JPH01148942A - Retardation measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the retardation of an object to be measured having a light impervious film provided to the single surface thereof, by providing a polarizer and a 1/4 wavelength plate to a reciprocating optical system formed by the reflection of the light emitting from a measuring light source by the film formed to the object to be measured. CONSTITUTION:The beam 16 emitted from laser 2 reciprocates in an object 5 to be measured by a polarizer 3, a 1/4 wavelength plate 4 and the reflecting film 5b on the object 5 to be measured to return to a light detector 8 through the wavelength plate 4 and the polarizer 3. The intensity of the returned light 16' is inputted too a CPU 17 through an A/D converter 10'. In the measurement of luminous intensity, the wavelength plate 4 is rotationally adjusted by a pulse motor 9 controlled by the CPU 17 so that the intensity of the return beam 16' becomes max. The beam intensity at that time is stored and the rotary position of the wavelength plate 4 is stored and, further, the wavelength plate is rotated by 45 deg. and the intensity of the return beam at that time is stored. By this operation, the retardation of the reciprocating path of the object 5 to be measured can be calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a retardation measuring device, and more particularly to a measuring device suitable for measuring the retardation of a workpiece having a light reflecting film or the like formed on one side thereof. .

[Conventional technology]

For conventional retardation measurements.

It is described in "Mechanics of Materials Volume 2" (Kame Yuasa, Corona Publishing, 1972). (S'enarmont correction method using light transmission using a polarizing microscope, Tardy correction method, and measurement method using an ellipsometer). However, these measurement methods do not take into account retardation measurements of objects to be measured in which a film or the like that does not transmit light is formed on one side of the object.

[Problem that the invention attempts to solve]

The above-mentioned conventional technology has a problem in that retardation cannot be measured because it does not take into account retardation measurement when a film or the like that does not transmit light is formed on one side of the object to be measured, as described above. .

An object of the present invention is to make it possible to measure the retardation of an object to be measured when a film or the like that does not transmit light is formed on one side of the object and the film has a certain degree of reflectance. .

Means for Solving Problem C] The above purpose is to install a polarizer and a 1/4 wavelength plate in a reciprocating optical system in which the light emitted from the measurement light source is reflected by a film etc. formed on the treasure to be measured. That is, a photodetector was provided that had the function of a reciprocating circular polarizer, and that the quarter-wave plate could be rotated in a plane substantially perpendicular to the optical axis, and that could measure the intensity of the returning light. achieved by the device.

[For production]

The measurement is light, the back photon emitted from the light source, and a 174 wavelength plate.

The light travels back and forth through the object to be measured, passes through a quarter-wave plate, and a polarizer before reaching the photodetector. The 174-wavelength plate is rotated and adjusted so that the intensity of the light that reaches the photodetector is maximized, and the light intensity at that time is defined as Io. The 174 wavelength plate is rotated 45'' from the rotation position.If the intensity of the light returning to the photodetector at that time is used as a function, the relationship between the birefringence phase difference S of the light when it passes through the object to be measured is as follows. It is shown by the formula.

■ One = S i n ” I −−−−−−−−−−−
−−−−−−−(1)O Therefore, the retardation R in the round trip of the object to be measured
can be determined using equation (1) and the following equation.

R=□ λ −−−−−−−−−−−−−−−−−−−
-1----(1')2π Here, λ is the measurement wavelength. Incidentally, the retardation of the object to be measured on a one-way road is 172, which is the value shown by equation (2).

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. First, the configuration will be explained with reference to FIG.

An H e -N e laser 2 that emits light with wavelengths λ = 633 and a photodetector using an SL photodiode element are provided at the end of the retardation measuring device 1.
A support stand 6 for supporting and fixing the object to be measured 5 is provided at the other end. The object to be measured 5 is assumed to have a light reflecting film (reflectance is not particularly specified) formed on one side of the support base 6.
During the round trip in which the light emitted from the He-Ne laser 2 returns to the photodetector, a prism type polarizer 3 made of calcite is inserted from the He-Ne laser 2 side, and a 1/4 wavelength plate 4.
is provided. The quarter wavelength plate 4 is a pulse motor.
9, it is a mechanism that can automatically rotate in a plane substantially perpendicular to the optical axis. The intensity of the feedback light detected by the photodetector 8 is transmitted to the microcomputer 1 via the A/D and D/A converter 10.
2, and is configured to perform arithmetic processing and output the processing results. Here, in order to measure the normal incidence retardation of the measured object with a birefringence phase difference error of 1 degree or less, the extinction ratio of the polarizer 3 must be 5X10-' or less, and the birefringence position of the quarter-wave plate 4 must be It is desirable that the phase difference error be ±0.3' or less, and that the angle between the emitted light 16 and the returned light 16' in FIG. 2 be 1° or less.

FIG. 2 is a block diagram of FIG. 1.

The operation of the present invention will be explained with reference to FIG. H
The light 16 emitted from the e-N e laser is polarized by a polarizer 3,
1/4 wavelength plate4. The reflection film 5b of the object to be measured 5 moves back and forth through the object to be measured, and the 174 wavelength plate 4. It returns to the photodetector 8 via the polarizer 3. The light reflected by the reflective film is detected by the photodetector 8.
Adjust with the adjustment screw 7 of the support base 6 so that it returns to . The intensity of the returned light 16' is input to the CPU 17 of the microcomputer 12 via the A/D converter 10'. A cover 11 is provided to prevent outside light from entering the CPU 1 for measuring light intensity.
7, the quarter-wave plate 4 is rotated and adjusted by the pulse motor 9 so that the intensity of the feedback light 16' is maximized.

At that time, the light intensity value 0 is memorized and the 1/4 wavelength plate 4 is
The rotational position of is memorized, and the 174-wave plate is further rotated by 45 degrees. The intensity of the return light 16 at that time is memorized. Through this operation, the retardation of the reciprocating path of the object to be measured 5 can be determined using the above-mentioned equations (1) and (2).

The above operations and arithmetic processing are performed on the keyboard 13. This is performed by a program input from the floppy disk 14. The processing results are displayed on CRT15. It is output by the printer 18 or the like.

FIG. 3 shows the measurement of retardation when the beam is incident on the object 5 to be measured obliquely. A prism 19 is provided in order to return the reflected light from the reflective film 5b to the photodetector 8.
to return to. Thereby, not only the normal incidence retardation of the object to be measured 5 but also the oblique incidence retardation can be determined. The prism used was made of material BK7 and had an apex angle of 600 mm.

〔Effect of the invention〕

According to the present invention, it functions as a reciprocating circular polarizer using the reflected light from a film formed on one side of the object to be measured, and the light intensity of the reflected feedback light accompanying the rotation of the quarter-wave plate. Since it can be measured, it has the effect of making it possible to measure the retardation of an object to be measured that has a film or the like that does not transmit light on one side of the object.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, and FIGS. 2 and 3 are block diagrams relating to the present invention. 1... Retardation measuring device, 2... He-N
e laser, 3... polarizer, 4... 1/4 wavelength plate,
5... Object to be measured, 6... Support stand, 8... Photodetector, 9... Pulse motor, 10... A/D, D/A converter, 12... Microcomputer, 19...prism. 3,000 figures

Claims (1)

[Claims] 1. In a reciprocating optical system that uses unpolarized laser light as a light source and utilizes light reflection from the object to be measured, a prism-type polarizer and a quarter-wave plate are installed, and the quarter-wave plate is aligned with the optical axis. A light that can be rotated in a substantially perpendicular plane and that can measure the intensity of light that returns from the output of the laser light to a polarizer, a quarter-wave plate, an object to be measured, a quarter-wave plate, and a polarizer in this order. A radardation measuring device characterized by being provided with a detector.