The present invention relates to to an apparatus for recording and/or reproducing user data (such as video signal data and audio signal data) onto and/or from an optical disk which utilizes a laser beam having a wavelength of 680 (nm) or less and a lens system having a numerical aperture (NA) of 0.7 or more and arranged to have a working distance of 560 µm or less so as to enable a relatively large amount of data to be recorded onto the optical disk. Video and/or audio data may be recorded onto and/or reproduced from a number of different types of storage media such as a tape cassette and a so-called digital versatile disc (DVD). However, as hereinbelow described, the tape cassette and the DVD may have disadvantages associated therewith. A video tape cassette for consumer use may have approximately 2 hours of data recorded thereon. Although such recording time may be acceptable for consumer use, the reproduction quality may not always be acceptable. For example, repeated use of a video tape cassette may adversely affect or even destroy data recorded on the respective tape BO that upon reproduction relatively poor quality video/audio data may be provided. Additionally, the video tape cassette may not be conducive for enabling particular functions or operations, such as an easy access function, to be performed by a video tape cassette recorder/reproducer. A rewritable type DVD may have a shape and size approximately similar to that of a compact disc (CD) and may have 2,6 GB of data (such as video and/or audio data) recorded on one face thereof. Such amount of data may only provide approximately 1 hour of recording/reproduction time. Such relatively small amount of time may be unacceptable. For example, such small amount of recording time may necessitate the need for several DVDs to record a single motion picture. As a result, such use of multiple DVDs may be inconvenient for a user or consumer. An apparatus for recording and/or reproducing data onto/from a DVD may utilize a laser beam having a wavelength of 650 (nm) and a lens optical system having a numerical aperture of 0.6. Such apparatus may be operative to provide a number of functions or operations, such as editing, trick play, or the like. Additionally, such apparatus may utilize an effective access technique so as to enable operational modes to be quickly switched. A DVD, used in conjunction with a DVD player, may enable relatively high quality reproduction and may facilitate the operation of a number of functions, such as an easy access function. However, to enable two houre of recording/reproducing time from one side of a DVD (eo as to provide the same recording/reproducing time as with the video tape cassette) and to enable the above functions (editing, easy acces3, and so forth) would require approximately 8 GB of data, whereas, as previously described, a single-sided DVD may only enable 2 . 6 GB of data to be recorded thereon. OBJECTS AND SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk apparatus capable of recording a relatively large capacity data onto an optical disk device. More specifically, it is an object of the present invention to provide an optical disk apparatus in which user data may be recorded onto an optical disk by utilizing an optical head for irradiating a laser beam having a wavelength of approximately 680 (nm) or less to the optical disk and having a lens with a numerical aperture (NA) of approximately 0 , 7 or more and a working distance of approximately 560 (µm) or less. Another object of the present invention is to provide an optical disk apparatus wherein the user data is recorded onto the optical disk as a number of pita or marks in which the shortest pit length or shortest mark length is approximately 0.3 (µm) or less or in which a line record density is approximately 0.23 (µm/bit) or less. A still further object of the present invention is to provide an optical disk apparatus wherein the user data is recorded onto the optical disk with a track pitch of 0.6 {µm) or less . A yet further object of the present invention is to provide an optical disk apparatus wherein the user data may be transmitted for recording onto the optical disk) and for reproduction therefrom with a data transmitting speed of approximately l1 08 Mbps or more. A still further object of the present invention is to provide an optical disk wherein redundant data is added to the ueer data and recorded thereto so as to provide a redundancy of approximately 23% or less. Another object of the present invention is to provide an optical disk which includes a light transmitting layer having a thickness value within a range of 10 through 177 (µm) with a discrepancy of +/- At in which At is defined by ∆t5.26(λ/NA4) (µm) wherein NA is numerical aperture and X is wavelength. A still further object of the present invention is to provide an optical disk rotatably arranged in a cartridge which provides access to the optical disk. Meandering of a groove carrying a guide groove of laser beam is varied successively in steps and a rotational speed of an optical disk is switched successively in steps in correspondence with the period of meandering. A further object of the present invention is to provide an optical disk apparatus wherein .one revolution of the optical diek is divided into a plurality of sectors based on address information which is recorded in a track, and wherein the user data is recorded in the sectors. A further object of the present invention is to provide an optical disk apparatus wherein user data is Recorded on grooves and lands of the optical disk. A still further object of the present invention is to provide an optical disk apparatus having a buffer memory wherein a speed of transmitting the user data for recording onto the optical disk is greater than a speed at which the data is supplied to the buffer memory and/or wherein a speed of transmitting the user data reproduced from the optical disk is greater than a speed at which the data is supplied from the buffer memory. A farther object of the present invention is to provide an optical disk apparatus wherein user data is arranged in predetermined blocks and an error correction code is added thereto, and wherein the user data is recorded to or reproduced from an optical disk in one or more blocks in which a block has 32 or more KB. In accordance with an aspect of the present invention, an optical disk apparatus for recording and/or reproducing user data onto and/or from an optical disk is provided which has an optical head for irradiating a laser beam having a wavelength of approximately 680 (nm) or less to the optical disk and having a lens with a numerical aperture (NA) of approximately 0 . 7 or more and a working distance of approximately 560 (µm) or less. I The present optical disk apparatus may record user data having a spot size approximately one half that of a DVD so as to provide relatively high recording density, As a result, such optical disk apparatus, when utilizing a Partial -Response Maximum- Likelihood (PRML) technique or the like or when the redundancy is reduced by using premastered address having relatively high efficiency and the like, may provide a recording capacity of approximately 8 GB on an optical disk. By setting the working distance to a relatively email value, an optical system may be formed by a lens having a small aperture and a relatively high numerical aperture of 0.7 or more- Further, in this situation, allowable center eccentricity between the lens faces and allowable face angle may be set to practical ranges . As an example, in this situation, when the working distance is set to 560 µM or less, a laser beam may be incident on an object lens with a beam diameter of 4 . 5 (mm) or less which is similar to a value utilized with a DVD. The shortest pit length associated with a DVD may be 0.4 µm. However, by utilizing the present optical disk apparatus with its numerical aperture, the shortest pit length or the shortest mark length may have a value of approximately 0.3 µm. By vising a shortest pit length or shortest mark length of 0,3 µm or less, a recording capacity of approximately 8 GB on an optical disk may be obtained Further, when a so-called (1, 7} RLL modulation technique is applied thereto, a line density of approximately 0.23 µm/bit may be obtained, and when a PRML technique or the like is applied, a line density of approximately 0.23 µm/bit or less may be achieved. With a line density of 0.23 µM/bit, a recording capacity of approximately 8 GB on an optical disk may be obtained. When the above relationships are used, a track pitch may be determined having a value of 0.6 (µm) which still provides a recording capacity of 8 GB. Further, when the data transmitting speed is set to 11.08 (Mbps) or more, a continuous video signal may be recorded and/or reproduced while maintaining sufficient time period in seeking or the like even wherein the recording involves multiplexing an audio signal and a video signal which has been subjected to data compression by a MPEG2 technique in which a rate of 6 Mbps or more is needed for images. Furthermore, user data may be efficiently recorded by adding redundant data BO as to perform a recording operation with a redundancy of 23% or less. When an optical disk is accessed by an optical system having a relatively high numerical aperture, a skew margin of the optical disk may be reduced or compensated for by reducing the thickness of a light transmitting layer. In this situation, stable access may be provided to an optical disk by providing a light transmitting layer with a thickness value within a range of 10 through 177 (µm) with a discrepancy of +/- ∆t in which At is defined by ∆t < 5.26 (X/NA4) µm wherein NA is numerical aperture and X is wavelength. Further, dust or a defect on the surface of the optical disk may have an adverse affect or influence on the data recorded thereon. For example, duet having a size of 100 µm or more may produce a so-called burst error. However, storing such optical disk in a cartridge which enables access to the optical disk for an optical system may prevent or reduce the exposure of the optical disk to dust and the like so as to prevent or reduce adverse affects which may be otherwise caused by dust and the like. Additionally, such cartridge may protect the optical disk from scratches and other types of damage. Furthermore, when meandering of a groove varies successively in steps and a rotational speed of an optical disk switches successively in steps in correspondence with the period of meandering, access may be provided to an optical disk by a so-called Zoned Constant Linear Velocity (ZCLV) technique. As a result, desired data may be efficiently recorded using an information recording face of the optical disk and lowering of access speed may be effectively avoided. Additionally, when one revolution of an optical disk ia divided into a plurality of sectors and user data is recorded in the sectors, access speed thereto may be improved. Further, by recording information on both lands and grooves, an optical disk having a relatively narrow track pitch may be simply fabricated and a tracking error signal may be detected with a satisfactory signal-to-noise (SN) ratio. Furthermore, when the speed of transmitting user data for recording onto an optical disk or the speed of transmitting data reproduced from an optical disk and inputting to a buffer memory is greater than a speed at which the data ie supplied to a buffer memory or the speed at which the data is outputted from the buffer memory, processing of a substitution(s) of a defect sector may be executed and functions such as simultaneous recording and reproducing, postrecording and the like may be performed. Additionally, error correction processing may be improved by performing such processing with a block having a size ""of 32 KB or more. Accordingly the present invention relates to an optical disk apparatus for recording and/or reproducing user data onto and/or from an optical disk, said apparatus having an optical head having a lens with a numerical aperture (NA) of 0.7 or more and a working distance of 560 (µm) or less for irradiating a laser beam having a wavelength of 680 (nm) or less to said optical disk. The subject invention also relates to a disk cartridge for accommodating and optical disk having data recorded thereon by use head wherein said optical disk can be rotated in said disk catridge but cannot be easily removed therefrom, said disk cartridge comprises: an opening extending in a radial direction of said optical disk; and a shutter for closing and exposing said opening when the shutter is respectively moved between first and second positions; wherein said optical head has a lens with a numerical aperture (NA) of 0.7 or more and a working distance of 560 (µm) or less and irradiates a laser beam having a wavelength of 680 (nm) or less to said optical disk. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a diagram of an o ptical disk apparatus according to a first embodiment of the present invention; Pig. 2 is a diagram of a mastering device which may be applied to the optical disk apparatus of Fig. 1; Fig.,3 is a plane view to which reference will be made in explaining zoning by the mastering device of Fig 2; Figs. 4A, 4B, 4C1, and 4C2 arc diagrams showing a constitution of a sector in the zoning of Fig. 3; Fig. 5 illustrates an optical disk formed by the mastering device of Fig. 3; Fig. 6 is a diagram illustrating a drive system of the optical disk apparatus of Fig. 1; Pig. 7 is a diagram of an optical head of the optical disk apparatus of Fig. 1; Fig. 8 is a sectional view of an object lens of the optical head of Fig. 7; Fig. 9 is a diagram of characteristic curves showing a relationship between working distance and beam diameter; Figs. IDA, 10B and IOC are diagrams to which reference will be made in explaining driving of an optical disk by the optical disk apparatus of Fig. 6; Fig. 11 is a flowchart of the processing procedure of a system control circuit in the optical disk apparatus of Fig. 6; Fig. 12 is a diagram of a sector structure which may be uliliued in the optical disk apparatus of Fig. 1; Fig. 13 is a diagram of an ECC block which may be utilized in the optical disk apparatus of Fig. 1; Fig. 14 ie a diagram of a frame structure which may be utilized in the optical disk apparatus of Fig. 1; Fig. 15 is a diagram to which reference will be made in explaining the flow of 2 channels of video signal and audio signal in the optical disk apparatus of Fig. 1; Figs. 16A, 16B, 16C1 and 16C2 are diagrams for explaining a normal recording and reproducing operation of the optical disk apparatus of Fig. 1; Pigs. 17A, 17B, 17C, 17D1, 17D2, 17D3 and 17D4 are diagrams for explaining a follow-up reproduction operation of the optical disk apparatus of Fig. 1; Figs. 18A, 18By 18C and 18D are diagrams for explaining the driving of an optical disk when 2 channels of video signal and audio signal are processed in the optical disk apparatus of Fig. 1; Figs. 19A, 19B, 19C, 19D1, 19D2, 19D3 and 19D4 are diagrams for explaining a multichannel mode operation of the optical disk apparatus of Fig. 1; Figs. 20A, 20B, 20C, 20D1, 20D2, 20D3 and 20D4 are diagrams for explaining a postrecording operation of the optical disk apparatus of Fig. 1; Fig, 21 ie a diagram showing external devices which may be used in postrecording; Figs. 22A1, 22A2, 22A3, 22B and 22C are diagrams for explaining a pointer reproduction operation of the optical disk apparatus of Fig. 1; Fig. 23 is a plane view for explaining access to an optical disk in respective zones; Fig. 24 is a diagram of a relationship between dust and buret error; Fig. 25 is a disassembled perspective view of a cartridge for an optical disk which may be utilized by the optical disk apparatus of Fig. 1 in which a shutter is omitted; Fig. 26 is a plane view showing a relationship between an opening and a sheet-like member of the cartridge of Pig. 25; Fig. 27 is a perspective view showing a relationship of a shutter or the like of the cartridge of Fig. 25; Fig. 28 is a plane view showing a relationship among the shutter, the opening and a damper member of the cartridge of Fig. 25; Fig. 29 is a plane view for explaining a movability restricting mechanism of the cartridge of Fig. 25; Fig, 30 ia a plane view showing a state in which a button 70A is pressed in comparison with Fig. 29; Fig. 31 is a plane view showing a state in which a button 71A is pressed in comparison with Fig. 30; Fig. 32 is a plane view showing a state in which the shutter is made movable in comparison with Fig. 31; Fig. 33 is a plane view for explaining a movability restricting mechanism of the cartridge of Fig. 25; Fig. 34 is a plane view showing a state in which a button 7QB is pressed in comparison with Fig. 33; Fig. 35 is a plane view showing a state in which the shutter is made movable in comparison with Fig. 34; Fig. 36 is a perspective view showing a loading mechanism of an optical disk apparatus; Fig. 37 is a diagram for explaining identification of an optical disk in an optical disk apparatus; Fig. 38 is a diagram of a mastering device according to another embodiment of the present invention; Fig. 39 illustrates a format of wobble data; Figs. 4QA, 40B, 40C, 40D, 40E and 40F are signal waveform diagrams for explaining the forming of a wobble signal r- Figs. 41A, 41B and 41C are signal waveform diagrams to which reference will be made in explaining the formation of a wobble signal; Fig. 42 is a diagram of an optical disk apparatus for use with an optical disk fabricated with the mastering device of Fig. 38; Figs, 43A and 43B are signal waveform diagrams for explaining the forming of clock by the optical disk apparatus of Fig. 42; Fig. 44 is a plane view of an optical disk for explaining the driving of the optical disk by the optical disk apparatus of Fig. 42; Fig, 45 illustrates a diagram of a frame structure which may be utilized in the optical disk apparatus of Fig. 42; Fig. 46 illustrates a diagram for explaining the use of a cluster of data in the optical disk apparatus of Fig. 42; Fig. 47 is a diagram of a mastering device according to another embodiment of the present invention; Figs. 48A, 48B.1, 48B2, 48C, 4BD and 48E are diagrams for explaining wobble data by the mastering device of Fig. 47; Figs. 49A, 49B, 49C, 49D, 49E and 49F are signal waveform diagrams for explaining processing of a wobble signal by the mastering device of Fig. 47; Fig. 50 is a diagram of an optical disk apparatus for use with an optical disk fabricated with the mastering device of Fig. 47; Fig. 51 is a diagram of a wobble signal processing circuit of the optical disk apparatus of Fig. 50; Figs. 52A, 52B, 52C, 52D, 52E, 52F, 52G, 52H and 521 are signal waveform diagrams for explaining an operation of the wobble signal processing circuit of Fig, 51; Figs. 53A, 53B, 53C, 53D, 53E, 53F, 53G and 53H are signal waveform diagrams for explaining an operation of the wobble signal processing circuit of Fig. 51; Figs. 54A, 54B, 54C, 54D1, 54D2 and 54D3 are diagrams for explaining a multichannel mode operation of the optical disk apparatus; Fig. 55 is a plane view of an optical disk for explaining a sector arrangement by the mastering device according to an embodiment of the present invention; Fig. 56 is a plane view of an optical disk for explaining a sector arrangement by a mastering device according to an embodiment of the present invention; Fig. 57 is a plane view of an optical disk for explaining a sector arrangement by a mastering device according to an embodiment of the present invention; Fig. 58 is a plane view of an optical disk for explaining a sector arrangement by a mastering device according to an embodiment of the present invention; and Fig. 59 illustrates an optical disk device to which reference will be made in explaining data transmission rates, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed explanation will now be provided of embodiments of the present invention with reference to the accompanying drawings. Fig. 2 is a diagram of a mastering device 1 according to a first embodiment of the present invention. As hereinbelow more fully described, an optical disk may be fabricated by use of an original disk 2 which may be formed by exposing a laser beam thereon with the use of the mastering device 1. The original disk 2 may have a coating resist on the surface of, for example, a glass substrate. Such disk may be rotated by a spindle motor 3 with a constant angular velocity, in accordance with the mastering device 1. An optical head 4 may irradiate a laser beam L to the original disk 2 in such a manner so as to be displaced successively from an inner peripheral side to an outer peripheral side of the original disk in synchronism with the rotation of the original disk by a predetermined threading mechanism. As a result, the optical head 4 may form a track in a spiral shape from the inner peripheral side to the outer peripheral side of the original disk 2. In this case, the optical head 4 is controlled by the threading mechanism to move or displace the beam approximately 1.0 (µm) in a period in which the original disk 2 is rotated one rotation. As such, in the case of so-called land and groove recording, a track may be formed having a track pitch of approximately 0.5 (µm) . Incidentally, such track pitch in the case of land and groove recording is 1.48 times as much as the track pitch used in a DVD (which may be 0.74 µm) . By utilizing the mastering device 1, desired data may be recorded on an optical disk formed from the original disk 2 with a line record density of about 0.21 (µm/bit) . As a result, 8 (GB) or more of data may be recorded on an optical disk by the following relationship. 4.7 x ((0.74 x 0.267)/(0.5 x 0.21)) > 8 ... (1) Incidentally, in Equation (1) , numeral 4.7 indicates recording capacity (GB) of a DVD ROM or read only type DVD and numeral 0.74 and numeral 0.267 indicate a track pitch (µm) and a line record density (µm/bit) of DVD. Accordingly, a recording capacity by data processing the same as that of DVD is shown in Equation (1). Further, in forming an optical disk, the optical head 4 may set the spot diameter of the laser beam L such that the width of a groove formed by exposure of the laser beam L and the width of a land between contiguous grooves are substantially equal. Further, the spot shape and the amount of light of the laser beam are set such that an effective exposure x-ange by the laser beam may be increased by about 120 (%) with regard to the width of the groove of a final target. Therefore, the optical head 4 may expose the original disk 2 to the laser beam such that an optical disk fabricated therefrom may have land and groove recording. Further, the optical system or the optical head 4 may be movable along a radial direction of the original disk 2. A drive circuit 5 may drive the optical head 4 in accordance with a drive signal SD received from a synthesizing circuit 8. In such situation, the drive circuit 5 may switch the condition in which the optical head 4 is driven in accordance with a position in which the laser beam is irradiated with a timing synchronized to the rotation of the original disk 2, in which the original disk 2 may be arranged or zoned as illustrated by Pig. 3. Incidentally, grooves and lands of the disk 2 are also illustrated in Fig. 3. That is, the mastering device 1 may successively form a track on the original disk 2 such that a region having a radius of 24 (mm) through 58 (mm) may be set to an information recording face of an optical disk having a diameter of 120 (mm) which is substantially equal to that of a compact disk. In this case, the drive circuit 5 may switch the condition in which the optical head 4 is driven such that a sector structure may be formed by dividing the information recording face into radially shaped regions. Further, by successively changing in steps the timing of the switching from the inner peripheral side to the outer peripheral side, a number of zones ZO through Zn may be formed by dividing the information recording face in shapes of concentric circles. Thereby, the drive circuit 5 forms a number of sectors on one track in the zone ZO at the innermost periphery and the number of sectors on one track is increased by 1 in accordance with successive displacement to zone 21, .... on the outer peripheral side. Marks A and B indicate boundaries of sectors which are magnified in Fig. 3. At such sector boundaries, the front of each sectoi- is allocated to an addrese area AR2 and a successive remaining area AR1 is allocated to a user area. The drive circuit 5 under control of a system control circuit (not shown) may move or displace the position of the irradiating laser beam in the user area ARl in accordance with the drive signal so such that grooves are formed to meander in the user area ARl. Further, in. an initial portion of the address area AR2, the displacement of the position of the irradiating laser beam may be interrupted and the light amount of the laser beam may be intermittently increased by the drive signal SD whereby a pit row may be formed on a track center formed by a groove. Further, at a later portion of the address area AR2, the position of the irradiating laser beam may be displaced onto the track center formed by a land on the inner peripheral side and the light amount of the laser beam may be intermittently increased by the drive aignal SD by which a pit row is formed on the track center formed by the land. Therefore, the drive circuit 5 may perform a recording operation by forming a pit row on a track center in correspondence with the address data of the sector formed by a succeeding groove at the earlier or initial half of the address area AR2 and may perform a recording operation by forming a pit row on a track center iti correspondence with the address data of the sector formed by a succeeding land on the inner peripheral side at the later half of the address area AR2. Furthermore, when an optical disk is to be fabricated from the original disk 2, the drive circuit 5 may control the light amount of the irradiating laser beam such that the depths of the pits and grooves have a value or values which are approximately equal to 1/6 through 1/5 wavelength of the laser beam (which may have a wavelength of 650 (nm)). Additionally, the groove may have an amplitude or width of approximately 15 through 30 (nm). A wobble signal generating circuit 7 may generate a sine wave signal having a predetermined frequency in synchronism with the rotation of the original disk 2 as a wobble signal (WB) and may supply the same to the synthesizing circuit 8. Moreover, the wobble signal WB may be obtained by increasing the frequency successively in steps in correspondence with the zoning arrangement described above with regard to Fig. 3, As a result, the wobble signal WB from the wobble signal generating circuit 7 may cause the position of the irradiating laser beam to be displaced such that the groove may meander or vary for 397 periods per one sector. In this way, a length corresponding to 5 periods of the groove may be allocated to the address area (header area) AR2, the groove may be formed to meander or vary for 3573 periods at the track of the zone ZO on the innermost periphery and the meandering of the groove may successively increase by 397 periods per one track in accordance with a shift of the zone on the outer peripheral side. Further, 25 bytes of data may be allocated to the user area ARI in one meandering period of the groove and such one period may have a length of about 42 (//m) . An address signal forming circuit 6 may form an address signal SA whose value may change successively in accordance with the displacement of the optical head 4 as controlled by the system control circuit and may supply the formed address signal SA to the synthesizing circuit 8. More particularly, the address signal forming circuit 6 may receive a timing signal (such as a - frequency generating (FG) signal or the like) in synchronism with the rotation of the original disk 2 by the spindle motor 3 or the like and may perform a counting operation on the timing signal by a predetermined counter. The address signal forming circuit 6 may form a sector header in a first or an earlier half and in a second or later half of the address area AR2, as shown in Figs. 4A, 4B, 4C1 and 4C2. As shown therein, the header may include sector marks SM, timing data for synchronization VFO, address marks AM, address data ID, and a postamble PA. Each sector header may have 61 bytea of data and the address area AR2 may have 8 Kbytes. (The numbers shown in Figs. 4B, 4C1 and 4C2 indicate numbers of bytes.) The sector mark SM may indicate the start of the sector head and may have 4 bytes of data. The synchronization timing data VFO areas may be utilized in locking a phase-locked loop (PLL) circuit in the optical disk device and may have 26 bytes and 16 bytes, respectively, from the front side. The address mark AM is a synchronization signal of address and may have 1 byte. The address data ID may provide an indication of the position of the irradiating laser beam and may have 6 bytes, 2 bytes of which constitute an error detection code. The same data may be recorded twice for the address data ID so as to improve the reliability thereof. The postamble PA may be arranged or utilized in setting the polarity of a signal and may have one The address signal forming circuit 6 may convert the sector header formed as mentioned above into a serial data row and may modulate the serial data row in a predetermined manner and may output the modulated signal as the address signal SA. The address signal forming circuit 6 may output the address signal SA with a timing corresponding to the scanning of the laser beam L. The synthesizing circuit 8 may receive the wobble signal WB and the address signal SA and may synthesize the same to form the drive signal SD comprising a displacement signal for displacing the optical system of the optical head 4 and a light amount control signal for controlling the light amount of the laser beam and may output such signal or signals to the drive circuit 5. Therefore, in an optical disk formed by the original disk 2, the information recording face may be divided into shapes of concentric circles and pref orrnatted such that the number of sectors is gradually increased from zones on the inner peripheral side toward zones on the outer peripheral side. Further, the address area AR2 may be formed at the front of each sector, in which the address of the sector of a succeeding groove and the address of the sector of a succeeding land are recorded in the address area AR2, and desired data may be recorded in the succeeding user area AR1 . As shown in Fig. 4B, the user area ARl includes an interposing gap of a byte, a guard of 24 bytes, a VFO of 25 bytes, 2 synchronization bytes, 9672 bytes of user data, a postamble (PA) of 1 byte, a guard of 52 bytes, and a buffer of 16 bytes which may be arranged successively as shown therein. The gap is a region which may be utilized for switching lands and grooves and/or for switching the amount of laser beam. The guard may be used to restrain fluidity of record material by overwriting and promote overwriting cycle of the record area when a so-called phase change media are used as record media, The synchronization byte may be used to lock a PLL circuit in the optical disk device, the postamble may be used in setting the polarity, and the buffer is a redundant area of the record area for absorbing jitter by eccentricity or the like, Fig. 5 illustrates a perspective view of an optical disk formed by the original disk 2 and a sectional view showing a section of the optical disk obtained by cutting the optical disk at a portion of a groove. The optical disk may have a thickness of 1.2 (mm) and with the phase change type optical disk, an information recording face may be formed by successively forming an aluminum film, a ZnS-Si02 film, a GeSbTe film and a ZnS-SiO2 film on a disk substrate- In the case of a magneto-optical disk, an information recording face may be formed by successively forming an aluminum film, a SiN film, a TbFeCo film and an 3iN film on a disk substrate. In the case of a write once type disk, an information recording face may be formed by successively forming a film sputtered with aluminum or gold and a predetermined organic pigment film on a disk substrate. Further, a light transmitting face for transmitting a laser beam and leading the laser beam to the information recording face may be formed on the information recording face and may have a thickness of about 0.1 (mm). Thereby, with such optical disk, even when a laser beam is irradiated from an optical system having a high numerical aperture via the light transmitting face, desired data may be recorded to or reproduced from the information recording face so as to effectively avoid an influence due to skew. Incidentally, such optical disk may have a diameter of 120 (mm) and may be arranged such that a region having a radius of from 24 (mm) through 58 (mm) is allocated as a recording region. Further, the optical disk may be stored and held in a predetermined cartridge formed to enable the kind of the optical disk contained therein to be identified and formed to be usable with an optical disk device such that when access is made by the optical system having a high numerical aperture dust or the like may be effectively avoided. A phase change type optical disk may be formed so as to enable desired data to be recorded by locally changing the crystal structure of the information recording face by irradiating a laser beam or may be formed to enable recorded data to be reproduced by detecting a change in an amount of return -light. Further, in the case of a magneto-optical disk, such disk may be formed such that desired data can be thermomagnetically recorded by applying a magnetic field at the position of irradiating laser beam and such that recorded data can be reproduced by utilizing a magnetic Kerr effect by detecting a plane of polarization of return light. In the case of a write once type disk, such disk may be formed such that desired data can be recorded by locally destructing the information recording face by irradiating a laser beam and such that recorded data can be reproduced by detecting a change in the amount of return light. In these cases, with respect to the optical disk, in respective zones, the original disk 2 may be driven to rotate under a condition of constant angular velocity, the frequency of the wobble signal may be switched successively in steps and the groove may be formed by the wobble signal WB. As a result, the optical disk is zoned and in each zone, the period of meandering the groove converted into a rotational angle of the optical disk may be formed constant. Further, two kinds of optical dieks may be fabricated, one where the information recording face is formed only on one face thereof and another where an information recording face is formed on both faces. The optical diek where the information recording face is formed on both faces thereof may be fabricated by pasting together optical disks which are fabricated from thin disk substrates with a thickness of 1.2 (mm) and a thickness of each light transmitting layer of 0.1 (mm). Fig. 6 is a diagram of a processing system of a wobble signal for an optical disk device for making an optical disk mentioned above. According to the optical disk device 10, a laser beam may be irradiated from an optical head 11 to an optical disk 12 and return light may be received. That is, as shown by Fig. 7, in the optical head 11, a semiconductor laser 13 may emit a laser beam having a wavelength of 650 (nm) in accordance with a predetermined drive or control signal SL. In a reproducing operation, the semiconductor laser 13 may emit a laser beam with a constant light amount. By contrast, in a recording operation, a laser beam may be emitted while intermittently increasing the light amount and pits or marks may be formed on an information recording device of the optical disk 12 by increasing the light amount of laser beam. A collimator lens 14 successive thereto converts the laser beam emitted by the semiconductor laser 13 into a parallel ray, a shaping lens 15 successive thereto corrects astigmatism of the laser beam and the laser beam is emitted to an object lens 17 after being transmitted through a beam splitter 16. The object lens 17 may converge the laser beam onto the information recording face of the optical disk 12 and may receive return light therefrom. In the optical disk device 10, when the optical disk 12 is an optical disk exclusively for reproduction, data recorded on the optical disk 12 can be reproduced in accordance with a change in an amount of return light. Further, when the optical disk 12 is a phase change type optical disk, desired data may be recorded by locally changing the crystal structure at the position of irradiating laser beam and recorded data can be reproduced in accordance with a change in the amount of return light. Further, when the optical disk 12 is a write once type optical disk, desired data may be recorded by locally destructing the position of irradiating the laser beam and recorded data can be reproduced in accordance with a change in the amount of return light. By contrast, when the optical disk 12 is a magneto-optical disk, a modulation coil 18 arranged at the proximity of the object lens 17 may be driven by a predetermined drive circuit 19 and a predetermined modulation magnetic field may be applied at the position of irradiating laser beam by which desired data is recorded by applying a method of thermomagnetic recording and recorded data can be reproduced by detecting a change in a plane of polarization of the return light. The beam splitter 16 may transmit a laser beam incident from the shaping lens 15 and may emit a laser beam to the object lens and, additionally, the beam splitter 16 may reflect return light incident from the object lens l"7 and may separate the optical path and emit return light to a beam splitter 20. The beam splitter 20 may separate the return light into two streaks of light fluxes by transmitting and reflecting the return light. Return light reflected by the beam splitter 20 is incident on a lens 21 which converts the return light into a converging light flux. A cylindrical lens 22 provides astigmatism to the return light emitted from the lens 21. An optical detector 23 receives return light emitted from the cylindrical lens 22. The optical detector 23 can divide a light receiving face into predetermined shapes and can output light receiving results of divided respective receiving faces. Thereby, the optical detector 23 may detect a reproducing signal RF where the signal level is changed in accordance with the amount of return light, a push pull signal PP where the signal level is changed in accordance with a displacement of the position of irradiating laser beam in respect of a groove or pit row and a focus error signal FE where the signal level ie changed in accordance with a defocus amount by converting light receiving results of the respective light receiving faces in current to voltage by a current to voltage converting circuit and thereafter performing addition and subtraction operation by a matrix circuit . Additionally, return light which has been transmitted through the beam splitter 20 may be incident on a 1/2 wavelength plate 25 which may change the plane of polarization of the return light. A lens 26 converts the return light emitted from the 1/2 navelength plate into converging light flux. A polarized beam splitter 27 reflects a predetermined polarization component and transmits the remaining component by which the light is separated into two streaks of light fluxes where the light amounts are changed complimentarily in accordance with the plane of polarization. Optical detectors 28 and 29 respectively receive the two streaks of light fluxes separated by the polarized beam splitter 27 and output light receiving results or signals in which the signal levels are changed in accordance with the amounts of receiving light. A differential amplifier 30 outputs a reproducing signal MO having a signal level which may be changed in accordance with the plane of polarization of return light by providing a result of differential amplification by the light receiving results of the two optical detectors 28 and 29 via a current to voltage converting circuit. Thereby, the optical head 11 can record desired data and reproduce recorded data with various kinds of the optical disks 12. Fig, 6 is a sectional view of the object lens 17 in the optical head 11. As shown therein, the object lens 17 may include a first lens 17A and a second lens 17B, in which the first lens 17A and the second lens 17B may be formed by nonspherical plastic lenses or glass molds and may be movable by a drive actuator 17D upwardly, downwardly, leftwardly and rightwardly as viewed onto Fig. B. Thereby, in the optical disk device 10, tracking control and focus control can be carried out by integrally moving the first lens 17A and the second lens 17B. Further, the second lens 17B on the incident side of a laser beam may be formed with a comparatively large aperture whereas the first lens 17A on the side of the optical disk 12 may be formed with a small aperture and respective focal lengths and an interval therebetween may be set to provide a total numerical aperture of 0.78 of the object lens 17. The object lens 17 may satisfy the following relationships in which X designates a wavelength of a laser beam, NA designates a numerical aperture of the object lens 17, t designates a thickness of the light transmitting layer of the optical disk 12, At designates dispersion of t, and 0 designates a skew margin of the optical disk 12: 0E± 84.115 X (λ/NA3/t) (2) ∆t=<±5.26 x (λ/NA4) (µm) (3) Here, Equation (2) shows a relationship between the skew margin capable of stably providing access to an optical disk and an optical syetcm (Japanese Unexamined Patent Publication No. JP-A-3-22S65Q). A compact disk or the like may have a skew margin 8 of about 0.6. Further, the skew margin 0 may be sec to 0.4" for a DVD. In the optical disk 12, even when the thickness of the light transmitting layer is set to 0.1 (mm) and the numerical aperture NA of an optical system is set to a large valuet sufficiently stably access can be made to the optical disk 12. Further, Equation (3) shows a dispersion of the thickness t of the light transmitting layer allowable to an optical system in which the constant 0,526 is a value calculated in reference to a compact disk. At may have a value of ±100 (µm) for a compact disk and ±30 (µm) for a DVD. Thereby, in the optical disk device 10, even when the thickness of the light transmitting layer is dispersed, access can be stably made to the optical disk 12. The optical head 11 may satisfy the following relationship by irradiating a laser beam having a wavelength of 650 (nm) to the optical disk 12 via an optical system having a numerical aperture of 0.78-. 8 = 4.7 x [ (0.65/0.60) (NA/A)]2 .... (4) Incidentally, in the above equation, numeral 4.7 indicates the recording capacity (GB) of DVD and numeral 0.65 and numeral 0.6 respectively indicate the wavelength of a laser beam and numerical aperture of an optical system for a DVD. Thereby, by using the optical head 11, a recording capacity of about 8 (GB) can be secured by processing data by a format similar to that of a DVD. In the object lens 17, the first lens 17A is arranged so as to project to the side of the optical disk 12 and to have a working distance DW for the numerical aperture. Further, characteristics and arrangements of the first lens 17A and the second lene 17B may be selected, the working distance DW may be set to about 560 (µm) by which according to the optical head 11, eccentricity allowance between lens faces, face angle allowance and the radius of curvature of the object lens 17 can be set to ranges whereby mass production can be efficiently carried out, the total shape can be downsized and/or collisions with the optical disk can effectively be avoided. That is, as shown by Fig. 9, when the numerical aperture is increased in the case where the same beam diameter of a laser beam is maintained, it is necessary to arrange the object lens proximate to the information recording face of the optical disk by that amount. Incidentally, in Fig. 9, the working distance is shown with the thickness of the light transmitting layer as 0. Therefore, if the optical head is arranged to provide a sufficient interval to the optical disk, the beam diameter of laser beam may be increased significantly in comparison with other systems. By contrast, the beam diameter of the laser beam of a DVD system may be about 4.5 (mm) , which may be an upper-limit value of the present system. When the optical head is arranged in close proximity to the optical disk, the beam diameter of the laser beam may be reduced by a corresponding amount- In such situation, the shape of the optical system may be reduced. To ensure that high accuracy formation is obtained, the object lens should be accurately fabricated and arranged. Further, the system should be arranged to avoid a collision between the optical head and the optical disk. Therefore, according to the present embodiment, the working distance DW is set to about 560 (/xm) and these conditions are satisfied. The lens face of the first lens 17A on the side of the optical disk 12 may be formed to have a flat shape which enables focus control to be readily carried out and even when the optical disk 12 is skewed, the lens may be prevented from colliding with the surface of the light transmitting layer. Further, the diameter of the object lens .17 on the side of the optical disk 12 may be reduced in steps and the lens face on the aide of the optical disk 12 may have a small diameter sufficient for leading a laser beam to the optical disk 12, The modulation coil IB may be arranged to surround the front end side of the first lens 17A and such that the side face on the side of the optical disk 12 is substantially flush with the lens face of the first lens 17A. As such, the modulation coil 16 is arranged as close as possible to the optical disk 12 within a range not projected from the lens face of the first lens 17A and is capable of applying a modulated magnetic field efficiently at the position of irradiating laser beam. Further, temperature rise due to the modulation coil 18 may be reduced by a heat radiating plate 17E arranged on the side of the lens. As a result/ various characteristic changes caused by a temperature rise can be restricted to acceptable ranges. According to the optical disk device 10 (Fig. 6}, a spindle motor 33 may drive or rotate the optical disk 12 under the control of a system control circuit 34. In a normal operational mode, the spindle motor 33 may drive or rotate the optical disk 12 such that the frequency of a reading/writing clock R/W CK formed by a phase-locked loop (PLL) circuit 35 becomes constant by which, as shown by Figs. IDA, 10B and IOC, the optical disk 12 may be driven or rotated by a so-called "Zone Constant Linear Velocity" (ZCLV) method. Further, in this case, the ZCLV zoning may correspond to the zoning explained with reference to Fig, 3. That is, the spindle motor 33 may switch the rotational speed of the optical disk 12 successively in steps in accordance with the position of irradiating laser beam (Fig. IDA), by which according to the optical disk device 10, the linear speed and the line record density are not significantly varied between the inner peripheral side and the outer peripheral side thereby promoting the record density (Figs. 10B and IOC) and effectively avoiding or preventing a reduction of access speed. By contrast, in a special operational mode such as postrecording or the like, the spindle motor 33 may drive or rotate the optical disk 12 with a predetermined rotational speed under the control of the system control circuit 34. A threading motor 36 may move the optical head 11 in a radial direction of the optical disk 12 under control of the system control circuit 34. Such motor may enable a seeking operation to be carried out. An address detecting circuit 37 may receive the reproducing signal RF having a signal level which may change in accordance with the amount of return light from the optical head 11 and may binarize the reproducing signal RF. Further, address data ID may be detected from the binarized signal with a synchronization signal allocated to the sector head as a reference and may be outputted to the system control circuit 34 and the detected timing may also be provided to a cluster counter 38. Thereby, in the optical disk device 10, the position of irradiating laser beam can be specified on the basis of the address data Preformatted to the optical disk 12 by the system control circuit 34 and the timing of the sector can be confirmed by the cluster counter 38. Further, the address detecting circuit 37 may perform error detection processing by use of an error detection code allocated to each address data ID and may selectively output the address data ID which is determined to be correct. A push pull (PP) signal may be supplied from the optical head 11 to a band-pass filter 39A of the wobble signal detecting circuit 39 so as to sample or obtain a wobble signal WB. Farther, the wobble signal detecting circuit 39 may binarize the wobble signal WB with 0 level as a reference whereby edge information of the wobble signal WB may be sampled in a comparing circuit (COM) 39B. A wobbling period detecting circuit 40 may receive a binarized signal SI and may determine whether the wobble signal WB has changed by a correct period by determining or comparing timing of a corresponding edge with the timing of each edge of the binarized signal SI as a reference. Further, the wobbling period detecting circuit 40 may output edge information which has been selectively determined to have a correct period to the PLiL circuit 35. Thereby, the wobbling period detecting circuit 40 may prevent the clock CK from being displaced or adversely affected by dust or the like which may be on the optical disk 12. The binarized signal outputted from the wobbling period detecting circuit 40 may be supplied to a phase comparing circuit (PC) 35A of the PLL circuit 35 so as to compare the phase of the binarized signal with the phase of the clock CK outputted from a divider 35B. The predetermined clock CK may be obtained and/or outputted from the divider 35B by switching a dividing ratio set by the system control circuit 34. A low frequency component obtained as a result of the phase comparison outputted from the phase comparing circuit 35A may be sampled by a low pass filter (LPF) 35C and an output therefrom may be supplied to a voltage control type oscillating (VCO) circuit 36D so as to control the oscillation frequency thereof. Further, an oscillating output of the voltage control type oscillating circuit 36D may be divided by the divider 35B so as to form the high accuracy clock CK. With regard to the divider 35H, by setting the system control circuit 34 in correspondence with zoning which has been explained in reference to Fig. 3, the dividing ratio may be set to successively increase in accordance with the displacement of the position of irradiating laser beam to the outer peripheral aide of the optical disk 12. Thereby, in the PLL circuit 35, in accordance with the displacement of the position of irradiating laser beam to the outer peripheral side of the optical disk 12, successively in steps, the frequency of the oscillating output of the voltage control type oscillating circuit 36D may be increased compared with the frequency of the wobble signal WB and the oscillating output may be outputted as the clock R/W CK for writing and reading. In the normal operational mode of the optical disk device 10, by driving or rotating the optical disk 12 with the spindle motor 33 such that the frequency of the clock R/W CK for reading and writing becomes constant and by recording desired data with the clock R/W CK for reading and writing as a reference, the line record density may be prevented from changing significantly between the inner peripheral side and the outer peripheral side and, as a result, the record density may be increased. The cluster counter 38 counts the clock R/W CK for reading and writing with the detection result from the address detecting circuit 37 as a reference by which the laser beam irradiating position is specified with high accuracy by referring to the clock R/W CK for reading and writing. Further, based on the result of such counting, the cluster counter 38 may obtain and/or output a cluster start pulse to the system control circuit 34. Here, a cluster is a unit for recording and reproducing data to and from the optical disk 12 and the cluster start pulse is a pulse for instructing or identifying the timing or start of the cluster. When the cluster counter 38 cannot detect the timing or starting of the sector from the address detecting circuit 37 due to, for example, dust or the like on the surface of the disk, the cluster counter 38 may interpolate the cluster start pulse by a synchronization processing with the counting result of the clock R/W CK for reading and writing as a reference. The system control circuit 34 may include a computer for controlling an operation or operations of the optical disk device 10. For example, such control circuit may control the operation of the threading motor 36 or the like on the basis of the successively inputted address data ID and may control an overall operation by switching the operational mode in accordance with the laser beam irradiating position and/or in accordance with an input from an external device. Further, during processing, the system control circuit 34 may switch the dividing ratio of the divider 35B by use of dividing ratio data stored in a memory 42 in accordance with the laser beam irradiating position with the address data ID as a reference. The system control circuit 34 may reduce the rotational speed of the optical disk successively in steps from zones on the inner peripheral side toward zones on the outer peripheral side to be in correspondence with the zones ZO, 21, ...., Zn.t and Z0 explained above in reference to Fig. 3 and may cause an equal record density for each sector to be provided in respect of zones on the inner peripheral side and zones on the outer peripheral side. On the other hand, in a special operational mode such as postrecording or the like where recording and reproducing processings are repeated alternately in respect of user data DU1 and DU2 of 2 channels or where the user data DU1 and DU2 of 2 channels are alternately reproduced from the optical disk 12 and are outputted concurrently, the system control circuit 34 may control the operation of a spindle servo circuit such that the rotational speed of the optical disk 12 is not switched even if zones are switched for reproducing user data. Thereby, in the case where recording and reproducing processings are alternately repeated, in the reproducing operation, the system control circuit 34 may reproduce user data DCJ at the rotational speed of the optical disk 12 in a recording operation immediately before the reproducing operation even when zones are switched. Further, in the case where the user data DUl and DU2 of 2 channels are alternately reproduced from the optical disk 12 and outputted concurrently, one user data may be reproduced from the optical disk 12 in a state where the optical disk 12 is driven to rotate at the rotational speed in reproducing the other user data. Further, in these cases, with regard to a channel on the recording side and a channel on other reproducing side, the system control circuit 34 may record and reproduce the user data by driving the optical disk 12 to rotate at a rotational speed twice that which may be set with respect of the corresponding zones by applying the ZCLV method. During operation of the optical disk device, a time period may be necessary to stabilize the rotational speed when the rotational speed of the optical disk is switched. Accordingly, the optical disk device 10 may switch a recording and reproducing operation only with await time or the like needed for locking the PLL circuit in a period of time which may be significantly shorter than that in switching the rotational speed by omitting the time period necessary for switching the rotational speed of the optical disk 12. In this case, the rotational speed of the optical disk 12 may be set to about twice the rotational speed in the normal operational mode in the ZCLV control applied to a channel on the recording side and a channel on the other reproducing side. Thereby, in processing user data of 2 channels, the system control circuit 34 may record and reproduce the user data DU to and from the optical disk 12 at high speed and intermittently and a time period sufficient for seeking operation or the like or processing of the other channel can be realized, Fig. 11 is a flowchart showing a processing involved in the setting of the rotational speed of. the optical disk in the system control circuit 34. According to the system control circuit 34, when a user selects the operational mode, the operation proceeds from step SPl to step SP2 where a determination is made as to whether the operational mode selected by the user is the above-described operational mode of post recording or the like and when a negative result is obtained, the operation proceeds step SP3 , Here, according to the system control circuit 34, after setting the operational mode of the spindle servo circuit to a ZCLV operational mode, the operation proceeds to step SP4 and the processing procedure is finished. On the other hand, when the operational mode selected by the user is the above-described operational mode of postrecording or the like, as indicated by an affirmative result in step SP2, the operation of the system control circuit 34 proceeds to step SP5 . Here, the system control circuit 34 stops switching the rotational speed (that is, sets operational mode to CAV) as, for example, that which may occur with respect to a channel on the repx'oducing side when 2 channels are respectively recorded and reproduced and with respect to either channel when 2 channels are respectively reproduced. The operation of the system control circuit 34 may then proceed to step SP6 so as to set the ZCLV operational mode at the above-described rotational speed for the spindle control of a remaining channel and thereafter, the operation proceeds to step SP4 whereupon the processing is terminated. In the state where the rotational speed of the optical disk .12 is controlled as described above, the system control circuit 34 may allocate data of 1 cluster to 4 continuous sectors with the address areas AR2 set to the respective sectors as references by executing control of writing and reading in accordance with the cluster start pulse outputted from the cluster counter 38. Thereby, the system control circuit 34 may increase the numbers of clusters successively allocated to respective zones from zones on the inner peripheral side toward zones on the outer peripheral side, Further, the system control circuit 34 may instruct or control a tracking servo circuit to switch the movable direction of the object lens 17 in respect of the polarity of the tracking error signal by which the scanning of a laser beam is controlled to switch between a groove and a land between grooves. As a result, the optical disk device 10 may perform so-called land and groove recording. Fig. 1 is a diagram of a recording and reproducing system of the optical diek device 10. In the optical disk device 10, a disk discriminator 50 identifies the kind or type of optical disk which is being utilized by, for example, recess portions formed in a cartridge and outputs an identification number or result to the system control circuit 34. The optical disk device 10 is adaptable for use with a number of types of optical disks and switches the operation of the recording and reproducing system in accordance with the type of loaded optical disk. An encoder 51 may receive an input signal SIN which may comprise a video signal and/or an audio signal from an external device in recording, editing or the like and may process the video signal and audio signal in an analog to digital conversion processing and subject them to data compression by a format prescribed in MPEG (Moving Picture Experts Group). Further, the encoder 51 may form the data-compressed video signal and audio signal in buckets and may add a bucket header, control data and the like to each bucket. The encoder 51 may subject the data-compressed video signal and audio signal to time division multiplexing by successively oxitputting these buckets to form a bit stream user data DU. The encoder 51 may be able to concurrently process 2 channels of video signals and audio signals and concurrently output 2 channels of user data DU1 and DU2 in correspondence with the 2 channels of video signals and audio signals and may concurrently execute the processing of the 2 channels as necessary by control of the system control circuit 34 . In a manner somewhat opposite to that of the encoder 51, a decoder 52 may form a digital video signal and/or a digital audio signal by subjecting the user DU outputted from a recording and repz-oducing ciz-cuit 53 to data expansion by a format prescribed in MPEG in reproducing and editing, and may convert the digital video signal and the digital audio signal into an analog signal SOUT and oxitput the same. Similar to the encoder 51, the decoder 52 may be able to concurrently execute decoding processings of 2 channels of video signals and audio signals SOUT 1 and SOUT2 and may concurrently execute the processing of 2 channels as necessary by switching operation under control of the system control circuit 34. The recording and reproducing circuit 53 may store the user data DU outputted from the encoder 51 to a memory 5v in recording and editing and may record the user data DU to the optical disk 12 by processing it by a predetermined block unit. That is, as shown by Fig. 12, the recording and reproducing circuit 53 may successively block the user data DU in a unit having 2048 bytes and may add address data and error detection code having 16 bytes to each block. To form a sector data block having 2048 bytes + 16 bytes. The address data is address data of the sector data block. Incidentally, the sector of the user data DU differs from the sector by the preformat described above in reference to Fig. 3. Further, the error detection code may be an error detection code of the address data. Further, as shown by Fig. 13, the recording and reproducing .circuit 53 may form an ECC data block (182 bytes x 208 bytes) by 16 of the sector data blocks. That is, the recording and reproducing circuit 53 may arrange 16 of the sector data blocks each comprising 2048 bytes + 16 bytes by a unit of 172 bytes successively in the order of raster scanning and form error correction code (PI) comprising inner code in the horizontal direction and error correction code (PO) comprising outer code in the vertical direction. Furthermore, the recording and reproducing circuit 53 may interleave the ECC block and form a frame structure shown by Fig. 14. That is, the recording and reproducing circuit 53 may allocate a frame synchronizing signal (FS) of 2 bytes to each 91 bytes of the ECC data block of 182 bytes x 206 bytes thereby forming 412 frames by one ECC data block. The recording and reproducing circuit 53 may form data of 1 cluster having the frame structure shown in Pig. 14 and may allocate the one cluster to 4 continuous sectors. The recording and reproducing circuit 53 may set the redundancy to 23 (%) or less and may efficiently record the user data by adding redundant data such as the frame synchronizing signal, error correction code, the frame address and so on to the user data. In this way, a redundancy of 23 (%) (which is similar to that in a DVD system) still ensures sufficient recording capacity. Incidentally, increasing the redundancy to more than 23 (?