A complete simulation procedure of the holographic process using Fourier approach is proposed. The algorithm elaborated allows determining the field distributions in the object and hologram Fresnel regions. To show some advantages of the method proposed one-dimensional computer simulations for a simple amplitude object case using Fresnel and Fourier holo-graphic configurations are presented. The usefulness of the algorithm for image reconstruction from a hologram registered by CCD camera is demonstrated.
Keywords: digital holography, Fourier transformation.
Thermal sources which radiation can be modulated by supplying
the heater with alternating voltage are used in gasanalysers operating
on the basis of absorption of infrared radiation. Suitability of the source
for direct modulation (i.e. with-out the use of a mechanical chopper) can
be determined by frequency limit of modulation and energetic efficiency.
Two IR source models, which heaters are made of platinum foil, have been
studied. The maximum operating temperature of the sources was 1000oC.
The models varied with regard to the way of heat transfer. Conduction through
layer of gas between the platinum foil and the substrate was a dominating
way of exchanging heat for the first source. Cooling of the heater of the
second source took place due to the heat conduction in
the platinum foil. Frequency limits obtained for the examined thermal source
models are 2 and 5-times higher than for microbulbs, respectively, which
are a commonly applied infrared source in simple gas analysers.
Keywords: infrared sources, gas sensors, gas analysis.
In the paper an unisochronous four-level signalling is proposed as a method of two different bit rate data multiplexing in standard single mode, intensity modulation fiber optic transmission system. The method is described and its main limitation – some inherent jitter – is pointed out and estimated. After a brief discussion about transmitter (multiplexer) and receiver (demultiplexer) solution, an experimental transmission system is presented. In the system, the 155 Mb/s and 50 Mb/s data streams were uccessfully multiplexed. Measured systems sensitivity predisposes it to be used in short and medium haul links.
Keywords: data multiplexing, fiberoptic transmission, four-level signalling.
The main objective of this paper is to produce an applications-oriented review covering infrared techniques and devices. At the beginning infrared systems fundamentals are presented with emphasize on thermal emission, scene radiation and con-trast, cooling technics, and optics. Special attention is put on night vision and thermal imaging concepts. Next section shortly concentrates on selected infrared systems and is arranged in order to increase complexity; from smart weapon seek-ers, image intensifier systems, thermal imaging systems, to space-based systems. Finally, other important infrared techniques and devices are shortly described between them the most important are: non-contact thermometers, radiometers, LIDAR, and gas sensors.
Keywords: thermal emission, contrast, infrared detectors, infrared optics, smart weapon seekers, image intensifier sys-tems, thermal imaging systems, space-based systems, non-contact thermometers, radiometers, LIDAR, infra-red gas sensors.
A Raman spectroscopic study was carried out in order to
investigate the synthesis process of organically modified silane (ORMOSIL)
hybrid polymers. These materials were prepared for optoelectronic application,
using the sol-gel technology. Our aim was to analyse the ability of Raman
measurements to estimate the efficiency and correctness of particular stages
of the technological process. To synthesise a hybrid for optical planar
waveguides, denoted as GSiC, a system of 3-glycidoxypropyl-trimethoxysilane/
methacryloxy-propyltrimethoxysilane (GPTS/ MPTS) was
used as a precursor. To diagnose the first step – gelation – the Raman
spectra of monomers and gel were recorded. Analysis showed that gelation
parameters should be improved to in-crease the efficiency of monomers hydrolysis
and epoxy ring opening in GPTS. After next two steps – deposition and hardening
– Raman microscopy was used for the characterisation of polymer thin films.
Information about the film thickness, open-ing of double C=C bonds in MPTS
and types of bonds in organic and inorganic part was obtained. Raman spectroscopy
proved its considerable potential in technological process
diagnostics. A molecular structure of components can be con-trolled at
relevant stages of the synthesis. This is necessary in order to design
new materials on a molecular level and obtain required properties and good
quality of the final product.
Keywords: Raman spectroscopy, optical materials, hybrid polymers, sol-gel.
Photoelectric method is one of the most precise methods
for measuring parameters of semiconductor structures, e.g., contact potential
difference or potential barrier high for internal photoemission. Those
parameters determine such important MOS transistor parameter like the threshold
voltage V T or the flatband voltage V FB . Application of the photoemission
phenomenon requires effective utilisation of the light source’s energy
and focusing it on the surface of a small structure. This paper dis-cusses
the issues related to the construction of an illumination system for photoelectric
tests of semiconductor structures for
ultraviolet light range. Light sources as well as systems
for radiation shaping were described. Additionally, advantages and disadvantages
of mirror and lenses systems, possibility of correcting certain aberrations
and obtaining appropriate frontal distance required for introducing micromanipulators
with measurement needles were discussed. Information included in this paper
had a major impact on the construction of the multitask system for photoelectric
tests of semiconductor structures, the authors of which received the title
Technology Master – Warsaw 2001 (Mistrz Techniki – Warszawa 2001) and the
first level award of the of Polish Federation of Engineering Association
(Naczelna Organizacja Techniczna) for great technology achievements.
Keywords: UV light sources, semiconductor structures, illuminating systems, optical beam shaping, monochromator.
The authors present observations on influences of head
movements and forced respiration on the magnitudes of signals ac-quired
with the new, non-invasive technique of near-infrared transillumination/back
scattering sounding NIR-T/BSS which signals depend upon and reflect the
instantaneous width of the subarachnoid space and the amplitude of its
pulsation of cerebrovascular origin. For elimination of influence of the
changing volume of blood in superficial vessels of skin in the fron-tal
region, each experiment was performed twice – without and with simultaneous
non-invasive exclusion of blood flow in that region through skin compression.
It was observed that the recorded changes in the NIR-T/BSS signals reflecting
those in the instantaneous width of the subarachnoid space and its cerebrovascular
pulsation follow the time-pattern of the evoking factor, i.e. either the
rhythm of
the head movements or of the forced respiration, which
can be demonstrated on the basis of spectral analysis of the acquired transillumination
signals.
Keywords: subarachnoid space, transillumination, spectral analysis.