JP2007121175A - Displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constitution facilitating specification of the cause of a fault. <P>SOLUTION: This displacement sensor 1 comprises a head section 11 and a controller 12. The head section 11 comprises a projecting means for projecting light toward a workpiece W, and a position detecting means. The controller 12 is constituted so that the distance to the workpiece W can be measured based on a voltage signal S1 from the position detecting means. The controller 12 can switch between measuring mode and body diagnostic mode. When the body diagnostic mode is set, a false detection signal is generated, and provided to a CPU via an amplifier section and A/D converter. A memory 39 records reference information used as a reference of the measurement result when the false detection signal is provided, and abnormality of the controller 12 is determined based on the measurement result when the false detection signal is provided and the reference information stored in the memory 39. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a displacement sensor.

Conventionally, a laser beam is irradiated toward the object to be detected, and reflected light from the object to be detected is received by the position detection element, and the detection object is detected based on the detection signal output from the position detection element. A displacement sensor for measuring distance is provided. For example, in Patent Document 1 below, light from a light source is irradiated on a detected object, the reflected light is received by an image sensor, and the detected object is detected from the light source and the image sensor based on the light receiving position of the reflected light in the image sensor. An optical displacement meter that measures the distance to is disclosed.
JP 2001-50711 A

  By the way, in the displacement sensor as described above, an abnormal measurement value may occur for some reason. The cause of such an abnormal measurement value is an external factor on the user side or a factor inside the displacement sensor. Conventionally, it is difficult to specify the factor, and it takes a lot of time to investigate the cause. It was.

  The present invention has been completed based on the above-described circumstances, and an object thereof is to provide a configuration in which the cause of a defect can be easily identified.

As means for achieving the above object, the invention of claim 1
Light projecting means for projecting toward the object to be detected, and a position for receiving the reflected light from the object to be detected at a position corresponding to the distance to the object to be detected and outputting a detection signal according to the distance A head unit comprising detection means;
A main body provided with a measuring unit to which the head unit is attached and which measures a distance to the detected object based on a detection signal from the position detecting unit;
Pseudo signal storage means for storing data for generating a pseudo detection signal;
Switching means capable of switching between a measurement mode for performing measurement processing by the measurement means and a main body diagnosis mode for diagnosing the main body,
Control means for providing the pseudo detection signal to the measuring means when the main body diagnosis mode is set by the switching means;
Reference information storage means for recording reference information as a reference of a measurement result when the pseudo detection signal is given to the measurement means;
A body part abnormality determination unit for determining abnormality of the body part based on a measurement result of the measurement unit when the pseudo detection signal is given and the reference information stored in the reference information storage unit; ,
It is provided with.

The invention according to claim 2 is the displacement sensor according to claim 1,
The main body is provided with update means for updating data for generating the pseudo detection signal stored in the pseudo signal storage means.

The invention according to claim 3 is the displacement sensor according to claim 2,
The main body includes external information input means for inputting data for generating the pseudo detection signal from the outside,
The update means updates data for generating the pseudo detection signal stored in the pseudo signal storage means based on data input by the external information input means.

The invention of claim 4
Light projecting means for projecting toward the object to be detected, and a position for receiving the reflected light from the object to be detected at a position corresponding to the distance to the object to be detected and outputting a detection signal according to the distance A head unit comprising detection means;
A main body provided with a measuring unit to which the head unit is attached and which measures a distance to the detected object based on a detection signal from the position detecting unit;
A switching unit capable of switching between a measurement mode for performing measurement processing by the measurement unit and a head unit diagnosis mode for diagnosing the head unit;
Reference result information storage means for preliminarily storing reference result information based on the measurement result by the measurement means when the object to be detected is arranged;
Based on the measurement result by the measurement unit when the switching unit is switched to the head unit diagnosis mode and the reference result information stored in the reference result information storage unit, an abnormality of the head unit is determined. A head part abnormality determining means for performing,
It is provided with.

According to a fifth aspect of the present invention, in the displacement sensor according to any one of the first to third aspects,
The switching unit is configured to be able to switch between a measurement mode for performing measurement processing by the measurement unit and a head unit diagnosis mode for diagnosing the head unit,
Furthermore,
Reference result information storage means for preliminarily storing reference result information based on the measurement result by the measurement means when the object to be detected is arranged;
Based on the measurement result by the measurement unit when the switching unit is switched to the head unit diagnosis mode and the reference result information stored in the reference result information storage unit, an abnormality of the head unit is determined. A head part abnormality determining means for performing,
Is provided.

The invention of claim 6 is the displacement sensor according to any one of claims 1 to 5,
The switching means is characterized in that a switching operation based on an external operation is possible.

The invention of claim 7 is the displacement sensor according to any one of claims 1 to 6,
An amplification circuit that amplifies and outputs a detection signal from the position detection means in the head unit;
The displacement sensor according to any one of claims 1 to 6, wherein the pseudo light reception signal is input to the measurement means via the amplifier circuit.

The invention according to claim 8 is the displacement sensor according to any one of claims 1 to 7,
The position detection means outputs the detection signal as an analog signal,
The main body includes an A / D conversion circuit that converts the detection signal, which is an analog signal, into a digital signal and supplies the digital signal to the measurement unit,
The body part abnormality determining means is
Based on the data stored in the pseudo signal storage means, output means for outputting the pseudo light reception signal as a digital signal;
A D / A conversion circuit for converting the pseudo light reception signal output by the output means into an analog signal;
With
When the main unit diagnosis mode is set by the switching unit, the pseudo light receiving signal converted to an analog signal through the D / A conversion circuit is controlled by the control unit. The signal is supplied to the measurement means via a conversion circuit.

<Invention of Claim 1>
According to the invention of claim 1, when an abnormal value is obtained at the time of measurement, it is possible to detect if there is an abnormality in the main body by switching to the main body diagnosis mode, and conversely abnormal If there is no error, it can be specified that there is an abnormality in the other part. Therefore, it is easy to identify the cause part of the abnormality, and the cause of the problem can be investigated satisfactorily.

<Invention of Claim 2>
According to the invention of claim 2, the degree of freedom in setting a pseudo light reception signal can be increased.

<Invention of Claim 3>
According to invention of Claim 3, it becomes a suitable structure which a user is easy to set a pseudo light reception signal uniquely.

<Invention of Claim 4>
According to the invention of claim 4, when an abnormal value is obtained at the time of measurement, it is possible to detect if there is an abnormality in the head part by switching to the head part diagnosis mode, and conversely abnormal If there is no error, it can be specified that there is an abnormality in the other part. Therefore, it is easy to identify the cause part of the abnormality, and the cause of the problem can be investigated satisfactorily.

<Invention of Claim 5>
According to the fifth aspect of the present invention, it is possible to switch not only to the main body part diagnosis mode but also to the head part diagnosis mode, and it is possible to easily identify not only the main body part abnormality but also the head part abnormality. Therefore, it becomes easier to identify the cause of the abnormality, and the cause of the problem can be investigated more effectively.

<Invention of Claim 6>
According to the invention of claim 6, since the diagnosis can be easily started by an external operation, the usability can be improved.

<Invention of Claim 7>
According to the invention of claim 7, when an abnormality occurs in the amplifier circuit of the main body, the abnormality can be suitably detected.

<Invention of Claim 8>
According to the eighth aspect of the present invention, when an abnormality occurs in the A / D conversion circuit of the main body, the abnormality can be suitably detected.

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to the drawings.
1. Overall Configuration FIG. 1 is an overall schematic diagram of a displacement sensor 1 of the present embodiment. The displacement sensor 1 has a configuration in which a sensor head portion 11 corresponding to a head portion and a controller portion 12 corresponding to a main body portion are connected via a signal cable.

  The sensor head unit 11 has a laser diode (LD) 15 as a light projecting element, an LD drive circuit 16 for driving the laser diode 15, and a laser beam L 1 emitted from the laser diode 15 on the surface of the workpiece W. And a projection lens 17 to be irradiated. These laser diode 15, LD drive circuit 16, and light projection lens 17 correspond to the “light projection means” of the present invention.

  Further, the sensor head unit 11 includes a light receiving lens 18, a CCD linear sensor 19 as a position detecting element that receives the laser light L 2 transmitted through the light receiving lens 18, and a CCD drive circuit for driving the CCD linear sensor 19. 20. The light receiving lens 18, the CCD linear sensor 19, and the CCD drive circuit correspond to position detecting means.

  The laser light L1 emitted from the laser diode 15 passes through the light projecting lens 17 and is irradiated onto the workpiece W. Then, the diffusely reflected light L 2 on the workpiece W passes through the light receiving lens 18 and enters the CCD linear sensor 19. The charge accumulated in the CCD linear sensor 19 according to the received light amount and the relative position of the work is read out by the CCD drive circuit 20 and converted into a time-series voltage signal.

  When the CCD drive circuit 20 gives a predetermined transfer clock to the CCD linear sensor 19, the CCD linear sensor 19 sequentially transfers the charges accumulated in each pixel one pixel at a time. Then, the CCD drive circuit 20 outputs a time-series voltage signal S1 (the voltage signal S1 corresponds to a detection signal) corresponding to the accumulated charges of all the pixels.

  The controller unit 12 includes a CPU 35 (FIG. 2), a memory 39 (FIG. 2), and operation keys 41. In the “measurement mode” and the “sampling mode”, the CPU 35 gives a drive signal to the LD drive circuit 16 to cause the laser diode 15 to perform a light projecting operation, and drives the CCD drive circuit 20 in a predetermined cycle to thereby provide a CCD linear sensor. The light receiving operation for transferring the accumulated charge of each of the 19 pixels is executed, and the voltage signal S1 from the CCD driving circuit 20 is received.

  With the above configuration, in the sensor head unit 11, the light receiving position P of the diffuse reflected light L2 on the light receiving surface 19a of the CCD linear sensor 19 moves according to the distance from the light projecting lens 17 to the irradiation spot Q of the workpiece W. The CPU 35 can measure the height displacement of the workpiece W by analyzing the voltage signal S1 and detecting the light receiving position P of the diffusely reflected light L2 on the light receiving surface 19a of the CCD linear sensor 19.

  More specifically, the CPU 35 receives the voltage signal S <b> 1 from the CCD drive circuit 20, detects a pixel having the maximum light reception amount from all the pixels on the light receiving surface 19 a of the CCD linear sensor 19, and stores a measurement data storage area in the memory 39. Store in chronological order. At this time, the CPU 35 functions as a “measuring unit” of the present invention.

2. Measurement Function As described above, the displacement sensor 1 is provided with the head portion 11 and the main body portion 12, and the head portion 11 includes a light projecting unit that projects light toward the work W (detected object), and the work W. Position detecting means is provided for receiving reflected light from a position at a position corresponding to the distance to the workpiece W and outputting a voltage signal S1 (detection signal) according to the distance.

  The main body 12 has a function of measuring the distance to the object to be detected based on the detection signal from the position detecting means, to which the head 11 is attached. In the present embodiment, the CPU 35 functions as such a measuring unit.

  The controller 12 has an amplifier circuit 31 (amplifier 31 corresponds to an amplifier circuit) that amplifies and outputs a detection signal from a position detection element in the head unit, and the amplified detection signal is converted into an A / D converter. 33 (A / D converter 33 corresponds to an A / D conversion circuit), digitized, and input to CPU 35.

  In the configuration according to this embodiment, an analog voltage signal S1 is output as a detection signal by the light receiving lens 18, CCD linear sensor 19, and CCD drive circuit 20 corresponding to the position detection means. The controller 12 that receives S1 is configured to convert the detection signal, which is an analog signal, into a digital signal by the A / D converter 33 and to supply the digital signal to the CPU 35 that is a measuring means.

3. Abnormality diagnosis function The main body 12 in the displacement sensor 1 of the present embodiment also has a function of determining an abnormality. The CPU 35 functions as a main body abnormality determination unit of the present invention, and further has functions as a switching unit, a control unit, and a head unit abnormality determination unit.

  FIG. 3 is a flowchart illustrating a mode setting process for switching between a measurement mode for performing the measurement process and a main body diagnosis mode for diagnosing the main body. A program for executing this flowchart is stored in the memory 39 and is activated based on an external operation (specifically, an input operation by the operator with the operation key 41). The memory 39 also has functions as pseudo signal storage means, reference information storage means, and reference result information storage means of the present invention.

  When a predetermined operation is performed with the operation key 41, the program is activated, and it is determined whether information for instructing execution of system diagnosis is input with the operation key 41. When execution of system diagnosis (that is, setting of a main body diagnosis mode for diagnosing the main body) is instructed, the process proceeds to Y in S10, the main body diagnosis mode is set, and a system diagnosis process described later is performed. .

If the information for instructing the system diagnosis is not input, the process proceeds to N in S10. When the process proceeds to N in S10, or after the system diagnosis process is completed, it is determined whether or not information instructing execution of the form diagnosis is input in S30. If execution of the form diagnosis (that is, setting of the head part diagnosis mode for diagnosing the head part) is instructed, the process proceeds to Y in S30, the head part diagnosis mode is set, and the form diagnosis process described later is performed. . When the process proceeds to N in S30, or after the form diagnosis process is completed, it is determined whether or not to end in S50. If the operation key 41 is instructed to end, or if no information is input for a predetermined time, the process proceeds to Y in S50 and the process ends. If the process is not ended in S50, the process proceeds to Y, and the processes after S10 are repeated.
Note that the processing shown in FIG. 3 is merely an example, and it is needless to say that other processing methods can be used as long as both the setting of the main body diagnosis mode and the setting of the head diagnosis mode can be realized.

  Next, system diagnosis processing when the main unit diagnosis mode is set will be described. In the present embodiment, the main body unit 12 is configured to be able to generate a pseudo detection signal. When the main body unit diagnosis mode is set, the pseudo detection signal is converted into a received light signal processing circuit ( In the present embodiment, the control is performed so as to be given to the CPU as the measuring means via the amplifier circuit 31 and the A / D converter 33). In addition, reference information serving as a reference for measurement results when a pseudo detection signal is supplied to the CPU 35 via the light reception signal processing circuit is recorded in the memory 39 in advance, and the pseudo detection signal is given. The abnormality of the controller 12 is determined based on the measurement result of the CPU 35 and the reference information stored in the memory 39.

FIG. 4 is a flowchart illustrating the flow of the system diagnosis process.
When the process is started, first, a switching signal is output in S110. The switching signal is a signal for instructing switching of the switch SW. In the main body diagnosis mode, the light receiving signal processing circuit (the amplifier circuit 31 and the A / D converter 33) is operated by the sensor head unit based on the switching signal output from the CPU 35. The switch operation is performed so that it is connected to the D / A converter 37 (D / A converter 37 corresponds to a D / A converter circuit) without being connected to the 11 position detecting means.

  In S120, a pseudo waveform table corresponding to data is read out by the CPU 35 to generate a pseudo light reception signal, and in S130, a pseudo light reception signal corresponding to the pseudo waveform table is generated and a D / A converter. 37. The pseudo light reception signal is output as a digital signal by the CPU 35 based on the pseudo waveform table stored in the memory 39, and is the same as the voltage signal S 1 sent from the sensor head unit 11 by the D / A converter 37. Converted to analog signal. The analog pseudo received light signal is supplied to the amplifier circuit 31 via the switch SW, amplified, and then input to the A / D converter 33. Then, the CPU 35 acquires the digitized pseudo light reception signal output from the A / D converter 33 (S140).

  The CPU 35 compares the waveform based on the inputted pseudo light reception signal with the reference information, and determines whether or not there is an abnormality (S150). Note that the determination of abnormality may be made by comparing cells corresponding to the peak value, or may be made by comparing the entire waveforms. For example, the abnormality can be determined by comparing the position and value of the peak value in the pseudo waveform table with the position and value of the peak value in the reception result of the pseudo light reception signal. The reference information may be the above-described pseudo waveform table as long as it corresponds to a normal result, or may be different information.

  In the present embodiment, the data for generating the pseudo detection signal stored in the memory 39 can be updated. The controller 12 is provided with external information input means (for example, an operation key 41 or an input terminal) for inputting data for generating a pseudo detection signal from the outside, and the CPU 35 is provided with the external information input means. Based on the input data, data for generating a pseudo detection signal stored in the memory 39 is updated. Note that it is possible to make the memory 39 have first data that cannot be updated and second data that can be updated as data for generating a pseudo detection signal. May be.

  If it is determined that there is an abnormality according to the above determination, the process proceeds to Y in S150, and an output indicating that an abnormality has occurred somewhere in the controller 12 (for example, display on the display unit 43) is performed (S170). . If it is not abnormal, the process proceeds to N in S150, and an output indicating normality (for example, display on the display unit 43) is performed (S160).

  Next, the form diagnosis process performed in S40 of FIG. 3 will be described. As described above, in the mode setting process, it is possible to switch between the measurement mode for performing the measurement process and the head part diagnosis mode for diagnosing the sensor head part 11, and form diagnosis is performed when the head part diagnosis mode is set. Processing is executed.

  In this embodiment, the reference result information based on the measurement result when the reference workpiece W is arranged can be stored in the memory 39 in advance. Specifically, a voltage signal S1 is generated when a user places a reference workpiece and performs a measurement operation, and waveform data based on the voltage signal S1 obtained by detecting the reference workpiece is stored in advance as reference waveform data. 39 is stored.

  When the head part diagnosis mode is switched, that is, when the above-described form diagnosis process is executed, the user performs measurement by arranging the same reference work as when the reference waveform data is generated. Then, by comparing the measurement result (measurement waveform data) at this time with the reference result information (that is, reference waveform data) stored in the memory 39, the abnormality of the sensor head unit 11 can be determined.

  The configuration according to the present embodiment is also configured to output the reference result information (reference waveform data) stored in the memory 39 and the measured measurement result (measurement waveform data). This output may be output to the display unit 43 or may be output to the outside.

  According to the configuration of the present embodiment, when an abnormal value is obtained during measurement, it is possible to detect if there is an abnormality in the main body by switching to the main body diagnosis mode, and conversely, abnormal If there is no error, it can be specified that there is an abnormality in the other part. Therefore, it is easy to identify the cause part of the abnormality, and the cause of the problem can be investigated satisfactorily.

  Further, it is possible to switch not only to the main body diagnosis mode but also to the head diagnosis mode, so that not only the abnormality of the main body but also the abnormality of the head can be easily identified. Therefore, it is easier to identify the cause of the abnormality, and the cause of the problem can be investigated more effectively.

  Further, a result information output means for outputting the reference result information stored in the reference result information storage means and the measurement result by the measuring means is provided. Therefore, it is easy to compare the reference result information and the information related to the measurement result, which is advantageous for analysis.

  Further, the switching means can perform a switching operation based on an external operation. Therefore, diagnosis can be easily started by an external operation, and usability is improved.

  Furthermore, an amplification circuit that amplifies and outputs a detection signal from the position detection means in the head unit is provided, and the pseudo light reception signal is input to the amplification circuit and amplified through the amplification circuit. A signal is input to the measuring means. When an abnormality occurs in the amplifier circuit of the main body, the abnormality can be suitably detected.

  The position detection means outputs a detection signal as an analog signal, and the main body section includes an A / D converter that converts the detection signal converted into an analog signal into a digital signal and supplies the digital signal to the measurement means. Is based on the pseudo data stored in the pseudo data storage means, output means for outputting a pseudo light reception signal as a digital signal, and D for converting the pseudo light reception signal output by the output means into an analog signal. / A converter, and when the main unit diagnosis mode is set by the switching unit, a pseudo light reception signal converted into an analog signal through the D / A converter is controlled by the control unit. It is given to the measuring means via an A / D converter. Therefore, when an abnormality occurs in the A / D converter of the main body, the abnormality can be detected suitably.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiment, the pre-stored pseudo data is used. However, the user can register the pseudo data, and the CPU 35 outputs a pseudo light reception signal based on the pseudo data. You may make it perform abnormality determination.
(2) In each of the above embodiments, the position detection unit is of a linear image sensor type using the CCD linear sensor 19 as a position detection element. However, the position detection unit is not limited to this, and a PSD (Position Sensitive Detector) is used as the position detection element. ) Using the PSD method.

(3) In each of the above embodiments, the sensor head unit 11 is a so-called diffuse reflection type that receives diffusely reflected light from the workpiece W. However, the present invention is not limited thereto, and for example, the workpiece W has a regular reflection surface. If it is, the so-called specular reflection type that irradiates the workpiece W with the laser light L1 from the laser diode 15 obliquely from above and receives the specular reflection light may be used.
(4) The memory 39 shown in the above embodiment may be configured by a single storage unit, or may be configured by a plurality of storage units (for example, ROM, RAM, nonvolatile memory, etc.).

Overall schematic diagram of displacement sensor according to embodiment 1 of the present invention The block diagram which mainly shows the internal structure of the controller 12 mainly Flowchart illustrating the flow of mode setting processing Flowchart illustrating the flow of system diagnosis processing

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Displacement sensor 11 ... Sensor head part (head part)
12 ... Controller (main part)
15 ... Laser diode (light projection means)
16 ... LD drive circuit (light projection means)
17 ... Projection lens (projection means)
18. Light receiving lens (position detecting means)
19 ... CCD linear sensor (position detecting means)
20 ... CCD drive circuit (position detecting means)
31 ... Amplifier section (amplification circuit)
33 ... A / D converter (A / D conversion circuit)
35 ... CPU (measuring means, updating means, switching means, control means, body part abnormality determining means, head part abnormality determining means, result information output means)
37 ... D / A converter (D / A converter circuit)
39. Memory (pseudo signal storage means, reference information storage means, reference result information storage means)
W: Workpiece (object to be detected)
S1 ... Voltage signal (detection signal)

Claims (8)

Light projecting means for projecting toward the object to be detected, and a position for receiving the reflected light from the object to be detected at a position corresponding to the distance to the object to be detected and outputting a detection signal according to the distance A head unit comprising detection means;
A main body provided with a measuring unit to which the head unit is attached and which measures a distance to the detected object based on a detection signal from the position detecting unit;
Pseudo signal storage means for storing data for generating a pseudo detection signal;
Switching means capable of switching between a measurement mode for performing measurement processing by the measurement means and a main body diagnosis mode for diagnosing the main body,
Control means for providing the pseudo detection signal to the measuring means when the main body diagnosis mode is set by the switching means;
Reference information storage means for recording reference information as a reference of a measurement result when the pseudo detection signal is given to the measurement means;
A body part abnormality determination unit for determining abnormality of the body part based on a measurement result of the measurement unit when the pseudo detection signal is given and the reference information stored in the reference information storage unit; ,
A displacement sensor comprising: 2. The displacement sensor according to claim 1, wherein the main body is provided with update means for updating data for generating the pseudo detection signal stored in the pseudo signal storage means. The main body includes external information input means for inputting data for generating the pseudo detection signal from the outside,
3. The update unit updates data for generating the pseudo detection signal stored in the pseudo signal storage unit based on data input by the external information input unit. The displacement sensor described in 1. Light projecting means for projecting toward the object to be detected, and a position for receiving the reflected light from the object to be detected at a position corresponding to the distance to the object to be detected and outputting a detection signal according to the distance A head unit comprising detection means;
A main body provided with a measuring unit to which the head unit is attached and which measures a distance to the detected object based on a detection signal from the position detecting unit;
A switching unit capable of switching between a measurement mode for performing measurement processing by the measurement unit and a head unit diagnosis mode for diagnosing the head unit;
Reference result information storage means for preliminarily storing reference result information based on the measurement result by the measurement means when the object to be detected is arranged;
Based on the measurement result by the measurement unit when the switching unit is switched to the head unit diagnosis mode and the reference result information stored in the reference result information storage unit, an abnormality of the head unit is determined. A head part abnormality determining means for performing,
A displacement sensor comprising: The switching unit is configured to be able to switch between a measurement mode for performing measurement processing by the measurement unit and a head unit diagnosis mode for diagnosing the head unit,
Furthermore,
Reference result information storage means for preliminarily storing reference result information based on the measurement result by the measurement means when the object to be detected is arranged;
Based on the measurement result by the measurement unit when the switching unit is switched to the head unit diagnosis mode and the reference result information stored in the reference result information storage unit, an abnormality of the head unit is determined. A head part abnormality determining means for performing,
The displacement sensor according to claim 1, wherein a displacement sensor is provided. 6. The displacement sensor according to claim 1, wherein the switching unit is capable of switching operation based on an external operation. An amplification circuit that amplifies and outputs a detection signal from the position detection means in the head unit;
The displacement sensor according to any one of claims 1 to 6, wherein the pseudo light reception signal is input to the measurement means via the amplifier circuit. The position detection means outputs the detection signal as an analog signal,
The main body includes an A / D conversion circuit that converts the detection signal, which is an analog signal, into a digital signal and supplies the digital signal to the measurement unit,
The body part abnormality determining means is
Based on the data stored in the pseudo signal storage means, output means for outputting the pseudo light reception signal as a digital signal;
A D / A conversion circuit for converting the pseudo light reception signal output by the output means into an analog signal;
With
When the main unit diagnosis mode is set by the switching unit, the pseudo light receiving signal converted to an analog signal through the D / A conversion circuit is controlled by the control unit. The displacement sensor according to any one of claims 1 to 7, wherein the displacement sensor is provided to the measurement means via a conversion circuit.

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