A Study on Real-Time Modification of the Refractive Index of A Surrounding Medium using a Uniform Microsphere In Digital Holographic Microscopy

An accurate refractive index of the surrounding medium is required to measure the accurate depth of the specimen in digital holographic microscopy (DHM). Many researchers have reported a method that uses blood smear to avoid overlapping of red blood cells (RBCs). Moreover, they have applied the refractive index of the blood plasma. However, the blood smear is not blood plasma, so that it cannot obtain the accurate depth information. In addition, it is difficult to measure the refractive index of the surrounding medium in every experiment. To solve this problem, in this paper, we propose a new method to record a hologram using a sample of a mixture of blood and a uniform microsphere. We have already known the size of the microsphere in the experiment. Thus, we can modify the refractive index of the surrounding medium. Finally, we can measure the accurate depth information of the specimen using the modified refractive index of the surrounding medium. The proposed method can be used not only in RBCs but also in the study of cells or microbial.