Sean, I am not a laser engineer so I can't give definitive answers but I do have a bit of laser experience as I make my living repairing medical lasers. I do have few thoughts on the subject.
Some energy is reflected and some not. That is the way the whole scheme works. Areas that reflect enough light are interpreted as one digital state and those that don't are interpreted as the other state.
When I point my red laser pointer at a disc I see that it scatters the light. Depending on the coating or lack of coating on the top of the disc some discs transmit a portion of the light. I can see it through the disc. Those that have a heavier coating of paint seem to block it. I have no way of knowing if they absorb it or reflect it. The pointer is a shorter wavelength than the laser in the CD player (around 650 nm vs 790 nm) but they are close enough to reasonably assume that they would act in a similar fashion. It is possible to coat a surface with materials that will act upon a narrower range of wavelengths than this so it is possible that my assumptions are wrong.
The big question is whether this scattered/reflected light will be picked up by the sensor in the player and cause errors. It seems like it would be very simple to set up test equipment to capture the bit stream from a digital output and see if it changes with various disc treatments. I don't have this type of equipment so I can't do it but it can't be all that difficult for someone who does. It would be interesting to see what the results of such tests were.
Some energy is reflected and some not. That is the way the whole scheme works. Areas that reflect enough light are interpreted as one digital state and those that don't are interpreted as the other state.
When I point my red laser pointer at a disc I see that it scatters the light. Depending on the coating or lack of coating on the top of the disc some discs transmit a portion of the light. I can see it through the disc. Those that have a heavier coating of paint seem to block it. I have no way of knowing if they absorb it or reflect it. The pointer is a shorter wavelength than the laser in the CD player (around 650 nm vs 790 nm) but they are close enough to reasonably assume that they would act in a similar fashion. It is possible to coat a surface with materials that will act upon a narrower range of wavelengths than this so it is possible that my assumptions are wrong.
The big question is whether this scattered/reflected light will be picked up by the sensor in the player and cause errors. It seems like it would be very simple to set up test equipment to capture the bit stream from a digital output and see if it changes with various disc treatments. I don't have this type of equipment so I can't do it but it can't be all that difficult for someone who does. It would be interesting to see what the results of such tests were.