Polarization grating based star simulator

Patent metadata

Field	Value
Publication number	US-11768384-B2
Application number	US-202217567578-A
Country	US
Kind code	B2
Filing date	Jan 3, 2022
Priority date	Jan 7, 2021
Publication date	Sep 26, 2023
Grant date	Sep 26, 2023

Abstract

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.

First claim

What is claimed is:

1. A star map projection system consisting of:
a laser that emits a laser beam;
a polarization grating that spatially reduces the laser beam to a reduced laser beam;
an attenuator that attenuates the reduced laser beam to form an attenuated laser beam;
a first Risley element in a first holder that deflects the reduced laser beam to form a first angled laser beam, the first holder providing independent rotation of the first Risley element;
a second Risley element in a second holder that receives the first angled laser beam and forms a second angled laser beam which is directed onto a screen, the second holder providing independent rotation of the second Risley element;
a controller that independently rotates each Risley element to position the simulated star laser beam onto a pre-defined location on the screen;
a pair of rotation actuators in communication with the controller through a device interface that are respectively engaged to the first and second holders for rotation of the Risley elements, the controller comprising
a memory containing an application and a lookup table, wherein the controller comprises a processor that executes the application to:
monitor current rotation positions respectively of the first and second Risley elements reported by the first and second rotation actuators;
determine a pre-defined location on the screen;
determine a change in rotation positions of the first and second Risley elements specified in the lookup table based on current rotation positions and a two-dimensional position of the second angled laser beam; and
actuate the first and second rotation actuators to effect a change in the rotation positions of the first and second Risley elements.

2. The star map projection system of claim 1 , wherein the attenuator consists of a dynamic attenuator that is communicatively coupled to the controller to adjust an amount of attenuation by the dynamic attenuator.

3. The star map projection system of claim 1 , wherein the pair of Risley optical elements each comprise a Risley prism.

4. The star map projection system of claim 1 , wherein the pair of Risley optical elements each comprise a Risley grating.

5. The star map projection system of claim 1 , wherein the pair of Risley optical elements each comprise a photonic crystal.

Assignees

• Us Govt As Represented By Secy Of Air Force
• Us Air Force

Inventors

• Lentz Joshua

Classifications

• G02B27/4261 Primary

  having a diffractive element with major polarization dependent properties · CPC title

• G02B5/1842

  Gratings for image generation (G02B5/1847 takes precedence) · CPC title

• G02B26/0891 Primary

  forming an optical wedge · CPC title

• G03B21/142

  Adjusting of projection optics · CPC title

• G02B5/1871

  Transmissive phase gratings · CPC title