Digital holographic microscopy through a Mirau interferometric objective

Abstract

Digital Holographic Microscopy (DHM) typically uses either Michelson or Mach–Zehnder interferometers as interferometric tools to attain digital holograms. These interferometers need not only good optical alignment in order to compensate the spherical aberration, but also a special optical path difference compensation system when a low coherence illumination source is used. A Mirau interferometric objective appears as an alternative to overcome these difficulties and achieve reduced quadratic aberration in DHM. We show experimental results of the feasibility to perform DHM using this kind of objective; the tests conducted were in-line and off-axis configurations. In addition, we show not only the unique feature of the refocusing capability of DHM in a NBS 1963A resolution card showing its corresponding amplitude and phase images, but also a profile phase comparison of a 4.2μm high micro lens using interferometry and DHM, extending the depth of focus of the microscope objective as proof of the proposal. As far as we know, this device has not been used in DHM.