CN1822124A - Optical disk device - Google Patents

Abstract

In an optical disc device for recording or reproducing on an optical disc such as a DVD-R, in which pre-pits are formed on the land adjacent to the groove, the pre-pit is reliably detected. After the signals of the four-divided photosensors A to D are adjusted by AGC (26c), (26d), the difference is calculated by the differential amplifier (26e), and binarized by the binarizer (26f) to detect the mark Early warning pit information during the period. On the other hand, the upper limit of the signal output by the AGC (26c), (26d) is limited to a certain value by the limiting amplifier (26g), (26h), thereby removing the noise during the marking period. Thereafter, the differential amplifier (26i) is used to calculate the difference between the two signals, and the binarizer (26j) is used to binarize it to detect the pre-pit information during the interval. The logical sum of the two signals is calculated by a logical sum calculator (26k), and output to the controller (20) as pre-signal pit information.

Description

CD device

technical field

The present invention relates to an optical disc device, and in particular to a detection technique for prepits formed on an optical disc.

Background technique

Conventionally, in optical discs such as DVD-R/RW, a track having a pre-pit of address information of an information recording track (track) and adjacent to the information track is, for example, a groove formed adjacent to the outer peripheral side of a groove (groove). The land is used to determine the in-plane position of the optical disc by detecting the pre-pit during data recording and reproduction, so as to perform data recording and reproduction.

In general, pre-pit detection is performed as follows. That is, the reflected light of the laser beam irradiated at the center of the information recording track is converted into an electrical signal by the photosensor divided into four in the radial direction and the circumferential direction, and the two outputs outputted by the photosensor divided in the radial direction are calculated. difference between the signals. Then, the modulation component of the recording power is removed by difference calculation, and the pre-pit contained in the difference signal is extracted and decoded.

A pre-pit detection device is described in Japanese early publication 2000-311344, which detects the circuit and detection interval (space) of the pre-pit during the period of the mark (mark) (the period during which the optical disc is irradiated with recording power to form the pit) Circuits for pre-pits in periods (periods between marks) are arranged in parallel to individually detect pre-pits in a mark period and a space period, and output the logical sum of the two.

However, when calculating the difference between the two signals output by the optical sensor divided in the radial direction, the modulation component of the recording power cannot be completely removed, especially in the edge portion after the start of recording and after the end of recording. The modulation component becomes noise (noise). Moreover, when the laser power at the time of recording power is higher than that at the time of reproduction power, the amount of reflected light at the time of recording power also increases, so that the noise level at the time of recording power becomes larger, and becomes the pre-pit voltage at the time of reproduction power. same level or higher. In this case, the noise at the time of recording power and the pre-pit signal at the time of reproduction power cannot be distinguished in terms of levels. Even if the difference signal is binarized with a predetermined threshold value to extract the pre-pit signal, it is not easy to extract the pre-pit signal of the reproduction power. That is to say, when removing the noise at the time of recording power with a large critical value, the pre-pit signal at the time of reproduction power is removed; Noise is also extracted as a pre-pit signal. Furthermore, since there is a mark period during the recording power application period and a space period during the reproduction power application period, the above-mentioned problem can also be considered that it is difficult to extract the pre-pit signal during the space period.

On the other hand, as described in Japanese early publication 2000-311344, the circuit for detecting pre-signal pits during the mark period and the circuit for detecting pre-signal pits during the interval period are arranged in parallel, although it is possible to detect the pre-signal pit during the mark period and the interval period individually. However, it is necessary to form a gate signal circuit for separately processing signals during the mark period and the space period, which complicates the circuit.

In addition, the difference (pull-push signal) between the two photosensors divided in the radial direction is configured based on the detection of the pre-pit signal, and the reflectance change of the pit (mark) formed in the groove is generated as noise. mix-in, making it difficult to detect only the pre-pit signal. Of course, it is also conceivable to add circuits to remove such noises, but this will lead to more complicated circuit configuration.

Contents of the invention

In view of the problems of the above known technologies, the present invention aims to provide an optical disc device capable of reliably detecting pre-pit data with a relatively simple structure even during intervals or during laser irradiation of reproduction power.

In order to achieve the above object, the present invention, in the optical disc device for detecting and recording the pre-pit information preformed on the optical disc, has: at least one two-divided photodetector, which is divided into two in the radial direction of the aforementioned optical disc, for When recording data, the return light of the laser irradiated on the optical disc is converted into an electrical signal. The gain adjuster is used to individually adjust the gain of the two signals output by the aforementioned two-divided photodetector. The limiter is used to limit the gain adjusted The upper limit level of the two signals, the calculator, used to calculate the difference between the two signals output by the aforementioned limiter, and the extraction device, extracting the aforementioned pre-signal pit information contained in the difference signal output by the aforementioned calculator .

Here, the limitation level of the aforementioned limiter is preferably a level of the returned light that is lower than the recording power and greater than the level of the returned light that is reproduced.

Moreover, it is preferable to have a second calculator for calculating the difference between the two signals after gain adjustment, and a second extracting device for extracting the aforementioned predictor contained in the difference signal output by the aforementioned second calculator. The pit information, and the calculating means are used to calculate the logic sum of the aforementioned extracting means and the aforementioned second extracting means.

According to this, the optical disc device of the present invention, after adjusting the gains of the two signals output by the photodetector that is at least divided into two in the radial direction of the optical disc, for example, the two signals output by the four-divided photodetector, limits the upper limit of the two signals with a limiter level. Limiting the upper limit level by the limiter means, in other words, substituting the return optical signal level of the recording power of the signal to a constant value. According to this, the noise component contained in the return optical signal at the time of recording power is removed, and the difference between the two signals can be calculated, and the pre-signal pit at the time of reproduction power (interval period) can be extracted without being affected by the noise at the time of recording power. information.

Moreover, the pre-signal pit information of the recording power can also be the same as the known ones. The difference between the two signals is calculated without limiting the upper limit level, and the pre-signal pit information contained in the difference signal is detected. By calculating the pre-signal pit information during the mark The logical sum of the pit information and the pre-pit information of the interval period can detect the pre-pit information of any one of the mark period and the interval period.

In order to achieve the above object, the present invention detects the pre-pit information formed in advance on the optical disc and records or reproduces the optical disc device, and has: an irradiation device that irradiates the information recording track with a main (main) laser, and uses The secondary (sub) laser light irradiates the information recording track with respect to the track on which the pre-pit is formed, and the detecting device detects the pre-pit information based on the return light signal of the sub laser light.

Here, the aforementioned detection device preferably has: a four-divided optical sensor, which is individually divided into two in the radial direction and the circumferential direction of the aforementioned optical disc, for converting the return light from the aforementioned sub-laser into an electrical signal, and an adder and subtractor for Calculate the sum or difference of the signals output by the two optical sensors divided in the circumferential direction of the four-divided optical sensor. The extraction device extracts the pre-pit information by cutting and processing the signals output by the aforementioned adder and subtractor.

Moreover, the above-mentioned extracting device preferably has: a detection device for detecting the wobble of the information recording track based on the signal output by the optical sensor on the side of the information recording track among the two optical sensors divided in the radial direction of the aforementioned four-divided optical sensor. wobble) signal, setting means, based on the aforementioned wobble signal, set the processing window in the signal output from the aforementioned adder-subtractor, and the extraction means extracts the pre-signal pit information synchronized with the aforementioned wobble signal.

Moreover, the above-mentioned extracting device preferably has: a four-divided optical sensor, which is individually divided into two in the radial direction and the circumferential direction of the aforementioned optical disc, for converting the return light from the aforementioned secondary laser into an electrical signal, and a gain adjuster for adjusting The signal levels output by the two photosensors divided in the circumferential direction of the four-split photosensor, the subtractor, the difference between the two signals after gain adjustment, and the extraction device are used to cut and process the output of the aforementioned subtractor signal to extract the pre-pit information.

Moreover, the above-mentioned extracting device preferably has: a detection device, by sampling the signal output by the photosensor on the information recording track side of the two photosensors divided in the radial direction of the aforementioned four-divided photosensor at the timing of the reproduced signal, to obtain Detecting the wobble signal of the information recording track, setting means, based on the wobble signal, setting a processing window in the signal output from the subtractor, and the extracting means extracts the pre-pit information synchronized with the wobble signal.

In this device, it is preferable to further have an information delay processing device, which delays and processes the detected pre-pit information based on the relative positions of the main laser and the secondary laser.

According to this, the present invention irradiates a single laser light as known, and does not detect the pre-pit signal contained in the return light of the laser light. While the information recording track is irradiated with the main laser beam (main beam), the information recording track is formed. The track of the pre-pit (for example the land "land") is irradiated with a sub-laser (sub-beam). Then, the pre-pit information is detected based on the return light signal of the secondary laser light. Since the reflectivity of the sub-laser will change in the pit portion, the circuit configuration will not be complicated and only the pre-pit information can be reliably detected.

And, when carrying out the recording and reproducing of data with the main laser, when carrying out the occasion of pre-pit information detection with the sub-laser, because the relative positions of the main laser and the sub-laser are different, it is preferable to adjust the pre-pit position and the sub-laser detection. The main laser position is consistent. When the sub-laser is ahead of the main laser, it can be achieved by delaying the detection of the pre-pit information.

Description of drawings

FIG. 1 is a block diagram illustrating the optical disc device of the first embodiment;

Figure 2 shows the relationship between the groove, the land, the land pre-pit (LPP) and the synchronization signal;

Figure 3 is an explanatory diagram illustrating the relationship between the synchronization frame and the synchronization information;

FIG. 4 is an explanatory diagram showing the configuration of four split photodetectors;

FIG. 5 is a block diagram showing the composition of the pre-pit detection unit in FIG. 1;

FIG. 6 is a sequence flow chart (Part 1) of the first embodiment;

FIG. 7 shows a sequence flow chart (the second) of the first embodiment;

FIG. 8 is a sequence flow chart (part three) of the first embodiment;

FIG. 9 is a sequence flow chart (the fourth) of the first embodiment;

FIG. 10 is an explanatory diagram of an output signal output by a logic sum calculator;

FIG. 11 is an explanatory diagram illustrating irradiation of laser light in the second and third embodiments;

FIG. 12 is an explanatory diagram showing the composition of the main four-divided photodetector and the auxiliary four-divided photodetector;

FIG. 13 is a block diagram showing the composition of the pre-pit detection unit in FIG. 17;

FIG. 14 is a sequence flowchart of the second embodiment;

FIG. 15 is a flow chart showing other timings of the second embodiment;

FIG. 16 is a sequence flowchart of the third embodiment;

FIG. 17 is a block diagram of the optical disc device of the second embodiment.

Graphical labeling instructions

10: Disc 12: Spindle motor

14, 15: Optical read head 16: Laser diode driver

18: Encoder 20: Controller

22: Radio frequency (RF) signal processing unit 24: Decoder

26, 27: Pre-Xun Pit Detection Department

26a, 26b, 27a, 27g, 27i: adders

26c, 26d, 27b, 27h: automatic gain control

26e, 26i: Differential amplifier 26f, 26j: Binarizer

26k: Logic and calculator 27c: Addition and subtraction

27d, 27k: filter 27e, 27m: splitter

27f: Gateway circuit 27j: Sample and hold circuit

100: Pre-information pit 200: Synchronization information

300: main laser 400, 500: secondary laser

Detailed ways

Hereinafter, an embodiment of the present invention will be described with a DVD-R as an optical disc based on the drawings.

FIG. 1 is a block diagram of an optical disc device according to a first embodiment. The optical disc device (DVD-R) 10 is rotationally driven by a spindle motor 12 at a CAV (constant angular velocity) (or CLV (constant linear velocity)), and is placed on a land as an information recording track of the optical disc 10 at a predetermined speed. A land prepit (LPP) is formed at intervals, and the in-plane position of the optical disc 10 can be located by detecting the land prepit.

The optical pick-up head 14 is arranged facing the optical disc 10 , and the laser beam of recording power is irradiated on the optical disc 10 to record data, and the laser beam of reproducing power is irradiated to reproduce the recorded data. When recording, the recording data output by the controller (controller) 20 is modulated by a decoder (encoder) 18, and then the driving signal is converted by a laser diode (laser diode, LD) drive unit 16 to drive the optical pickup head. Laser diodes (LDs). To describe in more detail, during the mark period of forming a pit, record with a single pulse of recording power at 3T, and record with multiple pulses of recording power (multipulse or pulse train) at 4T to 14T. )) to record. Laser irradiation with reproduction power (bias power) during the interval does not form pits. When reproducing, the four-divided optical sensor in the optical pickup head 14 supplies the electric signal transformed by the amount of returned light to a radio frequency (radio frequency, RF) signal processing unit 22, and after being demodulated by a decoder (decoder) 24, it is used as The reproduced data is supplied to the controller 20 .

The RF signal processing unit 22 has an amplifier, an equalizer, a binarization unit, a PLL unit, etc., and the RF signal is boosted and then binarized, and a synchronization signal is formed in the PLL unit and output to the decoder 24 . Furthermore, the RF signal is also supplied to the pre-pit detection unit 26 . The decoder 24 decodes the reproduced signal based on the reproduced binarized signal or the synchronous clock, performs error correction and supplies it to the controller 20 .

The pre-pit detector 26 detects the signal component of the pre-pit formed on the land adjacent to the groove (the land adjacent to the outer peripheral side of the groove) included in the reproduced RF signal, and supplies the signal component to the controller 20 . The configuration of the pre-pit detection unit 26 and the pre-pit detection processing will be described later.

The controller 20 is constituted by a microcomputer (Micom) or the like, and supplies the recorded data to the encoder 18 and supplies the detected pre-pit information to the encoder 18 . While modulating the recording data, the encoder 18 periodically inserts synchronization information based on the pre-pit detection information to supply the data signal to the LD driver 16 .

Moreover, other focusing signals or tracking signals are also formed to control the focus and tracking servo system of the optical pick-up head 14 through the focus servo or the tracking servo. These are the same as the known ones. Its description is omitted.

FIG. 2 is a schematic diagram of the recording mode of the optical disc 10 in this embodiment. As previously described, the land of the optical disc 10 is formed with pre-pit 100 at predetermined intervals. On the other hand, the data recorded in the groove is divided into each SYNC frame (frame) as a predetermined information unit, 26 SYNC frames constitute a sector (sector), and 16 sectors constitute an ECC (error correction code) , error correcting code) block. Then, a synchronization message (SYNC) 200 for retrieving each synchronization of the SYNC frame is inserted at the front of the individual SYNC frame. The synchronization information SYNC uses 14T which is longer than the longest 11T which appears in the data modulation part which does achieve SYNC frame synchronization. Then, the SYNC pulse of the 14T standard of DVD-R can select one of marks and spaces. Furthermore, in FIG. 2 , the groove wobbles at a predetermined frequency, and here the number of revolutions of the optical disc 10 can be detected and controlled by detecting the wobble frequency.

FIG. 3 is a schematic diagram showing the relationship among the SYNC frame, the synchronization information (SY) and the pre-pit. The SYNC frame is obviously divided into even frame (EVEN frame) and odd frame (ODD frame). The pre-signal pit is usually formed corresponding to the even frame. However, between two adjacent grooves of the recording required groove When pre-pits are arranged at approximately the same position, since the return light will be mixed with two pre-pit components, in order to avoid such interference, they are shifted and arranged in odd-numbered frames. Furthermore, the wobble frequency is eight times the SYNC frame frequency, and pre-pits are arranged at the first three wobble apexes in one SYNC frame. Since there are 13 pre-signal pits of three bits in one sector (13 even-numbered frames in 26 frames), one sector contains 3*13 pre-signal pit information. The relative addresses are formed at 0, 2, 4, 6, and 8 of the SYNC frame, and the user data are formed at 10, 12, 14, 16, 18, 20, 22, and 24 of the SYNC frame. The pre-signal pit at the first position among the three vertices becomes the SYNC pre-signal pit indicating the synchronous position. The optical disc device can detect the synchronous position by detecting the SYNC pre-common pit, and allocate 14T of synchronous information at this synchronous position during data recording. to record data.

FIG. 4 is a schematic diagram showing the relationship between the arrangement of the four-segmented photosensors and the laser spots in the optical pickup head 14 . The four-divided optical sensor is divided in the radial direction of the optical disc 10 and divided in two in the circumferential direction. The optical sensors divided into two in the radial direction are (A, D) and (B, C), and the optical sensors divided in the circumferential direction are (A, B) and (C, D). Located on the land side where the pre-pit (LPP) 100 is formed are photosensors (A, D).

FIG. 5 is a schematic block diagram illustrating the structure of the pre-pit detection unit 26 in FIG. 1 . The pre-signal pit sensing section 26 is composed of adders 26a, 26b, automatic gain control (auto gain control, AGC) 26c, 26d, limiting amplifiers (limiter amp) 26g, 26h, differential amplifiers 26e, 26i, and a binarizer. 26f, 26j, and logic and calculator 26k.

The signals output from the sensors A and D of the four-divided photosensors are supplied to the adder 26a. The adder 26a calculates the sum of the two signals to supply the (A+D) signal to the AGC 26c.

On the other hand, the signals output from the photosensors B and C are supplied to an adder 26b. The adder 26b calculates the sum of the two signals to supply the (B+C) signal to the AGC 26d.

The AGCs 26c and 26d adjust the gain so that the levels of the (A+D) signal and the (B+C) signal almost match, and output the signals to the differential amplifier 26e. That is, the (A+D) signal is output to the non-inversion output terminal (+), and the (B+C) signal is output to the inversion output terminal.

The differential amplifier 26e functions as a second calculator to calculate the difference between the two signals and output (A+D)-(B+C) to the binarizer 26f.

The function of the binarizer 26f is as a second extraction device, which binarizes the (A+D)-(B+C) signal output by the differential amplifier 26e with a predetermined critical value, extracts the pre-signal pit information and outputs it to Logic and calculator 26k. These adders 26a, 26b, AGC26c, 26d, differential amplifiers 26e, 26i, binarizers 26f, 26j, and logic sum calculator 26k are configured to calculate the output from the two photosensors output in the radial direction. The same as the known circuit for detecting the signal difference of the pre-signal pit information, the pre-signal pit signal during the mark period can be extracted by properly adjusting the threshold value (the threshold value of the degree of noise removal during the mark period), but the pre-signal pit signal during the interval period It is not easy to extract the signal from the pit. As mentioned above, the recording power of the laser light during the marking period is large, and the noise level contained in the amount of returned light is also large, and this noise level is the same as or even larger than that of the pre-pit during the interval period.

Here, the pre-pit detection unit 26 of this embodiment is further provided with limiting amplifiers 26g, 26h, a differential amplifier 26i (first calculator) and a binarizer 26j (extracting device) in the configuration of the above-mentioned known circuit. These are used to detect the pre-signal pit information during the interval. Then, the pre-pit information of the mark period output by the binarizer 26f and the logical sum are calculated to detect the pre-pit information of the two periods of the mark and the interval.

That is, the gain-adjusted (A+D) signal output from the AGC 26c is supplied to the limiting amplifier 26h as well as the differential amplifier 26e. The limiting amplifier 26h is an amplifier that limits the upper limit level of the input signal, in other words, when the upper limit value of the input signal exceeds a predetermined upper limit value, it replaces it with the upper limit value and outputs it. The (A+D) signal output from the limiting amplifier 26h limited to the upper limit level is supplied to the differential amplifier 26i.

On the other hand, the gain-adjusted (B+C) signal output from the AGC 26d is supplied to the limiting amplifier 26g as well as the differential amplifier 26e. The limiting amplifier 26g also limits the upper limit level of the input signal like the limiting amplifier 26h, and the (B+C) signal output from the limiting amplifier 26h limited to the upper limit level is supplied to the differential amplifier 26i.

Furthermore, the upper limit values of the limiting amplifiers 26h and 26g are, for example, a level higher than the return light level of the interval period by a certain amount, and a level lower than the return light level of the recording power. That is, return light level of recording power (return light level B after pit formation)>upper limit>return light level of reproduction power. Furthermore, the upper limit values of the two limiting amplifiers 26g and 26h may be the same.

The differential amplifier 26i functions as a calculator to calculate the difference between the two signals limited to the upper limit level, and outputs the calculated (A+D)-(B+C) signal to the binarizer 26j . Although the noise or the pre-pit signal during the mark period is removed by the limiting amplifiers 26g, 26h, the pre-pit signal during the interval is not limited by the limiting amplifiers 26g, 26h. The binarizer 26j can reliably extract the pre-pit signal during the interval without being affected by the noise during the mark period by calculating the difference between the modulation component of the remaining recording power and the pre-pit signal from which the noise has been removed.

The logical sum calculator 26k calculates the logical sum of two signals and outputs it to the controller 20 . Since the pre-pit signal during the mark period is output from the binarizer 26f, and the pre-pit signal during the space period is output from the binarizer 26j, the pre-pit signal between the mark period and the space period can be detected by calculating the logical sum of the two. Signal pit.

The above processing is described in more detail using a sequence diagram.

Signals of the light sensors AD are shown in FIG. 6 . Figure 6 shows (A) the signal output by photosensor A, (B) the signal output by photosensor B, (C) the signal output by photosensor C, and (D) the signal output by photosensor D . Since the laser power during marking increases as recording power, the signal level of its return light also increases. Furthermore, since the recording power is multipulse, the return optical signal is also multipulse. However, for the convenience of illustration, the actual envelope of the return optical signal is shown. At the time point after the recording power is irradiated, the signal level of the return light becomes extremely large (level A) because no pit is formed, and the return light signal folded back by the pit is also reduced with the formation of the pit. becomes a constant value (level B). On the other hand, since the laser light of the reproduction power is irradiated during the interval, the return light signal also becomes a constant value. If the pre-pit signal LPP exists in the mark period, the signal due to the LPP is included in the return optical signal, and the signal level is only reduced by the return portion due to the LPP. And the same is true for the interval period. In the figure, LPPw represents the LPP component in the mark period, and LPPr represents the LPP component in the space period. LPP randomly appears between marks and during any of the intervals.

, since the photosensors A and D are located on the side of the land where the pre-pit LPP is formed, LPPw or LPPr appears as a signal with a reduced level, and the signals output by the photosensors B and C are reduced in level through the light refraction phenomenon. A signal that increases on the contrary (phase-inverted signal).

(A) and (B) of FIG. 7 respectively show the (A+D) and (B+C) signals whose gains have been adjusted by the AGCs 26c and 26d. Also, (C) is a schematic diagram of the (A+D)-(B+C) signal output from the differential amplifier 26e. The noise level in the mark period is on the same level as the level of the pre-pit LPPr in the mark period. From this, it can be seen that although the pre-pit LPPw in the mark period can be detected, it is difficult to detect the LPPr.

(A) and (B) of FIG. 8 respectively show the signal output from the limiting amplifier 26h and the signal output from the limiting amplifier 26g. The dotted line part in the figure indicates that the defect is caused by limiting the upper limit level to a certain value through the limiting amplifiers 26g and 26h. The noise during the marking period is removed so that the LPPr during the space period continues to remain. Although LPPw during marking is removed like noise, since LPPw can be detected by the binarizer 26f, there is no problem.

(A) and (B) of FIG. 9 respectively show the signal output from the differential amplifier 26i and the signal output from the binarizer 26j. By calculating the difference between the two signals, components or noise accompanying recording power modulation during the mark period are removed, and only LPPr during the space period exists. If such a signal is binarized using a predetermined threshold value as shown in the dot lock line, it is possible to reliably extract only the LPPr in the interval period.

The signals supplied to the controller 20 by the logic sum calculator 26k are shown in FIG. 10 . Since the logical sum calculator 26k outputs the logical sum of the mark period LPPw output from the binarizer 26f and the interval period LPPr output from the binarizer 26f, a mixed signal of LPPw and LPPr is output as shown. Therefore, even if LPP exists in either the mark period or the space period, LPP can be reliably detected.

However, in this embodiment, instead of separately sampling and holding the return optical signal during the mark period and the space period as known, the structure can be simplified because the LPP in the space period can be detected only by using the upper limit level of the limit signal.

As mentioned above, although the Example of this invention was described, this invention is not limited to this, Various changes are possible.

For example, the present embodiment is described using a DVD-R, but it can also be applied to an optical disc (DVD-RW) in which pre-pit can be formed arbitrarily.

Furthermore, in this embodiment, a low pass filter may be provided in the rear stage of the differential amplifier 26i, and then binarized by the binarizer 26j.

Furthermore, as shown in Figure 3, the LPP is located at the peak position of the swing, that is, it exists synchronously with the swing signal, so the gateway (gate) used to control the swing signal of the number of revolutions can also be binarized The device 26j draws LPPr only near the apex of the swing. The binarizer 26f also sets a gateway for the wobble signal, and can extract LPPw.

Moreover, in the above-mentioned first embodiment, the laser beam irradiated to the optical disc 10 by the optical pickup 14 is only the main laser beam (main beam) for irradiating the information recording track. The embodiment of the surface pre-pits is used for illustration.

However, in addition to the main laser, it is also possible to further irradiate the land on which the pre-pit information is formed related to the groove with a sub-laser (sub-beam), and use this laser to detect the land pre-pit. The sub-laser can be formed by splitting using the main laser. A second embodiment using this laser is described below.

FIG. 17 shows a block diagram of the structure of the optical disc device of this embodiment. In the same figure, the same components as in FIG. 1 are assigned the same symbols and their descriptions are omitted.

The optical pick-up head 15 is provided with a main four-split photosensor that converts the return light of the main laser beam into an electrical signal and a sub-four-split photosensor that converts the return light of the sub-laser light into an electrical signal, and the output signal of the main four-split photosensor The above-mentioned RF signal processing unit 22 is supplied, and the signal output from the sub-fourth photosensor is supplied to the pre-pit detection unit 27 described later.

The pre-pit detector 27 includes the reproduced signal RF, and detects the pre-pit formed on the land adjacent to the groove (the land adjacent to the outer peripheral side of the groove) based on the signal supplied from the sub-quarter division photosensor. The signal components are supplied to the controller 20. The configuration of the pre-pit detection unit 27 and the pre-pit detection processing will be described later.

In this embodiment, as mentioned above, the pre-signal pits are located at the vertices of the first 3 swings in one SYNC frame, that is, they are formed synchronously with the fluctuation signal, and the processing window is set at this point to eliminate noise and Detected the warning pit information.

FIG. 11 shows a schematic diagram of the positional relationship between the laser beam irradiated by the optical pickup head 15 on the optical disc 10 and the grooves and lands. The main laser beam 300 of the optical pickup 15 is irradiated on the groove to perform data recording and reproduction. On the other hand, the sub-laser 400 obtained by splitting the main laser 300 is irradiated to the approximate center of the pre-pits adjacent to the lands forming the groove. That is, the main laser 300 and the secondary laser 400 are arranged at half periods of the groove. Moreover, since the pre-pit (LPP) is formed on the land surface on the outer peripheral side of the groove in the figure, the secondary laser light 400 is irradiated on the outer peripheral side land surface, and if the main laser beam 300 is divided into three, the adjacent The two lands of the trench are irradiated with the sub-laser 500 together. In the figure, such a secondary laser is shown as a dotted line. However, since the pre-pit (LPP) formed on the land on the inner peripheral side further has the pre-pit (LPP) on the groove on the inner peripheral side, this information cannot be directly used.

FIG. 12 is a schematic diagram of the structure of two four-divided optical sensors disposed on the optical pickup head 15 . (a) shows the configuration of the main four-divided optical sensor, which is divided into four in the radial direction and two in the circumferential direction to form a structure. The individual photosensors are photosensors A to D. FIG. The two optical sensors divided in the radial direction are (A and D) and (B and C), and the two optical sensors divided in the circumferential direction are (C and D) and (A and B). Reflected light from the main laser beam 300 enters the main four-segment photosensor.

On the other hand, (b) shows the configuration of the sub-quadrant optical sensor, and the same individual halves as the main quadrant optical sensor are formed in the radial direction and the circumferential direction. The individual photosensors are photosensors E to H. The two optical sensors divided in the radial direction are (E and H) and (F and G), and the two optical sensors divided in the circumferential direction are (G and H) and (E and F). The reflected light of the secondary laser light 400 enters the secondary four-segment photosensor. Also, in the sub-quadrant optical sensor, (G and H) are located on the upstream side with respect to the rotation direction of the optical disc 10 . That is, the pre-pit is first detected with (G and H), and then detected with (E and F).

FIG. 13 is a block diagram showing the configuration of the pre-pit detection unit 27 in FIG. 17 . The pre-pit detector 27 has adders 27a, 27g, 27i, automatic gain control (AGC) 27b, 27h, adder-subtractor 27c, filter 27d, 27k, slicer (slicer) 27e, 27m, sample hold (S /H) circuit 27j and gateway circuit 27f.

The signals output from the photosensors E and F constituting the sub-quadrant photosensors are added by the adder 27 a and output to the AGC 27 b. Then, the signals output from the photosensors G and H constituting the sub-quadrant photosensors are added by the adder 27g and supplied to the AGC 27h. AGC27b and AGC27h adjust the levels of the two signals to be consistent, and then output them to the adder-subtractor 27c. Moreover, when reproducing, the laser light of the reproduction power is irradiated by the optical pick-up head 15. Since the sub-laser 400 also always maintains a certain power, the signal levels output by the optical sensors E～H are slightly the same, and there is no need to go through AGC27b, 27h in particular. Gain adjustment. Therefore, the operation of AGC 27b and 27h may also be turned off during regeneration (as will be described later, it is not particularly necessary when calculating the sum of the two). Specifically, the controller 20 may supply the AGC 27b, 27h with a recording/reproduction selection signal, and the operation of the AGC 27b, 27h may be turned on or off based on the selection signal. AGC27b and 27h output the gain-adjusted signal to the adder-subtractor 27c.

The adder-subtractor 27c calculates the sum or the difference of the (E+F) signal output from AGC27b and the (G+H) signal output from AGC27h, and outputs it to the filter 27d. Either the sum or the difference can be calculated at the time of reproduction, and the difference value can be calculated at the time of recording. Whether to calculate either the sum or the difference can be switched based on the above-mentioned selection signal. In this embodiment, especially the case where the pre-pit information is detected during reproduction, the adder-subtractor 27c calculates the sum of the two signals.

The filter 27d smoothes the sum signal output by the adder-subtractor 27c, that is, (E+F)+(G+H), and outputs it to the divider 27e.

The divider 27e extracts the upper level of the signal at a predetermined critical level, specifically a predetermined level higher than the base level, and outputs it to the gateway circuit 27f.

On the other hand, the signals output from the photosensors F and G are also supplied to the adder 27i. The adder 27i adds and calculates two signals to become (F+G), and supplies to a sample-and-hold (S/H) circuit 27j. The sample-and-hold circuit 27j samples and holds the signal when the laser power is at the reproduction power, and since the reproduction power is always at the reproduction power, the function is not particularly necessary. On and off of the sample hold circuit 27j can be switched based on a selection signal. The sample hold circuit 27j outputs the (F+G) signal to the filter 27k.

The filter 27k smoothes (F+G) and supplies it to the divider 27m.

The divider 27m takes out the upper level and the lower level of the (F+G) signal at a predetermined threshold level, specifically at a zero level, and supplies it to the gateway circuit 27f. The photosensors F and G are photosensors located on the side of the groove, and include a wobble signal of the groove. Therefore, by dividing the upper level and lower level of the (F+G) signal, the top and bottom of the swing signal can be detected.

The gateway circuit 27f sets the processing window based on the signal output by the divider 27m. Specifically, the gateway circuit 27f is turned on at the peak of the swing signal to output the signal, and turned off at other points to block the signal. From the signals output by the divider 27e, only the signal at the top of the wobble signal is extracted to be output to the controller 20 as the pre-pit signal (LPP).

In FIG. 14 and FIG. 15 , a sequence flow chart of the above-mentioned processing is shown. (a) of FIG. 14 is the output of the adder 27g, that is, the (G+H) signal. The signals output from the photosensors G and H include a wobble signal corresponding to the wobble of the groove, and LPP exists at the apex of the wobble signal. In addition, although the amount of returning light for laser light refraction is actually reduced at the portion where LPP exists, this is shown as an inverted signal for the convenience of illustration.

(b) of FIG. 14 is the output of the adder 27a, that is, the (E+F) signal. This signal also includes a wobble signal, the apex of which has an LPP. The two photosensors (E+F) and (G+H) divided into two in the circumferential direction have a front-rear positional relationship with respect to the pre-signal pit. Therefore, as shown in (a) and (b), the LPP first appears on the (G+H) signal, and the LPP appears on the (E+F) signal after a predetermined time delay. Therefore, when these signals are added by the adder-subtractor 27c, the LPPs contained in the two signals are added to obtain the signal shown in (c). Moreover, since the actual signal contains various noises, and the level of LPP is relatively small, it is not easy to distinguish these noises from the level.

On the other hand, (a) of FIG. 15 shows the (E+F)+(G+H) signal shown in (c) of FIG. 14 , and includes noise outside the LPP.

(b) of FIG. 15 shows the swing signal output by the adder 27i, that is, the (F+G) signal. Moreover, although this signal also includes LPP, it is omitted in the figure because it is subsequently divided and processed by the divider 27m.

(c) of FIG. 15 is a schematic diagram of the signal output by the adder 27i being smoothed by the filter 27k, and then divided and processed by the divider 27m as a binary signal. This is a binary signal that turns on at the top of the swing and turns off at the bottom of the swing. The gateway circuit 27f processes the signal supplied from the divider 27e based on this binary signal. That is, when the binary signal is on, the gateway is turned on, and when the binary signal is off, the gateway is turned off. In this way, only signals near the top of the swing signal are output, and as shown in (d) of FIG. 15 , only the signal at the top of the swing signal is extracted as the original LPP, and the signal not at the top of the swing signal is removed as noise.

According to this, the present embodiment can extract the pre-pit information based on the return light of the sub-laser 400 during regeneration. The pre-pit information is detected by the position of the sub-laser 400 , not by the position of the main laser 300 as known. Therefore, based on the pre-signal pit information detected by the main laser 300 in the controller 20, in order to detect the synchronous position and the OR position and use the occasion of the mutual division method (algorithm), the detected pre-signal pit information must be delayed by a predetermined time. . Specifically, the delay time is calculated from the distance between the main laser beam 300 and the secondary laser beam 400 in the circumferential direction (the rotation direction of the optical disc 10) and the linear velocity, and the delay time is delayed by software in the controller 20, or in the pre-pit detection unit 27. The post-setting delay circuit is delayed by hardware. Accordingly, the master laser 300 can also be used to detect the pre-pit for processing.

In the above-mentioned second embodiment, the pre-pit information is detected during reproduction for illustration. Next, the third embodiment is described in the case of detecting the pre-pit information in the recording mode, that is, when the laser light of the recording power output by the optical pickup 15 is irradiated. In addition, when recording on the optical disc 10, recording is performed by multi-pulse, that is, a signal of 3T is recorded by a single pulse, and data of 4T or more is recorded by a plurality of pulses.

FIG. 16 is a timing diagram of this embodiment. Although the block diagram of this embodiment is the same as the block diagram of Figure 17, it should be noted that this embodiment is based on the selection signal output by the controller 20, the AGC27b, 27h and the sample and hold circuit 27j are turned on, and the addition and subtraction The device 27c calculates the difference between the two signals.

(a) of FIG. 16 is the recording power, and multi-pulse is shown. A group of multi-pulses are used to record 1 data. The pulse width of the previous pulse and the power (duty) of the subsequent pulse are determined according to predetermined rules to form a 4T-14T signal.

(b) of FIG. 16 is the output of the adder 27g, that is, the (G+H) signal. Also, the swing component is omitted for convenience of description. The actual signal is the signal of FIG. 15( a ) or ( b ) superimposed on the signal of FIG. 16( b ). In the case of the return light of the main laser 300, since the initial pre-pit of the recording power is not formed and the amount of reflected light is large, if the signal pit is formed later, the amount of return light reflected by it is reduced to become a complicated signal change, and the signal changes Part of contains LPP. On the other hand, the return light of the secondary laser 400 is not affected by the pits as shown in the figure, but only shows the modulation of the laser power by the recording pulse, and the modulation includes LPP.

(c) of FIG. 16 shows that the output of the adder 27a, that is, the (E+F) signal, delays the (G+H) signal for a predetermined time to appear LPP. (E+F) signal and (G+H) signal are adjusted with AGC27b, 27h gain, and after their levels are slightly adjusted to be the same, the difference is calculated by adder and subtractor 27c and output (G+H)-(E+F) . After performing the difference calculation, the modulation component and the swing component of the laser power are removed.

(d) of FIG. 16 is the output of the adder-subtractor, that is, the signal of (G+H)-(E+F) only extracts the LPP. Thereafter, as in the second embodiment, the gateway circuit 27f is turned on at the peak timing of the wobble signal, and only the original LPP is extracted to output to the controller 20 after removing the noise. However, the sample-and-hold circuit 27j samples the position of the apex of the wobble signal without being affected by the modulation of the laser power during the reproduction power (interval period). Moreover, the divider 27e may also take out any one of the upper part or the lower part, divide and process the two sides of the upper part and the lower part to detect LPP, and output when both sides detect LPP, and if only one side is detected, it is judged as noise. can be ignored. The means for delaying the pre-pit information detected by the pre-pit detection unit 27 is the same as that of the second embodiment.

Accordingly, since the present embodiment extracts the pre-pit information based on the returned light of the recorded sub-laser 400 , the configuration is simpler than that of the main laser 300 , and the pre-pit information can be extracted reliably. Then, by combining the above-described embodiments, it is possible to detect pre-pit information regardless of any period during reproduction or recording.

The embodiments of the present invention have been described above, but the present invention is not limited thereto, and various changes are possible.

Moreover, the second and third embodiments detect the pre-pit information based on the return light of the sub-laser 400, but it is also possible to use the return light of the main laser 300 to detect the pre-pit information in the same way as the known ones, and adopt a method with a small error rate. party.

The effect of the invention

As described above, according to the present invention, it is possible to reliably detect pre-pit information with a simple configuration.

Claims (5)

1. An optical disc device, which detects a pre-pit information preformed on an optical disc and records or reproduces it, characterized in that: the optical disc device has: An irradiation device, while irradiating an information recording track with a main laser, forms a track with a pre-pit related to the information recording track with one laser irradiation; A detection device, which detects the pre-pit information based on the returned light signal of the laser, wherein the detection device also has: A light sensor is divided into two blocks in the radial direction and the circumferential direction of the disc, and converts the return light from the laser into an electrical signal; An adder and subtractor for calculating the sum or difference of the signals of the two blocks divided by the optical sensor in the circumferential direction of the disc; An extraction device extracts the pre-pit information by cutting and processing the signal output by the adder-subtractor. 2. The optical disc device as claimed in claim 1, wherein the extracting device further has: A detection device, based on a signal output by a block on the side of the information recording track among the two blocks divided in the radial direction of the optical sensor, detects a wobble signal of the information recording track; A setting device sets a processing window in the signal output from the adder-subtractor based on the wobble signal, and the extraction device extracts the pre-pit information synchronized with the wobble signal. 3. An optical disc device, which detects a pre-pit information preformed on an optical disc and records or reproduces it, characterized in that: the optical disc device has: an irradiating device for irradiating an information recording track with a main laser beam, and at the same time irradiating the information recording track with a primary laser beam corresponding to the track on which the pre-pit is formed; A detection device for detecting the pre-pit information based on the returned light signal of the laser, wherein the detection device has: A light sensor is divided into two blocks in the radial direction and the circumferential direction of the disc, and converts the return light from the laser into an electrical signal; A gain adjuster, which adjusts the signal level output by the optical sensor in the two blocks divided in the circumferential direction of the optical disc; a subtractor for calculating the difference between the gain-adjusted two signals; An extracting device extracts the pre-pit information by cutting and processing the signal output by the subtracter. 4. The optical disc device as claimed in claim 3, wherein the extracting device further has: A detection device, by sampling the signal output by the block on the side of the information recording track divided in the radial direction of the optical sensor at the timing of the reproduced signal, to detect a wobble signal of the information recording track; A setting device sets a processing window in the signal output from the subtracter based on the wobble signal, and the extraction device extracts the pre-pit information synchronized with the wobble signal. 5. The optical disc device according to any one of claims 1 to 4, characterized in that it also has an information delay processing device, based on the relative relationship between the main laser and the secondary laser, delay processing the detected Information pit information.

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