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
(.lamda.1, .lamda.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:
.lamda.1/.lamda.2=d1/d2.