Infrared Integrated Systems Limited

Plessey Handel Und Investments A.g.

Stephen George Porter

John Fox

Bhajan Singh

Bryan Lorrain Humphreys Wilson

John Lindsay Galloway

Stephen Hollock

David Appleby

David Harry Broughton

Graham Robert Jones

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.

Location of events in a three dimensional space under surveillance

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, so as to impose a non linear relationship between areas in the image and object planes.

Use of distorting optics in imaging systems

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.

Testing resistance bolometer arrays

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.

Radiation detection apparatus

A two dimensional array of resistive bolometers (B) is arranged in rows and columns. Amplifiers (A , A 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 (M , M etc).

Method of multiplexing column amplifiers in a resistive bolometer array

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.

Dynamic offset correction in detector arrays

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. The event located within the scene may in addition be illuminated with a visible or infrared beam or a searchlight switched on and/or directed by the identification of an event by the thermal array.

Thermal tracker

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.

Use of detector arrays to detect cessation of motion

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.

Detector-array with mask warning

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

Sensors using detector arrays

A pyroelectric detector which includes at least one pyroelectric element consisting of a pyroelectric material sandwiched between first and second electrodes, and a semiconductor chip having a field effect transistor formed on one surface thereof and having an electrical contact for the gate electrode of the transistor formed on the surface thereof, opposite to said one surface, the gate electrode contact of the chip being secured in electrical contact to the first one of the electrodes of the pyroelectric element, the size of the chip being such that a major portion of the first electrode is not covered by the chip.

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Towcester, United Kingdom

Stephen George Porter