Hi,
I was wondering how tracking is exactly being done in a 1-beam system?
I have been looking for more detailed information on the www but haven't found it yet.
Maybe a link to some more info?
Thanks... ;-)
I was wondering how tracking is exactly being done in a 1-beam system?
I have been looking for more detailed information on the www but haven't found it yet.
Maybe a link to some more info?
Thanks... ;-)
The beam from a single laser passes through a diffraction grating, which converts the single beam into a central peak plus two side peaks that are strong enough to be take part in the tracking system. https://www.physics.udel.edu/~watson/scen103/cd-tracking.html
Some CD players use two additional lasers to help control the disc’s rotation and the scanning laser’s focus.
Is this what you are looking for? If so, more reading here: http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/cdplay3.html
Some CD players use two additional lasers to help control the disc’s rotation and the scanning laser’s focus.
Is this what you are looking for? If so, more reading here: http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/cdplay3.html
In simple words, the reflected beam is kind of a tiny circle. It falls on four photodiodes arranged in a cross shape. If the laser deviates vertically from its ideal position, the shape of the reflected light will be an ellipse, and two of the opposite diodes get less light or more light (depending on the distance of the laser from the reflexion layer on the CD) than the other two. Similarly when the laser is off track, there will be unbalanced condition of adjacent diodes. The servo makes sure that all four diodes get the same amount of light, by moving the laser up-down and radially.
Thanks Galu,
Isn't this the way a 3-beam system works?
For what I know, a single beam system doesn't have two satellite spots to track.
A single beam system only has 4 diodes on the receiving side... ;-)
Thanks Galu.
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