Patent ID: 7522268

Claim:
A distance measuring device for measuring a distance by projecting a pulsed laser beam to an object to be measured and by receiving a reflected light from the object to be measured, comprising a first light emitting unit for projecting a pulsed laser beam for distance measurement, a second light emitting unit for emitting a correction pulsed laser beam, a distance measuring light optical path to guide the pulsed laser beam for distance measurement toward a first photodetection unit, an internal reference light optical path for splittinq an internal reference pulsed light from the pulsed laser beam for distance measurement and for guiding to a second photodetection unit, a correction light optical path for splitting the correction pulsed laser beam and for guiding to the first photodetection unit and the second photodetection unit, a light amount adjusting means for repeatedly changing light intensities of the correction pulsed laser beam and the internal reference pulsed light from the maximum to the minimum, a storage unit for storing a plurality of photodetection signals from said first photodetection unit and said second photodetection unit which are obtained by changing the light intensities of the correction pulsed laser beam and the internal reference pulsed light from the maximum to the minimum, and a control arithmetic unit for calculating a distance based on difference of photodetection time of the pulsed lights from the first photodetection unit and the second photodetection unit, wherein said control arithmetic unit calculates a distance by using a combination of the reflected light with the stored internal reference pulsed light having a light intensity equal to or approximately equal to the light intensity of the reflected light.