An optical backscatter filter (10) for use with continuous wave laser radar systems. The filter removes undesired frequency components corresponding to optical backscatter from a received input signal (12) to extract a desired return signal (32) associated with a target. The received signal (32) is processed optically, requiring only an electronic notch filter (24) and one electronic mixer (30) to finally extract the desired return signal (32).
A distance measurement device that provides high speed and accuracy. A light divider separates pulsed light emitted from an ultrashort pulse fiber laser into reference light A and signal light. A scanning mirror unit irradiates an object with the signal light and receives scattered light B, which is reflected from the object. An optical path length adjustment unit adjusts an optical path length of the reference light A. A differential detector detects the degree of interference of the reference light A having the adjusted optical path length with the scattered light B and outputs the detected degree of interference as an interference signal. A computer specifies an adjustment value, set in the optical path length adjustment unit, to attain a specific optical path length maximizing the interference signal and uses the specified adjustment value to compute the distance from the scanning mirror unit to the object.
A radar system which is used for determining optical range includes a frequency analyzer for the analysis of differential frequency signals, which originate from a mixture of the transmitted signal with the received signals, for example reflected from a fog bank. The frequency spectrum images the distance profile of the fog bank.
A three-dimensional image capturing device performs sensing operations of a first reflected light beam component and a second reflected light beam component. In the sensing operation of the first reflected light beam component, the pulse shape of a distance measuring light beam is triangular. The electric charge accumulating period starts at the same time as the disappearance of a pulse of the distance measuring light beam, and ends after the disappearance of a pulse of the reflected light beam. In the sensing operation of the second reflected light beam component, the pulse shape of a correction light beam is rectangular. The electric charge accumulating period starts at the same time as the disappearance of a pulse of the correction light beam, and ends after the disappearance of a pulse of the reflected light beam. A signal charge obtained by the first reflected light beam component sensing operation is divided by a signal charge obtained by the second reflected light beam component sensing operation.
An ultra-fast electrooptic analog-to-digital converter is described. The A/D converter includes an electrooptic modulator that generates a modulated light beam from an incident light beam in response to an applied modulation signal. An optical demultiplexer is positioned to receive the modulated light beam. The optical input of a respective one of a plurality of photodetectors is optically coupled to a respective one of a plurality of demultiplexed modulated light beams. Each of the plurality of photodetectors generates an electrical signal in response to an intensity of the demultiplexed modulated light beam that is coupled to its optical input. A plurality of charge comparators compares electrical signals generated in response to the intensities of the demultiplexed modulated light beam to a reference signal. The output of each of the plurality of charge comparators generates a digital representation of the incident light beam.
A distance-measuring system includes a light source for transmitting a beam of light to a target, thereby generating a received beam. A calibration unit periodically calibrates the system by positioning a calibration target between the light source and the target so that the transmitted beam is interrupted, thereby generating a received calibration beam. The calibration unit also generates a calibration signal which is indicative of when the calibration target is generating the received calibration beam. A target sensor receives the reflected target and calibration beams and provides a target signal indicative of the reflected target and calibration beams. A reference sensor receives light from the light source and provides a reference signal to the processing circuitry. Processing circuitry receives the calibration, target, and reference signals and calculates the distance to the target based upon the target and reference signals and/or calibrates the system based upon the calibration signal. The processing circuitry may provide data based upon the calibration and target signals to a computer for distance calculations and calibration. A beam splitter may be provided between the light source and the target to allow the transmitted beam to be incident on the target while deflecting the received beam to be incident on the target sensor, so that the light transmitted to the target and reflected back to the target sensor is substantially coaxial.
