Effects of low polymer content in a liquid-crystal microlens

Abstract

A small number of bifunctional monomers are mixed with a nematic liquid crystal (LC) and cured with a distributed electric field, which is produced by a circular-hole-patterned electrode structure. A gradient type of lens, that is, a LC microlens, is investigated for various polymer concentrations. Addition of 3% polymer is enough to freeze the gradient-index properties of the structure in the form of a convex lens, and a polymer-stabilized LC microlens is demonstrated. Although a lower concentration of polymer cannot hold the distribution properties in a curing process, it can maintain the variable focus as a nematic material can. The polymer networks can also eliminate the disclination line that usually appears and causes the lens in this type of LC device to deteriorate.

Fast-Response Liquid Crystal Microlens

“…Various approaches for fabricating LC microlens array have been proposed. The common is to create a gradient refractive index distribution among LC directors either by an inhomogeneous electric field [9,10,[15][16][17]20,22,23,54] or by an inhomogeneous LC morphology [11][12][13][14]18,19,21,55,56].…”

“…They are expected to be essential optical devices with widespread applications. Generally speaking, LC lenses can be divided into two categories according to their aperture size: those with a large aperture size (>1 mm) are suitable for portable devices, such as pico projectors, imaging system for cell phones, endoscopic system, and ophthalmic lenses [4][5][6][7][8], while those with a small aperture size (<1 mm) are suitable for microlens arrays and their applications include image processing [9][10][11][12][13][14][15][16][17][18][19], optical communication [20,21], lab on a chip, switchable 2D/3D displays [22,23], etc. The progresses of LC lenses with a large aperture size have been reviewed by Fowler et al in 1990 [24] and more recently by Lin et al in 2011 [25].…”

Modeling and design of an optimized patterned electrode liquid crystal microlens array with dielectric slab

“…The hole patterned electrode method employs the photolithography and etching technology to generate an array of holes on the electrode layer and attains a special electric field distribution in the liquid crystal cell, which will realign the liquid crystal director to form a refractive index profile as a lens array. Among the above mentioned approaches, the hole patterned electrode method is relatively preferable because of its low operating voltage, high numerical aperture, ease of fabrication and excellent capabilities of tunable focal length [9,10]. Although, according to some previous works, the occurrence of disclination lines often deteriorated the optical performance of the liquid crystal microlens, and the cause was usually attributed to the formation of inverse domain and tilt wall [11][12][13].…”

Modal liquid crystal lens driven by low voltage produced from a wireless controlling and driving system

“…By changing the driving voltage across the LC cell prepared, its focal length can be continuously varied. [1][2][3][4][5][6][7][8][9][10][11][12][13] For the adaptive optics application in typical biomedicine, the operation mode of the wireless driving and power transforming of LC microlens is desired. There has been a growing interest in the fabrication of wireless control, driving and power transforming system for LC devices in the range of low voltage such as a few voltages.…”