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AndyW
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I have read that that 'spot size' for reading a track on a CD is twice the wavelength, e.g. on a CD the track separation is 15 microns which can be read by a 700nm laser. But where does this physical rule come from?
Also, the DVD standard uses a 640nm laser. That would imply a track separation of about 13 microns, but in actual fact it is 7.4 microns. Why is this?
Thanks
Also, the DVD standard uses a 640nm laser. That would imply a track separation of about 13 microns, but in actual fact it is 7.4 microns. Why is this?
Thanks