Pseudo-Digital Image Subsampling With Low-Resolution ADC Averaging
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Solution Overview
Problem
Current image subsampling techniques, such as analog and digital averaging, face challenges including increased routing complexity, color distortion, and the need for additional memory, particularly in digital averaging.
Innovation Solution
A pseudo-digital averaging method and apparatus that performs subsampling in the analog domain using individual signal quantization without final total quantization, allowing for a higher frame rate and reduced color distortion, achieved through k*k subsampling and correlated double sampling, with signals converted and added at lower resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital averaging is used for subsampling, then quantization precision is improved, but device complexity and memory requirements increase
Solution Approach 1:
The patent divides the pixel array into multiple color filter sets (e.g., first color, second color, third color pixels) and processes each set separately through dedicated sampling and conversion paths. This segmentation allows quantization to be applied to individual color channels independently, reducing the overall complexity compared to processing all pixels through a single digital averaging path while maintaining quantization precision for each color component.
Solution Approach 2:
The patent extracts and processes different color components through separate analog-to-digital conversion paths before combining them. By taking out each color set and converting it to digital signals independently at lower resolution, the system avoids the need to read and store all full-resolution bits in memory, thereby reducing memory requirements while maintaining measurement precision through subsequent digital addition and averaging.
2Device complexity
If analog averaging is used for subsampling, then device complexity is reduced, but color distortion increases due to different sampling timings
Solution Approach 1:
The patent introduces an intermediary digital conversion stage for each color set that acts as a mediator between analog sampling and final digital averaging. Each color component is converted to digital signals through dedicated ADCs with synchronized timing, eliminating the color distortion caused by asynchronous sampling while keeping the analog routing simple. The digital addition stage then performs the averaging function without the timing issues that plague pure analog averaging approaches.
3Measurement precision
If full resolution reading is performed for all pixels, then measurement precision is maintained, but productivity decreases due to increased data processing requirements
Solution Approach 1:
The patent applies partial action by performing analog-to-digital conversion at lower resolution for each color set rather than converting all pixels at full resolution. The system subsamples by processing k rows at a time and combining results, which reduces the total number of high-precision conversions needed. This partial processing approach maintains sufficient measurement precision for the final image while significantly improving productivity by reducing the data processing burden.
Solution Approach 2:
The patent performs preliminary analog sampling and holding of multiple rows before digital conversion, and conducts lower-resolution conversion for intermediate results. This preliminary action allows the system to prepare data in an optimized format before final full-resolution reconstruction, enabling faster processing rates while maintaining the ability to produce high-quality output images through subsequent digital addition and averaging operations.
Data Source
AI summary
A method of k*k subsampling, where k is an integer greater than one, a full frame readout on a plurality of pixels arranged in rows and columns, each pixel belonging to one of at least two sets, a first set configured to sense a first value of an image parameter and a second set configured to sense a second value of the image parameter, the method including sampling signals of k pixels of at least one set in a first row to output subsampled signals, converting the subsampled signals into digital signals having a lower resolution than the full frame readout, repeating sampling and converting for k rows, and adding digital signals for the first to kth rows within the at least one set.