| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized thin lens for an optical pickup having necessary optical characteristics and giving a high production yield by specifying a range of the central thickness of the optical face of a lens and the thickness of the shingle part of the lens. SOLUTION: When the central thickness of the optical face of a lens and the thickness of the shingle part of the lens are represented by T1 and T2, respectively, 0<T1<=1.5 and 0<T2<=0.4×T1 are satisfied. An upper die is moved upward to open a cavity and a glass material having a prescribed area is put in the cavity. An inert gas is substd. for the atmosphere around the cavity, the glass material is heated to a prescribed temp. and this prescribed temp. is maintained. The upper die is moved downward to press the glass material while maintaining the prescribed temp. and the glass material is formed in the shape of an objective lens by maintaining a prescribed pressure. Slow cooling is started while maintaining the prescribed pressure and then the pressure is reduced. After rapid cooling, the upper die is moved upward to open the cavity and the resultant objective lens 26 in which the central thickness T1 of the optical face 26b is larger than the thickness T2 of the shingle part 26a is taken out. |
