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

Abstract

Interferenceless coded aperture correlation holography (I-COACH) is an incoherent digital holography technique for imaging 3D objects without two-wave interference. In I-COACH, the object beam is modulated by a pseudorandom coded phase mask (CPM) and propagates to the camera where its intensity pattern is recorded. The image of the object is reconstructed by a cross-correlation of the object intensity pattern with a point intensity response of the system, whereas the light from both the object and the point, are modulated by the same CPM. In order to recover the image of the object without bias level and background noise, multiple intensity recordings are necessary for both objects as well as the point object, which in turn significantly reduces the time resolution of imaging. In this study, a non-linear reconstruction technique is developed to reconstruct the image of the object with only a single camera shot. Furthermore, the proposed technique is adaptive to different experimental conditions in the sense of finding different optimal parameters for each experiment. The new method has been implemented on a regular I-COACH system in both transmission as well as reflection illumination modes.

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

“…Moreover, Lucy-Richardson method is not suitable for real-time monitoring as it is an iterative process and consumes more computational time compared to the other methods especially if the number of required iterations is large. By comparing the results, it is clear that the non-linear correlation has the minimum background noise and narrowest correlation peak for all types of angular variations due to its adaptive nature [20]. The execution time of the above methods are almost equal except that a longer time was noticed for the Lucy-Richardson method owing to its iterative nature.…”

“…However, studies conducted later revealed that the matched filter is not the ideal candidate for a decorrelation, as it suffers from substantial background noise. In this study, the decorrelation has been studied using a variety of filters and techniques, namely a matched filter, a phase-only filter [21], a non-linear correlation [20], a Wiener filter [22] and the Lucy-Richardson iterative algorithm [22]. The results are compared based on the background noise, computation time and the width of the correlation peak.…”

“…In the phase-only filter technique, the correlation is computed as = |ℑ −1 { [ (̃0)]|̃| [− (̃)]}| , which suppresses the background noise and narrows the correlation peak [21]. In the case of the non-linear correlation, the correlation is computed as [20], and (m,n) are the indexes of the correlation matrix. The search for the optimal parameters of o and r is done only once for some arbitrary tilt and the same parameters are used for the entire measurements.…”

Review of 3D Imaging by Coded Aperture Correlation Holography (COACH)

“…The SNR of the reconstructed images can be improved by recording multiple intensity patterns using different scatterers and averaging over the entire reconstructions as in the case of COACH systems [52]. Alternatively, improvement of the SNR can be achieved using a nonlinear correlator in which both spectral amplitudes of I OBJ and of I PSH are raised to a power of two independent parameters, which are optimized for maximum SNR [70,71].…”

Randomly Multiplexed Diffractive Lens and Axicon for Spatial and Spectral Imaging

“…The system without the two-beam interference was named interferenceless COACH or I-COACH [19]. In the subsequent studies, the number of camera shots were reduced to two [20] and finally to one [21] via the development of the non-linear filter.…”