JP5461761B2 - Distance / speed meter and distance / speed measurement method - Google Patents

Description

  The present invention relates to a distance / velocity meter and a distance / velocity measuring method for measuring a distance to a measurement target and a speed of the measurement target using a self-coupling effect of a laser.

  Distance measurement using light interference by a laser has long been used as a highly accurate measurement method without disturbing the measurement object for non-contact measurement. Recently, a semiconductor laser is being used as a light source for optical measurement in order to reduce the size of the apparatus. A typical example is one using an FM heterodyne interferometer. This is capable of relatively long distance measurement and good accuracy, but has the disadvantage that the optical system becomes complicated because an interferometer is used outside the semiconductor laser.

  On the other hand, a measuring instrument using interference (self-coupling effect) in the semiconductor laser between the laser output light and the return light from the measurement object has been proposed (for example, Non-Patent Document 1, Non-Patent Document). 2, see Non-Patent Document 3). According to such a self-coupled laser measuring instrument, the semiconductor laser with a built-in photodiode serves as the functions of light emission, interference, and light reception, so that the external interference optical system can be greatly simplified. Therefore, the sensor unit is only a semiconductor laser and a lens, and is smaller than the conventional one. In addition, the distance measurement range is wider than the triangulation method.

  FIG. 26 shows a composite resonator model of an FP type (Fabry-Perot type) semiconductor laser. In FIG. 26, 101 is a semiconductor laser, 102 is a wall opening of a semiconductor crystal, 103 is a photodiode, and 104 is an object to be measured. Part of the reflected light from the measurement object 104 easily returns to the oscillation region. The small amount of light that has returned returns to the laser beam in the resonator 101, and the operation becomes unstable, causing noise (composite resonator noise or return light noise). The change in the characteristics of the semiconductor laser due to the return light appears remarkably even if the amount of return light relative to the output light is very small. Such a phenomenon is not limited to a Fabry-Perot type (hereinafter referred to as FP type) semiconductor laser, but also other types such as a vertical cavity surface emitting laser type (hereinafter referred to as a VCSEL type) and a distributed fed back laser type (hereinafter referred to as a DFB laser type). This also appears in the same semiconductor laser.

If the oscillation wavelength of the laser is λ and the distance from the wall open surface 102 closer to the measurement target 104 to the measurement target 104 is L, the return light and the laser light in the resonator 101 are as follows when the following resonance condition is satisfied. Strengthen and slightly increase the laser power.
L = nλ / 2 (1)
In formula (1), n is an integer. This phenomenon can be sufficiently observed even if the scattered light from the measurement object 104 is very weak, because the apparent reflectance in the resonator 101 of the semiconductor laser increases, causing an amplification effect.

  Since the semiconductor laser emits laser beams having different frequencies according to the magnitude of the injection current, an external modulator is not required when modulating the oscillation frequency, and direct modulation is possible by the injection current. FIG. 27 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 103 when the oscillation wavelength of the semiconductor laser is changed at a certain rate. When L = nλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the resonator 101 becomes 0 ° (same phase), and the return light and the resonator 101 When L = nλ / 2 + λ / 4, the phase difference is 180 ° (opposite phase), and the return light and the laser light in the resonator 101 are the weakest. Therefore, when the oscillation wavelength of the semiconductor laser is changed, a place where the laser output becomes strong and a place where the laser output becomes weak appear alternately, and the laser output at this time is detected by the photodiode 103 provided in the resonator 101. As shown in FIG. 27, a stepped waveform having a constant period is obtained. Such a waveform is generally called an interference fringe.

  Each stepped waveform, that is, each interference fringe is called a mode pop pulse (hereinafter referred to as MHP). MHP is a phenomenon different from the mode hopping phenomenon described later. For example, if the number of MHPs is 10 when the distance to the measurement object 104 is L1, the number of MHPs is 5 at half the distance L2. That is, when the oscillation wavelength of the semiconductor laser is changed for a certain time, the number of MHPs changes in proportion to the measurement distance. Therefore, if the MHP is detected by the photodiode 103 and the frequency of the MHP is measured, the distance can be easily measured. Note that the mode hopping phenomenon peculiar to the FP type semiconductor laser is a phenomenon in which a discontinuous portion occurs in the oscillation wavelength in accordance with the continuous increase / decrease in the injection current, as shown in FIG. There is a slight hysteresis when the injection current increases and decreases.

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

As described above, the self-coupled laser measuring instrument can greatly simplify the interference optical system outside the resonator, thereby reducing the size of the apparatus, eliminating the need for a high-speed circuit and being resistant to disturbance light. There is an advantage. Furthermore, since the return light from the measurement object may be very weak, there is an advantage that the measurement object is not affected by the reflectance, that is, the measurement object is not selected.
However, conventional interferometric measuring instruments, including self-coupled instruments, have the problem that even if they can measure the distance to a stationary measurement object, they cannot measure the distance of a measurement object with speed. . Further, in the conventional interferometric measuring instrument, since the frequency of the MHP during the measurement period is extracted, if the frequency of the disturbance light is about the same as the frequency of the MHP to be measured, the disturbance light cannot be removed and the measurement is performed. There was a problem that an error occurred.

  The present invention has been made in order to solve the above problems, and is a distance / velocimeter capable of measuring not only the distance to a stationary measurement object but also the speed of the measurement object while removing the influence of disturbance light, and The object is to provide a distance / speed measurement method. In particular, to provide a distance / velocity meter and a distance / velocity measurement method that can measure not only the distance to a stationary measurement target but also the speed of the measurement target while taking advantage of the self-coupled laser measuring instrument. With the goal.

The distance / velocity meter according to the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period that includes at least a period during which the oscillation wavelength continuously increases monotonously, and a period during which the oscillation wavelength continuously decreases monotonously. And the second oscillation period including at least two periods alternately exist, and the amplitude of the oscillation waveform having the first oscillation period and the second oscillation period as one period changes for each period. A laser driver that modulates the oscillation wavelength of the semiconductor laser; a light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement object into an electrical signal; and a plurality of output signals from the light receiver. Removal means for removing frequency components whose frequency does not change over a period, and laser light emitted from the semiconductor laser included in the output signal of the light receiver after removing the frequency components Frequency measuring means for measuring the frequency of the interference waveform caused by the return light from the measurement object for each of the first oscillation period and the second oscillation period; and interference in the first and second oscillation periods Counting means for obtaining the number of interference waveforms from the converted frequencies in the first and second oscillation periods after the waveform frequency is converted into a value when the amplitude of the oscillation waveform is a reference amplitude, respectively, An operation for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the minimum oscillation wavelength and the maximum oscillation wavelength in the period in which the number of interference waveforms is counted by the means, and the number of interference waveforms obtained by the counting means. Means.
The distance / velocity meter according to the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period that includes at least a period in which the oscillation wavelength continuously increases monotonously, and an oscillation wavelength that continuously decreases monotonously. And at least one of a frequency and an amplitude of an oscillation waveform having one cycle of the first oscillation period and the second oscillation period. A laser driver that modulates the oscillation wavelength of the semiconductor laser so as to change every period; a light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement object into an electrical signal; and Counting means for counting the number of signals included in the output of the light receiver for each of the first oscillation period and the second oscillation period, the laser light emitted from the semiconductor laser, and the measurement Calculating means for calculating the number of interference waveforms caused by the return light from the elephant for each of the first oscillation period and the second oscillation period based on the counting results of the counting means over a plurality of periods; At least one of the distance to the measurement object and the velocity of the measurement object is calculated from the minimum oscillation wavelength and the maximum oscillation wavelength in the period in which the number of interference waveforms is counted by the calculation means and the number of interference waveforms obtained by the calculation means. And an arithmetic means.

The distance and velocity meter of the present invention includes a semiconductor laser which emits laser beam to a measurement target, the oscillation wavelength and a first oscillation period including at least a period in which the oscillation wavelength continuously monotonically increases continuously and monotonously decreases And at least two second oscillation periods including at least a period to be generated, and an amplitude of an oscillation waveform having one cycle of the first oscillation period and the second oscillation period changes for each period. In addition, a laser driver that modulates the oscillation wavelength of the semiconductor laser, a light receiver that converts the optical output of the semiconductor laser into an electrical signal, and a frequency component that does not change in frequency over a plurality of periods are removed from the output signal of the light receiver. A self-coupling between the laser light emitted from the semiconductor laser and the return light from the measurement object included in the output signal of the light receiver after removing the frequency component. Frequency measuring means for measuring the frequency of the interference waveform caused by the effect for each of the first oscillation period and the second oscillation period; and the frequency of the interference waveform in the first and second oscillation periods, respectively. Counting means for obtaining the number of interference waveforms from the converted frequencies in the first and second oscillation periods after the waveform amplitude is converted into a value when the amplitude is a reference amplitude, and a minimum in each oscillation period of the semiconductor laser Calculation means for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the oscillation wavelength, the maximum oscillation wavelength, and the number of interference waveforms obtained by the counting means.
The distance / velocity meter according to the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period that includes at least a period in which the oscillation wavelength continuously increases monotonously, and an oscillation wavelength that continuously decreases monotonously. And at least one of a frequency and an amplitude of an oscillation waveform having one cycle of the first oscillation period and the second oscillation period. A laser driver that modulates the oscillation wavelength of the semiconductor laser, a light receiver that converts the optical output of the semiconductor laser into an electrical signal, and the number of signals included in the output of the light receiver, so as to change every period, A counting means for counting each of the first oscillation period and the second oscillation period, and a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object. Calculating means for calculating the number of interference waveforms for each of the first oscillation period and the second oscillation period based on the counting results of the counting means over a plurality of periods, and for each oscillation period of the semiconductor laser Calculation means for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the minimum oscillation wavelength and the maximum oscillation wavelength and the number of interference waveforms obtained by the calculation means.

Further, in one configuration example of the distance / velocity meter according to the present invention, the calculation means is a candidate value for the distance to the measurement object based on the minimum oscillation wavelength and the maximum oscillation wavelength of the semiconductor laser and the counting result of the counting means. And a distance / speed calculation unit that calculates the speed candidate value of the measurement target, and a history that is a difference between the distance candidate value calculated by the distance / speed calculation unit and the previously calculated distance candidate value A history displacement calculation unit that calculates displacement, a state determination unit that determines the state of the measurement object based on the calculation results of the distance / speed calculation unit and the history displacement calculation unit, and a determination result of the state determination unit And a distance / speed determination unit that determines at least one of the distance to the measurement object and the speed of the measurement object.
Further, in one configuration example of the distance / velocity meter according to the present invention, the distance / velocity calculation unit and the history displacement calculation unit may change the state of the measurement target to a minute displacement state or a movement that moves more rapidly than the minute displacement state. The distance candidate value, the velocity candidate value, and the history displacement for each of the case where the measurement object is assumed to be in a minute displacement state and the case where the measurement object is assumed to be in a displacement state. The state determination unit calculates the measurement based on the calculation results of the distance / velocity calculation unit and the history displacement calculation unit, for each cycle of the first oscillation period and the second oscillation period. Whether the object is in a minute displacement state or a displacement state is determined for each calculation, and whether the measurement object is moving at a constant velocity or accelerating is determined for each calculation.
Further, in one configuration example of the distance / velocity meter according to the present invention, the state determination unit has a constant sign of the history displacement calculated on the assumption that the measurement object is in a minute displacement state, and the measurement object. When the velocity candidate value calculated on the assumption that the measurement object is in the minute displacement state and the average value of the absolute values of the history displacement calculated on the assumption that the measurement object is in the minute displacement state are equal, It is determined that the measurement object is moving at a constant velocity in a minute displacement state.
Further, in one configuration example of the distance / velocity meter according to the present invention, the state determination unit has a constant sign of the history displacement calculated on the assumption that the measurement target is in a displacement state, and the measurement target is When the velocity candidate value calculated on the assumption that the object is in a displacement state is equal to the average value of the absolute values of the history displacement calculated on the assumption that the object to be measured is in a displacement state, the measurement object is It is determined that the movement is performed at a constant speed in the displacement state.

Moreover, in one configuration example of the distance / velocity meter of the present invention, the state determination unit reverses the sign of the history displacement calculated on the assumption that the measurement target is in a minute displacement state for each calculation, And the candidate value of the speed calculated on the assumption that the measurement object is in a minute displacement state and the average value of the absolute values of the history displacement calculated on the assumption that the measurement object is in a minute displacement state If they do not match, it is determined that the measurement object is accelerating in a minute displacement state.
Further, in one configuration example of the distance / velocity meter according to the present invention, the state determination unit may calculate the absolute value of the velocity candidate value calculated on the assumption that the measurement target is in a displacement state as the wavelength of the semiconductor laser. The velocity candidate value calculated on the assumption that the measurement object is in a minute displacement state and the absolute value of the history displacement calculated on the assumption that the measurement object is in a minute displacement state. If the average value does not match, it is determined that the measurement object is accelerating in a minute displacement state.
Further, in one configuration example of the distance / velocity meter according to the present invention, the state determination unit reverses the sign of the history displacement calculated on the assumption that the measurement target is in a displacement state for each calculation, and When the velocity candidate value calculated on the assumption that the measurement object is in a displacement state and the average value of the absolute values of the history displacement calculated on the assumption that the measurement object is in a displacement state do not match The measurement object is determined to be accelerating in a displaced state.
Further, in one configuration example of the distance / velocity meter according to the present invention, the state determination unit may calculate the absolute value of the velocity candidate value calculated on the assumption that the measurement target is in a minute displacement state of the semiconductor laser. The velocity candidate value calculated on the assumption that the measurement object is in a displacement state and the absolute value of the history displacement calculated on the assumption that the measurement object is in a displacement state. When the average value does not match, it is determined that the measurement object is accelerating in a displaced state.
Further, in one configuration example of the distance / velocity meter according to the present invention, when the measurement target is in a motion state having a minute displacement, the calculation unit calculates the integration result of the displacement instead of the calculation result. This is a change in the distance to the measurement object.

Further , the distance / velocity measuring method of the present invention radiates a wave whose wavelength is modulated so that the amplitude changes every period to the measurement object, and is generated between the wave reflected by the measurement object and returning to the measurement object. When a frequency component whose frequency does not change over a plurality of periods is removed from the detected interference information, and after the frequency component is removed, the amplitude of the wavelength-modulated wave is a reference amplitude After converting to the value of, based on the information on the interference after conversion, the candidate value of the distance to the measurement target and the speed to the measurement target are calculated respectively, and the corresponding speed and distance value from among these candidate values Are selected one by one.
Further, the distance / velocity measuring method of the present invention radiates a wavelength-modulated wave so that at least one of frequency and amplitude changes for each period to an object to be measured, and outputs the receiver to convert the wave into an electric signal. The number of signals included in the signal is counted, and the number of interference waveforms generated between the wave reflected back to the measurement object and the radiated wave is calculated based on the result of the counting over a plurality of periods, and the interference Based on the number of waveforms, candidate values for the distance to the measurement target and the speed for the measurement target are calculated, and the corresponding speed and distance values are selected one by one from these candidate values. Is.

Further, the present invention distance and speed measuring method of the present invention, the oscillation wavelength is first comprising at least a continuously monotonically increasing period oscillation interval and the oscillation wavelength is the second comprising at least a continuous monotone decreasing period The oscillation wavelength of the semiconductor laser is such that the oscillation period alternately exists for at least two periods, and the amplitude of the oscillation waveform with the first oscillation period and the second oscillation period as one period changes for each period. An oscillation procedure that modulates the optical output of the semiconductor laser, a removal procedure that removes a frequency component whose frequency does not change over a plurality of periods from the output signal of the light receiver that converts the optical output of the semiconductor laser into an electrical signal, and after the removal of the frequency component The frequency of the interference waveform generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, included in the output signal of the light receiver, The frequency measurement procedure for measuring each of the oscillation period and the second oscillation period, and the frequency of the interference waveform in the first and second oscillation periods are converted to values when the amplitude of the oscillation waveform is a reference amplitude, respectively. Later, a counting procedure for obtaining the number of interference waveforms from the converted frequencies in the first and second oscillation periods, a minimum oscillation wavelength and a maximum oscillation wavelength in a period for counting the number of interference waveforms by this counting procedure, And a calculation procedure for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the number of interference waveforms obtained by the counting procedure.
The distance / velocity measuring method of the present invention of the present invention includes a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second period including at least a period in which the oscillation wavelength continuously decreases monotonously. An oscillation period alternately exists for at least two periods, and at least one of a frequency and an amplitude of an oscillation waveform having the first oscillation period and the second oscillation period as one period changes for each period. The oscillation procedure for modulating the oscillation wavelength of the semiconductor laser, and the number of signals included in the output of the light receiver for converting the optical output of the semiconductor laser into an electrical signal, are expressed in the first oscillation period and the second oscillation period. The counting procedure for counting each of the number of interference waveforms generated by the self-coupling effect of the laser light emitted from the semiconductor laser and the return light from the measurement object over a plurality of periods A calculation procedure for calculating each of the first oscillation period and the second oscillation period based on a counting result, a minimum oscillation wavelength and a maximum oscillation wavelength in a period in which the number of interference waveforms is counted by the calculation procedure, and the calculation And a calculation procedure for calculating at least one of the distance to the measurement object and the speed of the measurement object from the number of interference waveforms obtained in the procedure.
Further, in one configuration example of the distance / velocity measuring method of the present invention, when the measurement target is in a motion state having a minute displacement, an integration result of the displacement is used instead of the calculation result. The distance from the measurement object is changed.

  According to the present invention, not only the distance to the measurement object but also the speed (size, direction) of the measurement object can be measured. In addition, according to the present invention, it is possible to determine whether the measurement object is moving at a constant velocity or accelerating from the minimum oscillation wavelength and maximum oscillation wavelength of the laser measuring instrument and the counting result of the counting means. In the present invention, the oscillation wavelength of the semiconductor laser is modulated so that the frequency (or amplitude) of the oscillation waveform changes every period, and the frequency component whose frequency does not change over a plurality of periods from the output signal of the light receiver is disturbed. The frequency of the interference waveform contained in the output signal of the receiver after removing the frequency component is converted to the value when the frequency (or amplitude) of the oscillation waveform is the reference frequency (or reference amplitude) Later, by obtaining the number of interference waveforms from the converted frequency, the influence of the disturbance light can be removed even when the frequency of the disturbance light is approximately the same as the frequency of the interference waveform.

  In the present invention, the oscillation wavelength of the semiconductor laser is modulated so that at least one of the frequency and amplitude of the oscillation waveform changes every period, the number of signals included in the output of the light receiver is counted, and the number of interference waveforms is calculated. By calculating based on the counting results over a plurality of periods, the influence of disturbance light can be removed even when the frequency of disturbance light is approximately the same as the frequency of the interference waveform.

[First Embodiment]
The present invention is a method for simultaneously calculating distance and velocity based on interference signals of a wave emitted in sensing using wavelength modulation and a wave reflected by an object. Therefore, the present invention can also be applied to optical interferometers other than self-coupling and interferometers other than light. More specifically, the case where the self-coupling of the semiconductor laser is used will be described. When the laser oscillation wavelength is changed while irradiating the measurement target from the semiconductor laser, the oscillation wavelength changes from the minimum oscillation wavelength to the maximum oscillation wavelength. The displacement of the measurement object during the change (or during the change from the maximum oscillation wavelength to the minimum oscillation wavelength) is reflected in the number of MHPs. Therefore, the state of the measurement object can be detected by examining the number of MHPs when the oscillation wavelength is changed. The above is the basic principle of the present invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a distance / speed meter according to the first embodiment of the present invention. The distance / velocity meter shown in FIG. 1 condenses light from a semiconductor laser 1 that emits laser light to a measurement target, a photodiode 2 that converts the optical output of the semiconductor laser 1 into an electrical signal, and the semiconductor laser 1. A lens 3 that irradiates the measurement target 12 and collects return light from the measurement target 12 and makes it incident on the semiconductor laser 1, and a first oscillation period in which the oscillation wavelength continuously increases monotonously and the oscillation wavelength are continuous. So that the second oscillation period monotonically decreasing alternately exists for at least two periods, and the frequency of the oscillation waveform having the first oscillation period and the second oscillation period as one period changes for each period. A laser driver 4 that modulates the oscillation wavelength of the laser 1, a current-voltage conversion amplifier 5 that converts and amplifies the output current of the photodiode 2 into a voltage, and a signal that differentiates the output voltage of the current-voltage conversion amplifier 5 twice. Extraction The frequency component of the disturbance light included in the output voltage of the path 11 and the signal extraction circuit 11 is removed, and the interference information included in the output voltage of the signal extraction circuit 11 is changed to a value when the frequency of the oscillation waveform is the reference frequency. After the conversion, the counting device 8 that counts the number of MHPs from the converted information, the arithmetic device 9 that calculates the distance to the measuring object 12 and the speed of the measuring object 12, and the display device that displays the calculation result of the arithmetic device 9 10 and. The current-voltage conversion amplifier 5, the signal extraction circuit 11, and the counting device 8 constitute a removing unit, a frequency measuring unit, and a counting unit.

  Hereinafter, for ease of explanation, it is assumed that a semiconductor laser 1 of a type that does not have the above-described mode hopping phenomenon (VCSEL type, DFB laser type) is used. In the case of using a type (FP type) semiconductor laser 1 having a mode hopping phenomenon, this fact is noted.

  For example, the laser driver 4 supplies the semiconductor laser 1 with a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time and whose frequency changes every period as an injection current. Thus, the semiconductor laser 1 alternately repeats the first oscillation period in which the oscillation wavelength continuously increases in proportion to the magnitude of the injection current and the second oscillation period in which the oscillation wavelength continuously decreases, And it drives so that the frequency of the triangular wave which makes 1st oscillation period and 2nd oscillation period 1 period changes for every period.

  FIG. 2 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 1. In FIG. 2, t-1 is the t-1th oscillation period, t is the tth oscillation period, t + 1 is the t + 1th oscillation period, t + 2 is the t + 2nd oscillation period, t + 3 is the t + 3rd oscillation period, and t + 4 is The t + 4th oscillation period, λa is the minimum value of the oscillation wavelength in each period, and λb is the maximum value of the oscillation wavelength in each period. 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. As is clear from FIG. 2, the frequency of the triangular wave is not constant and changes every period T. In the example of FIG. 2, assuming that the frequency of the triangular wave in the period t−1 and t is fHz, the frequency in the period t + 1 and t + 2 is 2 × fHz, and the frequency in the period t + 3 and t + 4 is fHz. That is, the frequency of the triangular wave changes as f, 2 × f, f, 2 × f,.

  The drive current is a drive current having a waveform in which the first oscillation period and the second oscillation period are alternately continued for at least three periods, and the oscillation wavelength continuously monotonously increases in the first oscillation period. If the drive current has a waveform including at least a period during which the oscillation wavelength continuously includes a period during which the oscillation wavelength continuously decreases monotonically, a drive current having a waveform other than the triangular wave illustrated (for example, a sine wave) Can be used. For example, in order to suppress current consumption, a driving current having an intermittent waveform with a pause period every two peaks (that is, every four periods) can be used (FIG. 3).

  Laser light emitted from the semiconductor laser 1 is collected by the lens 3 and enters the measurement object 12. The light reflected by the measurement object 12 is collected by the lens 3 and enters the semiconductor laser 1. However, condensing by the lens 3 is not essential. The photodiode 2 converts the light output of the semiconductor laser 1 into a current. The current-voltage conversion amplifier 5 converts the output current of the photodiode 2 into a voltage and amplifies it. The signal extraction circuit 11 has a function of extracting a superimposed signal from a modulated wave. For example, two differentiation circuits 6 and 7 are used. The differentiation circuit 6 differentiates the output voltage of the current-voltage conversion amplifier 5, and the differentiation circuit 7 differentiates the output voltage of the differentiation circuit 6. 4A schematically shows the output voltage waveform of the current-voltage conversion amplifier 5, FIG. 4B schematically shows the output voltage waveform of the differentiation circuit 6, and FIG. 4C shows the differentiation. 6 is a diagram schematically showing an output voltage waveform of a circuit 7. FIG. These are obtained by removing the oscillation waveform (carrier wave) of the semiconductor laser 1 of FIG. 2 from the waveform (modulated wave) of FIG. 4A, which is the output of the photodiode 2, and the MHP waveform (superimposition) of FIG. (Wave) is extracted.

  The frequency of the MHP generated by the laser light emitted from the semiconductor laser 1 and the return light from the measurement object 12 has a property of being proportional to the frequency and amplitude of the triangular wave. On the other hand, the frequency of disturbance light does not depend on the frequency and amplitude of the triangular wave. Therefore, by using such a property, it is possible to distinguish between MHP and disturbance light and remove the influence of disturbance light.

  FIG. 5 is a block diagram showing an example of the configuration of the counting device 8. The counting device 8 uses the Fast Fourier Transform (hereinafter referred to as FFT) to change the frequency characteristics of the output of the signal extraction circuit 11 (FIG. 4C) for each of the first oscillation periods t-1, t + 1, t + 3 and the second. FFT unit 81 that measures every oscillation period t, t + 2, t + 4, storage unit 82 that stores the measurement result of FFT unit 81, and frequency of disturbance light from the frequency characteristics of the output of signal extraction circuit 11, The determination unit 83 that measures the frequency of the MHP, the multiplication unit 84 that converts the frequency of the MHP measured by the determination unit 83 into a value when the frequency of the triangular wave is the reference frequency, and the frequency of the MHP converted by the multiplication unit 84 Is converted to the number of MHPs.

First, the FFT unit 81 of the counting device 8 measures the frequency characteristics of the output of the signal extraction circuit 11 every first oscillation period t-1, t + 1, t + 3 and every second oscillation period t, t + 2, t + 4.
The storage unit 82 stores the measurement result of the FFT unit 81. The determination unit 83 compares the measurement result of the FFT unit 81 with the measurement result of the previous cycle stored in the storage unit 82 and removes the frequency of disturbance light from the frequency characteristic of the output of the signal extraction circuit 11.

  FIG. 6 is a diagram showing the triangular wave frequency dependence of MHP and disturbance light. FIG. 6 (A) schematically shows the waveform of MHP at the output of the signal extraction circuit 11, and FIG. 6 (B) is the signal extraction circuit 11. The waveform of the disturbance light in the output of is schematically shown. 7A shows the frequency spectrum of the output of the signal extraction circuit 11 when the frequency of the triangular wave is fHz, and FIG. 7B shows the output of the signal extraction circuit 11 when the frequency of the triangular wave is 2 × fHz. The frequency spectrum of is shown.

  When the frequency of the triangular wave is changed every period T, the frequency of the MHP changes in proportion to the frequency of the triangular wave as shown in FIG. That is, when observed in the frequency spectrum, when the frequency of the triangular wave is fHz, the frequency of the MHP that was fsHz as shown in FIG. 7A becomes 2 × fHz as shown in FIG. 7B. 2 × fsHz as shown in FIG. On the other hand, the frequency of disturbance light is constant even if the frequency of the triangular wave changes as shown in FIGS. 6B, 7A, and 7B.

  Therefore, the determination unit 83 obtains a signal strength difference between the measurement result of the FFT unit 81 and the measurement result of the previous cycle stored in the storage unit 82 for each frequency, and the measurement result of the FFT unit 81 and the measurement of the previous cycle are measured. A signal whose frequency does not change as a result, that is, a signal whose signal intensity difference is equal to or smaller than a predetermined intensity difference threshold is determined as a signal due to the influence of disturbance light, and this signal is removed from the measurement result of the FFT unit 81. Then, the determination unit 83 determines the signal having the maximum intensity as the MHP signal in the measurement result of the FFT unit 81 after removing the disturbance light signal, and measures the MHP frequency.

  Next, the multiplication unit 84 multiplies the MHP frequency measured by the determination unit 83 by a coefficient corresponding to the frequency of the triangular wave when the MHP frequency is measured. If the reference frequency of the triangular wave is fHz and the frequency of the triangular wave when the MHP frequency is measured is α × fHz, the coefficient by which the MHP frequency is multiplied is 1 / α. For example, when the frequency of the triangular wave when the MHP frequency is measured is 2 × fHz, the frequency of the MHP is twice that when the frequency of the triangular wave is fHz. Therefore, the coefficient 1 / α = By multiplying by 1/2, the frequency of MHP can be converted to a value when the triangular wave is constant at the reference frequency fHz. The frequency of the triangular wave is notified from the laser driver 4. The multiplier 84 determines the coefficient value according to the frequency of the triangular wave notified from the laser driver 4.

The conversion unit 85 converts the MHP frequency after the coefficient multiplication into the number of MHPs. If the MHP frequency after the coefficient multiplication is fsHz and the reference frequency of the triangular wave is fHz, the number of MHPs can be calculated as fs × {C / (2 × f)} (C is the speed of light).
Thus, the number of MHPs can be acquired by removing the influence of disturbance light from the output voltage of the signal extraction circuit 11. The counting device 8 performs the above-described processing every first oscillation period t-1, t + 1, t + 3 and every second oscillation period t, t + 2, t + 4. Hereinafter, the number of MHPs measured by the counting device 8 in the first oscillation period t−1 is expressed as MHPt−1 (the part of t−1 is a subscript of the variable MHP. The same applies hereinafter), and the second oscillation period. Let MHPt be the number of MHPs at t.

  The arithmetic unit 9 determines the distance from the measurement object 12 based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1, the number of MHPs MHPt-1 in the oscillation period t-1, and the number MHPt of MHPs in the oscillation period t-1. And the speed of the measuring object 12 is calculated. As described above, the semiconductor laser 1 is generally operated so that the value of λb−λa, which is the difference between the maximum oscillation wavelength λb and the minimum oscillation wavelength λa, is always constant. When the semiconductor laser 1 is operated so that the value of is not necessarily constant, it is necessary to normalize the number of MPHs by the value of λb−λa in the target period prior to the calculation of the speed.

  FIG. 8 is a block diagram showing an example of the configuration of the arithmetic device 9, and FIG. 9 is a flowchart showing the operation of the arithmetic device 9. The arithmetic unit 9 measures the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1 and the number of MHPs MHPt-1 during one oscillation period t-1 and the number MHPt MHPt during the second oscillation period t-1. The distance / velocity calculation unit 91 calculates the candidate value for the distance to the distance 12 and the candidate value for the speed of the measurement target 12, and the distance candidate value calculated by the distance / speed calculation unit 91 is calculated one cycle before. A history displacement calculation unit 92 that calculates a history displacement that is a difference from the distance candidate value, a distance / speed calculation unit 91, a storage unit 93 that stores the calculation results of the history displacement calculation unit 92, and a distance / speed calculation unit 91 The state determination unit 94 that determines the state of the measurement target 12 based on the calculation result of the history displacement calculation unit 92 and the distance to the measurement target 12 and the speed of the measurement target 12 are determined based on the determination result of the state determination unit 94. Distance / speed accuracy And a fixed portion 95.

  Here, the start point of the period t is defined as time t. Assume that the state of the measurement object 12 is either a minute displacement state that satisfies a predetermined condition or a displacement state in which the movement is larger than the minute displacement state. When the average displacement of the measuring object 12 per oscillation period t-1 and oscillation period t is V, the minute displacement state is a state satisfying (λb−λa) / λb> V / Lb (however, Lb is a distance at time t), and the displacement state is a state satisfying (λb−λa) / λb ≦ V / Lb. In addition, if the displacement V is normalized by the time which combined the period t-1 and the period t, the speed of the measuring object 12 can be obtained.

First, the distance / speed calculation unit 91 of the arithmetic unit 9 calculates the distance candidate values Lα (t) and Lβ (t) and the displacement candidate values Vα (t) and Vβ (t) at the current time t as And stored in the storage unit 93 (step S1 in FIG. 9).
Lα (t) = λa × λb × ('MHPt-1' + 'MHPt')
/ {4 × (λb−λa)} (2)
Lβ (t) = λa × λb × (| 'MHPt-1'-'MHPt' |)
/ {4 × (λb−λa)} (3)
Vα (t) = ('MHPt-1'-'MHPt') × λ / 4 (4)
Vβ (t) = ('MHPt-1' + 'MHPt') × λ / 4 (5)
Note that the quotation mark 'in the expression is added to distinguish the MHP subscript from the operator (the same applies hereinafter). In equations (4) and (5), λ is the wavelength at time t−1 one cycle before the current time t. For example, in the example of FIG. 2, the wavelength λ is λa. When the current time is time t + 1 in FIG. 2, the wavelength λ is λb.
The above equations (2) and (3) assume that the semiconductor laser 1 is of a type that does not have a mode hopping phenomenon. If a semiconductor laser 1 having a mode hopping phenomenon is used, it is necessary to use the following equations (2A) and (3A) instead of the above equations (2) and (3).
Lα (t) = λa × λb × ('MHPt-1' + 'MHPt')
/ {4 × (λb−λa−Σλmp)} (2A)
Lβ (t) = λa × λb × (| 'MHPt-1'-'MHPt' |)
/ {4 × (λb−λa−Σλmp)} (3A)
Here, λmp represents the size of the frequency width that has become discontinuous due to the mode hopping phenomenon (FIG. 28). When a plurality of mode hopping phenomena occur in one period t, all λmp have almost the same magnitude. Σλmp is a value obtained by adding all the magnitudes λmp of the frequency discontinuity width caused by the mode hopping phenomenon occurring in one period t.

  The candidate values Lα (t) and Vα (t) are values calculated on the assumption that the measurement object 12 is in a minute displacement state, and the candidate values Lβ (t) and Vβ (t) are values in which the measurement object 12 is in a displacement state. It is a value calculated assuming that there is. The arithmetic unit 9 performs the calculations of Expressions (2) to (5) for each start time of each period shown in FIG.

Subsequently, the history displacement calculation unit 92 of the arithmetic device 9 for each of the minute displacement state and the displacement state, the distance candidate value at the current time t, and the time one cycle before (t−1) stored in the storage unit 93. The history displacement, which is the difference from the distance candidate value in), is calculated by the following equation and stored in the storage unit 93 (step S2 in FIG. 9).
Vcalα (t) = Lα (t) −Lα (t−1) (6)
Vcalβ (t) = Lβ (t) −Lβ (t−1) (7)

The historical displacement Vcalα (t) is a value calculated on the assumption that the measurement target 12 is in a minute displacement state, and the historical displacement Vcalβ (t) is a value calculated on the assumption that the measurement target 12 is in a displacement state. . The arithmetic device 9 performs the calculations of the equations (6) to (7) at every start time t. In the equations (4) to (7), the direction in which the measuring object 12 approaches the distance / velocity meter of the present embodiment is defined as a positive velocity, and the direction in which the measurement object 12 moves away is defined as a negative velocity.
Next, the state determination unit 94 of the arithmetic device 9 determines the state of the measurement target 12 using the calculation results of the expressions (2) to (7) stored in the storage unit 93 (step S3 in FIG. 9). .

  FIG. 10 shows an example of velocity candidate values Vα (t), Vβ (t) and history displacements Vcalα (t), Vcalβ (t) when the measurement object 12 moves in a minute displacement state (equal speed movement). Indicates. In the example of FIG. 10, the speed of the measurement target 12 is 0.0005 m / period, the minimum oscillation wavelength λa of the semiconductor laser 1 is 680 nm, and the maximum oscillation wavelength λb is 681 nm. As can be seen from FIG. 10, when the measuring object 12 is moving in a minute displacement state, the sign of the history displacement Vcalα (t) calculated on the assumption that the measuring object 12 is in the minute displacement state is constant (example in FIG. 10). In this case, the velocity candidate value Vα (t) calculated on the assumption that the measurement object 12 is in a minute displacement state is equal to the average value of the absolute values of the history displacement Vcalα (t). On the other hand, the sign of the history displacement Vcalβ (t) calculated on the assumption that the measurement object 12 is in the displacement state is inverted every start time t. That is, the sign differs between the first oscillation period and the second oscillation period.

  Therefore, the state determination unit 94 assumes that the sign of the history displacement Vcalα (t) calculated on the assumption that the measurement object 12 is in a minute displacement state is constant and the measurement object 12 is in a minute displacement state. If the speed candidate value Vα (t) and the average value of the absolute values of the history displacement Vcalα (t) are equal, it is determined that the measurement object 12 is moving in a minute displacement state.

  FIG. 11 shows an example of velocity candidate values Vα (t), Vβ (t) and history displacements Vcalα (t), Vcalβ (t) when the measurement object 12 moves in a displaced state (constant velocity motion). Show. In the example of FIG. 11, the speed of the measurement target 12 is 0.002 m / period, the minimum oscillation wavelength λa of the semiconductor laser 1 is 680 nm, and the maximum oscillation wavelength λb is 681 nm. As can be seen from FIG. 11, when the measurement object 12 is moving in the displacement state, the sign of the history displacement Vcalβ (t) calculated assuming that the measurement object 12 is in the displacement state is constant (in the example of FIG. ) And the velocity candidate value Vβ (t) calculated on the assumption that the measurement object 12 is in the displacement state and the average value of the absolute values of the history displacement Vcalβ (t) are equal. On the other hand, the sign of the history displacement Vcalα (t) calculated on the assumption that the measurement object 12 is in a minute displacement state is inverted every start time t.

  Accordingly, the state determination unit 94 calculates the speed calculated on the assumption that the sign of the history displacement Vcalβ (t) calculated on the assumption that the measurement object 12 is in the displacement state is constant and that the measurement object 12 is in the displacement state. Is equal to the average value of the absolute values of the history displacement Vcalβ (t), it is determined that the measurement object 12 is moving in the displacement state.

  FIG. 12 shows candidate values Vα (t), Vβ (t) and hysteresis displacements Vcalα (t), Vcalβ (() when the measurement object 12 is in a minute displacement state and vibrates (acceleration motion) around a certain position. An example of t) is shown. In the example of FIG. 12, the maximum speed of the measurement target 12 is 0.000002 m / period, the minimum oscillation wavelength λa of the semiconductor laser 1 is 680 nm, and the maximum oscillation wavelength λb is 681 nm. As can be seen from FIG. 12, when the measurement object 12 vibrates, the velocity candidate value Vα (t) calculated assuming that the measurement object 12 is in the minute displacement state and the measurement object 12 is in the minute displacement state. The calculated absolute value of the history displacement Vcalα (t) does not agree with the average value. Similarly, the average value of the absolute values of the velocity candidate value Vβ (t) calculated assuming that the measurement object 12 is in the displacement state and the history displacement Vcalβ (t) calculated assuming that the measurement object 12 is in the displacement state are the same. do not do.

  FIG. 13 is an enlarged view of the vicinity of speed 0 in FIG. As can be seen from FIG. 13, the sign of the history displacement Vcalα (t) calculated assuming that the measurement object 12 is in a minute displacement state is inverted every start time t, and the history is calculated assuming that the measurement object 12 is in a displacement state. Even if there is a change in sign at the displacement Vcalβ (t), this change is not every start time t.

  Therefore, the state determination unit 94 reverses the sign of the history displacement Vcalα (t) calculated on the assumption that the measurement target 12 is in the minute displacement state at every start time t, and the measurement target 12 is in the minute displacement state. If the velocity candidate value Vα (t) calculated on the assumption that the average value of the absolute values of the history displacement Vcalα (t) does not match, it is determined that the measurement object 12 vibrates in a minute displacement state.

  Focusing on the velocity candidate value Vβ (t) shown in FIG. 12, the absolute value of Vβ (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 94 has an absolute value of the velocity candidate value Vβ (t) calculated on the assumption that the measurement object 12 is in the displacement state, and the measurement object 12 is in the minute displacement state. If the velocity candidate value Vα (t) calculated on the assumption that the average value of the absolute values of the history displacement Vcalα (t) does not match, it is determined that the measurement object 12 vibrates in a minute displacement state. Good.

  FIG. 14 shows an example of the history displacements Vcalα (t) and Vcalβ (t) when the measurement object 12 is in a displaced state and vibrates (acceleration motion) around a certain position. In the example of FIG. 14, the maximum speed of the measurement target 12 is 0.01 m / period, the minimum oscillation wavelength λa of the semiconductor laser 1 is 680 nm, and the maximum oscillation wavelength λb is 681 nm. In FIG. 14, since the value is small, the speed candidate values Vα (t) and Vβ (t) are not described.

  Although not explicitly shown in FIG. 14, similarly to the case of FIG. 12, it is assumed that the velocity candidate value Vα (t) calculated assuming that the measurement target 12 is in a minute displacement state and the measurement target 12 is in a minute displacement state. The velocity absolute value Vβ (t) calculated assuming that the measurement object 12 is in the displacement state and the measurement object 12 in the displacement state are not consistent with the average value of the absolute values of the history displacement Vcalα (t) calculated in the above. Also, the average value of the absolute values of the history displacement Vcalβ (t) calculated as above does not match.

  On the other hand, as can be seen from FIG. 14, the sign of the history displacement Vcalβ (t) calculated assuming that the measuring object 12 is in the displaced state is inverted every start time t, and is calculated assuming that the measuring object 12 is in the minute displacement state. In the history displacement Vcalα (t), there is a change in the sign, but this change is not every start time t.

  Therefore, the state determination unit 94 assumes that the sign of the history displacement Vcalβ (t) calculated on the assumption that the measurement object 12 is in the displacement state is inverted every start time t, and the measurement object 12 is in the displacement state. If the calculated velocity candidate value Vβ (t) and the average value of the absolute values of the history displacement Vcalβ (t) do not coincide with each other, it is determined that the measurement object 12 vibrates in the displacement state.

  FIG. 15 is an enlarged view of the vicinity of speed 0 in FIG. Focusing on the velocity candidate value Vα (t), the absolute value of Vα (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 94 has the absolute value of the velocity candidate value Vα (t) calculated on the assumption that the measurement target 12 is in a minute displacement state equal to the wavelength change rate, and the measurement target 12 is in the displacement state. If the velocity candidate value Vβ (t) calculated on the assumption that the average value of the absolute values of the history displacement Vcalβ (t) does not match, it may be determined that the measurement object 12 vibrates in the displacement state. .

  FIG. 16 shows the determination operation of the state determination unit 94 described above. The distance / speed determination unit 95 of the arithmetic device 9 determines the speed of the measurement target 12 and the distance from the measurement target 12 based on the determination result of the state determination unit 94 (step S4 in FIG. 9).

  That is, when it is determined that the measurement target 12 is moving in a minute displacement state, the distance / speed determination unit 95 sets the speed candidate value Vα (t) as the speed of the measurement target 12 and uses the distance candidate value Lα ( t) is a distance from the measurement object 12, and when it is determined that the measurement object 12 is moving in a displaced state, the velocity candidate value Vβ (t) is the velocity of the measurement object 12, and the distance candidate value Lβ ( Let t) be the distance to the measurement object 12.

  In addition, when it is determined that the measurement target 12 is vibrating in a minute displacement state, the distance / speed determination unit 95 sets the speed candidate value Vα (t) as the speed of the measurement target 12 and uses the distance candidate value Lα ( t) is a distance from the measurement object 12, and when it is determined that the measurement object 12 is vibrating in a displaced state, the velocity candidate value Vβ (t) is the velocity of the measurement object 12, and the distance candidate value Lβ ( Let t) be the distance to the measurement object 12. When the measurement object 12 is vibrating, the actual distance is an average value of the distance Lβ (t).

The arithmetic unit 9 performs the processes in steps S1 to S4 as described above at every start time t until, for example, the user gives an instruction to end the measurement (YES in step S5).
The display device 10 displays the distance to the measurement target 12 and the speed of the measurement target 12 calculated by the calculation device 9.

  As described above, in the present embodiment, the first oscillation period t−1 in which the oscillation wavelength continuously increases and the second oscillation period t in which the oscillation wavelength continuously decreases alternately in the semiconductor laser 1. Repeatedly, the number of MHPs contained in the output signal of the photodiode is counted for each of the first oscillation period t-1 and the second oscillation period t, and the counting result and the minimum oscillation wavelength λa of the semiconductor laser 1 are calculated. From the maximum oscillation wavelength λb, the distance to the measurement object 12 and the speed of the measurement object 12 can be calculated. As a result, in the present embodiment, (a) the apparatus can be reduced in size, (b) a high-speed circuit is not required, (c) strong against disturbance light, and (d) a measurement target is not selected. While taking advantage of the self-coupled laser measuring instrument, not only the distance to the measuring object 12 but also the speed of the measuring object 12 can be measured. Moreover, according to this Embodiment, it can be determined whether the measuring object 12 is carrying out the constant velocity exercise | movement or the acceleration exercise | movement.

  According to FIG. 10, when the measuring object 12 is moving in a minute displacement state, the measured speed Vα (t) is also 0.0005 m / period with respect to the speed 0.0005 m / period of the measuring object 12, and the speed It can be seen that the measurement result is consistent with the true value. FIG. 17 shows the distance Lα (t) measured in the example of FIG. 10 and the true value of the distance. According to FIG. 17, it can be seen that the distance measurement result matches the true value.

  According to FIG. 11, when the measuring object 12 is moving in a displaced state, the measured speed Vβ (t) is 0.002 m / period with respect to the speed of the measuring object 12 being 0.002 m / period, It can be seen that the measurement result matches the true value. FIG. 18 shows the distance Lβ (t) measured in the example of FIG. 11 and the true value of the distance. According to FIG. 18, it can be seen that the distance measurement result matches the true value.

  FIG. 19 shows the velocity Vα (t) measured in the example of FIG. 12 and the true value of the velocity when the measurement object 12 vibrates in a minute displacement state, and FIG. 20 shows the distance measured in the example of FIG. The average value of Lα (t) and the distance Lα (t) and the true value of the distance are shown. 19 and 20, it can be seen that the measurement result of the speed matches the true value, and the measurement result of the distance and the average value of the distance matches the true value.

  FIG. 21 shows the velocity Vβ (t) measured in the example of FIG. 14 and the true value of the velocity when the measurement object 12 vibrates in a displaced state, and FIG. 22 shows the distance Lβ measured in the example of FIG. The average value of (t), the distance Lβ (t), and the true value of the distance are shown. According to FIGS. 21 and 22, it can be seen that the measurement result of the speed matches the true value, and the measurement result of the average value of the distance matches the true value.

  The arithmetic device 9 in the present embodiment can be realized by, for example, a computer having a CPU, a storage device, and an interface, and a program for controlling these hardware resources. A program for operating such a computer as the arithmetic device 9 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 processing described in this embodiment in accordance with this program. In addition, the display device 10 of the present invention simultaneously displays the distance (displacement) of the measurement target and the speed of the measurement target in real time.

  Note that when the measurement object 12 vibrates with a very small displacement (for example, the maximum speed of 2 nm), the actual distance change (amplitude) is several nanometers, but since the distance calculation resolution is lower than the displacement resolution, an error occurs. growing. Therefore, when the object to be measured is in a motion state having a minute displacement, the accuracy is improved by using a value obtained by integrating the displacement (velocity) instead of the calculation result as a change in distance.

[Second Embodiment]
In the first embodiment, the frequency of the triangular wave is changed every period T. However, since the frequency of the MHP is also proportional to the amplitude of the triangular wave, the laser driver 4 changes the amplitude of the triangular wave as shown in FIG. It may be changed every T. In the example of FIG. 23, assuming that the amplitude of the triangular wave in the period t−1 and t is A, the amplitude in the period t + 1 and t + 2 is 2 × A.

  In the present embodiment, the amplitude of the triangular wave is notified from the laser driver 4. Assuming that the reference amplitude of the triangular wave is A and the amplitude of the triangular wave when the MHP frequency is measured is α × A, the coefficient by which the MHP frequency is multiplied is 1 / α. Therefore, the multiplying unit 84 may multiply the MHP frequency measured by the determining unit 83 by a coefficient 1 / α corresponding to the amplitude of the triangular wave when the MHP frequency is measured. Other configurations and processing of the distance / speed meter are the same as those in the first embodiment. Thus, also in this embodiment, the same effect as that of the first embodiment can be obtained.

[Third Embodiment]
In the first and second embodiments, after measuring the frequency of MHP, this frequency is converted into the number of MHPs. However, the number of MHPs can also be directly measured. Also in the present embodiment, the overall configuration of the distance / speed meter is the same as that of the first embodiment, and therefore, description will be made using the reference numerals in FIG.

  FIG. 24 is a block diagram showing an example of the configuration of the counting device 8 of the present embodiment. The counting device 8 of the present embodiment includes a counter 86 that counts the number of signals output from the signal extraction circuit 11 for each of the first oscillation periods t-1, t + 1, t + 3 and for each of the second oscillation periods t, t + 2, t + 4. The storage unit 87 stores the count result of the counter 86, and the calculation unit 88 calculates the number of MHPs from the count result of the counter 86 and the past count result stored in the storage unit 87.

First, the counter 86 of the counting device 8 counts the number of signals output from the signal extraction circuit 11 every first oscillation period t−1, t + 1, t + 3 and every second oscillation period t, t + 2, t + 4. The storage unit 87 stores the count result of the counter 86.
FIG. 25 is a diagram showing the triangular wave amplitude dependence of MHP and disturbance light. FIG. 25A schematically shows the waveform of MHP at the output of the signal extraction circuit 11, and FIG. 25B is the signal extraction circuit 11. The waveform of the disturbance light in the output of is schematically shown.

The number N of MHPs does not depend on the frequency of the triangular wave as shown in FIG. 6 (A), but as shown in FIG. 25 (A), the amplitude of the triangular wave is multiplied by y to make it a y-fold number. Can do. On the other hand, the number Nn of disturbance light signals is inversely proportional to the frequency of the triangular wave as shown in FIG. 6B, but does not depend on the amplitude of the triangular wave as is apparent from FIG.
Therefore, by changing the amplitude and frequency of the triangular wave for each period T, the number N of MHPs and the number of disturbance light signals Nn can be changed for each period T. The influence can be removed.

The number of signals Nall combining MHP and disturbance light when the triangular wave frequency is 1 / x times and the amplitude is y times can be expressed as follows.
Nall = N × y + Nn × x (8)
This number of signals Nall is a value observed by the counter 86. From Expression (8), the number N of MHPs can be obtained as the following expression.
N = (Nall−Nn × x) / y (9)

Here, it is assumed that the triangular wave before one cycle is the reference frequency and the reference amplitude, and at this time, the number of signals measured by the counter 86 and stored in the storage unit 87 is Nall _old, and the frequency of the current triangular wave after one cycle is set. Is 1 / x times the reference frequency and the amplitude is y times the reference amplitude, and the number of signals measured by the counter 86 at this time is Nall _new , the following simultaneous equations are obtained.
N = (Nall _old− Nn × 1) / 1 = (Nall _new− Nn × x) / y
(10)

The calculation unit 88 can obtain the number N of MHPs by solving the simultaneous equations of Expression (10). Thus, the number of MHPs can be acquired by removing the influence of disturbance light from the output voltage of the signal extraction circuit 11. The counting device 8 performs the above-described processing every first oscillation period t-1, t + 1, t + 3 and every second oscillation period t, t + 2, t + 4.
Other configurations and processing of the distance / speed meter are the same as those in the first embodiment. Thus, also in this embodiment, the same effect as that of the first embodiment can be obtained. In the present embodiment, at least one of the frequency and amplitude of the triangular wave may be changed for each period.

In the first to third embodiments, the frequency or amplitude of the triangular wave is changed to 1 time, 2 times, 1 time, 2 times,... It goes without saying that it is not limited to twice.
In addition, when the appearance frequency of disturbance light periodically changes, it becomes difficult to remove disturbance light when it coincides with the modulation period of the triangular wave. Therefore, the frequency or amplitude of the triangular wave is increased by one, two, one, two, or two. It is preferable to change at random instead of a fixed rule such as double.

  In addition, since the MHP signal is not a sine wave, it generally includes odd harmonics. Therefore, if the frequency or amplitude of the triangular wave is changed to an odd multiple when the frequency of the disturbance light and the frequency of the MHP match, the disturbance light harmonic and the MHP become the same frequency. It becomes difficult to remove. Therefore, the amount of change in the frequency (or amplitude) for each period of the triangular wave is preferably an even multiple of the reference frequency (or reference amplitude).

  The present invention can be applied to a technique for measuring the distance to the measurement target and the speed of the measurement target.

It is a block diagram which shows the structure of the distance and speedometer used as the 1st Embodiment of this invention. It is a figure which shows one example of the time change of the oscillation wavelength of the semiconductor laser in the 1st Embodiment of this invention. It is a figure which shows the other example of the time change of the oscillation wavelength of the semiconductor laser in the 1st Embodiment of this invention. It is a figure which shows typically the output voltage waveform of the current-voltage conversion amplifier in the 1st Embodiment of this invention, and the output voltage waveform of a differentiation circuit. 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 figure which shows the triangular wave frequency dependence of a mode pop pulse and disturbance light. It is a frequency spectrum figure which shows the frequency change of the mode pop pulse and disturbance light when a triangular wave frequency changes. 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 flowchart which shows operation | movement of the arithmetic unit in the 1st Embodiment of this invention. It is a figure which shows one example of the candidate value of a speed | velocity | rate and log | history displacement in case the measurement object is moving in the minute displacement state in the 1st Embodiment of this invention. It is a figure which shows one example of the candidate value of speed | velocity | rate and log | history displacement in case the measurement object is moving in the displacement state in the 1st Embodiment of this invention. It is a figure which shows an example of the candidate value of a speed | velocity | rate and log | history displacement in case the measurement object is vibrating in the minute displacement state in the 1st Embodiment of this invention. It is the figure which expanded a part of FIG. It is a figure which shows an example of the historical displacement in case the measurement object is vibrating in the displacement state in the 1st Embodiment of this invention. It is the figure which expanded a part of FIG. It is a figure which shows the determination operation | movement of the state determination part of the arithmetic unit in the 1st Embodiment of this invention. It is a figure which shows the distance measured when the measuring object is moving in the micro displacement state in the 1st Embodiment of this invention, and the true value of distance. It is a figure which shows the distance measured when the measuring object is moving in the displacement state in the 1st Embodiment of this invention, and the true value of distance. It is a figure which shows the speed and true value of speed which were measured when the measuring object was vibrating in the minute displacement state in the first embodiment of the present invention. It is a figure which shows the distance measured when the measuring object is vibrating in the minute displacement state in the 1st Embodiment of this invention, the average value of distance, and the true value of distance. It is a figure which shows the speed measured when the measuring object vibrates in the displacement state in the 1st Embodiment of this invention, and the true value of speed. It is a figure which shows the distance measured when the measuring object is vibrating in the displacement state in the 1st Embodiment of this invention, the average value of distance, and the true value of distance. It is a figure which shows one example of the time change of the oscillation wavelength of the semiconductor laser 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 figure which shows the triangular wave amplitude dependence of a mode pop pulse and disturbance light. It is a figure which shows the compound resonator model of the semiconductor laser in the conventional laser measuring device. It is a figure which shows the relationship between the oscillation wavelength of a semiconductor laser, and the output waveform of a built-in photodiode. It is a figure which shows the magnitude | size of the width of the frequency which became discontinuous by the mode hopping phenomenon.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplifier, 6, 7 ... Differentiation circuit, 8 ... Counting device, 9 ... Arithmetic device, 10 ... Display device, 11 DESCRIPTION OF SYMBOLS ... Signal extraction circuit, 12 ... Measurement object, 81 ... FFT part, 82 ... Memory | storage part, 83 ... Determination part, 84 ... Multiplication part, 85 ... Conversion part, 86 ... Counter, 87 ... Memory | storage part, 88 ... Calculation part, 91 ... distance / speed calculation unit, 92 ... history displacement calculation unit, 93 ... storage unit, 94 ... state determination unit, 95 ... distance / speed determination unit.

Claims (18)

A semiconductor laser that emits laser light to the object to be measured;
The first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist alternately for at least two periods, and A laser driver that modulates an oscillation wavelength of the semiconductor laser so that an amplitude of an oscillation waveform having one oscillation period and the second oscillation period as one period changes for each period;
A light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement object into an electrical signal;
Removing means for removing a frequency component whose frequency does not change over a plurality of periods from the output signal of the light receiver;
The frequency of the interference waveform generated by the laser light emitted from the semiconductor laser and the return light from the measurement object, included in the output signal of the light receiver after removing the frequency component, is defined as the first oscillation period. Frequency measuring means for measuring each of the second oscillation periods;
After converting the frequency of the interference waveform in the first and second oscillation periods to a value when the amplitude of the oscillation waveform is a reference amplitude, respectively, interference is performed from the converted frequency in the first and second oscillation periods. Counting means for determining the number of waveforms;
At least one of the distance to the measurement object and the velocity of the measurement object is calculated from the minimum oscillation wavelength and the maximum oscillation wavelength in the period of counting the number of interference waveforms by the counting means and the number of interference waveforms obtained by the counting means. And a distance / speed meter characterized by comprising: A semiconductor laser that emits laser light to the object to be measured;
The first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist alternately for at least two periods, and A laser driver that modulates the oscillation wavelength of the semiconductor laser so that at least one of the frequency and the amplitude of the oscillation waveform having one oscillation period and the second oscillation period as one period changes for each period;
A light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement object into an electrical signal;
Counting means for counting the number of signals included in the output of the light receiver for each of the first oscillation period and the second oscillation period;
The number of interference waveforms generated by the laser light emitted from the semiconductor laser and the return light from the measurement object is determined based on the counting results of the counting means over a plurality of periods, and the second oscillation period and the second oscillation period. A calculating means for calculating each of the oscillation periods;
The calculation means calculates at least one of the distance to the measurement object and the speed of the measurement object from the minimum oscillation wavelength and the maximum oscillation wavelength in the period in which the number of interference waveforms is counted and the number of interference waveforms obtained by the calculation means. And a distance / speed meter characterized by comprising: A semiconductor laser that emits laser light to the object to be measured;
The first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist alternately for at least two periods, and A laser driver that modulates an oscillation wavelength of the semiconductor laser so that an amplitude of an oscillation waveform having one oscillation period and the second oscillation period as one period changes for each period;
A light receiver for converting the optical output of the semiconductor laser into an electrical signal;
Removing means for removing a frequency component whose frequency does not change over a plurality of periods from the output signal of the light receiver;
The frequency of the interference waveform generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, which is included in the output signal of the light receiver after removing the frequency component, Frequency measuring means for measuring each of the oscillation period and the second oscillation period;
After converting the frequency of the interference waveform in the first and second oscillation periods to a value when the amplitude of the oscillation waveform is a reference amplitude, respectively, interference is performed from the converted frequency in the first and second oscillation periods. Counting means for determining the number of waveforms;
Arithmetic means for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the minimum and maximum oscillation wavelengths in each oscillation period of the semiconductor laser and the number of interference waveforms obtained by the counting means; A distance / speed meter characterized by comprising: A semiconductor laser that emits laser light to the object to be measured;
The first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist alternately for at least two periods, and A laser driver that modulates the oscillation wavelength of the semiconductor laser so that at least one of the frequency and the amplitude of the oscillation waveform having one oscillation period and the second oscillation period as one period changes for each period;
A light receiver for converting the optical output of the semiconductor laser into an electrical signal;
Counting means for counting the number of signals included in the output of the light receiver for each of the first oscillation period and the second oscillation period;
The number of interference waveforms generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object is calculated based on the first oscillation period based on the counting result of the counting means over a plurality of periods. Calculating means for calculating each of the second oscillation periods;
Arithmetic means for calculating at least one of the distance to the measurement object and the velocity of the measurement object from the minimum and maximum oscillation wavelengths in each oscillation period of the semiconductor laser and the number of interference waveforms obtained by the calculation means; A distance / speed meter characterized by comprising: The distance / speed meter according to claim 3 or 4 ,
The computing means is
A distance / velocity calculation unit for calculating a candidate value for the distance to the measurement target and a candidate value for the speed of the measurement target based on the minimum oscillation wavelength and the maximum oscillation wavelength of the semiconductor laser and the counting result of the counting unit;
A history displacement calculator that calculates a history displacement that is a difference between the distance candidate value calculated by the distance / speed calculator and the distance candidate value calculated last time;
A state determination unit that determines the state of the measurement object based on the calculation results of the distance / speed calculation unit and the history displacement calculation unit;
A distance / speed meter comprising: a distance / speed determining section that determines at least one of a distance to the measurement object and a speed of the measurement object based on a determination result of the state determination section. The distance / speed meter according to claim 5 ,
The distance / velocity calculation unit and the history displacement calculation unit assume that the state of the measurement object is either a minute displacement state or a displacement state whose movement is steeper than the minute displacement state, and the measurement object is a minute displacement state. The distance candidate value, the velocity candidate value, and the history displacement for each of the case of assuming that the displacement state is assumed and the case of being in the displacement state, the first oscillation period, the second oscillation period, and Is calculated for each period
The state determination unit determines for each calculation whether the measurement object is in a minute displacement state or a displacement state based on the calculation results of the distance / speed calculation unit and the history displacement calculation unit, and the measurement A distance / speed meter that determines whether the object is moving at an equal speed or an acceleration at every calculation. The distance / speed meter according to claim 6 ,
The state determining unit is configured to calculate the speed calculated on the assumption that the sign of the history displacement calculated on the assumption that the measurement object is in a minute displacement state is constant and the measurement object is in a minute displacement state. And the average value of the absolute values of the historical displacement calculated on the assumption that the measurement object is in a minute displacement state are equal to each other, it is determined that the measurement object is moving at a constant velocity in the minute displacement state A distance / speed meter characterized by The distance / speed meter according to claim 6 ,
The state determination unit is configured to calculate the speed candidate calculated on the assumption that the sign of the history displacement calculated on the assumption that the measurement target is in a displacement state is constant and the measurement target is in a displacement state. When the value and the average value of the absolute values of the history displacement calculated on the assumption that the measurement object is in a displacement state are equal, it is determined that the measurement object is moving at a constant velocity in the displacement state. Distance and speed meter. The distance / speed meter according to claim 6 ,
The state determination unit calculates on the assumption that the sign of the history displacement calculated on the assumption that the measurement object is in a minute displacement state is inverted for each calculation and the measurement object is in a minute displacement state. If the average value of the absolute value of the history displacement calculated on the assumption that the measured object is in a minute displacement state does not match the average value of the historical displacement, the measurement object is accelerated in the minute displacement state. A distance / speed meter that is characterized as being The distance / speed meter according to claim 6 ,
The state determination unit is configured such that an absolute value of the velocity candidate value calculated on the assumption that the measurement target is in a displacement state is equal to a wavelength change rate of the semiconductor laser, and the measurement target is in a minute displacement state. If the speed candidate value calculated on the assumption that the measurement object is in a minute displacement state does not match the absolute value of the absolute value of the historical displacement, the measurement object is a minute displacement A distance / velocity meter that is determined to be accelerating in a state. The distance / speed meter according to claim 6 ,
The state determination unit is calculated on the assumption that the sign of the history displacement calculated on the assumption that the measurement object is in a displacement state is reversed for each calculation, and the measurement object is in a displacement state. When the velocity candidate value and the average value of the absolute value of the history displacement calculated on the assumption that the measurement object is in a displacement state do not match, it is determined that the measurement object is accelerating in a displacement state A distance / speed meter characterized by The distance / speed meter according to claim 6 ,
The state determination unit is configured such that the absolute value of the velocity candidate value calculated on the assumption that the measurement object is in a minute displacement state is equal to the wavelength change rate of the semiconductor laser, and the measurement object is in a displacement state. When the velocity candidate value calculated on the assumption that the measurement object is in a displacement state and the average value of the absolute values of the history displacement calculated on the assumption that the measurement object is in a displacement state do not match, A distance / velocimeter characterized by determining that it is accelerating. The distance / speed meter according to claim 3 or 4 ,
When the measurement object is in a motion state having a minute displacement, the calculation means uses the integration result of the displacement as a change in the distance from the measurement object instead of the calculation result.・ Speedometer.   Waves that have been wavelength-modulated so that the amplitude changes every period are radiated to the measurement object, and interference generated between the wave reflected back to the measurement object and the radiated wave is detected, and the detected interference information is used. A frequency component whose frequency does not change over a plurality of periods is removed, and after interference information after removing the frequency component is converted into a value when the amplitude of the wavelength-modulated wave is a reference amplitude, Based on the information, each of candidate values for the distance to the measurement object and the speed for the measurement object is calculated, and one corresponding speed and distance value is selected from each of these candidate values. Distance / speed measurement method.   A wave that has been wavelength-modulated so that at least one of frequency and amplitude changes every period is radiated to the measurement object, and the number of signals included in the output of the light receiver that converts the wave into an electrical signal is counted. The number of interference waveforms generated between the reflected wave and the radiated wave is calculated based on the result of the counting over a plurality of periods, and the distance from the measurement object is calculated based on the number of the interference waveforms. And a speed / distance measurement method characterized by calculating candidate values of speed with respect to the measurement object and selecting one corresponding speed and distance value from these candidate values. In the distance / velocity measurement method that emits laser light to a measurement object using a semiconductor laser,
The first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist alternately for at least two periods, and An oscillation procedure for modulating the oscillation wavelength of the semiconductor laser so that the amplitude of an oscillation waveform with one oscillation period and the second oscillation period as one period changes for each period;
A removal procedure for removing a frequency component whose frequency does not change over a plurality of cycles from an output signal of a light receiver that converts an optical output of the semiconductor laser into an electrical signal;
The frequency of the interference waveform generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, which is included in the output signal of the light receiver after removing the frequency component, A frequency measurement procedure for measuring each of the oscillation period and the second oscillation period;
After converting the frequency of the interference waveform in the first and second oscillation periods to a value when the amplitude of the oscillation waveform is a reference amplitude, respectively, interference is performed from the converted frequency in the first and second oscillation periods. A counting procedure to determine the number of waveforms;
From the minimum oscillation wavelength and the maximum oscillation wavelength in the period of counting the number of interference waveforms by this counting procedure, and the number of interference waveforms determined by the counting procedure, at least one of the distance to the measurement target and the speed of the measurement target is determined. A distance / speed measuring method comprising: a calculation procedure for calculating. In the distance / velocity measurement method that emits laser light to a measurement object using a semiconductor laser,
The first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist alternately for at least two periods, and An oscillation procedure for modulating the oscillation wavelength of the semiconductor laser so that at least one of the frequency and the amplitude of the oscillation waveform having one oscillation period and the second oscillation period as one period changes for each period;
A counting procedure for counting the number of signals included in the output of a light receiver that converts the optical output of the semiconductor laser into an electrical signal for each of the first oscillation period and the second oscillation period;
The number of interference waveforms caused by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object is calculated based on the first oscillation period based on the counting result of the counting procedure over a plurality of periods. A calculation procedure for calculating each of the second oscillation periods;
At least one of the distance to the measurement object and the speed of the measurement object is calculated from the minimum oscillation wavelength and the maximum oscillation wavelength in the period in which the number of interference waveforms is counted by the calculation procedure, and the number of interference waveforms obtained by the calculation procedure. A distance / speed measuring method comprising: a calculation procedure for calculating. The distance / speed measuring method according to claim 16 or 17 ,
In the calculation procedure, when the measurement object is in a motion state having a minute displacement, the integration result of the displacement is used as a change in the distance to the measurement object instead of the calculation result.・ Speed measurement method.

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