JPH04160318A - Optical encoder - Google Patents

Abstract

PURPOSE:To improve S/N thereby to achieve high performance by blocking projection of light to an end face of the outer periphery of a rotary disk by a blocking member mounted in a light emitting unit. CONSTITUTION:A lens 10 is partially removed at a part confronting to the vicinity of an outer peripheral end of a rotary disk 8. At the same time, a block-like shielding member 11 is built in a case 1. As a result, the light from a light emitting element 2 is shut and never cast on the outer peripheral end face of the disk 8. A ring part 11a is integrally provided at an upper end of the member 11. The ring part 11a is fitted and fixed into an opening of the upper end of the case 1. The member 11 is placed at a predetermined position in the case 1, and the ring part 11a is fitted, then the member 11 is fixed by an adhesive. In this manner, the member 11 can be mounted easily in a stable manner.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical encoder, and more specifically, a light emitting unit is sandwiched between a rotating disk made of a light-transmitting material in which light-transmitting slits are formed by metal film deposition. The present invention relates to an optical encoder having a configuration in which a light receiving unit and a light receiving unit are arranged facing each other.

(Prior Art) FIG. 3 shows a cross section of a conventional optical encoder of this kind.

This optical encoder consists of a light emitting unit 3 equipped with a light emitting element 2 in a case l made of a transparent material, and a light receiving unit 7 comprising a light shielding plate 4 having an aperture for passing light and a light receiving element 5 attached to a base 6. are arranged opposite to each other with the vicinity of the outer periphery of the rotating disk 8 made of glass sandwiched therebetween, and light-transmitting slits are formed in the circumferential direction at a pitch of several + um by vapor deposition of a metal film 9 at the portion of the rotating disk 8 that crosses the optical path. Element 2
The structure is such that the light is converted into parallel light by a lens 10 formed in the case 1 and irradiated toward the light receiving element 5. This optical encoder exhibits high resolution despite its small size by having extremely small slits with a pitch of several um by depositing the metal film 9 as described above.

(Problem to be Solved by the Invention) However, in the above configuration, if there is a scratch or the like on the outer peripheral end surface of the rotating disk 8, the light irradiated on the outer peripheral end surface will be diffusely reflected and enter the rotating disk 8, as shown in the figure. As shown by the broken line, the light enters the light-receiving element 5 after repeated diffuse reflections, causing a problem in that the S/N ratio deteriorates and the performance deteriorates.

The parallel light from the lens 10 as described above is transmitted to the rotating disk 8.
In order to avoid the positional relationship that reaches the outer peripheral end surface of the light emitting unit 3, for example, it is possible to use a small light emitting unit 3 with a small lens lO diameter, but in that case, a commonly used type of light emitting unit cannot be used. First, a light emitting unit must be manufactured separately, which increases costs, and even if a small light emitting unit 3 is used, good parallel light cannot be obtained depending on the small diameter lens 10.

It is also possible to arrange the light emitting unit 3 closer to the center of the rotating disk 8;
Since the rotating shaft 20 protrudes upward from the center of the upper surface of the rotating shaft 20, the rotating shaft 20 becomes an obstacle and there is a limit to relative placement toward the center position. Of course, this would be possible if the rotary disk 8 had a larger diameter, but this would increase the size of the device.

Furthermore, it is conceivable to apply a coating or the like to the outer circumferential end surface of the rotating disk 8 to prevent the incidence of disturbance light, but this poses problems in processing cost, stabilization of quality, etc., and is difficult in practice.

The present invention has been made in view of the above-mentioned circumstances, and is intended to solve the above-mentioned conventional problems by making simple improvements to the light emitting unit.

(Means for Solving the Problems) In order to achieve the above object, the optical encoder of the present invention has a structure in which a light shielding member for blocking light irradiation to the outer peripheral end surface of the rotating disk is attached to the light emitting unit. .

(Function) According to the configuration of the present invention, the light emitted from the light emitting element of the light emitting unit is prevented from being irradiated onto the outer peripheral end surface of the rotating disk by the light shielding member attached to the unit.

(Embodiment) FIG. 1 shows an embodiment of an optical encoder according to the present invention.

The basic configuration of this optical encoder is the same as the conventional one, and a description of the basic configuration will be omitted.

In this embodiment of the present invention, the lens 10 is partially removed at a portion facing the outer peripheral end of the rotating disk 8, and a block-shaped light shielding member 11 made of an opaque plastic material or the like is incorporated into the case l. The light from the light emitting element 2 is blocked by the light shielding member 11 so that the outer peripheral end surface of the rotating disk 8 is not irradiated with the light.

A ring portion 11a that is fitted and fixed into the upper end opening of the case I is integrally connected to the upper end of the light shielding member 11. When installing, the ring portion 11a is placed in a state where the light shielding member 11 is located at a predetermined position within the case l.
It is fitted into the upper opening of the case 1 and fixed with adhesive. In this way, by integrally providing the ring portion 11a, the light shielding member 11 is configured to be easily and stably attached.

Another embodiment of the invention is shown in FIG.

In this embodiment, a plate-shaped light shielding member 11 is attached or fixed to the lower surface of the case l of the light emitting unit 3 to prevent the light from the light emitting element 2 from being irradiated onto the outer peripheral end surface of the rotating disk 8. ing.

(Effects of the Invention) As explained above, according to the present invention, it is possible to avoid the incidence of disturbance light from the outer peripheral end surface of the rotating disk, and thereby, it is possible to avoid the incidence of disturbance light from the outer peripheral end surface of the rotating disk. In optical encoders, the S/N ratio has been improved and higher performance equipment has become available.

Further, since the configuration is obtained by attaching the light shielding member to a commonly used light emitting unit, it has the practical advantage of being simple and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of an optical encoder according to the present invention, FIG. 2 is a longitudinal sectional view of another embodiment, and FIG. 3 is a longitudinal sectional view of a conventional example. 3... Light emitting unit, 7... Light receiving unit, 8... Rotating disk, 9... Metal film, 11... Light shielding member.

Claims (1)

[Claims] (1) Optical type in which a light emitting unit (3) and a light receiving unit (7) are arranged facing each other with a rotating disk (8) made of a transparent material in which a transparent slit is formed by vapor deposition of a metal film (9). In the encoder, the rotating disk (8)
An optical encoder characterized in that a light shielding member (11) is attached to a light emitting unit (3) to prevent light from being irradiated onto an outer peripheral end surface of the optical encoder.