Reproducing apparatus for reproducing a rotary recording medium recorded with a color video signal

The present invention provides a novel and useful reproducing apparatus for reproducing a rotary recording medium recorded with a color video signal. Another and more specific object of the present invention is to provide a reproducing apparatus capable of reproducing any one of the NTSC disc, the disc, or the SECAM disc so that a reproduced picture is obtained in a receiver of any of the three systems, that is, the NTSC system, the system, or the SECAM system. According to the apparatus of the present invention, an arbitrary disc can be reproduced regardless of the color video signal system, and a reproduced picture can be obtained by an arbitrary receiver regardless of the system it uses.

BACKGROUND OF THE INVENTION 
The present invention generally relates to reproducing apparatuses for 
reproducing a rotary recording medium (hereinafter simply referred to as a 
disc) recorded with a color video signal, and more particularly to a 
reproducing apparatus capable of compensating for the phase shift and 
reproducing a disc recorded with a color video system of any of the three 
system, that is, a disc recorded with a NTSC system color video signal 
(hereinafter referred to as an NTSC disc), a disc recorded with a 
system color video signal (hereinafter referred to as a system disc), 
or a disc recorded with SECAM system color video signal (hereinafter 
referred to as a SECAM system disc). The reproducing apparatus according 
to the present invention is capable of obtaining a finely reproduced 
picture with a receiver of any one of the above three systems, that is, 
the NTSC system, the system, or the SECAM system. 
Generally, as a color video signal system, there are the NTSC system, the 
system, the SECAM system, and the like. The color television 
broadcasting uses any one of the above systems, and the system used is 
usually unified within a country. However, in the case of a disc 
reproducing apparatus, there are times when it is desirable to reproduce a 
disc of a system other than the color television broadcasting system used 
in that country, according to the program contents of the video signal 
recorded in the disc. Accordingly, it is highly desirable for the disc 
reproducing apparatus to have a construction such that the disc 
reproducing apparatus can reproduce a disc of any one of the above 
systems. 
Furthermore, it is desirable for the disc reproducing apparatus to be 
designed so that a color television receiver of any one of the above 
systems can be connected to this disc reproducing apparatus. By this kind 
of a design, it becomes unnecessary to manufacture reproducing apparatuses 
exclusively for one particular system according to the color television 
broadcasting system used, and a single kind of reproducing apparatus may 
be used in any country using any one of the above systems. This feature 
will especially be effective when neighboring countries used different 
color television broadcasting systems. 
In addition, in the reproducing apparatus, due to such causes as irregular 
rotation of the disc, eccentricity of the disc, and curves formed in the 
recording surface of the disc, a time-base fluctuation component 
(hereinafter referred to as jitter) is included within the reproduced 
color video signal. Accordingly, in the conventional disc reproducing 
apparatus, a circuit is provided for compensating for the above jitter. 
This circuit separates a horizontal synchronizing signal from the 
reproduced color video signal, compares the phases of the separated 
horizontal synchronizing signal and an output signal of a crystal 
oscillator, and compensates for the jitter by use of an output error 
signal obtained as a result of the phase comparison. 
However, the jitter within the reproduced color video signal could not be 
sufficiently compensated, by use of the jitter compensation circuit alone, 
in the above conventional reproducing apparatus. There was a disadvantage 
in that some jitter still remained within the reproduced color video 
signal after performing jitter compensation by the above jitter 
compensation circuit. On the other hand, generally, an automatic phase 
compensation circuit (APC circuit), an automatic chrominance control 
circuit (ACC circuit), and the like are provided in a television receiver. 
However, the television receiver is generally designed to receive 
broadcast signals having no jitter and displays a received image on the 
screen, and measures are not taken with respect to signals having jitter. 
Hence, when the reproduced signal in which some still remains as described 
above, is supplied as it is to the television receiver, the hue and color 
saturations of the reproduced color picture varies according to the 
performance of the APC circuit and the ACC circuit which differ according 
to the manufacturer of the television receiver. Therefore, there was a 
disadvantage in that a reproduced color picture having a regular and 
stable quality could not be obtained. 
SUMMARY OF THE INVENTION 
Accordingly, it is a general object of the present invention to provide a 
novel and useful reproducing apparatus for reproducing a rotary recording 
medium recorded with a color video signal, in which the above described 
disadvantages have been overcome. 
Another and more specific object of the present invention is to provide a 
reproducing apparatus capable of reproducing any one of the NTSC disc, the 
disc, or the SECAM disc so that a reproduced picture is obtained in a 
receiver of any of the three systems, that is, the NTSC system, the 
system, or the SECAM system. According to the apparatus of the present 
invention, an arbitrary disc can be reproduced regardless of the color 
video signal system, and a reproduced picture can be obtained by an 
arbitrary receiver regardless of the system it uses. 
Still another object of the present invention is to provide a reproducing 
apparatus capable of reproducing any one of the NTSC disc, the disc, 
or the SECAM disc, by effectively eliminating the phase shift. 
Other objects and further features of the present invention will be 
apparent from the following detailed description when read in conjunction 
with the accompanying drawings.

DETAILED DESCRIPTION 
In FIG. 1, a disc 11 on which a color video signal of four fields is 
recorded for one track turn, for example, as variations in geometrical 
configuration, is placed onto a turntable 12. The disc is rotated at a 
predetermined rotational speed by a motor 13, together with the turntable 
12. In a case where the disc 11 is a disc or a SECAM disc, the motor 
13 is rotated at a rotational speed of 750 rpm. On the other hand, when 
the disc 11 is a SECAM disc, the motor 13 is rotated at a rotational speed 
of 892.85712 rpm. Since the motor 13 is rotated at the above described 
rotational speed, a horizontal scanning frequency f.sub.H of the 
reproduced NTSC system color video signal becomes equal to a horizontal 
scanning frequency of 15.625 kHz of the system color video signal. 
Accordingly, the reproduced NTSC system color video signal is processed as 
an artificial system color video signal. 
The color video signal recorded on the disc 11 is picked up by a 
reproducing stylus 15 of a signal pickup device 14, according to 
variations in electrostatic capacitance between the disc 11 and the 
reproducing stylus 15. The signal thus picked up by the signal pickup 
device 14 is supplied to a circuit 16 consisting of a preamplifier and a 
FM-demodulating circuit, wherein the signal is demodulated. An output 
color video signal of the above circuit 16 is supplied to a frequency 
converter 17, a subtraction circuit 18, and a horizontal synchronizing 
signal separation circuit 19. The above color video signal is, for 
example, a signal obtained by multiplexing a luminance signal having a 
band of zero to approximately 3 MHz and a carrier chrominance signal 
having a band of 2.56 MHz .+-.500 kHz, within a commmon band. 
A horizontal synchronizing signal (the frequency f.sub.H of the horizontal 
synchronizing signal is 15.625 kHz) separated at the horizontal signal 
separation circuit 19 is supplied to a phase comparator 20. The phase 
comparator 20 compares the phases of the above separated horizontal 
synchronizing signal and a signal obtained from a 1/325-frequency divider 
21 having a frequency f.sub.H. An output error voltage of the phase 
comparator 20 is supplied to a voltage controlled oscillator (VCO) 22, to 
control the oscillation frequency of the VCO 22. The output oscillation 
frequency of the VCO 22 is 325f.sub.H. An output of the VCO 22 is supplied 
to the 1/325-frequency divider 21 and a 1/2-frequency divider 24. The 
above phase comparator 20, the VCO 22, and the frequency divider 21 
construct a phase locked loop (PLL) circuit in order to control the 
oscillation frequency of the VCO 22 so that a jitter component within the 
color video signal is relatively eliminated. 
The output of the phase comparator 20 is also applied to an arm stetcher (a 
jitter compensation mechanism, not shown) of the signal pickup device, 
through an arm stretcher circuit 23. The position of the reproducing 
stylus 15 along the relative scanning direction with respect to the disc 
11 is corrected by the above mechanism, to perform the jitter compensation 
mechanically. 
The output signal of the VCO 22 having the frequency of 325f.sub.H, is 
supplied to the 1/2-frequency divider 24 wherein the frequency is 
frequency-divided into a frequency of 325f.sub.H /2. This signal having 
the frequency of 325f.sub.H /2 is supplied to a frequency converter 25. A 
signal from the frequency divider 24 is frequency-converted at the 
frequency converter 25, by a signal obtained from a voltage controlled 
type crystal oscillator (VXO) 28 having a frequency of 4.43 MHz. 
Accordingly, the signal from the frequency divider 24 is 
frequency-converted into a signal having a frequency of 6.99 MHz. An 
output signal of the frequency converter 25 is supplied to frequency 
converters 17 and 30. 
The color video signal (having a carrier chrominance signal having a 
frequency of 2.56 MHz) including the jitter component, which is obtained 
from the circuit 16, is frequency-converted into a signal having a 
frequency of 4.43 MHz by a signal (having a frequency of 6.99 MHz) from 
the frequency converter 25, at the frequency converter 17. The output 
signal of the frequency converter 17 is supplied to a comb filter 29. A 
carrier chrominance signal having a frequency of 4.43 MHz which is 
obtained at the above comb filter 29, is supplied to a chrominance signal 
demodulating circuit 31, a phase comparator 27, and the frequency 
converter 30. The comb filter 29 has a 1H delay circuit for delaying by an 
interval equal to one horizontal scanning period (1H) of the system or 
the SECAM system. The reason why the reproduced horizontal scanning 
frequency is set so that the horizontal scanning frequencies of the 
system and the SECAM system can be obtained regardless of the system of 
the video signal recorded on the disc being reproduced, and the delay time 
of the comb fitler 29 is set to one horizontal scanning period of the 
system and the SECAM system, is that a 1H delay circuit is respectively 
provided in the system receiver and the SECAM system receiver. By this 
arrangement, it becomes possible to obtain a normal picture in the 
system receiver and the SECAM system receiver. 
The phase comparator 27 compares the phases of the carrier chrominance 
signal from the above comb filter 29 having the frequency of 4.43 MHz, and 
a reference signal supplied from a crystal oscillator 26 which has a 
frequency of 4.43 MHz. An output error voltage of the phase comparator 27 
is applied to the VXO 28, to control the oscillation frequency of the VXO 
28. Accordingly, the oscillation frequency of the VXO 28 fluctuates 
according to the jitter component present in the carrier chrominance 
signal which is obtained from the comb filter 29. A closed loop consisting 
of the frequency converters 17 and 25, the comb filter 29, the phase 
comparator 27, and the VXO 28 constructs an automatic phase compensation 
(APC) circuit. Thus, compensation is performed by the above described arm 
stretcher and the PLL circuit, to compensate relatively for the remaining 
jitter component. An oscillation frequency f.sub.sc of the crystal 
oscillator 26 can be described by an equation f.sub.sc 
=(N/2).multidot.f.sub.H, where N is an odd integer. In the present 
embodiment of the invention, the frequency f.sub.sc is selected to 
approximately 4.43 MHz. 
The carrier chrominance signal obtained from the comb filter 29, having the 
frequency of 4.43 MHz, is frequency-converted by a signal from the 
frequency converter 25 having the frequency of 6.99 MHz and a time-base 
which fluctuates according to the jitter component, at the frequency 
converter 30. The carrier chrominance signal including the jitter 
component and having the frequency of 2.56 MHz, is supplied to the 
subtraction circuit 18 from the frequency converter 30. The color video 
signal including the jitter component is supplied to the subtraction 
circuit 18 through a delay circuit 32 for matching the timing. Hence, the 
carrier chrominance signal is eliminated from the color video signal at 
the subtraction circuit 18, and only the luminance signal is obtained. 
This luminance signal thus obtained, is supplied to adders 42, 43, and 44. 
The output signal of the circuit 16 is also supplied to a vertical 
synchronizing signal separation circuit 33 wherein the vertical 
synchronizing signal is separated. The separated vertical synchronizing 
signal is supplied to an adder 34, and added with the signal from the 
1/325-frequency divider 21 having the horizontal scanning frequency 
f.sub.H. Thus, a composite synchronizing signal is obtained from the adder 
34. This composite synchronizing signal is supplied to an NTSC signal 
modulating circuit 36, a signal modulating circuit 37, and a SECAM 
signal modulating circuit 38. 
The chrominance signal demodulating circuit 31 has a circuit construction 
shown in the systematic block diagram in FIG. 2, for example. The output 
carrier chrominance signal of the comb filter 29 supplied to the 
chrominance signal demodulating circuit 31 from an input terminal 51, is 
supplied to detectors 52 and 53, and to a burst gate 54. This carrier 
chrominance signal is mostly eliminated of the jitter component, however, 
slight jitter component still remains within the carrier chrominance 
signal. 
A color burst signal extracted at the burst gate 54 is supplied to a phase 
comparator 55. The phase comparator 55 compares the phases of the signal 
supplied thereto and the output signal from a VXO 57 having a frequency of 
4.43 MHz. An output phase error signal of the phase comparator 55 is 
applied to the VXO 57 through a lowpass filter 56, to control the 
oscillation frequency of the VXO 57. In addition to being supplied to the 
phase comparator 55, the output signal of the VXO 57 is also supplied 
directly to the detector 52, and to the detector 53 through a 
90.degree.-phase shifter 58. Accordingly, color difference signals from 
which the jitter component is completely compensated, are obtained from 
the above detectors 52 and 53. These color difference signals are 
respectively supplied to modulating circuits 36, 37, and 38 through 
lowpass filters 59, 60 and output terminals 61 and 62, respectively. 
The filtering band of the above lowpass filter 56 is selected so as to 
sufficiently pass the jitter component. In a case where the disc 11 is 
rotated at a rotational speed of 852.85712 rpm or 750 rpm, for example, 
the jitter frequency is 15 Hz or 12.5 Hz. Thus, in this case, the upper 
limit frequency of the filtering band of the lowpass filter 56 is selected 
in the range of 60 Hz, for example, so that the signal having this 
frequency of 15 Hz or 12.5 Hz is sufficiently passed. 
An output signal of a crystal oscillator 35 having a frequency of 3.58 MHz, 
is supplied to the NTSC signal modulating circuit 36 as a chrominance 
subcarrier. The modulating circuit 36 has a circuit construction shown in 
the block system in FIG. 3, for example. The color difference signals from 
the chrominance signal demodulating circuit 31, are supplied to modulators 
73 and 74 through terminals 71 and 72, respectively. The output signal of 
the crystal oscillator 35 is directly supplied to the modulator 73 through 
the terminal 75, and supplied to the modulator 74 through a 
90.degree.-phase shifter 76. The chrominance signals subjected to 
quadrature two-phase modulation at the modulators 73 and 74, is supplied 
to the adder 42 through a terminal 77. The chrominance signal and the 
luminance signal from the subtraction circuit 18, are multiplexed at the 
adder 42. Accordingly, an NTSC system color video signal (to be accurate, 
this is an artificial NTSC system color video signal) is obtained from a 
terminal 45. 
The chrominance signal and the luminance signal added at the adder 42 are 
respectively compensated of the phase shift component, however, they 
include the same time-base fluctuation component. But, this time-base 
fluctuation component is the same, respectively, with respect to the 
chrominance signal and the luminance signal. Hence, relatively, no 
inconveniences are introduced. Moreover, the time-base fluctuation 
component is compensated at an automatic frequency control (AFC) circuit 
provided in the receiver, and color aberration is not introduced in the 
reproduced picture. 
An output of a crystal oscillator 39 having a frequency of 4.43361875 MHz, 
is supplied to a switching circuit 41 on one hand, and supplied to the 
switching circuit 41 after being phase-shifted by 180.degree. at a 
180.degree.-phase shifter 40. 
The above switching circuit 41 is supplied with the output signal (having 
the frequency f.sub.H equal to 15.625 kHz) of the 1/325-frequency divider 
21, and performs a switching operation for every one horizontal scanning 
period (1H). Hence, the switching circuit 41 alternately switches the 
signals from the crystal oscillator 39 and the 180.degree.-phase shifter 
40 for every 1H, and supplies the switched signal to the signal 
modulating circuit 37. 
The signal modulating circuit 37 modulates the chrominance sub carrier 
from the switching circuit 41, by the color difference signals from the 
demodulating circuit 31. A quadrature two-phase modulated signal obtained 
from the modulating circuit 37 is supplied to the adder 43, and added with 
the luminance signal from the subtracting circuit 18. Thus, a system 
(or artificial system) color video signal is obtained from the 
terminal 46. 
The color difference signals supplied to the SECAM signal modulating 
circuit 38 from the chrominance signal demodulating circuit 31, are added 
with the composite synchronizing signal from the adder 34. Moreover, these 
color difference signals are switched over by a horizontal scanning 
frequency signal within the composite synchronizing signal for every one 
horizontal scanning period, and line-sequentially converted into a 
chrominance signal. The chrominance signal from the modulating circuit 38 
is supplied to the adder 44, and added with the luminance signal from the 
subtracting circuit 18. Accordingly, a SECAM system (or an artificial 
SECAM system) color video signal is obtained from the terminal 47. 
The output signal of the crystal oscillator 26 is supplied to a circuit 48 
consisting of a frequency multiplier and frequency divider. The frequency 
multiplying ratio or the frequency dividing ratio of the circuit 48 is 
changed over by a signal applied to a terminal 49 according to whether the 
disc being reproduced is of the NTSC system, the system, or the SECAM 
system. Accordingly, according to the output from the circuit 48, the 
motor 13 is rotated at a rotational speed of 892.85712 rpm when the disc 
is the NTSC disc, and 750 rpm when the disc is the or SECAM disc. 
If the color television receiver used to obtain the reproduced picture is 
of the NTSC system, the receiver is connected to the terminal 45. 
Similarly, if the receiver is of the system or the SECAM system, the 
receiver is respectively connected to the terminals 46 and 47. 
Generally, the jitter component includes a phase shift component having a 
phase shift from a certain reference signal to give undesirable effects to 
the color phase, and a time shift component having a period different from 
that of the certain reference signal. However, the output signal including 
jitter, obtained from the comb filter 15, is eliminated only of the phase 
shift component at the demodulating circuit 16. 
According to the reproducing apparatus of the present invention, modulation 
in accordance with the NTSC system, the system, and the SECAM system 
is respectively performed at the modulating circuits 36, 37, and 38, by 
using the color difference signals from the demodulating circuit 31. Thus, 
when any one of the NTSC system, the system, or the SECAM system disc 
is reproduced, the NTSC system color video signal, the system color 
video signal, and the SECAM system color video signal are respectively 
obtained from the terminals 45, 46, and 47, simultaneously. Therefore, 
regardless of which disc is reproduced, the reproduced picture can be 
obtained in the NTSC system color television receiver, the system 
color television receiver, and the SECAM color television receiver. 
When the NTSC disc is reproduced, the horizontal scanning frequency is 
reproduced as the horizontal scanning frequency of 15.625 kHz of the 
system and the SECAM system, which is different from the original 
horizontal scanning frequency of 15.734 kHz of this NTSC disc. Moreover, 
the carrier chrominance signal (of the frequency 4.43 MHz) of the 
system and the SECAM system is obtained and processed at the comb filter 
15 including the 1H delay circuit for delaying by the interval equal to 
one horizontal scanning period of the system and the SECAM system. 
Accordingly, when the NTSC system color video signal obtained from the 
output terminal 45 is reproduced by the NTSC system color television 
receiver, the reproduced picture obtained is slightly distorted along the 
horizontal direction. However, this distortion is only in the range of few 
percent at the most, and does not introduce any problems from the 
practical point of view. In addition, in this case, the horizontal 
scanning frequency of 15.5625 kHz of the system and the SECAM system 
is obtained, and the modulation and the SECAM modulation are performed 
by using the color difference signals from the demodulating circuit 31 
which is supplied with the carrier chrominance signal (of 4.43 MHz) of the 
system and the SECAM system. Hence, when the system color video 
signal obtained from the output terminal 46 and the SECAM system color 
video signal obtained from the output terminal 47 are respectively 
reproduced by the system color television receiver and the SECAM 
system color television receiver, the reproduced picture becomes slightly 
distorted along the vertical direction, although correct along the 
horizontal direction. However, this distortion along the vertical 
direction is in the range of few percent at the most, and is not a problem 
practically. 
On the other hand, when the system and SECAM system discs are 
reproduced, the original horizontal scanning frequency of 15.625 kHz of 
the system and the SECAM system is produced and processed. Thus, when 
the system color video signal from the output terminal 46 and the 
SECAM system color video signal from the output terminal 47 are 
respectively reproduced by the system television receiver and the 
SECAM system television receiver, the reproduced picture is correct and 
normal with respect to the horizontal and vertical directions of the 
reproduced picture. In addition, in this case, when the NTSC system color 
video signal from the output terminal 45 is reproduced by the NTSC system 
television receiver, the reproduced picture becomes slightly distorted 
both along the horizontal and vertical directions. However, the distortion 
is small, and is not a problem practically. 
Accordingly, strictly speaking, regardless of which disc is reproduced, 
that, is, the NTSC disc, the disc, or the SECAM disc, an artificial 
NTSC system color video signal is always obtained from the terminal 45. 
When the disc is reproduced, the regular system color video signal 
is obtained from the terminal 46, while an artificial system color 
video signal is obtained from the terminal 46 when the NTSC disc or the 
SECAM disc is reproduced. The regular SECAM system color video signal is 
obtained from the terminal 47 when the SECAM disc is reproduced. On the 
other hand, an artificial SECAM system disc is obtained when the NTSC disc 
or the disc is reproduced. 
Further, the present invention is not limited to these embodiments, but 
various variations and modifications may be made without departing from 
the scope of the present invention.