Optical element, light source apparatus, optical head apparatus, and optical information processing apparatus

A light source apparatus, comprising:

• a first light source for emitting light having a first wavelength and polarized in a first direction;
• a second light source for emitting light having a second wavelength different from the first wavelength and polarized in the first direction;
• a wavelength plate that functions substantially as a nλ plate (n is an integer) with respect to light having the first wavelength, and functions substantially as a (2m+1)λ/2 plate (m is an integer) with respect to light having the second wavelength;
• and
• a diffraction element that transmits light polarized in the first direction and diffracts light polarized in a second direction orthogonal to the first direction,
• wherein the wavelength plate converts light emitted from the second light source into light polarized in the second direction so as to transmit it, and transmits light emitted from the first light source without converting a polarization direction thereof, and
• the diffraction element diffracts the light emitted from the second light source, passing through the wavelength plate,
• whereby the light emitted from the second light source, diffracted by the diffraction element, has an apparent emission point different from an emission point of the second light source.

An optical element comprising:

• a wavelength plate that functions substantially as a nλ plate (n is an integer) with respect to light having a first wavelength, and functions substantially as a (2m+1)λ/2 plate (m is an integer) with respect to light having a second wavelength;
• and
• a diffraction element that transmits light polarized in a first direction and diffracts light polarized in a second direction orthogonal to the first direction,
• wherein the wavelength plate and the diffraction element are disposed so that an angle formed by an advanced-phase axis of the wavelength plate and the first direction is substantially 45°.

An optical element comprising:

• a first wavelength plate that functions substantially as a nλ plate (n is an integer) with respect to light having a first wavelength, and functions substantially as a (2m+1)λ/2 plate (m is an integer) with respect to light having a second wavelength;
• a second wavelength plate that functions substantially as a n′λ plate (n′ is an integer) with respect to light having the first wavelength, and functions substantially as a (2m′+1)λ/2 plate (m′ is an integer) with respect to light having the second wavelength;
• and
• a diffraction element that transmits light polarized in a first direction and diffracts light polarized in a second direction orthogonal to the first direction,
• wherein the first wavelength plate, the diffraction element, and the second wavelength plate are disposed in this order so that an angle formed by an advanced-phase axis of the first wavelength plate and the first direction and an angle formed by an advanced-phase axis of the second wavelength plate and the first direction both are substantially 45°.

A method for adjusting a position of an emission point,

• in an optical system including a first light source for emitting light having a first wavelength and polarized in a first direction, and a second light source for emitting light having a second wavelength different from the first wavelength and polarized in the first direction, comprising:
• allowing light emitted from the first light source and light emitted from the second light source to be incident upon a wavelength plate that functions substantially as a (2m+1)λ/2 plate (m is an integer) with respect to light having the first wavelength and functions substantially as a nλ plate (n is an integer) with respect to light having the second wavelength, the wavelength plate converting light emitted from the first light source into light polarized in a second direction orthogonal to the first direction so as to transmit it and transmitting light emitted from the second light source without converting a polarization direction thereof;
• and
• allowing the transmitted light to be incident upon a diffraction grating so that the light polarized in the first direction is diffracted and the light polarized in the second direction is transmitted,
• thereby adjusting a position of an emission point so that the light emitted from the second light source has an apparent emission point different from an emission point of the second light source.

A method for adjusting a position of an emission point,

• in an optical system including a first light source for emitting light having a first wavelength and polarized in a first direction, and a second light source for emitting light having a second wavelength different from the first wavelength and polarized in the first direction, comprising:
• allowing light emitted from the first light source and light emitted from the second light source to be incident upon a wavelength plate that functions substantially as a nλ plate (n is an integer) with respect to light having the first wavelength and functions substantially as a (2m+1)λ/2 plate (m is an integer) with respect to light having the second wavelength, the wavelength plate transmitting light emitted from the first light source without converting a polarization direction thereof and converting light emitted from the second light source into light polarized in a second direction orthogonal to the first direction so as to transmit it;
• and
• allowing the transmitted light to be incident upon a diffraction grating so that the light polarized in the second direction is diffracted and the light polarized in the first direction is transmitted,
• thereby adjusting a position of an emission point so that the light emitted from the second light source has an apparent emission point different from an emission point of the second light source.