JP3089744B2 - VTR recording circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording circuit of a VTR which can select and record a tape type, a recording quality and a recording time.

[0002]

2. Description of the Related Art For example, an 8 mm VTR has been proposed in which a normal recording mode and a high image quality recording mode can be selected as recording image quality. The frequency distribution of each signal in each recording mode is shown in FIGS. 7A and 7B.
Differs from both the recording mode as shown in FIG. 7 (a) and (b) the frequency band of the luminance signal, the center carrier frequency 5MH _Z in the normal recording mode, as the FM modulation signal of the deviation 1.2MH _Z, Center carrier frequency 7MH _Z in quality recording mode, are respectively recorded as an FM-modulated signal of the deviation 2.0 mH _Z.

[0003] In addition to the evaporation tape (ME tape), there has been proposed a tape capable of using a coating tape (MP tape). However, the application tape is inferior in the characteristics of the electromagnetic conversion system as compared with the vapor deposition tape, and when recording is performed in a high-quality recording mode using the application tape, the reversal phenomenon is easily caused. Therefore, when a high-quality recording mode and a long-time recording mode are selected using a coating tape, a luminance signal has conventionally been passed through a trap circuit. The trap circuit for applying a trapping around 2 MH _Z of the recording luminance signal, a frequency characteristic as shown in FIG.

[0004]

In the conventional configuration, the high-frequency component of the recording luminance signal is suppressed as shown in FIG.
Although the reversal phenomenon can be suppressed, there is a disadvantage that the image quality is significantly deteriorated and the resolution required as a minimum in the high image quality recording mode cannot be maintained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a VTR recording circuit which can maintain the image quality in a high image quality recording mode while preventing the reversal phenomenon.

[0006]

In order to achieve the above object, a recording circuit of a VTR according to the present invention uses a vapor-deposited tape and a coated tape as types of tape, and a normal recording mode and a high-quality recording mode as recording quality. In a VTR that can select and record each of a standard time recording mode and a long time recording mode as a recording time, in a high image quality recording mode, a filter characteristic of a high frequency component is changed depending on the type of the tape, and the In the case of the coating tape, a low-pass filter that suppresses a high-frequency characteristic of a luminance signal to a low level, and a white clip level is varied according to a mode of the recording time in a high-quality recording mode of the coating tape,
A white / dark clipping circuit for lowering a white clip level of the luminance signal which has been subjected to the pre-emphasis processing in the case of the long time recording mode with respect to the standard time recording mode.

[0007]

When the high-quality recording mode and the long-time recording mode are selected by using a coating tape, the high-frequency characteristics of the luminance signal are suppressed and the white clip level of the luminance signal subjected to the pre-emphasis processing is reduced. Since the inversion phenomenon can be prevented from occurring, and the inversion phenomenon is prevented by a synergistic effect of both, the amount of reduction in the high-frequency component of the luminance signal due to the low-pass filter can be suppressed to a small extent, and the image quality is less deteriorated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show examples applied to an 8 mm VTR of the present invention.

FIG. 1 is a circuit block diagram of a recording circuit of an 8 mm VTR. In FIG. 1, a composite video signal for recording is supplied to a Y / C separation circuit 2 via an amplifier 1.
Where it is separated into a chroma signal and a luminance signal.
The separated chroma signal is supplied to a chroma processing system (not shown), and the separated luminance signal is supplied first to the low-pass filter 3 of the luminance processing system.

The low-pass filter 3 is configured to vary the filter characteristics of the high-frequency component in three stages by the control signal of the system controller 11. That is, the control signal indicates the selection of the type of recording image quality and the type of tape. When the normal recording mode is selected, the filter characteristic shown in FIG. 2A is set to a lower cut-off frequency than in the high-quality recording mode. When the high-quality recording mode is selected and the evaporation tape is used, the filter characteristic shown in FIG. 2C is obtained. When the high-quality recording mode is selected and the coating tape is used, the cutoff is as high as when using the evaporation tape. Although the frequency is set, the filter characteristics are changed to the filter characteristics shown in FIG.

The pre-emphasis circuit 4 performs a pre-emphasis process for enhancing a high-frequency component of the luminance signal passed through the low-pass filter 3, and outputs the processed luminance signal to the white / dark clip circuit 5.

The white / dark clip circuit 5 clips the overshoot and undershoot of the luminance signal at the white clip level and the dark clip level, respectively, and varies the white clip level by the control signal of the system controller 11. That is, the control signal indicates the selection of the combination of the type of tape and the type of recording time when the high-quality recording mode is selected. When the vapor deposition tape is used (regardless of the recording time) or when the coating tape and the standard time recording mode are selected, FIG. A level of white clip level,
When the application tape and the long-time recording mode are selected, the B level in FIG. 3 which is 20% lower than the A level is changed to the white clip level.

The FM modulator 7 FM-modulates the luminance signal clipped as described above based on the control signal. As the center frequency of 5MH _Z if the control signal indicates the selection of the normal recording mode, also respectively output to the mixing circuit 8 and FM modulation centered frequency 7MH _Z is to indicate the selection of high-quality recording mode . The mix circuit 8 mixes the FM luminance signal with the chroma signal, the stereo FM audio signal, and the ATF signal, and outputs the mixed signal to the head 10 via the head amplifier 9.

The system controller 11 has a tape identification signal indicating whether the mounted tape is a vapor deposition tape or a coating tape, a recording image quality selection signal indicating whether the selected recording image quality is a normal recording mode or a high image quality recording mode, and Standard recording time (SP) mode or long recording time (LP)
An SP / LP selection signal indicating whether the mode is the mode or the like is led, and the control signals described above are sent to the low-pass filter 3, the white / dark clipping circuit 5, and the FM modulation circuit 7 according to the contents of these signals. Are output.

FIG. 4 is a circuit diagram of a control section of the low-pass filter 3. In FIG. 4, since the low-pass filter 3 of this embodiment is also used in the reproduction mode, a selection signal of the recording / reproduction mode is also input. The resistances R ₁ and R ₂ are set to the same resistance value, and the voltage (control voltage) at the common connection point of the _two resistances R ₁ and R ₂ is supplied to the controlled part. In the normal recording mode, the transistor Tr ₁ is turned on,
Since the other transistors Tr ₂ and Tr ₃ are turned off, the control voltage becomes 5 V, which shows the filter characteristic shown in FIG. In the high-quality recording mode of the coating tape, the transistor Tr _{1 is used.}
Is turned off, and the other transistors Tr ₂ and Tr ₃ are turned on, so that the control voltage becomes 2.5 V, showing the filter characteristic shown in FIG. 2B. In the high-quality recording mode of the vapor-deposited tape, since all the transistors Tr ₁ , Tr ₂ , Tr ₃ are off, the control voltage becomes 0 V, and the filter characteristic shown in FIG.

FIG. 5 is a circuit diagram of a control unit of the white / dark clip circuit 5. 5, a series circuit of a resistor R ₃ and resistor R ₄ and a series circuit of a resistor R ₅ and the transistor Tr ₄ is connected in parallel, the voltage of the common connection point (control voltage) is supplied to the controlled unit . High image quality recording mode and a long time recording mode of application tape transistor Tr ₄ is turned on to the control voltage is white clip level is set to level B of Figure 3 to the L level. And, in the other high-quality recording mode transistor Tr ₄ is a control voltage for the off-white clip level is set to the A level of Figure 3 becomes H level.

The operation of the above configuration will be described below.
When the normal recording mode is selected, regardless of the type of tape and the recording time, the low-pass filter 3 exhibits the filter characteristic of FIG.

In addition, when a high quality recording mode is selected using a vapor-deposited tape, the low pass filter 3 exhibits the filter characteristic shown in FIG.

Further, when the high quality recording mode is selected using the application tape, the low-pass filter 3 exhibits the filter characteristic of FIG. 2B regardless of the recording time, so that the high-frequency component is sufficiently maintained. When the recording time is in the standard time recording mode, the white / dark clip circuit 5 has a lower electromagnetic conversion efficiency than that of the vapor deposition tape.
Is high as in the case of the vapor deposition tape, but the high-pass component is somewhat suppressed by the low-pass filter 3, so that high image quality can be obtained without inversion. When the recording time is in the long-time recording mode, the electromagnetic conversion efficiency is even worse than the above, but since the white clip level of the white / dark clipping circuit 5 is lower than the above, the high-pass component is somewhat suppressed by the low-pass filter 3. At the same time, high image quality required for the high image quality recording mode can be obtained without causing the reversal phenomenon.

[0020]

As described above, according to the present invention, in the high-quality recording mode, in the case of the coated tape, the high-frequency characteristics are suppressed slightly lower than that of the vapor-deposited tape, the coated tape is used, and the recording time is long. In this case, since the white clip level is lowered, there is an effect that the image quality required for the high-quality recording mode can be maintained while preventing the reversal phenomenon in the high-quality recording mode of the applied tape regardless of the recording time mode.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a recording circuit of an 8 mm VTR (Example).

FIG. 2 shows filter characteristics of a low-pass filter;
(A) is a characteristic diagram in a normal recording mode, (b) is a characteristic diagram in a high-quality recording mode of a coated tape, and (c) is a characteristic diagram in a high-quality recording mode of a vapor-deposited tape (Example).

FIG. 3 is a diagram showing a white clip level in each mode (Example).

FIG. 4 is a circuit diagram of a control unit of the low-pass filter (embodiment).

FIG. 5 is a circuit diagram of a control unit of the white / dark clip circuit (embodiment).

6A is a frequency distribution diagram of each signal in a normal recording mode, and FIG. 6B is a frequency distribution diagram of each signal in a high image quality recording mode.

FIG. 7 is a frequency characteristic diagram of a trap circuit (conventional example).

[Explanation of symbols]

3: low-pass filter, 5: white / dark clip circuit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/91-5/956 G11B 5/027 502

Claims (1)

(57) [Claims] 1. Recording by selecting a vapor deposition tape and a coating tape as types of tape, selecting a normal recording mode and a high image quality recording mode as recording quality, and selecting a standard time recording mode and a long time recording mode as recording time. Possible VT
R, in a high-quality recording mode, a low-pass filter that varies a filter characteristic of a high-frequency component according to the type of the tape, and suppresses a high-frequency characteristic of a luminance signal to a low level in the case of the coating tape with respect to the deposition tape; In the high image quality recording mode, the white clip level is varied according to the mode of the recording time. A VTR recording circuit comprising a dark clip circuit.