JP5421568B2 - Physical quantity sensor and physical quantity measuring method - Google Patents

Description

  The present invention relates to a physical quantity sensor and a physical quantity measurement method for measuring a physical quantity such as a distance to an object and a 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. Is.

  Conventionally, as a distance meter using light interference by a laser, a laser measuring device using interference (self-coupling effect) inside a semiconductor laser between laser output light and return light from a measurement object has been proposed. (For example, refer nonpatent literature 1, nonpatent literature 2, nonpatent literature 3). FIG. 11 shows a composite resonator model of an FP type (Fabry-Perot type) semiconductor laser. In FIG. 11, 101 is a semiconductor laser, 102 is a wall opening of a semiconductor crystal, 103 is a photodiode, and 104 is an object to be measured.

When the oscillation wavelength of the laser is λ and the distance from the wall open surface 102 closer to the measurement target 104 to the measurement target 104 is L, the return light from the measurement target 104 and the resonator 101 are satisfied when the following resonance condition is satisfied. The inner laser beams strengthen each other, and the laser output increases slightly.
L = qλ / 2 (1)
In Formula (1), q is an integer. This phenomenon can be sufficiently observed even if the scattered light from the measurement object 104 is very weak, because the apparent reflectance in the resonator 101 of the semiconductor laser increases, causing an amplification effect.

  Since the semiconductor laser emits laser beams having different frequencies according to the magnitude of the injection current, an external modulator is not required when modulating the oscillation frequency, and direct modulation is possible by the injection current. FIG. 12 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 103 when the oscillation wavelength of the semiconductor laser is changed at a certain rate. When L = qλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the resonator 101 becomes 0 ° (the same phase), and the return light and the resonator 101 When L = qλ / 2 + λ / 4, the phase difference becomes 180 ° (opposite phase), and the return light and the laser light in the resonator 101 are the weakest. Therefore, when the oscillation wavelength of the semiconductor laser is changed, a place where the laser output becomes strong and a place where the laser output becomes weak appear alternately, and the laser output at this time is detected by the photodiode 103 provided in the resonator 101. As shown in FIG. 12, a step-like waveform having a constant period is obtained. Such a waveform is generally called an interference fringe.

Each stepped waveform, that is, each interference fringe is called a mode pop pulse (hereinafter referred to as MHP). MHP is a phenomenon different from the mode hopping phenomenon. For example, if the number of MHPs is 10 when the distance to the measurement object 104 is L1, the number of MHPs is 5 at half the distance L2. That is, when the oscillation wavelength of the semiconductor laser is changed for a certain time, the number of MHPs changes in proportion to the measurement distance. Therefore, if the MHP is detected by the photodiode 103 and the frequency of the MHP is measured, the distance can be easily measured.
However, conventional interferometric instruments, including self-coupled instruments, have the problem that they can measure the distance to a stationary measurement object, but cannot measure the distance of a measurement object with speed. .

  In view of this, the inventor has proposed a distance / speed meter that can measure not only the distance to a stationary measurement object but also the speed of the measurement object (see Patent Document 1). The configuration of this distance / speed meter is shown in FIG. The distance / velocity meter of FIG. 13 condenses the light from the semiconductor laser 201 that emits laser light to the object to be measured, the photodiode 202 that converts the optical output of the semiconductor laser 201 into an electrical signal, and the light from the semiconductor laser 201. A lens 203 that irradiates the measurement target 210 and collects return light from the measurement target 210 and makes it incident on the semiconductor laser 201. A first oscillation period and an oscillation wavelength in which the oscillation wavelength continuously increases in the semiconductor laser 201. A laser driver 204 that alternately repeats a second oscillation period in which the current continuously decreases, a current-voltage conversion amplifier 205 that converts and amplifies the output current of the photodiode 202 into a voltage, and a current-voltage conversion amplifier 205 Signal extraction circuit 206 that differentiates the output voltage of the signal twice and a counting circuit that counts the number of MHPs included in the output voltage of the signal extraction circuit 206 With a 07, a calculation unit 208 for calculating the distance and speed of the measurement target 210 to the measurement target 210, and a display device 209 for displaying the calculation result of the arithmetic unit 208.

  The laser driver 204 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 201 as an injection current. Accordingly, the semiconductor laser 201 alternately repeats the first oscillation period in which the oscillation wavelength continuously increases at a constant change rate and the second oscillation period in which the oscillation wavelength continuously decreases at a constant change rate. To be driven. FIG. 14 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201. In FIG. 14, P1 is the first oscillation period, P2 is the second oscillation period, λa is the minimum value of the oscillation wavelength in each period, λb is the maximum value of the oscillation wavelength in each period, and Tt is the period of the triangular wave.

  Laser light emitted from the semiconductor laser 201 is collected by the lens 203 and enters the measurement object 210. The light reflected by the measurement 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 MHPs 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 determines the distance from the measurement object 210 based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1, the number of MHPs in the first oscillation period P1, and the number of MHPs in the second oscillation period P2. And the speed of the measuring object 210 is calculated.

JP 2006-31080 A Tadashi Ueda, Satoshi Yamada, Susumu Shito, “Distance Meter Using Self-Coupling Effect of Semiconductor Laser”, Proceedings of the 1994 Tokai Branch Joint Conference of Electrical Engineering Society, 1994 Satoshi Yamada, Susumu Shito, Norio Tsuda, Tadashi Ueda, “Study on a small rangefinder using the self-coupling effect of a semiconductor laser”, Aichi Institute of Technology research report, No. 31 B, p. 35-42, 1996 Guido Giuliani, Michele Norgia, Silvano Donati and Thierry Bosch, “Laser diode self-mixing technique for sensing applications”, JOURNAL OF OPTICS A: PURE AND APPLIED OPTICS, p. 283-294, 2002

The self-coupled distance meter shown in FIG. 11 can measure the distance to the measurement object, and the distance / velocity meter shown in FIG. 13 determines the distance to the measurement object and the speed of the measurement object. It can be measured simultaneously.
However, the conventional self-coupled laser measuring instrument shown in FIGS. 11 and 13 has the following problems. FIG. 15 is a diagram for explaining a problem of the conventional self-coupled laser measuring instrument, and is a diagram showing a change over time in the counting result of the counting circuit 207. In FIG. 15, Nu is the counting result of the first oscillation period P1, and Nd is the counting result of the second oscillation period P2.

  When the distance change rate of the object to be measured is larger than the oscillation wavelength change rate of the semiconductor laser, the time change of the counting result Nu becomes a shape in which the negative waveform shown by 150 in FIG. The time change of the counting result Nd takes a form in which the negative waveform indicated by 151 in FIG. 15 is folded back to the positive side. When the counting result is turned back, an error may occur in the counting result, and a physical quantity such as a distance or a speed may be erroneously calculated.

  SUMMARY An advantage of some aspects of the invention is to provide a physical quantity sensor and a physical quantity measuring method capable of reducing the possibility of erroneous calculation of physical quantities.

The physical quantity sensor of the present invention includes at least a semiconductor laser that emits laser light to a measurement target, a first oscillation period that includes at least a period in which the oscillation wavelength continuously increases monotonously, and a period in which the oscillation wavelength continuously decreases monotonously. Oscillation wavelength modulation means for operating the semiconductor laser so that the second oscillation period including it alternately exists, and a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement target When detecting means for detecting an electrical signal including an interference waveform, measuring means for measuring a physical quantity of the measuring object from information on the interference waveform contained in the output signal of the detecting means, and when the measuring object is stationary average, so that the predefined period, the semiconductor laser of the period of the cycle or a predetermined number of interference waveforms measured immediately before the adjustment of the interference waveform A that adjustment means to adjust the amplitude or frequency of the carrier wave of the oscillation wavelength modulation, before Symbol measuring means, the number of the interference waveforms contained in an output signal of said detecting means, the said first oscillation period The signal extraction means for counting each of the second oscillation periods, the minimum oscillation wavelength and the maximum oscillation wavelength in the period for counting the number of interference waveforms by this signal extraction means, and the distance to the measurement object from the counting result of the signal extraction means And an arithmetic means for calculating at least one of the speeds of the measurement object.

Further , in one configuration example of the physical quantity sensor of the present invention, the adjusting unit may be configured such that the number of the interference waveforms in the first oscillation period is substantially the same as the number of the interference waveforms in the second oscillation period. The amplitude or frequency of the carrier wave is adjusted so that the period of the interference waveform at this time becomes a predetermined period.
Further, in one configuration example of the physical quantity sensor of the present invention, the adjusting means calculates the average value of the number of interference waveforms, thereby calculating the number of interference waveforms proportional to the average distance between the semiconductor laser and the measurement target. A distance proportional number calculating means for obtaining a certain distance proportional number, a period calculating means for calculating the period of the interference waveform from the distance proportional number, and a period calculated by the period calculating means to be a predetermined period. It comprises carrier wave adjusting means for adjusting the amplitude or frequency of the carrier wave.
Further, in one configuration example of the physical quantity sensor of the present invention, 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.

In the physical quantity measuring method of the present invention, the first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonically are alternated. An oscillation procedure for operating the semiconductor laser to exist in a detection procedure, and 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, From the interference waveform information included in the output signal obtained by this detection procedure, a measurement procedure for measuring the physical quantity of the measurement object, and immediately before the period or adjustment of the interference waveform when the measurement object is stationary the average period of the measured predetermined number of interference waveforms is such that the predefined period, adjusts the amplitude or frequency of the oscillation wavelength modulation of a carrier of the semiconductor laser A that adjustment procedures, the measurement procedure, the signal count for each number of the second oscillation interval and the first oscillation period of the interference waveform that is included in the output signal obtained in the detection procedure From the extraction procedure, the minimum oscillation wavelength and the maximum oscillation wavelength in the period of counting the number of interference waveforms by this signal extraction procedure, and the counting result of the signal extraction procedure, at least one of the distance to the measurement target and the speed of the measurement target is determined. It consists of a calculation procedure to calculate .

  According to the present invention, by providing an adjustment means capable of adjusting the amplitude or frequency of the carrier wave of the oscillation wavelength modulation of the semiconductor laser, it is possible to reduce the possibility that the interference waveform count result will be folded, The possibility of miscalculating physical quantities such as distance and speed can be reduced.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a physical quantity sensor according to the first embodiment of the present invention.
The physical quantity sensor in FIG. 1 condenses the light from the semiconductor laser 1 that emits laser light to the object 10 to be measured, the photodiode 2 that converts the light output of the semiconductor laser 1 into an electrical signal, and the light from the semiconductor laser 1. The lens 3 that collects the return light from the object 10 and makes it incident on the semiconductor laser 1, the laser driver 4 that serves as an oscillation wavelength modulation means for driving the semiconductor laser 1, and the output current of the photodiode 2 A current-voltage conversion amplification unit 5 that converts and amplifies the voltage, a filter unit 6 that removes a carrier wave from the output voltage of the current-voltage conversion amplification unit 5, and a self-coupled signal included in the output voltage of the filter unit 6. A signal extraction unit 7 that counts the number of mode hop pulses (hereinafter referred to as MHP), a calculation unit 8 that calculates the distance to the object 10 and the speed of the object 10 from the number of MHPs, and a calculation unit 8 A calculation result display unit 9 for displaying, and an adjustment section 11 capable of adjusting the amplitude or frequency of the oscillation wavelength modulation of a carrier of the semiconductor laser 1.

  The photodiode 2 and the current-voltage conversion amplification unit 5 constitute a detection unit, and the signal extraction unit 7 and the calculation unit 8 constitute a measurement unit. Hereinafter, for ease of explanation, it is assumed that a semiconductor laser 1 of a type that does not have a mode hopping phenomenon (VCSEL type, DFB laser type) is used.

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

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

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

  The signal extraction unit 7 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 signal extraction unit 7 may use a counter composed of logic gates, or may measure the frequency of MHP (that is, the number of MHPs per unit time) using FFT (Fast Fourier Transform).

  Next, the calculation unit 8 calculates the distance to the object 10 and the speed of 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 signal extraction unit 7. FIG. 3 is a block diagram showing an example of the configuration of the calculation unit 8, and FIG. 4 is a flowchart showing the operation of the calculation unit 8. The computing unit 8 calculates a distance / velocity calculating unit that calculates a candidate value for the distance to the object 10 and a candidate value for the speed of the object 10 based on the minimum oscillation wavelength λa, the maximum oscillation wavelength λb, and the number of MHPs of the semiconductor laser 1. 80, a history displacement calculation unit 81 that calculates a history displacement that is a difference between the distance candidate value calculated by the distance / speed calculation unit 80 and the distance candidate value calculated immediately before, and a distance / speed calculation unit 80 A storage unit 82 that stores the calculation results of the history displacement calculation unit 81, a state determination unit 83 that determines the state of the object 10 based on the calculation results of the distance / speed calculation unit 80 and the history displacement calculation unit 81, and a state determination The distance / speed determination unit 84 determines the distance to the object 10 and the speed of the object 10 based on the determination result of the unit 83.

  In the present embodiment, it is assumed that the state of the object 10 is either a minute displacement state that satisfies a predetermined condition or a displacement state in which the movement is larger than the minute displacement state. When the average displacement of the object 10 per oscillation period P1 and oscillation period P2 is V, the minute displacement state is a state satisfying (λb−λa) / λb> V / Lb (where Lb is time (distance at time t), the displacement state is a state satisfying (λb−λa) / λb ≦ V / Lb.

First, the distance / speed calculation unit 80 of the calculation unit 8 calculates the distance candidate values Lα (t) and Lβ (t) and the speed candidate values Vα (t) and Vβ (t) at the current time t as follows: And stored in the storage unit 82 (step S10 in FIG. 4).
Lα (t) = λa × λb × (MHP (t−1) + MHP (t))
/ {4 × (λb−λa)} (2)
Lβ (t) = λa × λb × (| MHP (t−1) −MHP (t) |)
/ {4 × (λb−λa)} (3)
Vα (t) = (MHP (t−1) −MHP (t)) × λb / 4 (4)
Vβ (t) = (MHP (t−1) + MHP (t)) × λb / 4 (5)

  In Expressions (2) to (5), MHP (t) is the number of MHPs calculated at the current time t, and MHP (t−1) is the number of MHPs calculated one time before MHP (t). is there. For example, if MHP (t) is the counting result of the first oscillation period P1, MHP (t-1) is the counting result of the second oscillation period P2, and conversely, MHP (t) is the second counting period. If it is the counting result of the oscillation period P2, the MHP (t−1) is the counting result of the first oscillation period P1.

  The candidate values Lα (t) and Vα (t) are values calculated on the assumption that the object 10 is in a minute displacement state, and the candidate values Lβ (t) and Vβ (t) are obtained when the object 10 is in a displacement state. This is a calculated value. The calculation unit 8 performs the calculations of Expressions (2) to (5) at each time (every oscillation period) when the number of MHPs is measured by the signal extraction unit 7.

Subsequently, the history displacement calculation unit 81 of the calculation unit 8 for each of the minute displacement state and the displacement state, the distance candidate value at the current time t and the distance candidate value at the previous time stored in the storage unit 82. The historical displacement, which is the difference between the two, is calculated as follows and stored in the storage unit 82 (step S11 in FIG. 4). In the equations (6) and (7), the distance candidate values calculated one time before the current time t are Lα (t−1) and Lβ (t−1).
Vcalα (t) = Lα (t) −Lα (t−1) (6)
Vcalβ (t) = Lβ (t) −Lβ (t−1) (7)

The history displacement Vcalα (t) is a value calculated on the assumption that the object 10 is in a minute displacement state, and the history displacement Vcalβ (t) is a value calculated on the assumption that the object 10 is in a displacement state. The calculation unit 8 performs the calculations of Expressions (6) to (7) at each time when the number of MHPs is measured by the signal extraction unit 7. In the equations (4) to (7), the direction in which the object 10 approaches the distance / velocity meter of the present embodiment is defined as a positive velocity, and the direction in which the object 10 moves away is defined as a negative velocity.
Next, the state determination unit 83 of the calculation unit 8 determines the state of the object 10 using the calculation results of the expressions (2) to (7) stored in the storage unit 82 (step S12 in FIG. 4).

  As described in Patent Document 1, the state determination unit 83 has a constant sign of the history displacement Vcalα (t) calculated on the assumption that the object 10 is in a minute displacement state, and the object 10 is in a minute displacement state. If the velocity candidate value Vα (t) calculated on the assumption that the velocity is equal to the average value of the absolute values of the history displacement Vcalα (t) is equal, it is determined that the object 10 is moving at a constant velocity in a minute displacement state. .

  Further, as described in Patent Document 1, the state determination unit 83 has a constant sign of the history displacement Vcalβ (t) calculated on the assumption that the object 10 is in the displacement state, and the object 10 is in the displacement state. If the velocity candidate value Vβ (t) calculated on the assumption that the average displacement is equal to the absolute value of the absolute value of the history displacement Vcalβ (t), it is determined that the object 10 is moving at a constant velocity in the displacement state.

  Further, as described in Patent Document 1, the state determination unit 83 measures the number of MHPs with the sign of the history displacement Vcalα (t) calculated on the assumption that the object 10 is in a minute displacement state. When the velocity 10 calculated by assuming that the object 10 is in a minute displacement state and the average value of the absolute values of the history displacement Vcalα (t) do not coincide with each other, the object 10 is It is determined that a movement other than a constant speed movement is performed in a minute displacement state.

  Focusing on the velocity candidate value Vβ (t), the absolute value of Vβ (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 83 assumes that the absolute value of the velocity candidate value Vβ (t) calculated on the assumption that the object 10 is in the displacement state is equal to the wavelength change rate, and that the object 10 is in the minute displacement state. If the velocity candidate value Vα (t) calculated in this way and the average value of the absolute values of the history displacement Vcalα (t) do not match, it is determined that the object 10 is moving in a minute displacement state other than the constant velocity motion. May be.

  Further, as described in Patent Document 1, the state determination unit 83 calculates the number of MHPs at which the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 10 is in the displacement state is measured. When the velocity candidate value Vβ (t) calculated on the assumption that the object 10 is in the displacement state does not match the average value of the absolute values of the history displacement Vcalβ (t), the object 10 is in the displacement state. It is determined that the person is exercising other than the uniform speed movement.

  When attention is paid to the velocity candidate value Vα (t), the absolute value of Vα (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 83 assumes that the absolute value of the velocity candidate value Vα (t) calculated on the assumption that the object 10 is in the minute displacement state is equal to the wavelength change rate, and that the object 10 is in the displacement state. If the calculated velocity candidate value Vβ (t) and the average value of the history displacement Vcalβ (t) do not coincide with each other, it is determined that the object 10 is moving in a displaced state other than the uniform velocity motion. May be.

The distance / speed determination unit 84 of the calculation unit 8 determines the speed of the object 10 and the distance to the object 10 based on the determination result of the state determination unit 83 (step S13 in FIG. 4).
That is, when it is determined that the object 10 is moving at a constant speed in a minute displacement state, the distance / speed determining unit 84 sets the speed candidate value Vα (t) as the speed of the object 10 and uses the distance candidate value Lα ( t) is a distance from the object 10, and when it is determined that the object 10 is moving at a constant speed in a displaced state, the velocity candidate value Vβ (t) is the velocity of the object 10, and the distance candidate value Lβ (t ) Is the distance to the object 10.

  Further, when it is determined that the object 10 is moving in a minute displacement state other than the constant velocity motion, the distance / speed determination unit 84 sets the speed candidate value Vα (t) as the speed of the object 10 and sets the distance The candidate value Lα (t) is set as the distance from the object 10. However, the actual distance is an average value of the distance candidate values Lα (t). In addition, when it is determined that the object 10 is moving in a state of displacement other than the constant velocity motion, the distance / speed determination unit 84 sets the speed candidate value Vβ (t) as the speed of the object 10 and uses the distance candidate. The value Lβ (t) is the distance from the object 10. However, the actual distance is an average value of the distance candidate values Lβ (t).

  Note that Vβ (t) is always a positive value and Vα (t) is either a positive or negative value due to the magnitude relationship between MHP (t−1) and MHP (t). It is not a representation of 10 speed directions. When the number of MHPs of the semiconductor laser whose oscillation wavelength is increasing is larger than the number of MHPs of the semiconductor laser whose oscillation wavelength is decreasing, the speed of the object 10 is positive (direction approaching the laser). )

The calculation unit 8 performs the processing of steps S10 to S13 for each time (every oscillation period) when the number of MHPs is measured by the signal extraction unit 7.
The display unit 9 displays the distance to the object 10 and the speed of the object 10 calculated by the calculation unit 8 in real time.

Next, the adjusting unit 11 adjusts the amplitude of the triangular wave drive current (carrier wave amplitude) through the laser driver 4 when, for example, a carrier wave adjustment instruction signal is input by the operator at the initial setting when the object 10 is stationary. .
FIG. 5 is a block diagram illustrating a configuration example of the adjustment unit 11. The adjustment unit 11 includes a binarization unit 110, a period measurement unit 111, and a carrier wave adjustment unit 112.

  6 (A) to 6 (D) are diagrams for explaining the operation of the adjusting unit 11, and FIG. 6 (A) schematically shows the waveform of the output voltage of the filter unit 6, that is, the waveform of MHP. 6B is a diagram illustrating an output of the binarization unit 110 corresponding to FIG. 6A, FIG. 6C is a diagram illustrating a sampling clock CLK input to the adjustment unit 11, and FIG. FIG. 6D is a diagram illustrating a measurement result of the period measurement unit 111 corresponding to FIG.

  First, the binarization unit 110 of the adjustment unit 11 determines whether the output voltage of the filter unit 6 illustrated in FIG. 6A is a high level (H) or a low level (L), and the binarization unit 110 illustrated in FIG. Such a determination result is output. At this time, the binarizing unit 110 determines that the output voltage of the filter unit 6 is high level when the output voltage of the filter unit 6 increases to be equal to or higher than the threshold value TH1, and the output voltage of the filter unit 6 decreases 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 measuring unit 111 measures the period of the rising edge of the output of the binarizing unit 110 (that is, the MHP period) every time a rising edge occurs. At this time, the period measuring unit 111 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 111 sequentially measures Tα, Tβ, and Tγ as the MHP period. As is apparent from FIGS. 6C and 6D, the sizes of the periods Tα, Tβ, and Tγ are 5 [samplings], 4 [samplings], and 2 [samplings], respectively. The frequency of the sampling clock CLK is assumed to be sufficiently higher than the highest frequency that the MHP can take.

  The carrier wave adjustment unit 112, at the time of initial setting when the object 10 is stationary, for example, according to a carrier wave adjustment instruction signal input from an operator, the period T0 in which the MHP cycle T measured by the cycle measurement unit 111 is defined in advance. Thus, the amplitude of the triangular wave drive current (the amplitude of the carrier wave) is adjusted through the laser driver 4. Here, the predetermined cycle T0 is a cycle corresponding to a value of 1/2 of the maximum frequency fmax of MHP that can be processed by the physical quantity sensor (T0 = 2 / fmax). 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. 7 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. In response to the instruction from the carrier wave adjustment unit 112, the laser driver 4 drives the maximum drive current while fixing the maximum value to a constant value (in the example of FIG. 7, the upper limit CL of the drive current defined by the semiconductor laser 1). The amplitude AMP of the drive current is adjusted by increasing or decreasing the minimum value of the current. In this way, the amplitude of the drive current can be adjusted.

  As described above, in the present embodiment, the measurement dynamic range related to the speed of the object 10 can be maximized by setting the cycle of the measured MHP to a predetermined cycle T0, and the signal extraction unit 7 The possibility that aliasing will occur in the counting result can be reduced, and the possibility of miscalculating physical quantities such as distance and speed can be reduced.

The carrier wave adjustment unit 112 adjusts the frequency of the triangular wave drive current (carrier wave frequency) through the laser driver 4 so that the MHP cycle T measured by the cycle measurement unit 111 becomes a predetermined cycle T0. Good.
In this embodiment, the period T of the MHP used for adjustment is the period when the object 10 is stationary. However, 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. According to this method, even in the case of the object 10 that cannot be stationary, the amplitude or frequency of the carrier wave can be adjusted.

Further, the adjustment unit 11 may determine whether the object 10 is stationary based on the count result of the signal extraction unit 7. That is, the carrier wave adjustment unit 112 is configured such that the number of MHPs in the first oscillation period P1 in which the oscillation wavelength of the semiconductor laser 1 increases is substantially the same as the number of MHPs in the second oscillation period P2 in which the oscillation wavelength decreases. It is determined that the object 10 is stationary, and the amplitude or frequency of the triangular wave drive current is adjusted through the laser driver 4 so that the MHP period T measured by the period measurement unit 111 at this time becomes a predetermined period T0. May be.
Moreover, in this Embodiment, although both the distance with the object 10 and the speed of the object 10 are measured, it cannot be overemphasized that either one may be measured.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 8 is a block diagram illustrating a configuration example of the adjustment unit 11 according to the present embodiment. The adjustment unit 11 calculates the average value of the count results of the carrier extraction unit 112a, the count result of the signal extraction unit 7, and the count result of the signal extraction unit 7, so that the semiconductor laser 1 and the object 10 The distance proportional number calculation unit 114 for obtaining the number of MHPs proportional to the average distance (hereinafter referred to as distance proportional number) NL, the count result of the signal extraction unit 7 one time before, and the past count result from this count result The sign adding unit 115 for adding a positive or negative sign to the latest count result of the signal extraction unit 7 in accordance with the magnitude relationship with the double of the distance proportional number NL calculated by using the distance proportional number NL and the period of MHP from the distance proportional number NL It is comprised from the period calculation part 116 which calculates.

  The counting result of the signal extraction unit 7 is stored in the storage unit 113 of the adjustment unit 11. The distance proportional number calculation unit 114 of the adjustment unit 11 obtains the distance proportional number NL from the count result of the signal extraction unit 7. FIG. 9 is a diagram for explaining the operation of the distance proportional number calculation unit 114, and is a diagram illustrating the time change of the counting result of the signal extraction unit 7. In FIG. 9, Nu is the counting result of the first oscillation period P1, and Nd is the counting result of the second oscillation period P2.

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

  As apparent from FIG. 14, the first oscillation period P1 and the second oscillation period P2 are alternately visited, so that the count result Nu and the count result Nd also appear alternately. The counting results Nu and Nd are the sum or difference of the distance proportional number NL and the number of MHPs proportional to the displacement of the object 10 (hereinafter referred to as the displacement proportional number) NV. The distance proportional number NL corresponds to the average value of the sine waveform shown in FIG. The difference between the counting result Nu or Nd and the distance proportional number NL corresponds to the displacement proportional number NV.

The distance proportional number calculation unit 114 calculates the distance proportional number NL by calculating the average value of the counting results for the even number of times measured up to two times before the current time t as shown in the following equation.
NL = {N (t−2) + N (t−3)} / 2 (8)

  In equation (8), N (t−2) represents the number N of MHPs measured two times before the current time t, and N (t−3) is measured three times before the current time t. This indicates that the number of MHPs is N. If the count result N (t) at the current time t is the count result Nu of the first oscillation period P1, the count result N (t-2) two times before is also the count result Nu of the first oscillation period P1. The count result N (t−3) three times before is the count result Nd in the second oscillation period P2. On the other hand, if the count result N (t) at the current time t is the count result Nd of the second oscillation period P2, the count result N (t-2) two times before is also the count result of the second oscillation period P2. Nd, and the count result N (t−3) three times before is the count result Nu in the first oscillation period P1.

Expression (8) is an expression when the distance proportional number NL is obtained from the count results for two times. However, when the count result of 2m (m is a positive integer) is used, the distance proportional number calculation unit 114 uses the following formula. The distance proportional number NL is calculated as follows.
NL = {N (t−2m−1) + N (t−2m) +... + N (t−2)} / 2m
... (9)

However, Expressions (8) and (9) are expressions used at the beginning of measurement of the distance to the object 10 and the speed of the object 10, and from the middle, a signed count result described later is used instead of Expression (8). The distance proportional number NL is calculated from the equation.
NL = {N ′ (t−2) + N ′ (t−3)} / 2 (10)
N ′ (t−2) is a count result with a sign after performing a later-described code addition process on the count result N (t−2) two times before, and N ′ (t−3) is a count result three times before. It is a count result with a code | symbol after performing a code provision process to N (t-3). Expression (10) is used after the count result N (t) at the current time t becomes the seventh count result from the start of the measurement of the number of MHPs.

Further, in the case where the equation (9) is used at the beginning of measurement, the distance proportional number NL is calculated by the following equation using a signed count result instead of the equation (9) from the middle.
NL = {N ′ (t−2m−1) + N ′ (t−2m) +... + N ′ (t−2)} / 2m
(11)
Expression (11) 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 measurement of the number of MHPs.

The distance proportional number NL is stored in the storage unit 113. The distance proportional number calculation unit 114 performs the calculation process of the distance proportional number NL as described above at each time (every oscillation period) when the number of MHPs is measured by the signal extraction unit 7.
When the count results used for calculating the distance proportional number NL are sufficiently large, the distance proportional number NL may be calculated from the odd number of count results.

Next, the code assigning unit 115 counts the signal extraction unit 7 according to the magnitude relationship between the count 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 the result N (t). Specifically, the code assigning unit 115 executes the following expression.
If N (t−1) ≧ 2NL Then N ′ (t) → −N (t) (12)
If N (t−1) <2NL Then N ′ (t) → + N (t) (13)

  As shown in FIG. 15, when the rate of change of the distance of the object 10 is larger than the rate of change of the oscillation wavelength of the semiconductor laser 1, the time change of the counting result Nu is that the negative waveform indicated by 150 in FIG. Similarly, the time change of the counting result Nd becomes a shape in which the negative waveform indicated by 151 in FIG. 15 is folded back to the positive side. In Patent Document 1, the state of the object 10 in the portion where the counting result is folded is defined as the displacement state. On the other hand, the state of the object 10 in the portion where the counting result is not folded is the above-described minute displacement state.

  In order to obtain the physical quantity of the object 10 in vibration including the displacement state, it is determined whether the object 10 is in the displacement state or the minute displacement state. If the object 10 is in the displacement state, the object 10 is folded back to the positive side. It is necessary to correct the counting result so as to draw the locus indicated by 150 and 151 in FIG. Expressions (12) and (13) are expressions for determining whether the object 10 is in a displacement state or a minute displacement state. In FIG. 15, N (t−1) ≧ 2NL is established in the displacement state where the counting result is folded. Therefore, as shown in the equation (12), when N (t−1) ≧ 2NL is satisfied, the count result N (t) at the current time t of the signal extraction unit 7 is given a negative sign. The signed count result is N ′ (t).

  On the other hand, N (t−1) <2NL is established in the minute displacement state in which the counting result is not folded in FIGS. Therefore, as shown in the equation (13), when N (t−1) <2NL is satisfied, the count result N (t) at the current time t of the signal extraction unit 7 is given a positive sign. The signed count result is N ′ (t).

The signed count result N ′ (t) is stored in the storage unit 113. The code assigning unit 115 performs the above-described code assigning process at each time (every oscillation period) when the number of MHPs is measured by the signal extracting unit 7.
Note that the condition for establishing equation (12) may be N (t−1)> 2NL, and the condition for establishing equation (13) may be N (t−1) ≦ 2NL.

Next, the period calculation unit 116 calculates the MHP period T from the distance proportional number NL as in the following equation.
T = C / (2 × f × NL) (14)
Here, f is the frequency of the triangular wave, and C is the speed of light.

The carrier wave adjustment unit 112a may adjust the amplitude or frequency of the triangular wave drive current through the laser driver 4 so that the MHP cycle T calculated by the cycle calculation unit 116 becomes a predetermined cycle T0.
In the present embodiment, the amplitude or frequency of the carrier wave can be adjusted even in the case of the object 10 that cannot be stationary. However, the present embodiment is effective when the vibration period of the vibrating object 10 is sufficiently slower than the frequency of the carrier wave (for example, 1/10).

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the first and second embodiments, the photodiode 2 and the current-voltage conversion amplifying unit 5 are used as detection means for detecting an electrical signal including an MHP waveform. However, the MHP waveform is not used without using a photodiode. It is also possible to extract. FIG. 10 is a block diagram showing a configuration of a physical quantity sensor according to the third embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The physical quantity sensor of the present embodiment uses a voltage detection unit 12 as detection means instead of the photodiode 2 and the current-voltage conversion amplification unit 5 of the first and second embodiments.

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

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

  In the first to third embodiments, at least the signal extraction unit 7, the calculation unit 8, and the adjustment unit 11 are realized by, for example, a computer having a CPU, a memory, and an interface, and a program for controlling these hardware resources. can do. The CPU executes the processes described in the first to third embodiments according to the program stored in the memory.

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

It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 1st Embodiment of this invention. It is a wave form diagram showing typically the output voltage waveform of the current-voltage conversion amplification part in the 1st embodiment of the present invention, and the output voltage waveform of a filter part. It is a block diagram which shows an example of a structure of the calculating part in the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the calculating part in the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the adjustment part in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the adjustment part in the 1st Embodiment of this invention. It is a figure for demonstrating the adjustment method of the amplitude of the triangular wave drive current supplied to a semiconductor laser from a laser driver in the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the adjustment part in the 2nd Embodiment of this invention. It is a figure which shows one example of the time change of the count result of the signal extraction part in the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 3rd Embodiment of this invention. It is a figure which shows the compound resonator model of the semiconductor laser in the conventional laser measuring device. It is a figure which shows the relationship between the oscillation wavelength of a semiconductor laser, and the output waveform of a built-in photodiode. It is a block diagram which shows the structure of the conventional distance and speedometer. It is a figure which shows one example of the time change of the oscillation wavelength of a semiconductor laser in the distance and speedometer of FIG. It is a figure for demonstrating the problem of the conventional self-coupling type laser measuring device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplification part, 6 ... Filter part, 7 ... Signal extraction part, 8 ... Calculation part, 9 ... Display part, 10 ... object, 11 ... adjustment part, 12 ... voltage detection part, 80 ... distance / speed calculation part, 81 ... history displacement calculation part, 82 ... storage part, 83 ... state determination part, 84 ... distance / speed determination part, 110 ... Binarization unit, 111... Period measurement unit, 112, 112a ... carrier wave adjustment unit, 113 ... storage unit, 114 ... distance proportional number calculation unit, 115 ... sign addition unit, 116 ... cycle calculation unit.

Claims (8)

A semiconductor laser that emits laser light to the object to be measured;
The semiconductor laser is operated so that a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist. Oscillation wavelength modulation means
Detection means for detecting an electrical signal including an interference waveform generated by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object;
From the information of the interference waveform included in the output signal of the detection means, measurement means for measuring the physical quantity of the measurement object,
The oscillation wavelength of the semiconductor laser is such that the period of the interference waveform when the measurement object is stationary or the average of the period of the predetermined number of interference waveforms measured immediately before adjustment is a predetermined period. a that adjustment means to adjust the amplitude or frequency of the modulation of a carrier,
The measuring means includes
Signal extraction means for counting the number of interference waveforms included in the output signal of the detection means for each of the first oscillation period and the second oscillation period;
Calculation means for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the minimum oscillation wavelength and the maximum oscillation wavelength in the period for counting the number of interference waveforms by the signal extraction means and the counting result of the signal extraction means. a physical quantity sensor, characterized by comprising a. The physical quantity sensor according to claim 1 ,
When the number of the interference waveforms in the first oscillation period and the number of the interference waveforms in the second oscillation period are substantially the same, the adjusting means has a cycle in which the period of the interference waveform is defined in advance. The physical quantity sensor is characterized in that the amplitude or frequency of the carrier wave is adjusted so that The physical quantity sensor according to claim 1 ,
The adjusting means includes
A distance proportional number calculating means for calculating a distance proportional number which is the number of interference waveforms proportional to an average distance between the semiconductor laser and the measurement object by calculating an average value of the number of the interference waveforms;
A period calculating means for calculating a period of the interference waveform from the distance proportional number;
A physical quantity sensor comprising: a carrier wave adjusting unit that adjusts the amplitude or frequency of the carrier wave so that the cycle calculated by the cycle calculating unit is a predetermined cycle. The physical quantity sensor according to any one of claims 1 to 3 ,
The physical period sensor is characterized in that 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. The semiconductor laser is operated such that a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist. Oscillation procedure and
A detection procedure for detecting an electrical signal including an interference waveform caused by a self-coupling effect between laser light emitted from the semiconductor laser and return light from a measurement object;
From the information of the interference waveform included in the output signal obtained by this detection procedure, a measurement procedure for measuring the physical quantity of the measurement target,
The oscillation wavelength of the semiconductor laser is such that the period of the interference waveform when the measurement object is stationary or the average of the period of the predetermined number of interference waveforms measured immediately before adjustment is a predetermined period. and a to that adjustment procedure adjusting the amplitude or frequency of the modulation of a carrier,
The measurement procedure is as follows:
A signal extraction procedure for counting the number of the interference waveforms included in the output signal obtained by the detection procedure for each of the first oscillation period and the second oscillation period;
Arithmetic procedure for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the minimum oscillation wavelength and the maximum oscillation wavelength in the period of counting the number of interference waveforms by this signal extraction procedure and the counting result of the signal extraction procedure physical quantity measuring method characterized by comprising a. The physical quantity measuring method according to claim 5 ,
In the adjustment procedure, when the number of the interference waveforms in the first oscillation period and the number of the interference waveforms in the second oscillation period are substantially the same, the period of the interference waveform at this time is a predetermined period. The physical quantity measurement method is characterized by adjusting the amplitude or frequency of the carrier wave so that The physical quantity measuring method according to claim 5 ,
The adjustment procedure includes:
A distance proportional number calculation procedure for obtaining a distance proportional number that is the number of interference waveforms proportional to the average distance between the semiconductor laser and the measurement object by calculating an average value of the number of the interference waveforms;
A cycle calculation procedure for calculating a cycle of the interference waveform from the distance proportional number;
A physical quantity measuring method comprising: a carrier wave adjusting procedure for adjusting an amplitude or a frequency of the carrier wave so that a cycle calculated by the cycle calculating procedure is a predetermined cycle. In the physical-quantity measuring method of any one of Claims 5 thru | or 7 ,
2. The physical quantity measuring method according to claim 1, wherein 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 measuring method.

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