Technology for Small Form Factor Optical Storage

Philips has demonstrated the world’s first fully functional miniature optical disc drive using blue laser technology. Up to 1 Gbyte of data can be stored on a single-sided optical disc of just 3 cm in diameter, matching the size constraints of portable devices such as digital cameras, mobile phones, PDAs and portable Internet devices. This prototype illustrates Philips’ leadership in optical storage technology, which is driven by superb media robustness and the low cost per Mbyte of the storage medium, making it optimally suited for large-scale distribution of pre-recorded content.

Drastic size reduction

Recent advances in blue laser technology, and Philips innovations in the area of optical storage media and miniaturised opto-mechanics are the ideal ingredients for small form factor optical drives. The resulting high storage density can be exploited to reduce the disc size while still providing a high storage capacity (e.g. 1 Gbyte on a disc of 3 cm diameter, i.e. more than on a present CD ROM). To fulfil the stringent space requirements of portable devices, all dimensions need to be reduced, particularly the building-height. This issue is addressed by the drastically miniaturized optical system now demonstrated by Philips.

From glass to plastic

The main factor determining the building height of optical disc drives is the optical objective lens system. Through the development of the world’s smallest objective lens for blue laser recording, the height of the optical disc drive was reduced to 7.5 mm, from the 12.5 mm or more typical in current drives. The lens was made of plastic, instead of glass, allowing greater design freedom and hence a smaller drive height. Another step was the development of an ultra-thin version of the actuator that positions and focuses the laser beam onto the optical disc.

Using these miniature key components, a first fully functional prototype optical drive of just 5.6 x 3.4 x 0.75 cm3 was realized. Further research is underway to achieve an even higher level of miniaturization. The demonstrator set-up, with the driving electronics currently still on a separate board, successfully played back MP3 data from a 3 cm diameter optical disc.