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The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. [1] It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.
The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris' dilator and sphincter muscles. Light energy enters the eye through the cornea, through the pupil and then through the lens. The lens shape is changed for near focus (accommodation) and is controlled by the ciliary muscle.
The pupil function or aperture function describes how a light wave is affected upon transmission through an optical imaging system such as a camera, microscope, or the human eye. More specifically, it is a complex function of the position in the pupil [ 1 ] or aperture (often an iris ) that indicates the relative change in amplitude and phase ...
Light enters the eye at the cornea, passing through the pupil to reach the lens. Most fish species seem to have a fixed pupil size, but elasmobranches (like sharks and rays) have a muscular iris which allows pupil diameter to be adjusted. Pupil shape varies, and may be e.g. circular or slit-like. [5]
Muscles around the iris change the size of the pupil, regulating the amount of light that enters the eye [3] and reducing aberrations when there is enough light. [4] The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing is achieved by telescoping the lens in a similar manner to that of a camera. [5]
The exit pupil is the image of the aperture stop formed by the optics behind it, and the location and size of the pupil are determined by chief rays and marginal rays. The image side of the lens of an SLR camera; the exit pupil is the light area in the middle of the lens. In optics, the exit pupil is a virtual aperture in an
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A slit pupil can indicate the common multifocal system, while a circular pupil usually specifies a monofocal system. When using a circular form, the pupil will constrict under bright light, increasing the f-number, and will dilate when dark in order to decrease the depth of focus. [49] Note that a focusing method is not a requirement.