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SCHOTT presently supplies about 7.5 million lenses per year for the scanning systems of optical data storage systems. Demand is expected to keep increasing.
Anne Hardy, Journalist, Frankfurt, Germany

Spherical Lenses Lead the Way to the Mass Market

SCHOTT manufactures high-quality spherical lenses in series for the scanning heads of optical data storage systems. Working closely with its client Philips, SCHOTT has been able to capture for the first time a mass market for optical glass.

“Spectacles” for the scanning head

The most important and complex component of an optical data storage system is the drive. Its heart, the scanning head, is made of glass components that must meet the extremely high demands that high tech applications place on them.

As the digital writing on discs becomes smaller, the scanning head has to be closer to the surface. The job of the objective lens consists in focusing the laser beam with extreme precision on the pattern being scanned, which consists of information written in the form of peaks and pits. If the reading distance is shortened – which is the case if a DVD is read – then it can only be done if the lens has a high numerical aperture. The “stronger spectacles” needed must be made of special glass with a high refractive index or manufactured using a patented lens production technique.

”Glass enables us to react with extreme flexibility to the increased demands placed on the material,” explains Ulrich Siepe, logistics director of the Optical Glass Division. With this product, SCHOTT has an important trump in its hands, needed in the tough rules that govern the consumer mass market, where the innovation cycles are short and the cost pressure is unusually high. This is the reason SCHOTT and Philips have joined forces in the manufacture of scanning heads. Thanks to the regular exchange of their development potential, both partners have achieved a gradual and continuous drop in production costs.

Off to new markets

The quality control of spherical lenses.
SCHOTT‘s current annual production of spherical lenses (7.5 million pieces) is used for manufacturing objective lenses for CD/RW players, the devices made for rewritable CDs. For ”burning” the information on the CD, it is necessary to use laser beams of a significantly higher energetic density than the conventional ones needed for reading purposes. Optical special glass is ideally suited for this purpose. The next step in the cooperation with Philips will be a new generation of DVD-based reading and writing devices, the DVD+RW players.

The successful cooperation with Philips encourages SCHOTT to seek other applications for spherical lenses in other branches (telecommunications, for example). The first negotiations with potential new clients have already taken place.