Image Sensor Microlens Flat Surface Refraction Light Focusing
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Solution Overview
Problem
Conventional CMOS-type image sensors face challenges in maximizing light intensity focused on photosensitive areas due to limitations in microlens formation and separation regions, which reduces sensor sensitivity and requires additional conformal deposition to improve focusing, but this complicates control of curvature and accuracy.
Innovation Solution
Incorporating refringent surfaces with different refractive coefficients, inclined with respect to the exposition surface, to deviate light beams from peripheral regions towards photosensitive areas, in conjunction with microlenses, to optimize light focusing and reduce separation region width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If microlenses are formed by heating resin blocks to create convex external surfaces for optimal light focusing, then light focusing efficiency is improved, but separation regions must be maintained between microlenses which reduces the exposition surface area and requires additional conformal deposition steps that complicate curvature control
Solution Approach 1:
The patent changes the geometric parameters of the microlens by forming it with a flat external surface instead of a convex surface. This parameter change eliminates the need for conformal deposition while maintaining effective light focusing, thereby reducing manufacturing complexity without sacrificing illumination intensity.
Solution Approach 2:
The patent extracts the conformal deposition step from the manufacturing process by designing a microlens whose flat external surface inherently provides the necessary optical function. This removes the complex curvature control requirements associated with conformal deposition while maintaining light focusing efficiency.
2Area of stationary object
If separation regions are reduced to minimum width to increase exposition surface area, then sensor sensitivity is improved, but control of microlens curvature becomes more difficult and accuracy decreases
Solution Approach 1:
The patent changes the surface geometry parameter of the microlens from convex to flat. This parameter change allows separation regions to be minimized or eliminated entirely, maximizing exposition surface area while the flat geometry inherently simplifies curvature control and maintains manufacturing accuracy.
3Illumination intensity
If additional conformal deposition is performed to improve light focusing, then illumination intensity on photosensitive areas is improved, but the radius of curvature control becomes less accurate and device complexity increases
Solution Approach 1:
The patent extracts the conformal deposition step from the manufacturing process by designing a microlens whose flat external surface inherently provides the necessary optical function. This removes the source of curvature control inaccuracies while maintaining effective light focusing onto the photosensitive area.
Solution Approach 2:
The patent changes the microlens external surface parameter from curved to flat. This parameter change eliminates the conformal deposition process, thereby removing the associated curvature control accuracy issues while maintaining illumination intensity through the flat surface geometry.
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 ensures that almost all light reaching the exposition surface is directed towards the photosensitive area, enhancing sensor sensitivity by improving light focusing efficiency and reducing the need for thick microlenses, thus simplifying curvature control and increasing sensor performance.
Implementation Method 1
Incorporating refringent surfaces with different refractive coefficients, inclined with respect to the exposition surface, to deviate light beams from peripheral regions towards photosensitive areas
Implementation Method 2
a microlens 29, 30 is arranged on equalizing layer 27, opposite to photosensitive area 14, 16 to focus the light beams towards photosensitive area 14, 16
Data Source
AI summary
An image sensor includes a substrate, transparent layers covering the substrate and delimiting an exposition surface exposed to light, separate photosensitive areas at the substrate level and, for each photosensitive area, a first optical means capable of deviating towards the photosensitive area light reaching a central region of a portion of the exposition surface. The sensor further includes, for each photosensitive area, a second optical means, separate from the first optical means, capable of deviating towards the photosensitive area light reaching a peripheral region of the portion of the exposition surface surrounding the central region.