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# How does a CD-RW/DVD Combo work ?Does it use single or Multiple lens for CD and DVD respectively ?

Posted on 2004-03-20
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Last Modified: 2010-04-03
I want to know how exactly does a CD-RW/DVD Combo work...I remember that it is single lens and there was a nice article in www.howstuffworks.com. However I am unable to find the information on the website.Any answers will be appreciated and anything which supplements to the answer provided by weblinks such as howstuffworks.com will be highly appreciated.
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Question by:prashanth_sach
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Timotheus1 earned 375 total points
ID: 10642303
As far as I know, DVD's require a shorter wavelength of light to be read, this allows the pits and lands, (The physical representation of 1's and 0's) to be closer together in two dimensions, (the number of bits per inch of track, and the radial distance between tracks.

My best guess is that the lens is simply focused so that the laser falls on a wider area,

I suppose it's like, the tighter focus is fine when the data track is wide, (DVD-Rom reading a CD, is like a motorcycle going down the highway, whereas the laser on a CD-Rom is more like the width of a full size car. but then a DVD is more like a hallway. you can ride the motorcycle down the hallway, but not the car.

All the DVD-ROM/CD-RW drive has to do is alter the focus of the laser so that it covers more of the width of the blank CD's "groove" to insure compatibulity with older CD-ROM drives.
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Author Comment

ID: 10642884
Cool...Agreed
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