Technological peculiarities of designing various video display systems projects
Key photometric parameters
It is estimated that the major part of information (about 80%) is perceived by a human through the visual channel (Ware, 2000). Nowadays, electronic displays have received large distribution in electronic, measuring and medical equipment. They represent themselves the most effective and promising class of electronic devices, designed to convert electrical signals into visible images created by a single or a set of discrete elements.
However, designing and building electronic systems and information display means requires the consideration of psycho-physiological features of human vision. The reaction of the visual analyzer primarily depends on the energy characteristics of light which is set during the particular project to be provided with video display systems (Ware, 2000).
The process of quantitative measurement of the radiant flux parameters, which causes a physiological sensation of brightness, lies in the sphere of photometry. The main photometric parameters include: luminous flux, luminous intensity, luminance, intensity of illumination, luminance contrast (Ware, 2000; Shupp et al., 2009). At the same time, it should be considered that the quality of visual perception of information by a person is determined by the following characteristics, which can also be attributed as features that should be taken into account when projecting the appropriate video display systems (Shupp et al., 2009):customj research paper
• time; and
Factors of quality of video information perception
Let us consider the above mentioned factors. Energy characteristics include: the range of perceived brightness, contrast threshold, relative visibility (color perception). Spatial characteristics of the visual analyzer are determined by sizes of objects perceived by eyes and their location in space. These characteristics include: resolution (visual acuity), range of vision (Shupp et al., 2009; Andrews et al., 2011). The main temporal characteristics of the visual analyzer include the latent period of the visual response and critical flicker frequency.
Thus, the minimum (threshold) value of the brightness of the light spot detected by eye on a black background is called the lower absolute limit of sensitivity. The upper absolute limit of sensitivity is characterized by pain. The range of brightness between the upper and lower thresholds of sensitivity lies between 10-6 and 106 cd/m2. Sensitivity of the eye, in turn, is a lighting causing a sensation of light. The smaller the difference between light and dark room is, the faster the growth of light sensitivity is, which is set at a relatively constant level in 40-60 min (Shupp et al., 2009; Andrews et al., 2011; Ware, 2000).
The maximum sensitivity lies in the area of yellow-green color. The brightest seem to be the objects painted in colors that lie in the range of the maximum sensitivity of the eye. Contrast against the background affects the perception of color. The following combination of signs are better perceived: blue on white, black on yellow, green on white, black on white, white on red, red on yellow (Ware, 2000).
For the normal sight, the threshold of the acuity of vision is equal to 1 arc minute. The recommended value of threshold of visual acuity is in the calculations is set at 2-3’. The view angle needed for reliable identification of the information model depends on its complexity assessed by the number of the smallest perceptible discrete elements it can be divided into (Yost et al., 2007).
Field of view is defined with a fixed gaze as an area of space within which the projection of the image on the retina is possible. It depends on the capabilities of the optical system of the eye, the area and distribution of photoreceptors (Ware, 2000).
The perception of alphanumeric information with a fixed position of statement assumes the movement of the eye through the line of text, thus increasing the angular size of the information field horizontally up to 500. Format of informational field of alphanumeric video display systems is often chosen equal to 5:3 (Yost et al., 2007).
Critical flicker frequency increases with the increase of brightness and angular sizes of scintillating elements. For images with the brightness of up to several hundred cd/m2 the critical flicker frequency is taken equal to about 50 Hz (Berbecel, 2003).