Holography and Digital Holography
Rajpal Singh Sirohi · 2025
Holography is a two-step process that involves recording of a hologram and then reconstruction of the object from the hologram. Recording of the object wave uses interference phenomenon by which amplitude and phase of the object wave is converted to irradiance variation to which the detectors in optical region respond, whereas reconstruction involves diffraction of light from the fine fringes generating several diffraction waves, one of which is the replica of the original object wave. One of the many applications of holography is holographic interferometry (HI), which allows the interferometric measurements on real objects. Essentially the response of the object to external agency (force, temperature) can be studied. Several types of holographic interferometries such as real-time, double-exposure, time-averaged, sandwich, heterodyne, etc., are described. Time-averaged holography is used to study vibrating objects. When recording of a hologram is done on a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) and digital operations are carried out, it is called digital holography or digital HI.