Aspheric Dichroic Beam Splitter for Aberration Control
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Solution Overview
Problem
Dichroic beam splitters with parallel entry and exit surfaces suffer from significant image quality degradation due to aberrations such as astigmatism and coma, especially when used in dual-channel optical systems with infrared and visible or near-infrared channels, leading to reduced performance and the need for additional compensators.
Innovation Solution
The implementation of a dichroic beam splitter with non-parallel entry and exit surfaces, where the exit surface is aspheric and tilted relative to the entry surface, along with optimized aspheric coefficients to minimize astigmatism and coma, and a reduced thickness to decrease chromatic aberrations, using materials with low dispersive power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If parallel entry and exit surfaces are used in a dichroic beam splitter, then the structure is simple and easy to manufacture, but significant image quality degradation occurs due to aberrations such as astigmatism and coma
Solution Approach 1:
The patent applies spheroidality by replacing the planar exit surface with an aspheric surface that has specific curvature characteristics. The aspheric surface is designed with particular aspheric coefficients to compensate for optical aberrations (astigmatism and coma) that occur when light passes through the beam splitter. This curved surface geometry allows the system to maintain simple parallel surfaces while correcting the image quality degradation, thereby resolving the contradiction between manufacturing simplicity and image quality precision.
2Manufacturing precision
If the beam splitter thickness is reduced to decrease chromatic aberrations, then chromatic aberration is minimized, but the structural strength and stability may be compromised
Solution Approach 1:
The patent applies composite materials by using a beam splitter constructed from multiple materials with different optical properties. Specifically, the beam splitter comprises a first material with low dispersive power to minimize chromatic aberration, and a second material with higher dispersive power to compensate for optical path differences. This composite structure allows the beam splitter to maintain reduced thickness for minimizing chromatic aberration while the combination of materials provides the necessary structural strength and optical performance, resolving the contradiction between thinness and strength.
3Manufacturing precision
If non-parallel surfaces with aspheric curvature are used, then aberrations are minimized and image quality is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the aspheric coefficients and surface curvature parameters of the exit surface. By optimizing these parameters (aspheric coefficients, tilt angle, curvature radius), the design achieves effective aberration correction without requiring overly complex surface geometries. The parameter optimization allows the aspheric surface to compensate for optical aberrations while maintaining manufacturability, thus resolving the contradiction between aberration correction precision and manufacturing complexity.
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 configuration improves image quality by reducing aberrations, minimizing astigmatism, and reducing the complexity and size of the beam splitter, while also compensating for astigmatism and chromatic effects, enhancing the performance of dual-channel optical systems.
Implementation Method 1
Dichroic beam splitters are often used to split incident light into two separate spectral bands, a 'pass band' which is transmitted through the beam splitter, and a 'stop band' which is reflected by the beam splitter
Implementation Method 2
The planar entry surface is tilted relative to the opposite aspheric exit surface... determining aspheric coefficients that will minimize astigmatism effects on light passing through the dichroic beam splitter
Data Source
AI summary
Dichroic beam splitters having non-parallel entry and exit surfaces, reduced distance between such surfaces, and an aspherical exit surface can be advantageously used in dual channel optical systems, particularly when one channel is dedicated to infrared light and the other channel is dedicated to visible or near-infrared light.