Pulse or digital communications – Synchronizers – Phase displacement – slip or jitter correction
Reexamination Certificate
1998-09-11
2002-04-02
Chin, Stephen (Department: 2734)
Pulse or digital communications
Synchronizers
Phase displacement, slip or jitter correction
C375S238000, C375S376000, C327S100000, C369S053130
Reexamination Certificate
active
06366631
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a jitter measurement device for signals reproduced from an optical disc, which measures the jitter component of the reproduced signal of optical disc by storing digital data in accordance with an indicated modulation rule; and jitter measurement method for reproduced signal of optical disc. In addition, this invention relates to a method and device for optical disc recording and/or reproducing.
BACKGROUND
The optical disc drive which reproduces the optical disc, in which the digital data is stored, detects reforming (RF) signals, and binarizes this RF signals, then generates the digital data. Specifically, the optical disc drive binarizes the RF signals, as shown in
FIG. 7
(
a
), at the indicated slice level, and generates the digital data as shown in
FIG. 7
(
b
).
Furthermore, the digital data which has been modulated according to the indicated modulation method, is generally recorded in the optical disc. For examples, for so-called compact disk, provided that one cycle of digital data is T, a signal to be recorded will be modulated from a signal with the cycle of 3T to that with 11T, and the waveform of each cycle will be randomly recorded. As another example, for digital video disc, provided that one cycle of digital data is T, a signal to be recorded will be modulated from a signal with the cycle of 3T to that with 14T, and the waveform of each cycle will be randomly recorded. The optical disc drive in which the digital data which has been modulated according to the indicated modulation method, is generally recorded, reproduces a signal from the optical drive; then it binarizes this signal, and generates digital data.
By the way, the digital data which has been binarized by the optical disc drive, should be generally reproduced in the way that noise riding on cyclic direction; that is, in the way that jitter component is contained. For examples, in case of picking up only the waveform with cycle of 3T, out of the RF signals reproduced from the optical disc, the cycle of the waveform if this RF signal will be 3T±&sgr;(&sgr;: jitter component), in which the jitter component is contained, as against the theoretical cycle 3T.
As for the reasons why such binarized digital data is reproduced containing the jitter component, for examples, we can consider the influence of noise which is included in the recording signal of the optical disc, or the influence from the characteristic of the optical pickup which detects the signals recorded in the optical disc.
Currently, a jitter measurement device which detects the jitter component of digital data reproduced from optical disc is known. The said jitter measurement device measures the jitter component of the RF signals reproduced from the optical disc. It is used for obtaining the characteristic of the optical disc or the optical pickup.
In the following sections, we will explain the first to the third jitter measurement device, which has currently been used for measuring of the jitter component of the RF signals reproduced from optical disc.
One known jitter measurement device, which has currently been used for measuring of the jitter component, computes the time breadth of digital data as voltage value, by using integration circuit, and measures the jitter component.
FIG. 8
is a waveform diagram explaining the method of operation for the first jitter measurement device on an input RF signal. First, the input RF signal is binarized by thresholding at a slice level to generate digital data. The first jitter measurement device starts an integration circuit on the leading edge of a positive transition in the digital data. The integration circuit is stopped on the trailing edge and the voltage from the integration circuit is read out. The output voltage indicates the time breadth of the digital data.
Therefore, the said first jitter measurement device can detect the jitter value which has been converted into the voltage value (&sgr;V), by comparing the said output voltage from the integration circuit with the voltage value corresponding to the integrated cycle.e
We would remind you that the said first jitter measurement device can only detect the jitter component corresponding to the waveform of cycle
1
, among the waveforms of multiple cycles, which have been modulated and recorded in the optical disc, by using one(1) integration circuit; because the characteristic of the integration circuit is determined in accordance with time constant. Namely, if the optical disc to be reproduced is a compact disc, the said first jitter measurement device can only detect the jitter component of the waveform with cycle of 3T, by using one(1) integration circuit; but it cannot detect the jitter component of the waveform with the other cycles, for example, the waveform with cycle from 4T to 11T.
A second known jitter measurement device, which has currently been used for measuring of the jitter component, has adopted a device so-called “time interval analyser”. It counts the time breadth of digital data by using a high-speed clock, and detects the jitter component by using the said count output. The second jitter measurement device, as shown in
FIG. 9
, binarizes the RF signals at the indicated slice level, and generates the digital data. Second, the said second jitter measurement device let the clock circuit operate, as well as starts counting the clock number which is the output from the said clock circuit, at the time point when the RF signal reaches to the slice level, that is, at the leading edge of the digital data. Third, the said second jitter measurement device let the clock circuit stop at the time point when the RF signal reaches to the next slice level, that is, at the trailing edge of the digital data. The count number at this point is considered to be the time breadth of digital data for the said second jitter measurement device.
Therefore, the said second jitter measurement device can detect the jitter value, by comparing the said count number of the counter with the count number at the indicated cycle.
The third known type of jitter measurement device, which has currently been used for measuring of the jitter component, has adopted the first jitter measurement device and the said second jitter measurement device.
First, the third jitter measurement device, as shown in
FIG. 10
, binarizes the RF signals at the indicated slice level, and generates the digital data. During this operation, in the third second jitter measurement device, the clock circuit continues generating clock at the indicated clock frequency. Second, the said third jitter measurement device lets the clock circuit operate, as well as counts the clock number which is the output from the said clock circuit, by using a counter, at the time point when the RF signal reaches to the slice level, that is, at the leading edge of the digital data. In addition, the said third jitter measurement device starts operating the integration circuit at the said leading edge of the digital data. Third, the said third jitter measurement device stop operating the integration circuit, at the timing of the clock which has been generated immediately after the leading edge of the digital data. Then, the said third jitter measurement device measures the output voltage V
1
of the integration circuit, and converts the said output voltage V
1
into the time breadth, which is to be the first time breadth t
1
of the digital data.
The third jitter measurement device once again starts operating the integration circuit at the timing of the clock immediately before the time point when the RF signal reaches to the next slice level, that is, at the timing of the clock immediately before the trailing edge of the digital data. Then, the said third jitter measurement device stops operating the integration circuit at the time point when the RF signal reaches to the next slice level, that is, at the trailing edge of the digital data.
The third jitter measurement device detects the count number if the counter at the trailing edge of the digital
Hashimoto Yukari
Kohama Shunsuke
Nakayama Akihito
Shintani Kenji
Chin Stephen
Frommer William F.
Frommer & Lawrence & Haug LLP
Liu Shuwang
Simon Darren M.
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