JP3399998B2 - Magnetic recording / reproducing device - Google Patents

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial applications Conventional technology (Fig. 7) Problems to be Solved by the Invention (FIG. 7) Means for Solving the Problems (FIGS. 1, 5 and 6) Action (Figs. 1, 5 and 6) Example (1) Configuration of Example (FIGS. 1 to 6) (2) Effects of the embodiment (3) Other embodiments The invention's effect

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus and can be applied to, for example, a tape recorder for recording / reproducing audio signals.

[0003]

2. Description of the Related Art Conventionally, some tape recorders for recording / reproducing audio signals can automatically set the signal level of an AC bias to an optimum value by recording / reproducing a test signal.

That is, in this type of tape recorder, a bias signal is generated by a predetermined oscillating circuit, and the current value of the bias signal is sequentially changed to, for example, a frequency of 400.
After recording the test signal of [Hz], frequency 10
Record the test signal at [kHz]. Further, in this kind of tape recorder, after rewinding the magnetic tape, the recorded test signal is reproduced and the signal level thereof is detected.

By doing so, as shown in FIG. 7, in this type of tape recorder, it is possible to obtain a reproduction signal whose signal level changes according to the current value of the bias signal. Therefore, in this kind of tape recorder,
After detecting the bias current value I1 at which the signal levels of the reproduction signal become equal with two test signals having different frequencies, the current value of the bias signal is set to this bias current value I1.
As a result, the frequency characteristic of the reproduced signal can be maintained at a constant value.

[0006]

By the way, if a dropout occurs when the bias current is set in this way, the tape recorder of this type cannot correctly detect the signal level of the reproduction signal. Further, even if the running of the magnetic tape fluctuates temporarily, the signal level of the reproduction signal cannot be detected correctly. For this reason, conventionally, in this type of tape recorder, if dropout or running fluctuation of the magnetic tape occurs, there is a problem that the bias current cannot be correctly set to an optimum value.

As one method of solving this problem, a method of lengthening the recording time of the test signal can be considered. In other words, even if dropouts and running fluctuations of the magnetic tape occur temporarily, if the test signal recording time is lengthened so that the signal level of the reproduced signal can be detected many times, the signal level of the reproduced signal can be increased accordingly. It is considered that the bias current can be correctly detected, and thus the bias current can be correctly set to the optimum value. However, this method has a problem that it takes time to set the bias current because the recording time of the test signal is lengthened.

The present invention has been made in consideration of the above points, and an object thereof is to propose a magnetic recording / reproducing apparatus capable of easily and surely setting the bias current to an optimum value.

[0009]

In order to solve such a problem, in the present invention, the test signal recording means 2, 5, 6 for recording the test signal STEST on the magnetic tape by sequentially switching the current value of the AC bias signal SB. 7, 8, 12,
14 and bias current setting means 2, 7, 14, 16, 17, 18, 19 for setting an AC bias current value based on the reproduction result SPB of the test signal STEST, and the bias current setting means 2, 7, 14 are provided. , 16, 17, 18,
Reference numeral 19 denotes a test signal STE corresponding to the switching of the current value.
By detecting the signal level of the reproduction signal SPB of ST, the signal level detection results P1, P2,
P3, P4, P5, P6, ... Are obtained discretely, and discrete signal level detection results P1, P2, P3, P4, P5, P are obtained.
6, ... For consecutive signal level detection results P1,
P2, P3, P4, P5, P6, ... Are sequentially set to fixed values, and AC bias current values are set based on the fixed values, and bias current setting means 2, 7, 14, 16, 17,
18, 19 are the discrete signal level detection results P at the beginning.
At least one of 1, P2, P3, P4, P5, P6, ... Is set to the fixed value P1, and the signal level detection result P2 continuous to the fixed value P1 is set to the fixed value P2 with reference to the fixed value P1. After the setting, the signal level detection result P3 that continues further on the basis of the newly set fixed value P2 is set as the fixed value P.
3 and newly set the fixed value P2, (P3, P
4, ...) as a reference for continuous signal level detection results P
3 (P4, P5, ...) Is set to a definite value, and the discrete signal level detection results P1, P2, P are sequentially repeated.
3, P4, P5, P6, ... are successively determined values P1, P2,
P3, P4, P5, P6, ... And the bias current setting means 2, 7, 14, 16, 17, 18, 19 determines the fixed value P1 (P2, P3, ...) And the fixed value P1 (P2. ,
P2 (P3, ...)
Signal level detection results other than 3, P4, ...) P3 (P
4, P5, ...) And the fixed value P1 (P2, P3, ...)
Based on and, a predetermined interpolation process is executed and the interpolation value f
(X) is obtained, and the fixed value P1 is based on the interpolation value f (x).
(P2, P3, ...) Continuous signal level detection result P
2 (P3, P4, ...) Is corrected and the fixed value P1 (P2,
P2 (P3, ...)
3), P4, ...) Are set to the definite value P2 (P3, P4, ...).

Further, in the present invention, the interpolation processing is performed by the fixed value P1 (P2, P3, ...) And the fixed value P1 (P2, P.
3, ...), the signal level detection result P2 (P3,
Signal level detection results other than P4, ...) P3 (P4, P
5, ...) and the fixed value P1 (P2, P3, ...) As a reference.

[0011]

Operation: Continuous signal level detection results P1, P2, P
3, P4, P5, P6, ... Are sequentially set to the fixed value, and the AC bias current value is set based on the fixed value. At this time, the fixed value P1 (P2, P3, ...) And the fixed value P1 are set.
(P2, P3, ...) Continuous signal level detection result P
Signal level detection result P3 other than 2 (P3, P4, ...)
(P4, P5, ...) And the fixed value P1 (P2, P3, ...)
...) is used as a reference to execute a predetermined interpolation process to obtain an interpolation value f
(X) is obtained, and the fixed value P1 is based on the interpolation value f (x).
(P2, P3, ...) Continuous signal level detection result P
2 (P3, P4, ...) Is corrected and the fixed value P2 (P3,
P4, ...) Even if any of the signal level detection results P1, P2, P3, P4, P5, P6 ,.
2, P3, P4, P5, P6, ... Can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Configuration of the embodiment In FIG. 1, 1 indicates a tape recorder as a whole,
The system control circuit 2 controls the entire operation to record and reproduce the audio signal. That is, in the tape recorder 1, the audio signal S input from a predetermined input terminal
After the AI signal level is corrected by the attenuator 3, the selection circuit 4
To the amplifier circuit 5 via.

In the tape recorder 1, the amplifier circuit 5
Then, the audio signal is amplified to a predetermined signal level and then output to the adder circuit 6, where the AC bias signal SB output from the bias oscillator (bias OSC) 7 is added and output to the magnetic head 8 for recording. As a result, the tape recorder 1 can record an audio signal by applying the AC bias recording method.

On the other hand, at the time of reproduction, in the tape recorder 1, the reproduction signal output from the reproducing magnetic head 9 is amplified by the reproduction amplifier circuit 10 to demodulate the audio signal SPB, and this audio signal SPB is externally output. Output to the terminal. As a result, in the tape recorder 1, the system control circuit 2 can switch the entire operation mode to record and reproduce the audio signal.

On the other hand, in the tape recorder 1, when a new magnetic tape is set and switched to the recording mode, it is automatically switched to the bias setting mode.
The bias current is automatically set to the optimum value. In other words, the system control circuit 2 outputs the control signal S1 to the test oscillator (test OSC) 12, and the test oscillator 12 correspondingly outputs the control signal STE.
Start output of ST.

Further, in the system control circuit 2, by outputting the switching signal SEL to the selection circuit 4,
The contacts of the selection circuit 4 are switched so that the tape recorder 1 can record the test signal STEST output from the test oscillator 12 in place of the audio signal SAI. In this state, the system control circuit 2
In addition, after the frequency switching signal S2 is output to the test oscillator 12 to set the frequency of the test signal STEST to the frequency 400 [Hz], the control signal is output to the magnetic tape running system in this state to output the tape recorder 1 Switch the operation mode to recording mode.

As a result, in the tape recorder 1,
Test signal STEST of frequency 400 [kHz] for a predetermined period
It is designed to record. This test signal STE
At the time of recording ST, the system control circuit 2 outputs a signal level switching signal SL to the bias oscillator 7 via the digital-analog conversion circuit (D / A) 14, and correspondingly, in the bias oscillator 7,
The bias current value is switched by switching the signal level of the bias signal SB according to the signal level of the signal level switching signal SL.

As a result, in the system control circuit 2, as shown in FIG. 2, the bias current value is set to the maximum value and the test signal STEST of frequency 400 [Hz] is recorded during the period of 360 [msec]. After that, the bias current value is successively decreased at 90 [msec] cycles to reduce the test signal STE.
ST is recorded, and finally the bias current value is set to the minimum value, and this test signal STEST is set for a period of 360 [msec].
To record. Further, when the test signal STEST having the frequency of 400 [Hz] is recorded in this manner, the system control circuit 2 then outputs the frequency switching signal S2 to the test oscillator 12 to change the frequency of the test signal STEST to the frequency of 10 [kHz]. To the test signal STE of frequency 10 [kHz] by switching the bias current in sequence.
ST is recorded and the magnetic tape running system is stopped and controlled.

Subsequently, in the system control circuit 2, after controlling the magnetic tape running system to rewind the magnetic tape,
The mode is switched to the reproduction mode, and the signal level of the reproduction signal SPB is detected for the test signal STEST recorded in this way. That is, in the tape recorder 1, the reproduction signal SPB is given to the detection circuit 16 and envelope detection is performed to detect the signal level of the reproduction signal SPB, and the logarithmic conversion circuit 17 converts the signal level detection result into a logarithmic value. .

Further, in the tape recorder 1, the output signal of the logarithmic conversion circuit 17 is converted into a digital value by the analog digital conversion circuit (A / D) 18, and this digital value is output to the system control circuit 2. As a result, the tape recorder 1 detects the reproduction signal level of the test signal STEST at a predetermined cycle.

At this time, the analog digital conversion circuit 18
, The output signal of the logarithmic conversion circuit 17 is set to 90% as shown by the arrow in FIG.
It is designed to be converted into a digital value in a [msec] cycle,
As a result, the system control circuit 2 can detect the signal level of the reproduction signal SPB four times each for the maximum value and the minimum value of the bias current. That is, as shown in FIG. 4, the normal dropout occurs in a short period, so that the maximum value and the minimum value of the bias current are 36 as in this embodiment.
The test signal STEST is recorded for a period of 0 [msec],
If the signal level of the reproduced signal SPB can be detected four times each, the correct signal level can be detected at any timing (in this case, at the timings t1 and t4) even if a dropout occurs. You can

As a result, the system control circuit 2 detects the maximum value of each of the signal level detection results obtained for the maximum value and the minimum value of the bias current, so that the correct signal level can be obtained even when a dropout or the like occurs. It is designed to capture the detection results. Thus, in the system control circuit 2, the signal level detection result thus fetched is stored in the memory circuit 19, and subsequently the processing procedure shown in FIG. 5 is sequentially executed to detect the fixed value of the signal level detection result.

That is, as shown in FIG. 6, in the case of this embodiment, the system control circuit 2 sequentially outputs the detection results P1, P2, ... Of the respective signal levels in accordance with respective predetermined judgment criteria. It is determined whether or not the detection result is correct in the order of level detection, and if it is determined that the detection result is correct, each detection result is set to a definite value. On the other hand, when it cannot be determined that the detection result is correct, the system control circuit 2 replaces the detection result with the interpolation value obtained by the interpolation calculation process and sets it to the fixed value, which causes dropout or the like. Even if it does, the correct detection result can be estimated.

That is, in the system control circuit 2,
After shifting from step SP1 to step SP2 and setting the first counter (represented by the symbol j) to the value 1, the second counter (represented by the symbol i) is set to the value 1 from the first counter j in the following step SP3. Set a large value. Here, in the case of this embodiment, in the system control circuit 2, the signal level detection results P1, ..., P5, which are successively and successively taken in for the test signals STEST of each frequency, respectively.
Are sequentially read from the memory circuit 19 in the order of detection so as to correspond to the values of the first and second counters j and i, and are processed.

As a result, in the system control circuit 2, the detection result having the highest signal level among the four detection results obtained at the maximum bias current state for the test signal STEST of frequency 400 [Hz] (in FIG. 6). (Represented by the symbol P1) is designated by the first counter j, and subsequently the detection result (represented by the symbol P2 in FIG. 6) obtained with the bias current reduced is designated by the second counter i. There is. Subsequently, in the system control circuit 2, the process proceeds to step SP4, and the detection result (represented by symbol P3 in FIG. 6) following the detection result designated by the second counter i and the first counter j are designated. By executing the arithmetic processing represented by the following equation using the detection result P1, the corresponding interpolation value f (x) is obtained for the detection result P2 subsequent to the detection result P1 designated by the first counter j. calculate.

[0027]

[Equation 1]

Here, DATA (i + 1) and DATA
(J) represents the detection result subsequent to the detection result specified by the second counter i and the detection result specified by the first counter j, and x is the detection result specified by the first counter j. It represents the counter value of the detection result following the result. As a result, the system control circuit 2 applies the linear interpolation method using the detection result subsequent to the detection result specified by the second counter i and the detection result specified by the first counter j. Calculate the interpolated value f (x).

When the interpolated value f (x) is obtained in this way, the system control circuit 2 continues to step S.
Moving to P5, it is determined whether the interpolation value f (x) is larger than the corresponding detection result. That is, as shown in FIG. 7, in the magnetic tape, when the signal level of the reproduction signal is represented by taking the bias current on the horizontal axis, the central portion draws a curve in the direction in which the signal level increases. Accordingly, when the interpolation value f (x) obtained by applying the linear interpolation method is larger than the corresponding detection result, it can be determined that an error has occurred in the detection result due to dropout or the like.
In this case, it can be determined that the interpolation value f (x) is more likely than the actual detection result.

According to this criterion, the system control circuit 2
In step SP5, when a positive result is obtained in step SP5, the detection result DATA (i) is replaced with the interpolation value f (x), and then the process proceeds to step SP8, whereby the actual detection result is calculated with a more reliable interpolation value f ( x).
On the other hand, if a negative result is obtained in step SP5, the system control circuit 2 directly outputs step S5.
After moving to P7 and incrementing the second counter i here, it moves to step SP8.

In the system control circuit 2, the detection result designated by the second counter i has a frequency of 400 [H].
[z] is the last detection result of the test signal STEST, and if a negative result is obtained here, the process returns to step SP4. As a result, the system control circuit 2 sequentially detects the detection result of the test signal STST of frequency 400 [Hz] in steps SP3-SP4-SP5-SP6-S.
P7-SP8-SP3 or step SP3-SP4-S
P5-SP7-SP8-SP3 processing loop LOOP1
repeat.

As a result, in the system control circuit 2, the detection result detected under the maximum bias current condition (that is, the detection result P1 in FIG. 6) is set to a fixed definite value, and the second counter i counts. The value is sequentially updated and the detection result following the detection result designated by the second counter i (that is, the sequential detection results P3, P4, P5, P6 ...
..) and the fixed value P1 to perform linear interpolation processing to obtain an interpolated value f (x) corresponding to the detection result P2, and the detection result following the fixed value P1 based on this interpolated value f (x). P2
Is judged whether it is a correct detection result,
If it is determined that the detection result is incorrect, the detection result is replaced with the interpolation value f (x).

That is, when the method of linear interpolation is applied to the detection results sandwiching the determination object in this way to judge whether or not the detection results are correct, for example, the detection results P2 and P4 adjacent to the detection result P3 are linear. When the interpolation method is applied, in this case, the detection result P4 which is the reference of the linear interpolation is detected to have a small signal level due to dropout or the like, so that it becomes difficult to obtain a correct determination reference for the detection result P3. In this case, if a determination criterion for the detection result P3 is created by applying a linear interpolation method between the detection result P5 and the detection result P2 that follow the detection result P4, a correct determination criterion can be obtained.

Even when the signal level of the detection result P5 is detected to be low due to dropout or the like, a linear interpolation method is applied between the subsequent detection results P6 and P2 to determine the detection result P3. If you create, you can get the correct criteria. In addition, even if it is not possible to obtain a correct detection result for the entire test signal STEST recorded at a frequency of 400 [Hz] due to an extremely large dropout, the long-term test signal with the bias current set to the maximum and minimum values By recording STEST, a correct detection result can be reliably obtained for the maximum value and the minimum value of this bias current, and this processing loop LOOP1 can be repeated to finally obtain a correct judgment criterion.

As a result, in the stem control circuit 2,
The second counter i is sequentially incremented to increase the loop LO
After the processing of OP1 is repeated, when the detection result designated by the second counter i becomes the detection result obtained in the state of the minimum bias current, an affirmative result is obtained in step SP8, and the process proceeds to step SP9. Here, in the system control circuit 2, by incrementing the first counter j, the detection result designated by the first counter j is switched to the detection result which is the determination target by repeating the loop LOOP1. Thus, the detection result that is the object of this determination is set to the definite value. At this time, in the system control circuit 2, by applying the linear interpolation method and replacing the detection result erroneously detected with the interpolation value f (x), a more reliable interpolation value f ( x) can be set to a fixed value.

When the definite value is set in this way, the system control circuit 2 then proceeds to step SP10, where the detection result designated by the first counter j is one before the minimum bias current. Judge whether it is a detection result or not. If a negative result is obtained here, the system control circuit 2
In step S3, the processing procedure is executed by returning to step SP3, and the detection result following the set value thus set is
The processing procedure of loop LOOP1 is repeated to set the fixed value.

As a result, in the system control circuit 2, after the detection result detected in the state of the maximum bias current is first set to the definite value, the detection results following the definite value are sequentially judged whether or not they are correct. Is set to a definite value, and when this definite value setting processing is completed up to the detection result immediately before the state of the minimum bias current, a positive result is obtained in step SP10.
The processing proceeds to step SP11 to complete this processing procedure.

In this way, when the definite value is obtained for the test signal STEST of frequency 400 [Hz], then in the system control circuit 2, the test signal STEST of frequency 10 [kHz] is also shown in FIG. By executing the processing procedure shown, a definite value is also detected for the test signal STEST of this frequency 10 [kHz]. Further, when the definite value of the detection result is obtained for the test signal STEST having the frequency 400 [Hz] and the frequency 10 [kHz] in this way, the system control circuit 2 outputs the frequency 400
A definite value having the same value is detected at [Hz] and a frequency of 10 [kHz], and the current value of the bias signal SB is set to the bias current value of this definite value.

(2) Effects of the Embodiments According to the above configuration, after the signal level detection result of the reproduction signal obtained by recording the test signal for a long time under the maximum bias current condition is initially set to the definite value, For signal level detection results that continue to this fixed value, you can obtain a highly reliable signal level detection result by setting fixed values based on sequential interpolation values as a reference. Even when recorded, the bias current can be surely set to the optimum value, and thus the bias current value can be easily and surely set to the optimum value.

(3) Other Embodiments In the above embodiments, the case where the maximum value of the bias current is first set to the definite value is described, but the present invention is not limited to this, and the minimum value of the bias current is set. May be initially set to a fixed value.

Further, in the above-mentioned embodiment, the case where the characteristic of the magnetic tape is approximated to a straight line and the point which internally divides this straight line is set as the interpolation value is described, but the present invention is not limited to this, and this straight line is used. The point to be divided may be set as an interpolation value.

Further, in the above embodiment, the case where the interpolation value is detected by applying the linear interpolation method has been described, but the present invention is not limited to this, and for example, a plurality of definite values are set and a quadratic curve is set. It is also possible to detect the interpolation value by approximating the above.

Further, in the above-mentioned embodiment, the case has been described in which the interpolation value and the signal level detection result are simply compared to determine whether or not the detection result is correct. However, the present invention is not limited to this, and the interpolation value is used, for example. After adding a predetermined correction value, it may be compared with the signal level detection result to determine whether or not the detection result is correct.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the tape recorder has been described. However, the present invention is not limited to this, and the AC bias recording method is applied to record and reproduce various input signals. It can be widely applied to magnetic recording and reproducing devices.

[0045]

As described above, according to the present invention, the test signal is reproduced to obtain the signal level detection result of the reproduction signal corresponding to the switching of the bias current, and this signal level detection result is sequentially compared with the interpolated value. And set to a fixed value,
It is possible to obtain a highly reliable signal level detection result, which allows the bias current to be reliably set to the optimum value even when the test signal is recorded for a short time as a whole, thus making it easy and reliable to set the optimum bias current value. It is possible to obtain a magnetic recording / reproducing apparatus that can be set to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a tape recorder according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining recording of the test signal.

FIG. 3 is a signal waveform diagram for explaining sampling of the reproduction signal.

FIG. 4 is a signal waveform diagram for explaining dropout correction.

FIG. 5 is a flowchart for explaining the correction of the signal level detection result.

FIG. 6 is a characteristic curve diagram for explaining the operation.

FIG. 7 is a characteristic curve diagram showing a change in signal level of a reproduction signal with respect to a bias current value.

[Explanation of symbols]

1 ... tape recorder, 2 ... system control circuit, 4 ...
... Selection circuit, 5, 10 ... Amplification circuit, 6 ... Addition circuit,
8, 9 ... Magnetic head, 7 ... Bias oscillator, 1
2 ... Test oscillator, 14 ... Digital analog conversion circuit, 16 ... Detection circuit, 17 ... Logarithmic conversion circuit,
18 ... Analog digital conversion circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/027-5/027 502

Claims (2)

(57) [Claims] 1. A test signal recording means for recording a test signal on a magnetic tape by sequentially switching the current value of an AC bias signal, and a bias current setting means for setting an AC bias current value based on the reproduction result of the test signal. The bias current setting means discretely obtains the signal level detection result of the reproduction signal by detecting the signal level of the reproduction signal of the test signal in response to the switching of the current value, For successive signal level detection results, successive signal level detection results are sequentially set to a definite value, and the AC bias current value is set with reference to the definite value. At least one of various signal level detection results
After setting one to a fixed value and setting the signal level detection result continuous to the fixed value to the fixed value with the fixed value as a reference,
Based on the newly set fixed value, the continuous signal level detection result is set to the fixed value, and the continuous signal level detection result is set to the fixed value based on the newly set fixed value. The discrete signal level detection result is sequentially and repeatedly set to a definite value, and the bias current setting means includes the signal level detection result other than the definite value and the signal level detection result continuous to the definite value, and A predetermined interpolation process is executed on the basis of the fixed value to obtain an interpolated value, and a signal level detection result continuous to the fixed value is corrected based on the interpolated value to detect a signal level continuous to the fixed value. A magnetic recording / reproducing apparatus, wherein the result is set to the fixed value. 2. The interpolation processing is linear interpolation based on the fixed value and the signal level detection result other than the signal level detection result continuous to the fixed value, and the fixed value. Item 1. The magnetic recording / reproducing apparatus according to Item 1.