Toroidal Microlens for High Dynamic Range Imaging Pixels
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Solution Overview
Problem
Conventional imaging systems often produce images with artifacts due to low dynamic range, leading to overexposure or underexposure in scenes with both bright and dark portions, and combining multiple low dynamic range images to achieve high dynamic range introduces additional artifacts, especially in dynamic scenes.
Innovation Solution
The implementation of image sensors with high dynamic range pixels, utilizing toroidal microlenses or other microlens groups to direct light to multiple photosensitive areas, which mitigates cross-talk at high incident light angles and provides phase detection functionality, enabling improved light sensitivity and depth sensing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional microlenses are used in image sensors, then manufacturing is simple, but dynamic range is limited causing overexposure or underexposure artifacts
Solution Approach 1:
The image sensor divides each pixel into multiple photosensitive areas (first photosensitive area and second photosensitive area) that can independently detect light intensity. This segmentation allows different regions to capture different intensity ranges, effectively expanding the dynamic range without requiring complex external processing systems.
Solution Approach 2:
Different photosensitive areas are assigned different characteristics - the first photosensitive area is optimized for detecting higher light intensity while the second photosensitive area is optimized for detecting lower light intensity. This local differentiation of properties allows the system to handle both bright and dark regions simultaneously, resolving the over/underexposure problem.
2Illumination intensity
If multiple low dynamic range images are combined to achieve high dynamic range, then dynamic range improves, but artifacts are introduced especially in dynamic scenes
Solution Approach 1:
The system performs preliminary separation of light intensity detection by directing different intensity ranges to different photosensitive areas before any processing occurs. This pre-separation avoids the need for post-capture image combination operations that introduce artifacts, as the high dynamic range capability is achieved at the sensor level rather than through image processing.
3Use of energy by moving object
If conventional pixels are used, then device complexity is low, but light sensitivity is insufficient for high dynamic range imaging
Solution Approach 1:
The invention extends the light detection capability from a single-plane conventional pixel to a multi-layer structure with photosensitive areas at different depths. By utilizing the vertical dimension within the pixel, the system achieves enhanced light sensitivity and dynamic range without significantly increasing the horizontal footprint or overall device 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 solution enhances the dynamic range of image sensors, reducing artifacts and improving light sensitivity, allowing for effective imaging in both low and high light environments while maintaining cost efficiency through integrated circuit design.
Implementation Method 1
Toroidal microlenses or other microlens groups may be used to direct light to the two or more photosensitive areas
Implementation Method 2
The toroidal microlenses may be shaped to direct light to the corners of the pixel to mitigate cross-talk at high incident light angles
Implementation Method 3
Each pixel receives incident photons (light) and converts the photons into electrical signals
Data Source
AI summary
An image sensor may include high dynamic range imaging pixels having an inner sub-pixel surrounded by an outer sub-pixel. To steer light away from the inner sub-pixel and towards the outer sub-pixel, the high dynamic range imaging pixels may be covered by a toroidal microlens. To mitigate cross-talk caused by high-angled incident light, various microlens arrangements may be used. A toroidal microlens may have planar portions on its outer perimeter. A toroidal microlens may be covered by four additional microlenses, each additional microlens positioned in a respective corner of the pixel. Each pixel may be covered by four microlenses in a 2×2 arrangement, with an opening formed by the space between the four microlenses overlapping the inner sub-pixel.