Abstract:
A thermal emitter (2) device includes a cavity structure that comprises an active medium (8) for allowing thermal emissions to occur. A photonic crystal structure (4) is positioned on one side of the cavity structure. The photonic crystal structure comprises alternating layers of high index (10) and low index (12) materials and acts as a first mirror for the cavity structure. A highly reflective mirror structure (6) is positioned on another side of the cavity structure and acting as both the high-temperature source of radiation and a second mirror for the cavity structure.
Abstract:
An optical sensor for detecting a chemical in a sample region includes an emitter for producing light, and for directing the light through the sample region. The sensor also includes a detector for receiving the light after the light passes through the sample region, and for producing a signal corresponding to the light the detector receives. The sensor further includes a thermo-optic filter disposed between the emitter and the detector. The optical filter has a tunable passband for selectively filtering the light from the emitter. The passband of the optical filter is tunable by varying a temperature of the optical filter. The sensor also includes a controller for controlling the passband of the optical filter and for receiving the detection signal from the detector. The controller modulates the passband of the optical filter and analyzes the detection signal to determine whether an absorption peak of the chemical is present.
Abstract:
A field test-kit for analyzing arsenic concentration in water samples incudes a portable infrared beam photometer for measuring light absorbance in aqueous specimens. An infrared ligth emittng diode (120A, 120B) is configured to direct a beam of light through a specimen. A photodetecotr diode (130A, 130B) measures the intensity of light passing through the specimen. The photodetector (130A, 130B) output voltages relate to the light absorbed in the specimen and are displayed on a LCD (160) screen. To test for arsenic, molybdenum-blue color complexes. The light absorbance of a specimen with both arsenates and phosphates bound in molybdenum-blue color complexes is compared to that of a reference specimen in which phosphates but not arsenates are bound and converted. A quantitative value for the arsenic concentration in the water sample is determined from the differential light absorbance of the two specimens.
Abstract:
A source for reducing drift of a hot spot by producing infrared (IR) light with an insulating housing; an electrical power supply; first and second resistance elements having first and second resistivities; a third resistance element having a third resistivity; the third resistance element disposed between the first and second resistance elements, with the resistivity of the third resistance element having a value greater than the resistivity of both the first and second resistance elements. Alternatively, the first and second resistance elements can have cross-sectional areas that are greater than that of the third resistance. A method of reducing drift of a hot spot in a radiating element of a source of IR illumination by applying constant polarity substantially constant direct current from the power supply and reversing polarity in less than 24 hours, by a square wave AC source, or a Class E amplifier at constant power.
Abstract:
A blackbody radiation device (110) includes a planar filament emission element (102) and a planar detector (104) for respectively producing and detecting radiation having width d1/1 less than about 0.1 to test a sample gas, where 1 is the wavelength of the radiation; a reflector (108); a window (W); an electrical control (118); and a data output element (116).
Abstract:
A power circuit (15) for use with a resistive thermal radiation source (1) in which the power delivered to the radiation source (1) will remain constant within a preselected deviation over a fixed period of time as the source resistant (2) of the radiation source (1) varies between an initial source resistance and a second source resistance at operating temperature.
Abstract:
Described is a sensor (1) operating according to the light absorption principle, for detecting CO2. The sensor (1) comprises a housing (2) having therein a measuring chamber (3). On both sides of the measuring chamber (3) are arranged a source (20) and a detector (30) for measuring light (23). The source (20) is a bulk piece of dysprosium-doped lanthanum sulfide glass, which receives pump light (12) generated by an LED (10). The LED (10) can be fed by means of a solar cell (40). The detector (30) generates an electric signal which is representative of the amount of measuring light received (23), which amount is indicative of the amount of CO2 in the measuring chamber (3). The sensor (1) according to the present invention is very simple, compact, inexpensive and energy-saving.
Abstract:
Agencement de source de radiation infrarouge, notamment pour une utilisation dans l'analyse spectrale infrarouge. On applique à un substrat électriquement isolant (2) un et de préférence au moins deux films séparés électriquement conducteurs (2a, 2b) adaptés à être chauffés par l'application d'un courant électrique dépendant du temps. Deux ou plusieurs films peuvent former un groupe de radiations (réseau) dans lequel chaque film (2a, 2b) est adapté à être mis sous tension séparément avec un courant électrique provenant d'un circuit électrique d'attaque (1) et permettant d'appliquer au film ou films un courant électrique dépendant du temps, de préférence sous forme d'impulsion, de sorte que des impulsions de radiation infrarouge sont émises. Le courant électrique est commandé dans le temps afin de pouvoir distinguer l'une de l'autre dans un détecteur (6) les impulsions de radiation provenant des films respectifs. L'épaisseur du substrat et la conductivité thermique, la chaleur et la densité spécifiques du matériau de substrat sont choisies de manière à adapter la constante de temps thermique à la gamme de fréquence d'impulsion du circuit d'attaque.