Imaging systems with holographic optical sectioning: Coherent and incoherent methods

In modern imaging science, an important problem is to achieve imaging of a plane free of degradation by light scattered from outside the plane of focus. Out-of-plane noise suppression imaging techniques have been called optical sectioning based on terminology from early microscopy. In this dissertation, we describe two new methods to achieve optical sectioning using holography.; The first method, a holographic synthetic aperture imaging system that combines the influence of synthetic aperture (SA) imaging, holography, spatial chirp compression, and confocal imaging is coherent. A diffraction-limited wave optic analysis is employed to study the out-of-plane noise suppression characteristics of the holographic SA imaging system. It is shown that the system's sectioning performance solely depends on the size of the synthetic aperture operating in an aberration free condition. A principle for achieving out-of-plane noise suppression by spatial chirp compression using digital holography is demonstrated experimentally. By incorporating spatial chirp compression, the system is able to maintain signal to noise ratio by illuminating the object with less intense fields over longer signal integration times. Anticipated system performance due to apodization, phase errors, aberrations, and the effect of detector size are investigated quantitatively. An interesting observation is that with this approach aberrations can be corrected digitally after the signal has been collected, due to its holographic nature.; The second method extends previous work in low coherence holographic imaging and is incoherent. A general model based on achromatic interferometers is developed for analyzing noise suppression in low-coherence image-plane holography. It shows that temporal incoherence can produce out-of-plane noise suppression similar to that provided by a spatially incoherent source through the dispersion of the interferometer. Out-of-plane noise suppression is analyzed for an interferometric imaging system, termed a quasi-holographic imaging system, where two object-carrying beams are used to form the hologram unlike conventional holography where only one beam carries the object signal. The analysis indicates that the quasi-holographic system operating in reflection has sectioning capability comparable to that of the holographic system, with excellent noise rejection, as confirmed by experimental results.