JPH0666596A - Optical displacement detector - Google Patents

Abstract

PURPOSE:To reduce a manufacturing cost of a moving plate formed in a condensing lens zone and to improve its reliability. CONSTITUTION:An optical displacement detector comprises a moving plate 1 to be displaced along a plane, a fixed light source 4 for irradiating the plate 1 with an incident light, and a fixed photoreceiver 5 disposed oppositely to the source 4. A lens zone 3 is extended on the plate 1, and when it is displaced, an effective incident light 8 is condensed to generate a moving image 10. The photoreceiver 5 has a photoreceiving surface 6 disposed along a moving direction of the image 10, and outputs a moving plate displacement detection signal from the image photoreceiving position. A pair of prism zones 7 disposed in parallel along both edges of the zone 3 are provided, a invalid incident light 11 or a peripheral indecent light is refracted to the outside out of the surface 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement detecting device. More specifically, the present invention relates to a moving plate structure of an apparatus in which a disc-shaped moving plate that is rotationally displaced is interposed between a fixed light source and a fixed light receiving element, and the displacement is optically detected.

[0002]

2. Description of the Related Art As a conventional optical displacement detecting device, a structure in which a continuous slit is formed on a moving plate is known, and is disclosed in, for example, Japanese Patent Laid-Open No. 60-225024. As shown in FIG. 3, the disc-shaped moving plate 101 is rotationally displaced about the rotation shaft 102. A spiral continuous slit 103 is formed on the surface along the circumferential direction. The fixed light source 104 and the fixed light receiving element 105 are arranged to face each other via the moving plate 101. Light receiving element 10
The light receiving surface 106 of No. 5 is linearly provided along the radial direction of the moving plate 101.

The operation will be briefly described with reference to FIG. The light receiving position of the light transmitted through the slit 103 changes as the movable plate rotates. The light receiving element 105 outputs a detection signal according to the light receiving position. The rotation angle of the moving plate 101 and the detection signal have a linear relationship, and the rotation displacement is detected. In order to improve the detection accuracy and increase the resolution, it is necessary to narrow the width of the slit 103. However, if the slit width is reduced, the amount of transmitted light decreases and the S /
The N ratio deteriorates.

FIG. 5 shows another conventional example. This is disclosed in, for example, Japanese Patent Laid-Open No. 62-122223. A slanting cylindrical lens 202 is formed on the surface of the moving plate 201 which is linearly displaced. The fixed light source 203 and the fixed light receiving element 204 are arranged to face each other via the moving plate 201. The light receiving surface 205 is linearly provided so as to be orthogonal to the displacement direction of the moving plate 201. An arithmetic circuit 206 is connected to the pair of differential output terminals of the light receiving element 204.

This conventional example is characterized in that a cylindrical lens 202 is used in place of the slit 103 of the previous conventional example shown in FIG. The cylindrical lens 202 collects light emitted from the light source 203 and forms an image on the light receiving surface 205.
07 is generated. The image formation 207 moves in the orthogonal direction with the linear displacement of the moving plate 201. Compared with the case where the slit is used, the cylindrical lens 202 has a condensing function, and therefore, an advantage that the amount of received light is increased can be obtained. The light receiving element 204 outputs a pair of output signals A and B which differentially change according to the light receiving position of the image formation 207. The arithmetic circuit 206 performs (AB) / (A + B) arithmetic processing and outputs a detection signal corresponding to the displacement or position of the moving plate 201.

[0006]

The problem to be solved by the present invention will be briefly described with reference to FIG. The moving plate 201 is generally made of a transparent resin material, and the cylindrical lens 202 is integrally molded. A light transmission preventing coating 208 is applied to shield the peripheral area other than the lens portion from the light source 203. Temporarily, coating 2
Without 08, the light projected through the peripheral area becomes direct or stray light and irradiates the light receiving surface 205, and the S / N ratio is extremely deteriorated. However, there is a problem or problem that the film formation of the light transmission preventing coating 208 is complicated in terms of manufacturing technology and the component cost of the moving plate 201 becomes high. or,
The coating 208 has a problem or a problem that peeling or cracks may occur due to deterioration and thus lack long-term reliability. It is preferable that the coating 208 completely shields the peripheral region, but a material capable of absorbing a certain amount of incident light can provide a predetermined effect, which is advantageous in terms of cost. However, in this case, a considerable deterioration of the S / N ratio cannot be avoided.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a lens-integrated moving plate structure which has excellent cost performance and excellent reliability. The following measures have been taken in order to achieve this object. That is, the optical displacement detection device according to the present invention has, as a basic component, a movable plate that is displaced along a plane,
It is composed of a fixed light source for irradiating the movable plate with incident light and a fixed light receiving element facing the fixed light source. A condenser lens band is extended on the moving plate to collect incident light and generate an image that moves in accordance with the displacement. On the other hand, the fixed light receiving element has a linear light receiving surface arranged along the moving direction of the image formation, and is capable of outputting the displacement detection signal from the light receiving position of the image formation. In such a configuration, as a feature of the present invention,
Parallel prism bands are provided along both side edges of the lens band. For example, the lens band and the prism band are spirally extended along the surface of the circular moving plate that is rotationally displaced, and the light receiving surface is arranged along the radial direction of the circular moving plate. Preferably, the lens band and the prism band are integrally formed with the moving plate made of a transparent optical material.

[0008]

In the present invention, prism bands are provided in parallel along both side edges of the lens band so that peripheral incident light is refracted and deviated from the light receiving surface. The light incident on the lens band is condensed and forms an image on the light receiving surface. Since this image formation moves along with the displacement of the moving plate, the light receiving surface has a predetermined length along the moving direction, and is generally set wider than the width dimension of the lens band. Correspondingly, the incident light from the fixed light source also has a predetermined spread and is generally larger than the width of the lens band. Therefore, part of the incident light that illuminates the moving plate is condensed by the lens band, while peripheral incident light passes through the prism band. Peripheral incident light is refracted and deflected by this prism band and directed outside the light receiving surface. Therefore, only the incident light condensed by the lens band is taken into the light receiving surface, and the displacement detection accuracy is improved. By setting the apex angle and width of the prism band appropriately according to the length of the light receiving surface, the width of the lens band, the distance between the lens band and the light receiving surface, etc. You can get the function of.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of an optical displacement detection device according to the present invention. As shown in the perspective view of (A), the circular moving plate 1 is rotationally displaced around the rotating shaft 2 along a plane. A lens band 3 is spirally formed on the surface of the moving plate 1 along the circumferential direction. The lens band 3 is made of a cylindrical lens and is formed integrally with the movable plate 1 using a transparent optical material. The present invention is not limited to this, and a Fresnel lens may be used instead of the cylindrical lens. If the wall thickness of the cylindrical lens is increased in order to enhance the light collecting ability, sink marks may occur during resin molding and the lens accuracy may deteriorate. In this case, the thick portion can be removed by using a Fresnel lens. A fixed light source 4 including an LED or the like is arranged above the moving plate 1. The fixed light source 4 preferably emits parallel light to irradiate the circular movable plate 1 along the radial direction so as to include the passing range of the lens band 3. on the other hand,
A fixed light receiving element 5 is arranged below the movable plate 1 so as to face the fixed light source 4. The fixed light receiving element 5 is composed of, for example, a differential output type light spot position detecting element, and a PSD or the like can be used. The light-receiving surface 6 provided on the surface of the fixed light-receiving element 5 has a longitudinal shape with a predetermined size and is arranged along the radial direction of the circular movable plate 1. Finally, as a feature of the present invention, a pair of prism bands 7 are provided along both side edges of the lens band 3. Like the lens band 3, the prism band 7 is also integrally formed with the movable plate 1 made of a transparent optical material.

FIG. 1B shows a sectional shape of the moving plate 1 along the radial direction. As described above, the lens band 3 is composed of a cylindrical lens having a predetermined focal length. The effective incident light 8 emitted from the fixed light source is condensed by the lens band 3 and forms an image 10 on the light receiving surface 6 of the light receiving element 5 along the optical axis 9.
To generate. On the other hand, the invalid incident light 11, that is, the peripheral incident light that is incident on the peripheral region other than the lens band 3, is refracted outward by the prism bands 7 located on both sides and deviates from the light receiving surface 6.
In this example, the prism band 7 is formed on the back surface side of the moving plate 1, but it is not necessarily limited to this and may be formed on the front surface side. By appropriately setting the apex angle and the width dimension of the prism band 7 in accordance with the width dimension of the lens band 3, the longitudinal dimension of the light receiving surface 6, the distance between the lens band 3 and the light receiving surface 6, etc. Even when the lens band 3 is displaced with respect to 6, it is possible to make the peripheral incident light 11 always deviate from the light receiving surface 6.

Next, the operation of the optical displacement detection device shown in FIG. 1 will be described in detail with reference to FIG. As mentioned above,
The lens band 3 is formed in a spiral shape around the rotation axis 2. Therefore, the center line 12 passing through the center of the width portion of the lens band 3
Draws a spiral. A line group orthogonal to the center line 12 serves as an optical axis of the lens band 3 and represents an image forming portion. This center line 1
2 corresponds to the slit 103 of the conventional example shown in FIG. In this example, the center line 12 draws a spiral, but the present invention is not limited to this. In general, the distance between the center line 12 and the rotating shaft 2 may be continuously changed with the rotation. It should be noted that both end portions in the circumferential direction of the lens band 3 are separated by a predetermined angular distance, and define an effective angle range.

Below the rotary moving plate 1, a light receiving element having a light receiving surface 6 having a predetermined longitudinal dimension along the radial direction is fixedly arranged. As is apparent from the figure, when the movable plate 1 is rotationally displaced, the intersection of the center line 12 and the light-receiving surface 6 moves in the radial direction in plan view. In other words, the displacement information can be obtained by detecting the change in the imaging position along the longitudinal direction of the light receiving surface 6 as the movable plate 1 rotates.

In the embodiment shown in FIGS. 1 and 2, the circular displacement plate is used to detect the rotational displacement information. However, the present invention is not limited to this, and for example, similar to the conventional example shown in FIG. 5, a slanting cylindrical lens is provided on the surface of a moving plate that is linearly displaced to detect linear displacement. Is also good.

[0014]

As described above, according to the present invention, a pair of prism bands are provided in parallel along both side edges of the lens band to refract and deflect the peripheral incident light. Therefore, it is designed so that the light projected through other than the lens band does not directly enter the light receiving surface. Therefore, it is not necessary to shield the peripheral area other than the lens band of the transparent moving plate with the light transmission preventing coating, and thus the manufacturing cost of the moving plate can be reduced and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an optical displacement detection device according to the present invention.

FIG. 2 is a plan view showing the arrangement relationship of the same components.

FIG. 3 is a perspective view showing an example of a conventional optical displacement detection device.

FIG. 4 is a graph showing output characteristics of the conventional optical displacement detection device shown in FIG.

FIG. 5 is a perspective view showing another example of a conventional optical displacement detection device.

[Explanation of symbols]

 1 Moving plate 2 Rotation axis 3 Lens band 4 Fixed light source 5 Fixed light receiving element 6 Light receiving surface 7 Prism band 8 Effective incident light 9 Optical axis 10 Imaging 11 Invalid incident light (peripheral incident light) 12 Center line

Claims (3)

[Claims] 1. A movable plate that is displaced along a plane, a fixed light source that irradiates the movable plate with incident light, and a movable light plate that extends on the movable plate and collects and moves the incident light in accordance with the displacement. Optical displacement detection including a lens band for generating an image and a fixed light receiving element having a light receiving surface arranged along the moving direction of the image and outputting a detection signal of the displacement from the position of the image formation. In the device, an optical displacement detection device is characterized in that a prism band is provided along a side edge of the lens band so that peripheral incident light is refracted to be deviated from the light receiving surface. 2. The optical displacement detection device according to claim 1, wherein the lens band and the prism band are integrally formed with a moving plate made of a transparent optical material. 3. The lens band and the prism band are spirally extended along the surface of the circular moving plate which is rotationally displaced, and the light receiving surface is arranged along the radial direction of the circular moving plate. The optical displacement detection device according to claim 1, characterized in that.