Development of Microlens for High-Density Small-Form-Factor Optical Pickup

Abstract

A microlens of numerical aperture (NA) 0.85 a small-form-factor optical pickup, following the specifications of the Blu-ray disc (BD), was designed, fabricated and evaluated. To avoid difficulties in the fabrication of a high-NA objective lens and to obtain a low chromatic aberration, a new hybrid lens unit was designed to have a refractive lens and a diffractive lens. The micro-plano-aspheric refractive lens was fabricated using glass molding technology, and the diffractive lens was fabricated in a two-dimensional array using the electron beam mastering and consecutive UV embossing process. For the evaluation of the developed lens unit, diffraction efficiency was measured with the proposed diffraction efficiency measurement method, and the wavefront error of the lens unit was evaluated using a modified Mach–Zehnder interferometer. The measured average efficiency of the diffractive lens was approximately 85% and the RMS wavefront error of the lens unit was 0.0376 λrms.

Design and fabrication of high numerical aperture and low aberration Bi-convex micro lens array

“…Although hemispherical lens provides high NA, the image quality is relatively poor due to its high aberration that reduces the resolution of image. A micro lens array with high NA and low aberration is in particular needed as it features narrow focal spot, high lamination, and high resolution [1][2][3][4][5]. Many efforts have been employed, including non-spherical lens, Fresnel lens, and reflective-diffractive compound lens, to improve aberration.…”