Abstract: The invention provides a method and an apparatus for determining the difference between the transit times of measuring pulse signals from a transmitter to a receiver along a measuring signal path establishing an unknown time of travel which is representative for a physical quantity of interest, and the transit times of reference pulse signals generated by the same transmitter and forwarded to the same receiver along a reference signal path establishing a known, constant time of travel, whereby for the measurement of each of said transit times the time distance between a trigger signal triggering the generation of the respective measuring pulse or reference pulse signal and a time-significant signal is measured which is generated in a defined time relation to the instant at which the respective pulse signal is received by said receiver.

Abstract: The invention provides a distance measuring apparatus for determining the distance of a target object as a function of the transit time of a measurement light pulse which is emitted by a transmitter in the transmission portion of the apparatus towards the target object, reflected thereby and received by the receiving portion of the measuring apparatus and for attainment of superior measurement accuracy the intensity of the measurement light pulse is correlated to the distance and reflectivity of the target object as well as to the "transparency" of the transmission medium between the measuring apparatus and the target object, such correlation being effected by optical damping of either the transmitted light pulses and/or the reference light pulse and/or the light pulses reflected by the target.