Application of polymer graded-index materials for aberration correction of progressive addition lenses

Abstract

Graded-index (GRIN) progressive addition lens (PAL) was successfully fabricated, and GRIN's potential for aberration correction of PAL was confirmed. GRIN material was prepared by partial diffusion of methyl methacrylate (MMA (n d at polymer = 1.492)) monomer into cross-linked benzyl methacrylate (BzMA (n d at polymer=1.568)) flat gel, and GRIN-PAL was prepared by polymerization of the GRIN material attached to a mold of commercially available PAL. GRIN polymer materials have been used for various applications such as rod lenses and optical fibers. GRIN represents gradual change of refractive index in a material, which adds or reduces light focusing power of the material. PAL is a multifocal spectacle lens for presbyopia. However, some localized aberrations (especially astigmatism) in PAL have not yet been reduced satisfactorily for decades by optimizing surface geometry of a lens. In this research, we propose to employ GRIN materials for astigmatism reduction of PALs. BzMA flat gel was prepared by UV polymerization of BzMA, crosslinking agent ethylene glycol dimethacrylate (EDMA) and photopolymerization initiator DAROCURE 1173. MMA monomer was diffused into BzMA flat gel from a portion of periphery for several hours. The obtained GRIN material was attached to a mold of commercially available PAL and polymerized by UV. As a result, reduction of astigmatism was confirmed locally in the fabricated PAL and GRIN-PAL using lens meter. In conclusion, GRIN-PAL was successfully fabricated. The validity of GRIN employment for the astigmatism reduction in PAL was demonstrated experimentally.

Analytic Models of a Thin Glass–Polymer Laminate and Development of a Rational Engineering Design Methodology

“…Figures 5-8 plot the effective thickness for deflection and stress by FEA, respectively, along with the Wolfel model. For 5 mm glass/lmm interlayer laminates, the interlayer is much thinner than glass, and the effective thickness approach has been proven to be applicable to this common glass laminate structure [4][5][6][7]. Conversely, the thicknesses of the interlayer and glass are almost the same for the 1 mm glass/1 mm interlayer laminates, and this situation is common when thin glass is used for laminate glass applications.…”

“…This use raises the possibility of fabricating laminates whose glass polymer thickness ratio can be reduced readily to a range of 0.1-1. Laminates that consist of thin glass and a thick ionoplast interlayer have recently been shown to ex hibit strengths equivalent to 3 mm-5 mm monolithic glass [4]. Because laminates now primarily consist of polymers, thin glass ionomer (TGIO) laminates demonstrate significant strength/ weight ratio advantages over monolithic glass or laminated glass made using conventional structures.…”

Thomas Young's contributions to geometrical optics

“…[29][30][31][32][33][34][35] For example, bifocal or varifocal lenses could be produced in this way. [36][37][38][39] Advances in free-form surfacing have reduced the need to consider the gradient-index alternative.…”