Abstract:
The present invention describes an apparatus and method for optical disk drive signal processing. For improving the bandwidth for signal transmitting between an optical disk drive (ODD) controller and an optical pick-up unit (OPU) via a flexible cable, a physical address pre-processing unit is mounted on the optical pick-up unit of a Optical disk drive. The long settling time problem conventionally due to a voltage change in the writing process can be resolved. The apparatus and method extract the physical address in the high-writing process of the Optical disk drive.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention uses a physical address pre-processing unit mounted on an optical pick-up unit of an optical disk drive to improve the bandwidth of the transmission between an optical disk control unit and the optical pick-up unit, and to extract a physical address in a high-speed writing process.  
         [0003]     2. Description of Related Art  
         [0004]     The optical disk drive is a standard device for the desktop or the laptop computer. In both the read-only and re-writable type, the read/write speed of optical disk drive is becoming highly and well developed.  
         [0005]     Reference is made to  FIG. 1 , which shows a conventional optical disk drive with a signal processing system. The drive includes an optical pick-up unit  12 , an optical disk control unit  14 , and a flexible cable  16  therebetween. The optical pick-up unit  12  further includes a laser diode driver  120 , laser diode  122 , and a photo detector integrated chip (PDIC)  126 . Moreover, the optical disk control unit  14  further includes a servo controller  140  and an analog pre-amplifier  142 , wherein the analog pre-amplifier  142  includes a physical address generation unit  144 .  
         [0006]      FIG. 2  shows a schematic drawing of the record layer of an optical disk in tangential direction. The direction  34  is the tangential direction of the optical disk track  32 . The laser beam produced by the laser diode  122  is focused on the optical disk record layer  30  of the optical disk track  32 .  
         [0007]      FIG. 3  shows a detailed structure of the photo detector integrated chip of the prior art. The photo detector integrated chip  126  received the laser beam reflected by the optical disk and transform an optical signal of the laser beam into a plurality of pre-s ample/hold electrical signal. As shown in the schematic drawing, the photo detector integrated chip  126  is divided into four quadrants, A, B, C, and D. In the photo detector integrated chip  126 , each of the four quadrants receives the optical signal and transforms the received optical signal into the electrical signals respectively. After that, the electrical signals are transmitted to a gain buffer  42 , and generates the pre-sample/hold electrical signals, including a first electrical signal  420 , a second electrical signal  422 , a third electrical signal  424  and a fourth electrical signal  426 . Then the physical address of the optical disk drive can be extracted from the pre-sample/hold electrical signals, and the steps of extraction are described below.  
         [0008]     First, generating a determination signal by subtracting the sum of the first electrical signal  420  and the fourth electrical signal  426  from the sum of the second electrical signal  422  and the third electrical signal  424 . Next, the determination signal is transmitted to a physical address generation unit  144  of the optical disk control unit  14  for further physical address extraction.  
         [0009]     As the schematic drawing shown in  FIG. 4 , the pre-sample/hold electrical signal from the photo detector integrated chip transforming the laser beam reflected by the optical disk is described. The laser diode  122  writes the information in the optical disk  10  on which a plurality of surface grooves  60  is formed. As the power of laser from the laser diode  122  is written into the grooves, the wave signal of the pre-sample/hold electrical signal shown as a wave pattern  62  in  FIG. 4  is unstable.  
         [0010]      FIG. 5  shows the wave pattern of a transmitted pre-sample/hold electrical signal, which is the pre-sample/hold electrical signal been transmitted from the photo detector integrated chip  126  to the optical disk control unit  14  via a flexible cable. Corresponding to the surface groove  80  in  FIG. 5 , the settling time from the peak to the stable state will be stretched, e.g. the curve  51  of the wave pattern  82 , after which the zone of S/H will be too narrow to perform sample/hold during the high-speed writing process. Therefore, the erroneous physical address of the track will cause the error decoding.  
         [0011]     The block diagram of the physical address generation unit  144  of the optical disk control unit  14  is shown in  FIG. 6 . There are four pre-sample/hold electrical signals  420 ,  422 ,  424  and  426  generated from the photo detector integrated chip shown in  FIG. 3 . The sample/hold unit  70  receives the four transmitted pre-sample/hold electrical signals  420 ,  422 ,  424 ,  426  and a sample/hold timing  74 , and then generates four transmitted post-sample/hold electrical signals  702 ,  704 ,  706  and  708 . Next, those post-sample/hold electrical signals  702 ,  704 ,  706  and  708  are transmitted to a physical address decoding unit  72 , and a physical address signal  720  is generated from the physical address decoding unit  72 .  
         [0012]     The prior method for optical disk drive signal processing comprises the steps described as follows:  
         [0013]     The laser beam emitted from the laser diode  122  to optical disk  10  is controlled by the laser diode driver  120  of the optical pick-up unit  12 . Subsequently, the laser beam is focused on the optical disk record layer and the optical signals are received by the photo detector integrated chip  126  of the optical pick-up unit  12 . The optical signals are then transformed into pre-sample/hold electrical signals via the photo detector integrated chip  126  and the post-sample/hold electrical signals are transmitted to the optical disk control unit  14  through the flexible cable  16 . The physical address of the optical disk  10  wherein the laser beam is reflected is generated by the physical address generation unit  144  of the analog pre-amplifier  142  of the optical disk control unit  14 , and the physical address is provided to the servo controller  140  for further signal processing.  
         [0014]     In the prior art, since the laser power provided by the laser diode  122  makes the pulse modulation with the data to be written to the optical disk  10  when the optical disk drive working in the high-speed writing process, the post-sample/hold electrical signal output from the photo detector integrated chip  126  is also the high-frequency pulse signal as shown in  FIG. 4 . After that, the high-frequency pulse signal is transmitted to the optical disk control unit  14  via the flexible cable  16 , and then the high-frequency pulse signal undergoes sample/hold and decoding in the optical disk control unit  14 . However, the flexible cable  16  is not flawless, and interference, including narrow bandwidth and mismatch, prolongs the settling time and mismatches the optical signals. Finally, accuracy and efficiency are difficult to maintain in reading the physical address and recovering the wobble signal as shown in  FIG. 5 .  
         [0015]     For overcoming the physical limitation of the flexible cable, especially when working in high-frequency transmission, the present invention discloses an apparatus for setting a physical address pre-processing unit in the optical pick-up unit and the method thereof for improving the efficiency and accuracy in decoding the physical address of the optical disk.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention relates to an apparatus and method for optical disk drive signal processing. A physical address pre-processing unit is installed on an optical pick-up unit for decreasing the bandwidth requirement of a flexible cable and improving the settling time as the voltage changes in the writing process. In implementation, the optical disk drive can perform sample/hold and extract the physical address smoothly.  
         [0017]     The apparatus to extract the physical address of the present invention comprises the following elements. An optical pick-up unit includes a laser diode, which emits a laser beam focused on an optical disk record layer. A photo detector integrated chip receives the laser beam reflected from the optical disk and transforms the laser beam into a pre-sample/hold electrical signal. A physical address pre-processing unit is installed in the optical pick-up unit, receives the pre-sample/hold electrical signal and generates an post-sample/hold electrical signal after performing sample/hold. An optical disk control unit includes a physical address generation unit. The post-sample/hold electrical signal is transmitted to the physical address generation unit via a flexible cable to produce the physical address of the optical disk.  
         [0018]     The method includes the following steps. A laser beam is emitted from a laser diode and focused on an optical disk record layer of an optical disk. The laser beam is reflected from the optical disk by a photo detector integrated chip and transformed into a plurality of pre-sample/hold electrical signals. The pre-sample/hold electrical signal is received by a physical address pre-processing unit and a post-sample/hold electrical signal is produced after performing sample/hold. The post-sample/hold electrical signal is transmitted to a physical address generation unit of an optical disk control unit via a flexible cable and then becomes a transmitted post-sample/hold electrical signal. Finally, the physical address of the optical disk is produced by a physical address generation unit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, in which:  
         [0020]      FIG. 1  is a schematic drawing of an optical disk control system of the prior art;  
         [0021]      FIG. 2  is a schematic drawing of tangential view of a record layer of an optical disk of the prior art;  
         [0022]      FIG. 3  shows the inner structure of a photo detector integrated chip of the prior art;  
         [0023]      FIG. 4  is a schematic drawing of the wave pattern of the pre-sample/hold electrical signal transformed by the photo detector integrated chip of the prior art;  
         [0024]      FIG. 5  is a diagram of the wave pattern of the transmitted pre-sample/hold electrical signal output from a flexible cable of the prior art;  
         [0025]      FIG. 6  is a schematic drawing of a physical address generation unit of the prior art;  
         [0026]      FIG. 7  is a schematic drawing of an optical disk control system in the present invention;  
         [0027]      FIG. 8  is a diagram of the related wave pattern of the present invention;  
         [0028]      FIG. 9  is a diagram of the related wave pattern corresponding the  FIG. 1  of the prior art; and  
         [0029]      FIG. 10  is a flow chart of steps of producing the physical address in the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0030]     To allow the Examiner to understand the technology, means and functions adopted in the present invention, reference is made to the following detailed description and attached drawings.  
         [0031]     The present invention provides a physical address generation mechanism for optical disk drive signal processing to solve the transmission limitation in high frequency due to the limiting physical property of a flexible cable between an optical pick-up unit and an optical disk control unit. To improve the efficiency and accuracy for extracting a physical address when the optical disk drive working in the high-speed writing process, a physical address pre-processing unit is installed in an optical pick-up unit.  
         [0032]     Reference is made to  FIG. 7 , which is the block diagram of the optical disk drive including an optical disk control unit  24  and an optical pick-up unit (OPU)  22 . The optical disk control unit  24  is connected to the optical pick-up unit  22  by a flexible cable  16 . The optical pick-up unit  22  includes a laser diode driver (LDD)  222  and a physical address pre-processing unit  220 . The physical address pre-processing unit  220  is included in the diode driver (LDD)  222 , or alternatively, the physical address pre-processing unit  220  can also be installed outside the laser diode driver  222 .  
         [0033]     The optical pick-up unit  22  further includes a laser diode  224  and a photo detector integrated chip (PDIC)  228 . The optical disk control unit  24  further includes a servo controller  240  for controlling the motion of the optical disk drive, an analog pre-amplifier  242  and the physical address post-generation unit  244 , which is used to extract the physical address of the optical disk drive wherein the laser beam is reflected.  
         [0034]     The optical disk drive controlling system described above illustrates that the optical pick-up unit  22  emits a laser beam on an optical disk  20  using the laser diode  224  controlled by the laser diode driver  222 . After that, the laser beam is focused on an optical disk record layer (referring to  FIG. 2  of the background of the invention), and the reflected laser beam as optical signal is assembled by the photo detector integrated chip  228 . After that, the optical signal is transformed into pre-sample/hold electrical signal by the photo detector integrated chip  228 . The physical address pre-processing unit  220  receives the pre-sample/hold electrical signal, and samples and holds the pre-sample/hold electrical signal with lower power and cancels the part with high power, and then generates a post-sample/hold electrical signal. The post-sample/hold electrical signal can be sent smoothly from the optical pick-up unit  22  to the optical disk control unit  24  via the flexible cable  16 . Then the physical address of the optical disk  20  wherein the reflected laser beam can be extracted using the physical address post-generation unit  244  of the analog pre-amplifier  242 . Thus, the extracted physical address is employed for the following signal processing by the servo controller  240  of the optical disk control unit  24 .  
         [0035]     Referring to  FIG. 6  of the prior art, the physical address generation unit  144  of the analog pre-amplifier  142  of the optical disk control unit  14  transform the pre-sample/hold electrical signals  420 ,  422 ,  424 ,  426  transmitted from the photo detector integrated chip  126  via the flexible cable  16  into  702 ,  704 ,  706 ,  708  by performing the sample/hold, that is, sampling and holding the pre-sample/hold electrical signals  420 ,  422 ,  424 ,  426  with lower power and canceling the part with high power. However, the present invention perform the sample/hold by using the physical address pre-processing unit  220  which receives the pre-sample/hold electrical signals  420 ,  422 ,  424 ,  426  directly via an internal wire line instead of the flexible line used in the prior art, transforms the pre-sample/hold electrical signals  420 ,  422 ,  424 ,  426  into the post-sample/hold electrical signals  702 ,  704 ,  706 ,  708 , and sends the post-sample/hold electrical signals  702 ,  704 ,  706 ,  708  to the physical address post-generation unit  244  via the flexible cable  16 . Finally, the physical address signal is extracted by the physical address post-generation unit  244 . In addition to a sample/hold unit, the physical address pre-processing unit  220  further includes a combination of a low pass filter, an add-subtract operator and a gain buffer.  
         [0036]     Corresponding to the optical disk groove  90 , the curve (b)-(f) in  FIG. 8  of the present invention shows the signaling wave pattern of the pre-sample/hold electrical signals and the post-sample/hold electrical signal, the pre-sample/hold electrical signals including the first electrical signal  420 , second electrical signal  422 , third electrical signal  424 , fourth electrical signal  426  and an output signal  92 , respectively. After performing the sample/hold on those signals  420 ,  422 ,  424 ,  426 , an area with low and smooth waves corresponding to the optical disk groove  90  is selected as a sampling region  94 , and the remaining regions, except the sampling regions  94 , are selected as the holding region  96 . The output signal  92  shown in  FIG. 8  is formed after the add-subtract operator, that is: (first electrical signal+fourth electrical signal)−(second electrical signal+third electrical signal). Obviously, the output signal  92  without high-power wave pattern is used for the extraction of the physical address, which is in error when the sample/hold region is too narrow in high frequency of the high-speed operating optical disk.  
         [0037]      FIG. 9  shows the wave pattern of the transmitted post-sample/hold electrical signal from the optical pick-up unit  22  to the optical disk control unit  24  and the transmitted pre-sample/hold electrical signals corresponding to  FIG. 1  of the prior art, wherein the physical address generation unit  244  receives the transmitted pre-sample/hold electrical signals  420 ,  426 ,  422  and  424 , which all are transmitted via the flexible cable  16 . The optical disk groove  100  is the track of an optical disk, and the wave  102  is the output signal after the sample/hold and add-subtract operator. The noise and shifting existing on the four transmitted pre-sample/hold electrical signals  420 ,  426 ,  422  and  424  will cause error extraction of the track of the optical disk due to the narrow sampling region  104 .  
         [0038]     Reference is made to  FIG. 10 , which illustrates the steps of the method for optical disk drive signaling processing.  
         [0039]     First, a laser beam is emitted from a laser diode controlled by a laser diode driver and focused on an optical disk record layer of an optical disk (step S 100 ). A plurality of optical signals reflected from the optical disk is received by a photo detector integrated chip and transformed into a plurality of pre-sample/hold electrical signals (step S 102 ). The pre-sample/hold electrical signals are received by a physical address pre-processing unit of an optical pick-up unit (step S 104 ). An output signal is produced after performing sample/hold, optionally through additional steps including low pass filter, add-subtract operator or gain buffer (step S 106 ). The output signal is transmitted to an optical disk control unit via a flexible cable (step S 108 ). A physical address of the optical disk is extracted by a physical address decoding unit of a physical address post-generation unit (step S 110 ). Finally, the physical address extracted is sent to a servo controller of the optical disk control unit for further processing.  
         [0040]     In particular, the present invention relates to an apparatus and method for optical disk drive signal processing, in which a physical address pre-processing unit is installed on an optical pick-up unit for increasing the bandwidth of a flexible cable and avoiding the problematic long settling time when the voltage is changed in writing process. The optical disk drive can then perform sample/hold and extract the physical address smoothly.  
         [0041]     The many features and advantages of the present invention are apparent from the written description above and it is intended that the appended claims cover all. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.