JP3580018B2 - Recording device and optical disk drive including recording device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recording device, and more particularly to a recording device suitable for an optical disk stamper (die) for mass-producing optical disks and an optical disk drive.
[0002]
[Prior art]
Optical discs are classified into read-only discs and recording / playback discs, and the latter are roughly classified into write-once discs and rewritable discs according to the recording method of a data area on the disc surface. In addition, it can be classified into an in-groove system and an on-land system according to the design of grooves formed on the disk surface. Each of the above disks is usually manufactured through the following steps. That is, a resist master formed by applying a photoresist to a glass base plate is exposed to a laser beam for cutting (recording), and the resist master is developed to form a pit arrangement corresponding to a recording signal (a nickel master). And a metal stamper is manufactured by performing electroforming. Then, a large number of optical disks are copied using this metal stamper.
[0003]
[Problems to be solved by the invention]
The cutting laser beam is controlled so that pits having a length corresponding to the pulse width of each recording signal (digital signal) forming information to be recorded on the optical disk are arranged on the disk surface. Need to be irradiated. However, the laser beam for cutting has a laser spot having a predetermined diameter, and the light intensity distribution in the cross section thereof is not a rectangular wave but can be approximated by a Gaussian function (normal distribution) usually called a Gaussian beam. And it is easy to cause intersymbol interference. Therefore, even if the laser beam controlled according to the pulse width of the recording signal is irradiated, a pit having a length obtained by adding the pulse width of the recording signal to the diameter of the laser spot is formed on the resist master. An error corresponding to the diameter of the laser spot occurs. Such an error is particularly remarkable in a high-density optical disk developed in recent years in response to a demand for improvement in recording density. In the case of a high-density optical disk, the pit length is relatively smaller than the beam spot diameter of a cutting or reading laser compared to a conventional disk, so that the above-described error is more likely to occur.
[0004]
On the other hand, when reproducing recorded information, a laser beam for reading is applied to the pit array on the disk surface, and the presence or absence of pits (the positions of both edges of the pits) is determined according to the type of the disk by the reflectance, reflected light amount, Kerr effect, The determination is performed using an optical method such as the Faraday effect. However, the reading laser beam has a laser spot larger than the diameter of the cutting laser beam, and the light intensity distribution in the cross section thereof can be approximated by a Gaussian function. Therefore, the pit formed on the disk surface including the above error is read as a recording signal having a length obtained by adding the length of the pit to the diameter of the laser spot of the reading laser beam. Therefore, the information recorded on the disc cannot be accurately reproduced.
[0005]
Other reasons for the inability to accurately reproduce the recorded information described above include non-uniform laser power due to fluctuations in focusing, non-uniform development processing on the resist master, and processing from the metal master to the completion of the disc. There are many factors such as the accuracy of multi-stage transfer. Also, in the case of the above-described high-density optical disk, the pit length is relatively smaller than the beam spot diameter of the cutting or reading laser as compared with the conventional disk, so that the intersymbol interference is smaller than that of the conventional disk. Another reason is that it is greatly affected by Therefore, in a high-density optical disk, it is necessary to reduce the intersymbol interference component. Further, disturbances such as electric noise and mechanical vibration in the optical disk drive can be assumed as a reason. However, it is actually difficult to predict many of these factors and accurately calculate the pit length corresponding to the pulse width of each recording signal constituting the recording information by calculation.
[0006]
Therefore, an object of the present invention is to make it possible to read recorded information more accurately.
[0007]
[Means for Solving the Problems]
A recording apparatus according to a first aspect of the present invention includes a weighting unit, a signal level adding unit, a pulse signal delay unit, and a pulse width varying unit. The weighting means makes the level of the first pulse signal, which is a bit string representing information to be recorded, different for each bit according to the light intensity distribution of the laser beam spot for recording information on the medium. Weighting is applied to the first pulse signal. The signal level adding means adds and outputs the level of the first pulse signal for each predetermined bit. The pulse signal delay unit inputs the level of the bit to which the maximum weight has been assigned by the weighting unit, and delays the rise time and the fall time of the level. The pulse width varying means varies the pulse width of the second pulse signal for controlling the laser light based on a comparison result between the signal level addition value from the signal level adding means and the signal level from the pulse signal delay means. I do.
[0008]
According to the first aspect of the present invention, the pulse width of the second pulse signal for controlling the laser light is varied based on the comparison result between the signal level addition value and the signal level of the oblique wave. Accordingly, it is possible to prevent the occurrence of an error in reading recorded information due to intersymbol interference or the like. Further, in a pit array pattern having a short space where a reading error is likely to occur, it is also possible to prevent the short space from being located at or near the position where the light intensity of the laser beam of the reproducing laser beam is maximized. It is possible.
[0009]
In a preferred embodiment according to the first aspect, a variable resistor circuit including variable resistors of a number corresponding to a predetermined number of bits is used as the weighting means. Further, as a pulse signal delay means, an integrator that generates oblique waves corresponding to the rising and falling of the level by integrating the level of the bit to which the maximum weight is assigned with time, and an output from the integrator. A limiter circuit that limits the amplitude of the oblique wave is used.
[0010]
A recording apparatus according to a second aspect of the present invention includes a signal level adding unit, a pulse signal delay unit, an offset adjusting unit, and a pulse width varying unit. The signal level adding means adds the level of the first pulse signal, which is a bit string representing information to be recorded, for each predetermined bit, and outputs the result. The pulse signal delay means inputs the level of a bit of the first pulse signal corresponding to the maximum portion of the light intensity of the laser beam spot for recording information on the medium, and calculates the rise time and fall time of the level. Delay. The offset adjusting means adjusts the offset of the output signal from the signal level adding means. The pulse width varying unit is configured to control the laser beam based on a comparison result between the signal level addition value output from the signal level addition unit via the offset adjustment unit and the signal level from the pulse signal delay unit. The pulse width of the pulse signal is varied.
[0011]
According to the second aspect of the present invention, the pulse width of the second pulse signal for controlling the laser beam based on the comparison result between the offset-adjusted signal level addition value and the oblique wave signal level Is variable, the pulse width of the second pulse signal can be reduced uniformly. Thus, it is possible to prevent a portion having a short space from being located at or near a portion where the light intensity of the laser spot of the reproducing laser beam is maximized, thereby preventing a reading error of recorded information due to intersymbol interference or the like. Can be prevented.
[0012]
In a preferred embodiment according to the second aspect, the level of the first pulse signal, which is a bit string representing information to be recorded, is adjusted according to the light intensity distribution of a laser beam spot for recording information on a medium. A variable resistor circuit having variable resistors of a number corresponding to the number of bits of the first pulse signal is further provided as weighting means for assigning weight to the first pulse signal by making each bit different. Thereby, the degree of freedom of weighting is increased.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 shows an outline of a mastering process to which the present invention is applied.
[0015]
The present invention is applied to a step denoted by reference numeral 1 in each step described in FIG. 1, namely, a premastering (preparation of recording signal) step and a cutting (recording) step. The mastering process is a technique for making a mold used for mass-producing an optical disk as a high-density information recording medium (memory) by a (resin) molding technique. Omitted.
[0016]
FIG. 2 shows an overall configuration of a cutting device (laser recording device) according to the first embodiment of the present invention.
[0017]
The above device is used in step 1 of FIG. 1 and includes, as its basic components, a laser device 3 as a recording light source and a control signal light source, and an optical modulation device for modulating a laser beam with an information signal or a control signal to be recorded. The device 5 includes an optical system 7 for guiding a laser beam onto the resist master 9. The above apparatus further includes a focus servo system 13 for causing the condenser lens 11 of the optical system 7 to follow the resist master 9 with submicron accuracy, rotating the resist master 9 with high accuracy, and moving the resist master 9 relative to the optical system 7. And a signal modulation / demodulation device for information. The optical modulator 5 includes an electro-optic effect (E / O) optical modulator 5a utilizing a change in refractive index due to application of an electric field, and an acousto-optic effect (A / O) utilizing the relationship between an acoustic wave and a light wave in a medium. O) There is an optical modulator 5b. An output signal from the recording signal correction device according to the first embodiment of the present invention is applied to an electro-optic effect (E / O) optical modulator 5a.
[0018]
FIG. 3 shows the overall configuration of the recording signal correction device according to the first embodiment of the present invention.
[0019]
As shown, the apparatus includes a recording signal generator 21, a shift register 23, a weighting circuit 25, an adding circuit 27, a ramp circuit 29, and a comparing circuit 31.
[0020]
The recording signal generator 21 generates a clock pulse of a predetermined frequency and outputs it to the shift register 23. The recording signal generator 21 also reads information to be recorded on the disk to be copied, generates digital signals based on the information, and outputs each digital signal to the shift register 23 in synchronization with the clock pulse.
[0021]
In the present embodiment, for example, a TTL 8-bit shift register is employed as the shift register 23, and a serial input / parallel output shift register is configured using the 8-bit shift register. The shift register 23 is driven in synchronization with a clock pulse output from the recording signal generator 21. That is, using this clock pulse as a shift pulse, the data serially input from the leftmost bit B1 in FIG. 3 is shifted right by one bit. When data is written to all bits B1 to B8, these data are output simultaneously (as parallel data).
[0022]
The weighting circuit 25 includes channels B1 to B8 corresponding to the bits B1 to B8 of the shift register 23, respectively. The weighting circuit 25 is also driven in synchronization with the clock pulse, reads the parallel data output from the shift register 23, and sets each channel based on a weighting pattern corresponding to each of the predetermined bits B1 to B8 for the parallel data. Data weighting is performed for each of B1 to B8. As an example of the weighting, a weighting coefficient 26 obtained from a curve (a Gaussian function = normal distribution) 24 showing the light intensity distribution in the laser spot cross section of the cutting laser beam shown in FIG. 4A is used. (See FIG. 4B). The weighting coefficient 26 is set so as to correspond to the light intensity distribution in the cross section of the laser spot as shown in FIG. The weighting coefficient 26 is located at the center of the light intensity distribution and has the largest light intensity value at the bits B4 and B5, and becomes smaller toward both ends of the light intensity distribution and becomes smaller at the light intensity value. It is set to be minimum at B1 and B8. Therefore, the weighting circuit 25 assigns a weighting coefficient corresponding to each of the channels B1 to B8 to the data output from the shift register 23 and outputs the data.
[0023]
The adding circuit 27 inputs the parallel data to which the weighting coefficient as described above is assigned to each of the channels B1 to B8 by the weighting circuit 25. Then, the parallel data is converted into staircase serial data by performing an arithmetic processing of sequentially adding (or subtracting) the data (that is, the voltage level of the digital signal) of each of the channels B1 to B8, and then outputting the data to the comparison circuit 31. I do.
[0024]
The ramp circuit 29 reads only the data of the bit B4 (= pulse signal) of the parallel data output from each of the bits B1 to B8 of the shift register 23, and compares the ramp voltage (oblique voltage) corresponding to the data. 31. As shown in FIG. 5, the ramp circuit 29 includes an integrator 33 and a limiter circuit 35 connected to an output side thereof. The integrator 33 includes an operational amplifier 33a, a capacitor 33b connected to the negative feedback circuit, an input resistor 33c, and an output resistor 33d. The limiter circuit 35 is composed of two constant voltage diodes 35a and 35b connected in series in opposite directions.
[0025]
As a first modified example of the limiter circuit 35, as shown in FIG. 6, a series body of diodes 37a, 37b, and 37c connected in the same direction, and a diode 37d connected in the opposite direction to all of them. , 37e, and 37f in parallel.
[0026]
As a second modified example of the limiter circuit 35, as shown in FIG. 7, operational amplifiers 39a and 39b, a diode 39c having an anode terminal connected to the output side of the operational amplifier 39a, and an output of the operational amplifier 39b. There is also a limiter circuit 39 having a configuration including a diode 39d having a cathode terminal connected to its side. In the limiter circuit 39, a negative reference voltage is applied to the non-inverting input terminal of the operational amplifier 39a, and a positive reference voltage having an absolute value equal to the reference voltage is applied to the non-inverting input terminal of the operational amplifier 39b. Applied.
[0027]
Returning to FIG. 3 again, the comparison circuit 31 compares the voltage level of the output signal (staircase wave) from the addition circuit 27 with the voltage level of the output signal (ramp wave) from the ramp circuit 29. Then, the signal rises in synchronization with the cross point between the rising slope of the output signal of the ramp circuit 29 and the output signal of the adding circuit 27, and falls on the falling slope of the output signal of the ramp circuit 29 and the output signal of the adding circuit 27. 2 and generates a pulse signal falling in synchronization with the cross point, and outputs the pulse signal to the E / O modulator 5a (or A / O modulator 5b) in FIG.
[0028]
Next, the operations of the weighting circuit 25, the addition circuit 27, the ramp circuit 29, and the comparison circuit 31 are described in time series and spatial relation between the output waveform from each circuit and the pit array formed on the disk surface. A description will be given with reference to FIG. 8 which is a timing chart showing various positional relationships.
[0029]
8A to 8C, each region T1 separated by a plurality of broken lines drawn at regular intervals in parallel with the vertical direction of the drawing is a time interval corresponding to each of the bits B1 to B8 described above. Is shown. Further, in FIG. 8D, each region T2 separated by a plurality of broken lines drawn at equal intervals in parallel with the vertical direction of the drawing is formed on the resist master corresponding to each of the above-described bits B1 to B8, respectively. Shows the spatial spacing of.
[0030]
First, the waveform of a signal output from the bit B4 of the shift register 23 to the ramp circuit 29 is, as shown by reference numeral 101 in FIG. 8A, a voltage centered on a zero point indicated by an alternate long and short dash line in the figure. The level is switched between positive and negative. The length of the pulse width of the output waveform from the bit B4 corresponds to the magnitude of the absolute value of the voltage level. When the above-described parallel data is output from each of the bits B1 to B8 of the shift register 23, the ramp circuit 29 rises at the timing when the polarity of the output waveform 101 of the bit B4 is switched from negative to positive, and when the falling occurs. At the timing when the polarity of the output waveform 101 is switched from positive to negative, the operation is performed to generate ramp waves synchronized with each other.
[0031]
That is, the integrator 33 and the limiter circuit 35 change the polarity of the output waveform 101 of the bit B4 from negative to positive at times t0, t5, t10, and the like. At times t2, t8, t13, etc., when switching from positive to negative, signal processing of the output waveform 101 is performed to generate the falling edge of the ramp wave, respectively. This signal processing is executed by integrating the output waveform 101 with time in the integrator 33 and limiting the amplitude of the ramp waveform in the limiter circuit 35. As a result, as shown by reference numeral 105 in FIG. 8B, a ramp wave (oblique wave) whose voltage level switches between positive / negative around a zero point indicated by a dashed line is output from the ramp circuit 29 as an output signal. , To the comparison circuit 31.
[0032]
On the other hand, the adding circuit 27 adds the parallel data output from the weighting circuit 25 for each of the channels B1 to B8. As a result, a staircase wave whose voltage level switches between positive / negative around the zero point as shown by reference numeral 103 in FIG. 8B is applied to the comparison circuit 31 as an output signal from the addition circuit 27. It will be.
[0033]
The comparison circuit 31 compares the voltage level of the ramp wave 105 with the voltage level of the staircase wave 103. Then, the rising point synchronized with the cross points j (corresponding to time t1), 1 (corresponding to time t7), n (corresponding to time t11) between the ramp wave 105 and the staircase wave 103, and the cross point k (corresponding to time t3) Corresponding), m (corresponding to time t9), p (corresponding to time t15) and the like, and generate a pulse signal 107 (FIG. 8 (c)) having a falling edge synchronized with it. This pulse signal 107 is output to E / O modulator 5a (or A / O modulator 5b) shown in FIG. Thereby, in the cutting apparatus of FIG. 2, the spatial position of both edges coincides with the time-sequential position of the rising and falling of the pulse signal 107 as shown by the reference numeral 109 in FIG. The resist is exposed on the resist master in a pit arrangement.
[0034]
Here, the falling of the pulse signal 107 is synchronized with the cross points k ′ (corresponding to time t4) and p ′ (corresponding to time t14) between the ramp wave 105 and the zero point in FIG. Are synchronized with the cross points l ′ (corresponding to time t6) and n ′ (corresponding to time t12) between the ramp wave 105 and the zero point in FIG. 8B (for the cross points m and m ′). Are substantially the same at time t9).
[0035]
First, the right edge of the pit 109a is shifted from a position corresponding to the time t3 to a position corresponding to the time t4, and the left edge of the pit 109c is shifted from a position corresponding to the time t7 to a position corresponding to the time t6. It will shift. Therefore, the space 109b between the pits 109a and 109c is reduced by (t3-t4) on the left side and by (t6-t7) on the right side. On the other hand, the length of the pit 109e is reduced by (t11-t12) on the left side and by (t14-t15) on the right side. As described above, when recording information is read from the disk in which the pit array is formed with the space 109b and the pit 109e contracted, the reading laser beam has a laser spot larger than the diameter of the cutting laser beam, Since the light intensity distribution can also be approximated by a Gaussian function, intersymbol interference is apt to occur and accurate reproduction of recorded information cannot be performed.
[0036]
In addition, when the light intensity of the laser spot of the reading laser beam is maximized, that is, when the bits B4 and B5 and the right edge of the pit 109a and the left edge of the pit 109c are positionally overlapped, Intersymbol interference is much more likely to occur than in the case where the light intensity is minimized, that is, when the light intensity overlaps with the bit B1 or B8. The same applies to the case of the pit 109e.
[0037]
Therefore, in the present embodiment, the data of each of the channels B1 to B8 is weighted in the manner described above, and the output waveform (==) from the bit B4 corresponding to the portion where the light intensity distribution in the Gaussian beam is maximized. A ramp wave 105 is generated from the pulse signal (101). Then, a rise is made at a cross point j, l, n between each rising of the ramp wave 105 and the staircase wave 103, and a cross point k, m (= m ') is made between each falling of the ramp wave 105 and the staircase wave 103. , P are synchronized by generating a pulse signal 107 synchronized with each other by the comparison circuit 107, so that the shift amounts (t3-t4), (t6-t7), (t11-t12), (t14-t15) Is corrected.
[0038]
In the pit array 109, a relatively long pit such as the pits 109a and 109c is formed in a region where the polarity of the staircase wave 103 is positive, while a relatively short space such as the space 109b is formed. On the other hand, in the region where the polarity of the staircase wave 103 is negative, a relatively short pit such as the pit 109e is formed, whereas a relatively long space such as the space 109d is formed.
[0039]
Here, each of the deviation amounts (t3-t4), (t6-t7), (t11-t12), and (t14-t15) is the voltage of the staircase wave 103 at the cross point between the ramp wave 105 and the staircase wave 103. It is proportional to the magnitude of the absolute value of the level.
[0040]
FIG. 9 schematically shows an output waveform from the comparison circuit 31. In the figure, ΔT indicates the compensated timing in the output signal from the recording signal correction device according to the present embodiment, and this timing is represented by the following equation (1).
[0041]
ΔT = Σαi · Bi (1)
Here, αi is a weight (weighting coefficient) that can be arbitrarily set on the circuit, and Bi indicates a voltage level state of the shift register 23 (Hi = 1, Lo = −1).
[0042]
Next, the optical disc duplicated based on the resist master from the recording apparatus of the present embodiment is less likely to cause intersymbol interference than the optical disc duplicated based on the resist master from the conventional recording apparatus. The reason why a reading error is unlikely to occur will be described with reference to FIGS.
[0043]
FIG. 10 shows a relationship between a plurality of pit arrangement patterns in which one pit edge exists at a position where the light intensity of the laser spot of the reproduction laser beam is maximized, and their reproduction signals.
[0044]
In FIG. 10, in the pit arrangement of the pattern D having the longest space, the reproduced signal comes to an ideal cross position where there is almost no intersymbol interference and there is almost no cross point error with the reference voltage level as indicated by reference numeral 203d. On the other hand, in the pit arrangement of the pattern C, since the space is shorter than the pit arrangement of the pattern D, the waveform of the reproduced signal is distorted downward and greatly collapsed as compared with the reproduced signal 203d as indicated by reference numeral 203c. . Further, in the pit arrangement of the pattern B, since the space is shorter than that of the pit arrangement of the pattern C, the waveform of the reproduced signal is distorted downward and greatly collapsed as compared with the reproduced signal 203c as shown by reference numeral 203b. Further, in the pit arrangement of the pattern A, since the space is shorter than that of the pit arrangement of the pattern B, the waveform of the reproduced signal is distorted downward and greatly collapsed as compared with the reproduced signal 203b, as indicated by reference numeral 203a. Has a waveform similar to. From this, it is clear that the shorter the space, the more the pattern of the pit arrangement has a waveform distorted downward and greatly collapsed, and the level of the reproduced signal shifts downward, resulting in a temporal shift. Become.
[0045]
As a result, the rising gradient of each of the reproduced signals 203a to 203d is the steepest as shown in FIG. Is the gentlest. Therefore, the cross point between each reproduced signal and the threshold level indicating the reference voltage is the ideal cross point for the reproduced signal 203d and the position farthest from the ideal cross point for the reproduced signal 203a. The difference Δtd from the cross point is the largest Δtda indicating the difference of the reproduction signal 203a, and then decreases in the order of Δtdb and Δtdc.
[0046]
This is because, when the portion having a short space is located in the vicinity of the portion where the light intensity of the laser beam of the reproducing laser beam is maximized and in the vicinity thereof, the reading error of the recorded information becomes largest due to intersymbol interference and the like, When the laser spot is located at a portion where the light intensity of the laser spot is low, it indicates that the above-mentioned problem is not so serious. Therefore, in the present embodiment, the weighting circuit 25 assigns a weighting coefficient corresponding to the light intensity distribution (Gaussian beam) of the laser spot to the data of each of the channels B1 to B8 as described above, and performs the signal processing as described above. It is what went.
[0047]
As described above, according to the first embodiment of the present invention, the weighting circuit 25 performs weighting for the number of bits (8 bits) of the shift register 23 to thereby reduce the read error of all the pit array patterns. Since the compensation amount can be determined, the adjustment of the compensation amount can be simplified and the adjustment work can be shortened.
[0048]
In this method, a recording compensator is composed of a digital circuit (which may include firmware), and a compensation amount corresponding to each pit arrangement pattern is created in advance as a table in a memory, and a pit is recorded by a digital circuit or the like during operation. It is superior to the conventional method of recognizing an array pattern, searching a table for a corresponding compensation amount from the table, and thereby controlling the edge timing of a pulse signal for modulating the cutting laser beam. This is because, in this method, the compensation amount must be set for all the pit arrangement patterns, and it takes a lot of trouble.
[0049]
FIG. 12 shows the overall configuration of a recording signal correction device according to the second embodiment of the present invention.
[0050]
The first embodiment is different from the first embodiment in that a waveform shaping circuit 51 and a variable resistance circuit 53 are provided in place of the weighting circuit 25 shown in FIG. 3, and an offset adjusting circuit 59 is connected to the output side of the adding circuit 27. The configuration is different from the recording signal correction device according to the embodiment. Note that the recording signal generator 21, the shift register 23, the adding circuit 27, the ramp circuit 29, and the comparing circuit 31 are the same as those shown in FIG. 3, so that detailed description thereof will be omitted.
[0051]
The waveform shaping circuit 51 includes channels B1 to B8 corresponding to the bits B1 to B8 of the shift register 23. The waveform shaping circuit 51 removes a potential change in each state such as surge, overshoot, and undershoot from the TTL level waveform of the shift register 23 output from each of the bits B1 to B8. Then, the output waveform from each of the bits B1 to B8 after the signal processing is converted into a double-current signal (a signal in which Hi becomes a positive potential and Lo becomes a negative potential centering on the ground level), and each of the channels B1 to B8 is converted. The data is output from B8 to the variable resistance circuit 53 as parallel data.
[0052]
The variable resistor circuit 53 includes eight variable resistors 53a to 53h connected to the channels B1 to B8 of the waveform shaping circuit 51, respectively. By manually operating these variable resistors 53a to 53h by the operator of the cutting device, desired weights are assigned to the parallel data from the waveform shaping circuit 51 for each of the channels B1 to B8 (for example, in FIG. 4B). (Weighting as shown).
[0053]
The offset adjustment circuit 59 includes an addition circuit 59a, a terminal 59b to which the reference voltage Vref is applied, and a variable resistor 59c for dividing the reference voltage Vref and applying the divided voltage to the reference voltage input terminal of the addition circuit 59a. The adder circuit 59a receives the serial data (staircase wave) output from the adder circuit 27 and adjusts the offset of the serial data based on the input voltage obtained by dividing the reference voltage Vref by the variable resistor 59c. Output to the comparison circuit 31.
[0054]
Next, the operations of the above-described addition circuit 27, ramp circuit 29, offset adjustment circuit 59, and comparison circuit 31 will be described with reference to FIG. 13 which is a timing chart showing output waveforms from each circuit.
[0055]
FIG. 13A shows an output waveform from the ramp circuit 29 and an output waveform from the adder circuit 27 before and after the offset is adjusted by the offset adjusting circuit 59.
[0056]
Reference numeral 305 indicates an output waveform (ramp wave) from the ramp circuit 29. The ramp wave 305 is obtained by integrating the waveform of the data of the channel B4 in the parallel data output from the waveform shaping circuit 51 (neither of which is given a weighting coefficient as in the first embodiment) with respect to time. Is generated by Reference numeral 303b denotes an output waveform (staircase wave) from the addition circuit 27 corresponding to the zero point 307b before the offset adjustment by the offset adjustment circuit 59. Further, reference numeral 303a indicates an output waveform (step wave) corresponding to the zero point 307a after the offset adjustment. These staircase waves 303a and 303b are added to the parallel data output from the waveform shaping circuit 51 in the adding circuit 27 for each channel (converted to serial data) as in the first embodiment. Is generated by
[0057]
As is apparent from the figure, by shifting the zero point of the staircase wave from the level indicated by reference numeral 307b to the level indicated by reference numeral 307a by offset adjustment, the staircase wave is also shifted from the position indicated by reference numeral 303b to the position indicated by reference numeral 303a. Level shift. Therefore, each cross point between the ramp wave 305 and the staircase wave is also changed.
[0058]
As a result, the pulse signal output from the comparison circuit 31 also changes from the pulse signal 309b before the offset adjustment (see FIG. 13C) to the pulse signal 309a with a narrow pulse width after the offset adjustment (see FIG. 13B). Is changed to That is, comparing the pulse signal 309b and the pulse signal 309a, a difference of Δtd1 occurs between the first pulses at the falling edge, and a difference of Δtd2 at the rising edge between the second pulses. At the fall, a difference of Δtd3 is generated. Further, a difference of Δtd4 occurs between the third pulses at the rise (here, the relations of Δtd1 = Δtd3 and Δtd2 = Δtd4 are established).
[0059]
As described above, according to the second embodiment of the present invention, the zero point of the staircase wave is shifted from the level denoted by reference numeral 307b to the level denoted by reference numeral 307a by offset adjustment, whereby the output from the comparison circuit 31 is obtained. The pulse width of the pulse signal can be reduced uniformly, thereby making it possible to prevent a reading error from occurring due to the occurrence of intersymbol interference in the reproducing laser beam when reproducing the recorded information from the disk. Therefore, the present embodiment functions effectively against a problem that an error corresponding to the diameter of the laser spot occurs uniformly in the pulse width of the recording signal.
[0060]
FIG. 14 is a block diagram showing the overall configuration of an optical disk drive to which the above-described first embodiment of the present invention is applied.
[0061]
As shown, the optical disk drive includes a recording signal generator 21, an edge timing controller 61, a laser driver 63, a semiconductor laser 65, a coupling lens 67, a reproduction signal generator 69, a polarization beam splitter, (PBS) 71 and an objective lens 73 are provided. The edge timing controller 61 includes the shift register 23, the weighting circuit 25, the adding circuit 27, the ramp circuit 29, and the comparing circuit 31 shown in FIG. 3, respectively.
[0062]
By configuring the edge timing controller 61 with each of the circuits described above, a laser spot can be used to write the recorded information 81 on the disk surface of the optical disk 75 or to reproduce the recorded information 81 from the disk surface. It is possible to prevent the occurrence of an error in reading recorded information due to the intersymbol interference. Since the configuration and function of each unit other than the edge timing controller 61 are well known, detailed description thereof will be omitted.
[0063]
The above description relates to each embodiment of the present invention, and does not mean that the present invention is limited to only the above content. As a method of weighting the data of each of the channels B1 to B8 by the weighting circuit 25 performed in the first embodiment, various modes other than the above-described modes can be assumed.
[0064]
For example, a stamper and a disk are actually manufactured using a table of a specific weighting pattern, and a reproduction signal of recorded information of the manufactured disk is observed with an oscilloscope or a time interval analyzer. Then, the amount of deviation between the reproduced signal and the pit array pattern on the disk surface is checked, and the weighting coefficient of each bit in the weighting pattern is corrected based on this. By repeating this operation many times, it becomes possible to obtain a weighting pattern that minimizes the above-mentioned deviation amount.
[0065]
Further, in this specification, the shift register 23, the weighting circuit 25, the adding circuit 27, the ramp circuit 29, the waveform shaping circuit 51, and the variable resistance circuit 53 correspond to 8 bits, but the present invention is not limited to this. is not.
[0066]
【The invention's effect】
As described above, according to the present invention, it is possible to more accurately read recorded information.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a mastering process to which the present invention is applied.
FIG. 2 is a block diagram of the overall configuration of a cutting device to which the present invention is applied.
FIG. 3 is a block diagram of the overall configuration of the recording signal correction device according to the first embodiment.
FIG. 4 is a diagram showing a light intensity distribution of a laser beam and a weighting coefficient for correcting a recording signal.
FIG. 5 is a diagram showing an internal configuration of the lamp circuit according to the first embodiment.
FIG. 6 is a diagram showing a first modification of the limiter circuit of FIG. 5;
FIG. 7 is a diagram showing a second modification of the limiter circuit of FIG. 5;
8 is a timing chart showing a time-series positional relationship between the operation of each unit of the apparatus shown in FIG. 3 and pits formed on a disk surface.
FIG. 9 is a diagram schematically illustrating an output waveform of the comparison circuit of FIG. 3;
FIG. 10 is an explanatory diagram showing a relationship between a laser spot of a reproduction laser beam, a plurality of pit arrangement patterns, and their reproduction signals.
FIG. 11 is a partially enlarged view of FIG. 10;
FIG. 12 is a block diagram of the overall configuration of a recording signal correction device according to a second embodiment.
FIG. 13 is a timing chart showing the operation of each unit of the apparatus shown in FIG.
FIG. 14 is a block diagram of the overall configuration of an optical disk drive to which the first embodiment is applied.
[Explanation of symbols]
21 Recording signal generator
23 shift register
25 Weighting circuit
27 Addition circuit
29 lamp circuit
31 Comparison circuit
33, 35, 37 limiter circuit
51 Waveform shaping circuit
53 Variable resistance circuit
59 Offset adjustment circuit
61 Edge Timing Controller
63 Laser Driver
65 Semiconductor Laser
69 Playback signal detector
75 Optical Disk

Claims (6)

The first pulse is obtained by making the level of a first pulse signal, which is a bit string representing information to be recorded, different for each bit in accordance with the light intensity distribution of a laser beam spot for recording information on a medium. Weighting means for weighting the signal;
Signal level adding means for adding and outputting the level of the first pulse signal for each predetermined bit;
Pulse signal delay means for inputting the level of the bit to which the maximum weight has been given by the weighting means, and delaying the rise time and fall time of the level,
A pulse width for varying a pulse width of a second pulse signal for controlling the laser light based on a comparison result between a signal level addition value from the signal level addition means and a signal level from the pulse signal delay means; Variable means,
A recording device comprising: The recording device according to claim 1,
The recording apparatus according to claim 1, wherein the weighting means is a variable resistance circuit including variable resistances of a number corresponding to the predetermined number of bits. The recording device according to claim 1,
The pulse signal delay unit integrates the level of the bit with the maximum weight over time to generate oblique waves corresponding to the rise and fall of the level, and an integrator that generates And a limiter circuit for limiting the amplitude of the oblique wave. Signal level adding means for adding and outputting the level of a first pulse signal, which is a bit string representing information to be recorded, for each predetermined bit;
A pulse signal for inputting a bit level of the first pulse signal corresponding to the maximum portion of the light intensity of a laser beam spot for recording information on a medium, and delaying a rise time and a fall time of the level. Delay means;
Offset adjusting means for adjusting the offset of the output signal from the signal level adding means,
A second pulse for controlling the laser light based on a comparison result between a signal level addition value output from the signal level addition means via the offset adjustment means and a signal level from the pulse signal delay means; Pulse width varying means for varying the pulse width of the signal;
A recording device comprising: The recording apparatus according to claim 4,
The first pulse is obtained by making the level of a first pulse signal, which is a bit string representing information to be recorded, different for each bit in accordance with the light intensity distribution of a laser beam spot for recording information on a medium. The recording apparatus according to claim 1, further comprising a variable resistance circuit having variable resistors of a number corresponding to the number of bits of the first pulse signal, as weighting means for weighting the signal. In an optical disk drive that can record information on an optical disk,
The first pulse is obtained by making the level of a first pulse signal, which is a bit string representing information to be recorded, different for each bit in accordance with the light intensity distribution of a laser beam spot for recording information on a medium. Weighting means for weighting the signal;
Signal level adding means for adding and outputting the level of the first pulse signal for each predetermined bit;
Pulse signal delay means for inputting the level of the bit to which the maximum weight has been given by the weighting means, and delaying the rise time and fall time of the level,
A pulse width for varying a pulse width of a second pulse signal for controlling the laser light based on a comparison result between a signal level addition value from the signal level addition means and a signal level from the pulse signal delay means; Variable means,
An optical disc drive comprising:

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