Journal of Applied Spectroscopy, Vol. 85, No. 4, September, 2018 (Russian Original Vol. 85, No. 4, July–August, 2018)
INFORMATION TRANSFORMATION ALGORITHMS IN ECHO-HOLOGRAPHY
G. I. Garnaeva,
*
L. A. Nefediev, and E. I. Khakimzyanova UDC 535.2+535.317.1
The fi ltering of optical signals and the transformation of information using stimulated echo-holography is examined
in the case where it is excited by an information-carrying object laser pulse and a pulse that serves as a frequency
fi lter. It is shown that the shape of the response of the stimulated echo hologram depends on the duration, amplitude,
area, and temporal structure of the exciting pulses. This can be used for logical operations with signals.
Keywords: echo hologram, information recording, object laser pulse, temporal form of response, frequency fi lter.
Introduction. Optical data processing is one of the three methods for signal processing currently in use: analog,
digital, and optical. The greatest advances in optical signal processing began in the 1960
′
s with the invention of lasers. That
opened up great possibilities in terms of productivity and speed of processing (especially multichannel) and very simple
designs for rather complicated operations. The actual parameters of optical signal processing devices are, however, still far
from the theoretical limits. This difference is explained to a great extent by the inadequacies of devices for input of signals into
optical processors, i.e., spatial-temporal modulators of light. A major shortcoming of devices for optical signal processing is
their narrowspecialization and the lack of signifi cant advances in creating universal or even tunable devices. Thus, at present
the three forms of signal processing devices supplement each other, with optical systems providing high capacity, specialized
devices that perform a large number of fairly complicated operations of the same kind.
Optical data processing methods are based on the conversion of spatially modulated optical signals in optical devices
and systems using the principles of geometric and wave optics. Data processing involves the conversion, analysis, and
synthesis of multidimensional functions describing the properties and state of objects in the material world. Optical data
processing is carried out in an optical processor — an analog optical or electro-optical device — which changes, in a certain
way, the amplitude and phase of a spatially modulated optical signal containing information about an object.
The major advantages of optical data processing systems are: high information capacity, multichannel operation
(a large number of channels processed in parallel), high speed, and multifunctionality (Fourier, Fresnel, Hilbert, etc., integral
transformations, calculation of two-dimensional convolutions, correlations, etc.). Optical data processing systems are divided
into systems using incoherent and coherent (laser) light sources. Coherent data processing techniques have become most
popular in recent years. The areas of practical applications for optical data processing include: mobile image recognition
and processing systems, on-board orientation and aiming systems in military technology, devices for extracting weak
signals against passive and active noise backgrounds, synthetic aperture radar stations, large-capacity computing machinery,
metrology, robot technology, and nondestructive testing.
Photon echo processors (PEP), which are in the class of multifunctional analog devices, are of special interest.
Because of the presence of control signals, their pulse characteristic can be programmed in real time and various forms of
operation can be obtained, ranging from simple memory to integral transformations. Here, as with the optical processor,
a PEP can operate in temporal, spatial, and spatial-temporal domains, with coherent or incoherent data processing [1]. Thus,
in principle, PEP offer a fairly rich set of instrumentation for processing of signals and images by analog, as well as digital,
methods, and make it possible to combine both in a single device.
The problem of retranscribing data has been regarded as a bottleneck for PEP: a new transcription can be carried
out after establishment of thermal equilibrium (~3T
1
), which is determined by the longitudinal relaxation time T
1
, i.e.,
Kazan Federal University, 16a Kremlyovskaya Str., Kazan, 420008, Russia; email: nefediev@yandex.ru, guzka-1@
yandex.ru, elzahakim@yandex.ru. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 85, No. 4, pp. 620–626,
July–August, 2018. Original article submitted November 20, 2017.
_____________________
*
To whom correspondence should be addressed.
0021-9037/18/8504-0673 ©2018 Springer Science+Business, LLC 673
DOI 10.1007/s10812-018-0703-8