JPH08128808A - Displacement sensor and displacement detection method - Google Patents

Abstract

(57) [Abstract] [Purpose] To be able to confirm the state in advance when an erroneous distance detection signal is obtained depending on the direction of the change in the reflectance of the surface state of the detected object. [Structure] A light projecting element 11 and a position detecting element 12 for receiving reflected light of light emitted from the light projecting element 11 are provided. The distance to the object is detected by the position received by the position detection element 12. Then, a position detecting element 13 for monitoring is provided in a direction perpendicular to a surface connecting the position detecting element 12 and the light projecting element 11 at a position perpendicular to the position detecting element 12 via the light projecting element 11. When the light receiving position of the position detecting element 13 fluctuates from the center, an erroneous distance signal due to a change in reflectance is obtained, so this is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement sensor for detecting a distance to an object and a displacement detecting method therefor.

[0002]

2. Description of the Related Art FIG. 6 is a schematic view showing an example of a conventional optical displacement sensor. As shown in the figure, the optical displacement sensor 1 has, for example, a light emitting diode as the light projecting element 2, and emits light parallel to the detection region. When the object 3 arrives at the detection area, light is reflected from the object. A curve A in FIG. 6 is a diagram showing the intensity distribution of reflected light. The displacement sensor 1 receives the reflected light, and therefore has a lens 4 and a position detection element (PSD) 5 adjacent to the light projecting element 2. Since the position of the center of gravity of the reflected light differs depending on the distance to the object depending on the PSD 5, the distance to the object is detected based on the signal from the PSD 5.

[0003]

However, in such a conventional optical displacement sensor, if the surface state of the object 3 is not uniform, the barycentric position is different at the boundary where the reflectance changes, and the correct displacement can be measured. There was a drawback that you couldn't. This is because, for example, if the intensity distribution of the reflected light is shown by the curve B in FIG. 7, the position of the center of gravity of the reflected light deviates from the optical axis, and the distance to the object changes. FIG. 8 shows the relationship between the direction of change of the reflectance on the surface of the detection object 3 and the light emitting / receiving axis. FIG.
As shown in (a), when the reflectance changes in parallel with the plane P including the projection axis and the normal line of the light receiving surface as indicated by the arrow D, the light receiving position of the light is the original light receiving position. Differently, a lot of reflected light is obtained on the high reflectance side, so that the correct position cannot be detected. On the other hand, as shown in FIG. 8B, when the plane P including the projection axis and the normal line of the light receiving surface and the direction in which the reflectance of the detection object 3 changes (arrow D) are perpendicular, the position detection element Since the influence on 5 is symmetrical, the influence on the light receiving position is reduced. As described above, there is a drawback in that the distance to the object may or may not change depending on the direction of change in the reflectance of the surface state of the object.

The present invention has been made in view of the above conventional problems, and it is possible to accurately measure the distance to an object in consideration of the change in the reflectance of the detected object and in consideration of this influence. An object of the present invention is to provide a displacement sensor capable of

[0005]

According to a first aspect of the invention of the present application, a light projecting element for irradiating light in a predetermined direction and a light receiving region which is arranged at a predetermined distance from the light projecting element and is directed toward the light projecting element are provided. An at least one-dimensional first position detecting element having:
First signal processing means for detecting the distance to the object based on the light receiving position received by the position detecting element, and a predetermined distance from the plane including the projection axis and the normal line of the light receiving surface of the first position detecting element. It is provided with a second position detecting element for monitor arranged apart from each other, and a second signal processing means for judging whether or not the position received by the second position detecting element is within a predetermined range. It is what

In the invention according to claim 2 of the present application, the second position detecting element is located at a position perpendicular to the first position detecting element with the light projecting element as a center when viewed from the light projecting axis of the light projecting element. It is characterized in that it is arranged in parallel with the first position detecting element.

In the invention of claim 3 of the present application, the second signal processing means is based on the light receiving position determining means for determining the light receiving position received by the second position detecting element and the output of the light receiving position determining means. And a prohibiting means for prohibiting the output of the first signal processing means when the light receiving position is not near the center based on the output of the determining means. It is what

According to a fourth aspect of the present invention, the first and second position detecting elements are PSDs.

According to a fifth aspect of the present invention, the light projecting element emits light in a predetermined direction, and the light projecting element is disposed at a predetermined distance from the light projecting element and has at least one light receiving region toward the light projecting element.
The three-dimensional position detection element receives the reflected light emitted from the light projecting element from the object whose distance is detected, detects the distance to the object based on the light receiving position of the first position detecting element, and the light projecting axis And a second position detecting element for monitoring is arranged at a predetermined distance from a surface including the normal line of the light receiving surface of the first position detecting element, and whether the position received by the second position detecting element is within a predetermined range. It is characterized by determining whether or not the change in the reflectance of the surface of the detection object is affected by determining whether or not it is determined.

[0010]

According to the present invention having such a feature, in addition to the first position detecting element for detecting the position of the object and the first signal processing means, the second position detecting element for monitoring is provided. There is. When the reflectance changes in a direction perpendicular to the plane including the projection axis and the normal line of the light receiving surface of the first light receiving element, the barycentric position of the reflected light obtained by the second position detecting element is Change from the center. Therefore, when an erroneous position detection signal is output based on this change, that fact is determined in advance. According to the second aspect of the invention, the first and second position detecting elements are arranged vertically with respect to the light projecting element so that the sensitivity of the second position detecting element is maximized. According to the invention of claim 3, the light receiving position of the second position detecting element is discriminated, it is discriminated whether or not the position is near the center, and the output of the first signal processing means is prohibited when the position is not near the center. It was done.

[0011]

1 is a schematic view showing an optical system of a displacement sensor according to an embodiment of the present invention as viewed from the front, and FIG. 2 is a perspective view thereof. In these figures, the lenses and the like are omitted and only the light emitting and receiving elements are shown. As shown in these drawings, the displacement sensor 10 has, for example, a light emitting diode as a light projecting element 11 as in the conventional example, and its optical axis is perpendicular to the paper surface of FIG. Since the reflected light is received when an object arrives on the optical axis of the light projecting element 11, the first position detecting element 12 is provided at a position apart from the light projecting element 11 by a predetermined distance. The position detecting element 12 has a light emitting element 1 in the detecting direction.
It is a one-dimensional light receiving element which is in the direction of the arrow shown in FIG. 1 and in which the distance to the light projecting element 11 changes continuously. When an object arrives at a position that intercepts the light projection axis, the position of the center of gravity of the received light varies depending on the distance to the object, so the distance to the object can be detected. In the present embodiment, the light projecting element 1 is separated by a predetermined distance from the surface (indicated by P1 in the figure) including the light projecting axis of the light projecting element 11 and the normal line of the light receiving surface of the position detecting element 12.
As shown in the drawing, a second position detecting element 13 for monitoring the reflectance change is provided at a position perpendicular to the position detecting element 12 with 1 as the center. The detection direction of the position detection element 13 for monitoring is parallel to the detection direction of the position detection element 12.
The position detecting element 13 determines whether or not the change in the reflectance of the surface state of the object whose distance is detected is in the direction affected by the distance measurement. When the detection position is not in the center, it can be determined that the position is affected. Here, the position detection elements 12 and 13 are assumed to use PSD, for example.

FIG. 3 is a block diagram showing the configuration of the signal processing circuit of this displacement sensor. As shown in this figure, the light projecting element 11 is periodically driven by the light projecting element drive circuit 14 so that a predetermined light amount is obtained. The position detecting element (PSD) 12 for displacement detection produces a current output at both ends according to the distribution of the amount of received light, and the pair of outputs is I /
The V converters 15 and 16 convert the voltage signals. I
The outputs of the / V converters 15 and 16 are the adder 17 and the subtractor 18
Are respectively added and subtracted by and output to the division circuit 19. The division circuit 19 outputs the barycentric position to which light is emitted by dividing the subtracted value by the added value. I / V converters 15 and 16, adder 17 and subtracter 1
8. The division circuit 19 constitutes first signal processing means for detecting the distance to the object based on the light receiving position received by the position detecting element 12. The output of the division circuit 19 is output to the analog switch 20.

On the other hand, a position detecting element (PSD) 1 for monitor
Similarly, 3 also produces a current output at both ends thereof, and the pair of outputs is converted into a voltage signal by the I / V converters 21 and 22. The outputs of the I / V converters 21 and 22 are added and subtracted by the adder 23 and the subtractor 24, respectively, and output to the division circuit 25. The division circuit 25 outputs the barycentric position to which light is applied by dividing the subtracted value by the added value. The output of the division circuit 25 is output to the window comparator 26. The window comparator 26 outputs to the analog switch 20, for example, an H level output if the input signal is a signal within a predetermined width above and below 0 indicating the center position of the position detection element 13, and an L level output if the input signal exceeds this width. It also outputs to the display circuit 27. Further, the reference value input section 28 inputs a reference value that determines a range within which the signal of the output of the division circuit 25 is 0, which is the H level. The I / V converters 21 and 22, the adder 23, the subtractor 24, and the division circuit 25 constitute a light receiving position determining means for determining the light receiving position of the second position detecting element 13, and the window comparator 26 and the reference. Value input section 2
Reference numeral 8 is a discrimination means for discriminating whether or not the light reception position is near the center based on the output of the light reception position discrimination means, and the analog switch 2
0 constitutes a prohibiting means for prohibiting the output of the first signal processing means on the basis of the output, and these are the second means for judging whether or not the position received by the second position detecting element is within a predetermined range. Signal processing means.

Next, the operation of this embodiment will be described. The light projecting element driving unit 14 drives the light projecting element 11 intermittently or continuously. In this way, in FIG. 1, the light is emitted from the light projecting element 11 in the upward direction of the paper surface. Then, when an object arrives at a position that intercepts the projection axis of the displacement sensor, the reflected light is obtained in concentric circles. FIG. 4 shows the light projecting element 1 shown in FIG.
FIG. 3 is a diagram showing the positions of 1 and position detection elements 12 and 13 and reflected light. When the distance to the object is different, the light receiving position of the position detecting element 12 changes due to the principle of the triangulation method as in the conventional example. As shown in the figure, if the object is close, the reflected light is received in the vicinity of the outer circumference passing the right side of the position detection element 12. If the object is far away, the reflected light will be small concentric circles,
That is, the concentric circle on the left end side of the position detection element 12 becomes the light receiving position. Therefore, as shown in FIG. 1B, the light receiving level obtained by the position detecting element 12 when the distance to the object is long is, for example, as indicated by the curve C1, and when the object is close, such as C3, depending on the distance to the object. Change. Therefore, the distance to the object can be measured. Assuming that the surface of the detection object has a uniform reflection surface with no change in reflectance, the position detecting element 1 for monitoring according to the distance to the object.
The received light amount of No. 3 changes its received light level as shown by the curves D1 to D3 shown in FIG. 1C, but the center of gravity is always at the center position.

Now, a case where the reflectance of the surface of the detection object is different as shown in FIG. 8 will be described. In this case,
As shown in, the influence on the displacement sensor differs depending on the detection direction. As shown in FIG. 8A, when the reflectance changes in a direction parallel to the plane including the light projecting axis and the normal line of the light receiving surface, if this object arrives, it is used for the monitor shown in FIG. The received light distribution of the position detection element 13 changes, for example, as shown in FIG. This is because, in FIG. 4, if the portion having a high reflectance is on the left side in the spot of the light projecting axis of the light projecting element 11, more light is reflected to the right side from the central axis of the position detecting element 13. Further, if the region of the detection object having a high reflectance is on the right side within the spot of the projection axis, the reflected light causes more reflection from the central axis of the position detection element 13 to the left side. On the other hand, as shown in FIG. 8B, if the reflectivity changes in the direction perpendicular to the plane including the normal line of the light projecting axis and the light receiving surface, the change of the light receiving level due to the change of the reflectivity The position detection signal 13 is in the vertical direction, and the change of the position detection element 13 is the same as that in FIG. Therefore, the current at both ends of the position detecting element 13 is converted into a voltage, and the adding circuit 2
3, the subtraction circuit 24 performs addition and subtraction, and by dividing this, the position signal of the center of gravity of the display received by the position detection element 13 is obtained. When the output of the division circuit 25 is a value near 0, the H level output is output from the window comparator to the analog switch 20. In this way, the position signal detected based on the output of the position detection element 12 is output to the outside as a position signal via the analog switch 20. When the output of the division circuit 25 exceeds the reference value and is different on the positive or negative side, the window comparator 26 outputs an L level. In this case, the analog switch 2
0 is turned off, and that effect is displayed on the display device 27. Therefore, the position detection signal obtained from the division circuit 19 is not output to the outside, and an incorrect position detection signal can be prohibited.

A malfunction caused by such a change in the reflectance of the surface of the object is as shown in FIGS. 1 and 2, in which the position detecting element for monitoring is horizontal to the line connecting the light projecting element 11 and the position detecting element 12. It is obtained by arranging the position detecting element at the position in parallel with the detection direction of the position detecting element 12. The monitor position detecting element 13 is shown in FIG.
It is not possible to measure even if they are arranged vertically with being overlapped with each other or arranged in a direction symmetrical to the light projecting element 11 on a line connecting the light projecting element 11 and the position detecting element 12. Further, even during this period, the detection sensitivity decreases as it deviates from the vertical direction.

In this embodiment, the position detecting element for the monitor is P
Although it is configured as an SD, it may be configured using a one-dimensional CCD sensor or a multi-divided photodiode. The position detecting elements 12 and 13 are one-dimensional position detecting elements,
As shown by the broken line in FIG. 4, the two-dimensional position detecting element 12A,
13A may be used. Also in this case, if only the change in the direction shown in FIG. 1 is detected, the signal processing circuit shown in FIG. 3 can be used as it is, and the reliability of the position detection signal can be confirmed more accurately. Further, the position detecting element for monitoring may be arranged at a position symmetrical to the position detecting element 13.

FIG. 5 is a view showing the arrangement of the position detecting element 12 for detecting the distance. As shown in FIGS. 1 and 2, when the position detecting element is arranged in the direction perpendicular to the light projecting axis, the light receiving axis does not change linearly according to the change in the distance to the object. A linearization circuit for linearizing the output of 19 is required. In FIG. 5, the one-dimensional position detection element 12 is arranged in parallel with the light projection axis. Then, the distance to the object can be detected based on the center position without using the linearization circuit.

[0019]

As described above in detail, according to the present invention, when the reflectance of the surface state of the object is changed,
There are cases where the position detection is greatly affected by the direction of the reflectance change. In such a case, the influence can be detected by the position detecting element for monitoring in advance, and if the error is considered to be large, the position detecting signal can be prohibited to output an accurate position detecting signal. Therefore, an effect that a highly reliable detection signal can be obtained is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical system portion of a displacement sensor according to an embodiment of the present invention as viewed from the front side of a light projection axis.

FIG. 2 is a perspective view showing an optical system portion of the displacement sensor according to the present embodiment.

FIG. 3 is a block diagram illustrating a configuration of a signal processing circuit unit according to the present exemplary embodiment.

FIG. 4 is a schematic view showing an optical system portion and a position of reflected light thereof when viewed from the front side of the projection axis of the present embodiment.

FIG. 5 is a schematic view showing a configuration of a displacement sensor according to another embodiment of the present invention.

FIG. 6 is a schematic diagram showing a configuration of a conventional displacement sensor.

FIG. 7 is a schematic diagram showing an example of a case where a surface state of an object of a conventional displacement sensor changes.

FIG. 8 is a schematic diagram showing the relationship between the direction in which the reflectance of the detection object changes and the displacement sensor.

[Explanation of symbols]

 10 Displacement sensor 11 Light emitting element 12, 12A, 13, 13A Position detecting element 14 Light emitting element driving section 15, 16, 21, 22 I / V converter 17, 23 Adder 18, 24 Subtractor 19, 25 Division Circuit 20 Analog switch 26 Window comparator 27 Display device 28 Reference value input section

Claims (5)

[Claims] 1. A at least one-dimensional first position detecting element having a light projecting element for irradiating light in a predetermined direction and a light receiving region which is arranged at a predetermined distance from the light projecting element and faces the light projecting element. A first signal processing means for detecting a distance to an object based on a light receiving position received by the first position detecting element; a method of the light projecting axis and the light receiving surface of the first position detecting element; A second position detecting element for monitor arranged at a predetermined distance from a surface including the line, and a second signal processing means for judging whether or not the position received by the second position detecting element is within a predetermined range. And a displacement sensor comprising: 2. The first position detecting element, wherein the first position detecting element is centered on the light projecting element when viewed from a light projecting axis of the light projecting element.
2. The displacement sensor according to claim 1, wherein the displacement sensor is arranged at a position perpendicular to the position detecting element of 1 above and in parallel with the first position detecting element. 3. The second signal processing means has a light receiving position determining means for determining a light receiving position received by the second position detecting element, and a light receiving position is centered based on an output of the light receiving position determining means. And a prohibiting means for prohibiting the output of the first signal processing means when the light receiving position is not near the center based on the output of the determining means. Claim 2 characterized by the above-mentioned.
The displacement sensor described. 4. The first and second position detecting elements are PS
The displacement sensor according to any one of claims 1 to 3, wherein the displacement sensor is D. 5. A light emitting element irradiates light in a predetermined direction, and a distance is provided by at least a one-dimensional position detecting element having a light receiving region which is arranged at a predetermined distance from the light emitting element and is directed toward the light emitting element. The reflected light emitted from the light projecting element from the object to be detected is received, the distance to the object is detected based on the light receiving position of the first position detecting element, and the light projecting axis and the first position are detected. A second position detecting element for monitoring is arranged at a predetermined distance from a surface including the normal line of the light receiving surface of the detecting element, and it is determined whether or not the position received by the second position detecting element is within a predetermined range. Displacement detection method characterized by determining whether or not it is affected by the reflectance change of the surface of the detection object.