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

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.