Frequently Asked Questions About Compact Discs

Please contact Media Sciences if your questions are not answered on these pages.

Are CDs damaged by irradiation of U.S. mail?

Tests conducted by Media Sciences in early 2002 on CD-ROM discs, recorded CD-R discs, and unrecorded CD-R discs indicate that electron beam irradiation of the type used to sterilize U.S. mail does not impair media interchange. Tests were performed using one CD-ROM disc, four recorded CD-R discs (cyanine, phthalocyanine, and azo dyes,) and two unrecorded CD-R discs. Comprehensive quality tests were conducted, after which each disc was secured in a jewel case placed inside a bubble-pack envelope. This package was irradiated by a 10 Mev electron beam using a dose of 40 kGy. Each sample was then retested, and results were compared with pre-irradiation values. Both unrecorded CD-R discs were then recorded and tested.

Polycarbonate substrates of all samples had a slight brown tint after irradiation. Infrared reflectance at 780 nm decreased by an average of 1%, ranging between no change to a decrease of 1.8%. BLER and E11 error rates increased by an average of 1.13X after irradiation, ranging between no change and 1.66X. Peak error rates averaged over 1 sec. were always less than 60 frames-per-second, well below the ISO limit of 220. Radiation-induced errors resulted from small, random defects and were easily correctable by the standard cross interleave Reed-Solomon code. Uncorrectable errors were not generated by irradiation. No correlation between changes and CD-R dye types or metallization was observed.

Values for radial tracking (push-pull), radial noise, I3, I11, asymmetry, cross talk, jitter, and effect length were not modified by irradiation. Wobble amplitude, wobble carrier-to-noise, radial noise, push-pull, radial contrast, and ATIP errors of both unrecorded CD-R discs remained unchanged. These results indicate that average pit geometries and the CD-R pregroove were not degraded by electron beam irradiation. Although interchange of CD-ROM and CD-R discs was not degraded, contaminants on the surface of a CD disc, or packaging, could be affected by radiation and, in turn, might degrade CD discs.

Media Sciences thanks Titan Scan Technologies for irradiating all samples without fee. In particular, the direction and support of Michael O'Dell and Dr. Darren McKnight of Titan is gratefully acknowledged. Assistance provided by the United States Postal Service Consumer Affairs Office is appreciated.