JP4234273B2 - Optical disk playback device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk reproducing apparatus having a vibration measuring device that measures vibration caused by the eccentric gravity center of an optical disk.
[0002]
[Prior art]
In recent years, the optical disc reproducing apparatus has remarkably improved the recording / reproducing speed. Optical disk playback devices have improved playback speed by increasing the rotational speed of the optical disk.
[0003]
However, when the rotation speed of the optical disk is increased, the vibration caused by the eccentric gravity center of the optical disk adversely affects the control of the servo and the like, causing a problem that the user of the optical disk reproducing apparatus is uncomfortable. In order to prevent the adverse effect of vibration caused by a disk with a large eccentric gravity center, when a disk with a large eccentric gravity center is mounted, the optical disk reproducing device limits the rotation speed of the optical disk. Measurement of vibration amplitude is an important technique for preventing an adverse effect of vibration caused by a disk having a large eccentric gravity center in an optical disk reproducing apparatus.
[0004]
FIG. 6 shows a block diagram of a conventional optical disc playback apparatus 600. 1 is a base, 2 is a disk motor attached to the base 1, 3 is an insulator supporting the base 1, 4 is a disk attached to the disk motor 2, and 21 is an acceleration sensor attached to the base 1 , 22 is a measuring unit that determines the mass eccentricity based on the output of the acceleration sensor 21.
[0005]
When the disk motor 2 is rotated at a predetermined number of revolutions, a centrifugal force proportional to the eccentric mass of the disk 4 is generated. The base 1 supported by the insulator 3 vibrates with an amplitude determined by the amount of eccentric gravity of the disk 4, the mass of the base 1 and the entire components mounted thereon, and the spring constant of the insulator 3.
[0006]
The vibration of the base 1 is converted into an electric signal by the acceleration sensor 21. The measurement unit 22 measures the vibration amplitude of the base 1 based on the electrical signal converted by the acceleration sensor 21.
[0007]
[Problems to be solved by the invention]
However, the optical disk reproducing apparatus 600 described above has a problem that the cost increases due to the mounting of the acceleration sensor 21 and the cost increases due to the mounting of a signal amplification amplifier for amplifying the signal from the acceleration sensor 21.
[0008]
There is also a problem that it is necessary to secure a mounting space between the acceleration sensor 21 and the signal amplification amplifier.
[0009]
An object of the present invention is to provide an optical disk reproducing apparatus having a vibration detecting apparatus that can measure vibration amplitude at low cost and without using an acceleration sensor and a signal amplifier.
[0010]
[Means for Solving the Problems]
  An optical disc reproducing apparatus of the present invention is an optical disc reproducing device for reproducing information recorded on an optical disc, wherein an information recording track is formed on the optical disc, and the optical disc has an eccentricity and an eccentric center of gravity. The eccentricity is defined as a deviation between the rotation center of the optical disk and the center of the information recording track, and the eccentric gravity center is a deviation between the rotation center of the optical disk and the gravity center of the optical disk. The optical disk playback device includes: a disk motor that rotates the optical disk; a base on which the disk motor is fixed and elastically suspended from the outside; and a base that is mounted on the base and is mounted on the optical disk. An optical head that emits a light beam and reads a reproduction signal, and a reproduction signal when the light beam crosses the information recording track. A track cross detection unit for generating a track cross pulse Zui, the track cross direction detecting unit for detecting the track cross direction in which the light beam indicates the direction crossing the information recording track,Lower than the natural frequency (foA) of the optical headThe first rotational speed and, Higher than the natural frequency (foA) of the optical head and lower than the natural frequency (foM) of the baseThe rotation speed of the disk motor is controlled to rotate the disk motor at a second rotation speed, and the rotation angle θ [i] of the disk (i is a natural number, 0 ° ≦ θ [i] ≦ 360 ° ) Including a motor control unit that outputs rotation angle information of the disk motor, and the detected rotation angle of the track motor and the output rotation angle when the rotation speed of the disk motor is the first rotation speed. The first count result N (θ [i]) is obtained by counting the track cross pulses from the rotation angle θ [i−1] to the rotation angle θ [i] based on the information, and the disk When the rotation speed of the motor is the second rotation speed, the rotation angle θ [i−1] is based on the detected track cross direction and the output rotation angle information. ] To obtain the second count result N (θ [i]) by counting the track cross pulses from the rotation angle θ [i] to the rotation angle θ [i],A subtraction result M (θ [i]) is obtained by subtracting the first count result N1 (θ [i]) from the second count result N2 (θ [i]), and the subtraction result M (θ [i]). i]), the vibration amplitude of the base is obtained from the maximum valueAnd the above-mentioned purpose is achieved thereby..
[0019]
According to an aspect of the present invention, an optical disc reproducing apparatus uses an originally provided optical head for vibration detection. The optical disk reproducing apparatus counts the number of times the light beam emitted from the optical head traverses the information recording track that the optical disk originally has, and changes the relative position between the optical disk and the optical head displaced together with the base by 1 μm. Measure with front and back accuracy. As a result, it is possible to provide an optical disc reproducing apparatus having a vibration detecting apparatus that can measure vibration amplitude at low cost and without using an acceleration sensor and a signal amplification amplifier.
[0020]
According to another aspect of the present invention, the state of vibration of the base caused by the eccentricity of the information recording track and the eccentric gravity center of the optical disk is a sine wave, and the eccentric direction of the information track Even when the direction of the eccentric gravity center is different, more accurate vibration measurement can be performed.
[0021]
The optical disk is rotated at a first rotational speed selected in the same manner as described above, and one rotation of the disk is divided into a plurality of numbers, and a signed track count is performed for each division unit. Get the data. Next, the optical disk is rotated at the second rotational speed selected in the same manner as described above, and sine wave data obtained by combining the vibration of the base and the eccentricity of the information recording track is obtained, and the difference is calculated. Thus, vibration amplitude is measured by obtaining sinusoidal data only for vibration and selecting the maximum value. Further, the sine wave uses the fact that the absolute value is the same and the sign is different at the position where the phase angle is different by 180 degrees, and when obtaining the track count data, the absolute value of the data value having the disc rotation angle different by 180 degrees is obtained. If the difference is more than a certain value, the accuracy can be further improved by re-measuring the data by assuming that the data contains noise.
[0022]
As described above, the vibration amplitude can be measured by correcting the influence of the eccentric direction and the eccentric gravity center of the information recording disk.
[0023]
According to still another aspect of the present invention, the count result of the counting unit and the second rotation at the first rotation number every 60 degrees are obtained by dividing the circumference of the disk into six and performing track counting. The subtraction result of the number with the counting result of the counting unit is represented by a vector having the corresponding disk rotation angle as a phase angle and the signed subtraction result as an absolute value, and six difference vectors between adjacent vectors of the phase angle. Since the calculation is performed and the average of the absolute values of these six vectors is calculated, the vibration amplitude can be measured with higher accuracy.
[0024]
According to still another aspect of the present invention, the counting unit averages the count data for a plurality of rotations of the disk, so that the accuracy of vibration amplitude measurement can be improved.
[0025]
According to still another aspect of the present invention, the measurement unit is higher than the second rotation number in addition to the measurement of the vibration amplitude based on the counting result of the counting unit at the first and second rotation numbers. Third rotation speed, higher if necessary Fourth, fifth. . Based on the counting result at the Nth rotation speed, the vibration amplitude is measured with higher accuracy. Taking advantage of the fact that vibration amplitude measurement accuracy can be increased as a result of the vibration amplitude increasing in proportion to the square of the rotation speed of the optical disk, the measurement unit measures vibration amplitude at a low rotation speed for a disk with a large eccentric center of gravity. The vibration amplitude is measured at a high rotational speed for a disk with a small eccentric gravity center. For this reason, vibration measurement can be performed while suppressing the vibration amplitude of the base below a certain value.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0027]
In this specification, the eccentricity refers to a deviation between the rotation center of the optical disc mounted on the optical disc reproducing apparatus and the center of the information recording track. The eccentric center of gravity refers to a deviation between the center of rotation of the optical disk mounted on the optical disk reproducing apparatus and the center of gravity of the optical disk.
[0028]
(Embodiment 1)
FIG. 1 shows a block diagram of an optical disc playback apparatus 100 according to Embodiment 1 of the present invention. In FIG. 1, 1 is a base, 2 is a disk motor fixed to the base 1, 3 is an insulator supporting the base 1, 4 is a disk mounted on the disk motor 2, 5 is an optical head, 6 Is an elastic material for suspending the optical head 5 from the base 1, 7 is a light beam applied to the disk 4 from the optical head 5, and 8 is a concentric circle or a spiral at a constant pitch on the information recording surface 4 A of the disk 4. The generated information recording track, 9 is a track cross detecting section for generating a track cross pulse and a transverse signal from the signal reproduced when the light beam 7 crosses the information recording track 8, and 10 is the track cross pulse. A counting unit 11 for counting, a measuring unit 11 for determining the amount of eccentric gravity from the counting result of the counting unit 10, and a control unit 12 for controlling the rotational speed of the disk motor 2 and the measuring unit 11. A motor control unit that outputs a rotation angle information Te.
[0029]
The optical head 5 is kept at a constant distance from the disk 4 so that the focal point of the light beam 7 is positioned on the information recording surface 4A of the disk 4. The relative position of the optical head 5 in the radial direction (arrow R direction) of the disk 4 with respect to the disk 4 depends on the spring constant of the elastic member 6 made of a material such as metal, resin or rubber and the mass of the optical head 5. It has a vibration characteristic represented by a determined natural frequency foA.
[0030]
The base 1 is supported by an insulator 3 made of a material such as metal, resin, or rubber. When the centrifugal force generated by the rotation of the disk 4 is transmitted to the base 1 through the disk motor 2, the mass of the entire component including the base 1 and the optical head 5 mounted on the base 1, the disk motor 2 and the disk 4. And the base 1 vibrate based on the characteristic represented by the natural frequency foM determined by the spring constant of the insulator 3.
[0031]
The motor control unit 12 rotates the disk motor 2 at a first rotational speed that is sufficiently lower than the natural frequency foA. The optical disk 4 mounted on the disk motor 2 rotates at the first rotational speed.
[0032]
The optical head 5 vibrates integrally with the base 1 at a first rotational frequency sufficiently lower than the natural frequency foA. The relative position between the optical head 5 and the optical disk 4 hardly changes. For this reason, at a first rotational frequency sufficiently lower than the natural frequency foA, the light beam 7 traverses the number of information recording tracks 8 corresponding to the amount of eccentricity of the information recording track 8. The light beam 7 generates a track cross corresponding to the number of information recording tracks 8 traversed.
[0033]
The track cross detection unit 9 detects a track cross corresponding to the number of information recording tracks 8 traversed by the light beam 7 based on the reproduction signal of the optical head 5. The track cross detection unit 9 generates a track cross pulse corresponding to the detected track cross. The track cross detection unit 9 outputs the generated track cross pulse to the counting unit 10.
[0034]
The counting unit 10 counts track cross pulses during one rotation of the disk 4 based on the rotation angle information from the motor control unit 12. The measuring unit 11 stores a track cross pulse count result N1 for one rotation of the disk 4 counted by the counting unit 10.
[0035]
Next, the motor control unit 12 rotates the disk motor 2 at a second rotational speed that is higher than the natural frequency foA and lower than the natural frequency foM. Centrifugal force is generated in the disk 4 due to the eccentric center of gravity of the disk 4. The base 1 vibrates with an amplitude determined by the amount of eccentric gravity of the disk 4, the mass of the base 1 and the entire components mounted thereon, and the spring constant of the insulator 3.
[0036]
When the disk motor 2 rotates at a second rotational speed higher than the natural frequency foA and lower than the natural frequency foM, only the base 1, the disk motor 2 and the disk 4 vibrate together, and the optical head 5 is in a stationary state. Become. For this reason, the relative displacement between the disk 4 and the optical head 5 is equal to the vibration displacement of the base 1. As a result, the light beam 7 generates track crosses having the number of tracks corresponding to the sum of the eccentric amount of the information recording track 8 and the vibration amplitude of the base 1.
[0037]
The track cross detection unit 9 detects a track cross corresponding to the number of tracks corresponding to the sum of the eccentric amount of the information recording track 8 and the vibration amplitude of the base 1 based on the reproduction signal of the optical head 5. The track cross detector 9 generates a track cross pulse corresponding to the number of tracks corresponding to the sum of the eccentric amount of the information recording track 8 and the vibration amplitude of the base 1. The track cross detection unit 9 outputs the generated track cross pulse to the counting unit 10.
[0038]
The counting unit 10 counts track cross pulses during one rotation of the disk 4 based on the rotation angle information from the motor control unit 12. The measurement unit 11 subtracts the count result N1 from the count result N2 counted by the measurement unit 10 to obtain the vibration amplitude of the base 1.
[0039]
(Embodiment 2)
FIG. 2B shows a block diagram of an optical disc playback apparatus 200 according to Embodiment 2 of the present invention. The same components as those of the optical disc reproducing apparatus 100 according to Embodiment 1 in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0040]
The optical disc playback apparatus 200 according to the second embodiment is different from the optical disc playback apparatus 100 according to the first embodiment in that the optical disc playback apparatus 200 includes a track cross direction detection unit 13, a storage unit 14, and a filter unit 15. It is.
[0041]
In the optical disk reproducing apparatus 100 according to the first embodiment, when the direction of the eccentricity of the optical disk 4 and the direction of the eccentric gravity center are different, the eccentricity amount of the information recording track 8 and the vibration of the base 1 at the second rotational speed. Since the track cross of the number of tracks corresponding to the sum of the amplitude is not generated, the vibration amplitude of the base 1 cannot be obtained.
[0042]
For example, if the direction of the eccentricity and the direction of the eccentric gravity center of the optical disk 4 are opposite to each other, as shown in FIG. 2A, the waveform of the eccentricity and the waveform of the eccentric gravity center with respect to the rotation angle of the disk have an inverse phase relationship. . As a result, since the number of track crosses corresponding to the amount obtained by adding the eccentricity amount of the information recording track 8 and the vibration amplitude of the base 1 in the same phase at the second rotational speed does not occur, the vibration amplitude of the base 1 Cannot be asked.
[0043]
Since the optical disk reproducing apparatus 200 according to Embodiment 2 includes the track cross direction detection unit 13, a track count with a sign can be performed. The optical disc reproducing apparatus 200 according to the second embodiment divides one rotation of the disc into a plurality of numbers, performs a track count with a sign for each division unit, and obtains first sine wave data representing the eccentricity of the information recording track 8. obtain. Next, the optical disk 4 is rotated at the second rotational speed to obtain second sine wave data in which the vibration of the base 1 and the eccentricity of the information recording track 8 are combined. The difference between the first sine wave data and the second sine wave data is calculated, the sine wave data of only the vibration of the base 1 is obtained, and the maximum value is selected to measure the vibration amplitude.
[0044]
2B, 1 is a base, 2 is a disk motor fixed to the base 1, 3 is an insulator supporting the base 1, 4 is a disk mounted on the disk motor 2, 5 is an optical head, 6 Is an elastic material for suspending the optical head 5 from the base 1, 7 is a light beam applied to the disk 4 from the optical head 5, and 8 is generated on the information recording surface of the disk 4 in a concentric or spiral shape with a constant pitch. The information recording track 9, 9 is a track cross detecting section for generating a track cross pulse from the signal reproduced when the light beam 7 crosses the information recording track 8, and 13 is the light beam 7 crossing the information recording track 8. The track cross direction detecting unit 10 detects the track cross direction from the reproduced signal when the track cross direction detecting unit 13 outputs the track cross direction according to the output of the track cross direction detecting unit 13. A counting unit that counts up or down a pulse, a storage unit that stores a counting result, a filter unit that removes a counting result having a large error from the data in the storing unit, and a measurement that determines a mass eccentricity from the counting result Reference numeral 12 denotes a motor control unit that controls the rotational speed of the disk motor 2 and outputs rotation angle information to the counting unit 10, the storage unit 14, and the measurement unit 11.
[0045]
As in the first embodiment, the optical head 5 is kept at a constant distance from the disk 4 so that the focal point of the light beam 7 is positioned on the information recording surface 4A of the disk 4. The relative position in the radial direction (arrow R direction) with respect to the disk 4 is represented by the natural frequency foA determined by the spring constant of the elastic member 6 made of a material such as metal, resin, or rubber and the mass of the optical head 5. With vibration characteristics.
[0046]
The base 1 is supported by an insulator 3 made of a material such as metal, resin, or rubber. When the centrifugal force generated by the rotation of the disk 4 is transmitted through the disk motor 2, it is represented by the natural frequency foM determined by the mass of the base 1 and the entire components mounted on the base 1 and the spring constant of the insulator 3. The base 1 vibrates based on the characteristics.
[0047]
The motor control unit 12 rotates the disk motor 2 at a first rotational speed that is sufficiently lower than the natural frequency foA.
[0048]
The optical head 5 vibrates integrally with the base 1. The relative position of the disk 4 and the optical head 5 hardly changes. For this reason, the light beam 7 crosses the number of information recording tracks 8 corresponding to the amount of eccentricity of the information recording track 8. The light beam 7 generates a track cross corresponding to the number of information recording tracks 8 traversed.
[0049]
The track cross detector 9 detects a track cross based on the reproduction signal from the optical head 5. The track cross detection unit 9 generates a track cross pulse and outputs it to the counting unit 10. The above is the same as that of the first embodiment described above.
[0050]
The track cross direction detection unit 13 detects the track cross direction from the reproduction signal from the optical head 5. Based on the rotation angle information from the motor control unit 12, the counting unit 10 determines that the rotation angle of the disk 4 is an angle θ1, θ2,. . θi. . Every time it coincides with θk (= 360), the track cross pulse from the angle θ [i−1] to θ [i] (i = 1... k) is counted. The storage unit 14 stores the track cross direction detected by the track cross direction detection unit 13 and the count result N1 (θ [i]) counted by the counting unit 10.
[0051]
The filter unit 15 includes N1 (θ [i]) and N1 (θ [i] +180) (i = 1,...) For all count results N1 (θ [i]) stored in the storage unit 14. It is determined whether or not the difference in absolute value from k / 2) is equal to or less than a certain value. If there is a combination of the count results N1 (θ [i]) exceeding the above-mentioned fixed value even in one set, the counting unit 10 again determines the rotation angle of the disk 4 based on the rotation angle information from the motor control unit 12. Are divided into k angles θ1, θ2,. . θi. . Every time it coincides with θk (= 360), the track cross pulse from the angle θ [i−1] to θ [i] (i = 1... k) is counted.
[0052]
Next, as in the first embodiment, the motor control unit 12 rotates the disk motor 2 at a second rotational speed that is higher than the natural frequency foA and lower than the natural frequency foM. Centrifugal force is generated in the disk 4 due to the eccentric center of gravity of the disk 4. The base 1 vibrates with an amplitude determined by the amount of eccentric gravity of the disk 4, the mass of the base 1 and the entire components mounted thereon, and the spring constant of the insulator 3.
[0053]
The optical head 5 is stationary. For this reason, the relative displacement between the disk 4 and the optical head 5 is equal to the vibration displacement of the base 1. As a result, the light beam 7 generates a track cross having the number of tracks corresponding to the amount obtained by adding the eccentric amount of the information recording track 8 to the vibration amplitude of the base 1.
[0054]
The track cross detector 9 detects a track cross based on the reproduction signal of the optical head 5. The track cross detection unit 9 generates a track cross pulse. The track cross detection unit 9 outputs a track cross pulse to the counting unit 10.
[0055]
The track cross direction detection unit 13 detects the track cross direction from the reproduction signal from the optical head 5. The counting unit 10 performs the same counting as in the case of the first rotation speed described above, and the storage unit 14 stores the count result N2 (θ [i]).
[0056]
The filter unit 15 counts all the data stored in the storage unit 14 with the count result N2 (θ [i]) and the count result N2 (θ [i] +180) (i = 1, 2,... K / 2). It is determined whether or not the difference between the absolute values is less than a certain value. If even one set has a combination that exceeds the above-mentioned fixed value, the count result N2 is discarded, and the counting unit 10 again divides the circumference of the disk by k based on the rotation angle information from the motor control unit 12. Angles θ1, θ2,. . θi. . Every time it coincides with θk (= 360), the track cross pulse from the angle θ [i−1] to θ [i] (i = 1... k) is counted.
[0057]
For each of θ [i] (i = 1, 2,... K), the measurement unit 11 counts from the count result N2 (θ [i]) to the count N1 (θ [i]) (i = 1, 2 ... k). ) Are respectively subtracted to obtain a subtraction result M (θ [i]). The measurement unit 11 can obtain the vibration amplitude of the base 1 from the maximum value in the subtraction result M (θ [i]) (i = 1, 2... K).
[0058]
(Embodiment 3)
FIG. 3 shows a block diagram of the third embodiment of the present invention. The same components as those of the optical disc playback apparatus 200 according to Embodiment 2 in FIG. 2B are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0059]
The optical disc playback apparatus 300 according to the third embodiment is different from the optical disc playback apparatus 200 according to the second embodiment in that the optical disc playback apparatus 300 includes a vector calculation unit 16 connected to the measurement unit 11.
[0060]
The count result N1 (θ [i]) and the count result N2 (θ [i]) (i = 1, 2,... K) are stored in the storage unit 14 to obtain the subtraction result M (θ [i]). The steps up to this are the same as in the second embodiment. However, with k = 6, one round of the disk is divided into 6 and track crosses are counted.
[0061]
4A and 4B are graphs showing the relationship between the rotation angle of the disk, the amount of eccentricity of the information recording track 8, and the displacement of the optical head 5. FIG. FIG. 4A shows a measurement result when the disk 4 is rotated at the first rotational speed. Reference numeral 51 denotes an eccentric waveform of the information recording track 8, and 52 denotes a displacement waveform of the optical head 5. A point indicated by a black circle on the eccentric waveform 51 of the information recording track 8 is a count result N1 (θ [i]) (i = 1, 2.0.6) obtained by counting the track cross pulse.
[0062]
FIG. 4B shows the measurement result when the disk 4 is rotated at the second rotational speed. 53 is an eccentric waveform of the information recording track 8, 54 is a displacement waveform of the optical head 5, and 55 is a relative displacement between the information recording track 8 and the optical head 5. A point indicated by a black circle on the relative displacement 55 between the information recording track 8 and the optical head 5 is a count result N2 (θ [i]) (i = 1, 2.2.6) obtained by counting track cross pulses.
[0063]
A displacement waveform 54 of the optical head 5 represents the vibration of the optical head 5 due to the eccentric center of gravity of the disk 4. From the waveform 55 representing the relative displacement between the information recording track 8 and the optical head 5, the eccentric amplitude and phase of the information recording track 8 do not change even if the rotational speed of the disk 4 changes. 53 and the eccentric waveform 51 of the information recording track 8 are equal.
[0064]
As shown in FIGS. 4A and 4B, the count result N1 (θ [i]) on the eccentric waveform 51 of the information recording track 8 and the count result N2 on the relative displacement 55 between the information recording track 8 and the optical head 5 ( θ [i]) is a sine wave when the disk rotation angle θ [i] is a variable. Accordingly, the subtraction result M (θ [i]) obtained by subtracting the count result N1 (θ [i]) on the eccentric waveform 51 from the count result N2 (θ [i]) on the relative displacement 55 also becomes a sine wave. The vibration amplitude of the base 1 can be obtained from the maximum value in the subtraction result M (θ [i]).
[0065]
5A to 5C, the count result N1 (θ [i]) on the eccentric waveform 51, the count result N2 (θ [i]) on the relative displacement 55, and the subtraction result M (θ [i]) are obtained. , N1 (θ [i]), N2 (θ [i]) and M (θ [i]), and the phase angle θ [i], and the count result N1 (θ [i]) The positions of the vectors representing the count result N2 (θ [i]) and the subtraction result M (θ [i]) correspond to the vertices of an equilateral triangle inscribed in a circle passing through the origin.
[0066]
Referring to FIG. 5A, the count result N1 (θ [i]) on the eccentric waveform 51 is represented by a vector having a magnitude N1 (θ [i]) and a phase angle θ [i]. Each position of the vectors representing (θ [i]), N1 (θ [i + 1]), and N1 (θ [i + 2]) corresponds to a vertex of an equilateral triangle inscribed in a circle passing through the origin. FIG. 5A shows an example in which the positions of the vectors representing the count results N1 (0), N1 (60), and N1 (120) correspond to the vertices of an equilateral triangle that is inscribed in the circle 61 having the origin.
[0067]
Referring to FIG. 5B, the count result N2 (θ [i]) on the relative displacement 55 is represented by a vector having a magnitude of N2 (θ [i]) and a phase angle of θ [i]. Each position of the vector representing (θ [i]) corresponds to a vertex of an equilateral triangle inscribed in a circle passing through the origin. FIG. 5B shows an example in which the positions of the vectors representing the count results N2 (0), N2 (60) and N2 (120) correspond to the vertices of an equilateral triangle inscribed in the circle 62 having the origin.
[0068]
Referring to FIG. 5C, when subtraction result M (θ [i]) is represented by a vector having magnitude M (θ [i]) and phase angle θ [i], subtraction result M (θ [i]) Each position of the vector representing corresponds to a vertex of an equilateral triangle inscribed in a circle passing through the origin. FIG. 5C shows an example in which the positions of the vectors representing the subtraction result M (300), the subtraction result M (0), and the subtraction result M (60) correspond to the vertices of an equilateral triangle inscribed in the circle 63 having the origin. Show.
[0069]
The absolute value of the difference vector (M (i), i) − (M (i + 1), i + 1) (i = 0, 60, 120, 180, 240, 300) between adjacent vectors is the length of one side of the equilateral triangle. Therefore, these six difference vectors (M (0), 0) − (M (60), 60), (M (60), 60) − (M (120), 120), (M (120 ), 120)-(M (180), 180), (M (180), 180)-(M (240), 240), (M (240), 240)-(M (300), 300), By calculating the average value of the absolute values of (M (300), 300) − (M (0), 0), the measurement error included in the actual subtraction result M (θ [i]) can be reduced. I can do it.
[0070]
Further, since the length of one side of the equilateral triangle is proportional to the amplitude of the subtraction result M (θ [i]) that changes in a sine wave shape, the vibration amplitude of the base 1 can be measured.
[0072]
In the first to third embodiments, the example in which the vibration amplitude measurement is performed at the two rotation speeds of the first rotation speed and the second rotation speed has been described, but the present invention is not limited to this. 3rd rotation speed higher than 2nd rotation speed, 4th rotation speed. . A plurality of rotation speeds are provided, and vibration amplitude measurement is performed while sequentially switching the rotation speed from a low rotation speed to a high rotation speed, and when a large vibration occurs at a low rotation speed because the eccentric gravity center of the disk 4 is large, At that time, the vibration amplitude measurement is completed, and when the eccentric gravity center of the disk 4 is small, the vibration amplitude measurement is performed at a rotational speed higher than the second rotational speed, thereby suppressing the generated vibration to a certain level or less. Highly accurate vibration measurement can be performed.
[0073]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an advantageous effect that it is possible to provide a vibration detection apparatus that can measure vibration amplitude at low cost and without using an acceleration sensor and a signal amplification amplifier.
[0074]
Further, according to the present invention, there is provided a vibration detection device capable of measuring vibration amplitude at low cost and in a small space without using an acceleration sensor and a signal amplification amplifier even when the direction of eccentricity of the optical disk is different from the direction of eccentric gravity center. The advantageous effect that it can be provided is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a vibration detection apparatus according to Embodiment 1 of the present invention.
FIG. 2A is a signal waveform diagram when the direction of eccentricity and the direction of eccentric gravity center of the optical disc according to Embodiment 1 of the present invention are different.
FIG. 2B is a block diagram showing a vibration detection apparatus according to Embodiment 2 of the present invention.
FIG. 3 is a block diagram showing a vibration detection apparatus according to a third embodiment of the present invention.
FIG. 4A is a signal waveform diagram at a first rotational speed according to Embodiment 3 of the present invention.
FIG. 4B is a signal waveform diagram at the second rotation speed in the third embodiment of the present invention.
FIG. 5A is a distribution diagram of measurement data of a count result N1 (θ [i]) in Embodiment 3 of the present invention.
FIG. 5B is a distribution diagram of measurement data of a count result N2 (θ [i]) according to Embodiment 3 of the present invention.
FIG. 5C is a distribution diagram of measurement data of a subtraction result M (θ [i]) in Embodiment 3 of the present invention.
FIG. 6 is a block diagram showing a conventional vibration detection device.
[Explanation of symbols]
1 base
2 Disc motor
3 Insulator
4 discs
5 Optical head
6 Elastic material
7 Light beam
8 Information recording track
9 Track cross detector
10 counter
11 Measurement unit
12 Motor controller

Claims (1)

An optical disk playback device for playing back information recorded on an optical disk,
An information recording track is formed on the optical disc, and the optical disc can have an eccentricity and an eccentric gravity center, and the eccentricity is between the rotation center of the optical disc and the center of the information recording track. Defined as a deviation, and the eccentric gravity center is defined as a deviation between the rotation center of the optical disc and the gravity center of the optical disc,
The optical disc playback apparatus comprises:
A disk motor for rotating the optical disk;
A base on which the disk motor is fixed and elastically suspended from the outside;
An optical head mounted on the base, emitting a light beam to the optical disc, and reading a reproduction signal;
A track cross detector for generating a track cross pulse based on a reproduction signal when a light beam crosses the information recording track;
A track cross direction detector for detecting a track cross direction representing a direction in which a light beam crosses the information recording track;
A first rotational frequency lower than the natural frequency (foA) of the optical head; a second rotational frequency higher than the natural frequency (foA) of the optical head and lower than the natural frequency (foM) of the base ; The disk motor includes a rotation angle θ [i] (where i is a natural number, 0 ° ≦ θ [i] ≦ 360 °) and the rotation number of the disk motor is controlled to rotate the disk motor. A motor control unit that outputs rotation angle information of
When the rotation speed of the disk motor is the first rotation speed, the rotation angle θ is changed from the rotation angle θ [i−1] based on the detected track cross direction and the output rotation angle information. A first count result N (θ [i]) is obtained by counting the track cross pulses up to [i], and is detected when the rotational speed of the disk motor is the second rotational speed. The second count result N is obtained by counting the track cross pulses from the rotation angle θ [i−1] to the rotation angle θ [i] based on the track cross direction and the output rotation angle information. A counting unit for obtaining (θ [i]);
A subtraction result M (θ [i]) is obtained by subtracting the first count result N1 (θ [i]) from the second count result N2 (θ [i]), and the subtraction result M (θ [i]). i]), and a measurement unit that obtains the vibration amplitude of the base from the maximum value .

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