Controller and optical interference distance measuring sensor

Abstract

The signal generated by the primary interferometer is sampled at an appropriate timing. A controller (110) is provided with: a light source (140); a main interferometer (150) that generates a main interference signal; a sub-interferometer (160) that generates a sub-interference signal; a variable delay amount generation unit that generates a variable delay amount; a correction signal generation unit (171) that generates a correction signal for correcting the sampling period of the main interference signal on the basis of the sub interference signal and the variable delay amount; a processing unit (118) that measures the distance to the measurement object (T) on the basis of the main interference signal and the correction signal; and a variable delay amount setting unit (195) that sets a variable delay amount on the basis of at least one of a peak value of a signal based on a digital signal of the main interference signal sampled on the basis of the correction signal and a peak value of a signal based on a digital signal of a reflected signal generated by the main interferometer (150) and sampled on the basis of the correction signal.

Description

Technical Field

[0001] The invention relates to a controller and an optical interference distance measuring sensor. Background Art

[0002] In recent years, optical distance measuring sensors that measure the distance to a measurement object in a non-contact manner have become popular. For example, as an optical distance measuring sensor, there is known an optical interference distance measuring sensor that generates interference light based on reference light and measurement light based on light projected from a wavelength scanning light source, and measures the distance to the measurement object based on the interference light.

[0003] Conventionally, as such an optical band reflection measurement device, the following optical band reflection measurement device is known, which includes: a scanning light source; an auxiliary interferometer that adds a predetermined delay time difference to a part of the output light of the scanning light source to interfere and output as an auxiliary interference signal; a measurement interferometer that inputs a part of the output light of the scanning light source to the measured optical fiber and causes the reflected light from the measured optical fiber to interfere with a part of the output light of the scanning light source and output as a measurement interference signal; a linearization unit that uses the auxiliary interference signal to correct the nonlinearity of wavelength scanning of the scanning light source for the measurement interference signal; and a Fourier transform unit that performs Fourier transform on the output signal of the linearization unit and outputs a signal of the band, the linearization unit having a plurality of linearization units each having a different delay time, and the Fourier transform unit having a weighted addition / Fourier transform unit that adds different weights to the output signals of the plurality of linearization units and outputs a Fourier transformed result (see Patent Document 1). In this optical band reflection measurement device, the nonlinearity of wavelength scanning is corrected over a wide range of the measured optical fiber.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-181115 Summary of the invention

[0007] Problems to be solved by the invention

[0008] On the other hand, in an optical interferometer ranging sensor including a controller and an optical fiber cable including an optical fiber connecting the controller to a sensor head, when the length of the optical fiber is changed, the optical path length of the light propagating from the main interferometer to the sensor head via the optical fiber and from the sensor head to the main interferometer also becomes longer, so sometimes a timing deviation occurs between the signal generated by the main interferometer and the signal generated by the sub-interferometer to correct the sampling period.

[0009] In addition, when the distance from the sensor head to the object to be measured is longer than the length of the optical fiber, the round-trip time of the light irradiated from the sensor head to the object to be measured, reflected by the object to be measured, and returned to the sensor head becomes longer. Therefore, in this case, there may be a timing deviation between the signal generated by the main interferometer and the signal generated by the sub-interferometer to correct the sampling period. As a result, the signal of the main interferometer cannot be accurately sampled, and an error may occur in the distance to the object to be measured.

[0010] The present invention has been made in view of such circumstances, and one of its objects is to provide a controller and an optical interferometric distance measuring sensor capable of sampling a signal generated by a main interferometer at an appropriate timing.

[0011] Means for solving problems

[0012] A controller of one embodiment of the present disclosure is connected to a sensor head that irradiates light to a measurement object via an optical fiber cable, wherein the controller includes: a light source that projects light while changing the wavelength of the light; a main interferometer that is connected to the sensor head via an optical fiber included in the optical fiber cable, is supplied with light projected from the light source, and generates a main interference signal based on measurement light and reference light, wherein the measurement light is irradiated to the measurement object by the sensor head and is reflected, and the reference light travels along an optical path that is at least partially different from that of the measurement light; and a sub-interferometer that is supplied with light projected from the light source, and generates a sub-interference signal based on two lights that travel along different optical paths. a main interference signal; a variable delay amount generating unit that generates a variable delay amount; a correction signal generating unit that generates a correction signal for correcting a sampling period of a main interference signal based on the secondary interference signal and the variable delay amount; a processing unit that measures a distance to a measurement object based on the main interference signal and the correction signal; and a variable delay amount setting unit that sets the variable delay amount based on at least one of the peak values ​​of the following two signals: a signal based on a digital signal of the main interference signal sampled based on the correction signal; and a signal based on a digital signal of a reflected signal generated by the main interferometer and sampled based on the correction signal.

[0013] According to this method, the variable delay amount is set according to at least one of the peak value of the signal of the digital signal based on the main interference signal sampled according to the correction signal and the peak value of the signal of the digital signal based on the reflected signal generated by the main interferometer and sampled according to the correction signal. Thus, it is possible to set a variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal. Here, by setting the variable delay amount according to the peak value of the signal of the digital signal based on the reflected signal sampled according to the correction signal, even in a state where there is no measurement object. In addition, by setting the variable delay amount according to the peak value of the signal of the digital signal based on the main interference signal sampled according to the correction signal, it is possible to set the variable delay amount that also reduces the timing deviation that may occur when the distance from the sensor head to the measurement object is longer than the length of the optical fiber due to the round-trip time of the light to travel the distance. Therefore, it is possible to sample the signal generated by the main interferometer at an appropriate timing based on the correction signal of the secondary interference signal and the variable delay amount, and it is possible to measure the distance to the measurement object with high accuracy.

[0014] In the above aspect, the variable delay amount setting unit may set the variable delay amount based on at least one of a peak intensity of a digital signal based on the main interference signal and a peak intensity of a digital signal based on the reflected signal.

[0015] According to this method, the variable delay amount is set based on at least one of the peak intensity of the digital signal based on the main interference signal and the peak intensity of the digital signal based on the reflected signal. Thus, the variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal can be easily set.

[0016] In the above aspect, the variable delay amount setting unit may set the variable delay amount based on at least one of a maximum value of peak intensities of digital signals based on the plurality of main interference signals and a maximum value of peak intensities of digital signals based on the plurality of reflected signals.

[0017] According to this aspect, the variable delay amount is set based on at least one of the maximum value of the peak intensities of the digital signal based on the plurality of main interference signals and the maximum value of the peak intensities of the digital signal based on the plurality of reflected signals. Thus, the variable delay amount is set based on the maximum value of the plurality of peak intensities, so that the variable delay amount that can further reduce the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal can be set compared to the case where the variable delay amount is set based on the peak intensity of the digital signal based on one main interference signal or the peak intensity of the digital signal based on one reflected signal.

[0018] In the above aspect, the variable delay amount setting unit may set the variable delay amount based on at least one of a predetermined peak value width of a digital signal based on the main interference signal and a predetermined peak value width of a digital signal based on the reflection signal.

[0019] According to this method, the variable delay amount is set based on at least one of the peak value width of the digital signal based on the main interference signal and the peak value width of the digital signal based on the reflected signal. Thus, the variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal can be easily set.

[0020] In the above aspect, the variable delay amount setting unit may set the variable delay amount based on at least one of the minimum value of the peak specified value width of the digital signal based on the plurality of main interference signals and the minimum value of the peak specified value width of the digital signal based on the plurality of reflected signals.

[0021] According to this aspect, the variable delay amount is set based on at least one of the minimum half-peak width of the digital signal based on the plurality of main interference signals and the minimum half-peak width of the digital signal based on the plurality of reflected signals. Thus, the variable delay amount is set based on the minimum value of the plurality of peak prescribed value widths, so that the variable delay amount that can further reduce the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal can be set compared to the case where the variable delay amount is set based on the peak prescribed value width of the digital signal based on one main interference signal or the peak prescribed value width of the digital signal based on one reflected signal.

[0022] In the above-mentioned method, the variable delay amount setting unit may set the variable delay amount in such a manner that at least one of the number of measurement points included in the peak specified value width of the digital signal based on the main interference signal and the number of measurement points included in the peak specified value width of the digital signal based on the reflected signal is less than a specified number.

[0023] According to this method, the variable delay amount is set so that at least one of the number of measurement points included in the peak value width of the digital signal based on the main interference signal and the number of measurement points included in the peak value width of the digital signal based on the reflected signal is less than a predetermined number. Thus, the variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal can be easily set.

[0024] In the above aspect, the reflection signal may be generated by a part of the light projected from the light source and supplied to the main interferometer being reflected by a member having a reflection surface formed in the main interferometer.

[0025] According to this method, a reflection signal is generated by reflecting a portion of light projected from a light source and supplied to a main interferometer by a member having a reflection surface formed in the main interferometer. Thus, even when there is no object to be measured and the main interference signal cannot be obtained, a reflection signal can be obtained from the reflection surface of the main interferometer, so that the variable delay amount can be set without preparing an object to be measured.

[0026] In the above aspect, the variable delay amount generator may include a variable delay line that generates a delay corresponding to a variable delay amount in a sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal in a time axis direction and outputs the delay to the correction signal generator.

[0027] According to this embodiment, the variable delay amount generating unit includes a variable delay line, which generates a delay corresponding to the variable delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and outputs the delay to the correction signal generating unit. Thus, by outputting the sub-interferometer signal that has been electrically delayed, the correction signal generating unit can easily generate the correction signal as an electrical signal.

[0028] In the above aspect, the correction signal generating unit may generate a pulse signal as the correction signal based on a signal delayed in the time axis direction by a variable delay amount in a sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal.

[0029] According to this method, a pulse signal is generated as a correction signal based on a signal that is delayed in the time axis direction by a variable delay amount in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. This makes it easy to make the timing of sampling the main interference signal consistent (achieve synchronization).

[0030] In the above aspect, an AD converter may be further provided for sampling a main interferometer signal obtained by converting a main interference signal into an electrical signal based on a correction signal and converting the main interferometer signal into a digital signal.

[0031] According to this embodiment, an AD converter is further provided, which samples the main interferometer signal obtained by converting the main interference signal into an electrical signal based on the correction signal and converts it into a digital signal. This makes it easy to realize a structure that converts the main interferometer signal into a digital signal with a corrected sampling period.

[0032] An optical interference ranging sensor according to an embodiment of the present disclosure includes a controller and an optical fiber cable connected to the controller, wherein the controller includes: a light source that projects light while changing the wavelength of the light; a main interferometer that is connected to a sensor head via an optical fiber included in the optical fiber cable, is supplied with light projected from the light source, and generates a main interference signal based on measurement light and reference light, wherein the measurement light is irradiated onto a measurement object through the sensor head and is reflected, and the reference light travels along an optical path that is at least partially different from that of the measurement light; and a sub-interferometer that is supplied with light projected from the light source, and generates a sub-interference signal based on two lights that travel along different optical paths. interference signal; a variable delay amount generating unit, which generates a variable delay amount; a correction signal generating unit, which generates a correction signal for correcting the sampling period of the main interference signal based on the secondary interference signal and the variable delay amount; a processing unit, which measures the distance to the measurement object based on the main interference signal and the correction signal; and a variable delay amount setting unit, which sets the variable delay amount based on at least one of the peak values ​​of the following two signals: a signal based on the digital signal of the main interference signal sampled according to the correction signal; and a signal based on the digital signal of the reflected signal generated by the main interferometer and sampled according to the correction signal.

[0033] According to this method, the variable delay amount is set according to at least one of the peak value of the signal of the digital signal based on the main interference signal sampled according to the correction signal and the peak value of the signal of the digital signal based on the reflected signal generated by the main interferometer and sampled according to the correction signal. Thus, it is possible to set a variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal. Here, by setting the variable delay amount according to the peak value of the signal of the digital signal based on the reflected signal sampled according to the correction signal, even in a state where there is no measurement object. In addition, by setting the variable delay amount according to the peak value of the signal of the digital signal based on the main interference signal sampled according to the correction signal, it is possible to set the variable delay amount that also reduces the timing deviation that may occur when the distance from the sensor head to the measurement object is longer than the length of the optical fiber due to the round-trip time of the light to travel the distance. Therefore, it is possible to sample the signal generated by the main interferometer at an appropriate timing based on the correction signal of the secondary interference signal and the variable delay amount, and it is possible to measure the distance to the measurement object with high accuracy.

[0034] Effects of the Invention

[0035] According to the present invention, the signal generated by the main interferometer can be sampled at appropriate timing. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 1 is a schematic external view showing an outline of the displacement sensor 10 of the present disclosure.

[0037] Figure 21 is a flowchart showing a process of measuring the measurement object T by the displacement sensor 10 of the present disclosure.

[0038] Figure 3 1 is a functional block diagram showing an overview of a sensor system 1 using the displacement sensor 10 of the present disclosure.

[0039] Figure 4 1 is a flowchart showing a process of measuring the measurement object T by the sensor system 1 using the displacement sensor 10 of the present disclosure.

[0040] Figure 5A This is a diagram for explaining the principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure.

[0041] Figure 5B This is a diagram for explaining another principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure.

[0042] Fig. 6A It is a perspective view showing a schematic structure of the sensor head 20 .

[0043] Figure 6B 2 is a schematic diagram showing the internal structure of the sensor head 20 .

[0044] Figure 7 It is a block diagram for explaining signal processing in the controller 30 .

[0045] Figure 8 1 is a flowchart showing a method of calculating the distance to the measurement object T executed by the processing unit 59 in the controller 30 .

[0046] Fig. 9A This is a diagram showing how a waveform signal (voltage vs. time) is frequency-converted into a spectrum (voltage vs. frequency).

[0047] Fig. 9B This is a diagram showing how a frequency spectrum (voltage vs. frequency) is transformed into a frequency spectrum (voltage vs. distance) by distance.

[0048] Fig. 9C This is a diagram showing a state where a peak is detected based on a frequency spectrum (voltage vs. distance) and a distance value corresponding thereto is calculated.

[0049] Fig.10 1 is a schematic diagram showing an outline of the structure of an optical interference distance measuring sensor 100 according to an embodiment of the present invention.

[0050] Fig.11 1 is a schematic diagram showing a specific example of a structure for generating a reflected wave in the main interferometer 150 .

[0051] Fig.12This is a diagram for explaining the relationship between the peak value of the digital signal based on the main interference signal and the peak value of the digital signal based on the reflected signal and the variable delay amount.

[0052] Fig.13 This is a diagram for explaining the relationship between the half-peak width of the digital signal based on the main interference signal and the half-peak width of the digital signal based on the reflection signal, and the conditions of FFT.

[0053] Fig.14 This is a flowchart for explaining an example of a processing procedure performed by the controller 110 in one embodiment.

[0054] Fig.15 This is a flowchart for explaining another example of the processing procedure performed by the controller 110 in one embodiment.

[0055] Fig.16 This is a flowchart for explaining another example of the processing procedure performed by the controller 110 in one embodiment.

[0056] Fig.17 FIG. 1 is a schematic diagram showing an outline of the structure of another optical interference distance measuring sensor 101 according to an embodiment of the present invention.

[0057] Fig.18 A diagram showing a variation of an interferometer that generates interference light using measurement light and reference light. DETAILED DESCRIPTION

[0058] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, each embodiment described below is only a specific example for implementing the present invention, and does not limit the present invention. In addition, in order to facilitate the understanding of the description, the same reference numerals are marked as much as possible for the same components in each drawing, and repeated descriptions are sometimes omitted.

[0059] [Overview of Displacement Sensor]

[0060] First, the outline of the displacement sensor of the present disclosure will be described.

[0061] Figure 1 FIG. 1 is a schematic diagram showing the appearance of the displacement sensor 10 of the present disclosure. Figure 1 As shown, the displacement sensor 10 includes a sensor head 20 and a controller 30 , and measures the displacement of the measurement object T (the distance to the measurement object T).

[0062] The sensor head 20 and the controller 30 are connected via an optical fiber 40, and an objective lens 21 is mounted on the sensor head 20. The controller 30 includes a display unit 31, a setting unit 32, an external interface (I / F) unit 33, an optical fiber connection unit 34, and an external storage unit 35, and has a measurement processing unit 36 ​​inside.

[0063] The sensor head 20 irradiates the light output from the controller 30 to the measurement object T, and receives the reflected light from the measurement object T. The sensor head 20 has a reference surface inside, and the reference surface is used to reflect the light output from the controller 30 and received via the optical fiber 40 so as to interfere with the reflected light from the measurement object T.

[0064] The sensor head 20 is provided with an objective lens 21 which is detachable. The objective lens 21 may be replaced with an objective lens having an appropriate focal length according to the distance between the sensor head 20 and the measurement object T, or a variable-focus objective lens may be used.

[0065] Furthermore, when installing the sensor head 20 , the object T may be irradiated with guide light (visible light) to install the sensor head 20 and / or the object T so that the object T is appropriately located within the measurement area of ​​the displacement sensor 10 .

[0066] The optical fiber 40 is connected to the optical fiber connection portion 34 disposed in the controller 30 and extends to connect the controller 30 to the sensor head 20. Thus, the optical fiber 40 is configured to guide the light projected from the controller 30 to the sensor head 20, and guide the return light from the sensor head 20 to the controller 30. In addition, the optical fiber 40 can be detachable from the sensor head 20 and the controller 30 and can have various lengths, thicknesses, characteristics, etc.

[0067] The display unit 31 is composed of, for example, a liquid crystal display or an organic EL display, etc. The display unit 31 displays the set value of the displacement sensor 10, the amount of light received by the return light from the sensor head 20, and the displacement of the measurement object T measured by the displacement sensor 10 (the distance to the measurement object T).

[0068] The setting unit 32 performs settings required for measuring the measurement object T by, for example, operating a mechanical button or a touch panel by a user. All or part of these required settings may be preset, or may be set from an external connection device (not shown) connected to the external I / F unit 33. In addition, the external connection device may be connected via a network in a wired or wireless manner.

[0069] Here, the external I / F unit 33 is composed of, for example, Ethernet (registered trademark), RS232C, and analog output, etc. The external I / F unit 33 may be connected to other connected devices to perform required settings from the external connected devices, or output measurement results measured by the displacement sensor 10 to the external connected devices.

[0070] The controller 30 may also fetch data stored in the external storage unit 35 to perform settings required for measuring the measurement object T. The external storage unit 35 is an auxiliary storage device such as a USB (Universal Serial Bus) memory, and stores settings required for measuring the measurement object T in advance.

[0071] The measurement processing unit 36 ​​in the controller 30 includes, for example, a wavelength scanning light source that projects light while continuously changing the wavelength, a light receiving element that receives the return light from the sensor head 20 and converts it into an electric signal, and a signal processing circuit that processes the electric signal. In the measurement processing unit 36, various processes are performed using a control unit and a storage unit, so that the displacement of the measurement object T (the distance to the measurement object T) is finally calculated based on the return light from the sensor head 20. The details of these processes will be described later.

[0072] Figure 2 FIG. 1 is a flowchart showing a process of measuring the measurement object T by the displacement sensor 10 of the present disclosure. Figure 2 As shown, the process includes steps S11 to S14.

[0073] In step S11, the sensor head 20 is set. For example, guide light is irradiated from the sensor head 20 toward the measurement target T, and the sensor head 20 is set at an appropriate position with reference thereto.

[0074] Specifically, the amount of light received by the return light from the sensor head 20 may be displayed on the display unit 31 in the controller 30, and the user may check the amount of light received while adjusting the orientation of the sensor head 20 and the distance (height position) from the measurement object T. Basically, if the light from the sensor head 20 can be irradiated perpendicularly (at an angle closer to perpendicular) to the measurement object T, the amount of light reflected from the measurement object T increases, and the amount of light received by the return light from the sensor head 20 also increases.

[0075] In addition, the objective lens 21 may be replaced with one having an appropriate focal length according to the distance between the sensor head 20 and the measurement target object T.

[0076] Furthermore, in the event that appropriate settings cannot be made when measuring the measurement object T (for example, the amount of light received required for measurement cannot be obtained, or the focal length of the objective lens 21 is inappropriate, etc.), an error or incomplete setting may be displayed on the display unit 31, or output to an externally connected device, to notify the user.

[0077] In step S12 , various measurement conditions are set when measuring the measurement object T. For example, the user operates the setting unit 32 in the controller 30 to set the calibration data (linear calibration function, etc.) inherent to the sensor head 20 .

[0078] In addition, various parameters may be set. For example, the sampling time, the measurement range, and the threshold value for determining whether the measurement result is normal or abnormal may be set. Furthermore, the measurement cycle may be set according to the characteristics of the measurement object T, such as the reflectivity and material of the measurement object T, and the measurement mode may be set according to the material of the measurement object T.

[0079] The measurement conditions and various parameters are set by operating the setting unit 32 in the controller 30 , but may be set from an externally connected device or by loading data from the external storage unit 35 .

[0080] In step S13 , the sensor head 20 installed in step S11 measures the measurement object T according to the measurement conditions and various parameters set in step S12 .

[0081] Specifically, in the measurement processing unit 36 ​​of the controller 30, light is projected from the wavelength scanning light source, and the return light from the sensor head 20 is received by the light receiving element, and the signal processing circuit performs frequency analysis, distance conversion, peak detection, etc., to calculate the displacement of the measurement object T (the distance to the measurement object T). The details of the specific measurement processing will be described later.

[0082] In step S14, the measurement result measured in step S13 is output. For example, the displacement of the measurement object T (the distance to the measurement object T) measured in step S13 is displayed on the display unit 31 in the controller 30 or output to an externally connected device.

[0083] In addition, whether the displacement of the measurement object T (the distance to the measurement object T) measured in step S13 is within a normal range or abnormal may also be displayed or output as a measurement result based on the threshold value set in step S12. Furthermore, the measurement conditions, various parameters, and measurement modes set in step S12 may also be displayed or output together.

[0084] [Overview of the system including the displacement sensor]

[0085] Figure 3 1 is a functional block diagram showing an overview of a sensor system 1 using the displacement sensor 10 of the present disclosure. Figure 3 As shown, the sensor system 1 includes a displacement sensor 10, a control device 11, a control signal input sensor 12, and an external connection device 13. In addition, the displacement sensor 10 is connected to the control device 11 and the external connection device 13, for example, through a communication cable or an external connection line (for example, including an external input line, an external output line, and a power line, etc.), and the control device 11 is connected to the control signal input sensor 12 through a signal line.

[0086] The displacement sensor 10 is used as Figure 1 and Figure 2 As described above, the displacement of the measurement object T (the distance to the measurement object T) is measured. Then, the displacement sensor 10 may output the measurement result and the like to the control device 11 and the external connection device 13 .

[0087] The control device 11 is, for example, a PLC (Programmable Logic Controller), and provides various instructions to the displacement sensor 10 when the displacement sensor 10 measures the object T to be measured.

[0088] For example, the control device 11 can output a measurement timing signal to the displacement sensor 10 based on an input signal from a control signal input sensor 12 connected to the control device 11, or can output a zero reset command signal (a signal for setting the current measured value to 0) to the displacement sensor 10.

[0089] The control signal input sensor 12 outputs an on / off signal to the control device 11, indicating the timing of the displacement sensor 10 measuring the measurement object T. For example, the control signal input sensor 12 is set near the production line where the measurement object T moves, detects that the measurement object T moves to a predetermined position, and outputs an on / off signal to the control device 11.

[0090] The external connection device 13 is, for example, a PC (Personal Computer), and can perform various settings on the displacement sensor 10 through user operations.

[0091] As a specific example, a measurement mode, an operation mode, a measurement cycle, and a material of the measurement object T are set.

[0092] As the setting of the measurement mode, an “internal synchronous measurement mode” in which measurement is periodically started inside the control device 11 , an “external synchronous measurement mode” in which measurement is started based on an input signal from outside the control device 11 , or the like is selected.

[0093] As the setting of the operation mode, an “operation mode” for actually measuring the measurement object T, an “adjustment mode” for setting measurement conditions for measuring the measurement object T, or the like is selected.

[0094] The measurement period is a period for measuring the object T, and can be set according to the reflectivity of the object T. Even when the reflectivity of the object T is low, the object T can be properly measured by extending the measurement period and setting the measurement period appropriately.

[0095] Regarding the measurement object T, the "rough surface mode" suitable for the case where diffuse reflection is more common as a component of reflected light, the "mirror mode" suitable for the case where specular reflection is more common as a component of reflected light, or the "standard mode" in between them is selected.

[0096] In this way, by making appropriate settings according to the reflectivity and material of the measurement object T, the measurement object T can be measured with higher accuracy.

[0097] Figure 4 1 is a flowchart showing a process of measuring the measurement object T by the sensor system 1 using the displacement sensor 10 of the present disclosure. Figure 4 As shown, this process is the process in the above-mentioned external synchronization measurement mode, and includes steps S21 to S24.

[0098] In step S21, the sensor system 1 detects the measurement object T as the object to be measured. Specifically, the control signal input sensor 12 detects that the measurement object T has moved to a predetermined position on the production line.

[0099] In step S22, the sensor system 1 issues a measurement instruction so that the displacement sensor 10 measures the measurement object T detected in step S21. Specifically, the control signal input sensor 12 outputs an on / off signal to the control device 11 to instruct the timing of measuring the measurement object T detected in step S21, and the control device 11 outputs a measurement timing signal to the displacement sensor 10 based on the on / off signal to issue a measurement instruction so that the measurement object T is measured.

[0100] In step S23, the displacement sensor 10 measures the measurement object T. Specifically, the displacement sensor 10 measures the measurement object T based on the measurement instruction received in step S22.

[0101] In step S24 , the sensor system 1 outputs the measurement result measured in step S23 . Specifically, the displacement sensor 10 displays the measurement result on the display unit 31 , or outputs it to the control device 11 or the external connection device 13 via the external I / F unit 33 .

[0102] In addition, here, use Figure 4 The process in the case of the external synchronous measurement mode in which the object T is detected by the control signal input sensor 12 to measure the object T is described, but the present invention is not limited to this. For example, in the case of the internal synchronous measurement mode, instead of steps S21 and S22, the displacement sensor 10 is instructed to measure the object T by generating a measurement timing signal based on a preset cycle.

[0103] Next, the principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure will be described.

[0104] Figure 5A 1 is a diagram for explaining the principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure. Figure 5A As shown, the displacement sensor 10 includes a sensor head 20 and a controller 30. The sensor head 20 includes an objective lens 21 and a plurality of collimating lenses 22a to 22c, and the controller 30 includes a wavelength scanning light source 51, an optical amplifier 52, a plurality of isolators 53 and 53a to 53b, a plurality of optical couplers 54 and 54a to 54e, an attenuator 55, a plurality of light receiving elements (e.g., photodetectors (PD)) 56a to 56c, a plurality of amplifier circuits 57a to 57c, a plurality of analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a to 58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generating unit 61.

[0105] The wavelength scanning light source 51 projects the laser light obtained by scanning the wavelength. As the wavelength scanning light source 51, for example, if a method of modulating VCSEL (Vertical Cavity Surface Emitting Laser) by using current is applied, it is difficult to cause mode hopping due to the short resonator length, and the wavelength can be easily changed, which can be realized at low cost.

[0106] The optical amplifier 52 amplifies the light projected from the wavelength scanning light source 51. The optical amplifier 52 may be, for example, an EDFA (erbium-doped fiber amplifier), and may be, for example, an optical amplifier dedicated to 1550 nm.

[0107] The isolator 53 is an optical element that transmits incident light in one direction, and may be disposed immediately after the wavelength scanning light source 51 in order to prevent the influence of noise generated by return light.

[0108] Thus, the light projected from the wavelength scanning light source 51 is amplified by the optical amplifier 52, and is branched to the main interferometer and the sub-interferometer by the optical coupler 54 via the isolator 53. For example, in the optical coupler 54, the ratio of the light branched to the main interferometer and the sub-interferometer may be more than 90% branched on the main interferometer side.

[0109] The light branched to the main interferometer is further branched into the direction of the sensor head 20 and the direction of the second optical coupler 54 b by the first optical coupler 54 a .

[0110] The light branched toward the sensor head 20 by the first-stage optical coupler 54a passes through the collimating lens 22a and the objective lens 21 from the end of the optical fiber in the sensor head 20 and is irradiated to the measurement object T. Then, the end (end face) of the optical fiber becomes a reference surface, and the light reflected on the reference surface interferes with the light reflected on the measurement object T to generate interference light, which returns to the first-stage optical coupler 54a, and is then received by the light receiving element 56a and converted into an electrical signal.

[0111] The light branched from the first-stage optical coupler 54a to the second-stage optical coupler 54b goes to the second-stage optical coupler 54b via the isolator 53a, and is further branched from the second-stage optical coupler 54b to the direction of the sensor head 20 and the direction of the third-stage optical coupler 54c. The light branched from the optical coupler 54b to the sensor head 20 is irradiated to the measurement object T from the end of the optical fiber through the collimating lens 22b and the objective lens 21 in the sensor head 20 as in the first stage. Then, the end (end face) of the optical fiber becomes a reference surface, and the light reflected from the reference surface interferes with the light reflected from the measurement object T to generate interference light, which returns to the second-stage optical coupler 54b and is branched to the directions of the isolator 53a and the light receiving element 56b respectively through the optical coupler 54b. The light branched from the optical coupler 54b to the direction of the light receiving element 56b is received by the light receiving element 56b and converted into an electrical signal. On the other hand, the isolator 53a allows light to pass from the preceding optical coupler 54a to the succeeding optical coupler 54b and blocks light from the succeeding optical coupler 54b to the preceding optical coupler 54a, so that light branched from the optical coupler 54b toward the isolator 53a is blocked.

[0112] The light branched from the second-stage optical coupler 54b to the third-stage optical coupler 54c goes to the third-stage optical coupler 54c via the isolator 53b, and is further branched from the third-stage optical coupler 54c to the sensor head 20 and the attenuator 55. The light branched from the optical coupler 54c to the sensor head 20 is irradiated to the measurement target T from the end of the optical fiber in the sensor head 20 through the collimating lens 22c and the objective lens 21, similarly to the first and second stages. Then, the end (end face) of the optical fiber serves as a reference surface, and the light reflected from the reference surface interferes with the light reflected from the measurement target T to generate interference light, which returns to the third-stage optical coupler 54c and is branched to the isolator 53b and the light receiving element 56c by the optical coupler 54c. The light branched from the optical coupler 54c to the light receiving element 56c is received by the light receiving element 56c and converted into an electrical signal. On the other hand, the isolator 53b transmits light from the preceding optical coupler 54b to the succeeding optical coupler 54c and blocks light from the succeeding optical coupler 54c to the preceding optical coupler 54b, so that light branched from the optical coupler 54c toward the isolator 53b is blocked.

[0113] In addition, since the light branched by the third-stage optical coupler 54 c in a direction other than the sensor head 20 is not used for measuring the measurement object T, it may be attenuated by an attenuator 55 such as a terminator to avoid reflection and return.

[0114] In this way, the main interferometer has a three-level optical path (three channels), and is an interferometer that uses twice the distance (round trip) from the end (end face) of the optical fiber of the sensor head 20 to the measured object T as the optical path length difference, and generates three interference lights corresponding to the optical path length difference.

[0115] The light receiving elements 56 a to 56 c receive the interference light from the main interferometer as described above, and generate electrical signals corresponding to the amount of received light.

[0116] The amplifier circuits 57a to 57c amplify the electrical signals output from the light receiving elements 56a to 56c, respectively.

[0117] AD converters 58a to 58c receive the electrical signals amplified by amplifier circuits 57a to 57c, respectively, and convert the electrical signals from analog signals to digital signals (AD conversion). Here, AD converters 58a to 58c perform AD conversion based on the correction signal from correction signal generator 61 in the sub-interferometer.

[0118] In order to correct the nonlinearity of the wavelength when the wavelength scanning light source 51 is scanned in the sub-interferometer, an interference signal is obtained by the sub-interferometer to generate a correction signal called a K clock.

[0119] Specifically, the light branched from the optical coupler 54 to the sub-interferometer is further branched by the optical coupler 54d. Here, the optical paths of the branched lights are configured to have an optical path length difference by using optical fibers of different lengths between the optical coupler 54d and the optical coupler 54e, for example, and interference light corresponding to the optical path length difference is output from the optical coupler 54e. In addition, the balanced detector 60 receives the interference light from the optical coupler 54e, removes noise by taking the difference of the signal with the opposite phase, and amplifies the optical signal and converts it into an electrical signal.

[0120] In addition, the optical coupler 54d and the optical coupler 54e only need to branch the light in a ratio of 50:50.

[0121] The correction signal generation unit 61 detects the nonlinearity of the wavelength when the wavelength scanning light source 51 is scanning based on the electrical signal from the balance detector 60, generates a K clock corresponding to the nonlinearity, and outputs it to the AD converters 58a to 58c.

[0122] The intervals of the waves of the analog signals input to the AD converters 58a to 58c in the main interferometer are not equal due to the nonlinearity of the wavelength when the wavelength scanning light source 51 is scanned. The sampling time is corrected based on the above-mentioned K clock so that the intervals of the waves in the AD converters 58a to 58c become equal, and AD conversion (sampling) is performed.

[0123] In addition, as described above, the K clock is a correction signal for sampling the analog signal of the main interferometer, and therefore needs to be generated at a higher frequency than the analog signal of the main interferometer. Specifically, the optical path length difference between the optical coupler 54d and the optical coupler 54e in the sub-interferometer can be made longer than the optical path length difference between the end (end face) of the optical fiber in the main interferometer and the measurement object T, or the correction signal generating unit 61 can multiply the frequency (e.g., 8 times) to increase the frequency.

[0124] The processing unit 59 obtains the digital signals after the nonlinearity is corrected and AD-converted by the AD conversion units 58a to 58c, and calculates the displacement of the measurement object T (the distance to the measurement object T) based on the digital signals. Specifically, in the processing unit 59, the digital signals are frequency-converted using fast Fourier transform (FFT), and the distance is calculated by analyzing them. The detailed processing in the processing unit 59 will be described later.

[0125] In addition, since high-speed processing is required in the processing unit 59 , it is often realized by an integrated circuit such as an FPGA (field-programmable gate array).

[0126] Here, a three-stage optical path is provided in the main interferometer, and the sensor head 20 irradiates the measurement object T with measurement light from each optical path, and based on the interference light (return light) obtained from each optical path, the distance to the measurement object T is measured (multi-channel). The channels in the main interferometer are not limited to three stages, and may be one or two stages, or may be four or more stages.

[0127] Figure 5B FIG. 1 is a diagram for explaining another principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure. Figure 5B As shown, the displacement sensor 10 includes a sensor head 20 and a controller 30. The sensor head 20 includes an objective lens 21 and a plurality of collimating lenses 22a to 22c, and the controller 30 includes a wavelength scanning light source 51, an optical amplifier 52, a plurality of isolators 53 and 53a to 53b, a plurality of optical couplers 54 and 54a to 54j, an attenuator 55, a plurality of light receiving elements (e.g., photodetectors (PD)) 56a to 56c, a plurality of amplifier circuits 57a to 57c, a plurality of analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a to 58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generating unit 61. Figure 5B The displacement sensor 10 shown is different from the above in that it mainly includes optical couplers 54f to 54j. Figure 5A The structure of the displacement sensor 10 shown is different. The principle of the different structure is the same as that of Figure 5A Compare and elaborate.

[0128] The light projected from the wavelength scanning light source 51 is amplified by the optical amplifier 52, and is branched to the main interferometer side and the sub-interferometer side by the optical coupler 54 via the isolator 53. However, the light branched to the main interferometer side is further branched into measurement light and reference light by the optical coupler 54f.

[0129] like Figure 5A As described in the first embodiment, the measuring light is irradiated to the measuring object T through the collimating lens 22a and the objective lens 21 by the first-stage optical coupler 54a, and is reflected by the measuring object T. Figure 5A In the method, the end (end face) of the optical fiber is used as a reference surface, and the light reflected by the reference surface interferes with the light reflected by the measurement object T to generate interference light. Figure 5B In the example, no reference surface for reflecting light is provided. Figure 5B In, not as Figure 5ASince the light reflected by the reference surface is generated in this way, the measurement light reflected by the measurement target object T returns to the first-stage optical coupler 54 a.

[0130] Similarly, the light branched from the first-stage optical coupler 54a to the second-stage optical coupler 54b is irradiated to the measurement target T by the second-stage optical coupler 54b through the collimating lens 22b and the objective lens 21, and is reflected by the measurement target T and returns to the second-stage optical coupler 54b. The light branched from the second-stage optical coupler 54b to the third-stage optical coupler 54c is irradiated to the measurement target T by the third-stage optical coupler 54c through the collimating lens 22c and the objective lens 21, and is reflected by the measurement target T and returns to the third-stage optical coupler 54c.

[0131] On the other hand, the reference light branched by the optical coupler 54f is further branched by the optical coupler 54g to the optical couplers 54h, 54i, and 54j.

[0132] In the optical coupler 54h, the measurement light reflected by the measurement object T output from the optical coupler 54a interferes with the reference light output from the optical coupler 54g, generating interference light, which is received by the light receiving element 56a and converted into an electrical signal. In other words, the measurement light and the reference light are branched by the optical coupler 54f, and interference light corresponding to the optical path length difference between the measurement light (the optical path from the optical coupler 54f through the optical coupler 54a, the collimating lens 22a, and the objective lens 21, which is reflected by the measurement object T and reaches the optical coupler 54h) and the reference light (the optical path from the optical coupler 54f through the optical coupler 54g to the optical coupler 54h) is generated, and the interference light is received by the light receiving element 56a and converted into an electrical signal.

[0133] Similarly, in the optical coupler 54i, interference light corresponding to the difference in optical path length between the optical path of the measurement light (the optical path from the optical coupler 54f via the optical coupler 54a, 54b, the collimating lens 22b, and the objective lens 21, which is reflected by the measured object T and reaches the optical coupler 54i) and the optical path of the reference light (the optical path from the optical coupler 54f via the optical coupler 54g to reach the optical coupler 54i) is generated, and the interference light is received by the light receiving element 56b and converted into an electrical signal.

[0134] In the optical coupler 54j, interference light corresponding to the optical path length difference between the optical path of the measurement light (the optical path from the optical coupler 54f via the optical coupler 54a, 54b, 54c, the collimating lens 22c, the objective lens 21, the reflected optical object T and reaching the optical coupler 54j) and the optical path of the reference light (the optical path from the optical coupler 54f via the optical coupler 54g to the optical coupler 54j) is generated, and the interference light is received by the light receiving element 56c and converted into an electrical signal. For example, the light receiving elements 56a to 56c may be balanced photodetectors.

[0135] In this way, the main interferometer has a three-level optical path (three channels), which generates three interference lights corresponding to the optical path length differences between the measurement light reflected by the measured object T and input into the optical couplers 54h, 54i and 54j respectively and the reference light input into the optical couplers 54h, 54i and 54j respectively via the optical couplers 54f and 54g.

[0136] Alternatively, the optical path length difference between the measurement light and the reference light may be set to be different in the three channels. For example, the optical path length of the optical coupler 54g may be set to be different from that of the optical couplers 54h, 54i, and 54j.

[0137] Then, based on the interference lights obtained respectively, the distance to the measurement target object T and the like are measured (multi-channel).

[0138] [Sensor head structure]

[0139] Here, the structure of the sensor head used for the displacement sensor 10 will be described.

[0140] Fig. 6A is a perspective view showing a schematic structure of the sensor head 20. Figure 6B This is a schematic diagram showing the internal structure of the sensor head.

[0141] like Fig. 6A As shown, the sensor head 20 accommodates the objective lens 21 and the collimator lens in the lens holder 23. For example, the size of the lens holder 23 is about 20 mm for one side surrounding the objective lens 21 and about 40 mm for the length in the optical axis direction.

[0142] like Figure 6B As shown, one objective lens 21 and three collimating lenses 22a to 22c are housed in the lens holder 23. Light from the optical fiber is guided to the three collimating lenses 22a to 22c via the optical fiber array 24, and the light passing through the three collimating lenses 22a to 22c is irradiated to the measurement target T via the objective lens 21.

[0143] In this way, the optical fibers, the collimating lenses 22 a to 22 c , and the optical fiber array 24 are held by the lens holder 23 together with the objective lens 21 , thereby constituting the sensor head 20 .

[0144] In addition, the lens holder 23 constituting the sensor head 20 may be made of a metal (for example, A2017) that is high in strength and can be processed with high precision.

[0145] Figure 7 30 is a block diagram for explaining signal processing in the controller 30. Figure 7As shown, the controller 30 includes a plurality of light receiving elements 71 a to 71 e , a plurality of amplifier circuits 72 a to 72 c , a plurality of AD converters 74 a to 74 c , a processing unit 75 , a differential amplifier circuit 76 , and a correction signal generator 77 .

[0146] In the controller 30, as Figure 5A As shown, the light projected from the wavelength scanning light source 51 is branched to the main interferometer and the sub-interferometer by the optical coupler 54, and the main interference signal and the sub-interference signal obtained are processed respectively, thereby calculating the distance value to the measurement target object T.

[0147] The plurality of light receiving elements 71a to 71c correspond to Figure 5A The light receiving elements 56a to 56c shown receive the main interference signals from the main interferometer, respectively, and output them as current signals to the amplifier circuits 72a to 72c, respectively.

[0148] The plurality of amplifier circuits 72a to 72c convert the current signal (IV conversion) into a voltage signal and amplify the voltage signal.

[0149] The plurality of AD converters 74a to 74c correspond to Figure 5A The AD converters 58a to 58c shown convert the voltage signals into digital signals (AD conversion) based on the K clock from the correction signal generator 77 described later.

[0150] The processing unit 75 is equivalent to Figure 5A The processing unit 59 shown converts the digital signals from the AD conversion units 74a to 74c into frequencies using FFT, analyzes them, and calculates the distance value to the measurement target object T.

[0151] The plurality of light receiving elements 71d to 71e and the differential amplifier circuit 76 correspond to Figure 5A The balanced detector 60 shown receives the interference light in the sub-interferometer, outputs a phase-inverted interference signal, removes noise by taking the difference between the two signals, and amplifies the interference signal and converts it into a voltage signal.

[0152] The correction signal generating unit 77 corresponds to Figure 5A The correction signal generating unit 61 shown in the figure binarizes the voltage signal through the comparator to generate the K clock and outputs it to the AD conversion units 74a to 74c. The K clock needs to be generated at a higher frequency than the analog signal of the main interferometer, so the correction signal generating unit 77 can also multiply the frequency (for example, 8 times) to make it high frequency.

[0153] Figure 8 4 is a flowchart showing a method of calculating the distance to the measurement object T executed by the processing unit 59 in the controller 30. Figure 8As shown, the method includes: steps S31 to S34.

[0154] In step S31 , the processing unit 59 performs frequency conversion of the waveform signal (voltage vs. time) into a frequency spectrum (voltage vs. frequency) using the following FFT. Fig. 9A This is a diagram showing how a waveform signal (voltage vs. time) is frequency-converted into a spectrum (voltage vs. frequency).

[0155]

[0156] N: number of data points

[0157] In step S32 , the processing unit 59 converts the frequency spectrum (voltage vs. frequency) distance into the frequency spectrum (voltage vs. distance). Fig. 9B This is a diagram showing how a frequency spectrum (voltage vs. frequency) is transformed into a frequency spectrum (voltage vs. distance) by distance.

[0158] In step S33 , the processing unit 59 calculates a distance value corresponding to the peak value based on the frequency spectrum (voltage vs. distance). Fig. 9C : is a diagram showing a situation where a peak is detected based on a spectrum (voltage vs. distance) and a distance value corresponding thereto is calculated. Fig. 9C As shown, here, in the three channels, peak values ​​are detected based on the spectrum (voltage vs. distance), and the distance values ​​corresponding to the peak values ​​are calculated.

[0159] In step S34, the processing unit 59 averages the distance values ​​calculated in step S33. Specifically, in step S33, the processing unit 59 detects peak values ​​based on the spectrum (voltage vs. distance) in each of the three channels and calculates the distance values ​​corresponding thereto, and then averages them and outputs the averaged calculation result as the distance to the measurement object T.

[0160] In addition, in step S34, when the processing unit 59 averages the distance values ​​calculated in step S33, it is preferred to average the distance values ​​whose SNR is above the threshold. For example, in any of the three channels, although a peak is detected based on its spectrum (voltage vs. distance), if the SNR is less than the threshold, it is determined that the distance value calculated based on the spectrum is of low reliability and is not adopted.

[0161] Next, regarding the present disclosure, a detailed description will be given as a specific embodiment, centering on the more characteristic structure, function and properties. In addition, the optical interference ranging sensor shown below is equivalent to using Figure 1 The displacement sensor 10 illustrated in FIG. 9 is a light interference ranging sensor having a basic structure, function, and properties, all or part of which are used Figure 1The structure, function and properties included in the displacement sensor 10 described in Figure 9 are the same.

[0162] <One Implementation Method>

[0163] [Structure of optical interferometric distance measuring sensor]

[0164] Fig.10 FIG. 1 is a schematic diagram showing the general structure of an optical interference ranging sensor 100 according to an embodiment of the present invention. Fig.10 As shown, the optical interference distance measuring sensor 100 is configured to include a controller 110 and an optical fiber cable 130 connecting the controller 110 and a sensor head 121. The optical interference distance measuring sensor 100 may also be configured to further include the sensor head 121.

[0165] The controller 110 includes a wavelength scanning light source 140, an optical branching unit 111, a main interferometer 150 and a sub-interferometer 160, a first photodiode (PD) 112, an amplifier circuit 114, a second photodiode (PD) 116, a variable delay line 191, a correction signal generating unit 171, an AD conversion unit 181, a processing unit 118 and a variable delay amount setting unit 195.

[0166] The optical fiber cable 130 is an optical fiber group composed of one or more optical fibers. The optical fiber cable 130 is configured to be detachable from the controller 110 and the sensor head 121, that is, it can be installed and removed. The optical fiber cable 130 is configured to include an optical fiber 131, for example. The optical fiber 131 has an optical path length proportional to the length, and the length of the optical fiber 131 is set based on the distance to the measurement object T.

[0167] The wavelength scanning light source 140 projects light while continuously changing the wavelength of the light. That is, the wavelength of the light projected from the wavelength scanning light source 140 continuously changes. In addition, the light projected from the wavelength scanning light source 140 is supplied to the main interferometer 150 and the sub-interferometer 160 via the light branching unit 111 composed of, for example, an optical coupler. In the wavelength scanning light source 140, the wavelength is continuously controlled by changing the magnitude of the input current. The input current waveform mainly uses a triangular wave or a sawtooth wave.

[0168] The main interferometer 150 is connected to the optical fiber 131 of the optical fiber cable 130 , supplies the light projected from the wavelength scanning light source 140 to the sensor head 121 via the optical fiber 131 , and guides the return light from the sensor head 121 to the first photodiode 112 .

[0169] Specifically, the light guided from the main interferometer 150 to the sensor head 121 is irradiated as measurement light to the measurement target T via, for example, a collimator lens or an objective lens disposed in the sensor head 121 . Then, the reflected light from the measurement target T returns to the sensor head 121 .

[0170] In addition, part of the light guided from the main interferometer 150 to the sensor head 121 is reflected as reference light by a reference surface such as provided at the end of the optical fiber 131. Then, the measurement light and the reference light interfere with each other, thereby generating interference light (also referred to as a "main interference signal") corresponding to the optical path length difference between the measurement light and the reference light.

[0171] In this way, the main interferometer 150 is supplied with the light projected from the wavelength scanning light source 140, and generates a main interference signal based on the measurement light irradiated to the measurement object T by the sensor head 121 and reflected, and the reference light that travels along an optical path that is at least partially different from that of the measurement light. In addition, since the main interference signal is generated by supplying the light projected from the wavelength scanning light source, the main interferometer 150 and the sensor head 121 can also be included and referred to as a main interferometer.

[0172] The first photodiode 112 receives the main interference signal generated by the main interferometer 150 and converts it into an electric signal. The electric signal converted by the first photodiode 112 is, for example, a current signal.

[0173] The amplifier circuit 114 amplifies the electric signal input from the first photodiode 112 at a predetermined gain (also referred to as "gain"). When a current signal is input from the first photodiode 112, the amplifier circuit 114 converts the current signal into a voltage signal (also referred to as "IV conversion") and amplifies it. The amplified electric signal is output to the AD conversion unit 181.

[0174] The light projected from the wavelength scanning light source 140 is branched by the light branching section 111 and supplied to the sub-interferometer 160, and the sub-interferometer 160 generates a sub-interference signal based on two lights traveling along optical paths of different optical path lengths. Specifically, the light is branched into two lights traveling along optical paths of different optical path lengths by the first optical coupler 161, and then synthesized and interfered by the second optical coupler 162, thereby generating a sub-interference signal based on the optical path length difference. The sub-interference signal propagates in the optical fiber 163 and is guided to the second photodiode 116. On the other hand, the remaining port of the second optical coupler 162 is connected to an optical fiber having a coreless optical fiber terminal, or is connected to an attenuator.

[0175] The second photodiode 116 receives the sub-interference signal propagating through the optical fiber 163 of the sub-interferometer 160 and converts it into an electric signal (hereinafter also referred to as a "sub-interferometer signal"). The electric signal converted by the second photodiode 116 is, for example, a current signal.

[0176] Furthermore, the electrical signals output from the second photodiode 116 may be amplified at a predetermined gain by an amplifier circuit (not shown). In this case, the amplifier circuit outputs the amplified electrical signals to the variable delay line 191 .

[0177] The variable delay line 191 is configured to generate a variable delay amount. The variable delay line 191 of this embodiment corresponds to an example of a "variable delay amount generating unit" in the present invention.

[0178] More specifically, the variable delay line 191 is configured to generate a delay corresponding to a variable delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and output the delay to the correction signal generator 171. The variable delay amount of the variable delay line 191 is generated based on a control signal input from a variable delay amount setting unit described later.

[0179] The variable delay line 191 is an electronic component that delays the propagation of an electrical signal, and is configured to include a component that can change the delay, such as a programmable delay line. In addition, the electronic component of the variable delay line 191 is not limited to a programmable delay line, and may be other electronic components as long as the electrical signal generates a changeable delay (lag) corresponding to a variable delay amount. In addition, the structure, type, number, etc. of the variable delay line 191 are not limited.

[0180] In this way, the variable delay line 191 generates a delay corresponding to the variable delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and outputs it to the correction signal generator 171. Thus, by outputting the sub-interferometer signal in which the electrical delay is generated, the correction signal generator 171 can easily generate the correction signal as an electrical signal.

[0181] The correction signal generating unit 171 is configured to generate a correction signal (also referred to as a "K clock signal" or simply "K clock") based on the secondary interference signal and the variable delay amount. The correction signal is a signal for correcting the sampling period of the main interference signal generated by the main interferometer 150. The secondary interference signal is nonlinear like the main interference signal due to the nonlinearity of the wavelength during scanning. Therefore, the correction signal generating unit 171 can generate a correction signal, i.e., a K clock signal, for appropriately sampling the analog signal of the main interference signal and performing AD conversion by grasping the nonlinearity of the wavelength during scanning based on the secondary interference signal.

[0182] In order to generate an appropriate correction signal in the correction signal generating unit 171, it is necessary to appropriately grasp the nonlinearity of the main interference signal received by the first photodiode 112 in the correction signal generating unit 171. To this end, it is preferable to match the characteristics (nonlinearity) of the main interference signal and the sub-interference signal, in other words, to make the main interference signal and the sub-interference signal coincide in time.

[0183] More specifically, the correction signal generator 171 is configured to generate a correction signal based on a delayed sub-interferometer signal. That is, the correction signal is generated based on a signal that is delayed in the time axis direction in the sub-interferometer signal obtained by converting the sub-interferometer signal into an electrical signal. The delay is a time corresponding to the variable delay amount described above.

[0184] In addition, the correction signal generating unit 171 may generate a pulse signal as a correction signal based on a signal that has a delay corresponding to the variable delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. In this way, the timing of sampling the main interference signal can be easily made consistent (synchronized).

[0185] The AD converter 181 is configured to sample the main interferometer signal obtained by converting the main interference signal into an electrical signal based on the correction signal and convert it into a digital signal. The interval of the waves of the analog signal of the main interference signal input to the AD converter 181 is not equal. The AD converter 181 samples the analog signal of the main interference signal and performs AD conversion based on the sampling period (sampling interval) of the correction signal, i.e., the K clock signal, so that the interval of the waves in the main interference signal becomes equal.

[0186] In this way, the AD converter 181 samples the main interferometer signal obtained by converting the main interference signal into an electrical signal based on the correction signal and converts it into a digital signal, thereby easily realizing a structure for converting the main interferometer signal into a digital signal with a corrected sampling period.

[0187] The processing unit 118 is configured to calculate the distance to the measurement target object T based on the main interference signal generated by the main interferometer 150 and the sub-interference signal generated by the sub-interferometer 160 .

[0188] In more detail, the processing unit 118 is configured to calculate the distance to the measured object T based on the main interference signal received by the first photodiode 112 and amplified by the amplifier circuit 114, and the correction signal generated based on the secondary interference signal received by the second photodiode 116 and the variable delay amount generated by the variable delay line 191.

[0189] Specifically, in the AD conversion unit 181, the nonlinear analog signal based on the main interference signal is converted into a digital signal with a sampling period corrected by a correction signal based on the secondary interference signal and a variable delay amount. Therefore, the processing unit 118 uses FFT, etc. to convert the digital signal into a frequency, and analyzes them to calculate the distance value to the measured object T.

[0190] The variable delay amount setting unit 195 is configured to set the variable delay amount based on at least one of the peak value of the digital signal based on the main interference signal sampled based on the correction signal and the peak value of the digital signal based on the reflection signal generated by the main interferometer and sampled based on the correction signal.

[0191] In more detail, the signal converted into a digital signal by the AD conversion unit 181 and converted into a frequency by the processing unit 118 using FFT is input to the variable delay amount setting unit 195. The variable delay amount setting unit 195 is configured to set the variable delay amount based on the signal. The signal input to the variable delay amount setting unit 195 is, for example, a signal obtained by converting the digital signal of the main interference signal into a frequency by FFT and a signal obtained by converting the digital signal of the reflection signal into a frequency by FFT. Alternatively, the signal input to the variable delay amount setting unit 195 may also be a signal obtained by converting the digital signal of the main interference signal into a power spectrum for each number of measurement points (number of data points) by FFT and a signal obtained by converting the digital signal of the reflection signal into a power spectrum for each number of measurement points (number of data points) by FFT. In addition, the variable delay amount set by the variable delay amount setting unit 195 is the variable delay amount generated by the variable delay line 191 described above.

[0192] Here, the reflection signal generated by the main interferometer 150 will be described.

[0193] Fig.11 1 is a schematic diagram showing a specific example of a structure for generating a reflected wave in the main interferometer 150. Fig.11 As shown, a reflecting surface 126a for reflecting light is formed in the main interferometer 150. Specifically, the sensor head 121 includes an objective lens 126 for irradiating light to the measurement object T, and a collimating lens 127 disposed between the end of the optical fiber 131 and the objective lens 126. The reflecting surface 126a is formed on the back side of the objective lens 126 in the sensor head 121 (the surface on the optical fiber 131 side in the sensor head 121).

[0194] In addition, the sensor head 121 may not include the collimator lens 127 between the end of the optical fiber 131 and the objective lens 126 , or may include only the collimator lens 127 instead of the objective lens 126 . In this case, the reflective surface may be formed on the collimator lens 127 .

[0195] As described above, a part of the light input to the sensor head 121 via the optical fiber 131 is irradiated to the measurement object T as measurement light and is reflected by the measurement object. In addition, another part of the light input to the sensor head 121 is reflected as reference light by the reference surface 131a provided at the end of the optical fiber 131. A main interference signal (interference light) is generated based on the measurement light and the reference light, and the distance from the sensor head 121 to the measurement object T is detected as the peak value of the signal obtained by frequency conversion using FFT.

[0196] In addition, another part of the light input to the sensor head 121 via the optical fiber 131 is reflected by the reflection surface 126a formed on the objective lens 126. Then, a reflection signal (interference light) is generated based on the reflected light reflected by the reflection surface 126a and the reference light, and the position of the objective lens 126 in the sensor head 121, specifically, the position of the reflection surface 126a is detected as the peak value of the signal obtained by frequency conversion using FFT.

[0197] In this way, the reflection signal is generated by a part of the light projected from the wavelength scanning light source 140 and supplied to the main interferometer 150 being reflected by the member having the reflection surface 126a formed in the main interferometer 150. Thus, even when the main interference signal cannot be obtained due to the absence of the measurement target T, the reflection signal can be obtained from the reflection surface of the main interferometer, so that the variable delay amount can be set without preparing (arranging) the measurement target.

[0198] The reflective surface 126a formed on the objective lens 126 may be formed on the front surface of the objective lens 126. The reflective surface 126a may be formed by applying a partial reflective coating to the objective lens 126, for example, by utilizing Fresnel reflection with a very small reflectivity (about 5% or less).

[0199] In addition, the reflective surface may be formed on a member inside the sensor head 121. This member may utilize a part of the member constituting the sensor head 121, or may be a member separately disposed inside the housing as a member for generating a reflection signal.

[0200] [Relationship between the peak value of the digital signal based on the main interference signal and the peak value of the digital signal based on the reflected signal and the variable delay amount]

[0201] Fig.12 This is a diagram for explaining the relationship between the peak value of the digital signal based on the main interference signal and the peak value of the digital signal based on the reflected signal and the variable delay amount. Fig.13This is a diagram for explaining the relationship between the half-peak width of the digital signal based on the main interference signal and the half-peak width of the digital signal based on the reflected signal and the FFT conditions. In addition, except for the cases explicitly stated below, the digital signal of the reflected signal is used for explanation, and the description of the case of using the digital signal of the main interference signal is omitted.

[0202] In an existing optical interferometer ranging sensor, when the length of the optical fiber of the optical fiber cable connecting the controller and the sensor head is changed, the optical path length of the light propagating from the main interferometer to the sensor head and from the sensor head to the main interferometer through the optical fiber also becomes longer. Therefore, a timing deviation may occur between the main interference signal and the reflected signal generated by the main interferometer and the correction signal generated by the sub-interferometer to correct the sampling period.

[0203] In addition, in the existing optical interferometer ranging sensor, when the distance from the sensor head to the measured object is longer than the length of the optical fiber, the round-trip time of the light that is irradiated from the sensor head to the measured object and reflected by the measured object and returns to the sensor head becomes longer. Therefore, in this case, a timing deviation may also occur between the main interference signal and the reflected signal generated by the main interferometer and the correction signal generated by the sub-interferometer to correct the sampling period.

[0204] Here, in the signal obtained by converting the digital signal into a frequency using FFT (hereinafter also referred to as a "frequency signal"), Fig.12 As shown, an ideal frequency signal without the above-mentioned timing deviation has a predetermined peak value, for example, a peak intensity (peak signal intensity) of a predetermined value PI, and a half-peak width of a predetermined value PHW.

[0205] As described above, in the optical interference ranging sensor 100 of this embodiment, the reflection signal and the main interference signal generated by the main interferometer 150 are respectively converted into digital signals by the AD conversion unit 181, and become signals obtained by the processing unit 118 by converting the digital signals into frequencies using FFT, and the frequency signals are respectively input into the variable delay amount setting unit 195.

[0206] In addition, as described above, the optical interference ranging sensor 100 of this embodiment converts the analog signal based on the reflection signal or the main interference signal into a digital signal by correcting the sampling period based on the secondary interference signal and the correction signal of the variable delay amount in the AD conversion unit 181. Therefore, by setting an appropriate variable delay amount, the timing deviation can be reduced (eliminated), and the frequency signal of the digital signal of the reflection signal and the main interference signal has the same Fig.12 The peak value shown is the same as the prescribed peak value in the ideal frequency signal.

[0207] More specifically, when the peak intensity in the frequency conversion signal of the digital signal of the reflected signal and the main interference signal is high, for example, when the peak intensity is greater than or equal to the predetermined value PI, it can be determined that the set variable delay amount is appropriate. That is, the peak intensity in the frequency conversion signal of the digital signal of the reflected signal and the main interference signal becomes an indicator of the appropriate variable delay amount.

[0208] In addition, when the half-peak width in the frequency conversion signal of the digital signal of the reflected signal and the main interference signal is small (narrow), for example, the half-peak width is less than the specified value PHW or is the same degree, it can be judged that the set variable delay amount is appropriate. That is, the half-peak width in the frequency conversion signal of the digital signal of the reflected signal and the main interference signal becomes an indicator of the appropriate variable delay amount. In addition, as an indicator of the appropriate variable delay amount, the half-peak width can also be generalized and the width of the specified value relative to the peak value (hereinafter also referred to as "peak specified value width") can be used. In this case, in addition to being half the value of the peak value, the specified value can also be, for example, 1 / e, 1 / e2, etc. When using the half-peak width, similarly, when the peak specified value width is small (narrow), for example, the peak specified value width is less than the specified value or is the same degree, it can be judged that the set variable delay amount is appropriate.

[0209] As described above, in the optical interferometer ranging sensor 100 of this embodiment, the variable delay amount setting unit 195 sets the variable delay amount based on at least one of the peak value of the signal of the digital signal based on the main interference signal sampled according to the correction signal and the peak value of the signal of the digital signal based on the reflected signal generated by the main interferometer and sampled according to the correction signal.

[0210] In this way, by setting a variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal based on at least one of the peak value of the digital signal based on the main interference signal sampled based on the correction signal and the peak value of the digital signal based on the reflected signal generated by the main interferometer and sampled based on the correction signal. Here, by setting the variable delay amount based on the peak value of the digital signal based on the reflected signal sampled based on the correction signal, even in a state where there is no measurement object T. In addition, by setting the variable delay amount that reduces the timing deviation that may occur due to the round-trip time of light traveling back and forth across the distance when the distance from the sensor head 121 to the measurement object T is longer than the length of the optical fiber 131, based on the peak value of the digital signal of the main interference signal sampled based on the correction signal. Therefore, by sampling the signal generated by the main interferometer at an appropriate timing based on the correction signal of the secondary interference signal and the variable delay amount, the distance to the measurement object T can be measured with high accuracy.

[0211] In addition, the variable delay amount setting unit 195 sets the variable delay amount based on at least one of the peak intensity of the digital signal based on the main interference signal and the peak intensity of the digital signal based on the reflected signal. Thus, it is possible to easily set the variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflected signal and the secondary interference signal.

[0212] Furthermore, the variable delay amount setting unit 195 sets the variable delay amount based on at least one of the peak value width of the digital signal based on the main interference signal and the peak value width of the digital signal based on the reflection signal. Thus, it is possible to easily set the variable delay amount that reduces the timing deviation that may occur between the main interference signal and the reflection signal and the secondary interference signal.

[0213] In addition, in the signal of the power spectrum of each measurement point number (data point number) converted by FFT, the number of samples (also referred to as "measurement point number" or "data point number") included in the range of the peak value width of the signal depends on the conditions of FFT, such as the presence or absence of zero padding, the presence or absence of a window function, and the type of window function. In other words, if the conditions of FFT are determined, it is ideal that the number of measurement points included in the range of the peak value width of the signal converted into the power spectrum of each measurement point number becomes a prescribed number (hereinafter also referred to as "prescribed number"). In addition, zero padding is a general method of adding zeros to the measurement data to improve the frequency resolution. For example, if zero padding is performed by adding the same number of zeros as the number of measurement points so that the number of measurement points becomes twice the number of data points, the frequency resolution becomes twice. In this application, "Npad" (Npad is a positive integer) is used as a coefficient to determine how many times the number of measurement points actually measured is to be filled by zero. Specifically, when Npad=2, 5000 points of zero data are added to the 5000 measurement points to make 10000 points. When Npad=3, 10000 points of zero data are added to the 5000 measurement points to make 15000 points. Therefore, the number of measurement points after zero padding the actually measured number of measurement points N is N×Npad.

[0214] For example, Fig.13 As shown by the single-dot chain line in the figure, when an ideal sine wave without noise is transformed into a power spectrum for each measurement point by FFT without a window function, i.e., a rectangular window and without zero padding, the number of measurement points included in the range of the peak value of the signal, such as the half-peak width, is 1 point. Fig.13As shown by the solid line in the figure, when the above-mentioned sine wave is transformed into a power spectrum of each measurement point by a general window function, such as a Hamming window, and an FFT without zero filling, the number of measurement points included in the range of the half-peak width of the signal becomes two points by the determination of the window function itself. In addition, in FFT, when a window function other than a Hamming window, such as a Hanning window or a Gaussian window, is used, it also becomes two points by the determination of the window function itself, except for some exceptions. And, as Fig.13 As shown by the dashed line in the middle, when the above-mentioned sine wave is transformed into a power spectrum for each measurement point by FFT with a Hamming window and zero padding (Npad=2), the number of measurement points included in the range of the half-peak width of the signal becomes 2 points due to the determination of the window function itself, and the number of data points becomes 4 points because the zero padding doubles the number of data points. Fig.13 In the graph of , the intensity values ​​on the vertical axis are depicted in a normalized manner.

[0215] Thus, in the digital signal of the ideal reflection signal and the main interference signal, when the FFT using a window function such as a Hamming window that removes some exceptions is used to transform into a power spectrum for each measurement point, the number of measurement points included in the range of the half-peak width of the signal is 2 points, and when the FFT using zero-padding is used to transform into a power spectrum for each measurement point, the number of measurement points included in the range of the half-peak width of the signal can be expressed as 2×Npad.

[0216] In fact, due to the influence of jitter or noise when acquiring data, the number of measurement points included in the range of the half-peak width of the signal converted into the power spectrum of each measurement point may be expanded by about 1 point. Considering this situation, when the number of measurement points included in the range of the half-peak width of the signal converted into the power spectrum of each measurement point is less than 2×Npad+2, the digital signals of the reflection signal and the main interference signal can be regarded as ideal, that is, the timing deviation is small. In addition, this situation is extended to the peak specified width. When the number of measurement points included in the range of the peak specified value width of the signal converted into the power spectrum of each measurement point is less than the specified number, the digital signals of the reflection signal and the main interference signal can be regarded as an ideal state with a small timing deviation.

[0217] In this embodiment, Fig.12 and Fig.13 The example in which the half-peak width is the half-peak full width is shown, but it is not limited to this. The half-peak width can be the half-peak half width. Similarly, the peak specified value width can be either the specified value full width or the specified value half width.

[0218] [Variable delay setting process]

[0219] Fig.14This is a flowchart for explaining an example of a processing procedure performed by the controller 110 in one embodiment.

[0220] Fig.15 This is a flowchart for explaining another example of the processing procedure performed by the controller 110 in one embodiment.

[0221] Fig.16 This is a flowchart for explaining another example of the processing procedure performed by the controller 110 in one embodiment.

[0222] In the following description, it is assumed that values ​​are stored for the maximum number max (max is an integer greater than or equal to 2) and the maximum delay amounts Dn (n=1, 2, . . . , max), and are stored in advance in a storage unit such as a memory.

[0223] (Specific Example 1: Processing Procedure of Variable Delay Amount Setting Process S210)

[0224] In the variable delay amount setting process S210 , the variable delay amount is set based on the maximum value among the plurality of peak intensities.

[0225] like Fig.14 As shown, first, the variable delay amount setting unit 195 sets "1" to the suffix n (S211). The suffix n is a suffix indicating one of the max delay amounts. Each delay amount Dn stores values ​​representing different delay times, and each value is arranged in ascending or descending order, for example.

[0226] Next, the variable delay amount setting unit 195 reads out the delay amount Dn corresponding to the suffix n from the pre-stored max delay amounts, and sets the read delay amount Dn as the variable delay amount (S212). Specifically, the variable delay amount setting unit 195 generates a control signal based on the delay amount Dn read out in step S212, and outputs the control signal to the variable delay line 191. Thus, the variable delay amount generated by the variable delay line 191 is set.

[0227] Next, the wavelength scanning light source 140 projects light, and the reflected signal generated by the main interferometer 150 is converted into a digital signal by the AD conversion unit 181, and a frequency signal after FFT conversion is obtained by the processing unit 118 (S213). When the reflected signal in step S213 is converted into a digital signal, the sampling period is corrected using the correction signal based on the variable delay amount set in step S212. In addition, in the case of the main interference signal whose description is omitted, the sampling period is also corrected using the correction signal based on the variable delay amount set in step S212.

[0228] Next, the variable delay setting unit 195 analyzes the frequency signal obtained in step S213 to detect the peak intensity, and stores the detected peak intensity value in the intensity In corresponding to the suffix n (S214). The intensity In with the stored value is stored in a storage unit such as a memory. Thus, the peak intensity value when the delay amount Dn is set is obtained.

[0229] Next, the variable delay amount setting unit 195 determines whether the suffix n is equal to the maximum number max ( S215 ).

[0230] If the result of step S215 is that the suffix n is not equal to the maximum number max, the variable delay amount setting unit 195 adds "1" to the suffix n (step S216) and returns to step S212. Then, steps S212 to S215 are repeated until the suffix n is equal to the maximum number max.

[0231] On the other hand, if the result of determination in step S215 is that the suffix n is equal to the maximum number max, the digital signal of the reflected signal is converted into a frequency signal using FFT for all the max delay amounts, and the peak intensity of the frequency signal is detected. In this case, it is considered that the intensity showing the maximum value among the max intensities In detected and stored in S214 is the peak intensity of the frequency signal after the digital signal of the reflected signal with the smallest timing deviation is transformed using FFT. Therefore, the variable delay amount setting unit 195 searches for the intensity In showing the maximum value from the stored max intensities In (S217).

[0232] Then, the variable delay amount setting unit 195 reads the delay amount Dn corresponding to the suffix n of the intensity In searched in step S217, and sets the read delay amount Dn as the variable delay amount (S218). Specifically, similarly to step S212, the variable delay amount setting unit 195 generates a control signal based on the delay amount Dn read in step S217, and outputs the control signal to the variable delay line 191. Thus, the variable delay amount generated by the variable delay line 191 is set to a delay amount that makes the peak intensity in the frequency signal obtained by converting the digital signal of the reflection signal to the maximum value.

[0233] In this way, the variable delay amount setting unit 195 sets the variable delay amount based on at least one of the maximum value of the peak intensities of the digital signal based on the plurality of main interference signals and the maximum value of the peak intensities of the digital signal based on the plurality of reflection signals. Thus, the variable delay amount is set based on the maximum value of the plurality of peak intensities, so that the variable delay amount that can further reduce the timing deviation that may occur between the main interference signal and the reflection signal and the sub-interference signal can be set compared to the case where the variable delay amount is set based on the peak intensity of the digital signal based on one main interference signal or the peak intensity of the digital signal based on one reflection signal.

[0234] (Specific Example 2: Processing Procedure of Variable Delay Amount Setting Process S230)

[0235] In the variable delay amount setting process S230, the variable delay amount is set based on the minimum value among the plurality of peak predetermined value widths. Fig.15 In the example shown, the case where the half-peak width is used as the peak predetermined value width is described.

[0236] In addition, each step from step S231 to step S233 of the variable delay amount setting process S230 is the same or substantially the same as each step from step S211 to step S213 of the variable delay amount setting process S210 described above, and therefore the respective descriptions are omitted.

[0237] like Fig.15 As shown, after step S233, the variable delay amount setting unit 195 analyzes the frequency signal obtained in step S233 to detect a peak value (S234). The detected peak value is a peak value having a maximum peak intensity in the frequency signal.

[0238] Next, the variable delay setting unit 195 calculates the half-peak width for the peak value detected in step S234, and stores the calculated half-peak width value in the half-peak width FWHMn corresponding to the suffix n (S235). The calculated half-peak width is, for example, the full width at half maximum (FWHM). The half-peak width FWHMn whose value is stored is stored in a storage unit such as a memory. Thus, the half-peak width value when the delay amount Dn is set is obtained.

[0239] Next, the variable delay amount setting unit 195 determines whether the suffix n is equal to the maximum number max ( S236 ).

[0240] If the result of step S236 is that the suffix n is not equal to the maximum number max, the variable delay amount setting unit 195 adds "1" to the suffix n (step S237) and returns to step S232. Then, steps S232 to S236 are repeated until the suffix n is equal to the maximum number max.

[0241] On the other hand, if the result of determination in step S236 is that the suffix n is equal to the maximum number max, the conversion of the digital signal of the reflected signal into a frequency signal using FFT is terminated for all the max delay amounts, the peak of the frequency signal is detected, and the half-peak width is calculated. In this case, it is considered that the half-peak width showing the minimum value among the max half-peak widths FWHMn calculated and stored in step S235 is the half-peak width of the frequency signal obtained by converting the digital signal of the reflected signal with the smallest timing deviation using FFT. Therefore, the variable delay amount setting unit 195 searches for the half-peak width FWHMn showing the minimum value from the stored max half-peak widths FWHMn (S238).

[0242] Then, the variable delay amount setting unit 195 reads the delay amount Dn corresponding to the suffix n of the half-peak width FWHMn searched in step S238, and sets the read delay amount Dn as the variable delay amount (S239). Specifically, similarly to step S232, the variable delay amount setting unit 195 generates a control signal based on the delay amount Dn read in step S238, and outputs the control signal to the variable delay line 191. Thus, the variable delay amount generated by the variable delay line 191 is set to a delay amount that makes the half-peak width in the frequency signal after the digital signal of the reflection signal is converted to the minimum value.

[0243] In this way, the variable delay amount setting unit 195 sets the variable delay amount based on at least one of the minimum value of the peak value width of the digital signal based on the plurality of main interference signals and the minimum value of the peak value width of the digital signal based on the plurality of reflected signals. Thus, the variable delay amount is set based on the minimum value of the plurality of peak value widths, so that the variable delay amount that can further reduce the timing deviation that may occur between the main interference signal and the reflected signal and the sub-interference signal can be set compared to the case where the variable delay amount is set based on the peak value width of the digital signal based on one main interference signal or the peak value width of the digital signal based on one reflected signal.

[0244] (Specific Example 3: Processing Procedure of Variable Delay Amount Setting Process S250)

[0245] In the variable delay amount setting process S250, the variable delay amount is set so that the number of measurement points included in the peak value width of the frequency signal is less than the prescribed number. Fig.16 In the example shown, the case where the half-peak width is used as the peak predetermined value width and 2×Npad+2 is used as the predetermined number is described.

[0246] In addition, each step from step S251 to step S252 of the variable delay amount setting process S250 is the same or substantially the same as each step from step S231 to step S232 of the above-mentioned variable delay amount setting process S230, and therefore the respective descriptions are omitted.

[0247] like Fig.16 As shown, after step S252, the wavelength scanning light source 140 projects light, and the reflected signal generated by the main interferometer 150 is converted into a digital signal by the AD conversion unit 181, and the signal converted into a power spectrum for each measurement point number (data point number) is obtained by the processing unit 118 using FFT (S253). When the reflected signal in step S253 is converted into a digital signal, the sampling period is corrected using the correction signal based on the variable delay amount set in step S252. In addition, in the case of the main interference signal whose description is omitted, the sampling period is also corrected using the correction signal based on the variable delay amount set in step S252.

[0248] Next, the variable delay setting unit 195 analyzes the signal converted into the power spectrum for each measurement point obtained in step S252, and detects a peak value (S254). The detected peak value is a peak value having a maximum peak intensity in the signal.

[0249] Next, the variable delay setting unit 195 calculates the half-peak width for the peak detected in step S254, and stores the number of measurement points included in the range of the calculated half-peak width in the half-peak width FWHMn corresponding to the suffix n (S255). The calculated half-peak width is, for example, the full width at half maximum (FWHM). The half-peak width FWHMn storing the number of measurement points is stored in a storage unit such as a memory. Thus, the number of measurement points included in the range of the half-peak width when the delay amount Dn is set is obtained.

[0250] Next, the variable delay amount setting unit 195 determines whether the number of measurement points included in the range of the half maximum width calculated and stored in the half maximum width FWHMn in step S255 is less than 2×Npad+2 (half maximum width FWHMn<2×Npad+2) ( S256 ).

[0251] When the judgment result of step S256 is that the number of measurement points included in the range of the half-peak width stored in the half-peak width FWHMn is not less than 2×Npad+2, that is, the number of measurement points of the half-peak width FWHMn is greater than 2×Npad+2 (half-peak width FWHMn≥2×Npad+2), the variable delay amount setting unit 195 determines whether the suffix n is equal to the maximum number max (S257).

[0252] If the result of determination in step S257 is that the suffix n is not equal to the maximum number max, the variable delay amount setting unit 195 adds "1" to the suffix n (step S258), and returns to step S252. Then, steps S252 to S257 or step S258 are repeated until the number of measurement points included in the range of the half-peak width stored in the half-peak width FWHMn is less than 2×Npad+2, or until the suffix n is equal to the maximum number max.

[0253] On the other hand, if the result of determination in step S257 is that the suffix n is equal to the maximum number max, there is no case where the number of measurement points included in the range of the half-peak width stored in the half-peak width FWHMn is less than 2×Npad+2 for all the max delay amounts. In this case, the variable delay amount setting process S250 is terminated. In addition, it is considered that there are some hardware reasons, such as the optical fiber being too long or the measurement object T being placed far away, so the controller 110 displays or outputs an error.

[0254] On the other hand, if the result of determination in step S256 is that the number of measurement points included in the range of the half-peak width stored in the half-peak width FWHMn is less than 2×Npad+2, it is considered that the number of measurement points of the half-peak width FWHMn stored in the immediately preceding step S255 is the number of measurement points included in the range of the half-peak width of the signal obtained by transforming the digital signal of the reflection signal whose timing deviation is less than the prescribed value into the power spectrum of each measurement point using FFT. Therefore, the variable delay amount setting unit 195 reads the delay amount Dn corresponding to the suffix n of the half-peak width FWHMn calculated and stored in the immediately preceding step S255, and sets the read delay amount Dn as the variable delay amount (S259). Specifically, the variable delay amount setting unit 195 generates a control signal based on the delay amount Dn read in step S259, and outputs the control signal to the variable delay line 191, as in step S252. Thus, the variable delay amount generated by the variable delay line 191 is set to a delay amount in which the half-peak width in the frequency signal after the digital signal of the reflected signal is converted is smaller than a predetermined value.

[0255] In this way, the variable delay amount setting unit 195 sets the variable delay amount so that at least one of the number of measurement points included in the peak value width of the digital signal based on the main interference signal and the number of measurement points included in the peak value width of the digital signal based on the reflected signal is less than the prescribed number. In this way, the variable delay amount for reducing the timing deviation that may occur between the main interference signal and the reflected signal and the sub-interference signal can be easily set.

[0256] Furthermore, the sequence and flowchart described in this embodiment may be reversed in order as long as no contradiction occurs in the processing.

[0257] The processing described in the present embodiment may be executed, for example, in the initial setting when the power of the controller is turned on, or may be executed each time the distance to the measurement object T is measured.

[0258] Furthermore, the variable delay amount is not limited to the case of setting according to the process described in this embodiment. In addition to the above process, the following process is also considered as the setting process of the variable delay amount. For example, in the signal obtained by performing distance transformation on the digital signal of the reflection signal using FFT, a peak corresponding to the position of the reflection surface formed on the sensor head 121 is detected. In addition, if the length of the optical fiber 131 changes, the position of the peak in the digital signal of the reflection signal also changes, so the position of the peak and the length of the optical fiber 131 can be associated in advance, and the length of the optical fiber 131 can be determined based on the position of the peak of the digital signal of the reflection signal, and the variable delay amount based on the determined length of the optical fiber 131 can be set. In addition, according to the length of the optical fiber 131, the user can select any one of the specified multiple variable delay amounts and set the selected variable delay amount. In addition, the length of the optical fiber 131 and the distance from the sensor head 121 to the measurement object T can be associated with the variable delay amount in advance, and the user can input the length of the optical fiber 131 and the approximate distance to the measurement object T, and the variable delay amount can be set based on the input length of the optical fiber 131 and the approximate distance to the measurement object T. In addition, a dedicated ROM (Read Only Memory) specific to the length of the optical fiber 131 may be inserted into the controller 110, and the value read from the dedicated ROM may be set as the variable delay amount. Furthermore, the frequency signal may be displayed on a display unit such as a display for the digital signal of the reflected signal, and the user may observe the peak values ​​of several frequency signals with different variable delay amounts, select or input the variable delay amount, and set it.

[0259] In this embodiment, an example is shown in which the optical interference ranging sensor 100 includes a controller 110 and an optical fiber cable including an optical fiber connecting one sensor head to the controller 110, but the present invention is not limited thereto. The optical interference ranging sensor may also include: a controller; and an optical fiber cable connected to two or more sensor heads and including the same number of optical fibers as the sensor heads. In the following, for the sake of simplicity, the configuration of a case in which the optical interference ranging sensor includes a controller and an optical fiber cable including two optical fibers connected to two sensor heads, respectively, is described.

[0260] [Structure of the optical interference distance measurement sensor when connected to two sensor heads]

[0261] Fig.17 Schematic diagram showing the general structure of an optical interference distance measuring sensor when connected to two sensor heads. Fig.17 In, with Fig.10 The same or similar components as those of the optical interference ranging sensor 100 shown in the figure are marked with the same or similar reference numerals, and their descriptions are omitted as appropriate. Fig.10 The same functions and effects brought about by the same configuration of the optical interference distance measuring sensor 100 shown are not mentioned in sequence.

[0262] like Fig.17 As shown, the optical interference distance measuring sensor 101 includes a controller 110 and an optical fiber cable 130 connecting the controller 110 with a sensor head 121 and a sensor head 122 . Fig.17 The optical fiber cable 130 is shown with Fig.10 Compared to the optical fiber cable 130 shown, the optical fiber cable 130 also includes an optical fiber 132 . Fig.17 The controller 110 is shown with Fig.10 The controller 110 shown is different in that the main interferometer 150 includes a first main interferometer 151 and a second main interferometer 152 , and further includes a first photodiode 113 , an amplifier circuit 115 , a variable delay line 192 , a correction signal generator 172 , and an AD converter 182 .

[0263] The optical fiber cable 130 is configured to include an optical fiber 131 and an optical fiber 132. The optical fiber cable 130 is configured to be detachable relative to the controller 110 and the sensor heads 121 and 122, respectively, that is, it can be installed and removed. The optical fiber 131 has a length L1, and the optical fiber 132 has a length L2. The length L1 of the optical fiber 131 is set based on the distance to the measurement object T1, and the length L2 of the optical fiber 132 is set based on the distance to the measurement object T2. The measurement object T2 is assumed to exist at a different distance from the measurement object T1 and at a different distance from the measurement object T2. Fig.17 In the example shown, the object is at a relatively long distance. Therefore, the length L2 of the optical fiber 132 is longer than the length L1 of the optical fiber 131 (length L2>length L1).

[0264] The main interferometer 150 has two optical paths (two channels), and is configured to include a first main interferometer 151 and a second main interferometer.

[0265] The first main interferometer 151 is connected to the optical fiber 131 of the optical fiber cable 130 , supplies light projected from the wavelength scanning light source 140 to the sensor head 121 via the optical fiber 131 , and guides return light from the sensor head 121 to the first photodiode 112 .

[0266] Specifically, the light guided from the first main interferometer 151 to the sensor head 121 is irradiated as measurement light to the measurement target T via, for example, a collimator lens or an objective lens provided in the sensor head 121 . Then, the reflected light from the measurement target T returns to the sensor head 121 .

[0267] In addition, part of the light guided from the first main interferometer 151 to the sensor head 121 is reflected as reference light by a reference surface such as provided at the end of the optical fiber 131. Then, interference light (also referred to as a "main interference signal") corresponding to the optical path length difference between the measurement light and the reference light is generated by interference between the measurement light and the reference light.

[0268] In this way, the first main interferometer 151 is supplied with the light projected from the wavelength scanning light source 140, and generates a main interference signal based on the measurement light irradiated by the sensor head 121 to the measurement object T and reflected, and the first reference light that travels along an optical path that is at least partially different from that of the measurement light. In addition, since the main interference signal is generated by supplying the light projected from the wavelength scanning light source, the first main interferometer 151 and the sensor head 121 can also be included and referred to as the first main interferometer. The first main interferometer and Fig.10 The main interferometer 150 shown also generates a reflection signal based on the reflected light from the reflection surface and the reference light.

[0269] The second main interferometer 152 is connected to the optical fiber 132 of the optical fiber cable 130 , supplies the light projected from the wavelength scanning light source 140 to the sensor head 122 via the optical fiber 132 , and guides the return light from the sensor head 122 to the first photodiode 113 .

[0270] Specifically, the light guided from the second main interferometer 152 to the sensor head 122 is irradiated as measurement light to the measurement target T via, for example, a collimator lens or an objective lens provided in the sensor head 122 . Then, the reflected light from the measurement target T returns to the sensor head 122 .

[0271] In addition, part of the light guided from the second main interferometer 152 to the sensor head 122 is reflected as reference light by a reference surface such as provided at the end of the optical fiber 132. Then, interference light (also referred to as a "main interference signal") corresponding to the optical path length difference between the measurement light and the reference light is generated by the interference of the measurement light and the second reference light.

[0272] In this manner, the second main interferometer 152 is supplied with the light projected from the wavelength scanning light source 140, and generates a main interference signal based on the measurement light irradiated by the second sensor head 122 and reflected from the measurement object T, and the reference light traveling along an optical path at least partially different from that of the measurement light. In addition, since the main interference signal is generated by supplying the light projected from the wavelength scanning light source, the second main interferometer 152 and the sensor head 122 can also be referred to as the second main interferometer. The second main interferometer and Fig.10 The main interferometer 150 shown also generates a reflection signal based on the reflected light from the reflection surface and the reference light.

[0273] The first photodiode 112 receives the main interference signal generated by the first main interferometer 151 and converts it into an electric signal. The first photodiode 113 receives the main interference signal generated by the second main interferometer 152 and converts it into an electric signal.

[0274] The amplifier circuit 115 amplifies the electric signal input from the first photodiode 113 at a predetermined gain. When a current signal is input from the first photodiode 113 , the amplifier circuit 115 converts the current signal into a voltage signal and amplifies the signal. The amplified electric signal is output to the AD converter 182 .

[0275] The second photodiode 116 receives the sub-interference signal propagating in the optical fiber 163 of the sub-interferometer 160 and converts it into a sub-interferometer signal which is an electrical signal. The second photodiode 116 outputs the converted electrical signal to the variable delay line 191 and the variable delay line 192. In addition, when the electrical signal output from the second photodiode 116 is branched to the variable delay line 191 and the variable delay line 192, impedance matching may be performed between the second photodiode 116 and the variable delay line 191 and the variable delay line 192 to prevent reflection.

[0276] The variable delay line 192 is configured to generate a variable delay amount. The variable delay line 192 of this embodiment corresponds to an example of a "variable delay amount generating unit" in the present invention.

[0277] More specifically, the variable delay line 192 is configured to generate a delay corresponding to a variable delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and output the delay to the correction signal generator 171. The variable delay amount of the variable delay line 192 is generated based on a control signal input from the variable delay amount setting unit 195. Therefore, the variable delay amount generated by the variable delay line 192 may be the same as the variable delay amount generated by the variable delay line 191, and may be different from it.

[0278] The variable delay line 192 is an electronic component that delays the propagation of an electrical signal, and is configured to include a component that can change the delay, such as a programmable delay line. In addition, the electronic component of the variable delay line 191 is not limited to a programmable delay line, and can be other electronic components as long as the electrical signal generates a changeable delay (lag) corresponding to the variable delay amount. In addition, the structure, type, number, etc. of the variable delay line 192 are not limited.

[0279] The correction signal generating unit 172 is configured to generate a correction signal (also referred to as a "K clock signal" or simply "K clock") based on the sub-interference signal and the variable delay amount of the variable delay line 192. The correction signal is a signal for correcting the sampling period of the main interference signal generated by the second main interferometer 152. The sub-interference signal is nonlinear like the main interference signal of the second main interferometer 152 due to the nonlinearity of the wavelength during scanning. Therefore, the correction signal generating unit 172 can generate a correction signal, i.e., a K clock signal, for appropriately sampling and performing AD conversion on the analog signal of the main interference signal of the second main interferometer 152 by grasping the nonlinearity of the wavelength during scanning based on the sub-interference signal.

[0280] Furthermore, in order to generate an appropriate correction signal in the correction signal generating unit 172, it is necessary to appropriately grasp the nonlinearity of the main interference signal of the second main interferometer 152 received by the first photodiode 113 in the correction signal generating unit 172. Therefore, it is preferable to match the characteristics (nonlinearity) of the main interference signal and the sub-interference signal of the second main interferometer 152.

[0281] In more detail, the correction signal generating unit 172 is configured to generate a correction signal based on the delayed sub-interferometer signal. That is, the correction signal is generated based on a signal that is delayed in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. The delay is a time corresponding to the variable delay amount of the variable delay line 192.

[0282] Alternatively, the correction signal generator 172 may generate a pulse signal as a correction signal based on a signal having a delay in the time axis direction corresponding to the variable delay amount of the variable delay line 192 in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal.

[0283] The AD converter 182 is configured to sample the main interferometer signal obtained by converting the main interference signal of the second main interferometer 152 into an electrical signal based on the correction signal of the correction signal generator 172, and convert it into a digital signal. The wave intervals of the analog signal of the main interference signal of the second main interferometer 152 input to the AD converter 182 are not equal intervals. The AD converter 182 samples the analog signal of the main interference signal at a sampling period (sampling interval) corrected based on the correction signal of the correction signal generator 172, that is, the K clock signal, and performs AD conversion in such a manner that the wave intervals in the main interference signal become equal intervals.

[0284] The variable delay amount setting unit 195 is configured to set the variable delay amount based on at least one of the peak value of the digital signal based on the main interference signal sampled based on the correction signal and the peak value of the digital signal based on the reflection signal generated by the main interferometer and sampled based on the correction signal.

[0285] The variable delay amount setting unit 195 receives a signal converted into a digital signal by the AD conversion unit 181 and converted into a frequency signal by the processing unit 118 using FFT, and a signal converted into a digital signal by the AD conversion unit 182 and converted into a frequency signal by the processing unit 118 using FFT. The variable delay amount setting unit 195 is configured to set the variable delay amount of the variable delay line 191 based on the signal converted into a digital signal by the AD conversion unit 181 and converted into a frequency signal by the processing unit 118 using FFT. In addition, the variable delay amount setting unit 195 is configured to set the variable delay amount of the variable delay line 192 based on the signal converted into a digital signal by the AD conversion unit 182 and converted into a frequency signal by the processing unit 118 using FFT.

[0286] The signal input to the variable delay amount setting unit 195 is a signal obtained by converting the digital signal of the main interference signal of the first main interferometer 151 into a frequency signal through FFT, and a signal obtained by converting the digital signal of the reflected signal of the first main interferometer 151 into a frequency signal through FFT, and a signal obtained by converting the digital signal of the main interference signal of the second main interferometer 152 into a frequency signal through FFT, and a signal obtained by converting the digital signal of the reflected signal of the second main interferometer 152 into a frequency signal through FFT. Alternatively, the signal input to the variable delay amount setting unit 195 may be a signal obtained by converting the digital signal of the main interference signal of the first main interferometer 151 into a power spectrum for each measurement point (number of data points) by FFT, a signal obtained by converting the digital signal of the reflected signal of the first main interferometer 151 into a power spectrum for each measurement point (number of data points) by FFT, a signal obtained by converting the digital signal of the main interference signal of the second main interferometer 152 into a power spectrum for each measurement point (number of data points) by FFT, and a signal obtained by converting the digital signal of the reflected signal of the second main interferometer 152 into a power spectrum for each measurement point (number of data points) by FFT. In addition, the variable delay amount set by the variable delay amount setting unit 195 is two variable delay amounts, namely, the variable delay amount generated by the variable delay line 191 and the variable delay amount generated by the variable delay line 192.

[0287] The variable delay amount of the variable delay line 191 and the variable delay amount of the variable delay line 192 can also be respectively adjusted by executing the above Figures 14 to 16 The variable delay amount of the variable delay line 191 and the variable delay amount of the variable delay line 192 may be set in parallel or in series in a predetermined order.

[0288] In this way, even in the case where the main interferometer 150 has two optical paths (two channels) and is connected to the sensor head 121 and the sensor head 121 via the optical fiber cable 130 including two optical fibers 131 and 132, the variable delay amount of the variable delay line 191 for reducing the timing deviation that may occur between the main interference signal and the reflected signal of the first main interferometer 151 and the secondary interference signal, and the variable delay amount of the variable delay line 192 for reducing the timing deviation that may occur between the main interference signal and the reflected signal of the second main interferometer 152 and the secondary interference signal can be set respectively.

[0289] [Modification of interferometer]

[0290] In the above-described embodiment, the optical interference distance measuring sensors 100 and 101 use a Fizeau interferometer that generates reference light by using the end of an optical fiber as a reference surface in the main interferometer 150 , but the interferometer is not limited to this.

[0291] Fig.18 FIG. 1 is a diagram showing changes in an interferometer that generates interference light using measurement light and reference light. Fig.18 In (a), in the optical path through the main interferometer 150, interference light is generated based on the optical path length difference between the reference light with the end (end face) of the optical fiber as the reference surface and the measurement light irradiated from the sensor head and reflected by the measurement object T. This is the structure of the main interferometer 150 (Fizeau interferometer) of the optical interference ranging sensor 100, 101 of the above-mentioned embodiment, and the reference surface can also be configured to reflect light (Fresnel reflection) due to the difference in refractive index between the optical fiber and air. In addition, a reflective film can be applied to the end of the optical fiber, or a non-reflective coating can be implemented at the end of the optical fiber, and a reflective surface such as a lens surface can be configured separately.

[0292] exist Fig.18 In (b), in the optical path passing through the main interferometer 150, a measurement optical path Lm for guiding the measurement light to the measurement object T and a reference optical path Lr for guiding the reference light are formed, and a reference surface (Michelson interferometer) is arranged at the end of the reference optical path Lr. The reference surface can be coated with a reflective film at the end of the optical fiber, or a non-reflective coating can be implemented at the end of the optical fiber, and a reflector or the like can be arranged separately. In this structure, interference light is generated by setting an optical path length difference between the optical path length of the measurement optical path Lm and the optical path length of the reference optical path Lr.

[0293] exist Fig.18In (c), a measurement optical path Lm for guiding measurement light to the measurement object T and a reference optical path Lr for guiding reference light are formed in the optical path passing through the main interferometer 150, and a balanced detector (Mach-Zehnder interferometer) is arranged in the reference optical path Lr. In this structure, interference light is generated by providing an optical path length difference between the optical path lengths of the measurement optical path Lm and the reference optical path Lr.

[0294] Thus, the main interferometer is not limited to the Fizeau interferometer described in the embodiment, and may be, for example, a Michelson interferometer or a Mach-Zehnder interferometer. As long as interference light can be generated by setting the optical path length difference between the measurement light and the reference light, any interferometer may be applied, and other structures such as a combination thereof may also be applied. In addition, similarly, regarding the sub-interferometer not shown, it may be any of a Fizeau interferometer, a Michelson interferometer, and a Mach-Zehnder interferometer. As long as interference light can be generated by setting the optical path length difference between the measurement light and the reference light, any interferometer may be applied, and other structures such as a combination thereof may also be applied.

[0295] In addition, the above-described embodiments are used to make the understanding of the present invention easy, and are not used to limit the interpretation of the present invention. The present invention can be changed / improved without departing from its main purpose, and its equivalent is also included in the present invention. That is, as long as the features of the present invention are possessed, the mode in which the embodiments are appropriately designed and changed by those skilled in the art is also included in the scope of the present invention. For example, the various elements and their configurations, materials, conditions, shapes, sizes, etc. possessed by the embodiments are not limited to the illustrated contents and can be appropriately changed. In addition, the embodiments are illustrative, and of course, partial replacement or combination of the structures shown in different embodiments can be performed, and as long as the features of the present invention are included, these are also included in the scope of the present invention.

[0296] [Note 1]

[0297] A controller (110) is connected to a sensor head (121) for irradiating light to a measurement object (T) via an optical fiber cable (130), the controller (110) comprising: a light source (140) for irradiating light while changing the wavelength of the light; a main interferometer (150) connected to the sensor head (121) via an optical fiber (131) included in the optical fiber cable (130), supplied with the light projected from the light source (140), and generating a main interference signal based on measurement light and reference light, the measurement light being irradiated from the sensor head (121) to the measurement object (T) and reflected, the reference light traveling along an optical path at least partially different from that of the measurement light; and a sub-interferometer (160) supplied with the light projected from the light source (140). light, generating a secondary interference signal based on two lights traveling along different optical paths; a variable delay amount generating unit, which generates a variable delay amount; a correction signal generating unit (171), which generates a correction signal for correcting the sampling period of the main interference signal based on the secondary interference signal and the variable delay amount; a processing unit (118), which measures the distance to the measurement object (T) based on the main interference signal and the correction signal; and a variable delay amount setting unit (195), which sets the variable delay amount based on at least one of the peak values ​​of the following two signals: a signal based on a digital signal of the main interference signal sampled based on the correction signal; and a signal based on a digital signal of a reflected signal generated by the main interferometer (150) and sampled based on the correction signal.

[0298] [Note 11]

[0299] An optical interference ranging sensor (100) includes a controller (110) and an optical fiber cable (130) connected to the controller (110), wherein the controller (110) includes: a light source (140) that projects light while changing the wavelength of the light; a main interferometer (150) that is connected to a sensor head (121) via an optical fiber (131) included in the optical fiber cable (130), is supplied with light projected from the light source (140), and generates a main interference signal based on measurement light and reference light, wherein the measurement light is irradiated by the sensor head (121) toward a measurement object (T) and is reflected, and the reference light travels along an optical path that is at least partially different from that of the measurement light; and a sub-interferometer (160) that is supplied with light projected from the light source (140). light, generating a secondary interference signal based on two lights traveling along different optical paths; a variable delay amount generating unit, which generates a variable delay amount; a correction signal generating unit (171), which generates a correction signal for correcting the sampling period of the main interference signal based on the secondary interference signal and the variable delay amount; a processing unit (118), which measures the distance to the measurement object (T) based on the main interference signal and the correction signal; and a variable delay amount setting unit (195), which sets the variable delay amount based on at least one of the peak values ​​of the following two signals: a signal based on a digital signal of the main interference signal sampled based on the correction signal; and a signal based on a digital signal of the reflected signal generated by the main interferometer (150) and sampled based on the correction signal.

[0300] Description of symbols

[0301] 1: sensor system; 10: displacement sensor; 11: control device; 12: sensor for control signal input; 13: external connection device; 20: sensor head; 21: objective lens; 22a: collimating lens; 22b: collimating lens; 22c: collimating lens; 23: lens holder; 24: optical fiber array; 30: controller; 31: display unit; 32: setting unit; 33: external I / F unit; 34: optical fiber connection unit; 35: external storage unit; 36: measurement processing unit; 40: optical fiber; 51: wavelength scanning unit Scanning light source; 52: optical amplifier; 53, 53a, 53b: isolator; 54, 54a, 54b, 54c, 53d, 54e, 54f, 54g, 54h, 54i, 54j: optical coupler; 55: attenuator; 56a, 56b, 56c: light receiving element; 57a, 57b, 57c: amplifier circuit; 58a, 58b, 58c: AD conversion unit; 59: processing unit; 60: balanced detector; 61: correction signal generation unit; 71a, 71b, 71c, 71d, 71e: light receiving element; 72a, 72b, 72c: amplifier circuit; 74a, 74b, 74c: AD conversion unit; 75: processing unit; 76: differential amplifier circuit; 77: correction signal generation unit; 100, 101: optical interference ranging sensor; 110: controller; 111: optical branching unit; 112, 113: first photodiode; 114, 115: amplifier circuit; 116: second photodiode; 118: processing unit; 121, 122: sensor head; 130: optical fiber cable; 131, 132: optical fiber; 140: wavelength scanning light source; 150: main interferometer; 151: first main interferometer; 152: second main interferometer; 160: sub-interferometer; 161: first optical coupler; 162: second optical coupler; 163: optical fiber; 171, 172: correction signal generating unit; 181, 182: AD conversion unit; 191, 192: variable delay line; 195: variable delay amount setting unit; Lm: measurement optical path; Lr: reference optical path; T, T1, T2: measurement object.

Claims

1. A controller connected to a sensor head for irradiating light to a measurement object via an optical fiber cable, wherein: The controller has: A light source that projects light while changing the wavelength of the light; a main interferometer connected to the sensor head via an optical fiber included in the optical fiber cable, supplied with light projected from the light source, and generating a main interference signal based on measurement light, the measurement light being irradiated to the measurement object by the sensor head and reflected, and reference light traveling along an optical path at least partially different from that of the measurement light; a secondary interferometer supplied with the light projected from the light source and generating a secondary interference signal based on two lights traveling along different optical paths; a variable delay amount generating unit that generates a variable delay amount; a correction signal generating unit for generating a correction signal for correcting a sampling period of the main interference signal based on the sub-interference signal and the variable delay amount; a processing unit that measures the distance to the measurement object based on the main interference signal and the correction signal; and A variable delay amount setting unit sets the variable delay amount based on at least one of the peak values ​​of the following two signals: a signal based on a digital signal of the main interference signal sampled according to the correction signal; and a signal based on a digital signal of a reflected signal generated by the main interferometer and sampled according to the correction signal.

2. The controller according to claim 1, wherein: The variable delay amount setting unit sets the variable delay amount based on at least one of a peak intensity of a digital signal based on the main interference signal and a peak intensity of a digital signal based on the reflected signal.

3. The controller according to claim 2, wherein: The variable delay amount setting unit sets the variable delay amount based on at least one of a maximum value of peak intensities of digital signals based on the plurality of main interference signals and a maximum value of peak intensities of digital signals based on the plurality of reflected signals.

4. The controller according to claim 1, wherein: The variable delay amount setting unit sets the variable delay amount based on at least one of a predetermined peak value width of a digital signal based on the main interference signal and a predetermined peak value width of a digital signal based on the reflection signal.

5. The controller according to claim 4, wherein: The variable delay setting unit sets the variable delay based on at least one of a minimum value of a signal peak predetermined value width of digital signals based on the plurality of main interference signals and a minimum value of a signal peak predetermined value width of digital signals based on the plurality of reflected signals.

6. The controller according to claim 1, wherein: The variable delay amount setting unit sets the variable delay amount so that at least one of the number of measurement points included in the peak value width of the digital signal based on the main interference signal and the number of measurement points included in the peak value width of the digital signal based on the reflected signal is less than a predetermined number.

7. The controller according to claim 1, wherein: The reflection signal is generated by a portion of the light projected from the light source and supplied to the main interferometer being reflected by a member having a reflection surface formed in the main interferometer.

8. The controller according to claim 1, wherein: The variable delay amount generating unit includes a variable delay line that generates a delay corresponding to the variable delay amount in a sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal in a time axis direction and outputs the delay to the correction signal generating unit.

9. The controller according to claim 1, wherein: The correction signal generating unit generates a pulse signal as the correction signal based on a signal in which a delay corresponding to the variable delay amount is generated in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal.

10. The controller according to claim 1, wherein: The controller further includes an AD converter that samples a main interferometer signal obtained by converting the main interference signal into an electrical signal based on the correction signal and converts the main interferometer signal into a digital signal.

11. An optical interference ranging sensor, comprising a controller and an optical fiber cable connected to the controller, wherein: The controller has: A light source that projects light while changing the wavelength of the light; a main interferometer connected to the sensor head via the optical fiber included in the optical fiber cable, supplied with the light projected from the light source, and generating a main interference signal based on the measurement light and the reference light, the measurement light being irradiated to the measurement object by the sensor head and reflected, and the reference light traveling along an optical path at least partially different from that of the measurement light; a secondary interferometer supplied with the light projected from the light source and generating a secondary interference signal based on two lights traveling along different optical paths; a variable delay amount generating unit that generates a variable delay amount; a correction signal generating unit for generating a correction signal for correcting a sampling period of the main interference signal based on the sub-interference signal and the variable delay amount; a processing unit that measures the distance to the measurement object based on the main interference signal and the correction signal; and A variable delay amount setting unit sets the variable delay amount based on at least one of the peak values ​​of the following two signals: a signal based on a digital signal of the main interference signal sampled according to the correction signal; and a signal based on a digital signal of a reflected signal generated by the main interferometer and sampled according to the correction signal.

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