JP3512161B2 - Optical disk drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo of an optical disk device using an optical disk in which information is recorded in advance on all or part of a recording surface by pits having an uneven shape.

[0002]

2. Description of the Related Art In an optical disk reproducing apparatus for reproducing an optical disk in which information is previously recorded in pits having concave and convex shapes on a disk surface, various tracking servo techniques for positioning a light beam on a pit row have been used. It has been proposed, for example, JP-A-58-1501.
The disclosure is made in Japanese Patent Publication No. 45.

FIG. 7 is a block diagram of tracking servo based on the phase difference (time difference) method.
This is a redrawing of the configuration shown in FIG. 3 to FIG.

In the phase difference (time difference) method, the reflected light beam from the optical disk is divided into four parts in the radial direction and the tangential direction of the optical disk.
A photodetector having two elements receives light, obtains the sum signal of the outputs of those photodetectors located diagonally, and detects the phase difference (time difference) of the sum signal to perform tracking. In FIG. 7, reflected light from the disk is collected and incident on the photodetector 2, and each portion outputs a signal according to the amount of incident light. The summing amplifiers 3-1 and 3-2 are portions a and c, and b and d of the photo detector 2 which are diagonally located.
Of the comparators (comparison circuit) 5-1 and 5-
Output to 2. The comparators 5-1 and 5-2 include reference signals + Ref1 and + Ref2 and a summing amplifier 3-1,
The output signals of 3-2 are compared and the resulting binarized signal is output.

Since the reflected light of the light beam is diffracted by the pits, the intensity distribution of the reflected light on the photodetector fluctuates with time depending on the positional relationship between the light beam and the pits. For example, when the light beam follows directly above the pit row, the sum signals of the outputs of the elements (a + c) and (b + d) at the diagonal positions of the photodetector on the pits change the same, so the comparator 5- The output signals 1 and 5-2 also change at the same timing. Further, when the light beam follows a position deviated from directly above the pit row, the sum signals of the outputs (a + c) and (b + d) have a phase difference (time difference) corresponding to the deviation amount. Either changes first depending on the direction of.

Therefore, the phase difference (time difference) between the output signals of the comparators 5-1 and 5-2 is detected by the phase comparison circuit 7, and a pulse corresponding to the phase difference (time difference) is output, and this pulse is output to the LPF ( By extracting only the low frequency components by the low pass filters 8-1 and 8-2 and calculating the difference by the difference circuit 9, it is possible to obtain the tracking signal indicating the deviation amount and the direction between the light beam and the pit row.

A push-pull method is another example of the technique for obtaining the tracking servo signal.

The push-pull method is a method in which a difference in light amount between the inner peripheral side and the outer peripheral side of the reflected light beam divided in the tangential direction is obtained and used as a tracking signal. FIG. 8 shows a tracking servo signal by the push-pull method. FIG. 7 shows an example of a block configuration diagram for generating

When a light beam is applied to a pit row, the reflected light is diffracted by the pits due to the positional relationship between the two, but in the push-pull method, the reflected light is divided into two directions on the inner and outer sides of the optical disk. It is divided and detected, and a tracking servo signal is generated based on the average intensity.

In FIG. 8, the reflected light is condensed on the four-divided photodetector because of the above-mentioned phase difference (time difference).
Same as the method, but the adder circuits 3-1 and 3-2 add output signals of the elements located on the inner circumference side and the outer circumference side, instead of the elements located diagonally of the photodetector, and the result of the addition Is output to the difference circuit 17. The difference circuit 17 outputs the difference result of the two signals from the adder circuits 3-1 and 3-2 to the LPF 18, removes the high frequency component of each pit from the difference result, and in other words the low frequency component, in other words, The principle of the push-pull method is to obtain, as a tracking servo signal, an extracted signal component corresponding to a slight average deviation between the light beam and the pit row.

[0011]

At present, pit (mark) length recording is generally used in an optical disc, in which information is included in the length of a pit and a mark at the same time as the presence or absence of the pit or mark. If information is given, it is possible to expect the recording of a larger amount of information. This has already been
The application is filed as Japanese Patent Application No. 11-184604.

[0012] This is a technique, but new information is included by utilizing the fact that the diffraction pattern due to the interference of light generated in the pit having an uneven shape differs depending on the depth of the pit.

FIG. 9 is a schematic view showing the principle of reproducing information recorded by the pit depth. When the wavelength of light is λ and the refractive index of the optical disc substrate is n, the pit 31 is a relatively shallow pit with a depth of (λ / 6n) less than (λ / 4n), and the pit 32 represented by diagonal lines is deep. It is a relatively deep pit of about (λ / 3n) beyond (λ / 4n). When these pit rows are scanned with a light beam in the direction of the arrow in the figure, the sum signal (a) of the amount of light incident on the photodetector is located when the light beam is located on the pit 31 and on the pit 32. There is no clear difference from time. In other words, the information based on the sum signal of the light amount does not have a large difference in the pit depth, but rather the more stable the information can be reproduced if there is a clear change in the light amount depending on the presence or absence of the pit. It is desirable that the difference does not occur so much, and it is better that the pit depth does not carry information.

However, paying attention to the tangential push-pull signal (b), which is a signal obtained by dividing the reflected light into the front half and the rear half in the traveling direction of the light beam, the tangential push-pull signal (b), when the light beam approaches or escapes from the pit. The polarity of the generated pulse-like signal is reversed due to the difference in the diffraction pattern of light due to the depth of the pit. This is a separate phenomenon that is completely independent of the change in the summation signal due to the presence or absence of pits.

Therefore, by detecting the polarity of the tangential push-pull signal, it becomes possible to include new information not only in the pit length / presence, but also in the pit depth. This is the above-mentioned Japanese Patent Application No. 1 filed by the applicant.
It is the summary of No. 1-184604.

However, the fact that the polarity of the tangential push-pull signal is inverted depending on the pit depth means that the diffraction pattern of the reflected light changes depending on the pit depth. Therefore, in the phase difference method or push-pull method that uses the intensity distribution of the diffraction pattern of the reflected light, the polarity of the tracking signal may be reversed between the deep pits and the shallow pits. For example, the conventional method cannot correctly perform tracking servo control.

The present invention provides a technique capable of correctly performing tracking servo control even on an optical disc having pits with different depths as described above.

[0018]

[Means for Solving the Problems] In order to solve the above problems,
The present invention has taken the following means.

[0019] That is, the first means uses an optical disk having a region for recording information by the pits before
The pit depth detecting means for detecting the depth of the pits based on the reflection from the pits of the optical disc, and the tracking signal for causing the light beam to follow the pit row based on the output of the pit depth detecting means. It is characterized by comprising a polarity reversing means for reversing the polarity.

A second means is the optical disk device of the first means, wherein the pit depth detecting means has a signal according to the amount of reflected light of the light beam applied to the pit,
Based on the signal according to the difference in the intensity distribution in the tangential direction of the pit row, based on the polarity of the signal according to the difference in the intensity distribution at the change point of the signal according to the light amount of the reflected light, the pit It is characterized by detecting the depth of.

A third means is the optical disk device of the second means, wherein the pit depth detecting means compares a signal corresponding to a difference in intensity distribution in the tangential direction with two reference values. And second comparing means for binarizing the signal, third comparing means for binarizing the signal corresponding to the light quantity of the reflected light with another reference value, and the third comparing means. It is characterized in that the pit depth is detected based on the reference result by referring to the outputs of the first and second comparing means at the change timing of the output of the comparing means.

The fourth means is, in the optical disk device of the first means, the reflected light of the light beam applied to the pits is received by a light receiving element, and the phase difference of the output signals from the light receiving element is detected by the phase difference. The detection means detects the tracking signal to generate the tracking signal, and the polarity of the tracking signal is switched according to the detection result of the pit depth detection means.

Further, the fifth means, in the optical disc apparatus of the first means, receiving the reflected light of the laser beam irradiated to the pits, the difference in the intensity distribution in the radial direction of the optical disc by the light receiving element, that Of the output signal from the light receiving element
The difference means generates a tracking signal based on the intensity difference, and switches the polarity of the tracking signal according to the detection result of the pit depth detecting means.

The sixth means is the fourth means or the fifth means.
In the optical disk device of the means, the light receiving element has an arrangement capable of detecting intensity distributions of the reflected light of the light beam in directions substantially parallel to the tangential direction of the row of pits and the radial direction of the optical disk. And

A seventh means is characterized in that, in the optical disk device of the sixth means, the light receiving elements are arranged in a substantially "square" shape.

According to an eighth aspect, in the optical disk device of the sixth means, the light receiving element includes an element capable of detecting an intensity distribution substantially parallel to the radial direction of the optical disk and an element not detecting the intensity distribution. Characterize things.

A ninth means is the optical disk device of the first means, wherein the wavelength of the light beam is λ, the refractive index of the substrate of the optical disk is n, and arbitrary integers are k and m, The depth of the pit formed on the optical disk used is (kλ / 2n) <D1 <{(λ / 4n) + (kλ /
2n)} and {(λ / 4n) + (mλ / 2n)}
D satisfying the condition of <D2 <{(m + 1) · λ / 2n}
It is characterized by being classified into either 1 or D2.

The tenth means is characterized in that, in the optical disk device of the ninth means, at least one of the integers k and m is set to 0.

The eleventh means is characterized in that, in the optical disk device of the tenth means, information is included in the depth of the pits.

The twelfth means is the optical disk device of the first, ninth, or tenth means, in which a recording type optical disk for irradiating light to form recording marks having different reflectances is mounted. In this case, the pit depth of the optical disc is selected so that the polarity of the tracking signal with respect to this is a polarity that causes tracking servo deviation.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram of a main part when the present invention is applied to an optical disk device using a so-called phase difference method for generating a tracking signal.

The reflected light from the optical disk is collected and incident on the photodetector 2, and the photodetector 2 outputs a signal proportional to the amount of each incident light. This photodetector has a suitable arrangement for splitting the reflected light into two directions, that is, the traveling direction of the light beam, in other words, the tangential direction of the pit row formed on the optical disc and the radial direction of the optical disc.

The adder circuits 3-1 and 3-2 add the sum signals of the outputs from the diagonally located portions a and c, b and d of the photodetector 2, and the adder circuits 3-3 and 3-4 the light beam. A sum signal of outputs from a and d in the traveling direction and b and c in the opposite direction to the traveling direction of the light beam is output.

Further, the adder circuit 4 calculates the total sum of the outputs of the photodetector 2 and outputs it. The outputs of the adder circuits 3-1 and 3-2 are compared with preset reference voltages + Ref1 and + Ref2 by the comparators 5-1 and 5-2, respectively, and the binarized signal as the comparison result is sent to the selection circuit 6. Is entered.

The switch (selection circuit) 6 switches which of the R and V input terminals of the phase comparator circuit 7 the output of the comparators 5-1 and 5-2 is input, and the output of the FF circuit described later. This switching is performed by a signal.

The phase comparison circuit 7 compares the R input and the V input, and outputs a pulse having a width corresponding to the phase difference between the two, depending on which phase difference is advanced. For example, in this example, a pulse having a width corresponding to the delay amount is output from the U output when the V input is delayed compared to the R input, and from the D output when the V input is advanced. .

From the U output signal and the D output signal of the phase comparison circuit 7, only the low frequency components are extracted by the LPFs 8-1 and 8-2, respectively, and are input to the difference circuit 9, and the difference circuit 9 is L.
The difference between the outputs of the PFs 8-1 and 8-2, that is, the difference between the low frequency components of the output of the phase comparison circuit 7 is output as a tracking signal.

On the other hand, the output of the adder circuit 4 for obtaining the sum of the output signals from the photodetector 2 is compared with the reference voltage + Ref4 by the comparator (comparison circuit) 10, and the resulting binary signal, in other words, pit. This signal is indicative of the magnitude of the reflected light amount depending on the presence or absence of, and is input to the edge detection circuit 11. The edge detection circuit 11 outputs a pulse at the falling edge, which corresponds to the transition from non-pit to pit in FIG. 1, among the rising and falling edges of the output signal of the comparator 10.

Further, among the elements of the photodetector 2, the outputs of the adder circuits 3-3 and 3-4, which respectively obtain the outputs of the elements located in the front-back direction with respect to the light beam traveling direction, are input to the difference circuit 12. The output of the difference circuit 2 is a signal indicating the intensity distribution difference of the reflected light in the tangential direction (Tangent) of the pit row, and is therefore called a tangential push-pull signal, which is a comparator (comparison circuit) 13
-1, 13-2 are input. The comparator 13-1 compares the tangential push-pull signal with a preset reference voltage + Ref3, and outputs “H” when the tangential push-pull signal is larger than + Ref3, while the comparator 13-2 outputs the tangential push-pull signal. It is compared with a preset reference voltage -Ref3 and outputs "H" when the tangential push-pull signal is smaller than -Ref3.

The outputs of the comparators 13-1 and 13-2 are connected to one input terminals of AND gates (mask circuits) 14-1 and 14-2, respectively, and the outputs of the AND gates 14-1 and 14-2. For the other input terminal,
The output of the edge detection circuit 11 is connected.

Therefore, AND gates 14-1, 14-2
When the pulse is output from the output of the edge detection circuit 11, the pulse is output according to which of the outputs of the comparators 13-1 and 13-2 is "H".

From a different point of view, these AND gates 1
4-1 and 14-2 are comparators 13-1 and 13-2.
Of the tangential push-pull signal, which is the output of
It can also be said that the quantized one is output with reference to the change point of the binarized reflected light amount signal output from the edge detection circuit 11.

Alternatively, the comparators 13-1, 13-2
It can be said that even when the output is generated, the edge detection circuit 11 works to mask the pulse and output it only at a specific timing when the pulse is generated.

The outputs of the AND gates 14-1 and 14-2 are connected to the clock inputs of the FF circuits 15-1 and 15-2. Further, since the D input is connected to the "H" level, the output of the FF circuits 15-1 and 15-2 becomes "H" when the pulse is input to the clock input, and the pulse is input to the reset terminal. Then, the connection is such that the output becomes "L".

On the other hand, at the reset terminal of the FF circuit 15-1, the output of the pulse generation circuit 15-2 for generating a pulse at the rising edge of the output Q of the FF circuit 15-2 is connected to the FF circuit 15-.
Since the output of the pulse generation circuit 15-1 that generates a pulse at the rising edge of the output Q of the FF circuit 15-1 is connected to the reset terminal of 2, the output of either the FF circuit 15-1 or 15-2 When Q rises, in other words, when a pulse is output from the AND gate circuit 14-1 or 14-2 to the FF circuits 15-1 and 15-2, respectively, the other FF circuit is reset. ing.

The outputs Q of the FF circuits 15-1 and 15-2 are connected to the control terminals C1 and C2 of the switch 6, respectively, when the output of the FF circuit is "H" and the output of the FF circuit is "L". The terminal O1 of the switch 6 is connected to the A1 side and the terminal O2 of the switch 6 is connected to the B2 side. The output of the comparator 5-1 is selected as the R input of the phase comparison circuit 7, and the output of the comparator 5-2 is connected as the V input. To be done. On the contrary, when the state is inverted and the output of the FF circuit is "L" and the output of the FF circuit is "H", the terminal O1 of the switch 6 is connected to the B1 side and O2 is connected to the A2 side, and the phase comparison circuit 7 The output of the comparator 5-2 is selected for the R input, and the output of the comparator 5-1 is selected for the V input.

As described above, the phase comparison circuit 7 compares the phase difference between the R input and the V input and outputs a pulse according to the direction and amount of the lead / lag, so that the R input and the V input.
When the inputs are swapped, the pulse output terminals are swapped.

Therefore, if the state of the output Q of the FF circuits 15-1 and 15-2 changes, the polarity of the tracking signal output from the difference circuit 9 is inverted.

Next, in an optical disc having pits with different depths, the waveform and timing of each part in FIG. 1 when the light beam follows the pit row will be described with reference to FIG.

In FIG. 2, 31 is a pit having a relatively shallow depth,
The hatched 32 is a relatively deep pit. When the light beam 1 follows these, the output signal (a) of the adder circuit 4, which represents the amount of reflected light, changes in level depending on the presence or absence of a pit. The level decreases as you approach, and increases as you exit.

On the other hand, the tangential push-pull signal (b), which is the output of the difference circuit 12, is the difference in the intensity distribution of the reflected light of the light beam in the tangential direction of the pit row as described above. When the first half and the second half of the light beam in the traveling direction are different, more specifically, at the time when the light beam is near the front and rear edges of the pit, such as when the light beam approaches or exits the pit, It becomes a pulse-shaped signal having a reverse polarity.

The intensity distribution of the reflected light from the pits is the result of being influenced by the diffraction of the light beam by the pits. Particularly, the wavelength of the light (light beam) used is λ, and the refractive index of the optical disk substrate is n. Then, the direction of diffraction is reversed at the boundary of (λ / 4n).

Therefore, the depth of the pit is the above (λ / 4n).
If a shallower one less than this and a deeper one exceeding this are formed at the boundary, the polarity of the tangential push-pull signal when the light beam approaches or exits the pit is reversed.

Therefore, the pit depth can be determined and detected by observing the polarity of the tangential push-pull signal (b) at the time when the level of the output signal (a) of the adder circuit 4 indicating the reflected light amount changes. If the processing for reversing the polarity of the tracking signal is performed based on this, correct tracking servo control can be performed regardless of the pit depth. This is the basic idea of the present invention.

At the same time, the depth of the pits is detected from the tangential push-pull signal or the like, and depending on the difference, for example, the deep pits have a different meaning to increase the recording density or have additional information. Is also good. Even for such an optical disc, the switching of the tracking servo signal polarity according to the present invention is effective, and even if the pits having different pit depths are mixed, the tracking can be properly performed, and the reproduction of the above-mentioned additional information can be accurately performed. You can do it.

In FIG. 2, the tangential push-pull signal (b) is positive when the light beam approaches the shallow pit 31 and negative when exiting the deep pit 3.
Regarding 2, the change is shown as the opposite of this. Of course, even if this relationship is reversed, it may be possible to easily cope with it by slightly changing the circuit connection or the like.

Returning to FIG. 2, the description of the operation will be continued. The output signal (a) of the adder circuit 4 is binarized by the reference voltage + Ref4 by the comparator 10 to obtain (c), which is not the depth of the pit but "H" and " Change the L "level. The level is changed near the edge of the pit, and the edge detection circuit 11 outputs the pulse signal (d) only at the trailing edge of (c), that is, when the light beam reaches the pit.

On the other hand, the tangential push-pull signal (b) is compared with the reference values + Ref3 and -Ref3 which are different reference values by the comparators 13-1 and 13-2, respectively, and the binary signals shown in (e) and (f) are obtained. Become. The logical product of these and the output (d) of the edge detection circuit 11 is A
The outputs (g) and (h) of the ND gates 14-1 and 14-2 are the output of the comparator 13-1 at the time when the output pulse (d) of the edge detection circuit 11 is generated in the shallow pit. Since it becomes the H "level, the AND gate 14-1
A pulse is generated at the output (g) of the above, and the output Q of the FF circuit 15-1 is set to the “H” level. On the contrary, in the case of a deep pit, the output of the comparator 13-2 becomes “H” level at the time when the output pulse (d) of the edge detection circuit 11 is generated, so that the output (g) of the AND gate 14-2 is pulsed. Occurs, and the output Q of the FF circuit 15-2 is set to the “H” level.

As described above, the FF circuits 15-1 and 1
The switch 6 is switched by the output Q of 5-2 and the input signal to the phase comparison circuit 7 is switched, so that the polarity of the tracking servo signal is automatically switched so as to be appropriate according to the pit depth. Be seen.

In FIG. 1, a switch (selection circuit)
6 has a configuration in which the input of the phase comparison circuit 7 is switched, but this is the output of the phase comparison circuit 7 and the L and L terminals.
The polarity of the tracking servo signal can be switched in the same manner even when the output of the phase comparison circuit 7 is switched between the PFs 8-1 and 8-2.

Alternatively, the phase comparison circuit 7 itself has, for example, two sets of circuits for detecting the phase difference between the R input and the V input,
One of them detects the lead / lag of the V input with reference to the R input,
In the case where the other is configured to detect the lead / lag of the R input with reference to the V input, etc., the FF circuits 15-1 and 15
-Use output Q of -2 to operate only one of
The operation of the phase comparison circuit 7 may be directly switched.

Alternatively, the switch 6 may be replaced with LPFs 8-1, 8-
2 and the difference circuit 9 to switch the polarity of the tracking servo signal here, and an inverting amplifier that inverts the output of the difference circuit 9 is additionally provided. Alternatively, a configuration may be used in which the tracking servo signal is selected.

Further, in FIG. 1, the switch 6 has a structure for selecting and outputting the binarized (digital) signal which is the output from the comparators 5-1, 5-2. Gates 6-1 to 6-4, OR gate 6-
5 and 6-6 and inverters 6-7 and 6-8 may be used.

Further, in FIG. 1, the AND gates 14-1 and 14-2 are omitted and the output of the edge detection circuit 11 is FF.
While being directly applied to the clock inputs of the circuits 15-1 and 15-2, the D input of the FF circuit 15-1 is connected to the output of the comparator 13-1 instead of being fixed to the "H" level, and the D input of the FF circuit 15-2 is also connected. Even if the input is not fixed to the "H" level and the output is connected to the comparator 13-2, the same operation can be obtained.

Alternatively, even if the operation of the edge detection circuit 11 is such that a pulse is output at the rising edge instead of the falling edge of the output of the comparator 10, the pulse is generated at both the rising edge and the falling edge. However, it is possible to obtain a structure in which the polarity of the tracking servo signal is automatically switched according to the pit depth in the same manner with some circuit changes.

In each element of this embodiment, the element output of each photodetector is binarized through the comparator, and thereafter, most of the processing is performed by processing the binarized signal. In particular, after the comparators 13-1 and 13-2 regarding the tangential push-pull signal and the comparator 10 regarding the sum signal of the light amount and thereafter, the part for detecting the pit depth or the switch 6 until the control of the switch 6 is shown in FIG. In the case of the configuration as shown in (1), even the switch 6 can be made into a digital IC and can be easily integrated.

Further, in this embodiment, the tracking servo signal is generated by the phase difference method, but this phase difference method collects the light beam when the light beam is made to follow the pit row on the optical disc having a large eccentricity. In addition to the advantage that an offset is unlikely to occur in the tracking servo signal even if the objective lens to be displaced is greatly displaced, the signal from the photodetector is
Since the phase difference detection after digitization can be processed by a digital circuit, there is a further advantage in terms of circuit integration.

When attention is paid to the photodetector 2, in this embodiment, elements are arranged so as to detect intensity distributions of the reflected light of the light beam which are substantially parallel to the tangential direction of the pit row and the radial direction of the optical disk. . Therefore, from the output of the photodetector, based on the intensity distribution of the reflected light,
It is possible to generate both the tangential push-pull signal, the push-pull signal, and the signal corresponding to the sum of the reflected light amounts.

More specifically, the arrangement of the elements is substantially a "square" type. Since this substantially "T-shaped" photodetector has been widely used in the optical pickup of an optical disk device, it is possible to generate a focus error signal by a so-called astigmatism method, and it is more conventional than that. While utilizing without adding a new element to the optical pickup, it is possible to enjoy the advantage of the present invention that the pit depth is detected and the polarity of the tracking servo signal can be automatically switched.

By the way, as described above, if the pit has one kind of depth like the conventional optical disc, the level of the output signal (a) of the adder circuit 4 which can be said to be the sum signal of the reflected light amount changes. Since the polarity of the change in the tangential push-pull signal (b) is constant, the polarity of the tracking servo signal is fixed to be suitable for the pit depth, and compatibility with the conventional optical disc is maintained.

Alternatively, a tangential push-pull signal can be obtained as well as a sum signal of the reflected light amount in a recording type optical disc in which recording marks having different reflectances are formed by irradiation of light instead of pits. This is because when the light beam approaches the recording mark and escapes,
This is because an intensity distribution difference occurs in the front-back direction of the light beam traveling direction of the reflected light.

At this time, the change in the polarity of the tangential push-pull signal becomes constant due to the reflectance of the recording mark, so that the polarity of the tracking servo signal is fixed,
Information can be reproduced normally by the recording mark.

However, when the contents of an optical disc having information on the depth of pits are copied to an optical disc of such a recording type, only the information based on the total amount of reflected light can be copied, but the information on the depth of pits cannot be copied. Therefore, copying of the information provided in the pit depth is prevented.

Alternatively, by using the fact that the polarity of the tracking servo signal is fixed in a recording type optical disk forming recording marks having different reflectances, the polarity of the tracking servo signal is fixed to the opposite polarity. It is also possible to adjust the pit depth. In this case, the tracking servo control can be correctly performed on the optical disc in which the information is recorded in the pits, but when a recording-type optical disc that is a copy of this is mounted, the polarity of the tracking servo signal reverses, causing track deviation, Since it can not be reproduced, it can be applied to a new copy protection measure.

[Embodiment 2] Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the structure of the photodetector that receives the reflected light is the same as in the first embodiment.
This is an example of using a different one from the one in the shape of "rice field".

In general, a photodetector of a substantially "T-shaped" type is often used in an optical pickup made by combining individual optical parts. Although not described in the previous embodiment, a focus servo signal is often generated from this "square-shaped" type photodetector, and in that case, an optical technique called astigmatism method is used together. Is mostly.

However, in this astigmatism method, the adjustment of the optical system is somewhat sensitive and the number of individual parts is large, so the assembly and adjustment costs tend to be rather high.

On the other hand, in recent years, a photodetector, a semiconductor laser as a light source, etc. are integrated in one package,
Ones that reduce the number of individual parts and facilitate the adjustment of the optical system are being widely used. This is a so-called hologram laser unit, and part of the optical system is replaced with a kind of diffraction grating called a hologram, and even the reproduction of a focus servo signal and a tracking servo signal and recorded information signal It can be generated from the output of the photodetector built in.

FIG. 4 is a block diagram of a main part when the present invention is applied to an optical disk device using a so-called phase difference method for generating a tracking signal. The arrangement of the elements of the photodetector 22 is substantially "ta". It is not a "character" type, but a slightly deformed one. In addition, with respect to the previous embodiment,
The names of the photo detector elements have been changed.

The photodetector 22 in FIG. 4 also has four elements a, b, c and d as in the first embodiment, but the reflected light is divided by the hologram which is the diffraction grating described above, and is divided into fragments. Then, the light is focused on each element. The elements a and b scan the light beam out of the reflected light.
The hologram is designed so that the portion corresponding to the first half of the traveling direction is received, but the amount of incident light on both is changed according to the shift of the focal position with respect to the optical disk. The focus servo signal can be obtained from the difference. Further, the elements c and d receive the portion corresponding to the rear half of the reflected light, but are arranged so as to receive the light on the inner and outer peripheral sides of the optical disk, respectively. Therefore, the elements c and d will be described later. Similarly, the tracking signal can be obtained by the phase difference method, the push-pull method, or the like. The sum of the outputs of all the elements reflects the change in the amount of reflected light, that is, the information signal recorded on the optical disc.

As described above, in order to obtain the tangential push-pull signal, the difference in the amount of light in the traveling / scanning direction of the reflected light of the light beam, in other words, the tangential direction of the pit row, can be obtained. 4, the adder circuit 3-4 obtains the outputs of the elements a and b that receive the reflected light corresponding to the front half, while the elements c and d that receive the reflected light corresponding to the rear half are obtained.
Is obtained by the adder circuit 3-3, and the difference between the addition results of the two is obtained by the difference circuit 12.

Further, the adder circuit 4 for obtaining the sum signal of the light quantity is connected so as to obtain the output sum of the a, b, c, d and 4 elements as in the case of FIG.

On the other hand, in order to generate the tracking signal by the phase difference method, the adder circuits 3-1 and 3 seen in FIG.
-2 does not exist in this FIG. This is the detector 22
This is because the element arrangement of No. 2 is different as described above, and thus the signal used for the phase difference method cannot be obtained even if the signals of the elements a and b are used. In other words, it can be said that the elements a and b are elements arranged so as not to detect the intensity distribution in the radial direction of the optical disk in the reflected light, and the elements c and d are elements arranged to be detectable. The difference from the photo detector in which the elements are arranged in the shape of the above-mentioned "Tar-shaped" is that, as described above, the arrangement suitable for incorporating the hologram laser unit into a small element component is selected. Due to.

If there are outputs of the two elements that receive the reflected light in the inner and outer peripheral directions, which is the radial direction of the optical disk, the outputs will have a phase difference corresponding to the relative positional deviation between the light beam and the pit row. Appears, it is possible to generate a tracking signal by the phase difference method. Therefore, in FIG. 4, the outputs of the elements c and d are directly added to the comparators 5-1 and 5-2 without being added to the others.

The operation and timing of the circuit shown in FIG. 4 are the same as those already described in the previous embodiment and will not be described.

When attention is paid to the photo detector 22,
Also in this embodiment, the elements are arranged so that the intensity distributions of the reflected light in the directions substantially parallel to the tangential direction of the pit row and the radial direction of the optical disk can be detected. (The elements c and d detect the intensity distribution in the direction substantially parallel to the radial direction of the optical disk, and the intensity distribution in the direction substantially parallel to the tangential direction of the pit row is detected for the pair of elements a and b. Therefore, as in the first embodiment, the tangential push-pull signal, the signal required for the phase difference method, and the signal corresponding to the total amount of reflected light are output from the photodetector. Both can be generated.

Furthermore, since the arrangement of the elements is suitable for the hologram laser unit as described above, the pit depth can be detected and the tracking servo can be performed even in an optical pickup downsized using the hologram laser unit. It is possible to enjoy the advantage of the present invention that the polarity of the signal can be automatically switched.

Third Embodiment Next, a third embodiment according to the present invention will be described with reference to FIG.

Like the first embodiment, this embodiment uses a photodetector in which elements are arranged in a substantially "square" shape, but the phase difference method is not used for generating the tracking servo signal. The push-pull method is used.

In FIG. 5, the tangential push-pull signal and the total signal of the reflected light amounts are obtained, the pit depth is detected and judged based on the sum signal, and the switch 6 is changed over in the first embodiment. There is no change. The operation is also the same.

On the other hand, in this embodiment, it is assumed that the push-pull method is used as described above to generate the tracking servo signal. In the push-pull method, the reflected light of the light beam is divided into the inner circumference side and the outer circumference side of the optical disk, and the intensity difference between them is obtained as a tracking servo signal.

Therefore, in FIG. 5, the adder circuit 3-
1, the sum of the outputs of the elements a and b that receive the components of the reflected light on the inner circumference side of the optical disc is obtained, while the adder circuit 3-2 calculates the sum of the outputs of the elements c and d that receive the components on the outer circumference side of the optical disc. The difference circuit 17 calculates the difference between the output amplitudes of the two without passing through the phase comparison circuit. The low frequency component of the difference result is extracted by the LPF 18 and output as a tracking servo signal.

The switch 6 is switched according to the detected depth of the pit. In FIG. 5, the addition circuit 3 is used.
The polarities are switched when the outputs of -1 and 3-2 are connected to the difference circuit 17. Of course, a configuration may be employed in which a separate inverting amplifier is provided at the output of the difference circuit 17 and one of the outputs of this and the difference circuit 17 is switched to be the tracking servo signal.

In this embodiment, the push-pull method is used to generate the tracking servo signal. However, in the push-pull method, the tracking servo is applied not only to the pit row but also to the optical disc in which the continuous guide grooves are mixed. Can generate signals.

[Embodiment 4] A fourth embodiment of the present invention will be described with reference to FIG.

In this embodiment, as in the second embodiment, a photodetector incorporated in the hologram laser unit, which is not in the shape of a "square", is used, while the tracking servo signal is generated in the third embodiment. It is assumed that the push-pull method is applied as in the above embodiment. The names of the respective elements of the photodetector 22 are changed from those in the substantially "square" shape in the first and third embodiments, and are the same as those in the second embodiment.

In FIG. 6, a tangential push-pull signal and a signal corresponding to the amount of reflected light are obtained from the photodetector 22, the adder circuits 3-3 and 3-4, the adder circuit 4 and the circuits thereafter, and the pit depth is obtained. The connection and operation of the parts for detecting the are similar to those of the second embodiment.

The difference is the connection of the elements c and d of the photodetector 22, and the difference circuit 1 via the switch 6.
7 and is configured to obtain the difference in output amplitude.

As already described in the description of the third embodiment, the push-pull method divides the reflected light of the light beam into the inner peripheral side and the outer peripheral side of the optical disc and obtains the intensity difference between them to obtain the tracking servo signal. is there. On the other hand, as described in the description of the second embodiment, the elements c and d receive the light corresponding to the rear half of the reflected light, but are arranged to receive the light on the inner and outer circumference sides of the optical disk. Therefore, if the output difference between these elements c and d is obtained, it is possible to obtain a tracking servo signal by the push-pull method as in the case of using a photo detector of a substantially "square" type.

In this embodiment, the switch 6 is the element c,
Although the output from d is switched and given to the differential circuit 17 to switch the polarity of the tracking servo signal, a configuration may be adopted in which a separate inverting amplifier is provided to switch the output from the differential circuit 17. .

As already described in the first embodiment, in the present invention, the diffraction direction of the reflected light from the pits, and hence the intensity distribution thereof, differs depending on the depth of the pits, and the light to be used (e.g. The wavelength of the light beam
(Λ / 4n), where n is the refractive index of the substrate of the optical disk
It is used to reverse at the boundary. Although not described individually, this is a common principle in any of the embodiments.

However, the depth that causes the reversal of the diffraction direction is not only (λ / 4n), but actually exists every time the depth increases (λ / 2n) with reference to this. Therefore, more generally, when the wavelength of the light beam is λ, the refractive index of the substrate of the optical disc is n, and an arbitrary integer is k, m, the pit depth is (kλ / 2n) <D1 <{( λ / 4n) + (kλ / 2
n)} and {(λ / 4n) + (mλ / 2n)} <D2 <{(m +
1) · λ / 2n} If the condition is classified into either D1 or D2, the diffraction direction of the reflected light is reversed between the pits belonging to these groups, so the pit depth is detected. However, the polarity of the tracking servo signal can be switched.

Therefore, in manufacturing an optical disk, if there is a reason that it is easier to manufacture when there is a certain pit depth, then k and m may be selected so as to satisfy the condition. Since it is not necessary for k and m to have the same value, there is a large degree of freedom in selecting the pit depth.

Generally, it is said that the production is easier and the quality of the reproduced signal is better when the pit depth is kept to the minimum necessary depth. It suffices to set at least one of them to 0.

[0106]

The optical disk device having the structure of the first means of the present invention detects the difference in the depth of the pits and automatically switches the polarity of the tracking servo signal, so that the pits formed at different depths. Tracking servo signals can be accurately controlled even for optical discs with pit depth, and since the polarity of the tracking servo signal is not switched for optical discs with a single pit depth, it is compatible with conventional optical discs. Have sex.

The optical disk device according to the second means of the present invention is the optical disk device according to the first means, in which the tangent line of the pit string at the change point of the signal according to the amount of the reflected light of the light beam applied to the pit string. The pit depth is detected based on the polarity of the signal according to the difference in intensity distribution in the direction. Since these signals are signals that can be easily generated from the optical pickup, there is no need to provide a new photodetector or sensor in the optical pickup, and the pit depth can be determined.

An optical disk device according to a third means of the present invention is the optical disk device according to the second means, wherein the optical disk device corresponds to a signal corresponding to a difference in intensity distribution in the tangential direction and a light amount of the reflected light. The signal is binarized by comparison means,
The pit depth is determined based on the change timing and level of the signal. Therefore, most of the circuit means for detecting the pit depth can be integrated as a digital IC,
Excellent in reliability, cost, and mounting area.

An optical disk device according to a fourth means of the present invention is the optical disk device according to the first means, in which the tracking signal is generated by the phase difference method and the pit depth detecting means detects the tracking signal. Switches the tracking signal polarity. Therefore, even if the objective lens is largely displaced, an offset is unlikely to occur in the tracking servo signal, and most of the phase difference detection means required for the phase difference method are digital circuits, so that further circuit integration can be achieved and reliability and cost can be improved. It is also excellent in terms of mounting area.

An optical disk device according to a fifth means of the present invention is the optical disk device according to the first means, in which a tracking signal is generated by the push-pull method and the pit depth detecting means detects the tracking signal. The feature is that the polarity of the tracking signal is switched. Therefore, the tracking servo signal can be generated not only in the pit row but also in the optical disc formed by mixing continuous grooves.

An optical disk device according to a sixth means of the present invention is the optical disk device according to the fourth means or the fifth means, wherein the light receiving element is for the reflected light of the light beam,
Since the arrangement is such that the intensity distributions in the directions substantially parallel to the tangential direction of the pit row and the radial direction of the optical disk can be detected, it is possible to appropriately generate a signal necessary for detecting the pit depth.

An optical disk device according to a seventh means of the present invention is the optical disk device according to the sixth means, wherein the light receiving element is in a substantially "square" shape which has been widely used in conventional optical pickups. Since it is arranged, the conventional optical pickup can be used without adding a new element.

An optical disk device according to an eighth means of the present invention is the optical disk device according to the sixth means, in which the light receiving element is an element capable of detecting an intensity distribution substantially parallel to the radial direction of the optical disk. And elements are arranged. Since the arrangement of these elements is suitable for the hologram laser unit, the hologram laser unit can be used to downsize the optical pickup and the device.

An optical disk device according to a ninth means of the present invention is the optical disk device of the first means, wherein the wavelength of the light beam is λ, the refractive index of the substrate of the optical disk is n,
When arbitrary integers are k and m, the depth of the pit formed on the optical disk used is (kλ / 2n) <D1 <
{(Λ / 4n) + (kλ / 2n)} and {(λ /
4n) + (mλ / 2n)} <D2 <{(m + 1) · λ /
It is characterized by being classified into either D1 or D2 that satisfies the condition of 2n}. Therefore, the tracking servo signal can be automatically switched depending on the depth of the pit, and the degree of freedom in designing at the time of manufacturing the optical disc is increased.

An optical disk device according to a tenth means of the present invention is characterized in that, in the optical disk device of the ninth means, at least one of the integers k and m is set to 0. Therefore, it is possible to suppress the manufacturing time and cost of the optical disc and to improve the quality of the reproduced signal.

The optical disk device according to the eleventh means of the present invention is the optical disk device according to the first means, the ninth means, or the tenth means, wherein information is included in the depth of the pit. It is characterized by things. For this reason, the polarity of the tracking servo signal can be automatically switched, and the information corresponding to the depth can be separately reproduced from the target pit for which the switching has been performed, thereby improving the recording density and obtaining additional information. Can be done.

An optical disk device according to the twelfth means of the present invention is the optical disk device according to the first means, the ninth means or the tenth means, in which the recording marks having different reflectances are irradiated by irradiating light. When a recording-type optical disc forming the optical disc is mounted, the pit depth of the optical disc is selected so that the polarity of the tracking signal with respect to the optical disc is a polarity that causes tracking servo deviation. Therefore, if the information on the optical disc in which the information is recorded in the pits is illegally copied onto the recording-type optical disc, the tracking servo control cannot be performed normally and the information cannot be reproduced, so that it can be used as a copy preventing means.

[Brief description of drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation of each unit of the configuration of FIG.

FIG. 3 is an explanatory diagram of another configuration of the switch 6 in FIG.

FIG. 4 is a block diagram according to another embodiment of the present invention.

FIG. 5 is a block diagram according to another embodiment of the present invention.

FIG. 6 is a block diagram according to still another embodiment of the present invention.

FIG. 7 is a diagram illustrating the principle of the phase difference method.

FIG. 8 is an explanatory diagram of the principle of the push-pull method.

FIG. 9 is an explanatory diagram of a relationship between a pit depth and a tangential push-pull signal.

[Explanation of symbols]

1: light beam, 2: photodetector, 3-1, 3-
2, 3-3, 3-4: Adder circuit, 4: Adder circuit, 5-
1, 5-2: Comparator (comparison circuit), 6: Switch (selection circuit), 6-1, 6-2, 6-3, 6-4: AN
D gate, 6-5, 6-6: OR gate 6-7, 6-
8: Inverter, 7: Phase comparison circuit, 8-1, 8-2:
LPF, 9: difference circuit, 10: comparator (comparison circuit), 11: edge detection circuit, 12: difference circuit, 13-
1, 13-2: comparator (comparison circuit), 14-1,
14-2: AND gate (mask circuit), 15-1, 1
5-2: FF circuit, 16-1, 16-2: pulse generation circuit, 17: difference circuit, 18: LPF circuit 22: photo detector, 31, 32: pit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 7/09

Claims (12)

(57) [Claims] 1. A with using an optical disk having a region which records information by a pit, the peak of the optical disc
Pit depth detection means for detecting the depth of the pits based on the reflection from the pit, and the polarity of the tracking signal for causing the light beam to follow the pit row based on the output of the pit depth detection means. An optical disk device comprising a polarity reversing means for controlling. 2. The pit depth detecting means is based on a signal according to a light amount of reflected light of a light beam applied to the pit and a signal according to a difference in intensity distribution in a tangential direction of the pit row, At the change point of the signal according to the light amount of the reflected light, based on the polarity of the signal according to the difference in the intensity distribution,
The depth of the pit is detected, and the depth of the pit is detected.
The optical disk device described in 1. 3. The pit depth detecting means comprises first and second comparing means for binarizing a signal corresponding to a difference in intensity distribution in the tangential direction by comparing it with two reference values. Third comparing means for binarizing a signal corresponding to the light quantity of the reflected light by comparing it with another reference value, and the first and second timings at the change timing of the output of the third comparing means. 3. The optical disk device according to claim 2 , wherein the pit depth is detected based on the reference result of the output of the comparison means. 4. A reflected light of a light beam applied to the pit is received by a light receiving element, a phase difference of output signals from the light receiving element is detected by a phase difference detecting means to generate a tracking signal, and the pit is formed. The optical disk device according to claim 1, wherein the polarity of the tracking signal is switched according to the detection result of the depth detecting means. 5. A light receiving element receives a difference in intensity distribution in the radial direction of the optical disc of the reflected light of the light beam applied to the pit, and the intensity of the output signal from the light receiving element.
The optical disc apparatus according to claim 1, wherein a tracking signal is generated by a difference means based on the difference, and the polarity of the tracking signal is switched according to the detection result of the pit depth detection means. 6. The light-receiving element is for reflecting light of the light beam,
6. The optical disk device according to claim 4, wherein the optical disk device has an arrangement capable of detecting intensity distributions in directions substantially parallel to a tangential direction of the row of pits and a radial direction of the optical disk. 7. The optical disk device according to claim 6, wherein the light receiving elements are arranged in a substantially "square" shape. 8. The optical disk device according to claim 6, wherein the light receiving element is provided with an element capable of detecting an intensity distribution substantially parallel to a radial direction of the optical disk and an element not capable of detecting the intensity distribution. 9. When the wavelength of the light of the light beam is λ, the refractive index of the substrate of the optical disc is n, and arbitrary integers are k and m, the depth of the pit formed on the optical disc to be used is (kλ / 2n) <D1 <{(λ / 4n) + (kλ / 2n)} and {(λ / 4n) + (mλ / 2n)} <D2 <{(m + 1) · λ / 2n} satisfying the conditions D1 2. The optical disc device according to claim 1, wherein the optical disc device is classified into any one of D. 10. At least one of the integers k and m is 0.
The optical disk device according to claim 9, wherein 11. The optical disk device according to claim 1, wherein information is included in the depth of the pits. 12. When a recording type optical disc which irradiates light to form recording marks having different reflectances is mounted, the polarity of the tracking signal with respect to the recording type optical disc is such that tracking servo deviation occurs. The optical disk device according to claim 1, 9, or 10, wherein the depth of the pit is selected.