A method for measuring the refractive index (RI) of a small volume of liquid and a capillary wall is presented in this paper. A transparent capillary filled with liquid is used as a cylindrical positive lens; subsequently, the focal length of the lens is derived through the base of paraxial approximation, which is recorded as a function of the RIs of the liquid and capillary wall. With the RI of a capillary wall known, the RI of the liquid can be obtained by measuring the focal length of the lens, which is characterized by a microquantity liquid, spatial resolution, and easy operation. The RI of the capillary wall can be calculated without ruining the capillary if the capillary is filled with a standard liquid (RI is known), the deviation of which is less than 0.003 RIU. The factors affecting accuracy of the measurement, for instance, the depth of a field (DOF) in a reading microscope system and the outer and inner diameters of a capillary are analyzed, while illustrating that the effective DOF plays an essential role in accurate measurement.
© 2013 Optical Society of America
Instrumentation, Measurement, and Metrology
Original Manuscript: April 9, 2013
Revised Manuscript: June 6, 2013
Manuscript Accepted: June 24, 2013
Published: July 19, 2013
Qiang Li and Xiaoyun Pu, "Measurement of the refractive index of microquantity liquid filled in a capillary and a capillary wall without destruction," Appl. Opt. 52, 5318-5326 (2013)