Laser range finders are now rather developed with a wide application field concerning indoor robotic, non destructive testing, inspection and security control or automotive intelligent cruise control. Interferometry, self-mixing, fringe pattern projection, triangulation and flight time measurement methods are the most important methods. Flight time based methods require a modulation of the optical beam, which can be made by pulse, sine wave or chirp signal or even pseudo random code signal. The aim of this paper is to present rather simple techniques leading to low cost systems. Pulse modulation is typically interesting in case of wide range measurement, but is also developed for medium range. The main interest of the phase-shift measurement method is the conversion of a short time of flight interval into a wider interval through the phase of the signal. That is obtained either by the heterodyne process which keeps the phase shift constant or by the intermediate frequency sampling technique. This phase-shift method is dedicated to medium or short range. Modulating signal with a wider spectrum should lead to more powerful system. In this way the FMCW-like method, based on a chirped frequency signal, is a new technique developed as for radar leading also to rather simple systems. Nevertheless the implementation of the method present some problems. With more complex modulating signals the detection needs important signal processing developments, but it should be possible to use the technology already developed for telecommunication systems or for GPS by the way ofpseudo-random codes. Finally it is possible to move towards smart systems by combining several modulating signals and introducing digital control in the system.