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

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.