| 摘要 |
PROBLEM TO BE SOLVED: To achieve both the improvement of distance resolution and the lengthening of a measuring range. SOLUTION: The range finder comprises both a laser driver 4 for making a semiconductor laser 1 alternately repeat a first oscillation period in which its oscillation wavelength increases and a second oscillation period in which its oscillation wavelength decreases and a counting device 8 for counting the number of interference waveforms contained in output of a photodiode 2, which converts output of the semiconductor laser 1 into electrical signals. The counting device 8 counts interference waveforms for every split period acquired by diving the first and second oscillation periods, determines a ratio between a total of results of counting in a first group of the split periods containing at least a split period of a minimum driving current when a driving current of the semiconductor laser 1 is minimum and a total of results of counting in a second group of the split periods, and controls the amplitude of a driving current in such a way that ratios may lie within a range of prescribed numerical values in the case where the ratios are outside the range of the prescribed numerical values in both first and second oscillation periods. COPYRIGHT: (C)2008,JPO&INPIT
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