Method of implementing uniform background charge subtraction in a radiation sensing array

摘要

Uniform background charge subtraction in a radiation sensing array is realized by removing the background charge from the array detectors several times during each array integration time. Radiation sensing arrays of the type to which the method of the invention can be applied include a radiation sensor with a charge storage reservoir to which there is coupled a CCD output register having a channel with multiple charge storage sites. Signal background and bias charge is accumulated in the charge storage reservoir and transferred to a CCD storage site by a transfer gate. Charge in the CCD storage site can be shifted to another storage site in the CCD channel or it can be dispersed to drain by means of a drain barrier gate. According to the method of the invention a number of times during each array integration period the charge accumulated in the charge storage reservoir is transferred to a CCD charge storage site and then returned in part to the reservoir leaving a metered amount in the charge storage site. This is then dispersed to drain. After a set number of repetitions the signal charge is skimmed from the total charge remaining in the charge storage reservoir and transferred to the CCD charge storage site. The signal charge is then shifted along the CCD channel to another storage site clearing the device for another cycle of operation.