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Digital holography has evolved as a robust and informative means of microscopy. Both the amplitude and phase of the electric field originating from the sample are reconstructed at the imaging sensor, affording a gateway to advanced imaging methodologies, such as phase imaging, 3-D imaging, and metrology. Digital holographic microscopes can be built in either reflection or transmission modes and can be used for detection in either the image [digital holographic microscopy (DHM)] or Fourier [digital Fourier holographic microscopy (DFHM)] planes. This Spotlight will begin with an introduction to DHM via a brief history of holography. Section 2 will discuss the different options and modalities available for consideration when designing a digital holographic microscope, including each of their advantages and disadvantages with respect to their applications. Ultimately, the resolution and performance of DHM depend on the detector specifications, which will be discussed in Section 3. Sections 4 and 5 will then give detailed descriptions of the designs of both DHM and DFHM devices, respectively. Both systems described will be of simple design, using a Mach–Zehnder interferometer to introduce a reference arm to facilitate the recovery of phase information at the detector. Section 6 will briefly cover a few advanced applications of DHM. Modeled and physical images are provided throughout the text as examples. Some advanced mathematics is necessary for holographic reconstruction and will be reduced here to the most crucial equations. In addition, familiarity with a scientific computing language and basic image processing will be needed to apply the methods presented, as those details are beyond the scope of this book. Given these conditions, the intended audience for this Spotlight begins with advanced undergraduate students and graduate students in physics, optics, electrical engineering, and so on. As such, it is accessible to all professionals, researchers, and faculty in the aforementioned fields.
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