Static information storage and retrieval – Analog storage systems – Thermoplastic
Reexamination Certificate
1999-09-02
2002-01-29
Hindi, Nabil (Department: 2651)
Static information storage and retrieval
Analog storage systems
Thermoplastic
C369S047350
Reexamination Certificate
active
06343028
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an interface circuit that is suitable for use in digital audio equipment and digital video equipment. It also relates to an optical disk (disc) manufacturing system for manufacturing optical disks such as compact disks and digital video disks, and more particularly to a manufacturing system that can manufacture optical disks that record digital waveform data faithfully with respect to the original sound or image, without the influence of such non-code components as jitter components and waveform distortion components (ripple components).
2. Description of the Related Art
FIG. 1
is a block diagram that shows an example of the case in which an interface circuit of the past is applied to, for example, a compact disk (CD) player.
The digital signal processing unit
61
is provided with a servo circuit
63
, which controls the rotational drive system of a CD
62
, a digital signal processing circuit
64
, which processes signals read from the CD
62
, and a quartz oscillator
65
that serves as a synchronization reference.
The interface circuit
66
is formed by a transmitting-side interface circuit
66
a
within the digital signal processing unit
61
and a receiving-side interface circuit
66
within an analog signal processing unit
67
. The transmitting interface circuit
66
a and the receiving-side interface circuit
66
b
are joined by means of an optical transmission element.
The analog signal processing unit
67
is provided with a digital filter
68
and a digital-analog (D/A) converter
69
.
As shown in
FIG. 1
, the digital signal processing unit
61
and the analog signal processing unit
67
are of separate construction (D/A-separated construction). This is done to prevent electrical noise that is generated in the servo circuit
63
or the digital signal processing circuit
64
from influencing the analog signal processing unit
67
, as this can adversely affect the sound quality. When a D/A-separated system is housed in one and the same enclosure, great care is taken with respect to unwanted radiation.
In general, the power supply of the analog signal processing unit
67
is kept separate from the digital signal processing unit
61
, as a measure to prevent the deterioration of sound quality by the power supply ground line.
Having taken the above-noted measures, a digital signal is transmitted from the digital signal processing unit
61
to the analog signal processing unit
67
, with optical transmission, which features total electrical isolation and no unwanted radiation, being used in both separate and single-enclosure implementations.
However, the adverse affect on sound quality that the digital signal processing unit
61
has on the analog signal processing unit
67
is still not entirely eliminated, and optical transmission is accompanied by the following problems.
(a) In the process of sending a digital signal from the digital signal processing unit to the analog signal processing unit, a jitter component and a waveform distortion component (a ripple component) are added to the digital signal waveform, these representing a deterioration of the digital signal waveform.
(b) A jitter component that is generated in the digital signal processing unit, which is the cause of a deterioration in sound quality, is transmitted to the analog signal processing unit via the digital signal transmission.
One measure taken to solve the above-noted problems (a) and (b), is that of using a clock having the accuracy of a quartz element is used in the digital signal processing unit to perform resampling of the digital signal immediately before transmission. Another measure to solve the above-noted problems is that of compensating the variation of pulse width in the optical transmission in the analog signal processing unit, and using two stages of PLLs to improve the accuracy of the timing clock.
An additional method is that of moving the quartz oscillator, which serves as the synchronization or timing reference from its usual position in the digital signal processing unit to the analog signal processing unit, and using the resultant synchronization signal to more reliably establish synchronization of the digital signal processing unit, and to resample readout data using a clock of quartz oscillator accuracy in the analog signal processing unit, thereby improving the accuracy of the digital signal.
While the above measures do have some effect, it is intrinsically not possible to eliminate causes of sound quality deterioration jitter and waveform distortion components) that are added in the process of digital signal transmission from the disk to the analog signal processing unit.
The jitter components and waveform distortion components are non-correlated components, which are not correlated to the original audio signal (the signal before being recorded digitally on a CD, for example). In contrast to these non-correlated components, harmonic distortion components of the analog signal can be referred to as correlated components. Because the level of a non-correlated component perceived by the human ears is extremely high, the annoyance imparted audible sound quality by a non-correlated component is greater than that from a correlated component.
In a digital signal, even if the binary (0 and 1) coding itself remains the same, these non-correlated components cause the audio quality to change.
FIG. 2
shows a transmitted digital signal, in which (a) is a digital signal that is transmitted from a digital signal processing unit via an interface circuit to an analog signal processing unit, (b) is the original coding information that is read from the disk, and (c) shows the jitter and waveform components that are generated within the digital signal processing unit.
The original coding information shown in
FIG. 2
, (b) has the jitter component and waveform distortion component (non-correlated components) that are shown in
FIG. 2
, (c) superimposed on it, thereby making the transmitted signal (shown in
FIG. 2
, (c)), which is transmitted to the analog signal processing unit.
In this manner, once the non-correlated components are added to the digital signal, they cannot be removed by digital transmission that is used for the purpose of separating the digital and analog circuitry. Although an optical fiber is immune to the superimposition of external noise, because it does not have the function of removing non-correlated components that are already included in a digital signal, these non-correlated components are transmitted along with the digital signal, so that there is almost no effect of improving the non-correlated distortion.
Additionally, once these non-correlated components are transmitted, they intrude into the ground and power supply lines within the analog signal processing unit, so that while subsequent waveform shaping or the like can make an apparent improvement in the appearance of the digital waveform, the non-correlated components pass directly through the digital-analog converter, and act to change the analog quality.
In the past, one known recording method that enables faithful playback of a recorded original sound was that of direct cutting. This direct cutting method is that of using the sound from a performance as either an analog or a digital signal for immediate direct recording onto a recording medium. Using the direct cutting method, because the original sound can be directly recorded onto a recording medium, it is possible to faithfully record the original sound onto a recording medium and play back the sound therefrom, with almost no noise or deterioration of the sound quality.
To record using the above-noted direct cutting method, however, it is necessary either that a performer be brought to a location at which the direct cutting recording equipment is installed, or that the direct cutting recording equipment be brought to the location of the performance. Additionally, if a mistake occurs during a performance, because it is not possible to perform editing, such as having the p
Berkowitz Marvin C.
Hindi Nabil
Nath Gray M.
Nath & Associates PLLC
Victor Company of Japan Ltd.
LandOfFree
Interface circuit and optical disk manufacturing system that... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Interface circuit and optical disk manufacturing system that..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interface circuit and optical disk manufacturing system that... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2858434