An effort to enhance the threshold contrast index of gas Cherenkov detectors

Because of being capable of excluding the most of secondary gamma rays interference, gas Cherenkov detectors have been the primary candidate for fusion gamma rays detection. It is a goal worthy of long-term efforts to enhance the threshold contrast index used for evaluating the ability of GCD to exclude below-threshold interference. The paper presents the way of enhancing the index through ultraviolet reflection selective suppression of scintillation signal in the detectors. Both theoretical estimation and experimental verification demonstrate that the threshold contrast index can be enhanced by 5.5 times after applying this method. This provides possibilities of obtaining better fusion gamma rays detection waveforms and higher confidence diagnostic information.

Methodology for estimating the efficiency of optical-electronic systems using an analytical model. Functions of threshold contrast and modulation transfer

Efficiency assessment is an integral part of the stages of development, testing and operation of optoelectronic systems. The lack of a unified methodology for assessing the effectiveness of optoelectronic systems leads to the fact that different assessment methods are used to compare different systems, as a result of which the results obtained are contradictory and do not provide objective data for making appropriate decisions at various stages of the life cycle of optoelectronic systems. One of the ways to solve this problem is the development of an analytical model, which can be the basis for the construction of a unified set of intellectual support for the design and maintenance of optical-electronic systems at all stages of the life cycle. The aim of the study is to form an analytical model for evaluating the effectiveness of optoelectronic systems, in terms of the functions of threshold contrast and modulation transfer. As a result, the analysis of models for evaluating the efficiency of the optoelectronic systems NVL 1975, FLIR92, NVTerm, NVTermIP and NV-IPM was carried out, and the main differences between these models were considered. The functions of the threshold system contrast and the threshold contrast of the human visual system are considered. The effect on the form of the threshold contrast function of the modulation transfer function (frequency-contrast characteristic) of the system and the external environment, as well as space-time noise, is shown. Then, a description is given of the components of the modulation transfer function of the system and the environment: the modulation transfer function of the turbulence of the atmosphere, the transfer function of the motion modulation of the optoelectronic system, the modulation transfer function of the optical system, the detector modulation transfer function; image processing modulation transmission functions. Monitor modulation transfer functions. The main parameters of the modulation transfer function, which are used to estimate the resolution of the optoelectronic system, are considered. Examples of evaluating the resolving power of various optoelectronic systems are given and the effect of smearing caused by the movement of the carrier of the optoelectronic system on the image quality for different values of exposure time is shown. The practical significance lies in the fact that the research results were applied in the development of tactical and technical requirements for optoelectronic systems, in the development of optoelectronic systems at the stages of preliminary and technical design, showed the consistency of the calculation results with the results of using existing systems.

Testing the CIE system for mesopic photometry in a threshold detection experiment

Results from a mesopic threshold detection experiment using static, quasi-monochromatic, 2° incremental detection targets were used to test the International Commission on Illumination (CIE) recommended system for mesopic photometry based on visual performance. An experimental apparatus was built to produce different mesopic backgrounds (four different spectral compositions at two different luminances, 0.1 cd/m2 and 1.0 cd/m2) on which the targets were projected at different eccentricities (2.65° and 10°). The CIE system was tested by two methods, variability of mesopic threshold contrast for different target chromaticities and trend analysis for mesopic threshold contrast plotted against background mesopic luminance. The mesopic threshold contrast did not remain constant among the different target centroid wavelengths within a given viewing condition. The inter-observer variability of the mesopic contrast threshold dataset was considerable.

The threshold contrast thickness evaluated with different CDMAM phantoms and software

The image quality in digital mammography is described by specifying the thickness and diameter of disks with threshold visibility. The European Commission recommends the CDMAM phantom as a tool to evaluate threshold contrast visibility in digital mammography [1, 2]. Inaccuracy of the manufacturing process of CDMAM 3.4 phantoms (Artinis Medical System BV), as well as differences between software used to analyze the images, may lead to discrepancies in the evaluation of threshold contrast visibility. The authors of this work used three CDMAM 3.4 phantoms with serial numbers 1669, 1840, and 1841 and two mammography systems of the same manufacturer with an identical types of detectors. The images were analyzed with EUREF software (version 1.5.5 with CDCOM 1.6. exe file) and Artinis software (version 1.2 with CDCOM 1.6. exe file). The differences between the observed thicknesses of the threshold contrast structures, which were caused by differences between the CDMAM 3.4 phantoms, were not reproduced in the same way on two mammography units of the same type. The thickness reported by the Artinis software (version 1.2 with CDCOM 1.6. exe file) was generally greater than the one determined by the EUREF software (version 1.5.5 with CDCOM 1.6. exe file), but the ratio of the results depended on the phantom and diameter of the structure. It was not possible to establish correction factors, which would allow correction of the differences between the results obtained for different CDMAM 3.4 phantoms, or to correct the differences between software. Great care must be taken when results of the tests performed with different CDMAM 3.4 phantoms and with different software application are interpreted.

General markers of conscious visual perception and their timing

The goal of the present investigation was to identify reliable markers of conscious visual perception and to characterize their onset latency and its variability. To that end many visual stimuli from different categories were presented at near-threshold contrast and contrastive analyses were carried out on 100 balanced subsets of the data. N200 and P300 were the two reliable markers of conscious perception common to all perceived stimuli and absent for all nonperceived stimuli. The estimated mean onset latency for both markers was shortly after 200 ms. However, the onset latency of both of these markers of conscious perception showed considerable variability depending on which subsets of the data were considered. Some of this variability could be attributed to noise, but it was first and foremost the amplitude fluctuation in the condition without conscious perception that explained the variability in onset latencies of the markers of conscious perception. The present results help to understand why different studies have observed different onset times for the neural correlates of conscious perception. Moreover, the consciousness markers explored here have more generality as stimulus specificity was reduced.