KR19990026835A - How to adjust the focus bias of the optical disc player - Google Patents

Abstract

The present invention relates to a method for adjusting the focus bias of an optical disc player by using a table in which a focus bias value capable of minimizing the jitter amount is stored for each predetermined range of jitter amount, and detecting the jitter amount of the optical disc player. First step; A second step of searching the table for a focus bias value corresponding to the amount of jitter detected in the first step; And a third step of adjusting the focus bias of the optical disc player to the focus bias value retrieved in the second step, thereby reducing the time required for focus bias adjustment. It can be effected.

Description

How to adjust the focus bias of the optical disc player

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc player, and more particularly, to a focus bias adjustment method of an optical disc player capable of adjusting a focus bias value in correspondence with the amount of jitter detected during reproduction of an optical disc.

In general, optical disc players include compact disk players (CDPs), laser disk players (LDPs), compact disk graphic players (CDGPs), and video compact disk players (VCDPs). video compact disk player) has been developed and widely used. Also, recently, a digital video disk (DVD) using MPEG-2 moving picture compression technology and a digital video disk player for playing the same have been developed. It can record and play back gigabytes (GB) of data including moving images on a 12cm optical disc such as a CD, and it is also designed to be compatible to play current CDs and VCDs.

Such an optical disc player has been developed to record and reproduce image and audio data on a semi-permanent optical disc as audio and video media have developed.

Such an optical disc player reproduces an image and / or audio recorded on an optical disc and outputs it through a screen and / or a speaker, and has a higher signal-to-noise ratio than conventional image and / or audio reproducing apparatus, resulting in better image quality and / or Or it can reproduce the signal with sound quality, it does not generate noise due to irregular reproduction and modulation, very low distortion, no ghost and random access, so it is rapidly developed and widely distributed. There is a trend.

On the other hand, in order for the optical disc player to accurately read the program recorded on the optical disc, the signal surface of the optical disc should be located within the depth of focus of the laser beam irradiated by the optical pickup. I did the same function. Here, the focus bias means adjusting the signal plane of the optical disc to be located within a constant depth of focus of the laser beam of the optical pickup unit. The focus servo is an optical disc in which the signal plane of the optical disc is located within a constant depth of focus of the laser beam of the optical pickup unit. This means adjusting the focus to correspond to the minute variation.

Hereinafter, referring to FIG. 1 in which the waveforms of the original signal and the reproduction signal recorded on the optical disc are shown, when the focusing bias is correctly adjusted, as shown in FIG. 1A, the conversion point of the reproduction signal and the original signal is located on the time side. Will match.

However, if the focus bias is not correctly adjusted, as shown in Fig. 1B, since the signal level of the reproduction signal is detected small, a conversion point position error [Delta] t occurs between the conversion point of the reproduction signal and the original signal. This error is commonly referred to as jitter.

Therefore, in order to reduce jitter in the related art, after detecting the amount of jitter corresponding to each focus bias value while changing the focus bias value, the focus bias is adjusted to the focus bias value when the detected jitter amount is minimum. .

However, in such a conventional method, since each of the amount of jitter must be detected while adjusting the focus bias value in order to find the focus bias value that minimizes jitter, the time required to adjust the focus bias value is reduced. There was a big problem with consumption.

Accordingly, the present invention has been made in view of the above-described problems of the related art, and an object of the present invention is to change the focus bias value and to detect the value of the jitter amount without minimizing the jitter amount. The present invention provides a method of adjusting a focus bias of an optical disc player that can adjust a focus bias value that can minimize jitter.

In order to achieve the above object, in the present invention, in the method for adjusting the focus bias of the optical disc player using a table in which a focus bias value capable of minimizing the jitter amount is stored for each predetermined range of jitter amount, A first step of detecting the jitter amount of the optical disc player; A second step of searching the table for a focus bias value corresponding to the amount of jitter detected in the first step; And a third step of adjusting the focus bias of the optical disc player to the focus bias value retrieved in the second step.

1 is a waveform diagram showing a reproduction signal and an original signal of an optical disc to explain jitter generation;

2 is a block diagram of hardware for implementing a method of adjusting the focus bias of an optical disc player according to the present invention;

3 is a detailed flowchart illustrating a focus bias adjustment method of an optical disc player according to the present invention;

* Explanation of symbols for main parts of the drawings

D: optical disc 100: optical pickup

200: jitter amount detection unit 300: system control unit

400: storage unit 500: focus bias adjustment unit

The above and other objects and advantages of the present invention will become more apparent from the preferred embodiments described below with reference to the accompanying drawings.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a block diagram of hardware for implementing the method of adjusting the focus bias of the optical disc player according to the present invention. The optical pickup unit 100, the jitter amount detection unit 200, the system control unit 300, and the storage unit 400 are shown in FIG. And a focus bias adjustment unit 500, and each function thereof is as follows.

First, the optical pickup unit 100 includes an objective lens and an actuator coil (not shown), and irradiates a laser beam having a predetermined power level to the optical disk signal surface, and then is reflected from the signal surface of the optical disc. The RF signal is detected from the reflected light and provided to the jitter amount detector 200.

The jitter amount detector 200 detects the jitter amount from the RF signal provided by the optical pickup unit 100 and provides the jitter amount to the system controller 300.

The system controller 300 searches the table stored in the storage 400 and controls the focus bias adjuster 500 to adjust the focus bias to a focus bias value corresponding to the jitter amount provided by the jitter amount detector 200. do.

The storage unit 400 stores a table of focus bias values capable of minimizing the jitter amount for each predetermined range of the jitter amount. At this time, the focus bias value that can minimize the jitter amount for each jitter amount may be detected through a number of experiments in the design of the optical disc player system.

The focus bias adjustment unit 500 is a kind of bias voltage supply unit, and by providing the predetermined bias voltage to the actuator coil provided in the optical pickup unit 100 under the control of the system control unit 300, the focus bias adjustment unit 500 may be used. Focus bias adjustment is made to match the focus in the focusing error signal.

Hereinafter, a process of implementing the focus bias adjustment method of the optical disc player according to the present invention in hardware including the component members that perform the above-described function will be described with reference to FIG. 3.

3 is a detailed flowchart illustrating a focus bias adjustment method of an optical disc player according to the present invention.

First, when the optical disc D is mounted in the optical disc player (S10), the system control unit 300 controls the optical disc player to play the optical disc mounted in the optical disc player for a predetermined time in order to detect the jitter amount of the optical disc player. do.

The optical disc player reproduces the optical disc for a predetermined time under the control of the system control unit 300, reads the RF signal from the optical disc, and provides the read RF signal to the jitter amount detecting unit 200. (S 20)

The jitter amount detection unit 200 detects the jitter amount by the RF signal provided from the optical disc player, and provides the system control unit 300 with information about the detected jitter amount Jn. (S30)

The system control unit 300 refers to the bias value compared to the jitter amount stored in the storage unit 400, and the bias value Fbn for the jitter amount Jn equal to the jitter amount Jn detected by the jitter amount detection unit 200. After searching for, the control of the focus bias adjustment unit 500 to perform the bias adjustment to the searched bias value (S 40). At this time, in the storage unit 400, a bias value for minimizing the jitter amount for each jitter amount range is stored in a table form, and the bias value compared to the jitter amount is stored as shown in Table 1 below by an experiment. Will be.

Jitter amount (Δt) Focus bias value (V) J0 to J1 Fb! J1 to J2 Fb2 J2 to J3 Fb3 J3 to J4 Fb4 -------- ---------

The focus bias adjusting unit 500 includes the optical pickup 100 with the focus bias value Fbn retrieved from the storage 400 by the system controller 300 in operation S 40 by the control of the system controller 300. To the actuator coil (not shown). (S50)

Therefore, the actuator coil (not shown) can reduce the amount of jitter by performing the focus servo with the objective lens (not shown) near or far from the signal surface of the optical disc in response to the bias value. have.

That is, if the jitter amount Jn detected by the jitter amount detection unit 200 in step S 30 is a value between the jitter amount ranges in Table 1, the system controller 300 determines the jitter amount in Table 1 stored in the storage unit 400. After searching for the bias value Fb2 corresponding to J1 to J2, the focus bias adjusting unit 500 is controlled to adjust the focus bias value to Fb2, and the focus bias adjusting unit 500 controls the Fb2 value by the control of the system controller 300. To an actuator coil (not shown) provided in the optical pickup unit 100.

The actuator coil (not shown) corresponds to the Fb2 value supplied from the focus bias adjustment unit 500, thereby performing the focus servo while keeping the objective lens (not shown) close to or far from the signal surface of the optical disk. Since the focal point of the actual objective lens and the focal point of the focus error signal coincide, the jitter amount can be reduced.

As described above, according to the present invention, the focus bias value which can minimize the detected jitter amount is directly searched without detecting jitter amount caused by the change of the focus bias value, and the focus of the optical disc player is detected by the detected bias. By adjusting the bias, there is an effect that the time required for adjusting the focus bias can be shortened.

Claims (1)

A method of adjusting the focus bias of an optical disc player using a table in which a focus bias value capable of minimizing the jitter amount is stored for each predetermined range of jitter amount, A first step of detecting the jitter amount of the optical disc player; A second step of searching the table for a focus bias value corresponding to the amount of jitter detected in the first step; And a third step of adjusting the focus bias of the optical disc player to the focus bias value retrieved in the second step.