Optical scanning device

An optical scanning device for scanning an optical record carrier comprising an information layer, the optical scanning device comprising:

• a radiation source for generating a radiation beam;
• an objective lens, located in an optical path between the radiation source and the information layer, for converging a radiation beam to a spot on the information layer;
• and
• an optical element having
• a first reflective surface, said first reflective surface being selectively reflective and capable of reflecting a first radiation beam and transmitting a second radiation beam, and
• a second reflective surface arranged to receive said second radiation beam when transmitted by said first reflective surface, and to reflect said second radiation beam through said first reflective surface,
• wherein said second reflective surface is separated from said first surface by a varying spacing, said varying spacing corresponding to a difference in phase profile to be generated between said first and second radiation beams, and said second reflective surface comprises a phase structure in the form of stepped annular zones, the zones forming a non-periodic pattern of different heights corresponding to the difference in phase profile to be generated.

An optical scanning device for scanning an optical record carrier comprising an information layer, the optical scanning device comprising:

• a radiation source for generating a radiation beam;
• an objective lens, located in an optical path between the radiation source and the information layer, for converging a radiation beam to a spot on the information layer;
• and
• an optical element having a first reflective surface, said first reflective surface being selectively reflective and capable of reflecting a first radiation beam and of transmitting a second radiation beam, and being arranged to reflect radiation in a polarization-selective manner, and a second reflective surface arranged to receive said second radiation beam when transmitted by said first reflective surface, and to reflect said second radiation beam through said first reflective surface, said second reflective surface being separated from said first surface by a varying spacing, said varying spacing corresponding to a difference in phase profile to be generated between said first and second radiation beams, and said second reflective surface having a phase structure in the form of stepped annular zones, the stepped annular zones forming a non-periodic pattern of different heights corresponding to the difference in phase profile to be generated,
• wherein said optical scanning device further comprises an electro-optical element switchable between a first state, in which the polarization of light exiting the electro-optical element has a first orientation relative to a predetermined polarization of light entering the electro-optical element, and a second state, in which the polarization of light exiting the electro-optical element has a second orientation relative to said predetermined polarization, said electro-optical element thereby providing said first and second radiation beams, respectively, with orthogonal polarizations.