Digital pixel image sensor
AssigneeFacebook Technologies, LLC
InventorXinqiao Liu
Life of this patent
Estimating the term…
Abstract
Disclosed herein are techniques for digital imaging. A digital pixel image sensor includes a digitizer in each pixel of a plurality of pixels, where the digitizer digitizes analog output signals from a photodiode of the pixel using a comparator, a global reference ramp signal, and a clock counter. In some embodiments, the comparator includes a pre-charging circuit, rather than a constant biasing circuit, to reduce the power consumption of each pixel. In some embodiments, each pixel includes a digital or analog correlated double sampling (CDS) circuit to reduce noise and provide a higher dynamic range.
Claims26
A digital pixel image sensor, comprising:
- a plurality of pixels, each pixel comprising:
- a photodiode;
- and
- a charge storage device configured to output a voltage representing a quantity of charge generated by the photodiode;
- a first counter configured to supply count values for digitizing the voltage output by the charge storage device of each and every pixel of the plurality of pixels;
- a memory;
- and
- one or more comparators configured to digitize the voltage output by the charge storage device of each and every pixel of the plurality of pixels based on comparing the respective voltage against a ramp signal to output a decision for the respective pixel, the decision controlling the count values of the first counter stored at the memory for the respective pixel,
- wherein the ramp signal is controlled by the count values supplied by the first counter.
A method comprising:
- starting a first counter to output count values, wherein the count values of the first counter control a ramp signal;
- exposing a photodiode of each and every pixel of a plurality of pixels of an image sensor to light during an exposure period to generate charge;
- generating, by a charge storage device of each and every pixel of the plurality of pixels, a voltage representing a quantity of the charge generated by the photodiode of the respective pixel;
- and
- comparing, using one or more comparators, the voltage of the charge storage device of each and every pixel of the plurality of pixels against the ramp signal to output a decision for the respective pixel,
- wherein the decision controls the count values of the first counter stored at a memory for the respective pixel.
A digital pixel image sensor, comprising:
- a global counter configured to supply count values;
- a plurality of pixels, each pixel comprising, within the pixel:
- a photodiode;
- a charge storage device configured to output a voltage representing a quantity of charge generated by the photodiode;
- a comparator configured to digitalize the voltage output by the charge storage device based on comparing the voltage against a reference signal to generate an output;
- and
- a digital output generator configured to generate a latch signal based on the output of the comparator;
- and
- a memory configured to store a count value from the global counter for each and every pixel of the plurality of pixels based on the latch signal of the digital output generator of the respective pixel.
A digital pixel image sensor, comprising:
- a global counter configured to supply count values;
- a plurality of pixels, each pixel comprising:
- a photodiode;
- and
- a charge storage device configured to output a voltage representing a quantity of charge generated by the photodiode;
- one or more comparators configured to compare the respective voltage of the charge storage device of each and every pixel of the plurality of pixels against a ramp signal to generate an output for the respective pixel;
- one or more digital output generators configured to generate a latch signal for each and every pixel of the plurality of pixels based on the output of the one or more comparators for the respective pixel;
- and
- a memory configured to store a count value from the global counter for each and every pixel of the plurality of pixels based on the latch signal for the respective pixel from the one or more digital output generators.
Dependencies are inferred from the claim text.