Method and device for protecting a preamplifier in reading signals on a defect disc
A device for protecting a preamplifier in reading signals on a defect disc from disturbance and instability is provided. The device includes a defect detection unit, a logic combination unit and a preamplifier. The defect detection unit receives a plurality of defect detection signals to detect various defects for setting a plurality of defect flag signals. The logic combination unit performs logic operation on the defect flag signals in order to detect a specified defect. The preamplifier receives data from a pickup head and generates an RF signal for data process, servo control signals for a servo control unit and various signals for defect detection. The preamplifier includes an equalizer and an auto gain control (AGC) unit. Wherein the equalizer uses corresponding boost gain or cut-off frequency to equalize and recover an IRF signal affected by the specified defect. The AGC unit controls a gain for the equalized RF signal affected by the specified defect. A method for protecting a preamplifier in reading signals on a defect disc is also provided.
1. Field of the Invention
This invention generally relates to the field of device protection of Optical disc drive (ODD). More particularly, the present invention relates to a method and device that protects a preamplifier of ODD in reading signals on a defect disc.
2. Description of the Prior Art
Nowadays, disc-type storage media are broadly used in keeping data due to their storage capacity. Such disc-type storage media like optical discs, i.e. CD-R discs, CD-RW discs, DVD-R discs, DVD-RW discs, DVD+R discs, DVD+RW discs, or DVD-RAM discs etc., also provide better protection to the data stored on them against damage. However, these characteristics mentioned above do not mean the optical discs are faultless storage media for storing data because some defects might take place on their bare surfaces. For example, a deep scratch, a shallow scratch, and even a fingerprint. These defects could result in not only reading or writing errors but also a system disturbance while the system reads or writes data. Hence, it is an important thing to detect existing defects for protecting the system from a disturbed or instable situation.
It is well known to use the difference of signal amplitude, such as an RF level (RFLVL) or a sub-beam added (SBAD) signal, to detect an existing defect.
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In view of the drawbacks mentioned with the prior art of device protection, there is a continued need to develop a new and improved method and device that overcomes the disadvantages associated with the prior art of device protection. The advantages of this invention are that it solves the problems mentioned above.
SUMMARY OF THE INVENTIONA device for protecting a preamplifier in reading signals on a defect disc from disturbance and instability is provided. The device includes a defect detection unit, a logic combination unit and a preamplifier. The defect detection unit receives a plurality of defect detection signals to set a plurality of defect flag signals, wherein the plurality of defect flag signals include at least an envelope of RF signal and bit modulation signals. The logic combination unit performs logic operation on the defect flag signals in order to detect a specified defect. The preamplifier receives data from a pickup head and generates an RF signal for data process, servo control signals for a servo control unit and various signals for defect detection. The preamplifier includes an equalizer and an auto gain control (AGC) unit. Wherein the equalizer uses corresponding boost gain or cut-off frequency to equalize and recover an RF signal affected by the specified defect. The AGC unit controls a gain for the equalized RF signal affected by the specified defect.
A method for protecting a preamplifier in reading signals on a defect disc is also provided. The method includes the following steps. At first, receiving a plurality of defect detection signals to set a plurality of defect flag signals, wherein the plurality of defect detection signals include at least an envelope of RF signal and bit modulation signals. Next, performing logic operation on the defect flag signals in order to detect a specified defect. When detecting a specified defect, using corresponding boost gain and cut-off frequency to equalize and recover an RF signal affected by the specified defect. Finally, controlling a gain for the equalized RF signal affected by the specified defect.
BRIEF DESCRIPTION OF THE DRAWINGSThe foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Some embodiments of the invention will now be described in greater detail. Nevertheless, it should be noted that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.
Moreover, some irrelevant details are not drawn in order to make the illustrations concise and to provide a clear description for easily understanding the present invention.
A defect detection unit 260 receives the various signals from the preamplifier 220, and EFM signals from the slicer 230 and the PLL 240 to detect different kinds of defects through different defect detections to set corresponding defect flag signals. Wherein, the different defect detections include ADefect detection, ADefect1 detection, EFMDefect detection, RPDefect detection, Interruption detection, and DSPDefect detection, so as to set ADefect flag signal, ADefect1 flag signal, EFMDefect flag signal, RPDefect flag signal, Interruption flag signal and DSPDefect flag signal. A microprocessor or a Digital Signal Processor (DSP) could be used as the defect detection unit 260. The firmware of the foregoing defect detections could be stored in the detection unit 260 to perform corresponding defect detection. A logic combination unit 270 performs an appropriate logic operation, simply, such as an OR operation or an AND operation, on the defect flag signals to precisely improve the defect detection. As the operation result indicates in a defect situation, the logic combination unit 270 triggers defect protection methods and devices to protect the corresponding units, such as the servo control unit 210, the preamplifier 220, the slicer 230, the PLL 240, and the decoder 250.
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An RF signal 42 has a shallow and narrow hollow thus its envelope signal 421 also has the same form. According to the ADefect1 detection, an ADefect1 flag signal 426 is set from “0” to “1” while the envelope signal 421 is lower than the ADefect1 level 402. An RFRP (peak hold) signal 422 and an RFRP (bottom-inverse) signal 423 respectively show the peak envelope and the inversed bottom envelope of the RF signal 42. Further, an RFRP (peak-bottom) signal 424 is formed through an RFRP (peak hold) signal 422 subtracting an RFRP (bottom-inverse) signal 423. An RPDefect flag signal 428 is set from “0” to “1” as the RFRP (peak-bottom) signal 424 is lower than the RPDefect level 405. However, an ADefect flag signal 425, an EFMDefect flag signal 427, and an Interruption flag signal 429 have no response to the shallow and narrow hollow, since the envelope signal 421 is always higher than the ADefect level 401, unsatisfying the conditions of the EFMDefect detection mentioned before, and is always lower than the Interruption level 404, respectively. The shallow and narrow hollow probably caused by a shallow scratch can be only detected out through the ADefect1 and the RPDefect detection, since its depth and width are insufficient for other defect detection.
An RF signal 43 has a shallow and wide hollow thus its envelope signal 431 also has the same form. An ADefect1 flag signal 436 is set from “0” to “1” while the envelope signal 431 is lower than the ADefect1 level 402. An EFMDefect flag signal 437 is set from “0”, to “1” as well, because the hollow is wide enough and generates abnormal data length. An RFRP (peak hold) signal 432 and an RFRP (bottom-inverse) signal 433 respectively show the peak envelope and the inversed bottom envelope of the RF signal 43. Further, an RFRP (peak-bottom) signal 434 is formed through the RFRP (peak hold) signal 432 subtracting the RFRP (bottom-inverse) signal 433. An RPDefect flag signal 438 is set from “0” to “1” as the RFRP (peak-bottom) signal 434 is lower than the RPDefect level 405. However, an ADefect flag signal 435 and an Interruption flag signal 439 have no response to the shallow and width hollow, since the envelope signal 431 is always higher than the ADefect level 401 and is always lower than the Interruption level 404. The shallow and wide hollow possibly caused by a shallow defect can be only detected out through the ADefect1, the EFMDefect and the RPDefect detection, since its depth and width are insufficient for other defect detections.
An RF signal 44 has a shallow and wide hollow thus its envelope signal 441 also has the same form. An ADefect1 flag signal 446 is set from “0” to “1” while the envelope signal 441 is lower than the ADefect1 level 402. An RFRP (peak hold) signal 442 and an RFRP (bottom-inverse) signal 443 respectively show the peak envelope and the inversed bottom envelope of the RF signal 44. Further, an RFRP (peak-bottom) signal 444 is formed through the RFRP (peak hold) signal 442 subtracting the RFRP (bottom-inverse) signal 443. An RPDefect flag signal 448 has no response to the shallow and width hollow, since the RFRP (peak-bottom) signal 444 is always higher than the RPDefect level 405. Moreover, an ADefect flag signal 445, an EFMDefect flag signal 447, and an Interruption flag signal 449 neither have no response to the shallow and wide hollow, since the envelope signal 441 is always higher than the ADefect level 401, unsatisfying the conditions of the EFMDefect detection mentioned before, and is always lower than the Interruption level 404, respectively. The shallow and wide hollow probably resulted from a fingerprint can be just detected out via the ADefect1 detection in this situation, since its depth and width are very deficient for other defect detections.
As for an RF signal 45 and an RF signal 46, both of them are caused from strong signal strengths, such as strong optical reflection, also called an interruption defect. The RF signal 45 has strong amplitudes at its peak and its bottom envelope thus its peak envelope signal 451 has the corresponding form. An EFMDefect flag signal 457 is set from “0” to “1” since the interruption defect is wide enough and generates abnormal data length. An Interruption flag signal 459 is also set from “0” to “1” as the envelope signal 451 is higher than the Interruption level 404. As for other flag signals, an ADefect1 flag signal 456 and an ADefect flag signal 455 have no response to the envelope signal 451 because the envelope signal 451 is always higher than the ADefect1 level 402 and the ADefect level 401. An RFRP (peak hold) signal 452 and an RFRP (bottom-inverse) signal 453 respectively show the peak envelope and the inversed bottom envelope of the RF signal 45. Further, an RFRP (peak-bottom) signal 454 is formed through the RFRP (peak hold) signal 452 subtracting the RFRP (bottom-inverse) signal 453. An RPDefect flag signal 458 has no response to this kind of interruption defect, since the RFRP (peak-bottom) signal 454 is higher than the RPDefect level 405 at all times. This kind of interruption defect can be just detected out via the EFMDefect and the Interruption detection mentioned before.
The RF signal 46 forms an inversed hollow from its bottom envelope thus its peak envelope signal 461 has the corresponding form. An EFMDefect flag signal 467 is set from “0” to “1” since the interruption defect is wide enough and generates abnormal data length. An RFRP (peak hold) signal 462 and an RFRP (bottom-inverse) signal 463 respectively show the peak envelope and the inversed bottom envelope of the RF signal 46. Further, an RFRP (peak-bottom) signal 464 has a deep hollow formed by the RFRP (peak hold) signal 462 subtracting the RFRP (bottom-inverse) signal 463. An RPDefect flag signal 468 is set from “0” to “1” while the RFRP (peak-bottom) signal 464 is lower than the RPDefect level 405. An Interruption flag signal 469 is set from “0” to “1” while the envelope signal 461 is higher than the Interruption level 404. However, an ADefect1 flag signal 466 and an ADefect flag signal 465 have no response to the signal 461 because the envelope signal 461 is higher than the ADefect1 level 402 and the ADefect level 401. This kind of interruption defect can be only detected out via the EFMDefect, the RPDefect, and the Interruption detection mentioned before.
Generally speaking, the ADefect1 detection is more suitable than the ADefect detection for small and shallow scratch detection. The RPDefect detection is more sensitive for small scratch detection. Hence, it should be understood that the defect detection mentioned in the present invention could be combined in variety for particular defect detection. For example, combining the ADefect1 and the EFMDefect detection via a logic “OR” operation for small scratch detection, or combining the ADefect1 and the EFMDefect detection via a logic “AND” operation for small scratch detection except unwanted fingerprint, etc.
Through applying aforementioned defect detection and a suitable combination thereof to trigger a protection method and device, a preamplifier can be protected from instability. Herein, the suitable combination prefers the EFMDefect detection. However, it should be understood that the aforementioned defect detection could trigger the protection method and device by individual and various combinations.
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Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.
Claims
1. A device for protecting a preamplifier in reading signals on a defect optical disc, said device comprising:
- a defect detection unit, receiving a plurality of defect detection signals to set a plurality of defect flag signals, wherein said plurality of defect detection signals comprise at least an envelope of a RF signal and bit modulation signals;
- a logic combination unit, performing logic operation on said defect flag signals in order to detect a specified defect; and
- a preamplifier, receiving data from a pickup head and generates said RF signal for data process, servo control signals for a servo control unit and various signals for defect detection, wherein said preamplifier comprising: an equalizer, using corresponding boost gain or cut-off frequency to equalize and recover said RF signal affected by said specified defect; and an auto gain control (AGC) unit, controlling a gain for an equalized RF signal affected by said specified defect.
2. The device according to claim 1, wherein said various signals further include an envelope signal of an RF signal, bit modulation signal, a peak envelope of said RF signal, a bottom envelope of said RF signal, and a peak to bottom envelope of said RF signal.
3. The device according to claim 1, wherein said gain of the AGC unit is a fixed gain while said specified defect is detected.
4. The device according to claim 1, wherein said gain of the AGC unit is a previous gain by said specified defect arising while said specified defect is detected.
5. A method for protecting a preamplifier in reading signals on a defect optical disc, said method comprising:
- receiving a plurality of defect detection signals to set a plurality of defect flag signals, wherein said plurality of defect detection signals comprise at least an envelope of RF signal and bit modulation signals;
- performing logic operation on said defect flag signals in order to detect a specified defect; and
- using corresponding boost gain and cut-off frequency to equalize and recover an RF signal affected by said specified defect, while a specified defect is detected.
6. The method according to claim 5, further comprising controlling a gain for an equalized RF signal affected by the specified defect.
7. The method according to claim 6, further comprising using a fixed gain as said gain to avoid said RF signal, affected by said specified defect, being charging up while said specified defect is detected.
8. The method according to claim 6, further comprising using a previous gain, generated before said specified defect arising, as said gain to avoid said RF signal, affected by said specified defect, being charging up while said specified defect is detected.
9. A device for protecting a preamplifier in reading signals on a defect optical disc, said device comprising:
- a defect detection unit, receiving a plurality of defect detection signals to set a plurality of defect flag signals, wherein said plurality of defect detection signals comprise at least an envelope of a RF signal and bit modulation signals; and
- a logic combination unit, performing logic operation on said defect flag signals in order to detect a specified defect;
- wherein said logic combination unit controls said preamplifier to use a fixed gain or a previously preserved gain by said specified defect raising, so as to avoid a RF signal, affected by said specified defect, being charging up.
10. The device according to claim 9, wherein an auto gain control (AGC) unit within said preamplifier uses said fixed gain to avoid said RF signal, affected by said specified defect, being charging up while said specified defect is detected.
11. The device according to claim 9, wherein an auto gain control (AGC) unit within said preamplifier preserves said previous gain by said specified defect raising to avoid said RF signal, affected by said specified defect, being charging up while said specified defect is detected.
Type: Application
Filed: Mar 16, 2006
Publication Date: Oct 5, 2006
Inventors: Yi-Lin Lai (Taipei), Yi-Sung Chan (Taipei)
Application Number: 11/376,173
International Classification: G11C 29/00 (20060101);