Optical distance measurement device and optical distance measurement method

Abstract

This optical distance measurement device (1) comprises: a signal acquisition unit (91) that acquires an I signal and a Q signal of polarized lights orthogonal to each other; a phase difference estimation calculation unit (92) that estimates a phase difference between the I signal and the Q signal of one polarized light; a phase difference acquisition unit (93) that acquires a phase difference between the I signal and the Q signal of the other polarized light and a phase difference between the polarized lights on the basis of a correlation between phase differences between the I signal and the Q signal of the polarized lights; an addition unit (95) that adds the signals of the polarized lights orthogonal to each other while matching the phases between the polarized lights; a spectrum acquisition unit (96) that acquires a spectrum of the signal added while matching the phases between the polarized lights; and a distance measurement unit (97) that measures a distance to an object (TG) on the basis of the spectrum.

Description

Optical distance measuring device and optical distance measuring method

[0001] This disclosed technology relates to an optical distance measuring device and an optical distance measuring method.

[0002] There is an optical ranging technique that measures the distance to an object by splitting wavelength-swept light from a light source into a reference light and a measurement light, and combining the reflected light from the object after the measurement light is shone on the object with the reference light that does not pass through the object to obtain interference light. In this optical ranging technique, the interference light is divided into a horizontal polarization component (p polarization) and a vertical polarization component (s polarization) that are orthogonal to each other, and each is independently IQ detected. The intensity of the received signal is increased by polarization diversity, which is the sum of the detected signals of different polarizations. In order to perform accurate IQ detection, the IQ imbalance, which is the phase error between the I signal and the Q signal, is obtained, and polarization diversity requires retardation information, which is the phase difference between orthogonal polarizations. For example, Patent Document 1 describes a conventional technique for correcting IQ imbalance.

[0003] Japanese Patent Publication No. 2005-348195

[0004] Conventional techniques have the problem of high computational load in obtaining the IQ imbalance and retardation of mutually orthogonal polarizations. For example, obtaining the IQ imbalance requires phase difference estimation calculations using Fourier transforms, and when dealing with mutually orthogonal polarizations, this phase difference estimation calculation must be performed for all polarizations.

[0005] The disclosed technology aims to solve the above-mentioned problems and to provide an optical ranging device that can reduce the computational load required to acquire mutually orthogonal polarization IQ imbalances and retardations.

[0006] The optical distance measuring device according to the disclosed technology splits light from a light source that outputs wavelength-swept light into reference light and measurement light, and measures the distance to an object based on I signals and Q signals separated from mutually orthogonal polarizations in the interference light of reflected light from the object and the reference light that does not pass through the object, and comprises: a signal acquisition unit that acquires I signals and Q signals of mutually orthogonal polarizations; a phase difference estimation calculation unit that estimates the phase difference between the I signal and Q signal of one polarization by a phase difference estimation calculation including a Fourier transform; a phase difference acquisition unit that acquires the phase difference between the I signal and Q signal of the other polarization based on the correlation of the phase differences between the I signal and Q signal of the other polarization, and acquires the phase difference between polarizations using the estimated phase difference and the acquired phase difference; an addition unit that generates signals of mutually orthogonal polarizations by matching the phases of the I signal and Q signal and adding them using the estimated phase difference and the acquired phase difference, and adds the polarized signals by matching the phases between polarizations; a spectrum acquisition unit that acquires the spectrum of the signals added by matching the phases between polarizations; and a distance measuring unit that measures the distance using the acquired spectrum.

[0007] According to the disclosed technology, the phase difference between the I signal and Q signal of one polarization of mutually orthogonal polarizations is estimated by a phase difference estimation calculation including a Fourier transform. Based on the correlation of the phase differences between the I signals and Q signals of the other polarization, the phase difference between the I signal and Q signal of the other polarization is obtained, and the phase difference between the polarizations is obtained using the estimated phase difference and the obtained phase difference. In this way, the optical ranging device according to the disclosed technology can obtain the IQ imbalance and retardation of the other polarization by performing the computationally intensive phase difference estimation calculation only once to estimate the IQ imbalance of one polarization. This reduces the computational load required to obtain the IQ imbalance and retardation of mutually orthogonal polarizations.

[0008] Figure 1 is a block diagram showing the configuration of an optical distance measuring device according to Embodiment 1. Figure 2 is a flowchart showing the optical distance measuring method according to Embodiment 1. Figure 3 is a flowchart showing the details of the processing in step ST2 of Figure 2. Figure 4 is a flowchart showing the details of the processing in step ST3 of Figure 2. Figure 5 is a diagram showing an overview of signal intensity amplification by IQ detection and polarization diversity. Figure 6 is a block diagram showing a modified configuration of the optical distance measuring device according to Embodiment 1. Figures 7A and 7B are block diagrams showing the hardware configuration that realizes the functions of the signal processing unit included in the optical distance measuring device according to Embodiment 1.

[0009] Embodiment 1. The optical ranging device according to Embodiment 1 splits light from a light source that outputs wavelength-swept light into reference light and measurement light, and measures the distance to the object using the I (in-phase) signal and Q (orthogonal) signal separated from the p-polarized and s-polarized signals of the received signal of the interference light between the reflected measurement light (reflected by the object) and the reference light that does not pass through the object (hereinafter referred to as the "measurement interference signal"). In the optical ranging device according to Embodiment 1, the signal intensity of the measurement interference signal is increased by IQ detection and polarization diversity.

[0010] (Signal Strength Improvement Using IQ Detection) In IQ detection, the I signal and Q signal in the interfering light are separated by splitting the interfering light into two optical paths with a path length difference that gives a phase difference of π / 2. The I signal and Q signal are converted into electrical signals by photoelectric conversion, and the electrical signals of the I signal and Q signal are converted into digital signals. Using the digital signals of the I signal and Q signal, the signal Sig is obtained according to the following equation (1). In the following equation (1), in order to subtract the π / 2 phase difference between the I signal and the Q signal, the Q signal is multiplied by the imaginary number i to match the phase and then added together, thereby increasing the signal strength of the signal Sig. Sig = I + iQ (1)

[0011] Actual devices have design tolerances, making it difficult to separate an I signal and a Q signal that have an accurate phase difference of π / 2. For this reason, IQ imbalance occurs in which the phase difference deviates from π / 2 by several degrees. If the I signal and the Q signal are added together without considering IQ imbalance, unnecessary components caused by the phase difference deviation will mix into the measurement interference signal, and there is a possibility that the signal intensity of the measurement interference signal will not increase sufficiently.

[0012] (Improvement of signal intensity using polarization diversity) In polarization diversity, IQ detection is performed on the p-polarized wave and s-polarized wave of interference light, thereby obtaining a detection signal Sig for p-polarized light represented by the following formula (2) ｐ and a detection signal Sig for s-polarized light represented by the following formula (3) ｓ is obtained. Using these detection signals Sig ｐ and Sig ｓ , the measurement interference signal Sig ｄｉｖ is obtained according to the following formula (4). In the following formula (4), Δφ ｐ is the IQ imbalance of p-polarized light, and Δφ ｓ is the IQ imbalance of s-polarized light. Furthermore, Δφ ｒｅｔ is a phase difference caused by birefringence, and this is the phase difference due to retardation. Sig ｐ =I ｐ +iQ ｐ exp(-iΔφ ｐ ) (2) Sig ｓ =I ｓ +iQ ｓ exp(-iΔφ ｓ ) (3) Sig ｄｉｖ =Sig ｐ +Sig ｓ exp(-iΔφ ｒｅｔ ) (4)

[0013] In the above formula (4), in order to subtract the phase difference between polarized lights, the detection signal Sig ｓ is multiplied by exp(-iΔφ ｒｅｔ ) to align the phases, and then the phases are added together, whereby the measurement interference signal Sig ｄｉｖThe signal intensity increases further. When p-polarized and s-polarized light passes through an optical fiber or optical crystal, if they have different refractive indices, a phase delay occurs because their propagation speeds differ due to the effect of birefringence. The phase difference due to retardation is the phase difference between polarizations due to this phase delay. Therefore, if the phase difference due to retardation is not accurately determined, the signal intensity of the measured interference signal may not increase sufficiently.

[0014] Conventional techniques involve obtaining I and Q signals separated from the p-polarized signal of the measured interference signal, performing a Fourier transform on these signals to identify the principal component frequencies (peak frequencies) of the I and Q signals, and then calculating the phase difference of the principal components to estimate the phase difference, including the IQ imbalance in the p-polarized signal. Similarly, for s-polarized signals, the phase difference, including the IQ imbalance in the s-polarized signal, was estimated by a phase difference estimation calculation that included the Fourier transform. Similarly, for retardation, the phase difference due to retardation was estimated by a phase difference estimation calculation that included the Fourier transform of the p-polarized and s-polarized signals of the measured interference signal.

[0015] The Fourier transform is performed on a set of digital data that constitutes a signal, resulting in a very large computational load. While the computational load of the Fourier transform can be mitigated by employing the Fast Fourier Transform (FFT), the load increases with each subsequent FFT iteration. Conventional techniques require three phase estimation calculations to obtain the IQ imbalance in p-polarization, the IQ imbalance in s-polarization, and the retardation between p-polarization and s-polarization, resulting in a high computational load.

[0016] Therefore, the optical ranging device according to Embodiment 1 acquires IQ imbalance and retardation based on the correlation of the phase difference between the I signal and the Q signal between p-polarization and s-polarization, without using the spectra of the I signal and the Q signal. Specifically, in the optical ranging device according to Embodiment 1, the phase difference between the I signal and the Q signal in one of the p-polarization and s-polarizations is determined by a phase difference estimation calculation using the spectra of the I signal and the Q signal. The phase difference between the I signal and the Q signal of the other polarization, and the phase difference between p-polarization and s-polarization are acquired based on the correlation of the phase difference between the I signal and the Q signal between p-polarization and s-polarization, without using the spectra of the I signal and the Q signal. In this way, the optical ranging device according to Embodiment 1 can acquire the IQ imbalance and retardation of the other polarization by performing only one computationally intensive phase difference estimation calculation to acquire the IQ imbalance of one of the p-polarization or s-polarizations. This reduces the computational load required to acquire the IQ imbalance and retardation in p-polarization and s-polarization.

[0017] (Basic Configuration of Optical Distancing Device) Figure 1 is a block diagram showing the configuration of the optical distance measuring device 1 according to Embodiment 1. As shown in Figure 1, the optical distance measuring device 1 is a device that measures the distance to an object TG, and comprises a wavelength-swept light source 2, an optical coupler 3, a circulator 4, a polarizing beam splitter 5, a 90-degree optical hybrid 6, a photoelectric conversion unit 7, an AD conversion unit 8, a signal processing unit 9, and a lens barrel 10. In Figure 1, solid arrows represent optical signals propagating through optical fibers, and dashed arrows represent electrical signals.

[0018] Furthermore, in the example shown in Figure 1, polarizing beam splitters 5 are provided in the optical path from which the reference light is output and the optical path from which the measurement light is output, and two 90-degree optical hybrids 6 are provided, one for inputting p-polarized light and the other for inputting s-polarized light. In addition, four photoelectric conversion units 7 are provided as first to fourth photoelectric conversion units, and similarly, the AD conversion unit 8 is also provided as first to fourth AD conversion units.

[0019] Since the signal processing unit 9 acquires the IQ imbalance and retardation of p-polarized and s-polarized light to perform distance measurement, the optical distance measuring device 1 only needs to have the functions of the signal processing unit 9. That is, the wavelength-swept light source 2, optical coupler 3, circulator 4, polarizing beam splitter 5, 90-degree optical hybrid 6, photoelectric conversion unit 7, and AD conversion unit 8 may be provided by external measuring devices separate from the optical distance measuring device 1.

[0020] (Wavelength Sweep Light Source) The wavelength sweep light source 2 outputs wavelength-swept light based on a sweep signal. The wavelength sweep light source 2 includes an electrical unit and a light source unit, which are not shown in Figure 1. The electrical unit generates a potential sweep signal and outputs the generated sweep signal to the light source unit. The light source unit generates and outputs wavelength-swept light whose wavelength changes in synchronization with the potential of the sweep signal. The wavelength-swept light output from the wavelength sweep light source 2 is output to the optical coupler 3 via an optical fiber.

[0021] (Optical Coupler) The optical coupler 3 splits the wavelength-swept light into reference light and measurement light, outputting the reference light to an optical path that does not pass through the object TG, and outputting the measurement light to an optical path that passes through the object TG. The optical paths are made of optical fibers. The optical fiber from which the reference light is output is connected to one of the two polarizing beam splitters 5. The optical fiber from which the measurement light is output is connected to the other polarizing beam splitter 5 via the circulator 4.

[0022] (Circulator) The circulator 4 is installed in the optical fiber that constitutes the optical path through which the measurement light from the optical coupler 3 is output. The circulator 4 outputs the measurement light to the microscope tube 10, and outputs the light that has been reflected by the object TG and returned to the microscope tube 10 to the polarizing beam splitter 5. The microscope tube 10 is an optical component that irradiates the object TG with the light output from the circulator 4 through an air layer, and returns the reflected light that has been reflected by the object TG back to the circulator 4.

[0023] (Polarizing Beam Splitter) The polarizing beam splitter 5 is an optical element that separates and outputs p-polarized and s-polarized components from the input light. For example, the polarizing beam splitter 5 is configured with a coating and a prism that transmit p-polarized light and reflect s-polarized light. A polarizing beam splitter 5 provided in the optical path from which the reference light is output separates the reference light into p-polarized and s-polarized components, outputs the p-polarized component of the reference light to the p-polarized 90-degree optical hybrid 6, and outputs the s-polarized component of the reference light to the s-polarized 90-degree optical hybrid 6. A polarizing beam splitter 5 provided in the optical path from which the measurement light is output separates the measurement light into p-polarized and s-polarized components, outputs the p-polarized component of the measurement light to the p-polarized 90-degree optical hybrid 6, and outputs the s-polarized component of the measurement light to the s-polarized 90-degree optical hybrid 6.

[0024] (90-degree optical hybrid) The 90-degree optical hybrid 6 is an optical element that generates I and Q signals by shifting the phase of two input optical signals by 90 degrees (π / 2). For example, the 90-degree optical hybrid 6 mixes the input reference light and measurement light to create measurement interference light, and then branches the measurement interference light to output it into two optical paths. The optical path from which one of the branched lights is output has an optical path length difference that gives a phase difference of π / 2 to the other light. As the interference light propagates through the two optical paths, it outputs I and Q components of light.

[0025] The 90-degree optical hybrid 6 on the p-polarization side combines the p-polarization component of the reference light and the p-polarization component of the measurement light to obtain a p-polarized measurement interference signal, and separates the IQ components from the p-polarized measurement interference signal. In other words, the 90-degree optical hybrid 6 on the p-polarization side separates the I signal Ip and the Q signal Qp from the p-polarized measurement interference signal. ｐ This is a p-polarized signal with an I component, and it is output to the first photoelectric conversion unit, which is one of the four photoelectric conversion units 7. Q signal Q ｐ This signal is p-polarized and has a Q component, and is output to the second photoelectric conversion unit, which is one of the four photoelectric conversion units 7.

[0026] The s-polarized 90-degree optical hybrid 6 combines the s-polarized component of the reference light and the s-polarized component of the measurement light to obtain a measurement interference signal of s-polarization, and separates the IQ component from the measurement interference signal of s-polarization. That is, the s-polarized 90-degree optical hybrid 6 separates the I signal from the measurement interference signal of s-polarization. ｓ and Q signal Q ｓ The signals are separated. ｓ This is an s-polarized signal with an I component, and it is output to the third photoelectric conversion unit, which is one of the four photoelectric conversion units 7. Q signal Q ｓ This is an s-polarized signal with a Q component, and it is output to the fourth photoelectric conversion unit, which is one of the four photoelectric conversion units 7.

[0027] (Photoelectric conversion unit) The photoelectric conversion unit 7 receives the I signal I output from the 90-degree optical hybrid 6. ｐ Q signal Q ｐ I signal I ｓ and Q signal Q ｓ The light is converted into an electrical signal. For example, the photoelectric conversion unit 7 includes a light-receiving element and a transimpedance amplifier (TIA), which are not shown in Figure 1. The light-receiving element converts the light intensity of the signal input from the 90-degree optical hybrid 6 into an electrical signal, and the electrical signal is amplified by the TIA and output as an analog signal.

[0028] The first photoelectric conversion unit, the photoelectric conversion unit 7, receives the I signal I input from the 90-degree optical hybrid 6. ｐ By converting it to photoelectricity, the I signal I ｐ It generates an electrical signal. I signal I ｐ The electrical signal is output to the first AD converter, which is one of the four AD converters 8. The second photoelectric converter, the photoelectric converter 7, receives the Q signal Q input from the 90-degree optical hybrid 6. ｐ By converting it to photoelectricity, the Q signal Q ｐ It generates an electrical signal. Q signal Q ｐ The electrical signal is output to the second AD conversion unit, which is one of the four AD conversion units 8.

[0029] The third photoelectric conversion unit, the photoelectric conversion unit 7, receives the I signal I input from the 90-degree optical hybrid 6. ｓ By converting it to photoelectricity, the I signal I ｓIt generates an electrical signal. I signal I ｓ The electrical signal is output to the third AD converter, which is one of the four AD converters 8. The fourth photoelectric converter, the photoelectric converter 7, receives the Q signal Q input from the 90-degree optical hybrid 6. ｓ By converting it to photoelectricity, the Q signal Q ｓ It generates an electrical signal. Q signal Q ｓ The electrical signal is output to the fourth AD conversion unit, which is one of the four AD conversion units 8.

[0030] (AD Conversion Unit) The AD conversion unit 8 converts the input analog signal into an analog-to-digital signal and outputs a digital signal. The first AD conversion unit, the AD conversion unit 8, receives the I signal I from the photoelectric conversion unit 7. ｐ By converting the electrical signal to analog-to-digital, the I signal ｐ It generates a digital signal. I signal I ｐ The digital signal is output to the signal processing unit 9. The second AD conversion unit, the AD conversion unit 8, receives the Q signal Q from the photoelectric conversion unit 7. ｐ By converting the electrical signal to analog-to-digital, the Q signal Q ｐ Generates a digital signal. Q signal Q ｐ The digital signal is output to the signal processing unit 9.

[0031] The third AD conversion unit, the AD conversion unit 8, receives the I signal I from the photoelectric conversion unit 7. ｓ By converting the electrical signal to analog-to-digital, the I signal ｓ It generates a digital signal. I signal I ｓ The digital signal is output to the signal processing unit 9. The fourth AD conversion unit, the AD conversion unit 8, receives the Q signal Q from the photoelectric conversion unit 7. ｓ By converting the electrical signal to analog-to-digital, the Q signal Q ｓ Generates a digital signal. Q signal Q ｓ The digital signal is output to the signal processing unit 9.

[0032] (Signal Processing Unit) The signal processing unit 9 processes the digital signal I signal I ｐ Q signal Q ｐ I signal Iｓ and Q signal Q ｓ The system acquires these signals and uses them to measure the distance to the target object TG. As shown in Figure 1, the signal processing unit 9 is configured to include a signal acquisition unit 91, a phase difference estimation calculation unit 92, a phase difference acquisition unit 93, a table 94, an addition unit 95, a spectrum acquisition unit 96, and a distance measurement unit 97.

[0033] (Signal Acquisition Unit) The signal acquisition unit 91 acquires mutually orthogonal p-polarized and s-polarized I signals and Q signals. For example, the signal acquisition unit 91 receives the I signal from the AD conversion unit 8 via the input interface 100 shown in Figures 7A and 7B, which will be described later. ｐ Q signal Q ｐ I signal I ｓ and Q signal Q ｓ The digital signals are acquired. Signal I ｐ Q signal Q ｐ I signal I ｓ , and Q signal Q ｓ This is output to the phase difference estimation calculation unit 92.

[0034] (Phase Difference Estimation Calculation Unit) The phase difference estimation calculation unit 92 uses the spectra of the I signal and the Q signal to estimate the phase difference between the I signal and the Q signal for one of the p-polarized and s-polarized signals. That is, the phase difference estimation calculation unit 92 calculates the spectra of the I signal and the Q signal for one of the p-polarized and s-polarized signals, and uses the calculated spectra to estimate the phase difference between the I signal and the Q signal for the other polarization. For example, the I signal of p-polarized ｐ and Q signal Q ｐ When performing phase difference estimation calculation, the phase difference estimation calculation unit 92 calculates the I signal I ｐ and Q signal Q ｐ Perform a Fourier transform on the I signal I ｐ and Q signal Q ｐ By identifying the principal component frequencies and comparing them with the phases corresponding to the identified principal component frequencies, the phase difference Δφ is obtained. ｐ The phase difference Δφ is estimated by the phase difference estimation calculation unit 92. ｐ This is output to the phase difference acquisition unit 93. In Figure 1, the phase difference estimation calculation unit 92 receives the I signal I from the signal acquisition unit 91. ｐ Q signal Q ｐI signal I ｓ and Q signal Q ｓ The result is output to the addition unit 95.

[0035] (Phase Difference Acquisition Unit) The phase difference acquisition unit 93 acquires the phase difference between the I signal and Q signal of the other polarization based on the correlation of the phase difference between the I signal and Q signal of the p-polarized and s-polarized signals, and uses the acquired phase difference and the phase difference estimated by the phase difference estimation calculation unit 92 to acquire the phase difference between the p-polarized and s-polarized signals. For example, Δφ is the IQ imbalance in the p-polarized signal. ｐ The value of Δφ, which is the IQ imbalance in s-polarization. ｓ The value of and Δφ, which is the retardation between ps polarizations. ｒｅｔ The correspondence between the values ​​is determined in advance through experiments, etc., and these correspondence tables are prepared as setting data for Table 94. The phase difference acquisition unit 93 identifies the phase difference value corresponding to the phase difference estimated by the phase difference estimation calculation unit 92 from Table 94, and acquires the identified value as the phase difference between the I signal and Q signal of the other polarization, and the phase difference between polarizations.

[0036] (Example of correlation information A) The correlation information set in table 94 may, for example, be information showing the correlation between the phase difference between the I signal and the Q signal in terms of polarization, and the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations. If the phase difference between the I signal and the Q signal is proportional to the relationship between p-polarization and s-polarization as shown in equation (5) below, then for example, the proportionality constant is set in table 94. If the phase difference between the I signal and the Q signal and the phase difference between polarizations (retardation) are proportional to the relationship shown in equation (6) below, then for example, the proportionality constant is set in table 94. Furthermore, since fluctuations in IQ imbalance and retardation are mainly caused by temperature fluctuations or strain, correlation information may be set in table 94 in correspondence with temperature. In this case, the phase difference acquisition unit 93 identifies the correlation information corresponding to the device temperature from table 94. This makes it possible to acquire IQ imbalance and retardation corresponding to the device temperature. Δφ ｐ ∝Δφ ｓ (5) Δφ ｓ ∝Δφ ｒｅｔ (6)

[0037] For example, the phase difference acquisition unit 93 is configured to use the phase difference Δφ estimated by the phase difference estimation calculation unit 92 ｐ to identify the corresponding proportionality coefficient, and obtain the phase difference Δφ between the I signal and the Q signal for s-polarized light through a simple calculation using the identified proportionality coefficient ｓ . As described above, the "acquisition of phase difference" in the first embodiment includes acquisition through simple calculation. Furthermore, the phase difference acquisition unit 93 is configured to, based on the acquired phase difference Δφ ｓ identify the corresponding proportionality coefficient, and obtain the phase difference Δφ caused by retardation through a simple calculation using the identified proportionality coefficient ｒｅｔ . In this way, the optical ranging device 1 only needs to perform one phase difference estimation calculation to estimate the phase difference Δφ ｐ , and can obtain the phase difference Δφ ｓ and the phase difference Δφ ｒｅｔ .

[0038] (Example B of Correlation Information) Furthermore, the correlation information set in the table 94 may be correlation information indicating the correlation between polarizations of the phase difference between the I signal and the Q signal. In this case, a correlation equation indicating the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations is set in the phase difference acquisition unit 93. For example, the correlation equation may be an approximate equation obtained through experiments or the like. This correlation equation is an equation with low calculation load that can obtain output data only by substituting the estimated phase difference as a parameter. For example, by inputting the phase difference Δφ ｐ and the phase difference Δφ ｓ as parameters, the phase difference Δφ ｒｅｔ can be calculated. Calculation using this correlation equation can significantly reduce the calculation load compared to Fourier transform for time-domain signals.

[0039] (Table) The table 94 is table data in which correlation information is set. In FIG. 1, the table 94 is stored in a memory included in the signal processing unit 9. It should be noted that the table 94 may be stored in an external storage device provided separately from the optical ranging device 1. In this case, the phase difference acquisition unit 93 acquires the correlation information from the table 94 by establishing a communication connection to the external storage device using the communication function included in the optical ranging device 1.

[0040] (Example C of correlation information) Note that the phase difference may be obtained using only the correlation formula without providing a table 94. For example, the phase difference acquisition unit 93 may use the phase difference estimated by the phase difference estimation calculation unit 92, a correlation formula showing the correlation between the phase difference between the I signal and the Q signal in terms of polarization, and a correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations to calculate and obtain the phase difference between the I signal and the Q signal of the other polarization, and the phase difference between polarizations. The correlation formula showing the correlation between the phase difference between the I signal and the Q signal in terms of polarization can be, for example, an approximate formula obtained through experiments. By inputting the phase difference estimated by the phase difference estimation calculation unit 92 to this correlation formula, the phase difference between the I signal and the Q signal of the other polarization is calculated. The correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations can be, for example, an approximate formula obtained through experiments. By inputting the phase difference estimated by the phase difference estimation unit 92 and the phase difference between the I signal and Q signal of the other polarization obtained as described above into this correlation equation, the phase difference between polarizations is calculated. In this way, the IQ imbalance and retardation of p-polarization and s-polarization can be obtained by performing the computationally intensive phase difference estimation calculation just once.

[0041] (Addition Unit) The addition unit 95 uses the phase difference estimated by the phase difference estimation calculation unit 92 and the phase difference acquired by the phase difference acquisition unit 93 to add the phase-aligned I signal and Q signal, and adds the p-polarized signal and s-polarized signal obtained by the addition while aligning the phase between the p-polarized and s-polarized signals. For example, the addition unit 95 uses the phase difference estimation calculation unit 92 to obtain the I signal I ｐ Q signal Q ｐ I signal I ｓ Q signal Q ｓ , phase difference Δφ ｐ , phase difference Δφ ｓ and phase difference Δφ ｒｅｔ The summing unit 95 then substitutes these into equations (2) and (3) above to obtain the p-polarized detection signal Sig. ｐ and the s-polarized detection signal Sig ｓ The p-polarized detection signal Sig is calculated. ｐ This includes the IQ signal I, which is related to IQ imbalance.ｐ Phase difference Δφ between them ｐ To subtract the Q signal Q ｐ By multiplying by the imaginary number i to align the phases and then adding them together, Sig ｐ The signal strength increases. s-polarized detection signal Sig ｓ Similarly, the I signal I, including IQ imbalance ｓ Phase difference Δφ between them ｓ To subtract the Q signal Q ｓ By multiplying by the imaginary number i to align the phases and then adding them together, Sig ｓ The signal strength increases.

[0042] Furthermore, the summing unit 95 processes the p-polarized detection signal Sig ｐ and the s-polarized detection signal Sig ｓ By substituting this into equation (4) above, the received signal Sig of the measured interference signal is obtained. ｄｉｖ The calculated signal Sig ｄｉｖ The signal Sig is output to the spectrum acquisition unit 96. ｄｉｖ The phase difference between p-polarized and s-polarized light is Δφ. ｒｅｔ In order to subtract, the detection signal Sig ｓ ni exp(-iΔφ ｒｅｔ By multiplying by ) to align the phase and then adding them together, the measured interference signal Sig ｄｉｖ The signal strength increases further.

[0043] (Spectrum acquisition unit) The spectrum acquisition unit 96 acquires the spectrum of a signal obtained by adding p-polarized and s-polarized signals with phase alignment by the summing unit 95. Signal Sig ｄｉｖ This is a signal whose intensity changes with each wavelength. The result of Fourier transforming the signal resampled over the wavelength range is a spectrum with peaks corresponding to the difference in optical path length between the optical path of the reference light and the optical path of the measurement light, and this becomes the depth profile of the object TG. For example, the spectrum acquisition unit 96 acquires the signal Sig from the summing unit 95. ｄｉｖ The signal Sig is obtained by performing a Fourier transform on it to calculate the spectrum. By analyzing the peaks in this spectrum, the distance to the target object TG can be calculated. ｄｉｖ The spectrum is output to the distance measuring unit 97.

[0044] (Distance measuring unit) The distance measuring unit 97 measures the distance to the target object TG based on the spectrum acquired by the spectrum acquisition unit 96. For example, the distance measuring unit 97 measures the signal Sig output from the spectrum acquisition unit 96. ｄｉｖ When the spectrum is obtained, the signal Sig ｄｉｖ The optical path length difference is calculated based on the peak position in the spectrum, and the distance to the target object TG is measured based on the calculated optical path length difference.

[0045] Next, the optical distance measurement method according to Embodiment 1 will be described. Figure 2 is a flowchart showing the optical distance measurement method according to Embodiment 1, illustrating a series of operations by the optical distance measurement device 1. The signal acquisition unit 91 acquires the p-polarized I signal I ｐ and Q signal Q ｐ And the s-polarized I signal I ｓ and Q signal Q ｓ The signal acquisition unit 91 acquires the p-polarized I signal I from the AD conversion unit 8. ｐ and Q signal Q ｐ And the s-polarized I signal I ｓ and Q signal Q ｓ To obtain the following.

[0046] The phase difference estimation calculation unit 92 uses the spectra of the I signal and the Q signal to estimate the phase difference between the I signal and the Q signal for one of the two polarizations, p-polarization and s-polarization (step ST2). Figure 3 is a flowchart showing the details of the process in step ST2 of Figure 2, and the phase difference estimation calculation determines the I signal in p-polarization. ｐ and Q signal Q ｐ Phase difference Δφ ｐ This shows the case where the phase difference is estimated. The phase difference estimation calculation unit 92 calculates the I signal I ｐ and Q signal Q ｐ When the (p-polarized IQ component) is obtained (step ST1A), the I signal I ｐ and Q signal Q ｐ The Fourier transforms are performed on each of them (step ST2A). The phase difference estimation calculation unit 92 calculates the I signal I ｐ and Q signal Q ｐThe principal component frequencies are identified from the spectrum (step ST3A). The phase difference estimation unit 92 compares the phases at the identified principal component frequencies to determine the I signal I ｐ and Q signal Q ｐ Phase difference Δφ ｐ We estimate (step ST4A).

[0047] Next, the phase difference acquisition unit 93 acquires the phase difference between the I signal and the Q signal of the other polarization based on the correlation of the phase difference between the I signal and the Q signal between the p-polarized and s-polarized signals, without using the spectra of the I signal and the Q signal, and acquires the phase difference between the p-polarized and s-polarized signals using the phase difference estimated by the phase difference estimation calculation unit 92 and the acquired phase difference (step ST3). Figure 4 is a flowchart showing the details of the process in step ST3 of Figure 2, and the phase difference estimation calculation determines the I signal in the p-polarized signal ｐ and Q signal Q ｐ Phase difference Δφ ｐ This shows the case where it is estimated. As shown in Figure 4, the phase difference acquisition unit 93 acquires the I signal I in p polarization. ｐ and Q signal Q ｐ Phase difference Δφ ｐ Based on this, from Table 94, the I signal in s polarization I ｓ and Q signal Q ｓ Phase difference Δφ ｓ , and the phase difference Δφ due to retardation between p-polarized and s-polarized light. ｒｅｔ Obtain (Step ST1B).

[0048] For example, if table 94 contains a correspondence table of phase difference values ​​between the I signal and the Q signal between p-polarization and s-polarization, the phase difference acquisition unit 93 will obtain the I signal in p-polarization from table 94. ｐ and Q signal Q ｐ Phase difference Δφ ｐ The corresponding I signal in s-polarization ｓ and Q signal Q ｓ Phase difference Δφ ｓThe value of is obtained. Alternatively, the phase difference acquisition unit 93 may calculate the phase difference using a correlation formula based on the correlation between the polarizations of the phase difference between the I signal and the Q signal. The same applies when acquiring the phase difference due to retardation between polarizations.

[0049] The summing unit 95 uses the phase difference estimated by the phase difference estimation calculation unit 92 and the phase difference acquired by the phase difference acquisition unit 93 to add the phase-aligned I signal and Q signal, and adds the p-polarized signal and s-polarized signal obtained by the addition while aligning the phase between the p-polarized and s-polarized signals (step ST4). For example, the summing unit 95 calculates the p-polarized detection signal Sig according to the above equations (2) and (3). ｐ and the s-polarized detection signal Sig ｓ The summing unit 95 calculates the p-polarized detection signal Sig according to the above formula (4). ｐ and the s-polarized detection signal Sig ｓ Using the signal Sig ｄｉｖ The result is calculated and output to the spectrum acquisition unit 96.

[0050] The spectrum acquisition unit 96 acquires the spectrum of the signal obtained by aligning the phases between polarizations and adding them (step ST5). For example, the signal Sig is acquired from the adder 95. ｄｉｖ When you obtain the time-domain signal Sig ｄｉｖ A Fourier transform is performed on the signal to obtain the frequency spectrum, which is then output to the distance measuring unit 97.

[0051] The distance measuring unit 97 measures the distance to the target object TG based on the acquired spectrum (step ST6). For example, the distance measuring unit 97 uses the signal Sig acquired from the spectrum acquisition unit 96. ｄｉｖ The distance to the target object TG is measured using the optical path length difference calculated from the peak position (principal component frequency) of the frequency spectrum. By having the optical distance measuring device 1 perform the above method, the IQ imbalance and retardation of p-polarized and s-polarized light can be obtained by performing only one computationally intensive phase difference estimation calculation.

[0052] Next, we will explain signal intensity amplification by IQ detection and polarization diversity. Figure 5 is a diagram illustrating the overview of signal intensity amplification by IQ detection and polarization diversity. As shown in the upper part of Figure 5, the optical distance measuring device 1 uses IQ detection of the measurement interference signal to obtain the I signal in p polarization. ｐ and Q signal Q ｐ And, the I signal in s polarization ｓ and Q signal Q ｓ Obtain it.

[0053] The optical distance measuring device 1 adjusts the phase according to the above equation (2) and outputs the I signal I ｐ and Q signal Q ｐ By adding them together, the signal Sig is obtained as shown in the middle of Figure 5. ｐ The intensity of the signal is increased by 3 dB. Similarly, the optical distance measuring device 1 adjusts the phase of the s-polarized signal according to equation (3) above and adjusts the phase of the I signal I ｓ and Q signal Q ｓ By adding them together, the signal Sig is obtained as shown in the middle of Figure 5. ｓ The signal strength will increase by 3 dB.

[0054] The optical distance measuring device 1 adjusts the phase and obtains the p-polarized signal Sig according to the above equation (4). ｐ and the s-polarized signal Sig ｓ By adding them together, the signal Sig is obtained as shown in the lower part of Figure 5. ｄｉｖ The signal strength is increased by 6 dB. Thus, the optical distance measuring device 1 is capable of improving signal strength through IQ detection and polarization diversity.

[0055] Next, a modified example of the optical distance measuring device according to Embodiment 1 will be described. Figure 6 is a block diagram showing the configuration of optical distance measuring device 1A, which is a modified example of optical distance measuring device 1. In Figure 6, solid arrows represent optical signals propagating through optical fibers, and dashed arrows represent electrical signals. Similar to optical distance measuring device 1, optical distance measuring device 1A is a device that measures the distance to an object TG, and comprises a wavelength-swept light source 2, an optical coupler 3, a circulator 4, a polarizing beam splitter 5, a 90-degree optical hybrid 6, a photoelectric conversion unit 7, an AD conversion unit 8, a signal processing unit 9A, and a lens barrel 10.

[0056] In the optical distance measuring device 1A, the polarizing beam splitter 5, the 90-degree optical hybrid 6, the photoelectric conversion unit 7, and the AD conversion unit 8 are housed inside a common housing 11. For example, the optical distance measuring device 1A uses an integrated coherent receiver (ICR) in which the polarizing beam splitter 5, the 90-degree optical hybrid 6, the photoelectric conversion unit 7, and the AD conversion unit 8 are integrated, enabling IQ detection for each of the two polarizations. Here, the ICR is an optical component capable of converting electrical signals into optical signals for long-distance transmission. In this case, the housing 11 is a chip package in which the polarizing beam splitter 5, the 90-degree optical hybrid 6, the photoelectric conversion unit 7, and the AD conversion unit 8 are integrated.

[0057] The temperature control device 12 is a device that controls the temperature inside the housing 11 and is connected wirelessly or via a wire to the phase difference acquisition unit 93A of the signal processing unit 9. For example, the temperature control device 12 includes a temperature sensor, a PID control circuit, a heater, and a cooling mechanism. The PID control circuit compares the temperature inside the housing 11 detected by the temperature sensor with a set temperature and controls the temperature inside the housing 11 using the heater or cooling mechanism so that it is maintained at the set temperature.

[0058] Fluctuations in IQ imbalance and retardation in p-polarized and s-polarized signals are mainly due to temperature fluctuations or strain. Since the device integrated into the housing 11 as an ICR is relatively small in size, it is less susceptible to large external stresses and therefore less affected by strain. Furthermore, if the temperature of the housing 11 is controlled, a large, uneven temperature distribution will not occur inside the housing 11. Therefore, the optical distance measuring device 1A identifies correlation information corresponding to the device temperature from the temperature-associated correlation information, and acquires the phase difference between the I signal and the Q signal and the phase difference between polarizations based on the identified correlation information. As a result, the optical distance measuring device 1A can acquire IQ imbalance and retardation corresponding to the device temperature.

[0059] For example, table 94 is set with correlation information showing the correlation between IQ imbalance and retardation in relation to temperature. The phase difference acquisition unit 93A acquires from table 94 the correlation information corresponding to the set temperature of the housing 11 acquired from the temperature control device 12, which corresponds to the phase difference between the I signal and the Q signal in one polarization estimated by the phase difference estimation calculation unit 92. Then, the phase difference acquisition unit 93A uses the acquired correlation information to acquire the phase difference between the I signal and the Q signal of the other polarization, and the phase difference between the polarizations.

[0060] (Example of correlation information D) Table 94 may be a table in which correlation information showing the correlation between the polarizations of the phase difference between the I signal and the Q signal, and the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations is set in correspondence with temperature. The phase difference acquisition unit 93A identifies the correlation information corresponding to the phase difference estimated by the phase difference estimation calculation unit 92 and the temperature inside the housing 11, and based on the identified correlation information, it determines the phase difference Δφ between the I signal and the Q signal of the other polarization. ｓ , and acquire the phase difference between polarizations. For example, the phase difference acquisition unit 93A acquires the estimated phase difference Δφ ｐ Furthermore, a proportionality constant corresponding to the temperature inside the housing 11 is identified, and the phase difference Δφ between the I signal and the Q signal in s polarization is determined by a simple calculation using the identified proportionality constant. ｓ The phase difference acquisition unit 93A acquires the acquired phase difference Δφ. ｓ The corresponding proportionality constant is identified, and the phase difference Δφ due to retardation is calculated using a simple calculation with the identified proportionality constant. ｒｅｔ This allows the optical distance measuring device 1A to perform the computationally intensive phase difference estimation calculation, which involves a phase difference of Δφ. ｐ To estimate the phase difference Δφ, it is done only once. ｓ and phase difference Δφ ｒｅｔ You can obtain it.

[0061] (Example of correlation information E) Table 94 may contain correlation information that shows the correlation between the phase difference between the I signal and the Q signal in terms of polarization, corresponding to temperature. The phase difference acquisition unit 93A has a correlation formula that shows the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations, corresponding to temperature. The phase difference acquisition unit 93A identifies the correlation information from Table 94 that corresponds to the phase difference estimated by the phase difference estimation calculation unit 92 and the temperature inside the housing 11, and acquires the phase difference between the I signal and the Q signal of the other polarization based on the identified correlation information. Then, the phase difference acquisition unit 93A calculates and acquires the phase difference between polarizations using the correlation formula that corresponds to the temperature inside the housing 11. This correlation formula is a computationally intensive formula that allows output data to be obtained simply by substituting the estimated phase difference as a parameter, for example, the phase difference Δφ ｐ and phase difference Δφ ｓ When you input this as a parameter, the phase difference Δφ ｒｅｔ This is calculated. Calculations using this correlation formula can reduce the computational load significantly compared to Fourier transforms on time-domain signals.

[0062] (Example of correlation information F) Without providing a table 94, the phase difference acquisition unit 93A may acquire the phase difference using only a correlation formula associated with temperature. For example, the phase difference acquisition unit 93A is set to have a correlation formula that shows the correlation between the phase difference between the I signal and the Q signal in terms of polarization, and a correlation formula that shows the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations, both associated with temperature. The phase difference acquisition unit 93A identifies the above correlation formula that corresponds to the temperature inside the housing 11, and uses the identified correlation formula to calculate and acquire the phase difference between the I signal and the Q signal and the phase difference between polarizations. The correlation formula that shows the correlation between the phase difference between the I signal and the Q signal in terms of polarization can be, for example, an approximate formula obtained through experiments. By inputting the phase difference estimated by the phase difference estimation calculation unit 92 to this correlation formula, the phase difference between the I signal and the Q signal of the other polarization is calculated. The correlation formula that shows the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations can be, for example, an approximate formula obtained through experiments. By inputting the phase difference estimated by the phase difference estimation unit 92 and the phase difference between the I signal and Q signal of the other polarization obtained as described above into this correlation formula, the phase difference between polarizations is calculated. In this case as well, the computationally intensive phase difference estimation calculation only needs to be performed on one polarization, thus reducing the computational load required to obtain the IQ imbalance and retardation of p-polarization and s-polarization.

[0063] Next, the hardware configuration that realizes the functions of the signal processing unit 9 of the optical distance measuring device 1 will be described. The functions of the signal processing unit 9, including the signal acquisition unit 91, the phase difference estimation calculation unit 92, the phase difference acquisition unit 93, the addition unit 95, the spectrum acquisition unit 96, and the distance measuring unit 97, are realized by processing circuits. That is, the signal processing unit 9 includes processing circuits for executing the processes from step ST1 to step ST6 shown in Figure 2. The processing circuits may be dedicated hardware, or they may be a CPU (Central Processing Unit) that executes a program stored in memory.

[0064] Figure 7A is a block diagram showing the hardware configuration for realizing the functions of the signal processing unit 9. Figure 7B is a block diagram showing the hardware configuration for executing the software that realizes the functions of the signal processing unit 9. In Figures 7A and 7B, the signal acquisition unit 91 acquires signals of the IQ component in p-polarization and s-polarization from the AD conversion unit 8 via the input interface 100. The distance measurement unit 97 outputs distance measurement data to the target object TG to the outside via the output interface 101.

[0065] If the processing circuit is a dedicated hardware processing circuit 102 as shown in Figure 7A, the processing circuit 102 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The functions of the signal processing unit 9, including the signal acquisition unit 91, the phase difference estimation calculation unit 92, the phase difference acquisition unit 93, the addition unit 95, the spectrum acquisition unit 96, and the distance measurement unit 97, may be implemented by separate processing circuits, or these functions may be implemented together in a single processing circuit.

[0066] When the processing circuit is the processor 103 shown in Figure 7B, the functions of the signal processing unit 9, including the signal acquisition unit 91, phase difference estimation calculation unit 92, phase difference acquisition unit 93, addition unit 95, spectrum acquisition unit 96, and distance measurement unit 97, are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 104.

[0067] The processor 103 reads and executes a program stored in the memory 104, thereby realizing the functions of the signal processing unit 9, including the signal acquisition unit 91, the phase difference estimation calculation unit 92, the phase difference acquisition unit 93, the addition unit 95, the spectrum acquisition unit 96, and the distance measurement unit 97. For example, the signal processing unit 9 includes a memory 104 for storing a program that, when executed by the processor 103, will result in the execution of steps ST1 to ST6 shown in Figure 2. These programs cause the computer to execute the procedures or methods of processing performed by the signal acquisition unit 91, the phase difference estimation calculation unit 92, the phase difference acquisition unit 93, the addition unit 95, the spectrum acquisition unit 96, and the distance measurement unit 97. The memory 104 may also be a computer-readable storage medium that stores a program for causing the computer to function as the signal acquisition unit 91, the phase difference estimation calculation unit 92, the phase difference acquisition unit 93, the addition unit 95, the spectrum acquisition unit 96, and the distance measurement unit 97.

[0068] Memory 104 includes, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically-EPROM) (registered trademark), as well as magnetic disks, flexible disks, optical disks, compact disks, minidiscs, DVDs, and the like.

[0069] Some of the functions of the signal processing unit 9, including the signal acquisition unit 91, phase difference estimation calculation unit 92, phase difference acquisition unit 93, addition unit 95, spectrum acquisition unit 96, and distance measurement unit 97, may be implemented by dedicated hardware, while other parts may be implemented by software or firmware. For example, the functions of the signal acquisition unit 91 and the phase difference estimation calculation unit 92 may be implemented by a processing circuit 102, which is dedicated hardware, while the functions of the phase difference acquisition unit 93, addition unit 95, spectrum acquisition unit 96, and distance measurement unit 97 may be implemented by the processor 103 reading and executing a program stored in the memory 104. In this way, the processing circuit can implement the above functions by hardware, software, firmware, or a combination thereof.

[0070] As described above, the optical distance measuring device 1 or 1A according to Embodiment 1 includes: a signal acquisition unit 91 that acquires I signals and Q signals of p-polarization and s-polarization; a phase difference estimation calculation unit 92 that estimates the phase difference between the I signal and Q signal of one polarization by a phase difference estimation calculation including a Fourier transform; a phase difference acquisition unit 93 or 93A that acquires the phase difference between the I signal and Q signal of the other polarization based on the correlation of the phase differences between the I signal and Q signal of p-polarization and s-polarization, and acquires the phase difference between p-polarization and s-polarization using the estimated phase difference and the acquired phase difference; an addition unit 95 that generates mutually orthogonal p-polarization and s-polarization signals by matching the phase of the I signal and Q signal using the estimated phase difference and the acquired phase difference, and adds the p-polarization signal and s-polarization signal while matching the phase between the polarizations; a spectrum acquisition unit 96 that acquires the spectrum of the added signals; and a distance measuring unit 97 that measures the distance to the target object TG based on the spectrum. The phase difference between the I signal and Q signal of one of the p-polarized and s-polarized polarizations is estimated by phase difference estimation calculation. Based on the correlation of the phase differences between the I signal and Q signal between the p-polarized and s-polarized polarizations, the phase difference between the I signal and Q signal of the other of the p-polarized and s-polarized polarizations is obtained, and the phase difference between the p-polarized and s-polarized polarizations is obtained. As a result, the optical distance measuring device 1 or 1A only needs to perform the computationally intensive phase difference estimation calculation for one of the polarizations, thereby reducing the computational load required to obtain the IQ imbalance and retardation of the p-polarized and s-polarized polarizations.

[0071] In the optical distance measuring device 1 or 1A according to Embodiment 1, the phase difference acquisition unit 93 or 93A identifies correlation information corresponding to the estimated phase difference from a table 94 which contains correlation information showing the correlation between the polarizations of the phase difference between the I signal and the Q signal, and the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations. Based on the identified correlation information, it acquires the phase difference between the I signal and the Q signal of the other polarization, and the phase difference between the polarizations. As a result, the optical distance measuring device 1 or 1A can acquire the IQ imbalance and retardation of p-polarization and s-polarization by performing a computationally intensive phase difference estimation calculation only once.

[0072] In the optical distance measuring device 1 or 1A according to Embodiment 1, the phase difference acquisition unit 93 or 93A identifies the correlation information corresponding to the estimated phase difference from a table 94 in which correlation information showing the correlation between the polarizations of the phase difference between the I signal and the Q signal is set, acquires the phase difference between the I signal and the Q signal of the other polarization based on the identified correlation information, and calculates and acquires the phase difference between polarizations using the estimated phase difference, the acquired phase difference, and a correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations. As a result, the optical distance measuring device 1 or 1A can acquire the IQ imbalance and retardation of p-polarization and s-polarization by performing a computationally intensive phase difference estimation calculation only once.

[0073] In the optical distance measuring device 1 or 1A according to Embodiment 1, correlation information is set in table 94 in relation to temperature. The phase difference acquisition unit 93 or 93A identifies the correlation information corresponding to the device temperature from table 94. As a result, the optical distance measuring device 1 or 1A can acquire IQ imbalance and retardation as values ​​corresponding to temperature by performing a computationally intensive phase difference estimation calculation only once.

[0074] In the optical distance measuring device 1 or 1A according to Embodiment 1, the phase difference acquisition unit 93 or 93A uses the estimated phase difference, a correlation formula showing the correlation between the phase difference between the I signal and the Q signal in terms of polarization, and a correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations to calculate and acquire the phase difference between the I signal and the Q signal of the other polarization and the phase difference between polarizations. As a result, the optical distance measuring device 1 or 1A can acquire the IQ imbalance and retardation of p-polarization and s-polarization by performing a computationally intensive phase difference estimation calculation only once.

[0075] The optical distance measuring device 1 or 1A according to Embodiment 1 includes a polarization beam splitter 5 that splits the reference light into p-polarized and s-polarized light, and splits the measurement light into p-polarized and s-polarized light, a 90-degree optical hybrid 6 that separates the I signal and Q signal from the p-polarized and s-polarized light in the interference light of the measurement light and the reference light, a photoelectric conversion unit 7 that converts the I signal and Q signal separated from the p-polarized and s-polarized light into electrical signals, and an AD conversion unit 8 that converts the electrical signals into digital signals. The signal acquisition unit 91 acquires the p-polarized and s-polarized I signal and Q signal from the AD conversion unit 8. As a result, the optical distance measuring device 1 or 1A can acquire the signals necessary for distance measurement.

[0076] In the optical distance measuring device 1A according to Embodiment 1, a polarizing beam splitter 5, a 90-degree optical hybrid 6, a photoelectric conversion unit 7, and an AD conversion unit 8 are provided inside a common housing 11. The phase difference acquisition unit 93A identifies the estimated phase difference and correlation information corresponding to the temperature inside the housing 11 from a table 94 in which correlation information showing the correlation between the polarizations of the phase difference between the I signal and the Q signal, and the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations is set in correspondence with temperature. Based on the identified correlation information, it acquires the phase difference between the I signal and the Q signal of the other polarization and the phase difference between the polarizations. As a result, the optical distance measuring device 1A can acquire IQ imbalance and retardation with values ​​corresponding to temperature by performing a computationally intensive phase difference estimation calculation only once.

[0077] In the optical distance measuring device 1A according to Embodiment 1, a polarizing beam splitter 5, a 90-degree optical hybrid 6, a photoelectric conversion unit 7, and an AD conversion unit 8 are provided inside a common housing 11. The phase difference acquisition unit 93A identifies the estimated phase difference and the correlation information corresponding to the temperature inside the housing 11 from a table 94 in which correlation information showing the correlation between the polarizations of the phase difference between the I signal and the Q signal is set in correspondence with temperature. Based on the identified correlation information, it acquires the phase difference between the I signal and the Q signal of the other polarization, and calculates and acquires the phase difference between polarizations using the estimated phase difference, the acquired phase difference, and a correlation formula between the phase difference between the I signal and the Q signal and the phase difference between polarizations. As a result, the optical distance measuring device 1A can acquire IQ imbalance and retardation with values ​​corresponding to temperature by performing a computationally intensive phase difference estimation calculation only once.

[0078] In the optical distance measuring device 1A according to Embodiment 1, a polarizing beam splitter 5, a 90-degree optical hybrid 6, a photoelectric conversion unit 7, and an AD conversion unit 8 are provided inside a common housing 11. The phase difference acquisition unit 93A identifies a correlation formula that corresponds to the temperature inside the housing 11 from among correlation formulas that show the correlation between the polarizations of the phase difference between the I signal and the Q signal, and correlation formulas that show the correlation between the phase difference between the I signal and the Q signal and the phase difference between polarizations. Using the identified correlation formula and the estimated phase difference, the unit calculates and acquires the phase difference between the I signal and the Q signal of the other polarization and the phase difference between polarizations. As a result, the optical distance measuring device 1A can acquire IQ imbalance and retardation with values ​​corresponding to temperature by performing a computationally intensive phase difference estimation calculation only once.

[0079] Step ST3: The optical distance measuring method according to Embodiment 1 includes: Step ST1: A signal acquisition unit 91 acquires I signals and Q signals of p-polarization and s-polarization; Step ST2: A phase difference estimation calculation unit 92 estimates the phase difference between the I signal and Q signal of one polarization by a phase difference estimation calculation including a Fourier transform; Step ST3: A phase difference acquisition unit 93 or 93A acquires the phase difference between the I signal and Q signal of the other polarization based on the correlation of the phase differences between the I signal and Q signal of the p-polarization and s-polarization, and uses the estimated phase difference and the acquired phase difference to acquire the phase difference between the p-polarization and s-polarization; Step ST4: An addition unit 95 uses the estimated phase difference and the acquired phase difference to align the phases of the I signal and Q signal and add them to generate mutually orthogonal p-polarization and s-polarization signals, and adds the p-polarization signal and the s-polarization signal while aligning the phases between the polarizations; Step ST5: A spectrum acquisition unit 96 acquires the spectrum of the signals that have been added while aligning the phases between the polarizations; and Step ST6: A distance measuring unit 97 performs distance measurement based on the spectrum. By performing the above method, the optical distance measuring device 1 or 1A can reduce the computational load required to acquire the IQ imbalance and retardation of p-polarized and s-polarized light.

[0080] Furthermore, any component of the embodiment can be modified or any component of the embodiment can be omitted.

[0081] The optical distance measuring device according to the disclosed technology can be used, for example, in a non-contact optical sensor.

[0082] 1, 1A Optical distance measuring device, 2 Wavelength sweep light source, 3 Optical coupler, 4 Circulator, 5 Polarizing beam splitter, 7 Photoelectric conversion unit, 8 AD conversion unit, 9, 9A Signal processing unit, 10 Lens tube, 11 Housing, 12 Temperature control device, 91 Signal acquisition unit, 92 Phase difference estimation calculation unit, 93, 93A Phase difference acquisition unit, 94 Table, 95 Addition unit, 96 Spectrum acquisition unit, 97 Distance measuring unit, 100 Input interface, 101 Output interface, 102 Processing circuit, 103 Processor, 104 Memory.

Claims

1. An optical distance measuring device that splits light from a light source that outputs wavelength-swept light into reference light and measurement light, and measures the distance to an object based on I signals and Q signals separated from mutually orthogonal polarizations in the interference light of the reflected light from the object and the reference light that does not pass through the object, comprising: a signal acquisition unit that acquires the I signals and Q signals of mutually orthogonal polarizations; a phase difference estimation calculation unit that estimates the phase difference between the I signal and Q signal of one polarization by a phase difference estimation calculation including a Fourier transform; a phase difference acquisition unit that acquires the phase difference between the I signal and Q signal of the other polarization based on the correlation of the phase differences between the I signals and Q signals of the polarizations, and acquires the phase difference between the polarizations using the estimated phase difference and the acquired phase difference; an addition unit that generates signals of mutually orthogonal polarizations by aligning the phases of the I signal and Q signal and adding them using the estimated phase difference and the acquired phase difference, and adds the signals of the polarizations while aligning the phases between the polarizations; and a spectrum acquisition unit that acquires the spectrum of the signals added while aligning the phases between the polarizations. An optical distance measuring device comprising: a distance measuring unit that performs distance measurement using the acquired spectrum; 2. The optical distance measuring device according to claim 1, wherein the phase difference acquisition unit identifies the correlation information corresponding to the estimated phase difference from a table in which correlation information showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations is set, and the phase difference between the I signal and the Q signal and the phase difference between the polarizations is set, and acquires the phase difference between the I signal and the Q signal of the other polarization and the phase difference between the polarizations based on the identified correlation information.

3. The optical distance measuring device according to claim 1, wherein the phase difference acquisition unit identifies the correlation information corresponding to the estimated phase difference from a table containing correlation information showing the correlation of the phase difference between the I signal and the Q signal between the polarizations, acquires the phase difference between the I signal and the Q signal of the other polarization based on the identified correlation information, and calculates and acquires the phase difference between the polarizations using the estimated phase difference, the acquired phase difference, and a correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations.

4. The optical distance measuring device according to claim 2 or 3, wherein the table has the correlation information set in correspondence with temperature, and the phase difference acquisition unit identifies the correlation information corresponding to the device temperature from the table.

5. The optical distance measuring device according to claim 1, wherein the phase difference acquisition unit calculates and acquires the phase difference between the I signal and the Q signal of the other polarization and the phase difference between the polarizations using the estimated phase difference, a correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations, and a correlation formula showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations.

6. An optical distance measuring device according to any one of claims 1 to 5, comprising: a polarization beam splitter that splits the reference light into mutually orthogonal polarizations and splits the measurement light into mutually orthogonal polarizations; a 90-degree optical hybrid that separates an I signal and a Q signal from the mutually orthogonal polarizations in the interference light of the measurement light and the reference light; a photoelectric conversion unit that converts the I signal and Q signal separated from the mutually orthogonal polarizations into electrical signals; and an AD conversion unit that converts the electrical signals into digital signals, wherein the signal acquisition unit acquires the I signal and Q signal of the polarization from the AD conversion unit.

7. The optical distance measuring device according to claim 6, wherein the polarizing beam splitter, the 90-degree optical hybrid, the photoelectric conversion unit, and the AD conversion unit are provided in a common housing, and the phase difference acquisition unit identifies the estimated phase difference and the correlation information corresponding to the temperature inside the housing from a table set in association with temperature, which shows the correlation between the polarizations of the phase difference between the I signal and the Q signal and the correlation between the phase difference between the polarizations, and the correlation information showing the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations, and based on the identified correlation information, acquires the phase difference between the I signal and the Q signal of the other polarization and the phase difference between the polarizations.

8. The optical distance measuring device according to claim 6, wherein the polarizing beam splitter, the 90-degree optical hybrid, the photoelectric conversion unit, and the AD conversion unit are provided in a common housing, and the phase difference acquisition unit identifies the estimated phase difference and the correlation information corresponding to the temperature inside the housing from a table in which correlation information showing the correlation between the phase difference between the I signal and the Q signal in the polarizations is set in correspondence with temperature, acquires the phase difference between the I signal and the Q signal of the other polarization based on the identified correlation information, calculates and acquires the phase difference between the polarizations using the estimated phase difference, the acquired phase difference, and a correlation formula between the phase difference between the I signal and the Q signal and the phase difference between the polarizations.

9. The optical distance measuring device according to claim 6, wherein the polarizing beam splitter, the 90-degree optical hybrid, the photoelectric conversion unit, and the AD conversion unit are provided in a common housing, and the phase difference acquisition unit identifies a correlation formula that corresponds to the temperature inside the housing from among correlation formulas that show the correlation between the phase difference between the I signal and the Q signal and the polarization, and correlation formulas that show the correlation between the phase difference between the I signal and the Q signal and the phase difference between the polarizations, and uses the identified correlation formula and the estimated phase difference to calculate and acquire the phase difference between the I signal and the Q signal of the other polarization and the phase difference between the polarizations.

10. An optical distance measuring device that performs distance measurement to an object based on I and Q signals separated from mutually orthogonal polarizations in the interference light between the reflected light from a light source that outputs wavelength-swept light and the reference light that does not pass through the object, wherein the optical distance measuring device performs optical distance measurement based on I signals and Q signals separated from mutually orthogonal polarizations in the reflected light from the object and the reference light that does not pass through the object, the optical distance measuring device comprises the steps of: a signal acquisition unit acquiring I signals and Q signals of mutually orthogonal polarizations; a phase difference estimation calculation unit estimating the phase difference between the I signal and Q signal of one of the polarizations by a phase difference estimation calculation including a Fourier transform; a phase difference acquisition unit acquiring the phase difference between the I signal and Q signal of the other polarization based on the correlation of the phase differences between the I signal and Q signal of the polarization, and acquiring the phase difference between the polarizations using the estimated phase difference and the acquired phase difference; and an addition unit generating signals of mutually orthogonal polarizations by matching the phases of the I signal and Q signal and adding them using the estimated phase difference and the acquired phase difference, A method for measuring optical distance, comprising: a step of a spectrum acquisition unit acquiring the spectrum of a signal obtained by aligning the phases between the polarizations and adding them together; and a step of a distance measuring unit performing distance measurement using the acquired spectrum.

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