JP2946515B2 - Noise removal circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise elimination circuit suitable for use in a reproduced signal of a video disk or the like.

[Summary of the Invention]

The present invention relates to a noise elimination circuit, which forms a logical filter for chrominance signal elimination using one horizontal period delay line for dropout compensation, and performs noise elimination using the output of the filter, thereby providing noise with better characteristics. The removal is performed.

[Conventional technology]

For example, a video disk reproducing apparatus has conventionally been configured as shown in FIG. In the figure, reference numeral (1) denotes an optical video disk, for example. The disk (1) is rotated at a predetermined speed by a motor (2), and a signal recorded on the disk (1) is an optical head. Read in (3). The tracking of the optical head (3) and the like are performed by the servo circuit (4).

Further, the signal from the head (3) is supplied to the time axis correction circuit (6) through the reproduction amplifier (5), and the corrected signal is supplied to the demodulation circuit (7). The demodulated signal is supplied to a subtractor (9) constituting a noise elimination circuit via a switch (8), and a signal from the subtracter (9) is taken out to a video output terminal (10).

The signal from the demodulation circuit (7) is synchronized with the synchronization separation circuit (11).
Is supplied to the phase comparator circuit (12), and is compared with a signal from the reference oscillator (13). This comparison output is supplied to the drive circuit (14) of the motor (2), and the rotation speed servo of the disk (1) is performed.

Further, a signal from the demodulating circuit (7) is supplied to a burst extracting circuit (16) through a burst shaping circuit (15), and a signal is supplied to a burst pulse generating circuit (17). The burst signal is supplied to the sampling circuit (15) and the sampling circuit (16) and shaped and extracted. This burst signal is supplied to the phase comparator circuit (18) and compared with the signal from the reference oscillator (13). The comparison output is supplied to the drive circuit (19) to drive the time axis correction circuit (6). .

The other fixed contact of the switch (8) is passed through a delay line (1HD1) (20) for a signal from the switch (8) for one horizontal period and a phase shifter (21) for inverting only the band component of the chroma signal in the signal. Supplied to Further, a signal from the time axis correction circuit (6) is supplied to a dropout detection circuit (22), and the switch (8) is switched to the other fixed contact during a period in which the dropout is detected. As a result, the demodulated signal is replaced with the signal one horizontal period before the dropout period, and the dropout compensation is performed by the vertical correlation of the video signal.

In this apparatus, noise removal is performed as described below. That is, the signal from the switch (8) is supplied to a chroma signal component trap circuit (23), and the luminance signal component from which the chroma signal component has been removed is subtracted through a high-pass filter (24) and a limiter (25).
And is subtracted from the original signal.

As a result, a high-frequency luminance signal component which is usually regarded as noise is removed, and a signal from which noise has been removed is output to the output terminal (10).

[Problems to be solved by the invention]

However, in the above-described configuration, since the extraction of the luminance signal is performed by trapping the chroma signal, most of the high frequency components of the luminance signal are lost at the time of the extraction.

For this reason, the conventional apparatus cannot sufficiently remove noise and cannot obtain a good reproduced image.

The present application has been made in view of such points.

[Means for solving the problem]

The present invention provides a demodulating means for demodulating a signal read from a recording medium, a dropout detecting means for detecting a dropout of a signal read from the recording medium, and a video signal from the demodulating means. Delay means for delaying a period, switching means for switching and outputting a video signal from the demodulation means and an output signal from the delay means based on an output from the dropout detection means, and an output signal from the delay means A band-pass filter for extracting a nearby component of a chroma signal from the input signal; a high-pass filter to which an addition signal obtained by adding an output signal from the band-pass filter and a video signal from the demodulation means is supplied; and an output from the high-pass filter. A limiter to which a signal is supplied, and an output signal from the limiter being reduced from the video signal from the demodulation means. The noise elimination circuit of the reproducing apparatus of a recording medium comprising a subtracting means for.

[Action]

According to this, a luminance signal passing type logical filter is formed by adding the signal from the delay unit and the original signal,
By performing noise removal using this addition signal,
Conventionally, a noise component near a chroma signal, which has been lost due to a trap of the chroma signal or the like, can also be removed, and good noise removal with excellent high-frequency characteristics can be performed.

〔Example〕

In FIG. 1, a signal from a switch (8) is supplied to an adder (26), and a signal from a delay line (20) is a band-pass filter (27) for extracting a nearby component of a chroma signal.
To the adder (26), and the added signal from the adder (27) is supplied to a high-pass filter (24) that extracts high-frequency components regarded as normal noise including components near the above-mentioned chroma signal. Is done. The rest is configured similarly to the circuit described in the prior art.

Therefore, in this configuration, a luminance signal passing type logical filter (comb filter) is configured by adding the signal delayed by one horizontal period and the original signal. For this reason, a luminance signal component from which only the chroma signal component has been removed is extracted from the output of this filter (the output of the adder (26)), and the high-frequency component of the luminance signal is also stored in this signal. And good noise elimination can be performed.

The conventional general time axis correction is performed after the dropout compensation. In this case, the dropout compensation is performed only for the luminance signal due to the problem of the phase variation of the chroma signal, and one horizontal period delay is performed. The line was not supplied with a chroma signal component. Therefore, the above-described logic filter for removing the chroma signal cannot be applied to the conventional delay line for dropout compensation.

Thus, according to the above-described apparatus, a luminance signal passing type logical filter is formed by adding the signal from the delay means and the original signal, and by using this added signal to perform noise removal, conventionally, a chroma signal The noise component near the chroma signal which has been lost due to traps or the like can also be removed, and good noise removal with excellent high-frequency characteristics can be performed.

The above-described apparatus is not limited to a video disc, and can be applied to dropout compensation of a reproduction signal such as a VTR.

〔The invention's effect〕

According to the present invention, a luminance signal passing type logical filter is formed by adding the signal from the delay means and the original signal, and by using this added signal to remove noise, it has been possible to trap a chroma signal or the like. As a result, noise components in the vicinity of the chroma signal that have been lost can be removed, and good noise removal with excellent high-frequency characteristics can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the present invention, and FIG. 2 is a diagram for explaining a conventional technique. (1) is a video disk, (3) is an optical head, (6)
Is a time axis correction circuit, (7) is a demodulation circuit, (8) is a switch, (9) is a subtractor, (10) is an output terminal, (20) is a delay line, (21) is a phase shifter, (22) ) Is a dropout detection circuit, (24) is a high-pass filter, (25) is a limiter,
(26) is an adder, and (27) is a bandpass filter.

Continuation of front page (56) References JP-A-1-126090 (JP, A) JP-A-64-89792 (JP, A) JP-A-61-29583 (JP, U) (58) Fields studied (Int .Cl. ⁶ , DB name) H04N 5/91-5/956 H04N 9/79-9/898

Claims (1)

(57) [Claims] A demodulator for demodulating a signal read from the recording medium; a dropout detector for detecting a dropout of the signal read from the recording medium; Delay means for delaying a horizontal period, switching means for switching and outputting a video signal from the demodulation means and an output signal from the delay means based on an output from the dropout detection means, and an output from the delay means A band-pass filter for extracting a nearby component of a chroma signal from the signal; a high-pass filter to which an addition signal obtained by adding an output signal from the band-pass filter and a video signal from the demodulation means is supplied; A limiter to which an output signal is supplied; and an output signal from the limiter, a video signal from the demodulating means. A noise elimination circuit for a recording medium reproducing apparatus, comprising: