Wavelength Variable Interference Filter Gap Control
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Solution Overview
Problem
Existing wavelength variable interference filters face challenges in accurately adjusting the gap between reflection films over a wide range due to nonlinear sensitivity changes with respect to applied voltage, leading to limited control and complex system configurations.
Innovation Solution
The implementation of an electrostatic actuator configuration with independent first and second electrostatic actuators, where bias voltage is applied to the first actuator and feedback voltage is applied to the second actuator, maintaining constant sensitivity and simplifying the control circuitry by using Equation (1) to set the bias voltage, allowing for precise gap adjustment across a wide range without the need for gain adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrostatic actuator is used to control the gap between reflection films, then the control circuit can be simplified, but the sensitivity of the actuator changes nonlinearly with the gap amount, limiting the controllable gap range
Solution Approach 1:
The single electrostatic actuator is divided into two independent actuators: a first electrostatic actuator for coarse adjustment and a second electrostatic actuator for fine adjustment. This segmentation allows each actuator to operate within an optimized gap range, with the first actuator handling larger gap changes and the second actuator providing precise control, thereby extending the overall controllable gap range while maintaining circuit simplicity
Solution Approach 2:
The first electrostatic actuator performs preliminary coarse adjustment to bring the gap between reflection films close to the target value. This preliminary action reduces the remaining gap error to a small range where the second electrostatic actuator can effectively perform fine adjustment, optimizing the overall control performance across a wide gap range
2Adaptability or versatility
If the gain of the control circuit is changed according to the interelectrode gap amount, then the control circuit can function optimally over a wider gap range, but the system becomes complicated
Solution Approach 1:
The control range is segmented into two zones: a coarse adjustment zone handled by the first electrostatic actuator and a fine adjustment zone handled by the second electrostatic actuator. Each actuator operates with a fixed gain optimized for its specific zone, eliminating the need for dynamic gain adjustment while achieving optimal control performance across the entire gap range
Solution Approach 2:
The first electrostatic actuator performs excessive adjustment by moving the gap beyond the precise target point to a nearby position within the fine adjustment range. This partial action approach allows the second actuator to handle only the small residual error, maintaining fixed gain operation for both actuators while achieving high precision 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 enables highly accurate and simplified control of the gap between reflection films, allowing for precise extraction of target wavelengths with reduced costs and complexity, as the sensitivity of the second electrostatic actuator remains constant regardless of the gap size, and the need for high-bit D/A converters is minimized.
Implementation Method 1
electrostatic actuators, wherein a bias voltage is applied to the first electrostatic actuator and a feedback voltage is applied to the second electrostatic actuator
Data Source
Figure 1
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AI summary
A optical module includes, a wavelength variable interference filter (5) which include reflection films (54, 55) opposite to each other and an electrostatic actuator portion including a first electrostatic actuator (561) and a second electrostatic actuator (562) and changing a gap between the reflection films, and a voltage control portion (15) which controls voltage which is applied to the electrostatic actuator portion, the voltage control portion includes, a bias driving portion (151) which applies bias voltage to the first electrostatic actuator, a gap detector (152), and a feedback control portion (153) which applies feedback voltage corresponding to a detected gap amount to the second electrostatic actuator.