JPS6083268A - Video reproducing device for rotating magnetic recording body - Google Patents

Abstract

PURPOSE:To distribute a damage to a recording surface during long-time still reproduction to respective tracks uniformly and minimize it by making an advance to a next track one after another when the still reproduction exceedes a maximum permissible time. CONSTITUTION:A track is reproduced by a head 26 repeatedly in an on-track state and a video signal processing circuit 36 performs conversion into a composite video signal by, for example, one-frame, two-field interlaced scanning to reproduce a still image. A timer 122 monitors the total time of the continuous still reproduction from one track. When this reproduction exceedes the specific time, i.e. 15min, a main control part 104 leads the head 26 to the next track, so damage to the recording surface is prevented. Thus, the still reproduction is carried on by advancing the head 26 up to the final recorded track and when the head 26 reaches an unrecorded part, the feed direction of the head 26 is inverted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating magnetic recording medium video reproducing apparatus, particularly a rotating magnetic recording medium video+RF reproduction apparatus for reproducing images recorded on a rotating magnetic recording medium such as a magnetic disk or a magnetic drum. Regarding equipment. In particular, the present invention relates to a rotating magnetic recording medium video reproducing apparatus that reproduces information recorded on tracks formed concentrically on a magnetic disk.

Hill'' U1 Week Recently, we have been using a combination of imaging devices such as solid-state image sensors and image pickup tubes, and recording devices that use magnetic disks, which are inexpensive and have a relatively large storage capacity, to take still photographs of subjects purely electronically. Electronic still camera systems have been developed that record on a rotating disk and reproduce images using a separate television system or printer.

A plurality of trunks are normally recorded on a rotating magnetic recording medium at predetermined intervals. In rotating magnetic recording media used in electronic still camera systems, for example, a track pitch of 100 g r is recorded on a small disk with a diameter of about 50 am.
In other words, 50 tracks are recorded with a track width of about 50 to 60 JLm and a guard band width of about 50-50-40. In the reproducing apparatus, this magnetic disk rotates at a constant speed of, for example, 3 ei00 revolutions per minute, and the video signal is reproduced at a field or frame rate.

In a reproducing apparatus that reproduces video from each track recorded at such a fine track pitch, track following control of the reproducing magnetic head, that is, movement control to the optimum track position, is performed, for example, by a so-called hill-climbing tracking method. During recording, the recording head is moved at a predetermined track pitch by a stepping motor without applying a tracking servo, and during playback, the envelope of the output signal of each track is detected and the optimal track is identified from the peak position. The tracking servo is applied by

In the mountain climbing tracking method, tracking control is performed according to the envelope level of the recording signal. The optimal tracking state is when the magnetic head is at the positive peak of the envelope level. Whether the head is near the peak or not depends on whether or not the head is near the peak.
Compare the envelope levels at two head positions,
They are distinguished by the fact that there is virtually no difference between them.

A video signal is still reproduced from the recording track at, for example, field speed. If one field video signal is repeatedly played back from the same track for a long time, the playback head will be in sliding contact with the finely structured magnetic disk for a long time as described above, which may damage the recording surface of the disk. be. Therefore, in order to protect the recording surface and the playback head, it is desirable to monitor the maximum allowable time using a still playback 1± timer from the same trunk. When this timer times out, e.g. - The configuration may be such that the magnetic head is moved to the rank, still playback is continued for images of other fields, and this operation is repeated when a timeout occurs.

For example, as in the example mentioned above, 5
In the case of a magnetic disk on which less than 0 tracks can be recorded, if the device is left in still playback mode like this, the magnetic head is sequentially moved and it does not take a long time to reach the final recording track. . Therefore, it is best to take some action when the final track is reached.
This is desirable in terms of protection of the disk recording surface and operability of the device.

SUMMARY OF THE INVENTION In view of these demands, it is an object of the present invention to provide a rotating magnetic recording medium image reproducing apparatus that minimizes damage to the recording surface of a rotating magnetic recording medium due to long-time still playback.

According to the present invention, the present invention has a magnetic head, and the magnetic head receives video signals from a plurality of tracks formed on a rotating magnetic recording body with trajectories such that the relative positions of the recording start and end coincide with each other. a video signal circuit that reads and outputs the video signal, a head moving means that moves the magnetic head to a desired position among the tracks, and a video signal circuit that detects the envelope of the video signal read by the magnetic head from the rotating magnetic recording medium. In a rotating magnetic recording video reproducing apparatus for reproducing a video signal from a rotating magnetic recording body, the control means includes a control means for performing tracking control using an envelope, and the control means detects that a magnetic head is located in an unrecorded portion of the rotating magnetic recording body. and a timer for detecting that the time during which the magnetic head is continuously positioned over one track on the rotating magnetic recording body exceeds a predetermined value. When the means detects that the predetermined value is exceeded, the head moving means is controlled to move the magnetic head to the next track on the rotating magnetic recording body, and the determining means determines that the magnetic head is located in an unrecorded portion of the rotating magnetic recording body. If so, the head moving means is controlled to move the magnetic head in the opposite direction.

In addition, in this specification, "a plurality of tracks formed with trajectories such that the relative positions of the recording start and end coincide with each other" refers to, for example, in a magnetic disk, a large number of tracks formed concentrically around a rotation axis. Tracks, and in the case of magnetic drums, many tracks are formed parallel to each other in the circumferential direction, such that one track is formed without changing the relative position of the recording head with respect to the rotating magnetic recording medium. Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the apparatus of this embodiment shown in FIG.
4 is removably attached. The magnetic disk IO has a magnetic recording material sheet with a diameter of about 5011II11, and a plurality of recording tracks, for example, 50 recording tracks are recorded concentrically on the recording surface 16 at intervals of dO (for example, about 1100p, see FIG. 3B). Ru. In this embodiment, the signal recorded on the recording track is a video signal, which may be, for example, a color video signal in which a luminance signal (luminance signal) and a chroma signal are FM-modulated. For example, a field video signal forming one field of an image is recorded onto one track by rask scanning.

The DC motor 12 has a frequency generator 18 that generates an AC frequency signal and is powered by a servo circuit 20 so that the disk 10 can be rotated at a predetermined rotational speed, e.g.
It is servo controlled to rotate at a constant speed of 0 revolutions/minute. The servo circuit 20 is a control device +00 that controls the entire device.
, and controls the rotational driving and stopping of the disk 10 in response to the signal DISK.

A pulse generator 22 is disposed at a predetermined position near the recording surface 16 of the disk 10, and is connected to the servo circuit 20 and the control device 100 via an amplifier 24. As a result, a timing mark formed corresponding to a predetermined position on the recording surface 16 is detected, and a timing pulse PG is formed.

A magnetic transducer or magnetic head 26 is disposed on the seventh side of the recording surface 16 and is carried by a support mechanism 28 . This support mechanism is driven by a step motor (PM) 30, as conceptually shown by a dotted line 28, and moves the head 26 in both radial directions along the recording surface 16, as shown by arrow R. It is configured such that any track on 16 can be selected.

The magnetic head 26 may have a magnetic recording function, but in this embodiment, it has a playback function of detecting a video signal from the trunk already recorded on the recording surface 16 and converting the corresponding 1 into a magnetic signal. Examples are shown below. As mentioned above, in this embodiment, since the disk 10 rotates at a constant speed of 3,800 revolutions/minute, one track's worth of video signal, that is, one field of FM modulated video signal 200 (second 2A) will be reproduced from the magnetic head 26. By demodulating this as shown at the bottom of FIG. 2A, this becomes compatible with standard color television systems such as the NTSC system.

The (A raw output 32 of the magnetic head 26 is connected to a video signal processing circuit 36 and an envelope detection circuit 38 through a preamplifier 34. The video signal processing circuit 3B processes the video signal detected by the head 28! 7, for example, is a circuit that outputs a composite color video signal in NTSC format to the device output 40. This is demodulated and
The vertical synchronization signal "7.VSYNC" (Figure 28) is extracted from the SC format composite color video signal, and the control device 1
It has the function of supplying this to 00. Also, the control device 10
0, it receives the signal EE, separates the circuit system of the magnetic head 2B from the processing circuit 36, puts the processing circuit 36 in the EE state (electrical system connection state 7gi), and outputs other signals, such as broadcasting signals, to the device output. In addition, upon receiving the signal MUTE, the effective horizontal scanning period of the video signal is set as a blank signal, and a mute ink operation is performed. Note that the function of converting to such a standard formant is not essential to this device, and the processing circuit 3
6 may have a function of extracting synchronization from the video signal sensed by the head 26 and a function of outputting this to the terminal 40 under the control of the control device 100 to 11i.

The envelope detection circuit 38 detects the envelope 200 (FIG. 2A) of the FM modulated video signal recorded on the track of the recording surface 16 and outputs a voltage corresponding to this to the output 42. It is a circuit. This is connected to an analog◆digital converter (AD) via an envelope amplifier 44.
C) Connected to 4B. In this embodiment, the ADO 4B quantizes the quantization level of 258 and outputs it as 8-bit data to the control device +00 in response to a request from the iJI control device 100.

The control device 100 is a control device that controls the entire device 9 according to the operations of the operator, as will be described in detail later.
For example, it is advantageously constructed by a microprocessor system.

In this embodiment, a reproduction key PL instructs to start and stop the apparatus, a forward direction key FW to move the head 26 in the forward direction of the track number (for example, from an outer track to an inner track), and a head 26. The controller 100 is provided with a reverse direction key RV for moving the controller in the opposite direction.
It is connected to the.

-1--The track number designated by the FW, RV, etc. is visually displayed on the display device 48, such as a light emitting diode or CRT display, connected to the control device 100. Of course, it may also have a function of audibly displaying a warning or the like.

In this embodiment, the step motor 30 is a four-phase drive pulse-operated motor, and responds to one drive pulse to
It rotates 8'. Therefore, 20 pulses make one rotation. The head support mechanism 2B includes a step motor 30.
The configuration is such that the L pulse applied to the radiator moves the radiator 26 approximately 5 pm in the direction of the arrow R. Therefore, ten pulses will move the vent 26 approximately 50 pm.

This drive pulse is supplied from a drive circuit 50 consisting of a current amplifier, and the latter generates an excitation coil drive pulse for the step motor 30 according to an excitation pattern instructed by the control device 100. Such excitation pattern generation control is performed by a head feed control section 102 shown in FIG. 4.

FIG. 4 shows an example of the internal configuration of the control device 100 shown in FIG. 1, and in particular, conceptual functional blocks in an example where the control device 100 is configured with a microprocessor system are indicated by reference numerals in the 100s. It is. The operation of this embodiment will be described in detail with reference to the functional block diagram of FIG. 4 as well as other flowcharts.

For example, the control device 100 turns on the signal DISK, rotates the disk IO at a constant speed, and controls a certain track (
Assume that the vent 26 is exactly on track at position 4- of position H1 (FIG. 3B). Therefore, a case will be described in which tracking is performed by operating the forward key FW or reverse key RV to move the head 26 to a corresponding adjacent track. After the reproduction key PL is operated, for example, when the FW main key is operated, the main control unit 104 starts the "tracking" operation (300) in FIG. 58 in response.

First, when the signal MUTE is turned on (302), the video signal processing circuit 36 mutes the video signal in response. This is because when the head 26 is being transported through a section where the recording signal level is low between the recording and racks,
This is to avoid displaying a distorted image on the video monitor device connected to the end of the device terminal 40 and causing discomfort to the viewer.

Next is the main control section! 04 executes a head transport step 304 in which the head transport controller 102 is controlled to transport the head 26 in the forward direction by a distance d1.

Before explaining step 304, a general explanation about the envelope will be given. As shown in FIG. and is input as an envelope waveform 250 to the ADC 4B through the amplifier 46. As will be described later, when there is a request from the control device 100, this is manually inputted to the control device 100 in the form of corresponding digital data. If the two trunks are correctly recorded at a predetermined interval dO (+00.u,m in this example), the peak-to-peak distance of the envelope 250 should substantially match dO, as shown in Figure 3B. . Therefore, in this embodiment, first, in order for the head 26 to correctly on-track at a positive peak, that is, a mountain, the head 26 is moved to a position H2 at a certain distance dl in the middle of the regular track interval, that is, the track pitch do. Detect the envelope level in the state. Position H of this distance dl
2 is preferably about the center of the track spacing;
In this example di is approximately equal to dO/2. This corresponds to a negative peak or valley if recorded at the regular track spacing do.

Therefore, in step 304, the head 26 is moved in the forward direction d.
Transfer by l. This head feeding is performed by a routine 360 as shown in FIG. This routine 3
60 will be explained in detail later. Here, the head feeding is temporarily stopped, and the envelope detection section 106 is controlled to perform an envelope detection step 306. This is done in the "envelope detection" routine shown in Figure 7, and the AD
Envelope data converted into digital data at Od6t is read at discrete sampling points, and weighting is performed by addition.

To explain in more detail with reference to FIG. 2A, the head 26
When the vehicle is on-track, the FM modulated video signal read from the trunk has a waveform as shown by reference numeral 200. In other words, in this embodiment, after demodulation, one
One field of video signals (lower end of FIG. 2A) is reproduced for each rotation. Note that the horizontal synchronizing signal is not shown at the bottom of FIG. 2A to avoid complicating the diagram.

In the "envelope detection" routine 380 shown in FIG.
After (382, 384), ADO4f is sequentially executed at n sampling points occurring at a predetermined time interval t2.
((7) Read envelope data (38B).

In this embodiment, since a field video signal compatible with the NTSC system is read from the disk IO, one field (
IV) The period is approximately 16.7 ms. Advantageously, this sampling takes place over a period of 1v, evenly spaced and at an odd number of points, so that in this example tl is 2
, 7 ms, E2 is 1.5 ms, and n is 9. Therefore, the center of the screen is point E.

That is, the position is 8.7 milliseconds from the signal VSYNC:. Such time is managed by a timer 116.

In this manner, in this embodiment, data is read by the ADC 46 at nine sampling points A to A, and envelope data is taken into the control device 100 (3813). The control device 100 reads the envelope data in the envelope detection unit 106, temporarily stores it in the memory, that is, the envelope storage unit (area) 108, and multiplies each sampling value by a predetermined weight to integrate the data (3H ).

In this embodiment, as shown in FIG. 2A, the weights are 1, 2 degrees, 4.8 degrees, respectively, for the sampling points A to A. ?
, 8, 4.2 and l. This value is relative to each sampling point and is not limited thereto. For example, simple addition may be used, but a particularly advantageous point is that sample values are given greater weight in the center than in the periphery of the field screen. This is mainly due to the following reasons.

The disk IO is removably attached to the drive shaft 14,
The chunking state differs each time it is attached or detached. In other words, the disks are not necessarily mounted exactly in alignment with the center of a recording track that is a concentric circle, resulting in eccentricity in which the center point is shifted. Moreover, this eccentricity varies depending on the mounting position. Furthermore, the recording tracks themselves do not necessarily have their center positions accurately aligned during recording, and eccentricity occurs, and furthermore, variations occur each time the recording track is mounted. When such eccentricity occurs, the image quality produced from the track will be as shown in Figure 2A.
As shown in the examples of 00a, 200b and 200C, the level changes depending on the chucking state.

Therefore, in order to reduce the influence of this variation on the reproduced image, as shown in Figure 2B, a large weight is given to the sampling points near the center of the screen, and a relatively small weight is given to the sampling points on the periphery. It is advantageous to attach This kind of weighting uses the envelope level obtained by addition, and is called [mountain climbing lidranking control].
By doing this, the central part of the screen, which is most important for viewing images, will be reproduced in the best condition.

After completing the sampling and weight addition of n (9) points (388), the addition result is stored in memory as the envelope level at the head position H2 (Step 7).
390), and the "r envelope detection" routine is completed.

Returning to FIG. 5A, the main controller 1o4 again controls the head feed controller 102 to move the head 28 a distance M in the same transport direction.
Only d2 is transferred (308). This transfer distance fid2 is the normal inter-track distance d, which is the sum of the above-mentioned transfer distance #d1.
It is advantageous to select it to be slightly shorter than O. This will be explained in detail later.

Referring to FIG. 3B, when tracks are recorded at a regular track interval dO, in this apparatus, during tracking, the head 26 is moved to a position H immediately before being moved to a distance dO.
At step 3, head feeding is temporarily stopped, and at that position H3, the aforementioned "envelope detection" (Fig. 7) is performed. Therefore, as mentioned above, the normal track amount ratio gidO is 1
After envelope detection is performed by moving the head 26 by a distance d1 substantially equal to /2, the head 26 is further moved by a distance ad2 slightly shorter than the distance Mdl, and sampling and weighting are performed by addition. In this example, this distance d2 is about 45,i,, so the difference d3 of dl+62 with respect to dO is about 5 gm.

, more specifically, when the controller 26 is moved by a distance of 11111d2, the signal MtlTE is turned off (310).
. If a track is recorded at the normal position H4, there will be an area where the video signals of both tracks will crosstalk while the head 26 is being moved from the old position to position H3, which is close to H4, and this will cause the video signals to be displayed on the playback monitor. There is a possibility that the disturbance may cause discomfort to the viewer. However, when the head 26 is moved to the vicinity of position H3, the head 26 is almost on track, so there is little possibility that image disturbance will occur even if muting is canceled, so the mute period is limited. As will be described later, it takes a minimum of +3V to complete tracking, so if the mute period is not long, the viewer will see a screen with a long non-image period, which will cause discomfort to the viewer. Therefore, this is also advantageous in that the mute period is short.

The main control unit 104 believes! l=; MIITE turned off (
310) After that, "envelope detection" (routine 380, FIG. 7) is performed again (312).

Next, the level comparison/determination section 110 compares whether the envelope level detected at position iWH3 is lower than a predetermined level level 1 (314). This level Ll is
The head 26 travels through a portion of the recording surface 16 where the video signal trunk is not recorded, and at that time, the weight is set to a value slightly larger than the value added by "envelope detection" (118, Fig. 4). . For example, in this embodiment, it is set to approximately lθ% of the envelope level detected from a normal recording track.

In this comparison 314, if the envelope level is below the predetermined level Ll, there is a possibility that no track is recorded there. Then, the head 26 is further moved in the same direction by a distance d3 (3113), and "envelope detection" is performed at position H4 (322, Fig. 5B).
. This transfer 111d3 is, for example, a step morph 3.
It is set equal to the moving distance of the head 26 by one pulse of 0. In this example, this lf 5 p-m
That's about it. Here, a comparison is again made with the predetermined level L1 (324), and if the envelope level is level 1 or less at 1H4, then the level L1 is
The following condition occurs twice in a row (328), and it is determined that no video signal track is recorded there, and a predetermined action is taken. Such state counting is performed by counter 120.

Therefore, in this embodiment, it is determined whether the overall timer described later has already timed out at this time (327), and if it has not timed out,
The video signal processing circuit 38 is separated from the head 26 and the EE
state. This is instructed to the processing circuit 3B by detecting the fall of the signal PG in 17 control device 1 (3213) and turning on the signal EE' in synchronization with this (330). It may be displayed on the device 48 that the head 26 has moved to the unrecorded area and the system has been switched to the EE state. Furthermore, instead of turning on the signal EE, the signal qMUTE may be turned on to mute the video. Alternatively, the head 26 may be returned to a home position, such as an outermost track position, or transported in the opposite direction. In other words, it may be configured to return to the immediately previous recording track.

By the way, returning to FIG. 5A, in the level comparison 3]4 at position 113, the encaple rope level is at the predetermined level J.
If it is less than l/Li, the previous envelope level, that is, the envelope level at position H2, is compared with the current envelope level (318).

This comparison is performed to determine whether the level difference between the two is greater than a predetermined value ΔL, and which is larger between the previous time and this time. In other words, it is determined which of the two levels is significantly larger. The reason for introducing the concept of significant difference in level comparison will be explained later. Note that in this embodiment, in step 310, the signal MUTE is
is turned off, but instead of this, the signal S″fMUTE may be turned off when it is determined to be “a certain level or higher” in the comparison 314. In the latter case, the envelope level This is right-handed because the video is always muted when the level is below a predetermined level.

In the comparison 318, the envelope level at the position H3 is usually greater than the significant difference of 65, so the head 28
is determined to be near the mountain of the envelope, and the head 26 is further moved in the same direction by a distance #d3 (318).
, the above-mentioned envelope detection step 322 (5th B)
Figure). This corresponds to the case shown in the f:1S3B diagram.

However, in comparison 318, if the envelope level at position H3 is not greater than that at position H2 by a significant difference of 65 or more, the recording track spacing is too narrow or too wide, as shown in FIG. 3A or 3C. This is the case. Therefore, if this determination is not made and the envelope level is detected and compared at a position further advanced by a distance Md3, for example, if the track spacing is too wide and the head 26 is in the valley as shown in FIG. There is a risk that no significant difference will be detected and trunking will end at this point. In such a case, move to the operation of returning the head 26 in the opposite direction and confirming that it is in the valley (
320), speed up the climbing control. The return distance d4 may be large enough to confirm that it is in the valley, for example approximately 1/2 of di. In other words, in this embodiment, the distance may be approximately equal to 1/4 of the length of the distance. In this example this is approximately 25pm. An envelope detection step 322 is performed at this position H5.

As can be seen from the above explanation, when tracking from one track to the next, with this device, the head 26 is not directly transferred by an inter-track pressure of 11111 dO, but once the trunk opening #, dO is approximately The envelope level is detected by moving the distance @:dl to the vicinity of the center. For example, when the magnetic disk 10 on which video tracks are recorded with a so-called electronic camera is used, or when the head 26 is moved by a manual transport mechanism, each track is not necessarily recorded at a regular track interval dO. This is to prevent the head 26 from stopping at the valley of the envelope even in such a case by detecting the intermediate envelope level.

The reason why it is assumed that there is no level difference in level comparison unless there is a difference of a predetermined value, that is, a significant difference of 61 or more, is as follows.

Various noises are mixed into the envelope detected from the track. For example, if the control device 100 is realized by a processing device and the sampling time in the envelope detection J380 (FIG. 7) varies due to an interrupt, the error 7g will also occur due to the variation in the sampling time. In particular, AOC<F:, which converts an envelope into a digital data format, produces noise due to accumulation of quantization errors. Although the head 26 is transferred by a relatively short transfer distance d3 near the envelope mountain, the envelope levels detected at those locations are close in value to each other. Therefore, the convergence of the system may be distorted or the head 2C may vibrate.

The head 2G is moved by the minimum head transfer pressure #d3 in the water device near the peak or valley of the envelope, and if the change in the envelope level does not have a significant difference of 61 or more, it is determined that there is a peak or valley. For this purpose, the significant difference ΔL is such that when the head 2B is at a peak or valley in an ideal state, the head 2B is moved by this minimum transfer pressure 1lllld3.
The value is set to a value that is suitably larger than the envelope level change that occurs when the envelope level is transferred. In this embodiment, the minimum transfer distance d3 is set to a transfer distance corresponding to one pulse of the step motor 30. Therefore, the value of the significant difference ΔL is
=/ f” Transfer F: Seki l that occurs when Ai is 8!・No 2/
The size is set in consideration of the above-mentioned noise influence on the level change, that is, the noise margin. this is,
Even if (f normal weight 4 = J times added), it may be about a few percent of the envelope level. By doing this,
The determination of peaks or valleys can be made with less influence of noise, and furthermore, "vibration" of the head, which will be described later, can be prevented to some extent.

By the way, if the envelope level detected in step 322 is equal to or higher than the predetermined level 11 (324).

Compare this with the previous envelope level (332)
. In this case, in the flow of the EiSA diagram, step 31
11f, 318 or 32(l), the previous envelope level is at position H3. If the current envelope level is larger than the previous one by a significant difference Δ, the envelope level is Since there is a possibility that the head 26 is approaching a mountain, the head 26 is further moved in the same direction (344), and the loop including the envelope detection stamp 322 is repeated until it is determined that there is no significant difference (332). If the data is recorded at a regular track position as in the case of , it is unlikely that a significant difference will be determined in the comparison 332, and the flow will normally proceed downward in the 7tS5B diagram.

For ease of understanding, the explanation of "vibration" in the judgment box 334 etc. will be left later.
In step 36, it is determined whether "no significant difference" has occurred four times in a row, for example. This number of 81 is the counter 120
(ftS4 figure).

If a significant difference is not found four times in a row in the comparison 336, the head 26 is returned by a distance @d3 in the opposite direction 348. ), further steps such as envelope detection 322 and level determination 332 will be repeated. In this case, when there is no significant difference, the head 2B is moved in the opposite direction and the envelope detection and determination are repeated in order to eliminate the influence of video signal dropout, which will be described later. . Thus, under normal conditions,
Envelope level detection and level comparison are performed twice for each of the two envelope detection positions H3 and H4.

Even if it is once determined that there is no significant difference in F, it may temporarily occur due to poor contact when the head 26 reads the video signal from the track (11 may be added by chance due to a dropout of the video signal due to JI). Therefore, in order to eliminate such dropouts from affecting tracking control, level detection and comparison are performed in total four times near the peak of the envelope as described above.
I'm going around and reconfirming it.

When executing step 348, in addition to this, 5B (4
As you can see, in step 328 the level is 1.
There are cases where the following vibrations did not occur twice in a row, and cases where the vibrations did not occur four times in a row. In either case, it is determined that there is no significant difference or that the level difference is significantly low, and the head 26 is returned by a distance d3 in the opposite direction (34B).

As mentioned above, the transfer is temporarily stopped at position H3 just before the head 28 is transferred to the trunk-to-trunk distance dO, and the envelope level is detected there to minimize the tracking time while performing such reconfirmation. This is for the purpose of

For example, as shown in FIG. 10, suppose that the head 26 is moved to a position H4 located at a distance MdO, the envelope levels are compared, and then the head 26 is moved a distance d3 in either direction.
For example, if the configuration is such that the head 26 is moved to position H3 and the same operation is repeated for confirmation, it will take at least an additional 1v period to place the head 26 at the optimum track position. That is, positions H4, H3, H
The confirmation operation is executed in the order of 4 and H3, and the process returns to the optimum position H4. However, in this device, first from position H3 to 1 (
Confirmation operations are performed in the order of 4, H3, )+4, and convergence can be achieved at the final position H4. Detecting and comparing envelope levels for one head position requires at least time for the head 26 to go around the track, so the present apparatus can reach the optimal track 1v period earlier than in the former case.

This confirmation operation may be performed at position H3, then H4, and then again at H4 after a short period of time, and then returned to 113. Alternatively, position H4 may be performed first, then H6, and so on.
Therefore, you may try H6 again after a while, and then return to H4. Alternatively, the positioner may be performed first, then H3, then after a short period of time, H3 may be performed again, and then return to H4. Of course, similarly to this, it is also possible to first perform position H6, then perform H4, wait a while, then perform H4 again, and then return to H6.

By the way, the head support mechanism 2B from the step motor 30 to the head 26 achieves high positional accuracy for minute movements of about 5 gm of the head 26, and also has high deceleration in order to obtain high torque with the small motor 30. It is advantageous to have a reduction ratio of, for example, 100:1 v degrees. However, since the gears used include some backlash, play occurs in the movement of the head 2G.

Therefore, normally, in the step of returning distance #d3 mentioned in -L,
The step motor 30 is driven in the reverse direction for two pulses, and then in the forward direction for one pulse. If you do it like this.

Theoretically, the backlash in both directions should be canceled out and the result should be a return distance of 111id3, but in reality, the return distance may be longer than this. Therefore, even if you perform "envelope detection" again at the returned position, the value may be different from the previously detected value. Therefore, even if you compare it with the envelope level just before that, it will always be determined that there is no significant difference. is not guaranteed.

Therefore, "vibration" of the head may occur in which the head 2B is repeatedly moved in the forward direction and moved in the reverse direction, and this continues for a long time. In other words, in the forward direction, it is determined that there is no significant difference and the difference is transferred in the reverse direction, and in the backward direction, it is determined that there is no significant difference, and a
, there is a difference, and the data is transferred in the forward direction, and this process may be repeated.

To prevent this vibration J from continuing indefinitely.

The occurrence is detected in step 334, and when this occurs a predetermined number of times, for example four times in a row (34G), it is assumed that on-track has been achieved and a predetermined operation, that is, an operation to turn off the EE state, is started. Specifically, in response to the fall of the signal PG (340), the signal EE is turned off (34).
2). Note that, since the system is usually not in the EE state until then, this operation is effective when it is in the EE state for some reason. At that time, start the overall timer and start monitoring the still playback time for that track (34
1). This time monitoring will be described later. In addition, if the on-track track is not on track, the main control unit 104 causes the display device 48 to hide the RJF chart.

When "no significant difference" is detected four times in a row in step 336, this means that the envelope levels for a total of four points spaced apart in both directions by a minute distance d3t are distributed without any significant difference from each other. It means there is. In other words, at this time, since the envelope level 26 is in a part where the level changes gradually, such as a peak or a valley, the two can be distinguished by determining whether or not this envelope level is less than or equal to the predetermined value L2. (33B). The value L2 is detected in the valley between normal tracks, and the weighting is set appropriately larger than the added level. This value may be about a fraction of the normal envelope level.

As a result, if the envelope level is equal to or less than 2, it is determined to be a valley, and if it exceeds this value, it is determined to be a peak.

If it is a valley, move the head 26 by a distance fad2 350
), then an "envelope detection" step 322 is executed. In this way, by moving the head 26 in the same direction by the distance fid2 when the envelope level is low, the head 26 can be moved to the valley where the envelope level is low.
is stopped to prevent accidental tracking at valleys. This allows mountain climbing control to be performed quickly. Note that in step 350, the structure is not configured to transfer in the opposite direction.
This is because the case where the peaks are too close as shown in figure A has already been excluded, so the case in which the track spacing is too wide as shown in figure fiS3c is targeted in step 35θ.

If it exceeds the predetermined level L2 and is determined to be a mountain, this indicates a properly on-track state, and the EE state is canceled as a confirmation action as described above (340, 3).
42). This causes the head 2B to connect to the video signal processing circuit 3.
6, and the video signal recorded on the trunk is played back. From the start of head movement to on-track, this is the fastest on-trunk, although it varies depending on the motor/\5v to 6v for rad movement
The head movement is completed in the time required for a total of 12V-13V (7V for , tiger, and king).

In the on-track state, the track is on head 2.
6, the video signal 1) processing circuit 36
For example, the signal is converted into a composite video signal obtained by interlaced scanning of two fields per frame, and the video is reproduced as a still image. The overall timer set in step 341 described above is, for example, timer 122 (FIG. 1).
Still II is realized continuously on one track.
The total amount of time generated is monitored. This timer counts 31 the elapsed time since it was started in step 341, and when this times out after a predetermined time, for example 15 minutes, the main controller 104 starts the tracking sequence 300 in order to move the head 26 to the next track. do. Therefore, since the Sochir iIf data moves to the next track, it is possible to prevent damage to the recording surface 18 due to the head 26 running for a long time on one track mVf.

In this way, the maximum still playback time for one track is limited, so if this device is left in still playback mode for a long time, the head will not be able to reach the last track recorded on the recording surface 16. 26 shifts to perform still playback, and the overall timer may time out at this point. At that time, the tracking sequence 300 (FIG. 5A) is activated and the head 28 is moved to the non-recording area, so the processing flow is changed to "level L1".
Two times in a row? '' The program proceeds to step 32G (FIG. 5B), where the contents of the O/H all timer are read. Since the overall timer has now timed out, the process flow proceeds to step 328 (FIG. 5A) with jump symbol 2 and sets the head 26 feed direction in the opposite direction. Below, the processing is performed by head 2.
6 in the reverse direction.

In this way, when the still playback continues for the maximum monitoring time for each track until the end of the recording track, the direction of feed of the head 26 is reversed and the same operation is repeated. In addition,
Instead of reversing the head feeding direction, the head 26 is returned to the home position, for example, the position of the lowest track number,
The configuration may be such that still playback continues from this point.

Alternatively, the configuration may be such that when the overall timer times out, the signal DISK (FIG. 1) is turned off, the disk motor 12 is stopped, and the video signal processing circuit 36 is placed in the EE state. In that case, display device 4
The overall timeout may be displayed at 8, and the still playback may be restarted by operating a key such as the playback key PL.

Incidentally, head feeding operations such as step 304 are performed by the head feeding control section 102 according to a routine 380 shown in FIG.
It will be held in

The main control unit 104 first sets the number of pulses corresponding to the transfer distance required in those steps in the head feed control unit (382). In this embodiment, for example, the distance is 1 tdl, 5
0I1. In this embodiment, the step motor 30 has a four-phase drive coil, and the rotor rotates 18 degrees for every l pulse.

The excitation patterns of these four-phase coils are stored in a memory (excitation pattern storage section 112), and the excitation signals φA to φD are changed by sequentially incrementing the excitation patterns each time the excitation is performed.
Rotate the rotor. Therefore, when the rotation is stopped, the final excitation pattern is stored in the memory.

Therefore, when rotating the step motor 30 by a predetermined number of pulses, if the drive coil is not being excited (384),
Reads the final excitation pattern from the previous excitation stored in memory and drives the coil according to this (
38B). This a final excitation pattern should be at the rotor stop + L position that was taken when the previous drive was stopped, so the rotor position may have changed due to some reason such as a slight load change between the previous drive and the current drive. Even if there is some deviation, the rotor can be pulled into the final stop position of the previous excitation by excitation using the previous final excitation pattern. Therefore, the rotor can be rotated in synchronization with the drive pulse without losing synchronization due to subsequent excitation. As a result, in this embodiment, if the deviation is up to ±18°, the rotor can be returned to the normal phase. This pull-in is performed for a to period (for example, about 10 milliseconds) (38
8).

Next, the rotor is rotated by a rotation angle corresponding to 1 pulses by rotating the excitation pattern one phase at a time in a rotation direction corresponding to the head transport direction based on the initial position drawn in as described above (370).

In this device, as shown in Fig. 11, for example, if the previous excitation pattern was φA and φB, these are first excited for 10 milliseconds, then φB and φG are excited for 6 milliseconds, and then φC9φD is excited. 5.5 milliseconds excitation, then φD, φA
is excited for 5 milliseconds, and the excitation period gradually decreases.

By gradually shortening the excitation period of each phase in this way, the rotor can reach the desired speed in a short time without losing synchronization. In this embodiment, in a steady state, the duty ratio is 50% with excitation for 4 milliseconds. When stopping, on the other hand, the pulse width is gradually increased, the rotor is pulled into a desired stopping position, and then excitation is stopped.

This eliminates the shift in the stop position that would occur due to the inertia of the rotor due to sudden excitation stop.

Gradual decrease in excitation period during such startup and stop and W
In step 372, the full count value set in timer 4 (FIG. 4) is changed according to a predetermined schedule according to the set number of pulses, and when the timer 114 times out, the set number of pulses is decremented by 1. ), this is realized by repeating the stepping motion of the excitation pattern until it reaches O (3?o).

The setting of the timer 114 is performed by the routine 400 shown in the fJSB diagram.
It is carried out by As you will see, first, in step 402, from the contents of the pulse counter PLSCT, 5
Set the absolute value of the subtracted value in register A. Next, in step 404, it is determined whether the value obtained by subtracting 1 from the contents of register A is positive or negative, and if this is negative, register A is
(406), and if it is not negative, set the contents of register A to 2
Set the multiplied value to register A (40B). Therefore, in step 410, a value obtained by multiplying the contents of register A by 256 (microseconds) and adding 4 milliseconds is set in the timer.

For example, if the pulse counter PLSC:T is set to 1o, the timer 114 is set to 6 milliseconds, and if it is set to 7, the timer 114 is set to 4.5 milliseconds. An example of the setting is shown in FIG. In the figure, PLSCT values of 10 to 6 are used for starting, and values of 4 to 1 are used for stopping.

Up to this point, we have mainly described the case where the track is advanced from step to step by operating the key FW or RV to the next track in either direction. However, this device is also configured to be able to randomly access any desired trunk.

For example, if the key FW or RV is operated intermittently while the playback key PL is operated to enter the non-playback mode, the main control unit 104. The track number of the track counter displayed on the display device 48 is sequentially incremented accordingly. When the desired track number is displayed and the playback key PL is operated, the main control unit 104 performs random access.
12A and 12B).

Therefore, compare the target track number 5'i with the current track number (422), and if the two are not equal, set the step motor 30 to a number equivalent to the difference in tracks minus 1. Set the number of pulses corresponding to (424.428). The reason why 1 is subtracted from the track difference is because in the tracking operation to the target track, "envelope detection" is first performed at the above-mentioned mid-track position iH2 (Figure 3B). Tracking routine 300 (fifth
This is to make the transition to Figures A and 5B). When (target track number - current track number) is IF, a positive feed direction is set, and when it is negative, a negative feed direction is set (
42Ei.

430).

Then, the step motor 30 is driven to move the trunk 2B to the old trunk position before the destination trunk. This is executed in steps 432 to 458, of which steps 432 to 442 are followed.

This may be substantially the same as steps 364 to 374 of the routine 360 (FIG. 6). That is, the rotor is retracted to the initial position and the rotational speed of the motor 30 is gradually increased and decreased.

In this device 4, muting is performed in the intermediate region between each track and the next track. In the case of random access, the central part of the inter-track pressure #dO, for example 1
/3 section is muted. Therefore, the main control unit 104 sets a mute counter using the counter 124 or the like, and increments the mute counter each time the step motor 30 is excited by one pulse (444). When the count value of the mute counter becomes equal to N/3, the signal MUTE is turned on and control returns to step 438 via interlace symbol 4.

Helad 26 is further transferred. Thereafter, when the count value of the mute counter becomes equal to 2N/3, the signal MUTE is turned off and control returns to step 438 via interlace symbol 4 to further move the head 26. by this,
In the middle part of each track, the video signal is muted in the 173 section.

When the count f of the mute counter reaches N (450).

The mute counter is reset, the number of pulses in the pulse counter is decremented by 1, and the control returns to step 438 via interlace symbol 4 to continue driving the motor 3o. When the pulse counter reaches O, it means that the head 28 has been moved to the old track position before the desired track, and the process moves to tracking operation 460. In step 4EiO, the tracking routine 300 described above is executed.

In this way, by performing the hill-climbing tracking operation immediately before the target track, the average call time in random access can be minimized. Also, the objective tiger-7
Even until reaching the target track, the video is not completely muted during that period, but as it passes through each track to the destination track, muting is canceled for parts of the video that do not cause disturbances. This does not cause discomfort to the viewer, and it is possible to clearly see that random access is in progress.

In this way, when the playback device is set to the still playback mode for a long time, and the maximum permissible still playback time for one track is exceeded, the present invention sequentially shifts to the next track and continues the still playback. However, when the playhead reaches the last recording trunk, the same operation continues with the playhead being transported in the opposite direction. Alternatively, instead of continuing this still reproduction operation, a predetermined measure may be taken, such as deenergizing the drive system or reproduction system of the rotating magnetic recording medium and displaying a message to that effect. Therefore, damage to the recording surface of the rotating magnetic recording medium due to long-time still playback is evenly distributed to each I rack, and this can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2A,
28+4 and FIGS. 38 to 3C are explanatory diagrams for explaining the envelope level detection operation of the video signal in the embodiment of FIG. 1, and FIG. 4 shows the functions of the control device shown in FIG. 1. Functional block diagram, Figure 5A, Figure 5B [Δ, Figure 6, Figure 7, Figure 8, ff
512A and 12B are flowcharts showing examples of the operation of the control device of the embodiment shown in FIGS. 1 and 4, and FIGS. 9, 1θ, and 11 are explanations of the operations in these flowcharts. FIG. Theory 1 1θ10. Magnetic disk 2B, . . . Magnetic head 2B, . . Head transport mechanism 30, . . Step motor 3B, . . . Video signal processing circuit 3B, . . Envelope detection. Circuit 100, . . . Control device 102, . . Rad feed control section 104, . . . Main control section 1 (H, Envelope detection section 110, . . . Level comparison judgment section 2E3 Figure L' 3 A recess , 38 Figure 8 Figure φA φB Ice qI'71 ψC Mine/Q Area Qin 11 Figure 11 □ - 11% group (Millimeter 11 S'$, t2A concave 4 books 12BI2)

Claims (1)

[Claims] 1. Having a magnetic head, the magnetic head reads video signals from a plurality of tracks formed on a rotating magnetic recording body with trajectories such that the relative positions of the recording start and end coincide with each other. a video signal circuit for outputting a video signal; a head moving means for moving the magnetic head to a desired position among the tracks; In a rotating magnetic recording video reproducing apparatus for reproducing a video signal from the rotating magnetic recording body, the control unit includes a control unit that performs tracking control based on a detected envelope, and the control unit in No. 71 is configured to perform tracking control using the detected envelope. determining means for determining that the magnetic head is present in the part; and detecting that the time period during which the magnetic head is continuously located in one trunk of the rotating magnetic recording body exceeds a predetermined value. and a time limit means for controlling the head moving means to move the magnetic head to the next track on the rotating magnetic recording body when the time limit means detects that the predetermined value is exceeded. and when the determining means determines that the magnetic head is located in an unrecorded portion of the rotating magnetic recording body, controlling the head moving means to move the magnetic head in the opposite direction. A rotating magnetic recording medium video reproducing device characterized by: 2. The apparatus according to claim 1, wherein the determination means includes a comparison means for comparing the level of the envelope of the signal read by the magnetic helad from the rotating magnetic recording body with a predetermined reference level; The predetermined reference level is set to a value significantly smaller than the envelope level between two adjacent tracks, and the determining means determines that when the detected envelope level is below the reference level, the rotating magnetic field A rotating magnetic recording medium image reproducing apparatus characterized in that it is determined that the magnetic head is located in an unrecorded portion of the recording medium.