Information Technology Reference
In-Depth Information
The possibilities of the optical information input option can be significantly
enhanced by using a set of molecular components of the medium selectively
sensitive to radiation in different spectral regions. Other physical stimuli, such as
electric fields, electrochemical processes, local changes in the temperature of the
environment, etc., can also be used to enter information in a reaction-diffusion
medium.
5.1.2
Information Processing
In order to accomplish a specific selected operation of information processing, a
corresponding dynamic mode of the spatiotemporal evolution of the medium needs
to be specified. The medium converts its original distribution of reactant concen-
trations into some final state, which is regarded as a solution to the problem. In turn,
the dynamic mode is determined by the state of the medium, i.e., its composition
(relative concentrations of its molecular components) and temperature.
As shown below, the properties of the input information also play an important
role. Since optical input of information is particularly convenient, the source data
represent some images. An image can exist in two forms, which are equivalent in
terms of information it contains—positive and negative. However, these variants
behave differently in the course of their evolution in reaction-diffusion media.
There is some arbitrariness in determining the positive and negative forms of the
image. For definiteness, let us call positive an image corresponding to its natural
perception by the human vision. However, in some cases it is difficult to determine
what perception should be called natural. In this case we call a black image,
carrying information, on a white background a positive image. In any case the
input picture may be reduced to a set of values—the optical densities
D
i
(
D
0
<
D
1
, where
D
0
and
D
1
are the minimum and maximum values of optical
density). A negative image we will define is a corresponding set of inverted optical
densities
DN
i
¼D
1
D
i
.
Optical input of information determines one more characteristic property of the
functioning of the reaction-diffusion processor. The solution of the problem is
based on continuous recording of the evolution of the image in the medium, e.g., by
a video camera. This, however, is only possible if the process of evolution can be
observed, i.e., the medium is continuously illuminated by light. This additional
“technological” illumination of the light-sensitive medium can naturally influence
its dynamic regime (see zero isoclines, Fig.
5.2
). Let the state of the medium
correspond to the vibrational mode. If after image input it gets illuminated in the
process of registering by a minimum light intensity that can be registered, a typical
oscillatory process occurs in the medium (Fig.
5.3
). But if the same medium at the
same exposures of the input image is illuminated during the recording by suffi-
ciently intense light emission, a process corresponding to the excitable regime
emerges and develops in the medium.
D
i
<
