Measuring device and measuring method

Abstract

A measuring device 100 includes: a laser device 110 that outputs a frequency-modulated laser beam having multiple modes; a branching component 120 that branches the frequency-modulated laser beam into a reference light and a measurement light; a beat signal generation component 150 that generates a plurality of beat signals by mixing the reference light and the reflected light reflected by irradiating the measurement light onto an object 10 to be measured; a conversion component 160 that converts the plurality of beat signals into digital signals by sampling the beat signals at a frequency greater than or equal to four times the resonance frequency of the laser resonator; and a calculation component 170 that calculates the distance from the measuring device 100 to the object 10 to be measured based on the provided digital signals.

Description

Technical Field

[0001] The present invention relates to a measuring device and a measuring method. Background Art

[0002] There is known a frequency-shifted feedback laser (FSFL) that includes a frequency shifter in a resonator and outputs a plurality of longitudinal-mode lasers whose oscillation frequencies linearly change with time. In addition, there is known an optical rangefinder that uses such an FSFL (for example, see Patent Document 1: the specification of Japanese Patent No. 3583906, and Non-Patent Document 1: "Distance Sensing by FSF Laser and Its Application", Takefumi HARA, Optonews, Vol. 7, No. 3, 2012, pp. 25-31). Summary of the Invention

[0003] Problems to be Solved by the Invention

[0004] An optical rangefinder using a frequency-shifted feedback laser (FSFL) can acquire a large amount of three-dimensional information in a non-contact manner and has been used in, for example, design and production sites. In such an optical rangefinder, electrical noise may be generated in a light receiving device, a measurement circuit, etc. and superimposed on an electrical signal, which causes a decrease in measurement accuracy. Usually, in order to prevent a decrease in measurement accuracy, the results of a plurality of measurements are averaged, but there is a problem that the measurement time increases and the throughput decreases.

[0005] The present invention focuses on these aspects, and an object of the present invention is to suppress a decrease in measurement accuracy while shortening the measurement time of an optical rangefinder with a simple configuration.

[0006] Means for Solving the Problems

[0007] A first aspect of the present invention provides a measuring device for measuring the distance to a measurement object, the measuring device comprising: a laser device having a laser resonator and outputting a frequency-modulated laser beam having multiple modes; a branching component that branches a part of the frequency-modulated laser beam output by the laser device into reference light and branches at least some of the remaining part of the frequency-modulated laser beam into measurement light; a beat signal generation component that generates a plurality of beat signals by mixing the reference light and the reflected light reflected by irradiating the measurement light onto the measurement object; a conversion component that samples the plurality of beat signals at a frequency greater than or equal to four times the resonance frequency of the laser resonator to convert the plurality of beat signals into digital signals; and a calculation component that calculates the distance from the measuring device to the measurement object based on the digital signals.

[0008] The conversion component may include a frequency conversion component that converts the digital signal into frequency information, and the calculation component may include: a division component that divides the frequency information converted by the frequency conversion component into frequency information corresponding to a plurality of frequency bands having a predetermined bandwidth; a detection component that detects the frequency position of the beat signal for each of the divided frequency information; and a distance calculation component that calculates the distance from the measuring device to the measurement object based on the detected frequency positions of the plurality of beat signals.

[0009] The distance calculation component may calculate the distances from the measuring device to the measurement object corresponding to the frequency positions of the plurality of beat signals respectively, and average the calculated distances.

[0010] The distance calculation component may convert the corresponding frequency positions of the plurality of beat signals, average the converted frequency positions, and calculate the distance from the measuring device to the measurement object corresponding to the averaged frequency position.

[0011] The conversion component may include a frequency conversion component that converts the digital signal into frequency information, and the calculation component may include: a division component that divides the frequency information converted by the frequency conversion component into a plurality of frequency information corresponding to a plurality of frequency bands having a predetermined bandwidth; an integration component that converts the plurality of divided frequency information into frequency information corresponding to one predetermined frequency band, and then integrates the signal levels of each frequency; a detection component that detects the frequency position of the beat signal of the integrated frequency information; and a distance calculation component that calculates the distance from the measuring device to the measurement object based on the detected frequency position of the beat signal.

[0012] The division component may set the predetermined bandwidth to the same bandwidth as the resonance frequency v c, and the integrating component can set the first frequency band with the lowest frequency among the multiple divided frequency information as the corresponding one frequency band, shift k - 1 frequency information in the low - frequency direction to convert it into the frequency information of the first frequency band by subtracting (k - 1)×v from the frequency of the k - th frequency band, and then integrate the signal level for each frequency. The k - th frequency band is the k - th subsequent frequency band after the first frequency band. c to convert it into the frequency information of the first frequency band, and then integrate the signal level for each frequency. The k - th frequency band is the k - th subsequent frequency band after the first frequency band.

[0013] The dividing component can set the predetermined bandwidth to be equal to or less than the bandwidth of the resonance frequency.

[0014] The measuring device may further include: an extracting component that extracts a signal component superimposed on the frequency - modulated laser beam output from the laser device and corresponding to the resonance frequency of the laser resonator. Among them, the converting component further includes a clock signal providing component that generates a clock signal with a frequency greater than or equal to four times the resonance frequency of the laser resonator based on the signal component.

[0015] The clock signal providing component may include a PLL circuit that uses the frequency of the signal component as a reference frequency and outputs a frequency signal with a frequency greater than or equal to four times the reference frequency as the clock signal.

[0016] A second aspect of the present invention provides a measuring method for a measuring device for measuring the distance to a to - be - measured object, the method including the following steps: outputting a frequency - modulated laser beam with multiple modes from a laser device having a laser resonator; branching a part of the frequency - modulated laser beam into reference light, and branching at least some of the remaining part of the frequency - modulated laser beam into measuring light; generating a plurality of beat signals by mixing the reference light and the reflected light reflected by irradiating the measuring light onto the to - be - measured object; converting the plurality of beat signals into digital signals by sampling the beat signals at a frequency greater than or equal to four times the resonance frequency of the laser resonator; and calculating the distance from the measuring device to the to - be - measured object based on the digital signals.

[0017] Advantages of the Invention

[0018] According to the present invention, there are the following advantages: while shortening the measurement time of the optical rangefinder through a simple configuration, the reduction of measurement accuracy is suppressed. Description of the Drawings

[0019] Figure 1 Shows a configuration example of the measuring device 100 according to the present embodiment and the to - be - measured object 10.

[0020] Figure 2 Shows a configuration example of the laser device 110 according to the present embodiment.

[0021] Figure 3 Shows an example of a laser beam output from the laser device 110 according to the present embodiment.

[0022] Figure 4 Shows an example of the relationship between (i) the frequency of the beat signal detected by the measuring device 100 according to the present embodiment and (ii) the distance d between the optical head member 140 and the object to be measured 10.

[0023] Figure 5 Shows a configuration example of the beat signal generation component 150 and the conversion component 160 according to the present embodiment.

[0024] Figure 6 Shows an example of the outline of the quadrature detection performed by the beat signal generation component 150 and the conversion component 160 according to the present embodiment.

[0025] Figure 7 Shows an example of the frequency information output by the conversion component 160 according to the present embodiment.

[0026] Figure 8 Shows a configuration example of the conversion component 160 and the calculation component 170 provided in the measuring device 100 according to the present embodiment.

[0027] Figure 9 Shows a modified example of the conversion component 160 and the calculation component 170 provided in the measuring device 100 according to the present embodiment.

[0028] Figure 10 Shows a modified example of the measuring device 100 according to the present embodiment and the object to be measured 10. Detailed Description

[0029] [Configuration Example of Measuring Device 100]

[0030] Figure 1 Shows a configuration example of the measuring device 100 according to the present embodiment and the object to be measured 10. The measuring device 100 optically measures the distance between the measuring device 100 and the object to be measured 10. In addition, the measuring device 100 can measure the three-dimensional shape of the object to be measured 10 by scanning the position of the laser beam irradiated on the object to be measured 10. The measuring device 100 includes a laser device 110, a branching component 120, an optical circulator 130, an optical head component 140, a beat signal generation component 150, a conversion component 160, a calculation component 170, and a display component 180.

[0031] The laser device 110 has a laser resonator and outputs a frequency-modulated laser beam having multiple modes. The laser device 110 is provided with a frequency shifter in the resonator and outputs multiple longitudinal mode lasers whose oscillation frequencies linearly change over time. The laser device 110 is, for example, a frequency shift feedback laser (FSFL). The FSFL will be described later.

[0032] The branching component 120 branches the frequency-modulated laser beam output from the laser device 110, branches a part of it into reference light, and branches at least some of the remaining part into measurement light. The branching component 120 is, for example, a one-in-two-out optical fiber coupler. In Figure 1 the example, the branching component 120 supplies the measurement light to the optical circulator 130 and supplies the reference light to the beat signal generation component 150.

[0033] The optical circulator 130 has multiple input / output ports. For example, the optical circulator 130 outputs the light input from one port to the next port, and also outputs the light input from the next port to the port after that. Figure 1 An example is shown in which the optical circulator 130 has three input / output ports. In this case, the optical circulator 130 outputs the measurement light provided by the branching component 120 to the optical head component 140. In addition, the optical circulator 130 outputs the light input from the optical head component 140 to the beat signal generation component 150.

[0034] The optical head component 140 irradiates the light input from the optical circulator 130 toward the object to be measured 10. The optical head component 140 includes, for example, a collimating lens. In this case, the optical head component 140 first uses the collimating lens to adjust the light input from the optical circulator 130 via the optical fiber into a beam shape and then outputs the light.

[0035] In addition, the optical head component 140 receives the reflected light of the measurement light irradiated onto the object to be measured 10. The optical head component 140 uses the collimating lens to focus the received reflected light onto the optical fiber and supplies it to the optical circulator 130. In this case, the optical head component 140 can include a common collimating lens, and the collimating lens can irradiate the object to be measured 10 with the measurement light and can receive the reflected light from the object to be measured 10. The distance between the optical head component 140 and the object to be measured 10 is defined as d.

[0036] Alternatively, the optical head component 140 may include a condenser lens. In this case, the optical head component 140 focuses the light input from the optical circulator 130 via the optical fiber onto the surface of the object 10 to be measured. The optical head component 140 receives at least a part of the reflected light reflected from the surface of the object 10 to be measured. The optical head component 140 uses the condenser lens to focus the received reflected light onto the optical fiber and supplies the light to the optical circulator 130. Also in this case, the optical head component 140 may include a general condenser lens, and the condenser lens may irradiate the object 10 to be measured with the measurement light and receive the reflected light from the object 10 to be measured.

[0037] The beat signal generation component 150 receives the reflected light from the optical circulator 130, which is the measurement light irradiated onto the object 10 to be measured and reflected therefrom. In addition, the beat signal generation component 150 receives the reference light from the branching component 120. The beat signal generation component 150 mixes the reflected light and the reference light to generate a beat signal. The beat signal generation component 150 includes, for example, a photoelectric conversion element that converts the beat signal into an electrical signal and outputs the electrical signal.

[0038] Here, since the reflected light has traveled back and forth over the distance between the optical head component 140 and the object 10 to be measured, there is a difference in the propagation distance corresponding to at least the distance 2d as compared with the reference light. Since the oscillation frequency of the light output from the laser device 110 changes linearly over time, there is a frequency difference in the oscillation frequencies of the reference light and the reflected light that depends on the propagation delay corresponding to the difference in the propagation distance. The beat signal generation component 150 generates a beat signal corresponding to such a frequency difference.

[0039] The conversion component 160 converts the beat signal generated by the beat signal generation component 150 into a digital signal. In addition, the conversion component 160 performs frequency conversion on the converted digital signal to detect the frequency of the beat signal. Here, the frequency of the beat signal is defined as ν B 。

[0040] The calculation component 170 detects the difference in the propagation distance between the reference light and the measurement light based on the conversion result of the conversion component 160. The calculation component 170 calculates the distance d from the optical head component 140 to the object 10 to be measured based on the frequency ν B of the beat signal.

[0041] The display component 180 displays the calculation result of the calculation component 170. The display component 180 may include a display or the like to display the calculation result. In addition, the display component 180 may store the calculation result in a storage unit or the like. The display component 180 may provide the calculation result to an external device via a network or the like.

[0042] The above-described measuring device 100 can measure the distance d between the measuring device 100 and the object 10 to be measured by analyzing the frequency difference between the reflected light of the measuring light irradiated on the object 10 to be measured and the reference light. That is, the measuring device 100 can form a non-contact and non-destructive optical rangefinder. Next, a more detailed configuration of the measuring device 100 will be described.

[0043] [Configuration Example of Laser Device 110]

[0044] Figure 2 A configuration example of the laser device 110 according to the present embodiment is shown. Figure 2 The laser device 110 of shows an example of FSFL. The laser device 110 includes a laser resonator, and a laser beam oscillates in the laser resonator. The laser resonator of the laser device 110 includes a laser resonator containing a frequency shifter 112, a gain medium 114, a WDM coupler 116, a pump light source 117, and an output coupler 118.

[0045] The frequency shifter 112 shifts the frequency of the input light by an approximately constant frequency. The frequency shifter 112 is, for example, an acousto-optic frequency shifter (AOFS) having an acousto-optic element. Here, the frequency shift amount of the frequency shifter 112 is defined as +ν s . That is, the frequency shifter 112 shifts the frequency of the light circulating around the resonator so that the frequency increases by ν for each round s .

[0046] The gain medium 114 is supplied with pump light, and the gain medium 114 amplifies the input light. The gain medium 114 is, for example, an optical fiber doped with impurities. The impurities are, for example, rare earth elements such as erbium, neodymium, ytterbium, terbium, thulium, etc. The pump light is supplied to the gain medium 114 from the pump light source 117 via the WDM coupler 116. The output coupler 118 outputs a part of the light that has been laser-oscillated in the resonator to an external device.

[0047] That is to say, Figure 2 the shown laser device 110 includes a fiber ring laser having a frequency shifter 112 in the resonator. The laser device 110 preferably further includes an isolator in the resonator. Moreover, the laser device 110 may have an optical bandpass filter that allows light in a predetermined wavelength band in the resonator to pass through. The frequency characteristics of the laser beam output from the laser device 110 will be described below.

[0048] Figure 3Shows an example of a laser beam output from the laser device 110 according to the present embodiment. Figure 3 On the left side, the spectrum of the laser beam output by the laser device 110 at time t0 is shown. In this spectrum, the horizontal axis represents the light intensity, and the vertical axis represents the light frequency. In addition, the multiple longitudinal modes of the spectrum are represented by the number q. The frequencies of the multiple longitudinal modes are arranged at approximately constant frequency intervals. Assume τ RT (= 1 / ν c ) represents the time for light to travel around the resonator, and the multiple longitudinal modes are arranged at intervals of 1 / τ RT (= ν c ), as shown in the following equation. It should be noted that ν0 is the initial frequency of the spectrum at time t0. In addition, ν c is the resonance frequency ν c of the laser resonator.

[0049] [Equation 1]

[0050]

[0051] Figure 3 On the right side, the frequency change over time of the multiple longitudinal modes output by the laser device 110 is shown. On the Figure 3 right side, the horizontal axis represents time, and the vertical axis represents frequency. That is, Figure 3 on the right side, the frequency change over time of the laser beam output from the laser device 110 is shown, and on the left side, the instantaneous frequency of the laser beam at time t0 is shown.

[0052] In the laser device 110, every time the light in the resonator travels around the resonator, the frequency shifter 112 increases the frequency of the light traveling around the resonator by ν s . That is, since the frequency of each mode increases by ν RT every time τ s passes, the rate of change of frequency dν / dt (i.e., the chirp rate) becomes approximately equal to ν s / τ RT . Therefore, the multiple longitudinal modes represented by Equation 1 change over time t as shown in the following equation.

[0053] [Equation 2]

[0054]

[0055] [Details of the distance measurement process]

[0056] The measuring device 100 according to the present embodiment measures the distance d between the optical head member 140 and the object to be measured 10 by using a laser device 110 that outputs frequency components represented by Equation 2. It is assumed that the optical path difference between the reference light and the reflected light is only the distance 2d, that is, the reciprocating distance d, and the propagation delay corresponding to the distance 2d is Δt. That is, when the measurement light is reflected at time t and returns from the object to be measured 10, the frequency of the returned reflected light approximately matches the past frequency that is earlier than time t by the time Δt, and thus can be represented by the following equation.

[0057] [Equation 3]

[0058]

[0059] On the other hand, the reference light at time t can be represented by the following equation in a manner similar to Equation 2, where the reference light is ν q' (t).

[0060] [Equation 4]

[0061]

[0062] Since the beat signal generation component 150 superimposes the reflected light and the reference light, a plurality of beat signals are generated between the plurality of longitudinal modes represented by Equation 3 and the plurality of longitudinal modes represented by Equation 4. It is assumed that the frequency of such a beat signal is ν B (m, d), ν B (m, d) can be represented by the following equation based on Equation 3 and Equation 4, where m is the interval of the longitudinal mode numbers (= q - q'), and Δt = 2d / c.

[0063] [Equation 5]

[0064]

[0065] According to Equation 5, the distance d is represented by the following equation, where 1 / τRT = vc.

[0066] [Equation 6]

[0067]

[0068] It can be understood from Equation 6 that the distance d can be calculated from the frequency observation result of the beat signal by determining the interval m of the longitudinal mode numbers. It should be noted that when changing the frequency shift amount ν s of the laser device 110, the interval m can be determined by detecting the change in the beat signal. Since such a method for determining the interval m is known, as described in Patent Document 1 and the like, its detailed description is omitted.

[0069] Since the observed beat signal is always a positive frequency, in the calculation, the beat signal generated on the negative frequency side is folded back onto the positive side and observed as an image signal. Next, the generation of such an image signal will be described.

[0070] Figure 4 An example of the relationship between the frequency of the beat signal detected by the measuring device 100 according to the present embodiment and the distance d between the optical head unit 140 and the object 10 to be measured is shown. In Figure 4 it, the horizontal axis represents the distance d and the vertical axis represents the frequency ν B (m, d). Figure 4 The multiple straight lines shown by the solid line in are graphs showing the relationship of the frequency ν B (m, d) of the beat signal with respect to the distance d for each of the multiple m values (as shown in Equation 5).

[0071] As Figure 4 shown, multiple beat signals corresponding to the m values are generated. However, since the multiple longitudinal modes included in each of the reflected light and the reference light are arranged at an approximately constant frequency interval ν c , multiple beat signals having equal m values are superimposed at approximately the same frequency on the frequency axis. For example, when observing the frequency band between 0 and ν c , multiple beat signals are superimposed at approximately the same frequency and observed as a single-line spectrum.

[0072] In addition, the absolute value of the frequency ν B (m, d) of the beat signal in the negative range less than 0 is further observed as an image signal. That is, Figure 4 the graph of the region where the vertical axis of is less than 0 is folded back with the frequency 0 as the boundary. Figure 4 The folded image signal is shown by multiple dashed lines. Since only the positive and negative signs of the folded image signal are reversed, the image signal is superimposed on the observed frequency axis at the same frequency as the absolute value of the frequency before folding. For example, when observing the frequency band between 0 and ν c , the beat signal and the image signal are located at different frequencies, unless the frequencies of the beat signal and the image signal become ν c / 2.

[0073] As described above, in the observation frequency band between 0 and ν c , two line spectra are generated, which are (i) the beat signal ν B (m, d) and (ii) the image signal ν B (m′, d), and the m value of the image signal ν B (m′, d) is different from the m value of the beat signal ν BThe m values of (m, d) are different. Here, as an example, m' = m + 1. In this case, the beat signal generation component 150 can eliminate such an image signal by using quadrature detection. Next, the beat signal generation component 150 and the conversion component 160 using quadrature detection will be described.

[0074] Figure 5 FIG. shows a configuration example of the beat signal generation component 150 and the conversion component 160 according to the present embodiment. The beat signal generation component 150 performs quadrature detection on the reflected light and the reference light. The beat signal generation component 150 includes an optical 90-degree hybrid 152, a first photoelectric conversion component 154, and a second photoelectric conversion component 156.

[0075] The optical 90-degree hybrid 152 branches the input reflected light and the input reference light into two parts respectively. The optical 90-degree hybrid 152 multiplexes one of the branched reflected lights and one of the branched reference lights by using an optical coupler or the like to generate a first beat signal. The optical 90-degree hybrid 152 multiplexes the other branched reflected light and the other branched reference light by using an optical coupler or the like to generate a second beat signal. Here, the optical 90-degree hybrid 152 generates a beat signal after generating a 90-degree phase difference between the two branched reference lights. For example, the optical 90-degree hybrid 152 multiplexes the branched reflected light and one of the branched reference lights, and multiplexes the branched reflected light and the light generated by passing the other branched reference light through a π / 2 wavelength plate.

[0076] The first photoelectric conversion component 154 and the second photoelectric conversion component 156 receive the multiplexed reflected light and reference light and convert them into electrical signals. Each of the first photoelectric conversion component 154 and the second photoelectric conversion component 156 may be a photodiode or the like. Each of the first photoelectric conversion component 154 and the second photoelectric conversion component 156 is, for example, a balanced photodiode. In Figure 5 it is assumed that the first photoelectric conversion component 154 generates a first beat signal and the second photoelectric conversion component 156 generates a second beat signal. As described above, the beat signal generation component 150 performs quadrature detection by multiplexing two reference lights and two reflected lights with a 90-degree phase difference, and outputs the two beat signals to the conversion component 160.

[0077] The conversion component 160 performs frequency analysis on the two beat signals. Here, an example in which the conversion component 160 performs frequency analysis using the first beat signal as the I signal and the second beat signal as the Q signal will be described. The conversion component 160 includes a first filter component 162, a second filter component 164, a first AD converter 202, a second AD converter 204, a clock signal providing component 210, and a frequency analysis component 220.

[0078] The first filter component 162 and the second filter component 164 reduce signal components in frequency bands different from the frequency band that the user or the like wants to analyze. Here, the frequency band that the user or the like wants to analyze is set to 0 to ν c The first filter component 162 and the second filter component 164 are, for example, low-pass filters that pass signal components having a frequency equal to or less than ν c . In this case, the first filter component 162 supplies the first beat signal obtained by reducing signal components having a frequency higher than the frequency ν c to the first AD converter 202. In addition, the second filter component 164 supplies the second beat signal obtained by reducing signal components having a frequency higher than the frequency ν c to the second AD converter 204.

[0079] The first AD converter 202 and the second AD converter 204 convert analog signals into digital signals. For example, the first AD converter 202 converts the first beat signal into a digital signal, and the second AD converter 204 converts the second beat signal into a digital signal. The clock signal supply component 210 supplies a clock signal to the first AD converter 202 and the second AD converter 204. By doing so, the first AD converter 202 and the second AD converter 204 convert the analog signal into a digital signal at a sampling rate approximately the same as the clock frequency of the received clock signal.

[0080] Here, when the observation frequency band is from 0 to v c , the frequency of the beat signal is at most the resonance frequency v of the laser resonator c . Therefore, the clock signal supply component 210 supplies a clock signal having a frequency greater than or equal to twice the resonance frequency v of the laser resonator c to the first AD converter 202 and the second AD converter 204, so that the beat signal can be observed.

[0081] The frequency analysis component 220 converts the first beat signal and the second beat signal into frequency data. As an example, the frequency analysis component 220 performs a digital Fourier transform (DFT) on the first beat signal and the second beat signal. The frequency analysis component 220 adds the first beat signal converted into frequency data as the real part, and adds the second beat signal converted into frequency data as the imaginary part, and eliminates the image signal. It should be noted that after converting the beat signal into a digital signal, the conversion component 160 can configure the frequency analysis component 220 using an integrated circuit or the like. The quadrature detection in the beat signal generation component 150 and the frequency analysis in the conversion component 160 will be described below.

[0082] Figure 6 An example outlining the quadrature detection of the beat signal generation component 150 and the conversion component 160 according to the present embodiment is shown. In Figure 6 , the horizontal axis represents the frequency of the beat signal, and the vertical axis represents the signal intensity. Figure 6 The spectrum of one of the I signal and the Q signal is shown. The spectra of both the I signal and the Q signal have approximately the same spectral shape, as Figure 6 shown in the upper part of. In the I signal and the Q signal, for example, beat signals ν c are observed in the frequency band between frequency 0 and v B (m, d) and the image signal ν B (m + 1, d). In this case, in the I signal and the Q signal, the original beat signal -ν B (m + 1, d) of the image signal and the beat signal -ν B (m, d) exist in the frequency band between frequency 0 and -v c on the negative side.

[0083] Here, since the I signal and the Q signal are signal components obtained by quadrature detection by the beat signal generation component 150, even though they have the same spectral shape, they contain different phase information. For example, in the frequency band between frequency 0 and v c on the positive side, the phases of the image signal ν B (m + 1, d) of the I signal and the image signal ν B (m + 1, d) of the Q signal are inverted with respect to each other. Similarly, in the frequency band between frequency 0 and -v c on the negative side, the phases of the beat signal -ν B (m, d) of the I signal and the beat signal -ν B (m, d) of the Q signal are inverted with respect to each other.

[0084] Therefore, as Figure 6 shown in the lower part of, when the frequency analysis component 220 calculates I + jQ using the I signal and the Q signal, in the frequency band between frequency 0 and v c , the beat signals with frequency ν B (m, d) are enhanced with respect to each other, while the image signals with frequency ν B (m + 1, d) are canceled out with respect to each other. Similarly, in the frequency band between frequency 0 and -v c , the beat signals with frequency -ν B (m + 1, d) are enhanced with respect to each other, while the beat signals with frequency -ν B (m, d) are canceled out with respect to each other.

[0085] According to the frequency analysis result of the frequency analysis component 220, for the frequency ν in the frequency band between frequency 0 and v c ​B (m, d), a beat signal is observed. Since the measuring device 100 can cancel the image signal in this way, the frequency ν of the beat signal can be detected. B (m, d). For example, the frequency analysis component 220 takes the frequency with the highest signal intensity of the converted frequency signal as the frequency ν of the beat signal. B (m, d) is output.

[0086] Here, the distance d measured by the measuring device 100 is represented by Equation 6. It can be seen from Equation 6 that the distance d can be calculated by using three frequencies v c , ν s and ν B (m, d). Among the three frequencies, ν B (m, d) can be detected as described above. In addition, since v c and ν s are frequencies determined based on the components used in the laser device 110, v c and ν s can be regarded as fixed values. Therefore, the calculation component 170 uses the frequency ν B (m, d) of the beat signal detected by the conversion component 160 and the predetermined v c and ν s to calculate the distance d.

[0087] As described above, the measuring device 100 can measure the distance d from the optical head component 140 to the object to be measured 10. In the measuring device 100 as described above, since electrical noise may be superimposed on light receiving devices such as the first photoelectric conversion component 154 and the second photoelectric conversion component 156 and measurement circuits such as the beat signal generation component 150 and the conversion component 160, the measurement accuracy may be reduced. To prevent such a reduction in measurement accuracy, averaging the results of multiple measurements can be considered, but this will increase the measurement time and may lead to a reduction in throughput.

[0088] [Multiple beat signals]

[0089] The measuring device 100 according to the present embodiment extends the observation band for the beat signal to measure multiple beat signals generated in multiple different frequency bands. As Figure 4 shown, the beat signal generation component 150 mixes the reflected light and the reference light to generate multiple beat signals ν B (m, d) with different moduli m. Therefore, by extending the observation band of the beat signal ν B (m, d) for the conversion component 160, the beat signal ν B (m, d) generated at different frequencies can be observed.

[0090] Figure 7 illustrates an example of the frequency information output by the conversion component 160 according to the present embodiment. The frequency information represents information indicating the signal frequency and the signal level corresponding to each signal frequency. In Figure 7 , the horizontal axis represents the frequency and the vertical axis represents the signal level. Figure 7 illustrates a plurality of beat signals after a plurality of image signals have been eliminated by quadrature detection. The beat signals are observed in the following manner: for each of a plurality of frequency bands whose bandwidth approximately corresponds to the resonance frequency v c , one beat signal is observed. Here, the plurality of frequency bands are defined as the first frequency band, the second frequency band,..., and the k-th frequency band in ascending order of frequency, and the frequency of the beat signal in the first frequency band is defined as ν B1 , the frequency of the beat signal in the second frequency band is defined as ν B2 , and the frequency of the beat signal in the k-th frequency band is defined as ν Bk .

[0091] When the measuring device 100 observes k beat signals from the first beat signal to the k-th beat signal, the observed frequency band is k×v c . In this case, the clock signal providing component 210 can provide a clock signal having a frequency equal to or greater than 2k×v c to the first AD converter 202 and the second AD converter 204. It can be seen that in order for the measuring device 100 to observe two or more beat signals, the clock signal needs to have at least a frequency greater than or equal to four times the resonance frequency v c .

[0092] As Figure 3 and Figure 4 shown, a plurality of beat signals are generated at corresponding frequency positions in each frequency band. For example, in an ideal case, such as when the distance d between the measuring device 100 and the object to be measured 10 is constant and the noise superimposed on the electrical signal is small enough to be negligible, the frequency ν Bk of the k-th beat signal approximately matches the frequency ν B1 of the first beat signal minus (k - 1)×v c . In this way, ideally, a plurality of beat signals are generated at approximately constant frequency intervals v c .

[0093] Therefore, the measuring device 100 frequency-shifts a plurality of beat signals by corresponding frequency intervals, converts the beat signals into signal components in the same frequency band, and then averages the signal components, thereby reducing the influence of noise. Next, the measuring device 100 will be described.

[0094] [Configuration example of conversion component 160 and calculation component 170]

[0095] Figure 8 Shows a configuration example of the conversion component 160 and the calculation component 170 provided in the measurement device 100 according to the present embodiment. Since Figure 8 the conversion component 160 has the same configuration as the conversion component 160 described in Figure 5 , components in the conversion component 160 having approximately the same operations are denoted by the same reference numerals, and their descriptions are omitted. Figure 8 The conversion component 160 and the calculation component 170 shown in c are configured such that the measurement device 100 has an observation frequency band of 2×ν

[0096] The conversion component 160 samples a plurality of beat signals at a frequency greater than or equal to four times the resonance frequency v c of the laser resonator, and converts the beat signals into digital signals. That is, the clock signal providing component 210 provides a clock signal having a frequency greater than or equal to four times the resonance frequency v c of the laser resonator to the first AD converter 202 and the second AD converter 204. The first AD converter 202 and the second AD converter 204 respectively convert the analog signals into an I signal and a Q signal, and the I signal and the Q signal are digital signals including a plurality of beat signals and a plurality of image signals. Since the conversion component 160 samples a plurality of beat signals at a frequency greater than or equal to four times the resonance frequency v c of the laser resonator, and converts the beat signals into digital signals, the observation frequency band of the beat signals is expanded four times or more. Therefore, a digital signal including four or more measurement results including the distance d can be obtained from one detection result of the beat signals.

[0097] It should be noted that the first filter component 162 and the second filter component 164 pass signal components in a frequency band greater than or equal to twice the resonance frequency v c . For example, the clock signal providing component 210 outputs a clock signal having a frequency equal to or greater than 2k×v c , and the first filter component 162 and the second filter component 164 pass signal components in the frequency band from 0 to k×v c .

[0098] The conversion component 160 includes a frequency conversion component 310. The frequency conversion component 310 converts the I signal and the Q signal, which are digital signals, into frequency information. The frequency conversion component 310 converts the digital signals into frequency information using, for example, digital Fourier transform. The frequency conversion component 310 calculates I + jQ using the converted I signal and Q signal, and outputs a calculation result obtained by canceling the image signal.

[0099] The calculation component 170 calculates the distance d from the measurement device 100 to the object 10 to be measured based on the frequency data of the digital signal converted by the frequency conversion component 310. The calculation component 170 includes a division component 172, a detection component 174, and a distance calculation component 176.

[0100] The division component 172 divides the frequency information converted by the frequency conversion component 310 into frequency information corresponding to a plurality of frequency bands having a predetermined bandwidth. For example, assume that the division component 172 divides the frequency information into first frequency information and second frequency information. The first frequency information includes (i) a part of the signal frequency indicated by the frequency information before division and (ii) the signal level corresponding to the signal frequency. The second frequency information includes (i) the remaining part of the signal frequency indicated by the frequency information before division and (ii) the signal level corresponding to the remaining part of the signal frequency. The division performed by the division component 172 corresponds to creating the above-mentioned first frequency information and second frequency information.

[0101] The division component 172 sets the predetermined bandwidth to be equal to or less than the bandwidth of the resonance frequency v c As an example, as Figure 8 shown in the example of, the division component 172 divides the frequency information according to a bandwidth approximately matching the resonance frequency v c For example, assume that the frequency of the clock signal output by the clock signal providing component 210 is 2f. Then, the division component 172 divides the frequency information according to an integer k, which is the largest integer less than or equal to f c / v c .

[0102] The detection component 174 detects the frequency position of the beat signal for each of the divided frequency information. The detection component 174 detects, for example, the frequency position where the signal level is maximized in each frequency band, and sets the detected frequency position as the frequencies ν B1 , ν B2 , …… ν Bk of the plurality of beat signals.

[0103] The distance calculation component 176 calculates the distance d from the measurement device 100 to the object 10 to be measured based on the detected frequency positions of the plurality of beat signals. For example, the distance calculation component 176 calculates the distances d from the measurement device 100 to the object 10 to be measured corresponding to the frequency positions of the plurality of beat signals, respectively.

[0104] In this case, the distance calculation component 176 calculates the distance d1 from the measurement device 100 to the object 10 to be measured, which corresponds to the frequency ν B1 . In addition, the distance calculation component 176 calculates the distance corresponding to subtracting v B2 from the frequency ν cand the obtained frequency (ν B2 - v c ), the corresponding distance d2. Similarly, the distance calculation unit 176 calculates the distance corresponding to the frequency obtained by subtracting (k - 1)×v Bk from the frequency ν c , that is, the frequency [ν Bk -(k - 1)×v c . k .

[0105] Then, the distance calculation unit 176 averages the calculated distances. The distance calculation unit 176 outputs, for example, a value obtained by averaging the distances d1, d2,... d k as the distance d. Therefore, even if electrical noise generated in the optical receiving device, the measurement circuit, etc. is superimposed on the electrical signal, since the measurement results of a plurality of distances d are averaged, the measuring device 100 can reduce the influence of the noise.

[0106] In addition, since the measuring device 100 detects a plurality of beat signals by expanding the measurement frequency band, it is possible to obtain calculation results of distances d in a number greater than the number of measurements of the measurement light beam. For example, the measuring device 100 can calculate the average value of the measurement results of a predetermined number of distances d from the detection result of one beat signal. Therefore, the measuring device 100 can improve the throughput by shortening the measurement time while improving the measurement accuracy.

[0107] In the measuring device 100 according to the present embodiment, an example in which the calculation unit 170 averages the calculation results of a plurality of distances d has been described, but the present invention is not limited thereto. The measuring device 100 may calculate the distance d after averaging the corresponding frequencies of the beat signals.

[0108] In this case, the distance calculation unit 176 converts the corresponding frequency positions of the plurality of beat signals detected by the detection unit 174. The distance calculation unit 176 uses, for example, the frequencies ν B1 , ν B2 , …… ν Bk of the plurality of beat signals to convert the corresponding frequency positions ν c in the observation frequency band between frequency 0 and v B1 , (ν B2 - v c ), …… [ν Bk -(k - 1)×v c .[[]END]]

[0109] Then, the distance calculation unit 176 averages the converted frequency positions and calculates the distance d from the measuring device 100 to the object 10 to be measured corresponding to the averaged frequency position. Even in this case, even if the electrical noise generated in the optical receiving device, the measuring circuit, etc. is superimposed on the electrical signal, the measuring device 100 can average the detection results of different beat signals, so the measuring device 100 can reduce the influence of the noise.

[0110] In the measuring device 100 according to the present embodiment, an example in which the calculation unit 170 averages the calculation result of the distance d or the detection result of the beat signal has been described above, but the present embodiment is not limited thereto. The measuring device 100 can divide the spectrum of the beat signal to generate a plurality of divided spectra, superimpose the plurality of divided spectra, and calculate the distance d based on the superimposed spectrum. Next, such a measuring device 100 will be described.

[0111] [Variant examples of the conversion unit 160 and the calculation unit 170]

[0112] Figure 9 Variant examples of the conversion unit 160 and the calculation unit 170 provided in the measuring device 100 according to the present embodiment are shown. Since Figure 9 the conversion unit 160 and the calculation unit 170 shown in Figure 7 have the same configuration as the conversion unit 160 and the calculation unit 170 described in

[0113] the conversion unit 160 and the calculation unit 170 shown in Figure 7 have the same configuration as the conversion unit 160 and the calculation unit 170 described in

[0114] the conversion unit 160 and the calculation unit 170 shown in c the conversion unit 160 and the calculation unit 170 shown in c the conversion unit 160 and the calculation unit 170 shown in c the conversion unit 160 and the calculation unit 170 have the same configuration, components with approximately the same operations are denoted by the same reference numerals, and their descriptions are omitted. The calculation unit 170 of the variant example includes a division unit 172, an integration unit 178, a detection unit 174, and a distance calculation unit 176.

[0113] The division unit 172 divides the frequency information converted by the frequency conversion unit 310 into frequency information corresponding to a plurality of frequency bands having a predetermined bandwidth. For example, as Figure 7 shown, the division unit 172 divides the frequency information into frequency information corresponding to k frequency bands such as a first frequency band, a second frequency band,..., and a kth frequency band.

[0114] The integration unit 178 converts a plurality of pieces of divided frequency information into frequency information corresponding to one predetermined frequency band. Taking the first frequency band as the predetermined frequency band, the integration unit 178 converts a plurality of pieces of divided frequency information into frequency information corresponding to the first frequency band, for example. In this case, the integration unit 178 subtracts v c from the frequency of the second frequency band and shifts it in the low-frequency direction. In addition, the integration unit 178 subtracts 2×v c from the frequency of the third frequency band and shifts it in the low-frequency direction. In this way, the integration unit 178 subtracts (k - 1)×v c from the frequency of the kth frequency band., and shift the frequency represented by the k - 1 pieces of frequency information toward the lower frequency. In this way, the integration component 178 converts the k pieces of frequency information into information corresponding to the first frequency band.

[0115] Then, for each frequency, the integration component 178 integrates the signal levels of the multiple pieces of divided frequency information. As a result, since multiple beat signals are integrated, it is desirable that the signal levels at approximately the same frequency position become the maximum value. When noise or the like appears, a random noise level is superimposed on such beat signals. As the number k of frequency bands to be integrated increases, this noise component is smoothed to become an approximately constant value. Therefore, fluctuations in the peak frequency of the beat signal caused by noise are suppressed.

[0116] The detection component 174 detects the frequency position of the beat signal in the integrated frequency information. The detection component 174 detects, for example, the frequency position where the signal level is maximized in the first frequency band, and sets the detected frequency position as the frequency ν of the beat signal. B .

[0117] The distance calculation component 176 calculates the distance d from the measuring device 100 to the object 10 to be measured based on the detected frequency position ν of the beat signal. B As described above, the measuring device 100 can integrate the observation results of the beat signals in multiple frequency bands to average the noise components to be superimposed, thereby reducing the influence of noise. The measuring device 100 of the variant example can also improve throughput by shortening the measurement time.

[0118] The above - mentioned measuring device 100 according to the present embodiment averages or superimposes signal components based on multiple observed beat signals to reduce the influence of noise, but the present embodiment is not limited thereto. The measuring device 100 can be configured to be switchable between (i) an operation in which no averaging process is performed and (ii) an operation in which an averaging process is performed.

[0119] In this case, for example, a clock signal providing component 210 is provided to switch the frequency of the clock signal to be provided in response to a user input or the like. A setting conversion component 160 is provided to be able to switch between a frequency analysis component 220 and a frequency conversion component 310. Alternatively, the frequency analysis component 220 can switch between a frequency analysis operation and a frequency conversion operation in response to a user input or the like. Similarly, the calculation component 170 switches between (i) an operation in which no averaging process is performed and (ii) an operation in which an averaging process is performed in response to a user input or the like.

[0120] By doing so, the measuring device 100 can switch the processing according to the measurement accuracy desired by the user or the like, and thus can output the measurement result within an appropriate processing time. In addition, the measuring device 100 can be configured to be able to switch the observation frequency band in response to a request from the user or the like. In this case, since the measuring device 100 can change the number k of beat signals used for the averaging process, the processing can be set more finely according to the required measurement accuracy.

[0121] In the measuring device 100 according to the present embodiment, an example has been described above in which the clock signal providing component 210 provides a clock signal having a frequency greater than or equal to four times the resonance frequency v of the laser resonator to the first AD converter 202 and the second AD converter 204, but the present invention is not limited thereto. For example, an external signal generating device may provide a clock signal having a frequency greater than or equal to four times the resonance frequency v of the laser resonator to the first AD converter 202 and the second AD converter 204 of the conversion component 160. Alternatively, the measuring device 100 may also generate a clock signal based on the frequency-modulated laser beam output from the laser device 110. Next, such a measuring device 100 will be described. c of the laser resonator to the first AD converter 202 and the second AD converter 204 of the conversion component 160. Alternatively, the measuring device 100 may also generate a clock signal based on the frequency-modulated laser beam output from the laser device 110. Next, such a measuring device 100 will be described. c of the laser resonator to the first AD converter 202 and the second AD converter 204 of the conversion component 160. Alternatively, the measuring device 100 may also generate a clock signal based on the frequency-modulated laser beam output from the laser device 110. Next, such a measuring device 100 will be described.

[0122] Figure 10 FIGS. show a modified example of the measuring device 100 according to the present embodiment and the object 10 to be measured. In this case, the measuring device 100 further includes an extraction component. In the measuring device 100 according to the modified example, operations that are approximately the same as those of the measuring device 100 in the embodiment shown are denoted by the same reference numerals, and the description thereof is omitted. The measuring device 100 further includes an extraction component 320. Figure 1 FIGS. show a modified example of the measuring device 100 according to the present embodiment and the object 10 to be measured. In this case, the measuring device 100 further includes an extraction component. In the measuring device 100 according to the modified example, operations that are approximately the same as those of the measuring device 100 in the embodiment shown are denoted by the same reference numerals, and the description thereof is omitted. The measuring device 100 further includes an extraction component 320.

[0123] As Figure 3 and Figure 4 described, the laser device 110 outputs a frequency-modulated laser beam having a frequency with a plurality of longitudinal modes, and the plurality of longitudinal modes are arranged at a frequency interval approximately matching the resonance frequency v. Therefore, the electrical signal of the frequency-modulated laser beam generated by the photoelectric conversion includes a signal component of the resonance frequency v. The extraction component 320 extracts the signal component that is superimposed on the frequency-modulated laser beam output from the laser device 110 and corresponds to the resonance frequency v of the laser resonator. It should be noted that the branching component 120 is, for example, a one-in-three-out fiber coupler. Alternatively, the branching component 120 may be a combination of two one-in-two-out optical couplers. c described, the laser device 110 outputs a frequency-modulated laser beam having a frequency with a plurality of longitudinal modes, and the plurality of longitudinal modes are arranged at a frequency interval approximately matching the resonance frequency v. Therefore, the electrical signal of the frequency-modulated laser beam generated by the photoelectric conversion includes a signal component of the resonance frequency v. The extraction component 320 extracts the signal component that is superimposed on the frequency-modulated laser beam output from the laser device 110 and corresponds to the resonance frequency v of the laser resonator. It should be noted that the branching component 120 is, for example, a one-in-three-out fiber coupler. Alternatively, the branching component 120 may be a combination of two one-in-two-out optical couplers. c described, the laser device 110 outputs a frequency-modulated laser beam having a frequency with a plurality of longitudinal modes, and the plurality of longitudinal modes are arranged at a frequency interval approximately matching the resonance frequency v. Therefore, the electrical signal of the frequency-modulated laser beam generated by the photoelectric conversion includes a signal component of the resonance frequency v. The extraction component 320 extracts the signal component that is superimposed on the frequency-modulated laser beam output from the laser device 110 and corresponds to the resonance frequency v of the laser resonator. It should be noted that the branching component 120 is, for example, a one-in-three-out fiber coupler. Alternatively, the branching component 120 may be a combination of two one-in-two-out optical couplers. c described, the laser device 110 outputs a frequency-modulated laser beam having a frequency with a plurality of longitudinal modes, and the plurality of longitudinal modes are arranged at a frequency interval approximately matching the resonance frequency v. Therefore, the electrical signal of the frequency-modulated laser beam generated by the photoelectric conversion includes a signal component of the resonance frequency v. The extraction component 320 extracts the signal component that is superimposed on the frequency-modulated laser beam output from the laser device 110 and corresponds to the resonance frequency v of the laser resonator. It should be noted that the branching component 120 is, for example, a one-in-three-out fiber coupler. Alternatively, the branching component 120 may be a combination of two one-in-two-out optical couplers.

[0124] The extraction component 320 includes, for example, a photoelectric conversion component and a filter component. The photoelectric conversion component converts the frequency-modulated laser beam output from the laser device 110 into an electrical signal. Among the electrical signals converted by the photoelectric conversion component, the filter component allows the signal component having the resonance frequency v of the laser resonator to pass through. The filter component has at least one of, for example, a high-pass filter, a low-pass filter, a band-pass filter, and a band-stop filter. The extraction component supplies the extracted signal component having the resonance frequency v to the clock signal supply component 210. c In this case, the filter component allows the signal component having the resonance frequency v of the laser resonator to pass through. The filter component has at least one of, for example, a high-pass filter, a low-pass filter, a band-pass filter, and a band-stop filter. The extraction component supplies the extracted signal component having the resonance frequency v to the clock signal supply component 210. c The extraction component supplies the extracted signal component having the resonance frequency v to the clock signal supply component 210.

[0125] In this case, the clock signal supply component 210 generates a clock signal having a frequency greater than or equal to four times the resonance frequency v of the laser resonator based on the received signal component. The clock signal supply component 210 can include, for example, a frequency multiplier. Alternatively, the clock signal supply component 210 can include a PLL circuit that uses the frequency of the received signal component as a reference frequency and outputs a frequency signal having a frequency greater than or equal to four times the reference frequency as the clock signal. As described above, when the measuring device 100 generates a clock signal from the frequency-modulated laser beam output from the laser device 110, a circuit including a frequency oscillator, etc. can be omitted, so that the configuration of the measuring device 100 can be made simpler. c In this case, the clock signal supply component 210 generates a clock signal having a frequency greater than or equal to four times the resonance frequency v of the laser resonator based on the received signal component. The clock signal supply component 210 can include, for example, a frequency multiplier. Alternatively, the clock signal supply component 210 can include a PLL circuit that uses the frequency of the received signal component as a reference frequency and outputs a frequency signal having a frequency greater than or equal to four times the reference frequency as the clock signal. As described above, when the measuring device 100 generates a clock signal from the frequency-modulated laser beam output from the laser device 110, a circuit including a frequency oscillator, etc. can be omitted, so that the configuration of the measuring device 100 can be made simpler.

[0126] Preferably, at least a part of the conversion component 160 and the calculation component 170 provided in the measuring device 100 according to the present embodiment is formed of an integrated circuit or the like. At least a part of the conversion component 160 and the calculation component 170 includes, for example, a field programmable gate array (FPGA), a digital signal processor (DSP), and / or a central processing unit (CPU).

[0127] When at least a part of the conversion component 160 and the calculation component 170 is formed of a computer or the like, the part includes a storage unit and a control unit. The storage unit includes, for example, a read-only memory (ROM) that stores the basic input / output system (BIOS) of the computer or the like that implements the conversion component 160 and the calculation component 170, etc., and a random access memory (RAM) that serves as a work area. The storage unit can store an operating system (OS), programs, applications, and / or various information. The storage unit can include a large-capacity device such as a hard disk drive (HDD) and / or a solid-state drive (SSD).

[0128] The control unit is a processor such as a CPU, and serves as at least a part of the conversion component 160 and the calculation component 170 by executing the programs stored in the storage unit. The control unit can include a graphics processing unit (GPU) or the like.

[0129] The present invention is described based on exemplary embodiments. The technical scope of the present invention is not limited to the scope described in the above embodiments, and various changes and modifications can be made within the scope of the present invention. For example, all or part of the device can be configured using any unit that is functionally or physically distributed or integrated. In addition, new exemplary embodiments generated by any combination thereof are included in the exemplary embodiments of the present invention. Furthermore, the effects of the new embodiments brought about by the combination also have the effects of the original exemplary embodiments.

[0130] Description of Reference Numerals

[0131] 10 Object to be Measured

[0132] 100 Measuring Device

[0133] 110 Laser Device

[0134] 112 Frequency Shifter

[0135] 114 Gain Medium

[0136] 116 WDM Coupler

[0137] 117 Pump Light Source

[0138] 118 Output Coupler

[0139] 120 Branch Component

[0140] 130 Optical Circulator

[0141] 140 Optical Head Component

[0142] 150 Beat Signal Generation Component

[0143] 152 Optical 90 - Degree Hybrid

[0144] 154 First Photoelectric Conversion Component

[0145] 156 Second Photoelectric Conversion Component

[0146] 160 Conversion Component

[0147] 162 First Filter Component

[0148] 164 Second Filter Component

[0149] 170 Calculation Component

[0150] 172 Division Component

[0151] 174 Detection Component

[0152] 176 Distance Calculation Component

[0153] 178 Integrating component

[0154] 180 Display component

[0155] 202 First AD converter

[0156] 204 Second AD converter

[0157] 210 Clock signal providing component

[0158] 220 Frequency analysis component

[0159] 310 Frequency conversion component

[0160] 320 Extraction component

Claims

1. A measuring device for measuring the distance to a target object to be measured, the measuring device comprising: a laser device having a laser resonator and outputting a frequency-modulated laser beam having multiple modes, wherein the laser resonator has a frequency shifter that shifts the frequency of the input light by an approximately constant frequency; a branching component that branches a part of the frequency-modulated laser beam output by the laser device into reference light and branches at least some of the remaining part of the frequency-modulated laser beam into measurement light; a beat signal generation component that generates a plurality of beat signals by mixing the reference light and the reflected light reflected by irradiating the measurement light onto the target object to be measured; a conversion component that converts the plurality of beat signals into a digital signal including a plurality of beat signals within an observation band by sampling the beat signals at a frequency greater than or equal to four times the resonance frequency of the laser resonator; and a calculation component that calculates the distance from the measuring device to the target object to be measured based on the digital signal by averaging a plurality of distances calculated from the plurality of beat signals or by averaging the frequency positions of the plurality of beat signals.

2. The measuring device according to claim 1, wherein the conversion component includes a frequency conversion component that converts the digital signal into frequency information, and the calculation component includes: a partitioning component that partitions the frequency information converted by the frequency conversion component into frequency information corresponding to a plurality of frequency bands having a predetermined bandwidth; a detection component that detects the frequency position of the beat signal for each of the plurality of partitioned frequency information; and a distance calculation component that calculates the distance from the measuring device to the target object to be measured based on the detected frequency positions of the plurality of beat signals.

3. The measuring device according to claim 2, wherein, The distance calculation component calculates the distances from the measuring device to the target object to be measured corresponding to the frequency positions of the plurality of beat signals respectively and averages the plurality of calculated distances.

4. The measuring device according to claim 2, wherein, The distance calculation component converts the corresponding frequency positions of the plurality of beat signals, averages the converted frequency positions, and calculates the distance from the measuring device to the target object to be measured corresponding to the averaged frequency position.

5. The measuring device according to claim 1, wherein, The conversion component includes a frequency conversion component that converts the digital signal into frequency information, and the calculation component includes: a partitioning component that partitions the frequency information converted by the frequency conversion component into a plurality of frequency information corresponding to a plurality of frequency bands having a predetermined bandwidth; an integration component that converts the plurality of partitioned frequency information into frequency information corresponding to one predetermined frequency band, and then integrates the signal level of each frequency; a detection component that detects the frequency position of the beat signal of the integrated frequency information; and a distance calculation component that calculates the distance from the measuring device to the target object to be measured based on the detected frequency position of the beat signal.

6. The measuring device according to claim 5, wherein, The dividing component sets the predetermined bandwidth to a bandwidth v that is the same as the resonant frequency c , and The integrating component sets the first frequency band with the lowest frequency among the multiple divided frequency information as the corresponding one frequency band, shifts k-1 pieces of frequency information in the low-frequency direction to convert them into the frequency information of the first frequency band by subtracting (k-1)×v from the frequencies of the k-th frequency band, and then integrates the signal levels for each frequency. The k-th frequency band is the k-th subsequent frequency band after the first frequency band. c to convert them into the frequency information of the first frequency band, and then integrates the signal levels for each frequency. The k-th frequency band is the k-th subsequent frequency band after the first frequency band.

7. The measuring device according to claim 2, wherein, The partitioning component sets the predetermined bandwidth to be equal to or less than the bandwidth of the resonance frequency.

8. The measuring device according to any one of claims 1 to 7, further comprising: An extraction component extracts a signal component that is superimposed on a frequency-modulated laser beam output from a laser device and corresponds to the resonance frequency of the laser resonator. The conversion component further includes a clock signal providing component that generates a clock signal having a frequency greater than or equal to four times the resonance frequency of the laser resonator based on the signal component.

9. The measuring device according to claim 8, wherein, The clock signal providing component includes a PLL circuit that uses the frequency of the signal component as a reference frequency and outputs a frequency signal having a frequency greater than or equal to four times the reference frequency as the clock signal.

10. A measuring method for a measuring device for measuring the distance to a measurement object, the method comprising the following steps: Output a frequency-modulated laser beam having multiple modes from a laser device having a laser resonator, wherein the laser resonator has a frequency shifter that shifts the frequency of the input light to an approximately constant frequency; Branch a part of the frequency-modulated laser beam into reference light, and branch at least some of the remaining part of the frequency-modulated laser beam into measurement light; Generate a plurality of beat signals by mixing the reference light and the reflected light reflected by irradiating the measurement light onto the measurement object; Convert the plurality of beat signals into a digital signal including a plurality of beat signals within an observation band by sampling the beat signals at a frequency greater than or equal to four times the resonance frequency of the laser resonator; And Based on the digital signal, calculate the distance from the measuring device to the measurement object by averaging a plurality of distances calculated from the plurality of beat signals or by averaging the frequency positions of the plurality of beat signals.

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