Catadioptric Microscope Objective with Minimal Central Obscuration
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Solution Overview
Problem
Current microscope objectives, particularly catadioptric designs, face challenges in achieving high resolution below 400 nm and stable operation across the deep UV to near IR spectral range while minimizing central obscuration and maintaining practical dimensions.
Innovation Solution
A dry catadioptric microscope objective design featuring a primary front-surface concave mirror with no through-hole and a plane-parallel rear-surface secondary mirror, devoid of lens elements between the mirrors, which minimizes central obscuration and allows for broadband operation from 190 nm to 900 nm with a numerical aperture of 0.9 or greater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a catadioptric design with a primary mirror is used, then broadband operation from DUV to near IR is achieved, but central obscuration increases and limits the optical transfer function
Solution Approach 1:
The patent inverts the conventional catadioptric configuration by placing the plane-parallel plate with reflective coating in front of the concave mirror instead of behind it. This inversion allows the light path to be reconfigured so that the plate serves as the primary reflecting element while the concave mirror acts as a secondary element, thereby reducing central obscuration while maintaining broadband spectral operation from 190 nm to 900 nm
Solution Approach 2:
The patent extracts and removes the central obscuration problem by eliminating the need for a through-hole in the primary mirror substrate. The plane-parallel plate with reflective coating is positioned to reflect light before it reaches the concave mirror, allowing the concave mirror substrate to remain solid without openings, thus removing the source of central obscuration while preserving the broadband reflective operation
2Adaptability or versatility
If an off-axis catadioptric design is used to increase spectral bandwidth, then operational spectral bandwidth increases, but the objective becomes bulky and complicated
Solution Approach 1:
The patent employs asymmetric positioning of the plane-parallel plate relative to the optical axis and the concave mirror, creating an optimized light path that achieves broadband spectral operation without requiring a bulky off-axis configuration. The asymmetric arrangement allows compact folding of the optical path while maintaining wide spectral bandwidth from deep UV to near IR
Solution Approach 2:
The patent nests the plane-parallel plate with reflective coating within the compact catadioptric structure, positioning it in front of the concave mirror in a nested configuration. This nesting allows both optical elements to work together in a compact arrangement that achieves broadband operation without the bulk and complexity of traditional off-axis designs
3Ease of operation
If a primary mirror with a through-hole is used, then light transmission is enabled, but manufacturing complexity and optical artifacts increase
Solution Approach 1:
The patent extracts the light transmission function from the primary mirror substrate by introducing a separate plane-parallel plate with reflective coating. This plate is positioned to reflect light before it reaches the concave mirror, allowing the concave mirror substrate to remain solid without through-holes, thereby eliminating manufacturing complexity and associated optical artifacts while maintaining light transmission
Solution Approach 2:
The plane-parallel plate with reflective coating serves as an intermediary element that enables light transmission and reflection without requiring modifications to the concave mirror substrate. This intermediary plate handles the light path control, allowing the concave mirror to maintain its solid substrate structure, thus simplifying manufacturing while enabling the required optical functionality
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 design achieves low aberration and high sensitivity across the spectral range, reducing optical artifacts and facilitating easier manufacturing, while maintaining a compact size and low obscuration, thus enhancing imaging performance in deep UV and near IR applications.
Implementation Method 1
a primary front-surface concave mirror, which has a first substrate with a concave front surface carrying a reflective coating thereon
Implementation Method 2
a secondary rear-surface mirror, which has a second substrate (optionally configured as a plane-parallel plate)
Implementation Method 3
a first group of lenses defining an afocal optical relay unit; a second group of lenses, said second group of lenses having a positive refractive optical power
Data Source
AI summary
A catadioptric microscope objective color-corrected for any wavelength in 190 nm to 1000 nm operational range and containing primary spherical front-surface mirror devoid of a through-hole and rear-surface plane-parallel mirror, each of which mirrors has a corresponding reflective annular coating defining an aperture formed in such coating coaxially with the optical axis. The objective, devoid of a Mangin element, is configured such that for any optical field with a diameter smaller than about 50 microns the Strehl ratio is no lower than 0.0781, and/or longitudinal spherical aberration is no larger than 0.0008 mm, and/or the astigmatism is smaller than 0.0005 mm, and/or distortion is smaller than 0.012 percent within the operational range.