The pictures we take come from the pixels on the sensor, which process light into electrical signals that combine to output the picture. When the captured object is too bright and a lot of electric charge is squeezed into a single pixel, the resulting image is overexposed.
The basic idea of LOFIC (Lateral Overflow Integration Capacitor, lateral overflow collective capacitor) is that when the charge exceeds the maximum capacity (maximum well capacity) that the pixel can originally carry, the excess charge will flow to the adjacent capacitors without overflowing Come. In this way, the highlighted picture can be clearly displayed. A simple indication is as follows:
Its pixel structure is as follows:
Pixel circuit consists of fully depleted photodiode (PD), transfer switch (T), floating diffusion (FD) that converts charge to voltage, reset switch (R), source follower amplifier (SF), pixel select switch (X) , lateral overflow integrating capacitor ( ) and connection switch (S) between FD and CS. The high full well capacity is achieved by a lateral overflow integrating capacitor that integrates the photoelectrons overflowing from the PD during the integration time. Lower input-related noise is achieved through higher conversion gain and minimized FD capacitance. Small pixel sizes can be achieved because additional circuit elements are suppressed.
As long as the PD reaches half of the saturated well capacitance (Skim level) during exposure, the related circuit action will be triggered to transfer the charge to the CS capacitance. When reading, the PD signal is read first, followed by the PD and CS capacitances and the total signal. English skim is commonly used to describe the action of skimming oil on water, so LOFIC is also called Skimming pixel.
Its working sequence is as follows:
