Solid-State Imaging Device Noise Reduction via Pixel Segmentation
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Solution Overview
Problem
Solid-state imaging devices face challenges in miniaturization, where reducing pixel size to enhance resolution leads to decreased photoelectric conversion unit area and sensitivity, while maintaining noise reduction and flexibility in design.
Innovation Solution
The implementation of a solid-state imaging device with effective and reference pixels, where the reference pixel outputs a signal based on applied voltage, allowing for differential signal processing to reduce noise and increase flexibility in transistor parameter settings, without the need for a minute capacitor, thus enabling larger photoelectric conversion units and reduced 1/f noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is miniaturized to enhance resolution, then resolution is improved, but photoelectric conversion unit area and sensitivity are reduced
Solution Approach 1:
The pixel is segmented into effective pixels for photoelectric conversion and reference pixels for noise reference, allowing independent optimization of each function. The reference pixel is further segmented from the effective pixels, enabling separate signal processing paths that improve noise reduction without compromising the photoelectric conversion area.
Solution Approach 2:
The invention changes the operational parameters of the reference pixel by applying different voltages (Vr1, Vr2) to its floating diffusion region at different timing, creating reference signals that match the timing characteristics of effective pixel signals. This parameter change enables accurate noise subtraction while maintaining large photoelectric conversion units.
2Device complexity
If amplifying MOS transistors serve dual functions as input stage transistors, then device complexity is reduced, but design flexibility is limited
Solution Approach 1:
The transistor functions are segmented into separate roles: input stage MOS transistors for signal input and amplifying MOS transistors for signal amplification. This segmentation allows independent optimization of each transistor's parameters for its specific function, greatly enhancing design flexibility while maintaining clear functional boundaries.
Solution Approach 2:
The invention introduces intermediate buffering stages between the input stage and amplifying transistors, allowing the amplifying MOS transistors to operate independently without being constrained by input stage requirements. This intermediary structure enables separate parameter optimization for both stages.
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 allows for increased flexibility in setting transistor parameters, reduces noise, and maintains sensitivity by allowing larger photoelectric conversion units without suppressing the area of the photodiode, thereby improving image quality by minimizing horizontal smears and lateral stripes.
Implementation Method 1
an effective pixel including a photoelectric conversion unit configured to generate electric charge by photoelectric conversion
Data Source
AI summary
A solid-state imaging device is configured such that an effective pixel and a reference pixel are connected to first and second signal lines, respectively. The solid-state imaging device includes a difference signal output unit configured to perform difference processing on a signal output from a first amplifying transistor included in the effective pixel and a signal output from a second amplifying transistor included in the reference pixel. The difference signal output unit is provided separately from the first and second amplifying transistors.