3. Disc Materials
1) CD-ROM disc
• It is composed of Silver _ colored aluminum plate and Reflective layer.
• Groove (Pit) of aluminum plate make a track.
• Laser wavelength : 780 nm, Laser Power (Read): 0.5mW
• Signal is detected by the
difference of reflective beam
intensity between "pit" and
"Land" on the disc.
2) CD-R disc
• It is so-called WORM (Write Once Read Many) CD.
• It is composed of polycarbonate layer, Organic dye layer, Reflective layer, and Protective
layer.Gold/Silver Reflective layer is used to enhance the reflectivity
• According to the kinds of Organic dye layer, it is divided by Green CD, Gold CD, Blue CD.
• Laser Wavelength : 780 nm, Laser Power (read) : 0.7 mW
• Recording Power : 8x(14~20mW), 16x(25~35mW)
• When some part of dye layer is exposed to laser heat, it's color changs black.Therefore, writing and
reading is enabled by the difference of reflectivity between changed part and unchanged part.
• Polycarbonate layer has Pre_Groove which make a Track.
Organic Dye Layer
Dark Green/Bright Green