JP3244553B2 - Still image playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing a video signal recorded on a magnetic disk by an electronic still camera or the like.

[0002]

2. Description of the Related Art Conventionally, in an electronic still camera, a magnetic disk is used as a recording medium, and a magnetic head is displaced in a radial direction of the magnetic disk to be positioned on a predetermined track. The video signal is reproduced. Due to the manufacturing accuracy of the chucking mechanism that mechanically fixes the magnetic disk, the center of rotation of the magnetic disk does not always exactly match the geometric center position,
A video signal may be recorded on a track eccentric with respect to the center of the magnetic disk.

[0003]

When reproducing a video signal recorded on such an eccentric track, a clear image can be reproduced by displacing the magnetic head along the eccentric track. it can. However, since the conventional magnetic head is driven by an electronic actuator such as a stepping motor, the response is slow, and therefore the magnetic head has to be fixed at a position where the average value of the output signal in one round of the track is maximized. Therefore, conventionally, when a video signal is recorded on an eccentric track, the video cannot be reproduced with high accuracy. SUMMARY OF THE INVENTION An object of the present invention is to provide a still image reproducing apparatus capable of reproducing a video with high accuracy by making a magnetic head follow an eccentric track as much as possible.

[0004]

Means for Solving the Problems still picture reproducing apparatus according to the present invention, a magnetic head for reproducing a video signal recorded on each track of the recording medium, film reproduced by a magnetic head
Envelope detection means for detecting the envelope of the image signal
And the envelope of the reproduced video signal for one round of the playback track.
Set the magnetic head at the position where the average value of the rope is maximum
First magnetic head position setting means, first magnetic head position
Detected at the position determined by the
Set the threshold value based on the envelope and
Block dividing means for dividing a video signal reproduced for one round of a reproduction track into a plurality of blocks based on the threshold value
And the envelope of the video signal to be reproduced for each block
Position of the magnetic head so that the
And a second magnetic head position setting means for determining . Further, a still image reproducing apparatus according to the present invention
Reproduces the video signal recorded on each track of the recording medium
And the radius of the trajectory of the magnetic head
At the first position approximately equal to the radius of the playback track,
First magnetic head moving means for moving the head, and a magnetic head.
The radius of the track of the playback track is smaller than the radius of the playback track.
Size of the magnetic head eccentric from the rotation center of the track of the magnetic head
The second magnetic head that moves the magnetic head to the second position
The track moving means and the radius of the locus of the magnetic head
Playback track is less than the track radius of the magnetic head.
At the third position, which is smaller by the amount of eccentricity from the center of
And third magnetic head moving means for moving the magnetic head.
It is characterized by.

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
FIG. 1 shows a control circuit built in an electronic still camera according to one embodiment of the present invention.

A system control circuit 11 is a conventionally known microcomputer for controlling the entire camera, and includes a CPU,
It has an OM and a RAM. The system control circuit 11 includes an operation unit 12 having various operation switches.
And a display unit 13 for displaying a setting state of the camera and the like.

The magnetic disk D is rotated by a spindle motor 21, and the spindle motor 21 is driven and controlled by a spindle servo circuit 22. The PG coil 23 detects the rotation timing of the magnetic disk D, and outputs this detection signal to the spindle servo circuit 22. The spindle servo circuit 22 is the system control circuit 1
1 to rotate the spindle motor 21 at a constant rotation speed (for example, 3600 rpm). The magnetic head 24 is a tracking motor (stepping motor) 2
5, the magnetic disk D is displaced in the radial direction, and the tracking motor 25 is controlled by the system control circuit 11 via the tracking motor drive circuit 26. That is, while the magnetic disk D is rotating, the magnetic head 24 is located on a predetermined track of the magnetic disk D, and records a video signal and an ID code on this track, or a video signal and an ID code recorded on this track. Read the ID code.

An image of a subject is formed on a solid-state image pickup device (CCD) 32 by an aperture and a lens 31. CC
D 32 is connected to the imaging circuit 33, and the image formed on the CCD 32 is read out by the imaging circuit 33. The horizontal synchronization signal and the vertical synchronization signal are input from the synchronization signal generation circuit 34 to the imaging circuit 33 for controlling the driving of the CCD 32 and controlling the reading of the video signal by the imaging circuit 33. The image signal is divided into a color difference signal and a luminance signal in the imaging circuit 33, and two color difference signals (RY, B
−Y) are alternately arranged every 1H (horizontal scanning period).
Then, the color difference signal and the luminance signal are output from the imaging circuit 33 and AD-converted by the AD converter 35.

The AD converter 35 is connected to a video memory 37 via a switch 36. The video memory 37 has a sufficient storage capacity to store at least one screen of video signal. The switch 36 is switched to the AD converter 35 side (R) when recording a video signal, and is switched to the AD converter 51 side (P) to be described later when reproducing the video signal.

[0010] The video memory 37 is connected to the D
The FM converter 43 is connected to the A converter 42 and the DA converter 42. The FM modulation circuit 43 is connected to a recording amplifier 45, and the recording amplifier 45 is connected to the magnetic head 24 via a switch 46. When recording a video signal, the switch 41 is switched to the DA converter 42 (R), and the switch 46 is switched to the recording amplifier 45 (R). Therefore, the video signal stored in the video memory 37 is DA-converted, FM-modulated, amplified by the recording amplifier 45, and recorded on a predetermined track of the magnetic disk D via the magnetic head 24.

The video memory 37 is connected to an AD converter 51 via a switch 36, and the AD converter 51 is connected to an FM demodulation circuit 52. The FM demodulation circuit 52 is connected to a reproduction amplifier 53, and the reproduction amplifier 53 is connected to the magnetic head 24 via a switch 46. When reproducing the video signal recorded on the magnetic disk D, the switch 36 is switched to the AD converter 51 side (P), and the switch 46 is switched to the reproduction amplifier 53 side (P). Therefore, a video signal recorded on a predetermined track of the magnetic disk D is
After being amplified by the reproduction amplifier 53, it is FM-demodulated and A / D converted and stored in the video memory 37.

The video memory 37 is connected to a video signal processing circuit 54 via a switch 41. The video signal processing circuit 54 is connected to a DA converter 55,
Can be connected to a display device or the like. When reproducing the video signal recorded on the magnetic disk D, the switch 41 is switched to the video signal processing circuit 54 side (P). Therefore, the video signal is read out from the video memory 37 and subjected to predetermined processing by the video signal processing circuit 54,
The signal is A-converted and output to a display device or the like as an NTSC signal.

The horizontal synchronizing signal and the vertical synchronizing signal included in the video signal output from the FM demodulation circuit 52 are separated from the video signal by a synchronization signal separating circuit 61. The synchronization signal separation circuit 61 is connected to a write sampling pulse generation circuit 63 via a switch 62. Switch 6
2 is also connected to the synchronizing signal generating circuit 34, and is switched to the synchronizing signal generating circuit 34 (R) when recording a video signal, and is also switched to the synchronizing signal separating circuit 61 (P) when reproducing a video signal. Can be The write sampling pulse generation circuit 63 generates a sampling pulse based on the horizontal synchronization signal and the vertical synchronization signal output from the synchronization separation circuit 61 or the synchronization signal generation circuit 34,
Output to the D converters 35 and 51 and the write address generation circuit 64. The AD converters 35 and 51 AD-convert the video signal in synchronization with the sampling pulse. The write address generating circuit 64 synchronizes with the sampling pulse for writing to the video memory 37.
Control the address of

The synchronizing signal generating circuit 34 is directly connected to the read sampling pulse generating circuit 65 in addition to the switch 62. Read sampling pulse generation circuit 65
Generates a sampling pulse based on the horizontal synchronizing signal and the vertical synchronizing signal output from the synchronizing signal generation circuit 34, and outputs this to the DA converters 42 and 55 and the read address generation circuit 66. The DA converters 42 and 55 are
The video signal is DA-converted in synchronization with the sampling pulse. The read address generation circuit 66 controls the address of the video memory 37 in synchronization with the sampling pulse for reading from the video memory 37.

When recording a video signal, the switch 36 is connected to the AD converter 35 (R), and the switch 62 is connected to the synchronous signal generating circuit 3.
4 (R). Therefore, the video signal output from the imaging circuit 33 is output to the AD converter 35
In the above, the A / D conversion is performed in synchronization with the sampling pulse output from the write sampling pulse generation circuit 63 based on the control of the synchronization signal generation circuit. This video signal is stored in the video memory 37 in the synchronization signal generation circuit 3.
4 is stored at an address determined by the write address generation circuit 64 based on the control of the fourth step.

When reproducing a video signal, the switch 36 is connected to the AD converter 51 (P), and the switch 62 is connected to the synchronizing signal separating circuit 6.
Each is switched to the first side (P). Therefore, the video signal read from the magnetic disk is supplied to the AD converter 5
In 1, under the control of the synchronization signal separation circuit 61, AD conversion is performed in synchronization with the sampling pulse output from the write sampling pulse generation circuit 63. This video signal is stored in the video memory 37 at an address determined by the write address generation circuit 64 based on the control of the synchronization signal separation circuit 61.
Is read out from the address determined by the read address generation circuit 66 based on the control of.

In this embodiment, when the video signal is reproduced,
An envelope detection circuit 68 is provided in order to sufficiently increase the SN ratio of the video signal and reproduce a clear video. The envelope detection circuit 68 is provided between the reproduction amplifier 53 and the system control circuit 11. That is, the envelope detection output of the video signal output from the reproduction amplifier 53 is detected by the envelope detection circuit 68,
It is input to the system control circuit 11. The system control circuit 11 controls the position of the magnetic head 24 based on the envelope detection output as described later.

FIG. 2 shows a track T of the magnetic disk D,
This shows the relationship between the trajectories K1 to K3 of the magnetic head 24. The trajectories K1 to K3 of the magnetic head 24 are relative to each other due to the rotation of the magnetic disk D. In FIG. 2, three types of radial positions of the magnetic head 24 with respect to the magnetic disk D are shown. That is, the magnetic head 24 is located relatively outside in the state B, relatively inward in the state C, and at an intermediate position between the states B and C in the state A. Twenty-four trajectories K1 to K3 are eccentric to the right with respect to the track T.

In the state A, the diameter of the track T and the diameter of the locus K1 of the magnetic head 24 are substantially equal, and the track T and the locus K
1 is close to the upper part P1 and the lower part P2.
Therefore, the magnetic head 24 can accurately detect the video signal at the upper part P1 and the lower part P2 of the track T. On the other hand, in the state B, the diameter of the track K2 of the magnetic head 24 is larger than the diameter of the track T, and the track T and the track K2 are close to each other at the left portion P3. Therefore, the magnetic head 24 moves to the left portion P of the track T.
The video signal in 3 can be accurately detected. In the state C, the diameter of the track K3 of the magnetic head 24 is smaller than the diameter of the track T, and the track T and the track K3 are close to each other at the right portion P4. Therefore, the magnetic head 24 can accurately detect the video signal at the right portion P4 of the track T. In the present embodiment, as described below, the track T is divided into a plurality of blocks, and the position of the magnetic head 24 is radially controlled so as to be closest to the track T for each block, thereby recording on each block. The output of the output video signal is maximized.

FIG. 3 shows the operation of the present embodiment.
The PG pulse W is output from the PG coil 23 and is generated every time the magnetic disk D makes one rotation. The FG pulse U is output in accordance with the rotation of the spindle motor 21, and for example, 18 pulses are generated during one rotation of the magnetic disk D. In this embodiment, the video signal of one screen is recorded on one track of the magnetic disk D.

The envelope detection output AE corresponds to the state A in FIG. 2 and periodically fluctuates. This is because the magnitude of the output value of the video signal changes because the track of the magnetic disk D and the trajectory of the magnetic head 24 are eccentric to each other. The state A in FIG. 2 is a case where the position of the magnetic head 24 is determined so that the average value of the envelope detection output over one round of the track is maximized, and this average value is determined here as the threshold value S. ing. Then, the envelope detection output AE is equal to the threshold value S.
Rise of the FG pulse immediately after crossing
At T4, the video signal of one track is divided into first to fifth blocks.

That is, in the change of the envelope detection output AE in the state of FIG. 2A, in the first block, the envelope detection output AE is lower than the threshold value S, and in the first block, the envelope detection output AE is insufficient. Period. In the first block, at the rising edge T1 of the third FG pulse counted from the PG pulse, the envelope detection output AE exceeds the threshold value S, and here is a period in which the envelope detection output AE is satisfied. This makes the track a second block. At the rising edge T2 of the fourth FG pulse in the second block, the envelope detection output AE is lower than the threshold value S again, and this is a period in which the envelope detection output AE is insufficient. Thus, the track becomes the third block. Hereinafter, similarly, the third block becomes the fourth block at the rising edge T3 of the third FG pulse, and the fourth block ends at the rising edge T4 of the fourth FG pulse. The fifth block starts from T4 when the FG pulse rises,
T5 at the rise of the FG pulse immediately after the output of the G pulse
Ends with

On the other hand, in the state of FIG. 2B, the manner of change of the envelope detection output BE is different from the state of A, and the envelope detection output BE has the threshold value S in the first block and the fifth block. Higher than
In other blocks, it is lower than the threshold value S. On the other hand, in the state C of FIG. 2, the envelope detection output CE
Is higher than the threshold value S in the third block, and lower than the threshold value S in other blocks.

Therefore, the position of the magnetic head 24 is
By controlling the block and the fifth block to be in the state B, the second and fourth blocks to be in the state A, and the third block to be in the state C, the video signal is controlled. The envelope detection output E increases over one track of the magnetic disk D. As a result, the SN ratio of the video signal can be made sufficiently high over the entire track, and a clear video can be displayed by a display device or the like.

FIGS. 4 to 7 are flowcharts of a program for controlling the position of the magnetic head 24. The operation of this flowchart will be described with reference to FIG.

In step 101, the end flag Q is cleared, and in step 102, the spindle motor 21 is started. In step 103, the spindle motor 21 enters the lock-in state and its rotation is stabilized.
In step 104, the automatic tracking of the magnetic head 24 is performed. That is, hill-climbing control is performed for one round of the track, and 1
The position of the magnetic head 24 is set so that the average value of the envelope detection output of the video signal for the circumference becomes maximum. The position of the magnetic head 24 is stored in a memory (not shown) and used in step 161 described later.
The position of the magnetic head 24 is controlled using the outermost or innermost circumference of the magnetic disk D as a reference position, that is, by controlling the motor drive amount (the number of drive steps) of the tracking motor 25 from this reference position to the target position. Is done.

A state in which the average value of the envelope detection output is maximum is shown in FIG. 2A, and the average value is set as a threshold value S (FIG. 3) of the envelope detection output AE. The method of setting the threshold value S is not limited to this, and may be set based on, for example, an allowable S / N ratio of the video signal. Step 105
Then, a video signal for one round of the reproduction track is reproduced at this head position, and this reproduction signal is written to the video memory 37 (FIG. 1).

Next, when it is confirmed in step 111 that the PG pulse W has been output, step 112
, The counter C1 is cleared to 0. Each time the FG pulse is detected, the value of the counter C1 is set to step 1
Since it is incremented by 1 at 15, it matches the number of FG pulses. The value of the counter C1 is
Since one rotation of the magnetic disk D corresponds to one screen, a schematic relative position from the first pixel of the screen is shown. In step 113, it is determined whether or not the counter C1 has become equal to the maximum value, that is, whether or not the number of FG pulses has reached the maximum value (the number of FG pulses between two PG pulses) counted from the PG pulses. You.

Immediately after the output of the PG pulse W, the number of FG pulses has not yet reached the maximum value, so that step 114 is executed, and the output of the FG pulse is detected. If an FG pulse is detected, step 115
, The counter C1 is incremented by one.
In step 116, the current envelope detection output AE
Is lower than the threshold value S.
At present, the magnetic head 24 is in the state of A in FIG. 2, and the envelope detection output AE is in the first block of FIG. That is, the current envelope detection output AE is lower than the threshold value S, and therefore, steps 121 and subsequent steps are executed next.

In step 121, the value of the counter C1 is set as the first boundary NG1 of the block. In step 122, it is determined whether the value of the counter C1 has become equal to the maximum value. That is, it is determined whether or not the number of FG pulses has reached the maximum value counted from the PG pulse. Here, since the counter C1 has not yet reached the maximum value, the process proceeds to step 123, where the output of the FG pulse is detected. When the FG pulse is detected, step 124 is executed.
, The counter C1 is incremented by one.
In step 125, the current envelope detection output AE
Is greater than or equal to a threshold value S.
Initially, since the envelope detection output AE is lower than the threshold value S, steps 122 to 125 are repeatedly executed. However, as shown in FIG. 3, the rising edge T1 of the third FG pulse counting from the PG pulse, as shown in FIG. In step (1), the envelope detection output AE becomes equal to or larger than the threshold value S, and step 131 and subsequent steps are executed.

In step 131, the value of the counter C1 is set as a boundary NG2 at the end of the block. In step 132, it is determined whether or not the value of the counter C1 has become equal to the maximum value. When the processing of the first block is being performed, the value of the counter C1 has not yet reached the maximum value, so the flow proceeds to step 133. In step 133, the automatic tracking of the magnetic head 24 is performed between the boundaries NG1 and NG2, that is, for the first block. That is, the hill-climbing control is performed for the first block, and the position of the magnetic head 24 is set so that the average value of the envelope detection output of the video signal in this block is maximized. As a result, the locus of the magnetic head 24 becomes the state of B in FIG. 2 (a state where the diameter is relatively large), and a video signal corresponding to the envelope detection output BE is obtained.

At step 141, the counter C2 is cleared to zero. The counter C2, like the counter C1, is incremented by one in step 144 each time an FG pulse is detected, so that the counter C2 matches the number of FG pulses, that is, the counter relative to the first pixel on the screen. Indicates the position. When it is confirmed in step 142 that the PG pulse W has been output, in step 143, the output of the FG pulse is detected.
When the FG pulse is detected, the counter C2 is incremented by one in step 144. Step 1
At 45, it is determined whether the value of the counter C2 has become equal to the first boundary NG1 of the block. While the value of the counter C2 is not equal to the boundary NG1, step 143
When the value of the counter C2 becomes equal to the boundary NG1, steps 151 to 157 are executed, and the video signal of the block is written to the video memory 37.

In step 151, writing of a video signal to the video memory is started. When the output of the FG pulse is detected in step 152, it is determined in step 153 whether or not the value of the counter C2 has reached the maximum value. During the processing of the first block, the value of the counter C2 does not reach the maximum value.
2 is incremented by one. And step 1
At 56, it is determined whether the value of the counter C2 has become equal to the boundary NG2 at the end of the block. Until the value of the counter C2 becomes equal to the boundary NG2, steps 152 to 156 are repeatedly executed, and the counter C2
When the value of 2 becomes equal to the boundary NG2, the process proceeds to step 157, and the writing of the video signal to the video memory ends.

In step 153, the counter C
If it is determined that the value of 2 has reached the maximum value, step 155 is executed, and the value of the counter C2 is set to 1, that is, the value corresponding to the first pixel of the screen. Such a state occurs when the processing of the fifth block is being performed in the example of FIG. 3, and in this case, the boundary NG2 is set to 1 by the processing of step 135 described later.

In the case of a block whose envelope detection output is lower than the threshold value S (for example, the first block in the example of FIG. 3), the envelope detection output exceeds the threshold value S as described above. The magnetic head 24 is displaced to the position, and the video signal is written to the video memory 37 in this state. That is, steps 111 to 1
By executing step 57, the video signal is reproduced in a state where the envelope detection output becomes high, and this video signal is written into the video memory 37. That is, the content of the video memory 37 is rewritten to a signal that gives a clearer video.

Next, at step 161, the magnetic head 24
Is returned to the first auto tracking position. That is, the magnetic head 24 is returned to the position where the average value of the envelope detection output of the video signal for one round of the track determined in step 104 and stored in the memory is maximized. At step 162, it is determined whether or not the end flag Q has been set.
Since has not been set yet, step 163 and subsequent steps are executed.

At step 163, the counter C3 is cleared to zero. As will be understood from the following description, the operation of the previous steps 111 to 15 is performed by the operation of the counter C3.
The value of “the first boundary NG1 of the block” in the process of No. 7 is held. Now, when the output of the PG pulse W is detected in step 164, F is output in step 165.
The output of the G pulse is detected. When the FG pulse is detected, the counter C3 is incremented by 1 in step 166. In step 167, the counter C3
Is less than or equal to the value of the counter C1, that is, the value of the boundary NG1 determined in the previous step 121. When the value of the counter C3 is equal to or less than the value of the counter C1, steps 165 to 167 are repeatedly executed. When the value of the counter C3 becomes larger than the counter C1, the process proceeds to step 115.

In steps 115 and subsequent steps, the same processing as described above is performed. That is, a block (the third block in the example of FIG. 3) in which the envelope detection output AE is below the threshold value S is detected, and the position of the magnetic head 24 is adjusted so that the envelope detection output of this block exceeds the threshold value. Is determined, the video signal is reproduced, and the video signal in the video memory 37 is rewritten.

If it is determined in step 113 that the value of the counter C1 has reached the maximum value while the above processing is being performed on the last block (the fifth block in the example of FIG. 3), 171 is executed, and the spindle motor 21 stops. And step 172
Then, an image is output by a display device (not shown) or the like, and this program ends. If it is determined in step 122 that the value of the counter C1 has reached the maximum value, in step 135, the boundary NG2 is set to 1
Is set, and the end flag Q is set in step 136. Then, Step 133 and the subsequent steps are executed, and after the video signal is rewritten into the video memory 37, the process proceeds from Step 162 to Step 171, where Step 172 is executed and this program ends.

As described above, according to this embodiment, the video signal is divided into a plurality of blocks on the memory 37, and the magnetic head 24 is controlled to an optimum position for each block.
That is, since the magnetic head 24 follows the track in units of blocks, the magnetic head 24 can sufficiently respond even by tracking control using a commonly used electromagnetic actuator. Therefore, even if the video signal is recorded on the eccentric track, the magnetic head 24 can be displaced substantially along the eccentric track, whereby a clear video can be reproduced.

Note that a vertical synchronizing signal of a video signal may be used instead of the PG pulse, and a horizontal synchronizing signal of the video signal may be used instead of the FG pulse.

[0042]

As described above, according to the present invention, the magnetic head can follow the eccentric track as much as possible, and the effect that the video can be reproduced with high accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a control circuit of an electronic still camera to which an embodiment of the present invention has been applied.

FIG. 2 is a diagram showing a relationship between a track of a magnetic disk and a locus of a magnetic head.

FIG. 3 is a diagram illustrating the operation of the embodiment apparatus.

FIG. 4 is a flowchart of a program for performing a video signal reproducing operation.

FIG. 5 is a flowchart of a program for performing a video signal reproducing operation.

FIG. 6 is a flowchart of a program for performing a video signal reproducing operation.

FIG. 7 is a flowchart of a program for performing a video signal reproducing operation.

[Description of Signs] D Magnetic Disk

Claims (4)

(57) [Claims] 1. A magnetic head for reproducing a video signal recorded on each track of a recording medium, an envelope detection means for detecting an envelope of a video signal reproduced by the magnetic head, and a reproduction for one round of a reproduction track. a first magnetic head positioning means for the average value of the envelope of the video signal defining said magnetic head in a first position at which the maximum was, first defined by said first magnetic head position setting means
A threshold value is set based on the envelope detected at the position 1, and the threshold value and the second
Larger or smaller than the envelope value detected at position 1
By comparing the video signal reproduced for one round of the reproduction track with the threshold value of the envelope.
A first block that is greater than the
The second block whose value is smaller than the threshold value.
A block dividing means for dividing into a click, the average value of the envelope of the video signal reproduced in the second block, second defining said magnetic head so as to exceed the threshold value to the second position And a magnetic head position setting means. 2. The method according to claim 1, wherein the threshold value is the first place.
2. The still image reproducing apparatus according to claim 1, wherein the average value is an average value of the envelope detected by the apparatus. 3. The video signal of the first block.
Regeneration is performed at the first location and the second
2. The still picture according to claim 1 , wherein the reproduction of the video signal in the lock is performed at the second position , and the video signal reproduced in each of the blocks is written to a video memory. Picture playback device. Wherein said first movies image signal of the track one round played at the position written into the video memory, then said video memory second corresponding to the second block
4. The still picture reproducing apparatus according to claim 3 , wherein the still picture reproducing apparatus replaces the video signal reproduced at the position of (b).