CN101677002A

CN101677002A - Method applicable to CDs for generating tracking error signals

Info

Publication number: CN101677002A
Application number: CN200810213134A
Authority: CN
Inventors: 马军; 金基勇
Original assignee: Samsung Semiconductor China R&D Co Ltd; Samsung Electronics Co Ltd
Current assignee: Samsung Semiconductor China R&D Co Ltd; Samsung Electronics Co Ltd
Priority date: 2008-09-18
Filing date: 2008-09-18
Publication date: 2010-03-24

Abstract

The invention provides a method applicable to CDs (compact disks) for generating tracking error (TE) signals. The method comprises the following steps: detecting the balance degree of a photoelectricdetector; and confirming whether the value of the balance degree thereof is smaller than a first threshold value, if so, generating the TE signals by using a differential phase detection (DPD) method,and if not, generating the TE signals by using a 3-beam method.

Description

The method that is used for the generation tracking error signal of CD video disc

Technical field

The present invention relates to the method for a kind of generation tracking error (TE) signal, specifically, relate to a kind of like this method, described method is being play CD video disc (for example, CD, the VCD that there is scuffing on some surfaces, CD-R, CD-RW) and use during the DVCD video disc differential phase detection (DPD) method to produce the TE signal selectively, improving the TE quality of signals, thereby improve the error correcting capability of player.

Background technology

The TE signal is a very important baseband signal for CD player.It mainly acts on is exactly the track (Track) that is used for following the tracks of on the video disc, guarantees the information that laser head can search accurately to be needed.In all present CD player solutions, all adopt the method for DPD to produce the TE signal, adopt the 3-beam method for the CD video disc for the DVD video disc.

The play CD video disc the time, adopt traditional 3-beam method, for most video disc, can meet the demands basically, obtain mass ratio TE signal preferably.But also there are some problems here.

At first, have for some disc surface to scratch and foul, and some have used video disc many times, the TE quality of signals that adopts the method for 3-light beam to obtain is very poor, therefore can cause following the tracks of track, to such an extent as to can't play or ability to play descends.

Secondly, for the DVCD video disc, this video disc is owing to need storage than general CD video disc more contents, so its track space little than common CD video disc.The track space of common CD video disc is 1.6um, and the track space of DVCD is approximately 1.2um.The diameter of the hot spot that the CD laser instrument produces is greatly about 1.74um.Therefore, when adopting the CD laser instrument to play the DVCD video disc, because spot diameter is too many above track width, the TE signal quality that obtains can descend, and causes ability to play to descend.

Thereby, scratch or CD, the DVCD of foul at having, need a kind of new TE signal creating method, can more effectively avoid of the influence of condition such as disc surface scuffing, to improve the error correcting capability of player to the TE signal quality.

Summary of the invention

According to an aspect of the present invention, provide a kind of method of generation tracking error signal of the CD of being used for video disc, described may further comprise the steps: detect the photoelectric detector quality of balance; Whether the value of determining the photoelectric detector quality of balance is less than first threshold; If the value of photoelectric detector quality of balance less than first threshold, then adopts the differential phase detection method to produce tracking error signal; Otherwise, adopt the 3-beam method to produce tracking error signal.

Description of drawings

By the detailed description of reference accompanying drawing to exemplary embodiment of the present, above and other feature of the present invention and aspect will become clearer, wherein:

Fig. 1 illustrates by using the 3-beam method to produce the diagrammatic sketch of structure of the device of TE signal;

Fig. 2 A-2C is the diagrammatic sketch that the principle of operation of 3-beam method is shown;

Fig. 3 illustrates to be included in the diagrammatic sketch of structure that DPD method that being used in the CD drive drive DVD produces the device of tracking error signal;

Fig. 4 A-4C is the diagrammatic sketch that the DPD principle of operation is shown;

Fig. 5 switches to the process flow diagram that the DPD method produces the method for TE signal according to an exemplary embodiment of the present invention when the play CD video disc;

Fig. 6 is the process flow diagram that the DPD method that switches to when the play CD video disc of another exemplary embodiment according to the present invention produces the method for TE signal.

Embodiment

Below, exemplary embodiment of the present invention is described with reference to the accompanying drawings.

Fig. 1 illustrates by using the 3-beam method to produce the diagrammatic sketch of structure of the device of TE signal.Fig. 2 A-2C is the diagrammatic sketch that the principle of operation of 3-beam method is shown.

In the 3-beam method, the laser that laser instrument sends is divided into 3 bundle light by optical disc surface reflection and by grating, and focused beam and two follow the rail light beam.Photoelectric detector detects two and follows the rule light beam, and detected two are followed rail light beam E and F behind subtracter, produce magnitude of voltage TE signal.The TE signal indication is as follows:

TE＝E-F

Can determine whether laser instrument follows rail by the intensity that detects the TE signal.

With reference to Fig. 2 A, before or after the luminous point that focused beam produces, on track, form and follow some A and the B that the rail light beam produces by each.More particularly, depart from 1/4th intervals by each some A and B that follows the generation of rail light beam about the point that focused beam produces.

Fig. 2 B shows by what focused beam produced and is precisely defined at ideal point at the center of track.Follow some A that the rail light beam produces and the part of B is positioned on the track by two.The rail light beam that follows corresponding to an A and B reflects from CD, and is input to photoelectric detector.Photoelectric detector receives and to follow rail light beam and the corresponding light detecting signal of the amount of output and input signal as input signal.As shown in Figure 1, the output with photoelectric detector is input to subtracter.At this moment, because the output of photoelectric detector has identical absolute value, so the output of subtracter is 0.

Shown in Fig. 2 B or 2C, when the some off-track center that produces by focused beam, differ from one another with the amount of an A and some B respective input signals.Therefore, when input signal passes through subtracter, produce error signal.The polarity of error signal is represented the direction of focused beam off-track, and the scale of error signal shows the degree that departs from.

Fig. 3 illustrates to be included in the diagrammatic sketch of structure that DPD method that being used in the CD drive drive DVD produces the device of tracking error signal.Fig. 4 A-4C is the diagrammatic sketch that the DPD principle of operation is shown.

With reference to Fig. 3, the DPD method is by with a on the main device for testing light, b, c, the addition of d signal diagonal line, after balanced device, again with (a+c) and (b+d) phase differential of signal be converted to electric signal and obtain tracking error signal TE.As follows by RF signal and TE signal that the device of Fig. 3 produces:

RF＝a+b+c+d

TE＝phase(a+c)-phase(b+d)

Here, the TE signal is the tracking error signal that produces by the DPD method.

When light beam accurately focused on the track center, the distribution of light beam was shown in Fig. 4 B.At this moment, the value of TE signal is 0.Thereby instant CD rotation mobile beam on trajectory direction, the value of TE signal also remains 0.

When the center of BEAM SQUINT track, the distribution of light beam is shown in Fig. 4 A or Fig. 4 C.Thereby, thereby when on the direction of disc spins at track during mobile beam, will produce the TE signal.With reference to Fig. 4 A to Fig. 4 C, the TE signal is from RF signal travel(l)ing phase 90 degree.For this reason, the direction of tracking error and the number of degrees can detect with reference to the phase place and the amplitude of RF signal.

Usually, after inserting video disc, player at first detects the type of video disc, and the type according to video disc adopts diverse ways to produce the TE signal then.For example, adopt the 3-beam method for CD; Adopt the DPD method for DVD.And scratch or CD, the DVCD of foul having, the defective of disc surface can cause certain influence to the intensity of the signal of reflection usually, such as signal intensity is on the weak side or signal has noise.In this case, if also adopt the 3-beam method to produce TE signal (that is: TE=E-F), the TE signal quality that then obtains is relatively poor, will certainly influence the broadcast and the error-correcting performance of video disc.

Because the DPD method adopts the phasic difference of signal to obtain the TE signal, so the surface imperfection of video disc (for example, scuffing or foul) is just much smaller for the influence of the TE signal that produces.Therefore, if when playing surperficial defective CD video disc, generate the TE signal, then make the servo-drive system of CD player more stable, thereby reach better result of broadcast meeting with the DPD method.

In addition, for DVCD,, adopt the DPD method can obtain mass ratio TE signal preferably with respect to the track width of 1.2um.Therefore, if adopt the DPD method to produce TE, then can improve the broadcast performance of DVCD video disc.

But, be not that all surface is had scuffing, has the CD video disc of foul all to adopt the DPD method to produce the TE signal.Here, need to consider that two parameters determine whether that the mode that will produce TE switches to the DPD method from the 3-beam method.

First parameter that need consider is called as the photoelectric detector quality of balance, abbreviates PDBal as, the degree of the laser off-center position that this parametric representation reflects.When PDBal hour, can adopt the DPD method to produce the TE signal; When PDBal was big, the TE signal performance that adopts the DPD method to produce was relatively poor.Usually, the light that reflects under normal circumstances is in the centre of a, b, c, four unit of d, but owing to there is more or less process variations in the process of making, causing photoelectric detector is not to be on the desirable position, but with desirable position some side-play amounts is arranged.In this case, if side-play amount is less, then can ignore, but when side-play amount was bigger, if also use the DPD method to produce the TE signal, the TE signal quality that then obtains was relatively poor, the broadcast of video disc and error-correcting performance reduce.

The parameter of second needs consideration is the range value of TE signal, abbreviates TEPP as.This TEPP parameter is indicated the amplitude size of TE signal, promptly characterizes the quantity of information of TE signal.Scratch or foul if disc surface has, then can influence the intensity of TE signal, promptly TEPP is less relatively.Therefore, if TEPP is bigger, i.e. the intensity of the TE signal of 3-beam method generation is bigger, illustrates that scuffing or foul are less to the influence of video disc, can switch to the DPD method again and produce the TE signal; Otherwise, illustrate that scuffing or foul are bigger to the influence of video disc, produce the TE signal if do not switch to the DPD method, the TE signal quality that adopted the 3-light beam to produce originally is relatively poor, will certainly influence play quality.

Fig. 5 is the process flow diagram that the DPD method that switches to when the play CD video disc of first exemplary embodiment according to the present invention produces the method for TE signal.

Below, switch to the condition that the DPD method produces the TE signal when being described in the play CD video disc with reference to Fig. 5.

At step S501, detect the value of PDBal.

At step S502, use the 3-beam method to produce the TE signal, and detect TE range value, i.e. second parameter TEPP.

At step S503, determine that whether PDBal is less than first threshold.If PDBal then proceeds to step S504 less than first threshold (that is, the side-play amount of photoelectric detector is less), whether the value of determining the TEPP parameter is less than second threshold value.If the value of TEPP parameter then switches to the DPD method and produces the TE signal less than second threshold value (that is, the amplitude of the TE signal that produces by the 3-beam method is less, that is to say that the scuffing of video disc or foul are bigger to the influence of video disc).

If determine that at step S503 PDBal is not less than first threshold (that is, the side-play amount of photoelectric detector is bigger, is not suitable for adopting the DPD method to produce the TE signal), then finishes hand-off process and play-overs the CD video disc.That is, under the bigger situation of PDBal parameter, be not suitable for adopting the DPD method to produce the TE signal, do not play-over video disc so do not carry out blocked operation.

If determine that at step S504 the value of TEPP parameter is not less than second threshold value (promptly, the amplitude of the TE signal that produces by the 3-beam method is bigger, the scuffing or the foul that is to say video disc are little to the influence of video disc, needn't switch to the DPD method and produce the TE signal), then finish hand-off process and play-over the CD video disc.

That is to say, only under all less situation of the first parameter PDBal and the second parameter TEPP, just switch to the DPD method.

But the present invention is not limited to this.For example, when being had relatively high expectations, play quality, just switches to the DPD method less than first threshold as long as satisfy the first parameter PDBal to relative hour of the requirement of time delay.At this moment, the entire method flow process changes to some extent.For example, step S502, S504 will be omitted, and promptly relevant with second parameter TEPP operation will not be performed.Below, with reference to Fig. 6 to being described in detail in this case.

Fig. 6 is the process flow diagram that the DPD method that switches to when the play CD video disc that second exemplary embodiment according to the present invention is shown produces the method for TE signal.

At step S601, detect the value of PDBal.

At step S602, determine that whether PDBal is less than first threshold.If PDBal then proceeds to step S603 less than first threshold (that is, the side-play amount of photoelectric detector is less), switch to the DPD method and produce the TE signal; Otherwise, produce the TE signal by the 3-beam method.

In addition, the invention is not restricted to the order of the process flow diagram that illustrates.For example, the order of step S502 and S501 can be exchanged, or the order of step S503 and S504 is exchanged, perhaps step S502 is placed between S503 and the S504.That is to say that only otherwise break away from principle of the present invention, institute changes and all comprises within the scope of the invention.

It should be appreciated by those skilled in the art, under the situation that does not break away from the spirit and scope of the present invention, can carry out various changes in form and details.Therefore, aforesaid exemplary embodiment is the purpose in order to illustrate only, and should not be interpreted as limitation of the present invention.Scope of the present invention is defined by the claims.

Claims

1, a kind of method that is used for the generation tracking error signal of CD video disc, described may further comprise the steps:

Detect the photoelectric detector quality of balance;

Whether the value of determining the photoelectric detector quality of balance is less than first threshold;

If the value of photoelectric detector quality of balance less than first threshold, then adopts the differential phase detection method to produce tracking error signal; Otherwise, adopt the 3-beam method to produce tracking error signal.

2, the method for claim 1 is characterized in that described method is further comprising the steps of before producing tracking error signal based on definite differential phase detection method as a result:

Use the 3-beam method to produce tracking error signal, and detect the range value of tracking error signal;

Whether the range value of determining tracking error signal is less than second threshold value;

If the range value of tracking error signal less than second threshold value, then adopts the differential phase detection method to produce tracking error signal.

3, method as claimed in claim 1 or 2 is characterized in that the degree of described photoelectric detector quality of balance indication from the laser off-center position that CD reflection is returned.