Abstract: A scanning method used by a laser radar for scanning a predetermined scanning region with a laser beam so that the whole of the scanning region is illuminated with the laser beam, is disclosed in which a laser beam makes a first spiral scanning outwardly or inwardly and then makes a second spiral scanning inwardly or outwardly so that the rotational direction of the second spiral scanning is the same as that of the first spiral scanning, and the first spiral scanning and the second spiral scanning are repeated. According to this scanning method, the output of drive means for driving an optical system which causes a laser beam to perform a scanning, can be reduced, since a maximum power necessary for causing a body large in inertia to make a curvilinear or rotational motion is far smaller than a maximum power necessary for causing the body to make a linear motion.

Abstract: A method and an apparatus are disclosed in which paying attention to the fact that the rate of attenuation of laser lilght propagating in the atmosphere changes depending on meteorological conditions, the rate of attenuation is detected and the optimum laser beam emission or divergence angle is controlled in accordance with the detected rate of attenuation. There are also disclosed a method and an apparatus in which the optimum beam angle is controlled in accordance with a distance to a target existing in the atmosphere or the shape of the target. Further, there are disclosed a method and an apparatus in which the optimum beam angle is controlled taking either two or all of the rate of attenuation, the distance to the target and the shape of the target into consideration.