| 摘要 |
The range of air conversion optical path length L of all optical components in the forward passage of an optical system between a laser emission point and the surface of a disc-shaped recording medium is determined by: <?in-line-formulae description="In-line Formulae" end="lead"?>i(n<SUB>0</SUB>xd)+DeltaL/2<L<(i+1)(n<SUB>0</SUB>xd)-DeltaL/2<?in-line-formulae description="In-line Formulae" end="tail"?> (i is an arbitrary integer) where d is resonator length of a laser diode, n<SUB>0 </SUB>is active layer refractive index of the laser diode, and DeltaL is acceptable surface blurring in the specification of the disc-shaped recording medium, thereby reducing laser noise (optical feedback noise) that is generated when emitted laser beam from a laser diode is interfered with the optical feedback, which is a part of laser beam that has been focused on the recording surface of the disc and has moved back through the forward passage of the optical system to return to the laser diode.
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