JPS63201520A - optical encoder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD The present invention relates to an optical encoder for detecting angular displacement of an object.

BACKGROUND ART A typical prior art involves forming a large number of slits at equal intervals in the circumferential direction in a disc-shaped rotating member made of a light-shielding material, and transmitting light from a light source placed on one side of the rotating member. is emitted, the light is detected through the slit by a light-receiving element placed on the other side of the rotating member, and the output of the light-receiving element is counted, thereby detecting the amount of angular displacement.

Problems to be Solved by the Invention In such prior art, if the detection accuracy is to be improved, the number of slits F must be increased, and there is a limit to making the slits smaller. The outer diameter of the member must be increased, resulting in a larger configuration.

The second object of the present invention is to provide an optical encoder that is highly accurate and can be miniaturized.

Means for Solving the Problems The present invention provides an optical disk that has a plurality of pits formed at intervals in the circumferential direction and is attached to an object whose angular displacement is to be detected, and a laser that irradiates the pits with laser light. A light source, a pair of light receiving elements that receive reflected light from pits at positions shifted in the circumferential direction of the optical disc, and at least one of the angular displacement position and the angular displacement direction of the optical disc based on the output of each light receiving element. An optical encoder is characterized in that it includes means for determining.

According to the present invention, an optical disk having a plurality of bits formed at intervals in the circumferential direction is attached to an object that is angularly displaced, the bits are irradiated with laser light from a laser light source, and the reflected light is reflected. Detection is performed by a pair of light receiving elements, and these pair of light receiving elements receive the reflected light from the bit at one position shifted in the circumferential direction of the disc. By using an optical disk and a laser beam in this manner, it becomes possible to detect the amount of angular displacement with much higher precision than the slit described in connection with the prior art.

The light receiving elements are provided in pairs, and these light receiving elements receive reflected light from the bits at positions shifted in the circumferential direction of the mini optical disc, as described above. Therefore, the output of the light receiving element has a phase difference, which allows the direction of angular displacement of the optical disc to be determined. By counting the output of either one of the pair of light receiving elements, the angular displacement position of the optical disc can be determined.

Example FIG. 1 is a sectional view of one embodiment of the present invention.

An optical disk 3 is fixed to an output shaft 2 of a motor 1 that drives a working end of an industrial robot.

A detection means 4 is located at a fixed position close to the optical disc 3.
is provided.

FIG. 2 is a plan view of the optical disc 3. This optical disk 3 has a thin disk shape, and a large number of bits 6 are formed on its surface along tracks 5 at equal intervals in the circumferential direction. The track 5 lies on a virtual circle centered on the rotational axis of the output shaft 2, which is the object whose angular displacement is to be detected. The distance between the pits 6 is, for example, 2μ, which is the length of the bit 6 in the circumferential direction! 2 is, for example, 2 μm, and the radial @dl of the bit 6 is, for example, 0.5 μm.

Reference numeral 7 is the diameter of a spot of laser light irradiated onto the optical disk 3, which will be described later. d2 is, for example, 1.4 to 2μ. The optical disc 3 has a base made of polycarbonate and an aluminum layer formed on the surface thereof, a bit 6 is formed on the aluminum layer, and a transparent protective layer Ii is formed on the aluminum layer. . The width d1 of bit 6 is between VA, f'l and bit 6
The circumferential length of! The spot diameter d2 of the laser beam, which is smaller than 2, is the length of the interval No. 1 and the length of the bit 6 in the same direction! Less than 2.

Referring again to FIG. tlS1, in the detection means 4, the laser light from the semiconductor laser light source 8 irradiates the bit 6 along the track 5 of the optical disc 3 via the semi-transparent reflecting mirror and the lens 9. The reflected light on the track 5 passes through the lens 9, the half mirror 10, and the lens 11, and is guided to a pair of light receiving elements 12 and 13. The light receiving elements 12 and 13 each receive reflected light from the bits 6 at positions shifted in the circumferential direction of the optical disc 3.

As shown in FIG. 3 (1), when the bit 6 of the optical disc 3 is partially irradiated with the laser beam spot 7, the amount of light received by the light receiving element 12 is as shown in FIG. 4 (1). is large as shown by solid color, and the amount of light received by the other light receiving element 13 is small as shown by hatching. Therefore, each output level of the light receiving elements 12 and 13 is as shown in Fig. 5 (1
) and reference marks 12a, 13a in range A of FIG. 5(2).
As shown in each.

The optical disc 3 is angularly displaced in the direction of the arrow 14, and as shown in FIG.
As shown in 2), the laser beam spoiler Y7 is bit 6.
, the amount of light received by the light receiving elements 12 and 13 is as shown in Fig.
), the output levels of the light receiving elements 12 and 13 are as shown in Fig. 5 (1) and f:tS.
It is small as shown by range B in Figure s (2).

When the optical disc 3 is further displaced by two angles and a part of the laser beam 6 is irradiated with the laser beam spotter, the amount of light received by the light receiving element 12 changes as shown in FIG. 4 (3). becomes smaller, and the amount of light received by the light receiving element 13 becomes larger.

As a result, [C] in Figures 5(1) and 5(2)
As shown, the output level of the light receiving element 12 remains small, and the output level of the light receiving element 12 increases.

In this way, when the optical disc 3 is angularly displaced as shown by the arrow 14 in FIG. The amount of angular displacement of the optical disc 3 can be determined by counting the output of at least one of the light receiving elements 12 and 13.

FIG. 6 is a block diagram showing the electrical configuration related to the light receiving elements 12, 13. Light receiving element 12.

The output from 13 is applied to an angular displacement direction determining circuit 18 via amplifier circuits 16 and 17. Angular displacement direction discrimination circuit 1
8 is the light receiving element 12 as mentioned above.

The optical disc 3 moves in the angular displacement direction 14 based on the phase difference of 13.
When it is determined that the optical disc 3 rotates in the direction opposite to the angular displacement direction 14, the output of the light receiving element 12 is derived from one line, and the ζ up/down counter 20 is counted up. When you do, line 21
The output of the light receiving element 12 is derived through the counter 20, which causes the counter 20 to count down. Thus, the count value of the counter 20 represents the angular displacement position of the optical disc 3.

Effects As described above, according to the present invention, the displacement position of an object can be detected with high precision using an optical disc and a laser beam, and the configuration thereof can be miniaturized. Therefore, the present invention can be implemented in connection with, for example, industrial robots, and its applications are expanded. Such an optical disk, a laser light source, and a light receiving element that receives reflected light from a pit can be mass-produced, and the cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a plan view of an optical disk 3, FIG. 3 is a plan view showing the relationship between the pit 6 and the optical slot 7, and FIG. 4 is a pair of light receiving A simplified diagram showing the amount of light received by the element 12.13, FIG. 5 shows the light receiving element 12.1.
FIG. 6 is a block diagram showing the electrical configuration related to the light receiving elements 12 and 13. 2... Output shaft, 3... Optical disk, 4... Detection means, 5... Track, 6... Pit, 7... Spot, 8... Semiconductor laser light source, 9, 11... ... Lens, 10... Reflected light, 12.13... Light receiving element, 1
6.17...Amplification circuit, 18...Angular displacement direction discrimination circuit, 20...Up/down counter agent Patent attorney Keibu Saikyo Figure 3 m4 Figure 5 Figure 6

Claims (1)

[Claims] Having a plurality of pits formed at intervals in the circumferential direction,
An optical disc that is attached to an object whose angular displacement is to be detected, a laser light source that irradiates laser light onto the pits, a pair of light receiving elements that receive reflected light from the pits at positions shifted in the circumferential direction of the optical disc, and each light receiving element. An optical encoder comprising means for determining at least one of an angular displacement position and an angular displacement direction of an optical disc based on the output of the optical disc.