Objective lens formed of a single lens and having high numerical aperture and an optical pickup apparatus adopting the same

An optical pickup apparatus comprising:

• a light source to generate and emit a light beam having a predetermined wavelength;
• an objective lens to focus the light beam emitted from said light source to form a light spot on a recording surface of a recording medium;
• and
• a photodetector to receive the light beam reflected by the recording surface of the recording medium,
• wherein said objective lens is formed of a single lens such that a working distance between said objective lens and the recording surface is less than a thickness at the center of said objective lens, and
• wherein a thickness at the center of said objective lens is 0.8 times or more an effective diameter of said objective lens.

An optical pickup apparatus comprising:

• a light source to generate and emit a light beam having a predetermined wavelength;
• an objective lens to focus the light beam emitted from said light source to form a light spot on a recording surface of a recording medium;
• and
• a photodetector to receive the light beam reflected by the recording surface of the recording medium,
• wherein said objective lens is formed of a single lens and a working distance between said objective lens and the recording surface is less than a thickness at the center of said objective lens, and
• wherein when an NA of said objective lens is 0.8 or more, a working distance of said objective lens satisfies the Inequality
• WD≦αBW−0.2T,
• wherein WD is the working distance, BW is a diameter of an incident light beam, T is the thickness at the center of said objective lens, α=1/(2 tan θ), and θ=Arcsin(NA).

An optical pickup apparatus comprising:

• a light source to generate and emit a light beam having a predetermined wavelength;
• an objective lens to focus the light beam emitted from said light source to form a light spot on a recording surface of a recording medium;
• and
• a photodetector to receive the light beam reflected by the recording surface of the recording medium,
• wherein said objective lens is formed of a single lens and a working distance between said objective lens and the recording surface is less than a thickness at the center of said objective lens, and
• wherein a maximum slope angle of a surface of said objective lens on which light is incident is between 50° and 55°.

An optical pickup apparatus comprising:

• a light source to generate and emit a light beam having a predetermined wavelength;
• an objective lens to focus the light beam emitted from said light source to form a light spot on a recording surface of a recording medium;
• a photodetector to receive the light beam reflected by the recording surface of the recording medium, and
• a reflection type compound prism formed of a plurality of prisms to make an incident light beam emitted from said light source proceed by reducing a size of the light beam in a direction of height towards said objective lens by using a difference in angle between surfaces of the prisms, and the light beam reflected by a surface forming an angle less than 45° with respect to a horizontal plane which is perpendicular to the direction of height, so as to proceed toward said objective lens disposed in the direction of height,
• wherein said objective lens is formed of a single lens and a working distance between said objective lens and the recording surface is less than a thickness at the center of said objective lens.

An optical pickup apparatus comprising:

• a light source to generate and emit a light beam having a predetermined wavelength;
• an objective lens to focus the light beam emitted from said light source to form a light spot on a recording surface of a recording medium;
• and
• a photodetector to receive the light beam reflected by the recording surface of the recording medium,
• wherein said objective lens is formed of a single lens and a thickness at the center of said objective lens is 0.8 times or more an effective diameter of said objective lens.