JPS59119511A - Information reproducer - Google Patents

Abstract

PURPOSE:To reduce the generation of noises by supplying an audible signal to an LPF which attenuates a high band component including a high band of the audible band and higher than said high band, compensating the drop-out with the LPF output and increasing and compensating the high band of the compensation output. CONSTITUTION:The RF signal is converted into an audio signal A via a BPF1 and an FM wave detector 2 and supplied to an LPF7. This LPF7 has the characteristics to attenuate a high frequency component including the high audible band. As a result, the subcarrier superposed on the wave detection output of the detector 2 is greatly attenuated and erased substantially. Then the drop-out is compensated in response to the level of the audio signal of a main channel. The high band component of an audible range which is attenuated by the LPF7 is increased and restored by a high boost circuit 8. In this case, the input supplied to the wave detection stage of a subchannel uses an output signal A of the detector 2. Thus the approximately exact compensation is possible with reduction of noises.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information reproducing apparatus, and more particularly to an information reproducing apparatus having a dropout compensation function for reproduced information from a recording medium.

In order to reproduce recorded information, a dropout compensation device that detects and compensates for so-called dropout compensation is essential in order to obtain a good reproduction signal. In the case of a video disc as a recording medium, it is common for audio information to be multiplexed in addition to video information using a frequency multiplexing method. It is also designed to be carried out.

FIG. 1 is a block diagram of an audio information reproducing circuit in a reproducing apparatus for a video disc on which information is multiplexed.
In the band pulse filter) 1, only the A-diocarrier frequency and frequency components in its vicinity are extracted. This extracted signal undergoes FM detection in a wave detector 2 to become an audible band signal, which is input to an LPF (low pass filter) 3.

This LPF 3 removes high-frequency components outside the audible band to eliminate noise. The LP, , F outputs (A> are compensated for dropout in the dropout compensator 4, but the configuration of this compensator 4 is such that the sensor output (B) generated from the dropout sensor 5 compensates for the dropout. It consists of an analog switch, a hold capacitor, etc. installed between the output terminal of this switch and a reference potential point.
When a dropout occurs, the level of the LPF output (△) immediately before the sensor output (B) is generated is held and sent to the next stage circuit to compensate for the dropout.
be.

The output (C) of this dropout error [-compensation 4] is applied to a de-emphasis circuit 6, which restores the signal that has been pretensioned during recording to the original signal.

It should be noted that the output signal of BPF1 is used as an input to the dropout sensor 5, and a level drop in this BPF output signal is detected and a sensor output (B) is generated.

Here, in the case of a video disc, the audio A information is often recorded as 2-channel information, for example, the first channel is 2.3M1-1z.

1:M of the second dial to the 2.8MHz carrier, respectively.
A method of modulating and recording is used. Recently, these first and second channels (main channels)
In addition to this, attempts have been made to multiplex record two channel information, but in this case, the audio signals of the third and fourth channels (subchannels), which should be added by 1', are added to, for example, 47.2 channels. 1z subcarrier and then FM modulate the FM of both these channels.
waves are superimposed on the A--D A signals of the first and second channels, respectively. After that, the above-mentioned 2,
A method has been proposed in which the carrier signal 7 of 3 MHz and 2.8 MHz is modulated and recorded on a recording disk together with video information.

On the other hand, the cutoff frequency of the noise reduction filter P F 3 is selected to be higher than the audible band, for example 30KH2, so as not to deteriorate the frequency characteristics in the audible band of the audio signal. Therefore, when the reproduction signal of the 4-channel audio multiplexed recording information as described above is entered into the block of FIG. 1, the FM detector 2
In addition to the main channel, there is +- (Z
Since the subchannel carrier V of is superimposed and appears, this subchannel carrier also appears at the output (Δ) of L P F 3 whose frequency is relatively low, and the second
The waveform is 4 as shown in the figure (Δ). In the figure, the gentle sinusoidal waveform is the main channel audio signal, and the high frequency rising waveform is the subchannel FM signal.
It's a wave.

Now, when a dropout occurs as shown by the symbol a in Fig. 2 (△), the dropout sensor output (13
) is shown in Figure (B). The phase shift between the dropout generation timing and the sensor output generation timing is caused by a delay time due to the time constants of the detector 2 and the LPF 3.

Therefore, the dropout complementary IR output becomes as shown in Figure (C), which has the drawback of being output as noise. That is, the de[J tube out compensation level depends on the carrier level of the nav channel, making accurate compensation difficult.

Such a phenomenon also occurs when noise lower than the cutoff frequency of the LPF 3 is superimposed on the signal. In this case, the dropout compensation level becomes dependent on the superimposed noise level, which is disadvantageous.

SUMMARY OF THE INVENTION An object of the present invention is to provide an information reproducing apparatus having a dropout compensation/compensation function that enables accurate dropout compensation and noise reduction.

The information reproducing apparatus according to the present invention converts the A-D A signal in the reproduced information into an audible signal, inputs the audible signal to an LPF that attenuates high-frequency components including the high-frequency range of the audible band, and converts the audible signal into an audible signal. Dropout compensation is performed on the LPF output, and the high frequency range of this compensation output is enhanced and corrected,
It is characterized in that it compensates for the high-frequency components of the audible band that are attenuated by the PF.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 1 are not designated by the same reference numerals. It is converted into an audio signal (A> by passing through the RF multiplied signal BPFl and the detector 2, and is input to LPF 7. This LPF
The frequency characteristics shown in FIG. 4 are different from those shown in FIG. The output j (B) of this LPF 7 is input to the high boost circuit 8 via the dropper 1 to complement (ξ
At the LP [near], the high-frequency components of the audible band attenuated are enhanced and corrected, and then the de-emphasis circuit 6
The input is loud. It should be noted that the dropout compensator 4 is operated by the output (C) of the double D dropout sensor 5 as in the example shown in FIG.

By covering in this way, in the detection output by the detector 2, the rib channel width is reduced as shown in FIG. 5 (Δ).
As shown in Figure (F3), the superimposed V signal 1a is greatly attenuated and almost disappears when it passes through the LPF 7. As a result, even if a dropout occurs as shown in figure (a), the sensor output in figure (C)
As shown in D), dropout compensation is performed based on the A-D signal level of the main channel. The audible high-frequency components attenuated by the LPF 7 are enhanced and restored by the high boost circuit 8.

In this case, there will be no problem if the output signal 8 (A>) of the FM detector 2 is used as the input to the rib channel detection stage.

The dropout compensation level is not affected by high-frequency noise, and substantially accurate compensation is possible.

In the above example, the high boost circuit 8 and the i'-emphasis circuit 6 are separated, but a single circuit having comprehensive characteristics of both circuits may be used, or a high A boost circuit may also be provided.

In this way, according to the present invention, the dropout compensation is performed by attenuating the high-frequency components, so that compensation can be performed using approximately the average level of the FM detection output, which is dependent on noise and the level of the subchannel carrier. There is an advantage that there is no such thing.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a conventional information reproducing device, FIG. 2 is an operation waveform diagram of each part of the block in FIG. il1, FIG. 3 is a block diagram of an embodiment of the present invention, and FIG.
Figure 5 is a diagram showing the operation waveforms of each part of the block diagram in Figure 3. 7...L P F 8...High boost circuit applicant Pioneer Co., Ltd. agent Patent attorney Motohiko Fujimura

Claims (1)

[Claims] An information reproducing apparatus for reproducing recorded information including audio information, which includes means for converting the audio information in the C1 reproduction information into an audible signal, and receiving the audible signal as an input and outputting high frequency components including the high frequency range of the audible band. The present invention is characterized by comprising filter means for reducing attenuation, compensating means for compensating for dropout at the output of the filter means, and means for enhancing and correcting the high frequency range of the audible band at the output of the compensating means. Information reproducing device.