Human color vision. color vision deviations

color vision

The human eye contains two types photosensitive cells(photoreceptors): highly sensitive rods and less sensitive cones. The rods function in relatively low light conditions and are responsible for the operation of the night vision mechanism, but at the same time they provide only a color-neutral perception of reality, limited to the participation of white, gray and black colors. Cones work at higher light levels than rods. They are responsible for the mechanism of daytime vision, distinctive feature which is the ability to provide color vision.

In primates (including humans), the mutation caused the appearance of an additional, third type of cones - color receptors. This was caused by the expansion of the ecological niche of mammals, the transition of some species to a diurnal lifestyle, including on trees. The mutation was caused by the appearance of an altered copy of the gene responsible for the perception of the middle, green-sensitive region of the spectrum. It provided better recognition of the objects of the "day world" - fruits, flowers, leaves.

Visible solar spectrum

In the human retina, there are three types of cones, the sensitivity maxima of which fall on the red, green and blue parts of the spectrum. As early as the 1970s, it was shown that the distribution of cone types in the retina is uneven: "blue" cones are closer to the periphery, while "red" and "green" cones are randomly distributed, which has been confirmed more than detailed studies V early XXI century. The matching of cone types to the three "primary" colors enables the recognition of thousands of colors and shades. Spectral sensitivity curves three types cones partially overlap, which contributes to the phenomenon of metamerism. Very strong light excites all 3 types of receptors, and therefore is perceived as blindingly white radiation (the effect of metamerism). Uniform stimulation of all three elements, corresponding to the weighted average daylight, also causes a sensation of white.

Light with different wavelength stimulates differently different types cones. For example, yellow-green light stimulates L and M-type cones equally, but stimulates S-type cones to a lesser degree. Red light stimulates L-type cones much more strongly than M-type cones, and S-type cones do not stimulate almost at all; green-blue light stimulates M-type receptors more than L-type, and S-type receptors a little more; light with this wavelength also stimulates the rods most strongly. Violet light stimulates S-type cones almost exclusively. The brain perceives combined information from different receptors, which provides different perception light with different wavelengths. Opsin genes are responsible for color vision in humans and monkeys. According to supporters of the three-component theory, the presence of three different proteins that respond to different wavelengths is sufficient for color perception. Most mammals have only two of these genes, so they have two-color vision. In the event that a person has two proteins encoded by different genes that are too similar, or one of the proteins is not synthesized, color blindness develops. N. N. Miklukho-Maclay established that the Papuans of New Guinea, who live in the thick of the green jungle, lack the ability to distinguish green. The three-component theory of color vision was first expressed in 1756 by M. V. Lomonosov, when he wrote "about the three matters of the bottom of the eye." A hundred years later, it was developed by the German scientist G. Helmholtz, who does not mention the famous work of Lomonosov "On the Origin of Light", although it was published and briefly presented in German. In parallel, there was an opponent theory of color by Ewald Hering. It was developed by David H. Hubel and Torsten N. Wiesel. They received Nobel Prize 1981 for their discovery. They suggested that the brain does not receive information about red (R), green (G) and blue (B) colors at all (Jung-Helmholtz color theory). The brain receives information about the difference in brightness - about the difference between the brightness of white (Y max) and black (Y min), about the difference between green and red colors (G - R), about the difference between blue and yellow flowers(B - yellow), and yellow (yellow = R + G) is the sum of red and green flowers, where R, G and B are the brightness of the color components - red, R, green, G, and blue, B. We have a system of equations - K b-b \u003d Y max - Y min; K gr \u003d G - R; K brg = B - R - G, where K b-w, K gr , K brg - functions of the white balance coefficients for any lighting. In practice, this is expressed in the fact that people perceive the color of objects in the same way under different light sources (color adaptation). Opponent theory generally better explains the fact that people perceive the color of objects in the same way under extremely different light sources (color adaptation), including different colors of light sources in the same scene. These two theories are not entirely consistent with each other. But despite this, it is still assumed that the three-stimulus theory operates at the level of the retina, however, the information is processed and the brain receives data that is already consistent with the opponent's theory.

This is one of essential functions the eye that the cones provide. Rods are incapable of perceiving colors.

The entire spectrum of colors that exists in the environment consists of 7 primary colors: red, orange, yellow, green, blue, indigo and violet.

Any color has the following characteristics:

1) hue is the main quality of color, which is determined by the wavelength. This is what we call "red", "green", etc.;

2) saturation - characterized by the presence in the main color of an impurity of a different color;

3) brightness - characterizes the degree of proximity of a given color to white. This is what we call "light green", "dark green", etc.

In total, the human eye is able to perceive up to 13,000 colors and their shades.

The ability of the eye to color vision is explained by the Lomonosov-Jung-Helmholtz theory, according to which all natural colors and their shades result from the mixing of the three primary colors: red, green and blue. In accordance with this, it is assumed that there are three types of color-sensitive cones in the eye: red-sensitive (in most irritated by red rays, less green and even less blue), green-sensitive (most irritated by green rays, least blue) and blue-sensitive (most excited by blue rays, least red). From the total excitation of these three types of cones, a sensation of one color or another appears.

Based on the three-component theory of color vision, people who correctly distinguish the three primary colors (red, green, blue) are called normal trichromats.

Color vision disorders can be congenital or acquired. Congenital disorders (they are always bilateral) affect about 8% of men and 0.5% of women, who are mainly inducers and transmit congenital disorders through the male line. Acquired disorders (can be either unilateral or bilateral) occur in diseases optic nerve, chiasm, central fossa of the retina.

All color vision disorders are grouped in the Chris-Nagel-Rabkin classification, according to which the following are distinguished:

1. monochromasia - vision in one color: xanthopsia (yellow), chloropsia (green), erythropsia (red), cyanopsia (blue). The latter often occurs after cataract extraction and is transient.

2. dichromasia - complete non-perception of one of the three primary colors: protanopsia (perception of red color completely disappears); deuteranopsia (the perception of green color completely drops out, color blindness); tritanopsia (complete blue color blindness).

3. abnormal trichromacy - when it does not fall out, but only the perception of one of the primary colors is disturbed. In this case, the patient distinguishes the main color, but gets confused in shades: protanomaly - the perception of red is disturbed; deuteranomaly - the perception of green is disturbed; tritanomaly - the perception of blue is disturbed. Each type of abnormal trichromasia is divided into three degrees: A, B, C. Degree A is close to dichromasia, degree C is normal, degree B occupies an intermediate position.

4. achromasia - vision in gray and black colors.

Of all color vision disorders, anomalous trichromasia is the most common. It should be noted that a violation of color vision is not a contraindication to military service, but limits the choice of the type of troops.

Diagnosis of color vision disorders is carried out using Rabkin's polychromatic tables. Against the background of circles of different colors, but of the same brightness, they show numbers and figures that are easily distinguishable by normal trichromats, and hidden numbers and figures that are distinguished by patients with one or another type of disorder, but do not distinguish between normal trichromats.

For objective research color vision, mainly in expert practice, anomaloscopes are used.

Color vision is formed in parallel with the formation of sharpness
vision and appears in the first 2 months of life, and at first the perception of the long-wave part of the spectrum (red) appears, later - the medium-wave (yellow-green) and short-wave (blue) parts. At 4-5 years old, color vision is already developed and is being improved further.

There are laws of optical mixing of colors that are widely used in design: all colors, from red to blue, with all transitional shades, are placed in the so-called. Newton's circle. In accordance with the first law, if you mix the primary and secondary colors (these are colors that lie at opposite ends of Newton's color wheel), then you get the sensation of white. According to the second law, if two colors are mixed through one, the color located between them is formed.

Color perception, like visual acuity, is a function of the cone apparatus of the retina..

color vision — is the ability of the eye to perceive light waves of various wavelengths, measured in nanometers.

color vision — is the ability visual system perceive different colors and their shades. The sensation of color occurs in the eye when the photoreceptors of the retina are exposed to electromagnetic oscillations in the visible part of the spectrum.

The whole variety of color sensations is formed by shifting the main seven colors of the spectrum - red, orange, yellow, green, blue, indigo and violet. Exposure to the eye of individual monochromatic rays of the spectrum causes a sensation of one or another chromatic color.. The human eye perceives the region of the spectrum between the rays with a wavelength of 383 to 770 nm. Rays of light with a long wavelength cause a sensation of red, with a short wavelength - blue and violet colors. The wavelengths in between cause the sensation of orange, yellow, green and blue flowers.

The physiology and pathology of color perception is most fully explained by the three-component theory of color vision of Lomonosov-Jung-Helmholtz. According to this theory, there are three types of cones in the human retina, each of which perceives the corresponding primary color. Each of these types of cones contains different color-sensitive visual pigments - some for red, others for green, and still others for blue. With the full function of all three components, normal color vision is provided, called normal trichromasia, and the people who have it — trichromacy.

The whole variety of visual sensations can be divided into two groups:

achromatic- perception of white, black, gray colors, from lightest to darkest;
chromatic- perception of all tones and shades of the color spectrum.

Chromatic colors are distinguished by hue, lightness or brightness, and saturation.

Color tone — it is a sign of each color that allows you to attribute this color to a particular color. The lightness of a color is characterized by the degree of its proximity to white color.

Color saturation — degree of difference from achromatic of the same lightness. The whole variety of color shades is obtained by mixing only three primary colors: red, green, blue.

The laws of mixing colors apply if both eyes are irritated different colors. Therefore, binocular color mixing does not differ from monocular color mixing, which indicates the role of the central nervous system in this process.

Distinguish acquired and congenital color vision disorders. Congenital disorders depend on three components - such vision is called — dichromasia. When two components are missing, vision is called — monochromatic.

Acquired are rare: in diseases of the optic nerve of the retina and central nervous system.

The assessment of color perception is carried out in accordance with the Chris-Nagel-Rabkin classification, which provides for:

normal trichromasia- color vision, in which all these receptors are developed and function normally;
anomalous trichromasia- one of the three receptors is not functioning properly. It is divided into: protanomaly, characterized by an anomaly in the development of the first (red) receptor; deuteranomaly, characterized by an abnormal development of the second (green) receptor; - tritanomaly, characterized by an anomaly in the development of the third (blue) receptor;
dichromasia- color vision, in which one of the three receptors does not function. Dichromacy is subdivided into:

protanopia- blindness mainly to red;
deuteranopia- blindness mainly to green;
tritanopia Blindness predominantly to blue.

monochromasia or achromasia — complete absence color vision.

More significant color vision disorders, referred to as partial color blindness, occur when the perception of one color component is completely lost. It is believed that those suffering from this disorder - dichromates- can be protanopes when red falls deuteranopes- green and tritanopes- purple component.

See Features visual analyzer and methods of their research

Saenko I. A.

Nursing guide / N. I. Belova, B. A. Berenbein, D. A. Velikoretsky and others; Ed. N. R. Paleeva.- M.: Medicine, 1989.
Ruban E. D., Gainutdinov I. K. Nursing in ophthalmology. - Rostov n / a: Phoenix, 2008.

color vision

The phenomenology of color perception is described by the laws of color vision, derived from the results of psychophysical experiments. Based on these laws, several theories of color vision have been developed over a period of more than 100 years. And only in the last 25 years or so has it become possible to directly test these theories by electrophysiology methods by recording the electrical activity of single receptors and neurons of the visual system.

Phenomenology of color perception

Color tones form a “natural” continuum. Quantitatively, it can be depicted as a color wheel on which a sequence of appearances is given: red, yellow, green, cyan, magenta and again red. Hue and saturation together define chroma, or the level of color. Saturation refers to how much white or black is in a color. For example, if you mix pure red with white, you get a pink hue. Any color can be represented by a point in a three-dimensional "color body". One of the first examples of a “color body” is the color sphere of the German artist F. Runge (1810). Each color here corresponds to a specific area located on the surface or inside the sphere. This representation can be used to describe the following most important qualitative laws of color perception.

In modern metric color systems, color perception is described on the basis of three variables - hue, saturation and lightness. ??o is done in order to explain the laws of color shift, which will be discussed below, and in order to determine the levels of identical color perception. In metric three-dimensional systems, a non-spherical color solid is formed from an ordinary color sphere by means of its deformation. The purpose of creating such metric color systems (in Germany, the DIN color system developed by Richter is used) is not a physiological explanation of color vision, but rather an unambiguous description of the features of color perception. However, when an exhaustive physiological theory color vision (so far there is no such theory), it must be able to explain the structure of the color space.

Theories of color vision

Three-component theory of color vision

Color vision is based on three independent physiological processes. The three-component theory of color vision (Jung, Maxwell, Helmholtz) postulates the presence of three various types cones that act as independent receivers when the light is at a photopic level.

Combinations of signals received from receptors are processed in neural systems ah perception of brightness and color. The correctness of this theory is confirmed by the laws of color mixing, as well as by many psychophysiological factors. For example, at the lower limit of photopic sensitivity, only three components can differ in the spectrum - red, green and blue.

Opponent color theory

If a bright green ring surrounds a gray circle, then the latter acquires a red color as a result of simultaneous color contrast. The phenomena of simultaneous color contrast and sequential color contrast served as the basis for the theory of opponent colors, proposed in the 19th century. Goering. Hering suggested that there were four primary colors—red, yellow, green, and blue—and that they were paired in pairs through two antagonistic mechanisms—the green-red mechanism and the yellow-blue mechanism. A third opponent mechanism has also been postulated for the achromatically complementary colors of white and black. Due to the polar nature of the perception of these colors, Hering called these color pairs "opponent colors". From his theory it follows that there can be no such colors as "greenish-red" and "bluish-yellow".

Zone theory

Color vision disorders

Various pathological changes, violating color perception, can occur at the level of visual pigments, at the level of signal processing in photoreceptors or in the high parts of the visual system, as well as in the diopter apparatus of the eye itself. Described below are color vision disorders that are congenital and almost always affect both eyes. Cases of impaired color perception with only one eye are extremely rare. In the latter case, the patient has the opportunity to describe the subjective phenomena of impaired color vision, since he can compare his sensations obtained with the help of the right and left eyes.

color vision anomalies

Anomalies are usually called those or other minor violations of color perception. They are inherited as an X-linked recessive trait. Individuals with a color anomaly are all trichromats, i.e. they, like people with normal color vision, need to use the three primary colors to fully describe the visible color. However, anomalies are less able to distinguish some colors than normal-sighted trichromats, and in color matching tests they use red and green in different proportions. Testing on an anomaloscope shows that if the color mixture has more red than normal, and with deuteranomaly, the mixture has more green than necessary. IN rare cases tritanomaly, the work of the yellow-blue channel is disrupted.

Dichromates

Various forms of dichromatopsia are also inherited as X-linked recessive traits. Dichromats can describe all the colors they see with just two pure colors. Both protanopes and deuteranopes have a disrupted red-green channel. Protanopes confuse red with black, dark grey, brown, and in some cases, like deuteranopes, with green. certain part spectrum seems achromatic to them. For protanope this region is between 480 and 495 nm, for deuteranope between 495 and 500 nm. Rarely seen tritanopes confuse yellow and blue. The blue-violet end of the spectrum seems to them achromatic - like a transition from gray to black. The region of the spectrum between 565 and 575 nm is also perceived by tritanopes as achromatic.

Complete color blindness

Less than 0.01% of all people suffer from complete color blindness. They see monochromats the world like a black and white film, i.e. only gradations of gray are distinguished. Such monochromats usually show a violation of light adaptation at a photopic level of illumination. Due to the fact that the eyes of monochromats are easily blinded, they poorly distinguish the shape in daylight, which causes photophobia. That's why they wear dark Sunglasses even in normal daylight. In the retina of monochromats histological examination usually no anomalies are found. It is believed that instead of visual pigment, their cones contain rhodopsin.

Rod apparatus disorders

Diagnosis of color vision disorders

Since there is whole line professions that require normal color vision (for example, drivers, pilots, machinists, fashion designers), color vision should be checked for all children in order to subsequently take into account the presence of anomalies when choosing a profession. In one of simple tests“pseudo-isochromatic” Ishihara tables are used. These tablets are marked with spots of different sizes and colors, arranged so that they form letters, signs or numbers. Spots of different colors have the same level of lightness. Persons with impaired color vision are not able to see some symbols (this depends on the color of the spots from which they are formed). Using various options Ishihara tables, it is possible to reliably detect color vision disorders. Accurate diagnosis possible with color mixing tests.

Literature:
1. J. Dudel, M. Zimmerman, R. Schmidt, O. Grusser et al. Human Physiology, 2 vol., translated from English, Mir, 1985
2. Chap. Ed. B.V. Petrovsky. Popular medical encyclopedia, Art. “Vision”, “Color vision”, “Soviet Encyclopedia”, 1988
3. V. G.

color vision

Eliseev, Yu. I. Afanasiev, N. A. Yurina. Histology, "Medicine", 1983

visual sensation- individual perception of a visual stimulus that occurs when direct and reflected from objects rays of light reach a certain threshold intensity. A real visual object in the field of view evokes a complex of sensations, the integration of which forms the perception of the object.

Perception of visual stimuli. The perception of light is carried out with the participation of photoreceptors, or neurosensory cells, which are secondary sensory receptors. This means that they are specialized cells that transmit information about light quanta to retinal neurons, including first to bipolar neurons, then to ganglion cells, the axons of which make up the fibers of the optic nerve; information then goes to subcortical neurons (thalamus and anterior colliculus) and cortical centers(primary projection field 17, secondary projection fields 18 and 19) of vision. In addition, horizontal and amacrine cells are also involved in the processes of transmission and processing of information in the retina. All retinal neurons form the nervous apparatus of the eye, which not only transmits information to the visual centers of the brain, but also participates in its analysis and processing. Therefore, the retina is called the part of the brain that is placed on the periphery.

Over 100 years ago, based on morphological features Max Schultze divided photoreceptors into two types - rods (long thin cells with a cylindrical outer segment and an inner one equal in diameter) and cones (having a shorter and thicker domestic segment). He drew attention to the fact that nocturnal animals ( bat, owl, mole, cat, hedgehog) rods predominated in the retina, while cones dominated in diurnal animals (pigeons, chickens, lizards). Based on these data, Schultze proposed the theory of duality of vision, according to which rods provide scotopic vision, or vision at a low level of illumination, and cones implement photopic vision and work in brighter light. It should, however, be noted that cats see perfectly during the day, and hedgehogs kept in captivity easily adapt to a daytime lifestyle; snakes, in the retina of which there are mainly cones, are well oriented at dusk.

Morphological features of rods and cones. In the human retina, each eye contains about 110-123 million rods and about 6-7 million cones, i.e. 130 million photoreceptors. In area yellow spot there are mainly cones, and on the periphery - rods.

Image construction. The eye has several refractive media: the cornea, the fluid of the anterior and posterior chambers of the eye, the crystal face and vitreous body. Image construction in such a system is very difficult, because each refractive medium has its own radius of curvature and refractive index. Special calculations have shown that it is possible to use a simplified model - reduced eye and consider that there is only one refractive surface - the cornea and one nodal point(through it the beam will fly without refraction), located at a distance of 17 mm in front of the retina (Fig. 60).

Rice. Fig. 60. Nodal point location. 61. Image construction, and back focus of the eye.

To build an image of an object AB two rays are taken from each point limiting it: after being refracted, one ray passes through the focus, and the second goes through the nodal point without refraction (Fig. 61). The point of convergence of these rays gives the image of points A And B- points A1 And B2 and, accordingly, the subject A1B1. The image is real, inverted and reduced. Knowing the distance from the object to the eye OD, the magnitude of the subject AB and the distance from the nodal point to the retina (17 mm), the image size can be calculated. To do this, from the similarity of triangles AOB and L1B1O1, the equality of the ratios is derived:

The refractive power of the eye is expressed as diopters. A lens with a focal length of 1 m has a refractive power of one diopter. To determine the refractive power of a lens in diopters, one should be divided by the focal length in the centers. Focus- this is the point of convergence after refraction of rays parallel to the lens. focal length call the distance from the center of the lens (for the eye from the nodal point) ho focus.

The human eye is set to look at distant objects: parallel rays coming from a very distant luminous point converge on the retina, and, therefore, there is a focus on it. Therefore, the distance OF from retina to nodal point ABOUT is the focal length for the eye. If we take it equal to 17 mm, then the refractive power of the eye will be equal to:

Color vision. Most people are able to distinguish between primary colors and their many shades. This is due to the effect on photoreceptors of electromagnetic oscillations of different wavelengths, including those that give the sensation of purple (397-424 nm), blue (435 nm), green (546 nm), yellow (589 nm) and red (671- 700 nm). Today, no one doubts that for normal human color vision, any given color tone can be obtained by additive mixing of 3 primary color tones - red (700 nm), green (546 nm) and blue (435 nm) . White color gives a mixture of rays of all colors, or a mixture of three primary colors (red, green and blue), or by mixing two so-called paired complementary colors: red and blue, yellow and blue.

Light rays with a wavelength of 0.4 to 0.8 microns, causing excitation in the cones of the retina, cause the appearance of a sensation of the color of the object. The sensation of red color arises under the action of rays with the largest wavelength, violet - with the smallest.

There are three types of cones in the retina that respond differently to red, green, and purple. Some cones react mainly to red, others to green, and still others to purple. These three colors were called primary. The recording of action potentials from single retinal ganglion cells showed that when the eye is illuminated with rays of different wavelengths, excitation in some cells - dominators- occurs under the action of any color, in others - modulators- only at a certain wavelength. In this case, 7 different modulators were identified, responding to a wavelength from 0.4 to 0.6 μm.

By optical mixing of primary colors, all other colors of the spectrum and all shades can be obtained. Sometimes there are violations of color perception, in connection with which a person does not distinguish between certain colors. Such a deviation is noted in 8% of men and 0.5% of women. A person may not distinguish one, two, and in more rare cases, all three primary colors, so that the entire environment perceived in gray tones.

Adaptation. The sensitivity of retinal photoreceptors to the action of light stimuli is extremely high. One stick of the retina can be excited by the action of 1-2 light quanta. Sensitivity may change as the light changes. In the dark it increases, and in the light it decreases.

Dark adaptation, i.e. a significant increase in the sensitivity of the eye is observed when moving from a bright room to a dark one. In the first ten minutes of being in the dark, the sensitivity of the eye to light increases tens of times, and then within an hour - tens of thousands of times. At the core dark adaptation there are two main processes - the restoration of visual pigments and an increase in the area of the receptive field. At first, the visual pigments of the cones are restored, which, however, does not lead to large changes in the sensitivity of the eye, since the absolute sensitivity of the cone apparatus is low. By the end of the first hour of staying in a dark note, the rhodopsin of the rods is restored, which increases the sensitivity of the rods to light by 100,000-200,000 times (and, consequently, increases peripheral vision). In addition, in the dark, due to the weakening or removal of lateral inhibition (neurons of the subcortical and cortical centers of vision take part in this process), the area of the excitatory center of the receptive field of the ganglion cell increases significantly (at the same time, the convergence of photoreceptors to bipolar neurons increases, and bipolar neurons - on the ganglion cell). As a result of these events due to spatial summation on the periphery of the retina light sensitivity in the dark it increases, but at the same time visual acuity decreases. Activation of the sympathetic nervous system and an increase in the production of catecholamines increase the rate of dark adaptation.

Experiments have shown that adaptation depends on influences coming from the central nervous system. Thus, the illumination of one eye causes a drop in the sensitivity to light of the second eye, which was not exposed to illumination.

color vision and methods for its determination

It is assumed that impulses coming from the central nervous system cause a change in the number of functioning horizontal cells. With an increase in their number, the number of photoreceptors connected to one ganglion cell increases, i.e., the receptive field increases. This provides a reaction at a lower intensity of light stimulation. With an increase in illumination, the number of excited horizontal cells decreases, which is accompanied by a decrease in sensitivity.

During the transition from darkness to light, temporary blindness occurs, then the sensitivity of the eye gradually decreases, i.e. light adaptation takes place. It is associated mainly with a decrease in the area of the receptive fields of the retina.

Biophysics of color vision

COLOR AND COLOR MEASUREMENT

Various phenomena of color vision show especially clearly that visual perception depends not only on the type of stimuli and the work of receptors, but also on the nature of signal processing in nervous system. Different parts of the visible spectrum seem to us differently colored, and there is a continuous change in sensations during the transition from violet and blue through green and yellow to red. However, we can perceive colors that are not in the spectrum, such as purple, which is obtained by mixing red and blue. Completely different physical conditions visual stimulation can lead to identical color perception. For example, monochromatic yellow cannot be distinguished from a specific mixture of pure green and pure red.

The phenomenology of color perception is described by the laws of color vision, derived from the results of psychophysical experiments. Based on these laws, several theories of color vision have been developed over a period of more than 100 years. And only in the last 25 years or so has it become possible to directly test these theories by methods of electrophysiology - by recording the electrical activity of single receptors and neurons of the visual system.

Phenomenology of color perception

The visual world of a person with normal color vision is extremely saturated with color shades. A person can distinguish approximately 7 million different color shades. Compare - in the retina, there are also about 7 million cones. However, a good monitor is able to display about 17 million colors (more precisely, 16'777'216).

This whole set can be divided into two classes - chromatic and achromatic shades. The achromatic hues form a natural progression from the brightest white to the deepest black, which corresponds to the sensation of black in the phenomenon of simultaneous contrast (a gray figure on a white background appears darker than the same figure on a dark one). Chromatic shades are associated with the color of the surface of objects and are characterized by three phenomenological qualities: hue, saturation and lightness. In the case of luminous light stimuli (for example, a colored light source), the attribute “lightness” is replaced by the attribute “illuminance” (brightness). Monochromatic light stimuli with same energy, but different wavelengths cause a different sensation of brightness. Spectral brightness curves (or spectral sensitivity curves) for both photopic and scotopic vision are constructed based on systematic measurements the amount of radiated energy required for different wavelength light stimuli (monochromatic stimuli) to produce an equal subjective sensation of brightness.

Perceived colors form a continuum; in other words, close colors pass one into another smoothly, without a jump.
Each point in a color body can be exactly defined by three variables.
In the structure of the color body there are pole points - such complementary colors as black and white, green and red, blue and yellow, are located on opposite sides of the sphere.

In modern metric color systems, color perception is described on the basis of three variables - hue, saturation and lightness. This is done in order to explain the laws of color displacement, which will be discussed below, and in order to determine the levels of identical color perception. In metric three-dimensional systems, a non-spherical color solid is formed from an ordinary color sphere by means of its deformation. The purpose of creating such metric color systems (in Germany, the DIN color system developed by Richter is used) is not a physiological explanation of color vision, but rather an unambiguous description of the features of color perception. However, when a comprehensive physiological theory of color vision is put forward (as yet there is no such theory), it must be able to explain the structure of color space.

color mixing

Additive color mixing occurs when light rays of different wavelengths fall on the same point on the retina. For example, in an anomaloscope, an instrument used to diagnose color vision disorders, one light stimulus (for example, pure yellow at a wavelength of 589 nm) is projected onto one half of the circle, while some mixture of colors (for example, pure red at a wavelength of 671 nm and pure green with a wavelength of 546 nm) - on the other half. An additive spectral mixture that gives a sensation identical to a pure color can be found from the following “color mixing equation”:

a (red, 671) + b (green, 546) c (yellow, 589)(1)

The symbol means sensation equivalence and has no mathematical meaning, a, b and c are illumination coefficients. For a person with normal color vision for the red component, the coefficient should be taken approximately equal to 40, and for the green component - approximately 33 relative units (if the illumination for the yellow component is taken as 100 units).

If we take two monochromatic light stimuli, one in the range from 430 to 555 nm and the other in the range from 492 to 660 nm, and mix them additively, then the hue of the resulting color mixture will either be white or will correspond to a pure color with a wavelength between wavelengths of mixed colors. However, if the wavelength of one of the monochromatic stimuli exceeds 660, and the other does not reach 430 nm, then purple color tones are obtained, which are not in the spectrum.

White color. For each color tone color wheel there is such a different color tone that, when mixed, gives a white color. Constants (weighting factors a and b) mixing equations

a(F1 ) + b (F2 )K (white) (2)

depend on the definition of "white".

Color and vision

Any pair of hues F1, F2 that satisfies equation (2) is called complementary colors.

Subtractive color mixing. It differs from additive color mixing in that it is a purely physical process. If white is passed through two wide-bandwidth filters, first yellow and then cyan, the resulting subtractive mixture will be green, since only green light can pass through both filters. An artist mixing paint produces subtractive color mixing because the individual paint granules act as color filters with a wide bandwidth.

TRICHROMATICITY

For normal color vision, any given color tone (F4) can be obtained by additively mixing three defined color tones F1-F3. This necessary and sufficient condition is described following equation color perception:

a(F1 ) + b (F2 ) + c (F3 ) d (F4 } (3)

According to the international convention, pure colors with wavelengths of 700 nm (red), 546 nm (green) and 435 nm (blue) are chosen as primary (primary) colors F1, F2, F3, which can be used to build modern color systems. ). In order to obtain white color with additive mixing, the weight coefficients of these primary colors (a, b and c) must be related by the following relationship:

a + b + c + d = 1 (4)

The results of physiological experiments on color perception, described by equations (1) - (4), can be represented in the form of a chromaticity diagram (“color triangle”), which is too complex to be depicted in this work. Such a diagram differs from the three-dimensional representation of colors in that one parameter is missing here - “lightness”. According to this diagram, when two colors are mixed, the resulting color lies on a straight line connecting the two original colors. In order to find pairs of complementary colors from this diagram, it is necessary to draw a straight line through the “white point”.

Colors used in color television are obtained by additive mixing of three colors selected by analogy with equation (3).

THEORIES OF COLOR VISION

Three-component theory of color vision

It follows from equation (3) and the color diagram that color vision is based on three independent physiological processes. The three-component theory of color vision (Jung, Maxwell, Helmholtz) postulates the presence of three different types of cones that work as independent receivers if the illumination is photopic. Combinations of signals received from receptors are processed in neural systems for perception of brightness and color. The correctness of this theory is confirmed by the laws of color mixing, as well as by many psychophysiological factors. For example, at the lower limit of photopic sensitivity, only three components can differ in the spectrum - red, green and blue.

The first objective data supporting the hypothesis of the presence of three types of color vision receptors were obtained using microspectrophotometric measurements of single cones, as well as by recording color-specific cone receptor potentials in the retinas of animals with color vision.

Opponent color theory

If a bright green ring surrounds a gray circle, then the latter acquires a red color as a result of simultaneous color contrast. The phenomena of simultaneous color contrast and sequential color contrast served as the basis for the theory of opponent colors, proposed in the 19th century. Goering. Hering suggested that there were four primary colors—red, yellow, green, and blue—and that they were paired in pairs through two antagonistic mechanisms—the green-red mechanism and the yellow-blue mechanism. A third opponent mechanism was also postulated for achromatically complementary colors - white and black. Due to the polar nature of the perception of these colors, Hering called these color pairs "opponent colors". From his theory it follows that there can be no such colors as "greenish-red" and "bluish-yellow".

Thus, the theory of opponent colors postulates the presence of antagonistic color-specific neural mechanisms. For example, if such a neuron is excited under the action of a green light stimulus, then the red stimulus should cause its inhibition. The opponent mechanisms proposed by Goering received partial support after they learned how to register activity nerve cells directly associated with receptors. So, in some vertebrates with color vision, “red-green” and “yellow-blue” horizontal cells were found. In cells of the “red-green” channel, the resting membrane potential changes and the cell hyperpolarizes if light of the 400-600 nm spectrum falls on its receptive field, and depolarizes when a stimulus with a wavelength of more than 600 nm is applied. Cells of the "yellow-blue" channel hyperpolarize under the action of light with a wavelength of less than 530 nm and depolarize in the range of 530-620 nm.

Based on such neurophysiological data, simple neural networks can be constructed that allow one to explain how to interconnect three independent cone systems in order to cause a color-specific response of neurons at higher levels of the visual system.

Zone theory

At one time, there were heated debates between the supporters of each of the theories described. However, these theories can now be considered complementary interpretations of color vision. Criss' zonal theory, proposed 80 years ago, attempted to combine these two competing theories synthetically. It shows that the three-component theory is suitable for describing the functioning of the receptor level, and the opponent theory is suitable for describing neuronal systems more high level visual system.

COLOR VISION DISORDERS

Various pathological changes that disrupt color perception can occur at the level of visual pigments, at the level of signal processing in photoreceptors or in the high parts of the visual system, as well as in the diopter apparatus of the eye itself.

Described below are color vision disorders that are congenital and almost always affect both eyes. Cases of impaired color perception with only one eye are extremely rare. In the latter case, the patient has the opportunity to describe the subjective phenomena of impaired color vision, since he can compare his sensations obtained with the help of the right and left eyes.

color vision anomalies

However, anomalies are less able to distinguish some colors than normal-sighted trichromats, and in color matching tests they use red and green in different proportions. Testing on an anomaloscope shows that with protanomaly in accordance with ur. (1) there is more red in the color mixture than normal, and in deuteranomaly there is more green than necessary in the mixture. In rare cases of tritanomaly, the yellow-blue channel is disrupted.

Dichromates

Various forms of dichromatopsia are also inherited as X-linked recessive traits. Dichromats can describe all the colors they see with only two pure colors (Eq. 3). Both protanopes and deuteranopes have a disrupted red-green channel. Protanopes confuse red with black, dark grey, brown, and in some cases, like deuteranopes, with green. A certain part of the spectrum seems achromatic to them. For protanope, this region is between 480 and 495 nm, for deuteranope, between 495 and 500 nm. Rarely seen tritanopes confuse yellow and blue. The blue-violet end of the spectrum seems to them achromatic - like a transition from gray to black. The region of the spectrum between 565 and 575 nm is also perceived by tritanopes as achromatic.

Complete color blindness

Less than 0.01% of all people suffer from complete color blindness. These monochromats see the world around them as a black and white film, i.e. only gradations of gray are distinguished. Such monochromats usually show a violation of light adaptation at a photopic level of illumination. Due to the fact that the eyes of monochromats are easily blinded, they poorly distinguish the shape in daylight, which causes photophobia. Therefore, they wear dark sunglasses even in normal daylight. In the retina of monochromats, histological examination usually does not find any anomalies. It is believed that instead of visual pigment, their cones contain rhodopsin.

Rod apparatus disorders

People with rod anomalies perceive color normally, but they have a significantly reduced ability to dark adapt. The reason for such “night blindness”, or nyctalopia, may be the insufficient content of vitamin A1 in the food consumed, which is the starting material for the synthesis of retinal.

Diagnosis of color vision disorders

Since color vision disorders are inherited as an X-linked trait, they are much more common in men than in women. The frequency of protanomaly in men is approximately 0.9%, protanopia - 1.1%, deuteranomaly 3-4% and deuteranopia - 1.5%. Tritanomaly and tritanopia are extremely rare. In women, deuteranomaly occurs with a frequency of 0.3%, and protanomaly - 0.5%.

Since there are a number of professions that require normal color vision (for example, drivers, pilots, machinists, fashion designers), color vision should be checked for all children in order to subsequently take into account the presence of anomalies in choosing a profession. One simple test uses "pseudo-isochromatic" Ishihara tables. These tablets are marked with spots of different sizes and colors, arranged so that they form letters, signs or numbers. Spots of different colors have the same level of lightness. Persons with impaired color vision are not able to see some symbols (this depends on the color of the spots from which they are formed). Using various versions of the Ishihara tables, it is possible to reliably detect color vision disorders. Accurate diagnosis is possible using color mixing tests based on equations (1) - (3).

Literature

J. Dudel, M. Zimmerman, R. Schmidt, O. Grusser, et al. Human Physiology, 2 vol., translated from English, Mir, 1985

Ch. Ed. B.V. Petrovsky. Popular medical encyclopedia, st.. “Vision” “Color vision”, “Soviet Encyclopedia”, 1988

V.G. Eliseev, Yu.I. Afanasiev, N.A. Yurina. Histology, "Medicine", 1983 Add document to your blog or website Your assessment of this document will be the first one. Your mark:

In the visual analyzer, the existence of mainly three types of color receivers, or color-sensing components, is allowed (Fig. 35). The first (protos) is most strongly excited by long light waves, weaker by medium waves, and even weaker by short ones. The second (deuteros) is more strongly excited by medium, weaker - by long and short light waves. The third (tritos) is weakly excited by long waves, stronger by medium waves, and most of all by short waves. Therefore, light of any wavelength excites all three color receivers, but to varying degrees.

Rice. 35. Three-component color vision (scheme); the letters indicate the colors of the spectrum.

Color vision is normally called trichromatic, because to obtain more than 13,000 different tones and shades, only 3 colors are needed. There are indications of the four-component and polychromatic nature of color vision.

Color vision disorders can be congenital or acquired.

Congenital color vision disorders are in the nature of dichromasia and depend on the weakening or complete loss of the function of one of the three components (with the loss of a component that perceives red - protanopia, green - deuteranopia and blue - tritanopia).

Most common form dichromasia - a mixture of red and green colors. For the first time, dichromacy was described by Dalton, and therefore this type of color vision disorder is called color blindness. Congenital tritanopia (blindness to blue color) is almost never found.

A decrease in color perception occurs in men 100 times more often than in women. Among the boys school age color vision disorder is found in about 5%, and among girls - only in 0.5% of cases. Color vision disorders are inherited.

Acquired color vision disorders are characterized by the vision of all objects in any one color. This pathology is explained different reasons. So, erythropsia (seeing everything in red light) occurs after blinding the eyes with light with an enlarged pupil. Cyanopsia (blue vision) develops after cataract extraction, when a lot of short-wavelength light rays enter the eye due to the removal of the lens that delays them.

Chloropsia (vision in green) and xanthopsia (vision in yellow) arise due to the coloring of the transparent media of the eye with jaundice, poisoning with quinacrine, santonin, nicotinic acid etc. Violations of color vision are possible with inflammatory and dystrophic pathology proper choroid and retinas. The peculiarity of the acquired disorders of color perception is primarily that the sensitivity of the eye is reduced in relation to all primary colors, since this sensitivity is changeable, labile.

Color vision is most often studied using Rabkin's special polychromatic tables (vowel method).

There are also silent methods for determining color vision. It is better for boys to offer selection of mosaics of the same tone, and for girls - selection of threads.

The use of tables is especially valuable in children's practice, when many subjective research due to the small age of patients is not feasible. The numbers on the tables are available, and for the younger age we can limit ourselves to the fact that the child leads the brush with a pointer along the number, which he distinguishes, but does not know how to call it.

It must be remembered that the development of color perception is delayed if the newborn is kept in a room with poor lighting. In addition, the formation of color vision is due to the development of conditioned reflex connections. Therefore, for proper development color vision, it is necessary to create conditions for children with good lighting and with early age draw their attention to bright toys by placing these toys at a considerable distance from their eyes (50 cm or more) and changing their colors. When choosing toys, keep in mind that fovea most sensitive to the yellow-green and orange parts of the spectrum and less sensitive to blue. With increasing illumination, all colors except blue, blue-green, yellow and purple-crimson are perceived as yellow-white colors due to a change in brightness.

Children's garlands should have yellow, orange, red and green balls in the center, and balls with an admixture of blue, blue, white, dark must be placed at the edges.

The color distinguishing function of the human visual analyzer is subject to daily biorhythm with a maximum sensitivity at 13-15 hours in the red, yellow, green and blue parts of the spectrum.

Kovalevsky E.I.

The ability of a person to distinguish colors is important for many aspects of his life, often giving it emotional coloring. Goethe wrote: “Yellow color pleases the eye, expands the heart, invigorates the spirit and we immediately feel warmth. Blue color, on the contrary, represents everything in a sad way. Contemplation of the diversity of colors of nature, paintings by great artists, color photographs and artistic color films, color television give a person aesthetic pleasure.

Veliko practical value color vision. Distinguishing colors allows you to better know the world around you, produce the finest color chemical reactions, manage spaceships, the movement of railway, road and air transport, to diagnose changes in the color of the skin, mucous membranes, fundus, inflammatory or tumor foci, etc. Without color vision, the work of dermatologists, pediatricians, eye doctors and others who have to have dealing with different colors of objects. Even the performance of a person depends on the color and illumination of the room in which he works. For example, the pinkish and green color of the surrounding walls and objects calms, yellowish, orange - invigorates, black, red, blue - tires, etc. Taking into account the effect of colors on psycho-emotional state issues of painting walls and ceilings in rooms for various purposes (bedroom, dining room, etc.), toys, clothes, etc.

The development of color vision goes parallel to the development of visual acuity, but it is possible to judge its presence much later. The first more or less distinct reaction to bright red, yellow and green colors appears in a child by the first six months of his life. The normal formation of color vision depends on the intensity of light.

It has been proven that light travels in the form of waves of various wavelengths, measured in nanometers (nm). The part of the spectrum visible to the eye lies between rays with wavelengths from 393 to 759 nm. This visible spectrum can be divided into sections with different chromaticity. Rays of light with a long wavelength cause a sensation of red, with a small wavelength - blue and violet. Rays of light, the length of which lies in the gap between them, causes the sensation of orange, yellow, green and blue colors (Table 4).

All colors are divided into achromatic (white, black and everything in between, gray) and chromatic (others). Chromatic colors differ from each other in three main ways: hue, lightness and saturation.
Hue is the main amount of each chromatic color, a sign that allows you to attribute a given color by similarity to a particular color of the spectrum (achromatic colors do not have a hue). The human eye can distinguish up to 180 color tones.
Lightness, or brightness, of a color is characterized by the degree of its proximity to white. Brightness is the simplest subjective sensation of the intensity of light reaching the eye. human eye can distinguish up to 600 gradations of each color tone by its lightness, brightness.

The saturation of a chromatic color is the degree to which it differs from an achromatic color of the same lightness. This is, as it were, the "density" of the main color tone and various impurities to it. The human eye can distinguish approximately 10 gradations of different saturation of color tones.

If we multiply the number of distinguishable gradations of color tones, lightness and saturation of chromatic colors (180x600x10 "1,080,000)", then it turns out that the human eye can distinguish over a million color shades. In reality, the human eye distinguishes only about 13,000 color shades.

The human visual analyzer has a synthetic ability, which consists in optical mixing of colors. This is manifested, for example, in the fact that complex daylight is perceived as white. Optical color mixing is caused by simultaneous excitation of the eye with different colors and instead of several component colors, one resulting color is obtained.

A mixture of colors is obtained not only when both colors are sent to one eye, but also when monochromatic light of one tone is directed into one eye, and another into the other. Such binocular color mixing suggests that the main role in its implementation is played by central (in the brain), and not peripheral (in the retina) processes.

M. V. Lomonosov in 1757 for the first time showed that if 3 colors are considered primary in the color wheel, then by mixing them in pairs (3 pairs) you can create any others (intermediate in these pairs in the color wheel). This was confirmed by Thomas Jung in England (1802), and later by Helmholtz in Germany. Thus, the foundations of the three-component theory of color vision were laid, which is schematically as follows.
In the visual analyzer, the existence of mainly three types of color receivers, or color-sensing components, is allowed (Fig. 35). The first (protos) is most strongly excited by long light waves, weaker by medium waves, and even weaker by short ones. The second (deuteros) is more strongly excited by medium, weaker - by long and short light waves. The third (tritos) is weakly excited by long waves, stronger by medium waves, and most of all by short waves. Therefore, light of any wavelength excites all three color receivers, but to varying degrees.

Congenital color vision are in the nature of dichromasia and depend on the weakening or complete loss of the function of one of the three components (with the loss of a component that perceives red - protanopia, green - deuteranopia and blue - tritanopia). The most common form of dichromacy is a mixture of red and green. For the first time, dichromacy was described by Dalton, and therefore this type of color vision disorder is called color blindness. Congenital pai tritanopia (blindness to blue color) is almost never found.

A decrease in color perception occurs in men 100 times more often than in women. Among boys of school age, color vision disorder is found in about 5%, and among girls - only in 0.5% of cases. Color vision disorders are inherited.
Acquired color vision disorders are characterized by the vision of all objects in any one color. This pathology is due to various reasons. So, erythropsia (seeing everything in red light) occurs after blinding the eyes with light with an enlarged pupil. Cyanopsia (blue vision) develops after cataract extractions, when a lot of short-wavelength light rays enter the eye due to the removal of the lens that delays them. Chloropsia (green vision) and xanthopsia (yellow vision) occur due to the coloration of the transparent media of the eye with jaundice, poisoning with quinacrine, santonin, nicotinic acid, etc. Color vision disorders are possible with inflammatory and degenerative pathology of the choroid and retina proper . The peculiarity of the acquired disorders of color perception is primarily that the sensitivity of the eye is reduced in relation to all primary colors, since this sensitivity is changeable, labile.

Color vision is most often studied using Rabkin's special polychromatic tables (vowel method).
There are also silent methods for determining color vision. It is better for boys to offer selection of mosaics of the same tone, and for girls - selection of threads.

The use of tables is especially valuable in pediatric practice, when many subjective studies are not feasible due to the small age of patients. The numbers on the tables are available, and for the youngest age, you can limit yourself to the fact that the child leads them with a brush with a pointer along the number that he distinguishes, but does not know how to call it.

It must be remembered that the development of color perception is delayed if the newborn is kept in a room with poor lighting. In addition, the formation of color vision is due to the development of conditioned reflex connections. Therefore, for the correct development of color vision, it is necessary to create good lighting conditions for children and, from an early age, draw their attention to bright toys, placing these toys at a considerable distance from their eyes (50 cm or more) and changing their colors. When choosing toys, it should be borne in mind that the fovea is most sensitive to the yellow-green and orange parts of the spectrum and is not very sensitive to blue. With increasing illumination, all colors except blue, blue-green, yellow and purple-crimson are perceived as yellow-white colors due to a change in brightness.
Children's garlands should have yellow, orange, red and green balls in the center, and balls with an admixture of blue, blue, white, dark must be placed at the edges.

The color distinguishing function of the human visual analyzer is subject to a daily biorhythm with a maximum sensitivity at 13-15 hours in the red, yellow, green and blue parts of the spectrum.