JPH0253728B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a photoelectric transmission encoder used, for example, to detect the rotation angle of a rotary table of a machine tool, or to detect the linear movement distance of a reciprocating table. .

BACKGROUND ART FIG. 2 is a diagram for explaining the principle of a conventional technique used for detecting linear movement distance. This is a thin plate-shaped body, in which slit-shaped transparent parts 11, 11, ... and non-transparent parts 12, 12, ... are formed alternately at regular intervals and with the same width at a constant minute distance. 1 transparent body 10, transparent parts 21, 21, . . . and non-transparent parts 22, 22, . . . in the same way as above.
The first and second transparent bodies 1 are brought into a polymerized state with a gap between them and the second transparent bodies 20 formed alternately.
A light emitting part 1 and a light receiving part 2 are placed opposite each other with 0 and 20 in between, and the light emitting part 1 has a width several times as large as the pitch of the light transmitting part 11, and the light is emitted over the entire width of the light emitting part 1. The light receiving section 2 has the same width as the light projecting section 1 and has a light receiving element over its entire width. This allows the substantially parallel light emitted from the light projecting section 1 to be transferred to the light transmitting section 1 of the first light transmitting body 10.
1, 11, . . ., the light receiving portion 2 receives the light that has passed through the light transmitting portions 21, 21, . It is designed to generate a voltage that is still,
Normally, either one of the transparent bodies 10 or 20 is stationary and the other is integrated with the object to be detected, but there are cases where the two are connected to different moving bodies to detect the relative movement amount. , light emitting/receiving section 1, 2
will also be combined with either one. In the above, the light transmitting body 10 and the light projecting body 20 are arranged at the pitch (light transmitting parts 11, 11, ... or 21, 2).
Each time the relative movement is made by an arrangement interval of 1......, the transparent parts 11, 11,...
The overlapping area of 1,... changes periodically, and as a result, the amount of light reaching the light-receiving part 2 from the light-transmitting part 1 changes periodically, and a periodically changing alternating voltage signal is extracted from the light-receiving part 2. . Therefore, by measuring the number of cycles of this alternating voltage signal,
0 and the relative movement amount of the light projector 20 is determined. still,
The above is for detecting a linear movement distance, but the only difference is that for detecting a rotation angle, one or both of the transparent body 10 and the light projecting body 20 are formed around the disk. And there is nothing else different.

Problems to be Solved by the Invention By the way, the detection resolution of this kind of thing is determined by the pitch of the transparent parts 11, 11, . . . and the transparent parts 21, 21, . In order to form such a device, the pitch must be made smaller, which imposes constraints on both production and cost.

The present invention attempts to solve the problem of miniaturization of the pitch when realizing a high-resolution photoelectric transmission encoder.

Means for Solving the Problems The present invention has three transparent bodies in which transparent parts and non-transparent parts are formed alternately, and the first and third transparent bodies are sandwiched between the second transparent body. transparent bodies are arranged facing each other, and one or both of the second transparent body and the first and third transparent bodies on both sides of the second transparent body are movable relative to the other in a direction orthogonal to the facing direction. a light transmitting part and a light receiving part are disposed with first to third transparent bodies in between, and the widths of the transparent part and the non-transparent part of the first and third transparent bodies are the same. The arrangement pitch of the transparent parts of the second transparent body is the same as the arrangement pitch of the first and third transparent parts, and the width of the transparent part is smaller than the width of the non-transparent part. ,
The width of the light emitting part and the light receiving part is multiple times the width of the above-mentioned light transmitting part pitch, and each of them has a light emitting element and a light receiving element on the entire width thereof, and the light emitted by the light emitting part is scattered light. This is a photoelectric transmission encoder with special features.

Function Scattered light is emitted from the light projecting part onto the first transparent body, and the light that has passed through the transparent part is emitted onto the second transparent body, passes through the transparent part, and then is emitted onto the second transparent body. The light reaches the third transparent body and finally passes through the transparent part and is introduced into the light receiving part. Therefore, the larger the space connecting the incident angle of the scattered light and the transparent parts of the first to third transparent bodies, the larger the amount of transmitted light, and if any non-transparent part is located in the optical path. will be shaded there. That is, when looking at the case where the transparent part of the second transparent body and the transparent parts of the first and third transparent bodies completely oppose each other, the normal to the transparent part of the second transparent body ( If the radiation angle of the emitted light from the transparent part with respect to the line perpendicular to the center of the transparent part is large, the emitted light will be blocked by the non-transparent part of the first transparent body, and the emitted light will be blocked by the non-transparent part of the first transparent body. Although it becomes difficult to reach the light-transmitting part, the radiation light with a small radiation angle from the light projection point with a large angle is transmitted to the front of the second light-transmitting body through the light-transmitting part of the first light-transmitting body in front of it. The light reaches the light-transmitting part and then reaches the light-receiving surface of the light-receiving part via the light-transmitting part of the third light-transmitting body, so the amount of light reaching the light-receiving surface of the light-receiving part out of the light emitted from each light emitting point in the whole light-receiving part is becomes large. Next, in the case of a 1/2 pitch deviation, if the radiation angle with respect to the normal is small, contrary to the above, it will be blocked by the non-transparent part of the first transparent body, but
Radiant light from a light projection point with a large radiation angle reaches the transparent part of the second transparent body via the transparent part in front of the first transparent body, and the transmitted light is transmitted to the next third transparent body. Since the light reaches the light-receiving surface of the light-receiving section through the light-transmitting part of the light-transmitting body, the amount of light that reaches the light-receiving surface of the light-receiving section out of the light emitted from each light projecting point in the whole light-receiving section is large, as described above. Next, looking at the case where the pitch is shifted by 1/4 and 3/4, if the radiation angle with respect to the normal is small, only a part of the radiation is blocked by the non-transparent part of the first transparent body. If it does not reach the transparent part of the second transparent body and the radiation angle becomes large, even if it passes through the transparent part of the second transparent body, it will not reach the non-transparent part of the third transparent body. Therefore, in the entire light receiving section, the amount of light that reaches the light receiving surface of the light receiving section out of the light emitted from each light projecting point is smaller than in the above case. In this way, the amount of light that finally reaches the light receiving section varies depending on the opposing positional relationship between the light-transmitting parts of the first and third light-transmitting bodies and the light-transmitting parts of the second light-transmitting body. , the maximum is reached when the transparent parts of both are completely facing each other and the arrangement pitch is shifted by 1/2, and the minimum is reached when the arrangement pitch is shifted by 1/4 and 3/4, and the period between the maximum and minimum is monotonous. Change. As a result, an alternating voltage is generated in the light-receiving section that causes a periodic change of two periods each time the first and third light-transmitting bodies and the second light-transmitting body move relative to each other by one pitch.

The above is a case where the positions of the light-transmitting parts of the first and third light-transmitting bodies are completely matched and facing each other.
Even if the positions of the light-transmitting parts of the third light-transmitting body are shifted and facing each other, the result is the same as above (however, the maximum position is different), and the first and third light-transmitting bodies and the second light-transmitting body Each relative movement of the body by one pitch generates an alternating voltage that causes a periodic change of two periods.

Embodiment FIG. 1 shows an embodiment of the present invention for detecting linear movement distance, and the transparent body 10 with the same number as in FIG. 2 is the same as that in FIG.
Transparent parts 11, 11, ... and non-transparent part 12 of the same width
are formed alternately. The first transparent body 10
A second transparent body 20' is disposed facing the transparent part 21', 21', . . . and a non-transparent part 2.
2', 22', . . . are formed alternately, the arrangement pitch of the transparent parts 21', . . . is equal to the pitch of the transparent parts 11, . The width of the transparent part 22' is smaller than the width of the transparent part 22', and in the figure, the width of the transparent part 21' is smaller than 50% of the pitch, for example 25%,
That is, the transparent portion 21' is formed to have a size ⅓ of the non-transparent portion 22'. The second transparent body 20'
A third light-transmitting body 30 having exactly the same structure as the first light-transmitting body 10 is disposed facing the opposite surface of are formed alternately. Then, the first and third transparent bodies 1
On the outside of 0 and 30, there is a light projector 1' that emits scattered light.
and a light-receiving section 2 are arranged, and both are facing each other.

In the above structure, the scattered light emitted from the projector 1' reaches the first transparent body 10, and the light that has passed through the transparent parts 11, 11, . . . reaches the second transparent body 20'. The light is emitted upward, and then the transparent part 2
The light passing through 1', 21', . . . passes through the third transparent body 3.
0, and finally the transparent parts 31, 31,...
The light that has passed through... reaches the light receiving section 2. At this time,
The amount of light reaching the light receiving section 2 is determined by the amount of light that reaches the light receiving section 2.
0,30 transparent parts 11,11,...,31,3
1, ... and the transparent parts 21', 2 of the second transparent body 20'
It changes depending on the opposing positional relationship with 1'...

3 to 6 show the above-mentioned transparent parts 11, 11,...
31, 31, . . . and the transparent parts 21', 21', . The light spot is modeled and shown on the horizontal axis, and the distances between the light emitter 1' and the first transparent body 10 and between the light receiver 2 and the third transparent body 30 are shown here. Transparent parts 21', 21', ... (transparent parts 11, 1
1, . . . ), and the intervals between the first, second, and third transparent bodies 10, 20', and 30 are set to 1/2 pitch. The state shown in Figure 3 is the transparent part 1.
1, 11, ... and transparent parts 21', 21', ... are 1/
2 pitches, that is, the center position of the transparent part 21' of the second transparent body with respect to the center of the transparent part 11 is the center position of the transparent part 1
They face each other with a difference of 1/2 of the distance between them.
The transparent body 20' is shifted to the left by 1/4 pitch from the state shown in the figure, and in FIG. 5, the transparent body 20' is shifted by 1/2 pitch to the left from the state shown in FIG. 11, . . . and the transparent portion 21' completely oppose each other, and FIG. 6 shows a state in which the transparent body 20' is shifted by 3/4 pitch to the left from the state shown in FIG. The area surrounded by the line with an arrow indicates the light rays that pass through one light-transmitting part 11 in the center of the light-transmitting body 10 among the scattered light from one point of the light projector 1'. The hatched part shows the amount of light passing through the second and third transparent parts 21' and 31, and the lower part of each figure shows the amount of light that reached the light receiving part 2 relative to the total amount of light passing through the transparent part 11. The ratio is shown as a percentage.

That is, light is reflected from the light projecting element of the light projecting section over various radiation angles (scattered light).
Now, looking at one arbitrarily selected light projecting element of the light projecting section, among the scattered light, the light transmitting section 11
The amount of light passing through is constant regardless of the position of the transparent portion 21'. Here, the amount of transmitted light (the area surrounded by the solid line with arrows in FIGS. 3 to 6) is set to 100%. Next, this amount of light passing through the second light projector 2
0', but if there is a transparent part 21' on that optical path, only the light of that part of the optical path will pass there (third and fifth hatched parts). Then, the passing light is directed toward the third light-transmitting body 30, and if there is a light-transmitting part 31 in the optical path, it passes there and reaches the light-receiving element of the light-receiving part 2 (states shown in FIGS. 3 and 5). If there is a transparent portion 32, the light is blocked there (the state shown in FIG. 4). The lower part of FIGS. 3 to 6 shows that the light is emitted from the light projecting element at each position of the light projecting part 1', and the light is emitted from the light transmitting part 11.
The ratio of the amount of light that returns to the light receiving section 2 out of the amount of light (100%) that has passed through is shown with the position of each light emitting element on the horizontal axis.For example, in Fig. 3, the light emitting position of the light emitting section 1' The proportion of positions that intersect a line (not shown) depending from is radiated from that position,
This is the amount of light that passes through the light-transmitting parts 11, 21', and 31 and reaches the light-receiving part 2, and the figure shows a case where the ratio is 25%. Similarly, if we look at the light projecting element located slightly to the right of that position, near the center of FIG.
Since there is no amount of reflected light as a result, it is shown as 0%. Then, the light emitted from each of these positions returns to the light receiving section 2 at the rate described above, and when looking at the whole, the amount of light that returns there ends up being the same in each figure in Figures 3 to 6. It corresponds to the value obtained by adding the ratios shown in the lower row.

Hereinafter, using FIG. 3 above as an example, we will explain the relationship between the position of the light emitting element and the ratio of the amount of light that reaches the light receiving section 2 out of the amount of light that passes through the light transmitting parts 11, 21', and 31, that is, the lower part of FIG. The basis for obtaining the ratio will be explained diagrammatically with reference to FIGS. 7 to 17. 7th to 1st
In FIG. 7, the light projecting section 1' and the light receiving sections 11, 21', and 31, which are given the same numbers as in FIG. 3, are the same as in FIG. 3, and are arranged in the same manner. 7th to 1st
Fig. 7 shows a case where the light emitting element position changes to the right in units of 1/4 pitch from the left end of the transparent section 11 at the left end, that is, 0, 1/4, 1/2, . . . from the reference position.
...Emitted from the light projecting element located at 7/4 pitch,
The relationship between the light passing through the second light-transmitting section 11 from the left and the light passing through the light-transmitting section 21' (hatched) is shown in sequence. When the light emitting element position shown in FIGS. 7 to 9 is at 0, 1/4, and 1/2 pitch positions, the entire light-transmitting part 21' is located within the range of light passing through it, and all of the light passing through it reaches the light-receiving part 2. The amount of light reaching the target is large.
It is 33.3%. Next, in the 3/4 pitch state shown in Figure 10, the entire transparent part 21' is located within the range of the passing light, but a part of the passing light is blocked by the non-transparent part (filled areas in the figure). part), the amount of light reaching the light receiving part 2 is reduced from the above, to 25%. Next, in the 1, 5/4, and 3/2 pitches in Figures 11 to 13, only a part of the transparent part 21' is located within the passing light range, or it is not located at all, and a part of it is located. Even in this case, the transmitted light is blocked by the non-light-transmitting portion 32 and becomes 0%. Next, 7/4 in Figures 14 to 17,
The conditions of 2, 9/4, and 5/2 pitches are 5/2 in Figure 12 above.
There is a symmetrical relationship with the above-mentioned figures 10 to 7, centering on the position of 4 pitches, and they are 25%, 33.3%, etc., respectively. This is plotted in the lower part of Figure 3.

Note that this is a result for the light passing through one transparent section 11, but the same is true for each transparent section 11, and for a plurality of transparent sections 11, the result is the same for the light passing through one transparent section 11. The resulting patterns are added together with their positional relationship shifted.

Now, FIGS. 4 to 6 show the state of the passing light with respect to the emitted light from one light projecting element in the upper part, and the states of the light passing through the light emitted from the light projecting element at one point in the upper part, and the states of the above-mentioned lights 7 to 17 in the lower part of each figure.
The position of the light projecting element obtained by the same graphical analysis as shown in the figure and the ratio of the amount of light reaching the light receiving section 2 out of the amount of light passing through the light transmitting section 11 are shown. Looking at the cases where the pitch is shifted by 1/4 and 3/4 in FIGS. 4 and 6, when the radiation angle is small, only a part of the emitted light passes through because it is blocked by the non-transparent part 22'. Furthermore, when the radiation angle becomes large, the passing light is blocked by the transparent part 11, or even if it passes, it is blocked by the non-transparent part 32, so in the end, the light receiving part as a whole accounts for only a portion of the light emitted from each light emitting point. The amount of light reaching the light-receiving surface of the light-receiving section is the fifth
It is smaller than the cases shown in FIG. 3 and FIG. After all, the area of this pattern has a corresponding relationship with the amount of light that returns to the entire light receiving section 2. Therefore, the amount of light that reaches the light receiving section 2 corresponds to the state shown in FIGS. 4 and 6, that is, both transparent parts 11 and 21' are shifted by 1/4 and 3/4 pitch, respectively. It reaches a minimum when

As a result, a voltage signal corresponding to the amount of light introduced from the light receiving section 2, that is, a voltage signal corresponding to the amount of light introduced, that is, a voltage signal corresponding to the first and third light transmitting bodies 10, 30 and the second light transmitting body 20' is relatively 1/2.
An alternating voltage signal that changes periodically with each pitch movement is generated, resulting in an alternating voltage signal having twice the resolution as that of the prior art.

In the above embodiment, the light emitting/receiving section 1',
2 and the transparent body 10, 30, the transparent body 10, 20',
30 are the same as and 1/2 times the pitch of the transparent part, respectively, but the present invention is not limited to this. The ratio of the transparent parts 21', 21', . . . of the body to the pitch may also be set to an appropriate ratio smaller than 50%. That is, in FIG. 18, the distances between the light emitter 1' and the light-transmitting body 10, between the light-transmitting body 10 and the light-transmitting body 20', and between the light-transmitting body 20' and the light-transmitting body 30 are calculated as the light-transmitting part pitch. The ratio of the amount of light that reaches the light receiving part 2 out of the amount of light passing through the transparent part 11 in the case of The figure shows a 3/4 pitch, and as in the case of FIGS. 3 to 6, the amount of light changes twice during one pitch. Also, Figure 19 shows
When the width of the transparent part 21' is set to 50% of the pitch, the proportion of the amount of light that reaches the light receiving part 1' out of the amount of light passing through the transparent part 11 is calculated as the ratio of the amount of light that reaches the light receiving part 1'.
1' complete polymerization state, 1/4 pitch, 1/2 pitch, 3/4
The figure shows the pitch, and even in this case, the amount of light changes twice during one pitch.

Effects of the Invention The present invention makes the light-transmitting part of the second light-transmitting body located between the first and third light-transmitting bodies smaller than 50% of the pitch thereof, and scattering the light source of the light projecting part. By using it as a light source, it is possible to extract an output with twice the resolution of conventional technology, making it easier to achieve higher resolution both from the production and economic aspects, and making it possible to obtain high-resolution rotation angles and distances. Detection is easily achieved.

[Brief explanation of drawings]

Fig. 1 is a front view showing an embodiment of the present invention, Fig. 2 is a front view showing a conventional technique, Figs. 3 to 6 are explanatory diagrams of the operation of the present invention, and Figs. The analytical diagrams shown in FIGS. 18 and 19 for explaining the proportion of the amount of light reaching the light-receiving part are obtained under conditions in which the intervals between the three light-transmitting bodies are different from those in FIGS. 3 to 6.
FIG. 4 is a diagram showing the ratio of the amount of light reaching the light receiving section under different conditions of the light-transmitting body. 1': Light emitter, 2: Light receiver, 10, 20, 3
0: Transparent body, 11, 21', 31: Transparent part, 12,
22', 32: Non-transparent part.

Claims (1)

[Claims] 1. It has three transparent bodies in which transparent parts and non-transparent parts are formed alternately, the first and third transparent bodies are arranged facing each other with the second transparent body in between, and one or both of a pair of a second transparent body and a first and third transparent body on both sides thereof are supported so as to be movable relative to the other in a direction orthogonal to the opposing direction; A light transmitting part and a light receiving part are arranged with a light transmitting body in between, the widths of the light transmitting part and the non-light transmitting part of the first and third light transmitting bodies are the same, and the width of the light transmitting part of the first and third light transmitting bodies is the same, and The arrangement pitch of the transparent parts is the above-mentioned first,
The arrangement pitch is the same as that of the third transparent part, and the width of the transparent part is smaller than the width of the non-transparent part, and the width of the light emitting part and the light receiving part is multiple times the pitch of the transparent part. 1. A photoelectric transmissive encoder, each having a light projecting element and a light receiving element over its entire width, and the light projected by the light projecting part is scattered light.