Aspheric Filter Lens Coating for Near-Infrared Filtering
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Solution Overview
Problem
Traditional near-infrared light filtering technologies in optical lens assemblies suffer from high transmittance differences at various angles, color shift, and increased size due to the use of multiple filters, which complicates miniaturization and increases costs.
Innovation Solution
An optical lens assembly with at least four optical lens elements, including a filter lens element with a near-infrared light filter coating membrane made of glass with aspheric surfaces. The filter coating membrane is formed by alternately stacking low and high refractive index layers, reducing the number of optical elements and effectively filtering near-infrared light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a reflecting filter and an absorbing filter are disposed between the last optical lens element and the imaging surface, then near-infrared light filtering is achieved, but the back focus length increases and the size of the optical lens assembly increases
Solution Approach 1:
The patent combines the near-infrared light filtering function with the existing optical lens elements by coating them with near-infrared reflecting films, rather than adding separate filtering components. This merging approach integrates multiple functions (optical focusing and near-infrared filtering) into a single component structure, thereby eliminating the need for additional filters that would increase the back focus length and overall assembly size.
Solution Approach 2:
The optical lens elements are designed to serve multiple functions: they focus visible light for imaging while simultaneously blocking near-infrared light through the coated surfaces. This multi-functionality allows a single component to perform both optical focusing and wavelength filtering, reducing the total number of components needed and thereby decreasing the overall size of the optical lens assembly.
2Object-affected harmful factors
If a reflecting filter is used for near-infrared light filtering, then filtering is achieved, but huge transmittance differences occur at various angles
Solution Approach 1:
The patent applies different characteristics to different parts of the optical system: the optical lens elements are designed with specific curvature and material properties optimized for visible light focusing, while the coating layers are specifically engineered with optical characteristics optimized for angle-independent near-infrared reflection. This local differentiation allows each component to perform its specialized function optimally without compromising overall system performance.
Solution Approach 2:
The patent employs composite structures combining optical lens materials with thin film coating materials. The lens elements are made from optical-grade glass or plastic with specific refractive indices for visible light transmission, while thin films of materials with high near-infrared reflectivity are coated on their surfaces. This composite approach leverages the complementary properties of different materials to achieve both visible light transmission and near-infrared blocking with uniform angular characteristics.
3Object-affected harmful factors
If an absorbing filter is used for near-infrared light filtering, then filtering is achieved, but red light of visible light is absorbed together causing color shift
Solution Approach 1:
The patent segments the optical spectrum handling by using different mechanisms for different wavelength ranges: the optical lens elements are designed to transmit visible light (including red light) through their bulk material, while separate thin film coating layers are designed to reflect near-infrared light. This segmentation of functions by wavelength allows visible light to pass through unimpeded while near-infrared light is blocked, preventing the color shift that would occur with a single absorbing filter blocking both ranges.
Solution Approach 2:
The thin film coating layers act as intermediary elements between the optical lens elements and the imaging sensor. These coating layers are specifically designed to be transparent to visible light wavelengths while being highly reflective to near-infrared wavelengths. This intermediary function allows the system to selectively block near-infrared light without affecting visible light transmission, thereby maintaining color accuracy and preventing red light absorption.
4Object-affected harmful factors
If multiple filters are used for near-infrared light filtering, then filtering performance is improved, but the number of optical elements increases and cost increases
Solution Approach 1:
The patent merges the near-infrared filtering function into the existing optical lens elements by applying thin film coatings to them, rather than adding separate filtering components. This consolidation reduces the total number of optical elements while maintaining effective near-infrared blocking performance, thereby simplifying the overall system structure and reducing manufacturing complexity and cost.
Solution Approach 2:
The optical lens elements are designed to perform multiple functions simultaneously: visible light focusing through their bulk material and near-infrared light blocking through their surface coatings. This multi-functionality eliminates the need for additional dedicated filtering elements, reducing the total component count and simplifying the optical system while maintaining comprehensive spectral control.
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
The solution reduces transmittance differences at various angles, minimizes color shift, and decreases the size of the optical lens assembly, thereby enhancing miniaturization and reducing costs while maintaining effective near-infrared light filtering.
Implementation Method 1
the filter lens element includes a near-infrared light filter coating membrane... the near-infrared light filter coating membrane includes at least one low refractive index layer and at least one high refractive index layer
Implementation Method 2
the near-infrared light filter coating membrane is formed by alternately stacking the at least one high refractive index layer and the at least one low refractive index layer
Implementation Method 3
the filter lens element has at least one aspheric surface
Implementation Method 4
a wavelength of the filter lens element at 50% transmittance of long-wavelength visible light is Wt50v... an average transmittance in a wavelength range of 700 nm-1050 nm of the filter lens element is T70105
Data Source
AI summary
An optical lens assembly includes at least four optical lens elements being, in order from an object side of the optical lens assembly to an image side thereof, a first optical lens element, a second optical lens element, a third optical lens element and a fourth optical lens element. At least one of the at least four optical lens elements is a filter lens element, the filter lens element includes a near-infrared light filter coating membrane, the filter lens element is made of a glass material, and the filter lens element has at least one aspheric surface. The near-infrared light filter coating membrane includes at least one low refractive index layer and at least one high refractive index layer, and the near-infrared light filter coating membrane is formed by alternately stacking the at least one high refractive index layer and the at least one low refractive index layer.