JP2938475B2 - Optical head positioning method for optical disk recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a reference position at the time of assembling an optical head in an optical disk recording / reproducing apparatus.

2. Description of the Related Art In an optical disk recording / reproducing apparatus, an optical head accesses an arbitrary track on a disk. For this purpose, the optical head needs to know a reference position of a track as an initial setting of access. Hereinafter, a conventional example of the access operation will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is an explanatory diagram for explaining an access state of the optical head, and FIG. 5 is an explanatory diagram showing an outline of a configuration of a general optical disk recording / reproducing apparatus. Referring to FIG. 1, reference numeral 1 denotes an optical disk which is rotated by a spindle motor 2. Reference numeral 3 denotes an optical head which focuses a light beam on the optical disk 1 by an objective lens 4. The objective lens 4 is moved in the horizontal direction by an actuator 5 to select a track on the optical disc 1. Further, the optical head 3 is largely moved in the track direction by the stepping motor 6 and can access an arbitrary track. Incidentally, when the optical head 3 is moved by the stepping motor 6, as shown in FIG. 4, the optical head 3 itself does not move finely but moves at intervals of, for example, 100 tracks.
When an arbitrary track is accessed, an access procedure is determined such that the position of step 1 of the stepping motor 6 accesses 199 tracks from 100, and the position of step 2 accesses 200 to 299 tracks. At this time, to access an arbitrary track, the optical head 3 is moved to the position of the track 150 or 250, 350 by the stepping motor 6 as shown in FIG.
The objective lens 4 moves by jumping the track by the actuator 5 within the range of the track and accesses an arbitrary track.

In the above configuration, the optical head 3 is moved at an interval of 100 tracks by the stepping motor 6, but if the initial position is deviated, for example, the objective lens 4 is moved to the track 18
Move to position 0, and as a result, track access is +20,-
The lens will have to move 80 tracks, and will have to move more than necessary in the negative direction. As a result, the number of track jumps increases and the access time increases, or the objective lens 4 moves more than necessary, causing the optical axis to shift and the quality of the reproduced signal to deteriorate. Therefore, the objective lens 4 is connected to the actuator 5
In the neutral position, the optical head 3 and the stepping motor 6 must be moved simultaneously to adjust the objective lens 4 to the position of the track 150. However, in practice, the test disk may be rotated and eccentric during the assembly adjustment of the optical disk recording / reproducing apparatus. At one moment, the test disk is located at the midpoint between the tracks 100 and 200, which is the range of step 1. Even if it could be adjusted, it would not be at the intermediate point at the next moment.By repeating the adjustment and reading the track position many times, the objective lens would be almost at the intermediate point in consideration of the eccentricity of the disk. 4 can be brought, but there is a big problem that it takes a very long time to adjust and the efficiency is high.

Therefore, an object of the present invention is to provide a method for simply and accurately adjusting a reference position in order to solve the above problems.

Means for Solving the Problems The present invention monitors the drive current of an actuator for driving the objective lens through a low-pass filter after accessing an intermediate track of the objective lens, and obtains the obtained drive current. The position of the stepping motor is adjusted so that the positive and negative amplitudes of the sine wave signal due to the rotation eccentricity of the disk are equal while the servo is applied.

In the above method, even if the objective lens accesses the intermediate track, if the initial position of the stepping motor is shifted, the objective lens is not always located at the center point of the actuator, so that the drive current of the actuator maintains that position. Current flows in one direction. By simultaneously moving the stepping motor and the optical head while monitoring this current, the current value is adjusted to the position where the current value flows by the same amount, so that the objective lens is near the center of the actuator and at the middle position of the track. Thus, the substrate position of the optical head can be easily adjusted.

Embodiment One embodiment of the present invention will be described with reference to FIGS.
FIG. 1a is an explanatory diagram illustrating a state in which a reference position adjusting device for an optical head is connected to an optical disk recording / reproducing device;
FIG. 1b is a diagram showing an actuator drive current at the time of unadjustment, and FIG. 1 is a diagram explaining an actuator drive current at the time of adjustment.

The same parts as those of the prior art will be described using the same reference numerals.
The objective lens 4 of the optical head 3 that performs the rough feed for each track is a neutral position where no current flows to the actuator 5 for moving the optical head 3, and is an intermediate point between the tracks 100 and 200 which is an access range at the step position. Track 15
Must be at 0. However, if the initial adjustment has not been made, the track 150 is not necessarily located on the track 150. Therefore, the relative positions of the stepping motor 6 and the optical head 3 are simultaneously moved so that the relative positions do not change, and the initial adjustment is performed. Regardless of the position of the objective lens 4, the actuator 5 is driven and the track is jumped by the track.
Come to 150 and apply servo to keep the track position. At this time, the drive current of the actuator 5 is monitored at both ends of the series resistor 8 with an oscilloscope 9 so that the position of the objective lens 4 on the actuator 5 can be determined. That is, the track 1 moves by plus or minus several tens of μm in synchronization with the rotation of the motor 2 due to the eccentricity of the disk 1, but a current as shown in FIG. If the objective lens 4 is not near the neutral position of the actuator 5, the drive current has a DC offset as shown in FIG. Accordingly, by moving the stepping motor 6, the position of the stepping motor is adjusted so that the drive current of the actuator 5 does not have a DC offset as shown in FIG. , The access to the tracks 100 to 200 can be accessed with substantially the same amount of track jump in both the plus and minus directions, and the position setting of the optical head 3 is optimized.

Another embodiment will be described with reference to FIGS.
FIG. 2 is a diagram showing a circuit configuration, and FIG. 3 is a diagram showing a monitor signal of an actuator drive current in the circuit of FIG. 2 using a filter. The same parts as those in the embodiment of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. According to the figure, the present embodiment is similar to the embodiment of FIG. 1 except that a filter circuit 10 composed of a coil, a capacitor and a resistor is connected to a series resistor 8 of an actuator 5 and its output is viewed with an oscilloscope 9. Make adjustments in the manner described above. 1, the operating current of the actuator 5 includes a signal for following the eccentricity of the disk, a signal for following the acceleration of the disk itself, and other noise components. Although the signal has a lot of noise components, the purpose is to adjust with a signal of the basic frequency synchronized with the eccentricity, so that the adjustment accuracy is deteriorated with the signal as it is. In this embodiment, by using the filter circuit 10, the signal becomes almost only an eccentric fundamental frequency as shown in FIG. 3, and the accuracy of adjustment can be improved. For example, if the disk speed is 1800
At RPM, the fundamental frequency of the eccentricity is 30 Hz, so if the filter constants are L = 300 mH, C = 90 μF, and R = 10Ω, noise components other than 30 Hz will be 1/10 or less and the alignment accuracy will be about 5 μm was possible. This is about 20 μm when a filter is not used, which may be practical depending on the optical disk device, but is indispensable in a drive having a high recording density and requiring higher accuracy.

Effect of the Invention As described above, the adjustment method according to the method of the present invention enables more accurate adjustment with a simple configuration, and the conventional method requires at least 10 times of alignment and repeated position measurement. However, almost necessary positioning can be performed by one adjustment.

[Brief description of the drawings]

FIG. 1a is an explanatory diagram illustrating a state where an optical disk recording / reproducing device is connected to a reference position adjusting device for an optical head according to the present invention, and FIG. 1b is a diagram illustrating an actuator drive current when no adjustment is performed. FIG. 1c is a diagram for explaining an actuator driving current at the time of adjustment, and FIG. 2 is a circuit diagram for explaining another embodiment, in which a reference position adjusting device is connected to an optical disk recording / reproducing device. FIG. 3 is a diagram showing monitor signals of the actuator drive current in FIG. 2, FIG. 4 is an explanatory diagram for explaining an access state of the optical head, and FIG. 5 is a diagram of a general optical disk recording / reproducing apparatus. FIG. 3 is an explanatory diagram showing a schematic configuration. 3 ... optical head, 4 ... objective lens, 5 ... actuator, 6 ... stepping motor.

Claims (1)

(57) [Claims] After accessing an intermediate track of an objective lens, a drive current of an actuator for driving the objective lens is monitored via a low-pass filter, and a sinusoidal rotation eccentricity of a disk obtained thereby is obtained. A method for positioning an optical head of an optical disk recording / reproducing apparatus, wherein the position of a stepping motor is adjusted so that the positive and negative amplitudes of a wave signal are equalized while a servo is applied.