Optical head with passive temperature compensation

An optical pickup apparatus, comprising:

• a base;
• a light source provided on the base;
• a light detector provided on the base for detecting light emitted by the light source and then reflected by an optical recording medium;
• and
• a light separating device, divided into at least a first area and a second area, for separating the light incident on each of the first area and the second area into a plurality of light components and directing each of the light components in a prescribed direction,
• wherein
• the light detector includes a light receiver, divided into a first light receiving region and a second light receiving region, for receiving the light components directed by the first area of the light separating device,
• the first light receiving region and the second light receiving region are located so that a second direction is inclined with respect to a direction perpendicular to a first direction, where the first direction is a direction of a phantom straight line connecting a light emitting point of the light source and a focal point on the light detector of the light transmitted through the light separating device, and the second direction is a direction of a dividing line for dividing the light receiver into the first light receiving region and the second light receiving region,
• the second direction is inclined so that when the focal point on the light detector moves while having a component of the direction perpendicular to the second direction because of a change in the wavelength of the light emitted by the light source and expansion or contraction of the base, which are both caused by a temperature change of the optical pickup apparatus, a change in an amount of the light component incident on the first light receiving region and a change in an amount of the light component incident on the second light receiving region are each within a prescribed tolerable limit,
• the light separating device being divided into at least the first area and the second area, wherein the areas have different grating pitches, by a dividing line which is substantially perpendicular to a tracking direction of the optical recording medium, and the light incident on the areas being directed to different light receiving regions of the light detector.