Proceedings of Topical Meeting on Optoinformatics (pdf-format, 1.21 ...

SAINT-PETERSBURG, October 17 – 20, 2005 63
THE ANALYSIS OF RESOLUTION CAPABILITY OF THE OPTICAL
COHERENT TOMOGRAPH
K.L. Khohlov, V.K. Sokolov
Baltic State Technical University,
1 st Krasnoarmeyskaya str.1, 198005, St.Petersburg, Russia
E-mail: xkl1478@mail.ru
In the report questions <strong>of</strong> resolution enhancement <strong>of</strong> a coherent laser optical
tomograph <strong>of</strong> high-resolution capability in short-range infrared a band are considered. The
tomograph focused on use for early diagnostics <strong>of</strong> pathological modification in a thyroid
gland <strong>of</strong> the human. Traditional methods <strong>of</strong> ultrasonic do not provide in this case, the
required resolution in tens micron, and X-ray methods cannot be used because <strong>of</strong> their
harm for the patient.
The carried out analysis <strong>of</strong> methods <strong>of</strong> an optical tomography has shown, that to the
most suitable for the solution <strong>of</strong> a task in view, the method optical coherent tomography
with use optical heterodyne. The method allows to detect the ballistic photons forming the
shadow image <strong>of</strong> a stratum <strong>of</strong> tissue, similar to the X-ray image. At use short-range
infrared areas (700-1300 nanometers), relevant to a spectral window <strong>of</strong> the s<strong>of</strong>t tissue <strong>of</strong>
the human, depth <strong>of</strong> penetration can achieve 10-12 cm. Magnifications <strong>of</strong> the resolution
can be achieved in two stages:
1. The diameter <strong>of</strong> fibers in sourcing and detecting arrays can be reduced. It allows to
reduce scanning aperture. The accessible type <strong>of</strong> fibers and length <strong>of</strong> waves restrict
resolution capability.
2. Realization posterior processing <strong>of</strong> the received images, implemented electronic or
optoelectronic processor working in actual time. We use the optical processor which
represents the television system covered with an optical back coupling and implementing
algorithm inverse filtering.
At the given stage <strong>of</strong> our work we analyzes with help <strong>of</strong> mathematical models the
opportunities <strong>of</strong> the first method. The inverse filtration means gathering some additional
information on a transfer function <strong>of</strong> imaging system and about properties <strong>of</strong> the object <strong>of</strong>
observation.
The dependences <strong>of</strong> the resolution on a standing <strong>of</strong> an objective plane concerning a
plane <strong>of</strong> the image and source, dependence <strong>of</strong> the resolution on character <strong>of</strong> allocation <strong>of</strong>
complex amplitudes under the aperture <strong>of</strong> a fibril are analysed. The model allows to take
into account influence <strong>of</strong> the size <strong>of</strong> the aperture <strong>of</strong> an emitter, the receiver on the
resolution <strong>of</strong> a tomograph. The criterion <strong>of</strong> the resolution is diameter <strong>of</strong> a spot <strong>of</strong> the image
is formed in a image plane. The boundary <strong>of</strong> a spot is defined or on the first minimum in
the diffraction pattern, or on a level exp 1 − .
Further we plan measuring coefficients <strong>of</strong> absorption and dispersion <strong>of</strong> medium <strong>of</strong>
observation and improvement <strong>of</strong> a model, terminating connection <strong>of</strong> a transfer function <strong>of</strong>
figuring system and definition <strong>of</strong> methods <strong>of</strong> its compensation.
1. Edited by Steve Webb. “The Physics <strong>of</strong> Medical Imaging”. M.:”Mir”, 1991 - 408с.
2. F. Stuart Foster, Charles J. Pavlin “Advances in ultrasound biomicroscopy”:
Ultrasound in Med. and Biol., vol. 26, No. 1, pp. 1-27, 2000.
3. V.I.Danilenko, A.A.Shmarin. ”New morphological spheroids objects and a
morphgenesis <strong>of</strong> pathological body height <strong>of</strong> tissues”.