JPH05164989A - Method for uniforming light quantity distribution in shape measurement - Google Patents

Abstract

PURPOSE:To stabilize measured values by interposing many translucent reflecting films between a surface to be measured where the light from a light source is made incident and a photodetecting element for for detecting reflected light from the surface to be measured. CONSTITUTION:A incident light 3 such as laser light from a light source 2 in a measuring instrument 1 is reflected by the object surface of a body 4 to be measured to become reflected light 5, which is reflected by a mirror 6 in the measuring instrument 1 and strikes on the photodetection surface of a photodetecting element 7. In this process, the incident light 3 causes speckle interference on the surface of the body 4 to be measured to become reflected light 5 having an intensity irregularity of light corresponding to surface roughness. Then this reflected light 5 when reflected by the mirror 6 is reflected, bit by bit, by the reflecting surfaces of many translucent reflecting films which are thick enough to make the phase of the reflected light 5 constant. In this case, the incident light 5 is reflected, bit by bit, by the laminated translucent reflecting films to become luminous flux having width determined by the number of the reflecting films, so groups of light beams of the reflected light 5 from the surface to be measured is put one over another, bit by bit, to make intensity differences uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for making a light quantity distribution of light uniform in a process of measuring a shape using a laser beam or the like.

[0002]

2. Description of the Related Art Conventionally, a method of inserting a diffusion plate or a method of electrically processing the output of a light receiving element has been used as a method of making the light quantity distribution uniform. In the former method in which a diffuser plate is inserted, optical characteristics tend to deteriorate due to light attenuation or excessive scattering. Further, in the latter method of electrically processing the output of the light receiving element, since the output of each cell of the light receiving element is integrated, there is a problem that the position of high light intensity is deviated and recognized. Also, after A / D converting the output of the light receiving element,
Although a smoothing method can be considered, there is a problem that the calculation time is long and it is not suitable for real-time measurement.

[0003]

The object of the present invention is to stabilize the measured values by making uniform the microscopic intensity unevenness of the reflected light due to speckle interference in the shape measurement using a laser beam, for example, by a simple method. To provide the means.

[0004]

In view of the above object, the present invention has a thickness that makes the phase of reflected light constant between a surface to be measured which reflects incident light from a light source and a light receiving element for detecting reflected light. By interposing a large number of semitransparent reflective films, the intensity distribution of the light incident on the light receiving element is made uniform, and the accuracy of the measured value is improved.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an overall measuring system.
Incident light 3 such as laser light emitted from the light source 2 inside the measuring instrument 1 is reflected by the measurement surface of the DUT 4 and becomes reflected light 5 which is reflected by the mirror 6 inside the measuring instrument 1 and received. It enters the light receiving surface of the element 7. In this process, the incident light 3 is usually the object to be measured 4
The speckle interference occurs on the surface to be measured and the reflected light 5 has unevenness of light intensity corresponding to the surface roughness.

The reflected light 5 is gradually reflected by a large number of reflecting surfaces 8 in the process of being reflected by the mirror 6.
FIG. 2 shows the structure of the reflecting surface 8. Incident light 5 is generated by a plurality of laminated semi-transparent reflective films 81, 82, 83, 84,
By being reflected little by little at 85, the reflection films 81, 8
Since the light flux has a width determined by the number of 2, 83, 84, and 85, the light ray groups of the reflected light 5 from the surface to be measured are gradually overlapped to make the intensity difference uniform and reduce the intensity difference.

FIG. 3 shows an example of the output waveform of the light receiving element 7. Since a general output waveform does not pass through the reflecting surface 8 of the mirror 6, it has a sharp saw-tooth shape, but when reflected by the reflecting surface 8 of the mirror 6 as in the present invention, the light receiving element 7 has a The output waveform is smooth without sharp peaks and valleys.

[0008]

Other Embodiments In the above embodiment, a plurality of semitransparent reflective films 81, 82, 83, 84 and 85 are formed in a laminated state with one mirror 6, but the mirror 6 composed of a single transparent reflective film. By combining a plurality of semi-transparent reflective films 8
1, 82, 83, 84, 85 may be formed. Also, by dividing the reflection direction into two directions at right angles where the reflected light 5 travels, it becomes possible to adapt to an area sensor.

[0009]

According to the present invention, the following unique effects can be obtained. Since only the semitransparent reflection film of the mirror as the optical component is formed, the size and weight can be reduced. Since the optical processing is the main and no electrical processing is involved, the data processing is simplified. Since there is no optical element such as a diffusing plate that attenuates light or excessively scatters in the middle of the optical path, the amount of light received by the light receiving element does not decrease, and the optical characteristics do not deteriorate. To be Since it can be used not only for laser light but also for ordinary optical measurement, it can be applied in a wide range of measurement and measurement fields.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a measurement system.

FIG. 2 is an explanatory diagram of a structure of a semitransparent reflection film of a mirror and a reflection state of reflected light.

FIG. 3 is an explanatory diagram of a waveform of reflected light.

[Explanation of symbols]

 1 Measuring instrument 2 Light source 3 Incident light 4 Object to be measured 5 Reflected light 6 Mirror 7 Light receiving element 8 Reflective surface 81, 82, 83, 84, 85 Semi-transparent reflective film

Claims (1)

[Claims] 1. A measuring surface that reflects incident light from a light source and a light receiving element for detecting reflected light from the measuring surface,
Uniformity of the light intensity distribution in shape measurement characterized by uniforming the intensity distribution of the reflected light incident on the light receiving element by interposing a number of semitransparent reflective films with a thickness that makes the reflected light phase almost constant Method.