JPH1054735A - Encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the output precision of an encoder by providing a window reflection preventing film between a window coating forming the window of a grating and the grating. SOLUTION: A plurality of slit coatings 2 such as chromium are formed on one surface 1a of a rotary disc 1 formed of a glass plate or the like, and slits 3 are formed between the coatings 2, respectively. A grating 4 of glass plate or the like is fixed and arranged in a position adjacent to the disk 1, and a window coating 5 such as chromium is formed on an opposed surface 4a to the rotary disc 1. The coating 5 is formed on the grating 4 through a window reflection preventing film 5A such as chromium oxide. Thus, a window 6 for passing the light B from a light source 3 is formed in a part where the coating 5 and the reflecting preventing film 5A are not formed. When the light B is incident, a disturbance light A is also incident, but the disturbance light A is reflected by a light receiving element 7, absorbed by the reflecting preventing film 5A, and prevented from being incident on a light receiving element 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder, and more particularly, to a novel improvement for improving the S / N ratio of a rotation detection signal by forming an anti-reflection film on a grating side or a disk side or both. .

[0002]

2. Description of the Related Art Conventionally, as an encoder of this kind, a configuration shown in FIGS. 3 and 4 has been generally employed. That is, in FIG. 3, reference numeral 1 denotes a rotating disk made of a glass plate or the like, and a plurality of slit coatings 2 made of chrome or the like are formed on one surface (the back surface in FIG. 3) 1a of the rotating disk 1. And
Between each slit coating 2, light A from light source 3
A slit 3 for passing light B out of B and C is formed.

At a position adjacent to the rotating disk 1 (a lower position in FIG. 3), a grating 4 made of a glass plate or the like is provided.
A window coating 5 made of chrome or the like is formed on an opposing surface 4a of the grating 4 which faces the rotating disk 1. The window coating 5
A window 6 through which the light B passes is formed in a portion where is not formed. First and second light receiving elements 7 and 8 which are provided at positions different in phase from each other are disposed outside the grating 4 (the lower position in FIG. 3).

Next, the operation will be described. When the light B is incident from the light source 3 in the state of FIG. 3, the light incident state on each of the light receiving elements 7 and 8 becomes the well-known state of FIGS. 4A and 4B. The pattern of the coating 5 is actually formed. Therefore, in the state described above, FIG.
When light enters as shown in FIGS. 4A and 4B, the output signals from the light receiving elements 7 and 8 are converted into the signals shown in FIGS.
Was output as shown in.

[0005]

A conventional encoder is:
Because of the above configuration, the following problems exist. That is, in the state of only the window coating using chrome, the light reflected by the first light receiving element is reflected by the window coating 5 and enters the second light receiving element.
As shown in FIGS. 4C and 4D, a noise component was output separately from the signal component, and the output signal from each light receiving element was an output signal containing a noise component and having a poor S / N ratio.

[0006]

An encoder according to the present invention allows light from a light source to reach a light receiving element through a slit of a rotating disk and a window of a grating, and generates a rotation detection signal corresponding to the rotation of the rotating disk. In an encoder obtained from the light receiving element, an antireflection film for a window is provided between a window coating forming a window of the grating and the grating.

More specifically, the present invention is configured such that an antireflection film for a slit is provided on an outer surface of a coating for a slit for forming a slit of the rotating disk.

More specifically, the window coating is made of chromium, and the window antireflection film is made of chromium oxide.

More specifically, the window coating and the slit coating are made of chromium, and the slit antireflection film is made of chromium oxide.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an encoder according to the present invention will be described below with reference to the drawings. In addition,
The same or equivalent parts as those in the conventional example will be described using the same reference numerals. In FIG. 1, reference numeral 1 denotes a rotating disk made of a glass plate or the like. On one surface (the back surface in FIG. 1) 1a of the rotating disk 1, a plurality of slit coatings 2 made of chrome or the like are formed. The slits 3 are formed between the slit coatings 2 so that the light B among the lights A, B, and C from the light source 3 passes therethrough.

At a position adjacent to the rotating disk 1 (a lower position in FIG. 3), a grating 4 made of a glass plate or the like is provided.
A window coating 5 made of chrome or the like is formed on an opposing surface 4a of the grating 4 which faces the rotating disk 1. The window coating 5
Is formed on the grating 4 via a window antireflection film 5A made of a low reflection material such as chromium oxide. Therefore, the window coating 5 and the window antireflection window 5A
The window 6 through which the light B passes is formed in a portion where is not formed. An outer position of the grating 4 (FIG. 1)
(Lower position in the figure), the first and second light receiving elements 7 and 8 provided at positions different in phase from each other are arranged.

Next, the operation will be described. When light B from the light source 3 enters in the state of FIG.
The pattern of the window coating 5 and the window antireflection film 5A is actually formed so that the state of light incident on the window coating is in the well-known state shown in FIGS. 2A and 2B. Accordingly, in the above-described state, when light B enters as shown in FIGS. 2A and 2B, light A, which is disturbance light, also enters at the same time. The light is reflected and absorbed by the window antireflection film 5A, and is prevented from entering the second light receiving element 8. Therefore, when light enters each of the light receiving elements 7 and 8 as shown in FIGS. 2A and 2B, the output signal from each of the light receiving elements 7 and 8 does not include a noise component as in the related art. (C) and (D) of FIG. 2 consisting of pulses in a normal state.
An output signal, which is a rotation detection signal of the encoder, can be obtained. In the configuration of FIG. 1 described above, the case where the light incident direction is directed from top to bottom has been described. However, by changing the mounting direction of the encoder, not only the vertical direction but also the reverse It is possible in any direction, such as in the case of from above, in the horizontal direction, that is, in the horizontal direction. Also,
In the above-described embodiment, the case where the window antireflection film 5A is provided only on the window coating 5 has been described. However, the slit coating 2 has the slit antireflection film 2A (FIG. 1).
(Shown by a dotted line in FIG. 3), and either one of the antireflection films may be used, or both antireflection films may be used. Further, the above-described anti-reflection film,
Although the case where chromium oxide is used has been described, a low reflection material other than chromium oxide can also be used.

[0013]

Since the encoder according to the present invention is configured as described above, the following effects can be obtained. That is, since an antireflection film is formed on one or both of the rotating disk and the grating to suppress the reflection of disturbance light, the output signal output from each light receiving element must be output in a state that does not include a noise component. And the output accuracy of the encoder can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an encoder according to the present invention.

FIG. 2 is a waveform diagram showing incident light and an output signal of FIG.

FIG. 3 is a configuration diagram schematically showing a conventional encoder.

FIG. 4 is a waveform diagram showing an incident light and an output signal of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating disk 2 Slit coating 2A Slit antireflection film 3 Slit 4 Grating 5 Window coating 6 Window 7, 8 Light receiving element

Claims (4)

[Claims] The light from a light source (3) is made to reach a light receiving element (7, 8) through a slit (3) of a rotating disk (1) and a window (6) of a grating (4). In an encoder configured to obtain a rotation detection signal according to the rotation of the disk (1) from the light receiving element (7, 8), a window coating (5) forming a window (6) of the grating (4) and the window coating (5). An encoder comprising a window antireflection film (5A) provided between the grating and the grating (4). 2. An encoder according to claim 1, wherein an antireflection film for slits is provided on an outer surface of a coating for slits forming the slits of the rotating disk. . 3. The encoder according to claim 1, wherein said window coating (5) is made of chromium, and said window anti-reflection film (5A) is made of chromium oxide. 4. The encoder according to claim 2, wherein the window coating (5) and the slit coating (2A) are made of chrome, and the slit antireflection film (2A) is made of chromium oxide. .