Frequency-contrast Characteristics Research Articles

Монокулярная и бинокулярная визоконтрастная чувствительность у детей младшего школьного возраста

Purpose.. To evaluate monocular and binocular contrast sensitivity to achromatic and monochromatic colors in children of primary school age from the specific regions in the North of Russian Federation. Material and methods. 36 children of the city of Tyumen and 422 children, students at the secondary school of the village of Beloyarsk of the Priuralsky district and the village of Kharampur of the Purovsky district of the Yamalo-Nenets Autonomous District, were examined. Contrast perimetry using an atlas of test images was performed to assess the frequency-contrast characteristics (FCC) of the visual system of the examined individuals. The results of the study underwent statistical analysis using the IBM SPSS Statistics ver. 22.0 software package. Results. The monocular spatial contrast sensitivity of the children from the specific regions in the North of Russian Federation in comparison with the residents of Tyumen is significantly lower (p<0.001). The formation of the binocular visual system in children from the specific regions in the North of Russian Federation. is faster. In the area of high spatial frequencies in children, the formation of perception of blue color falls behind, which is not observed in low spatial frequencies. At the same time, in the area of medium frequencies, the perception of all monochromatic colors stays far behind, especially green. Conclusion. Normative indicators of frequency-contrast sensitivity to achromatic color of primary school children have been formed. It is established that binocular spatial contrast sensitivity in children of primary school age from the specific regions in the North of Russian Federation is formed faster than monocular spatial-frequency components, in comparison with schoolchildren of Tyumen. Key words: spatial contrast sensitivity, visual analyzer, primary school age, the specific regions in the North of Russian Federation

Experimental Estimation of Frequency-Contrast Characteristics of Active Pulsed Television Systems under Conditions of Enhanced Turbidity of Aerosol Media

Results of laboratory experiments on studying the influence of scattering and absorbing media on the quality of object imaging with active pulsed television optoelectronic systems (OESs) are discussed. It is shown that the quality of object images in active pulsed vision systems or their frequency-contrast characteristics can be studied both by direct measurements or indirectly using Fourier transforms of test object images or derivatives of functions determined in experiments. A previously formulated theoretical statement that the image quality for objects screened by turbid media when using active pulsed OESs with backscattered noise signal selection can be higher almost by an order of magnitude than when using an OES operating with laser side illumination and constantly opened receiver has been confirmed experimentally.

Experimental estimation of frequency-contrast characteristics of active pulsed TV OES under conditions of enhanced aerosol medium turbidity

Experimental estimation of frequency-contrast characteristics of active pulsed TV OES under conditions of enhanced aerosol medium turbidity

Phenomenological Description of Local Extremes on Contrast Sensitivity Curves

Previous studies have demonstrated that human contrast sensitivity curves have marked extremes [4]. This phenomenon has not yet been investigated. The present report describes studies of plots of frequency-contrast characteristics obtained using gratings with orientations of 0 degrees , 90 degrees , and 135 degrees . The results showed that: 1) periodically located extremes were marked on the averaged curve obtained using gratings with an orientation of 0 degrees , while use of gratings with orientations of 90 degrees and 135 degrees gave weak peaks; 2) on repeat testing, the amplitudes of extremes decreased sharply, to the level of disappearance by day 5 of testing. These data lead to the suggestion that the phenomenon of local extremes is not associated with random errors by the subjects but reflects the specific characteristics of information processing by the visual system.

Analysis of frequency-contrast characteristics of digital X-ray image detectors

The effect of various computing procedures on the results of estimation of parameters used for MTF calculation is analyzed. Experimentally evaluated modulation transfer functions of some types of digital X-ray image detectors are presented.

A spatiotemporal functional model of the primary links of the visual system

This paper proposes a spatiotemporal functional model of the primary links of the visual system. This model is used as a basis for analyzing the Broca-Sulzer effect, the effect whereby the apparent sharpness of moving smeared light boundaries increases, for analytically obtaining the Bloch-Charpentier and Pieron laws, and for deriving formulas for calculating the spatial and temporal frequency-contrast characteristics of the visual system. The applicability of the model is illustrated by a number of examples, and it is shown that the results of the calculations agree well with the experimental data. It is pointed out that time delays of the signals in the visual system have an important role in describing the dynamic processes that take place in it. © 2004 Optical Society of America

Applicability of approximate methods of calculation of the frequency-contrast characteristics of aerosol layers within the wavelength range of 0.4–14 μm

The spectral dependences of the optical characteristics governing radiation transfer in scattering media are analyzed within the wavelength range of 0.4–14 μm for three types of aerosols. The wavelength ranges where approximate methods of calculation of frequency-contrast characteristics are applicable are established; the corresponding limitting masses of aerosol particles in a layer per unit of surface area are determined for which approximate methods provide acceptable accuracy.

Characteristics of temperature-sensitive luminescent screens designed for detection of infrared radiation

An analysis is made of the theoretical and real values of the threshold energy sensitivity of thermographic luminescent screens for detection of infrared radiation. A description is given of a method for determining the frequency-contrast characteristics by reconstructing them from the response to the application of step-like signal. The maximum resolution of a luminescent converter is determined.