JP5596915B2 - Physical quantity sensor and physical quantity measuring method - Google Patents

Description

  The present invention relates to a physical quantity sensor and a physical quantity measuring method for measuring displacement and velocity of an object from information on interference caused by a self-coupling effect between laser light emitted from a semiconductor laser and return light from the object.

  Displacement (velocity) measurement methods using the interference principle, such as FMCW (Frequency Modulated Continuous Wave) radar, standing wave radar, and self-mixing laser sensor, In calculating the velocity, signal processing such as FFT (Fast Fourier Transform) or interference fringe counting processing is generally used. However, in order to realize high resolution by FFT, there is a problem that long sampling time and data with a high sampling period are required, and enormous processing time is required. In addition, in the interference fringe counting process, it is necessary to physically vibrate the sensor or analyze the amplitude of the interference fringe in order to measure a displacement of less than a half wavelength, which is the periodic motion of the measurement target. There is a problem that only vibrations can be measured, and there is another problem that it takes time to count interference fringes.

  On the other hand, the inventor has proposed a wavelength modulation type laser measuring instrument using the self-coupling effect of a semiconductor laser (see Patent Document 1). The configuration of this laser measuring instrument is shown in FIG. 20 includes a semiconductor laser 201 that emits laser light to an object 210, a photodiode 202 that converts the optical output of the semiconductor laser 201 into an electrical signal, and a light that is collected from the semiconductor laser 201. 210 irradiates the lens 210 and collects the return light from the object 210 and makes it incident on the semiconductor laser 201. The first oscillation period and the oscillation wavelength continuously increase in the semiconductor laser 201. A laser driver 204 that alternately repeats a second oscillation period that decreases in time, a current-voltage conversion amplifier 205 that converts and amplifies the output current of the photodiode 202 into a voltage, and an output voltage of the current-voltage conversion amplifier 205 Is extracted twice, and a counting circuit 207 that counts the number of MHPs included in the output voltage of the signal extraction circuit 206 , Having an arithmetic unit 208 which calculates the speed of the distance and the object 210 with the object 210, a display device 209 for displaying the calculation result of the arithmetic unit 208.

  The laser driver 204 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 201 as an injection current. Accordingly, the semiconductor laser 201 alternately repeats the first oscillation period in which the oscillation wavelength continuously increases at a constant change rate and the second oscillation period in which the oscillation wavelength continuously decreases at a constant change rate. To be driven. FIG. 21 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201. In FIG. 21, P1 is the first oscillation period, P2 is the second oscillation period, λa is the minimum value of the oscillation wavelength in each period, λb is the maximum value of the oscillation wavelength in each period, and Tt is the period of the triangular wave.

  Laser light emitted from the semiconductor laser 201 is collected by the lens 203 and enters the object 210. The light reflected by the object 210 is collected by the lens 203 and enters the semiconductor laser 201. The photodiode 202 converts the optical output of the semiconductor laser 201 into a current. The current-voltage conversion amplifier 205 converts the output current of the photodiode 202 into a voltage and amplifies it, and the signal extraction circuit 206 differentiates the output voltage of the current-voltage conversion amplifier 205 twice. The counting circuit 207 counts the number of mode pop pulses (MHP) included in the output voltage of the signal extraction circuit 206 for each of the first oscillation period P1 and the second oscillation period P2. Based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 201, the number of MHPs in the first oscillation period P1, and the number of MHPs in the second oscillation period P2, the arithmetic unit 208 The speed of the object 210 is calculated. According to such a self-coupled laser measuring instrument, it is possible to perform displacement measurement with a resolution of about half a wavelength of the semiconductor laser 201 and distance measurement with a resolution inversely proportional to the wavelength modulation amount of the semiconductor laser 201.

JP 2006-31080 A

  According to the self-coupled laser measuring instrument, it is possible to measure the displacement and speed of the measurement object with a higher resolution than conventional FMCW radars, standing wave radars, self-mixing laser sensors, and the like. However, a self-coupled laser measuring instrument requires a certain amount of measurement time (in the example of Patent Document 1, a half cycle of a carrier wave of oscillation wavelength modulation of a semiconductor laser) in the same manner as FFT, in calculating displacement and speed. Therefore, there is a problem that a measurement error occurs in the measurement of the measurement object whose speed change is fast. Further, since it is necessary to count the number of MHPs in signal processing, there is a problem that it is difficult to realize a resolution of less than a half wavelength of the semiconductor laser.

  The present invention has been made to solve the above-described problems, and provides a physical quantity sensor and a physical quantity measuring method capable of measuring the displacement and speed of an object with high resolution and reducing the time required for the measurement. For the purpose.

The physical quantity sensor of the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period in which the oscillation wavelength continuously increases monotonously, and a second oscillation period in which the oscillation wavelength continuously decreases monotonously. An oscillation wavelength modulation means for operating the semiconductor laser so that at least one of them repeatedly exists, and an electrical signal including an interference waveform generated by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement target Detection means for detecting the signal, signal extraction means for measuring the period of the interference waveform included in the output signal of the detection means every time the interference waveform is input, and comparing the measurement result of the signal extraction means with a reference period A period correction unit that corrects the measurement result, and based on the individual periods corrected by the period correction unit, the displacement and the speed of the measurement object are reduced. Also characterized in that comprises a calculation means for calculating one.
Further, in one configuration example of the physical quantity sensor of the present invention, the calculating means includes a frequency of a sampling clock for measuring a period of the interference waveform, the reference period, an average wavelength of the semiconductor laser, and the period correcting means. At least one of the displacement and speed of the measurement object is calculated from the amount of change of the corrected period with respect to the reference period.
Further, in one configuration example of the physical quantity sensor of the present invention, the period correction unit may be configured such that k is less than 1 when the period of the interference waveform measured by the signal extraction unit is less than a predetermined number k times the reference period. A positive value), a cycle obtained by combining the cycle of the interference waveform and the cycle of the next measured interference waveform is set as a cycle of the corrected interference waveform, and the combined waveform is set as one waveform, and the signal extracting means When the period of the interference waveform measured by (1) is not less than (m−k) times the reference period and less than (m + k) times the reference period (m is a natural number of 2 or more), the period of the interference waveform is represented by m. Each of the equally divided periods is a corrected period, and there are m waveforms with the corrected period.
In one configuration example of the physical quantity sensor of the present invention, the predetermined number k is 0.5.

Further, in one configuration example of the physical quantity sensor of the present invention, the period correction unit is configured such that the period of the interference waveform when the measurement target is stationary or a period of a predetermined number of interference waveforms measured immediately before the correction. Is the reference period.
Moreover, in one configuration example of the physical quantity sensor of the present invention, the counting unit further counts the number of the interference waveforms included in the output signal of the detection unit for each of the first oscillation period and the second oscillation period. A distance calculating means for calculating a distance from the object to be measured from a minimum oscillation wavelength, a maximum oscillation wavelength and a counting result of the counting means in a period in which the number of interference waveforms is counted by the counting means, and the distance calculating means calculates Period calculation means for obtaining the period of the interference waveform from the measured distance, and the period correction means uses the period obtained by the period calculation means as the reference period.
Moreover, in one configuration example of the physical quantity sensor of the present invention, the counting unit further counts the number of the interference waveforms included in the output signal of the detection unit for each of the first oscillation period and the second oscillation period. A distance proportional number calculating means for calculating a distance proportional number which is the number of interference waveforms proportional to an average distance between the semiconductor laser and the measurement object by calculating an average value of the number of the interference waveforms; and the distance proportional Period calculation means for calculating the period of the interference waveform from the number, and the period correction means uses the period obtained by the period calculation means as the reference period.

  Further, the physical quantity measuring method of the present invention is a semiconductor in which at least one of the first oscillation period in which the oscillation wavelength continuously increases monotonically and the second oscillation period in which the oscillation wavelength continuously decreases monotonously exists. An oscillation procedure for operating the laser, a detection procedure for detecting an electrical signal including an interference waveform caused by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, and the detection procedure A signal extraction procedure for measuring the period of the interference waveform included in the output signal every time an interference waveform is input, and a period correction for correcting the measurement result by comparing the measurement result of the signal extraction procedure with a reference period And a calculation procedure for calculating at least one of the displacement and the velocity of the measurement object based on each cycle corrected by the cycle correction procedure. It is an.

  According to the present invention, by calculating based on the period of each interference waveform, it is possible to measure the displacement and speed of the measurement object with higher resolution than before. Further, in the conventional self-coupled laser measuring instrument, it takes a measurement time of a half cycle of the carrier wave, but in the present invention, the displacement and speed of the measurement object can be obtained from the period of each interference waveform. Therefore, the time required for measurement can be greatly shortened, and it is possible to deal with a measurement object whose speed changes rapidly. Furthermore, in the present invention, the error in the period of the interference waveform can be corrected by comparing the measurement result of the signal extraction means with the reference period, so that the measurement accuracy of displacement and speed can be improved.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a physical quantity sensor according to the first embodiment of the present invention.
The physical quantity sensor in FIG. 1 condenses the light from the semiconductor laser 1 that emits laser light to the object 10 to be measured, the photodiode 2 that converts the light output of the semiconductor laser 1 into an electrical signal, and the light from the semiconductor laser 1. The lens 3 that collects the return light from the object 10 and makes it incident on the semiconductor laser 1, the laser driver 4 that serves as an oscillation wavelength modulation means for driving the semiconductor laser 1, and the output current of the photodiode 2 A current-voltage conversion amplification unit 5 that converts and amplifies the voltage, a filter unit 6 that removes a carrier wave from the output voltage of the current-voltage conversion amplification unit 5, and a self-coupled signal included in the output voltage of the filter unit 6. A signal extraction unit 7 that measures the period of a mode hop pulse (hereinafter referred to as MHP), and an operation that calculates the displacement and speed of the object 10 based on the individual periods measured by the signal extraction unit 7. Has a part 8, and a display unit 9 for displaying the calculation result of the calculating unit 8.

  The photodiode 2 and the current-voltage conversion amplification unit 5 constitute detection means. Hereinafter, for ease of explanation, it is assumed that a semiconductor laser 1 of a type that does not have a mode hopping phenomenon (VCSEL type, DFB laser type) is used.

  The laser driver 4 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 1 as an injection current. As a result, the semiconductor laser 1 has a first oscillation period P1 in which the oscillation wavelength continuously increases at a constant change rate in proportion to the magnitude of the injection current, and the oscillation wavelength continuously decreases at a constant change rate. It is driven to alternately repeat the second oscillation period P2. The time change of the oscillation wavelength of the semiconductor laser 1 at this time is as shown in FIG. In the present embodiment, the rate of change of the oscillation wavelength of the semiconductor laser 1 needs to be constant.

  Laser light emitted from the semiconductor laser 1 is collected by the lens 3 and enters the object 10. The light reflected by the object 10 is collected by the lens 3 and enters the semiconductor laser 1. However, condensing by the lens 3 is not essential. The photodiode 2 is disposed in the semiconductor laser 1 or in the vicinity thereof, and converts the optical output of the semiconductor laser 1 into a current. The current-voltage conversion amplification unit 5 converts the output current of the photodiode 2 into a voltage and amplifies it.

  The filter unit 6 has a function of extracting a superimposed signal from the modulated wave. FIG. 2A is a diagram schematically showing the output voltage waveform of the current-voltage conversion amplification unit 5, and FIG. 2B is a diagram schematically showing the output voltage waveform of the filter unit 6. These figures are obtained by removing the oscillation waveform (carrier wave) of the semiconductor laser 1 of FIG. 2 from the waveform (modulated wave) of FIG. 2A corresponding to the output of the photodiode 2, and the MHP of FIG. A process of extracting a waveform (interference waveform) is shown.

Next, the signal extraction unit 7 measures the period of MHP included in the output voltage of the filter unit 6 every time MHP is generated. Here, the MHP that is a self-coupled signal will be described. As shown in FIG. 3, when the distance from the mirror layer 1013 to the object 10 is L and the oscillation wavelength of the laser is λ, the return light from the object 10 and the optical resonance of the semiconductor laser 1 are satisfied when the following resonance conditions are satisfied. The laser light in the chamber strengthens and the laser output increases slightly.
L = qλ / 2 (1)
In Formula (1), q is an integer. This phenomenon can be sufficiently observed even if the scattered light from the object 10 is extremely weak, because the apparent reflectance in the resonator of the semiconductor laser 1 increases, causing an amplification effect.

  FIG. 4 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 2 when the oscillation wavelength of the semiconductor laser 1 is changed at a certain rate. When L = qλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the optical resonator becomes 0 ° (the same phase), and the return light and the optical resonator The laser beam is the most intense, and when L = qλ / 2 + λ / 4, the phase difference is 180 ° (reverse phase), and the return light and the laser beam in the optical resonator are most weakened. Therefore, when the oscillation wavelength of the semiconductor laser 1 is changed, a place where the laser output becomes stronger and a place where the laser output becomes weaker appear alternately. When the laser output at this time is detected by the photodiode 2, as shown in FIG. A stepped waveform with a constant period can be obtained. Such a waveform is generally called an interference fringe. Each stepped waveform, that is, each interference fringe is MHP. As described above, when the oscillation wavelength of the semiconductor laser 1 is changed for a certain period of time, the number of MHPs changes in proportion to the measurement distance.

FIG. 5 is a block diagram illustrating a configuration example of the signal extraction unit 7. The signal extraction unit 7 includes a binarization unit 70 and a period measurement unit 71.
6 (A) to 6 (D) are diagrams for explaining the operation of the signal extraction unit 7. FIG. 6 (A) schematically shows the waveform of the output voltage of the filter unit 6, that is, the waveform of MHP. 6B is a diagram illustrating an output of the binarization unit 70 corresponding to FIG. 6A, and FIG. 6C is a diagram illustrating a sampling clock CLK input to the signal extraction unit 7. 6 (D) is a diagram illustrating a measurement result of the period measurement unit 71 corresponding to FIG. 6 (B).

  First, the binarization unit 70 of the signal extraction unit 7 determines whether the output voltage of the filter unit 6 shown in FIG. 6A is high level (H) or low level (L), and FIG. A determination result such as At this time, the binarizing unit 70 determines that the output voltage of the filter unit 6 is high level when the output voltage is equal to or higher than the threshold value TH1, and the output voltage of the filter unit 6 decreases and the threshold value TH2 By determining that the level is low when (TH2 <TH1) or less, the output of the filter unit 6 is binarized.

  The period measuring unit 71 measures the period of the rising edge (that is, the MHP period) of the output of the binarizing unit 70 every time a rising edge occurs. At this time, the period measuring unit 71 measures the MHP period with the period of the sampling clock CLK shown in FIG. 6C as one unit. In the example of FIG. 6D, the period measurement unit 71 sequentially measures Tα, Tβ, and Tγ as the MHP period. As is apparent from FIGS. 6C and 6D, the sizes of the periods Tα, Tβ, and Tγ are 5 [samplings], 4 [samplings], and 2 [samplings], respectively. The frequency of the sampling clock CLK is assumed to be sufficiently higher than the highest frequency that the MHP can take.

  Next, the calculation unit 8 calculates the displacement and speed of the object 10 from the change in the cycle of each MHP based on the measurement result of the signal extraction unit 7. FIG. 7 is a block diagram illustrating a configuration example of the calculation unit 8. The calculation unit 8 includes a storage unit 80, a period correction unit 81, and a physical quantity calculation unit 82.

  The storage unit 80 stores the measurement result of the signal extraction unit 7. The period correction unit 81 is any of the MHP period when the object 10 is stationary, the MHP period at the calculated distance, or the moving average value of a predetermined number of MHP periods measured immediately before the current correction. The measurement result of the signal extraction unit 7 is corrected by comparing the current measurement result of the signal extraction unit 7 with the reference cycle T0. FIG. 8A to FIG. 8F are diagrams for explaining the operation of the period correction unit 81.

When the MHP cycle T measured by the signal extraction unit 7 is less than 0.5T0 as shown in FIG. 8A, the cycle correction unit 81 follows the MHP cycle T and the next cycle as shown in FIG. 8B. The period combined with the measured MHP period Tnext is taken as the corrected MHP period T ′.
In addition, the period correction unit 81, as shown in FIG. 8C, when the MHP period T measured by the signal extraction unit 7 is 1.5T0 or more and less than 2.5T0, as shown in FIG. 8D. The periods obtained by dividing the MHP period T into two equal parts are defined as corrected periods T1 ′ and T2 ′, respectively.

  Further, when the MHP cycle T measured by the signal extraction unit 7 is 2.5T0 or more and less than 3.5T0 as shown in FIG. 8 (E), the cycle correction unit 81, as shown in FIG. 8 (F). The periods obtained by dividing the MHP period T into three equal parts are defined as corrected periods T1 ′, T2 ′, and T3 ′, respectively. The same applies to 3.5T0 or more. In other words, the period correction unit 81 determines that the MHP period T measured by the signal extraction unit 7 is (m−0.5) T0 or more and less than (m + 0.5) T0 (m is a natural number of 2 or more). A period obtained by equally dividing the period T into m is defined as a corrected period. The period correction unit 81 performs the correction process as described above every time a measurement result is output from the signal extraction unit 7.

FIG. 9 is a diagram for explaining the principle of correcting the measurement result of the signal extraction unit 7, and schematically showing the waveform of the output voltage of the filter unit 6, that is, the waveform of MHP.
Originally, the cycle of MHP differs depending on the distance to the object 10, but if the distance to the object 10 is unchanged, the MHP appears in the same cycle. However, due to noise, the MHP waveform may be missing or a waveform that should not be counted as a signal may be generated, resulting in an error in the MHP cycle.

  When signal loss occurs, the MHP cycle Tw at the location where the loss occurs is approximately twice the original cycle. That is, when the MHP cycle is approximately twice or more the reference cycle T0, it can be determined that the signal is missing. Therefore, the signal loss can be corrected by dividing the period Tw into two equal parts.

  Further, the MHP cycle Ts at the location where noise is counted is approximately 0.5 times the original cycle. That is, when the MHP cycle is less than about 0.5 times the reference cycle T0, it can be determined that the signals are excessively counted. Therefore, by adding the period Ts and the next measured period Tnext, it is possible to correct erroneously counted noise.

  The above is the principle of correcting the measurement result of the signal extraction unit 7. In the present embodiment, the threshold value for determining the period Ts in which the noise is counted is set to a value 0.5 times the reference period T0, and the period Tw in which the signal is considered to be missing is determined. The threshold value is not a value twice the reference period T0 but a value 1.5 times, and the reason for the 1.5 times will be described later.

Next, the physical quantity calculation unit 82 calculates the displacement and speed of the object 10 from changes in the individual periods of the MHP corrected by the period correction unit 81 with respect to the reference period T0. When the sampling clock frequency is fad [Hz], the reference period is T0 [samplings], the oscillation average wavelength of the semiconductor laser 1 is λ [m], and the corrected MHP period is n [samplings] longer than the reference period T0. Then, the displacement D [m] of the object 10 in the corrected MHP cycle is expressed by the following equation.
D = n × λ / (2 × T0) (2)

  When the corrected MHP period is shortened by n [samplings] from the reference period T0, the sign of the period change amount n in Expression (2) may be negative. In the first oscillation period P1 in which the oscillation wavelength of the semiconductor laser 1 increases, when the displacement D is positive, the moving direction of the object 10 is a direction away from the semiconductor laser 1, and when the displacement D is negative, the moving of the object 10 is performed. The direction is a direction approaching the semiconductor laser 1. In the second oscillation period P2 in which the oscillation wavelength decreases, when the displacement D is positive, the moving direction of the object 10 is a direction approaching the semiconductor laser 1, and when the displacement D is negative, the moving direction of the object 10 is. Is a direction away from the semiconductor laser 1.

Since the corrected MHP cycle is (T0 + n) / fad, the velocity V [m / s] of the object 10 in the corrected MHP cycle is expressed by the following equation.
V = n × λ / (2 × T0) × fad / (T0 + n) (3)

The physical quantity calculation unit 82 can calculate the displacement D of the object 10 according to Equation (2), and can calculate the velocity V of the object 10 according to Equation (3). For example, the sampling clock frequency fad is 16 [MHz], the reference period T0 is 160 [samplings], the average wavelength of the semiconductor laser 1 is 850 [nm], and the corrected MHP period is 1 [samplings] longer than the reference period T0. Then, the displacement D of the object 10 in this MHP cycle can be calculated as 5.31 [nm], and the velocity V can be calculated as 1.05 [mm / s]. The physical quantity calculation unit 82 performs the above calculation process for each corrected period of the MHP.
The display unit 9 displays the calculation result of the calculation unit 8.

  Here, the number of MHPs related to the distance from the object 10 per half cycle of the oscillation wavelength modulated carrier wave (triangular wave) of the semiconductor laser 1 is Nl. If the absolute value of the maximum velocity of the object 10 is converted to the displacement per carrier wave period, λ / 2 × Na, the number of MHPs per carrier half cycle is Nl ± Na. When the displacement per carrier wave cycle is moving at a speed of λ / 2 × Nb, the number of MHPs per carrier half cycle is Nl + Nb, and therefore the MHP cycle corresponding to this number is observed. In order to obtain the displacement D and the speed V of the object 10, the number of MHPs per half cycle of the carrier wave is calculated backward from each MHP period, and the displacement D and the speed V of the object 10 are calculated from the number of MHPs. The above equations (2) and (3) are based on such a derivation principle.

  In the self-coupled laser measuring instrument disclosed in Patent Document 1, the resolution of the displacement and velocity of the object is about half the wavelength λ / 2 of the semiconductor laser. On the other hand, in the present embodiment, the resolution of the displacement D and the velocity V is λ / 2 × n / T0, so that a resolution of less than half wavelength λ / 2 can be realized, and measurement with higher resolution than in the past is possible. Can be realized.

  As described above, in the present embodiment, the displacement D and the velocity V of the object 10 can be measured with higher resolution than before. Further, in the self-coupled laser measuring instrument disclosed in Patent Document 1, it takes a measurement time of a half cycle of the carrier wave, whereas in the present embodiment, the displacement of the object 10 from each MHP cycle. Since D and velocity V can be obtained, the time required for measurement can be greatly shortened, and the object 10 having a fast change in velocity can be dealt with. Further, in the present embodiment, since the error of the MHP cycle can be corrected, the measurement accuracy of the displacement D and the velocity V can be improved.

Note that the period of each MHP varies in a normal distribution even when the object 10 is stationary, and therefore processing such as moving average may be performed on the calculated displacement.
Moreover, in this Embodiment, although both the displacement and speed of the object 10 are measured, it cannot be overemphasized that only either one may be measured.

  Next, the reason why the threshold value for determining the cycle Tw that the signal is assumed to be missing is set to 1.5 times the reference cycle T0 will be described. When the oscillation wavelength change of the semiconductor laser 1 is linear, the MHP cycle is normally distributed around the reference cycle T0 (FIG. 10).

Here, consider a case where a loss occurs in the MHP waveform. Since the original MHP cycle is a normal distribution centered on T0, the MHP cycle when a loss occurs during measurement because the strength of the MHP is small is normal distribution with an average value of 2T0 and a standard deviation of 2σ ( It becomes f) of FIG. When j [%] MHP is missing, the signal extraction unit 7 counts the number of MHPs in either the first oscillation period P1 or the second oscillation period P2, and as a result, the number of MHPs is N. Then, the frequency of the MHP cycle in which the cycle is doubled due to this omission is Nw (= j [%] · N). Further, the frequency of the period of approximately T0 after being decreased due to the missing at the time of measurement is g shown in FIG. 11, and the decrease of the frequency shown in h of FIG. 11 is 2Nw (= 2j [%]). Therefore, the original number N ′ of MHPs when no MHP loss occurs in either the first oscillation period P1 or the second oscillation period P2 can be expressed by the following equation.
N ′ = N + j [%] = N + Nw (4)

  Next, a threshold for correcting the measurement result of the MHP cycle will be considered. Here, it is assumed that p [%] is divided into two by noise out of the frequency Nw of the MHP period whose period is doubled due to missing during measurement. Of the missing MHPs, the frequency of the MHP period divided into two is Nw ′ (= j · p [%] · N). The frequency distribution of the period of the MHP divided into two again is as shown in FIG. When the threshold value of the period regarded as Nw is 1.5T0, the frequency of the MHP period with a period of 0.5T0 or less is 0.5Nw ′ (= 0.5p [%] · Nw), and the period is from 0.5T0. The frequency of the MHP period up to 1.5T0 is Nw ′ (= p [%] · Nw), and the frequency of the MHP period of 1.5T0 or more is 0.5 Nw ′ (= 0.5 p [%] · Nw). )

Accordingly, the frequency distribution of all MHP cycles is as shown in FIG. 13, and the threshold of the frequency Ns corresponding to the above Ts is 0.5T0, and the frequency Nw corresponding to the above Tw is the threshold. When the value is 1.5T0, the count result N can be expressed by the following equation.
N = (N′−2Nw) + (Nw−Nw ′) + 2Nw ′ = N′−Nw + Nw ′
... (5)

From the equation (5), the corrected result is as follows, and it can be seen that the original number N ′ of MHPs is calculated when no MHP is lost during counting.
N−0.5Nw ′ + (0.5Nw ′ + (Nw−Nw ′))
= (N-Nw + Nw ') + (0.5Nw' + (Nw-Nw '))
= N '(6)

  From the above, it can be seen that the counting result N can be corrected by setting the cycle threshold value for obtaining the frequency Nw to 1.5 times the reference cycle T0. The MHP cycle T and the counting result N are in a relationship of T = M / N, where M is the number of sampling clocks per half cycle of the triangular wave. Since M is a constant value, it is considered that a signal has been lost. It can be seen that the threshold for determining the cycle Tw may be 1.5 times the reference cycle T0, as in the case of the count result N.

  In the present embodiment, the reference period T0 is the MHP period in a state where the object 10 is stationary. However, the present invention is not limited to this, and the calculation unit 8 has a predetermined number measured immediately before correction. The moving average value of the MHP periods may be used as the reference period T0. According to this method, even in the case of the object 10 that cannot be stationary, the reference period T0 can be obtained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 14 is a block diagram showing a configuration example of the calculation unit 8 according to the second embodiment of the present invention. The calculation unit 8 includes a storage unit 80, a cycle correction unit 81, a physical quantity calculation unit 82, a counting unit 83, a distance calculation unit 84, and a cycle calculation unit 85. The overall configuration of the physical quantity sensor may be the same as in the first embodiment, but the rate of change of the oscillation wavelength of the semiconductor laser 1 is constant, and the maximum value λb and the minimum value λa of the oscillation wavelength are constant, respectively. The difference λb−λa also needs to be constant.

  The counting unit 83 counts the number of MHPs included in the output of the filter unit 6 for each of the first oscillation period P1 and the second oscillation period P2. The counting unit 83 may use a counter composed of logic gates, or may measure the frequency of MHP (that is, the number of MHPs per unit time) using FFT (Fast Fourier Transform).

  Next, the distance calculation unit 84 calculates the distance to the object 10 based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1 and the number of MHPs counted by the counting unit 83. In the present embodiment, it is assumed that the state of the object 10 is either a minute displacement state that satisfies a predetermined condition or a displacement state in which the movement is larger than the minute displacement state. When the average displacement of the object 10 per oscillation period P1 and oscillation period P2 is V, the minute displacement state is a state satisfying (λb−λa) / λb> V / Lb (where Lb is time (distance at time t), the displacement state is a state satisfying (λb−λa) / λb ≦ V / Lb.

First, the distance calculation unit 84 calculates the distance candidate values Lα (t) and Lβ (t) and the speed candidate values Vα (t) and Vβ (t) at the current time t as the following equations.
Lα (t) = λa × λb × (MHP (t−1) + MHP (t))
/ {4 × (λb−λa)} (7)
Lβ (t) = λa × λb × (| MHP (t−1) −MHP (t) |)
/ {4 × (λb−λa)} (8)
Vα (t) = (MHP (t−1) −MHP (t)) × λb / 4 (9)
Vβ (t) = (MHP (t−1) + MHP (t)) × λb / 4 (10)

  In Expressions (7) to (10), MHP (t) is the number of MHPs calculated at the current time t, and MHP (t−1) is the number of MHPs calculated one time before MHP (t). is there. For example, if MHP (t) is the counting result of the first oscillation period P1, MHP (t-1) is the counting result of the second oscillation period P2, and conversely, MHP (t) is the second counting period. If it is the counting result of the oscillation period P2, the MHP (t−1) is the counting result of the first oscillation period P1.

  The candidate values Lα (t) and Vα (t) are values calculated on the assumption that the object 10 is in a minute displacement state, and the candidate values Lβ (t) and Vβ (t) are obtained when the object 10 is in a displacement state. This is a calculated value. The distance calculation unit 84 performs the calculations of Expressions (7) to (10) at every time (every oscillation period) when the counting unit 83 measures the number of MHPs.

Subsequently, the distance calculation unit 84 calculates, for each of the minute displacement state and the displacement state, a history displacement that is a difference between the distance candidate value at the current time t and the distance candidate value at the immediately preceding time as follows: calculate. In the equations (11) and (12), the candidate values for the distance calculated one time before the current time t are Lα (t−1) and Lβ (t−1).
Vcalα (t) = Lα (t) −Lα (t−1) (11)
Vcalβ (t) = Lβ (t) −Lβ (t−1) (12)

The history displacement Vcalα (t) is a value calculated on the assumption that the object 10 is in a minute displacement state, and the history displacement Vcalβ (t) is a value calculated on the assumption that the object 10 is in a displacement state. The distance calculation unit 84 performs calculations of Expressions (11) to (12) at each time when the number of MHPs is measured by the counting unit 83. In Expressions (9) to (12), the direction in which the object 10 approaches the physical quantity sensor of the present embodiment is defined as a positive speed, and the direction in which the object 10 moves away is defined as a negative speed.
Next, the distance calculation unit 84 determines the state of the object 10 using the calculation results of Expressions (7) to (12).

  As described in Patent Document 1, the distance calculation unit 84 has a constant sign of the history displacement Vcalα (t) calculated on the assumption that the object 10 is in a minute displacement state, and the object 10 is in a minute displacement state. If the velocity candidate value Vα (t) calculated on the assumption that the velocity is equal to the average value of the absolute values of the history displacement Vcalα (t) is equal, it is determined that the object 10 is moving at a constant velocity in a minute displacement state. .

  Further, as described in Patent Document 1, the distance calculation unit 84 has a constant sign of the history displacement Vcalβ (t) calculated on the assumption that the object 10 is in the displacement state, and the object 10 is in the displacement state. If the velocity candidate value Vβ (t) calculated on the assumption that the average displacement is equal to the absolute value of the absolute value of the history displacement Vcalβ (t), it is determined that the object 10 is moving at a constant velocity in the displacement state.

  Further, as described in Patent Document 1, the distance calculation unit 84 measures the number of MHPs with the sign of the history displacement Vcalα (t) calculated on the assumption that the object 10 is in a minute displacement state. When the velocity 10 calculated by assuming that the object 10 is in a minute displacement state and the average value of the absolute values of the history displacement Vcalα (t) do not coincide with each other, the object 10 is It is determined that a movement other than a constant speed movement is performed in a minute displacement state.

  Focusing on the velocity candidate value Vβ (t), the absolute value of Vβ (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the distance calculation unit 84 assumes that the absolute value of the velocity candidate value Vβ (t) calculated on the assumption that the object 10 is in the displacement state is equal to the wavelength change rate, and that the object 10 is in the minute displacement state. If the velocity candidate value Vα (t) calculated in this way and the average value of the absolute values of the history displacement Vcalα (t) do not match, it is determined that the object 10 is moving in a minute displacement state other than the constant velocity motion. May be.

  Further, as described in Patent Document 1, the distance calculation unit 84 calculates the number of MHPs at which the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 10 is in the displacement state is measured. When the velocity candidate value Vβ (t) calculated on the assumption that the object 10 is in the displacement state does not match the average value of the absolute values of the history displacement Vcalβ (t), the object 10 is in the displacement state. It is determined that the person is exercising other than the uniform speed movement.

  When attention is paid to the velocity candidate value Vα (t), the absolute value of Vα (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the distance calculation unit 84 assumes that the absolute value of the velocity candidate value Vα (t) calculated on the assumption that the object 10 is in the minute displacement state is equal to the wavelength change rate, and that the object 10 is in the displacement state. If the calculated velocity candidate value Vβ (t) and the average value of the history displacement Vcalβ (t) do not coincide with each other, it is determined that the object 10 is moving in a displaced state other than the uniform velocity motion. May be.

  The distance calculation unit 84 determines the distance from the object 10 based on the determination result. That is, when it is determined that the object 10 is moving at a constant velocity in a minute displacement state, the distance calculation unit 84 sets the distance candidate value Lα (t) as the distance from the object 10, and the object 10 is in a displacement state, etc. When it is determined that the vehicle is moving at a speed, the distance candidate value Lβ (t) is set as the distance to the object 10.

  The distance calculation unit 84 sets the distance candidate value Lα (t) as the distance from the object 10 when it is determined that the object 10 is moving in a minute displacement state other than the constant velocity movement. However, the actual distance is an average value of the distance candidate values Lα (t). Further, when it is determined that the object 10 is moving other than the constant velocity motion in the displaced state, the distance calculation unit 84 sets the distance candidate value Lβ (t) as the distance to the object 10. However, the actual distance is an average value of the distance candidate values Lβ (t).

  Next, the period calculation unit 85 obtains the MHP period from the distance calculated by the distance calculation unit 84. The frequency of MHP is proportional to the measurement distance, and the period of MHP is inversely proportional to the measurement distance. Therefore, if the relationship between the MHP cycle and the distance is obtained in advance and registered in the database (not shown) of the cycle calculation unit 85, the cycle calculation unit 85 may correspond to the distance calculated by the distance calculation unit 84. Is obtained from the database, the MHP cycle can be obtained. Alternatively, if a mathematical expression indicating the relationship between the MHP cycle and the distance is obtained and set in advance, the cycle calculation unit 85 substitutes the distance calculated by the distance calculation unit 84 into the mathematical formula, thereby changing the MHP cycle. Can be calculated.

  The period correction unit 81 may correct the measurement result of the signal extraction unit 7 as described in the first embodiment, with the period obtained by the period calculation unit 85 as the reference period T0. The operation of the physical quantity calculation unit 82 is the same as that of the first embodiment. In the present embodiment, the reference period T0 can be obtained even in the case of the object 10 that cannot be stationary.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 15 is a block diagram showing a configuration example of the calculation unit 8 according to the third embodiment of the present invention. The calculation unit 8 stores a storage unit 80, a period correction unit 81, a physical quantity calculation unit 82, a counting unit 86 that counts the number of MHPs included in the output voltage of the filter unit 6, a counting result of the counting unit 86, and the like. By calculating the average value of the counting results of the storage unit 87 and the counting unit 86, the distance for obtaining the number of MHPs (hereinafter referred to as distance proportional number) NL proportional to the average distance between the semiconductor laser 1 and the object 10 The proportional number calculation unit 88 and the counting unit 86 according to the magnitude relationship between the count result of the previous time of the counting unit 86 and the double of the distance proportional number NL calculated using the past count result from this count result. The sign adding unit 89 for adding a positive or negative sign to the latest count result of the above, and the cycle calculating unit 90 for calculating the MHP cycle from the distance proportional number NL. The overall configuration of the physical quantity sensor may be the same as that of the first embodiment.

  The counting unit 86 counts the number of MHPs included in the output of the filter unit 6 for each of the first oscillation period P1 and the second oscillation period P2. The counting unit 86 may use a counter including a logic gate, or may measure the frequency of MHP (that is, the number of MHPs per unit time) using FFT. The counting result of the counting unit 86 is stored in the storage unit 87.

  The distance proportional number calculation unit 88 obtains the distance proportional number NL from the counting result of the counting unit 86. FIG. 16 is a diagram for explaining the operation of the distance proportional number calculation unit 88, and is a diagram showing the time change of the counting result of the counting unit 86. In FIG. 16, Nu is the counting result of the first oscillation period P1, and Nd is the counting result of the second oscillation period P2.

  When the distance change rate of the object 10 is smaller than the oscillation wavelength change rate of the semiconductor laser 1 and the object 10 is oscillating simply, the time change of the count result Nu and the time change of the count result Nd are as shown in FIG. A sine waveform with a phase difference of 180 degrees is obtained. In Patent Document 1, the state of the object 10 at this time is a minute displacement state.

  As is clear from FIG. 21, since the first oscillation period P1 and the second oscillation period P2 come alternately, the count result Nu and the count result Nd also appear alternately. The counting results Nu and Nd are the sum or difference of the distance proportional number NL and the number of MHPs proportional to the displacement of the object 10 (hereinafter referred to as the displacement proportional number) NV. The distance proportional number NL corresponds to the average value of the sine waveform shown in FIG. The difference between the counting result Nu or Nd and the distance proportional number NL corresponds to the displacement proportional number NV.

The distance proportional number calculation unit 88 calculates the distance proportional number NL by calculating the average value of the counting results for the even number of times measured up to two times before the current time t as shown in the following equation.
NL = {N (t−2) + N (t−3)} / 2 (13)

  In Expression (13), N (t−2) represents the number N of MHPs measured two times before the current time t, and N (t−3) is measured three times before the current time t. This indicates that the number of MHPs is N. If the count result N (t) at the current time t is the count result Nu of the first oscillation period P1, the count result N (t-2) two times before is also the count result Nu of the first oscillation period P1. The count result N (t−3) three times before is the count result Nd in the second oscillation period P2. On the other hand, if the count result N (t) at the current time t is the count result Nd of the second oscillation period P2, the count result N (t-2) two times before is also the count result of the second oscillation period P2. Nd, and the count result N (t−3) three times before is the count result Nu in the first oscillation period P1.

Expression (13) is an expression for obtaining the distance proportional number NL based on the count results for two times. However, when the count result of 2m (m is a positive integer) is used, the distance proportional number calculation unit 88 uses the following formula. The distance proportional number NL is calculated as follows.
NL = {N (t−2m−1) + N (t−2m) +... + N (t−2)} / 2m
(14)

However, Expressions (13) and (14) are expressions used at the beginning of measurement of the distance to the object 10 and the speed of the object 10, and from the middle, a signed count result described later is used instead of Expression (13). The distance proportional number NL is calculated from the equation.
NL = {N ′ (t−2) + N ′ (t−3)} / 2 (15)
N ′ (t−2) is a count result with a sign after performing a later-described code addition process on the count result N (t−2) two times before, and N ′ (t−3) is a count result three times before. It is a count result with a code | symbol after performing a code | symbol provision process to N (t-3). Expression (15) is used after the count result N (t) at the current time t becomes the seventh count result from the start of the measurement of the number of MHPs.

Further, when using the equation (14) at the beginning of measurement, the distance proportional number NL is calculated from the middle using the following equation using the signed count result instead of the equation (14).
NL = {N ′ (t−2m−1) + N ′ (t−2m) +... + N ′ (t−2)} / 2m
... (16)
Expression (16) is used after the count result N (t) at the current time t becomes the (2m × 2 + 3) th count result from the start of measuring the number of MHPs.

The distance proportional number NL is stored in the storage unit 87. The distance proportional number calculation unit 88 performs the processing for calculating the distance proportional number NL as described above at every time (every oscillation period) when the number of MHPs is measured by the counting unit 86.
When the count results used for calculating the distance proportional number NL are sufficiently large, the distance proportional number NL may be calculated from the odd number of count results.

Next, the sign assigning unit 89 counts the counting result of the counting unit 86 according to the magnitude relationship between the counting result N (t−1) measured one time before the current time t and the multiple 2NL of the distance proportional number NL. A positive or negative sign is assigned to N (t). Specifically, the sign assigning unit 89 executes the following expression.
If N (t−1) ≧ 2NL Then N ′ (t) → −N (t) (17)
If N (t−1) <2NL Then N ′ (t) → + N (t) (18)

  FIG. 17 is a diagram for explaining the operation of the code assigning unit 89, and is a diagram showing a time change of the counting result of the counting unit 86. When the distance change rate of the object 10 is larger than the oscillation wavelength change rate of the semiconductor laser 1, the time change of the counting result Nu becomes a shape in which the negative waveform indicated by 170 in FIG. The time variation of the counting result Nd takes a form in which the negative waveform indicated by 171 in FIG. 17 is folded back to the positive side. In Patent Document 1, the state of the object 10 in the portion where the counting result is folded is defined as the displacement state. On the other hand, the state of the object 10 in the portion where the counting result is not folded is the above-described minute displacement state.

  In order to obtain the physical quantity of the object 10 in vibration including the displacement state, it is determined whether the object 10 is in the displacement state or the minute displacement state. If the object 10 is in the displacement state, the object 10 is folded back to the positive side. It is necessary to correct the counting result so that the locus indicated by 170 and 171 in FIG. 17 is drawn. Expressions (17) and (18) are expressions for determining whether the object 10 is in a displacement state or a minute displacement state. In FIG. 17, N (t−1) ≧ 2NL is established in the displacement state where the counting result is folded. Therefore, as shown in the equation (17), when N (t−1) ≧ 2NL is established, the count result N (t) at the current time t of the counting unit 86 is given a negative sign. The count result is N ′ (t).

  On the other hand, N (t−1) <2NL is established in the minute displacement state in which the counting result is not folded in FIGS. 16 and 17. Therefore, as shown in Expression (18), when N (t−1) <2NL is established, the count result N (t) at the current time t of the counting unit 86 is given a positive sign. The count result is N ′ (t).

The signed count result N ′ (t) is stored in the storage unit 87. The code assigning unit 89 performs the code assigning process as described above at every time (every oscillation period) when the counting unit 86 measures the number of MHPs.
Note that the condition for establishing equation (17) may be N (t−1)> 2NL, and the condition for establishing equation (18) may be N (t−1) ≦ 2NL.

Next, the period calculation unit 90 calculates the MHP period T from the distance proportional number NL as in the following equation.
T = C / (2 × f × NL) (19)
Here, f is the frequency of the triangular wave, and C is the speed of light.

  The period correction unit 81 may correct the measurement result of the signal extraction unit 7 as described in the first embodiment with the period calculated by the period calculation unit 90 as the reference period T0. The operation of the physical quantity calculation unit 82 is the same as that of the first embodiment. In the present embodiment, the reference period T0 can be obtained even in the case of the object 10 that cannot be stationary.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the semiconductor laser 1 oscillates in a triangular wave shape. However, the present invention is not limited to this, and the semiconductor laser 1 in the first and third embodiments as shown in FIG. May be oscillated in a sawtooth shape. That is, in the present embodiment, the semiconductor laser 1 may be operated so that either the first oscillation period P1 or the second oscillation period P2 exists repeatedly. However, in the second embodiment, it is necessary to oscillate the semiconductor laser 1 in a triangular wave shape.

  Even when the semiconductor laser 1 oscillates in a sawtooth shape as in the present embodiment, the rate of change of the oscillation wavelength of the semiconductor laser 1 needs to be constant. The operation in the first oscillation period P1 or the second oscillation period P2 is the same as in the case of triangular wave oscillation. As shown in FIG. 18, in the case of sawtooth oscillation in which only the first oscillation period P1 exists repeatedly, the processing in the first oscillation period P1 may be repeated, and the saw in which only the second oscillation period P2 exists repeatedly. Needless to say, in the case of wavy oscillation, the processing of the second oscillation period P2 may be repeated.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. In the first to fourth embodiments, the photodiode 2 and the current-voltage conversion amplifying unit 5 are used as detection means for detecting an electrical signal including an MHP waveform. However, the MHP waveform is not used without using a photodiode. It is also possible to extract. FIG. 19 is a block diagram showing a configuration of a physical quantity sensor according to the fifth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The physical quantity sensor of the present embodiment uses a voltage detection unit 12 as detection means instead of the photodiode 2 and the current-voltage conversion amplification unit 5 of the first embodiment.

  The voltage detector 12 detects and amplifies the voltage between the terminals of the semiconductor laser 1, that is, the anode-cathode voltage. When interference occurs between the laser light emitted from the semiconductor laser 1 and the return light from the object 10, an MHP waveform appears in the voltage between the terminals of the semiconductor laser 1. Therefore, it is possible to extract the MHP waveform from the voltage between the terminals of the semiconductor laser 1.

The filter unit 6 removes the carrier wave from the output voltage of the voltage detection unit 12. Other configurations of the physical quantity sensor are the same as those in the first embodiment.
Thus, in the present embodiment, the MHP waveform can be extracted without using a photodiode, and the physical quantity sensor components can be reduced as compared with the first embodiment, thereby reducing the cost of the physical quantity sensor. Can be reduced. In this embodiment, since no photodiode is used, the influence of disturbance light can be eliminated.

  In the first to fifth embodiments, at least the signal extraction unit 7 and the calculation unit 8 can be realized by, for example, a computer having a CPU, a memory, and an interface, and a program for controlling these hardware resources. . The CPU executes the processes described in the first and fifth embodiments according to the program stored in the memory.

  The present invention can be applied to a technique for measuring a physical quantity of an object from information on interference caused by a self-coupling effect between laser light emitted from a semiconductor laser and return light from the object.

It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 1st Embodiment of this invention. It is a wave form diagram showing typically the output voltage waveform of the current-voltage conversion amplification part in the 1st embodiment of the present invention, and the output voltage waveform of a filter part. It is a figure for demonstrating a mode hop pulse. It is a figure which shows the relationship between the oscillation wavelength of a semiconductor laser, and the output waveform of a photodiode. It is a block diagram which shows the structural example of the signal extraction part in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the signal extraction part in the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the calculating part in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the period correction | amendment part in the 1st Embodiment of this invention. It is a figure for demonstrating the correction principle of the measurement result of the signal extraction part in the 1st Embodiment of this invention. It is a figure which shows frequency distribution of the period of a mode hop pulse. It is a figure which shows the frequency distribution of the period of the mode hop pulse which became a 2 times period. It is a figure which shows frequency distribution of the period of the mode hop pulse divided into two among the mode hop pulses lost at the time of counting. It is a figure which shows frequency distribution of the period of the mode hop pulse divided into two among the mode hop pulses lost at the time of counting. It is a block diagram which shows the structural example of the calculating part in the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the calculating part in the 3rd Embodiment of this invention. It is a figure which shows one example of the time change of the count result of the counting part in the 3rd Embodiment of this invention. It is a figure which shows the other example of the time change of the count result of the counting part in the 3rd Embodiment of this invention. It is a figure which shows the other example of the time change of the oscillation wavelength of the semiconductor laser in the 4th Embodiment of this invention. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 5th Embodiment of this invention. It is a block diagram which shows the structure of the conventional laser measuring device. It is a figure which shows one example of the time change of the oscillation wavelength of a semiconductor laser in the laser measuring device of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplification part, 6 ... Filter part, 7 ... Signal extraction part, 8 ... Calculation part, 9 ... Display part, 10 ... object, 12 ... voltage detection unit, 70 ... binarization unit, 71 ... cycle measurement unit, 80, 87 ... storage unit, 81 ... cycle correction unit, 82 ... physical quantity calculation unit, 83, 86 ... counting unit, 84 ... Distance calculation unit, 85, 90... Cycle calculation unit, 88... Distance proportional number calculation unit, 89.

Claims (14)

A semiconductor laser that emits laser light to the object to be measured;
Oscillation wavelength modulation means for operating the semiconductor laser so that at least one of a first oscillation period in which the oscillation wavelength continuously increases monotonously and a second oscillation period in which the oscillation wavelength continuously decreases monotonously exists ,
Detection means for detecting an electrical signal including an interference waveform generated by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object;
Signal extraction means for measuring the period of the interference waveform included in the output signal of the detection means every time the interference waveform is input;
Period correction means for correcting the measurement result by comparing the measurement result of the signal extraction means with a reference period;
A physical quantity sensor comprising: a calculation unit that calculates at least one of the displacement and the velocity of the measurement object based on each cycle corrected by the cycle correction unit. The physical quantity sensor according to claim 1,
The calculation means includes a frequency of a sampling clock for measuring the period of the interference waveform, the reference period, an average wavelength of the semiconductor laser, and an amount of change of the period corrected by the period correction means with respect to the reference period. A physical quantity sensor that calculates at least one of a displacement and a velocity of the measurement object. The physical quantity sensor according to claim 1 or 2,
When the period of the interference waveform measured by the signal extraction unit is less than a predetermined number k times the reference period (k is a positive value less than 1), the period correction unit The cycle that combines the cycle of the measured interference waveform is set as the cycle of the corrected interference waveform, the waveform that combines the cycles is one waveform, and the cycle of the interference waveform measured by the signal extraction unit is the reference cycle. If it is greater than (m−k) times and less than (m + k) times the reference period (m is a natural number greater than or equal to 2), the period obtained by dividing the period of this interference waveform into m equal parts is used as the corrected period. A physical quantity sensor characterized in that there are m waveforms having a later period. The physical quantity sensor according to claim 3,
The physical quantity sensor, wherein the predetermined number k is 0.5. The physical quantity sensor according to any one of claims 1 to 4,
The period correcting unit uses the period of the interference waveform when the measurement object is stationary or an average of a period of a predetermined number of interference waveforms measured immediately before the correction as the reference period. Physical quantity sensor. The physical quantity sensor according to any one of claims 1 to 4,
And counting means for counting the number of the interference waveforms included in the output signal of the detection means for each of the first oscillation period and the second oscillation period;
A distance calculating means for calculating a distance from the object to be measured from a minimum oscillation wavelength and a maximum oscillation wavelength and a counting result of the counting means in a period of counting the number of interference waveforms by the counting means;
A period calculating means for determining the period of the interference waveform from the distance calculated by the distance calculating means,
The physical quantity sensor characterized in that the period correction means uses the period obtained by the period calculation means as the reference period. The physical quantity sensor according to any one of claims 1 to 4,
And counting means for counting the number of the interference waveforms included in the output signal of the detection means for each of the first oscillation period and the second oscillation period;
A distance proportional number calculating means for calculating a distance proportional number which is the number of interference waveforms proportional to an average distance between the semiconductor laser and the measurement object by calculating an average value of the number of the interference waveforms;
A period calculating means for calculating a period of the interference waveform from the distance proportional number,
The physical quantity sensor characterized in that the period correction means uses the period obtained by the period calculation means as the reference period. An oscillation procedure for operating the semiconductor laser so that at least one of the first oscillation period in which the oscillation wavelength continuously increases monotonously and the second oscillation period in which the oscillation wavelength continuously decreases monotonously exists;
A detection procedure for detecting an electrical signal including an interference waveform caused by a self-coupling effect between laser light emitted from the semiconductor laser and return light from a measurement object;
A signal extraction procedure for measuring the period of the interference waveform included in the output signal obtained by the detection procedure every time the interference waveform is input;
A period correction procedure for correcting the measurement result by comparing the measurement result of the signal extraction procedure with a reference period;
A physical quantity measurement method comprising: a calculation procedure for calculating at least one of a displacement and a velocity of the measurement object based on each cycle corrected by the cycle correction procedure. The physical quantity measuring method according to claim 8,
The calculation procedure includes the frequency of a sampling clock for measuring the period of the interference waveform, the reference period, the average wavelength of the semiconductor laser, and the amount of change of the period corrected by the period correction procedure with respect to the reference period. A physical quantity measuring method, wherein at least one of the displacement and speed of the measurement object is calculated. The physical quantity measuring method according to claim 8 or 9,
In the period correction procedure, when the period of the interference waveform measured in the signal extraction procedure is less than a predetermined number k times the reference period (k is a positive value less than 1), the period of the interference waveform and the next The cycle that combines the cycle of the measured interference waveform is set as the cycle of the corrected interference waveform, the waveform that combines the cycles is one waveform, and the cycle of the interference waveform measured in the signal extraction procedure is the reference cycle. If it is (m−k) times or more and less than (m + k) times the reference period (m is a natural number of 2 or more), the period obtained by equally dividing the period of the interference waveform into m is the corrected period, A physical quantity measuring method characterized in that there are m corrected period waveforms. The physical quantity measuring method according to claim 10,
The physical quantity measuring method, wherein the predetermined number k is 0.5. The physical quantity measuring method according to any one of claims 8 to 11,
The period correction procedure is characterized in that an average of a period of the interference waveform when the measurement object is stationary or a period of a predetermined number of interference waveforms measured immediately before the correction is used as the reference period. Physical quantity measurement method. The physical quantity measuring method according to any one of claims 8 to 11,
A counting procedure for counting the number of the interference waveforms included in the output signal obtained by the detection procedure for each of the first oscillation period and the second oscillation period;
A distance calculation procedure for calculating the distance to the measurement object from the minimum oscillation wavelength and the maximum oscillation wavelength in the period of counting the number of interference waveforms by this counting procedure and the counting result of the counting procedure;
A cycle calculation procedure for determining the cycle of the interference waveform from the distance calculated by the distance calculation procedure,
The period correction procedure uses the period obtained in the period calculation procedure as the reference period. The physical quantity measuring method according to any one of claims 8 to 11,
A counting procedure for counting the number of the interference waveforms included in the output signal obtained by the detection procedure for each of the first oscillation period and the second oscillation period;
A distance proportional number calculation procedure for obtaining a distance proportional number that is the number of interference waveforms proportional to the average distance between the semiconductor laser and the measurement object by calculating an average value of the number of the interference waveforms;
A cycle calculation procedure for calculating the cycle of the interference waveform from the distance proportional number,
The period correction procedure uses the period obtained in the period calculation procedure as the reference period.

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