Off-Axial Three-Mirror Freeform Optical System Design
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Solution Overview
Problem
Conventional off-axial three-mirror optical systems with freeform surfaces are limited in applications with large field angles and small F-number, and have complex assembly and alignment processes due to separate primary, secondary, and tertiary mirrors.
Innovation Solution
An off-axial three-mirror optical system with freeform surfaces, where each mirror's surface is designed as an xy polynomial surface up to the fifth order without odd items of x, allowing for larger field angles, smaller F-number, and simplified assembly by positioning mirrors closer together, facilitating easier fabrication and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional off-axial three-mirror optical systems with freeform surfaces are used, then the structure can be simplified compared to rotationally symmetric surfaces, but the system is limited to small field angles and large F-number applications
Solution Approach 1:
The patent employs freeform surfaces with asymmetric geometry instead of conventional rotationally symmetric surfaces. The primary mirror, secondary mirror, and tertiary mirror all utilize freeform surfaces that lack rotational symmetry, enabling the system to achieve large field angles (up to 45 degrees) and small F-numbers while maintaining simplified structural complexity
Solution Approach 2:
The patent changes the geometric parameters of the mirror surfaces by adopting freeform surface equations with multiple coefficients (including conic constants and higher-order terms). This parameter optimization allows the system to achieve both large field angles and small F-numbers simultaneously, overcoming the limitations of conventional designs
2Adaptability or versatility
If the primary mirror, secondary mirror, and tertiary mirror are positioned separately in conventional off-axial three-mirror systems, then each mirror can be independently designed, but the assembly and alignment processes become complicated
Solution Approach 1:
The patent merges the positioning relationships between the primary mirror, secondary mirror, and tertiary mirror through optimized freeform surface designs. By carefully coordinating the positions and orientations of all three mirrors with their freeform surfaces, the system achieves compact configuration that simplifies assembly and alignment while maintaining independent design flexibility for each mirror
3Measurement precision
If freeform surfaces are used to achieve large field angles and small F-number, then the field of view and imaging quality are improved, but the manufacturing and alignment difficulty increases
Solution Approach 1:
The patent uses freeform surfaces with asymmetric geometry on all three mirrors (primary, secondary, and tertiary) to achieve large field angles and small F-numbers. The asymmetric surface profiles correct optical aberrations across the wide field of view, delivering high imaging quality while the systematic design approach manages fabrication complexity
Solution Approach 2:
The patent optimizes multiple parameters of the freeform surfaces including conic constants, higher-order coefficients, and mirror positioning parameters. This comprehensive parameter optimization achieves superior imaging quality and large field coverage while providing a systematic framework that facilitates manufacturing and alignment processes
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 system achieves higher modulation transfer functions, enabling a larger field of view, better imaging quality, and higher input energy with improved resolution, while simplifying the assembly and alignment processes.
Implementation Method 1
an incident light path, a reflected light path of the primary mirror, a reflected light path of the secondary mirror, and a reflected light path of the tertiary mirror
Data Source
AI summary
An off-axial three-mirror optical system with freeform surfaces includes a primary mirror, a secondary mirror, a tertiary mirror, and a detector. The primary mirror is located on an incident light path. The secondary mirror is located on a primary mirror reflecting light path. The tertiary mirror is located on a secondary mirror reflecting light path. The detector is located on a tertiary mirror reflecting light path. Each of the primary mirror, the secondary mirror, and the tertiary mirror is an xy polynomial freeform surface up to the fifth order.