Microlens

A different type of microlens has two flat and parallel surfaces and the focusing action is obtained by a variation of refractive index across the lens.

With optical sensor arrays, tiny lens systems serve to focus and concentrate the light onto the photo-diode surface, instead of allowing it to fall on non-photosensitive areas of the pixel device.

In the 17th century, Robert Hooke and Antonie van Leeuwenhoek both developed techniques to make small glass lenses for use with their microscopes.

[1] The principle has been repeated by performing photolithography into materials such as photoresist or UV curable epoxy and melting the polymer to form arrays of multiple lenses.

The Samsung NX1 mirrorless system camera packs 28.2 million micro-lenses onto its CMOS imaging chip, one per photo-site, each with a side length of just 3.63 micrometer.

The sustained ~2 GW/cm2 intensity for femtosecond pulsed irradiation shows its potential in high power and/or harsh environment applications.

The end product is cost effective, miniaturized optics that enable the reduced form factor of camera modules for mobile devices.

[citation needed] More recently, the availability of arrays of spherical micro-lenses has enabled Gabriel Lippmann's idea for integral photography to be explored and demonstrated.

[17][18] Colloidal micro-lenses have also enabled single molecule detection when used in conjunction with a long working distance, low light collection efficiency objective lens.

[19] Micro-lens arrays are also used by Lytro to achieve light field photography (plenoptic camera) that eliminates the need for initial focusing prior to capturing images.

For example, because it is not practical to locate the principal planes of such small lenses, measurements are often made with respect to the lens or substrate surface.

It is useful to know the distance at which the maximum amount of light is concentrated in the fibre aperture and these factors have led to new definitions for focal length.

[22][23][24][25] Examples of micro-optics are to be found in nature ranging from simple structures to gather light for photosynthesis in leaves to compound eyes in insects.