Abstract
We present a lensless, interferenceless incoherent digital holography technique based on the principle of coded aperture correlation holography. The acquired digital hologram by this technique contains a three-dimensional image of some observed scene. Light diffracted by a point object (pinhole) is modulated using a random-like coded phase mask (CPM) and the intensity pattern is recorded and composed as a point spread hologram (PSH). A library of PSHs is created using the same CPM by moving the pinhole to all possible axial locations. Intensity diffracted through the same CPM from an object placed within the axial limits of the PSH library is recorded by a digital camera. The recorded intensity this time is composed as the object hologram. The image of the object at any axial plane is reconstructed by cross-correlating the object hologram with the corresponding component of the PSH library. The reconstruction noise attached to the image is suppressed by various methods. The reconstruction results of multiplane and thick objects by this technique are compared with regular lens-based imaging.
Highlights
Digital holography systems are found to possess various advantages compared to their regular imaging counterparts[1,2,3,4], for instance, their inherent three-dimensional (3D) imaging capabilities
40 intensity patterns were recorded by replacing the pinhole by the National Bureau of Standards (NBS) object (5.6 lp/mm) and 20 object holograms were synthesized using the intensity patterns from the same coded phase mask (CPM) pairs as used for the point spread hologram (PSH)
LI-coded aperture correlation holography (COACH) is superior to its precursors namely COACH and interferenceless COACH (I-COACH) owing to its compact lensless optical configuration
Summary
Digital holography systems are found to possess various advantages compared to their regular imaging counterparts[1,2,3,4], for instance, their inherent three-dimensional (3D) imaging capabilities. There has been an increasing interest among researchers in incoherent digital holography systems due to various benefits ranging from the use of low-cost light sources to enhancement in the image resolution[11,12,13] One such well-established incoherent digital holography system called Fresnel incoherent correlation holography (FINCH)[14] makes use of the digital signal processing and self-referencing interference to achieve a lateral resolution beyond that of a conventional equivalent imaging system[15]. A modified COACH system for 3D imaging and simultaneous wavelength sensing was developed by amplifying the wavelength sensitivity with a diffractive objective lens[17] In this case, the PSHs were cataloged for different axial locations and for different wavelengths
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