Optical interferometric distance measuring sensor

Abstract

The present invention provides an optical interferometric ranging sensor capable of setting appropriate measurement conditions based on the measurement distance to the object being measured. The optical interferometric ranging sensor (100) includes: a light source (110) that projects light while changing the wavelength; an interferometer (130) that is supplied with light projected from the light source and generates interference light based on a measurement light and a reference light, wherein the measurement light is light that is reflected from the object being measured (T) by a sensing head (131) and the reference light is light that travels along at least a portion of an optical path different from the measurement light; a light receiving unit (140) that receives the interference light from the interferometer and converts it into an electrical signal; a processing unit (150) that calculates the distance from the sensing head to the object being measured based on the electrical signal converted by the light receiving unit; a discrimination unit (160) that discriminates the sensing head based on a beat signal generated by the interferometer; and a setting unit (170) that sets measurement conditions corresponding to the sensing head discriminated by the discrimination unit.

Description

Technical Field

[0001] This invention relates to optical interferometric ranging sensors. Background Technology

[0002] In recent years, optical ranging sensors that measure distances to objects without contact have become increasingly popular. For example, as an optical ranging sensor, there is a known optical interferometric ranging sensor that generates an interference beam based on a reference beam and a measurement beam by means of light projected from a wavelength scanning light source, and measures the distance to the object based on this interference beam.

[0003] In the optical measuring apparatus described in Patent Document 1, a stable measuring result is obtained by coherently interfering the return beam component of the reference beam reflected by multiple fiber end faces with the reflection component of the measuring beam reflected by the surface of the object being measured.

[0004] Patent Document 1: Japanese Patent No. 2686124

[0005] However, in the optical measuring device disclosed in Patent Document 1, it is necessary to set the corresponding sensor head and measurement conditions according to the measurement distance to the object being measured. That is, the following problem exists: a sensor head corresponding to the range of the measurement distance must be installed according to the measurement distance to the object being measured, and the appropriate measurement conditions must be manually set each time. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide an optical interferometric ranging sensor capable of setting appropriate measurement conditions based on the measurement distance to the object being measured.

[0007] One aspect of the present invention relates to an optical interferometric ranging sensor comprising: a light source that projects light while changing its wavelength; an interferometer that is supplied with light projected from the light source and generates interference light based on a measurement light and a reference light, wherein the measurement light is light that is reflected from a measurement object by a sensing head, and the reference light is light that travels along at least a portion of an optical path 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 sensing head to the measurement object based on the electrical signal converted by the light receiving unit; a discrimination unit that discriminates the sensing head based on a beat signal generated by the interferometer; and a setting unit that sets measurement conditions corresponding to the sensing head discriminated by the discrimination unit.

[0008] According to this aspect, the discrimination unit identifies the sensor head based on the beat signal generated by the interferometer, and the setting unit sets the measurement conditions corresponding to the sensor head identified by the discrimination unit. Therefore, appropriate measurement conditions can be set according to the measurement distance to the object being measured, and the distance to the object being measured can be measured appropriately. For users, this reduces the work of confirming the type of sensor head or manually setting the corresponding measurement conditions each time.

[0009] In the above aspects, it is also possible that the setting unit adjusts the scanning ratio, represented by the frequency scanning width per scanning time, for the light projected from the light source based on the sensor head identified by the discrimination unit.

[0010] According to this aspect, the setting unit adjusts the scanning ratio for the light projected from the light source based on the sensing head identified by the discrimination unit. Therefore, the signal peak of the interference light received by the light receiving unit can be appropriately detected in the circuit band processed by the processing unit.

[0011] In the above aspects, it is also possible to further include a correction signal generation unit that generates a correction signal for sampling when the interference light received by the light receiving unit is converted into an electrical signal, and a setting unit adjusts the degree of frequency doubling of the correction signal based on the sensing head identified by the discrimination unit.

[0012] According to this aspect, the setting unit adjusts the degree of frequency harmonication of the correction signal generated by the correction signal generation unit based on the sensor head identified by the discrimination unit. Therefore, the interference light received by the light receiving unit can be sampled appropriately. As a result, the distance to the object being measured can be measured appropriately.

[0013] In the above aspects, the discrimination unit may also discriminate the sensor head based on at least one of the peak frequency and the number of peaks of the beat signal.

[0014] According to this aspect, the identification unit identifies the sensor head based on at least one of the peak frequency and the number of peaks of the beat signal. Therefore, the user does not need to confirm the type of the sensor head and can easily identify it.

[0015] In the above aspects, the beat signal may also be generated by a portion of the light projected from the light source and supplied to the interferometer being reflected in the interferometer by a component having a formed reflective surface.

[0016] According to this aspect, since the beat signal is generated by a portion of the light projected from the light source and supplied to the interferometer being reflected by a component having a formed reflective surface in the interferometer, the user does not need to confirm the type of the sensor head and can easily identify the sensor head.

[0017] Alternatively, the reflective surface may be formed inside the sensor head.

[0018] According to this aspect, since the reflective surface is formed inside the sensor head, it reduces the confirmation and preparation work other than sensor head installation for the user, and makes it easy to identify the sensor head.

[0019] In the above aspects, the reflective surface may also be formed in the objective lens included in the sensor head.

[0020] According to this aspect, since the reflective surface is formed in the objective lens included in the sensor head, no additional components are required, and the sensor head can be easily identified.

[0021] Alternatively, the reflective surface may be formed in the collimating lens included in the sensor head.

[0022] According to this aspect, since the reflective surface is formed in the collimating lens included in the sensor head, no additional components are required, and the sensor head can be easily identified.

[0023] Alternatively, the reflective surface may be formed inside the optical fiber that supplies light projected from the light source to the sensing head.

[0024] According to this aspect, since the reflective surface is formed inside the optical fiber that supplies light projected from the light source to the sensor head, the sensor head can be easily identified even if the reflective surface is not formed in the sensor head.

[0025] Invention Effects

[0026] According to the present invention, an optical interferometric ranging sensor capable of setting appropriate measurement conditions based on the measurement distance to the object being measured can be provided. Attached Figure Description

[0027] Figure 1 This is a schematic diagram showing the outline of the displacement sensor 10 involved in this disclosure.

[0028] Figure 2 This is a flowchart illustrating the process of measuring the object T using the displacement sensor 10 disclosed herein.

[0029] Figure 3 This is a functional block diagram showing the general outline of a sensor system 1 using the displacement sensor 10 disclosed herein.

[0030] Figure 4 This is a flowchart illustrating the process of measuring an object T by using a sensor system 1 with a displacement sensor 10 as disclosed herein.

[0031] Figure 5A This is a diagram illustrating the principle of measuring an object T using the displacement sensor 10 disclosed herein.

[0032] Figure 5B This is a diagram illustrating another principle of measuring an object T using the displacement sensor 10 involved in this disclosure.

[0033] Figure 6AThis is a three-dimensional diagram showing the approximate structure of the sensor head 20.

[0034] Figure 6B This is a schematic diagram showing the internal structure of the sensor head 20.

[0035] Figure 7 This is a block diagram used to illustrate the signal processing in controller 30.

[0036] Figure 8 This is a flowchart illustrating the method executed by the processing unit 59 in the controller 30 to calculate the distance to the object T being measured.

[0037] Figure 9A This is a diagram showing how a waveform signal (voltage vs. time) is converted from frequency to spectrum (voltage vs. frequency).

[0038] Figure 9B This is a diagram illustrating the conversion of the spectrum (voltage vs. frequency) to the spectrum (voltage vs. distance) from distance.

[0039] Figure 9C This is a diagram illustrating the detection of peaks based on the spectrum (voltage vs. distance) and the calculation of their corresponding distance values.

[0040] Figure 10 This is a schematic diagram showing the general structure of the optical interferometric ranging sensor 100 according to the first embodiment of the present invention.

[0041] Figure 11 This is a specific example illustrating the relationship between the measurement distance to the object T, the type of the sensor head 131, and the circuit frequency band in the processing unit 150.

[0042] Figure 12 This is a schematic diagram showing a specific example of a sensor head 131 configured to distinguish between a short-range sensor head 131a and a long-range sensor head 131b.

[0043] Figure 13 This is a diagram used to illustrate coherent FMCW.

[0044] Figure 14 This is a flowchart of the processing flow of a measurement condition setting method M100 that identifies the type of sensor head 131 and sets measurement conditions corresponding to the identified type of sensor head 131.

[0045] Figure 15 This is a schematic diagram illustrating a specific example of a sensor head 131 configured to distinguish between a short-range sensor head 131a and a long-range sensor head 131b by means of a collimating lens.

[0046] Figure 16This is a schematic diagram illustrating a specific example of a sensor head 131 configured to distinguish between a short-range sensor head 131a and a long-range sensor head 131b by forming a reflective surface on a structural component inside the sensor head 131.

[0047] Figure 17A This is a schematic diagram illustrating a specific example of how the type of sensor head 131 can be identified by forming a reflective surface on the optical fiber.

[0048] Figure 17B This is a schematic diagram illustrating a specific example of how the type of sensor head 131 can be identified by forming a reflective surface at the front end (end face) of the optical fiber on the controller 101 side.

[0049] Figure 18 This is a schematic diagram illustrating a specific example of a sensor head 131 configured to distinguish between a short-range sensor head 131a and a long-range sensor head 131b based on the number of peaks in the beat signal.

[0050] Figure 19 This is a flowchart of the measurement condition setting method M101, which identifies the type of sensor head 131 based on the number of peaks detected in the beat signal and sets measurement conditions corresponding to the identified type of sensor head 131.

[0051] Figure 20 This is a schematic diagram showing the general structure of the optical interferometric ranging sensor 200 according to the second embodiment of the present invention.

[0052] Figure 21 This is a flowchart of the measurement condition setting method M200, which identifies the type of sensor head 131 and sets measurement conditions corresponding to the identified type of sensor head 131.

[0053] Figure 22 This is a diagram showing the distortion of an interferometer that uses measuring light and reference light to produce interference light.

[0054] Explanation of reference numerals in the attached figures

[0055] 1…Sensor system, 10…Displacement sensor, 11…Control device, 12…Sensor for control signal input, 13…External connection device, 20…Sensing head, 21…Objective lens, 22a-22c…Collimating lens, 23…Lens holder, 24…Fiber optic array, 30…Controller, 31…Display unit, 32…Setting unit, 33…External interface (I / F) unit, 34…Fiber optic connection unit, 35…External storage unit, 36…Measurement processing unit, 40…Fiber optic cable, 51…Wavelength scanning light source, 52…Optical amplifier, 53, 53a-53b…Isolators, 54, 54a-54e…Optical couplers, 55…Attenuator, 56a-56c…Light receiving element, 58…AD converter, 59…Processing unit, 60…Balance detector, 61…Correction signal generation unit, 71a-71e…Light receiving element, 72a-72c…Amplifier circuit, 74a-74… c…AD conversion unit, 75…processing unit, 76…differential amplifier circuit, 77…correction signal generation unit, 100, 200…optical interferometric ranging sensor, 101…controller, 110…wavelength scanning light source, 120, 121…optical branching unit, 130…interferometer, 131, 131a, 131b…sensor head, 132, 132a, 132b…objective lens, 133a, 133b…reference plane, 134a, 1 34b, 136a, 136b, 138, 139…reflecting surfaces, 135a, 135b…collimating lenses, 137a, 137b…specified components, 140…light-receiving unit, 141…light-receiving circuit, 142…AD conversion unit, 150…processing unit, 160…discrimination unit, 170, 270…setting unit, 210…correction signal generation unit, T…measurement object, Lm…measuring optical path, Lr…reference optical path Detailed Implementation

[0056] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings. It should be noted that the embodiments described below are merely specific examples for implementing the present invention and are not intended to limit the scope of the invention. Furthermore, for ease of understanding, the same reference numerals are sometimes used to denote the same constituent elements in the drawings, and repeated descriptions are omitted.

[0057] [Overview of Displacement Sensors]

[0058] First, a summary of the displacement sensor involved in this disclosure will be given.

[0059] Figure 1 This is a schematic diagram showing the outline of the displacement sensor 10 involved in this disclosure. Figure 1 As shown, the displacement sensor 10 includes a sensing head 20 and a controller 30, and measures the displacement (distance to the object T) of the object being measured.

[0060] The sensor head 20 is connected to the controller 30 via an optical fiber 40, and an objective lens 21 is mounted on the sensor head 20. In addition, the controller 30 includes a display unit 31, a setting unit 32, an external interface (I / F) unit 33, an optical fiber connection unit 34, and an external storage unit 35, and further includes a measurement processing unit 36 ​​inside.

[0061] The sensor head 20 illuminates the object being measured, T, with light output from the controller 30, and receives the reflected light from the object being measured, T. The sensor head 20 has an internal reference surface that is used to reflect the light output from the controller 30 and received via the optical fiber 40 and interfere with the reflected light from the object being measured, T.

[0062] It should be noted that an objective lens 21 is mounted on the sensor head 20, but this objective lens 21 is detachable. The objective lens 21 can be replaced with an objective lens with an appropriate focal length depending on the distance between the sensor head 20 and the object T being measured, or a variable focus objective lens can also be used.

[0063] Furthermore, when setting the sensor head 20, guide light (visible light) can also be irradiated onto the object being measured T, so that the sensor head 20 and / or the object being measured T are properly positioned within the measurement area of ​​the displacement sensor 10.

[0064] Optical fiber 40 is connected to and extends from optical fiber connector 34 disposed on controller 30, connecting controller 30 to sensor head 20. Thus, optical fiber 40 is configured to guide light projected from controller 30 to sensor head 20, and further guide return light from sensor head 20 to controller 30. It should be noted that optical fiber 40 can be detached from sensor head 20 and controller 30, and various optical fibers can be used in terms of length, thickness, and characteristics.

[0065] The display unit 31 is, for example, composed of 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 light received from the return light from the sensor head 20, and the measurement results such as the displacement of the object T (distance to the object T) measured by the displacement sensor 10.

[0066] The setting unit 32 allows users to configure settings for measuring the object T, for example, by operating mechanical buttons or a touch panel. All or some of these settings can be preset or configured from an external connection device (not shown) connected to the external I / F unit 33. Alternatively, the external connection device can be connected via a network in a wired or wireless manner.

[0067] Here, the external I / F unit 33 may be configured with Ethernet (registered trademark), RS232C, or analog output, for example. Alternatively, the external I / F unit 33 may be connected to other connection devices and make the required settings from those external connection devices, or output measurement results measured by the displacement sensor 10 to the external connection devices.

[0068] Alternatively, the controller 30 can retrieve data stored in the external storage unit 35 to make the settings required 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 stores the settings required for measuring the object T in advance.

[0069] The measurement processing unit 36 ​​in the controller 30 includes, for example, a wavelength scanning light source that projects light while continuously changing its wavelength, a light-receiving element that receives the returned light from the sensing head 20 and converts it into an electrical signal, and a signal processing circuit that processes the electrical signal. In the measurement processing unit 36, based on the returned light from the sensing head 20, various processes are performed using a control unit and a storage unit to ultimately calculate the displacement (distance to the measured object T) of the object T. Details of these processes will be described later.

[0070] Figure 2 This is a flowchart illustrating the process of measuring the object T using the displacement sensor 10 disclosed herein. For example... Figure 2 As shown, the process includes steps S11 to S14.

[0071] In step S11, the sensor head 20 is set. For example, a guide light is shone from the sensor head 20 onto the object T to be measured, and the sensor head 20 is set in an appropriate position using the object as a reference.

[0072] Specifically, the amount of light received from the sensor head 20 can be displayed on the display unit 31 in the controller 30. The user can check the amount of light received while adjusting the orientation of the sensor head 20 and its distance (height position) from the object being measured T. Basically, if the light from the sensor head 20 can be shone onto the object being measured T perpendicularly (at an angle closer to perpendicular), the amount of reflected light from the object being measured T will be large, and the amount of light received from the sensor head 20 will also be large.

[0073] Alternatively, the objective lens 21 with an appropriate focal length can be replaced according to the distance between the sensor head 20 and the object T being measured.

[0074] Furthermore, if the measurement object T cannot be properly set (for example, the amount of light required for measurement cannot be obtained, or the focal length of the objective lens 21 is inappropriate), the error or incomplete setting can be displayed on the display unit 31 or output to an external connected device to notify the user.

[0075] In step S12, various measurement conditions are set when measuring the object T. For example, the inherent calibration data (function for correcting linearity, etc.) of the sensor head 20 are set by the setting unit 32 in the user operation controller 30.

[0076] In addition, various parameters can be set. For example, the sampling time, measurement range, and threshold for setting the measurement result as normal or abnormal can be set. Furthermore, the measurement period can be set according to the characteristics of the object T, such as its reflectivity and material, and the measurement mode corresponding to the material of the object T can be set.

[0077] It should be noted that these measurement conditions and various parameters can be set by the setting unit 32 in the operation controller 30, but they can also be set by external connection devices or by retrieving data from the external storage unit 35.

[0078] In step S13, the sensor head 20 set in step S11 is used to measure the object T according to the measurement conditions and various parameters set in step S12.

[0079] Specifically, in the measurement processing unit 36 ​​of the controller 30, light is projected from the wavelength scanning light source, the light receiving element receives the returned light from the sensing head 20, and the signal processing circuit performs frequency analysis, distance conversion, and peak detection to calculate the displacement (distance to the object T) of the object being measured. Detailed information regarding the specific measurement processing will be described later.

[0080] In step S14, the measurement results measured in step S13 are output. For example, the displacement (distance to the object T) of the object measured in step S13 is displayed on the display unit 31 of the controller 30, or output to an external connected device.

[0081] Furthermore, the displacement (distance to the object T) measured in step S13 can also be displayed or output as a measurement result, based on the threshold set in step S12, indicating whether it falls within the normal range or is abnormal. Moreover, the measurement conditions, various parameters, and measurement modes set in step S12 can also be displayed or output.

[0082] [Overview of a system including displacement sensors]

[0083] Figure 3 This is a functional block diagram illustrating the general structure of a sensor system 1 using the displacement sensor 10 disclosed herein. (See diagram for example.) Figure 3 As shown, the sensor system 1 includes a displacement sensor 10, a control device 11, a control signal input sensor 12, and an external connection device 13. It should be noted that the displacement sensor 10 is connected to the control device 11 and the external connection device 13, for example, via a communication cable or an external connection line (e.g., including an external input line, an external output line, and a power line), and the control device 11 is connected to the control signal input sensor 12 via a signal line.

[0084] If used Figure 1 and Figure 2 As described, the displacement sensor 10 measures the displacement (distance to the object T) of the object being measured. The displacement sensor 10 can then output its measurement results to the control device 11 and the external connection device 13.

[0085] The control device 11 is, for example, a PLC (Programmable Logic Controller), which provides various indications to the displacement sensor 10 when the displacement sensor 10 measures the object T.

[0086] For example, based on the input signal from the control signal input sensor 12 connected to the control device 11, the control device 11 can output a measurement timing signal to the displacement sensor 10, or it can output a zeroing command signal (a signal used to set the current measurement value to 0) to the displacement sensor 10, etc.

[0087] The control signal input sensor 12 outputs a timing on / off signal to the control device 11, indicating that the displacement sensor 10 is measuring the object T. For example, the control signal input sensor 12 only needs to be placed near the production line where the object T is moving, detect when the object T moves to the specified position, and output an on / off signal to the control device 11.

[0088] The external connection device 13 is, for example, a PC (Personal Computer), which allows the user to operate and make various settings on the displacement sensor 10.

[0089] As a specific example, the measurement mode, action mode, measurement cycle, and the material of the object T to be measured are set.

[0090] As for the setting of the measurement mode, you can choose either the "internal synchronous measurement mode" in which the measurement starts periodically inside the control device 11, or the "external synchronous measurement mode" in which the measurement starts based on the input signal from outside the control device 11.

[0091] As for setting the operation mode, you can select the "operation mode" to actually measure the object T, or the "adjustment mode" to set the measurement conditions for measuring the object T.

[0092] The measurement period is the period during which the object T is measured. It can be set according to the reflectivity of the object T. However, if the reflectivity of the object T is low, the measurement period can be extended and the measurement period can be set appropriately to measure the object T.

[0093] For the object T being measured, select the "rough surface mode" which is suitable for cases where diffuse reflection is more of a component of reflected light, the "mirror mode" which is suitable for cases where specular reflection is more of a component of reflected light, or the "standard mode" which is an intermediate between them.

[0094] In this way, by making appropriate settings based on the reflectivity and material of the object T being measured, the object T can be measured with higher precision.

[0095] Figure 4 This is a flowchart illustrating the process of measuring the object T using the sensor system 1 with the displacement sensor 10 disclosed herein. Figure 4 As shown, this process is the same as the process in the external synchronous measurement mode described above, including steps S21 to S24.

[0096] In step S21, sensor system 1 detects the object to be measured, T. Specifically, a control signal is input to sensor 12 to detect that the object to be measured, T, has moved to a predetermined position on the production line.

[0097] In step S22, the sensor system 1 provides a measurement instruction to measure the object T detected in step S21 via the displacement sensor 10. Specifically, the control signal input sensor 12 outputs an on / off signal to the control device 11, thereby indicating the timing for measuring 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 to provide a measurement instruction for measuring the object T.

[0098] 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.

[0099] In step S24, the sensor system 1 outputs the measurement result obtained in step S23. Specifically, the displacement sensor 10 displays the measurement processing result on the display unit 31, or outputs it to the control device 11 or external connection device 13 via the external I / F unit 33.

[0100] It should be noted that the term used here is... Figure 4 The process for measuring the object T by detecting it with sensor 12 via a control signal input in an external synchronous measurement mode has been described, but it is not limited to this. For example, in the case of an internal synchronous measurement mode, instead of steps S21 and S22, a measurement timing signal is generated based on a preset period, thereby instructing the displacement sensor 10 to measure the object T.

[0101] Next, the principle of measuring the object T by means of the displacement sensor 10 disclosed herein will be explained.

[0102] Figure 5A This is a diagram illustrating the principle of measuring the object T using the displacement sensor 10 disclosed herein. (See diagram for example.) Figure 5A As shown, the displacement sensor 10 includes a sensing head 20 and a controller 30. The sensing head 20 includes an objective lens 21 and multiple collimating lenses 22a-22c. The controller 30 includes a wavelength scanning light source 51, an optical amplifier 52, multiple isolators 53 and 53a-53b, multiple optical couplers 54 and 54a-54e, an attenuator 55, multiple light-receiving elements (e.g., photodetectors (PD)) 56a-56c, multiple amplification circuits 57a-57c, multiple analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a-58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generation unit 61.

[0103] The wavelength scanning light source 51 projects laser light that has been scanned in wavelength. As the wavelength scanning light source 51, for example, if a method of modulating a VCSEL (Vertical Cavity Surface Emitting Laser) with current is used, then due to the short resonator length, mode hopping is not easily caused, and wavelength changes are easy to achieve, which can be implemented at low cost.

[0104] Optical amplifier 52 amplifies the light projected from wavelength scanning light source 51. Optical amplifier 52 may be an EDFA (erbium-doped fiber amplifier), or a dedicated 1550nm optical amplifier.

[0105] Isolator 53 is an optical element that directs the incident light in one direction. In order to prevent the influence of noise generated by the returned light, it can also be configured immediately after wavelength scanning light source 51.

[0106] In this way, the light projected from the wavelength scanning light source 51 is amplified by the optical amplifier 52 and then branched by the optical coupler 54 to the main interferometer and the sub-interferometer via the isolator 53. For example, in the optical coupler 54, the light can also be branched to the main interferometer and the sub-interferometer in a ratio of 90:10 to 99:1.

[0107] The light branched to the main interferometer is then branched by the first-stage optical coupler 54a in the direction of the sensor head 20 and the second-stage optical coupler 54b.

[0108] The light branching from the first-stage optical coupler 54a toward the sensing head 20 passes through the collimating lens 22a and the objective lens 21 from the front end of the optical fiber in the sensing head 20 and illuminates the object T being measured. The front end (end face) of the optical fiber then becomes a reference surface. The light reflected from this reference surface interferes with the light reflected from the object T to generate interference light, which returns to the first-stage optical coupler 54a. This interference light is then received by the light-receiving element 56a and converted into an electrical signal.

[0109] The light branching from the first-stage optical coupler 54a to the second-stage optical coupler 54b passes through the isolator 53a and then towards the second-stage optical coupler 54b. The second-stage optical coupler 54b further branches towards the sensor head 20 and the third-stage optical coupler 54c. The light branching from the optical coupler 54b towards the sensor head 20, similar to the first-stage coupler, passes through the collimating lens 22b and objective lens 21 from the front end of the optical fiber in the sensor head 20 and illuminates the object being measured, T. The front end (end face) of the optical fiber then becomes a reference surface. The light reflected from this reference surface interferes with the light reflected from the object being measured, T, generating interference light that returns to the second-stage optical coupler 54b. Through this coupler 54b, the light branches towards the isolator 53a and the light-receiving element 56b, respectively. The light branching from the optical coupler 54b towards the light-receiving element 56b is received by the light-receiving element 56b and converted into an electrical signal. On the other hand, isolator 53a allows light to pass from the preceding stage optical coupler 54a to the following stage optical coupler 54b, and blocks light from the following stage optical coupler 54b to the preceding stage optical coupler 54a. Therefore, the light branching from the optical coupler 54b to the isolator 53a is blocked.

[0110] The light branching from the second-stage optical coupler 54b to the third-stage optical coupler 54c passes through the isolator 53b and then towards the third-stage optical coupler 54c. From there, it further branches towards the sensor head 20 and the attenuator 55. The light branching from the optical coupler 54c towards the sensor head 20, like the first and second stages, passes through the collimating lens 22c and objective lens 21 in the sensor head 20 and illuminates the object being measured, T. The end face of the optical fiber then becomes a reference surface. The light reflected from this reference surface interferes with the light reflected from the object being measured, T, generating interference light that returns to the third-stage optical coupler 54c. From there, it branches towards the isolator 53b and the light-receiving element 56c. The light branching from the optical coupler 54c towards the light-receiving element 56c is received by the light-receiving element 56c and converted into an electrical signal. On the other hand, isolator 53b allows light to pass from the preceding stage optical coupler 54b to the following stage optical coupler 54c, and blocks light from the following stage optical coupler 54c to the preceding stage optical coupler 54b. Therefore, the light branching from the optical coupler 54c to the isolator 53b is blocked.

[0111] It should be noted that the light branched towards the non-sensor head 20 through the third-stage optical coupler 54c is not used for the measurement of the object T. Therefore, it can be attenuated by an attenuator 55, such as a terminator, to prevent it from being reflected back.

[0112] Thus, the main interferometer has a three-level optical path (three channels), which is an interferometer that uses twice the distance (round trip) from the front end (end face) of the optical fiber of the sensing head 20 to the object T to be measured as the optical path length difference, and generates three interference beams corresponding to the optical path length difference.

[0113] As described above, 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.

[0114] Amplifier circuits 57a to 57c amplify the electrical signals output from light-receiving elements 56a to 56c, respectively.

[0115] The AD conversion units 58a to 58c respectively receive the electrical signals amplified by the amplifier circuits 57a to 57c, and convert the electrical signals from analog signals to digital signals (AD conversion). Here, the AD conversion units 58a to 58c perform AD conversion based on the correction signal from the correction signal generation unit 61 in the sub-interferometer.

[0116] In the sub-interferometer, in order to correct the nonlinearity of the wavelength during the scanning of the wavelength scanning light source 51, the sub-interferometer is used to acquire the interference signal and generate a correction signal called the K clock.

[0117] Specifically, the light branched to the sub-interferometer by optical coupler 54 is further branched by optical coupler 54d. Here, the optical paths of the branched light are configured, for example, to have a path length difference by using optical fibers of different lengths between optical couplers 54d and 54e, and interference light corresponding to this path length difference is output from optical coupler 54e. Then, the balanced detector 60 receives the interference light from optical coupler 54e, and by taking the difference of the signal with opposite phase, it removes noise while amplifying the optical signal and converting it into an electrical signal.

[0118] It should be noted that both optical coupler 54d and optical coupler 54e only need to split the light in a 50:50 ratio.

[0119] The correction signal generation unit 61 determines the nonlinearity of the wavelength of the wavelength scanning light source 51 during scanning based on the electrical signal from the balance detector 60, generates a K clock corresponding to the nonlinearity, and outputs it to the AD conversion units 58a to 58c.

[0120] Due to the nonlinearity of the wavelength during scanning by the wavelength scanning light source 51, the intervals of the analog signals input to the AD conversion units 58a-58c in the main interferometer are not equal. In the AD conversion units 58a-58c, AD conversion (sampling) is performed by correcting the sampling time based on the aforementioned K clock to make the intervals of the waves equal.

[0121] It should be noted that the K clock, as described above, is a correction signal used to sample the analog signal of the main interferometer. Therefore, it needs to be generated at a higher frequency than the analog signal of the main interferometer. Specifically, the optical path length difference between the optical coupler 54d and the optical coupler 54e in the sub-interferometer can be made longer than the optical path length difference between the front end (end face) of the optical fiber in the main interferometer and the object being measured, or the frequency can be multiplied (e.g., by 8 times) by the correction signal generation unit 61 to achieve a higher frequency.

[0122] Processing unit 59 acquires digital signals that have undergone nonlinear correction and A / D conversion respectively by A / D conversion units 58a-58c, and calculates the displacement (distance to the object T) of the object being measured based on the digital signals. Specifically, in processing unit 59, a fast Fourier transform (FFT) is used to perform frequency conversion on the digital signals, and the distance is calculated by analyzing them. Detailed processing in processing unit 59 will be described later.

[0123] It should be noted that, in the processing unit 59, due to the requirement of high-speed processing, it is mostly implemented by integrated circuits such as FPGA (field-programmable gate array).

[0124] Furthermore, a three-level optical path is set up in the main interferometer here. Measurement light is irradiated onto the object T from each optical path through the sensor head 20, and the distance to the object T is measured based on the interference light (return light) obtained from each path (multi-channel). The number of channels in the main interferometer is not limited to three levels; it can be one level, two levels, or even four or more levels.

[0125] Figure 5B This is a diagram illustrating another principle of measuring the object T using the displacement sensor 10 involved in this disclosure. (See diagram for example.) Figure 5B As shown, the displacement sensor 10 includes a sensing head 20 and a controller 30. The sensing head 20 includes an objective lens 21 and multiple collimating lenses 22a-22c. The controller 30 includes a wavelength scanning light source 51, an optical amplifier 52, multiple isolators 53 and 53a-53b, multiple optical couplers 54 and 54a-54j, an attenuator 55, multiple light-receiving elements (e.g., photodetectors (PD)) 56a-56c, multiple amplification circuits 57a-57c, multiple analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a-58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generation unit 61. Figure 5B The displacement sensor 10 shown is mainly similar to the one equipped with optical couplers 54f to 54j. Figure 5A The displacement sensor 10 shown has a different configuration. Regarding the principle based on this different configuration, the edges and... Figure 5A The comparison sides will be explained in detail.

[0126] The light projected from the wavelength scanning light source 51 is amplified by the optical amplifier 52 and branched by the optical coupler 54 via the isolator 53 to the main interferometer side and the sub-interferometer side. However, the light branched to the main interferometer side is further branched by the optical coupler 54f into the measurement light and the reference light.

[0127] like Figure 5A As described above, through the first-stage optical coupler 54a, the measuring light passes through the collimating lens 22a and the objective lens 21 to illuminate the object being measured, T, and is reflected by the object being measured. Here, in... Figure 5A In this process, the front end (end face) of the optical fiber is used as a reference surface. The light reflected from this reference surface interferes with the light reflected from the object being measured (T) to generate interference light. Figure 5B In this context, no reference plane for the reflected light is set. That is, in... Figure 5B In the middle, no such results were produced. Figure 5A The light reflected from the reference surface is thus returned to the first-stage optical coupler 54a by the measurement object T.

[0128] Similarly, light branching from the first-stage optical coupler 54a to the second-stage optical coupler 54b passes through the second-stage optical coupler 54b, through the collimating lens 22b and the objective lens 21, and illuminates the object being measured, T. It is then reflected by the object being measured and returns to the second-stage optical coupler 54b. Light branching from the second-stage optical coupler 54b to the third-stage optical coupler 54c passes through the third-stage optical coupler 54c, through the collimating lens 22c and the objective lens 21, and illuminates the object being measured, T. It is then reflected by the object being measured and returns to the third-stage optical coupler 54c.

[0129] On the other hand, the reference light branched by optical coupler 54f is further branched by optical coupler 54g to optical couplers 54h, 54i and 54j.

[0130] In optical coupler 54h, the measurement light reflected by the object T being measured, output from optical coupler 54a, interferes with the reference light output from optical coupler 54g to generate interference light, which is received by light-receiving element 56a and converted into an electrical signal. In other words, by branching the measurement light and reference light through optical coupler 54f, interference light is generated corresponding to the difference in optical path length between the measurement light (the optical path from optical coupler 54f through optical coupler 54a, collimating lens 22a, objective lens 21, reflected by the object T being measured, and reaching optical coupler 54h) and the reference light (the optical path from optical coupler 54f through optical coupler 54g to optical coupler 54h). This interference light is received by light-receiving element 56a and converted into an electrical signal.

[0131] Similarly, in the optical coupler 54i, interference light is generated corresponding to the optical path length difference between the measurement light (the optical path from the optical coupler 54f through the optical couplers 54a, 54b, collimating lens 22b, objective lens 21, reflected by the measured object T and reaching the optical coupler 54i) and the reference light (the optical path from the optical coupler 54f through the optical coupler 54g and reaching the optical coupler 54i). This interference light is received by the light receiving element 56b and converted into an electrical signal.

[0132] In optical coupler 54j, interference light is generated corresponding to the optical path length difference between the measurement light (the optical path from optical coupler 54f through optical couplers 54a, 54b, 54c, collimating lens 22c, objective lens 21, reflected by the measured object T, and reaching optical coupler 54j) and the reference light (the optical path from optical coupler 54f through optical coupler 54g, reaching optical coupler 54j). This interference light is received by light-receiving element 56c and converted into an electrical signal. It should be noted that light-receiving elements 56a to 56c can, for example, be balanced photodetectors.

[0133] Thus, in the main interferometer, there is a three-level optical path (three channels) that generates three interference beams corresponding to the optical path length differences between the measurement beam reflected by the measured object T and input to optical couplers 54h, 54i, and 54j, and the reference beam input to optical couplers 54h, 54i, and 54j via optical couplers 54f and 54g, respectively.

[0134] It should be noted that, for example, the optical path lengths of optical coupler 54g and each of the optical couplers 54h, 54i and 54j can be set differently so that the difference in optical path length between the measuring light and the reference light is different in the three channels.

[0135] Then, based on the interference light obtained from each, the distance to the object T being measured is measured (multi-channel).

[0136] [Structure of the sensor head]

[0137] Here, the structure of the sensing head used in the displacement sensor 10 will be described.

[0138] Figure 6A This is a three-dimensional diagram showing the approximate structure of the sensor head 20. Figure 6B This is a schematic diagram showing the internal structure of the sensor head.

[0139] like Figure 6A As shown, the objective lens 21 and collimating lens of the sensor head 20 are housed in the lens holder 23. For example, regarding the dimensions of the lens holder 23, the length of one side surrounding the objective lens 21 is approximately 20 mm, and the length in the optical axis direction is approximately 40 mm.

[0140] like Figure 6B As shown, a lens holder 23 houses an objective lens 21 and three collimating lenses 22a-22c. Light from the optical fiber is guided to the three collimating lenses 22a-22c via the fiber array 24, and then the light passing through the three collimating lenses 22a-22c is directed to the object T being measured via the objective lens 21.

[0141] In this way, these optical fibers, collimating lenses 22a-22c, and fiber array 24, together with objective lens 21, are held by lens holder 23 to form sensor head 20.

[0142] Alternatively, the lens holder 23 constituting the sensor head 20 can also be made of a high-strength metal that can be machined with high precision (e.g., A2017).

[0143] Figure 7 This is a block diagram used to illustrate signal processing in controller 30. For example... Figure 7As shown, the controller 30 includes multiple light-receiving elements 71a to 71e, multiple amplifier circuits 72a to 72c, multiple AD conversion units 74a to 74c, a processing unit 75, a differential amplifier circuit 76, and a correction signal generation unit 77.

[0144] In controller 30, such as Figure 5A As shown, the light projected from the wavelength scanning light source 51 is branched from the optical coupler 54 to the main interferometer and the sub-interferometer. The main interference signal and the sub-interferometer obtained from each are processed to calculate the distance to the object T being measured.

[0145] Multiple light-receiving elements 71a to 71c are equivalent to Figure 5A The light-receiving elements 56a to 56c shown receive the main interference signal from the main interferometer and output it as a current signal to the amplifier circuits 72a to 72c.

[0146] Multiple amplifier circuits 72a to 72c convert the current signal (IV conversion) into a voltage signal and amplify it.

[0147] Multiple A / D conversion units 74a-74c are equivalent to Figure 5A The AD conversion units 58a to 58c shown convert voltage signals (AD conversion) into digital signals based on the K clock from the correction signal generation unit 77 described later.

[0148] Processing unit 75 is equivalent to Figure 5A The processing unit 59 shown uses FFT to convert the digital signals from the AD conversion units 74a to 74c into frequencies, analyzes them, and calculates the distance value to the object T being measured.

[0149] Multiple light-receiving elements 71d to 71e and differential amplifier circuit 76 are equivalent to Figure 5A The balanced detector 60 shown receives the interference light from the sub-interferometer and outputs the phase-inverted interference signal. By taking the difference between the two signals, noise is removed on one hand, and the interference signal is amplified and converted into a voltage signal on the other.

[0150] The correction signal generation unit 77 is equivalent to Figure 5A The correction signal generation unit 61 shown uses a comparator to binarize the voltage signal, generate a K clock, and outputs it to the AD conversion units 74a-74c. The K clock needs to be generated at a higher frequency than the analog signal of the main interferometer. Therefore, the frequency can also be multiplied (e.g., by 8 times) by the correction signal generation unit 77 to generate a higher frequency.

[0151] Figure 8 This is a flowchart illustrating the method for calculating the distance to the object T being measured, executed by the processing unit 59 in the controller 30. (Example) Figure 8As shown, the method includes steps S31 to S34.

[0152] In step S31, the processing unit 59 uses the following FFT to convert the frequency of the waveform signal (voltage vs. time) into a spectrum (voltage vs. frequency). Figure 9A This is a diagram showing how a waveform signal (voltage vs. time) is converted from frequency to spectrum (voltage vs. frequency).

[0153] [Mathematical Expression 1]

[0154]

[0155] N: Number of data points

[0156] In step S32, the processing unit 59 converts the spectrum (voltage vs. frequency) distance into a spectrum (voltage vs. distance). Figure 9B This is a diagram illustrating the conversion of the spectrum (voltage vs. frequency) to the spectrum (voltage vs. distance) from distance.

[0157] In step S33, the processing unit 59 calculates the distance value corresponding to the peak based on the spectrum (voltage vs. distance). Figure 9C This is a graph illustrating the scenario where peaks are detected based on the spectrum (voltage vs. distance) and their corresponding distance values ​​are calculated. For example... Figure 9C As shown, in this case, peaks are detected based on the spectrum (voltage vs. distance) in the three channels, and the distance value corresponding to each peak is calculated.

[0158] In step S34, the processing unit 59 averages the distance values ​​calculated in step S33. Specifically, since the processing unit 59 detected peaks for each of the three channels based on the spectrum (voltage vs. distance) in step S33 and calculated the corresponding distance values, it averages them and outputs the averaged calculation result as the distance to the object T to be measured.

[0159] It should be noted that in step S34, the preferred processing unit 59 averages distance values ​​with an SNR greater than or equal to a threshold when averaging the distance values ​​calculated in step S33. For example, in any of the three channels, although a peak is detected based on its spectrum (voltage vs. distance), if the SNR is less than the threshold, it is determined that the reliability of the distance value calculated based on that spectrum is low, and therefore it is not used.

[0160] Next, regarding this disclosure, more characteristic configurations, functions, and properties will be described in detail as specific embodiments. It should be noted that the optical interferometric ranging sensor shown below is equivalent to using... Figures 1 to 9C The displacement sensor 10 described herein contains all or part of the basic components, functions, and properties of the optical interferometric ranging sensor as described above, and is used in conjunction with the displacement sensor 10. Figures 1 to 9CThe displacement sensor 10 described herein contains general components, functions, and properties.

[0161] <First Implementation>

[0162] [Composition of an optical interferometric ranging sensor]

[0163] Figure 10 This is a schematic diagram showing the general configuration of the optical interferometric ranging sensor 100 according to the first embodiment of the present invention. Figure 10 As shown, the optical interferometric ranging sensor 100 includes a wavelength scanning light source 110, a light branching section 120, an interferometer 130, a light receiving section 140, a processing section 150, a discrimination unit 160, and a setting unit 170. It should be noted that the interferometer 130 includes a sensing head 131 with an objective lens 132, and the light receiving section 140 includes a light receiving circuit 141 and an AD conversion section 142. The light receiving circuit 141 includes a light receiving element.

[0164] The wavelength scanning light source 110, the light branch 120, the light receiving part 140, and the processing part 150 are included in the controller 101. The discrimination unit 160 and the setting unit 170 may be included as functions executed by the processing part 150, or they may be additionally equipped with a control part, etc., as functions executed by the control part.

[0165] The wavelength scanning light source 110 is connected directly or indirectly to the light branch 120 via other components (optical amplifier 52, isolator 53, optical coupler 54, etc.) to project light while continuously changing the wavelength. In other words, the wavelength of the light projected from the wavelength scanning light source 110 changes continuously.

[0166] Light projected from wavelength scanning light source 110 is supplied to interferometer 130 via optical branch 120 and optical fiber.

[0167] The optical branch 120, for example, is composed of an optical coupler, a circulator, etc., to supply light projected from the wavelength scanning light source 110 to the interferometer 130, and then guides the return light from the interferometer 130 to the light receiving section 140. Furthermore, when the optical branch 120 uses a 2×2 optical coupler, an attenuator or the like can be provided for the light branching to the other side to attenuate the light and reduce the return light toward the optical coupler.

[0168] The interferometer 130 includes a sensing head 131 with an objective lens 132. Light supplied to the interferometer 130 is input to the sensing head 131 via an optical fiber. A portion of the light input to the sensing head 131 is used as measurement light and is incident on the object T being measured via the objective lens 132, and is reflected by the object T. The measurement light reflected by the object T is then focused by the objective lens 132 of the sensing head 131 and input into the sensing head 131. Another portion of the light input to the sensing head 131 is used as reference light and is reflected by a reference surface located at the front end of the optical fiber. Thus, by interfering with the measurement light and the reference light, interference light corresponding to the difference in optical path length between the measurement light and the reference light is generated, and this interference light is output from the interferometer 130.

[0169] It should be noted that the sensor head 131 may also have a collimating lens disposed between the front end of the optical fiber and the objective lens 132, or it may be configured with a collimating lens but without the objective lens 132.

[0170] The interference light output from the interferometer 130 is received by the light-receiving unit 140 via the light branch 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 converter 142. The light-receiving circuit 141 includes, for example, a light-receiving element that functions as a photodetector, receives the light output from the light branch 120, and converts it into an electrical signal corresponding to the amount of light received. The AD converter 142 converts this electrical signal from an analog signal into a digital signal.

[0171] The processing unit 150 calculates the distance from the sensor head 131 to the object T to be measured based on the digital signal converted by the light receiving unit 140. For example, the processing unit 150 is a processor implemented by an integrated circuit such as an FPGA, which uses FFT to perform frequency conversion on each input digital signal and calculates the distance to the object T to be measured based on it.

[0172] It should be noted that the distance from the sensor head 131 to the object being measured T typically refers to the distance from the front end of the sensor head 131 to the object being measured T, which is calculated by the processing unit 150, but is not limited to this. For example, as the distance from the sensor head 131 to the object being measured T, the processing unit 150 may also calculate the distance from the front end of the optical fiber connected to the sensor head 131 to the object being measured T, the distance from the objective lens 132 disposed in the sensor head 131 to the object being measured T, or the distance from a reference position preset inside the sensor head 131 to the object being measured T, etc.

[0173] Here, the measurement distance to the object T, the type of sensor head 131, and the circuit frequency band in the processing unit 150 will be explained.

[0174] Figure 11This is a specific example illustrating the relationship between the measurement distance to the object T, the type of sensor head 131, and the circuit frequency band in the processing unit 150. For example... Figure 11 As shown in (A), when the measurement distance to the object T is short, a short-range type sensor head 131a with an objective lens 132a having an appropriate focal length relative to the object T is used. On the other hand, as Figure 11 As shown in (B), when the measurement distance to the object T is long, a long-distance type sensor head 131b with an appropriate objective lens 132b based on the focal length relative to the object T is used.

[0175] exist Figure 11 In (A), within the controller 101, the processing unit 150 detects the signal peak of the interference light received by the light-receiving unit 140. The processing unit 150 calculates the distance from the sensing head 131a to the object T to be measured based on the frequency of this signal peak. However, in order to appropriately calculate the distance to the object T in the processing unit 150, measurement conditions need to be set in the processing unit 150 so that the frequency of the signal peak of the interference light received by the light-receiving unit 140 enters the circuit frequency band of the light-receiving unit 140. That is, measurement conditions appropriately set to correspond to the short-range sensing head 131a.

[0176] On the other hand, Figure 11 In (B), when a long-distance sensor head 131b is used due to the long measurement distance to the object T, it is assumed that the frequency of the signal peak of the interference light received by the light-receiving unit 140 is detected in the high-frequency band in the processing unit 150. However, if the measurement conditions corresponding to the short-distance type are set, the frequency of the signal peak of the interference light received by the light-receiving unit 140 cannot be detected, and the distance from the sensor head 131b to the object T may not be properly calculated in the processing unit 150. In other words, the processing unit 150 needs to set the measurement conditions corresponding to the long-distance type so that the frequency of the signal peak of the interference light received by the light-receiving unit 140 enters the circuit frequency band of that light-receiving unit 140.

[0177] In other words, it identifies whether the sensor head 131 is a short-range sensor head 131a or a long-range sensor head 131b, and sets the measurement conditions corresponding to the identified sensor head type.

[0178] [Regarding the identification of sensor head types]

[0179] The discrimination unit 160 identifies the type of the sensor head 131 based on the beat signal generated by the interferometer 130.

[0180] Figure 12This is a schematic diagram illustrating a specific example of a sensor head 131 configured to distinguish between a short-range sensor head 131a and a long-range sensor head 131b. For example... Figure 12 As shown in (A), a portion of the light input to the optical fiber sensor head 131a is used as measurement light to illuminate the object T being measured, and is reflected by the object T. Furthermore, another portion of the light input to the sensor head 131a is used as reference light and is reflected by a reference surface 133a located at the front end of the optical fiber. Interference light is generated based on this measurement light and reference light, and the distance from the sensor head 131a to the object T is detected as a signal peak.

[0181] Furthermore, another portion of the light input to the sensor head 131a via the optical fiber is reflected by the reflective surface 134a of the objective lens 132a. Based on this reflected light and the aforementioned reference light, 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, a position closer to the reference surface 133a than the front end position LH of the sensor head 131a) is detected as a signal peak.

[0182] It should be noted that the reflective surface 134a formed on the objective lens 132a can be formed on the surface of the objective lens 132a or on the back side. In addition, the reflective surface 134a can be formed by applying a local reflective coating to the objective lens 132a, for example, by using Fresnel reflection with a very low reflectivity (around 5%).

[0183] Similarly, in Figure 12 In (B), a reflective surface 134b is also formed on the objective lens 132b inside the sensor head 131b (specifically, at a position closer to the reference surface 133b than the front end position LH of the sensor head 131b). 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. Thus, a beat signal (interference light) is generated based on this reflected light and the aforementioned reference light, and the position Lp of the objective lens 132b (specifically the reflective surface 134b) inside the sensor head 131b is detected as a signal peak.

[0184] Thus, a beat signal is generated by the interferometer 130, which includes sensing head 131a or sensing head 131b. This beat signal is received by the light receiving unit 140 and, as... Figure 12 (A) and Figure 12 The detection signal peak is shown in (B).

[0185] For example, by placing the objective lens 132a in the short-range sensor head 131a and the objective lens 132b in the long-range sensor head 131b in different positions, the discrimination unit 160 can identify the type of the sensor head 131 based on the peak of the beat signal.

[0186] [Measurement conditions corresponding to the type of sensor head]

[0187] The setting unit 170 sets the measurement conditions corresponding to the type of sensor head 131 identified by the discrimination unit 160. (Return) Figure 11 ,like Figure 11 As shown in (B), as a measurement condition set in the processing unit 150, for example, the scanning ratio of the wavelength scanning light source 110 is adjusted so that the frequency of the signal peak of the interference light received by the light receiving unit 140 is in the high frequency band and enters the circuit frequency band of the light receiving unit 140.

[0188] Here, the scan ratio is represented by the frequency scan width per scan time, calculated based on the frequency scan width and scan time in FMCW (Frequency-Modulated Continuous Wave) mode, using the scan ratio α = δf / T (δf: frequency scan width, T: scan time). A detailed explanation of coherent FMCW (Frequency-Modulated Continuous Wave) is provided.

[0189] Figure 13 This is a diagram used to illustrate coherent FMCW. As described above, light is projected from the wavelength scanning light source 110 while continuously changing the wavelength (frequency). Interference light is generated based on the difference in optical path length between the measurement light that illuminates the measurement object T and is reflected, and the reference light that is reflected by the front end of the optical fiber, i.e., the reference surface.

[0190] like Figure 13 As shown, regarding the light projected from the wavelength scanning light source 110, interference occurs due to the delay of the light from the reference light corresponding to the difference in optical path length. Then, the beat signal (interference light), which has a beat frequency (the difference in frequency between the measurement light and the reference light), is received by the light receiving unit 140. The beat frequency is calculated as fb = δf / T·2Ln / c (δf: frequency scanning width, T: scanning time, L: distance from the fiber tip (reference plane) to the object T being measured, n: refractive index in the optical path difference, c: speed of light).

[0191] Return again Figure 11 ,like Figure 11 As shown in (B), for the measurement conditions set in the processing unit 150, the scanning ratio α (δf / T) can be adjusted to be smaller so that the frequency (beat frequency) of the signal peak of the interference light received by the light receiving unit 140 enters the circuit frequency band of the light receiving unit 140.

[0192] [Measuring condition setting method corresponding to the type of sensor head]

[0193] Next, the process of setting measurement conditions corresponding to the type of sensor head 131 will be explained in detail.

[0194] Figure 14 This is a flowchart illustrating the processing flow of a measurement condition setting method M100 that identifies the type of sensor head 131 and sets measurement conditions corresponding to that identified type of sensor head 131. For example... Figure 14 As shown, the measurement condition setting method M100 includes steps S110 to S150, each step of which is executed by the processor included in the optical interferometric ranging sensor 100.

[0195] In step S110, the discrimination unit 160 detects the signal peak based on the interference light received by the light receiving unit 140 within the range up to the front end position LH of the sensing head.

[0196] In step S120, the discrimination unit 160 calculates the distance Lp corresponding to the signal peak detected in step S110.

[0197] In step S130, the discrimination unit 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.

[0198] As a specific example, in the short-range sensor head 131a, the objective lens 132a (reflecting surface 134a) is pre-configured such that Lp = L1, and in the long-range sensor head 131b, the objective lens 132b (reflecting surface 134b) is pre-configured such that Lp = L2. Here, regarding the distance Lp calculated in step S120, by comparing |Lp-L1| with |Lp-L2|, it is determined whether Lp is closer to (equivalent to) L1 or L2.

[0199] When it is determined in step S130 that the distance Lp is equivalent to L1 ("Yes" in step S130), the discrimination unit 160 identifies that the sensor head 131 used is a short-range type sensor head 131a. Then, in step S140, the setting unit 170 sets the measurement conditions corresponding to the short-range type sensor head 131a. As a specific example, the setting unit 170 sets the scanning ratio α1 of the wavelength scanning light source 110 as the measurement condition corresponding to the short-range type sensor head 131a.

[0200] On the other hand, when it is determined in step S130 that the distance Lp is equivalent to L2 (no in step S130), the discrimination unit 160 identifies that the sensor head 131 used is a long-range type sensor head 131b. Then, in step S150, the setting unit 170 sets the measurement conditions corresponding to the long-range type sensor head 131b. As a specific example, the setting unit 170 sets the scanning ratio α2 of the wavelength scanning light source 110 as the measurement condition corresponding to the long-range type sensor head 131b.

[0201] It should be noted that the measurement condition setting method M100 can be executed at the time of measurement when measuring the object T, such as before the measurement begins, or it can be executed repeatedly each time the object T is measured.

[0202] As described above, in the optical interferometric ranging sensor 100 according to the first embodiment of the present invention, the discrimination unit 160 distinguishes whether the sensor head 131 is a short-range or long-range type based on the beat signal generated by the interferometer 130. Then, the setting unit 170 adjusts the scan ratio as the measurement condition corresponding to the type of sensor head 131 identified by the discrimination unit 160. Thus, appropriate measurement conditions can be set according to the measurement distance to the object T, and the measurement distance to the object T can be measured appropriately. For the user, this reduces the work of confirming the type of sensor head 131 or manually setting the corresponding measurement conditions each time.

[0203] It should be noted that when using Figure 12 The sensor heads 131a and 131b described herein employ a configuration in which a collimating lens is placed between the tip of the optical fiber and the objective lenses 132a and 132b. As a result, the incident light entering the objective lenses 132a and 132b is collimated light, thus allowing for a high degree of freedom in the positioning of the reflecting surfaces 134a and 134b within the objective lenses 132a and 132b.

[0204] Furthermore, the short-range sensor head 131a and the long-range sensor head 131b are not limited to... Figure 12 The configuration shown can be any other configuration as long as it is capable of identifying the type of sensor head 131 based on the beat signal generated by interferometer 130. Hereinafter, examples of configurations capable of identifying the type of sensor head 131 will be shown.

[0205] [Specific examples of the ability to identify the type of sensor head 131]

[0206] (Specific example 1)

[0207] Figure 15This is a schematic diagram illustrating a specific example of a sensor head 131 configured with a collimating lens to distinguish between a short-range sensor head 131a and a long-range sensor head 131b. For example... Figure 15 As shown, the short-range sensor head 131a and the long-range sensor head 131b are equipped with collimating lenses 135a and 135b respectively, without objective lenses.

[0208] Reflective surfaces 136a and 136b are formed on a portion of collimating lenses 135a and 135b, respectively, and the reflective surfaces 136a and 136b reflect a portion of the light transmitted through the optical fiber input sensor heads 131a and 131b.

[0209] Therefore, by placing the collimating lens 135a in the short-range sensor head 131a and the collimating lens 135b in the long-range sensor head 131b at different positions, the discrimination unit 160 can distinguish the type of the sensor head 131 based on the peak of the beat signal.

[0210] In use Figure 15 The sensor heads 131a and 131b described herein are simple in configuration without an objective lens, thus making it easy to detect the peak of the beat signal.

[0211] (Specific example 2)

[0212] Figure 16 This is a schematic diagram illustrating a specific example of a sensor head 131 configured to distinguish between short-range type sensor head 131a and long-range type sensor head 131b by forming a reflective surface on a structural component inside the sensor head 131. For example... Figure 16 As shown, the short-range sensor head 131a and the long-range sensor head 131b are equipped with their respective internal components 137a and 137b.

[0213] The specified components 137a and 137b are configured such that a portion of the light input to the sensor heads 131a and 131b via optical fibers is reflected inside the respective housings of the short-range type sensor head 131a and the long-range type sensor head 131b.

[0214] Therefore, by arranging the specified component 137a in the short-range type sensor head 131a and the specified component 137b in the long-range type sensor head 131b in different positions, the discrimination unit 160 can distinguish the type of sensor head 131 based on the peak of the beat signal.

[0215] In use Figure 16In the described sensor heads 131a and 131b, it is not necessary to form a reflecting surface on the collimating lens or the objective lens. The peak of the beat signal can be easily detected simply by configuring the specified components 137a and 137b to reflect a portion of the light input to the sensor heads 131a and 131b.

[0216] It should be noted that the specified components 137a and 137b can also be formed as part of the components constituting the short-range type sensor head 131a and the long-range type sensor head 131b, or can be separately formed as components for generating the peak of the beat signal.

[0217] (Concrete example 3)

[0218] Figure 17A This is a schematic diagram illustrating a specific example of how the type of sensor head 131 can be identified by forming a reflective surface in the optical fiber. For example... Figure 17A As shown, a reflective surface 138 is formed inside the optical fiber that supplies light to the sensing head 131, rather than inside the sensing head 131 itself. Specifically, the reflective surface 138 can be formed by applying a local reflective coating to the connection portion of the optical fiber.

[0219] For example, when using a short-range sensor head 131a or a long-range sensor head 131b, if a reflective surface 138 is formed at different positions in the connected optical fiber, the discrimination unit 160 can identify the type of sensor head 131 based on the peak of the beat signal.

[0220] It should be noted that, for example, in the case of a Fizeau interferometer, since the front end (end face) of the optical fiber is located at the position of optical path difference 0, the peak of the beat signal appears by reflecting back from the position of optical path difference 0 to the front end of the sensing head 131.

[0221] Figure 17B This is a schematic diagram illustrating a specific example of how the type of sensor head 131 can be identified by forming a reflective surface at the tip (end face) of the optical fiber on the controller 101 side. For example... Figure 17B As shown, a reflective surface 139 is formed at the front end (end face) of the optical fiber supplying light to the sensor head 131 on the controller 101 side, rather than inside the sensor head 131. Specifically, the reflective surface 139 can be formed by applying a local reflective coating to the front end (end face) of the optical fiber on the controller 101 side.

[0222] It should be noted that, for example, in the case of a Fizeau interferometer, since the front end (end face) of the optical fiber is located at the position of optical path difference 0, the peak of the beat signal appears by an amount corresponding to the optical path length, which is reflected back from the position of optical path difference 0 to the front end of the sensing head 131.

[0223] Using this, when using short-range sensor head 131a or long-range sensor head 131b, if optical fibers of different lengths (optical path lengths) are used, the discrimination unit 160 can distinguish the type of sensor head 131 based on the peak of the beat signal.

[0224] As described above, a reflective surface is formed inside the sensor head 131, which includes a collimating lens, an objective lens, and other components, as well as inside and at the end face of the optical fiber, to generate a beat signal in the interferometer 130. When using a short-range sensor head 131a or a long-range sensor head 131b, if different peaks are detected in the beat signal, the discrimination unit 160 can identify the type of sensor head 131 based on the peaks of the beat signal.

[0225] It should be noted that, in cases where the signal is configured to detect different peaks in the beat signal, it is also possible to use... Figure 12 as well as Figures 15-17B The components described are combined. For example, when using a short-range sensor head 131a, a specified component 137a is arranged inside the sensor head 131a. Figure 16 When using a long-distance sensing head 131b, a reflective surface 138 is formed inside the optical fiber. Figure 17A ),etc.

[0226] (Concrete example 4)

[0227] Figure 18 This is a schematic diagram illustrating a specific example of a sensor head 131 configured to distinguish between a short-range sensor head 131a and a long-range sensor head 131b based on the number of peaks in the beat signal. For example... Figure 18 As shown, the short-range sensor head 131a and the long-range sensor head 131b have different configurations. The type of sensor head 131 is distinguished not by the frequency (position, distance) of the peak of the beat signal generated in the interferometer 130, but by the number of peaks.

[0228] Specifically, such as Figure 18As shown in (A), the short-range 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 reflecting surface 136a of the collimating lens 135a and the reflecting surface 134a of the objective lens 132a. A beat signal (interference light) is then generated based on each of these reflected beams and the reference light reflected by the reference surface 133a located at the front end of the optical fiber. As a result, within the sensor head 131a (specifically, at a position closer to the reference surface 133a than the front end position LH of the sensor head 131a), the position Lp1 of the collimating lens 135a (specifically, the reflecting surface 136a) and the position Lp2 of the objective lens 132a (specifically, the reflecting surface 134a) are detected as signal peaks.

[0229] On the other hand, such as Figure 18 As shown in (B), the long-range sensor head 131b has a collimating lens 135b but no objective lens. A portion of the light input to the sensor head 131b via the optical fiber is reflected by the reflecting surface 136b of 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 located at the front end of the optical fiber. As a result, within the sensor head 131b (specifically, at a position closer to the reference surface 133b than the front end position LH of the sensor head 131b), the position Lp of the collimating lens 135b (specifically, the reflecting surface 136b) is detected as a signal peak.

[0230] Thus, the short-range sensor head 131a has a collimating lens 135a and an objective lens 132a, and the long-range sensor head 131b has a collimating lens 135b. Therefore, the discrimination unit 160 can distinguish the type of sensor head 131 based on the number of peaks detected in the beat signal.

[0231] Figure 19 This is a flowchart illustrating the processing flow of a measurement condition setting method M101 that identifies the type of sensor 131 based on the number of peaks detected in the beat signal and sets measurement conditions corresponding to the identified type of sensor 131. (Example) Figure 19 As shown, the measurement condition setting method M101 includes steps S111, S131, S140 and S150, each step being executed by the processor included in the optical interferometric ranging sensor 100.

[0232] In step S111, the discrimination unit 160 detects signal peaks based on interference light received by the light-receiving unit 140 within a range up to the front end position LH of the sensing head. For example, the discrimination unit 160 can detect signal peaks with a signal intensity of a predetermined value or higher.

[0233] In step S131, the discrimination unit 160 determines the number of signal peaks detected in step S111.

[0234] As a specific example, in the short-range sensing head 131a, the collimating lens 135a and the objective lens 132a are pre-configured with a signal peak count of 2 (e.g., Figure 18 In the long-range sensor head 131b, a collimating lens 135b is pre-configured with a signal peak count of 1 (e.g., [missing information]). Figure 18 (B)

[0235] Then, the discrimination unit 160 determines whether the signal peak count detected in step S111 is 2, and distinguishes whether it is set as a short-range sensor head 131a or a long-range sensor head 131b.

[0236] When it is determined in step S131 that the number of signal peaks = 2 (Yes in step S131), the discrimination unit 160 identifies that the sensor head 131 used is a short-range type sensor head 131a. Then, in step S140, the setting unit 170 sets the measurement conditions corresponding to the short-range type sensor head 131a. As a specific example, the setting unit 170 sets the scanning ratio α1 of the wavelength scanning light source 110 as the measurement condition corresponding to the short-range type sensor head 131a.

[0237] On the other hand, when it is determined in step S131 that the signal peak count is not 2 ("No" in step S131), the discrimination unit 160 identifies that the sensor head 131 used is a long-range type sensor head 131b. Then, in step S150, the setting unit 170 sets the measurement conditions corresponding to the long-range type sensor head 131b. As a specific example, the setting unit 170 sets the scanning ratio α2 of the wavelength scanning light source 110 as the measurement condition corresponding to the long-range type sensor head 131b.

[0238] It should be noted that in this embodiment, the discrimination unit 160 distinguishes between using a short-range type of sensor head 131a and a long-range type of sensor head 131b, but includes distinguishing whether the short-range and long-range types of sensor heads can be switched within a single sensor head 131. For example, even when using a sensor head 131 that can switch between short-range and long-range types by changing (configuring, adding, or deleting) the collimating lens, objective lens, and predetermined components inside the housing within a single sensor head 131, the discrimination unit 160 can still distinguish the sensor head 131.

[0239] <Second Implementation>

[0240] Next, in the second embodiment of the present invention, a setting unit that replaces the scanning ratio described in the first embodiment, or sets other measurement conditions based thereon, will be described. In this embodiment, for configurations identical to those of the optical interferometric ranging sensor 100 according to the first embodiment, the same reference numerals are used in the accompanying drawings and detailed descriptions are omitted; the description will mainly focus on configurations different from those in the first embodiment.

[0241] Figure 20 This is a schematic diagram showing the general configuration of the optical interferometric ranging sensor 200 according to the second embodiment of the present invention. Figure 20 As shown, the optical interferometric ranging sensor 200 includes a wavelength scanning light source 110, a light branching section 120, an interferometer 130, a light receiving section 140, a processing section 150, a discrimination unit 160, and a setting unit 270. It should be noted that the interferometer 130 includes a sensing head 131 with an objective lens 132, and the light receiving section 140 includes a light receiving circuit 141 and an AD conversion section 142. The light receiving circuit 141 includes a light receiving element. Furthermore, the optical interferometric ranging sensor 200 includes a light branching section 121 (e.g., an optical coupler) that branches the light projected from the wavelength scanning light source 110 to the main interferometer (interferometer 130) and the sub-interferometer.

[0242] If used Figure 5A , Figure 5B as well as Figure 7 As explained, the sub-interferometer is used to correct the nonlinearity of the wavelength during scanning by the wavelength scanning light source 110. The correction signal generation unit 210 generates a correction signal called the K clock and outputs it to the AD conversion unit 142. In the AD conversion unit 142, the interference light received from the interferometer 130 is subjected to AD conversion (sampling) based on the correction signal. Therefore, the nonlinearity of the wavelength during scanning by the wavelength scanning light source 110 is corrected.

[0243] The processing unit 150 calculates the distance from the sensor head 131 to the object T to be measured based on the digital signal after AD conversion by the AD converter 142. However, if the number of sampling points during AD conversion by the AD converter 142 is insufficient, the distance may not be calculated properly. In other words, to properly calculate the distance to the object T, an appropriate number of sampling points need to be acquired in each cycle of the signal converted by the AD converter 142.

[0244] Here, as described in the first embodiment of the present invention, when the measurement distance to the object T is short, the discrimination unit 160 identifies that a short-range type sensor head 131a is used, and when the measurement distance to the object T is long, the discrimination unit 160 identifies that a long-range type sensor head 131b is used.

[0245] The setting unit 270 controls the correction signal generation unit 210 based on the type of sensor head 131 identified by the discrimination unit 160, thereby adjusting the degree of frequency harmonics of the correction signal. For example, if the discrimination unit 160 identifies that a short-range sensor head 131a is being used, the setting unit 270 sets the frequency of the correction signal to a fourth harmonic; if the discrimination unit 160 identifies that a long-range sensor head 131b is being used, the setting unit 270 sets the frequency of the correction signal to an eighth harmonic.

[0246] It should be noted that the frequency of the correction signal is not limited to the fourth or eighth harmonic. In order to properly calculate the distance to the object T being measured, it is only necessary to adjust the frequency to a level that allows for the acquisition of an appropriate number of sampling points in the signal converted by the AD converter 142.

[0247] Furthermore, when adjusting the degree of frequency doubling of the correction signal, the scanning ratio of the wavelength scanning light source 110 described in the first embodiment of the present invention can also be considered. For example, if the scanning ratio of the wavelength scanning light source 110 is adjusted, for example, as a measurement condition set in the processing unit 150, so that the frequency of the signal peak of the interference light received by the light receiving unit 140 enters the circuit frequency band of the light receiving unit 140, the degree of frequency doubling of the correction signal can also be adjusted accordingly.

[0248] [Measuring condition setting method corresponding to the type of sensor head]

[0249] Next, the process of setting measurement conditions corresponding to the type of sensor head 131 will be explained in detail.

[0250] Figure 21 This is a flowchart of the measurement condition setting method M200, which identifies the type of sensor head 131 and sets measurement conditions corresponding to that identified type of sensor head 131. For example... Figure 21 As shown, the measurement condition setting method M200 includes steps S110 to S130, S240 and S250, each step of which is executed by the processor included in the optical interferometric ranging sensor 100.

[0251] Steps S110 to S130 are the same as the measurement condition setting method M100 in the first embodiment of the present invention.

[0252] When the discrimination unit 160 determines that the sensor head 131 is a short-range type sensor head 131a ("Yes" in step S130), in step S240, the setting unit 270 sets the measurement conditions corresponding to the short-range type sensor head 131a. As a specific example, the setting unit 270 sets the scanning ratio α1 of the wavelength scanning light source 110 and sets the frequency multiplication factor M1 of the correction signal as the measurement conditions corresponding to the short-range type sensor head 131a.

[0253] On the other hand, when the discrimination unit 160 determines that the sensor head 131 used is a long-range type sensor head 131b ("No" in step S130), in step S250, the setting unit 270 sets the measurement conditions corresponding to the long-range type sensor head 131b. As a specific example, the setting unit 270 sets the scanning ratio α2 of the wavelength scanning light source 110 and sets the frequency multiplication factor M2 of the correction signal as the measurement conditions corresponding to the long-range type sensor head 131b.

[0254] As described above, in the optical interferometric ranging sensor 200 according to the second embodiment of the present invention, the discrimination unit 160 distinguishes whether the sensor head 131 is a short-range or long-range type based on the beat signal generated by the interferometer 130. Then, as measurement conditions corresponding to the type of sensor head 131 identified by the discrimination unit 160, the setting unit 270 replaces the scanning ratio or adjusts the degree of frequency doubling of the correction signal based on it. Thus, appropriate measurement conditions can be set according to the measurement distance to the object T, and the measurement distance to the object T can be measured appropriately. For the user, this reduces the work of confirming the type of sensor head 131 or manually setting the corresponding measurement conditions each time.

[0255] [Examples of interferometers]

[0256] In the above embodiments, the optical interferometric ranging sensors 100 and 200 use a Fizeau interferometer that generates reference light by using the front end of the optical fiber as a reference surface in the interferometer 130, but the interferometer is not limited to this.

[0257] Figure 22 This is a diagram showing the distortion of an interferometer that produces interference using measuring and reference lights. Figure 22In (a), in the optical path after branching through the optical branch 120, interference light is generated based on the optical path length difference between the reference light, which uses the front end (end face) of the optical fiber as a reference surface, and the measurement light, which is irradiated from the sensing head and reflected by the object being measured, T. It can also be configured as an interferometer 130 of the optical interference ranging sensors 100 and 200 described in the above embodiments (Fizeau interferometer), where the reference surface reflects light through the difference in refractive index between the optical fiber and air (Fresnel reflection). Alternatively, a reflective film can be coated on the front end of the optical fiber, or a non-reflective coating can be applied to the front end of the optical fiber, and a reflective surface such as a lens can be separately configured.

[0258] exist Figure 22 In (b), after the optical path branches through the optical branch 120, a measurement optical path Lm is formed to guide the measurement light to the object T being measured, and a reference optical path Lr is formed to guide the reference light. A reference surface (Michelson interferometer) is arranged at the very front of the reference optical path Lr. The reference surface can be a reflective coating applied to the front end of the optical fiber, or a non-reflective coating can be applied to the front end of the optical fiber, and a mirror or the like can be separately arranged. In this configuration, interference light is generated by setting a difference in optical path length between the measurement optical path Lm and the reference optical path Lr.

[0259] exist Figure 22 In (c), a measurement optical path Lm guiding the measurement light to the object T and a reference optical path Lr guiding the reference light are formed in the optical path after the optical branch 120, and a balance detector (Mach-Zehnder interferometer) is arranged in the reference optical path Lr. In this configuration, interference light is generated by setting an optical path length difference between the optical path lengths of the measurement optical path Lm and the reference optical path Lr.

[0260] Thus, the interferometer is not limited to the Fizeau-type interferometer described in each embodiment. For example, it can also be a Michelson interferometer, a Mach-Zehnder interferometer, or any interferometer, as long as interference light can be generated by setting the difference in optical path length between the measuring light and the reference light. Combinations of these or other configurations can also be used.

[0261] It should be noted that in the various embodiments of the present invention, the optical interferometric ranging sensors 100 and 200 are described as single-channel, but are not limited thereto. For example, multiple optical couplers or the like can be used to branch the light projected from the wavelength scanning light source 110 to form a multi-stage optical interferometric ranging sensor. The present invention can also be applied to multi-stage optical interferometric ranging sensors.

[0262] The embodiments described above are for the purpose of understanding the present invention and are not intended to limit or explain the present invention. The elements, their configurations, materials, conditions, shapes, and dimensions, etc., included in the embodiments are not limited to those illustrated and can be appropriately modified. Furthermore, the configurations shown in different embodiments can be partially substituted for or combined with each other.

[0263] [appendix]

[0264] An optical interferometric ranging sensor (100) comprises:

[0265] The light source (110) projects light while changing its wavelength;

[0266] An interferometer (130) is supplied with light projected from the light source and generates interference light based on a measurement light and a reference light, wherein the measurement light is light that is irradiated onto the object being measured by a sensing head and reflected, and the reference light is light that travels along at least a portion of an optical path different from the measurement light.

[0267] The light receiving unit (140) receives interference light from the interferometer and converts it into an electrical signal;

[0268] The processing unit (150) calculates the distance from the sensing head to the object being measured based on the electrical signal converted by the light receiving unit;

[0269] The discrimination unit (160) identifies the sensing head based on the beat signal generated by the interferometer; and

[0270] The setting unit (170) sets the measurement conditions corresponding to the sensor head identified by the discrimination unit.

Claims

1. An optical interferometric ranging sensor, comprising: The light source projects light while changing its wavelength; An interferometer is supplied with light projected from the light source and generates interference light based on a measurement light and a reference light, wherein the measurement light is light that is reflected from the object being measured by a sensing head, and the reference light is light that travels along at least a portion of an optical path different from the measurement light. The light-receiving part receives the interference light from the interferometer and converts it into an electrical signal; The processing unit calculates the distance from the sensing head to the object being measured based on the electrical signal converted by the light receiving unit. The discrimination unit identifies the sensing head based on the beat signal generated by the interferometer; as well as The setting unit sets the measurement conditions corresponding to the sensing head identified by the discrimination unit. The beat signal is generated because a portion of the light emitted from the light source and received by the interferometer is reflected by the components of the interferometer, including a reflective surface, and the reflected light interferes with the reference light of the interferometer.

2. The optical interferometric ranging sensor according to claim 1, wherein, The setting unit adjusts the scanning ratio, represented by the frequency scanning width per scanning time, for the light projected from the light source based on the sensor head identified by the discrimination unit.

3. The optical interferometric ranging sensor according to claim 1 or 2, wherein, The optical interferometric ranging sensor also includes a correction signal generation unit, which generates a correction signal used for sampling when converting the interference light received by the light receiving unit into an electrical signal. The setting unit adjusts the degree of frequency multiplication of the correction signal based on the sensor head identified by the discrimination unit.

4. The optical interferometric ranging sensor according to claim 1 or 2, wherein, The discrimination unit identifies the sensor head based on at least one of the peak frequency and the number of peaks of the beat signal.

5. The optical interferometric ranging sensor according to claim 1, wherein, The reflective surface is formed inside the sensor head.

6. The optical interferometric ranging sensor according to claim 5, wherein, The reflective surface is formed in the objective lens included in the sensing head.

7. The optical interferometric ranging sensor according to claim 5 or 6, wherein, The reflective surface is formed in the collimating lens included in the sensing head.

8. The optical interferometric ranging sensor according to claim 1, wherein, The reflective surface is formed inside the optical fiber that supplies light projected from the light source to the sensing head.

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