BURN-Proof Special Lecture

Dr. Yumika who is familiar with UM Doctor software will deliver a detailed commentary on BURN-Proof technology irregularities. In the fourth lecture, we would like to explain the new technology "Safe-BP" which prevents recording errors by detecting mechanical performance defects.

We, Sanyo Electric Co., Ltd., have set "speed" and "comfort" as our goal to develop in the 40x high speed recording in CD-R/RW drive. In consequence, users have been freed from "Buffer Under Run Errors" with the BURN-Proof technology, and this technology enables users to record data on discs securely. However, the more the recording speed increases, the less we can ignore the influence on the pickup servo of a slight deviation from mechanical accuracy of media.

Consequently, we have developed "Safe-BP", which is the ideal recording system, on super high speed recording by a half height drive with further improvement of the "Shock-BP", which was developed at CRD-SBP15A.

"Safe-BP" stops the recording at the site of the recording error, and restarts the recording while changing the recording speed by monitoring the pickup servo in real time. You can enjoy comfortable high speed recording without being concerned about deterioration of recording quality or interruption of recording.

Let's start the explanation of "Safe-BP".

When recording on CD-R media, the laser is irradiated on the organic pigment of the record material, and a record mark (pit) is printed at the high temperature of 300 degrees. This laser gives a servo control of the pick up lens, so that optimum power is achieved for the record side of the disk.
When the linear velocity of a CD is 1.2m/sec., the linear velocity of the CD will be 48m/sec. at 40x speed, which is equivalent to 180km per hour.

A CD-R/RW drive records the data on the disc in accordance with the prerecorded guiding groove (Groove). Therefore, the control of the pickup lens (pickup servo) is very important so that the drive can trace the guiding groove correctly.
The higher the recording speeds, the greater the variation of guiding groove's meandering (tracking) and the depth (focus) of the media becomes a problem for the media. Generally, The lens servo which focuses this laser output on the record side of the disk is called "the focus servo", and the servo which precisely traces the track engraved on the disk is called "the tracking servo ".

"Safe-BP" has reached an adequate detection performance at more than 40x speed with the improvement of the electric circuit for the detection of any disarrangement of the pickup servo, which is adopted at "Shock-BP".
When a disarrangement of this servo is detected at high speed recording, a drive stops the recording immediately and restarts recording at lower speed.

A high speed recording has been available for CD-R/RW drive with the advance of discs and semiconductors. However, it is impossible to totally eliminate all deviation from mechanical accuracy. The adoption of "Safe-BP" technology will relieve users from anxiety over the high speed recording and give them assurance of a comfortable high speed recording.

The following graph of the wave shapes is the recording start signal, the servo error detection signal, prerecorded ATIP standard signal of a disc and the tracking servo error signal in order from top. The lower wave shape is the enlarged wave shape which is enclosed within the square. The wave shape at the left side indicates the starting point of the 32x recording.
The interval of the prerecorded ATIP standard signal will be 13.3 msec. At standard speed, and approximately 420usec.(=13.3/32) at 32x speed. The wave shape at the right side indicates the starting point of 40x recording, and the interval of the prerecorded ATIP standard signal will be approximately 330usec.

Please look at the wave shape of tracking. The amplitude has been raised to allow easy observation of the errors. You can see that the servo error at 40x speed has been slightly increased on the measurement with the same disc.
Even though there is no problem with a recording condition at 32x CD-R/RW drives, the slight disarrangement of tracking servo and focus servo will widely influence on the recording quality in 40x CD-R/RW drives. Of course, each servo at each speed has been tuned to optimize recording. However, it seems almost impossible to support all available discs on the market.

Therefore, we have developed "Safe-BP" which stops the recording before the servo is out of order and then restarts recording at the lower recording speed while monitoring the servo condition in real time so that users can enjoy high speed recording without anxiety.

The following is the action which detects the disarrangement of servo.

Experimentally, the detection condition is so set this time that it can detect any disarrangement of servo easily. Note that the level of tracking servo error is slightly depressed as compared with the previous level when the disarrangement of servo has just been detected.

Even at 40x speed recording, the accurate monitoring of servo errors has been available. "Safe-BP" will become the essential function in the future age of super high speed recording.

- The detection of disarrangement of servo for Safe-BP - In addition to the ordinary servo filter, the "Safe-BP" has adopted a special detection filter to detect pickup servo errors. Furthermore, Shock-Proof technology, which is adopted for "Shock BP", has improved the detection response. However, "Safe-BP "may work when a vibration or impact occurs because they also may cause the disarrangement of disc servo.

In addition to "Safe-BP", SANYO Electric Co., Ltd. is jointly evaluating the mechanical performance of discs with the media makers and is providing a list of recommended media. Moreover, we are jointly studying the improvement of disc performance with them.
The CD-R/RW drive which realizes the most suitable high speed recording for discs has become a reality with the adoption of "Safe-BP" in addition to "FlexSS-BP".

< Chapter 1 [About the quality of a BURN-Proof's link portion]
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