Image sensors generating digital signals from light integration processes
AssigneeSyscan Technology (Shenzhen) Co., Limited
InventorAlpha Hou
Life of this patent
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Abstract
The purpose of the present invention is to provide a generic solution for direct readout of the charge signals from the photodetectors in an image sensor to minimize possible signal distortions. The disclosed image sensor uses a time measurement circuit for each of the photodetectors. The time elapsed for each of the photodetectors to reach a reference signal is measured and converted to a digital representation that is subsequently readout as the digital signals.
Claims28
A system for generating digital signals in a sensor, the system comprising:
- an array of photodetectors, each responsive to light impinged thereupon and independently producing a charge signal after the photodetectors are collectively reset by a reset signal;
- a counter receiving a time mark signal and producing a count number with reference to the time mark signal;
- a plurality of time mark measurement modules collectively receiving a reference signal and the count number from the counter, each of the time mark measurement modules coupled to one of the photodetectors and outputting a digital representation of the charge signal from the one of the photodetectors with reference to the reference signal and the count number from the counter, wherein the reference signal has a magnitude level piecewise adjusted over time;
- and
- a plurality of register circuits, each connected to one of the time mark measurement modules and receiving the digital representation therefrom, wherein the digital representation from each of the time mark measurement modules is sequentially shifted out to form the digital signals.
A system for generating M-bit digital signals in a sensor, the system comprising:
- an array of N photodetectors, each coupled to a transistor and charged to a voltage level when being reset by a reset signal, in response to light impinged upon the photodetectors, each of the photodetectors producing a charge signal by discharging respectively from the voltage level at a rate in proportion to the light intensity;
- N gate circuits collectively receiving a reference signal that is piecewise increased over time, each of the N gate circuits receiving respectively the charge signal from the each of the N photodetectors and producing a pulse signal when the charge signal reaches the reference signal in magnitude;
- a counter receiving a time mark signal and producing a count number with reference to time marks in the time mark signal;
- N latch circuits collectively receiving the count number;
- each of the N latch circuits further communicating respectively with the each of gate circuits and latching in respectively the count number as soon as the pulse signal is received from the each of the N gate circuits;
- and
- N register circuits, each coupled to one of the N latch circuits and receiving the count number therefrom, the count number being sequentially shifted out of the N register circuits to produce the digital signals.
A method for generating digital signals in a sensor comprising photodetectors thereon, the method comprising:
- accumulating incident photons in the photodetectors to generate a charge signal in each of the photodetectors;
- comparing, using a comparing circuit, the charge signal with a reference signal that is piecewise increased over time;
- producing a pulse signal by the comparing circuit when the charge signal reaches the level of the reference signal;
- measuring time elapsed by a latch circuit receiving a count number from a counter for the charge signal to have reached the level of the reference signal;
- and
- dumping bits of signals representing the measured time to a register circuit for readout process.
Dependencies are inferred from the claim text.