Interference Measuring Device Piezoelectric Stage Optical Path Control
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Solution Overview
Problem
Interference measuring devices face challenges in accurately measuring surface form over a wide dynamic range due to the limited operational range and speed of piezoelectric actuators, which restricts the precision and range of optical path length difference adjustment.
Innovation Solution
The device employs a combination of a piezoelectric actuator and a stage with a stepping motor, where the piezoelectric actuator provides high positional accuracy and the stage offers a wider operational range, with a control unit managing their movements to adjust the optical path length difference across multiple target values, ensuring accurate and wide-range surface form measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric actuator is used to adjust the optical path length difference, then the measurement precision is improved, but the dynamic range is limited
Solution Approach 1:
The optical path length difference adjustment function is segmented into two independent systems: a piezoelectric actuator for fine adjustment (high precision) and a stepping motor for coarse adjustment (wide range). Each actuator operates within its optimal range, with the piezoelectric actuator providing sub-micrometer precision and the stepping motor providing millimeter-range movement, together resolving the contradiction between precision and dynamic range
Solution Approach 2:
Two不同类型的 actuators (piezoelectric actuator and stepping motor) are merged into a single integrated adjustment system. The control unit coordinates both actuators to work together, combining the advantages of high precision (from piezoelectric) and wide range (from stepping motor) to achieve both accurate measurement and wide dynamic range coverage
2Adaptability or versatility
If the range for adjusting optical path length difference is widened, then the dynamic range of measurement is improved, but the measurement precision deteriorates
Solution Approach 1:
The adjustment range is segmented into coarse (stepping motor) and fine (piezoelectric actuator) components. The stepping motor handles the wide-range positioning while the piezoelectric actuator refines the position with high precision, allowing the system to achieve both wide dynamic range and high measurement precision simultaneously
3Measurement precision
If a piezoelectric actuator alone is used for adjustment, then the measurement precision is improved, but the operational range is limited
Solution Approach 1:
The piezoelectric actuator and stepping motor are merged into a coordinated system where the stepping motor extends the operational range by providing millimeter-scale movement, while the piezoelectric actuator maintains high precision through sub-micrometer control. This combination resolves the contradiction between limited range and high precision
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 approach enables high-accuracy surface form measurement over a wide dynamic range by effectively utilizing the strengths of both the piezoelectric actuator and the stage, enhancing the precision and range of optical path length difference adjustments.
Implementation Method 1
a piezoelectric actuator for moving the first subject or the second subject
Implementation Method 2
causes a first reflected beam occurring when the first branched beam is reflected by a first subject and a second reflected beam occurring when the second branched beam is reflected by a second subject to interfere with each other
Implementation Method 3
an imaging optical system for focusing the interfering light outputted from an interference optical system
Data Source
AI summary
An interference measuring device comprises light sources lenses, an aperture, an optical multiplexer, an optical branching filter, a half mirror, an imaging unit, an analyzing unit, a light receiving unit, a displacement detecting unit, a piezoelectric actuator, a drive unit, a mirror, a stage, a drive unit, and a control unit. According to a result of optical path length difference detection by the displacement detecting unit, the control unit controls optical path length difference adjusting operations by the piezoelectric actuator and stage through the drive units such that the optical path length difference becomes a plurality of target values in sequence. The control unit subjects the moving operation by the piezoelectric actuator to a feedback control such that the optical path length difference becomes each of the target values upon the moving operation by the stage as well.