The sensor features a split readout scheme in which the top and bottom halves of the sensor are read out independently. Each column within each half of the sensor is equipped with dual column level amplifiers and dual analog-to- digital converters (ADC), represented as a block diagram in below. This architecture was designed to minimize read noise and maximize dynamic range simultaneously.
The dual column level amplifier/ADC pairs have independent gain settings, and the final image is reconstructed by combining pixel readings from both the high gain and low gain readout channels to achieve a wide intra-scene dynamic range from such a small pixel pitch.
Each pinned-photodiode pixel has 5 transistors (‘5T’ design), enabling the novel ‘global shutter’ mode (described in more detail below) and also facilitating correlated double sampling (CDS) and a lateral anti-blooming drain. The sensor is integrated with a microlens array that serves to focus much of the incident light per pixel away from the transistors and onto the exposed silicon, enhancing the QE (analogous to use of microlenses in interline CCDs to focus light away from the column masks).
The sensor is configured to offer low dark current and extremely low read noise with true CDS. Non-linearity is less than 1% and is further correctable to < 0.2%. The sensor also has anti-blooming of >10,000:1, meaning that the pixels can be significantly oversaturated without charge spilling into neighboring pixels. It is also possible to use the anti-blooming capability to hold all or parts of the sensor in a state of ‘reset’, even while light is falling on these pixels. The time to transfer charge after the exposure is complete is less than 1μs, rendering the sensor useful for fast electronic shuttering and ‘double exposure’ techniques such as Particle Imaging Velocimetry (PIV).
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