JPS5942513B2 - noise reduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for reducing noise components in a video signal.

A method shown in FIG. 1 is a conventional method for reducing noise components from video signals.

FIG. 1 shows a frequency spectrum diagram of all video signals. The low frequency component A and the high frequency component B at the beginning of Figure 1 are divided from the video signal in Figure 1 A, and the high frequency component B is applied to a suppression circuit (limiter) to eliminate the noise component as shown in Figure 1 C. Take it out. By inverting the phase of this signal and adding it to the original input video signal A, a video signal as shown in FIG. 1B, in which the noise component C has been canceled, is obtained. FIG. 2 shows another method, in which a low frequency component C and a high frequency component D in FIG. 2 are generated from the video signal in FIG. 2E.

Then, a high frequency component as shown in FIG. 2, which has the noise component reduced from the high frequency component D, is created, and is mixed with the low frequency component C, to obtain a video signal with the noise component reduced from the high frequency component, as shown in FIG. 2, H. Third
1 and 2 are well-known diode limiter clippers for obtaining the suppression or noise reduction high-frequency components of C and B in FIGS. 1 and 2, respectively.

Next, problems with the aforementioned noise reducer will be explained.

FIG. 4 shows the relationship between high frequency components and noise components. Noise is included in the input video signal as shown in Figure 4, and when the high frequency component is extracted, the noise component becomes as shown in Figure 4 according to the degree of low frequency attenuation in the high frequency component. . When this is suppressed by a transmitter, a noise component as shown in FIG. 4 is obtained. This is phase inverted and mixed with the original input video signal to obtain a video signal with reduced noise.
However, among the suppressed noise components, there are parts that do not contain noise components, as shown by the force in Figure 4. This results in areas with little noise reduction, which is unfavorable in terms of image quality. In particular, in order to reduce this force part, if the cutoff frequency for high-frequency component separation is set in the high-frequency part, the force' part becomes narrower with respect to the force as shown in Figure 4 La and M, and noise is generated as shown in C. Parts where noise reduction is particularly small, such as the negative part in the video signal after cancellation, do not occur. However, because the cutoff frequency is high, low-frequency noise is no longer reduced as shown in c, and the overall noise reduction effect is small. The present invention is intended to reduce the above drawbacks,
One embodiment will be described below based on the drawings.

FIG. 5 shows noise or suppressed noise in the high frequency video component. Assuming that the noise in the video signal is y, the noise in the high frequency component follows the high frequency component separation characteristic and becomes like evening light. When this is suppressed, it becomes like Re. In the present invention, by further amplifying the low range of the suppressed noise component A as shown in G, it is possible to obtain an increased noise component in the low range as shown in T. In this way, even if the high-frequency cutoff frequency is relatively high, noise can be reduced down to the low frequency range by performing noise cancellation using the noise shown in (2). Furthermore, the gap shown in FIG. 4 is narrowed, and desirable image quality can be obtained. FIG. 6 shows its configuration. A video signal with noise is applied to an input terminal 1, and a high frequency component is extracted by a high frequency converter 2.

This is applied to a suppression circuit 3 to extract only the noise portion.
Then, the low frequency part of the noise is again amplified by the low frequency amplification amplifier 4, and the phase is inverted by 180 times by the phase inverter 5. On the other hand, the original input video signal is passed through a buffer 6 and mixed with the phase-inverted noise in a mixer 7, and a video signal with reduced high-frequency noise is obtained from an output terminal 8. According to the above invention,
The dead zone for noise reduction is reduced, and noise can be reduced down to lower frequencies.

[Brief explanation of the drawing]

Figures 1 and 2 are spectrum diagrams showing the operation of the conventional example, Figure 3 is a circuit diagram of the conventional suppression device, Figure 4 is a noise component and signal waveform diagram showing the operation of the conventional example, and Figure 5 is a diagram showing the operation of the conventional example. A spectrum diagram showing the operation of an embodiment of the present invention, and FIG. 6 is a block diagram thereof. 2... High-frequency wave filter, 3... Suppression circuit,
4...Low frequency boost amplifier, 5...Phase inverter, 7...Mixer.

Claims (1)

[Claims] 1: a first means for extracting high frequency components in a video signal; a second means for suppressing the high frequency signal obtained by the first means and mainly extracting only high frequency noise components; a third means for further enhancing the low-frequency attenuation part of the signal obtained by the second means; and a third means for inverting the phase of the signal obtained by the third means and adding it to the original input video signal. The fourth cancels noise components in relatively high-frequency signals.
A noise reduction device characterized in that it has means.