Otto Højager Attermann Nielsen

Spectral characterisation of dairy products using photon time-of-flight spectroscopy

In this paper, we present, for the first time, the absorption and reduced scattering spectra of commercially available milk and yoghurt products, obtained using photon-time-of-flight spectroscopy. The ability of this technique to separate the contributions from absorption and scattering in the sample provides important information on the chemical composition and micro-structural properties, which are not available with the traditional techniques used in dairy production. The instrument operates in the spectral range from 500 nm to 1030 nm. The reduced scattering coefficient varies from 5 cm−1 for milk with 0.1% fat in the near infrared range, to 60 cm−1 for yoghurt with 3.0% fat in the green wavelength regime. The absorption is within the range of 0.05–0.5cm−1, with only small variation in the absolute value between products. Our results show that the reduced scattering clearly distinguishes milk and yoghurt with the same fat content and can offer a reliable way of monitoring structural formation during milk fermentation.

Supercontinuum light sources for hyperspectral subsurface laser scattering: applications for food inspection

A materials structural and chemical composition influences its optical scattering properties. In this paper we investigate the use of subsurface laser scattering (SLS) for inferring structural and chemical information of food products. We have constructed a computer vision system based on a supercontinuum laser light source and an Acousto-Optic Tunable Filter (AOTF) to provide a collimated light source, which can be tuned to any wavelength in the range from 480 to 900 nm. We present the newly developed hyperspectral vision system together with a proof-of-principle study of its ability to discriminate between dairy products with either similar chemical or structural composition. The combined vision system is a new way for industrial food inspection allowing non-intrusive online process inspection of parameters that is hard with existing technology.

Motion analysis of optically trapped particles and cells using 2D Fourier analysis

Motion analysis of optically trapped objects is demonstrated using a simple 2D Fourier transform technique. The displacements of trapped objects are determined directly from the phase shift between the Fourier transform of subsequent images. Using end- and side-view imaging, the stiffness of the trap is determined in three dimensions. The Fourier transform method is simple to implement and applicable in cases where the trapped object changes shape or where the lighting conditions change. This is illustrated by tracking a fluorescent particle and a myoblast cell, with subsequent determination of diffusion coefficients and the trapping forces.

Evaluation of the ID220 single photon avalanche diode for extended spectral range of photon time-of-flight spectroscopy

This paper describe the performance of the ID220 single photon avalanche diode for single photon counting, and investigates its performance for photon time-of-flight (PToF) spectroscopy. At first this report will serve as a summary to the group for PToF spectroscopy at the Department of Physics, Lund University (Sweden) together with ID Quantique Inc. (Geneve, Switzerland). As such, the report does not give an introduction to PToF spectroscopy, which may be found om the Doctoral on the topic [2, 3, 19]. The report focuses on a description of the detectors ability to measure the PToF distribution of infrared light. First, a motivation for using the ID220 for measuring PToF distribution is given, followed by a brief description of the experimental setup in which the detector was characterized. Following this, the quantification of delay using cross correlation between PToF distributions is described. This allows the changes in delay and shape to be characterized. A technique for reducing measurement artefacts by lowering the repetition rate of the light source is also investigated. Lastly, the applicability of the detector for PTOF spectroscopy is discussed and conclusions drawn about its suitability for this application. Version History Version Date Change revision 1.0 15 / 7 / 2013 First summary of measurements 1.1 20 / 10 / 2013 Updated results section 1.2 11 / 1 / 2014 Included description of single photon avalanche diodes.

Broadband optical characterization of material properties

Optical inspection of material properties is of great interest to industry because it can perform objective and non-invasive characterisation of large sample quantities. This may be used in various ways to lower production costs and improve product quality. In this thesis the objective has been to develop and investigate the applicability of optical broadband characterization techniques in industrially relevant production process. Both combined broad and high resolution techniques have the potential to provide important information on scattering properties related to particle size distributions, as well as details of the absorption spectrum which relate to chemical composition. The thesis focuses on two production process from the food industry. The first process is from the dairy industry where discrimination between chemical and structural properties is of importance. To explore the applicability of optical techniques for this purpose, the fermentation of milk into yogurt has been used as a model system. Studies have been conducted on commercially available products, but also of on-line measurement of the fermentation process. The second process is from the aquaculture industry, quantification of the fish feed additive astaxanthin has been investigated. A measurement campaign has been carried out on a series of pellets specially produced for the purpose. To investigate these process, the following three measurement techniques have been developed and applied. (I)A camera based inspection system for spectrallyresolved Static Light Scattering (SLS). (II) Photon Time-of-Flight (PToF) spectroscopy, which is a state of the art technique for characterization of turbid media. (III) A new hyperspectral imaging system based on full-field illumination by diffuse laser light. This thesis reports on the design and operation of the different measurement techniques together with the necessary theoretical

Broadband photon time of flight spectroscopy: advanced spectroscopic analysis for ensuring safety and performance of pharmaceutical tablets

We report on extended spectroscopic analysis of pharmaceutical tablets performed with broadband photon time-of-flight absorption/scaring spectroscopy. Precise monitoring of absorption and scattering spectra enables cost-efficient monitoring of key safety and performance parameters of the drugs.