Spot-Array Imaging System Aberration Correction
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Solution Overview
Problem
Scanned-Spot-Array Optical Lithography and Microscopy systems face challenges in achieving diffraction-limited performance due to stringent requirements for high-NA microlenses and projection lenses, leading to complex and expensive systems with tradeoffs between microlens and projection lens design constraints.
Innovation Solution
The use of micro-optics upstream of the projection lens to separate radiation into discrete source spots, compensate for imperfect imaging performance, and optimize radiation intensity and polarization, allowing for non-uniform spot distribution and aberration correction to relax projection lens design requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-NA microlenses are used to achieve diffraction-limited imaging performance, then imaging quality is improved, but manufacturing difficulty and cost increase significantly
Solution Approach 1:
The patent divides the optical system into multiple functional components: microlenses for spot generation, projection lens for imaging, and aberration correctors for performance optimization. This segmentation allows each component to be optimized independently, reducing the manufacturing difficulty of individual high-NA microlenses while maintaining overall diffraction-limited performance through coordinated design of all segments.
Solution Approach 2:
The patent introduces aberration corrector elements as intermediary components between the microlens array and the projection lens. These correctors compensate for optical aberrations introduced by the microlenses and projection lens, enabling the use of microlenses with relaxed manufacturing tolerances while still achieving diffraction-limited imaging performance at the image plane.
2Manufacturing precision
If stringent optical tolerances are maintained for projection lens to achieve diffraction-limited performance, then imaging quality is improved, but system complexity and cost increase
Solution Approach 1:
Aberration corrector elements are positioned in the optical path between the microlens array and the projection lens to compensate for optical aberrations. This intermediary approach allows the projection lens to operate with relaxed tolerances while maintaining diffraction-limited performance, thereby reducing system complexity and cost.
Solution Approach 2:
The patent employs variable parameters in the aberration corrector design, including adjustable surface profiles and positions, to dynamically compensate for optical aberrations. This allows the system to maintain optimal performance across varying conditions without requiring the projection lens to meet stringent fixed tolerances, reducing overall system complexity.
3Ease of operation
If uniform spot distribution is used in the spot array, then simplicity of design is maintained, but imaging performance suffers due to projection lens aberrations
Solution Approach 1:
The patent implements non-uniform spot distribution in the spot array, where the spacing and positioning of individual spots are locally optimized to compensate for projection lens aberrations. This local quality approach allows spots in different regions of the field to be positioned optimally, maintaining diffraction-limited performance across the entire image plane while managing design complexity through systematic optimization.
Solution Approach 2:
The patent introduces asymmetric spot positioning patterns that deliberately break the uniform symmetry of traditional spot arrays. This asymmetry is designed to counterbalance the asymmetric aberration patterns of the projection lens, thereby improving imaging performance across the field while maintaining manageable design complexity through computational optimization.
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 enables high-throughput maskless printing and confocal imaging with reduced complexity and cost by improving imaging performance and relaxing stringent optical tolerances, allowing for more efficient and cost-effective systems.
Implementation Method 1
a first array of microlenses... which focus the modulated radiation onto a second array of diffraction-limited focused spots
Implementation Method 2
an array of diffraction-limited focused-radiation spots is raster-scanned over a printing surface
Implementation Method 3
an aberration corrector... configured to optimally correct the point-imaging performance of the projection lens for each individual focus spot
Implementation Method 4
The spots may be individually modulated by a spatial light modulator
Implementation Method 5
the radiation reflected from (or transmitted through) the surface at each spot is collected and detected
Data Source
AI summary
In a scanned-spot-array lithography system, a modulated array of radiant-energy source spots is imaged by a projection lens onto a printing surface, which is scanned in synchronization with the spot modulation to print a synthesized, high-resolution raster image. Similarly, in a scanned-spot-array microscopy system, an array of radiant-energy source spots is imaged by a projection lens onto an inspection surface, and radiation reflected from or transmitted through the image spots is collected and detected to acquire a synthesized, high-resolution raster image of the surface. In either case, the spot-generation optics can be configured to counterbalance and neutralize imperfect imaging characteristics of the projection lens, enabling perfectly flat-field, distortion-free, and aberration-free point imaging of the entire spot array. The spot-generation optics can also be further configured to achieve narrow-band achromatization of the optical system, and to optimally control the intensity and polarization characteristics of the image-plane radiation.