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Sensors 2017, 17(7), 1604;

A Smartphone-Based Automatic Measurement Method for Colorimetric pH Detection Using a Color Adaptation Algorithm

Department of Electronic Engineering Education, Andong National University, 1375 Gyeongdong-ro, Andong, Gyeongsangbuk-do 36729, Korea
FIT BEST Laboratory, Department of Chemical, Biological, and Bioengineering, North Carolina A&T State University, 1601 E. Market St., Greensboro, NC 27411, USA
Author to whom correspondence should be addressed.
Received: 5 June 2017 / Revised: 26 June 2017 / Accepted: 7 July 2017 / Published: 10 July 2017
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This paper proposes a smartphone-based colorimetric pH detection method using a color adaptation algorithm for point-of-care applications. Although a smartphone camera can be utilized to measure the color information of colorimetric sensors, ambient light changes and unknown built-in automatic image correction operations make it difficult to obtain stable color information. This paper utilizes a 3D printed mini light box and performs a calibration procedure with a paper-printed comparison chart and a reference image which overcomes the drawbacks of smartphone cameras and the difficulty in preparing for the calibration procedure. The color adaptation is performed in the CIE 1976 u’v’ color space by using the reference paper in order to stabilize the color variations. Non-rigid u’v’ curve interpolation is used to produce the high-resolution pH estimate. The final pH value is estimated by using the best-matching method to handle the nonlinear curve properties of multiple color patches. The experimental results obtained using a pH indicator paper show that the proposed algorithm provides reasonably good estimation of pH detection. With paper-printed accurate color comparison charts and smart color adaptation techniques, superior estimation is achieved in the smartphone-based colorimetric pH detection system for point-of-care application. View Full-Text
Keywords: colorimetric sensor measurement; pH detection; smartphone-based measurement colorimetric sensor measurement; pH detection; smartphone-based measurement

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Kim, S.D.; Koo, Y.; Yun, Y. A Smartphone-Based Automatic Measurement Method for Colorimetric pH Detection Using a Color Adaptation Algorithm. Sensors 2017, 17, 1604.

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