JPH09284721A - Magnetic reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve picture quality by eliminating noises at the time of high- speed reproduction by providing a pair of EP heads for economy reproduction and switching the outputs of SP heads for ordinary reproduction to EP head outputs synchronously with the rotation of a rotary drum corresponding to a prescribed switching signal at the time of high-speed reproduction. SOLUTION: The respective outputs from a pair of EP heads 2 and 3 and SP heads 4 and 5 are respectively amplified by head amplifiers 7, 9, 8 and 10, inputted to SWA11 and SWB12 and switched synchronously with the rotation of the drum. The output of a drum flip-flop pulse DP generation circuit 17 is supplied to a head switching pattern HP generation circuit 19 as well, its output is inputted to a phase change circuit 20, a comparator 15 compares the output signals from the SWA11 and SWB12 while referring to a pattern for which phase shift is performed to the head switching pattern, and the signal of the higher regenerative output is inputted to a control circuit 18. Based on that output, the continuous head amplifier outputs are selected as the input signals of a demodulation circuit 1 4 by an SWC13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic reproducing apparatus, and more particularly to a magnetic reproducing apparatus capable of performing high speed reproduction without generating a noise bar during high speed reproduction of a tape recorded in an economy reproduction mode.

[0002]

2. Description of the Related Art In a conventional magnetic reproducing apparatus, for example, as shown in Japanese Patent Publication No. 63-22714, a high speed reproduction (hereinafter referred to as speed search) in a standard reproduction mode (hereinafter referred to as SP mode) is performed. , A reproduction head of a normal reproduction head (hereinafter referred to as an SP head) and an economy reproduction head (hereinafter referred to as an EP head) in a combination head configured by combining reverse azimuth heads are compared, Switching is performed so that the head output with the higher output level is obtained.

Also, an economy reproduction mode (hereinafter referred to as EP
In the speed search in the mode), EP
Since the head width of the SP head is wider than the track width recorded in the mode, signals are picked up from the tracks adjacent to each other, and the reproduction output from the track originally necessary for reproduction cannot be obtained correctly. Since it is not possible to correctly compare the reproduction outputs of the head and the EP head, the head is not switched and reproduction is performed only by the EP head.

FIG. 13 and FIG. 14 are explanatory diagrams showing the relationship between the track pattern recorded in the EP mode in the conventional magnetic reproducing apparatus and the head locus when a speed search of 5 × speed is performed in the forward direction (fast-forward direction). It is a figure. In the figure, the horizontal axis represents the elapsed time from the field start end (track start end) as the start point (0 second) to the field end, and the reproducing head is switched (head switch) at time A (VHS-VTR). At NTS
(16.7 msec for normal playback of C). The vertical axis represents the tape running amount (tape moving amount), which is expressed by one scale for each track pitch. In the VHS-VTR EP mode, the track pitch is 19.3 μm, and in the SP mode, the track pitch is 58 μm.

In FIG. 13, the head width of the EP head is, for example, 2
FIG. 6 is an explanatory diagram showing a relationship with a locus of a video head when performing a 5 × speed search when a high-speed reproduction is performed by providing a dedicated head having a size of 6 μm. (Width = track pitch, which is 19.3 μm), the head width is wider than that, and during the speed search, a noise bar is generated on the screen in the portion P where the reproduced signal is small as shown in FIG. 13C.

In recent years, in order to improve the image quality of normal reproduction in the EP mode, the head width of the EP head is often adjusted to a track width (here, 19.3 μm) or a value close to it. . FIG.
FIG. 6 is an explanatory diagram showing a relationship between a track pattern and a head locus when a speed search at 5 × speed is performed when the head width of the EP head is 19.3 μm, for example.
When a track having a track width of 19.3 μm in the EP mode is reproduced at high speed using an EP head having a head width of 19.3 μm, the reproduced signal becomes small in the portion Q shown in FIG. 14C, and a noise bar is generated.

[0007]

Since the conventional magnetic recording / reproducing apparatus is constructed as described above, when the head width of the EP head is equal to or about the same as the track width, FIG. As shown in (c), the portion Q where the reproduced signal cannot be sufficiently obtained during the speed search in the EP mode.
However, there is a problem in that the noise bar on the screen is thicker and thicker than that at the portion P when reproducing is performed with the head width of 26 μm shown in FIG. 13C, and the speed search screen in the EP mode is difficult to see. .

The present invention has been made to solve the above-mentioned problems, and magnetic reproduction capable of obtaining a good screen in which a noise bar does not appear on the screen during a speed search of a signal recorded in the EP mode. The purpose is to obtain the device.

[0009]

In a magnetic reproducing apparatus according to a first aspect of the present invention, a first magnetic head for reproducing a signal corresponding to a first mode and a signal corresponding to a second mode are reproduced. Rotating drum having at least one pair of combined heads integrally configured with a second magnetic head, head output switching means for switching outputs from the first and second magnetic heads, and the rotating drum. Switching signal output means for outputting a predetermined switching signal for switching the operation of the head output switching means in synchronism with the rotation of the head, and the switching signal output means for high speed reproduction of the signal corresponding to the first mode. According to the output, a signal corresponding to the first mode is reproduced by the second magnetic head.

In the magnetic reproducing apparatus according to the second invention, the magnetic reproducing apparatus according to the first invention has a phase setting means for setting the phase of the switching signal.

The magnetic reproducing apparatus according to the third aspect of the present invention is the magnetic reproducing apparatus according to the second aspect of the present invention, wherein the phase setting amount of the switching signal is determined on the basis of the tracking shift amount during normal reproduction. is there.

In a magnetic reproducing apparatus according to a fourth aspect of the present invention, in the magnetic reproducing apparatus according to the first aspect of the present invention, a switching signal is output based on the rotation information of the rotary drum and the reproduction signal amplitude from the first magnetic head. It is configured as follows.

In the magnetic reproducing apparatus according to the fifth aspect of the invention, there is provided a first magnetic reproducing apparatus for reproducing a signal corresponding to the first mode.
From the first and second magnetic heads, and a rotary drum having at least one pair of combination heads integrally formed with the second magnetic head for reproducing a signal corresponding to the second mode. Output switching means for switching the output of the first magnetic head, and a switching signal output for generating a switching signal for switching the operation of the head output switching means in synchronization with the rotation of the rotary drum. Means for reproducing the signal corresponding to the first mode by the second magnetic head according to the output from the switching signal output means during high speed reproduction of the signal corresponding to the first mode.

In the magnetic reproducing apparatus according to the sixth aspect of the present invention, in the magnetic reproducing apparatus according to the fifth aspect of the present invention, a head switching signal at the time when the magnitude relationship between the output level from the first magnetic head and a predetermined level changes. It is configured to change the state of.

In the magnetic reproducing apparatus according to the seventh invention, in the magnetic reproducing apparatus according to the fifth invention, the head switching signal is generated based on the time point when the output level from the first magnetic head becomes the minimum. It is composed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the magnetic reproducing apparatus according to the first invention, switching of head outputs from the first and second magnetic heads during reproduction of a signal corresponding to the first mode during high-speed reproduction, The signal corresponding to the first mode is reproduced by the second magnetic head in response to a predetermined switching signal synchronized with the rotation of the rotary drum.

In the magnetic reproducing apparatus according to the second invention, the phase of the head output switching signal is set in the magnetic reproducing apparatus according to the first invention.

In the magnetic reproducing apparatus according to the third aspect of the invention, in the magnetic reproducing apparatus according to the second aspect of the invention, the phase setting amount of the switching signal is determined based on the tracking shift amount during normal reproduction.

In a magnetic reproducing apparatus according to a fourth aspect of the invention, in the magnetic reproducing apparatus according to the first aspect of the invention, a switching signal is output based on the rotation information of the rotary drum and the reproduction signal amplitude from the first magnetic head. I did it.

In the magnetic reproducing apparatus according to the fifth aspect of the invention, the head output switching signals from the first and second magnetic heads during reproduction of the signal corresponding to the first mode during high speed reproduction are rotated by the rotary drum. A signal corresponding to the first mode is reproduced by the second magnetic head according to the generated switching signal in synchronism with the above.

In the magnetic reproducing apparatus according to the sixth aspect of the present invention, in the magnetic reproducing apparatus according to the fifth aspect of the present invention, a head switching signal at the time when the magnitude relationship between the output level from the first magnetic head and a predetermined level changes. The state of is changed.

In the magnetic reproducing apparatus according to the seventh invention, in the magnetic reproducing apparatus according to the fifth invention, the head switching signal is generated based on the time point when the output level from the first magnetic head becomes minimum. did.

Hereinafter, the magnetic reproducing apparatus according to the present invention will be described.
A specific description will be given based on the drawings showing one embodiment thereof. In the drawings, the same reference numerals indicate the same or corresponding ones as those in the related art.

Embodiment 1. FIG. 1 is a block diagram showing a configuration of a magnetic reproducing apparatus according to an embodiment of a magnetic reproducing apparatus according to the present invention. In FIG. 1, 2 is an EP head having a right azimuth (hereinafter referred to as an EP-R head), 3 is an EP head having a left azimuth (hereinafter, EP head)
-L head), 4 is an SP head having left azimuth (hereinafter referred to as SP-L head), and 5 is an SP head having right azimuth (hereinafter referred to as SP-R head), as shown in FIG. An EP-R head 2 and an EP-L head 3, and an SP-R head 5 and an SP-L head 4 are attached to the rotary drum 1 so as to face each other by approximately 180 °.
In addition, EP-R head 2, SP-L head 4, EP-L
Each combination of the head 3 and the SP-R head 5 is called a combination head. Further, in the following description, the EP-R head 2 and the EP-L head 3 are collectively referred to as an EP head pair, and the SP-R head 5 and the SP-L head 4 are collectively referred to as an SP head pair.

Reference numerals 7, 9, 8 and 10 denote EP-R head 2, SP-L head 4, EP-L head 3 and SP-R, respectively.
A head amplifier for amplifying the output from the head 5, 1
Reference numeral 1 is a switch (hereinafter referred to as SWA) for switching the output from the head amplifiers 7 and 8 (that is, the output of either one of the EP head pairs), and 12 is the output from the head amplifiers 9 and 10 (that is, SP). A switch (hereinafter, referred to as SWB) for switching the output of any one of the head pairs, 13 is a switch for switching the outputs from SWA11 and SWB12 (hereinafter, referred to as SWC), 14 is a demodulation circuit, Reference numeral 15 is a comparator.

Reference numeral 16 is a drum phase detection head for detecting a rotation phase which is rotation information of the rotary drum 1, and 17 is a drum flip-flop pulse for receiving a rotation phase signal output from the drum phase detection head and outputting a rotation phase pulse. Generating circuit (hereinafter referred to as DP generating circuit), 18 is SWC
A control circuit for controlling the opening / closing of 13, a head switching pattern generating circuit (hereinafter referred to as an HP generating circuit) 19 for generating a head switching pattern based on the output from the DP generating circuit 17, and a tracking deviation 22. A terminal for inputting the tracking correction amount corresponding to the amount,
Reference numeral 21 is a terminal for inputting a tuning signal for performing a tuning operation described later, and 20 is at least one of a tuning signal input from the terminal 21 or the terminal 22, a tracking correction amount, or an output signal from the DP generation circuit 17. It is a phase changing circuit for changing the phase of the head switching pattern output from the HP generating circuit 19 based on one signal (advancing or delaying the head switching pattern on the time axis).

The operation of the first embodiment will be specifically described below with reference to the drawings. Here, the head widths of the EP-R head 2 and the EP-L head 3 are 19.
3 μm, SP-L head 4 has a head width of 58 μm, SP
A case where the head width of the −R head 5 is 48 μm and the step is adjusted so that the centers of the heads have the same height will be described.

EP-R head 2, SP-L head 4, E
The head outputs of the P-L head 3 and SP-R head 5 are amplified by head amplifiers 7, 9, 8 and 10, respectively, and the output of the EP head pair is input to SWA11 and the output of the SP head pair is input to SWB12. It

The rotation phase signal output from the drum phase detection head 16 is input to the DP generation circuit 17, and the output of the DP generation circuit 17 is input to SWA11 and SWB12. Depending on the rotation of the drum 1 by this signal input (in synchronization)
SWA11 and SWB12 are switched.

The output of the DP generating circuit 17 is also supplied to the HP generating circuit 19, and the output from the HP generating circuit 19 is input to the phase changing circuit 20 to perform the phase shift of the head switching pattern (phase shift amount). Is determined appropriately, but the phase shift amount may be 0 in some cases). The output from the comparator 15 that receives the phase-shifted head switching pattern and the output signals from the SWA 11 and SWB 12 (that is, SWA
11, a comparison output between the outputs from the SWB 12) is input to the control circuit 18, and the SWC 13 is controlled based on the output from the control circuit 18 to select the output to be input to the demodulation circuit 14. As a result, the output of either SWA11 or SWB12 is demodulated by the demodulation circuit 14.

FIG. 3 shows a pattern at the time of forward 5 × speed search. Hereinafter, selection of reproduction output in each case of normal reproduction, speed search in SP reproduction mode, and speed search in EP reproduction mode will be described with reference to FIGS. In the (normal reproduction) SP reproduction mode, the SWC 13 is set to output the output from the SWB 12 to the demodulation circuit 14, and the demodulation signal corresponding to the output from the demodulation circuit 14 (that is, the output of the SP head pair). Is output. In the EP playback mode, the SWC
Reference numeral 13 is set to output the output from the SWA 11 (that is, the output of the EP head pair) to the demodulation circuit 14, and the demodulation circuit 14 outputs a demodulation signal corresponding to the output from the SWA 11.

(Speed Search in SP Playback Mode) The playback outputs from SWA11 and SWB12 are compared by the comparator 15, and the control circuit 18 controls the SWC so as to obtain the playback output on the side with the higher playback output based on the comparison result.
13 is controlled and output to the demodulation circuit 14. (Speed search in EP reproduction mode) From the HP generation circuit 19 to the EP-R head 2, SP-L head 4, EP
The head switching pattern preset as shown in, for example, FIG. 3C is set according to the head width of each of the -L head 3 and the SP-R head 5 and the relative level difference on the drum, and the drum shown in FIG. It is generated in synchronization with the flip-flop pulse and output to the control circuit 18.

At this time, the control circuit 18 switches the SWC 13 based on the head switching pattern as shown in FIG. 3C, and the head amplifier output having the continuity as shown in FIG. By outputting, a good screen without noise bars can be obtained.

The head switching pattern set in advance for setting the period for switching to the SP head is set so as not to pick up the signals of the adjacent tracks. FIG. 4 shows a track pattern and a head locus when a speed search is performed using an SP head having a head width of 48 μm. That is, since the head width of each of the SP-R and SP-L heads is wider than the track width of 19.3 μm formed by the EP head, at the time of speed search, as shown in FIG. A period for reproducing the signal from the contact track (period B in FIG. 4B) occurs (in FIG. 4A, reproduction is performed using an SP head having a head width of 48 μm). Show case). In this case, when many signals from the adjacent tracks are reproduced, the screen is disturbed. Therefore, in order to prevent the signals from the adjacent tracks from being affected during the period in which the SP head is switched, the screen shown in FIG. It is preferable to set the period shown in A.

In FIG. 4A, the head width is 48 μm.
Although the speed search is performed by using the SP head as described above, when the SP head having the head width of 58 μm is used, a period corresponding to the period A shown in FIG. However, in this case, the period for switching to the SP head is compared by comparing the degree of deterioration of the screen due to insufficient reproduction output from the EP head with the degree of influence of the SP head's adjacent tracks. Just decide.

The same operation is performed when the search speed is changed to a speed other than 5 × or when a speed search in the reverse direction is performed. FIG. 5 shows a scanning pattern in the reverse 5 × speed search. In the case of the speed search in the reverse direction, the concept of the speed search in the forward direction described with reference to FIG. 3 can be applied. That is,
In particular, when performing a speed search in the EP reproduction mode, the HP generation circuit 19 outputs the EP-R head 2, SP-
Based on the head width of each of the L head 4, the EP-L head 3, and the SP-R head 5 and the relative level difference on the drum, a preset head switching pattern as shown in FIG. The control circuit 1 is generated in synchronization with the drum flip-flop pulse shown in (b).
Output to 8.

At this time, the control circuit 18 switches the SWC1 based on the head switching pattern as shown in FIG. 5C, for example.
By switching 3 and outputting the head amplifier output having continuity as shown in FIG. 5D to the demodulation circuit 14, there is no noise bar in the reverse speed search as in the normal speed search. A good screen can be obtained.

In particular, in the case of the above-described embodiment, for example, a recording track having a track width of 19.3 μm recorded on a magnetic tape corresponding to the EP mode which is the first mode is equivalent to the track width. When a speed search (high-speed reproduction) is performed using an EP head having a width of, the noise bar portion on the screen generated due to the decrease in signal reproduction produces a more reproduced signal, for example, in the second mode. SP used when playing a certain SP mode
Since reproduction is performed using the head, it is not necessary to provide a dedicated reproduction head, and it is possible to suppress the generation of noise bars and obtain a good reproduced image.

Further, since the head switching signal is output based on the output of a predetermined pattern set in advance, means for comparing the reproduction signal levels is unnecessary, and the head switching signal can always be output stably. Therefore, it is possible to suppress the generation of the noise bar and obtain a good reproduced image without being affected by the output decrease due to the temporal change of the head output or the influence of the noise signal mixed in the reproduced signal from the magnetic head.

In particular, according to the magnetic reproducing apparatus described in this embodiment, when a magnetic head having a head width substantially matching the track width is used for high speed reproduction, a predetermined switching signal is used. Since the reproduction output is switched, it is very effective in signal reproduction when the reproduction signal level cannot be sufficiently obtained due to the recording state on the recording medium and the deterioration of the recording medium.

Embodiment 2 Another embodiment of the magnetic reproducing apparatus according to the present invention will be described below. FIG. 6 is a diagram showing the relationship between the recording track and the magnetic head locus when the tracking is deviated. When reproducing a tape whose tracking is deviated during recording, the recorded track and the video head are out of phase with each other. Therefore, when switching is performed with a head switching pattern in which the phase is fixed during speed search, FIG. ), A portion where the reproduction output cannot be obtained by the EP head (period A in the figure) and a portion where the SP head picks up the signal of the adjacent track next to each other (period B in the figure) increase, and There are many screens.

The HP generation circuit 19 outputs a head switching pattern (signal) having a preset timing corresponding to the noise bar generation portion on the screen. Here, a tuning button (not shown) that allows input of a signal for shifting the timing of the head switching pattern on the time axis (hereinafter referred to as tuning) is provided so that the viewer (user) can display the screen. By pressing the tuning button while watching, the signal output from the pulse output section composed of, for example, an up / down counter is input to the phase changing circuit 20 as a tuning signal from the terminal 21, and the rotational phase output from the DP generating circuit 17 is changed. The phase between the drum flip-flop pulse shown and the head switching pattern output from the HP generation circuit 19 is relatively shifted (for example, the head switching pattern is advanced or delayed on the time axis based on the rotation phase pulse). ), The heads are switched at the optimum phase, and as shown in FIG. Good screen can be obtained without noise bars by outputting the head amplifier output with a connection resistance to the demodulation circuit 14.

Embodiment 3 Another embodiment of the magnetic reproducing apparatus according to the present invention will be described below. According to the above-described embodiment, the viewer is configured to perform the tuning manually, but the following description will be given to the configuration configured to perform the tuning based on the tracking deviation amount.

A signal indicating the tracking correction amount corresponding to the tracking deviation amount during the normal reproduction in the EP mode is input to the phase changing circuit 20 from the terminal 22 and is output from the DP generating circuit 17 to the drum flip-flop pulse and the HP generating circuit. The phase with respect to the head switching pattern output from No. 19 is relatively shifted based on the correction amount converted from the tracking deviation at the time of normal reproduction in the EP mode (for example, the head switching pattern is based on the rotation phase pulse). Is advanced or delayed on the time axis) to switch the head at the optimum phase. The tracking correction amount in this case may be configured such that the viewer gives the tracking correction amount from the outside so as to obtain an optimum screen while looking at the screen, or based on the track deviation amount detected by the tracking servo. The tracking correction amount may be applied.

The following is a detailed description with reference to FIG.
The amount of tracking deviation at the time of normal reproduction is T1, that is, FIG.
As shown in (a), the tape is T1 with respect to the head locus.
When the tape pattern and the head locus are deviated by 1/4 cycle of the drum rotation. Hereafter, T1 is referred to as a relative phase deviation amount. In order to obtain a reproduced image, it is necessary to delay the tape phase by T1 to match the tape pattern with the head locus.

Therefore, in order to obtain a good reproduction signal when performing N times speed search, the relative phase shift amount T1
As a converted amount, for example, a phase shift of T1 / N occurs, and a preset head switching pattern shown in FIG. 7C is timed by T1 / N as shown in FIG. 7D. If the speed is relatively advanced or delayed, the speed search is performed as shown in FIG.
By outputting a continuous head amplifier output to the demodulation circuit 14 as shown in (d), it is possible to obtain a satisfactory screen having a sufficient reproduction output and no noise bar.

In the above description, the correction of the tracking shift amount during the speed search is advanced or delayed on the time axis by the amount of the relative phase shift of the head switching pattern so as to obtain a good screen. However, the reproducing operation may be performed without changing the phase between the drum flip-flop pulse output from the DP generation circuit 17 and the head switching pattern output from the HP generation circuit 19.

That is, the tape feed phase may be changed by a capstan servo, and the tape phase may be shifted relative to the head locus. In this case, when the amount of tracking deviation at the time of normal reproduction is T, when performing N times speed search, it can be realized by changing the tape feed phase by T / N. As a result, as shown in FIG. 3D, by outputting the head amplifier output having continuity to the demodulation circuit 14, it is possible to obtain a satisfactory screen having a sufficient reproduction output and no noise bar.

Embodiment 4 Another embodiment of the magnetic reproducing apparatus according to the present invention will be described below. In the following description, an example of a mode in which the head switching pattern is set based on the reproduction output envelope detection output of the EP head will be described.

The operation of the fourth embodiment will be described below with reference to FIG.
This will be specifically described with reference to FIG. Here, EP-
R head 2 and EP-L head 3 each have a head width of 1
9.3 μm, the head width of the SP-L head 4 is 58 μm,
The case where the head width of the SP-R head 5 is 48 μm and the step is adjusted so that the centers of the heads are at the same height will be described.

EP-R head 2, SP-L head 4, E
The outputs from the P-L head 3 and the SP-R head 5 are amplified by head amplifiers 7, 9, 8 and 10, respectively,
The output of the P head pair is input to SWA11, and the output of the SP head pair is input to SWB12.

The rotation phase signal output from the drum phase detection head 16 is input to the DP generation circuit 17, and the output of the DP generation circuit 17 is input to SWA11 and SWB12. With this signal input, the SWA 11,
Switch SWB12 respectively.

The output of the DP generation circuit 17 is the control circuit 1
8 as well. The output from the DP generation circuit 17, the output from the comparator 15 that receives the output signals from the SWA11 and SWB12 (that is, the comparison output between the outputs from the SWA11 and SWB12), and the output from the SWC13 are input to the control circuit 18. The envelope detection output for is input from the envelope detection circuit 23. A control output for controlling the SWC 13 is output from the control circuit 18, and the SWA 1 is output based on the state of the SWC 13.
The demodulation circuit 14 demodulates the output of either SW1 or SWB12.

FIG. 9 shows a pattern at the time of forward 5 × speed search. Hereinafter, with reference to FIG. 9, normal reproduction, S
The selection of the reproduction output in each of the speed search in the P reproduction mode and the speed search in the EP reproduction mode will be described. In the (normal reproduction) SP reproduction mode, the SWC 13 is set to output the output from the SWB 12 to the demodulation circuit 14, and the demodulation circuit 14 outputs a demodulation signal corresponding to the output from the SWB 12. Further, in the EP reproduction mode, the SWC 13 is set to output the output from the SWA 11 to the demodulation circuit 14, and the demodulation circuit 14 outputs the demodulation signal corresponding to the output from the SWA 11.

(Speed Search in SP Playback Mode) The playback outputs from SWA11 and SWB12 are compared by the comparator 15, and the control circuit 18 switches the SWC so as to obtain the playback output on the side with the higher playback output based on the comparison result.
13 is controlled and output to the demodulation circuit 14. (Speed search in EP reproduction mode) After the speed search is started, the SWC 13 is set to select the output from the SWA 11, and the reproduction output is input from the SWC 13 to the demodulation circuit 14 and the envelope detection circuit 23.
After the tape running speed becomes constant, the control circuit 18 obtains, for example, the EP head output shown in FIG.
The envelope detection waveform output from the envelope detection circuit 23 as shown in (d) is compared with a predetermined threshold value (head switching level), for example, as shown in FIG.
As shown in (d), a head switching pattern is generated such that head switching is performed at a level lower than the threshold value.

Here, the predetermined threshold value is determined so as to correspond to the site where the noise bar is generated on the screen. For example, if a value of 1/3 of the peak value of the envelope detection waveform is set as the threshold value as a signal level at which a noise bar appears, the head is switched in the portion of the envelope smaller than the value of 1/3 of the peak value of the envelope detection waveform. Generate a head switching pattern like
Subsequent head switching is performed using this generated switching pattern. Further, the head switching pattern may be reset, for example, once every five scans.

The threshold value in the above case may be determined based on the peak value of the envelope detection waveform obtained in the first rotation of the head 1 after the speed search is started, for example, 5 rotations. It is also possible to store the peak value of the minute envelope detection waveform in a memory or the like, take the average value of the peak values, and use 1/3 of this average value as the threshold value. By doing this, it is possible to set a threshold value according to the magnitude of the reproduction signal level, and for example, due to individual differences such as different types of tapes or even tracking differences between tapes of the same type. It becomes possible to switch the heads that do not exist.

Alternatively, in order to generate the head switching pattern, the levels of the envelope detection waveform output from the envelope detection circuit 23 are set to Hi (SP head side) and L of the drum flip-flop pulse shown in FIG. 9B.
o (on the EP head side) is measured for each period (that is, for each combi head), and a period during which the level of the measured envelope detection waveform is equal to or lower than a predetermined level is obtained using, for example, a digital counter, Figure 9
A head switching pattern as shown in (e) may be generated.

The control circuit 18 controls the head switching pattern on the basis of the Hi period of the head switching pattern as shown in FIG. 9E (that is, the period in which the level of the envelope detection waveform is below a predetermined level). Hi
The SWC 13 is switched so as to select a reproduction signal reproduced by one of the SP head pairs during the period,
For example, by outputting a continuous head amplifier output as shown in FIG. 9F to the demodulation circuit 14, a good screen without noise bars can be obtained.

At this time, the period for switching to the SP head is set so that signals from adjacent tracks are not picked up so much.
That is, since the head widths of the SP-R and SP-L heads are 46 μm and 56 μm, respectively, they are wider than the track width of 19.3 μm formed by the EP head. In the case where a period during which the signal is reproduced occurs, the screen is disturbed if a large amount of the signal from the adjacent track is reproduced, so the period for switching to the SP head is set so as not to be affected by the signal from the adjacent track. . When the search speed is changed to a search speed other than the one described in the above one example,
The same operation can be performed when performing a speed search in the reverse direction.

Embodiment 5 Another embodiment of the magnetic reproducing apparatus according to the present invention will be described below. An example of obtaining a head switching pattern by using the minimum level in the envelope detection waveform level will be described with reference to FIGS. Note that FIG.
Shows the pattern of 1 field at the time of speed search of the forward direction 9 times speed, and with reference to this figure, reproduction from the change point of the drum flip-flop pulse from Lo to Hi (hereinafter referred to as the edge of the drum flip-flop pulse) A method for obtaining the interval between the minimum output points will be described.

When performing the N times speed search, the number of points at which the reproduction output appears on the screen of one field is the minimum.
Since it is (N-1) / 2, assuming that the time of one field including the drum correction is T2, the interval T3 of the points at which the reproduction output becomes the minimum is: T3 = T2 / {(N-1) / 2} It can be expressed as (1).

Therefore, in the case of 9 × speed, N = 9, and the minimum point of the reproduction output appearing on the screen of one field is (N-1) / 2 = (9-1) / 2 = 4 (Fig. 10
(D)), and the interval T3 between the points at which the reproduction output is minimized is T3 = T2 / 4.

By the way, in the EP mode speed search, the reproduction output of the EP mode video head is selected by the SWC 13 for a predetermined period from the edge of the drum flip-flop pulse, and is input to the envelope detection circuit 23. The predetermined period in this case is set so that even if the tracking shift tape is reproduced, one or more EP heads always cross the reverse azimuth track and the minimum point of reproduction output appears. That is, it is set to be equal to or more than the interval of the minimum point of the reproduction output calculated from the tape speed and the drum rotation period including the correction amount at the time of speed search. The envelope detection waveform output from the envelope detection circuit 23 is input to the control circuit 18, and the minimum point of the envelope detection waveform with respect to the drum flip-flop pulse is measured for each field.

The noise interval in the speed search is
The head switching pattern is constant because it is output periodically according to the rotation cycle of the drum 1 and the tracking state, and is generated with reference to the point R at which the level in the envelope detection waveform as shown in FIG. The control circuit 18 switches the SWC 13 based on the above, and the period during which the reproduction output obtained by using the EP head pair decreases is S
When reproduction is performed using the P head pair and a continuous head amplifier output is output to the demodulation circuit 14, a good screen without noise bars can be obtained. At this time, the period of switching to the SP head is set so that signals from adjacent tracks are not picked up so much. After that, head switching is performed using the generated head switching signal.

The setting of the period for switching to the SP head will be described below. The minimum point of the reproduction output is obtained by first determining the minimum point R in the envelope detection waveform of the reproduction signal by, for example, setting a threshold level and counting the intermediate time point of the period exceeding this threshold level. From R, the time point of the interval T3 according to the above equation 1 is r1, the time point of the next interval T3 is r2, and the next interval T
The time point of 3 is set as r3 and set as a switching basic signal.

A head having a period T4 with little influence of the reproduction output of the adjacent track next to the set time point of r1, r2, r3 so that the reproduction signal is not affected even if the head is switched to the SP head. Switching pulse (Fig. 10
(E)) is generated. By applying the head switching pulse generated in this way to the SWC 13,
SP for playback output near 1, r2, r3 (period width T4)
By switching so as to obtain from the head, and by outputting the head amplifier output having continuity to the demodulation circuit 14, a good screen without noise bars can be obtained. At this time, since the minimum point of the reproduction output at the time point R is near the vertical synchronizing signal and the vertical blanking period, it has almost no influence on the actual screen. Further, when the search speed is changed and the speed search in the reverse direction is similarly operated, a good screen can be obtained.

FIG. 11 is a flow chart for explaining the switching timing of the EP head and SP head, and FIG.
FIG. 12 is an explanatory diagram showing the operation in FIG. 11 in time series. In FIG. 11, S0 is a step for starting the switching operation of the EP head and the SP head, and S1 is the DP generation circuit 17
The minimum point position in the envelope detection waveform from the time point (when t = 0) of the edge of the drum flip-flop pulse when the interrupt timing t (hereinafter referred to as interrupt timing t) that has elapsed from the edge of the drum flip-flop pulse that is the output from Step S2 for determining whether or not occurs during the period T0 in which the detection is not performed. S2 is whether the interrupt timing t occurs during the period from the period T0 described above to the period T0 plus the interval T3 at which the reproduction output is minimum. S3 is a step of determining whether the envelope value set last time is compared with S,
4 is a step of initializing the memory for detecting the minimum envelope, S5 is a step of updating the time point of the minimum point of the envelope detection waveform, and S6 is an EP obtained from the minimum point of the envelope detection waveform in which the interrupt timing t is stored. A step of determining whether the head has been used,
S7 is a step of selecting the output of SWB12 by SWC13, S8 is a step of selecting the output of SWA11 by SWC13, and S9 is a step of ending the above steps and returning to step S0.

The operation will be described below with reference to the flowchart shown in FIG. When high-speed playback starts,
In order to switch the EP head and SP head appropriately, the steps from step S0 are executed. An operation command unit (hereinafter referred to as a microcomputer) configured by a microcomputer or the like (not shown) outputs a start command for a high-speed reproduction operation, and generates an interrupt timing t. When the drum flip-flop pulse is 16.7 msec, for example, the step of the interrupt timing t is set to about 264 μsec which is a period corresponding to about 1/64 of the drum flip-flop pulse (that is, the drum flip-flop pulse). 64 during the H period
Interrupts twice. Therefore, the interrupt timing t increases at every step 264 μsec). Since the setting of the step of the interrupt timing t affects the detection accuracy of the minimum point position, it is set within the range where the detection accuracy is not affected.

It is determined whether or not this interrupt timing t is generated during the period T0 in which the minimum point position in the envelope detection waveform is not detected from the edge of the drum flip-flop pulse, and is generated during this period T0. If it is the interrupt timing, the process moves to step S4 to initialize the memory for detecting the minimum position of the envelope by setting the maximum value in the memory, for example. Furthermore, it moves to step S8 and SWC1
EP by selecting the output of SWA11 by 3
The playback output is obtained using the head.

In step S1, if the interrupt timing t does not occur from the edge of the drum flip-flop pulse to the period T0, step S2
Then, it is determined whether or not the interrupt timing t has occurred in the period between T0 and T0 + T3. If the interrupt timing t occurs during this period, the process proceeds to step S3, and the envelope value at the interrupt timing t is compared with the previous envelope value to execute step S3 for the first time or If it is determined that it is smaller than the envelope output value, the interrupt timing t at this point is newly stored as Tmin, and the process proceeds to step S8. In step S8, S
The output of the SWA 11 is selected by the WC 13, and high speed reproduction using the EP head is performed.

When it is determined in step S2 that the interrupt timing t is not between T0 and T0 + T3, the process proceeds to step S6. In step S6, Tmin +
T4 / 2 + T3 × (k−1) (expressed as Xk in FIG. 11, k
= 1, 2, 3 ...) to Tmin−T4 / 2 + T3 ×
When the interrupt timing t occurs during k (expressed as Yk in FIG. 11, k = 1, 2, 3, ...), step S
8, the output of SWA11 is selected by SWC13, and high-speed reproduction output is obtained from the EP head.

In step S6, Tmin + T4
/ 2 + T3 × (k−1) (expressed as Xk in FIG. 11. k =
1, 2, 3, ...) to Tmin−T4 / 2 + T3 × k
(Expressed as Yk in FIG. 11, when the interrupt timing t occurs outside the period of k = 1, 2, 3, ...) Moves to step S7, the output of SWB12 is selected by SWC13, and high speed is output from the SP head. Get playback output.

When step S8 or step S7 is completed, the process proceeds to step S9, the process returns to step S0 and the steps after step S0 are repeated to obtain the reproduction obtained by executing the high speed reproduction while switching the EP head and the SP head. Since the signal level can be set higher than the level at which noise appears continuously on the screen, high-speed reproduction without noise bars can be realized.

The change point of the drum flip-flop pulse corresponds to the position where the magnetic tape begins to wind around the drum, that is, the portion where the magnetic head starts to contact the magnetic tape, and therefore the magnetic head and the magnetic tape sometimes contact each other. In some cases, the condition is not good enough to obtain sufficient playback output. In such a case, if the minimum point R in the envelope detection waveform of the reproduction signal is set as described above,
In some cases, the positions of the subsequent switching basic signals r1, r2, and r3 may not match well with the noise position on the screen. In such a case, the contact state between the magnetic head and the magnetic tape becomes good without performing the threshold level judgment operation from the envelope detection waveform for a predetermined period from the change point of the drum flip-flop pulse, and the envelope detection of the reproduction output is performed. The threshold determination operation may be started as described above after the waveform becomes stable.

In this case, the contact state is judged by comparing the peak level of the envelope detection waveform at the positions of the switching basic signals r1, r2 and r3 with the peak level at the changing point of the drum flip-flop pulse. If the peak level at the pulse change point is smaller, the minimum point R in the envelope detection waveform of the reproduction signal may be obtained again at the next drum flip-flop pulse change point.

Alternatively, by comparing the level of the envelope detection waveform at the time point T3 / 2 from the minimum point R in the envelope detection waveform of the reproduction signal with the peak level of the envelope detection waveform, these are approximately within a predetermined range. If they do not match, the minimum point R in the envelope detection waveform of the reproduction signal may be obtained again at the next changing point of the drum flip-flop pulse.

Further, according to the above-described embodiment, the head switching signal is once generated, and the subsequent head switching is performed based on the generated head switching signal. The head switching signal may be regenerated every time. As a result, the influence of the fluctuation of the signal level due to the reproducing portion of the recording medium can be suppressed, and a good reproducing state can be secured even when the signal recording is performed using a different recording device in the middle of the recording medium.

[0079]

Since the magnetic reproducing apparatus according to the present invention is constructed as described above, it has the following effects.

According to the magnetic reproducing apparatus of the first invention, the signal corresponding to the first mode is output according to the output from the predetermined switching signal output means during the high speed reproduction of the signal corresponding to the first mode. Is configured to be reproduced by the second magnetic head. Therefore, the signal loss when the signal corresponding to the first mode is reproduced by the first magnetic head is reproduced by the second magnetic head. By obtaining it, it is possible to reproduce without signal loss,
It is possible to obtain a good screen without generating a noise bar on the screen, and head switching is performed according to the output from a predetermined switching signal, so it is stable even when noise is mixed in the reproduced signal. This has the effect of enabling high-speed playback of a good screen.

According to the magnetic reproducing apparatus of the second aspect of the present invention, the phase of the switching signal is set in the magnetic reproducing apparatus of the first aspect of the invention. Can be adjusted, and the head can be switched appropriately for the part where the noise bar is generated, so that a good screen can be stably obtained without the noise bar being generated on the screen when the signal corresponding to the first mode is reproduced. it can.

According to the magnetic reproducing apparatus of the third invention, in the magnetic reproducing apparatus of the second invention, the phase setting amount is determined based on the tracking deviation amount during the normal reproduction. Even if the signal corresponding to the first mode of the magnetic tape in which the recording track recorded by another magnetic recording device is slightly different is reproduced, a noise bar does not occur on the screen and a good screen is optimally tracked. It can be obtained stably in the state.

According to the magnetic reproducing apparatus of the fourth invention, in the magnetic reproducing apparatus of the first invention, the switching signal is generated based on the rotation information of the rotary drum and the reproduction signal amplitude from the first magnetic head. Since the signal is output, the signal corresponding to the first mode can be reproduced reliably and stably without generating a noise bar on the screen at any special reproduction speed.

According to the magnetic reproducing apparatus of the fifth aspect of the invention, the head output switching signals from the first and second magnetic heads during reproduction of the signal corresponding to the first mode during high speed reproduction are transmitted to the rotary drum. Since the signal is generated based on the output of the first magnetic head in synchronization with the rotation and the signal corresponding to the first mode is reproduced by the second magnetic head in accordance with the generated switching signal. Since the signal output reproduced from the first magnetic head decreases and the reproduced signal can be obtained from the second magnetic head by accurately catching the noise-rich portion on the screen, a noise bar is generated on the screen. It is possible to obtain a good screen without fail without fail.

According to the magnetic reproducing apparatus of the sixth aspect of the present invention, in the magnetic reproducing apparatus of the fifth aspect of the invention, at the time when the magnitude relationship between the output level from the first magnetic head and a predetermined level changes. Since the switching signal is generated so that the state of the switching signal changes, a predetermined level can be set according to the state of the reproducing signal, and the signal output reproduced from the first magnetic head decreases, Since the reproduction signal can be obtained from the second magnetic head by accurately catching the portion on the screen where the noise is large, it is possible to reliably and stably obtain a good screen without generating a noise bar on the screen. .

According to the magnetic reproducing apparatus of the seventh invention, in the magnetic reproducing apparatus of the fifth invention, the head switching signal is generated based on the time point when the output level from the first magnetic head becomes minimum. As a result, the generated switching signal can be stably obtained, and the part where the noise bar is generated on the screen can be accurately captured for any special playback speed, and the noise bar is not generated on the screen. A good screen can be obtained reliably and stably.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic reproducing device according to first, second and third embodiments of the present invention.

FIG. 2 is an explanatory diagram showing the arrangement of EP and SP heads on a rotary drum.

FIG. 3 is an explanatory diagram showing a relationship between a track pattern and a head locus during speed search using the magnetic reproducing apparatus according to the first embodiment of the present invention.

FIG. 4 is an EP mode 19.3 during speed search using the magnetic reproducing apparatus according to the first embodiment of the present invention.
Explanatory drawing showing the relationship between the track width of the μm track width and the 48 μm SP head.

FIG. 5 is an explanatory diagram showing a relationship between a track pattern and a head locus during a reverse speed search using the magnetic reproducing apparatus according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between a track pattern and a head locus when there is a tracking shift using the magnetic reproducing apparatus according to the second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a relationship between a track pattern and a head locus when there is a track deviation at the time of normal reproduction using the magnetic reproducing apparatus according to the third embodiment of the present invention.

FIG. 8 is a block diagram of a magnetic reproducing device according to embodiments 4 and 5 of the present invention.

FIG. 9 is an explanatory diagram showing a relationship between a track pattern and a head locus during a speed search using the magnetic reproducing apparatus according to the fourth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a relationship between a track pattern and a head locus during a speed search using the magnetic reproducing apparatus according to the fifth embodiment of the present invention.

FIG. 11 is a flowchart of reproducing head switching during speed search using the magnetic reproducing method according to the fifth embodiment of the present invention.

FIG. 12 is an explanatory diagram representing a time-series representation of a reproduction operation at the time of speed search using the time reproduction method according to the fifth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a relationship between an EP mode track width and a head locus of an EP head having a head width of 26 μm in a conventional magnetic reproducing apparatus.

FIG. 14 is an explanatory diagram showing a relationship between an EP mode track width and a head locus of an EP head having a head width of 19.3 μm in a conventional magnetic reproducing apparatus.

[Explanation of Codes] 1 rotating drum, 2 EP-R head, 3 EP-L head, 4 SP-L head, 5 SP-R head, 11
SWA, 12 SWB, 13 SWC, 14 demodulation circuit, 15 comparator, 17 DP generation circuit, 18
Control circuit, 19 HP generation circuit, 20 phase change circuit, 2
3 Envelope detection circuit.

Claims (7)

[Claims] 1. A first magnetic head for reproducing a signal corresponding to a first mode and a second magnetic head for reproducing a signal corresponding to a second mode are integrally configured. A rotary drum having at least one pair of combined heads, a head output switching means for switching the outputs from the first and second magnetic heads, and an operation of the head output switching means in synchronization with the rotation of the rotary drum. Switching signal output means for outputting a predetermined switching signal for switching, and corresponding to the first mode according to the output from the switching signal output means during high speed reproduction of a signal corresponding to the first mode. A magnetic reproducing apparatus characterized in that a signal is reproduced by the second magnetic head. 2. A magnetic reproducing apparatus according to claim 1, further comprising phase setting means for setting the phase of the switching signal. 3. The magnetic reproducing apparatus according to claim 2, wherein the phase setting amount of the switching signal is determined based on the tracking shift amount during normal reproduction. 4. The magnetic reproducing apparatus according to claim 1, wherein the switching signal is output based on the rotation information of the rotary drum and the reproduction signal amplitude from the first magnetic head. 5. A first magnetic head for reproducing a signal corresponding to a first mode and a second magnetic head for reproducing a signal corresponding to a second mode are integrally configured. A rotary drum having at least one pair of combined heads, a head output switching means for switching the outputs from the first and second magnetic heads, and an operation of the head output switching means in synchronization with the rotation of the rotary drum. Switching signal output means for generating a switching signal for switching based on the output of the first magnetic head, and output from the switching signal output means during high-speed reproduction of a signal corresponding to the first mode. The above 1st
A magnetic reproducing apparatus characterized in that a signal corresponding to the mode is reproduced by the second magnetic head. 6. The state of the head switching signal is changed at the time when the magnitude relationship between the output level from the first magnetic head and a predetermined level is changed. Magnetic reproducing device. 7. The magnetic reproducing apparatus according to claim 5, wherein the head switching signal is generated based on a time point when the output level from the first magnetic head becomes minimum.