JPH06317405A - Laser displacement gauge - Google Patents

Abstract

PURPOSE:To provide a laser displacement gauge which can flexibly cope with two- direction scanning at a high speed by using the same light receiving unit. CONSTITUTION:In a light emitting optical system, a first and second scanning optical systems 10 and 13 obliquely scan two optical paths in parallel with the orthogonal two axes of a measuring stage 1 from upper positions of the measuring surface of the stage 1 by scanning a laser beam with a scanner 4 and expanding the laser beam to a required beam diameter, and then, converging the expanded beam to a required beam diameter through an ftheta lens 6. In addition, the scanning speed is made constant and the optical paths are switched to between a direct advancing direction and 90 deg. direction by means of an optical, patch switching mechanism 7. In a light receiving optical system, in addition, a light receiving unit 16 constituted of a condenser lens 14 which is positioned in the regular reflecting direction of the optical system 10 and receives reflected light and a photoreceptor element 15 which is positioned to the image forming position of the lens 14 and receives reflected light is switched between the light receiving positions of the systems 10 and 13 by means of a light receiving position switching mechanism 18 by changing the reflecting direction of the system 13 to the direction parallel to the regular reflecting direction of the system 10 by means of a reflecting mirror 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser displacement meter,
In particular, the present invention relates to a laser displacement meter for measuring the shape of an object for which the scanning direction needs to be switched to the XY two directions depending on the measurement location of the IC lead.

[0002]

2. Description of the Related Art A conventional laser displacement meter will be described with reference to the drawings.

FIG. 4 is a perspective view of an optical system showing a conventional laser displacement meter.

This laser displacement meter is equipped with a scanning optical meter for scanning an IC, which is a measurement object 55 placed on a measurement stage 50 having a uniaxial stage.

This scanning optical system comprises a laser 51, a beam expander 52 for expanding the beam diameter of the laser 51 to a required beam diameter, and a laser beam of a measuring stage 50 from directly above the measuring stage 50. A galvano mirror 53 for scanning in a direction orthogonal to the feed direction, and an fθ lens for converging the laser beam scanned by the galvano mirror 53 to a required beam diameter on the measurement surface of the measuring stage 50 and scanning at a constant speed. 54
Have and.

Of the reflected light of the scanned laser light of the object to be measured 55, a part of the light reflected in the direction orthogonal to the scanning direction is condensed by the condenser lens 57 from diagonally above, and the condenser lens 5
The laser light that has passed through 7 is condensed in the scanning direction by the cylindrical lens 58, and this laser light is further condensed by the condenser lens 57.
Then, the light is received by the light receiving element 59 placed at the imaging position of the cylindrical lens 58.

FIG. 5 is a plan view for explaining the principle of measuring the height of the measuring object 55 shown in FIG.

Laser light is applied to the object 55 to be measured from directly above, and reflected light from the object 55 to be measured is passed through a condenser lens 57 in a direction inclined by an angle θ from the incident direction of the laser, and a light receiving element 59.
When the light is received at, when the magnification of the condenser lens 57 is m,
Height t of measuring object 55 and distance d on light receiving element 59
The relationship between (the distance between the light receiving position of the reflected light from the height t and the light receiving position of the reflected light from the surface of the measurement table 50) is given by t = d / (m × sin θ). Therefore, the height of the measuring object 55 can be measured by measuring the displacement of the light receiving position on the light receiving element 59.

FIG. 6 is a plan view for explaining the relationship between the measurement position and the scanning direction by the laser displacement meter of FIG.

When measuring the lead shape of the IC 61, usually high resolution is required in the lead arrangement direction, but since the lead direction is relatively low resolution, optical scanning is performed in the lead arrangement direction in order to realize high speed measurement. The method of sending to the stage is taken. That is, as shown in FIG. 6A, when measuring the lead shape in the vertical direction of the IC 61, optical scanning is performed in the X direction 62, and the stage is fed in the direction 63 orthogonal to this to perform measurement.

Further, as shown in FIG. 6 (b), when measuring the lead shape of the IC 61 in the left-right direction, optical scanning is performed in the Y direction 65, and the stage is fed in the direction 64 orthogonal to this to perform measurement.

Therefore, in the conventional laser displacement meter shown in FIG. 4, since the scanning direction is limited to one direction, in order to measure the four sides of the IC 61, the laser displacement meter shown in FIG.
It was necessary to use two sets for the measurement in the Y2 direction or add a rotating mechanism for rotating the measured object or the entire laser displacement meter by 90 degrees.

In addition to the IC lead shape measurement, in the shape measurement of the mounted component, the adjacent component may block the irradiation laser beam depending on the scanning direction, and there is an example in which the scanning direction is changed and the measurement is performed again. .

[0014]

The above-mentioned conventional laser displacement meter has a limited scanning direction, so that when the IC lead is required to be scanned in two XY directions, the object to be measured or the optical head. It is necessary to rotate any one of them 90 degrees or prepare two optical heads of the same type.
If the object to be measured or the optical head is large, a large rotating mechanism is required, and the device becomes large and expensive. Further, the optical head is often a precision assembly component such as a lens, and there is a danger in practical use because there is a risk that shock and vibration at the time of rotational movement may induce positional displacement.

Further, when XY bidirectional scanning is performed by one optical head, usually two light receiving optical systems are required, which is expensive, and since the characteristics of both are different, a means for calibrating both and guaranteeing a measured value is provided. is necessary.

[0016]

The laser displacement meter of the present invention comprises (a) a measuring stage having a biaxial stage;
(B) A laser, a scanner for scanning the laser beam, a beam expander for expanding the laser beam to a required beam diameter, and a laser beam expanded by the beam expander for the required beam diameter on the measurement surface of the measuring stage. The fθ lens that converges on the optical axis and keeps the scanning speed constant, the optical path switching mechanism that switches the optical path of the laser light that has passed through the fθ lens to the straight and 90 degree directions, and the straight light in the two optical paths that are switched by the optical path switching mechanism. A first scanning optical system composed of a plurality of mirrors for scanning parallel to one axis (hereinafter referred to as the X direction) of the measurement stage from obliquely above the measurement surface of the measurement stage, and another for switching by an optical path switching mechanism A direction (Y direction) in which the laser light on the optical path (90 degree direction) is orthogonal to the scanning direction of the first scanning optical system.
A light projecting optical system having a second scanning optical system composed of a plurality of mirrors for scanning, and (c) a light collecting unit which is placed in the regular reflection direction of the first scanning optical system and receives reflected light. Reflection direction of the laser beam emitted from the second scanning optical system placed above the measurement stage and the light receiving unit that is placed at the image forming position of the lens and the condenser lens and receives the reflected light. And a light receiving position switching mechanism for switching the light receiving unit between a light receiving position of the first scanning optical system and a light receiving position of the second scanning optical system. A light-receiving optical system having
(D) A signal processing circuit for reading the output of the light receiving element at a constant sampling time in synchronization with the scanning of the scanner and calculating the height from the light receiving position by the triangulation method.

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a perspective view of an optical system showing an embodiment of a laser displacement meter according to the present invention. The optical system of this laser displacement meter includes a projection optical system that scans a laser beam onto a measurement object 2 placed on a measurement stage 1 having a biaxial stage, and a laser beam scanned by this projection optical system. The light receiving optical system for receiving the reflected light from the object to be measured.

This projection optical system measures a laser 3, a scanner 4 for scanning the laser beam, a beam expander for expanding the laser beam to a required beam diameter, and a laser beam expanded by the beam expander 5. An fθ lens 6 that converges a required beam diameter on the measurement surface of the stage 1 and keeps the scanning speed constant;
The optical path switching mechanism 7 that switches the optical path of the laser light that has passed through the θ lens 6 to the straight direction and the 90 degree direction, and the straight traveling light in the two optical paths that are switched by the optical path switching mechanism 7 is diagonally above the measurement surface of the measurement stage 1. To two mirrors 8 for scanning parallel to one axis (hereinafter referred to as X direction) of the measurement stage 1,
The first scanning optical system 10 constituted by 9 and the laser beam of another optical path (90 degree direction) switched by the optical path switching mechanism 7 are orthogonal to the scanning direction of the first scanning optical system 10 (Y direction). And a second scanning optical system 13 composed of two mirrors 11 and 12 for scanning.

The light receiving optical system is a condenser lens 14 placed in the regular reflection direction of the first scanning optical system 10 for receiving the reflected light.
The light receiving element 15 placed at the image forming position of the condenser lens 14 and receiving the reflected light (hereinafter, the condenser lens 14 and the light receiving element 15 are collectively referred to as a light receiving unit 16) is placed above the measuring stage 1 A folding mirror 17 for changing the reflection direction of the laser light emitted by the scanning optical system 13 to a direction parallel to the regular reflection direction of the first scanning optical system 10, and the light receiving unit 1.
Light receiving position switching mechanism 1 for switching 6 to the light receiving position of the first scanning optical system 10 and the light receiving position of the second scanning optical system 13.
8 and.

FIG. 2 is a plan view for explaining the light receiving position switching mechanism 18 of FIG.

The laser light 19 is first switched by the optical path switching mechanism 7 to a straight light and 90 degrees rightward. The straight light changes its optical path to the right by 90 ° by the mirror 8 and is reflected by the mirror 9 to scan the measurement surface in the X direction 20. The laser beam scanned in the X direction 20 is reflected to the right and received by the condenser lens 14 to form an image on the light receiving element 15. On the other hand, the laser light whose optical path has been changed to the right by 90 degrees by the optical path switching mechanism 7 changes its optical path downward by the mirror 11 and is reflected by the mirror 12 to scan the measurement surface in the Y direction 21. Here, by making the optical path lengths of the two optical paths switched by the optical path switching mechanism 7 equal to the measurement surface, the first and second scanning conditions can be made the same. The laser beam scanned in the Y direction 21 is reflected downward, but is reflected by the mirror 17 to change the optical path to the right. That is, it is parallel to the direction of the reflected light in the first scan. Therefore, by horizontally moving the light receiving unit 16 to the lower left by the light receiving position switching mechanism 18 to equalize the light receiving distance, light can be received under the same conditions as the first scanning optical system.

FIG. 3 is a block diagram of a general signal processing circuit when a PSD is used for the light receiving element 15 of FIG.

Two outputs of PSD 22 (A and B)
Are amplified by the preamplifier 23 and the preamplifier 23, respectively,
The light receiving position of the PSD 22 is obtained by performing the normalization ((A−B) / (A + B)) by the divider 24, and the height of the object to be measured is calculated from the variation of the light receiving position by the triangulation method.

[0025]

As described above, the laser displacement meter of the present invention is capable of performing laser scanning from two directions orthogonal to each other by the optical path switching mechanism and switching the position of the light receiving optical system by a simple linear movement. Since light can be received by the same light receiving unit, it can respond flexibly and at high speed even to the measurement object that needs to change the scanning direction depending on the measurement location, and one light receiving unit can support both scans by simple optical path switching. Therefore, the device cost including signal processing can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical system showing an embodiment of a laser displacement meter according to the present invention.

FIG. 2 is a plan view for explaining a light receiving position switching mechanism 18 of FIG.

FIG. 3 is a block diagram of a general signal processing circuit when a PSD is used for the light receiving element 15 of FIG.

FIG. 4 is a perspective view of an optical system showing a conventional laser displacement meter.

5 is a plan view for explaining the principle of measuring the height of the measuring object 55 in FIG.

FIG. 6 is a plan view for explaining the relationship between the measurement location and the scanning direction by the laser displacement meter of FIG. FIG. 6 (a),
FIG. 6B is a plan view for explaining the measurement of the lead shape in each scanning direction.

[Explanation of symbols]

 1,50 Measurement Stage 2,55 Measurement Object 3,51 Laser 4 Scanner 5,52 Beam Expander 6,54 fθ Lens 7 Optical Path Switching Mechanism 8, 9, 11, 12 Mirror 10 First Scanning Optical System 13 Second scanning optical system 14,57 Condensing lens 15,59 Light receiving element 16 Light receiving unit 17 Folding mirror 18 Light receiving position switching mechanism 19,60 Laser light 20 X direction 21 Y direction 22 PSD 23,23 Preamplifier 24 Divider 53 Galvano mirror 58 Cylindrical lens 61 IC 62,65 Optical scanning direction 63,64 Stage feed direction

Claims (1)

[Claims] 1. A measuring stage having (a) a biaxial stage, (b) a laser, a scanner for scanning a laser beam from the laser, and a beam expander for expanding the laser beam to a required beam diameter. , An fθ lens that converges the laser beam expanded by the beam expander to a required beam diameter on the measurement surface of the measurement stage and keeps the scanning speed constant, and a straight path in the optical path of the laser light that has passed through the fθ lens And an optical path switching mechanism for switching in the 90-degree direction, and straight traveling light in two optical paths switched by the optical path switching mechanism obliquely above the measurement surface of the measurement stage from one axis of the measurement stage (hereinafter referred to as the X direction). And a first scanning optical system composed of a plurality of mirrors for scanning in parallel with each other, and a laser beam of another optical path (90 degree direction) switched by the optical path switching mechanism of the first scanning optical system. A projection optical system having a second scanning optical system composed of a plurality of mirrors for scanning in a direction (Y direction) orthogonal to the scanning direction; and (c) the first scanning optical system. A light receiving unit, which is placed in the direction of specular reflection and includes a condenser lens for receiving reflected light and a light receiving element for receiving reflected light, which is placed at the image forming position of the condenser lens, and is placed above the measurement stage to provide the light receiving unit. A folding mirror for changing the reflection direction of the laser light emitted by the second scanning optical system to a direction parallel to the regular reflection direction of the first scanning optical system, and the light receiving unit for the light receiving position of the first scanning optical system. And a light receiving position switching mechanism for switching to the light receiving position of the second scanning optical system, and (d) the output of the light receiving element is read at a fixed sampling time in synchronism with the scanning of the scanner to form a triangle from the light receiving position. Surveying Laser displacement gauge which comprises a signal processing circuit for calculating the height at.