Optical Filter Polarization Dependence Suppression
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Solution Overview
Problem
Conventional optical filters used in solid-state image sensing devices suffer from significant polarization dependence during oblique incidence, leading to poor color reproducibility and increased transmittance at wavelengths near 700 nm and 1150 nm, which affects the precision of color reproduction and noise sensitivity.
Innovation Solution
An optical filter design incorporating an absorption layer with specific near-infrared absorbents and a dielectric multilayered reflection layer, optimized to minimize polarization dependence by carefully positioning transmittance curves and reflection bands, ensuring low transmittance at oblique angles and reducing noise sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric multilayered film is used to cut-off ultraviolet and infrared light, then the optical filter can block near-infrared light effectively, but the spectral transmittance curve changes with incident angle causing polarization dependence
Solution Approach 1:
The patent changes the optical parameters of the dielectric multilayered film by adjusting film thicknesses and refractive indices to minimize the shift in spectral transmittance curve with incident angle. Specifically, the optical film thicknesses are designed to satisfy specific relationships that compensate for angle-dependent shifts, thereby reducing polarization dependence while maintaining near-infrared blocking performance
Solution Approach 2:
The patent uses a composite structure combining a dielectric multilayered film with specific optical properties and an absorption layer. The dielectric multilayered film is composed of multiple layers with different refractive indices, and its optical characteristics are engineered to work synergistically with the absorption layer to achieve both effective near-infrared blocking and minimized polarization dependence
2Illumination intensity
If the absorption layer contains near-infrared absorbing dye, then visible light transmission is maintained, but transmittance increases at critical wavelengths (700 nm and 1150 nm) affecting color precision
Solution Approach 1:
The patent applies local quality by creating specific transmittance characteristics at different wavelength regions. The optical filter is designed to have high transmittance in the visible region (400-700 nm) while maintaining low transmittance at critical wavelengths (700 nm and 1150 nm). This is achieved by optimizing the absorption layer composition and the dielectric multilayered film structure to provide wavelength-selective filtering properties
Solution Approach 2:
The patent uses feedback in the design process by iteratively optimizing the optical film thicknesses and material properties based on the desired spectral transmittance characteristics. The design parameters are adjusted according to the observed shifts in spectral transmittance curves at different incident angles, ensuring that transmittance remains low at critical wavelengths while maintaining high visible light transmission
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 effectively suppresses polarization dependence and transmittance increases at critical wavelengths, enhancing color reproducibility and reducing noise in solid-state image sensing devices.
Implementation Method 1
an absorption layer containing a near-infrared absorbent having a maximum absorption in a wavelength of 660 to 785 nm
Implementation Method 2
a reflection layer formed of a dielectric multilayered film which cuts-off light in an ultraviolet wavelength region and an infrared wavelength region
Data Source
AI summary
An optical filter includes: an absorption layer containing a first near-infrared absorbent having a maximum absorption in a wavelength of 660 to 785 nm, and satisfying (i-1) in 620 to 670 nm, on a shorter wavelength side of a wavelength λ (DA_Tmin) exhibiting the maximum absorption, there is a wavelength λSh (DA_T50%) at which a transmittance becomes 50%; and a reflection layer formed of a dielectric multilayered film satisfying (ii-1) in 670 to 1200 nm, there is a near-infrared reflection band in which a transmittance with respect to light at an incident angle of 0° becomes 50% or less, and a wavelength λSh (A2_Ts50%) at which a transmittance of light of an s polarization component out of light at an incident angle of 30° becomes 50%, on a shorter wavelength side of the near-infrared reflection band, is positioned on a longer wavelength side of the wavelength λSh (DA_T50%).