The Eye
Parts of the eye.
The optical system of your eye works rather like that of the camera, where a converging lens forms a tiny upside-down image of the distant world on a 'screen.'The eye is made up of several parts, some of which are shown in the diagram to the left.
Parts of the Eye
Parts of the Eye
- The human eye is like a camera:
- Iris- like the diaphragm of a camera it controls the amount of light entering. It is the coloured part of the eye and opens and closes around a central hole to control the light entering the eye.
- Pupil- this is the hole in the iris. It is like the aperture in a camera which is where the light enters.
- Cornea and Lens- these cause light to converge creating a sharp image. The cornea is a transparent bulge on top of the pupil that focuses light. Light is refracted more through the cornea than the lens.
- Sclera- the sclera is commonly known as "the white of the eye." It is the tough, opaque tissue that serves as the eye's protective outer coat. Six tiny muscles connect to it around the eye and control the eye's movements. The optic nerve is attached to the sclera at the very back of the eye.
- Light sensitive cells- these cells act like film in a camera, they “store” the image.
- Retina- converts light signals into electrical signals that will travel to the brain.
- Optic Nerve- used to transmit the signals from the retina to the brain.
The Camera
The main components of a camera are the lens, aperture, shutter and film.
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- The lens (or set of lenses) which is primarily a convex lens provides the camera with an image from outside of the camera,
- The aperture controls the amount of light passing through the lens to the film plane,
- The shutter controls the amount of time that the image is exposed to the film plane and finally
- The film plane where either photographic film or digital receptors allow the image to be created and stored for future viewing/use.
The Eye/The Camera
Below are some similarities between the eye and the camera
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- Your Cornea behaves much like the front lens element of a lens. Together with the lens, which is behind the iris, they are the eye's focusing elements. The cornea takes widely diverging rays of light and bends them through the pupil, the round opening in the central portion of the coloured iris.
- Your Iris and pupil act like the aperture of a camera. The iris is a muscle which, when contracted, covers all but a small central portion of the lens, allows adjustable control of the quantity of light entering the eye so that the eye can work well in a wide range of viewing conditions, from dim to very bright light.
- Finally, your Retina is the sensory layer that lines the very back of our eyes. It acts very much like the imaging sensor chip in a digital camera. The retina has numerous photoreceptor nerve cells that help change the light rays into electrical impulses and send them through the optic nerve to the brain where an image (of what we see) is finally received and perceived. Because of this reception and perception function, retina is, perhaps, the most important component of our eyes. As with the camera, if the "film" is bad in the eye (i.e. the retina), no matter how good rest of the eye is, we will not get a good quality image or picture.