JPS60624A - Tracking servo locking device - Google Patents

Abstract

PURPOSE:To realize an excellent special reproduction by exerting an electromagnetic force in the direction to block a simple harmonic motion for a prescribed period and increasing an apparent damping factor for the movement of optical components so as to eliminate the failure in the locking operation of a tracking servo loop. CONSTITUTION:Let a time be T1, from a point of time when an objective lens 3 is released from a control mechanism to 1/8-1/4 of the period T of the simple harmonic motion elapsed after the tracking servo loop is opened. Then a prescribed amount of electromagnetic force is exerted in a direction to block the simple harmonic motion for a period (t') less than T/4 from the time T1. The positional change of the objective lens 3 at that time has a small amplitude as shown in (a), then the maximum speed becomes small and the objective lens 3 exists always in the vicinity of a center axis of a driving device where the potential energy is small and the system is stable, thereby increasing remarkably the chance locking the tracking servo loop. Thus, the information read from a disc is attained surely in the period of T/4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical information reading device, and more specifically, to perform a suitable tracking servo loop pull-in operation in order to perform good interlaced playback. This invention relates to a tracking servo pull-in device.

[Background of the invention]

FIG. 1 is a perspective view showing an outline of an optical information reading device. In FIG. 1, 1 is a disk.

2 is an objective lens driving device, 3 is an objective lens, 4 and 5 are each objective lens support springs, 6 is a coil, 7 and 8 are each a magnetic yoke, and P is a converging light beam.

10 indicates a magnet.

Next, the operation will be explained. Convergent light 9 is irradiated onto the information recording track on the disc 1, which is an information recording medium, and information from the reflected light is read and reproduced through the objective lens 3. In order to accurately focus the light on the track, use an objective lens! 0 device 2 is used. In the objective lens drive device 2, the objective lens 3 is supported by an objective lens support spring 4.5, and the support springs 4, 5 are magnetized.10. The magnetic circuit consisting of the magnetic yoke 7.8 and the electromagnetic force generated by the current flowing through the coil 6 cause movement in the optical axis direction (Z direction) and the tracking direction (X direction).

Alternatively, convergent light 9 is driven in the tangential direction (Y direction) by means not shown so that each detected error signal becomes zero, and is emitted through the objective lens 3.
Accurately control the direction of irradiation.

By the way, when performing skip playback, which is a type of special playback, from the inner circumference to the outer circumference of the disc 1, the slide mechanism (not shown in the figure)
The tracking servo loop continues to be sent in the direction of A at a constant high speed, and at the same time, the tracking servo loop is opened and closed at a constant cycle, and information about disk 1 is intermittently read. Therefore, while the tracking servo loop is closed (reading information from the disk 1), the objective lens 3 is positioned closer to the inner circumference 1 of the disk 1 than the center axis of the three-dimensional drive device 2! ! It is located at l. Then, when the °C tracking servo loop is opened, the 3-dimensional lens 3 released from the servo control mechanism begins to freely oscillate. Figure 2 shows this in a diagram.

f1', Figure 2 is a graph showing changes in the position of the four-dimensional lens 3, where the horizontal axis is time and fa 1llll+ I'i
C indicates the positional displacement of the objective lens and the driving device 2 from the central axis. When the damping coefficient (ζ) in the free vibration is small, the movement of the objective lens 3 has a large amplitude.

It becomes a simple harmonic motion with less reduction of 11.

Next, the tracking servo loop is closed and the tracking servo loop is retracted in line 7:c. At this time, the point at which the tracking servo loop can be easily retracted is when the objective lens for the disk 1 This is the point in time when the relative velocity of 3 becomes small. In other words, the second
Specifically shown in the figure is the vicinity of points Pl sp and Ih. By the way, in the conventional method, even if F! When tracking servo pull-in is performed at the point in time, if a disturbance happens to enter the servo system during this operation, the objective lens 3 will not move in translation due to the influence of the disturbance, and the tracking servo pull-in will fail. was there. Moreover, if the retraction at that point fails, the next time when retraction can be easily performed is P, and 11 Until P2 arrives, that is, the time period of simple harmonic period T, information is read from disk 1. becomes impossible. In other words, in the conventional method, when the damping coefficient ζ is small, it is easily affected by external disturbances, and there are cases where the tracking servo loop fails to pull in, especially when it is difficult to control the vertical position of the objective lens, such as in a three-dimensional drive device. As a result, in video disc players and the like, the pitch of each picture becomes irregular during interlaced playback, causing picture disturbance.

[Purpose of the invention]

The present invention eliminates the drawbacks of the conventional method as described above.
Therefore, it is an object of the present invention to provide a tracking servo pull-in device that eliminates the failure of the tracking servo loop pull-in mu fg and is useful for realizing good special playback.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention has a method in which the optical component performing the simple harmonic motion is stopped by an optical component drive device.
By applying an electromagnetic force for a certain period of time in the direction of sustaining one simple harmonic motion, the apparent damping coefficient (ζ)' in the motion of the optical component VJK is calculated.
increased.

[Example of invention]

Hereinafter, as an embodiment of the present invention, a case will be described in which the present invention is applied to interlaced playback, which is one type of special playback. 7: "Oh, right away, Figure 3 is a graph showing changes in the position of the objective lens 3 in the embodiment of the present invention. The horizontal axis represents time, and the vertical axis represents the positional displacement from the central axis of the objective lens driving device 2. FIG. 3Cb) is a graph showing an example of the temporal timing of the electromagnetic force applied to the objective lens 3 in the embodiment of the present invention, where the horizontal axis shows time, and the vertical axis shows the applied electromagnetic force. .

Please refer to FIG. As mentioned above, in the interlaced playback, the objective lens driving device 2 is sent in the direction A by the slide mechanism (not shown) at a constant high speed, the tracking servo loop is opened and closed, and the information from the disk 1 is transferred. is read intermittently.

See Figure 3. Now, it is assumed that the tracking servo loop is opened and the time T is when a time period of 3 to 3 times the simple harmonic period T has elapsed since the objective lens 3 was released from the control mechanism. Next, for a period (t/) less than 4 from time T1, a constant electromagnetic force is applied in a direction to prevent simple harmonic motion. The positional change of the objective lens 3 at this time is expressed as shown in FIG. 3 (α).

In Fig. 3 (α), the amplitude is clearly smaller than in Fig. 2, so the maximum speed is also smaller, and the objective lens 3 is always located near the center axis of the most stable drive device with the smallest potential energy. Therefore, the chance of pulling in the tracking servo loop increases rapidly. Therefore, information can be reliably read from the disk 1' in 40 cycles.

〔Effect of the invention〕

According to the present invention, in the optical information reading device, there is no possibility that the tracking servo loop fails to pull in during special reproduction, etc., and information can be reliably read from the disc 1. In addition, in an optical component drive device, even if the behavior of the optical component and the braking coefficient (ζ) for convergent light are small, the apparent ζ can be increased, providing a greater degree of freedom in selecting the support for the optical system component. can give. In particular, it becomes possible to use a metal spring with little change over time for the support material, and the reliability of the drive device is also improved. Further, in the embodiment described above, the objective lens 3 was used as an optical component for moving the irradiation position of the convergent light 9 in the tracking direction, but the same effect can be obtained by using a reflecting mirror or the like.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an optical reading device, FIG. 2 is a graph showing changes in the position of an optical component (objective lens 3) in a conventional device, and FIG. FIG. 6 is a graph showing an example of the temporal timing of the electromagnetic force applied to the optical component according to the present invention. Explanation of symbols 1 Disc 2 . . . Objective lens drive device 3... Objective lens 4.5... Objective lens support spring 6... Coil 7, 8... Magnetic yoke 9... Convergent light 10... Magnet agent patent attorney Akira Takahashi
Husband number rfyJ

Claims (1)

[Claims] 1) A disk as an information recording medium, an optical component for reading and reproducing information by irradiating the information recording track on the disk with convergent light, and elastically supporting the optical component. a tracking servo that drives the elastic support means so that the convergent light accurately tracks the track;
and the supporting means supporting the optical component and a tracking servo device. In an optical information reading device comprising a drive device for moving the optical discs relative to the disk, the drive device drives the optical discs while turning on and off the servo device for interlaced playback or the like. When moving parts and servo devices relative to the disk,
The optical component, which has started free vibration by the elastic support means whose drive is canceled due to the servo device being turned from on to off, is stopped from free vibration after 4 to 4 hours of the vibration period T has elapsed. A tracking servo pull-in device characterized in that means is provided for applying an external force in the direction for a period of less than '/4T, and that the servo device is turned back on from off after the application of the external force.