Optical pickup

An optical pickup, comprising:

• a light source;
• a collimator lens that collects divergent light from the light source so as to form parallel light;
• a beam shaping element that alters an intensity distribution of the parallel light;
• an objective lens that collects light passing through the beam shaping element onto an information recording medium;
• and
• a parallel plate that is disposed between the light source and the collimator lens,
• wherein an inclination angle of the parallel plate with respect to an optical axis is changed with a variation amount of temperature.

An optical pickup, comprising:

• a light source;
• and a collimator lens that collects divergent light from the light source so as to form parallel light, whereby the light from the light source is collected onto an information recording medium,
• wherein the light source and the collimator lens are attached to a base, and
• a change in optical relationship concerning image-formation, which is generated from:
• a change in optical path length between a luminous point of the light source and a principal point of the collimator lens due to a temperature change;
• and a change in focal length of the collimator lens, is compensated for with a shift of a relative position between the base and at least one of the light source and the collimator lens.

An optical pickup, comprising:

• a light source;
• a collimator lens that collects divergent light from the light source so as to form parallel light;
• a beam shaping element that alters an intensity distribution of the parallel light;
• an objective lens that collects light passing through the beam shaping element onto an information recording medium;
• and
• a phase plate with concentric steps, the phase plate being disposed at a position before or after the collimator lens,
• wherein the phase plate is designed so as to correct a phase distribution of light that is generated due to a temperature change in a structure including the light source and the collimator lens into a state before the light enters the beam shaping element to be converted back into a plane wave.