Pixel Read Circuitry Analog Threshold Comparison
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Solution Overview
Problem
Existing image sensor technologies require complex two-step digitalization and memory-intensive comparison processes, limiting dynamic range and frame rate, especially when using rolling shutters with increasing resolutions.
Innovation Solution
A method and circuitry for reading pixel voltages from an image sensor that involves controlling each pixel to store and output voltage values at specific instances, comparing these values with a threshold, and generating output pixel values based on sampled values, reducing the need for multiple digitalizations and simplifying the integration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two-step digitalization and comparison process is used to increase dynamic range, then measurement precision is improved, but device complexity and processing time increase
Solution Approach 1:
The patent extracts the essential information needed for dynamic range measurement by comparing pixel voltage against a reference threshold, discarding unnecessary intermediate processing steps. Only the comparison result and selected voltage sample are retained, removing complex dual digitalization requirements while preserving dynamic range capability
Solution Approach 2:
Instead of performing full digitalization of both voltage samples and then comparing, the patent inverts the approach by performing analog comparison first against a reference threshold, then selectively digitalizing only the necessary voltage sample. This reverses the traditional processing sequence to reduce computational complexity
2Measurement precision
If two-step digitalization and memory-intensive comparison is performed to enhance dynamic range, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs the voltage threshold comparison action preliminarily in the analog domain before digitalization. By determining which voltage sample is needed based on the comparison result prior to full digital processing, the system avoids unnecessary computational steps and reduces overall processing time while maintaining dynamic range measurement accuracy
3Manufacturing precision
If rolling shutter with increasing resolution is used to capture images, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The patent applies partial action by performing only the necessary comparison and selective sampling operations rather than complete dual digitalization for all pixels. This partial processing approach maintains image quality for high-resolution rolling shutter captures while significantly reducing processing time to achieve acceptable frame rates
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 dynamic range, reduces processing time, and increases frame rate by minimizing hardware resources and fixed pattern noise, while maintaining image quality.
Implementation Method 1
Photodiodes 101 and 102 are reverse polarized, and their electrical behavior is similar to that of capacitors, allowing a voltage to be stored by them, which is discharged during an integration phase of the image sensor
Data Source
AI summary
A method of reading voltages from an image sensor having an array of pixels, each pixel Having at least one photodiode connectable to a storage node, the method including: controlling each pixel in a row of pixels to store and output a first voltage value at a first instance, a second voltage value at a second instance, and a third voltage value at a third instance, the first, second and third voltage values being representative of charge accumulated by the photodiodes during an integration phase; comparing the first voltage value from each pixel with a reference threshold; sampling for each pixel, based on the comparison, one of the second and third voltage values, and generating an output pixel value based on the sampled one of the second and third voltage values.