JPH0877571A - Optical information recording / reproducing device - Google Patents

Abstract

(57) [Summary] [Purpose] Accurate track counting,
Be able to control the seek operation accurately. [Structure] The optical beam emitted from a light source is recorded on the optical disc 1
An objective lens that converges upward, an actuator 12 that moves the objective lens in the tracking direction, a lens position detector 15 that detects the position of the objective lens in the tracking direction, and a means that controls the actuator 12 to control the tracking operation. , Objective lens and actuator 1
In an optical information recording / reproducing apparatus having a linear motor 14 for moving an optical head including 2 in a track crossing direction, when the linear motor 14 is driven to seek the optical head to a target position, the linear motor 14 is driven. After the start, the tracking control means is held in the ON state, and when the detection value by the lens position detector 15 reaches a predetermined value, the tracking control means is turned off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus such as a magneto-optical disk apparatus, and more particularly to a seek control apparatus for a recording / reproducing head used for recording / reproducing.

[0002]

2. Description of the Related Art Conventionally, as a method of accessing a target position of a recording medium by a recording / reproducing head in an information recording / reproducing apparatus of this type, access control is generally performed by controlling the speed of the recording / reproducing head. is there. Such speed control is to sequentially monitor the speed of the head and control the speed of the recording / reproducing head according to a predetermined operation schedule based on the speed. FIG. 8 is a diagram showing a relationship between a target speed, an actual speed, and an actuator applied current in a general speed control method. In FIG. 8, the target speed V _ref
Is a predetermined speed profile, the speed V _n is the actual head speed, and the speed control is performed so that the speed V _n of the recording / reproducing head follows the target speed V _ref . The target speed value V _ref can be _calculated according to the following formula.

V _ref = (2 · α (S−λ / 2 · N) ^1/2 (1) where S is the target moving distance, λ is the track pitch, α is the deceleration acceleration, and N is the moving distance. It is a zero-cross count value of the corresponding tracking error signal, and there are a method of obtaining the current speed V _n of the recording / reproducing head from the track count value and a method of obtaining it by pulse counting between tracks. The current speed can be calculated as follows from the track count value advanced in a fixed cycle.

V _n = (λ / 2 · N) / T _s (2) where T _s is the sampling time.

On the other hand, in the track-to-track counting method, the zero cross point of the tracking error signal is detected, the time Δt _n between this zero cross point and the next zero cross point is measured, and the current speed is calculated from the obtained measured value and the track pitch. Desired. That is, since the distance between the zero cross points is 1/2 of the track pitch λ, the current speed is calculated from this distance and the time Δt _{n when} passing through the distance. Therefore, the current speed at this time can be obtained by the following equation (3).

V _n = λ / 2 × 1 / Δt _n (3) The speed of the moving recording / reproducing head is detected, and speed control is performed so that the current speed follows the target speed. Be seen. When counting tracks,
A signal obtained by binarizing the tracking error signal is counted, and the speed of the recording / reproducing head is obtained based on the counted value as described above.

[0007]

However, in the above-described conventional seek control method, when the tracks crossed by the recording / reproducing head are counted, a mistrack count occurs, which seriously affects the speed control of the recording / reproducing head. There was a problem. This problem will be described with reference to FIG. 9A is a drive signal of a linear motor that drives the recording / reproducing head, and FIG. 9B is a tracking control signal that controls whether the tracking servo is turned on or off.
FIG. 9C shows the position signal of the objective lens that converges the light beam on the recording medium, FIG. 9D shows the drive current of the linear motor, and FIG. 9E shows the tracking error signal. Further, in FIG. 9, the signals of the respective parts are shown in response to the switching from the track following operation to the seek operation.

Generally, the tracking error signal is shown in FIG.
Even during the track following operation as shown in (e), there is some vibration due to position control error and noise. Therefore, normally, the tracking error signal is not binarized as it is, but when the level of the tracking error signal exceeds a certain value, it is determined that the seek operation has been started, and a so-called hysteresis operation is introduced, so that the track count value is changed to the tracking error signal. It is devised so that it is not affected by the noise component of. In addition,
As described in Japanese Patent No. 32470, a method for preventing mistrack count by providing an additional circuit is also known.

However, when the track following operation shifts to the seek operation, the drive current of the linear motor is as shown in FIG. 9 (d).
As described above, since the linear motor does not steeply rise due to the inductance and also has frictional resistance, the carriage having the recording / reproducing head cannot move immediately.
On the other hand, when the actuator provided in the recording / reproducing head on the carriage moves by the inertial action of the following tracking operation when the track following operation is stopped, the carriage is mounted on the linear motor in this case. Therefore, when the linear motor is started, the actuator vibrates, and the light beam crosses the track. FIG. 9C shows how the actuator vibrates. When the linear motor is started, the objective lens position signal vibrates as indicated by the broken line due to the actuator vibration. Also, if the center of the disc and the center of the spill dollar are deviated, the disc is eccentrically rotating, so the actuator is away from the mechanical center during the track following operation, and if the track following operation is stopped at this time, The beam of light may also cross the track due to the action of the actuator to return to the center of the mechanism. The tracking error signal in FIG. 9 (e) shows such a situation, and the vibration or movement of the actuator as described above crosses the track in the direction opposite to the moving direction of the light beam. Then, when the linear motor reaches a sufficient speed, its moving direction is reversed as shown in FIG. 9E, and seek to the initial target position is started.

As described above, in the conventional case, when the seek operation is started, the linear motor is not instantaneously accelerated and the recording / reproducing head is not seeking, but the optical vibration is caused by the vibration of the actuator or the eccentricity of the disk. Since the beam crosses the tracks, a mistrack count occurs in which the number of tracks where the recording / reproducing head is not actually moving is counted. As a result, the track count is erroneously counted immediately after the start of the seek operation, the speed control becomes unstable, and the seek is performed at the incorrect current position due to the miss track count, so that the accurate seek operation cannot be performed. There was a problem.

The present invention has been made in view of the above problems, and an object thereof is to maintain the tracking operation at the start of the seek operation and turn off the tracking operation when the lens position reaches a predetermined position. Accordingly, it is an object of the present invention to provide an optical information recording / reproducing apparatus capable of obtaining an accurate track count value and accurately controlling a seek operation.

[0012]

An object of the present invention is to provide an objective lens which converges a light beam emitted from a light source onto an information recording medium, and a first moving means which moves the objective lens in a tracking direction. A means for detecting the position of the objective lens in the tracking direction, a means for controlling the first moving means to control the tracking operation of the light beam, and an optical head including the objective lens and the first moving means. In an optical information recording / reproducing apparatus having a second moving means for moving in the track crossing direction, when the second moving means is driven to move the optical head to a target position, the second moving means is used. Hold the tracking control means in the ON state after the start of driving, and turn off the tracking control means when the detection value by the detection means reaches a predetermined value. It is achieved by an optical information recording and reproducing apparatus characterized.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the optical information recording / reproducing apparatus of the present invention. In FIG. 1, an optical disk device is shown as an example of the information recording / reproducing device. In FIG. 1, reference numeral 1 denotes an optical disc which is an information recording medium, and is rotated at a constant speed by driving a drive system (not shown). Reference numeral 2 denotes an optical system for optically recording information on the optical disc 1 or reproducing recorded information on the optical disc 1. The optical system 2 includes various optical elements such as a semiconductor laser that is a light source for recording and reproduction, an objective lens that narrows the laser light flux into a minute light spot, and an optical sensor that detects reflected light from the optical disc 1. . Reference numeral 12 is a tracking actuator that moves an objective lens (not shown) provided in the optical system 2 in the tracking direction, and 13 is a focus actuator that moves the objective lens in the focus direction. The optical system 2 and the two actuators 12 and 13 are incorporated in the optical head, and are configured so that they can be moved in the radial direction of the optical disc 1 to access a desired track.
Reference numeral 14 is a linear motor for moving the optical head in the radial direction of the optical disk 1, and 10 is a driver for the linear motor 14.

Reference numeral 3 is a tracking error detector for detecting a tracking error signal based on the output of an optical sensor in the optical system 2, and reference numeral 4 is a focus error detector for similarly detecting a focus error signal based on the sensor output. The error signal detected by each of the error detectors 3 and 4 is converted into a digital signal by the A / D converter 5, and then output to the digital signal processing unit 6. Reference numeral 15 is a lens position detector for detecting the position of the objective lens in the tracking direction, and the detection value of this lens position detector 15 is also A
The digital signal is converted by the / D converter 5 and output to the digital signal processing unit 6. The digital signal processing unit 6 forms the main control unit of the optical disc apparatus of this embodiment, and the digital signal processing unit 6 performs tracking control of the light beam, focus control, seek control of the optical head, and the like. The digital signal processing unit 6 is composed of an I / O control unit 7 for controlling signal input / output, a CPU 8 for executing arithmetic processing required for control according to a predetermined control program, and a memory 9 for storing various data. ing. CPU
In 8, the command values of the tracking actuator 12, the focus actuator 13, and the linear motor 14 are obtained by a predetermined calculation process, and the obtained command values are converted into analog signals by the D / A converter 11 and then sent to each. Sent.

Next, the operation of the above embodiment will be described with reference to FIGS. 2, 3 and 4. 2 is a flow chart showing the operation sequence of the seek operation of the above embodiment, FIG. 3 is a flow chart showing the operation sequence of the speed control of the optical head, and FIG. 4 is a linear motor (LM) when shifting from the tracking operation to the seek operation. ) 14 drive signal, tracking control signal, lens position signal of lens position detector 15, drive current of linear motor 14, and tracking error signal.

First, in FIG. 2, when an optical head access is instructed by a controller (not shown), the CPU 8
Now, control the driver 10 via the D / A converter 11,
The driving of the linear motor 14 is started (S1). Then, immediately after the linear motor 14 is started to be driven, the tracking operation is held in the ON state (S2). Here, FIG.
(A) is a drive signal of the linear motor (LM) 14, FIG.
4B shows a tracking control signal for controlling whether the tracking operation is turned on or off. Even if the LM drive signal is output from the CPU 8 as shown in FIG. 4A, immediately after the start of seek, the tracking control signal shown in FIG. The tracking operation is held in the ON state as shown in FIG. Note that, in FIG. 2, the operation of holding the tracking operation of S2 in the ON state does not have to be performed again, but is clearly shown in the flowchart of FIG. 2 in order to clearly distinguish it from the conventional one.

Next, the CPU 8 sets a flag indicating that the seek operation mode has been entered (S3), and then the lens position signal of the lens position detector 15 is changed to the D / A converter 5.
Is taken into the CPU 8 by (S4). Based on the lens position signal, the CPU 8 determines whether or not the position of the objective lens has reached the predetermined position (S5), and when the position of the objective lens reaches the predetermined position, the tracking operation is turned off (S6). Here, the tracking operation is turned off when the objective lens is located at the center of the optical system 2. It should be noted that the seek control operation is in a waiting state until the position of the objective lens reaches a predetermined position, but during the waiting time, the CPU 8 executes control other than seek control such as focus control. Here, FIG. 4C shows the lens position signal Lp of the lens position detector 15, but in FIG. 4C, at the point P at the start of seek, the position of the objective lens is the center of the mechanism due to the eccentricity of the optical disc 1. It shows a state in which it is further displaced. At this time, when the seek operation is started from point P, the drive current of the linear motor 14 does not instantly rise due to the inductance as shown in FIG.
Acceleration by 4 is gentle at first and gradually increases. In this case, in the present embodiment, the tracking control is not turned off at the start of the seek but is kept in the on state, and the tracking control is turned off at the point Q where the objective lens is located at the center of the seek. No attempt is made, and no track cross occurs in the direction opposite to the moving direction after the point Q.

Further, in the CPU 8, position control for controlling the tracking actuator 12 is performed so that the detection signal of the lens position detector 15 becomes zero after the point Q (the objective lens is located at the center). . That is, the seek operation by the linear motor 14 is performed with the tracking actuator 12 positioned in the center of the mechanism. At this time, some vibration occurs in the optical system 2 due to mechanical resonance or disturbance, and this vibration causes a slight vibration of the lens position signal as shown in FIG. 4C. But already Q
Since the acceleration by the linear motor 14 is large after the point, the track count is not erroneous.

Now, return to FIG. When the tracking control is turned off at the point Q, the track count operation is started by setting the track count and counting the number of tracks crossed by the light beam (S7). This is shown in Fig. 4 (e).
This is to count the pulse signal obtained by binarizing the tracking error signal as shown in (1) by a binarizing circuit (not shown), and the moving distance of the light beam can be detected by counting the pulse signal. . In FIG. 4E, one cycle of the tracking error signal corresponds to one track. Then, the speed detection of the optical head is started (S
8). As a method of detecting the velocity, for example, as described above, there is a method of measuring the time Δt during which the light beam passes between tracks and calculating from the obtained Δt and the track pitch λ. After that, speed control is set to start speed control in seek control of the optical head (S9). This speed control is executed by a digital servo every fixed cycle, and here, it is executed at a sampling cycle of 25 KHz. After the speed control is started, the speed control flag set in S3 is monitored. When this flag becomes the end flag, the optical head reaches the target track and the speed control is ended (S10).

Next, the speed control operation of the optical head will be described with reference to FIG. This speed control is executed by the CPU 8 by the digital servo, and is executed in parallel with other processing other than the seek operation. In FIG. 3, when the speed control interrupt is input, the tracking error signal is set to 2
The count value of the counter that counts the binarized signal is read (S1), the current position of the optical head is determined from the count value, and it is determined whether the target position has been reached (S2). If the target position has not been reached, the target speed V
_The current speed V _n is calculated by _ref and equation (3) (S
3), linear motor 1 from the obtained target speed and current speed
The command value of the driver 10 of 4 is calculated (S4). The command value to the driver 10 is calculated by the following equation.

A _ct = K (V _ref −V _n ) ... (4) K is a feedback gain of the speed control system.

The command value thus obtained is output from the CPU 8 to the D / A converter 11 via the I / O control unit 7, and further D / A
The converter 11 converts the analog signal and outputs the analog signal to the driver 10. In this way, the linear motor 14 is driven (S
5), the optical head is speed-controlled so as to follow the target speed. When a series of speed control is completed when the speed control interrupt is input and the speed control interrupt is input again in the next cycle, similar processing is performed. In this way, the speed control is repeatedly performed at a predetermined cycle, and when the optical head reaches the target position in S2, the capture mode is set and the seek control is ended (S6). The setting of the capture mode is to set the light beam into the target track after the seek operation is finished and start the tracking control to set the light beam to the track following mode.

Next, the relationship between the position of the objective lens and the moving direction will be described with reference to FIG. First, FIG. 5A shows the positional relationship between the optical system 2 and the optical disc 1 when the optical system 2 is tilted in the moving direction (shifted from the center of the mechanism). When started, the tracking operation is held up to point Q as described above, so that the objective lens approaches the center thereof without causing track crossing. After that, the tracking operation is turned off at the point Q. At that time, since the linear motor 14 is accelerated and the objective lens is located at the center of the mechanism of the tracking actuator 12, track crossing by the tracking actuator 12 itself occurs. Absent. Therefore, in this case, the tracking error signal becomes as shown in FIG. 4E, and the light beam does not cross the track in the opposite direction to the moving direction, so that the tracks can be accurately counted.

On the other hand, when the optical system 2 is tilted in the direction opposite to the moving direction as shown in FIG. 5B, the Q point is farther from the mechanism center of the tracking actuator 12 than the P point, so that the tracking operation is performed. When is turned off, the optical system 2 moves in the direction Z toward the center of the mechanism. However, this moving direction Z is the moving direction F of the linear motor 14.
Since it is in the same direction as,
However, it is possible to count the tracks accurately as well.

FIG. 6 is a flow chart showing another embodiment of the present invention. In this embodiment, the tracking operation is turned on / off depending on whether the objective lens (optical system 2) is tilted in the moving direction or in the direction opposite to the moving direction. In FIG. 6, when the linear motor 14 is driven by the seek command (S1), the lens position signal of the lens position detector 15 is taken into the CPU 8 via the A / D converter 5, and the CPU 8 converts the lens position signal into the lens position signal. Based on this, it is determined whether the seek direction and the current lens position inclination direction are the same (S2). That is, the seek is performed from the current position of the optical disc 1 to the inner circumference side or the outer circumference side. At this time, the direction of tilt of the objective lens is checked from the lens position signal to determine whether the lens is tilted in the movement direction or the movement direction. And it is judged whether it is tilted in the opposite direction.

Here, if the tilt direction and the moving direction of the objective lens are the same as shown in FIG. 7A, the tracking operation is maintained (S) just as in the previous embodiment.
3), flag setting (S4), and lens position signal input to the lens position detector 15 (S5).
Then, based on the lens position signal, it is determined whether the position of the objective lens is not in the predetermined position, that is, the objective lens is the optical system 2
It is determined whether or not it is located at the center of the position (S6), and when it reaches a predetermined position, the tracking operation is turned off (S).
7). Even after the tracking operation is turned off, track count setting (S8), speed detection start (S9), and speed control setting (S10) are performed in exactly the same manner as in FIG. 2, and the seek operation is ended when the speed control flag ends ( S1
1). Here, in the case where the objective lens is tilted in the moving direction as described above, when the seek operation is started from the point P as shown in FIG. 7A, the tracking operation is held in the ON state up to the point Q. Therefore, the objective lens approaches the center without track crossing. When the tracking operation is turned off at the point Q, the linear motor 14 is accelerated at that time, and the objective lens is located at the center of the mechanism of the tracking actuator 12, so the track cross by the tracking actuator 12 itself does not occur. Therefore, in this case, the mistrack count does not occur, which is exactly the same as in FIG.

On the other hand, if the result of determination in S2 is that the tilt direction and the moving direction of the objective lens are opposite as shown in FIG. 7B, the tracking operation is immediately turned off (S1).
2) Then, a flag indicating that the seek operation has been started is set (S13). Then wait for a certain time (S1
4), a series of speed control such as track count setting (S8), speed detection start (S9), speed control setting (S10), etc. are performed. The waiting time in S14 may be the time during which the tracking actuator 12 moves about 1/4 track after it starts moving to the center of the mechanism.

In this way, when the tilt direction of the objective lens is opposite to the moving direction, at the point P at which the tracking operation is turned off as shown in FIG. Since they are separated from each other, when the tracking operation is turned off, the optical system 2 moves in the direction Z toward the center of the mechanism. Since this moving direction Z is the same as the moving direction F of the linear motor 14, track crossing in the opposite direction as shown in FIG. 9 does not occur. Further, in the previous embodiment, when the objective lens is more inclined, the objective lens may exceed the movable range, but in the present embodiment, when the inclination direction of the objective lens is opposite to the moving direction, FIG. Since the tracking operation is turned off at the point P as in (b), the problem that the objective lens exceeds the movable range does not occur.

[0029]

As described above, according to the present invention, after the seek operation is started, the tracking operation is maintained and the tracking operation is turned off when the lens position reaches a predetermined position, so that the track cross is performed in the direction opposite to the moving direction. Since it does not occur, there is an effect that the track count can be accurately performed and the seek operation can be accurately controlled.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical information recording / reproducing apparatus of the present invention.

2 is a flowchart showing a seek control operation of the embodiment of FIG.

FIG. 3 is a flowchart showing in detail the speed control operation of FIG.

FIG. 4 is a time chart showing signals at various parts during the seek operation of the embodiment of FIG.

5 is a diagram showing the positional relationship between the optical system and the disc when the tilt direction and the moving direction of the objective lens in the embodiment of FIG. 1 are different from each other.

FIG. 6 is a flowchart showing a second embodiment of the present invention.

7 is a diagram showing the positional relationship between the optical system and the disc when the tilt direction and the moving direction of the objective lens in the embodiment of FIG. 6 are different from each other.

FIG. 8 is a diagram for explaining seek control of a general recording / reproducing head.

FIG. 9 is a diagram for explaining a problem that a mistrack count occurs during seek of a conventional recording / reproducing head.

[Explanation of symbols]

 1 Optical Disc 2 Optical System 3 Tracking Error Detector 4 Focus Error Detector 5 A / D Converter 6 Digital Signal Processor 8 CPU 10 Driver 11 A / D Converter 12 Tracking Actuator 13 Focus Actuator 14 Linear Motor

Claims (3)

[Claims] 1. An objective lens for converging a light beam emitted from a light source onto an information recording medium, a first moving means for moving the objective lens in a tracking direction, and a position of the objective lens in the tracking direction is detected. Means to do
It has a means for controlling the tracking operation of the light beam by controlling the first moving means, and a second moving means for moving the optical head including the objective lens and the first moving means in the track crossing direction. In the optical information recording / reproducing apparatus, when the second moving means is driven to seek the optical head to a target position, the tracking control means is kept in the ON state after the driving of the second moving means is started. The optical information recording / reproducing apparatus is characterized in that the tracking control means is turned off when the detection value of the detection means reaches a predetermined value. 2. The optical information recording / reproducing apparatus according to claim 1, further comprising means for determining whether or not the tilt direction and the moving direction of the objective lens are the same, based on the detection value of the lens position detecting means. However, as a result of the judgment by the judging means, if the tilt direction and the moving direction of the objective lens are opposite, the tracking operation is turned off after the driving of the second moving means is started, and the optical information recording is characterized. Playback device. 3. The optical information recording / reproducing apparatus according to claim 1, wherein the tracking operation is turned off when the lens position detecting means indicates a value located at the center of the objective lens position. Information recording / reproducing device