# Lens Basics

##### by Waqar Ul Hasan - ( 2016-10-11 )

Understanding the basics of Lenses

Lenses are one of the most crucial and complex state of the art Science. From a eyesight glasses to a camera or microscope to a Hubble telescope. Their use is everywhere. Understanding lenses requires the study of optics and its applications known as lenses.

#### What is a Lens ?

Description required. ....

#### Lenses Types :

Normally, a Lens has two optical surfaces and this a way we classified the lenses based on their surfaces curvature.

#### 1 - Biconvex Lens :

In a Biconvex / double convex lens, both optical surfaces of a lens are bulged outward. Like a sphere or an egg. And similarly, If both surfaces of a lens have equal radius of curvature, then the lens is known as equiconvex lens.

#### 2 - Plano-Convex Lens :

If the surface of a lens is flat on one side and convex on the other side is known as a Plano-Convex lens.

#### Meniscus Lens : (Convex-Concave)

If a lens is Convex on one side and Concave on the other side is known as Meniscus lens.

#### 3 - Positive Meniscus Lens :

A Meniscus Lens can be either Positive or Negative. This depends on the relative angle of curvature between the two surfaces of a lens. For Instance, If a Meniscus Lens has a higher angle of curvature (more curved) on the convex surface and lower angle of curvature (less curved) on the concave surface. Such a lens will be thicker in its centre axis and thinner on its edges, is called a Positive Meniscus Lens.

#### 4 - Negative Meniscus Lens :

Conversely, If a Meniscus Lens has a lower angle of curvature (less curved) on its convex surface and higher angle of curvature (more curved) on its concave surface. Such a lens will be thinner in its center axis and thicker on its edges, is called a Negative Meniscus Lens.

#### 5 - Plano-Concave Lens :

If the surface of a lens is flat on one side but concave on the other side is known as a Plano-Concave lens.

#### 6 - Biconcave Lens :

If a lens optical surfaces are concave or bulged inward is called a biconcave lens, like a cave or a moon in its 1st to 6th calender dates. And similarly, if both surfaces have equal radius of curvature, the lens is called equiconcave.

#### Other Types :

#### 7 - Thin lens :

If lens has equal angle of curvature between its two surfaces, is called a Thin Lens. Such a lens has a zero optical power and will not converge or diverge the light. In practice a Real Lens (meniscus lens) must have a non-zero thickness. In order to obtain zero-optical power, such a lens should have a slightly different angle of curvature between its surfaces. In order to account for the lens thickness.

#### 8 - Prism :

( Text Pending )

#### 10 - Toric / Torus / sphere-cylindrical lens

( Text Pending )

#### 11 - Aspheric lens

#### Corrective Lenses :

Examples : Eye glasses, spectacles, contact lenses, intraocular lenses.

#### Barlow Lens :

A Barlow lens is basically a concave lens that when placed between a telescopes objective lens or mirror and the eyepiece, will increase the magnification of the telescope. A Barlow lens will connect directly to your eyepiece. The most common Barlow is the 2x Barlow [01].

The following is the picture of a 5x Barlow lens from TeleVue (Japan). It provide a very high magnification than 2x lens and therefore its quite sensitive. Also this kind of lens has more lenses in its build so it blocks quite a bit of light. Usually not good for night observations.

#### Lens Production:

Use a 3D-Printer to produce lenses of all kind and shape.

Keywords : Lens Types, Understanding of Lens