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Introduction to the eye optics

Œil and optical: the basics

This page is an introduction to the optical eye, also called physiological Optics: it provides a simplified and accessible description how the eye processes light get it to allow the Visual ways send information that will give birth to the Visual sensation to the brain.

 "There are eyes that receive light and there are eyes that give it... "(Paul Claudel)

Introduction to the vision

The vision is the result of a useful interaction between the eye and the light. If visual sensation seat in the brain, the eye is a light sensor body.

The first step of the Visual casecade can be described as optical: she intended to form on the retina, the light-sensitive tissue that lines the inside wall of the eyeball, as fairly as possible of the surrounding world. The light is "information", which, when it is emitted by a light source, travel in the surrounding space. The journey takes this information is generally in the form of straight lines called "spokes". When the eye captures these rays, it captures some of the information emitted by the light source.

To allow our brains to produce a visual sensation, the eye to send this information to the retina, which is a neurological tissue connected to the brain through the Visual channels.  The retinal image is born of the focus on the retina of the light rays emitted by the objects observed and then picked up by the eye. To form a sufficiently sharp retinal image, transparent ocular structures must print the captured light rays a route leading to converge on the retina; one speaks of «» refraction "light rays. The path of light rays in the cornea and the crystalline lens obeys the laws of refraction; Knowing these laws is so essential to understand and predict the way so the eye perceives the world around.  Myopia, hyperopia or astigmatism are so many refractive errors (called "") ametropia"), which stem from an imperfect (flawed drive) refraction light rays to the retina."

eye rays and optics

The eye is a light sensor: the rays, who realized the path of 'light information' are emitted by a source object. So that this information can be used to form a "picture" of the source, so that it is received by an optical system (an ' objective') whose role is to deflect the rays received so that they converge in one same point, ideally located in the plane of a light-sensitive surface. In the case of the human eye, the optical system is formed by the cornea and the lens, and the photosensitive surface is located within the retina and covered with cells called photoreceptors.

The study of the fundamental laws of optics may prove off-putting or arid, particularly when it is presented without direct and explanatory link with some concrete phenomena: even the most basic concepts such as the propagation of light rays can then appear devoid of true meaning for the non-specialist reader. The study of the refraction of light by the eye focuses essentially on the propagation of light through the optical system and the eye is part of optics known as "geometric". This area is essential to understand the mechanisms, consequences and means of correction of the optical defects of the eye (the what). It is unfortunately not enough to fully understand the mechanism of the formation of retinal images.

The notions of additional optics, arising from the field of optics, so-called 'wave' used to explain certain phenomena involved in the formation of these images.

This introduction to the eye optics pages have therefore aims to explain how is the initial stage of the vision, which is an optical step: they are aimed at the novice readers, who may not have knowledge in optics, but who wish to understand how is the initial stage of the vision, which involves light emitted by sources present in our visual environment and the eye. It must serve as an introduction or even "intermediation", by providing the fundamentals and prerequisites useful to address topics more specialized site content.

Some repetitions are voluntary, in order to emphasize the most important concepts. So the reader can understand how exploration methods, modeling, and correction of the refraction of the eye are designed better.

We'll thus successively:

-The General principles that govern the light path of the light source in the retina : this step is important, because it determines the quality of the image captured rays will form on the retinal screen.

-THEretinal image : we will explore how it is possible to study the quality of this image with respect to the light source, which requires to break it down into sub basic units: a set of image points, or a set of spatial frequencies

-The path of the rays through the elements of the eye that refract the light: the cornea and the lens. This optical path depends on physical properties and obeying certain laws, such as the law of refraction.


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