JPS61112905A - Optical measuring apparatus - Google Patents

Abstract

PURPOSE:To simplify a signal-processing system, by irradiating a light beam of positive or negative spreading angle onto a measuring surface of a specimen, and receiving the reflected, beam by an optical detector provided with at least two light-receiving range. CONSTITUTION:When a light beam 15 is irradiated onto a measuring surface 3 with a positive spreading angle, a reflected beam 18 irradiated onto a photo-diode 17 is spread also and beam pattern 21 or 21' is depicted. This pattern 21, as an inclination angle theta included by the reference plane 7 of the surface 3 increases, moves to the B side from the A range side as shown by an arrow X. Consequently, with increase of the angle theta, a light quantity of the incident beam onto the range A is on the decrease and that onto the range B on the increase, so that the difference signal (A-B) determined by a differential amplifier subsides monotonically with the increasing angle theta. As a result, the inclination angle theta can be obtained by the difference signal (A-B). By adjusting the light beam 15 provided with a spreading angle of the angle is throttled accurately in the neighborhood of the measuring surface, an inclination angle of an extremely small surface can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical measurement device that measures the inclination angle of a surface to be measured using a light beam.

<Prior art> Conventionally, as this type of optical measurement device, for example,
There is something like the one shown in the figure. This optical application measurement device is
A narrow parallel light beam 2 from an e-Ne (helium-neon) laser device 1 is irradiated onto a surface to be measured 3.
The parallel reflected light 5 is received by a photodetector capable of detecting the position, such as a photodiode array 6, and the inclination angle of the surface to be measured 3 with respect to the reference surface 7 is measured based on the receiving position of the reflected light 5. ing.

However, the above-mentioned conventional optical measurement equipment requires a photodiode array or television camera as a photodetector that can detect the receiving position of reflected light with good resolution, making it expensive and requiring a complex signal processing system. It has the disadvantage of becoming.

<Object of the Invention> Therefore, an object of the present invention is to provide an optical application measurement device that is inexpensive and has a simple signal processing system.

<Structure and operation of the invention> In order to achieve the above object, the structure of the present invention includes a means for irradiating a surface to be measured with a light beam having a positive or negative spread angle, and a means for reflecting the light beam from the surface to be measured. and a photodetector having at least two light-receiving areas for receiving light; The inclination angle of the surface to be measured is measured by calculating, for example, the difference between the mutual ratios of the amounts of light received by the light-receiving areas.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

v, Fig. 1 [Here, 11 is a laser diode that emits a light beam 12 with a positive spread angle (an angle that expands in the direction of travel), and 13 is a laser diode that focuses the light beam 12 and has a negative spread angle. The convex lens 15 having a divergence angle (an angle that narrows in the direction of travel) comes out from the convex lens 13 with a negative divergence angle, focuses on one point, and then is covered with a positive divergence angle. The light beam 17 that enters the measurement surface 3 is a two-split photodiode into which reflected light with a positive spread angle from the measurement surface 3 is incident.

The photodiode 17 has two disks as shown in FIG.
This area A has divided areas A and B.

Detection outputs A and B corresponding to the amount of light received by B are input to, for example, a differential amplifier (not shown), and a difference signal (A-B) of the detection outputs is obtained from the differential amplifier.

According to the above configuration, since the light beam 15 is incident on the surface to be measured 3 with a positive spread angle, the reflected light 18 that is incident on the photodiode 17 also has a spread, that is, as shown in FIG. Then, a beam pattern 21 or 21' of the reflected light 18 with a spread is generated on the photodiode 17. As the inclination angle θ of the surface to be measured 3 with respect to the reference surface 7 increases, the beam pattern 21 moves from the region A side to the region B as shown by the arrow X in FIG.

Therefore, as the inclination angle θ increases, the amount of light incident on area A decreases and the amount of light incident on area B increases. Therefore, as shown in FIG. 3, the difference signal (A-B) between the two detection outputs A and B obtained by the differential amplifier described above monotonically decreases as the tilt angle θ increases. Therefore, the inclination angle θ is determined from this difference signal (A−B).

When the surface to be measured 3 is small, it is convenient to irradiate a light beam 15 with a negative spread angle and focus it near the surface to be measured, as shown in FIG. Furthermore, by precisely adjusting this converging point on the surface to be measured, it is possible to measure the inclination angle of a very small surface, which is difficult with conventional methods.

If a parallel beam with no divergence angle is incident on the two-split photodiode 17, a beam pattern of 31°31° will occur as shown in FIG.
As shown in Fig. 5, the range in which the difference signal (A-B) between the detection outputs A and B changes as the inclination angle θ changes becomes narrower, and in other ranges, the difference signal (A-B) between the detection outputs A and B becomes narrower. A
-B) remains unchanged and, in fact, detection of the tilt angle becomes impossible.

In the above embodiment, a two-segment type photodiode is used, but if the surface to be measured 3 is two-dimensionally inclined, two-dimensional angle measurement is possible by using a four-segment photodiode. be. Also, multiple photodetectors may be used. Further, in the above embodiment, the laser diode 11 and the convex lens 13 are used as means for irradiating the surface to be measured with a light beam having a positive or negative spread angle, but it is needless to say that the present invention is not limited to these. Practicing the invention requires a lens to provide the beam with the appropriate divergence angle. However, since semiconductor lasers have a very large divergence angle,
Any metrology application requires a lens to reduce the divergence angle, and therefore no additional special lens is required to apply the present invention. As described above, the usefulness of the present invention is further demonstrated when a semiconductor laser is used.

<Effects of the Invention> As is clear from the above description, according to the present invention, it is possible to obtain an optical application measurement device that is inexpensive and can easily implement a signal processing system.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, and FIG. FIG. 4 is a front view of the photodiode, FIGS. 3 and 5 are graphs showing difference signals of detection outputs with respect to tilt angle θ, and FIG. 6 is an explanatory diagram of a conventional example. 3... Surface to be measured, 11... Laser diode, 13
... Convex lens, 17... Photodiode, A, B.
··region.

Claims (1)

[Claims] (1) A photodetector having means for irradiating a surface to be measured with a light beam having a positive or negative spread angle, and at least two light-receiving areas that receive light reflected from the surface to be measured of the light beam. An optical application measurement device, characterized in that the inclination angle of the surface to be measured is measured based on the mutual ratio of the amount of light received by the two or more light receiving areas.