A laser based coordinate measuring device measures a position of a remote target. The laser based coordinate measuring device includes a stationary portion, a rotatable portion, and at least a first optical fiber. The stationary portion has at least a first laser radiation source and at least a first optical detector, and the rotatable portion is rotatable with respect to the stationary portion. The first optical fiber system, which optically interconnects the first laser radiation source and the first optical detector with an emission end of the first optical fiber system, has the emission end disposed on the rotatable portion. The emission end emits laser radiation to the remote target and receives laser radiation reflected from the remote target with the emission direction of the laser radiation being controlled according to the rotation of the rotatable portion.

Laser-based coordinate measuring device and laser-based method for measuring coordinates

Disclosed is a laser radar device having a wide two-dimensional field of view, a large receiving aperture, and responsivity to short pulse light. Specifically disclosed is a laser radar device provided with a laser light source which generates pulse laser light, a scanner which transmits a transmission pulse to a target while two-dimensionally scanning a pencil-shaped transmission beam and outputs scan angle information, a reception lens which receives reception light that has arrived, a long light-receiving element array which converts the reception light to reception signals and outputs the reception signals, a transimpedance amplifier array which amplifies the reception signals, an adder circuit which adds the reception signals from respective elements of the transimpedance amplifier array, a distance detection circuit which measures the light round-trip time to the target of an output signal from the adder circuit, and a signal processing unit which obtains the distances to multiple points on the target on the basis of the light round-trip time and the light speed by causing the scanner to perform a two-dimensional scan operation while associating the two-dimensional scan operation with the scan angle information to thereby measure the three-dimensional shape of the target.

Laser radar device

A laser radar apparatus for producing a pulse modulated transmitted light beam and receiving reflected light beams from road mounted retroreflectors. In the preferred embodiment, a floodlight beam illuminates a portion of a roadway from 20 to 150 in front of a vehicle. Reflected beams from retroreflectors mounted in the roadway are received by the radar unit which calculates distance D and angle θ between the laser radar apparatus and each retroreflector. Distance D is calculated by measuring the propagation delay of the pulse modulated light beam. Angle θ data is indicated by measuring where on a receiver photodiode array the light beam is incident.

Laser radar for a vehicle lateral guidance system

A laser scanner sensor for measuring the spatial properties of objects in a scene within a range less than a predetermined maximum object distance. Applications of the laser scanner system includes measurement of the dimensional weight of parcel(s) being transported by a moving forklift. In the laser scanner sensor, a laser diode supplies a laser beam that is intensity-modulated by a reference waveform from a waveform generator. A variation of the optical scanning sensor system scans a field of measurement which the moving forklift traverses. The forklift has at least three retroreflectors attached to act as calibration targets within the viewing field. The scanner system intensity-modulates the laser beam, and receives reflected intensity-modulated light and supplies it to an optical processing system that includes an aperture that transmits a first percentage of light reflected from the maximum object distance and a second, lesser percentage of light reflected from objects closer than the maximum object distance. A photodectector receives the processed light and converts the energy into an amplitude-modulated range signal. Range values are then determined about every 0.1-inches along a scan line. A number of scan lines are assembled in the computer and displayed on a screen as a 3-D image. The 3-D image is then analyzed by the computer to extract the volume of the objects carried on the forklift tines. The volume is then converted to Dimensional Weight (DIM WT) which is used by the shipper to determine tare.

Laser scanning system and applications

A laser scanner for measuring the spatial properties of objects in a scene within a range less than a predetermined maximum object distance. A laser diode supplies a laser beam that is intensity-modulated by a reference waveform from a waveform generator. An optical scanning system scans the scene with the intensity-modulated laser beam, and receives reflected intensity-modulated light and supplies it to an optical processing system that includes an aperture that transmits a first percentage of light reflected from the maximum object distance and a second, lesser percentage of light reflected from objects closer than the maximum object distance. A photodetector receives the processed light and converts the energy into an amplitude-modulated range signal. A mixer down-converts the frequency into an IF frequency, and a first circuit converts the range signal to the form of a square wave. A phase comparator receives the processed range signal and the reference waveform and outputs a highly accurate signal indicative of the phase difference therebetween. In some embodiments a calibration target may be situated within the scene having a plurality of steps with predefined distances to use as a calibration for measurements of the spatial relationships within the scene.

Laser scanning system

A scanning laser radar system utilizing a frequency modulated (fm)-continuous wave (cw) beam to coherently detect echo signal returns from an object in a predetermined region. The frequency of the beam is repeatedly changed as a function of time to produce a symmetrical triangular-shaped frequency modulated waveform. The echo signals received are frequency shifted, as a function of range and Doppler shift, from the signal being transmitted at that time. The frequency shift is detected by homodyning a portion of the instantaneous transmitted signal with the received echo signal to produce an output signal having a frequency which is substantially constant during a portion of the frequency modulation period. The constant frequency portion of the output signal is related to the range and Doppler speed of the target. Target information such as range, Doppler speed, intensity and angle information are derived by processing the output signal. The signal to noise ratio of the output signal is improved by using a frequency modulation period greater than the scanning time across an arc of a size equal to a predetermined multiple of the beamwidth because with such relationship the time duration of the constant amplitude portion of the output signal is increased. Further, with such arrangement, because of the relatively long modulation period, the ambiguity in detection of the range to the target is reduced. The system is particularly useful in terrain following or obstacle avoidance applications.

FM-CW laser radar system

A laser heterodyne system is disclosed wherein received reflections of a beam of coherent light are amplified in a laser. The amplified received reflections are heterodyned with the light produced by the laser and the resulting beat frequency is detected using a photodetector. A controller, responsive to the beat frequency, controls, in one case, the frequency of a transmitting laser, and hence the frequency of the received light, and, in another case, the frequency of the light produced by the amplifying laser so that, in either case, the difference between the frequency of the received light and the frequency of the light produced by the amplifying laser is adjusted to maximize the amplification of the received light by the amlifying laser prior to detection by the photodetector.

Laser heterodyne system

Ringing caused by acoustic resonances in an electro-optical crystal modulator and commencing at the trailing edge of a pulse may be suppressed by the combination of a second electro-optical crystal and a polarizer. The polarization of the ringing passing through the second crystal is rotated 90° by applying an appropriate voltage to the second crystal at the trailing edge of the pulse. The polarizer, properly oriented, then blocks the ringing. The crystals may comprise such materials as Cadmium Telluride or Gallium Arsenide.

Optical modulator with ringing suppression

The recent development of optical phased arrays (OPAs) enables practical, electronically programmable, control of laser beams for laser radar and other advanced optical sensors. OPAs are the direct analog of microwave phased array antennas; they are electronically programmable optical elements that control the phase distribution on an optical aperture in order to control beam direction and shape. Operating principles and construction of OPAs are briefly described and current and potential performance capabilities are summarized. An OPA supports spatial-domain beam control such as agile or continuous scanning patterns, adaptive electronic focus control, and far-field beam shape control, as well as the generation of multiple beams from a single input beam (pattern generation, or fanout). OPAs also support time-domain beam control, including precision time delay or positioning of short pulses, pulse compression and expansion, and the generation of dense pulse bursts from a single pulse. All of these functions are software controllable, which enables mission-flexible and mission-adaptive optical systems, including so-called 'smart' optical systems with autonomous alignment and calibration capabilities. These and other electronically programmable capabilities are discussed. As a concrete example of an advanced sensor enabled by the OPA, the potential for an adaptable-format, high-resolution, multi-beam laser radar with no moving parts is discussed.

Electronic beam control for advanced laser radar

A CO2 waveguide laser frequency modulation (FM) system which applies the Fourier series components of a triangular drive waveform selectively to the tuning PZT at one end of the waveguide and the FM PZT at the other end to achieve an improvement over the waveform than can be achieved by applying the fundamental and its harmonics to the FM PZT alone The system applies the fundamental component to the tuning PZT and the odd harmonics to the FM PZT The frequency-separated drive signals are applied in proper phase to the PZT's at each end of the waveguide via waveform synthesizer, frequency splitter and amplifiers The waveform synthesizer includes a ROM containing digitized values of segments of the waveform amplitudes and a digital-to-analog converter for converting the digital ROM data to an analog signal

Clarke E. Harris

Papers

FM-CW laser radar system

Laser heterodyne system

Optical modulator with ringing suppression

Electronic beam control for advanced laser radar

Apparatus and method for frequency modulating a waveguide laser