Illumination Apparatus Phase Control Feedback Loop
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Solution Overview
Problem
Existing illumination apparatuses for fringe scanning methods face challenges in precisely controlling the phase difference between optical arms to generate desired interference fringes for accurate three-dimensional shape measurement, which affects the magnitude distribution and accuracy of the interference fringe.
Innovation Solution
An illumination apparatus comprising an input arm, splitter, phase modulator, and phase detector that splits and modulates the light beam to generate and measure the phase difference between output light beams, allowing for precise control and detection of the phase difference using return light beams, enabling accurate interference fringe generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the phase difference between optical arms is controlled with high precision to generate desired interference fringes, then the accuracy of three-dimensional shape measurement is improved, but the device complexity increases due to the need for precise phase control mechanisms
Solution Approach 1:
The patent implements a feedback mechanism where the phase detector measures the actual phase difference between optical arms and feeds this information back to the phase modulator. The phase modulator then adjusts the phase difference based on the detected value to achieve the desired phase difference, enabling closed-loop control that improves measurement accuracy while automating the control process
Solution Approach 2:
The patent replaces mechanical phase control mechanisms with optical-based detection and electronic modulation. Instead of using mechanical devices to physically adjust optical paths, the system uses optical interference detection combined with electronic phase modulation to achieve precise phase control, thereby reducing mechanical complexity
2Measurement precision
If the phase difference is precisely controlled to enhance interference fringe generation, then the detection sensitivity is improved, but the difficulty of detecting and measuring phase difference increases
Solution Approach 1:
The patent introduces an intermediary optical path where reference light beams are combined with measurement light beams to create an interference pattern. This intermediary interference fringe serves as a mediator that converts the abstract phase difference into a measurable intensity pattern, making phase detection straightforward through intensity measurement rather than direct phase measurement
Solution Approach 2:
The patent transforms the phase difference parameter into an intensity parameter through optical interference. By converting the hard-to-measure phase difference into an easily measurable light intensity variation in the interference fringe pattern, the system simplifies the detection process while maintaining high sensitivity
3Manufacturing precision
If the magnitude distribution of interference fringe is precisely controlled according to phase difference, then the quality of structured illumination is improved, but the loss of time increases due to repeated phase adjustments
Solution Approach 1:
The system performs preliminary calibration by detecting the actual phase difference once and using this information to pre-adjust the phase modulator settings. This preliminary action establishes the correct operating point, eliminating the need for repeated time-consuming adjustments during subsequent measurements while maintaining high illumination quality
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 solution allows for precise control of the phase difference, enhancing the accuracy of interference fringe generation and three-dimensional shape measurement, improving detection sensitivity and range, and enabling effective feedback control for achieving desired phase differences.
Implementation Method 1
an optical coupler that splits a coherent light beam into light beams that propagate through the two respective waveguides
Implementation Method 2
a phase modulator that provides a difference in the optical length between the two waveguides
Implementation Method 3
By providing interference between the light beams after they pass through the two respective waveguides, the illumination apparatus generates an interference fringe
Implementation Method 4
an image of the projected interference fringe is captured and analyzed so as to calculate the surface peak and bottom information
Data Source
AI summary
An illumination apparatus generates an interference fringe. An input arm receives an input light beam from a light source. A splitter splits the input light beam that has passed through the input arm into a first output arm and a second output arm. A phase modulator changes a phase difference between the output light beams of the first output arm and the second output arm. A phase detector detects the phase difference between output light beams respectively output from the first output arm and the second output arm based on a return light beam generated by combining a first reflected light beam and a second reflected light beam respectively reflected by ends of the first output arm and the second output arm.