Optical Head-Mounted Display System for Laser Safety Eyewear

A new method is described for optical data transmissions from satellites using laser arrays for fine pointing of laser beams that use body pointing. It combines a small lens system and a VCSEL/Photodetector Array in a novel way to provide a fine pointing capability for laser beams that are pointed by body pointing of a CubeSat. As Fig. 1 shows, an incoming laser beam (green or blue, with rightward arrows), transmitted from a ground terminal, enters the lens system, which directs it to an element of the pixel array (gray rectangle). Each element, or pixel, consists of a VCSEL component/photodetector pair. The photodetector detects the incoming beam, and the VCSEL component returns a modulated beam to the lens system (green or blue, with leftward arrows), which sends it to the ground terminal. As the incoming beam changes direction, e.g., from the blue to the green incoming direction, this change is detected by the adjacent photodetector, and the laser paired with that photodetector is turned on to keep the outgoing laser beam on target. The laser beams overlap so that the returning beam continues to point at the ground terminal. The VCSEL component may consist of a single VCSEL or a cluster of VCSELs. Figure 2 shows the propagation of two overlapping laser beams. The system can very accurately point finely focused diffraction-limited laser beams. Also, simultaneous optical multiple access (OMA) is possible from different transceivers within the area covered by the laser array. For this electro-optical system, reaction times to pointing changes and vibrations are on the nanosecond time scale, much faster than mechanical fine pointing systems.

This invention provides a new method for optical data transmissions from satellites using laser arrays for laser beam pointing. The system is simple, static, compact, and provides accurate pointing, acquisition, and tracking (PAT). It combines a lens system and a vertical-cavity surface-emitting laser VCSEL)/Photodetector Array, both mature technologies, in a novel way for PAT. It can improve the PAT system's size, weight, and power (SWaP) in comparison to current systems. Preliminary analysis indicates that this system is applicable to transmissions between satellites in low-Earth orbit (LEO) and ground terminals. Computer simulations using this design have been made for the application of this innovation to a CubeSat in LEO. The computer simulations included modeling the laser source and diffraction effects due to wave optics. The pointing used a diffraction limited lens system and a VCSEL array. These capabilities make it possible to model laser beam propagation over long space communication distances. Laser beam pointing is very challenging for LEO, including science missions. Current architectures use dynamical systems, (i.e., moving parts, e.g., fast-steering mirrors (FSM), and/or gimbals) to turn the laser to point to the ground terminal, and some use vibration isolation platforms as well. This static system has the potential to replace the current dynamic systems and vibration isolation platforms, dependent on studies for the particular application. For these electro-optical systems, reaction times to pointing changes and vibrations are on the nanosecond time scale, much faster than those for mechanical systems. For LEO terminals, slew rates are not a concern with this new system.

A laser or a light source is incident on a detector. It usually passes through a shutter that can open and then close to limit the amount of light hitting the detector. There are limitations on the speed, size and cost of such apertures. The design of this technology uses DLP mirror technology. It can rapidly deflect the incoming light beam onto an aperture, which blocks the beam path, or through the aperture, which allows it to go onto the detector. The DLP mirror in this shutter uses an aperture design that is nearly 3 orders of magnitudes faster (shorter exposure time) than similar-sized aperture using conventional commercial-off-the-shelf mechanical shutters and 1-2 orders of magnitude smaller and cheaper than higher-performing custom-made shutters that are used by a few labs around the world. The DLP mirror is actuated via a computer controlled oscillator circuit. A laser beam directed to the mirror is either passed to a target detector, or diverted, based on the inputs from the circuit. In this manner, the DLP mirror / circuit can act as a fast shutter, modulator, or chopper for the light beam. One novel feature of this invention is the application of the DLP to divert a beam onto or off a detector for instrumentation systems.

This suite of technologies includes a method, algorithms, and computer processing techniques to provide for image photometric correction and resolution enhancement at video rates (30 frames per second). This 3D (2D spatial and range) resolution enhancement uses the spatial and range information contained in each image frame, in conjunction with a sequence of overlapping or persistent images, to simultaneously enhance the spatial resolution and range and photometric accuracies. In other words, the technologies allows for generating an elevation (3D) map of a targeted area (e.g., terrain) with much enhanced resolution by blending consecutive camera image frames. The degree of image resolution enhancement increases with the number of acquired frames.

State of the art space-based LIDARs typically require a telescope with sufficient area to increase the return signal on the detector to levels above the noise floor of the detectors. Two major drivers of the signal-to-noise ratio (SNR) on the detectors are the laser output energy and the round trip distance traveled by the laser signal. The SNR on the detectors can be increased by increasing the telescope reflector area or by decreasing the system noise. If these techniques are not an option, this method can be used to separate stray light from polarized laser light in the LIDAR system and improve the SNR. The method includes generating a beam of azimuthally polarized or OAM light utilizing an optical transmitter comprising a laser light source. The method includes providing an optical receiver including optical sensors at a focal plane with a photon sieve that produces a ring pattern on the focal plane corresponding to a laser return signal. The ring pattern comprises azimuthally polarized or OAM light that is transmitted by the transmitter and reflected towards the receiver. The photon sieve is utilized to cause stray light that is not polarized to cluster centrally, and away from the ring pattern created by the LIDAR signal. This technology could also be used with space based and terrestrial LIDAR for encrypted line of sight communications. The unique revolution frequencies of the LIDAR make any attempt to intercept the communication pointless for those who don&#39t know the specific mode of the source. The lidar system also has use cases for short range navigation for Urban Air Mobility (UAM) vehicles providing input as to whether there is significant enough clear air turbulence on a given path as to be dangerous to an aerial vehicle.