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Optical Sensing With an Ordinary Mobile Phone
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-81006ISBN: 978-91-7519-807-1 (print)OAI: oai:DiVA.org:liu-81006DiVA: diva2:549813
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
List of papers
1. Spectral Fingerprinting on a Standard Mobile Phone
Open this publication in new window or tab >>Spectral Fingerprinting on a Standard Mobile Phone
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
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65730 (URN)10.1155/2010/381796 (DOI)
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
2. Colorimetric analysis of water and sand samples performed on a mobile phone
Open this publication in new window or tab >>Colorimetric analysis of water and sand samples performed on a mobile phone
2011 (English)In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 84, no 4, 1118-1123 p.Article in journal (Refereed) Published
Abstract [en]

Analysis of water and sand samples was done by reflectance measurements using a mobile phone. The phone’s screen served as light source and front view camera as detector. Reflected intensities for white, red, green and blue colors were used to do principal component analysis for classification of several compounds and their concentrations in the water. Classification of iron (III), chromium (VI) and sodium salt of humic acid was obtained using reflected intensities from blue and green light for concentrations 2-10 mg/l. Analysis of As(III) from 25-400 μg/l based on reflection of red light was performed utilizing the bleaching reaction of tincture of iodine containing starch. Enhanced sensitivity to low concentrations of arsenic was obtained by adding reflected intensities from white light to the analysis. Model colored sand samples representing discoloration caused by the presence of arsenic in groundwater were also analyzed.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
mobile phone, home analysis, colorimetric assay, multivariate analysis, arsenic detection
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65732 (URN)10.1016/j.talanta.2011.03.016 (DOI)000291078100016 ()
Available from: 2011-02-18 Created: 2011-02-18 Last updated: 2017-12-11Bibliographically approved
3. Assessment of a mobile phone for use as a spectroscopic analytical tool for foods and beverages
Open this publication in new window or tab >>Assessment of a mobile phone for use as a spectroscopic analytical tool for foods and beverages
2011 (English)In: International journal of food science & technology, ISSN 0950-5423, E-ISSN 1365-2621, Vol. 46, no 11, 2428-2436 p.Article in journal (Refereed) Published
Abstract [en]

A mobile phone was used to perform optical analyses of foods and beverages. The phone’s screen served as illumination source and front view camera recorded images. Reflected intensities were used to discriminate among the different samples analysed by principal component analysis. Samples studied illustrated the technique’s potential analytical capabilities with respect to adulteration and authenticity. Three coloured additives (red, green and blue) in the concentration range 2-10 mg/l in a lemon lime beverage were discriminated. Adulteration by up to 25% water of milk with 3% fat content was detected with an estimated detection limit of about 3% water. Changes occurring on a green onion surface over a 48 h aging period at room temperature were monitored. Five different cuts from lamb carcasses weighing 9 and 14 kg were classified by the method. Considerable additional work with regard to sampling, data treatment and quantifying results is necessary before the goal of using the technique as a point of purchase analytical tool can be realised.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2011
Keyword
Mobile phone, point of purchase, adulteration, authenticity, colourants, milk, vegetable freshness, meat cuts, multivariate analysis
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-70849 (URN)10.1111/j.1365-2621.2011.02766.x (DOI)000296377300027 ()
Note
Funding agencies|Pakistans Higher Education Commission (HEC)||Available from: 2011-09-20 Created: 2011-09-20 Last updated: 2017-12-08Bibliographically approved
4. Classification and quantitative optical analysis of liquid and solid samples using a mobile phone as illumination source and detector
Open this publication in new window or tab >>Classification and quantitative optical analysis of liquid and solid samples using a mobile phone as illumination source and detector
2013 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 185, 354-362 p.Article in journal (Refereed) Published
Abstract [en]

A mobile phone has been used both as illumination source and image detector for quantitative optical analysis of colored liquid samples (4 different colorants) and solid samples (printed color patterns, plastic beads and colored sand grains). Even though the measurement conditions were far from ideal, because the light source was strongly polychromatic and the illumination was not a collimated light beam with homogeneous light intensity, a logarithmic concentration dependence, in accordance with the Beer-Lambert law, described the data of the colored liquids quite well. By utilizing blue-blue (420-510 nm), green-green (480-590 nm) and red-red (575-695 nm) illumination/detection combinations, each sample could be assigned a unique color signature for classification that agreed with reference absorbance spectra measured with a spectrometer. Quantification of validation samples within a few percent of the actual values was achieved. Also the long-term repeatability of the measurements was investigated and was surprisingly good for such a simple system. Analysis of the colored solid samples was more complex with results being dependent on the morphology and colorimetric properties of the samples.

Place, publisher, year, edition, pages
Elsevier, 2013
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-81003 (URN)10.1016/j.snb.2013.05.009 (DOI)000321509600049 ()
Available from: 2012-09-05 Created: 2012-09-05 Last updated: 2017-12-07Bibliographically approved
5. Optical sensing with a mobile phone applied to liquid solutions
Open this publication in new window or tab >>Optical sensing with a mobile phone applied to liquid solutions
2012 (English)Manuscript (preprint) (Other academic)
Abstract [en]

The use of a mobile phone with a front side camera for the classification of liquid samples is described. The classification is based on the observation that there are different regions of the image captured by the mobile camera, one containing specular reflected light and one due to diffuse reflected light with transmission through the liquid. The specular reflected light contains information about the refractive index of the liquid sample whereas the diffuse light contains information about the color and absorption properties of the liquid. The information in the specular light is first elucidated. It is found that the reflectance of the region with specular reflected light increases linearly with increasing refractive index, n, in the range 1.33 < n < 1.38 as expected from the Fresnel equations. The information in the specular light is then used together with the previously described diffuse light from another region of the image to analyze several types of liquid samples. It is shown that a combination of the two areas of the image improves the classification abilities of the mobile phone.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-81005 (URN)
Available from: 2012-09-05 Created: 2012-09-05 Last updated: 2015-05-29Bibliographically approved

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