Properties of the human eye

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Properties of the human eye And it is known that the vast majority of information about the world around us we receive with the help of our organs of vision. “Better to see once than hear a hundred times” - this is not said in vain.

The ability to see is given to us without any effort or any technical means. The retina of our eye contains light-receiving elements - rods and cones. With the help of cones, the so-called daytime vision (in high light) is carried out. The rods serve as an organ of twilight vision (in low light).

Rods and cones contain special chemicals in which chemical reactions occur under the influence of light rays, causing electrical signals. These signals are sent along nerve fibers to the corresponding parts of the brain. It is no coincidence that the first projects of transmitting images at a distance copied the structure of the human eye.

Let's get acquainted with the basic properties of the human eye. This is necessary to understand many of the phenomena associated with the construction of television systems.

Inertia. The inertia of human vision is understood to mean two phenomena. In humans, the sensation of light occurs with some delay (usually after 0.05-0.2 s, depending on the intensity of the light); the perception of light also does not disappear immediately, it lasts about 0.1 s.

Persistence of vision is used in cinematography. When showing images that quickly replace each other, the viewer has a feeling of continuous movement, if I have enough such images (usually 24 frames per second).

Sensitivity - the ability of the eye to see (distinguish) objects in low light.

Resolution - the properties of the eye to see individual details in the object under consideration, to distinguish separately two closely spaced luminous points.

Properties of the human eye Resolution determines the most important parameter of a television system - the number of lines of image decomposition.

Color sensitivity is the property of the eye to distinguish the colors of the observed objects. The sensitivity of the eye to different colors is not the same. It has been established that the human retina contains three types of optic nerves: some of them are sensitive to green rays, others to red, and still others to blue. When all three types of optic nerves are equally irritated, a person sees white. The absence of irritation of all three types of nerves gives the perception of a black color.

The human eye reacts to light radiation ranging from 380 to 780 nm. The maximum sensitivity of the eye falls on a wavelength of about 550 nm, which corresponds to green.

The phenomenon of the formation of intermediate colors from the three basic ones is called the summation of colors. At the same time, green, red and blue are taken as the main colors, which are approximately evenly distributed in the spectrum. A very interesting experience can be done at home using three lanterns - red, green and blue. If you light the screen in such a way that the areas of the screen illuminated by them partially overlap, then the place where all three colors will overlap will appear to us as white. The area illuminated simultaneously by red and green rays will take on yellow, red and blue - magenta, etc. Thus, mixing colors, you can change the color content of the transmitted image within certain limits.