We applied phase-shifting digital holography to microscopy in this paper. At first lensless microscopy is proposed, in which no optical adjustment is necessary. Then, the method is applied to relax the limitation of focal depth in traditional optical microscopy. A theory for image formation and experimental verification using a few specimens are described.keywords: microscopy, digital holography, phase shiftingDue to the finite focal depth of an imaging lens, a limitation to normal optical microscopy-is that, only the 2-dimensional (2-D) information of an object can be obtained at one time. Besides, it is not convenient for quantitative analysis the observed image. Optical sectioning microscopy (OSM) and scanning confocal microscopy (SCM) which use opto-electronic detection have been proposed for quantitative analysis of a 3-D object. However, the former requires critical mechanical adjustment, while the latter uses timeconsuming mechanical 3-D scanning. Holographic microscopy can solve these problems because it can record 3-D information at one time. But, the chemical processing of holograms and the mechanical focusing at the reconstructed images cause more or less trouble. A 3-D imaging technique without use of photographic recording called optical scanning holography has recently been reported. However, there are also some trouble owing to the twin-image noise.
Digital holographic microscopy based on a modified lateral shearing interferometer for three-dimensional visual inspection of nanoscale defects on transparent objects
