Abstract: A surveillance system using an array of detectors onto which energy from the scene under surveillance is focused can indicate the direction of an event that has been recognized. The invention uses two or more arrays to locate events in three dimensions, and to define regions within the three dimensional space being surveyed. The events are located by detecting which elements from the respective arrays are stimulated by the occurrence of an event, and determining the location of the event to be at the intersection of the fields of view of the stimulated elements.

Abstract: An optical detection system for forming an image of a field of view in an object plane onto an image plane in which the electromagnetic radiation image is transmitted to a detector array at the image plane via an optical distorting element such as a reflector 11, so as to impose a non linear relationship between areas in the image and object planes.

Abstract: A method of testing resistance bolometer arrays involves applying different voltages to different bolometers so as to produce a detectable difference between adjacent bolometers under normal conditions. The voltages may be applied in a recognizable pattern so that faults can be readily identified from a visual display of the array.

Abstract: A radiation detection apparatus is capable of detecting and locating events, such as a fire or the appearance of an intruder, in a scene under surveillance. The apparatus comprises an array of detector elements, e.g. infrared detectors. The apparatus has two fields of view, namely a first field of view defined by a lens providing a single focussed image of a distant scene on the array and a second field of view defined by a reflector arranged between a plane of the array and a plane of the lens whereby to reflect onto the detector array radiation entering the lens from outside the first field of view. One or more processors are provided to distinguish events in the second field of view from those in the first field of view.

Abstract: A two dimensional array of resistive bolometers (B) is arranged in rows and columns. Amplifiers (A0, A1 etc) amplify signals obtained from the bolometers. Instead of providing one amplifier per column, a smaller number of amplifiers is used each of which is connected to a plurality of column sense lines (L) via a multiplexer (M0, M1 etc).

Abstract: A two dimensional array of resistive bolometers (B) is arranged in rows and columns. Amplifiers (A0, A1 etc) amplify signals obtained from the bolometers. Instead of providing one amplifier per column, a smaller number of amplifiers is used each of which is connected to a plurality of column sense lines (L) via a multiplexer (M0, M1 etc).

Abstract: A two dimensional array of resistive bolometers (B) is arranged in rows and columns. Amplifiers (A0, A1 etc) amplify signals obtained from the bolometers. Instead of providing one amplifier per column, a smaller number of amplifiers is used each of which is connected to a plurality of column sense lines (L) via a multiplexer (M0, M1 etc).

Abstract: A signal processing technique applied to the readout of two-dimensional detector arrays provides a dynamic correction mechanism for the varying offsets of the different elements of the array. The outputs of the elements are supplied to an offset correction circuit operative to compensate for the differences in the d.c. or low frequency outputs from a predetermined voltage wherein a fraction of the difference is subtracted at each successive cycle to gradually reduce the difference.

Abstract: A two dimensional array of resistive bolometers (B) is arranged in rows and columns. Amplifiers (A0, A1 etc) amplify signals obtained from the bolometers. Instead of providing one amplifier per column, a smaller number of amplifiers is used each of which is connected to a plurality of column sense lines (L) via a multiplexer (M0, M1 etc).

Abstract: A signal processing technique applied to the readout of two-dimensional detector arrays provides a dynamic correction mechanism for the varying offsets of the different elements of the array. The outputs of the elements are supplied to an offset correction circuit operative to compensate for the differences in the d.c. or low frequency outputs from a predetermined voltage wherein a fraction of the difference is subtracted at each successive cycle to gradually reduce the difference.

Abstract: A surveillance system using an array of detectors onto which energy from the scene under surveillance is focused can indicate the direction of an event that has been recognized. The invention uses two or more arrays to locate events in three dimensions, and to define regions within the three dimensional space being surveyed. The events are located by detecting which elements from the respective arrays are stimulated by the occurrence of an event, and determining the location of the event to be at the intersection of the fields of view of the stimulated elements.

Abstract: An image of a scene is focused onto a two dimensional array of passive infrared sensing elements mounted on and connected to an integrated circuit, and used to detect the location of events within the scene; for example, movement, change in temperature, or the emission of a gas. In this invention knowledge of the location of the event is derived from the detection of signals from one or more elements of the array, and is used to control the operation of a mechanism such that a portion of the scene including the event location is imaged onto a video imaging device operating in the visible or near infrared. Such mechanisms include a zoom lens or mirror arrangement and mechanical scanning in elevation and/or azimuth. Examples of suitable imaging devices for use with the thermal detector array include CCD camera chips and other electrically scanned silicon photovoltaic arrays. The CCD array might for example be used in a CCD camera, which is used to identify an intruder, or to read the number plate of a car.

Abstract: An optical detection system for forming an image of a field of view in an object plane onto an image plane in which the electromagnetic radiation image is transmitted to a detector array at the image plane via an optical distorting element such as a reflector 11, so as to impose a non linear relationship between areas in the image and object planes.

Abstract: A method of testing resistance bolometer arrays involves applying different voltages to different bolometers so as to produce a detectable difference between adjacent bolometers under normal conditions. The voltages may be applied in a recognisable pattern so that faults can be readily identified from a visual display of the array.

Abstract: A sensor comprising an array of detectors for e.g. infrared radiation of the type for use in security or surveillance application has means for identifying the entry of an object into a first selected area of a scene and means for generating a warning or alarm signal after a first predetermined period of time during which there is no movement of the body within the first selected area.

Abstract: Sensors using detector arrays (1) are intended for identifying events within a scene (12). A sensor comprising an array of pyroelectric infrared detectors (1) is mounted directly onto an integrated readout circuit (2) so that each of its elements is in electrical contact with one of the inputs to the readout circuit. The detector array (1) on its readout circuit (2) is positioned at the focus of an infrared transmitting lens (11) so that an image of a scene (12) is formed on the array. The readout circuit (2) and array (1) are enclosed in a package (18) which is connected via a circuit board (19) to a microprocessor (20). The microprocessor (20) and readout circuit (2) work together to detect the occurrence and position of events within a scene (12). Application examples are the detection and identification of location of flames or intruders within the field of view.

Abstract: When an array of thermal detectors with appropriate read-out means is used as a sensor to detect events such as intruders or fire, it may be disabled accidentally or deliberately by placing a mask over the array to shield it from the scene. The act of placing a mask over the array induces a simultaneous transient signal from all of the detectors, or at least a majority of the detectors, and is followed by a period when those detectors give rise only background noise or clutter. The characteristics of these signals is used to generate a warning signal to indicate that the sensor has been disabled.

Abstract: A ceramic material, which consists of lead zirconate with not greater than 20 atomic per cent of bismuth substituted for the lead, according to the formula Pb.sub.1.sub.-3x/2 Bi.sub.x ZrO.sub.3. Titanium to a concentration of not more than 50 atomic per cent can be substituted for the zirconium according to the formula Pb.sub.1.sub.-3x/2 Bi.sub.x Zr.sub.1.sub.-y Ti.sub.y O.sub.3. Potassium to a concentration of 2 to 20 atomic per cent can also be substituted for the lead in any of these materials, according to either the formula Pb.sub.1.sub.-3x/2.sub.-z/2 Bi.sub.x K.sub.z SrO.sub.3 or the formula Pb.sub.1.sub.-3x/2.sub.-z/2 Bi.sub.x K.sub.z Zr.sub.1.sub.-y Ti.sub.y O.sub.3. Uranium can also be included in any one of these ceramic materials to a concentration of not more than 10 atomic per cent. All of the ceramic materials can be produced by ceramic processes and sintering techniques.