Sensor Circuit Identical Capacitors Noise Cancellation
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Solution Overview
Problem
Conventional light sensors, such as global shutter and rolling shutter sensors, are affected by environmental noises during the readout interval, leading to decreased sensing efficiency due to undesired noise charges influencing the exposure data, which cannot be effectively separated from the image signal.
Innovation Solution
A circuit arrangement that utilizes capacitors with identical physical characteristics to store sensing and reset signals, allowing for the cancellation of noise-induced voltage deviations through identical influences on both capacitors, thereby improving sensing efficiency by eliminating noise voltage during signal readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If exposure data is temporarily stored during readout interval, then global shutter operation is enabled, but sensing noises from external light pollute the exposure data causing image distortion
Solution Approach 1:
The patent creates a copy of the floating diffusion node (FD2) that experiences identical noise conditions as the signal storage node (FD1). By duplicating the node structure and exposing it to the same environmental noise, the noise component can be separated from the signal through differential processing, enabling global shutter operation without noise pollution.
Solution Approach 2:
The patent introduces an intermediate reference node (FD2) that acts as a mediator between the signal storage node and the readout circuit. This intermediary node captures only the noise component, allowing the readout circuit to subtract the noise from the signal node, thereby recovering the clean exposure data.
2Productivity
If readout time of different pixels has time difference, then sequential readout is enabled, but exposure data readout later is influenced more by sensing noises
Solution Approach 1:
The patent performs preliminary noise capture at the floating diffusion node level before readout occurs. By having the reference node (FD2) continuously track noise during the entire exposure and readout intervals, the noise compensation is prepared in advance, allowing all pixels to be corrected regardless of their readout timing.
3Reliability
If charges are stored in floating diffusion node, then sensing signal is captured, but noise charges cannot be separated from exposure data causing signal distortion
Solution Approach 1:
The patent segments the charge storage function into two separate floating diffusion nodes: one dedicated to signal storage (FD1) and another to noise reference (FD2). This segmentation allows the noise and signal to be physically separated and independently processed, enabling complete noise removal while preserving the exposure data.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution effectively cancels out noise voltage, enhancing the accuracy of exposure data retrieval and improving overall sensing efficiency by ensuring that both sensing and reset signals are equally affected by noise charges, thus reducing distortion and improving image signal quality.
Implementation Method 1
the present disclosure provides an improvement on the sensor circuit that duplicates a voltage deviation caused by additional electrons using the capacitive sensing
Implementation Method 2
arranges a capacitor or multiple identical capacitors in the signal path to be coupled to, by the floating effect, charges stored in the floating diffusion node
Data Source
AI summary
There is provided a circuit to improve the sensing efficiency of pixels that uses the induction effect of a capacitor to duplicate a voltage deviation caused by additional electrons and uses a circuit to cancel out the voltage deviation during reading pixel data thereby improving the sensing efficiency.