JPH0114982Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a circuit configuration of a magnetic recording/reproducing device.

Magnetic recording and reproducing devices (hereinafter referred to as VTRs) that record and reproduce image signals have image signal bandwidths ranging from 0 to several MHz, and therefore image signals are usually converted into FM waves and recorded.

Therefore, if a frequency component outside the band of the VTR recording signal is input, an overmodulated recording signal will be generated within the VTR, and the reproducibility of recording and reproduction will deteriorate.

Therefore, the recording signal system circuit in the VTR is equipped with a low-pass filter (hereinafter referred to as a low-pass filter), which is a band-limiting pre-filter whose cutoff frequency is higher than the highest frequency that should always be recorded.
is inserted to block signals with frequency components outside the band.

However, when a low-pass filter is inserted into a recording signal system circuit, disturbances occur in the amplitude and phase characteristics even in the signal components within the band to be recorded by the low-pass filter.
This is considered to be one of the problems with devices such as VTRs that play back, where reproducibility is important.

In order to solve these problems, this idea
The present invention provides a VTR in which the connection configuration of a low-pass filter is changed when the spectrum of an image signal to be recorded is known or can be detected.

The circuit configuration of the main parts of the VTR of this invention will be explained below.

Figure 1 shows one embodiment of this invention.
0 is a signal switching circuit, 20 is a recording signal system circuit for recording image signals, and 30 and 40 are other VTRs and TV cameras that supply image signals to be recorded.

The signal switching circuit 10 has interlocking switches S ₁ ,
The switch S ₁ selects an external recording signal and connects the recording signal to the terminal T _v , and the switch S ₂ switches the changeover switches S ₃ and S ₄ in the recording signal system circuit 20 _. A control signal H or L is supplied to the control terminal _Tc .

On the other hand, the recording signal system circuit 20 is controlled to be in the switching position shown by the solid line when the control signal of the control terminal _Tc is H, and to be in the switching position shown by the dotted line when the control signal is L. Changeover switch _S3 ,
S ₄ and low pass filter LPF, FM modulator MOD,
It consists of an FM demodulator DEM, etc.

Therefore, as shown in this figure, the signal switching circuit 10
However, when the external VTR 30 is selectively inputting the image signal being played back, the image signal is input directly to the FM modulator MOD without passing through the low-pass filter LPF, and is recorded on the tape T, but the signal switching circuit When 10 selects the image signal from the TV camera 40, the image signal from the TV camera 40 passes through the low pass filter LPF and then the FM modulator.
It is input to MOD and recorded on tape T.

In other words, the TV camera 40 is predicted to include an out-of-band frequency component in the image signal to be recorded.
When selecting , a low pass filter LPF is interposed in the recording signal system circuit 20, and the FM modulator
To prevent overmodulation with the MOD, but the playback output of an external VTR 30 that does not include frequency components outside the band in the image signal to be recorded should be input to the FM modulator MOD without passing through the low-pass filter LPF. become.

When a VTR including such a signal switching circuit 10 and recording signal system circuit 20 is used and the low-pass filter LPF is inactivated in response to an external input signal, the amplitude characteristic fluctuation ΔG, which is problematic as a characteristic of the low-pass filter LPF, is , the influence of the phase characteristic variation ΔT can be removed when recording an image signal that does not have frequency components outside the band (in the case of the VTR 30 mentioned above). Good image quality can be maintained even during operations.

The embodiment shown in FIG. 1 shows the case where one low-pass filter LPF is used, but if several low-pass filters are provided, a separate switch may be provided for each of them. Furthermore, it goes without saying that semiconductor switches can be used as the changeover switches _S3 and _S4 .

Figures 2a, b, and c show other embodiments of this invention, in which a VTR equipped with a low-pass filter and its switching circuit is operated by a command signal output from an externally connected image device. It is controlled as explained in the figure, and in Figure 2a, when the TV camera 51 is connected as an external image device, the VTR 50 is automatically controlled by the command signal S _c of the TV camera 51. The built-in low-pass filter 50a is controlled to operate.

In addition, in Fig. 2b, the time base correction circuit (TBC) 5
2 is connected, the command signal S _c of the time axis correction circuit 52 disables the low pass filter 50a of the VTR 50.

Furthermore, in FIG. 2c, operation of the low-pass filter 50a in the VTR 50 is controlled by operating the editing machine 53, and the command signal S is controlled in accordance with the input signal changeover switch of the editing machine 53. It is designed to output _c . The command signal in such an embodiment may be one based on positive or negative polarity, one using frequency modulation, or one using an intermittent signal.

As explained above, the magnetic recording and reproducing apparatus of this invention uses a built-in band-limiting pre-filter, which is a low-pass Since the bypass connection circuit of the filter can be controlled, fluctuations in the amplitude characteristics and phase characteristics caused by inserting this low-pass filter can be easily removed as necessary, especially when dubbing several times. By using the present invention in a magnetic recording and reproducing device that serves as an editing machine, it has the advantage that editing can be performed without deteriorating image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main circuit configuration of the VTR of this invention, and FIGS. 2a, b, and c are explanatory diagrams showing other embodiments of this invention. In the figure, S ₁ and S ₂ are switches, S ₃ and S ₄ are changeover switches, LPF is a low-pass filter, MOD is an FM modulator, and DEM is an FM demodulator.

Claims (1)

[Claims for Utility Model Registration] A recording system circuit includes a low-pass filter that limits the frequency band of an input image signal to be recorded, and a switch circuit that forms a bypass circuit for the low-pass filter; A magnetic recording/reproducing device characterized in that the switch circuit is switched and controlled by a control signal that detects a width.