Image Sensor Spatial Integration Control
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Solution Overview
Problem
Current semiconductor-based image sensors have limited dynamic range due to saturation of pixels in bright areas and high noise levels, leading to loss of image details and poor sensitivity, especially in CMOS devices with active and passive components.
Innovation Solution
Implementing separate integration times for different spatial patterns in the image sensor array, using separate transfer gates or reset gates for CMOS sensors and separate transfer gates for CCD sensors, allowing for programmable integration times that extend the dynamic range by maintaining valid data in both dark and bright regions through interpolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a single integration time is used for all pixels, then the device complexity is low, but the dynamic range is limited due to saturation in bright areas and insufficient signal in dark areas
Solution Approach 1:
The image sensor array is divided into multiple regions with different integration times. Specifically, first and second regions are defined with different integration times (first and second integration times respectively), allowing simultaneous capture of both bright and dark areas without saturation or insufficient signal. This spatial segmentation resolves the contradiction by enabling extended dynamic range while maintaining manageable device complexity through region-based control.
2Measurement precision
If longer integration time is used to improve sensitivity in dark areas, then signal-to-noise ratio improves, but bright areas become saturated and lose detail
Solution Approach 1:
Different regions of the image sensor are assigned different integration times based on local illumination conditions. The first region uses a first integration time optimized for its illumination level, while the second region uses a second integration time optimized for its different illumination level. This local optimization allows each region to achieve appropriate signal-to-noise ratio without causing saturation in other regions, thereby preserving image details across the entire dynamic range.
3Stress or pressure
If multiple integration times are implemented for different regions, then dynamic range is extended, but the device complexity increases due to additional control circuits
Solution Approach 1:
The sensor is segmented into distinct regions (first and second regions) with different integration times, allowing extended dynamic range capture. The segmentation approach enables controlled complexity by dividing the sensor into manageable regions rather than requiring individual control for each pixel, thus extending dynamic range while keeping control circuit complexity at an acceptable level.
Solution Approach 2:
The integration time is made dynamic and region-dependent rather than uniform across the entire sensor. By implementing different integration times for different regions based on local illumination requirements, the system achieves extended dynamic range while the dynamic control mechanism is managed through region-based assignment rather than pixel-by-pixel control, balancing performance with complexity.
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 effectively extends the dynamic range and sensitivity of the image sensor, preserving image content in high-light regions while maintaining low fixed pattern noise, allowing for a single frame capture with spatially adaptive image processing and simplified exposure control.
Implementation Method 1
All are basically comprised of a set or array of photodetectors that convert incident light into an electrical signal that can be readout and used to construct an image correlated to the incident light pattern
Data Source
AI summary
An image sensor includes a plurality of pixels; a color filter pattern spanning at least a portion of the pixels, wherein the color filter pattern forms a color filter kernel having colors in a predetermined arrangement; and a mechanism for controlling integration time of the pixels, wherein the integration time of the plurality of pixels is spatially variant in a pattern that is correlated with the color filter array kernel.