Optical Filter Angle-Dependent Color Shift Reduction
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Solution Overview
Problem
Conventional optical filters for CMOS sensors suffer from color differences due to varying angles of incidence, leading to distorted images, especially in high-pixel-density imaging devices like cameras with BSI-type CMOS sensors.
Innovation Solution
An optical filter with a light absorption layer and a near-infrared reflection layer, where the light absorption layer has an absorption maximum in the 670 to 720 nm range and the near-infrared reflection layer has 50% transmittance in the 690 to 720 nm range, is designed to minimize color differences by controlling the ΔE* value to ≤1.5, ensuring consistent color reproduction across different angles of incidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical filter is used, then the CMOS sensor can block infrared light, but the transmission spectrum shifts with angle of incidence causing color distortion
Solution Approach 1:
The patent optimizes specific parameters of the optical filter including the absorption maximum wavelength (670-720 nm) and the 50% transmittance wavelength of the near-infrared reflection layer (690-720 nm). By precisely controlling these wavelength parameters and the thickness of each layer, the filter maintains consistent transmission characteristics across different angles of incidence, resolving the color distortion issue while preserving infrared blocking capability
Solution Approach 2:
The optical filter employs a composite structure combining a light absorption layer and a near-infrared reflection layer. This multi-layer composite design allows the filter to simultaneously achieve broadband infrared rejection and maintain stable visible light transmission across varying angles, preventing color distortion while blocking infrared wavelengths
2Reliability
If the optical filter blocks all infrared light, then infrared distortion is prevented, but visible light transmittance decreases reducing image quality
Solution Approach 1:
The optical filter is segmented into distinct functional layers: a light absorption layer that handles visible light wavelength selection and a near-infrared reflection layer that specifically targets infrared wavelengths. This segmentation allows each layer to be optimized independently - the absorption layer maintains high visible light transmittance while the reflection layer provides selective infrared blocking, achieving both goals simultaneously
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 optical filter effectively prevents shifts in transmission spectra due to angle changes, maintaining high transmittance in the visible region while minimizing infrared transmittance, thus ensuring accurate color reproduction and reducing image distortion recognizable by the human eye.
Implementation Method 1
the light absorption layer has an absorption maximum in a wavelength range of 670 to 720 nm
Implementation Method 2
a wavelength at which the near-infrared reflection layer has a light transmittance of 50% is in a range of 690 to 720 nm
Data Source
AI summary
An optical filter comprising a light absorption layer and a near-infrared reflection layer, and an imaging device comprising the optical filter are provided. Wherein the light absorption layer has an absorption maximum in a wavelength range of 670 to 720 nm, a wavelength at which the near-infrared reflection layer has a light transmittance of 50% is in a range of 690 to 720 nm, and the optical filter satisfies the following Mathematical Formula 1:ΔE*≤1.5 [Mathematical Formula 1]wherein the ΔE* value represents a color difference between light that is incident in a vertical direction of the optical filter and passes through the optical filter and light that is incident at an angle of 30° with respect to the vertical direction of the optical filter and passes through the optical filter.