Image Pickup Device Noise Cancellation via Extraction
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Solution Overview
Problem
Current CMOS imagers face challenges in detecting ultramicro pixel output signals, particularly in photon counting, due to random noise and fixed noise, especially at ultralow illuminance levels, where a technique to thoroughly cancel and reduce noise to detect single photons has not been established.
Innovation Solution
The image pickup device incorporates an amplification transistor with a photodiode generating electric charges and a selection transistor connected to a signal line, where the amplification transistor's third terminal is grounded, along with a specific reset and initialization process to enhance noise cancellation and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a general pixel circuit with source follower amplification is used, then the circuit can operate with standard components and layout, but random noise and fixed noise prevent detection of ultramicro pixel output signals
Solution Approach 1:
The patent extracts and removes the noise-generating components (source follower amplification circuit and fixed current circuit) from the pixel circuit. By eliminating these components that generate random noise and fixed noise, the pixel can detect ultramicro output signals including single photon events without being overwhelmed by noise from the amplification and current supply circuits.
Solution Approach 2:
The patent segments the pixel circuit into minimal functional components: photodiode for charge generation, transfer transistor for charge movement, and selection transistor for signal output. This segmentation removes unnecessary amplification stages and fixed current circuits that generate noise, keeping only the essential charge transfer and selection functions needed for low-noise operation.
2Measurement precision
If the parasitic capacitance of the floating diffusion region is reduced through miniaturization, then conversion efficiency and sensitivity improve, but the pixel circuit becomes more difficult to manufacture with smaller features
Solution Approach 1:
The patent uses a simple, minimalistic pixel circuit design with basic transistors and photodiodes that can be manufactured using standard CMOS processes. By avoiding complex amplification circuits and fixed current sources, the design achieves low parasitic capacitance and high sensitivity while remaining manufacturable with conventional fabrication techniques.
3Measurement precision
If photon counting mode is implemented to achieve high SN ratio, then analog signal transmission and amplification noise are eliminated, but the system requires specialized circuit configuration to handle digital data from beginning to end
Solution Approach 1:
The patent extracts and eliminates the analog signal transmission and amplification stages that generate noise. By directly outputting digital data from the pixel through the selection transistor without intermediate analog processing, the system achieves photon counting capability with high signal-to-noise ratio while simplifying the overall signal chain.
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
This configuration enables reliable detection of low-intensity light by minimizing random noise and maintaining high conversion efficiency, allowing for sensitive photon counting and improved signal-to-noise ratios even at low illuminance levels.
Implementation Method 1
each pixel converts incident light to electrons by a photodiode
Data Source
AI summary
An image pickup device including an amplification transistor (136) and a photodiode (134) is provided. The photodiode is configured to generate an electric charge and provide the electric charge to a first terminal of the amplification transistor. The image pickup device also includes a selection transistor (131) having a first terminal electrically connected to a second terminal of the amplification transistor and a second terminal of the selection transistor electrically connected to a signal line (129) is provided. In particular, a third terminal of the amplification transistor is electrically connected to a ground potential.