Dynamic Interferometer Illuminator Steering Mirror Trajectory Control
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Solution Overview
Problem
Existing interferometers face challenges in achieving dynamic positioning precision and response to accurately and repeatably reproduce desired illumination shapes within the camera's integration time, leading to errors in optical path length difference measurements.
Innovation Solution
An illumination system for interferometers is developed, comprising a source of system light, a steering-mirror assembly, a tracking mechanism, a focus lens assembly, and an electronic controller. This system dynamically controls the steering-mirror assembly to follow a predetermined motion trajectory, ensuring precise and stable illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a static illumination source shape is used, then physical stability is improved, but dynamic response and positioning precision deteriorate
Solution Approach 1:
The patent employs a dynamic illumination source that can change its spatial distribution over time, transitioning from static to dynamic operation. The system uses a point source that moves through a defined trajectory within the integration time, allowing the illumination pattern to adapt dynamically while maintaining stability through controlled motion rather than fixed geometry.
Solution Approach 2:
The system pre-calculates and pre-positions the illumination trajectory within the camera's integration time, ensuring that the desired spatial distribution is established before measurement begins. This preliminary action allows the system to achieve both stability in the measurement process and precision in the illumination pattern through planned motion.
2Measurement precision
If a dynamic illumination source is used to improve positioning precision, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a single point source combined with a steering mechanism to generate multiple illumination patterns (rings, arcs, circles) by varying the trajectory, rather than requiring multiple separate source elements. This multi-functional approach achieves diverse illumination shapes with one basic component, reducing overall device complexity while maintaining precision.
Solution Approach 2:
The system employs fast steering mirrors or similar dynamic elements to reposition the point source along predetermined trajectories at high speeds. This dynamic capability allows the system to achieve precise illumination patterns without requiring complex static optical elements, as the precision is achieved through controlled motion rather than complex geometry.
3Manufacturing precision
If the illumination source is focused to a point in the back focal plane, then wavefront quality is improved, but spatial coherence and interference contrast deteriorate
Solution Approach 1:
The patent dynamically varies the position of the point source in the back focal plane during the camera's integration time, tracing out extended shapes such as rings or arcs. This dynamic positioning allows the system to maintain the wavefront quality benefits of point-source illumination while creating extended spatial patterns that improve interference contrast and coherence through the temporal averaging of multiple positions.
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 system achieves high precision and dynamic response, reducing errors in shape reproduction and optical path length difference measurements, thereby enhancing the accuracy and reliability of interferometric metrology techniques.
Implementation Method 1
a steering-mirror assembly to receive and reflect the system-light in at least two orthogonal directions
Implementation Method 2
a focus lens assembly to focus the system light reflected off the steering mirror assembly onto a 2-dimensional plane corresponding to the source plane of the interferometer
Implementation Method 3
Changes in the wavefront after reflection from the surface(s) of interest are captured by a camera and analyzed to recover the surface topography
Data Source
AI summary
Disclosed is an illumination system for an interferometer including: a source of system light; a steering-mirror assembly to receive and reflect the system-light in at least two orthogonal directions; a tracking mechanism to track an angular orientation of the steering-mirror assembly in the two orthogonal directions and provide electronic signals representative of the angular orientation; a focus lens assembly to focus the system light reflected off the steering mirror assembly onto a focused spot on a 2-dimensional plane corresponding to a source plane of the interferometer; and an electronic controller operatively coupled to the steering-mirror assembly and configured to cause the focused spot on the source plane to follow a predetermined motion trajectory.