General Electric Company

Other

Samuel C Wang

John M Swab

Martin D Gibbons

Michael L Winn

David N Ludington

Marshall K Quick

Kenneth J Fuhr

Gordon H Danielson

The invention relates to a multiple channel readout circuit optimized for a cryogenically operated IR sensor head. The circuit is applicable to the individual channel preamplifiers of a charge injection device (CID) IR sensor. Since the thermal leakage must be minimized, the voltages on the principal current supply path to the individual preamplifiers will vary when a strong signal is present on any channel. Crosstalk is avoided by using a four transistor cascode preamplifier circuit having a source follower output, in which the gate of the transistor, which acts as a load to the two cascoded transistors, is isolated from the drain of the load transistor, connected to a gate load node common to the other channels, and the node connected via a single connection of high thermal impedance to a terminal external to the cryogenic environment, at which filtering may be provided as needed.

Multiple channel readout circuit optimized for a cryogenically operated

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 novel readout circuit for a charge injection device is disclosed permitting selection of the integration time to optimize performance. A primary application of the invention is to IR sensing in which performance is required at both low and very high levels of radiation. The readout circuit, in one practical configuration, utilizes a dump pulse recurring at the interval required to scan all elements, in advance of the read pulse also recurring at the scanning interval. The integration time may be adjusted in multiples of the readout period for a single element up to the frame scanning interval, or in approximate fractions of the readout period for a single element, or, at the limit, in a fraction of a microsecond.

Integration time control for a radiation sensitive charge injection

The invention relates to a charge injection device for optical sensing including a novel readout circuit facilitating an extended dynamic range. The invention has primary application to linear arrays for IR sensing. Sensitive, low-level operation is achieved in a primary readout means by allowing the charge to accumulate in the potential well of the individual sensor elements over the line period with each element being reset at the pixel readout rate and by using a charge injection pulse to clear stored charge from the individual sensor elements. A secondary readout means is also provided in which the charge is allowed to accumulate over a period not exceeding the pixel readout interval for unsaturated large signal operation and by sensing the change in depth of the potential well. The two readout means are combined in the eventual display to provide an improvement of typically three orders of magnitude in the dynamic range of the CID.

Readout circuit for an optical sensing charge injection device

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.

Read and clear readout circuit and method of operation of an IR sensing

The invention relates to an improved readout circuit and readout method for an IR sensing array. The invention, given a limited time interval for reading out the signal from a sensor element in an array of sensor elements, permits a longer time to be devoted to the injection of charges into the substrate, thereby reducing device 'lag' (the retention of uninjected charges). The readout is carried out by a two step, direct coupled, injection process. The first step involves independent, but simultaneous resetting of the sensor elements and the preamplifier input (at a node having sufficient capacity to supply the charges required for injection). The voltages are suitable for IR induced charge storage in the sensor elements, and for subsequent injection by the nodal capacity. A first sample is taken by a correlated double sampling circuit from the preamplifier output during the first step as the resetting stabilizes. In the second step, the selected sensor element is connected to the preamplifier input to cause the charge injection. At the same time the preamplifier is responding to the charge transfer. The second sample is taken from the preamplifier output at the end of injection. The reduction in lag over conventional AC coupled readout circuits is 80%.

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Manlius, NY, United States of America

Samuel C Wang