JP5081778B2 - Vibration amplitude measuring apparatus and vibration amplitude measuring method - Google Patents

Description

  The present invention relates to a vibration amplitude measuring device and a vibration amplitude measuring method for measuring the vibration amplitude of a vibrating object.

Conventionally, a technique for analyzing a vibrating object using a semiconductor laser has been proposed (see, for example, Patent Document 1).
In the measurement apparatus disclosed in Patent Document 1, a laser beam is irradiated onto an object from a semiconductor laser having a fixed oscillation frequency, and a part of reflected light shifted from the Doppler frequency from the object is returned to the semiconductor laser as light. Generate a self-mixing effect. Then, a change in the output of the semiconductor laser caused by the vibration of the object is detected by a photodiode.

  At this time, the Doppler beat wave appearing in the output of the photodiode reverses the inclination according to the direction of the displacement of the object due to the self-mixing effect, and therefore the direction of the displacement of the object can be determined from the inclination of the Doppler beat wave. In the measurement device disclosed in Patent Document 1, object displacement information is obtained by counting the number of Doppler beat waves with the counter circuit while switching between addition and subtraction of the counter circuit in accordance with the direction of the displacement. If the displacement information of the object can be obtained, the vibration amplitude (maximum displacement) of the object can be obtained.

  The inventor has also proposed a wavelength modulation type distance / velocimeter using the self-coupling effect of a semiconductor laser (see Patent Document 2). The configuration of this distance / speed meter is shown in FIG. The distance / velocity meter of FIG. 12 includes a semiconductor laser 201 that emits laser light to an object, a photodiode 202 that converts the optical output of the semiconductor laser 201 into an electrical signal, and a light that is collected from the semiconductor laser 201 to collect the object. 210 irradiates the lens 210 and collects the return light from the object 210 and makes it incident on the semiconductor laser 201. The first oscillation period and the oscillation wavelength continuously increase in the semiconductor laser 201. A laser driver 204 that alternately repeats a second oscillation period that decreases in time, a current-voltage conversion amplifier 205 that converts and amplifies the output current of the photodiode 202 into a voltage, and an output voltage of the current-voltage conversion amplifier 205 A signal extraction circuit 206 that differentiates the signal twice, 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 and 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. 13 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201. In FIG. 13, 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 T is the period of the triangular wave.

  Laser light emitted from the semiconductor laser 201 is collected by the lens 203 and enters the object 210. The light reflected by the object 210 is collected by the lens 203 and enters the semiconductor laser 201. The photodiode 202 converts the optical output of the semiconductor laser 201 into a current. The current-voltage conversion amplifier 205 converts the output current of the photodiode 202 into a voltage and amplifies it, and the signal extraction circuit 206 differentiates the output voltage of the current-voltage conversion amplifier 205 twice. The counting circuit 207 counts the number of mode pop pulses (MHP) included in the output voltage of the signal extraction circuit 206 for each of the first oscillation period P1 and the second oscillation period P2. Based on the minimum oscillation wavelength λa and 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, the arithmetic unit 208 The speed of the object 210 is calculated. According to such a distance / speed meter, the vibration amplitude of the object can be calculated by integrating the calculated speed with the time corresponding to the half cycle of vibration.

Japanese Patent No. 3282746 JP 2006-31080 A

  The measuring apparatus disclosed in Patent Document 1 has a problem that a mechanism for fixing the wavelength of the semiconductor laser with high accuracy is required, and measures only at a very short distance because it is vulnerable to optical disturbance noise. There was a problem that it was not possible.

  In the distance / velocity meter disclosed in Patent Document 2, it is necessary to calculate the velocity of the object in order to calculate the vibration amplitude of the object, but there is a problem that the method of calculating the velocity is complicated. In the distance / velocimeter disclosed in Patent Document 2, there are two types of speed candidate values depending on the magnitude relationship between the distance change rate of the object and the wavelength change rate of the semiconductor laser, and the latest calculated distance value and the immediately preceding value The true value of the speed is selected from the two types of speed candidate values according to the sign change of the difference from the calculated value. However, if the speed of the object (change in distance) is extremely small compared to the resolution of the distance, the sign of the distance difference may be reversed due to noise or the like, and the selection of the speed candidate value may be incorrect. There was a possibility that the calculation accuracy would be lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vibration amplitude measuring device and a vibration amplitude measuring method capable of easily and accurately obtaining the vibration amplitude of an object.

  The vibration amplitude measuring apparatus of the present invention includes a semiconductor laser that emits laser light to a measurement object, 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 such that at least second oscillation periods including at least alternately exist, and self-coupling effect of laser light emitted from the semiconductor laser and return light from the measurement target Detecting means for detecting an electric signal including an interference waveform generated by the signal, and signal extraction for counting the number of the interference waveforms included in the output signal of the detecting means for each of the first oscillation period and the second oscillation period And a distance 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 counting results of the signal extraction means. An interference waveform proportional to the displacement of the object to be measured by calculating an absolute value of a difference between a distance proportional number calculating means for obtaining a proportional number and an average value of the latest count result and the past count result of the signal extracting means. Displacement proportional number calculating means for obtaining a displacement proportional number that is the number of displacements, and displacement direction determining means for determining the displacement direction of the measurement object by comparing the distance proportional number with the latest count result of the signal extracting means Then, based on the determination result of the displacement direction determination means, obtain the sum of the number of displacements per vibration half cycle of the measurement object, and obtain the product of this sum and the average half wavelength of the semiconductor laser to obtain the measurement An amplitude calculating means for calculating the vibration amplitude of the object is provided.

  The vibration amplitude measuring apparatus according to the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period including at least a period in which the oscillation wavelength continuously monotonously increases, and the oscillation wavelength continuously monotonously decreases. The oscillation wavelength modulation means for operating the semiconductor laser so that the second oscillation period including at least the period to be alternately exists, the laser light emitted from the semiconductor laser, and the return light from the measurement object Detection means for detecting an electric signal including an interference waveform caused by the coupling effect, and the number of the interference waveforms included in the output signal of the detection means are counted for each of the first oscillation period and the second oscillation period. By calculating the average value of the signal extraction means and the counting result of the signal extraction means, the number of interference waveforms proportional to the average distance between the semiconductor laser and the measurement object can be obtained. The distance proportional number calculation means for obtaining the distance proportional number and the latest count result of the signal extraction means and the average value of the past count results are compared, and only when the latest count result is larger or the latest count Only when the result is smaller, by calculating the absolute value of the difference between the latest count result of the signal extraction means and the average value of the past count results, the number of interference waveforms proportional to the displacement of the measurement object is calculated. A displacement proportional number calculating means for obtaining a certain displacement proportional number, a displacement direction determining means for determining the displacement direction of the measurement object by comparing the distance proportional number and the latest count result of the signal extracting means, and Based on the discrimination result of the displacement direction discriminating means, the sum of the number of displacements per half vibration period of the measurement object is obtained, and the product of this sum and the average half wavelength of the semiconductor laser is obtained. It is characterized in further comprising an amplitude calculating means for calculating the vibration amplitude of the object.

Further, one configuration example of the vibration amplitude measuring apparatus of the present invention further includes 2 of the distance proportional number calculated using the count result of the signal extraction means one time before and the past count result from the count result. A sign adding unit that adds a positive or negative sign to the latest count result of the signal extraction unit according to a magnitude relationship with a multiple; and the distance proportional number calculation unit includes all count results used for calculating the distance proportional number The displacement proportional number calculation means uses the signed count result to which the sign providing means is added to all the count results used to calculate the displacement proportional number. The addition count result is used.
In one configuration example of the vibration amplitude measuring apparatus of the present invention, the amplitude calculating unit integrates the displacement proportional number over a period of n (n is a positive integer) times the vibration half cycle of the measurement target. By obtaining the product of the sum of the displacement proportional numbers per vibration half cycle and the average half wavelength of the semiconductor laser, obtained by calculating the sum of the displacement proportional numbers and dividing the sum by n. The amplitude is calculated.

  The vibration amplitude measurement method of the present invention includes a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously. Oscillation procedure for operating the semiconductor laser to be alternately present, and detection 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 target Procedure, 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, and a count of the signal extraction procedure 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 results. Displacement for obtaining a displacement proportional number which is the number of interference waveforms proportional to the displacement of the measurement object by calculating the absolute value of the difference between the latest count result of the signal extraction procedure and the average value of the past count results A proportional number calculation procedure, a displacement direction determination procedure for determining the displacement direction of the measurement object by comparing the distance proportional number and the latest count result of the signal extraction procedure, and a determination result of the displacement direction determination procedure Amplitude calculation procedure for calculating the vibration amplitude of the measurement object by obtaining the sum of the displacement proportional number per vibration half cycle of the measurement object based on the above and obtaining the product of this sum and the average half wavelength of the semiconductor laser Are provided.

  The vibration amplitude measurement method of the present invention includes a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously. Oscillation procedure for operating the semiconductor laser to be alternately present, and detection 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 target Procedure, 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, and a count of the signal extraction procedure 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 results. The latest count result of the signal extraction procedure is compared with the average value of the past count results, and the signal extraction procedure is performed only when the latest count result is larger or only when the latest count result is smaller. A displacement proportional number calculation procedure for obtaining a displacement proportional number, which is the number of interference waveforms proportional to the displacement of the measurement object, by calculating an absolute value of a difference between the latest count result and an average of past count results The displacement direction determining procedure for determining the displacement direction of the measurement object by comparing the distance proportional number and the latest counting result of the signal extraction procedure, and the measurement based on the determination result of the displacement direction determining procedure An amplitude calculation procedure for calculating the vibration amplitude of the measurement object by obtaining the sum of the number of displacements proportional to the vibration half cycle of the object and obtaining the product of this sum and the average half wavelength of the semiconductor laser. And it is characterized in Rukoto.

  According to the present invention, it is possible to realize a wavelength modulation type vibration amplitude measuring apparatus using the self-coupling effect of a semiconductor laser. Since the wavelength modulation type measurement device can easily separate the interference waveform and disturbance due to the self-coupling effect, it can be made stronger against disturbance light and can measure the vibration amplitude compared to the conventional fixed wavelength type measurement device. The distance can be increased. In addition, a mechanism for fixing the wavelength of the semiconductor laser with high accuracy is not required. Furthermore, in the present invention, the vibration amplitude of an object can be calculated by a simpler method than a wavelength modulation type distance / velocimeter, and processing such as selecting a candidate velocity value like a distance / velocity meter is unnecessary. Therefore, it is possible to reduce the possibility of a decrease in vibration amplitude calculation accuracy.

  Further, according to the present invention, the latest of the signal extraction means is determined according to the magnitude relationship between the count result one time before the signal extraction means and the double of the distance proportional number calculated using the previous count result. In the distance proportional number calculation means, the displacement proportional number calculation is performed by using the signed count results in which the signs are given to all the count results used for the calculation of the distance proportional number. In the means, the distance change rate of the object to be measured is larger than the oscillation wavelength change rate of the semiconductor laser by using the signed count result given the sign by the sign assigning means for all the count results used for calculating the displacement proportional number. Even in this case, the vibration amplitude of the measurement target can be obtained correctly.

[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 vibration amplitude measuring apparatus according to the first embodiment of the present invention.
The vibration amplitude measuring apparatus in FIG. 1 collects light from a semiconductor laser 1 that emits laser light to an object 10 to be measured, a photodiode 2 that converts the optical output of the semiconductor laser 1 into an electrical signal, and light from the semiconductor laser 1. A lens 3 that radiates and emits light, collects return light from the object 10 and makes it incident on the semiconductor laser 1, a laser driver 4 that serves as an oscillation wavelength modulation unit that drives the semiconductor laser 1, and an output of the photodiode 2 A current-voltage conversion amplification unit 5 that converts current into voltage and amplifies it; 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), an amplitude measurement unit 8 that obtains the vibration amplitude of the object 10 based on the counting result of the signal extraction unit 7, And a display unit 9 for displaying the measurement result of the width measurement section 8.

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

  The laser driver 4 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 1 as an injection current. As a result, the semiconductor laser 1 has a first oscillation period P1 in which the oscillation wavelength continuously increases at a constant change rate in proportion to the magnitude of the injection current, and the oscillation wavelength continuously decreases at a constant change rate. It is driven to alternately repeat the second oscillation period P2. The time change of the oscillation wavelength of the semiconductor laser 1 at this time is as shown in FIG. In the present embodiment, the 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. In these figures, the oscillation waveform (carrier wave) of the semiconductor laser 1 in FIG. 13 is removed from the waveform (modulation wave) in FIG. 2A corresponding to the output of the photodiode 2, and the MHP in FIG. A process of extracting a waveform (interference waveform) is shown.

Next, operations of the signal extraction unit 7 and the amplitude measurement unit 8 will be described. FIG. 3 is a flowchart showing the operations of the signal extraction unit 7 and the amplitude measurement unit 8.
The signal extraction unit 7 counts the number of MHPs included in the output voltage of the filter unit 6 for each of the first oscillation period P1 and the second oscillation period P2 (step S1 in FIG. 3). 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).

Here, the MHP that is a self-coupled signal will be described. As shown in FIG. 4, when the distance from the mirror layer 1013 to the object 10 is L and the oscillation wavelength of the laser is λ, the return light from the object 10 and the optical resonance of the semiconductor laser 1 when the following resonance conditions are satisfied. The laser light in the chamber strengthens and the laser output increases slightly.
L = qλ / 2 (1)
In Formula (1), q is an integer. This phenomenon can be sufficiently observed even if the scattered light from the object 10 is extremely weak, because the apparent reflectance in the resonator of the semiconductor laser 1 increases, causing an amplification effect.

  FIG. 5 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 2 when the oscillation wavelength of the semiconductor laser 1 is changed at a certain rate. When L = qλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the optical resonator becomes 0 ° (the same phase), and the return light and the optical resonator The laser beam is the most intense, and when L = qλ / 2 + λ / 4, the phase difference is 180 ° (reverse phase), and the return light and the laser beam in the optical resonator are most weakened. Therefore, when the oscillation wavelength of the semiconductor laser 1 is changed, a place where the laser output becomes strong and a place where the laser output becomes weak alternately appear repeatedly. When the laser output at this time is detected by the photodiode 2, as shown in FIG. A stepped waveform with a constant period can be obtained. Such a waveform is generally called an interference fringe. Each stepped waveform, that is, each interference fringe is MHP. As described above, when the oscillation wavelength of the semiconductor laser 1 is changed for a certain period of time, the number of MHPs changes in proportion to the measurement distance.

  Next, the amplitude measurement unit 8 calculates the vibration amplitude of the object 10 based on the number of MHPs counted by the signal extraction unit 7. FIG. 6 is a block diagram showing an example of the configuration of the amplitude measuring unit 8. The amplitude measuring unit 8 is proportional to the average distance between the semiconductor laser 1 and the object 10 by calculating the average value of the counting result of the signal extracting unit 7 and the storage unit 80 that stores the counting result of the signal extracting unit 7. The distance proportional number calculation unit 81 for obtaining the number of MHPs (hereinafter referred to as a distance proportional number) NL, the count result of the signal extraction unit 7 one time before, and a count result in the past than this count result is used. A sign adding unit 82 for adding a positive or negative sign to the latest count result of the signal extraction unit 7 according to the magnitude relationship with the double of the distance proportional number NL, and the latest signed count result and the past signed count result. A displacement proportional number calculation unit 83 for obtaining the number of MHPs proportional to the displacement of the object 10 (hereinafter referred to as a displacement proportional number) NV by calculating an absolute value of a difference from the average value of the distance, and a distance proportional number calculation unit Distance proportional number N obtained by 81 Is compared with the count result of the signal extraction unit 7 to obtain a sum of a displacement direction discriminating unit 84 for discriminating the displacement direction of the object 10 and a displacement proportional number NV per vibration half cycle of the object 10. An amplitude calculation unit 85 that calculates the vibration amplitude of the object 10 by calculating the product of the average half wavelength of the semiconductor laser 1.

  The counting result of the signal extraction unit 7 is stored in the storage unit 80 of the amplitude measurement unit 8. The distance proportional number calculation unit 81 of the amplitude measurement unit 8 calculates the distance proportional number NL from the count result of the signal extraction unit 7 (step S2 in FIG. 3). FIG. 7 is a diagram for explaining the operation of the distance proportional number calculation unit 81, and is a diagram showing the time change of the counting result of the signal extraction unit 7. In FIG. 7, 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 2, the state of the object 10 at this time is a minute displacement state.

  As is apparent from FIG. 13, 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 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 81 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 (2)

  In equation (2), 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 (2) 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 81 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
... (3)

However, equations (2) and (3) are equations used at the beginning of measurement of vibration amplitude. From the middle, the distance proportional number NL is calculated by the following equation using a signed count result described later instead of equation (2). To do.
NL = {N ′ (t−2) + N ′ (t−3)} / 2 (4)
N ′ (t−2) is a count result with a sign after performing a later-described code addition process on the count result N (t−2) two times before, and N ′ (t−3) is a count result three times before. It is a count result with a code | symbol after performing a code | symbol provision process to N (t-3). Formula (4) is used after the count result N (t) at the current time t becomes the seventh count result from the start of the measurement of the number of MHPs.

Further, when using the equation (3) at the beginning of the measurement, the distance proportional number NL is calculated from the middle using the following equation using the signed count result instead of the equation (3).
NL = {N ′ (t−2m−1) + N ′ (t−2m) +... + N ′ (t−2)} / 2m
... (5)
The expression (5) 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 80. The distance proportional number calculation unit 81 performs the processing for calculating the distance proportional number NL as described above at every time (every oscillation period) when the number of MHPs is measured by the 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 82 counts the signal extracting 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) (step S3 in FIG. 3). Specifically, the sign assigning unit 82 executes the following expression.
If N (t−1) ≧ 2NL Then N ′ (t) → −N (t) (6)
If N (t−1) <2NL Then N ′ (t) → + N (t) (7)

  FIG. 8 is a diagram for explaining the operation of the code assigning unit 82, and is a diagram showing the time change of the counting result of the signal extracting unit 7. 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 becomes a shape in which the negative waveform shown by 80 in FIG. The time variation of the counting result Nd takes a form in which the negative waveform indicated by 81 in FIG. 8 is folded back to the positive side. In Patent Document 2, the state of the object 10 in the portion where the counting result is folded is referred to as a 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 vibration amplitude in the vibration including the displacement state, it is determined whether the object 10 is in the displacement state or the minute displacement state, and when 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 a locus indicated by 80 and 81 in FIG. Expressions (6) and (7) are expressions for determining whether the object 10 is in a displacement state or a minute displacement state. In the displacement state in which the counting result is folded in FIG. 8, N (t−1) ≧ 2NL is established. Therefore, as shown in Expression (6), when N (t−1) ≧ 2NL is established, 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 folding of the counting result does not occur in FIGS. Therefore, as shown in Expression (7), when N (t−1) <2NL is satisfied, a value obtained by adding a positive sign to the counting result N (t) at the current time t of the signal extraction unit 7 The signed count result is N ′ (t).

The signed count result N ′ (t) is stored in the storage unit 80. The code assigning unit 82 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.
It should be noted that the condition for establishing equation (6) may be N (t−1)> 2NL, and the condition for establishing equation (7) may be N (t−1) ≦ 2NL.

Subsequently, the displacement proportional number calculation unit 83 calculates the signed count result N ′ (t) and the average value of the even-numbered signed count results calculated up to one time before the current time t as shown in the following equation. By calculating the absolute value of the difference, the displacement proportional number NV is obtained (step S4 in FIG. 3).
NV = | N ′ (t) − {N ′ (t−2m) + N ′ (t−2m + 1) +.
+ N ′ (t−1)} / 2m | (8)

The displacement proportional number NV is stored in the storage unit 80. The displacement proportional number calculation unit 83 performs the calculation process of the displacement proportional number NV as described above at every time (every oscillation period) when the number of MHPs is measured by the signal extraction unit 7.
When the number of signed count results used for calculating the average value is sufficiently large, the average of the signed count result N ′ (t) and the odd-numbered signed count results calculated up to one time before the current time t The displacement proportional number NV may be calculated by calculating the absolute value of the difference from the value.

  Next, the displacement direction discriminating unit 84 discriminates the displacement direction of the object 10 by comparing the distance proportional number NL obtained by the distance proportional number calculating unit 81 with the count result of the signal extracting unit 7 (step in FIG. 3). S5). The displacement direction discriminating unit 84 determines that the counting result Nd when the oscillation wavelength of the semiconductor laser 1 is increasing is larger than the distance proportional number NL or the counting result Nd when the oscillation wavelength of the semiconductor laser 1 is decreasing. If it is smaller than the distance proportional number NL, it is determined that the moving direction of the object 10 is a direction approaching the semiconductor laser 1, and the counting result Nu is smaller than the distance proportional number NL or the counting result Nd is larger than the distance proportional number NL. In this case, it is determined that the moving direction of the object 10 is a direction away from the semiconductor laser 1. The displacement direction determination unit 84 performs the displacement direction determination process as described above at every time (every oscillation period) when the number of MHPs is measured by the signal extraction unit 7.

Next, the amplitude calculator 85 integrates the displacement proportional number NV over the period of the vibration half cycle of the object 10 to obtain the sum ΣNV of the displacement proportional number NV per vibration half cycle, and the displacement is expressed as shown in the following equation. The vibration amplitude A of the object 10 is calculated by obtaining the product of the sum ΣNV of the proportional number NV and the average half wavelength λ / 2 of the semiconductor laser 1 (step S6 in FIG. 3).
A = ΣNV × (λ / 2) (9)
λ = (λb + λa) / 2 (10)

The vibration half cycle of the object 10 can be obtained from the determination result of the displacement direction determination unit 84. That is, the time from when the moving direction of the object 10 is changed to the direction away from the direction approaching the semiconductor laser 1 to the next approaching direction is the vibration half cycle. Alternatively, the time from when the moving direction of the object 10 changes from the direction moving away from the semiconductor laser 1 to the approaching direction to the next moving away is the vibration half cycle. The amplitude calculator 85 performs the vibration amplitude calculation process as described above for each vibration half cycle.
The display unit 9 displays the value of the vibration amplitude A calculated by the amplitude measurement unit 8.

  As described above, in this embodiment, the wavelength modulation type vibration amplitude measuring apparatus using the self-coupling effect of the semiconductor laser is used. In the wavelength modulation type measuring apparatus, since the MHP generation period can be given regularity by modulating the laser oscillation wavelength, the MHP and the disturbance can be easily separated. For this reason, since it becomes strong against disturbance light compared with the measuring device disclosed by patent document 1, the distance which can measure a vibration amplitude can be lengthened. In addition, a mechanism for fixing the wavelength of the semiconductor laser with high accuracy is not required.

  Furthermore, in the present embodiment, the vibration amplitude of the object can be calculated by a simpler method than the distance / speed meter disclosed in Patent Document 2. Further, in the present embodiment, processing such as selecting a speed candidate value as in the distance / velocity meter disclosed in Patent Document 2 is not required, so that the possibility of causing a decrease in vibration amplitude calculation accuracy is reduced. be able to.

[Second Embodiment]
In the first embodiment, the vibration amplitude of the object 10 is calculated for each vibration half cycle, but may be calculated for each period that is an integral multiple of the vibration half cycle. When obtaining the vibration amplitude A of the object 10 in a period of n (n is a positive integer) times the vibration half cycle, the amplitude calculation unit 85 integrates the displacement proportional number NV over a period of n times the vibration half cycle. The sum ΣNV of the displacement proportional number NV is obtained, and the sum of the displacement proportional number NV per vibration half cycle (ΣNV) / n is obtained by dividing this ΣNV by n, and the sum of the displacement proportional number NV as shown in the following equation: The vibration amplitude A of the object 10 is calculated by calculating the product of (ΣNV) / n and the average half wavelength λ / 2 of the semiconductor laser 1.
A = (ΣNV) / n × (λ / 2) (11)

  In this way, the vibration amplitude can be calculated every period that is an integral multiple of the vibration half cycle of the object 10. It goes without saying that the first embodiment is a case where n = 1.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. Also in the present embodiment, the configuration of the vibration amplitude measuring apparatus is the same as in the first and second embodiments, and therefore, description will be made using the reference numerals in FIGS. In the present embodiment, the processes after step S4 in FIG. 3 are different from those in the first and second embodiments.

  The displacement proportional number calculation unit 83 of the amplitude measurement unit 8 calculates the average value of the signed count results N ′ (t) at the current time t and the even-numbered signed count results calculated up to one time before the current time t { N ′ (t−2m) + N ′ (t−2m + 1) +... + N ′ (t−1)} / 2m and only when the signed count result N ′ (t) is larger The displacement proportional number NV is calculated by (8) (step S4 in FIG. 3). Alternatively, the displacement proportional number calculation unit 83 calculates the average value of the signed count result N ′ (t) and the even-numbered signed count result {N ′ (t−2m) + N ′ (t−2m + 1) +. '(T-1)} / 2m may be compared, and the displacement proportional number NV may be calculated only when the signed count result N' (t) is smaller.

Similar to the first embodiment, when the number of signed count results used to calculate the average value is sufficiently large, the average value may be obtained from the odd number of signed count results.
The operation of the displacement direction determination unit 84 is the same as that of the first embodiment.

  The amplitude calculation unit 85 obtains a sum ΣNV of the displacement proportional number NV by integrating the displacement proportional number NV over a period of n times the vibration half cycle, and divides this ΣNV by n to obtain the displacement proportional per vibration half cycle. By obtaining the sum (ΣNV) / n of the number NV and obtaining the product of the sum (ΣNV) / n of the displacement proportional number NV and the average half wavelength λ / 2 of the semiconductor laser 1 as shown in Equation (11), The vibration amplitude A of the object 10 is calculated (step S6 in FIG. 3).

  In the first to third embodiments, the calculation accuracy of the average value of the count results used in steps S2 to S4 increases as the count result used for calculating these average values increases, but the vibration amplitude increases. Since the possibility of erroneous calculation increases as the time increases, it is preferable to gradually increase the number of count results used for calculating the average value only when obtaining high accuracy.

  Hereinafter, a case where an erroneous calculation occurs due to counting results being returned will be described with reference to FIG. When the calculation result of the distance proportional number NL includes the counted result (the portion 90 in FIG. 9), the distance proportional number NL is erroneously calculated as 91 in FIG. 9, and the count result N (t−1) is originally Even if it is larger than twice the distance proportional number NL, it does not become twice or more than the erroneously calculated distance proportional number NL, and therefore N (t) is not determined as a folded count result. Even if an erroneous calculation has occurred, if there is a case where the counted result returned in the calculation of the distance proportional number NL is not included (92 portion in FIG. 9), the distance proportional number NL becomes a correct value, and thereafter The returned counting result is correctly calculated. Therefore, as shown in FIG. 10, when the count result N smaller than the distance proportional number NL is generated three times in succession (the portion 93 in FIG. 10), the distance proportional number calculation unit 81 displays the distance proportional number NL. The average value of the first two counting results (94 and 95 in FIG. 10) is set as the distance proportional number NL.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the photodiode 2 and the current-voltage conversion amplification 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. 11 is a block diagram showing a configuration of a vibration amplitude measuring apparatus according to the fourth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The vibration amplitude measuring apparatus according to the present embodiment uses a voltage detector 11 as detection means instead of the photodiode 2 and the current-voltage conversion amplifier 5 according to the first to third embodiments.

  The voltage detector 11 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 11. Other configurations of the vibration amplitude measuring apparatus are the same as those in the first to third embodiments.
Thus, in this embodiment, the MHP waveform can be extracted without using a photodiode, and the parts of the vibration amplitude measuring device can be reduced as compared with the first to third embodiments. The cost of the vibration amplitude measuring device can be reduced. In this embodiment, since no photodiode is used, the influence of disturbance light can be eliminated.

  In the present embodiment, it is preferable that the drive current supplied from the laser driver 4 to the semiconductor laser 1 is controlled near the laser oscillation threshold current. Thereby, it becomes easy to extract MHP from the voltage between the terminals of the semiconductor laser 1.

  In the first to fourth embodiments, at least the signal extraction unit 7 and the amplitude measurement unit 8 are realized by, for example, a computer having a CPU, a storage device, and an interface, and a program for controlling these hardware resources. Can do. The CPU executes the processes described in the first to fourth embodiments in accordance with a program stored in the storage device.

  The present invention can be applied to a technique for measuring the vibration amplitude of an object using a laser.

It is a block diagram which shows the structure of the vibration amplitude measuring device 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 flowchart which shows operation | movement of the signal extraction part and amplitude measurement part in the 1st Embodiment of this 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 one example of a structure of the amplitude measurement part in the 1st 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 1st Embodiment of this invention. It is a figure which shows the other example of the time change of the count result of the signal extraction part in the 1st Embodiment of this invention. It is a figure for demonstrating the problem in the 1st, 2nd embodiment of this invention. It is a figure for demonstrating the detection method of the miscalculation in the 1st, 2nd embodiment of this invention. It is a block diagram which shows the structure of the vibration amplitude measuring device which concerns on the 4th Embodiment of this invention. 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.

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 ... Amplitude measurement part, 9 ... Display part, DESCRIPTION OF SYMBOLS 10 ... Object, 11 ... Voltage detection part, 80 ... Memory | storage part, 81 ... Distance proportional number calculation part, 82 ... Sign assigning part, 83 ... Displacement proportional number calculation part, 84 ... Displacement direction discrimination | determination part, 85 ... Amplitude calculation part.

Claims (8)

A semiconductor laser that emits laser light to a measurement object;
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;
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;
A distance proportional number calculating means for calculating 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 counting results of the signal extracting means;
Displacement proportionality is obtained by calculating the absolute value of the difference between the latest count result of the signal extraction means and the average value of past count results, thereby obtaining a displacement proportional number that is the number of interference waveforms proportional to the displacement of the measurement object. A number calculating means;
A displacement direction discriminating means for discriminating the displacement direction of the measurement object by comparing the distance proportional number and the latest counting result of the signal extracting means;
Based on the discrimination result of the displacement direction discriminating means, a sum of the number of displacements per vibration half cycle of the measurement object is obtained, and a product of this sum and the average half wavelength of the semiconductor laser is obtained. A vibration amplitude measuring device comprising amplitude calculating means for calculating vibration amplitude. A semiconductor laser that emits laser light to a measurement object;
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;
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;
A distance proportional number calculating means for calculating 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 counting results of the signal extracting means;
The latest count result of the signal extraction means is compared with the average value of the past count results, and only when the latest count result is larger or only when the latest count result is smaller, the signal extraction means A displacement proportional number calculating means for obtaining a displacement proportional number that is the number of interference waveforms proportional to the displacement of the measurement object by calculating an absolute value of a difference between the latest count result and an average value of past count results;
A displacement direction discriminating means for discriminating the displacement direction of the measurement object by comparing the distance proportional number and the latest counting result of the signal extracting means;
Based on the discrimination result of the displacement direction discriminating means, a sum of the number of displacements per vibration half cycle of the measurement object is obtained, and a product of this sum and the average half wavelength of the semiconductor laser is obtained. A vibration amplitude measuring device comprising amplitude calculating means for calculating vibration amplitude. In the vibration amplitude measuring device according to claim 1 or 2,
Further, according to the magnitude relationship between the count result one time before the signal extraction means and a double of the distance proportional number calculated using the past count results from the count result, the latest of the signal extraction means. A sign providing means for adding a positive or negative sign to the counting result;
The distance proportional number calculation means uses a signed count result in which a sign is given by the sign assigning means to all count results used to calculate the distance proportional number,
The vibration proportionality measuring device, wherein the displacement proportional number calculating means uses a signed count result in which a sign is given by the sign assigning means to all count results used for calculating the displacement proportional number. In the vibration amplitude measuring device according to claim 1 or 2,
The amplitude calculating unit integrates the displacement proportional number over a period of n (n is a positive integer) times the vibration half cycle of the measurement target to obtain a sum of the displacement proportional number, and divides the sum by n. A vibration amplitude measuring apparatus that calculates the vibration amplitude of the measurement object by calculating the product of the sum of the number of displacement proportional per vibration half cycle and the average half wavelength of the semiconductor laser. 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 procedure
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;
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;
By calculating the average value of the counting results of this signal extraction procedure, 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;
Displacement proportionality is obtained by calculating the absolute value of the difference between the latest count result of the signal extraction procedure and the average value of past count results, thereby obtaining a displacement proportional number that is the number of interference waveforms proportional to the displacement of the measurement object. Counting procedure,
A displacement direction determination procedure for determining the displacement direction of the measurement object by comparing the distance proportional number and the latest counting result of the signal extraction procedure;
Based on the determination result of the displacement direction determination procedure, the sum of the displacement proportional number per vibration half cycle of the measurement object is obtained, and the product of the sum and the average half wavelength of the semiconductor laser is obtained, thereby obtaining the measurement object. A vibration amplitude measurement method comprising: an amplitude calculation procedure for calculating a vibration amplitude. 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 procedure
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;
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;
By calculating the average value of the counting results of this signal extraction procedure, 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;
The latest count result of the signal extraction procedure is compared with the average value of the past count results, and only when the latest count result is larger or only when the latest count result is smaller, the signal extraction procedure A displacement proportional number calculation procedure for calculating a displacement proportional number that is the number of interference waveforms proportional to the displacement of the measurement object by calculating an absolute value of a difference between the latest count result and an average value of past count results;
A displacement direction determination procedure for determining the displacement direction of the measurement object by comparing the distance proportional number and the latest counting result of the signal extraction procedure;
Based on the determination result of the displacement direction determination procedure, the sum of the displacement proportional number per vibration half cycle of the measurement object is obtained, and the product of the sum and the average half wavelength of the semiconductor laser is obtained, thereby obtaining the measurement object. A vibration amplitude measurement method comprising: an amplitude calculation procedure for calculating a vibration amplitude. In the vibration amplitude measuring method according to claim 5 or 6,
Further, between the distance proportional number calculation procedure and the displacement proportional number calculation procedure, the distance proportionality calculated using a count result one time before the signal extraction procedure and a past count result from the count result. A sign assigning procedure for assigning a positive or negative sign to the latest count result of the signal extraction procedure according to a magnitude relationship with a double of the number;
The distance proportional number calculation procedure uses a signed count result in which signs are given by the sign assigning means to all count results used for calculating the distance proportional number,
The displacement proportional number calculation procedure uses a signed count result in which a sign is given by the sign assigning procedure to all count results used for calculating the displacement proportional number. In the vibration amplitude measuring method according to claim 5 or 6,
In the amplitude calculation procedure, the displacement proportional number is integrated over a period of n (n is a positive integer) times the vibration half cycle of the measurement object to obtain a sum of the displacement proportional numbers, and the sum is divided by n. A vibration amplitude measuring method, wherein the vibration amplitude of the measurement object is calculated by calculating the product of the sum of the number of displacement proportional per vibration half cycle and the average half wavelength of the semiconductor laser.

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