How CDs are made...

Microscopic pits representing encoded data are first formed by exposing photo-resist material with a laser beam. This beam is modulated according to the input source data.

After the exposed areas are developed to produce pits, a rigid metal negative to the master, called the Father or Master stamper, is produced by an electroplating process (see Figure 2). Multiple positive image Mothers may be electroplated from the Father stamper. In turn, negative image Son stampers are plated from each Mother to produce multiple copies of the original master. Mass replication of the source begins by mounting a Father or Son in a molding press. Melted plastic is injected into the cavity and allowed to cool. The pits from the stamper are accurately reproduced in a plastic substrate, forming the original positive image.

Each disc is finished by successively applying a reflective layer, protective lacquer, and printed labeling or screen printing (see Figure 3). Due to close proximity to the data, the labeled side of a disc is extremely susceptible to permanent damage, much more so than the clear disc substrate on the side which the laser "reads" through.

If a disc has damage to the label side, it cannot be fixed. If the damage is on the clear side, the CD Fix-It Kit is what you need. If your discs are perfect and your player is old, it may need cleaning with CD 2000's Laser Lens Cleaner.

How data is generated

The pits which are formed during the mastering and molding processes are read by a small optical system which includes a laser and an optical detector.

The disc and corresponding pit structures rotate under the laser beam during playback. The pits cause the amount of reflected light traveling from the disc to the detector to fluctuate, creating a high frequency signal. The drive determines points in time where this signal crosses a certain threshold value. These crossings, signifying a logical "1", occur at each pit edge. Again, this process can be distorted by a dirty lens or disc.

Due to physical limitations of pit size, it is necessary to maintain at least two "0"s between each "1". An encoding scheme called Eight-to-Fourteen Modulation (EFM) translates every 8 bit combination to a 14 bit code to be written to the disc. Three merging bits are used between each byte to further ensure the separation of "1"s.

CD Readback System A compact optical head in a CD player or drive "reads" the pits. Light emitted from a laser is collected by a collimating lens and focused by an objective lens through the clear disc substrate onto the pits. Light of high intensity (between pits) or low intensity (on a pit) is reflected from the metallized surface back through the objective lens.

What causes "skipping" and "error"?

If the disc or objective lens is contaminated by dirt, dust, smoke build-up, scratches or the like, the signal will not be interpreted as it was encoded. Instead, the bit stream decoded by the detector will be distorted by the contaminants. Oversampling can help to defeat contaminants and error correction systems also help by interpolating lost data (which is essentially a form of distortion). While both systems constantly work to defeat minor scratches and dust, both have limitations.

If laser light is severely distorted by build-up of dirt, dust, scratches or other damage to the disc or the objective lens, the light will be diffused or refracted and fail to "read" properly. Failure to "read" and follow the instructions embedded in program data can cause a wide range of errors within a player or drive, perceived as "skipping", "freezing", "mis-tracking", "crashing" and the like.

That is why you need the CD Fix-It Kit.

Not all damage to a disc is obvious, sometimes its even undetectable to the naked eye. Another cause is damage to the delicate information and reflective coating under the very thinly protected labeled or printed side. Blunt damage is not detectable by the eye, but can cause pits to flatten and become unreadable. Even worse are label side scratches which can remove the reflective coating (usually detectable by naked eye), causing the disc to be ruined permanently. This type of damge is impossible to repair by any means.

If you hold a disc up to a bright light and can see light through scratches or holes, even the tiniest pinhole, that portion of the data is destroyed and cannot be repaired.

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website designed and maintained by Dave Barbieri

All Raw Materials, Printing and Packaging Supplies are Made with Pride in the USA. We use paper made from 100% De-Inked newspapers and magazines. We Recycle and Re-Use corrugated boxes. We shred used paper and junkmail and Re-Use it as packing material. Please Help Save Our Planet. Waste less paper; wash and Re-Use CD Softies. Lighten the Landfill. Save a CD. CD Fix-It is Environmentally Safe: No toxins or CFCs. Not all CDs can be repaired, but CD Fix-It is clinically proven to fix most skipping CDs. CD 2000, CD Fix-It, DVD Fix-It, Game Fix-It, CD Clean-It, DVD Clean-It and CD Softies are registered trademarks of CD 2000, Inc. Other trademarks, tradenames or servicemarks are the property of their respective owners. ©2004 CD 2000, Inc.