A modulated light beam from a radiation source on a structure whose posit is to be measured is split into a first beam which propagates through the atmosphere to a first detector and a second beam which travels through an optical fiber to a second detector. The first and second detectors recover the modulation on the first and second beams, the phases of which are compared to determine the distance. In a preferred embodiment, the light source is a sine-wave modulated laser.

Elements of an optical system are placed at points (A) and the spatial coordinates of these points are measured. The optical system comprises on the one hand an optical device which may be mounted on board an aircraft (2) and on the other hand reflectors (10) such as reflectors of the cube corner type. The optical device includes a pulsed laser source and a detector which is sensitive to the radiation emanating from the laser source. The desired spatial coordinates are determined from measuremen...

A high speed laser ranging device composed of a transmitter/receiver unit and a target including a retroreflector adapted to receive a laser pulse (Ii) transmitted by the unit and to return it parallel to itself. This transmitter/receiver unit travels, with respect to the target, along a relative path with an overall relative velocity V, and normal to an instantaneous line joining it to the target, with a transverse relative velocity v.sub.t which, on average, is of the order of at least 1 km/se...

Time of transit of a propagated electric signal at lightspeed is used as a measure of distance from a transmitter (laser 32) to a receiver (photodetector 39) via a target (reflector 14). A continuous modulating signal of fixed frequency (10.700 MHz) is transmitted. The distance traversed is measured by a timer which compares the phase at transmission with that at reception. The invention involves a heterodyne down-conversion technique involving two crystal oscillators (30, 31), which are phase-l...

A semiconductor laser pulse compression radar system utilizes a semiconductor laser source 16 for generating light for transmission towards a target 27. A modulator 15 pulses and modulates the light according to a preselected code, and a transmitter telescope 18 launches the light. Portions of the pulsed light reflected by the target 27 are gathered by a receiver telescope 28 and are converted to electrical current pulses by an avalanche photodiode 30. The pulses of electrical current are demodu...

An optical distance measuring apparatus is disclosed which is operable in accordance with a phase difference detecting process wherein a processing system including a central processing unit and a digital type mix-down circuit detects and calculates a phase difference between the electrical phase of a signal output from a light receiving portion in response to receipt of a reflected light beam and the electrical phase of a reference signal output from a reference oscillator so as to determine a ...

A distance measuring device using two kinds of modulation frequencies is disclosed. More particularly, the distance measuring device is an electro-optical distance meter for measuring a distance by combining the results of fine measurement and rough measurement. The fine measurement is effected by detecting a phase difference between a modulation signal generated from a light emitting device and a reflected modulation signal generated from a light receiving device, while the rough measurement is...

A blast furnace with a blowpipe (12) opening through the furnace wall (11) has apparatus for analysis (20) in a raceway (18) adjacent the blowpipe opening in a bed of the blast furnace. The apparatus includes means (24) arranged in relation to the blast furnace to transmit an optical signal into the raceway and means (30) for monitoring a received signal derived from reflection or scattering of the transmitted optical signal in the raceway. Means (32) is provided to analyse the received signal i...

A laser radar detection system (10) is provided for detecting targets located within a detection field and discriminating between unresolved and resolved detected objects (32,34). The detection system (10) employs a laser radar sensor (12) for transmitting a frequency modulated optical transmit signal (22) which scans a desires field and receiving a return signal (24) from objects located therein. The laser radar sensor (12) includes a photo mixer (20) for providing the difference between the re...

The sensor includes a range finder having means for emitting a directional output of pulsed energy toward a fixed area, and includes a transmitter section which divides pulsed energy into divergent beams, which are then received as reflective energy in a receiver section. The receiver alternately selects between outputs of two detectors receiving reflections from the beam and provide inputs for purposes of determining time of flight, and for measuring the time interval between interceptions of t...