Beam shaping element, and light source unit and optical pickup using same

A light source unit comprising:

• a beam shaping element having, on one surface thereof, a set of diffraction gratings in such a manner that intervals between the gratings farer from a vicinity of an optical axis and nearer to a periphery are narrower, wherein each interval between the respective gratings changes along a direction in which each grating-shaped pattern extends;
• and
• a light source for radiating a light beam into the beam shaping element,
• at least one of positions of the beam shaping element and the light source being adjusted by a positional adjustment method including the step of relatively moving the light source along a plane of the beam shaping element while keeping constant distance between the plane of the beam shaping element and the light source, so as to correct displacement of a light emitting point.

A light source unit comprising:

• a beam shaping element having, on one surface thereof, a set of diffraction gratings in such a manner that intervals between the gratings farer from a vicinity of an optical axis and nearer to a periphery are narrower, wherein each interval between the respective gratings monotonously increases or monotonously decreases along a direction in which each grating-shaped pattern extends;
• and
• a light source for radiating a light beam into the beam shaping element,
• at least one of positions of the beam shaping element and the light source being adjusted by a positional adjustment method including the step of relatively moving the light source along a plane of the beam shaping element while keeping constant distance between the plane of the beam shaping element and the light source, so as to correct displacement of a light emitting point.

An optical pickup comprising:

• a light source for radiating a light beam in an elliptical shape;
• a beam shaping element for shaping the light beam received from the light source into a substantially round shape, having, on one surface thereof, a set of diffraction gratings in such a manner that intervals between the gratings farer from a vicinity of an optical axis and nearer to a periphery are narrower, wherein each interval between the respective gratings changes along a direction in which each grating-shaped pattern extends;
• a collimating means for parallelizing the light beam shaped into the substantially round shape by the beam shaping element;
• and
• a condensing means for condensing the light beam parallelized by the collimating means.

An optical pickup comprising:

• a light source for radiating a light beam in an elliptical shape;
• a beam shaping element for shaping the light beam received from the light source into a substantially round shape, having, on one surface thereof, a set of diffraction gratings in such a manner that intervals between the gratings farer from a vicinity of an optical axis and nearer to a periphery are narrower, wherein each interval between the respective gratings monotone increases or monotone decreases along a direction in which each grating-shaped pattern extends;
• a collimating means for parallelizing the light beam shaped into the substantially round shape by the beam shaping element;
• and
• a condensing means for condensing the light beam parallelized by the collimating means.