JPS6310380B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention measures the reflectance over the required area of the surface of a spherical mirror or a plane mirror such as a total reflection mirror, a partial reflection mirror, or a transmission mirror with an anti-reflection film, and calculates the distribution of reflectance. The present invention relates to a sample driving device and driving method for measuring reflectance distribution for display.

Conventionally, the reflectance of a plane mirror or spherical mirror is measured by measuring the reflectance of the irradiated area at a point where the optical axis of the reflectance measurement system and the test sample intersect, and then replacing it with the reflectance of the entire plane or spherical mirror. was.

This is based on the premise that the reflectance is constant over the required range of the plane mirror or spherical mirror.

However, in reality, the reflectance cannot be considered to be constant over the entire surface of the optical component to be tested, and it is often impossible to design an optical design without knowing the distribution of reflectance over the entire required area.

For example, reflectance distribution of folding mirrors used in gas lasers and total reflection mirrors of rear mirrors, output coupling mirrors, etc.
Usually, the surface facing inside the discharge tube has the required reflectance, and the surface facing outside is coated with an anti-reflection film.The partial transmittance and the reflectance distribution of the anti-reflection film are as follows: It seems to play an important role in the output mode of gas lasers.

In addition, especially in the case of a spherical mirror, the radius of curvature of the mirror that is actually polished is often different from the designed value, and the variation in the radius of curvature appears as a variation in the reflectance with respect to the direct optical axis.

As described above, measurement of the spatial distribution of reflectance is essential for designing precision optical equipment, but is not well known in the past.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sample drive device for measuring reflectance distribution and a method for driving the same, which can measure the spatial distribution of reflectance of a plane mirror or a spherical mirror with high precision and in a short time.

FIG. 1 shows a plan view of a sample driving device for measuring reflectance distribution according to the present invention.

In this embodiment, three tables are placed on a base 5, and they are an A table 6, a Z table 7, and an X table 8 from the base 5 side.

The A table 6 is configured to slide in a fan shape on the base 5 around the A axis, and the Z table 7 is arranged so as to be movable in the Z direction in the figure on the A table 6. 8 is disposed on the Z table 7 so as to be movable in the X direction. The X direction and the Z direction are set to be orthogonal. A sample holder 10 is mounted on the X table 8 via a connecting rod 9.
is attached, and the sample holder 10 is attached so as to be rotatable in the direction B about the connecting rod 9.

1 is a pulse motor that is the driving force for X-axis movement, and 11 is a ball screw that moves the X table 8. 2 is a pulse motor that is the driving force for Z-axis movement, and 21 is a ball screw that moves the Z table 7. 3 is a pulse motor that is the motive force for moving the A-axis rotation in the S direction on the circumference of radius R, and 31 is a ball screw for moving the A table 6 along the S direction. 4 is a pulse motor which is the driving force for rotating the connecting rod 9 by 360 degrees in the direction B. The reflectance of the sample 12 placed on the sample holder 10 is measured using a beam from the reflectance measurement system 13 while being rotated by a constant angle by the pulse motor 4 .

Next, the method of driving this device will be described.

To find out the spatial distribution of reflectance on the surface of the optical component under test, select the number of axes for driving the specimen and select the driving method so that the normal to any minute measurement area on the surface always matches the optical axis of the measurement light source. It is necessary to devise an idea.

Therefore, if the test sample is a concave spherical mirror, the following procedure may be used.

(i) Sample 1, which is a test optical component, is placed in the sample holder 10.
Set 2. Sample 12, which is the optical component to be tested
The origin of the sample 12 is determined in advance, and the sample 12 is aligned with respect to the sample holder 10 using a normal fine movement device so that the normal to the origin coincides with the optical axis of the beam from the measurement light source in the reflectance measurement system 13. I'll go.

(ii) When measuring the reflectance at point M shown in Figure 2 A, draw a perpendicular line from M on the optical axis, let P be the foot of the perpendicular line on the optical axis, and set the distance β of MP and the distance β of OP. Find the distance δ. O is the origin of sample 12.

Furthermore, the optical axis is the Z axis, and one axis perpendicular to the optical axis is the X axis.
An axis (in this case, an axis in a plane parallel to the surface of the base 5), and the angle α between the normal line at point M and the optical axis is determined. C is the center point of the radius of curvature.

(iii) As shown in Figure 2B, move the sample by β in the negative direction of the X-axis. O′ is sample 1 before movement
This is the position of the origin of No. 2.

(iv) As shown in FIG. 2C, the sample is translated by δ in the positive direction of the Z axis to bring measurement point M to point O'.

(v) A-axis perpendicular to the X-axis and Z-axis (perpendicular to the page)
is erected so that it passes through point M, and rotated by α around the A axis so that the normal to point M coincides with the optical axis. This situation is shown in Figure 2D.

(vi) As shown in Figure 2 E, X-Z passes through the origin O.
Let the axis in the plane (normal to the origin O) be the B axis,
The reflectance of points on the same circumferential circle as point M is measured while rotating around the B-axis at constant angular intervals.

(vii) Through the above four-axis control, it was possible to bring all the measurement points whose normal line forms an angle α to the optical axis onto the optical axis. Then, by the reverse operation of operation (), rotate around the A axis by α in the opposite direction to operation (), then by the reverse operation of operation (), move by δ in the negative direction of the Z axis, and finally, by the operation () ), the origin O is moved by β in the positive direction of the X-axis, and the origin O is returned to the optical axis.

Next, for other measurement points, distance β + △
β, δ+Δδ, angle α+Δα are determined, the reflectance is measured by the above-mentioned operation, and this is repeated thereafter.

By the method described in (i) to (vii), if the test sample is a concave spherical mirror, bring the entire reflectance distribution measurement area onto the measurement optical axis and measure the reflectance for vertically incident light. Can be done.

In a drive system like the one shown in FIG. 1, cumulative errors are likely to occur depending on the machining accuracy and assembly accuracy of parts. In order to bring this error within the range required by the reflectance measurement system, we adopted a method of calibrating the amount of movement in each axis as shown below.

In the case of this example, the amount of movement and rotation on each axis was designed as follows per pulse, depending on the combination of the number of gears used in the drive system.

△X = △Z = 0.0002mm △A = 0.069 seconds △B = 1.2 minutes The difference between the set travel amount calculated from the above design value and the actual travel amount is precisely measured using a laser length measuring device. Ru. The results are shown in FIG.

The difference between the actual movement amount and the set movement amount shows a linear change with respect to the movement amount setting value.

This is illustrated for the X-axis, but the Z-axis, A, B
Measurements were also made for each axis.

Therefore, by correcting the number of pulses of the movement amount setting value based on this calibration diagram, it is possible to bring the actual movement amount close to the setting value with high accuracy.

Using this method, we were able to perform positioning with an accuracy of ±0.002 mm, which is required in a reflectance measurement system.

In the above embodiment, the case of a concave mirror sample was shown, but it is easy to imagine that even if the sample is a convex spherical mirror, accurate positioning can be performed using the same sample driving method.

The present invention has the following effects.

1 By using this device, it has become possible to measure the reflectance distribution not only of a plane mirror, which was conventionally possible, but also of a spherical mirror with curvature.

2. In the driving method of this device, the cumulative error could be minimized by returning to the origin every time a measurement on one concentric circle of the sample was completed.

3. In the driving method of this device, by adopting a method of measuring reflectance along concentric circles, it has become possible to drive the sample with the smallest drive axis. In addition, since the amount of drive in the X direction only needs to be the radius of the sample, the length of the ball screw, which requires precision, can be halved.

4 In this device, as a drive motor,
By using a pulse motor, the amount of movement of each axis can be easily calibrated, making it possible to minimize errors in the amount of movement.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a sample driving device for reflectance distribution measurement which is an embodiment of the present invention, Fig. 2 is a diagram explaining the operating procedure of the sample driving method of the present invention, and Fig. 3 is a diagram used in the present invention. FIG. 3 is a diagram showing an example of a calibration straight line. 1, 2, 3, 4,...Pulse motor, 5...
Base, 6...A table (third table), 7...
...Z table (second table), 8...X table (first table), 9...connecting rod, 10...sample holder, 11, 21, 31...ball screw,
12...Sample, 13...Reflectance measurement system.

Claims (1)

[Claims] 1. A sample holder that holds a sample, a connecting rod that has a function of rotating the sample holder, and a connecting rod that holds the sample holder via the connecting rod and that rotates in a direction perpendicular to the axial direction of the connecting rod. a first table installed movably; a second table on which the first table is placed and installed movably in a direction perpendicular to the movement direction of the first table; and the second table. and a third table placed on the base, the third table being rotatable around an axis perpendicular to the surface of the base. Sample drive device for measuring reflectance distribution. 2. The sample driving device for reflectance distribution measurement according to claim 1, wherein the first, second, and third tables and the connecting rod are driven by rotation of a pulse motor. 3. A sample holder that holds a sample, a connecting rod that has a function of rotating the sample holder, and a connecting rod that holds the sample holder via the connecting rod and is movable in a direction perpendicular to the axial direction of the connecting rod. a first table, a second table on which the first table is placed and which is movably installed in a direction orthogonal to the movement direction of the first table; and a second table on which the second table is placed and a base. and a third table installed on a base, the third table being rotatable around an axis perpendicular to the surface of the base. When driving, the first operation is to set the origin of the sample placed in the sample holder in advance and adjust the normal direction at this origin to match the optical axis, and to move the light from a desired measurement point on the surface of the sample. A second operation for determining the length β of the perpendicular line drawn to the axis, the distance δ between the point where the perpendicular line intersects the optical axis and the origin, and the angle α between the normal line at the measurement point and the optical axis; a third operation to move the table by a distance β; a fourth operation to move the second table by a distance δ in the optical axis direction; and a third operation to move the third table at an angle around an axis perpendicular to the table at the measurement point. A fifth operation of rotating the sample by α to match the normal line at the measurement point with the optical axis, and a sixth operation of measuring the reflectance distribution by rotating the sample installed in the sample holder via the connecting rod. A method for driving a sample for measuring reflectance distribution, comprising at least the following. 4 2nd operation, 3rd operation, 4th operation, 5th operation
The reflectance on the concentric circles is measured based on the operation and the sixth operation, and then the fifth operation, the fourth operation, the third operation, and the reverse operation of the second operation are performed in this order to obtain the initial value. 4. The method of driving a sample for measuring reflectance distribution according to claim 3, wherein the operation of returning to the state is one cycle, and the reflectance distribution is measured by repeating this cycle. 5 The first, second, and third tables and connecting rods are driven by the rotation of a pulse motor, and a calibration straight line is prepared in which the relationship between the amount of movement and the number of pulses is accurately measured in advance, and the , the second and third tables, and the connecting rod are driven based on the number of pulses specified from the calibration straight line. Measurement sample drive method.