JPS6215933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical head for use in an optical disk file device.

In general, in optical disk file devices, during playback operations, and especially in disk file devices with track following guide grooves and disk file devices that can be erased and rewritten, during both recording and playback operations, the center and rotation of the disk are Since it is common for there to be an eccentricity between the center of the beam and the center of the beam, special control means must be provided to ensure that the focusing spot follows and scans the track or guide groove.

In addition, when the recording medium moves vertically due to surface runout of the disk, etc.,
The condensing lens must follow this and the drive must be controlled so that the focal position of the light beam always matches the surface of the recording medium.

Optical heads conventionally used for this type of light beam control are equipped with a voice coil type drive mechanism to perform focusing tracking control in the optical axis direction of the condenser lens, and are designed to perform focusing control in the direction of the optical axis of the condenser lens. Regarding the direction, many cameras perform tracking follow-up control using a drive mechanism that rotates or translates a mirror, a lens, or both using a movable coil.

However, these drive mechanisms constitute a magnetic circuit to move the coil, and use a metal spring as a support member for the coil. has a configuration in which the servo follow-up control signal is fed back only during normal recording and reproducing operations. For this reason, when an optical disk file device is used as a search device and an optical head carriage is driven to position at high speed, when the carriage accelerates or decelerates, it is supported in a direction perpendicular to the optical axis of the condenser lens and parallel to the driving direction of the carriage. Unnecessary vibrations occur in a spring that has a function, and these unnecessary vibrations have disadvantages such as deteriorating positioning accuracy, making servo control impossible, and delaying search access time.

The present invention has been made to eliminate these drawbacks of the prior art, and its purpose is to enable feedback control even during high-speed search access, so that the tracking follow-up control means can always be kept in the closed servo system. An object of the present invention is to provide an optical head that can be controlled and driven in a loop to prevent unnecessary vibrations during acceleration and deceleration of a carriage.

In order to achieve such an object, the optical head according to the present invention is provided with means for detecting the amount of radial displacement of the recording medium of the condenser lens, and uses the output signal of the detection means as a feedback signal for tracking follow-up control. The device is configured to control and drive the means.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a focus adjustment drive mechanism, which has a function of driving the condenser lens 1a in the direction of the optical axis perpendicular to the plane of the paper so as to focus the light beam on the main surface of the disk-shaped recording medium. have. This focus adjustment drive mechanism 1 includes a mounting bracket 1b.
A spring 2 is attached through the
It functions as a support member for the lens optical axis drive mechanism 5, which is composed of a magnetic circuit 3 and a voice coil 4 inserted into the magnetic gap.
This lens optical axis drive mechanism 5 drives the focus adjustment drive mechanism 1 in the direction indicated by the arrow AB in the figure parallel to the plane of the paper, thereby moving the condenser lens 1a to record a disk shape perpendicular to the optical axis. It has the function of driving the medium in the radial direction. Further, reference numeral 6 denotes a displacement amount detection section, which has a function of detecting the amount of displacement of the condensing lens 1a in the recording medium radial direction by the lens optical axis drive mechanism 5 and outputting it as an electric signal. Here, the displacement detection section 6 uses the surface of the mounting bracket 1b as the surface to be measured, and the sensor diameter is 9.1 mmφ, and the output linearized and corrected by a linear analyzer (not shown) exhibits displacement-dependent characteristics as shown in FIG. The distance between this displacement detection probe and the surface of the mounting bracket 1b is Lo when the lens optical axis drive mechanism 5 is in a mechanically stable state. ≒0.7mm, and linear area 2・ΔL of displacement output is ±
It is set so that a thickness of about 250 μm can be obtained.

Next, the lens optical axis drive mechanism 5 having the above configuration is
The servo control operation will be explained using the block diagram shown in FIG.

First, during normal recording and playback, switch SW ₁ is set to the B side, and the signal from the tracking error detector 7, which detects the deviation of the focal spot from the signal track, is fed back to create a servo system closed loop, and the disc shape is adjusted. Servo control is performed according to the radial movement of concentric or spiral signal tracks on the recording medium. In addition, in FIG. 3, 5a indicates a drive amplifier.

On the other hand, when an access command is issued to perform a high-speed search access operation, immediately turn switch SW ₁ to A.
side, the output signal of the displacement detection section 6 is fed back so that the command voltage Ei corresponds to the command displacement Xi, a closed loop of the servo system is created, and the linear region of the displacement output characteristic shown in Fig. 2, C. -D
The servo locks to the commanded position between. This results in
For example, unnecessary vibrations of the lens optical axis drive mechanism 5 caused by impacts during acceleration and deceleration of the optical head carriage can be eliminated.

In addition, in order to determine the timing for switching to the recording/reproducing operation after the search access operation is finished and the positioning of the optical head carriage is completed, in this embodiment, marks recorded in the same radial direction on the disk-shaped recording medium are used. Utilizes the output synchronization signal pulse. In this case, there is an eccentricity between the center of the recording medium and the center of rotation, and even if the signal track moves several hundred μm in the radial direction, the synchronous signal pulse generation mark will hardly move in the radial direction. is equal to zero. Therefore, when the positioning interval of the optical head carriage and the signal track pitch interval are equal, the lens optical axis drive mechanism 5 is servo-locked with the command displacement Xi = 0, and after the search access operation is completed, the synchronization signal pulse from the mark is Switch SW1 as a trigger
By switching the signal to the B side, a desired signal track can be accessed. Thereafter, control can be performed by feeding back the signal from the tracking error detector 7 so as to follow the eccentricity of this signal track.

Furthermore, when the positioning interval of the optical head carriage is larger than the signal track pitch interval, for example, the positioning interval of the optical head carriage is Pc=40.
μm, and when the signal track pitch interval is Pt = 2 μm, during high-speed search access operation, the optical head carriage performs coarse movement access at a pitch of 40 μm, and the lens optical axis drive mechanism 5 performs coarse movement access at a pitch of 2 μm, depending on the desired access distance ΔX. and fine movement access at the same time. That is, when the coarse movement access amount of the optical head carriage is n pitch and the fine movement access amount of the lens optical axis drive mechanism 5 is m pitch, the desired access distance is ΔX=Pc・n+
Access is driven so that Pt·m=40n+2m (|m|<Pc/Pt). For example, ΔX=750μm
For this access, coarse movement of the carriage by n = 19 pitches and fine movement of the lens optical axis drive mechanism 5 by m = -5 pitches are performed at the same time, resulting in 40 x 19 + 2 x (-
5) = 750 (μm).

Therefore, in such a case, the command displacement Xi for the lens optical axis drive mechanism 5 is set at Pt, which is 2 μm in the above example, and is adjusted according to the amount of access to the desired signal track. command displacement
Xi, in this example Pt・m=2×(-5)=-10(μ
If the command voltage Ei is applied such that When positioning is completed, a desired signal track can be accessed by switching SW1 to the B side using a synchronizing signal pulse as a trigger.

In this way, during the positioning access drive of the optical head carriage, the lens optical axis drive mechanism 5 also performs fine servo control drive for track access at the same time, and the desired signal is generated on the same radius where no movement occurs in the disk radial direction. Since the track is captured, it is possible to eliminate track access errors caused by eccentricity of the signal track, thereby increasing track access accuracy and shortening track access time.

In the above-mentioned embodiment, only the case where the displacement amount detection section 6 is constituted by a capacitance type minute displacement detection probe has been described, but it may be configured by an eddy current type minute displacement detector or a magnetoresistive type minute displacement detection probe. A similar effect can be obtained by using a detector, an optical minute displacement detector, or the like.

Furthermore, in the above-described embodiment, only the case where marks for generating synchronizing signal pulses were provided on the same radius of the disk-shaped recording medium was explained, but if the disk is not to be reloaded after being removed, Even if a synchronizing signal pulse generation mark is provided on the same radius on an encoder or the like directly connected to a motor that rotationally drives this disk, the same effect as described above can be obtained.

As explained above, according to the optical head according to the present invention, by constantly controlling the lens optical axis drive mechanism for tracking follow-up control using a servo system closed loop, unnecessary vibrations due to impacts during acceleration and deceleration of the optical head carriage are generated. can be removed, or even if they occur, they can be kept to an extremely small level. Therefore, when accessing the optical head carriage for positioning, the access time can be shortened and the positioning accuracy can be improved, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a displacement output characteristic diagram of the displacement amount detection section, and FIG. 3 is a block diagram showing the servo control operation of the lens optical axis drive mechanism. DESCRIPTION OF SYMBOLS 1... Focus adjustment drive mechanism, 1a... Condenser lens, 1b... Mounting bracket, 2... Spring, 3... Magnetic circuit, 4... Voice coil, 5... Lens optical axis drive mechanism, 6... Displacement amount detection section, 7... Tracking error detector.

Claims (1)

[Claims] 1. An optical head mounted on an optical head carriage for high-speed positioning for use as a retrieval device for an optical disk file device that records and reproduces signals concentrically or spirally on a disk-shaped recording medium. a condensing lens for condensing light onto a medium as a condensing spot; a focusing drive mechanism for driving the condensing lens in the direction of its optical axis; A lens optical axis driving mechanism for driving in the radial direction of a disk-shaped recording medium, and a detection means for detecting the amount of displacement of the condensing lens in the radial direction, when the optical head carriage performs a high-speed search access operation, An optical head characterized in that the lens optical axis drive mechanism is controlled and driven using the output signal of the detection means as a feedback signal.