Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
1999-06-30
2001-05-22
Hindi, Nabil (Department: 2753)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S047440, C369S053140, C369S053420
Reexamination Certificate
active
06236630
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the recovery of data from rotating data storage disks such as, typically, compact disks (CDs) used as read-only memories (ROMs) in computer systems. More specifically, the invention concerns how to determine optimum speeds of rotation for CD-ROMs or like data storage disks of varying physical qualities for error-free, and hence speedier, reading thereof.
Although originally developed for consumer audio reproduction in place of analog phonograph records, CDs have now found widespread commercial acceptance as compact, high-speed, large-capacity ROMs for computers. The only difference of CD-ROMs from audio CDs is that the CD-ROMS are driven at speeds up to twelve times as high as the standard audio CD speed (1.2-1.4 meters per second).
There have been problems left unsolved in use of CD-ROMs with high-speed CD-ROM drives in computer systems. CD-ROMs are presently being made under the same design specifications and manufacturing standards as low-speed audio CDs. Inevitably, therefore, a substantial percentage of CD-ROMs on the market are not of truly satisfactory quality for use as high-speed computer data storage media. Some have their center holes cut eccentrically; others have an uneven weight distribution circumferentially. When driven at a speed as high as, say, 12 times the standard audio CD speed, such eccentric disks are very likely to overload the tracking servo of the CD-ROM drive whereby the radial position of the beam spot on the disk is maintained in alignment with the spiral data track. The overloading of the tracking servo may result in the overheating of the voice-coil actuator for tracking control, in the degradation of its performance and, in the worst case, in the burning of the actuator coil.
Such low-grade disks are also very easy to wobble when driven at high speed. Disk wobbling may go so far as to overload the beam focusing servo of the CD-ROM drive, again resulting in the overheating of the focusing actuator of voice-coil construction, in the degradation of its performance and, in the worst case, in the burning of the focusing actuator coil. The malfunctioning of both tracking and focusing servos is very undesirable because of ensuing read errors and retries, which is very time-consuming and so runs counter to the objective of high speed data recovery for which CD-ROMs are intended.
The wobbling of low grade disks can give rise to additional inconveniences. A wobbling disk may cause vibration of the complete CD-ROM drive and, in consequence, of the hard disk drive (HDD) in particular which is currently being preferentially built into the computer system along with the CD-ROM drive. The vibration of the HDD is even more undesirable because it may invite both read and write errors, to the detriment of the reliability of the complete computer system. Even if not so excessive as to cause read and write errors, the vibration of the CD-ROM drive certainly gives a shoddy image to the user or to prospective buyers.
It might be contemplated that all such troubles and inconveniences would be avoidable if only high quality CD-ROMs, altogether free from the physical defects pointed out earlier, were used. CD-ROM drive manufacturers cannot, and should not, expect their products to be used only that way, since in the current state of affairs the existence of poor quality CD-ROMs must be more or less taken for granted.
SUMMARY OF THE INVENTION
The present invention has it as an object to enable speedy data recovery from CD-ROMs or other data storage disks of low quality without any such troubles and inconveniences as have been encountered heretofore.
Another object of the invention is to recover data from disks of varying physical qualities at the highest possible speed suiting each particular disk without causing read errors or retries.
Still another object of the invention is to make utmost use of the preexisting parts and components of CD-ROM drives or like apparatus in order that the inventive concepts may be carried out in such apparatus without any substantial alteration in construction.
Briefly summarized in one aspect thereof, the invention provides what may be termed a disk check method, suitable for implementation in an apparatus for data recovery from rotating data storage disks of varying physical qualities, the apparatus having a disk drive motor for imparting rotation to a disk, and a power supply for powering the disk drive motor.
The disk check method, or a method of determining a speed at which each disk is to be read according to its quality, is such that a prescribed voltage, preferably a full supply voltage, is first applied from the power supply to the disk drive motor thereby causing rotation thereof together with a data storage disk loaded into the apparatus. Then, upon lapse of a preassigned length of time from the moment the prescribed voltage is started to be applied to the motor, the steady state speed of rotation of the motor is detected, the motor being in steady state rotation at that time because the preassigned length of time is not less than the known startup period of the motor during which the motor picks up speed before attaining a steady state speed. The speed at which the disk is to be read is then determined on the basis of the detected steady state speed of the motor.
The present invention as summarized above is based upon the discovery that disks with varying degrees of defects such as eccentricity and irregular weight distribution cause corresponding changes in the steady state speed of rotation of the disk drive motor: the poorer the disk quality, the lower the steady state speed. The steady state speed of the disk drive motor decreases when it is driving a poor quality disk, because of the loss of the kinetic energy of the motor due to the vibration of the disk and of the complete disk drive mechanism.
The checking of disk quality in terms of the steady state rotational speed of the motor offers the distinct advantage, over other possible methods of disk quality evaluation, that it requires no sensors or like expensive devices for measuring the variable, means for sensing the motor speed being preexistent in CD-ROM drives or like devices in which the inventive method is to be carried out.
Preferably, in consideration of possible fluctuations in supply voltage, the actual voltage that has been applied to the disk drive motor as it attains the steady state rotation may also be detected. A read speed for each disk may then be determined on the basis of the detected actual motor voltage in addition to the steady state speed of the motor. Still more accurate evaluation of disk quality will be possible in this manner.
In a preferred embodiment of the invention to be disclosed subsequently, disks are classified according to their qualities, as determined above, into either of three categories, good, intermediate, and poor. Good quality disks are read at twelve times the standard audio CD speed, intermediate quality disks at eight times that speed, and poor quality disks at four times that speed. Driven at the appropriate speeds, the disks will cause less vibration and, in consequence, less read errors and retries, thereby affording speedier reading.
It might be feared that read errors were averted at the sacrifice of disk speed. Such fears are unjustified. Experiment has proved that the errorless reading of poor and intermediate quality disks at the reduced speeds demands far less periods of time than higher speed reading of such disks which necessarily involves read errors and retries. The advantages of such reduced speed data recovery from disks of other than good quality will be even better appreciated by taking into consideration all the aforementioned difficulties accruing from the high speed reading of these disks.
According to a further feature of the present invention, the read speed that has been determined as above for each disk loaded into the apparatus is held until that disk is unloaded therefrom. Therefore, no matter how many times the disk is set into and out of rot
Kubo Mitsumasa
Okada Yukihiko
Hindi Nabil
Teac Corporation
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
LandOfFree
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