Shared Floating Diffusion Pixel Layout for HDR and Parallax Imaging
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Solution Overview
Problem
Current imaging devices face challenges in acquiring high dynamic range images and parallax information with minimal memory configuration, particularly when dealing with pixels of different sensitivities, leading to increased circuit scale and power consumption.
Innovation Solution
The configuration of an imaging device where multiple photoelectric conversion units share a floating diffusion unit, allowing charges from different sensitivity photoelectric conversion units to be read from distinct floating diffusion units, enabling simultaneous acquisition of images with varying sensitivities without the need for memory retention during HDR synthesis and distance measurement processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If multiple photoelectric conversion units share one floating diffusion unit, then the photosensitive area is increased, but the reading operation becomes complex requiring multiple read operations and memory accumulation
Solution Approach 1:
The patent divides the pixel structure by providing separate floating diffusion units for different photoelectric conversion units. Specifically, first photoelectric conversion units have first floating diffusion units, while second photoelectric conversion units have second floating diffusion units, allowing independent charge reading without complex sharing mechanisms.
Solution Approach 2:
Each floating diffusion unit is designed to handle multiple functions: charge accumulation, charge reading, and signal amplification. This multi-functionality simplifies the overall circuit structure by eliminating the need for separate memory accumulation circuits that would otherwise be required when sharing floating diffusion units.
2Area of moving object
If charges are read from the same floating diffusion unit, then the photosensitive area is maximized, but memory capacity increases due to signal accumulation requirements
Solution Approach 1:
The patent segments the charge reading paths by providing distinct floating diffusion units for different photoelectric conversion units. This segmentation allows parallel charge reading without the need to accumulate signals in memory, thereby reducing memory capacity requirements while maintaining maximum photosensitive area.
3Measurement precision
If multiple imaging devices are used for distance measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple photoelectric conversion units with different sensitivities within a single imaging device. By having first photoelectric conversion units with high sensitivity and second photoelectric conversion units with low sensitivity under the same microlens array, the device can perform both high dynamic range imaging and parallax-based distance measurement using a single integrated structure.
Solution Approach 2:
The imaging device is designed with multi-functionality to perform both HDR imaging and distance measurement simultaneously. The presence of photoelectric conversion units with different sensitivities allows the same device to capture images across different brightness ranges while also enabling parallax calculation for depth perception, eliminating the need for separate imaging devices.
4Illumination intensity
If photoelectric conversion unit area is increased for low light sensitivity, then low light performance is improved, but saturation occurs more easily in high light conditions
Solution Approach 1:
The patent applies local quality by creating different photoelectric conversion units with different sensitivities in different locations within the pixel array. First photoelectric conversion units have high sensitivity for low light conditions, while second photoelectric conversion units have low sensitivity to prevent saturation in high light conditions. Each unit is optimized for its specific function based on local requirements.
Solution Approach 2:
The patent segments the photoelectric conversion function into multiple units with different characteristics. By dividing the pixel into first photoelectric conversion units (high sensitivity) and second photoelectric conversion units (low sensitivity), the system can simultaneously capture both low light and high light scenes without either unit suffering from its respective limitation.
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 reduces the memory required for digital signal retention, enhances circuit efficiency, and minimizes power consumption while enabling the simultaneous acquisition of high dynamic range and parallax images.
Implementation Method 1
a plurality of photoelectric conversion units share a floating diffusion unit, allowing charges from different sensitivity photoelectric conversion units to be read
Data Source
AI summary
An imaging device includes pixels each of which includes a microlens and a plurality of photoelectric conversion units. The pixels include a first pixel and a second pixel adjacent to the first pixel, a first photoelectric conversion unit included in the first pixel and a second photoelectric conversion unit included in the second pixel are configured to share a first floating diffusion unit, sensitivity of the second photoelectric conversion unit is lower than sensitivity of the first photoelectric conversion unit in a wavelength range in which the first photoelectric conversion unit has a peak of the sensitivity, and a charge of a photoelectric conversion unit other than the first photoelectric conversion unit and the second photoelectric conversion unit is read from a floating diffusion unit different from the first floating diffusion unit in each of the first pixel and the second pixel.