Range finder/velocimeter and range-finding/velocimetry method

1. A range finder/velocimeter characterized by comprising:

a semiconductor laser which emits laser light to a measurement target;

a laser driver which causes said semiconductor laser to operate such that a first oscillation period including at least a period of continuously and monotonically increasing an oscillation wavelength and a second oscillation period including at least a period of continuously and monotonically decreasing the oscillation wavelength alternately exist for at least two periods;

a light-receiving device which converts laser light emitted from said semiconductor laser and return light from the measurement target into electrical signals;

counting means for counting the number of interference waveform components caused by laser light emitted from said semiconductor laser and return light from the measurement target which are contained in an output signal from said light-receiving device in at least part of each of the first oscillation period and the second oscillation period; and

computing means for calculating a distance to the measurement target and a velocity of the measurement target from a shortest Lasing wavelength and a longest Lasing wavelength in a period during which the number of interference waveform components is counted by said counting means and a counting result obtained by said counting means.

2. A range finder/velocimeter according to claim 1 , characterized in that said counting means counts the number of interference waveform components caused by a self-mixing effect/self-coupling effect between laser light emitted from said semiconductor laser and return light from the measurement target.

3. A range finder/velocimeter according to claim 1 , characterized in that said computing means uses a shortest Lasing wavelength and a longest Lasing wavelength in each oscillation period of said semiconductor laser as a shortest Lasing wavelength and a longest Lasing wavelength in a period during which said counting means counts the number of interference waveform components.

4. A range finder/velocimeter according to claim 3 , characterized in that said computing means comprises

a distance/velocity calculating unit which calculates a candidate value of a distance to the measurement target and a candidate value of a velocity of the measurement target on the basis of a shortest Lasing wavelength and a longest Lasing wavelength of said semiconductor laser and a counting result obtained by said counting means,

a distance subtraction calculating unit which calculates a distance subtraction as a difference between the distance candidate value calculated by said distance/velocity calculating unit and a previously calculated distance candidate value;

a state determination unit which determines a state of the measurement target on the basis of calculation results obtained by said distance/velocity calculating unit and said distance subtraction calculating unit, and

a distance/velocity confirming unit which confirms a distance to the measurement target and a velocity of the measurement target on the basis of a determination result obtained by said state determination unit.

5. A range finder/velocimeter according to claim 4 , characterized in that

said distance/velocity calculating unit and said distance subtraction calculating unit calculate a distance candidate value, a velocity candidate value, and a distance subtraction for each period as a sum of the first oscillation period and the second oscillation period in each of a case in which the measurement target is in a micro displacement region in which movement of the measurement target is smaller than a reference and a case in which the measurement target is in a normal displacement region in which the movement is larger than the reference, upon regarding the state of the measurement target as one of the micro displacement region and the normal displacement region, and

said state determination unit determines whether the measurement target is in the micro displacement region or the normal displacement region and whether the measurement target is in uniform motion or accelerated motion, on the basis of calculation results obtained by said distance/velocity calculating unit and said distance subtraction calculating unit, for each calculation by said distance/velocity calculating unit and said distance subtraction calculating unit.

6. A range finder/velocimeter according to claim 5 , characterized in that

said state determination unit determines that the measurement target is in uniform motion in the micro displacement region, when a sign of a distance subtraction calculated on the assumption that the measurement target is in the micro displacement region is constant, and a velocity candidate value calculated on the assumption that the measurement target is in the micro displacement region is equal to an absolute average value of distance subtractions calculated on the assumption that the measurement target is in the micro displacement region.

7. A range finder/velocimeter according to claim 5 , characterized in that

said state determination unit determines that the measurement target is in uniform motion in the normal displacement region, when a sign of a distance subtraction calculated on the assumption that the measurement target is in the normal displacement region is constant, and a velocity candidate value calculated on the assumption that the measurement target is in the normal displacement region is equal to an absolute average value of distance subtractions calculated on the assumption that the measurement target is in the normal displacement region.

8. A range finder/velocimeter according to claim 5 , characterized in that

said state determination unit determines that the measurement target is in accelerated motion in the micro displacement region, when a sign of a distance subtraction calculated on the assumption that the measurement target is in the micro displacement region is inverted for each calculation, and a velocity candidate value calculated on the assumption that the measurement target is in the micro displacement region does not coincide with an absolute average value of distance subtractions calculated on the assumption that the measurement target is in the micro displacement region.

9. A range finder/velocimeter according to claim 5 , characterized in that said state determination unit determines that the measurement target is in accelerated motion in the micro displacement region, when an absolute value of a velocity candidate value calculated on the assumption that the measurement target is in the normal displacement region is equal to a wavelength change rate of said semiconductor laser, and a velocity candidate value calculated on the assumption that the measurement target is in the micro displacement region does not coincide with an absolute average value of distance subtractions calculated on the assumption that the measurement target is in the micro displacement region.

10. A range finder/velocimeter according to claim 5 , characterized in that

said state determination unit determines that the measurement target is in accelerated motion in the normal displacement region, when a sign of a distance subtraction calculated on the assumption that the measurement target is in the normal displacement region is inverted for each calculation, and a velocity candidate value calculated on the assumption that the measurement target is in the normal displacement region does not coincide with an absolute average value of distance subtractions calculated on the assumption that the measurement target is in the normal displacement region.

11. A range finder/velocimeter according to claim 5 , characterized in that said state determination unit determines that the measurement target is in accelerated motion in the normal displacement region, when an absolute value of a velocity candidate value calculated on the assumption that the measurement target is in the micro displacement region is equal to a wavelength change rate of said semiconductor laser, and a velocity candidate value calculated on the assumption that the measurement target is in the normal displacement region does not coincide with an absolute average value of distance subtractions calculated on the assumption that the measurement target is in the normal displacement region.

12. A range finder/velocimeter according to claim 4 , characterized by further comprising an integrating unit which calculates an integral of a velocity confirmed by said distance/velocity confirming unit when the velocity is lower than a reference value,

wherein said state determination unit sets a distance change amount to zero when the integral calculated by said integrating unit is smaller than a distance calculation resolution.

13. A range-finding/velocimetry method comprising the steps of:

applying a wavelength-modulated wave to a measurement target;

detecting interference caused between the applied wave and a return wave reflected by the measurement target; and

calculating a distance to the measurement target and a velocity of the measurement target on the basis of information associated with the detected interference, wherein

the step comprises the step of causing a semiconductor laser to operate such that a first oscillation period including at least a period of continuously and monotonically increasing an oscillation wavelength and a second oscillation period including at least a period of continuously and monotonically decreasing the oscillation wavelength alternately exist for at least two periods,

the step or detecting comprises the steps of

converting laser light emitted from the semiconductor laser and return light from the measurement target into electrical signals by using a light-receiving device, and

counting the number of interference waveform components produced by a self-mixing effect/self-coupling effect between laser light emitted from the semiconductor laser and return light from the measurement target which are contained in an output signal from the light-receiving device in at least part of each of a first oscillation period and a second oscillation operation, and

the step of calculating comprises the step of computing a distance to the measurement target and a velocity of the measurement target from a shortest Lasing wavelength and a longest Lasing wavelength in a period during which interference waveform components are counted, and the number of counted interference waveform components.

14. A range-finding/velocimetry method according to claim 13 , characterized in that the step of calculating comprises the steps of

calculating a distance to the measurement target and a velocity of the measurement target on the basis of information associated with the detected interference, and

selecting one distance value and one velocity value from calculated candidate values.

15. A range-finding/velocimetry method according to claim 13 , wherein

the step of calculating further comprises the steps of

calculating an integral of the velocity when a calculated velocity is lower than a predetermined reference value, and

setting a distance change amount to zero when a calculated integral is smaller than a distance calculation resolution.