Abstract: The lidar arrangement (1) has a transmitter (3) for linearly polarized radiation (12), a receiver (5) with a first receiving device which measures intensity of the backscattered radiation (15) coinciding approximately with the transmitted radiation cone (12) in a polarization plane of the cone and in a perpendicular polarization plane, wherein the receiver further includes a second receiving device which measures the intensity of backscattered radiation (17) outside the transmitted cone (12), the outer backscattered radiation has the shape of a conical shell which surrounds the backscattered conical shell of the first mentioned backscattered radiation (15) and of the transmitted cone (12); the received separate radiation cones (15 and 17) are split in a polarization analyzing optical element into two mutually perpendicular partial light beams, each consisting of an inner partial beam portion (15a, 15b) and an outer partial beam portion (17a and 17b), the inner and outer partial beam portions are separately de

Abstract: A ceilometer operating according to a gating method integrates output signals from a light receiver. The output signals are passed by analog gating means during consecutive time slots following each other at the transmitter frequency and being phase shifted relative to transmitted light pulses. The phase shift of the time slots is varied stepwise after preset time intervals. Signals integrated during a time interval are digitalized, processed n a microprocessor and stored in a memory according to height values determined by respective phase shifts of the time slots. The micro-processors forms a smooth function of the signals accordint to height values, differentiates the smooth function, computes maxima and minima, determines maxima differing from a preset threshold value, and selects a maximum which with increasing height value is followed by a minimum.

Abstract: An onboard power supply and metering unit is connected, via an overboard cable e.g., 1000 meters long, to an underwater light-pulse projecting unit and a fluoroescence-sensing receiver unit. The operating power is transmitted to the underwater units by an onboard constant-current source, instead of a voltage source. Likewise, the output signal of the receiver unit is transmitted through the cable in the form of a current, not a voltage. The current of the receiver's photodiode is integrated, the peak value of the integral determined and held, this held value logarithmized, the logarithmized value sampled and held, and the held voltage converted to a current constituting the output signal. The offset of the peak detector and the input stage of the log amplifier are balanced automatically, by a balancing signal applied during pulse measurements, but derived between pulse measurements.