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Spectral Fingerprinting on a Standard Mobile Phone
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
2010 (English)In: Journal of Sensors, ISSN 1687-725X, E-ISSN 1687-7268, Vol. 2010, 381796- p.Article in journal (Refereed) Published
Abstract [en]

Spectral fingerprinting of chemical indicators, using computer screens as light sources and web cameras as imaging detectors, is an emerging approach for chemical sensing with the potential to coexist in common consumer electronic devices.The migration of this technique to mobile phones is key to extend this sensing approach to the most ubiquitous and familiar type of instrumentation. Here, we investigate the feasibility and performance of spectral fingerprinting on reference samples using a standard mobile phone as a complete measuring platform, where the screen provides controlled illumination while the front camera is the imaging detector. Key elements for the execution of such experiments are the software design, the definition of the sample layout, the type of alignment between the phone and the sample, and the influence of ambient illumination. This paper demonstrates the feasibility of reflectance fingerprinting on standard mobile phones and identify the operating conditions of the key parameters that produce an adequate evaluation performance.

Place, publisher, year, edition, pages
Hindawi , 2010. Vol. 2010, 381796- p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-65730DOI: 10.1155/2010/381796OAI: oai:DiVA.org:liu-65730DiVA: diva2:398565
Note

Original Publication: Zafar Iqbal and Daniel Filippini, Spectral Fingerprinting on a Standard Mobile Phone, 2010, Journal of Sensors, (2010), 381796. http://dx.doi.org/10.1155/2010/381796 Licensee: Hindawi Publishing http://www.hindawi.com/

Available from: 2011-02-18 Created: 2011-02-18 Last updated: 2017-12-11Bibliographically approved
In thesis
1. A Standard Mobile Phone as a Chemical Sensor
Open this publication in new window or tab >>A Standard Mobile Phone as a Chemical Sensor
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes work to investigate the potential of using an ordinary mobile phone to perform chemical sensing by colorimetric analysis of reflected light. The wide availability and familiarity of mobile phones make them excellent devices for aiding consumers in making on site tests in their everyday lives. A major part of the work has been the development of the necessary software to be able to use a standard mobile phone to study diffuse reflection with the screen as illumination source and the front view camera for collection of spectral information.

Java Micro Edition was used to control the hardware resources of the phone. The NetBeans 6.5 platform facilitated the design, development, testing and implementation of a dedicated Mobile Information Device  applet for performing the necessary tasks associated with controlling the screen light and recording the reflected light intensities. MATLAB was employed to extract spectral information from the recorded images.

Initially, tests with a virtual sample having areas with different colors were performed. Optimization of the alignment of the sample and the distance between the camera and the sample were carried out and the influence of ambient light was investigated. The lateral resolution of the images enables optical readout of sensor arrays as well as arrays for diagnostics.

The potential of using the technique for direct measurement of properties related to the quality of drinking water, food and beverages was also investigated. Liquid samples were prepared in deionized water. Colored compounds such as iron(III)chloride and humic acid in the concentration range 2-10 mg/l were classified from their reflected intensities. Colorless arsenic(III) was analyzed by its bleaching reaction with iodine/starch. An alternative arsenic detection method based on measurement of discoloration of iron containing sand was demonstrated.

We have also demonstrated that mobile phones can be used for qualitative analysis of food and drink, such as cold drinks, meat,  vegetables and milk in terms of general food quality.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 26 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1505
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65733 (URN)LIU-TEK-LIC-2011: 44 (Local ID)978-91-7393-051-2 (ISBN)LIU-TEK-LIC-2011: 44 (Archive number)LIU-TEK-LIC-2011: 44 (OAI)
Presentation
2011-10-14, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2011-02-18 Created: 2011-02-18 Last updated: 2015-03-24Bibliographically approved
2. Optical Sensing With an Ordinary Mobile Phone
Open this publication in new window or tab >>Optical Sensing With an Ordinary Mobile Phone
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A major portion of the world’s population (≈ 80% of the total) lives in developing countries where lab instruments such as spectrophotometers are not widely available as their purchasing as well as maintenance is normally unaffordable. On the other hand, there are now around five billion mobile phone subscriptions worldwide and the current generation of standard mobile phones has several capabilities to perform user-defined analysis. This thesis contains work with respect to asses potentials and weaknesses of a standard mobile phone for use as a simplified spectrophotometric unit (as both the light source and detector) to perform analysis in the visible region (400-700 nm). A part of the work has been the development of the necessary software to be able to use an ordinary mobile phone to study diffuse and specular reflectance properties of the targeted samples using phone’s screen as controllable illumination source and the front view camera for simultaneous collection of spectral information.

Papers I-III contain exploratory work performed to assess the potential of using the mobile phone as an optical sensor system. Papers IV and V present studies of more basic character of the interactions between the light from the phone screen and the sample, in particular for liquid samples.

In paper I, tests with a virtual array of chemical indicators having areas with different colours were performed. Optimization of the alignment of the sample and the distance between the camera and the sample were carried out and the influence of ambient light was investigated. The lateral resolution of the images enables optical readout of sensor arrays as well as arrays for diagnostics.

In paper II, the potential of using the technique for direct measurement of properties related to the quality of drinking water, food and beverages was investigated. Liquid samples were prepared in deionized water. Coloured compounds such as iron(III)chloride and humic acid were analyzed in the concentration range 0-10 mg/liter and were classified by their reflectance profiles with respect to the contamination type and its concentration. Colourless arsenic(III) was analyzed by its bleaching reaction with iodine/starch. An alternative arsenic detection method based on measurement of discolouration of iron containing sand was demonstrated.

In paper III, it has been demonstrated that mobile phones can be used for qualitative analysis of foods and beverages, such as cold drinks, meat, vegetables and milk in terms of general food quality, safety and authenticity.

In paper IV, the ability of the mobile phone system to measure absorption properties of liquid solutions is investigated. Different concentrations of colored solutions (reactive blue 2, Congo red and Metanil yellow) give rise to measurement data that are well described by the Beer-Lambert law. This is surprising since the measurement conditions were far from ideal, with a light source that was strongly polychromatic and an illumination that was not a collimated light beam with homogeneous light intensity. By analyzing red, green and blue light that was transmitted through the liquid a unique signature for classification and quantification was obtained. Also the repeatability and accuracy of the measurements were investigated and were surprisingly good for such a simple system. Analyses of reflectance properties of colored solid samples are also included and were more complex with results being dependent on the morphology and colorimetric properties of the different types of these samples.

In paper V, it is found that different parts of the image data contain different information about liquid samples. While one part of the image gives information about the absorption properties as investigated in detail in paper IV, another part gives information about the refractive index of the sample. Measurements of samples with varying refractive index show trends expected from the Fresnel equations at zero incidence angle. Combined information from the two areas of the image offers new possibilities to classify samples.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 56 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1473
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-81006 (URN)978-91-7519-807-1 (ISBN)
Public defence
2012-09-26, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2012-09-05 Created: 2012-09-05 Last updated: 2015-03-24Bibliographically approved

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