JPH06347230A - Method and apparatus for measuring shape - Google Patents

Abstract

PURPOSE:To decrease the incident angle of reflected light on a condenser lens and to make it possible to measure a shape highly accurately by providing abberation decreasing means, which decrease the abberation generated after the passing of the reflected light from a material to be measured through the condenser lens. CONSTITUTION:After the one-dimensional scanning of a projected light beam 4a, reflected lights 5a and 5b from the surface of a material to be measured 5 are condensed on either closer lens of at least two condenser lenses 6a and 6b, which are abberation decreasing means provided at both right and left sides with respect to the beam scanning direction of a rotary mirror 4. At this time, the image of the reflected light 5a (5b), which is condensed on the condenser lens 6a (6b) is focused on a position detecting element 7a (7b). The reflected lights 5a and 5b from the material to be measured 5 are condensed with at least two condenser lenses 6a and 6b, which are the abberation decreasing means. Therefore, the incident angles of the reflected lights 5a and 5b with respect to the condenser lenses 6a and 6b become smaller than in the case wherein the light is condensed only wit one condenser lens. The abberation of the light after the condensation is decreased, and the highly accurate shape measurement can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type shape measuring technique for scanning the surface of an object with a laser beam and detecting the reflected light in an apparatus for measuring the shape of the object.

[0002]

2. Description of the Related Art Conventionally, as a non-contact method for measuring the shape of an object, a light cutting method utilizing light has been widely used.

This light cutting method is a method in which slit light passing through a lens is projected onto an object to be measured at an angle of 45 degrees, and the reflected light is observed by a microscope, a camera or the like.

When obtaining the three-dimensional shape of an object using the light section method, the shape of the surface of the object can be measured by sub-scanning the slit light.

In addition to the light cutting method using light, a laser scanning type shape measuring device using a laser beam is also used.

This is because the laser beam is one-dimensionally scanned, the reflected light is imaged on the position detecting element, the one-dimensional surface displacement is obtained, and further sub-scanning is performed, whereby the third order of the object to be measured is obtained. The original surface shape is obtained.

[0007]

However, the above-mentioned conventional optical cutting method and laser scanning type shape measuring apparatus are simple shape measuring methods, but the irradiation light and the laser beam are installed in the collector. When scanning on the side opposite to the optical lens, the angle of incidence of the reflected light on the condenser lens increases, so the astigmatism and coma aberration of the image displayed on the position detection element increases and the measurement There is a problem that errors are likely to occur.

Therefore, an object of the present invention is to provide a shape measuring technique capable of performing highly accurate shape measurement by reducing the incident angle of reflected light with respect to a condenser lens.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0010]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

That is, the shape measuring apparatus of the present invention is a shape measuring apparatus which reflects a laser beam on a rotating mirror and scans the surface of an object to be measured, and after the reflected light from the object to be measured passes through a condenser lens. Aberration reducing means for reducing aberrations such as astigmatism and coma that occur are provided.

The aberration reducing means is at least two condenser lenses for condensing the reflected light from the object to be measured.

[0013]

According to the above-mentioned means, since the aberration reducing means for condensing the reflected light from the object to be measured, which comprises, for example, at least two condensing lenses, is provided, the incident angle of the reflected light with respect to the condensing lens can be adjusted. Can be made smaller.

Therefore, it is possible to reduce aberrations such as astigmatism and coma of the light condensed by the aberration reducing means (condenser lens).

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram showing the configuration and measurement principle of a shape measuring apparatus which is an embodiment of the present invention. Also, FIG.
FIG. 4 is a theoretical diagram showing the amount of displacement of the surface of the object to be measured in the shape measuring apparatus which is an embodiment of the present invention.

First, the configuration of the shape measuring apparatus of this embodiment will be described with reference to FIG. 1. A semiconductor laser 1 for emitting a laser beam and a beam diaphragm lens 2 for narrowing down the laser beam 1a emitted from the semiconductor laser 1 are described. And the collimated light 2a narrowed down by the beam diaphragm lens 2
A right-angle prism 3 for changing the optical path of the object, a rotary mirror 4 for scanning the collimated light 2a whose optical path is changed by the right-angle prism 3 with respect to the object 5 to be measured, and reflected lights 5a and 5b from the object 5 to be measured. It is composed of at least two condenser lenses (aberration reducing means) 6a, 6b for condensing and position detecting elements 7a, 7b for detecting the displacement of the surface of the DUT 5.

Next, the measurement principle of the shape measuring apparatus of this embodiment will be described with reference to FIG.

First, the laser beam 1a emitted from the semiconductor laser 1 is narrowed down by the beam diaphragm lens 2 and becomes collimated light 2a.

Further, the optical path of the collimated light 2a is changed by the rectangular prism 3.

Next, the collimated light 2 whose optical path has been changed
a is turned into a light projection beam 4a by the rotating mirror 4 such as a galvanometer, and the light projection beam 4a is the object 5 to be measured.
The surface is scanned one-dimensionally.

After scanning, the reflected lights 5a and 5b from the surface of the object to be measured 5 are at least 2 which are aberration reducing means provided on the left and right sides of the rotating mirror 4 in the beam scanning direction.
The light is condensed by the one of the two condenser lenses 6a and 6b, whichever is closer.

At this time, the reflected light 5a focused on the condenser lens 6a is focused on the position detecting element 7a, and the reflected light 5b focused on the condenser lens 6b is focused on the position detecting element 7b. It is imaged.

The reflected lights 5a, 5 from the object 5 to be measured
b is condensed by at least two condenser lenses 6a and 6b which are aberration reducing means, so that the condenser lens 6a, 6b is condensed more than the case where only one condenser lens is condensed.
The incident angle of the reflected lights 5a and 5b with respect to 6b becomes small, and it becomes possible to reduce the aberration of the condensed light.

Next, a calculation method for obtaining the displacement amount of the surface of the object 5 to be measured in the shape measuring apparatus of this embodiment will be described with reference to FIGS. 1 and 2.

The displacement amount is represented by a vertical distance D from the center 8 of the beam deflection (or the center 9 of the condenser lens) to the surface of the DUT 5 and a horizontal distance X of the DUT 5. Is.

Here, the beam projection angle of the projection beam 4a projected through the rotary mirror 4 such as a galvanometer is θ, the distance between the beam deflection center 8 and the condenser lens center 9 is A, and the condenser lens center 9 is When the distance between the position detection element light receiving surface 10 is B and the displacement of the image point on the position detection element 7 is C,
The displacement amount is D = (A * B * SINθ) / (B * CO
Sθ-C * SINθ), X = (A * C * SINθ) /
It is obtained by the calculation formula of (B * COSθ-C * SINθ).

As a result, the one-dimensional displacement amount of the surface of the object to be measured 5 can be measured by the calculation formula.

Further, by rotating or moving the object to be measured 5 or the shape measuring apparatus according to the present embodiment and sub-scanning, the numerical values (D and X) representing the displacement amount are combined, and the object to be measured 5 is measured. The surface shape of can be measured three-dimensionally.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, although the semiconductor laser is used as the irradiation source of the laser beam in this embodiment, the laser actually used may be a He-Ne laser.

Further, although the rotary mirror in this embodiment uses a galvanometer, a polygon mirror can be used to realize higher speed beam scanning.

[0032]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.
It is as follows.

(1). Since the aberration reducing means for condensing the reflected light from the object to be measured, for example, at least two condensing lenses are installed, the incident angle of the reflected light on the condensing lens becomes small, so that the condensed light is collected. Astigmatism, coma, and other aberrations are reduced, and highly accurate shape measurement can be realized.

(2). The aberration reducing means is at least 2
Since two condenser lenses are installed, highly accurate shape measurement can be realized without increasing the size of the entire apparatus.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration and a measurement principle of a shape measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a theoretical diagram showing the amount of displacement of the surface of the object to be measured in the shape measuring apparatus which is an embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor Laser 1a Laser Beam 2 Beam Stop Lens 2a Collimated Light 3 Right Angle Prism 4 Rotating Mirror 4a Projected Beam 5 DUT 5a, 5b Reflected Light 6a, 6b Condenser Lens (Aberration Reduction Means) 7a, 7b Position Detection Element 8 Beam shake center 9 Condenser lens center 10 Position detection element light receiving surface θ Beam projection angle A Distance between beam shake center and condensing lens center B Distance between condensing lens center and position detecting element light receiving surface C Position detecting element Image point displacement D Vertical distance from the center of beam deflection to the surface of the measured object X Horizontal distance of the measured object

Claims (3)

[Claims] 1. A method for scanning a laser beam on a measured object to measure the shape of the measured object in a non-contact manner, wherein the laser beam is scanned by a rotating mirror to remove the measured object from the measured object. The reflected light of the above is imaged on each position detecting element through at least two condenser lenses, and the calculation is performed from the projection angle of the laser beam and the position of the image forming point of the reflected light on the position detecting element. A shape measuring method, which comprises deriving a shape of a surface of the object to be measured. 2. A device for measuring the shape of the object to be measured in a non-contact manner by scanning the object to be measured with a laser beam, the rotating mirror scanning the laser beam, and the object to be measured. A shape measuring device comprising: an aberration reducing means for reducing the aberration of the reflected light from and a position detecting element for detecting the amount of displacement of the surface of the object to be measured. 3. The shape measuring apparatus according to claim 2, wherein the aberration reducing means is at least two condenser lenses for condensing reflected light from the object to be measured.