JPH0215431A - Tracking error signal detecting system and optical information recording medium - Google Patents

Abstract

PURPOSE:To improve error signal detecting accuracy by operating the sum and difference of respective sum signals (A+C) and (B+D) from the divided parts of the two opposite angles of four-division light receiving elements, and obtaining a sum signal (A+B+C+D) and a differential signal (A+C)-(B+D) at the divided parts of the two opposite angles. CONSTITUTION:A light receiver consists of radially four-divided quadripartite light receiving elements 41, and divided parts 41a to 41d respectively photoelectrically convert incident light quantities, and produce output signals A to D. The elements 41 are arranged so that the position of a photo converter 19 in an optical system, namely, the center of the far field of reflected light from an information recording surface 11 may correspond to an optical axis, and a dividing line 42 is parallel with the direction of an information track, and orthogonal to another dividing line 43. For the respective signals A to D, the sum and difference of the respective sum signals (A+C) and (B+D) from the divided parts of the two opposite angles of the elements 41 are operated by arithmetic elements 44 and 45, and the sum signal (A+B+C+D) and the differential signal (A+C)-(B+D) of the signals from the divided parts of the two opposite angles in the elements 41 can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a tracking error signal detection method and an optical Regarding information recording media.

[Conventional technology]

Conventionally, in optical disk devices, etc., information is recorded and/or reproduced on an optical information recording medium having parallel, concentric, spiral, etc. information tracks. A tracking error signal detection method using a medium was published in Japanese Patent Application Laid-Open No. 62-18.
It is known from Publication No. 3037 and the like.

FIG. 7 to FIG. 1O are explanatory diagrams of this tracking error signal detection method. In FIG. 7, 1°2 indicates the center line of adjacent information tracks on an optical information recording medium such as an optical disk, and 3, 4, 5, 6 indicate the left and right (both sides) of these center lines 1 and 2, respectively. ) shows a pair of wobbled pits, which are shifted by the same distance and are shifted by about 1/4 times the pitch of the information track before and after the center line 1.2. Further, 7 and 8 indicate pits for timing marks, and 9 indicates a spot of a focused laser beam irradiated onto the optical information recording medium. The spot 9 of this focused laser beam scans the information track by moving relatively at a constant speed.

Figure 10 shows an optical system (
Pick-up) - Here is an example. An optical disk 12 having a transparent substrate 10 and an information recording surface 11 including concavo-convex pits is rotated by a spindle motor 13 at a constant rotational speed or constant linear speed. On the other hand, the laser beam emitted from the laser diode 14 passes through the collimator lens 15. Polarizing prism 16.1/4 wavelength plate 17° A condensing lens 18 having a numerical aperture of around 0.5 irradiates the information recording surface 11 of the optical disc 12 with a light spot diameter of around 1 μm full width at half maximum, and the spot is focused on the optical disc 12. The information track is scanned at a constant speed, and the reflected light is passed through a polarizing prism 16.1
/ 4 wavelength plate 17. The light enters the retroreflective optical system consisting of the condenser lens 18 again, is reflected by the polarizing prism 16, and is detected by the photodetector 19 as a change in the amount of reflected light, thereby obtaining a reproduced signal a.

The wobbled pits 3, 4, 5, and 6 and the timing mark pits 7.8 are uneven pits with a depth of about λ/4 (λ is the wavelength of the laser beam), and a metal film is placed on top of these uneven pits. A light reflecting layer such as Te, Se, Bi,
A light-absorbing and reflective recording film made of metal 2 alloy such as Ti, cyanine dye, triphenylmethane dye, squarylium dye, pyrylium dye, etc. is provided. The light intensity of the condensed beam spot 9 is weakened to such an extent that the shape of the concave and convex pits is not changed, and the beam spot 9 moves along the information track, and is reproduced by the optical system as a reproduced signal a in a time series 43 as shown in FIG.
number is obtained. In FIG. 9, 20.21 is a signal corresponding to wobbled pits 3, 4 or 5, 6, and 22
is a signal corresponding to timing mark pit 7.8. The focused beam spot 9 is the center line 1 of the information track,
2, the amplitudes of the signals 20 and 21 are the same, but when the focused beam spot 9 shifts downward in FIG. 7 with respect to the center lines 1 and 2 of the information tracks, the amplitudes of the signals 21 The amplitude of the signal 20 becomes larger than the amplitude of the signal 21 when the focused beam spot 9 shifts upward in FIG. 7 with respect to the center lines 1 and 2 of the information tracks. Using this, the information track center line 1 of the focused beam spot 9 is determined from the time series signal a.
, 2 is detected, and based on this detection signal, the tracking actuator operates to align the focused beam spot 9 with the information track center line 1.degree. 2, thereby performing tracking servo control. wobbled pit 3,
4.5°6 is combined with the timing mark pit 7.8 to form a predetermined pattern (a pattern selected so as not to appear in other information signals), and that pattern can be extracted from the time series signal a. The timing of passage of the track is detected by the electric circuit means, and based on the detected timing, only the signals 20 and 21 corresponding to the wold pits 3 and 4.5° 6 are extracted to obtain the above-mentioned tracking error signal. In addition, the pattern of pit rows consisting of wobbled pits 3, 4, 5, 6 and timing mark pits 7.8 is such that 500 to 2,000 sets are provided at equal intervals on one track of the optical disk 12, and the frequency of tracking error No. 48 is A method for obtaining necessary and sufficient signals considering the band is also known.

Also, Optics Vol. 11, No. 6, pp. 634-639 rDA
The optical head J for D is irradiated with a condensed beam on the surface including the information track of the optical information recording medium, and in the far field of the reflected light, the center coincides with the optical axis and one dividing line is in the direction of the information track. The reflected light is received by a four-division light-receiving element arranged so that the other dividing line is parallel to the direction of the information track and perpendicular to the direction of the information track, and signals A, B, Sum signal of C and D (A+B+C+
Using D) as a reference signal, the signal of the difference between the signals from the diagonally divided parts of the 4-split light receiving element (A + C) - (B + D
A tracking error signal detection method that performs heterodyne detection of ) is described.

[Problem to be solved by the invention]

In the above-mentioned conventional tracking error signal detection method, in the former case, the optical information recording medium is a Wald pit 3, 4 or 5
, 6 are provided before and after the center line 1°2 of the information track with a shift of about 1/4 times the pitch of the information track. There is an inconvenience in that it must be used only in cases where the wobbled pits can be arranged in a straight line in the radial direction, such as in an optical disk. If it is to be used in an optical disk of a constant linear velocity type that can increase the recording capacity, Wald pits 3, 4 or 5, 6 are arranged at random positions with respect to the circumferential direction of the information track, as shown in FIG. Therefore, when the focused laser beam spot 9 passes the position 3A where the Waldo pit is located in the adjacent track, the crosstalk between the information tracks increases, and to avoid this, the pitch of the information tracks should be increased by 1.25 times. This has the disadvantage that the density of the information track is reduced. Furthermore, an offset occurs in the tracking signal due to the inclination of the optical disk, which tends to cause i-rack slippage. Further, the latter method can only be applied to an optical information recording medium having an information track in which a pit train signal is continuously formed, and cannot be applied to an optical information recording medium of an additional recording type or an erasing type.

The present invention eliminates the above-mentioned drawbacks, improves the accuracy of dragging servo control, and provides a tracking error signal detection method and manufacturing method that can be applied to additional recording type, 1'1 type, or constant linear velocity type optical information recording media. An object of the present invention is to provide an optical information recording medium that can easily increase the density of information tracks.

[Means to solve the problem]

The present invention provides a tracking error signal detection method according to claim 1, in which a surface including an information track of an optical information recording medium is provided with a pattern of a predetermined pit row formed by a plurality of uneven pits at a predetermined interval on the center line of the information track. A focused beam is irradiated to the far field of the reflected light, the center of which is aligned with the optical axis, one dividing line is parallel to the direction of the information track, and the other dividing line is perpendicular to the direction of the information track. The reflected light is received by the four-division light-receiving element arranged as shown in FIG.

4 above at the rising edge of the sum signal of C and D (A+B+C+D)
The difference signal (A + C) - (B + D) between the signals from the diagonally divided parts of the divided light receiving element and the sum signal (A + B + C + D) corresponding to each pit of the pattern.
) is the difference signal (B + D) - (
It is characterized by extracting A + C). The optical information recording medium according to the second aspect of the present invention has a pattern of a predetermined pit row formed by a plurality of concave and convex pits at a predetermined interval on the center line of the information track.

[For production]

An information track of an optical information recording medium is scanned by a focused beam.

〔Example〕

2 to 4 are diagrams for explaining an embodiment of the optical information recording medium according to claim 2, and in the figures, 21, 22, 23.
, 24.31, 32.33 are a plurality of uneven pits 211 to 213, 221 to 223, 231 to 213 in this embodiment.
233,241-243,311-313,321-3
23. This is a predetermined pit row pattern consisting of 113 pits from 331 to 333. Reference numerals 1 and 2 are center lines of adjacent information tracks on the optical information recording medium consisting of the optical disk of this embodiment, and 9 is a focused laser beam spot. The uneven pit has an effective depth of 0.125λ to 0.35λ, preferably 0.20λ to 0.30λ, and may be concave or convex. Here, λ is the wavelength of the laser beam used for recording and reproducing information on the optical information recording medium.

The effective depth means taking into account corrections when the cross-sectional shape of the pit is sloping. That is, in a rectangular pit, the maximum depth is equal to the effective depth, but in a sagging pit, for example, in a V-shaped pit, the maximum depth is 1.6 of the effective depth.
Double. The predetermined pit string pattern is formed of a plurality of uneven pits, and is intended to select and recognize the position of the uneven pit string from among the information pit strings for detecting a tracking error signal. Therefore, this predetermined pit row pattern is distinguished from other information pit rows on the information track (including uneven pit rows or pit rows formed by changes in the reflectance of a light absorption/reflection film, etc.). It is sufficient to select a pattern that deviates from the modulation rule used for recording. As shown in Figure 4, information signals (address signals, data signals, etc.) D
ATA is provided along the information track between the predetermined pit row patterns. Also, all information pits are provided on the center line of the information track. Furthermore, since the predetermined pit row patterns 21, 31, 22, and 32 do not involve crosstalk with adjacent tracks, there is no need to align the information tracks with each other as shown in FIG. It may be placed at any position Δ above. Since there are no wolved pits, even if the predetermined pit row pattern 22.32 is located at a position such as the third section, there is no increase in crosstalk due to pits on adjacent tracks. In addition, the interval between the predetermined pit row patterns is arbitrary, but in order to facilitate the means for recognizing the predetermined pit row pattern 1 to 1, it is preferable to use one rotation at equal rotation angles or at equal intervals in the track direction. It is preferable to distribute 300 to 3000 pairs per person.

FIG. 5 shows a circuit used in an embodiment of the present invention, and FIG. 6 is a timing chart thereof.

The light receiver 41 consists of a four-part light receiving element divided radially into four parts, and each of the divided parts 41a, 41b, 41c, and 41d photoelectrically converts the amount of incident light and outputs a signal A, +3°C.
, D. This 4-split light-receiving element 41 is arranged so that its center coincides with the optical axis at the position of the photodetector 19, that is, the far field of the reflected light from the information recording surface 11 in the optical system shown in FIG. 42 is parallel to the direction of the information track, and another dividing line 43 is oriented perpendicular to the direction of the information track. In this example, the optical information recording medium 1 in the optical system shown in FIG.
2, the optical information recording medium shown in FIGS. 2 to 4 is used. Each divided portion 41a, 41 of the four-divided light receiving element 41
Signals A, B, C, and D from b, 41c, and 41d are divided into diagonal portions 41a of the four-divided light-receiving element 41 by arithmetic units 44.45.

Each sum signal of signals from 41c, 41b, and 41d (A+C
), (B+D) are calculated, and the sum signal (A + C), (B + D) is calculated by the calculating unit 46.47, and the sum signal (A + B + C + D) and 4 are calculated.
diagonal divided portions 41a in the divided light receiving element 41;
The difference signal (A +
C)-(B + D) is obtained. Figure 6 is (6-1
), the information tracks 1 and 4 on the optical disk 12 are
8 and condensing laser beam spot 9 by condensing lens 18
When the two move relatively at a constant speed in the direction of the arrow, the predetermined pit row pattern 49 on the information track 48 causes the arithmetic unit 4 to
Sum signal (A+B+C+D) obtained from 6, arithmetic unit 47
The diagonal divided portions 41a, 41c, 41 obtained from
The signal of the difference between the signals b and 41d (A 10) - (B +
D) and these processed signals are shown in time series.

FIG. 6 (6-2) shows the sum signal (A
+B+C+D), and pulses appear in the direction in which the received light level decreases corresponding to the position of the uneven pit on the information track 48. FIG. 6 (6-3) shows a signal corresponding to the position of the uneven pit, obtained by detecting the peak position of each pulse in the pulse train. Figure 6 (6-4) ~
(6-6) shows the difference signal (A+C)-(B+D) between the signals of the diagonal divided portions 41a, 41c, 41b, and 41d obtained from the calculation lm47, and the focused laser beam spot 9 is located on the information track 48. It shows each signal when passing to the left, center, and right of . This signal (A+C
)-(B+D), the polarity is reversed when the focused laser beam spot 9 shifts from the center of the information track 48 to the left and right, and a tracking error signal is obtained by detecting the polarity and level. For example, FIG. 6 (6
In the signal d(A+B+C+D)/dt as shown in -7), negative and positive pulses appear at the leading edge and trailing edge of the uneven pit, respectively. Based on this signal d(A+B+C+D)/dt, the uneven pit trailing edge detection signal as shown in FIG. 6 (6-8), the uneven pit leading edge detection signal as shown in FIG. 6 (6-9) A detection signal is obtained. The trailing edge detection signal of the uneven pit in Fig. 6 (6-8) and the difference signal (A + C) - (B
+ D) from the signal obtained by multiplying by
9) uneven pit front edge detection signal and difference signal (A + C
)-(B 10) is subtracted, coarse tracking error signals TE as shown in FIG. 6 (6-10) to (6-12) are obtained. The coarse tracking error signal TE can also be obtained in other ways, for example by using the difference signal (A+C)-(B+D) and the differential signal d(A+B+C+D).
)/dt. The coarse tracking error signal TH includes signals generated by uneven pits other than the above-mentioned predetermined uneven pits, recording pits, or scratches on the information track, and as it is, it contains a lot of noise and has a large fluctuation in signal gain, so it is difficult to control the tracking servo. cannot be performed accurately. Therefore, it is necessary to obtain a highly accurate tracking error signal with less noise and less gain fluctuation by extracting only the tracking error signal obtained by a predetermined uneven pit row pattern (49, etc.) from the coarse tracking error signal TE. be. In order to recognize the above-mentioned predetermined concavo-convex pit string pattern, the correlation between the time-series pattern of the sum signal (A+B+C+D) and the above-mentioned predetermined concave-convex pit string pattern is taken in time series, and when a correlation of more than a predetermined value is obtained, It is sufficient to generate a predetermined uneven pit row pattern detection signal, and this detection signal is illustrated in FIGS. 6 (6-13) and (6-15). Further, the uneven pit row pattern described above is not limited to the example shown in the figure, as various patterns characterized by the length of the pits, the positions of the pits, or a combination thereof can be used. Figure 6 (6-
In the example of 13), a pattern is detected from the interval between two uneven pits of the predetermined uneven pits 1 to 49 in the row pattern 49 to obtain a detection pulse P. Based on this detection pulse P1, a gate pulse G shown in FIG. 6 (6-14) is generated, and this gate pulse G□ converts the rough tracking error signal TE into a tracking error signal due to the last uneven pit of a predetermined uneven pit row pattern. can be extracted. In the example shown in FIG. 6 (6-15), a pattern is detected from the combination of the uneven pits of the entire predetermined uneven pit row pattern 49, and when the last pit of the predetermined uneven pit string pattern 49 is detected, the detection pulse P2 is generated. For example,
Based on this detection pulse P2, a gate pulse G2 shown in FIG. 6 (6-16) is generated, and a tracking error signal can be extracted from the rough tracking error signal TE using this gate pulse G2. In FIG. 6, it appears that the detection pulse P2 is generated before the gate pulse G2, but the gate pulse G2 is determined based on the detection pulse of the predetermined uneven pit string pattern 49 before the predetermined uneven pit string pattern 49. This is a gate pulse generated with a time delay corresponding to the interval between pit rows. In addition, the coarse tracking error signal TE is converted into a detection pulse P by an appropriate delay circuit.
2 by a time corresponding to the length of a predetermined uneven pit row, the rough tracking error signal TE
It is also possible to extract a tracking error signal due to a predetermined concavo-convex pit row in which the detection pulse P2 is detected.

FIG. 1 shows a circuit used in an embodiment of the invention.

The peak of the sum signal (A+B+C+D) from the arithmetic unit 46 is detected by the peak detection circuit 50, and becomes a binary signal having pulses corresponding to the peak. ), and when the patterns match, a pattern detection pulse is output from the pattern comparison circuit 51. The gate signal generation circuit 52 generates a gate signal based on the pattern detection pulse from the pattern comparison circuit 51. on the other hand,
The sum signal (A+B+C+D) from the calculator 46 is differentiated by the differentiating circuit 53 to become d(A+B+C+D)/dt, and the multiplier circuit 54 outputs the difference signal (A+C
)−(B + D) to yield the coarse tracking error signal TE. This coarse tracking error signal TE is delayed by a delay circuit 55 for a time corresponding to the length of a predetermined concavo-convex pit row pattern, and is gated by an analog gate circuit 56 with a gate signal from the gate signal generation circuit 52 to obtain the desired purpose. Only the tracking error signal based on the predetermined concavo-convex pit row pattern is extracted.

In the optical information recording medium according to the present invention, there is no particular restriction on the information track portion other than the predetermined concavo-convex pit row pattern for tracking error signal detection. For example, an information signal consisting of uneven pits may exist on the information track, a mirror surface, a fine uneven surface, a groove, or a land formed by grooves existing between the information tracks may exist, and additional recording may be performed. Additional recorded information signals may also be present on possible optical information recording media.

〔Effect of the invention〕

As described above, according to the present invention, in the tracking error signal detection method of claim 1, an optical information recording medium is provided with a pattern of a predetermined pit row formed by a plurality of uneven pits at a predetermined interval on the center line of an information track. A condensed beam is irradiated onto the surface including the information track, and in the far field of the reflected light, the center coincides with the optical axis, and one dividing line is formed to indicate the information 1-
The reflected light is received by a four-division light-receiving element arranged parallel to the direction of the rack and other dividing lines perpendicular to the direction of the information track, and the four-division light-receiving element corresponds to each pit of the pattern. Signals A and B from each divided part of
, C, D sum signal (A+B+C+D) at the rising edge of the signal (A+G)-(B+D), which is the difference between the signals from the diagonally divided portions of the four-split light receiving element, and each pixel of the pattern. A signal (B + D) − (A
+C), it is possible to arrange uneven pits for tracking error detection on the center line of the information track, and it can be applied to additional recording type or erasable type optical information recording media. It can be applied not only to optical information recording media of the type but also to optical information recording media of a constant linear velocity type.

Moreover, since the tracking error signal is extracted from a specific uneven pit, a stable tracking error signal with less noise and less gain fluctuation can be obtained, and the accuracy of tracking servo control can be improved.

In addition, the optical information recording medium according to claim Sa has a pattern of a predetermined pit row formed by a plurality of uneven pits at a predetermined interval on the center line of the information track, so manufacturing is facilitated.
The density of information tracks can be increased.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit used in an embodiment of the present invention, FIGS. 2 to 4 are diagrams for explaining an embodiment of an optical information recording medium according to the present invention, and FIG. b) is a plan view showing a four-division light receiving element and a block diagram showing a circuit used in an embodiment of the present invention, FIG. 6 is a timing chart for explaining the present invention in detail, and FIGS. 7 to 9 are FIG. 10, which is a diagram for explaining a conventional tracking error signal detection method, is a diagram showing an example of an optical system for detecting a tracking error signal. 50...Peak detection circuit, 51...Pattern comparison circuit, 52...Gate signal generation circuit. 53... Differentiation circuit, 54... Multiplication circuit, 56... Analog gate circuit. Figure Figure Figure Figure Figure

Claims (1)

[Claims] 1. A condensed beam is directed onto a surface including an information track of an optical information recording medium in which a pattern of a predetermined pit row formed by a plurality of concave and convex pits at a predetermined interval is provided on the center line of the information track. The far field of the reflected light was arranged so that its center coincided with the optical axis, one dividing line was parallel to the direction of the information track, and the other dividing line was perpendicular to the direction of the information track. The reflected light is received by a 4-split light receiving element, and a sum signal (
The difference signal (A+C
)-(B+D) and the above-mentioned 4 at the falling edge of the sum signal (A+B+C+D) corresponding to each pit of the pattern.
A tracking error signal detection method characterized by extracting a difference signal (B+D)-(A+C) between signals from diagonally divided portions of a divided light receiving element. 2. An optical information recording medium characterized by having a pattern of a predetermined pit row formed by a plurality of concave and convex pits at a predetermined interval on the center line of an information track.