KR940003921Y1 - Brightness noise removing circuit of vcr - Google Patents

Abstract

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Description

VRL luminance noise cancellation circuit

1 is a block diagram of a conventional V-Cal.

2 is a frequency characteristic diagram of a composite video signal.

3 is a frequency characteristic diagram of a low pass filter in FIG.

4 is a signal waveform diagram in each part of the circuit for explaining the operation of the present invention in FIG.

5 is a detailed circuit of the luminance noise removing unit of FIG.

6A and 6B are filtering characteristics of each low pass filter of FIG. 5;

* Explanation of symbols for main parts of the drawings

1, 4: band filter 2, 7'H: amplifier

3: Sub-converter 5: Main converter

6: killer part 7: low pass filter

7 ': luminance noise canceling unit 7'A: mode switching unit

7'B, 7'C: Constant voltage part 7'D, 7'E: Buffer part

7'F, 7'G: Low pass filter 8: Luminance signal processor

9: adder 10: mixed amplifier

11: current amplifier H1, H2: head

In order to reduce the luminance noise of the V-seal, the low-pass carrier frequency is 661 KHZ and 881 KHZ in PAL and 627-KHZ MESECAM. It is configured to remove the noise component of the luminance signal in the color band by using it properly. Especially, it is the luminance that removes the luminance noise during recording and playback of PAL / SECAM multi-system and is suitable for recording and reproducing vivid color signals. The present invention relates to a noise canceling circuit.

First turning conventionally a block of V CR, as also shown as this, and to remove the luminance signal in the video signal (V _i) and the color signal (C) band pass filter (1) of 4.43MHZ to extract the band pass filter ( A band for removing the signal of 3.8MHZ from the signals of 5.06MHZ and 3.8MHZ output to the subconverter (3) and the amplifying unit (2) for amplifying the chroma signal (C) output to 1) at an appropriate level. A main converter 5 and a killer section 6 for low-converting the chroma signal by comparing the filter 4 with the chroma signal C inputted from the amplifier 2 and the output signal of the band pass filter 4. A low pass filter 7 which receives the output signal of the main converter 5 and passes only a 1.4-1.5 MHz signal, and a luminance signal processor 8 which extracts a luminance signal from the image signal Vi; The adder 9 adds the output signal of the luminance signal processor 8 to the output signal of the low pass filter 7, and outputs the output signal of the adder 9. A conventional circuit comprising a mixed amplifier 10 for amplifying to a level and a current amplifier 11 for amplifying the output current of the mixed amplifier 10 and outputting the amplified output to the heads H1 and H2. Referring to Figure 2 the operation of as follows.

The input signal (V _i) after the luminance signal is removed and through a band pass filter (1) of 4.43MHZ is only chroma signal (C) passes through the band filter (1), while passing through the re-amplification unit (2) The signals of 5.06MHZ and 3.8MHZ, which are amplified to an appropriate level and output to the sub-converter 3, are removed through the band filter 4 while removing the signals of 3.8MHZ.

On the other hand, the main converter 5 compares the chromaticity signal input from the amplifying unit 2 with the output signal of the band pass filter 4 to low-frequency convert the chromaticity signal and output it. The output signal of the main converter 5 is again supplied to the adder 9 by passing a signal of 1.4-1.5MHZ by the killer 6 and the low pass filter 7, and at this time, the luminance signal processor 8. is supplied to the adder 9, it extracts the luminance signal in the video signal (V _i).

Accordingly, the adder 9 adds the output signal of the luminance signal processing unit 8 to the output signal of the low pass filter 7, which is amplified to an appropriate level through the mixing amplifier 10 and then head ( H1) and H2 are recorded on the recording medium.

Here, the frequency of the PAL / MESECAM is distributed as shown in FIG. 2, and the low pass filter 7 of FIG. 1 filters as shown in FIG. 3 to filter the chroma signal for all the PAL / MESECAM signals. This is mixed.

As a result of the distribution of low-converted subcarriers, which are output signals of the main converter, low-pass filters are recorded at 627KHZ for PAL and 661KHZ and 881KHZ for MESECAM, so that the low pass filter passes only signals of carrier ± 500KHZ during recording and playback. However, in the existing system, the filter for the PAL + MESECAM signal is configured without the filter for each mode, so that the distribution of the color filter and the luminance signal are overlapped during recording and playback. There was a defect that was introduced and adversely affects the image quality.

The present invention devised a circuit that can remove the luminance noise in order to solve such a conventional defect will be described in detail by the accompanying drawings.

The fourth turning Thus, as shown, and the band filter (1) for extracting a video signal (V _i), the color signal (C) from said band pass filter (1 a block diagram of a luminance noise reduction circuit of the subject innovation V CR A band filter for amplifying the chroma signal C outputted to a predetermined level, and a 3.8 MHZ signal removed from the west of the 5.06 MHZ and 3.8 MHZ outputted to the subconverter 3. (4), a main converter (5) and a killer unit (6) for low-converting the chroma signal by comparing the chroma signal (C) input from the amplifier (2) with the output signal of the band pass filter (4). Luminance noise removal unit 7 'for filtering the chromaticity signal by receiving the output signal of the main converter 5 through different pass bands according to the PAL / MESECAM signal, and the image signal ( and a luminance signal processor (8) for extracting a luminance signal from the V _i), a luminance signal to an output signal of the luminance noise remover (7 ') An adder 9 that adds the output signal of the processor 8, a mixed amplifier 10 that amplifies the output signal of the adder 9 to an appropriate level, and amplifies the output current of the mixed amplifier 10 The current amplifier 11 outputs the heads H1 and H2.

FIG. 5 is a detailed circuit diagram of the luminance noise removing unit 7 'in FIG. 4, which is composed of a transistor Q1 and a resistor R1 to output a switching control signal according to a PAL / MESECAM detection signal. Each of the mode switching unit 7'A, transistors and resistors Q2, Q3, R2, R3, and Q4, Q5, R4, and R5 is configured by the output signal of the mode switching unit 7'A. The constant voltage part 7 'is composed of a constant voltage part 7'B, 7'C which outputs a constant voltage when selected, and a transistor Q6, a resistor R6-R8 and a capacitor C1 in the PAL mode. B) a buffer part 7'D for buffering and amplifying a PAL signal input from the killer part 6 by receiving a constant voltage from the battery; and a transistor Q7, resistors R12-R14, and a capacitor C2. In the mode, the buffer unit 7'E receives a constant voltage from the constant voltage unit 7'C and buffers and amplifies the MESECAM signal input from the killer unit 6, the resistors R9, R10, and the capacitor C3, C4) and coil (L1) L2) and a low pass filter 7'F for passing only the PAL chromaticity signal from the output signal of the buffer unit 7'D, resistors R15 and R16, capacitors C5 and C6 and coils L3 and L4, the low pass filter 7'G which passes only the chroma signal for MESECAM from the output signal of the buffer part 7'E, transistors Q8 and Q9, resistors R11 and R17 and a capacitor And an amplification part (7'H) configured to receive the output signals of the low pass filter (7'F) and (7'G) and amplify and output them to a predetermined level. If described in detail with reference to Figure 6 attached the action and effect as follows.

The input signal (V _i) after the luminance signal is removed and through a band pass filter (1) of 4.43MHZ is only chroma signal (C) passes through the band filter (1), while through the back amplifying section (2) Amplified to proper level. The 5.06 MHZ and 3.8 MHZ signals output to the sub-converter 3 are removed through the band filter 4 while the 3.8 MHZ signals are removed.

On the other hand, the main converter 5 performs a low pass conversion of the chroma signal through the comparison process between the chroma signal input from the amplifier 2 and the output signal of the band pass filter 4 (subcarriers of PAL: 627 KHZ, SECAM Subcarriers: 661KHZ and 881KHZ), and the output signal of the main converter 5 is supplied to the luminance noise removing unit 7 'through the killer unit 6 again.

Accordingly, the luminance noise removing unit 7 'removes the luminance noise, which will be described in detail with reference to FIG.

According to the detection output of the PAL / MESECAM signal, one of the constant voltage unit 7'B and the constant voltage unit 7'C is operated. For example, the high potential, which is the PAL detection signal, is applied to the input terminal PAL "H". When supplied, since the transistor Q2 is turned on as the transistor Q3 is turned on, a constant voltage is supplied to the buffer portion 7'D through the transistor Q2, while the transistor Q5 is turned on as the transistor Q1 is turned on. Is turned off, so that a low potential is applied to the base of the transistor Q4, whereby the transistor Q4 is turned off so that the constant voltage is not supplied to the buffer portion 7'E.

Accordingly, the buffer unit 7'B operates among the buffer units 7'B and 7'C, and the PAL signal output to the killer unit 6 is buffered and amplified through the transistor Q6. The low-pass filter portion 7'F is configured to have the characteristics as shown in Fig. 6a, so that only the pure PAL chromaticity signal (subcarrier: 627KHZ) that does not include the luminance FM signal is passed. The chroma signal thus passed is again output through the transistor Q8 and the capacitor C7.

On the other hand, when a low potential, which is a MESECAM detection signal, is supplied to the input terminal PAL "H", the constant voltage part 7'B cannot be driven by the low potential as described above, while the constant voltage part 7 ' Since C) is driven, the MESECAM signal output from the killer unit 6 is buffered and amplified through the buffer unit 7'E, and then supplied to the low pass filter 7'G, and the low pass filter unit 7 '. Since is configured to have the characteristics as shown in FIG. 6b, only the pure color signal for MESECAM without luminance component is output through the low pass filter 7'G and then output again through the transistor Q9 and the capacitor C7.

The chroma signal for the PAL / MESECAM output as described above is then ringed by the adder 9 with the luminance signal through the normal luminance signal processing unit 8 and then amplified to an appropriate level through the mixing amplifier 10, which is in turn amplified. After amplification at the section 11, the data is recorded on the magnetic recording medium through the heads H1 and H2.

On the other hand, during reproduction, the luminance noise signal is removed by the luminance noise removing unit 7 'while being processed in the reverse process.

As described in detail above, the present invention automatically changes the filter passband by the PAL / MESECAM mode director output and passes the filter that passes the subcarrier during recording and playback of the PAL / MESECAM multi-system. There is an advantage in that noise generated when the band overlaps with the color band can be removed.

Claims (2)

And the video signal and the band-pass filter (1) for extracting a chroma signal (C) from (V _i), the amplification unit 2 for amplifying the chrominance signal (C) output to the band filter (1) to an appropriate level, the sub- A band filter 4 for removing the signal of 3.8 MHZ from the west of the 5.06 MHZ and 3.8 MHZ output to the converter 3, the chroma signal C and the band filter input from the amplifier 2; The broadcast mode in filtering the chroma signal by receiving the output signal of the main converter 5 through the main converter 5 and the killer unit 6 for low-conversion the chroma signal by comparing the output signal of (4). (PAL / MESECAM) Unlike the pass band according to the signal by the luminance-noise removing filtering the chrominance signals (7 ') and, with a luminance signal processing unit (8) for extracting a luminance signal from the video signal (V _i), the And an adder 9 which adds the output signal of the luminance signal processing section 8 to the output signal of the luminance noise removing section 7 '. VCI luminance noise canceling circuit. The method according to claim 1, wherein the mode switching unit 7'A outputs a switching control signal according to the detected PAL / MESECAM signal and the output signal of the mode switching unit 7'A is selected. Constant voltage unit 7'B, 7'C outputting a constant voltage when the PAL signal is supplied from the killer unit 6 by receiving constant voltage from the constant voltage unit 7'B in the PAL mode. A buffer unit 7'D for buffering and amplifying, and a buffer unit 7'E for buffering and amplifying a MESECAM signal input from the killer unit 6 by receiving a constant voltage from the constant voltage unit 7'C in the MESECAM mode. And a low pass filter 7'F for passing only the PAL chromaticity signal from the output signal of the buffer portion 7'D, and a low pass for passing only the MESECAM chromaticity signal from the output signal of the buffer portion 7'E. The luminance noise removing unit 7 is supplied to the filter 7'G and the amplifying unit 7'H which receives the output signals of the low pass filter units 7'F and 7'G and amplifies and outputs them to a predetermined level. ') A luminance noise removing circuit of V-C.