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04 Nov 2005
A device for testing next generation DVDs could help disc makers spot manufacturing flaws.
TOPTICA Photonics of Germany has developed a reference drive for testing the quality of Blu-ray and HD DVD optical discs. Dubbed HUSKY and said to be the first of its kind, the drive can identify production faults such as a worn disc stamper or poor molding conditions.
Blu-ray and HD DVD disc manufacturers are being forced to operate within much tighter production tolerances thanks to the tiny data structures found on next generation optical discs. While defects such as tilt, sputter variations, layer thickness or bubbles in the disc can be studied by a variety of in-line inspection methods, the disc’s microscopic bit structure can only be analyzed using opto-electrical reference drives.
To be effective, these systems must guarantee that all measured errors are due to flaws in the disc and are not influenced by the drive reading the disc. “The challenge for us is to ensure that all of our reference drives are identical,” Thomas Renner of TOPTICA told Optics.org. “Every unit is calibrated during the manufacturing process against a master reference disc supplied by Sony, Philips or Toshiba.”
In comparison, commercial optical drives use data correction algorithms to compensate for both mechanical faults and disc defects. This approach makes the device more affordable, by reducing the emphasis on high quality components, but also hides the source of any error.
Crucially, TOPTICA’s reference drive gives disc makers direct access to the raw optical data. Users can monitor electrical signals and generate a so-called “eyepattern”, an electronic version of the disc’s data structure, which can then be processed to determine any manufacturing flaws.
The HUSKY unit features a high-quality, optical pick-up manufactured in-house that contains a 405 nm laser diode and focusing and detection optics. It ships with an NA=0.65 lens for HD DVD format testing and an NA=0.85 lens for Blu-ray operation, where the data structures are covered with a thinner (100 µm) transparent protective layer.
According to Renner, the HD-DVD / Blu-Ray test market could ultimately be worth as much as the equivalent DVD sector, which relies on thousands of reference drives worldwide. TOPTICA’s HUSKY drive has already been snapped up by AudioDev, a Swedish manufacturer of test equipment, for use in production testers for Microsoft’s Xbox360 discs.
Author
James Tyrrell is reporter on Optics.org and Opto & Laser Europe magazine.
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