An optical pick-up capable of reproducing information excellently on both CD
and
DVD, which are significantly different in terms of three kinds of factors, a base
material thickness, a wavelength of a light source, and NA, and detecting TE signals
by three kinds of methods, that is, the phase difference method, the PP method,
and the 3-beam method, which are necessary to record and reproduce information.
The optical pick-up is formed by integrating laser light sources having two kinds
of wavelengths (1, 2) for detecting TE signals; photodetectors,
and hologram for generating the diffracted light for detecting signals. The distance
d1 between the center of the photo detecting portion PD0 and the
light emitting spot of the first semiconductor laser light source and a distance
d2 between the center of the photo detecting portion PD0 and the
light emitting spot of the second semiconductor laser light source substantially
satisfy the following relationship:
