The Use of Digital In-Line Holography for Biological Samples Observation

This paper presents the performance of digital in-line holography for imaging applications of biological samples. The basic concept and procedure of digital in-line holography were shown based on convolution operation. An auto-focusing method based on wavelet transform was presented for digital holography. In this method, the max amplitude of high-frequency coefficients in the focal windows was used to evaluate the definition of the reconstructed image. Experimental results of biological sample plate observation demonstrate that the focusing method presented in this paper could achieve the automatic digital focusing in digital in-line holography, and the reconstructed image resolution is equivalent to the resolution of digital microscope with 1X micro lens. In particular, experimental results of schistosoma cercariae observation demonstrate that the digital in-line holography can be used to detect some plankton on the water surface.