lenslet

A lenslet is a single optical element in a micro-lens array, a collection of tiny lenses arranged in a regular pattern. Lenslets are used to sample or redirect light at a finer scale than conventional lenses, forming the basis of devices that manipulate light field, image sensing, or light distribution.

In typical use, hundreds to millions of lenslets are integrated into a substrate such as a glass or plastic sheet placed in front of a sensor or behind a light source. Each lenslet is a small refracting element, often plano-convex or aspheric, with a focal length chosen to match the system’s pitch and the sensor geometry. The arrangement can be square, hexagonal, or other lattice patterns, affecting sampling geometry and optical efficiency.

Common applications include plenoptic or light-field cameras, where a lenslet array sits between the main camera lens and the image sensor to record multiple viewpoints. Lenslets are also used in Shack-Hartmann wavefront sensors to measure local wavefront slopes by analyzing the positions of focal spots. In image sensors, microscopic lenslets placed above photodiodes improve fill factor and response to oblique light, enhancing sensitivity.

Manufacturing and alignment: lenslets are manufactured by molding, glass forming, or photolithographic methods, followed by precise alignment to the underlying sensor or substrate. Tolerances on pitch, focal length, and centering are critical for image quality and accurate sampling.

See also: micro-lens array, plenoptic camera, Shack–Hartmann sensor, integral imaging.