Disk recording and reproducing apparatus

A multi-head disk recording and reproducing apparatus, wherein sector synchronization signals obtained from a first optical pick-up and a second optical pick-up are input to a phase comparator where phases are compared, and a preceding sector synchronization signal is output to an overall control unit. In the overall control unit, the processing is carried out with respect to a first optical pick-up and second optical pick-up by a procedure using this input preceding sector synchronization signal as a reference. First, during a term where addresses are determined in the pick-ups, a sled servo and a spindle servo operation are carried out with respect to each pick-up. When the maximum time t of phase deviation has elapsed and addresses are determined, a tracking servo, focus servo, laser control, and other operations are instructed to the control units based on the addresses.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a disk recording and reproducing apparatus 
for performing the recording and/or reproduction of signals to and from a 
disk-like recording medium. 
2. Description of the Related Art 
For example, where it is intended to record and/or reproduce signal with 
respect to a disk-like recording medium, for example, an optical disk, at 
a high speed, there is known a technique in which the recording and 
reproduction of the signal are simultaneously carried out with respect to 
one optical disk by using two optical pick-ups (OP) so as to double the 
data transfer rate. 
In such a multi-head optical disk apparatus, the following control has been 
carried out for each optical pick-up. 
Each head performs the recording and/or reproduction of the signal in units 
of sectors, so even in a case where a plurality of optical pick-ups are 
used, the references for the timing of these processing procedures must be 
matched with the divisions of the sectors. For this reason, first, a 
timing is detected and address information is read at that timing, then 
the sector of the intended address is sought. At this time, processing 
procedures such as a selection of whether to use a sled seek (coarse seek) 
or to use a track jump (fine seek) up to that address and the setting of 
the power of the laser are carried out. 
Reproduction timings, that is, phases of respectively reproduced sector 
synchronization signals in such a plurality of optical pick-ups where a 
sector of the reproduced RF signal is used as a reference, can not be 
matched with a high precision. This is because, even if each optical 
pick-up is arranged at a position a whole multiple of the sector dividing 
angle, it is de facto impossible to obtain a sufficient precision due to 
the limits of the assembly precision and eccentricity of the disk. For 
this reason, the address detection timing is different in each optical 
pick-up and also the timing limit of the setting of the power of the laser 
and so on are different. For this reason, a control circuit for every 
optical pick-up is necessary and, further, a control circuit for 
integrating them becomes necessary. 
A concrete explanation will be made of a control circuit of such a 
multi-head optical disk apparatus by referring to FIG. 1. 
FIG. 1 is a view showing a reference example of the control circuit of an 
optical disk apparatus. This control circuit is provided with a first 
optical pick-up 11 and a second optical pick-up 21 for performing the 
recording and reproduction of the signal, a first servo control unit 13 
and a second servo control unit 23 for performing focusing and tracking, a 
first laser control unit 14 and a second laser control unit 24 for 
controlling the power of each laser, and a first microcomputer 91 and a 
second microcomputer 92 for controlling these parts. 
A sector synchronization signal and a sector address information 
respectively separated from the reproduced RF signal are input to the 
first microcomputer 91 and the second microcomputer 92 from the first RF 
signal processing unit 12 and the second RF signal processing unit 22. The 
first microcomputer 91 and the second microcomputer 92 respectively start 
the processing accompanied with the input of the sector synchronization 
signals and read the sector address information from the first RF signal 
processing unit 12 and the second RF signal processing unit 22. In order 
to perform the control as mentioned above, the first microcomputer 91 
outputs control signals to the first servo processing unit 13 and the 
first laser control unit 14, and the second microcomputer 92 outputs 
control signals to the second servo processing unit 23 and the second 
laser control unit 24. 
Further, the first microcomputer 91 and the second microcomputer 92 send 
information such as seek completion and address read ending to the 
integrated microcomputer 93 for controlling them. Control information such 
as "change the laser to erase power" and "seek address 1000" is sent from 
the integrated microcomputer 93. By this, the first optical pick-up 11 and 
the second optical pick-up 21 can perform the recording and/or 
reproduction of the signal at a high speed in cooperation with each other. 
In the disk recording and reproducing apparatus as mentioned above, 
however, it suffers from the disadvantage in that three microcomputers are 
necessary for the control circuit in a case of the circuit of FIG. 1, so 
the circuit becomes large in scale and complex and, in addition, the cost 
is increased. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a disk recording and 
reproducing apparatus having a control circuit that can easily and 
efficiently control circuits for a plurality of heads where the disk-like 
recording medium is simultaneously accessed by these plurality of heads. 
Accordingly, a disk recording and reproducing apparatus of the present 
invention has a plurality of heads for recording or reproducing a signal 
to or from a disk-like recording medium; a plurality of position control 
means corresponding to the heads controlling the positions of the heads; a 
plurality of output control means for controlling the output from the 
heads for recording or reproducing the signal with respect to said 
disk-like recording medium; a plurality of reproduced signal processing 
means corresponding to the heads for extracting at least the 
synchronization signal output with the same phase for every sector on the 
disk recording medium based on the reproduced signals obtained from the 
heads; a phase comparing means for comparing a plurality of the 
synchronization signals respectively extracted by the plurality of 
reproduced signal processing means with each other and selecting the 
signal having the earliest phase; and a head control means for controlling 
the plurality of position control means and the plurality of output 
control means by using the selected signal as a reference signal at a 
timing based on this reference signal. 
Preferably, the head control means comprises a single microcomputer for 
controlling the plurality of position control means and the plurality of 
output control means respectively corresponding to the plurality of heads 
based on the reference signal. 
Preferably, the head control means performs at least rotation control of 
the disk-like recording medium during a period where the synchronization 
signals are obtained from all of the plurality of the heads. 
Preferably, two heads among the plurality of heads are arranged on two 
radii of the disk-like recording medium having an angle of 90 degrees 
relative to each other. 
Preferably, the head control means performs at least a sled servo of these 
plurality of heads during a period where address signals are read and 
fetched from all of the plurality of the heads.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An explanation will next be made of the optical disk apparatus of an 
embodiment of the disk recording and reproducing apparatus of the present 
invention by referring to FIG. 2 to FIG. 7. 
FIG. 2 is a block diagram of the configuration of the optical disk 
apparatus of the present embodiment. 
An optical disk apparatus 1 has a first optical head processing unit 10, a 
second optical head processing unit 20, and a control unit 30. The first 
optical head processing unit 10 has a first optical pick-up 11, a first RF 
signal processing unit 12, a first servo processing unit 13, and a first 
laser control unit 14, and the second optical head processing unit 20 has 
a second optical pick-up 21, a second RF signal processing unit 22, a 
second servo processing unit 23, and a second laser control unit 24. 
Further, the control unit 30 has a phase comparator 31 and an overall 
control unit 32. 
First, an explanation will be made of the recording and/or reproduction 
method of the signal to and from the optical disk medium by the optical 
disk apparatus 1 by referring to FIG. 3 and FIG. 4. 
The optical disk apparatus 1 divides a user recording region of an optical 
disk 40 into two areas, i.e., a first area 41 constituted by tracks on the 
inner circumference side and a second area 42 constituted by tracks on the 
outer circumference side as shown in FIG. 3, and performs the recording 
and reproduction of the signal in parallel by different optical pick-ups. 
The optical disk apparatus 1 controls the rotation of the optical disk 40 
by a constant angular velocity (CAV) system. Accordingly, each track 
43.sub.-i (i is a track number) on the optical disk 40 is provided with a 
sector 44.sub.-ij (i is the track number, and j is a sector number of each 
track) corresponding to the predetermined angle .alpha. as shown in FIG. 
4. 
Next, an explanation will be made of the configuration of the parts of the 
optical disk apparatus 1. 
The first optical head processing unit 10 is a circuit for performing the 
recording and/or reproduction of a signal with respect to a first area 41 
of the optical disk 40 mentioned above, and the second optical head 
processing unit 20 is a circuit for performing the recording and/or 
reproduction of a signal with respect to a second area 42. The 
corresponding parts have substantially the same function. 
An explanation will be made next of the first optical pick-up 11 and second 
optical pick-up 21 by referring to FIG. 5. 
As shown in FIG. 5, the first optical pick-up 11 and the second optical 
pick-up 21 are arranged on the optical disk 40 provided on straight lines 
having a predetermined angle relative to each other and intersecting the 
center of the optical disk 40. The first optical pick-up 11 performs the 
recording and/or reproduction of the signal with respect to the first area 
41, while the second optical pick-up 21 performs the recording and/or 
reproduction of the signal with respect to the second area 42. These first 
optical pick-up 11 and second optical pick-up 21 are provided at an angle 
corresponding to a whole multiple of the angle .alpha. corresponding to 
the sector 44.sub.-ij shown in FIG. 4, so that the processing can be 
carried out with respect to the sectors to be accessed with almost the 
same phase. In the present embodiment, it is 90 degrees. 
The first RF signal processing unit 12 and the second RF signal processing 
unit 22 extract desired signals from the RF signals respectively detected 
at the first optical pick-up 11 and the second optical pick-up 21. For 
example, the first RF signal processing unit 12 and the second RF signal 
processing unit 22 extract the sector synchronization signals indicating 
the division of the sectors from the input RF signals and output the same 
to the comparator 31 of the control unit 30. Further, they extract the 
sector address signals from the input RF signals and output the same to 
the overall control unit 32 of the control unit 30 according to request. 
The first servo processing unit 13 and the second servo processing unit 23 
control the positions of the first optical pick-up 11 and the second 
optical pick-up 21 based on the control signal input from the overall 
control unit 32, respectively. The first servo processing unit 13 and the 
second servo processing unit 23 respectively have sled servo units for 
moving the entire first optical pick-up 11 and second optical pick-up 21 
in a tracking direction, tracking servo units for moving the object lenses 
of the first optical pick-up 11 and the second optical pick-up 21 in the 
tracking direction so as to make the first and second optical pick-ups 11 
and 12 suitably follow the intended track of the optical disk 40, and 
focus servo units for controlling distances with respect to the optical 
disks 40 of the object lenses so that light beams emitted from the first 
optical pick-up 11 and the second optical pick-up 21 are suitably focused 
on the recording surfaces of the optical disks 40. These parts are 
controlled based on the control signals input from the overall control 
unit 32. 
The first laser control unit 14 and the second laser control unit 24 
control the intensities of the light beams emitted from the first optical 
pick-up 11 and the second optical pick-up 21 based on the control signals 
input from the overall control unit 32. These optical beams are set to 
predetermined intensities in accordance with the operation modes such as 
the read, write, and erase modes of the data. 
The phase comparator 31 of the control unit 30 compares the sector 
synchronization signal input from the first RF signal processing unit 12 
and the sector synchronization signal input from the second RF signal 
processing unit 22, selects the one preceding sector synchronization 
signal, and outputs the same to the overall control unit 32. 
The overall control unit 32 controls the first servo processing unit 13 and 
the first laser control unit 14 of the first optical head processing unit 
10 and the second servo processing unit 23 and the second laser control 
unit 24 of the second optical head processing unit 20 by using the sector 
synchronization signal input from the phase comparator 31 as a signal of 
reference. In the present embodiment, the overall control unit 32 is 
constituted by a microcomputer. 
An explanation will be made next of the above processing in the overall 
control unit 32 by referring to FIG. 6. The flowchart shown in FIG. 6 
shows the flow of the processing executed with respect to a predetermined 
sector on the optical disk 40. 
First, the signal indicating the detection of the preceding sector 
synchronization signal is input from the phase comparator 31 to the 
overall control unit 32 as an interruption signal in a state where the 
focus servo is applied to the first and second pick-ups 11 and 21 (step 
S1). The overall control unit 32 gives the control signals to the servo 
processing units 13 and 23 in a time division manner so that the sled 
servo and spindle servo with respect to the spindle motor of the first 
optical pick-up 11 and the second optical pick-up 21 are carried out 
during a period where the addresses at which the first optical pick-up 11 
and the second optical pick-up 21 are located are determined (step S2). 
Next, it is checked whether or not the predetermined time t determined in 
advance has elapsed after the sector synchronization signal is input at 
step S1 (step S3). Where it has lapsed, the sector addresses are read and 
fetched from the first RF signal processing unit 12 and the second RF 
signal processing unit 22 (step S4). Where the predetermined time t has 
not elapsed, the elapse of time is awaited. Note that, this time t is the 
time corresponding to the time the same as or more than the maximum value 
of the phase difference of the signal obtained from the first optical 
pick-up 11 and the signal obtained from the second optical pick-up 21 and 
determined by taking all of mechanical attachment error etc. into account. 
Next, the overall control unit 32 performs the focus servo and tracking 
servo with respect to the first servo processing unit 13 and the second 
servo processing unit 23 and the laser output control etc. with respect to 
the first laser control unit 14 and the second laser control unit 24 in a 
time division manner based on the read and fetched addresses (step S5). 
Note that, these servo processings performed at step S5 in the overall 
control unit 32 generate trigger signals for indicating the start of each 
servo operation etc. to the servo processing units 13 and 23 and the laser 
control units 14 and 24. 
When these processings are carried out with respect to the pick-ups, one 
series of control processing is terminated (step S6), the processing 
routine returns to step S1 for performing the servo operation of each 
pick-up with respect to the next sector and the processing is repeatedly 
carried out. 
Next, an explanation will be made of the operation of the optical disk 
apparatus 1. 
First, in the optical disk apparatus 1, the recording and/or reproduction 
of the signal is carried out with respect to the optical disk 40 by using 
two heads, i.e., the first optical pick-up 11 and the second optical 
pick-up 21. These two heads, i.e., the first optical pick-up 11 and the 
second optical pick-up 21, are provided at angles of 90 degrees relative 
to each other as shown in FIG. 5. The first optical pick-up 11 accesses 
the first area 41 on the inner circumference side of the optical disk 40, 
and the second optical pick-up 21 accesses the second area 42 on the outer 
circumference side of the optical disk 40. 
The first optical pick-up 11 and the second optical pick-up 21 are designed 
so as to be able to perform processing with respect to the sector with the 
same phase, but in actuality, as shown in FIG. 7, the RF signals are 
output from the pick-ups in a state where the phases are deviated by 
exactly the time t at the maximum. 
Therefore, the sector synchronization signals are separated from these RF 
signals, input to the phase comparator 31, and compared in the phases 
thereof and the preceding sector synchronization signal is output to the 
overall control unit 32. In the overall control unit 32, the processing is 
carried out with respect to the first optical pick-up 11 and the second 
optical pick-up 21 by the procedure shown in FIG. 6 by using this input 
sector synchronization signal as a reference. Specifically, first, the 
sled servo and spindle servo operation are carried out with respect to the 
pick-ups during a period where the addresses are determined in the 
pick-ups. When the addresses are determined, the tracking servo, focus 
servo, laser control, and other operations are carried out based on these 
addresses. The overall control unit 32 will control both of the first 
optical pick-up 11 and the second optical pick-up 21 by just repeating 
this processing. 
In this way, in the optical disk apparatus 1 of the present embodiment, the 
recording and/or reproduction of the signal are almost simultaneously 
carried out with respect to a single optical disk medium by using two 
optical pick-ups. Therefore the recording and/or reproduction of a signal 
at a transfer rate of two times that of the usual optical disk is 
possible. Then, at this time, since two pick-ups are controlled together 
by one overall control device, specifically one microcomputer, these two 
pick-ups can be efficiently used without overhead and an increase and 
complication of the configuration of the apparatus due to the use of two 
pick-ups can be suppressed to the smallest limit. 
Further, in the present embodiment, since the sled servo and the spindle 
servo operation are carried out during a period from when the preceding 
sector synchronization signal is detected to when the addresses are 
determined, the microcomputer constituting the overall control unit can be 
effectively used. Further, periodical processing can be carried out during 
this period, therefore processings of various control operations such as 
digital signal processing based on a sampling theorem can be effectively 
scheduled, therefore the control can be carried out more effectively and 
adequately by one microcomputer. 
Note that, the present invention is not limited to the present embodiment 
and can be modified in any preferred manner. 
For example, in the optical disk 40 of the present embodiment, two pick-ups 
were used, but the number is not limited to two, that is, three or four is 
possible. It is also possible to adopt a configuration in which access is 
almost simultaneously made with respect to any number of pick-ups. Even in 
a case where there are three or more pick-ups, these plurality of pick-ups 
can be suitably controlled by a similar configuration to that of the 
present embodiment. Namely, it is sufficient so far as the sector 
synchronization signals obtained from these plurality of pick-ups are 
compared, the earliest sector synchronization signal is selected in the 
phase comparator, and the pick-ups are controlled by the same procedure as 
that shown as the flowchart in FIG. 6 by using the earliest sector 
synchronization signal as a reference in the overall control unit 32. 
Further, in the present embodiment, the output of the phase comparator is 
input to the microcomputer, which serves as the overall control unit, as 
it is, but it is also possible to pass the same through a PLL (phase 
locked loop) circuit for noise processing and jitter reduction and then 
input the same. When performing this, the omission of a pulse of the 
sector synchronization signal can be more reliably prevented, and the 
processing can be started at more stable timing. Note that, as this PLL 
circuit, any usually well known circuit can be applied. 
Further, in the present embodiment, the sector synchronization signal 
selected at the phase comparator is input as the interruption signal to 
the microcomputer of the overall control unit and the control processing 
is started, but it is also possible to start the processing not by 
interruption, but by polling processing for supervising the polarity of 
the output of the phase comparator. 
Further, in the present embodiment, a sector synchronization signal was 
used as the signal for comparing the signals obtained from the pick-ups, 
but the signal is not limited to this. Any signals can be used so far as 
the signals are output with the same phase at one sector. 
Further, in the present embodiment, the sled servo and the spindle servo 
operation are carried out during a period from when the preceding sector 
synchronization signal is detected to when the addresses are determined, 
but it is also possible to perform any processing other than them during 
this term. For example, if there is time, processing such as self 
diagnosis can be carried out too. 
Further, such a control device is not limited to only an optical disk, but 
can be applied to any recording and reproducing apparatus in which a 
disk-like recording medium is to be processed such as a hard disk drive or 
a floppy disk drive apparatus. 
According to the disk recording and/or reproducing apparatus of the present 
invention, when recording and/or reproduction is carried out with respect 
to a disk-like recording medium by a plurality of heads, the circuits for 
these plurality of heads can be efficiently controlled by a control 
circuit having a simple configuration such as a single microcomputer. As a 
result, a multi-head disk recording and reproducing apparatus capable of 
performing high speed data transfer, having a higher performance, having a 
simpler configuration, and cheaper in cost can be provided.