JP2718393B2 - Two beam interval measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an apparatus for measuring an interval between two light beams, and more particularly to a two-beam interval measuring apparatus suitable for measuring an interval between two beams of an optical disk master on which exposure is performed using two beams.

[0002]

2. Description of the Related Art Heretofore, no suitable device has been proposed as such a two-beam interval measuring device. Therefore, the present inventors are studying an apparatus that measures the interval between two beams by using a conventionally proposed light beam diameter measurement technique. That is, the light beam diameter measuring technique disclosed in JP-A-58-168921, JP-B-59-20650, JP-A-60-95738, etc. uses an optical sensor when a light beam crosses with a knife edge. This is based on a change in output. If this technology is used, a configuration as shown in FIG. 4 can be considered.

Now, it is assumed that a P-polarized beam 2 and an S-polarized beam 3 are traveling side by side in proximity to each other. Said 2 traversed by 1
An optical sensor 19 for receiving a beam, a differentiating circuit 20 for differentiating a detection signal e output from the optical sensor 19, a beam interval calculating unit 21 for calculating a two-beam interval from the differential signal f output from the differentiating circuit 20; Consists of

The light sensor 19 comprises a P-polarized beam 2 and an S-polarized beam 3 traversed by the knife edge 1 at a constant speed.
And outputs a two-beam combined light quantity change 22 in which the P-polarized light quantity change 10 and the S-polarized light quantity change 11 are combined as shown in FIG. 5A as a detection signal e. The differentiating circuit 20 differentiates the detection signal e output from the optical sensor 19 with respect to time, and combines the P-polarized beam waveform 12 and the S-polarized beam waveform 13 as shown in FIG.
The beam combining waveform 23 is output as a differential signal f.

The beam interval calculator 21 calculates the beam interval based on the time interval between the peaks 24 and 25 of the two-beam composite waveform 23 output from the differentiating circuit 20 as the differential signal f. For example, when the speed at which the knife edge crosses both beams is V μm / μs, and both peak intervals of the differential signal are obtained as t μs, the beam interval is calculated according to a calculation formula of V × t μm.

[0006]

As described above, the two-beam interval measuring device conceived by using the conventional light beam diameter measuring device technique has a structure in which each of the two beams 2 and 3 traversed by the knife edge 1 is used. Since the change in the light amount is received by the optical sensor 19 as a combined two-beam change in the light amount, the change in the light amount of one beam is affected by the change in the light amount of the other beam. There has been a problem that the beam center cannot be obtained accurately and the beam interval cannot be measured accurately.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-beam interval measuring apparatus capable of measuring the interval between two adjacent beams with high accuracy.

[0008]

According to the present invention, there is provided a knife edge member for crossing a P-polarized beam and an S-polarized beam in a parallel state in a parallel direction thereof, and a beam separating means for separating both beams by a difference in polarization direction. An optical sensor for receiving the P-polarized light beam and the S-polarized light beam separated by the beam separating means; and a means for calculating an interval between the polarized light beams based on a detection signal output from each optical sensor.

The means for calculating the interval between the polarized beams includes a differentiating circuit for differentiating a detection signal output from each optical sensor, and a two-beam interval for calculating a two-beam interval from the differential signal obtained from each differentiating circuit. And a calculation unit.

Further, the beam separating means is constituted by a polarizing beam splitter. Alternatively, it comprises a beam splitter that separates both polarized beams into two, a P-polarized analyzer arranged on one of the separated optical paths, and an S-polarized analyzer arranged on the other.

[0011]

The P-polarized light beam and the S-polarized light beam blocked by the knife edge member are detected by the optical sensor while being separated by the beam separating means. The center of each polarized light beam is accurately obtained without being affected by the change in the light amount, and the beam interval between the two polarized light beams can be measured with high accuracy.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of a two-beam interval measuring apparatus according to the present invention. Here, the apparatus is configured as a device for measuring the distance between the P-polarized beam 2 and the S-polarized beam 3 that are traveling side by side in the proximity state, and a knife edge 1 that vertically crosses both polarized beams 2 and 3, and a knife edge 1 A polarization beam splitter 4 for separating the two beams traversed by 1 by a difference in polarization direction, and optical sensors 5 and 6 for receiving the P polarization beam 2 and the S polarization beam 3 separated by the polarization beam splitter 4, respectively; Differential circuits 7 and 8 for differentiating the detection signals a and b output from the optical sensors 5 and 6 with time, and a beam interval for calculating a two-beam interval from the differential signals c and d output from the differential circuits 7 and 8. And a calculation unit 9.

According to this configuration, when the knife edge is at a position retracted from the optical path of each of the polarized beams 2 and 3, each of the polarized beams 2 and 3 is incident on the polarization beam splitter 4, and the P-polarized beam 2 is It transmits and reflects the S-polarized beam 3. Then, the knife edge 1 is moved at a constant speed along the direction in which the polarized beams are arranged, and the knife edge sequentially blocks the P-polarized beam 2 and the S-polarized beam 3 with the movement. For this reason, the optical sensor 5 receives the P-polarized beam 2 split by the polarization beam splitter 4, and outputs a light quantity change 10 of the P-polarized beam as a detection signal a as shown in FIG. Similarly, the optical sensor 6 receives the S-polarized beam 3 split by the polarizing beam splitter 4, and outputs a light amount change 11 of the S-polarized beam as a detection signal b.

Therefore, the differentiating circuit 7 time-differentiates the detection signal a output from the optical sensor 5 and outputs a P-polarized beam waveform 12 as shown in FIG. Similarly, the differentiating circuit 8 time-differentiates the detection signal b output from the optical sensor 6 and outputs the S-polarized beam waveform 13 as a differential signal d. Then, the beam interval calculator 9
Then, the peak 14 of the P-polarized beam 12 output by the differentiating circuit 7 as the differentiated signal c and the differentiating circuit 8
Outputs the S-polarized beam waveform 13 as a differential signal d
The beam interval is calculated from the time interval from the peak 15 of FIG.

For example, the speed at which the knife edge traverses both beams is V μm / μs, and the peak interval between both differential signals is t.
When μs is obtained, the beam interval is calculated according to the calculation formula of V × tμm.

Therefore, in this apparatus, the P-polarized light beam 2 and the S-polarized light beam 3 are separated from each other by separate optical sensors 5, 6 respectively.
Is detected and a signal is output, so that the center of each polarized light beam can be accurately obtained without affecting the light intensity change of one polarized light beam by the light intensity change of the other polarized light beam. Can be measured with high accuracy.

FIG. 3 is a block diagram of a second embodiment of the present invention, in which parts equivalent to those in FIG. 1 are denoted by the same reference numerals. In the second embodiment, the beam splitter 16 separates incident light into two directions, and has no dependence on polarization. An analyzer 17 that transmits only the P-polarized light beam 2 and an analyzer 18 that transmits only the S-polarized light beam 3 are disposed on each of the optical paths of the transmitted light and the reflected light in the beam splitter 16. And the analyzer 17
And the optical sensor 6 is arranged behind the analyzer 18.

Therefore, the optical sensor 5 outputs the P-polarized beam 2 transmitted through the analyzer 17 among the P-polarized beam 2 and the S-polarized beam 3 separated by the beam splitter 16.
Only receive light. The optical sensor 6 receives only the S-polarized beam 3 transmitted through the analyzer 18 among the P-polarized beam 2 and the S-polarized beam 3 separated by the beam splitter 16. Each of the optical sensors 5 and 6 is configured as shown in FIG.
As shown in (a), the light amount change 11 of each beam is output as detection signals a and b. Further, differentiating circuits 7 and 8 time-differentiate the detection signals a and b output from the optical sensors 5 and 6, respectively, and obtain the polarization beam waveforms 12 and
13 is output as differential signals c and d.

Therefore, the knife edge 1 sequentially blocks both polarized beams so as to sequentially block the light, so that each of the optical sensors 5 and 6 detects this, and the differential signals c and d are output from the differential circuits 7 and 8. Then, the beam interval calculator 9 calculates the beam interval from the time interval between the peaks 14 and 15 of the P-polarized beam waveforms 12 and 13 which are the differential signals c and d from the differentiating circuits 7 and 8, respectively. This arithmetic expression is the same as in the first embodiment.

Therefore, also in the second embodiment,
The P-polarized light beam and the S-polarized light beam are detected by separate optical sensors, respectively, and a signal is output. Therefore, the change in the light amount of one polarized light beam is not affected by the change in the light amount of the other polarized light beam. Can be accurately obtained, and the beam interval between the two polarized beams can be measured. In this embodiment, an analyzer is used instead of a relatively expensive polarizing beam splitter, and therefore, it is more advantageous than the first embodiment in terms of cost reduction.

[0021]

As described above, according to the present invention, the P-polarized beam and the S-polarized beam, which are shielded by the knife edge member,
Since the light is detected by the optical sensor while being separated by the beam separation means, the change in the amount of light of one polarized beam does not affect the change in the amount of light of the other polarized beam, and the center of each polarized beam is accurately obtained. , It is possible to measure the beam interval between the two polarized beams with high accuracy.

Further, since the beam separating means can be constituted by a polarizing beam splitter, it is possible to measure the interval between two beams with a simple structure. Alternatively, both polarized beams are each 2
By configuring the beam splitter to be separated, the P-polarized light analyzer arranged on one of the separated optical paths, and the S-polarized light analyzer arranged on the other side, a relatively expensive polarizing beam splitter becomes unnecessary. Cost reduction can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an output of a photosensor and an output of a differentiating circuit of FIG. 1;

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a two-beam interval measuring device studied in advance by the present inventors.

FIG. 5 is a characteristic diagram showing an output of a photosensor and an output of a differentiating circuit in the apparatus of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Knife edge 2 P polarization beam 3 S polarization beam 4 Polarization beam splitter 5, 6 Optical sensor 7, 8 Differentiation circuit 9 Beam interval calculation unit 16 Beam splitter 17, 18 Analyzer

Claims (4)

(57) [Claims] 1. A knife edge member that traverses a P-polarized beam and an S-polarized beam in a juxtaposed state in the juxtaposed direction,
A beam separating unit that separates the two beams by a difference in polarization direction, an optical sensor that receives the P-polarized beam and the S-polarized beam separated by the beam separating unit, and a detection signal output from each optical sensor. Means for calculating an interval between the respective polarized beams based on the two-beam interval. 2. The means for calculating the interval between each polarized light beam includes:
2. The device according to claim 1, further comprising: a differentiating circuit that differentiates a detection signal output from each optical sensor; and a two-beam interval calculating unit that calculates a two-beam interval from a differential signal obtained from each of the differentiating circuits.
Beam spacing measurement device. 3. The two-beam interval measuring apparatus according to claim 1, wherein the beam splitting means is a polarization beam splitter. 4. A beam splitter for splitting both polarized beams into two beams, a P-polarized analyzer arranged on one of the separated optical paths, and an S-polarized analyzer arranged on the other.
3. The two-beam interval measuring apparatus according to claim 1, comprising a polarization analyzer.