Shared-Counter Image Sensor with Conditional-Reset Amplifiers
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Solution Overview
Problem
Conventional CMOS image sensors have limitations such as a small dynamic range due to the linear relationship between photon strikes and pixel value, leading to saturation under brightening conditions, and pixel size is dictated by the required dynamic range, which does not scale with shrinking process geometries, resulting in inefficient use of space and performance limitations in high-end cameras.
Innovation Solution
The implementation of a binary-pixel image sensor with conditional-reset sense amplifiers and non-uniform sampling thresholds, allowing for variable temporal oversampling and spatially distributed thresholds, enabling increased dynamic range and scalability with process geometries, while sharing counter circuits among pixels for data compression and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CMOS image sensors use linear relationship between photon strikes and pixel value, then the sensor structure is simple, but the dynamic range is small and saturation occurs under brightening conditions
Solution Approach 1:
The patent applies dynamics by making the sampling interval variable rather than fixed. The counter resets conditionally based on whether the pixel value exceeds a threshold, creating adaptive sampling intervals that are short when the pixel is bright (preventing saturation) and long when the pixel is dark (maintaining sensitivity). This dynamic adjustment of sampling timing extends the dynamic range without requiring complex additional hardware structures.
Solution Approach 2:
The patent changes the parameter of sampling interval from a fixed value to a variable value that depends on the pixel's current state. By monitoring the pixel value and adjusting the sampling interval accordingly (shorter intervals for bright pixels, longer intervals for dark pixels), the system achieves extended dynamic range. The counter threshold parameter is also adjusted to optimize performance across different lighting conditions.
2Reliability
If pixel size is increased to achieve reasonable dynamic range, then the dynamic range improves, but the pixel footprint consumes area hundreds or thousands of times the minimum transistor size
Solution Approach 1:
The patent uses dynamic sampling intervals to achieve high dynamic range in small pixels. Instead of relying on large pixel area to accumulate more photons, the system dynamically adjusts how frequently it samples each pixel based on its brightness level. This allows small pixels to achieve the same effective dynamic range as much larger pixels would provide in conventional sensors.
Solution Approach 2:
The patent replaces the mechanical/approach of increasing physical pixel size with an electronic/software-based solution involving conditional counter resetting and variable sampling intervals. This substitution allows dynamic range extension through algorithmic control rather than physical scaling, enabling small pixels to achieve performance previously only attainable with large pixels.
3Area of stationary object
If pixel size is reduced to match shrinking process geometries, then the area efficiency improves, but the dynamic range becomes insufficient
Solution Approach 1:
The patent compensates for the reduced dynamic range of small pixels through dynamic sampling interval adjustment. The conditional reset mechanism detects when a small pixel approaches saturation and shortens the sampling interval accordingly, effectively extending the measurable range. This allows miniaturized pixels to maintain adequate dynamic range despite their smaller photon-collecting area.
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 the dynamic range and scalability of image sensors, allowing for higher performance in future generations of imaging devices by achieving a logarithmic sensitivity profile and increased pixel densities without the physical impediments of conventional architectures.
Implementation Method 1
the photo diode tends to be four or more micrometers at each edge in order to achieve a reasonable dynamic range
Data Source
AI summary
An image sensor generates first digital samples and second digital samples during respective first and second sampling intervals, the first digital samples including at least one digital sample of each pixel of a first plurality of pixels, and the second digital samples including at least one digital sample of each pixel of a second plurality of pixels. A sum of the first digital samples is accumulated within a first counter as the first sampling interval transpires, and a sum of the second digital samples is accumulated within the first counter as the second sampling interval transpires.