Switching photosensitive matrix device

Details Switching photosensitive matrix device Switching photosensitive matrix device

1993-07-14

1994-10-11

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

356 5, 2502083, H01J 4014

Patent

active

053549813

ABSTRACT:
The disclosure describes one unit cell of a PNPN photoswitch array for an image sensor, including a PNPN light-activated thyristor (LAT), in the form of a two-terminal device, and a load FET. The FET functions as a load and as an on-off switch in series. The output of is a voltage at a first n node that controls the FET switch that connect a voltage-ramp input line to a capacitor and a diode that are connected in parallel. The other side of the diode is the input source of the unit cell that feeds charge into a vertical CCD analog shift register. At the start of a cycle of operation, such as the beginning of a sweep of a radiation beam and prior to a pulse of a target reflection pulse, being directed onto the pnpn photoswitch, the voltage level at the first node is high. At the time when a pulse of radiation is directed onto the photoswitch the first node goes low turning the switching transistor off. The capacitor has a charge level at an analog value representative of the elapsed time between the beginning of the cycle, such as the beginning of a radiation beam sweep, an the occurrence of the pulse reflected from a target. At the end of a cycle the charge is transferred into a CCD readout register.

REFERENCES:
patent: 4821036 (1989-04-01), Daffarn
patent: 5107103 (1992-04-01), Gruss et al.
patent: 5118180 (1992-06-01), Wichmann et al.

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