Technique of dual-wavelength micro-lens imaging which can eliminate thermal noise for accurate on-site concentration measurement

• Published in: Sensors and actuators. B, Chemical Vol. 257; pp. 766 - 771
• Main Authors: He, Jiang, Jiang, Guang-Yun, Zhao, Xue-Cen, Huang, Yao-Xiong
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-03-2018; Elsevier Science Ltd
• Subjects: Accurate on-site concentration measurement; Dual-wavelength micro-lens imaging; Heat detection; Lenses; Measurement; Microlenses; Mixing or inhomogeneous solutions; Noise control; Refractivity; Sodium chloride; Thermal imaging; Thermal noise; Variation; Wave division multiplexing; Dual-wavelength micro-lens imaging; Thermal noise; Accurate on-site concentration measurement; Mixing or inhomogeneous solutions
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2017.10.148

•A novel technique for real time continuous on site accurate measurement of solution concentration.•Determines the local refractive index/concentration of an inhomogeneous solution with micro-lens imaging.•Employing two wavelengths for the imaging to eliminate thermal noise disturbance.•The accuracy and precision of refractive index detection is ±10−6.•Can obtain accurate concentration just 0.001% deviating from true value under temperature fluctuation.
The present paper reports a novel dual-wavelength micro-lens imaging technique which uses micro-lens as the sensor and can eliminate thermal noise for on-site real time and continues accurate concentration detection in mixing or inhomogeneous solutions. By simply immersing micro-lenses into sample solution and deducing the refractive indices of the solution from their images taken with two wavelengths, the technique can eliminate random thermal noise for accurate solution concentration measurement. With the technique, the accuracy and precision of refractive index detection was improved to ±10−6. Detections on NaCl and glucose solutions demonstrated that the measured concentrations were just about 0.005%–0.01% away from true values for one centigrade temperature fluctuation, and can catch the temporal concentration variation at a speed of two measurements per second.