Iterative Noise Reduction in Digital Holographic Microscopy

Abstract

Digital holographic microscopy (DHM) is an optical technique useful to retrieve quantitative information of microscopic objects with subwavelength axial accuracy (Haddad et al., 1992; Zhang-Yamaguchi, 1998; Pedrini et al., 1999; Ferraro et al., 2005). An important feature of DHM is its non-invasive character that allows the appropriate study of microorganisms in vivo (Car et al., 2004; Marquet et al., 2005; Rappaz et al., 2005, Colomb et al., 2006; Javidi et al., 2006; Charriere et al., 2006). Some DHM setups employ microscope objectives to form the image of the object (Ferraro et al., 2003; Mann et al., 2005; Colomb et al., 2006). However, it is also possible to implement DHM in a lensless setup, where the light field scattered from the object is used instead of its projected image (Wagner et al., 1999; Schnars-Juptner, 2002; Repetto et al., 2004; Cruz et al., 2008; Oh et al., 2010). A conventional setup in DHM is based on the use of an external reference wave (RW), which interferes with the field generated by the object, forming an intensity pattern which is known as hologram of the field (Takeda et al., 1982; Kreis, 1986; Yamaguchi-Zhang, 1997; Yamaguchi et al., 2001; Arrizon-Sanchez, 2004; Liebling, 2004; Quian, 2006; Meneses-Fabian, 2006; Guo, 2007; Cruz et al., 2009). Alternately, it is possible to omit the external RW, with a consequent simplification of the optical setup (Pedrini, 1998; Xu, 2002; Javidi, 2005; Morlens, 2006; Garcia-Sucerquia, 2006; Hwang-Han, 2007; Singh-Asundi, 2009). In any case, either the object hologram or the intensity of the field scattered by object are recorded with an electronic intensity meter, such as a charge-coupled device (CCD). As a final step of DHM, the recorded object hologram (and other intensity patterns) are digitized and processed in a computer, with the aim of reconstructing the microscopic features of the object. In this chapter we first discuss the lensless setup that employs an off-axis RW, which is known as “lensless off axis digital holography” (LOADH) setup. We also consider a more simplified optical setup, which omits both the lens and the external RW. We refer to this system using the expression “referenceless on axis digital holography” (RLOADH) setup. In RLOADH it is still possible and convenient to split the field propagated from the object into a non scattered field and a scattered field. Even when the non scattered field is not added externally, it is often identified as a RW. The LOADH and RLOADH approaches employ fewer optical components, and tend to be cheaper and more robust, than other DHM setups. In consequence, the necessity of special