Optical interferometry distance sensor

Abstract

To provide an optical interferometric range sensor capable of setting an appropriate measurement condition according to a measurement distance to a measurement target.SOLUTION: An optical interferometric range sensor 100 includes: a light source 110 that emits light while changing a wavelength; an interferometer 130 that receives the light emitted from the light source and generates interference light based on measurement light emitted from a sensor head 131 to a measurement target T and reflected from the measurement target and reference light traveling on an optical path at least partially different from an optical path of the measurement light; a light receiver 140 that receives the interference light from the interferometer to convert the interference light into an electric signal; a processor 150 that calculates a distance from the sensor head to the measurement target on the basis of the electric signal resulting from conversion performed by the light receiver; determination means 160 that determines the sensor head on the basis of a beat signal generated by the interferometer; and setting means 170 that sets a measurement condition corresponding to the sensor head determined by the determination means.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present invention relates to an optical interference distance measurement sensor.

Background Art

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

[0003] In the optical measurement device described in Patent Document 1, a stable measurement result is obtained by coherently interfering the return light beam component of the reference beam reflected by a plurality of optical fiber end faces and the reflection component of the measurement beam reflected by the surface of the measurement object.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the optical measurement device disclosed in Patent Document 1, it is necessary to set a corresponding sensor head and measurement conditions according to the measurement distance to the measurement object. That is, there is a problem that, according to the measurement distance to the measurement object, for example, a sensor head corresponding to the range of the measurement distance must be attached and appropriate measurement conditions must be manually set each time.

[0006] Therefore, an object of the present invention is to provide an optical interference distance measurement sensor capable of setting appropriate measurement conditions according to the measurement distance to a measurement object.

Means for Solving the Problems

[0007] An optical interferometry distance measuring sensor according to one aspect of the present invention comprises: a light source that emits light while changing its wavelength; an interferometer that generates interference light based on measurement light supplied from the light source, which is irradiated onto an object to be measured by a sensor head and reflected; and reference light that follows an optical path at least partially different from the measurement light; a light receiving unit that receives the interference light from the interferometer and converts it into an electrical signal; a processing unit that calculates the distance from the sensor head to the object to be measured based on the electrical signal converted by the light receiving unit; a discrimination means for discriminating the sensor head based on a beat signal generated by the interferometer; and a setting means for setting measurement conditions corresponding to the sensor head discriminated by the discrimination means.

[0008] In this embodiment, the discrimination means identifies the sensor head based on the beat signal generated by the interferometer, and the setting means sets the measurement conditions corresponding to the sensor head identified by the discrimination means. This allows for setting appropriate measurement conditions according to the measurement distance to the object to be measured, and enables accurate measurement of the distance to the object. For the user, this reduces the need to manually check the type of sensor head and set the corresponding measurement conditions each time.

[0009] In the above embodiment, the setting means may adjust the sweep ratio, which is expressed as a frequency sweep width per sweep time, for the light emitted from the light source, based on the sensor head determined by the discrimination means.

[0010] According to this embodiment, the setting means adjusts the sweep ratio for the light emitted from the light source based on the sensor head identified by the discrimination means, and in the circuit bandwidth processed by the processing unit, it is possible to appropriately detect signal peaks based on interference light received by the light receiving unit.

[0011] In the above embodiment, the system further includes a correction signal generation unit that generates a correction signal used for sampling when converting the interference light received by the light receiving unit into an electrical signal, and the setting means may adjust the degree of frequency multiplication of the correction signal based on the sensor head determined by the discrimination means.

[0012] According to this embodiment, the setting means can appropriately sample the interference light received by the light receiving unit in order to adjust the degree of frequency multiplication of the correction signal generated by the correction signal generation unit based on the sensor head identified by the discrimination means. As a result, the distance to the object to be measured can be measured appropriately.

[0013] In the above embodiment, the discrimination means may determine the sensor head based on at least one of the peak frequency and number of peaks of the beat signal.

[0014] According to this embodiment, the discrimination means identifies the sensor head based on at least one of the peak frequency and number of peaks of the beat signal, so that the user does not need to check the type of sensor head and can easily identify the sensor head.

[0015] In the above embodiment, the beat signal may be generated when a portion of the light emitted from a light source and supplied to the interferometer is reflected by a member having a reflective surface formed in the interferometer.

[0016] According to this embodiment, the beat signal is generated when a portion of the light emitted from the light source and supplied to the interferometer is reflected by a member having a reflective surface formed in the interferometer. Therefore, the user does not need to check the type of sensor head and can easily identify the sensor head.

[0017] In the above embodiment, the reflective surface may be formed inside the sensor head.

[0018] According to this aspect, since the reflecting surface is formed inside the sensor head, for the user, operations such as confirmation and preparation other than the attachment of the sensor head are reduced, and the sensor head can be easily discriminated.

[0019] In the above aspect, the reflecting surface may be formed on the objective lens included in the sensor head.

[0020] According to this aspect, since the reflecting surface is formed on the objective lens included in the sensor head, there is no need to separately prepare parts or the like, and the sensor head can be easily discriminated.

[0021] In the above aspect, the reflecting surface may be formed on the collimating lens included in the sensor head.

[0022] According to this aspect, since the emitting surface is formed on the collimating lens included in the sensor head, there is no need to separately prepare parts or the like, and the sensor head can be easily discriminated.

[0023] In the above aspect, the reflecting surface may be formed inside the optical fiber that supplies the light projected from the light source to the sensor head.

[0024] According to this aspect, since the reflecting surface is formed inside the optical fiber that supplies the light projected from the light source to the sensor head, the sensor head can be easily discriminated without forming a reflecting surface on the sensor head.

Advantages of the Invention

[0025] According to the present invention, it is possible to provide an optical interference distance measuring sensor capable of setting appropriate measurement conditions according to the measurement distance to the measurement object.

Brief Description of the Drawings

[0026] [Figure 1] It is an external schematic view showing an outline of the displacement sensor 10 according to the present disclosure. [Figure 2]This flowchart shows the procedure for measuring the object T using the displacement sensor 10 related to this disclosure. [Figure 3] This is a functional block diagram showing an overview of the sensor system 1 in which the displacement sensor 10 described herein is used. [Figure 4] This flowchart shows the procedure for measuring an object T using a sensor system 1 that employs the displacement sensor 10 described herein. [Figure 5A] This figure illustrates the principle by which the displacement sensor 10 relating to this disclosure measures the object T to be measured. [Figure 5B] This figure illustrates another principle by which the object T is measured by the displacement sensor 10 relating to this disclosure. [Figure 6A] This is a perspective view showing the schematic configuration of the sensor head 20. [Figure 6B] This is a schematic diagram showing the internal structure of the sensor head 20. [Figure 7] This is a block diagram illustrating the signal processing in controller 30. [Figure 8] This flowchart shows the method for calculating the distance to the object T to be measured, as performed by the processing unit 59 in the controller 30. [Figure 9A] This diagram illustrates how a waveform signal (voltage vs. time) is frequency-converted into a spectrum (voltage vs. frequency). [Figure 9B] This diagram illustrates how a spectrum (voltage vs. frequency) is converted to a spectrum (voltage vs. distance) through distance conversion. [Figure 9C] This diagram shows how peaks are detected based on the spectrum (voltage vs. distance), and how the corresponding distance values ​​are calculated. [Figure 10] This is a schematic diagram showing the configuration of an optical interferometry distance measuring sensor 100 according to the first embodiment of the present invention. [Figure 11] This is a specific example illustrating the relationship between the measurement distance to the object T, the type of sensor head 131, and the circuit bandwidth in the processing unit 150. [Figure 12]This is a schematic diagram showing a specific example of a sensor head 131 configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b. [Figure 13] This is a diagram to explain coherent FMCW. [Figure 14] This flowchart shows the processing flow of the measurement condition setting method M100, which determines the type of sensor head 131 and sets measurement conditions corresponding to the determined type of sensor head 131. [Figure 15] This schematic diagram shows a specific example of a sensor head 131 that is configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b by arranging a collimating lens. [Figure 16] This schematic diagram shows a specific example of a sensor head 131 that is configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b by forming a reflective surface on the internal structural components of the sensor head 131. [Figure 17A] This schematic diagram shows a specific example of how the type of sensor head 131 can be determined by forming a reflective surface on the optical fiber. [Figure 17B] This schematic diagram illustrates a specific example of how the type of sensor head 131 can be determined by configuring a reflective surface on the tip (end face) of the optical fiber on the controller 101 side. [Figure 18] This schematic diagram shows a specific example of a sensor head 131 configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b based on the number of peaks in the beat signal. [Figure 19] This flowchart shows the processing flow of the measurement condition setting method M101, which determines the type of sensor head 131 according to the number of peaks detected in the beat signal and sets measurement conditions corresponding to the determined type of sensor head 131. [Figure 20] This is a schematic diagram showing the configuration of an optical interferometry distance measuring sensor 200 according to a second embodiment of the present invention. [Figure 21]This flowchart shows the processing flow of the measurement condition setting method M200, which determines the type of sensor head 131 and sets measurement conditions corresponding to the determined type of sensor head 131. [Figure 22] This diagram shows variations of interferometers that generate interference light using a measurement light and a reference light. [Modes for carrying out the invention]

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are merely examples of specific actions for carrying out the present invention and are not intended to limit the scope of the invention. Furthermore, in order to facilitate understanding of the explanation, the same reference numerals are used for identical components in the drawings whenever possible, and redundant explanations may be omitted.

[0028] [Overview of Displacement Sensors] First, I will explain the overview of the displacement sensor related to this disclosure. Figure 1 is a schematic diagram showing the external appearance of the displacement sensor 10 according to this disclosure. As shown in Figure 1, the displacement sensor 10 comprises a sensor head 20 and a controller 30, and measures the displacement of the object to be measured T (distance to the object to be measured T).

[0029] The sensor head 20 and the controller 30 are connected by an optical fiber 40, and an objective lens 21 is attached to the sensor head 20. The controller 30 also 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 internally has a measurement processing unit 36.

[0030] The sensor head 20 irradiates the object T to be measured with light output from the controller 30 and receives the reflected light from the object T. The sensor head 20 has a reference surface inside that reflects the light output from the controller 30 and received via the optical fiber 40, and interferes with the reflected light from the object T as described above.

[0031] The sensor head 20 is equipped with an objective lens 21, which is detachable. The objective lens 21 can be replaced with an objective lens having an appropriate focal length depending on the distance between the sensor head 20 and the object T to be measured, or a variable-focus objective lens may be used.

[0032] Furthermore, when installing the sensor head 20, guide light (visible light) may be shone onto the object T to be measured, and the sensor head 20 and / or the object T to be measured may be positioned so that the object T is appropriately located within the measurement area of ​​the displacement sensor 10.

[0033] The optical fiber 40 is connected to and extends from the optical fiber connection part 34 located on the controller 30, connecting the controller 30 and the sensor head 20. Thus, the optical fiber 40 is configured to guide light emitted from the controller 30 to the sensor head 20, and further guide the reflected light from the sensor head 20 back to the controller 30. The optical fiber 40 is detachable from the sensor head 20 and the controller 30, and various optical fibers with different lengths, thicknesses, and characteristics can be used.

[0034] The display unit 31 is composed of, for example, a liquid crystal display or an organic EL display. The display unit 31 displays the set value of the displacement sensor 10, the amount of reflected light received from the sensor head 20, and measurement results such as the displacement of the object to be measured T (distance to the object to be measured T) measured by the displacement sensor 10.

[0035] The setting unit 32 allows the user to operate, for example, mechanical buttons or a touch panel, to perform the necessary settings for measuring the object T. All or part of these necessary settings may be pre-configured, or they may be configured by an external device (not shown) connected to the external I / F unit 33. The external device may be connected via a network by wire or wireless.

[0036] Here, the external I / F unit 33 consists of, for example, Ethernet®, RS232C, and analog output. The external I / F unit 33 may be connected to other connected devices so that necessary settings can be made from those external connected devices, or it may output measurement results measured by the displacement sensor 10 to the external connected devices.

[0037] Furthermore, the controller 30 may acquire data stored in the external storage unit 35, thereby performing the necessary settings for measuring the object T. The external storage unit 35 is, for example, an auxiliary storage device such as a USB (Universal Serial Bus) memory, which has the necessary settings for measuring the object T pre-stored in it.

[0038] The measurement processing unit 36 ​​in the controller 30 includes, for example, a wavelength-swept light source that emits light while continuously changing the wavelength, a photodetector that receives the reflected light from the sensor head 20 and converts it into an electrical signal, and a signal processing circuit that processes the electrical signal. Based on the reflected light from the sensor head 20, the measurement processing unit 36 ​​performs various processes using the control unit and memory unit, etc., so that the displacement of the object to be measured T (distance to the object to be measured T) is ultimately calculated. Details of these processes will be described later.

[0039] Figure 2 is a flowchart showing the procedure for measuring an object T using the displacement sensor 10 according to this disclosure. As shown in Figure 2, the procedure includes steps S11 to S14.

[0040] In step S11, the sensor head 20 is installed. For example, guide light is shone from the sensor head 20 onto the object T to be measured, and the sensor head 20 is installed in the appropriate position using this as a reference.

[0041] Specifically, the display unit 31 of the controller 30 displays the amount of reflected light received from the sensor head 20, and the user may adjust the orientation of the sensor head 20 and the distance (height position) from the object to be measured T while checking the amount of received light. Basically, if the light from the sensor head 20 can be shone perpendicularly (or at an angle as close to perpendicular as possible) to the object to be measured T, the amount of reflected light from the object to be measured T will be large, and the amount of reflected light received from the sensor head 20 will also be large.

[0042] Furthermore, the objective lens 21 may be replaced with one having an appropriate focal length depending on the distance between the sensor head 20 and the object T to be measured.

[0043] Furthermore, if the appropriate settings cannot be made when measuring the object T to be measured (for example, if the amount of light required for measurement cannot be obtained, or if the focal length of the objective lens 21 is inappropriate), the system may notify the user of an error or incomplete setting by displaying it on the display unit 31 or outputting it to an externally connected device.

[0044] In step S12, various measurement conditions are set when measuring the object T to be measured. For example, the user sets the unique calibration data (such as a function to correct linearity) of the sensor head 20 by operating the setting unit 32 on the controller 30.

[0045] Furthermore, various parameters may be set. For example, sampling time, measurement range, and thresholds for determining whether a measurement result is normal or abnormal may be set. In addition, the measurement period may be set according to the characteristics of the object T to be measured, such as its reflectance and material, and the measurement mode may be set according to the material of the object T to be measured.

[0046] These measurement conditions and various parameters are set by operating the setting unit 32 in the controller 30, but they may also be set from an externally connected device or by acquiring data from the external storage unit 35.

[0047] In step S13, the sensor head 20 installed in step S11 measures the object T according to the measurement conditions and various parameters set in step S12.

[0048] Specifically, in the measurement processing unit 36 ​​of the controller 30, light is emitted from the wavelength-swept light source, the reflected light from the sensor head 20 is received by the photodetector, and the signal processing circuit performs frequency analysis, distance conversion, and peak detection to calculate the displacement of the object to be measured T (distance to the object to be measured T). Details of the specific measurement process will be described later.

[0049] In step S14, the measurement results measured in step S13 are output. For example, the displacement of the object T measured in step S13 (distance to the object T) is displayed on the display unit 31 of the controller 30 or output to an externally connected device.

[0050] Furthermore, the displacement of the object T measured in step S13 (distance to the object T) may also be displayed or output as a measurement result, indicating whether it is within the normal range or abnormal based on the threshold set in step S12. In addition, the measurement conditions, various parameters, and measurement mode set in step S12 may also be displayed or output.

[0051] [Overview of the system including the displacement sensor] Figure 3 is a functional block diagram showing an overview of a sensor system 1 in which the displacement sensor 10 according to this disclosure is used. As shown in Figure 3, the sensor system 1 comprises a displacement sensor 10, a control device 11, a control signal input sensor 12, and an external connection device 13. The displacement sensor 10 is connected to the control device 11 and the external connection device 13 by, for example, a communication cable or an external connection cord (including, for example, an external input line, an external output line, and a power line), and the control device 11 and the control signal input sensor 12 are connected by a signal line.

[0052] As explained using Figures 1 and 2, the displacement sensor 10 measures the displacement of the object T (distance to the object T). The displacement sensor 10 may also output the measurement results to the control device 11 and the external connection device 13.

[0053] The control device 11 is, for example, a PLC (Programmable Logic Controller), which gives various instructions to the displacement sensor 10 when the displacement sensor 10 measures the object T to be measured.

[0054] For example, the control device 11 may 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 it may output a zero reset command signal (a signal to set the current measured value to 0) to the displacement sensor 10.

[0055] The control signal input sensor 12 outputs an on / off signal to the control device 11 that indicates the timing for the displacement sensor 10 to measure the object T. For example, the control signal input sensor 12 can be installed near a production line where the object T moves, and it can detect when the object T moves to a predetermined position and output an on / off signal to the control device 11.

[0056] The external device 13 is, for example, a PC (Personal Computer), which allows the user to make various settings for the displacement sensor 10 by operating it.

[0057] Specific examples include setting the measurement mode, operating mode, measurement cycle, and the material of the object T being measured.

[0058] As for the measurement mode setting, options such as "internal synchronous measurement mode," which starts measurement periodically within the control device 11, or "external synchronous measurement mode," which starts measurement in response to an input signal from outside the control device 11, can be selected.

[0059] For setting the operating mode, you can select either the "operation mode" which actually measures the object T to be measured, or the "adjustment mode" which sets the measurement conditions for measuring the object T to be measured.

[0060] The measurement period is the period during which the object T is measured, and it should be set according to the reflectance of the object T. However, even if the reflectance of the object T is low, the object T can still be measured appropriately by setting the measurement period to be longer.

[0061] For the object T being measured, a "rough surface mode" suitable for cases where diffuse reflection is relatively abundant in the reflected light component, a "specular surface mode" suitable for cases where specular reflection is relatively abundant in the reflected light component, or an intermediate "standard mode" are selected.

[0062] In this way, by making appropriate settings according to the reflectance and material of the object T to be measured, the object T can be measured with higher accuracy.

[0063] Figure 4 is a flowchart showing the procedure for measuring an object T by a sensor system 1 using the displacement sensor 10 according to this disclosure. As shown in Figure 4, the procedure is for the external synchronous measurement mode described above and includes steps S21 to S24.

[0064] In step S21, the sensor system 1 detects the object to be measured, T. Specifically, the control signal input sensor 12 detects that the object to be measured T has moved to a predetermined position on the production line.

[0065] In step S22, the sensor system 1 instructs the displacement sensor 10 to measure the object T detected in step S21. Specifically, the control signal input sensor 12 outputs an on / off signal to the control device 11, instructing it on the timing to measure the object T detected in step S21. Based on this on / off signal, the control device 11 outputs a measurement timing signal to the displacement sensor 10, instructing it to measure the object T.

[0066] In step S23, the object T is measured by the displacement sensor 10. Specifically, the displacement sensor 10 measures the object T based on the measurement instruction received in step S22.

[0067] In step S24, the sensor system 1 outputs the measurement results measured in step S23. Specifically, the displacement sensor 10 displays the measurement results on the display unit 31 or outputs them to the control device 11 or external connection device 13 via the external I / F unit 33.

[0068] In this document, Figure 4 illustrates the procedure for the external synchronous measurement mode, in which the object T is detected by the control signal input sensor 12 and measured. However, the procedure is not limited to this. For example, in the internal synchronous measurement mode, instead of steps S21 and S22, a measurement timing signal is generated based on a preset period to instruct the displacement sensor 10 to measure the object T.

[0069] Next, the principle by which the object T is measured by the displacement sensor 10 according to this disclosure will be explained. Figure 5A is a diagram illustrating the principle by which an object T is measured by the displacement sensor 10 according to this disclosure. As shown in Figure 5A, the displacement sensor 10 comprises 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-swept 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 photodetectors (e.g., photodetectors (PDs)) 56a to 56c, a plurality of amplification 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 generation unit 61.

[0070] The wavelength-swept light source 51 emits laser light with a swept wavelength. For example, if a method is applied to modulate a VCSEL (Vertical Cavity Surface Emitting Laser) with current as the wavelength-swept light source 51, mode hopping is less likely to occur due to the short resonator length, the wavelength can be easily changed, and it can be realized at low cost.

[0071] The optical amplifier 52 amplifies the light emitted from the wavelength-swept light source 51. The optical amplifier 52 may, for example, use an EDFA (erbium-doped fiber amplifier) ​​and may be, for example, an optical amplifier dedicated to 1550 nm.

[0072] The isolator 53 is an optical element that transmits incident light in one direction and may be placed immediately after the wavelength-swept light source 51 to prevent the effects of noise generated by reflected light.

[0073] In this manner, the light emitted from the wavelength-swept light source 51 is amplified by the optical amplifier 52 and then split into a main interferometer and a secondary interferometer by the optical coupler 54 via the isolator 53. For example, the optical coupler 54 may be configured to split the light into the main interferometer and the secondary interferometer in a ratio of 90:10 to 99:1.

[0074] The light that has been split to the main interferometer is further split by the first-stage optical coupler 54a into two directions: one towards the sensor head 20 and the other towards the second-stage optical coupler 54b.

[0075] The light, branched towards the sensor head 20 by the first-stage optical coupler 54a, passes through the collimating lens 22a and objective lens 21 from the tip of the optical fiber in the sensor head 20 and is irradiated onto the object T to be measured. The tip (end face) of the optical fiber then becomes a reference surface, and the light reflected from this reference surface interferes with the light reflected from the object T to be measured, generating interference light, which returns to the first-stage optical coupler 54a, and is then received by the photodetector 56a and converted into an electrical signal.

[0076] The light branched by the first-stage optical coupler 54a toward the second-stage optical coupler 54b proceeds to the second-stage optical coupler 54b via the isolator 53a, and is further branched by the second-stage optical coupler 54b toward the sensor head 20 and the third-stage optical coupler 54c. The light branched from the optical coupler 54b toward the sensor head 20, similar to the first stage, passes from the tip of the optical fiber through the collimating lens 22b and the objective lens 21 at the sensor head 20 and is irradiated onto the object to be measured T. The tip (end face) of the optical fiber then becomes a reference surface, and the light reflected from this reference surface interferes with the light reflected from the object to be measured T, generating interference light which returns to the second-stage optical coupler 54b, and is branched by the optical coupler 54b toward the isolator 53a and the photodetector 56b, respectively. Light branched from the optical coupler 54b toward the photodetector 56b is received by the photodetector 56b and converted into an electrical signal. On the other hand, the isolator 53a transmits light from the preceding optical coupler 54a to the subsequent optical coupler 54b, and blocks light from the subsequent optical coupler 54b to the preceding optical coupler 54a. Therefore, light branched from the optical coupler 54b toward the isolator 53a is blocked.

[0077] The light branched by the second-stage optical coupler 54b toward the third-stage optical coupler 54c passes through the isolator 53b and goes to the third-stage optical coupler 54c, where it is further branched toward the sensor head 20 and the attenuator 55. The light branched from the optical coupler 54c toward the sensor head 20 passes through the collimating lens 22c and the objective lens 21 from the tip of the optical fiber in the sensor head 20, similar to the first and second stages, and is irradiated onto the object to be measured T. The tip (end face) of the optical fiber then becomes a reference surface, and the light reflected from this reference surface interferes with the light reflected from the object to be measured T, generating interference light which returns to the third-stage optical coupler 54c, where it is branched toward the isolator 53b and the photodetector 56c, respectively. Light branched from the optical coupler 54c towards the photodetector 56c is received by the photodetector 56c and converted into an electrical signal. On the other hand, the isolator 53b transmits light from the preceding optical coupler 54b to the subsequent optical coupler 54c, and blocks light from the subsequent optical coupler 54c to the preceding optical coupler 54b. Therefore, light branched from the optical coupler 54c towards the isolator 53b is blocked.

[0078] Furthermore, the light that is branched away from the sensor head 20 by the third-stage optical coupler 54c is not used to measure the object T, so it is preferable to attenuate it by an attenuator 55, such as a terminator, so that it does not reflect back.

[0079] Thus, the main interferometer has three optical paths (3 channels), each with an optical path length difference equal to twice the distance (round trip) from the tip (end face) of the optical fiber of the sensor head 20 to the object T being measured, and generates three interference beams corresponding to the optical path length difference.

[0080] As described above, the light-receiving elements 56a to 56c receive interference light from the main interferometer and generate an electrical signal corresponding to the amount of light received.

[0081] The amplification circuits 57a to 57c each amplify the electrical signals output from the photodetectors 56a to 56c.

[0082] The AD conversion units 58a to 58c each receive the electrical signals amplified by the amplification circuits 57a to 57c and convert the analog signals into digital signals (AD conversion). Here, the AD conversion units 58a to 58c perform AD conversion based on the correction signals from the correction signal generation unit 61 in the sub-interferometer.

[0083] In the secondary interferometer, in order to correct the wavelength nonlinearity during the sweep of the wavelength-swept light source 51, the interferometer acquires the interference signal and generates a correction signal called a K-clock.

[0084] Specifically, the light branched to the sub-interferometer by the optical coupler 54 is further branched by the optical coupler 54d. Here, the optical paths of each branched light are configured to have a difference in optical path length, for example, by using optical fibers of different lengths between the optical coupler 54d and the optical coupler 54e, and interference light corresponding to this difference in optical path length is output from the optical coupler 54e. The balance detector 60 then receives the interference light from the optical coupler 54e, removes noise by taking the difference between it and a signal with the opposite phase, and amplifies the optical signal to convert it into an electrical signal.

[0085] Furthermore, both the optical coupler 54d and the optical coupler 54e should split the light in a 50:50 ratio.

[0086] The correction signal generation unit 61, based on the electrical signal from the balance detector 60, grasps the nonlinearity of the wavelength during the sweep of the wavelength-swept light source 51, generates a K clock corresponding to the nonlinearity, and outputs it to the AD conversion units 58a to 58c.

[0087] Due to the nonlinearity of the wavelength during the sweep of the wavelength-swept light source 51, the intervals between the waves of the analog signals input to the AD conversion units 58a to 58c in the main interferometer are not equal. In the AD conversion units 58a to 58c, the sampling time is corrected based on the K clock described above to make the intervals between waves equal, and then AD conversion (sampling) is performed.

[0088] Furthermore, as mentioned above, the K clock is a correction signal used to sample 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 may be made longer than the optical path length difference between the tip (end face) of the optical fiber and the object T being measured in the main interferometer, or the frequency may be multiplied (for example, by 8 times) in the correction signal generation unit 61 to increase the frequency.

[0089] The processing unit 59 acquires digital signals that have been AD converted while nonlinearity is corrected by the AD conversion units 58a to 58c, and calculates the displacement of the object T (distance to the object T) based on these digital signals. Specifically, the processing unit 59 calculates the distance by frequency converting the digital signals using the Fast Fourier Transform (FFT) and analyzing them. The detailed processing in the processing unit 59 will be described later.

[0090] Furthermore, since high-speed processing is required in the processing unit 59, it is often implemented using an integrated circuit such as an FPGA (field-programmable gate array).

[0091] Furthermore, in this system, the main interferometer is provided with three optical paths, and the sensor head 20 illuminates the object T to be measured from each optical path with measurement light. Based on the interference light (reflected light) obtained from each path, the distance to the object T is measured (multi-channel). The number of channels in the main interferometer is not limited to three; it may be one or two, or four or more.

[0092] Figure 5B is a diagram illustrating another principle by which an object T is measured by the displacement sensor 10 according to the present disclosure. As shown in Figure 5B, the displacement sensor 10 comprises 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-swept 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 photodetectors (e.g., photodetectors (PDs)) 56a to 56c, a plurality of amplification 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 generation unit 61. The displacement sensor 10 shown in Figure 5B differs from the configuration of the displacement sensor 10 shown in Figure 5A, mainly in that it is equipped with optical couplers 54f to 54j. The principle of this different configuration will be explained in detail, with comparison to Figure 5A.

[0093] Light emitted from the wavelength-swept light source 51 is amplified by the optical amplifier 52 and split via the isolator 53 to the main interferometer side and the sub-interferometer side by the optical coupler 54. The light split to the main interferometer side is further split into measurement light and reference light by the optical coupler 54f.

[0094] As explained in Figure 5A, the measurement light passes through the collimating lens 22a and the objective lens 21 via the first-stage optical coupler 54a and is irradiated onto the object to be measured T, where it is reflected. In Figure 5A, the tip (end face) of the optical fiber is used as a reference surface, and the light reflected from this reference surface interferes with the light reflected from the object to be measured T, generating interference light. However, in Figure 5B, there is no reference surface from which light is reflected. That is, in Figure 5B, as in Figure 5A, no light is reflected from the reference surface, so the measurement light reflected from the object to be measured T returns to the first-stage optical coupler 54a.

[0095] Similarly, light branched from the first optical coupler 54a towards the second optical coupler 54b passes through the collimating lens 22b and objective lens 21 by the second optical coupler 54b and is irradiated onto the object to be measured T, which is reflected back to the second optical coupler 54b. Light branched from the second optical coupler 54b towards the third optical coupler 54c passes through the collimating lens 22c and objective lens 21 by the third optical coupler 54c and is irradiated onto the object to be measured T, which is reflected back to the third optical coupler 54c.

[0096] Meanwhile, the reference light branched by optical coupler 54f is further branched by optical coupler 54g to optical couplers 54h, 54i, and 54j.

[0097] In the optical coupler 54h, the measurement light reflected from the object T to be measured, 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 photodetector 56a and converted into an electrical signal. In other words, the optical coupler 54f splits the measurement light into a measurement light and a reference light, and interference light is generated according to the difference in optical path length between the optical path of the measurement light (the optical path from the optical coupler 54f, through the optical coupler 54a, collimating lens 22a, and objective lens 21, reflected from the object T to be measured, and reaching the optical coupler 54h) and the optical path of the reference light (the optical path from the optical coupler 54f, through the optical coupler 54g, and reaching the optical coupler 54h), and this interference light is received by the photodetector 56a and converted into an electrical signal.

[0098] Similarly, in the optical coupler 54i, interference light is generated according to the difference in optical path length between the optical path of the measurement light (the optical path from optical coupler 54f, through optical couplers 54a, 54b, collimating lens 22b, and objective lens 21, reflected by the object T to be measured, and reaching optical coupler 54i) and the optical path of the reference light (the optical path from optical coupler 54f, through optical coupler 54g, and reaching optical coupler 54i). This interference light is received by the photodetector 56b and converted into an electrical signal.

[0099] In the optical coupler 54j, interference light is generated according to the difference in optical path length between the optical path of the measurement light (the optical path from optical coupler 54f, through optical couplers 54a, 54b, 54c, collimating lens 22c, and objective lens 21, reflected by the object T to be measured, and reaching optical coupler 54j) and the optical path of the reference light (the optical path from optical coupler 54f, through optical coupler 54g, and reaching optical coupler 54j). This interference light is received by the photodetector 56c and converted into an electrical signal. Note that the photodetectors 56a to 56c may be, for example, balanced photodetectors.

[0100] Thus, the main interferometer has three optical paths (3 channels), and generates three interference beams corresponding to the difference in optical path length between the measurement light reflected by the object T being measured and input to optical couplers 54h, 54i, and 54j, and the reference light input to optical couplers 54h, 54i, and 54j, respectively, via optical couplers 54f and 54g.

[0101] Furthermore, the difference in optical path length between the measurement light and the reference light may be set differently for each of the three channels, for example, by setting the optical path lengths between optical coupler 54g and each of the optical couplers 54h, 54i, and 54j to be different.

[0102] Then, based on the interference light obtained from each source, the distance to the object T is measured (multi-channel).

[0103] [Sensor head structure] Here, we will describe the structure of the sensor head used in the displacement sensor 10. Figure 6A is a perspective view showing the schematic configuration of the sensor head 20, and Figure 6B is a schematic diagram showing the internal structure of the sensor head.

[0104] As shown in Figure 6A, the sensor head 20 has an objective lens 21 and a collimating lens housed in a lens holder 23. For example, the size of the lens holder 23 is such that the length of one side surrounding the objective lens 21 is about 20 mm, and the length in the optical axis direction is about 40 mm.

[0105] As shown in Figure 6B, the lens holder 23 houses one objective lens 21 and three collimating lenses 22a to 22c. Light from the optical fiber is guided through the optical fiber array 24 to the three collimating lenses 22a to 22c, and the light that has passed through the three collimating lenses 22a to 22c is then irradiated onto the object to be measured T through the objective lens 21.

[0106] Thus, these optical fibers, collimating lenses 22a to 22c, and optical fiber array 24 are held together with the objective lens 21 by the lens holder 23 to constitute the sensor head 20.

[0107] Furthermore, the lens holder 23 constituting the sensor head 20 may be made of a metal (for example, A2017) that is high-strength and can be machined with high precision.

[0108] Figure 7 is a block diagram illustrating signal processing in the controller 30. As shown in Figure 7, the controller 30 comprises a plurality of photodetectors 71a to 71e, a plurality of amplification circuits 72a to 72c, a plurality of AD conversion units 74a to 74c, a processing unit 75, a differential amplification circuit 76, and a correction signal generation unit 77.

[0109] As shown in Figure 5A, the controller 30 splits the light emitted from the wavelength-swept light source 51 into a main interferometer and a sub-interferometer using an optical coupler 54, and calculates the distance to the object T to be measured by processing the main and sub-interferometer signals obtained from each.

[0110] Multiple photodetectors 71a to 71c correspond to the photodetectors 56a to 56c shown in Figure 5A, and each receives the main interference signal from the main interferometer and outputs it as a current signal to the amplification circuits 72a to 72c, respectively.

[0111] Multiple amplification circuits 72a to 72c convert current signals into voltage signals (IV conversion) and amplify them.

[0112] Multiple AD conversion units 74a to 74c correspond to the AD conversion units 58a to 58c shown in Figure 5A, and convert voltage signals into digital signals (AD conversion) based on the K clock from the correction signal generation unit 77, which will be described later.

[0113] The processing unit 75 corresponds to the processing unit 59 shown in Figure 5A. It 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 object T to be measured.

[0114] Multiple photodetectors 71d to 71e and a differential amplifier circuit 76 correspond to the balanced detector 60 shown in Figure 5A. Each receives interference light from the sub-interferometer, one outputs an interference signal with inverted phase, and the interference signal is amplified and converted into a voltage signal while removing noise by taking the difference between the two signals.

[0115] The correction signal generation unit 77 corresponds to the correction signal generation unit 61 shown in Figure 5A. It binarizes the voltage signal using a comparator, generates a K-clock, and outputs it to the AD conversion units 74a to 74c. Since the K-clock needs to be generated at a higher frequency than the analog signal of the main interferometer, the frequency may be multiplied (for example, by 8 times) in the correction signal generation unit 77 to increase its frequency.

[0116] Figure 8 is a flowchart showing a method for calculating the distance to the object T to be measured, which is performed by the processing unit 59 in the controller 30. As shown in Figure 8, the method includes steps S31 to S34.

[0117] In step S31, the processing unit 59 uses the following FFT to frequency-convert the waveform signal (voltage vs time) into a spectrum (voltage vs frequency). Figure 9A shows how the waveform signal (voltage vs time) is frequency-converted into a spectrum (voltage vs frequency).

number

[0118] In step S32, the processing unit 59 converts the spectrum (voltage vs frequency) to a distance spectrum (voltage vs distance). Figure 9B shows how the spectrum (voltage vs frequency) is converted to a distance spectrum (voltage vs distance).

[0119] In step S33, the processing unit 59 calculates the distance value corresponding to the peak based on the spectrum (voltage vs distance). Figure 9C shows how peaks are detected based on the spectrum (voltage vs distance) and the corresponding distance values ​​are calculated. As shown in Figure 9C, in this case, peaks are detected in each of the three channels based on the spectrum (voltage vs distance), and the distance value corresponding to each peak is calculated.

[0120] In step S34, the processing unit 59 averages the distance values ​​calculated in step S33. Specifically, in step S33, the processing unit 59 detects peaks in each of the three channels based on the spectrum (voltage vs distance) and calculates the corresponding distance values. It then averages these values ​​and outputs the averaged result as the distance to the object T to be measured.

[0121] In step S34, the processing unit 59 prefers to average the distance values ​​calculated in step S33, specifically those with an SNR equal to or greater than a threshold. For example, if a peak is detected in any of the three channels based on its spectrum (voltage vs distance), but the SNR is below a threshold, the distance value calculated based on that spectrum is deemed unreliable and will not be used.

[0122] Next, the present disclosure will be described in detail as a specific embodiment, focusing on its more distinctive configuration, function, and properties. The optical interferometry distance measuring sensor shown below corresponds to the displacement sensor 10 described using Figures 1 to 9, and all or part of the basic configuration, function, and properties included in the optical interferometry distance measuring sensor are common to the configuration, function, and properties included in the displacement sensor 10 described using Figures 1 to 9.

[0123] <First Embodiment> [Configuration of an optical interferometry distance measuring sensor] Figure 10 is a schematic diagram showing the configuration of an optical interferometry distance measuring sensor 100 according to the first embodiment of the present invention. As shown in Figure 10, the optical interferometry distance measuring sensor 100 comprises a wavelength sweep light source 110, an optical branching unit 120, an interferometer 130, a light receiving unit 140, a processing unit 150, a discrimination means 160, and a setting means 170. The interferometer 130 includes a sensor head 131 having an objective lens 132, and the light receiving unit 140 includes a light receiving circuit 141 including a light receiving element and an AD conversion unit 142.

[0124] The wavelength-swept light source 110, the optical branching unit 120, the light receiving unit 140, and the processing unit 150 are included in the controller 101. The discrimination means 160 and the setting means 170 may be included as functions performed by the processing unit 150, or they may be functions performed by a separate control unit or the like.

[0125] The wavelength-swept light source 110 is connected to the optical branching section 120 either directly or indirectly via other components (such as the optical amplifier 52, isolator 53, and optical coupler 54), and emits light while continuously changing its wavelength. In other words, the light emitted from the wavelength-swept light source 110 has a continuously changing wavelength.

[0126] Light emitted from the wavelength-swept light source 110 is supplied to the interferometer 130 via the optical branching unit 120 and the optical fiber.

[0127] The optical branching section 120 is composed of, for example, an optical coupler or a circulator, and supplies light emitted from the wavelength-swept light source 110 to the interferometer 130, and further guides the reflected light from the interferometer 130 to the light receiving section 140. Furthermore, if a 2x2 optical coupler or the like is used in the optical branching section 120, an attenuator or the like may be provided to reduce the amount of reflected light to the optical coupler by attenuating the light branched to the other side.

[0128] The interferometer 130 includes a sensor head 131 having an objective lens 132. Light supplied to the interferometer 130 is input to the sensor head 131 via an optical fiber. A portion of the light input to the sensor head 131 is irradiated onto the object to be measured T via the objective lens 132 as measurement light and reflected by the object to be measured T. The measurement light reflected by the object to be measured T is then focused by the objective lens 132 of the sensor head 131 and input to the sensor head 131. Another portion of the light input to the sensor head 131 is reflected as reference light by a reference surface provided at the end of the optical fiber. The measurement light and the reference light interfere with each other, generating interference light corresponding to the difference in optical path lengths between the measurement light and the reference light, and this interference light is output from the interferometer 130.

[0129] The sensor head 131 may have a collimating lens positioned between the tip of the optical fiber and the objective lens 132, or it may have a collimating lens instead of the objective lens 132.

[0130] The interfering light output from the interferometer 130 is received by the light receiving unit 140 via the optical branching unit 120 and converted into an electrical signal. Specifically, the light receiving unit 140 has a light receiving circuit 141 including a light receiving element and an AD conversion unit 142. The light receiving circuit 141 includes a light receiving element, such as a photodetector, and receives the light output from the optical branching unit 120 and converts it into an electrical signal according to the amount of light received. The AD conversion unit 142 converts the electrical signal from an analog signal to a digital signal.

[0131] The processing unit 150 calculates the distance from the sensor head 131 to the object T based on the digital signal converted by the light receiving unit 140. For example, the processing unit 150 is a processor implemented with an integrated circuit such as an FPGA, which performs frequency conversion on each input digital signal using FFT and calculates the distance to the object T based on that.

[0132] The distance from the sensor head 131 to the object T is typically the distance from the tip of the sensor head 131 to the object T, and the processing unit 150 calculates this distance, but is not limited to this. For example, the processing unit 150 may calculate the distance from the sensor head 131 to the object T as the distance from the tip of the optical fiber connected to the sensor head 131 to the object T, the distance from the objective lens 132 placed on the sensor head 131 to the object T, or the distance from a preset reference position inside the sensor head 131 to the object T.

[0133] Here, we will explain the measurement distance to the object T, the type of sensor head 131, and the circuit bandwidth in the processing unit 150.

[0134] Figure 11 shows a specific example illustrating the relationship between the measurement distance to the object T, the type of sensor head 131, and the circuit bandwidth in the processing unit 150. As shown in Figure 11(A), when the measurement distance to the object T is short, a short-range type sensor head 131a with an appropriate objective lens 132a based on the focal length to the object T is used. On the other hand, as shown in Figure 11(B), when the measurement distance to the object T is long, a long-range type sensor head 131b with an appropriate objective lens 132b based on the focal length to the object T is used.

[0135] In Figure 11(A), the controller 101 detects a signal peak in the processing unit 150 based on the interference light received by the light receiving unit 140. The processing unit 150 calculates the distance from the sensor head 131a to the object T based on the frequency of the signal peak. However, in order for the processing unit 150 to properly calculate the distance to the object T, it is necessary to set the measurement conditions in the processing unit 150 so that the frequency of the signal peak based on the interference light received by the light receiving unit 140 falls within the circuit bandwidth of the light receiving unit 140. In other words, the measurement conditions corresponding to the short-range type sensor head 131a are set appropriately.

[0136] On the other hand, in Figure 11(B), when the measurement distance to the object T is long and a long-range type sensor head 131b is used, the processing unit 150 is expected to detect the frequency of the signal peak based on the interference light received by the light receiving unit 140 in the high-frequency band. If the measurement conditions corresponding to the short-range type described above are set, the frequency of the signal peak based on the interference light received by the light receiving unit 140 cannot be detected, and the processing unit 150 may not be able to properly calculate the distance from the sensor head 131b to the object T. In other words, the processing unit 150 needs to set the measurement conditions to correspond to the long-range type so that the frequency of the signal peak based on the interference light received by the light receiving unit 140 falls within the circuit bandwidth of the light receiving unit 140.

[0137] In other words, the system determines whether the sensor head 131 is a short-range type sensor head 131a or a long-range type sensor head 131b, and sets the measurement conditions corresponding to the determined sensor head type.

[0138] [Regarding sensor head type identification] The discrimination means 160 determines the type of sensor head 131 based on the beat signal generated by the interferometer 130.

[0139] Figure 12 is a schematic diagram showing a specific example of a sensor head 131 configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b. As shown in Figure 12(A), a portion of the light input to the sensor head 131a via the optical fiber is irradiated onto the object to be measured T as measurement light and reflected by the object to be measured T. Another portion of the light input to the sensor head 131a is reflected as reference light by a reference surface 133a provided at the tip of the optical fiber. Interference light is generated based on the measurement light and the reference light, and the distance from the sensor head 131a to the object to be measured T is detected as a signal peak.

[0140] Furthermore, another portion of the light input to the sensor head 131a via the optical fiber is reflected by the reflective surface 134a formed on the objective lens 132a. Based on this reflected light and the reference light described above, a beat signal (interference light) is generated, and the position Lp of the objective lens 132a (specifically, the reflective surface 134a) within the sensor head 131a (specifically, on the side of the reference surface 133a from the tip position LH of the sensor head 131a) is detected as a signal peak.

[0141] The reflective surface 134a formed on the objective lens 132a may be formed on the front surface or on the back surface of the objective lens 132a. Furthermore, the reflective surface 134a may be formed by applying a partial reflection coating to the objective lens 132a, or by utilizing Fresnel reflection with a very low reflectivity (approximately 5% or less).

[0142] Similarly, in Figure 12(B), a reflective surface 134b is formed on the objective lens 132b within the sensor head 131b (specifically, on the side of the reference surface 133b from the tip position LH of the sensor head 131b), and another portion of the light input to the sensor head 131b via the optical fiber is reflected by the reflective surface 134b formed on the objective lens 132b. A beat signal (interference light) is then generated based on this reflected light and the reference light described above, and the position Lp of the objective lens 132b (specifically, the reflective surface 134b) within the sensor head 131b is detected as a signal peak.

[0143] In this way, a beat signal is generated by the interferometer 130 including the sensor head 131a or sensor head 131b, and this beat signal is received by the light receiving unit 140 to detect the signal peak as shown in Figures 12(A) and 12(B).

[0144] The discrimination means 160 can determine the type of sensor head 131 according to the peak of the beat signal, for example, by arranging the objective lens 132a, which is located in the short-range type sensor head 131a, and the objective lens 132b, which is located in the long-range type sensor head 131b, at different positions.

[0145] [Regarding measurement conditions corresponding to sensor head types] The setting means 170 sets measurement conditions corresponding to the type of sensor head 131 determined by the discrimination means 160. Returning to Figure 11, as shown in Figure 11(B), the processing unit 150 adjusts the sweep ratio of the wavelength-swept light source 110 as a measurement condition to be set so that the frequency of the signal peak based on the interference light received by the light-receiving unit 140 is in the high-frequency band and falls within the circuit band of the light-receiving unit 140.

[0146] Here, the sweep ratio is expressed as the frequency sweep width per unit of sweep time, and is calculated based on the frequency sweep width and sweep time in the FMCW (Frequency-Modulated Continuous Wave) method using the formula α = δf / T (δf: frequency sweep width, T: sweep time). Coherent FMCW (Frequency-Modulated Continuous Wave) will be explained in detail below.

[0147] Figure 13 is a diagram illustrating coherent FMCW. As described above, light is projected from the wavelength-swept light source 110 while continuously changing the wavelength (frequency), and interference light is generated based on the difference in optical path length between the measurement light that illuminates the object to be measured T and is reflected, and the reference light that is reflected by the reference surface, which is the tip of the optical fiber.

[0148] As shown in Figure 13, interference occurs when the light emitted from the wavelength-swept light source 110 is delayed by the difference in optical path length from the reference light. This interference is then received by the light-receiving unit 140 as a beat signal (interference light) having a beat frequency, which is the difference in frequency between the measurement light and the reference light. The beat frequency fb is calculated as fb = δf / T·2Ln / c (δf: frequency sweep width, T: sweep time, L: distance from the tip of the optical fiber (reference plane) to the object T to be measured, n: refractive index in the optical path difference, c: speed of light).

[0149] Returning to Figure 11, as shown in Figure 11(B), the measurement conditions set in the processing unit 150 should be adjusted to reduce the sweep ratio α(δf / T) so that the frequency of the signal peak (beat frequency) based on the interference light received by the light receiving unit 140 falls within the circuit bandwidth of the light receiving unit 140.

[0150] [Method for setting measurement conditions corresponding to the type of sensor head] Next, we will specifically explain the process flow for setting measurement conditions corresponding to the type of sensor head 131.

[0151] Figure 14 is a flowchart showing the processing flow of the measurement condition setting method M100, which determines the type of sensor head 131 and sets measurement conditions corresponding to the determined type of sensor head 131. As shown in Figure 14, the measurement condition setting method M100 includes steps S110 to S150, each of which is performed by the processor included in the optical interferometry distance measuring sensor 100.

[0152] In step S110, the discrimination means 160 detects a signal peak based on interference light received by the light receiving unit 140 within the range up to the tip position LH of the sensor head.

[0153] In step S120, the discrimination means 160 calculates the distance Lp corresponding to the signal peak detected in step S110.

[0154] In step S130, the discrimination means 160 determines whether the sensor head 131a is set as a short-range type or the sensor head 131b is set as a long-range type, based on the distance (position) Lp calculated in step S120.

[0155] For example, in the short-range type sensor head 131a, the objective lens 132a (reflective surface 134a) is positioned in advance so that Lp = L1, and in the long-range type sensor head 131b, the objective lens 132b (reflective surface 134b) is positioned in advance so that Lp = L2. Here, the distance Lp calculated in step S120 is compared with |Lp-L1| and |Lp-L2| to determine whether Lp is closer to (corresponds to) L1 or L2.

[0156] If it is determined in step S130 that the distance Lp corresponds to L1 (Yes in step S130), the discrimination means 160 determines that the sensor head 131 being used is a short-range type sensor head 131a. Then, in step S140, the setting means 170 sets the measurement conditions corresponding to the short-range type sensor head 131a. Specifically, the setting means 170 sets the sweep ratio α1 of the wavelength-swept light source 110 as the measurement condition corresponding to the short-range type sensor head 131a.

[0157] On the other hand, if it is determined in step S130 that the distance Lp corresponds to L2 (No in step S130), the discrimination means 160 determines that the sensor head 131 being used is a long-range type sensor head 131b. Then, in step S150, the setting means 170 sets the measurement conditions corresponding to the long-range type sensor head 131b. Specifically, the setting means 170 sets the sweep ratio α2 of the wavelength-swept light source 110 as the measurement condition corresponding to the long-range type sensor head 131b.

[0158] The measurement condition setting method M100 may be executed at the time when setting the measurement conditions when measuring the object T, for example, before the start of measurement, or it may be executed each time the object T is measured.

[0159] As described above, according to the optical interferometry distance measuring sensor 100 of the first embodiment of the present invention, the discrimination means 160 determines whether the sensor head 131 is a short-range type or a long-range type based on the beat signal generated by the interferometer 130. The setting means 170 then adjusts the sweep ratio as a measurement condition corresponding to the type of sensor head 131 determined by the discrimination means 160. This makes it possible to set appropriate measurement conditions according to the measurement distance to the object T, and to measure the measurement distance to the object T appropriately. For the user, the task of checking the type of sensor head 131 and manually setting the corresponding measurement conditions each time is reduced.

[0160] In the sensor heads 131a and 131b described using Figure 12, a collimating lens was positioned between the tip of the optical fiber and the objective lenses 132a and 132b. As a result, the incident light on the objective lenses 132a and 132b is collimated light, providing greater flexibility in the position of the reflective surfaces 134a and 134b on the objective lenses 132a and 132b.

[0161] Furthermore, the short-range sensor head 131a and the long-range sensor head 131b are not limited to the configuration shown in Figure 12, and other configurations are also acceptable as long as the type of sensor head 131 can be determined based on the beat signal generated by the interferometer 130. Examples of configurations that can determine the type of sensor head 131 are given below.

[0162] [Specific examples of how the type of sensor head 131 can be identified] (Specific example 1) Figure 15 is a schematic diagram showing a specific example of a sensor head 131 that is configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b by arranging a collimating lens. As shown in Figure 15, the short-range type sensor head 131a and the long-range type sensor head 131b are equipped with collimating lenses 135a and 135b, respectively, without an objective lens.

[0163] Reflective surfaces 136a and 136b are formed on parts of the collimating lenses 135a and 135b, respectively, which reflect a portion of the light input to the sensor heads 131a and 131b via optical fibers.

[0164] Furthermore, by arranging the collimating lens 135a, which is located in the short-range type sensor head 131a, and the collimating lens 135b, which is located in the long-range type sensor head 131b, in different positions, the discrimination means 160 can determine the type of sensor head 131 according to the peak of the beat signal.

[0165] As illustrated in Figure 15, the sensor heads 131a and 131b have a simple configuration without an objective lens, making it easy to detect the peak of the beat signal.

[0166] (Specific example 2) Figure 16 is a schematic diagram showing a specific example of a sensor head 131 that is configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b by forming a reflective surface on the structural components inside the sensor head 131. As shown in Figure 16, predetermined components 137a and 137b are arranged inside the housings of the short-range type sensor head 131a and the long-range type sensor head 131b, respectively.

[0167] The specified components 137a and 137b are formed to reflect a portion of the light input to the sensor heads 131a and 131b via optical fibers, respectively, inside the housings of the short-range type sensor head 131a and the long-range type sensor head 131b.

[0168] Furthermore, by arranging a predetermined component 137a, which is located inside the short-range type sensor head 131a, and a predetermined component 137b, which is located inside the long-range type sensor head 131b, in different positions, the discrimination means 160 can determine the type of sensor head 131 according to the peak of the beat signal.

[0169] In the sensor heads 131a and 131b described with reference to Figure 16, there is no need to form reflective surfaces on the collimating lens or objective lens. By simply arranging predetermined components 137a and 137b to reflect a portion of the light input to the sensor heads 131a and 131b, the peak of the beat signal can be easily detected.

[0170] The specified components 137a and 137b may utilize parts of the components that make up the short-range type sensor head 131a and the long-range type sensor head 131b, or they may be formed separately as components for generating the peak of the beat signal.

[0171] (Specific example 3) Figure 17A is a schematic diagram showing a specific example of how the type of sensor head 131 can be determined by forming a reflective surface in the optical fiber. As shown in Figure 17A, the reflective surface 138 is formed inside the optical fiber that supplies light to the sensor head 131, rather than inside the sensor head 131. Specifically, the reflective surface 138 is preferably formed by applying a partial reflective coating to the connecting portion of the optical fiber.

[0172] For example, when using a short-range type sensor head 131a or a long-range type sensor head 131b, if the reflective surfaces 138 are formed at different positions in the connected optical fiber, the discrimination means 160 can determine the type of sensor head 131 according to the peak of the beat signal.

[0173] For example, in the case of a Fizeau interferometer, the tip (end face) of the optical fiber is considered to be the position with zero path difference. Therefore, the peak of the beat signal will appear folded back from this position with zero path difference towards the tip of the sensor head 131.

[0174] Figure 17B is a schematic diagram illustrating a specific example of how the type of sensor head 131 can be determined by forming a reflective surface on the tip (end face) of the optical fiber on the controller 101 side. As shown in Figure 17B, the reflective surface 139 is formed not inside the sensor head 131, but on the tip (end face) of the optical fiber supplying light to the sensor head 131 on the controller 101 side. Specifically, the reflective surface 139 is preferably formed by applying a partial reflective coating to the tip (end face) of the optical fiber on the controller 101 side.

[0175] For example, in the case of a Fizeau interferometer, the tip (end face) of the optical fiber is considered to be the position with zero path difference. Therefore, the peak of the beat signal will appear folded back from that position with zero path difference towards the tip of the sensor head 131 by the length of the optical path.

[0176] By utilizing this, when using a short-range type sensor head 131a or a long-range type sensor head 131b, if optical fibers of different lengths (optical path lengths) are used, the discrimination means 160 can determine the type of sensor head 131 according to the peak of the beat signal.

[0177] As described above, a reflective surface is formed inside the sensor head 131, including the collimating lens, objective lens, and other components, as well as inside and on the end face of the optical fiber, to generate a beat signal in the interferometer 130. When using a short-range type sensor head 131a or a long-range type sensor head 131b, if the system is configured to detect different peaks in the beat signal, the discrimination means 160 can determine the type of sensor head 131 according to the peaks in the beat signal.

[0178] Furthermore, when configuring the system to detect different peaks in the beat signal, a combination of the configurations described using Figures 12 and 15-17 may be used. For example, when using a short-range sensor head 131a, a predetermined component 137a is placed inside the sensor head 131a (Figure 16), and when using a long-range sensor head 131b, a reflective surface 138 is formed inside the optical fiber (Figure 17A).

[0179] (Specific example 4) Figure 18 is a schematic diagram showing a specific example of a sensor head 131 configured to distinguish between a short-range type sensor head 131a and a long-range type sensor head 131b based on the number of peaks in the beat signal. As shown in Figure 18, the short-range type sensor head 131a and the long-range type sensor head 131b have different configurations, and the type of sensor head 131 is determined not by the frequency (position, distance) of the peaks in the beat signal generated by the interferometer 130, but by the number of peaks.

[0180] Specifically, as shown in Figure 18(A), the short-range type sensor head 131a has a collimating lens 135a and an objective lens 132a. A portion of the light input to the sensor head 131a via the optical fiber is reflected by the reflective surface 136a formed on the collimating lens 135a and the reflective surface 134a formed on the objective lens 132a. A beat signal (interference light) is then generated based on each of these reflected lights and the reference light reflected by the reference surface 133a provided at the tip of the optical fiber. As a result, within the sensor head 131a (specifically, on the side of the reference surface 133a from the tip position LH of the sensor head 131a), the position Lp1 of the collimating lens 135a (specifically, the reflective surface 136a) and the position Lp2 of the objective lens 132a (specifically, the reflective surface 134a) are detected as signal peaks.

[0181] On the other hand, as shown in Figure 18(B), the long-range type sensor head 131b has a collimating lens 135b and no objective lens. A portion of the light input to the sensor head 131b via the optical fiber is reflected by the reflective surface 136b formed on the collimating lens 135b. A beat signal (interference light) is then generated based on this reflected light and the reference light reflected by the reference surface 133b provided at the tip of the optical fiber. As a result, the position Lp of the collimating lens 135b (specifically, the reflective surface 136b) is detected as a signal peak within the sensor head 131b (specifically, on the side of the reference surface 133b from the tip position LH of the sensor head 131b).

[0182] Thus, the short-range type sensor head 131a has a collimating lens 135a and an objective lens 132a, and the long-range type sensor head 131b has a collimating lens 135b, allowing the discrimination means 160 to determine the type of sensor head 131 according to the number of peaks detected in the beat signal.

[0183] Figure 19 is a flowchart showing the processing flow of the measurement condition setting method M101, which determines the type of sensor head 131 according to the number of peaks detected in the beat signal and sets measurement conditions corresponding to the determined type of sensor head 131. As shown in Figure 19, the measurement condition setting method M101 includes steps S111, S131, S140 and S150, each step being performed by the processor included in the optical interferometry distance measuring sensor 100.

[0184] In step S111, the discrimination means 160 detects a signal peak based on interference light received by the light receiving unit 140 within the range up to the tip position LH of the sensor head. For example, the discrimination means 160 may detect a signal peak whose signal intensity is greater than or equal to a predetermined value.

[0185] In step S131, the discrimination means 160 determines the number of signal peaks detected in step S111.

[0186] For example, in the short-range type sensor head 131a, the collimating lens 135a and objective lens 132a are pre-configured so that the number of signal peaks = 2 (for example, Figure 18(A)), while in the long-range type sensor head 131b, the collimating lens 135b is pre-configured so that the number of signal peaks = 1 (for example, Figure 18(B)).

[0187] The discrimination means 160 then determines whether the number of signal peaks detected in step S111 is 2 or not, and determines whether the sensor head 131a is set as a short-range type or the sensor head 131b is set as a long-range type.

[0188] If it is determined in step S131 that the number of signal peaks is 2 (Yes in step S131), the discrimination means 160 determines that the sensor head 131 being used is a short-range type sensor head 131a. Then, in step S140, the setting means 170 sets the measurement conditions corresponding to the short-range type sensor head 131a. Specifically, the setting means 170 sets the sweep ratio α1 of the wavelength-swept light source 110 as the measurement condition corresponding to the short-range type sensor head 131a.

[0189] On the other hand, if it is determined in step S131 that the number of signal peaks is not 2 (No in step S131), the discrimination means 160 determines that the sensor head 131 being used is a long-range type sensor head 131b. Then, in step S150, the setting means 170 sets the measurement conditions corresponding to the long-range type sensor head 131b. Specifically, the setting means 170 sets the sweep ratio α2 of the wavelength-swept light source 110 as the measurement condition corresponding to the long-range type sensor head 131b.

[0190] In this embodiment, the discrimination means 160 determined whether a short-range type sensor head 131a or a long-range type sensor head 131b was being used. However, it also includes determining whether a sensor head 131 can be switched between short-range and long-range types. For example, even if a sensor head 131 is used that can be switched between short-range and long-range types by changing (arranging, adding, and deleting) the configuration of the collimating lens, objective lens, and predetermined components inside the housing, the discrimination means 160 will determine the sensor head 131.

[0191] <Second Embodiment> Next, in the second embodiment of the present invention, setting means for setting other measurement conditions in place of, or in addition to, the sweep ratio described in the first embodiment will be described. In this embodiment, the same components as those of the optical interferometry distance sensor 100 according to the first embodiment will be denoted by the same reference numerals in the drawings, and detailed explanations will be omitted. The focus will be on components that differ from the first embodiment.

[0192] Figure 20 is a schematic diagram showing the configuration of an optical interferometry distance measuring sensor 200 according to a second embodiment of the present invention. As shown in Figure 20, the optical interferometry distance measuring sensor 200 comprises a wavelength-swept light source 110, an optical branching unit 120, an interferometer 130, a light-receiving unit 140, a processing unit 150, a discrimination means 160, and a setting means 270. The interferometer 130 includes a sensor head 131 having an objective lens 132, and the light-receiving unit 140 includes a light-receiving circuit 141 including a light-receiving element and an AD conversion unit 142. Furthermore, the optical interferometry distance measuring sensor 200 includes an optical branching unit 121 (for example, an optical coupler) that branches the light emitted from the wavelength-swept light source 110 into a main interferometer (interferometer 130) and a sub-interferometer.

[0193] As explained using Figures 5A, 5B, and 7, the secondary interferometer is used to correct the wavelength nonlinearity during the sweep of the wavelength-swept light source 110. The correction signal generation unit 210 generates a correction signal called a K-clock and outputs it to the AD conversion unit 142. In the AD conversion unit 142, the interfering light received from the interferometer 130 is AD converted (sampled) based on the correction signal, thereby correcting the wavelength nonlinearity during the sweep of the wavelength-swept light source 110.

[0194] The processing unit 150 calculates the distance from the sensor head 131 to the object T based on the digital signal converted by the AD conversion unit 142. However, if the number of sampling points during AD conversion by the AD conversion unit 142 is insufficient, the calculation may not be accurate. In other words, in order to accurately calculate the distance to the object T, it is necessary to acquire an appropriate number of sampling points per cycle in the signal converted by the AD conversion unit 142.

[0195] Here, as described in the first embodiment of the present invention, if the measurement distance to the object T is short, the discrimination means 160 determines that a short-range type sensor head 131a is being used, and if the measurement distance to the object T is long, the discrimination means 160 determines that a long-range type sensor head 131b is being used.

[0196] The setting means 270 controls the correction signal generation unit 210 to adjust the degree of frequency multiplication of the correction signal based on the type of sensor head 131 determined by the discrimination means 160. For example, if the discrimination means 160 determines that a short-range type sensor head 131a is being used, the setting means 270 may multiply the frequency of the correction signal by 4, or if the discrimination means 160 determines that a long-range type sensor head 131b is being used, the setting means 270 may multiply the frequency of the correction signal by 8.

[0197] Furthermore, the frequency of the correction signal is not limited to 4x and 8x multiplication; it should be adjusted to a degree of multiplication that allows for the acquisition of an appropriate number of sampling points in the signal converted by the AD conversion unit 142 in order to properly calculate the distance to the object T being measured.

[0198] Furthermore, when adjusting the degree of frequency multiplication of the correction signal, the sweep ratio of the wavelength-swept light source 110 described in the first embodiment of the present invention may be taken into consideration. For example, if the sweep ratio of the wavelength-swept light source 110 is adjusted as a measurement condition set in the processing unit 150 so that the frequency of the signal peak based on the interference light received by the light-receiving unit 140 falls within the circuit band of the light-receiving unit 140, the degree of frequency multiplication of the correction signal may be adjusted accordingly.

[0199] [Method for setting measurement conditions corresponding to the type of sensor head] Next, we will specifically explain the process flow for setting measurement conditions corresponding to the type of sensor head 131.

[0200] Figure 21 is a flowchart showing the processing flow of the measurement condition setting method M200, which determines the type of sensor head 131 and sets measurement conditions corresponding to the determined type of sensor head 131. As shown in Figure 21, the measurement condition setting method M200 includes steps S110 to S130, S240 and S250, each of which is performed by the processor included in the optical interferometry distance measuring sensor 100.

[0201] Steps S110 to S130 are the same as the measurement condition setting method M100 in the first embodiment of the present invention.

[0202] If the discrimination means 160 determines that the sensor head 131 being used is a short-range type sensor head 131a (Yes in step S130), then in step S240, the setting means 270 sets the measurement conditions corresponding to the short-range type sensor head 131a. Specifically, the setting means 270 sets the sweep ratio α1 of the wavelength-swept light source 110 and the frequency multiplier M1 of the correction signal as the measurement conditions corresponding to the short-range type sensor head 131a.

[0203] On the other hand, if the discrimination means 160 determines that the sensor head 131 being used is a long-range type sensor head 131b (No in step S130), then in step S250, the setting means 270 sets the measurement conditions corresponding to the long-range type sensor head 131b. Specifically, the setting means 270 sets the sweep ratio α2 of the wavelength-swept light source 110 and the frequency multiplier M2 of the correction signal as the measurement conditions corresponding to the long-range type sensor head 131b.

[0204] As described above, according to the optical interferometry distance measuring sensor 200 of the second embodiment of the present invention, the discrimination means 160 determines whether the type of sensor head 131 is a short-range type or a long-range type based on the beat signal generated by the interferometer 130. The setting means 270 then adjusts the degree of frequency multiplication of the correction signal in addition to, or instead of, the sweep ratio as a measurement condition corresponding to the type of sensor head 131 determined by the discrimination means 160. This makes it possible to set appropriate measurement conditions according to the measurement distance to the object to be measured T, and to measure the measurement distance to the object to be measured T appropriately. For the user, the work of checking the type of sensor head 131 and manually setting the corresponding measurement conditions each time is reduced.

[0205] [Variations of interferometers] In the embodiments described above, the optical interferometers 100 and 200 used a Fizeau interferometer that generates reference light by using the tip of an optical fiber as a reference plane in the interferometer 130, but the interferometer is not limited to this.

[0206] Figure 22 shows variations of an interferometer that generates interference light using measurement light and reference light. In Figure 22(a), in the optical path branched by the optical branching section 120, interference light is generated based on the difference in optical path length between the reference light, which uses the tip (end face) of the optical fiber as the reference surface, and the measurement light, which is irradiated from the sensor head and reflected by the object T being measured. This is the configuration of the interferometer 130 of the optical interference distance measuring sensors 100 and 200 according to the above-described embodiments (Fizeau interferometer), and the reference surface may be configured to reflect light due to the difference in refractive index between the optical fiber and air (Fresnel reflection). Alternatively, a reflective film may be coated on the tip of the optical fiber, or an anti-reflective coating may be applied to the tip of the optical fiber, and a separate reflective surface such as a lens surface may be provided.

[0207] In Figure 22(b), the optical path branched by the optical branching section 120 forms a measurement optical path Lm that guides measurement light to the object to be measured T, and a reference optical path Lr that guides reference light, with a reference surface placed at the end of the reference optical path Lr (Michelson interferometer). The reference surface may have a reflective coating on the tip of the optical fiber, or an anti-reflective coating may be applied to the tip of the optical fiber and a mirror or the like may be placed separately. In this configuration, interference light is generated by creating a difference in optical path length between the optical path length of the measurement optical path Lm and the optical path length of the reference optical path Lr.

[0208] In Figure 22(c), the optical path branched by the optical branching unit 120 forms a measurement optical path Lm that guides measurement light to the object to be measured T, and a reference optical path Lr that guides reference light, with a balance detector (Mach-Zehnder interferometer) placed in the reference optical path Lr. In this configuration, interference light is generated by creating a difference in optical path length between the measurement optical path Lm and the reference optical path Lr.

[0209] Thus, the interferometer is not limited to the Fizeau-type interferometer described in each embodiment, but may also be a Michelson interferometer or a Mach-Zehnder interferometer, for example. Any interferometer that can generate interference light by setting the difference in optical path length between the measurement light and the reference light may be used, or combinations thereof or other configurations may be used.

[0210] In each embodiment of the present invention, the optical interferometry distance measuring sensors 100 and 200 have been described as single-channel, but the invention is not limited to this. For example, the light emitted from the wavelength-swept light source 110 may be branched using multiple optical couplers or the like to configure a multi-stage optical interferometry distance measuring sensor. The present invention can also be applied to a multi-stage optical interferometry distance measuring sensor.

[0211] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The elements, arrangement, materials, conditions, shapes, and sizes of the embodiments are not limited to those exemplified and can be modified as appropriate. Furthermore, it is possible to partially substitute or combine the configurations shown in different embodiments.

[0212] [Appendix] A light source (110) that projects light while changing its wavelength, An interferometer (130) is provided with light emitted from the aforementioned light source, which is supplied and irradiated onto an object to be measured by a sensor head and reflected, and a reference light that follows at least a partially different optical path from the aforementioned measurement light, which generates interference light. A light receiving unit (140) receives interference light from the interferometer and converts it into an electrical signal, A processing unit (150) that calculates the distance from the sensor head to the object to be measured based on the electrical signal converted by the light receiving unit, A discrimination means (160) for identifying the sensor head based on the beat signal generated by the interferometer, The system includes a setting means (170) for setting measurement conditions corresponding to the sensor head identified by the discrimination means, Optical interferometry distance sensor (100). [Explanation of symbols]

[0213] 1...Sensor system, 10...Displacement sensor, 11...Control equipment, 12...Control signal input sensor, 13...External connection equipment, 20...Sensor head, 21...Objective lens, 22a~22c...Collimating lens, 23...Lens holder, 24...Optical fiber array, 30...Controller, 31...Display unit, 32...Setting unit, 33...External interface (I / F) unit, 34...Optical fiber connection unit, 35...External storage unit, 36...Measurement processing unit, 40...Optical fiber, 51...Wavelength sweep light source, 52...Optical amplifier, 53, 53a~53b...Isolator, 54, 54a~54e...Optical coupler, 55...Attenuator, 56a~56c...Photodetector, 58...AD conversion unit, 59...Processing unit, 60...Balance detector, 61...Correction signal generation unit, 71a~71e...Photodetector, 72a~72 c...Amplifier circuit, 74a~74c...AD conversion unit, 75...Processing unit, 76...Differential amplifier circuit, 77...Correction signal generation unit, 100,200...Optical interferometer, 101...Controller, 110...Wavelength sweep light source, 120,121...Optical branching unit, 130...Interferometer, 131,131a,131b...Sensor head, 132,132a,132b...Objective lens, 133a,133b...Reference lens Illuminating surface, 134a, 134b, 136a, 136b, 138, 139… Reflecting surface, 135a, 135b… Collimating lens, 137a, 137b… Designated component, 140… Light receiving unit, 141… Light receiving circuit, 142… AD conversion unit, 150… Processing unit, 160… Discrimination means, 170, 270… Setting means, 210… Correction signal generation unit, T… Object to be measured, Lm… Measurement optical path, Lr… Reference optical path

Claims

1. A light source that projects light while changing its wavelength, An interferometer that generates interference light based on measurement light, which is supplied with light emitted from the aforementioned light source, irradiated onto an object to be measured by a sensor head and reflected, and reference light, which follows an optical path that is at least partially different from the measurement light. A light receiving unit that receives interference light from the interferometer and converts it into an electrical signal, A processing unit that calculates the distance from the sensor head to the object to be measured based on the electrical signal converted by the light receiving unit, A determination means for determining whether the sensor head is a short-range type or a long-range type based on at least one of the peak frequency and number of peaks of the beat signal generated by the interferometer, The system includes setting means for setting measurement conditions corresponding to the type of sensor head determined by the determination means, The beat signal is generated when a portion of the light emitted from the light source and supplied to the interferometer is reflected by a member having a reflective surface formed in the interferometer. The configuration of the reflective surface differs between the short-range type sensor head and the long-range type sensor head. Optical interferometry distance sensor.

2. The setting means adjusts the sweep ratio, which is expressed as a frequency sweep width per sweep time, for the light emitted from the light source, based on the sensor head determined by the determination means. The optical interferometry distance sensor according to claim 1.

3. The system further includes a correction signal generation unit that generates a correction signal used for sampling when converting the interference light received by the light receiving unit into an electrical signal, The setting means adjusts the degree of frequency multiplication of the correction signal based on the sensor head determined by the determination means. The optical interferometry distance sensor according to claim 1 or 2.

4. The reflective surface is formed inside the sensor head. The optical interferometry distance sensor according to claim 1.

5. The reflective surface is formed on the objective lens included in the sensor head. The optical interferometry distance sensor according to claim 4.

6. The reflective surface is formed on the collimating lens included in the sensor head. The optical interferometry distance sensor according to claim 4 or 5.

7. The reflective surface is formed inside the optical fiber that supplies light emitted from the light source to the sensor head. The optical interferometry distance sensor according to any one of claims 1 to 6.

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