Chapter 2 DIGITAL HOLOGRAPHY AND MULTI- WAVELENGTH INTERFERENCE TECHNIQUES

Recent developments in digital holography techniques are presented. The Fourier transform and convolution methods to calculate the diffraction fields are compared with the angular spectrum method, which allows short reconstruction distances down to zero with flexibility in the control of image noise. Examples of applications of digital holography in biological microscopy are presented with submicron lateral resolution. The phase imaging digital holography using two wavelengths is described that achieves unambiguous phase unwrapping, even for noisy images common in biological imaging. The wavelength scanning digital interference holography (WSDIH) is described that allows tomographic imaging by numerical superposition of many holograms using a series of different wavelengths to synthesize short coherence length. The WSDIH technique is applied to image sub-surface structures of an animal tissue down to 1.5 mm depth with 10 |im axial resolution.