Improved Pulsed Laser Distance Measurement Technique by Means of Ga-As Laser Source and Statistic Distance Data Processing

Abstract

The last few years have seen a significant progress in the field of distance measurement by means of modulated light which in comparison with incoherent sources offers superior accuracy and larger range of measuring. Particularly favorable is the Ga-As laser source which allows comparatively simple and entirely electronic modulation. The intensity is usually sine, frequency or pulse modulated. The basic principle of the sine modulation is to measure phase shifts between the emitted and the echoed signals, which can be done very accurately. By more or less sophisticated methods and with the measurement time from a few seconds to a few minutes an accuracy of under 1 cm and range of up to several kilometers can be achieved, using large retro-reflectors. On the other hand the methods of pulse modulation, which base on precision measurement of the light pulse flight time interval, are simpler and electronically better manageable - but the accuracy of distance measurement here hardly reaches a few centimeters.