Wavefront Manipulator for Optical Aberration Correction
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Solution Overview
Problem
Current optical systems face challenges in maintaining excellent optical quality when changing the focus position over a large range, particularly in photolithographic masks and microscopy, due to wavefront errors introduced by varying refractive indices and substrate thicknesses, leading to spherical and other aberrations.
Innovation Solution
An optical system with a scanning unit that allows lateral displacement of the focus relative to the optical axis, combined with a wavefront manipulator positioned in the pupil plane or a conjugate plane, which corrects wavefront errors to achieve an RMS wavefront error of less than 100 mλ, enabling high-quality focusing over a wide range without mechanical movement of the mask or sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the focus position is changed over a large range in photolithographic masks and microscopy, then the focusing range is improved, but wavefront errors are introduced due to varying refractive indices and substrate thicknesses, leading to spherical and other aberrations that deteriorate optical quality
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the wavefront manipulator to compensate for wavefront errors that occur when the focus position changes. By modifying the wavefront parameters in real-time, the system maintains optimal optical quality across a large focusing range, resolving the contradiction between extended focusing range and maintained optical quality
Solution Approach 2:
The system employs feedback mechanisms where wavefront errors are detected and measured, then fed back to the wavefront manipulator for correction. This closed-loop feedback ensures that optical quality is maintained throughout the large focusing range by continuously compensating for aberrations introduced during focus position changes
2Reliability
If a wavefront manipulator is introduced to correct wavefront errors, then optical quality is improved, but device complexity increases due to additional optical components and control mechanisms
Solution Approach 1:
The wavefront manipulator is designed to perform multiple functions: it corrects spherical aberrations, compensates for refractive index variations, and maintains focus quality across different depths. This multi-functionality justifies the added complexity by providing comprehensive wavefront correction capabilities in a single integrated component
Solution Approach 2:
The wavefront manipulator acts as an intermediary element between the focusing lens and the sample, mediating the optical path to correct wavefront errors without requiring fundamental changes to the existing optical system. This intermediary approach allows for modular integration that manages overall system complexity
3Adaptability or versatility
If the focus is displaced laterally relative to the optical axis, then scanning capability is improved, but aberrations increase due to off-axis positioning
Solution Approach 1:
When lateral scanning is performed, the wavefront manipulator dynamically adjusts wavefront parameters to compensate for off-axis aberrations. By changing wavefront correction parameters in real-time during scanning, the system maintains optical quality while providing versatile scanning capability across different lateral 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
This solution ensures excellent optical quality and a large focusing range, allowing for precise correction of defects in photolithographic masks and improved imaging in microscopy by effectively managing wavefront errors and aberrations, thereby enhancing the efficiency and accuracy of photolithographic processes and microscopic imaging.
Implementation Method 1
a wavefront manipulator (5, 405), which is designed in such a way that the root mean square (RMS) wavefront error is less than 100 mλ, preferably less than 20 mλ, in at least two focal positions
Implementation Method 2
a focusing unit (13, 213, 313, 413, 513, 613, 713), which is designed to focus rays onto a focus (35, 435, 535, 635, 735), with the focusing unit (13, 213, 313, 413, 513, 613, 713) being arranged in a movable manner along an optical axis
Data Source
AI summary
An optical system includes a scanning unit, a first lens-element group including at least a first lens element, and a focusing unit which is designed to focus beams onto a focus, wherein the focusing unit includes a second lens-element group including at least a second lens element and an imaging lens. The imaging lens further includes a pupil plane and a wavefront manipulator. The wavefront manipulator is arranged in the pupil plane of the imaging lens or in a plane that is conjugate to the pupil plane, or the scanning unit of the optical system is arranged in a plane that is conjugate to the pupil plane and the wavefront manipulator is arranged upstream of the scanning unit in the light direction. The focus of the second lens-element group lies in the pupil plane of the imaging lens in all focal positions of the focusing unit.