Optical Filter with Light-Absorbing Material for Incident Angle Stability
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Solution Overview
Problem
Existing optical filters do not have sufficient transmittance for near-infrared light around 850 nm and are affected by incident angle changes, leading to spectral sensitivity issues in solid state image sensors.
Innovation Solution
An optical filter configuration using a light-absorbing material Y900-1000 with a maximum absorption wavelength between 900 nm to 1,000 nm, combined with a dielectric multilayer film, to achieve excellent transmittance in visible and specific near-infrared light regions while providing effective shielding in the near-infrared region, even at high incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dielectric multilayer film is used to achieve spectral selectivity, then transmission and shielding characteristics can be controlled, but the spectral transmittance curve shifts depending on the incident angle
Solution Approach 1:
The patent combines a dielectric multilayer film with a light-absorbing material layer to create a composite optical filter. The dielectric multilayer film provides spectral selectivity through interference effects, while the light-absorbing material layer compensates for incident angle dependence by absorbing stray light and stabilizing the spectral characteristics across different angles of incidence.
Solution Approach 2:
The optical filter uses a composite structure consisting of a dielectric multilayer film and a light-absorbing material layer. This composite design allows the filter to achieve both precise spectral control (through the dielectric layers) and incident angle stability (through the light-absorbing material), resolving the contradiction between manufacturing precision and reliability.
2Measurement precision
If an optical filter transmits near-infrared light around 850 nm, then sensor detection capability is improved, but transmittance for this region is insufficient
Solution Approach 1:
The patent optimizes the optical parameters of the dielectric multilayer film, including layer thicknesses and refractive indices, to enhance transmittance in the 850 nm near-infrared region. By carefully controlling these parameters, the filter achieves high transmittance (60% or more) at the target wavelength while maintaining spectral selectivity and incident angle stability.
3Object-affected harmful factors
If the optical filter shields near-infrared light around 940 nm, then stray light from 3D sensing devices is reduced, but transmittance in the 800 nm to 1,000 nm sensing region must be maintained
Solution Approach 1:
The optical filter exhibits different optical properties at different wavelengths: it provides high transmittance in the 800-850 nm sensing region while providing strong shielding in the 940 nm region. This local quality variation is achieved through the dielectric multilayer structure designed with specific optical thicknesses and refractive indices that create wavelength-dependent transmission characteristics.
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 achieves excellent transmittance in visible and near-infrared light regions, maintains effective shielding in specific near-infrared light regions, and minimizes spectral curve shifts at high incident angles, enhancing color reproducibility and image quality in imaging devices.
Implementation Method 1
a light-absorbing material Y900-1000 having a maximum absorption wavelength in a wavelength region of 900 nm to 1,000 nm
Implementation Method 2
a dielectric multilayer film... an optical film thickness of the dielectric multilayer film changes depending on an incident angle of light
Implementation Method 3
as the incident angle of light increases, reflection characteristics shift to a short wavelength side
Data Source
AI summary
The present invention pertains to an optical filter including: a light-absorbing material Y900-1000 having a maximum absorption wavelength in a wavelength region of 900 nm to 1,000 nm, and a dielectric multilayer film, in which the optical filter satisfies all of spectral characteristics (i-1) to (i-6), and the optical filter may satisfy spectral characteristic (i-7).