The Smart, White-Light Dazzler (SWLD) is a nonlethal weapon designed to aim and deliver a dazzling and disabling light flash of maximum eye-safe energy to a selected target. The two key features of the SWLD technology are its self-aiming and power-adjusting capabilities; optical barriers, such as dark glasses, rifle scopes, binoculars, etc., and iris aperture, whether the eyes are light or dark adapted, are automatically taken into account by using a low-power infrared (IR) laser to probe and return a glint from the eye(s) of the target. Using the retro-reflected glint the dazzle pulse is adjusted and directed to arrive at the target with maximum allowable nonlethal energy at any range from 1 m to 100 m.
The collateral risk of this technology is very small. If the weapon is misaimed dramatically, the returned glint may come from an unintended person who will then be dazzled. Although this person will be incapacitated for 2-3 minutes, he will suffer no long-term effects. We assume all persons in dangerous situations would rather be accidentally, temporarily dazzled than suffer more serious consequences.
The SWLD adds an important tool to the spectrum of nonlethal responses available for use by military and law enforcement personnel. Applications include dispersing persons in crowd control and disabling terrorists in hijacking situations. The dazzle process may be repeated, choosing the next most susceptible target until a crowd is subdued. One important application in counter-terrorism is onboard planes where a pilot can fire a SWLD through a cockpit-door window and dazzle a hijacker with no damage to passengers.
We have previously described a holographic laser apparatus that 'cleans up' a laser beam by discarding off-axis rays. The device uses two matched holograms carefully oriented with respect
to one another so that the Bragg effect from the first hologram cleans up first one direction and then the second hologram cleans up the orthogonal direction. The device works well and reduces
the beam divergence to 0.8 mrad with a 3.0 mm thick hologram. However, there are practical difficulties with this configuration including sensitivity to the mutual alignment of the holograms
and a cleaned-up beam which is inconveniently not in the same horizontal plane as the input laser beam. We describe here a much simpler design using a single hologram that improves performance and avoids these difficulties.
A solar photovoltaic energy collection system using a reflection hologram is described herein. The system uses a single-axis tracking system in conjunction with a spectral- splitting holographic element. The hologram accurately focuses the desired regions of the solar spectrum to match the bandgaps of two ro more different solar cells, while diverting unused IR wavelengths away. Other applications for solar holography include daylighting and greenhouses.
Using holographic methods to fabricate antireflection coatings is attractive because arbitrarily small reflectivities may be achieved at a single wavelength with a simple photographic process. In this paper, we discuss the theoretical aspects of these holograms and the technical aspects of fabricating them. We present numerical simulations that predict the spectral response of the coating as a function of the bandwidth of the recording source and the thickness and modulation of the emulsion. These results are confirmed with spectrophotometer measurements of actual coatings. Recording holographic antireflection coatings requires a single collimated light source. The hologram-air interface is sued to create the second wave; this allows the coating to automatically correct for variation in the surface of the hologram. However, this method requires a post recording coating procedure to produce a diffracted wave with the correct phase shift. After the hologram is recorded and processed, a thin layer of SiO<SUB>2</SUB> or MgF<SUB>2</SUB> is applied to the hologram to adjust the phase shift between the diffracted wave and the surface reflection. Additionally this coating procedure enhances the durability of the coating and, if MgF<SUB>2</SUB> is used, lowers the refractive index modulation required for complete cancellation of the surface reflection.
Simultaneous quantitative measurements of both the temperature and velocity fields for 2D transient natural convection in an enclosure are made using calibrated multichannel electronic interferometry and digital particle image velocimetry. Calibrated multichannel electronic interferometry, a technique for quantitative flow visualization of transient phenomena, is discussed. This technique uses an interferometer combined with diffraction gratings to generate the three phase shifted interferograms simultaneously. The optical system is calibrated using standard piezoelectric phase shifting. The alignment is determined using spatial crosscorrelation. The calibration and alignment routines account for errors due to the separation of the phase shifted interferograms. Digital particle image velocimetry is implemented simultaneously with the interferometric measurements using a separate video channel. The system is used to examine the development of transient natural convection in enclosures at three angles of inclination.