JPS601687B2 - Optimal recording bias detection method for magnetic recording and playback equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining an optimum recording bias for a magnetic recording/reproducing machine.

There are different types of magnetic tape, such as L/H tape, chrome tape, and ferrichrome tape.Tape recorders are usually adjusted using the standard tape for each type, but even tapes of the same type have different characteristics. However, it is difficult to optimally set all the recording characteristics for these various tapes.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optimal recording bias detection method for a tape recorder that detects various types of tapes.

The method of the present invention first sets the recording level to the standard level of the target tape, and then changes the recording bias sequentially between the upper and lower limits. The value M is detected, and it is determined that the number of occurrences of the reproduced signal with the maximum value M is a predetermined number (for example, 3) or more, and when the number of occurrences of the reproduced signal reaches 3 or more, the It is characterized in that the recording bias B corresponding to the reproduced signal is set as the optimum recording bias.

In addition, if the number of times the signal occurs to reach the maximum value M is not 3 or more, a predetermined value M, which is lower than the maximum value M, is regarded as the maximum value, and the number of times the signal occurs to reach that value M is set to 3 or more again. The optimum recording bias is detected by determining whether the

The present invention will be explained below with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an embodiment of the present invention, in which the recording level adjustment signal fL (700 degrees) and the recording equalizer (EQ) adjustment signal f (1 plate Hz) are selected by a changeover switch. is selected and input to the line switch 2a.

The line switch 2a selects either the line input signal or the aforementioned adjustment signal fL (or fH) and applies it to the flat amplifier 3. The increased signal is input to the recording level setting circuit 4, the level of which is varied and set to an appropriate level, and then applied to the recording equalizer setting circuit 5. The recording equalizer setting circuit 5 is configured to vary the equalizer characteristics, and its output is superimposed on the recording bias signal fB (100K) and recorded on the tape 7 by the recording head 6. The recording bias signal fB is
It is applied to a recording bias setting circuit 8 for varying and appropriately setting the bias level, and its output is superimposed on the recording signal via a bias amplifier 9.

The tape recording signal is regenerated into an electric signal by a regeneration head 10 and then sent to a reproduction equalizer circuit 11 and a flat amplifier 12.
After increasing the power, the signal is input to the line amplifier 14 via the switch 13.

The output of the line amplifier 14 becomes a line output via the line switch 2b. The output of the reproducing flat amplifier 12 is also converted to a DC level by a detection circuit 15 and becomes one input of a comparator 16.

The reference signal that is the other input to the comparator 16 is the D/A
The output of the converter 17 is used, and the converter 17 converts the parallel binary digital signal output from the port output PA of the PM 18 into a DC level. The output of the comparator 16 is applied to the boat input P, of the PIA 18. A binary digital signal is output from the boat output PB of the PM 18 and is interpreted by the decoder 19 to provide control signals 101 and 1 for controlling the post-recording level setting circuit 4, EQ setting circuit 5 and recording bias setting circuit 8.
02 and 103.

In addition, the changeover switch 1 and line switches 2a and 2b are controlled on and off by the boat outputs P2 and P3 of the PM 18, respectively, and the boat output P4 of the PIA 18 controls the input system (mechanical system) and amplifier system (electrical system) of the tape recorder. A predetermined control signal is applied to the boat input P5, including a signal indicating whether or not an absent recording state is set from the mechanical system or amplifier system of the aircraft. And the CPU as the central processing unit
20, a ROM (read only memory) 21a in which a program for controlling the CPU 20 is stored in advance, and a RAM (random access memory) 21 that can be freely written and accessed, and a keyboard for giving external commands. 22 is connected to the input/output port Pc of the PIA 18.

Note that during normal operation, the RAM 21 is supplied with power from the device power supply, but when the power is cut off, power is applied from a backup power source such as a battery, so that the stored contents are always retained. It is now possible.

FIG. 2A shows a specific example of the recording level setting circuit 4, in which the impedance between the input/output line and the ground is varied by the 6-bit parallel digital control signal 101 of the decoder 19. It is composed of R, 2R, . . . 32R and D-FF. The input/output ratio of the recording level corresponding to the control signal 101 is shown in FIG. The magnitude of the 6-bit control signal 101 is digitally represented in 64 steps from the minimum value 00 (H) to the maximum value bait (in hexadecimal notation), and 00 (H) means that the control signal 101 is (000000). is step 0, 3F is (111111) and is step 64, and 20(H) is the intermediate step (1
00000). Here, the recording level is changed stepwise in 64 steps using a 6-bit control signal, but increasing the number of bits will widen the variable range and increase the resolution. Note that (H) indicates that it is shown in hexadecimal notation, and other control signals 102
, 103 as well. FIG. 3A shows another example of the recording level setting circuit 4, in which the impedance between the inverting input of the operational amplifier OP and the ground is varied by a control signal 101 to obtain the characteristics shown in FIG. 3B. . The circuits shown in Figures 2 and 3 above can be constructed at extremely low cost, and when controlling multiple channels, their characteristics can be precisely matched. For example, the recording level can be controlled at the same time for both the L and R channels. Since it becomes possible to use a control signal, the circuit configuration is further simplified. 4A and 4B are diagrams showing still another example of the recording level setting circuit 4, in which the digital control signal 101 is converted into a DC voltage by an A/D converter, and this voltage is applied to the drive circuit 401 in A. A so-called voltage controlled variable resistance element VC consisting of a CdS photocoupler is
The recording level is varied by controlling R402. B is V
CR402 (L, R channels) is directly controlled by DC voltage. Figure C is a diagram showing the characteristics. In the circuits shown in A and B, the transmission line for control only requires the use of one line for direct current voltage. It has the advantage of requiring less. FIG. 5A shows a specific circuit example of the recording bias setting circuit 8.
It varies the resistance value between the bias signal line and ground in accordance with the bit control signal I03, and is composed of a switching transistor Q, resistors R, 2R, . . . , 32, D-FF, an inverter INV, and the like.

Reference numeral 801 indicates a bias amplifier that amplifies the 10-dish ratio.

FIG. 5B shows how the bias signal current changes with respect to the control signal 103. 6A and 6B are circuit diagrams showing other examples of the recording bias setting circuit 8, and A is a circuit diagram showing the digital control signal 103 through D-FF, switching transistor Q, resistor network R, 2R, . . . , 32R, etc., and convert it into a DC voltage by using
cc is variable.

In addition, EH indicates the erase head, and B indicates the bias oscillator 8.
The impedance of a photocoupler 803 that varies the output level of 02 is controlled by a digital control signal 103. FIG. 8A shows a specific example of the recording equalizer setting circuit 5, which changes the value of the capacitive element Cs for equalizer characteristics in accordance with the control signal 102 of the decoder 19 to appropriately select the amount of compensation for the 1-side Hz signal. It consists of an operational multiplier OP, a switching transistor Q, a capacitor network C, 2C, . . . , 32C, and a D-FF.

B in the same figure shows the change in capacitance value with respect to the digital control signal 102, and C shows the frequency characteristic of the recording signal current using the digital control signal 102, that is, the capacitance value as a parameter. FIG. 9A is a diagram showing another example of the recording equalizer setting circuit 5, in which the gain of the amplifier 501 is controlled by the control signal 102.
, D-FF, switching transistor Q and resistance network R
, 2R, ...32R to obtain the equivalent capacitance C
This is to control x=(1-A)C.

Here, A is the gain of the amplifier 501, C is the feedback capacitance of the amplifier 501, the input impedance is infinite, and the output impedance is zero. In this circuit, since a resistor is used instead of a precision capacitive element as shown in FIG. 8, parts are relatively easy to obtain. B in the same figure shows the change characteristic of the equivalent capacitance Cx, and C shows the change characteristic of the recording electric particle compensation amount. 10th
The figure is an example of a schematic plan view of the keyboard 22, and shows "A".
By pressing the "UTO" switch, the device will switch to CPU2.
Under automatic control from the river, the operation of adjusting the recording bias, recording level, and EQ characteristics is started.

Also, by pressing the "MEMORY" key and pressing one of the number keys, the optimum data of recording bias, recording level and EQ characteristics automatically set for the tape to be used will be stored in RAM2.
Stored at 1. Therefore, by pressing the "TAPE" key again and pressing the same numeric keys as above, the data can be read out. If you press the ``TAPE'' key and do not press any number keys, you can go from the automatic shift setting mode to the standard recording bias, recording level, and EQ characteristics. Here, the standard state is a signal in which the bias current control signal, recording level control signal, and EQ control signal are in the middle step of the variable range (for example, 20 (H)).
This refers to the standard tape adjusted condition, which corresponds to the fixed bias and level/EQ condition of a tape recorder without an automatic adjustment device.

Immediately after the power line is turned on, it is not in the recording mode, and sometimes it is always set to this standard condition.

As a result, it is possible to record immediately in the standard state, just like a normal tape recorder, immediately after turning on the power without performing automatic settings. . Also, in the standard state, TONE
A signal is output from the output port P4 of the PIA 18, allowing manual bias adjustment, level adjustment, and EQ adjustment only at this time.

This makes it possible to adjust the standard settings to suit the user's preferences. During automatic adjustment, the TONE signal is always not output, and this is canceled regardless of the manual adjustment position. FIG. 7 shows a manual bias adjustment circuit. In the figure, when the TONE signal becomes "H", Q is turned on, Q2 is turned on, Q is turned on, and Q4 is turned off, and the output of the bias oscillator changes. When the TONE signal is "L", Q is off, Q2 is off, Q3 is off, Q4 is on, and the resistance value of VR is constant at the midpoint, and the bias oscillation output is also constant. "BIAS", "LEVE" as indicator lamps
"L" and "EQ" lamps are provided, and their blinking is controlled according to the operation of the device. There is also a "TAPE" display, which uses a 7-segment display element to display the type of tape, that is, in the standard state, one of standard tape, chrome tape, and ferrichrome tape, according to the user's selection. In the case of standard tape, "1" is indicated, and in the case of chrome and ferrichrome tapes, "2" and "3" are indicated, respectively.
In addition, when automatically adjusted setting data (corresponding to each digital control signal) is stored in or retrieved from RAM, the tape numbers 1 to 1 corresponding to the RAM are stored.
9 is displayed. The operation of the above-mentioned device will be explained below in Fig. 14A.
11 to 1 according to the flowchart shown in
This will be explained with reference to the operational waveform diagram in FIG. 3 as necessary.

First, the chart in FIG. 14A shows an example in which the tape recorder has an absent recording function, which automatically determines whether the device is set to the absent recording state.

In other words, as soon as the power is turned on, a control signal indicating whether or not the answering recording is set is sent to PM1.
8, the CPU 2 judges the signal and sends each command signal to set the device to the recording characteristics that were set just before the power was turned on, if the absentee recording is set. Output each. In other words, when setting up a recording while the user is away, the user can set the memo IJ circuit 2 by key operation in advance so that the recording level, recording bias, and EQ characteristics have values corresponding to the tape to be used.
Since the tape recorder is set by starting from step 1, each characteristic value should be stored in the memory 21 when the power is turned off. Therefore, if the CPU 20 determines that the recording mode is set to the recording mode when the user is away, the recording level, recording bias, and EQ characteristics are set by the setting circuits 4, 5, and 8 to the above characteristic values, and the recording level, recording bias, and EQ characteristics are set by the setting circuits 4, 5, and 8. is in a standby state. If the tape recorder is not set for recording during an absence, control signals 101, 102 and 103 are outputted so as to set the standard recording characteristics of a standard tape, respectively.

However, it is in a state of waiting for a key input instruction. 8 in Fig. 14 shows "AUTO" to start automatic adjustment of recording characteristics.
This is a chart for setting the equipment when the `` switch is pressed, and it determines whether it is in the ``STOP'' state or not in the ``PAUSE'' state, and sets the rear device to the ``REC/PLAY'' state. do. At the same time, the operation of the recording bias manual adjustment circuit is prohibited,
Switch line input switches S2a and S2b as desired. Furthermore, it is set to prohibit the tape from stopping when the tape counter is reset (0'').The operator then determines the tape type preset and sets the recording level, bias, and settings corresponding to the tape. Each setting circuit is controlled according to the EQ characteristics.The following explanation assumes that a standard tape is used.At this time, the "BIAS", "LEVEL" and "EQ" lamps on the keyboard are all turned off. FIG. 14C is a chart for automatic magnetic tape detection, in which the minimum value 00 (H) of the digital signal is output to the output port PA of the PIA 18, and the
After being converted into an analog signal corresponding to 00 (H) by the /A converter 17, it becomes the reference input of the comparator 16.

Then, the switch selects fL=40 plate z as a recording signal based on the boat output P2 of PM18. Here, since the reproduction output is zero in the leader tape portion, the output of the detector 15 is a cloud voltage, and the output of the comparator 16 is at a low level.

As soon as the magnetic tape section is reached, the reproduction level becomes high and the comparator output is inverted to a high level. With this high level signal P, tape detection is performed and the built-in tape counter is reset to "n". Such a state is shown in period C of FIG. FIG. 14D is a chart for rough adjustment of the recording level for setting the optimum recording bias.

. This adjustment is performed with the bias and recording equalizer set to standard settings. In other words, if this adjustment is not performed, the playback level cannot be digitally converted for tapes with different sensitivities such as 121, 122, and 123, compared to the bias current vs. playback level characteristics of the standard tape shown in Figure 12A. In order to fit within this range, it is necessary to widen the digital conversion range, or on the other hand, in order to accurately find the maximum reproduction level of the bias current characteristic, the resolution of the digital conversion section must be 0.1 steps. . Therefore, by performing this coarse level adjustment, the level is adjusted to point A in FIG. 12B, so that the resolution can be set to 0.1 and the range that can be digitally converted can be narrowed. Furthermore, the reason why the level to be roughly adjusted is not set at the center value 20 (H) is to widen the range of the larger level since the bias curve necessarily passes through point A in FIG. 12B.

A digital output indicating a standard level OA (001010) is generated at the output port PA, and an analog level corresponding to the OA value becomes a reference input to the converter 16. At this time, the "BIAS" lamp changes from an off state to a blinking state. and a control input signal 10 for the recording level setting circuit 4.
A recording level value at which 1 changes appropriately and becomes equal to the reference input of the comparator 16 is selected. In this example, the 11th
As shown in period D in the figure, a binary search method is used. . In other words, by comparing the playback level and the reference level, the difference is 1/2, 1/4, 1/8,...1
/64 and the recording level at which the playback level is equal to the reference level is detected by adding and subtracting the bell. Note that, of course, other methods may be used instead of the binary search method. At this time, if the playback level increases and reaches a level corresponding to the upper limit value that can be digitally processed thereafter, an error signal is output, and all lamp displays are set to a blinking state to issue an adjustable warning. Once the recording level corresponding to the standard playback level OA is set, the recording bias is set according to the flowchart as shown in FIGS. 14E and F.

That is, the 6-bit digital control signal 103 is set to 00.
(H) to 64 steps, each corresponding playback level is converted to a 6-bit digital signal and stored in memory, and when all playback is completed, the contents of each memory are used to optimize the playback level. This is done by a so-called level sweep method that detects and sets the recording bias. The playback level is digitized by the comparator 16 and the D/A converter 1.
According to 7, it is done by so-called successive approximation type A/D conversion, and the playback level is converted into a value from 00 (H) to bait according to the 16 ship method, and playback levels outside the range cannot be processed, so the playback level is reduced to dregs. If it is included in the value, an error signal will be generated and adjustment will not be possible. For example, curves 61 and 62 in Figure 12B
This is the case as shown in . Such playback characteristics will not appear because the recording level has been set in advance in flowchart D, but if the tape being used is not in the optimum position due to user error (for example, if the tape to be used in the chrome position is In the case of the L/H tape position, curves 61 and 62 are obtained. To read the playback level at each bias current, there is a time lag from the recording bed to the playback head, t, = (distance between the recording head and the playback head)/tape speed, so the bias is adjusted at t = o as shown in Figure 12C. B, and after a time lag t, the playback level is A/D converted and written to RAM, and then the bias is set to B2 and the same procedure is repeated. For example, t, = 10.
Even if the time is 0, 64×100×10 −3 =6.4 seconds or more is necessarily required. Therefore, the time required to set the reproduction level can be shortened by increasing the bias at regular intervals and inputting the data after each time t, as shown in FIG. ○ in the same figure shows the case where the time to increase the bias is set to and '2, and the bias is set to B2 after seconds, and the playback level is A/D converted at the same time as B3 after to seconds. This is written into the RAM as the reproduction level for bias B.

If you continue this in the same way, to x 64 ten = 3. Writing of the assistance iron data is completed and time is reduced. t)
o; tA/2, but it is clear that the time can be shortened by making it shorter. In addition, if the occurrence of playback output at bias B (or cue signal) is detected and reading of the playback level is started, t becomes unlimited and can be used even with a tape deck (2-head machine) that is used for different times. becomes.

The 64 pieces of playback data stored in the memo are subjected to determination and arithmetic processing by the CPU 20.

That is, the number of signals with the maximum value M of the playback level is determined, and if the number of signals is, for example, 3 (generally n) or more, the corresponding minimum value B of the recording bias, (actually, a digital signal indicating the corresponding control signal 103) is determined. ) first memorize. However, when the reproduction level characteristics shown in FIG. 12E and F are obtained, the maximum value is set to (M-1). (M-
By reading 2), it is possible to prevent cases E and F from becoming unadjustable, and to prevent malfunctions due to dropouts or extreme fluctuations in bells. Even if the maximum value M is decreased sequentially to (M-1) and (M-2) in this way, if the number of signals is not 3(n) or more, it is determined that adjustment is impossible and an error signal is generated. This operation is repeated again to obtain the recording bias B2 in the same manner, and the average value B=(B, 1 B2)/2 of both is calculated using the previously obtained value B.

After that, the optimum bias value B'=B+N is determined. child)
N is an appropriate predetermined value, and by adding N, correction is made so that the average value calculation does not result in a shallow bias value. The playback levels during the sweep of recording bias adjustment are shown in periods E and F in FIG.

The digital signal serving as the control signal 103 corresponding to the optimal recording bias B' determined in this way is stored in a predetermined location in the memory, and the recording bias setting circuit 8 is controlled and set by this digital signal. At this time, the "BIAS" lamp changes from flashing to constantly lit. 14G and 14 are flowcharts for recording level adjustment, in which the reference input of the comparator 16 is set to a reference level corresponding to 20 (H), and the binary search shown in period G of FIG. 13A is performed. The recording level is coarsely adjusted using the method.

At this time, the "LVEL" lamp changes from off to blinking. At this time as well, an error signal will be generated if the reproduction level is outside the digital processing range. When the level phase adjustment is completed, fine adjustment is performed. In this case, as shown in FIG. Count the number of times n that is high.

If the counting result satisfies, for example, 8<n<12, the recording level at that time is set as the optimum recording level. If n<8,
If n>12, the recording level is raised or lowered by one step, and compared and counted again. 8)
For example, the tuning is repeated four times until <n<12.
Also, the digital signal indicating the control signal 101 for achieving the recording level obtained in this way is * or 00 (H).
If so, this is also an error signal and adjustment is disabled.

Then, when the level is set and memorized again, “LEVEL
” lamp is always on. The above operating waveforms are shown in FIG. 13A. FIG. 14, J, is a flowchart of EQ (recording equalizer) characteristic adjustment, in which the recording signal is first switched from fL=40 Hz to f KHz.

At this time, the "EQ" lamp goes from off to blinking. Thereafter, the EQ setting circuit 5 is controlled by the control signal 102, and as shown in FIG. 13A, the recording level adjustment is performed in the same manner as in the previous recording level adjustment. To describe only the different parts, if the digital signal for the control 102 that indicates the EQ characteristic is 00 (H) in the fine adjustment stage, an error signal will be generated, and if it is a carp, the bias is too deep, so the recording bias is decreased by one step, and the recording level adjustment, EQ adjustment, that is, the recording compensation amount adjustment is performed again. In this case, if the above-described determination loop has been performed four times, it is determined that adjustment is not possible and an error signal is generated. Once the optimum EQ characteristics are determined and stored in this way, the "EQ" lamp will be lit at all times and the adjustment will be completed. Figure 14 K shows the device “ST”
3 is a flowchart for returning to the "OP" state.

In the figure, the tape stops at the ``0'' position of the counter, but this is because the counter was reset at ``n'' at the start (n is a positive integer), so the tape has overflowed by a distance corresponding to the n count. There will be a line. This is to erase the signals (fL, fH) recorded during automatic adjustment. According to the present invention, memory, CPU and PFA
etc. can be configured with a microprocessor such as a microcomputer, so not only can an extremely small and highly reliable device be obtained, but also other operations such as control operations of counters, timers, etc. can be performed simply by increasing the program. becomes.

Another advantage is that optimum recording characteristics are automatically determined for any type of tape.

[Brief explanation of drawings]

FIG. 1 is a basic block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of a recording level setting circuit, B is a characteristic diagram thereof,
3A is a diagram showing another example of the recording level setting circuit, B is a characteristic diagram thereof, FIGS. 4A and B are diagrams illustrating still another example of the recording level setting circuit, C is a characteristic diagram thereof, Figure 5A is a diagram showing an example of a green bias setting circuit, B is its characteristic diagram, Figure 6A
, B is a diagram showing another example of a recording bias setting circuit. FIG. 7 is a diagram showing an example of a manual control circuit for recording bias, and FIG.
Figure A is a diagram showing an example of a recording EQ setting circuit, B and C are characteristic diagrams thereof, and Figure 9A is a diagram showing another example of a recording EQ setting circuit.
B and C are its characteristic diagrams, and Figure 10 is a schematic diagram of the keyboard.
11 to 13 are operational waveform diagrams, and FIG. 14 is a flowchart. Explanation of symbols of main parts 4... Recording level setting circuit, 5... Recording EQ setting circuit, 8...
・Recording bias setting circuit, 16... comparator,
17...D/A converter, 20...CPU,
21...RAM, 21a...ROM. Figure 2 Box Ball Figure 3 Figure 4 Figure 5 Group Figure 7 Saba a Figure Roof L'0 Figure Frequent Figure Traditional '3 Figure Curtain Figure Brother '2 Figure Group'4 Figure Traditional'4 Figure Multi'4 figure'4 figure

Claims (1)

[Claims] 1. A step of setting a recording level to a predetermined level in response to a start signal, and a step of generating an end signal after sequentially changing a recording bias between an upper limit and a lower limit in response to the start signal. and storing reproduction signal levels corresponding to each of the recording biases in a storage means, and detecting the maximum value M using the reproduction signal levels stored in the storage means in response to the end signal and reproducing the data. a step of determining that the number of times the signal level becomes equal to the maximum value M is equal to or greater than a predetermined number and generating a determination signal;
A method for detecting an optimal recording bias for a magnetic recording/reproducing machine, comprising the step of determining the recording bias corresponding to the first reproduction signal among the number of occurrences as the optimal recording bias in accordance with the determination signal. 2. The method according to claim 1, wherein in the step of generating the determination signal, an error signal is generated when the level of the reproduced signal exceeds a predetermined level. 3. A step of setting the recording level to a predetermined level in response to the start signal, a step of generating a termination signal after sequentially changing the recording bias between an upper limit and a lower limit in response to the start signal, and each of the recording biases. a step of storing reproduction signal levels corresponding to each in a storage means, and detecting a maximum value M of the reproduction signal level using the reproduction signal levels stored in the storage means in response to the end signal; a step of determining that the number of times the reproduction signal level becomes equal to M is greater than or equal to a predetermined number and generating a first determination signal; and a second determination when the number of times that the reproduced signal level becomes equal to the maximum value M is smaller than the predetermined number. a step of generating a signal, and determining in response to the second determination signal that the number of times the reproduced signal level becomes equal to a value M_1, which is a predetermined value lower than the maximum value M, is equal to or greater than the predetermined number, and generating a third determination signal. and a step of setting the recording bias corresponding to the first reproduction signal of the number of times as the optimum recording bias in response to the first or third determination signal. How to find the optimal recording bias for your machine. 4. In the step of generating the second determination signal, an error signal is generated when the number of times the reproduced signal level becomes equal to the value M_1 is smaller than the predetermined number. Method described.