Gerard E. van Rosmalen

Confocal compact scanning optical microscope based on compact disc technology

A compact scanning optical microscope (SOM) based on the optics and the mechanics of a compact disc (CD) player has been constructed. The low weight and compact construction of a CD player offer the possibility of scanning the entire microscope with respect to a stationary object. The compact scanning optical microscope is capable of measuring object-induced amplitude and phase changes of the light and is equipped with automatic focusing. The laser in the CD player is replaced by the endface of a single-mode fiber. The end face of the fiber acts both as the emitting source and as a point detector. Thus confocal detection is obtained without the problem of positioning a point detector with respect to a point source.

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.

Prototype Optical Tape Recorder

In 1994 a new concept for an optical tape recorder, based on a very fast spinning polygon, was presented. Since then, a prototype tape recorder has been developed on the basis of this technology. In order to reduce the complexity of the system, the optical configuration was redesigned. Also, a new polygon with 10 facets was developed. Finally, the tape transport mechanism was modified in order to further decrease the access time. The result is a smaller recorder consisting of fewer components and having better performance than the original one. Typically, a storage capacity on the order of 50–100 Gbyte is possible in a small cassette. Bit rates are up to 25 Mbit/s. An access time of less than 3 s was realized for 50 Gbytes of storage capacity.

Optical tape system: evaluation of recorder and media

A linear optical tape recorder has been developed and its performance is evaluated. Write-once and rewritable tape samples are tested and on the basis of these results the expected performance of the recorder is concluded. In the recorder data are written and read back with the spot from a single laser that is scanned over the surface with a 10- faced polygon, rotating at up to 3500 Hz. The data density is 1.6 micrometers 2/user-bit, offering 70 Gbyte storage capacity in a VHS-C like cassette. Read and write data rates up to 4.4 and 3.2 Mbytes respectively can be achieved. A novel tape guiding systems winds the tape at a velocity exceeding 20 m/s, offering an average access-time of 1.5 s.

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.

Compact optical tape recording system

A new optical tape recorder, based on a very fast rotating polygon is described. This system combines a high data rate with a high storage density and fast access. The recorder is compact and, apart from the polygon, requires only simple mechanics.