Pixel-level background light subtraction
AssigneeSony Semiconductor Solutions Corporation
InventorsKatsuhiko Hanzawa, Jinsuk Kang, Selcuk Sen
Life of this patent
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Abstract
A pixel circuit, a method for performing a pixel-level background light subtraction, and an imaging device are disclosed. In one example of the present disclosure, the pixel circuit includes an overflow gate transistor, a photodiode, and two taps. Each tap of the two taps is configured to store a background signal that is integrated by the photodiode, subtract the background signal from a floating diffusion, store a combined signal that is integrated by the photodiode at the floating diffusion, and generate a demodulated signal based on a subtraction of the background signal from the floating diffusion and a storage of the combined signal that is integrated at the floating diffusion.
Claims24
A pixel circuit comprising:
- a single overflow gate transistor electrically connected to a node;
- a photodiode electrically connected to the node and a chassis ground, the photodiode is configured to
- receive background light,
- receive a combination of the background light and a demodulated light that is generated by a modulated light source and reflected from an object,
- integrate a background signal based on the background light that is received, and
- integrate a combined signal based on the combination of the background light and the demodulated light;
- and
- two taps, each tap of the two taps is configured to
- store the background signal that is integrated,
- subtract the background signal from a floating diffusion,
- store the combined signal that is integrated at the floating diffusion, and
- generate a demodulated signal based on a subtraction of the background signal from the floating diffusion and a storage of the combined signal that is integrated at the floating diffusion.
A method for performing a pixel-level background light subtraction, the method comprising:
- integrating, with a photodiode of a pixel circuit, a background signal based on background light received by the photodiode;
- storing a charge of the background signal that is integrated in injection capacitors of the pixel circuit;
- subtracting the charge that is stored in the injection capacitors from floating diffusions of the pixel circuit;
- integrating, with the photodiode, a combined signal based on a combination of background light and demodulated light received by the photodiode;
- storing charges of the combined signal in the floating diffusions;
- and
- reading out a demodulated signal from each the floating diffusions, wherein the demodulated signal is a difference between the charge of the combined signal and the charge of the background signal that is stored at the each of the floating diffusions, and wherein the demodulated signal from the each of the floating diffusions has a different phase.
An imaging device comprising:
- a controller;
- and
- an array of pixels including at least one pixel circuit that includes
- a single overflow gate transistor electrically connected to a node;
- a photodiode electrically connected to the node and a chassis ground, the photodiode is configured to
- receive background light,
- receive a combination of the background light and a demodulated light that is generated by a modulated light source and reflected from an object,
- integrate a background signal based on the background light that is received, and
- integrate a combined signal based on the combination of the background light and the demodulated light;
- and
- two taps, each tap of the two taps is configured to
- store the background signal that is integrated,
- subtract the background signal from a floating diffusion,
- store the combined signal that is integrated at the floating diffusion, and
- generate a demodulated signal based on a subtraction of the background signal from the floating diffusion and a storage of the combined signal that is integrated at the floating diffusion.
Dependencies are inferred from the claim text.