General Electric Company

Other

Michael L Winn

Samuel C Wang

John M Swab

Martin D Gibbons

Gordon H Danielson

The invention relates to charge injection devices (CID) for sensing IR image intensity information obtained from a two dimensional array of dual-gate sensing sites on an InSb or HgCdTe substrate, and more particularly to a novel push-pull readout circuit which eliminates the pedestal due to capacitive coupling between gates on the same pixel of a dual gate CID. The CID is scanned in rows and read out in parallel columns. Pedestal cancellation is achieved in one example by resetting the prior row as a selected row is injected. In a second example pedestal cancellation is achieved by adding an additional row which is reset as each row is injected, while in a third example a pedestal cancellation network is provided associated with each column output circuit.

Push-pull readout of dual gate CID arrays

A readout circuit for IR sensing charge injection devices (CID) is disclosed, the CID comprising a two-dimensional array of dual-gate sensing sites on an InSb or HgCdTe substrate. The novel readout circuit, which operates in the charge sharing mode (CSM) in extracting image information, is modified to correct for the subtractive effect present when the CSM mode is used. The readout circuit includes a plurality of processors, one for each column, from which a single serial output may be obtained by a demultiplexer, and into which signals derived from successive pixel sites on the associated column are coupled. A first quantity representing the subtractive error is obtained without injection from each column line by double sampling during a first interval. A second quantity representing the signal corrected for subtractive error is obtained with injection from a pixel site by double sampling during a second interval, the samples being increased by the error quantity. The subtractive error compensation may be applied in cases involving either unsaturated or saturated signal fields.

Readout circuit for dual-gate CID imagers with charge sharing corrected

The invention relates to a read and clear readout circuit and a method of operation of an IR sensing array. The invention eliminates 'readout circuit lag' which reduces transient response for an individual sensor, and reduces angular resolution of an array. 'Readout circuit lag' also emphasizes longer duration IR background causing unwanted saturation and restriction of the dynamic range. Readout circuit lag arises from the capacitance of the sensor elements and the capacitance of the readout circuit at a node to which the sensor elements are periodically coupled for readout, the IR induced charge being partitioned between these capacitances, with that attributable to the sensor capacitance not being injected, causing readout circuit lag. Elimination of such lag is achieved by following each readout step, with a clear or clear and skim step that removes charge to the clear level or to the skim level, precluding the lag earlier described.

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Liverpool, NY, United States of America

Michael L Winn