Objective lens for optical pick-up devices, optical pick-up devices, and optical information recording and/or reproducing apparatus

An objective lens for optical pick-up devices comprising:

• a first optical element placed on a light source side;
• and
• a second optical element having light focusing characteristics and placed on an optical information recording medium side,
• wherein the objective lens satisfies the following Equation (2):
• 2.0×10−6<τ×|A|×(h2/h1)2<2.1×10−4 (2)
• where, τ [mm] is spacing along an optical axis between an optical surface on the light source side of the first optical element and an optical surface on the optical information recording medium side of the first optical element,
• A is amount of change in refractive index of the first optical element for a 1° C. temperature raise from 25° C.,
• h1 is height from an optical axis of marginal light beam at the optical surface on the light source side of the first optical element, and
• h2 is height from the optical axis of the marginal light beam at the optical surface on the optical information recording medium side.

An optical pick-up device comprising:

• an objective lens having a first optical element placed on a light source side and a second optical element having light focusing characteristics and placed on an optical information recording medium side,
• wherein the objective lens satisfies the following Equation (1):
• 0.1<D×τ<6 (1)
• where, τ [mm] is spacing along an optical axis between an optical surface on the light source side of the first optical element and an optical surface on the optical information recording medium side of the first optical element;
• and
• D [mm] is an external diameter of the first optical element.

An optical pick-up device comprising:

• an objective lens having a first optical element placed on a light source side and a second optical element having light focusing characteristics and placed on an optical information recording medium side,
• wherein the objective lens satisfies the following Equation (2):
• 2.0×10−6<τ×|A|×(h2/h1)2<2.1×10−4 (2)
• where, τ [mm] is spacing along an optical axis between an optical surface on the light source side of the first optical element and an optical surface on the optical information recording medium side of the first optical element,
• A is amount of change in refractive index of the first optical element for a 1° C. temperature raise from 25° C.,
• h1 is height from an optical axis of marginal light beam at the optical surface on the light source side of the first optical element, and
• h2 is height from the optical axis of the marginal light beam at the optical surface on the optical information recording medium side.

An optical information recording and/or reproducing apparatus comprising:

• an optical pick-up device having an objective lens, wherein
• the objective lens have a first optical element placed on a light source side and a second optical element having light focusing characteristics and placed on an optical information recording medium side, and satisfies the following Equation (1):
• 0.1<D×τ<6 (1)
• where, τ [mm] is spacing along an optical axis between an optical surface on the light source side of the first optical element and an optical surface on the optical information recording medium side of the first optical element;
• and
• D [mm] is an external diameter of the first optical element.

An optical information recording and/or reproducing apparatus comprising:

• an optical pick-up device having an objective lens, wherein
• the objective lens have a first optical element placed on a light source side and a second optical element having light focusing characteristics and placed on an optical information recording medium side, and satisfies the following Equation (2):
• 2.0×10−6<τ×|A|×(h2/h1)2<2.1×10−4 (2)
• where, τ [mm] is spacing along an optical axis between an optical surface on the light source side of the first optical element and an optical surface on the optical information recording medium side of the first optical element,
• A is amount of change in refractive index of the first optical element for a 1° C. temperature raise from 25° C.,
• h1 is height from an optical axis of marginal light beam at the optical surface on the light source side of the first optical element, and
• h2 is height from the optical axis of the marginal light beam at the optical surface on the optical information recording medium side.