KR19980085469A - 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; A divider for dividing a system clock to output a reference clock for the square wave pulse output from the waveform shaping unit; A comparator for comparing a square wave pulse of the waveform shaping unit with a reference clock of the divider and outputting a signal corresponding to a difference between a phase and a period corresponding thereto; An edge detector detecting a rising edge and a falling edge of a signal corresponding to the difference between the phase and the period output from the comparator; A controller which measures the amount of jitter for the signal corresponding to nT based on the rising edge and the falling edge of the signal corresponding to the difference between the phase and the period detected by the edge detector; 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 the nT output from the filter unit and converting the signal into a square wave pulse; A divider for dividing a system clock to output a reference clock for the square wave pulse output from the waveform shaping unit; A comparator for comparing a square wave pulse of the waveform shaping unit with a reference clock of the divider and outputting a signal corresponding to a difference between a phase and a period corresponding thereto; An edge detector detecting a rising edge and a falling edge of a signal corresponding to the difference between the phase and the period output from the comparator; A controller which measures the amount of jitter for the signal corresponding to nT based on the rising edge and the falling edge of the signal corresponding to the difference between the phase and the period detected by the edge detector; 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 amount of an optical disk system according to a preferred embodiment of the present invention;

2 is a timing diagram for explaining 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: dispenser 80: comparison

90: edge detection unit 100: OSD unit

110: monitor D: disk

Hereinafter, with reference to the accompanying drawings 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, Figure 2 is a timing diagram for explaining a preferred embodiment of the present invention.

Referring to FIGS. 1 and 2, an apparatus for measuring jitter of an optical disc system performs optical pickup on a loaded disc to convert data (video, audio, and text) contained in the disc into RF (Radio Frequency) signals and output the optical signal. The RF signal amplified by the pick-up unit 30 and the optical pickup unit 30 based on a predetermined degree of amplification and then output is amplified by the RF signal amplified unit 40, nT ( n is a signal corresponding to an integer, a period of T: 1 channel bits, for example, a filter unit 50 that detects and outputs 11T, and an nT RF signal output from the filter unit 50, and square wave pulses ( The waveform shaping unit 60 outputs to A) of FIG. 2, the system clock divider, the divider 70 outputting the reference clock (B of FIG. 2) of the signal corresponding to nT described above, and the jitter amount of the optical disk system. When the measurement mode is entered, the square wave pulse (A in FIG. 2) and the divider (7) output from the waveform shaping unit 60 Comparing unit for receiving the reference clock (B of FIG. 2) output from 0) at the same time and comparing the phase and period of the two signals and outputting a signal (C of FIG. 2) corresponding to the difference between phase and period ( 80) detects the rising edge and the falling edge of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80, and outputs a rising edge detection signal and a falling edge detection signal corresponding thereto; With reference to the rising edge and falling edge of the signal (C of FIG. 2) corresponding to the difference between the phase and the period detected from the edge detector 90 and the edge detector 90, The controller 20 detects the period of the signal (C of FIG. 2) and measures the jitter amount corresponding thereto, the key input unit 10 providing various key signals to the controller 20, and the measured value from the controller 20. The OSD unit 100 outputs the jitter amount through the monitor 110. do.

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 controller 20 resets the internal clock and cycles the signal corresponding to the difference between the phase and the period output from the comparator 80 (C in FIG. 2). Detect.

Here, a process of detecting the period of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80 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 (A in FIG. 2), and provides the same to the comparison unit 80.

At the same time, the divider 70 divides the system clock and provides the comparison unit 80 with a reference clock (B in FIG. 2) for the square wave pulse (A in FIG. 2) output from the waveform shaping unit 60. .

Then, the comparator 80 compares the phases of the square wave pulse (A in FIG. 2) of the waveform shaping unit 60 and the reference clock (B in FIG. 2) provided by the divider 70, and thus, C in FIG. 2. The edge detector 90 provides a signal corresponding to the difference between phase and period as shown in FIG.

The edge detector 90 detects the rising edge and the falling edge of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80. Provide a rising edge detection signal.

When the controller 20 receives the rising edge detection signal from the edge detector 90, the controller 20 drives a built-in counter to clock the signal corresponding to the difference between the phase and the period output from the comparator 80 (FIG. 2C). Start counting.

As described above, while the control unit 20 counts the clock of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80, the edge detector 90 performs this phase and period. When the falling edge is detected by detecting the falling edge from the signal (C of FIG. 2) corresponding to the difference of, the falling edge detection signal is provided to the controller 20.

When the falling edge detection signal is provided from the edge detector 90, the controller 20 ends the counting of the clock of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80.

Therefore, the controller 20 measures the clock number of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80, as described above, and corresponds to the signal corresponding to the difference between the phase and the period. The period of (C in FIG. 2) can be measured.

As such, when the period of the signal (C of FIG. 2) corresponding to the difference between the phase and the period output from the comparator 80 is detected, the controller 20 determines that the signal corresponding to the difference between the detected phase and the period ( The amount of jitter can be calculated with reference to the cycle of FIG. 2C.

Then, the controller 20 controls the OSD unit 100 to display the calculated jitter amount on the monitor 110. The OSD unit 100 displays the jitter amount provided from the control unit 20 on the monitor 110 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 signal corresponding to the difference between the phase and the period measured by the controller 20 (see FIG. 2). The cycle of C) also changes.

As described above, while the jitter amount is being displayed on the monitor 110, the controller 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.

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 a signal corresponding to the nT output from the filter unit 50 and converting the signal to a square wave pulse; A divider (70) for dividing a system clock to output a reference clock for the square wave pulse output from the waveform shaping unit (60); A comparator (80) for comparing a square wave pulse of the waveform shaping unit (60) with a reference clock of the divider (70) and outputting a signal corresponding to a difference between a phase and a period corresponding thereto; An edge detector (90) for detecting rising and falling edges of a signal corresponding to the difference between the phase and the period output from the comparing unit (80); A controller (20) for measuring the amount of jitter for the signal corresponding to the nT based on the rising edge and the falling edge of the signal corresponding to the difference between the phase and the period detected by the edge detector (90); Jitter amount measuring apparatus of the optical disk system having an OSD unit 100 for displaying the jitter amount measured by the control unit 20 on the screen through a monitor.