JPH0358487B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of adjusting laser light using a jig in a laser device that uses an optical modulation element to intermittent laser light.

For example, in a laser printer, fine adjustment is required to adjust the optical axis of the laser, especially the adjustment of the light modulation element.
Have difficulty.

FIG. 1 shows a diagram of the arrangement of optical components in the light modulation element section. Conventionally, the positions of the input lens 4, the output lens 5, and the light modulation element 6 relative to the laser beam 1 have been adjusted by moving them individually and measuring the amount of laser beam 7 used for character writing to maximize the amount of light. . However, due to the characteristics of the light modulation element 6, if the incident angle θ of the laser beam deviates from the normal value by 1 mrad, the amount of the laser beam 7 decreases by 10%. The angle of incidence θ on the light modulation element is influenced by the focal length F of the input lens 4 and the amount of deviation A between the center line connecting the center of rotation 9 and the center of the input lens 4 and the laser beam 1. Here, the deviation amount A
is given in advance for intermittent laser light by the light modulation element 6. For example, if F=150 mm and θ is off by 1 mrad, the error ΔA of A is as follows since θ≈0.

ΔA≒150×tan (1mrad)=0.15mm Therefore, in order to obtain a sufficient amount of laser beam 7, the installation error of A must be 0.15mm or less. Furthermore, it is clear that if the center line connecting the center of rotation 9 and the center of the incident lens 4 is not parallel to the laser beam 1, the incident angle θ will be shifted and the amount of the laser beam 7 will be reduced.

In this way, the entrance lens 4 for the laser beam 1
The mounting of the light modulation element 6 and the light modulation element 6 must be done with high precision. Conventionally, the input lens 4, the output lens 5, and the light modulation element 6 had to be moved individually relative to the laser beam, making it difficult to adjust the mounting position. .

An object of the present invention is to eliminate the drawbacks of the conventional adjustment methods described above and to facilitate adjustment.

The present invention focuses the laser light incident on the light modulation element to an optimum diameter, and the laser light used for character writing among the laser light emitted from the light modulation element before entering the input lens. Focusing on the fact that the laser light emitted from the output lens passes through the same optical axis, we used a guide jig to adjust the laser light without the light modulation element and the above two lenses. Then, the light modulation element and the input and output lenses are integrally mounted and adjusted to have a constant relationship with the laser beam.

Adjustment of laser light using the guide jig according to the present invention will be explained with reference to the drawings.

2 fixed at a specified position on the laser device main body B
The reflecting mirror 2 is adjusted so that the incident laser beam 1 passes through the holes of the two guide jigs. This adjusts the reference optical axis. Next, an assembly C of the lenses 4 and 5 and the light modulation element 6 is formed in advance so that the rotation center 9 of the light modulation element 6 is on the center line connecting the centers of the input lens 4 and the output lens 5. Note that the distance from the center of rotation 9 to each lens 4, 5 is set equal to the focal length F of each lens.
In this embodiment, the focal lengths of the entrance lens 4 and the exit lens 5 are made equal. The above assembly C is installed between two guide jigs 3 so that the center line is offset by A from the reference optical axis. At this time, the incident laser beam 1 that has entered the incident lens 4 is directed toward the rotation center 9 and is modulated by the light modulation element 6 . The diffracted laser beam 7 used for writing characters passes through the exit lens 5 and then through the hole in the guide jig 3. The unmodulated straight laser beam 8 travels straight and is blocked by the guide jig 3. Here, the value of A is determined by the carrier frequency f of the light modulation element, the laser light wavelength λ, the speed of sound V in the light modulation element, and the focal length F of the lens. The calculation formula is as follows.

A=Ftan(f/2V) Note that (λf/2V) is the modulation angle θ by the light modulation element, and the unit is rad.

By the above adjustment method using the guide jig, the input lens 4 and the output lens 5 for the incident laser beam 1 are
Then, the position adjustment of the light modulation element is completed. After that, since the mounting error of the light modulation element 6 to the lenses 4 and 5 and the mounting error of the above-mentioned assembly to the incident laser beam 1 are both minute errors due to component processing precision, in order to correct these errors, It is easy to adjust the light intensity of the diffracted laser beam 7 used for writing to maximize it.

According to the present invention, the jig for setting the reference optical axis as described above is used, and the individual optical members are integrally formed to adjust the optical axis of the laser device having the polarization device, so that it is possible to accurately adjust the optical axis of the laser device having the polarization device. Optical axis adjustment, which requires high precision, can be performed much more easily and quickly than in the past.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a light modulation element section. FIG. 2 is a schematic diagram showing a method for adjusting the optical path of a laser beam using a jig according to the present invention, FIG. 3 is a longitudinal cross-sectional view of an assembly of a lens and a light modulation element according to the present invention, and FIG. FIG. 2 is a schematic diagram showing the positional relationship between the jig and the assembly. In the figure, 1 is an incident laser beam, 2 is a reflection mirror, 3 is a guide jig, 4 is an input lens, 5 is an output lens, 6 is a light modulation element, 7 is a diffracted laser beam,
8 is a straight laser beam, and 9 is a rotation center. B is the laser device main body, and C is the assembly.

Claims (1)

[Claims] 1. In a laser device that uses a light modulation element to intermittent laser light, the light modulation element, the entrance lens and the output lens provided before and after the light modulation element are positioned such that the rotation center of the light modulation element and the lens center are on a straight line. Next, the laser beam is adjusted to pass through the reference optical axis on the laser device using a guide jig, and the assembly is mounted on the laser device and the laser beam is Optical axis adjustment method by combining light.