JPS61239789A - Video disc player - Google Patents

Abstract

PURPOSE:To make possible to reproduce both high quality disc and standard disc by identifying the kind of a disc mounted and switching the frequency characteristic of a front equalizer amplifier in the FM demodulator according to the identification content. CONSTITUTION:The frequency characteristic of equalizer amplifier 5 is switched according to the identification output obtained from the disc identification circuit 10. As a result, FM up/down side band level is corrected to same level for the input to an FM demodulator 6 of the next step. The drop-out correction, the frequency conversion of a sub-carrier, the time base correction and other appropriate signal processing is done at a video signal processing circuit 7, and in case of the reproduction of a standard disc, a standard color television signal is outputted from a video output terminal 11. And in case of the reproduction of a high quality disc, a band compressed high quality television signal of the FM demodulation signal is outputted to a video output terminal 12 through a buffer amplifier 8.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Applications> The present invention relates to a video tape recorder capable of playing back both high-definition discs and standard discs.

<Summary of the Invention> The present invention identifies the type of loaded disc and switches the frequency characteristics of the Ifraiser amplifier in the front stage of the FM demodulator depending on the content, thereby making it possible to play both high-quality discs and standard discs. This is what I did.

<Prior Art> Generally, on a video disc, video and audio signals are FM-modulated and recorded as uneven signals (pits) along spiral recording grooves (hereinafter referred to as tracks).

Then, in the reproducing player, the disc recording signal is detected optically as a change in intensity of the reflected light of the focused light beam, or as a change in capacitance using a sensor equipped with an electrode.

Currently, the FM frequency band of standard discs recording standard television signals such as NTSC and PAL is 6.
1 to 7.9 MHz, or 7.6 to 7.9 MHz, etc. Therefore, as a band that covers up to the upper and lower FM sidebands in the reproduction system, the luminance signal band is 3.1 MHz, respectively.
For 4.2MHz, 3.6~IIMH2 or 3.9
~13. '5MHz. (See the non-grooved capacitive spectrum shown in FIG. 2) On the other hand, the luminance signal band of a high-definition television signal requires 8.1 MHz even after band compression.

Figure 3 shows an example of the FM spectrum when recording this on a high-quality disc.
When Yaria is set to 6.6 to 15 MHz, the band that covers the upper and lower sidebands is 0.9 to 24.1 MHz, which is wider than the standard television signal described above.

<Problems to be Solved by the Invention> For this reason, when playing two types of discs, a standard disc and a high-definition disc, in one video disc player, two systems of playback circuits with different frequency bandwidths are usually required. The disadvantage was that it required a system and was quite expensive.

<Means for Solving the Problems> The present invention has been made in view of the above points, and it is a method to identify the type of loaded disc, that is, whether a high-quality disc or a standard disc is currently loaded in the player. In addition to providing disk identification means, an equalizer amplifier with switchable frequency characteristics is provided before the FM demodulator.

<Operation> This allows the characteristics of the equalizer amplifier to be switched according to the type of loaded disc based on the disc identification output, and the playback circuit system such as the preamplifier and FM demodulator can be used in common when playing both discs. It is.

<Example> FIG. 1 shows one example of the present invention, where 1
is a pickup, 2 is a disk, 3 is a preamplifier, 4 is a tracking servo circuit, 5 is an equalizer amplifier with switchable frequency characteristics, 6 is an FM demodulator, 7 is a video signal processing circuit, 8 is a buffer amplifier, 9 is a 10 is a disc identification circuit for identifying the type of disc 2; 11 is a standard video output terminal; 12 is a high-definition video output terminal; and 13 and 14 are audio output terminals.

First, the pickup l detects the FM signal previously recorded on the disk 2, and the preamplifier 3 in the next stage detects the FM signal for about 40 seconds.
B amplify. The frequency band of this preamplifier 3 is as follows:
0.9 to 24.1 MH2 is required to be common to both the standard disk and the high-quality disk. Next, the equalizer amplifier 5 corrects the attenuation of high frequency components that occurs as the recording bit density increases, and particularly corrects image quality deterioration at the inner circumference of the disk. That is, the frequency characteristics of the equalizer amplifier 5 are switched based on the identification output obtained from the disc identification circuit 10, and when playing back a standard disc having a recording spectrum as shown in FIG. 2, the frequency characteristics shown in FIG. When performing amplification operation with a characteristic that has a peak near the upper sideband (10MH2°) as shown in Figure 1jlA, and reproducing a high-quality disc having a recording spectrum as shown in Figure 8, the characteristics shown in Figure 4 are used. As shown by the solid line B, the amplification operation is performed with a characteristic having a peak around 13 MHz, and as a result, the FM wave upper and lower sideband levels at the input stage to the next stage FM demodulator 6 are corrected to be the same.

The demodulated output demodulated by the FM demodulator 6 is applied to a video signal processing circuit 7, a buffer amplifier 8, and an audio signal processing circuit 9. The video signal processing circuit 7 performs appropriate signal processing such as dropout correction, color subcarrier frequency conversion, and time base correction, and outputs a standard color television signal from the video output terminal 11 in the case of standard disc playback. - When playing high-quality discs,
A band-compressed high-quality previgilon signal of FM demodulation output is outputted to a video output terminal 12 via a buffer amplifier 8.

Also, in the audio signal processing circuit 9, the first. It separates and demodulates the FM waves of each second channel, performs signal processing such as de-emphasis and noise reduction, and outputs audio signals to audio output terminals 13 and 14.

The details of the operation of the tracking servo circuit 4 will be omitted here, but the disk recording signal detection sensor of the pickup 1 traces the center of the track or performs a sensor kick during special reproduction.

Next, a specific circuit diagram of the equalizer amplifier 5, which is particularly related to the present invention, is shown in FIG. 5, and will be explained according to this diagram.

First, the FM signal obtained from preamplifier 3 is connected to capacitor C.
1 to C4 and coils L1+L2, and only the FM upper and lower primary sideband 1 components are supplied to the base of transistor Q1. This transistor Ql includes resistors R2, R3 and capacitor C5+
Together with C7+Cg and coil L3, it constitutes a tuned amplifier. Here, the capacitors C7 and C8 function for emitter peaking, and in particular, the switching transistor Q2 is connected in series with the capacitor C8.

Now, when playing back a standard disc, the "H rubel" signal is applied to the base of the transistor Q2 as a discrimination output from the disc identification circuit 10, so the transistor Q2 is turned on, and at this time, two capacitors C7 and C8 are connected to the emitter of the transistor Q2. They are inserted in parallel, and in this case an amplification operation is performed with the characteristics shown in FIG. 4A.

On the other hand, when playing a high-quality disc, the disc identification circuit 10
Since a @L” level signal is applied to the base of the transistor Q2, the transistor Q2 is maintained in a cut-off state, and at this time, only the capacitor C7 is connected to the emitter of the transistor Q2. Amplification operation is performed with wideband characteristics as shown in Figure B.

In this manner, the frequency characteristics of the equalizer amplifier 5 are switched in accordance with the disc identification output, and an amplification operation is performed in accordance with the loaded disc.

<Effects of the Invention> As described above, according to the video disc player of the present invention, it is possible to play back both high-definition discs and standard discs while sharing a playback circuit system such as a preamplifier and an FM demodulator. This makes it possible to construct the system at low cost.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the video disc player of the present invention, Fig. 2 is a recording signal spectrum of a standard disc, Fig. 3 is a recording signal spectrum of a high-quality disc, and Fig. 4 is a diagram used in the above embodiment. A frequency characteristic diagram of the equalizer amplifier shown in FIG. 5 is a specific circuit diagram of the same equalizer amplifier. l...Pickup, 2...Disc, 5
... Equalizer amplifier, 6 ... FM demodulator, 7
...Video signal processing circuit, 9...Audio signal processing circuit, IO...Disk identification circuit Agent Patent attorney Aihiko Fukushi (and 2 others) Taka1 figure m'4* (MH2) Rei2 figure Station a setting (MH2) Fig. 4

Claims (1)

[Claims] 1. A video disc player capable of playing both high-definition television signal recording video discs (hereinafter referred to as high-quality discs) and standard television signal recording video discs (hereinafter referred to as standard discs). disc identification means for identifying whether the loaded disc is a high-quality disc or a standard disc; FM demodulation means for FM demodulating a signal picked up from the disc; and a preceding stage of the FM demodulation means. an equalizer amplification means which is provided in the disk identification means and is capable of switching the frequency characteristics according to the identification output from the disc identification means, and performs appropriate signal processing on the video signal component of the FM demodulation output obtained from the FM demodulation means to produce a desired video signal. video signal processing means for deriving a signal output;
A video disc player comprising: audio signal processing means for performing appropriate signal processing on the audio signal component of the FM demodulated output to derive a desired audio signal output.