Abstract: A lidar and optical rangefinder receiver improves signal detection in the presence of varying levels of environmental light and other noise sources. The occurrence of false triggers, due to noise, during periods when no optical pulse is emitted is used to adjust the pulse detection threshold level and simultaneously calibrate the time-of-flight timer. The photodetector's response to ambient light is also used to adjust the threshold level. Example systems include signal detection electronics with dynamic thresholding and real-time calibration of timing electronics, in which the threshold level for signal detection is adjusted in response to both information acquired during calibration cycles and ambient light measured between active rangefinding cycles.

Abstract: A receiver module for a lidar system includes a collection lens for collecting light from a scene to form an image of the light. The receiver module also includes a mask for spatially filtering the light imaged by the collection lens to at least partly transmit a light pulse backscattered from an object in the scene. The mask is opaque apart from at least one non-circular light-transmissive region. Each non-circular light-transmissive region has orthogonal length and width. The length exceeds the width and is sufficient to transmit light incident on the collection lens at a range of incidence angles in a first angular dimension. The receiver module also includes a photodetector for detecting the light pulse collected by the lens and transmitted by the mask.

Abstract: A laser assembly includes a laser source which emits a beam transmitted through optics carried by an insulating window and thence through a pressure window supported in a thermally-insulating mount. A thermally conductive carrier ring contacts the face of the pressure window opposite the laser source and has in its outer face an annular groove receiving plural coils of an electrical resistance heating wire coupled to a current source for heating the pressure window to prevent condensation thereon.

Abstract: The liquid level sensor includes a modulated laser diode and collimating optics for collimating the diode output to produce an optical measurement signal beam transmitted to the fluid boundary through a diffuser to diverge the beam. A detector detects reflections of the beam from the fluid boundary to produce an output signal which is amplified and inverted to drive the modulator. The frequency of the modulation, which depends on the distance to the fluid boundary, is measured and the distance is derived from that measurement.