Sweat beads on the forehead, cars honk, a passerby waves his hands. Stress level often increases when parking. The visual system is best suited to estimate the distance to the sports car behind us and to the concrete bollard in front of us.
- Although images arrive on our retinas in two dimensions, we have a good eye for three dimensions. This is due to the additional evaluations of information that the visual system makes – such as shadows, overlays, and empirical values about sizes.
- In addition, the visual cortex in the brain calculates the position of an object in space from the different angle of view of the two eyes on an object, the retinal disparity.
- Retinal disparity enables stereoscopic vision
- Further clues to the depth of space are given to the brain by the position of the eyeballs as they fixate on a point, and by stereoscopic vision, the fact that the two images from the eyes are merged into one in the brain.
Retina
The retina is the inner eye skin covered with pigment epithelium. The retina is characterized by an inverse (reversed) arrangement: Light must first pass through several layers before it reaches the photoreceptors (cones and rods). The signals from the photoreceptors are transmitted via the optic nerve to the processing areas of the brain. The reason for the inverse arrangement is the developmental origin of the retina, which is an outpouching of the brain.
The retina is about 0,2 to 0,5 mm thick.
Cortex
Cerebral cortex/cortex cerebri/cerebral cortex
The cortex cerebri, or cortex for short, refers to the outermost layer of the cerebrum. It is 2.5 mm to 5 mm thick and rich in nerve cells. The cerebral cortex is strongly folded, comparable to a handkerchief in a cup. This creates numerous convolutions (gyri), fissures (fissurae) and furrows (sulci). When unfolded, the surface area of the cortex is about 1.800 cm 2 .
Eye
Eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for perception of light stimuli – of electromagnetic radiation of a certain frequency range. The light visible to humans is in the range between 380 and 780 nanometers.
In the 19. In the 19th century, physicist Charles Wheatstone developed the stereoscope, the great-grandfather of 3D cinema. A stereoscope looks like a pair of binoculars with a windshield, in front of which two slightly different images are clamped. If you look through a stereoscope, each eye sees an image. These then merge in the brain to form a three-dimensional perception. Nothing else happens in the new 3D movies, whose boom was founded by James Cameron’s Avatar. Here, too, the hero Jake Sully jumps out at us from the screen only because our right eye sees a different image than our left eye. However, special recording methods and high-tech glasses make today’s three-dimensional cinema world almost as realistic as real life.
Eye
Eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for perceiving light stimuli – electromagnetic radiation of a specific frequency range. The light visible to humans lies in the range between 380 and 780 nanometers.
Perception
The term describes the complex process of acquiring and processing information from stimuli in the environment as well as from the internal states of a living being. The brain combines the information, which is perceived partly consciously and partly unconsciously, into a subjectively meaningful overall impression. If the data, which it receives from the sense organs, are not sufficient for this, it supplements these with empirical values. This can lead to misinterpretations and explains why we succumb to optical illusions or fall for magic tricks.
Our environment is three-dimensional and our perceptual apparatus has obviously adapted to it. You reach for the telephone receiver on the left side of the desk – and catch it. You throw the crumpled piece of paper in the direction of the wastebasket – and, unless your name is Michael Jordan, you don’t always hit it. But the shot almost never misses by several meters. What seems obvious becomes all the more astonishing when you realize that a telephone receiver and a wastepaper basket produce a two-dimensional image on the retina. And this applies to everything we look at. But although their image in the eye is two-dimensional, we perceive the world in three dimensions. How that?
In order to track down the spatial arrangement of things, the visual system evaluates different information. Shadows and superimpositions are included in the calculations, as are empirical values about the size of an object. However, the main reason for our ability to see in three dimensions at short to medium distances is the fact that we have two eyes whose entrance openings – the pupils – are about six to seven centimeters apart.
When both eyes look at the same object, they always do so from a slightly different angle. That is, a slightly different image falls on the retina of the left eye than on the retina of the right eye. This can be easily checked by holding up the thumb with an outstretched arm directly in front of the nose and fixing a point behind it, say the corner of the monitor. If you now pinch the left and right eye alternately, the thumb seems to jump back and forth – in relation to the fixation point. It is imaged in the retina of the left eye and in the retina of the right eye on corresponding locations. The images of closer objects, such as the thumb in our self-test, are offset from these corresponding retinal locations. From the so-called retinal disparity, i.e. the lateral offset and the difference between the images of an object on the two retinas, the brain deciphers the spatial depth. The closer the fixation plane and the object are to each other, the smaller the differences. If you fixate on the sports car when parking and your thumb barely jumps back and forth, it’s already too late to brake and you’re rear-ended.
Retina
The retina is the inner eye skin covered with pigment epithelium. The retina is characterized by an inverse (reversed) arrangement: Light must first pass through several layers before it hits the photoreceptors (cones and rods). The signals of the photoreceptors are transmitted via the optic nerve to processing areas of the brain. The reason for the inverse arrangement is the developmental origin of the retina, it is an outpouching of the brain.
The retina is about 0.2 to 0.5 mm thick.
Eye
Eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for the perception of light stimuli – of electromagnetic radiation of a certain frequency range. The light visible to humans is in the range between 380 and 780 nanometers.
Eye
Eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for the perception of light stimuli – of electromagnetic radiation of a certain frequency range. The light visible to humans is in the range between 380 and 780 nanometers.
Nose
The olfactory organ of vertebrates. In the nasal cavity the air is cleaned by cilia, in the upper area lies the olfactory epithelium, with which odors are absorbed.
Double vision with and without alcohol
Already in 19. In the nineteenth century, the English physicist Charles Wheatstone (1802 to 1875) recognized, that the brain assembles a three-dimensional image from two two-dimensional images of the environment from the two eyes. He coined the term stereoscopic vision for it and invented the first stereoscope, the great-grandfather of 3D cinema.
The place where the two different images become one whole is the visual cortex. This part of the cerebrum, also called the visual cortex, extends roughly from the horse’s tail to the ears. There, the various aspects of a visual impression are decoded by specialized nerve cells: Color, contours, brightness, movement as well as spatial arrangement and extension of objects. The neurons responsible for the latter receive input from the left and right retina and calculate information about the distance from the differences, the retinal disparity.
As important as it is for our spatial perception that the eyes provide two images of the external world, it would be troublesome to see both separately. Because then we would see everything twice. Therefore, the two images are fused in the visual cortex, into a single overall image. How this two become one works is still unclear. But it works and makes us see as if we were a cyclops with only one eye in the middle. Mostly anyway. Sometimes, however, two barmen are suddenly pouring drinks and two southern beauties are lolling synchronously at the bar. Then one has looked too deeply into the glass. Alcohol is a substance that can cause the brain to lose control of the cerebellum’s coordination of eye movements, so that the brain can no longer unite the images of the two eyes.
Eye
Eyeball/Bulbus oculi/eye bulb
The eye is the sensory organ for the perception of light stimuli – of electromagnetic radiation of a certain frequency range. The light visible to humans lies in the range between 380 and 780 nanometers.
Cortex
Cerebral cortex/cortex cerebri/cerebral cortex
The cerebral cortex, or cortex for short, is the outermost layer of the cerebrum. It is 2.5 mm to 5 mm thick and rich in neurons. The cerebral cortex is strongly folded, comparable to a handkerchief in a cup. Thus, numerous convolutions (gyri), fissures (fissurae) and furrows (sulci) are formed. Folded out, the surface of the cortex is about 1.800 cm 2 .
Neuron
The neuron is a cell of the body specialized in signal transmission. It is characterized by the reception and transmission of electrical or chemical signals.
Neuron
The neuron is a cell of the body specialized in signal transmission. It is characterized by the reception and transmission of electrical or chemical signals.
Retina
The retina is the inner eye skin covered with pigment epithelium. The retina is characterized by an inverse (reversed) arrangement: Light must first penetrate several layers before it hits the photoreceptors (cones and rods). The signals from the photoreceptors are transmitted via the optic nerve to processing areas of the brain. The reason for the inverse arrangement is the developmental origin of the retina, it is an outpouching of the brain.
The retina is about 0.2 to 0.5 mm thick.
Perception
The term describes the complex process of obtaining and processing information from stimuli in the environment and from the internal states of a living being. The brain combines the information, which is perceived partly consciously and partly unconsciously, to form a subjectively meaningful overall impression. If the data it receives from the sensory organs is not sufficient for this, it supplements it with empirical values. This can lead to misinterpretation and explains why we succumb to optical illusions or fall for magic tricks.
Eye
eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for the perception of light stimuli – electromagnetic radiation of a certain frequency range. The light visible to humans lies in the range between 380 and 780 nanometers.
Cerebellum
The cerebellum (cerebellum) is an important part of the brain, located at the back of the brain stem and below the occipital lobe. It consists of two cerebellar hemispheres, which are covered by the cerebellar cortex (cerebellar cortex) and plays among other things an important role in automated motor processes.
Targeted squint
How our eyes move also plays a role in oculomotor depth cues. The brain obtains information about spatial depth from the movements of the eyes. However, this only works for short distances, such as when we look at our passenger while he leans over to us. The closer he comes to us, the more our eyes turn towards our nose to fixate him. At the same time, the ciliary muscles in the eye tense up more strongly in order to bring the image into focus, to accommodate, as they say. By the convergence, i.e. how strongly we squint, and the tension of the muscles, the brain recognizes how close our passenger is to us. Whether this relatively imprecise mechanism contributes to spatial vision at all, and if so to what extent, is a matter of controversy among scientists. "I would be surprised, however, if the brain does not use information that is immediately available to it," says biopsychologist Professor Onur Gunturkun of the Ruhr University in Bochum.
eye
eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for perceiving light stimuli – electromagnetic radiation of a certain frequency range. The light visible to humans lies in the range between 380 and 780 nanometers.
Nose
The olfactory organ of vertebrates. In the nasal cavity, the air is cleaned by cilia, in the upper area lies the olfactory epithelium, with which odors are absorbed.
Eye
Eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for the perception of light stimuli – of electromagnetic radiation of a certain frequency range. The light visible to humans is in the range between 380 and 780 nanometers.
Detecting depth with only one eye
When the opponent obscures the goalkeeper, the opponent stands closer to one. Not only Winfried Hannes knows this from experience. This depth hint of the interposition uses the brain. The shadows of teammates and opponents also reveal something about their position and distance. Similarly, patterns indicate depth: Leaves of grass in the other half of the field appear closer together than directly in front of you. Anyone standing in a soccer goal can see the hint of the linear perspective. The parallel stands and edges of the field appear to converge in the distance. Pass, cross, shot, goal. Due to the fast movements in soccer, another depth clue comes into play, the movement parallax: When Hannes dribbles to the goal, closer teammates move faster over his net skins.
Monocular, binocular and oculomotor depth cues hit us simultaneously. The more clues, the better we can estimate distances. Like a detective, the brain adds up the clues and thus substantiates a spatial impression. Images with contradictory combinations of depth cues, such as the famous staircase painting by M.C. Escher therefore bring our spatial orientation into a spin. In reality, when in doubt, the brain trusts the information provided by stereoscopic vision.
Convergence
Convergence of neurons results from the synaptic connection of several neurons with a single transmitting neuron. Thus z. B. In the eye, the information received by up to 130 receptors is transmitted to only one neuron in the retina. The opposite is divergence, when one neuron passes signals to several other neurons.
Eye
Eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for perceiving light stimuli – electromagnetic radiation of a certain frequency range. The light visible to humans is in the range between 380 and 780 nanometers.
Eye
eyeball/bulbus oculi/eye bulb
The eye is the sensory organ for the perception of light stimuli – of electromagnetic radiation of a certain frequency range. The light visible to humans is in the range between 380 and 780 nanometers.