A new bi-aspheric molded glass lens for single lens pick-up system

Abstract

We have developed a bi-aspheric lens, intended for a compact disc (CD) player pick-up, which is manufactured by a high precision glass molding process and has been mass-produced. The lens realizes a single-lens system for a CD player pickup, that has function of both an objective lens and a collimator lens, while conventional system use 4 or 5 spherical lenses. The lens has a small size (5.0 mm diameter X 4.2 mm thickness) and has weight of only 300 mg. With the small lens we have also developed a very small size CD player pick-up, having a height of 13.3 mm, much shorter than 18.5 mm height of our former one. The off-axis wave-front aberration at an image height of 150 microns has been designed to be 0.035 wave rms. Such performance should be considered excellent, where a relative local shift between a laser diode and a lens is avoidable due to a tracking, a focusing and a set up error. The observed on-axis transmitted wave-front aberrations of the molded lenses are less than 0.03 wave rms.