| 摘要 |
PROBLEM TO BE SOLVED: To reduce the defocusing amount due to change in ambient temperature in an optical head used for various kinds of disk drives. SOLUTION: When the linear expansion coefficient of glass material for a collimator 4 is expressed by A, the temperature coefficient of the refraction index by B, and the linear expansion coefficient of a housing by C on which the collimator 4 and a semiconductor laser supporting base 2 are mounted, by making their relationship as B>=C when A>=C, and B<0 when A<C, a variation in the spacing between the collimator 4 and the semiconductor 1 due to temperature change and a variation in the operating distance, due to temperature change, directionally cancel each other, and this brings a good temperature characteristic. |
