Variable Wavelength Interference Filter Substrate Design
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Solution Overview
Problem
Variable wavelength interference filters face a challenge in maintaining high resolving power due to substrate bending caused by internal stress from driving electrodes, particularly when these electrodes are formed on low-rigidity portions, leading to decreased precision in light transmission.
Innovation Solution
The design includes a second substrate with a movable portion and a connection maintaining portion of lower thickness, where the second electrode is placed on a thicker portion, avoiding internal stress on the connection maintaining portion, and optionally using an anti-bending film to counteract compressive stress, thereby reducing substrate bending and improving resolving power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the driving electrode is formed on the low-rigidity portion of the substrate, then the flatness of the reflective film is secured through transformation of the low-rigidity portion, but the substrate bends due to internal stress of the driving electrode, causing the reflective film to bend and decreasing the resolving power
Solution Approach 1:
The substrate is divided into a low-rigidity portion (where the driving electrode is formed and can transform to maintain reflective film flatness) and a high-rigidity portion (where the connection maintaining portion is formed to prevent substrate bending). This segmentation allows different regions to serve different functions: one region accommodates the necessary transformation for flatness while the other region maintains structural stability to prevent bending and preserve resolving power.
Solution Approach 2:
Different portions of the substrate are given different rigidity characteristics. The low-rigidity portion allows transformation to maintain reflective film flatness, while the high-rigidity portion resists bending to maintain resolving power. The connection maintaining portion is specifically designed with higher rigidity to counteract the bending tendency caused by internal stress in the driving electrode.
2Adaptability or versatility
If the gap interval is adjusted by applying driving voltages to control light transmission wavelength, then the variable wavelength function is achieved, but high voltage consumption occurs due to the need for precise gap control
Solution Approach 1:
The connection maintaining portion is pre-formed during substrate fabrication to establish a stable structural foundation that resists bending. This preliminary structural preparation reduces the amount of voltage needed during operation to maintain the desired gap interval, as the high-rigidity portion provides passive support that counteracts internal stress without requiring continuous active 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
This configuration reduces substrate bending, enhances the resolving power of the variable wavelength interference filter, allows for precise control of the gap interval with lower voltage consumption, and improves the responsiveness of the reflective film.
Implementation Method 1
driving electrodes are arranged on the faces of two substrates so as to face each other, and, by applying driving voltages to the driving electrodes, a gap interval can be adjusted in accordance with an electrostatic attractive force
Implementation Method 2
variable wavelength interference filter that selects and outputs light of a desired target wavelength from incident light
Implementation Method 3
reflective films are arranged on the opposing faces of two substrates so as that the reflective films face each other across a gap
Data Source
AI summary
A variable wavelength interference filter includes: a first reflective film disposed on a face of a first substrate facing a second substrate; a second reflective film disposed on a face of the second substrate facing the first substrate and the first reflective film; a first electrode disposed on the face of the first substrate; and a second electrode disposed on the face of the second substrate. The second substrate includes a movable portion on which the second reflective film is disposed and a connection maintaining portion maintaining the movable portion to be movable in a substrate thickness direction, the connection maintaining portion circumscribes the movable portion and is thinner than the movable portion, and the second electrode is disposed on a portion of the second substrate that is thicker than the connection maintaining portion.