JP3058299B2 - 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 photoelectric conversion type displacement sensor used for detecting an amount of displacement of an object.

[0002]

2. Description of the Related Art Generally, a photoelectric conversion type displacement sensor using a light emitting element and an optical position detector is provided with a signal shape correction circuit in order to obtain a linear output signal. Become. For this reason, the applicant of the present application has proposed a displacement sensor that can obtain a linear output signal by devising the arrangement of the light emitting element and the optical position detector without first providing a signal shape correction circuit. .

As shown in FIG. 10, a light emitting device (L
D or LED) 1 is projected perpendicularly to the projection surface of the detection target 13. Further, the light receiving surface 3 of the light position detector 2 is arranged in parallel with the projection optical axis O,
The light receiving surface 3 is configured to receive the reflected light L2 reflected on the projection surface of the detection target 13.

According to such a configuration, the optical position detector 2
Since the incident position of the reflected light L2 on the light receiving surface 3 changes along the direction of the projection optical axis O with the displacement of the detection target 13, the output voltage of the light position detector 2 changes proportionally accordingly. , A linear output signal is obtained. Conventionally, such a displacement sensor condenses the projection light L1 projected by the light-emitting element 1 with a condenser lens (formed on one side of the Fresnel lens 4) to form a small-diameter parallel light. Is projected on. Further, the reflected light L2 reflected by the reflected light of the detection target 13 is made incident on the light receiving surface 3 of the optical position detector 2 via a light receiving lens (formed on the other side of the Fresnel lens 4).

[0005] Thus, the projection light L projected by the light emitting element 1
Since the light-emitting element 1 needs to be brought close to the condenser lens in order to make the parallel light of a small diameter by the condenser lens, the light-emitting element 1 is mounted via the heat sink block 6. A bonding wire 8 is provided between the light emitting element 1 and the substrate 5.
It is wired with.

Further, the optical position detector 2 cannot be directly mounted on the substrate 5 because it needs to be disposed parallel to the projection optical axis O. Therefore, the optical position detector 2 is attached to the substrate 5 via the L-shaped bracket 7. Have been. Bonding wires 9 and 10 are provided between the optical position detection base 2 and the substrate 5.

Reference numeral 11 in the drawing denotes a sensor main body, and reference numeral 12 denotes a light emitting plate attached to a projection light receiving opening of the sensor main body.

[0008]

However, in such a conventional displacement sensor, a heat sink block 6 is required to mount the light emitting element 1 on the substrate 5, and the optical position detector 2 is mounted on the substrate 5. This requires an L-shaped bracket or a light receiving lens, which increases the number of sensor components. In addition, the light emitting element 1 has a heat sink block 6
A die bond is required, and the optical position detector 2 is L
In addition to the need for die bonding to the metal fitting 7 and the need for wire bonding, there has been a problem that the assembly process of the sensor is significantly complicated.

A condenser lens for the projection light L1 and a reflected light L
The Fresnel lens 4 which is the light receiving lens of No. 2 is
It is also necessary to adjust the alignment with respect to the optical position detector 2. Generally, the assembly process of the conventional displacement sensor is
1) die bonding of the optical position detector 2 to the L-shaped bracket 7 attached to the substrate 5; 2) wire bonding to the optical position detector 2; 3) adhesion of the heat sink block 6 to the substrate 5; Die bonding of light emitting element 1 to block, 5) wire bonding to light emitting element 1, 6) alignment adjustment of Fresnel lens 4, 7)
It is performed in the order of cancellation.

Accordingly, the present invention has been made in view of the above-mentioned circumstances, and aims to reduce the number of sensor components and simplify the sensor assembly process.

[0011]

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 substantially perpendicular to a surface of a detection target; A pinhole 24 for passing the reflected light, and a PSD 22 as an optical position detector for receiving the reflected light passing through the pinhole, the light receiving surface being arranged so as to be parallel to the optical axis of the detection light. It is composed of

According to a second aspect of the present invention, there is provided a displacement sensor which emits detection light substantially perpendicularly to a surface of a detection target, and an LD as a light emitting element, and transmits the reflection light reflected on the surface of the detection target. And a PSD 22 as an optical position detector that receives the reflected light passing through the pinhole 24 and whose light receiving surface is perpendicular to the optical axis of the detection light.

According to a third aspect of the present invention, there is provided the displacement sensor according to the first or second aspect, wherein a flat plate is provided in conjunction with the actuator, and the flat plate is a reflecting plate for reflecting the light projected from the light emitting element. It is characterized by.

[0014]

In the displacement sensor according to the first aspect, light projected substantially perpendicularly to the surface of the detection target 16 from the LD 20 is reflected by the surface of the detection target 16 and passes through the pinhole 24. Later, the light is received by the PSD 23 arranged so that the light receiving surface is parallel to the optical axis of the projection light. Thus, the displacement of the detection target 16 is detected.

The displacement sensor according to claim 2 is an LD20.
Is reflected from the surface of the detection target 16 substantially perpendicularly to the surface of the detection target 16, and after passing through the pinhole 24, the light receiving surface becomes perpendicular to the optical axis of the projection light. Is received by the PSD 23 arranged as described above. Thus, the displacement of the detection target 16 is detected.

The displacement sensor according to claim 3 is an LD20.
Is reflected by the flat plate 30 interlocked with the actuator 31, whereby the amount of movement of the actuator 31 is detected.

[0017]

1 is a longitudinal sectional side view showing an embodiment of a displacement sensor according to the present invention, and FIG. 2 is an exploded perspective view. On one side of the sensor main body 15, a circular through hole 18 is formed in a vertical direction with respect to the projection surface 17 of the detection target 16, and
On the other side of the sensor main body 15, a square-shaped concave portion 19 opening downward is formed. A light emitting element 20 made of a semiconductor laser (LD) is mounted on one end of the through hole 18, and a condenser lens (convex lens) 21 for focusing on a predetermined position is mounted on the other end.

The projection light L3 projected by the light emitting element 20 is projected perpendicularly onto the projection surface 17 of the detection target 16, and the above-mentioned condenser lens 21 is arranged on the projection optical axis O. A light position detector (PSD) 22 is mounted in the concave portion 19. The light receiving surface 23 of the optical position detector 22 has a projection optical axis O
And are arranged in parallel. The reflected light L4 reflected on the projection surface 17 of the detection target 16 is
The light enters the light receiving surface 23 via the circular pinhole 24 of FIG.

The light emitting element 20 and the light position detector 22 are mounted on the stem 25 and the lead frame 26, and have been completed up to wire bonding. And
Each leg of the stem 25 and the lead frame 26 is
Is fixed to the substrate 27 by inserting it into the holes 28 and 29. In the case of the present displacement sensor, the projection light L3 projected by the light emitting element 20 is focused on a predetermined position by a condenser lens 21.
Is projected onto the projection surface 17 of the detection target 16. When the detection target 16 is displaced within a predetermined range, the projection surface 1
The reflected light 14 from 7 surely passes through the pinhole 24 and enters the light receiving surface 23 of the light position detector 22 with a small diameter.

FIG. 3 shows a measurement result of an output signal obtained from the displacement sensor. In this displacement sensor, the detection target 16
In the range of 4 mm to 7 mm, a good linear output signal was obtained. The resolution was also as good as ± 8 μm as compared with the noise level measurement.

In this displacement sensor, the number of parts can be reduced because the light receiving portion is only a pinhole and does not require a lens.
In addition, when mounting the light emitting element 20 and the optical position detector 22, only an assembly in which die bonding and wire bonding are already small is assembled, so that the assembly process can be significantly simplified.

FIG. 4 shows a displacement sensor according to a second embodiment of the present invention. In the case of the present displacement sensor, a light emitting diode (LED) in which a condenser lens that focuses on a predetermined position is integrated is used as the light emitting element 30, and the number of components is reduced.
Other configurations are the same as those of the displacement sensor of the first embodiment.

In the structures of the first and second embodiments, as shown in FIG. 5, since .DELTA.ABO and .DELTA.abo are in a proportional relationship, the distance m between the projection optical axis O and the pinhole 24, the pinhole The distance M between the PSD 24 and the PSD light receiving surface 23 is the distance from the detection target 13 to the pinhole 24, h,
Assuming that the distance from No. 4 to the center concave portion of the PSD light receiving surface is H, the following relationship is established. (H / M) = (h / m) Therefore, one pinhole and one PSD can detect only a specific narrow range.

Therefore, as shown in FIG. 6, PSDs 22 a and 22 b are arranged in parallel with the projection optical axis O with respect to one pinhole 24, and are arranged vertically on the inner wall of the recess 19. Also,
FIG. 7 shows an example in which the two pinholes 24a and 24b are at different distances with respect to the projection optical axis O. When the detection target 13 is near the symbol A, the PSD 22a is used. Is an example in which detection is performed by the PSD 22b.

With this configuration, the detection target 13 can be detected by the PSD 22a when it is near the symbol A, and by the PSD 22b when it is near the symbol B. Since the detection area is separately received and received, the total As a result, it is possible to detect a wide range. Further, since the detection range can be determined depending on which PSD is used for detection, the detection area is equivalently adjusted. In this case, two PSDs are used, but the number may be larger, and in the example of FIG. 6, the PSDs are arranged on a straight line with respect to the light source, but need not necessarily be on a straight line.

As shown in FIG. 7, for example, as shown in FIG. 7, light incident on the PSD is incident at a certain angle, so that the obtained photocurrent is limited. Also,
If the detection distance is to be increased, the structure shown in FIG.
It is necessary to maintain a similarity relationship between the sensor body and ｏabo, and the length of the sensor body in the lateral direction becomes longer, and the shape becomes larger.

Therefore, as shown in FIG. 8, the light receiving surface of the PSD 22 is disposed so as to be substantially perpendicular to the optical axis of the reflected light L4. In this example, the PSD 22 is attached to the substrate 27 so as to be substantially perpendicular to the optical axis of the reflected light L4.

With such a configuration, the light incident on the PSD 22 is substantially perpendicular to the light receiving surface of the PSD 22, so that the obtained photocurrent is also large. And P
Since the measurement position can be made closer or farther only by moving the position of the SD 22 right and left, it is possible to cope with an increase in the detection distance without increasing the size of the sensor body.

FIG. 9 shows an application of the displacement sensor having the structure shown in FIG. 9A, which is used, for example, for measuring the wear of the cutting edge of a drill or a cutting tool. This is a flat plate 3 with a diffusion surface
The actuator 31 attached with “0” directly touches a detection target such as a drill or a cutting tool (not shown). As a result, the actuator 31 moves against the force of the spring 32.

When the actuator 31 moves, a signal having the characteristics shown in FIG. 9B is obtained from the sensor 32 having the above-described structure. Since the displacement amount and the output signal have a linear relationship, the displacement amount for a certain output signal becomes constant. When a certain value of this output signal, for example, V0 is determined, the displacement amount becomes a fixed displacement amount d0, and the switch 33 is turned on by this value. / Off. FIG. 9C is a schematic diagram illustrating the detection direction of the displacement sensor.

[0031]

As described above, according to the displacement sensor of the first aspect, since the light receiving surface of the light receiving element is disposed in parallel with the optical axis of the light emitting element, the light receiving lens is not required, and the structure is not required. Is simplified.

According to the displacement sensor of the present invention, since the light receiving surface of the light receiving element is disposed substantially perpendicular to the reflected light from the detection object, the photocurrent obtained from the light receiving element increases and the detection current increases. This has the effect that the shape does not increase even if the distance increases.

According to the displacement sensor of the third aspect, the light projected from the T light emitting element is reflected by the flat plate interlocking with the actuator, so that the movement amount of the actuator can be detected. Have.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view of the displacement sensor shown in FIG.

3 is a graph showing an example of output signal characteristics of the displacement sensor shown in FIG.

FIG. 4 is a sectional view showing a second embodiment of the displacement sensor according to the present invention.

FIG. 5 is a cross-sectional view for explaining a problem.

FIG. 6 is a sectional view showing a third embodiment of the displacement sensor according to the present invention.

FIG. 7 is a sectional view showing a fourth embodiment of the displacement sensor according to the present invention.

FIG. 8 is a sectional view showing a fifth embodiment of the displacement sensor according to the present invention.

FIG. 9 shows a sixth embodiment of the displacement sensor according to the present invention.

FIG. 10 is a sectional view showing an example of a conventional displacement sensor.

[Explanation of symbols]

 1, 20, 30 Light emitting elements L1, L3 Projection light L2, L4 Reflected light 2, 22 Optical position detector 3, 23 Light receiving surface 4 Condensing lens (Fresnel lens) 5, 27 Substrate 6 Heat sink block 7 Metal fitting 8, 9, REFERENCE SIGNS LIST 10 Bondin wire 11 Sensor main body 12 Light emitting plate 13 Object to be detected 15 Sensor main body 16 Object to be detected 17 Projection surface 18 Through hole 19 Concave 21 Condenser lens (convex lens) 24 Pinhole 25 Stem 26 Lead frame 28, 29 Hole O Projection Optical axis 30 Flat plate 31 Actuator 32 Sensor 33 Switch

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuyuki Hayami 10 Hanazono Dodocho, Ukyo-ku, Kyoto-shi, Kyoto OMRON Corporation Field (Int.Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01C 3/00-3/32 H01H 35/00

Claims (3)

(57) [Claims] 1. A light emitting element for projecting detection light substantially perpendicularly to a surface of a detection target, a pinhole for passing light reflected by the surface of the detection target, and a light receiving surface. And a light position detector that is disposed so as to be parallel to the optical axis of the detection light and receives the reflected light that has passed through the pinhole. 2. A light-emitting element for projecting detection light substantially perpendicularly to a surface of a detection target, a pinhole for passing light reflected by the surface of the detection target, and a light-receiving surface. And a light position detector which is disposed so as to be perpendicular to the optical axis of the detection light and receives the reflected light passing through the pinhole. 3. 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.