Inkjet-printed freeform gradient refractive index Alvarez-Lohmann optics for vision correction in respiratory masks

Traditional approaches to satisfying optical performance requirements within application constraints leverage the degrees of freedom (DOF) provided by multiple surface shapes distributed among lenses composed of materials with different dispersion properties. Using homogeneous-index lens materials, the radius, conic constant, or higher order aspheric surfaces provide the DOF necessary to provide optical power and address certain geometric aberrations, while using lens materials with different dispersion properties provides the DOF necessary to compensate for chromatic aberrations. Nevertheless, to achieve the DOF necessary to achieve the performance required of compact head-mounted and mobile camera imaging systems, lens stacks must be composed of a significant number of complex shaped optical elements, resulting in undesirable size, weight, and cost.Recent advancements in inkjet print manufacture of three-dimensional (3D) freeform gradient-index (GRIN) optical materials have increased available design DOF by integrating volumetric index gradients within the bulk of the optical material. The 3D index gradients achieve optical power while reducing aberrations. Moreover, when the refractive index spectra of the optical feedstock are precisely formulated, dispersion may be independently controlled within the lens. The 3D GRIN optical materials may be machined and polished with aspheric or freeform surface shapes that further increase the DOF and provide lens designer unprecedented flexibility in lens designs with reduced lens counts.The performance benefits and applications of 3D GRIN optical elements are demonstrated, showcasing their potential to reduce size, weight, and cost in optical systems.

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Three-dimensional gradient index microlens arrays for light-field and holographic imaging and displays

Williams¹,

Dupuy²,

Brown³

et al. 2023

Appl. Opt.

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The geometric, intensity, and chromatic distortions that are a result of the limitations of the material and processes used to fabricate micro-optical lens arrays (MLAs) degrade the performance of light-field systems. To address these limitations, inkjet print additive manufacturing is used to fabricate planar gradient index (GRIN) lenslet arrays, in which volumetric refractive index profiles are used to embed optical functions that would otherwise require multiple homogeneous index MLA surfaces. By tailoring the optical ink feedstock refractive index spectra, independent control over dispersion is achieved, and achromatic performance is made possible. Digital manufacturing is shown to be beneficial for optimizing individual micro-optical channels in arrays wherein the shape, size, aspect ratio, focal length, and optical axis orientation of the lenslets vary as a function of the position within the optical field. Print fabrication also allows opaque inter-lens baffling and aperture stops that reduce inter-channel cross talk, improve resolution, and enhance contrast. These benefits are demonstrated in a light-field display testbed.

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Inkjet-printed freeform gradient refractive index Alvarez-Lohmann optics for vision correction in respiratory masks

Cited by 5 publications

References 60 publications

Thin wide range varifocal diffractive Alvarez lenses actuated by dielectric elastomers

Thin wide range varifocal diffractive Alvarez lenses actuated by dielectric elastomers

Increased degrees of freedom afforded by 3D freeform gradient index optics

Three-dimensional gradient index microlens arrays for light-field and holographic imaging and displays

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