Azimuthal Phase Mask for Coronagraph Starlight Suppression
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Solution Overview
Problem
Detecting planets outside the solar system is challenging due to the significant brightness difference between stars and planets, requiring effective light attenuation in coronagraph imaging systems, particularly for star systems where phase masks offer better diffraction management.
Innovation Solution
A phase mask assembly with a continuous phase variation in the azimuthal direction is used within a coronagraph system, featuring a transparent material with varying thickness to apply a sinusoidal phase shift, ensuring a null intensity region at the center of the image while minimizing distortion, fabricated using precision techniques like diamond turning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase mask with continuous azimuthal phase variation is used, then the null intensity region is improved and the primary Airy pattern is suppressed, but the manufacturing precision requirement increases
Solution Approach 1:
The patent applies parameter changes by varying the thickness of the phase mask continuously in the azimuthal direction according to a sinusoidal function. This continuous parameter variation creates the desired phase profile that suppresses the primary Airy pattern and produces a high-quality null intensity region. The thickness variation is precisely controlled through diamond turning to achieve the required phase modulation.
2Reliability
If the phase mask thickness varies continuously in azimuthal direction, then the diffraction effect is improved, but the device complexity increases
Solution Approach 1:
The patent employs spheroidality by implementing a continuous azimuthal phase variation that corresponds to a curved or rounded thickness profile. The sinusoidal variation in thickness creates a smooth, continuous surface that is free of sharp discontinuities, thereby improving diffraction management and reducing scattering effects while maintaining a relatively simple single-element structure.
3Ease of manufacture
If an occulting disk is used to block star light, then the implementation is simple, but the diffraction effect deteriorates
Solution Approach 1:
The patent replaces the mechanical occulting disk with an optical phase mask that uses refractive index and thickness variation to achieve starlight suppression. Instead of mechanically blocking light with a simple disk, the phase mask uses continuous azimuthal phase variation to redirect and cancel the primary Airy pattern, thereby eliminating the harmful diffraction effects while maintaining ease of manufacture through precision optical fabrication.
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 approach effectively separates the desired off-axis planet image from the brighter central star image by creating a null intensity region, suppressing the primary Airy pattern and allowing the detection of fainter planet images without significant distortion.
Implementation Method 1
The phase mask assembly has a first surface and a second surface. The first surface and the second surface are configured such that the distance between the first surface and the second surface varies continuously in an azimuthal direction around the phase mask.
Implementation Method 2
it is more suitable to use a phase mask for star systems because the entrance aperture dominates the diffraction effect of images
Implementation Method 3
A reimaging portion mitigates the undesired central image. The reimaging portion includes a phase mask assembly that applies a continuous phase variation in an azimuthal direction to an image received from the first imaging lens, such that a null intensity region is produced in the center of the received image.
Data Source
AI summary
Systems and methods for shifting the phase of incident light to induce a continuous phase variation in an azimuthal direction. A phase mask assembly has a first surface and a second surface. The first surface and the second surface are configured such that the distance between the first surface and the second surface varies continuously in an azimuthal direction around the phase mask. This mask can be used in a coronagraph system to effectively suppress the on-axis star image for the detection of off-axis planets.