JP2720494B2 - Recording / reproducing method of multilevel signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in the following order. A Field of application in industry B Outline of the invention C Conventional technology D Problems to be solved by the invention E Means for solving the problems (FIGS. 1, 2 and 6) (FIG. 2, FIG. 2 and FIG. 6) G Example (G1) Overall Configuration of Optical Disk Apparatus (FIGS. 1 and 2) (G2) Recording and Reproduction Method of Multilevel Signal (FIGS. 3 to 6) (G3) Other Embodiments H Advantageous Effects of the Invention A Industrial Field of the Invention The present invention relates to a recording / reproducing method of a multilevel signal, and more particularly, to record a multilevel signal on an optical disc by displacing a groove and to record the multilevel signal. This is suitable for application when reproducing a quantified signal. B. Summary of the Invention The present invention relates to a method for recording / reproducing a multilevel signal, in which a synchronization signal and an amplitude reference signal having a maximum value and a minimum value of the multilevel signal are arranged between data recording areas, and A synchronization signal is obtained by the amount of the reflected light beam, the reflected light beam 2 is received by the two-divided optical detector, and the amplitude reference signal is reproduced using the difference signal of the output signal to set the transition level of the multilevel signal. Further, the difference signal is second-order differentiated to detect its transition timing, and based on the transition level and the transition timing, the amount of groove displacement and the groove length are detected, so that the data recording area is multi-valued. The signal can be reproduced. C. Prior Art Conventionally, in this type of optical disc device, a groove (hereinafter, called a groove) that extends a digital signal having three or more values (hereinafter, referred to as a multilevel signal) in the circumferential direction of the optical disc. A method of improving the recording density by performing recording using the same has been considered. That is, in this optical disk device, a groove whose depth is λ / 8 with respect to the wavelength λ of the reproducing light beam and which is displaced in the radial direction of the optical disk in accordance with the multilevel signal is formed on the optical disk. Have been. By irradiating the groove with a reproducing light beam and condensing the reflected light of the light beam on a two-divided optical detector divided in the direction in which the groove extends, the output signal of the two-divided optical detector is obtained. Using the difference signal (so-called push-pull signal), the amount of displacement in the lateral direction of the groove (that is, in the radial direction of the optical disc) is several / 100 [μ
m], and the recording track on which the multilevel signal is recorded can be formed at a high density, and the recording density of the spectral disk device can be improved. D Problems to be Solved by the Invention By the way, in such an optical disk, the groove length displaced in accordance with the multilevel signal generally has a fixed length, and the push-pull signal is transmitted at a predetermined clock signal timing. By sampling, the amount of displacement of the groove of the optical disk can be detected to reproduce the multi-valued signal. However, in such a case, the recording density of the optical disk is determined by the frequency of the clock signal of the multilevel signal.
In order to perform high-density recording, it is necessary to select a higher frequency for the clock signal, and there has been a problem that the shortest pit frequency exceeds the band of the reproducing optical system. In such a case, for example, a binary digital signal is
(Eight fourteen modulation), like a compact disk device that records at different pit lengths, the binary digital signal is modulated by a predetermined modulation method, and the amount of lateral displacement of the groove is calculated. in addition,
A method of recording and reproducing a multilevel signal with an arbitrary groove length and thereby performing higher-density recording on an optical disk as a whole can be considered. The present invention has been made in view of the above points, and has a recording / reproducing method of a multilevel signal capable of reproducing an optical disk having a groove formed with a displacement amount and a groove length according to the multilevel signal with high accuracy. It is intended to propose a method. E. Means for Solving the Problem In order to solve such a problem, in the present invention, the groove 4 is displaced in a direction perpendicular to the direction in which the groove 4 extends, the amount of displacement and the extension of the displaced groove 4 a data recording area AR _DT which multilevel signal is recorded based on the groove length becomes in the direction of length, and a predetermined synchronization signal formed by intermittently grooves 4, the maximum value and the minimum value of the multi-level signal A reference signal recording area in which an amplitude reference signal obtained by displacing groove 4 by a predetermined groove length in response thereto is recorded.
By forming the AR _REF, the recording tracks which the optical disc 2 on the data recording area AR _DT and the reference signal recording area AR _REF arranged at predetermined intervals to form, of the light beam L ₁ irradiated on the optical disc 2 based on the amount S _RF of the reflected light beam L _2, reproduces the synchronization signal from the reference signal recording area AR _REF, receives the reflected light beam L ₂ in two divided light Deitekuta 10, obtained from the two divided light Deitekuta 10 output Using the difference signal S _PP of the signals S _PD1 and S _PD2, the amplitude reference signal is reproduced from the reference signal recording area AR _REF , and the transition levels L1, L2, L3 using the maximum value and the minimum value of the multilevel signal. it sets a L4, L5, using a differential signal S _PP4 obtained by second-order differential of the difference signal S _PP, the difference signal S transition timing t ₁ of _{PP, t 2, t 3,} t 4, the ...... Detect, transition level L1, L2, L3, L4, L5 and transition timing
_{t 1, t 2, t 3} , t 4, on the basis of ..., by detecting the amount of displacement and the grooves length of the groove 4, and from the data recording area AR _DT to reproduce a multilevel signal. An amplitude reference signal consisting of the maximum value and the minimum value of F acting synchronizing signal and the multi-level signal is arranged between the data recording area AR _DT, a synchronization signal at a light quantity S _RF of the reflected light beam L ₂ from the optical disc 2 together to obtain the reflected light beam L ₂ receiving two split light Deitekuta 10, the maximum and minimum values of the multilevel signal by reproducing the amplitude reference signal using the difference signal S _PP of the output signal S _PD1, S _PD2 transition levels L1, L2, L3, L4, L5 is set and the transition timing t _1, t ₂ further difference signal S _PP 2 derivative to using,
t ₃ , t ₄ , ... are detected and the transition levels L1, L2, L3, L4, L5
And transition timings t ₁ , t ₂ , t ₃ , t ₄ ,.
By which it is adapted to detect the displacement amount and the groove length of the groove 4 can play a multi-level signal from the reliable data recording area AR _DT. G Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings. (G1) Overall Configuration of Optical Disk Device In FIG. 1, reference numeral 1 denotes an optical disk device as a whole to which a multilevel signal recording / reproducing method according to the present invention is applied.
An optical disc 2 on which a multi-valued signal composed of four-valued digital signals is recorded in a groove is driven by a spindle motor 3 and is controlled to rotate around an axis O at a predetermined rotation speed. In practice, as shown in FIG. 2, the optical disc 2 is provided with a data recording area _ARDT and a reference signal recording area AR at predetermined intervals.
Is divided to _REF, the recording tracks made by the grooves 4 are formed concentrically with Toratsukupitsuchi T _P. Groove 4, as depth with respect to the wavelength lambda of the light beam L ₁ is irradiated on the optical disc 2 becomes the value lambda / 8, groove width T _W becomes T _P / 2 with respect to further Toratsukupitsuchi T _P Is formed. 1 Here, in the data recording area AR _DT of the groove 4, the groove center GC is upward from Toratsukusenta TC.
First state S ₁ offset by 5ΔA, 0.5ΔA upward
A second state S ₂ offset only by 0.5, a third state S ₃ offset 0.5 A below the track center TC, and a fourth state S ₄ offset 1.5 A below the track center TC.
Each of the four values of the digital signal [3] ₄ , [2] ₄ , [1] ₄ or

[0] It is formed with a predetermined groove length corresponding to ₄ . On the other hand, the reference signal recording area AR _REF is divided into a synchronization signal recording area AR _SYS and an amplitude signal recording area AR _AD ,
A synchronization signal and a reference signal are recorded, respectively. That is, in the synchronous signal recording area AR _SYS , the pits P formed by the intermittent of the groove 4 are repeated on the track center TC at a predetermined cycle of the clock signal. A synchronization signal whose signal level changes is recorded. In the subsequent amplitude signal recording area AR _AD, offset information composed at the maximum value and the minimum value of the groove 4 formed in the data recording area AR _DT is recorded. That is, the data recording area AR _DT, a first state in which the grooves 4 are farthest offset upward from Toratsukusenta TC
And S _1, and the fourth state S ₄ in which the most offset on the lower side, forming a long groove length than the groove length of the data recording area AR _DT (for example, continuous period 5T increments respectively clock period T) Have been. In the optical disk device 1, the light beam L ₁ having the wavelength λ emitted from the laser light source 5 is converted into parallel light through the collimator lens 6, transmitted through the beam splitter 7, and then transmitted through the objective lens 8. Focus on Disk 2
A light spot SP _PB for reproduction is formed. The reflected light beam L ₂ to thereby reproducing Supotsuto SP _PB is reflected on the optical disc 2 is a beam splitter 7 is bent 90 ° through the objective lens 8, divided into recording track direction through the condenser lens 9 The light is condensed on the split optical detector 10. The light reception output signal obtained from the light receiving elements 10A and 10B of the two-divided light Deitekuta 10 S _PD1 and S _PD2 is inputted to the subtraction circuit 11 and the adding circuit 12 of each operational amplifier circuit configuration. Here subtraction circuit 11, the difference between the light reception output signals S _PD1 and S _PD2 of bisected light Deitekuta 10 calculates, and sends a Putsushiyupuru signal S _PP obtained result in multi-level signal reproducing circuit 13. The adder circuit 12 calculates the sum of the light receiving output signals S _PD1 and S _PD2, and sends the sum signal S _RF which is obtained as a result to the clock signal generating circuit 14 formed of a PLL circuit configuration. Thus, the clock signal generating circuit 14, give a clock signal S _CK based on the reference signal recording region AR _REF synchronizing signal recording region AR _SYS synchronization signal recorded on, sends it to the multilevel signal reproducing circuit 13 I do. Thus, the multi-valued signal reproduction circuit 13
Groove 4 recorded in AR _REF amplitude signal recording area AR _AD
Based on the offset information, performs predetermined signal processing on the input Putsushiyupuru signal S _PP, the data recording area AR _DT
The four-valued digital signal DT recorded in is reproduced. In the case of recording the signals thus displacing the groove 4 in the transverse direction, varying the width T _W of the groove against Toratsukupitsuchi T _P, the width T _W of the groove Toratsukupitsuchi
When 1/2 of the value T _P / 2 in T _P, whereas the modulation of the Putsushiyupuru signal S _PP is maximized, the modulation of the sum signal S _RF becomes almost zero. Accordance connexion, in this embodiment, by selected width T _W of the groove 4 to the value T _P / 2, the period in which reading light Supotsuto SP _PB is caused to scan a data recording area AR _DT and the amplitude signal recording area AR _AD between the signal level of the Putsushiyupuru signal S _PP whereas changes in proportion to the radial displacement of the groove 4, the signal level of the sum signal S _RF is maintained at a predetermined value. In contrast, during the period in which the reproducing light Supotsuto SP _PB is caused to scan a synchronizing signal recording area AR _SYS, since the groove 4 is intermittently formed on Toratsukusenta T _C, Putsushiyupuru signal S _PP signal level whereas maintains the 0 level, the signal level of the sum signal S _RF is changed in accordance with the intermittence of the groove 4. Thus, the synchronization signal is recorded in the synchronization signal recording area AR _SYS by the intermittent of the groove 4 and the multi-valued signal and the reference signal are recorded in the data recording area AR _DT and the amplitude signal recording area AR _AD by the amount of displacement of the groove 4 in the radial direction. by recording, the only multi-level signal and the reference signal can be obtained as Putsushiyupuru signal S _PP via subtraction circuit 11, also be obtained by only the sum signal S _RF synchronization signal via the summing circuit 12 Accordingly, the synchronization signal can be reliably and easily detected by separating the synchronization signal from the multilevel signal and the reference signal. (G2) Method of Reproducing Multilevel Signal In the case of this optical disc device 1, the multilevel signal reproducing circuit 13
Is configured as shown in FIG. 3, Putsushiyupuru signal S _PP to be inputted is once converted into digital data DT _PP via the analog-to-digital converter 15, is input to the memory circuit 16. Memory circuit 16, for example, the reference signal recording region AR _REF and a data recording area memory being connected so as to store digital data DT _PP of one recording unit of made of AR _DT is built two, clock signal S _CK The digital data for one recording unit is stored in one memory based on the synchronization timing signal S _SYS obtained from the timing generation circuit 17 to which
Stores the DT _PP, reading stored contents of a storage unit of the other of the memory as digital data DT _PP1. The digital data DT _PP1 is converted to a push-pull signal S _PP1 which is an analog signal via a digital-to-analog conversion circuit 18, and then input to a signal reproduction processing circuit 19. The signal reproduction processing circuit 19 receives the input push-pull signal.
Against S _PP1, performs predetermined signal processing by using the clock signal S _CK inputted from the timing generator circuit 17, depending on the Corde queuing scheme of the multi-level signal reproduced data DT _PB obtained result by the decoder 20 Decoding, and thus the multi-valued signal DT is transmitted. In the case of this embodiment, as shown in FIG. 4, the signal reproduction processing circuit 19 receives the push-pull signal S _PP1 ,
Transition timing detector 21 the value of the multilevel signal to detect the timing of transitions on the basis of the level change of the Putsushiyupuru signal S _PP1, or change in level of Putsushiyupuru signal S _PP1 is by what value change in the multilevel signal transition level setting unit 22 that sets the transition level, and is composed of a data reproducing circuit 23 for reproducing data based on the transition timing and transition level Putsushiyupuru signal S _PP1. In this transition level setting unit 22 detects a portion corresponding to the amplitude signal recording area AR _AD at the beginning of the Putsushiyupuru signal S _PP1 inputted at first level detecting circuit 24, represented Te Putsushiyupuru signal S _PP1 Niyotsu The maximum value and the minimum value of the multi-valued signal are detected and sent to the subsequent transition level calculation circuit 25 as the maximum value signal _SMAX and the minimum value signal _SMIN . In the case of a multi-level signal composed of a 4-level digital signal, the displacement of the groove 4 is actually the value of the multi-level signal.

[0] ₄ ,
[1] ₄ , [2] ₄ , [3] It is made to have linearity in accordance with ₄ , and as shown in FIG.

From [0] ₄ , [1] ₄ , [2] ₄ or [3] ₄ , the value after transition

In order to make a transition to [0] ₄ , [1] ₄ , [2] ₄ or [3] ₄ , there are five types of transitions as represented by the following equation: ₄ C ₂ −1 = 5 (1) Level L1, L2, L3, L4,
Pass through L5. Accordance connexion In this transition level calculation circuit 25 based on the maximum value signal S _MAX and minimum value signal S _MIN, between maximum and minimum values of the Putsushiyupuru signal S _PP1 6 equal parts, the five levels of the intermediate As transition levels L1, L2, L3, L4, L5,
The data is transmitted to the data reproducing circuit 23. On the other hand, in the transition timing detecting section 21, the groove 4 (FIG. 6 (A)) displaced in the horizontal direction in response to the multilevel signal composed of the quaternary digital signal is read by the reproduction light spot SP.
Putsushiyupuru signal based on the reflected light beam L ₂ irradiated with _PB
S _PP1 (FIG. 6 (B)) is input to the differentiating circuit 26. As a result, a differential signal S _PP2 (FIG. 6 (C)) which rises and falls according to the amount of change of the push-pull signal S _PP1 can be obtained. By inputting this differential signal S _PP2 to the rectifier circuit 25, it is possible to obtain the absolute value differential signal S _PP3 rising according to the amount of change in Putsushiyupuru signal S _PP1. Subsequently, the absolute value differential signal _SPP3 is input to the window generating circuit 28 and the second differentiating circuit 29. In this window generating circuit 28, the absolute value differential signal S _PP3 is compared with a predetermined reference voltage V _TH (FIG. 6 (D)), and during the period when the absolute value differential signal S _PP3 exceeds the reference voltage V _TH , A window signal _SWD (FIG. 6 (E)) having a logic "H" level is generated, and this is sent to the zero-cross point detection circuit 30.
To send to. Further, in the differentiating circuit 29, the input absolute value differential signal S _PP3 is further differentiated, and the second order differential signal S falling and rising according to the variation of the absolute value differential signal S _PP3 is _{obtained.
PP4} (FIG. 6 (F)) is obtained and sent to the zero-cross point detection circuit 30. Thus, in the zero-cross point detection circuit 30, while the window signal S _WD is a period having a logic "H" level, and detects the timing at which the second-order differential signal S _PP4 becomes a value "0", consisting in the detection result Zero cross point detection signal S
_ZP (FIG. 6 (G)) is sent to the data reproducing circuit 23. Thus, in the transition timing detection unit 21, by differentiating the Putsushiyupuru signal _PP1 inputted second floor, it is configured so as to be able to correctly detect the timing for switching the Putsushiyupuru signal S _PP1. Here, in the data reproduction circuit 23, the transition levels L1, L2, L3, L4, L5 inputted from the transition level setting unit 22 are set.
(Sixth shown by broken lines in FIG. (B)) and on the basis of the zero-crossing point detection signal S _ZP inputted from the transition timing detector 21, the rising edge of the zero-crossing point detection signal S _ZP timing t
_{1, t 2, t 3,} t 4, in ..., Putsushiyupuru signal S inputted
Detects the level of _PP1 that is closest to the transition levels L1 to L5.This detection result and the value of the immediately preceding multilevel signal

Based on [0] ₄ , [1] ₄ , [2] ₄ or [3] ₄ , the value of the multilevel signal after transition

[0] ₄ , [1] ₄ ,
[2] ₄ or [3] ₄ is sequentially obtained, and in this way, reproduced data DT _PB (FIG. 6 (H)) is created by correctly detecting the amount of lateral displacement of the groove 4 and the groove length. Have been made to gain. Actually, the value of the immediately preceding multilevel signal

[0] ₄ , [1]
_4, [2] The ₄ or [3] _4, the maximum value of the Putsushiyupuru signal S _PP1 corresponding to the amplitude signal recording area AR _AD preceding the data area AR _DT [3] ₄ or minimum value

[0] ₄ with respect to the, it is configured so as to be able to sequentially reproduce the value of the subsequent data area AR _DT. According to the above method, the synchronization signal and the amplitude reference signal including the maximum value and the minimum value of the multi-level signal are arranged between the data recording areas, and the synchronization signal is obtained by the amount of the reflected light beam from the optical disk. The reflected light beam is received by a two-divided optical disk, the amplitude reference signal is reproduced by using the difference signal of the output signal, that is, the push-pull synchronization signal, and the transition level of the multi-valued signal is set. By differentiating and detecting the transition timing and detecting the amount of groove displacement and groove length based on the transition level and transition timing, the multi-valued signal can be reliably reproduced from the data recording area. . (G3) Other Embodiments (1) In the above-described embodiment, the case where the signal reproduction processing circuit 19 is configured by an analog signal processing circuit has been described. However, the present invention is not limited to this. It is composed of a digital signal processing processor and the like, converts the input push-pull signal into an analog-to-digital signal, differentiates this digital data by the second order to detect the transition timing, and reproduces the amplitude reference signal to reproduce the transition of the multilevel signal. The level may be calculated. (2) In the above-described embodiment, the case where the groove is displaced based on the quaternary digital signal as the multi-valued signal has been described, but the present invention is not limited to this, and the present invention is not limited to this.
The present invention can be widely applied to a case where an optical disk whose groove is displaced based on a digital signal of a value or more is reproduced. H Effects of the Invention As described above, according to the present invention, the amount of groove displacement and the groove length are detected based on the transition level and the transition timing, so that the multi-valued signal can be reliably transmitted from the data recording area. A method for recording and reproducing a multilevel signal that can be reproduced can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the overall configuration of an optical disc apparatus to which a method of recording and reproducing a multilevel signal according to an embodiment of the present invention is applied, and FIG. 2 is used to explain the grooves on the optical disc. FIG. 3 is a block diagram showing a multi-level signal reproduction circuit, FIG. 4 is a block diagram showing a signal reproduction processing circuit,
FIG. 5 is a schematic diagram for explaining a transition level, and FIG. 6 is a timing chart for explaining a recording / reproducing method of a multilevel signal. DESCRIPTION OF SYMBOLS 1 ... Optical disc device, 2 ... Optical disc, 4 ... Groove, 10 ... Divide optical detector, 13 ... Multilevel signal reproduction circuit, 19 ... Signal reproduction circuit, AR _REF ... Reference signal recording Area, AR _DT ... Data recording area.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor: Tamotsu Yamagami 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-2-172039 (JP, A) JP-A Sho 63-214919 (JP, A)

Claims (1)

(57) [Claims] A groove is displaced in a direction orthogonal to a direction in which the groove extends, and a multilevel signal is recorded based on the amount of the displacement and a groove length that is the length of the displaced groove in the extension direction. A data recording area, a predetermined synchronization signal obtained by intermittently interposing the groove, and an amplitude reference signal obtained by displacing the groove by the predetermined groove length according to the maximum value and the minimum value of the multi-level signal. Is formed on the optical disk to form a recording track in which the data recording area and the reference signal recording area are arranged at predetermined intervals, and a light beam irradiated on the optical disk The synchronous signal is reproduced from the reference signal recording area based on the amount of the reflected light beam, and the reflected light beam is received by the two-divided optical detector.
Using the difference signal of the output signal obtained from the split optical detector, the amplitude reference signal is reproduced from the reference signal recording area, and the transition level is set using the maximum value and the minimum value of the multilevel signal. Detecting a transition timing of the difference signal using a differential signal obtained by second-order differentiating the difference signal; detecting the displacement amount and the groove length of the groove based on the transition level and the transition timing; And reproducing the multi-level signal from the data recording area.