JP2010078560A - Device and method for measuring oscillation frequency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce oscillation frequency to which response can be made, without increasing a memory capacity. <P>SOLUTION: A device for measuring the oscillation frequency includes a semiconductor laser 1 which radiates laser light, a laser driver 4 which makes the laser 1 operate so that a first oscillation period wherein an oscillation wavelength increases continuously and a second oscillation period wherein the oscillation wavelength decreases continuously may exist alternately, a photodiode 2 and a current-voltage conversion amplification part 5 which detect an electric signal containing an interference waveform produced by a self-combination effect of the laser light radiated from the laser 1 with an optical return from an object 11, a signal extraction part 7 which counts the number of the interference waveforms contained in an output of the current-voltage conversion amplification part 5, a frequency measuring part 8 which determines the oscillation frequency of the object 11, based on the result of counting of the signal extraction part 7, and a dormant period setting part 10 which is capable of setting a dormant period between measuring points where the number of interference waveforms is counted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vibration frequency measuring device and a vibration frequency measuring method for measuring a vibration frequency 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. If the direction of displacement of the object can be determined, the vibration frequency of the object can be obtained from the period of displacement.
FIG. 22A shows an example of a Doppler beat wave that appears in the output of the photodiode in the measuring device disclosed in Patent Document 1, and FIG. 22B shows the direction of displacement of the object from the slope of the Doppler beat wave. An example of the output voltage of the direction discriminating circuit is shown.

  In the measurement device disclosed in Patent Document 1, since noise is actually present in the Doppler beat wave, it may be very difficult to determine the inclination of the Doppler beat wave, and when the acceleration of vibration of the object is small ( For example, when the vibration frequency is low), the speed of the object is low near the maximum point of the vibration amplitude, so that asymmetry hardly occurs. The actual waveform of the Doppler beat wave is a triangle that is almost symmetrical with respect to time. When the velocity of the object displacement is low, the Doppler beat wave becomes small, and the slope when the intensity of the Doppler beat wave increases and the slope when the intensity decreases are the same in absolute value. It cannot be determined. As a result, the measuring apparatus disclosed in Patent Document 1 has a problem that the error in vibration frequency measurement is very large.

  On the other hand, the inventor has proposed a wavelength modulation type laser measuring instrument using the self-coupling effect of a semiconductor laser (see Patent Document 2). The configuration of this laser measuring instrument is shown in FIG. 23 includes a semiconductor laser 201 that emits laser light to an object 210, a photodiode 202 that converts the light output of the semiconductor laser 201 into an electrical signal, and a light that is collected from the semiconductor laser 201 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 Is extracted twice, and a counting circuit 207 that counts the number of MHPs included in the output voltage of the signal extraction circuit 206 , Having an arithmetic unit 208 which calculates the speed of the distance and the object 210 with the object 210, a display device 209 for displaying the calculation result of the arithmetic unit 208.

  The laser driver 204 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 201 as an injection current. Accordingly, the semiconductor laser 201 alternately repeats the first oscillation period in which the oscillation wavelength continuously increases at a constant change rate and the second oscillation period in which the oscillation wavelength continuously decreases at a constant change rate. To be driven. FIG. 24 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201. In FIG. 24, P1 is the first oscillation period, P2 is the second oscillation period, λa is the minimum value of the oscillation wavelength in each period, λb is the maximum value of the oscillation wavelength in each period, and Tt is the period of the triangular wave.

  Laser light emitted from the semiconductor laser 201 is collected by the lens 203 and enters the object 210. The light reflected by the object 210 is collected by the lens 203 and enters the semiconductor laser 201. The photodiode 202 converts the optical output of the semiconductor laser 201 into a current. The current-voltage conversion amplifier 205 converts the output current of the photodiode 202 into a voltage and amplifies it, and the signal extraction circuit 206 differentiates the output voltage of the current-voltage conversion amplifier 205 twice. The counting circuit 207 counts the number of mode pop pulses (MHP) included in the output voltage of the signal extraction circuit 206 for each of the first oscillation period P1 and the second oscillation period P2. Based on the minimum oscillation wavelength λa and 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. If the number of MHPs is measured using such a self-coupled laser measuring device technique, the vibration frequency of the object can be calculated from the number of MHPs.

Japanese Patent No. 3282746 JP 2006-31080 A

According to the self-coupled laser measuring instrument disclosed in Patent Document 2, the measurement accuracy of the vibration frequency of the object can be improved as compared with the measuring apparatus disclosed in Patent Document 1.
However, in the laser measuring instrument disclosed in Patent Document 2, it is necessary to perform signal processing over a time equal to or longer than the half cycle of the wavelength modulation carrier wave of the semiconductor laser (half cycle of the triangular wave in FIG. 24) in order to measure the number of MHPs. Therefore, in order to calculate the vibration frequency of the object, measurement data for the number of MHPs of at least 10 points per one vibration period of the object is required. For this reason, when the vibration frequency of the object is lowered and the vibration cycle is lengthened, there is a problem that the time required to obtain 10 points of measurement data becomes long and a huge memory capacity is required.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a vibration frequency measuring device and a vibration frequency measuring method that can reduce the vibration frequency that can be handled without increasing the memory capacity. And

The vibration frequency measuring apparatus of the present invention includes 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 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 Between the measuring means, the frequency measuring means for obtaining the vibration frequency of the measurement object based on the counting result of the signal extracting means, and the respective measurement points for measuring the number of the interference waveforms. Is characterized in further comprising an idle period setting means capable of setting the stop period.
In addition, one configuration example of the vibration frequency measurement device according to the present invention further includes a sequential process in which the signal extraction unit and the frequency measurement unit execute a process each time the interference waveform data is obtained; A process in which data is accumulated by the signal extraction means, and can be switched to one of batch processes in which the signal extraction means and the frequency measurement means execute processing when the data amount reaches a predetermined amount It is characterized by comprising switching means.
Further, in one configuration example of the vibration frequency measuring device according to the present invention, the pause period setting means sets the pause period in accordance with a pause period setting instruction signal input from the outside.
Further, in one configuration example of the vibration frequency measuring device according to the present invention, the process switching means switches between the sequential process and the batch process in accordance with a process switching instruction signal input from the outside. is there.

  Further, in one configuration example of the vibration frequency measuring device of the present invention, the frequency measuring means compares the count results of the first and second oscillation periods that are temporally adjacent to each other, and calculates the count results. Binarization means for binarization, binarization output period measurement means for measuring the period of the binarization output outputted from the binarization means, and constant from the measurement result of the binarization output period measurement means This is a representative value of the binarized output cycle frequency distribution creating means for creating the binarized output cycle frequency distribution in time and the binarized output cycle distribution from the binarized output cycle frequency distribution. A reference period calculating means for calculating a reference period, and a binary value for counting the number of pulses of the binarized output in a period of the same fixed period as the period for which the binarized output period frequency distribution creating means is a target of the frequency distribution creation A binarized output counting means and the binarized output From the frequency distribution of the period, the sum Ns of the frequencies of the class that is less than the first predetermined number of times of the reference period and the sum Nw of the frequencies of the class that are more than the second predetermined number of times of the reference period are obtained, The correction means for correcting the counting result of the binarized output counting means based on the frequencies Ns and Nw, and the vibration frequency of the measuring object is calculated based on the counting result corrected by the correcting means and the predetermined time. It comprises a frequency calculation means.

  Further, in one configuration example of the vibration frequency measuring device of the present invention, the frequency measuring means compares the count results of the first and second oscillation periods that are temporally adjacent to each other, and calculates the count results. Binarization means for binarization, binarization output period measurement means for measuring the period of a predetermined number of pulses of the binarization output outputted from the binarization means, and a fixed number of the binarization outputs A binarized output period frequency distribution creating means for creating a frequency distribution of the binarized output period from the measurement result of the binarized output period measuring means performed on the pulse, and a binarized output period A reference period calculating means for calculating a reference period which is a representative value of the distribution of the binarized output periods from the frequency distribution, and a sum of the periods of the binarized outputs from the measurement result of the binarized output period measuring means. Periodic sum calculation means for calculating and the binary value From the frequency distribution of the output period, a sum Ns of class frequencies that is not more than a first predetermined number of times of the reference period and a sum Nw of class frequencies that are not less than a second predetermined number of times of the reference period are obtained. A correcting means for correcting the fixed number based on the frequencies Ns and Nw, a vibration frequency of the measurement object based on a sum corrected by a value corrected by the correcting means and a period calculated by the period sum calculating means. It is characterized by comprising frequency calculating means for calculating.

Further, in one configuration example of the vibration frequency measuring device of the present invention, the pause period setting means includes a predetermined number of the binarized outputs in the data capacity that can be processed by the signal extracting means and the frequency measuring means. When the data of the interference waveform corresponding to the pulse of the number cannot be processed, the pause period is set so that the data capacity includes the data of the interference waveform corresponding to the predetermined number of pulses of the binarized output. A pause period increase setting means for setting the length of the pause period, and the binarized output when the minimum required number of counting results of the interference waveform are not included in one cycle of the binarized output The period is a pause period reduction setting means for shortening the pause period so that the minimum necessary number of counting results of the interference waveform are included in one cycle.
Further, in one configuration example of the vibration frequency measuring device according to the present invention, the processing switching means may include a counting result of the minimum necessary number of the interference waveforms in one cycle of the binarized output. The sequential processing is switched to batch processing.

  The vibration frequency 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 And 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 the signal extraction procedure. It is possible to set a pause period between the frequency measurement procedure for obtaining the vibration frequency of the measurement object based on the counted result and each measurement point for measuring the number of the interference waveforms It is characterized in further comprising a stop period setting procedure.

  According to the present invention, by providing a pause period setting means capable of setting a pause period between each measurement point for measuring the number of interference waveforms, even when the vibration frequency of the measurement object is low, It becomes possible to perform signal processing over a period of one or more periods of vibration, and to calculate the vibration frequency. As a result, according to the present invention, the vibration frequency that can be dealt with can be reduced without increasing the memory capacity.

  Further, in the present invention, the vibration frequency can be calculated even when the vibration frequency of the measurement target is high by providing the process switching means capable of switching to either the sequential process or the batch process.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the vibration frequency measuring apparatus according to the first embodiment of the present invention.
The vibration frequency measuring device in FIG. 1 collects light from a semiconductor laser 1 that emits laser light to an object 11 to be measured, a photodiode 2 that converts the light 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 11 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), and a frequency measurement unit that obtains the vibration frequency of the object 11 based on the counting result of the signal extraction unit 7 When includes a display unit 9 for displaying the measurement result of the frequency measurement unit 8, and a pause period setting unit 10 capable of setting the dead time between each measurement point for measuring the number of MHP.

  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 11. The light reflected by the object 11 is collected by the lens 3 and enters the semiconductor laser 1. However, condensing by the lens 3 is not essential. The photodiode 2 is disposed in the semiconductor laser 1 or in the vicinity thereof, and converts the optical output of the semiconductor laser 1 into a current. The current-voltage conversion amplification unit 5 converts the output current of the photodiode 2 into a voltage and amplifies it.

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

Next, operations of the signal extraction unit 7 and the frequency measurement unit 8 will be described. FIG. 3 is a flowchart showing the operations of the signal extraction unit 7 and the frequency 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 be composed of a counter that samples the MHP waveform with a sampling clock and counts the number of MHPs, or uses MFT sampling data from the MHP sampling data using FFT (Fast Fourier Transform). The number of MHPs per hour) may be measured. The frequency of the sampling clock is assumed to be sufficiently higher than the highest frequency that MHP can take.

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 11 is L and the oscillation wavelength of the laser is λ, the return light from the object 11 and the optical resonance of the semiconductor laser 1 are satisfied when the following resonance conditions are satisfied. The laser light in the chamber strengthens and the laser output increases slightly.
L = qλ / 2 (1)
In Formula (1), q is an integer. This phenomenon can be sufficiently observed even if the scattered light from the object 11 is very 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 frequency measurement unit 8 calculates the vibration frequency of the object 11 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 frequency measuring unit 8. The frequency measurement unit 8 is output from the storage unit 80 that stores the count result of the signal extraction unit 7, the binarization unit 81 that binarizes the count result of the signal extraction unit 7, and the binarization unit 81. A cycle measuring unit 82 that measures the cycle of the binarized output, a frequency distribution creating unit 83 that creates a frequency distribution of the binarized output cycle, and a reference cycle that is a representative value of the binarized output cycle distribution A reference period calculating unit 84 for calculating, a counter 85 serving as a binarized output counting means for counting the number of pulses of the binarized output, a correcting unit 86 for correcting the counting result of the counter 85, and the corrected counting result And a frequency calculation unit 87 that calculates the vibration frequency of the object 11 based on the frequency.

  The counting result of the signal extraction unit 7 is stored in the storage unit 80 of the frequency measurement unit 8. The binarization unit 81 of the frequency measurement unit 8 binarizes the count result of the signal extraction unit 7 stored in the storage unit 80 (step S2 in FIG. 3). FIG. 7 is a diagram for explaining the operation of the binarization unit 81, FIG. 7A is a diagram showing a change over time of the oscillation wavelength of the semiconductor laser 1, and FIG. 7B is a count of the signal extraction unit 7. FIG. 7C is a diagram illustrating the time change of the result, and FIG. 7C is a diagram illustrating the output D (t) of the binarization unit 81. In FIG. 7B, Nu is the counting result of the first oscillation period P1, and Nd is the counting result of the second oscillation period P2.

The binarization unit 81 compares the count results Nu and Nd in two temporally adjacent oscillation periods P1 and P2, and binarizes these count results. Specifically, the binarizing unit 81 executes the following expression.
If Nu (t) ≧ Nd (t−1) then D (t) = 1 (2)
If Nu (t) <Nd (t-1) then D (t) = 0 (3)
If Nd (t) ≦ Nu (t−1) then D (t) = 1 (4)
If Nd (t)> Nu (t-1) then D (t) = 0 (5)

  In Expressions (2) to (5), (t) represents the number of MHPs measured at the current time t, and (t−1) represents the MHP measured one time before the current time t. It represents a number. Equations (2) and (3) are obtained when the count result at the current time t is the count result Nu of the first oscillation period P1 and the previous count result is the count result Nd of the second oscillation period P2. is there. In this case, the binarization unit 81 sets the output D (t) at the current time t to “1” if the count result Nu (t) at the current time t is equal to or greater than the previous count result Nd (t−1). ”(High level), and when the count result Nu (t) at the current time t is smaller than the previous count result Nd (t−1), the output D (t) at the current time t is set to“ 0 ”(low). Level).

  Equations (4) and (5) are obtained when the count result at the current time t is the count result Nd of the second oscillation period P2, and the previous count result is the count result Nu of the first oscillation period P1. is there. In this case, the binarization unit 81 sets the output D (t) at the current time t to “1” if the count result Nd (t) at the current time t is equal to or less than the previous count result Nu (t−1). When the count result Nd (t) at the current time t is larger than the count result Nu (t−1) of the previous time, the output D (t) at the current time t is set to “0”.

  Thus, the counting result of the signal extraction unit 7 is binarized. The output D (t) of the binarization unit 81 is stored in the storage unit 80. The binarization unit 81 performs the above binarization process at each time (every oscillation period) when the number of MHPs is measured by the signal extraction unit 7.

  Binarizing the counting result of the signal extraction unit 7 means determining the direction of displacement of the object 11. That is, when the counting result Nu when the oscillation wavelength of the semiconductor laser 1 is increasing is equal to or larger than the counting result Nd when the oscillation wavelength is decreasing (D (t) = 1), the moving direction of the object 11 is When the counting result Nu is smaller than the counting result Nd (D (t) = 0), the moving direction of the object 11 is a direction away from the semiconductor laser 1. Therefore, basically, if the cycle of the binarized output shown in FIG. 7C can be obtained, the vibration frequency of the object 11 can be calculated.

  The period measuring unit 82 measures the period of the binarized output D (t) stored in the storage unit 80 (step S3 in FIG. 3). FIG. 8 is a diagram for explaining the operation of the period measurement unit 82. In FIG. 8, H1 is a threshold value for detecting the rising edge of the binarized output D (t), and H2 is a threshold value for detecting the falling edge of the binarized output D (t).

  The period measuring unit 82 detects the rising of the binarized output D (t) by comparing the binarized output D (t) stored in the storage unit 80 with the threshold value H1, and binarized output The period of the binarized output D (t) is measured by measuring the time tu from the rise of D (t) to the next rise. The period measuring unit 82 performs such measurement every time a rising edge occurs in the binarized output D (t).

  Alternatively, the period measuring unit 82 detects the falling edge of the binarized output D (t) by comparing the binarized output D (t) stored in the storage unit 80 with the threshold value H2. The period of the binarized output D (t) may be measured by measuring the time tdd from the trailing edge of the digitized output D (t) to the next trailing edge. The period measuring unit 82 performs such measurement every time a falling edge occurs in the binarized output D (t).

  The measurement result of the period measurement unit 82 is stored in the storage unit 80. Next, the frequency distribution creating unit 83 creates a frequency distribution of periods in a certain time T (T> Tt, for example, 100 × Tt, that is, a time corresponding to 100 triangular waves) from the measurement result of the period measuring unit 82. (FIG. 3, step S4). FIG. 9 is a diagram showing an example of the frequency distribution. The frequency distribution created by the frequency distribution creating unit 83 is stored in the storage unit 80. The frequency distribution creating unit 83 creates such a frequency distribution every T hours.

  Subsequently, the reference period calculation unit 84 calculates a reference period T0 that is a representative value of the period of the binarized output D (t) from the frequency distribution created by the frequency distribution creation unit 83 (step S5 in FIG. 3). In general, the representative value of the cycle is the mode value or the median value. However, in the present embodiment, the mode value or the median value is not suitable as the representative value of the cycle. Therefore, the reference period calculation unit 84 sets the class value that maximizes the product of the class value and the frequency as the reference period T0. Table 1 shows a numerical example of the frequency distribution and the product of the class value and the frequency in this numerical example.

  In the example of Table 1, the mode value (class value) having the maximum frequency is 1. On the other hand, the class value that maximizes the product of the class value and the frequency is 6, which is different from the mode value. The reason why the class value that maximizes the product of the class value and the frequency is set as the reference period T0 will be described later. The calculated value of the reference period T0 is stored in the storage unit 80. The reference period calculation unit 84 performs such calculation of the reference period T0 every time the frequency distribution is generated by the frequency distribution generation unit 83.

  On the other hand, the counter 85 operates in parallel with the period measuring unit 82 and the frequency distribution creating unit 83, and binarized output in a period of the same fixed time T as the period for which the frequency distribution creating unit 83 is a target of frequency distribution creating. The number N of rising edges of D (t) (that is, the number of “1” pulses of the binarized output D (t)) is counted (step S6 in FIG. 3). The count result N of the counter 85 is stored in the storage unit 80. The counter 85 counts such binarized output D (t) every T time.

From the frequency distribution created by the frequency distribution creation unit 83, the correction unit 86 calculates the sum Ns of the class frequencies that are 0.5 times or less of the reference period T0 and the frequency of the class that is 1.5 times or more of the reference period T0. And the count result N of the counter 85 is corrected as follows (step S7 in FIG. 3).
N ′ = N−Ns + Nw (6)
In Equation (6), N ′ is the corrected count result. The corrected count result N ′ is stored in the storage unit 80. The correction unit 86 performs such correction every T time.

  FIG. 10 is a diagram schematically showing the total number Ns and Nw of frequencies. In FIG. 10, Ts is a class value 0.5 times the reference period T0, and Tw is a class value 1.5 times the reference period T0. Needless to say, the class in FIG. 10 is a representative value of the period. In FIG. 10, the frequency distribution between the reference periods T0 and Ts and between the reference periods T0 and Tw is omitted in order to simplify the description.

11A and 11B are diagrams for explaining the correction principle of the counting result of the counter 85. FIG. 11A shows the binarized output D (t), and FIG. 11B shows FIG. 11A. It is a figure which shows the count result of the corresponding counter 85. FIG.
Originally, the cycle of the binarized output D (t) varies depending on the vibration frequency of the object 11, but if the vibration frequency of the object 11 is not changed, the pulse of the binarized output D (t) appears in the same cycle. However, due to noise, the MHP waveform may be missing or a waveform that should not be counted as a signal. As a result, the waveform of the binarized output D (t) should not be counted as a missing or signal. A waveform is generated, and an error occurs in the count result of the binary output D (t).

  When signal loss occurs, the cycle Tw of the binarized output D (t) at the location where the loss occurs is approximately twice the original cycle. That is, when the period of the binarized output D (t) is approximately twice or more than the reference period T0, it can be determined that the signal is missing. Therefore, the total frequency Nw of the periods equal to or higher than the period Tw is regarded as the number of missing signals, and this missing signal can be corrected by adding this Nw to the count result N of the counter 85.

  Further, the cycle Ts of the binarized output D (t) at the portion where the original signal is divided by spike noise or the like is shorter than 0.5 times the signal shorter than the original cycle and 0.5 times. Becomes two of the long signals. That is, when the period of the binarized output D (t) is approximately 0.5 times or less of the reference period T0, it can be determined that the signals are excessively counted. Therefore, the sum Ns of the frequencies of the class having the period Ts or less is regarded as the number of times that the signal is excessively counted, and the Ns is subtracted from the count result N of the counter 85, thereby correcting the erroneously counted noise. The above is the correction principle of the counting result shown in Expression (6).

The frequency calculation unit 87 calculates the vibration frequency fsig of the object 11 as follows based on the corrected count result N ′ calculated by the correction unit 86 (step S8 in FIG. 3).
fsig = N ′ / T (7)
The display unit 9 displays the value of the vibration frequency fsig calculated by the frequency measurement unit 8.

  As described above, in this embodiment, the count results of the first and second oscillation periods P1 and P2 that are temporally adjacent to each other are compared to binarize the MHP count result, and the binarized output D The period of (t) is measured to create a frequency distribution of periods at a fixed time T, and a reference period T0 that is a representative value of the distribution of periods of the binarized output D (t) is calculated from the frequency distribution of periods. The number of pulses of the binarized output D (t) is counted in the period of the fixed time T. From the frequency distribution, the sum Ns of the frequencies of the class that is 0.5 times or less of the reference period T0 and 1.5 of the reference period T0. A binarized output D (t) is obtained by obtaining the sum Nw of the frequencies of the class that is more than twice and correcting the count result of the pulses of the binarized output D (t) based on these frequencies Ns and Nw. The measurement error of the vibration frequency of the object 11 can be improved. It can be.

Next, the reason why the class value that maximizes the product of the class value and the frequency is set as the reference period T0 will be described.
In a self-coupled laser measuring apparatus using wavelength modulation (triangular wave modulation in this embodiment), the number of MHPs in each counting period is the number of MHPs proportional to the distance from the object 11 and the object 11 in the counting period. The sum or difference with the number of MHPs proportional to the displacement (velocity). Depending on the ratio of the maximum speed of vibration of the object 11 and the distance between the object 11 and the wavelength change rate of the semiconductor laser 1, the signal status obtained by the measuring device can be divided into the following two types.

  First, the case where the ratio of the maximum speed of vibration of the object 11 and the distance between the object 11 is smaller than the wavelength change rate of the semiconductor laser 1 will be described. FIG. 12 is a diagram for explaining a signal obtained by the vibration frequency measuring device of this embodiment in this case, and FIG. 12 (A) is a diagram showing a change with time of the distance to the object 11, and FIG. FIG. 12C is a diagram showing the time change of the counting result of the signal extraction unit 7, and FIG. 12D is a binarized output by the binarization unit 81. It is a figure which shows D (t). In FIG. 12B, 130 indicates a portion where the speed is low, 131 indicates that the moving direction of the object 11 is a direction approaching the semiconductor laser 1, and 132 indicates that the moving direction of the object 11 is far from the semiconductor laser 1. Indicates that the direction.

  When the ratio of the maximum speed of vibration of the object 11 and the distance to the object 11 is smaller than the wavelength change rate of the semiconductor laser 1, the number of MHPs proportional to the distance to the object 11 is the displacement of the object 11 during the counting period ( The absolute value of the difference between the counting result Nu when the oscillation wavelength of the semiconductor laser 1 is increasing and the counting result Nd when the oscillation wavelength is decreasing is always larger than the number of MHPs proportional to the speed). It is always proportional to the displacement of the object 11 in the two counting periods (in this embodiment, the oscillation periods P1 and P2). In this case, when Nu−Nd is plotted in time series, the vibration speed with the approaching direction to the semiconductor laser 1 being positive is shown. Therefore, the sign of Nu-Nd indicates the direction of motion of the object 11, and the displacement of the object 11 can be binarized by this sign.

At this time, the frequency distribution of the period created by the frequency distribution creating unit 83 is as shown in FIG.
As shown in FIG. 12C, when white noise due to, for example, ambient light is added at a location 133 where the speed of the object 11 is low, the magnitude relationship between the count results Nu and Nd may be reversed from the original relationship. . As a result, as shown in FIG. 12D, the sign of the binarized output D (t) becomes a value opposite to the original value at the place 134 where the sign of the binarized output D (t) switches. There is.
Further, for example, when spike noise caused by disturbance light or the like is added, the sign of the binarized output D (t) is locally inverted at a location 135 as shown in FIG.

  As a result, as shown in FIG. 13, the frequency distribution of the period created by the frequency distribution creating unit 83 includes a normal distribution 140 centered on the reference period T0, a frequency 141 due to sign inversion caused by spike noise, It becomes the sum with the frequency 142 due to the sign inversion caused by noise. Further, the frequency of signal loss 143 when binarization is performed often does not occur unless low-frequency noise having a large speed is mixed.

  Next, a case where the ratio of the maximum speed of vibration of the object 11 and the distance between the object 11 is larger than the wavelength change rate of the semiconductor laser 1 will be described. FIG. 14 is a diagram for explaining a signal obtained in this case by the vibration frequency measurement device according to the present embodiment. FIG. 14A is a diagram showing a time change of the distance to the object 11, and FIG. FIG. 14C is a diagram showing the time change of the counting result of the signal extraction unit 7, and FIG. 14D is a binarized output by the binarization unit 81. It is a figure which shows D (t). In FIG. 14B, 150 indicates a portion where the speed is low, 151 indicates that the moving direction of the object 11 is a direction approaching the semiconductor laser 1, and 152 indicates that the moving direction of the object 11 is far from the semiconductor laser 1. Indicates that the direction.

  When the ratio of the maximum speed of vibration of the object 11 and the distance to the object 11 is larger than the wavelength change rate of the semiconductor laser 1, the number of MHPs proportional to the distance to the object 11 is near the maximum speed of the object 11. Since the number is smaller than the number of MHPs proportional to the displacement (velocity) of the object 11 during the counting period, the counting result Nu when the oscillation wavelength of the semiconductor laser 1 is increasing and the counting when the oscillation wavelength is decreasing. The difference between the result Nd is proportional to the displacement of the object 11 in two counting periods (in this embodiment, the oscillation periods P1 and P2), and the sum of the counting result Nu and the counting result Nd is the object in the two counting periods. There is a period proportional to 11 displacements.

  In this case, the vibration speed of the object 11 can be expressed by synthesizing a graph in which Nu−Nd and Nu + Nd are plotted in time series as shown in FIG. However, since the direction of the speed always coincides with the magnitude relationship between Nu and Nd, the sign of Nu−Nd indicates the movement direction of the object 11, and the displacement direction of the object 11 (speed direction or The motion direction can be binarized. At this time, the frequency distribution of the period created by the frequency distribution creating unit 83 is the same as in FIG.

  When correcting the MHP counting result as in the embodiment described later, it is important to correct the loss of the MHP waveform due to low-frequency noise when the MHP is small. In the case of correcting the binarized output D (t) obtained by binarizing 11 displacements, it is important to correct high-frequency noise.

  The change of the sign in a short period due to the high frequency noise may exceed the frequency of the original vibration period of the object 11, and when the mode value or the median value is used as a representative value of the period, it is erroneously more than the vibration period. There is a concern that correction may be applied based on a short noise period. Therefore, in the period of a certain time T for calculating the vibration frequency, the ratio of the signal of a certain class, that is, the class value having the largest product of the class value and the frequency is set as the reference period T0, and the count result of the counter 85 is corrected. To implement. The above is the reason why the class value that maximizes the product of the class value and the frequency is the reference period T0.

  Next, the operation of the suspension period setting unit 10 of the present embodiment will be described. In order to calculate the vibration frequency of the object 11, a memory (not shown) is required for the signal extraction unit 7, and a memory (storage unit 80) is also required for the frequency measurement unit 8. As described above, basically, if the period of the binarized output D (t) can be obtained, the vibration frequency of the object 11 can be calculated, but the vibration frequency of the object 11 is low and the vibration period is low. Becomes longer, processing is performed endlessly to obtain the cycle of the binarized output D (t), and a huge memory capacity is required.

  Therefore, the suspension period setting unit 10 according to the present embodiment, for example, according to a suspension period setting instruction signal input from an operator, between each measurement point for measuring the number of MHPs (the measurement point of the counting result Nu and the next measurement point). The signal extraction unit 7 and the frequency measurement unit 8 are controlled so as to provide a certain pause period between the counting result Nd measurement points and between the counting result Nd measurement point and the next counting result Nu measurement point. Then, the measurement necessary for the measurement of the number of MHPs and the calculation of the vibration frequency is thinned out. The pause period may be a time that is an integral multiple of the carrier wave (triangular wave) period Tt, for example. That is, the number of MHPs is measured with an interval longer than the half cycle of the carrier wave, which is the original measurement interval.

  By providing a pause period for measurement, similarly, the binarization unit 81 of the frequency measurement unit 8 also performs binarization processing with an interval longer than the half cycle of the carrier wave, which is the original processing interval. Further, the fixed time T used in the frequency measuring unit 8 is extended according to the pause period. That is, the fixed time T may be extended by the rest period inserted between the measurement points assumed in the original fixed time T. For example, if the original fixed time T is 100 × Tt and the pause period is a time Tt for one cycle of the carrier wave, 100 measurements and 99 pause periods are required, so the fixed time T is 199 × Tt. Extended.

  As described above, by thinning out the measurement, even when the vibration frequency of the object 11 is low, it is possible to perform signal processing over a period of one cycle or more of the vibration of the object 11 and to calculate the vibration frequency. Become. For example, the frequency of the carrier wave is 10 [kHz], the maximum frequency of MHP that can be processed by the vibration frequency measuring device is 1 [MHz], the number of MHPs, and the period of the binarized output D (t) are used. If the sampling clock frequency is 2 [MHz], the memory capacity is 20000 points (corresponding to 100 carrier cycles), and the signal processing time for 1 carrier cycle is 10 [ms] The lowest possible vibration frequency is 10 [kHz] / 100 [pieces] = 100 [Hz].

  On the other hand, if a pause period of m periods (here, m = 1) of the carrier wave is provided, signal processing can be performed only for the time of 100 measurements and 99 pause periods. The vibration frequency is 1 / (99 × m × 0.1 [ms] + 100 × 0.1 [ms]) = 50 Hz, and it can be seen that the vibration frequency can be dealt with lower than when no pause period is provided.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the present embodiment, the period of the binarized output D (t) is measured by a method different from that in the first embodiment. Also in the present embodiment, the configuration of the vibration frequency measuring device is the same as that of the first embodiment, and therefore, description will be made using the reference numerals in FIGS. 1 and 6. FIG. 15 is a diagram for explaining the operation of the period measurement unit 82 of the present embodiment.

  The period measurement unit 82 of the present embodiment sets the rise of the binarization output D (t) when the binarization output D (t) stored in the storage unit 80 changes from “0” to “1”. The time when the binarized output D (t) changes from “1” to “0” is the falling edge of the binarized output D (t). Then, the period measuring unit 82 measures a time tud from the rising edge of the binarized output D (t) to the next falling edge, and time from the falling edge of the binarized output D (t) to the next rising edge. The period of the binarized output D (t) is measured by measuring tdu. The period measurement unit 82 performs such measurement every time either the rising or falling edge of the binarized output D (t) is detected.

  As described above, the cycle of the binarized output D (t), more precisely, the half cycle can be measured. By measuring the half cycle of the binarized output D (t), T0 calculated by the reference cycle calculation unit 84 is not a cycle, but is exactly the reference half cycle T0. Other configurations are the same as those of the first embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the present embodiment, the period of the binarized output D (t) is measured by a method different from that in the first and second embodiments. Also in the present embodiment, the configuration of the vibration frequency measuring device is the same as that of the first embodiment, and therefore, description will be made using the reference numerals in FIGS. 1 and 6.

The period measuring unit 82 of the present embodiment measures the period of the binarized output D (t) by measuring the time tu from the rise of the binarized output D (t) to the next rise, The period of the binarized output D (t) is measured by measuring the time tdd from the fall of the binarized output D (t) to the next fall. The period measurement unit 82 performs such measurement every time either the rising or falling edge of the binarized output D (t) is detected.
As described above, the cycle of the binarized output D (t) can be measured. Other configurations are the same as those of the first embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the time for obtaining the frequency distribution of the cycle of the binarized output D (t) and the number of pulses of the binarized output D (t) is set to a certain time T. The time may be variable.
FIG. 16 is a block diagram showing an example of the configuration of the frequency measurement unit 8a of the present embodiment. The frequency measurement unit 8a includes a storage unit 80, a binarization unit 81, a cycle measurement unit 82a, a frequency distribution creation unit 83a, a reference cycle calculation unit 84, a correction unit 86a, a frequency calculation unit 87a, a cycle, And a sum calculation unit 88.

  FIG. 17 is a flowchart showing operations of the signal extraction unit 7 and the frequency measurement unit 8a of the present embodiment. The operations of the semiconductor laser 1, the photodiode 2, the laser driver 4, the current-voltage conversion amplification unit 5, the filter unit 6, the signal extraction unit 7, and the storage unit 80 and the binarization unit 81 of the frequency measurement unit 8a are as follows. This is the same as the embodiment.

  The period measuring unit 82a measures the period of a predetermined number N (N is a natural number of 2 or more, for example, 100) pulses of the binarized output D (t) stored in the storage unit 80 (step in FIG. 17). S9). As a method for measuring the cycle of the binarized output D (t), any method of the first to third embodiments may be used. The measurement result of the period measurement unit 82a is stored in the storage unit 80. The period measurement unit 82a performs such measurement every time N pulses of “1” of the binarized output D (t) are generated.

The frequency distribution creating unit 83a creates a frequency distribution of the period from the measurement result of the period measuring unit 82a performed on the fixed number N pulses of the binarized output D (t) (step S10 in FIG. 17). The frequency distribution created by the frequency distribution creating unit 83 a is stored in the storage unit 80. The frequency distribution creating unit 83a creates such a frequency distribution every time N “1” pulses of the binarized output D (t) are generated.
The operation of the reference period calculation unit 84 is the same as that in the first embodiment (step S5 in FIG. 17).

The period sum calculation unit 88 calculates the total sum T of the periods measured for a certain number N pulses of the binarized output D (t) from the measurement result of the period measurement unit 82a stored in the storage unit 80 ( FIG. 17 step S11). The calculated total sum T of the periods is stored in the storage unit 80.
However, when the method of the third embodiment is used as the method of measuring the period of the binarized output D (t), 1/2 of the calculated value is set as the total sum T of the periods.

  Based on the frequency distribution created by the frequency distribution creating unit 83a, the correcting unit 86a calculates the sum Ns of the class frequencies that are 0.5 times or less of the reference period T0 and the frequency of the class that is 1.5 times or more of the reference period T0. And a fixed number N is corrected as shown in equation (6) (step S12 in FIG. 17). The corrected value N ′ is stored in the storage unit 80. The correction unit 86a performs such correction each time N “1” pulses of the binarized output D (t) are generated.

  The frequency calculation unit 87a calculates the vibration frequency fsig of the object 11 as in Expression (7) based on the corrected value N ′ calculated by the correction unit 86a and the total sum T of periods calculated by the period sum calculation unit 88. (Step S13 in FIG. 17).

Other configurations are the same as those of the first embodiment. Thus, even when the frequency measurement unit 8a is used instead of the frequency measurement unit 8 as in the present embodiment, the measurement accuracy of the vibration frequency of the object 11 can be improved.
In the first embodiment, it is necessary to extend the fixed time T according to the pause period. However, in the present embodiment, a cycle of a fixed number N pulses of the binarized output D (t). Therefore, it is not necessary to extend the time T according to the suspension period.

  In the first embodiment, since the time for obtaining the frequency distribution of the period of the binarized output D (t) and the number of pulses of the binarized output D (t) is fixed at a certain time T, the period May not coincide with the fixed time T. For this reason, in the first embodiment, a measurement error may occur in the vibration frequency of the object 11.

  On the other hand, in the present embodiment, the total sum of the cycles calculated by the cycle sum calculation unit 88 is made equal to the time T used in the equation (7), so the same effect as the first embodiment. As well as the measurement accuracy of the vibration frequency can be further improved.

  In addition, regarding the T of the population when obtaining the vibration frequency fsig of the object 11, if there is a pulse corresponding to the above Ns at the boundary of the population, both unevenness as shown in FIGS. 18B and 18C. However, it is difficult to determine whether a pulse with a short Ns is included in T because it cannot be determined whether it is concave noise or convex noise. May occur. 18A shows the case where there is no noise, FIG. 18B shows the case where there is a concave noise 190 corresponding to Ns, and FIG. 18C shows the case where there is a convex noise 191 corresponding to Ns. ing. Therefore, in the cases shown in FIGS. 18B and 18C, it is preferable to select T so that there are no Ns pulses before and after the T boundary.

[Fifth Embodiment]
In the first to fourth embodiments, the suspension period setting unit 10 manually provides a suspension period, for example, according to an instruction from the operator. However, the necessity of setting the suspension period and the required length of the suspension period are automatically set. You may make it determine automatically.
FIG. 19 is a block diagram showing an example of the configuration of the suspension period setting unit 10a of the present embodiment. The suspension period setting unit 10 a includes a suspension period increase setting unit 100 and a suspension period decrease setting unit 101.

  The pause period increase setting unit 100 corresponds to a predetermined number (for example, 100) of pulses of the binarized output D (t) in the data capacity that can be processed by the signal extraction unit 7 and the frequency measurement units 8 and 8a. When sampling data to be processed can be processed, it is determined that it is not necessary to provide a pause period. Here, the sampling data is data obtained by sampling the MHP waveform with the sampling clock in the signal extraction unit 7.

  In addition, the pause period increase setting unit 100 has sampling data corresponding to a predetermined number of pulses of the binarized output D (t) in the data capacity that can be processed by the signal extraction unit 7 and the frequency measurement units 8 and 8a. If the object 11 cannot be processed, it is determined that the vibration of the object 11 is slow, a pause period is set, and sampling data corresponding to a predetermined number of pulses of the binarized output D (t) is included in the processable data capacity. Set the length of the pause period to be included.

  On the other hand, when the period of the binarized output D (t) does not include the minimum required number of MHPs (for example, 10), the pause period decrease setting unit 101 vibrates the object 11 quickly. The pause period is shortened so that the minimum necessary number of MHP count results are included in one cycle of the binarized output D (t). The determination of the suspension period decrease setting unit 101 can be performed based on the input / output of the binarization unit 81.

Other configurations are the same as those of the first to fourth embodiments. In this way, in the present embodiment, it is possible to automatically determine whether or not the suspension period needs to be set and the necessary length of the suspension period.
Sampling used to measure the frequency of the carrier wave 10 [kHz], the maximum frequency of MHP that can be processed by the vibration frequency measuring device 1 [MHz], the number of MHPs, and the period of the binarized output D (t) Assuming that the clock frequency is 2 [MHz], the memory capacity is 20000 points (corresponding to 100 carrier cycles), and the time required for signal processing for one carrier cycle is 10 [ms] (here m = 1) If a pause period of 1) is provided, at least 10 counting results and 9 pause periods are required in one cycle of the binarized output D (t). The frequency is 1 / (9 × m × 0.1 [ms] + 10 × 0.1 [ms]) = 526 Hz.

  On the other hand, when the rest period is set to 0 by the function of the rest period reduction setting unit 101, the maximum vibration frequency that can be handled is 10 [kHz] / 10 = 1 kHz, which is a higher vibration frequency than when the rest period is provided. It can be seen that

[Sixth Embodiment]
In the first to fifth embodiments, the signal extraction unit 7 and the frequency measurement units 8 and 8a perform sequential processing to execute processing every time MHP sampling data is obtained. If it is early, processing may not catch up even if the pause period is eliminated. Therefore, in such a case, the sampling data of MHP is accumulated in a memory (not shown) of the signal extraction unit 7, and when the data amount of the signal extraction unit 7 reaches a predetermined amount, It is preferable to perform batch processing in which the frequency measuring units 8 and 8a execute processing.

FIG. 20 is a block diagram showing a configuration of a vibration frequency measuring apparatus according to the sixth embodiment of the present invention. The vibration frequency measuring device according to the present embodiment is obtained by adding a process switching unit 12 to the vibration frequency measuring device according to the first embodiment.
The process switching unit 12 instructs the signal extraction unit 7 and the frequency measurement unit 8 to switch from sequential processing to batch processing or from batch processing to sequential processing in accordance with, for example, a process switching instruction signal input from an operator.

Thus, in this embodiment, by switching from sequential processing to batch processing, signal processing can be performed even when the vibration frequency of the object 11 is high, and the vibration frequency can be calculated.
In the present embodiment, the case where the present invention is applied to the first embodiment has been described. However, the present invention is not limited to this, and may be applied to other second to fifth embodiments. Yes.

[Seventh Embodiment]
In the sixth embodiment, the processing switching unit 12 manually switches between sequential processing and batch processing, for example, according to an instruction from an operator. However, processing switching may be performed automatically.
That is, the process switching unit 12 causes the object 11 to vibrate quickly when the count result of the minimum required number (for example, 10) of MHPs is not included in one cycle of the binarized output D (t). And switching from sequential processing to batch processing may be performed.

  Note that switching from batch processing to sequential processing may be performed automatically or manually. In the case of automatic switching, the process switching unit 12 slows the vibration of the object 11 when the minimum required number of MHP count results are included in one cycle of the binarized output D (t). What is necessary is to switch from batch processing to sequential processing.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. In the first to seventh embodiments, the photodiode 2 and the current-voltage conversion amplification unit 5 are used as detection means for detecting an electric signal including an MHP waveform. However, the MHP waveform is not used without using a photodiode. It is also possible to extract. FIG. 21 is a block diagram showing a configuration of a vibration frequency measuring apparatus according to the eighth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The vibration frequency measuring apparatus according to the present embodiment uses a voltage detection circuit 13 as detection means instead of the photodiode 2 and the current-voltage conversion amplification unit 5 according to the first to seventh embodiments.

  The voltage detection circuit 13 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 11, 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 circuit 13. Other configurations of the vibration frequency measuring device are the same as those in the first to seventh embodiments.
Thus, in this embodiment, the MHP waveform can be extracted without using a photodiode, and the parts of the vibration frequency measuring device can be reduced as compared with the first to seventh embodiments. The cost of the vibration frequency 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 eighth embodiments, at least the signal extraction unit 7, the frequency measurement units 8, 8a, the pause period setting units 10, 10a, and the process switching unit 12 are, for example, a computer including a CPU, a memory, and an interface. And a program for controlling these hardware resources. The CPU executes the processes described in the first to eighth embodiments in accordance with the program stored in the memory.

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

It is a block diagram which shows the structure of the vibration frequency 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 frequency 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 frequency measurement part in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the binarization part in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the period measurement part in the 1st Embodiment of this invention. It is a figure which shows one example of the frequency distribution of the period in the 1st Embodiment of this invention. It is a figure which represents typically the frequency used for correction | amendment of the count result of a counter in the 1st Embodiment of this invention. It is a figure for demonstrating the correction principle of the count result of the counter in the 1st Embodiment of this invention. For explaining a signal obtained by the vibration frequency measuring apparatus according to the first embodiment of the present invention when the ratio of the maximum speed of vibration of the object and the distance between the object and the object is smaller than the wavelength change rate of the semiconductor laser. FIG. It is a figure which shows the frequency distribution of the period produced according to the binarization output of FIG. For explaining a signal obtained by the vibration frequency measuring apparatus according to the first embodiment of the present invention when the ratio of the maximum speed of vibration of the object and the distance between the object is larger than the wavelength change rate of the semiconductor laser. FIG. It is a figure for demonstrating operation | movement of the period measurement part in the 2nd Embodiment of this invention. It is a block diagram which shows one example of a structure of the frequency measurement part in the 4th Embodiment of this invention. It is a flowchart which shows operation | movement of the signal extraction part and frequency measurement part in the 4th Embodiment of this invention. It is a figure for demonstrating the setting method of fixed time when noise exists in a binarization output. It is a block diagram which shows one example of a structure of the idle period setting part in the 5th Embodiment of this invention. It is a block diagram which shows the structure of the vibration frequency measuring device which concerns on the 6th Embodiment of this invention. It is a block diagram which shows the structure of the vibration frequency measuring device which concerns on the 8th Embodiment of this invention. It is a figure which shows an example of the Doppler beat wave which appears in the output of a photodiode in the conventional measuring device, and a figure which shows an example of the output voltage of the direction discriminating circuit which discriminate | determines the direction of the displacement of an object from the inclination of a Doppler beat wave. It is a block diagram which shows the structure of the conventional laser measuring device. It is a figure which shows one example of the time change of the oscillation wavelength of a semiconductor laser in the laser measuring device of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplification part, 6 ... Filter part, 7 ... Signal extraction part, 8, 8a ... Frequency measurement part, 9 ... Display , 10, 10a ... pause period setting unit, 11 ... object, 12 ... processing switching unit, 13 ... voltage detection circuit, 80 ... storage unit, 81 ... binarization unit, 82, 82a ... period measurement unit, 83, 83a ... Frequency distribution creation part, 84 ... Reference period calculation part, 85 ... Counter, 86, 86a ... Correction part, 87, 87a ... Frequency calculation part, 88 ... Period sum calculation part, 100 ... Pause period increase setting part, 101 ... Pause Period decrease setting part.

Claims (16)

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;
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 frequency measuring means for obtaining a vibration frequency of the measurement object based on a counting result of the signal extracting means;
A vibration frequency measuring device comprising: a pause period setting means capable of setting a pause period between each measurement point for measuring the number of interference waveforms. In the vibration frequency measuring device according to claim 1,
Further, every time the interference waveform data is obtained, the signal extraction means and the frequency measurement means perform processing, and the interference waveform data is accumulated by the signal extraction means, so that the data amount is A vibration frequency measuring apparatus comprising a process switching means capable of switching to either one of batch processes in which the signal extracting means and the frequency measuring means execute processing when a predetermined amount is reached. In the vibration frequency measuring device according to claim 1,
The suspension period setting means sets the suspension period in accordance with a suspension period setting instruction signal input from the outside. In the vibration frequency measuring device according to claim 2,
The process switching means switches between the sequential process and the batch process according to a process switching instruction signal input from the outside. In the vibration frequency measuring device according to claim 1,
The frequency measuring means includes
Binarization means for comparing the count results of the first and second oscillation periods adjacent in time and binarizing these count results;
A binarized output period measuring means for measuring the period of the binarized output outputted from the binarizing means;
A binarized output period frequency distribution creating means for creating a frequency distribution of the period of the binarized output in a fixed time from the measurement result of the binarized output period measuring means;
A reference period calculating means for calculating a reference period that is a representative value of the distribution of the binarized output period from the frequency distribution of the period of the binarized output;
A binarized output counting unit that counts the number of pulses of the binarized output in a period of a fixed time that is the same as a period for which the binarized output cycle frequency distribution generating unit is a target of frequency distribution generation;
From the frequency distribution of the period of the binarized output, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the reference period and the sum of the frequencies of the class that is greater than or equal to the second predetermined number of times of the reference period Nw and a correction means for correcting the counting result of the binarized output counting means based on these frequencies Ns and Nw;
A vibration frequency measuring apparatus comprising: a counting result corrected by the correcting means; and a frequency calculating means for calculating a vibration frequency of the measurement object based on the predetermined time. In the vibration frequency measuring device according to claim 1,
The frequency measuring means includes
Binarization means for comparing the count results of the first and second oscillation periods adjacent in time and binarizing these count results;
Binarized output period measuring means for measuring the period of a certain number of binarized output pulses output from the binarizing means;
Binarized output period frequency distribution creating means for creating a frequency distribution of the binarized output period from the measurement result of the binarized output period measuring means implemented for a fixed number of pulses of the binarized output;
A reference period calculating means for calculating a reference period that is a representative value of the distribution of the binarized output period from the frequency distribution of the period of the binarized output;
A period sum calculating means for calculating a total sum of the periods of the binarized output from the measurement result of the binarized output period measuring means;
From the frequency distribution of the period of the binarized output, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the reference period and the sum of the frequencies of the class that is greater than or equal to the second predetermined number of times of the reference period Nw and a correction means for correcting the fixed number based on these frequencies Ns and Nw;
A vibration frequency measuring apparatus comprising: a frequency calculating means for calculating a vibration frequency of the measurement object based on a value corrected by the correcting means and a total sum of periods calculated by the period sum calculating means. In the vibration frequency measuring device according to claim 5 or 6,
The suspension period setting means includes:
When the data of the interference waveform corresponding to the predetermined number of pulses of the binarized output cannot be processed in the data capacity that can be processed by the signal extraction unit and the frequency measurement unit, the pause period is set, A pause period increase setting means for setting the length of the pause period so that interference waveform data corresponding to a predetermined number of pulses of the binarized output is included in the data capacity;
When the minimum required number of interference waveform count results are not included in one cycle of the binarized output, the minimum required number count result of the interference waveform is included in one cycle of the binarized output. The vibration frequency measuring device is characterized by comprising a pause period decrease setting means for shortening the pause period so as to be included. In the vibration frequency measuring device according to claim 5 or 6,
The process switching means switches from the sequential process to the batch process when the minimum required number of the interference waveform count results are not included in one cycle of the binarized output. Measuring device. In a vibration frequency measurement method for measuring a vibration frequency of a measurement object using a 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;
A frequency measurement procedure for obtaining a vibration frequency of the measurement object based on a counting result obtained by the signal extraction procedure;
A vibration frequency measurement method comprising: a pause period setting procedure capable of setting a pause period between each measurement point for measuring the number of interference waveforms. The vibration frequency measurement method according to claim 9, wherein
Further, each time the interference waveform data is obtained, a sequential process for executing the signal extraction procedure and the frequency measurement procedure, and the interference waveform data are accumulated, and when the data amount reaches a predetermined amount. A vibration frequency measurement method comprising a process switching procedure capable of switching to either one of batch processes for executing the signal extraction procedure and the frequency measurement procedure. The vibration frequency measurement method according to claim 9, wherein
In the suspension period setting procedure, the suspension period is set according to a suspension period setting instruction signal input from the outside. In the vibration frequency measuring method according to claim 10,
In the process switching procedure, the sequential process and the batch process are switched in accordance with a process switching instruction signal input from the outside. The vibration frequency measurement method according to claim 9, wherein
The frequency measurement procedure includes:
A binarization procedure for comparing the count results of the first and second oscillation periods that are temporally adjacent and binarizing these count results;
A binarized output cycle measuring procedure for measuring the binarized output cycle obtained by the binarizing procedure;
A binarized output cycle frequency distribution creating procedure for creating a binarized output cycle frequency distribution in a predetermined time from the measurement result of the binarized output cycle measuring procedure;
A reference period calculation procedure for calculating a reference period that is a representative value of the distribution of the binarized output period from the frequency distribution of the period of the binarized output;
A binarized output counting procedure for counting the number of pulses of the binarized output in a period of a fixed time that is the same as the period for which the binarized output period frequency distribution generating procedure is a target of frequency distribution generation;
From the frequency distribution of the period of the binarized output, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the reference period and the sum of the frequencies of the class that is greater than or equal to the second predetermined number of times of the reference period Nw and a correction procedure for correcting the counting result of the binarized output counting procedure based on these frequencies Ns and Nw;
A vibration frequency measurement method comprising: a counting result corrected by the correction procedure; and a frequency calculation procedure for calculating a vibration frequency of the measurement object based on the predetermined time. The vibration frequency measurement method according to claim 9, wherein
The frequency measurement procedure includes:
A binarization procedure for comparing the count results of the first and second oscillation periods that are temporally adjacent and binarizing these count results;
A binarized output period measuring procedure for measuring the period of a certain number of binarized output pulses obtained by the binarizing procedure;
A binarized output cycle frequency distribution creating procedure for creating a frequency distribution of the binarized output cycle from the measurement result of the binarized output cycle measuring procedure performed for a certain number of pulses of the binarized output;
A reference period calculation procedure for calculating a reference period that is a representative value of the distribution of the binarized output period from the frequency distribution of the period of the binarized output;
A cycle sum calculation procedure for calculating a sum of cycles of the binarized output from a measurement result of the binarized output cycle measurement procedure;
From the frequency distribution of the period of the binarized output, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the reference period and the sum of the frequencies of the class that is greater than or equal to the second predetermined number of times of the reference period Nw and a correction procedure for correcting the fixed number based on these frequencies Ns and Nw;
A vibration frequency measurement method comprising: a frequency calculation procedure for calculating a vibration frequency of the measurement object based on a value corrected by the correction procedure and a total sum of the cycles calculated by the cycle sum calculation procedure. The vibration frequency measurement method according to claim 13 or 14,
The suspension period setting procedure includes:
In the data capacity that can be processed by the signal extraction procedure and the frequency measurement procedure, when the interference waveform data corresponding to a predetermined number of pulses of the binarized output cannot be processed, the pause period is set, A pause period increase setting procedure for setting the length of the pause period so that interference waveform data corresponding to a predetermined number of pulses of the binarized output is included in the data capacity;
When the minimum required number of interference waveform count results are not included in one cycle of the binarized output, the minimum required number count result of the interference waveform is included in one cycle of the binarized output. A vibration frequency measurement method comprising: a pause period decrease setting procedure for shortening the pause period so as to be included. The vibration frequency measurement method according to claim 13 or 14,
The vibration is characterized in that the processing switching procedure switches from the sequential processing to the batch processing when the minimum required number of the interference waveform count results are not included in one cycle of the binarized output. Frequency measurement method.

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