Nonlinear Optical Image Processing with Bacteriorhodopsin Polymer Films

Abstract

Real-time medical image processing through nonlinear optical Fourier filtering and transient Fourier holography is demonstrated using bio-organic polymer films of Bacteriorhodopsin (bR). In nonlinear Fourier filtering, the photo-controlled light modulation characteristics of bR films are exploited for early detection of microcalcifications in analog (screen film) as well as digital mammograms. bR films are well known for light modulation between the two states: the initial stable B state with broad absorption band with maximum at 570 nm and the relatively long lived M state with absorption maximum at 412 nm. The spatial frequency information carried by a blue probe beam is selectively manipulated in the bR film by changing the position and intensity of a yellow control beam. In transient Fourier holography, photoisomerizative gratings are recorded and reconstructed in bR films. The laser output from an Ar-Kr ion is expanded and split into two beams. One of them, the object beam is Fourier transformed by a lens on to the bR film placed at the Fourier plane. The second beam (reference beam) overlaps the Fourier transform of the object beam on the bR film thereby recordi00000000ng a Fourier hologram. When the object beam is blocked, the reference beam performs the reconstruction of the recorded Fourier hologram. The filtered spectrum is inverse Fourier transformed on to the CCD camera. The image processing is based on the fact that the desired spatial frequency band is recorded with optimum diffraction efficiency and matching the reference beam intensity to their intensity in the Fourier spectrum. A novel feature of the technique is the ability to transient display selected spatial frequencies in the reconstructing process which enables the radiologist to study the features of interest in time scale. Both the techniques are This work is supported by National Cancer Institute, NIH grant 1R21CA89673-01A1. The high quality photographic images of the clinical mammograms were obtained from the University of Massachusetts Medical School, Worcester, MA. We thank Dr. Carl D'orsi and Prof. Andrew Karellas for providing them. We also thank Mr. Paul Foster of our Physics Department for providing phantom objects.

Photonic Applications of Bacteriorhodopsin

“…A significant advantage of this system is that it is environmental friendly. Over the years we studied the basic nonlinear optics, four-wave mixing, phase conjugation, z-scan, and photoinduced anisotropy using microwatt power lasers and successfully exploited the unique properties for a variety of applications -all optical switching, modulation, optical Fourier processing, optical computing, power limiting for laser eye protection, medical image processing for early detection of breast cancer, transient Fourier holography etc [1][2][3][4][5][6][7][8][9][10][11][12][13].Spatial filtering, a simple image processing technique, is ideally suited to enhance the pathological changes in medical images such as microcalcifications in mammograms. It is well-known from Fourier optics that an optical lens can transform a plane wave into a paraboloidal wave focused at the focal plane of the lens [14].…”

Bacteriorhodopsin-based assemblies and their enhanced photoelectric and bioelectric properties

“…Blue light illumination, on the other hand, can reconvert the M state to the initial B 570 state within only several hundred nanoseconds (283)(284)(285)(286). It can also translocate protons but in the opposite direction; that is, from the EC to the CP side (287).…”