Optical pickup apparatus and method for adjusting optical axis thereof

A method for adjusting the optical axis of an optical system comprising the steps of:

• a case in which a laser light beam radiating device is mounted, a window in said case through which said laser light beam emerges,
• a beam expander movably mounted on said case and for enlarging the diameter of said laser light beam radiated from a laser light beam radiating device, adjusting said beam expander along x and z axis so that the optical axis of the beam expander coincides with the optical axis of the laser light beam radiated from said case, moving said beam expander in the y direction relative to said case, locking said beam expander to said case, moving said laser light beam radiating device in the x and z directions relative to said case to adjust the laser light beam, and
• wherein said laser light beam radiating device comprises a laser medium arranged between a pair of mirror members constituting a resonator, a laser light source for radiating a laser light beam from an incident side one of said mirror members for exciting said laser medium, a non-linear optical crystal element irradiated with a light beam emanated from said laser medium, and a reflective mirror for deviating the optical axis of the outgoing light beam from said mirror members, said method further comprising an adjustment step of bringing the optical axis of said beam expander into coincidence with the optical axis of the light beam deflected by said reflective mirror.

An optical pickup apparatus comprising:

• a laser light beam radiating device having a laser medium arranged between a pair of mirror members constituting a resonator, a laser light source for irradiating said laser medium from a light incident side one of said mirror members for exciting said laser medium, and a non-linear optical crystal element irradiated with an outgoing laser beam from said laser medium;
• a beam expander for enlarging the diameter of the light beam radiated from said laser light beam radiating device, said beam expander being arranged so that its optical axis is coincident with the optical axis of the laser light beam radiated from said laser light radiating device;
• a optical system arranged so that its optical axis is coincident with the optical axis of the light beam from said beam expander, said optical system causing the light beam from said laser light radiating device to be converged on an one point which is placed on outer side of the optical axis of the laser light beam and
• wherein said apparatus further comprises a case, said laser light beam radiating device is housed within said case which has an opening in which an optical element that exhibits wavelength selectivity is mounted so that its surface is tilted at an angle .phi. which is other than zero relative to a reference plane which is normal with respect to an axis of an outgoing light beam.

A laser light beam radiating device comprising:

• a laser medium arranged between a pair of mirror members constituting a resonator;
• a laser light source for radiating a laser light from an incident side one of said mirror members for exciting said laser medium;
• a non-linear optical crystal irradiated with a light beam emanated from said laser medium,
• a deflective mirror for deviating the laser light beam radiated from said resonator by 90 degrees to an optical axis;
• a casing having housed therein said pair of mirror members, said laser medium, said light source, said non-linear optical crystal element and said 90 degrees deflective mirror, said casing also having a window in which an optical element that exhibits wavelength selectivity and is mounted so as to receive the laser light beam which has been deflected by said deflective mirror, and said optical element mounted so that its surface is tilted at an angle .phi. which is other than zero relative to a reference plane which is normal to said optical axis.

An optical pickup apparatus comprising:

• a laser light beam radiating device having a laser medium arranged between a pair of mirror members constituting a resonator, a laser light source for radiating a laser light from an incident side one of said mirror members for exciting said laser medium, a non-linear optical crystal element irradiated with a light beam emanated from said laser medium, a deflective mirror for deviating the laser light beam from one of said mirror members by 90 degrees to an optical axis, a casing having housed therein said pair of mirror members, said laser medium, said laser light source, said non-linear optical crystal element and said deflective mirror, said casing having a window in which an optical element that exhibits wavelength selectivity and is mounted so as to receive the laser light beam radiated from said deflective mirror, said optical element mounted so that its surface is tilted at an angle .phi. which is other than zero relative to a reference plane which is normal to said optical axis;
• a beam expander arranged on the optical axis of the light beam radiated from said optical element;
• a collimator lens for collimating the light beam transmitted through said beam expander into a parallel beam;
• an objective lens for converging the light beam from said collimator lens on a recording medium;
• a beam splitter arranged between said objective lens and said beam expander for separating the laser light beam radiated from said laser light beam radiating device from the light beam reflected from said recording medium;
• and
• a photodetector for receiving the light beams separated by said beam splitter.