optical axis due to the distortion is reduced. Then, it is an object of the present invention to provide a laser optical device which obtains a good image quality without pitch unevenness.

[0007]

According to another aspect of the present invention, there is provided a laser optical device incorporated in a writing device for writing a laser beam on a medium to be scanned, which comprises a light source unit and a light source unit. , An imaging optical system, an optical substrate on which a deflector is installed, and a fixing portion for fixing the optical substrate to the writing device. The material forming the optical substrate is harder than the fixing portion. The feature is that the material is applied.

Furthermore, in the laser optical device according to the second aspect of the present invention, the Young's modulus of the material forming the fixing portion is 0.
Greater than ^{2 × 10 10 N / m 2} , as well as smaller than ^{7.5 × 10 10 N / m 2} , and the Young's modulus of the material constituting the fixing portion is set smaller than the Young's modulus of the material constituting the optical base It is characterized by that.

[0009]

Since the optical base is not deformed, the light source unit installed on the optical base, the imaging optical system, and the deflector do not change in their mutual relations. Therefore, the optical base is used as a base. As a measure for preventing the optical axis of the laser optical unit from moving to cause pitch unevenness in each rotation cycle of the deflector, a material for forming the optical substrate is used to fix the optical substrate to the writing device. It was set to be harder than the material forming the fixed part. That is, instead of integrally forming the optical base and the fixing part with a series of the same material, when fixing the fixing part made of a relatively non-hard material to the hard optical base and fixing it to the writing device. The deformation of the optical substrate, which should occur in the above, is absorbed and relieved by the elasticity of the fixing portion.

When the optical base is fixed to the writing device, if the flatness of the contact portions for fixing the optical base and the optical base is not good, the optical base is liable to be deformed due to the fixing, and the deformation is not caused. There is a limit to the improvement of processing accuracy. There is a method of three-point support as a fixing method to prevent deformation,
With three-point support, vibration is easily emphasized when the deflector is driven,
It is necessary to firmly fix it by four-point support, and on the other hand, when the optical substrate is deformed, vibration is likely to occur, or irregular pitch of scanning lines due to rotation of the deflector occurs. Therefore, in the present invention, a material that is harder than the fixing portion is used as the material that constitutes the optical substrate so that the optical substrate is not deformed and is firmly fixed to the writing device and vibration is not emphasized.

In a further limited manner, Young's material of the fixing portion is larger than 0.2 × 10 ¹⁰ N / m ² and 7.5 × 10 ¹⁰ N.
/ M ² and the Young's modulus of the material forming the fixing portion was set smaller than the Young's modulus of the material forming the optical substrate.

[0012]

Embodiments will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a laser optical device according to an embodiment. In FIG. 1, a fixing portion 2 is provided around the optical base 1.
4 are fixed, and the fixing portion 2 is screwed to the mounting seat 7 of the writing device. A light source unit 3, a first image-forming optical system 4, a deflector 5, a second image-forming optical system, and the like are provided on the upper surface of the optical substrate 1, and the deflector 5 is driven by a motor (not shown) and has a shaft 8 Rotate around.

The light beam emitted from the light source unit 3 is converged by the first image forming optical system 4 and is incident on the mirror 9 of the deflector 5 as a thin beam, and the reflected light thereof is transmitted through the second image forming optical system 6. After that, it is ejected in the direction of arrow A.

With the rotation of the deflector 5, the emitted reflected light is linearly scanned in a plane parallel to the optical substrate 1.

Therefore, when the optical substrate 1 is deformed and the flatness is deteriorated, the emission direction of the light beam is changed, and the correct scanning cannot be performed.

In this embodiment, in order to prevent the deformation of the optical substrate 1, the material of the optical substrate 1 is silicon nitride (ceramic) and the material of the fixing portion 2 is aluminum as the first embodiment. Adhesion having sufficient strength was used as a means for fixing the two. As a second embodiment, the optical substrate 1
The material of the above is aluminum, and the material of the fixing portion 2 is 6 nylon, and as a means for fixing the fixing portion 2 to the optical substrate 1, an adhesive having sufficient strength is used. As a third embodiment, the material of the optical substrate 1 is silicon nitride (ceramic, Si3N).
4), the material of the fixing portion 2 is 6 nylon, and as a means for fixing the fixing portion 2 to the optical substrate 1, an adhesive having sufficient strength is used. The term "adhesion having sufficient strength" means that the adhesive does not fall off and is not deformed by the adhesive, and can be selected from commercially available adhesives.

The fixing method is not limited to the above-mentioned adhesion, and the fixing portion 2 may be fixed to the optical substrate 1 with the screw 11 as shown in FIG.

The material of the fixing portion 2 is made of 6 nylon and aluminum. The reason is that the Young's modulus of 6 nylon is 0.2 × 10 ¹⁰ N / m.
² , the Young's modulus of aluminum is 7.5 × 10 ¹⁰ N / m ^2, which is for checking the limit.

Further, the reason why silicon nitride is used as the material of the optical substrate 1 is that silicon nitride has a higher Young's modulus than aluminum and is convenient for maintaining flatness.

The results of actually measuring the amount of movement of the optical axis after mounting in Examples 1, 2 and 3 are as follows.
Before, it was as small as 3 μ to 8 μ in the X direction, which was sufficient for practical use.

[0022]

With the above construction, when the laser optical device is incorporated in the writing device, deformation and distortion are unlikely to occur, so that the optical axis does not move and abnormal vibration does not occur. It is possible to obtain good image quality without

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment.

FIG. 2 is a sectional view of a fixing method.

[Explanation of symbols]

 1 Optical Base 2 Fixed Part 3 Light Source Unit 4 First Imaging Optical System 5 Deflector 6 Second Imaging Optical System 7 Writing Device Mounting Seat 8 Axis 9 Mirror 10 Collimator Lens 11 Screw

Claims (2)

[Claims] 1. A laser optical device incorporated in a writing device for writing a laser beam on a medium to be scanned, the optical substrate having a light source unit, an imaging optical system, and a deflector, and the optical substrate. And a fixing portion for fixing the optical substrate to the writing device, wherein a material that constitutes the optical substrate is a harder material than the fixing portion. 2. The Young's modulus of the material forming the fixing portion is 0.2.
× greater than ¹⁰ 10 N / m ^2, as well as smaller than ^{7.5 × 10 10 N / m 2} , that is set smaller than the Young's modulus of the material constituting the optical base the Young's modulus of the material constituting the fixing portion The laser optical device according to claim 1, which is characterized in that.