An optical infrared laser reads the digital pits and gaps of information stored on a disc. The information passes through the plastic layer of a disc and is reflected back off the foil layer. The reader then decodes the information. When scratches, fingerprints or debris interrupt this process, the laser is unable to read the information. This results in skipping, freezing or digital scramble of the information. The most common cause of this is damage to the plastic bottom layer of a disc.
Types of Damage
Play side damage: Play side scratches or marks are the most common type of damage. Scratches that originate on the plastic layer can be identified by a double image reflection of the mark. By holding the disc at an angle near a light source and tilting the disc back and forth, this double image should move with the angle created. Circular scratches pose more of a laser read problem than vertical or straight lines due to the reading rotation of the disc. The depth of the scratch also weighs in importance. Deep gouges create more severe laser read diffraction.
Top side damage: Pinholes or gouges through a disc cause a permanent loss of data. A simple test can determine if your disc has suffered this type of damage. Hold the disc with the flat side between you and a light source. An eclipse may reveal cracks of light permeating through the disc. These pinholes are indicative of top, or label surface damage.
Another form of damage, known as 'Etch A Sketch' may appear on the reflective foil layer of the disc. This damage is difficult to determine but is most easily seen in the reflective test described above. Rather than a double image, a flat, dark, jagged line will be apparent. Unfortunately, top side damage cannot be repaired. To avoid suffering this type of damage, we recommend our Label Scratch Guards.
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