MFDigital CD DVD Information Library
Thursday, June 24, 2004
CD Manufacturing > Quality Assurance > QA Tests and Signals
Quality Assurance Test and Signals
During production runs samples are taken from each press and signals measured:
- Reflectivity relates to the depth of the pits and the ability to read the disc easily.
- Asymmetry checks are needed to find out how central the I3 signal is in relation to the rest of the signal.
- I3 is the signal coming from the shortest pits.
- I11 is the signal coming from the longest pits.
- Push Pull is called the radial tracking signal which allows the laser to seek to a random position on the disc quickly.
- Cross Talk measures the difference between the reflectivity from the pits being scanned and the unwanted signal from the adjacent rows of pits.
- Birefringence within the polycarbonate is a measure of the optical properties of the disc substrate.
Special industry test equipment is used to make these measurements and results are printed out and used to assess the performance of the replication equipment.