JPH0467709B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a rotating recording medium reproducing apparatus, particularly a tracking device for a rotating recording medium reproducing apparatus that reproduces information signals such as video signals recorded on a rotating magnetic recording medium such as a magnetic disk. Regarding.

Background technology Recently, imaging devices such as solid-state imaging devices and image pickup tubes,
In combination with a recording device that uses a magnetic disk, which is inexpensive and has a relatively large storage capacity, as a recording medium, the subject is still photographed purely electronically and recorded on a rotating disk, and the images are reproduced using a separate television system or printer. An electronic still camera system has been developed.

In the rotating magnetic recording media used in electronic still camera systems, for example, a small disk with a diameter of about 50 mm has a track pitch of about 100 μm, that is, a track width of about 50 to 60 μm, and a guard band width of about 50 to 40 μm. 50 tracks are recorded. In a recording or reproducing device, this magnetic disk rotates at a constant speed of, for example, 3600 revolutions per minute.
Video signals are recorded or reproduced in units of fields or frames.

Recording media used for such magnetic recording, especially magnetic disks, are prone to tracking defects due to compatibility, eccentricity, thermal expansion, etc. There is a problem in that crosstalk occurs when multiple tracks are scanned.

In order to avoid this problem, there is a method in which the magnetic head for information recording records a tracking signal by applying tracking servo, and the reproducing head applies tracking servo using this tracking signal. However, it is not practical to provide a tracking servo mechanism that requires precise control to a small, lightweight recording device such as a camera.

Therefore, one method is to use the guard band method or FM azimuth method as the recording method, and to prevent some tracking failures during playback, to prevent the playback head from scanning the adjacent track, or to prevent the signal of the adjacent track even if it scans. There is a way to compensate by not picking it up.

Along with this, a so-called mountain climbing method is also used. This means that the recording head moves at a predetermined track pitch using a stepping motor without applying a tracking servo, and the reproducing head detects the envelope of the output signal of each track and identifies the optimal track from its peak position. The tracking servo is applied by

The head position at which the envelope peaks is determined by moving the magnetic head a predetermined pitch, reading the envelope value at that position, and comparing this with the envelope value detected at the previous head position. Ru.

Digital processing systems are generally advantageously applied to perform this comparison. for that,
The video signal detected by the reproduction magnetic head is subjected to envelope detection, and the envelope output is converted into a digital value by an analog-to-digital converter and input to a digital processing system.
In order to eliminate false detections due to system disturbances such as noise, it is advantageous to subject only envelope levels exceeding a predetermined threshold to this comparison operation.

However, in this type of hill-climbing control, tracking is performed by detecting the peak position of the envelope, so the head must be moved in both directions.
Therefore, the response time of the system also becomes relatively long.

Incidentally, in a rotating recording medium such as a magnetic disk that rotates steadily at a predetermined speed, the inner track of the recording medium has a slower linear velocity relative to the head, so that the envelope level of the frequency signal detected by the head becomes lower. In general, if the frequency bands of the frequency signals recorded on the track are the same, the envelope level depends on the state of contact of the head with the track, the linear velocity of the track with respect to the head, and the radius of the track. , the latter is much more dominant than the former. Therefore, from a macroscopic perspective, the envelope output level decreases approximately in proportion to the radius of the track.

Even in situations where the envelope level fluctuates depending on the head position, it is necessary to perform tracking quickly and with high accuracy.

Purpose The present invention overcomes the drawbacks of the prior art and
It is an object of the present invention to provide a rotating recording body tracking device capable of quickly tracking with sufficient accuracy regardless of the position of the head.

DISCLOSURE OF THE INVENTION According to the present invention, there is provided a reproducing head that reads signals from a plurality of tracks formed on a rotary recording medium that rotates steadily at a predetermined rotational speed with a locus in which the starting and ending ends of recording coincide; A head moving means for movably supporting the rotating recording medium, an envelope detecting means for detecting the envelope of the signal read by the reproducing head, and a head moving means are controlled to move the reproducing head to a desired position on the track. In the rotating recording body tracking device, the head moving means has a position detecting means for detecting the position of the reproduction head on the rotating recording body, and the control means controls the head movement means to move the reproduction head. The two positions where the envelope level detected by the envelope detection means is equal to the reference value are determined for one track, the center position of both positions is determined, and the head moving means is controlled to locate the center position. The control means changes the reference value according to the position of the playback head detected by the position detection means, and when the position of the playback head is on a track with a larger diameter among the plurality of tracks, A rotating recording body tracking device is provided that allows a reference value to be higher than when the track is on a track with a small diameter.

In addition, in this specification, "a plurality of tracks formed by trajectories whose recording start and end coincide with each other" means
For example, in a magnetic disk, a large number of tracks are formed concentrically around the rotation axis, and in a magnetic drum, a large number of tracks are formed in parallel in the circumferential direction. It means something recorded so as to form one track without changing its relative position.

DESCRIPTION OF EMBODIMENTS Next, embodiments of a rotating recording medium tracking device according to the present invention will be described in detail with reference to the accompanying drawings.

In the apparatus of this embodiment shown in FIG. 1, a rotating recording medium 10 such as a magnetic disk is removably mounted on a spindle 14 driven by a DC motor 12. In this embodiment, the magnetic disk 10 has a sheet of magnetic recording material with a diameter of about 50 mm, and a plurality of recording tracks, for example 50, are recorded concentrically on the recording surface 16 at a pitch of about 100 μm, for example. 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 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 raster scanning.

The DC motor 12 has a frequency generator 18 that generates an AC frequency signal, is supplied with power by a servo circuit 20, and is configured to rotate the disk 10 at a predetermined rotation speed, for example, 3600 revolutions/minute. Servo controlled. The servo circuit 20 is connected to a control device 60 that controls the entire device, and receives signals.
In response to DISK, the rotational drive and stop of the disk 10 is controlled.

A phase generator 22 is disposed at a predetermined position near the recording surface 16 of the disk 10, and this is connected to an amplifier 24.
It is connected to the servo circuit 20 and the control device 60 via. As a result, the timing mark placed at a predetermined position on the core 21 is detected,
A timing pulse PG is formed.

A magnetic transducer or magnetic head 26 is disposed above the recording surface 16 and is carried by a support mechanism 28. This support mechanism is indicated by the dotted line 2
Step motor (PM) as conceptually shown in 8.
30, the head 26 is moved in both radial directions along the recording surface 16 as shown by arrow R, and is configured to be able to select any track on the recording surface 16.

A head position detection mechanism 64 is mechanically associated with the support mechanism 28, and a signal corresponding to the position of the head 26 on the recording surface 16 is outputted to its output 66. In this embodiment, this signal is transmitted to the motor 3, which will be described later.
0, and the signal detected by the head 26 from a track recorded in an almost ideal state on the magnetic disk 10, as shown in FIG. A track position pulse 100 (B in the same figure) is generated at a head position that approximately corresponds to the position where the envelope peaks, and a track pulse 102 is generated at a head position that is spatially out of phase by 180 degrees. (C).

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 a track already recorded on the recording surface 16 and converting it into a corresponding electric signal. Things are exemplified. As mentioned above, in this embodiment, the disk 10 rotates at a constant speed of 3600 revolutions/minute, so 1
One track of video signals, that is, one field of FM modulated video signals, is reproduced from the magnetic head 26 every 1/60 second of rotation. By demodulating this, it becomes compatible with standard color television systems such as the NTSC system.

The reproduction output 32 of the magnetic head 26 is supplied to the preamplifier 3.
4 to a video signal processing circuit 36 and an envelope detection circuit 38. The video signal processing circuit 36 is a circuit that processes the video signal detected by the head 26 and outputs it to the device output 40 as a composite color video signal in, for example, NTSC format. This is a vertical synchronization signal from the demodulated composite color video signal in NTSC format.
It has a function of extracting VSYNC and supplying it to the control device 60. Further, a control signal 68 is received from the control device 60 to control the video signal output. Note that the function of converting to a standard format as described above is not essential to the present device; the processing circuit 36 has a function of extracting synchronization from the video signal sensed by the head 26 and simply converting it to the terminal 4 under the control of the control device 60.
It may also have a function of outputting to 0.

The envelope detection circuit 38 is a detection circuit that detects the envelope of the FM modulated video signal recorded on the track of the recording surface 16 and outputs a voltage corresponding to the envelope to the output 42. The output 42 is input to an envelope amplifier 44, the latter output 72 being input 7 to an analog-to-digital converter (ADC) 46.
0 and one input 74 of comparator 72.

The other input 76 of comparator 72 is a digital
connected to the output of analog converter (DAC) 78;
The output 80 is input to the control device 60.
The comparator 72 is a circuit that compares the voltages of both inputs 74 and 76 and outputs a corresponding signal to the output 80 when the former exceeds the latter.

The DAC 78 has an input 82 connected to the control device 60 and outputs a voltage corresponding to the instruction signal Y from the control device 60 to the input 76 of the comparator 72 as a comparison threshold signal.
This is a digital-to-analog converter that supplies it as Vth.

The ADC 46 has 256 quantization levels in this embodiment, and converts the envelope level signal of the input 74 into 8
This circuit converts the data into bit data and outputs it to the control device 60 in response to a request.

The control device 60 is a control device that centralizes control of the entire device according to operations by an operator, as will be described later, and is advantageously configured by a microprocessor system including a CPU 90 and a memory 92, for example.

In this embodiment, there are a playback key PL for instructing to start and stop the device, a track selection (random access) key AV for moving the magnetic head 26 to a separately set desired track position, and a track selection (random access) key AV for moving the magnetic head 26 to a separately set desired track position. Forward key to move in a direction (e.g. from outer track to inner track)
FW and a reverse key RV for moving the head 26 in the opposite direction, these are connected to a control device 60.

The number of the track to be selected is entered on a keypad 84, which includes a numeric keypad, connected to the control device 60. In this embodiment, the entered track number is visibly displayed on a display device 48, such as a light emitting diode or CRT display, connected to the control device 60. Of course, it may also include a functional unit that audibly displays a warning or the like.

In this embodiment, the step motor 30 is a four-phase drive pulse motor, and rotates approximately 15 degrees in response to one drive pulse. Therefore
One rotation takes 24 pulses. The head support mechanism 28 is
The head 26 is moved approximately 4.2 μm in the direction of arrow R with one pulse supplied to the step motor 30. The excitation time for one pulse is, for example, about 2 to 3 milliseconds. Therefore, in 24 pulses the head 26 is moved approximately 100 μm.

The drive pulses are supplied from a drive circuit 50 consisting of a current amplifier, which generates excitation coil drive pulses for the step motor 30 in accordance with the excitation pattern instructed by the controller 60. The position of the head 26 on the recording surface 16 is detected by the head position detection mechanism 64 as described above, but the excitation coil drive pulses of the step motor 30 are counted by the control device 60, and this counted value is Accordingly, the head position may be identified.

Controller 60 and servo circuit 20 are responsive to a reference clock generated by reference generator (OSC) 62. In this embodiment, the servo circuit 20 is supplied with a reference signal of 60 Hz, which is the same as the field frequency of the raster scan video signal recorded on the magnetic disk 10, and the control device 60 is supplied with a high-speed clock, for example, 3.58 MHz. Ru.

In this embodiment, so-called hill-climbing control is not performed for the tracking of the head 26, but tracking is performed based on the basic principle described below.

As shown in FIG. 3, an envelope 110 of a signal recorded on a certain track of the magnetic disk 10
is detected by the envelope detection circuit 38, first, the head positions X1 and X2 of the two points 112 and 114 at which the envelope 110 crosses a predetermined reference value, that is, the threshold value Vth, are determined, respectively. In this embodiment, these head positions are counted based on a predetermined home position (HP) of the magnetic head 26. It is advantageous that this original return position is normally set further outside the outermost track of the magnetic disk 10. This return of the head 26 to its original position is detected by a switch 33 which is mechanically responsive thereto.

Therefore, in this embodiment, the two head positions determined as distances from the original return position are
The position of the simple average of X1 and X2, that is, the center position of both X (= (X1 +
to be transferred. Therefore, if a signal is recorded on the disk 10 with the envelope 110 in an ideal state, the position of the peak 116 should almost match the position X. This depends on the fact that the ideal envelope has a substantially symmetrical shape.

In addition, in this embodiment, this envelope 110
As shown in FIG. 4, the threshold value Vth for determining the head positions X1 and X2, in which the head 26 takes a value equal to the threshold value Vth, is the radial position of the track where the head 26 is currently located, in other words, the track number. It takes a variable value depending on. In other words, the closer the head 26 is to the outer periphery, the higher the threshold value Vth is, and the closer the head 26 is to the inner periphery, the lower the threshold value Vth is controlled.

In this embodiment, it is advantageous to set this threshold value Vth to approximately 1/2 of the envelope peak value.
Therefore, in this embodiment, the instruction signal data Y of the threshold value Vth to be set in the comparator 72 for the desired track number N is given as follows: Y=(A.N+B)/2 (1). However, A is a quantity related to the rate of change of the threshold value, ie, the slope (in this example, it is negative), and B is a quantity related to the envelope value, ie, the tangent in the first track.

More specifically, the magnetic disk 26 rotates steadily at a predetermined speed, but the tracks closer to the inner circumference have a slower linear velocity relative to the head. Therefore, head 2
The envelope level of the frequency signal detected and detected at step 6 becomes low. In general, if the frequency bands of the frequency signals recorded on the track are the same, the envelope level depends on the state of contact of the head with the track, the linear velocity of the track with respect to the head, and the radius of the track. , the latter is much more dominant than the former.
Therefore, from a macroscopic perspective, the envelope output level decreases approximately in proportion to the radius of the track.

Therefore, if the device is configured so that the threshold value Vth takes a constant value regardless of the head position, the threshold value will be
It is preferable to set the level to a relatively low level considering that the peak of 0 can be clearly identified. However, if you do this, the outermost track will be compared with the low tail of the envelope, which is highly susceptible to disturbances such as noise.
The identification accuracy may be significantly reduced. In order to avoid such a situation, in this example, the threshold value
Vth is variable depending on the head position.

Next, referring to FIGS. 5A to 5C, the control device 6 for randomly accessing a desired track
The operation of 0 will be explained. First, in a system initialization step 200, the track counter (TRCT) is reset to "0" and the start address M of the data buffer area for storing envelope data is set. These areas are of course set in the memory 92. Therefore, when the magnetic head 26 is moved in the opposite direction (204) and returned to its original position, this is detected by the operation of the switch 33 (202).

When a magnetic disk pack having a magnetic disk 10 is loaded into this device, the core 21 is attached to the spindle 1.
4, and the pack loading completion switch and the pack switch operate (206, 208). Therefore, the controller 60 moves the head 26 in the forward direction (210) and inputs the input 66 from the head position detection mechanism 64.
The track position pulse 100 obtained at the position is detected (212), and the envelope at that position is read through the ADC 46 (214).

If an envelope is detected (216), the address (M+
The envelope value is written to the storage location of the data buffer specified by TRCT (220). In the flowchart, parentheses ( ) indicate the contents of the storage location of the address specified within the parentheses.
If no envelope is detected, write a certain value there, for example "*" (218).

In this way, the track counter TRCT is set to a predetermined limit value, for example when the storage capacity of the magnetic disk 10 is reached.
If there are 50 tracks, the counter TRCT is incremented (224) with the forward movement of the head 26 until it reaches "55", etc. (222), and this envelope is read and written to the data buffer area corresponding to each track. Getting older.

When the counter TRCT reaches the limit value, the head transfer is stopped (226), and the counter continues until the track position where the contents of the data buffer are no longer ``*''.
Reduce TRCT (230, 232, 228). Note that if no envelope is detected in any of the tracks, a message indicating that the pack is an unrecorded pack is displayed on the display device 48 (234).

If there is a track position where the envelope data is stored in the buffer by decrementing the counter TRCT, this is stored as the final track position ENDTR (236). Further, the counter TRCT continues to be decremented (238), and if there is a track position where the envelope data is stored in the buffer (240), this is set as the first track position STATTR and the content of the storage position of the data buffer of that track, i.e. The envelope value is stored in area B (242). This is repeated until the counter TRCT becomes "0". Therefore, when the counter TRCT becomes "0", the true first track position on disk 10 is stored in the area STATTR, and the envelope value of the first track is stored in the area B. .

Therefore, the control device 60 stores these data.
A rate of change (gradient) A for changing the threshold value Vth with respect to the head position is calculated from ENDTR, STATTR, (M+STATTR) and (M+ENDTR) (246).

Therefore, the control device 60 moves the head 26 back to the original return position (248, 250), and when the AV key is pressed (252), the desired target track number N set on the keypad 84 is used to perform the formula (248, 250). 1) and outputs this value Y to the DAC 78 (254).

Next, head 26 is transported in the forward direction (256) and track pulses 102 are counted (258). When it is detected from the count value that the head 26 has reached the target track (260), the state of the output 80 of the comparator 72 is read and the point in time when this is reversed is detected (262). When it is reversed, the position of the head 26 at that time is read from the output 66 of the head position detection mechanism 64 (264), and the value is stored in the area X1 (266).
Furthermore, when the state of the output 80 of the comparator 72 is read and the point in time when this is reversed is detected (268), the position of the head 26 at that time is read from the output 66 of the head position detection mechanism 64 (270), and the value is set in the area X2.
(272), and head transfer is stopped (274).

Therefore, the control device 60 calculates a simple average value X of the values of the area X1 and the same value of the area X2 (276), and moves the head 26 to that position X (278). This transfer can be performed by the controller 60 by monitoring the output 66 of the head position detection mechanism 64. In this way, the magnetic head 26
is tracked to the position of the target track N set on the keypad 84.

By the way, in the example explained with reference to FIGS. 5A to 5C, the average of the positions of the envelope threshold Vth is calculated only for the target track and tracking is performed at that position.
In the example explained with reference to the figure, after initialization, the track positions of all tracks are first determined and stored in the same manner, and when a target track is specified,
This is to track the memorized position. Note that in FIGS. 6A to 6D, steps having the same content as in FIGS. 5A to 5C are indicated by the same reference numerals to avoid duplication of detailed explanation.

In the initial setting step 300, in addition to the operations in the initial setting step 200 shown in FIG. 5A, the starting address POBF of the track position buffer area for storing track position data is set. These areas are of course set in the memory 92. Hereinafter, steps 202 to 246 may be the same as in the previous example.

After calculating the slope A in step 246, the controller 60 decrements the track counter TRCT (302) and moves the head 26 in the opposite direction (304).
When the track pulse 102 is received from the output 66 of the head position detection mechanism 64, that is, when the track pulse 102 for the last track of the disk 10 is received (306), the controller 60 replaces N in equation (1) with a track counter. Enter the TRCT value and set the threshold
Data Y of Vth is calculated and set to the input 76 of the comparator 72 (308).

Therefore, the controller 60 controls the output 80 of the comparator 72.
reads the state of and detects when this is reversed (310). When it is reversed, the position of the head 26 at that time is read from the output 66 of the head position detection mechanism 64 (312), and the value is stored in the area X1 (314).
Furthermore, when the state of the output 80 of the comparator 72 is read and a point in time when this is reversed is detected (316), the position of the head 26 at that time is read from the output 66 of the head position detection mechanism 64 (320), and the value is placed in the area X2. Accumulate (320). Therefore, a simple average value X of the values of the area X1 and the value of the area X2 is calculated, and this is stored at the address indicated by POBF+TRCT in the track position data buffer (322).

This operation is carried out while the counter TRCT is being decremented while the head 26 is being moved in the reverse direction.
Repeat (324) until becomes "0" (348). That is, for each track, the envelope is
The average position of the two head positions resulting in Vth is sequentially stored in the track position buffer. counter
When TRCT becomes "0", it waits for AV key input (326).

When the AV key is pressed (326), the keypad 84
The head 26 is transported in the forward or reverse direction to the desired target track number N set in (328).
~336). At this time, the difference between the current track number and the target track number is set in the counter TRCT (336, 332), and is decremented each time the track pulse 102 is input (338, 340). Therefore, head 2
When the head 6 reaches the vicinity of its target track, the counter TRCT becomes "0" (342), and the head transfer is temporarily stopped (344).

Therefore, the contents of the track position buffer corresponding to this track, that is, the stored contents of the track position buffer indicated by (POBF)+N, are read out, and the drive circuit 50 is set so that the output 66 from the head position detection mechanism 64 becomes equal to this. is controlled to move the head 26 to that position (346). In this way, the magnetic head 26 is tracked to the position of the target track N set by the keypad 84.
That is, in this example, the track positions for all tracks are first determined and stored, and when a target track is specified, tracking is performed to the stored position.

Effects In this way, the rotating recording body tracking device according to the present invention does not perform mountain-climbing tracking and
For each track, the envelope is tracked to the average of the two head positions where the threshold value is taken, that is, to the center position. Furthermore, this threshold value is modified so that it becomes lower for tracks with shorter track radii. Therefore, tracking control with sufficient accuracy can be quickly performed regardless of the position of the head, and in particular, random access to a desired track can be effectively realized.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of a rotating recording medium tracking device according to the present invention, and FIG.
Waveform diagrams showing pulses related to the position of the magnetic head in the embodiment shown in FIG. 1, FIGS. 3 and 4.
5A to 5C are waveform diagrams for explaining the principle of the present invention for the same embodiment, and FIGS. 6A to 6D are waveform diagrams for explaining the principles of the present invention in the same embodiment. FIG. Explanation of symbols of main parts, 10...Magnetic disk,
26... Magnetic head, 28... Head transfer mechanism, 30
...Step motor, 38...Envelope detection circuit, 60...Control device, 64...Head position detection mechanism, 72...Comparator, 84...Keypad.

Claims (1)

[Scope of Claims] 1. A playback head that reads signals from a plurality of tracks formed on a rotary recording body that rotates steadily at a predetermined rotational speed with a trajectory in which the start and end of recording coincide; a head moving means for movably supporting the rotary recording body; an envelope detecting means for detecting an envelope of a signal read by the reproducing head; and controlling the head moving means to position the head at a desired position on the track. A rotating recording body tracking device including a control means for moving the reproduction head, wherein the head moving means has a position detection means for detecting a position of the reproduction head on the rotation recording body, and the control means includes a position detecting means for detecting a position of the reproduction head on the rotation recording body. controlling the head moving means to move the playback head, finding two positions on one track where the envelope level detected by the envelope detecting means is equal to a reference value, and determining the center of the two found positions. the position of the playback head is determined by controlling the head moving means to move the playback head to the central position, and the control means varies the reference value according to the position of the playback head detected by the position detection means. A rotating recording body tracking device characterized in that when the reproducing head is located on a track with a larger diameter among the plurality of tracks, the reference value is set higher than when the reproducing head is located on a track with a smaller diameter. 2. In the device according to claim 1,
A rotating recording medium tracking device, wherein the control means includes comparison means for comparing the envelope detected by the envelope detection means with the reference value. 3. The apparatus according to claim 1, wherein the control means has designation means for designating a desired one of the tracks, and when the desired track is designated, the control means selects the head from the head. controlling a moving means to transport the playback head toward the designated track, and when the playback head is transported across the designated track, determining the two positions and moving the playback head toward the designated track; A rotary recording medium tracking device characterized in that the reproducing head is moved to the central position by determining the position and controlling the head moving means. 4. The apparatus according to claim 1, wherein the control means includes designation means for designating a desired one of the tracks, and stores the position of the head detected by the head position detection means. and storage means, the control means controls the head moving means to move the playback head, and when the playback head is moved across each track, the position detected by the position detection means is stored. Then, for each track, two positions where the level of the envelope detected by the envelope detecting means shows the reference value are determined, and for each track, the center position of the two determined positions is determined and stored in the storage means. and, when a desired one of the tracks is specified by the specifying means, controlling the head moving means to move the reproduction head to the memorized central position for the specified track. A rotating recording body tracking device characterized by: 5. In the device according to claim 1,
A rotating recording body tracking device, wherein the rotating recording body includes a magnetic disk.