Laser ceilometer with safety power-reduction feature

Abstract

A laser ceilometer emits a pulsed and narrow beam of visible or invisible laser radiation directly vertically upwards. The effective power level of the emitted radiation is lower, but only by a safety margin, than can result in eye damage to naked-eye observers viewing the directly emitted beam directly, but is higher than the power level resulting in eye damage to an observer viewing the directly emitted beam directly through a telescope having an objective of 80 mm diameter. When, in the course of cleaning or adjustment work, or for any reason, the ceilometer is tilted from its normal, vertically upwards aimed orientation towards a horizontally aimed orientation, by an angle of more than 10.degree. with respect to the upwards vertical, the effective emitted laser power is reduced to a level additionally preventing eye damage to such telescope users, by automatic reduction of the pulse amplitude, and/or the pulse duration, and/or the pulse repetition frequency, but without terminating the emission of laser radiation. Alternatively, the emission of laser radiation ceases altogether until the ceilometer reassumes its vertically upwards aimed orientation. This latter alternative may be accomplished by interposing a neutral density glass filter into the laser beam.

Dependencies are inferred from the claim text.