JP2005221724A - Liquid crystal driving device, disk drive device, and liquid crystal driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify construction of a liquid crystal driving device with respect to a liquid crystal element disposed in an optical pickup. <P>SOLUTION: Driving of the liquid crystal element for phase compensation in the optical pickup is realized by using a PWM (Pulse Width Modulation) signal. Fixed voltage is applied to the liquid crystal element and period during which the fixed voltage is applied is changed by a pulse duty ratio of the PWM signal, that is, effective voltage applied to the liquid crystal element is controlled by the pulse duty ratio of the PWM signal to change a phase compensation quantity of a laser beam. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal drive device, a disk drive device, and a liquid crystal drive device, and more particularly to driving of a liquid crystal element for phase compensation and the like provided in an optical pickup.

JP 11-219539 A JP 2002-222536 A

For example, various disc media such as CD (Compact Disc), MD (Mini Disc), DVD (Digital Versatile Disc), Blu-ray Disc (Blu-Ray Disc) have been developed, audio data, video data, computer use data, etc. It is used in various data recording / reproducing systems.
In a recording / reproducing apparatus (disk drive apparatus) for these optical disks (including magneto-optical disks), laser light is irradiated from a optical head (optical pickup) to a disk medium to record or reproduce data on the disk.

  In addition, as various types of discs such as the above-mentioned CD and MD, other types of discs have been developed which basically maintain compatibility. For example, when an MD disk system is taken as an example, MD and MD-DATA for audio use developed as the first generation MD have been conventionally known, and in recent years, Hi-MD with higher density has been developed. The next generation MD called is being developed. In addition, various formats having different physical structures have been formulated in the MD as the Hi-MD (for example, described below as a first next generation MD and a second next generation MD).

In such a disk system in which various types exist on the same system, it is required that the disk drive device maintain recording / reproduction compatibility with respect to these various disks.
One element for maintaining compatibility is the phase of the laser output from the optical head, the laser spot shape, and the size. That is, in order to perform recording / reproduction with respect to a disk having a physically different structure, it is necessary to perform processing such as changing the phase compensation amount of the laser beam according to the disk.
For example, in order to adjust the phase compensation of such laser light, it is known to arrange a liquid crystal element on the laser light path in the optical head. For example, Patent Documents 1 and 2 disclose a technique for performing phase adjustment, spot shaping, or laser beam path branching by a liquid crystal element.

For the liquid crystal element disposed in the optical head, the phase adjustment of the laser beam is performed by controlling the orientation angle of the liquid crystal element using a liquid crystal driving circuit as shown in FIG.
A liquid crystal element 120 in FIG. 10A is a liquid crystal element disposed on a laser beam path in the optical head. As is well known, the liquid crystal element 120 is formed by enclosing a liquid crystal material between two glass substrates, and gives a potential difference between transparent electrodes (drive electrodes) formed on the glass substrates on both sides thereof. Thus, the structure is such that the orientation angle of the liquid crystal material is changed. In the figure, terminals 121 and 122 indicate drive electrodes, respectively.

A liquid crystal driving circuit for the liquid crystal element 120 includes a D / A converter 112, an EX-OR gate 115, switch elements 116 and 117, and resistors R1 and R2.
For example, a control signal for driving the liquid crystal is input to the terminal 111 from a control unit of the disk drive device provided with the liquid crystal driving circuit. The control signal is supplied as 8-bit data, for example.
This control signal as 8-bit data is converted into an analog voltage Vo by the D / A converter 112. Between the voltage Vo and the ground, a switch element 116 made up of a resistor R1 and an N channel MOS-FET is connected, and a switch element 117 made up of an N channel MOS-FET is connected like the resistor R2. A connection point between the resistor R1 and the switch element 116 is a voltage application point to the drive electrode 121 of the liquid crystal element 120, and a connection point between the resistor R2 and the switch element 117 is a voltage application point to the drive electrode 122.
That is, the voltage Vo is applied to the drive electrode 121 via the resistor R1 (voltage X) while the switch element 116 is turned off, and the voltage Vo is applied via the resistor R2 while the switch element 117 is turned off. Applied to the drive electrode 122 (voltage Y).

A reference clock (signal X ′) is supplied from the terminal 113 to the gate of the switch element 116. Further, the output signal Y ′ of the EX-OR gate 115 is supplied to the gate of the switch element 117. The EX-OR gate 115 receives the reference clock from the terminal 113 and the ON / OFF signal from the terminal 114. It should be noted that the ON / OFF signal is always at the H level during the period of driving the liquid crystal element 120, that is, at least the period when the laser output is executed in the disk drive device. As the output Y ′ of the EX-OR gate 115, the ON / OFF signal is “H”, so that the period when the reference clock is “H” is “L”, and the period when the reference clock is “L” is “H”. It becomes. That is, the signal Y ′ is obtained by inverting the reference clock.
As a result, the switch elements 116 and 117 are alternately turned on, so that the voltages X and Y applied to the drive electrodes 121 and 122 of the liquid crystal element 120 are as shown in FIG. Since the liquid crystal element 120 is driven to be aligned by the potential difference between the drive electrodes 121 and 122, the drive voltage of the liquid crystal element 120 is the voltage Y-X in FIG.

In such a liquid crystal driving circuit, since the level of the voltage Vo is set by the value of the control signal of 8-bit data applied to the terminal 111, the level of the driving voltage (Y-X) of the liquid crystal element 120 is set by the value of the control signal. You can control it. Therefore, the control unit (system controller) of the disk drive device can adjust the amount of phase compensation of the laser beam by the liquid crystal element 120 by setting the value of the control signal according to, for example, the type of disk on which recording / reproduction is performed. .
If the liquid crystal element 120 is always driven, the deterioration of the liquid crystal element 120 proceeds. Therefore, the ON / OFF signal is set to “L” during a period in which laser output is not performed. In this case, the reference clock (X ′) and the signal Y ′ are in phase, and the switch elements 116 and 117 are simultaneously turned on / off. Therefore, the drive voltages X and Y applied to the drive electrodes 121 and 122 are in phase, and the potential difference, that is, the liquid crystal drive voltage (Y−X) can be set to zero.

Such a conventional liquid crystal driving circuit has the following problems.
Because of the configuration using the D / A converter 112, it is difficult to reduce the circuit scale. Further, since the D / A converter 112 is used, it is not easy to incorporate a liquid crystal driving circuit in the digital IC.
Further, a microcomputer as a system controller supplies a control signal, a reference clock, and an ON / OFF signal to the liquid crystal drive circuit, and at least ports for these outputs must be secured. As a microcomputer of a disk drive device, securing the number of ports is an important issue for various controls, and using three ports for a liquid crystal drive circuit is a burden on the system design. It has become.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal driving device having a simpler configuration as a liquid crystal driving device for a liquid crystal element arranged in an optical pickup.

The liquid crystal drive device of the present invention includes a PWM signal generating means for generating a PWM (Pulse Width Modulation) signal as a liquid crystal drive control signal for the liquid crystal element, and the first and second drive electrodes of the liquid crystal element. The first and second switch means for alternately applying the fixed voltage by the switching operation and the period during which the first and second switch means apply the fixed voltage to the first and second drive electrodes, respectively. Switch control means for generating first and second switching control signals for the first and second switch means on the basis of the PWM signal so that a period according to the pulse duty of the PWM signal is obtained. Is provided.
The switch control means performs a logical operation on the PWM signal to generate the first and second switching control signals, and uses the PWM signal as a clock for the logical operation.

The disk drive apparatus according to the present invention is a disk drive apparatus that records or reproduces information by irradiating a disk recording medium with laser light, and outputs the laser light, and also provides phase compensation on the laser light path. Optical pickup means including the liquid crystal element, PWM signal generating means for generating a PWM signal as a liquid crystal drive control signal for the liquid crystal element, and switching operations for the first and second drive electrodes of the liquid crystal element, respectively The period when the first and second switch means for alternately applying the fixed voltage and the first and second switch means apply the fixed voltage to the first and second drive electrodes respectively is Based on the PWM signal, the first and second switch means for the first and second switch means are set to have a period according to the pulse duty. And a switch control means for generating a quenching control signal.
The switch control means performs a logical operation on the PWM signal to generate the first and second switching control signals, and uses the PWM signal as a clock for the logical operation.
The PWM signal generating means generates a PWM signal in which the pulse duty is changed according to the type of the disk to be recorded or reproduced.

  The liquid crystal drive method of the present invention includes first and second switch means for applying a fixed voltage to the first and second drive electrodes of a liquid crystal element disposed in an optical pickup, for example. It is a liquid crystal drive method in a liquid crystal drive device. A step of generating a PWM signal as a liquid crystal drive control signal for the liquid crystal element, and a period during which the first and second switch means apply the fixed voltage to the first and second drive electrodes, respectively, are the PWM signal. Generating a first and second switching control signal based on the PWM signal, and generating the first and second switching control signals in the first and second switching control signals. Supplying the fixed voltage to the liquid crystal element by supplying the switch means.

  The present invention as described above is a system that realizes driving of a liquid crystal element for phase compensation in, for example, an optical pickup using a PWM signal. In the liquid crystal drive for phase compensation, an AC voltage of 500 Hz or more is applied to the electrodes of the liquid crystal element, and the phase compensation amount of the laser beam is changed by changing the effective voltage. Conventionally, as described above, the voltage applied to the liquid crystal element itself is controlled using the D / A converter. However, in the present invention, a fixed voltage is applied to the liquid crystal element, and the application period is It is made to change with the pulse duty of a PWM signal. That is, the effective voltage applied to the liquid crystal element is controlled by the pulse duty of the PWM signal.

According to the present invention, liquid crystal drive control can be performed without using a D / A converter by controlling the effective value of the AC drive voltage applied to the liquid crystal element using the PWM signal. By not using the D / A converter, the circuit scale of the liquid crystal driving device can be reduced, and the effects of cost reduction and power consumption reduction can be obtained.
Further, not using a D / A converter allows a circuit as a liquid crystal driving device to be easily incorporated into a digital IC, which is suitable for device design.
Further, the PWM signal is logically operated to generate the first and second switching control signals, and the PWM signal is used as a clock for the logical operation, so that it is not necessary to supply the clock by another system. Further, if the on / off state of the first and second switch means is fixed, for example, by fixing the PWM signal for generating the switching control signal to L level, the liquid crystal drive can be stopped. In other words, the function realized in the prior art by the three signals of the control signal, the reference clock, and the ON / OFF signal given to the D / A converter can be realized by one system of only the PWM signal. As a result, the number of ports required for driving the liquid crystal in the microcomputer as the system controller can be reduced, and the port resources can be used effectively.

Hereinafter, embodiments of the present invention will be described with reference to an example of a recording / reproducing apparatus (disk drive apparatus) corresponding to a mini-disc type disk.
FIG. 1 is a block diagram showing an internal configuration example of a recording / reproducing apparatus 1 as an embodiment.
The recording / reproducing apparatus 1 as this embodiment is a recording / reproducing apparatus for a mini-disc (MD) type disc that is a magneto-optical disc on which data recording is performed by a magnetic field modulation type. However, not only music mini-discs that are already in widespread use, but also high-density recording that can be used for storage of various data for computer use (also called next-generation discs). It is a playback device.

Further, the recording / reproducing apparatus 1 of this example is a device capable of data communication with an external device such as a personal computer (or network) 50, for example.
For example, the recording / reproducing apparatus 1 can function as an external storage device for the personal computer 50 by being connected to the personal computer 50 via a transmission path 51 such as a USB cable. In addition, music or various data is downloaded via a personal computer 50 or connected to the network by providing a function that can be directly connected to the network, and the disc loaded in the storage unit 2 in the recording / playback apparatus 1 is downloaded. It can also be saved.

On the other hand, the recording / reproducing apparatus 1 functions as an audio device, for example, without being connected to the personal computer 50 or the like. For example, music data input from another audio device or the like can be recorded on a disc, and music data recorded on the disc can be reproduced and output.
That is, the recording / reproducing apparatus 1 of this example is an apparatus that can be used as a general-purpose data storage device by being connected to the personal computer 50 or the like, and can also be used as an audio recording / reproducing device by itself.

Here, prior to the description of the configuration of the recording / reproducing apparatus 1 of the present example, an outline of a next-generation disk (called Hi-MD) by magneto-optical recording, which the recording / reproducing apparatus 1 supports, will be described.
First, such a next-generation disc uses a FAT (File Allocation Table) system as a file management system to record and reproduce content data such as audio data so that compatibility with current personal computers can be achieved. Is.
Further, by improving the current MD system, such as an error correction method and a modulation method, the data recording capacity is increased and the data reliability is increased.

Two types of specifications are currently being developed as recording and playback formats for next-generation discs. For the sake of explanation, these will be referred to as a first next generation MD and a second next generation MD. The first next generation MD may be referred to as “Hi-MD1”, and the second next generation MD may be referred to as “Hi-MD3”.
The first next-generation MD is a specification that uses a disk that is exactly the same as the disk used in the current MD system, and the second next-generation MD is a disk that is used in the current MD system. The external shape is the same, but by using magnetic super-resolution (MSR) technology, the recording density in the linear recording direction is increased and the recording capacity is further increased.

In the current MD system (audio MD or MD-DATA), a magneto-optical disk having a diameter of 64 mm housed in a cartridge is used as a recording medium. The disc has a thickness of 1.2 mm, and a center hole having a diameter of 11 mm is provided at the center thereof. The cartridge has a length of 68 mm, a width of 72 mm, and a thickness of 5 mm.
In the specifications of the first and second next generation MDs, the shape of the disc and the shape of the cartridge are all the same. Regarding the start position of the lead-in area, the first and second next-generation MD disks start from a radial position of 29 mm and are the same as the disks used in the current MD system.
That is, compatibility with the conventional MD system on the outer shape is ensured.

  Regarding the track pitch, in the second next generation MD, it is considered to be 1.2 μm to 1.3 μm (for example, 1.25 μm). On the other hand, the track pitch is set to 1.6 μm in the first next generation MD that uses the disk of the current MD system. The bit length of the first next generation MD is 0.44 μm / bit, and the second next generation MD is 0.16 μm / bit. The redundancy is 20.50% for both the first and second next generation MDs.

In the second generation MD specification disk, the recording capacity in the linear density direction is improved by using a magnetic super-resolution technique. In the magnetic super-resolution technology, when a predetermined temperature is reached, the cut layer becomes magnetically neutral, and the magnetic wall transferred to the recording layer is transferred, so that a minute mark can be seen in the beam spot. It is a thing using what becomes.
Specifically, in the second generation MD disc, a magnetic layer serving as a recording layer for recording information, a cutting layer, and a magnetic layer for reproducing information are stacked on a transparent substrate. The cutting layer is an exchange coupling force adjusting layer. When the temperature reaches a predetermined temperature, the cut layer becomes magnetically neutral, and the domain wall transferred to the recording layer is transferred to the reproducing magnetic layer. As a result, minute marks can be seen in the beam spot. At the time of recording, a minute mark can be generated by using a laser pulse magnetic field modulation technique.

In the second generation MD disc, the groove is deepened and the groove is sharpened to improve detrack margin, crosstalk from the land, crosstalk of the wobble signal, and focus leakage. Yes. That is, in the second next-generation MD specification disk, the groove depth is, for example, 160 nm to 180 nm, the groove inclination is, for example, 60 degrees to 70 degrees, and the groove width is, for example, 600 nm to 700 nm.
Regarding the optical specification, in the specification of the first next generation MD, the laser wavelength λ is 780 nm, and the numerical aperture NA of the objective lens of the optical head is 0.45. Similarly, in the specification of the second next generation MD, the laser wavelength λ is 780 nm, and the aperture ratio NA of the optical head is 0.45.
As the recording method, the groove recording method is adopted for both the first and second next generation MDs. That is, the groove (groove on the disk surface of the disk) is used as a track for recording and reproduction.

Furthermore, as an error correction coding system, convolutional codes based on ACIRC (Advanced Cross Interleave Reed-Solomon Code) are used in the current MD system, but in the specifications of the first and second next generation MDs, RS A block-complete code combining a Reed Solomon-Long Distance Code (LDC) and a Burst Indicator Subcode (BIS) is used.
By adopting a block completion type error correction code, a linking sector becomes unnecessary. In an error correction method combining LDC and BIS, an error location can be detected by BIS when a burst error occurs. Using this error location, erasure correction can be performed by the LDC code.

As an addressing method, a wobbled groove method is used in which a single spiral groove is formed and wobbles as address information are formed on both sides of the groove. Such an address system is called ADIP (Address in Pregroove).
The specification of ADIP is the same as that of the current MD system. However, in the current MD system, a sector of 2352 bytes is used as an access unit for recording and reproduction, whereas the first and second next generation MDs are used. In the specification, 64 Kbytes are used as a recording / reproducing access unit (recording block).
In the current MD system, a convolutional code called ACIRC is used as an error correction code, whereas in the specifications of the first and second next generation MDs, a block completion type combining LDC and BIS. Is used.
Therefore, in the specification of the first next generation MD that uses the disk of the current MD system, the handling of the ADIP signal is made different from that in the current MD system. In the second next-generation MD, the specification of the ADIP signal is changed so as to match the specification of the second next-generation MD.

  As for the modulation method, EFM (8 to 14 Modulation) is used in the current MD system, whereas RLL (1, 7) PP (RLL) is used in the specifications of the first and second next generation MDs. Run Length Limited, PP; Parity Preserve / Prohibit rmtr (repeated minimum transition run length)) (hereinafter referred to as 1-7pp modulation). Further, the data detection method is Viterbi using partial response PR (1, 2, 1) ML in the first next generation MD and using partial response PR (1, -1) ML in the second next generation MD. It is a decoding method.

  Further, the disk drive system is CLV (Constant Linear Verocity), and the linear velocity is 2.7 m / second in the first next generation MD specification, and 1.98 m in the second next generation MD specification. Per second. In the specification of the current MD system, it is 1.2 m / second for a 60-minute disk and 1.4 m / second for a 74-minute disk.

In the specification of the first next-generation MD in which a disk used in the current MD system is used as it is, the total data recording capacity per disk is about 300 Mbytes (when an 80-minute disk is used). By changing the modulation method from EFM modulation to 1-7pp modulation, the window margin is changed from 0.5 to 0.666, and in this respect, a 1.33 times higher density can be realized.
Further, since the error correction method is a combination of BIS and LDC from the ACIRC method, the data efficiency is improved, and in this respect, 1.48 times higher density can be realized. Overall, a data capacity of about twice that of the current MD system was realized using exactly the same disk.
On the other hand, in the second-generation MD specification disk using magnetic super-resolution, the recording density is further increased in the linear density direction, and the total data recording capacity is about 1 Gbyte.
The data rate is 4.4 Mbit / sec in the first next generation MD, and 9.8 Mbit / sec in the second next generation MD.

FIG. 2A shows the configuration of the first next-generation MD disk.
The first next-generation MD disc is a diverted version of the current MD system disc. That is, a dielectric film, a magnetic film, a dielectric film, and a reflective film are laminated on a transparent polycarbonate substrate. Further, a protective film is laminated thereon.
In the first next-generation MD disk, as shown in FIG. 2A, a P-TOC (pre-mastered TOC (Table Of Contents)) area is provided in the lead-in area on the inner periphery of the disk. This is a pre-mastered area as a physical structure, and control information and the like are recorded as P-TOC information by embossed pits.

The outer periphery of the lead-in area in which the P-TOC area is provided in this way is a recordable area (a magneto-optical recording area), which is a recordable / reproducible area in which a groove is formed as a guide groove for a recording track. ing. A U-TOC (user TOC) is provided on the inner periphery of the recordable area.
The U-TOC in this case has the same configuration as the U-TOC used for recording disc management information in the current MD system. For confirmation, the U-TOC is management information that can be rewritten according to the order of tracks (audio tracks / data tracks), recording, erasing, etc. in the current MD system. The start position, end position, and mode are managed for the parts constituting the track.

  An alert track is provided on the outer periphery of the U-TOC. The alert track is a warning track on which a warning sound indicating that this disc is used in the first next generation MD system and cannot be reproduced by a player of the current MD system is recorded.

FIG. 2B shows the configuration of the recordable area of the disc of the first next generation MD specification.
As shown in FIG. 2B, a U-TOC and an alert track are provided at the beginning (inner circumference side) of the recordable area. In the area including the U-TOC and the alert track, the data is modulated by EFM and recorded so that it can be reproduced by a player of the current MD system.
An area where data is modulated and recorded by 1-7pp modulation of the next generation MD1 system is provided on the outer periphery of the area where the data is modulated and recorded by the EFM modulation. The area where data is modulated and recorded by EFM modulation and the area where data is modulated and recorded by 1-7pp modulation are separated by a predetermined distance, and a guard band is provided. .
Since such a guard band is provided, it is possible to prevent a malfunction from being caused by mounting the disc of the first next generation MD specification on the current MD player.

A DDT (Disc Description Table) area and a secure track are provided at the beginning (inner circumference side) of an area where data is modulated and recorded by 1-7pp modulation. The DDT area is provided for performing a replacement sector process for a physically defective sector (recording block).
A unique ID (UID) is further recorded in the DDT area. The UID is an identification code unique to each recording medium, and is based on a predetermined random number, for example.
The secure track stores information for protecting the content.

Furthermore, a FAT (File Allocation Table) area is provided in an area where data is modulated and recorded by 1-7pp modulation. This FAT area is an area for managing data in the FAT system.
The FAT system performs data management conforming to the FAT system used in general-purpose personal computers. The FAT system performs file management by a FAT chain using a directory indicating entry points of files and directories at the root and a FAT table in which FAT cluster connection information is described.
In such a first-generation MD specification disc, the U-TOC area has information on the start position of the alert track and the start position of the area where the data is modulated by 1-7pp modulation and recorded. This information is recorded.

Here, when the first next-generation MD disc having the above-described configuration is mounted on the player of the current MD system, the U-TOC area is read, and the position of the alert track is known from the U-TOC information. The alert track is accessed and the playback of the alert track is started. In the alert track, a warning sound is recorded indicating that this disc is used in the first next generation MD system and cannot be reproduced by a player of the current MD system.
This warning sound informs that this disc cannot be used with the current MD system player.
Note that the warning sound in this case may be a warning in a language such as “cannot be used with this player”. Of course, a buzzer sound may be used.

  On the other hand, when the disc of the first next generation MD is mounted on the player compliant with the first next generation MD, the U-TOC area is read, and the data is 1-7pp modulated from the U-TOC information. The start position of the recorded area is known, and the above-mentioned DDT, secure track, and FAT area are read. As described above, in the 1-7pp modulation data area, data management is performed by the FAT system, not by the U-TOC.

Next, FIG. 3A shows a configuration of a second next-generation MD disk.
Also in this case, the disk is formed by laminating a dielectric film, a magnetic film, a dielectric film, a reflective film on a transparent polycarbonate substrate, and a protective film on the upper layer.
In the case of the second next-generation MD disc, as shown in the figure, control information is recorded in the lead-in area on the inner periphery of the disc by an ADIP signal.
In the second next-generation MD disc, the lead-in area is not provided with a P-TOC by embossed pits, and instead, control information by an ADIP signal is used. The recordable area starts from the outer periphery of the lead-in area, and is a recordable / reproducible area in which a groove is formed as a guide groove for a recording track. In this recordable area, data is modulated and recorded by the 1-7 pp modulation method.

Whether a certain disk is the first next generation MD1 or the second next generation MD can be determined from, for example, lead-in information.
That is, if a P-TOC due to an embossed pit is detected in the lead-in, it can be determined that the disc is the current MD or the first next-generation MD. If control information based on the ADIP signal is detected in the lead-in and the P-TOC due to the embossed pit is not detected, it can be determined that the second next-generation MD.
Note that the determination of the first and second next-generation MDs is not limited to such a method. It is also possible to discriminate from the phase of the tracking error signal between on-track and off-track. Of course, a detection hole for disc identification may be provided in the cartridge or the like.

As the configuration of the recordable area of the disc of the second next generation MD specification, as shown in FIG. 3B, an area where data is modulated and recorded by the 1-7pp modulation method is formed. A DDT area and a secure track are provided at the beginning (inner circumference side) of an area where data is modulated and recorded by the 1-7pp modulation method.
Also in this case, the DDT area is an area for performing a replacement sector process on a physically defective sector (recording block). The UID described above is recorded in the DDT area. Further, in this case, information for protecting the content is stored in the secure track.
A FAT area is provided in an area where data is modulated and recorded by 1-7pp modulation. The FAT area is an area for managing data in the FAT system. The FAT system performs data management conforming to the FAT system used in general-purpose personal computers.

In the second next-generation MD disc, no U-TOC area is provided as can be seen from the figure. That is, the second next-generation MD disc is assumed to be used only by a player compliant with the next-generation MD.
In a player compliant with the next-generation MD, when a second next-generation MD disc is loaded, the DDT, secure track, and FAT area at a predetermined position are read, and data management is performed using the FAT system. It will be.

In order to cope with the next generation disc as described above, the recording / reproducing apparatus 1 of this example shown in FIG. 1 includes a storage unit configured as shown in FIG. Recording / playback is assumed.
In FIG. 4, in the storage unit 2, the loaded disk 40 is rotationally driven by the spindle motor 29 by the CLV method. The disc 40 is irradiated with laser light from the optical head 19 during recording / reproduction.
In this case, as the disk 40, there is a possibility that the current MD specification disk, the first next generation MD specification disk, and the second next generation MD specification disk may be mounted. Therefore, the linear velocity differs depending on these discs.
For this reason, the spindle motor 29 is rotated in accordance with different linear velocities corresponding to the loaded disks 40.

  The optical head 19 performs a high level laser output for heating the recording track to the Curie temperature during recording, and a relatively low level laser output for detecting data from reflected light by the magnetic Kerr effect during reproduction. . For this reason, the optical head 19 is equipped with a laser diode as laser output means, an optical system including a polarization beam splitter, an objective lens, and the like, and a detector for detecting reflected light. The objective lens provided in the optical head 19 is held so as to be displaceable in the radial direction of the disk and in the direction of contacting and separating from the disk, for example, by a biaxial mechanism.

An example of the configuration of the optical system in the optical head 19 is shown in FIG.
In the optical head 19, a laser diode 41, which is a light source for emitting laser light, is provided, an irradiation light path for irradiating the signal recording surface of the disk 40 with the laser light emitted from the laser diode 41, and disk 40 signal recording. An optical system that forms a return optical path through which return light reflected from the surface passes, and a photodetector 51 that detects the amount of return light guided by the return optical path of the optical system.
The optical system includes an As correction plate 42, a grating 43, a beam splitter 44, a collimator lens 46, a mirror 47, an objective lens 48, a Wollaston prism 49, and a multi lens 50. Further, a liquid crystal element 45 for phase compensation of laser light is disposed between the beam splitter 44 and the collimator lens 46.
In the liquid crystal element 45, the orientation angle of the liquid crystal sealed is controlled by the drive voltage applied to the drive electrode, and thereby the phase of the laser light is adjusted.

In this optical system, the laser light emitted from the laser diode 41 during reproduction passes through the As correction plate 42 and the grating 43 and enters the beam splitter 44. The beam splitter 44 transmits the laser light and makes it incident on the liquid crystal element 45. The liquid crystal element 45 performs phase adjustment according to the type of the disk 40. The laser light that has passed through the liquid crystal element 45 is converted into parallel light by the collimator lens 46, reflected by the mirror 47, condensed by the objective lens 48, and applied to the signal recording surface of the disk 40.
The return light reflected from the signal recording surface of the disk 40 passes through the objective lens 48, mirror 47, collimator lens 46, and liquid crystal element 45, is reflected by the beam splitter 44 toward the photodetector 51, and is divided by the Wollaston prism 49. Then, the light is condensed by the multi lens 50 and is incident on the light receiving surface on the photodetector 51.
A plurality of, for example, two, four-divided light receiving surfaces each having a four-divided light receiving region are provided on the photodetector 51, and a received light amount signal detected by the photodetector 51 is supplied to the RF amplifier 21 shown in FIG.

In FIG. 4, the magnetic head 18 is disposed at a position facing the optical head 19 with the disk 40 interposed therebetween. The magnetic head 18 performs an operation of applying a magnetic field modulated by the recording data to the disk 40.
Although not shown, a sled motor and a sled mechanism are provided to move the entire optical head 19 and the magnetic head 18 in the radial direction of the disk.
In the case of the second next-generation MD disk, the optical head 19 and the magnetic head 18 can form minute marks by performing pulse drive magnetic field modulation. In the case of the current MD disc or the first next-generation MD disc, the magnetic field modulation method is used.

  In addition to the recording / reproducing head system using the optical head 19 and the magnetic head 18 and the disk rotation driving system using the spindle motor 29, the storage unit 2 in FIG. 4 includes a recording processing system, a reproducing processing system, a servo system, and the like.

In the recording processing system, in the case of the disc of the current MD system, at the time of recording an audio track, error correction coding is performed by ACIRC, data is recorded by being modulated by EFM, and the first and second next generations. In the case of MD, there is provided a portion for performing error correction coding by a system combining BIS and LDC, and modulating and recording by 1-7pp modulation.
The playback processing system uses EFM demodulation and error correction processing by ACIRC during playback of the current MD system disc, and partial response and Viterbi decoding during playback of the first and second next generation MD system discs. A portion for performing 1-7pp demodulation based on data detection and error correction processing by BIS and LDC is provided.
Further, a part for decoding an address based on an ADIP signal of the current MD system or the first next generation MD and a part for decoding an ADIP signal of the second next generation MD are provided.

Information detected as reflected light by laser irradiation of the optical head 19 on the disk 40 (photocurrent obtained by detecting the laser reflected light with a photodetector) is supplied to the RF amplifier 21.
The RF amplifier 21 performs current-voltage conversion, amplification, matrix calculation, and the like on the input detection information, and reproduces a reproduction RF signal, a tracking error signal TE, a focus error signal FE, and groove information (track on the disk 40) as reproduction information. ADIP information recorded by wobbling) is extracted.

When reproducing the disc of the current MD system, the reproduced RF signal obtained by the RF amplifier is processed by the EFM demodulator 24 and the ACIRC decoder 25.
That is, the reproduced RF signal is binarized by the EFM demodulator 24 to be converted into an EFM signal sequence, EFM demodulated, and further subjected to error correction and deinterleave processing by the ACIRC decoder 25. That is, at this time, the ATRAC compressed data state is entered.
At the time of reproducing the disk of the current MD system, the selector 26 is selected on the B contact side, and the demodulated ATRAC compressed data is output as reproduced data from the disk 40.

On the other hand, when reproducing the first and second next-generation MD discs, the reproduction RF signal obtained by the RF amplifier 21 is processed by the RLL (1-7) PP demodulator 22 and the RS-LDC decoder 25. . That is, the reproduced RF signal is detected by the RLL (1-7) PP demodulator 22 by means of data detection using PR (1, 2, 1) ML or PR (1, -1) ML and Viterbi decoding. ) Reproduced data as a code string is obtained, and RLL (1-7) demodulation processing is performed on this RLL (1-7) code string. Further, the RS-LDC decoder 23 performs error correction and deinterleave processing.
When the first and second next-generation MD discs are reproduced, the selector 26 is selected on the A contact side, and the demodulated data is output as reproduced data from the disc 40.

The tracking error signal and focus error signal output from the RF amplifier 21 are supplied to the servo circuit 27, and the groove information is supplied to the ADIP demodulator 30.
The ADIP demodulator 30 performs band limitation on the groove information by a bandpass filter to extract a wobble component, and then performs FM demodulation and biphase demodulation to demodulate the ADIP signal.
The thus-demodulated ADIP address, which is absolute address information on the disk, is supplied to the system controller 8 shown in FIG. The system controller 8 executes necessary control processing based on the ADIP address.
The groove information is supplied to the servo circuit 27 for spindle servo control.

The servo circuit 27 generates a spindle error signal for CLV servo control, for example, based on an error signal obtained by integrating the phase error with the reproduction clock (PLL clock at the time of decoding) with respect to the groove information.
Further, the servo circuit 27 performs various servo control signals (tracking control signals) based on a spindle error signal, a tracking error signal supplied from the RF amplifier 21, a focus error signal, a track jump command, an access command, or the like from the system controller 8. , A focus control signal, a thread control signal, a spindle control signal, etc.) are generated and output to the motor driver 28. That is, various servo control signals are generated by performing necessary processing such as phase compensation processing, gain processing, and target value setting processing on the servo error signal and command.

The motor driver 28 generates a required servo drive signal based on the servo control signal supplied from the servo circuit 27. The servo drive signal here includes a biaxial drive signal for driving the biaxial mechanism (two types of focus direction and tracking direction), a sled motor drive signal for driving the sled mechanism, and a spindle motor drive signal for driving the spindle motor 29. It becomes.
With such a servo drive signal, focus control and tracking control for the disk 40 and CLV control for the spindle motor 29 are performed.

When recording audio data on the disc of the current MD system, the selector 16 is connected to the B contact, so that the ACIRC encoder 14 and the EFM modulator 15 function.
In this case, the compressed data supplied from the cache memory 3 shown in FIG. 1 as recording data is subjected to interleaving and error correction code addition by the ACIRC encoder 14 and then EFM modulation by the EFM modulation unit 15.
The EFM modulation data is supplied to the magnetic head driver 17 via the selector 16, and the magnetic head 18 applies a magnetic field to the disk 40 based on the EFM modulation data, thereby recording an audio track.

On the other hand, when data is recorded on the first next generation MD or the second next generation MD2 disc, the selector 16 is connected to the A contact, and the RS-LDC encoder 12 and the RLL (1-7) PP modulation unit 13 are connected. Will work. In this case, high-density data from the cache memory 3 is subjected to interleaving and RS-LDC error correction code addition by the RS-LDC encoder 12, and then RLL (1-7) PP modulation unit 13 performs RLL (1 -7) Modulation is performed.
Then, the recording data as the RLL (1-7) code string is supplied to the magnetic head driver 17 via the selector 16, and the magnetic head 18 applies a magnetic field based on the modulation data to the disk 40, thereby data tracks. Is recorded.

The laser driver / APC 20 causes the laser diode to perform a laser emission operation during reproduction and recording as described above, but also performs a so-called APC (Automatic Laser Power Control) operation.
That is, although not shown, a detector for laser power monitoring is provided in the optical head 19, and the monitor signal is fed back to the laser driver / APC 20. The laser driver / APC 20 compares the current laser power obtained as the monitor signal with the set laser power and reflects the error in the laser drive signal, so that the laser power output from the laser diode is , It is controlled to stabilize at the set value.
As the laser power, values as reproduction laser power and recording laser power are set by the system controller 8 in a register in the laser driver / APC 20.

  The liquid crystal drive circuit 31 is a circuit that is driven by applying a drive voltage to the liquid crystal element 45 for phase compensation of laser light provided in the optical head 19 as shown in FIG. Although the liquid crystal drive circuit 31 will be described later, a drive voltage is applied to the liquid crystal element 45 in accordance with a PWM signal from the system controller 8.

  Each operation of the storage unit 2 (access, various servos, data writing, data reading, etc.) is executed based on an instruction from the system controller 8 shown in FIG.

Returning to FIG. 1, the overall configuration of the recording / reproducing apparatus 1 of this example will be described.
In FIG. 1, a cache memory 3 is a cache memory that buffers data recorded on the disk 40 by the storage unit 2 having the above configuration or data read from the disk 40 by the storage unit 2, for example, D- It consists of RAM.
Writing / reading data to / from the cache memory 3 is controlled by a task activated in the system controller (CPU) 8.

  The USB interface 4 performs processing for data transmission when connected to the personal computer 50 through a transmission path 51 as a USB cable, for example.

The input / output processing unit 5 performs processing for input / output of recording / playback data, for example, when the recording / playback apparatus 1 functions alone as an audio device.
The input / output processing unit 5 includes, for example, an analog audio signal input unit such as a line input circuit / microphone input circuit, an A / D converter, and a digital audio data input unit as an input system. It also includes an ATRAC compression encoder / decoder. The ATRAC compression encoder / decoder is a circuit for executing compression / decompression processing of audio data by the ATRAC system. Of course, the recording / reproducing apparatus of the present embodiment may adopt a configuration capable of recording / reproducing compressed audio data in other formats such as MP3. In this case, these compressed audio data An encoder / decoder corresponding to the format may be provided.
In this embodiment, video data is not limited to a format that can be recorded / reproduced. For example, MPEG4 can be considered. The input / output processing unit 5 may be provided with an encoder / decoder corresponding to such a format.
Further, the input / output processing unit 5 includes an analog audio signal output unit such as a digital audio data output unit and a D / A converter and a line output circuit / headphone output circuit as an output system.

  In this case, the input / output processing unit 5 includes an encryption processing unit (not shown). In the encryption processing unit, for example, the AV data to be recorded on the disk is encrypted by a predetermined algorithm. For example, when the AV data read from the disk is encrypted, a decryption process for decryption is executed as necessary.

  Audio data is recorded on the disc as processing via the input / output processing unit 5 when, for example, digital audio data (or an analog audio signal) is input to the input / output processing unit 5 as an input TIN. Input linear PCM digital audio data or linear PCM audio data obtained by analog audio signal input and converted by an A / D converter is ATRAC compression encoded as necessary and stored in the cache memory 3. . Then, the data is read from the cache memory 3 and transferred to the storage unit 2 at a predetermined timing (data unit corresponding to an ADIP cluster). In the storage unit 2, the transferred compressed data is modulated by a predetermined modulation method and recorded on the disk.

  When mini-disc type audio data is reproduced from the disk 40, the storage unit 2 demodulates the reproduced data to the ATRAC compressed data state and transfers it to the cache memory 3. Then, it is read from the cache memory 3 and transferred to the input / output processing unit 5. The input / output processing unit 5 performs ATRAC compression decoding on the supplied compressed audio data to obtain linear PCM audio data, which is output from the digital audio data output unit. Alternatively, line output / headphone output is performed as an analog audio signal by a D / A converter.

The system controller 8 performs overall control in the recording / reproducing apparatus 1 and communication control with the connected personal computer 50.
The ROM 8a stores an operation program for the system controller 8, fixed parameters, and the like.
The RAM 8b is used as a work area by the system controller 8 and is a storage area for various necessary information.
For example, various management information and special information read from the disk 40 by the storage unit 2, for example, the management information of the music track such as the above-described P-TOC data, U-TOC data, FAT data, etc. are taken into the cache memory 3. However, the system controller 8 takes necessary information out of the management information into the RAM 8b for processing.
The cache management memory 9 is composed of, for example, an S-RAM, and stores information for managing the state of the cache memory 3. The system controller 8 controls data cache processing while referring to the cache management memory 9.

The display unit 6 displays various information to be presented to the user based on the control of the system controller 8. For example, character data such as operation state, mode state, name of music, track number, time information, and other information are displayed.
In the operation unit 7, various operation buttons, a jog dial, and the like are formed as various operators for user operations. The user gives a required operation instruction to the recording / reproducing apparatus 1 by operating the operation unit 7. The system controller 8 performs a predetermined control process based on the operation information input by the operation unit 7.

Note that the configuration of the recording / reproducing apparatus 1 described so far is merely an example. For example, the input / output processing unit 5 may include not only audio data but also an input / output processing system corresponding to video data.
Further, the connection with the personal computer 50 is not USB, but another external interface such as IEEE 1394 may be used.
Further, as the operation unit 7, it is possible to provide an operation element similar to that illustrated above on the remote controller.

In such a recording / reproducing apparatus, as described above, the liquid crystal driving circuit 31 for driving the liquid crystal element 45 disposed in the optical head 19 will be described below.
The liquid crystal drive circuit 31 is configured as shown in FIG.
In FIG. 6, a liquid crystal element 45 is a liquid crystal element arranged on the laser beam path in the optical head 19 as shown in FIG. The liquid crystal element 45 is formed by enclosing a liquid crystal material between two glass substrates, and by applying a potential difference between transparent electrodes (drive electrodes) formed on the glass substrates on both sides of the liquid crystal element 45, The orientation angle is changed. In the figure, terminals 45x and 45y indicate drive electrodes, respectively.
The potential difference (Y−X) between the voltages X and Y applied to the drive electrodes 45x and 45y becomes the drive voltage applied to the liquid crystal, and the liquid crystal drive circuit 31 applies an AC voltage of 500 Hz or more as the drive voltage. The phase compensation amount of the laser beam is changed by changing the effective voltage applied at that time.

The liquid crystal drive circuit 31 includes a latch circuit (D flip-flop) 63, AND gates 64 and 65, switch elements 66 and 67, and resistors R1 and R2.
A fixed voltage Vcc1 is applied to the terminal 61. For example, Vcc1 = 3V.
A PWM signal as a liquid crystal drive control signal is input from the system controller 8 to the terminal 62. This PWM signal is input to AND gates 64 and 65. The PWM signal is also input to the clock input unit of the latch circuit 63.
The latch circuit 63 is supplied with a voltage of about 2 V, for example, as the operating voltage Vcc2. The latch circuit 63 latches the inverted Q output as a data input and the PWM signal as a clock. That is, latching is performed at the carrier frequency timing of the PWM signal. The Q output as the latch output is supplied to the AND gate 64, and the inverted Q output is supplied to the AND gate 65.
The latch circuit 63 and the AND gates 64 and 65 perform logical operation processing of the PWM signal, thereby generating switch control signals X ′ and Y ′ for the switch elements 66 and 67.

Between the fixed voltage Vcc1 and the ground, a switch element 66 made of a resistor R1 and an N-channel MOS-FET is connected. Similarly to the resistor R2, a switch element 67 made of an N-channel MOS-FET is connected. A connection point between the resistor R1 and the switch element 116 is a voltage application point to the drive electrode 45x of the liquid crystal element 45, and a connection point between the resistor R2 and the switch element 67 is a voltage application point to the drive electrode 45y.
That is, the voltage Vcc1 is applied to the drive electrode 45x via the resistor R1 (voltage X) while the switch element 66 is turned off, and the voltage Vcc1 is applied via the resistor R2 while the switch element 67 is turned off. Applied to the drive electrode 45y (voltage Y).
The switch elements 66 and 67 are turned on / off by switch control signals X ′ and Y ′ from the AND gates 64 and 65, respectively.

The operation of the liquid crystal drive circuit 31 will be described with reference to FIGS.
For example, the system controller 8 generates a PWM signal based on a 10-bit value using the clock CKpwm of FIG. The clock CKpwm is, for example, 1.41 MHz (= 32 fs, fs is 44.1 KHz).
Although the generated PWM signal is shown in FIG. 7B, it is 10 bits, so one cycle of the PWM signal repetition cycle is the clock CKpwm · 2 ¹⁰ . The frequency of the PWM signal is 1.38 KHz.
For example, when a PWM signal as shown in FIG. 7B is supplied to the liquid crystal drive circuit 31, the switch control signals X ′ and Y ′ generated by the logical operation processing of the latch circuit 63 and the AND gates 64 and 65 are shown in FIG. (C) As in (d).
Then, the switch element 66 is turned off while the switch control signal X ′ is H (= Vcc2), and during that time, the voltage Vcc1 is applied as the voltage X to the drive electrode 45x, and the switch control signal Y ′ is H (= Vcc2). During this period, the switch element 67 is turned off, and during that time, the voltage Vcc1 is applied as the voltage Y to the drive electrode 45y. Therefore, the drive voltage (Y-X) of the liquid crystal element 45 is as shown in FIG. One cycle of the repetition cycle of liquid crystal driving by this driving voltage (Y-X) is a clock CKpwm · 2 ¹⁰ · 2. The frequency of the AC drive voltage for driving the liquid crystal is 689 Hz.
Since the driving voltage is integrated by the responsiveness of the liquid crystal element 45, an AC effective voltage represented by Vcc1 × √ (1-duty) is applied to the liquid crystal element 45. Note that the duty is the value of the pulse duty of the PWM signal.

As can be seen from this, in order to vary the drive voltage for the liquid crystal element 45, the system controller 8 may change the pulse duty of the PWM signal. In other words, a PWM signal corresponding to a 10-bit control value may be generated.
As shown by an arrow A in FIG. 7B, the system controller 8 changes the pulse duty (that is, performs PWM modulation).
For example, FIG. 8B shows a case where the pulse duty of the PWM signal is reduced, and as a result, switch control signals X ′ and Y ′ as shown in FIGS. 8C and 8D are generated and applied to the liquid crystal element 45. The drive voltage (Y-X) is as shown in FIG. In this case, the effective voltage applied to the liquid crystal element 45 is smaller than in the case of FIG.
FIG. 9B shows a case where the pulse duty of the PWM signal is maximized. As a result, switch control signals X ′ and Y ′ as shown in FIGS. The applied drive voltage (Y-X) is as shown in FIG. In this case, the maximum value as the effective voltage is applied to the liquid crystal element 45.
Thus, the drive voltage of the liquid crystal element 45 is controlled by the PWM signal, and the orientation angle is controlled. That is, the system controller 8 only needs to generate a PWM signal indicating a predetermined phase compensation amount according to the type of the loaded disk 40, for example. For example, the phase compensation amount is adjusted according to the depth of the groove. In this case, the disk 40 is an audio MD, MD-DATA, or the first next generation MD, and the disk 40 is What is necessary is just to generate | occur | produce the PWM signal from which pulse duty differs with the case of 2nd next generation MD.
Of course, various phase compensation conditions are assumed in addition to the disc type, and therefore, a PWM signal obtained by pulse width modulation of a control value corresponding to the conditions may be generated.
The liquid crystal element 45 can also be used for laser spot shaping, polarization adjustment, optical path branching, etc. In these cases, it can also be driven by a PWM signal.

  By the way, the fact that the liquid crystal element 45 is always driven by alternating current promotes the deterioration of the liquid crystal element 45, and therefore it is preferable to stop the drive from applying the alternating voltage when unnecessary. In that case, the system controller 8 may give an L level signal to the terminal 62 of the liquid crystal drive circuit 31. That is, the output of the PWM signal is stopped and the signal is set to the L level. Then, the switch control signals X ′ and Y ′ become L level, and the switch elements 66 and 67 are turned on. Accordingly, the drive electrodes 45x and 45y of the liquid crystal element 45 are both at the same potential at the ground level, that is, the liquid crystal drive is stopped.

As described above, in this embodiment, liquid crystal drive control can be performed without using a D / A converter by controlling the effective value of the AC drive voltage applied to the liquid crystal element by the PWM signal. By not using the D / A converter, the circuit scale of the liquid crystal drive circuit 31 can be reduced, and the effects such as cost reduction and power consumption reduction can be obtained.
Further, not using the D / A converter allows the liquid crystal drive circuit 31 to be easily incorporated into the digital IC, which is suitable for device design.
Further, the PWM signal is logically operated to generate the first and second switching control signals, and the PWM signal is used as a clock for the logical operation, so that it is not necessary to supply the clock by another system. Further, if the switching elements 66 and 67 are fixed to the on state by fixing the PWM signal for generating the switching control signal to, for example, the L level, the liquid crystal driving can be stopped. In other words, as previously described with reference to FIG. 10, the function realized by the three systems of signals, that is, the control signal given to the D / A converter, the reference clock, and the ON / OFF signal, can be realized by one system of only the PWM signal. . As a result, the number of ports required for driving the liquid crystal in the microcomputer as the system controller 8 can be reduced, and port resources can be used effectively.

For example, various modifications of the liquid crystal driving circuit 31 of FIG. 6 are conceivable. The logic circuit configuration is not limited to the configuration of the latch circuit 63 and the AND gates 64 and 65 shown in the figure. Further, other switch elements such as P-channel MOS-FETs may be used as the switch elements. In this case, it goes without saying that the logic circuit configuration for generating the switch control signals X ′ and Y ′ is changed accordingly. .
The PWM signal frequency described above and the frequency of the liquid crystal driving AC voltage corresponding thereto are examples.

  In this example, a recording / reproducing apparatus in a mini-disc system has been described. However, the present invention can also be applied to other optical disc recording / reproducing systems such as CDs, DVDs (Digital Versatile Discs), and Blu-ray discs. Furthermore, the liquid crystal driving device and the liquid crystal driving method can be widely applied to various devices using liquid crystal elements.

It is a block diagram of the recording / reproducing apparatus of embodiment of this invention. It is explanatory drawing of the disk with which the recording / reproducing apparatus of embodiment respond | corresponds. It is explanatory drawing of the disk with which the recording / reproducing apparatus of embodiment respond | corresponds. It is a block diagram of the storage part of the recording / reproducing apparatus of embodiment. It is explanatory drawing of the optical system of the optical head of embodiment. It is explanatory drawing of the structure of the liquid crystal drive circuit of embodiment. It is explanatory drawing of the operation | movement waveform of the liquid crystal drive circuit of embodiment. It is explanatory drawing of the operation | movement waveform of the liquid crystal drive circuit of embodiment. It is explanatory drawing of the operation | movement waveform of the liquid crystal drive circuit of embodiment. It is explanatory drawing of the conventional liquid crystal drive circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Recording / reproducing apparatus, 2 Storage part, 3 Cache memory, 4 USB interface, 5 Input / output processing part, 6 Display part, 7 Operation part, 8 System controller, 8a ROM, 8b RAM, 9 Cache management memory, 19 Optical head, 31 Liquid crystal drive circuit, 45 Liquid crystal element, 63 Latch circuit, 64, 65 AND gate, 66, 67 Switch element

Claims (6)

PWM signal generating means for generating a PWM signal as a liquid crystal drive control signal for the liquid crystal element;
First and second switch means for alternately applying a fixed voltage to the first and second drive electrodes of the liquid crystal element by a switching operation;
Based on the PWM signal, the period in which the first and second switch means apply the fixed voltage to the first and second drive electrodes, respectively, is a period according to the pulse duty of the PWM signal. Switch control means for generating first and second switching control signals for the first and second switch means;
A liquid crystal driving device comprising:   2. The switch control means according to claim 1, wherein the switch control means performs a logical operation on the PWM signal to generate the first and second switching control signals, and uses the PWM signal as a clock for the logical operation. The liquid crystal driving device described. In a disk drive device that records or reproduces information by irradiating a disk recording medium with laser light,
An optical pickup means for outputting the laser beam and having a liquid crystal element on the path of the laser beam;
PWM signal generating means for generating a PWM signal as a liquid crystal drive control signal for the liquid crystal element;
First and second switch means for alternately applying a fixed voltage to the first and second drive electrodes of the liquid crystal element by a switching operation;
Based on the PWM signal, the period in which the first and second switch means apply the fixed voltage to the first and second drive electrodes, respectively, is a period according to the pulse duty of the PWM signal, Switch control means for generating first and second switching control signals for the first and second switch means;
A disk drive device comprising:   4. The switch control means according to claim 3, wherein the switch control means performs a logical operation on the PWM signal to generate the first and second switching control signals, and uses the PWM signal as a clock for the logical operation. The disk drive device described.   4. The disk drive device according to claim 3, wherein the PWM signal generating means generates a PWM signal having a pulse duty changed according to a type of a disk to be recorded or reproduced. As a liquid crystal driving method in a liquid crystal driving device including first and second switch means for applying a fixed voltage to the first and second driving electrodes of the liquid crystal element,
Generating a PWM signal as a liquid crystal drive control signal for the liquid crystal element;
A period in which the first and second switch means apply the fixed voltage to the first and second drive electrodes, respectively, is a period according to the pulse duty of the PWM signal. Generating a switching control signal based on the PWM signal;
Applying the fixed voltage to the liquid crystal element by supplying the first and second switching control signals to the first and second switch means;
A liquid crystal driving method comprising:

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