JPH05340726A - Noncontact probe for three-dimensional shape measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a noncontact probe for three-dimensional shape measuring instruments which can measure the shape of a surface to be measured with high accuracy. CONSTITUTION:Laser light directed to an optical axis shifting section 2 from a laser light source 1 comes out from the section 2 after the light is shifted perpendicularly to its optical axis in the section 2 and is divided into measuring light 9a and reference light 10 by means of a light dividing means 3. The measuring light 9a is focused onto a surface 8 to be inspected through an objective optical system 4 and reflected measuring light 9b from the surface 8 is directed to an interference optical system 5 after advancing through above-mentioned optical path in the opposite direction and passing through the means 13 and emitted from the system 5 as interference light 11 in which the light 9b interferes with the reference light 10. A detecting section 6 detects the light quantity of the light 11 and a signal processing section 7 finds the shape of the surface 8 by processing the light quantity.

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 shape of a free-form or aspherical lens or mirror with high accuracy, and more particularly to a non-contact probe using optical means. Is.

[0002]

2. Description of the Related Art Conventionally, as an optical device using a non-contact type probe by optical means, for example, Japanese Patent Publication No. 2-11.
The device disclosed in Japanese Patent No. 084 is known. The non-contact type probe of this conventional device will be described with reference to FIG. In the figure, the radiation light source 12 is a measuring light (frequency f ₁ )
And the reference light (frequency f ₂ ) of two frequencies are emitted, and the light emitted from the first light separating means 13 is emitted.
Separated in. That is, the measuring light of frequency f ₁ goes straight through the first light separating means 13 and further the second light separating means 18
Through the objective lens 14 and is reflected by the object surface 22 to be measured. Then, this reflected light travels backward in the above optical path and enters the first light separating means 13 again. On the other hand, the reference light having the frequency f ₂ is separated by the first light separating means 13 in the upward direction of the figure, is then reflected by the interference optical system 15, and is incident on the first light separating means 13 again. All of these lights are condensed on the photodetector 17 by the condenser lens 16. And
The fluctuation of the beat frequency generated by the photodetector 17 is detected and processed by the signal processing means 24, and the measured object surface 22 is measured.
Measure the displacement of.

Here, the object surface 22 to be measured is moved by the moving means 23.
It is possible to move in the R direction and rotate in the θ direction in the cylindrical coordinate system R-θ-Z (provided that the optical axis direction of the measurement light is from the Z axis and the Z axis). The distance is R). When the object surface 22 to be measured is displaced from the focus position, the optical system 19 and the photodetector 20 detect the reflected light partially separated by the second light separating means 18 to obtain a focus error signal. In accordance with this signal, the movable table 21 is driven to move the objective lens 14, and the distance between the objective lens 14 and the object surface 22 to be measured is always kept constant.

In the conventional apparatus having the above structure, when the object surface 22 to be measured moves, the Z-axis component V _{Z of the} moving speed.
Causes a Doppler shift, and the frequency of the reflected light is f ₁
Therefore, f ₁ − (1-2V _Z / C) (C: speed of light). The light of this frequency and the light of the frequency f ₂ separated by the first light separating means 13 interfere with each other in the interference optical system 15, and the interference light passes through the condenser lens 16 and the photodetector 17
Focused on the beat frequency f ₁ + Δf−f ₂ (where Δf = −f ₁ × 2V _Z
/ C) is detected. If f ₁ −f ₂ is known by another means (not shown), Δf can be obtained, and from this, the displacement of the measured object surface 22 can be known by the signal processing means 24. On the other hand, when the moving means 23 is moved in the R direction and rotated in the θ direction, the inclination of the measurement point on the measured object surface 22 with respect to the optical axis of the non-contact probe changes. For this, the objective lens 14 is moved in the direction perpendicular to the optical axis of the probe so that the light is incident perpendicularly to the measurement point. At this time, since the position of the measurement point in the optical axis direction changes, the focus error signal is detected by the photodetector 20 and the objective lens 14 is moved in the optical axis direction. By the above operation, the displacement of the measured object surface 22 when the non-measured object is moved in the R direction and rotated in the θ direction can be known, and the shape of the measured object surface 22 can be obtained.

[0005]

However, in the above-mentioned conventional non-contact type probe, since the optical axis of only the measurement light is moved according to the inclination of the object surface to be measured, the reference light that does not move the optical axis is moved. There is a problem in that the optical path length changes due to the movement of the optical axis, and therefore an error occurs in the displacement information of the measured object surface, making it impossible to perform highly accurate measurement.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a non-contact type probe of a three-dimensional shape measuring apparatus capable of measuring the shape of a measuring surface with high accuracy.

[0007]

In order to achieve the above object, in the non-contact type probe of the three-dimensional shape measuring apparatus of the present invention, a laser light source and a light beam from the laser light source are used as reference light and measurement light. Light splitting means for splitting into a light flux, an objective optical system for condensing the separated measurement light on the surface to be inspected, and interference optics for making the optical paths of the measurement light reflected from the surface to be inspected and the reference light coincide with each other. A non-contact probe of a three-dimensional shape measuring apparatus comprising a system, a detection unit that receives the interference light from the detection unit to detect the amount of light, and a signal processing unit that detects the displacement of the surface to be inspected from the signal of the detection unit. An optical axis moving unit, which is arranged between the laser light source and the light separating means, moves the optical axis of the light beam from the light source in a direction perpendicular to the optical axis direction.

[0008]

In the non-contact type probe of the three-dimensional shape measuring apparatus of the present invention having the above structure, the optical axes of the measuring light and the reference light are moved at the same time.

Next, the operation of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of a non-contact type probe of the three-dimensional shape measuring apparatus of the present invention. In the figure,
Reference numeral 1 is a laser light source, 2 is an optical axis moving unit, and 3 is a light separating means. The laser light incident on the optical axis moving unit 2 from the laser light source 1 is moved by the optical axis moving unit 2 in the direction perpendicular to the optical axis direction and emitted, and the measurement light 9 a is emitted by the light separating means 3.
And the reference light 10 are separated. The separated measurement light 9a is condensed and incident on the surface 8 to be measured by the objective optical system 4. At this time, the optical axis moving unit 2 and the objective optical system 2 are arranged so that the surface 8 to be measured and the measurement light 9a are always vertical. Operate system 4. For that purpose, the inclination of the surface 8 to be inspected is detected by another optical system (not shown), or the inclination of the surface 8 to be inspected is calculated in advance.

The reflected measurement light 9b from the surface 8 to be inspected travels in the reverse direction of the above-mentioned optical path, passes through the light separating means 3 and enters the interference optical system 5, and interferes with the reference light 10 and the interference light 11 is generated. Will be emitted. The light amount of the interference light 11 is detected by the detector 6,
The signal processing unit 7 performs processing to obtain the shape of the surface 8 to be inspected. That is, by moving the relative position of the surface 8 to be inspected and the non-contact type probe in a plane perpendicular to the optical axis of the non-contact type probe,
The displacement of the test surface 8 is measured by reading the change in the interference light 11 according to the displacement of the test surface 8.

Hereinafter, a third embodiment of the present invention will be described with reference to the accompanying drawings.
Several embodiments of the non-contact type probe of the dimension measuring apparatus will be described. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

[0012]

First Embodiment First, a first embodiment of the present invention will be described. Figure 2
FIG. 1 is a diagram showing a configuration of Example 1 of the present invention. As shown in the figure, in this embodiment, the optical axis moving unit 2 is composed of a reflecting mirror 2a and a moving stage 2b for moving the reflecting mirror 2a, and a beam splitter 3a is used as a light separating means. The objective optical system 4 is composed of a lens 4a for collecting the measurement light 9a and a moving stage 4b for movably supporting the lens 4a in the optical axis direction. The reflection mirror 5a is arranged so as to face the beam splitter 3a and reflects the reflection measurement light 9b from the surface 8 to be inspected. Further, the detector 6 includes a lens 6a that collects the interference light of the reference light 10 and the reflected measurement light 9b, and a light receiving element 6b. However, lens 6
The a is not always necessary, and may be omitted if the interference light can be detected only by the light receiving element 6b.

Next, the operation of the first embodiment will be described. The light flux emitted from the laser light source 1 is reflected by the reflection mirror 2a and enters the beam splitter 3a. Here, the measurement light 9a separated by the beam splitter 3a is detected by the tilt of the surface 8 to be detected by another optical system (not shown) or is calculated in advance by calculating the tilt of the surface 8 to be measured. The reflection mirror 2a is moved so that the light is incident vertically on the reflection mirror 2a. The light beam from the reflection mirror 2a is split into the measurement light 9a and the reference light 10 by the beam splitter 3a. The separated measurement light 9a is vertically incident on the surface 8 to be inspected by the lens 4a. The lens 4a is moved in the optical axis direction according to the displacement of the surface to be inspected, and the position of the surface to be inspected 8 is focus-detected by another optical system (not shown) to constantly detect the focal plane of the lens 4a. Match with surface 8. The reflected measurement light 9b reflected by the surface 8 to be inspected travels in the same optical path as the incident optical path, travels straight through the beam splitter 3a, and then is reflected by the reflection mirror 5a to become the same optical path as the reference light 10 and become the interference light. Becomes The interference light from the beam splitter 3a enters the lens 6a,
The light is received by the light receiving element 6a. A signal according to the amount of light from the light receiving element 6a is processed by the signal processing unit 7, and the test surface 8 is moved by a moving stage (not shown) in a plane perpendicular to the optical axis of the non-contact probe. Then, the change of the interference light according to the displacement of the surface 8 to be inspected can be read and the displacement of the surface 8 to be inspected can be measured.

The unique effect of the first embodiment is that the number of parts is small and the structure can be constructed at low cost.

[0015]

Second Embodiment Next, a second embodiment of the present invention will be described. Figure 3
FIG. 6 is a diagram showing a configuration of a second exemplary embodiment of the present invention. As shown, in this embodiment, the optical axis moving unit 2 includes an afocal optical system 2c composed of two lenses, and an afocal optical system 2c.
It is composed of a moving stage 2b for moving c vertically to the optical axis thereof, and a half mirror 3b is used as a light separating means. The objective optical system 4 is composed of a lens 4a that is movable in the optical axis direction for collecting the measurement light 9a, and a fixed lens 4c. Further, the interference optical system uses the reflected measurement light 9 that has passed through the half mirror 3b.
b for further reflecting b, a half mirror 5b for separating the reference light 10 separated by the half mirror 3b, and a reflected mirror 5a for reflecting the reflected light of the half mirror 5b back to the original optical path. A reflection mirror 5c arranged on a moving stage (not shown) carrying a measurement object.
And a half mirror 5d that superimposes the reflected reference light and the reflected measurement light reflected by the reflection mirror 5a to cause interference.

Next, the operation of the second embodiment will be described. The light beam emitted from the laser light source 1 is transmitted by the afocal optical system 2
It is incident on c and is emitted as a light beam having the same angle as the incident light. Here, the measurement light 9a separated by the half mirror 3b is detected by a different optical system (not shown) to detect the inclination of the surface 8 to be detected or by calculating the inclination of the surface 8 to be measured in advance. The afocal optical system 2c is moved so as to be vertically incident on the. The light flux from the afocal optical system 2c is transmitted by the half mirror 3b to the measurement light 9a and the reference light 10
And separate. The separated measurement light 9a is vertically incident on the surface 8 to be inspected by the lens 4a and the lens 4c. The lens 4a is moved in the optical axis direction in accordance with the displacement of the surface 8 to be inspected, and the position of the surface 8 to be inspected is detected by another optical system (not shown) so that the focal planes of the lenses 4a and 4c are constantly detected. Inspection surface 8
And match. The reflected measurement light 9b reflected on the surface 8 to be inspected travels in the same optical path as the incident optical path, returns to the half mirror 3b again, and is further reflected by the reflection mirror 5a. On the other hand, the reference light 10 separated by the half mirror 3b is
After being reflected by the half mirror 5b and the reflection mirror 5c, the half mirror 5d interferes with the measurement light reflected from the reflection mirror 5a. The interference light from the half mirror 5d enters the lens 6a and is received by the light receiving element 6a. A signal according to the amount of light from the light receiving element 6a is processed by the signal processing unit 7, and the test surface 8 is moved by a moving stage (not shown) in a plane perpendicular to the optical axis of the non-contact probe. If
The change of the interference light according to the displacement of the test surface 8 can be read and the displacement of the test surface 8 can be measured.

The unique effect of the second embodiment is that the displacement caused by the movement of the moving stage on which the object to be measured is mounted is canceled, so that the measurement can be performed with higher accuracy.

[0018]

Third Embodiment Next, a third embodiment of the present invention will be described. Figure 4
FIG. 8 is a diagram showing a configuration of a third exemplary embodiment of the present invention. As shown in the figure, in this embodiment, the optical axis moving unit 2 is composed of an optical fiber 2d, a lens 2e, and a moving stage 2b for moving them, and a beam splitter 3a is used as a light separating means.
Is used. The objective optical system 4 includes a lens 4a that is movable in the optical axis direction to collect the measurement light 9a,
It is composed of a fixed lens 4c. The interference optical system further includes a reflection mirror 5a that further reflects the reflected measurement light 9b that has passed through the beam splitter 3a, an afocal optical system 5e that relays the reference light 10 separated by the half mirror 3b, and this afocal. Optical system 5e
It is composed of a reflection mirror 5c for reflecting the reference light 10 from the above, and a beam splitter 5f for superposing and interfering the reflection reference light and the reflection measurement light reflected by the reflection mirror 5a.

Next, the operation of the third embodiment will be described. The light flux emitted from the laser light source 1 enters the beam splitter 3a via the optical fiber 2d and the lens 2e. Here, the measurement light 9a separated by the beam splitter 3a is detected by the tilt of the surface 8 to be detected by another optical system (not shown) or is calculated in advance by calculating the tilt of the surface 8 to be measured. The optical fiber 2d and the lens 2e are moved so that the light is vertically incident on the lens. The light beams from the optical fiber 2d and the lens 2e are separated into the measurement light 9a and the reference light 10 by the beam splitter 3a. The separated measurement light 9a is vertically incident on the surface 8 to be inspected by the lenses 4a and 4c. The lens 4a is moved in the optical axis direction in accordance with the displacement of the surface 8 to be inspected, and the position of the surface 8 to be inspected is detected by another optical system (not shown) so that the focal planes of the lenses 4a and 4c are constantly detected. The surface to be inspected 8 is made to match. The reflected measurement light 9b reflected by the surface 8 to be inspected travels in the same optical path as the incident optical path, travels straight in the beam splitter 3a, and further, the reflection mirror 5a.
Reflect on. Then, the reference light 10 separated by the beam splitter 3a passes through the afocal optical system 5e and the reflection mirror 5c, and is reflected by the beam splitter 5f at the reflection mirror 5a.
Interferes with the measurement light reflected from. The interference light from the beam splitter 5f enters the lens 6a and is received by the light receiving element 6a. A signal according to the amount of light from the light receiving element 6a is
If the surface 8 to be inspected is processed by the signal processing unit 7 and moved in a plane vertical to the optical axis of the non-contact type probe by a moving stage (not shown), the surface 8 to be inspected is displaced. It is possible to read the change in the interference light and measure the displacement of the surface 8 to be inspected.

As a unique effect of the third embodiment, since the non-contact type probe main body and the laser light source are separated by using the optical fiber, it is possible to reduce the size and heat of the laser light source 1. Since it can be cut off from the main body, errors such as temperature drift are reduced, and it is possible to measure with higher accuracy.

[0021]

As described above, according to the non-contact type probe of the three-dimensional shape measuring apparatus of the present invention, even if the optical axis is moved, there is a difference in the optical path length between the measuring light and the reference light. Since it does not exist, the displacement of the measurement surface can be measured with extremely high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a non-contact type probe of a three-dimensional shape measuring apparatus of the present invention.

FIG. 2 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a non-contact type probe of a conventional three-dimensional shape measuring apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 laser light source 2 optical axis moving parts 2a, 5a, 5c reflection mirrors 2b, 4b moving stages 2c, 5e afocal optical system 2d optical fibers 2e, 4a, 4c, 6a lens 3 light separating means 3a, 5f beam splitters 3b, 5b , 5d Half mirror 4 Objective optical system 5 Interference optical system 6 Detector 6b Light receiving element 7 Signal processing unit 8 Test surface 9a Measuring light 9b Reflected measuring light 10 Reference light 11 Interfering light 12 Radiation light source 13 First light separating means 14 Objective lens 15 Interference optical system 16 Condensing lens 17 Photodetector 18 Second light separating means 19 Optical system 20 Photodetector 21 Moving table 22 Non-measuring object plane 23 Moving means 24 Signal processing means

Claims (1)

[Claims] 1. A laser light source, a light separating means for separating a light flux from the laser light source into two light fluxes of a reference light and a measurement light, and an objective optical system for condensing the separated measurement light on a surface to be inspected. An interference optical system that causes the measurement light reflected from the surface to be measured and the reference light to interfere with each other by an optical path, a detection unit that receives the interference light and detects the amount of light, and a surface to be measured from the signal of the detection unit. A non-contact type probe of a three-dimensional shape measuring apparatus comprising a signal processing unit for detecting the displacement of the light source, the optical axis of the light flux from the light source being arranged between the laser light source and the light separating means. A non-contact probe for a three-dimensional shape measuring apparatus, comprising an optical axis moving unit that moves in a direction perpendicular to the axial direction.