JPH0253727B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a photoelectric reflective 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-like body with slit-shaped light-transmitting parts 11, 11, ... and light-shielding parts 1 at minutely fixed distances.
2, 12, .
23, . . . and a reflector 20 in which non-reflective portions 24, 24, . The light emitting part has a width multiple times the width of the above-mentioned light transmitting part pitch, has a light emitting/receiving element over the entire width, and the light emitted is parallel light, and the light emitting part Translucent section 1 transmits substantially parallel light emitted from
1, 11, . . ., the irradiated light is reflected by the reflection portions 23, 23, . The light is received by the section 1, and a voltage corresponding to the amount of light received is generated. Note that normally one of the transparent body 10 and the reflector 20 is kept stationary and the other is integrated with the object to be detected, but there are cases where the two are coupled to different moving bodies to detect the amount of relative movement. In that case, the light emitting/receiving section 1 will also be coupled to either one. In the above, the transparent body 10 and the reflector 20 are arranged at the pitch (transparent parts 11, 11, . . . , reflective parts 23, 23, . . .
Each time there is a relative movement by the amount (array interval) of A periodically changing alternating voltage signal is taken out from the light emitting/receiving section. Therefore, by measuring the number of cycles of this alternating voltage signal, the amount of relative movement between the transparent body 10 and the reflector 20 can be determined.

Note that the above is for detecting the linear movement distance, but for detecting the rotation angle, the transparent body 10 and the reflector 2 are used.
The only difference is that one or both of the zeros are formed around the disk, and there are no other differences.

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 reflective parts 23, 23, . In order to form a product, the pitch must be made smaller, which imposes constraints on both production and cost.

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

Means for Solving the Problems The present invention includes a light transmitting body and a reflecting body, one or both of which are movable relative to the other, superimposed at intervals in a direction perpendicular to the direction of movement, and the light transmitting bodies are arranged alternately. A photoelectric reflective type that has a transparent part and a non-transparent part formed, the reflector has a reflective part and a non-reflective part formed alternately, and a light emitting and receiving part is arranged on the outside of the transparent body. In the encoder, the width of the transparent part and the non-transparent part of the transparent body are the same, and the width of the reflective part of the reflective body is the same as that of the transparent part, and the width of the reflective part is the same as the width of the reflective part. The width of the light emitting/receiving part is several times the width of the light transmitting part, and the light emitting/receiving part has a light emitting/receiving element over the entire width, and the light emitted is scattered light. It is.

Function Scattered light is emitted from the light emitting/receiving section onto the transparent body,
The light that has passed through the transparent portion is irradiated onto the reflector at various angles of incidence. As a result, the reflective part that the light reaches and its position differ depending on the incident angle, and as a result, the angle of reflection of the reflected light from the reflective part also varies in various directions, and some of the reflected light reaches the transparent part of the transparent body again. Only that light is introduced into the light emitting/receiving section. In this way, the amount of light that finally reaches the light emitting/receiving section varies depending on the opposing positional relationship between the transparent section of the light transmitting body and the reflecting section of the reflector. /2 shift maximum, 1/4 of array pitch,
and the minimum when shifted by 3/4, and the maximum,
The minimum interval changes monotonically. In other words, when looking at the case where the transparent part and the reflective part completely oppose each other, if the radiation angle of the emitted light with respect to the normal line of the reflective part (the line perpendicular to the center of the reflective part) is large, the emitted light will be emitted by the non-transparent part. However, the emitted light with a small radiation angle from the light emitting point with a large angle reaches the reflective part in front of it through the transparent part in front of it and is reflected. Since the light reaches the light-receiving surface, the amount of light that reaches the light-receiving surface of the light-emitting and receiving section again out of the light emitted from each light-emitting point in the entire light-emitting and receiving section becomes large. Next, in the case of a 1/2 pitch shift, conversely to the above, if the radiation angle with respect to the normal is small, it will be blocked by the non-transparent part, but the emitted light from the projection point with a large radiation angle will be blocked in front of the reflective part. The reflected light reaches the reflective part via the transparent part, and the reflected light reaches the light-receiving surface of the light emitting/receiving part via the next transparent part.
Similarly to the above, in the entire light projecting and receiving section, the amount of light that reaches the light receiving surface of the light projecting and receiving section again out of the light emitted from each light projecting point is large. 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 will reach the reflective part because it is blocked by the non-transparent part. Also, if the radiation angle becomes large, even if it is reflected, it will be blocked by the back surface of the non-transparent part, so in the end, the amount of light emitted from each light emitting point will reach the light receiving surface of the light emitting and receiving part again. is smaller than in the above case. As a result, an alternating voltage is generated in the light emitting/receiving section, which causes two periodic changes each time the transparent body and the reflector move one pitch relative to each other.

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. A reflector 20 is disposed facing the transparent body 10.
3', 23', ... and non-reflective parts 24', 24', ...
are formed alternately, and the arrangement pitch of the reflective portions 23', . . . is the same as that of the transparent portions 11, .
The width is equal to the pitch of the non-reflective portion 24'...
In the figure, the reflective part 23' is formed to have a pitch smaller than 50%, for example 25%, that is, the reflective part is 1/3 the size of the non-reflective part. On the outside of the transparent body 10, a light emitting/receiving section 1' is provided which has the same structure as shown in FIG. 2 and has a scattered light source instead of a parallel light source for projecting light.

In the above system, among the scattered light emitted from the light emitter/receiver 1', the light that passes through the transparent parts 11, 11, . . . is emitted onto the reflector 20', and the incident angle is various. , transparent parts 11, 11,...
and the reflecting portions 23', 23', . . . to which the incident light reaches depending on the opposing positional relationship of the reflecting portions 23', 23', .
and the reflecting portions 23', 23', . The amount of light returned is also different.

3 to 6 show the above-mentioned transparent parts 11, 11,...
The opposing positional relationship between the reflectors 23', 23', . Here, the distances between the light emitting/receiving section 1' and the light-transmitting body 10, and between the light-transmitting body 10 and the reflector 20' are shown as reflecting sections 23', 23', . . .
The arrangement pitch of the translucent parts 11, 11, . . . is the same as and 1/2 times that, and the pitch of the reflective parts 23', 23', . . . is 25%. The state shown in Fig. 3 is the transparent parts 11, 11, . . . and the reflective parts 23', 23', .
is 1/2 pitch, that is, the center position of the reflecting part 23 is opposed to the center of the transparent part 11 by 1/2 of the distance P between the transparent parts 11, and FIG. 4 is from the state of FIG. 3. The reflector 20' shifts to the left by 1/4 pitch, and in FIG. 5, the reflector 20' shifts to the left by 1/2 pitch from the state shown in FIG. Part 23'
are completely opposed to each other, and FIG. 6 shows a state in which the reflector 20' is shifted to the left by 3/4 pitch from the state shown in FIG. The area surrounded by the line with an arrow represents the scattered light from one point of the light projector/receiver 1' that passes through one light transmitting section 11 in the center of the light transmitter 10 and is reflected by the reflector 2.
The hatched part in the figure shows the amount of light reflected by the reflective part 23', and the lower part of each figure shows the amount of light emitted from the transparent part 11 relative to the total amount of light passing through the transparent part 11. The percentage of the amount of light that is reflected by the reflecting part 23' and returned to the light emitting and receiving part via the light transmitting part 11 (not necessarily the same as the light transmitting part 11 through which the incident light passed) is expressed as a percentage. This is what is shown.

That is, light is emitted from the light projecting element of the light projecting/receiving section over various radiation angles (scattered light).
Now, when we look at one arbitrarily selected light emitting element of the light emitting and receiving section, out of the scattered light, the light transmitting section 1
1, the amount of light passing through the reflecting part 11 of the reflector 20' is
is constant regardless of the position of 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 passing light reaches the reflector 20', but only the light on the optical path where the reflecting section 11 was located on the emitted optical path is reflected there (hatched portions in Figures 3, 4, and 6). become. Then, the reflected light is again directed towards the light-transmitting body 10, and if there is a light-transmitting part 11 in its optical path, it passes through it and reaches the light-receiving element of the light emitting/receiving part 1' (states shown in Figs. 3 and 4). If there is a transparent part 12, the light is blocked there (the state shown in FIG. 6). The lower part of Figures 3 to 6 shows the amount of light (100%) emitted from the light emitting element at each position of the light emitting/receiving section 1' and returning to the light emitting/receiving section 1' after passing through the transparent section 11. The ratio of the amount of light is shown with the position of each light emitting element on the horizontal axis. For example, in FIG. The ratio of the amount of light that returns to the light emitting/receiving section 1' out of the amount of light emitted is shown as a value of 33% at the position where the above-mentioned broken line hangs down. Similarly, if we look at the light projecting element located near the center of FIG.
Shown as %. Then, the light emitted from each of these positions returns to the light emitting/receiving section 1' at the rate described above, and when looking at the whole, the amount of light that returns there ends up being as shown in each of Figures 3 to 6. It corresponds to the value obtained by adding the ratios shown in the lower row of each column.

Hereinafter, using FIG. 3 as an example, the relationship between the position of the light emitting element and the ratio of the amount of light emitted therefrom and returning to the light emitting/receiving part 1' out of the amount of light that has passed through the light transmitting part 11 will be explained.
That is, the basis for obtaining the ratios shown in the lower part of FIG. 3 will be explained diagrammatically with reference to FIGS. 7 to 17.

In Figures 7 to 17, a light emitting/receiving part 1', a light transmitting part 11, and a reflecting part 2 are given the same numbers as in Figure 3.
3' is the same as in FIG. 3 and is similarly arranged. FIGS. 7 to 17 show the light-transmitting part 11 at the left end.
When the position of the light emitting element changes to the right in 1/4 pitch increments based on the left edge of The relationship between the transmitted light emitted from the element and passed through the second transparent section 11 from the left and the reflected light (hatching) 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 reflecting portion 23' is located within the passing light range, and all of the reflected light is transmitted to the light emitting/receiving portion 1'. , so the amount of light that reaches it is large, 33.3%. Next, 3/ in Figure 10
In the 4-pitch state, the entire reflecting section 23' is located within the passing light range, but part of the reflected light is blocked by the non-transparent section (solid area in the figure) and reaches the light emitting/receiving section 1'. The amount of light reaching the target is 25%, which is lower than the above. Next, in the case of 1, 5/4, and 3/2 pitches in Figs. 11 to 13, only a part of the reflecting part 23' is located within the passing light range, or it is not located at all, and if it is partially located, However, the reflected light is blocked by the non-transparent part and becomes 0%. Next, the 14th to 1st
The states of 7/4, 2, 9/4, and 5/2 pitches in Figure 7 are symmetrical to those in Figures 10 to 7 above, centering on the position of 5/4 pitch in Figure 12 above, and each has a 25% , 33.3
%... 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 reflected light with respect to the emitted light from one light projecting element in the upper part, and the states of the reflected light from the 7 to 17 points in the lower part of each figure are shown in the upper part.
It shows the position of the light projecting element determined by a graphical analysis similar to that shown in the figure, and the ratio of the amount of light that returns to the light projecting/receiving section 1' out of the amount of light that passes through the light transmitting section 11.
Looking at the cases of 1/4 and 3/4 pitch deviations in Figures 4 and 6, we can see that when the radiation angle is small, only a portion of the emitted light reaches the reflective part because it is blocked by the non-transparent part. Furthermore, when the radiation angle becomes large, the light passing through is blocked by the transparent part 11, and even if it is reflected, it is blocked by the back surface of the non-transparent part. The amount of light that reaches the light receiving surface of the light emitting/receiving section again is smaller than in the cases of FIGS. 3 and 5. After all, the area of this pattern has a corresponding relationship with the amount of light that returns to the entire light emitting/receiving section 1', and therefore the amount of light returning to the light emitting/receiving section is determined by the states shown in FIGS. 5 and 3. In other words, the maximum value is reached when the transparent part 11 and the reflective part 23' are completely overlapped and they are shifted by 1/2 pitch, and the minimum is achieved when the transparent part 11 and the reflective part 23' are shifted by 1/4 or 3/4 pitch, as shown in Figures 4 and 6. Then,
It increases and decreases monotonically between its maximum and minimum, and between its minimum and maximum.

As a result, the light emitting/receiving section 1' outputs a voltage signal corresponding to the amount of reflected light introduced into the transparent body 1.
0 and the reflector 20' relative to each other by 1/2 pitch, an alternating voltage signal that changes periodically is generated, and as a result, an alternating voltage signal that has twice the resolution as that of the prior art is generated. It becomes a voltage signal.

In the above embodiment, the distance between the light emitting/receiving section 1' and the light transmitting body 10 and between the light transmitting body 10 and the reflector 20 are set to be the same and 1/2 times the pitch of the light transmitting section, respectively. It is not limited to this, and the same effect can be achieved by appropriately selecting the reflector, and the ratio of the reflecting portion to the pitch may also be set to an appropriate ratio smaller than 50%.

That is, FIG. 18 shows the light emitting and receiving body 1' and the light transmitting body 1.
The ratio of the amount of light that returns to the light emitting/receiving section 1' out of the amount of light that passes through the transparent section 11 when both the distance between the transparent body 10 and the reflector 20 is taken as the pitch of the transparent section is expressed as:
These are shown for the completely polymerized state of the transparent part 11 and the reflective part 23', 1/4 pitch, 1/2 pitch, and 3/4 pitch, respectively, and the distance between 1 pitch is similar to the case of FIGS. 3 to 6. Two changes in light intensity occur. Also,
FIG. 19 shows the ratio of the amount of light that returns to the light emitting/receiving section 1' out of the amount of light that passes through the transparent section 11 when the width of the reflective section 23' is set to 50% of the pitch, respectively. The figure shows the fully polymerized state of the portion 23', 1/4 pitch, 1/2 pitch, and 3/4 pitch, and even in these cases, the light intensity changes twice between each pitch.

Effects of the Invention The present invention makes the ratio of the reflecting part to the reflecting part pitch of the reflector smaller than 50%, and uses a scattering light source as the light source of the light emitting/receiving part, thereby obtaining an output with twice the resolution of the conventional technology. It was made into
Increasing the resolution becomes easier from both a production and economical perspective, and high-resolution detection of rotation angles and distances can be easily realized.

[Brief explanation of the drawing]

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 that returns to the light emitting/receiving section are for the reflection section under conditions where the distance between the light transmitting body and the reflecting body is different from that in FIGS. 3 to 6, respectively. FIG. 7 is a diagram showing the proportion of the amount of light returning to the light emitting/receiving section under conditions of different widths. 1': Light projecting and receiving body, 10: Transparent body, 11: Transparent part,
12: non-transparent part, 20': reflective part, 24': non-reflective part.

Claims (1)

[Claims] 1 A transparent body and a reflective body, one or both of which are movable relative to the other, are superimposed at intervals in a direction perpendicular to the moving direction, and the transparent body has transparent parts and non-transparent parts formed alternately. In a photoelectric reflective encoder, the reflector has reflective parts and non-reflective parts formed alternately, and the light transmitting and receiving part is arranged outside the transparent body. and the width of the non-transparent part are the same,
In the reflector, the array pitch of the reflective parts is the same as that of the transparent part, and the width of the reflective part is smaller than the width of the non-reflective part. What is claimed is: 1. A photoelectric reflective encoder characterized in that it is double in size, has a light emitting/receiving element over its entire width, and that the emitted light is scattered light.