The present invention applies to the art of wind sensing using lidar, and in particular to the art of detecting the speed of objects such as air-borne particles and molecules in the atmosphere in order to determine the speed and direction of the wind which is carrying them. The present invention is a beam director for directing a beam transmitted from a lidar at objects to produce backscattered light and for directing the backscattered light into a lidar receiver. The preferred embodiment of the director comprises a rotatable holographic optical element for directing the transmitted beam in various directions, and then through the same rotatable holographic optical element direct backscattered light from various directions into a receiver. In one alternative embodiment of the director, a prism is disposed in the director for directing the transmitted beam. The lidar having the beam director is moved in a vehicle such as a satellite, so that wind characteristics such as wind speed and direction at a number of altitudes and over a large area can be measured.
A constellation of satellites comprising at least two satellites in the same orbit is used to measure atmospheric wind speeds by means of a spatial wind lidar; each satellite carries a Doppler lidar, with a fixed sight axis. The orbit is a polar or quasi-polar orbit, with an orbital altitude from 350 to 500 km. The sight angles and the distribution of the satellites in the orbit are chosen so that the tracks on the surface of the Earth of the sight axes of the satellites of the constellation are substantially coincident over half of the surface of the Earth and regularly distributed over the other half of the surface of the Earth.
A system for measuring components of the velocity of wind along two axes that are transverse to the line of sight of the system includes first and second light emitter arrays disposed along crossed first and second axes, respectively, for illuminating the distribution with light, a detector for receiving light backscattered from the distribution, and a controller to activate the arrays, receive detector signals, and calculate the projections of the velocity of the distribution onto the first and second axes. The light emitters of each array can be positioned at irregular distances and provide the system with the capability of discerning the direction of movement of the distribution along the two axes.
A 3D MultiSpectral Lidar. The system comprises a laser transmitter light source, a laser detection assembly, optics that couple the outgoing and incoming laser signals, a digital camera assembly for collecting passive light, a position and orientation system, and processing hardware. The system provides real-time georectified three dimensional images and topography using an airborne platform. The system collects time-synchronous lidar range and image data in an optical receiver. The individual images are then mosaiced and orthorectified in real-time. The lidar range data and image data are then coupled to a position and orientation system to transform the three dimensional range images to a single geographically referenced multispectral three dimensional image.
The present invention is directed to a laser communication transmitter and receiver for wireless optical communication. The laser communication transmitter uses a small diameter so correspondingly divergent beam to provide improved bit error rates. A laser communication receiver includes a diffractive optical element to permit detectors at different spatial locations to detect different wavelengths of the optical signal. An immersion lens may be employed to focus the optical signal to a spot size smaller than the photoactive area of the detector.
The present invention is directed to a laser communication receiver for wireless optical communication. A laser communication receiver includes a diffractive optical element to permit detectors at different spatial locations to detect different wavelengths of the optical signal. An immersion lens may be employed to focus the optical signal to a spot size smaller than the photoactive area of the detector. In one detector configuration, the optical signal is folded by a reflective surface and focused on a plurality of stacked detectors. The present invention further provides a method of manufacturing a detector and immersion lens assembly that provides a high degree of alignment between the lens and the corresponding detector.
