JPH0734483Y2 - Magnetic recording / playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus having a function of automatically adjusting a recording signal level and a recording bias current.

(Prior Art) Conventionally, in this type of device, in order to correct the variations in the recording sensitivity and characteristics of the magnetic tape, after adjusting the recording signal level, the recording bias current is further adjusted to adjust the high frequency range. The characteristic is corrected.

(Problems to be solved by the invention) Due to the characteristics of the magnetic tape, when the recording bias current is changed to correct the high frequency characteristics, the recording sensitivity of the magnetic tape also changes, and in some cases the set recording signal level It is necessary to correct the reproduction again. If the necessity of the readjustment is not judged, the automatic adjustment ends without spending time for the extra adjustment or, on the contrary, without the accurate adjustment.

(Means for Solving the Problem) The first test is performed so that each reproduction level of the first test signal and the second test signal having a frequency higher than that of the first test signal becomes a desired level. Level adjustment to adjust the recording level based on the playback level of the signal,
A magnetic recording / reproducing apparatus adapted to automatically adjust a bias adjustment for adjusting a recording bias current based on a reproduction level of the second test signal, wherein the level adjustment and the bias adjustment are alternately automatically adjusted. Possible adjusting means, and for detecting the adjustment amount of the recording bias current at the end of the bias adjustment and ending the automatic adjustment when the adjustment amount is smaller than a predetermined amount, and continuing the automatic adjustment when the adjustment amount is larger. The detection means for generating the detection signal of 1 to the adjusting means is provided.

(Operation) Depending on the adjustment amount of the recording bias current, it is determined whether the automatic adjustment should be ended or continued, and the automatic adjustment is executed.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention, in which reference numeral 1 denotes a central processing unit (hereinafter referred to as CPU), which outputs a digital output signal which has been processed to a D / A converter 2. Output to. The D / A converter 2 converts these digital signals into analog signals and outputs the control signals S ₁ and S ₂ to the bias current control circuit 3 and the signal level control circuit 5, respectively. The bias current control circuit 3 controls the bias current generation circuit 4 based on the control signal S ₁ to mix a desired recording bias current.
Output to 10. Further, the signal level control circuit 5 also controls the gain of the voltage control circuit 6 (hereinafter referred to as VCA) based on the control signal S ₂ to output a desired output voltage signal V ₃ . The oscillator 7 oscillates a sine wave signal V ₂ having a predetermined frequency and level based on the control signal S ₃ from the output port P ₁ of the CPU ₁ and outputs it to _one fixed terminal 8 ₁ of the switch 8. Switch 8 is the recording input signal V ₁ of the the recording signal input terminal 17 to the fixed terminal ₈₂ of the other side is inputted, the output signal selected on the basis of the inversion command signal S ₄ from the output port P ₂ of CPU1 outputted from the movable terminal 8 ₃ to the input of VCA6. Voltage signal from VCA6
The V ₃ is current-amplified by a predetermined equalization by the recording amplifier 9, further mixed with a recording bias current by the mixing circuit 10, and then output to the recording head 11 and recorded on the magnetic tape 19.

On the other hand, the detection circuit 13 amplifies, detects, and rectifies the reproduction signal from the reproduction head 12, and outputs its output voltage V ₄ from the A / D converter 1
Output to 4. Therefore, the A / D converter 14 outputs a digital signal corresponding to the reproduction signal level to the input port P _{3 of the} CPU 1,
Enables playback level detection by U1. Playhead
The reproduction signal from 12 is a normal reproduction equalizer amplifier 15,
An output signal is output from the output terminal 18 via the line amplifier 16.

The operation will be described with the above configuration.

2 to 6 are flowcharts of the CPU 1 showing the operation of the present invention, and FIG. 2 mainly shows a flow of recording signal level adjustment. The flow is started by a start command signal from a start command input terminal (not shown), and standard data of level and bias prepared for each type of recording tape (for example, metal, chrome, normal, etc.) is 6 bits. It is output to the D / A converter 2 as a digital signal. The D / A converter 2 converts this digital signal into an analog voltage signal, outputs the control signal S ₁ to the bias current control circuit 3 to set the bias current, and outputs the control signal S ₂ to the signal level control circuit 5. After outputting and setting the gain of VCA6, the outputs of these control signals S ₁ and S ₂ are held. Then its output port P ₁
Control signal with the S ₃ by an oscillator 7 outputs a 400Hz sine wave signal V ₂ having a predetermined level, the fixed terminal ₈₁ side movable terminal 8 ₃ of the switch 8 in the control signal S ₄ from the output port P ₂ from Then, the magnetic tape 19 is used to record and reproduce a 400 Hz sine wave signal. And recording head 11 and playback head 12
After waiting for a predetermined time in consideration of the tape running time loss between the two, the reproduction signal reproduced by the reproducing head 12 is detected by the detection circuit 13,
It is input via the A / D converter 14 and its reproduction level is detected.

Next, the oscillation output of oscillator 7 is stopped, and the internal ROM of CPU1
Based on the scale prepared in advance, a new gain setting of VCA6 is performed so that the reproduction level becomes equal to the desired reference level. Gain setting data based on the difference between the detected reproduction level and the reference level is stored in this scale.

Next, the flow of recording bias current adjustment is performed, and the recording bias current based on the 6-bit bias data 100000 is output from the bias current generation circuit 4 to the mixing circuit 10. Then, the oscillator 7 oscillates a sine wave of 15 kHz at a predetermined level, waits for the tape running loss time, and then detects the reproduction level.

Fig. 3 shows the flow for setting the MSB (BIT5) signal. The desired reference level is compared with the detected playback level. If the difference is within the specified error range, this bias data is output as is. And jumps to the END CHECK flow, and when it is lower than that, bias data is output as 010000, and when it is higher, it is output as 110000, and reproduction level detection is performed again.

The next Fig. 4 shows the setting flow of the next bit (BIT4). The reproduction level is detected by the newly set bias current value and compared again with the reference level. If the difference is within the specified error range, , This bias data is output as it is and EN
Jump to the D CHECK flow, and if lower,
Bias data is output as × 01000 (× indicates a set bit), and conversely, when it is high, it is output as × 11000, and reproduction level detection is performed again.

Following the same flow, each subsequent bit (BIT3 to BIT
Determine 1) and move to the LSB (BIT0) flow shown in FIG.

The same flow is performed here, but after the bias data is finally output, the process moves to the END CHECK flow.

By thus setting the bits in order from the MSB, 6-bit bias data can be determined by detecting the reproduction level a maximum of 6 times.

Fig. 6 shows the END CHECK performed after the LSB setting flow or when the playback level falls within the specified error range on the way.
The flow is shown.

In this END CHECK flow, stop the 15kHz sine wave oscillation,
Bias data is compared. This comparison is a comparison between the data set last time and the data set this time. If the difference is within the predetermined level, the flow is terminated, and if it is not the predetermined level, the readjustment point shown in the flowchart of FIG. Adjust the level and bias. This EN
The D CHECK flow is for obtaining an accurate recording level and frequency characteristics for the reasons described later. The previously set data is the standard bias data in the first adjustment and the second adjustment. Shows the bias data adjusted for the first time, and shows the bias data adjusted for the second time if it is the third time, except for the standard bias data for the first adjustment, which is always set by the previous adjustment. The bias data is shown. Therefore, in this example,
Level adjustment of all the components necessary for executing this, including the flow of CPU1 from FIG. 2 to FIG. 5, that is, the components except the reproduction equalizer amplifier 15 and line amplifier 16 in FIG. And END CHECK shown in FIG.
The constituent elements including the flow and executing this function correspond to the detection means that detects the adjustment amount of the recording bias current and determines whether or not to continue the automatic adjustment.

Fig. 7 is a graph of the reproduction level change when recording the sine wave of 400Hz and 15kHz by changing the recording bias current value in a general magnetic tape. The horizontal axis is the standard recording bias current. The range up to ± 5 dB is logarithmic, and the vertical axis is the playback level, which is also logarithmic. 1 in the figure is 40
A change curve of 0 Hz and a change curve of 15 kHz are shown at 2, respectively, and a known recording equalizer and a reproduction equalizer are used for this recording and reproduction.

As is clear from the figure, the recording bias current was changed from -5 dB to +5.
When it is varied to dB, the reproduction level of 400Hz gradually increases with the increase of bias current, and eventually decreases at + 2.5dB. Moreover, the level changes about 7 dB with respect to the recording bias current change from -5 dB to +1 dB, which changes drastically.

On the other hand, the reproduction level at 15kHz increases up to -3dB, but then begins to decrease.

Therefore, in the above flowchart, if the adjustment is completed by simply adjusting the recording bias current after adjusting the recording level at 400 Hz, if the bias adjustment amount is large, the adjusted reproduction level value of 400 Hz will also change. There is a possibility that desired level and frequency characteristics may not be obtained.

In consideration of such a case, in the present invention, the adjustment amount at the time of adjusting the recording bias current is checked by the END CHECK flow, and if the adjustment amount is smaller than the predetermined amount, the reproduction level change of 400 Hz is slight. Judge and finish automatic adjustment,
If it is larger, the adjustment is performed again from the above-mentioned readjustment point. Since this readjustment is performed based on the bias current value selected in the previous adjustment, the adjustment amount of the recording bias current at this time is smaller than that in the previous time. Therefore 2
As the adjustment is repeated three times, the probability of falling within the predetermined change range increases, and the adjustment ends.

The present invention is not limited to the above embodiment,
It goes without saying that various modes such as recording and reproducing the adjustment signal at the same time can be adopted.

According to the present invention, since the number of adjustments is selected according to the adjustment amount of the recording bias current, more accurate recording / playback level and frequency characteristic can be obtained, and particularly unnecessary adjustment can be omitted. As a result, the adjustment time can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 to 6 are flow charts showing an operation flow of the embodiment, and FIG. 7 is a diagram for explaining the present invention. 1 ... Central processing unit, 2 ... D / A converter, 3 ... Recording bias current control circuit, 4 ... Recording bias current generation circuit, 5
... recording signal level control circuit, 6 ... voltage control circuit, 7 ... oscillator, 8 ... switch, 9 ... recording amplifier, 10 ... mixing circuit, 11 ... recording head, 12 ... reproducing head, 13 ... detection circuit, 14 ... A / D converter, 15 ... playback amplifier, 16 ... line amplifier, 17 ... recording signal input terminal, 18 ... signal output terminal, 19 ... magnetic tape

Claims (1)

[Scope of utility model registration request] 1. A reproduction level of the first test signal so that respective reproduction levels of the first test signal and a second test signal having a frequency higher than that of the first test signal become desired levels. In the magnetic recording / reproducing apparatus, the level adjustment for adjusting the recording level based on the above and the bias adjustment for adjusting the recording bias current based on the reproduction level of the second test signal are respectively performed. And an adjustment means capable of automatically adjusting the bias adjustment alternately, and detecting the adjustment amount of the recording bias current at the end of the bias adjustment and ending the automatic adjustment when the adjustment amount is smaller than a predetermined amount, Further, when it is large, the magnetic recording / reproducing apparatus is provided with a detection means for generating a detection signal for continuing the automatic adjustment to the adjustment means.