Abstract
In this Chapter, we discuss the latest advances in digital holography (DH) and digital holographic microscopy (DHM). Specifically, we study the different setup configurations such as single and multiwavelength approaches in reflection and transmission modes and the reconstruction algorithms used. We also propose two novel telecentric recording configurations for single and multi-wavelength digital holographic microscopy (TMW-DHM) systems. Brief theory and results are shown for each of the experimental setups discussed. The advantages and disadvantages of the different configurations will be studied in details. Typical configuration features are, ease of phase reconstruction, speed, vertical measurement range without phase ambiguity, difficulty in applying optical and numerical post-processing aberration compensation methods. Aberrations can be due to: (a) misalignment, (b) multiwavelength method resulting in Chromatic aberrations, (c) the MO resulting in parabolic phase curvature, (d) the angle of the reference beam resulting in linear phase distortions, and (e) different optical components used in the setup, such as spherical aberration, astigmatism, coma, and distortion. We conclude that telecentric configuration eliminates the need of extensive digital automatic aberration compensation or the need for a second hologram’s phase to be used to obtain the object phase map through subtraction. We also conclude that without a telecentric setup and even with post-processing a residual phase remains to perturb the measurement. Finally, a custom developed user-friendly graphical user interface (GUI) software is employed to automate the reconstruction processes for all configurations.
Highlights
In analog holography the reconstruction is performed by illuminating a holographic film by the conjugate of the reference beam ER∗, and the real image is obtained from the last term of Eq (1): jERj2EO∗ : The first two terms on the right hand side and the third term contribute to the zero order and the virtual image, respectively
In future work we seek to explore the sensitivity of speckle statistics to the roughness of the object relative to the optical wavelength. In this Chapter, we developed the theory, the reconstruction algorithms, and discussed the different experimental configurations for digital holography and digital holographic microscopy
We concluded that single wavelength setups are used for heights that do not exceed few microns while multiwavelength-based setups are used for heights that can reach 100’s of microns depending on the synthetic wavelength used
Summary
In analog holography the reconstruction is performed by illuminating a holographic film by the conjugate of the reference beam ER∗ , and the real image is obtained from the last term of Eq (1): jERj2EO∗ : The first two terms on the right hand side and the third term contribute to the zero order and the virtual image, respectively. One of the beams forms the reference, while the other is reflected off the object, both interfere on a CCD camera to form a Fresnel hologram.
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