Record carrier body with an optical servo track and optical apparatus for writing and reading information from the carrier

Claim 2

In an appartus for writing information in a record carrier body provided with a radiation sensitive layer and a servo track comprised of optically detectable spaced apart servo areas, the apparatus comprising a first radiation source which produces a write beam, a second radiation source which produces a servo beam, means for switching the radiation intensity of the write beam in accordance with the information to be written, an objective system for focussing the write beam and the servo beam to a write spot and a servo spot on the information layer and the servo track, respectively, and means for producing relative movement between said spots and said record carrier body, the improvement wherein in the path of the servo beam coming from the record carrier body there is included a radiation-sensitive detector at whose output a signal is obtained which provides an indication of the speed of the servo spot relative to said carrier body, a comparator circuit having a first input connected to the output of the radiation sensitive detector and a second input for receiving a reference signal proportional to the rate at which the information to be written is applied.

Claim 3

Apparatus as claimed in claim 1, wherein said record body is disc-shaped and said servo track is comprised of a plurality of generally, circular, concentric servo track portions, and wherein the write spot and the servo spot are radially offset relative to each other by a distance of the order of half a radial spacing between adjacent servo track portions.

Claim 4

Apparatus as calimed in claim 1, including a plurality of write sources of radiation each producing a write beam, the write spots formed by the write beams being radially displaced from each other, and means associated with each write beam for switching the intensity of the write beam in accordance with the information to be written by the relevant beam.

Claim 5

A record carrier body for storing information recorded by a write beam of radiation, said carrier body comprising a substrate provided with a radiation sensitive layer and a plurality of spaced apart, optically detectable servo areas defining an elongated servo track for guiding said write beam during recording so that the information is recorded on said radiation sensitive layer along an information track spaced from said servo track upon relative movement of said body and said write beam, said servo areas being spaced from each other by a constant distance in the longitudinal direction of said servo track so that, upon illumination of said servo track by a beam of radiation, said servo areas produce a periodic change in the beam which is proportional to the speed of said relative movement; said constant distance being such that said periodic change has a frequency which is substantially outside the frequency spectrum of the information to be recorded.

Claim 6

A record carrier body for storing information recorded by a write beam of radiation, said carrier body comprising a substrate provided with a radiation sensitive layer and a plurality of spaced apart, optically detectable servo areas defining an elongated servo track for guiding said write beam during recording so that the information is recorded on said radiation sensitive layer along an information track spaced from said servo track upon relative movement of said body and said write beam, said servo areas being spaced from each other by a constant distance in the longitudinal direction of said servo track so that, upon illumination of said servo track by a beam of radiation, said servo areas produce a periodic change in the beam which is proportional to the speed of said relative movement; said constant distance being such that said periodic change has a frequency which is substantially outside the frequency spectrum of the information to be recorded.

Claim 7

A record carrier body as claimed in claim 4, when the servo track has a phase structure.

Claim 8

The record carrier body according to claim 4 including a plurality of said servo tracks, said servo tracks being generally parallel and spaced from each other with the radiation sensitive layer extending between adjacent pairs of said servo tracks so that said information is written in at least one information track which is generally parallel to and extends between adjacent pairs of said servo tracks.

Claim 9

The record carrier according to claim 4 wherein said radiation sensitive layer comprises a photoresist.

Claim 10

The record carrier according to claims 4 or 7 including an intermediate layer which is disposed between said substrate and said radiation sensitive layer and which extends over and covers said servo track, said intermediate layer and said radiation sensitive layer being transparent to said radiation with which said servo track is illuminated.

Claim 11

Apparatus for recording information on a record carrier body provided with a radiation sensitive layer and an optically detectable, elongated servo track comprised of a plurality of spaced apart servo areas, said apparatus comprising means for producing a write beam of radiation, means for modulating said write beam in accordance with information to be recorded, means for producing a servo beam or radiation, means for focussing said write beam and said servo beam to a write spot and a servo spot on said radiation sensitive layer and said servo track, respectively, means for producing relative movement between said record body and said spots, means for detecting radiation of said servo beam coming from said record body which has been modulated by said servo track, said detecting means producing a first signal indicative of the speed of movement of said servo spot relative to said record carrier body, and means responsive to said first signal for controlling the rate at which said information is recorded on said record body.

Claim 12

Apparatus for recording information on a record carrier body provided with a radiation sensitive layer and an optically detectable, elongated servo track comprised of a plurality of spaced apart servo areas, said apparatus comprising means for producing a write beam of radiation, means for modulating said write beam in accordance with information to be recorded, means for producing a servo beam or radiation, means for focussing said write beam and said servo beam to a write spot and a servo spot on said radiation sensitive layer and said servo track, respectively, means for producing relative movement between said record body and said spots, means for detecting radiation of said servo beam coming from said record body which has been modulated by said servo track, said detecting means producing a first signal indicative of the speed of movement of said servo spot relative to said record carrier body, and means responsive to said first signal for controlling the rate at which said information is recorded on said record body.

Claim 13

The apparatus according to claim 9 wherein said controlling means includes means for comparing said first signal with a reference signal and generating a second signal indicative of the difference therebetween.

Claim 14

The apparatus according to claim 10 including means responsive to said second signal for deflecting said spots relative to said body in a direction generally parallel to said servo track.

Claim 17

A record carrier comprising a disc-shaped substrate having a plurality of generally circular, concentric information track portions each comprised of a plurality of spaced apart information areas representing information readable by a read beam of radiation, and a generally circular servo track portion disposed between adjacent information track portions for radially guiding the read beam, said servo track portions being comprised of a plurality of optically detectable spaced apart servo areas, said servo areas in each circular servo track portion being spaced from each other by a predetermined, constant distance so that, upon illumination of said servo track portions by a beam of radiation, said servo areas produce a periodic change in the beam which is proportional to the speed of movement of said beam of radiation relative to said body; one of said information track portions and said servo track portions having a phase structure and the other of said information track portions and servo track portions having an amplitude structure.

Claim 18

A record carrier comprising a disc-shaped substrate having a plurality of generally circular, concentric information track portions each comprised of a plurality of spaced apart information areas representing information readable by a read beam of radiation, and a generally circular servo track portion disposed between adjacent information track portions for radially guiding the read beam, said servo track portions being comprised of a plurality of optically detectable spaced apart servo areas, said servo areas in each circular servo track portion being spaced from each other by a predetermined, constant distance so that, upon illumination of said servo track portions by a beam of radiation, said servo areas produce a periodic change in the beam which is proportional to the speed of movement of said beam of radiation relative to said body; one of said information track portions and said servo track portions having a phase structure and the other of said information track portions and servo track portions having an amplitude structure.

Claim 21

Apparatus for recording information on a record carrier body provided with a radiation sensitive layer and an optically detectable, elongated servo track comprising a plurality of servo areas spced from each other by a predetermined distance in the longitudinal direction of said servo track, said apparatus comprising means for producing a write beam of radiation, means for modulating said write beam in accordance with information to be recorded, means for producing a servo beam of radiation, means for focussing said write beam and said servo beam to a write spot and a servo spot on said radiation sensitive layer and said servo track, respectively, means for producing relative movement between said record body and said spots, means responsive to radiation of said servo beam coming from said record body which has been modulated by said servo track for producing a first signal indicative of the speed of movement of said servo spot relative to said record carrier body in said longitudinal direction and a second signal indicative of the displacement of said servo spot from the center of said servo track in a direction transverse to said longitudinal direction, first means responsive to said first signal for controlling the speed of said relative movement and second means responsive to said second signal for moving said write spot in a direction transverse to said longitudinal direction.

Claim 22

Apparatus for recording information on a record carrier body provided with a radiation sensitive layer and an optically detectable, elongated servo track comprising a plurality of servo areas spced from each other by a predetermined distance in the longitudinal direction of said servo track, said apparatus comprising means for producing a write beam of radiation, means for modulating said write beam in accordance with information to be recorded, means for producing a servo beam of radiation, means for focussing said write beam and said servo beam to a write spot and a servo spot on said radiation sensitive layer and said servo track, respectively, means for producing relative movement between said record body and said spots, means responsive to radiation of said servo beam coming from said record body which has been modulated by said servo track for producing a first signal indicative of the speed of movement of said servo spot relative to said record carrier body in said longitudinal direction and a second signal indicative of the displacement of said servo spot from the center of said servo track in a direction transverse to said longitudinal direction, first means responsive to said first signal for controlling the speed of said relative movement and second means responsive to said second signal for moving said write spot in a direction transverse to said longitudinal direction.

Claim 23

The apparatus according to claim 16, wherein said signal producing means includes a radiation sensitive detector disposed in the path of said modulated radiation of said servo beam coming from said record carrier body.

Claim 24

The apparatus according to claim 14, wherein said write spot is spaced a predetermined distance from said servo spot in a direction transverse to said servo track so that upon said relative movement, the information is recorded by said write spot along an information track which is generally parallel to and spaced from said servo track.

Claim 25

The apparatus according to claim 17 including means for producing, from said radiation of said servo beam, a pair of auxiliary beams which are focussed by said focussing means into a pair of auxiliary spots on said record carrier body, each of said auxiliary spots being offset in opposite directions from said servo spots, and wherein said signal producing means includes further means for detecting radiation of said auxiliary beams coming from said record carrier.

Claim 26

A record carrier body for storing information which is recorded thereon by a write beam of radiation, said carrier body comprising a substrate provided with a plurality of servo areas defining an elongated servo track which is detectable by a servo beam of radiation having a wavelength different from that of the write beam, said servo areas being spaced from each other by a predetermined distance in the longitudinal direction of said servo tracks, said carrier body further comprising a layer which is sensitive to the radiation of said write beam and which extends over and covers said servo track, said layer being transparent to the radiation of said servo beams so that when said servo track is scanned by said servo beam, said servo areas produce a periodic change in the beam which is proportional to the speed of relative movement between said carrier body and said servo beam for controlling the rate at which the information is recorded by the write beam on said layer and for guiding said write beam so that the information is recorded along an elongated information track at a predetermined position spaced from said servo track.

Claim 27

A record carrier body for storing information which is recorded thereon by a write beam of radiation, said carrier body comprising a substrate provided with a plurality of servo areas defining an elongated servo track which is detectable by a servo beam of radiation having a wavelength different from that of the write beam, said servo areas being spaced from each other by a predetermined distance in the longitudinal direction of said servo tracks, said carrier body further comprising a layer which is sensitive to the radiation of said write beam and which extends over and covers said servo track, said layer being transparent to the radiation of said servo beams so that when said servo track is scanned by said servo beam, said servo areas produce a periodic change in the beam which is proportional to the speed of relative movement between said carrier body and said servo beam for controlling the rate at which the information is recorded by the write beam on said layer and for guiding said write beam so that the information is recorded along an elongated information track at a predetermined position spaced from said servo track.

Claim 28

The record carrier body according to claim 20 including an intermediate layer disposed between said substrate and said radiation sensitive layer, said intermediate layer being transparent to the radiation of the servo beam.

Claim 29

The record carrier according to claim 20 wherein said radiation sensitive layer comprises a photoresist.