KR100617148B1 - method for setting focus bias in optical disc playback/record system - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention is to provide a focus bias setting method for removing adverse effects of focus bias during seek and improving reproduction by setting adaptive focus bias, wherein a focus error of a disk for playback by operating a focus servo is provided. Adjusting the servo so that is 0 (zero) and operating the tracking servo, forcibly changing the focus bias value to the adjusted focus servo, and finding and setting the focus bias value that is the minimum jitter as the focus bias; Attempting to read the corresponding data through the seek in response to the set focus bias to determine whether an error occurs in the data reading; and if it is determined that the error does not occur, the corresponding data is transmitted to the host computer. Transmitting and determining that an error has occurred Change the focus bias to 0 (zero) and seek to the corresponding data position on the disc corresponding to the focus bias changed to 0 (zero); recover the changed focus bias to the initially set focus bias and resume reading the data. It involves a step of trying.

Focus Bias, Seek, Defocus, Jitter, Optical Disc

Description

Method for setting focus bias in optical disc playback / record system}

1 is a flowchart showing an optical disc reproducing method according to the prior art.

2 and 3 are diagrams illustrating a focus bias setting method in an optical disc reproducing / recording system according to the prior art.

4A and 4B are flowcharts illustrating a focus bias setting method in an optical disc reproducing / recording system according to the present invention.

5 is a diagram showing an example of jitter change when the focus bias setting is changed in the optical disk reproducing / recording system according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of setting focus bias in an optical disc reproducing / recording system, and to a method of eliminating adverse effects of focus bias during seek and improving reproduction by setting adaptive focus bias.

Since the development of a CD with a thickness of 1.2 mm and a diameter of 12 cm, many studies have been conducted to improve the recording density of optical discs.As a result, two substrates having a thickness of 0.6 mm and a diameter of 12 cm are bonded to each other, various types of recording density can be increased. Research on the DVD family is almost complete, including structured DVDs (types 5 / -9 / -10 / -18), write-once DVD-Rs, and rewritable DVD-RAMs. New optical disc markets such as multi and super multi are forming.

A DVD (Digital Versatile Disc) -5 type optical disc has a recording capacity of 4.7 Gbyte on one side, which is about seven times the capacity of 780 Mbytes of CD.

This improvement in recording density can be achieved by miniaturization of optical spots, efficiency of signal processing of modulation codes or error correction codes, and physical changes of optical discs, ie pit size, track pitch reduction, and light incidence. The distance between the surface and the light reflecting surface is reduced (thickness reduction CD: 1.2 mm, DVD: 0.6 mm).

The CD and DVD systems developed and commercialized up to now are read-only memory (ROM), recordable data type (Recordable: -R) that can record information once, and can read, write, and erase information repeatedly. There are repeatable types (Rewritable, -RAM, -RW).

In such a CD / DVD, especially an optical disc reproducing / recording system of the DVD system (DVD-SL, DVD-DL, DVD + R, DVD-R, DVD + RW, DVD-RW, DVD-RAM), defocusing between pickups Due to the difference in the defocus between the disc and the inner and outer circumferences, the playback performance is highly dependent on the focus bias setting.

1 is a flowchart showing an optical disc reproducing method according to the prior art.

Referring to FIG. 1, first, when a disc is inserted into a system, a laser is turned on (S10), and it is determined whether the disc is a CD or a DVD system (S20). Since the reproducing optical wavelength is different for each disc, the disc is set to the corresponding wavelength through the disc identification.

Next, the focus servo is operated (S30) to control the focus actuator so that the focus error FE becomes 0 (zero) to perform servo adjustment (S40). That is, focus offset and gain, tracking offset, and gain are adjusted through the servo adjustment. Then, the tracking servo is operated to detect the track formed on the optical disk (S50).

However, due to characteristics such as defocus difference between pickups and defocus difference between inner and outer circumferences of the disc due to non-uniformity and warpage of the optical disc, optimal jitter may be achieved even when the focus error is zero by adjusting the focus servo. Can't.

Therefore, in the CD or DVD system, in particular, the DVD system, the focus bias value is set to force the focus servo to be the best jitter so that the minimum (optimal) jitter is calculated (S60).

The focus bias setting method is described in detail with reference to FIGS. 2 and 3, which will be described below with reference to the drawing.

As shown in FIG. 2A, the focus servo finds a focusing point at which the focus error FE becomes zero, and adjusts the focus bias value to adjust the focus bias according to the minimum value of jitter.

In this case, in order to assist physical understanding in adjusting the focus bias in FIG. 3, the focus of the laser beam at the position where the focus error becomes zero, that is, the focusing point, is offset in the positive or negative direction.

In more detail, if the bias is applied to the focus servo by moving the focus of the laser beam up and down in the focusing point as shown in FIG. 3 and applying the positive and negative values in several steps, the focus error as shown in FIG. The offset is generated by a bias value applied as a positive value and a negative value with respect to zero. And the jitter according to this will be one case different from each other, as shown in Figure 2 (b), Figure 2 (c), Figure 2 (d).

In this case, FIG. 2B illustrates a case where a bias value causing minimum jitter is 0 and FIG. 2C illustrates a case where the bias value causing minimum jitter is positive. 2 (d) shows a case where the bias value causing the minimum jitter is negative.

Therefore, the focus bias adjustment is performed by referencing the defocus specification of the pickup as the maximum value, dividing the corresponding value into several steps, forcing the bias, and storing the jitter value calculated when each bias is applied, and then storing the jitter. Compare the values and select the bias value with the lowest jitter value and set it as the focus bias.

When the focus bias value is set through the focus bias adjustment as described above, the TOC (Table Of Contents) of the disk is read, and the stored capacity, file, directory information, etc. of the disk are stored in the memory (S70).

Next, when a data request is detected by the host computer, the data is read at the set focus bias (S80), an error correction is performed, and then the data is checked (S90).

As a result of the check, if there is no problem reading the data, the data is transmitted to the host computer (S100). As a result of the check, if there is a problem, the user moves to the corresponding data position through a seek and retrys data reading (S120).

At this time, when a problem occurs in reading data and retrying to read the data continuously, the data reading is attempted only until the number of times of the retrying reaches a preset maximum value (S110).

When the number of retries exceeds a preset maximum value as a result of the check of the data read (S110), it is determined that the read has failed and a read error report is transmitted to the host (S130).

However, the focus bias setting method in the optical disc reproducing / recording system according to the related art described above has the following problems.

First, if the focus bias value is incorrectly adjusted due to distortion of the jitter signal when adjusting the focus bias due to scratch or finger print of the disk, the data read will be attempted with the wrong focus bias. It causes a decrease in regeneration power.

Second, the focus bias value that causes the optimum jitter value is often different depending on the position of the disk, ie, inner, quartet, and outer circumference. In general, focus bias is set only on the inner circumference of the disk. do.

Third, if the focus bias is adjusted too large, the focus servo abnormally reacts with a scratch or the like on the disk, causing frequent focus drops, resulting in data read delays.                         

Fourth, when the focus bias is large, when the pickup is moved to the position of the disk where the data is stored, the DC offset due to the focus error causes frequent focus drops at seek time, resulting in data read delay.

Accordingly, an object of the present invention is to provide a focus bias setting method capable of eliminating adverse effects of focus bias at the time of seek for optical disc playback / recording.

Another object of the present invention is to improve the reproduction power by setting the adaptive focus bias.

A feature of the focus bias setting method in the optical disc reproducing / recording system according to the present invention for achieving the above object is to operate the focus servo to adjust the servo so that the focus error of the disc for reproducing is zero. Operating a tracking servo, forcibly changing a focus bias value of the adjusted focus servo, finding a focus bias value that is the minimum jitter, and setting the focus bias value as a focus bias, and seeking according to the set focus bias. Attempting to read the corresponding data through) to determine whether an error occurs in reading the data, and if it is determined that the error does not occur, transmitting the data to the host computer, and as a result of the check, If it is determined to occur, change the focus bias to 0 (zero) and set it to 0 (zero). Is changed in correspondence to the focus bias makin comprises a method comprising the steps of a seek to the data position on the disk, and recovery of the changed focus bias is set to a first focus bias retries the data reading.

Another feature of the focus bias setting method in the optical disc reproducing / recording system according to the present invention for achieving the above object is to operate the focus servo to adjust the servo so that the focus error of the disc for reproducing is zero and the tracking servo Operating a search force, forcibly changing a focus bias value in the adjusted focus servo, finding a focus bias value that is the minimum jitter, and setting the focus bias value as a focus bias, and seeking a seek in accordance with the set focus bias. Attempting to read the corresponding data through the data to check whether an error occurs in reading the data, and if it is determined that the error has not occurred, transmitting the corresponding data to a host computer; If so, retry reading the data via seek. The first retry step and the number of retries are classified into a plurality of levels within a maximum value (time) to wait after requesting data from a host computer, and different focus bias values are set for each level, and then differently set. A second retry step of retrying reading of the corresponding data through a seek corresponding to a focus bias value, and comparing the number of retries with a preset maximum value, determining that the read fails when the value is greater than the maximum value Sending an error report to the host.

Another feature of the focus bias setting method in the optical disc reproducing / recording system according to the present invention for achieving the above object is to operate the servo so that the focus error of the disc for reproducing becomes zero. Adjusting and operating a tracking servo, forcibly changing a focus bias value to the adjusted focus servo, finding a focus bias value that is the minimum jitter, and setting the focus bias to seek bias, and seeking according to the set focus bias. attempting to read the corresponding data through the (seek) to check whether an error occurs in reading the data, transmitting the corresponding data to the host computer if it is determined that the error has not occurred, If it is determined that an error has occurred, change the focus bias to zero. Seeking to the corresponding data position on the disk corresponding to the focus bias changed to zero, and waiting for the number of retries after requesting data from the host computer before retrying to read the corresponding data through the seek. Classifying the data into a plurality of levels within a maximum value (time), setting a focus bias value differently for each of the classified levels, and reading corresponding data through a seek corresponding to the differently set focus bias values And retrying and comparing the number of retries with a preset maximum value, determining that the read failed when the value is greater than the maximum value, and transmitting a read error report to the host.

In this case, the second retrying or retrying step may be performed in comparison with M (an integer within a maximum value range), in which the number of retries is smaller than the maximum value. retrying to read the corresponding data through (seek), and comparing the retry count with N (an integer within a maximum value range) that is smaller than the maximum value and larger than the set value M. If less than the set value N, setting a predetermined focus bias value to 0, retrying to read the corresponding data through the seek corresponding to the focus bias set to 0, and comparing the number of retries with the set value N, If it is larger than the set value N and less than the maximum value, the preset focus bias value is set to the opposite polarity, and the solution through the seek corresponding to the set focus bias value is set. And retrying reading of the data.

The change in the focus bias value may be such that the focus of the laser beam has an offset in the positive or negative direction with respect to the focusing point that is servo-adjusted so that the focus error is zero.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

A preferred embodiment of a focus bias setting method in an optical disc reproducing / recording system according to the present invention will be described with reference to the accompanying drawings.

4A and 4B show a flowchart of a focus bias setting method in the optical disc reproducing / recording system according to the present invention.

Referring to FIGS. 4A and 4B, when a disc is inserted into a system, a laser is first turned on (S10), it is determined whether the disc is a CD or a DVD system, and the wavelength of the corresponding optical disc is set (S20). Next, the focus servo is operated (S30) to control the focus actuator so that the focus error FE becomes zero (zero) to perform servo adjustment (S40). That is, focus offset and gain, tracking offset, and gain are adjusted through the servo adjustment.

Then, the tracking servo is operated to adjust the track formed on the optical disk (S50).

However, optimal jitter cannot be achieved even when the focus error is zero due to characteristics such as defocus difference between pickups and defocus difference between inner and outer circumferences of the disk due to non-uniformity and warpage of the optical disk.

Therefore, in the CD or DVD system, especially the DVD system, the focus servo value is set so as to force the focus servo to be the best jitter so that the minimum (optimal) jitter is calculated (S60).

The focus bias setting method is described in detail with reference to FIGS. 2 and 3, and a description thereof will be omitted.

When the focus bias value is set through the focus bias adjustment as described above, the TOC (Table Of Contents) of the disk is read, and the stored capacity, file, directory information, etc. of the disk are stored in the memory (S70).

Next, when a data request is detected by the host computer, the data is read (S80), an error correction, and the like are checked (S90).

As a result of the check, if there is no problem reading the data, the data is transmitted to the host computer (S100).

In addition, as a result of the data read check, if there is a problem in reading the data, the user moves to the corresponding data position through the seek and retrys the data read (S200). When retrying, the number of retries is counted. The data read operation is continuously attempted only until the counted number of retries reaches a preset maximum value (S110).

At this time, after adjusting the focus bias value set to adjust the defocus difference and the like before the seek (S190) to a value set to zero during focus servo adjustment (S190), the pickup is moved to the position of the disk where the data is stored. The seek is performed (S200).

Therefore, the pickup is moved to the position of the disk where the data is stored in the state where the focus bias is conventionally adjusted, thereby causing frequent focus drop at the DC offset due to the focus error, thereby preventing the data read delay.

As a result of the data read check (S110), when the number of retries exceeds a preset maximum value due to a problem in reading data, it is determined that the read has failed and a read error report is transmitted to the host (S130).

In addition, as a result of the data read check, when it is determined that the number of retries due to a problem in reading data is smaller than the set value M compared to the M set to be smaller than the maximum value (S140), the focus bias value is previously focused. It is set as it is set in the adjustment (S150). Next, after the seek is performed by adjusting the focus bias value to 0 (zero) (S190), the data is reattempted by recovering the set focus bias value (S210).

In addition, as a result of the data read check, when it is determined that the number of retries due to a problem in reading data is greater than the set value M (S140), the set value N is set to be larger than the set value M and smaller than the maximum value (S140). S160).

When it is determined that the number of retries is greater than the set value M and smaller than the set value N, as a result of the comparison with the set value N, the set focus bias value is set to 0 through focus bias adjustment (S170). Next, the focus bias value is adjusted to 0 (zero) (S190) and the seek is performed (S200). Then, the data is retried to the focus bias value set to 0 (zero) and the data read is retried (S210).

When it is determined that the number of retries is greater than N and smaller than the maximum value as a result of the comparison with the set value N (S160), the focus bias value set through focus bias adjustment is set to the opposite polarity (S180). Next, the focus bias value is adjusted to 0 (zero) (S190), the seek is performed (S200), and then restored to the focus bias value set to the opposite polarity, and data reading is retried (S210).

In this case, the maximum value, the set value M, N is an integer set by dividing within one retry time since the host computer generally waits for about 7 seconds after requesting data from the host computer.

5A, 5B, and 5C illustrate changes in jitter when the focus bias setting is changed in the optical disc reproducing / recording system according to the present invention.

When the preset focus bias value is a negative value (S150), the focus error signal becomes a positive value as shown in FIG. 5 (a), and the value of the jitter signal is a reference as shown in FIG. 5 (b). Then, the read retry is repeated until the number of retries reaches M as shown in FIG.

When the read error occurs and retry is attempted, when the focus bias value is cleared to zero (S170), the focus error signal becomes zero as shown in FIG. 5 (a), and the jitter signal as shown in FIG. 5 (b). The value will change. Let's assume that jitter is worse than the first. As shown in FIG. 5C, read retries are performed until the number of retries reaches N. FIG.

Next, when the number of retries is greater than N and the focus bias value is inverted (S180), the focus error signal is also inverted as shown in FIG. 5A. As shown in FIG. 5B, when the jitter becomes the minimum and the read succeeds, the retry count is initialized to 0 as shown in FIG. 5C, and the focus bias value is optimized.

At this time, when the number of retries is the same as N or M and the jitter becomes the minimum and the data is successfully read, the focus bias value at this time is optimal.

As described above, whenever a data read failure occurs, the number of retries is monitored and the focus bias is cleared or inverted to set the optimum focus bias. As a result, it is possible to solve a case in which the focus bias between the inner and outer circumferences of the disk needs to be changed (particularly, the polarity is reversed), or the case where the focus bias value adversely affects reproduction in the scratched portion due to the scratches of the disk.

In addition, in the present invention, the focus bias values are limited to three types of preset values, 0 (clear), and inversion values, but when the focus bias value is adjusted through the above method by dividing into more levels, It will be possible to more effectively set the optimal performance bias bias with optimal jitter.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

The focus bias setting method in the optical disc reproducing / recording system according to the present invention as described above has the following effects.

First, in CD and DVD recording / playback systems, focus bias is set to zero during seek and focus bias is recovered after seek, thereby reducing the occurrence of focus drops due to focus bias during seek. (access) can improve performance.

Second, when the reproducibility is reduced due to misadjustment of the focus bias or the characteristics of the disc, the focus bias value is removed or the polarity is changed to cause optimum jitter. Thus, the reproducibility can be improved and stabilized at the focus bias value that minimizes errors.

Third, by changing the focus bias value when retrying due to data error, it eliminates the influence of misadjusted bias or the reproducing effect due to the difference between the inner and outer bias of the disk. have                     

Fourth, since it can be easily implemented in firmware, no additional circuit is required.

Claims (11)

Operating the focus servo and operating the tracking servo so that the focus error of the disc for playback is zero to operate the focus servo; Forcibly changing a focus bias value in the adjusted focus servo to find a focus bias value that is the minimum jitter, and setting the focus bias value as a focus bias; Determining whether an error occurs in data reading by attempting to read the corresponding data through a seek corresponding to the set focus bias; If it is determined that no error has occurred, transmitting the corresponding data to the host computer; If it is determined that an error has occurred, retrying to read the corresponding data through the sequential search for each level corresponding to the focus bias value set for each level; Comparing the number of retries with a preset maximum value, determining that the read has failed when the value is greater than the maximum value, and transmitting a read error report to the host. How to set up. The method of claim 1, Before performing the data read in the retrying step, Changing the set focus bias to zero and searching for a corresponding data position on the disk corresponding to the focus bias changed to zero; And restoring the changed focus bias to a set focus bias. The method of claim 1 The retrying step A first retry step of retrying reading of the corresponding data through a seek if it is determined that an error has occurred; The number of retries is classified into a plurality of levels within a maximum value (time) waiting after a data request from a host computer, and each focus bias value is set differently for each level, and then searched according to differently set focus bias values. and a second retrying step of retrying reading of the corresponding data through the seek.  4. The method of claim 3, wherein the second retry step is When the number of retries is smaller than the maximum value M (an integer within a range of maximum values), when the number of times is less than the set value M, retrying to read the corresponding data through a seek in response to the preset focus bias. Steps, When the number of retries is smaller than the maximum value and larger than the set value M (an integer within the maximum value range), the preset focus bias value is set to 0 when the value is greater than the set value M and less than the set value N. Retrying to read the corresponding data through the search corresponding to the focus bias set to 0; When the number of retries is compared with the set value N, if the value is greater than the set value N and less than the maximum value, the preset focus bias value is set to the opposite polarity, and the corresponding data read through the search is retried according to the set focus bias. A focus bias setting method in an optical disc reproducing / recording system, characterized in that it comprises a step of performing. The method of claim 1, The focus bias value set differently for each level is set to an initial set value, 0 (clear), and an inverted value. Setting a focus bias, Clearing the set focus bias to zero and searching for the requested data position; And recovering the focus bias after the seek. The method of claim 6, And the focus bias recovery is set to the focus bias set before the seek. The method of claim 6, The focus bias is set to a different focus bias depending on a range of retries. The method of claim 8, And setting a predetermined focus bias value as it is if the range of the retry number is within the first range. The method of claim 8, And if the range of the retry counts is within the second range, focus bias is set to zero. The method of claim 8, And if the range of the retry number is not within the second range, focus bias is switched to the opposite polarity.

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