Abstract:
A shock detector for an optical disc recorder and method for controlling the recording using a shock signal. The shock detector includes a first detecting unit for detecting the amplitude of a first kind of reference signal passing through a band-pass filter and outputting a first detecting signal, a second detecting unit for detecting the level of a second kind of reference signal and outputting a second detecting signal, a third detecting unit for detecting the revolution of a third kind of reference signal and outputting a third detecting signal, and a judging unit for receiving the first detecting signal, the second detecting signal and the third detecting signal, and enabling a shock signal when the first detecting signal, the second detecting signal and the third detecting signal are simultaneously enabled. Therefore, the shock detector does not need an additional shock sensor.

Description:
This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 091123388 filed in Taiwan on Oct. 9, 2002, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a shock detection and shock-proof apparatus for an optical disc recorder, and more particularly to a shock detector for an optical disc recorder capable of detecting the shock level of the recorder without using an additional shock sensor, and an apparatus for controlling link recording when the shock level is greater than a threshold to protect the recording quality. 
   2. Description of the Related Art 
   The optical disk recorders, such as the CD-RW recorders and the DVD recorders, have become more and more popular recently. They are widely applied in various environments including many conditions full of vibrations. Consequently, to ensure the data integrity, the recorder must have the shock proof function to keep the best recording quality when the recorder is suffering impact or shock during recording. 
   The current technology mostly utilizes a shock sensor to detect the external impact applied to the recorder, and increases the gain of the servo controller to enhance the system&#39;s shock resistance. For example, U.S. Pat. No. 6,219,317 entitled “Optical disc recording and/or reproducing apparatus and method” has disclosed an apparatus and a method using a shock sensor to detect the shock level and switching the gain of a tracking/focus-locking servo controller to make the gain of the servo controller greater to enhance the shock resistance as the shock is greater than a threshold. However, because the method is recording data while the disk driver is impact, this method cannot ensure that the objective lens of the optical head is always kept at a correct tracking/focus-locking position, and thus the reading and recording quality of the disc cannot be assured. In addition, this method needs an additional shock sensor to detect the shock level, so that the cost is higher and the assembling processes are more complicated. 
   SUMMARY OF THE INVENTION 
   In view of the above-mentioned problems, an object of the invention is to provide a shock detector for an optical disc recorder, which generates a shock signal by utilizing signals having generated in the current optical disc recorder system. 
   Another object of the invention is to provide a shock proof recording method using a shock signal to control the optical disc recording. 
   To achieve the above-mentioned objects, a shock detector for an optical disc recorder of the present invention includes a first detecting unit for detecting the amplitude of a first kind of reference signal passing through a band-pass filter and outputting a first detecting signal, a second detecting unit for detecting the level of a second kind of reference signal and outputting a second detecting signal, a third detecting unit for detecting the revolution of a third kind of reference signal and outputting a third detecting signal, and a judging unit for receiving the first, the second and the third detecting signals, and enabling a shock signal when the first, the second and the third detecting signals are simultaneously enabled. 
   The first kind of reference signal includes the tracking error signal, the focusing error signal, and the central error signal. The second kind of reference signal includes the sub-beam sum signal and the RF ripple signal. The third kind of reference signal includes the rotating frequency identifying signal of a spindle motor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a shock detector of an optical disc recorder of the present invention. 
       FIG. 2  shows a flow chart for controlling the recording of the write-once optical disc according to a shock signal of the present invention. 
       FIG. 3  shows a flow chart for controlling the recording of the rewritable optical disc according to a shock signal of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The shock detector for optical disc recorders and the shock proof control method using the same will be described with reference to the accompanying drawings. 
   The “shock proof” is defined hereafter as the following. During recording situation, a recorder uses a shock detection scheme to monitor the external impact applied to the recorder, and judges the strength of the shock. If the shock is stronger than a threshold level, the recording action will be stopped and a link procedure will be active to avoid recording during the shock period. After the shock level decreased and is smaller than a safe level, the recorder is controlled to seek the link zone at which the previous recording is stopped and to enable the link recording and to continue recording. 
   In general, when the recorder is reading or recording, some feedback control signals are provided, such as the tracking error signal TE, the focusing error signal FE, the central error signal CS (or referred to as a main push pull signal MPP), the sub-beam sum signal SBAD, the RF ripple signal RFRP, and the rotating frequency identifying signal of spindle motor FG Among these control signals, when the recorder is impacted, a resonant frequency will be added to the control signals such as the tracking error signal TE, the focusing error signal FE and the central error signal CS, the levels of the sub-beam sum signal SBAD and the RF ripple signal RFRP will be changed, and the frequency of the frequency identifying signal FG will also be changed. The invention utilizes the combinations of these signals to judge whether the shock is occurred. 
     FIG. 1  is a block diagram of a shock detector of an optical disc recorder of the present invention. Referring to  FIG. 1 , the shock detector  10  for the optical disc recorder includes a first detecting unit  11 , a second detecting unit  12  and a third detecting unit  13  for detecting different kinds of signals, respectively, and an AND gate  14  for integrating output signals from each detecting unit and generating a shock signal. 
   The first detecting unit  11  includes a band-pass filter  111 , two hysteresis comparators  112  and  113 , and an OR gate  114 . The first detecting unit  11  receives a first kind control signal, such as the tracking error signal TE, the focusing error signal FE or the central error signal CS, and detects the amplitudes of the first kind control signal passing through the band-pass filter. Since the frequencies of the tracking error signal TE, the focusing error signal FE, and the central error signal CS will include a resonant frequency when the optical disc recorder is impacted, the first detecting unit  11  utilizes a band-pass filter  111  to extract the resonant frequency components caused by the impact and to generate a first eigenvalue CS_ 1 . The frequency range of the band-pass filter  111  may be configured according to the resonant frequency of the loader&#39;s mechanism. Then, the first detecting unit  11  utilizes the first and second hysteresis comparators  112  and  113  to compare the first eigenvalue CS_ 1  with a first set of threshold values RH_ 1 , RL_ 1  and a second set of threshold values RH_ 2 , RL_ 2 , respectively, and outputs a first detecting signal DS_ 1 . The first high threshold value RH_ 1  is greater than the first low threshold value RL_ 1 , and the second high threshold value RH_ 2  is greater than the second low threshold value RL_ 2 . The OR gate  114  receives the outputs from the first and second hysteresis comparators  112  and  113 , and generates the first detecting signal DS_ 1 . When the first eigenvalue CS_ 1  is greater than the first high threshold value RH_ 1  or smaller than a second low threshold value RL_ 2 , the first detecting signal DS_ 1  is H; and when the first eigenvalue CS_ 1  is smaller than a first low threshold value RL_ 1  and greater than a second high threshold value RH_ 2 , the first detecting signal DS_ 1  is L. The first detecting signal DS_ 1  is kept unchanged in other conditions. The hysteresis comparators are used in order to prevent the first detecting signal DS_ 1  from changing too frequently. Of course, typical comparators can also be used to replace the hysteresis comparators. If the typical comparators are used, the first high threshold value RH_ 1  equals to the first low threshold value RL_ 1  and the second high threshold value RH_ 2  equals to the second low threshold value RL_ 2 . 
   The second detecting unit  12  includes a low-pass filter  121 , a subtracter  122  and a hysteresis comparator  123 . The second detecting unit  12  receives a second kind control signal, such as the sub-beam sum signal SBAD or the RF ripple signal (RFRP), and detects the level of the second kind control signal. Since the level of the sub-beam sum signal SBAD and the RF ripple signal (RFRP) will be changed when the optical disc recorder is impacted, the second detecting unit  12  utilizes the low-pass filter  121  to extract a level average SBADLPF, and utilizes a subtracter  122  to compute a difference between the average SBADLPF and the second kind control signal to generate a second eigenvalue CS_ 2 . Then, the second detecting unit  12  utilizes the hysteresis comparator  123  to compare the second eigenvalue CS_ 2  with a third set of threshold values RH_ 3 , RL_ 3 , and to output a second detecting signal DS_ 2 . The third high threshold value RH_ 3  is greater than the third low threshold value RL_ 3 . When the second eigenvalue CS_ 2  is greater than the third high threshold value RH_ 3 , the second detecting signal DS_ 2  is H; and when the second eigenvalue CS_ 2  is smaller than the third low threshold value RL_ 3 , the second detecting signal DS_ 2  is L. Using the hysteresis comparator  123  can prevent the second detecting signal DS_ 2  from changing too frequently. Of course, a typical comparator can be used to replace the hysteresis comparator. If a typical comparator is used, the third high threshold value RH_ 3  equals to the third low threshold value RL_ 3 . 
   The third detecting unit  13  includes a counter  131 , an averaging unit  132 , a subtracter  133 , and a hysteresis comparator  134 . The third detecting unit  13  receives a third kind control signal, such as the rotating frequency identifying signal F, and detects the pulse length of the third kind control signal. Since the pulse length of the frequency identifying signal FG will be changed when the optical disc recorder is impacted, the third detecting unit  13  utilizes the counter  131  to detect the length of each pulse of the third kind control signal, and utilizes the averaging unit  132  to average the pulse lengths. The counter  131  counts the pulse number of a high-frequency clock for each pulse of the third kind control signal and outputs the count value as the pulse length. Thereafter, the third detecting unit  13  utilizes the subtracter  133  to compute the differences between each pulse length and the average length and to generate a third eigenvalue CS_ 3 . The third detecting unit  13  utilizes the hysteresis comparator  134  to compare the third eigenvalue CS_ 3  with a fourth set of threshold values RH_ 4 , RL_ 4 , and to output a third detecting signal DS_ 3 , wherein the fourth high threshold value RH_ 4  is greater than the fourth low threshold value RL_ 4 . When the third eigenvalue CS_ 3  is greater than the fourth high threshold value RH_ 4 , the third detecting signal DS_ 3  is H; and when the third eigenvalue CS_ 3  is smaller than the fourth low threshold value RL_ 4 , the third detecting signal DS_ 3  is L. The hysteresis comparator is used to prevent the third detecting signal DS_ 3  from changing too frequently. Of course, a typical comparator also may be used to replace the hysteresis comparator. If a typical comparator is used, the fourth high threshold value RH_ 4  equals to the fourth low threshold value RL_ 4 . 
   Since a scratched zone on the optical disc may also cause some control signals to be changed, such that the first detecting signal DS_ 1  and the second detecting signal DS_ 2  are enabled, misjudgment may be made if the shock signal is generated according only to the first detecting signal DS_ 1  and the second detecting signal DS_ 2 . Consequently, the shock detector  10  utilizes the AND gate  14  to integrate three detecting signals DS_ 1 , DS_ 2  and DS_ 3  to avoid misjudgment. In addition, when the optical disc recorder is impacted, the three detecting signals DS_ 1 , DS_ 2  and DS_ 3  will also be enabled, and no shock condition will be missed. Of course, the first detecting unit  11  of this embodiment is adapted to detecting the control signal, such as the tracking error signal TE, the focusing error signal FE, and the central error signal CS, so it is possible to only detect one of the signals. The second detecting unit  12  of this embodiment is adapted to detecting the sub-beam sum signal SBAD and the RF ripple signal (RFRP), so it is possible to only detect one of the signals. 
     FIG. 2  shows a flow chart of a controlling method for controlling the recording process of the write-once optical disc (e.g., CD-R, DVD-R) according to a shock signal. Referring to  FIG. 2 , the control method includes the following steps. 
   Step S 200 : start the recording process. 
   Step S 202 : detect the recording mode. If the recording mode is an interrupt mode, jump to step S 214 . If the recording mode is a normal mode, execute the step S 204 . 
   Step S 204 : detect the shock signal. If the shock signal is enabled, jump to step S 210 . If the shock signal is not enabled, execute the step S 206 . 
   Step S 206 : execute recording process and jump back to step S 202 . 
   Step S 210 : change the recording mode to the interrupt mode and set a high gain to the servo-loop. Then, enable a stop recording process and jump back to step S 202 . 
   Step S 214 : detect the shock signal. If the shock signal is enabled, repeat the step S 214 . If the shock signal is disabled, execute the next step S 216 . 
   Step S 216 : search the interrupted position. 
   Step S 218 : detect the shock signal. If the shock signal is enabled, repeat the step S 218 . If the shock signal is disabled, execute the next step S 220 . 
   Step S 220 : change the recording mode to the normal mode and set a low gain to the servo-loop. Then, enable a link recording process and jump back to step S 206 . 
     FIG. 3  shows a flow chart of a controlling method for controlling the rewritable optical disc (e.g., CD-RW, DVD+/−RW) recording according to a shock signal. Referring to  FIG. 3 , the control method includes the following steps. 
   Step S 300 : start the recording process. 
   Step S 302 : detect the recording mode. If the recording mode is an interrupt mode, jump to step S 314 . If the recording mode is a normal mode, execute the step S 304 . 
   Step S 304 : detect the shock signal. If the shock signal is enabled, jump to step S 310 . If the shock signal is not enabled, execute the step S 306 . 
   Step S 306 : execute normal recording process and jump back to step S 302 . 
   Step S 310 : change the recording mode to the interrupt mode and set a high gain to the servo-loop. Then, enable a stop recording process. 
   Step S 312 : store N blocks of encoded buffer data as repeated writing data when the link recording process is enabled. Jump back to step S 302 . 
   Step S 314 : detect the shock signal. If the shock signal is enabled, repeat the step S 314 . If the shock signal is disabled, execute the next step S 316 . 
   Step S 316 : search the interrupted recording position. 
   Step S 318 : detect the shock signal. If the shock signal is enabled, repeat the step S 318 . If the shock signal is disabled, execute the next step S 320 . 
   Step S 320 : change the recording mode to the normal mode and set a low gain to the servo-loop. Then, enable a link recording process. 
   Step S 322 : start recording the stored N blocks of encoded buffer data from the position of the N-th block before the interrupted recording position. Jump back to step S 306  to execute normal recording process. 
   The difference between the shock proof method for the write-once optical disc of  FIG. 2  and that for the rewritable optical disc of  FIG. 3  is that the shock proof method for the rewritable optical disc can rewrite the prior N blocks of problematic recorded data caused by shocks in the stop-writing region so as to enhance the recording correctness. 
   The above-mentioned step mainly utilizes the shock signal to enable the interrupted recording procedure and link recording procedure. The interrupted recording procedure and link recording procedure are disclosed in the Applicant&#39;s U.S. patent application Ser. No. 09/800,896, which was filed on Mar. 8, 2001 and entitled “LINK WRITING METHOD FOR A RECORDABLE COMPACT DISK AND DRIVER FOR USING THE METHOD” to control recording of link connection after the shock is eliminated. 
   In the above-mentioned steps, steps S 218  and S 318  mainly identify whether or not shocks have occurred again during the writing position seeking process so as to ensure that the continuous recording process of steps S 206  and S 306  will not fail owing to shocks. Of course, these steps also may be omitted. 
   While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific construction and arrangement shown and described, since various other modifications may occur to those ordinarily skilled in the art.