Anamorphic Lens Interferometry via Adapted Measurement Structures
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Solution Overview
Problem
Existing methods struggle to measure the imaging quality of anamorphic optical imaging systems with high precision due to the challenges posed by their direction-dependent imaging scales, leading to suboptimal interference patterns and reduced signal quality.
Innovation Solution
The development of a measuring method and system that adapts the first and second measurement structures to the anamorphic imaging system's scale ratio, using two-dimensionally periodic structures to generate low-disturbance interference patterns with a higher signal-to-noise ratio, enabling precise interferometric measurements through shearing interferometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement structures are used for anamorphic imaging systems, then the measurement setup is simple, but the interference pattern quality deteriorates due to direction-dependent imaging scales
Solution Approach 1:
The measurement structures are designed with direction-dependent periodicities that match the anamorphic imaging system's scale ratio in different directions. The first measurement structure has periodicity P1 in the first direction and P1' in the second direction, while the second measurement structure has corresponding periodicities P2 and P2' that account for the different imaging scales β1 and β2, creating locally optimized interference patterns for each direction
Solution Approach 2:
The measurement structures intentionally introduce asymmetric periodicities to match the anamorphic system's inherent asymmetry. The periodicity ratio P1/P1' differs from P2/P2' to compensate for the direction-dependent imaging scales, transforming the asymmetric imaging characteristics into a symmetric interference pattern that can be properly evaluated
2Measurement precision
If the imaging scale is increased to improve resolution, then the resolution capability improves, but the interference signal strength decreases
Solution Approach 1:
The periodicities of the measurement structures are specifically adjusted as parameters to match the imaging scale ratio. By setting P1/P1' = β1/β2 and P2/P2' = β1/β2, the interference signal strength is maximized for the given imaging scale, allowing high resolution measurements without signal loss
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 allows for reliable wavefront detection and phase difference quantification in anamorphic imaging systems, achieving high precision measurements with improved signal strength and reduced error, even in systems with non-uniform imaging scales.
Implementation Method 1
The superposition of the waves generated by diffraction at the diffraction grating gives rise to a superposition pattern in the form of an interferogram
Implementation Method 2
The coherence of the radiation passing through the projection lens is determined by the object pattern. The superposition of the waves generated by diffraction at the diffraction grating
Data Source
Figure 1
Figure 2A~2
Figure 3A~3
AI summary
A measuring method and a measuring system for interferometrically measuring the imaging quality of an optical imaging system are configured, by adapted design of measurement structures of associated structure carriers, to carry out a wavefront measurement on an imaging system which has a first imaging scale β1 in a first direction and a second imaging scale β2 in a second direction, perpendicular to the first direction, said second imaging scale differing from the first imaging scale by a scale ratio (β1/ β2) ≠ 1 (anamorphic imaging system). A first measurement structure (MS1) on a first structure carrier to be arranged on the object side of the imaging system has a two-dimensional mask structure suitable for shaping the coherence of measurement radiation. A second measurement structure (MS2) on a second structure carrier to be arranged on the image side of the imaging system has a diffraction grating. The first and second measurement structures are adapted to one another taking account of the scale ratio in such a way that an interference pattern arises upon an imaging of the first measurement structure (MS1) onto the second measurement structure (MS2) with the aid of the anamorphic imaging system.