JP2703022B2 - Recording current control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording current control device for setting a recording current suitable for magnetic recording / reproduction, and more particularly to a magnetic recording / reproduction device for recording / reproducing a video signal using a rotary transformer. The present invention relates to a recording current control device suitable for application to a recording / reproducing device.

[Conventional technology]

Conventionally, in a home VTR, as described in pages 75 to 78 of the document "Introductory VTR (written by Kotaro Yokokawa, Tokyo Denki University Press)", the recording current flowing through the recording video head winding is In order to set a suitable value for obtaining the maximum reproduction voltage, recording current adjustment by means such as a variable resistor is provided. The recording current value for obtaining the maximum reproduction voltage, that is, the optimum recording current value is hereinafter referred to as ORC (Optimum Recor
ding Current). However, the value of ORC changes due to variations in the characteristics of the tape and the head in each VTR. That is, ORC shows a different value in each set of mass-produced VTRs. Also, in the same VTR,
ORC shows different values when the tape used as the recording medium is different. In addition, there is a change in ORC due to temperature dependence of tape and head characteristics and a change with time. On the other hand, in the conventional recording current adjustment, the average ORC value is determined while taking into account the various factors mentioned above as much as possible, and the mass production VTR
A method has been used in which the average ORC value is uniformly applied to the set. Therefore, each VTR
At the time of recording / reproducing, the set value of the recording current often caused a deviation from the ORC. This means that the reproduction voltage can only take out a value smaller than the maximum value, which causes a reversal phenomenon and S / N deterioration in the VTR reproduced image.

[Problems to be solved by the invention]

In the above prior art, despite a variety of ORC value variation factors, a fixed recording current value was applied to the set, so that the recording current value was liable to be deviated from the ORC,
This is a cause of deterioration of the reproduction image quality.

An object of the present invention is to automatically detect an ORC value at a time when a recording operation of each set is to be performed and perform a practical recording / reproducing operation at a recording current value set based on the ORC value. An object of the present invention is to eliminate image quality degradation caused by ORC value variation.

[Means for solving the problem]

The object is to perform a magnetic recording operation and a reproducing operation using a plurality of different recording current values before performing a practical recording / reproducing operation, and select a desired recording current value by a comparison judgment operation using the reproduction output amplitude as information. This can be achieved by providing a means for determining a recording current setting state during a practical recording / reproducing operation using the desired recording current value as information. Furthermore, in a magnetic recording / reproducing apparatus which has a rotary transformer typified by a home VTR and records a video signal, the signal frequency used in the automatic detection operation of the desired recording current is preferably suitable for magnetic recording. Setting to be close to the carrier frequency of the luminance signal modulated (by FM modulation or the like) so as to synchronize with the rotation operation of the rotary transformer to perform the selection switching operation of the recording head and the reproduction head in the above means, and By selecting a head having the same azimuth (or the same head) as a recording head and a reproducing head used in a pair of recording / reproducing operations, and stopping the recording medium traveling during the recording / reproducing operation, the recording and reproducing operations can be performed. Occasionally, by specific technical means such as controlling the magnetic head to run on almost the same part on the recording medium It is revealed.

[Action]

According to the above-described means, just before attempting to perform a practical recording / reproducing operation in each set, an ORC value suitable for the characteristics of the head and the tape at that time is detected, so that the optimum recording current setting is always performed. Is possible.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a recording head for recording a signal for ORC detection, 2 is a magnetic tape, 3 and 8 are rotary transformers, 4 is a recording amplifier, 5 is a gain switching control unit for controlling gain switching of the storage amplifier 4, Reference numeral 6 denotes a comparison / judgment unit which compares the magnitudes of a plurality of input DC potentials and issues an instruction regarding gain setting to a gain switching control unit based on the result, and 7 denotes a magnetic head 1 recorded on the magnetic tape 2 by the magnetic head 1. A reproducing head for reproducing the reproduced signal, 9 a reproducing preamplifier,
Reference numeral 10 denotes a detection circuit for smoothing the output of the reproduction preamplifier 9 and converting the output to a DC potential.

Taking a household VHS-VTR as an example, it is desirable that the frequency of the signal input to the recording amplifier 4 be set near the carrier of the FM modulated luminance signal. At the time of recording, the signal amplified by the recording amplifier 4 is applied to the magnetic head 1 via the rotary transformer 3 and recorded on the magnetic tape 2. At this time, recording is performed at a plurality of different recording current values in accordance with an instruction from the gain switching control unit 5. At the time of reproduction, the signal written on the magnetic tape 2 is detected by the magnetic head 7, input to the preamplifier 9 via the rotary transformer 8, and the amplified output signal is input to the detection circuit 10. The signal smoothed by the detection circuit 10 is input to the comparison / determination unit 6. The comparison determination unit 6 compares the N types of input signal potentials in magnitude, and
Search for ORC. FIG. 2 shows an example of the recording current versus preamplifier output signal amplitude characteristics. In FIG. 2, the ORC value is a recording current value for obtaining the maximum output data D4, which is about 40 mAPP. Based on this result, an instruction is sent from the comparison / determination unit 6 to the gain switching unit 5, and the magnetic head 1 is used during practical recording and reproduction.
The amplification degree of the recording separator 4 is controlled such that the luminance signal FM carrier component of the recording current applied to the recording current is approximately equal to the ORC value. In addition, in order to minimize interference with other signals superimposed and recorded on the FM luminance signal, the recording current may be controlled to be slightly lower than the ORC value.

Next, switching between recording and reproduction effective in realizing the above function in a system for performing azimuth recording using a rotating cylinder and head switching accompanying this will be described. FIG. 3 is a time chart showing an example of switching timing of recording and reproduction, and FIG. 4 is a head arrangement diagram showing an example of a head arrangement in a rotating cylinder. In FIG. 4, 11 and 16 are rotating cylinders, 12, 14 and 17 are plus azimuth heads, 1
3, 15, and 18 represent minus azimuth heads.

FIG. 4 (A) shows a plus azimuth head 12 and a minus azimuth head at a position approximately 180 degrees opposite to each other.
15 and a pair of a plus azimuth head 14 and a minus azimuth head 13 are arranged. When expressed, it is selected as an integral multiple of 1H (often about twice), and is the mainstream in recent home VTRs as an effective head arrangement for reducing noise bars during special playback. It is. In this head arrangement, there are roughly two head selection methods for using the same azimuth head for recording and reproduction. First, for example, the signal recorded by the head 14
It is a method of recording on one side and reproducing on the other side of the same azimuth head, which is about 180 degrees crossed, such as reproducing at 12.

FIG. 3A shows an example of the recording and reproduction switching timing in this case. In FIG. 3 (A), recording and reproduction are switched every time the cylinder rotates half a turn. Specifically, the SW30 signal is used for the NTSC system, and the SW25 signal is used for the PAL system.
It can be easily realized by performing switching control using signals as information. The second method is to use the same head for recording and reproduction, such that a signal recorded by the head 14 is reproduced by the head 14 as well. FIG. 3B shows an example of the switching timing between recording and reproduction in this case. In FIG. 3 (B), recording and reproduction are switched every time the cylinder makes one rotation, and this is similar to the first method in that the switching using the SW30 signal or SW25 signal as information is effective. As for the switching timing of a plurality of types of recording current values, there is also a method of recording by allocating one type of current value to a half-rotation period of a rotating cylinder. The speed can be further increased by the method of assigning the recording current value. At this time, recording a pilot signal at the boundary of the time-divided area to give information on the change point of the recording current value is also effective in correctly detecting the reproduced signal.

FIG. 4 (B) shows the simplest configuration of the head in the rotary cylinder, in which a plus azimuth head 17 and a minus azimuth head 18 are arranged at positions crossed by 180 degrees. In the case of this head configuration, the first switching method described above cannot be used, but the second method can be applied.

In addition, it is necessary for the magnetic head to travel on the same portion of the magnetic medium during recording and reproduction, and to achieve this purpose, the magnetic tape must be moved during a pair of recording and reproduction operations. It is effective to stop running.

〔The invention's effect〕

According to the present invention, in a magnetic recording / reproducing apparatus, even if a variation or a change in the ORC value occurs due to a variation in the characteristics of the magnetic head and the recording medium of each apparatus, a temperature dependency, or a change over time, the practical recording / reproduction operation Immediately before, the ORC value can be automatically detected and the recording current value can be set to an optimum value, so that the image quality deterioration due to the above-described factors is greatly improved.

[Brief description of the drawings]

FIG. 1 is a signal processing block diagram of one embodiment of the present invention, and FIG.
FIG. 3 is an example of a characteristic diagram showing a change in an output signal amplitude with respect to a change in a recording current. FIG. 3 is a time chart showing an example of a switching timing between recording and reproduction in one embodiment of the present invention.
FIG. 4 is a head layout diagram showing a head layout according to one embodiment of the present invention. 1 ... recording head, 2 ... magnetic tape, 3/8 ... rotary transformer, 4 ... recording amplifier, 5 ... gain switching control section, 6 ... comparison / determination section, 7 ... reproduction head, 9 ... Regeneration preamplifier, 10 Detector circuit, 11/16 Rotating cylinder, 12/14/17 Plus azimuth head, 13/15
・ 18 ... minus azimuth head.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Susumu Otsuka 1410 Inada, Katsuta-shi, Ibaraki Pref. Hitachi, Ltd. Tokai Plant (56) References JP-A-62-62403 (JP, A) JP-A-49 -27211 (JP, A)

Claims (1)

(57) [Claims] 1. A recording current control method for a magnetic recording / reproducing apparatus having a rotary transformer and an azimuth head, wherein a recording current value flowing through a magnetic head winding is subjected to magnetic recording operation and reproduction operation by a plurality of different recording current values. Let
A desired recording current value is selected by a comparison judgment operation using the reproduction output amplitude as information, and a recording current setting state during a practical recording / reproduction operation is determined using the desired recording current value as information. In synchronization with the cycle, the selection switching operation of the recording head and the reproducing head at the time of selecting the desired recording current is performed, and at the time of selecting the desired recording current, one recording head continuously contacts the magnetic medium. A period is divided into a plurality of periods, and a recording operation using a plurality of types of recording current values is performed in the one period;
Furthermore, a recording current control method characterized in that a pilot signal is recorded at the boundary of the time-divided area.