KR19980085468A - Jitter amount measuring device of optical disk system - Google Patents

Abstract

The present invention relates to a jitter amount measuring apparatus of an optical disc system for detecting and displaying an amount of jitter for an RF signal corresponding to data recorded on an optical disc, the apparatus comprising: nT (n: integer, T: 1 channel bit period) from the RF signal A filter unit for detecting and outputting a signal to be output; A waveform shaping unit shaping a signal corresponding to the nT output from the filter unit and converting the signal into a square wave pulse; An edge detector detecting a rising edge and a falling edge of the square wave pulse output from the waveform shaping portion; A signal corresponding to nT by detecting a period of the square wave pulse based on the rising edge and the falling edge of the square wave pulse detected by the edge detector, comparing the detected period of the square wave pulse with a predetermined period; A control unit for measuring the amount of jitter for the controller; And an OSD unit for displaying the jitter amount measured by the controller on a screen through a monitor.

Description

Jitter amount measuring device of optical disk system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring jitter of an optical disc system. In particular, the jitter amount of an optical disc system that can measure and display the jitter amount, which is one of the items for evaluating the stability of the servo of the optical disc system, can be displayed through a monitor. It relates to a measuring device.

With the development of audio and video media, optical disc players have been developed for recording and reproducing video and audio data on semi-permanent optical discs.

Such an optical disc player reproduces video and audio recorded on an optical disc and outputs it through a screen and a speaker, and has a higher signal-to-noise ratio than conventional video and audio playback devices, and thus can reproduce signals with better image quality and sound quality. Noise is not generated by irregular reproduction and modulation, distortion is small, there is no ghost and random access is possible.

In addition, such optical disk players include a compact disk player (CDP), a laser disk player, a compact disk graphic player (CDGP) and a video compact disk player (VCDP). And the like, and recently, digital video discs (DVD) using MPEG-2 moving picture compression technology and digital video disc players for reproducing the same have been developed. It can record and play back gigabytes (GB) of data, including moving images, and is designed to be compatible to play current compact discs and video compact discs.

In general, the optical disc system ideally matches the phase of the original signal with the phase of the reproduction signal when the disc is reproduced, but in reality, the phase error, i.e., jitter, occurs between the two signals described above.

The reason why such jitter occurs will be described in detail as follows.

First, jitter occurs because the reproducing spot has a finite size by diffraction. In detail, when the mark recorded on the disc is read, the interval between the marks is narrow, which causes waveform interference since the front and back marks are affected. This waveform interference causes jitter.

Second, jitter occurs when aberrations are already present in the reproducing optical system or aberrations are caused by external factors. Such aberrations cause distortion in the waveform of the reproducing signal and cause jitter.

Third, jitter is caused by noise. These noises include laser noise, cross talk due to diffracted light from adjacent tracks, and circuit noise.

Finally, jitter occurs because the circuit for absorbing the influence of the rotational fluctuations of the disc fails to absorb the fluctuations, resulting in a phase error.

As described above, jitter is a reference for determining the stability of the optical disk system to the servo.

Therefore, the user can determine the stability of the servo of the optical disc system with reference to the jitter amount, so that when the jitter amount is detected, the stability of the servo of the optical disc system can be recognized.

However, in the conventional optical disc system, it is difficult for most users to measure the amount of jitter, and there is a problem in that a separate measuring device must be provided to measure the amount of jitter.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object thereof is to provide a jitter amount measuring apparatus of an optical disc system that can measure and display a jitter amount on a screen.

In order to achieve the above object, the present invention provides a jitter amount measuring apparatus of an optical disc system that detects and displays a jitter amount for an RF signal corresponding to data contained in an optical disc, wherein nT (n: integer, A filter unit for detecting and outputting a signal corresponding to a T: 1 channel bit period); A waveform shaping unit shaping a signal corresponding to nT output from the filter unit and converting the signal to a square wave pulse; An edge detector detecting a rising edge and a falling edge of the square wave pulse output from the waveform shaping portion; A signal corresponding to nT by detecting a period of the square wave pulse based on the rising edge and the falling edge of the square wave pulse detected by the edge detector, comparing the detected period of the square wave pulse with a predetermined period; A control unit for measuring the amount of jitter for the controller; And an OSD unit for displaying the jitter amount measured by the controller on a screen through a monitor.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

1 is a block diagram of an apparatus for measuring jitter of an optical disk system according to a preferred embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

10: key input unit 20: control unit

30: optical pickup unit 40: RF signal amplification unit

50: filter part 60: waveform shaping part

70: edge detection unit 80: OSD unit

90: Monitor D: Disc

Hereinafter, with reference to the accompanying Figure 1 will be described in detail the operation of the preferred embodiment according to the present invention.

1 is a block diagram of a jitter amount measuring apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 1, an apparatus for measuring jitter of an optical disc system includes an optical pickup unit configured to perform optical pickup on a loaded disk, converting data (video, audio, and text) contained in the disk into RF (Radio Frequency) signals and outputting the RF signal. 30, nT (n: integer) in the RF signal amplified by the RF signal amplifying unit 40 and the RF signal amplifying unit 40 which amplifies the RF signal of the optical pickup unit 30 based on a predetermined amplification degree and outputs the amplified RF signal. , A waveform corresponding to a period corresponding to a T: 1 channel bit), for example, a filter unit 50 that detects and outputs 11T, and an nT RF signal output from the filter unit 50, and outputs a square wave pulse. Edge detector 70 and edge detector for detecting the upper and lower edges of the square wave pulse output from the shaping unit 60 and the waveform shaping unit 60 and outputting the rising edge detection signal and the falling edge detection signal corresponding thereto. Rise of Square Wave Pulse Detected from 70) With reference to the edge and the falling edge, the controller 20 and the controller 20 which measure the jitter amount for the signal corresponding to nT described above by comparing the detected period of the square wave pulse with the predetermined period are various keys. And a key input unit 10 for providing a signal, and an OSD unit 80 for outputting the jitter amount measured by the control unit 20 through the monitor 90.

The operation description of the preferred embodiment of the present invention configured as described above is as follows.

First, while the optical disc system is being reproduced, the control unit 20 determines whether the jitter amount measurement key signal is input from the key input unit 10, and when the jitter amount measurement key signal is provided, the optical disc system measures the jitter amount in the playback mode. Switch to mode.

When the optical disc system is switched from the playback mode to the jitter amount measurement mode, the control unit 20 resets the internal clock and detects the period of the square wave pulse output from the waveform shaping unit 60.

Here, the process of detecting the period of the square wave pulse output from the waveform shaping unit 60 will be described in detail.

The optical pickup unit 30 reads the data contained in the disk D, converts the data into an RF signal, and transmits the converted data to the RF signal amplifier 40. The RF signal amplifying unit 40 amplifies the RF signal transmitted from the optical pickup unit 30 based on a predetermined amplification degree and provides the same to the filter unit 50.

At this time, the RF signal transmitted to the filter unit 50 is mixed with a signal having a plurality of channel bit periods 3T to 11T. Therefore, the filter unit 50 detects a signal corresponding to nT (n: integer, T: 1 channel bit period), for example, 11T, in order to obtain the jitter amount from the RF signal in which the plurality of channel bit periods are mixed. do.

Next, the filter unit 50 provides the waveform shaping unit 60 with a signal corresponding to the detected nT. The waveform shaping unit 60 forms a signal corresponding to nT provided from the filter unit 50, converts the signal to a square wave pulse, and provides the edge detection unit 70.

The edge detector 70 detects the rising edge and the falling edge of the square wave pulse output from the waveform shaping unit 60. When the rising edge is detected, the edge detector 70 provides the rising edge detection signal to the controller 20.

When the edge detector 70 receives the rising edge detection signal, the controller 20 drives a built-in counter to count the clock of the square wave pulse output from the waveform shaping unit 60.

As described above, while the control unit 20 counts the clock of the square wave pulse output from the waveform shaping unit 60, the edge detector 70 detects the falling edge from the square wave pulse and detects the falling edge. Provide a falling edge detection signal.

When the falling edge detection signal is provided from the edge detector 70, the controller 20 ends the counting of the clock of the square wave pulse output from the waveform shaping unit 60.

Therefore, the control unit 20 can obtain one period of the signal corresponding to nT detected from the filter unit 50 by measuring the clock number of the square wave pulse signal output from the waveform shaping unit 60 as described above. It repeats until the quantity measurement signal is input and calculates one period of the signal corresponding to nT.

As such, when one period of the signal corresponding to nT is calculated, the control unit 20 reads a reference period of the signal corresponding to nT preset in the internal memory, and determines the period and subtraction of the signal corresponding to the calculated nT. To calculate the amount of jitter.

Then, the controller 20 controls the OSD unit 80 so that the calculated jitter amount is displayed on the monitor 90. The OSD unit 80 displays the jitter amount provided from the control unit 20 on the monitor 90 so that the user can recognize it.

In this case, since the data read out from the optical pickup unit 30 is not a fixed value but the value of the data changes as time passes, the period of a signal corresponding to nT measured by the controller 20 also changes. Therefore, the jitter amount displayed on the monitor 90 also changes.

As described above, while the jitter amount is displayed on the monitor 90, the control unit 20 controls the optical disc system to perform normal playback when the jitter amount measurement end signal is provided through the key input unit 10. FIG.

As described above, the apparatus for measuring jitter of the optical disc system according to the present invention measures the jitter amount, which is one of the items for evaluating the stability of the servo of the optical disc system, and displays the measured jitter amount on the screen. The displayed jitter amount has an effect of determining the stability of the optical disk system.

While the invention has been shown and described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various modifications, changes and omissions can be made without departing from the spirit and scope of the invention.

Claims (1)

In the jitter amount measuring apparatus of the optical disc system for detecting and displaying the jitter amount for the RF signal corresponding to the data recorded on the optical disc: A filter unit 50 for detecting and outputting a signal corresponding to nT (n: integer, T: 1 channel bit period) from the RF signal; A waveform shaping unit (60) for shaping the nT RF signal outputted from the filter unit (50) and converting the RF signal into a square wave pulse; An edge detector (70) for detecting rising and falling edges of the square wave pulses output from the waveform shaping unit (60); The period of the square wave pulse is detected based on the rising edge and the falling edge of the square wave pulse detected by the edge detector 70, and the period of the detected square wave pulse is compared with a predetermined period to the nT. A control unit 20 for measuring the amount of jitter for a corresponding signal; Jitter amount measuring apparatus of the optical disk system having an OSD unit 80 for displaying the jitter amount measured by the control unit 20 on the screen through a monitor.