JPH07103729A - Apparatus for measuring surface shape - Google Patents

Abstract

PURPOSE:To provide a system for measuring a surface shape at high velocity with high accuracy. CONSTITUTION:A laser beam 7 passing a collimator lens 3 is cast at right angles to a surface of a target 16 sequentially through a rotary mirror 6 for scanning in an X direction, collimator lenses 10, 11, a rotary mirror 9 for scanning in a Y direction and a principal lens 15. A cast light 17 is scanned in the X and Y directions by the rotary mirrors 6 and 9. A reflected light 20 at the target 16 is condensed by the principal lens 15 and returned back in an optical path of the cast light IT to a mirror 4 with a pin hole. A returned light 21 is reflected by the mirror 4 to advance to a mirror 22 of a quadrangular pyramid. An image is surely detected by any one of PSDs 23-26 of the mirror 22 set corresponding to each mirror. This optical scanning enables high-speed measurements. The alignment of lenses becomes unnecessary because of the use of the principal lens both for projection and for receipt of light. Highly accurate measurements are achieved also because of the use of the PSDs 23-26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional scanning type surface profile measuring device capable of three-dimensional measurement.

[0002]

2. Description of the Related Art Methods for measuring surface displacement are roughly classified into a contact type and a non-contact type, and the contact type is generally a stylus type using a differential transformer. In the non-contact type, a triangulation method using a laser beam, an electrostatic capacity method that applies a capacitance change between metal surfaces, an optical fiber method that uses a change in the amount of reflected light emitted from an optical fiber, and a magnetic field with a high-frequency magnetic field The eddy current method in which an eddy current is generated on the body surface and the change in the magnetic field is applied is common. Since all of these measurement methods measure the surface displacement in spots, when measuring the three-dimensional surface displacement, the target or the sensor head is mechanically moved two-dimensionally. Further, in order to measure a one-dimensional surface shape, a method (light cutting method) has been devised in which slit-shaped light is projected onto a target surface and an image is formed on the two-dimensional CCD. In this method as well, when measuring a three-dimensional shape, mechanical one-dimensional movement is still required. Regarding the measurement technology,
For example, “Nikkei Mechanical” 1979 issued by Nikkei BP
Aug. 6, issue P73 to P80 "Measure surface roughness with laser light during processing", and also "TOSHIBA REVIEW" issued by Ohmsha, May 1989, May 1, 1989, P41
3 to P416.

[0003]

In the three-dimensional shape measuring system having a mechanical moving mechanism, the moving mechanism is mechanical, so that it takes a long time for measurement and the size of the apparatus becomes large. Further, in the light cutting method using the CCD image sensor, the resolution of the CCD image sensor is, for example, 700
Since it is about dots, it is difficult to make precise measurements. Further, since the conventional optical measurement method has a structure that collects reflected light from one direction, it is said that a so-called blind spot may occur depending on the shape of the surface of the target that is the object to be measured. It was made clear by the present inventor.

An object of the present invention is to provide a surface profile measuring device which can achieve highly accurate measurement.

Another object of the present invention is to provide a surface profile measuring apparatus capable of achieving high speed measurement.

Another object of the present invention is to provide a surface profile measuring apparatus which does not cause measurement failure due to occurrence of blind spots in measurement. The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0007]

According to the surface shape measuring apparatus of the present invention, a laser beam emitted from a semiconductor laser is made into a desired laser beam by a collimating lens, and this laser beam is made into a pinhole of a mirror having a pinhole. It passes through the optical path of the optical system arranged with the rotating mirror for X-direction scanning, the relay lens, the relay lens, the rotating mirror for Y-direction scanning, and the main lens, and drops the light onto the target surface. The reflected light at is condensed by the main lens to reverse the optical path of the projected light and the optical path is changed by the mirror having the pinhole, and the return light is received by the quadrangular pyramid mirror, and the return light is The structure is such that the light is dispersed in four directions and each of the dispersed lights is detected by the position detection element. The reflection points of the X-direction scanning rotary mirror and the Y-direction scanning rotary mirror are located at the focal points of the two relay lenses, and the Y-direction scanning rotary mirror is located at the focal point of the main lens. In addition, the light emitted from the main lens toward the target surface becomes parallel light and is emitted vertically to the target surface.

[0008]

The surface shape measuring apparatus of the present invention performs two-dimensional scanning by controlling the rotation of the rotary mirror for scanning in the X and Y directions, and does not employ a mechanical moving mechanism such as relative movement of the target with respect to the main lens. Since it has a conventional scanning mechanism, high-speed measurement is possible.

Since the surface shape measuring apparatus of the present invention has a structure in which the same main lens is used as the light projecting / receiving lens and two lenses are not used, the alignment between the two lenses is different from the conventional one. It is not necessary and the measurement accuracy is high.

In the surface profile measuring apparatus of the present invention, the two-dimensional scanning is optically performed by the rotation control of the reflecting mirror,
Since the light projecting lens is also used as the condenser lens, the size of the entire apparatus is reduced.

In the surface profile measuring apparatus of the present invention, the returning light is dispersed in four directions by using the quadrangular pyramid mirror, and the respective scattered light is detected by the position detecting elements, so that a blind spot occurs in the detection of the image. It becomes possible to measure the surface shape reliably.

The surface shape measuring apparatus of the present invention is a position detecting element (PS) having a resolution of 40,000 dots for detecting the movement of an image point.
Since D) is used, high resolution of the image becomes possible and highly accurate measurement becomes possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing a main part of an optical system of a two-dimensional scanning surface profile measuring apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory view showing a calculation example of a position vector of a measuring point. In the two-dimensional scanning surface profile measuring apparatus of the present invention, as shown in FIG. 1, a semiconductor laser 1 as a light source emits a laser beam 2, and the laser beam 2 shows a collimating lens 3 and a pinhole-equipped mirror 4. It reaches the rotating mirror (rotating mirror for X-direction scanning) 6 through a pinhole that does not exist. The semiconductor laser 1 becomes a laser beam 7 by the collimator lens 3 and passes through the pinhole. The rotation mirror 6 for X-direction scanning is rotationally controlled by a motor 8 to scan a target in the X-direction, which will be described later. The laser beam 7 whose direction is changed by the rotating mirror 6 for scanning in the X direction is transmitted to another rotating mirror (Y
It is directed toward the direction scanning rotary mirror) 9. Then, the X-direction scanning rotary mirror 6 and the Y-direction scanning rotary mirror 9
Two relay lenses 10 and 11 are arranged between them. The relay lens 10 on the side of the X-direction scanning rotating mirror 6
Is set such that the reflection point of the X-direction scanning rotary mirror 6 coincides with the focal position of the relay lens 10. Further, a relay lens 11 facing the rotating mirror 9 for scanning in the Y direction.
Are set so that the reflection point of the Y-direction scanning rotary mirror 9 is located at the focal position of the relay lens 11. The Y-direction scanning rotary mirror 9 is used for the laser beam 7 to the target.
Are scanned in the Y direction. The Y-direction scanning rotary mirror 9 is driven by the rotation control of the motor 12.

On the other hand, the laser beam 7 that has passed through the relay lens 11 and reflected by the Y-direction scanning rotary mirror 9 is sent to the main lens 15. This main lens 1
5 faces the target 16 and the main lens 1
The focal position of No. 5 is set to be the reflection point of the Y-direction scanning rotary mirror 9. Therefore, the laser beam 7, which is dropped from the main lens 15 to the target 16, that is, the projected light 17 is parallel to each other and is projected perpendicularly to the surface of the target 16. In such a mechanism, the projected light 17 can be two-dimensionally scanned on the surface of the target 16 by controlling the rotation of the X-direction scanning rotary mirror 6 and the Y-direction scanning rotary mirror 9. .

On the other hand, in this surface shape measuring apparatus, since the projected light 17 is projected perpendicularly to the surface of the target 16, the reflected light 20 on the surface of the target 16 is reflected.
Is condensed by the main lens 15, and thereafter, the Y direction scanning rotary mirror 9, the relay lens 11, the relay lens 10,
The X-direction scanning rotary mirror 6 and the pinhole-equipped mirror 4 are sequentially returned in the reverse order along the optical path of the projected light 17. Then, this return light 21 is reflected by the pinhole-equipped mirror 4
After reaching, the light is reflected by the mirror of the pinhole-equipped mirror 4 and proceeds to the quadrangular pyramid mirror 22. A position detecting element (PSD) 23, corresponding to each surface of the quadrangular pyramid mirror 22,
24, 25, 26 are provided. The PSD 23,
Each of 24, 25, and 26 has a resolution of 40,000 dots. Further, the PSD 23 is set in the direction of 0 °, the PSD 24 is set in the direction of 90 °, and the PSD 25 is set.
Is set in the direction of 180 °, and the PSD 26 is set in the direction of 270 °. Therefore, the return light 21 reaching the apex portion of the quadrangular pyramid mirror 22 reaches any one of the four mirrors of the quadrangular pyramid mirror 22 and is reflected (dispersed) even if the return light 21 shifts vertically and horizontally. Any of the PSDs 23, 24, 25, and 26 set to face the four mirrors will detect it, so that no dead angle occurs and reliable detection is possible. Further, the return light 21 that has traveled to the apex of the quadrangular pyramid mirror 22 and has a small displacement is dispersed into four mirrors, and the respective dispersed light 30 is four PSD2.
3, 24, 25 and 26 will be detected respectively. Due to the surface displacement of the target 16, the PS
Since the image points on D23, 24, 25 and 26 move, X of the laser beam 7 dropped at each position of the target 16 is moved.
If the Y coordinate is detected in advance, the three-dimensional surface shape of the target surface can be measured.

The three-dimensional surface shape measurement of the target surface can be obtained by calculating the position vector of the measurement point. Figure 2
FIG. 6 is an explanatory diagram showing the relationship between the projected light 17 and the reflected light 20 that are projected onto the measurement point P on the surface of the target 16.
In such a figure, the distance d between the irradiation point of the laser beam 7 (center of the main lens 15) and the measurement point P is as shown in (1) below.
Given by the formula.

[0017]

[Equation 1]

If the three-dimensional unit vector of the laser beam is A _V (A _x , A _y , A _z ), the position vector P _V of the measurement point P is given by the following equation (2).

[0019]

[Equation 2]

In these equations and FIG. 2, A is the laser beam irradiation opening (center of the main lens), B is the condenser lens, that is, the center of the main lens 15, C is the image point on the position detecting element, and γ _V (A, b) is a two-dimensional unit vector of the laser beam, L is the distance between the irradiation opening of the laser beam and the center of the condenser lens, m is the distance between the center of the condenser lens and the light receiving surface of the position detection element, and Δx Is the displacement of the image point on the position detecting element.

From these equations, the position detecting element (PSD)
It is possible to measure the three-dimensional surface shape of the surface of the target 16 from the moving amount of the image point at.

In such a surface profile measuring device,
The target 16 is placed and fixed on a sample table (not shown).
After that, the laser light 2 is emitted from the semiconductor laser 1, and this laser light is made into a desired laser beam 7 by the collimator lens 3. This laser beam 7 is a pinhole mirror 4
Through the pinhole to reach the X-direction scanning rotary mirror 6 and is reflected. The reflected laser beam 7 is a relay lens 1
It reaches the rotary mirror 9 for Y-direction scanning through 0 and 11,
It is reflected again by the directional scanning rotary mirror 9 to become the projected light 17, which passes through the main lens 15 and is projected onto the surface of the target 16. Further, the reflected light 20 reflected on the surface of the target 16 is a returning light which reverses the optical path of the projected light 17, the main lens 15, the Y direction scanning rotary mirror 9, the relay lens 11, the relay lens 10, and the X direction scanning. The return light 21 that travels sequentially with the rotating mirror 6 and reaches the mirror with pinhole 4 and is reflected by the mirror with pinhole 4 is reflected by the quadrangular pyramid mirror 22 and at least one or more position detecting elements among the four. (PSD: 23, 24, 25, 26).

[0023]

【The invention's effect】

(1) The surface profile measuring apparatus of the present invention performs two-dimensional scanning by controlling the rotation of the rotary mirror for scanning in the X and Y directions, and does not employ a mechanical movement mechanism such as relative movement of the target with respect to the main lens. Since such a scanning mechanism is used, it is possible to obtain the effect of enabling high-speed measurement. For example, when measuring the shape of a square target surface of 5 cm in length and width, it took several minutes to measure when using the conventional mechanical XY stage, but according to the present invention,
It can be measured in several hundreds of milliseconds, and the measurement time is about 1/600.

(2) Since the surface profile measuring apparatus of the present invention has a structure in which the same main lens is used as a light projecting / receiving lens and two lenses are not used, there is a gap between the two lenses as in the conventional case. The effect that the alignment becomes unnecessary and the measurement accuracy increases can be obtained.

(3) According to the above (2), since the surface profile measuring apparatus of the present invention uses the same main lens as the light projecting / receiving lens, the size of the apparatus can be reduced by sharing the lens. The effect is obtained.

(4) According to the above (1) and (3), in the surface profile measuring apparatus of the present invention, the two-dimensional scanning is optically performed by the rotation control of the reflecting mirror, and the light projecting lens condenses. Since it is also used as a lens, the effect of downsizing the entire device can be obtained. For example, the surface profile measuring device of the present invention is 10 cm long, 10 cm wide,
The external dimensions are about 50 cm in height, and the size can be reduced to about 1/10 of the conventional one.

(5) Since the surface profile measuring apparatus of the present invention has a structure for scanning the laser beam with an optical system using a rotating mirror, and has a structure for sharing a light projecting lens and a condensing lens. The device can be downsized and the manufacturing cost can be reduced. For example, in terms of cost, the cost can be reduced to about half that of conventional products.

(6) The surface profile measuring apparatus of the present invention uses a quadrangular pyramid mirror to reflect (disperse) the returned light in four directions,
Since each of the reflected lights is detected by the position detection element, a dead angle does not occur in the detection of the image, and the effect that the reliable surface shape measurement can be performed is obtained.

(7) Since the surface profile measuring apparatus of the present invention uses the position detecting element (PSD) whose resolution reaches 40,000 dots for detecting the movement of the image point, high resolution of the image becomes possible and high. The effect that accuracy measurement can be obtained is obtained.

(8) Due to the above (1) to (7), according to the present invention, it is possible to provide a small-sized and inexpensive two-dimensional scanning surface profile measuring apparatus that enables high-speed scanning and achieves highly accurate measurement. The synergistic effect of being able to do is obtained.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say, for example,
Although a semiconductor laser was used as the light source in the above embodiment,
Other laser generators, such as gas lasers, may be used. Further, the rotating mirror may be a polygon mirror.

In the above description, the case where the invention made by the present inventor is mainly applied to the surface shape measuring technique which is the field of application which is the background of the invention has been described. Detection element (P
Since SD) is used, it can be applied to, for example, a surface roughness measuring technique. The present invention is applicable to at least three-dimensional surface measurement technology.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a main part of an optical system of a two-dimensional scanning surface profile measuring apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a calculation example of a position vector of a measurement point in the two-dimensional scanning surface profile measuring apparatus according to the present invention.

[Description of Reference Signs] 1 ... Semiconductor laser, 2 ... Laser light, 3 ... Collimating lens, 4 ... Pinhole mirror, 6 ... X-direction scanning mirror, 7 ... Laser beam, 8 ... Motor, 9 ... Y-direction scanning Rotating mirror, 10, 11 ... Relay lens, 12 ... Motor, 15 ... Main lens, 16 ... Target, 17 ... Projected light, 20 ... Reflected light, 21 ... Return light, 22 ... Square pyramid mirror, 23, 24, 25 , 26 ... Position detection element (PS
D), 30 ... dispersed light.

Claims (3)

[Claims] 1. A laser beam is two-dimensionally scanned by an X-direction scanning rotary mirror and a Y-direction scanning rotary mirror respectively provided in the optical path, and the laser beam is made into parallel projected light by a main lens. The light is projected onto the target surface, the reflected light on the target surface is condensed by the main lens and returned in the opposite direction along the optical path of the projected light, and the optical path is changed by a reflecting mirror provided in the middle of the optical path. A surface shape measuring apparatus characterized in that it is configured so that it is guided to a polygonal pyramidal reflecting mirror and each return light dispersed by the polygonal pyramidal reflecting mirror is detected by a detecting element. 2. A relay lens is provided in an optical path between the X-direction scanning rotary mirror and the Y-direction scanning rotary mirror, and a reflection point of the X-direction scanning rotary mirror is provided. The surface shape measuring device according to claim 1, wherein a reflection point of the rotating mirror for scanning in the Y direction serves as a focal point of the relay lens facing. 3. The surface shape measuring apparatus according to claim 1, wherein the detection element is a position detection element.