Charge-injection imaging: Operating techniques and performances characteristics

Abstract

The charge-injection device (CID) imaging technique employs intracell transfer and injection to sense photon-generated charge at each sensing site. Sites are addressed by an X-Y coincident-voltage technique that is not restricted to standard scanning. Free-format (random) site selection is possible. An epitaxial structure provides a buried collector to prevent recollection of the injected charge. In sequential injection, the charge is injected into the substrate and the resulting displacement current sensed. In parallel injection, the functions of signal charge detection and injection have been separated. The injection operation is used to reset (empty) the charge storage capacitors after line readout has been completed. Nondestructive readout (NDRO) is possible by deferring the injection operation. Low-loss NDRO operation has been achieved using a cooled imager. High sensitivity, low dark current, high modulation transfer function (MTF), and low blooming are some additional advantages of sensing signal charge levels within the array. Compared to the charge-coupled device (CCD), the CID approach results in a relatively high output capacitance; however, this is not considered to be a performance-limiting factor for most imaging applications.