Diamond turning and soft lithography processes for liquid tunable lenses

Abstract

Making use of the capability of high precision diamond turning in producing 3-dimensional free form optical surfaces with excellent surface finish, molds for various types of liquid tunable microlenses are fabricated. Subsequently, a rapid prototyping process known as soft lithography is applied to the fabricated mold to replicate multiple lens structures. This method provides an efficient and reliable way of generating rotationally symmetric free form optical surfaces that are otherwise difficult to produce with conventional methods such as lithography and etching methods. Using atomic force microscopy, white light interferometry and a mechanical profiler, it is verified that the surface quality and dimensional accuracy of the replicas are preserved. We demonstrate the practical usefulness of the proposed fabrication methods by developing and experimentally testing three different liquid tunable lenses, namely (1) a diffractive/refractive hybrid lens that reduces chromatic aberration within the visible spectrum, (2) a double focusing lens and (3) an aspherical lens that minimizes spherical aberration.

Miniature Solid Tunable Lenses and Their Applications: A Review

“…(1,2) There have been extensive trials to achieve liquid lenses with deformable geometric shapes employing various driving mechanisms. (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) They include diverse flexible-membrane lenses, electrowetting-based lenses, and dielectrophoretic lenses. (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) Rather than modulating the geometric shape of the lens, one can also choose to vary the refractive index of the lens material.…”

Replication of optical microlens array using photoresist coated molds

“…Direct fabrication of lens arrays by diamond turning in polymer materials have been demonstrated [23][24][25][26][27][28] to achieve the high optical surface quality. Although the direct diamond turning process is a one step process, due to process difficulty and expensive tooling, the fabrication process cost could be in the order of USD 100 -1000 /mm 2 .…”

Diffractive microlens with a cascade focal plane fabricated by single mask UV-photolithography and common KOH:H2O etching

“…Fabricating DOEs with a three-dimensional microrelief profile characterized by highly focusing efficiency and low-cost technological flow and ease of replication represents both a challenge and a technological barrier to the development of modern diffractive microoptics. In an effort to develop a highly efficient method for fabricating DOEs with a complicated phase microstructure distribution, different works have been conducted [7][8][9][10][11]. The technique consisting mainly of single mask ultraviolet (UV) photolithography and dualstep wet KOH etching for fabricating refractive microoptics structures with continuous profiles, such as typical aspherical refractive lenses, was studied in [12].…”