KR100549663B1 - Optical Recording Medium And Apparatus For Driving The Same - Google Patents

Abstract

The present invention relates to an optical recording medium having a wobbled pit array structure and a driving apparatus thereof.

The optical recording medium of the present invention is characterized in that it is formed in correspondence with an information signal and is wobbled so that the pit rows wobbed continuously or intermittently at regular intervals form a track, and adjacent pit rows have inverted phases.

In the optical recording medium driving apparatus of the present invention, a light converging means for irradiating a light beam to a wobbling optical recording medium such that the pit rows wobbling continuously or intermittently at regular intervals form a track, and adjacent pit rows have an inverted phase. And light detecting means for detecting and photoelectrically converting the amount of light reflected from the optical recording medium, and a tracking error from at least four light detecting signals detected by the light detecting means. Tracking error detecting means for detecting a signal and tracking control means for performing tracking control of the light beam based on the tracking error signal.

According to the present invention, the adjacent pit rows (tracks) are formed to be wobbled with phases opposite to each other, so that the track pitch can be narrowed with respect to the light spot having a specific wavelength, thereby greatly improving the recording density.

Description

Optical Recording Medium and Apparatus {Optical Recording Medium And Apparatus For Driving The Same}

The present invention relates to an optical recording medium, and more particularly, to an optical recording medium having a wobbled pit thermal structure and a driving method thereof.

Recently, optical recording media, magneto-optical recording media, etc. have been developed and commercialized as information recording media for recording various kinds of information such as audio and video information. Of these, optical recording media include CD-ROM (CD-Read Only Memory) and DVD-ROM (Digital Versatile Disc-ROM), including CDs (Compact Disc), which have already been generalized, and CD-R ( WORM (Write Once Read Many) type recording media such as CD-Recordable and DVD-R, and rewritable recording media such as CD-Rewritable (CD-RW) and DVD-Random Access Memory (DVD-RAM) It is being spread or developed.

Referring to FIG. 1, a pit row 12 formed in a track on a conventional optical recording medium 10 is shown.

The optical recording medium 10 shown in Fig. 1 is a recording medium for reproduction only, and stores information in the form of a pit row 12 which constitutes a track that runs from the inner circumference to the outer circumference in a spiral or concentric manner. The information recorded in the form of the pit rows 12 is reproduced by detecting the amount of reflected light by irradiating a light beam while following the track at a constant speed. In this case, the focus for controlling the focused state of the light beam irradiated to the track and the tracking for controlling the track of the light beam are adjusted according to the electrical signal detected from the reflected light incident on the photodetector. In addition, since the reproduced information on the optical recording medium is known, that is, the position of the track to which the light beam is irradiated, the optical disc is randomly accessed.

However, since a signal is not recorded in the recording disc, a track structure for guiding the information tracking status is applied. For example, an optical recording medium such as a CD-R, a DVD-RAM or the like has a track formed in the form of a hill and a valley. In addition, in order to indicate physical location information and the like for enabling information access random access, the boundary side of the tracks of adjacent mountains and valleys is wobbled at regular intervals. In this case, the pit rows are formed in a straight line along the track reference line on the track of the goal or the track of the hill and the goal.

Recently, as a recording medium for recording a large amount of information such as a moving picture is required, various methods for increasing the recording density of an optical disc have been attempted. For example, in the case of CDs and DVDs, a method of reducing the size of a recording mark or pit or reducing the track pitch between tracks has been attempted. In addition, techniques have been developed that use a short wavelength light source and increase the numerical aperture of the objective lens to reduce the spot diameter of the light beam. However, since the spot diameter of the light beam is ultimately limited, it is inevitable to reduce the size of the pit or the distance between the tracks.

For example, an optical disc for exclusive use of reproduction typically manufactures a disc of a disc on which a desired pit is formed using an exposure apparatus, and inverts and transfers the pit formed on the disc to produce a stamper, and then duplicates the disc using the stamper, that is, a disk substrate. It is produced by molding. Recently, with the development of argon (Ar) lasers and the like, it is possible to form micropits, but since there is no light source corresponding to the micropits in the playback apparatus, as a result, the size and track of the pit are within a range that can be read by the playback apparatus. The pitch was bound to be limited.

In addition, as blue lasers have been recently developed, it is possible to provide a micro light spot, thereby reducing the size of the pit and the track pitch. There is a problem of causing such a phenomenon as to decrease the reliability of recording and reproduction. As a result, it is difficult for an optical disc to significantly improve the recording density due to the limitation of the track pitch.

Accordingly, it is an object of the present invention to provide an optical recording medium having a wobbled pit array structure and capable of increasing recording density and a driving apparatus thereof.

In order to achieve the above object, the optical recording medium of the present invention is formed in response to an information signal, so that the wobbled pit rows continuously or intermittently formed at regular intervals form a track, and adjacent pit rows have inverted phases. It is characterized by bling.

The pit row of the optical recording medium of the present invention is characterized in that it is formed in the form of a wobble bent to both sides with respect to the track center line.

In the optical recording medium of the present invention, the pit rows are formed in the valleys when the structures of the hills and valleys are formed, and the areas provided between adjacent pit rows have a mountain structure.

The track pitch, which is the distance between adjacent track centerlines of the optical recording medium of the present invention, is characterized by having a value of at least 1/2 of the optical spot diameter of a specific wavelength.

In the optical recording medium driving apparatus of the present invention, a light converging means for irradiating a light beam to a wobbling optical recording medium such that the pit rows wobbling continuously or intermittently at regular intervals form a track, and adjacent pit rows have an inverted phase. And photodetection means for detecting the amount of light reflected from the optical recording medium and photoelectric conversion, and a tracking error signal from at least four photodetection signals detected by the photodetection means. And tracking control means for performing tracking control of the light beam based on the tracking error signal.

The optical recording medium driving apparatus of the present invention is characterized by further comprising reproducing signal processing means for generating a reproducing signal by signal processing using at least two light detecting signals of the at least four light detecting signals.

The tracking control means of the optical recording medium driving apparatus of the present invention is characterized in that the light collecting means controls the light collecting means so that the light beam follows the center line of the track.

The tracking error detecting means of the optical recording medium driving apparatus of the present invention comprises: band filtering means for detecting first to fourth wobble signals from the at least four light detecting signals; First subtracting means for subtracting the first and third wobble signals to generate a first difference signal; second subtracting means for subtracting the second and fourth wobble signals to generate a second difference signal; Addition means for adding up the first and second difference signals, third subtraction means for subtracting the first and second difference signals to generate a third difference signal, a sum signal from the addition means and the third difference signal Multiplying means for generating the tracking error signal.

Other objects and advantages of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 to 5.

2 illustrates a relationship between a track structure of an optical recording medium and a spot diameter of a light beam irradiated onto the track according to an embodiment of the present invention.

In the optical disc 20 of FIG. 2, the pit rows 14A are arranged to be wobbled with a constant period to form a wobbling track 14. Basically, when one pit row structure is examined, the pit width and the change interval Δt of the wobble portion are set to appropriate values as shown in (A). Here, the change interval Δt of the wobble portion has a relatively small value compared to the pit width. Then, the radially adjacent tracks 14 and 14 'have phases that are inverted with each other. In particular, the track pitch Tp, which is the distance between the center lines of adjacent tracks 14 and 14 ', is set relatively small. The conventional track pitch Tp shown in FIG. 1 has a value close to an optical spot diameter of a specific wavelength band, while the track pitch Tp shown in FIG. 2 has a value of about 1/2 of the optical spot diameter. Will have In other words, when a conventional light beam follows the centerline of an arbitrary track 14, its light spot diameter leads to the centerline of the adjacent tracks 14 'and 14 "on the inner and outer circumferential sides of the track 14. In this case, even if the track pitch Tp has a relatively small value compared to the optical spot diameter, the adjacent tracks 14 'and 14 "are formed to have inverted phases from each other, so that the following playback and tracking methods It is possible to detect and track accurate reproduction signals. Thus, according to the optical recording medium according to the present invention, it is possible to relatively narrow the track pitch Tp, thereby increasing the recording density.

3 is a block diagram illustrating an optical recording medium driving apparatus according to an exemplary embodiment of the present invention. The optical recording medium driving apparatus illustrated in FIG. 3 is configured to detect a reflected light beam while irradiating a light beam onto the optical recording medium 20. The optical pickup 22, the tracking error detector 24 that detects the tracking error signal from the output signal of the optical pickup 22, and the tracking actuator (not shown) of the optical pickup 22 are controlled in accordance with the tracking error signal. A tracking control section 26 and a playback signal processing section 28 for detecting a playback signal from the output signal of the optical pickup 22.

In the optical recording medium driving apparatus of FIG. 3, the optical recording medium 20 has a relatively narrow track pitch Tp as shown in FIG. 2 and the wobbling pit rows 14A such that adjacent tracks are inverted with each other. Store information in the form of. The optical pickup 22 irradiates a light beam so as to follow the track center line on the information recording surface of the optical recording medium 20 which is rotated by a spindle motor (not shown). At this time, the light spot diameter irradiated on the optical recording medium 20 reaches the centerline of both tracks 14 'and 14 "adjacent to the inner circumference and the outer circumference side, as shown in FIG. The optical pickup 22 also detects the amount of light reflected from the optical record carrier 20 by a photodetector (not shown) and converts it into an electrical signal. It consists of the detection pieces to convert the amount of light incident on each of the light detection pieces into a plurality of electrical signals The reproduction signal processing unit 28 is the center portion 2 of the plurality of electrical signals output from the optical pickup 22 The high frequency signal is detected using two electrical signals output from the two photodetectors, and then the reproduction signal processor 28 performs a signal processing process such as equalization and slicing on the high frequency signal to perform a channel bit stream ( Ch The tracking error detection unit 24 detects the tracking error signal Te by using a plurality of electrical signals input from the optical pickup 22. The tracking control unit 26. Tracks a straight track center line by adjusting a current signal or a voltage signal supplied to a tracking actuator (not shown) of the optical pickup 22 in response to the tracking error signal Te input from the tracking error detector 24. The objective lens is moved to the left and right directions, i.e., the inner circumference or the outer circumference.

4 illustrates the configuration of the tracking error detector 24 shown in FIG. 3 in detail, and the tracking error detector 24 shown in FIG. 4 is connected to the photodetector 30 of the optical pickup 22. To a fourth band pass filter (BPF) 32A, 32B, 32C, 32D, a first subtractor 34A connected to output terminals of the first and third band pass filters 32A, 32C, A second subtractor 34B connected to the output terminals of the second and fourth band pass filters 32B and 32D, and an adder 36 and a third connected in parallel to the output terminals of the first and second subtractors 34A and 34B. The 3 subtractor 38 and the multiplier 40 connected to the output terminal of the adder 36 and the 3rd subtractor 38 are comprised.

The photodetector 30 shown in FIG. 4 is composed of photodetection pieces PDa, PDb, PDc, and PDd divided into four in the track direction so that the distribution state of the light beam irradiated to the track can be accurately detected. Each of the four-segment photodetection pieces PDa, PDb, PDc, and PDd arranged in parallel with each other in the radial direction converts the amount of reflected light into an electrical signal and is proportional to the amount of reflected light so as to be proportional to the amount of reflected light. , PC, PD). Here, the second and third photodetection signals PB and PC corresponding to the amount of light irradiated and reflected on the track to be accessed are added and amplified by the addition amplifier 44 included in the reproduction signal processing unit 28 to reproduce the reproduction signal. It is converted to a high frequency signal (RF) including a. Subsequently, the reproduction signal processing unit 28 performs signal processing on the high frequency signal RF to reproduce information in the form of a channel bit stream. The first band pass filter 32A of the tracking error detection unit 24 filters the first photodetection signal PA to a specific band, that is, a low frequency band, so that the track 14 'adjacent to the outer circumference side based on an arbitrary track 14 is detected. Detect the first wobble signal SA having the same phase as the wobble portion of? The second band pass filter 32B detects the second wobble signal SB having a phase opposite to the wobble portion of an arbitrary track 14 by filtering the second photodetection signal PB to a low frequency band. The third band pass filter 32C detects the third wobble signal SC having the same phase as the wobble portion of an arbitrary track 14 by filtering the third photodetection signal PC into the low frequency band. The fourth band pass filter 32D has a phase opposite to the wobble portion of the track 14 ″ adjacent to the inner circumferential side based on an arbitrary track 14 by filtering the fourth photodetection signal PD to a low frequency band. 4 detects the wobbling signal SD The first subtractor 34A generates the first difference signal Sca obtained by subtracting the first wobble signal SA from the third wobble signal SC. The second subtractor 34B generates a second difference signal Sbd obtained by subtracting the fourth wobbling signal SD from the second wobbling signal SB. The sum signal SM is generated by adding the signals Sca and Sbd, and the third subtractor 38 subtracts the first difference signal Sca from the second difference signal Sbd. The multiplier 40 generates the tracking error signal Te by multiplying the sum signal SM and the third difference signal SS.

The tracking control unit 26 connected to the tracking error detection unit 24 having the structure described above with reference to FIG. 4 integrates the tracking error signal Te and supplies the current supplied to the tracking actuator 42 included in the optical pickup 22. A DC offset signal Dv for controlling the signal or the voltage signal is generated. The tracking actuator 52 causes the light beam to follow the centerline of the track 14 by moving the objective lens in the radial direction of the disc in response to the DC offset signal Dv. Hereinafter, the tracking control operation according to the present invention will be described in detail with reference to FIGS. 5 to 7. Here, it can be seen that the track 14 shown in FIGS. 5 to 7 exaggerates the wobble form in order to easily explain the tracking control operation performed by detecting the wobble part. In practice, the wobble portion of the track 14 is wobbled gently because it has a change interval Δt of a relatively small wobble portion as shown in Fig. 2A.

Referring to FIG. 5, signals output from the respective components shown in FIG. 4 are illustrated when the light beam is irradiated accurately with respect to the center line of the track 14 and irradiated in the order of a, b, and c.

The first wobble signal SA output from the first band pass filter 32A has the same phase as the wobble portion of the track 14 'adjacent to the outer circumferential side of the track 14 to be accessed, and the second band pass filter. The second wobbling signal SB output at 32B has a phase opposite to that of the wobble portion of the track 14 to be accessed. Here, since two adjacent tracks 14 and 14 'have opposite phases, the first and second wobbling signals SA and SB have the same phase, and the amplitude of the second wobbling signal SB is equal to zero. It is relatively larger than one wobbling signal SA. The third wobbling signal SC output from the third band pass filter 32C has the same phase as the wobble portion of the track 14 to be accessed and the fourth war output from the fourth band pass filter 32D. The bling signal SD has a phase opposite to the wobble portion of the track 14 "adjacent to the inner circumferential side of the track 14 to be accessed. Here, the third and fourth wobbling signals SC and SD have the same phase. And the amplitude of the third wobbling signal SC is greater than the amplitude of the fourth wobbling signal SD, which causes the third wobbling signal SC to be output from the first subtractor 34A. The difference signal Sca of the first wobble signal SA has the same phase as the third wobble signal SC and an amplitude corresponding to the sum of the amplitudes of the first and third wobble signals SA and SC. In addition, the difference signal Sbd between the second wobble signal SB and the fourth wobble signal SD output from the second subtractor 34B is the same as the second wobble signal SB. It has an image and has an amplitude corresponding to the sum of the amplitudes of the second and fourth wobbling signals SA and SC, and accordingly, the first and second difference signals Sca and Sbd generated by the adder 36. The sum signal SM is represented by the base voltage (0 V), and the third difference signal SS obtained by subtracting the first difference signal Sca from the second difference signal Sbd by the third subtractor 38 is The amplitude corresponding to the sum of the amplitudes of the first and second difference signals Sca and Sbd has the same phase as the second difference signal Sbd, and as a result, the sum signal SM and the third signal are multiplied by the multiplier 40. The tracking error signal Te generated by multiplying the difference signal SS and the DC offset signal Dv generated by the tracking control unit 26 are both represented as base voltages. Since it is irradiated to the center of 14), the tracking actuator 42 keeps the objective lens in that state.

Referring to FIG. 6, signals output from the respective components illustrated in FIG. 4 are illustrated when the light beam is irradiated in the order of a, b, and c, circumferentially around the track 14 to be accessed.

When the light beam is biased toward the outer circumference of the track 14 to be accessed, the first wobbling signal SA output from the first band pass filter 32A and the third war output from the third band pass filter 32C The amplitude of the bling signal SC appears to be reduced than when the center line of the track 14 is irradiated (indicated by a dashed line). On the other hand, the amplitude of the second wobbling signal SB output from the second band pass filter 32B and the fourth wobbling signal SD output from the fourth band pass filter 32D is determined by the track 14. It will be increased when irradiated to the center line (indicated by the dashed line). Accordingly, the first difference signal Sca generated by the first subtractor 34A has a smaller amplitude than the second difference signal Sbd output from the second subtractor 34B and has phases opposite to each other. Accordingly, the sum signal SM of the first and second difference signals Sca and Sbd generated by the adder 36 corresponds to the amplitude corresponding to the difference between the amplitudes of the first and second difference signals Sca and Sbd. It has the same phase as the difference signal Sbd. In addition, the third difference signal SS obtained by subtracting the first difference signal Sca from the second difference signal Sbd by the third subtractor 38 has the amplitudes of the first and second difference signals Sca and Sbd. It has the same amplitude as the sum and the same phase as the second difference signal Sbd. As a result, the tracking error signal Te generated by multiplying the sum signal SM and the third difference signal SS in the multiplier 40 is represented as a positive envelope signal. The tracking error signal Te is integrated by the tracking control unit 26 and converted into a DC offset signal Dv that maintains a positive voltage level. In response to the positive DC offset signal Dv, the tracking actuator 42 moves the objective lens toward the inner circumference so that the light beam follows the centerline of the track 14 to be accessed.

Referring to FIG. 7, signals output from the respective elements illustrated in FIG. 4 are illustrated when the light beam is irradiated in the order of a, b, and c, oriented toward the inner circumference with respect to the track 14 to be accessed.

When the light beam is biased toward the inner circumference of the track 14 to be accessed, the first wobbling signal SA output from the first band pass filter 32A and the third war output from the third band pass filter 32C The amplitude of the bling signal SC appears to be increased than when the center line of the track 14 is irradiated (indicated by a dashed line). On the other hand, the amplitude of the second wobbling signal SB output from the second band pass filter 32B and the fourth wobbling signal SD output from the fourth band pass filter 32D is determined by the track 14. It appears to be reduced than when irradiated to the center line (indicated by a dashed line). Accordingly, the first difference signal Sca generated by the first subtractor 34A has a larger amplitude than the second difference signal Sbd output from the second subtractor 34B and has phases opposite to each other. Accordingly, the sum signal SM of the first and second difference signals Sca and Sbd generated by the adder 36 corresponds to the amplitude corresponding to the difference between the amplitudes of the first and second difference signals Sca and Sbd. It has the same phase as the difference signal Sca. In addition, the third difference signal SS obtained by subtracting the first difference signal Sca from the second difference signal Sbd by the third subtractor 38 has the amplitudes of the first and second difference signals Sca and Sbd. It has the same amplitude as the sum and the same phase as the second difference signal Sbd. As a result, the tracking error signal Te generated by multiplying the sum signal SM and the third difference signal SS by the multiplier 40 is represented as a negative envelope signal. The tracking error signal Te is integrated by the tracking control unit 26 and converted into a DC offset signal Dv that maintains the negative voltage level. According to this negative DC offset signal Dv, the tracking actuator 42 moves the objective lens toward the outer circumference so that the light beam follows the center line of the track 14 to which the light beam is to be accessed.

On the other hand, in the above-described embodiment, the case where the present invention is applied to an optical recording medium for reproduction only is exemplified, but the present invention can also be applied to a recordable optical recording medium. In this case, adjacent tracks 14 and 14 'having opposite phases correspond to grooves, and regions 16 formed between adjacent tracks 14 and 14' correspond to mountains. .

In the above-described embodiment, the case in which the wobbled track 14 is continuously formed over the entire optical recording medium is exemplified, but the present invention can also be applied to the case in which the wobbled track 14 is formed intermittently.

As a result, the optical recording medium according to the present invention is wobbled so that adjacent pit rows (i.e., tracks) have phases opposite to each other, so that the track pitch can be set relatively narrow compared to the light spot of a specific wavelength.

As described above, according to the optical recording medium according to the present invention, adjacent pit rows (tracks) are formed to be wobbed with phases opposite to each other, thereby narrowing the track pitch for optical spots having a specific wavelength, thereby greatly improving recording density. Will be. Further, according to the optical recording medium driving apparatus according to the present invention, it is possible to reproduce accurate information while irradiating a light beam to follow the center line of the track to be accessed with respect to the optical recording medium.

Furthermore, the optical recording medium according to the present invention can be applied not only to a recordable optical recording medium having a hill and valley structure, but also to an optical recording medium having wobbled pit rows intermittently formed.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 schematically shows a track structure formed on a conventional optical record carrier.

2 is a view showing the relationship between the structure of the track formed on the optical recording medium and the optical spot diameter according to the embodiment of the present invention.

3 is a diagram showing the configuration of an optical record carrier driving apparatus according to an embodiment of the present invention.

4 is a diagram illustrating in detail the configuration of the tracking error detection unit shown in FIG. 3;

FIG. 5 is a waveform diagram showing an output signal from each component shown in FIG. 4 when the center line of the track of the light beam is irradiated correctly. FIG.

FIG. 6 is a waveform diagram illustrating signals output from each component shown in FIG. 4 when the light beam is biased toward the outer circumferential side with respect to the center line of the track of the light beam. FIG.

FIG. 7 is a waveform diagram showing signals output from each component shown in FIG. 4 when being irradiated to the inner circumferential side with respect to the center line of the track of the light beam. FIG.

<Description of Symbols for Main Parts of Drawings>

10, 20: optical record carrier 12, 14: track

12A, 14A: Pit Row 16: Empty Area between Adjacent Tracks

22 optical pickup 24 tracking error detection unit

26: tracking control unit 28: playback signal processing unit

30: photodetector

32A, 32B, 32C, 32D: first to fourth band pass filters

34A, 34B: first and second subtractors 36: adder

38: third subtractor 40: multiplier

42: tracking actuator 44: addition amplifier

Claims (8)

An optical recording medium formed in response to an information signal, wherein the pit rows wobbling continuously or intermittently at regular intervals form a track, and wherein the adjacent pit rows are wobbled so as to have inverted phases. The method of claim 1, The pit row is formed in a wobble form bent to both sides with respect to the track center line. The method of claim 1, If you have a mountain and valley structure Wherein the pit rows are formed in the valleys and areas provided between adjacent pit rows have an acid structure. The method of claim 1, Track pitch, the distance between adjacent track centerlines, An optical recording medium having a value of at least about 1/2 of an optical spot diameter of a specific wavelength. Condensing means for irradiating a light beam onto the wobbled optical recording medium such that the pit rows wobbling continuously or intermittently at regular intervals form a track, and adjacent pit rows have inverted phases; A photodetector comprising a photodetector divided into radially divided parts and configured to detect and photoelectrically convert the amount of light reflected from the optical record carrier; Tracking error detection means for detecting a tracking error signal from the light detection signal detected by the light detection means; And tracking control means for performing tracking control of the light beam based on the tracking error signal. The method of claim 5, wherein And reproducing signal processing means for generating a reproducing signal by signal processing using at least two light detecting signals of at least four light detecting signals. The method of claim 5, wherein The tracking control means And drive the light collecting means such that the light beam follows the center line of the track. The method of claim 5, wherein The tracking error detecting means Band filtering means for detecting the first to fourth wobble signals from at least four light detection signals; First subtraction means for subtracting the first and third wobble signals to generate a first difference signal; Second subtraction means for subtracting the second and fourth wobble signals to generate a second difference signal; Adding means for summing the first and second difference signals; Third subtraction means for subtracting the first and second difference signals to generate a third difference signal; And multiplication means for generating the tracking error signal by multiplying the sum signal from the adding means and the third difference signal.