| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical head that can prevent an amount of astigmatism from being increased when a distance between a light source and a condenser lens is changed in the case of beam shaping by an optical head optical system using a light whose wavelength is 500 nm or below and prevent the recording and reproducing characteristics from being considerably deteriorated especially due to a temperature change or the like. SOLUTION: A beam shading magnification and a condenser lens focal distance of the optical head optical system are decided under a condition to specify an upper limit of the astigmatism in addition to an RIM intensity and an optical utilizing efficiency that are conditions to obtain an excellent spot shape. The condition of the astigmatism is obtained from a relation among the beam shaping magnification, the focal distance of the condenser lens, and the astigmatism amount. Thus, the excellent recording and reproducing characteristic is compatible with the temperature characteristic. |
