Tiny Gigabytes

Using blue laser technology, up to 1 Gbyte of data can be stored on a single-sided optical disc just 3cm in diameter – more than can be stored on an existing CD ROM Addressing the size constraints of dictated to developers by portable devices such as digital cameras, mobile phones, PDAs and portable Internet devices the prototype was unveiled by Philips. Recent advances in blue laser technology mean that disc sizes can be reduced and still provide high storage capacity (e.g. 1 Gbyte on a 3cm disc). To fulfil the stringent space requirements all dimensions need to be reduced. This issue is addressed by the drastically miniaturised optical system now demonstrated by Philips. The main factor determining the height of optical disc drives is the 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. Made of plastic, instead of glass, the lens allowed greater design freedom and hence a smaller drive height. Another important step was the development of an ultra-thin actuator to position and focus the laser beam onto the optical disc. Using these miniature components, a first fully functional prototype optical drive of just 5.6 x 3.4 x 0.75cm was realised. Further research is underway to achieve an even higher level of miniaturisation. The demonstrator set-up, with the driving electronics currently still on a separate board, successfully played back MP3 data from the 3cm optical disc.