Incoherent digital holograms acquired by interferenceless coded aperture correlation holography system without refractive lenses

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.

Implementation of a speckle-correlation-based optical lever with extended dynamic range

“…A computational module based on a completely open source GNU Linux-GNU Octave is presented with assistive computational codes to use a low-cost web camera for scientific application. The presented codes are not limited to SC-OptLev but can be adapted for many digital holography applications, especially for correlation optical systems [26][27][28], where real-time processing of holograms and simultaneous monitoring of many planes of an object are required.…”

Non-linear adaptive three-dimensional imaging with interferenceless coded aperture correlation holography (I-COACH)

“…1. Unlike previous I-COACH configurations [12,14,16], the present setup does not have any refractive lens [17]. The principle of I-COACH is concisely summarized in the following.…”

“…Equation 3shows that the intensity on the sensor plane is a shifted version of the intensity response for a point object located on the optical axis   dominant bias terms, the cross-correlation between them yields an undesired background noise distribution. In the past, in order to eliminate the bias terms, and the background distribution, three, or at least two, intensity patterns with different CPMs, were recorded and combined to yield a bipolar or complex holograms [12,14,16,17]. The two CPMs were selected such that their cross-correlation is negligible compared to their autocorrelation.…”

“…The setup is trained in the first step using a pinhole with a diameter of 80 μm in one of the optical channels and a PSH library is created corresponding to different axial locations. Unlike the previous I-COACH versions [12,17] which require at least two or more camera shots, only one camera shot is necessary at every new axial location of the pinhole resulting in a faster training stage. After the training stage, a digit '8' from National Bureau of Standards (NBS) resolution target (Thorlabs) is mounted at a distance of 20 cm from the SLM and the object hologram is recorded.…”

Resolution-enhanced imaging using interferenceless coded aperture correlation holography with sparse point response

“…Lately, a new technique named, interferenceless coded aperture correlation holography (I-COACH) 17 has been developed which has imaging features better than of regular imaging in some aspects. Moreover, I-COACH has 3D imaging capabilities which can be done using three 18 , or two 19 camera shots, or even a single shot 20,21 . In I-COACH, light radiated form the object is modulated by coded random phase mask (CPM), propagates in the free space and recorded by a digital camera as an object hologram.…”