Catadioptric Optical System Variable Transmittance Coating
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Solution Overview
Problem
Catadioptric optical systems suffer from obscuration issues that degrade the modulation transfer function (MTF), leading to reduced image contrast and light efficiency, despite previous attempts to control obscuration using partial reflection coatings and semitransparent coatings.
Innovation Solution
The implementation of a catadioptric optical system with a baffle to block direct light and a partially transparent surface around the optical axis, allowing transmissivity to vary radially at the exit pupil plane, optimizing the obscuration ratio and MTF by using a rotationally symmetric variable transmittance coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a catadioptric optical system uses an axisymmetric mirror to collect light, then light collection efficiency is improved, but obscuration ratio increases causing MTF degradation
Solution Approach 1:
The patent applies local quality by creating a radially variable transmittance coating on the catadioptric optical element. The transmittance varies from the center to the periphery of the element, with different regions having different optical properties. This allows the central region to handle direct light differently from the peripheral regions that handle reflected light, optimizing both light collection and reducing obscuration effects on the MTF.
Solution Approach 2:
The patent changes the transmittance parameter radially across the catadioptric optical element. By varying the transmittance from center to periphery, the system optimizes the balance between collecting direct light (improving light efficiency) and controlling the obscuration effect (improving MTF). This parameter change allows different parts of the light cone to be transmitted with different efficiencies.
2Loss of energy
If a baffle is placed to block direct light and form a shielded portion, then obscuration control is improved, but light transmission is reduced
Solution Approach 1:
The radially variable transmittance coating creates local quality differences across the optical element. Regions closer to the center have different transmittance characteristics compared to peripheral regions, allowing the system to selectively transmit or block light based on its origin (direct vs. reflected) while maintaining overall light transmission efficiency.
Solution Approach 2:
Instead of completely blocking direct light with a baffle (excessive action), the patent uses a partial action approach by employing a radially variable transmittance coating that partially transmits and partially blocks light depending on the radial position. This partial action maintains better light transmission while still achieving obscuration control.
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 configuration reduces obscuration and enhances the modulation transfer function, improving light efficiency and image contrast, while maintaining a balance between obscuration control and light transmission.
Implementation Method 1
a catadioptric optical subsystem configured to collect light from an object plane
Implementation Method 2
a catadioptric optical subsystem configured to collect light from an object plane
Implementation Method 3
a baffle to shut off light traveling toward the image plane without being reflected by the catadioptric optical subsystem
Implementation Method 4
the catadioptric optical subsystem includes a partially transparent surface around the optical axis of the optical system so that transmissivity of a region, other than the shielded portion, at the exit pupil plane varies in a radial direction of the exit pupil plane
Data Source
AI summary
An optical system to form an image on an image plane includes, a catadioptric optical subsystem configured to collect light from an object plane; and a refractive optical subsystem configured to form the image on the image plane, the catadioptric and refractive optical subsystems being arranged in order from the object plane to the image plane along an optical axis of the optical system. A baffle to shut off light traveling toward the image plane without being reflected by the catadioptric optical subsystem is placed in the optical system, in order to form a shielded portion in a center of an exit pupil plane of the optical system, and the catadioptric optical subsystem includes a partially transparent surface around the optical axis of the optical system so that transmissivity of a region, other than the shielded portion, at the exit pupil plane varies in a radial direction of the exit pupil plane.