Optical fiber cable, controller connected thereto, and optical interferometry distance measuring sensor using them.

Abstract

To easily adjust a length of an optical fiber cable according to a measurement environment.SOLUTION: An optical fiber cable is used in an optical interferometric ranging sensor having a light source unit for supplying light while sweeping a wavelength at a fixed period, light splitting means for splitting the light into measurement light and reference light, multiplexing means for multiplexing the reference light and reflected light from a measurement target, interference light detection means for detecting interference light multiplexed by the multiplexing means, and distance calculation means for calculating a distance to the measurement target by subjecting the interference light to frequency analysis. The optical fiber cable has a first optical fiber for guiding at least a portion of the light supplied from the light source unit and the measurement light that has been split off by the splitting means, and a second optical fiber for guiding at least a portion of the light supplied from the light source unit and the reference light that has been split by the splitting means.SELECTED DRAWING: Figure 5A

Description

Technical Field

[0001] The present invention relates to an optical fiber cable, a controller connected thereto, and an optical interference distance measuring sensor using them.

Background Art

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

[0003] For example, Patent Document 1 discloses an optical coherence tomography apparatus including an optical beam controller, branching means for branching a plurality of optical beams from the optical beam controller into object light and reference light, irradiation means for irradiating a plurality of object light beams onto a measurement object, and interference means for causing interference between object light scattered from the measurement object and reference light and guiding it to a light receiver.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In an apparatus that uses interference light between measurement light and reference light as described above, for example, a configuration may be adopted in which measurement light is guided through an optical fiber cable that connects a controller and a sensor head. However, when the optical fiber cable is replaced, the optical path length difference between the measurement light and the reference light may deviate from the initial setting, making it difficult to adjust the length of the optical fiber cable according to the measurement environment.

[0006] Therefore, the present invention aims to provide an optical fiber cable that can easily adjust the length of the optical fiber cable according to the measurement environment, a controller connected thereto, and an optical interferometry distance measuring sensor using the same. [Means for solving the problem]

[0007] An optical fiber cable according to one aspect of the present invention is an optical fiber cable used in an optical interferometry distance measuring sensor, comprising: a light source unit that supplies light while sweeping the wavelength at a constant period; an optical splitting means that splits the light supplied from the light source unit into a measurement light and a reference light; a multiplexing means that combines the reflected light from a measurement target and the reference light when the measurement light split by the optical splitting means is irradiated onto the measurement target; an interference light detection means that detects interference light between the reflected light and the reference light combined by the multiplexing means; and a distance calculation means that calculates the distance to the measurement target by frequency analysis of the interference light detected by the interference light detection means, wherein the optical fiber cable comprises a first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light split by the splitting means, and a second optical fiber that guides at least a portion of the light supplied from the light source unit and the reference light split by the splitting means.

[0008] According to this embodiment, the optical fiber cable has a first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light divided by the division means, and a second optical fiber that guides at least a portion of the light supplied from the light source unit and the reference light divided by the division means. Therefore, within the optical fiber cable, both the measurement light and the reference light are guided, or the light before it is divided into measurement light and reference light is guided, so the setting of the optical path length difference between the measurement light and the reference light does not change even when the optical fiber cable is replaced. Accordingly, it is possible to easily adjust the length of the optical fiber cable according to the measurement environment.

[0009] In the above embodiment, the first optical fiber may include the optical path for the measurement light, and the second optical fiber may include the optical path for the reference light.

[0010] According to this embodiment, since both the measurement light and the reference light are guided within the optical fiber cable, the setting of the optical path length difference between the measurement light and the reference light does not change even when the optical fiber cable is replaced, and therefore, the length of the optical fiber cable can be easily adjusted according to the measurement environment.

[0011] In the above embodiment, the second optical fiber may be the first optical fiber.

[0012] According to this embodiment, the configuration of the optical fiber cable is simplified.

[0013] In the above embodiment, a light-splitting means may be further included.

[0014] This embodiment improves the design flexibility of optical fiber cables.

[0015] In the above embodiment, a reference surface that reflects reference light may be further included.

[0016] This embodiment improves the design flexibility of optical fiber cables.

[0017] A controller according to one aspect of the present invention comprises: a light source unit that supplies light while sweeping the wavelength at a constant period; an optical splitting means that splits the light supplied from the light source unit into a measurement light and a reference light; a multiplexing means that combines the reflected light from a measurement target and the reference light when the measurement light split by the optical splitting means is irradiated onto the measurement target; an interference light detection means that detects interference light between the reflected light and the reference light combined by the multiplexing means; and a distance calculation means that calculates the distance to the measurement target by frequency analysis of the interference light detected by the interference light detection means, the controller further comprising: a first connection part connected to a first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light split by the splitting means; and a second connection part connected to a second optical fiber that guides at least a portion of the light supplied from the light source unit and the reference light split by the splitting means.

[0018] According to this embodiment, the optical fiber cable has a first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light divided by the division means, and a second optical fiber that guides at least a portion of the light supplied from the light source unit and the reference light divided by the division means. Therefore, within the optical fiber cable, both the measurement light and the reference light are guided, or the light before it is divided into measurement light and reference light is guided, so the setting of the optical path length difference between the measurement light and the reference light does not change even when the optical fiber cable is replaced. Accordingly, it is possible to easily adjust the length of the optical fiber cable according to the measurement environment.

[0019] An optical interferometry distance measuring sensor according to one aspect of the present invention is an optical interferometry distance measuring sensor having an optical fiber cable and a controller, wherein the controller has a light source unit that supplies light while sweeping the wavelength at a constant period, an optical splitting means that splits the light supplied from the light source unit into measurement light and reference light, a multiplexing means that combines the reflected light from the measurement target and the reference light when the measurement light split by the optical splitting means is irradiated onto the measurement target, an interference light detection means that detects interference light of the reflected light and the reference light combined by the multiplexing means, and a distance calculation means that calculates the distance to the measurement target by frequency analysis of the interference light detected by the interference light detection means, and the optical fiber cable has a first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light split by the splitting means, and a second optical fiber that guides at least a portion of the light supplied from the light source unit and the reference light split by the splitting means, the optical interferometry distance measuring sensor.

[0020] According to this aspect, the optical fiber cable has a first optical fiber that guides at least a part of the light supplied from the light source unit and the measurement light split by the splitting means, and a second optical fiber that guides at least a part of the light supplied from the light source unit and the reference light split by the splitting means. Therefore, in the optical fiber cable, both the measurement light and the reference light are guided, or the light before being split into the measurement light and the reference light is guided. Thus, the setting of the optical path length difference between the measurement light and the reference light does not change even when the optical fiber cable is replaced. Therefore, it is possible to easily adjust the length of the optical fiber cable according to the measurement environment.

[0021] In the above aspect, the optical fiber cable may further include a reference surface that reflects the reference light.

[0022] According to this aspect, the degree of freedom in the design of the optical fiber cable is improved.

Advantages of the Invention

[0023] According to the present invention, it is possible to provide an optical fiber cable capable of connecting an appropriate second optical fiber to a secondary interferometer corresponding to a first optical fiber connected to a main interferometer, a controller connected thereto, and an optical interference distance measurement sensor using them.

Brief Description of the Drawings

[0024] [Figure 1] It is an external schematic view showing an outline of a displacement sensor 10 according to the present disclosure. [Figure 2] It is a flowchart showing a procedure for measuring a measurement object T by the displacement sensor 10 according to the present disclosure. [Figure 3] It is a functional block diagram showing an outline of a sensor system 1 in which the displacement sensor 1 according to the present disclosure is used. [Figure 4] It is a flowchart showing a procedure for measuring a measurement object T by the sensor system 1 in which the displacement sensor 10 according to the present disclosure is used. [Figure 5A]This figure illustrates the principle by which the displacement sensor 10 relating to this disclosure measures the object T to be measured. [Figure 5B] This figure illustrates another principle by which the object T is measured by the displacement sensor 10 relating to this disclosure. [Figure 6A] This is a perspective view showing the schematic configuration of the sensor head 20. [Figure 6B] This is a schematic diagram showing the internal structure of the sensor head 20. [Figure 7] This is a block diagram illustrating the signal processing in controller 30. [Figure 8] This flowchart shows the method for calculating the distance to the object T to be measured, as performed by the processing unit 59 in the controller 30. [Figure 9A] This diagram illustrates how a waveform signal (voltage vs. time) is frequency-converted into a spectrum (voltage vs. frequency). [Figure 9B] This diagram illustrates how a spectrum (voltage vs. frequency) is converted to a spectrum (voltage vs. distance) through distance conversion. [Figure 9C] This diagram shows how peaks are detected based on the spectrum (voltage vs. distance), and how the corresponding distance values ​​are calculated. [Figure 10] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 11A] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 11B] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 12] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 13A] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 13B] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 14] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 15] This is a schematic diagram showing an example of the configuration of an optical fiber cable. [Figure 16] This is a diagram illustrating a variation of an optical fiber cable. [Figure 17] This is a diagram illustrating a variation of an optical fiber cable. [Modes for carrying out the invention]

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are merely examples of specific actions for carrying out the present invention and are not intended to limit the scope of the invention. Furthermore, in order to facilitate understanding of the explanation, the same reference numerals are used for identical components in the drawings whenever possible, and redundant explanations may be omitted.

[0026] [Overview of Displacement Sensors] First, I will explain the overview of the displacement sensor related to this disclosure. Figure 1 is a schematic diagram showing the external appearance of the displacement sensor 10 according to this disclosure. As shown in Figure 1, the displacement sensor 10 comprises a sensor head 20 and a controller 30, and measures the displacement of the object to be measured T (distance to the object to be measured T).

[0027] The sensor head 20 and the controller 30 are connected by an optical fiber cable 40, and an objective lens 21 is attached to the sensor head 20. The controller 30 also includes a display unit 31, a setting unit 32, an external interface (I / F) unit 33, an optical fiber connection unit 34, and an external storage unit 35, and internally has a measurement processing unit 36.

[0028] The sensor head 20 irradiates the object T to be measured with light output from the controller 30 and receives the reflected light from the object T. The sensor head 20 has a reference surface inside that reflects the light output from the controller 30 and received via the optical fiber cable 40, and interferes with the reflected light from the object T as described above.

[0029] The sensor head 20 is equipped with an objective lens 21, which is detachable. The objective lens 21 can be replaced with an objective lens having an appropriate focal length depending on the distance between the sensor head 20 and the object T to be measured, or a variable-focus objective lens may be used.

[0030] Furthermore, when installing the sensor head 20, guide light (visible light) may be shone onto the object T to be measured, and the sensor head 20 and / or the object T to be measured may be positioned so that the object T is appropriately located within the measurement area of ​​the displacement sensor 10.

[0031] The optical fiber cable 40 is connected to and extends from an optical fiber cable connection part 34 located on the controller 30, connecting the controller 30 and the sensor head 20. The optical fiber cable 40 may include at least one optical fiber 41P that guides the reference light and at least one optical fiber 42P that guides the measurement light. In this way, the optical fiber cable 40 is configured to guide the light emitted from the controller 30 to the sensor head 20 via the optical fiber 42P, and further guide the light returned from the sensor head 20 to the controller 30 via the optical fiber 42P. The optical fiber cable 40 is detachable from the sensor head 20 and the controller 30, and various optical fiber cables in terms of length, thickness, and characteristics can be used. The optical fiber cable 40 may be configured as a single-core cable with one core formed in one cladding, or as a multi-core cable with multiple cores formed in one cladding. In the case of a multi-core cable, the distance between the multiple optical paths becomes shorter, making it possible to suppress fluctuations between the measurement optical path and the reference optical path due to bending and temperature fluctuations applied to the optical fiber cable 40.

[0032] The display unit 31 is composed of, for example, a liquid crystal display or an organic EL display. The display unit 31 displays the set value of the displacement sensor 10, the amount of reflected light received from the sensor head 20, and measurement results such as the displacement of the object to be measured T (distance to the object to be measured T) measured by the displacement sensor 10.

[0033] The setting unit 32 allows the user to operate, for example, mechanical buttons or a touch panel, to perform the necessary settings for measuring the object T. All or part of these necessary settings may be pre-configured, or they may be configured by an external device (not shown) connected to the external I / F unit 33. The external device may be connected via a network by wire or wireless.

[0034] Here, the external I / F unit 33 consists of, for example, Ethernet®, RS232C, and analog output. The external I / F unit 33 may be connected to other connected devices so that necessary settings can be made from those external connected devices, or it may output measurement results measured by the displacement sensor 10 to the external connected devices.

[0035] Furthermore, the controller 30 may acquire data stored in the external storage unit 35, thereby performing the necessary settings for measuring the object T. The external storage unit 35 is, for example, an auxiliary storage device such as a USB (Universal Serial Bus) memory, which has the necessary settings for measuring the object T pre-stored in it.

[0036] The measurement processing unit 36 ​​in the controller 30 includes, for example, a wavelength-swept light source that emits light while continuously changing the wavelength, a photodetector that receives the reflected light from the sensor head 20 and converts it into an electrical signal, and a signal processing circuit that processes the electrical signal. Based on the reflected light from the sensor head 20, the measurement processing unit 36 ​​performs various processes using the control unit and memory unit, etc., so that the displacement of the object to be measured T (distance to the object to be measured T) is ultimately calculated. Details of these processes will be described later.

[0037] Figure 2 is a flowchart showing the procedure for measuring an object T using the displacement sensor 10 according to this disclosure. As shown in Figure 2, the procedure includes steps S11 to S14.

[0038] In step S11, the sensor head 20 is installed. For example, guide light is shone from the sensor head 20 onto the object T to be measured, and the sensor head 20 is installed in the appropriate position using this as a reference.

[0039] Specifically, the display unit 31 of the controller 30 displays the amount of reflected light received from the sensor head 20, and the user may adjust the orientation of the sensor head 20 and the distance (height position) from the object to be measured T while checking the amount of received light. Basically, if the light from the sensor head 20 can be shone perpendicularly (or at an angle as close to perpendicular as possible) to the object to be measured T, the amount of reflected light from the object to be measured T will be large, and the amount of reflected light received from the sensor head 20 will also be large.

[0040] Furthermore, the objective lens 21 may be replaced with one having an appropriate focal length depending on the distance between the sensor head 20 and the object T to be measured.

[0041] Furthermore, if the appropriate settings cannot be made when measuring the object T to be measured (for example, if the amount of light required for measurement cannot be obtained, or if the focal length of the objective lens 21 is inappropriate), the system may notify the user of an error or incomplete setting by displaying it on the display unit 31 or outputting it to an externally connected device.

[0042] In step S12, various measurement conditions are set when measuring the object T to be measured. For example, the user sets the unique calibration data (such as a function to correct linearity) of the sensor head 20 by operating the setting unit 32 on the controller 30.

[0043] Furthermore, various parameters may be set. For example, sampling time, measurement range, and thresholds for determining whether a measurement result is normal or abnormal may be set. In addition, the measurement period may be set according to the characteristics of the object T to be measured, such as its reflectance and material, and the measurement mode may be set according to the material of the object T to be measured.

[0044] These measurement conditions and various parameters are set by operating the setting unit 32 in the controller 30, but they may also be set from an externally connected device or by acquiring data from the external storage unit 35.

[0045] In step S13, the sensor head 20 installed in step S11 measures the object T according to the measurement conditions and various parameters set in step S12.

[0046] Specifically, in the measurement processing unit 36 ​​of the controller 30, light is emitted from the wavelength-swept light source, the reflected light from the sensor head 20 is received by the photodetector, and the signal processing circuit performs frequency analysis, distance conversion, and peak detection to calculate the displacement of the object to be measured T (distance to the object to be measured T). Details of the specific measurement process will be described later.

[0047] In step S14, the measurement results measured in step S13 are output. For example, the displacement of the object T measured in step S13 (distance to the object T) is displayed on the display unit 31 of the controller 30 or output to an externally connected device.

[0048] Furthermore, the displacement of the object T measured in step S13 (distance to the object T) may also be displayed or output as a measurement result, indicating whether it is within the normal range or abnormal based on the threshold set in step S12. In addition, the measurement conditions, various parameters, and measurement mode set in step S12 may also be displayed or output.

[0049] [Overview of the system including the displacement sensor] Figure 3 is a functional block diagram showing an overview of a sensor system 1 in which the displacement sensor 10 according to this disclosure is used. As shown in Figure 3, the sensor system 1 comprises a displacement sensor 10, a control device 11, a control signal input sensor 12, and an external connection device 13. The displacement sensor 10 is connected to the control device 11 and the external connection device 13 by, for example, a communication cable or an external connection cord (including, for example, an external input line, an external output line, and a power line), and the control device 11 and the control signal input sensor 12 are connected by a signal line.

[0050] As explained using Figures 1 and 2, the displacement sensor 10 measures the displacement of the object T (distance to the object T). The displacement sensor 10 may also output the measurement results to the control device 11 and the external connection device 13.

[0051] The control device 11 is, for example, a PLC (Programmable Logic Controller), which gives various instructions to the displacement sensor 10 when the displacement sensor 10 measures the object T to be measured.

[0052] For example, the control device 11 may output a measurement timing signal to the displacement sensor 10 based on an input signal from a control signal input sensor 12 connected to the control device 11, or it may output a zero reset command signal (a signal to set the current measured value to 0) to the displacement sensor 10.

[0053] The control signal input sensor 12 outputs an on / off signal to the control device 11 that indicates the timing for the displacement sensor 10 to measure the object T. For example, the control signal input sensor 12 can be installed near a production line where the object T moves, and it can detect when the object T moves to a predetermined position and output an on / off signal to the control device 11.

[0054] The external device 13 is, for example, a PC (Personal Computer), which allows the user to make various settings for the displacement sensor 10 by operating it.

[0055] Specific examples include setting the measurement mode, operating mode, measurement cycle, and the material of the object T being measured.

[0056] As for the measurement mode setting, options such as "internal synchronous measurement mode," which starts measurement periodically within the control device 11, or "external synchronous measurement mode," which starts measurement in response to an input signal from outside the control device 11, can be selected.

[0057] For setting the operating mode, you can select either the "operation mode" which actually measures the object T to be measured, or the "adjustment mode" which sets the measurement conditions for measuring the object T to be measured.

[0058] The measurement period is the period during which the object T is measured, and it should be set according to the reflectance of the object T. However, even if the reflectance of the object T is low, the object T can still be measured appropriately by setting the measurement period to be longer.

[0059] For the object T being measured, a "rough surface mode" suitable for cases where diffuse reflection is relatively abundant in the reflected light component, a "specular surface mode" suitable for cases where specular reflection is relatively abundant in the reflected light component, or an intermediate "standard mode" are selected.

[0060] In this way, by making appropriate settings according to the reflectance and material of the object T to be measured, the object T can be measured with higher accuracy.

[0061] Figure 4 is a flowchart showing the procedure for measuring an object T by a sensor system 1 using the displacement sensor 10 according to this disclosure. As shown in Figure 4, the procedure is for the external synchronous measurement mode described above and includes steps S21 to S24.

[0062] In step S21, the sensor system 1 detects the object to be measured, T. Specifically, the control signal input sensor 12 detects that the object to be measured T has moved to a predetermined position on the production line.

[0063] In step S22, the sensor system 1 instructs the displacement sensor 10 to measure the object T detected in step S21. Specifically, the control signal input sensor 12 outputs an on / off signal to the control device 11, instructing it on the timing to measure the object T detected in step S21. Based on this on / off signal, the control device 11 outputs a measurement timing signal to the displacement sensor 10, instructing it to measure the object T.

[0064] 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.

[0065] In step S24, the sensor system 1 outputs the measurement results measured in step S23. Specifically, the displacement sensor 10 displays the measurement results on the display unit 31 or outputs them to the control device 11 or external connection device 13 via the external I / F unit 33.

[0066] In this document, Figure 4 illustrates the procedure for the external synchronous measurement mode, in which the object T is detected by the control signal input sensor 12 and measured. However, the procedure is not limited to this. For example, in the internal synchronous measurement mode, instead of steps S21 and S22, a measurement timing signal is generated based on a preset period to instruct the displacement sensor 10 to measure the object T.

[0067] Next, the principle by which the object T is measured by the displacement sensor 10 according to this disclosure will be explained. Figure 5A is a diagram illustrating the principle by which an object T is measured by the displacement sensor 10 according to this disclosure. As shown in Figure 5A, the displacement sensor 10 comprises a sensor head 20, an optical fiber cable 40, and a controller 30. The sensor head 20 includes an objective lens 21 and a plurality of collimating lenses 22a to 22c, and the controller 30 includes a wavelength-swept light source 51, an optical amplifier 52, a plurality of isolators 53 and 53a to 53b, a plurality of optical couplers 54 and 54a to 54e, an attenuator 55, a plurality of photodetectors (e.g., photodetectors (PDs)) 56a to 56c, a plurality of amplification circuits 57a to 57c, a plurality of analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a to 58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generation unit 61. The optical fiber cable 40 includes optical fibers 41Pa to 41Pc and optical fibers 42Pa to 42Pc.

[0068] The wavelength-swept light source 51 emits laser light with a swept wavelength. For example, if a method is applied to modulate a VCSEL (Vertical Cavity Surface Emitting Laser) with current as the wavelength-swept light source 51, mode hopping is less likely to occur due to the short resonator length, the wavelength can be easily changed, and it can be realized at low cost.

[0069] The optical amplifier 52 amplifies the light emitted from the wavelength-swept light source 51. The optical amplifier 52 may, for example, use an EDFA (erbium-doped fiber amplifier) ​​and may be, for example, an optical amplifier dedicated to 1550 nm.

[0070] The isolator 53 is an optical element that transmits incident light in one direction and may be placed immediately after the wavelength-swept light source 51 to prevent the effects of noise generated by reflected light.

[0071] In this manner, the light emitted from the wavelength-swept light source 51 is amplified by the optical amplifier 52 and then split into a main interferometer and a secondary interferometer by the optical coupler 54 via the isolator 53. For example, the optical coupler 54 may be configured to split 90% or more of the light into the main interferometer.

[0072] The light that has been split to the main interferometer is further split by the first-stage optical coupler 54a into two directions: one towards the sensor head 20 and the other towards the second-stage optical coupler 54b.

[0073] The light branched towards the sensor head 20 by the first-stage optical coupler 54a is further branched by the optical coupler 62a towards the first-stage optical fibers 41Pa and 42Pa of the optical fiber cable 40. The light branched towards optical fiber 41Pa becomes the reference light, and the light branched towards optical fiber 42Pa becomes the measurement light. That is, the reference light incident on optical fiber 41Pa from end 41Ia is guided through optical fiber 41Pa, reflected by the reference surface 41Ra, guided through optical fiber 41Pa towards end 41Ia, and supplied from end 41Ia to optical coupler 62a. On the other hand, the measurement light incident on optical fiber 42Pa from end 42Ia is guided through optical fiber 42Pa, incident on the optical fiber in the sensor head 20 from end 42Oa, and in the sensor head 20, passes through the collimating lens 22a and objective lens 21 to irradiate the object T to be measured. The measurement light reflected by the object T is then incident on the end 42Oa of the optical fiber 42Pa via the sensor head 20, guided through the optical fiber 42Pa, and supplied from the end 42Ia to the optical coupler 62a. The reference light supplied from the end 41Ia of the optical fiber cable 40 and the measurement light supplied from the end 42Ia of the optical fiber cable 40 interfere at the optical coupler 62a, generating interference light, and at least a portion of this interference light is supplied to the photodetector 56a. The interference light received by the photodetector 56a is converted into an electrical signal.

[0074] The light branched by the first-stage optical coupler 54a toward the second-stage optical coupler 54b proceeds to the second-stage optical coupler 54b via the isolator 53a, and is further branched by the second-stage optical coupler 54b toward the sensor head 20 and the third-stage optical coupler 54c. The light branched from optical coupler 54b toward the sensor head 20 is branched by optical coupler 62b toward the second-stage optical fibers 41Pb and 42Pb of the optical fiber cable 40, similar to the first stage. The light branched toward optical fiber 41Pb becomes the reference light, and the light branched toward optical fiber 42Pb becomes the measurement light. That is, the reference light incident on optical fiber 41Pb from end 41Ib is guided through optical fiber 41Pb, reflected by the reference surface 41Rb, guided through optical fiber 41Pb toward end 41Ib, and supplied from end 41Ib to optical coupler 62b. Meanwhile, the measurement light that enters the optical fiber 42Pb from end 42Ib is guided through the optical fiber 42Pb and enters the optical fiber in the sensor head 20 from end 42Ob. In the sensor head 20, it passes through the collimating lens 22b and the objective lens 21 and is irradiated onto the object to be measured T. The measurement light reflected by the object to be measured T enters end 42Ob of the optical fiber 42Pb via the sensor head 20, is guided through the optical fiber 42Pb, and is supplied from end 42Ib to the optical coupler 62b. The reference light supplied from end 41Ib of the optical fiber cable 40 and the measurement light supplied from end 42Ib of the optical fiber cable 40 interfere at the optical coupler 62b, generating interference light, and at least a portion of this interference light is supplied to the photodetector 56b. The interference light received by the photodetector 56b is converted into an electrical signal.

[0075] The light branched by the second-stage optical coupler 54b toward the third-stage optical coupler 54c proceeds to the third-stage optical coupler 54c via the isolator 53b, and is further branched by the third-stage optical coupler 54c toward the sensor head 20 and the attenuator 55. The light branched from optical coupler 54c toward the sensor head 20 is branched by optical coupler 62c toward the third-stage optical fibers 41Pc and 42Pc of the optical fiber cable 40, similar to the first and second stages. The light branched toward optical fiber 41Pc becomes the reference light, and the light branched toward optical fiber 42Pc becomes the measurement light. That is, the reference light incident on the optical fiber 41Pc from end 41Ic is guided through the optical fiber 41Pc, reflected by the reference surface 41Rc, guided through the optical fiber 41Pc toward end 41Ic, and supplied from end 41Ic to optical coupler 62c. Meanwhile, the measurement light that enters the optical fiber 42Pc from end 42Ic is guided through the optical fiber 42Pc and enters the optical fiber in the sensor head 20 from end 42Oc. In the sensor head 20, it passes through the collimating lens 22c and the objective lens 21 and is irradiated onto the object to be measured T. The measurement light reflected by the object to be measured T enters end 42Oc of the optical fiber 42Pc via the sensor head 20, is guided through the optical fiber 42Pc, and is supplied from end 42Ic to the optical coupler 62c. The reference light supplied from end 41Ic of the optical fiber cable 40 and the measurement light supplied from end 42Ic of the optical fiber cable 40 interfere at the optical coupler 62c, generating interference light, and at least a portion of this interference light is supplied to the photodetector 56c. The interference light received by the photodetector 56c is converted into an electrical signal.

[0076] Furthermore, the light that is branched away from the sensor head 20 by the third-stage optical coupler 54c is not used to measure the object T, so it is preferable to attenuate it by an attenuator 55, such as a terminator, so that it does not reflect back.

[0077] Thus, the main interferometer has three optical paths (3 channels), each with an optical path length difference equal to twice the distance (round trip) from the tip (end face) of the optical fiber of the sensor head 20 to the object T being measured, and generates three interference beams corresponding to the optical path length difference.

[0078] As described above, the light-receiving elements 56a to 56c receive interference light from the main interferometer and generate an electrical signal corresponding to the amount of light received.

[0079] The amplification circuits 57a to 57c each amplify the electrical signals output from the photodetectors 56a to 56c.

[0080] The AD conversion units 58a to 58c each receive the electrical signals amplified by the amplification circuits 57a to 57c and convert the analog signals into digital signals (AD conversion). Here, the AD conversion units 58a to 58c perform AD conversion based on the correction signals from the correction signal generation unit 61 in the sub-interferometer.

[0081] In the secondary interferometer, in order to correct the wavelength nonlinearity during the sweep of the wavelength-swept light source 51, the interferometer acquires the interference signal and generates a correction signal called a K-clock.

[0082] Specifically, the light branched to the sub-interferometer by the optical coupler 54 is further branched by the optical coupler 54d. Here, the optical paths of each branched light are configured to have a difference in optical path length, for example, by using optical fibers of different lengths between the optical coupler 54d and the optical coupler 54e, and interference light corresponding to this difference in optical path length is output from the optical coupler 54e. The balance detector 60 then receives the interference light from the optical coupler 54e, removes noise by taking the difference between it and a signal with the opposite phase, and amplifies the optical signal to convert it into an electrical signal.

[0083] Furthermore, both the optical coupler 54d and the optical coupler 54e should split the light in a 50:50 ratio.

[0084] The correction signal generation unit 61, based on the electrical signal from the balance detector 60, grasps the nonlinearity of the wavelength during the sweep of the wavelength-swept light source 51, generates a K clock corresponding to the nonlinearity, and outputs it to the AD conversion units 58a to 58c.

[0085] Due to the nonlinearity of the wavelength during the sweep of the wavelength-swept light source 51, the intervals between the waves of the analog signals input to the AD conversion units 58a to 58c in the main interferometer are not equal. In the AD conversion units 58a to 58c, the sampling time is corrected based on the K clock described above to make the intervals between waves equal, and then AD conversion (sampling) is performed.

[0086] Furthermore, as mentioned above, the K clock is a correction signal used to sample the analog signal of the main interferometer, and therefore needs to be generated at a higher frequency than the analog signal of the main interferometer. Specifically, the optical path length difference between the optical coupler 54d and the optical coupler 54e in the sub-interferometer may be made longer than the optical path length difference between the tip (end face) of the optical fiber and the object T being measured in the main interferometer, or the frequency may be multiplied (for example, by 8 times) in the correction signal generation unit 61 to increase the frequency.

[0087] The processing unit 59 acquires digital signals that have been AD converted while nonlinearity is corrected by the AD conversion units 58a to 58c, and calculates the displacement of the object T (distance to the object T) based on these digital signals. Specifically, the processing unit 59 calculates the distance by frequency converting the digital signals using the Fast Fourier Transform (FFT) and analyzing them. The detailed processing in the processing unit 59 will be described later.

[0088] Furthermore, since high-speed processing is required in the processing unit 59, it is often implemented using an integrated circuit such as an FPGA (field-programmable gate array).

[0089] Furthermore, in this system, the main interferometer is provided with three optical paths, and the sensor head 20 illuminates the object T to be measured from each optical path with measurement light. Based on the interference light (reflected light) obtained from each path, the distance to the object T is measured (multi-channel). The number of channels in the main interferometer is not limited to three; it may be one or two, or four or more.

[0090] Figure 5B is a diagram illustrating another principle by which an object T is measured by the displacement sensor 10 according to the present disclosure. As shown in Figure 5B, the displacement sensor 10 comprises a sensor head 20, an optical fiber cable 40, and a controller 30. The sensor head 20 includes an objective lens 21 and a plurality of collimating lenses 22a to 22c, and the controller 30 includes a wavelength-swept light source 51, an optical amplifier 52, a plurality of isolators 53 and 53a to 53b, a plurality of optical couplers 54 and 54a to 54j, an attenuator 55, a plurality of photodetectors (e.g., photodetectors (PDs)) 56a to 56c, a plurality of amplification circuits 57a to 57c, a plurality of analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a to 58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generation unit 61. The optical fiber cable 40 includes optical fibers 42Pa to 42Pc and optical fibers 43Pa to 43Pc.

[0091] Light emitted from the wavelength-swept light source 51 is amplified by the optical amplifier 52 and split via the isolator 53 to the main interferometer side and the sub-interferometer side by the optical coupler 54. The light split to the main interferometer side is further split into measurement light and reference light by the optical coupler 54f.

[0092] The measurement light passes sequentially through the optical fiber 42Pa of the optical fiber cable 40, the collimating lens 22a and objective lens 21 of the sensor head 20, via the first-stage optical coupler 54a, and is irradiated onto the object to be measured T, where it is reflected. The measurement light reflected by the object to be measured T enters the end 42Oa of the optical fiber 42Pa via the sensor head 20, is guided through the optical fiber 42Pa, and is supplied from the end 42Ia to the optical coupler 54h via the optical coupler 54a.

[0093] Similarly, the light branched from the first optical coupler 54a towards the second optical coupler 54b passes through the optical fiber 42Pb of the optical fiber cable 40, the collimating lens 22b and objective lens 21 of the sensor head 20 sequentially, and is irradiated onto the object to be measured T. After being reflected by the object to be measured T, it returns to the second optical coupler 54b and is supplied to the optical coupler 54i via optical coupler 54b. The light branched from the second optical coupler 54b towards the third optical coupler 54c passes through the optical fiber 42Pc of the optical fiber cable 40, the collimating lens 22c and objective lens 21 of the sensor head 20 sequentially, and is irradiated onto the object to be measured T. After being reflected by the object to be measured T, it returns to the third optical coupler 54c and is supplied to the optical coupler 54j via optical coupler 54c.

[0094] Meanwhile, the reference light branched by the optical coupler 54f is further branched by the optical coupler 54g in the direction of the respective ends 43Ia to 43Ic of the optical fiber cable 40. The reference light incident on each of the ends 43Ia to 43Ic of the optical fiber cable 40 is guided through the optical fibers 43Pa to 43Pc of the optical fiber cable 40, respectively. On the opposite side of the ends 43Ia to 43Ic of the optical fibers 43Pa to 43Pc, ends 43Oa to 43Oc are provided. The reference light guided through the optical fibers 43Pa to 43Pc is supplied from ends 43Oa to 43Oc to the optical couplers 54h, 54i, and 54j, respectively.

[0095] In the optical coupler 54h, the measurement light reflected from the object T to be measured, output from the optical coupler 54a, and the reference light, output from the optical coupler 54g and guided through the optical fiber 43Pa in the optical fiber cable 40, interfere with each other, generating interference light which is received by the photodetector 56a and converted into an electrical signal. In other words, the optical coupler 54f splits the measurement light into a measurement light and a reference light, and interference light is generated according to the difference in optical path length between the optical path of the measurement light (the optical path from the optical coupler 54f, through the optical coupler 54a, optical fiber 42Pa, collimating lens 22a, objective lens 21, reflected from the object T to be measured, and reaching the optical coupler 54h) and the optical path of the reference light (the optical path from the optical coupler 54f, guided through the optical fiber 43Pa via the optical coupler 54g, and reaching the optical coupler 54h), and this interference light is received by the photodetector 56a and converted into an electrical signal.

[0096] In the optical coupler 54i, interference light is generated according to the difference in optical path length between the optical path of the measurement light (the optical path from optical coupler 54f, through optical couplers 54a, 54b, optical fiber 42Pb, collimating lens 22b, and objective lens 21, reflected by the object T to be measured, and reaching optical coupler 54i) and the optical path of the reference light (the optical path from optical coupler 54f, guided through optical coupler 54g and optical fiber 43Pb, and reaching optical coupler 54i). This interference light is received by the photodetector 56b and converted into an electrical signal.

[0097] In the optical coupler 54j, interference light is generated according to the difference in optical path length between the optical path of the measurement light (the optical path from optical coupler 54f, through optical couplers 54a, 54b, 54c, optical fiber 42Pc, collimating lens 22c, and objective lens 21, reflected by the object T to be measured, and reaching optical coupler 54j) and the optical path of the reference light (the optical path from optical coupler 54f, guided through optical coupler 54g and optical fiber 43Pc, and reaching optical coupler 54j). This interference light is received by the photodetector 56c and converted into an electrical signal. Note that the photodetectors 56a to 56c may be, for example, balanced photodetectors.

[0098] Thus, the main interferometer has three optical paths (3 channels), and generates three interference beams corresponding to the difference in optical path length between the measurement light reflected from the object T being measured and input to optical couplers 54h, 54i, and 54j, and the reference light input to optical couplers 54h, 54i, and 54j, respectively, via optical couplers 54f and 54g and optical fiber cable 40.

[0099] Furthermore, the difference in optical path length between the measurement light and the reference light may be set differently for each of the three channels, for example, by setting the optical path lengths between optical coupler 54g and each of the optical couplers 54h, 54i, and 54j to be different.

[0100] Then, based on the interference light obtained from each source, the distance to the object T is measured (multi-channel).

[0101] [Sensor head structure] Here, we will describe the structure of the sensor head used in the displacement sensor 10. Figure 6A is a perspective view showing the schematic configuration of the sensor head 20, and Figure 6B is a schematic diagram showing the internal structure of the sensor head.

[0102] As shown in Figure 6A, the sensor head 20 has an objective lens 21 and a collimating lens housed in a lens holder 23. For example, the size of the lens holder 23 is such that the length of one side surrounding the objective lens 21 is about 20 mm, and the length in the optical axis direction is about 40 mm. An optical fiber cable 40 is connected to the sensor head 20.

[0103] As shown in Figure 6B, the lens holder 23 houses one objective lens 21 and three collimating lenses 22a to 22c. The light from the optical fibers that guide the measurement light contained in the optical fiber cable 40 is directed to the collimating lenses 22a to 22c, and the light that has passed through the three collimating lenses 22a to 22c is then irradiated onto the object to be measured T via the objective lens 21. In the example shown in Figure 6B, there are three collimating lenses, but the number of collimating lenses may be a number corresponding to the number of optical fibers that guide the measurement light contained in the optical fiber cable 40.

[0104] In this way, these optical fiber cables 40 and collimating lenses 22a to 22c are held together with the objective lens 21 by the lens holder 23 to constitute the sensor head 20.

[0105] Furthermore, the lens holder 23 constituting the sensor head 20 may be made of a metal (for example, A2017) that is high-strength and can be machined with high precision.

[0106] Figure 7 is a block diagram illustrating signal processing in the controller 30. As shown in Figure 7, the controller 30 comprises a plurality of photodetectors 71a to 71e, a plurality of amplification circuits 72a to 72c, a plurality of AD conversion units 74a to 74c, a processing unit 75, a differential amplification circuit 76, and a correction signal generation unit 77.

[0107] As shown in Figure 5A, the controller 30 splits the light emitted from the wavelength-swept light source 51 into a main interferometer and a sub-interferometer using an optical coupler 54, and calculates the distance to the object T to be measured by processing the main and sub-interferometer signals obtained from each.

[0108] Multiple photodetectors 71a to 71c correspond to the photodetectors 56a to 56c shown in Figure 5A, and each receives the main interference signal from the main interferometer and outputs it as a current signal to the amplification circuits 72a to 72c, respectively.

[0109] Multiple amplification circuits 72a to 72c convert current signals into voltage signals (IV conversion) and amplify them.

[0110] Multiple AD conversion units 74a to 74c correspond to the AD conversion units 58a to 58c shown in Figure 5A, and convert voltage signals into digital signals (AD conversion) based on the K clock from the correction signal generation unit 77, which will be described later.

[0111] The processing unit 75 corresponds to the processing unit 59 shown in Figure 5A. It converts the digital signals from the AD conversion units 74a to 74c into frequencies using FFT, analyzes them, and calculates the distance value to the object T to be measured.

[0112] Multiple photodetectors 71d to 71e and a differential amplifier circuit 76 correspond to the balanced detector 60 shown in Figure 5A. Each receives interference light from the sub-interferometer, one outputs an interference signal with inverted phase, and the interference signal is amplified and converted into a voltage signal while removing noise by taking the difference between the two signals.

[0113] The correction signal generation unit 77 corresponds to the correction signal generation unit 61 shown in Figure 5A. It binarizes the voltage signal using a comparator, generates a K-clock, and outputs it to the AD conversion units 74a to 74c. Since the K-clock needs to be generated at a higher frequency than the analog signal of the main interferometer, the frequency may be multiplied (for example, by 8 times) in the correction signal generation unit 77 to increase its frequency.

[0114] Figure 8 is a flowchart showing a method for calculating the distance to the object T to be measured, which is performed by the processing unit 59 in the controller 30. As shown in Figure 8, the method includes steps S31 to S34.

[0115] In step S31, the processing unit 59 uses the following FFT to frequency-convert the waveform signal (voltage vs time) into a spectrum (voltage vs frequency). Figure 9A shows how the waveform signal (voltage vs time) is frequency-converted into a spectrum (voltage vs frequency).

number

[0116] In step S32, the processing unit 59 converts the spectrum (voltage vs frequency) to a distance spectrum (voltage vs distance). Figure 9B shows how the spectrum (voltage vs frequency) is converted to a distance spectrum (voltage vs distance).

[0117] In step S33, the processing unit 59 calculates the distance value corresponding to the peak based on the spectrum (voltage vs distance). Figure 9C shows how peaks are detected based on the spectrum (voltage vs distance) and the corresponding distance values ​​are calculated. As shown in Figure 9C, in this case, peaks are detected in each of the three channels based on the spectrum (voltage vs distance), and the distance value corresponding to each peak is calculated.

[0118] In step S34, the processing unit 59 averages the distance values ​​calculated in step S33. Specifically, in step S33, the processing unit 59 detects peaks in each of the three channels based on the spectrum (voltage vs distance) and calculates the corresponding distance values. It then averages these values ​​and outputs the averaged result as the distance to the object T to be measured.

[0119] In step S34, the processing unit 59 prefers to average the distance values ​​calculated in step S33, specifically those with an SNR equal to or greater than a threshold. For example, if a peak is detected in any of the three channels based on its spectrum (voltage vs distance), but the SNR is below a threshold, the distance value calculated based on that spectrum is deemed unreliable and will not be used.

[0120] Next, the present disclosure will be described in detail as a specific embodiment, focusing on its more distinctive configuration, function, and properties. The optical interferometry distance measuring sensor shown below corresponds to the displacement sensor 10 described using Figures 1 to 9, and all or part of the basic configuration, function, and properties included in the optical interferometry distance measuring sensor are common to the configuration, function, and properties included in the displacement sensor 10 described using Figures 1 to 9.

[0121] <Embodiment> [Fiber Optic Cable Configuration] The optical fiber cables shown in Figures 10-12 can be applied to, for example, the displacement sensor 10 shown in Figure 5A.

[0122] Figure 10 is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 110 has three optical fibers 110Fs for measurement light, three optical fibers 110Fr for reference light, and a connector section 110C connected to the optical fibers 110Fs and 110Fr. Inside the connector section 110C, three optical waveguides 111p and three optical waveguides 112p are formed. The optical waveguides 111p and 112p are configured to guide light as cores with a refractive index higher than the surrounding cladding.

[0123] The optical waveguide 111p is optically connected to the optical fiber 110Fr and guides the reference light that has propagated within the optical fiber 110Fr toward the end 111r. The end 111r is coated with a metal such as aluminum and serves as a reference surface. Therefore, the reference light that has been guided within the optical waveguide 111p and reached the end 111r is reflected by the end 111r and guided back towards the optical fiber 110Fr within the optical waveguide 111p.

[0124] The optical waveguide 112p is optically connected to the optical fiber 110Fs and guides the measurement light that has propagated through the optical fiber 110Fs toward its end 112o. The measurement light that reaches end 112o is supplied into the sensor head 20, guided through the inside of the optical waveguide and optical fiber, and irradiated onto the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided through 112o into the optical waveguide 112p and then propagates through the optical fiber 120Fs.

[0125] The method for fabricating the connector portion 110C and the optical waveguides 111p and 112p is not particularly limited, but they may be fabricated, for example, by flame deposition using glass. Alternatively, the optical waveguides 111p and 112p may be formed as optical fibers, and these optical fibers may be sandwiched between the glass forming the base of the connector portion 110C.

[0126] Figure 11A is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 120 has three optical fibers 120Fs for measurement light, three optical fibers 120Fr for reference light, a connector section 120C connected to the optical fibers 120Fs and 120Fr, and a mirror 123. Inside the connector section 120C, three optical waveguides 121p and three optical waveguides 122p are formed. The optical waveguides 121p and 122p are configured to guide light as cores with a refractive index higher than the surrounding cladding.

[0127] The optical waveguide 121p is optically connected to the optical fiber 120Fr and guides the reference light that has propagated through the optical fiber 120Fr toward end 121o. The reference light that reaches end 121o is emitted from end 121o and reflected by mirror 123 located in front of end 121o. The reference light reflected by mirror 123 is incident on end 121o and guided through the optical waveguide 121p toward the optical fiber 120Fr.

[0128] Here, Figure 11B is a schematic diagram showing an example of the configuration of an optical fiber cable. As shown in Figure 11B, the reference light emitted from the end 121o of the connector 120C may be sequentially reflected by the retroreflector 125 and the mirror 124, then reflected again by the retroreflector 125, and then incident on the end 121o, and guided through the optical waveguide 121p toward the optical fiber 120Fr.

[0129] Returning to Figure 11A, the optical waveguide 122p is optically connected to the optical fiber 120Fs and guides the measurement light that has propagated through the optical fiber 120Fs toward the end 122o. The measurement light that reaches the end 122o is supplied into the sensor head 20, guided through the inside of the optical waveguide and optical fiber, etc., and irradiates the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided through 122o into the optical waveguide 122p and then propagates through the optical fiber 120Fs.

[0130] The method for manufacturing the connector portion 120C and the optical waveguides 121p and 122p is not particularly limited, but they may be manufactured, for example, by flame deposition using glass. Alternatively, the optical waveguides 121p and 122p may be formed as optical fibers, and these optical fibers may be sandwiched between the glass forming the base of the connector portion 120C.

[0131] Figure 12 is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 130 has three optical fibers 130Fs for measurement light and three optical fibers 130Fr for reference light. The three optical fibers 130Fs for measurement light and the three optical fibers 130Fr for reference light are fixed to each other by a resin or the like (not shown). The ends of the optical fibers 130Fs and 130Fr are fixed to ferrules and mounted in a housing.

[0132] The end 131r of the optical fiber 130Fr is coated with a metal such as aluminum and serves as a reference surface. Therefore, the reference light guided through the optical fiber 130Fr and reaching the end 131r is reflected by the end 131r and guided through the optical fiber 130Fr in the opposite direction.

[0133] The measurement light that reaches the end 132o of the optical fiber 130Fs is supplied into the sensor head 20, guided through the inside of the optical waveguide or optical fiber, and irradiated onto the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided into the optical fiber 130Fs via 132o and propagates within the optical fiber 130Fs.

[0134] The optical fiber cables shown in Figures 13A to 15 can be applied to, for example, the displacement sensor 10 shown in Figure 5B.

[0135] Figure 13A is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 210 has three optical fibers 210Fs for measurement light, three optical fibers 210Fr for reference light, and a connector section 210C connected to the optical fibers 210Fs and 210Fr. Inside the connector section 210C, three optical waveguides 211p and three optical waveguides 212p are formed. The optical waveguides 211p and 212p are configured to guide light as cores with a refractive index higher than the surrounding cladding.

[0136] The optical waveguide 211p is optically connected to the optical fiber 210Fr and guides the reference light that has propagated through the optical fiber 210Fr from one end to the other end of the optical fiber 210Fr via a substantially U-shaped folded section 211m. The shape of the folded section 211m is not particularly limited and can be arbitrarily configured based on a set value for the difference in optical path length between the measurement light and the reference light.

[0137] The optical waveguide 212p is optically connected to the optical fiber 210Fs and guides the measurement light that has propagated through the optical fiber 210Fs toward its end 212o. The measurement light that reaches end 212o is supplied into the sensor head 20, guided through the inside of the optical waveguide and optical fiber, and irradiates the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided through 212o into the optical waveguide 212p and then propagates through the optical fiber 210Fs.

[0138] The method for fabricating the connector portion 210C and the optical waveguides 211p and 212p is not particularly limited, but they may be fabricated, for example, by flame deposition using glass. Alternatively, the optical waveguides 211p and 212p may be formed as optical fibers, and these optical fibers may be sandwiched between the glass forming the base of the connector portion 210C.

[0139] Figure 13B is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 220 has three optical fibers 220Fs for measurement light, six optical fibers 220Fr for reference light, and a connector section 220C connected to the optical fibers 220Fs and 220Fr. Inside the connector section 220C, six optical waveguides 221p and three optical waveguides 222p are formed. The optical waveguides 221p and 222p are configured to guide light as cores with a refractive index higher than the surrounding cladding.

[0140] The optical waveguide 221p includes optical waveguides 221p1 and 221p2. Optical waveguide 221p1 is optically connected to the optical fiber 220Fr and guides the reference light that has propagated through the optical fiber 220Fr from one end of the optical fiber 220Fr, and exits from end 221s of optical waveguide 221p1. The reference light exited from end 221s is reflected by the retroreflector 224, then incident on end 221t, and guided through optical waveguide 221p2 towards the optical fiber 120Fr.

[0141] The optical waveguide 222p is optically connected to the optical fiber 220Fs and guides the measurement light that has propagated through the optical fiber 220Fs toward its end 222o. The measurement light that reaches the end 222o is supplied into the sensor head 20, guided through the inside of the optical waveguide and optical fiber, and irradiates the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided through 222o into the optical waveguide 222p and then propagates through the optical fiber 220Fs.

[0142] The method for fabricating the connector section 220C and the optical waveguides 221p and 222p is not particularly limited, but they may be fabricated, for example, by flame deposition using glass. Alternatively, the optical waveguides 221p and 222p may be formed as optical fibers, and these optical fibers may be sandwiched between the glass forming the base of the connector section 220C.

[0143] Figure 14 is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 230 has three optical fibers 230Fs for measurement light, three optical fibers 230Fr1 for reference light, and three optical fibers 230Fr2 for reference light. The three optical fibers 230Fs for measurement light, the three optical fibers 230Fr1 for reference light, and the three optical fibers 230Fr2 for reference light are fixed to each other by a fixing part 234 made of resin or the like.

[0144] The measurement light that reaches the end 232o of the optical fiber 230Fs is supplied into the sensor head 20, guided through the inside of the optical waveguide or optical fiber, and irradiated onto the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided into the optical fiber 230Fs via 232o and propagates within the optical fiber 230Fs.

[0145] The optical fiber 230Fr1 guides the reference light that has propagated within it, and the light is emitted from its end 231s. The reference light emitted from end 231s is reflected by the retroreflector 233, then incident on end 231t, and guided within the optical fiber 230Fr2.

[0146] Figure 15 is a schematic diagram showing an example of the configuration of an optical fiber cable. The optical fiber cable 240 has three optical fibers 240Fs for measurement light and three optical fibers 240Fr for reference light. The three optical fibers 240Fs for measurement light and the three optical fibers 240Fr for reference light are fixed to each other by a fixing part 243 made of resin or the like.

[0147] The optical fiber 240Fr guides the reference light that has propagated through the optical fiber 240Fr from one end and guides it to the other end of the optical fiber 240Fr via a roughly U-shaped folded portion 241m. The shape of the folded portion 241m is not particularly limited and can be arbitrarily configured based on a set value for the difference in optical path length between the measurement light and the reference light.

[0148] The optical fiber 240Fs guides the measurement light that has propagated within the optical fiber 240Fs toward its end 242o. The measurement light that reaches the end 242o is supplied into the sensor head 20, guided through the inside of the optical waveguide or optical fiber, and irradiated onto the object to be measured T. The measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided into the optical fiber 240Fs via 242o and propagates within the optical fiber 240Fs.

[0149] [Differentiation] Figure 16 is a diagram illustrating a modified example of an optical fiber cable.

[0150] The optical fiber cable 41 has optical fibers 44Pa to 44Pc, 45Pa to 45Pc, 46Pa to 46Pc, 47Pa to 47Pc, and optical couplers 63a to 63c. Light emitted from the wavelength-swept light source 51 is supplied from each of the optical couplers 54a to 54c to each of the optical fibers 44Pa to 44Pc via ends 44Ia to 44Ic. The optical fibers 44Pa to 44Pc guide the light to the optical couplers 63a to 63c, which then split the light into a reference light via optical fibers 45Pa to 45Pc and a measurement light via optical fibers 47Pa to 47Pc.

[0151] Reference light guided through the optical fiber 45Pa~45Pc is reflected by reference surfaces 45Ra~45Rc provided at the ends of the optical fiber 45Pa~45Pc, guided through the optical fiber 45Pa~45Pc again, and supplied to optical couplers 63a~63c. Measurement light guided through the optical fiber 47Pa~47Pc is supplied into the sensor head 20 from the ends 47Oa~47Oc of the optical fiber 47Pa~47Pc, guided through the inside of the optical waveguide and optical fiber, and irradiated onto the object to be measured T. Measurement light reflected by the object to be measured T is again incident into the sensor head 20, and this measurement light is guided through the ends 47Oa~47Oc into the optical fiber 47Pa~47Pc before being supplied to optical couplers 63a~63c.

[0152] The reference light supplied from optical fibers 45Pa to 45Pc and the measurement light supplied from optical fibers 47Pa to 47Pc interfere in optical couplers 62a to 62c, generating interference light, and at least a portion of this interference light is supplied to photodetectors 56a to 56c via optical fibers 46Pa to 46Pc. The interference light received by photodetectors 56a to 56c is converted into an electrical signal.

[0153] Figure 17 is a diagram illustrating a modified example of an optical fiber cable.

[0154] The optical fiber cable 42 has optical fibers 48Pa to 48Pc and 49Pa to 49Pc. Light emitted from the wavelength-swept light source 51 is supplied from each of the optical couplers 54a to 54c to each of the optical fibers 48Pa to 48Pc via ends 48Ia to 48Ic. The optical fibers 48Pa to 48Pc guide the light to ends 48Oa to 48Oc. Light supplied from ends 48Oa to 48Oc to the sensor head 20 is supplied to the optical couplers 23a to 23c via the optical fibers 24Pa to 24Pc of the sensor head 20. The optical couplers 23a to 23c split the supplied light into a reference light via optical fibers 25Pa to 25Pc and a measurement light via optical fibers 27Pa to 27Pc.

[0155] Reference light guided through the optical fibers 25Pa to 25Pc is reflected by reference surfaces 25Ra to 25Rc provided at the ends of the optical fibers 25Pa to 25Pc, guided through the optical fibers 25Pa to 25Pc again, and supplied to optical couplers 23a to 23c. Measurement light guided through the optical fibers 27Pa to 27Pc is irradiated onto the object to be measured T via collimating lenses 22a to 22c and the objective lens 21. The measurement light reflected by the object to be measured T is guided through the optical fibers 27Pa to 27Pc and supplied to optical couplers 23a to 23c.

[0156] The reference light supplied from optical fibers 25Pa to 25Pc and the measurement light supplied from optical fibers 27Pa to 27Pc interfere in optical couplers 23a to 23c, generating interference light, and at least a portion of this interference light is supplied to photodetectors 56a to 56c via optical fibers 26Pa to 26Pc and optical fibers 49Pa to 49c of optical fiber cable 42. The interference light received by photodetectors 56a to 56c is converted into an electrical signal.

[0157] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The elements, arrangement, materials, conditions, shapes, and sizes of the embodiments are not limited to those exemplified and can be modified as appropriate. Furthermore, it is possible to partially substitute or combine the configurations shown in different embodiments. [Explanation of symbols]

[0158] 1...Sensor system, 10...Displacement sensor, 11...Control equipment, 12...Control signal input sensor, 13...External connection equipment, 20...Sensor head, 21...Objective lens, 22a~22c...Collimating lens, 23...Lens holder, 30...Controller, 31...Display unit, 32...Setting unit, 33...External interface (I / F) unit, 34...Optical fiber connection unit, 35...External storage unit, 36...Measurement processing unit, 40, 41, 42...Optical fiber cable, 51...Wavelength sweep light source, 52...Optical amplifier, 53, 53a~53b...Isolator, 54, 54a~54e...Optical coupler, 55...Attenuator, 56a~56c...Photodetector, 58...AD conversion unit, 59...Processing unit, 60...Ballast 61...Photodetector, 62a~62c...Corrected signal generation unit, 62a~62c...Optical coupler, 63a~63c...Optical coupler, 71a~71e...Photodetector, 72a~72c...Amplification circuit, 74a~74c...AD conversion unit, 75...Processing unit, 76...Differential amplifier circuit, 77...Corrected signal generation unit, 100~105...Optical interferometer, 110...Controller, 111...Wavelength sweep light source, 112...Main interferometer, 112a~112c...Optical coupler, 113,113a~113c...First photodetector (photodetector), 114...Second interferometer, 114a,114b,114d...Optical coupler, 114c...Circulator, 115...Second photodetector (photodetector), 116...Processing unit, T...Measurement target

Claims

1. A light source unit that supplies light while sweeping the wavelength at a constant period, A light splitting means for splitting the light supplied from the light source unit into a measurement light and a reference light, A multiplexing means for combining the reflected light from the object to be measured and the reference light when the measurement light divided by the light splitting means is irradiated onto the object to be measured, An interference light detection means for detecting interference light between the reflected light combined by the wave-combining means and the reference light, A fiber optic cable unit detachably connected to a controller of an optical interference distance measuring sensor, the controller having a distance calculation means that calculates the distance to the measurement target by frequency analysis of the interference light detected by the interference light detection means, A first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light divided by the optical splitting means, A second optical fiber guides at least a portion of the light supplied from the light source unit and the reference light divided by the light splitting means, A reference surface that reflects the aforementioned reference light, A fiber optic cable unit having [a certain feature].

2. The first optical fiber includes the optical path of the measurement light, The second optical fiber includes the optical path of the reference light, The optical fiber cable unit according to claim 1.

3. The optical fiber cable unit according to claim 1, wherein the second optical fiber is the first optical fiber.

4. The optical fiber cable unit according to claim 1, further comprising the optical splitting means.

5. A light source unit that supplies light while sweeping the wavelength at a constant period, A light splitting means for splitting the light supplied from the light source unit into a measurement light and a reference light, A multiplexing means for combining the reflected light from the object to be measured and the reference light when the measurement light divided by the light splitting means is irradiated onto the object to be measured, An interference light detection means for detecting interference light between the reflected light combined by the wave-combining means and the reference light, A controller comprising: a distance calculation means for calculating the distance to the measurement target by frequency analysis of the interference light detected by the interference light detection means, A fiber optic cable unit having a reference surface that reflects the aforementioned reference light is detachably connected. A first connecting portion connected to a first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light divided by the light splitting means, A second connection part connected to a second optical fiber through which at least a portion of the light supplied from the light source unit and the reference light divided by the light splitting means is guided, SAT controller.

6. An optical interferometry distance sensor comprising a controller and an optical fiber cable unit detachably connected to the controller, The aforementioned controller, A light source unit that supplies light while sweeping the wavelength at a constant period, A light splitting means for splitting the light supplied from the light source unit into a measurement light and a reference light, A multiplexing means for combining the reflected light from the object to be measured and the reference light when the measurement light divided by the light splitting means is irradiated onto the object to be measured, An interference light detection means for detecting interference light between the reflected light combined by the wave-combining means and the reference light, The system includes a distance calculation means that calculates the distance to the measurement target by frequency analysis of the interference light detected by the interference light detection means, The optical fiber cable unit is A first optical fiber that guides at least a portion of the light supplied from the light source unit and the measurement light divided by the optical splitting means, A second optical fiber guides at least a portion of the light supplied from the light source unit and the reference light divided by the light splitting means, A reference surface that reflects the aforementioned reference light, Optical interferometry distance sensor.

7. The optical interference distance sensor according to claim 6, wherein the optical fiber cable unit further includes a reference surface for reflecting the reference light.

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