Diagonal Binning in HDR Pixel Arrays
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Solution Overview
Problem
CMOS image sensors face challenges with reduced pixel photosensitivity and dynamic range due to miniaturization, leading to irregular spacing between optical centers during pixel binning, which results in jagged lines and lower image resolution.
Innovation Solution
The configuration of four pixel cells under a shared microlens and color filter, with signals combined along diagonals during readout, reduces spatial color artifacts and minimizes irregular spacing between optical centers, improving image resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel binning is performed to increase sensitivity and reduce readout time, then light collection efficiency improves, but irregular spacing between optical centers produces jagged lines and reduces image resolution
Solution Approach 1:
The patent applies asymmetric binning by configuring pixels in a 2x2 block structure where diagonal pixels (top-left with bottom-right, top-right with bottom-left) are paired for signal summation. This asymmetric diagonal pairing arrangement ensures that the combined optical centers remain regularly spaced throughout the sensor array, preventing the jagged line artifacts that would result from conventional orthogonal binning while maintaining reduced readout time and improved light collection efficiency
2Manufacturing precision
If pixel size is reduced to increase sensor resolution, then pixel density increases, but photosensitivity and dynamic range are lost
Solution Approach 1:
The patent merges signals from multiple individual pixels by organizing them into 2x2 blocks and summing the signals from diagonally paired pixels. This merging approach effectively creates larger virtual pixels with enhanced photosensitivity and dynamic range while maintaining the physical density of smaller pixels, thereby resolving the contradiction between high resolution and adequate light sensitivity
3Loss of time
If orthogonal binning is used to combine pixel signals, then readout time decreases, but spatial color artifacts and irregular spacing between optical centers occur
Solution Approach 1:
The patent employs asymmetric diagonal pairing within 2x2 pixel blocks, where pixels are paired along diagonal axes rather than orthogonal rows or columns. This diagonal asymmetry ensures that when signals are summed, the resulting optical centers maintain regular spacing patterns that prevent spatial color artifacts and jagged line distortions, while still achieving reduced readout time through the binning operation
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 enhances image quality by maintaining a single optical center during binning, resulting in improved resolution and reduced jagged lines, compared to orthogonal binning schemes.
Implementation Method 1
Each pixel cell may have one or more photodiodes... the image sensor converts the light into electrical signals
Implementation Method 2
each pixel is overlaid with a monochromatic color filter which is in turn overlaid with a microlens to focus light on to a photodiode
Data Source
AI summary
An image sensor has a pixel cell array comprising clusters of pixel cell blocks each block having four pixel cells under the same microlens and filter wherein during readout electrical signals from two pixels positioned along a first diagonal are binned followed by binning the signals from two pixels positioned along the remaining second reverse diagonal in order to reduce spatial color artifacts associated with orthogonal binning schemes and minimize gaps or irregular spacing between optical centers within an image read out from the array of pixel cells.