JPH0634486A - Beam shape measuring instrument - Google Patents

Abstract

(57) [Summary] [Object] To provide a beam shape measuring device capable of measuring a beam diameter immediately after emission and a beam diameter at an arbitrary position in a state where the optical path length is increased. In a beam shape measuring device for performing beam shaping by guiding a beam 4 emitted from a laser light source to a beam shape measuring instrument 5, an emission while the beam 4 emitted from a laser light source is directed to the beam shape measuring instrument 5. An optical path separation optical system 11 including a first wavelength plate 6 and a polarization beam splitter 7 for branching an incident beam is provided on the optical path immediately after, and the optical path length is set to be long on the optical path branched by the polarization beam splitter 7. For this purpose, a pair of corner cube prisms 12 and 13 are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam shape measuring apparatus used in a master exposure apparatus or the like for manufacturing a master optical disk.

[0002]

2. Description of the Related Art As a conventional beam shape measuring apparatus, for example, there is one disclosed in Japanese Utility Model Laid-Open No. 2-118232 under the title "Beam Diameter Measuring Apparatus". Therefore, a conventional example of this type of device will now be described with reference to FIG. The beam emitted from the laser light source 1 is shaped into a beam by passing through a lens 2 and an optical element such as an AO modulator (not shown), and then guided to a beam shape measuring device 3 to measure the beam shape. . In this case, in order to accurately grasp the shape of the emitted beam, the divergence state of the beam is measured at a position A immediately after beam shaping and a position B (1 to 3 m) far away from the beam, and if the divergence of the beam diameter is measured. If it is large, the optical element is finely adjusted so as to have an appropriate beam shape, so that the beam becomes parallel light that has as little divergence as possible.

[0003]

Generally, a laser light source 1 is used.
The beam emitted from is as thin as φ1 mm, and the shape of the beam cannot be determined. At the same time, the beam is 0.5 mrad.
It has a divergence angle of (0.5 mm at 1 m). In this case, when measured at a position away from the laser light source 1, TE
Although the M mode becomes clear, the beam shape measuring instrument 3 as described above can perform the measurement only at the measured positions A and B. For this reason, when examining the beam divergence and the beam shape, the beam shape measuring instrument 3 must be moved, which requires a large space.

Further, in recent years, a variety of optical systems have been required due to the high density of discs, and in the case of an optical system such as a recording apparatus, there is no space, and it is difficult to measure by moving the position as described above. Is.

Further, the beam used for recording on the disk master is shaped in the optical system, but if the arrangement of the optical element is bad and there is aberration of the beam, the recorded groove (guide groove) and pit are desired. I can't get one.

[0006]

According to a first aspect of the present invention, in a beam shape measuring apparatus for performing beam shaping by guiding a beam emitted from a laser light source to a beam shape measuring instrument, the beam is emitted from the laser light source. An optical path separation optical system including a first wave plate and a polarization beam splitter for branching the incident beam is provided on the optical path immediately after the beam is emitted while the beam is directed to the beam shape measuring instrument, and the beam is split by the polarization beam splitter. A pair of corner cube prisms are arranged on the optical path to increase the optical path length.

According to a second aspect of the invention, in the first aspect of the invention, the pair of corner cube prisms are formed in different sizes, and the central axes of the corner cube intersections are displaced from each other. I placed it in.

According to the invention of claim 3, claim 1 or 2
In the described invention, the incident beam is guided to the intersection of one of the large and small corner cube prisms.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, a second wavelength plate and a total reflection plate are added to the optical path separating optical system including the first wavelength plate and the polarization beam splitter. Let

According to the invention of claim 5, claim 2 or 3
In the described invention, the target is arranged at the incident beam position of the corner cube prism.

According to the invention described in claim 6, claims 1, 2,
In the invention described in 3, 4, or 5, a corner cube prism having a small shape is provided with a rotation mechanism capable of rotating the prism around the optical axis.

According to the invention of claim 7, claims 1, 2 and
In the invention described in 3, 4, 5 or 6, a moving mechanism capable of moving this prism in the beam incident direction is attached to a large-sized corner cube prism.

According to the invention described in claim 8,
In the invention described in 3, 4, 5, 6 or 7, a moving mechanism capable of moving the beam shape measuring instrument in a direction orthogonal to the incident optical axis is attached.

[0014]

According to the present invention, since the beam travels back in the pair of corner cube prisms many times, there is no need to take a long optical path as in the conventional case, and a large space can be obtained in a small space. It becomes possible to take the optical path length.

According to the second aspect of the present invention, since the exit position can be returned to the same position as the entrance position of the beam into the corner cube prism, a mirror or the like for guiding the beam shape measuring device as in the prior art. Is unnecessary.

According to the third aspect of the invention, since the beams are arranged so as to be incident on either of the intersections of the large and small corner cube prisms, it is possible to make the positions of the incoming and outgoing beams the same. A mirror or the like for guiding to the shape measuring instrument is unnecessary.

According to the fourth aspect of the invention, the beam branching and the beam combining can be performed by an optical system having a simplified arrangement.

According to the fifth aspect of the invention, by placing the target at the incident beam position, the incident beam position and the outgoing beam position can be aligned.

In the sixth aspect of the invention, the position of the beam incident on the beam shape measuring instrument can be changed by rotating the small corner cube prism around the optical axis by the cube rotating mechanism.

In the seventh aspect of the invention, the optical path length can be freely selected by moving the large corner cube prism in the beam incident direction by the cube moving mechanism.

According to the eighth aspect of the present invention, the beam shape measuring device is moved in the direction of the incident optical axis by the moving mechanism so that the incident position shifts to the corner cube prism and the beam position shift due to the influence of the returning light (small shift). The rotation of the corner cube prism) can be dealt with even if it is out of the beam shape measurement range.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. First, the configuration of this device will be described with reference to FIG. On the optical path immediately after the incident beam 4 emitted from the laser light source (not shown) is directed to the beam shape measuring instrument 5, in order to split and combine the incident beam 4, λ / 2 as the first wave plate is formed. Plate 6 and polarization beam splitter 7
A λ / 4 plate 8 as a second wave plate arranged at a position branched from the polarization beam splitter 7, a total reflection mirror 9 as a total reflection plate, and a λ / 4 plate 8 on the side opposite to the λ / 4 plate 8. A λ / 4 plate 10 is arranged on the optical path. These 4 ~
The members 10 constitute an optical path separation optical system 11.

On the optical path passing through the λ / 4 plate 10,
A large corner cube prism 12 and a small corner cube prism 13 are arranged as a corner cube prism for increasing the optical path length. The large and small corner cube prisms 12 and 13 are arranged in a state where the central axes P and Q of the corner cube intersections are displaced from each other by Δ. Here, the incident beam 4 is guided to the corner cube intersection a of the large corner cube prism 12. A pinhole 14 as a target is arranged on the optical path between the λ / 4 plate 10 and the large corner cube prism 12.

Also, the large corner cube prism 1
2 has its side surface supported by a support plate 15, and its bottom surface portion is fixed on a guide rail 16 as a cube moving mechanism. Since the guide rail 16 is movably placed on the base 17 in the beam incident direction X, the large corner cube prism 12 can be moved in the beam incident direction X.

On the other hand, the small corner cube prism 1
The side surface of 3 is held by a holder 18, and the holder 18 is held by a holding plate 20 via a bearing 19. As a result, the small corner cube prism 13
Is rotatable about the incident optical axis. In this case, the holder 18, the bearing 19, and the holding plate 20 form a cube rotation mechanism 21. The holding plate 20 can be screwed to the holding tool 18 by using a screw 22, so that the rotation can be stopped.

Further, the beam shape measuring instrument 5 is placed on a guide rail 23 as a moving mechanism and can be moved in a direction orthogonal to the incident optical axis Y. The guide rail 23 can be fixed by a screw 24 attached to one end of the base 17.

A method of measuring the beam shape when the optical path length is changed in such a configuration will be described. First, if you want to know the beam shape immediately after the output,
By passing it through the λ / 2 plate 6 into a beam state in which no phase difference is generated, and by making the incident beam 4 in such a state enter the polarization beam splitter 7, the incident beam 4 is transmitted as it is and the beam shape is changed. Since it directly enters the measuring device 5, it is possible to measure the beam shape immediately after the emission.

On the other hand, when it is desired to know the beam shape when the optical path length is increased, the incident beam 4 is caused to have a phase difference by rotating the λ / 2 plate 6. The beam having such a phase difference changes its traveling direction by being incident on the polarization beam splitter 7, and travels toward the total reflection mirror 9 via the λ / 4 plate 8. The beam reflected by the total reflection mirror 9 passes through the polarization beam splitter 7 and travels straight as it is to the corner cube intersection point a (incident beam position) of the large corner cube prism 12.
Be led to. Then, the incident beam 4 goes back several times to several tens of times between the large corner cube prism 12 and the small corner cube prism 13 facing each other, and travels again, and again, the corner cube intersection point of the large corner cube prism 12 again. a (this time is the exit beam position)
Then, the light is emitted from this position. After that, the incident beam 4 having the long optical path length in this way is transmitted by the λ / 4 plate 10
Causes a phase difference, changes the optical path by the polarization beam splitter 7, and guides it to the beam shape measuring instrument 5.
The beam shape can be measured when the optical path length is long.

[0029] When the optical path length of incident from the incident beam position a to a large corner cube prism 12 to approximate the FIG. 1 as a scale, reaching to about 1600 mm, the intersection O ₁ ~ intersection O ₂
Compared with the distance of 65 mm, it is 24 times. To obtain the optical path length of 3 m, the distance L between the positions of the large corner cube prism 12 and the small corner cube prism 13 can be set to 154 mm.
When it is difficult to increase the optical path length Lk-4b4, it is possible to increase the optical path length by increasing the diameter of the corner cube prisms 12 and 13 and increasing the number of round trips of the optical path. do it.

A pinhole 14 is arranged in the optical path of the large-corner cube prism 12 immediately before the incidence, whereby the incident beam position and the outgoing beam position can be aligned with each other. This eliminates the need to move the beam shape measuring instrument 5. When measuring the beam shape, the pinhole 14 is removed.

Since the small corner cube prism 13 is rotatably attached, the incident beam position and the outgoing beam position can be aligned with each other or separated from each other, whereby returning light (back surface reflection) can be obtained. The effect of can be eliminated.

Since the large corner cube prism 12 is movable in the incident optical axis direction X by the guide rail 16, it is possible to freely select the optical path length and thereby prevent beam vignetting. .

FIG. 2 shows the corner cube prism 12,
13 is a perspective view of the configuration of FIG. FIG. 3 shows large and small corner cube prisms 1 in the configuration of FIG.
2 shows the beam states at 2 and 13, and the incident beam position and the outgoing beam position are the same. On the other hand, FIG. 4 shows a state in which the incident position is incident on the large corner cube prism 12 with a deviation, and the exit beam position which is the turning point with respect to the point a of the incident beam position is a point. b. Further, FIG. 5 shows a case where the corner cube prisms 12 (larger prisms or smaller prisms) having the same diameter are moved at the intersections by Δa. In such a case, as shown in FIG. Instead of returning to the same position, the positional relationship shown in FIG. 4 is obtained. Therefore, when such a positional deviation occurs, the beam shape measuring instrument 5
Is moved in the direction orthogonal to the Y-axis using the guide rails 23 and finely adjusted, whereby the positional relationship shown in FIG. 4 can be returned to the positional relationship shown in FIG. As a result, the positional deviation of the beam (rotation of the small corner cube prism 13) due to the influence of the incident light on the corner cube prisms 12 and 13 and the returned light is finely adjusted even if it is out of the beam shape measurement range, and the original normal state is obtained. It is possible to return to a normal state.

Further, FIG. 6 shows an example in which the difference in diameter between the large corner cube prism 12 and the small corner cube prism 13 is made larger than that in FIG. In this case, the beam positions returning to the same position as in FIG. 3 are in the cases of and, and the incident position of becomes the emission position of 'and becomes a different position. Therefore,
If the small corner cube prism 13 is made too small in this way, the number of times of folding is reduced and the optical path length cannot be made long. Therefore, it is necessary to pay sufficient attention when designing the optical system.

[0035]

According to the first aspect of the present invention, in a beam shape measuring apparatus for performing beam shaping by guiding a beam emitted from a laser light source to a beam shape measuring instrument, the beam emitted from the laser light source is the beam An optical path splitting optical system including a first wavelength plate for splitting an incident beam and a polarizing beam splitter is provided on the optical path immediately after being emitted toward the shape measuring instrument, and is provided on the optical path split by the polarizing beam splitter. Since a pair of corner cube prisms are arranged to make the optical path length long, the beam travels back inside the pair of corner cube prisms many times, and there is no need to purposely increase the optical path length as in the conventional case. It is possible to obtain a large optical path length in a small space, which allows evaluation in the optical system of a narrow optical disc master exposure machine. For example, to reduce the aberration of the optical system, it is capable of obtaining a proper groove shape.

According to a second aspect of the invention, in the first aspect of the invention, the pair of corner cube prisms are formed in different sizes, and the central axes of the corner cube intersections are displaced from each other. Since it is placed in the corner cube prism, it is possible to return the exit position to the same position as the entrance position of the beam into the corner cube prism, and there is no need for a mirror or the like to guide the beam shape measuring instrument as in the conventional case. It is possible to reduce the size and to eliminate the need to move the beam shape measuring instrument.

According to a third aspect of the invention, in the first or second aspect of the invention, the incident beam is guided to the corner cube intersection of either one of the large and small corner cube prisms. It is possible to make them the same, and there is no need for a mirror or the like for guiding the beam shape measuring instrument. This makes it possible to reduce the size of the device and eliminate the need to move the beam shape measuring instrument. is there.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, a second wavelength plate and a total reflection plate are added to the optical path separation optical system including the first wavelength plate and the polarization beam splitter. Therefore, the beam branching and the beam combining can be performed by the optical system having the configuration arranged in a simplified manner, and the space can be reduced.

In the invention according to claim 5, in the invention according to claim 2 or 3, since the target is arranged at the incident beam position of the corner cube prism, it becomes possible to match the incident beam position and the outgoing beam position, This eliminates the need to move the beam shape measuring instrument.

The invention according to claim 6 is the same as claims 1, 2 and
In the invention described in 3, 4, or 5, since a rotation mechanism capable of rotating this prism around the optical axis is attached to the corner cube prism having a small shape, the beam position incident on the beam shape measuring instrument can be changed. This makes it possible to eliminate the influence of the returning light (back surface reflection).

The invention described in claim 7 is the same as in claim 1,
In the invention described in 3, 4, 5 or 6, since a moving mechanism that can move this prism in the beam incident direction is attached to the large-sized corner cube prism, the vignetting of the beam can be prevented by freely selecting the optical path length. It can be done.

The invention according to claim 8 is the same as claim 1,
In the invention described in 3, 4, 5, 6 or 7, since a moving mechanism capable of moving the beam shape measuring instrument in the direction orthogonal to the incident optical axis is attached, the incident position shift to the corner cube prism and The positional deviation of the beam due to the influence of the returning light can be dealt with even if it is out of the beam shape measurement range.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state of a beam shape measuring apparatus according to an embodiment of the present invention.

FIG. 2 is an external view showing a configuration of a corner cube prism.

FIG. 3 is a schematic diagram showing beam entrance and exit positions.

FIG. 4 is a schematic diagram showing a state in which a beam entering / exiting position is displaced.

FIG. 5 is an optical path diagram showing a situation where a corner cube prism having the same diameter has a positional deviation.

FIG. 6 is an optical path diagram showing a state in which the difference in diameter between large and small corner cube prisms is large.

FIG. 7 is an optical path diagram showing a state of a conventional beam shape measuring apparatus.

[Explanation of symbols]

 4 beam 5 beam shape measuring instrument 6 first wave plate 7 polarizing beam splitter 8 second wave plate 9 total reflection plate 11 optical path separation optical system 12 large corner cube prism 13 small corner cube prism 14 target 16 cube moving mechanism 21 cube rotating mechanism 23 Moving mechanism

Claims (8)

[Claims] 1. A beam shape measuring apparatus for performing beam shaping by guiding a beam emitted from a laser light source to a beam shape measuring instrument, wherein the beam emitted from said laser light source is emitted while heading to said beam shape measuring instrument. An optical path splitting optical system including a first wave plate for splitting an incident beam and a polarizing beam splitter is provided on the optical path immediately after, and a pair for increasing the optical path length on the optical path split by the polarizing beam splitter. A beam shape measuring device characterized by arranging a corner cube prism. 2. The beam according to claim 1, wherein the pair of corner cube prisms are formed to have different sizes, and the central axes of the corner cube intersections are arranged with their positions displaced from each other. Shape measuring device. 3. The beam shape measuring apparatus according to claim 1, wherein the incident beam is guided to the intersection of one of the large and small corner cube prisms. 4. The beam shape measurement according to claim 1, wherein a second wavelength plate and a total reflection plate are added to an optical path separation optical system including a first wavelength plate and a polarization beam splitter. apparatus. 5. The target is arranged at the incident beam position of the corner cube prism.
Alternatively, the beam shape measuring device according to item 3. 6. The small-sized corner cube prism is provided with a cube rotation mechanism capable of rotating the prism around the optical axis.
The beam shape measuring device according to 2, 3, 4 or 5. 7. A large-sized corner cube prism is provided with a cube moving mechanism capable of moving the prism in the beam incident direction.
The beam shape measuring device according to 3, 4, 5 or 6. 8. A moving mechanism capable of moving the beam shape measuring instrument in a direction orthogonal to an incident optical axis thereof is attached thereto.
Beam shape measuring device described.