Variable Wavelength Interference Filter for Wide-Band Peak Purity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable wavelength interference filters face challenges in widening the dispersible band without introducing unintended transmittance peaks, leading to increased size or reduced light transmission.
Innovation Solution
A variable wavelength interference filter design featuring symmetrical multilayer films with six or more layers, where the optical film thicknesses are arranged symmetrically about the gap, and the reflection phase variation is limited to 120 degrees within a 700 nm wavelength band, ensuring a single transmittance peak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multilayer film designed based on multiple design wavelengths is used to widen the dispersible band, then the dispersible band becomes wider (about 600 nm), but unintended transmittance peaks appear at wavelengths close to the design wavelengths, requiring additional filtering components that increase device size or reduce light transmission
Solution Approach 1:
The patent applies parameter changes by precisely controlling the optical film thickness of each layer in the multilayer film. Specifically, the optical film thickness is designed to be λd/4 where λd is the design wavelength, and this parameter is optimized to achieve a single transmittance peak within a wide dispersible band of 600 nm or more, eliminating unintended peaks without requiring additional filtering components
Solution Approach 2:
The patent uses composite materials by constructing a multilayer film with alternating high-refractive-index layers and low-refractive-index layers. This composite structure creates interference patterns that produce a single dominant transmittance peak while maintaining a wide dispersible band, avoiding the need for multiple separate filtering layers
2Reliability
If the optical film thickness of each layer is designed to be λd/4 based on a single design wavelength, then a single transmittance peak appears at the design wavelength, but the dispersible band is limited to about 200 nm width
Solution Approach 1:
The patent applies universality by designing a multilayer film that simultaneously achieves multiple objectives: maintaining a single transmittance peak at the design wavelength while enabling a wide dispersible band of 600 nm or more. This is accomplished by optimizing the optical film thickness parameter across multiple layers to create a universal structure that works for both narrowband and wideband applications
3Reliability
If additional filtering components are added to block light at unintended transmittance peaks, then the spectral filter performance is improved, but the overall size of the spectral filter increases
Solution Approach 1:
The patent applies merging by integrating the function of blocking unintended transmittance peaks directly into the multilayer film structure itself, rather than adding separate filtering components. The optimized multilayer structure inherently eliminates unintended peaks through its interference characteristics, combining the functions of transmission and rejection in a single integrated component
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 design achieves a wider dispersible band with a single transmittance peak, preventing unintended peaks and maintaining high reflectance, suitable for use as a spectral filter.
Implementation Method 1
a multilayer film in which high-refractive index layers and low-refractive index layers are alternately stacked is used as a general reflective film
Implementation Method 2
a pair of reflective films provided to the pair of substrates and opposed to each other across a gap
Implementation Method 3
an electrostatic actuator for changing the gap. When one of the pair of substrates is displaced toward the other by the electrostatic actuator, the gap dimension between the pair of reflective films changes
Data Source
AI summary
A variable wavelength interference filter according to the present embodiment includes a first reflective film and a second reflective film opposed to each other via a gap, and an actuator section that changes the gap to thereby change a peak wavelength of transmitted light transmitted through the first reflective film and the second reflective film. Each of the first reflective film and the second reflective film is a multilayer film formed of totally six or more layers by alternately stacking high-refractive index layers and low-refractive index layers lower in refractive index than the high-refractive index layers. Optical film thicknesses of the layers constituting the first reflective film and optical film thicknesses of the layers constituting the second reflective film have respective arrangements symmetric about the gap. In a setting wavelength band in which the peak wavelength appears, and which has a width no smaller than 700 nm, a variation range of a reflection phase in each of the multilayer films of the first reflective film and the second reflective film is within 120 degrees.