Four-Mirror All-Reflective Optical System for Compact Multispectral Imaging
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Solution Overview
Problem
Existing optical imaging systems for satellites face challenges in achieving a small form factor while maintaining high resolution and versatility across various spectral ranges, particularly in multispectral and hyperspectral imaging, due to limitations in design flexibility and chromatic aberration.
Innovation Solution
An all-reflective optical system comprising a four-mirror design with a concave primary mirror, a convex secondary mirror, a concave tertiary mirror, and a concave quaternary mirror, along with beam splitters and folding mirrors, allows for simultaneous multi-color imaging and adaptable spectral range coverage without chromatic aberration, using materials with specific thermal expansion properties for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional three-mirror anastigmat or Korsch designs are used, then chromatic aberration is corrected, but the system size becomes large and resolution capability is limited
Solution Approach 1:
The patent employs asymmetric mirror configurations where the primary, secondary, tertiary, and quaternary mirrors have different curvatures, orientations, and positions. This asymmetric arrangement allows the system to achieve high resolution imaging in a compact form factor by optimizing the optical path length and focal properties without requiring the symmetric configurations of traditional designs
Solution Approach 2:
The patent utilizes multi-dimensional spatial arrangement of the four mirrors, positioning them at different locations and orientations in three-dimensional space. This dimensional optimization allows the optical system to achieve long effective focal lengths and high resolution capability while maintaining a compact physical footprint suitable for satellite deployment
2Adaptability or versatility
If conventional optical designs are used, then structural stability is achieved, but design flexibility for multispectral imaging is limited
Solution Approach 1:
The patent designs the four-mirror optical system to serve multiple spectral imaging functions simultaneously. The same optical configuration supports panchromatic, multispectral, and hyperspectral imaging modes by adjusting sensor parameters and filter configurations, eliminating the need for separate optical systems for different spectral ranges
Solution Approach 2:
The patent incorporates adjustable and reconfigurable elements in the optical system, including movable mirrors, adjustable filters, and reconfigurable sensor arrangements. These dynamic components allow the system to adapt its spectral response and imaging characteristics based on mission requirements, providing design flexibility without compromising structural stability
3Volume of moving object
If compact optical systems are used, then form factor is reduced, but chromatic aberration increases
Solution Approach 1:
The patent replaces refractive optical elements (lenses) with reflective elements (mirrors) to eliminate chromatic aberration. The four-mirror all-reflective design ensures that light paths for different wavelengths are reflected rather than refracted, maintaining equal focal points for all colors while achieving a compact form factor suitable for satellite deployment
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 high resolution imaging with a small form factor, supports diverse spectral ranges, and is adaptable for various imaging modes, including panchromatic, multispectral, and hyperspectral imaging, while minimizing chromatic aberration and distortion, enabling efficient operation in satellite and aerial applications.
Implementation Method 1
an all-reflective optical system comprises a concave primary mirror having a central aperture and a radius, the primary mirror having one of a parabolic, non-parabolic conical, or aspherical surface; a convex secondary mirror facing the primary mirror, the secondary mirror having an aspherical surface
Implementation Method 2
one or more folding mirrors arranged to deflect rays from the quaternary mirror to the image plane, wherein the one or more folding mirrors may be configured to fold a ray path
Data Source
AI summary
An all-reflective or reflective and cata-dioptric optical system includes a concave primary mirror having a central aperture and a radius, the primary mirror having one of a parabolic, non-parabolic conical, or aspherical surface, a convex secondary mirror facing the primary mirror, the secondary mirror having an aspherical surface, where an optical axis extends from a vertex of the primary mirror to a vertex of the secondary mirror, a concave tertiary mirror arranged behind the primary mirror, the tertiary mirror having one of a parabolic, non-parabolic conical or aspherical surface, a concave quaternary mirror arranged in the central aperture of the primary mirror or behind the primary mirror, the quaternary mirror having one of a spherical, parabolic, non-parabolic conical or aspherical surface, and/or at least one image plane having one or more aggregated sensors. Additional multispectral imaging may utilize beam splitter(s), folding mirror(s), focal length optimizer(s) and/or additional image planes.