White light interferometry on human blood film using white light emitting diode

摘要

A white light emitting diode (LED) does not offer uniform irradiance in the visible region of electromagnetic spectrum. However, the additional irradiance in the blue regions is found to be complementary of the absorption spectrum peaks of human blood. Here, we have utilized such spectral characteristics of a typical white LED light as a source of white light interferometry for the measurement of thickness of blood film, additional irradiance of the LED spectrum is supposed to take care the imaginary component of refractive index of human blood. The thickness of blood duly measured by our developed technique is found to be essentially dictated by mean diameter of red blood cells as depicted by dynamic light scattering (DLS) studies on the corresponding blood samples. This technique can also follow the changes of the red blood cells diameter in isotonic, hypotonic and hypertonic solutions consistent with DLS studies on corresponding blood samples. Even quantitative agreement of the measured thickness of the blood film with the values obtained from DLS studies can be made on taking the surface roughness of the glass substrates (cover slips) as measured from Field Emission Scanning Electron Microscopy (FESEM). We have also proposed a low cost version of our developed technique, where, the relatively expensive spectrograph has been replaced by a band pass filter wheel.