Patent ID: 7990521
Filing Date: 2011-08-02
Classification: G01B,G01P,G01S

Abstract:
1. A distance/speed meter comprising: a first semiconductor laser which emits first laser light to a measurement target; a second semiconductor laser which emits second laser light to the measurement target parallelly to the first laser light; a first laser driver which drives said first semiconductor laser such that an oscillation interval in which at least an oscillation wavelength monotonically increases repeatedly exists; a second laser driver which drives said second semiconductor laser such that an oscillation wavelength increases/decreases inversely to the oscillation wavelength of said first semiconductor laser; a first light-receiving device which converts at least an optical output from said first semiconductor laser into an electrical signal; a second light-receiving device which converts at least an optical output from said second semiconductor laser into an electrical signal; counting means for counting the number of interference waveforms generated by the first laser light and return light of the laser light from the measurement target and contained in an output signal from said first light-receiving device, and the number of interference waveforms generated by the second laser light and return light of the laser light from the measurement target and contained in an output signal from said second light-receiving device; and computing means for calculating at least one of a distance to the measurement target and a speed of the measurement target from a minimum oscillation wavelength and a maximum oscillation wavelength of said first semiconductor laser and said second semiconductor laser and a counting result obtained by said counting means, wherein said counting means obtains the number of interference waveforms contained in an output signal from said light-receiving device corresponding to a semiconductor laser, of said first semiconductor laser and said second semiconductor laser, whose oscillation wavelength has increased, in a first counting interval shorter than the oscillation interval, obtains the number of interference waveforms contained in an output signal from said light-receiving device corresponding to a semiconductor laser, of said first semiconductor laser and said second semiconductor laser, whose oscillation wavelength has decreased, in a second counting interval shorter than the oscillation interval and at least partially different in time from the first counting interval, and alternately obtains the numbers of interference waveforms from an output signal from said light-receiving device corresponding to said semiconductor laser whose oscillation wavelength has increased and from an output signal from said light-receiving device corresponding to said semiconductor laser whose oscillation wavelength has decreased.