Optical disks and recording and reproducing system using the same

Claim 2

An optical disk recording and reproducing system of the type in which information is recorded or reproduced with a light beam which is focused on an optical disk characterized in that at least one side of said optical disk is formed with grooves which are V-shaped or inverted-trapezoid-shaped in cross section in the radial direction, and the spot of a light beam is focused on the side wall surfaces of the V-shaped or inverted-trapezoid-shaped grooves for recording or reproducing information.

Claim 3

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that the optical depth of each of said V-shaped or inverted-trapezoid-shaped grooves is about one quarter of the wavelength of said light beam.

Claim 4

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that when the index of refraction of a medium which is in contact with said V-shaped or inverted-trapezoid-shaped grooves and through which said light beam is incident on one of the side wall surfaces of one of said V-shaped or inverted-trapezoid-shaped grooves is about 1.5, the included angle between the adjacent side walls of said V-shaped or inverted-trapezoid-shaped grooves is greater than 159 degrees but smaller than 166 degrees.

Claim 5

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that when the index of refraction of a medium which is in contact with said V-shaped or inverted-trapezoid-shaped grooves and through which said light beam is incident on one of the side wall surfaces of one of said V-shaped or inverted-trapezoid-shaped grooves is about 1.0, the included angle between the adjacent side walls of said V-shaped or inverted-trapezoid-shaped grooves is greater than 149 degrees but smaller than 159 degrees.

Claim 6

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that the diameter of the cross section of said light beam at least in the radial direction of said optical disk is selected smaller than the diameter of a lens which focuses said light beam on said optical disk so that the incidence of said light beam upon predetermined peripheral portions of said lens adjacent to the rim thereof can be avoided, whereby the reproduction of the recorded information can be carried out by detecting the variations in time in the intensity of the light rays which are reflected from said optical disk and which pass through said predetermined peripheral portions of said lens.

Claim 7

An optical disk recording and reproducing system as set forth in Claim 5 further characterized in that a photodetector which has a first unit cell and a second unit cell is disposed in the passage of the rays of light reflected from said optical disk in such a way that said first and second unit cells are symmetrically located with respect to each other about the center of the image projected over the surface of said photodetector of said lens and the portions of the projected image of said lens corresponding to said predetermined peripheral portions thereof are substantially coincident with said first and second unit cells so that said first and second unit cells can receive the rays of light which are reflected from said optical disk and which pass through said predetermined peripheral portions of said lens and the outputs from said first and second unit cells are used for reproduction of the stored information.

Claim 8

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that the optical depths of said V-shaped or inverted-trapezoid-shaped grooves are varied at least at two; that is, a first and a second frequencies in such a way that said first and second frequencies alternate every time when said optical disk makes one complete rotation, whereby in response to the detection of variations at said first and second frequencies in the intensity of light reflected back from said optical disk, the spot of said light beam is so controlled to track along the center line of each of the side wall surfaces of said V-shaped or inverted-trapezoid-shaped grooves for recording or reproducing information.

Claim 9

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that a train of tracking control pits spaced apart from each other by a predetermined first pitch or frequency is previously recorded along each of the crest lands of said V-shaped or inverted-trapezoid-shaped grooves of said optical disk, a train of tracking control pits spaced apart from each other by a predetermined second pitch or frequency is recorded along each of the bottom lands of said V-shaped or inverted-trapezoid-shaped grooves, and in the case of recording or reproduction, in responsive to the detection of the variations at said first and second frequencies in intensity of light reflected from said optical disk, the spot of said light beam is so controlled to track or scan the center line of each of the side wall surfaces of said V-shaped or inverted-trapezoid-shaped grooves of said optical disk.

Claim 10

An optical disk recording and reproducing system as set forth in Claim 1 further characterized in that said V-shaped or inverted-trapezoid-shaped grooves are in the form of a spiral; and the spot of said light beam is shifted by a distance equal to half of the pitch; that is, one half of the distance between the adjacent crests of said spiral V-shaped or inverted-trapezoid-shaped groove in the direction opposite to the direction in which the spot of said light beam is shifted relative to the center of said optical disk toward the center thereof, every time when said optical disk makes one complete rotation.

Claim 11

An optical disk of the type information is recorded thereon or read out therefrom with the spot of a light beam focused thereon, characterized in that one side of said optical disk is formed with grooves which are V-shaped or inverted-trapezoid-shaped in cross section in the radial direction of said optical disk and which have the shape as defined in Claim 3 or 4, and in the case of recording or reproducing, the spot of said light beam tracks successively the side wall surfaces of said V-shaped or inverted-trapezoid-shaped grooves.

Claim 12

An optical disk as set forth in Claim 10 further characterized in that the surfaces of said V-shaped or inverted-trapezoid-shaped grooves are coated or deposited with a thin film of a photosensitive recording medium.

Claim 13

An optical disk as set forth in Claim 11 further characterized in that information is recorded in terms of the variations of the reflexibility or transmittance of said photosensitive recording medium caused by,the exposure thereof to said spot of said light beam.

Claim 14

An optical disk as set forth in Claim 11 further characterized in that information is recorded in terms of local evaporation due to the exposure to said spot of the light beam of said photosensitive recording medium.

Claim 15

An optical disk as set forth in Claim 10 further characterized in that information is pre-recorded on the side wall surfaces of said V-shaped or inverted-trapezoid-shaped grooves.

Claim 16

An optical disk as set forth in Claim 14 further characterized in that said information pre-recorded on each of said side wall surfaces of said V-shaped or inverted-trapezoid-shaped grooves comprises a train of raised or recessed pits; that is, a train of alternately arrayed lands and valleys, so that the light reflected back from each of the raised pits or lands is out of phase with the light reflected back from the exterior thereof; that is, the undisturbed portion.

Claim 17

An optical disk as set forth in Claim 10 further characterized in that the depth of said V-shaped or inverted-trapezoid-shaped grooves are so varied that the variations in said depth alternate between a first and α-second frequency every time when said optical disk makes one complete rotation.

Claim 18

An optical disk as set forth in Claim 10 further characterized in that a first train of tracking control pits of a first frequency is recorded along each of the crests of said V-shaped or inverted-trapezoid-shaped grooves, and a second train of tracking control pits of a second frequency is recorded along each of the bottom lands of said V-shaped or inverted-trapezoid-shaped grooves, said first and second frequencies being different from each other.

Claim 19

An optical disk as set forth in Claim 17 further characterized in that the pits of said first and second trains of tracking control pits exhibit a reflexibility or a transmittance which is different from that which the portions exterior of said pits exhibit.

Claim 20

An optical disk as set forth in Claim 17 further characterized in that the pits of said first and second trains of tracking control pits are in the form of a raised or recessed portion so that the light reflected from said raised or recessed portion is out of phase with the light reflected from the portion exterior thereof.

Claim 21

An optical disk as set forth in Claim 17 further characterized in that first and second light beams are used which can be modulated independently of each other, and said first and second light beams are simultaneously focused on said optical disk in such a way that said first light beam records said first train of tracking control pits of said first frequency along each of said crest lands of said V-shaped or inverted-trapezoid-shaped grooves and said second train of tracking control pits of said second frequency along each of said bottom lands of said V-shaped or inverted-trapezoid-shaped grooves while said second light beam scans or tracks successively said side wall surfaces thereof to record desired information, whereby a prerecorded optical disk with information and tracking control signals prerecorded thereon is provided.