JP3649172B2 - Disc recording device - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an optical disk recording apparatus in which a write synchronization signal is recorded on a disk in advance and a disk rotational speed deviation can be detected during recording.
[0002]
[Prior art]
In an optical disk recording apparatus, a disc rotational speed deviation is unavoidable due to eccentricity of the disc or turntable, cogging (torque unevenness) of the spindle motor, or the like. This disc rotational speed deviation causes a speed deviation (time error) of pits recorded on the disc. The time error increases as the servo gain of the spindle motor decreases. Since the servo gain of the spindle motor decreases as it goes to the outer periphery of the disk, the time error increases as it goes to the outer periphery of the disk, as shown in FIG. 5, especially in a player with a narrow band of the clock generator that reads the EFM signal. become. Also, the time error fluctuates in the time axis direction at the rotation frequency, and this fluctuation also increases as it goes to the outer periphery. For this reason, a signal reading error occurs as it goes to the outer periphery of the disk even during reproduction, and in some cases, an uncorrectable error also occurs.
[0003]
[Problems to be solved by the invention]
Conventionally, in order to reduce the rotational speed deviation of the disk as described above, this is dealt with by increasing the servo gain of the spindle motor. However, increasing the servo gain of the spindle motor has a limit in relation to the detection signal frequency for motor control, for example, and a satisfactory result is not necessarily obtained. In addition, increasing the servo gain has no effect on the speed deviation caused by cogging of the spindle motor.
[0004]
The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a disk recording apparatus capable of reducing time errors of pits recorded on a disk.
[0005]
[Means for Solving the Problems]
The disk device according to the present invention reads a rotation control means for controlling the rotation of the disk based on the output of the reference oscillator, and a write synchronization signal previously recorded as absolute position information on the disk rotated by the rotation control means. Read means, first clock generation means for outputting a first clock synchronized with the write synchronization signal read by the read means, and output from the EFM encoder at the time of recording in synchronization with the first clock Operation of second clock generation means for outputting a second clock having a frequency higher than that of the EFM signal, and a pulse modulation circuit for pulse-modulating the EFM signal by the second clock output from the second clock generation means A write strategy that is used as a clock and that has undergone pulse modulation processing of the EFM signal by the pulse modulation circuit. A signal processing unit that outputs a write signal that is a digital output, and a laser power control unit that controls a laser output for disk recording by a write signal that is a write strategy output obtained by the signal processing unit. .
[0006]
[Action]
According to the present invention, a signal capable of detecting a disc rotational speed deviation caused by the eccentricity of the disc or turntable, the cogging of the spindle motor, etc., for example, a write synchronization signal recorded in advance on the disc is detected and synchronized therewith. Signal processing. Specifically, for example, a clock for an EFM encoder, a pulse modulation circuit, etc. in the signal processing circuit is synchronized with the rotational speed deviation detection signal and a write signal to the disk is output. As a result, the time error of the disk is reduced, and it becomes possible to follow a speed deviation of a high frequency component that cannot be removed by the servo of the spindle motor. Also, according to the recording system of the present invention, errors do not increase even when the disk is on the outer periphery during disk reproduction, and the occurrence of uncorrectable errors is reliably prevented.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a compact disc-write once (CD-WO) recording apparatus according to an embodiment of the present invention. A spindle motor (disk motor) 2 that rotates the CD-WO disk 1, an optical pickup 3 that outputs a recording laser beam, an RF amplifier 4 that amplifies the output of the optical pickup 3, and this RF amplifier 4 There are provided a focus / tracking servo circuit 5 for performing focus control and tracking control using the output of the above, a spindle servo circuit 6 for controlling the rotation of the spindle motor 2 using the crystal oscillator 7 as a reference oscillator, and the like.
[0008]
An FM detection PLL circuit 8 that can detect the rotational speed deviation of the disk 1 is provided at the output of the RF amplifier 4. The disc 1 is recorded with ATIP (Absolute Time In Pre-groove) data wobbled before data is recorded, and the FM detection PLL circuit 8 generates a clock SCK synchronized with the recording time data therein. Based on the output clock SCK of the PLL circuit 8, the spindle servo circuit 6 operates. Further, in order to generate an operation clock CK for recording signal processing synchronized with the output clock SCK of the PLL circuit 8, a PLL circuit 9 using, for example, a 138 MHz VCO is provided. The signal processing circuit 10 is a write signal processing unit including an EFM encoder, a pulse modulation circuit, and the like. Here, an operation clock CK obtained by the PLL circuit 9 is used as a clock for the EFM encoder and the pulse modulation circuit. The laser output of the optical pickup 3 is controlled by the write signal obtained from the signal processing circuit 10 via the automatic laser power control circuit 11, and recording on the disk 1 is performed.
[0009]
According to this embodiment, since the operation clock of the signal processing circuit 10 is generated based on the ATIP synchronization signal read from the disk 1, the clock cycle is not fixed, and corresponds to the disk rotation speed deviation due to disk eccentricity or the like. As a result, the clock of the signal processing circuit 10 is fluctuated and a write signal is generated. FIG. 2 shows the gain characteristic (solid line) of the spindle servo and the gain characteristic (broken line) of the loop according to this embodiment. According to this embodiment, the rotational speed-gain characteristic is apparently eliminated by the motor delay (secondary delay), and only the first-order delay due to the PLL. That is, the actual gain characteristic is improved only within the shaded area in FIG.
[0010]
With this improvement in gain characteristics, as shown in FIG. 3 in comparison with the prior art, in this embodiment, the recorded pit speed deviation is kept small regardless of the radial position of the disk. As a result of the time error being reduced in the disk recorded according to this embodiment, the reading error does not increase on the outer periphery of the disk during reproduction. This is shown in FIG. 4 in comparison with the conventional example. Further, additional recording can be facilitated while satisfying a certain synchronization condition.
[0011]
The present invention is not limited to CD-WO, but can be similarly applied to other optical discs (including magneto-optical discs) capable of detecting disc rotational speed deviations during recording.
[0012]
【The invention's effect】
As described above, according to the present invention, the operation clock for recording signal processing (encoder, pulse modulation circuit) is synchronized with the rotational speed deviation (time error) of the disk to be recorded, thereby reducing the eccentricity of the disk. An optical disc recording apparatus capable of effectively reducing the time error caused is obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a disk recording apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a motor rotation speed-gain characteristic of the same embodiment.
FIG. 3 is a diagram showing a time error reduction effect according to the embodiment.
FIG. 4 is a diagram showing a reading error reduction effect during reproduction according to the same embodiment.
FIG. 5 is a diagram illustrating a state of occurrence of a time error according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Disk, 2 ... Spindle motor, 3 ... Optical pick-up, 4 ... RF amplifier, 5 ... Focus / tracking servo circuit, 6 ... Spindle servo circuit, 7 ... Crystal oscillator, 8 ... FM detection PLL circuit, 9 ... 138MHz VCOPLL circuit, 10 ... signal processing circuit, 11 ... automatic laser power control circuit.

Claims (1)

Rotation control means for controlling the rotation of the disk based on the output of the reference oscillator;
Reading means for reading out a synchronization signal for writing recorded in advance as absolute position information on the disk rotated by the rotation control means;
First clock generation means for outputting a first clock synchronized with the write synchronization signal read by the reading means;
A second clock generating means for outputting a second clock having a frequency higher than that of the EFM signal output from the EFM encoder at the time of recording in synchronization with the first clock;
The second clock output from the second clock generation means is used as an operation clock of a pulse modulation circuit that performs pulse modulation on the EFM signal, and a write strategy output obtained by subjecting the EFM signal to pulse modulation processing by the pulse modulation circuit. Signal processing means for outputting a certain write signal;
Laser power control means for controlling the laser output for disk recording by a write signal which is a write strategy output obtained by the signal processing means;
A disk recording apparatus comprising:

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