WO2011111181A1 - 物理量センサおよび物理量計測方法 - Google Patents
物理量センサおよび物理量計測方法 Download PDFInfo
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- WO2011111181A1 WO2011111181A1 PCT/JP2010/053967 JP2010053967W WO2011111181A1 WO 2011111181 A1 WO2011111181 A1 WO 2011111181A1 JP 2010053967 W JP2010053967 W JP 2010053967W WO 2011111181 A1 WO2011111181 A1 WO 2011111181A1
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- period
- physical quantity
- oscillation
- distance
- semiconductor laser
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02092—Self-mixing interferometers, i.e. feedback of light from object into laser cavity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/491—Details of non-pulse systems
- G01S7/4912—Receivers
- G01S7/4915—Time delay measurement, e.g. operational details for pixel components; Phase measurement
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/491—Details of non-pulse systems
- G01S7/4912—Receivers
- G01S7/4916—Receivers using self-mixing in the laser cavity
Definitions
- the present invention relates to a physical quantity sensor and a physical quantity measuring method for measuring displacement and speed 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.
- FIG. 15 includes a semiconductor laser 201 that emits 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 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 the 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 the semiconductor laser 201 with a triangular wave drive current that repeatedly increases and decreases at a constant rate of change 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.
- FIG. 16 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201.
- P1 is the first oscillation period
- P2 is the second oscillation period
- ⁇ a is the minimum value of the oscillation wavelength in each period
- ⁇ b is the maximum value of the oscillation wavelength in each period
- 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.
- the arithmetic unit 208 Based on the minimum oscillation wavelength ⁇ a and the maximum oscillation wavelength ⁇ b 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.
- the self-coupled laser measuring instrument it is possible to measure the displacement and speed of the measurement object with higher resolution than conventional FMCW radar, standing wave radar, self-mixing laser sensor, and the like.
- 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
- the calculation means measures 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 signal extraction means. At least one of the displacement and speed of the measurement object is calculated from the amount of change of the measured period with respect to the reference period.
- one configuration example of the physical quantity sensor of the present invention is characterized by further comprising carrier wave adjusting means capable of adjusting the amplitude or frequency of the carrier wave of the oscillation wavelength modulation of the semiconductor laser.
- the carrier wave adjusting means may have a cycle of the interference waveform when the measurement object is stationary or a cycle of a predetermined number of interference waveforms measured immediately before the adjustment. The amplitude or frequency of the carrier wave is adjusted so that the average becomes a predetermined period.
- the predetermined period is a period corresponding to a half value of a maximum frequency of an interference waveform that can be processed by the physical quantity sensor. It is what.
- the carrier wave adjusting means reduces the amplitude or frequency of the carrier wave by a predetermined amount. In one configuration example of the physical quantity sensor of the present invention, the carrier wave adjusting means increases the amplitude or frequency of the carrier wave by a predetermined amount.
- the calculation means uses the period of the interference waveform when the measurement object is stationary as the reference period.
- 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 calculation means uses the period obtained by the period calculation means as the reference period.
- 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 calculation means uses the period obtained by the period calculation means as the reference period.
- 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
- the displacement and speed of the measurement object can be measured with higher resolution than before by performing the calculation based on the measured period of each interference waveform. 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.
- the dynamic range of the measurement relating to the speed of the measurement object can be maximized, or the displacement or speed can be adjusted.
- the item to be emphasized can be selected as appropriate from the point of improving the resolution and improving the measurement accuracy of displacement and speed.
- FIG. 4 is a waveform diagram schematically showing an output voltage waveform of a current-voltage conversion amplification unit and an output voltage waveform of a filter unit in the first embodiment of the present invention. 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
- 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.
- the photodiode 2 and the current-voltage conversion amplification unit 5 constitute detection means.
- a semiconductor laser 1 of a type that does not have a mode hopping phenomenon VCSEL type, DFB laser type
- the laser driver 4 supplies the semiconductor laser 1 with a triangular wave drive current that repeatedly increases and decreases at a constant rate of change as an injection current.
- 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.
- the rate of change of the oscillation wavelength of the semiconductor laser 1 needs to be constant.
- the laser light emitted from the semiconductor laser 1 is condensed 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.
- 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
- FIG. 2B is a diagram schematically showing the output voltage waveform of the filter unit 6.
- FIG. 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.
- 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.
- MHP that is a self-coupled signal
- the MHP that is a self-coupled signal
- the distance from the mirror layer 1013 to the object 10 is L and the oscillation wavelength of the laser is ⁇
- 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 q ⁇ / 2
- 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.
- each stepped waveform that is, each interference fringe is MHP.
- 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.
- 6A to 6D are diagrams for explaining the operation of the signal extraction unit 7.
- FIG. 6A is a diagram schematically showing the waveform of the output voltage of the filter unit 6, that is, the waveform of MHP.
- (B) is a diagram showing the output of the binarization unit 70 corresponding to (A)
- (C) is a diagram showing the sampling clock CLK input to the signal extraction unit 7, and
- (D) is equivalent to (B). It is a figure which shows the measurement result of the period measurement part 71.
- FIG. 1 shows the measurement result of the period measurement part 71.
- 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 is decreased to decrease 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 measurement unit 71 measures the period of the rising edge of the output of the binarization unit 70 (that is, the MHP period) 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 T ⁇ , T ⁇ , and T ⁇ as the MHP period. As is apparent from FIGS. 6C and 6D, the sizes of the periods T ⁇ , T ⁇ , and T ⁇ 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.
- 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.
- the sampling clock frequency is fad [Hz]
- the reference period is N0 [samplings]
- the average oscillation wavelength of the semiconductor laser 1 is ⁇ [m]
- the MHP period to be calculated is n [samplings] longer than the reference period N0.
- the reference period N0 is an MHP period when the object 10 is stationary or an MHP period at a calculated distance.
- the sign of the period change amount n in Expression (2) may be negative.
- 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.
- 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.
- the distance from the object 10 can be calculated from the reference period T0.
- a calculation method there is a method in which the displacement is calculated as 0 in Patent Document 1.
- the calculation unit 8 can calculate the displacement D of the object 10 by the equation (2), and can calculate the velocity V of the object 10 by the equation (3).
- the frequency fad of the sampling clock is 16 [MHz]
- the reference period N0 is 160 [samplings]
- the average wavelength of the semiconductor laser 1 is 850 [nm]
- the period of the MHP to be calculated is 1 [samplings] longer than the reference period N0.
- the displacement D of the object 10 in the MHP cycle to be calculated can be calculated as 5.31 [nm]
- the velocity V can be calculated as 1.05 [mm / s].
- the calculation unit 8 performs the above calculation process every time MHP occurs.
- the display unit 9 displays the calculation result of the calculation unit 8.
- 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.
- the absolute value of the average velocity of the object 10 is converted to the displacement per half cycle of the carrier wave, ⁇ / 2 ⁇ Na
- the number of MHPs per carrier half cycle is Nl + Na or Nl ⁇ Na.
- the displacement per carrier half cycle is moving at a speed of ⁇ / 2 ⁇ Nb
- the number of MHPs per carrier half cycle is Nl + Nb or Nl ⁇ Nb, so the MHP cycle corresponding to this number is observed. .
- the number of MHPs per half cycle of the carrier wave is calculated backward from each MHP period, and the displacement D and 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.
- said average speed is an average speed between a certain one MHP.
- the resolution of the displacement and speed of the object is about half the wavelength ⁇ / 2 of the semiconductor laser.
- the resolution of the displacement D and the velocity V is ⁇ / 2 ⁇ n / N0, so that a resolution of less than half wavelength ⁇ / 2 can be realized, and measurement with higher resolution than in the past is possible. Can be realized.
- 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.
- FIG. 7 is a block diagram showing the configuration of the physical quantity sensor according to the second embodiment of the present invention.
- the same components as those in FIG. 1 are denoted by the same reference numerals.
- the physical quantity sensor of the present embodiment is obtained by adding a carrier wave adjustment unit 11 to the physical quantity sensor of the first embodiment.
- the carrier wave adjustment unit 11 performs a predetermined period T0 of the MHP cycle T measured by the signal extraction unit 7 in response to a carrier wave adjustment instruction signal input from an operator, for example, at the time of initial setting when the object 10 is stationary.
- the amplitude of the triangular wave drive current (the amplitude of the carrier wave) is adjusted through the laser driver 4.
- the maximum frequency fmax of the MHP that can be processed by the physical quantity sensor is determined by a circuit of the physical quantity sensor (for example, an operational amplifier included in the current-voltage conversion amplification unit 5).
- FIG. 8 is a diagram for explaining a method of adjusting the amplitude of the triangular wave drive current supplied from the laser driver 4 to the semiconductor laser 1.
- the laser driver 4 adjusts the amplitude AMP of the drive current while fixing the DC component (DC bias) CB of the drive current to a constant value.
- the dynamic range of measurement related to the velocity V of the object 10 can be maximized.
- the carrier wave adjustment unit 11 also adjusts the frequency of the triangular wave drive current (carrier frequency) through the laser driver 4 so that the MHP period T measured by the signal extraction unit 7 becomes a predetermined period T0. Good.
- the period T of the MHP used for adjustment is the period when the object 10 is stationary.
- the present invention is not limited to this, and a predetermined number of MHPs measured immediately before the adjustment are used.
- the amplitude or frequency of the carrier wave may be adjusted using the moving average of the period as the period T.
- the present embodiment is suitable when it is known that the object 10 is vibrating or when the speed of the object 10 is known to be large.
- the resolution of the displacement D and speed V of the object 10 is improved in proportion to the number of sampling clocks included in one cycle of MHP.
- the MHP frequency increases (the number of MHPs increases), so the number of sampling clocks included in one MHP cycle decreases, and the displacement D and speed The resolution of V decreases. That is, when the distance from the object 10 is A times, the number of sampling clocks included in one cycle of MHP is reduced to 1 / A times, and the resolution of the displacement D and the speed V is deteriorated A times.
- the carrier wave adjustment unit 11 reduces the amplitude or frequency of the triangular wave drive current (carrier wave amplitude or frequency) by a predetermined amount from the immediately preceding value through the laser driver 4. . If the carrier wave amplitude or frequency is adjusted to be small, the MHP cycle is longer than before the adjustment even if the distance to the object 10 is the same, so the number of sampling clocks included in one MHP cycle is increased. And the resolution of the displacement D and the velocity V can be improved. As an initial adjustment method, the adjustment method described in the second embodiment may be used.
- the MHP cycle is shortened and the resolution of the displacement D and the velocity V is reduced, but the number of MHPs is increased, and the frequency distribution of the MHP cycle is almost Gaussian.
- the reference period can be obtained with high accuracy.
- the MHP period becomes longer and the resolution of the displacement D and the velocity V improves, but the variance of the Gaussian distribution of the MHP period increases in proportion to the period, Since the number is reduced, the accuracy of the reference period is lowered.
- the following adjustment may be performed when it is desired to place importance on measurement accuracy because the distance to the object 10 is short. That is, for example, when a precision-oriented adjustment instruction signal is input from an operator, the carrier wave adjustment unit 11 increases the amplitude or frequency of the triangular wave drive current (carrier wave amplitude or frequency) by a predetermined amount from the previous value through the laser driver 4. . Thereby, the precision of the reference period of MHP can be improved, and the measurement precision of the displacement D and the speed V can be improved.
- the reference period N0 is the MHP period in a state where the object 10 is stationary, but this embodiment describes another method for obtaining the reference period N0.
- FIG. 9 is a block diagram showing a configuration example of the calculation unit 8 according to the fourth embodiment of the present invention.
- the calculation unit 8 includes a physical quantity calculation unit 80, a counting unit 81, a distance calculation unit 82, and a cycle calculation unit 83.
- the entire configuration of the physical quantity sensor may be the same as in the first to third embodiments, but the change speed of the oscillation wavelength of the semiconductor laser 1 is constant, and the maximum value ⁇ b of the oscillation wavelength and the minimum value ⁇ a of the oscillation wavelength are Each of them must be constant, and their difference ⁇ b- ⁇ a must also be constant.
- the counting unit 81 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 81 may use a counter composed of logic gates, or may measure an MHP frequency (that is, the number of MHPs per unit time) using FFT (Fast Fourier Transform).
- the distance calculation unit 82 calculates the distance from the object 10 based on the minimum oscillation wavelength ⁇ a and the maximum oscillation wavelength ⁇ b of the semiconductor laser 1 and the number of MHPs counted by the counting unit 81.
- 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.
- the minute displacement state is a state satisfying ( ⁇ b ⁇ a) / ⁇ b> V / Lb (where Lb is time (distance at t), the displacement state is a state satisfying ( ⁇ b ⁇ a) / ⁇ b ⁇ V / Lb.
- the distance calculation unit 82 calculates the distance candidate values L ⁇ (t) and L ⁇ (t) and the speed candidate values V ⁇ (t) and V ⁇ (t) at the current time t as the following equations.
- MHP (t) is the number of MHPs calculated at the current time t
- MHP (t ⁇ 1) is the number of MHPs calculated one time before MHP (t). is there.
- 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
- MHP (t) is the second counting period. If the result 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 L ⁇ (t) and V ⁇ (t) are values calculated on the assumption that the object 10 is in a minute displacement state, and the candidate values L ⁇ (t) and V ⁇ (t) are obtained when the object 10 is in a displacement state. This is a calculated value.
- the distance calculation unit 82 performs the calculations of the equations (4) to (7) at every time (every oscillation period) when the counting unit 81 measures the number of MHPs.
- the distance calculation unit 82 calculates the history displacement, which is the difference between the distance candidate value at the current time t and the distance candidate value at the immediately preceding time, for each of the minute displacement state and the displacement state, as follows: calculate.
- the candidate distance values calculated one time before the current time t are L ⁇ (t ⁇ 1) and L ⁇ (t ⁇ 1).
- the history displacement Vcal ⁇ (t) is a value calculated on the assumption that the object 10 is in a minute displacement state
- the history displacement Vcal ⁇ (t) is a value calculated on the assumption that the object 10 is in a displacement state.
- the distance calculation unit 82 performs the calculations of the equations (8) to (9) at each time when the number of MHPs is measured by the counting unit 81.
- the direction in which the object 10 approaches the physical quantity sensor of the present embodiment is defined as a positive speed
- the direction in which the object 10 moves away is defined as a negative speed.
- the distance calculation unit 82 determines the state of the object 10 using the calculation results of Expressions (4) to (9).
- the distance calculation unit 82 has a constant sign of the history displacement Vcal ⁇ (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 V ⁇ (t) calculated on the assumption that the velocity is equal to the average value of the absolute values of the history displacement Vcal ⁇ (t) is equal, it is determined that the object 10 is moving at a constant velocity in a minute displacement state. .
- the distance calculation unit 82 has a constant sign of the history displacement Vcal ⁇ (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 V ⁇ (t) calculated on the assumption that the average displacement is equal to the absolute value of the absolute value of the history displacement Vcal ⁇ (t), it is determined that the object 10 is moving at a constant velocity in the displacement state.
- the distance calculation unit 82 measures the number of MHPs with the sign of the history displacement Vcal ⁇ (t) calculated on the assumption that the object 10 is in a minute displacement state. If the velocity candidate value V ⁇ (t) calculated on the assumption that the object 10 is in a minute displacement state does not match the average value of the absolute values of the history displacement Vcal ⁇ (t), the object 10 is It is determined that a movement other than a constant speed movement is performed in a minute displacement state.
- the distance calculation unit 82 assumes that the absolute value of the velocity candidate value V ⁇ (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 V ⁇ (t) calculated in this way does not match the average value of the absolute values of the history displacement Vcal ⁇ (t), it is determined that the object 10 is moving in a minute displacement state other than the constant velocity motion. May be.
- the distance calculation unit 82 calculates the number of MHPs at which the sign of the history displacement Vcal ⁇ (t) calculated on the assumption that the object 10 is in the displacement state is measured.
- the velocity candidate value V ⁇ (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 Vcal ⁇ (t)
- the object 10 is in the displacement state. It is determined that the person is exercising other than the uniform speed movement.
- the distance calculation unit 82 assumes that the absolute value of the velocity candidate value V ⁇ (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 V ⁇ (t) and the average value of the history displacement Vcal ⁇ (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 82 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 82 sets the distance candidate value L ⁇ (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 L ⁇ (t) is set as the distance to the object 10.
- the distance calculation unit 82 sets the distance candidate value L ⁇ (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 L ⁇ (t). In addition, when it is determined that the object 10 is moving in a displaced state other than the constant velocity movement, the distance calculation unit 82 sets the distance candidate value L ⁇ (t) as the distance to the object 10. However, the actual distance is an average value of the distance candidate values L ⁇ (t).
- the period calculation unit 83 obtains the MHP period from the distance calculated by the distance calculation unit 82.
- the frequency of MHP is proportional to the measurement distance
- 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 a database (not shown) of the cycle calculation unit 83, the cycle calculation unit 83 will correspond to the MHP corresponding to the distance calculated by the distance calculation unit 82. Is obtained from the database, the MHP cycle can be obtained.
- the cycle calculation unit 83 substitutes the distance calculated by the distance calculation unit 82 into the mathematical formula, thereby setting the MHP cycle. Can be calculated.
- the physical quantity calculation unit 80 sets the cycle obtained by the cycle calculation unit 83 as the reference cycle N0, and 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. . That is, the physical quantity calculation unit 80 calculates the displacement D of the object 10 by the equation (2) described in the first embodiment, and calculates the velocity V of the object 10 by the equation (3). According to the present embodiment, the reference period N0 can be obtained even in the case of the object 10 that cannot be stationary.
- FIG. 10 is a block diagram showing a configuration example of the calculation unit 8 according to the fifth embodiment of the present invention.
- the calculation unit 8 includes a physical quantity calculation unit 80, a counting unit 84 that counts the number of MHPs included in the output voltage of the filter unit 6, a storage unit 85 that stores a counting result of the counting unit 84, and a counting unit 84.
- a positive or negative sign is assigned to the latest count result of the counting unit 84 according to the magnitude relationship between the count result of the previous time and the double of the distance proportional number NL calculated using the past count result.
- symbol provision part 87 which performs and the period calculation part 88 which calculates the period of MHP from the distance proportional number NL are comprised.
- the overall configuration of the physical quantity sensor may be the same as in the first to third embodiments.
- the counting unit 84 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 84 may use a counter composed of logic gates, or may measure an MHP frequency (that is, the number of MHPs per unit time) using FFT.
- the counting result of the counting unit 84 is stored in the storage unit 85.
- the distance proportional number calculation unit 86 obtains the distance proportional number NL from the counting result of the counting unit 84.
- FIG. 11 is a diagram for explaining the operation of the distance proportional number calculation unit 86, and is a diagram showing a change over time in the counting result of the counting unit 84.
- Nu is the counting result of the first oscillation period P1
- Nd is the counting result of the second oscillation period P2.
- 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 86 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.
- N (t ⁇ 2) represents the number N of MHPs measured two times before the current time t
- N (t ⁇ 3) is measured three times before the current time t. This indicates that the number of MHPs is N.
- 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.
- 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) is the count result Nu in the first oscillation period P1.
- Expression (10) is an expression for obtaining the distance proportional number NL based on the count results for two times, but when using the count result of 2m (m is a positive integer), the distance proportional number calculation unit 86 has the following formula:
- the distance proportional number NL is calculated as follows.
- Expressions (10) and (11) are expressions used at the beginning of measurement of the displacement and speed of the object 10, and are proportional to the distance by the following expression using a signed count result to be described later instead of Expression (10).
- the number NL is calculated.
- N ′ (t ⁇ 2) is a count result with a sign obtained after performing a later-described code addition process on the count result N (t ⁇ 2) two times before
- N ′ (t ⁇ 3) is a count result three times before. This is a signed count result after applying a sign providing process to N (t ⁇ 3).
- Expression (12) 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.
- the distance proportional number NL is calculated from the middle using the following equation using the signed count result instead of the equation (11).
- the expression (13) 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 85.
- the distance proportional number calculation unit 86 performs the calculation process of 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 84.
- the distance proportional number NL may be calculated from the odd number of count results.
- the sign assigning unit 87 counts the counting result of the counting unit 84 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 87 executes the following expression.
- FIG. 12 is a diagram for explaining the operation of the code assigning unit 87 and is a diagram showing a change in the counting result of the counting unit 84 over time.
- the time change of the counting result Nu becomes a form in which the negative waveform shown 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. 12 is folded back to the positive side.
- the state of the object 10 in the portion where the counting result is folded is defined as the displacement state.
- the state of the object 10 in the portion where the counting result is not folded is the above-described minute displacement state.
- Expressions (14) and (15) are expressions for determining whether the object 10 is in a displacement state or a minute displacement state.
- N (t ⁇ 1) ⁇ 2NL is established in the displacement state in which the counting result is turned back in FIG. 12, N (t ⁇ 1) ⁇ 2NL is established. Therefore, as shown in the equation (14), when N (t ⁇ 1) ⁇ 2NL is established, the count result N (t) at the current time t of the counting unit 84 is given a negative sign. The count result is N ′ (t).
- N (t ⁇ 1) ⁇ 2NL is established in the minute displacement state in which the counting result is not folded in FIGS. Therefore, as shown in Expression (15), when N (t ⁇ 1) ⁇ 2NL is satisfied, the result obtained by adding a positive sign to the counting result N (t) at the current time t of the counting unit 84 is The count result is N ′ (t).
- the signed count result N ′ (t) is stored in the storage unit 85.
- the code assigning unit 87 performs the above-described code assigning process at each time (every oscillation period) when the counting unit 84 measures the number of MHPs. It should be noted that the condition for establishing equation (14) may be N (t ⁇ 1)> 2NL, and the condition for establishing equation (15) may be N (t ⁇ 1) ⁇ 2NL.
- the period calculation unit 88 calculates the MHP period T from the distance proportional number NL as in the following equation.
- T C / (2 ⁇ f ⁇ NL) (16)
- f is the frequency of the triangular wave
- C is the speed of light.
- the physical quantity calculation unit 80 sets the cycle obtained by the cycle calculation unit 88 as a reference cycle N0, and 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. . That is, the physical quantity calculation unit 80 calculates the displacement D of the object 10 by the equation (2) described in the first embodiment, and calculates the velocity V of the object 10 by the equation (3). According to the present embodiment, the reference period N0 can be obtained even in the case of the object 10 that cannot be stationary.
- the semiconductor laser 1 is oscillated in a triangular wave shape.
- the present invention is not limited to this, and as shown in FIG. 13 in the first to third and fifth embodiments.
- the semiconductor laser 1 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.
- the rate of change of the oscillation wavelength of the semiconductor laser 1 is 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.
- the processing in the first oscillation period P1 may be repeated, and the saw in which only the second oscillation period P2 exists repeatedly.
- the processing of the second oscillation period P2 may be repeated.
- FIG. 14 is a block diagram showing a configuration of a physical quantity sensor according to the seventh embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG.
- the physical quantity sensor according to 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 according to the first to sixth embodiments.
- the voltage detector 12 detects and amplifies the voltage between the terminals of the semiconductor laser 1, that is, the anode-cathode voltage.
- 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 to sixth embodiments.
- an MHP waveform can be extracted without using a photodiode, and the physical quantity sensor components can be reduced as compared with the first to sixth embodiments. The cost can be reduced.
- the influence of disturbance light can be removed.
- At least the signal extraction unit 7, the calculation unit 8, and the carrier wave adjustment unit 11 are, for example, a computer having a CPU, a memory, and an interface, and a program that controls these hardware resources. Can be realized.
- the CPU executes the processes described in the first to seventh 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.
- 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, 11 ... carrier wave adjustment unit, 12 ... voltage detection unit, 70 ... binarization unit, 71 ... period measurement unit, 80 ... physical quantity calculation unit, 81, 84 ... counting unit, 82 ... distance calculation unit, 83 ... cycle Calculation unit, 85 ... storage unit, 86 ... distance proportional number calculation unit, 87 ... sign assigning unit, 88 ... cycle calculation unit.
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Abstract
Description
また、本発明の物理量センサの1構成例において、前記演算手段は、前記干渉波形の周期を計測するサンプリングクロックの周波数と、基準周期と、前記半導体レーザの平均波長と、前記信号抽出手段が計測した周期の前記基準周期に対する変化量とから、前記測定対象の変位と速度のうち少なくとも一方を算出することを特徴とするものである。
また、本発明の物理量センサの1構成例において、前記搬送波調整手段は、前記測定対象が静止しているときの前記干渉波形の周期または調整の直前に計測された所定数の干渉波形の周期の平均が、予め規定された周期になるように、前記搬送波の振幅または周波数を調整することを特徴とするものである。
また、本発明の物理量センサの1構成例において、前記予め規定された周期は、物理量センサが処理することの可能な干渉波形の最高周波数の1/2の値に対応する周期であることを特徴とするものである。
また、本発明の物理量センサの1構成例において、前記搬送波調整手段は、前記搬送波の振幅または周波数を所定量だけ小さくすることを特徴とするものである。
また、本発明の物理量センサの1構成例において、前記搬送波調整手段は、前記搬送波の振幅または周波数を所定量だけ大きくすることを特徴とするものである。
また、本発明の物理量センサの1構成例は、さらに、前記検出手段の出力信号に含まれる前記干渉波形の数を、前記第1の発振期間と前記第2の発振期間の各々について数える計数手段と、この計数手段によって干渉波形の数を数える期間における最小発振波長と最大発振波長と前記計数手段の計数結果とから前記測定対象との距離を算出する距離算出手段と、この距離算出手段が算出した距離から前記干渉波形の周期を求める周期算出手段とを備え、前記演算手段は、前記周期算出手段が求めた周期を前記基準周期とすることを特徴とするものである。
また、本発明の物理量センサの1構成例は、さらに、前記検出手段の出力信号に含まれる前記干渉波形の数を、前記第1の発振期間と前記第2の発振期間の各々について数える計数手段と、前記干渉波形の数の平均値を算出することにより前記半導体レーザと前記測定対象との平均距離に比例した干渉波形の数である距離比例個数を求める距離比例個数算出手段と、前記距離比例個数から前記干渉波形の周期を算出する周期算出手段とを備え、前記演算手段は、前記周期算出手段が求めた周期を前記基準周期とすることを特徴とするものである。
以下、本発明の実施の形態について図面を参照して説明する。
図1は本発明の第1の実施の形態に係る物理量センサの構成を示すブロック図である。図1の物理量センサは、測定対象の物体10にレーザ光を放射する半導体レーザ1と、半導体レーザ1の光出力を電気信号に変換するフォトダイオード2と、半導体レーザ1からの光を集光して放射すると共に、物体10からの戻り光を集光して半導体レーザ1に入射させるレンズ3と、半導体レーザ1を駆動する発振波長変調手段となるレーザドライバ4と、フォトダイオード2の出力電流を電圧に変換して増幅する電流-電圧変換増幅部5と、電流-電圧変換増幅部5の出力電圧から搬送波を除去するフィルタ部6と、フィルタ部6の出力電圧に含まれる自己結合信号であるモードホップパルス(以下、MHPとする)の周期を計測する信号抽出部7と、信号抽出部7が計測した個々の周期に基づいて物体10の変位や速度を算出する演算部8と、演算部8の算出結果を表示する表示部9とを有する。
L=qλ/2 …(1)
式(1)において、qは整数である。この現象は、物体10からの散乱光が極めて微弱であっても、半導体レーザ1の共振器内の見かけの反射率が増加することにより、増幅作用が生じ、十分観測できる。
図6の(A)~(D)は信号抽出部7の動作を説明するための図であり、(A)はフィルタ部6の出力電圧の波形、すなわちMHPの波形を模式的に示す図、(B)は(A)に対応する2値化部70の出力を示す図、(C)は信号抽出部7に入力されるサンプリングクロックCLKを示す図、(D)は(B)に対応する周期測定部71の測定結果を示す図である。
D=n×λ/(2×N0) …(2)
V=n×λ/(2×N0)×fad/(N0+n) …(3)
表示部9は、演算部8の算出結果を表示する。
また、本実施の形態では、物体10の変位と速度の両方を計測しているが、どちらか一方だけを計測してもよいことは言うまでもない。
次に、本発明の第2の実施の形態について説明する。図7は本発明の第2の実施の形態に係る物理量センサの構成を示すブロック図であり、図1と同一の構成には同一の符号を付してある。
本実施の形態の物理量センサは、第1の実施の形態の物理量センサに対して、搬送波調整部11を追加したものである。
なお、搬送波調整部11は、信号抽出部7が計測したMHPの周期Tが予め規定された周期T0になるように、レーザドライバ4を通じて三角波駆動電流の周波数(搬送波の周波数)を調整してもよい。
本実施の形態は、物体10が振動していると分かっているときや、物体10の速度が大きいと分かっているときに適している。
次に、本発明の第3の実施の形態について説明する。本実施の形態においても、センサの構成は第2の実施の形態と同様であるので、図7の符号を用いて説明する。
物体10の変位Dや速度Vの分解能は、MHPの1周期に含まれるサンプリングクロック数に比例して向上する。半導体レーザ1と物体10との距離が遠くなると、MHPの周波数が高くなる(MHPの個数が多くなる)ので、MHPの1周期に含まれるサンプリングクロック数は減少することになり、変位Dや速度Vの分解能は低下する。すなわち、物体10との距離がA倍になると、MHPの1周期に含まれるサンプリングクロック数は1/A倍に減少し、変位Dや速度Vの分解能はA倍悪化する。
つまり、搬送波調整部11は、例えばオペレータから分解能重視調整指示信号が入力されると、レーザドライバ4を通じて三角波駆動電流の振幅または周波数(搬送波の振幅または周波数)を直前の値から所定量だけ小さくする。搬送波の振幅または周波数が小さくなるように調整すると、物体10との距離が同じであっても、調整前に比べてMHPの周期が長くなるので、MHPの1周期に含まれるサンプリングクロック数を増やすことができ、変位Dや速度Vの分解能を向上させることができる。なお、初期の調整方法としては、第2の実施の形態で説明した調整方法を使用すればよい。
すなわち、搬送波調整部11は、例えばオペレータから精度重視調整指示信号が入力されると、レーザドライバ4を通じて三角波駆動電流の振幅または周波数(搬送波の振幅または周波数)を直前の値から所定量だけ大きくする。これにより、MHPの基準周期の精度を向上させることができ、変位Dや速度Vの計測精度を向上させることができる。
次に、本発明の第4の実施の形態について説明する。第1の実施の形態では、基準周期N0を物体10が静止している状態でのMHPの周期としたが、本実施の形態は基準周期N0の他の求め方を説明するものである。図9は本発明の第4の実施の形態に係る演算部8の構成例を示すブロック図である。演算部8は、物理量算出部80と、計数部81と、距離算出部82と、周期算出部83とから構成される。物理量センサの全体の構成は第1~第3の実施の形態と同じでよいが、半導体レーザ1の発振波長の変化速度が一定で、かつ発振波長の最大値λbおよび発振波長の最小値λaがそれぞれ一定で、それらの差λb-λaも一定である必要がある。
次に、距離算出部82は、式(4)~式(9)の算出結果を用いて、物体10の状態を判定する。
本実施の形態によれば、静止させることができない物体10の場合であっても、基準周期N0を求めることができる。
次に、本発明の第5の実施の形態について説明する。図10は本発明の第5の実施の形態に係る演算部8の構成例を示すブロック図である。演算部8は、物理量算出部80と、フィルタ部6の出力電圧に含まれるMHPの数を数える計数部84と、計数部84の計数結果等を記憶する記憶部85と、計数部84の計数結果の平均値を算出することにより、半導体レーザ1と物体10との平均距離に比例したMHPの数(以下、距離比例個数とする)NLを求める距離比例個数算出部86と、計数部84の1回前の計数結果とこの計数結果よりも過去の計数結果を用いて算出された距離比例個数NLの2倍数との大小関係に応じて計数部84の最新の計数結果に正負の符号を付与する符号付与部87と、距離比例個数NLからMHPの周期を算出する周期算出部88とから構成される。物理量センサの全体の構成は第1~第3の実施の形態と同じでよい。
なお、距離比例個数NLの算出に用いる計数結果が十分に多いときは、奇数回分の計数結果で距離比例個数NLを算出してもよい。
なお、式(14)の成立条件をN(t-1)>2NLにして、式(15)の成立条件をN(t-1)≦2NLにしてもよい。
T=C/(2×f×NL) …(16)
ここで、fは三角波の周波数、Cは光速である。
本実施の形態によれば、静止させることができない物体10の場合であっても、基準周期N0を求めることができる。
次に、本発明の第6の実施の形態について説明する。第1~第5の実施の形態では、半導体レーザ1を三角波状に発振させていたが、これに限るものではなく、第1~第3、第5の実施の形態において図13に示すように半導体レーザ1を鋸波状に発振させてもよい。すなわち、本実施の形態では、第1の発振期間P1または第2の発振期間P2のいずれか一方が繰り返し存在するように半導体レーザ1を動作させればよい。ただし、第4の実施の形態については、半導体レーザ1を三角波状に発振させる必要がある。
次に、本発明の第7の実施の形態について説明する。第1~第6の実施の形態では、MHP波形を含む電気信号を検出する検出手段としてフォトダイオード2と電流-電圧変換増幅部5とを用いたが、フォトダイオードを使用することなくMHP波形を抽出することも可能である。図14は本発明の第7の実施の形態に係る物理量センサの構成を示すブロック図であり、図1と同様の構成には同一の符号を付してある。本実施の形態の物理量センサは、第1~第6の実施の形態のフォトダイオード2と電流-電圧変換増幅部5の代わりに、検出手段として電圧検出部12を用いるものである。
こうして、本実施の形態では、フォトダイオードを使用することなくMHP波形を抽出することができ、第1~第6の実施の形態と比較して物理量センサの部品を削減することができ、物理量センサのコストを低減することができる。また、本実施の形態では、フォトダイオードを使用しないので、外乱光による影響を除去することができる。
Claims (20)
- 測定対象にレーザ光を放射する半導体レーザと、
発振波長が連続的に単調増加する第1の発振期間と発振波長が連続的に単調減少する第2の発振期間のうち少なくとも一方が繰り返し存在するように前記半導体レーザを動作させる発振波長変調手段と、
前記半導体レーザから放射されたレーザ光と前記測定対象からの戻り光との自己結合効果によって生じる干渉波形を含む電気信号を検出する検出手段と、
この検出手段の出力信号に含まれる前記干渉波形の周期を干渉波形が入力される度に計測する信号抽出手段と、
この信号抽出手段が計測した個々の周期に基づいて前記測定対象の変位と速度のうち少なくとも一方を算出する演算手段と、
を備える物理量センサ。 - 前記演算手段は、前記干渉波形の周期を計測するサンプリングクロックの周波数と、基準周期と、前記半導体レーザの平均波長と、前記信号抽出手段が計測した周期の前記基準周期に対する変化量とから、前記測定対象の変位と速度のうち少なくとも一方を算出する、
請求項1記載の物理量センサ。 - さらに、前記半導体レーザの発振波長変調の搬送波の振幅または周波数を調整することが可能な搬送波調整手段を備える、
請求項1または2記載の物理量センサ。 - 前記搬送波調整手段は、前記測定対象が静止しているときの前記干渉波形の周期または調整の直前に計測された所定数の干渉波形の周期の平均が、予め規定された周期になるように、前記搬送波の振幅または周波数を調整する、
請求項3記載の物理量センサ。 - 前記予め規定された周期は、物理量センサが処理することの可能な干渉波形の最高周波数の1/2の値に対応する周期である、
請求項4記載の物理量センサ。 - 前記搬送波調整手段は、前記搬送波の振幅または周波数を所定量だけ小さくする、
請求項3記載の物理量センサ。 - 前記搬送波調整手段は、前記搬送波の振幅または周波数を所定量だけ大きくする、
請求項3記載の物理量センサ。 - 前記演算手段は、前記測定対象が静止しているときの前記干渉波形の周期を前記基準周期とする、
請求項2記載の物理量センサ。 - さらに、前記検出手段の出力信号に含まれる前記干渉波形の数を、前記第1の発振期間と前記第2の発振期間の各々について数える計数手段と、
この計数手段によって干渉波形の数を数える期間における最小発振波長と最大発振波長と前記計数手段の計数結果とから前記測定対象との距離を算出する距離算出手段と、
この距離算出手段が算出した距離から前記干渉波形の周期を求める周期算出手段と、を備え、
前記演算手段は、前記周期算出手段が求めた周期を前記基準周期とする、
請求項2記載の物理量センサ。 - さらに、前記検出手段の出力信号に含まれる前記干渉波形の数を、前記第1の発振期間と前記第2の発振期間の各々について数える計数手段と、
前記干渉波形の数の平均値を算出することにより前記半導体レーザと前記測定対象との平均距離に比例した干渉波形の数である距離比例個数を求める距離比例個数算出手段と、
前記距離比例個数から前記干渉波形の周期を算出する周期算出手段と、を備え、
前記演算手段は、前記周期算出手段が求めた周期を前記基準周期とする、
請求項2記載の物理量センサ。 - 発振波長が連続的に単調増加する第1の発振期間と発振波長が連続的に単調減少する第2の発振期間のうち少なくとも一方が繰り返し存在するように半導体レーザを動作させる発振手順と、
前記半導体レーザから放射されたレーザ光と測定対象からの戻り光との自己結合効果によって生じる干渉波形を含む電気信号を検出する検出手順と、
この検出手順で得られた出力信号に含まれる前記干渉波形の周期を干渉波形が入力される度に計測する信号抽出手順と、
この信号抽出手順で計測された個々の周期に基づいて前記測定対象の変位と速度のうち少なくとも一方を算出する演算手順と、
を備える物理量計測方法。 - 前記演算手順は、前記干渉波形の周期を計測するサンプリングクロックの周波数と、基準周期と、前記半導体レーザの平均波長と、前記信号抽出手順が計測した周期の前記基準周期に対する変化量とから、前記測定対象の変位と速度のうち少なくとも一方を算出する、
請求項11記載の物理量計測方法。 - さらに、前記半導体レーザの発振波長変調の搬送波の振幅または周波数を調整することが可能な搬送波調整手順を備える、
請求項11または12記載の物理量計測方法。 - 前記搬送波調整手順は、前記測定対象が静止しているときの前記干渉波形の周期または調整の直前に計測された所定数の干渉波形の周期の平均が、予め規定された周期になるように、前記搬送波の振幅または周波数を調整する、
請求項13記載の物理量計測方法。 - 前記予め規定された周期は、処理することの可能な干渉波形の最高周波数の1/2の値に対応する周期である、
請求項14記載の物理量計測方法。 - 前記搬送波調整手順は、前記搬送波の振幅または周波数を所定量だけ小さくする、
請求項13記載の物理量計測方法。 - 前記搬送波調整手順は、前記搬送波の振幅または周波数を所定量だけ大きくする、
請求項13記載の物理量計測方法。 - 前記演算手順は、前記測定対象が静止しているときの前記干渉波形の周期を前記基準周期とする、
請求項12記載の物理量計測方法。 - さらに、前記検出手順で得られた出力信号に含まれる前記干渉波形の数を、前記第1の発振期間と前記第2の発振期間の各々について数える計数手順と、
この計数手順によって干渉波形の数を数える期間における最小発振波長と最大発振波長と前記計数手順の計数結果とから前記測定対象との距離を算出する距離算出手順と、
この距離算出手順で算出した距離から前記干渉波形の周期を求める周期算出手順と、を備え、
前記演算手順は、前記周期算出手順で求めた周期を前記基準周期とする、
請求項12記載の物理量計測方法。 - さらに、前記検出手順で得られた出力信号に含まれる前記干渉波形の数を、前記第1の発振期間と前記第2の発振期間の各々について数える計数手順と、
前記干渉波形の数の平均値を算出することにより前記半導体レーザと前記測定対象との平均距離に比例した干渉波形の数である距離比例個数を求める距離比例個数算出手順と、
前記距離比例個数から前記干渉波形の周期を算出する周期算出手順と、を備え、
前記演算手順は、前記周期算出手順で求めた周期を前記基準周期とする、
請求項12記載の物理量計測方法。
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