CMOS Imaging Pixel Circuit Simplification via Column Signal Processing
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Solution Overview
Problem
Conventional CMOS-type imaging devices require complex pixel configurations with multiple transistors and capacitive elements for signal processing, leading to increased size and complexity, which hinders miniaturization and efficiency.
Innovation Solution
The proposed imaging device simplifies the pixel configuration by eliminating the need for capacitive elements and reducing the number of transistors through simultaneous row reset and sequential column selection, allowing for direct transfer and amplification of signal charges, and converting current signals to voltage signals for easier matching with subsequent circuit stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional CMOS-type imaging devices use multiple transistors and capacitive elements for signal processing in each pixel, then signal processing capability is improved, but device size and complexity increase
Solution Approach 1:
The patent divides the imaging device into distinct functional units: imaging units with simplified pixels, column circuit units for signal processing, and a selection unit. By segmenting the signal processing functions from the pixel level to the column circuit level, each pixel only needs essential components (photodiode, transfer transistor, selection transistor) while complex processing occurs in dedicated column circuits, resolving the contradiction between processing capability and pixel complexity
Solution Approach 2:
The patent introduces vertical signal lines and column circuit units as intermediary components between the pixels and output. Instead of each pixel handling all processing independently, the intermediary column circuits perform amplification and signal processing functions, allowing pixels to remain simple while maintaining strong signal processing capability through the intermediary structures
2Ease of operation
If conventional imaging devices include capacitive elements for signal holding and processing, then signal processing functionality is improved, but device area increases
Solution Approach 1:
The patent extracts the capacitive element function from the pixel structure and relocates it to the column circuit units. The pixels only contain photodiodes and necessary transistors for charge transfer and selection, while the column circuits contain the capacitive elements for signal holding and processing. This extraction eliminates capacitive elements from pixels, reducing pixel area while preserving signal processing functionality in the column circuits
Solution Approach 2:
The patent moves signal processing functions from the two-dimensional pixel plane to the column circuit dimension. By organizing processing elements vertically in column circuits rather than horizontally within each pixel, the design achieves signal processing capability without increasing pixel area, effectively using a different spatial dimension for processing functionality
3Measurement precision
If conventional devices process signals sequentially row by row with individual control, then signal accuracy is improved, but processing speed decreases
Solution Approach 1:
The patent merges the control of multiple pixels in the same row by using a single selection pulse for all pixels in a row. The selection transistor in each pixel shares the same gate control signal, allowing simultaneous selection and processing of entire rows. This merging of control signals enables parallel processing of multiple pixels, increasing processing speed while maintaining signal accuracy through the coordinated operation of all selected pixels
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 results in a more compact and efficient imaging device with reduced transistor count, eliminating the need for capacitive elements and enabling miniaturization while facilitating easier signal processing and matching with subsequent circuit stages.
Implementation Method 1
a charge generation unit for generating signal charges corresponding to a size of an incident electromagnetic wave
Data Source
AI summary
An imaging device and an endoscopic device can be further miniaturized. A vertical selection unit simultaneously resets charge accumulation units of a plurality of pixels, and then a horizontal selection unit sequentially selects a plurality of first pixel signals corresponding to voltages of the charge accumulation units of the plurality of pixels and inputs the first pixel signals to an output unit. Further, a vertical selection unit simultaneously transfers the signal charges generated by the charge generation units in the plurality of pixels to the charge accumulation units, and then a horizontal selection unit sequentially selects a plurality of second pixel signals corresponding to the voltages of the charge accumulation units of the plurality of pixels and inputs the second pixel signals to the output unit.