Aspherical Axicon Relay Layout for Broadband Chromatic Correction
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Solution Overview
Problem
Existing optical lenses used in metrology applications for integrated circuit manufacturing suffer from significant chromatic aberration when handling broadband radiation, leading to distorted beam focusing and energy loss, which is not adequately addressed by current achromatic lenses like doublets and triplets.
Innovation Solution
A lens system comprising two aspherical axicon lens elements oriented to minimize chromatic aberration, with an aperture stop between them, designed to relay broadband radiation with reduced chromatic dispersion across a specified spectral range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical lenses are used to shape broadband radiation, then beam shaping function is provided, but chromatic aberration occurs causing distorted focusing and energy loss
Solution Approach 1:
The patent divides the optical system into multiple discrete lens elements (at least two lens elements with different Abbe numbers) arranged in sequence. Each lens element is optimized for specific wavelength ranges, and their combined effect corrects chromatic aberration across the broadband spectrum while maintaining beam shaping capability
Solution Approach 2:
The patent employs composite optical design by combining lens elements made from different optical materials with distinct dispersion properties (different Abbe numbers). This composite approach allows the system to achieve achromatic performance across broadband radiation by compensating for wavelength-dependent refractive index variations
2Object-affected harmful factors
If achromatic lenses like doublets and triplets are used to reduce chromatic aberration, then chromatic dispersion is reduced, but manufacturing complexity and alignment precision requirements increase
Solution Approach 1:
The patent systematically varies key optical parameters including the Abbe numbers, focal lengths, and spacing of lens elements to optimize chromatic aberration correction. By carefully selecting and adjusting these parameters, the system achieves effective dispersion reduction without requiring excessive numbers of lens elements, thus controlling manufacturing complexity
3Object-affected harmful factors
If more lens elements are added to correct chromatic aberration, then chromatic aberration is reduced, but transmission efficiency decreases due to increased reflections and absorptions
Solution Approach 1:
The patent introduces air gaps or optical adhesives as intermediary layers between lens elements. These intermediaries minimize reflection losses at interfaces through impedance matching and anti-reflective coating strategies, thereby maintaining high transmission efficiency while enabling the use of multiple lens elements for chromatic aberration correction
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 proposed lens system effectively minimizes chromatic aberration, ensuring precise beam shaping and improved transmission efficiency for broadband radiation, enhancing the accuracy of metrology tools in IC manufacturing.
Implementation Method 1
a first aspherical axicon lens element comprising a first refractive surface and a second refractive surface; a second aspherical axicon lens element comprising a third refractive surface similar to said second refractive surface and a fourth refractive surface similar to said first refractive surface
Data Source
AI summary
A lens system including: a first asphercal axicon lens element having a first refractive surface and a second refractive surface; a second aspherical axicon lens element having a third refractive surface similar to the second refractive surface and a fourth refractive surface similar to the first refractive surface, and an aperture stop located between the first asphercal axicon lens element and the second aspherical axicon lens element. The first aspherical axicon lens element and second aspherical axicon lens are mutually oriented such that the second refractive surface and third refractive surface are mutually facing. The first aspherical axicon lens element and the second aspherical axicon lens element are configured to minimize chromatic aberration for at least a spectral range of radiation relayed by the lens system.