An optical pickup device 20 comprises an objective lens, a light source
1 composed of a blue semiconductor laser with a wavelength ranging from
400 to 415 nm and a collimator lens 2 for collimating light L1 from
this light source 1 to provide substantially-collimated light, wherein Abbe
number v of a glass material of the collimator lens 2 satisfies 61v90,
a linear expansion coefficient satisfies 55107/K120,
and a refractive index temperature coefficient (dn/dt) satisfies -1.8106(dn/dt)/K+1.5.
Since the position at which the focal point of the collimator lens 2 was
displaced due to fluctuation of temperature and fluctuation of wavelength can be
compensated for at high accuracy, the optical pickup device can increase recording
density and storage capacity of an optical recording medium.