JPH04346029A - Optical encoder - Google Patents

Abstract

PURPOSE:To obtain an optical encoder for which the conpact configuration and light weight can be readily achieved. CONSTITUTION:A light emitting element 3, a photodetector 5 corresponding to the light emitting element and a scale 9, wherein four slits 9a, 9b, 9c and 9d having the different light transmittances are repeatedly aligned in the specified order, are assembled so that the slits cross the light path formed between both elements and the slits can be relatively displaced. Thus, the output, which indicates the constant increasing and decreasing patterns in response to the amount of the displacement and the direction of the displacement, is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical encoder for detecting relative displacement between two objects.

0002

2. Description of the Related Art FIG. 2 shows an outline of an optical encoder, which consists of an encoder body 1 having a light emitting element and a corresponding light receiving element, and a scale 2 having a slit. The encoder main body 1 and the scale 2 are connected to two objects that are relatively displaced, for example, a fixed part and a movable part (or a movable part and a fixed part) of a drive mechanism, and between a light emitting element and a light receiving element of the encoder main body 1. The scale 2 is installed so that the slits of the scale 2 perpendicularly intersect the formed light path.

FIG. 3 shows an example of a conventional optical encoder, for example, "Nikkei Mechanical 1990.9.3, p70"
This shows the optical encoder described in 2.
is a scale, 3 and 4 are light emitting elements, 5 and 6 are light receiving elements, 7
is a lens, and 8 is an index scale.

The scale 2 and the index scale 8 each have slits 2a, 8a and 8b with a slit pitch L, that is, a slit width L and a slit interval L, provided by etching or the like. Note that the slits 8a and 8b of the index scale 8 are provided so as to be shifted from each other by an L/2 pitch. Light emitting element 3 and light receiving element 5
is passed through the lens 7, slit 2a and slit 8a,
Further, the light emitting element 4 and the light receiving element 6 are arranged so as to be able to transmit and receive light through the lens 7, the slit 2a, and the slit 8b. Note that the lens 7 is for controlling the spread of the light by converting the light from the light emitting elements 3 and 4 into parallel light beams. The light emitting elements 3 and 4, the light receiving elements 5 and 6, the lens 7 and the index scale 8 are incorporated into the encoder main body 1 as shown in FIG.
, 4 and the lens 7, and the index scale 8 and the light receiving elements 5, 6 so as to be relatively movable in the direction of arrow A or the opposite direction.

In the above configuration, when the slit 2a of the scale 2 and the slit 8a of the index scale 8 overlap, the amount of light received by the light receiving element 5 becomes maximum. Further, when the scale 2 moves from this state in the direction of arrow A or the opposite direction, the amount of light received by the light receiving element 5 decreases, and when the slits 2a and 8a are completely shifted, the amount of light received becomes minimum. Therefore, the amount of light received by the light-receiving element 5, that is, the output of the light-receiving element 5, repeatedly increases and decreases depending on the slit pitch L. Similarly, the output of the light receiving element 6 also increases and decreases depending on the slit pitch L, but as mentioned above, the slit 8b is the same as the slit 8a.
Since the light receiving element 5 is shifted by L/2 pitch from the
The phase is shifted by 90° from the output of .

FIGS. 4(a) and 4(b) show signals A and B obtained by shaping the outputs of the light receiving elements 5 and 6 into square waves, respectively.
shows. By counting on/off of either one of these signals A and B, the relative displacement amount (drive amount) between the encoder main body 1 and the scale 2 can be detected. Furthermore, the relative displacement (movement) direction between the encoder main body 1 and the scale 2 can be detected from these signals A and B. That is, if signal B changes from off to on when signal A is on, scale 2 moves in the direction of arrow A, and if signal B changes from off to on while signal A is off, scale 2 moves in the direction of arrow A. You can see that it is moving in the opposite direction.

[0007]

However, the above configuration requires two light emitting elements and two light receiving elements, and also requires an index scale.
There was a problem that there was a limit to miniaturization. Further, in the above configuration, in order to increase the resolution of the encoder, the slit pitch of the scale and the index scale must be made small, and extremely precise etching processing is required.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide an optical encoder that can be easily reduced in size and weight, and in addition, an optical encoder that can easily improve resolution.

[0009]

Means for Solving the Problems In order to achieve the above object, the present invention provides a light emitting element, a light receiving element corresponding thereto, and a scale having a slit, the slit being formed between both elements. The optical encoder is composed of a scale that is configured to be relatively displaceable so as to intersect the light paths of the optical encoder. In addition, as a second aspect of the present invention, a translucent plate having a width L and having a first light transmittance is placed on a transparent substrate at an interval L.
A plurality of first scale plates are attached with a distance L between them, and a second scale plate is a second scale plate with a plurality of translucent plates having a width L and having a second light transmittance attached on a transparent substrate with an interval L between them. An optical encoder according to claim 1, comprising a scale in which semitransparent plates are stacked one on top of the other so as to be shifted by an L/2 pitch.

0010

[Function] According to claim 1 of the present invention, when the light-emitting element, the light-receiving element, and the scale are displaced relative to each other, the amount of light received by the light-receiving element changes according to the light transmittance of each slit of the scale. However, the change shows a constant increase/decrease pattern depending on the amount of displacement and the direction of displacement, and the amount and direction of displacement are detected from this. Further, according to claim 2, a scale is obtained in which four slits having different light transmittances are repeatedly formed every L/2 pitch by using a semi-transparent plate having a minimum width (pitch) of L.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an optical encoder according to the present invention. In the figure, the same components as those of the conventional example are denoted by the same reference numerals. That is, 3 is a light emitting element, 5 is a light receiving element, and 7 is a light emitting element.
is a lens, and 9 is a scale.

The scale 9 is constructed by overlapping and fixing a first scale plate 10 as shown in FIG. 5(a) and a second scale plate 20 as shown in FIG. 5(b). c)
It is constructed as shown in FIG. That is, as shown in FIG. 5(a), the first scale plate 10 is made by pasting semitransparent plates 12 made of translucent resin or the like with a width L on a transparent substrate 11 made of transparent resin or the like with a distance L between them. It has become. The second scale plate 20 is made by pasting a semi-transparent plate 22 made of a translucent resin or the like with a width L on a transparent substrate 21 made of a transparent resin or the like at a distance L, as shown in FIG. 5(b). It has become. The scale plates 10 and 20 are superimposed and fixed such that the positions of the semi-transparent plates 12 and 22 are shifted from each other by an L/2 pitch, and the scale 9 is constructed.

Here, the light transmittance of the semi-transparent plates 12 and 22 is different, so that the scale 9
Four slits 9a, 9b, 9c, and 9d having different light transmittances are repeatedly formed every L/2 pitch. Note that, when the light transmittances of the slits 9a to 9d are respectively a, b, c, and d, b<a<c<d here. Further, the scale 9 is arranged to be relatively movable in the direction of arrow B or the opposite direction between the light emitting element 3, the lens 7, and the light receiving element 5.

In the above configuration, when the scale 2 moves in the direction of arrow B or the opposite direction, the amount of light received by the light receiving element 5 changes according to the transmittance of light in the slits 9a to 9d, and the output of the light receiving element 5 changes. It increases or decreases every L/2 pitch in a constant pattern.

FIG. 6 shows a signal C obtained by shaping the output of the light receiving element 5 into a square wave. Rise and fall of this signal C (or on and off of the pulse signal obtained by differentiating this)
By counting, the relative displacement amount (driving amount) between the light emitting element 3, the light receiving element 5, the lens 7, and the scale 9 can be detected. Further, the relative displacement (movement) direction can be determined from the level change of the signal C before and after the displacement.

As described above, according to the embodiment, only one light-emitting element and one light-receiving element are required, and there is no need for an index scale as in the conventional example, making it easy to reduce the size and weight. This is advantageous when installing inside a drive mechanism or the like. In addition, using a translucent plate with a width L
Since it is possible to construct a scale with a slit pitch of /2, the slit pitch L on each scale plate is
The resolution can be easily improved without reducing the size. In the above embodiment, only two scale plates are stacked, but three or more scale plates may be stacked, and the resolution can be further improved.

[0017]

As explained above, according to claim 1 of the present invention, a light emitting element, a light receiving element corresponding to the light emitting element, and a scale having a slit are connected to each other through a light path in which the slit is formed between the two elements. The optical encoder has a scale in which at least two types of slits having different light transmittances are repeatedly arranged in a predetermined order, so that each of the scales has one light emitting element and one light emitting element. By using the light receiving element, it is possible to obtain an output that shows a constant increase/decrease pattern according to the amount of displacement and the direction of displacement without using an index scale, etc., and it can be easily made smaller and lighter than conventional ones. Can be done.

According to a second aspect of the present invention, a first scale plate includes a plurality of translucent plates each having a width L and having a first light transmittance mounted on a transparent substrate at intervals L; A translucent plate having a width L and having a second light transmittance is placed on a transparent substrate at an interval L.
Since the scale is constructed by stacking a plurality of second scale plates with each other separated from each other so that each semi-transparent plate is shifted by an L/2 pitch, it is possible to create a slit of L/2 by using a semi-transparent plate with a width L. A scale with a pitch can be constructed,
Resolution can be easily improved without reducing the slit pitch L in each scale plate.

[Brief explanation of the drawing]

[Fig. 1] A configuration diagram showing an embodiment of the optical encoder of the present invention.

[Figure 2] Perspective view showing an overview of the optical encoder

[Figure 3] Configuration diagram showing an example of a conventional optical encoder

[
Figure 4: Waveform diagram showing the output signal of a conventional optical encoder

[Figure 5] Explanatory diagram showing details of the scale of the optical encoder in Figure 1

[Figure 6] Waveform diagram showing the output signal of the optical encoder in Figure 1

[Explanation of symbols]

3... Light emitting element, 5... Light receiving element, 7... Lens, 9... Scale, 9a to 9d... Slit, 10... First scale plate,
20... Second scale plate, 11, 21... Transparent substrate, 12
, 22...Semi-transparent plate, L...Slit pitch, B...Displacement direction.

Claims (2)

[Claims] 1. An optical system comprising a light emitting element, a light receiving element corresponding to the light emitting element, and a scale having a slit, which are relatively displaceable in such a manner that the slit intersects a light path formed between the two elements. 1. An optical encoder comprising a scale in which at least two types of slits having different light transmittances are repeatedly arranged in a predetermined order. 2. A first scale plate having a plurality of translucent plates having a width L and having a first light transmittance mounted on a transparent substrate at intervals L, and a second scale plate having a second light transmittance mounted on the transparent substrate. and a second scale plate in which a plurality of semi-transparent plates having a width L and having a width L are attached at intervals L, and the scale is stacked such that each semi-transparent plate is shifted by L/2 pitch. The optical encoder according to claim 1.