Blooming control and dynamic range in charge-coupled imagers

In practical applications charge-coupled imagers (CCI´s) should be immune to picture degradation due to excessive local optical overloads while maintaining large dynamic range. Our analysis shows that a 500 × 500 CCI will have a sensitivity approaching the I-SIT (within a factor of 10) and an intra scene dynamic range of approximately 1000:1 for a scene contrast of 0.2. However, to maintain useful operation under excessive local overloads (up to 10⁵), some type of blooming control is required which is capable of removing the excess charge from the photosensitive area. Two general categories of blooming ccntrol structures for charge-coupled area sensors with illuminated registers will be described. Operation, design tradeoffs, and experimental data will be presented for: (a) blooming control structures which are process-compatibile with single-metal 3-phase CCI´s, and (b) for blooming control structures more suitable for sealed channel, silicon gate, 2-phase CCI´s. Blooming control methods will also be described for sensors having separate photodiodes with nonilluminated registers.