Abstract:
A method and device for measuring the soot load in the exhaust gas systems of diesel engines using a sensor which is mounted downstream of a particulate filter and comprises a sensor element, to measure the operability of the particulate filter. According to the method, the soot load of the sensor element is measured resistively or capacitively using electrodes. The measuring voltage of the sensor element is controlled depending on at least one actual operating parameter of the diesel engine.
Abstract:
A sampling accessory coupled to a hand-held reflectance spectrometer provides expanded sampling area which in turn provides better signal averaging from agricultural products which are often inhomogeneous. The sampling accessory includes a sample site repositioning means and a “sample cup” having a base that is transparent to near IR wavelengths.The hand-held reflectance spectrometer includes a shutter responsive to control signals from the control circuitry. When the shutter is closed, a reference measurement may be made. When the shutter is open, a sample measurement is taken.Sample repositioning and data acquisition within the cup may be performed by several means. Fresh sample regions may be exposed through either manual or motor driven sample cup rotation. Alternatively, the sample may be vibrated to induce fresh sample exposure at the window. A further embodiment includes illumination and/or detection paths that may be altered through electrically driven steering optics.
Abstract:
A near infrared (NIR) semiconductor laser system is shown for gas sensing. An embodiment is centered on the use of a system with a much wider tunable laser, which today has a scan band of more than 150 nanometers (nm) to as much as 250 nm or more. In some cases the scan band is about 400 nm or more. This is achieved in the current embodiment through the use of a widely tunable microelectromechanical system (MEMS) based Fabry-Perot filter as an integral part of the laser cavity. Using this technology, these systems are capable of capturing a variety of gases in the any of the well-known spectroscopic scan bands, such as the OH, NH or CH. For example, a single laser with a 250 nm scan band window between 1550-1800 nm can capture ten or as many as twenty hydrocarbon-based gases simultaneously.
Abstract:
A terahertz-wave generating device including an optical waveguide containing an electrooptic crystal includes: first and second optical waveguides through which first and second light beams respectively propagate; a propagation portion through which a first terahertz wave propagates, the first terahertz wave being generated from the second optical waveguide in a direction different from a direction of the second light beam; and a delay portion arranged at incidence sides of the first and second light beams and configured to delay the first light beam relative to the second light beam. The first optical waveguide and the second optical waveguide are arranged with the propagation portion interposed therebetween. A first equiphase surface of the first terahertz wave is substantially aligned with a second equiphase surface of a second terahertz wave generated from the first optical waveguide in a direction different from a direction of the first light beam.
Abstract:
A source of terahertz radiation at a fundamental terahertz frequency is tunable over a fundamental terahertz frequency range, and is coupled into a first waveguide. The first waveguide supports only a single transverse spatial mode within the fundamental terahertz frequency range. A solid-state frequency multiplier receives from the first waveguide the terahertz radiation and produces terahertz radiation at a harmonic terahertz frequency. A second waveguide receives the harmonic terahertz radiation. The tunable terahertz source can comprise a backward wave oscillator with output tunable over about 0.10-0.18 THz, 0.18-0.26 THz, or 0.2-0.37 THz. The frequency multiplier can comprises at least one varistor or Schottky diode, and can comprise a doubler, tripler, pair of doublers, doubler and tripler, or pair of triplers. The terahertz source can be incorporated into a terahertz spectrometer or a terahertz imaging system.
Abstract:
A sealed infrared radiation source includes an emitter membrane stimulated by an electrical current conducted through the membrane, which acts like an electrical conductor, wherein the membrane is mounted between first and second housing parts, at least one being transparent in the IR range, each housing part defining a cavity between the membrane and the respective housing part of each side of the membrane. The housing parts are at least partially electrical conductive, and a first of the housing parts is electrically coupled to a first end of the electrical conductor and insulated from the second end of the electrical conductor, the second housing part being electrically coupled to a second end of the electrical conductor and being insulated from the first end of the electrical conductor, thus allowing a current applied from the first housing part to the second housing part to pass through and heat the membrane.
Abstract:
The present invention provides devices, systems and methods for imaging and sensation of objects. In particular, the present invention provides devices, systems and methods for spectroscopic imaging and sensation of objects.
Abstract:
Methods and apparatus for providing a tunable absorption-emission band in a wavelength selective device are disclosed. A device for selectively absorbing incident electromagnetic radiation includes an electrically conductive surface layer including an arrangement of multiple surface elements. The surface layer is disposed at a nonzero height above a continuous electrically conductive layer. An electrically isolating intermediate layer defines a first surface that is in communication with the electrically conductive surface layer. The continuous electrically conductive backing layer is provided in communication with a second surface of the electrically isolating intermediate layer. When combined with an infrared source, the wavelength selective device emits infrared radiation in at least one narrow band determined by a resonance of the device. In some embodiments, the device includes a control feature that allows the resonance to be selectively modified. The device has broad applications including gas detection devices and infrared imaging.
Abstract:
A mid infrared spectrometer comprises a high brightness broadband source that generates an output with a broad spectral range in the order of hundreds of wave numbers, a wavelength dispersive element and a detector. In one embodiment, the source comprises an array of semiconductor laser devices operating simultaneously. Each device emits light at wavelength different from the wavelengths emitted by the other devices in the array and the devices are arranged so that the combined output continuously covers the broad spectral range. In another embodiment, each of the lasers in the array is a quantum cascade laser device. In still another embodiment, the quantum cascade laser devices in the array are operated in the regime of Risken-Nummedal-Graham-Haken (RNGH) instabilities. In yet another embodiment, each of the lasers in the array is a mode-locked quantum cascade laser device.
Abstract:
A portable device includes a base unit, an extension, and a mirror. The base unit includes a light source, a light detector, and at least one window through which light exits from, and is received by, the base unit. The extension is configured, during use, to be attached to the base unit and to extend from the at least one window, in a direction away from the base unit, the extension defining at least a portion of a sample volume in fluid communication with gases substantially surrounding one or more of the extension and the base unit. The mirror is attached to the extension at a distance from the at least one window. An optical path is defined between the mirror and the at least one window such that light from the light source moves through the sample volume along the optical path, and the mirror is aligned to reflect the light back to the at least one window for detection by the light detector.