Two step process for the fabrication of diffraction limited concave microlens arrays

Abstract

A two step process has been developed for the fabrication of diffraction limited concave microlens arrays. The process is based on the photoresist filling of melted holes obtained by a preliminary photolithography step. The quality of these microlenses has been tested in a Mach-Zehnder interferometer. The method allows the fabrication of concave microlens arrays with diffraction limited optical performance. Concave microlenses with diameters ranging between 30 µm to 230 µm and numerical apertures up to 0.25 have been demonstrated. As an example, we present the realization of diffusers obtained with random sizes and locations of concave shapes.

Two diffusion photopolymer for sharp diffractive optical elements recording

“…However, a wide range of values for monomer diffusion have been reported in the literature, e.g., 10 −7 to 10 −10 cm 2 ∕s [5][6][7][8]. One result of assuming faster values, i.e., 10 −7 cm 2 ∕s, is that changes in the surface relief profile, due to mass transfer, make it difficult to produce sharp structures on the layer such as blazed or binary gratings, axicons, or diffractive lenses [9,10].…”

“…Therefore, materials with low-matter transfer similar to photoresist can be used to record sharp diffractive optical elements with insignificant smoothing of the refractive index profiles [10].…”

Assessment of minimum permissible geometrical parameters of a near-to-eye display

“…One of the proposed solutions is based on a microlens array where each microlens coupled with one or several pixels [10,11]. In this case, for example, a microlens of size A=30 µm [19] gives t+a as small as 31 µm.…”

“…In order to see both the microdisplay located immediate vicinity of the eye and objects from ambient, it is necessary to have a switchselectable lens. Liquid crystal (LC) lenses are most suitable for such purposes [19][20][21][22]. Although they cannot compete with refractive lenses in low F-number, LC lenses, nevertheless, are suited for a microlens array for a contact lens [10,11].…”

High-performance light diffuser films by hierarchical buckling-based surface texturing combined with internal pores generated from physical gelation induced phase separation of binary polymer solution

“…Two different types of light diffusers have been studied, i.e., surface-relief type (or, surface scattering diffuser) [1e7] and particle diffusing type (or, bulk scattering diffuser) [8e17]. The former type exploits the light scattering by surface micro-textures, such as microlens [1], pyramids [2], hemispheres [3], and others [4]. This type of diffusers usually shows high transmittance but requires rather complex fabrication processes and expensive equipment [5e7].…”