Interference Measurement Device Phase Modulation Stability
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Solution Overview
Problem
Interference measurement techniques face challenges with instability due to wavefront errors, temperature gradients, detector sensitivity variations, and environmental factors like dust and stains, leading to reduced accuracy and unsuitability for real-time applications in production lines.
Innovation Solution
An interference measurement device that detects phase variations between an object beam and a reference beam using a laser source, splitter, object beam optical unit, combination unit, phase element, and detector, with differential signal processing to isolate phase variations independently of reference beam phase and detector sensitivity, thereby enhancing robustness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interference measurement is used, then measurement capability is provided, but measurement stability and accuracy degrade due to wavefront errors, temperature gradients, and detector sensitivity variations
Solution Approach 1:
The patent creates a virtual reference beam through phase modulation of the object beam, copying the reference beam characteristics without requiring a physical reference path. This eliminates sensitivity to environmental disturbances in the reference path while maintaining interference measurement capability
Solution Approach 2:
A phase modulation element is introduced as an intermediary to convert the object beam into multiple phase-shifted beams that interfere with each other. This mediator enables phase measurement without requiring a separate reference beam, isolating the measurement from environmental disturbances
2Measurement precision
If multiple measurements are performed to correct phase errors, then measurement accuracy improves, but measurement speed decreases
Solution Approach 1:
The patent applies periodic phase modulation to the object beam, creating multiple phase-shifted versions simultaneously. This periodic action enables extraction of phase information from a single captured interference pattern, achieving both high accuracy and real-time measurement capability
Solution Approach 2:
The phase modulation is applied preliminarily to the object beam before detection, encoding multiple phase states into a single beam. This preliminary encoding allows the system to obtain complete phase information without requiring multiple sequential measurements, enabling real-time operation
3Measurement precision
If wavefront correction elements are added to correct optical system aberrations, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the object beam self-reference by creating multiple phase-shifted copies of itself. The interference between these self-generated phase variants provides the measurement information without requiring external reference beams or complex correction elements, achieving simplicity and robustness simultaneously
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 provides high-speed, high-resolving power, and robust phase measurement capable of withstanding disturbances such as wavefront errors and detector sensitivity variations, making it suitable for real-time quality control in production environments.
Implementation Method 1
a laser beam source
Implementation Method 2
a splitter configured to split an emitted beam from the laser beam source into the object beam and the reference beam
Implementation Method 3
a phase element configured to vary mutual relationship in phase between the object beam and the reference beam
Implementation Method 4
an interference beam between the object beam that have reflected from or passed through a measurement object and the reference beam is measured so that a phase difference between the object beam and the reference beam is measured
Data Source
AI summary
An interference measurement device configured to detect a phase from an interference beam between an object beam and a reference beam, includes: a laser beam source; a splitter configured to split an emitted beam from the laser beam source into the object beam and the reference beam; an object beam optical unit configured to make only the object beam incident on a measurement object; a combination unit configured to combine the object beam and the reference beam; a phase element configured to vary mutual relationship in phase between the object beam and the reference beam; and a detector configured to detect the interference beam between the object beam and the reference beam. A signal of a spatial phase variation of the measurement object is directly operated, based on at least two measurement results of an intensity signal with the detector.