Patent Application
20060120263
The present invention relates to an optical recording medium, and more particularly, to an optical recording medium having grooves formed concentrically or spirally and prepits formed between and/or on the grooves. The present invention also relates to an information recording method and a recording unit for recording data on such a high-density recording medium.
Known examples of recordable optical disks include DVD-R (Digital Versatile Disc-Recordable) and DVD-RW (Digital Versatile Disc-Rewritable). On these recording disks, a recording track is formed with a fine wobble at a specified frequency (140 kHz). Prepits are provided on a land, wherein decoding of a signal detected from the prepit can determine the position on the disk.
It is known that a high recording density can be realized by using both the land and the groove as recording tracks. This is because of preventing an influence by interference between codes due to data on adjacent tracks. It is possible to create a disk having the same track density by doubling the groove cycle compared to a disk using only the groove as a recording track. This technique is effective for realizing large-capacity disks.
In order to use both the land and the groove on a disk, it is necessary to form physical address information identifiable from both the land and the groove so as not to unfavorably affect reproduction of data on the recording track. When both the land and the groove are used as recording tracks on the above-described DVD-R and DVD-RW disks, data recorded on the land is strongly interfered by prepits also recorded on the land. Thus, correct data reproduction has been difficult.
Grooves are formed on DVD-R and DVD-RW disks so that the wobble frequency of the grooves becomes constant on the entire disk surface. Such disks are subject to gradual misalignment between phases of grooves adjacent to both sides of a land. Consequently, a correct frequency cannot be detected from the recording track on the land.
The wobble arrangement as described in Patent Publication JP-A-2001-250239 can be used to solve the above problem that a correct wobble frequency cannot be detected on the land. JP-A-2001-250239 exemplifies the wobble arrangement such as shown in
Forming groove phases in this manner is also effective for using lands and grooves as recording tracks. Maintaining the constant land width makes it possible to correctly detect a wobble frequency on lands as well as on grooves. Even though wobble phases are aligned on the adjacent tracks, however, it is impossible to solve the first problem of interference between a prepit and data on the recording track. Prepits partially enter the data region on a recording format similar to those used for DVD-R and DVD-RW. Interference from prepits frequently causes data read errors.
On the other hand, there is a method of supplying address information to the recording track in such a manner as to frequency modulate the wobble on CD-R or CD-RW. In this case, the physical address information is recorded on the disk without using prepits to decrease deterioration of the reproduced signal quality due to interference from the physical address information. However, it is difficult to modulate the wobble so as to correctly detect the address information from both the land and the groove. Thus, it is considered that both the land and the groove cannot be used as recording tracks.
It is an object of the present invention to provide an optical recording medium having address information detectable from both a land and a groove without adversely affecting recording data when both the land and the groove are used as recording tracks, and information recording method and recording unit thereof.
It is to be noted that the present invention relates to a prepit arrangement for using both the land and the groove as recording tracks. This makes it possible to record the address information in a common format between an optical recording medium using both the land and the groove as recording tracks and a medium using either the land or the groove as a recording track, thereby allowing a common recording method to be used therebetween. This common method aims at using a common circuit concerning address identification and format management by the recording unit to ensure high compatibility between both the media. For this reason, the optical recording medium using only the land or the groove also requires arrangement of the address information compliant with the prepit arrangement on the optical recording medium using both the land and the groove.
The present invention provides, in a first aspect thereof, an optical recording medium including: grooves concentrically or spirally arranged from a radially inner periphery toward a radially outer periphery of the medium, lands each disposed between two of the grooves adjacent to each other in a radial direction of the medium, recording tracks each disposed in the groove and/or the land, and a plurality of prepit forming regions disposed in the groove and/or the land and each capable of receiving therein a single or plurality of prepits:
the plurality of prepit forming regions are disposed apart from one another by a distance which is 300 or more times a recording channel bit length:
each of the prepit forming regions having a fixed length which is 36 or less times the recording channel bit length along the groove or land.
The present invention provides, in a second aspect thereof, a method for recording data on the optical recording medium according to the present invention as described above, the method including the step of recording a pattern including a long mark or a long space having ten or more times the channel bit length so that the prepit on the recording track is covered with the long mark or long space on the prepit forming region.
The present invention provides, in a third aspect thereof, a recording unit for recording data on the optical recording medium according to the present invention as described above, the recording unit including: a prepit detecting section for detecting a prepit signal from a signal reproduced from the optical recording medium; a decoding section for decoding the prepit signal to output physical address information; a recording pattern generating section for admixing, based on data to be recorded, a recording pattern including a long mark or a long space having a length ten or more times the channel bit length to the data to be recorded, to generate physical address information; and a recording timing control section for detecting a recorded position based on the physical address information, and controlling timing for start of a recording pattern output from the recording pattern generating section and a channel bit frequency, wherein the recording timing control section controls output timing of the recording pattern so that the long mark or the long space output from the recording pattern generating section covers the prepit.
When the land and the groove are both used as recording tracks, the recording medium and the recording method according to the present invention can correctly detect wobble phases on the land and the groove and form prepits as information containing physical addresses detectable from the land and the groove.
The use of the recording method and the recording unit according to the present invention can protect a prepit forming region with a long mark or a long space. Even a recorded medium enables correct reading of information from a prepit. In addition, it is possible to prevent interference with a reproduced signal from a prepit and prevent a read error from occurring. These effects enable provision of the optical recording medium, the recording method, and the recording unit (or recording/reproducing unit) capable of high-density recording.
As described in preferred embodiments of the present invention, the long space or the long mark can be selected depending on a frame to be recorded. When a multi-layer medium is used, there is provided an effect of avoiding occurrence of an inter-layer crosstalk resulting from locally concentrating long marks or long spaces.
Embodiments of the present invention will be described in further detail with reference to the accompanying drawings so as to ascertain the foregoing and other objects, features, and advantages of the present invention.
On the groove, frames F1, F2, F3, and F4 are periodically arranged along the track in this order. Each zone is configured so that the number of frames per recording track is set to 4K+1 (where K is an integer). Frames F1, F2, F3, and F4 have a length equivalent to an integral multiple of the wobble frequency and are aligned with one another along the radial direction. A prepit forming region 2, which is shown shaded in the drawing, starts at the beginning of frame F1 on the groove and apart from the frame boundary along the recording track by twelve times the channel bit length T. The prepit forming region 2 is twelve times as long as the channel bit length T. The prepit forming region 2 is so wide as to cover three recording tracks including the groove and both adjacent lands. A prepit 1 is provided inside the prepit forming region. The prepit 1 is formed in such a manner that both walls of the groove are shifted approximately half the recording track toward the outer periphery side. Such prepits can be formed by using an exposure beam for prepit formation in addition to a beam for groove exposure during the exposure of a master disk. The exposure beam for prepit formation is radiated at a position shifted approximately half a track toward the outer periphery. That is, the prepit 1 is formed by decreasing the radiation amount of beam for groove exposure at the prepit formation position and by radiating the prepit formation beam toward the outer periphery side. If a prepit is formed to have a length which is four times the channel bit length along the recording track, different patterns can be formed depending on positions corresponding to prepits in the prepit forming region that is divided into three portions. The information including physical addresses is represented by patterns of forming prepits in a plurality of prepit forming regions arranged along the recording track.
A land is assigned with a frame number corresponding to a groove that is adjacent to the land in the direction of the outer periphery side. According to this frame arrangement, the land's frame F1 adjoins the inner periphery side of the groove's frame F1, whereas the land's frame F2 adjoins the outer periphery side of the groove's frame F1. On the groove, any prepit forming region is positioned near the beginning of frame F1. On the land, any prepit forming region is positioned near the beginnings of frames F1 and F2. Along the track direction, the shortest interval of prepit forming regions is measured between the prepit forming region on the land's frame F1 and that on the land's frame F2. Thus, the interval is ensured to be almost equal to the frame length.
An operation to record data on the disk uses a recording format having synchronization patterns including a long mark and a long space in each frame so that the long mark or the long space covers the prepit forming region on the recording track. For this reason, the length of the prepit forming region significantly influences the efficiency of the recording format. The prepit forming region needs to have a minimum length enough to form at most several prepits inside the same. In addition, the cycle of prepit forming regions must be ensured wide enough for the synchronization pattern length. The purpose thereof is to prevent the efficiency of data regions from degrading even when a synchronization pattern including the long mark or the long space is formed on the prepit forming region. In the prepit forming region, it is impossible to correctly obtain signals for the servo circuit used for positioning control of the focusing beam of the optical head. If a prepit forming region is made unnecessarily long, it disorders the positioning control to adversely affect the recording and reproducing performance. In consideration for this, it is necessary to configure the prepit forming region as short as possible and ensure a sufficient interval between them.
At least, the length of the prepit forming region is configured 36 channel bits or less equivalent to the three-byte length according to the (1,7) run-length limited coding. The prepit forming regions are arranged at an interval of 300 channel bits or more equivalent to approximately ten times the length of the prepit forming region. This makes it possible to protect the format efficiency against the presence of prepits. Further, it is possible to prevent prepits from adversely affecting signals for the servo circuit to realize optical disks suitable for high-density recording.
When the prepit forming region is ensured to be longer than 36 channel bits, it is necessary to use a synchronization pattern of four bytes or longer so as to stably form a long mark or a long space on the prepit forming region. Thus, a problem may arise in that addition of the synchronization pattern decreases the format efficiency. It is appropriate to determine the length of the prepit forming region to be up to 36 channel bits equivalent to three bytes. The prepit forming regions may be arranged at an interval of 300 channel bits or more equivalent to approximately ten times the prepit forming region length. This can limit the region of disordering signals for the servo circuit to approximately 10% or less of the entire region. It is desirable to arrange the prepit forming regions at an interval of 300 channel bits or more to prevent the servo characteristics from degrading and ensure the accuracy of the positioning control of the focusing beam by the optical head.
On the land, a prepit detection pulse is obtained at the beginning of frame F1 because the boundary is deformed between the land and the groove adjacent thereto in the direction of the outer periphery side. In addition, a prepit is also detected at the beginning of frame F2 because the boundary is deformed between the land and the groove adjacent to the inner periphery side. No prepit appears in frames F3 and F4. A prepit can be selected for detection only from frame F1 even on the land by using the frame cycle and the fact that no prepit is detected from the preceding frames. In this case, when the physical address information is obtained from the prepit on the land, that information becomes identical to the physical address information on the groove adjacent thereto in the direction of the outer periphery side. A tracking polarity is used to make a distinction between physical addresses for the land and the groove.
The following describes the recording and reproducing method using the optical recording medium according to the first embodiment of the present invention.
A prepit decoding circuit 7 decodes information containing a physical address, which is provided to the prepit, based on the prepit detection pulse timing and the number of pulses obtained by the prepit detection circuit and based on the timing of the binary signal of the wobble obtained by the wobble detection circuit, outputting the same. Data is recorded on the optical recording medium as follows. First, a host system (not shown) stores data to be recorded in a data buffer 13. Then, the host system (not shown) specifies a logical address of the data to be recorded to the recording/reproducing control circuit. The recording/reproducing control circuit encodes the data to be recorded based on the specified logical address and performs error correction coding. The recording/reproducing control circuit also calculates a physical address of the data to be recorded based on the logical address and outputs the physical address to the timing control circuit 11. The timing control circuit is supplied with the prepit detection pulse timing from the prepit detection circuit and the binary signal of the wobble from the wobble detection circuit 6. Based on the input pulse timing and binary signal, the timing control circuit synthesizes a recording clock synchronized with a rotational speed of the optical recording medium 3. The timing control circuit uses the physical address information output from the prepit decoding circuit 7, to detect the start position of the physical address for the data to be recorded. When identifying the physical address of the data to be recorded and supplied from the recording/reproducing control circuit, the timing control circuit outputs the recording clock and a recording gate signal to the format control circuit 10. The format control circuit adds a synchronization pattern to the data received from the recording/reproducing control circuit and applies coding modulation to the data. The format control circuit outputs a recording control pulse to an LD drive circuit 9 in synchrony with the recording clock. The optical head 4 then forms a recording pit on the optical recording medium 3.
The timing control circuit detects a phase difference between two timings. One is output timing of a pattern equivalent to the long mark or the long space determined by the recording clock frequency. The other is the timing for the wobble phase or the prepit detection pulse. Continuously providing the frequency control using a phase synchronization loop makes it possible to continue recording so as to form the long mark or the long space on prepits at any time.
Data is reproduced as follows. The optical head 4 reads the signal representing the contrast change from the optical recording medium. Based on this signal, a data determination circuit determines binary data. The format control circuit extracts the synchronization and decodes the data. The host system (not shown) specifies the logical address of data to be reproduced for the recording/reproducing control circuit. Based on this logical address, the recording/reproducing control circuit calculates a physical address and outputs the same to the timing control circuit. The format control circuit specifies the start timing of the reproduced data for the format control circuit based on the physical address obtained from the prepit decoding circuit and a synchronization extraction result from the binary data. The format control circuit extracts the specified timing data and outputs the same to the recording/reproducing control circuit. The recording/reproducing control circuit applies error correction to the input data, stores the reproduced data in the data buffer, and notifies completion of the data reading to the host system (not shown).
The following describes in more detail the physical format used for recording and reproduction. During recording, the format control circuit adds a synchronization pattern in the format as shown in
The synchronization pattern SY can be any of patterns each including 36 channel bits as shown in
In the case of using an optical recording medium according to the first embodiment of the present invention, the prepit forming region begins at the end of 12 channel bits after the frame boundary and has a length of 12 channel bits. Now, it is assumed here to select a pattern containing a space of 24 channel bit length from the synchronization patterns shown in
The prepit forming regions exist only on frames F1 and F2. Frames F1 and F2 may be used to select synchronization patterns containing long spaces. Frames F3 and F4 may be used to select synchronization patterns containing long marks. Since the long mark and the long space are mixed in this manner, it is possible to decrease a crosstalk from adjacent recording layers due to changes in the reflectance or the transmittance even on a medium having multiple recording layers, for example.
The above-described embodiment has presented the example of using the (1,7) run-length limited coding for modulation and configuring the frame with the 3-byte synchronization pattern and the 91-byte data. The modulation code and the frame configuration are not limited thereto and can be selected in accordance with system requirements. For example, it is also possible to use the same 8/16 modulation as used for DVD-R and DVD-RW and use a 2-byte synchronization pattern containing a mark or a space of 14 channel bit length. In addition, any wobble frequencies can be selected except the limitation that a common wobble phase is provided to the recording tracks adjacent to one another in each zone. The embodiment has presented the example where the frame length is an integral multiple of the wobble frequency. For example, four frames may include an integral multiple of wobbles. In this case, no error occurs in the prepit decoding because the F1 frame ensures the relative relationship between the wobble phase and the prepit position.
Forming prepits as described above decreases the size of a reproduced waveform from a prepit obtained on the groove compared to the deformation of groove's both walls as shown in
The above-described embodiments have presented the examples of covering the prepit forming region with the long space. However, for example, there may be a case of using a medium that increases a reflectance by forming a mark. In such a case, it may be preferable to regularly cover the prepit forming region with the long mark. It may be optional to record the long mark or the long space on the prepit forming region. The long mark or the long space need not necessarily be contained in a synchronization pattern on a frame where no prepit forming region is available.
The above-described embodiments have presented only the examples of forming one or more prepits within the prepit forming region. Further, it is possible to include a pattern for forming no prepit among the patterns each for forming a prepit in the prepit forming region. For example, it is possible to form one or zero prepit in a single prepit forming region and configure the address information to represent the presence or absence of the prepit. This case also enables a physical address to be decoded based on the continuity thereof. Moreover, adding an odd parity to the prepit at a proper cycle can further reduce the time length to establish the synchronization.
It is a principal object of the present invention to provide an optical recording medium having address information detectable from both a land and a groove without adversely affecting the recording data when both the land and the groove are used as recording tracks. Further, similar prepit arrangement and recording method can be applied to an optical recording medium using only the groove or the land as a recording track.
The example in
While there has been described the present invention based on the preferred embodiments, the optical recording medium, and the information recording method and recording unit according to the present invention are not limited to the above-described embodiments. The scope of the present invention also includes various changes and modifications made to the above-described embodiments.
The optical recording medium according to the present invention can be particularly suitably applied to DVD-R and DVD-RW capable of recording on both the land and the groove.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-238015 | Aug 2002 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP03/10244 | 8/12/2003 | WO | 2/17/2005 |
