Transparent Phase Plate High-Speed Interferometric Measurement
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Solution Overview
Problem
Conventional 3D metrology systems using fringe interferometry are limited by the slow data acquisition speed due to the requirement for precise mechanical translation mechanisms, which are hindered by settling times, making them unsuitable for high-speed phase shifting and real-time imaging applications.
Innovation Solution
A method involving a transparent phase plate with regions of different optical thickness, where the phase of coherent optical beams is modulated by moving the plate or steering the beam, allowing rapid switching between stable phase values without the need for precise mechanical translation, enabling high-speed phase shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precise mechanical translation mechanisms are used to shift fringes, then measurement precision is improved, but data acquisition speed deteriorates due to settling times
Solution Approach 1:
The patent replaces mechanical translation mechanisms with acoustic wave fields to achieve fringe phase shifting. Acoustic waves modulate the refractive index of the medium, creating phase shifts without mechanical movement, thereby eliminating settling time limitations while maintaining measurement precision
Solution Approach 2:
The patent changes the physical state of the medium by applying acoustic waves, which modulate the refractive index parameter. This allows dynamic control of light phase without mechanical displacement, enabling high-speed phase shifting while preserving measurement accuracy
2Manufacturing precision
If submicron precision mechanical translation is used, then phase shifting accuracy is improved, but system complexity and settling time increase
Solution Approach 1:
The patent substitutes complex mechanical translation mechanisms with a simpler acoustic wave generation system. The acoustic waves directly modulate the optical path length through refractive index changes, achieving submicron phase shifting accuracy without the complexity and settling time of mechanical systems
Solution Approach 2:
The patent utilizes the phase modulation capability of acoustic waves in the optical medium. By controlling the acoustic wave phase and amplitude, precise optical phase shifting is achieved without mechanical movement, simplifying the system while maintaining high precision
3Measurement precision
If precision motion of fringe projector is used, then measurement accuracy is improved, but real-time imaging capability deteriorates
Solution Approach 1:
The patent replaces mechanical motion of the fringe projector with acoustic wave-based phase modulation. This allows real-time phase shifting during image acquisition, enabling 3D measurements to be completed in a single shot or with minimal sequential captures, thereby achieving both high accuracy and real-time capability
Solution Approach 2:
The patent applies acoustic pre-modulation to the optical field before detection. By pre-establishing the phase-shifted fringe patterns through acoustic waves, the system captures all necessary phase information simultaneously, eliminating the time required for sequential mechanical positioning and capture
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-speed and accurate phase shifting with reduced settling times, allowing for real-time 3D measurements in applications like dental imaging, overcoming the limitations of conventional systems.
Implementation Method 1
A transparent plate having a pair of parallel surfaces, a first region having a first optical thickness and a second region having a second optical thickness is provided. The first and second optical thicknesses are different from each other.
Implementation Method 2
The transparent plate is moved from a first position with respect to the first beam to a second position with respect to the first beam. The second region of the transparent plate is illuminated with at least the first beam, wherein the phase difference of the pair of coherent optical beams has a second value.
Data Source
AI summary
Described are a method and apparatus for high-speed phase shifting of an optical beam. A transparent plate having regions of different optical thickness is illuminated by an optical beam along a path of incidence that extends through the regions. The transparent plate can be moved or the optical beam can be steered to generate the path of incidence. The optical beam exiting the transparent plate has an instantaneous phase value according to the region in which the optical beam is incident. Advantageously, the phase values are repeatable and stable regardless of the location of incidence of the optical beam within the respective regions, and phase changes at high modulation rates are possible. The method and apparatus can be used to modulate a phase difference of a pair of coherent optical beams such as in an interferometric fringe projection system.