What are the uses of optical lenses?

An optical lens is a transparent optical element used to converge or diffuse light emitted from a peripheral object. The transmitted light then forms a real or virtual image of the object.

Lenses are a good example of transmission optical components, which means they can pass or transmit light. Other transmission components include filters, windows, planes, prisms, beam splitters and waveplates, while the opposite category - reflectors (which reflect rather than transmit light) - includes optics and retroreflectors.

Optical lenses have been used since at least c 700 B.C. for a variety of applications, including:

Magnification

Optical aberration correction

Use as an igniter (burning glasses)

Image focusing

Image projection

Shapes and types

Lenses are available in a variety of shapes, including biconvex, biconcave, plano-convex, plano-concave, positively curved lunar, and negatively curved lunar.

A positive lens produces a collimated beam - assuming the beam travels parallel to the lens axis and through the lens - that converges or focuses on a point behind the lens. When referring to the diagram above, biconvex and plano-convex lenses are considered to be frontal.

Negative lenses cause the collimated beam to diverge and spread behind the lens. The two types of concave lenses - biconvex and plano-convex - are negative.

Curved-moon lenses - the third widespread type, also known as convex-concave lenses - can be positive or negative, depending on the curvature of the sides of the lens. Bent-moon lenses with steeper concave sides are negative, while lenses with steeper convex sides are positive. A bent-moon lens with equal curvature on both sides will neither converge nor diverge light.

Lens Classification

Lenses can be divided into the following categories. These categories are not mutually exclusive; for example, a spherical lens can also be achromatic.

Spherical Lenses

Spherical lenses (or single lenses) have a curved surface that converges or diverges light. All lenses are spherical in cross-section.

Cylindrical Lenses

Unlike spherical lenses, cylindrical lenses have curved surfaces that can be thought of as part of a cylindrical shape. This allows them to focus transmitted light to a line rather than a point. Cylindrical lenses are often used to change the aspect ratio of an image or to shape the laser beam.

Achromatic

Achromatic lenses (also called achromatic lenses) are used to minimize a special type of image distortion called chromatic aberration. This distortion occurs when a lens fails to focus all color wavelengths to the same point of convergence, resulting in blurred contrast and color fringing. Achromatic lenses use at least two separate lens elements - a high-dispersion concave and a low-dispersion convex surface - to achieve their correction effect.

Gradient Index Lenses

Gradient index (GRIN) lenses are simple planar lenses which continuously bend light rays within the lens until they finally converge on the focal point. This contrasts with conventional lenses, which primarily bend light abruptly when it exits the back of the lens material. GRIN lenses are therefore cost-effective and simple to employ. Additionally, the ability to precisely manufacture the length of the plane results in an enormous flexibility to fit application parameters.