JP6819376B2 - Displacement measuring device - Google Patents

Description

The present invention relates to a displacement measuring device. In particular, the present invention relates to a displacement measuring device including a sensor head having no electronic circuit.

A displacement measuring device (displacement sensor) is known as a device for inspecting the surface shape of an object to be measured. For example, Japanese Patent Application Laid-Open No. 2012-208102 (Patent Document 1) discloses a confocal measuring device that measures the displacement of a measurement object in a non-contact manner using a confocal optical system.

Japanese Unexamined Patent Publication No. 2012-208102

In the confocal measuring device described in Japanese Patent Application Laid-Open No. 2012-208102 (Patent Document 1), the sensor head does not have an electronic circuit, and the sensor head and the controller are separated. The user near the sensor head needs to check the display of the controller in order to grasp the measurement state of the displacement measuring device.

For example, when installing the sensor head, it is necessary to adjust the position where the sensor head is installed for accurate measurement. The measurable range of the displacement measuring device can be expressed as the range of the distance from the front surface of the sensor head. Generally, the manufacturer defines this range as the specifications of the displacement measuring device. In the present specification, a range predetermined as a measurable distance range of the displacement measuring device is referred to as a “prescribed distance range”.

Based on the position where the work is placed, the installation position of the sensor head is adjusted so that the position of the work is within the specified distance range. When the user is near the sensor head, it may be difficult to check the display of the controller depending on the distance from the controller to the user or the position of the user with respect to the controller.

An object of the present invention is to provide a technique for a user to easily recognize a measurement state of a displacement measuring device including a sensor head having no electronic circuit.

The displacement measuring device according to a certain aspect of the present invention has a sensor head having an optical system and not having an electronic circuit, a light projecting unit for generating irradiation light, and reflection of irradiation light received by the sensor head. A controller including a light receiving unit that receives light and a control unit that calculates the distance between the sensor head and the reflected position of the reflected light based on the amount of light received by the light receiving unit, and the sensor head that emits light from the light projecting unit. A first optical fiber that transmits light from the sensor head and a second optical fiber that transmits the reflected light from the sensor head to the controller are provided. The control unit emits a first mode for measuring the distance between the sensor head and the reflection position and whether or not the distance between the sensor head and the reflection position is in the center of the specified distance range. It has a second mode indicated by the light state. The defined distance range is defined as the range of measurable distances of the displacement measuring device, and the central portion of the defined distance range is defined as a predetermined distance near the center of the defined distance range. The first optical fiber and the second optical fiber may be the same.

According to the above configuration, it is possible to provide a displacement measuring device capable of easily recognizing whether or not the distance between the sensor head and the reflection position is in the central portion of the predetermined distance range. In the second mode, the user can confirm the measurement state of the displacement measuring device by the light emitted from the sensor head.

Preferably, in the second mode, the control unit determines whether or not the distance between the sensor head and the reflection position is within the central portion of the predetermined distance range, and the determination result is determined by the light projecting unit. Shown by the light projection condition.

With the above configuration, it is possible to provide a displacement measuring device capable of making the user easily recognize the central portion of the specified distance range. In the second mode, the user can confirm that the distance between the sensor head and the reflection position is within the central portion of the specified distance range by the light emitted from the sensor head.

Preferably, in the second mode, when the distance from the sensor head to the reflection position is within the central portion of the predetermined distance range, the control unit continuously lights the light projecting unit. In the second mode, when the distance from the sensor head to the reflection position is outside the central portion of the specified distance range and within the specified distance range, the control unit blinks the light projecting unit.

According to the above configuration, the user confirms that the distance between the sensor head and the reflection position is within the central portion of the specified distance range by confirming that the light is continuously emitted from the sensor head. be able to.

Preferably, when the distance from the sensor head to the reflection position is in the range outside the central portion of the specified distance range, the distance from the sensor head to the reflection position is outside the central portion of the specified distance range and within the specified distance range. When the distance is within the specified distance range, the control unit blinks the light projecting unit at the first interval, and the distance from the sensor head to the reflection position is within the specified distance range and is at the center of the specified distance range. When it is outside and outside the predetermined distance range, the control unit blinks the light projecting unit at a second interval larger than the first interval.

According to the above configuration, the user can check how far the distance between the sensor head and the reflection position is from the central portion of the specified distance range by the blinking interval of the light emitted from the sensor head.

Preferably, when the distance from the sensor head to the reflection position is outside the central portion of the specified distance range and within the specified distance range, the control unit is the distance from the sensor head to the reflection position and the central portion of the specified distance range. The blinking interval of the floodlight is increased as the difference between the upper limit and the lower limit increases.

According to the above configuration, the user can check how far the distance between the sensor head and the reflection position is from the central portion of the specified distance range by the blinking interval of the light emitted from the sensor head.

Preferably, when the distance from the sensor head to the reflection position is within the central portion of the predetermined distance range, the control unit controls the light projecting unit so that the light projecting power of the light projecting unit becomes a constant value. When the distance from the sensor head to the reflection position is outside the central part of the specified distance range and within the specified distance range, the control unit determines that the peak value of the light projection power of the light projector is from the sensor head to the reflection position. The light projecting unit is controlled so that the output is higher than the output of the light projecting unit when the distance is within the central portion of the specified distance range.

According to the above configuration, when the distance between the sensor head and the reflection position is outside the central portion of the specified distance range and within the specified distance range, the displacement measuring device blinks the light emitted from the sensor head while blinking. The distance from the sensor head to the reflection position can be measured.

According to the present invention, it is possible to provide a displacement measuring device capable of easily recognizing whether or not the distance between the sensor head and the reflection position is in the central portion of the predetermined distance range.

It is a figure for demonstrating the principle of distance measurement by the displacement measuring apparatus which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the structure of the light guide part of the displacement measuring apparatus according to this Embodiment. It is a schematic diagram which shows an example of the structure of the displacement measuring apparatus according to this embodiment. It is a figure for demonstrating the light projection state of a sensor head in a normal measurement mode (the first mode). It is a figure for demonstrating the light projection state of a sensor head in a defined distance range center confirmation mode (second mode). It is a signal waveform diagram for demonstrating the control of a light projection part in a normal measurement mode (the first mode). It is a signal waveform diagram for demonstrating the control of the light emitting part in the defined distance range center confirmation mode (second mode). It is a flowchart for demonstrating control of light projection by a control part of a controller. It is a figure for demonstrating another embodiment of the light projection state of a sensor head in a defined distance range center confirmation mode (second mode).

Embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

<A. Overview>
FIG. 1 is a diagram for explaining the principle of distance measurement by the displacement measuring device according to the embodiment of the present invention. With reference to FIG. 1, the displacement measuring device 1 includes a light guide unit 20, a sensor head 30, and a controller 100. In the embodiment of the present invention, the displacement measuring device 1 includes a sensor head 30 having an optical system but no electronic circuit. In the embodiments described below, as an example of such a sensor head, a sensor head 30 including a confocal optical system is shown. However, the type of optical system included in the sensor head 30 is not limited.

The sensor head 30 includes a chromatic aberration unit 32 and an objective lens 34. The controller 100 includes a light emitting unit 10, a light receiving unit 40, a control unit 50, and a display unit 60. The light receiving unit 40 includes a spectroscope 42 and a detector 44.

The irradiation light having a predetermined wavelength spread generated by the light projecting unit 10 propagates through the light guide unit 20 and reaches the sensor head 30. In the sensor head 30, the irradiation light from the light projecting unit 10 is focused by the objective lens 34 and irradiated to the measurement object 2. Since axial chromatic aberration occurs in the irradiation light by passing through the chromatic aberration unit 32, the focal position of the irradiation light emitted from the objective lens 34 differs for each wavelength. Of the wavelengths reflected on the surface of the object to be measured 2, only the light having the wavelength focused on the object 2 to be measured re-enters only the confocal fiber of the light guide portion 20 of the sensor head 30. Become.

The reflected light re-entered on the sensor head 30 propagates through the light guide unit 20 and is incident on the light receiving unit 40. In the light receiving unit 40, the reflected light incident on the spectroscope 42 is separated into each wavelength component, and the intensity of each wavelength component is detected by the detector 44. The control unit 50 calculates the distance (displacement) from the sensor head 30 to the measurement object 2 based on the detection result of the detector 44.

In the example shown in FIG. 1, for example, irradiation light including a plurality of wavelengths λ1, λ2, λ3 is projected on an extension line of the optical axis AX. Images are drawn at different positions (focus position 1, focus position 2, focus position 3) on the optical axis AX depending on the wavelength dispersion of the irradiation light. Since the surface of the object to be measured 2 coincides with the focal position 2 on the optical axis AX, only the component of the wavelength λ2 of the irradiation light is reflected at the focal position 2. That is, the focal position 2 corresponds to the reflection position of the irradiation light. The light receiving unit 40 detects a component having a wavelength of λ2. The control unit 50 calculates that the distance from the sensor head 30 to the measurement object 2 is a distance corresponding to the focal position of the wavelength λ2. The display unit 60 numerically displays the distance calculated by the control unit 50.

Of the plurality of light receiving elements constituting the detector 44 of the light receiving unit 40, the light receiving element that receives the reflected light changes according to the shape of the surface of the measurement object 2 with respect to the sensor head 30. Therefore, the distance change (displacement) with respect to the measurement object 2 can be measured from the detection results (pixel information) by the plurality of light receiving elements of the detector 44. As a result, the displacement measuring device 1 can measure the shape of the surface of the object 2 to be measured.

FIG. 2 schematically shows the configuration of the light guide unit 20 of the displacement measuring device 1 according to the present embodiment. As shown in FIG. 2A, the light guide unit 20 includes an input side cable 21 optically connected to the light projecting unit 10 and an output side cable 22 optically connected to the light receiving unit 40. A head-side cable 24 that is optically connected to the sensor head 30 may be included. Each end of the input side cable 21 and the output side cable 22 and the end of the head side cable 24 are optically coupled via a coupler 23 having a combine / demultiplexing structure. The coupler 23 is a 2 × 1 star coupler (2 inputs, 1 output / 1 input, 2 outputs) corresponding to a Y-branch coupler, and transmits the light incident from the input side cable 21 to the head side cable 24 and also transmits the head side cable. The light incident from the 24 is divided and transmitted to the input side cable 21 and the output side cable 22, respectively.

The input side cable 21, the output side cable 22, and the head side cable 24 may all be optical fibers having a single core 202. The optical fiber has a core 202, a clad 204, a coating 206, and an exterior 208. As shown in FIG. 2B, an optical fiber having a plurality of cores may be adopted for the light guide unit 20. Each of the couplers 231 and 232 transmits the light incident from the input side cable 21 to the head side cable 24, and divides the light incident from the head side cable 24 and transmits the light incident from the head side cable 24 to the input side cable 21 and the output side cable 22, respectively. To do.

<B. Device configuration>
FIG. 3 is a schematic view showing an example of the configuration of the displacement measuring device 1 according to the present embodiment. With reference to FIG. 3, the light projecting unit 10 generates irradiation light having a plurality of wavelength components. Typically, the light projecting unit 10 includes a white LED (Light Emitting Diode). Any light source may be used for the light projecting unit 10 as long as the displacement width of the focal position caused by the axial chromatic aberration can generate irradiation light having a wavelength range sufficient to cover the required measurement range.

The light receiving unit 40 includes a spectroscope 42 that separates the reflected light received by the sensor head 30 into each wavelength component, and a detector 44 that includes a plurality of light receiving elements arranged so as to correspond to the spectral directions of the spectroscope 42. Including. A diffraction grating is typically used as the spectroscope 42, but any other device may be used. The detector 44 may use a line sensor (one-dimensional sensor) in which a plurality of light receiving elements are one-dimensionally arranged corresponding to the spectral direction of the spectroscope 42, or a plurality of light receiving elements are two-dimensionally arranged on the detection surface. An arranged image sensor (two-dimensional sensor) may be used.

In addition to the spectroscope 42 and the detector 44, the light receiving unit 40 outputs the collimating lens 41 that parallelizes the reflected light emitted from the output side cable 22 and the detection result of the detector 44 to the control unit 50. The reading circuit 45 of the above may be included. If necessary, the light receiving unit 40 may be provided with a reduction optical system 43 for adjusting the spot diameter of the reflected light for each wavelength separated by the spectroscope 42.

The control unit 50 calculates the distance from the sensor head 30 to the measurement object 2 based on the respective detection values of the plurality of light receiving elements of the light receiving unit 40. The relational expression between the pixel, the wavelength, and the distance value is preset (for example, it is stored non-volatilely inside the control unit 50 at the time of product shipment). Therefore, the control unit 50 can calculate the displacement from the light receiving waveform (pixel information) output by the light receiving unit 40.

FIG. 3 shows an example in which a plurality of cables are connected in series to form a head-side cable in order to improve usability. That is, as the head side cable, three cables 241,243,245 are adopted. The cable 241 and the cable 243 are optically connected via the connector 242, and the cable 243 and the cable 245 are optically connected via the connector 244. Of course, the coupler 23 and the sensor head 30 may be optically connected via one cable.

The light guide unit 20 includes a combine / demultiplexing unit (coupler) 23 for optically coupling the input side cable 21, the output side cable 22, and the head side cable. Since the functions of the combine / demultiplexing unit 23 have been described with reference to FIG. 2, detailed description will not be repeated. In the displacement measuring device 1 according to the present embodiment, a coupler is adopted as a combine / demultiplexing structure. As a result, the light can be separated in the light guide unit 20, and the reflected light (measurement light) from the measurement object 2 propagating through the plurality of cores can be received by a single detector 44.

In the embodiment of the present invention, the displacement measuring device 1 has two control modes. The first mode is a mode for measuring the distance between the sensor head 30 and the reflection position. The second mode is a mode for confirming whether or not the distance between the sensor head 30 and the reflection position is in the center of the predetermined distance range. Hereinafter, the first mode is referred to as a "normal measurement mode", and the second mode is referred to as a "specified distance range center confirmation mode".

<C. Operation mode>
FIG. 4 is a diagram for explaining a light projection state of the sensor head 30 in the normal measurement mode (first mode). With reference to FIG. 4, the position 3 is a position where light of a certain wavelength, which is included in the irradiation light emitted from the sensor head 30, is focused, and corresponds to, for example, a position where the work should be placed.

The distance d is the relative distance between the sensor head 30 and the position 3. In the following description, it is assumed that the position 3 is fixed and the distance d is changed by moving the sensor head 30 along the optical axis direction of the sensor head 30. Of course, the position of the sensor head 30 may be fixed, and the distance d may be changed by moving the position 3 along the optical axis direction of the sensor head 30. In FIG. 4, D2 defines a defined distance range, and D1 defines the central portion of the defined distance range D2. The central portion D1 is a range defined as a predetermined distance near the center of the defined distance range D2.

In the normal measurement mode, the sensor head 30 constantly emits light regardless of whether or not the distance d is within the central portion D1 of the specified distance range D2. That is, light is continuously emitted from the sensor head 30.

FIG. 5 is a diagram for explaining a light projection state of the sensor head 30 in the specified distance range center confirmation mode (second mode). With reference to FIG. 5, when the distance d is within the central portion D1 of the specified distance range D2, light is constantly projected from the sensor head 30. That is, normal light projection is performed. On the other hand, when the distance d is outside the central portion D1 of the specified distance range D2 and within the specified distance range D2, blinking light is projected from the sensor head 30 (blinking light projection). That is, in the specified distance range center confirmation mode, whether the distance d is within the central portion D1 of the specified distance range D2, or whether the distance d is outside the central portion D1 of the specified distance range D2 and within the specified distance range D2. The mode of light projection differs depending on the situation.

FIG. 6 is a signal waveform diagram for explaining the control of the light projecting unit in the normal measurement mode (first mode). With reference to FIGS. 1 and 6, in the normal measurement mode, the control unit 50 continuously lights the light projecting unit 10. In the normal measurement mode, the light projecting unit 10 is always in the ON state.

FIG. 7 is a signal waveform diagram for explaining the control of the light projecting unit in the defined distance range center confirmation mode (second mode). With reference to FIGS. 1 and 7, when the distance d is within the central portion D1 of the specified distance range D2, the control unit 50 continuously lights the floodlight unit 10 as in the normal measurement mode. .. On the other hand, when the distance d is outside the central portion D1 of the specified distance range D2 and within the specified distance range D2, the control unit 50 blinks the light projecting unit 10. For this purpose, the control unit 50 repeatedly turns on and off the control signal for lighting the light projecting unit 10.

In both the normal measurement mode and the specified distance range center confirmation mode, the control unit 50 keeps the projection power of the projection unit 10 (output of the projection unit 10) substantially constant in the normal projection. .. On the other hand, when the control unit 50 blinks the light projecting unit 10 in the specified distance range center confirmation mode, the peak value of the output of the light projecting unit 10 is set to be higher than the output of the light projecting unit 10 in the case of constant light projection. The light projecting unit 10 is controlled so as to be high. That is, at the time of blinking light projection, the control unit 50 raises the on level of the control signal as compared with the time of normal light projection. As a result, the amount of light received on the controller 100 side can be increased when the light emitting unit 10 is blinking, so that the light receiving waveform can be easily acquired by the light receiving unit 40. Therefore, even when the distance d is outside the central portion D1 of the specified distance range D2 and within the specified distance range D2, the distance d can be measured.

The pulse interval of the projection is determined so that the user can recognize the blinking state and the displacement measuring device 1 can measure the displacement. In one example, both the pulse duration and the pulse interval are 50 ms or longer.

<D. Control flow>
FIG. 8 is a flowchart for explaining the control of the light projection by the control unit 50 of the controller 100. With reference to FIG. 8, in step S1, the control unit 50 selects the normal measurement mode (first mode). In step S2, the control unit 50 controls the light projecting unit 10 so that normal light projecting (constant light projecting) is executed (see FIG. 6).

In step S3, the control unit 50 determines whether to switch the mode to be executed from the normal measurement mode to the specified distance range center confirmation mode (second mode). When the control unit 50 determines that the mode to be executed remains the normal measurement mode (NO in step S3), the process is returned to step S2. On the other hand, for example, when a user's instruction is input to the control unit 50, the control unit 50 determines that the mode to be executed should be switched to the specified distance range center confirmation mode. In this case (YES in step S3), the process proceeds to step S4.

In step S4, the control unit 50 selects the specified distance range center confirmation mode. In step S5, the control unit 50 determines whether or not the distance d between the sensor head 30 and the position 3 is within the central portion D1 of the defined distance range D2. The specified distance range D2 and its central portion D1 can be determined for each type of sensor head 30. The controller 100 may store the specified distance range D2 defined for each type of the sensor head 30 and the central portion D1 thereof. The information in the form of the sensor head 30 connected to the controller 100 may be read, for example, from the recording medium in which the controller 100 has the sensor head information corresponding to the sensor head 30 written on a one-to-one basis.

When the distance d is within the central portion D1 of the specified distance range D2 (YES in step S5), the process proceeds to step S6. In this case, the control unit 50 controls the light projecting unit 10 so that normal light projecting (constant light projecting) is executed. The control unit 50 always turns on the control signal for lighting the light projecting unit 10 (see FIG. 7).

When the distance d is outside the central portion D1 of the specified distance range D2 and within the specified distance range D2 (NO in step S5), the process proceeds to step S7. In this case, the control unit 50 controls the light projecting unit 10 so that the blinking light projecting is executed. The control unit 50 repeatedly turns on and off the control signal for lighting the floodlight unit 10 (see FIG. 7).

In step S8, the control unit 50 determines whether to switch the mode to be executed from the predetermined distance range center confirmation mode to the normal measurement mode. Control unit 50, when the mode to be executed is determined to remain prescribed distance range centered check mode (NO in step S 8), the process returns to step S5. On the other hand, for example, when a user's instruction is input to the control unit 50, the control unit 50 determines that the mode to be executed should be switched to the normal measurement mode. In this case (YES in step S8), the process returns to step S1.

<E. Another embodiment>
FIG. 9 is a diagram for explaining another embodiment of the light projection state of the sensor head 30 in the specified distance range center confirmation mode (second mode). With reference to FIG. 9, a predetermined distance range D3 is set outside the central portion D1 of the specified distance range D2 and within the specified distance range D2. When the distance d is outside the central portion D1 of the specified distance range D2 and within the predetermined distance range D3, the light projected from the sensor head 30 blinks relatively quickly. On the other hand, when the distance d is outside the predetermined distance range D3 within the specified distance range D2 and within the specified distance range D2, the light projected from the sensor head 30 blinks relatively slowly. In this way, when the distance d is outside the central portion D1 of the specified distance range D2 and within the specified distance range D2, the control unit 50 sets the light projecting unit 10 so that the blinking interval differs according to the distance d. You may control it.

Furthermore, the blinking interval is not limited to be different in stages. With reference to FIG. 5 again, the control unit 50 increases the interval between blinking lights as the difference between the distance d and the upper limit or the lower limit of the central portion D1 of the specified distance range D2 increases. May be controlled.

<F. Advantages>
Consider an example in which the controller 100 side displays whether or not the distance d is within the central portion D1 of the specified distance range D2. For example, by turning on the indicator light of the controller 100, it is possible to indicate to the user that the distance d is within the specified distance range. Alternatively, by displaying the measured displacement value on the display unit 60 of the controller 100, the user can confirm whether or not the distance d is within the central portion D1 of the specified distance range D2.

However, it is conceivable that the sensor head 30 is installed at a position away from the controller 100. In such a case, the user is near the installation location of the sensor head 30. Therefore, it may be difficult for the user to confirm the display of the controller 100 depending on the distance from the controller 100 to the user or the position of the user with respect to the controller 100.

In this embodiment, the displacement measuring device 1 indicates that the distance d from the sensor head 30 to the position 3 (reflection position) is within the central portion D1 of the specified distance range D2, and the light is projected from the sensor head 30. Shown by state. Therefore, when the user installs the sensor head 30, the user can easily recognize the central portion of the specified distance range of the sensor head 30. The user does not have to check the display of the controller 100. Since the user can install the sensor head at an appropriate position, it is possible to easily construct an environment capable of accurate and stable measurement.

The embodiments disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Displacement measuring device, 2 Measurement target, 3 Position (reflection position), 10 Floodlight, 20 Light guide, 21 Input side cable, 22 Output side cable, 23 Coupler, 24 Head side cable, 30 Sensor head, 32 Chromatic aberration unit, 34 objective lens, 40 light receiving unit, 41 collimating lens, 42 spectroscope, 43 reduction optical system, 44 detector, 45 read circuit, 50 control unit, 60 display unit, 100 controller, 202 core, 204 clad, 206 Coating, 208 exterior, 241,243,245 cable, 242,244 connector, AX optical axis, D1 central part of specified distance range, D2 specified distance range, D3 specified distance range within D3 specified distance range, S1 to S8 steps, d Distance.

Claims (7)

Displacement measuring device
A sensor head that has an optical system and no electronic circuit,
A light projecting unit that generates irradiation light, a light receiving unit that receives reflected light of the irradiation light received by the sensor head, and a reflection position of the sensor head and the reflected light based on the amount of light received by the light receiving unit. A controller that includes a control unit that calculates the distance between
A first optical fiber that transmits the irradiation light from the light projecting unit to the sensor head, and
A second optical fiber that transmits the reflected light from the sensor head to the controller is provided.
The control unit has a first mode for measuring the distance between the sensor head and the reflection position, and whether the distance between the sensor head and the reflection position is in the center of a predetermined distance range. A displacement measuring device having a second mode in which the light is projected according to the light projected state of the light projecting unit. In the second mode, the control unit determines whether or not the distance between the sensor head and the reflection position is within the central portion of the predetermined distance range, and determines the determination result. The displacement measuring device according to claim 1, which is indicated by the light projection state of the light projection unit. In the second mode, when the distance from the sensor head to the reflection position is within the central portion of the specified distance range, the control unit continuously lights the light projecting unit.
In the second mode, when the distance from the sensor head to the reflection position is outside the central portion of the specified distance range and within the specified distance range, the control unit causes the light projecting unit. The displacement measuring device according to claim 2, which blinks. When the distance from the sensor head to the reflection position is in a range outside the central portion of the specified distance range, the distance from the sensor head to the reflection position is the central portion of the specified distance range. When it is outside and within a predetermined distance range within the specified distance range, the control unit blinks the light projecting unit at a first interval.
When the distance from the sensor head to the reflection position is outside the predetermined distance range and outside the specified distance range within the specified distance range, the control unit may display the light projecting unit. The displacement measuring device according to claim 3, wherein the displacement measuring device blinks at a second interval larger than the first interval. When the distance from the sensor head to the reflection position is outside the central portion of the specified distance range and within the specified distance range, the control unit uses the distance from the sensor head to the reflection position and the distance. The displacement measuring device according to claim 3, wherein the blinking interval of the light projecting unit is increased as the difference between the upper limit or the lower limit of the central portion of the specified distance range becomes larger. When the distance from the sensor head to the reflection position is within the central portion of the specified distance range, the control unit controls the light projection unit so that the light projection power of the light projection unit becomes a constant value. When the distance from the sensor head to the reflection position is outside the central portion of the specified distance range and within the specified distance range, the control unit determines that the peak value of the output of the light projecting unit is the sensor. Any of claims 3 to 5, which controls the light projecting unit so that the distance from the head to the reflection position is higher than the output of the light projecting unit when the distance from the head to the reflection position is within the central portion of the specified distance range. The displacement measuring device according to item 1. The displacement measuring device according to any one of claims 1 to 6, wherein the first optical fiber and the second optical fiber are the same.

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