In this paper, the authors try to determine a procedure for the best choice in selecting one or other type of sensors as a function of the object under observation, background and environmental conditions. In surveillance activities related with different missions and scenarios occurred in day and/or night time, the proper choice and use of video surveillance sensors is of huge importance. Starting from specific scenarios of surveillance, as for example the surveillance of the sky to detect drones, or surveillance of the ground area to detect some manmade objects or intruders, this paper approaches the problem of the image appearance in VIS, SWIR and LWIR spectral ranges, using different passive technologies of surveillance. Relevant images are comparative presented in relation with some theoretical quantifications made through mathematical models or through software simulations.
Starting from a few targets and backgrounds with known spectral reflectivity or emissivity, the contrast was used to show its influence on the signal strength reaching the surface of the video detector (imager) in similar environment conditions. Finally, the authors seek certain characteristics of the electro-optical system itself that can influence most the strength and quality of the optical signal with respect to influences on observation distances of the target. The possibility of using an active technology instead of a passive one, by introducing a pulsed laser illuminator, is also analyzed. The use of some polarizing filters is also considered but in this stage only in laboratory conditions, in order to improve the observability of an object in some special environmental circumstances.
Spectral system (acronym SPECTECH) is designed to meet the following basics:
a) to assure measuring tiny optical single lens in a standard configuration;
b) configured for reflected or transmitted beam light;
c) configured by user off line to monitor manufacturing or mounting optical components;
d) to be flexible to be equipped with more than one spectral detector. Initially, it is equipped with two spectral
detectors, but in short time to be able to use more than two.
e) configured as process spectrophotometer (continuously) to monitor manufacturing or mounting optical
f) to be updated or upgraded to meet other necessities.
SPECTECH system is a modular one, allowing spectral determinations in a wide range of spectrum (385-1100 nm) and
with two detectors UV-VIS (190-1100) and NIR (1000-1700nm) the domain can be wider, covering spectrum from 190
to 1700 nm. Keywords: spectral signal, spectrometry.
A compact single-frequency nanosecond green laser oscillator-amplifier system was developed. The single longitudinal
mode oscillator consists in a cavity-coupled acousto-optically Q-switched Nd:YAG microlaser emitting pulses of 50 μJ
energy, 10 nanosecond duration at 1064 nm wavelength. The oscillator pulses were amplified at 1-10 Hz repetition rate
in a two-pass Nd:YAG amplifier up to 28 mJ energy. Infrared amplified radiation was frequency doubled (532 nm) in a
KTP crystal with as much as 50% conversion efficiency. The pulsed green laser, with more than 1.5 m coherence length,
was used as light source for the holography unit in the sensor of a multi-task device for nondestructive diagnosis in art
A blue laser system for eye diseases (age related macular degeneration, sub-retinal neo-vascularisation in myopia and
presumed ocular histoplasmosis syndrome - POHS) photo-dynamic therapy, based on riboflavin as photosensitive
substance, has been developed. A CW diode laser at 445 nm wavelength was coupled through an opto-mechanical
system to the viewing path of a bio-microscope. The laser beam power in the irradiated area is adjustable between 1 mW
and 40 mW, in a spot of 3-5 mm diameter. The irradiation time can be programmed in the range of 1-19 minutes.
Currently, the laser system is under clinic tests.
We describe a field non-destructive Digital Speckle Pattern Interferometry diagnosis method to be applied in art
conservation works, using as the light source a home-made single-frequency pulsed micro-laser oscillator-amplifier
system. The green nanosecond laser-pulses are directed towards an interferometer set-up, where a beam splitter cube
divides the incoming beam to define the object, respectively the reference beams. The object beam illuminates the
artwork target and a CCD camera records the scattered light. The reference beam is directly coupled into the camera
head. The operation of the integrated system is governed by dedicated software, able to acquire and process the speckle
pattern images as to detect and locate the defects on the investigated artwork. The method was successfully applied inlab
and in-situ conditions. The results are illustrated for a variety of investigated artworks.
Changing the lens of a DSLR camera has the drawback of allowing small dust particles from the environment to be attracted onto the sensors' surface. As a result, unwanted blemishes may compromise the normally high quality of photographs. The particles can be removed by physically cleaning the sensor. A second, more general approach is to locate and remove the blemishes from digital photos by employing image processing algorithms.
This paper presents a model that allows computing the physical appearance (actual size, shape, position and transparency) of blemishes in a photograph as a function of camera settings.
In order to remove these blemishes with sufficient accuracy, an initial algorithm calibration must be performed for any given pair camera-lens. The purpose of this step is to estimate some parameters of the model that are not readily available. To achieve this, a set of "calibration images" must be carefully taken under conditions that will allow the blemishes to become easily identifiable. Then, based on the metadata stored in the photo's header, the actual appearance of the blemishes in the given photograph is computed and used in the automatic removing algorithm. Computing formulas and results of our experiments are also included.
In the situations where the classic refractometry methods cannot be applied, the immersion methods are used. Phase contrast microscopy is one of the methods that make evident the difference between the refractive index of an immersed sample and the refractive index of the immersion medium. The measurement of the refractive index of the sample is performed by changing under control the refractive index of the immersion medium, until this becomes equal to the index of the sample. The present work is aiming to answer to a series of questions concerning the performances that a system composed of a phase contrast microscope equipped with a CCD camera and a temperature control device should achieve in order to measure the refractive index with a prescribed measurement error. The possibilities of measurement of the refractive index by means of the controlled heating of the sample-immersion system assembly and by means of changing the concentrations of the components of the immersion medium are examined.
The spectral response of a non-uniform optical coating in a particular optical system is analyzed. The optical coating in the optical system is optimized having as targets the spectral responses (integral reflection factors) of the coating deposited on a diopter in a particular optical system. A conversation is established between the designing program for optical coatings and the designing program for optical systems. The designing program for optical coatings communicates to the designing program for optical systems the coating and the targets to be optimized. The designing program for optical systems evaluates the merit function and communicates it to the designing program for optical coatings, which accordingly modifies the optical coating parameters to attain an optimum, depending on the merit function evolution. The process is repeated until the merit function reaches an extreme.
The design, realization and characterization of a miniaturized objective are presented. The goal was to obtain an objective with a wide angular field in water, dedicated to noninvasive surgery. This demonstrator proves the usefulness of polymer microlenses (obtained by hot embossing) and outlines the critical steps of the manufacturing process. The objective is 4 mm long, has a diameter of 0.9 mm and an angular object field of 90 degrees (in water). It consists of one pair of concave glass microlenses and two polymethyl methacrylate (PMMA)/glass doublets. The starting design data were imposed by both the previously obtained PMMA microlens characteristics and by the application itself. The small-size-adapted classical technological flux used to manufacture the glass microlens is described and compared to the specific LIGA technological flux used to obtain the PMMA microlenses. Qualitative and quantitative functional characterizations of the components and of the obtained miniaturized optical system (e.g. object field, distortion, MTF, etc.) are performed and discussed. The problems encountered during manufacturing, assembling and characterization processes are outlined and their influence upon the functional characteristics is revealed.