Biomedical subjects

P Klysubun

Publications and source records attributed to P Klysubun.

4 recordsLinked to original sources

PubMed2001

Spatiotemporal digital microholography.

We develop the theoretical background of a holographic method in which the hologram is sampled simultaneously in space and in time by a charge-coupled device (CCD) sensor. With the use of temporal heterodyning (rather than spatial heterodyning, which is employed in conventional holography), in-line, single-sideband holograms of fields having an arbitrary degree of spatial coherence are recorded in an exposure time that can theoretically be as short as four frames of the CCD. The method is applied to microholography and is shown to avoid the main drawbacks of conventional holographic microscopy, namely, the need for high-spatial-bandwidth detectors and for a high degree of spatial coherence, which unavoidably leads to speckle noise. The possibility of a posteriori aberration compensation is demonstrated, and experimental results are presented.

Journal Article↗

PubMed2001

A posteriori processing of spatiotemporal digital microholograms.

In an accompanying paper [G. Indebetouw and P. Klysubun, J. Opt. Soc. Am. A 18, 319 (2001)], the theoretical background of a spatiotemporal digital microholographic method was described, and some experimental results were presented. Here the usefulness of the method for microholographic imaging of biological specimens such as cells is demonstrated. The vast possibility of a posteriori processing of the microholograms is discussed. Dark-field, phase-contrast, and interference-contrast images, as well as quantitative phase maps, all obtained a posteriori from the same microhologram, are illustrated as examples.

Journal Article↗

PubMed2000

Imaging properties of scanning holographic microscopy.

Scanning heterodyne holography is an alternative way of capturing three-dimensional information on a scattering or fluorescent object. We analyze the properties of the images obtained by this novel imaging process. We describe the possibility of varying the coherence of the system from a process linear in amplitude to a process linear in intensity by changing the detection mode. We illustrate numerically the properties of the three-dimensional point-spread function of the system and compare it with that of a conventional imaging system with equal numerical aperture. We describe how it is possible, by an appropriate choice of the reconstruction algorithm, to obtain an ideal transfer function equal to unity up to the cutoff frequency, even in the presence of aberrations. Some practical implementation issues are also discussed.

Diagnostic Imaging↗

PubMed1999

Ultraresolution in optical imaging using spatiotemporal scanning.

Spatial information exceeding the passband of an imaging system can be captured by using the optics to generate a spatiotemporal multiple beam interference pattern that is scanned over the object, rather than using it to image the object directly. The modulation of the higher temporal harmonics of the signal resulting from collecting the scattered light represents a mapping in the time domain of higher spatial harmonics of the data. Upon reconstruction, the additional temporal degrees of freedom are mapped back in the spatial domain where they represent spatial frequencies exceeding the passband of the optics. The spatial resolution is thus not limited by the spatial passband, but rather by the temporal bandwidth of the detection system. Due to hardware limitations, experimental demonstration is provided only for a one-dimensional scan of Ronchi gratings with 50 and 200 lines per inch.

Journal Article↗