JPH0421846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the optical axis of a laser beam.

By modulating the laser beam from a laser oscillator with an image signal and guiding the beam to an optical deflector via mirrors and lenses placed in the optical path of the laser beam, the beam is deflected and transferred onto the recording medium. In an image information recording device that records information by scanning, conventionally, a method of adjusting the optical axis of a laser beam directed toward an acousto-optic modulator is to adjust the mounting state of a laser oscillator.
In addition, as a method for adjusting the optical axis of a laser beam directed from an acousto-optic modulator to an optical deflector, by adjusting a reflective optical element (mainly a mirror) placed on the optical path, the laser beam can be adjusted to the correct position on the optical deflector. Efforts such as irradiation with laser beams are being carried out.

However, when adjusting the former according to the prior art, for example, when adjusting the mounting state of the laser oscillator, it is necessary to adjust the emission position of the laser beam two-dimensionally within a plane orthogonal to the optical axis. The disadvantage is that the work is very complicated.

For the latter adjustment, for example, a method is adopted in which the reflecting mirror is supported at three points and the inclination of the reflecting mirror is changed by adjusting the amount of movement in and out of each of these supporting parts. In this method, there are many degrees of freedom for adjustment, so the adjustment itself is a very difficult task, and the structure of the mechanism itself is complicated, which goes against the request for compactness and also leads to an increase in cost.

The present invention has been made in view of the above-mentioned problems, and it is possible to easily adjust the optical axis of a laser beam, and also to meet the demands for compactness and low cost. The purpose is to provide an axis adjustment method.

In order to achieve the above object, the present invention includes a laser oscillator, a mirror unit incorporating a mirror, and a lens unit incorporating a lens, which are each mounted on a common unit base reference plane, and which The mirror is rotatable about a rotation axis perpendicular to the reference plane of the unit base, and the lens of the lens unit is movable back and forth in a direction perpendicular to the reference plane of the unit base. By rotating the lens around the rotation axis and/or reciprocating the lens in a direction perpendicular to the unit base reference plane, the irradiation position of the laser beam is set at a predetermined position in space. The feature is that settings can be adjusted.
Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

An example of an image recording apparatus suitable for implementing the present invention is shown in FIG. To explain the outline of the device here, in the figure, reference numeral 1 is a laser beam light source.
A He-Ne laser is shown. The He-Ne laser 1
The continuous output beam of the He-Ne laser is guided to the acousto-optic modulator AOM, which is a modulator, through the first mirror _M1 and the first lens _L1 .

Then, the output beam modulated by the image signal in the acousto-optic modulator AOM is sent to the second mirror M ₂
and reaches the third mirror _M3 via _the first cylindrical lens CL1. After being reflected by the third mirror _M3 , the light passes through the lens _L4 and enters the rotating polygon mirror 2, which is a deflector. The rotating polygon mirror 2 rotates at a constant angular velocity in the direction of the arrow, and deflects and scans the laser beam containing the image signal at a constant angular velocity.

Then, the deflection-scanned laser beam is fθ
It passes through the lens 4, reaches the fourth mirror _M4 , and then, as shown in _{FIG .} The photoreceptor belt surface 6 is scanned at a constant speed.

In the figure, the reference numeral 7 indicates a synchronous mirror, and the reference numeral 8 indicates a synchronous cylindrical lens, and the light that passes through these optical systems and is guided to the synchronous detection element 9 is a photosensitive Used to determine the starting position on the body.

By the way, the various members shown in FIGS. 1 and 2 are assembled using the unit base 10, which has been machined with high plane accuracy, as a reference plane.

In the apparatus shown in FIG. 1, according to the present invention, the laser beam can be adjusted in the plane perpendicular to the optical axis of the laser beam in the vertical direction perpendicular to the surface of the unit base 10 and in the vertical direction perpendicular to the plane of the unit base 10.
Adjustments are made separately in the left and right directions parallel to the 0 plane.

For example, regarding the horizontal adjustment,
The adjustment is made by rotating the mirror M ₁ and the second mirror M ₂ about arbitrary rotation axes perpendicular to the plane of the paper.

A specific example of a mirror unit including the adjustment mechanism is shown in FIG.

In the figure, reference numeral 11 indicates a mirror mounting base, which has a side profile or approximately T-shape. The bottom plate of the mounting base 11 has one pin hole 12 approximately in the center, and one fixing hole 12 at each end.
3 and 14 are formed. A pin _P12 installed in the unit base 10 is rotatably fitted into this pin hole 12. Furthermore, the fixing holes 13 and 14 are arranged to match fixing holes H ₁₃ and H ₁₄ drilled in the unit base, respectively.
The position of the mounting base 11 is fixed by tightening the bolts inserted through H ₁₃ and fixing holes 14, H _14, respectively. Here, the fixing holes 13 and 14 are each pin holes 1
If it is formed with an arc-shaped elongated hole centered at position 2, there will be more room for selection of the rotation range for determining the fixing position of the mounting large 11.

Next, a groove 11a is formed in the vertical portion of the mounting base 11. There are two mounting screw holes 1 in the groove 11a.
5, 16 are formed, and the screw holes 15, 16
For example, the first mirror _M1 is mounted using the mirror mounting bracket 17. At that time, the first mirror
Cushion members 18 and 19 made of elastic members are interposed between M ₁ and the mirror mounting bracket 17.
Hold mirror _M1 stably.

The first
The mirror M ₁ and the mounting base 11 are rotated about a pin P ₁₂ which is a rotation axis perpendicular to the reference of the unit base 10 and is restricted to one degree of freedom. Therefore, with this rotation, the laser beam can be swung only in the left and right directions, making it easy to make correct adjustments.

Once the adjustment is completed, the positions are fixed by tightening the bolts inserted through the fixing holes 13, H ₁₃ and fixing holes 14, H ₁₄ , respectively.

This adjustment mechanism adjusts the laser beam only in the horizontal direction.
The laser beam from the -Ne laser 1 can be adjusted so as to be incident on a predetermined portion of the acousto-optic modulator AOM.

A similar adjustment mechanism as described above is also used for the second mirror _M2 . In that case, the adjustment mechanism performs horizontal adjustment in order to make the laser beam emitted from the acousto-optic modulator AOM enter the correct position on the rotating polygon mirror 2.

Next, the laser beam optical axis adjustment means for vertical adjustment will be explained.

First, the principle will be explained. In FIG. 4, the symbol L indicates an imaging lens, and the laser beam 20 incident on this imaging lens L
is now focused on point K at focal length f.

Here, the laser beam 20 is left as is,
If the imaging lens L is moved up by △y in a plane orthogonal to the optical axis of the laser beam 20, the focal point of the imaging lens L' will also move to point K', which is elevated by △y from point K. Recognize. Therefore, the imaging lens
The transmitted light of L′ is focused on the K′ point.

That is, in order to adjust the laser beam in the vertical direction, it is sufficient to move the imaging lens within a plane perpendicular to the optical axis of the laser beam.

The lens unit, which is a specific means, will be explained below with reference to FIGS. 5 and 6.

In the figure, reference numeral 21 indicates a lens mounting plate whose side surface is approximately L-shaped. A rectangular groove 22 is formed in the vertical surface portion 21a of the lens mounting plate 21, and a hole 23 for light transmission is formed in the center of the groove 22, penetrating the lens mounting plate 21. There is. On the other hand, a screw hole 24 communicating with the outside world is formed in the upper wall of this groove 22, and a screw 25 is screwed in from the outside.

A hole 26 communicating with the outside world is also formed in the lower wall of this groove 22, and an extensible coil spring 27 is loaded into the hole 26. After loading the spring 27, the plate 28 is fixed to the lens mounting plate 21 by screws 29 and 30. Now, a lens holder 31 having a U-shaped side surface is mounted inside the groove 22 so as to be able to slide vertically on the groove wall surface with the concave portion facing outward. This lens holder 31
A hole 32 for light transmission is also formed in the center of the hole 32, and the centers of this hole 32 and the hole 23 coincide with each other. A cylindrical lens CL ₁ of a size matching the recess (groove) of the lens holder 31 is mounted so that the direction of the groove of the recess matches the direction of the generatrix. At this time, the top of the circumferential surface of the cylindrical lens CL ₁ protrudes a little from the recess of the lens holder 31, and the free end portion of the lens holding plate 33 elastically contacts and holds the protrusion. The reason why the lens holding plate 33 comes into elastic contact with the cylindrical lens CL ₁ in this way is that the base end of the lens holding plate 33 is fixed only at the lower end of the vertical plane of the lens mounting plate 21 with the screws 34 and 35. Because there is. In addition, in the center part of this lens holding plate 33, there is a long hole 33a that is long in the vertical direction.
is formed.

In this way, in the assembled state, the lens holder 31 is held in the vertical direction by the tension force of the spring 27 and the screw 25, and the lens holder 31 and the cylindrical lens CL ₁ are held by the lens holding plate. It is held by 33.

With this configuration, if the screw 25 is tightened against the tension force of the spring 27, the lens holder 31
is guided by the side wall of the groove 22 and descends. Also, by loosening the screw 25, the lens holder 31 can be attached to the spring 2.
It rises by the amount pushed and released by 7.

The lens mounting plate 21 is mounted on the upper surface of the unit base 10, that is, on the reference surface of the unit base, using the mounting holes 36 and 37. Then, if necessary, the cylindrical lens CL ₁ is moved in the vertical direction, that is, in the direction perpendicular to the reference plane of the unit base, to adjust the laser beam to be incident on the desired position of the rotating polygon mirror 2.

The first lens _L1 , which is a spherical lens, is also adjusted in the vertical direction by means similar to the structure of the lens unit explained in FIGS. 5 and 6 above. However, in that case, as for the lens holder 31, a cylindrical cap-shaped lens holder 31' as shown in FIG. 7 is used to facilitate mounting of the spherical lens.

As explained above, in the present invention, adjustments are made in one degree of freedom with respect to lenses and mirrors based on a common reference plane.
If the mirror unit shown in the figure and the lens unit shown in FIGS. 5 and 6 are used together, accurate adjustment can be made. Further, since the above adjustment means are each independent small units, the optical system unit to which the present invention is applied can be made compact.

[Brief explanation of drawings]

FIG. 1 is a plan view illustrating the exposure optical system of an image recording apparatus suitable for carrying out the present invention, FIG. 2 is a side sectional view illustrating a part of the same figure, and FIG. Fig. 4 is an exploded perspective view illustrating an example of means for adjusting the optical axis of the laser beam in the left-right direction. Fig. 5 is an exploded perspective view illustrating an example of the configuration of a laser beam optical axis adjusting means in which the principle explained in the above figure is applied to the device;
The figure is a sectional view taken from the center of the device shown in the above figure in an assembled state, and FIG. 7 is a perspective view showing an example of a lens holder used with a spherical lens together with the spherical lens. 10...unit base, 21...lens mounting plate, 25...screw, _P12 ...pin, _M1 ...first mirror, _M2 ...second mirror, _L1 ... _first lens,
CL ₁ ...First cylindrical lens.

Claims (1)

[Claims] 1 Modulating a laser beam from a laser oscillator with an image signal, and directing the beam onto an optical deflector via a mirror or lens placed in the optical path of the laser beam, deflecting the beam and directing it onto the recording medium. A method for adjusting the optical axis of a laser beam applied to an image recording device that records information by scanning, the method comprising: the laser oscillator; a mirror unit incorporating the mirror; and a lens unit incorporating the lens. , mounted on a common unit base reference plane, and for the mirror unit, the mirror is rotatable around a rotation axis perpendicular to the unit base reference plane, and for the lens unit, the lens is mounted on the unit base. Allow it to freely reciprocate in the direction perpendicular to the reference plane,
By rotating the mirror about the rotation axis and/or reciprocating the lens in a direction perpendicular to the unit base reference plane, the irradiation position of the laser beam can be adjusted in space. A method for adjusting the optical axis of a laser beam, the method comprising adjusting the optical axis to a predetermined position.