JP3567101B2 - Optical recording information reproducing method and optical disk apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a method of increasing the recording capacity and recording additional information using the increased capacity on an optical disc on which information has been recorded in advance by pits having irregularities on the entire or partial recording surface. The present invention provides a technique for preventing a reduction in the recording capacity of main information and effectively using recorded additional information. More specifically, an optical disc in which information is included in the depth of a pit and a reproducing method thereof And an optical disk device.
[0002]
[Prior art]
The conventional optical disk is a binary recording in which binary data is made to correspond to the presence or absence of a pit.
In order to increase the density of a disk, the size of a pit is reduced, and a laser beam spot for reading the pit is also reduced. In addition, so-called multi-level recording, in which one pit has multi-level data, is also an effective means for increasing the density.
[0003]
For example, Japanese Patent Laying-Open No. 58-215735 proposes an optical disc in which multi-value data is recorded by setting the depth of a pit to a plurality of levels and changing the amount of reflected light to multiple levels. However, this method has a problem in that it is difficult to determine the level of the amount of reflected light, and there are many errors in reproduced data. On the other hand, Japanese Patent Application Laid-Open No. 5-205276 discloses a method of reproducing multi-valued recorded data by combining a reflected light amount level and a push-pull signal level.
[0004]
At present, an optical disc, such as a CD or a DVD, on which information is recorded by forming concavo-convex pits in advance, mainly uses a method called pit length recording, in which information is represented by the presence or absence of a pit and its length. Is recorded.
[0005]
In FIG. 11, when a light beam 1101 emitted from a pickup (not shown) onto an optical disk approaches a pit 131, the amount of reflected light changes as shown in FIG. Occurs. The reflected light is collected on a photodetector, taken out as an electric signal, and compared with a predetermined reference voltage to be binarized to obtain reproduced data (b). Based on this, information can be reproduced by detecting the presence or absence of the pit 131 and its length. This is the conventional principle of reproducing information on an optical disk on which a pit length is recorded.
[0006]
CDs and DVDs have greatly different capacities, which depend on the size of the formed pits and the density of the tracks as the pit rows. Also, the NA of the objective lens used and the wavelength of light are different, and the NA of the objective lens is around 0.4 for CD and the laser wavelength is about 780 nm to 830 nm, while the NA for DVD is 0.6 and the laser wavelength is about 830 nm. The wavelength of 650 nm is used, and there is also a difference in the size of the light beam generated due to the difference in the optical system.
[0007]
By the way, the information recorded on the optical disc can be divided into the information ultimately required by the user, that is, the main information and the additional information for efficiently reproducing the main information and improving the reliability of the main information. I can do it.
[0008]
The main information includes audio, images, characters, and the like. The additional information includes index information and navigation information for efficient playback, subtitles of the movie, sub-audio, error correction codes for improving the reliability of the main information, and address information indicating the position on the disc. And the like. In recent years, as a technique for preventing information on an optical disc from being illegally copied, a technique for recording information for preventing unauthorized copying in advance, and a technique for embedding protection information in main information, called a digital watermarking technique. Are considered, and these can be said to be additional information.
[0009]
Due to the presence of such additional information, the ratio of the additional information to the total capacity of the optical disk tends to increase. As the recording capacity on the optical disc is limited, an increase in additional information means a decrease in the main information. To solve this problem, it is necessary to increase the recording density of the optical disc to increase the recording capacity. Come.
[0010]
However, in order to increase the surface recording density of the optical disk, finer pits are formed at a high density for the above-described reason of the difference in capacity between the CD and DVD, and the optical system of the pickup is required to reproduce the pits. Need to be modified to create a smaller light beam spot.
[0011]
On the other hand, there is a technology disclosed in, for example, Japanese Patent Application Laid-Open No. 11-66607. This technique records normal main information as high-density pits P0 for CDs and also forms large, low-density pits P1 including some of them, as described in FIG. 1 or FIG. It is superimposed and recorded.
[0012]
The high density pit information (main information) is reproduced by irradiating a light beam spot having a diameter of about 2 [μm] from a CD reading optical head H0 shown in FIG. The additional information is reproduced by irradiating a light beam having a diameter of about 500 [μm] from the low-density reading optical head H1 having a large spot diameter.
[0013]
[Problems to be solved by the invention]
However, in the method disclosed in Japanese Patent Application Laid-Open No. 5-205276, it is necessary to prepare a beam spot for obtaining a push-pull signal separately from a beam spot for obtaining a reflected light amount, and two beam spots are required. It becomes. In order to perform the operation with one beam spot, it is necessary to shift the beam spot from the center of the track or to wobble the track to cause relative displacement between the beam and the center of the track.
[0014]
In such a case, there is a problem that the tracking control is not stable, and the track is easily shifted and a reproduction error is easily caused.
[0015]
Further, in the technique disclosed in Japanese Patent Application Laid-Open No. H11-66607, two types of optical heads (pickups) must be prepared, which leads to an increase in manufacturing costs and apparatus dimensions, and also an optical head for reproducing additional information. Control of the head (pickup) is also required. Further, since the additional information is formed as large pits, the amount of additional information that can be recorded is small, and it is difficult to avoid a decrease in the recording capacity of the main information due to the recording of the additional information.
[0016]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. With the improvement of the recording density, the tracking can be stabilized, the multi-valued data can be correctly reproduced, and the necessity of a new optical pickup, the cost and the apparatus are improved. Without increasing the dimensions, the recording capacity of the optical disk is increased, and additional information is recorded using the increased capacity, thereby preventing a decrease in the main information amount due to an increase in the additional information amount. An optical disk, a method of reproducing optically recorded information, and an optical disk device that effectively use the additional information are provided.
[0017]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has taken the following measures.
[0023]
That is, the present inventionIn the method of reproducing optical record informationIs the lightThe tangential push-pull signal on the disk is converted into two sets of binarized signals indicating that each of the positive and negative reference values has been exceeded, and each set of these second binarized signals is added and subtracted as positive and negative signals, It is characterized in that information is reproduced based on the result of the addition and subtraction.
[0024]
Also,Of the present inventionIn the method of reproducing optical record informationIs the lightBased on the amount of light reflected from the discZuAnd converts the tangential push-pull signal into two sets of second binary signals indicating that the signal has exceeded a predetermined reference value with positive and negative polarities, respectively. It is characterized in that information is reproduced by observing the second binarized signal at the changing point of the first binarized signal.
[0029]
Also,Of the present inventionWith optical disk deviceIs the lightThe tangential push-pull signal on the disk is converted into two sets of binarized signals indicating that each of the positive and negative reference values has been exceeded, and each set of these second binarized signals is added and subtracted as positive and negative signals, It is characterized in that information is reproduced based on the result of the addition and subtraction.
[0030]
AndOf the present inventionWith optical disk deviceIs the lightBased on the amount of light reflected from the discZuAnd converts the tangential push-pull signal into two sets of second binary signals indicating that the signal has exceeded a predetermined reference value with positive and negative polarities, respectively. It is characterized in that information is reproduced by observing the second binarized signal at the changing point of the first binarized signal.
[0053]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific examples to which the present invention is applied will be described in detail with reference to the drawings.
[0054]
Using an optical system consisting of a laser beam having a wavelength of 650 nm and a lens having an NA of 0.6, experiments were conducted on disks having a track pitch (interval between grooves = Wg + Wl =) 0.74 μm and various pit depths. Was.
[0055]
Polocarbonate having a refractive index of 1.5 was used for the disk substrate, and the reflection film was made of Al. Discs with two different pit depths were made using the methods described in US Pat. No. 5,246,531 and Canadian Patent No. 2062840. For tracking, a Differential Phase Detection (DPD) method is used, and the beam spot travels around the center of the track.
[Embodiment 1]
A first embodiment of the present invention will be described with reference to FIGS.
[0056]
FIG. 1 shows the relationship between the pit depth, the tangential push-pull signal amplitude, and the RF signal amplitude. The abscissa represents the depth of the pit, which is expressed based on the wavelength of the light used. In this experiment, λ / 8n = 54 nm, λ / 4n = 108 nm, 3λ / 8n = 162 nm, λ / 2n = 216 nm.
[0057]
The RF signal amplitude takes the maximum value when the pit depth is λ / 4n, and the vertical axis on the right side of FIG. The tangential push-pull (TPP) signal amplitude is maximum when the pit depth is λ / 8n, and the vertical axis on the left side of FIG.
[0058]
The polarity of the TPP signal is inverted at the pit depth λ / 4n, but in order to indicate this, in FIG. 1, the value of the TPP is negative in the region of λ / 4n <pit depth <λ / 2n. For
[0059]
Next, the TPP signal and the RF signal will be described with reference to FIGS. FIG. 2A shows a state in which a beam spot travels on a pit, and FIG. 2B shows a state in which the reflected light is guided to a detector composed of two divided light receiving elements A and B. I have. The TPP signal and the RF signal are obtained by the following calculation using the outputs of the two-divided light receiving elements A and B.
TPP = AB
RF = A + B
In FIG. 1, pits having a depth represented by D1 (80 nm) and D2 (135 nm) are produced, and the appearance of the corresponding RF signal and TPP signal will be described with reference to FIG.
[0060]
Here, since λ = 650 nm and n = 1.5, D1 <λ / 4n and λ / 4n <D2.
[0061]
The RF signal is a total signal of the amount of light returning to the light receiving elements A and B when the beam spot is applied to the optical disk. At the time when the beam spot is located on the pit, the light is affected by diffraction by the pit, and the amount of light returning to the light receiving element (which may be referred to as the amount of reflected light) decreases, so that the level of the RF signal decreases.
[0062]
On the other hand, the TPP signal is a signal indicating a bias in the amount of light in the pit length direction (tangential direction) of the reflected light when a beam spot is applied to a disk as an optical disk. When the beam spot approaches the edge of the pit, the diffraction direction of the light is deviated in the length direction of the pit, and the deviating direction differs depending on which edge before or after the pit. When the difference is obtained, a pulse-like signal having different polarities at the front and rear edges of the pit is obtained.
[0063]
However, which polarity signal appears at the leading and trailing edges of the pit also depends on the depth of the pit. For a pit having a depth D1 that satisfies the above condition, the leading edge of the pit has a positive direction, and the trailing edge has a leading edge. While a signal is output in the negative direction, the opposite is true for a pit having a depth of D2.
[0064]
As described above, the appearance of the signal at the leading and trailing edges of the pit is inverted between D1 and D2, and this is expressed in FIG. 1 as having a different polarity of the tangential push-pull signal.
[0065]
Referring again to FIG. 1, the absolute values of the RF signal amplitude and the TPP signal amplitude are substantially equal in both the pits having the depths D1 and D2 satisfying the above conditions, and only the polarity of the TPP signal is different.
[0066]
Hereinafter, a method of reproducing multi-value data using an RF signal and a TPP signal, and a configuration of a main part of the apparatus will be described with reference to FIGS. FIG. 4 is a block diagram showing a configuration of a main part of the reproducing apparatus, and FIG. 5 is a view for explaining a reproducing method and operation, and a waveform and timing at that time.
[0067]
First, consider the case where pits arranged as shown in FIG. 5A are reproduced. In FIG. 5, it is assumed that the pit depths are D1, D2, and D1 in order from the left. The output from the detector 1 composed of the light receiving elements A and B is determined by the differential amplifier 2 to obtain a TPP signal (FIG. 5C) while the sum is determined by the addition amplifier 3 and the RF signal (FIG. 5C). 5 (b)).
[0068]
The RF signal is subjected to frequency characteristic correction and the like for a reproduced signal from a particularly short pit by the equalizing circuit 7, and is binarized by the binarizing circuit 8 (FIG. 5 (d)). Sent.
[0069]
On the other hand, the TPP signal is compared by the comparator 4 with a positive reference value. If the TPP signal is larger than the reference value (the sign is positive and the absolute value is large), a pulse (+1) is output to the addition / subtraction circuit 6 (FIG. 5). (E)). Similarly, the comparator 5 compares the value with the negative reference value. If the value is smaller than the negative reference value (the sign is negative and the absolute value is large), the pulse (−1) is output to the addition / subtraction circuit 6 (FIG. 5). (F)). The addition / subtraction circuit 6 adds the pulses from the comparators 4 and 5, and leads the three states of -1, 0 and +1 to a demodulation circuit as a 2-bit output signal (FIG. 5 (g)).
[0070]
That is, the addition / subtraction circuit 6 calculates (adds in this example also the polarity thereof) two sets of pulse signals binarized by the comparators 4 and 5 from the tangential push-pull signal. As a result, in the pit portion, two states of -1 and +1 can be restored and reproduced according to the pit depth (in other words, the order in which the positive and negative pulses on the tangential push-pull signal appear). In a non-pit portion where no pits are formed, a state of 0 can be restored, and a total of three values of recorded information can be reproduced depending on the presence and depth of the pits. Therefore, it is possible to greatly improve the recording density of information on an optical disk as compared with the conventional case of so-called binary recording.
[0071]
Incidentally, in order to reproduce the recorded information in the same manner as the conventional binary recording / reproducing, all the pits should have the same depth. Referring to FIG. 5, for example, in the case of a pit having a depth D1, when the beam spot approaches the front edge, the tangential push-pull signal (TPP signal) (FIG. 5 (c)) is positive, and Since the pulses appear negative, if the pulses of FIGS. 5 (e) and 5 (f) are added together with the sign, a state of +1 is obtained in the pit portion and a state of 0 is obtained in the non-pit portion.
[0072]
In other words, in the method or apparatus for reproducing recorded information according to the present invention, the binarized information is made different in depth for a conventional binary-recorded optical disk having the same pit depth. The ternary information can be restored / reproduced for a new optical disc, and compatibility with a conventional optical disc on which binarized recording has been performed can be maintained.
[0073]
As described here, in order to perform multi-level recording by combining the RF signal and the TPP signal, two types of pits having depths D1 and D2 are sandwiched by a depth λ / 4n at which the polarity of the TPP signal is inverted. It may be formed on an optical disk, and the conditions of D1 and D2 are as shown in FIG.
0 <D1 <λ / 4n and λ / 4n <D2 <λ / 2n
What is necessary is just to be comprised so that may be satisfied.
[0074]
Further, the ranges of D1 and D2 are further limited from FIG.
λ / 8n <D1 <λ / 4n and λ / 4n <D2 <3λ / 8n
Then, it can be seen that both the RF signal and the TPP signal can be obtained with good balance and a large amplitude.
[0075]
That is, it is possible to improve the signal quality by obtaining a signal with a larger amplitude, and to reduce errors in reproducing recorded information.
[0076]
Although it has already been described that binary information can be reproduced even on a conventional optical disk having a constant pit depth, when an optical disk having a pit depth set as described above is used, the ternary information can be reproduced according to the pit depth. If the depth is further limited, both the RF signal and the TPP signal can be obtained in a well-balanced and large amplitude, so that the signal quality is improved and the error in reproducing the information can be reduced. It is suitable.
[Embodiment 2]
In the first embodiment described above, two sets of binary signals corresponding to the positive and negative of the tangential push-pull signal (TPP signal) are generated, and the recorded information is reproduced from the addition / subtraction result. . However, information on the same optical disk can be similarly reproduced by another method / configuration.
[0077]
First, returning to FIG. 5, attention is paid to the relationship between the binarized signal (d) of the RF signal (b) and the signals (e) and (f) obtained by binarizing the TPP signal (c) with positive and negative reference values. Then, the appearance timing of (e) or (f) at the change point of (d) is almost the same, and
(1) If (e) appears at the fall of (d), the reproduction information is +1
(2) If (f) appears at the fall of (d), the reproduction information becomes -1.
(3) At the rising edge of (d), the reproduction information is always 0.
In this case, it can be seen that reproduction information exactly the same as that of the first embodiment can be obtained.
FIG. 6 shows a configuration of a main part of a reproducing apparatus for reproducing the same information by this method / concept.
[0078]
The configuration is almost the same as that of the first embodiment shown in FIG. Pulses output from the comparators 4 and 5 ((e) and (f) in FIG. 5) are given as inputs to the latches 9 and 10, and the RF signal is converted into a binary signal ((b) in FIG. 5). These inputs are latched and output at the falling edge of)), while the latches 9 and 10 are cleared and output 0 at the rising edge regardless of these inputs.
[0079]
The outputs of the latches 9 and 10 are supplied to a demodulation circuit (not shown) together with the binarized signal of the RF signal (the output of the binarization circuit 8). If the output of the latch 10 is 1, the reproduced information is -1 if the output of the latch 10 is 1. If the output of both the latches 9, 10 is 0, the reproduced information is 0.
[0080]
Also in this second embodiment, it is natural that the pit depth of the optical disk used is preferably the one described in the first embodiment, and the advantages can be enjoyed as they are.
[0081]
In this embodiment, an optical system having a wavelength of 650 nm and an NA of 0.6 is used, but it is obvious that the effects of the present invention are not limited to the optical system. Further, the value of the pit depth is not limited to the value shown in the above embodiment, and according to the gist of the present invention, it is possible that various combinations are possible within the range of the claims. Needless to say.
[Embodiment 3]
A third embodiment of the present invention will be described below with reference to FIGS.
[0082]
The principle of reproducing information according to the present invention is slightly different from the conventional reproducing principle described with reference to FIG. 11, and therefore will be described first.
[0083]
FIG. 7 shows the basic principle of information reproduction in the present invention. In the present invention, information is given not only to the pit length but also to the pit depth by changing the depth of the pits having irregularities formed on the optical disc, and the depth is particularly shallow. It is classified into two types, deep and deep.
[0084]
Assuming that the wavelength of the light to be used is λ and the refractive index of the optical disk substrate is n, the pit 131 in FIG. 7 is a relatively shallow pit having a depth of about (λ / 6n). Are relatively deep pits having a depth of about (λ / 3n), and the respective depths are
0 <(pit 131 depth) <λ / 4n
And
λ / 4n <(depth of pit 132) <λ / 2n
It is configured to satisfy.
[0085]
When these pit trains are scanned by the light beam 1101 in the direction of the arrow in FIG. 7, light interference occurs in the pits and the amount of reflected light changes as described above with reference to FIG. (A) indicates a level change according to the presence or absence of a pit, and is binarized to obtain a sum signal binarized signal (c). The length of the pit can be determined from the sum signal binarized signal (c), but this is exactly the same as the principle of reproduction of the conventional optical disk described with reference to FIG.
[0086]
Next, a tangential push-pull signal (b), which is a signal obtained by dividing the light incident on the photodetector (in other words, the reflected light from the optical disk) into the first half and the second half in the traveling direction of the light beam and calculating the difference in the amount of light. Pay attention to. Considering the moment when the light beam enters or exits the pit, only the first half or the second half of the light beam will be located on the pit, and there will be a difference in the intensity distribution of the reflected light in the front-back direction. The tangential push-pull signal, which is obtained as described above, generates a pulse-like signal at the moment the light beam reaches or exits the pit, in other words, at the edge of the pit.
[0087]
The polarity of the tangential push-pull signal varies due to several factors, one of which is the pit depth. In FIG. 7, for convenience, a positive pulse is generated at the front edge (the moment the light beam 1101 approaches the pit) in the shallow pit 131, and a negative pulse is generated at the rear edge (the moment the light beam 1101 exits the pit). On the other hand, in the deep pit 132, a negative pulse is generated at the leading edge, and a positive pulse is generated at the trailing edge.
[0088]
This phenomenon is because the interference of the reflected light due to the pits or the diffraction pattern is inverted by the depth of the pits 131 and 132, and the polarity of the tangential push-pull signal is inverted by the depth of the pits 131 and 132. You can do it.
[0089]
By detecting the polarity of this tangential push-pull signal, it is possible to detect the depth of the pit, in other words, it is possible to include information in the pit depth.
[0090]
The tangential push-pull signal is compared with a positive / negative reference value. When the signal exceeds a predetermined level in the positive direction, a tangential push-pull signal positive polarity detection signal (d) is generated. If the tangential push-pull signal negative polarity detection signal (e) is generated when the level exceeds the level, the pit depth detection signal (f) can be obtained by combining these with the sum signal binary signal (c). Is obtained. That is, if a pulse is observed at (d) at the time of the fall of the sum signal binarized signal (c) and at (e) at the time of the rise, it is determined that the pit is a shallow pit, and vice versa. You can do it.
[0091]
Subsequently, a third embodiment of the present invention will be described below with reference to FIGS.
[0092]
FIG. 8 is a block diagram showing an example of a configuration of a portion for reproducing main information and additional information of the optical disc device according to the present invention.
[0093]
In FIG. 8, the reflected light 101 from the optical disk is focused on the center on the photodetector 102. The photodetector 102 is divided into four elements a, b, c, and d by a division line in the tangential direction of the pit row and a division line in the radial direction of the optical disk, and each part outputs a signal proportional to the amount of incident light. . The adder circuit 103-1 outputs a sum signal (b + c) of the elements b and c located on the rear side in the beam traveling direction, and the adder 103-2 outputs the element signal located on the front side in the beam traveling direction. The sum signal (a + d) of a and d is output. Further, the adder circuit 4 outputs the sum (a + b + c + d) of the outputs of the four elements.
[0094]
The outputs of the adders 103-1 and 103-2 are input to the difference circuit 105, and the result is a tangential push-pull signal indicating the difference in the intensity distribution in the first half of the reflected light, that is, the tangential direction of the pit row. The signals are input to the comparators 106-1 and 106-2. Comparators 106-1 and 106-2 compare the predetermined reference voltages + Ref1 and -Ref1 with the tangential push-pull signal, respectively. When the amplitude of the tangential push-pull signal is larger in the negative direction than -Ref1, the comparator 106-2 outputs "H" to the additional information reproducing circuit 8. The output of the adder circuit 104 is compared with a reference voltage + Ref2 by a comparator 107, and the resulting binary signal is sent to a main information reproducing circuit 109, an additional information reproducing circuit 108, and a controller 110 for controlling the operation of the optical disk device. Is output.
[0095]
The controller 110 controls the main information reproducing circuit 109, the servo control unit 111, the display unit 112, and the like.
[0096]
As described above, the tangential push-pull signal is inverted depending on the depth of the pit. Therefore, for example, if the tangential push-pull signal is configured to output a positive pulse at the front edge of a shallow pit and a negative pulse at the rear edge, and when a deep pit is reproduced, the tangential push-pull signal A negative pulse is output at the leading edge, and a positive pulse is output at the trailing edge. The additional information reproducing circuit 108 detects the depth of the pit based on this principle, and reproduces the information recorded according to the depth.
[0097]
FIG. 9 shows a more specific configuration of the additional information reproduction circuit 108. The output signal of the comparator 107 is input to the edge detection circuit 183. The edge detection circuit 183 detects the falling edge of the output signal of the comparator 107, that is, detects that the beam spot has approached the front edge of the pit, and outputs a pulse. This output pulse is input to one of the inputs of the NAND circuit 181, the clock input of the FF circuit 182, and the counter circuit 185.
[0098]
The other input of the NAND circuit 181 receives the output of the comparator 106-1. The output of the NAND circuit 181 is connected to the Reset input of the FF circuit 182, while the output of the comparator 106-2 is connected to the FF circuit. 182 is connected to the data input terminal D. The output Q of the FF circuit 182 is connected to a data restoration circuit 184, and the data restoration circuit 184 restores and reproduces additional information based on the output Q.
[0099]
The counter 185 is also connected to the output Q of the FF circuit 182, and counts the number and frequency of detecting deep pits based on the output Q and the signal from the preceding edge detection circuit 183. It will be described separately later.
[0100]
The output Q of the FF circuit 182, the data restoration circuit 184, and the counter 185 are also connected to the controller 110, which will be described later.
Subsequently, the operation timing will be described with reference to FIG. Of the pits shown at the top of the figure, 131 is a shallow pit and 132 is a deep pit.
[0101]
As the light beam 1101 passes over it, the output signal (a) of the adder circuit 104, which represents the amount of reflected light, shows a level change depending on the presence or absence of a pit, and the tangential push-pull signal (b) shows the level of the pit. At the time when the level of the output signal (a) of the edge, that is, the output signal (a) of the adder circuit changes, the pulse signal has a polarity corresponding to the depth.
[0102]
As described above, the output (c) of the comparator 107, the output (d) of the comparator 106-1, and the output (e) of the comparator 106-2 are a signal based on the output of the adding circuit 104, that is, a reflected light amount, and a tangential push-pull. This is a binary signal in the positive and negative directions of the signal.
[0103]
The edge detection circuit 183 outputs a pulse as shown in (f) at the leading edge of the pit, that is, at the fall of the output (c) of the comparator 107. When the light beam 1101 reaches the shallow pit 131, the output (d) of the comparator 106-1 becomes “H”, so that an “L” level pulse is output to the output (g) of the NAND circuit 181 and the FF is output. The circuit 182 is reset, and the Q terminal (the signal (h) in FIG. 10) which is the output of the FF circuit 182 becomes "L", indicating that the reproduced pit is a shallow pit.
[0104]
On the other hand, when the light beam 1101 reaches the deep pit 132, the output (e) of the comparator 106-2 becomes "H", so that the data input terminal D of the FF circuit 182 becomes "H" and the FF circuit 182 When an output pulse of the edge detection circuit 183, which is an input, is input, the output Q terminal (the signal (h) in FIG. 10) becomes "H" to indicate that it is a deep pit.
[0105]
The data restoration circuit 184 uses the output Q of the FF circuit 182 and the signal obtained for each pit from the edge detection circuit 183 to restore / reproduce the additional information recorded according to the pit depth, or to determine the presence of the additional information. The presence or absence is detected, and the result is output to the controller 110, and the controller 110 controls the operation of each unit of the optical disk device according to the result.
[0106]
Therefore, while the optical disc device can control various operations by the additional information, the recording capacity of the main information does not decrease and the overall recording capacity of the optical disc increases even if the additional information is recorded. It will be.
[0107]
In the above description, the main information is recorded based on the presence or absence and length of the pits. However, if the optical information has the main information recorded by the width and position of the pits or at least one of them, In other words, if the optical disc has pits formed thereon, the polarity of the tangential push-pull signal changes depending on the depth, and the technique of the present invention is applicable.
[0108]
When a conventional optical disk in which the pit depth is not intentionally changed is mounted on the optical disk device configured as described above and reproduced, the polarity of the tangential push-pull signal shows the same change in each pit. Therefore, the output ((h) in FIG. 10) of the FF circuit 182 is fixed at either the “H” or “L” level, and of course, significant additional information cannot be reproduced based on the pit depth. Information can be reproduced based on the change in the amount of reflected light depending on the presence or length of the pit. Specifically, the main information reproducing circuit 9 reproduces and decodes the main information from the output of the comparator 107 in FIG. When reproducing the main information, if there is no need for additional information based on the pit depth, the main information may be reproduced as it is. Specifically, for example, this case corresponds to a case in which an optical disc that does not require encryption / decryption key information when decrypting and reproducing the main information is not recorded.
[0109]
Therefore, the optical disk device of the present invention can also have reproduction compatibility with a conventional optical disk.
[0110]
That is, as in the case of the conventional optical disc apparatus for reproducing an optical disc, the main information is reproduced first, and the main information cannot be normally reproduced, or when the existence of the additional information is judged or predicted from the contents of the main information. Alternatively, the additional information may be reproduced.
[0111]
In this way, the compatibility of the conventional optical disc with the reproduction can be maintained, and if the main information can be normally reproduced, the power supply of the block related to the reproduction of the additional information, which does not require the operation for the time being, is controlled by the controller 110. Can be turned off by the control of (1), which is effective in reducing power consumption.
[0112]
In the configuration of the optical disk device described above, the main information is reproduced based on the sum signal indicating the amount of reflected light, and the additional information is the intensity distribution of the reflected light of the irradiated light beam in the tangential direction of the pit row. In this configuration, reproduction is performed with reference to a tangential push-pull signal indicating a difference.
[0113]
Therefore, when reproducing the main information, as described above, while having the reproduction compatibility with the conventional optical disk, the tangential push-pull signal has the pit depth of the pulse appearing at the above-mentioned (λ / 4n). Since the polarity is clearly inverted, the difference in the depth can be reliably determined, and a circuit for that purpose may have a simple configuration.
[0114]
In such a conventional optical disk, if the change in the amount of reflected light, in other words, the amplitude or S / N of a reproduction signal for obtaining main information can be obtained to some extent, it is not necessary to form pits deeper than that. Therefore, in the optical disc on which the additional information is recorded, the depth of the pit is formed to be deeper than that of the conventional optical disc or the pit not including the additional information. What is necessary is just to detect and judge that it exists, or to reproduce the additional information.
[0115]
Since it is not necessary to add additional information to all pits on the optical disk, it is advantageous in terms of productivity of the optical disk itself to form only the pits having additional information deep as described above.
[0116]
Also, when the optical disk device detects that a pit is deep, it is possible to easily distinguish a conventional optical disk from an optical disk having additional information in the pit depth.
[0117]
Referring to FIG. 9, the signal from the edge detection circuit 183 and the output Q of the FF circuit 182 are connected to the counter 185 similarly to the data restoration circuit 184. Since the output Q of the FF circuit 182 becomes “H”, the section, the number / frequency, or the number of changes is measured by a signal obtained for each pit from the edge detection circuit 183.
[0118]
When the additional information is used for a simple application, for example, when it is sufficient to determine whether or not a deep pit is included in a predetermined ratio or more, the additional information is restored by the data restoration circuit 184 described above. Needless to say, the value of the counter 185 may be read by the controller 110. In this way, the number and ratio of the pits having additional information, the appearance interval or the appearance frequency are measured, and if the result is equal to or more than a predetermined value, it can be determined that the additional information has been detected. Even in the case where there is disturbance or variation, it can be determined at least whether or not the optical disk has additional information.
[0119]
Alternatively, only when the value of the counter 185 is equal to or more than a predetermined value, the data restoration circuit 184 may restore / reproduce the additional information or the controller 110 may decode the restored additional information. .
[0120]
In addition, if the optical disk used is manufactured such that the number and ratio of the pits having the additional information, the appearance interval and the appearance frequency thereof are equal to or more than a predetermined value, the pits are detected and the additional information is detected. It is possible to determine the presence or absence. At the same time, even if the formation of the pit depth is disturbed or varied, it is easy to correctly determine only the presence or absence of additional information.
[0121]
Incidentally, the data restoration circuit 184 can reproduce the additional information from the output of the FF circuit 182 which is the result of the pit depth detection. In this case, one bit of the additional information is assigned to each pit in accordance with the depth, so that the output pulse of the edge detection circuit output for each pit corresponds to each bit of the additional information. It represents a clock.
[0122]
In general, the appearance frequency and length of pits on an optical disc are constant when averaged over a relatively long period of time, but these values are known values because they are determined by modulation or the like. Therefore, the information amount of one unit of the additional information to be recorded on the optical disk is defined according to this value, and the information amount is associated with the recording unit of the main information. It is also possible to synchronize the additional information. In this case, for example, subtitles may be added to the movie image of the main information, or audio or text information of the sightseeing guide may be used as the main information for a map or a landscape image, so that the content of the main information is adapted. The additional information can be reproduced.
[Embodiment 4]
A fourth embodiment of the present invention will be described below. In this embodiment, an example will be described in which the additional information described in the previous embodiment is mainly used as a defense / countermeasure against unauthorized copying.
[0123]
As is well known, not only read-only optical discs in which information is recorded in pits but also optical discs that can be recorded by forming marks having different reflectivities, for example, a dye or a phase change material are used. The type used is mentioned. It is possible to reproduce the irradiated light beam in the same manner as an optical disk recorded with pits, based on the change in the amount of reflected light of the recording mark.
[0124]
However, although a recordable optical disk can record the presence or absence and length of a recording mark, it cannot record information corresponding to the depth of a pit. Therefore, if information is recorded on the original optical disc that cannot be normally reproduced without additional information based on the pit depth, a dead copy of this information onto a recordable optical disc, that is, a pirated optical disc can be reproduced normally. As a result, it is possible to prevent the use of an illegal copy or a pirated optical disc on which the copy is made.
[0125]
Some examples of measures to be taken when this additional information cannot be reproduced or detected, in other words, countermeasures against illegal copying using the additional information will be given below.
[0126]
As a simple example, when the additional information is reproduced or not detected, the main information may be restricted under the control of the controller 110. For example, when playing back an optical disc on which a movie is recorded, the playback of the movie or audio, which is the main information, may be allowed for the first few minutes, or the playback itself may not be allowed at all.
[0127]
In this way, it is of course possible to prevent the illegally copied optical disc from being played back, but if the playback is restricted to allow partial playback, depending on the content, However, it is conceivable that the user may be motivated to purchase a legitimate optical disk on which information is recorded in pits, rather than illegal copying.
[0128]
Even if the additional information can be physically reproduced, if it does not match a kind of password recorded in advance as a part of the main information, the additional information may be treated as not being reproduced. This is the same in the following description.
[0129]
Alternatively, in the case where the additional information is not reproduced or detected, if the reproduction of the optical disk is not permitted, the subsequent operation as the optical disk device itself may be restricted.
[0130]
Specifically, even if the user instructs the removal of the optical disk, if the user rejects or ignores it, or performs only the operation of immediately ejecting the optical disk, the illegally copied disk cannot be reproduced. It can also be expected that the user is encouraged to feel guilty about the use of the illegally copied disk, and that his interest in the illegally copied disk is reduced thereafter.
[0131]
Alternatively, the power of the servo control circuit 111 may be turned off or the internal operation may be stopped by an instruction from the controller 110 to substantially cut off the servo signal path so that the information cannot be reproduced. However, in this case as well, not only can playback not be performed, but even the slight operation noise due to the servo operation of the optical disk device disappears, and the device stops immediately. Therefore, it seems that the device has become defective, so that the effect of diminishing interest in unauthorized copy discs can be further expected.
[0132]
Alternatively, if the additional information cannot be reproduced or detected, the mounted optical disc may be recordable, so that information indicating unauthorized copying is recorded in a specific portion of the optical disc, or part of the information is recorded. It is also conceivable that the subsequent reproduction is hindered by overwriting and destroying or erasing.
[0133]
In this way, unlike the level of simply ejecting the optical disk or rejecting the reproduction, it is possible to make the illegally copied optical disk that has been tried once reproduced impossible to be reproduced again by another optical disk device Therefore, a strong penalty can be imposed on an illegally copied disk.
[0134]
Of course, not all recordable optical discs are illegal copies, so it is better not to record or erase this information on optical discs that can reproduce main information without additional information.
[0135]
Although it is necessary to consider legal issues in realizing this method, it is an effective method if the strengthening of the penalty for illegal copying can be recognized by society.
[0136]
Alternatively, when the additional information cannot be reproduced or detected, the polarity of the tracking servo may be reversed. While this can prevent information from being reproduced on an optical disk that is considered to be an illegal copy, it reverses the servo polarity just in case when examining the cause of the inability to reproduce even though additional information is recorded. Then, a recovery method for attempting to reproduce the additional information can be used.
[0137]
Furthermore, when the additional information cannot be reproduced or detected, the fact is simply displayed visually on the display unit 112 in FIG. 2, more specifically, a display or an LED, or a synthesized voice or a buzzer sound. May be displayed audibly, or a warning may be issued using these methods. This can display or warn that the disc is an illegally copied disc, but can also inform the user that the disc is a conventional optical disc in which no additional information is simply recorded at the pit depth.
[Embodiment 5]
Subsequently, a fifth embodiment of the present invention will be described. The fourth embodiment has described the method of using the additional information mainly as a countermeasure against unauthorized copying. In the present embodiment, an example will be described in which additional information is used as auxiliary information for reproducing main information.
[0138]
Auxiliary information necessary for reproducing information from the optical disk includes a descrambling key of main information, a descrambling key, parity for error correction, a synchronization signal, and address information. In the conventional optical disk, such information is embedded in the main information, so that the recording capacity of the optical disk is consumed. However, if such information is recorded as additional information according to the pit depth, the consumption is avoided. Can do things. Also for the optical disk device, an increase in the recording capacity is preferable because it means an increase in the reproduction time from one optical disk.
[0139]
At the same time, any of the above auxiliary information is important, and if these cannot be reproduced as additional information, the main information cannot necessarily be reproduced. Therefore, it is possible to prevent the reproduction of the optical disk which has been illegally copied as described above without performing the operation described in the second embodiment on the optical disk apparatus side.
[0140]
The error correction parity is improved as the number of error correction parities increases, but the number of parities for the conventional optical disc is limited because the recording capacity of main information is reduced. In the case of the optical disc of the present invention, an increase in the amount of additional information does not directly lead to a decrease in the capacity of the main information. Therefore, the additional information recorded at the depth is used as the parity for error correction. The number of error correction parities corresponding to the correction ability can be set. If the error correction capability of the optical disk device also increases, the reliability of the reproduced signal increases, so that the probability of disturbance of images and sounds and data errors is further reduced.
[0141]
In this case, when reproducing a conventional optical disk such as a CD or DVD, as described above, it may be determined that the optical disk is a conventional optical disk based on the presence or absence of pits having different depths, or error correction may be performed using main information. If it can be performed, it may be determined that the optical disk is a conventional optical disk, and an error correction parity or the like embedded in the main information may be used.
[0142]
Alternatively, the additional information may be used as the address information. In this case, the address information is detected and reproduced in comparison with the detection and reproduction of the information embedded in the main information. If they are similar, if they are fixed, it is not necessarily impossible to decipher them, especially for an unauthorized user having skill. Piracy may be spread by copying the main information to another recordable optical disk and distributing the decrypted key.
[0143]
However, if the information such as the descrambling key and the descrambling key is frequently changed, for example, on a sector basis, the possibility of decryption by an unauthorized user can be significantly reduced. In the conventional optical disk, such a frequent key change could not be performed because the main information capacity was reduced, but in the present invention, since the main information capacity is not reduced by the additional information, the release key may be frequently changed. It is possible, and illegal copying is almost impossible.
[0144]
Alternatively, the auxiliary information may be, for example, captions, audio guides, simple still images and character information, operation guides, and the like.
[0145]
In this case, similar to the fourth embodiment, the additional information reproduced by the additional information reproducing circuit 108 is input to the controller 110. The controller 110 determines what the content of the additional information is. For example, in the case of subtitles, the content is output in synchronization with a moving image as main information, and in the case of operation guide information, a predetermined operation is performed.
[0146]
These auxiliary information may be recorded together with the main information. For example, in the case of an operation guide, for example, the optical disc device needs to read information in the area in advance and store the information in a memory. It is. Alternatively, during the reproduction of the main information, there may be a case where processing such as accessing the auxiliary information area slightly apart to read the auxiliary information and continuing to reproduce the main information again is required.
[0147]
However, if the optical disk having additional information according to the pit depth according to the present invention is used, the auxiliary information can be obtained in synchronization with or concurrently with the reproduction of the main information, so that the above processing is unnecessary. In addition, the memory can be reduced and the operation stability of the apparatus at the time of reproducing the main information can be improved.
[0148]
The optical disk device according to the present invention does not require any special mechanism or optical pickup, and a conventional mechanism or optical pickup can be used.
[0149]
Therefore, increase in cost and device size can be suppressed.
[0155]
【The invention's effect】
Of the present inventionIn the method of reproducing optical record informationIs the lightThe tangential push-pull signal on the disk is converted into two sets of binarized signals indicating that each of the positive and negative reference values has been exceeded, and each set of these second binarized signals is added and subtracted as positive and negative signals, It is characterized in that information is reproduced based on the result of the addition and subtraction. Therefore, it is possible to reproduce the information of the optical disk recorded ternary by a simple method.
[0156]
Also,Of the present inventionIn the method of reproducing optical record informationIs the lightBased on the amount of light reflected from the discZuAnd converts the tangential push-pull signal into two sets of second binary signals indicating that the signal has exceeded a predetermined reference value with positive and negative polarities, respectively. It is characterized in that information is reproduced by observing the second binarized signal at the changing point of the first binarized signal. Therefore, it is possible to reproduce the information of the ternary recorded optical disk by another simple method.
[0161]
Of the present inventionWith optical disk deviceIs the lightThe tangential push-pull signal on the disk is converted into two sets of binarized signals indicating that each of the positive and negative reference values has been exceeded, and each set of these second binarized signals is added and subtracted as positive and negative signals, It is characterized in that information is reproduced based on the result of the addition and subtraction. Therefore, it is possible to reproduce the information of the optical disc on which ternary recording has been performed with a simple configuration.
[0162]
AndOf the present inventionWith optical disk deviceIs the lightBased on the amount of light reflected from the discZuAnd converts the tangential push-pull signal into two sets of second binary signals indicating that the signal has exceeded a predetermined reference value with positive and negative polarities, respectively. It is characterized in that information is reproduced by observing the second binarized signal at the changing point of the first binarized signal. Therefore, it is possible to reproduce the information of the optical disc on which ternary recording has been performed with another simple configuration.
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between a pit depth, a tangential push-pull signal amplitude, and an RF signal amplitude.
FIG. 2 is a diagram illustrating a tangential push-pull signal.
FIG. 3 is a diagram illustrating a pit depth, an RF signal, and a tangential push-pull signal.
FIG. 4 is a block diagram showing a configuration of a main part of an information reproducing apparatus in the first embodiment of the present invention.
FIG. 5 is a diagram illustrating waveforms and operations of the playback device having the configuration of FIG. 4;
FIG. 6 is a diagram showing another configuration of the main part of the information reproducing apparatus according to the second embodiment of the present invention.
FIG. 7 is an explanatory diagram of the principle of information reproduction in the present invention.
FIG. 8 is a block diagram of a portion related to information reproduction of the optical disc device according to one embodiment of the present invention.
9 is a diagram illustrating a configuration example of an additional information reproduction circuit in FIG. 8;
FIG. 10 is a diagram illustrating operation timing.
FIG. 11 is an explanatory diagram of the principle of conventional information reproduction.
[Explanation of symbols]
1. Detector
2. Differential amplifier
3 .... summing amplifier
4 ・ ・ Comparator
5 ・ ・ Comparator
6 ··· Addition and subtraction circuit
7 ... Equalization circuit
8. Binarization circuit
9, 10, Latch
101 ... reflected light
102 Photo detector
103-1, 103-2... Addition circuit
104 addition circuit
105 ··· Difference circuit
106-1, 106-2 ··· Comparator
107 ··· Comparator
... Additional information reproducing circuit
109 ·· Main information reproduction circuit
110 Controller
111 servo control circuit
112 ··· Display
131 ... shallow pit
132-deep pit
181 NAND circuit
182 FF circuit
183 ··· Edge detection circuit
184 ·· Data restoration circuit
185 counter
1101 ... light beam

Claims (4)

An optical disk having pits having two types of depths (D1, D2) formed on a substrate, where 0 <D1 <λ, where λ is the wavelength of light to be used and n is the refractive index of the substrate of the optical disk. / 4n cutlet is configured to satisfy the λ / 4n <D2 <λ / 2n, the signal based on the reflected light of the optical disk, an optical recording information for reproducing the recorded data by combining tangential push-pull signal obtained from the pits In the reproduction method of
The tangential push-pull signal obtained from the pits on the optical disk is converted into two sets of second binarized signals indicating that a predetermined reference value has been exceeded in each of positive and negative polarities. the method of reproducing an optical recording information, characterized in that by adding or subtracting each set of digitized signal as positive and negative signals, for reproducing information based on the result of the subtraction. An optical disk having pits having two types of depths (D1, D2) formed on a substrate, where 0 <D1 <λ, where λ is the wavelength of light to be used and n is the refractive index of the substrate of the optical disk. / 4n cutlet is configured to satisfy the λ / 4n <D2 <λ / 2n, the signal based on the reflected light of the optical disk, an optical recording information for reproducing the recorded data by combining tangential push-pull signal obtained from the pits In the reproduction method of
A signal based on the amount of reflected light from the optical disk is converted into a first binary signal, and the tangential push-pull signal obtained from the pit is two sets indicating that the signal has exceeded a predetermined reference value with positive and negative polarities. second into a binary signal, reproduction of the optical recording information, characterized in that for reproducing a binary signal observed by the information of the second at the change point of the first binarized signal Method. An optical disk having pits having two types of depths (D1, D2) formed on a substrate, where 0 <D1 <λ, where λ is the wavelength of light to be used and n is the refractive index of the substrate of the optical disk. / 4n cutlet is configured to satisfy the λ / 4n <D2 <λ / 2n, the signal based on the reflected light amount of the optical disc, an optical disc apparatus for reproducing recorded data by combining tangential push-pull signal obtained from the pits ,
The tangential push-pull signal obtained from the pits on the optical disk is converted into two sets of second binarized signals indicating that a predetermined reference value has been exceeded in each of positive and negative polarities. An optical disc device, which adds or subtracts each set of valued signals as positive and negative signals and reproduces information based on the result of the addition and subtraction. An optical disk having pits having two types of depths (D1, D2) formed on a substrate, where 0 <D1 <λ, where λ is the wavelength of light to be used and n is the refractive index of the substrate of the optical disk. / 4n cutlet is configured to satisfy the λ / 4n <D2 <λ / 2n, the signal based on the reflected light amount of the optical disc, an optical disc apparatus for reproducing recorded data by combining tangential push-pull signal obtained from the pits ,
A signal based on the amount of reflected light from the optical disk is converted into a first binary signal, and the tangential push-pull signal obtained from the pit is two sets indicating that the signal has exceeded a predetermined reference value with positive and negative polarities. An optical disk device for converting information into a second binary signal, and observing the second binary signal at a change point of the first binary signal to reproduce information.

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