Entity

Time filter

Source Type


Geiser P.,Norsk Elektro Optikk AS | Paulsen K.G.,Neo Monitors AS
Proceedings of the Annual ISA Analysis Division Symposium | Year: 2015

Nitrogen oxides (NOx) and sulfur oxides (SOx) are typical pollutants emitted from all kinds of industrial processes. According to environmental protection regulations (e.g. by US EPA or Bundesumweltamt in Germany) the emission of these gases into ambient air must be limited. The increasingly strict regulations require the development of more sensitive instruments. Therefore, use of in-situ analyzers could provide more accurate emission measurements as well as being used for more efficient regulation systems. Tunable laser absorption spectroscopy (TLAS) has become the preferred measurement technique for many industrial applications in recent years, especially for in-situ measurements. Previously, mainly near-infrared lasers have been used in TLAS sensors. The advent of compact mid-infrared light sources like quantum cascade lasers (QCLs) and interband cascade lasers (ICLs) made it possible to measure gases that do not have any absorption bands in the near-infrared as well, like sulfur dioxide. In this presentation, a new sensor for sulfur dioxide (SO2) and new applications for NEO Monitors' nitric oxide (NO) sensor will be presented. These sensors are based on QCL and ICL technology. © Copyright 2015, International Society of Automation. All rights reserved. Source


Linnerud I.,Norsk Elektro Optikk AS | Paulsen K.G.,Neo Monitors AS
Proceedings of the Annual ISA Analysis Division Symposium | Year: 2012

Tuneable Diode Laser Absorption Spectroscopy (TDLAS) is well suited for measuring gas concentrations by using direct absorption measurements or by wavelength modulation with second harmonic detection. This document summarises the basic theory for both techniques. It is well known that by integrating the direct absorption peak, one can find the gas concentration without knowing the gas pressure or other line broadening effects. It is less well known that a similar integration technique can be applied to the second harmonic signal. The property that pressure and line broadening effects are eliminated by peak integration looks very attractive from a measurement point of view. This article discusses advantages and disadvantages of peak integration for both direct absorption and second harmonic detection compared to computing the gas concentration without peak integration. Theoretically, the peak integration should be done over an infinite frequency range, which is not achievable in practice. If a measurement accuracy better than 15-20% relative error is required, cutting the integration region needs to be corrected. Peak integration of the direct signal has significant challenges with the «baseline problem». Peak integration of the second harmonic signal does not have this problem, but may be more sensitive to noise in the wings of the absorption line. In most applications there are also nearby absorption lines from other gases, and these may easily influence and give cross interference effects on the gas to be measured. This is the case for peak integration of both direct and second harmonic signal. To reduce such effects it is necessary to make more careful measurements of the absorption line shape, and this counteracts the benefits with peak integration. It is therefore questionable whether the peak integration performs any better than a technique that computes the gas concentration more directly from the measured amplitude and line width. Source


Denstedt M.,Norwegian University of Science and Technology | Pukstad B.S.,Norwegian University of Science and Technology | Paluchowski L.,Norwegian University of Science and Technology | Hernandez-Palacios J.E.,Norwegian University of Science and Technology | And 2 more authors.
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2013

The healing process of chronic wounds is complex, and the complete pathogenesis is not known. Diagnosis is currently based on visual inspection, biopsies and collection of samples from the wound surface. This is often time consuming, expensive and to some extent subjective procedures. Hyperspectral imaging has been shown to be a promising modality for optical diagnostics. The main objective of this study was to identify a suitable technique for reproducible classification of hyperspectral data from a wound and the surrounding tissue. Two statistical classification methods have been tested and compared to the performance of a dermatologist. Hyperspectral images (400-1000 nm) were collected from patients with venous leg ulcers using a pushbroom-scanning camera (VNIR 1600, Norsk Elektro Optikk AS).Wounds were examined regularly over 4 - 6 weeks. The patients were evaluated by a dermatologist at every appointment. One patient has been selected for presentation in this paper (female, age 53 years). The oxygen saturation of the wound area was determined by wavelength ratio metrics. Spectral angle mapping (SAM) and k-means clustering were used for classification. Automatic extraction of endmember spectra was employed to minimize human interaction. A comparison of the methods shows that k-means clustering is the most stable method over time, and shows the best overlap with the dermatologist's assessment of the wound border. The results are assumed to be affected by the data preprocessing and chosen endmember extraction algorithm. Results indicate that it is possible to develop an automated method for reliable classification of wounds based on hyperspectral data. © 2013 SPIE. Source


Mei L.,Lund University | Brydegaard M.,Lund University | Brydegaard M.,Norsk Elektro Optikk AS
Laser and Photonics Reviews | Year: 2015

This work proves the feasibility of a novel concept of differential absorption lidar based on the Scheimpflug principle. The range-resolved atmospheric backscattering signal of a laser beam is retrieved by employing a tilted linear sensor with a Newtonian telescope, satisfying the Scheimpflug condition. Infinite focus depth is achieved despite employing a large optical aperture. The concept is demonstrated by measuring the range-resolved atmospheric oxygen concentration with a tunable continuous-wave narrow-band laser diode emitting around 761 nm over a path of one kilometer during night time. Laser power requirements for daytime operation are also investigated and validated with single-band atmospheric aerosol measurements by employing a broad-band 3.2-W laser diode. The results presented in this work show the potential of employing the continuous-wave differential absorption lidar (CW-DIAL) technique for remote profiling of atmospheric gases in daytime if high-power narrow-band continuous-wave light sources were to be employed. A novel concept of continuous-wave differential absorption lidar based on the Scheimpflug principle is demonstrated. The range-resolved atmospheric backscattering signal of a laser beam is retrieved by employing a tilted linear sensor with a Newtonian telescope, satisfying the Scheimpflug condition. The concept is validated by measuring the range-resolved atmospheric oxygen concentration with a tunable continuous-wave narrow-band laser diode emitting around 761 nm. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA. Source


Geiser P.,Norsk Elektro Optikk AS | Paulsen K.G.,Neo Monitors AS
Proceedings of the Annual ISA Analysis Division Symposium | Year: 2013

In more and more countries the emission of nitrogen oxides (NOx) and other industrial gases into ambient air has to be measured permanently due to environmental protection regulations. At the moment the measurement of nitric oxide (NO) as well as other environmental relevant gases can be performed, among others, by complex extractive systems (like FTIR or chemiluminescence instruments) or by tunable diode laser absorption spectrometers (TDLAS). Since many customers prefer in-situ measurements, NIR TDLAS spectrometers have become very popular for emission monitoring. Unfortunately some important gases, like nitric oxide, possess only weak overtone and combination absorption lines in the NIR and therefore NIR NO spectrometers have only a low sensitivity. The fundamental absorption bands in the mid-infrared spectral region are orders of magnitude stronger. The best absorption line in the 5.2 μm-band of NO is as an example approximately three orders of magnitude stronger than the best line in the 1.8 μm-band. Software simulations based on HITRAN and HITEMP databases have led to a selection of interference-free NO absorption lines in a typical industrial gas mixture. In cooperation with a laser manufacturer a quantum cascade laser chip for one of these absorption lines has been prepared and mounted into a High Heat Load (HHL) package. This laser source has again been integrated into a spectrometer which has been tested at an industrial site where it replaced an existing NIR TDLAS spectrometer. The comparative tests between MIR and NIR spectrometers show significant improvements in sensitivity as well as stability and hence the great potential of QCL-based MIR instruments. Source

Discover hidden collaborations