Freeform Off-Axial Three-Mirror Imaging System Design
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Solution Overview
Problem
Conventional freeform surface off-axial three-mirror imaging systems cannot simultaneously achieve large field and small F-number, limiting their ability to obtain high-resolution images over a large imaging range.
Innovation Solution
A method is developed to design a freeform surface off-axial three-mirror imaging system by establishing an initial system, selecting feature fields, constructing freeform surfaces, and extending the construction area, which involves surface fitting and Snell's law to determine feature data points and reconstruct the system, allowing for a larger field angle and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional freeform surface off-axial three-mirror imaging systems are designed for large field, then the field angle is increased, but the F-number becomes large and resolution decreases
Solution Approach 1:
The patent applies freeform asymmetric surfaces to the three mirrors instead of conventional rotationally symmetric surfaces. This asymmetry provides additional degrees of design freedom, allowing the system to simultaneously achieve large field angle and small F-number while maintaining high image resolution through optimized surface geometries
Solution Approach 2:
The patent changes the surface parameter from rotationally symmetric to freeform asymmetric surfaces, fundamentally altering the design space. This parameter change enables simultaneous optimization of multiple performance metrics including field angle, F-number, and image resolution that were previously mutually exclusive
2Area of moving object
If conventional freeform surface off-axial three-mirror imaging systems are designed for large field, then the field angle is increased, but aberrations increase and image quality deteriorates
Solution Approach 1:
The freeform asymmetric surfaces provide additional degrees of freedom for aberration correction. By optimizing the asymmetric surface geometries, the system can maintain high image quality and low aberrations across the entire large field angle range
Solution Approach 2:
The freeform surfaces allow different regions of the optical system to have locally optimized qualities. Each surface can be independently optimized to correct aberrations in specific field regions while maintaining overall system performance across the full field
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 method enables the creation of a freeform surface off-axial three-mirror imaging system with a large relative aperture and wide field, achieving high-resolution images with reduced aberrations and distortion, thus overcoming the limitations of conventional systems.
Implementation Method 1
freeform surface off-axial three-mirror imaging system
Data Source
AI summary
A freeform surface off-axial three-mirror imaging system comprising a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor. Each reflective surface of the primary mirror, the secondary mirror, and the tertiary mirror is an xy polynomial freeform surface. A field angle of the freeform surface off-axial three-mirror imaging system is larger than or equal to 60°×1°. An F-number of the freeform surface off-axial three-mirror imaging system is less than or equal to 2.5.