Vehicular Camera Microlens Array with Gradient Refractive Index
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Solution Overview
Problem
Conventional microlens arrays in vehicular cameras suffer from issues such as multi-reflections, diffractive effects, multi-order scattering, and visible glare dots, especially in 3D grating structures, which affect image quality and are difficult to coat with antireflective coatings.
Innovation Solution
The use of a microlens array with a gradient refractive index, where each microlens has a planar surface and a varying refractive index across its surface, allowing for efficient focusing of light without a curved surface, thereby reducing aberrations and enabling easier application of antireflection coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional 3D grating microlens array is used, then light focusing capability is achieved, but multi-reflections, diffractive effects, multi-order scattering, and visible glare dots occur affecting image quality
Solution Approach 1:
The patent changes the refractive index parameter from uniform to gradient distribution within the microlens material. This gradient refractive index (GRIN) structure modifies the light propagation path to reduce diffractive effects and multi-order scattering while maintaining focusing capability, thereby improving image quality by eliminating harmful optical artifacts
Solution Approach 2:
The patent employs composite material structure combining planar surface geometry with gradient refractive index material properties. This composite approach integrates the simplicity of planar surfaces (easy to coat with antireflective coatings) with the optical benefits of GRIN materials (reduced diffractive effects), resolving the contradiction between manufacturing ease and optical performance
2Reliability
If microlenses with curved surfaces are used, then light focusing is achieved, but antireflective coatings are difficult to apply
Solution Approach 1:
The patent changes the geometric parameter of the microlens surface from curved to planar. This planar surface geometry provides a uniform substrate that is much easier to coat with antireflective coatings compared to curved surfaces, while the gradient refractive index internally compensates for the lack of surface curvature in light focusing capability
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 image quality by reducing diffractive effects, multi-order scattering, and glare, while allowing for more efficient light bundling and increased quantum efficiency, thus improving the overall performance of vehicular cameras.
Implementation Method 1
Each individual microlens of the plurality of microlenses includes a respective plurality of refractive indices. Light incident at and passing through each individual microlens of the microlens array is incident at a respective sub-array of the photosensors
Data Source
AI summary
A vehicular camera includes an imaging array sensor and a microlens array that includes a plurality of microlenses disposed at the imaging array sensor. Each individual microlens is associated with a respective sub-array of photosensors of the imaging array sensor and has a respective plurality of refractive indices. The microlens array is disposed at the imaging array sensor so that light incident at the vehicular camera passes through the microlens array to be incident at the imaging array sensor. Light incident at and passing through each individual microlens is incident at the respective sub-array of the photosensors. A focus length of at least one microlens of the plurality of microlenses is different from a focus length of at least one other microlens of the plurality of microlenses. The vehicular camera is configured to be disposed at a vehicle equipped with a vehicular vision system.