Oversampled Pixel Comparison for Dense Image Sensor Arrays
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Solution Overview
Problem
As photo detector arrays become denser, the smaller area available for capacitors in each cell site leads to degraded dynamic range and performance due to the need for smaller capacitance values, making it challenging to accommodate increasingly dense arrays.
Innovation Solution
A noise source is used to compare with the analog electrical output from a photo sensor, generating a binary digital output, which is counted and stored to represent the light impinging on the sensor, eliminating the need for capacitors and A/D converters at each cell site, and allowing for dynamic gain control through resistor selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photo detector arrays are made denser to achieve finer image resolution, then image resolution is improved, but the area available for capacitors in each cell site decreases
Solution Approach 1:
The patent extracts and removes the capacitor component from the pixel cell structure. Instead of integrating a capacitor at each pixel site to store charge, the invention uses a different approach where pixels directly output digital signals through a noise source and comparator mechanism, eliminating the need for on-pixel capacitor storage and enabling denser array packing.
Solution Approach 2:
The patent replaces the traditional capacitor-based charge storage mechanism with an electronic signal processing approach using noise sources, comparators, and digital counters. This substitution transitions from a passive electrical storage element (capacitor) to an active digital signal generation and counting system, allowing for more compact cell designs.
2Area of stationary object
If capacitor size is reduced to accommodate denser arrays, then area requirements are met, but dynamic range and processing performance degrade
Solution Approach 1:
The patent changes the fundamental operating parameters of the pixel by introducing a noise source with a specific frequency (over-sampling ratio times the frame rate) and using a comparator to generate binary outputs. This parameter change enables the system to achieve adequate dynamic range through digital signal processing and averaging rather than relying on large capacitor values for charge storage.
Solution Approach 2:
The patent employs periodic action through the noise source that operates at a frequency equal to the over-sampling ratio times the frame rate. This periodic noise signal is compared with the pixel output during multiple times per frame, and the binary outputs are counted to reconstruct the analog signal with improved dynamic range and signal-to-noise ratio through oversampling.
3Ease of manufacture
If traditional capacitor-based digitization is used, then analog current is converted to digital signal, but device complexity increases due to required capacitors and A/D converters at each cell site
Solution Approach 1:
The patent extracts and removes the A/D converter component from each pixel cell. Instead of implementing a full analog-to-digital conversion process requiring capacitors and complex circuitry at each pixel, the invention uses a simplified approach with a noise source, comparator, and digital counter that directly outputs digital signals, significantly reducing per-pixel complexity.
Solution Approach 2:
The patent uses a noise source that generates a replicated noise signal for comparison with the pixel output. This noise copying approach allows the system to encode the analog pixel signal into a digital format through statistical analysis of the binary comparison outputs, avoiding the need for traditional A/D conversion hardware at each pixel.
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 enables efficient processing of dense photo detector arrays by maintaining performance and reducing area requirements, while allowing for automatic gain control to prevent overflow and ensure accurate light detection.
Implementation Method 1
an electronic light processing cell uses a photo sensor unit to provide an analog electrical output proportional to an amount of light impinging on the photo sensor
Data Source
AI summary
An exemplary electronic light processing cell uses a photo sensor unit to provide an analog electrical output proportional to an amount of light impinging on the photo sensor. A noise source provides a noise output that is compared by a comparator, during a plurality of times during a frame of an image, with the analog electrical output to generate a binary digital output representative of each comparison. A digital counter counts the binary digital outputs during the frame and stores a count at the end of a frame where the value of the stored count is proportional the light impinging the photo sensor. The value of the stored count is adapted for use by an image processing unit to render an image.