The brief overview of most important case studies concerned with use of laser techniques for documentation, replication and reconstruction of out-door sculptural monuments in St.Petersburg city is presented. Use of 3D laser scanning in combination with computer modelling and use of CNC milling machines and additive technologies open new perspective in Cultural Heritage preservation.
Irradiation of various types of microfungi spores by vacuum ultraviolet radiation (VUV) (λ = 172 nm, 2 mW/cm<sup>2</sup> ) was carried out in this work. It was found, that the VUV radiation leads to inactivation of spores in the dose range 10-240 mJ/cm<sup>2</sup> , depending on the fungal species. Shadowing effect of overlapping layers of spores was observed. Protective property of melanin at λ = 172 nm has been proven experimentally. Presence of melanin in the cell structure led to an increase of the inactivation dose of VUV radiation in more than one order. Fluorescence microscopy have revealed differences in the structure of the membrane of control and irradiated spore. VUV irradiation of DNA samples (200 ng) at λ=172 nm showed almost complete absence of double-stranded DNA parts at doses of more than 240 mJ/cm<sup>2</sup> .
In recent years there have been enormous advances in nautical archaeology through developments
in SONAR technologies as well as in manned and robotic submersible vehicles. The number of
sunken vessel discoveries has escalated in many of the seas of the world in response to the
widespread application of these and other new tools. Customarily, surviving artifacts within the
debris field of a wreck are collected and then moved to laboratories, centers, or institutions for
analyses and possible conservation. Frequently, the conservation phase involves chemical
treatments to stabilize an artefact to standard temperature, pressure, and humidity instead of an
undersea environment. Many of the artefacts encountered at an underwater site are now
characterized and restored in-situ in accordance with modern trends in art conservation. Two
examples of this trend are exemplified by the resting place of the wreck of the Titanic in the
Atlantic and the Cancun Underwater Park in the Caribbean Sea. These two debris fields have been
turned into museums for diving visitors.
Several research groups have investigated the possibility of adapting the well-established analytical
tool Laser Induced Breakdown Spectroscopy (LIBS) to in-situ elemental analyses of underwater
cultural, historic, and archaeological artefacts where discovered, rather than as a phase of a salvage
operation. As the underwater laser ablation associated with LIBS generates a “snowplough”
shockwave within the aqueous matrix, the atomic emission spectrum is usually severely attenuated
in escaping from the target. Consequently, probative experiments to date generally invoke a
submerged air chamber or air jet to isolate water from the interaction zone as well as employ more
complex double-pulse lasers. These measures impose severe logistical constraints on the
examination of widely dispersed underwater artefacts. In order to overcome this constraint we
report on water-immersion LIBS experiments performed with oblique laser irradiation and spectral
detection at the complementary angle so as to view emission from behind the shockwave. Targets
of silver, gold, and copper have been studied. It is found that this approach enables LIBS detection
in water both in emission and in absorption. It appears that underwater inverse LIBS may be
especially useful in underwater archaeology.
In 1973 The Center for Art Conservation Studies (CASS) was established at the University of
California, San Diego (UCSD). This was in response to demonstrations that were conducted during
January-March 1972 in Venice for UNESCO, Venice in Peril, International Fund for Monuments,
and the Italian Petroleum Institute (ENI). The feasibility investigation explored in-situ pulsed
holography, holographic interferometry, and laser ablation divestment for applications in art
conservation practice. During subsequent decades scores of UCSD graduate and undergraduate
students as well as conservators, conservation scientists, academics, and engineers who resided in
CASS as “Visiting Scholars” contributed to advancing the understanding and performance of
radiation technologies in the arts. Several technologies in addition to those involving optical
wavelengths were also investigated to aid in art conservation and conservation science. Magnetic
Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) were employed to detect and
map moisture within masonry. Lead isotopic analyses revealed authenticity and provenance of Benin
bronzes. Inside-out x-ray radiography facilitated the detection of defects in stone. Ultrasonic
imaging was introduced for the mapping of fresco strata. Photoacoustic Spectroscopy (PAS) was
used to characterize varnish layers on paintings. Digital image processing was introduced in order to
detect and visualize pentimenti within paintings as well as to perform virtual restoration and provide
interactive museum displays. Holographic images were employed as imaginary theater sets. In the
years that followed the graduation of students and the visits of professional collaborators, numerous
other applications of radiation ablation began appearing in a wide variety of other fields such as
aircraft maintenance, ship maintenance, toxic chemical remediation, biological sterilization, food
processing, industrial fabrication, industrial maintenance, nuclear decontamination, dermatology,
nuclear weapons effects simulation, and graffiti control. It was readily apparent that the customary
diffusion of advanced technologies from science and industry into the art conservation field had
been reversed. In this paper we trace the migration and adaptation of radiation divestment
developments in art conservation to numerous applications in science, industry, and consumer
products. Examples described include the robotized hybrid “Flashjet” aircraft paint stripping system,
the “Novotronic” anthrax remediation installation in the Pentagon Building, the InTa automated
graffiti removal system employing a carbon dioxide TEA laser, the Bellalite body hair removal
product incorporating flashlamp technology, and the Foodco line of optical radiation products for the
sterilization of food products. The Foodco products are also applied to the sterilization and/or
pasteurization of beverages and beverage containers. A similar device has been adapted to seafood irradiation in order to increase shelf life, as well as for the ablative removal of skin and scales. The
Goodyear Tire and Rubber Company, to etch logos and identification information into the sidewalls
of pneumatic tires, also developed a flashlamp-based ablation technology. The founders of the
CYMER Corporation applied UV irradiation technology to the manufacture of high-performance
integrated circuits (viz., memory chips, etc.) In several instances former CASS students and Visiting
Fellows consciously adapted the above-learned art conservation methodologies to still other
purposes. Thus, these examples of technology transfer may be termed: “Art in the service of
Science.” Alternatively, it is evident that many associated innovations developed from independent
activities, unconnected serendipity, or through the normal diffusion of information and knowledge
A new type of wave front sensor for applications in adaptive optics is presented. The main feature of the system is its possibility to be simultaneously used both as a wave front sensor for control of adaptive or multi-modular imaging telescopes and as a Fourier hyper spectral video spectrometer. The opportunity of work of such sensor, both on a special reference light source and on extended object is shown.
Two modifications of two-wavelength interferometry method are suggested for testing severely distorted mirrors in adaptive optics. One of them is conventional modification demanding optical phase measurements at two light wavelengths. Two diode lasers generating in mid-IR spectral range at room temperature and sparse-array photodetectors are used in this case. Another modification is method of two-wavelength dynamic holography. IN last case optically addressed liquid-crystal spatial light modulator is supposed to be used as a dynamic hologram. It is shown that the proposed modifications of the two-wavelength interferometry method are perspective for testing severely aberrated mirrors with distortions up to 1 mm (that corresponds to 10...20 degree of maximum wavefront local slope in the exit pupil of controllable optical system).
We present a novel technique to alleviate the problem of the global tilt in artificial guide stars for adaptive optics. This technique is based on the registration of trails of radio-excited plasma spots caused by the atmospheric tilt. Following the time trace of the trails one can find and measure the tilt produced by atmospheric turbulent layers. Different methods were applied to estimate the extent of the trails. We describe results of computer simulations, showing the performance of the proposed approach.
The concept for a new approach to generating and receiving optical system for sodium guide star excitation based on solid-state laser technology and the stimulated Raman scattering/amplification in compressed gases is presented. Requirements to laser system for laser guide star generation are analyzed. The most promising SRS media are chosen.
The problem of global tilt arises when the downgoing light from an artificial guide star traces in reverse the upgoing laser beam. The problem also exists if the upgoing beam is in the radio, since we still cannot determine its absolute position to the required accuracy. We propose a way to solve this problem by tracing the tails of the artificial guide star. Radio pulses breaking down the air into visible plasma create the beacon, and each pulse uses the residue plasma of its predecessor to restart the break down. As the radio beams wander on their way up, the new spot will not overlap perfectly with the previous one. Thus, the spot will have a small trail, which can help trace the history of the tilt. Comparison of the measurement of the previous pulse to the tail of the new one will provide the differential movement of the downgoing beam. Integrating this movement will yield the absolute pulse location. Cumulative errors are reduced by comparison to weak nearby natural guide stars. We ran simulations of the process, where we include random atmospheric tilts for the radio beam. We also checked the effect of intentional nutations of the upgoing beam and the effects of atmospheric winds on the plasma spot, as well as detection noise. We fitted the measured signal to the head and tail of each spot, and found their difference, which amounts to the change in tilts since the last pulse. We integrated this difference to find the absolute tilt. We show that indeed the tail trail can be traced to yield information about the tilt.
Last years advances in the field of coherent pumping of Nd:YAG lasers have resulted in appearence of compact high effective ones possessing unique features. It gives opportunity to use widely these lasers in interferometry.
Results of experimental study of thermo-optical characteristics of cw, lamp-pumped Nd:YAG lasers with selective reflectors are presented. Laser heads' reflectors with both high reflective, wide wavelength band standard metallic coating and selective interferometric coatings were used in experiments. Moreover, a new method of lamp-pumped laser head reflectors realization is proposed. This method's feature is making of the reflectors in form of thin polymer film with selective interferometric coating. This proposition is a way to fabricate simple and low-cost high- power technological laser head reflectors.
Experimental results are presented of the angular position stability measurement of the radiation beams emitted by lamp or diode-pumped cw Nd:YAG lasers with frequency doubling. Passive stabilization method based on the use of fiber optical wave guides is proposed and experimentally evaluated.
This paper reports about development of previously described diode- pumped Nd:YAG chip lasers with monolithic ring resonators. We have obtained cw single longitudinal- and transverse-mode operation at the wavelength of 1064 nm. The maximal output power of 80 mW has been achieved at pump power of 500 mW. The laser design features and parameters are described.
The paper deals with the problem of choosing proper wavelength for a wavefront sensor involving an internal laser source and a hologram on the surface of the primary mirror of a telescope. Some results of dimensional calculations for the optical arrangement for recording the hologram structure are presented. As a result a conclusion is drawn on the possibility of reducing the size of an optical stand for making this structure by increasing the operation wavelength of the control channel of a telescope.