CMOS Image Sensor Readout Circuit Area Reduction
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Solution Overview
Problem
CMOS image sensors with wide dynamic range face challenges in maintaining linear sensitivity characteristics and increasing circuit area and power consumption due to the need for multiple readout parts to process high and low sensitivity pixel signals.
Innovation Solution
An image pickup device with a pixel array generating high and low sensitivity pixel signals, using a pixel scanning circuit to output signals in a time division manner, and readout circuits that select and correct pixel signals based on a threshold value, with a correction coefficient generation circuit to ensure linear sensitivity, reducing the number of readout circuits needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two readout parts are used to process both high-sensitivity and low-sensitivity pixel signals, then the dynamic range is improved, but the circuit area and power consumption increase
Solution Approach 1:
The patent merges the functions of two separate readout parts into a single readout part that sequentially processes both high-sensitivity and low-sensitivity pixel signals through time-division multiplexing. The readout part includes switching elements that route different pixel signals to appropriate processing paths, allowing one readout part to perform the work of two while reducing circuit area and power consumption.
Solution Approach 2:
The patent introduces dynamic switching within the readout part to adaptively route different pixel signals at different time periods. The switching elements dynamically connect the pixel array output to either the high-sensitivity processing path or the low-sensitivity processing path based on the current time period, enabling a single readout part to handle multiple signal types that would traditionally require separate static readout paths.
2Adaptability or versatility
If two readout parts are used to process both high-sensitivity and low-sensitivity pixel signals, then the dynamic range is improved, but the power consumption increases
Solution Approach 1:
The patent merges the functions of two separate readout parts into a single readout part that sequentially processes both high-sensitivity and low-sensitivity pixel signals through time-division multiplexing. The readout part includes switching elements that route different pixel signals to appropriate processing paths, allowing one readout part to perform the work of two while reducing circuit area and power consumption.
Solution Approach 2:
The patent implements periodic switching between processing high-sensitivity pixel signals and low-sensitivity pixel signals in alternating time periods. During the first time period, the readout part processes high-sensitivity signals; during the second time period, it processes low-sensitivity signals. This periodic action allows a single readout part to handle both signal types sequentially, reducing the power consumption that would result from running two parallel readout parts simultaneously.
3Area of stationary object
If a common readout part is used for both high-sensitivity and low-sensitivity pixel signals, then the circuit area is reduced, but the sensitivity correction cannot be performed
Solution Approach 1:
The patent introduces dynamic switching within the readout part to adaptively route different pixel signals at different time periods. The switching elements dynamically connect the pixel array output to either the high-sensitivity processing path or the low-sensitivity processing path based on the current time period, enabling a single readout part to handle multiple signal types that would traditionally require separate static readout paths.
Solution Approach 2:
The patent performs preliminary separation of high-sensitivity and low-sensitivity pixel signals through time-division multiplexing before they enter the correction stage. By routing different signal types through different paths at different time periods, the system preserves the ability to apply appropriate correction coefficients to each signal type, maintaining sensitivity correction capability while using a single shared readout part.
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 approach allows for a wide dynamic range while minimizing the increase in circuit area and power consumption, enabling efficient processing of high and low sensitivity signals with improved linearity and reduced noise.
Implementation Method 1
Each pixel circuit of the pixel array includes a photodiode and an amplifier. The voltage generated in the photodiode is amplified by the amplifier and output to a column signal line.
Data Source
AI summary
This invention is an image pickup device that realizes a wide dynamic range while minimizing circuit area using a pixel array that can pick up a low-sensitivity image and a high-sensitivity image. This invention obtains information (S1/S2) needed for generating a correction coefficient using one more than the number of pixels readout circuits (RC1 to RCn+1). This significantly reduces the circuit area compared with the case of using twice as many readout circuits as pixels for generating the correction coefficient.