CN102192707A - Physical quantity transducer and physical quantity measuring method - Google Patents

Abstract

The invention discloses a physical quantity transducer, which is used for measuring the displacement and the speed of an object by high resolution capability so as to shorten the required time of measurement. The physical quantity transducer comprises a semiconductor laser (1), a laser driver (4), a photodiode (2), a current-voltage transformation amplifying part (5), a signal extraction part (7) and a calculation part (8), wherein the semiconductor laser (1) emits laser to a measured object (10), and the laser driver (4) is used for driving the semiconductor laser (1) to actuate so that at least one of a first oscillation period in which an oscillation wavelength is continuously and monotonously increased and a second oscillation period in which the oscillation wavelength is continuously and monotonously reduced reoccurs; the photodiode (2) and the current-voltage transformation amplifying part (5) are used for detecting electrical signals which comprise interference waveforms, and the interference waveforms are generated by the self-mixing effect of the laser emitted by the semiconductor laser (1) and returned light of the object (10); the signal extraction part (7) is used for measuring the cycle of the interference waveforms contained in the output signals of the current-voltage transformation amplifying part (5); and the calculation part (8) is used for correcting a measuring result by comparing the measuring result of the signal extraction part (7) with a reference cycle, and calculating at least one of the displacement and the speed of the object (10) according to the corrected cycles.

Description

Physical quantity sensor and physical quantity measurement method

technical field

The present invention relates to a physical quantity sensor and a method for measuring physical quantity. The physical quantity sensor measures the displacement and velocity of an object based on interference information generated by the self-mixing effect of laser light emitted from a semiconductor laser and returned light from the object.

Background technique

FMCW (Frequency Modulated Continuous Wave) radar, standing wave radar, self-mixing laser sensor and other methods of measuring displacement (velocity) using the principle of interference, when calculating the displacement and velocity of the measurement object based on the beat frequency and the frequency of interference fringes Generally, signal processing such as FFT (Fast Fourier Transform) or counting processing of interference fringes is adopted. However, there is a problem that in order to realize high-resolution capability by FFT, data with a long sampling time and a relatively high sampling period is required, and thus a very large processing time is required. In addition, in the counting process of interference fringes, in order to measure the displacement of less than half the wavelength, it is necessary to physically vibrate the sensor or analyze the amplitude of the interference fringes, so there is a possibility that only the periodic motion that is the measurement object can be measured. The problem of vibration and the problem that the counting process of interference fringes takes time.

On the other hand, the inventors proposed a wavelength-modulated laser measurement device utilizing the self-mixing effect of semiconductor lasers (see Patent Document 1). The structure of this laser measuring device is shown in FIG. 20 . The laser measuring device in FIG. 20 has: a semiconductor laser 201 that radiates laser light to an object 210; a photodiode 202 that converts the light output of the semiconductor laser 201 into an electrical signal; and a lens 203 that collects light from the semiconductor laser 201. And the light is irradiated to the object 210, and the return light of the object 210 is lased to make it incident on the semiconductor laser 201; so that the semiconductor laser 201 is in the first oscillation period in which the oscillation wavelength is continuously increased and the second oscillation period in which the oscillation wavelength is continuously reduced Alternately repeated laser driver 204; the output current of the photodiode 202 is converted into a voltage and amplified current-voltage conversion amplifier 205; the output voltage of the current-voltage conversion amplifier 205 is secondarily differentiated. The signal extraction circuit 206; the signal extraction circuit The counting circuit 207 for counting the number of MHP contained in the output voltage of 206; the calculation device 208 for calculating the distance to the object 210 and the speed of the object 210; and the display device 209 for displaying the calculation result of the calculation device 208.

The laser driver 204 supplies the semiconductor laser 201 with a triangular wave drive current that repeatedly increases and decreases at a predetermined rate of change over time as an injection current. Thus, the semiconductor laser 201 is driven so that the first oscillation period in which the oscillation wavelength continuously increases at a predetermined rate of change and the second oscillation period in which the oscillation wavelength continuously decreases at a predetermined rate of change are alternately repeated. FIG. 21 is a schematic diagram showing temporal changes in 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 triangle 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 light output of the semiconductor laser 201 into an electric 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 secondarily differentiates the output voltage of the current-voltage conversion amplifier 205 . The counting circuit 207 counts the number of mode-hop pulses (MHP) included in the output voltage of the signal extraction circuit 206 for the first oscillation period P1 and the second oscillation period P2 respectively. Calculation device 208 calculates the distance and The velocity of object 210 . According to such a self-mixing type laser measuring device, it is possible to measure the displacement of the resolving power of the semiconductor laser 201 at approximately half wavelength and the distance measurement of the resolving power inversely proportional to the wavelength modulation amount of the semiconductor laser 201 .

Patent Document 1 Japanese Patent Laid-Open No. 2006-313080

Contents of the invention

The problem to be solved by the invention

Compared with conventional FMCW radar, standing wave radar, self-mixing laser sensor, etc., the self-integrated laser measuring device can measure the displacement and velocity of the measuring object with high resolution. However, since the self-integrated laser measuring device requires a certain amount of measurement time (in the example of Patent Document 1, it refers to the half cycle of the carrier wave modulated by the oscillation wavelength of the semiconductor laser) to calculate the displacement and velocity like the FFT, There is a problem that a measurement error occurs in the measurement of a measurement object whose velocity changes rapidly. In addition, since the number of MHPs needs to be counted in the signal processing, there is another problem that it is difficult to realize the resolving power of the semiconductor laser less than half the wavelength.

In order to solve the above problems, the present invention aims to provide a physical quantity sensor and a physical quantity measurement method capable of measuring the displacement and velocity of an object with high resolution and shortening the time required for the measurement.

means of solving problems

The present invention provides a physical quantity sensor, comprising: a semiconductor laser that emits laser light to an object to be measured; an oscillation wavelength modulation unit that activates the operation of the semiconductor laser to make the first oscillation period in which the oscillation wavelength continuously monotonically increases and the second oscillation period in which the oscillation wavelength continuously monotonically decreases at least one of the two oscillation periods occurs repeatedly; a detection unit that detects an electrical signal including an interference waveform generated by a self-mixing effect of laser light emitted from the semiconductor laser and returned light from the measurement object; a signal extraction unit that measures the period of the interference waveform included in the output signal of the detection unit each time the interference waveform is input; a period correction unit that uses the measurement result of the signal extraction unit The measurement result is corrected by comparing it with a reference period, and a calculating unit calculates at least one of a displacement and a velocity of the measurement object based on each period corrected by the period correcting unit.

Furthermore, in a configuration example of the physical quantity sensor according to the present invention, the calculating means is based on the frequency of the sampling clock for measuring the period of the interference waveform, the reference period, the average wavelength of the semiconductor laser, and the The period correcting unit calculates at least one of the displacement and the velocity of the measurement object from the amount of change in the period after correction with respect to the reference period.

Also, in a configuration example of the physical quantity sensor of the present invention, the period correcting unit is configured to be smaller than a predetermined number k times of the reference period when the period of the interference waveform measured by the signal extracting unit, where k is If the positive value is less than 1, then the period after combining the period of the interference waveform and the period of the measured interference waveform is taken as the period of the corrected interference waveform, and the waveform obtained by combining the period is regarded as a waveform; When the period of the interference waveform measured by the signal extraction unit is more than (m-k) times the reference period and less than (m+k) times the reference period, wherein m is a natural number greater than 2, the interference waveform Periods obtained by dividing the period of m into equal parts are respectively used as corrected periods, and there are m waveforms of the corrected periods.

In addition, in one configuration example of the physical quantity sensor of the present invention, the predetermined number k is 0.5.

Furthermore, in a configuration example of the physical quantity sensor of the present invention, the period correcting means adjusts the period of the interference waveform when the measurement object is stationary or a predetermined number of interference waveforms measured immediately before the correction. The average value of the cycle is used as the reference cycle.

In addition, in one configuration example of the physical quantity sensor of the present invention, it further includes: a counting unit that counts the number of the interference waveforms included in the output signal of the detection unit during the first oscillation period and the Counting is carried out respectively during the second oscillation period; the distance calculation unit calculates the minimum oscillation wavelength, the maximum oscillation wavelength, and the counting result of the counting unit according to the counting unit during which the number of interference waveforms is counted. The distance between the measurement objects; the period calculation unit, which obtains the period of the interference waveform according to the distance calculated by the distance calculation unit, and the period correction unit uses the period obtained by the period calculation unit as the base cycle.

In addition, in one configuration example of the physical quantity sensor of the present invention, it further includes: a counting unit that counts the number of the interference waveforms included in the output signal of the detection unit during the first oscillation period and the Counting is performed during the second oscillation period; the distance proportional number calculation unit calculates the average value of the number of the interference waveforms to obtain an interference waveform proportional to the average distance between the semiconductor laser and the measurement object The number is the distance ratio number; the period calculation unit calculates the period of the interference waveform according to the distance ratio number, and the period correction unit uses the period obtained by the period calculation unit as the reference period .

The present invention provides a method for measuring a physical quantity, comprising: an oscillating step of activating the semiconductor laser so that at least one of the first oscillation period in which the oscillation wavelength continuously monotonically increases and the second oscillation period in which the oscillation wavelength continuously monotonically decreases occurs repeatedly ; The detection step detects an electrical signal containing an interference waveform generated by the self-mixing effect of the laser light emitted from the semiconductor laser and the return light of the measurement object; The period of the interference waveform in the output signal obtained in the detection step is measured; the period correction step is to correct the measurement result by comparing the measurement result of the signal extraction step with a reference period a calculating step of calculating at least one of the displacement and velocity of the measuring object based on each period corrected by the period correcting step;

Invention effect

According to the present invention, by performing calculation based on the period of each interference waveform, the displacement and velocity of the object can be measured with higher resolution than before. In addition, compared with the conventional self-mixing type laser measuring instrument, which takes half a cycle of the carrier wave to measure, in the present invention, the displacement and velocity of the measurement object can be obtained from the cycle of each interference waveform, Therefore, the time required for measurement is greatly shortened, and it is also possible to cope with measurement objects whose speed changes rapidly. Furthermore, in the present invention, by comparing the measurement result of the signal extraction unit with the reference period, the period error of the interference waveform can be corrected, so the measurement accuracy of displacement and velocity can be improved.

Description of drawings

FIG. 1 is a block diagram showing the configuration of a physical quantity sensor according to a first embodiment of the present invention.

2 is a waveform diagram schematically showing an output voltage waveform of a current-voltage conversion amplifying unit and an output voltage waveform of a filter unit according to the first embodiment of the present invention.

Fig. 3 is a diagram for explaining mode-hopping pulses.

FIG. 4 is a graph showing the relationship between the oscillation wavelength of a semiconductor laser and the output waveform of a photodiode.

5 is a block diagram showing a configuration example of a signal extraction unit according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of the signal extraction unit according to the first embodiment of the present invention.

7 is a block diagram showing a configuration example of a calculation unit according to the first embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation of the period correcting unit according to the first embodiment of the present invention.

FIG. 9 is a diagram for explaining the principle of correction of the measurement result of the signal extraction unit according to the first embodiment of the present invention.

Figure 10 is a graph showing the degree distribution of the period of a mode skip pulse.

Fig. 11 is a graph showing the degree distribution of the mode-hop pulse period which becomes twice the period.

Fig. 12 is a graph showing degree distribution of the period of the mode skip pulse divided into two equal parts among the mode skip pulses lacking in counting.

Fig. 13 is a graph showing the degree distribution of the period of the mode skip pulse divided into two equal parts among the mode skip pulses lacking in counting.

FIG. 14 is a block diagram showing a configuration example of a calculation unit in a second embodiment of the present invention.

15 is a block diagram showing a configuration example of a calculation unit in a third embodiment of the present invention.

FIG. 16 is a diagram showing an example of time changes in count results of the count unit in the third embodiment of the present invention.

Fig. 17 is a diagram showing another example of the time change of the counting result of the counting unit in the third embodiment of the present invention.

FIG. 18 is a graph showing another example of the temporal change of the oscillation wavelength of the semiconductor laser in the fourth embodiment of the present invention.

FIG. 19 is a block diagram showing the configuration of a physical quantity sensor according to a fifth embodiment of the present invention.

FIG. 20 is a block diagram showing the configuration of a conventional laser measuring device.

FIG. 21 is a graph showing an example of temporal changes in the oscillation wavelength of the semiconductor laser in the laser measuring device of FIG. 20 .

Detailed ways

first embodiment

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a physical quantity sensor according to a first embodiment of the present invention.

The physical quantity sensor of FIG. 1 has: a semiconductor laser 1 that emits laser light to an object 10 to be measured; a photodiode 2 that converts the light output of the semiconductor laser 1 into an electrical signal; Collect light and emit it, collect the return light of the object 10 and make the return light incident on the semiconductor laser 1; drive the laser driver 4 as the oscillation wavelength modulation unit of the semiconductor laser 1; convert the output current of the photodiode 2 A current-voltage conversion amplifying section 5 for voltage and amplification; a filter section 6 for removing a carrier wave from the output voltage of the current-voltage conversion amplifying section 5; A signal extraction unit 7 for measuring the period of the pulse (hereinafter referred to as MHP); a calculation unit 8 for calculating the displacement and velocity of the object 10 based on each period measured by the signal extraction unit 7; and a display for displaying the calculation result of the calculation unit 8 Part 9.

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

The laser driver 4 provides the semiconductor laser 1 with the triangular wave driving current repeatedly increasing and decreasing at a certain rate of change over time as the injection current. In this way, the semiconductor laser 1 is driven such that the first oscillation period P1 in which the oscillation wavelength continuously increases at a constant rate of change and the second oscillation period P2 in which the oscillation wavelength continuously decreases at a certain rate of change are alternately repeated in proportion to the magnitude of the injection current. . At this time, the temporal change of the oscillation wavelength of the semiconductor laser 1 is as shown in FIG. 21 . In this embodiment, the rate of change of the oscillation wavelength of the semiconductor laser 1 must be constant.

The 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, it is not necessary to collect light through the lens 3 . The photodiode 2 is provided inside or near the semiconductor laser 1, and converts the light output of the semiconductor laser 1 into an electric current. The current-voltage conversion amplifier 5 converts the output current of the photodiode 2 into a voltage and amplifies it.

The filter unit 6 has a function of extracting superimposed signals from modulated waves. FIG. 2(A) schematically shows the output voltage waveform of the current-voltage conversion amplifying section 5 , and FIG. 2(B) schematically shows the output voltage waveform of the filter section 6 . These figures show that the oscillation waveform (carrier wave) of the semiconductor laser 1 in FIG. 2 is removed from the waveform (modulated wave) in FIG. 2(A) corresponding to the output of the photodiode 2, and the extraction shown in FIG. The MHP waveform (interferometric waveform) of the process.

Next, the signal extraction unit 7 measures the period of the MHP included in the output voltage of the filter unit 6 every time MHP occurs. Here, MHP as a self-mixing signal will be described. As shown in Figure 3, if the distance from the mirror surface layer 1013 to the object 10 is L, and the oscillation wavelength of the laser is λ, when the following resonance conditions are satisfied, the returning light of the object 10 and the laser light in the optical resonator of the semiconductor laser device 1 strengthen each other , causing a slight increase in laser output.

L=qλ/2...(1)

In the formula (1), q is an integer. Even when the scattered light from the object 10 is very weak, this phenomenon is amplified by an increase in the reflectance appearing in the resonator of the semiconductor laser 1 and can be sufficiently observed.

FIG. 4 is a graph 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 constant rate. When L=qλ/2 shown in formula (1) is satisfied, the phase difference between the returning light and the laser in the optical resonator is 0° (same phase), and the returning light and the laser in the optical resonator are the maximum mutual enhancement, when L When =qλ/2+λ/4, the phase difference is 180° (reverse phase), and the return light and the laser light in the optical resonator are at maximum mutual attenuation. Therefore, if the oscillation wavelength of the semiconductor laser 1 is changed, the laser output increases and decreases alternately and repeatedly, and the laser output at this time is detected by the light-emitting diode 2, a stepped waveform with a certain period can be obtained as shown in FIG. 4 . Such waveforms are generally called interference fringes. The stepped waveform, that is, each interference fringe is MHP. As described above, when the oscillation wavelength of the semiconductor laser 1 is changed within a certain period of time, the number of MHPs changes in proportion to the measurement distance.

FIG. 5 is a block diagram showing 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. FIG. 6 (B) shows the output corresponding to the binarization unit 70 of FIG. 6(A), FIG. 6(C) is a diagram showing the sampling clock CLK input to the signal extraction unit 7, and FIG. 6(B) is a diagram of the measurement results of the period measuring unit 71.

First, the binarization unit 70 of the signal extraction unit 7 determines whether the output voltage of the filter unit 6 shown in FIG. 6(A) is high level (H) or low level (L), and outputs Such a judgment result. At this time, the binarization unit 70 determines that the output voltage of the filter unit 6 is high when the output voltage rises above the threshold TH1, and determines that the output voltage of the filter unit 6 is low when the output voltage drops below the threshold TH2 (TH2<TH1). level, so that the output of the filter unit 6 is binarized.

The period measuring unit 71 measures the period of the rising edge of the output of the binarization unit 70 (that is, the period of the MHP) every time a rising edge occurs. At this time, the period measurement unit 71 measures the period of the MHP with the period of the sampling clock CLK shown in FIG. 6(C) as a unit. In the example shown in FIG. 6(D), the period measuring unit 71 sequentially measures Tα, Tβ, and Tγ as the period of the MHP. According to FIG. 6(C) and FIG. 6(D), it can be seen that the sizes of periods Tα, Tβ, and Tγ are 5[samplings], 4[samplings], and 2[samplings], respectively. The frequency of the sampling clock CLK is sufficiently high compared to the highest available frequency of the MHP.

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

The storage unit 80 stores the measurement results of the signal extraction unit 7 . The period correction unit 81 uses as a reference any one of the period of the MHP when the object 10 is stationary, the period of the MHP in the calculated distance, or the moving average of a predetermined number of periods of the MHP measured before the current correction. In the period T0, 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 period T0. 8(A) to 8(F) are diagrams for explaining the operation of the period correction unit 81 .

When the period T of the MHP measured by the signal extraction unit 7 is less than 0.5T0 as shown in FIG. The synthesized period of the MHP period Tnext is used as the corrected MHP period T'.

Also, when the period T of MHP measured by the signal extracting unit 7 as shown in FIG. Periods obtained by dividing T into two equal parts are respectively used as corrected periods T1' and T2'.

Also, when the period T of the MHP measured by the signal extraction unit 7 as shown in FIG. Periods obtained by dividing the period T into three equal parts are used as corrected periods T1', T2', and T3' respectively. The same applies to the case of 3.5T0 or higher. That is, the period correcting unit 81, when the period T of the MHP measured by the signal extracting unit 7 is greater than or equal to (m-0.5) T0 and less than (m+0.5) T0 (m is a natural number greater than or equal to 2), sets Periods obtained by dividing the period T of the MHP into m equal parts are respectively used as corrected periods. The cycle correcting unit 81 performs the above correcting processing every time the signal extracting unit 7 outputs a measurement result.

FIG. 9 is a diagram illustrating the principle of correction of the measurement result of the signal extraction unit 7 , and schematically shows the output voltage waveform of the filter unit 6 , that is, the waveform of MHP.

Originally, the cycle of the MHP varies depending on the distance from the object 10 , but if the distance to the object 10 is constant, the MHP appears at the same cycle. However, due to noise, the waveform of the MHP may be missing, or a waveform that should not be used as a signal may be generated, resulting in an error in the period of the MHP.

When a signal gap occurs, the cycle Tw of the MHP at the point where the gap occurs is approximately twice the original cycle. That is, when the period of the MHP is approximately twice or more than the reference period T0, it can be determined that the signal is missing. In this way, by dividing the period Tw into two equal parts, it is possible to correct the lack of a signal.

Also, the period Ts of the MHP at the place where the noise is calculated is approximately 0.5 times the original period. That is, when the period of the MHP is less than approximately 0.5 times the reference period T0, it can be determined that the signal count is excessive. In this way, the erroneously counted noise is corrected by adding the period Ts to the period Tnext measured next time.

The above is the principle of correction of the measurement result of the signal extraction unit 7 . In the present embodiment, the threshold value for determining the period Ts considered to be calculated as noise is 0.5 times the value of the reference period T0, so that the threshold value used for determining the period Tw considered to be caused by a lack of signal is not the reference period The value of 2 times of T0 is 1.5 times, and the reason for determining 1.5 times will be described later.

Next, the physical quantity calculation unit 82 calculates the displacement and velocity of the object 10 based on changes in each period of the MHP corrected by the period correction unit 81 with respect to the reference period T0. Assuming that the frequency of the sampling clock is fad[Hz], the reference period is T0[samplings], the average oscillation wavelength of the semiconductor laser 1 is λ[m], and the period of the modified MHP is extended by n[samplings] from the reference period T0, the The displacement D[m] of the object 10 in the period of the corrected MHP is expressed by the following equation.

D=n×λ/(2×T0)…(2)

When the period of the modified MHP is shortened by n[samplings] from the reference period T0, the sign of the period change n in the formula (2) can be negative. In the first oscillation period P1 in which the vibration 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 direction of the object 10 is close to the semiconductor laser. 1 direction. In addition, in the second oscillation period P2 in which the oscillation wavelength is reduced, when the displacement D is positive, the moving direction of the object 10 is a direction close to the semiconductor laser 1, and when the displacement D is negative, the moving direction of the object 10 is away from the semiconductor laser 1. direction.

Also, since the period of the corrected MHP is (T0+n)/fad, the velocity V [m/s] of the object 10 in the period of the corrected MHP 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 the formula (2), and calculate the velocity V of the object 10 according to the formula (3). For example, if the frequency fad of the sampling clock is 16[MHz], the reference period T0 is 160[samplings], and the average wavelength of the semiconductor laser 1 is 850[nm], if the period of the modified MHP is increased by 1[samplings] from the reference period T0 ], it can be calculated that the displacement D of the object 10 in the period of the MHP is 5.31 [nm], and the velocity V is 1.05 [mm/s]. The physical quantity calculation unit 82 performs the calculation processing as described above for each period of the corrected MHP.

The display unit 9 displays the calculation result of the calculation unit 8 .

Here, let N1 be the number of MHPs associated with the distance from the object 10 per half cycle of the carrier wave (triangular wave) modulated by the oscillation wavelength of the semiconductor laser 1 . When the absolute value of the maximum velocity of the object 10 is changed to the displacement of each carrier cycle, it is λ/2×Na, and the number of MHPs in each carrier half cycle is N1±Na. When the displacement of each cycle of the carrier moves at the speed of λ/2×Nb, the number of MHPs in each half cycle of the carrier is N1+Nb, so that the cycle of the MHP corresponding to this number can be observed. In order to obtain the displacement D and velocity V of the object 10, the number of MHPs in each carrier half cycle can be calculated according to the period of each MHP, and the displacement D and velocity V of the object 10 can be calculated according to the number of MHPs. The above formulas (2) and (3) are based on such derivation principles.

In the self-mixing laser measuring device disclosed in Patent Document 1, the resolving power of displacement and velocity of an object is approximately half wavelength λ/2 of a semiconductor laser. In contrast, in the embodiment of the present invention, since the resolution of the displacement D and the velocity V is λ/2×n/T0, the resolution of less than the wavelength λ/2 can be realized, thereby achieving a higher resolution than the prior art Measurement is performed with high resolving power.

As described above, in the present embodiment, the displacement D and velocity of the object 10 can be measured with a higher resolution than in the prior art. Also, in the self-mixing laser measuring device disclosed in Patent Document 1, it takes a half-period measurement time of the carrier wave, but in this embodiment, since the displacement D of the object 10 can be obtained from the period of each MHP and the velocity V, the time required for the measurement can be greatly shortened, and it can be applied to the object 10 whose velocity changes rapidly. Furthermore, in this embodiment, since the error of the cycle of the MHP can be corrected, the measurement accuracy of the displacement D and the velocity V can be improved.

Also, even when the object 10 is at rest, the period of each MHP deviates from the normal distribution, so it is only necessary to perform processing such as moving average on the calculated displacement.

Also, in this embodiment, the displacement and the velocity of the object 10 are measured, but only one of them may be measured.

Next, the reason why the threshold value for specifying the period Tw in which the signal is considered to be missing is set to 1.5 times the reference period T0 will be described. When the oscillation wavelength of the semiconductor laser 1 changes linearly, the period of the MHP is normally distributed around the reference period T0 ( FIG. 10 ).

Here, consider a case where the waveform of the MHP is lacking. Originally, the cycle of the MHP is normally distributed around T0, so the cycle of the MHP when there is a gap in the measurement due to the low intensity of the MHP is a normal distribution with an average value of 2T0 and a standard deviation of 2σ (Fig. 11 f). When the MHP of j [%] 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, when the number of MHPs is N , the degree of the cycle of the MHP due to the lack of cycle being doubled is Nw (=j[%]·N). Also, since the frequency of the approximately T0 cycle after the lack of measurement is reduced is g as shown in FIG. 11 , the decrease in frequency shown in h in FIG. 11 is 2Nw (=2j[%]). Therefore, the original number N' of MHPs when no MHP deficiency occurs in either the first oscillation period P1 or the second oscillation period P2 can be represented by the following formula.

N'＝N+j[%]＝N+Nw ...(4)

Next, a threshold value for correcting the measurement result of the cycle of the MHP is considered. Here, a case is assumed in which p[%] is divided into two by noise in the frequency Nw of the cycle of the MHP which is doubled due to the missing cycle at the time of measurement. Among the missing MHPs, the degree of cycle of the MHP divided into two is Nw' (=j·p[%]·N). The degree distribution of the cycle of the MHP divided again in two is shown in FIG. 12 . If the threshold value of the period regarded as Nw is set to 1.5T0, the degree of the period of the MHP with a period of 0.5T0 or less is 0.5Nw' (=0.5p[%]·Nw), and the degree of the MHP with a period of 0.5T0 to 1.5T0 The degree of cycle is Nw' (=p[%]·Nw), and the degree of cycle of MHP having a cycle of 1.5T0 or more is 0.5Nw'(=0.5p[%]·Nw).

Therefore, the degree distribution of all MHP cycles is shown in Figure 13. Assuming that the threshold value of the cycle degree Ns corresponding to the above Ts is 0.5T0, and the threshold value of the cycle degree Nw corresponding to the above Tw is 1.5T0, the counting result N It can be represented by the following formula.

N=(N'-2Nw)+(Nw-Nw')+2Nw'=N'-Nw+Nw'

...(5)

According to the formula (5), the corrected result is as follows, and the original number N' of MHP can be calculated when there is no shortage of MHP during counting.

N-0.5Nw’+(0.5Nw’+(Nw-Nw’))

＝(N-Nw+Nw’)+(0.5Nw’+(Nw-Nw’))

=N' ...(6)

Based on the above, if the threshold value of the cycle when calculating the degree Nw is set to be 1.5 times the reference cycle T0, the counting result N can be corrected. If the number of sampling clocks in each half cycle of the triangular wave is M, then there is a relationship of T=M/N between the period T of the MHP and the counting result N. Since M is a certain value, it can be seen that it is used to determine the lack of signal The threshold value of the cycle Tw is the same as that of the counting result N, and may be 1.5 times the reference cycle T0.

Also, in the present embodiment, the reference period T0 is set as the period of the MHP in the stationary state of the object 10, but it is not limited to this, and the calculation unit 8 may also change the movement of the period of the predetermined number of MHPs measured before the correction. The average value is taken as the reference period T0. According to this method, even when the object 10 cannot stand still, 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. The calculation unit 8 includes a storage unit 80 , a period correction unit 81 , a physical quantity calculation unit 82 , a count unit 83 , a distance calculation unit 84 , and a period calculation unit 85 . The overall structure of the physical quantity sensor is the same as that of the first embodiment, but the change speed of the oscillation wavelength of the semiconductor laser 1 is constant, and the maximum value λb of the oscillation wavelength and the minimum value λa of the oscillation wavelength are respectively constant, and the difference between λb-λa also needs to be must.

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 use FFT (Fast Fourier Transform) to measure the frequency of MHPs (that is, the number of MHPs per unit time).

Next, the distance calculating 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, the state of the object 10 may be any of a state of slight displacement satisfying a predetermined condition, or a state of displacement larger than that of the state of slight displacement. When the average displacement of the object 10 in each period of the oscillation period P1 and the oscillation period P2 is V, the micro-displacement state means a state satisfying (λb-λa)/λb>V/Lb (however, Lb refers to the state at time t). distance), the displacement state refers to the state that satisfies (λb-λa)/λb≤V/Lb.

First, the distance calculating unit 84 calculates the candidate values Lα(t) and Lβ(t) of the distance and the candidate values Vα(t) and Vβ(t) of the speed at the current time t as follows.

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 formulas (7) to (10), MHP(t) is the number of MHPs calculated at the current time t, and MHP(t-1) refers to the MHPs calculated at the previous time of MHP(t). the number of . 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, on the contrary, if MHP(t) is the counting result of the second oscillation period P2 If , then MHP(t-1) is the counting result of the first oscillation period P1.

The candidate values Lα(t) and Vα(t) are values calculated assuming that the object 10 is in a state of slight displacement, and the candidate values Lβ(t) and Vβ(t) are values calculated assuming that the object 10 is in a state of displacement . The distance calculation unit 84 performs calculations of the expressions (7) to (10) at each timing (each oscillation period) when the number of MHPs is measured by the counting unit 83 .

Next, the distance calculation unit 84 calculates the difference between the candidate value of the distance at the current time t and the candidate value of the distance at the previous time, that is, the historical displacement, for the minute displacement state and the displacement state, respectively, by the following equations. Also, in the expressions (11) and (12), the candidate values of the distance calculated 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 historical displacement Vcalα(t) is a value calculated assuming that the object 10 is in a state of slight displacement, and the historical displacement Vcalβ(t) is a value calculated assuming that the object 10 is in a state of displacement. The distance calculation unit 84 performs calculations of expressions (11) to (12) at each timing when the number of MHPs is measured by the counting unit 83 . In addition, in the expressions (9) to (12), the direction in which the object 10 approaches the physical quantity sensor of this embodiment is determined as a positive velocity, and the direction in which the object 10 moves away is determined as a negative velocity.

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 sign of the historical displacement Vcalα(t) calculated assuming that the object 10 is in a state of slight displacement is constant, and the candidate value Vα(t) of the velocity calculated assuming that the object 10 is in a state of slight displacement When it is equal to the average value of the absolute value of the historical displacement Vcalα(t), the distance calculation unit 84 determines that the object 10 is moving at a constant speed in a state of slight displacement.

Also, as described in Patent Document 1, when the sign of the historical displacement Vcalβ(t) calculated assuming that the object 10 is in a displaced state is constant, and the candidate value Vβ(t) of the velocity calculated assuming that the object 10 is in a displaced state and When the average values of the absolute values of the historical displacements Vcalβ(t) are equal, the distance calculation unit 84 determines that the object 10 is moving at a constant speed in a displaced state.

Also, as described in Patent Document 1, the sign of the historical displacement Vcalα(t) calculated assuming that the object 10 is in a state of slight displacement is reversed at each time when the number of MHPs is measured, and the calculation is performed assuming that the object 10 is in a state of slight displacement. When the obtained velocity candidate value Vα(t) does not match the average value of the absolute value of the historical displacement Vcalα(t), the distance calculation unit 84 determines that the object 10 is moving at a slight displacement other than constant velocity motion.

Also, focusing on the candidate velocity value Vβ(t), the absolute value of Vβ(t) is constant, and this value is equal to the wavelength variation (λb−λa)/λb of the semiconductor laser 1 . At this time, the absolute value of the candidate velocity value Vβ(t) calculated assuming that the object 10 is in a displaced state is equal to the wavelength change rate, and the candidate velocity value Vα(t) calculated assuming that the object 10 is in a slightly displaced state ) and the average value of the absolute value of the historical displacement Vcalα(t) do not match, the distance calculation unit 84 determines that the object 10 is moving other than constant velocity motion in a state of slight displacement.

Also, as described in Patent Document 1, the sign of the historical displacement Vcalβ(t) calculated assuming that the object 10 is in a displaced state is reversed every time the number of MHPs is measured, and the historical displacement Vcalβ(t) is calculated assuming that the object 10 is in a displaced state. When the calculated candidate velocity value Vβ(t) does not match the average value of the absolute value of the historical displacement Vcalβ(t), the distance calculation unit 84 determines that the object 10 is moving other than constant velocity motion in a displaced state.

Also, focusing on the candidate velocity value Vα(t), the absolute value of Vα(t) is 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 candidate velocity value V α(t) calculated assuming that the object 10 is in a state of slight displacement is equal to the wavelength change rate, and the candidate velocity value V α(t) calculated assuming that the object 10 is in a state of displacement When the value Vβ(t) does not coincide with the average value of the absolute value of the historical displacement Vcalβ(t), it can be determined that the object 10 is moving other than constant velocity motion in a displaced state.

The distance calculation unit 84 specifies the distance to the object 10 based on the determination result. That is, when the distance calculation unit 84 determines that the object 10 is moving at a constant velocity in a state of slight displacement, the candidate distance value Lα(t) is used as the distance from the object 10, and when it is determined that the object is moving at a constant velocity in a state of displacement, A candidate distance value Lβ(t) is used as the distance to the object 10 .

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

Next, the period calculation unit 85 obtains the period of the MHP from the distance calculated by the distance calculation unit 84 . The frequency of the MHP is directly proportional to the measured distance, and the period of the MHP is inversely proportional to the measured distance. Here, if the relationship between the period and the distance of the MHP is obtained in advance and stored in the database (not shown) of the period calculation unit 85, the period calculation unit 85 can acquire the distance corresponding to the distance calculated by the distance calculation unit 84 from the database. The period of the corresponding MHP is obtained to obtain the period of the MHP. Alternatively, if an expression representing the relationship between the period of the MHP and the distance is obtained and set in advance, the period calculation unit 85 can obtain the period of the MHP by substituting the distance calculated by the distance calculation unit 84 into the expression.

The period correction unit 81 may correct the measurement result of the signal extraction unit 7 as described in the first embodiment, using 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, even when the object 10 cannot be made stationary, the reference period T0 can be obtained.

third embodiment

Next, a third embodiment of the present invention will be described. FIG. 15 is a block diagram of a configuration example of the calculation unit 8 according to the third embodiment of the present invention. The calculation part 8 has: a storage part 80; a period correction part 81; a physical quantity calculation part 82; a count part 86 for counting the number of MHPs included in the output voltage of the filter part 6; Storage section 87; By calculating the average value of the counting result of counting section 86, obtain the distance ratio of the number (hereinafter referred to as the distance ratio number) NL of the MHP proportional to the average distance between the semiconductor laser 1 and the object 10 Number calculating section 88; Sign giving section 89, it according to counting section 86 previous counting result and the magnitude relation of the double number of the distance proportional number NL calculated using the counting result before this counting result, to counting The latest counting result of the unit 86 is assigned a positive and negative sign; the period calculation unit 90 calculates the period of the MHP from the distance proportional number NL. The overall structure 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 be a counter composed of logic gates, or may be a device that uses FFT to count the frequency of MHPs (that is, the number of MHPs per unit time). 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 count result of the counting unit 86 . FIG. 16 is a diagram for explaining the operation of the distance-proportional number calculating unit 88 , and shows the time change of the counting result of the counting unit 86 . In FIG. 16, Nu is the count result of the first oscillation period P1, and Nd is the count result of the second oscillation period P2. The distance change rate of the object 10 is smaller than the oscillation wavelength change rate of the semiconductor laser 1. When the object 10 performs simple harmonic vibration, the time change of the counting result Nu and the time change of the counting result Nd are shown in FIG. 16 as a mutual phase difference of 180 degree of sine wave. In Patent Document 1, the state of the object 19 at this time is referred to as a micro-displacement state.

It can be seen from FIG. 21 that since the first oscillation period P1 and the second oscillation period P2 appear alternately, the counting result Nu and the counting 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 (hereinafter referred to as the displacement proportional number) NV. The distance proportional number NL corresponds to the average value of the sinusoidal waveform shown in FIG. 16 . Also, the difference between the count 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 average value of the even-numbered count results measured two times before the current time t as in the following formula, to calculate the distance-proportional number NL.

NL＝{N(t-2)+N(t-3)}/2 ...(13)

In formula (13), N(t-2) represents the number N of MHPs measured two times before the current time t, and N(t-3) represents the number of MHPs measured three times before the current time t. The number N of MHPs. If the counting result N(t) at the current moment t is the counting result Nu of the first oscillation period P1, then the counting result N(t-2) of the first two times is also the counting result Nu of the first oscillation period P1, and the counting result of the first three times is also the counting result Nu of the first oscillation period P1. The result N(t-3) is the counting result Nd of the second oscillation period P2. Conversely, if the counting result N(t) at the current moment t is the counting result Nd of the second oscillation period P2, then the counting results N(t-2) of the previous two times are also the counting results Nd of the second oscillation period P2, and the previous The counting result N(t-3) of three times is the counting result Nu of the first oscillation period P1.

Equation (13) is an expression for the case of calculating the distance proportional number NL from two counting results. When using 2m (m is a positive integer) counting results, the distance proportional number calculation unit 88 is as follows: Calculate the number NL of distance ratios.

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 the measurement of the distance to the object 10 and the speed of the object 10, and the signed counts described later are adopted from the middle. The following formula of the result is substituted for the formula (13), so that the distance ratio number NL is calculated.

NL＝{N’(t-2)+N’(t-3)}/2 …(15)

N'(t-2) is the signed counting result after performing the sign assignment process described later on the previous two counting results N(t-2), and N'(t-3) is the counting result of the first three times N(t-3) is the signed count result after performing the sign assignment process described later. Expression (15) is used after the count result N(t) at the current time t becomes the seventh count result from the measurement of the number of MHPs.

Also, when the formula (14) is used at the beginning of the measurement, the distance ratio number NL is calculated using the following formula using the signed count result without using the formula (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 the counting of the number of MHPs.

The distance ratio number NL is stored in the storage unit 87 . The distance-proportional number calculation unit 88 performs the above-mentioned calculation process of the distance-proportional number NL at each timing (each oscillation cycle) at which the number of MHPs is measured by the counting unit 86 .

In addition, when there are enough counting results for calculating the distance proportional number NL, the distance proportional number NL can also be calculated with an odd number of counting results.

Next, the sign assigning part 89 assigns the counting result N(t-1) of the counting part 86 according to the magnitude relationship between the counting result N(t-1) measured at the previous time at the current time t and the distance proportional number NL of 2 times 2NL. ) to give a plus or minus sign. The symbol assigning unit 89 specifically executes the following formula.

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 symbol assigning unit 9 and showing the time change of the counting result by the counting unit 86 . When the rate of change of the distance of the object 10 is greater than the rate of change of the oscillation wavelength of the semiconductor laser 1, the time change of the count result Nu is in a shape in which the waveform on the negative side turns back to the positive side as shown by 170 in FIG. It is a shape in which the waveform on the negative side shown at 171 in FIG. 17 turns back to the positive side. In Patent Document 1, the state of the object 10 at the part where the counting result turns back is a displaced state. On the other hand, the state of the object 10 at the portion where the counting result does not turn back is the above-mentioned slight displacement state.

In order to obtain the physical quantity of the object 10 in the vibration including the displacement state, determine whether the object 10 is in a displacement state or a small displacement state, when the object 10 is in a displacement state, the counting results of turning back to the positive side are as shown in 170 and 171 in Figure 17 The trajectory needs to be corrected like that. Expressions (17) and (18) are expressions for determining whether the object 10 is in a displacement state or a slight displacement state. In the displacement state in which counting result wrapping occurs in FIG. 17, N(t-1)≧2NL holds. Therefore, as shown in the expression (17), when N(t−1)≥2NL holds true, the count result N(t) of the counting unit 86 at the current time t is given a negative sign as the signed count result N '(t).

On the other hand, N(t-1)<2NL is established in the minute displacement state in which the count result does not wrap around in FIG. 16 and FIG. 17 . Therefore, as shown in the formula (18), when N(t-1)<2NL holds true, the counting result N(t) of the current time t of the counting unit 86 is given a positive sign, as a signed counting result N'(t).

The signed count result N'(t) is stored in the storage unit 87 . The sign assigning unit 89 performs the sign assigning process as described above at every timing (each oscillation cycle) when the number of MHPs is measured by the counting unit 86 .

Also, the establishment condition of formula (17) may be N(t-1)>2NL, and the establishment condition of formula (18) may be N(t-1)≤2NL.

Next, the period calculation unit 90 calculates the period T of the MHP according to the following formula from the distance proportional number NL.

T＝C/(2×f×NL) …(19)

Here, f is the frequency of the triangle wave, and C is the speed of light.

The period correction unit 81 corrects the measurement result of the signal extraction unit 7 as described in the first embodiment, using 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, even when the object 10 cannot be brought to a standstill, the reference period T0 can be obtained.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the semiconductor laser 1 is oscillated in a triangular wave, but the present invention is not limited thereto, and the semiconductor laser 1 may be oscillated in a sawtooth wave as shown in FIG. 18 in the third embodiment. That is, in the present embodiment, it is only necessary to drive the semiconductor laser 1 so that either the first oscillation period P1 or the second oscillation period P2 appears 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 is oscillated in a sawtooth wave 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 that in the triangular wave oscillation. As shown in FIG. 18 , in the case of the sawtooth-shaped oscillation repeatedly occurring only in the first oscillation period P1, the processing of the first oscillation period P1 may be repeated, and of course only the sawtooth-shaped oscillation repeatedly appearing in the second oscillation period P2 In the case of , the process 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, although the photodiode 2 and the current-voltage conversion amplifier 5 are used as detection means for detecting electrical signals including the MHP waveform, the MHP waveform may be extracted without using the photodiode. FIG. 19 is a block diagram showing the structure of a physical quantity sensor according to a fifth embodiment of the present invention, and the same structures as in FIG. 1 are denoted by the same symbols. The physical quantity sensor of this embodiment employs a voltage detection unit 12 as a detection unit instead of the photodiode 2 and the current-voltage conversion amplification unit 5 in the first embodiment.

The voltage detection unit 12 detects and amplifies the voltage between the terminals of the semiconductor laser 1 , that is, the voltage between the anode and the cathode. When the laser light emitted from the semiconductor laser 1 interferes with the returning light from the object 10 , the voltage between the terminals of the semiconductor laser 1 shows an MHP waveform. Thus, the MHP waveform can be extracted from the inter-terminal voltage of the semiconductor laser 1 . The filter unit 6 removes the carrier from the output voltage of the voltage detection unit 12 . Other structures of the physical quantity sensor are the same as those of the first embodiment.

In this way, in this embodiment, the MHP waveform can be extracted without using a photodiode, and the number of components of the physical quantity sensor can be reduced compared with the first embodiment, thereby reducing the manufacturing cost of the physical quantity sensor. Also, in this embodiment, since no photodiode is used, the influence of disturbance light can be eliminated.

Also, 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 processing described in the first to fifth embodiments according to the program stored in the memory.

Claims (14)

1. A physical quantity sensor, characterized in that, comprising: A semiconductor laser that emits laser light on the measurement object; The oscillation wavelength modulation unit activates the semiconductor laser so that at least one of the first oscillation period in which the oscillation wavelength continuously monotonically increases and the second oscillation period in which the oscillation wavelength continuously monotonically decreases appears repeatedly; a detection unit that detects an electric signal including an interference waveform generated by a self-mixing effect of laser light emitted from the semiconductor laser and returned light from the measuring object; a signal extraction unit that measures the period of the interference waveform included in the output signal of the detection unit each time the interference waveform is input; a period correction unit that corrects the measurement result by comparing the measurement result of the signal extraction unit with a reference period; A calculation unit that calculates at least one of a displacement and a velocity of the measurement object based on each period corrected by the period correction unit. 2. The physical quantity sensor according to claim 1, wherein the calculation unit is based on 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 cycle correcting unit calculates at least one of the displacement and the velocity of the measurement object from the amount of change in the cycle after correction relative to the reference cycle. 3. The physical quantity sensor according to claim 1 or 2, wherein the period correcting unit, when the period of the interference waveform measured by the signal extracting unit is smaller than a predetermined number k times the reference period, , where k is a positive value less than 1, then the period after combining the period of the interference waveform and the period of the measured interference waveform is taken as the period of the modified interference waveform, and the waveform obtained by combining the period is regarded as a waveform ; when the period of the interference waveform measured by the signal extraction unit is more than (m-k) times the reference period and less than (m+k) times the reference period, wherein m is a natural number greater than 2, Periods obtained by dividing the period of the interference waveform into m equal parts are used as corrected periods, and there are m waveforms of the corrected periods. 4. The physical quantity sensor according to claim 3, wherein the predetermined number k is 0.5. 5. The physical quantity sensor according to any one of claims 1 to 4, wherein the period correcting unit calculates the period of the interference waveform when the measurement object is stationary or the period calculated immediately before the correction. The average value of the measured cycles of the predetermined number of interference waveforms is used as the reference cycle. 6. The physical quantity sensor according to any one of claims 1 to 4, further comprising: a counting unit that counts the number of the interference waveforms included in the output signal of the detection unit during the first oscillation period and the second oscillation period; a distance calculation unit that calculates the distance to the measurement object based on the minimum oscillation wavelength, the maximum oscillation wavelength, and the counting result of the counting unit during the counting of the number of interference waveforms by the counting unit; a period calculation unit, which obtains the period of the interference waveform according to the distance calculated by the distance calculation unit, The period correction unit uses the period obtained by the period calculation unit as the reference period. 7. The physical quantity sensor as described in any one of claims 1 to 4, further comprising: a counting unit that counts the number of the interference waveforms included in the output signal of the detection unit during the first oscillation period and the second oscillation period; A distance proportional number calculation unit, which obtains the number of interference waveforms proportional to the average distance between the semiconductor laser and the measurement object, that is, the distance proportional number, by calculating the average value of the number of the interference waveforms; a period calculation unit, which calculates the period of the interference waveform according to the number of distance ratios, The period correction unit uses the period obtained by the period calculation unit as the reference period. 8. A method for measuring a physical quantity, comprising: an oscillating step of starting the semiconductor laser so that at least one of the first oscillation period in which the oscillation wavelength continuously monotonically increases and the second oscillation period in which the oscillation wavelength continuously monotonically decreases occurs repeatedly; a detecting step of detecting an electric signal including an interference waveform generated by a self-mixing effect of laser light emitted from the semiconductor laser and return light from the measuring object; a signal extraction step of measuring the period of the interference waveform included in the output signal obtained in the detection step every time the interference waveform is input; a period correction step of correcting the measurement result of the signal extraction step by comparing the measurement result with a reference period; The calculating step calculates at least one of the displacement and the velocity of the measurement object based on each cycle corrected by the cycle correcting step. 9. The physical quantity measuring method according to claim 8, wherein the calculation step is based on the frequency of a sampling clock for measuring the period of the interference waveform, the reference period, and the average wavelength of the semiconductor laser . At least one of the displacement and the velocity of the measuring object is calculated from the amount of change in the cycle corrected in the cycle correcting step relative to the reference cycle. 10. The physical quantity measurement method according to claim 8 or 9, wherein in the period correction step, the period of the interference waveform measured in the signal extraction step is smaller than a predetermined number k of the reference period times, where k is a positive value less than 1, then the period after combining the period of the interference waveform and the period of the measured interference waveform is taken as the period of the corrected interference waveform, and the waveform obtained by combining the period is taken as A waveform; when the period of the interference waveform measured by the signal extraction step is more than (m-k) times the reference period and less than (m+k) times the reference period, wherein m is 2 or more If it is a natural number, the periods obtained by dividing the period of the interference waveform into m equal parts are used as the corrected periods respectively, and there are m waveforms of the corrected periods. 11. The physical quantity measurement method according to claim 10, wherein the predetermined number k is 0.5. 12. The physical quantity measuring method according to any one of claims 8 to 11, wherein in the cycle correction step, the cycle of the interference waveform when the measurement object is stationary or the cycle to be corrected The average value of the cycles of the predetermined number of interference waveforms measured before is used as the reference cycle. 13. The physical quantity measuring method according to any one of claims 8 to 11, further comprising: a counting step of counting the number of the interference waveforms included in the output signal obtained in the detecting step during the first oscillation period and the second oscillation period; a distance calculation step of calculating the distance to the measurement object based on the minimum oscillation wavelength, the maximum oscillation wavelength during the counting of the number of interference waveforms in the counting step, and the counting result of the counting step; a period calculation step, obtaining the period of the interference waveform according to the distance calculated in the distance calculation step, In the cycle correction step, the cycle obtained in the cycle calculation step is used as the reference cycle. 14. The physical quantity measuring method according to any one of claims 8 to 11, further comprising: a counting step of counting the number of the interference waveforms included in the output signal obtained in the detecting step during the first oscillation period and the second oscillation period; The step of calculating the number of distance ratios is to obtain the number of interference waveforms proportional to the average distance between the semiconductor laser and the measurement object, that is, the number of distance ratios, by calculating the average value of the number of interference waveforms; a period calculation step, calculating the period of the interference waveform according to the distance ratio number, The cycle correction step uses the cycle obtained in the cycle calculation step as the reference cycle.

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