JPH11175982A - Disk driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quicken a process for switching laser light sources by maintaining a focused state just before while holdingly outputting a focus driving signal immadiately before executing the switching of the laser sources and turning a focus servo on in the maintained focused state. SOLUTION: A system controller 10 performing the switching operation from a state in which a laser diode 4a or 4b of one side is operated and a focus servo is set to the laser diode 4b or 4a of other side makes a servo processor 14 turn a focus servo loop off and also makes the processor perform a switching operation after maintain the focused state of an objective lens 2 immadiately before the switching operation and next turn the focus servo loop on. Thus, since it is unnecessitated to perform a focus search newly after the switching of the laser diodes 4a, 4b, the time required for the process switching the laser diodes is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk drive device capable of performing a reproducing operation or a recording operation for a recording medium such as an optical disk.

[0002]

2. Description of the Related Art As an optical disk recording medium, so-called C
CD type discs such as D-DA (Compact Disc-Digital Audio) and CD-ROM, and DVD (Digital Versatile) suitable for multimedia applications
Discs called Disc / Digital Video Disc) have been developed. Also, as the above-mentioned CD type disc,
A write-once disc called a CD-R (compact disc-recordable) has also been developed. In a disk drive device corresponding to these optical disks, a disk rotated by a spindle motor is irradiated with laser light from an optical pickup to a track on the disk, and reflected light is detected to detect data. Data is recorded by performing reading or irradiating a laser beam modulated by recording data.

In order to perform a recording or reproducing operation using a laser beam, the spot of the laser beam must be kept in focus on the recording surface of the disc. A focus servo mechanism for controlling a focus state by moving an objective lens, which is an end, in a direction approaching and separating from the disk is mounted.
The focus servo mechanism generally includes a two-axis mechanism having a focus coil for moving the objective lens in the direction of moving toward and away from the disk and a tracking coil for moving the object lens in the radial direction of the disk, and a focusing mechanism based on light reflected from the disk. An error signal (that is, a signal of the amount of deviation from the in-focus state) is generated, a focus drive signal is generated based on the focus error signal, and the focus servo circuit system is applied to the focus coil of the two-axis mechanism. I have. That is, a focus servo mechanism is configured as a feedback control system.

Also, as is well known, the range in which a focus state can be drawn based on a focus error signal is a very narrow range in which an S-shaped curve is observed as a focus error signal. Therefore, in order to execute the focus servo satisfactorily, an operation generally called a focus search is required as an operation for turning on the focus servo loop. In the focus search operation, a focus drive signal is applied to the focus coil so that the objective lens is forcibly moved within the focus stroke range. At this time, when the focus error signal is observed, an S-shaped curve is observed when the position of the objective lens is within a certain range. That S
The focus servo is turned on at a timing (or zero cross timing) at which a linear region of the character curve is obtained.

[0005]

By the way, as a new disk is developed, it is desired to provide a disk drive device having compatibility with an old disk. With regard to DVDs, it is desired to develop a disk drive device that supports both CDs and DVDs.
However, a dedicated pickup device (or a part of an optical type in the pickup device) is required for each of the CD and the DVD due to a difference in the layer structure of the disc. Then, depending on whether the loaded disk is a CD or a DVD, the dedicated portion is switched and used. However, mounting a plurality of pickup devices and a plurality of optical systems is disadvantageous in reducing the size and cost of the device, and therefore, a technology has been developed to allow the optical system and the like to be used as much as possible. However, there is a laser light source such as a laser diode as one of the parts that is difficult to use for two purposes. This is due to the different laser wavelengths that various disks can cope with favorably. Specifically, CD-R, CD
-If the compatible device is compatible with ROM (CD-DA) and DVD, the wavelength λ = 78 mainly due to the characteristics of CD-R.
Both a 0 nm laser light source and a λ = 650 nm laser light source will be required.

Here, CD-ROM, DVD and CD-ROM
The structure of R and the wavelength dependence of the laser light due to the structure will be described with reference to FIG. FIGS. 7 (a), 7 (b) and 7 (c) show CD-
The layer structure is shown as a cross section of a ROM, a CD-R, or a DVD. As shown in each figure, CD, CD-R, D
In both VDs, the thickness of the entire disk is 1.2 mm.
Although not shown, the disk is 12 cm in diameter.

The CD-ROM 100 shown in FIG. 7A has a transparent synthetic resin such as a transparent polycarbonate resin, a polyvinyl chloride resin, or an acrylic resin having a high light transmittance and having mechanical resistance or chemical resistance. A disk substrate (transparent layer) 101 is formed of the material. The pits are transferred to one main surface of the disk substrate 101 by a stamper incorporated in a molding die, and a signal surface 102 is formed. The pits on the signal surface 102 are formed on the disc substrate 101 as coded small holes having different circumferential lengths corresponding to predetermined information signals, and constitute recording tracks.

On the surface of the disk substrate 101 on which the signal surface 102 is formed, aluminum or the like having a high light reflectivity is deposited to form a reflective layer 103, and a protective layer 104 is further entirely coated to form a CD. -ROM 100 is formed. Laser light from the disk drive device is incident on the CD-ROM 100 from the disk surface 105 side, and the information recorded on the signal surface 102 is detected from the reflected light.

The CD-R 110 shown in FIG. 7B is a medium on which additional recording is possible and has the same physical characteristics (diameter, weight, thickness) and capacity as the CD-ROM 100.
Compared to OM100, small-volume production can be performed economically,
Because of its long life, it is suitable for data storage.

This CD-R 110 also has a disc surface 11
Transparent disk substrate (polycarbonate) viewed from 6 side
111 are arranged. And such a disk substrate 11
On top of this, a CD-R 110 is formed by sequentially laminating an organic dye layer 114, a gold reflective layer 113, and a protective layer 115. The CD-R 110 has a groove (groove) serving as a laser light irradiation guide, and the organic dye layer 112 covers the groove. Then, the heat of the irradiated laser beam causes the organic dye layer 112 and the polycarbonate disk substrate 111 to react with each other to form pits corresponding to information signals, thereby forming the signal surface 112 on which actual data is recorded. Is done.

Similarly, in the DVD of FIG. 7C, a disk substrate 121 is arranged from the disk surface 128 side, and a signal surface is formed on the other surface side of the disk substrate 121. In the case of a DVD, two types, a single-layer disk having one signal surface and a dual-layer disk having two signal surfaces, have been proposed. FIG. 2 shows an example of a disk. That is, the first signal surface 122 and the first
The first reflective layer 123 corresponding to the signal surface 122 forms a first layer data recording surface. The second signal surface 124 and the second reflective layer 125 corresponding to the second signal surface 124 form a second layer data recording surface. Second reflective layer 125
Is formed as an adhesive surface 126, through which the dummy plate 12
7 are adhered.

The first reflection layer 123 is a semi-transparent film, and is formed so as to reflect a certain ratio of laser light. As a result, if the laser beam is focused on the first signal surface 122, the first signal surface 122
When the laser light is focused on the second signal surface 124, the laser light passes through the first reflection layer 123 and is focused on the second signal surface 124. The signal recorded on the second signal surface 124 can be read from the light reflected by the second reflection layer 125. 1
In the case of a two-layer disc, the signal surface and the reflection layer
4 and the second reflection layer 125.

As can be seen from FIGS. 7 (a), 7 (b) and 7 (c), the signal surfaces 102 and 112 of the CD-ROM 100 and the CD-R 110 are almost equal to the thickness of the disk when viewed from the disk surfaces 105 and 116. (A signal surface 102, 1 to be focused on the laser spot at a position approximately 1.2 mm from the disk surface 105, 116 side)
12). On the other hand, the signal surface 122 (1
24) is formed at a position near the center of the thickness of the disk when viewed from the disk surface 128 side (the signal surface 122 (124) for focusing the laser spot at a position approximately 0.6 mm from the disk surface 128 side). As described above, the recording density of the pits formed on the signal surface 122 (124) is also lower than that of the CD-ROM 100 and the CD-R.
The density is higher than 110.

Due to such a difference, when a DVD reproducing apparatus is considered, a laser beam for reproduction has a wavelength of 650.
nm or less, and the objective lens has an aperture (NA) of about 0.6, and the disk surface 1
It is recommended that an optimized pickup be used to focus the laser spot approximately 0.6 mm from the 28 side.

Considering such a pickup, C
Considering D / DVD compatible machine, wavelength is 650nm
With the following laser light, the signal surface 1 of the CD-ROM 100
02 is not impossible to read. Also CD
-About 1.2 mm from the disk surface 105 side of the ROM 100
It is also possible to focus the laser spot at the position. For example, it has been generally accepted that a disk drive device corresponding to a CD type disk employs a laser beam having a wavelength of about 780 nm. R
Reproduction of the OM 100 is possible.

However, considering CD-R110, CD-R110
-R110 has an organic dye layer 114 having wavelength dependency, and accurate data reproduction cannot be performed when a laser beam of 650 nm or less is used. That is, in the CD-R 110, the light absorption of the irradiated laser light of 650 nm or less in the organic dye layer 114 increases, the reflectance decreases, and the modulation degree of the laser light due to the pits on the signal surface 112 decreases. I do. When data is recorded, pits are formed with an absorptance and reflectivity suitable for a laser beam having a wavelength of 780 nm. Therefore, a sufficient degree of modulation can be obtained even if this data is read with a laser beam having another wavelength. It has the characteristic that it cannot be performed.

From the above, the CD-ROM 100, C
When considering a disk drive device compatible with the D-R 110 and the DVD 120, it is necessary to provide at least a laser light source having a wavelength of 780 nm and a wavelength of 650 nm at least. That is, the laser light source is switched and used according to the loaded disk.

The actual switching operation of the laser light source is as follows.
When a disc is loaded, there is a case in which laser output is performed by one laser light source, disc discrimination is performed based on the reflected light information, and the laser light source to be operated is switched according to the result. For example, when loading a disc,
In the case of an apparatus that emits laser light of m, focus search is performed on the disk in the state of laser emission of 650 nm,
Start-up processing such as turning on the focus servo is performed. However, if the disc is a CD-R, the actual data cannot be read even if the start-up (various servo-on) is possible. As a result, the disc can be determined to be a CD-R, and the laser light source to be operated at this time is
It will be switched to 80 nm. Conversely, in the case of a device that emits 780 nm laser light when a disc is loaded, it would be inconvenient if the disc was a DVD. Therefore, the laser light source that operates when the disc was determined to be a DVD was 650 nm. Will be switched.

Further, for example, when the disc is a CD-ROM, the laser wavelength may be either. However, a short-wavelength laser is more advantageous in terms of reproduction characteristics and the like. The light source may be switched to a 650 nm laser light source.

For example, as in the above example, in the disk drive device, when a certain disk is loaded and one laser light source is driven and focused, the operation of switching to the emission drive of the other laser light source is performed. May be done. In such a case, the following operation procedure is required. That is, first, the laser light source being driven is turned off, and then the laser light emission from the other laser light source is started.
Then, focus search is performed in the laser emission state, and focus servo pull-in is performed.

That is, when the laser switching is performed, it is necessary to perform the focus pull-in again from the focus search. Since the focus search is a relatively time-consuming operation, the necessity of the focus search poses a problem in terms of the speed of operation of the disk drive. For example, if laser switching is required according to the disc discrimination result when a disc is loaded as described above,
Since the focus search is performed again with the laser after the switching, the processing time as the start-up processing until data can be read from the disk becomes long. In this way, quick response as a disk drive device is hindered, resulting in so-called performance degradation.

[0022]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to speed up the processing at the time of laser switching.

For this purpose, in the present invention, a holding means capable of holding and outputting a focus drive signal generated based on a focus error signal in a disk drive device is provided. The control means can execute switching control of the laser light source operated by the pickup means, and when switching the laser light source, apply the focus drive signal held and output from the holding means to the objective lens moving means. Control. Further, when the switching of the laser light source is completed, the control means stops the hold output from the hold means, a focus drive signal generated based on the focus error signal is applied to the objective lens moving means, and the focus servo operation is performed. Control is performed so as to start.
That is, when performing laser switching, the focus drive signal immediately before that is held and output, so that the focus state immediately before that (the objective lens position) is maintained. Then, after the laser light source is switched, by turning on the focus servo in the maintained focus state, the focus pull-in can be performed without performing the focus search. This is effective for an optical system in which the change of the focal point of the laser light from each laser light source is within, for example, several μm, that is, within the focus pull-in range.

Further, in the present invention, a holding means capable of holding and outputting a focus drive signal generated based on a focus error signal in the disk drive device is provided. The control means can execute switching control of the laser light source operated by the pickup means, and when switching the laser light source, apply the focus drive signal held and output from the holding means to the objective lens moving means. Further, after the switching of the laser light source is completed, a focus search control signal is supplied to the focus drive signal generation means, and a focus drive signal based on the focus search control signal is added to the focus drive signal being held and output. Is applied to the objective lens moving means. Further, the control means, during the focus search operation period executed by the supply of the focus search control signal after the switching of the laser light source is completed,
At a required timing, the hold output from the holding means is stopped, the supply of the focus search control signal is stopped, and the focus drive signal generated based on the focus error signal is applied to the objective lens moving means to perform the focus servo operation. Is controlled to be started. That is, when performing laser switching, the focus drive signal immediately before that is held and output, so that the focus state immediately before that (the objective lens position) is maintained. Then, after switching the laser light source, focus search is performed from the maintained focus state, and the focus servo is turned on. In this case, a focus search can be performed by performing a short-time focus search in a small range. This is effective in the case of an optical system in which the change of the focal point of the laser light from each laser light source is, for example, 10 μm or more, that is, beyond the focus pull-in range.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a disk drive apparatus using an optical disk as a recording medium will be described as an embodiment of the present invention. The optical disk loaded in the disk drive of this example is a CD-ROM, a CD-R, and a DVD. That is, each disk described with reference to FIG. 7 is used. Of course, the present invention can be applied to a disk drive device compatible with other types of optical disks. Although the disk drive device according to the embodiment is provided with two laser light sources, the change of the focal point of the laser light from each laser light source may be, for example, several μm due to the configuration and characteristics of the optical system. Preferred operation examples in the case of the optical system within the focus pull-in range and the case of the optical system in which the focus position change of the laser light from each laser light source is, for example, 10 μm or more, that is, beyond the focus pull-in range. Will be described as a first embodiment and a second embodiment.
First, the configuration of the disk drive device will be described with reference to FIGS. 1 and 2, but this configuration is common to the first and second embodiments.

FIG. 1 is a block diagram of a main part of the disk drive device 70 of the present embodiment. The disk 90 is loaded on the turntable 7, and is rotated at a constant linear velocity (CLV) or a constant angular velocity (CAV) by the spindle motor 1 during a reproducing operation. The pickup 1 reads data recorded on the disk 90 in the form of embossed pits or phase change pits.

In the pickup 1, laser diodes 4a and 4b serving as laser light sources, a photodetector 5 for detecting reflected light, an objective lens 2 serving as an output end of laser light, and a laser light passing through the objective lens 2 are provided. An optical system for irradiating the disk recording surface and guiding the reflected light to the photodetector 5 is formed. The objective lens 2 is held by a biaxial mechanism 3 so as to be movable in a tracking direction and a focus direction. The entire pickup 1 can be moved in the disk radial direction by a thread mechanism 8.

A laser diode 4 is used as a laser light source.
The laser diode 4a has a center wavelength of 650 nm, for example, a laser diode 4a.
It is assumed that On the other hand, the laser diode 4b has an output laser having a center wavelength of 780 nm, for example. That is, when the disk 90 is the DVD 120 shown in FIG. 7, the laser diode 4a is used, and when the disk 90 is the CD-R 110, the laser diode 4b is used. When the disc 90 is the CD-ROM 100, either laser diode can be used, but the laser diode 4a may be more suitable in some cases. Although the optical system will not be described in detail, the laser beam output from either one of the laser diodes 4a and 4b is guided to the objective lens 2 and
It is configured to irradiate zero.

The reflected light information from the disk 90 is detected by the photodetector 5, converted into an electric signal corresponding to the amount of received light, and supplied to the RF amplifier 9. The RF amplifier 9 includes a current-voltage conversion circuit, a matrix operation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements as the photodetector 5, and generates necessary signals by matrix operation processing. For example, it generates an RF signal as reproduction data, a focus error signal FE for servo control, a tracking error signal TE, and the like. The reproduction RF signal output from the RF amplifier 9 is supplied to a binarization circuit 11, and the focus error signal FE and the tracking error signal TE are supplied to a servo processor 14.

The reproduced RF signal obtained by the RF amplifier 9 is 2
By being binarized by the binarization circuit 11, a so-called EFM signal (8-14 modulated signal; in the case of CD-ROM, CD-R) or an EFM + signal (8-16 modulated signal; DV)
D) and supplied to the decoder 12. The decoder 12 performs EFM demodulation, error correction processing, and the like, and performs CD-ROM decoding, MPEG decoding, and the like as necessary to reproduce information read from the disk 90.

The decoder 12 stores the decoded data in a cache memory 20 as a data buffer. As the reproduction output from the disk drive device 70, the data buffered in the cache memory 20 is read and transferred and output.

The interface unit 13 is connected to an external host computer 80, and
The communication of the reproduction data, the read command, and the like is performed with the communication device.
That is, the reproduction data stored in the cache memory 20 is
The host computer 8 via the interface unit 13
0 is transferred and output. The read command and other signals from the host computer 80 are transmitted to the interface unit 1
3 to the system controller 10.

The servo processor 14 detects various types of focus, tracking, thread, and spindle servo drives based on a focus error signal FE and a tracking error signal TE from the RF amplifier 9 and a spindle error signal SPE from the decoder 12 or the system controller 10. A signal is generated to execute a servo operation.

That is, the focus drive signal F according to the focus error signal FE and the tracking error signal TE
D, generates a tracking drive signal TD and supplies it to the biaxial driver 16. The two-axis driver 16 drives the focus coil and the tracking coil of the two-axis mechanism 3 in the pickup 1. As a result, a tracking servo loop and a focus servo loop are formed by the pickup 1, the RF amplifier 9, the servo processor 14, the two-axis driver 16, and the two-axis mechanism 3.

When turning on the focus servo, a focus search operation must first be performed. The focus search operation is performed by the servo processor 14.
Generates a required focus drive signal FD when the focus servo is off, and forcibly moves the objective lens 2. Then, during the movement process, the focus error signal FE
The position where the S-shaped curve is obtained is detected. As is well known, the linear region of the S-shaped curve of the focus error signal is a range in which the position of the objective lens 2 can be drawn to the in-focus position by closing the focus servo loop. Therefore, while the objective lens 2 is forcibly moved as a focus search operation, the above-described retractable range is detected, and the focus servo is turned on at that timing, so that the laser spot is kept in focus thereafter. The focus servo operation is realized.

The above-described operations of the focus servo and the focus search are executed by the system controller 10 giving instructions to the servo processor 14. In order for the system controller 10 to perform these focus operation controls, it is necessary to monitor the focus error signal FE. For this reason, the focus error signal FE from the RF amplifier 9 is also supplied to the system controller 10. The system controller 10 takes in the focus error signal FE as digital data from the A / D conversion input terminal 10a.

The S-shaped curve is observed in the focus error signal FE when an appropriate amount of reflected light is obtained by the detector 5. At this time, the level is large as a so-called sum signal of the amount of reflected light. Become. The output of comparing this sum signal with a predetermined threshold level is
It is a so-called FOK signal indicating the section of the S-shaped curve,
It is conceivable that the system controller 10 also monitors the FOK signal at the time of processing such as a focus search. For example, the zero-cross point of the focus error signal, which is the timing of the focus servo pull-in, means a zero-cross point in the S-shaped curve. It becomes almost zero level, and even if the focus error signal is simply compared with the zero level during the movement of the objective lens, the zero cross point in the S-shaped curve region may not be detected accurately. Therefore, in order to eliminate zero crossings outside the S-shaped curve region, it is conceivable to perform zero cross detection using the FOK signal as a window.

In FIG. 1, the servo processor 14 further supplies the spindle motor driver 17 with a spindle drive signal generated according to the spindle error signal SPE. The spindle motor driver 17 applies, for example, a three-phase drive signal to the spindle motor 6 according to the spindle drive signal, and the CL of the spindle motor 6
Execute V rotation. In addition, the servo processor 14 generates a spindle drive signal in response to a spindle kick / brake control signal from the system controller 10, and causes the spindle motor driver 17 to execute operations such as starting, stopping, accelerating, and decelerating the spindle motor 6.

The linear velocity as the CLV rotation of the spindle motor 6 can be set to various speeds by the system controller 10. For example, the decoder 12 generates a reproduction clock synchronized with the EFM signal for use in the decoding process, and can obtain current rotation speed information from the reproduction clock. The system controller 10 or the decoder 12 generates a spindle error signal SPE for CLV servo by comparing such current rotational speed information with reference speed information. Therefore,
The system controller 11 can change the linear velocity as the CLV rotation by switching the value as the reference velocity information. For example, linear speeds such as 4 × speed and 8 × speed can be realized based on a certain normal linear speed. As a result, the data transfer rate can be increased. It should be noted that the rotation speed can be switched even in the CAV method.

The servo processor 14 generates a thread drive signal based on, for example, a thread error signal obtained as a low-frequency component of the tracking error signal TE or an access execution control from the system controller 10 and supplies the thread drive signal to the thread driver 15. . The thread driver 15 responds to the thread drive signal by the thread mechanism 8.
Drive. Although not shown in the thread mechanism 8, a main shaft for holding the pickup 1, a thread motor,
The pickup 1 has a required sliding movement by having a mechanism such as a transmission gear and driving the sled motor 8 by the sled driver 15 according to the sled drive signal.

The laser diode 4a in the pickup 1 is driven to emit laser light by a laser driver 18a. The system controller 10 controls the laser diode 4
When the reproducing operation for the disc 90 is executed using the control signal a, the control value of the laser power is set in the auto power control circuit 19a, and the auto power control circuit 19a performs the laser output according to the set laser power value. The laser driver 18a is controlled to be operated. A laser driver 18b and an auto power control circuit 19b are provided for the laser diode 4b.
When the reproduction operation for the disc 90 is executed by using b, the same control is performed on the auto power control circuit 19b.

When the apparatus is capable of performing a recording operation, a signal modulated according to the recording data is applied to the laser driver 18a or 18b. For example, when recording is performed on a recordable type disc 90 (CD-R or DVD as a phase change recording disc), the recording data supplied from the host computer to the interface unit 13 is subjected to error correction by an encoder (not shown). After processing such as code addition, EFM modulation, and EFM + modulation is performed, the data is supplied to the laser driver 18a or 18b. Then, the laser driver 18a or 18b causes the laser diode 4a or 4b to execute a laser emission operation according to the recording data, so that data recording on the disk 90 is performed.

The above-described various operations such as servo, decoding, and encoding are controlled by a system controller 10 formed by a microcomputer.
Then, the system controller 10 executes various processes in response to a command from the host computer 80. For example, when a read command requesting transfer of certain data recorded on the disk 90 is supplied from the host computer 80, first, seek operation control is performed for the designated address. That is, a command is issued to the servo processor 14 to execute the access operation of the pickup 1 targeting the address specified by the seek command. Thereafter, operation control necessary for transferring the data in the specified data section to the host computer 80 is performed. That is, data reading / decoding / buffering from the disk 90 is performed, and the requested data is transferred. If the data request from the host computer is made sequentially and the requested data is stored in the cache memory 20 in advance by, for example, a prefetch operation, the data read / write from the disk 90 is performed as a cache hit transfer. Requested data can be transferred without performing decoding / buffering.

Next, the configuration of the focus system of the disk drive of this embodiment will be described with reference to FIG. Servo processor 14
2, only the focus system is shown in FIG. 2, but as shown, an amplifying circuit 21, a phase compensating circuit 22,
A hold circuit 23, an adder circuit 24, and a D / A converter 25 are provided. Note that the hold circuit 23, the addition circuit 24, D
The / A converter 25 may be provided outside the IC as the servo processor 14. The D / A converter 25 converts voltage value data as a focus search control signal VSC from the system controller 10 into an analog voltage.
When the analog voltage output is performed with the / A conversion output function, the D / A converter 25 becomes unnecessary.

As described above, the focus error signal FE
Is generated by a matrix operation in the RF amplifier 9,
It is supplied to the servo processor 14. The servo processor 14 performs a required amplification process on the focus error signal FE by the amplifier circuit 21 and then performs a phase compensation process by the phase compensation circuit 22 to generate a focus drive signal FD based on the focus error signal FE. The focus drive signal FD may be generated by a PWM modulation process based on the focus error signal FE, and a method of filtering the PWM signal to obtain a focus drive voltage may be used. Such a circuit configuration may be used.

The hold circuit 23 includes amplifiers A1 and A2, a switch SW, and a capacitor C. The switch SW opens and closes the focus servo loop,
This is a switch for performing hold output control. The switch SW is turned on / off by a switch control signal Shd from the system controller 10. The capacitor C has a capacity for hold output.

The adder circuit 24 includes an adder amplifier A3 and resistors R1 to R4. The adder circuit 24 adds the output voltage of the hold circuit 23 and the output voltage of the D / A converter 25 to the two-axis driver 16 for format driving. Output as signal FD.

In the case of such a configuration, various focus-related operations are performed by the search control signal VSC and the switch control signal Shd from the system controller 10. That is, the focus search and the focus servo are executed, and an operation called focus hold at the time of laser switching, which is a characteristic operation of the present example, is executed.

First, when executing a focus search for pulling in the focus servo, the system controller turns off the switch SW and keeps the focus servo loop open, and adds a sweeping voltage value as the search control signal VSC to the addition circuit. 24. During execution of the focus search, the output from the hold circuit 23 is at a zero level, and thus the search voltage is applied to the two-axis driver 16 via the addition circuit 24 as the focus drive signal FD. Thereby, the objective lens 2 is forcibly moved within the focus stroke range. At this time, the system controller 10 monitors the focus error signal FE input from the A / D conversion input terminal 10a and detects the zero-cross timing of the focus error signal (or the linear period of the S-curve before and after the zero-cross). I do. Then, for example, at the zero cross timing, the movement of the objective lens by the search control signal VSC is terminated, and the switch SW is turned on to close the focus servo loop. Then, thereafter, the focus error signal F
The focus drive signal FD generated based on E is applied to the biaxial driver 16 via the hold circuit 23 and the adder circuit 24, and the objective lens is moved as focus servo. That is, the position of the objective lens 2 is drawn to the focus point, and that state is maintained thereafter.

As described above, while the focus servo loop is closed, the voltage level as the focus drive signal FD is held by the capacitor C. Therefore, when the switch SW is turned off thereafter, the focus drive signal FD immediately before the hold circuit 23 is output from the hold circuit 23.

The operation at the time of laser switching as the first embodiment of the disk drive device having the above-described focus system configuration will be described with reference to FIGS. This is a preferable example when the pickup 1 is equipped with an optical system in which the change of the focal point of the laser light from each of the laser diodes 4a and 4b is within a focus pull-in range of, for example, several μm. FIG. 3 shows a processing example of the system controller 10 at the time of laser switching, and FIG. 4 shows a state of the focus error signal FE and the focus drive signal FD at the time of laser switching.

One laser diode (4a or 4b)
Has been operated and the focus servo is being applied, it is necessary to switch the laser for some reason, that is, the switching operation from the laser diode 4a to the laser diode 4b or the switching operation from the laser diode 4b to the laser diode 4a. In this case, the process of the system controller 10 proceeds from step F101 to F102 in FIG.

In step F102, the switch control signal S
The switch SW is turned off by hd. As a result, the focus servo loop is turned off.
The voltage value of (the focus drive signal based on the focus error signal FE) is held and output. That is, the focus drive signal FD held via the adder circuit 24 is applied to the biaxial driver 16, whereby the objective lens 2 is maintained at the immediately preceding in-focus position state. Next, in step F103, one of the currently operating auto power control circuits (19a or 19b) is controlled, and one of the laser drivers (4a or 4a) is controlled.
Stop the laser output from b). Next, step F1
At 04, the other auto power control circuit (19b or 19a) is controlled to start laser output from the other laser driver (4b or 4a).

When the laser switching is completed in steps F103 and F104, the switch SW is turned on by the switch control signal Shd in step F105. As a result, the focus servo loop is turned on, and the focus drive signal FD based on the focus error signal FE is applied to the biaxial driver 16 via the addition circuit 24.
Even if the laser diodes 4a and 4b are switched, if the change of the in-focus position is a change within the focus pull-in range, the focus servo loop is turned on immediately after the completion of the laser switching, so that the position of the objective lens 2 is changed. Is brought into a new in-focus position state, and the in-focus state is maintained thereafter.

FIG. 4 shows the state of the operation executed in the processing of FIG. 3 when the switching operation is performed from the laser diode 4a to the laser diode 4b. As described above, for example, when a disc is loaded, first, the laser diode 4a is operated to emit a laser beam of 650 nm. In this state, a focus search is performed on the disc 90, and a startup process such as turning on a focus servo is performed. Do.
However, if the disc is a CD-R, it is necessary to perform an operation of switching the laser light source to be operated to the laser diode 4b, that is, the 780 nm laser when the discrimination can be made.

For example, when switching from the laser diode 4a to the laser diode 4b under such circumstances,
The processing in FIG. 3 is performed.
The time before proceeding to 102 is a time before the time t1 in FIG. 4, that is, the laser diode 4a is operated and the focus servo is applied. Step F
The start of the hold output at 102 is the time point t1, and the value of the immediately preceding focus drive signal FD is held and output from this time point as shown in the figure. The process of step F103 corresponds to time t2, and the laser diode 4a is turned off. When the reflected light goes to zero level, the focus error signal FE also goes to zero level. Step F1
04 corresponds to the time t3, and the laser diode 4b
Is turned on. At this time, the focus position by the laser diode 4b is different from the focus position by the laser diode 4a, but the change is within the focus pull-in range,
That is, a signal within the S-shaped curve area is observed as the focus error signal FE. Therefore, step F10
As a process 5, the switch SW is turned on at time t4 and the focus servo loop is closed, thereby performing servo pull-in / setting.

As described above, when the laser is switched, the in-focus position changes. However, in this example, by maintaining the focus state immediately before the laser is switched, a new focus search is performed after the laser is switched. It is not necessary to execute focus pull-in, so that the time required for the laser switching process is greatly reduced.

Next, an operation at the time of laser switching according to a second embodiment of the present invention will be described with reference to FIGS. 5 and 6 as a disk drive device having a focus system configuration as shown in FIG. This is because the pickup 1 has the laser diodes 4
The change of the focal point position of the laser light from a and 4b is, for example, 1
This is a suitable example when an optical system having a size of 0 μm or more, that is, exceeding the focus pull-in range is mounted. FIG. 5 shows a processing example of the system controller 10 at the time of laser switching, and FIG. 6 shows a state of the focus error signal FE and the focus drive signal FD at the time of laser switching.

In FIG. 5, the same processing steps as those in FIG. 3 are denoted by the same step numbers. That is, from one laser diode (4a or 4b) being operated and focus servo being applied, the laser is switched for some reason, that is, the laser diode 4a is switched to the laser diode 4b, or the laser diode 4b is switched.
If it is necessary to perform the switching operation from to the laser diode 4a, the process of the system controller 10 proceeds from step F101 to F102, F103, and F104 in FIG. That is, as in the example of FIG. 3, the switch SW is turned off by the switch control signal Shd, the hold output of the value of the immediately preceding focus drive signal FD is executed, and the objective lens 2 is maintained at the immediately prior focal position. Then, one of the currently operated laser drivers (4a or 4a)
The laser output from b) is stopped, and then the laser output from the other laser driver (4b or 4a) is started.

When the laser switching is completed in steps F103 and F104, the process proceeds to step F110, and the system controller 10 starts supplying the search control signal VSC. That is, since the search voltage is supplied to the addition circuit 24, the search voltage and the hold voltage are added in the addition circuit 24, and the focus drive signal FD as a result of the addition is sent to the biaxial driver 16. Applied. Therefore, the objective lens 2 performs the focus search operation starting from the position maintained by the hold voltage.

During the period in which the focus search movement of the objective lens 2 is performed by the processing from step F110, the system controller 10 monitors the zero cross timing of the focus error signal FE in step F111. When the zero-cross timing is detected, the search movement by the search control signal VSC is stopped in step F112, and the switch control signal Shd
Turns on the switch SW. As a result, the hold output is released, and the focus servo loop is turned on. At the timing when the focus servo loop is closed, the objective lens 2 is within the focus pull-in range with respect to the focus position from the newly output laser diode, so that the focus drive signal FD based on the focus error signal FE is output via the addition circuit 24. Applied to the biaxial driver 16, the position of the objective lens 2 is
It is drawn into a new focus position state, and the focus state is maintained thereafter.

FIG. 6 shows a laser diode 4a similar to FIG.
6 shows the state of the operation performed in the process of FIG. 5 when the switching operation is performed from the laser diode 4b to the laser diode 4b. When the switching operation is performed from the laser diode 4a to the laser diode 4b, the processing in FIG. 5 is performed. The time before the processing proceeds to step F102 is a time before the time t1 in FIG. The laser diode 4a is operated and the focus servo is applied.
Then, the start of the hold output in step F102 is t1
At this point, the value of the immediately preceding focus drive signal FD is held and output from this point as shown in the figure. Then, as processing of steps F103 and F104, the laser diode 4a is turned off at time t2 and the laser diode 4b is turned on at time t3. At this time, the focused position by the laser diode 4b is different from the focused position by the laser diode 4a, and the position of the objective lens 2 is out of the focus pull-in range.
Therefore, a focus search is performed after time t4 as a process of step F110, and as shown in FIG.
, The objective lens 2 is searched and moved from the held position. As the focus error signal FE, an S-shaped curve is observed from time t5. At time t6, the zero-crossing detection timing is reached. In step F112, the switch SW is turned on, and the focus servo loop is closed. /
Settling is performed.

As described above, when the laser is switched, the in-focus position changes beyond the focus pull-in range. In this example, the focus state immediately before the laser switching is maintained, and after the laser switching, the focus state is maintained. The focus pull-in is performed by executing the focus search from the position. In this case, the moving range as the focus search is a smaller range than the normal focus search. That is, the focus search is executed, but the search time is very short, so that the time required for the laser switching process is greatly reduced.

The switching operation from the laser diode 4b to the laser diode 4a is performed at the time t in FIG.
The moving direction of the focus search (the direction in which the voltage of the focus drive signal FD changes) corresponding to the four or later time points is opposite to that in the example of FIG.

The operation according to the first and second embodiments has been described above. However, the configuration of the disk drive apparatus, the processing procedure at the time of laser switching, the type of disk that can be used, and the like can be variously considered. Needless to say.

[0066]

As described above, according to the present invention, when switching the laser light source, the focus drive signal to be held and output is applied to the objective lens moving means. That is, the focus state immediately before (object lens position)
Keep it. Therefore, in the case of an optical system in which the change of the focal point position of the laser light from each laser light source is within the focus pull-in range, the objective lens position at the time when the switching of the laser light source is completed is determined with respect to the switched laser light. The focus pull-in range is within the focus pull-in range with respect to the in-focus position, and the focus pull-in can be performed without performing a focus search by turning on the focus servo in the maintained focus state. As a result, there is an effect that the processing time at the time of switching the laser light source can be greatly reduced, and the performance of the disk drive device can be improved.

In the present invention, when the laser light source is switched, a focus drive signal output as a hold is applied to the objective lens moving means. That is, the focus state (object lens position) immediately before is maintained. Therefore, in the case of an optical system in which the change of the focal point of the laser light from each laser light source exceeds the focus pull-in range, the position of the objective lens at the time when the switching of the laser light source is completed is determined by the focal point of the switched laser light Although it is not within the focus pull-in range with respect to the position, the state is not so far away. That is, by performing control (focus search from the hold position) so that the focus drive signal based on the focus search control signal is added to the focus drive signal output as the hold output and applied to the objective lens moving means, the focus drive signal is shortened. The focus can be pulled in by turning on the focus servo at that timing. That is, a long time is not required for the focus search, and the processing time at the time of switching the laser light source can be greatly reduced, so that the performance of the disk drive device can be improved.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a focus control system according to the embodiment.

FIG. 3 is a flowchart of a process at the time of laser switching according to the first embodiment.

FIG. 4 is an explanatory diagram of an operation at the time of laser switching according to the first embodiment.

FIG. 5 is a flowchart of a process at the time of laser switching according to a second embodiment.

FIG. 6 is an explanatory diagram of an operation at the time of laser switching according to a second embodiment.

FIG. 7 is an explanatory diagram of a layer structure of a CD-ROM, a CD-R, and a DVD.

[Explanation of symbols]

1 pickup, 2 objective lens, 2 biaxial mechanism, 4
a, 4b laser diode, 5 photo detector,
6 spindle motor, 8 thread mechanism, 9 RF amplifier, 10 system controller, 13 interface unit, 14 servo processor, 16 two-axis driver,
18a, 18b Laser driver, 19a, 19b A
PC circuit, 20 cache memory, 21 amplifier circuit,
22 phase compensation circuit, 23 hold circuit, 24 addition circuit, 25 D / A converter, 70 disk drive device, 80 host computer, 90 disk,

Claims (4)

[Claims] At least one of a plurality of laser light sources, one objective lens serving as an output end of laser light from the plurality of laser light sources, and a detection unit for detecting reflected light from a recording medium, Pickup means for performing a recording or reproducing operation on a recording medium by selectively using each laser light source, and by moving the objective lens in a direction of coming and going to the recording medium based on a supplied focus drive signal,
An objective lens moving means for setting a focus state of the laser beam on the signal recording surface of the recording medium, a focus error signal obtained from an output of the detection unit,
Alternatively, a focus drive signal generation unit that generates a focus drive signal based on the supplied focus search control signal, a hold unit that can hold and output a focus drive signal generated based on the focus error signal, and the focus drive signal generation Means for supplying the focus search control signal to the objective means and applying a focus drive signal based on the focus search control signal to the objective lens moving means. Control means capable of executing a focus servo operation by applying a focus drive signal based on the signal to the objective lens moving means. The switching control of the laser light source to be operated can be executed, and when the laser light source is switched, control is performed so that a focus drive signal held and output from the holding unit is applied to the objective lens moving unit. Characterized disk drive device. 2. The control means stops the hold output from the hold means when the switching of the laser light source is completed, and outputs a focus drive signal generated based on the focus error signal to the objective lens moving means. 2. The disk drive device according to claim 1, wherein the control is performed such that the focus servo operation is started by applying the control signal to the control signal. 3. At least a plurality of laser light sources, one objective lens serving as an output end of laser light from the plurality of laser light sources, and a detection unit for detecting reflected light from a recording medium, Pickup means for performing a recording or reproducing operation on a recording medium by selectively using each laser light source, and by moving the objective lens in a direction of coming and going to the recording medium based on a supplied focus drive signal,
An objective lens moving means for setting a focus state of the laser beam on the signal recording surface of the recording medium, a focus error signal obtained from an output of the detection unit,
Alternatively, a focus drive signal generation unit that generates a focus drive signal based on the supplied focus search control signal, a hold unit that can hold and output a focus drive signal generated based on the focus error signal, and the focus drive signal generation Means for supplying the focus search control signal to the objective means and applying a focus drive signal based on the focus search control signal to the objective lens moving means. Control means capable of executing a focus servo operation by applying a focus drive signal based on the signal to the objective lens moving means. The switching control of the laser light source to be operated can be executed, and when the laser light source is switched, the focus drive signal held and output from the holding means is applied to the objective lens moving means, and the switching of the laser light source is completed. After that, the focus search control signal is supplied to the focus drive signal generation means, and the focus drive signal based on the focus search control signal is added to the focus drive signal which is output as a hold, and the objective lens movement means A disk drive device for performing control so as to be applied to a disk drive. 4. The control unit stops a hold output from the hold unit at a required timing during a focus search operation period executed by supplying the focus search control signal after the switching of the laser light source is completed. Stopping the supply of the focus search control signal, and performing control so that a focus servo operation is started by applying a focus drive signal generated based on the focus error signal to the objective lens moving means. The disk drive device according to claim 3, wherein: