Abstract: An intruder detection system comprises an illumination means for illuminating a field of view with a modulated optical signal, modulated by a modulation signal; an optical receiver for receiving a delayed reflected signal; a cross correlator for calculating a cross correlation function between the modulation signal and the received delayed reflected signal; and means for detecting changes in the cross correlation function, a change being used to provide intruder detection. This system uses optical sensing and cross correlation calculation to enable an intruder detection signal to be obtained. This can enable a solid state, low cost, and reliable sensor to be provided for detecting intruders.

Abstract: Optical correlators are discussed, suitable for in-vehicle distance measurement. The correlators use modulation sequences based on maximal length sequences. A number of different modulation sequences are obtained by generator (32) from a single maximal length sequence, either by adding a variable number of cycles to the end of the maximal length sequence or by starting the maximal length sequence at different points in the sequence.

Abstract: An imaging system has a transmission system (2) for transmitting a modulated optical signal and a reception system (3) for receiving a received optical signal which is a reflected and delayed version of the transmitted signal. The reception system includes a controllable shutter arrangement for allowing reception in a controllable time window. A memory (4) collects reception data derived from different time windows, and a measure of distance is obtained corresponding to a maximum correlation between the received optical signal and the timing of the controllable time window. Surface profile information is derived from multiple distance measurements. The shutter arrangement enables the distance measurement (and the subsequent profile calculation) to be free from noise from other scattering sources.

Abstract: An Image analysis system uses a multiple-region light detector for detecting light received from the receiving optics, wherein different regions of the light detector can be actuated separately. Control electronics synchronises the timing and direction of illumination of the light source and the actuation of the light detector. The time of light of light signals from the light source to the actuated portion of the detector for all illuminated directions is measured, and distances are derived. A warning is generated if the derived distance is less than a predetermined threshold.

Abstract: An imaging system scans a light source output over an object to be imaged, and receives the reflected signal in a multi-region light detector, wherein different regions of the object to be imaged are imaged onto different regions of the detector by the receiving optics, and wherein different regions of the light detector can be actuated separately. The light source scanning is synchronized with the actuation of the light detector so that a region of the detector imaging the region of object being illuminated by the light source is actuated. The time of flight of light signals from the light source to the actuated portion of the detector is calculated for all scanning directions, to enable a three dimensional image of the object to be constructed.

Abstract: Optical distance equipment transmits an optical signal and determines distance by locating the peak of a correlation with the reflected signal. The number of calculations required for the correlation is greatly reduced by using a combination of a coarse and fine correlation. The accuracy of the distance measurement is also improved by calculating the point of intersection of two best fit lines to either side of the correlation peak. The signal is preferably modulated by a maximum length sequence.