Wavelength Variable Interference Filter Charging Prevention
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Solution Overview
Problem
Wavelength variable interference filters face challenges in controlling the distance between reflective films due to charging issues, such as electrostatic induction, leak current, and capacitive coupling, which affect the accuracy of gap adjustment and lead to Coulomb forces.
Innovation Solution
The implementation of a configuration with grounded electrodes along the outer edges of the substrates to prevent charging by allowing charges to escape, including a third electrode for the first substrate and a fourth electrode for the second substrate, which are non-contact and grounded, and providing a movable section with a holding section of different thickness dimensions to maintain parallelism and reduce film stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive electrodes are provided on the substrates to measure the space between substrates, then measurement capability is improved, but substrate charging occurs due to charge escape leading to control difficulty
Solution Approach 1:
A grounded electrode is introduced as an intermediary component between the capacitive electrode and the substrate. This grounded electrode serves as a charge sink that intercepts charges before they can escape to the substrate, thereby preventing substrate charging while preserving the measurement function of the capacitive electrode.
Solution Approach 2:
The invention converts the potentially harmful charge escape phenomenon into a beneficial effect by providing a controlled path for charge dissipation through the grounded electrode. Instead of charges randomly escaping to the substrate and causing harmful Coulomb forces, the grounded electrode provides a designated escape route that protects the substrate while maintaining measurement capability.
2Reliability
If reflective films are provided on substrates for wavelength filtering, then optical filtering function is improved, but substrate charging occurs due to capacitive coupling leading to control difficulty
Solution Approach 1:
The grounded electrode acts as an intermediary that decouples the capacitive interaction between the reflective films and the substrates. By providing a reference potential at the grounded electrode, it prevents direct capacitive coupling charges from transferring to the substrates, thereby maintaining optical filtering reliability while eliminating harmful substrate charging.
3Ease of operation
If voltage is applied between capacitive electrodes to adjust substrate distance, then gap adjustment capability is improved, but substrate charging occurs leading to reduced adjustment accuracy
Solution Approach 1:
The grounded electrode converts the harmful side effect of voltage application (charge accumulation on substrates) into a beneficial charge dissipation pathway. During gap adjustment, charges generated by applied voltage are safely directed to the grounded electrode instead of accumulating on substrates, preserving both the adjustability and the precision of gap 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 effectively prevents substrate charging, reduces Coulomb forces, and allows for precise adjustment of the inter-reflective film gap without interference, enhancing the accuracy and reliability of wavelength adjustment.
Implementation Method 1
it is possible to adjust a space between the substrates using electrostatic attraction by applying a voltage between the first electrode and the second electrode
Implementation Method 2
when the surfaces of the substrates are made of a material that is easily charged, electrostatic induction is caused by an electric field generated from ends of the capacitive electrodes
Implementation Method 3
a third electrode provided along the outer circumferential edge of the first electrode and in non-contact with the first electrode and grounded
Data Source
AI summary
A wavelength variable interference filter includes a fixed substrate, a movable substrate, a fixed reflective film provided on the fixed substrate, a movable reflection film provided on the movable substrate and opposed to the fixed reflective film via an inter-reflective film gap, a fixed electrode provided on the fixed substrate, a movable electrode provided on the movable substrate and opposed to the fixed electrode via an inter-electrode gap, a fixed charging preventing electrode provided along the outer circumferential edge of the fixed electrode and in non-contact with the fixed electrode and grounded, and a movable charging preventing electrode provided along the outer circumferential edge of the movable electrode and in non-contact with the movable electrode and grounded.