Stacked CMOS Image Sensor Segmentation for Wide Dynamic Range
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Solution Overview
Problem
Existing CMOS image sensors with global shutter function face challenges in achieving a wide dynamic range without reducing the size of the photodiode portion, leading to reduced sensitivity and longer readout times due to the need for multiple CCDs in each pixel.
Innovation Solution
The solution involves separating the photoelectric conversion unit and charge accumulation units into different chips, with the photoelectric conversion unit on a first chip and the charge accumulation, control, and readout units on a second chip, allowing for independent control and readout of charges from multiple accumulation units to generate signals for each pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple CCDs are provided in each pixel to expand dynamic range, then the dynamic range is improved, but the size of the photodiode portion is reduced and sensitivity deteriorates
Solution Approach 1:
The image sensor is divided into two separate chips: a first chip containing the photoelectric conversion units (photodiodes) and a second chip containing the charge accumulation units (CCDs). This segmentation allows the photodiode size to be maintained for high sensitivity while the CCDs on the second chip provide multiple charge accumulation capacities for expanded dynamic range.
Solution Approach 2:
The patent transitions from a planar single-chip architecture to a three-dimensional stacked multi-chip architecture. By stacking the first chip (photoelectric conversion) and second chip (charge accumulation) vertically, the patent achieves both large photodiode area for sensitivity and multiple CCDs for dynamic range expansion without lateral space constraints.
2Measurement precision
If multiple CCDs are provided in each pixel to expand dynamic range, then the dynamic range is improved, but the readout time increases
Solution Approach 1:
The patent implements simultaneous charge accumulation in multiple CCDs on the second chip while maintaining continuous operation. The control unit coordinates multiple charge transfer operations from the first chip to the second chip, allowing parallel processing of multiple charge signals without sequential delays, thus reducing overall readout time despite having multiple CCDs.
3Device complexity
If charge holding portion is disposed in each pixel of a single chip, then the structure is simplified, but the dynamic range expansion capability is limited
Solution Approach 1:
The image sensor is divided into two separate chips: a first chip containing the photoelectric conversion units (photodiodes) and a second chip containing the charge accumulation units (CCDs). This segmentation allows the photodiode size to be maintained for high sensitivity while the CCDs on the second chip provide multiple charge accumulation capacities for expanded dynamic range.
Solution Approach 2:
The patent creates a composite image sensor system integrating two different chip technologies: a first chip with photoelectric conversion units and a second chip with charge accumulation units. This composite structure combines the advantages of both chips to achieve both simplified individual unit design and enhanced overall dynamic range capability.
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 the capture of images with a wide dynamic range without reducing the photodiode size, improving sensitivity and reducing readout time by allowing for efficient charge management and signal generation across multiple CCDs.
Implementation Method 1
signal charges generated and accumulated in photoelectric conversion units of pixels
Data Source
AI summary
An image capturing apparatus comprises an image sensor and a generation unit configured to generate a signal of each of the pixels from the signals respectively read out from the plurality of charge accumulation units. The image sensor includes a plurality of pixels, each of the pixels including: a photoelectric conversion unit; a plurality of charge accumulation units for accumulating a charge generated in the photoelectric conversion unit; a control unit configured to control accumulation of charge in each of the plurality of charge accumulation units; and a readout unit configured to read out a signal corresponding to the charge from each of the plurality of charge accumulation units. The photoelectric conversion unit is formed in a first chip, and the plurality of charge accumulation units, the control unit, and the readout unit are formed in a second chip.