JPH0587905B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a disc-shaped recording medium (hereinafter referred to as a disk) that records and reproduces information in the form of a spiral track.
The present invention relates to a recording/reproducing device, particularly a device that speeds up access operations.

BACKGROUND OF THE INVENTION When recording information on a disk, there are two types of signal track configurations: concentric and spiral. for example,
Concentric tracks are common in magnetic disks, and spiral tracks are common in optical disks. In the case of a spiral track, since the track is continuous, it is divided at an appropriate radius and one round is considered one track. Therefore, the structure of the tracks and sectors in the spiral track is as shown in FIG. 5 (in the case of one track having eight sectors).

When performing random access on a spiral track, conventional random access devices employ the same random access method as in the case of concentric tracks.

An example of a conventional random access device will be described below with reference to FIG. FIG. 3 is a block diagram mainly showing an access control circuit of an example of a random access device for an optical disk (for example, Japanese Patent Publication No. 57-69536, Japanese Patent Publication No. 58-1982).
91536, etc.). However, only the parts necessary for explanation are shown, and the tracking control circuit etc. are omitted.

In FIG. 3, 1 is an optical disk, 2 is a spindle motor that drives it, and 3 is a rotating shaft. 4 is an optical head for detecting a focus error signal, a tracking error signal, and a signal on the disk, and a head drive motor 5
is driven in the radial direction of the disk 1 by.

The flow of control until the head moves to the target position will be explained below with reference to FIG.

The target track position input from the external controller is stored in the target track position register 18. The subtracter 20 calculates the difference between the current track position stored in the current track position register 16 and the target track position, outputs it to the track counter 7 as the number of tracks that the head should pass, and changes the polarity of the moving direction signal. Output to the applicator 11.
Based on the number of remaining tracks in the track counter 7, a speed generating circuit 8 for generating an optimum speed curve indicates the moving speed of the head, which is converted into an analog signal by a digital-to-analog (D/A) converter 9. The commanded speed and the actual speed sent from the speed detection circuit 13 are input to the speed error amplifier 10, and the error between the commanded speed and the actual speed is outputted from the speed error amplifier 10. Since this speed error signal is an absolute value, a polarity is given by the polarizer 11 in accordance with the movement signal, and the drive circuit 12 operates the head drive motor 5 to drive the head.

A tracking error signal is obtained by a tracking error signal detection circuit 6 based on the signal obtained from the optical head 4, and the number of remaining tracks in a track counter 7 is counted down based on this signal. Based on this tracking error signal, the speed detection circuit 13 detects the absolute value of the actual speed. The current track position of the head is disk 1.
The track position information recorded above is obtained by demodulating it in the track position detection circuit 14.

The control circuit moves the optical head according to the optimum velocity curve, switches to tracking operation at the target track, and accesses the target position.

Problems to be Solved by the Invention However, the random access device as described above is not configured to deal with the problems that occur when random accessing a spiral track, and therefore accurate access may not be possible in some cases.

Problems in random access of spiral tracks will be explained below.

Since the spiral tracks exist continuously, the recording/reproducing head in the tracking operation moves toward the outer circumference (or toward the inner circumference) as the disk rotates. The direction of movement depends on the rotation of the spiral and the rotation direction of the disk, but in the following explanation, the fifth
Consider the case where the disk on the spiral track shown in the figure is rotating counterclockwise with respect to the recording/reproducing head. In this case, the direction of movement is toward the outer circumference.

Therefore, even if the head can enter the track where the target position exists, if the entry position into the track is on the outer periphery of the target position, the head will move away from the target position due to the rotation of the disk, so it will be necessary to move it again. becomes. Therefore, in order to access the target position in one movement, the head must be moved to the inner circumferential side of the target position.

Also, since the disk rotates while the recording/reproducing head is moving, the moving head will shift toward the outer circumference (clockwise) as shown in Figure 6, and the head after moving will change when the rotation of the disk can be ignored. It will reach the outer circumferential side from the position of. If the travel time is long, it is possible that the vehicle will deviate from the target track by multiple tracks.

In conventional random access devices, these problems cannot be addressed because the difference between the target track position and the current track position is set as the number of tracks to be passed by the recording/reproducing head.

The present invention takes the above-mentioned problems into consideration and provides a random access device in a spiral track in which a target position can be accessed by moving the recording/reproducing head at most once, and as a result, the shortest access time can be achieved. It is.

Means for Solving the Problems In order to solve the above-mentioned problems, the random access device of the present invention has the following features: means for detecting the difference in rotation angle in the circumferential direction; means for determining the number of tracks to pass from the detected difference in track position and the difference in rotation angle in the circumferential direction; and means for moving the recording/reproducing head by the determined number of tracks. and means to do so.

Here, the rotation angle in the circumferential direction of the head position is
This is the angle formed by the radius passing through the head position of each track and the radius passing through the head position, and is hereinafter abbreviated as rotation angle.

Operation When the recording/reproducing head is moved using the random access method of the present invention having the above configuration, the head reaches within one revolution of the target position on the inner circumferential side (in the case of the spiral shape and the disk rotation direction). , the target position can be accessed at the latest by one rotation of the disk.

Embodiment Hereinafter, an embodiment of the random access device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a random access device of the present invention. In Figure 1,
14 is a track position detection circuit, and 15 is a rotation angle detection circuit, which demodulates the signal sent from the optical head 4 and detects the current position of the head. Each output is stored in a current track position register 16 and a current rotation angle register 17. The target track position and target rotation angle are input from an external controller and stored in a target track position register 18 and a target rotation angle register 19, respectively. The difference between the current track position and the target track position is determined by the subtractor 20.
The calculation unit 22 calculates the disk rotation angle while the head moves based on the track position difference thus obtained. The difference between the current rotation angle and the target rotation angle is the subtractor 21
The subtractor 23 calculates the difference from the disk rotation angle. Since this difference represents the deviation of the rotation angle from the target position, if this difference is divided by the divider 24 and converted into the number of tracks, it becomes the number of tracks required for correction. The difference between this corrected number of tracks and the track position determined by the subtracter 20 is added by an adder 25 to determine the number of tracks to be passed. Adder 2
In step 5, the addition result is output as an absolute value and a sign, that is, a moving direction.

By setting the absolute value of the derived track number in the track counter 7, setting the moving direction in the polarizer 11, and operating the same speed control circuit as shown in FIG. After moving the set number of tracks, it enters the target track and switches to tracking operation.
The target position is accessed before the disk rotates once.

The following will explain how the access control circuit configured as described above can achieve the desired operation.

For the sake of explanation, consider stretching the spiral track into a straight line as shown in Fig. 4. Let the current position of the optical head 4 on the disk be X ₁ (track position r ₁ , rotation angle θ ₁ ), and the target position X ₂ (r ₂ , θ ₂ ). Both the current position X ₁ and the target position X ₂ are absolute positions on the disk. Here, the track position r is a track number counted from the innermost track, and r=1 at the innermost track. The unit of rotation angle θ is radian, θ=0 at a suitable radius on the disk, and the clockwise direction is positive. Therefore, the target track position r ₂ corresponds to the track number of the target track, and the target rotation angle θ ₂ corresponds to the absolute position within the target track. The distance _{1 2} between X ₁ and X ₂ on a straight line is expressed by the following formula using angle as a unit.

_{1 2} = 2π (r ₂ − r ₁ ) + (θ ₂ − θ ₁ ) (rad)……(1
) When the optical head 4 starts from X ₁ and moves towards X ₂ , the head moves to the point P ₁ , as shown in FIG.
Cross the track at P ₂ , ..., _Po . As shown in the figure, due to the rotation of the disk while the head is moving, the position where the head crosses the track shifts toward the outer circumference (clockwise). _The distance _1o from _X1 for the position Pn where the head crosses the nth track is determined by the following equation.

_{1 o} = 2πn + Δθ (rad) ... (2) where Δθ is the disk rotation angle during the time required for the head to reach P _o . Further, when moving in the outer circumferential direction, n is positive, and when moving in the inner circumferential direction, n is negative.

If the number of passing tracks to be determined is K, then according to the above conditions, point P _K is located on the inner circumference side of X ₂ ,
And the distance _{2 K} should be shorter than one revolution. _{2K _}
= _{1 2} - _{1 K} , so 01/2π( _{1 2} - _{1 K} ) < 1 holds true, and by substituting equations (1) and (2), the following equation holds.

0(r ₂ −r ₁ )+1/2π(θ ₂ −θ ₁ −Δθ)−K<
1 By further modification, the following equation is obtained.

K(r ₂ −r ₁ )+1/2π(θ ₂ −θ ₁ −Δθ)<K+
1...(3) Since Δθ is a quantity determined by the difference in track positions (r ₂ −r ₁ ), it does not depend on K. Therefore, from equation (3), it can be seen that K is given by the sum of (r ₂ −r ₁ ) and the integer part of 1/2π(θ ₂ −θ ₁ −Δθ).

The track position difference (r ₂ -r ₁ ) is obtained from the output of subtractor 20. _The amount p ₍ r ₂
-r ₁ ) corresponds to the distance that the optical head 4 actually moves.

The moving speed of the optical head 4 is uniquely determined for the moving distance by the optimal speed curve generated by the speed generating circuit 8, as described in lines 18 to 20 of page 3, and therefore the reciprocal of the moving speed In other words, the time required for movement ΔT can be found by integrating the movement time per unit distance over the movement distance, and if the rotation period of the disk is T ₀ , the disk rotation angle Δθ is
It is given by 2πΔT/T ₀ . The arithmetic unit 22 calculates Δθ from the difference in track positions (r ₂ −r ₁ ) using a table prepared in advance using the method described above. The subtracter 21 calculates (θ ₂ −θ ₁ ), the subtracter 23 calculates (θ ₂ −θ ₁ −Δθ), and the divider 24 calculates 1/2π(θ ₂ −θ ₁ −Δθ ) is calculated. Finally, in the adder 25, the integer part of 1/2π(θ ₂ − θ ₁ −Δθ) and (r ₂ −r ₁ ) are summed,
The number of tracks to be passed is determined.

In this way, the number of tracks to be passed is determined with the error due to the spiral rotation removed, and the optical head 4 is moved.The head reaches less than one turn on the inner circumference side of the target position, and the disk makes one turn at the latest. Since the target position can be accessed until

As described above, according to this embodiment, by accurately detecting the rotation angle of the current position, accurate access operations can be realized and access time can be shortened.

FIG. 2 is a block diagram showing a passing track number deriving circuit for explaining a second embodiment of the present invention. The difference from the passing track number deriving circuit shown in FIG. 1 is that the rotation angle detection circuit 15 in FIG. Then, the target rotation angle register 19 is replaced by the target sector position register 28, respectively.

By converting the sector position into the rotation angle of the head of the sector and processing, it is possible to obtain the same operation as in the first embodiment. However, in this case, the accuracy of the rotation angle is rougher than in the first embodiment, so
An error may occur in the number of passing tracks obtained. Therefore, in deriving the number of passing tracks, it is necessary to take safety into account and set a sector one inner circumferential side of the sector to be accessed as the target sector.

In the second embodiment, instead of accurately detecting the rotation angle of the head position using a rotation angle detection circuit, the sector position recorded on the disk along with the track position is read and used, resulting in a simple configuration. A random access scheme according to the present invention can be implemented.

In each of the embodiments, the case of an optical disk is shown, but the random access device of the present invention can be generally applied to a disk on which signals are recorded and reproduced in the form of a spiral track.

Effects of the Invention As described above, the present invention detects the difference in track position and the difference in rotation angle between the current position and the target position of the recording/reproducing head, and calculates the optimum number of passing tracks by taking these into consideration. Therefore, the following effects can be obtained.

(1) Since the target position can be accessed by moving the head once at most, there is no need to move the head again for correction after movement.

(2) The shortest access time can be achieved with limited head movement capacity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an access control circuit of a random access device for spiral tracks in one embodiment of the present invention, and FIG. 2 is a block diagram showing a circuit for deriving the number of passing tracks in another embodiment of the present invention. Figure 3 is a block diagram of an access control circuit in an example of a conventional random access device;
The figure shows a spiral track developed into a straight line to determine the target position.
A diagram showing the relationship between the current position and the position where the head enters the track, Figure 5 shows the track of the spiral track,
FIG. 6 is a diagram showing an example of a sector configuration, and is a diagram showing a shift in head position due to rotation of the disk while the head is moving. 1... Optical disk, 4... Head drive motor, 5... Optical head, 14... Track position detection circuit, 15... Rotation angle detection circuit.

Claims (1)

[Claims] 1. Means for detecting the difference in the radial direction of the recording medium between the current position and the target position of the recording/reproducing head, means for detecting the difference in rotation angle in the circumferential direction, and the radial direction of the recording medium detected by these means. means for calculating the number of tracks to be passed by the recording/reproducing head from the difference in position and the difference in rotation angle in the circumferential direction; and means for calculating the number of tracks that the recording/reproducing head should pass through from the difference in the position of A random access device in a spiral track, characterized in that it comprises means for moving.