JP3058298B2 - Displacement sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement sensor for detecting a displacement of an object to be measured.

[0002]

2. Description of the Related Art An example of a conventional displacement sensor for detecting a displacement of an object to be measured is shown in FIGS. FIG.
, A laser diode LD3, which is a light emitting means, is provided on a base 1 via a first support member 2, and a Fresnel lens which irradiates the object 4 almost vertically with the light emitted from the LD3 as parallel light. And a light projecting lens 5. A position detecting element (PSD) 7 as a position detecting means is provided on the base 1 via a second support member 6 with its light receiving surface parallel to the optical axis of the LD 3.

The scattered light reflected from the object to be measured 4 is condensed by a light receiving lens 8 formed of a Fresnel lens integrally with the light projecting lens 5, and is incident on a light receiving surface of a PSD 7. . Each of the above-described members is housed in a case 9 provided on the base 1. A transparent glass 10 through which incident light and reflected light are transmitted is provided on the upper surface of the case 9.
Is provided.

In the conventional displacement sensor having the above-described structure, the center of the light receiving lens 8 is set to C as shown in FIG.
If the device under test 4 is displaced from the position of the symbol B to the position of the symbol A, the reflected light is reflected on the PSD 7 by the symbol b
Is moved from the position to the position of the symbol a. At this time, since the optical axis of the LD 3 and the light receiving surface of the PSD 7 are parallel, the triangle A
BC and triangle abc have similar shapes. Therefore AB / a
b is always constant, and the output from PSD 7 is
Is linear with respect to the displacement of As a result, the linear correction circuit becomes unnecessary.

[0005]

However, according to the displacement sensor described above, the light emitted from the LD 3 is not reflected by the object 4 to be measured.
, The reflected light returns to the LD 3 again when the DUT 4 has a mirror surface, does not enter the PSD 7, and the displacement of the DUT 4 cannot be detected. .

The present invention has been made in view of such a situation, and is intended to detect even a displacement of an object having a mirror surface with a linear output.

[0007]

According to a first aspect of the present invention, there is provided a displacement sensor, comprising: an LD as a light emitting element for projecting detection light obliquely onto a surface of the object to be measured; The pinhole 11 as a beam diameter limiting unit for transmitting the reflected light reflected by the beam with limiting its beam diameter.
And a PSD 7 serving as a light position detector that receives the reflected light passing through the pinhole 11 and whose light receiving surface is parallel to the optical axis of the detection light.

The displacement sensor according to claim 2 is an LD for projecting detection light obliquely to the surface of the object 4 to be measured.
3, the light reflected by the surface of the object 4, the bi
A beam diameter limiting section for the passage to restrict the over beam diameter
The light receiving surface is arranged in parallel with the normal axis of the surface of the device under test 4, and the PSD 7 receives reflected light passing through the pinhole 11.

The displacement sensor according to claim 3 is an LD for projecting detection light obliquely to the surface of the object 4 to be measured.
3, a light-receiving lens 8 as a light-collecting element for passing the light reflected on the surface of the object 4 and a light-receiving lens 8 arranged parallel to the normal axis of the surface of the object 4 And a PSD 7 for receiving the reflected light.

[0010] The displacement sensor according to the fourth aspect is the third aspect.
In the displacement sensor described in (1), a light receiving lens 8 as a light collecting element is disposed so that its optical axis is perpendicular to the optical axis of the detection light.

The displacement sensor according to the fifth aspect is the first aspect.
In the displacement sensor according to any one of the first to fourth aspects, a flat plate 41 interlocking with the actuator 42 is provided, and the flat plate 41 is a reflector that reflects light projected from the LD 3.

[0012]

According to the first aspect of the present invention, the displacement sensor projects detection light (projection light) obliquely from the LD to the surface of the object to be detected.
The reflected light that has passed through 1 is detected by the PSD 7 provided with the light receiving surface parallel to the optical axis of the detection light.

In the displacement sensor according to the second aspect, the detection light is projected obliquely from the LD 3 onto the surface of the object 4 to be detected.
The reflected light reflected by the surface of the object 4 and passing through the pinhole 11 is detected by the PSD 7 whose light receiving surface is arranged in parallel with the normal axis of the surface of the object 4.

According to a third aspect of the present invention, the displacement sensor causes the detection light to project obliquely from the LD to the surface of the object to be detected.
The reflected light reflected by the surface of the object 4 and passing through the light receiving lens 8 is detected by the PSD 7 whose light receiving surface is arranged in parallel with the normal axis of the surface of the object 4.

In the displacement sensor according to the fourth aspect, the detection light is projected obliquely from the LD 3 onto the surface of the object 4 to be detected.
The reflected light reflected by the surface of the object 4 and passing through the light-receiving lens 8 arranged so that the optical axis thereof is perpendicular to the optical axis of the detection light passes through the light-receiving surface to the surface of the object 4 to be measured. It is detected by the PSD 7 arranged in parallel with the normal axis.

According to a fifth aspect of the present invention, there is provided a displacement sensor.
In the displacement sensor according to any one of the fourth to fourth aspects, the reflected light reflected by the flat plate 41 interlocked with the actuator 42 is detected by the sensor 37 and the switch 44 is driven.

[0017]

FIG. 1 is a side view showing the structure of one embodiment of a displacement sensor according to the present invention. In FIG. 1, portions corresponding to those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted as appropriate. This embodiment is characterized in the pin hole 11 is the beam diameter limiting means for limiting the beam diameter of tilting the workpiece 4, and the reflected light so as to face the light receiving surface of PSD7 provided to the optical axis of the LD3 That is.

Next, the operation of the present embodiment will be described with reference to FIGS. It is assumed that the surface of the DUT 4 moves parallel to the positions indicated by the symbols L, M, and N due to the displacement.
The light emitted from the LD 3 irradiates the DUT 4 at different angles as represented by the projection beams 21 and 22 by the projection lens 5 and is focused on the surface 4M of the DUT 4 at the position of the symbol M. I will be scorched. Then, when the measurement object 4 is displaced by the projection beams 21 and 22, respectively, the surfaces 4L, 4M,
The light is reflected by 4N, and becomes reflected beams 21L, 21M, 21N and 22L, 22M, 22N.

Here, the reflected beams 21L and 2L indicated by oblique lines
The portion surrounded by 2N is a region where reflected light exists regardless of the position of the DUT 4 in any of L, M, and N. A pinhole 11 is provided in this area, and the reflected light enters the PSD 7 via the pinhole 11 as a thin beam.

Since the PSD 7 measures the center of gravity of the incident beam, the position of the incident beam can be detected with high accuracy even if the beam is spread to some extent. Therefore, a light receiving lens is not required, and only the pinhole 11 having an appropriate size may be provided. Since the light receiving surface of the PSD 7 is parallel to the optical axis of the LD 3, linear output is possible without a linear correction circuit as in the case of the conventional example shown in FIGS.

According to the displacement sensor of this embodiment, since the surface of the object 4 is inclined with respect to the optical axis of the LD 3, the reflected light is transmitted to the PSD 7 even if the surface of the object 4 is a mirror surface. Since the light can be incident and the optical axis of the detection light and the light receiving surface of the PSD 7 are substantially parallel to each other, the displacement of the measured portion can be detected with a linear output. Further, since a light receiving lens which has been conventionally required becomes unnecessary, the number of components can be reduced, and alignment can be made unnecessary, so that cost can be reduced.

FIG. 3 shows the structure of a displacement sensor according to a second embodiment of the present invention. In FIG. 3, portions corresponding to those of the embodiment shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In this embodiment, a mask 31 is provided on the front surface of the light projecting lens 5 provided on the light emitting surface of the LD 3, and the mask 31 is provided.
The pinhole 3 is located at the center of the LD3 located on the optical axis of the LD3.
2 is formed. Further, the case 9 at a position facing the light receiving surface of the PSD 7 is provided with an opening 33 into which the reflected light from the device under test 4 is incident.

Next, the operation of this embodiment will be described with reference to FIGS. The light emitted from the PD 3 becomes a parallel light projection beam 34 having a small beam diameter by the pinhole 32 and irradiates the DUT 4. At this time, the DUT 4 is L,
When displaced to the positions indicated by M and N, the respective reflected beams are reflected to the positions indicated by 34L, 34M and 34N. These beam positions are detected by the PSD 7.

According to the above embodiment, the same effect as that of the embodiment shown in FIG. 1 can be obtained. In addition, pinhole 1
The shapes of 1, 32 are not particularly limited.

FIG. 6 shows the structure of a displacement sensor according to a third embodiment of the present invention. In this embodiment, the LD 3 irradiates the DUT 4 obliquely, and the reflected light is received by the PSD 7 disposed in parallel with the normal 35 through the light receiving lens 8.

As shown in FIG. 5, the projected light beam
It has a finite size indicated by reference numerals 1 and 22 and focuses on a reference position indicated by symbol M.
Is reflected by the dotted line normal 35
They cross at the positions indicated by the symbols a and b above. As can be seen from the figure, the position of the DUT 4 can be regarded as being displaced on the normal axis.

Therefore, as shown in FIG.
If the light receiving surface of D7 is made parallel to the normal 35, then ABO and Δa
Bo is similar to that of bo, and linear output is possible without a linear correction circuit.

FIG. 6B shows another embodiment in which the position of the lens is not vertical but vertical as shown in FIG. 6A, and FIG. When the distance of the DUT 4 is short, the same performance can be obtained with the pinhole 11 instead of the light receiving lens 8.

In the above, the light condensed or collimated by the LD 3 or the like is projected on the object 4 and the reflected light is detected by the PSD 7.
Since the SD 7 measures the center of gravity of the incident light beam, if the projected light beam has an intensity distribution, it is affected by the intensity distribution, and the linearity of the sensitivity characteristic deteriorates.

To solve this problem, as shown in FIG. 7, the LD is passed through a diffusion plate 36 having a roughened surface of a transparent resin plate.
The projection light emitted from 3 and passed through the projection lens 5 may be diffused. With this arrangement, the beam intensity distribution of the projected light is made uniform by the diffusion plate 36, and stable sensitivity characteristics can be obtained even when the center of gravity of the beam is measured. FIG. 8A shows a case where the diffusion plate 35 is not used. The portion indicated by the symbol A is wavy, and the linear region is narrow. However, in the example where the diffusion plate 36 is used, as shown in FIG. There is no wavy portion and the linear region is wide.

In the above example, the mounting position of the LD 3 has been devised in order to irradiate the object 4 with the projection light obliquely. This makes it possible to perform position measurement even when the surface of the DUT 4 is a mirror surface. However, it is not economical to prepare both the sensor for the mirror surface and the sensor for the diffusion surface. Therefore, the device shown in FIG. 9 is designed so that the sensor for the diffusion surface can be used as it is for the mirror surface. Therefore, the adapter 38 is attached to the sensor 37 for the diffusion surface, and the adapter 38 is attached so that the upper surface of the adapter 38 becomes the measurement reference plane. The adapter 38 has a hole 38a for the LD 3 and a hole 38b for the pinhole 11, so that the projection light and the reflected light pass through those holes.

FIG. 9 (c) shows the result of measuring the position displacement of the silicon wafer which is a mirror surface in this way, and a good linear signal is obtained.

FIG. 10 shows still another embodiment, in which the optical axis 4 of the light-receiving lens 8 is shifted with respect to the optical axis of the projection light 39 which is the detection light.
0 is arranged vertically. With this configuration, the reflected light from the device under test 4 always has its PSD
7, the position of the PSD can be determined so that the light is focused on the light receiving surface of the PSD 7, and the resolution of the PSD 7 is improved, and high accuracy can be obtained.

FIG. 11 shows an application of the displacement sensor having the above-described structure, which is used, for example, for measuring the wear of the cutting edge of a drill, a cutting tool or the like. This is because the actuator 42 to which the flat plate 41 having the diffusion surface is attached is displaced as shown by a thick arrow by directly touching a detection target such as a drill or a cutting tool (not shown).
Numeral 2 moves against the force of the spring 43.

When the actuator 42 moves, a signal having the characteristic shown in FIG. 11B is obtained from the sensor 37 having the above-described structure. Figure 11 shows the displacement and output signal.
As shown in (b), the displacement is constant with respect to a certain output signal because of the linear relationship, and a certain value of this output signal,
For example, when V0 is determined, the displacement amount becomes the determined displacement amount d0, and the switch 44 can be turned on / off based on this value. FIG. 11C is a schematic diagram illustrating the detection direction of the displacement sensor.

[0036]

As described above, according to the displacement sensor of the first aspect, the optical axis of the light emitting means is inclined with respect to the surface of the object to be measured, and the reflected light is transmitted through the beam diameter limiting section. Since the light is received and the light receiving surface is arranged in parallel with the optical axis of the detection light, even if the surface of the object to be measured is a mirror surface, the displacement can be detected by a linear output with a simple configuration.

The displacement sensor according to claim 2, the optical axis of the light emitting means is inclined with respect to the surface of the object to be measured, bi reflected light
Light is received via the beam diameter limiter , and the light receiving surface is arranged parallel to the normal to the surface of the object. Thus, the position can be detected with high accuracy.

In the displacement sensor according to the third aspect, the optical axis of the light emitting means is tilted with respect to the surface of the object to be measured, the light is received via a light-collecting element for collecting reflected light, and the light-receiving surface is covered. Since it is arranged parallel to the normal line of the surface of the object, the detection sensitivity is improved, and even if the surface of the object to be measured is a mirror surface, its displacement can be detected with a linear output, and detection with good position accuracy is achieved. I can do it.

The displacement sensor according to the fourth aspect is the third aspect.
Is arranged so as to be perpendicular to the optical axis of the detection light, the reflected light from the object to be measured is always focused on the light receiving element, and a linear output is obtained.

In the displacement sensor according to the fifth aspect, the light projected from the light emitting element is reflected by the flat plate linked to the actuator, so that the displacement of the actuator can be detected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a displacement sensor according to the present invention.

FIG. 2 is a diagram showing a beam of the displacement sensor shown in FIG. 1;

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

FIG. 4 is a diagram showing a beam of the displacement sensor shown in FIG. 3;

FIG. 5 shows a problem of the device shown in FIG.

FIG. 6 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 8 is a diagram showing characteristics of the apparatus of FIG. 7;

FIG. 9 is a diagram showing a configuration of a fifth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a sixth embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a seventh embodiment of the present invention.

FIG. 12 is a diagram showing an example of a conventional displacement sensor.

FIG. 13 is a view for explaining the operation of the apparatus shown in FIG. 11;

[Explanation of symbols]

 Reference Signs List 1 base 2, 6 indicating member 3 LD (laser diode) 4 object to be measured 5 light projecting lens 7 PSD (position detecting element) 8 light receiving lens 9 case 10 transparent glass 11, 32 pinhole 21, 22 light beam 31 Mask 33 Opening 35 Normal 36 Diffusion Plate 37 Sensor 38 Adapter 39 Projection Light 40 Optical Axis 41 Flat Plate 42 Actuator 43 Spring 44 Switch

Continuation of the front page (56) References JP-U 4-113008 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01C 3/00- 3/32 H01H 35/00

Claims (5)

(57) [Claims] 1. A light emitting element for projecting detection light obliquely to a surface of a detection target, and a light diameter of a light reflected by the surface of the detection target.
A beam diameter limiting section for the passage to limit the are arranged so as the light-receiving surface is parallel to the optical axis of the detection light, the light position detector for receiving the reflected light passing through the beam diameter limiting section And a displacement sensor. 2. A light-emitting element for projecting detection light obliquely to the surface of a detection object, and a light beam reflected by the surface of the detection object having a beam diameter of
A beam diameter limiting section for the passage to limit the arranged parallel to the normal axis of the surface of the light-receiving surface is the detection object, an optical position detector for receiving the reflected light passing through the beam diameter limiting section And a displacement sensor. 3. A light-emitting element for projecting detection light obliquely to the surface of the detection target, a light-collecting element for collecting light reflected on the surface of the detection target, and a light-receiving surface. And a light position detector disposed parallel to a normal axis of the surface of the detection target and receiving the reflected light condensed by the light condensing element. 4. The displacement sensor according to claim 3, wherein the light-collecting element is arranged so that its optical axis is perpendicular to the optical axis of the detection light. 5. The displacement sensor according to claim 1, wherein a flat plate is provided in conjunction with the actuator, and the flat plate is a reflection plate for reflecting light projected from the light emitting element.