A novel constant linear velocity (CLV) control method employing sync pattern detection has been developed for the
multi-level run-length limited read-only disc. In the proposed method, the sync pattern is special designed and inserted in
the RF signal to detect the velocity error of the spindle. The differentiation method is adopted to detect the sync pattern
from the RF signal and is more easy and accurate than using the threshold level slicer. By using the proposed CLV
method, the spindle works robust in the CLV mode and the velocity error of the spindle can be suppressed less than
0.3%. The experimental result shows the novel CLV control method for the ML-RLL read-only disc is practicability.
Our team have proposed and implemented a new type of multi-level DVD, which features in using the waveform to
differentiate levels. Servo accuracy is an important issue for an optical disk system, since it can directly influence the
quality of readout signal. This paper analyses the influence of servo error on the readout signal for our multi-level DVD
using numerical simulation. A readout model is established, where focus error (FE) and tracking error (TE) is introduced.
A new parameter, waveform deviation, is proposed to quantitatively evaluate the influence. Simulation results show that
the influences of TE/FE on readout signal are similar. Each of them will shrink the dynamic range of readout signal.
When TE/FE exceeds a threshold, the waveform deviation will increase sharply.
The Radio Frequency (RF) signal of the Multi-Level Run-Length-Limited (ML-RLL) read-only disc is different from
that of DVD, so the readout system of the ML-RLL read-only disc is built specially. The readout system of the ML-RLL
read-only disc can realize servo control, RF signal readout and so on. The readout system consists of Digital Versatile
Disc (DVD) traverse, analog front-end and digital processing part. Analog front-end can realize front-end amplification
of the output signal of the optical pick-up and power drive of mechanism. Digital processing part mainly consists of
digital circuits, which functions are the servo controlling, demodulation and decoding of RF signal, general control and
so on. The whole system is implemented on two Field Programmable Gate Array (FPGA) chips and the experimental
results show a good performance. We tested the important signals, and experimental results are also given to verify the
performance of this development platform, which meets the controlling and detecting requirements to multi-level
read-only disc completely. The Bit Error Rate (SER) can achieve below 10<sup>-4</sup>.
Multi-level run-length limited (ML-RLL) recording technology can increase the capacity of the read-only disc without changing the optical and mechanical units. The characteristic of the push-pull signal of the multi-level run-length limited read-only disc is analyzed and compared with that of the conventional DVD read-only disc. Experimental results show the effect of the variation of pit depth is more than other parameters and the peak-to-peak amplitude of the push-pull signal in the ML-RLL read-only disc is about 2.9 times of that in the DVD read-only disc while the variance is nearly 3.2 times. The push-pull method in the ML-RLL read-only disc is more sensitive than that in the conventional DVD read-only disc.