Eye like optical
system
Prepared by 9th grade student Varvara Mikhalchenko
Sclera protection from damage
The cornea is protection and support. Functions
light transmission and light refraction
are ensured by transparency and
enchanting cornea.
Iris - determination of eye color
Pupil - regulation of the flow of rays
light coming into the eye and falling on
retina Light level control
retina.
Lens-provides
light transmission, refraction, acco
modification, protection.
Vitreous humor - fills the volume
the entire cavity eyeball.
Retina - lines the cavity of the eye
apple from the inside and performs the functions
perception of light and color
signals.
The optic nerve provides transmission
nerve impulses of light
irritation. Image Type
The optical system of the eye consists of the cornea, anterior chamber, lens and
vitreous body. The image of an object appearing on the retina of the eye is
real, diminished and inverted. Visual acuity
Visual acuity is the ability to distinguish boundaries and details.
visible objects. It is determined by the minimum angular
the distance between two points at which they are perceived
apart. Farsightedness and myopia
Farsightedness is a lack of vision when
which parallel rays after
refractions are collected not on the retina, but behind
her.
Myopia is a lack of vision in which
parallel rays are not collected at
retina, and closer to the lens. Treatment methods
There are currently three recognized methods of correction
myopia and farsightedness, namely:
Glasses
Contact lenses
Laser correction of myopia or farsightedness Binocular vision
Binocular vision - the ability to see clearly at the same time
image of an object with both eyes; in this case the person sees one thing
image of the object being looked at, that is, this is vision with two
eyes, with a subconscious connection in the visual analyzer (cortex
brain) images obtained by each eye into a single image.
Creates three-dimensionality of the image. Binocular vision is also called
stereoscopic.
Many people have binocular vision
animals, fish, insects, birds.
Slide 1
THE HUMAN EYE AS AN OPTICAL SYSTEM. CONSTRUCTION OF AN IMAGE ON THE RETINA. DISADVANTAGES OF THE OPTICAL SYSTEM OF THE EYE AND THE PHYSICAL BASIS FOR THEIR ELIMINATION. Completed by: Orgma student 123 gr. Lec.fak. Kochetova KristinaSlide 2
THE HUMAN EYE AS AN OPTICAL SYSTEM. A person perceives objects outside world by analyzing the image of each object on the retina. The retina is the light-receiving region. The images of objects around us are captured on the retina using the optical system of the eye. The optical system of the eye consists of: Cornea Lens Vitreous body
Slide 3
THE HUMAN EYE AS AN OPTICAL SYSTEM. The cornea, cornea (lat. cornea) is the anterior most convex transparent part of the eyeball, one of the light-refracting media of the eye. The human cornea occupies approximately 1/16 of its area outer shell eyes. It has the appearance of a convex-concave lens, with the concave part facing backwards; it is transparent, due to which light passes into the eye and reaches the retina. Normally, the cornea is characterized the following signs: sphericity specularity transparency high sensitivity absence blood vessels. Functions: protective and supporting functions (provided by its strength, sensitivity and ability to quickly recover), light transmission and refraction (provided by the transparency and sphericity of the cornea).
Slide 4
THE HUMAN EYE AS AN OPTICAL SYSTEM. The cornea has six layers: anterior epithelium, anterior limiting membrane (Bowman's membrane), ground substance of the cornea, or stroma Layer Dua, posterior limiting membrane (Descemet's membrane), posterior epithelium, or corneal endothelium.
Slide 5
THE HUMAN EYE AS AN OPTICAL SYSTEM. The lens (lens, lat.) is a transparent biological lens that has a biconvex shape and is part of the light-conducting and light-refracting system of the eye, and provides accommodation (the ability to focus on objects at different distances). There are 5 main functions of the lens: Light transmission: The transparency of the lens ensures the passage of light to the retina. Light refraction: Being a biological lens, the lens is the second (after the cornea) light refractive medium of the eye (at rest the refractive power is about 19 diopters). Accommodation: The ability to change its shape allows the lens to change its refractive power (from 19 to 33 diopters), which ensures focusing of vision on objects at different distances. Separating: Due to the location of the lens, it divides the eye into the anterior and posterior sections, acting as an “anatomical barrier” of the eye, keeping the structures from moving (prevents the vitreous from moving into the anterior chamber of the eye). Protective function: the presence of a lens makes it difficult for microorganisms to penetrate from the anterior chamber of the eye into vitreous in inflammatory processes.
Slide 6
THE HUMAN EYE AS AN OPTICAL SYSTEM Structure of the lens. The lens is similar in shape to a biconvex lens, with a flatter front surface. The diameter of the lens is about 10 mm. The main substance of the lens is contained in thin capsule, under the anterior part of which there is epithelium (on posterior capsule epithelium is absent). The lens is located behind the pupil, behind the iris. It is fixed with the help of the thinnest threads (“ligament of zinn”), which at one end are woven into the lens capsule, and at the other end they are connected to the ciliary body and its processes. It is thanks to the change in the tension of these threads that the shape of the lens and its refractive power change, as a result of which the process of accommodation occurs. Innervation and blood supply The lens does not have blood or lymphatic vessels, nerves. Exchange processes carried out through the intraocular fluid, which surrounds the lens on all sides.
Slide 7
THE HUMAN EYE AS AN OPTICAL SYSTEM. The vitreous body is a transparent gel that fills the entire cavity of the eyeball, the area behind the lens. Functions of the vitreous body: conduction of light rays to the retina, due to the transparency of the medium; maintaining the level intraocular pressure; ensuring the normal location of intraocular structures, including the retina and lens; compensation for changes in intraocular pressure due to sudden movements or injuries due to the gel component.
Slide 8
THE HUMAN EYE AS AN OPTICAL SYSTEM. STRUCTURE OF THE VITREOUS HUD The volume of the vitreous body is only 3.5-4.0 ml, while 99.7% of it is water, which helps maintain a constant volume of the eyeball. The vitreous body is adjacent to the lens in front, forming a small depression in this place; on the sides it borders with the ciliary body, and along its entire length with the retina.
Slide 9
Rays of light that are reflected from the objects in question necessarily pass through 4 refractive surfaces: the back and front surfaces of the cornea, the back and front surfaces of the lens.
Slide 10
CONSTRUCTION OF AN IMAGE ON THE RETINA. Each of these surfaces deflects the light beam from its original direction, which is why a real, but inverted and reduced image of the observed object appears at the focus of the optical system of the organ of vision.
Slide 11
The first to prove that the image on the retina is inverted by plotting the path of rays in the optical system of the eye was Johannes Kepler (1571 - 1630). To test this conclusion, the French scientist Rene Descartes (1596 - 1650) took a bull's eye and scraped it off. back wall an opaque layer, placed in a hole made in the window shutter. And then, on the translucent wall of the fundus, he saw an inverted image of the picture observed from the window.
Slide 12
Why then do we see all objects as they are, i.e. not upside down? The fact is that the process of vision is continuously corrected by the brain, which receives information not only through the eyes, but also through other senses. In 1896, American psychologist J. Stretton conducted an experiment on himself. He put on special glasses, thanks to which the images of surrounding objects on the retina of the eye were not reversed, but forward. He began to see all objects upside down. Because of this, there was a mismatch in the work of the eyes with other senses. The scientist developed symptoms seasickness. During three days he felt nauseous. However, on the fourth day the body began to return to normal, and on the fifth day Stretton began to feel the same as before the experiment. The scientist’s brain became accustomed to the new working conditions, and he began to see all objects straight again. But when he took off his glasses, everything turned upside down again. Within an hour and a half, his vision was restored, and he began to see normally again.
Slide 13
The process of refraction of light in the eye's optical system is called refraction. The doctrine of refraction is based on the laws of optics, which characterize the propagation of light rays in various media. The straight line that passes through the centers of all refractive surfaces is the optical axis of the eye. Light rays incident parallel to a given axis are refracted and collected at the main focus of the system. These rays come from objects at infinity, so the main focus of the optical system is the place on the optical axis where the image of objects at infinity appears. Divergent rays that come from objects located at a finite distance are collected at additional foci. They are located further than the main focus, because additional refractive power is needed to focus diverging rays. The more the incident rays diverge (the proximity of the lens to the source of these rays), the greater the refractive power required.
Slide 14
Slide 15
DISADVANTAGES OF THE OPTICAL SYSTEM OF THE EYE AND THE PHYSICAL BASIS FOR THEIR ELIMINATION. Thanks to accommodation, the image of the objects in question is obtained precisely on the retina of the eye. This is done if the eye is normal. An eye is called normal if, in a relaxed state, it collects parallel rays at a point lying on the retina. The two most common eye defects are myopia and farsightedness.
Slide 1
The eye as an optical system.
Completed by: Daria Novikova, 8th grade student
Slide 2
IN.
In ancient times, mystical properties were attributed to the eyes. They symbolized the meaning and essence of life; their images were considered amulets and amulets. The ancient Greeks painted beautiful elongated eyes on the bows of ships, and the Egyptians depicted all-seeing eye god Ra.
The eye as an optical system
Slide 3
We receive most of the information about the world around us through vision. The human organ of vision is the eye - one of the most advanced and at the same time simple optical instruments.
Slide 4
Structure of the eye
Slide 5
The human eye has a spherical shape. The diameter of the eyeball is about 2.5 cm. The outside of the eye is covered with a dense opaque membrane - the sclera. The anterior part of the sclera merges into the transparent cornea, which acts as a converging lens and provides 75% of the eye's ability to refract light.
Slide 6
The optical system of the eye can be considered as a converging lens. Main role This is where the lens plays.
Lenses
Concave collecting
Convex diffusers
Lens optical power: D= 1/F. Measured in diopters
Where F is the focal length. The focal length can be calculated using the thin lens formula:
1/F= 1/f+1/d
Slide 7
Correction of myopia is carried out by selecting diverging lenses
Farsightedness is corrected by selecting converging lenses
Correction of myopia and farsightedness
Slide 8
Simplified optical system of the eye
The radiation flux reflected from the observed object passes through the optical system of the eye and is focused on the inner surface of the eye - the retina, forming a reverse and reduced image on it (the brain “inverts” the reverse image, and it is perceived as direct). The optical system of the eye consists of the cornea, aqueous humor, lens and vitreous body. A special feature of this system is that the last medium passed by light immediately before the formation of an image on the retina has a refractive index different from unity.
Slide 9
Accommodation is the ability of the eye to adapt to clearly distinguish objects located at different distances from the eye. Accommodation occurs by changing the curvature of the surfaces of the lens through tension or relaxation of the ciliary body. When ciliary body tense, the lens stretches and its radii of curvature increase. As muscle tension decreases, the lens, under the influence of elastic forces, increases its curvature.
Accommodation
Slide 10
Myopia – this state often called myopia. It occurs when parallel rays of light entering the eye are focused in front of the retina. To obtain a clear image, a concave corrective lens must be placed in front of the cornea.
Myopia
Slide 11
Hypermetropia
Hypermetropia is a condition commonly referred to as farsightedness. It occurs when parallel rays of light entering the eye are focused behind the retina. A convex magnifying lens is required to obtain a clear image in this condition.
Slide 12
Presbyopia
As we age, our eyes lose their ability to focus. This makes activities that require careful consideration of objects, such as reading, problematic. The lens of the eye becomes less elastic and loses its ability to produce sufficient magnification. In such situations, a convex lens must be placed in front of the eye. Typically, people who have never worn glasses begin to need reading correction around the age of 45.
