Optical performance evaluation of hybrid micro lens with NA 0.85 for small form factor optical pickup

As a popularity of a portable digital device such as a cellular phone, a digital camera and a MP3 player is spreading, the demand of the mobile storage device increases rapidly. A Blu-ray technology using 406nm laser diode and 0.85 NA(Numerical Aperture) satisfies a miniaturization and a high capacity which are the requirements of the portable device. Because a Blu-ray optical storage device can store 1.5Gbyte on a 3cm disk, it is possible to distribute the media in great quantities and with cheaper price. In this paper, we analyze the optical performance of the hybrid micro lens which is manufactured using a micro fabrication technology. The measurements of the optical power, the spot size and the wavefront error are performed to evaluate the hybrid micro lens with 0.85 NA and the designed wavelength of 406nm. Using the measured data, we estimate if the performance of hybrid micro lens corresponds to the designed performance. Also, the processes of measuring an optical performance of hybrid micro lens, which is composed of the refractive lens and the diffractive lens, are proposed using laser diode of 406nm and finite optics.