JP5545914B2 - Physical quantity sensor and physical quantity measuring method - Google Patents

Description

  The present invention relates to a physical quantity sensor and a physical quantity measurement method for measuring a physical quantity such as a distance to an object and a speed of an object from information on interference caused by a self-coupling effect between laser light emitted from a semiconductor laser and return light from the object. Is.

  Conventionally, as a distance meter using light interference by a laser, a laser measuring device using interference (self-coupling effect) inside a semiconductor laser between laser output light and return light from a measurement object has been proposed. (For example, refer nonpatent literature 1, nonpatent literature 2, nonpatent literature 3). FIG. 15 shows a composite resonator model of an FP type (Fabry-Perot type) semiconductor laser. In FIG. 15, 101 is a semiconductor laser, 102 is a wall opening of a semiconductor crystal, 103 is a photodiode, and 104 is an object to be measured.

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

  Since the semiconductor laser emits laser beams having different frequencies according to the magnitude of the injection current, an external modulator is not required when modulating the oscillation frequency, and direct modulation is possible by the injection current. FIG. 16 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 103 when the oscillation wavelength of the semiconductor laser is changed at a certain rate. When L = qλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the resonator 101 becomes 0 ° (the same phase), and the return light and the resonator 101 When L = qλ / 2 + λ / 4, the phase difference becomes 180 ° (opposite phase), and the return light and the laser light in the resonator 101 are the weakest. Therefore, when the oscillation wavelength of the semiconductor laser is changed, a place where the laser output becomes strong and a place where the laser output becomes weak appear alternately, and the laser output at this time is detected by the photodiode 103 provided in the resonator 101. As shown in FIG. 16, a step-like waveform having a constant period is obtained. Such a waveform is generally called an interference fringe.

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

  In view of this, the inventor has proposed a distance / speed meter that can measure not only the distance to a stationary measurement object but also the speed of the measurement object (see Patent Document 1). The configuration of this distance / speed meter is shown in FIG. The distance / velocity meter of FIG. 17 condenses the light from the semiconductor laser 201 that emits laser light to the measurement target, the photodiode 202 that converts the light output of the semiconductor laser 201 into an electrical signal, and the light from the semiconductor laser 201. A lens 203 that irradiates the measurement target 210 and collects return light from the measurement target 210 and makes it incident on the semiconductor laser 201. A first oscillation period and an oscillation wavelength in which the oscillation wavelength continuously increases in the semiconductor laser 201. A laser driver 204 that alternately repeats a second oscillation period in which the current continuously decreases, a current-voltage conversion amplifier 205 that converts and amplifies the output current of the photodiode 202 into a voltage, and a current-voltage conversion amplifier 205 Signal extraction circuit 206 that differentiates the output voltage of the signal twice and a counting circuit that counts the number of MHPs included in the output voltage of the signal extraction circuit 206 With a 07, a calculation unit 208 for calculating the distance and speed of the measurement target 210 to the measurement target 210, and a display device 209 for displaying the calculation result of the arithmetic unit 208.

  The laser driver 204 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 201 as an injection current. Accordingly, the semiconductor laser 201 alternately repeats the first oscillation period in which the oscillation wavelength continuously increases at a constant change rate and the second oscillation period in which the oscillation wavelength continuously decreases at a constant change rate. To be driven. FIG. 18 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 201. In FIG. 18, P1 is the first oscillation period, P2 is the second oscillation period, λa is the minimum value of the oscillation wavelength in each period, λb is the maximum value of the oscillation wavelength in each period, and WT is the period of the triangular wave.

  Laser light emitted from the semiconductor laser 201 is collected by the lens 203 and enters the measurement object 210. The light reflected by the measurement object 210 is collected by the lens 203 and enters the semiconductor laser 201. The photodiode 202 converts the optical output of the semiconductor laser 201 into a current. The current-voltage conversion amplifier 205 converts the output current of the photodiode 202 into a voltage and amplifies it, and the signal extraction circuit 206 differentiates the output voltage of the current-voltage conversion amplifier 205 twice. The counting circuit 207 counts the number of MHPs included in the output voltage of the signal extraction circuit 206 for each of the first oscillation period P1 and the second oscillation period P2. The arithmetic unit 208 determines the distance from the measurement object 210 based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1, the number of MHPs in the first oscillation period P1, and the number of MHPs in the second oscillation period P2. And the speed of the measuring object 210 is calculated.

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

The self-coupled distance meter shown in FIG. 15 can measure the distance to the measuring object, and the distance / velocity meter shown in FIG. 17 determines the distance to the measuring object and the speed of the measuring object. It can be measured simultaneously.
However, these self-coupled laser measuring instruments have a problem that it takes time to detect an object. That is, in the self-coupled laser measuring instrument, as shown in FIG. 18, the number of MHPs and the frequency are measured by changing the oscillation wavelength of the semiconductor laser, and the distance to the object is calculated, but the distance is calculated. Until then, it is impossible to detect whether an object is present in the radiation direction of the semiconductor laser. In order to detect an object at high speed, the period WT of the triangular wave shown in FIG. 18 may be shortened. However, in order to shorten the period WT, it is necessary to increase the circuit speed or to reduce the distance resolution. There is a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a physical quantity sensor and a physical quantity measuring method capable of achieving both high-speed detection of an object and high-resolution measurement of a physical quantity.

The physical quantity sensor of the present invention includes a semiconductor laser that emits modulated laser light, and a light receiving device that is disposed in or near the semiconductor laser and that receives the laser light emitted from the semiconductor laser and converts it into an electrical signal. And an interference waveform generated by a stationary reference plane by detecting a period of an interference waveform generated by a self-coupling effect between the laser beam emitted from the semiconductor laser and the return light included in the output signal of the optical receiver An object detection means for determining that an object is present in the laser beam radiation direction when an interference waveform having a period different from the period satisfies a predetermined condition, and the object from the interference information included in the output signal of the light receiver and a measuring means for measuring a physical quantity, the reference plane is a reflective wall facing said semiconductor laser across a space that will the object enters the product The detecting means measures the period of the interference waveform during the counting period for counting the number of the interference waveforms every time the interference waveform is input, and the interference during the counting period from the measurement result of the period measuring means. A frequency distribution creating means for creating a frequency distribution of the period of the waveform, a representative value calculating means for calculating a representative value T0 of the distribution of the period of the interference waveform from the frequency distribution, and a counting period one cycle before the laser light A number deriving unit for obtaining the number N of interference waveforms having a period longer than a predetermined number of times of the representative value T0 in the detection period in the current counting period with respect to the calculated representative value T0, and in the detection period An object determination unit that determines that the object is present in the laser beam emission direction when the ratio N / Nall of the number N to the total number Nall of the interference waveforms whose periods are measured is equal to or greater than a predetermined threshold. It is made of a.

In one configuration example of the physical quantity sensor of the present invention, the predetermined number is 2, for example.

The physical quantity sensor of the present invention is arranged in or near the semiconductor laser that emits modulated laser light, and receives the laser light emitted from the semiconductor laser and converts it into an electrical signal. And a period of an interference waveform generated by a self-coupling effect between the laser beam emitted from the semiconductor laser and its return light, which is included in the output signal of the photodetector, and is detected by a stationary reference plane When an interference waveform having a period different from the period of the interference waveform satisfies a predetermined condition, an object detection unit that determines that an object is present in the laser light emission direction and interference information included in the output signal of the light receiver and a measuring means for measuring a physical quantity of the object, the reference plane is Do not the antireflection treatment of inner and outer surfaces of the transparent cover to protect the semiconductor laser is subjected Any one of the surfaces, wherein the object detection means measures the period of the interference waveform during the counting period for counting the number of the interference waveforms every time the interference waveform is input, and the period measurement means. A frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement results, a representative value calculating means for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution, With respect to the representative value T0 calculated in the counting period one cycle before the laser beam, the number N of interference waveforms whose period is shorter than a predetermined number of times of the representative value T0 in the current counting period is obtained. The number derivation means and the object in the radiation direction of the laser beam when the ratio N / Nall of the number N to the total number Nall of the interference waveforms whose period is measured during the detection period is equal to or greater than a predetermined threshold value. It is made of a determining object determination unit to be present.
In one configuration example of the physical quantity sensor of the present invention, the predetermined number is, for example, 0.5.

The physical quantity sensor of the present invention is arranged in or near the semiconductor laser that emits modulated laser light, and receives the laser light emitted from the semiconductor laser and converts it into an electrical signal. And a period of an interference waveform generated by a self-coupling effect between the laser beam emitted from the semiconductor laser and its return light, which is included in the output signal of the photodetector, and is detected by a stationary reference plane When an interference waveform having a period different from the period of the interference waveform satisfies a predetermined condition, an object detection unit that determines that an object is present in the laser light emission direction and interference information included in the output signal of the light receiver and a measuring means for measuring a physical quantity of the object, the reference plane is a reflective wall facing said semiconductor laser across a space that will the object enters, The recording object detecting means measures the period of the interference waveform during the counting period for counting the number of the interference waveforms every time the interference waveform is input, and from the measurement result of the period measuring means during the counting period. A frequency distribution creating means for creating a frequency distribution of the period of the interference waveform, a representative value calculating means for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution, and a period from the frequency distribution of the representative value A number deriving unit for obtaining a sum Nw of frequencies longer than a predetermined number of times of T0, and for obtaining a number N of interference waveforms having a period longer than a predetermined number of times of the representative value T0 in the detection period of the counting period; When the ratio N / Nw of the number N in the detection period in the current counting period to the frequency Nw in the counting period one cycle before the laser light is equal to or greater than a predetermined threshold, the laser light is emitted in the radiation direction. It is made of a determining object determination means and the body is present.
In one configuration example of the physical quantity sensor of the present invention, the predetermined number is, for example, 1.5.

  Further, one configuration example of the physical quantity sensor of the present invention further 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. A laser driver that operates the semiconductor laser so that oscillation periods alternately exist, and the measuring means is generated by a self-coupling effect between the laser beam and the return beam included in the output signal of the light receiver. Counting means for counting the number of interference waveforms for each of the first oscillation period and the second oscillation period, minimum oscillation wavelength and maximum oscillation wavelength in the period for counting the number of interference waveforms by the counting means, and the counting means And calculating means for calculating at least one of the distance to the object and the speed of the object from the counting result.

Further, the physical quantity measuring method of the present invention includes an oscillation procedure for emitting modulated laser light from a semiconductor laser, and an output signal of a light receiver disposed in or near the semiconductor laser. When the period of the interference waveform generated by the self-coupling effect between the emitted laser light and its return light is detected, and the interference waveform having a period different from the period of the interference waveform due to the stationary reference surface satisfies a predetermined condition, An object detection procedure for determining that an object is present in the radiation direction of the laser beam, and a measurement procedure for measuring a physical quantity of the object from interference information included in an output signal of the light receiver , A reflection wall facing the semiconductor laser across a space where an object is to enter, and the object detection procedure includes the interference during a counting period counting the number of interference waveforms A period measurement procedure for measuring the period of the shape every time an interference waveform is input, a frequency distribution creation procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measurement procedure, and the frequency A representative value calculation procedure for calculating a representative value T0 of the period distribution of the interference waveform from the distribution and the representative value T0 calculated in the counting period one period before the laser light in the current counting period. A procedure for deriving the number N of interference waveforms whose period is longer than a predetermined number times the representative value T0 in the detection period, and the ratio of the number N to the total number Nall of interference waveforms whose periods were measured during the detection period This comprises an object determination procedure for determining that the object is present in the laser light emission direction when N / Nall is equal to or greater than a predetermined threshold value .

Moreover , in one configuration example of the physical quantity measurement method of the present invention, the predetermined number is two, for example.

Further, the physical quantity measuring method of the present invention includes an oscillation procedure for emitting modulated laser light from a semiconductor laser, and an output signal of a light receiver disposed in or near the semiconductor laser. When the period of the interference waveform generated by the self-coupling effect between the emitted laser light and its return light is detected, and the interference waveform having a period different from the period of the interference waveform due to the stationary reference surface satisfies a predetermined condition, An object detection procedure for determining that an object is present in the radiation direction of the laser beam, and a measurement procedure for measuring a physical quantity of the object from interference information included in an output signal of the light receiver , is a surface reflection preventing process is not applied among the inner and outer surfaces of the transparent cover to protect the semiconductor laser, the object detection procedure, the counting interval of the interference waveform A period measurement procedure for measuring the period of the interference waveform every time an interference waveform is input, and a frequency distribution creation procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measurement procedure, A representative value calculating procedure for calculating a representative value T0 of the distribution of the period of the interference waveform from the frequency distribution, and a current count with respect to the representative value T0 calculated in a counting period one cycle before the laser beam. The number derivation procedure for obtaining the number N of interference waveforms whose period is shorter than the predetermined number times the representative value T0 in the detection period, and the number of all interference waveforms whose period is measured during the detection period. When the N ratio N / Nall is equal to or greater than a predetermined threshold value, the object determination procedure determines that the object is present in the laser light emission direction.
In one configuration example of the physical quantity measurement method of the present invention, the predetermined number is, for example, 0.5.

Further, the physical quantity measuring method of the present invention includes an oscillation procedure for emitting modulated laser light from a semiconductor laser, and an output signal of a light receiver disposed in or near the semiconductor laser. When the period of the interference waveform generated by the self-coupling effect between the emitted laser light and its return light is detected, and the interference waveform having a period different from the period of the interference waveform due to the stationary reference surface satisfies a predetermined condition, An object detection procedure for determining that an object is present in the radiation direction of the laser beam, and a measurement procedure for measuring a physical quantity of the object from interference information included in an output signal of the light receiver , A reflection wall facing the semiconductor laser across a space where an object is to enter, and the object detection procedure includes the interference during a counting period counting the number of interference waveforms A period measurement procedure for measuring the period of the shape every time an interference waveform is input, a frequency distribution creation procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measurement procedure, and the frequency A representative value calculating procedure for calculating a representative value T0 of the distribution of the period of the interference waveform from the distribution, a total Nw of frequencies whose period is longer than a predetermined number times the representative value T0 from the frequency distribution, and the counting period A number derivation procedure for obtaining the number N of interference waveforms whose period is longer than a predetermined number of times of the representative value T0 in the middle detection period, and the current counting period for the frequency Nw in the counting period one period before the laser beam This comprises an object determination procedure for determining that the object is present in the laser light emission direction when the ratio N / Nw of the number N in the detection period is equal to or greater than a predetermined threshold.
Moreover, in one configuration example of the physical quantity measurement method of the present invention, the predetermined number is, for example, 1.5.

  In the configuration example of the physical quantity measurement method of the present invention, the oscillation procedure includes at least a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a period in which the oscillation wavelength continuously decreases monotonously. The semiconductor laser is operated so as to alternately include second oscillation periods that include the self-coupling of the laser light and the return light included in the output signal of the light receiver. A counting procedure for counting the number of interference waveforms caused by the effect for each of the first oscillation period and the second oscillation period, and 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 object and the speed of the object from the counting result of the counting procedure.

  According to the present invention, by providing the object detection means, the object can be detected at high speed without shortening the period of the laser beam (period of the triangular wave), so that the object can be detected at high speed and the physical quantity can be measured with high resolution. Can be made compatible.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a distance / speed meter according to a first embodiment of the present invention. The distance / velocity meter in FIG. 1 condenses light from a semiconductor laser 1 that emits laser light, a photodiode 2 that is a light receiver that converts the optical output of the semiconductor laser 1 into an electrical signal, and the semiconductor laser 1. The lens 3 that collects the return light from the reflecting wall 10 or the object 12 and makes it incident on the semiconductor laser 1, the laser driver 4 that drives the semiconductor laser 1, and the output current of the photodiode 2 are converted into voltages. A current-voltage conversion amplifier 5 that converts and amplifies, a filter circuit 6 that removes a carrier wave from the output voltage of the current-voltage conversion amplifier 5, and a counting device 7 that counts the number of MHPs included in the output voltage of the filter circuit 6; A calculation device 8 for calculating the distance to the object 12 and the speed of the object 12, a display device 9 for displaying the calculation result of the calculation device 8 and the detection result of the object detection device 11 described later, And an object detecting device 11 for detecting whether the object 12 in the radial direction of the body laser 1 is present.

The current-voltage conversion amplifier 5, the filter circuit 6, the counting device 7, and the arithmetic device 8 constitute a measuring means. The current-voltage conversion amplifier 5, the filter circuit 6, and the counting device 7 constitute counting means.
Hereinafter, for ease of explanation, it is assumed that a semiconductor laser 1 of a type that does not have a mode hopping phenomenon (VCSEL type, DFB laser type) is used.

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

  Laser light emitted from the semiconductor laser 1 is collected by the lens 3 and enters the reflecting wall surface 10 when the object 12 does not exist in the radiation direction of the semiconductor laser 1 and enters the object 12 when the object 12 exists. . The light reflected by the reflecting wall surface 10 or the 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 is disposed in the semiconductor laser 1 or in the vicinity thereof, and converts the optical output of the semiconductor laser 1 into a current. The current-voltage conversion amplifier 5 converts the output current of the photodiode 2 into a voltage and amplifies it.

  The filter circuit 6 has a function of extracting a superimposed signal from the modulated wave. 2A schematically shows the output voltage waveform of the current-voltage conversion amplifier 5, and FIG. 2B schematically shows the output voltage waveform of the filter circuit 6. As shown in FIG. In these figures, the oscillation waveform (carrier wave) of the semiconductor laser 1 in FIG. 18 is removed from the waveform (modulation wave) in FIG. 2A corresponding to the output of the photodiode 2, and the MHP in FIG. A process of extracting a waveform (interference waveform) is shown.

The counting device 7 counts the number of MHPs included in the output voltage of the filter circuit 6 for each of the first oscillation period P1 and the second oscillation period P2. FIG. 3 is a block diagram showing an example of the configuration of the counting device 7 and the object detection device 11.
The counting device 7 includes a determination unit 70, an AND operation unit (AND) 71, and a counter 72.
The object detection device 11 includes a period measurement unit 110, a storage unit 111, a frequency distribution creation unit 112, a representative value calculation unit 113, a number derivation unit 114, and an object determination unit 115.

  4A to 4F are diagrams for explaining the operation of the counting device 7 and the object detection device 11, and FIG. 4A is a waveform of an output voltage of the filter circuit 6, that is, a waveform of MHP. 4B is a diagram illustrating an output of the determination unit 70 corresponding to FIG. 4A, and FIG. 4C is a gate signal input to the counting device 7 and the object detection device 11. FIG. 4D is a diagram illustrating a counting result of the counter 72 corresponding to FIG. 4B, FIG. 4E is a diagram illustrating a clock signal CLK input to the object detection device 11, and FIG. 4 (F) is a diagram illustrating a measurement result of the period measurement unit 110 corresponding to FIG. 4 (B).

  First, the determination unit 70 of the counting device 7 determines whether the output voltage of the filter circuit 6 shown in FIG. 4A is high level (H) or low level (L), as shown in FIG. Output the judgment result. At this time, the determination unit 70 determines the high level when the output voltage of the filter circuit 6 rises to be equal to or higher than the threshold value TH1, and the output voltage of the filter circuit 6 decreases and the threshold value TH2 (TH2 <TH1) The output of the filter circuit 6 is binarized by determining the low level when it becomes below.

  The AND 71 outputs the result of the logical product operation between the output of the determination unit 70 and the gate signal GS as shown in FIG. 4C, and the counter 72 counts the rise of the output of the AND 71 (FIG. 4D). . Here, the gate signal GS is a signal that rises at the beginning of the counting period (in the present embodiment, each of the first oscillation period P1 and the second oscillation period P2) and falls at the end of the counting period. Therefore, the counter 72 counts the number of rising edges of the output of the AND 71 during the counting period (that is, the number of rising edges of MHP). It should be noted that the counting periods only have to exist in the oscillation periods P1 and P2, respectively, and have a time width equal to or less than the oscillation periods P1 and P2.

  On the other hand, the period measurement unit 110 of the object detection device 11 measures the period of the rising edge of the AND 71 output during the counting period (that is, the period of MHP) every time a rising edge occurs. At this time, the period measurement unit 110 measures the MHP period with the period of the clock signal CLK shown in FIG. In the example of FIG. 4F, the period measurement unit 110 sequentially measures Tα, Tβ, and Tγ as MHP periods. As is clear from FIGS. 4E and 4F, the periods Tα, Tβ, and Tγ are 5 clocks, 4 clocks, and 2 clocks, respectively. The frequency of the clock signal CLK is assumed to be sufficiently higher than the highest frequency that the MHP can take. The storage unit 111 stores the measurement result of the period measurement unit 110.

  After the gate signal GS falls and the counting period ends, the frequency distribution creation unit 112 of the object detection device 11 creates a frequency distribution of the MHP period during the counting period from the measurement result stored in the storage unit 111. The storage unit 111 stores the frequency distribution created by the frequency distribution creation unit 112.

  Subsequently, the representative value calculation unit 113 of the object detection device 11 calculates the median value (median) T0 of the MHP cycle from the frequency distribution created by the frequency distribution creation unit 112. The storage unit 111 stores a median value T0 of the MHP cycle.

The number deriving unit 114 of the object detection device 11 refers to the storage unit 111 and performs an arbitrary calculation in the current counting period with respect to the median value T0 of the MHP period calculated in the counting period one triangular wave period WT before the current time. In this detection period d, the number N of MHPs whose period T satisfies the following equation is obtained.
2T0 <T (2)
In addition, the number deriving unit 114 obtains the total number Nall of MHPs whose cycles are measured during the detection period d by the cycle measuring unit 110.

  FIG. 5 is a diagram schematically showing the output voltage waveform of the filter circuit 6, for explaining the relationship between the counting period (each of the first oscillation period P1 and the second oscillation period P2) and the detection period d. FIG. The detection period d has a time width of a fixed time td (td <WT / 2). As shown in FIG. 5, a plurality of detection periods d can be set during the counting period.

  When the ratio N / Nall of the number N to the total number NALL of MHPs whose cycles are measured during the detection period d is equal to or greater than a predetermined threshold (for example, 60%), the object determination unit 115 of the object detection device 11 It is determined that the object 12 is present in the radiation direction, and an object detection signal indicating that the object 12 has been detected is output. In response to the output of the object detection signal, the display device 9 displays that the object 12 has been detected, and the arithmetic device 8 starts calculating the distance and speed. The object detection device 11 performs the object detection process as described above for each counting period and each detection period.

  FIG. 6 is a diagram showing the frequency distribution of the MHP cycle, and is a diagram for explaining the principle of object detection by the object detection device 11. When the object 12 does not exist in the radiation direction of the semiconductor laser 1, the light from the reflection wall surface 10 returns to the semiconductor laser 1. In this case, the MHP appears in the same period, and the period of the MHP is normally distributed around the median value T0.

  On the other hand, when the object 12 exists in the radiation direction of the semiconductor laser 1, the object 12 exists between the semiconductor laser 1 and the reflection wall surface 10, and therefore, an MHP having a lower frequency than when the object 12 does not exist. Appear. In other words, considering the frequency distribution of the MHP cycle, a distribution having a cycle longer than the median value T0 of the MHP cycle when the object 12 does not exist appears.

  Here, in the MHP waveform, due to noise, a loss may occur or a waveform that should not be counted as a signal may occur. In particular, in the case of the present embodiment, the return light when the object 12 is not present is light from the reflection wall surface 10, so that the intensity of MHP is small and signal loss may occur. When signal loss occurs, the MHP cycle at the location where the loss occurs is approximately twice the original cycle. In other words, since the MHP intensity is small and the missing MHP period is a normal distribution with the original MHP period centered on T0, the average value is 2T0 and the standard deviation is 2σ. Become.

Therefore, in order to eliminate the influence of such signal loss, the determination based on the formula (2) is performed, and it is determined that the object 12 exists in the radiation direction of the semiconductor laser 1 when an MHP having a period longer than 2T0 appears. To do.
Note that the threshold value used for determination by the object determination unit 115 is a predetermined value from the ratio N / Nall obtained in the initial state where the object 12 does not exist in the radiation direction of the semiconductor laser 1. For example, in the initial detection period d, if Nall is 100 and N is 5, N / Nall = 5%. For example, assuming that twice the value 10% is a threshold value, it is determined that the object 12 exists in the radiation direction of the semiconductor laser 1 when N / Nall is 10% or more.

  Next, the operation of the arithmetic device 8 when an object detection signal is output from the object detection device 11 will be described. The computing device 8 calculates the distance to the object 12 and the speed of the object 12 based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1 and the number of MHPs counted by the counting device 7. FIG. 7 is a block diagram showing an example of the configuration of the arithmetic device 8, and FIG. 8 is a flowchart showing the operation of the arithmetic device 8.

  The arithmetic device 8 is a distance / speed calculator that calculates a candidate value for the distance to the object 12 and a candidate value for the speed of the object 12 based on the minimum oscillation wavelength λa, the maximum oscillation wavelength λb, and the number of MHPs of the semiconductor laser 1. 80, a history displacement calculation unit 81 that calculates a history displacement that is a difference between the distance candidate value calculated by the distance / speed calculation unit 80 and the distance candidate value calculated immediately before, and a distance / speed calculation unit 80 A storage unit 82 that stores the calculation results of the history displacement calculation unit 81, a state determination unit 83 that determines the state of the object 12 based on the calculation results of the distance / speed calculation unit 80 and the history displacement calculation unit 81, and a state determination The distance / speed determination unit 84 determines the distance to the object 12 and the speed of the object 12 based on the determination result of the unit 83.

  In the present embodiment, it is assumed that the state of the object 12 is either a minute displacement state that satisfies a predetermined condition or a displacement state that moves more than the minute displacement state. When the average displacement of the object 12 per oscillation period P1 and oscillation period P2 is V, the minute displacement state is a state satisfying (λb−λa) / λb> V / Lb (where Lb is time (distance at time t), the displacement state is a state satisfying (λb−λa) / λb ≦ V / Lb.

First, the distance / speed calculation unit 80 of the arithmetic unit 8 calculates the distance candidate values Lα (t) and Lβ (t) and the speed candidate values Vα (t) and Vβ (t) at the current time t as follows: And stored in the storage unit 82 (step S10 in FIG. 8).
Lα (t) = λa × λb × (MHP (t−1) + MHP (t))
/ {4 × (λb−λa)} (3)
Lβ (t) = λa × λb × (| MHP (t−1) −MHP (t) |)
/ {4 × (λb−λa)} (4)
Vα (t) = (MHP (t−1) −MHP (t)) × λb / 4 (5)
Vβ (t) = (MHP (t−1) + MHP (t)) × λb / 4 (6)

  In Expressions (3) to (6), MHP (t) is the number of MHPs calculated at the current time t, and MHP (t−1) is the number of MHPs calculated one time before MHP (t). is there. For example, if MHP (t) is the counting result of the first oscillation period P1, MHP (t-1) is the counting result of the second oscillation period P2, and conversely, MHP (t) is the second counting period. If it is the counting result of the oscillation period P2, the MHP (t−1) is the counting result of the first oscillation period P1.

  The candidate values Lα (t) and Vα (t) are values calculated on the assumption that the object 12 is in a minute displacement state, and the candidate values Lβ (t) and Vβ (t) are obtained when the object 12 is in a displacement state. This is a calculated value. The arithmetic unit 8 performs the calculations of the equations (3) to (6) at every time (every oscillation period) when the counting device 7 measures the number of MHPs.

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

The history displacement Vcalα (t) is a value calculated on the assumption that the object 12 is in a minute displacement state, and the history displacement Vcalβ (t) is a value calculated on the assumption that the object 12 is in a displacement state. The arithmetic device 8 performs the calculations of the equations (7) to (8) at each time when the number of MHPs is measured by the counting device 7. In Expressions (5) to (8), the direction in which the object 12 approaches the distance / speedometer of the present embodiment is defined as a positive speed, and the direction in which the object 12 moves away is defined as a negative speed.
Next, the state determination unit 83 of the arithmetic device 8 determines the state of the object 12 using the calculation results of Expressions (3) to (8) stored in the storage unit 82 (Step S12 in FIG. 8).

  As described in Patent Document 1, when the object 12 is moving in a minute displacement state (equal speed motion), the sign of the history displacement Vcalα (t) calculated assuming that the object 12 is in the minute displacement state is The velocity candidate value Vα (t), which is constant and calculated assuming that the object 12 is in a minute displacement state, is equal to the average value of absolute values of the history displacement Vcalα (t). In addition, when the object 12 is moving at a constant speed in a minute displacement state, the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 12 is in the displacement state is reversed every time the number of MHPs is measured. .

  Therefore, the state determination unit 83 calculates the speed calculated on the assumption that the sign of the history displacement Vcalα (t) calculated on the assumption that the object 12 is in the minute displacement state is constant and that the object 12 is in the minute displacement state. Is equal to the average value of the absolute values of the history displacement Vcalα (t), it is determined that the object 12 is moving at a constant speed in a minute displacement state.

  As described in Patent Document 1, when the object 12 is moving in a displaced state (equal speed motion), the sign of the history displacement Vcalβ (t) calculated assuming that the object 12 is in the displaced state is constant. In addition, the velocity candidate value Vβ (t) calculated on the assumption that the object 12 is in the displacement state is equal to the average value of the absolute values of the history displacement Vcalβ (t). In addition, when the object 12 is moving at a constant speed in the displaced state, the sign of the history displacement Vcalα (t) calculated on the assumption that the object 12 is in the minutely displaced state is inverted every time the number of MHPs is measured.

  Therefore, the state determination unit 83 calculates the speed candidate calculated assuming that the sign of the historical displacement Vcalβ (t) calculated on the assumption that the object 12 is in the displacement state and the object 12 is in the displacement state. When the value Vβ (t) and the average value of the absolute values of the history displacement Vcalβ (t) are equal, it is determined that the object 12 is moving at a constant speed in the displaced state.

  As described in Patent Document 1, when the object 12 is in a minute displacement state and is moving other than a constant velocity motion, the velocity candidate value Vα (t calculated by assuming that the object 12 is in a minute displacement state ) And the average value of the absolute values of the history displacement Vcalα (t) calculated on the assumption that the object 12 is in a minute displacement state. Similarly, the average value of the absolute value of the velocity candidate value Vβ (t) calculated assuming that the object 12 is in the displaced state and the history displacement Vcalβ (t) calculated assuming that the object 12 is in the displaced state do not match.

  Further, when the object 12 is in a minute displacement state and is moving other than a constant velocity movement, the sign of the history displacement Vcalα (t) calculated on the assumption that the object 12 is in the minute displacement state is the number of MHPs. The history displacement Vcalβ (t) that is inverted at each time and calculated assuming that the object 12 is in a displaced state has a change in sign, but this change is not at every time when the number of MHPs is measured.

  Therefore, the state determination unit 83 reverses the sign of the history displacement Vcalα (t) calculated on the assumption that the object 12 is in a minute displacement state every time the number of MHPs is measured, and the object 12 is minutely displaced. When the velocity candidate value Vα (t) calculated on the assumption that the state is in the state does not coincide with the average value of the absolute values of the history displacement Vcalα (t), the object 12 performs a motion other than the uniform velocity motion in a minute displacement state. It is determined that

  Focusing on the velocity candidate value Vβ (t), the absolute value of Vβ (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 83 assumes that the absolute value of the velocity candidate value Vβ (t) calculated on the assumption that the object 12 is in the displacement state is equal to the wavelength change rate, and that the object 12 is in the minute displacement state. If the velocity candidate value Vα (t) calculated in this way and the average value of the absolute values of the history displacement Vcalα (t) do not match, it is determined that the object 12 is moving in a minute displacement state other than the constant velocity motion. May be.

  As described in Patent Document 1, when the object 12 is in a displacement state and is moving other than a constant velocity motion, the velocity candidate value Vα (t) calculated on the assumption that the object 12 is in a minute displacement state. And the average value of the absolute values of the history displacement Vcalα (t) calculated on the assumption that the object 12 is in the minute displacement state, and the velocity candidate value Vβ (t) calculated on the assumption that the object 12 is in the displacement state. Also, the average value of the absolute values of the history displacement Vcalβ (t) calculated on the assumption that the object 12 is in the displaced state does not match.

  In addition, when the object 12 is in a displaced state and is moving other than a constant velocity motion, the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 12 is in a displaced state is the time at which the number of MHPs is measured. In the history displacement Vcalα (t) calculated assuming that the object 12 is in a minute displacement state, the change is not at every time when the number of MHPs is measured.

  Therefore, the state determination unit 83 reverses the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 12 is in the displaced state at each time when the number of MHPs is measured, and the object 12 is in the displaced state. If the velocity candidate value Vβ (t) calculated on the assumption that there is no coincidence with the average value of the absolute values of the history displacement Vcalβ (t), the object 12 moves in a displaced state other than the uniform velocity motion. Is determined.

  When attention is paid to the velocity candidate value Vα (t), the absolute value of Vα (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 83 assumes that the absolute value of the velocity candidate value Vα (t) calculated on the assumption that the object 12 is in the minute displacement state is equal to the wavelength change rate, and that the object 12 is in the displacement state. If the velocity candidate value Vβ (t) calculated in this way and the average value of the absolute values of the history displacement Vcalβ (t) do not match, it is determined that the object 12 is moving in a displacement state other than a constant velocity motion. May be.

The distance / speed determination unit 84 of the arithmetic device 8 determines the speed of the object 12 and the distance to the object 12 based on the determination result of the state determination unit 83 (step S13 in FIG. 8).
That is, when it is determined that the object 12 is moving at a constant velocity in a minute displacement state, the distance / speed determining unit 84 sets the speed candidate value Vα (t) as the speed of the object 12 and uses the distance candidate value Lα ( t) is a distance from the object 12, and it is determined that the object 12 is moving at a constant speed in a displaced state, the speed candidate value Vβ (t) is the speed of the object 12, and the distance candidate value Lβ (t ) Is the distance to the object 12.

  Further, when it is determined that the object 12 is performing a motion other than the constant velocity motion in a minute displacement state, the distance / speed determination unit 84 sets the speed candidate value Vα (t) as the speed of the object 12 and determines the distance The candidate value Lα (t) is set as the distance from the object 12. However, the actual distance is an average value of the distance candidate values Lα (t). Further, when it is determined that the object 12 is moving in a state of displacement other than the uniform velocity motion, the distance / velocity determination unit 84 sets the velocity candidate value Vβ (t) as the velocity of the object 12 and sets the distance candidate. The value Lβ (t) is the distance from the object 12. However, the actual distance is an average value of the distance candidate values Lβ (t).

  Note that Vβ (t) is always a positive value and Vα (t) is either a positive or negative value due to the magnitude relationship between MHP (t−1) and MHP (t). It does not represent the direction of 12 speeds. When the number of MHPs of the semiconductor laser whose oscillation wavelength is increasing is larger than the number of MHPs of the semiconductor laser whose oscillation wavelength is decreasing, the velocity of the object 12 is positive (direction approaching the laser). )

The arithmetic device 8 performs the processing of steps S10 to S13 at every time (every oscillation period) when the number of MHPs is measured by the counting device 7.
The display device 9 displays the distance to the object 12 and the speed of the object 12 calculated by the arithmetic device 8 in real time.

  As described above, in the present embodiment, the object detection device 11 repeatedly performs the object detection process in each detection period d having a time width shorter than the period WT of the triangular wave, so that the object is detected at a higher speed than the self-coupled laser measuring instrument. 12 can be detected. On the other hand, the counting device 7, the arithmetic device 8, and the like operate as a self-coupled laser measuring instrument, so that the distance to the object 12 and the speed of the object 12 can be measured with high resolution. 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, it is possible to realize high-speed object detection and high-resolution measurement of the physical quantity of the object.

[Second Embodiment]
In the first embodiment, the reflection wall surface 10 is used as a reference surface for object detection. However, the antireflection treatment is applied only to one surface of the transparent body that forms the laser light incident / exit portion from the semiconductor laser 1 to provide a transparent surface. The surface of the body that has not been subjected to the antireflection treatment may be used as a reference surface for object detection.

  FIG. 9 is a block diagram showing a configuration of a distance / velocity meter according to the second embodiment of the present invention, and FIG. 10 is a schematic configuration of a main part of an input / output unit of a semiconductor laser according to the second embodiment of the present invention. The same reference numerals are given to the same components as those in FIG. The major difference between the present embodiment and the first embodiment is that there is no reflecting wall surface and the object detection processing of the object detection device 11a is different.

In FIG. 10, 130 is a sealed case for housing the semiconductor laser 1, 131 is a transparent cover (transparent body) such as glass provided on the front surface of the semiconductor laser 1 to protect the semiconductor laser 1, and 132 is on the surface of the transparent cover 131. An antireflection film (AR coating) is provided.
The transparent cover 131 is provided by being fitted into the window portion of the sealed case 130. Then, the semiconductor laser 1 is assembled in the sealed case 130 with the laser light incident / exit surface as the front surface facing the transparent cover 131.

  When laser light is input / output through a transparent body such as glass, the laser light is reflected slightly at the interface between the transparent body and air. In order to prevent such reflection, the surface of the transparent body is exclusively coated with a filler in which a low refractive index material is dispersed to form an antireflection film. Also in the present embodiment, an antireflection film 132 is provided on the surface of the transparent cover 131 in order to suppress unnecessary reflection on the transparent cover 131 serving as the laser light incident / exit surface. Only the antireflection film 132 is provided, and the antireflection film is not formed on the outer surface thereof, so that the laser beam is reflected on the outer surface of the transparent cover 131. A part of the laser light output from the semiconductor laser 1 is reflected by the outer surface of the transparent cover 131 and returned to the semiconductor laser 1.

  Of course, the outer surface of the transparent cover 131 is not subjected to the antireflection treatment, but the semiconductor laser 1 is intentionally subjected to a treatment necessary for obtaining a reflected light having an intensity that causes a self-coupling effect. May be. Specifically, the outer surface of the transparent cover 131 can be mirror-polished, or an optical film having a certain reflectivity can be formed by coating.

  According to the configuration shown in FIG. 10, when the object 12 is not present in the radiation direction of the semiconductor laser 1, a part of the laser light emitted from the semiconductor laser 1 is reflected by the outer surface of the transparent cover 131 and the semiconductor laser 1. Will return. As a result, in the semiconductor laser 1, interference due to the self-coupling effect between the output light and the reflected light from the transparent cover 131 occurs.

Also in the present embodiment, the operations of the photodiode 2, the laser driver 4, the current-voltage conversion amplifier 5, the filter circuit 6, the counting device 7, the arithmetic device 8, and the display device 9 are the same as those in the first embodiment. Description is omitted.
FIG. 11 is a block diagram showing an example of the configuration of the object detection device 11a of the present embodiment. The object detection device 11a includes a period measurement unit 110, a storage unit 111, a frequency distribution creation unit 112, a representative value calculation unit 113, a number derivation unit 114a, and an object determination unit 115.

The operations of the period measurement unit 110, the storage unit 111, the frequency distribution creation unit 112, and the representative value calculation unit 113 are the same as those in the first embodiment.
The number deriving unit 114a of the object detection device 11a refers to the storage unit 111, and performs an arbitrary value in the current counting period with respect to the median value T0 of the MHP period calculated in the counting period one triangular wave period WT before the current time. In this detection period d, the number N of MHPs whose period T satisfies the following equation is obtained.
0.5T0> T (9)
The detection period d is as described in the first embodiment. The number deriving unit 114a obtains the total number Nall of MHPs whose periods are measured during the detection period d by the period measuring unit 110.

When the ratio N / Nall of the number N to the total number Nall of MHPs whose cycles are measured during the detection period d is equal to or greater than a predetermined threshold value (for example, 60%), the object determination unit 115 12 is determined to be present, and an object detection signal indicating that the object 12 has been detected is output.
The object detection device 11a performs the object detection process as described above for each counting period and each detection period.

FIG. 12 is a diagram showing the frequency distribution of the MHP cycle, and is a diagram for explaining the principle of object detection by the object detection device 11a. When the object 12 does not exist in the radiation direction of the semiconductor laser 1, light from the outer surface of the transparent cover 131 that has not been subjected to antireflection prevention processing returns to the semiconductor laser 1. In this case, the MHP appears in the same period, and the period of the MHP is normally distributed around the median value T0.
The difference from the first embodiment is that since the distance from the semiconductor laser 1 to the outer surface of the transparent cover 131 is shorter than the distance from the semiconductor laser 1 to the reflecting wall surface 10, the MHP frequency is low and the median value of the period T0 is increased.

  On the other hand, when the object 12 is present in the radiation direction of the semiconductor laser 1, the object 12 exists farther than the transparent cover 131, and therefore MHP having a higher frequency appears than when the object 12 is not present. That is, considering the frequency distribution of the MHP cycle, a distribution having a cycle shorter than the median value T0 of the MHP cycle when the object 12 does not exist appears.

  Here, a waveform that should not be counted as a signal may occur in the MHP waveform due to noise. The period of MHP divided into two as a result of excessive noise counting is a frequency distribution symmetric with respect to 0.5T0 because the period before the division is a normal distribution centered on T0.

Therefore, in order to eliminate the influence of such noise count, the determination based on the formula (9) is performed, and when an MHP having a period shorter than 0.5T0 appears, the object 12 exists in the radiation direction of the semiconductor laser 1. Judge that.
Other operations are as described in the first embodiment. As described above, according to the present embodiment, the present invention can be applied even when one surface of the transparent cover 131 is used as a reference surface for object detection, and the same effects as those of the first embodiment can be obtained. Can be obtained.
When the object 12 appears in the vicinity of a reference plane (a reflection wall surface in the case of the first embodiment, a surface that has not been subjected to the antireflection treatment of the transparent body in the case of the second embodiment), a threshold value is set. However, in this case, object detection can be performed when a distance different from the distance from the reference plane is calculated by the described distance calculation method.

[Third Embodiment]
In the first and second embodiments, the detection period d has been described as having a fixed length having a time width of the constant time td, but the detection period d may be a variable length. When the detection period d has a variable length, a period in which a fixed number of MHPs appear appears as the detection period d, and the number N of MHPs whose period T satisfies Expression (2) or Expression (9) in the detection period d. And whether or not the object 12 exists is determined.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. Also in this embodiment, the 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.
The operations of the photodiode 2, the laser driver 4, the current-voltage conversion amplifier 5, the filter circuit 6, the counting device 7, the arithmetic device 8, and the display device 9 are the same as those in the first embodiment.

FIG. 13 is a block diagram illustrating an example of the configuration of the object detection device 11 according to the present embodiment. The object detection apparatus 11 includes a period measurement unit 110, a storage unit 111, a frequency distribution creation unit 112, a representative value calculation unit 113, a number derivation unit 114b, and an object determination unit 115b.
The operations of the period measurement unit 110, the storage unit 111, the frequency distribution creation unit 112, and the representative value calculation unit 113 are the same as those in the first embodiment.

The number deriving unit 114b of the object detection device 11 refers to the storage unit 111, and obtains the sum Nw of the frequencies of MHPs in which the period T satisfies the following expression during the counting period from the frequency distribution created by the frequency distribution creating unit 112. The storage unit 111 stores the frequency Nw.
1.5T0 <T (10)
In addition, the number deriving unit 114b obtains the number N of MHPs whose period T satisfies Equation (10) in an arbitrary detection period d in the counting period.

  FIG. 14 shows an example of the frequency distribution of the MHP cycle. In FIG. 14, Tw is a class value that is 1.5 times the median value T0. In FIG. 14, the frequency distribution between the median values T0 and Tw is omitted to simplify the description.

The object determination unit 115b emits the semiconductor laser 1 when the ratio N / Nw of the number N in the detection period d in the current counting period to the frequency Nw in the counting period one triangular wave period WT before the current is equal to or greater than a predetermined threshold. It is determined that the object 12 exists in the direction, and an object detection signal indicating that the object 12 has been detected is output. The object detection device 11 performs the object detection process as described above for each counting period and each detection period.
According to the present embodiment, the same effect as in the first embodiment can be obtained.

  As in the first embodiment, the threshold used by the object determination unit 115b for determination is a value determined in advance from the ratio N / Nw obtained in the initial state where the object 12 does not exist in the radiation direction of the semiconductor laser 1. It is.

[Fifth Embodiment]
In the first to fourth embodiments, the median value is used as the representative value of the MHP cycle, but the mode value may be used as the representative value of the cycle. Specifically, the representative value calculation unit 113 of the object detection devices 11 and 11a may calculate the mode value of the MHP cycle from the frequency distribution created by the frequency distribution creation unit 112. The number deriving units 114, 114a, and 114b may perform the same processing as in the first to fourth embodiments using the mode value instead of the median value T0.
Further, an average value may be used as a representative value of the MHP cycle. In this case, the representative value calculation unit 113 may calculate the average value of the MHP cycle.

  The counting device 7, the arithmetic device 8, and the object detection devices 11 and 11a in the first to fifth embodiments are, for example, a computer having a CPU, a storage device, and an interface, and a program for controlling these hardware resources. Can be realized. A program for operating such a computer is provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, or a memory card. The CPU writes the read program into the storage device, and executes the processes described in the first to fifth embodiments according to this program.

  In the first to fifth embodiments, the distance / speed meter is described as an example of the physical quantity sensor. However, the present invention is not limited to this, and a distance meter or a speed meter may be used. It may be a sensor that measures other physical quantities.

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

It is a block diagram which shows the structure of the distance and speedometer which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the output voltage waveform of the current-voltage conversion amplifier which concerns on the 1st Embodiment of this invention, and the output voltage waveform of a filter circuit. It is a block diagram showing an example of composition of a counting device and an object detection device concerning a 1st embodiment of the present invention. It is a figure for demonstrating operation | movement of the counting device and object detection apparatus which concern on the 1st Embodiment of this invention. It is a figure for demonstrating the relationship between the counting period in the 1st Embodiment of this invention, and a detection period. It is a figure for demonstrating the principle of the object detection by the object detection apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows one example of a structure of the arithmetic unit which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the arithmetic unit which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the distance and speedometer which concerns on the 2nd Embodiment of this invention. It is a figure which shows the principal part schematic structure of the incident / exit part of the semiconductor laser which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the object detection apparatus which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the principle of the object detection by the object detection apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the object detection apparatus which concerns on the 4th Embodiment of this invention. It is a figure which shows one example of the frequency distribution of the period of the mode hop pulse in the 4th Embodiment of this invention. It is a figure which shows the compound resonator model of the semiconductor laser in the conventional laser measuring device. It is a figure which shows the relationship between the oscillation wavelength of a semiconductor laser, and the output waveform of a built-in photodiode. It is a block diagram which shows the structure of the conventional distance and speedometer. It is a figure which shows one example of the time change of the oscillation wavelength of a semiconductor laser in the distance and speedometer of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplifier, 6 ... Filter circuit, 7 ... Counting device, 8 ... Arithmetic unit, 9 ... Display device, 10 ... Reflection Wall surface, 11, 11a ... object detection device, 12 ... object, 70 ... determination unit, 71 ... logical product calculation unit, 72 ... counter, 80 ... distance / speed calculation unit, 81 ... history displacement calculation unit, 82 ... storage unit, 83 ... State determination unit, 84 ... Distance / speed determination unit, 110 ... Period measurement unit, 111 ... Storage unit, 112 ... Frequency distribution creation unit, 113 ... Representative value calculation unit, 114, 114a, 114b ... Number derivation unit, 115 115b, an object determination unit, 130, a sealed case, 131, a transparent cover, 132, an antireflection film.

Claims (14)

A semiconductor laser that emits modulated laser light;
A light receiver that is disposed in or near the semiconductor laser and receives the laser light emitted from the semiconductor laser and converts it into an electrical signal;
The period of the interference waveform generated by the self-coupling effect between the laser beam emitted from the semiconductor laser and its return light included in the output signal of the light receiver is detected, and the period of the interference waveform by the stationary reference plane is An object detection means for determining that an object is present in the radiation direction of the laser beam when interference waveforms having different periods satisfy a predetermined condition;
Measuring means for measuring the physical quantity of the object from information of interference included in the output signal of the light receiver ,
The reference surface is a reflective wall surface facing the semiconductor laser across a space where the object is to enter,
The object detection means includes
A period measuring means for measuring a period of the interference waveform during a counting period for counting the number of the interference waveforms every time the interference waveform is input;
Frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measuring means,
Representative value calculating means for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution;
With respect to the representative value T0 calculated in the counting period one cycle before the laser beam, the number N of interference waveforms whose period is longer than a predetermined number of times of the representative value T0 in the current detection period. A desired number derivation means;
Object determination that determines that the object is present in the laser light emission direction when the ratio N / Nall of the number N to the total number Nall of interference waveforms whose periods are measured during the detection period is equal to or greater than a predetermined threshold. A physical quantity sensor comprising: means . The physical quantity sensor according to claim 1 ,
The physical quantity sensor according to claim 1, wherein the predetermined number is two. A semiconductor laser that emits modulated laser light;
A light receiver that is disposed in or near the semiconductor laser and receives the laser light emitted from the semiconductor laser and converts it into an electrical signal;
The period of the interference waveform generated by the self-coupling effect between the laser beam emitted from the semiconductor laser and its return light included in the output signal of the light receiver is detected, and the period of the interference waveform by the stationary reference plane is An object detection means for determining that an object is present in the radiation direction of the laser beam when interference waveforms having different periods satisfy a predetermined condition;
Measuring means for measuring the physical quantity of the object from information of interference included in the output signal of the light receiver,
The reference surface is any one of the inner and outer surfaces of the transparent cover that protects the semiconductor laser, which is not subjected to antireflection treatment ,
The object detection means includes
A period measuring means for measuring a period of the interference waveform during a counting period for counting the number of the interference waveforms every time the interference waveform is input;
Frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measuring means,
Representative value calculating means for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution;
With respect to the representative value T0 calculated in the counting period one cycle before the laser beam, the number N of interference waveforms whose period is shorter than a predetermined number of times of the representative value T0 in the current detection period. A desired number derivation means;
Object determination that determines that the object is present in the laser light emission direction when the ratio N / Nall of the number N to the total number Nall of interference waveforms whose periods are measured during the detection period is equal to or greater than a predetermined threshold. A physical quantity sensor comprising: means. The physical quantity sensor according to claim 3 ,
The physical quantity sensor according to claim 1, wherein the predetermined number is 0.5. A semiconductor laser that emits modulated laser light;
A light receiver that is disposed in or near the semiconductor laser and receives the laser light emitted from the semiconductor laser and converts it into an electrical signal;
The period of the interference waveform generated by the self-coupling effect between the laser beam emitted from the semiconductor laser and its return light included in the output signal of the light receiver is detected, and the period of the interference waveform by the stationary reference plane is An object detection means for determining that an object is present in the radiation direction of the laser beam when interference waveforms having different periods satisfy a predetermined condition;
Measuring means for measuring the physical quantity of the object from information of interference included in the output signal of the light receiver,
The reference surface is a reflective wall surface facing the semiconductor laser across a space where the object is to enter,
The object detection means includes
A period measuring means for measuring a period of the interference waveform during a counting period for counting the number of the interference waveforms every time the interference waveform is input;
Frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measuring means,
Representative value calculating means for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution;
The total number Nw of frequencies whose period is longer than a predetermined number of times of the representative value T0 is obtained from the frequency distribution, and the number of interference waveforms whose period is longer than the predetermined number of times of the representative value T0 in the detection period of the counting period. Number deriving means for obtaining N;
When the ratio N / Nw of the number N in the detection period in the current counting period to the frequency Nw in the counting period one cycle before the laser light is greater than or equal to a predetermined threshold, the object is present in the laser light emission direction Then, a physical quantity sensor comprising an object determining means for determining. The physical quantity sensor according to claim 5 ,
The physical quantity sensor according to claim 1, wherein the predetermined number is 1.5. The physical quantity sensor according to any one of claims 1 to 6 ,
Further, the semiconductor laser has a first oscillation period including at least a period during which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period during which the oscillation wavelength continuously decreases monotonously. Equipped with a laser driver to operate
The measuring means includes
Counting means for counting the number of interference waveforms generated by the self-coupling effect between the laser beam and the return beam included in the output signal of the light receiver for each of the first oscillation period and the second oscillation period; ,
Computation means for calculating at least one of the distance to the object and the speed of the object from the minimum oscillation wavelength and the maximum oscillation wavelength during the period of counting the number of interference waveforms by the counting means and the counting result of the counting means. A physical quantity sensor characterized by An oscillation procedure for emitting modulated laser light from a semiconductor laser;
Detects the period of the interference waveform generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light, which is included in the output signal of the light receiver disposed in or near the semiconductor laser, An object detection procedure for determining that an object is present in the radiation direction of the laser beam when an interference waveform having a period different from the period of the interference waveform by the reference surface satisfies a predetermined condition;
A measurement procedure for measuring a physical quantity of the object from information of interference included in an output signal of the light receiver ,
The reference surface is a reflective wall surface facing the semiconductor laser across a space where the object is to enter,
The object detection procedure includes:
A period measurement procedure for measuring a period of the interference waveform during a counting period for counting the number of the interference waveforms every time the interference waveform is input;
A frequency distribution creating procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of this cycle measuring procedure,
A representative value calculating procedure for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution;
With respect to the representative value T0 calculated in the counting period one cycle before the laser beam, the number N of interference waveforms whose period is longer than a predetermined number of times of the representative value T0 in the current detection period. A procedure for deriving the desired number;
Object determination that determines that the object is present in the laser light emission direction when the ratio N / Nall of the number N to the total number Nall of interference waveforms whose periods are measured during the detection period is equal to or greater than a predetermined threshold. physical quantity measuring method characterized by comprising a procedure. The physical quantity measuring method according to claim 8 ,
2. The physical quantity measuring method according to claim 1, wherein the predetermined number is two. An oscillation procedure for emitting modulated laser light from a semiconductor laser;
Detects the period of the interference waveform generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light, which is included in the output signal of the light receiver disposed in or near the semiconductor laser, An object detection procedure for determining that an object is present in the radiation direction of the laser beam when an interference waveform having a period different from the period of the interference waveform by the reference surface satisfies a predetermined condition;
A measurement procedure for measuring a physical quantity of the object from information of interference included in an output signal of the light receiver,
The reference surface is a surface that is not subjected to antireflection treatment among the inner surface and outer surface of the transparent cover that protects the semiconductor laser,
The object detection procedure includes:
A period measurement procedure for measuring a period of the interference waveform during a counting period for counting the number of the interference waveforms every time the interference waveform is input;
A frequency distribution creating procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of this cycle measuring procedure,
A representative value calculating procedure for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution;
With respect to the representative value T0 calculated in the counting period one cycle before the laser beam, the number N of interference waveforms whose period is shorter than a predetermined number of times of the representative value T0 in the current detection period. A procedure for deriving the desired number;
Object determination that determines that the object is present in the laser light emission direction when the ratio N / Nall of the number N to the total number Nall of interference waveforms whose periods are measured during the detection period is equal to or greater than a predetermined threshold. A physical quantity measurement method characterized by comprising a procedure. The physical quantity measuring method according to claim 10 ,
The physical quantity measuring method, wherein the predetermined number is 0.5. An oscillation procedure for emitting modulated laser light from a semiconductor laser;
Detects the period of the interference waveform generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light, which is included in the output signal of the light receiver disposed in or near the semiconductor laser, An object detection procedure for determining that an object is present in the radiation direction of the laser beam when an interference waveform having a period different from the period of the interference waveform by the reference surface satisfies a predetermined condition;
A measurement procedure for measuring a physical quantity of the object from information of interference included in an output signal of the light receiver,
The reference surface is a reflective wall surface facing the semiconductor laser across a space where the object is to enter,
The object detection procedure includes:
A period measurement procedure for measuring a period of the interference waveform during a counting period for counting the number of the interference waveforms every time the interference waveform is input;
A frequency distribution creating procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of this cycle measuring procedure,
A representative value calculating procedure for calculating a representative value T0 of the period distribution of the interference waveform from the frequency distribution;
The total number Nw of frequencies whose period is longer than a predetermined number of times of the representative value T0 is obtained from the frequency distribution, and the number of interference waveforms whose period is longer than the predetermined number of times of the representative value T0 in the detection period of the counting period. A number derivation procedure for obtaining N;
When the ratio N / Nw of the number N in the detection period in the current counting period to the frequency Nw in the counting period one cycle before the laser light is greater than or equal to a predetermined threshold, the object is present in the laser light emission direction Then, a physical quantity measurement method comprising an object determination procedure to be determined. The physical quantity measurement method according to claim 12 ,
The physical quantity measuring method, wherein the predetermined number is 1.5. The physical quantity measuring method according to any one of claims 8 to 13 ,
In the oscillation procedure, the first oscillation period including at least a period during which the oscillation wavelength continuously increases monotonously and the second oscillation period including at least a period during which the oscillation wavelength continuously decreases monotonously exist alternately. A procedure for operating the semiconductor laser;
The measurement procedure is as follows:
A counting procedure for counting, 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 and the return light, included in the output signal of the light receiver; ,
Comprising a calculation procedure for calculating at least one of the distance to the object and the speed of the object 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 counting result of the counting procedure. A physical quantity measurement method characterized by

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