Record carrier with optically readable phase structure having tracks with different phase depths and apparatus for reading such a record carrier

Claim 1

A record carrier comprising an information structure containing information adapted to be read with a beam of radiation of a single wavelength, said information structure having a plurality of adjacent information track portions each comprising a plurality of areas separated from each other along said track portion by intermediate regions having a different influence on the read beam than said areas, one track portion of a pair of said adjacent track portions containing areas of a first configuration which diffract the read beam of said single wavelength incident thereon into a zero order subbeam and a first order subbeam with a first phase difference therebetween and the other track portion of said pair containing areas of a second configuration which diffract the read beam of said single wavelength incident thereon into said zero and first order subbeams with a second phase difference therebetween which is different from said first phase difference.

Claim 15

An apparatus for reading a record carrier provided with an information structure containing optically readable information in the form of areas arranged along a plurality of adjacent information track portions and separated from each other along said track portions by intermediate regions which have a different influence on a read beam than the areas, the areas being adapted to diffract the read beam incident thereof into a zero order subbeam and a first order subbeam having a phase which is different from that of the zero order subbeam, the areas in adjacent track portions having different configurations such that the phase difference between said zero and first order subbeams diffracted by the areas of one of the adjacent track portions have a first phase difference which is different from the phase difference between said zero order and first order subbeams diffracted by the areas of the other of the adjacent track portions, said apparatus comprising a radiation source which produces a read beam, an objective system for focusing the read beam to a read spot on the information structure, and a radiation sensitive detection system for converting the read beam which has been modulated by the information structure into an electrical signal, the detection system comprising two radiation sensitive detectors which are disposed in the far field of the information structure each on one side of a line which is effectively transverse to the track direction, the outputs of the detectors being connected to inputs of a first electronic circuit in which the detector signals are added in first time intervals and subtracted in second time intervals, the output of the first electronic circuit being connected to an input of a second electronic circuit in which a switching signal is derived from the signal read from the record carrier, said switching signal being applied to a control input of the first electronic circuit and determining said time intervals.

Claim 16

An apparatus for reading a record carrier provided with an information structure containing optically readable information in the form of areas arranged along a plurality of adjacent information track portions and separated from each other along said track portions by intermediate regions which have a different influence on a read beam than the areas, the areas being adapted to diffract the read beam incident thereof into a zero order subbeam and a first order subbeam having a phase which is different from that of the zero order subbeam, the areas in adjacent track portions having different configurations such that the phase difference between said zero and first order subbeams diffracted by the areas of one of the adjacent track portions have a first phase difference which is different from the phase difference between said zero order and first order subbeams diffracted by the areas of the other of the adjacent track portions, said apparatus comprising a radiation source which produces a read beam, an objective system for focusing the read beam to a read spot on the information structure, and a radiation sensitive detection system for converting the read beam which has been modulated by the information structure into an electrical signal, the detection system comprising two radiation sensitive detectors which are disposed in the far field of the information structure each on one side of a line which is effectively transverse to the track direction, the outputs of the detectors being connected to inputs of a first electronic circuit in which the detector signals are added in first time intervals and subtracted in second time intervals, the output of the first electronic circuit being connected to an input of a second electronic circuit in which a switching signal is derived from the signal read from the record carrier, said switching signal being applied to a control input of the first electronic circuit and determining said time intervals.

Claim 18

An apparatus for reading information stored in a reflective information structure on a record carrier, the information structure having a plurality of adjacent track portions each comprised of a plurality of pits spaced along the track portion and separated from each other by intermediate regions which have a different influence on a read beam than said pits, said apparatus comprising means for producing a read beam of radiation of a single wavelength, means for focusing said read beam to a read spot on the information structure, means for producing relative movement between said record carrier and said read spot so that said read spot scans and is modulated by the pits, the pits in one track portion of a given pair of adjacent track portions of the information structure having a first geometrical depth equal to approximately one-quarter of said wavelength and the pits in the other track portion of said pair having a second geometrical depth equal to approximately one-eighth of said wavelength so that the pits in the respective track portions of said pair have a different influence on said read beam when scanned thereby, first means for converting the radiation of said read beam which has been modulated by pits of said first depth in said one track portion into a first electrical signal representative of information stored in said one track portion, said first means being insensitive to radiation of said read beam which has been modulated by the pits of said second depth in said other track portion, and second means for converting radiation of the read beam which has been modulated by the pits of said second depth in said other track portion into a second electrical signal representative of information stored in said other track portion, said second detecting means being insensitive to radiation of said read beam which has been modulated by said pits of said first depth in said one track portion.

Claim 19

An apparatus for reading information stored in a reflective information structure on a record carrier, the information structure having a plurality of adjacent track portions each comprised of a plurality of pits spaced along the track portion and separated from each other by intermediate regions which have a different influence on a read beam than said pits, said apparatus comprising means for producing a read beam of radiation of a single wavelength, means for focusing said read beam to a read spot on the information structure, means for producing relative movement between said record carrier and said read spot so that said read spot scans and is modulated by the pits, the pits in one track portion of a given pair of adjacent track portions of the information structure having a first geometrical depth equal to approximately one-quarter of said wavelength and the pits in the other track portion of said pair having a second geometrical depth equal to approximately one-eighth of said wavelength so that the pits in the respective track portions of said pair have a different influence on said read beam when scanned thereby, first means for converting the radiation of said read beam which has been modulated by pits of said first depth in said one track portion into a first electrical signal representative of information stored in said one track portion, said first means being insensitive to radiation of said read beam which has been modulated by the pits of said second depth in said other track portion, and second means for converting radiation of the read beam which has been modulated by the pits of said second depth in said other track portion into a second electrical signal representative of information stored in said other track portion, said second detecting means being insensitive to radiation of said read beam which has been modulated by said pits of said first depth in said one track portion.

Claim 20

An apparatus for reading an information structure on a record carrier, the information structure having at least one pair of adjacent track portions, one track portion of said pair comprising a plurality of first information areas and the other track portion of said pair comprising a plurality of second information areas, said information areas being spaced along the respective track portion and being separated from each other by intermediate regions, said first information areas being defined by pits of a first depth or hills of a first height and said second information areas being defined by pits of a second depth or hills of a second height which is smaller than said first depth or first height, respectively, said apparatus comprising means for producing a beam of radiation of a single wavelength, means for focusing said beam to a read spot on the information structure, means for producing relative movement between said record carrier and said read spot so that said read spot scans a given track portion and the radiation of the said beam is modulated by the information areas therein in accordance with information stored thereby, a pair of radiation sensitive detectors arranged in the path of said modulated radiation coming from the record carrier for converting said modulated radiation into corresponding electrical signals, means for adding said electrical signal so as to produce a first signal representative of information stored in said one track portion and means for subtracting said electrical signals so as to produce a second signal representative of information stored in said other track portion, said first information areas having a depth or height such as to optimize said first signal and minimize the effect of said first areas on said second signal and said second information areas having a depth or height such as to optimize said second signal and minimize the effect of said second areas on said first signal so as to reduce cross talk between said track portions.

Claim 21

An apparatus for reading an information structure on a record carrier, the information structure having at least one pair of adjacent track portions, one track portion of said pair comprising a plurality of first information areas and the other track portion of said pair comprising a plurality of second information areas, said information areas being spaced along the respective track portion and being separated from each other by intermediate regions, said first information areas being defined by pits of a first depth or hills of a first height and said second information areas being defined by pits of a second depth or hills of a second height which is smaller than said first depth or first height, respectively, said apparatus comprising means for producing a beam of radiation of a single wavelength, means for focusing said beam to a read spot on the information structure, means for producing relative movement between said record carrier and said read spot so that said read spot scans a given track portion and the radiation of the said beam is modulated by the information areas therein in accordance with information stored thereby, a pair of radiation sensitive detectors arranged in the path of said modulated radiation coming from the record carrier for converting said modulated radiation into corresponding electrical signals, means for adding said electrical signal so as to produce a first signal representative of information stored in said one track portion and means for subtracting said electrical signals so as to produce a second signal representative of information stored in said other track portion, said first information areas having a depth or height such as to optimize said first signal and minimize the effect of said first areas on said second signal and said second information areas having a depth or height such as to optimize said second signal and minimize the effect of said second areas on said first signal so as to reduce cross talk between said track portions.