Wide-Angle Catoptric System Aberration Control
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Solution Overview
Problem
Current observation telescopes, such as TMA and FMA types, face limitations in field width, leading to significant image degradation beyond 30° to 70° angles, which is insufficient for modern earth observation missions requiring larger instantaneous fields.
Innovation Solution
A wide-angle catoptric system with four mirrors, where the first mirror is convex and the second is concave, both with substantially equal radii of curvature, along with specific distances and shapes, including aspherical and oblate spheroid configurations, to achieve a wider field of 85° while minimizing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If TMA telescopes are used, then the telescope structure is relatively simple, but the field width is limited to 25°-30° with significant image degradation beyond this range
Solution Approach 1:
The optical system is divided into multiple independent mirrors (M1, M2, M3, M4) with specific functions. The first mirror M1 (convex) and second mirror M2 (concave) form a wide-angle objective, while the third mirror M3 and fourth mirror M4 correct aberrations. This segmentation allows each component to be optimized for its specific function, achieving both wide field width and image quality.
Solution Approach 2:
The patent employs curved mirror surfaces with specific radii of curvature. Mirror M1 has radius R1 and mirror M2 has radius R2, with the ratio R2/R1 within [0.9, 1.1]. The curved surfaces enable wide-angle light collection while the aspherical shapes of M3 and M4 correct optical aberrations, resolving the contradiction between simple structure and wide field performance.
2Area of stationary object
If FMA telescopes with four mirrors are used, then the field width increases to 70°, but image quality degrades at boundary conditions of +/-35°
Solution Approach 1:
Different mirrors have different surface qualities and functions. M1 and M2 provide wide-angle collection with spherical/aspherical surfaces, while M3 and M4 have precise aspherical shapes specifically designed to correct aberrations in different field regions. This local optimization of surface quality ensures high image quality across the entire 85° field width.
Solution Approach 2:
The patent optimizes specific parameters including the radius ratio R2/R1 within [0.9, 1.1], distance ratios between mirrors, and aspherical deformation coefficients. By carefully controlling these parameters, the system achieves wide field width while maintaining image quality at field boundaries, overcoming the limitations of conventional FMA designs.
3Area of stationary object
If the slit opening is increased to enlarge the field, then the field width increases, but aberrations and image distortion become very significant
Solution Approach 1:
The patent converts the potential harm of wide-angle light collection (which typically causes aberrations) into a benefit by using the specific M1-M2 mirror configuration with equal radii. This configuration naturally corrects certain aberrations, while M3 and M4 further correct remaining distortions, allowing large field width without significant image degradation.
Solution Approach 2:
The optical system combines different mirror types (convex and concave) with specific surface figures (spherical and aspherical) to create a composite optical system. This composite approach allows the system to simultaneously achieve wide field width and high image quality, overcoming the limitations of single-mirror or simple multi-mirror configurations.
4Area of stationary object
If a wide field of 85° is achieved, then the instantaneous field covered increases for earth observation missions, but the telescope size and complexity increase
Solution Approach 1:
The optical components are arranged in a compact nested configuration where mirrors M1, M2, M3, and M4 are positioned in sequence with optimized spacing. This nested layout minimizes the overall telescope length and volume while accommodating the four-mirror wide-angle design, making the system suitable for satellite deployment despite the increased field width.
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 provides a high-quality image over a larger field without significant aberrations, reducing spherical aberrations, coma, astigmatism, and field curvature, and maintains a compact size, exceeding the diffraction limit in image quality.
Implementation Method 1
a first mirror M1, a second mirror M2, a third mirror M3 and a fourth mirror M4... the first mirror is convex and the second mirror is concave and that the two mirrors M1, M2 have substantially the same radius of curvature
Implementation Method 2
M1 is aspherical to order 6; M2 is an ellipsoid; M3 and M4 are oblate spheroids... reducing spherical aberrations, coma, astigmatism, and field curvature
Data Source
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AI summary
The system has a convex mirror (M1) whose radius of curvature is equal to radius of curvature a concave mirror (M2). A ratio between the distance calculated from the concave mirror till a focal point of the system and the distance calculated from the concave mirror and a focal point of the convex mirror is comprised between 0 and 1. A concave mirror (M3) and a convex mirror (M4) are arranged in the system. The mirror (M1) is aspherical, the mirror (M2) is ellipsoid, and the mirrors (M3, M4) are flat spheroids.