JPH03236684A - Video noise reduction circuit - Google Patents

Abstract

PURPOSE:To display easy to see pattern without noise by operating a video noise reduction circuit while varying a control variable in response to a level of a luminance signal automatically. CONSTITUTION:One of branched signals is inputted to a nonlinear amplifier 10, a luminance signal level detected by a detection circuit is amplified by the nonlinear amplifier 10 and inputted to an output amplifier 6 in a coring circuit 5 and since the signal is decreased by a level V subjected ro coring at coring circuit 5, the level amplified by an amplifier 6 is adjusted automatically. Thus, a easy to see pattern without noise is displayed while suppressing the coring level low.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention particularly relates to a signal reproducing circuit for video equipment, and in particular, to a signal reproducing circuit for video equipment, in particular, a method for removing noise in high frequency components of a luminance signal to obtain a high-quality reproduced screen. This invention relates to a video noise reduction circuit.

[Conventional technology]

A conventional video noise reduction circuit uses a circuit having the configuration shown in the block diagram of FIG. The brightness signal is input to the noise reduction circuit 2, and by switching the switch 21 to the opposite side during normal playback, the brightness signal passes through the video noise reduction circuit 2 and is output as is to You. was.

[Problem to be solved by the invention]

Therefore, it is necessary to operate the changeover switch of the video noise reduction circuit 2 depending on the playback screen, and the amount of action of the video noise reduction circuit 2 is also input, which causes problems such as being able to change only two steps: off.

SUMMARY OF THE INVENTION An object of the present invention is to enable a video noise reduction circuit to automatically perform 20 stepping operations by changing the amount of action depending on the level of a luminance signal.

[Means to solve the problem]

As shown in Fig. 1, there is an LPF 3 that separates low frequency components from the input luminance signal Yin, a first circuit that amplifies and outputs the output of the LPF 3 with an amplifier 7, and a first circuit that separates the high frequency components of the same luminance signal. Separate with HPF4 and coring circuit 5
The second circuit consists of a second circuit which performs coring at a level set by the coring circuit 5, outputs it, inputs it to the amplifier circuit 6, amplifies it by the amplifier circuit 6, and outputs it. In the video noise reduction circuit 2 that adds the outputs of the second circuit and outputs Yout, a delay element 1, a detection circuit 8, and a first nonlinear amplifier 9 are provided to branch the input circuit for the luminance signal Yin. One of the branched signals is input to the detection circuit 8, which detects and outputs the luminance signal Yin level, and outputs it to the coring circuit 5 via the first nonlinear amplifier 9 for core level adjustment. The luminance signal Yin is input from a branch of the input circuit of the luminance signal Yin to the video noise reduction circuit 2 via a delay element 1 that delays the response operation time of a circuit such as a nonlinear amplifier, and is input to the circuit. The coring level is automatically set according to Yin, and furthermore, a second nonlinear amplifier 10 is provided, and the luminance signal Yin level detected by the detection circuit 8 is inputted to the second nonlinear amplifier 10, and the second nonlinear The luminance signal Yin level detected by the amplifier 10 is amplified and output, and inputted to the output amplification circuit 6 of the coring circuit to automatically adjust the amplification level.

[Effect]

FIG. 2 is a waveform diagram of each part for explaining the operation of the video noise reduction circuit of the present invention.

In the present invention, as shown in FIG. 1, a video noise reduction circuit 2 includes a delay element 1, a detection circuit 8, and a nonlinear amplifier 9.
and 10, the detection circuit 8 detects the signal level of the input luminance signal Yin, and inputs the detection signal to the nonlinear amplifier 9. The nonlinear amplifier 9 has a characteristic as shown in FIG. The amplified output is input to the coring circuit 5, and when the luminance signal level is large, a large voltage is applied to the coring circuit 5 to suppress the coring level ΔV shown in Fig. 2 (■) to a small value. When the brightness signal level is low, a small voltage is applied to the coring circuit 5 to increase the coring level ΔV to reduce noticeable noise when playing back screens with low brightness signal levels, and to suppress coring for other bright screens. As a result, high frequency components of the luminance signal are lost, resulting in loss of resolution and deterioration of image quality. Therefore, the coring level ΔV is kept low or coring is not performed.

Further, the detection output of the detection circuit 8 is branched, and the branched detection output is inputted to the amplifier 6 via the nonlinear amplifier 10, and is divided by the level ΔV cored by the coring circuit 5. Since the signal becomes smaller as shown in FIG. 2 (2), the amplifier 6 amplifies it as shown in FIG. 2 (2).

〔Example〕

FIG. 1 is a block diagram of a video noise reduction circuit showing an embodiment of the present invention, in which the luminance signal Yin shown in FIG. The signal is input to the delay element 1, and the delay element 1 delays the circuit operation of the circuit connected to the other branched circuit, and inputs the signal to the IC 2, which is commercially available for video noise reduction circuits. However, inside the IC2, the doujinshi power is branched and one of the branches is inputted to the LPF3, and the lower frequency components of the luminance signal Yin inputted to the LPF3 are output as shown in Fig. 2 (■). The signal is separated and input to an amplifier 7, where the low frequency component is amplified and added to the circuit output connected to the other branched part inside the IC2.

The other branched inside the IC2 is inputted to the HPF4, and the higher frequency components of the luminance signal Yin inputted by the HPF4 are separated as shown in FIG. 2 and inputted to the coring circuit 5. Level Δ set in coring circuit 5
Coring is performed in ■ to remove the noise in the high frequency part as shown in Figure 2 ■, and the level Δ shown in Figure 2 ■ is
A signal reduced by V is obtained, and the same signal is sent to amplifier 6.
is input to the coring circuit 5, amplified by the same amplifier 6, and outputted to the coring circuit 5.
By correcting the signal which has become smaller by the cored level △V, a waveform as shown in Fig. 2 (■) is obtained and outputted, and the waveform shown in Fig. 2 (■) is added and added to the output of the amplifier 7 to obtain the signal shown in Fig. 2 (■). A waveform as shown in is obtained, and a noise-free luminance signal Yout is obtained as an output signal of IC2.

The other branched from the input circuit of the delay element 1 is input to a detection circuit 8, which detects and outputs the luminance signal level using an emitter follower type amplifier incorporating a DC clamp circuit. The output is re-branched, and one of the re-branched outputs is inputted to the coring circuit 5 via the non-linear amplifier 9 for core level adjustment, and the non-linear amplifier 9
The amplified output is input to the coring circuit 5 using a device with the characteristics shown in Fig. 3, and when the luminance signal level is large, a large voltage is applied to the coring circuit 5, as shown in Fig. 2.
By keeping the coring level ΔV shown in FIG. decrease,
For other bright screens, coring causes loss of high frequency components of the luminance signal, impairing resolution and deteriorating image quality, so the coring level ΔV is kept low or coring is not performed.

Further, the other branched signal is inputted to the nonlinear amplifier 10, and the luminance signal level detected by the detection circuit is amplified and outputted by the same linear amplifier 10, and inputted to the output amplifier 6 of the coring circuit 5. Since the signal becomes smaller by the level ΔV cored by the coring circuit 5 as shown in FIG. 2, the level amplified by the amplifier 6 is automatically adjusted.

In the above embodiment, an IC is used for the video noise reduction circuit, but instead of using an IC, the first
It may also be configured with a circuit as shown in the block diagram in the figure.

〔Effect of the invention〕

As explained above, according to the present invention, the circuit operation of the video noise reduction circuit can be automatically performed by changing the amount of coring according to the level of the luminance signal, and when the luminance signal level is large, coring is performed automatically. By keeping the level ΔV small and increasing the coring level ΔV when the luminance signal level is low, noise that is noticeable on dark playback screens with low luminance signal levels is reduced, and by coring on other bright screens, the luminance Since high frequency components of the signal are lost, resolution is lost and image quality is degraded, it is possible to suppress the coring level ΔV to a low level and provide a noise-free, easy-to-see screen.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a video noise reduction circuit showing an embodiment of the present invention, FIG. 2 is a waveform diagram of each part for explaining the operation of the video noise reduction circuit of the present invention, and FIG. 3 is a nonlinear amplifier of the present invention. A characteristic diagram showing an example of use in
FIG. 4 is a block diagram of a conventional video noise reduction circuit. l--Delay element, 2--Video noise reduction IC, 3--, L P F, 4--
・HPF, 5 coring circuit, 6.7-...amplifier, 8--detection circuit, 9.10--nonlinear amplifier,
21...Choice switch, 22, 23, 24.25
−・−Resistor.

Claims (2)

[Claims] (1) A first circuit that separates low frequency components from the input luminance signal, and a second circuit that separates high frequency components of the same luminance signal and performs coring and amplification at a level set by the coring circuit. the first circuit and the second circuit.
In a video noise reduction circuit that adds and outputs the outputs of the circuits, the input circuit for the luminance signal is branched, one of the branched branches is input to a detection circuit, and the detection circuit detects the luminance signal level. The luminance signal is inputted to the coring circuit via a first nonlinear amplifier for core level adjustment, and is output from a branch of the input circuit of the luminance signal via a delay element that delays the response operation time of a circuit such as a nonlinear amplifier. A video noise reduction circuit characterized in that a coring level is automatically set according to a luminance signal input by inputting the coring level into the video noise reduction circuit. (2) A second nonlinear amplifier is provided, and the luminance signal level detected by the detection circuit is input to the second nonlinear amplifier, and the luminance signal level is amplified and outputted by the second nonlinear amplifier, and the luminance signal level detected by the detection circuit is input to the second nonlinear amplifier. 2. The video noise reduction circuit according to claim 1, wherein the signal is input to an output amplifier circuit to automatically adjust the amplification level.