Fused Silica Glass Overcomes Data Interference
Japanese scientists use fused silica glass for read/write comparable with Blu-Ray discs.
A reliable long-term technology for digital data storage has become crucial as both public and private historical records shift from paper to storage in digital form. The high water and heat resistance of fused silica glass means that such stored digital data may be accessed and read without the records degrading, even if temperatures are increased to 1,000 degrees C over a two-hour period.
This has been the achievement of the School of Engineering at Kyoto University in Japan. The Japanese scientists have successfully stored digital data within 100 layers of fused silica glass. Three years ago, the same group developed a method of reading and writing data, using a laser, in just four of the glass layers. This was equivalent to the recording density of a CD. This data could be read using an optical microscope.
In 2013, the Kyoto University team upped the number of layers to 26, a recording density comparable to that of a DVD. The current 100-layer storage facility is equivalent to the recording density of a Blu-ray Disc.
However, some problems arose along the way. Some of the data quality degraded, and there were reading errors that originated in the interference from data recorded in the separate layers.
To correct these problems, the scientists first had to use a correction lens for spherical aberrations. This is a phenomenon caused by the distortion of laser focal points in layers close to the targeted glass layer. The scientists attached the correction lens to an optical microscope to attain images of a high quality from the stared data.
The second significant problem was noise. This is the result of cross-talk, a form of interference from images in neighboring layers of fused silica glass. The scientists had to develop a special algorithm for the image processing. This was them applied to the images in the different glass layers in order to distinguish the real data from surrounding noise. The system worked by eliminating signals from images that were below a certain size limit.
At present, the 100-layer storage system has a recording density of 1.5 GB per square inch. This may be increased in future with an even greater number of layers, as long as the distortion and noise problems may be tackled successfully.
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