JPH09318322A - Optical displacement measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high precision range finding of wide dynamic range by feedback-controlling so that, both on the light emitting side and the photodetecting side, the signal corresponding to respective photodetecting amount is kept almost constant, and processing a position signal with one system through a switch circuit. SOLUTION: A position detecting element 21 outputs a pair of position signals 11 and 12 wherein the signal value ratio is decided according to the position of photodetecting spot, and they are, through a switch circuit 31 wherein the position signals are allowed to pass alternately at the cycle which is integer- times of modulation cycle of beam light, processed in time-division manner with one system circuit. In addition, a variable amplifier 24 is provided on photodetecting side and a modulation circuit 15 which changes optical output is provided on light emitting side, and in order that the addition value of the position signals 11 and 12 is kept constant, a feedback-control circuit 16 feedback-controls amplification ratio and optical output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating an object with a light beam and detecting reflected light from the object.
The present invention relates to an optical displacement measuring device that detects a distance to an object and a displacement of the object from a reference position by a triangulation method.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 29, an object 3 is irradiated with a light beam obtained by passing infrared light emitted from a laser diode 11 through a light projecting lens 12, and the light from the object 3 is emitted. Light receiving lens 2 which is an optical system for receiving diffusely reflected light
There is known an optical displacement measuring device configured to obtain the distance to the object 3 (or the displacement from the reference position) by applying the principle of the triangulation method by receiving light through the position detecting element 21 through 2. That is, the image of the light projection spot formed on the surface of the object 3 by irradiating the object 3 with the beam light is passed through the light receiving lens 22 and the position detecting element 2 is detected.
An image is formed on the light receiving surface of No. 1 to form a light receiving spot, and when the distance to the object 3 changes, the position at which the light receiving spot is formed changes, so that the distance to the object 3 is obtained. is there.

The laser diode 11 is driven by a drive signal output from the oscillator 13 and passed through the LD drive circuit 14, and outputs a modulated laser beam. Position detection element 2
1 is a PSD (Position Sensitive Device) arranged so that the longitudinal direction coincides with the moving direction of the light receiving spot.
Also, a photodiode in which two photodiodes are arranged in the moving direction of the light receiving spot is used. The PSD is a semiconductor device having a pin structure and includes a pair of electrodes and a common electrode provided at both ends in the longitudinal direction of a light receiving surface. When a light spot is formed on the light receiving surface, both ends are formed at the position of the light spot. Is divided depending on the position of the light spot. That is, by supplying a constant current from the common electrode, the position signals I1 and I2 having a current value of a ratio according to the position of the light spot are output from the electrodes at both ends. In this way, the position of the light spot is determined by the position signal I
Since it corresponds to the ratio of 1 and I2, the position of the light spot formed on the light receiving surface of the PSD is (I1-I2) / (I1 + I
2) Or it becomes the function of the value which modified this.

Therefore, the position signals I1 and I2, which are current signals output from the position detecting element 21, are respectively I / V.
Only the signal components Vd1 and Vd2 are extracted by converting them into voltage signals by the conversion circuits 23a and 23b, amplifying the voltage signals by the amplifiers 24a and 24b, respectively, and then synchronously detecting them by the detection circuits 25a and 25b. The detection timings of the detection circuits 25a and 25b are controlled by the timing signal generated by the timing circuit 28 based on the output of the oscillator 13. Since the signal components Vd1 and Vd2 extracted in this way have a pulsating wave shape (due to the laser light being modulated), an integrating circuit (actually, a low-pass filter = LPF) is used to extract the signal level. Position information signals V1 and V2 obtained by averaging the output values of the detection circuits 25a and 25b. This position information signal V1, V2
Is a voltage signal having a signal value that is proportional to the signal values of the position signals I1 and I2.
If 2) / (V1 + V2) is obtained, information corresponding to the distance to the object 3 can be obtained. That is, the calculation unit 27 includes a difference calculation unit 27a for obtaining (V1-V2),
A sum calculation unit 27b for obtaining (V1 + V2) and a difference calculation unit 2
And a division unit 27c that divides the output value of 7a by the output value of the sum calculation unit 27b. Here, (V1 + V2) obtained by the sum calculation unit 27b is the total current (I1 +) of the position detection element 21.
Since the value corresponding to I2) corresponds to the amount of received light, the output value of the analog output varies depending on the reflectance of the surface of the target object 3 and the difference in the intensity of the laser light from the laser diode 11. It is normalized so as not to be influenced by the output from the arithmetic unit 27. That is, ideally, the distance to the object 3 can be obtained even if the amount of received light changes.

[0005]

However, the above-mentioned conventional structure has the following problems. That is, the two position signals I1 and I output from the position detecting element 21
In the process of converting 2 into position information signals V1 and V2,
Since a separate circuit is provided for processing the position signals I1 and I2, the I / V conversion circuits 23a and 23b and the amplifier 24 are provided.
a, 24b, detection circuits 25a, 25b, integration circuit 26
Two a and 26b are required respectively. As a result, there arises a problem that the number of parts increases, the size increases, and the cost increases.

Further, the circuits of the two systems must have the same characteristics, but the gains of the circuits of the two systems differ due to variations in the components, and the position signal I1 for each of the position information signals V1 and V2. , I2 are different from each other, resulting in an error in the calculation result of the calculation unit 27. This kind of gain difference is due to variations in element constants and changes over time, errors that occur when the ambient temperature changes due to differences in the temperature characteristics of each circuit,
There is an error (transient error) that occurs when the object 3 moves due to the difference in frequency characteristics of each circuit.

Further, the arithmetic unit 27 is provided with a division unit 27c, and the division unit 27c is realized by using a divider (for example, AD534 (Analog Devices Co., Ltd.)) generally provided as an integrated circuit. To be done. This type of divider has a problem that the accuracy of the output value rapidly deteriorates when the input value, which is the voltage input, decreases. For example, AD534
The divider L (Analog Devices) has a maximum input voltage of 10V, and when the input voltage is 10V, the error of the output value is ± 0.2%, while the input voltage is 1V. When, the error of the output value is ± 0.8%.
As described above, when the input voltage is reduced to 1/10, the error in the output value increases four times. Further, when the input voltage becomes 1 V or less, the error increases in inverse proportion to the input voltage (that is, the error rapidly increases as the input voltage decreases).

The error in the output value of the divider directly affects the distance measurement accuracy, and it is relatively easy to set the error in other circuit parts to 0.5% or less. The error in the output value is the most important factor in determining the distance measurement accuracy. In order to realize an error of 1% or less using the above divider, the input voltage to the division unit 27c must be 1V or higher, and the dynamic range of the calculation unit 27 is 10 at most.
That means double.

On the other hand, the reflectance of white ceramics is 10
When expressed by an index of 0, the reflectance of the gray or dark blue object 3 is 5 to 10 and that of black rubber is about 1. That is, assuming that the input voltage (denominator) of the division unit 27c is 10 V when the white ceramics is the target object 3, it is measured if the index of the reflectance of the target object 3 located at the same distance is 10 or more. Distance becomes impossible. FIG. 30 shows this relationship. The thick line range in FIG. 30 is the input voltage range, and the thin line range is the resolution (related to accuracy) range. Also, FIG.
The shaded area of 0 indicates a range in which distance measurement is impossible. That is,
The reflectance index can only measure the range of 10 to 100.

Further, since the amount of received light changes depending on the distance to the object 3, even if the index of reflectance is 10 or more, distance measurement becomes impossible if the distance becomes large. Such a problem arises even if the integrated circuit forming the division unit 27c has a large dynamic range and high accuracy, and even if some improvement can be hoped for, it is a fundamental solution. It does not happen. Further, a divider having a large dynamic range and high precision is expensive, which causes a problem of cost increase.

As an attempt to compensate the dynamic range of the divider 27c, a technique has been proposed in which the amplification factors of the amplifiers 24a and 24b are switched stepwise according to the amount of received light. However, there is a problem that it is difficult to continuously obtain ranging results by following a wide range change in the amount of received light due to the generation of noise when changing the amplification factor and the delay of the switching time required for changing the amplification factor. is there. Further, as described above, the error of the amplification factor affects the distance measurement accuracy, so that the variation of the amplification ratio is likely to occur by switching the amplification factor, and it takes a lot of time and labor for the adjustment to maintain the distance measurement accuracy. The problem arises.

The present invention has been made in view of the above circumstances, and an object thereof is to have a large dynamic range with respect to the amount of received light, capable of highly accurate distance measurement, and moreover, a circuit component element more than a conventional one. An object is to provide an optical displacement measuring device capable of reducing the number.

[0013]

According to a first aspect of the present invention, a light emitting element irradiates an object with beam light modulated at an appropriate period, and a light projection spot formed on the surface of the object is detected by a position detecting element. In an optical displacement measuring device that detects the displacement of the object from the reference position based on the position of the light receiving spot obtained by forming an image on the light receiving surface, the position detection element uses a signal value ratio according to the position of the light receiving spot. Output a pair of position signals, which alternately pass the position signals at an integer multiple of the beam light modulation period, a variable amplifier for amplifying the position signals passing through the switch circuit, and an output of the variable amplifier. A signal processing unit that detects and outputs a distance measurement signal corresponding to the displacement of the object based on the detection output and a signal corresponding to the amount of light received by the position detection element, and the amount of light received by the position detection element To characterized in that it comprises a feedback control circuit for feedback controlling at least one of the amplification factor of the optical output and the variable amplifier of the light emitting element so as to maintain said signal substantially constant.

According to this structure, the feedback control is performed on the light emitting side and the light receiving side so as to keep the signals corresponding to the light receiving amounts substantially constant, so that the dynamic range with respect to the light receiving amount becomes extremely large. Further, since the position signal is processed by one system through the switch circuit, the occurrence of errors due to variations in parts is reduced. As a result, it is possible to perform distance measurement with high accuracy, and it is possible to reduce the number of circuit constituent elements as compared with the related art.

According to a second aspect of the present invention, in the first aspect of the invention, a reference value is set for the amount of light received by the position detecting element, and the feedback control circuit sets the light emitting element when the amount of light received exceeds the reference value. The optical output of the variable amplifier is decreased, and the amplification factor of the variable amplifier is increased when the amount of received light is smaller than the reference value. According to this configuration, when the amount of received light is increased, the light output is decreased to prevent saturation, and when the amount of received light is decreased, the amplification factor is increased to prevent the signal from being buried in noise.

A third aspect of the present invention is characterized in that, in the first aspect of the invention, the switch circuit is set to be twice or more a modulation cycle of the light beam. According to this structure, the influence of switching noise of the switch circuit is reduced by prolonging the switching cycle of the switch circuit.
According to a fourth aspect of the present invention, in the first aspect, the position signal output from the position detection element is a current signal,
It is characterized in that an I / V conversion circuit for converting each position signal into a current-voltage is provided in a stage prior to the switch circuit.

According to this structure, since a minute current signal is converted into a voltage signal and then input to the switch circuit, it is less susceptible to the switching noise of the switch circuit. The invention according to claim 5 is obtained by irradiating an object with a light beam modulated at an appropriate period from the light emitting element and forming a light projection spot formed on the surface of the object on the light receiving surface of the position detecting element. In the optical displacement measuring device that detects the displacement of the object from the reference position based on the position of the light receiving spot, the position detecting element outputs a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot. , A switch circuit that alternately passes the position signal at a cycle that is an integer multiple of the modulation cycle of the beam light, and the polarity of the position signal that passes through the switch circuit is inverted every half cycle of the modulation cycle of the beam light and each position signal is the same. A detection / arithmetic circuit that obtains a sum signal with polarity and a difference signal with different polarity, a pair of integration circuits that obtains each average value of the sum signal and difference signal, and the average of the difference signals among the outputs of each integration circuit. Sum of values Characterized in that it comprises a division unit for dividing the mean value of the item.

According to this structure, the calculation for calculating the difference and the calculation for calculating the sum are not required, and the measurement error due to the variation in the calculation of the sum difference can be prevented. The invention of claim 6 is
In the invention of claim 5, the detection / arithmetic circuit generates a difference signal by inverting the polarity of a component corresponding to one position signal of the components of the sum signal after obtaining the sum signal. .

According to a seventh aspect of the invention, in the fifth aspect of the invention, the detection / arithmetic circuit inverts the polarity of the component corresponding to one position signal of the components of the difference signal after obtaining the difference signal. It is characterized by generating a sum signal. The inventions of claims 6 and 7 are desirable embodiments of the invention of claim 5. The invention according to claim 8 is obtained by irradiating an object with a light beam modulated at an appropriate period from the light emitting element, and forming a light projection spot formed on the surface of the object on the light receiving surface of the position detecting element. In the optical displacement measuring device that detects the displacement of the object from the reference position based on the position of the light receiving spot, the position detecting element outputs a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot. , A switch circuit that alternately passes the position signal at an integer multiple of the modulation period of the light beam, and the polarity of the position signal that passes through the switch circuit is inverted every half period of the modulation period of the light beam and A detection / calculation means for obtaining a sum signal in which the signal obtained by multiplying the other position signal by a coefficient has the same polarity and a difference signal in which both position signals have different polarities, and for obtaining an average value of the sum signal and the difference signal; , Difference Characterized in that it comprises a division unit for dividing the mean value by the average value of the sum signal.

According to this configuration, the calculation for calculating the difference and the calculation for calculating the sum are not required, and the measurement error due to the variation in the calculation of the sum difference can be prevented. Moreover, since one of the position signals is multiplied by the coefficient, it is possible to correct the non-linearity of the position detecting element. According to a ninth aspect of the invention, in the eighth aspect of the invention, after the detection / calculation means obtains the difference signal, a signal obtained by multiplying a signal component of one polarity of the difference signal by a coefficient and inverting the other signal is used. The sum signal is generated by adding to the signal of.

According to a tenth aspect of the invention, in the invention of the eighth aspect, after the detection / calculation means obtains the difference signal, a signal component of each polarity of the difference signal is extracted and a coefficient is applied to one of the extracted signal components. The sum signal is generated by adding to the other signal component extracted by multiplying by. Claim 1
According to a first aspect of the invention, in the invention of the eighth aspect, the detecting / calculating means extracts a signal component having one polarity of the difference signal after obtaining the difference signal, and a signal obtained by multiplying the extracted signal component by a coefficient. It is characterized in that a sum signal is generated based on the difference signal.

According to a twelfth aspect of the present invention, in the eighth aspect of the invention, after the detection / calculation means obtains a signal in which the signal components corresponding to the respective position signals have the same polarity, the signal having one polarity of the signal It is characterized in that a component is extracted and a signal component of one polarity of the signal is inverted to generate a difference signal, and a sum signal is generated based on the signal and the extracted signal component of one polarity.

The inventions of claims 9 to 12 are preferred embodiments of the invention of claim 8.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows the configuration of this embodiment. The light beam applied to the object 3 is obtained by passing the infrared light emitted from the laser diode 11 through the light projecting lens 12 as in the conventional configuration. In the conventional configuration, the output of the oscillator 13 is passed through the LD drive circuit 14 to the laser diode 11
However, in the present embodiment, the timing signal t2 obtained by passing the output of the oscillator 13 through the timing circuit 28 is input to the modulator 15 as a carrier, and the modulator 15 uses the output of the feedback control circuit 16 described later. The carrier is amplitude-modulated and input to the LD drive circuit 14. That is, the emission intensity of the laser diode 11 changes according to the output value of the feedback control circuit 16.

On the other hand, the projection spot formed on the surface of the object 3 by irradiating the object 3 with the beam light is imaged on the light receiving surface of the position detecting element 21 made of PSD through the light receiving lens 22 to detect the position. Two position signals I1 and I2 are output from the position detecting element 21 in accordance with the position of the light receiving spot formed on the light receiving surface of the element 21. Since the ratio of the output values of both position signals I1 and I2 is determined according to the position of the light receiving spot, the displacement of the object 3 from the reference position can be obtained from the signal values of the position signals I1 and I2. Here, the position of the target object 3 on the extension line of the beam light when the light receiving spot is formed at the center of the effective length of the light receiving surface of the position detection element 21 is set as a reference position, and the distance of the target object 3 from the reference position. Change is calculated as displacement, but the projection lens 12
The distance to the target 3 may be obtained by setting the center position of the reference position as the reference position.

In the present embodiment, the switch circuits 31 and 32 are provided before and after the circuit which conventionally requires two systems, so that signals of two systems are processed in a time-division manner so that processing by one system is possible. The point has one characteristic. That is, the position signals I1 and I2 output from the position detecting element 21 are selectively passed through the switch circuit 31 to I / I.
It is input to the V circuit 23. As shown in FIG. 2, the position signals I1 and I2 are DC components DC1 and DC1 generated by ambient light or the like.
It is a sinusoidal signal centered on DC2, and the amplitude ratio corresponds to the position of the light receiving spot. Both position signals I1,
Which of I2 is input to the I / V conversion circuit 23 is controlled by the switching signal t1 output from the timing circuit 28. Here, the switching signal t1 is set so as to have a period twice that of the timing signal t2, as shown in FIG.

The output of the I / V conversion circuit 23 is the variable amplifier 2
4 and is amplified by an appropriate amplification factor. The variable amplifier 24 is an amplifier whose amplification factor is continuously adjusted according to the output of the above-mentioned feedback control circuit 16, and its specific operation will be described later. The output signal Va1. Va2 corresponds to a signal in which the position signals I1 and I2 are connected at the switching timing of the switch circuit 31, and this signal includes offset voltages Vdc1 and Vdc corresponding to DC components DC1 and DC2 of the position signals I1 and I2 due to disturbance light or the like.
dc2 is included. This output signal Va1. Va2 is synchronously detected by the detection circuit 25 (the synchronous detection here is a process of inverting the input signal every half cycle of the modulation cycle of the light beam emitted from the laser diode 11).
Signal component Vb1. Vb2 is extracted. Therefore, the signal components Vb1. Vb2 is the offset voltage Vdc1, Vd
It includes a component obtained by inverting c2. That is, in the pulsating flow waveform of one polarity, the offset voltage is Vdc1, Vdc
When it is 2, the offset voltage becomes -Vdc1 and -Vdc2 in the pulsating flow waveform of the other polarity.

In short ,. The detection circuit 25 detects the input signal in synchronization with the timing signal t2 from the timing circuit 28, and outputs the output signal Va1. Va2 is taken out as it is, and the output signal Va1. The polarity of Va2 is inverted and taken out. Further, at the time of synchronous detection, the output signal Va1. Offset voltages −Vdc1 and −Vdc2 that cancel the offset voltages Vdc1 and Vdc2 held by Va2 are generated to generate the signal component Vb.
1. It will be included in Vb2. This signal component Vb
1. Vb2 is a pulsating wave-shaped signal component Vd corresponding to the position signals I1 and I2 by the switch circuit 32 controlled by the switching signal t1 so as to be synchronized with the switch circuit 31.
1 and Vd2 are separated.

The signal components Vd1 and Vd2 separated by the switch circuit 32 are input to integrator circuits (actually low-pass filters = LPF) 26a and 26b, respectively, and the above-mentioned offset voltage is canceled by extracting the DC component. To be removed. The position information signals V1 and V2 output from the integrating circuits 26a and 26b are input to the difference calculation unit 27a, and a signal corresponding to the difference between the signal values of the position signals I1 and I2 can be obtained from the difference calculation unit 27a.

The position information signals V1 and V2 are input to the sum calculator 27b to obtain a signal corresponding to the sum of the signal values of the position signals I1 and I2. The output of the sum calculation unit 27b corresponds to the amount of light received by the position detection element 21, and in the present embodiment, this information is supplied to the reference voltage Vr by the comparison circuit 17.
In comparison with ef, the comparison circuit 17 inputs to the feedback control circuit 16 an output corresponding to the difference between the reference received light amount determined by the reference voltage Vref and the actual received light amount.
As described above, since the output of the feedback control circuit 16 determines the light emission amount of the laser diode 11, the light emission amount of the laser diode 11 is controlled so as to keep the light reception amount of the position detection element 11 at the light reception amount determined by the reference voltage Vref. Feedback control is performed, and as a result, the position detection element 1
The light receiving amount of 2 is kept constant. Further, the feedback control circuit 16 adjusts the amplification factor of the variable amplifier 24 so that the amount of received light (that is, the output of the sum calculation unit 27b) is kept constant, and as a result, the output value of the sum calculation unit 27b becomes It will be kept constant.

As described above, by performing the feedback control to keep the output of the sum calculation unit 27b constant, the denominator can be kept constant in the calculation of (V1-V2) / (V1 + V2), As a result (V1-V
The distance to the object 3 can be obtained by simply obtaining 2). In short, by guaranteeing that the denominator is constant, there is no need to find the denominator. That is, in the present embodiment, in addition to the difference calculation unit 27a and the sum calculation unit 27b, the modulation circuit 15, the feedback control circuit 16, the comparison circuit 17, the variable amplifier 2 are provided.
4 is also a constituent element of the arithmetic unit 27 '.

In the circuit configuration described above, the variable range (modulation voltage) of the optical output of the laser diode 11 and the variable range of the amplification factor of the variable amplifier 24 by the output of the feedback control circuit 16 are set to 1 to 100%, respectively. Laser diode 11 when modulation voltage is 100%
The same optical output as the conventional configuration can be obtained from the variable amplifier 24.
Is 1%, the amplification factor is similar to that of the conventional amplifier. In addition, an index that sets the amount of light received when the target object 3 (for example, white ceramics) serving as a reference of reflectance is located at a predetermined distance to 100 (this state is assumed to be 100) The modulation voltage (that is, the optical output) at this time is set to 100%, and the amplification factor of the variable amplifier 24 is set to 1%. When the reflectance (amount of received light) is larger than 100, the modulation voltage is lowered as the reflectance is larger as shown in FIG. 3, and when the reflectance is smaller than 100, the reflectance is small as shown in FIG. The amplification factor of the variable amplifier 24 is increased. In this way, since the modulation voltage and the amplification factor of the variable amplifier 24 can be changed by 100 times, the dynamic range is 10 times.
It becomes 0 × 100 = 10000 times. Further, when the amount of received light is larger than the reference value (index 100), the modulation voltage is made small, and when it is smaller than the reference value, the amplification factor is made large, so that the resolution is kept high as shown in FIG. The voltage corresponding to the amount of received light is kept constant as shown in FIG. In this way, the dynamic range is greatly increased and the distance measurement accuracy is improved. FIG.
The shaded area indicates the range in which distance measurement is impossible.

In the above description, the reference amount of received light is 10
Although it is set to 0, it may be set to an optimum value according to required specifications, specifications of individual circuit configurations, and the like. For example, when the object 3 having a small reflectance is important,
If it is desired to cope with the received light amount in the range of 00, the reference value of the received light amount may be set to 10. Further, in the case where the object 3 having a high reflectance is emphasized,
If it is desired to be able to cope with the received light amount in the range of 0 to 100,000, the reference value of the received light amount may be set to 1000. Further, if the variable range of at least one of the modulation voltage and the amplification factor of the variable amplifier 24 cannot be set to 100 times, the dynamic range becomes small, but the dynamic range of the conventional configuration is still 10 times. However, it is possible to obtain a sufficiently large dynamic range. For example, when the variable range of the modulation voltage is 100 times and the variable range of the amplification factor of the variable amplifier 24 is 10 times, the dynamic range is 1000 times, but by appropriately setting the reference value of the received light amount. The range can be measured over a wide range.

In the above-mentioned configuration, the position signals I1 and I2 output from the position detecting element 21 are transmitted to the laser diode 11.
Are alternately time-divisionally processed for each one of the light emission cycles of the I / V conversion circuit 23, the variable amplifier 24, and the detection circuit 2.
5 is shared, there is no error due to the variation of the constants of the components and the variation of the temperature characteristics as in the case of using the two-system circuit, and the two position signals I1 and I
Since 2 is synchronously detected by the same detection circuit 25, no offset error occurs. Further, an offset error generated at a stage prior to the detection circuit 25 can be canceled by passing through the detection circuit 25. The detection circuit 25
The slight offset error caused by 1 can be removed by the correction circuit having a relatively simple structure because the circuit has one system. Furthermore, since the two position signals I1 and I2 are processed by the same circuit, there is no difference in the frequency characteristics until they are separated by the switch circuit 32, and the modulation frequency of the signal for driving the laser diode 11 is maintained. Even if the change occurs, the distance measurement result and the transient error do not occur. For example, it is assumed that the distance to the target object 3 changes with time as shown in FIG. In the present embodiment, since there is no difference in the frequency response of the two position signals I1 and I2, an error due to the transient response does not occur in the distance measurement signal (V1-V2) as shown in FIG. When a difference occurs in the frequency response of the two position signals I1 and I2, an error occurs due to the transient response as shown in FIG. 4 (c).

In the above example, the cycle of the switching signal t1 is set to twice the cycle of the timing signal t2, but in the present embodiment, as shown in FIG. 5, this is set to six times. . In this way, when the cycle of the switching signal t1 is set to be three times or more the cycle of the timing signal t2, the switch circuit 3
It is possible to reduce the influence of noise that occurs when switching 1 and 32. This cycle can be appropriately set if it is an integral multiple.

(Embodiment 2) In this embodiment, as shown in FIG. 6, two I / V conversion circuits 23a and 23b are provided to convert the position signals I1 and I2 into voltage signals, respectively. And the optical output of the laser diode 11 is added to the sum calculation unit 2
It is different from the first embodiment in that it is not adjusted based on the output of 7b.

As in the configuration of the present embodiment, the minute position signals I1 and I2 are converted into voltage signals of appropriate magnitudes and then passed through the switch circuit 31, so that noise generated when the switching circuit 31 switches is generated. Is less likely to be affected by, and thus the error of the measurement result can be suppressed. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 3) In this embodiment, as shown in FIG. 7, feedback control based on the amount of received light is not performed, and the switch circuit 32 and the difference calculator 2 are used.
7a, the division unit 27c is provided without providing the sum calculation unit 27b, so that the distance measurement signal (V
1-V2) / (V1 + V2) is obtained.

The structure for projecting the light beam is the same as the conventional structure. Further, the position signals I1 and I2 output from the position detection element 21 are time-divided into the I / V conversion circuit 23 through the switch circuit 31, and the I / V conversion circuit 2
The point that the output of No. 3 is amplified by the amplifier 24 is the same as in the first embodiment. In the configuration of the first embodiment, the output signal Va1. Although Va2 was input to the detection circuit 25 for synchronous detection, this embodiment is characterized in that it is input to the detection / arithmetic circuit 25 'to generate the following signals.

In addition to the timing signal t2, the detection / arithmetic circuit 25 'has an arithmetic control signal t3 whose phase differs from that of the switching signal t1 by 90 degrees (advance here), as shown in FIG.
Is entered. The detection / calculation circuit 25 'uses this calculation control signal t3 to perform synchronous detection, and the output signal Va1. A signal having a form in which the polarities of the second half of the position signal I1 and the first half of the position signal I2 are inverted in Va2 is obtained. That is, FIG.
In this case, the differential signal (Vd1-V) that causes the signal component Vd1 corresponding to the position signal I1 to be positive and the signal component Vd2 corresponding to the position signal I2 to be negative by this synchronous detection.
d2) will be output.

On the other hand, if synchronous detection is performed using the timing signal t2, a sum signal (Vd1 + Vd2) is obtained in which both the signal components Vd1 and Vd2 corresponding to the position signals I1 and I2 have a positive polarity. After all, the difference signal (Vd1
-Vd2) and sum signal (Vd1 + Vd2) are position signals I
Since the signals correspond to the sum and difference of 1 and I2, if they are averaged by integrating circuits (low-pass filters) 26a and 26b, respectively, signals (V1-V2), (corresponding to the difference between the position signals I1 and I2) are obtained. V1 + V2) can be extracted. Therefore, if both signals are input to the divider 27c and division is performed, the distance measurement signal (V1-V2) / (V1 + V2)
Can be obtained.

As the detection / arithmetic circuit 25 'for performing the above-mentioned synchronous detection, specifically, the configuration shown in FIG. 9 can be adopted. That is, four operational amplifiers O
P1 to OP4 are used to make two pairs, one of the pair of operational amplifiers OP1 and OP3 performs non-inverting amplification, and the other of the pair of operational amplifiers OP2 and OP4 performs inverting amplification. The result of non-inverting amplification and the result of inverting amplification are alternately taken out for each. The switch element S1 is alternately switched by the arithmetic control signal t3, and the switch element S2 is alternately switched by the timing signal t3.

In the configuration of this embodiment, since the divider 27c is required, the dynamic range is similar to that of the conventional example, but since there is only one switch circuit 31, switching noise is reduced, and It is possible to suppress the occurrence of an error in the measurement result due to the deviation of the timing when using the plurality of switch circuits 31 and the deviation of the switching timing of the switch circuits 31. Furthermore, the difference calculation unit 2
Since neither 7a nor the sum calculator 27b is used, it is possible to suppress the occurrence of an error in the measurement result due to these calculation errors. Other configurations and operations are the same as those of the conventional example.

As another configuration of the detection / arithmetic circuit 25 ', the circuit configurations shown in FIGS. 10 and 12 can be considered. FIG.
In the circuit configuration shown in FIG. 0, the circuit configuration shown in FIG. 9 is a part that generates the sum signal (Vd1 + Vd2). In this configuration, after generating the difference signal (Vd1-Vd2), the difference signal (Vd1-Vd2) is generated. ) Is synchronously detected using the switching signal t1 to generate the sum signal (Vd1-Vd2). In short, as shown in FIG. 11, the difference signal (Vd1-V
The negative electrode part of d2) is inverted.

On the other hand, in the circuit configuration shown in FIG.
Contrary to the configuration shown in (1), the sum signal (Vd1 + Vd2) generated by the timing signal t2 is synchronously detected by the switching signal t1 to generate a difference signal (Vd1-Vd2). In this configuration, as shown in FIG. 13, by inverting the portion corresponding to the position signal I2 of the positive portion of the sum signal (Vd1 + Vd2), the difference signal (Vd1-Vd) is inverted.
2) is generated. Moreover, with this configuration, it is not necessary to separately generate the operation control signal t3, and the timing circuit 2
The configuration of 8 is simplified.

(Embodiment 4) As shown in FIG. 14, this embodiment has the same structure as that of Embodiment 3 shown in FIG.
In the detection / arithmetic circuit 25 ', by using the switching signal t1, the timing signal t2, and the arithmetic control signal t3,
A sum signal of (Vd1 + k · Vd2) is generated, and the sum signal is corrected. Such correction is well known in the art, and corrects the non-linearity of the output result with respect to the change in the amount of received light. The operation is almost the same as that of the third embodiment as shown in FIG.

As shown in FIG. 16, the detection / arithmetic circuit 2
The configuration for obtaining the difference signal (Vd1-Vd2) at 5'is similar to that of the third embodiment shown in FIG. Sum signal (V
The sum signal generation unit 33 that obtains d1 + k · Vd2) uses the switching signal t1 and the timing signal t2 to calculate the sum signal (V
d1 + k · Vd2) is calculated. Specifically, the sum signal generation unit 33 can employ various configurations as shown in FIG. In the configuration shown in FIG. 17A, the input signal is branched and attenuated by the variable resistor VR, and the component corresponding to the position signal I2 is controlled by controlling the analog switch AS1 using the switching signal t1. The signal is input to the operational amplifier OP4 for inverting amplification in a form adjusted by VR, and the input signal is directly amplified by the operational amplifier OP3 for non-inverting amplification.

The configuration shown in FIG. 17B has an operational amplifier O.
Positive voltage and 0 due to P5, OP6 and switch element S3
A circuit for generating a voltage of volt is configured, and this voltage is appropriately adjusted by the variable resistor VR and added to the input of the operational amplifier OP3 for inverting amplification. Switch element S
3 by controlling the switching signal t1, the position signal I2
KVd by adding an appropriate voltage only to the input signal corresponding to
A signal corresponding to 2 is generated.

The configuration shown in FIG. 17C has an operational amplifier O.
The differential voltage between the input voltage and the voltage of the DC power supply Vp can be output using P5, OP6, the switch element S3, and the DC power supply Vp, and the variable resistor VR is input to one of the operational amplifiers OP6. The input voltage can be adjusted by inserting. Therefore, the switching element S3 is switched to the switching signal t1.
When switched by, the level of the input signal corresponding to the position signal I2 can be adjusted to obtain a signal corresponding to kVd2. The configuration shown in FIG. 17D has an operational amplifier OP.
3, the switching signal t1 is used to determine whether the signal (Vd1 + Vd2) obtained by OP4 and the switch element S2 is passed through the voltage follower by OP5 or the amplifier including OP6 and the variable resistor VR.
By selecting with the switch element S3 controlled by, the signal corresponding to the position signal I2 can be corrected.

In the present embodiment as well, as in the third embodiment, it is possible to adopt a configuration in which after the difference signal (Vd1-Vd2) is obtained, the result is used to generate the sum signal (Vd1 + k · Vd2). . That is, as shown in FIG. 18, the negative component of the difference signal (Vd1-Vd2) may be inverted by using the operational amplifiers OP3 and OP4 and the switch element 2. Further, the amplification factor of the component corresponding to the position signal I2 is changed by using the variable resistor VR, and as a result, the sum signal (Vd1 + k · Vd2) is obtained. In this configuration, since only the switching signal t1 and the operation control signal t3 are used, the configuration is simpler than when three types of signals are used. FIG. 19 shows the operation when this circuit is used.

(Fifth Embodiment) In the fourth embodiment, only the divider 27c is provided without providing the difference computing unit 27a and the sum computing unit 27b, but in the present embodiment, as shown in FIG. 20, an adder 27d is provided. Is provided. That is, the detection / arithmetic circuit 2
5 ′ uses the switching signal t1 and the operation control signal t3,
The difference signal (Vd1-Vd2) and the signal components Vd1 and Vd2 of the pulsating flow waveform corresponding to the position signals I1 and I2 are extracted. Detection / arithmetic circuit 25 '
3 outputs of each are integrated circuit (low-pass filter) 26
a, 26c, 26d are averaged to obtain the signal component Vd
The outputs of the integrating circuits 26c and 26d corresponding to 1 and Vd2 are input to the adder 27d and added to the sum signal (Vd1 + k · Vd
2) is required. The difference signal (V
By inputting d1−Vd2) and the sum signal (Vd1 + k · Vd2) to the divider 27c, the distance measurement signal (Vd1−Vd2) / (Vd1 + k ·
Vd2) can be obtained. This operation is basically the same as that of the fourth embodiment, and the operation waveforms of the respective parts are shown in FIG.
become that way.

A concrete structure of the detection / arithmetic circuit 25 'shown in FIG. 20 is shown in FIG. 22, for example. The configuration for extracting the difference signal (Vd1-Vd2) in this configuration is the same as that shown in FIG. Difference signal (Vd1-Vd
If 2) is obtained, the signal components Vd1 and Vd2 can be extracted by separating and extracting the positive electrode component and the negative electrode component. That is, by using the operational amplifiers OP7 to OP10, the switch elements S4 and S5, and the inverter IN,
The positive component and the negative component of the difference signal (Vd1-Vd2) are extracted respectively.

(Sixth Embodiment) As shown in FIG. 23, the sixth embodiment is different from the fourth embodiment in the configuration of the arithmetic unit 27 ', and the other configurations are the same as those in the fourth embodiment. . That is, in the detection / arithmetic circuit 25 ', the difference signal (Vd1-Vd2) and the signal component Vd2 corresponding to the position signal I2 are extracted, averaged by the integrator circuits (low-pass filters) 26a, 26d, respectively, and added by the adder 27d. Generates a sum signal (Vd1 + k · Vd2) by using each average value of the difference signal (Vd1-Vd2) and the signal component Vd2. Difference signal (Vd1-Vd2) and sum signal (Vd1
+ K · Vd2) is input to the divider 27c, and the object 3
Ranging signal (Vd1-Vd2) / (V
Therefore, d1 + k · Vd2) is required. This operation is basically the same as that of the fourth embodiment, and the operation waveforms of the respective parts are as shown in FIG.

The concrete structure of the detection / arithmetic circuit 25 'shown in FIG. 23 is as shown in FIG. Here, the configuration for generating the difference signal (Vd1-Vd2) is similar to that shown in FIG. 9, and the configuration for extracting the signal component Vd2 corresponding to the position signal I2 is that of the fifth embodiment shown in FIG. Is the same as. Other configurations and operations are the same as those of the fifth embodiment.

(Embodiment 7) In this embodiment, as shown in FIG. 26, the configuration of an arithmetic unit 27 'is different from that of the fourth embodiment, and the other configurations are the same as those of the fourth embodiment. . That is, in the detection / arithmetic circuit 25 ', the difference signal (Vd1-Vd2), the signal (Vd1 + Vd2), and the signal component Vd2 corresponding to the position signal I2 are extracted, and integrated circuits (low-pass filters) 26a, 26b, 26d, respectively.
And averages the signal (Vd1
+ Vd2) and the average value of the signal component Vd2 are used to generate the sum signal (Vd1 + k · Vd2). Difference signal (Vd
1-Vd2) and the sum signal (Vd1 + k · Vd2) are input to the divider 27c, and a ranging signal (Vd1-Vd2) / (Vd1 + k · Vd2) corresponding to the distance to the object 3 is obtained. This operation is basically the same as that of the fourth embodiment, and the operation waveforms of the respective parts are as shown in FIG.

A concrete configuration of the detection / arithmetic circuit 25 'shown in FIG. 26 is shown in FIG. 28, for example. Here, the configuration for generating the signal (Vd1 + Vd2) is the same as that shown in FIG. 9, and the difference signal (Vd1-Vd
2) can be obtained by inverting the negative component of the signal (Vd1 + Vd2) using the operational amplifiers OP1 and OP2 and the switch element S1. The signal Vd2 corresponding to the position signal I2 is generated by the operational amplifiers OP9, OP10,
It is extracted using the switch element 5 and the inverter IN.
Other configurations and operations are the same as those of the fifth embodiment.

[0057]

According to the first aspect of the present invention, the light beam emitted from the light emitting element is irradiated to the object with the light beam modulated at an appropriate period, and the light emitting spot formed on the surface of the object is formed on the light receiving surface of the position detecting element. In the optical displacement measuring device that detects the displacement of the object from the reference position based on the position of the light receiving spot obtained by forming an image, the position detecting element has a pair of signal values whose ratio is determined depending on the position of the light receiving spot. Output position signal,
A switch circuit that alternately passes the position signal at an integer multiple of the beam light modulation period, a variable amplifier that amplifies the position signal that passes through the switch circuit, and an object that detects the output of the variable amplifier and that is based on the detected output. Of the light-emitting element so as to keep the signal corresponding to the displacement of the signal and the signal corresponding to the amount of light received by the position detection element substantially constant, and the signal corresponding to the amount of light received by the position detection element. A feedback control circuit that feedback-controls at least one of the optical output and the amplification factor of the variable amplifier is provided, and feedback control is performed so that the signals corresponding to the light-receiving amounts are substantially constant on the light-emitting side and the light-receiving side, respectively. Since this is performed, there is an advantage that the dynamic range with respect to the amount of received light becomes extremely large. Further, since the position signal is processed by one system through the switch circuit, the error caused by the variation of parts is reduced, so that highly accurate distance measurement is possible and the number of circuit components is reduced as compared with the conventional one. Has the advantage that

According to a second aspect of the invention, a reference value is set for the amount of light received by the position detection element, and the feedback control circuit decreases the light output of the light emitting element when the amount of light received exceeds the reference value. In the case of increasing the amplification factor of the variable amplifier when the amount of received light is smaller than the reference value, saturation is prevented by decreasing the light output when the amount of received light increases, and the amplification factor is increased when the amount of received light decreases. There is an advantage that the signal can be prevented from being buried in noise.

When the switch circuit is set to be twice as long as the modulation period of the light beam as in the third aspect of the invention, the influence of the switching noise of the switch circuit is affected by the lengthening of the switching period of the switch circuit. It has the advantage of being reduced. According to the invention of claim 4, the position signal output from the position detection element is a current signal, and an I / V conversion circuit for converting each position signal into a current-voltage is provided in a stage preceding the switch circuit. However, since the minute current signal is converted into a voltage signal and then input to the switch circuit, there is an advantage that it is less likely to be affected by the switching noise of the switch circuit.

According to the fifth aspect of the present invention, the light beam emitted from the light emitting element is irradiated onto the object with the light beam modulated at an appropriate period, and the light projection spot formed on the surface of the object is imaged on the light receiving surface of the position detecting element. In the optical displacement measuring device that detects the displacement of the object from the reference position based on the position of the light receiving spot obtained by the above, the position detecting element is a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot. And a switch circuit that alternately passes the position signal at an integer multiple of the beam light modulation cycle, and the polarity of the position signal that passes through the switch circuit is inverted every half cycle of the beam light modulation cycle and A detection / arithmetic circuit that obtains a sum signal with the same polarity and a difference signal with different polarities, a pair of integration circuits that obtains the average value of the sum signal and the difference signal, and the difference between the outputs of the integration circuits. signal It is provided with a division unit that divides the average value by the average value of the sum signal, which eliminates the need for the calculation of the difference and the calculation of the sum, and can prevent the measurement error due to the dispersion of the calculation of the sum difference. There is an advantage.

According to the eighth aspect of the present invention, the light beam emitted from the light emitting element is irradiated onto the object with the light beam modulated at an appropriate period, and the light projection spot formed on the surface of the object is imaged on the light receiving surface of the position detecting element. In the optical displacement measuring device that detects the displacement of the object from the reference position based on the position of the light receiving spot obtained by the above, the position detecting element is a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot. The switch circuit that alternately outputs the position signal at an integer multiple of the beam light modulation cycle, and the polarity of the position signal that passed through the switch circuit is inverted every half cycle of the beam light modulation cycle. Detection of a sum signal in which the position signal and the signal obtained by multiplying the other position signal by a coefficient have the same polarity and a difference signal in which both position signals have different polarities, and an average value of the sum signal and the difference signal is detected. Calculation And a division unit that divides the average value of the difference signal by the average value of the sum signal, which eliminates the need for the calculation of the difference and the calculation of the sum. Can be prevented. Moreover, since one of the position signals is multiplied by the coefficient, there is an advantage that it is possible to correct the non-linear positiveness of the position detecting element.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the above.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is an operation explanatory view of the above.

FIG. 5 is an operation explanatory view showing another operation example of the above.

FIG. 6 is a block diagram showing a second embodiment.

FIG. 7 is a block diagram showing a third embodiment.

FIG. 8 is an operation explanatory view of the above.

FIG. 9 is a main part circuit diagram of the above.

FIG. 10 is a main part circuit diagram of the above.

FIG. 11 is an operation explanatory diagram of the above.

FIG. 12 is a main part circuit diagram of the above.

FIG. 13 is an explanatory diagram of the operation of the above.

FIG. 14 is a block diagram showing a fourth embodiment.

FIG. 15 is an explanatory diagram of the operation of the above.

FIG. 16 is a main part circuit diagram of the same.

FIG. 17 is a main part circuit diagram of the above.

FIG. 18 is a main part circuit diagram of the same.

FIG. 19 is an operation explanatory diagram of the above.

FIG. 20 is a block diagram showing a fifth embodiment.

FIG. 21 is an explanatory diagram of the above operation.

FIG. 22 is a main part circuit diagram of the above.

FIG. 23 is a block diagram showing a sixth embodiment.

FIG. 24 is an explanatory diagram of the operation of the above.

FIG. 25 is a main-portion circuit diagram of the above.

FIG. 26 is a block diagram showing a seventh embodiment.

FIG. 27 is an explanatory diagram of the operation of the above.

FIG. 28 is a circuit diagram of an essential part of the above.

FIG. 29 is a block diagram showing a conventional example.

FIG. 30 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

 11 laser diode (light emitting element) 15 modulation circuit 16 feedback control circuit 17 comparison circuit 21 position detection element 23 I / V conversion circuit 23a I / V conversion circuit 23b I / V conversion circuit 24 variable amplifier 25 detection circuit 25 'detection / operation Circuit 26a Integrator circuit 26b Integrator circuit 26c Integrator circuit 26d Integrator circuit 27 'Calculator 27a Difference calculator 27b Sum calculator 27c Divider 27d Adder 31 Switch circuit 32 Switch circuit

Claims (12)

[Claims] 1. Light reception obtained by irradiating an object with a light beam modulated at an appropriate period from a light emitting element and forming a light projection spot formed on the surface of the object on a light receiving surface of a position detection element. In an optical displacement measuring device that detects the displacement of a target object from the reference position based on the position of the spot, the position detection element outputs a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot, and the position A switch circuit that alternately passes a signal at an integer multiple of the modulation period of the light beam, a variable amplifier that amplifies the position signal that has passed through the switch circuit, and the output of the variable amplifier is detected and the object of the object is detected based on the detected output. A signal processing unit that outputs a distance measurement signal corresponding to displacement and a signal corresponding to the amount of light received by the position detection element, and the signal corresponding to the amount of light received by the position detection element, should be kept substantially constant. An optical displacement measuring device, further comprising: a feedback control circuit that feedback-controls at least one of the light output of the light emitting element and the amplification factor of the variable amplifier. 2. A reference value is set for the amount of light received by the position detection element, and the feedback control circuit decreases the light output of the light emitting element when the amount of light received exceeds the reference value.
The optical displacement measuring device according to claim 1, wherein the amplification factor of the variable amplifier is increased when the amount of received light is smaller than the reference value. 3. The switch circuit is set to be at least twice as long as the modulation period of the light beam.
The optical displacement measuring device described. 4. The position signal output from the position detecting element is a current signal, and an I / V conversion circuit for converting each position signal into a current-voltage is provided in a stage preceding the switch circuit. The optical displacement measuring device according to claim 1. 5. A light receiving device obtained by irradiating an object with a light beam, which is modulated at an appropriate period, from the light emitting element, and forming a light projection spot formed on the surface of the object on the light receiving surface of the position detecting element. In an optical displacement measuring device that detects the displacement of a target object from the reference position based on the position of the spot, the position detection element outputs a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot, and the position A switch circuit that alternately passes a signal at an integer multiple of the modulation cycle of the beam light, and the polarity of the position signal that passed through the switch circuit is inverted every half cycle of the modulation cycle of the beam light, and each position signal has the same polarity. The detection / arithmetic circuit for obtaining the sum signal and the difference signal with different polarities, the pair of integrating circuits for obtaining each average value of the sum signal and the difference signal, and the average value of the difference signal among the outputs of each integrating circuit Sum signal An optical displacement measuring device comprising: a division unit that divides by an average value. 6. The detection / arithmetic circuit, after obtaining the sum signal, inverts the polarity of a component corresponding to one position signal among the components of the sum signal to generate a difference signal. 5. The optical displacement measuring device according to 5. 7. The detection / arithmetic circuit, after obtaining the difference signal, inverts the polarity of a component corresponding to one position signal of the components of the difference signal to generate a sum signal. 5. The optical displacement measuring device according to 5. 8. A light receiving device obtained by irradiating an object with a light beam modulated at an appropriate period from a light emitting element and forming a light projection spot formed on the surface of the object on a light receiving surface of a position detecting element. In an optical displacement measuring device that detects the displacement of a target object from the reference position based on the position of the spot, the position detection element outputs a pair of position signals whose signal value ratio is determined according to the position of the light receiving spot, and the position A switch circuit that alternately passes the signal at an integer multiple of the modulation period of the beam light, and the polarity of the position signal that passes through the switch circuit is inverted every half cycle of the modulation period of the beam light, and one position signal and the other A detection / calculation means for obtaining a sum signal in which the position signal is multiplied by a coefficient and having the same polarity and a difference signal in which both position signals have different polarities, and for obtaining an average value of the sum signal and the difference signal, Signal flat An optical displacement measuring device, comprising: a division unit that divides the average value by the average value of the sum signal. 9. The sum signal by detecting and calculating the difference signal, inverting the signal obtained by multiplying the signal component of one polarity of the difference signal by a coefficient, and adding the inverted signal to the signal of the other polarity. 9. The optical displacement measuring device according to claim 8, wherein: 10. The detecting / calculating means, after obtaining the difference signal, extracts a signal component of each polarity of the difference signal, multiplies one extracted signal component by a coefficient, and adds the extracted signal component to the other extracted signal component. 9. The optical displacement measuring device according to claim 8, wherein the sum signal is generated by the above. 11. The detection / calculation means, after obtaining the difference signal, extracts a signal component of one polarity of the difference signal, and sums the extracted signal component by a coefficient and the difference signal. 9. The optical displacement measuring device according to claim 8, which generates a signal. 12. The detection / calculation means extracts a signal component of one polarity of the signal and obtains a signal component of one polarity of the signal after obtaining a signal in which the signal components corresponding to the respective position signals have the same polarity. 9. The optical displacement measuring device according to claim 8, wherein the signal component is inverted to generate a difference signal, and the sum signal is generated based on the signal and the extracted signal component of one polarity.