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 the two divergent beams for a given object. The sensor also receives inputs indicating the time that each pulse is emitted and the selected outputs from the detector to indicate when returning energy is received from the corresponding pulse to determine the elapsed time between the two.
The deterioration of receiving environment of a reflected signal from a preceding vehicle in an auto-cruise control is immediately detected, so that the distance between the vehicle and the preceding vehicle detected by a distance sensor comprising a laser radar, is maintained constant. On the basis of data of the magnitude of received signals, which are detected by the distance sensor and accumulated over a predetermined time, a standard deviation (or a dispersion) and an average value of the magnitude of the received signal are calculated. If the standard deviation is equal to or larger than a reference value or the average value is equal to or smaller than a reference value when the distance sensor has not detected a reflected signal, it is determined that the environment of reception of the reflected signal from the preceding vehicle has deteriorated, whereby the auto-cruise control is discontinued, or the deterioration of the receiving environment is informed to a driver by an informing device.
A monitoring device (1) for spatial areas (2) includes emitters (3) that emit radiation pulses that are reflected by objects located within the spatial areas (2) toward receivers (4). The receivers (4) are connected to a run time determining unit (9) with whose aid a distance image of an object within the spatial areas (2) can be generated. A selection unit (10) evaluates the distance images and generates a detection signal at an output (11) when predetermined distance values occur in the distance images.
A vehicle detection and classification sensor provides accurate 3D profiling and classification of highway vehicles for speeds up to 100 mph. A scanning time-of-flight laser rangefinder is used to measure the distance to the highway from a fixed point above the road surface and then measure the distance to the surfaces of any vehicle that is viewed by the sensor. A rotating polygon scans a beam laser into two beams projected across the road surface at a fixed angle between them. The beam is pulsed at a high repetition rate for determining vehicle speeds with a high accuracy and uses the calculated speed and consecutive range measurements as the vehicle moves past the sensor to develop a three-dimensional profile of the vehicle. An algorithm is applied to the three-dimensional profile for providing a vehicle-classification.
When detecting an object in a given area, especially vehicles for the purposes of traffic control, there appear to be inaccuracies in the system based on measuring pulse propagation times. In order to avoid such inaccuracies, a sample of observed (measured) real values is compared with a gauging table having a sample of values stored therein, so that pulse propagation time measurements are no longer necessary.
A laser range camera provides both imaging and range information using laser radar techniques. A laser transmitter having a fan shaped beam that creates a column shaped beam in a far field is scanned along a single axis within a defined field of view using an acoustical optical device. A staring focal array of multiple line receivers having a long narrow field of view by using a linear array of fiber optics receives reflected energy from the scanned scene and transfers the received information to an avalanche photo diode by bundling the linear array into a circular array for interfacing with the diode. The range and intensity of each pixel within a scene is measured using a CCD measurement system which communicates with the receiver through the electrical signals. Range is determined for each pixel of the scene using the exposure characteristics of a CCD with analog type time of flight measurements. Range and intensity data are stored on odd and even CCD elements and used to display a three dimensional range image.
