Polarization Grating Star Simulator for Large FOV Testing
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Solution Overview
Problem
Current star simulation technologies lack the capability for high precision tracking over large fields of view (FOV) of 7 degrees or larger, with existing methods either limited to single spot calibration with high angular resolution or low angular resolution over a large FOV, and there is a need for a system that can simulate multiple stars with high accuracy.
Innovation Solution
A modular, multi-star simulator system utilizing a cycloidal diffractive waveplate (CDW) and opto-mechanical beam steering with polarization gratings, allowing for very high precision dynamic star locations and accurate brightness control, which includes a laser source, polarization grating-based image, and a diffuse screen for scattering light to create a star field, enabling independent movement of stars within the beam steering accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a spatial light modulator is used for multi-star simulation, then large field of view capability is achieved, but manufacturing precision and system complexity increase significantly
Solution Approach 1:
The system segments the star simulation function into multiple independent polarization grating elements, each responsible for specific star positions. This allows the large field of view to be achieved through modular arrangement while maintaining high precision through controlled polarization modulation of each segment.
Solution Approach 2:
The patent replaces mechanical spatial light modulators with a polarization grating-based optical system. This substitution eliminates the need for complex mechanical moving parts while achieving both large field of view and high precision through polarization optics, thereby reducing manufacturing precision requirements for mechanical components.
2Measurement precision
If single spot calibration is used, then high angular resolution is achieved, but field of view is limited to approximately 1 degree
Solution Approach 1:
The system transitions from single-spot calibration to multi-dimensional star field simulation by introducing polarization grating arrays that can simultaneously generate multiple star positions across a large field of view. This dimensional expansion maintains high angular resolution through polarization-controlled diffraction while covering degrees-scale fields of view.
3Area of stationary object
If low angular resolution is used, then large field of view is achieved, but tracking precision requirement of 1 μrad cannot be met
Solution Approach 1:
The patent changes the polarization state parameters of light through precisely controlled polarization gratings to achieve both large field of view and high tracking precision. By modulating polarization angles and diffraction orders, the system can position stars with μrad-level accuracy across degrees-scale fields of view, satisfying both requirements simultaneously.
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 precision and modularity in star simulation, allowing for the creation of a large FOV star tracker capable of testing high accuracy, with the ability to add additional stars and extend FOV by incorporating more polarization gratings, while maintaining precision and reducing system complexity and cost.
Implementation Method 1
The light is projected onto a diffuse screen where the light is scattered, creating a functional point source at the screen
Implementation Method 2
A modular, multi-star simulator system utilizing a cycloidal diffractive waveplate (CDW) and opto-mechanical beam steering with polarization gratings
Implementation Method 3
polarization grating-based image, and an opto-mechanical system for steering the light
Data Source
AI summary
A cycloidal diffractive waveplate based star simulator generates a star field with very high precision star locations and accurate brightness. The present disclosure provides a star simulator that allows for a large FOV, modular, multi-star simulator capable of very high precision dynamic star locations for testing of high accuracy, large FOV star trackers. The system is composed of a light source, a polarization grating-based image [1], and an opto-mechanical system for steering the light. The light is projected onto a diffuse screen where the light is scattered, creating a functional point source at the screen. A star tracker or other device under test views the screen which has a multitude of projected spots (each with its own light source and beam steering device) positioned in a star field distribution appropriate for the simulated viewing direction.