Development of microlens for integrated optical pickup using six sigma methodology

Abstract

Background/Objectives: Six Sigma methodology is a useful tool for R&D as well as for quality management. We employed Six Sigma methods in development of microlens array for small integrated optical pickup application. Methods/Statistical analysis: The standard DMAIC procedure was employed for carrying out the Six Sigma project. At first, we defined customer needs to plan the project. Secondly, we investigated current level to establish improvement goals. Then, we selected the potential factors affecting the performances of the microlens. We obtained optimum process conditions for the microlens fabrication with design of experiment. Finally, we made management and control plans to maintain the improved results. Findings: A microlens of numerical aperture (NA) 0.85, following the specifications of the Blu-ray disc (BD), was designed, fabricated and evaluated. A novel hybrid lens composed of a refractive lens and a diffractive lens was designed to overcome the difficulties in the fabrication of a high-NA objective lens and to reduce chromatic aberration. The refractive lens was fabricated with glass compression molding technique, and the diffractive lens was fabricated by employing the master molding with electron beam lithography and successive UV embossing process. The refractive lens and the diffractive lens were combined each other on a Si lens holder wafer which was fabricated by photolithography and Si deep reactive ion etching technique. For the evaluation of the optical characteristics of the developed hybrid lens, diffraction efficiency and the wavefront error were measured. The measured average efficiency of the diffractive lens was about 84% and the RMS wavefront error of the hybrid lens was 0.04 ·rms. Improvements/Applications: The resulting optical performances of the microlens array developed by using the Six Sigma methodology were proved to be sufficient to satisfy the required specifications of optical pickup for BD.