Method for preventing an optical recording device from erroneous defect detecting during writing

#1. Field of the Invention

#The present invention relates to a method of defect detecting in an optical recording device, and in particular, to a method for preventing erroneous defect detection when the optical recording device switches from read to write.

#2. Description of the Prior Art

#FIG. 1 is a waveform diagram illustrating the conventional detection of defect locations on a disk by comparing the SBAD signal and a reference signal.

#FIG. 2 is a waveform diagram illustrating the conventional detection of defect locations on a disk by comparing the SBAD signal and a reference signal which is output by a low pass filter having a higher threshold frequency.

#FIG. 3 is a waveform diagram illustrating the conventional detection of defect locations on a disk by comparing the SBAD signal and the reference signal at the start of writing.

#The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention. The scope of the invention is best defined by the appended claims.

#FIG. 6 shows the packet write format used when writing data to a disk. A packet is comprised of 1 link block (LNK), 4 run-in blocks (RI1–RI4), 32 user data blocks (UD1–UD32), and 2 run-out blocks (RO1–RO2). The first 5 blocks of a packet are a period of buffer time used for data identification and are provided in consideration of the fact that the laser output power from the optical head is unstable at the beginning of writing. Writing of real data will be started with the sixth block. After writing of the data is completed, the two run-out blocks (RO1–RO2) are used as the end of the packet write.

#As shown in FIG. 7, the present invention primarily takes advantage of the time of the first five blocks of the packet write to help an optical recording device to properly adjust relative settings during writing. The settings include the threshold frequency of the low pass filter, the upper limit, and the lower limit. Normally, the optical recording device has a SBAD signal generated by the optical head and a reference signal (SBAD_Ipf) obtained by passing the SBAD signal through a low-pass filter having a first threshold frequency. Also, a first upper limit and a first lower limit that are used for determining defect locations are preset. Because the short period of time immediately after writing is started is not user data block, a second set of settings can be used during this short period of time. In this short period of time, the first threshold frequency is increased to a second threshold frequency and the preset first upper limit and the first lower limit are changed to a second upper limit and a second lower limit. In this way, during the short period of time immediately after writing begins, the reference signal, which is output by the low pass filter having the second threshold frequency, can change quickly to approach the SBAD signal. If the second lower limit is extended enough, no defect area will be detected in the short period of time. This present method is different from the conventional method of changing the value of the reference signal to have the same value of the SBAD signal at the time that writing starts. In the meantime, the upper and lower limits for determining defective locations are changed; that is, the first upper limit is increased to the second upper limit, and the first lower limit is decreased to the second lower limit. In this way, misdetection of defect locations in the region of the starting location can be avoided.