2.2 KiB
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A lens
An optical lens is a very common and simple optical element, designed and made to focuse or disperse the light by the use of the refraction phenomenon. Because requires to focus in a point image the light emitted or diffused by any object point
A lens is a piece of transparent glass, quartz or plastic that usually exhibits a symmetry of revolution about an axis. Its thickness, along its axis of symmetry, is small compared to the radius of its* two main surfaces* that are *polished and either or both curved*.
The curvation of each surface can be charactérized as :
- convex : the surface bulges outwards in the center.
- concave : the surface curves inward in the center.
- plane : the surface is plane.
In the ideal case of lenses with negligeable thicknesses (thin lenses) or optical systems with negligeable length (thin lenses, mirrors and refracting surfaces in contact) :
- The dioptric power (or vergence) $\delta$ of a thin lens is simply the sum of the dioptric powers $\delta_{DS1}$ and $\delta_{DS2}$ of the two refracting surfaces $DS1$ and $DS2$ that compose the thin lens : $\delta=\delta_{DS1}+\delta_{DS2}$.
- The dioptric power (vergence) $\delta$ of thin lenses in contact or in contact with a mirror is simply the sum of their individual dioptric powers $\delta_i$ : $\delta=\sum \delta_i$.
In the more realistic and physical case, add a simple optical element of positive (respectively negative) dioptric power (or vergence) to an optical system will increase (resp. decrease) the total dioptric power of the system, so will increase the focalisation (resp. dispersion) of an incident light beam by the system.
!! Beyond : !! !! Lentils gave lenses their name
The final objective of lenses is to realize images, in the plane of a sensor to be recordered or to be seen with the naked eye. For this a