JP2011058833A - Counter, physical quantity sensor, method for counting, and method for measuring physical quantity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a counter which can correct a counting error with computational complexity smaller than usual, and a method for counting and a physical quantity sensor which can correct the counting error of MHP (mode hop pulse) with the computational complexity smaller than usual and thus can improve the measuring accuracy of the physical quantity and a method for measuring a physical quantity. <P>SOLUTION: An oscillation frequency measuring device has a laser driver 4 which makes a semiconductor laser 1 oscillate, the counter 7 which counts an interference waveform contained in an output of a photodiode 2 which converts an output of the semiconductor laser 1 into an electric signal, and an arithmetic device 8 which determines the physical quantity of an object 10 from the result of counting of the counter 7. The counter 7 measures the period of the interference waveform in a prescribed counting term, calculates the average value of the period of the interference waveform as a representative value from the result of the measurement and counts one measured period as one signal, and performs addition of n to the result of counting when the measured period is a multiple of (n+0.5) or more of the representative value to less than a multiple of (n+1.5) thereof, as to the all results of measurement of the periods during the counting period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a counting device that counts the number of signals, and an interference-type physical quantity sensor that measures the number of interference waveforms by using the counting device to obtain a physical quantity to be measured.

  Conventionally, a wavelength modulation type laser measuring instrument using the self-coupling effect of a semiconductor laser has been proposed (see Patent Document 1). The configuration of this laser measuring instrument is shown in FIG. 30 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. Of the laser driver 204 that alternately repeats the second oscillation period that decreases to a current, a current-voltage conversion amplification unit 205 that converts and amplifies the output current of the photodiode 202 into a voltage, and a current-voltage conversion amplification unit 205 A signal extraction circuit 206 for differentiating the output voltage twice, and a mode hop pulse (hereinafter referred to as MHP) included in the output voltage of the signal extraction circuit 206 Having a counting device 207 which counts the number of which), an arithmetic unit 208 which calculates the speed of the distance and the object 210 with the object 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. 31 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201. In FIG. 31, 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 amplification unit 205 converts and amplifies the output current of the photodiode 202 into a voltage, and the signal extraction circuit 206 differentiates the output voltage of the current-voltage conversion amplification unit 205 twice. The counting device 207 counts the number of MHPs included in the output voltage of the signal extraction circuit 206 for each of the first oscillation period P1 and the second oscillation period P2. Based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1, the number of MHPs in the first oscillation period P1, and the number of MHPs in the second oscillation period P2, 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.

In the laser measuring instrument as described above, for example, noise such as ambient light is counted as MHP, or there is MHP that cannot be counted due to missing teeth of the signal, and an error occurs in the number of MHPs counted by the counting device, There is a problem that an error occurs in the physical quantity such as the calculated distance and vibration frequency.
Therefore, the inventor measures the period of MHP during the counting period, creates a frequency distribution of the period during the counting period from the measurement result, calculates a representative value of the period of MHP from the frequency distribution, and represents the representative value from the frequency distribution. A total sum Ns of class frequencies that is less than or equal to a first predetermined number of values and a total sum Nw of class frequencies that are greater than or equal to a second predetermined number of values of the representative value are obtained, and based on these frequencies Ns and Nw By correcting the counting result of MHP, a counting device has been proposed that can eliminate the influence of missing or excessive counting during counting (see Patent Document 2).

JP 2006-31080 A JP 2009-47676 A

According to the counting device disclosed in Patent Document 2, generally good correction can be performed as long as SN (Signal to Noise ratio) does not extremely decrease.
However, in the counting device disclosed in Patent Document 2, a frequency distribution of the MHP cycle is created, a representative value of the MHP cycle is calculated from the frequency distribution, and the first predetermined number times or less of the representative value is calculated from the frequency distribution. It is necessary to obtain the sum Ns of the frequencies of the class N and the sum Nw of the frequencies of the class that is a second predetermined number times or more of the representative value, and the amount of calculation for correcting the error of the count result is large. There was a problem.

  The present invention has been made in order to solve the above-described problems. A counting device and a counting method capable of correcting a counting error with a smaller amount of calculation than the conventional method, and correcting an MHP counting error with a smaller amount of calculation than the conventional method. An object of the present invention is to provide a physical quantity sensor and a physical quantity measuring method capable of improving the physical quantity measurement accuracy.

The present invention provides a counting device that counts the signal having a substantially single frequency when the specific physical quantity and the number of signals have a linear relationship, and the specific physical quantity is constant. And a representative value calculating means for calculating an average value of the period of the input signal as a representative value from the latest or past measurement results of the signal period measuring means. And one cycle measured by the signal cycle measuring means is counted as one signal, and the cycle measured by the signal cycle measuring means is not less than (n + 0.5) times (n + 1.5) times the representative value. In this case (where n is a natural number of 1 or more), signal counting means is provided for performing the addition of n to the counting result for all the measurement results of the signal period measuring means during the counting period. so That.
Further, in one configuration example of the counting device of the present invention, the measurement result of the signal period measuring unit is further combined with a period of less than 0.5 times the representative value and a period measured immediately thereafter. Signal combining is performed until the combined period is a period after combining, and the combined signal waveform is a waveform for one period of one signal until the combined period becomes 0.5 times or more of the representative value. And the signal counting means performs the counting process on the processing result of the signal combining means in the counting period instead of performing the counting process on the measurement result of the signal period measuring means. .

Further, the counting device of the present invention includes a signal half-cycle measuring unit that measures a half cycle of an input signal in a certain counting period every time a half cycle of the signal is input, and the latest or past of the signal half-cycle measuring unit. From the measurement result, the representative value calculating means for calculating the average value of the half period of the input signal as a representative value, and counting the half period measured by the signal half period measuring means as one, the signal half period measurement When the half cycle measured by the means is not less than (2n) times (2n + 2) times the representative value (n is a natural number not less than 1), 2n is added to the count result during the counting period. A signal counting unit that performs all the measurement results of the signal half-cycle measuring unit; and a count result correcting unit that calculates a number obtained by multiplying the count result of the signal counting unit by 0.5 as the number of the input signals. To do .
In addition, one configuration example of the counting device according to the present invention further includes a half cycle having a length less than 0.5 times the representative value and a half measured before and after the measurement result of the signal half cycle measuring unit. The signal counting means includes a signal combining means that sets a period that is combined with at least one of the periods as a half period after combining, and a signal waveform that combines the periods as a waveform corresponding to a half period of one signal. Instead of performing the counting process on the measurement result of the half cycle measuring means, the counting process is performed on the processing result of the signal coupling means in the counting period.

Further, in one configuration example of the counting device according to the present invention, the signal combining means measures the measurement result of the signal half-cycle measuring means immediately after a half-cycle having a length less than 0.5 times the representative value. The combined cycle is defined as a combined half cycle, and the combined signal waveform is set to a waveform corresponding to a half cycle of one signal. The process is performed until it becomes five times or more.
Further, in one configuration example of the counting device according to the present invention, the signal combining unit is configured such that, for the measurement result of the signal half cycle measuring unit, a half cycle having a length less than 0.5 times the representative value is the representative value. When sandwiched between the m-th half cycle Tm having a length of 0.5 times or more and the p-th half cycle Tp (m and p are natural numbers) having a length of 0.5 times or more of the representative value, When (m + p) is an even number, the combined cycle from half cycle Tm to half cycle Tp is the combined half cycle, and when (m + p) is an odd number, the cycle is combined from half cycle Tm to half cycle Tn−1 Is a half cycle after combining, and a signal waveform obtained by combining the cycles is a waveform corresponding to the m-th half cycle.

  The physical quantity sensor of the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period in which the oscillation wavelength continuously increases monotonously, and a second oscillation period in which the oscillation wavelength continuously decreases monotonously. Oscillation wavelength modulation means for operating the semiconductor laser so that at least one of them repeatedly exists, and 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 A detecting means for detecting an electrical signal; and a counting device for counting the number of the interference waveforms, with an output signal of the detecting means as an input, and each of the first oscillation period and the second oscillation period as a counting period; And a calculating means for obtaining the physical quantity of the measurement object from the counting result of the counting device.

Further, the present invention provides a counting method in which the specific physical quantity has a linear relationship with the number of signals, and the signal has a substantially single frequency when the specific physical quantity is constant. A signal period measurement procedure that measures the period of the input signal every time a signal is input, and a representative value that calculates the average value of the period of the input signal as a representative value from the latest or past measurement results of this signal period measurement procedure The calculation procedure and one cycle measured in the signal cycle measurement procedure are counted as one signal, and the cycle measured in the signal cycle measurement procedure is not less than (n + 0.5) times (n + 1.5) times the representative value. If it is less than (n is a natural number equal to or greater than 1), the method includes a signal counting procedure for adding n to the counting result for all the measurement results of the signal period measuring procedure during the counting period. Do Than is.
In addition, according to one configuration example of the counting method of the present invention, the measurement result of the signal period measurement procedure is a combination of a period of less than 0.5 times the representative value and a period measured immediately thereafter. Signal combining is performed until the combined period is set to a period after combining and the combined signal waveform is a waveform for one period of one signal until the combined period becomes 0.5 times or more of the representative value. The signal counting procedure is characterized in that the counting process is performed on the processing result of the signal combining procedure in the counting period instead of performing the counting process on the measurement result of the signal period measurement procedure. .

In addition, the counting method of the present invention includes a signal half cycle measurement procedure for measuring a half cycle of an input signal in a certain counting period every time a half cycle of a signal is input, and the latest or past of the signal half cycle measurement procedure. From the measurement result, the representative value calculation procedure for calculating the average value of the half cycle of the input signal as a representative value, and the half cycle measured in the signal half cycle measurement procedure are counted as one, and the signal half cycle measurement When the half cycle measured in the procedure is (2n) times or more and less than (2n + 2) times the representative value (n is a natural number of 1 or more), 2n is added to the result of the counting. A signal counting procedure performed for all measurement results of the signal half-cycle measuring procedure, and a counting result correction procedure for calculating a number obtained by multiplying the counting result of the signal counting procedure by 0.5 as the number of the input signals, To do .
In addition, one configuration example of the counting method according to the present invention further includes a half cycle having a length less than 0.5 times the representative value and a half measured before and after the measurement result of the signal half cycle measurement procedure. A signal combining procedure in which a cycle that combines at least one of the cycles is a half cycle after combining, and a signal waveform that combines the cycles is a waveform corresponding to a half cycle of one signal, and the signal counting procedure includes the signal Instead of performing the counting process on the measurement result of the half cycle measurement procedure, the counting process is performed on the processing result of the signal combination procedure in the counting period.

Further, in one configuration example of the counting method of the present invention, the signal combining procedure may measure the measurement result of the signal half cycle measurement procedure at a half cycle having a length less than 0.5 times the representative value and immediately thereafter. The combined cycle is defined as a combined half cycle, and the combined signal waveform is set to a waveform corresponding to a half cycle of one signal. The process is performed until it becomes five times or more.
Further, in one configuration example of the counting method of the present invention, the signal combining procedure may be configured such that, for the measurement result of the signal half cycle measurement procedure, a half cycle having a length less than 0.5 times the representative value is the representative value. When sandwiched between the m-th half cycle Tm having a length of 0.5 times or more and the p-th half cycle Tp (m and p are natural numbers) having a length of 0.5 times or more of the representative value, When (m + p) is an even number, the combined cycle from half cycle Tm to half cycle Tp is the combined half cycle, and when (m + p) is an odd number, the cycle is combined from half cycle Tm to half cycle Tn−1 Is a half cycle after combining, and a signal waveform obtained by combining the cycles is a waveform corresponding to the m-th half cycle.

  Further, the physical quantity measuring method of the present invention is a semiconductor in which at least one of the first oscillation period in which the oscillation wavelength continuously increases monotonically and the second oscillation period in which the oscillation wavelength continuously decreases monotonously exists. An oscillation procedure for operating the laser, a detection procedure for detecting an electrical signal including an interference waveform caused by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, and the detection procedure A signal extraction procedure for counting the number of the interference waveforms included in the output signal for each of the first oscillation period and the second oscillation period, and the physical quantity of the measurement target is obtained from the counting result of the signal extraction procedure. A calculation procedure, wherein the signal extraction procedure receives the output signal obtained by the detection procedure, and each of the first oscillation period and the second oscillation period is a counting period. , And it is characterized in the use of the procedure of the.

  According to the present invention, the period of the input signal in a certain counting period is measured, and from this measurement result, the average value of the period of the input signal is calculated as a representative value, and the measured one period is counted as one signal. When the measured period is not less than (n + 0.5) times and less than (n + 1.5) times the representative value, n is added to the result of counting, and all the measurement results of the signal period measuring means during the counting period By doing so, the counting error can be corrected with a smaller amount of calculation than in the past.

  Further, in the present invention, for the measurement result of the signal period measuring means, a period obtained by combining a period having a length less than 0.5 times the representative value and a period measured immediately thereafter is defined as a combined period, and the period is A signal combining means is provided for performing the combined signal waveform as a waveform for one period of one signal until the combined period becomes 0.5 times or more of the representative value, and the signal counting means measures the signal period. Instead of performing the counting process on the measurement result of the means, the counting error can be further reduced by performing the counting process on the processing result of the signal combining means in the counting period.

  In the present invention, the half cycle of the input signal in a certain counting period is measured, and the average value of the half cycle of the input signal is calculated as a representative value from the measurement result, and the measured half cycle is counted as one. At the same time, when the measured half cycle is not less than (2n) times and less than (2n + 2) times the representative value, 2n is added to the count result for all the measurement results of the signal half cycle measuring means during the counting period. By calculating the number obtained by multiplying the counting result by 0.5 as the number of input signals, the counting error can be corrected with a smaller amount of calculation than in the past.

  Further, in the present invention, the measurement result of the signal half-cycle measuring means is obtained by combining a half-cycle having a length less than 0.5 times the representative value and at least one of the half-cycles measured before and after the half-cycle. Instead of providing a signal combining means that uses a half-cycle after combining, and a signal waveform that combines the periods is a waveform corresponding to a half-cycle of one signal, the signal counting means performs a counting process on the measurement result of the signal half-cycle measuring means. In addition, the counting error can be further reduced by performing the counting process on the processing result of the signal combining means in the counting period.

  Further, in the present invention, the signal combining means has a period obtained by combining a half period having a length less than 0.5 times the representative value and a half period measured immediately after the measurement result of the signal half period measuring means. Counting is performed by setting the half-cycle after combination and setting the signal waveform that combines the periods to be a waveform corresponding to a half cycle of one signal until the half-cycle after combination becomes 0.5 times or more of the representative value. The error can be further reduced.

  Further, in the present invention, the signal combining means is the m-th of the measurement result of the signal half-cycle measuring means in which the half cycle having a length less than 0.5 times the representative value is 0.5 times or more the representative value. Between the half cycle Tm and the p-th half cycle Tp (m and p are natural numbers) having a length equal to or more than 0.5 times the representative value, when (m + p) is an even number, The combined period up to the half period Tp is the combined half period, and when (m + p) is an odd number, the combined period from the half period Tm to the half period Tn-1 is set as the combined half period. By making the signal waveform into the waveform for the m-th half cycle, even if burst noise or popcorn noise over a quarter cycle of the signal to be measured is mixed in the signal input to the counting device, the counting error Can be reduced.

  In addition, in the present invention, by using a counting device that can correct the counting error with a smaller amount of calculation than before, the counting error of the interference waveform is corrected with a smaller amount of calculation than before and the measurement accuracy of the physical quantity is improved. Can be made.

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 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 flowchart which shows operation | movement of the counting device and arithmetic unit in the 1st Embodiment of this invention. It is a block diagram which shows one example of a structure of the counting device in the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the counting device in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the binarization part of a counting device and the AND operation part in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the period measurement part of the counting device in the 1st Embodiment of this invention. It is a figure for demonstrating the relationship between the period which the representative value calculation part of the counting device in the 1st Embodiment of this invention calculates a representative value, and the count period of correction | amendment object. It is a block diagram which shows one example of a structure of the arithmetic unit in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the binarization part of the arithmetic unit in the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the period measurement part of the arithmetic unit in the 1st Embodiment of this invention. It is a figure which shows an example of the frequency distribution of the period of the binarization output which binarized the count result of the counting device 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 the counter of the arithmetic unit in the 1st Embodiment of this invention. It is a figure for demonstrating the correction principle of the count result of the counter of the arithmetic unit 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 block diagram which shows one example of a structure of the counting device in the 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the counting device in the 2nd Embodiment of this invention. It is a figure for demonstrating operation | movement of the signal coupling | bond part of the counting device in the 2nd Embodiment of this invention. It is a block diagram which shows one example of a structure of the counting device in the 3rd Embodiment of this invention. It is a flowchart which shows operation | movement of the counting device in the 3rd Embodiment of this invention. It is a figure for demonstrating operation | movement of the half cycle measurement part of the counting device in the 3rd Embodiment of this invention. It is a block diagram which shows one example of a structure of the counting device in the 4th Embodiment of this invention. It is a flowchart which shows operation | movement of the counting device in the 4th Embodiment of this invention. It is a figure for demonstrating operation | movement of the signal coupling | bond part of the counting device in the 4th Embodiment of this invention. It is a figure for demonstrating operation | movement of the signal coupling | bond part of the counting device in the 5th Embodiment of this invention. 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.

[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 apparatus of 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 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 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 counting device 7 that counts the number of mode hop pulses (MHP), a computing device 8 that determines the vibration frequency of the object 10 based on the counting result of the counting device 7, and a computing device 8 And a display device 9 for displaying the results.

  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. 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.

Here, the MHP that is a self-coupled signal will be described. As shown in FIG. 3, 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 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 10 is extremely weak, because the apparent reflectance in the resonator of the semiconductor laser 1 increases, causing an amplification effect.

  FIG. 4 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 2 when the oscillation wavelength of the semiconductor laser 1 is changed at a certain rate. 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 stronger and a place where the laser output becomes weaker appear alternately. 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. 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, operations of the counting device 7 and the arithmetic device 8 will be described. FIG. 5 is a flowchart showing the operations of the counting device 7 and the arithmetic device 8.
The counting device 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. 5). FIG. 6 is a block diagram showing an example of the configuration of the counting device 7. The counting device 7 includes a binarizing unit 71, an AND operation unit (AND) 72, a period measuring unit 73, a representative value calculating unit 74, a counting unit 75, and a storage unit 76.

  FIG. 7 is a flowchart showing the operation of the counting device 7. 8A to 8C are diagrams for explaining the operation of the binarizing unit 71 and the AND 72. FIG. 8A shows the waveform of the output voltage of the filter unit 6, that is, the waveform of MHP. FIG. 8B is a diagram schematically illustrating the output of the binarization unit 71 corresponding to FIG. 8A, and FIG. 8C is a diagram illustrating the gate signal GS input to the counting device 7. It is.

  First, the binarization unit 71 of the counting device 7 determines whether the output voltage of the filter unit 6 shown in FIG. 8A is a high level (H) or a low level (L), and the binarization unit 71 of FIG. Such a determination result is output. At this time, the binarization unit 71 determines that the output voltage of the filter unit 6 is high level when the output voltage of the filter unit 6 is higher than or equal to the threshold value TH1, and the output voltage of the filter unit 6 is decreased to decrease the threshold value TH2. By determining that the level is low when (TH2 <TH1) or less, the output of the filter unit 6 is binarized (step S100 in FIG. 7).

  The AND 72 outputs the result of the logical product operation between the output of the binarizing unit 71 and the gate signal GS as shown in FIG. Here, the gate signal GS is a signal that rises at the beginning of the counting period (in the present embodiment, the first oscillation period P1 or the second oscillation period P2) and falls at the end of the counting period.

  FIG. 9 is a diagram for explaining the operation of the period measuring unit 73. The period measurement unit 73 measures the MHP period during the counting period (step S101 in FIG. 7). That is, the period measuring unit 73 detects the rising edge of the output of the AND72 by comparing the output of the AND72 during the counting period with the threshold value TH3, and compares the output of the AND72 with the threshold value TH4. The falling edge of the output of AND72 is detected. Then, the period measurement unit 73 measures the period of the output of the AND 72 during the counting period (that is, the period of the MHP) by measuring the time tu from the rise of the output of the AND 72 to the next rise. The period measurement unit 73 performs such measurement every time a rising edge occurs in the output of the AND 72.

Alternatively, the period measurement unit 73 may measure the MHP period by measuring the time tdd from the falling edge of the AND 72 output to the next falling edge. The period measurement unit 73 performs such measurement every time a falling edge occurs in the output of the AND 72.
The storage unit 76 stores the measurement result of the period measurement unit 73.

  Subsequently, the representative value calculation unit 74 calculates the representative value T0 of the MHP cycle during the counting period from the measurement result of the cycle measurement unit 73 (step S102 in FIG. 7). Here, the average value of the period is set as the representative value T0 as the representative value of the statistics obtained without creating the frequency distribution. The representative value T0 calculated by the representative value calculation unit 74 is stored in the storage unit 76.

The counting unit 75 counts the number of MHPs based on the measurement result of the period measuring unit 73 and the representative value T0 calculated by the representative value calculating unit 74 (step S103 in FIG. 7). The counting unit 75 counts one cycle measured by the cycle measuring unit 73 as one signal to obtain a counting result N. At this time, (n + 0.5) T0 ≦ T (i) <(n + 1.5) T0, That is, if the period T (i) measured by the period measuring unit 73 is not less than (n + 0.5) times (n + 1.5) times the representative value T0 (n is a natural number not less than 1 and not more than n _max ), the counting result N N is added to. The initial value of the counting result N is reset to 0 every counting period. The counting unit 75 performs the counting process as described above for all the measurement results of the period measuring unit 73 during the counting period. The final counting result N of the counting unit 75 for all the measurement results of the period measuring unit 73 during the counting period is the number of MHPs during the counting period. The counting result N of the counting unit 75 is stored in the storage unit 76.

N _max is defined as follows.
n _max ≦ T _max / T0 (2)
In Equation (2), T _max is the maximum value that the MHP cycle can take.

The basic principle of the counting process of the counting unit 75 is the same as the correction principle of the counting result disclosed in Patent Document 2, and based on this correction principle, the MHP counting and the correction of the counting result are realized at the same time. It is a thing.
The counting device 7 performs the above processing for each of the first oscillation period P1 and the second oscillation period P2.

  As the representative value T0 used by the counting unit 75, a value calculated from the measurement result of the period measuring unit 73 in the counting period one period before the carrier wave (triangular wave) before the counting period to be corrected may be used. Alternatively, a value calculated from the measurement result of the period measurement unit 73 in the counting period to be corrected may be used. FIG. 10 is a diagram showing a change over time of the oscillation wavelength of the semiconductor laser 1, and is a diagram for explaining the relationship between the period during which the representative value calculation unit 74 calculates the representative value T0 and the counting period to be corrected.

  When using the representative value T0 calculated from the measurement result of one cycle of the carrier wave before the correction target counting period, the counting unit 75, for example, the representative calculated in the first oscillation period P1-1 shown in FIG. The count process of the first oscillation period P1-2 is performed using the value T0, and the count process of the second oscillation period P2-2 is performed using the representative value T0 calculated in the second oscillation period P2-1. It will be. Further, when using the representative value T0 calculated from the measurement result of the correction target counting period, the counting unit 75 uses the representative value T0 calculated in the first oscillation period P1-1 shown in FIG. The counting process of one oscillation period P1-1 is performed, and the counting process of the second oscillation period P2-1 is performed using the representative value T0 calculated in the second oscillation period P2-1.

However, even when using the representative value T0 calculated from the measurement result of one cycle of the carrier wave before the counting period of the correction target, the initial value of the representative value T0 does not exist in the first process, so the correction target The representative value T0 is obtained from the measurement result of the period measuring unit 73 in the counting period, and the counting process is performed.
However, when the calculation result of one cycle before is used, it is more accurate to use (counting time / count value after counting process) than to use the representative value T0.

  Next, the computing device 8 calculates the vibration frequency of the object 10 based on the number of MHPs counted by the counting device 7. FIG. 11 is a block diagram showing an example of the configuration of the arithmetic unit 8. The arithmetic device 8 includes a storage unit 80 that stores the counting result of the counting device 7, a binarizing unit 81 that binarizes the counting result of the counting device 7, and the binarization output from the binarizing unit 81. A cycle measuring unit 82 that measures the cycle of the output, a frequency distribution creating unit 83 that creates a frequency distribution of the cycle of the binarized output, and a reference for calculating a reference cycle that is a representative value of the cycle distribution of the binarized output Period calculation unit 84, counter 85 serving as a binarized output counting means for counting the number of binarized output pulses, correction unit 86 for correcting the count result of counter 85, and object based on the corrected count result A frequency calculation unit 87 that calculates ten vibration frequencies.

  The counting result of the counting device 7 is stored in the storage unit 80 of the arithmetic device 8. The binarizing unit 81 of the arithmetic device 8 binarizes the counting result of the counting device 7 stored in the storage unit 80 (step S2 in FIG. 5). 12A to 12C are diagrams for explaining the operation of the binarizing unit 81, and FIG. 12A is a diagram showing a change with time of the oscillation wavelength of the semiconductor laser 1. FIG. FIG. 12B is a diagram showing a time change of the counting result of the counting device 7, and FIG. In FIG. 12B, 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 (3)
If Nu (t) <Nd (t-1) then D (t) = 0 (4)
If Nd (t) ≦ Nu (t−1) then D (t) = 1 (5)
If Nd (t)> Nu (t-1) then D (t) = 0 (6)

  In Expressions (3) to (6), (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. Expressions (3) and (4) 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 (5) and (6) 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 counting device 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 binarization process as described above at every time (every oscillation period) when the counting device 7 measures the number of MHPs.

  Binarizing the counting result of the counting device 7 means determining the direction of displacement of the object 10. 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 10 is When the counting result Nu is smaller than the counting result Nd (D (t) = 0), the moving direction of the object 10 is a direction away from the semiconductor laser 1. Therefore, basically, if the period of the binarized output shown in FIG. 12C can be obtained, the vibration frequency of the object 10 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. 5). FIG. 13 is a diagram for explaining the operation of the period measurement unit 82. In FIG. 13, 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. 5, step S4). FIG. 14 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 cycle calculation unit 84 calculates a reference cycle Tr that is a representative value of the cycle of the binarized output D (t) from the frequency distribution created by the frequency distribution creation unit 83 (step S5 in FIG. 5). 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 Tr. 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 used as the reference period Tr will be described later. The calculated value of the reference period Tr is stored in the storage unit 80. The reference period calculation unit 84 performs such calculation of the reference period Tr every time the frequency distribution is created by the frequency distribution creation 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 Na of rising edges of D (t) Na (that is, the number of “1” pulses of the binarized output D (t)) is counted (step S6 in FIG. 5). The counting result Na 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 creating unit 83, the correcting unit 86 calculates the sum Nsa of the class frequencies that are 0.5 times or less of the reference period Tr and the frequency of the class that is 1.5 times or more of the reference period Tr. And the count result Na of the counter 85 is corrected as follows (step S7 in FIG. 5).
Na ′ = Na−Nsa + Nwa (7)
In equation (7), Na ′ is the corrected count result. The corrected count result Na ′ is stored in the storage unit 80. The correction unit 86 performs such correction every T time.

  FIG. 15 is a diagram schematically showing the total number Nsa and Nwa of frequencies. In FIG. 15, Ts is a class value 0.5 times the reference period Tr, and Tw is a class value 1.5 times the reference period Tr. Needless to say, the class in FIG. 15 is a representative value of the period. In FIG. 15, in order to simplify the description, the frequency distribution between the reference periods Tr and Ts and between the reference periods Tr and Tw is omitted.

16 (A) to 16 (B) are diagrams for explaining the correction principle of the counting result of the counter 85, and FIG. 16 (A) is a diagram showing the binarized output D (t). FIG. 16B is a diagram illustrating a counting result of the counter 85 corresponding to FIG.
Originally, the cycle of the binarized output D (t) varies depending on the vibration frequency of the object 10, but if the vibration frequency of the object 10 is unchanged, 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 result of counting the pulses of the binarized 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 Tr, it can be determined that the signal is missing. Therefore, the sum of the frequencies Nwa of the class equal to or higher than the period Tw is regarded as the number of missing signals, and the missing signal can be corrected by adding this Nwa to the counting result Na 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 Tr, it can be determined that the signals are excessively counted. Therefore, it is possible to correct the noise that is erroneously counted by regarding the total sum Nsa of the frequencies of the classes equal to or less than the period Ts as the number of times the signal is excessively counted and subtracting this Nsa from the counting result Na of the counter 85. The above is the correction principle of the counting result shown in Expression (7).

Based on the corrected count result Na ′ calculated by the correction unit 86, the frequency calculation unit 87 calculates the vibration frequency fsig of the object 10 according to the following equation (step S8 in FIG. 5).
fsig = Na ′ / T (8)
The display device 9 displays the value of the vibration frequency fsig calculated by the arithmetic device 8.

  As described above, in the present embodiment, the MHP cycle in a certain counting period is measured, the average value of the MHP cycle is calculated as the representative value T0 from the measurement result, and the measured 1 cycle is used as one signal. In addition to counting, when the measured cycle is not less than (n + 0.5) times (n + 1.5) times the representative value T0, n is added to the count result. By performing all measurement results, the MHP counting error can be corrected with a smaller amount of calculation than before, so that the measurement accuracy of the vibration frequency of the object 10 can be improved.

  Furthermore, 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 (t) A frequency distribution of periods at a certain time T is measured, a reference period Tr that is a representative value of the distribution of the binarized output D (t) is calculated from the frequency distribution of the periods, and the constant time T In this period, the number of pulses of the binarized output D (t) is counted, and from the frequency distribution, the total frequency Nsa of the class that is 0.5 times or less of the reference period Tr and 1.5 times or more of the reference period Tr By calculating the total sum Nwa of frequencies of a certain class and correcting the count result of the pulses of the binarized output D (t) based on these frequencies Nsa and Nwa, the counting error of the binarized output D (t) Therefore, the measurement accuracy of the vibration frequency of the object 10 can be improved. It is possible to improve.

Next, the reason why the class value that maximizes the product of the class value and the frequency is set as the reference period Tr 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 10 and the object 10 in the counting period. The sum or difference with the number of MHPs proportional to the displacement (velocity). Depending on the magnitude relationship between the ratio of the maximum speed of vibration of the object 10 and the distance between the object 10 and the wavelength change rate of the semiconductor laser 1, the status of signals obtained by the measuring apparatus can be divided into the following two types.

  First, the case where the ratio of the maximum speed of vibration of the object 10 and the distance between the object 10 is smaller than the wavelength change rate of the semiconductor laser 1 will be described. FIG. 17A to FIG. 17D are diagrams for explaining signals obtained by the vibration frequency measuring device of the present embodiment in this case, and FIG. FIG. 17B is a diagram showing the time change of the speed of the object 10, FIG. 17C is a diagram showing the time change of the counting result of the counting device, and FIG. It is a figure which shows the binarization output D (t) which binarized the count result. In FIG. 17B, 160 indicates a portion where the speed is low, 161 indicates that the moving direction of the object 10 is a direction approaching the semiconductor laser 1, and 162 indicates that the moving direction of the object 10 is far from the semiconductor laser 1. Indicates that the direction.

  When the ratio of the maximum speed of vibration of the object 10 and the distance to the object 10 is smaller than the wavelength change rate of the semiconductor laser 1, the number of MHPs proportional to the distance to the object 10 is the displacement of the object 10 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). This is always proportional to the displacement of the object 10 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 movement direction of the object 10, and the displacement of the object 10 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. 17C, when white noise due to, for example, ambient light is added at a location 163 where the speed of the object 10 is low, a binary signal is output at a location 164 where the sign of the binarized output D (t) changes. The sign of the digitized output D (t) may be a value opposite to the original value. 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 165 as shown in FIG.

  As a result, as shown in FIG. 18, the frequency distribution of the period created by the frequency distribution creating unit 83 includes a normal distribution 190 centered on the reference period Tr, a frequency 191 due to sign inversion caused by spike noise, It becomes the sum with the frequency 192 due to the sign inversion caused by noise. Further, the frequency 193 of signal loss 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 10 and the distance between the object 10 is larger than the wavelength change rate of the semiconductor laser 1 will be described. FIG. 19A to FIG. 19D are diagrams for explaining signals obtained by the vibration frequency measuring device of this embodiment in this case, and FIG. FIG. 19B is a diagram showing the time change of the speed of the object 10, FIG. 19C is a diagram showing the time change of the counting result of the counting device 7, and FIG. It is a figure which shows the binarization output D (t) by the conversion part 81. FIG. In FIG. 19B, 220 indicates a portion where the speed is low, 221 indicates that the moving direction of the object 10 is a direction approaching the semiconductor laser 1, and 222 indicates that the moving direction of the object 10 is far from the semiconductor laser 1. Indicates that the direction.

  When the ratio of the maximum speed of vibration of the object 10 and the distance to the object 10 is larger than the wavelength change rate of the semiconductor laser 1, the number of MHPs proportional to the distance to the object 10 is near the maximum speed of the object 10. Since the number is smaller than the number of MHPs proportional to the displacement (velocity) of the object 10 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 10 in two counting periods (oscillation periods P1 and P2 in this embodiment), 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 10 displacements.

  In this case, the vibration speed of the object 10 can be expressed by combining graphs in which Nu−Nd and Nu + Nd are plotted in time series as shown in FIG. However, since the speed direction always matches the magnitude relationship between Nu and Nd, the sign of Nu-Nd indicates the direction of motion of the object 10, and the displacement of the object 10 can be binarized by this sign. it can.

  Similar to the case where the ratio of the maximum speed of vibration of the object 10 and the distance to the object 10 is smaller than the wavelength change rate of the semiconductor laser 1, white light caused by, for example, disturbance light at the portion 223 where the speed of the object 10 is small. When noise is added, the sign of the binarized output D (t) may be a value opposite to the original value at the location 224 where the sign of the binarized output D (t) switches. Further, for example, when spike noise due to disturbance light or the like is added, the sign of the binarized output D (t) is locally inverted at a location 225 as shown in FIG. At this time, the frequency distribution of the period created by the frequency distribution creating unit 83 is the same as in FIG.

  In the case of correcting the binarized output D (t) obtained by binarizing the displacement of the object 10 as in the present embodiment, 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 10, and when the mode value or the median value is used as the 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, correction of the count result of the counter 85 with the ratio of the signal of a certain class in the period of the fixed time T for calculating the vibration frequency, that is, the class value having the largest product of the class value and the frequency as the reference period Tr. To implement. The above is the reason for setting the class value that maximizes the product of the class value and the frequency as the reference period Tr.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 20 is a diagram showing an example of the configuration of the counting device according to the present embodiment. In the present embodiment, a counting device 7a is used instead of the counting device 7 of the first embodiment. The counting device 7a includes a binarizing unit 71, an AND 72, a period measuring unit 73, a representative value calculating unit 74a, a counting unit 75a, a storage unit 76, and a signal combining unit 77.

FIG. 21 is a flowchart showing the operation of the counting device 7a of the present embodiment. As described in the first embodiment, the binarization unit 71 binarizes the output of the filter unit 6 (step S100 in FIG. 21), and the period measurement unit 73 measures the MHP period during the counting period. (FIG. 21, step S101).
Similarly to the first embodiment, the representative value calculation unit 74a calculates the average value of the MHP periods during the counting period as the representative value T0 from the measurement result of the period measurement unit 73 (step S102 in FIG. 21). The representative value T0 calculated by the representative value calculation unit 74a is stored in the storage unit 76.

  Next, the signal combining unit 77 combines the period obtained by combining the period of less than 0.5 times the representative value T0 with the period measured immediately after the period of the measurement result of the period measuring unit 73. Then, the combined waveform is changed to a waveform for one cycle of one MHP until the combined cycle becomes 0.5 times or more of the representative value T0 (step S104 in FIG. 21). 22A to 22C are diagrams for explaining the operation of the signal coupling unit 77. FIG. 22A is a diagram schematically illustrating the waveform of MHP, and FIG. FIG. 22C is a diagram showing the measurement result of the measurement unit 73, and FIG.

  When the period measurement unit 73 measures the MHP period shown in FIG. 22A, the measurement results of periods T1, T2, T3, T4, T5, T6, and T7 are obtained as shown in FIG. 22B. Among these, the periods T1, T3, T4, T6, and T7 are caused by high frequency noise and the like. In this case, since the periods T1, T3 to T6 are less than 0.5 times the representative value T0, in the counting device 7 of the first embodiment, an error occurs in the counting results at the positions T3 to T7. .

  On the other hand, in this embodiment, when the signal combining unit 77 performs the signal combining process as described above, a processing result with periods T1 and T2 is obtained as shown in FIG. For example, the combined period T1 and T2 is a combined period T1, and the waveforms of T1 and T2 are combined as one MHP waveform. Here, the coupling is performed so that the period after the coupling is 0.5 times or more of the representative value T0. Similarly, a period obtained by combining the periods T3 to T7 in FIG. 22B is a combined period T2 as shown in FIG. 22C, and the waveform from T3 to T7 is a waveform for one period of one MHP. Combined. The half cycle is the time from the rise of MHP to the next fall, or the time from the fall to the next rise. The processing result of the signal combining unit 77 is stored in the storage unit 76.

  Next, the representative value calculation unit 74a calculates the average value of the periods as the representative value T0 for the MHP processed by the signal combining unit 77 (step S105 in FIG. 21). As a result, the representative value T0 stored in the storage unit 76 is updated to the latest value calculated in step S105.

Finally, the counting unit 75a counts the number of MHPs based on the processing result of the signal combining unit 77 and the representative value T0 calculated by the representative value calculating unit 74a in step S105 (step S106 in FIG. 21). The processing of the counting unit 75a is the same as that of the counting unit 75 of the first embodiment. However, it is not necessary to use the measurement result of the period measurement unit 73 as in the first embodiment, and the processing described in the first embodiment may be performed on the processing result of the signal combining unit 77. The counting unit 75a performs such a counting process for all processing results of the signal combining unit 77 during the counting period.
The counting device 7a performs the above processing for each of the first oscillation period P1 and the second oscillation period P2.

  Other configurations are the same as those of the first embodiment. In the first embodiment, when a decrease in the signal strength of MHP and mixing of burst noise into the signal input to the counting device 7 occur at the same time, the MHP may be counted low. According to this, such a counting error can be reduced.

  In the present embodiment, the processing in step S105 is not an essential component. This is because it is not always necessary to obtain the representative value again if the representative value before combining is obtained with high accuracy. When the process of step S105 is not executed, the counting unit 75a may use the representative value T0 calculated in step S102. However, when it is considered that the accuracy of the representative value T0 calculated in step S102 is low, the process of step S105 may be executed.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 23 is a diagram showing an example of the configuration of the counting device according to the present embodiment. In the present embodiment, a counting device 7b is used instead of the counting device 7 of the first embodiment. The counting device 7b includes a binarizing unit 71, an AND 72, a representative value calculating unit 74b, a counting unit 75b, a storage unit 76, a half cycle measuring unit 78, and a counting result correcting unit 79.

FIG. 24 is a flowchart showing the operation of the counting device 7b. The operations of the binarizing unit 71 and the AND 72 are the same as those in the first embodiment (step S100 in FIG. 24).
FIG. 25 is a diagram for explaining the operation of the half-cycle measuring unit 78. The half cycle measuring unit 78 measures the half cycle of the MHP during the counting period (step S107 in FIG. 24). That is, the half-cycle measuring unit 78 detects the rising edge of the output of the AND72 by comparing the output of the AND72 during the counting period with the threshold value TH5, and compares the output of the AND72 with the threshold value TH6. , The falling edge of the output of AND72 is detected. The half-cycle measuring unit 78 measures the time tud from the rising edge of the output of the AND 72 to the next falling edge, and measures the time tdu from the falling edge of the output of the AND 72 to the next rising edge. Measure the half cycle of the output of AND 72 in the middle (ie, half cycle of MHP). Thus, the half-cycle of MHP means time tud or tdu, and indicates a displacement point from a displacement point when binarized. The half-cycle measuring unit 78 performs the above measurement every time when either the rising edge or the falling edge of the output of the AND 72 is detected. The storage unit 76 stores the measurement result of the half cycle measurement unit 78.

  Subsequently, the representative value calculating unit 74b calculates a representative value T0 of the MHP half cycle during the counting period from the measurement result of the half cycle measuring unit 78 (step S108 in FIG. 24). Here, an average value of a half cycle is set as a representative value T0 as a representative value of statistics obtained without creating a frequency distribution. The representative value T0 calculated by the representative value calculation unit 74b is stored in the storage unit 76.

The counting unit 75b counts the number of MHP half cycles based on the measurement result of the half cycle measuring unit 78 and the representative value T0 calculated by the representative value calculating unit 74b (step S109 in FIG. 24). The counting unit 75b obtains the counting result N ′ by counting the half cycles measured by the half cycle measuring unit 78 as one. At this time, (2n) T0 ≦ T (i) <(2n + 2) T0, that is, a half cycle. If the half period T (i) measured by the measuring unit 78 is not less than (2n) times (2n + 2) times the representative value T0 (n is a natural number not less than 1 and not more than n _max ), 2n is added to the count result N ′. To do. The initial value of the counting result N ′ is reset to 0 every counting period. The counting unit 75b performs the counting process as described above for all the measurement results of the half-cycle measuring unit 78 during the counting period. The final count result N ′ of the counting unit 75b for all the measurement results of the half-cycle measuring unit 78 during the counting period is the number of MHP half-cycles during the counting period. The counting result N ′ of the counting unit 75 b is stored in the storage unit 76.

Finally, the counting result correction unit 79 calculates a number obtained by multiplying the counting result N ′ of the counting unit 75b by 0.5 as the number N of MHPs (step S110 in FIG. 24). The corrected count result N is stored in the storage unit 76.
The counting device 7b performs the above processing for each of the first oscillation period P1 and the second oscillation period P2.

  Other configurations are the same as those of the first embodiment. In the present embodiment, in addition to the effects of the first embodiment, even when noise having a frequency higher than that of MHP is continuously generated in the signal input to the counting device, the counting error of MHP is increased. The effect that it can correct | amend with high precision can be acquired.

As in the first embodiment, the representative value T0 used by the counting unit 75b is the measurement result of the half-cycle measuring unit 78 in the counting period one period before the carrier wave (triangular wave) before the counting period to be corrected. A value calculated from the measurement result of the half-cycle measuring unit 78 in the counting period to be corrected may be used. Even in the case of using the representative value T0 calculated from the measurement result of one cycle of the carrier wave before the correction target counting period, the initial value of the representative value T0 does not exist in the first process. The representative value T0 is obtained from the measurement result of the half-cycle measuring unit 78 and the counting process is performed.
However, when the calculation result of one cycle before is used, it is more accurate to use (counting time / count value after counting process) than to use the representative value T0.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 26 is a diagram showing an example of the configuration of the counting device according to the present embodiment. In the present embodiment, a counting device 7c is used instead of the counting device 7 of the first embodiment, and the second embodiment and the third embodiment are combined. The counting device 7c includes a binarizing unit 71, an AND 72, a representative value calculating unit 74b, a counting unit 75c, a storage unit 76, a signal combining unit 77c, a half cycle measuring unit 78, and a counting result correcting unit 79. It consists of.

FIG. 27 is a flowchart showing the operation of the counting device 7c of the present embodiment. The operations of the binarizing unit 71 and the AND 72 are the same as those in the first embodiment (step S100 in FIG. 27).
As described in the third embodiment, the half cycle measuring unit 78 measures the half cycle of the MHP during the counting period (step S107 in FIG. 27), and the representative value calculating unit 74b is measured by the half cycle measuring unit 78. From the result, the average value of the half periods of the MHP during the counting period is calculated as the representative value T0 (step S108 in FIG. 27).

  Next, the signal combining unit 77c combines the period obtained by combining the half period having a length less than 0.5 times the representative value T0 and the half period measured immediately after the measurement result of the half period measuring unit 78. The subsequent half cycle is set to a waveform corresponding to one MHP half cycle until the combined half cycle becomes 0.5 times or more of the representative value T0 (step S111 in FIG. 27). ). 28A to 28C are diagrams for explaining the operation of the signal coupling unit 77c. FIG. 28A is a diagram schematically illustrating the waveform of MHP, and FIG. The figure which shows the measurement result of the period measurement part 78, FIG.28 (C) is a figure which shows the process result of the signal coupling | bond part 77c.

  When the half cycle measuring unit 78 measures the half cycle of the MHP shown in FIG. 28 (A), as shown in FIG. 28 (B), half cycles T1, T2, T3, T4, T5, T6, T7, T8, T9, Measurement results of T10, T11, T12, T13, T14, T15, and T16 are obtained. Of these, the half periods T2, T3, T6 to T9, and T11 to T14 are caused by causes such as high frequency noise. In this case, since the half periods T2, T3, T6 to T14 are less than 0.5 times the representative value T0, T10 is recognized as the MHP half period in the counting device 7b of the third embodiment. Therefore, an error occurs in the counting result.

  On the other hand, in this embodiment, the signal combining unit 77c performs the signal combining process as described above, so that the half periods T1, T2, T3, T4, T5, as shown in FIG. A processing result of T6 is obtained. For example, the combined period of the half periods T2 to T4 is the combined half period T2, and the waveforms of T2 to T4 are combined as a waveform corresponding to one MHP half period. Similarly, the combined period of the half periods T6 to T10 is the combined half period T4, and the waveforms of T6 to T10 are combined as a waveform for one MHP half period. The processing result of the signal combining unit 77 c is stored in the storage unit 76.

  Next, the representative value calculation unit 74b calculates the average value of the half cycle as the representative value T0 for the MHP processed by the signal combining unit 77c (step S112 in FIG. 27). As a result, the representative value T0 stored in the storage unit 76 is updated to the latest value calculated in step S112.

  The counting unit 75c counts the number of MHP half cycles based on the processing result of the signal combining unit 77c and the representative value T0 calculated by the representative value calculating unit 74b in step S112 (step S113 in FIG. 27). The processing of the counting unit 75c is the same as that of the counting unit 75b of the third embodiment. However, it is not necessary to use the measurement result of the half cycle measurement unit 78 as in the third embodiment, and the processing described in the third embodiment may be performed on the processing result of the signal combining unit 77c. The counting unit 75c performs such counting processing for all processing results of the signal combining unit 77c during the counting period.

Finally, the counting result correction unit 79 calculates a number obtained by multiplying the counting result N ′ of the counting unit 75c by 0.5 as the number N of MHPs (step S114 in FIG. 27). The corrected count result N is stored in the storage unit 76.
The counting device 7c performs the above process for each of the first oscillation period P1 and the second oscillation period P2.

  Other configurations are the same as those of the first embodiment. In the first embodiment, when a decrease in the signal strength of MHP and mixing of burst noise into the signal input to the counting device 7 occur at the same time, the MHP may be counted low. According to this, such a counting error can be reduced.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. Also in the present embodiment, the configuration of the counting device and the flow of processing are the same as in the fourth embodiment, and therefore, the present embodiment will be described using the reference numerals in FIGS.
The processes in steps S100, S107, and S108 in FIG. 27 are the same as those in the fourth embodiment.

  Next, the signal coupling unit 77c of the present embodiment has a half cycle having a length less than 0.5 times the representative value T0 and a measurement result of the half cycle measuring unit 78 of 0.5 times or more of the representative value T0. (M + p) is an even number when sandwiched between the m-th half cycle Tm of length and the p-th half cycle Tp (m and p are natural numbers) of 0.5 times or more the representative value T0. In this case, the combined period from the half period Tm to the half period Tp is defined as the combined half period. When (m + p) is an odd number, the combined period from the half period Tm to the half period Tn−1 is defined as the combined half period. And the waveform with the combined period is the waveform for the m-th half cycle (step S111 in FIG. 27).

29A to 29C are diagrams for explaining the operation of the signal coupling unit 77c of the present embodiment, and FIG. 29A is a diagram schematically illustrating the waveform of MHP. FIG. 29B is a diagram showing a measurement result of the half-cycle measurement unit 78, and FIG. 29C is a diagram showing a processing result of the signal combining unit 77c of the present embodiment.
When the half cycle measuring unit 78 measures the half cycle of the MHP shown in FIG. 29A, measurement results of half cycles T1 to T20 are obtained as shown in FIG. 29B. In this case, since the half periods T2, T3, T6 to T14, and T16 to T19 are less than 0.5 times the representative value T0, in the counting device 7b of the third embodiment, T10 is a half of MHP. It is not recognized as a period, and a correction error occurs in the counting result.

  On the other hand, in the present embodiment, the signal combining unit 77c performs the signal combining process as described above, so that the processing results of half cycles T1, T2, T3, and T4 as shown in FIG. Is obtained. For example, the half periods T2 and T3 are sandwiched between half periods T1 and T4 having a length of 0.5 times or more of the representative value T0, and m + p is an odd number of 1 + 4 = 5. Therefore, the waveforms of T1 to T3 are combined as a waveform for one MHP half cycle, and the combined cycle of the half cycles T1 to T3 is the combined half cycle T1.

  Similarly, the half periods T6 to T14 are sandwiched between half periods T5 and T15 having a length of 0.5 times or more of the representative value T0, and m + p is an even number of 5 + 15 = 20. Therefore, the waveforms of T5 to T15 are combined as a waveform corresponding to one MHP half cycle, and the combined period of the half cycles T5 to T15 is a combined half cycle T3. Further, the half periods T16 to T19 are sandwiched between the combined half period T3 and the half period T20 having a length of 0.5 times or more of the representative value T0, and m + p is an odd number of 3 + 20 = 23. Therefore, the waveforms of the half periods T3, T16 to T19 are combined as a waveform corresponding to one MHP half period, and the combined period of the half periods T3, T16 to T19 is the combined half period T3. The processing result of the signal combining unit 77 c is stored in the storage unit 76.

  The processing in steps S112 to S114 is the same as that in the fourth embodiment. According to the fourth embodiment, the counting error can be reduced as compared with the third embodiment. However, burst noise or popcorn having a period of 1/4 or more of MHP is included in the signal input to the counting device 7b. When noise is mixed, burst noise and popcorn noise are counted, and a counting error may occur. On the other hand, in this embodiment, even when such noise is mixed, the counting error can be reduced.

  In the fourth embodiment and the fifth embodiment, the process of step S112 is not an essential component. This is because it is not always necessary to obtain the representative value again if the representative value before combining is obtained with high accuracy. When the process of step S112 is not executed, the counting unit 75c may use the representative value T0 calculated in step S108. However, when it is considered that the accuracy of the representative value T0 calculated in step S108 is low, the process of step S112 may be executed.

  As another example of the first to fifth embodiments, instead of the period measuring unit 82, the frequency distribution creating unit 83, the reference period calculating unit 84, the counter 85, and the correcting unit 86, the first to fifth examples are used. The period measuring unit 73, the representative value calculating units 74, 74a, 74b, the counting units 75, 75a, 75b, 75c, the storage unit 76, and the signal coupling unit 77 of the counting devices 7, 7a, 7b, 7c described in the embodiment. , 77c, half-cycle measuring unit 78, and counting result correcting unit 79 may be applied to realize the counting of the binary output D (t) pulses and the correction of the counting result.

  In the first to fifth embodiments, at least the counting devices 7, 7a, 7b, and 7c and the computing device 8 are, for example, a computer having a CPU, a storage device, and an interface, and a program for controlling these hardware resources. Can be realized. A program for operating such a computer is provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, or a memory card. The CPU writes the read program into the storage device, and executes the processes described in the first to fifth embodiments according to this program.

In the first to fifth embodiments, the case where the counting device of the present invention is applied to a vibration frequency measuring device has been described. However, the present invention is not limited to this, and the counting device of the present invention can be applied to other fields. Can be applied. When the counting device of the present invention is effective, the number of signals to be counted is a specific physical quantity (in the case of the first to fifth embodiments, the distance between the semiconductor laser 1 and the object 10 and the object 10 Displacement) and a specific physical quantity is constant when the signal has a substantially single frequency.
Further, even if the signal is not a single frequency, the spread of the periodic distribution such as the speed of an object oscillating at a frequency where the specific physical quantity is sufficiently lower than the counting period, for example, 1/10 or less, is possible. Is small, the counting device of the present invention is effective as a substantially single frequency.

  In the first to fifth embodiments, the vibration frequency measurement device has been described as an example of the physical quantity sensor. However, the present invention is not limited to this, and the present invention may be applied to other physical quantity sensors. That is, the tension of the object may be calculated from the counting result of the counting device, or the distance from the object and the speed of the object may be calculated from the counting result of the counting device as disclosed in Patent Document 1. Also good. As apparent from various physical quantities calculated by the physical quantity sensor, the specific physical quantity and the physical quantity calculated by the physical quantity sensor may be the same or different.

  The present invention can be applied to a counting device that counts the number of signals, and an interference-type physical quantity sensor that measures the number of interference waveforms by using the counting device to obtain a physical quantity to be measured.

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplification part, 6 ... Filter part, 7, 7a, 7b, 7c ... Counting device, 8 ... Arithmetic unit, 9 DESCRIPTION OF SYMBOLS ... Display apparatus, 10 ... Object, 71 ... Binarization part, 72 ... AND operation part, 73 ... Period measurement part, 74, 74a, 74b ... Representative value calculation part, 75, 75a, 75b, 75c ... Counting part, 76: Storage unit, 77, 77c: Signal combination unit, 78: Half cycle measurement unit, 79: Count result correction unit, 80 ... Storage unit, 81 ... Binarization unit, 82 ... Period measurement unit, 83 ... Frequency distribution creation , 84... Reference period calculation section, 85... Counter, 86. Correction section, 87. Frequency calculation section, 88.

Claims (14)

In the counting device that counts the signal having a linear relationship between the specific physical quantity and the number of signals and having a single frequency when the specific physical quantity is constant,
Signal period measuring means for measuring the period of the input signal in a certain counting period every time a signal is input;
Representative value calculating means for calculating an average value of the period of the input signal as a representative value from the latest or past measurement results of the signal period measuring means;
When one period measured by the signal period measuring means is counted as one signal, and the period measured by the signal period measuring means is not less than (n + 0.5) times and less than (n + 1.5) times the representative value (N is a natural number equal to or greater than 1) and a signal counting unit that adds n to the counting result for all measurement results of the signal period measuring unit during the counting period. The counting device according to claim 1, wherein
Further, with respect to the measurement result of the signal period measuring means, a period obtained by combining a period having a length less than 0.5 times the representative value and a period measured immediately thereafter is defined as a combined period, and the period is adjusted. Comprising signal combining means for making a signal waveform a waveform for one period of one signal until a period after combining becomes 0.5 times or more of the representative value;
The counting apparatus according to claim 1, wherein the signal counting means performs the counting process on the processing result of the signal combining means in the counting period instead of performing the counting process on the measurement result of the signal period measuring means. In the counting device that counts the signal having a linear relationship between the specific physical quantity and the number of signals and having a single frequency when the specific physical quantity is constant,
A signal half cycle measuring means for measuring a half cycle of an input signal in a certain counting period every time a half cycle of the signal is input;
Representative value calculating means for calculating an average value of the half period of the input signal as a representative value from the latest or past measurement result of the signal half period measuring means;
When the half period measured by the signal half period measuring means is counted as one, and the half period measured by the signal half period measuring means is not less than (2n) times (2n + 2) times the representative value (n Is a natural number of 1 or more), signal counting means for adding 2n to the counting result for all measurement results of the signal half-cycle measuring means during the counting period;
A counting apparatus comprising: counting result correcting means for calculating a number obtained by multiplying the counting result of the signal counting means by 0.5 as the number of the input signals. The counting device according to claim 3, wherein
Further, for the measurement result of the signal half-cycle measuring means, after combining a cycle that is a combination of a half cycle less than 0.5 times the representative value and at least one of the half cycles measured before and after the half cycle A signal combining means for making a signal waveform with a combined period into a half-cycle waveform of one signal,
The said signal counting means performs a counting process about the processing result of the said signal coupling | bonding means in the said counting period instead of performing a counting process about the measurement result of the said signal half cycle measuring means. The counting device according to claim 4, wherein
The signal combining unit is configured to combine a cycle obtained by combining a half cycle having a length less than 0.5 times the representative value and a half cycle measured immediately after the measurement result of the signal half cycle measurement unit. The counting is characterized in that a half cycle is performed, and the combined signal waveform is a waveform corresponding to a half cycle of one signal until the combined half cycle is 0.5 times or more of the representative value. apparatus. The counting device according to claim 4, wherein
The signal combining means has an m-th half of a measurement result of the signal half-cycle measuring means in which a half cycle having a length less than 0.5 times the representative value is 0.5 times or more of the representative value. When sandwiched between a cycle Tm and a p-th half cycle Tp (m and p are natural numbers) having a length of 0.5 times or more of the representative value, when (m + p) is an even number, the half cycle Tm is half The combined period up to the period Tp is the combined half period, and if (m + p) is an odd number, the combined period from the half period Tm to the half period Tn-1 is the combined half period. A counting device characterized in that the waveform is a waveform corresponding to the m-th half cycle. A semiconductor laser that emits laser light to the object to be measured;
Oscillation wavelength modulation means for operating the semiconductor laser so that at least one of a first oscillation period in which the oscillation wavelength continuously increases monotonously and a second oscillation period in which the oscillation wavelength continuously decreases monotonously exists ,
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;
The number of the interference waveforms is counted according to any one of claims 1 to 6, wherein an output signal of the detection means is input and each of the first oscillation period and the second oscillation period is a counting period. A counting device,
A physical quantity sensor comprising: an arithmetic means for obtaining a physical quantity of the measurement object from a counting result of the counting device. In the counting method of counting the signals that have a linear relationship between a specific physical quantity and the number of signals, and when the specific physical quantity is constant, the signal has a substantially single frequency.
A signal period measurement procedure for measuring the period of an input signal in a certain counting period every time a signal is input;
From the latest or past measurement results of this signal period measurement procedure, a representative value calculation procedure for calculating an average value of the period of the input signal as a representative value;
When one period measured in the signal period measurement procedure is counted as one signal, and the period measured in the signal period measurement procedure is not less than (n + 0.5) times and less than (n + 1.5) times the representative value (N is a natural number equal to or greater than 1), and a signal counting procedure for adding n to the counting result for all measurement results of the signal period measuring procedure during the counting period. The counting method according to claim 8, wherein
Further, for the measurement result of the signal period measurement procedure, a period obtained by combining a period having a length less than 0.5 times the representative value and a period measured immediately thereafter is defined as a combined period, and the period is adjusted. Comprising a signal combining procedure for making a signal waveform into a waveform for one period of one signal until a period after combining becomes 0.5 times or more of the representative value;
In the signal counting procedure, the counting process is performed on the processing result of the signal combination procedure in the counting period, instead of performing the counting process on the measurement result of the signal period measurement procedure. In the counting method of counting the signals that have a linear relationship between a specific physical quantity and the number of signals, and when the specific physical quantity is constant, the signal has a substantially single frequency.
A signal half cycle measurement procedure for measuring a half cycle of an input signal in a certain counting period every time a half cycle of the signal is input;
From the latest or past measurement results of this signal half cycle measurement procedure, a representative value calculation procedure for calculating the average value of the half cycle of the input signal as a representative value,
When the half cycle measured in the signal half cycle measurement procedure is counted as one and the half cycle measured in the signal half cycle measurement procedure is (2n) times or more and less than (2n + 2) times the representative value (n Is a natural number greater than or equal to 1), adding 2n to the counting result, a signal counting procedure for performing all the measurement results of the signal half-cycle measuring procedure during the counting period;
A counting method comprising: a counting result correcting procedure for calculating a number obtained by multiplying a counting result of the signal counting procedure by 0.5 as the number of the input signals. The counting method according to claim 10, wherein
Further, for the measurement result of the signal half cycle measurement procedure, after combining a cycle that is a combination of a half cycle less than 0.5 times the representative value and at least one of the half cycles measured before and after the half cycle A signal combining procedure in which a signal waveform obtained by combining the periods is a waveform corresponding to a half period of one signal,
In the counting method, the signal counting procedure performs a counting process on a processing result of the signal combination procedure in the counting period instead of performing a counting process on the measurement result of the signal half cycle measurement procedure. The counting method according to claim 11, wherein
In the signal combining procedure, the measurement result of the signal half cycle measuring procedure is obtained by combining a cycle obtained by combining a half cycle having a length less than 0.5 times the representative value and a half cycle measured immediately thereafter. The counting is characterized in that a half cycle is performed, and the combined signal waveform is a waveform corresponding to a half cycle of one signal until the combined half cycle is 0.5 times or more of the representative value. Method. The counting method according to claim 11, wherein
In the signal combining procedure, for the measurement result of the signal half cycle measurement procedure, the mth half of the length less than 0.5 times the representative value is 0.5 times the length of the representative value. When sandwiched between a cycle Tm and a p-th half cycle Tp (m and p are natural numbers) having a length of 0.5 times or more of the representative value, when (m + p) is an even number, the half cycle Tm is half The combined period up to the period Tp is the combined half period, and if (m + p) is an odd number, the combined period from the half period Tm to the half period Tn-1 is the combined half period. A counting method, wherein the waveform is a waveform corresponding to the m-th half cycle. An oscillation procedure for operating the semiconductor laser so that at least one of the first oscillation period in which the oscillation wavelength continuously increases monotonously and the second oscillation period in which the oscillation wavelength continuously decreases monotonously exists;
A detection procedure for detecting an electrical signal including an interference waveform caused by a self-coupling effect between laser light emitted from the semiconductor laser and return light from a measurement object;
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 calculation procedure for obtaining the physical quantity of the measurement object from the counting result of the signal extraction procedure,
14. The signal extraction procedure according to claim 8, wherein the output signal obtained by the detection procedure is input, and each of the first oscillation period and the second oscillation period is a counting period. A physical quantity measuring method using each of the described procedures.

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