Introductory Fourier transform spectroscopy

A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident illumination; detecting illumination reflected from the surface to form at least one detected signal; and determining the amount of relative motion parallel to the surface from said at least one detected signal, characterized in that said determining includes correcting for the effects of relative motion perpendicular to the surface.

Optical translation measurement

A laser based coordinate measuring device measures a position of a remote target. The laser based coordinate measuring device includes a stationary portion, a rotatable portion, and at least a first optical fiber. The stationary portion has at least a first laser radiation source and at least a first optical detector, and the rotatable portion is rotatable with respect to the stationary portion. The first optical fiber system, which optically interconnects the first laser radiation source and the first optical detector with an emission end of the first optical fiber system, has the emission end disposed on the rotatable portion. The emission end emits laser radiation to the remote target and receives laser radiation reflected from the remote target with the emission direction of the laser radiation being controlled according to the rotation of the rotatable portion.

Laser-based coordinate measuring device and laser-based method for measuring coordinates

The nascent field of high-temperature nanophotonics could potentially enable many important solid-state energy conversion applications, such as thermophotovoltaic energy generation, selective solar absorption, and selective emission of light. However, special challenges arise when trying to design nanophotonic materials with precisely tailored optical properties that can operate at high-temperatures (> 1,100 K). These include proper material selection and purity to prevent melting, evaporation, or chemical reactions; severe minimization of any material interfaces to prevent thermomechanical problems such as delamination; robust performance in the presence of surface diffusion; and long-range geometric precision over large areas with severe minimization of very small feature sizes to maintain structural stability. Here we report an approach for high-temperature nanophotonics that surmounts all of these difficulties. It consists of an analytical and computationally guided design involving high-purity tungsten in a precisely fabricated photonic crystal slab geometry (specifically chosen to eliminate interfaces arising from layer-by-layer fabrication) optimized for high performance and robustness in the presence of roughness, fabrication errors, and surface diffusion. It offers near-ultimate short-wavelength emittance and low, ultra-broadband long-wavelength emittance, along with a sharp cutoff offering 4∶1 emittance contrast over 10% wavelength separation. This is achieved via Q-matching, whereby the absorptive and radiative rates of the photonic crystal’s cavity resonances are matched. Strong angular emission selectivity is also observed, with short-wavelength emission suppressed by 50% at 75° compared to normal incidence. Finally, a precise high-temperature measurement technique is developed to confirm that emission at 1,225 K can be primarily confined to wavelengths shorter than the cutoff wavelength.

/pdf/enabling-high-temperature-nanophotonics-for-energy-1y6r4b21vm.pdf

Enabling high-temperature nanophotonics for energy applications

Recent advances in thermal infrared remote sensing include the increased availability of airborne hyperspectral imagers (such as the Hyperspectral Thermal Emission Spectrometer, HyTES, or the Telops HyperCam and the Specim aisaOWL), and it is planned that an increased number spectral bands in the long-wave infrared (LWIR) region will soon be measured from space at reasonably high spatial resolution (by imagers such as HyspIRI). Detailed LWIR emissivity spectra are required to best interpret the observations from such systems. This includes the highly heterogeneous urban environment, whose construction materials are not yet particularly well represented in spectral libraries. Here, we present a new online spectral library of urban construction materials including LWIR emissivity spectra of 74 samples of impervious surfaces derived using measurements made by a portable Fourier Transform InfraRed (FTIR) spectrometer. FTIR emissivity measurements need to be carefully made, else they are prone to a series of errors relating to instrumental setup and radiometric calibration, which here relies on external blackbody sources. The performance of the laboratory-based emissivity measurement approach applied here, that in future can also be deployed in the field (e.g. to examine urban materials in situ), is evaluated herein. Our spectral library also contains matching short-wave (VIS–SWIR) reflectance spectra observed for each urban sample. This allows us to examine which characteristic (LWIR and) spectral signatures may in future best allow for the identification and discrimination of the various urban construction materials, that often overlap with respect to their chemical/mineralogical constituents. Hyperspectral or even strongly multi-spectral LWIR information appears especially useful, given that many urban materials are composed of minerals exhibiting notable reststrahlen/absorption effects in this spectral region. The final spectra and interpretations are included in the London Urban Micromet data Archive (LUMA; http://LondonClimate.info/LUMA/SLUM.html).

https://centaur.reading.ac.uk/36997/1/IJPRS_Kotthaus_2014_albedo_emissivity.pdf

Derivation of an urban materials spectral library through emittance and reflectance spectroscopy

A procedure to calibrate a Fourier transform spectrometer is presented. Blackbody sources of three different temperatures are used to eliminate errors in the calibration that result from the limited accuracy of the temperature measurement of the calibration sources. With three spectra of blackbodies it is possible to assume that the temperatures are unknown variables as are the parameters of the functions that describe the spectrometer. A nonlinear Gaussian balancing calculation is used to determine these unknown variables and to minimize the influence of noise. A comparison between the results obtained with this method and a conventional calibration procedure is presented.

Calibration of a Fourier transform spectrometer using three blackbody sources

A newly designed Michelson interferometer for Fourier spectroscopy [ J. Opt. Soc. Am. A8, 1991 ( 1991)] utilizes a nutating retroreflector (cube corner mirror) to generate alterations in geometrical and optical paths. The practical optomechanical design of a Fourier-transform spectrometer incorporating a rotating retroreflector for path-length alteration is considered. [The instrument has been given the name MIROR, for Michelson Interferometer with a Rotating Retroreflector.] Two parameters of the instrument are essential: the maximum optical path difference, which yields the spectral resolution of the instrument, and the diameter of the transmitted beam, which determines the throughput and hence the achievable signal-to-noise ratio. The maximum allowable beam diameter is calculated as a function of the geometry and the orientation of the rotating retroreflector and the other optical components. The geometrical configuration and the orientation of all the optical components with respect to one another are also optimized for the maximum transmitted beam diameter when the required path difference is given. A principal investigation of different possible configurations of the optical components is presented. Then a quantitative optimization for an interferometer employing a retroreflector having a 5-in. (12.7-cm) aperture diameter requiring an optical path difference of more than 10 cm (spectral resolution better than 0.1 cm−1) is performed. Finally a simplified but enhanced design is described.

Optimization of a Michelson interferometer with a rotating retroreflector in optical design, spectral resolution, and optical throughput

For quantitative analysis of gas volumes, specifically combustion exhaust gases, by means of emission or absorption spectrometry in the ultraviolet, visible and infrared spectral range, geometrically defined and reproducibly adjustable observation planes are oriented perpendicular to the longitudinal axis of an exhaust stream. In a first series of measurements a number of m spectral measurements is performed, in such a way that the optical axis of a spectrometer is always located in the respective observation level but is shifted in a parallel direction by a first distance from one measurement to the next. In a second series of measurements n measurements are performed, in such a way that the optical axis is again located in the observation plane and is shifted in a parallel direction by a second distance from each measurement to the next. The (m+n) measurements produce two orthogonal sets of line of sights, which form a grid with (m·n) intersecting volumes. With the aid of the (m+n) measurements, each measurement yields the spectral transmission τ(v), or the spectral radiation intensity I(v) which is integrated via the total gas volume in the beam of rays of the spectrometer field of view.

Process for the quantitative analysis of gas volumes, specifically exhaust and waste gases from combustion systems or incineration plants, as well as systems for performing these processes

Animals (fawns, young rabbits, etc.) as well as clutches of ground-breeding bird species (pheasant, partridge, lapwing, snipe, curlew, etc.) in meadows and fields are at risk of injury, killing or destruction by agricultural machines. By using infrared, microwave and video sensors, which are attached individually or in combination at a suitable location on the machine, they can be tracked down and saved in good time. An additional position measuring device (DGPS) enables rescue measures without interrupting the agricultural processing measures.

Detecting animals and/or spawn of ground brooders in natural habitat involves mobile infrared, microwave and visible radiation detection, spatial correlation and electronic processing

A new application of IR sensors for the detection of game is presented. The device detects wildlife (mammals, birds) by using the difference in IR radiation of wildlife and its.

Volker Tank

Papers

Calibration of a Fourier transform spectrometer using three blackbody sources

Optimization of a Michelson interferometer with a rotating retroreflector in optical design, spectral resolution, and optical throughput

Process for the quantitative analysis of gas volumes, specifically exhaust and waste gases from combustion systems or incineration plants, as well as systems for performing these processes

Detecting animals and/or spawn of ground brooders in natural habitat involves mobile infrared, microwave and visible radiation detection, spatial correlation and electronic processing

Infrared sensor for the detection and protection of wildlife