JPH05141933A - Three-dimensional shape measuring device - Google Patents

Abstract

PURPOSE:To provide a device having high precision and high reliability by detecting the focal point position with a laser interferometer, and obtaining the inclination at the focal point position with a position detecting element. CONSTITUTION:The light transmitting a beam splitter 2, a polarization beam splitter 4, and a 1/4-wavelength plate 5 in sequence is condensed on a measured object 7. The reflected light from the measured object 7 is reflected on the polarization beam splitter 4 and fed to a half-mirror 12. Part of the light from the measured object 7 transmitting the half-mirror 12 is fed to a position detecting element 13, and the inclination at the focal point position on the measured object 7 is measured from the position of the incident light. A signal processing device 11 determines the shape of the measured object 7, and the three-dimensional shape of the measured object 7 is determined with higher precision from the inclination at the focal point position on the measured object 7 outputted from the position detecting element 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional shape measuring apparatus for measuring the surface shape of an object by utilizing the interference of laser light.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional three-dimensional shape measuring apparatus. In FIG. 3, the light emitted from the laser light source 1 is split into two by the beam splitter 2. One of the lights is reflected by the beam splitter 2, enters the reference mirror 3 and is reflected, and then enters the photodetector 9 via the beam splitter 2. The other light is transmitted through the beam splitter 2, is sequentially transmitted through the polarization beam splitter 4 and the quarter wavelength plate 5, and is circularly polarized. This light is condensed on the measurement target 7 by the objective lens 6. At this time, the position of the objective lens 6 in the optical axis direction is adjusted so as to focus on the measurement target 7. The reflected light from the measurement target 7 is collimated again by the objective lens 6 and becomes parallel light. Even if the surface of the measurement target 7 is inclined, the optical axis of the collimated parallel light is parallel to the optical axis of the incident light. Due to the reflection from the measurement target 7, the circularly polarized light becomes reverse circularly polarized light and passes through the quarter-wave plate 5. This light is
It is reflected by the polarization beam splitter 4 and is incident on the plane mirror 8. The incident light is reflected by the plane mirror 8, is again incident on the measurement target 7 via the polarization beam splitter 4 → the quarter wavelength plate 5 → the objective lens 6, and is reflected. The reflected light passes through the quarter-wave plate 5 via the objective lens 6 and passes through the polarization beam splitter 4. The light transmitted through the polarization beam splitter 4 is reflected by the beam splitter 2,
The light is incident on the photodetector 9, interferes with the light from the reference mirror 3, changes in interference fringes are measured, and changes in the focus on the measurement target 7 are measured. The measurement target 7 is fixed to the stage 10 and moved in a plane perpendicular to the optical axis to give a displacement to the focal position. From the measured displacement and the movement of the stage 10, the signal processing device 11 obtains the three-dimensional shape of the measurement target 7.

However, in the three-dimensional shape measuring apparatus shown in the above-mentioned prior art, the focus position on the measuring object 7 can be obtained by measuring the interference fringes detected on the photodetector 9, but the measurement is performed. There is a limit in improving the measurement accuracy of the apparatus because the inclination at the focal position on the target 7 is to be obtained at the same time, since it cannot be obtained unless the positions of three or more points are measured.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and at the same time as the focus position detection by the laser interferometer, the tilt at the focus position is also detected by using the position detection element. It is an object of the present invention to provide a highly accurate and highly reliable three-dimensional shape measuring apparatus by seeking.

[0005]

The structure of the present invention for solving the above-mentioned problems is to irradiate a light beam on a measurement object surface and a reference surface, and obtain the shape of the measurement object from the phase difference between the reflected lights. In the shape measuring apparatus, a laser light source, an optical component that splits the light emitted from the laser light source into two, an objective lens that focuses one of the light split by the optical component on the measurement target, and An optical isolator comprising a polarization beam splitter and a 1/4 wavelength plate on which first reflected light from a measurement target is incident via the objective lens;
A reference that causes the light that has entered the optical isolator to enter the measurement target again via the objective lens, and that reflects the other light branched by the optical component and a half mirror that transmits part of the incident light. Light detection for causing a mirror, reflected light from the reference mirror and second reflected light from the measurement target to interfere with each other through the optical component, and detecting a change in the focal position on the measurement target from the interference fringes. And a position detection element that receives the light transmitted through the half mirror and detects the tilt at the focus position on the measurement target from the position of the light, and moves the measurement target in the direction perpendicular to the optical axis. And a stage for displacing the focus position on the measurement target, a displacement output from the stage, a change in the focus position output from the photodetector, and a focus position output from the position detection element. Is characterized in that it has a structure in which a signal processing device for determining and displaying the shape of the measurement target from the gas.

[0006]

According to the present invention, the three-dimensional shape measuring apparatus using laser interference is provided with the position detecting element so that not only the focus position on the measurement object but also the tilt at the focus position can be detected at the same time. I am trying. Therefore, the measurement accuracy of the device can be further improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a three-dimensional shape measuring apparatus of the present invention. In FIG. 1, the same elements as those of FIG. In FIG.
Reference numeral 12 denotes a half mirror for allowing the first reflected light from the measurement target 7 to be incident on the measurement target again and transmitting a part of the incident light. Reference numeral 13 denotes a position detection element that receives the light transmitted through the half mirror 12 and detects the tilt at the focus position on the measurement target 7 from the position of the light.

In such a structure, the laser light emitted from the laser light source 1 is split into two by the beam splitter 2. One of the lights is reflected by the beam splitter 2, enters the reference mirror 3 and is reflected, and then enters the photodetector 9 via the beam splitter 2 again. The other light is transmitted through the beam splitter 2, is sequentially transmitted through the polarization beam splitter 4 and the quarter wavelength plate 5, and is circularly polarized. This light is condensed on the measurement target 7 by the objective lens 6. At this time, the position of the objective lens 6 in the optical axis direction is adjusted so as to focus on the measurement target 7. The reflected light from the measurement target 7 is collimated again by the objective lens 6 and becomes parallel light. Even if the surface to be measured is inclined, the optical axis of the collimated parallel light is parallel to the optical axis of the incident light. Due to the reflection from the measurement target 7, the circularly polarized light becomes the reverse circularly polarized light, and passes through the quarter wavelength plate 5 again. This light is reflected by the polarization beam splitter 4 and is incident on the half mirror-12. The incident light is partially transmitted by the half mirror 12, but the remaining light is reflected,
The polarized beam splitter 4 → 1/4 wavelength plate 5 → objective lens 6 is incident again on the measurement target 7 and reflected.
The reflected light is sequentially transmitted through the quarter-wave plate 5 and the polarization beam splitter 4 via the objective lens 6. The light transmitted through the polarization beam splitter 4 is reflected by the beam splitter 2, enters the photodetector 9, interferes with the light from the reference mirror 3, the change in the interference fringes is measured, and the focus on the measurement target 7 is measured. Measure the change in position.

Further, a part of the light from the object 7 to be measured which has passed through the half mirror 12 is incident on the position detecting element 13,
The tilt at the focus position on the measurement target 7 is measured from the position of the incident light. Here, in order to obtain the inclination of the measurement target 7 by the position detection element 13, as shown in FIG.
Assuming that the distance from the measurement target 7 to the position detection element 13 is L and the deviation from the optical axis on the position detection element 13 is D, the measurement target 7 is an inclination angle θ, and tan2θ = D / L holds. The tilt angle θ is obtained from θ = (½) tan ⁻¹ D / L.

The object 7 to be measured is fixed to the stage 10 and moved in a plane perpendicular to the optical axis to give a displacement to the focal position. From the measured displacement and the movement of the stage 10, the signal processing device 11 obtains the three-dimensional shape of the measurement target 7 and from the tilt at the focus position on the measurement target 7 output from the position detection element 13. , Measurement target 7
3D shape is required with higher accuracy.

Although not shown in the drawings, in the above embodiment, the autofocus mechanism is provided and the objective lens 6 is moved to always focus on the object 7 to be measured. The resolution can be increased.

[0012]

As described above in detail with reference to the embodiments, according to the present invention, a three-dimensional shape measuring apparatus using laser interference is provided with a position detecting element, so that the object to be measured can be measured. Since not only the position of the upper focus but also the tilt at the focus position on the measurement target can be detected at the same time, the measurement accuracy of the device can be further improved and a highly reliable three-dimensional shape measuring device can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a three-dimensional shape measuring apparatus of the present invention.

FIG. 2 is a diagram for explaining the operation of the device in FIG.

FIG. 3 is a conventional example of a three-dimensional shape measuring apparatus.

[Explanation of symbols]

 1 Laser Light Source 2 Beam Splitter 3 Reference Mirror 4 Polarizing Beam Splitter 5 1/4 Wave Plate 6 Objective Lens 7 Measurement Target 9 Photo Detector 10 Stage 11 Signal Processing Device 12 Half Mirror 13 Position Detection Element

Claims (1)

[Claims] 1. A three-dimensional shape measuring apparatus for irradiating a light beam on a surface to be measured and a reference surface, and determining the shape of the object to be measured from the phase difference between the reflected light, a laser light source, and light emitted from the laser light source. An optical component for branching the light into two, an objective lens for converging one of the lights branched by the optical component on the measurement target, and a first reflected light from the measurement target via the objective lens. An optical isolator consisting of a polarization beam splitter and a quarter-wave plate that are incident as an incident light, and the light that is incident on this optical isolator is incident on the measurement target again through the objective lens, and part of the incident light is transmitted. A half mirror, a reference mirror that reflects the other light branched by the optical component, a reflected light from the reference mirror, and a second light from the measurement target.
The reflected light of the interference through the optical component, a photodetector for detecting the change of the focus position on the measurement object from the interference fringes, the light transmitted through the half mirror is incident, the position of the light A position detecting element for detecting an inclination at a focus position on the measurement target from the stage, a stage for moving the measurement target in the direction perpendicular to the optical axis, and a stage for displacing the focus position on the measurement target; And a signal processing device that obtains and displays the shape of the measurement target from the displacement output from the device, the change in the focus position output from the photodetector, and the tilt at the focus position output from the position detection element, A three-dimensional shape measuring device characterized in that