Controller and optical interference distance measuring sensor

Abstract

And the deviation of sampling timing is reduced. A controller (110) is connected to each of a first sensor head (121) and a second sensor head (122), which irradiate light to an object to be measured, via an optical fiber cable (130). The controller is provided with: a light source (140); a first main interferometer (151) that generates a first main interference signal; a second main interferometer (152) that generates a second main interference signal; and a sub interferometer (160) that generates a sub interference signal, and the controller (110) is further provided with: a first correction signal generation unit (171) that generates a first correction signal; a retardation amount generation unit that generates a retardation amount based on an optical path length difference between an optical path length of the first optical fiber (131) and an optical path length of the second optical fiber (132); and a second correction signal generation unit (172) that generates a second correction signal for correcting the sampling period of the second main interference signal on the basis of the sub interference signal and the delay amount.

Description

Technical Field

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

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

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

[0004] Prior art literature

[0005] Patent Literature

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

[0007] Problems to be solved by the invention

[0008] On the other hand, in an optical interference distance measuring sensor including a controller and a plurality of sensor heads, it is required to cope with measurement objects at different distances by changing the length of an optical fiber connecting the controller and the sensor heads among the plurality of sensor heads.

[0009] However, when the lengths of the optical fibers in the main interferometer are different, the sampling timing between the main interferometer signal and the sub-interferometer signal deviates, and the signal generated by the interference of the two signals sometimes leads to a decrease in signal strength (signal level).

[0010] The present invention has been made in view of such circumstances, and one of its objects is to provide a controller and an optical interferometric distance measuring sensor capable of reducing the deviation of sampling timing.

[0011] Means for solving problems

[0012] A controller according to one embodiment of the present disclosure is connected to a first sensor head and a second sensor head for irradiating light to a measurement object via an optical fiber cable, wherein the controller comprises: a light source for projecting light while changing the wavelength of the light; a first main interferometer for generating a first main interference signal based on a first measuring light and a first reference light, the first measuring light being irradiated to the measurement object by the first sensor head and reflected, and the first reference light being traveled along an optical path at least partially different from that of the first measuring light; a second main interferometer for generating a second main interference signal based on a second measuring light and a second reference light, the second measuring light being irradiated to the measurement object by the second sensor head and reflected, and the second reference light being traveled along an optical path at least partially different from that of the second measuring light; and a sub-interferometer for generating a second main interference signal based on two lights traveling along different optical paths, the light being projected from the light source. A secondary interference signal, the optical fiber cable includes: a first optical fiber, which is connected to a first main interferometer, and transmits light from the first main interferometer to a first sensor head, and transmits light from the first sensor head to the first main interferometer; and a second optical fiber, which is connected to a second main interferometer, and transmits light from the second main interferometer to a second sensor head, and transmits light from the second sensor head to the second main interferometer, the second optical fiber having an optical path length different from that of the first optical fiber, and the controller also includes: a first correction signal generating unit, which generates a first correction signal for correcting a sampling period of the first main interference signal based on the secondary interference signal; a delay amount generating unit, which generates a delay amount based on an optical path length difference between an optical path length of the first optical fiber and an optical path length of the second optical fiber; and a second correction signal generating unit, which generates a second correction signal for correcting a sampling period of the second main interference signal based on the secondary interference signal and the delay amount.

[0013] According to this method, a delay amount based on the optical path length difference between the optical path length of the first optical fiber and the optical path length of the second optical fiber is generated, and a second correction signal for correcting the sampling period of the second main interference signal is generated based on the secondary interference signal and the delay amount. As a result, a delay corresponding to the optical path length difference between the optical path length of the first optical fiber and the optical path length of the second optical fiber can be generated in the second main interference signal. Therefore, the deviation of the timing when sampling the second main interference signal can be reduced, and the reduction of the signal strength of the sampled digital signal can be suppressed.

[0014] In the above aspect, the delay amount generating unit may include a third optical fiber that propagates the sub-interference signal and has an optical path length based on the optical path length difference.

[0015] According to this aspect, a third optical fiber is included that propagates the secondary interference signal and has an optical path length based on the optical path length difference between the first optical fiber and the second optical fiber. Thus, the delay amount can be easily set by changing the optical path length of the third optical fiber.

[0016] In the above aspect, the delay amount generating unit may include a delay line that generates a delay corresponding to the delay amount in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal in the time axis direction and outputs the delay to the second correction signal generating unit.

[0017] According to this aspect, a delay line is included, which generates a delay corresponding to the delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal and outputs it to the second correction signal generating unit. Thus, by outputting the sub-interferometer signal that has been electrically delayed, the second correction signal generating unit can easily generate the second correction signal as an electrical signal.

[0018] In the above aspect, the second correction signal generating unit may generate a pulse signal as the second correction signal based on a signal delayed in the time axis direction by the delay amount in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal.

[0019] According to this method, the second correction signal generating unit generates a pulse signal as the second correction signal based on a signal that is delayed in the time axis direction by a delay amount in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. Thus, the timing of sampling the second main interference signal can be easily made consistent (synchronized).

[0020] In the above aspect, an AD converter may be further provided for sampling a second main interferometer signal obtained by converting a second main interference signal into an electrical signal based on a second correction signal, and converting the second main interferometer signal into a digital signal.

[0021] According to this method, an AD conversion unit is further provided, which samples the second main interferometer signal obtained by converting the second main interference signal into an electrical signal based on the second correction signal and converts it into a digital signal. Thus, a structure for converting the second main interferometer signal into a digital signal with a corrected sampling period can be easily realized.

[0022] In the above aspect, the delay amount may be set so that the absolute value of the difference between the delay amount and the delay time of light due to the optical path length difference is smaller than the minimum sampling period in the AD converter.

[0023] According to this method, the delay amount is set so that the absolute value of the difference between the delay amount and the delay time of light based on the optical path length difference is smaller than the minimum sampling period in the AD converter. Thus, the reduction in the signal strength of the sampled digital signal can be suppressed to a predetermined ratio or less, for example, 10% or less.

[0024] In the above aspect, a processing unit may be further provided for measuring the distance to the measurement target object based on the sub-interference signal and at least one of the first main interference signal and the second main interference signal.

[0025] According to this aspect, a processing unit is further provided, the processing unit measuring the distance to the measurement object based on at least one of the first main interference signal and the second main interference signal and the sub-interference signal. Thus, a structure for measuring the distance to the measurement object can be easily realized.

[0026] An optical interference ranging sensor according to one embodiment of the present disclosure includes a controller and an optical fiber cable connected to the controller, wherein the controller includes: a light source that projects light while changing the wavelength of the light; a first main interferometer that is supplied with the light projected from the light source and generates a first main interference signal based on a first measurement light and a first reference light, wherein the first measurement light is irradiated to a measurement object through a first sensor head and reflected, and the first reference light travels along an optical path that is at least partially different from that of the first measurement light; a second main interferometer that is supplied with the light projected from the light source and generates a second main interference signal based on a second measurement light and a second reference light, wherein the second measurement light is irradiated to a measurement object through a second sensor head and reflected, and the second reference light travels along an optical path that is at least partially different from that of the second measurement light; and a sub-interferometer that is supplied with the light projected from the light source and generates a sub-interference signal based on two lights that travel along different optical paths. The optical fiber cable includes: a first optical fiber connected to a first main interferometer, transmitting light from the first main interferometer to a first sensor head, and transmitting light from the first sensor head to the first main interferometer; and a second optical fiber connected to a second main interferometer, transmitting light from the second main interferometer to a second sensor head, and transmitting light from the second sensor head to the second main interferometer, the second optical fiber having an optical path length different from that of the first optical fiber, and the controller further includes: a first correction signal generating unit, generating a first correction signal for correcting a sampling period of the first main interference signal based on a secondary interference signal; a delay amount generating unit, generating a delay amount based on an optical path length difference between an optical path length of the first optical fiber and an optical path length of the second optical fiber; and a second correction signal generating unit, generating a second correction signal for correcting a sampling period of the second main interference signal based on the secondary interference signal and the delay amount.

[0027] According to this method, a delay amount based on the optical path length difference between the optical path length of the first optical fiber and the optical path length of the second optical fiber is generated, and a second correction signal for correcting the sampling period of the second main interference signal is generated based on the secondary interference signal and the delay amount. As a result, a delay corresponding to the optical path length difference between the optical path length of the first optical fiber and the optical path length of the second optical fiber can be generated in the second main interference signal. Therefore, the deviation of the timing when sampling the second main interference signal can be reduced, and the reduction of the signal strength of the sampled digital signal can be suppressed.

[0028] Effects of the Invention

[0029] According to the present invention, it is possible to reduce the deviation in sampling timing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is a schematic external view showing an outline of the displacement sensor 10 of the present disclosure.

[0031] Figure 2 1 is a flowchart showing a process of measuring the measurement object T by the displacement sensor 10 of the present disclosure.

[0032] Figure 3 1 is a functional block diagram showing an overview of a sensor system 1 using the displacement sensor 10 of the present disclosure.

[0033] Figure 4 1 is a flowchart showing a process of measuring the measurement object T by the sensor system 1 using the displacement sensor 10 of the present disclosure.

[0034] Figure 5A This is a diagram for explaining the principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure.

[0035] Figure 5B This is a diagram for explaining another principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure.

[0036] Fig. 6A It is a perspective view showing a schematic structure of the sensor head 20 .

[0037] Figure 6B 2 is a schematic diagram showing the internal structure of the sensor head 20 .

[0038] Figure 7 It is a block diagram for explaining signal processing in the controller 30 .

[0039] Figure 8 1 is a flowchart showing a method of calculating the distance to the measurement object T executed by the processing unit 59 in the controller 30 .

[0040] Fig. 9AThis is a diagram showing how a waveform signal (voltage vs. time) is frequency-converted into a spectrum (voltage vs. frequency).

[0041] Fig. 9B This is a diagram showing how a frequency spectrum (voltage vs. frequency) is transformed into a frequency spectrum (voltage vs. distance) by distance.

[0042] Fig. 9C This is a diagram showing a state where a peak is detected based on a frequency spectrum (voltage vs. distance) and a distance value corresponding thereto is calculated.

[0043] Fig.10 1 is a schematic diagram showing an outline of the structure of an optical interference distance measuring sensor 100 according to an embodiment of the present invention.

[0044] Fig.11 FIG. 1 is a schematic diagram showing the outline of the structure of another optical interference distance measuring sensor 101 according to one embodiment of the present invention.

[0045] Fig.12 This is a diagram for explaining the sampling timing of the first main interferometer signal and the second main interferometer signal.

[0046] Fig.13 This is a diagram for explaining the relationship between the signal intensity of the second main interferometer signal converted into a digital signal and the time difference Δt.

[0047] Fig.14 1 is a schematic diagram showing an example of a specific configuration of the sub-interferometer 160 and its subsequent stages when three sensor heads are provided.

[0048] Fig.15 1 is a schematic diagram showing another example of the specific configuration of the sub-interferometer 160 and its subsequent stages when three sensor heads are provided.

[0049] Fig.16 A diagram showing a modification of an interferometer that generates interference light using measurement light and reference light. DETAILED DESCRIPTION

[0050] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, each embodiment described below is only a specific example for implementing the present invention, and does not limit the present invention. In addition, in order to facilitate the understanding of the description, the same reference numerals are marked as much as possible for the same components in each drawing, and repeated descriptions are sometimes omitted.

[0051] [Overview of Displacement Sensor]

[0052] First, the outline of the displacement sensor of the present disclosure will be described.

[0053] Figure 1FIG. 1 is a schematic diagram showing the appearance of the displacement sensor 10 of the present disclosure. Figure 1 As shown, the displacement sensor 10 includes a sensor head 20 and a controller 30 , and measures the displacement of the measurement object T (the distance to the measurement object T).

[0054] The sensor head 20 and the controller 30 are connected via an optical fiber 40, and an objective lens 21 is mounted on the sensor head 20. The controller 30 includes a display unit 31, a setting unit 32, an external interface (I / F) unit 33, an optical fiber connection unit 34, and an external storage unit 35, and has a measurement processing unit 36 ​​inside.

[0055] The sensor head 20 irradiates the light output from the controller 30 to the measurement object T, and receives the reflected light from the measurement object T. The sensor head 20 has a reference surface inside, and the reference surface is used to reflect the light output from the controller 30 and received via the optical fiber 40 so as to interfere with the reflected light from the measurement object T.

[0056] The sensor head 20 is provided with an objective lens 21 which is detachable. The objective lens 21 may be replaced with an objective lens having an appropriate focal length according to the distance between the sensor head 20 and the measurement object T, or a variable-focus objective lens may be used.

[0057] Furthermore, when installing the sensor head 20 , the object T may be irradiated with guide light (visible light) to install the sensor head 20 and / or the object T so that the object T is appropriately located within the measurement area of ​​the displacement sensor 10 .

[0058] The optical fiber 40 is connected to the optical fiber connection portion 34 disposed in the controller 30 and extends to connect the controller 30 to the sensor head 20. Thus, the optical fiber 40 is configured to guide the light projected from the controller 30 to the sensor head 20, and guide the return light from the sensor head 20 to the controller 30. In addition, the optical fiber 40 can be detachable from the sensor head 20 and the controller 30 and can have various lengths, thicknesses, characteristics, etc.

[0059] The display unit 31 is composed of, for example, a liquid crystal display or an organic EL display, etc. The display unit 31 displays the set value of the displacement sensor 10, the amount of light received by the return light from the sensor head 20, and the displacement of the measurement object T measured by the displacement sensor 10 (the distance to the measurement object T).

[0060] The setting unit 32 performs settings required for measuring the measurement object T by, for example, operating a mechanical button or a touch panel by a user. All or part of these required settings may be preset, or may be set from an external connection device (not shown) connected to the external I / F unit 33. In addition, the external connection device may be connected via a network in a wired or wireless manner.

[0061] Here, the external I / F unit 33 is composed of, for example, Ethernet (registered trademark), RS232C, and analog output, etc. The external I / F unit 33 may be connected to other connected devices to perform required settings from the external connected devices, or output measurement results measured by the displacement sensor 10 to the external connected devices.

[0062] The controller 30 may also fetch data stored in the external storage unit 35 to perform settings required for measuring the measurement object T. The external storage unit 35 is an auxiliary storage device such as a USB (Universal Serial Bus) memory, and stores settings required for measuring the measurement object T in advance.

[0063] The measurement processing unit 36 ​​in the controller 30 includes, for example, a wavelength scanning light source that projects light while continuously changing the wavelength, a light receiving element that receives the return light from the sensor head 20 and converts it into an electric signal, and a signal processing circuit that processes the electric signal. In the measurement processing unit 36, various processes are performed using a control unit and a storage unit, so that the displacement of the measurement object T (the distance to the measurement object T) is finally calculated based on the return light from the sensor head 20. The details of these processes will be described later.

[0064] Figure 2 FIG. 1 is a flowchart showing a process of measuring the measurement object T by the displacement sensor 10 of the present disclosure. Figure 2 As shown, the process includes steps S11 to S14.

[0065] In step S11, the sensor head 20 is set. For example, guide light is irradiated from the sensor head 20 toward the measurement target T, and the sensor head 20 is set at an appropriate position with reference thereto.

[0066] Specifically, the amount of light received by the return light from the sensor head 20 may be displayed on the display unit 31 in the controller 30, and the user may check the amount of light received while adjusting the orientation of the sensor head 20 and the distance (height position) from the measurement object T. Basically, if the light from the sensor head 20 can be irradiated perpendicularly (at an angle closer to perpendicular) to the measurement object T, the amount of light reflected from the measurement object T increases, and the amount of light received by the return light from the sensor head 20 also increases.

[0067] In addition, the objective lens 21 may be replaced with one having an appropriate focal length according to the distance between the sensor head 20 and the measurement target object T.

[0068] Furthermore, in the event that appropriate settings cannot be made when measuring the measurement object T (for example, the amount of light received required for measurement cannot be obtained, or the focal length of the objective lens 21 is inappropriate, etc.), an error or incomplete setting may be displayed on the display unit 31, or output to an externally connected device, to notify the user.

[0069] In step S12 , various measurement conditions are set when measuring the measurement object T. For example, the user operates the setting unit 32 in the controller 30 to set the calibration data (linear calibration function, etc.) inherent to the sensor head 20 .

[0070] In addition, various parameters may be set. For example, the sampling time, the measurement range, and the threshold value for determining whether the measurement result is normal or abnormal may be set. Furthermore, the measurement cycle may be set according to the characteristics of the measurement object T, such as the reflectivity and material of the measurement object T, and the measurement mode may be set according to the material of the measurement object T.

[0071] The measurement conditions and various parameters are set by operating the setting unit 32 in the controller 30 , but may be set from an externally connected device or by loading data from the external storage unit 35 .

[0072] In step S13 , the sensor head 20 installed in step S11 measures the measurement object T according to the measurement conditions and various parameters set in step S12 .

[0073] Specifically, in the measurement processing unit 36 ​​of the controller 30, light is projected from the wavelength scanning light source, and the return light from the sensor head 20 is received by the light receiving element, and the signal processing circuit performs frequency analysis, distance conversion, peak detection, etc., to calculate the displacement of the measurement object T (the distance to the measurement object T). The details of the specific measurement processing will be described later.

[0074] In step S14, the measurement result measured in step S13 is output. For example, the displacement of the measurement object T (the distance to the measurement object T) measured in step S13 is displayed on the display unit 31 in the controller 30 or output to an externally connected device.

[0075] In addition, whether the displacement of the measurement object T (the distance to the measurement object T) measured in step S13 is within a normal range or abnormal may also be displayed or output as a measurement result based on the threshold value set in step S12. Furthermore, the measurement conditions, various parameters, and measurement modes set in step S12 may also be displayed or output together.

[0076] [Overview of the system including the displacement sensor]

[0077] Figure 3 1 is a functional block diagram showing an overview of a sensor system 1 using the displacement sensor 10 of the present disclosure. Figure 3 As shown, the sensor system 1 includes a displacement sensor 10, a control device 11, a control signal input sensor 12, and an external connection device 13. In addition, the displacement sensor 10 is connected to the control device 11 and the external connection device 13, for example, through a communication cable or an external connection line (for example, including an external input line, an external output line, and a power line, etc.), and the control device 11 is connected to the control signal input sensor 12 through a signal line.

[0078] The displacement sensor 10 is used as Figure 1 and Figure 2 As described above, the displacement of the measurement object T (the distance to the measurement object T) is measured. Then, the displacement sensor 10 may output the measurement result and the like to the control device 11 and the externally connected device 13 .

[0079] The control device 11 is, for example, a PLC (Programmable Logic Controller), and provides various instructions to the displacement sensor 10 when the displacement sensor 10 measures the object T to be measured.

[0080] For example, the control device 11 can output a measurement timing signal to the displacement sensor 10 based on an input signal from a control signal input sensor 12 connected to the control device 11, or can output a zero reset command signal (a signal for setting the current measured value to 0) to the displacement sensor 10.

[0081] The control signal input sensor 12 outputs an on / off signal to the control device 11, indicating the timing of the displacement sensor 10 measuring the measurement object T. For example, the control signal input sensor 12 is set near the production line where the measurement object T moves, detects that the measurement object T moves to a predetermined position, and outputs an on / off signal to the control device 11.

[0082] The external connection device 13 is, for example, a PC (Personal Computer), and can perform various settings on the displacement sensor 10 through user operations.

[0083] As a specific example, a measurement mode, an operation mode, a measurement cycle, and a material of the measurement object T are set.

[0084] As the setting of the measurement mode, an “internal synchronous measurement mode” in which measurement is periodically started inside the control device 11 , an “external synchronous measurement mode” in which measurement is started based on an input signal from outside the control device 11 , or the like is selected.

[0085] As the setting of the operation mode, an “operation mode” for actually measuring the measurement object T, an “adjustment mode” for setting measurement conditions for measuring the measurement object T, or the like is selected.

[0086] The measurement period is a period for measuring the object T, and can be set according to the reflectivity of the object T. Even when the reflectivity of the object T is low, the object T can be properly measured by extending the measurement period and setting the measurement period appropriately.

[0087] Regarding the measurement object T, the "rough surface mode" suitable for the case where diffuse reflection is more common as a component of reflected light, the "mirror mode" suitable for the case where specular reflection is more common as a component of reflected light, or the "standard mode" in between them is selected.

[0088] In this way, by making appropriate settings according to the reflectivity and material of the measurement object T, the measurement object T can be measured with higher accuracy.

[0089] Figure 4 1 is a flowchart showing a process of measuring the measurement object T by the sensor system 1 using the displacement sensor 10 of the present disclosure. Figure 4 As shown, this process is the process in the above-mentioned external synchronization measurement mode, and includes steps S21 to S24.

[0090] In step S21, the sensor system 1 detects the measurement object T as the object to be measured. Specifically, the control signal input sensor 12 detects that the measurement object T has moved to a predetermined position on the production line.

[0091] In step S22, the sensor system 1 issues a measurement instruction so that the displacement sensor 10 measures the measurement object T detected in step S21. Specifically, the control signal input sensor 12 outputs an on / off signal to the control device 11 to instruct the timing of measuring the measurement object T detected in step S21, and the control device 11 outputs a measurement timing signal to the displacement sensor 10 based on the on / off signal to issue a measurement instruction so that the measurement object T is measured.

[0092] In step S23, the displacement sensor 10 measures the measurement object T. Specifically, the displacement sensor 10 measures the measurement object T based on the measurement instruction received in step S22.

[0093] In step S24 , the sensor system 1 outputs the measurement result measured in step S23 . Specifically, the displacement sensor 10 displays the measurement result on the display unit 31 , or outputs it to the control device 11 or the external connection device 13 via the external I / F unit 33 .

[0094] In addition, here, use Figure 4 The process in the case of the external synchronous measurement mode in which the object T is detected by the control signal input sensor 12 to measure the object T is described, but the present invention is not limited to this. For example, in the case of the internal synchronous measurement mode, instead of steps S21 and S22, the displacement sensor 10 is instructed to measure the object T by generating a measurement timing signal based on a preset cycle.

[0095] Next, the principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure will be described.

[0096] Figure 5A 1 is a diagram for explaining the principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure. Figure 5A As shown, the displacement sensor 10 includes a sensor head 20 and a controller 30. The sensor head 20 includes an objective lens 21 and a plurality of collimating lenses 22a to 22c, and the controller 30 includes a wavelength scanning light source 51, an optical amplifier 52, a plurality of isolators 53 and 53a to 53b, a plurality of optical couplers 54 and 54a to 54e, an attenuator 55, a plurality of light receiving elements (e.g., photodetectors (PD)) 56a to 56c, a plurality of amplifier circuits 57a to 57c, a plurality of analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a to 58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generating unit 61.

[0097] The wavelength scanning light source 51 projects the laser light obtained by scanning the wavelength. As the wavelength scanning light source 51, for example, if a method of modulating VCSEL (Vertical Cavity Surface Emitting Laser) by using current is applied, it is difficult to cause mode hopping due to the short resonator length, and the wavelength can be easily changed, which can be realized at low cost.

[0098] The optical amplifier 52 amplifies the light projected from the wavelength scanning light source 51. The optical amplifier 52 may be, for example, an EDFA (erbium-doped fiber amplifier), and may be, for example, an optical amplifier dedicated to 1550 nm.

[0099] The isolator 53 is an optical element that transmits incident light in one direction, and may be disposed immediately after the wavelength scanning light source 51 in order to prevent the influence of noise generated by return light.

[0100] Thus, the light projected from the wavelength scanning light source 51 is amplified by the optical amplifier 52, and is branched to the main interferometer and the sub-interferometer by the optical coupler 54 via the isolator 53. For example, in the optical coupler 54, the ratio of the light branched to the main interferometer and the sub-interferometer may be more than 90% branched on the main interferometer side.

[0101] The light branched to the main interferometer is further branched into the direction of the sensor head 20 and the direction of the second optical coupler 54 b by the first optical coupler 54 a .

[0102] The light branched toward the sensor head 20 by the first-stage optical coupler 54a passes through the collimating lens 22a and the objective lens 21 from the end of the optical fiber in the sensor head 20 and is irradiated to the measurement object T. Then, the end (end face) of the optical fiber becomes a reference surface, and the light reflected on the reference surface interferes with the light reflected on the measurement object T to generate interference light, which returns to the first-stage optical coupler 54a, and is then received by the light receiving element 56a and converted into an electrical signal.

[0103] The light branched from the first-stage optical coupler 54a to the second-stage optical coupler 54b goes to the second-stage optical coupler 54b via the isolator 53a, and is further branched from the second-stage optical coupler 54b to the direction of the sensor head 20 and the direction of the third-stage optical coupler 54c. The light branched from the optical coupler 54b to the sensor head 20 is irradiated to the measurement object T from the end of the optical fiber through the collimating lens 22b and the objective lens 21 in the sensor head 20 as in the first stage. Then, the end (end face) of the optical fiber becomes a reference surface, and the light reflected from the reference surface interferes with the light reflected from the measurement object T to generate interference light, which returns to the second-stage optical coupler 54b and is branched to the directions of the isolator 53a and the light receiving element 56b respectively through the optical coupler 54b. The light branched from the optical coupler 54b to the direction of the light receiving element 56b is received by the light receiving element 56b and converted into an electrical signal. On the other hand, the isolator 53a allows light to pass from the preceding optical coupler 54a to the succeeding optical coupler 54b and blocks light from the succeeding optical coupler 54b to the preceding optical coupler 54a, so that light branched from the optical coupler 54b toward the isolator 53a is blocked.

[0104] The light branched from the second-stage optical coupler 54b to the third-stage optical coupler 54c goes to the third-stage optical coupler 54c via the isolator 53b, and is further branched from the third-stage optical coupler 54c to the sensor head 20 and the attenuator 55. The light branched from the optical coupler 54c to the sensor head 20 is irradiated to the measurement target T from the end of the optical fiber in the sensor head 20 through the collimating lens 22c and the objective lens 21, similarly to the first and second stages. Then, the end (end face) of the optical fiber serves as a reference surface, and the light reflected from the reference surface interferes with the light reflected from the measurement target T to generate interference light, which returns to the third-stage optical coupler 54c and is branched to the isolator 53b and the light receiving element 56c by the optical coupler 54c. The light branched from the optical coupler 54c to the light receiving element 56c is received by the light receiving element 56c and converted into an electrical signal. On the other hand, the isolator 53b transmits light from the preceding optical coupler 54b to the succeeding optical coupler 54c and blocks light from the succeeding optical coupler 54c to the preceding optical coupler 54b, so that light branched from the optical coupler 54c toward the isolator 53b is blocked.

[0105] In addition, since the light branched by the third-stage optical coupler 54 c in a direction other than the sensor head 20 is not used for measuring the measurement object T, it may be attenuated by an attenuator 55 such as a terminator to avoid reflection and return.

[0106] In this way, the main interferometer has a three-level optical path (three channels), and is an interferometer that uses twice the distance (round trip) from the end (end face) of the optical fiber of the sensor head 20 to the measured object T as the optical path length difference, and generates three interference lights corresponding to the optical path length difference.

[0107] The light receiving elements 56 a to 56 c receive the interference light from the main interferometer as described above, and generate electrical signals corresponding to the amount of received light.

[0108] The amplifier circuits 57a to 57c amplify the electrical signals output from the light receiving elements 56a to 56c, respectively.

[0109] AD converters 58a to 58c receive the electrical signals amplified by amplifier circuits 57a to 57c, respectively, and convert the electrical signals from analog signals to digital signals (AD conversion). Here, AD converters 58a to 58c perform AD conversion based on the correction signal from correction signal generator 61 in the sub-interferometer.

[0110] In order to correct the nonlinearity of the wavelength when the wavelength scanning light source 51 is scanned in the sub-interferometer, an interference signal is obtained by the sub-interferometer to generate a correction signal called a K clock.

[0111] Specifically, the light branched from the optical coupler 54 to the sub-interferometer is further branched by the optical coupler 54d. Here, the optical paths of the branched lights are configured to have an optical path length difference by using optical fibers of different lengths between the optical coupler 54d and the optical coupler 54e, for example, and interference light corresponding to the optical path length difference is output from the optical coupler 54e. In addition, the balanced detector 60 receives the interference light from the optical coupler 54e, removes noise by taking the difference of the signal with the opposite phase, and amplifies the optical signal and converts it into an electrical signal.

[0112] In addition, the optical coupler 54d and the optical coupler 54e only need to branch the light in a ratio of 50:50.

[0113] The correction signal generation unit 61 detects the nonlinearity of the wavelength when the wavelength scanning light source 51 is scanning based on the electrical signal from the balance detector 60, generates a K clock corresponding to the nonlinearity, and outputs it to the AD converters 58a to 58c.

[0114] The intervals of the waves of the analog signals input to the AD converters 58a to 58c in the main interferometer are not equal due to the nonlinearity of the wavelength when the wavelength scanning light source 51 is scanned. The sampling time is corrected based on the above-mentioned K clock so that the intervals of the waves in the AD converters 58a to 58c become equal, and AD conversion (sampling) is performed.

[0115] In addition, as described above, the K clock is a correction signal for sampling the analog signal of the main interferometer, and therefore needs to be generated at a higher frequency than the analog signal of the main interferometer. Specifically, the optical path length difference between the optical coupler 54d and the optical coupler 54e in the sub-interferometer can be made longer than the optical path length difference between the end (end face) of the optical fiber in the main interferometer and the measurement object T, or the correction signal generating unit 61 can multiply the frequency (e.g., 8 times) to increase the frequency.

[0116] The processing unit 59 obtains the digital signals after the nonlinearity is corrected and AD-converted by the AD conversion units 58a to 58c, and calculates the displacement of the measurement object T (the distance to the measurement object T) based on the digital signals. Specifically, in the processing unit 59, the digital signals are frequency-converted using fast Fourier transform (FFT), and the distance is calculated by analyzing them. The detailed processing in the processing unit 59 will be described later.

[0117] In addition, since high-speed processing is required in the processing unit 59 , it is often implemented by an integrated circuit such as an FPGA (field-programmable gate array).

[0118] Here, a three-stage optical path is provided in the main interferometer, and the sensor head 20 irradiates the measurement object T with measurement light from each optical path, and based on the interference light (return light) obtained from each optical path, the distance to the measurement object T is measured (multi-channel). The channels in the main interferometer are not limited to three stages, and may be one or two stages, or may be four or more stages.

[0119] Figure 5B FIG. 1 is a diagram for explaining another principle of measuring the measurement object T by the displacement sensor 10 of the present disclosure. Figure 5B As shown, the displacement sensor 10 includes a sensor head 20 and a controller 30. The sensor head 20 includes an objective lens 21 and a plurality of collimating lenses 22a to 22c, and the controller 30 includes a wavelength scanning light source 51, an optical amplifier 52, a plurality of isolators 53 and 53a to 53b, a plurality of optical couplers 54 and 54a to 54j, an attenuator 55, a plurality of light receiving elements (e.g., photodetectors (PD)) 56a to 56c, a plurality of amplifier circuits 57a to 57c, a plurality of analog-to-digital (AD) conversion units (e.g., analog-to-digital converters) 58a to 58c, a processing unit (e.g., a processor) 59, a balance detector 60, and a correction signal generating unit 61. Figure 5B The displacement sensor 10 shown is different from the above in that it mainly includes optical couplers 54f to 54j. Figure 5A The structure of the displacement sensor 10 shown is different. The principle of the different structure is the same as that of Figure 5A Compare and elaborate.

[0120] The light projected from the wavelength scanning light source 51 is amplified by the optical amplifier 52, and is branched to the main interferometer side and the sub-interferometer side by the optical coupler 54 via the isolator 53. However, the light branched to the main interferometer side is further branched into measurement light and reference light by the optical coupler 54f.

[0121] like Figure 5A As described in the first embodiment, the measuring light is irradiated to the measuring object T through the collimating lens 22a and the objective lens 21 by the first-stage optical coupler 54a, and is reflected by the measuring object T. Figure 5A In the method, the end (end face) of the optical fiber is used as a reference surface, and the light reflected by the reference surface interferes with the light reflected by the measurement object T to generate interference light. Figure 5B In the example, no reference surface for reflecting light is provided. Figure 5B In, not as Figure 5A Since the light reflected by the reference surface is generated in this way, the measurement light reflected by the measurement target object T returns to the first-stage optical coupler 54 a.

[0122] Similarly, the light branched from the first-stage optical coupler 54a to the second-stage optical coupler 54b is irradiated to the measurement target T by the second-stage optical coupler 54b through the collimating lens 22b and the objective lens 21, and is reflected by the measurement target T and returns to the second-stage optical coupler 54b. The light branched from the second-stage optical coupler 54b to the third-stage optical coupler 54c is irradiated to the measurement target T by the third-stage optical coupler 54c through the collimating lens 22c and the objective lens 21, and is reflected by the measurement target T and returns to the third-stage optical coupler 54c.

[0123] On the other hand, the reference light branched by the optical coupler 54f is further branched by the optical coupler 54g to the optical couplers 54h, 54i, and 54j.

[0124] In the optical coupler 54h, the measurement light reflected by the measurement object T output from the optical coupler 54a interferes with the reference light output from the optical coupler 54g, generating interference light, which is received by the light receiving element 56a and converted into an electrical signal. In other words, the measurement light and the reference light are branched by the optical coupler 54f, and interference light corresponding to the optical path length difference between the measurement light (the optical path from the optical coupler 54f through the optical coupler 54a, the collimating lens 22a, and the objective lens 21, which is reflected by the measurement object T and reaches the optical coupler 54h) and the reference light (the optical path from the optical coupler 54f through the optical coupler 54g to the optical coupler 54h) is generated, and the interference light is received by the light receiving element 56a and converted into an electrical signal.

[0125] Similarly, in the optical coupler 54i, interference light corresponding to the difference in optical path length between the optical path of the measurement light (the optical path from the optical coupler 54f via the optical coupler 54a, 54b, the collimating lens 22b, and the objective lens 21, which is reflected by the measured object T and reaches the optical coupler 54i) and the optical path of the reference light (the optical path from the optical coupler 54f via the optical coupler 54g to reach the optical coupler 54i) is generated, and the interference light is received by the light receiving element 56b and converted into an electrical signal.

[0126] In the optical coupler 54j, interference light corresponding to the optical path length difference between the optical path of the measurement light (the optical path from the optical coupler 54f via the optical coupler 54a, 54b, 54c, the collimating lens 22c, the objective lens 21, the reflected optical object T and reaching the optical coupler 54j) and the optical path of the reference light (the optical path from the optical coupler 54f via the optical coupler 54g to the optical coupler 54j) is generated, and the interference light is received by the light receiving element 56c and converted into an electrical signal. For example, the light receiving elements 56a to 56c may be balanced photodetectors.

[0127] In this way, the main interferometer has a three-level optical path (three channels), which generates three interference lights corresponding to the optical path length differences between the measurement light reflected by the measured object T and input into the optical couplers 54h, 54i and 54j respectively and the reference light input into the optical couplers 54h, 54i and 54j respectively via the optical couplers 54f and 54g.

[0128] Alternatively, the optical path length difference between the measurement light and the reference light may be set to be different in the three channels. For example, the optical path length of the optical coupler 54g may be set to be different from that of the optical couplers 54h, 54i, and 54j.

[0129] Then, based on the respectively obtained interference lights, the distance to the measurement target object T and the like are measured (multi-channel).

[0130] [Sensor head structure]

[0131] Here, the structure of the sensor head used for the displacement sensor 10 will be described.

[0132] Fig. 6A is a perspective view showing a schematic structure of the sensor head 20. Figure 6B This is a schematic diagram showing the internal structure of the sensor head.

[0133] like Fig. 6A As shown, the sensor head 20 accommodates the objective lens 21 and the collimator lens in the lens holder 23. For example, the size of the lens holder 23 is about 20 mm for one side surrounding the objective lens 21 and about 40 mm for the length in the optical axis direction.

[0134] like Figure 6BAs shown, one objective lens 21 and three collimating lenses 22a to 22c are housed in the lens holder 23. Light from the optical fiber is guided to the three collimating lenses 22a to 22c via the optical fiber array 24, and the light passing through the three collimating lenses 22a to 22c is irradiated to the measurement target T via the objective lens 21.

[0135] In this way, the optical fibers, the collimating lenses 22 a to 22 c , and the optical fiber array 24 are held by the lens holder 23 together with the objective lens 21 , thereby constituting the sensor head 20 .

[0136] In addition, the lens holder 23 constituting the sensor head 20 may be made of a metal (for example, A2017) that is high in strength and can be processed with high precision.

[0137] Figure 7 30 is a block diagram for explaining signal processing in the controller 30. Figure 7 As shown, the controller 30 includes a plurality of light receiving elements 71 a to 71 e , a plurality of amplifier circuits 72 a to 72 c , a plurality of AD converters 74 a to 74 c , a processing unit 75 , a differential amplifier circuit 76 , and a correction signal generator 77 .

[0138] In the controller 30, as Figure 5A As shown, the light projected from the wavelength scanning light source 51 is branched to the main interferometer and the sub-interferometer by the optical coupler 54, and the main interference signal and the sub-interference signal obtained are processed respectively, thereby calculating the distance value to the measurement target object T.

[0139] The plurality of light receiving elements 71a to 71c correspond to Figure 5A The light receiving elements 56a to 56c shown receive the main interference signals from the main interferometer, respectively, and output them as current signals to the amplifier circuits 72a to 72c, respectively.

[0140] The plurality of amplifier circuits 72a to 72c convert the current signal (IV conversion) into a voltage signal and amplify the voltage signal.

[0141] The plurality of AD converters 74a to 74c correspond to Figure 5A The AD converters 58a to 58c shown convert the voltage signals into digital signals (AD conversion) based on the K clock from the correction signal generator 77 described later.

[0142] The processing unit 75 is equivalent to Figure 5A The processing unit 59 shown converts the digital signals from the AD conversion units 74a to 74c into frequencies using FFT, analyzes them, and calculates the distance value to the measurement target object T.

[0143] The plurality of light receiving elements 71d to 71e and the differential amplifier circuit 76 correspond to Figure 5AThe balanced detector 60 shown receives the interference light in the sub-interferometer, outputs a phase-inverted interference signal, removes noise by taking the difference between the two signals, and amplifies the interference signal and converts it into a voltage signal.

[0144] The correction signal generating unit 77 corresponds to Figure 5A The correction signal generating unit 61 shown in the figure binarizes the voltage signal through the comparator to generate the K clock and outputs it to the AD conversion units 74a to 74c. The K clock needs to be generated at a higher frequency than the analog signal of the main interferometer, so the correction signal generating unit 77 can also multiply the frequency (for example, 8 times) to make it high frequency.

[0145] Figure 8 4 is a flowchart showing a method of calculating the distance to the measurement object T executed by the processing unit 59 in the controller 30. Figure 8 As shown, the method includes: steps S31 to S34.

[0146] In step S31 , the processing unit 59 performs frequency conversion of the waveform signal (voltage vs. time) into a frequency spectrum (voltage vs. frequency) using the following FFT. Fig. 9A This is a diagram showing how a waveform signal (voltage vs. time) is frequency-converted into a spectrum (voltage vs. frequency).

[0147]

[0148] N: number of data points

[0149] In step S32 , the processing unit 59 converts the frequency spectrum (voltage vs. frequency) distance into the frequency spectrum (voltage vs. distance). Fig. 9B This is a diagram showing how a frequency spectrum (voltage vs. frequency) is transformed into a frequency spectrum (voltage vs. distance) by distance.

[0150] In step S33 , the processing unit 59 calculates a distance value corresponding to the peak value based on the frequency spectrum (voltage vs. distance). Fig. 9C : is a diagram showing a situation where a peak is detected based on a spectrum (voltage vs. distance) and a distance value corresponding thereto is calculated. Fig. 9C As shown, here, in the three channels, peak values ​​are detected based on the spectrum (voltage vs. distance), and the distance values ​​corresponding to the peak values ​​are calculated.

[0151] In step S34, the processing unit 59 averages the distance values ​​calculated in step S33. Specifically, in step S33, the processing unit 59 detects peak values ​​based on the spectrum (voltage vs. distance) in each of the three channels and calculates the distance values ​​corresponding thereto, and then averages them and outputs the averaged calculation result as the distance to the measurement object T.

[0152] In addition, in step S34, when the processing unit 59 averages the distance values ​​calculated in step S33, it is preferred to average the distance values ​​whose SNR is above the threshold. For example, in any of the three channels, although a peak is detected based on its spectrum (voltage vs. distance), if the SNR is less than the threshold, it is determined that the distance value calculated based on the spectrum is of low reliability and is not adopted.

[0153] Next, regarding the present disclosure, a detailed description will be given as a specific embodiment, centering on the more characteristic structure, function and properties. In addition, the optical interference ranging sensor shown below is equivalent to using Figure 1 The displacement sensor 10 illustrated in FIG. 9 is a light interference ranging sensor having a basic structure, function, and properties, all or part of which are used Figure 1 The structure, function and properties included in the displacement sensor 10 described in Figure 9 are the same.

[0154] <One Implementation Method>

[0155] [Structure of optical interferometric distance measuring sensor]

[0156] Fig.10 FIG. 1 is a schematic diagram showing the general structure of an optical interference ranging sensor 100 according to an embodiment of the present invention. Fig.10 As shown, the optical interference distance measuring sensor 100 includes a controller 110 and an optical fiber cable 130 connecting the controller 110 to a first sensor head 121 and a second sensor head 122. The optical interference distance measuring sensor 100 may further include the first sensor head 121 and the second sensor head 122.

[0157] The controller 110 includes a wavelength scanning light source 140, an optical branching unit 111, a main interferometer 150 and a sub-interferometer 160, first photodiodes (PD) 112 and 113, amplifier circuits 114 and 115, second photodiodes (PD) 116 and 117, a first correction signal generating unit 171, a second correction signal generating unit 172, AD conversion units 181 and 182, and a processing unit 118.

[0158] The optical fiber cable 130 is an optical fiber group composed of a plurality of optical fibers. The optical fiber cable 130 is configured to be freely detachable relative to the controller 110 and the first sensor head 121 and the second sensor head 122, that is, it can be installed and removed. The optical fiber cable 130 is configured to include, for example, a first optical fiber 131 and a second optical fiber 132. The first optical fiber 131 has an optical path length proportional to a length L1, and the second optical fiber 132 has an optical path length proportional to a length L2. The length L1 of the first optical fiber 131 is set based on the distance to the measurement object T1, and the length L2 of the second optical fiber 132 is set based on the distance to the measurement object T2. The measurement object T2 is assumed to exist at a different distance from the measurement object T1 and at a different distance from the measurement object T2. Figure 1 In the example shown, the object is at a relatively long distance. Therefore, the optical path length of the second optical fiber 132 is different from the optical path length of the first optical fiber 131 and is longer than the optical path length of the first optical fiber 131 .

[0159] The wavelength scanning light source 140 projects light while continuously changing the wavelength. That is, the wavelength of the light projected from the wavelength scanning light source 140 continuously changes. In addition, the light projected from the wavelength scanning light source 140 is supplied to the main interferometer 150 and the sub-interferometer 160 via the light branching unit 111 composed of, for example, an optical coupler. In the wavelength scanning light source 140, the wavelength is continuously controlled by changing the magnitude of the input current. The input current waveform mainly uses a triangular wave or a sawtooth wave.

[0160] The main interferometer 150 has multiple optical paths (multiple channels). Fig.10 In the example shown, the structure includes a first main interferometer 151 and a second main interferometer.

[0161] The first main interferometer 151 is connected to the first optical fiber 131 of the optical fiber cable 130 , supplies light projected from the wavelength scanning light source 140 to the first sensor head 121 via the first optical fiber 131 , and guides return light from the first sensor head 121 to the first photodiode 112 .

[0162] Specifically, for example, the light guided from the first main interferometer 151 to the first sensor head 121 is irradiated as the first measurement light to the measurement target T via the collimator lens and the objective lens arranged in the first sensor head 121 . Then, the reflected light from the measurement target T returns to the first sensor head 121 .

[0163] In addition, for example, a portion of the light guided from the first main interferometer 151 to the first sensor head 121 is reflected as the first reference light by a reference surface provided at the end of the first optical fiber 131 or the like. Then, interference light (also referred to as a "first main interference signal") corresponding to the optical path length difference between the first measurement light and the first reference light is generated by the interference of the first measurement light and the first reference light.

[0164] In this manner, the first main interferometer 151 is supplied with the light projected from the wavelength scanning light source 140, and generates a first main interference signal based on the first measurement light, which is irradiated to the measurement object T by the first sensor head 121 and reflected by the measurement object T, and the first reference light, which travels along an optical path that is at least partially different from the optical path of the first measurement light. In addition, since the first main interference signal is generated by being supplied with the light projected from the wavelength scanning light source, the first main interferometer 151 and the first sensor head 121 can also be included and referred to as the first main interferometer.

[0165] The second main interferometer 152 is connected to the second optical fiber 132 of the optical fiber cable 130 , supplies light projected from the wavelength scanning light source 140 to the second sensor head 122 via the second optical fiber 132 , and guides return light from the second sensor head 122 to the first photodiode 113 .

[0166] Specifically, for example, the light guided from the second main interferometer 152 to the second sensor head 122 is irradiated as the second measurement light to the measurement target T via the collimator lens and the objective lens arranged in the second sensor head 122 . Then, the reflected light at the measurement target T returns to the second sensor head 122 .

[0167] In addition, for example, a portion of the light guided from the second main interferometer 152 to the second sensor head 122 is reflected as the second reference light by a reference surface provided at the end of the second optical fiber 132 or the like. Then, interference light (also referred to as a "second main interference signal") corresponding to the optical path length difference between the second measurement light and the second reference light is generated by the interference of the second measurement light and the second reference light.

[0168] In this manner, the second main interferometer 152 is supplied with the light projected from the wavelength scanning light source 140, and generates a second main interference signal based on the second measurement light, which is irradiated to the measurement object T by the second sensor head 122 and reflected by the measurement object T, and the second reference light, which travels along an optical path that is at least partially different from the optical path of the second measurement light. In addition, since the second main interference signal is generated by being supplied with the light projected from the wavelength scanning light source, the second main interferometer 152 and the second sensor head 122 can also be included and referred to as a second main interferometer.

[0169] The first photodiode 112 receives the first main interference signal generated by the first main interferometer 151 and converts it into an electric signal. The electric signal converted by the first photodiode 112 is, for example, a current signal. The first photodiode 113 receives the second main interference signal generated by the second main interferometer 152 and converts it into an electric signal. Similarly, the electric signal converted by the first photodiode 113 is, for example, a current signal.

[0170] The amplifier circuit 114 amplifies the electric signal input from the first photodiode 112 at a predetermined gain (also referred to as "gain"). When a current signal is input from the first photodiode 112, the amplifier circuit 114 converts the current signal into a voltage signal (also referred to as "IV conversion") and amplifies it. The amplified electric signal is output to the AD conversion unit 181. The amplifier circuit 115 amplifies the electric signal input from the first photodiode 113 at a predetermined gain. When a current signal is input from the first photodiode 113, the amplifier circuit 115 converts the current signal into a voltage signal and amplifies it. The amplified electric signal is output to the AD conversion unit 182.

[0171] The light projected from the wavelength scanning light source 140 is branched by the light branching section 111 and supplied to the sub-interferometer 160, and the sub-interferometer 160 generates a sub-interference signal based on two lights traveling along optical paths of different optical path lengths. Specifically, the light is branched into two lights traveling along optical paths of different optical path lengths by the first optical coupler 161, and then synthesized and interfered by the second optical coupler 162, thereby generating a sub-interference signal based on the optical path length difference. The sub-interference signal propagates through the optical fiber 163 and is guided to the second photodiode 116, and propagates through the optical fiber 164 and is guided to the second photodiode 117.

[0172] The optical fiber 163 has an optical path length proportional to the length L1r, and the optical fiber 164 has an optical path length proportional to the length L2r. The optical fiber 164 of this embodiment is equivalent to an example of the "delay amount generating unit" in the present invention. In addition, the optical fiber 164 of this embodiment is also equivalent to an example of the "third optical fiber" in the present invention.

[0173] That is, the optical fiber 164 is configured to generate a delay amount based on the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132 .

[0174] Specifically, the optical fiber 164 propagates the secondary interference signal, and has an optical path length based on the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132. Therefore, the secondary interference signal guided to the second photodetector 117 via the optical fiber 164 is a secondary interferometer signal delayed by the optical fiber 164 (hereinafter also referred to as "delayed secondary interference signal"). In this way, the optical fiber 164 propagates the secondary interference signal, and has an optical path length based on the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132, and thus the delay amount can be easily set by changing the optical path length of the optical fiber 164.

[0175] The second photodiode 116 receives the sub-interference signal propagating in the optical fiber 163 of the sub-interferometer 160 and converts it into an electrical signal (hereinafter, also referred to as a "sub-interferometer signal"). The electrical signal converted by the second photodiode 116 is, for example, a current signal. The second photodiode 117 receives the sub-interference signal propagating in the optical fiber 164 of the sub-interferometer 160 and converts it into an electrical signal (hereinafter, also referred to as a "delayed sub-interferometer signal"). Similarly, the electrical signal converted by the second photodiode 116 is, for example, a current signal.

[0176] The electrical signals output from the second photodiodes 116 and 117 may be amplified at a predetermined gain by an amplifier circuit (not shown). In this case, the amplifier circuit outputs the amplified electrical signals to the first correction signal generator 171 and the second correction signal generator 172 .

[0177] The first correction signal generating unit 171 is configured to generate the first correction signal ("1K clock signal", or also simply referred to as "1K clock") based on the secondary interference signal. The first correction signal is a signal for correcting the sampling period of the first main interference signal generated by the first main interferometer 151. The secondary interference signal is nonlinear like the first main interference signal due to the nonlinearity of the wavelength during scanning. Therefore, the first correction signal generating unit 171 can generate the first correction signal, i.e., the 1K clock signal, for appropriately sampling and performing AD conversion on the analog signal of the first main interference signal by grasping the nonlinearity of the wavelength during scanning based on the secondary interference signal.

[0178] Furthermore, in order to generate an appropriate first correction signal in the first correction signal generating unit 171, it is necessary to appropriately grasp the nonlinearity of the first main interference signal received by the first photodiode 112 in the first correction signal generating unit 171. To this end, it is preferable to match the characteristics (nonlinearity) of the first main interference signal and the sub-interference signal, in other words, to make the first main interference signal and the sub-interference signal coincide in time.

[0179] The second correction signal generating unit 172 is configured to generate a second correction signal ("2K clock signal", or also simply referred to as "2K clock") based on the secondary interference signal and the delay amount. The second correction signal is a signal for correcting the sampling period of the second main interference signal generated by the second main interferometer 152. The secondary interference signal is nonlinear like the second main interference signal due to the nonlinearity of the wavelength during scanning. Therefore, the second correction signal generating unit 172 can generate the second correction signal, i.e., the 2K clock signal, for appropriately sampling and performing AD conversion on the analog signal of the second main interference signal by grasping the nonlinearity of the wavelength during scanning based on the secondary interference signal.

[0180] In this way, by generating a delay amount based on the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132, and generating a second correction signal for correcting the sampling period of the second main interference signal based on the secondary interference signal and the delay amount, it is possible to generate a delay in the second main interference signal corresponding to the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132. Therefore, it is possible to reduce the deviation of the timing when sampling the second main interference signal, and suppress the reduction of the signal strength of the sampled digital signal.

[0181] More specifically, the second correction signal generating unit 172 is configured to generate the second correction signal based on the delayed sub-interferometer signal. That is, the second correction signal is generated based on a signal that is delayed in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. The delay is a time corresponding to the above-mentioned delay amount.

[0182] Furthermore, in order to generate an appropriate second correction signal in the second correction signal generating unit 172, it is necessary to appropriately grasp the nonlinearity of the second main interference signal received by the first photodiode 113 in the second correction signal generating unit 172. To this end, it is preferable to match the characteristics (nonlinearity) of the second main interference signal and the delayed sub-interference signal, in other words, to make the first main interference signal and the sub-interference signal coincide in time.

[0183] In addition, the second correction signal generating unit 172 may generate a pulse signal as the second correction signal based on a signal delayed in the time axis direction by the delay amount described above in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. Thus, the sampling timing of the second main interference signal can be easily made consistent (synchronized).

[0184] Similar to the second correction signal generating unit 172 , the first correction signal generated by the first correction signal generating unit 171 may be a pulse signal.

[0185] The AD converter 181 is configured to sample the first main interferometer signal obtained by converting the first main interference signal into an electrical signal based on the first correction signal and convert it into a digital signal. The interval of the waves of the analog signal of the first main interference signal input to the AD converter 181 is not an equal interval. The AD converter 181 samples the analog signal of the first main interference signal and performs AD conversion based on the sampling period (sampling interval) corrected by the above-mentioned first correction signal, that is, the 1K clock signal, in such a way that the interval of the waves in the first main interference signal becomes an equal interval.

[0186] The AD conversion unit 182 is configured to sample the second main interferometer signal obtained by converting the second main interference signal into an electrical signal based on the first correction signal and convert it into a digital signal. The interval of the wave of the analog signal of the second main interference signal input to the AD conversion unit 182 is not an equal interval. The AD conversion unit 182 samples the analog signal of the second main interference signal and performs AD conversion based on the sampling period (sampling interval) corrected by the above-mentioned second correction signal, that is, the 2K clock signal, in such a way that the interval of the wave in the second main interference signal becomes an equal interval.

[0187] In this way, the AD conversion unit 182 samples the second main interferometer signal obtained by converting the second main interference signal into an electrical signal based on the second correction signal and converts it into a digital signal, thereby easily realizing a structure for converting the second main interferometer signal into a digital signal with a corrected sampling period.

[0188] The processing unit 118 is configured to calculate the distance to the measurement object T based on at least one of the first main interference signal generated by the first main interferometer 151 and the second main interference signal generated by the second main interferometer 152 , and the sub-interference signal generated by the sub-interferometer 160 .

[0189] In more detail, the processing unit 118 is configured to calculate the distance to the measuring object T based on the first main interference signal received by the first photodiode 112 and amplified by the amplifier circuit 114, the second main interference signal received by the first photodiode 113 and amplified by the amplifier circuit 115, and the secondary interference signal received by the second photodiodes 116 and 117.

[0190] Specifically, in the AD conversion unit 181, the nonlinear analog signal based on the first main interference signal is converted into a digital signal with a sampling period corrected by the first correction signal based on the secondary interference signal. Therefore, the processing unit 118 uses FFT, etc. to convert the digital signal into a frequency, and analyzes them to calculate the distance value to the measured object T.

[0191] In addition, in the AD conversion unit 182, the nonlinear analog signal based on the second main interference signal is converted into a digital signal with a sampling period corrected by the second correction signal based on the secondary interference signal and the delay amount. Therefore, the processing unit 118 uses FFT, etc. to convert the digital signal into a frequency, and analyzes them to calculate the distance value to the measured object T.

[0192] In this way, the processing unit 118 calculates the distance to the measurement object T based on at least one of the first main interference signal generated by the first main interferometer 151 and the second main interference signal generated by the second main interferometer 152 and the secondary interference signal generated by the secondary interferometer 160, thereby making it easy to realize a structure for measuring the distance to the measurement object T.

[0193] Fig.11 1 is a schematic diagram showing the general structure of another optical interference ranging sensor 101 according to one embodiment of the present invention. Fig.11 To Fig.10 The same or similar components as those of the optical interference ranging sensor 100 are marked with the same or similar reference numerals, and their descriptions are omitted as appropriate. Fig.10 The same functions and effects brought about by the same structure of the optical interference ranging sensor 100 shown are not mentioned in sequence.

[0194] like Fig.11 As shown, the optical interference distance measuring sensor 101 includes a controller 110 , a first sensor head 121 , and a second sensor head 122 , and further includes an optical fiber cable 130 connecting the controller 110 with the first sensor head 121 and the second sensor head 122 . Fig.11 The controller 110 of the optical interference ranging sensor 101 is shown with Fig.10 The controller 110 of the optical interference distance measuring sensor 100 shown in the figure is different in that a delay line 191 is provided instead of the optical fiber 164 .

[0195] The light projected from the wavelength scanning light source 140 is branched by the optical branching section 111 and supplied to the sub-interferometer 160 of the controller 110. The sub-interferometer 160 of the controller 110 generates a sub-interference signal based on two lights traveling along optical paths of different optical path lengths. Specifically, the light is branched into two lights traveling along optical paths of different optical path lengths by the first optical coupler 161, and then synthesized and interfered by the second optical coupler 162, thereby generating a sub-interference signal based on the optical path length difference. The sub-interference signal propagates in the optical fiber 163 and is guided to the second photodiode 116. On the other hand, the remaining port of the second optical coupler 162 is connected to an optical fiber having a coreless optical fiber terminal, or is connected to an attenuator.

[0196] The second photodiode 116 receives the second interference signal propagating in the optical fiber 163 of the sub-interferometer 160 and converts it into a sub-interferometer signal which is an electrical signal. The electrical signal converted by the second photodiode 116 is, for example, a current signal. In addition, the electrical signal output from the second photodiode 116 may be amplified at a predetermined gain by an amplifier circuit (not shown). In this case, the amplifier circuit outputs the amplified electrical signal to the first correction signal generator 171 and the delay line 191.

[0197] The delay line 191 is configured to generate a delay corresponding to the delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and output it to the second correction signal generator 172. The delay amount of the delay line 191 is set based on the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132, similarly to the delay amount of the optical fiber 164. The delay line 191 of this embodiment is equivalent to an example of the "delay amount generator" in the present invention. The delay line 191 outputs the delayed signal, that is, the delayed sub-interferometer signal, to the second correction signal generator 172.

[0198] The delay line 191 includes an electronic component that delays the propagation of an electrical signal, such as a delay line. The electronic component of the delay line 191 may be any component that delays the secondary interference signal, and its structure, type, number, etc. are not limited.

[0199] In this way, the delay line 191 generates a delay corresponding to the delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal and outputs it to the second correction signal generating unit 172, thereby outputting the sub-interferometer signal with electrical delay, so that the second correction signal generating unit 172 can easily generate the second correction signal as an electrical signal.

[0200] [Sampling Timing of the First Main Interferometer Signal and the Second Main Interferometer Signal]

[0201] Fig.12 1 is a diagram for explaining the sampling timing of the first main interferometer signal and the second main interferometer signal. Fig.12 In FIG. 1 , the upper section shows the signal of the first main interferometer signal based on the first interference signal of the first main interferometer 151 when sampling, and the lower section shows the signal of the second main interferometer signal based on the second interference signal of the second main interferometer 152 when sampling. In addition, in the following examples, except for the cases explicitly stated, Fig.10 The optical interference ranging sensor 100 shown in FIG. Fig.11 Description of the case of the optical interference ranging sensor 101 shown.

[0202] like Fig.12 As shown in the upper part of , the first main interferometer signal starts sampling based on the first correction signal at time t1, and the first correction signal is generated based on the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. In addition, the first main interferometer signal is sampled at a period corrected by the first correction signal and converted into a digital signal.

[0203] On the other hand, Fig.12As shown in the lower part of , the second main interferometer signal is not generated at the time point of time t1, but is generated at time t2 (t2>t1). The deviation at this time (hereinafter also referred to as "delay time t12") is the delay time of light caused by the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132.

[0204] In order to cope with the delay time t12 in the second main interferometer signal, Fig.10 The optical fiber 164 of the optical interference distance measuring sensor 100 shown generates a delay amount tdelay. The delay amount tdelay is expressed by the following equation (1) using the length L1r of the optical fiber 163, the length L2r of the optical fiber 164, and the speed c of light.

[0205] tdelay=|L2r-L1r| / c…(1)

[0206] Therefore, the second main interferometer signal starts sampling based on the second correction signal at time t2, and the second correction signal is generated based on the delay amount tdelay and the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal. In addition, the second main interferometer signal is sampled at a period corrected by the second correction signal and converted into a digital signal.

[0207] Preferably, the delay amount tdelay generated by the optical fiber 164 is set so that the absolute value of the difference between the delay amount tdelay and the light delay time t12 caused by the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132 is smaller than the minimum sampling period Tsmin in the AD converter 182 .

[0208] In other words, the delay amount tdelay is set so that the time difference Δt between the light delay time t12 and the delay amount tdelay satisfies the following equation (2).

[0209] Δt=|t12-tdelay| <Tsmin…(2)

[0210] [Relationship between the signal strength and time difference of the second main interferometer signal after conversion into a digital signal]

[0211] Fig.13 : is a diagram for explaining the relationship between the signal intensity of the second main interferometer signal after conversion into a digital signal and the time difference Δt. Fig.12 In the example, the signal intensity of the second main interferometer signal after being converted into a digital signal is the signal intensity normalized by taking the signal intensity when the time difference Δt is zero as the reference value "1". Fig.12 The example shown uses Fig.10 The optical interference ranging sensor 100 shown in FIG. Fig.11Description of the case of the optical interference ranging sensor 101 shown.

[0212] exist Fig.10 In the optical interference distance measuring sensor 100 shown in FIG. 1 , the distance from the first sensor head 121 to the measurement object T1 is 1 [m], the length L1 of the first optical fiber 131 is 2 [m], the distance from the second sensor head 122 to the measurement object T2 is 1 [m], the length L2 of the second optical fiber 132 is 10 [m], the refractive index of the first optical fiber 131 and the second optical fiber 132 is 1.5, and the speed of light c is 3×10 8 [m / s], the delay time t12 is calculated as 8×10 -8 Here, when the optical interference distance measuring sensor 100 includes the AD converters 181 and 182 with a maximum sampling time of 100 [MHz], the minimum sampling period Tsmin in the AD converters 181 and 182 is 1×10 -8 [s]. Substituting these values ​​into the above equation (2), the delay amount tdelay is set to 7×10 -8 [s] or more and 9×10 -8 [s] below.

[0213] like Fig.13 As shown in the figure, when the delay tdelay is set to 7×10 -8 [s] or more and 9×10 -8 [s] or less, the decrease in the signal strength of the second main interferometer signal after conversion into a digital signal can be suppressed to less than 10 [%]. For example, when the length L1r of the optical fiber 163 of the sub-interferometer 160 is 1 [m], the length L2r of the optical fiber 164 of the sub-interferometer 160 is set to 14 [m].

[0214] In this way, the delay amount tdelay is set so that the absolute value of the difference between the delay amount tdelay and the light delay time t12 caused by the optical path length difference between the optical path length of the first optical fiber 131 and the optical path length of the second optical fiber 132 is smaller than the minimum sampling period Tsmin in the AD conversion unit 182, thereby suppressing the reduction in the signal strength of the sampled digital signal to below a specified proportion, for example, below 10%.

[0215] In the present embodiment, an example is shown in which the optical interference ranging sensors 100 and 101 each include two sensor heads and an optical fiber cable including two optical fibers connecting each sensor head to the controller 110, but the present invention is not limited thereto. The optical interference ranging sensor may also include three or more sensor heads and an optical fiber cable including the same number of optical fibers. In the following, in order to simplify the description, the structure of the controller 110, in particular the structure of the sub-interferometer 160 and its subsequent stage (downstream) is described in the case where the optical interference ranging sensor includes three sensor heads and an optical fiber cable including two optical fibers.

[0216] [Detailed structure of the sub-interferometer and its subsequent stages when equipped with three sensor heads]

[0217] Fig.14 1 is a schematic diagram showing an example of a specific structure of a sub-interferometer 160 and its subsequent stages when three sensor heads are provided. Fig.15 This is a schematic diagram showing another example of the specific configuration of the sub-interferometer 160 and its subsequent stages when three sensor heads are provided.

[0218] like Fig.14 As shown, the light projected from the wavelength scanning light source 140 is branched by the light branching section 111 and supplied to the sub-interferometer 160, and the sub-interferometer 160 generates a sub-interference signal based on two lights that travel along optical paths of different optical path lengths. Specifically, the light is branched into two lights that travel along optical paths of different optical path lengths by the first optical coupler 161, and then synthesized by the second optical coupler 162 to interfere with each other, thereby generating a sub-interference signal based on the optical path length difference. The sub-interference signal propagates in the optical fiber 163 and is guided to the second photodiode 116, and propagates in the optical fiber 164 and is guided to the second photodiode 117. In addition, the sub-interference signal generates a delay amount in the same manner as the optical fiber 164. The sub-interference signal propagates in the optical fiber 165 and is guided to the second photodiode 119. The second photodiode 119 receives the sub-interference signal propagated through the optical fiber 165 of the sub-interferometer 160 and converts it into an electrical signal (hereinafter also referred to as a "delayed sub-interferometer signal").

[0219] The third correction signal generating unit 173 is configured to generate a third correction signal ("3K clock signal", or simply "3K clock") based on the secondary interference signal and the delay amount. The third correction signal is a signal for correcting the sampling period of the third main interference signal generated by the third main interferometer (not shown). The third correction signal generating unit 173 can generate the third correction signal, i.e., the 3K clock signal, for appropriately sampling and performing AD conversion on the analog signal of the third main interference signal by grasping the nonlinearity of the wavelength during scanning based on the secondary interference signal.

[0220] In addition, if Fig.15As shown, the light projected from the wavelength scanning light source 140 is branched by the light branching section 111 and supplied to the sub-interferometer 160, and the sub-interferometer 160 generates a sub-interference signal based on two lights traveling along optical paths of different optical path lengths. Specifically, the light is branched into two lights traveling along optical paths of different optical path lengths by the first optical coupler 161, and then synthesized and interfered by the second optical coupler 162, thereby generating a sub-interference signal based on the optical path length difference. The sub-interference signal propagates in the optical fiber 163 and is guided to the second photodiode 116. On the other hand, the remaining port of the second optical coupler 162 can be connected to an optical fiber having a coreless optical fiber terminal, or connected to an attenuator.

[0221] The second photodiode 116 receives the second interference signal propagated through the optical fiber 163 of the sub-interferometer 160 , converts it into a sub-interferometer signal which is an electrical signal, and outputs it to the first correction signal generator 171 and the delay line 191 .

[0222] The delay line 191 is configured to generate a delay corresponding to the delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and output it to the second correction signal generator 172. The delay line 191 outputs the delayed signal, that is, the delayed sub-interferometer signal, to the second correction signal generator 172 and the delay line 192. The delay line 192 is configured similarly to the delay line 191 to generate a delay corresponding to the delay amount in the time axis direction in the sub-interferometer signal obtained by converting the sub-interference signal into an electrical signal, and output it to the third correction signal generator 173. The delayed sub-interferometer signal is input from the delay line 191 to the delay line 192, and the sub-interferometer signal further delayed is output to the third correction signal generator 173.

[0223] [Modification of interferometer]

[0224] In the above-described embodiment, the optical interference distance measuring sensors 100 and 101 use a Fizeau interferometer that generates reference light by using the end of an optical fiber as a reference surface in the main interferometer 150 , but the interferometer is not limited to this.

[0225] Fig.16 FIG. 1 is a diagram showing changes in an interferometer that generates interference light using measurement light and reference light. Fig.16In (a), in the optical path through the main interferometer 150, interference light is generated based on the optical path length difference between the reference light with the end (end face) of the optical fiber as the reference surface and the measurement light irradiated from the sensor head and reflected by the measurement object T. This is the structure of the main interferometer 150 (Fizeau interferometer) of the optical interference ranging sensor 100, 101 of the above-mentioned embodiment, and the reference surface can also be configured to reflect light (Fresnel reflection) due to the difference in refractive index between the optical fiber and air. In addition, a reflective film can be applied to the end of the optical fiber, or a non-reflective coating can be implemented at the end of the optical fiber, and a reflective surface such as a lens surface can be configured separately.

[0226] exist Fig.16 In (b), in the optical path passing through the main interferometer 150, a measurement optical path Lm for guiding the measurement light to the measurement object T and a reference optical path Lr for guiding the reference light are formed, and a reference surface (Michelson interferometer) is arranged at the end of the reference optical path Lr. The reference surface can be coated with a reflective film at the end of the optical fiber, or a non-reflective coating can be implemented at the end of the optical fiber, and a reflector or the like can be arranged separately. In this structure, interference light is generated by setting an optical path length difference between the optical path length of the measurement optical path Lm and the optical path length of the reference optical path Lr.

[0227] exist Fig.16 In (c), a measurement optical path Lm for guiding measurement light to the measurement object T and a reference optical path Lr for guiding reference light are formed in the optical path passing through the main interferometer 150, and a balanced detector (Mach-Zehnder interferometer) is arranged in the reference optical path Lr. In this structure, interference light is generated by providing an optical path length difference between the optical path lengths of the measurement optical path Lm and the reference optical path Lr.

[0228] Thus, the main interferometer is not limited to the Fizeau interferometer described in the embodiment, and may be, for example, a Michelson interferometer or a Mach-Zehnder interferometer. As long as interference light can be generated by setting the optical path length difference between the measurement light and the reference light, any interferometer may be applied, and other structures such as a combination thereof may also be applied. In addition, similarly, regarding the sub-interferometer not shown, it may be any of a Fizeau interferometer, a Michelson interferometer, and a Mach-Zehnder interferometer. As long as interference light can be generated by setting the optical path length difference between the measurement light and the reference light, any interferometer may be applied, and other structures such as a combination thereof may also be applied.

[0229] In addition, the above-described embodiments are used to make the understanding of the present invention easy, and are not used to limit the interpretation of the present invention. The present invention can be changed / improved without departing from its main purpose, and its equivalent is also included in the present invention. That is, as long as the features of the present invention are possessed, the mode in which the embodiments are appropriately designed and changed by those skilled in the art is also included in the scope of the present invention. For example, the various elements and their configurations, materials, conditions, shapes, sizes, etc. possessed by the embodiments are not limited to the illustrated contents and can be appropriately changed. In addition, the embodiments are illustrative, and of course, partial replacement or combination of the structures shown in different embodiments can be performed, and as long as the features of the present invention are included, these are also included in the scope of the present invention.

[0230] [Note 1]

[0231] A controller (110) is connected to a first sensor head (121) and a second sensor head (122) for irradiating light to a measurement object via an optical fiber cable (130), wherein the controller (110) comprises: a light source (140) for projecting light while changing the wavelength of the light; a first main interferometer (151) for receiving the light projected from the light source (140) and generating a first main interference signal based on a first measurement light and a first reference light, wherein the first measurement light is irradiated to the measurement object by the first sensor head (121) and reflected, and the first reference light is transmitted along a path that is at least partially different from the first measurement light. a second main interferometer (152) supplied with light projected from the light source (140) and generating a second main interference signal based on second measuring light and second reference light, wherein the second measuring light is irradiated to the measuring object through the second sensor head (122) and reflected, and the second reference light travels along an optical path at least partially different from that of the second measuring light; a sub-interferometer (160) supplied with light projected from the light source (140) and generating a sub-interference signal based on two lights traveling along different optical paths; and a processing unit (118) for processing the sub-interference signal based on at least one of the first main interference signal and the second main interference signal and The optical fiber cable (130) comprises: a first optical fiber (131) connected to a first main interferometer (151) and transmitting light from the first main interferometer (151) to a first sensor head (121), and transmitting light from the first sensor head (121) to the first main interferometer (151); and a second optical fiber (132) connected to a second main interferometer (152) and transmitting light from the second main interferometer (152) to a second sensor head (122), and transmitting light from the second sensor head (122) to the second main interferometer (15 2), the second optical fiber (132) has an optical path length different from that of the first optical fiber (131), and the controller (110) further comprises: a first correction signal generating unit (171), which generates a first correction signal for correcting a sampling period of a first main interference signal based on a secondary interference signal; a delay generating unit, which generates a delay based on an optical path length difference between an optical path length of the first optical fiber (131) and an optical path length of the second optical fiber (132); and a second correction signal generating unit (172), which generates a second correction signal for correcting a sampling period of a second main interference signal based on the secondary interference signal and the delay.

[0232] [Note 8]

[0233] An optical interference ranging sensor (100) comprises a controller (110) and an optical fiber cable (130) connected to the controller (110), wherein the controller (110) comprises: a light source (140) which projects light while changing the wavelength of the light; a first main interferometer (151) which is supplied with the light projected from the light source (140) and generates a first main interference signal based on a first measuring light and a first reference light, wherein the first measuring light is irradiated to a measuring object through a first sensor head (121) and is reflected, and the first reference light is transmitted along a wavelength corresponding to the first measuring light to a measuring object; a second main interferometer (152) supplied with light projected from the light source (140) and generating a second main interference signal based on second measurement light and second reference light, wherein the second measurement light is irradiated to the measurement object through the second sensor head (122) and is reflected, and the second reference light travels along an optical path at least partially different from that of the second measurement light; a sub-interferometer (160) supplied with light projected from the light source (140) and generating a sub-interference signal based on two lights traveling along different optical paths, the optical fiber cable (130) comprising: a first main interferometer (152) supplied with light projected from the light source (140) and generating a second main interference signal based on second measurement light and second reference light, wherein the second measurement light is irradiated to the measurement object through the second sensor head (122) and is reflected, and the second reference light travels along an optical path at least partially different from that of the second measurement light. An optical fiber (131) connected to a first main interferometer (151) and transmitting light from the first main interferometer (151) to a first sensor head (121), and transmitting light from the first sensor head (121) to the first main interferometer (151); and a second optical fiber (132) connected to a second main interferometer (152) and transmitting light from the second main interferometer (152) to a second sensor head (122), and transmitting light from the second sensor head (122) to the second main interferometer (152), the second optical fiber (132) having a connection with the first optical fiber. The controller (110) further comprises: a first correction signal generating unit (171) which generates a first correction signal for correcting a sampling period of a first main interference signal based on a secondary interference signal; a delay generating unit which generates a delay based on a difference in optical path length between an optical path length of the first optical fiber (131) and an optical path length of a second optical fiber (132); and a second correction signal generating unit (172) which generates a second correction signal for correcting a sampling period of a second main interference signal based on the secondary interference signal and the delay.

[0234] Description of symbols

[0235] 1: sensor system; 10: displacement sensor; 11: control device; 12: sensor for control signal input; 13: external connection device; 20: sensor head; 21: objective lens; 22a: collimating lens; 22b: collimating lens; 22c: collimating lens; 23: lens holder; 24: optical fiber array; 30: controller; 31: display unit; 32: setting unit; 33: external I / F unit; 34: optical fiber connection unit; 35: external storage unit; 36: measurement processing unit; 40: optical fiber; 51: wavelength scanning light source; 52: optical amplifier; 53, 53a, 53b: Isolator; 54, 54a, 54b, 54c, 53d, 54e, 54f, 54g, 54h, 54i, 54j: optical coupler; 55: attenuator; 56a, 56b, 56c: light receiving element; 57a, 57b, 57c: amplifier circuit; 58a, 58b, 58c: AD converter; 59: processor; 60: balanced detector; 61: correction signal generator; 71a, 71b, 71c, 71d, 71e: light receiving element; 72a, 72b, 72c: amplifier circuit; 74a, 74b, 74c: AD converter; 75: Processing unit; 76: differential amplifier circuit; 77: correction signal generating unit; 100, 101: optical interference ranging sensor; 110: controller; 111: optical branching unit; 112, 113: first photodiode; 114, 115: amplifier circuit; 116, 116, 119: second photodiode; 118: processing unit; 121: first sensor head; 122: second sensor head; 130: optical fiber cable; 131: first optical fiber; 132: second optical fiber; 140: wavelength scanning light source; 150: main interferometer; 151: first main interferometer; 152: second 2 main interferometers; 160: sub-interferometer; 161: first optical coupler; 162: second optical coupler; 163: optical fiber; 164: optical fiber; 165: optical fiber; 171: first correction signal generating unit; 172: second correction signal generating unit; 173: third correction signal generating unit; 181, 182: AD conversion unit; 191, 192: delay line; Lm: measurement optical path; Lr: reference optical path; T, T1, T2: measurement object; t1: time; t2: time; t12: delay time; Tsmin: sampling period; vs: voltage; Δt: time difference.

Claims

1. A controller connected to a first sensor head and a second sensor head for irradiating light to a measurement object via optical fiber cables, wherein: The controller has: A light source that projects light while changing the wavelength of the light; a first main interferometer supplied with the light projected from the light source, generating a first main interference signal based on first measurement light irradiated to the measurement object by the first sensor head and reflected, and first reference light traveling along an optical path at least partially different from that of the first measurement light; a second main interferometer supplied with the light projected from the light source, generating a second main interference signal based on second measurement light irradiated to the measurement object by the second sensor head and reflected, and second reference light traveling along an optical path at least partially different from that of the second measurement light; as well as a secondary interferometer which is supplied with the light projected from the light source and generates a secondary interference signal based on two lights traveling along different optical paths, The optical fiber cable includes: a first optical fiber connected to the first main interferometer, transmitting light from the first main interferometer to the first sensor head, and transmitting light from the first sensor head to the first main interferometer; and a second optical fiber connected to the second main interferometer, transmitting light from the second main interferometer to the second sensor head, transmitting light from the second sensor head to the second main interferometer, The second optical fiber has an optical path length different from the optical path length of the first optical fiber, The controller also has: a first correction signal generating unit for generating a first correction signal for correcting a sampling period of the first main interference signal based on the sub-interference signal; a delay amount generating unit configured to generate a delay amount based on an optical path length difference between an optical path length of the first optical fiber and an optical path length of the second optical fiber; as well as A second correction signal generating unit generates a second correction signal for correcting a sampling period of the second main interference signal based on the sub-interference signal and the delay amount.

2. The controller according to claim 1, wherein: The delay amount generating unit includes a third optical fiber that propagates the sub-interference signal and has an optical path length based on the optical path length difference.

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

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

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

6. The controller according to claim 5, wherein: The delay amount is set so that an absolute value of a difference between the delay amount and a delay time of light caused by the optical path length difference is smaller than a minimum sampling period in the AD conversion unit.

7. The controller according to claim 1, wherein: The controller further includes a processing unit configured to measure a distance to the measurement object based on the sub-interference signal and at least one of the first main interference signal and the second main interference signal.

8. An optical interference ranging sensor, comprising a controller and an optical fiber cable connected to the controller, wherein: The controller has: A light source that projects light while changing the wavelength of the light; a first main interferometer supplied with the light projected from the light source, generating a first main interference signal based on first measurement light irradiated by the first sensor head to the measurement object and reflected, and first reference light traveling along an optical path at least partially different from that of the first measurement light; a second main interferometer supplied with the light projected from the light source, generating a second main interference signal based on second measurement light irradiated to the measurement object by a second sensor head and reflected, and second reference light traveling along an optical path at least partially different from that of the second measurement light; as well as a secondary interferometer which is supplied with the light projected from the light source and generates a secondary interference signal based on two lights traveling along different optical paths, The optical fiber cable includes: a first optical fiber connected to the first main interferometer, transmitting light from the first main interferometer to the first sensor head, and transmitting light from the first sensor head to the first main interferometer; and a second optical fiber connected to the second main interferometer, transmitting light from the second main interferometer to the second sensor head, transmitting light from the second sensor head to the second main interferometer, The second optical fiber has an optical path length different from the optical path length of the first optical fiber, The controller also has: a first correction signal generating unit for generating a first correction signal for correcting a sampling period of the first main interference signal based on the sub-interference signal; a delay amount generating unit configured to generate a delay amount based on an optical path length difference between an optical path length of the first optical fiber and an optical path length of the second optical fiber; as well as A second correction signal generating unit generates a second correction signal for correcting a sampling period of the second main interference signal based on the sub-interference signal and the delay amount.

Images