Optical Filter with Switchable Conductive Films for Humid Environments

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Solution Overview

Problem

Optical filters used in humid environments face fluctuations in light wavelength due to electrostatic forces caused by charged water molecules adhering to reflecting films, leading to instability in the distance between the films and subsequent variations in transmitted light wavelength, which affects their accuracy and productivity.

Innovation Solution

The optical filter design includes conductive films with exposed side surfaces and a switchable connection between them, allowing for the shorting of potential differences to maintain a consistent distance between reflecting films, preventing electrostatic forces and ensuring stable light transmission. This design also uses materials like silver for high reflectance and indium gallium oxide for protection, reducing the number of manufacturing processes and enhancing productivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the optical filter is used in humid environment, then the optical filter can operate in air containing moisture, but water molecules charge and adhere to reflecting films causing electrostatic forces that vary the distance between reflecting films, leading to wavelength fluctuation

Engineering Contradiction:
Improveoperation in humid environmentVSAvoidwavelength stability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies equipotentiality by providing a conductive film that electrically connects the first reflecting film and the second reflecting film, making them at the same electric potential. This eliminates the voltage difference between the films, preventing electrostatic forces from acting on them, and thus stabilizes the distance between the films against humid environment effects.

Inventive Principle:
Principle #12Equipotentiality

Solution Approach 2:

The conductive film acts as an intermediary element between the two reflecting films. It provides a electrical connection path that equalizes the potential of both films, mediating the interaction between the films and the humid environment by preventing charge accumulation and electrostatic force generation.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Manufacturing precision

If conventional manufacturing methods are used, then multiple processes are required to form reflecting films and conductive films separately, but this reduces productivity

Engineering Contradiction:
Improvefilm formation qualityVSAvoidmanufacturing efficiency
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The patent merges the formation of the reflecting film and the conductive film into a single simultaneous deposition process. Both films are formed at the same time in one manufacturing step, eliminating the need for separate processes and significantly improving productivity while maintaining the required film quality.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent uses a composite structure where the reflecting film and conductive film are formed together as a combined layer system. This composite approach allows both functional requirements (optical reflection and electrical conductivity) to be achieved in a single manufacturing process, improving efficiency without compromising performance.

Inventive Principle:
Principle #40Composite materials

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 maintains the accuracy of light wavelength transmission, prevents fluctuations, and increases the long-term reliability and productivity of optical filters by stabilizing the distance between reflecting films and using durable materials.

Implementation Method 1

a first conductive film disposed on a surface of the first reflecting film, the surface being opposed to the second reflecting film, in an overlapping manner, and having a light transmissive property and an electrical conductivity

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a voltage difference occurs between the reflecting films opposed to each other, and thus an electrostatic force acts between the reflecting films

Methodology Applied
Scientific EffectElectrostatic force: Electrostatics

Implementation Method 3

The optical filter has a structure having electrodes respectively disposed in the peripheries of these reflecting films, and at the same time having a diaphragm section disposed in the periphery of the reflecting film. The optical filter is capable of selectively taking out light with a wavelength corresponding to a gap between a pair of reflecting films opposed to each other

Methodology Applied
Scientific EffectOptical interference: Interference

Data Source

PatentEP2835678B1Optical filter, optical module, electronic apparatus, and method of manufacturing optical filter
Publication Date: 2021.07.21 SEIKO EPSON CORP
  • EP2835678B1 patent drawingFigure 1
  • EP2835678B1 patent drawingFigure 2A~2C
  • EP2835678B1 patent drawingFigure 3A~3B

AI summary

An optical filter includes a stationary substrate and a movable substrate disposed so as to be opposed to each other, a first reflecting film disposed on a movable substrate side of the stationary substrate, a second reflecting film disposed on a stationary substrate side of the movable substrate, and opposed to the first reflecting film, a first protective film disposed so as to overlap the first reflecting film, and having a light transmissive property and an electrical conductivity, a second protective film disposed so as to overlap the second reflecting film, and having a light transmissive property and an electrical conductivity, a first terminal to be connected to the first protective film, and a second terminal to be connected to the second protective film, and connection between the first terminal and the second terminal is electrically switched.