U.S. Philips Corporation

Raymond E King

Ian M Baker

In an imaging device, photocurrent generated by detector elements (1), e.g. cadmium mercury telluride photodiodes, may be integrated in resettable capacitors (2), and an output signal (S) may be derived by reading the potential of the capacitor (2) at the end of its integration period, e.g. using a source-follower MOST (3). In accordance with the invention first and second capacitors (2a and 2b) are switchably coupled in alternate parallel arms between each detector element (1) and the voltage-reading means (3), by means of an arrangement of input gates (8a and 8b) and output gates (9a and 9b). Since one of the first and second capacitors (2a or 2b) can be coupled to the detector element (1) while the other (2b or 2a) is coupled to the voltage-reading means (3), each detector element (1) can be switched from one to the other so as to be operated the whole time for photodetection without its signal being lost (i.e. not integrated) when reading the previous output signal from that detector element (1). This is particularly useful for coupling a row of storage capacitors via a 2-d switching array to a 2-d array of infrared detector elements (1). A similar arrangement of alternately-switchable first and second capacitors (2a and 2b) may be used for visible light imaging, and a modified arrangement may used with a CCD signal processing circuit.

Growing community of inventors

Chandlersford, United Kingdom

Raymond E King