Focused Electromagnetic Radiation Divergence Control
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Solution Overview
Problem
Existing material processing techniques using focused electromagnetic radiation, such as in fs-LASIK, face challenges in precisely controlling the focal position due to changes in laser beam divergence, thermal effects, and manufacturing inaccuracies, leading to variations in cutting depth during corneal surgery.
Innovation Solution
An apparatus with a divergence adjustment element, a pattern generator, and high-resolution detectors allows for closed-loop control of the focal position by adjusting beam divergence based on image processing of a pattern reflected from a partially reflective surface, enabling precise control without altering the focusing optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If focused electromagnetic radiation is used for material processing, then material processing precision is improved, but focal position stability deteriorates due to thermal effects and beam divergence changes
Solution Approach 1:
The patent implements a feedback control system where a pattern is projected onto a partially reflective surface, the reflected pattern is detected by a detector, and the focal position is determined by analyzing the detected pattern. This feedback loop continuously monitors and adjusts the focal position to compensate for thermal effects and beam divergence changes, thereby maintaining focal position stability while using focused electromagnetic radiation for material processing.
2Measurement precision
If interferometric measurement and control is used for focus control, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a pattern that is copied and projected onto a partially reflective surface in the optical path. The reflected pattern serves as an optical copy that contains information about the focal position. This approach simplifies the measurement system compared to traditional interferometric methods by using a pattern copy instead of complex interferometric setups, thereby reducing device complexity while maintaining measurement precision.
3Manufacturing precision
If adaptive mirrors are used for active wavefront control, then focal position control is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the focal position measurement function from complex adaptive mirror systems and implements it separately using a pattern projection and detection method. By taking out the measurement function and implementing it through a simpler pattern-based approach, the system achieves focal position control without requiring complex adaptive mirrors, thereby reducing device complexity and cost while maintaining control 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 solution reduces focal position variations to a few micrometers, maintaining accurate cutting depth and operational reliability by recognizing and compensating for thermal changes, beam direction shifts, and manufacturing inaccuracies, ensuring precise control during fs-LASIK procedures.
Implementation Method 1
an at least partially reflective surface in the optical path before the focus of the focused radiation, said pattern being imaged onto said at least partially reflective surface through at least part of said optical components
Implementation Method 2
at least one detector onto which an image of the pattern is reflected by said surface and which generates electrical signals corresponding to said image
Data Source
AI summary
An apparatus for processing material with focused electromagnetic radiation, comprises: a source emitting electromagnetic radiation, means for directing the radiation onto the material, means for focusing the radiation on or in the material, a unit for generating a pattern in the optical path of the electromagnetic radiation, an at least partially reflective surface in the optical path before the focus of the focused radiation, said pattern being imaged onto said at least partially reflective surface through at least part of said directing means and said focusing means, at least one detector onto which an image of the pattern is reflected by said surface and which generates electrical signals corresponding to said image, said image containing information on the position of the focus, a computer receiving said electrical signals and programmed to process said image so as to generate an electrical signal depending on the focal position, and a divergence adjustment element arranged in said optical path and adapted to receive said electrical signal of the computer so as to change a divergence of the electromagnetic radiation depending on said signal.