Astigmatic objective lens for optical head

   
   

An objective lens for an optical head converges a first laser beam having a relatively short wavelength and a second laser beam having a relatively long wavelength on first optical disc (DVD) and a second optical disc (CD), respectively. A protective layer of the first disc is thinner than a protective layer of the second optical disc. The objective lens is compensated for astigmatism with respect to the first beam, which is incident on the objective lens as an off-axis beam at a predetermined incident angle, by providing on-axis astigmatism corresponding to wave front aberration greater than or equal to 0.01.lambda. (rms), and the objective lens is configured such that the coma is compensated better in a case where the first laser beam is converged on the first optical disc than in a case where the second laser beam is converged on the second optical disc.

 
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