1,721,129 research outputs found
Optical method for monitoring the concentration of general anesthetics and other small organic molecules -- An example of phase transition sensing
No full textReconstruction of displacement waveforms with a single-channel laser-diode feedback interferometer
No full textSilicon Micromachined Device Testing by Infrared Low-Coherence Reflectometry
No full textWith the development of silicon micromachining technologies, non-contact measurement techniques for in-depth non-destructive inspection of layered and microstructured samples are becoming increasingly relevant. In this paper, we apply optical low-coherence reflectometry (OLCR) to detect the optical path between the interfaces of several silicon devices with characteristic distance in the range 3–17 μm. The implemented configuration is based on a fiberoptic Michelson interferometer that exploits infrared broadband radiation in the wavelength range of 1.2–1.7 μm, with coherence length shorter than 2 μm, for performing spot tomographic measurements. OLCR enabled out-of-plane measurements on a MEMS linear accelerometer and in-plane measurements on vertical periodic silicon/air microstructures. The optical distance between hidden interfaces was found well in agreement with the design parameters
A PC-interfaced, compact laser-diode feedback interferometer for displacement measurements
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Development of a fluorescence-based fiber optic sensor for rapid detection of general anesthetics and other lipid-soluble chemicals
No full textInterferometro a retroiniezione con diodo laser per misure di spostamenti con risoluzione del micrometro e senza ambiguità di segno
No full textAbsorption-based detection of urea concentration in hydroalcoholic solutions and white wine with a compact optical setup
No full textContactless detection of urea concentration in solution is very important in industrial, chemical, biological and agri-food applications. Urea, naturally contained in wine, when reacting with ethanol especially at high temperature may become the precursor of ethyl carbamate (urethane) which is carcinogen. Close monitoring of urea concentration in wine is necessary to prevent risks and diseases related to high urethane intake. In this work, we propose an optoelectronic measuring system for absorption-based detection of urea in water, in hydroalcoholic solutions with ethanol concentration of 12%, and in white wine with a 12% nominal concentration of ethanol. The urea concentration of the tested samples, contained in a 1-mm-deep rectangular glass capillary, was in the range from 0 up to 40 mg/mL. Two low-cost, low-power LEDs with emission spectra in the near infrared were employed as readout sources. The emission peaks of the selected LEDs were at λ = 1450 nm, where water absorbs more than urea, and at λ = 2350 nm, where urea absorption is higher than that of water. An amplified photodiode allowed to measure the transmitted optical power through the sample. To highlight the specificity of the measures, we also compared results of the optical measurements performed on urea-water solutions and on NaCl-water solutions. We demonstrate that measuring light intensity transmitted through each fluid mixture at the selected wavelengths allows not only to identify different urea concentrations, but also to distinguish samples of water-ethanol solutions from samples of white wine with the same urea concentration. This work represents the Proof of Principle of an optical method for specific urea detection in wine. Future work will be devoted to improving the system operation to enhance the limit of detection and to achieve recognition of urea concentration of the order of 0.001-0.003 mg/mL, typical values found in winery products
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