JPH01143906A - Measuring instrument for parallelism between front and rear surfaces of opaque body - Google Patents

Abstract

PURPOSE:To accurately and speedily measure the parallelism between both front and rear surfaces of the opaque plate body by allowing pieces of reflected luminous flux from reflection mirrors provided on respective optical paths from the prism border surface of a beam splitter to travel in the same optical path, and inserting a sample to be inspected into the optical path. CONSTITUTION:Parallel luminous flux i0 emitted by a projection device Q is split into reflected luminous flux i1 and transmitted luminous flux i2 by the prism border surface G of the beam splitter B. The reflection mirrors M1 and M2 are provided on the optical paths L1 and L2 of those pieces of luminous flux i1 and i2 and optical paths L3 and L4 after reflection are made coincident by angle adjusters for the mirror surfaces of the reflection mirrors M1 and M2. Therefore, two pieces of clockwise and counterclockwise luminous flux from the border surface G reaches a photodetecting device R in phase with each other and there is no interference fringes found in the current observation visual field. When the opaque sample S to be inspected is put between the optical paths L3 and L4, whether or not interference fringes appear in the visual field depends upon whether or not both top and reverse surfaces of the sample are parallel to each other as well as when the same S is not inserted, and the parallelism between the front and rear surfaces of the sample S is measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective of the Invention) This invention relates to an optical measuring means for measuring the mechanical precision of an object, so it is possible to easily and precisely measure the flatness of both the front and back surfaces of an opaque plate-like object in three speeds. The first object of the present invention is to provide a means for measuring .

A second object of the present invention is to provide an apparatus that can be easily used by the same means when measuring the flatness of both the front and back surfaces of a transparent body.

When it is desired to accurately measure the flatness of both the front and back surfaces of an opaque object, there is no known device that can be used quickly and easily, for example, on the order of seconds. This invention has been developed by researching and devising a means that can surely meet the purpose of use Q. Therefore, the invention will be explained below with reference to one embodiment shown in the drawings.

(Structure of the Invention) What is indicated by Q in the enclosed dashed line is a projector that emits the laser beam of 200 nm. According to the illustrated embodiment, although not shown, a helium-neon laser light generating device is used as a light source. In addition, according to the illustrated example, the optical path of the condensed laser beam is converted by the dihedral reflection prism Pl, and the beam can be emitted into a parallel beam by the collimator lens 1.

Reference numeral B denotes a beam splitter l2 which receives the parallel light beam 4 emitted from the above-mentioned light projection device q and splits it into a reflected light beam and a transparent light beam at the prism boundary surface G.

Ml is a first reflecting mirror, which is provided in the optical path L1 of the reflected light beam 11 from the prism boundary surface G of the beam splitter B.

Makoto 2 is the second reflecting mirror, and the light of the beam transmitted through the prism interface G of the beam splitter B is reflected w! It is provided in IL2.

The light receiving device is indicated by the concave chain line R, and the optical path L1 is an extension of the optical path L1 to the rear of the prism boundary surface G.
According to 5, the luminous flux emitted from the prism boundary surface G is received and condensed and projected. Therefore, according to the illustrated example, the aforementioned luminous flux is received by the collimator lens 2 and then by the two-sided reflective prism P2. It is now possible to change the direction, condense the light, and project it onto the target T.

According to this invention, the optical path L3 described above and the optical path L4 described above must match each other.

According to the illustrated example, the reflecting mirror 111 and the reflecting mirror M2 are each provided with a mirror angle adjusting tool (rM illustration is omitted),
Light path L3 and light path L4. ) It is now possible to get a match.

S is a test sample inserted into the optical path L3 and the optical path L4 which are made to coincide with each other. By inserting the test sample S in this way, the first The projection optical path of $2 to the test sample S is formed by the projection optical path of $2 and the optical path L2 and the optical path L4. In the illustration, the test sample S is drawn at a position approximately equidistant from the reflection mirror town of N1 and the reflection 11M2 of IE2, but according to the present invention, the position of the test sample S is as described below. , the matched optical path L
Any position 111G on 3T L4 can be selected.

This invention is made as described in 1 above, and the first reflecting mirror area is the reflected light beam 11 of the prism boundary surface G of the beam splitter B.
2 is provided in the optical path L1 of the second reflection m, and 2 is provided in the optical path L2 to the transmitted light beam of the prism boundary surface G of the beam splitter B, and the optical path L3 and the optical path L4 are made to coincide with each other. Therefore, starting from the prism boundary surface G,
From the reflection 111MI, it passes through the reflection mirror M2 and returns to the prism boundary surface G, that is, in the figure, the optical path length of the counterclockwise light beam, similarly starting from the E1 prism boundary surface G, the reflection mirror M2
The optical path length of the light beam around the stone that returns to the prism boundary surface G through reflection Ill is equal to each other no matter which point on the prism boundary surface G is the starting point.

Now, in a state where the test sample S is not inserted, the counterclockwise light beam that has returned to the prism boundary surface G is reflected at the prism boundary surface G, and the optical path L1 is extended to the rear of the prism boundary surface G as an optical path L5. On the other hand, the clockwise light flux returning to the prism boundary surface G passes through the prism boundary surface G and similarly reaches the light receiving device R through the extended optical path L5.

In other words, since the emitted light beam from the light projector Q and the reflected light beam by the beam splitter B and the transmitted light beam reach the light receiver @R in the same phase, there is no interference field in the field of view observed by the light receiver WgIR, and there is no bright light. Or dark, so-called one-color vision is asked.

Therefore, the test specimen a of an opaque body is placed in the optical path L3+L4 described above.
If S is inserted, the first projection optical path to the test sample S consisting of the optical path L1 and the optical path L3 described above, and the optical path L
The second projection optical path to the test sample S consisting of the optical path L4 and the optical path L4 form separate optical systems. Then, the light flux reflected by the test sample BS on the first projection optical path passes through the reflection l11M1 and the beam splitter B to the light receiving device! On the other hand, the light beam reflected by the test sample S of the light beam on the projection optical path of @2 reaches the light receiving device 1R via the reflection wA- and the beam splitter B.

Now, if we insert the test specimen Bs whose front and back surfaces are parallel to each other at a position that is half the distance between the reflector M1 and the reflector support 2, the optical path lengths of the optical paths L3 and L4 are equal. Therefore, the light flux reflected by the test sample S of the light flux applied to the first projection optical path is reflected by the light flux that passes through the reflector M1 and the beam splitter = B and reaches the light receiving device @, and the light flux applied to the second projection optical path. Since the light beam reflected by the test sample S has the same light wave phase as the light flux that has passed through the reflector M2 and the beam splitter B and reached the photoreceptor faR, as described above, the test sample S
Similar to the non-inserted state, a one-color visual field is observed by the light receiving device R.

By the way, the above-mentioned test sample S having parallel front and back surfaces,
When replacing the test sample SG with unsatisfactory front and back surfaces, there is a difference in the optical path length between the optical path L3 and the optical path L4, so the difference between the two light beams that reached the receiving device R as described above is A phase difference occurs, and as a result, light lag is observed by the light receiving device IH.

Referring to Figure 2, the direction where interference fringes are observed is now the length of the test sample US (if the test sample S is a disk, the diameter is the same as described above). The thickness of the end is hl
, h2, the parallelism of the front and back surfaces! given that
h 1 h 2 =Δh! =Δb/l・・・・・・
...(1). -10,000, the above phase difference is 2Δh Therefore, Δt1λ/2 (2) is damped. However, λ is the wavelength of light, and ■ is the order (shift amount) of the interference sound.

Therefore, by substituting equation (2) into equation (1), the parallelism de is f =, ^ /22...
...... (3).

Below is a numerical example: Light @Q has a wavelength of 0.633 mm.
A He-Ne laser is used, and l is 50 m+a.

! ! If there is one interference pigeon in the measurement field, that is, m = 1, then equation (3) is L; 6.33X 10' Rad.In other words, if the angle of inclination between the front and back planes is θ, then θ = t
A measurement value of an '6.33X 10-6 phantom 1.3 seconds is obtained.

By the way, the number of interference fringes in the observation field is 1
Since it is possible to determine /2, it is possible to easily measure the parallelism when the inclination angle θ is up to 65 seconds.

For determining the number of interference channels in the observation field, please refer to Figure 3.

In the above explanation, for convenience of explanation, the insertion position of the test sample S is assumed to be exactly at the center of the reflecting mirror M1 and the reflecting mirror 1112, and when the front and back surfaces of the test sample S are parallel to each other, the optical path L3 and The case where there is no difference in the optical path length of the optical path L4 is set as n. In fact, when the light source light is incoherent ordinary light, if the error in the insertion position of the test sample S exceeds 1 μm, it becomes difficult to observe interference when both the front and back surfaces are uneven. However, according to the present invention, since the light source light (laser light with high coherency is used), the insertion position of the test sample S and the reflecting mirror M1 are
, the error in orthogonality of the test sample S with respect to the optical path formed between the reflecting mirrors M2 is not a problem;
By inserting the test sample at an appropriate location between the test samples, it is possible to easily observe the interference error and measure the parallelism between both surfaces of the test sample S with considerably high accuracy.

Further, according to the present invention, it is possible to easily measure the parallelism of the front and back surfaces of a transparent body as well as an opaque body. In other words, the transparent test sample S is reflected by the reflective mirror M.
2, and a light shielding plate is inserted in the first projection optical path or the second projection optical path to the test sample S. That is, according to the illustrated example, a light shielding plate is displayed on the optical path L1 in the projection optical path, but such a light shielding plate is used not only for the optical path Ll but also for the optical path L3, or the optical path L2 in the second projection optical path. Alternatively, it may be provided in the optical path L4.

As an example, if a light shielding plate is inserted in the optical path L1 as in the above example, the light beam incident on the test sample S passes through the optical path L4. Referring to Figure 4, this large luminous flux l
From a, a light flux reflected by the surface of the test sample S and a light flux tc reflected by the bottom surface are generated, and the reflected light fluxes from these two dishes pass through the reflector M2 and the beam splitter B to the light receiving device! H, and interference i similar to that shown in FIG. 3 is observed due to the optical path difference between the two types of reflected light beams.

In this case, since the following holds true: molding = 2nΔh (where n is the refractive index of the test sample @S). Therefore, by substituting the calculated value of △h according to equation (4) and the length of the test sample S into equation (1), the value of parallelism r between the front and back surfaces or the inclination angle θ between the front and back surfaces can be easily calculated. be done.

(Effects of the Invention) Thus, according to the present invention, not only can the parallelism of both the front and back surfaces of an opaque body be measured with considerably high accuracy;
Inserting the test sample into the projection optical path for the test sample does not require precise positioning, so the measurement operation is easy, simple, and extremely quick, making it ideal not only for academic research but also for production sites. Also suitable for use. Another great feature of the present invention is that it is possible to measure the parallelism of the front and back surfaces of optical glass or other transparent materials similarly quickly and accurately.

[Brief explanation of the drawing]

Fig. 1 is an optical path diagram of the device according to the present invention, Fig. 2 is a longitudinal cross-sectional view of an opaque test sample, Fig. 3 is an explanatory diagram of the determination of the number of interferences i in the observation field of the light receiving device, and Fig. 4 1 is a diagram showing the optical path in measurement of a transparent test sample. B is a beam splitter, 1G is a prism boundary surface, q is a light emitter, R is a light receiver, Pl and P2 are two-sided reflective prisms, Kl and IC2 are collimator lenses, M1+H2 is a reflecting mirror, S is a test sample, D is a light-shielding plate, τ is a tarp"/tos L11L21L31L41L5 ia optical path s 4
+ Jl r /2 + 13 + 14 +4+ l
, tb+lc is the luminous flux. Patent applicant Mizojiri Optical Industry Co., Ltd. Figure 2 Figure 3 am -l -/ Figure -17-4-1-114

Claims (1)

[Claims] A light projection device Q that emits a parallel beam of laser light, a beam splitter B that receives the emitted light beam l_0 of the light projection device Q and splits it into a reflected light beam and a transmitted light beam, and a beam splitter B that receives the emitted light beam l_0 of the light projection device Q and splits the reflected light beam l_1 of the prism boundary surface G of the beam splitter B. The first reflecting mirror M_1 provided in the optical path L_1, the second reflecting mirror M_2 provided in the optical path L_2 of the transmitted light beam l_2 of the prism boundary surface G of the beam splitter B, and the back of the prism boundary surface G of the optical path L_1. and a light receiving device R that receives and condenses and projects the light beam l_5 emitted from the prism boundary surface G along an extended optical path L_5 to the optical path L_3 of the light beam l_3 reflected by the reflecting mirror M_1 of the light beam l_1 and the optical path L_3. The optical path L_4 of the reflected light beam l_4 of the reflecting mirror M_2 of L_2 is made to match each other, and the test sample S is placed in the optical paths L_3 and L_4.
By inserting the optical path L_1 and the optical path L_3, a first projection optical path toward the test sample S, and a second projection optical path toward the test sample S, consisting of the optical path L_2 and the optical path L_4. Parallelism measurement device for the front and back surfaces of an opaque body formed by