KR100200344B1 - Focus pull-in method in optical system - Google Patents

Abstract

The present invention relates to a focus pull-in method in an optical system, comprising: turning on the optical system, kicking the sled to the innermost position of the disc, The microcomputer reads the FEpk value, the microcomputer determines the presence of the disk, the system stops the system if there is no disk, and the focus pull-in mode if the disk exists. The speed of the focus drive to a certain point, the speed of the focus drive to a certain ratio, and the servo-on mode. The focus pull-in can always operate stably. To a forks pull-in method in an optical system.

Description

Focus Pull-In Method in Optical Systems

1 is a waveform diagram of signals used in a conventional focus pull-in method.

2 is a waveform diagram of signals used in a focus pull-in method in an optical system, according to an embodiment of the invention.

3 is a flow diagram illustrating a focus pull-in method in an optical system, according to an embodiment of the invention.

The present invention relates to a focus pull-in method in an optical system, and more particularly, to a focus pull-in method in an optical system in which focus pull-in can always operate stably. will be.

Optical systems such as Compact Disc Player (CDP) and Laser Disc Player (LDP) are used to precisely irradiate the disc with Spindle Servo and Laser Beam to rotate the disc. Focus Servo, Tracking Servo to accurately track Data Tracks on disk, and Sled Servo to drive Pick-up consist of.

Among them, the focus servo part is divided into a focus pull-in and a focus servo. A focus pull-in refers to an operation of moving a focus actuator to a position where a focus servo is available.

References include the Sony Data Book (Compact Disc 1990 Edition 210Page).

Hereinafter, a conventional focus pull-in method will be described with reference to the accompanying drawings.

1 is a waveform diagram of signals used in a conventional focus pull-in method.

As shown in FIG. 1, in the conventional focus pull-in method, the focus error signal 1 and the focus error signal FE 2 and the focus OK signal 3 are increased. At the zero cross point of the FE signal 2, a Focus Zero Cross (FZC) signal 4 having an inverted polarity is generated. At this time, the servo checks the FOK signal 3 first, and when the FOK signal 3 changes from ″ Low ″ to ″ High ″, the servo checks the FZC signal 4 thereafter. At this time, the FOK signal 3 still enters the focus servo at the moment when the FZC signal 4 changes from "High" to "Low" while maintaining "High".

However, the above-described conventional technique is to change the focus pull-in mode to the focus servo mode at the point where the FZC signal 4 changes from ″ High ″ to ″ Low ″ (point C in FIG. 1). There is a problem in that it becomes unstable and the inclination of the focus drive signal 1 is severe, which makes it difficult to proceed to the focus pull-in mode.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problem, and provides a focus pull-in method in an optical system in which the focus pull-in mode can be operated stably by adjusting the speed of the focus drive signal. It is to.

As a means for achieving the above object, the configuration of the present invention,

Turning on the power of the optical system,

Kicking the sled to the innermost position of the disc,

Reciprocating the focus drive to the disc surface to detect a focus error maximum value FEpk,

Determining the presence or absence of a disc by determining a degree of a focus error (FE) value generated;

Stopping the system if there is no disk in the above step, and proceeding to the focus pull-in mode if the disk is present;

Determining the focus error maximum value FEpk / 2 using the focus error maximum value FEpk detected in the above step, and focusing the drive at the maximum speed up to the focus error maximum value FEpk / 2; ,

Continuously detecting the focus error value FE, and determining a ratio of the focus error value to the maximum value FEpk;

Driving the focus drive speed at a speed corresponding to the determined ratio with respect to the maximum speed corresponding to the focus error maximum value FEpk;

Determining whether the detected focus error value FE is zero;

If the focus error value is zero, the process proceeds from the focus pull-in mode to the servo on mode.

By the above configuration, the most preferred embodiment that can be easily carried out by those skilled in the art with reference to the present invention will be described in detail with reference to the accompanying drawings.

3 is a flow diagram illustrating a focus pull-in method in an optical system, according to an embodiment of the invention.

As shown in Figure 3, the focus pull-in method in an optical system is

Turning on the power of the optical system (S10),

Kicking the sled to the innermost position of the disk (S20),

The microcomputer reads the FEpk value (S30),

The microcomputer determines whether a disk exists (S40),

In step S40, if there is no disk, stopping the system (S45);

In step S40, if there is a disk, a focus pull-in mode is performed (S50);

Speeding the focus drive to the FEpk / 2 point (S60);

Reducing the focus drive speed by half (S70),

Proceeding to the servo on mode (S80),

Determining whether a focus drop has occurred (S90),

If the focus drop has not occurred in the step (S90), the step of continuing the servo on mode (S80),

If the focus drop occurs in the step S90, moving to the position of the focus drive changed from the focus pull-in mode to the servo-on mode (S100);

After moving the position in the step (S100), and proceeds to the focus pull-in mode again (S50).

With the above configuration, the operation according to the embodiment of the present invention is as follows.

The system used in the embodiment of the present invention was implemented by using a digital servo having a RAM (Random Access Memory), and FIG. 2 shows a focus pull in an optical system according to an embodiment of the present invention. A waveform diagram of the signals used in the method. Here, 1 is a focus drive signal, 2 is Focus Error (FE) signal, 3 is Focus OK (FOK) signal, 4 is Focus Zero Cross (FZC) signal, and C point is FZC signal (4) Indicates the point of change from ″ to ″ Low ″.

Operation begins by first turning on the power of the optical system (S10).

When power is applied to the optical system, after the sled is kicked (S20) to the innermost position of the disc, the focus actuator is moved at a high speed (approximately 4-8 times faster than the speed of focus pull-in mode). Reciprocate once to the surface, i.e. near the target position which is the focus pull.

Here, the round tripping of the focus actuator near the target position, which is the focus pool, is primarily for detecting the focus error FE to be detected at the time of the focus pull as shown in FIG. 2 to obtain the maximum focus error value FEpk.

The maximum focus error value FEpk is half of the sum of the maximum value on the positive side and the maximum value on the negative side in FIG. 2.

The maximum focus error value FEpk thus obtained is stored in the servo, and the microcomputer reads this FEpk value (S30) to determine whether the microcomputer is present or not (S40). In addition to the microcomputer, it can be determined by the servo. If the FEpk value is greater than or equal to the set value, it is determined that there is no disk.

If the disk does not exist, the microcomputer stops the system (S45). If the disk exists, the microcomputer proceeds to the focus pull-in mode (S50).

Since the FEpk value is already known at the time of focus pull-in mode, the focus drive speed is initially increased by using this data (section A of FIG. 2).

The target point for the microcomputer to speed up the focus drive is the point at which half the FEpk is detected. Here, the microcomputer continuously detects the FE value during the progress of focus pull-in.

Then, the microcomputer determines how much the ratio of the detected FE value becomes less than the FEpk / 2 value, and drives the actuator at the resultant speed corresponding to the product of the determined ratio and the maximum speed.

This determination continues until the focus pull-in is completed, that is, until the focus zero cross signal, which is point C in FIG. 2, is detected.

Therefore, from the point FEpk / 2, the focus drive speed is reduced to 1/2 (section B of FIG. 2) from the present time (S70), and the stability when the change from the focus pull-in mode to the servo-on mode (S80) proceeds (S80). Increase

At this time, the position of the focus drive converted from the focus pull-in mode to the servo-on mode is memorized, and it is determined whether or not a focus drop that may occur during play is generated (S90). If not, continue to the servo on mode (S80), if a focus drop has occurred, immediately move the focus actuator to the stored point, that is, the position of the focus drive changed from the focus pull-in mode to the servo on mode ( S100), the process proceeds to the focus pull-in mode again (S50).

Thus, the focus pull-in speed after the focus drop is improved.

As described above, in the embodiment of the present invention, the speed of the focus drive is adjusted to increase the stability of the system when the transition from the focus pull-in mode to the servo-on mode, and the focus pull-in can always operate stably. It is possible to provide a focus pull-in method in an optical system having an effect.

This effect of the present invention can be used in the fields of Compact Disc Player (CDP), Laser Disc Player (LDP), and Digital Video Disc (DVD).

Claims (4)

Powering on the optical system, kicking the sled to the innermost position of the disk, reciprocating the focus drive to the disk surface to detect the focus error maximum value FEpk, Determining the presence of a disc by determining the degree of the FE) value, stopping the system if there is no disc in the above step, proceeding to the focus pull-in mode if there is a disc, and the focus error detected in the step. Determining the point of focus error maximum value FEpk / 2 using the maximum value FEpk, and focusing the drive at the maximum speed to the point of focus error maximum value FEpk / 2; and focus error value FE. To determine the ratio of the detected focus error value to the maximum value FEpk, and to set the focus drive speed to the focus error maximum value FEpk. Driving at a speed corresponding to the determined ratio with respect to a corresponding maximum speed; determining whether the detected focus error value FE is zero; and if the focus error value is zero, the servo on mode in the focus-pull mode. Focus-in method in an optical system, characterized in that the step of proceeding to. The method of claim 1, further comprising: determining whether a focus drop has occurred after the step of proceeding to the servo on mode; and if the focus drop has not occurred at the step, continuing the servo on mode; If a focus drop has occurred in the step, moving to the position of the focus drive changed from the focus pull-in mode to the servo-on mode, and after moving the position in the step, proceeding to the focus pull-in mode again. And a focus pull-in method in an optical system. The method of claim 1, wherein a predetermined point in the step of increasing the focus drive speed to a predetermined point is an FEpk / 2 point. 2. The method of claim 1, wherein the ratio in reducing said focus drive speed to a constant ratio is one half.