Disk apparatus and disk access method employing counterelectromotive voltage from second voice coil motor to control first voice coil motor

A disk apparatus according to the present invention includes a rotating means for rotating a disk, a head for accessing the disk, and a head moving means of moving the head in the radius direction of the disk. The head moving means includes a first voice coil motor as a drive source used when the head is moved, a second voice coil motor as a drive source used when the head is moved, a head guide means for guiding the head in the radius direction of the disk when the head is moved, a drive means for supplying a drive signal to the first voice coil motor during a first period in which the head is moved to a predetermined position on the disk and for supplying the drive signal to the first voice coil motor and the second voice coil motor during a second period in which the head is moved from the predetermined position on the disk to another position thereon, and a counterelectromotive voltage detecting means for detecting a counterelectromotive voltage from the second voice coil motor when the drive signal is not supplied to the second voice coil motor. The drive means drives the first voice coil motor based on an output from the counterelectromotive voltage detecting means so that the head should be moved to the predetermined position on the disk.

BACKGROUND OF THE INVENTION 
The present invention relates to an optical disk apparatus and particularly 
to a control system for moving an optical head for optically accessing to 
an optical disk loaded thereonto to read an information signal, to a 
predetermined position by a voice coil motor (VCM), for example. 
A general optical disk apparatus employs a voice coil motor (VCM) as a 
drive source of an optical head sliding mechanism (actuator) for moving an 
optical head in a radius direction of an optical disk. 
One of important factors for improving a performance of an optical disk 
apparatus is an operation of moving an optical head to a predetermined 
position, i.e., a high speed seek operation. A bang-bang control has been 
known as a most suitable control method for the seek operation. 
Since, when an actuator using the above VCM is employed, an acceleration 
(angular acceleration) of the VCM is proportional to a voltage applied 
thereto, an allowed maximum voltage of the actuator determined by 
specification of the actuator is applied to the VCM when a speed of the 
seek operation is increased, and a maximum voltage thereof having a 
reverse polarity is applied to the VCM when the speed of the seek 
operation is decreased. Thus, a maximum speed of the seek operation can be 
obtained. 
In this case, practically, a profile of a movement distance of an optical 
head is calculated for every desired seek distance based on a maximum 
voltage obtained in consideration of difference among drive devices, and 
is given to a seek servo system (feedback system) as a reference movement 
amount. Thus, it is possible to realize a high-speed seek operation which 
can cancel various differences among devices as much as possible. 
Specifically, when a seek operation of moving an optical head by a certain 
distance (i.e., a distance represented by tracks of a certain number), a 
distance (movement amount) by which the optical head should move at each 
time during the seek operation is previously or successively calculated, 
being compared with an actual movement amount of the optical head. A 
difference signal indicative of the difference between the calculated 
distance and the actual distance is supplied to a drive unit of a sled 
mechanism. Thus, the seek servo control can be realized. 
Before the optical head accesses the optical disk, the optical head must 
read an attribute information of the optical disk. The attribute 
information includes a medium information such as sensitivity, 
reflectivity or the like and a system information such as a track number 
or the like. 
Especially, a 5-inch magneto-optical (MO) disk includes a phase information 
other than the above medium information and the above system information. 
The phase information is located at a phase-encoded part (PEP) on an 
optical disk, and the medium information and the system information are 
located at a standard formatted part (SFP) thereon. 
As shown in FIG. 1, the attribute informations located at the PEP (i.e., 
the phase information) is recorded on an optical disk D at a control track 
PEP zone which is located at an outer-periphery side position as compared 
with a reflectivity zone at most inner peripheral position of the optical 
disk D. The attribute informations located at the SFP (i.e., the medium 
information and the system information) are recorded on an optical disk D 
at an inner control track SFP zone located at outer periphery side of the 
above control track PEP zone and at an outer control track SFP zone 
located at an inner periphery side of a read-out zone at an outermost 
periphery of the optical disk D. 
Various methods of making the optical head accessing the above attribute 
informations have been proposed. The three typical methods thereof are as 
follows. 
(1) As shown in FIG. 2, according to a first method, there is provided an 
optical head position detecting mechanism having an optical-head position 
sensor 101 of an optical head 104 formed of a linear encoder or the like 
provided near the inner periphery of the optical disk D other than a 
linear encoder (not shown) used upon the seek operation of accessing the 
attribute informations, and a stopper 103 provided in an outer housing of 
a spindle motor 102 for rotating the optical disk D (this first method is 
disclosed in Japanese laid-open patent publication NO. 250688/1990). 
According to the first method, the optical head 104 is initially moved to 
an inner periphery side of the optical disk D., i.e., a position where it 
is to be in contact with the stopper 103. Thereafter, a slight current 
flows through a VCM, thereby the optical head 104 being finely moved 
toward an outer periphery side of the optical disk D. When the optical 
head 104 is finely moved, a position of the PEP zone is detected based on 
a detection signal output from the position sensor 101 and, for example, a 
focus error signal output from the optical head 104, and the optical head 
104 reads out a PEP information from the detected PEP zone. 
(2) As shown in FIG. 3, according to a second method, an elastic (or 
springy) member 105 formed of an elastic rubber, a spring or the like is 
provided instead of the stopper 103 employed in the first method. 
According to the second method, the optical head 104 is moved to the inner 
periphery side of the optical disk D, i.e., in the direction in which the 
member 105 is pressed by the optical head 104 against its elasticity (or 
spring force). Thereafter, while the PEP zone is being detected based on 
the focus error signal from the optical head 104, for example, a pressing 
force of the VCM which serves to press the optical head 104 is gradually 
loosened, thereby the optical head 104 being returned to a position 
corresponding to the PEP zone. 
(3) Though not shown, according to a third method, the optical head is 
initially moved to a position corresponding to the innermost periphery 
position of the optical disk, thereafter being finely and gradually moved 
from the innermost periphery to the PEP zone without using any sensor or 
the like. Based on informations of time required for the movement of the 
optical head from the innermost periphery to the PEP zone and so on, a 
most preferable positioning drive force is learned and controlled. 
However, the above first to third methods may involve the following 
problems. 
Specifically, the first method requires the position sensor 101 formed of a 
linear encoder or the like which must be newly provided in an optical head 
slide mechanism. This may lead to disadvantage in manufacturing costs. 
The second method requires the elastic member 105, which leads to 
disadvantage in manufacturing costs. Moreover, the elastic member 105 
required in the second method is disadvantage in durability. 
The third method inevitably employs an operation of moving the optical head 
from the innermost periphery to the PEP zone many times to carry out the 
most preferable positioning control based on the time required for such 
movement. This may limit possibility of a faster access time. 
SUMMARY OF THE INVENTION 
In view of such aspects, it is an object of the present invention to 
provide a disk apparatus and a disk access method which, with low costs 
and with high reliability, allows an attribute information reading 
operation carried out at the preceding stage of an operation of accessing 
a disk and which allows the above attribute information to be read at high 
speed. 
According to a first aspect of the present invention, a disk apparatus 
according to the present invention includes a rotating means for rotating 
a disk, a head for accessing the disk, and a head moving means of moving 
the head in the radius direction of the disk. The head moving means 
includes a first voice coil motor as a drive source used when the head is 
moved, a second voice coil motor as a drive source used when the head is 
moved, a head guide means for guiding the head in the radius direction of 
the disk when the head is moved, a drive means for supplying a drive 
signal to the first voice coil motor during a first period in which the 
head is moved to a predetermined position on the disk and for supplying 
the drive signal to the first voice coil motor and the second voice coil 
motor during a second period in which the head is moved from the 
predetermined position on the disk to another position thereon, and a 
counterelectromotive voltage detecting means for detecting a 
counterelectromotive voltage from the second voice coil motor when the 
drive signal is not supplied to the second voice coil motor. The drive 
means drives the first voice coil motor based on an output from the 
counterelectromotive voltage detecting means so that the head should be 
moved to the predetermined position on the disk. 
According to a second aspect of the present invention, a disk access method 
according to the present invention is a method of accessing a 
predetermined position on a disk in a disk apparatus having a first voice 
coil motor as a drive source used when a head is moved in the radius 
direction of the disk and a second voice coil motor as a drive source used 
when the head is moved in the radius direction of the disk. The disk 
access method includes a counterelectromotive voltage detecting step of 
detecting a counterelectromotive voltage from the first voice coil motor, 
a first target movement speed referring step of referring to a first 
target movement speed of the head used when the head is moved to an 
innermost or outermost periphery of the disk, a head moving step of 
driving the voice coil motor based on the counterelectromotive voltage and 
the first target speed to move the head to the innermost or outermost 
periphery, a detecting step of detecting that the head reaches a position 
corresponding to the innermost or outermost periphery, a second target 
movement speed referring step of referring a second target movement speed 
of the head used when the head is moved from the innermost or outermost 
periphery to the predetermined position, a head moving step of driving the 
second voice coil motor based on the counterelectromotive voltage and the 
second target movement speed to move the head to the predetermined 
position, and a predetermined position detecting step of detecting that 
the head reaches the predetermined position.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An optical disk apparatus according to an embodiment of the present 
invention will be described with reference to FIGS. 4 through 10. In this 
embodiment, the optical disk apparatus according to the present invention 
is applied to a magnetic-field modulation type recording and reproducing 
apparatus employing a 5-inch magneto-optical (MO) disk, for example, as an 
optical disk. This recording and reproducing apparatus will hereinafter be 
referred to simply as a recording and reproducing apparatus according to 
this embodiment. 
The recording and reproducing apparatus according to this embodiment is 
formed of a disk recording and reproducing apparatus employing a 
magneto-optical disk as a recording medium. As shown in FIG. 4, the 
recording and reproducing apparatus has a cartridge holder (not shown) 
into which a disk cartridge (not shown) rotatably housing an optical disk 
D corresponding to, for example, a magnetic-field modulation system is 
inserted, a spindle motor 1 for rotating the magneto-optical disk D 
inserted into the cartridge holder, an optical head 2 for reproducing an 
information signal from the magneto-optical disk D, and a recording 
magnetic-field generating device 3 (incorporating an excitation coil) for 
applying a recording magnetic field to the magneto-optical disk D rotated 
by the spindle motor 1 and for magnetizing a portion (heated to a 
temperature exceeding a Curie temperature), which is being applied with 
rays of laser light L from the optical head 2, of a vertical magnetizing 
film (recording layer) of the magneto-optical disk D in response to a 
recording signal. The disk cartridge is not shown in FIG. 4 in order to 
avoid complicated contents of FIG. 4. 
The cartridge holder has therein a known shutter opening and closing 
mechanism (now shown) for opening and closing a shutter (not shown) of the 
disk cartridge. 
Therefore, when the disk cartridge is inserted into the cartridge holder, 
the shutter thereof is opened by the shutter opening and closing 
mechanism. At a position where the shutter is fully opened, i.e., the disk 
cartridge is completely inserted into the cartridge holder, an operation 
of loading the disk cartridge onto the recording and reproducing apparatus 
is finished. 
The spindle motor 1 is provided at a lower position corresponding to a 
center portion of the loaded disk cartridge, and can be moved by a known 
spindle motor upward/downward moving mechanism (not shown) mainly formed 
of a stepping motor and a rotation-linear movement converting mechanism, 
for example, upward and downward, i.e., in the direction in which the 
spindle motor is brought close to and away from the disk cartridge. A 
turntable 4 is provided at an upper end edge of a motor shaft of the 
spindle motor 1. 
When the disk cartridge is loaded onto the recording and reproducing 
apparatus, the spindle motor 1 is moved upward by the spindle motor 
upward/downward moving mechanism. During the above movement of the spindle 
motor 1, the turntable 4 is brought into the disk cartridge through a rear 
side opening portion of the disk cartridge. At this time, magnetic 
attraction of a magnet tightly bonds an upper surface of the turntable 4 
and a center hub of the magneto-optical disk D in the disk cartridge 
together and holds them, thereby the magneto-optical disk D in the disk 
cartridge being loaded onto the spindle motor 1. 
The optical head 2 is provided at a position below the rear side opening 
portion of the disk cartridge exposed to inside the recording and 
reproducing apparatus. The optical head 2 can be moved in the radius 
direction of the magneto-optical disk D in the disk cartridge by an 
optical head sliding mechanism 5 mainly formed of a voice coil motor and a 
guide shaft. The optical head sliding mechanism 5 and its drive control 
system will be described later on. 
The optical head 2 is formed as one unit which is the whole optical system 
having a laser light source formed of a semiconductor laser serving as a 
light source for light beams L, an objective lens for condensing the light 
beams L on the magneto-optical disk D, a photo detector for detecting 
returning light reflected by a surface of the magneto-optical disk D to 
convert the returning light into an electric signal (detection signal) 
having a current level corresponding to its light amount. 
The optical system has, other than the above optical parts, a collimator 
lens for setting the light beams L emitted from the laser light source in 
parallel, a phase grating for dividing the light beams L into at least 
three luminous-flux components, a beam splitter for separating the light 
beams L from the laser light source and the returning light from the 
magneto-optical disk D, and so on. 
The optical system has, in an optical path of the returning light, an 
imaging lens for converging the returning light on the photosensor and a 
multi-lens formed of a cylindrical lens and a concave lens for adjusting a 
focal length of the returning light and producing astigmatism. 
The optical system has a photodetector used for monitoring which is 
provided on the opposite side of the imaging lens side of tho beam 
splitter and which detects a part (an optical component reflected by a 
boundary surface of the beam splitter) of the light beams L (P 
polarization in this embodiment) from the laser light source to convert 
the detected light beam L into an electric signal (detection signal) 
having an output level (electrical level) corresponding to a light amount 
of the optical component. 
In this embodiment, characteristics of the beam splitter are set so that a 
transmittance of P polarization and a reflectivity of S polarization 
should be respectively set to TP=80% and RS=100%. As a result, 20% of the 
light beam L incident from the laser light source on the beam splitter are 
reflected by the boundary surface thereof and made incident on the 
photodetector used for monitoring. 
A light amount control circuit (generally called an automatic power control 
(APC) circuit) 6 for outputting a control signal to the laser light source 
based on the detection signal from the photodetector used for the 
monitoring so that the laser light source should oscillate stably is 
connected to the succeeding stage of the photodetector used for the 
monitoring. 
Specifically, the APC circuit 6 outputs a control signal Sp to the laser 
light source of the optical head 2 so that an output (light amount) of the 
light beam L emitted from the laser light source should have a value 
indicated by a set value data supplied from a system controller 18 
described later on and so that the laser light source should stably 
oscillate. The values indicated by the set value data supplied from the 
system controller 18 when an information signal is reproduced from the 
magneto-optical disk D and when an information signal is recorded thereon 
are different from each other. The values are set so that the output of 
the light beam used upon the recording of the information signal should be 
larger than that used upon the reproduction thereof. 
The objective lens of the optical head 2 is slightly moved by a 
two-dimensional actuator 7 in the direction in which the objective lens is 
brought close to and away from the magneto-optical disk D and in the 
radius direction thereof. The two-dimensional actuator 7 is formed of a 
magnetic circuit formed of, for example, a focus coil, a tracking coil and 
a magnet. 
The objective lens has a posture control mechanism (midpoint servo 
mechanism), not shown, for moving the objective lens to a predetermined 
center position while the laser beam L traces a portion which is not 
subjected to the tracking servo. The posture control mechanism has a 
fluctuation detecting circuit for outputting a signal having a waveform 
corresponding the fluctuation amplitude when the objective lens is 
fluctuated in the left and right directions, and a servo circuit for 
making an excitation current flowing through the tracking coil so that the 
signal waveform from the fluctuation detecting circuit should have a 
constant level (e.g., a level 0). 
The recording magnetic-field generating device 3 is provided at a position 
above an upper side opening portion, exposed to the inside of the 
recording and reproducing apparatus, of the disk cartridge. The recording 
magnetic-field generating device 3 can be freely moved by a known 
upward/downward moving mechanism (not shown) mainly formed of a stepping 
motor and a rotation-linear movement converting mechanism in the upward 
and downward directions, i.e., in the direction in which the recording 
magnetic-field generating device 3 is brought close to and away from the 
upper side opening portion of the disk cartridge. The recording 
magnetic-field generating device 3 is moved in the radius direction of the 
magneto-optical disk D by an interlocking mechanism (not shown) with being 
linked with the optical head 2. 
As shown in FIG. 4, other than the above APC circuit 6, a circuit system of 
the recording and reproducing apparatus according to the embodiment has an 
RF amplifier 11, an arithmetic circuit 12, an encoder 13, a magnetic-field 
generating circuit 14, a servo control circuit 15, a decoder 16, an 
optical-head slide driving circuit 17 and the system controller 18 for 
controlling these circuits. The system controller 18 is connected to a 
host computer 19 externally provided so that data should be transferred 
through an interface bus 20 (e.g., small computer system interface (SCSI) 
bus) and an interface circuit 21 between the recording and reproducing 
apparatus and the host computer 19. 
The interface circuit 21 interprets contents of a command supplied from the 
host computer 19 or the like connected to this recording and reproducing 
apparatus and transfers the contents of the operation command to the 
system controller 18. The interface circuit 21 also functions as a buffer 
for transmitting and receiving data to and from the host computer 19. In 
this case, the interface circuit 21 carries out error correction (with 
error correction codes (ECC)) for disk defects. 
The RF amplifier 11 converts a light detection signal (current signal) from 
the photosensor of the optical head 2 into a voltage signal to amplify the 
voltage signal with a predetermined gain. The arithmetic circuit 12 
generates various signals, i.e., a tracking error signal St, a focus error 
signal Sf and an RF signal Srf based on the light detection signal 
(voltage signal) from the RF amplifier 11. 
The encoder 13 subjects a recording data Dw supplied from tho host computer 
19 through the interface circuit 21 to an encoding processing with an 
error correction and an eight-to-fourteen modulation (EFM) to thereby 
convert the recording data Dw into recording information data. Further, 
the encoder 13 converts the recording information data into binary data to 
thereby output the recording data Dw-as an on/off signal So to the 
magnetic field generating circuit 14. 
The magnetic-field generating circuit 14 switches a direction of a current 
supply to the excitation coil of the recording magnetic-field generating 
device 3 to a positive direction or a negative direction based on the 
on/off signal So from the encoder 13. 
Specifically, when the current flows through the excitation coil in the 
positive direction, the portion heated over the Curie temperature by 
irradiation of the laser light from optical head 2 is magnetized in the 
positive direction, for example, and when the current flows through the 
excitation coil in the negative direction, the portion is magnetized in 
the negative direction. 
Then, the optical head 2 irradiates rays of a reproduction laser light L on 
the magneto-optical disk D. A photosensor formed of a pn junction 
photodiode, for example, incorporated in the optical head 2 detects a Kerr 
rotation angle included in a luminous flux of the reflected light 
modulated at the portion magnetized in the positive direction or the 
portion magnetized in the negative direction. Thus, the recording and 
reproducing apparatus can obtain a reproduced signal recorded on the 
magneto-optical disk D in the form of a magnetization information. 
The servo control circuit 15 incorporates a focus servo circuit, a tracking 
servo circuit, a spindle servo circuit, a sled servo circuit, a motor 
servo circuit for effecting servo control on a motor which is a drive 
source of various moving mechanisms, and so on. These servo circuits are 
inputted with a servo drive and control signal such as servo control data 
(e.g., a servo gain and so on) from the system controller 18, a drive 
signal or the like, and a servo calculation signal from the arithmetic 
circuit 12. 
The spindle servo circuit drives the spindle motor 1 based on the servo 
drive and control signal from the system controller 18, and rotates the 
magneto-optical disk D loaded on the turntable 4 in a constant angular 
velocity (CAV) system or a constant linear-velocity (CLV) system. If the 
magneto-optical disk D is a disk of a sample servo system, the servo drive 
and control signal is generated based on a clock signal obtained by 
multiplying (dividing) a frequency of a pulse signal resulting from 
detection of a clock pit formed on a servo region together with a servo 
pit or from detection of the servo pit by a PLL circuit, for example. 
The above focus servo circuit drives and controls the two-dimensional 
actuator 7 of the optical head 2 based on a focus error signal Sf from the 
arithmetic circuit 12, i.e., specifically based on a signal obtained when 
the arithmetic circuit 12 subjects to a predetermined calculation a 
detection signal resulting from irradiation of the laser light on a mirror 
surface formed on the magneto-optical disk D and corresponding to a 
reflected light amount. Thus, the focus servo circuit moves the objective 
lens in the direction in which the objective lens is brought close to and 
away from the magneto-optical disk D to thereby adjust a focal point. 
The above tracking servo circuit drives and controls the two-dimensional 
actuator 7 of the optical head based on a focus error signal Sf from the 
arithmetic circuit 12, i.e., specifically based on a signal obtained when 
the arithmetic circuit 12 subjects to a predetermined calculation a 
detection signal resulting from detection of a servo pit in the servo 
region formed on the magneto-optical disk D. Thus, the focus servo circuit 
moves the objective lens in the radius direction of the magneto-optical 
disk D to thereby adjust the tracking. 
While comparing a reference value data successively supplied from the 
system controller 18 and a data indicative of a present position of the 
optical head 2 (a positional data obtained from the linear encoder), the 
sled servo circuit outputs a control signal to the optical-head slide 
driving circuit 17 so that the optical head 2 should reach a position 
indicated by the reference position data. The optical-head slide driving 
circuit 17 drives and controls the voice coil motor serving as a drive 
source of the optical-head sliding mechanism 5 in response to a level (a 
current level, a voltage level, a frequency or the like) of the control 
signal from the sled servo circuit. 
The decoder 16 converts into a digital data the reproduced signal Srf from 
the arithmetic circuit 12, i.e., specifically a signal obtained by 
subjecting to a predetermined signal a P polarization component and an S 
polarization component of the reflected light modulated in response to 
magnetized information recorded in a recording layer of the 
magneto-optical disk D, and further decodes the digital data with using an 
error correction code added with the converted digital data to output the 
decoded digital data as a reproduced data Dp. The reproduced data Dp from 
the decoder 16 is supplied through the interface circuit 21 and the 
interface bus 20 to the host computer 19, for example, externally 
connected to the recording and the reproducing apparatus. Of the 
reproduced data Dp supplied to the host computer 19, a subcode Ds such as 
a sector synchronization signal, a sector address signal or the like is 
supplied to the system controller 18 which uses the subcode Ds to control 
rotation of the spindle motor 1 and control a scanning position of the 
optical head 2 upon the seek operation. 
As shown in FIGS. 5 through 7 which shows main parts of the recording and 
reproducing apparatus according to this embodiment, the optical-head 
sliding mechanism 5, the optical-head slide driving circuit 17 and the 
sled servo circuit 31 are arranged as follows. 
Specifically, as shown in FIG. 5, the optical-head sliding mechanism 5 has 
two guide shafts 33a, 33b for guiding a casing (hereinafter referred to as 
a carriage 32) housing the optical head formed as a unit in the radius 
direction of the magneto-optical disk D, and two voice coil motors (first 
and second voice coil motors 34a, 34b) serving as a drive source for 
moving the carriage 32 in the radius direction of the magneto-optical disk 
D. As shown in FIG. 5, the first and second voice coil motors 34a, 34b are 
respectively formed as short coil type voice coil motors. 
As shown in FIG. 6, the optical-head slide driving circuit 17 has two drive 
circuits (first and second motor drive circuits 41a, 41b) for supplying 
drive currents Si to the first and second voice coil motors 34a, 34b based 
on the control signal Sc input from the sled servo circuit 31. The motor 
drive circuits 41a, 41b supply the drive currents Si responding to the 
level of the control signal Sc supplied from the sled servo circuit 31 to 
the respective voice coil motors 34a, 34b so that the optical head 2 
should move toward the inner periphery or outer periphery of the 
magneto-optical disk D in response to a polarity of the control signal Sc. 
For example, when the positive-direction drive current Si flows through 
drive coils of the first and second voice coil motors 34a, 34b, the 
carriage 32 is moved toward the inner periphery side of the 
magneto-optical disk D along the guide shafts 33a, 33b. On the other hand, 
when the negative-direction drive current Si flows therethrough, the 
carriage 32 is moved toward the outer periphery side of the 
magneto-optical disk D along the guide shafts 33a, 33b. 
Especially, the recording and reproducing apparatus has a stopper 35 for 
forcibly stopping movement of the optical head 2 when the optical head 2 
is moved toward the inner periphery side of the magneto-optical disk D and 
then reaches a position corresponding to the innermost periphery of the 
magneto-optical disk D. The stopper 35 is formed of, for example, 
synthetic resin, a rubber or the like and bonded by an adhesive or the 
like to a metal plate piece 36 provided in the spindle motor 1 or a 
chassis or the like of the recording and reproducing apparatus. 
A switching circuit 42 is connected between the second motor driving 
circuit 41b and the second voice coil motor 34b. A counterelectromotive 
voltage detecting system 43 for detecting a counterelectromotive current 
Ia produced in the second voice coil motor 34b as a voltage signal Sv is 
connected between the switching circuit 42 and the sled servo circuit 31. 
The counterelectromotive voltage detecting system 43 has a voltage 
detecting circuit 44 for detecting the counterelectromotive current Ia 
produced in the second voice coil motor 34b to convert the detected 
current Ia into the voltage signal Sc corresponding to the level of the 
detected current Ia, an amplifier 45 for amplifying the voltage signal Sv 
from the voltage detecting circuit 44 with a predetermined gain, and an 
A/D converter 46 for converting the amplified voltage signal Sv from the 
amplifier 45 into a digital voltage data Dv to supply the digital voltage 
data Dv to the sled servo circuit 31. 
The switching circuit 42 has a first fixed contact 42a connected to the 
output side of the second motor drive circuit 41b, a second fixed contact 
42b connected to the input side of the voltage detecting circuit 44 and a 
movable contact 42c connected to a side of the second voice coil motor 
34b. The movable contact 42c is switched in response to a level of a 
switching control signal Sw output from the sled servo circuit 31. 
Specifically, when the switching control signal Sw is at a low level, the 
movable contact 42c is electrically connected to the first fixed contact 
42a, thereby the drive current Si from the second motor drive circuit 41b 
being supplied to the second voice coil motor 34b. When the switching 
control signal Sw is at a high level, the movable contact 42c is 
electrically connected to the second fixed contact 42b, thereby the drive 
current Si from the second motor drive circuit 41b being prevented from 
being supplied to the second voice coil motor 34b. Specifically, when the 
movable contact 42c is switched to the second fixed contact 42b side, the 
second voice coil motor 34b is brought in its drive stop state. 
The above first and second motor drive circuits 41a, 41b respectively have 
enable terminals. The enable terminal of the first motor drive circuit 41a 
is applied with a certain voltage V which constantly sets the first motor 
drive circuit 41 in its operable state. On the other hand, the enable 
terminal of the second motor drive circuit 41b is supplied with an 
operation selection signal Ss from the sled servo circuit 31. When the 
operation selection signal Ss supplied to the enable terminal of the 
second motor drive circuit 41b is at a high level, the second motor drive 
circuit 41b is brought in its operable state (in which it accepts the 
control signal Sc from the sled servo circuit 31), and when the operation 
selection signal Ss is at a low level, it is brought in its non-operable 
state (in which it does not accepts the control signal Ss from the sled 
servo circuit 31). 
Since the first motor drive circuit 41a drives the first voice coil motor 
34a when the second voice coil motor 34b remains in its stop state, when 
the carriage 32 is moved in the radius direction of the magneto-optical 
disk D, the drive coil of the second voice coil motor 34b traverses a 
magnetic flux produced by the magnet of the second voice coil motor 34b, 
thereby the counterelectromotive current Ia flowing through the drive coil 
of the second voice coil motor 34b. The counterelectromotive current Ia is 
supplied through the switching circuit 42 to the voltage detecting circuit 
44 of the counterelectromotive voltage detecting system 43 and derived by 
the voltage detecting circuit 44 as a counterelectromotive voltage 
(voltage signal Sv). 
A voltage level of the counterelectromotive voltage Sv is changed in 
proportion to a speed at which the drive coil of the second voice coil 
motor 34b traverses the magnetic flux produced by the magnet thereof, 
i.e., a movement speed of the carriage 32. 
The optical-head slide driving circuit 17 incorporates a PEP zone detecting 
circuit 47 for detecting that the optical head 2 reaches the PEP zone 
where the attribute information, especially the phase information of the 
magneto-optical disk D is recorded. 
The phase information is recorded on the PEP zone in the form of codes such 
as a bar code, for example, or the like by providing a large number of 
pits extended in the radius direction (hereinafter referred to as 
longitudinal pits for convenience) in the PEP zone along a circumference 
direction. 
A detection principle of the PEP zone detecting circuit 47 is as follows. 
The magneto-optical disk D has a mirror surface on the inner side of the 
PEP zone. The large number of longitudinal pits are provided in the PEP 
zone along the circumference direction of the magneto-optical disk D. 
Therefore, study of a signal waveform of the focus error signal Sf from the 
optical head 2 obtained when the optical head 2 positioned at the 
innermost periphery side of the magneto-optical disk D is moved toward the 
outer periphery thereof, reveals that the signal level of the focus error 
signal Sf is kept at a constant level while the rays of the laser light L 
are being irradiated on the inner periphery mirror surface and that, on 
the other hand, the signal level is changed to a high level (or a low 
level) every time when the rays of the laser light L traverses one of the 
above longitudinal pits after entering the PEP zone. 
Accordingly, a circuit such as a monostable multivibrator, for example, or 
the like for outputting a pulse signal Ps having a pulse width determined 
by a time constant of the circuit based on an input timing of a first 
trigger signal can be employed as the PEP zone detecting circuit 47. In 
this case, if the focus error signal from the optical head 2 (or the focus 
error signal Sf from the arithmetic circuit 12) is employed as the first 
trigger signal, then the PEP zone detecting circuit 47 outputs the pulse 
signal Ps having a constant pulse width after the rays of the laser light 
L enters the PEP zone and hence the signal level of the focus error signal 
is changed. As a result, it can be determined that a time when the pulse 
signal Ps is output is just a time when the PEP zone is detected. 
The above sled servo circuit 31 is formed of a microcomputer, for example. 
The sled servo circuit 31 has as a software an access pre-processing means 
for reading the attribute data of the magneto-optical disk D from the PEP 
zone, the SFP zone and so on-thereof, and an access control processing 
means for accessing the information signal recorded on the magneto-optical 
disk D through the optical head 2. 
While comparing the reference value data successively supplied from the 
system controller 18 and the data indicative of a present position of the 
optical head 2 (a positional data obtained from the linear encoder), the 
access control processing means outputs a control signal Sc to the 
optical-head slide driving circuit 17 so that the optical head 2 should 
reach a position indicated by the reference position data. This processing 
has been generally known and hence need not to be described in detail. A 
processing of the access pre-processing means will mainly be described 
below. 
As shown in FIG. 7, the sled servo circuit 31 has as a hardware a program 
ROM 51 for storing various programs such as the above access 
pre-processing means or the like, a data ROM 52 in which various fixed 
data are previously registered, an operation RAM 53 used for an operation 
of the program read out from the above program ROM 51, a data RAM 54 for 
storing data and the control signals from the system controller 18, data 
processed in various programs or the like, an input port 55 and an output 
port 56 for respectively inputting and outputting data from and to an 
external circuit, and a CPU (control device and a logical arithmetic 
device) 57 for controlling the above various circuits. 
The above various circuits transmit and receive data through a data bus DB 
among one another. Moreover, the above various circuits are controlled by 
the CPU 57 through an address bus and a control bus (both of which are not 
shown) derived from the CPU 57. 
The system controller 18 outputs the reference value data to the sled servo 
circuit 31 and further outputs a start signal Sd used for reading the 
attribute information thereto based on an input interruption signal issued 
based on the fact the magneto-optical disk D is loaded on the recording 
and reproducing apparatus. 
A processing of the access pre-processing means of the sled servo circuit 
31 will be described with reference to FIG. 8 which is a functional block 
diagram thereof and FIG. 9 which is a flowchart therefor. 
In step S1 of the flowchart shown in FIG. 9, simultaneously with energizing 
the recording and reproducing apparatus, the sled servo circuit 31 carries 
out its initial operation such as, for example, a system check of the 
microcomputer, a memory check thereof, a setup therefor or the like. The 
processing proceeds to step S2. 
In step S2, an access pre-processing means 61 (which is an access 
pre-processing program: see FIG. 8) is read out from the program ROM 51 
and stored in the operation RAM 53. At the same time, a work area used for 
temporarily storing data generated during operation of this access 
pre-processing program and for transmitting and receiving parameters 
between routines forming the access pre-processing program is allocated in 
the operation RAM 53. 
A fixed data storage area for storing various fixed data from the data ROM 
52 is allocated in the data RAM 54. The fixed data storage area has a 
first target value storage area for storing data (a first target value D1) 
concerning a target speed when the optical head 2 is moved from the 
outermost periphery of the magneto-optical disk D to the innermost 
periphery thereof, a set value storage area for storing a set value Da 
used to determine whether or not the optical head 2 reaches the position 
corresponding to the innermost periphery, a second target value storage 
area for storing data (second target value D2) concerning a target speed 
used until the PEP zone is detected, and a third target value storage area 
for storing data (third target value D3) concerning a target speed when 
the PEP data is read out from the PEP zone. 
In step S2, other than the above program transfer processing, the CPU 57 of 
the sled servo circuit 31 reads out the above various fixed data from the 
data ROM 52 to store them in the fixed data storage area. 
As shown in FIG. 8, the access pre-processing program 61 read out in the 
operation RAM 53 has a discriminating means 62 for carrying out various 
discriminations, an operation selection signal outputting means 63 for 
outputting an operation selection signal Ss through the output port 56 to 
the second motor drive circuit 41b, a switching control means 64 for 
outputting a switching control signal sw used for switching the movable 
contract 42c of the switching circuit 42 to the second motor drive circuit 
41b side or the counterelectromotive detecting system 43 side, a voltage 
data receiving means 65 for receiving the voltage data Dv input through 
the input port 55 from the counterelectromotive detecting system 43, a 
control signal outputting means 66 for respectively outputting the control 
signal Sc used for driving the first and second voice coil motors 34a, 34b 
through the output port 56 to the first and second motor driving circuits 
41a, 41b, an innermost periphery movement speed control means 67 for 
carrying a speed control so that the optical head 2 should be moved to 
ward the innermost periphery side at a predetermined speed, a PEP 
detecting speed control means 68 for controlling the optical head 2 to be 
moved at a predetermined speed until detection of the PEP zone, a PEP 
reading speed control means 69 for controlling the optical head 2 to be 
moved at a predetermined speed while the optical head 2 reads the PEP 
data, and a data reading request means 70 for requesting the system 
controller 18 to read the PEP data and the SFP data. 
The processing proceeds to step S3. In step S3 shown in FIG. 9, the access 
pre-processing program 61 discriminates through the discriminating means 
62 whether or not the start signal Sd is input from the system controller 
18. This discrimination is repeatedly carried out until the start signal 
Sd is input therefrom. Specifically, the access pre-processing program 61 
is brought in its standby state until the start signal Sd is input. 
When the magneto-optical disk D is loaded onto the recording and 
reproducing apparatus and the start signal Sd is input to the sled servo 
circuit 31 from the system controller 18, the processing proceeds to step 
S4, wherein the operation selection signal outputting means 63 of the 
access pre-processing program 61 outputs the low-level operation selection 
signal Ss indicative of a non-operation state through the output port 56 
to the second motor drive circuit 41b. The second motor drive circuit 41b 
prohibits its reception of the control signal Sc output from the sled 
servo circuit 31 based on the input low-level operation selection signal 
Ss from the sled servo circuit 31. Thus, supply of the drive current Si to 
the second voice coil motor 34b is stopped. 
The processing proceeds to step S5, wherein the switching control means 64 
outputs the high-level switching control signal sw through the output port 
56 to the switching circuit 42. The switching circuit 42 switches its 
movable contract 42c to the counterelectromotive voltage detecting system 
43 side, i.e., the fixed contact 42b side based on the input high-level 
switching control signal sw output from the sled servo circuit 31. 
The processing proceeds to step S6, wherein the control signal outputting 
means 66 outputs the control signal Sc used for driving the first voice 
coil motor 34a (to move the optical head 2 toward the innermost periphery 
of the magneto-optical disk D) through the output port 56 to the first 
motor drive circuit 41a. The first motor drive circuit 41a starts to 
supply the drive current Si to the first voice coil motor 34a based on the 
control signal Sc input from the sled servo circuit 31, thereby the 
optical head 2 starting to move toward the innermost periphery. At this 
time, the counterelectromotive current Ia having a level corresponding a 
speed of the optical head 2 flows through the second voice coil motor 34b, 
flowing through the switching circuit 42 to the counterelectromotive 
voltage detecting system 43. The counterelectromotive voltage detecting 
system 43 converts the supplied counterelectromotive current Ia into the 
voltage signal Sv and further converts the voltage signal Sv into the 
digital data (voltage data Dv) to output the digital data. 
The processing proceeds to step S7, wherein the voltage data receiving 
means 65 receives the voltage data Dv supplied from the 
counterelectromotive voltage detecting system 43 through the input port 
55, stores the received voltage data Dv in a voltage data storage register 
Ra (a register declared as a voltage data storage register of various 
registers used by the access pre-processing program 61). 
The processing proceeds to step S8, wherein the innermost movement speed 
control means 67 extracts the voltage data Dv stored in the voltage data 
storage register Ra from the first target value D1 concerning the target 
speed used when the optical head 2 is moved from the outermost periphery 
of the magneto-optical disk D to the innermost periphery thereof, thereby 
obtaining a changed amount .DELTA.D of the speed. 
The processing proceeds to step S9, wherein the discriminating means 62 
discriminates whether or not the optical head 2 has reached the position 
corresponding to the innermost periphery of the magneto-optical disk D. 
This discrimination is carried out by determining whether or not the above 
changed amount .DELTA.D exceeds the set value Da stored in the set value 
storage area. If the changed amount .DELTA.D is smaller than the set value 
Da, then it is determined that the optical head 2 has not reached the 
position corresponding to the innermost periphery of the magneto-optical 
disk D. Then, the processing proceeds to step S10. 
In step S10, the innermost periphery movement speed control means 67 
compares the first target value D1 and the voltage data Dv. If the value 
of the voltage data Dv is larger than the-first target value D1, then the 
control signal outputting means 66 lowers the level of the control signal 
Sc supplied to the first motor drive circuit 41a, thereby the movement 
speed of the optical head 2 being reduced. If on the other hand the value 
of the voltage data Dv is smaller than the first target value D1, then the 
control signal outputting means 66 increases the level of the control 
signal Sc supplied to the first motor drive circuit 41a, thereby the 
movement speed of the optical head 2 being increased. 
Then, the processing returns to step S7, and thereafter the processings in 
step S7 and the succeeding steps are carried out repeatedly. The 
processings from step S7 to step S10 are repeatedly carried out until it 
is determined in step S9 that the optical head 2 has reached the position 
corresponding to the innermost periphery. Though these processings, the 
optical head 2 is moved toward the innermost periphery of the 
magneto-optical disk D at a predetermined speed indicated by the first 
target value D1, and finally reaches the position corresponding to the 
innermost periphery. 
When the optical head 2 reaches the position corresponding to the innermost 
periphery, the optical head 2 is brought in contact with the stopper 35 
and hence forcibly stopped. At this time, the fluctuation detecting 
circuit of the midpoint servo mechanism included in the optical head 2 
outputs a signal having a waveform with a high peak value. 
Therefore, if not only comparison of the changed amount between the first 
target value D1 nd the voltage data Dv and the set value but also a 
processing of discriminating whether or not an amplitude of the signal 
output from the fluctuation detecting circuit of the midpoint servo 
mechanism of the optical head 2 has a certain signal level or higher is 
employed in the discrimination processing in step S9, then it is possible 
to precisely determine that the optical head 2 reaches the position 
corresponding to the innermost periphery of the magneto-optical disk D. 
The processing proceeds to step S11 (FIG. 10), wherein the control signal 
outputting means 66 outputs the control signal Sc used for driving the 
first voice coil motor 34a (to move the optical head 2 toward the PEP 
zone) through the output port 56 to the fist motor drive circuit 41a. As a 
result, the optical head 2 starts moving toward the PEP zone. At this 
time, the counterelectromotive current Ia having a level corresponding to 
the speed of the optical head 2 flows through the second voice coil motor 
34b, flowing through the switching circuit 42 to the counterelectromotive 
voltage detecting system 43. T he counterelectromotive voltage detecting 
system 43 converts the counterelectromotive current Ia into the voltage 
signal Sv and further converts the voltage signal Sv into the digital data 
(voltage data Dv) to output the digital data. 
The processing proceeds to step S12, wherein the voltage data receiving 
means 65 receives the voltage data Dv supplied from the 
counterelectromotive voltage detecting system 43 through the input port 55 
and stores it in the voltage data storage register Ra. 
The processing proceeds to step S13, wherein the PEP detecting speed 
control means 68 compares the second target value D2 which is stored in 
the second target value storage area and concerns the target speed used 
until detection of the PEP zone, with the voltage data Dv. If the value of 
the voltage data Dv is larger than the second target value D2, then the 
control signal outputting means 66 lowers the level of the control signal 
Sc supplied to the first motor drive circuit 41a, thereby the movement 
speed of the optical head 2 being reduced. If on the other hand the value 
of the voltage data Dv is smaller than the second target value D2, then 
the control signal outputting means 66 increases the level of the control 
signal Sc, thereby the movement speed of the optical head 2 being 
increased. 
The processing proceeds to step S14, wherein the discriminating means 62 
discriminates whether or not the PEP zone is detected. This discrimination 
is carried out by determining whether or not the pulse signal Ps from the 
PEP zone detecting circuit 47 is input therefrom. If it is determined in 
step S14 that the pulse signal Ps is not inputted, then the processing 
returns to step S12, and thereafter the processings in step S12 and in the 
succeeding steps are repeatedly carried out. THrough these repeated 
processings, the optical head 2 is moved toward the PEP zone at a 
predetermined speed indicated by the second target value D2 until 
detection of the PEP zone. 
If on the other hand it is determined in step S14 that the PEP zone is 
detected, then the processing proceeds to step S15, wherein the control 
signal outputting means 66 lowers the level of the control signal Sc 
supplied to the first motor drive circuit 41a, thereby the movement speed 
of the optical head 2 being reduced. 
The processing proceeds to step S16, wherein the data reading request means 
70 outputs a signal used to request the reading of the data (PEP data 
reading request signal SPEP) through the output port 56 to the system 
controller 18. 
The system controller 18 receives the information indicative of normal 
reading or abnormal reading output from the decoder 16 based on the PEP 
data reading request signal SPEP input from the sled servo circuit 31. If 
the information received from the decoder 16 indicates that the PEP data 
is normally read, then the system controller reads the PEP data output 
from the decoder 16 and stores the PEP data in a memory thereof. Further, 
the system controller 18 supplies a signal indicative "normal" to the sled 
servo circuit 31. If on the other hand the information indicates that the 
data is not normally read, then the operation of reading the PEP data is 
carried out several times over all the PEP zone. If the PEP data is 
normally read during the several operations of reading the PEP data, then 
the above processing is carried out. If on the other hand the PEP data 
cannot be normally read during the several operations of reading the PEP 
data, then the system controller 18 controls a display device such as a 
liquid crystal display or the like connected to the system controller 18 
to display a message "this disk has different format" and further supplies 
a signal indicative of "abnormal" to the sled servo circuit 31. 
The processing proceeds to step S17, wherein the voltage receiving means 65 
of the sled servo circuit 31 receives the voltage data Dv supplied thereto 
from the counterelectromotive voltage detecting system 43 through the 
input port 55 and the sled servo circuit 31 stores the received voltage 
data Dv in the voltage data storage register. 
The processing proceeds to step S18, wherein the PEP reading speed control 
means 69 compares the third target value D3 stored in the third target 
value storage area and concerning the target speed used upon the operation 
of reading the PEP data from the PEP zone with the voltage data Dv. If the 
value of the voltage data. Dv is larger than the third target value D3, 
then the control signal outputting means 66 lowers the level of the 
control signal Sc supplied to the first motor drive circuit 41a, thereby 
the speed of the optical head 2 being reduced. If on the other hand the 
value of the voltage data Dv is smaller than the third target value D3, 
then the control signal outputting means 66 increases the level of the 
control signal Sc, thereby the speed of the optical head 2 being 
increased. 
The processing proceeds to step S19, wherein the discriminating means 62 
discriminates whether or not the signal Sa is input from the system 
controller 18. If the signal Sa is not input, then the sled servo circuit 
31 determines that the PEP data is being read, and hence the processing 
returns to step S17, Thereafter the processings in step S17 and the 
succeeding steps are repeatedly carried out. Through the repeated 
processings, the optical head 2 is moved over the PEP zone at a 
predetermined speed indicated by the third target value D3 until the 
system controller 18 reads the PEP data or until the system controller 18 
detects that the PEP data could not normally be read. 
If on the other hand it is determined in step S19 that the signal Sa is 
input from the system controller 18, then the processing proceeds to step 
S20, wherein the discriminating means 62 determines whether the content of 
the signal Sa indicates "normal" or "abnormal". If the signal Sa indicates 
"normal", then the processing proceeds to step S21, and if on the other 
hand the signal Sa indicates "abnormal", then the access pre-processing 
program is forcibly stopped. 
In step S21, the operation selection signal outputting means 63 outputs a 
high-level operation selection signal Ss indicative of an operable state 
through the output port 56 to the second motor drive circuit 41b. The 
second motor drive circuit 41b accepts the control signal Sc output from 
the sled servo circuit 31 based on the high-level operation selection 
signal Ss input from the sled servo circuit 31, and outputs the drive 
current Si corresponding to a polarity and level of the control signal Sc. 
The processing proceeds to step S22, wherein the switching control means 64 
outputs the low-level switching control signal Sw through the output port 
56 to the switching circuit 42. The switching circuit 42 switches its 
movable contract 42c to the second motor drive circuit 41b side based on 
the low-level switching control signal Sw input from the sled servo 
circuit 31. This switching operation allows the drive current Si output 
from the second motor drive circuit 41b to be supplied to the second voice 
coil motor 34b. As a result, the optical head 2 is driven by the first and 
second voice motor coils 34a, 34b to thereby start moving stably. 
The processing proceeds to step S23, wherein the data reading request means 
70 outputs the signal used to request the reading of the SFP data (SFP 
data reading request signal SSFP) through the output port 56 to the system 
controller 18. 
Based on the SFP data reading request signal SSFP input from the sled servo 
circuit 31, the system controller 18 reads the SFP data output from the 
decoder 16 and stores it in the memory therein. In this case, since the 
SFP zone has a guide groove for tracking servo or sample pits formed 
therein, the SFP data is read out from the SFP zone while the tracking 
servo control is being carried out. 
The processing proceeds to step S24, wherein the access pre-processing 
program 61 of the sled servo circuit 31 starts the access control 
processing program and then ends its processing. Thereafter, the ordinary 
access operation is carried out in accordance with the access control 
processing program. 
As described above, according to the recording and reproducing apparatus of 
this embodiment, of the two voice coil motors 34a, 34b for moving the 
optical head 2 in the radius direction of the magneto-optical disk D, the 
second voice coil motor 34b is brought in its stop state. The optical head 
2 is moved by using only the first voice coil motor 34a. At this time, the 
counterelectromotive current Ia flowing through the excitation coil of the 
second voice coil motor 34b is converted into the voltage signal 
indicative of the speed information Dv, and the speed information Dv is 
supplied to the sled servo circuit 31. Therefore, it is possible to 
control the optical head 2 to move at a constant speed based on the 
supplied speed information Dv, without providing some special devices such 
as a speed sensor or the like. Moreover, it becomes unnecessary to provide 
a position sensor or an elastic (or springy) member used when the PEP zone 
is detected. This leads to advantage in manufacturing costs and eliminates 
consideration of durability of the elastic (or springy) member, which can 
increase reliability of the recording and reproducing apparatus itself. 
Since the counterelectromotive current Ia flowing through the excitation 
coil of the second voice coil motor 34b is converted into the voltage 
signal and the voltage signal is used as the speed information Dv, it is 
advantageous when the PEP data which is to be read at an operation start 
stage of the recording and reproducing apparatus and contains various 
attributes of the magneto-optical disk D is read. 
Specifically, the advantages obtained from this embodiment are as follows. 
(1) It is possible to move the optical head 2 at a constant speed (the 
first target value D1) based on the speed information Dv when the optical 
head 2 is once moved toward the innermost periphery of the magneto-optical 
disk D. 
(2) It is possible to easily discriminate whether or not the optical head 2 
reaches the position corresponding to the innermost periphery, by 
comparing the difference .DELTA.D between the first target value D1 and 
the speed information Dv and the predetermined value Da. 
(3) When the optical head 2 at the position corresponding to the innermost 
periphery is moved toward the PEP zone side, it is possible to move the 
optical head 2 at the speed (the second target value D2) allowing reliable 
detection of the PEP zone until the PEP zone is detected. 
(4) When the optical head 2 reads the PEP data from the detected PEP zone, 
it is possible to move the optical head 2 at the speed (the third target 
value) which is most preferable for reading the PEP data. 
While in this embodiment the present invention is applied to the reading of 
the PEP data recorded in the PEP zone located on the inner periphery side 
of the magneto-optical disk D, the present invention is not limited 
thereto and can be applied to the reading of the data recording in a 
portion where the tracking servo control cannot be carried out. 
As described above, the disk apparatus according to the embodiment of the 
present invention includes a rotation means for rotating the disk loaded 
onto the disk apparatus, a head for accessing the information signal 
recorded on the disk being rotated, and a head moving means for moving the 
head in the radius direction of the disk. Further, the head moving means 
has a plurality of voice coil motors serving as drive sources for the head 
moving means, the optical head guiding means for guiding the head in the 
radius direction of the disk, and the drive means for controlling the 
plurality of voice coil motors. Therefore, it is possible to carry out the 
attribute information reading operation carried out at the stage preceding 
to the access to the disk, with low manufacturing costs and high 
reliability. Moreover, it is possible to read the attribute information at 
high speed. 
Having described a preferred embodiment of the present invention with 
reference to the accompanying drawings, it is to be understood that the 
present invention is not limited to the above-mentioned embodiment and 
that various changes and modifications can be effected therein by one 
skilled in the art without departing from the spirit or scope of the 
present invention as defined in the appended claims.