摘要:
A system and method for free space, optical remote sensing of a potential threat agent using spectrally responsive sensor material. In one example the sensor material is formed by particles, which in one particular form are porous photonic crystals. The particles are dispersed into an area being monitored for the presence of the potential threat agent. A pair of lasers is used to generate optical light beams that are directed at the sensor particles after the particles have been dispersed. The light reflected by the sensor particles is then analyzed. The presence of the potential threat agent causes a shift in the spectral peak of light reflected from the sensor particles that can be sensed using photo detectors and a processing subsystem. The system can be tuned to remotely detect for specific chemical, biological or environmental agents that may be present within a given area.
摘要:
A system and method for free space, optical remote sensing of a potential threat agent using spectrally responsive sensor material. In one example the sensor material is formed by particles, which in one particular form are porous photonic crystals. The particles are dispersed into an area being monitored for the presence of the potential threat agent. A pair of lasers is used to generate optical light beams that are directed at the sensor particles after the particles have been dispersed. The light reflected by the sensor particles is then analyzed. The presence of the potential threat agent causes a shift in the spectral peak of light reflected from the sensor particles that can be sensed using photo detectors and a processing subsystem. The system can be tuned to remotely detect for specific chemical, biological or environmental agents that may be present within a given area.
摘要:
Apparatus and methods for calibrating an optical detector. In one embodiment an optical reference apparatus includes a body having an outer surface. At least a portion of the outer surface has a reflectance that can vary. The optical reference apparatus is adapted to be deployed with a cloud of optical sensors and has a terminal velocity that is about the same as the terminal velocity of the sensors. Further, the variation of the reflectance can be caused by a rotation of the optical reference apparatus (caused by an aerodynamic member). The sensors may be made from porous silicon and the optical reference apparatus may include a retroreflector. The apparatus also provides a method of referencing an optical signal. The method includes deploying an optical reference apparatus with a cloud of sensors and detecting a variation in its reflectance.
摘要:
The invention provides chromate-free coating mixtures, and coatings formed from these mixtures, that protect an underlying aluminum or aluminum alloy substrate from corrosion. The coating mixtures include a continuous phase selected from organic polymeric compositions, or sol-gels, and a distributed phase, dispersed or dissolved throughout the continuous phase. The distributed phase includes the corrosion-inhibiting chromate-free salts. In accordance with the invention, the mixture of salts includes (1) a first salt selected from (a) the esters of rare earth metals, such as cerium and lanthanum oxalates and acetates, and (b) the vanadate salts of alkali and alkali earth metals, such as sodium metavanadate and calcium metavanadate; and (2) a second salt that is a borate salt of alkali earth metals, such as barium metaborate. In certain embodiments, the coatings of the invention include both (a), and (b), in conjunction with the borate salt (2). In other embodiments, the chromate free salt is a chloride of a rare earth metal, or mixture of such chlorides, either alone or in combination with the first salt or the second salt, or both the first and second salts. Coatings of the invention provide protection to an underlying substrate, even after subjection to a 3000 hour salt spray test. Moreover, the coatings are resistant to degradation by SKYDROL, and are able to withstand impacts of 50 inch-pounds (forward) and 30 inch-pounds (reverse), so that they are well suited for use as protective coatings for aircraft.
摘要:
An LED having a broadband emission spectrum. In one embodiment, the LED comprises a layered semiconductor structure of length L, the structure including an active layer comprising multiple asymmetric quantum wells. A pair of stripe electrodes is formed on a surface of the structure, to thereby form at least one optical cavity having a pumped length less than L. Currents to the cavities are controlled as a function of temperature to produce broadband emission over a range of temperatures.
摘要:
A system and methods for detecting semiconductor-based photodiodes. The present embodiments provide a simple and practical approach for identifying optical reflection that is indicative of photon reflection from semiconductor-based photodiodes. Thus in certain applications the present embodiments may be used to detect the presence of OIEDs, which may use photodiodes as part of a detonation system.
摘要:
A detector and method for identifying a chemical vapor and determining its concentration in the ambient atmosphere. The chemical detector apparatus (120) preferably includes a plurality of surface acoustic wave (SAW) devices (10), each including a piezoelectric substrate (20), one-half (32) of which is coated with a selected polymer. The polymer characteristically absorbs one or more of a group of chemical vapors. Diffusion of a chemical vapor into the polymer increases its mass and proportionately changes the resonant frequency of the SAW device. A microcomputer control (186) is operative to determine a predicted time constant (or rate) for diffusion and a predicted equilibrium concentration of the chemical vapor within the polymer coating of the SAW device and to identify the chemical vapor and its relative concentration in the ambient atmosphere using the predicted values for these parameters long before the SAW device has reached equilibrium with the chemical vapor.
摘要:
The disclosed system includes a piezoelectric crystal exposed to an energy-absorptive medium of interest. A crystal oscillation circuit is included for sustaining oscillation of the crystal in contact with the fluid. To accomplish this, the circuit includes feedback elements for providing automatic gain control of the amplifier portion of the oscillator. In this manner, the conditions required for crystal oscillation are maintained independent of variations in the medium the crystal is exposed to. Information regarding the gain adjustment and oscillation frequency of the crystal are applied to a microprocessor-based system for determining fluid characteristics such as viscosity, density, and dielectric constant. Alternatively, this information is used to correct for the influence of such parameters on the resonant behavior of piezoelectric crystals undergoing mass change, in the analysis of, for example, corrosion, adsorption and electroplating. The relationship between the particular characteristics determined and the output information received from the oscillation circuit is dependent upon the hydrodynamic and electrokinetic coupling experienced between the medium and crystal.
摘要:
A sensing device which senses the presence and/or concentration of one or more gases contained in a mixture is disclosed. An electrically charged semiconductor whose surface is in contact with the mixture of gases is illuminated with light, either intermittently or constantly. Changes in the transient and steady state conductivity of the semiconductor are measured and amplified. The form of the functionality between the gas and the conductivity changes is unique to a particular gas at a particular concentration and is used both to detect the presence and/or concentration of the gas.
摘要:
A system and methods for detecting semiconductor-based photodiodes. The present embodiments provide a simple and practical approach for identifying optical reflection that is indicative of photon reflection from semiconductor-based photodiodes. Thus in certain applications the present embodiments may be used to detect the presence of OIEDs, which may use photodiodes as part of a detonation system.