| Popis: |
CCD image sensors have been utilized as the detectors in digital spot mammography for needle biopsy systems. The requirements of a detector for this application are large sensing area, large pixel size, moderate resolution, and low noise. A large area full-frame CCD image sensor has been developed that is 50 mm X 50 mm with 2084 X 2084 pixels. It is manufactured using a true two-phase, transparent gate, buried channel CCD process. The transparent gate process improves the quantum efficiency from 40 percent to 55 percent at 540 nm. The true two-phase CCD operates in accumulation mode for low dark current without compromising charge capacity. The sensor has two different output amplifiers optimized for either low signal applications or high dynamic range applications. At a 2 MHz pixel rate the dynamic range is 84 dB or 88 dB depending on which output amplifier is selected. The large sensor format allows the elimination of the demagnification requirement in digital spot mammography applications and may be useful for mid-field digital diagnostic systems. |
