US-12618946-B2 - Optical positioning and navigating system

Abstract

A method, apparatus and system for performing optical positioning. The apparatus comprises a laser transmitter configured to transmit a laser beam toward a retroreflector, where the location of retroreflector is known and the retroreflector reflects the laser beam and imparts modulation onto the laser beam. An optical receiver receives the reflected laser beam reflected from the retroreflector and a processor extracts a code from the modulation, determines the location of the retroreflector and calculates the distance from the apparatus to the retroreflector and uses the code and distance to determine a position of the apparatus.

Inventors

• Weimin Zhou

Assignees

• U.S. Army DEVCOM, Army Research Laboratory

Dates

Publication Date

20260505

Application Date

20211013

Claims (20)

1. 1 . Apparatus for performing optical positioning and navigating comprising: a laser transceiver configured to transmit a laser beam, which is pulsed or continuously activated with a waveform, toward a retroreflector located in a known position as a location reference, where the retroreflector reflects the laser beam back into the incoming laser beam's direction and imparts modulation onto the reflected laser beam corresponding to a retroreflector code; an optical receiver in the laser transceiver configured to receive a laser beam reflected from the retroreflector; one or more of filters, digitizers, demodulators, amplifiers, and combinations thereof configured to perform demodulation processing on the received laser beam to determine a retroreflector code; an inertial measurement unit; a compass; and a processor configured to determine a distance from the apparatus to the retroreflector and demodulated retroreflector code to determine the location of the retroreflector, use the code and distance to determine a position of the apparatus based on the pulse or waveform of the laser beam; and determine a new position with the inertial measurement unit and the compass outside the original retroreflector's area to deploy a new retroreflector.
2. 2 . The apparatus of claim 1 wherein the processor is configured to use the code to determine a reference location of the retroreflector.
3. 3 . The apparatus of claim 1 wherein the inertial measurement unit is configured to generate a change of position estimate for the apparatus as it moves relative to the retroreflector between location determinations.
4. 4 . The apparatus of claim 3 wherein the position is used to correct a position estimate generated by the inertial measurement unit.
5. 5 . The apparatus of claim 1 further comprising a display configured to display the position of the apparatus on a map and/or location(s) of one or more retroreflectors on the map.
6. 6 . The apparatus of claim 1 further comprising communication means for communicating with a server comprising a database of at least one retroreflector code associated with a reference location.
7. 7 . The apparatus of claim 1 wherein the retroreflector is ground-based or air-based.
8. 8 . An optical positioning and navigating system comprising: an end-user device comprising the apparatus of claim 1 ; and a server, communicatively coupled to the end user device, comprising a database of at least one retroreflector code associated with a reference location.
9. 9 . The optical positioning and navigating system of claim 8 wherein the end-user device further comprises an inertial measurement unit configured to generate a change of a position estimate for the end-user device.
10. 10 . The optical positioning and navigating system of claim 9 wherein the position is used to correct the position estimate generated by the inertial navigation unit.
11. 11 . The apparatus of claim 1 further comprising a clock to enable performance of a time-transfer function.
12. 12 . The apparatus of claim 1 further comprising an automated laser scanner to rotationally scan the laser beam or to point the laser beam at the expected location of a retroreflector.
13. 13 . An optical positioning system comprising: at least three active-retroflectors having a reflective surface which reflects light back into the incoming light's direction, wherein at least a portion of the reflective surface comprises a pattern which, when reflecting light, imparts modulation onto the reflected light corresponding to a retroreflector code; and the apparatus of claim 1 configured to determine a position based on retroreflector codes from the at least three active-retroflectors and distances from the at least three active-retroflectors by triangulation calculations.
14. 14 . The apparatus of claim 1 , wherein once three retroreflectors have been deployed, the apparatus can navigate within the three retroreflectors' area without using the inertial measurement unit and the compass.
15. 15 . A method of performing optical positioning and navigating of a system, the method comprising: transmitting a laser beam toward a retroreflector, which is pulsed or continuously activated with a waveform, where the retroreflector reflects the laser beam back into the incoming laser beam's direction and imparts modulation onto the reflected laser beam corresponding to a retroreflector code; receiving a laser beam reflected from the retroreflector; performing demodulation processing on the received laser beam to determine a retroreflector code; determining a distance to the retroreflector based on the pulse or waveform of the laser beam; using the demodulated retroreflector code and distance to determine a position; determining a new position using an inertial measurement unit and a compass outside the original retroreflector's area; and deploying a new retroreflector at the new position.
16. 16 . The method of claim 15 further comprising using the code to determine a reference location.
17. 17 . The method of claim 15 further comprising generating a change of a position estimate with the inertial measurement unit and the compass.
18. 18 . The method of claim 17 further comprising using the position to correct the position estimate generated by the inertial measurement unit.
19. 19 . The method of claim 15 further comprising displaying the position of the system on a map and/or displaying location(s) of one or more retroreflectors on the map.
20. 20 . The method of claim 15 further comprising communicating with a server comprising a database of at least one retroreflector code associated with a reference location.

Description

GOVERNMENT INTEREST The invention described herein may be manufactured, used and licensed by or for the U.S. Government. BACKGROUND Field Embodiments of the present invention generally relate to positioning systems and, more specifically, to optical positioning systems. Description of the Related Art Devices that determine their position have become ubiquitous. Nearly every mobile smartphone includes a Global Navigation Satellite System (GNSS) receiver such as a Global Positioning System (GPS) receiver. Such receivers rely upon radio frequency (RF) signals transmitted from a constellation of satellites to compute the position of the receiver. Unfortunately, GPS satellites are costly and the RF signals they transmit can be blocked or jammed resulting in a receiver not being able to compute its position. Therefore, there is a need in the art for a positioning system that does not rely on RF signals to compute a position. SUMMARY Embodiments of the present invention include an optical positioning system comprising a laser transceiver and a plurality of -retroreflectors, where the system computes a position of the laser transceiver based upon reflected light from the retroreflectors in accordance with the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above recited embodiment of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. FIG. 1 depicts a block diagram of an optical positioning system in accordance with at least one embodiment of the present invention; FIG. 2 depicts a block diagram of a laser transceiver of FIG. 1 in accordance with at least one embodiment of the present invention; FIG. 3 depicts a flow diagram of a method of operation for the laser transceiver of FIG. 2 in accordance with at least embodiment of the present invention; FIG. 4 depicts an exemplary map in accordance with at least one embodiment of the present invention. DETAILED DESCRIPTION Embodiments of the present invention include optical positioning system comprising an end-user laser transceiver device/unit (hereinafter referred to as the device or end user device) and a plurality of retroreflectors. In one embodiment, the device emits a laser beam that is reflected by a retroreflector. The retroreflector modulates the reflected laser beam with a unique code. The reflected laser beam is received by the device and the code is extracted from the received signal. In one embodiment, the code is correlated with a reference location of the retroreflector and the device computes a distance between the device and the reference location by the round trip travel time of the laser light. In another embodiment, the code may contain the reference location. The laser beam is pointed toward at least two additional retroreflectors to identify two additional reference locations and a distance of the device to those locations. Using the distance to each of the three reference locations and the reference locations, the device computes its position. In other embodiments, the device may include an automated laser scanner to rotationally scan the laser beam or to point the laser beam at the expected location of a particular retroreflector. The geographic locations of the retroreflectors may be contained in a database located within the device or external to the device, based on the device's location, may compute the relative location of the retroreflectors relative to the device to assist in pointing the laser. Alternatively or additionally, the device may display a map showing the device's location and the location of retroreflectors in the vicinity of the device. The laser may then be manually pointed toward additional retroreflectors to determine additional reference locations and ranges. In other embodiments, the device may comprise a compass and an inertial measurement unit (IMU) to allow the device to serve as a navigation unit and track its position while moving. With an IMU, the device can be moved between determining reference locations and the IMU information may be used to adjust the distances measured to each reference location such that the device's position may be determine even if it is moved between retroreflector measurements. FIG. 1 depicts a block diagram of an optical positioning system (OPS) 100 in accordance with an embodiment of the present invention. In the exemplary embodiment, the OPS 100 comprises at least one end-user device 102 and a plurality of retroreflectors 108-1, 108-2, 108-3 . . . 108-N (collectively referred to as retroreflectors 108). The end-user device may be a