| 摘要 |
PURPOSE:To increase the yield of laser by decreasing the light beam wavelength for recording/reproduction more than the wavelength of the erasing light beam and making the distribution of the light beam for recording/reproducing more isotropic than the distribution of an erasing beam. CONSTITUTION:The wavelength of the recording/reproducing laser 1 is 780+ or -15nm and the spread angle is expressed as theta11=11-15 deg., theta1=18-38 deg.. The wavelength of the erasing laser 7 is 860+ or -15nm and the spread angle is theta11=8-11 deg., theta1=18-38 deg.. The beam half value entire width (a) of the recording/ reproducing spot in a direction orthogonal to the track is expressed as a=0.35lambda1/NA (lambda1=recording/reproduction laser wavelength) and the beam half value entire width (b) of the erasure spot is expressed as b=0.53lambda2/N (lambda2 is the erasure laser wavelength). In such a case, a=0.82mum at the recording/ reproducing beam wavelength lambda1=780nm and b=0.91mum at the erasing beam wavelength lambda2=860mum. Thus, the recording/reproduction spot and the erasing spot have a difference of a nearly 0.1mum and no problem takes place even an error is generated in the tracking servo. |
