Solid State Image Pickup Device Column Amplification Noise Reduction
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Solution Overview
Problem
Conventional solid state image pickup devices suffer from low sensitivity, high noise, and increased chip area due to capacitance distribution and parasitic capacitors, leading to a poor signal-to-noise ratio and increased costs.
Innovation Solution
Incorporating a column amplification unit between the pixel and noise signal removal units to amplify pixel signals, reducing noise components and capacitance distribution, while using impedance conversion and boosting voltage to enhance sensitivity and reduce chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional solid state image pickup device structure is used, then the device can be manufactured with standard processes, but the sensitivity is low and noise is high due to capacitance distribution and parasitic capacitors
Solution Approach 1:
The invention divides the image pickup device into distinct functional blocks: pixel units with photoelectric conversion units, column selection units with amplification circuits, and noise cancellation units. This segmentation allows each block to be optimized independently, placing amplification circuits close to pixel units to reduce capacitance distribution effects and improve sensitivity while managing noise separately.
Solution Approach 2:
The invention introduces signal lines with minimized parasitic capacitance as intermediaries between photoelectric conversion units and amplification circuits. By carefully designing these intermediate connection structures and placing amplification circuits at strategic positions, the parasitic capacitance affecting sensitivity is reduced while maintaining signal integrity.
2Object-affected harmful factors
If noise cancellation units are added to reduce noise, then the signal-to-noise ratio improves, but the chip area increases
Solution Approach 1:
The invention combines multiple functions into integrated circuit blocks. Noise cancellation units are merged with column selection units and amplification circuits to form compact functional modules. This integration allows noise cancellation functionality to be added without proportionally increasing chip area, as shared resources and optimized layouts reduce the total space required.
Solution Approach 2:
The invention arranges circuit blocks in a three-dimensional layout strategy, stacking functional units vertically and optimizing signal paths to minimize horizontal space consumption. Column selection units and noise cancellation units are positioned to share vertical space and minimize interconnections, effectively reducing the two-dimensional chip footprint while maintaining all necessary noise cancellation functions.
3Measurement precision
If amplification circuits are placed close to pixel units to improve sensitivity, then signal strength increases, but parasitic capacitance on signal lines increases
Solution Approach 1:
The invention applies different design qualities to different regions of the circuit. Signal lines connecting photoelectric conversion units to amplification circuits are designed with minimized capacitance in critical regions, while other areas use standard routing. The amplification circuits themselves are positioned with asymmetric layouts that optimize input capacitance matching while minimizing output parasitic effects.
Solution Approach 2:
The invention changes the electrical parameters of signal lines and amplification circuit inputs by using specialized transistor designs and capacitance compensation techniques. Amplification circuits employ input structures with reduced parasitic capacitance, and signal line impedance is optimized to minimize capacitive loading effects, thereby maintaining sensitivity while controlling parasitic capacitance.
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 solution improves the signal-to-noise ratio, increases sensitivity, and reduces chip area with low power consumption, enabling high-quality image capture in varying light conditions.
Implementation Method 1
a photodiode PD that converts the incident light into a charge
Data Source
AI summary
A solid state image pickup device 110 is provided with: a plurality of pixel units 10 that are arranged two-dimensionally and include a photoelectric conversion unit (photodiode PD) that converts light into a charge and an amplification unit (amplifier Q13) that converts the charge into a voltage and outputs it; a plurality of noise signal removal units (noise cancellation units 40) that are provided one for each column and remove noises contained in the voltage outputted from the amplifier Q31 of the pixel unit 10 belonging to the column; and a plurality of column amplification units (column amplifiers 70) that amplify the voltage outputted from the amplifier Q13 of the pixel unit 10 and output the amplified voltage to the noise cancellation unit 40, and enables increase in sensitivity and reduction in noise with low power consumption.