Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2000-03-17
2004-01-13
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S275400
Reexamination Certificate
active
06678235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CLV (Constant Linear Velocity) disc applied to optical disc medium, a format of the above-mentioned CLV optical disc, and an optical disc medium recording and reproducing apparatus, in particular, the CLV disc and the CLV disc format in the large capacitance optical disc apparatus capable of recording and reproducing the information on the optical disc medium.
2. Discussion of the Background
In order to raise the speed of accessing the information recorded on the optical disc media, it is necessary to control the speed of moving the optical head precisely and with high speed. When the optical disc apparatus receives the indication of accessing the information from the upper-ranked apparatus, the optical disc apparatus calculates the relationship between the logical number of the information and the physical position as shown by the track number or the sector number on the optical disc, and the apparatus sends the optical head to the above-mentioned physical position.
Hereupon, as to such optical disc, there exist two types of recording method; those are, a CAV (Constant Angular Velocity) type recording method in which the angular velocity is constant and a CLV (Constant Linear Velocity) type recording method in which the linear velocity is constant.
In the CAV type method, since the amount of the information on one track is always constant regardless of the inner and outer circumferences of the disc, the logical information number and the track number (numerical value) can be easily calculatively converted from each other, and thereby the calculation thereof can be done in a very short time. However, according to such CAV type method, there arises a problem that the line density of the information at the outer circumference of the disc is lowered and thereby the entire memorizing capacity is lowered. In order to avoid such unfavorable problem, in a method called “modified CAV type method”, it is devised that the frequency of the recording signal is raised at the outer circumferential portion of the disc for the purpose of making uniform the line density on the respective inner and outer circumferential portions. However, in such way as mentioned above, there arises another problem that the structure of the formatter electric circuit becomes complicated.
From the viewpoint of the memorizing capacity and the simplification of the formatter electric circuit, the CLV type method is more preferable than the CAV type method. However, in the CLV type method, the amount of the information on one track differs in accordance with the radius position on the disc, and the calculative conversion between the information number and the physical position may become further complicated. As a result, the calculation of conversion therebetween cannot be done in a short time, and thereby, the access time may be elongated. Those matters are the problems of the CLV type method to be solved.
In recent years, as large-capacity optical disc media, DVD-ROM, DVD-R, and DVD-RAM, etc. have become popular, the requirement of increasing the memory capacity of these media continues to grow. Namely, it is desirable that the pitch be narrowed more and more and that the bit is made smaller. In such a situation, providing high-speed access to such an increased large-capacity media has become an important problem to be solved.
In order to solve the above mentioned problem, the published specification of Japanese Laid-Open Patent Publication No. 9-16980 filed by Nihon-Denki Co., Ltd. entitled, “A METHOD OF ACCESSING THE INFORMATION OF THE CLV OPTICAL DISC” has already described the method composed of the steps of: firstly determining only the moving direction of the optical head; driving, in advance, the optical head moving medium; obtaining, thereafter, the present position (track number) corresponding to the present address and the target position (track number) corresponding to the access target address by the calculation; calculating the track number therebetween (between the present position and the target position); and finally performing the access control.
However, there is a limitation in the realization of the high-speed operation obtained in such way as mentioned heretofore. Therefore, sufficient high-speed access cannot always be realized.
On the other hand, the published specification of Japanese Laid-upon Patent Publication No. 8-279129 filed by SONY Co., Ltd. entitled, “A METHOD OF MANUFACTURING THE CLV DISC” does not describe technology relating to the method of providing the usual CLV format. Instead, it describes the technology relating to a method of arranging sectors without causing any angular positional error obtained at the time of ideally driving with CLV. The above specification has already described the method composed of the steps of: causing the formatter to receive the start position of the start sector's address from the cutting machine with the same angular information; previously estimating the address situated at the same neighboring angular position as that of the start address by the calculation; changing the buffer length when the sector arrives at the above-mentioned estimated address; confirming thereby the arrival of the electric signal of the angular information sent from the cutting machine; sending the address signal of the next sector and thereby absorbing the variation of the angular position due to the error of the cutting start radius position and due to the change of the track pitch; and making uniform the sector angle between the different stampers.
However, according to the method as mentioned above, it is inevitably necessary to provide special processing such as the estimation of the sector arriving at the same neighboring angular position as that of the start sector and the compensation of the buffer length, etc.
As mentioned above, the background-art CLV optical disc requires a lot of time for performing the calculative conversion between the logical information number and the physical position. Therefore, the speed of accessing the disc information is inevitably lowered. This is a problem to be solved.
To provide a large capacity optical disc medium, it may be profitable to adopt the CLV (Constant Linear Velocity; Line Speed-Constant) format in which the line density of the information becomes constant. However, in the CLV format, in the case of accessing a specified sector, it is required to perform the control operation such that the revolution rate of the spindle motor for rotating the disc is changed in accordance with the disc radius position on which the sector exists and the scanning line speed of the reproducing track is made constant.
On the other hand, while the CAV (Constant Angular Velocity; Angular Velocity-Constant) format is inferior in terms of storage capacity, it is superior as to case of accessing. Namely, the respective sectors are arranged on the radius line of the disc, and all of the sectors can be accessed using the same disc revolution rate at the time of reproducing.
Furthermore, there exists an MCAV format taking advantage of the large capacity of the CLV format and the high-speed accessing of the CAV format. In the MCAV format, plural zones are provided in the radius direction of the disc, one circle of the track is divided into plural pieces of the sector in each of the respective zones, and the number of the divided sectors is increased toward the outer circumferential zone of the disc, and then the distribution of the information amount in the radius direction of the disc is approximated (brought close) to the information distribution of the CLV format and the respective sectors are aligned in the radius direction per each of the respective zones. In such format, regarding the movement between the zones, although it is necessary to change the revolution rate of the disc or to change the frequency of the clock for recording/reproducing under the condition of making constant the revolution rate, the high-speed accessing of the CAV format c
Ricoh & Company, Ltd.
Tran Thang V.
Vuong Bach
LandOfFree
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