JPH0397166A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve an inversion phenomenon and deterioration of an S/N ratio due to a recording state and variations of video head characteristics, etc., by detecting noise components and controlling automatically an RF equalizer characteristic, a noise canceling amt. and a picture control amt. in accordance with these noise component levels. CONSTITUTION:An output of an AGC circuit 5, i.e., an envelope level of a produced FM signal is detected by an envelope detecting circuit 14, and according to this detecting level, an RF equalizer circuit 6, a mixing circuit 115 in a line correlation noise canceler circuit 11 and a picture control circuit 12 are controlled. For example, the RF equalizer characteristic of the RF equalizer circuit 6 is peaked in the vicinity of a carrier frequency to make an enough margin against the inversion phenomenon by the envelope detecting circuit 14 in corresponding to the envelope level which is small, while the noise canceling amt. of the noise canceler circuit 11 is made large and a correction amt. of the picture control circuit 12 is made small so that the picture quality with importance of the S/N ratio is obtained. By this method, the inversion phenomenon and deterioration of the S/N ratio due to the recording state and variations of a video head at the time of reproducing are improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording and reproducing device that improves image quality deterioration caused by variations in recorded signal levels during the process of reproducing FM modulated signals. ．． [Prior Art] Fig. 2 shows the structure of a signal processing circuit for a reproduction system in a conventional magnetic recording/reproduction device, where l is a magnetic tape which is a magnetic recording medium, and 2 is a magnetic tape for recording video signals on the magnetic tape 1. A video head that performs playback, 3 a switcher circuit that switches the output of the video head 2, 4 a peaking circuit that corrects frequency characteristics, 5 an AGC circuit that maintains a constant gain, and 6 an RF equalizer circuit that corrects frequency characteristics. , 7 is a limiter circuit, 8 is an FM demodulation circuit, 9 is a de-emphasis circuit, 1
0 is a low-pass filter, 11 is a noise canceller circuit,
l2 is a picture control circuit, and 3 is an output terminal. Next, we will explain the operation. The reproduced FM signal taken out from the magnetic tape l by the video head 2 is converted into a continuous FM signal by the switcher circuit 3, and is converted into a continuous FM signal by the peaking circuit 4.
The frequency characteristics are corrected by Next, the AGC circuit 5 corrects variations in sensitivity of the video head 2, and R
The frequency characteristics are corrected by the F equalizer circuit 6. Further, the AM component is removed by the limiter circuit 7 and demodulated by the FM demodulation circuit 8. Furthermore, the de-emphasis circuit 9 corrects the pre-emphasis characteristic and the inverse characteristic during recording to reduce noise. Next, a low-pass filter 10 removes some unnecessary high frequency parts, a noise canceller circuit 11 removes some Takagi noise, a picture control circuit l2 improves the frequency characteristics and phase characteristics, and the resulting signal is output from the output terminal l3. ．． [Problems to be Solved by the Invention] Conventional magnetic recording and reproducing devices are configured as described above, but due to recording conditions and variations in the video head 2 during reproduction, the carrier level and side of the reproduced FM signal may vary. There were problems with variations in the relationship with the waveband level and the amount of envelope, resulting in inversion phenomena, deterioration of the S/N ratio, and variations in image quality. This invention was developed to solve the above-mentioned problems, and is a magnetic material that can improve the reversal phenomenon and deterioration of the S/N ratio caused by variations in recording conditions and video heads during playback. The purpose is to obtain a recording/playback device. [Means for Solving the Problems] A magnetic recording and reproducing device according to the present invention detects the envelope level of a reproduced FM signal, and adjusts the RF equalizer characteristics of the RF equalizer circuit, the noise cancellation amount of the noise canceler circuit, and the It is equipped with an envelope detection circuit that controls the control amount of the picture control circuit, and a noise detection circuit that detects the noise level of the FM'aiJ4 reproduced signal and controls the above-mentioned RF equalizer characteristics and the control amount of the picture control circuit. be. [Function] The envelope detection circuit and noise detection circuit of the present invention detect the envelope level and the noise level to detect the recording state or the state of the video head or recording medium, and adjust the optimum RF equalizer characteristics and noise according to this state. Determine the amount of cancellation and the amount of virtual control,
Set the image quality to the best setting. [Examples] Examples of the present invention will be described below with reference to the drawings. 1st
The figure shows the structure of the signal processing circuit of the reproduction system of the magnetic recording and reproducing apparatus according to this embodiment, and parts corresponding to numerals 1 to 4 in FIG. 2 are omitted. Further, each part indicated by numerals 5 to 13 is the same as the conventional one. However, the detailed structure of the line correlation noise canceler circuit l1 is shown, and 111 is an amplifier, 112
113 is an IH delay line, 113 is a differential amplifier, 114 is a beam converter circuit, and 115 is a mixing circuit. Further, l4 is an envelope detection circuit that detects the envelope level of the output of the AGC circuit 5, and the RF equalizer circuit 6 is activated according to the level.
, mixing circuit 11 of line correlation noise canceller circuit 11
5 and the picture control circuit 12. l5
is a noise detection circuit that detects the noise level from the output of the differential amplifier 113, and controls the RF equalizer circuit 6 and the picture control circuit 12 according to the noise level. In the above configuration, the basic operation of the circuit is the same as before. In the line correlation noise canceller circuit 11, an amplifier 111 amplifies the output of the low-pass filter 10, and
The H delay line 112 delays the output of the amplifier 111 by an IH period, the differential amplifier 113 differentially amplifies the output of the amplifier 111 and the output of the IH delay line 112 to extract the noise component, and the limiter circuit 114 extracts the noise component. The mixing circuit 115 subtracts the noise component which is the output of the limiter circuit 114 from the output of the amplifier 111 to remove the noise component.

On the other hand, the envelope detection circuit 14 detects the envelope level of the output of the AGC circuit 5, that is, the reproduced FM signal. The RF equalizer circuit 6, the mixing circuit 105 of the line correlation noise canceler circuit 11, and the picture control circuit 12 are controlled according to this detection level. For example, when playing back a soft tape that has been used repeatedly, the playback envelope level becomes smaller due to demagnetization, causing reversal phenomena and S
The image quality deteriorates due to the deterioration of the /N ratio. In this case, the envelope detection circuit 14 peaks the RF equalizer characteristics of the RF equalizer circuit 6 near the carrier frequency in response to the small envelope level to provide a margin for the inversion phenomenon, and also cancels the noise of the noise canceller circuit l1. The amount of correction is increased and the amount of correction of the picture control circuit l2 is decreased to achieve image quality that emphasizes the S/N ratio. In addition, if the recording condition is poor, such as when recording a chainer input of a broadcast channel with a weak electric field strength, the noise detection circuit 15 detects the baseband signal from the output of the differential amplifier 113 of the line correlation noise canceller circuit 11 during playback. The noise level of the signal is detected, and the RF equalizer characteristics of the RF equalizer circuit 6 and the correction amount of the picture control circuit 12 are controlled according to the noise level, so that the optimum image quality with a good S/N ratio is achieved. In the above embodiment, noise is detected from a part of the line correlation noise canceller circuit 11, but a separate circuit for noise detection may be provided. Also, AG detects the envelope level of the reproduced FM signal.
Although this is done using the output of the C circuit 5, the present invention is not limited to this. [Effects of the Invention] As described above, according to the present invention, the playback envelope level and the noise component in the baseband signal are detected during playback, and the RF equalizer characteristics, noise cancellation amount, and picture control amount are automatically adjusted according to these levels. This makes it possible to improve image quality deterioration due to inversion phenomena and S/N ratio deterioration due to variations in recording conditions and video head characteristics, dimensional differences between the recording video head and the playback video head, etc. ．．

[Brief explanation of drawings]

FIG. 1 is a processing circuit diagram of a reproduction system of a magnetic recording and reproduction apparatus according to the present invention, and FIG. 2 is a processing circuit diagram of a reproduction system of a conventional apparatus. 1... Magnetic tape, 2... Video head, 5...
AGC circuit, 6...RF equalizer circuit, 8...F
M demodulation circuit, 11 is a noise canceller circuit, l2...
Picture control circuit, l4... Envelope detection circuit, 15... Noise detection circuit, 113... Differential amplifier, 115... Mixing circuit.

Claims (1)

[Claims] A means for extracting a reproduction FM signal from a magnetic recording medium, and a reproduction F
an RF equalizer circuit that corrects the frequency characteristics of the M signal;
An FM demodulation circuit demodulates the reproduced FM signal whose frequency characteristics have been corrected, a noise canceller circuit which cancels noise components from the demodulated reproduced signal, and corrects the frequency characteristics and phase characteristics of the reproduced signal whose noise components have been canceled. In a magnetic recording and reproducing device equipped with a picture control circuit, the envelope level of the reproduced FM signal is detected, and the RF equalizer characteristics of the RF equalizer circuit, the noise cancellation amount of the noise canceler circuit, and the control amount of the picture control circuit are controlled according to the envelope level. Envelope detection circuit to control and FM
A magnetic recording/reproducing apparatus comprising a noise detection circuit that detects the noise level of a demodulated reproduction signal and controls the RF equalizer characteristics of an RF equalizer circuit and the control amount of a picture control circuit.