Jan W. Aarts

High Numerical Aperture Optical Recording : Active Tilt Correction or Thin Cover Layer?

Playback of a 12 cm diameter replicated ROM disc with a 0.6 mm substrate thickness and a storage capacity of 10 GB has been achieved using a light path with a dual-lens objective with NA=0.85 and active tilt control. The disc tilt margin exceeds ±0.7 degree. Also backward compatibility with digital versatile disc (DVD) has been demonstrated. Active tilt correction is not required for read out of a disc with a 0.1 mm transparent cover layer. This technique has also been studied experimentally. The merits and disadvantages of the two approaches are discussed.

Two-element objective lens and spherical aberration correction for Digital Video Recording (DVR)

This paper describes the advancements we have made in developing objective lenses and actuators for Digital Video Recording (DVR), which we see as the third generation in optical disk recording. Two generations of DVR prototype systems are presented. The first is an actuator to adjust the inter-lens distance of the two-element objective lens for spherical aberration correction, mounted in a focus/tracking actuator. The second prototype is a more efficient and faster focus/tracking actuator with a rigid two-element objective lens accompanied with an adjustable collimator lens for spherical aberration correction. The latter system is implemented into a prototype bit-engine.

Realization of an active-tilt-controlled high-numerical-aperture two-lens objective for optical recording

This report describes the realization of an actuator for a high-numerical-aperture objective lens, as part of an experimental optical disk player. The player is capable of reading a disk with 10GByte density and is fully compatible with the 120 mm Digital Video Disk Read-Only Disk standard. The objective consists of two lens elements, having one aspherical surface, and a free working distance of 50 micrometers . A special active-tilt-control (ATC) actuator is required to achieve sufficient tolerance for disk cover layer thickness and tilt between objective and disk. The ATC-actuator, containing the objective, is as small as a standard CD ROM objective, and therefore fits in a standard 2D-actuator for focus and radial tracking. The manufacturing and assembly of the ATC-actuator requires specialized prototyping techniques, such as the use of alignment molds, and assembly in a specialized clean room. We have controlled the free working distance within 1.1 micrometers and tilt within 0.7 mrad at 3kHz, while being carried in a Philips actuator, operating at 2kHz. The ATC-actuator was developed to investigate new options for future optical storage systems.