JPH0528908U - Optical position detector - Google Patents

Abstract

(57) [Abstract] [Purpose] One position detector receives two light spots and detects the relative distance between them. [Structure] A long electric resistor 12, first and second detection electrodes 13 and 14 are provided on a substrate 11, and photoconductors 15 and 16 are provided between them. Due to the first light spot P1 that is irradiated so as to be laid across between the electric resistor 12 and the first detection electrode 13, the photoconductor 15 has a low resistance and a conductive state is established between them. Resistor 12
The second light spot P2 that is irradiated so as to be bridged between the second detection electrode 14 and the second detection electrode 14 makes the photoconductor 16 have a low resistance and establish a conduction state between them. At this time,
The relative distance between the light spots P1 and P2 can be detected by obtaining the difference between the detection voltages appearing between the detection electrodes 13 and 14.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical position detecting device that detects the position of a light spot irradiated on a predetermined portion using a photoconductor.

[0002]

[Prior Art]

 The basic structure of this type of optical position detecting device is shown in FIG. That is, on a rectangular substrate 1 made of resin or ceramic or the like, an elongated electric resistor 2 (length L in the longitudinal direction) made of a material such as carbon is formed on one side along the longitudinal direction. Has been done. Connection terminals 2a and 2b for voltage application are formed at both ends of the electric resistor 2, and lead wires 3a and 3b are connected to the connection terminals 2a and 2b, respectively.

A long detection electrode 4 is formed on the substrate 1 at a position spaced apart from the electric resistor 2 by a predetermined distance, and a lead wire 5 is also connected to this. A photoconductor 6 is arranged in the gap between the electric resistor 2 and the detection electrode 4. The photoconductor 6 is made of, for example, a material such as CdS, CdSe, PbS, PbSe, etc., and has the property of increasing the conductivity of the portion irradiated with light.

Now, in such a configuration, now, a light spot P bridging between the electric resistor 2 and the detection electrode 4 is irradiated from the connection terminal 2a side of the electric resistor 2 to the position X. The detection principle will be described for the case. That is, first, the constant voltages Va and Vb are applied to the both connection terminals 2a and 2b of the electric resistor 2 in advance. At this time, the electric potential distribution in the longitudinal direction of the electric resistor 2 is distributed so as to change linearly from the voltage Va to the voltage Vb from the connection terminal 2a to the connection terminal 2b.

When the light spot P is irradiated as shown in the figure, the resistance value of the photoconductor 6 in the irradiated portion of the light spot P becomes small, and the electric resistor 2 and the detection electrode 4 are substantially in that portion. It becomes conductive. Therefore, the detection electrode 4 detects the voltage V (X) corresponding to the position where the light spot P is irradiated. The value of the detection voltage V (X) can be expressed by the following relational expression: V (X) = (Vb−Va) × X / L + Va (a) from the above relation. Therefore, the position X where the optical spot P is irradiated can be detected from this detection voltage V (X).

[0006]

[Problems to be solved by the device]

 By the way, when detecting the positions of the light spots in this way, it is necessary to detect the relative distance between the two light spots when they are irradiated. The position of each light spot is detected using this optical position detection device, and the relative distance is detected based on the detection result.

However, when a plurality of optical position detecting devices are used, relative consideration obtained based on individual detection results must be taken unless sufficient consideration is taken to eliminate variations in their characteristics and variations in arrangement position. There is a possibility that the detection accuracy of the distance value may decrease.

The present invention has been made in view of the above circumstances, and an object thereof is to accurately detect a relative distance between two light spots without considering characteristic variations and arrangement position variations. An object is to provide an optical position detection device that can perform such an operation.

[0009]

[Means for Solving the Problems]

 The optical position detecting device of the present invention has an elongated electric resistor 12 provided on a substrate 11 and both end portions of the electric resistor, as shown in the basic configuration shown in FIG. A pair of voltage application terminals 12a and 12b, first and second detection electrodes 13 and 14 arranged on both sides of the electric resistor with a predetermined gap therebetween, and the first and second detection electrodes 13 and 14, respectively. Of the detection electrodes 13 and 14 and the photoconductors 15 and 16 formed in the respective gaps so as to connect the electric resistance body 12 to the electric resistance body 12, and the electric resistance body 12 is provided with voltage application terminals 12a and 12b. In the state where a constant voltage is applied via the first detection electrode 13 and the electric resistor 12, the first light spot P1 irradiated so as to bridge the first detection electrode 13 and the electric resistor 12 and the second detection electrode 14 and the It is irradiated so as to bridge between the electric resistors 12. The relative distance along the electric resistor 12 between the second light spot P2 and the second light spot P2 is detected based on the difference between the voltages appearing at the first and second detection electrodes 13 and 14. Have.

[0010]

[Action]

 The operation of the optical position detecting device of the present invention will be described with reference to FIG. That is, by applying predetermined voltages Va and Vb (Va <Vb) to the voltage application terminals 12a and 12b of the electric resistor 12, a constant voltage VC (= Vb-Va) is given to the electric resistor 12. At this time, the electric potential distribution in the length direction of the electric resistor 12 changes from the voltage Va to Vb in proportion to the distance from the voltage applying terminals 12a 1 to 12b.

Therefore, when the voltage applying terminal 12a side of the electric resistor 12 is set as the reference position, the potential V (k) at the position of the distance k with respect to the entire length L of the electric resistor 12 is V The relation (k) = Va + (Vb−Va) × k / L (A) can be expressed in one-to-one correspondence.

Now, assuming that the light spots P1 and P2 are radiated to the positions of the distances X1 and X2 from the reference position of the electric resistor 12, respectively, the electric resistance 12 and Since the detection electrodes 13 and 14 are electrically connected to each other, the voltage of the electric resistor 12 at that position appears in each of the detection electrodes 13 and 14.

Therefore, according to the above equation (A), the detection voltages V (X1) and V (X2) obtained at the detection electrodes 13 and 14 are V (X1) = V (X1) = Va + (Vb-Va) * X1 / L ... (B) V (X2) = Va + (Vb-Va) * X2 / L ... (C).

Since the relative distance X between the light spots P1 and P2 is the difference between the distances X1 and X2, the difference between the expressions (B) and (C) described above, that is, the detection voltages V (X1) and V ( X2) and obtain the result by calculating the relative distance X (= X1−X2), so V (X1) −V (X2) = (Vb−Va) × (X1−X2) /L...(D) Therefore, X = {V (X1) -V (X2)} / (Vb-Va) * L ... (E) That is, X = {V (X1) -V (X2)} / VC It can be calculated as xL ... (F). That is, the ratio of the voltage value of the difference between the detected voltage V (X1) and V (X2) with respect to the applied voltage VC is obtained, and the product of this and the length L of the electric resistor 12 is obtained as the relative distance X. ..

[0015]

【Example】

 A first embodiment in which the optical position detecting device of the present invention is applied to a position detector of a rotation angle detecting device will be described below with reference to FIGS.

That is, in FIG. 4 showing the longitudinal side surface, the rotating shaft 21 is pivotally supported by the case 22, and this is rotated along with the rotation of the detection target (not shown). A disk-shaped rotary plate 23 is fixed to the rotary shaft 21. The rotary plate 23 is mainly made of a transparent member such as glass or plastic, and a metal film such as chromium is deposited on the surface of the rotary plate 23 to form an opaque layer 24.

The opaque layer 24 is partially removed by an etching process, and as shown in FIG. 3, a light transmitting portion 25 for detection and a light transmitting portion 26 for reference are formed. The reference light transmitting portion 26 is formed in an annular shape at a position having a predetermined radius from the rotation center O of the rotating plate 23. Further, the light-transmitting portion 25 for detection is located inside the light-transmitting portion 26 for reference, and the distance r to the rotation center of the rotary plate 23 is continuous in proportion to the rotation angle θ from the reference position (θ = 0 °). It is formed so that it may change. That is, when this relationship is expressed by an equation, r = a × θ + b (1) is obtained, where a and b are constants determined by the shape of the light-transmitting portion for detection 25.

A light emitting diode (hereinafter referred to as an LED) 27 is provided on the upper surface of the case 22, and a position detector 28 is provided so as to face the LED 27 with the rotating plate 23 interposed therebetween. .. The position detector 28 corresponds to the optical position detecting device in the present invention, and receives light from the LED 27 through the detecting light transmitting portion 15 and the reference light transmitting portion 16.

The position detector 28 is configured as shown in FIG. An elongated electric resistor 30 (longitudinal dimension L) made of carbon or the like is provided along the longitudinal direction at the center of the upper surface of a rectangular substrate 29 made of resin or ceramics. .. Voltage applying terminals 30a and 30b are arranged at both ends of the electric resistor 30. Detection electrodes 31 and 32 are formed on both sides of the electrical resistance antibody 30 so as to sandwich the electrical resistance antibody 30 at regular intervals. Photoconductors 33 and 34 are arranged in the respective gaps between the electric resistor 30 and the detection electrodes 31 and 32 so as to be connected to each other.

A part of one photoconductor 33 is covered with a light shielding plate 35, and a part of the other photoconductor 34 is covered with a light shielding plate 36. In this case, the light shield plate 35 covers the photoconductor 33 from the end on the voltage application terminal 30a side to about one-third of the entire length, and the light shield plate 36 of the photoconductor 34 on the voltage application terminal 30b side. It is arranged so as to cover about two-thirds of the entire length from the end.

The position detector 28 having such a configuration is arranged so that the detection direction thereof coincides with the semi-radial direction of the rotary plate 23. The light transmitted from the LED 27 through the light transmitting portion 15 for detection is irradiated onto the photoconductor 33 as a light spot P1, and the light transmitted through the light transmitting portion 16 for reference is irradiated onto the photoconductor 34 as a light spot P2. It is becoming like this.

Now, FIG. 5 shows an outline of the electrical configuration, in which predetermined voltages Va and Vb (Va <Vb) are applied to the voltage application terminals 30a and 30b of the position detector 28, respectively. ing. The detection electrodes 32 and 33 are connected to the two input terminals of the subtractor 37. The subtractor 37 calculates the difference between the input voltage values and outputs it.

Next, the operation of this embodiment will be described with reference to FIG.

First, the principle of detecting the relative distance X between the light spots P1 and P2 by the position detector 28 will be briefly described. That is, of the light from the LED 27, the light spot P1 which is transmitted through the light-transmitting portion 25 for detection and is applied to the position detector 28 hits the portions of the photoconductor 33 and the light shielding plate 36. It is assumed that the light spot P2 that passes through the light transmitting portion 26 and is irradiated onto the position detector 28 hits the portions of the photoconductor 34 and the light shielding plate 35. It is assumed that the irradiation positions of these light spots P1 and P2 are the positions of X1 and X2, respectively, when the end of the electric resistor 30 on the voltage application terminal 30a side is the reference position.

When the light spots P1 and P2 hit the position detector 28 as described above, the electric resistance values of the irradiated portions of the photoconductors 33 and 34 are lowered by the light spots P1 and P2, respectively, and the electric resistance 30 is reduced. And the detection electrode 31, and the electrical resistor 30 and the detection electrode 32 are practically in a conductive state. Therefore, the detection voltages V1 and V2 appear on the detection electrodes 31 and 32, respectively. Based on these detection voltages V1 and V2, the relative distance X between the light spots P1 and P2 can be obtained according to the equations (A) to (F) as described in the section of the operation of the present invention.

When the rotary shaft 21 and the rotary plate 23 rotate along with the rotation of the detection target (not shown), the detection light-transmitting portion 25 and the reference light-transmitting portion 26 rotate in response to the rotation. In this case, since the reference light-transmitting portion 26 is formed in an annular shape around the rotation center O of the rotary plate 23, even if the reference light-transmitting portion 26 is rotationally moved, in principle, the reference light-transmitting portion 26 is changed from the LED 27. The position of the light spot P2 that is incident on the position detector 28 via the optical axis does not change.

On the other hand, the light-transmitting portion 25 for detection, which rotates and moves in accordance with the rotation of the rotary plate 23, is formed in a spiral shape in which the radial distance changes according to the relationship shown in the equation (1). The position of the light spot P1 incident on the position detector 28 via the light transmitting portion 25 for detection continuously changes in accordance with the rotation angle θ of the rotating plate 23.

Now, in the position detector 28, assuming that the voltage appearing at the detection electrode 31 due to the light spot P1 is the detection voltage V1 and the voltage appearing at the detection electrode 32 due to the light spot P2 is the detection voltage V2, the respective detection voltages V1 , V2 can be expressed as follows.

That is, the detected voltage V1 of the position detector 28 is obtained as V1 = A × θ + B (2) from the relationship of the equation (1) (where A and B in the equation (2) are constants. And the detection voltage V2 of the position detector 28 is obtained as V2 = C (constant) (3).

Then, the subtractor 37 calculates the difference V1-V2 between the applied detection voltages V1 and V2 and outputs it as the output voltage V12. Therefore, the output voltage V12 is expressed by the above equations (2) and (3), and V12 is V12 = V1-V2 = A * [theta] + (BC) = A * [theta] + D (4). Is obtained as a value proportional to the rotation angle θ (however, D (= B−C) is a constant).

Therefore, as described above, the rotation angle θ of the rotary plate 23 is associated as shown in FIG. 6 based on the value of the output voltage V12 of the subtractor 37, so that 360 ° from the reference position (0 °). The rotation angle θ can be detected in almost the entire range up to °.

By the way, the rotary plate 23 is attached at a position eccentric to the rotary shaft 21, or “rattle” occurs between the rotary shaft 21 and the bearing portion of the case 22 to cause the rotary plate 23 to move. When the rotational position is unstable, the detection voltages V1 and V2 from the position detector 28 both fluctuate unstablely, and the relations of the equations (2) and (3) are satisfied. Disappear.

However, even in the case as described above, the relative position between the light transmitting portion 25 for detection and the light transmitting portion 26 for reference formed on the rotary plate 23 does not change, so the position detector 28 is used. The values of the detected voltages V1 and V2 are output as voltages added or subtracted equally by the amount of the eccentricity of the rotary plate 23.

Therefore, assuming that the deviation component of the detection voltage due to the eccentricity of the rotary plate 23 when the rotation angle is θ is ΔV, the detection voltages V1 and V2 of the position detector 28 are expressed by the equations (2) and (3). From this, it can be expressed as V1 = A × θ + B + ΔV (5) V2 = C + ΔV (6) From these, the output voltage V12 of the subtractor 37 can be calculated according to the equation (4), and the eccentricity of the rotating plate 23 can be calculated. Since the deviation component ΔV due to is canceled out, the result is the same as the result of the equation (4).

That is, even if there is a deviation component ΔV of the detection voltage caused by the eccentricity of the rotary plate 23, the relative positional relationship between the detection light transmitting portion 25 and the reference light transmitting portion 26 remains unchanged. Then, the deviation component ΔV is canceled by the subtraction in the subtractor 37, and the same detection result as in the normal case where no eccentricity occurs can be obtained.

According to the present embodiment as described above, the position detector 28 receives the two light spots and detects the relative distance X between them. Therefore, from the LED 27 to the light transmitting section 25 for detection and the reference light source. The two light spots P1 and P2 transmitted through the light transmitting portion 26 can be received by one position detector 28, and the rotation angle θ of the rotating plate 23 can be detected with a simple configuration. Further, as a result, even when the position of the light transmitted through the light-transmitting portion for detection 25 becomes unstable, such as when the rotary plate 23 is eccentric or "rotation" occurs on the rotary shaft 21, the rotary plate The rotation angle θ of 23 can be detected accurately.

7 and 8 show a second embodiment of the present invention, and only parts different from the first embodiment will be described below. That is, in the present embodiment, the detection light transmitting portion 25 in the first embodiment is replaced with a detection light transmitting portion 38 having an annular shape. This detection light transmitting portion 38 is The center P is set at a position slightly eccentric with respect to the rotation center O of the rotary plate 23.

By using such a light-transmitting portion for detection 38, the distance r from the rotation center O of the rotary plate 23 to the light-transmitting portion for detection 38 can be represented by r depending on the rotation angle θ of the rotary plate 23. = A * sin [theta] + b (7) (note that a and b are constants determined by the shape of the light-transmitting portion for detection 38).

Therefore, the position of the light from the LED 27, which is received by the position detector 28 via the detection translucent portion 38 by the rotation of the rotating plate 23, changes while satisfying the relationship shown in the above equation (7). At this time, the detection voltage V1 in the position detector 28 changes based on the above equation (7) according to the relationship expressed by V1 = A × sin θ + B (8) (where A and B are constants).

On the other hand, the detection voltage V 2 detected by the position detector 28 via the reference light-transmitting portion 26 is obtained as a constant value as in the first embodiment, and therefore the difference is subtracted by the subtractor 37. By the value of the output voltage V12 as a result of the calculation of, the relationship that changes according to the sine curve according to the rotation angle θ of the rotary plate 23 is obtained as shown in FIG. Thereby, the rotation angle θ of the rotary plate 23 can be uniquely determined within the range of ± 90 °, that is, 180 °, from the value of the output voltage V12.

Also in the second embodiment, one position detector 28 receives the light transmitted through the detection light transmitting part 38 and the light transmitted through the reference light transmitting part 26, and the position detector 2 Since the rotation angle θ of the rotary plate 23 is obtained by calculating the difference between the two detection voltages V1 and V2 obtained in step 8, the same effect as the first embodiment can be obtained and the rotation Even if the plate 23 has eccentricity or "rattle", accurate detection can be performed.

9 to 11 show a third embodiment of the present invention, and only portions different from the second embodiment will be described below. That is, in the third embodiment, the detection range of the rotation angle θ in the second embodiment is 180 °, whereas the rotation angle θ covers the entire circumference of the rotary plate 23, that is, 360 °. This makes it possible to uniquely detect θ.

In FIG. 9, in addition to the pair of the LED 17 and the position detector 28 provided in correspondence with the rotary plate 23, another pair of LEDs 17 and the position detector 28, which are separated by a rotation angle of 90 °, have the same configuration. An LED 39 and a position detector 40 are provided. The position detector 40 receives light from the LED 39 that passes through the detection light transmitting portion 26 and the reference light transmitting portion 38 at a position separated by a rotation angle of 90 ° from the position detector 28 and detects the relative distance between them. ..

Further, FIG. 10 shows an electrical configuration, and in addition to the electrical configuration in the second embodiment (see FIG. 3), a similar processing circuit is configured. That is, predetermined voltages Va and Vb are applied to the voltage application terminals 30a and 30b of the position detector 40, and the detection voltages V3 and V4 from the two detection electrodes are applied to the subtractor 41. The subtracter 41 calculates the difference between the input detection voltages V3 and V4 and outputs it as the output voltage V34. The output voltage V12 of the subtractor 37 and the output voltage V34 of the subtractor 41 are input to the calculator 42, and the rotation angle θ of the rotary plate 23 is calculated from these inputs. ing.

With such a configuration, the detection voltage V1 from the position detector 28 is obtained as a value that changes according to the sine function as shown in the equation (8), as in the second embodiment. Further, the detection voltage V3 from the position detector 40 can be obtained in the same manner as follows: V3 = A × cos θ + B (10) (where A and B are constants). That is, the detected voltage V3 has a value that changes according to the cosine function with respect to the rotation angle θ. Therefore, similarly to the second embodiment, the output voltages V12 and V34 from the subtractors 37 and 41 have the relationship shown in FIG. 11 with respect to the rotation angle θ. In the computing unit 42, according to the output voltages V12, V34 given from the subtracters 37, 41, the polarities and values of the output voltages V12, V34 correspond to the rotation angle θ over one revolution of the rotating plate 23 in a one-to-one correspondence. It is determined and output.

Therefore, according to the third embodiment as well, the same effects as those of the first and second embodiments can be obtained, and the rotation angle θ can be determined over the entire circumference of the rotary plate 23. Further, similarly to the first and second embodiments, even if the mounting state of the rotary plate 23 is eccentric or the bearing portion of the rotary shaft 21 has “rattle”, the rotation angle θ Can be accurately detected.

In each of the above embodiments, an optical system device is not provided between the LED and the position detector, but an optical system device such as a lens may be used if necessary. Of course, it is a good thing.

FIG. 12 shows a fourth embodiment of the present invention, and shows a configuration of a position detector 43 which can be used in place of the position detector 28 or 40 in each of the above embodiments. The part will be described.

That is, the first and second detection electrodes 44 and 45 are formed to have the lengths of the detection regions of the respective light spots P1 and P2, and the photoconductors 46 and 47 are similarly detected. It is formed in the length of.

As a result, for example, even if the light spots P1 or P2 are applied to both side portions of the electric resistor 30, only the portion which hits the photoconductor 46 or 47 acts. That is, the position detector 28 shown in FIG. 2 has a structure in which the light shields 35 and 36 cover the inconvenient part when the light spot P1 or P2 is irradiated. The example is different in that it is configured so that it is not substantially detected even if a light spot hits it, and the same operational effect as the position detector 28 can be obtained.

[0051]

[Effect of the device]

 According to the optical position detecting device of the present invention, the first and second light spots are simultaneously received and the relative distance between the light spots is detected. Since it is not necessary to provide each, a simple configuration is sufficient, and it is possible to prevent the detection accuracy from deteriorating due to variations in individual characteristics and variations in arrangement position.

[Brief description of drawings]

FIG. 1 is a perspective view showing the basic configuration of the present invention.

FIG. 2 is an external perspective view of an essential part showing a first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the overall configuration

FIG. 4 is a vertical sectional side view of the overall configuration.

FIG. 5 is an electrical configuration diagram.

FIG. 6 is a correlation diagram between output voltage and rotation angle.

FIG. 7 is a view corresponding to FIG. 3 showing a second embodiment of the present invention.

FIG. 8 is a view corresponding to FIG.

FIG. 9 is a view corresponding to FIG. 3 showing a third embodiment of the present invention.

FIG. 10 is a view corresponding to FIG.

FIG. 11 is a view corresponding to FIG.

FIG. 12 is a view corresponding to FIG. 2 showing a fourth embodiment of the present invention.

FIG. 13 is a view corresponding to FIG. 2 showing a conventional example.

[Explanation of symbols]

11, 29 are substrates, 12 and 30 are electric resistors, 12a,
12b, 30a, 30b are voltage application terminals, 13, 31,
44 is a first detection electrode, 14, 32 and 45 are second detection electrodes, 15, 16, 33, 34, 46 and 47 are photoconductors, 21 is a rotating shaft, 23 is a rotating plate, and 25 is for detection. Light-transmitting portion, 26 is a reference light-transmitting portion, 27 is a light emitting diode, 2
8 and 40 are position detectors (optical position detecting devices), and 35 and 36.
Is a light shielding plate, 37 and 41 are subtractors, and 42 is a calculator.

Claims (1)

[Scope of utility model registration request] 1. An elongated electric resistor provided on a substrate, a pair of voltage applying terminals formed at both ends of the electric resistor, and a predetermined gap between the electric resistor on both sides of the electric resistor. A first and a second detection electrode which are arranged so as to be present in the gap, and a photoconductor formed in each gap so as to connect the first and the second detection electrode to the electric resistor. A first light spot that is irradiated so as to bridge between the first detection electrode and the electric resistor in a state where a constant voltage is applied to the electric resistor through a voltage application terminal; A relative distance along the electric resistor between a second light spot irradiated so as to bridge between the second detection electrode and the electric resistor appears along the first and second detection electrodes. An optical position detecting device characterized by detecting based on a voltage difference.