JPH073342B2 - Optical encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical encoder using an optical scale for measuring displacement such as movement amount and rotation amount of an object to be measured, and particularly to a displacement direction of the object to be measured. The present invention also relates to an optical encoder having a simple structure capable of simultaneously detecting.

(Prior Art) Conventionally, an optical scale is used to detect the movement amount and rotation amount of an object to be measured. So-called optical encoders have been proposed in, for example, JP-A-59-63517, JP-B-57-12104, and JP-A-60-140119.

For example, Japanese Examined Patent Publication (Kokoku) No. 57-12104 proposes an optical encoder using an optical scale formed of a grooved grating having a triangular groove cross section made of a light transmissive member. According to the publication, two light-receiving elements each detect a light beam emitted in two directions on the inclined surface of a triangular groove, and as a result, a two-phase output signal having an electrical phase difference of 180 degrees ( Two-phase signals related to push-pull output) are taken out.

However, the optical encoder of the above publication is not a very preferable method for obtaining a two-phase output signal having a phase difference of 90 degrees, because it has adjusting means for equalizing the intensity relationship of the two-phase output signals.

(Problems to be Solved by the Invention) The present invention provides an optical scale having a V-shaped groove having a predetermined shape and a plane light transmitting portion, which can be easily manufactured by a manufacturing method such as a plastic mold, and a predetermined scale from the optical scale. By using the two light receiving elements arranged at the positions, it is possible to easily obtain two output signals having an arbitrary phase difference within the range of 0 degree to 180 degrees, particularly an output signal having a phase difference of 90 degrees. It is an object of the present invention to provide an optical encoder having a simple structure in which the displacement direction of an object to be measured can be easily obtained at the same time.

(Means for Solving Problems) A light beam from a light source is made incident on a first scale provided with a light transmitting portion on a grating, and the light beam from the light transmitting portion is perpendicular to the displacement direction of the object to be measured. Through a second scale in which a V-shaped groove and a planar light transmitting portion provided in the direction are periodically provided in the horizontal direction with respect to the displacement direction, with respect to each inclined surface of the V-shaped groove of the second scale. When light is received by the two light receiving elements provided as follows, when the V-shaped groove and its adjacent V-shaped groove pitch are P,
By setting the width of the inclined surface of the V-shaped groove to P / 4,
Two light receiving elements output two-phase output signals having a phase difference of 90 degrees, and the displacement direction and the displacement amount of the object to be measured are detected from the two-phase output signals.

(Embodiment) FIG. 1 is a schematic view of an optical encoder of the present invention, and FIG. 2 is a schematic view showing a traveling state of a light beam in a part of FIG.
In the figure, reference numeral 1 denotes a light emitting element, which has a lens portion 1a having a light condensing function. Reference numeral 2 is a fixed scale as a first scale, in which lattice-like light transmitting portions and light shielding portions are provided at equal intervals and at a pitch P. Reference numeral 3 denotes a movable scale as a second scale, which is arranged to face the fixed scale 2 and is attached to an object to be measured (not shown). Reference numerals 4a, 4b and 4c are light receiving elements, respectively, which receive light fluxes from respective regions of the movable scale 3 described later. Reference numeral 5 is an amplifier circuit, and 6 is a waveform shaping circuit, which shapes the output signal from the amplifier circuit 5. Reference numeral 7 is a direction discrimination counter, which discriminates the moving direction of the movable scale 3 using the output signal from the waveform shaping circuit 6 having two predetermined phase differences.

FIGS. 3A and 3B are a perspective view of the movable scale 3 shown in FIG. 1 and a cross-sectional view in the traveling direction of the light flux. The movable scale 3 is made of a parallel plate-shaped transparent material made of glass or plastic, and is fixed in a direction perpendicular to the movable direction D of the movable scale on the incident surface of the luminous flux from the light emitting element 1 as shown in FIG. The scale 2 is composed of V-shaped grooves 31 provided at intervals equal to the grating pitch P and plane light transmitting portions 32 provided at intervals equal to the pitch P in the horizontal direction with respect to the movable direction D.

The angles θ with respect to the flat surface 3d, which is the back surface of the two inclined surfaces 3a and 3c forming the V-shaped groove 32, are 45 degrees, and the flat light transmitting portion 3b is a flat surface.
It is parallel to 3d.

In this embodiment, of the parallel light flux from the light emitting element 1, the light flux that has passed through the transmission part of the fixed scale 2 is made incident on the movable scale 3. Then, the light fluxes passing through the V-shaped groove 31 and the plane light transmitting portion 32 of the movable scale 3 are refracted and simply passed through as shown in FIG. 4 to be incident on the respective light receiving elements 4a, 4b, 4c. There is.

Incidentally, in the present embodiment, the light receiving element 4b is not particularly provided, if the output signal from the light receiving element 4a, 4c is used, the displacement state of the movable scale can be obtained, but the phase of the output signal from the light receiving element 4a, 4c In order to make the relationship easier to understand, explanations are given below as necessary.

At this time, in this embodiment, the output signals from the light receiving elements 4a and 4c are
As shown in FIG. 3, the V-shaped groove 31 has a phase difference of 0 degree.
With a width of 1/2 of the pitch P, and the two inclined surfaces 3a and 3c have equal widths of P / 4, and the plane light transmitting portion 32 has a width of 1/2 of the pitch P. Is set.

In this embodiment, a parallel light flux having a spatially uniform intensity distribution is vertically incident on the movable scale 3, and the incident light flux is divided into three regions 3a, 3b, 3c of the movable scale 3 in three directions. Of these, the light beams emitted in the directions determined by the inclinations of the inclined surfaces 3a, 3c are made incident on the light receiving elements 4a, 4c, respectively, and the light beams vertically made incident on the plane light transmitting portion 3b are made incident on the light receiving element 4b. . Then, the displacement state of the movable scale 3 such as the moving amount and the moving direction is detected by using the two output signals having a predetermined phase difference from the light receiving elements 4a and 4c.

The output light from the light emitting element 1 may be monitored using the output signal from the light receiving element 4b.

Next, in the present embodiment, due to the relative position difference between the movable scale 3 and the fixed scale 2, the state of incidence of the light flux emitted from the light emitting element 1 on each of the light receiving elements 4a, 4b, 4c is fifth.
4 to 8 will be described as an example of four typical states.

In FIG. 5, the light transmitting portion 2a of the fixed scale 2 is the movable scale 3
This is the case where it overlaps with the planar light transmitting portion 3b. All the parallel light fluxes that have passed through the light transmitting portion 2a of the fixed scale 2 pass through the flat light transmitting portion 3b of the movable scale 3 and enter the light receiving element 4b. At this time, no light beam is incident on the light receiving elements 4a and 4c.

FIG. 6 shows that the light transmitting portion 2a of the fixed scale 2 is the movable scale 3
This is a case where the half area of the planar light transmitting portion 3b and the inclined surface 3a overlap. Half of the light flux that has passed through the light transmitting portion 2a of the fixed scale 2 is incident on the flat light transmitting portion 3b, and the other half is incident on the inclined surface 3a. As a result, the luminous flux emitted from the movable scale 3 enters the light receiving elements 4a and 4b. At this time, the light receiving element 4
No light beam enters c.

In FIG. 7, the light transmitting portion 2a of the fixed scale 2 is the movable scale 3
This is the case where the V-shaped groove is overlapped with both inclined surfaces 3a and 3c. Half of the light flux that has passed through the light transmitting portion 2a of the fixed scale 2 is incident on the inclined surface 3a, and the other half is incident on the inclined surface 3c. As a result, the two light receiving elements 4a, 4c The light beams are equally incident on each. At this time, no light flux enters the light receiving element 4b.

In FIG. 8, the light transmitting portion 2a of the fixed scale 2 is the movable scale 3
This is the case where half the area of the plane light transmitting portion 3b and the inclined surface 3c overlap. Half of the light flux that has passed through the light transmitting portion 2a of the fixed scale 2 is incident on the flat light transmitting portion 3b, and the other half is incident on the inclined surface 3c. As a result, the light flux is received by the light receiving elements 4b and 4c. Is incident. At this time, no light beam enters the light receiving element 4a.

Next, the change in the amount of light received by each of the light receiving elements 4a, 4b, 4c when the relative positions of the fixed scale 2 and the movable scale 3 shown in FIGS. Figure (A),
It shows in (B).

5A shows a schematic diagram corresponding to FIGS. 5 to 8, and FIG. 8B shows the change in the amount of light received by each light receiving element at that time, with the horizontal axis representing the change amount of the movable scale. There is. 9A, 9C
Indicates the relative displacement of the amount of light received by the light receiving elements 4a and 4c, and the phase relationship between the two is shifted by 90 degrees.

FIG. 10 (A) shows the output signal S from each light receiving element when the relative positions of the fixed scale 2 and the movable scale 3 are continuously displaced in the same manner as in FIG. 9 (B). It is a thing.

In the figure, it is assumed that the light emitted from the light emitting element 1 is a parallel light flux, the light emitted from the transmission part of the fixed scale is not diffracted, and there is no light amount loss on each of the entrance and exit surfaces of the movable scale. The output signal S in the case of doing is shown.

Further, FIG. 10 (B) shows the waveforms of the output signals from the respective light receiving elements 4a, 4b, 4c in the case where the above-mentioned assumptions do not hold true in FIG.

As shown in FIGS. 10A and 10B, in both cases, the output signals from the light receiving elements 4a and 4c have a phase difference of 90 degrees with each other.

The inclined surfaces 3a, 3 of the V-shaped groove of the movable scale 3 in this embodiment
c is not limited to the inclination angle of 45 degrees shown in FIG. 3, but any angle can be used as long as the light beam incident on the inclined surfaces 3a and 3c is easily separated into two directions and is incident on two light receiving elements. It may be degree.

However, if the inclination angle θ is too small, the separation angle of the light beam becomes small, and the light receiving element has to be arranged at a position distant from the movable scale, which is not preferable because the entire device becomes large. If the inclination angle θ is too large, the inclined surface 3
Since the light beam refracted by a and 3c is totally reflected on the surface d, which is the bottom surface, it is necessary to set the angle so that the light is not totally reflected.

In addition to this, if the tilt angle is large even if the light is not totally reflected, the light amount loss on the surface d increases, so it is preferable to set the tilt angle θ within the range of 30 <θ <60.

In this embodiment, as shown in FIG. 3B, the light incident surface of the movable scale 3 has a V-shaped groove 31 having the above-mentioned pitch.
(The width of the inclined surfaces 3a and 3c is 1 / 4P) and the plane light transmitting part 32 (its width is 1 / 2P), and the phase difference of 90 degrees is given to the output signals from the two light receiving elements 4a and 4c. Although the case is shown, by providing the V-shaped groove and the planar light transmitting portion with an arbitrary width within one pitch, an arbitrary phase difference can be imparted within the range of 0 to 180 degrees.

FIG. 11A shows an example in which the width of the V-shaped groove is 2 / 3P and the width of the plane light transmitting portion is 1 / 3P, and a phase difference of 120 degrees is given to the output signals from the two light receiving elements. It is a schematic diagram of an example. At this time, the width of the two inclined surfaces of the V-shaped groove is 1 / 3P, and the widths of the light transmitting portion and the light shielding portion of the fixed scale are each 1 / 2P.

FIGS. 11 (B) and 11 (C) show output signals from the respective light receiving elements obtained at this time in the same manner as FIGS. 10 (A) and 10 (B), and as shown in FIG. Output signals 11A and 11C having a phase difference of 120 degrees from each other are obtained from the light receiving element.

Generally, in the shape shown in FIG. 3B, the relationship between the width of the V-shaped groove at the pitch P and the phase difference δ of the output signals from the two light receiving elements with respect to the width b of the plane light transmitting portion is Becomes

At this time, the widths of the light transmitting portion and the light shielding portion of the fixed scale are both 1 / 2P.

In each of the above embodiments, the arrangement of the movable scale and the fixed scale is exchanged, the movable scale is arranged on the light emitting element 1 side, and the fixed scale is arranged on the light receiving element side. You can

FIG. 12 is a schematic diagram of an embodiment when the present invention is applied to a rotary encoder, and FIG. 13 is a schematic diagram of an embodiment when the present invention is applied to a linear encoder.

In FIGS. 12 and 13, 1 is a light emitting element, 2 is a fixed scale, 3 is a movable scale, and for example, FIG.
(B) is formed. Reference numerals 4a, 4b and 4c are light receiving elements.

The movable scales 3 are attached to the objects to be measured. The displacement direction and displacement amount of the object to be measured can be detected by receiving the light flux that has passed through the transmission part of the fixed scale 2 and the V-shaped groove of the movable scale 3 with the light receiving elements 4a and 4c providing a predetermined phase difference. It is detecting.

(Effect of the Invention) According to the present invention, an optical scale in which a V-shaped groove having a predetermined shape and a plane light transmitting portion are formed within one pitch is used, and a light flux passing through the optical scale is made incident on two light receiving elements, respectively. As a result, it is possible to achieve an optical encoder that can easily obtain two output signals having an arbitrary phase difference.

In particular, the directivity of the light source, which has been a problem with conventional detection methods,
It is possible to achieve an optical encoder that can obtain a stable output signal with an error in phase difference imparted due to a deviation of the azimuth angle between the fixed scale and the movable scale and a change in the gap between the fixed scale and the movable scale. .

[Brief description of drawings]

1 is a schematic perspective view of an optical encoder of the present invention, FIG.
FIG. 3 is a schematic view showing a traveling state of a part of the luminous flux of FIG. 1, FIGS. 3A and 3B are explanatory views of the movable scale of FIG.
FIG. 4 is an explanatory view of a light beam passing through the movable scale of FIG. 1, and FIGS. 5 to 8 are light beams passing through both scales when the fixed scale and the movable scale of FIG. 1 are at specific positions. And FIGS. 9 (A), (B), and FIGS. 10 (A), (B) are explanatory views when the fixed scale and the movable scale of FIG. 1 are continuously displaced, respectively. 11 (A), (B), and (C) are explanatory views of an embodiment in which the widths of the V-shaped groove and the plane light transmitting portion of the movable scale according to the present invention are changed, and FIG. FIG. 13 is a schematic view of an example in which is applied to a rotary encoder, and FIG. 13 is a schematic view of an example in which the present invention is applied to a linear encoder. In the figure, 1 is a light emitting element, 2 is a fixed scale, 3 is a movable scale, 4a, 4b and 4c are light receiving elements, 5 is an amplifier, 6 is a waveform shaping circuit, 7 is a direction discrimination counter, 31 is a V-shaped groove, 32 Is a plane light transmitting portion.

Claims (1)

[Claims] 1. A light beam from a light source is made incident on a first scale provided with a light transmitting portion on a grating, and the light beam from the light transmitting portion is
The V-shaped groove provided in the direction perpendicular to the displacement direction of the object to be measured and the plane light transmitting portion are provided via the second scale provided periodically in the horizontal direction with respect to the displacement direction. When light is received by the two light receiving elements provided on each inclined surface of the V-shaped groove, when the V-shaped groove and its adjacent V-shaped groove pitch are P,
By setting the width of the inclined surface of the V-shaped groove to P / 4,
An optical encoder, wherein two light receiving elements output two-phase output signals having a phase difference of 90 degrees, and the displacement direction and the displacement amount of the object to be measured are detected from the two-phase output signals.