JP3723529B2 - Optical head light emission output control device for optical disk recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical head light emission output control device of an optical disk recording apparatus that controls light emission output of an optical head in an optical disk recording apparatus that performs disk recording using a light beam from the optical head, and more particularly to variations in recording sensitivity of the disk. Correspondingly, the present invention relates to an optical head light emission output control device of an optical disk recording apparatus which corrects and records the light emission output of the optical head.
[0002]
[Prior art]
As an optical disk recording apparatus for recording a digital data signal on a disk using a light beam from an optical head, a CD-R corresponding to CD-R (Recordable) and CD-RW (ReWritable) of the CD (Compact Disc) family. The / RW drive is well known, and in this optical disk recording apparatus, the recording speed is increased.
[0003]
Currently, the maximum recording speed of CD-R corresponds to 40 times or 48 times the rated speed, and the recording speed of CD-RW corresponds to the maximum speed of 16 times the rated speed. In the case of -R, the CAV (Constant Angular Velocity) method in which the rotational speed of the disk is controlled to be constant for speeding up, or ZCLV (Zone Constant Linear) in which the speed of each disk is controlled to be constant at different linear speeds. Velocity) method is generally adopted.
[0004]
By the way, the discs recorded by such an optical disc recording apparatus have different materials to be used depending on the manufacturer and speed compatible grade, so that the recording sensitivity is different, or the recording sensitivity is different due to individual differences. It is also conceivable that the recording sensitivity varies depending on the recording site due to unevenness.
[0005]
Therefore, in the optical disk recording apparatus, the light emission output emitted from the optical head during recording is controlled to compensate for the difference in recording sensitivity, and the light emission output of the optical head is set to the optimum recording level optimum for recording on the disk. The
[0006]
The light emission output of the optical head is set by changing the light emission output step by step in a calibration area for light emission output setting provided separately from the program area for recording the actual data signal on the disc at the start of recording. A test signal is written on a trial basis, and the test signal is read by an optical head, and an RF (radio frequency) signal to be reproduced is used to remove the offset from the positive and negative amplitude values A and B. This is performed by detecting (depth of) = (A−B) / (A + B).
[0007]
Also, during the disk recording operation, the reflection level of the recording pulse is detected, or the recording mark recorded on the disk is detected by another light beam temporally positioned before the light beam used for recording. Then, so-called running OPC (Optimum Power Control) is performed to control the light emission output of the optical head to the optimum recording level.
[0008]
[Problems to be solved by the invention]
By the way, in the conventional optical head light emission output control device, this running OPC detects the amplitude values A and B on the plus side and the minus side by the peak hold and bottom hold of the RF signal, and these amplitude values A and B In general, each is converted to digital and then calculated by a microcomputer to detect the β value.
[0009]
However, in the above-described optical head light emission output control device, the β value is changed after the RF signal is read from the disk due to the limitation of the calculation processing time of the microcomputer and the digital conversion of the amplitude values A and B. There was a problem that a time delay until detection occurred and it was not possible to cope with high-speed disk recording.
[0010]
[Means for Solving the Problems]
The present invention generates a high-pass filter that removes an offset component from an RF signal read from a disk, an auto gain control circuit that controls the output of the high-pass filter to a constant level, and an offset component of an output from the auto gain control circuit. And a light emission output of the optical head according to the output of the low pass filter. That is, the RF signal from which the offset component is removed is limited to a certain level by the auto gain control circuit, and the amplitude value (A + B) obtained by adding the amplitude values A and B on the plus side and minus side of the RF signal is made constant. The offset component of the RF signal limited to a certain level is extracted by a low-pass filter, and thereby the difference value (A−B) of the amplitude values A and B on the plus side and minus side of the RF signal restricted to a certain level. ) Is generated. For this reason, the difference value (A−B) between the amplitude values A and B of the RF signal corresponds to the β value. Therefore, the light emission output of the optical head is controlled by controlling the light emission output of the optical head according to the output of the low-pass filter. Is set to the optimum recording level.
[0011]
【Example】
1 is a circuit block diagram showing an embodiment of an optical head light emission output control device of an optical disk recording apparatus according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of FIG. 1, and FIG. It is explanatory drawing explaining the irradiation position on the disc of a light beam.
[0012]
The light beam emitted from the optical head 1 is diffracted, and the zero-order beam of the diffracted light is applied to the disk as a main beam for writing the recording signal, and the ± first-order beam of the diffracted light is used for tracking control. The disk is irradiated as each subsequent sub beam.
[0013]
As shown in FIG. 3, each of these beams is irradiated with the preceding sub beam in a state where the main spot Sm formed on the disk by being irradiated with the main beam is correctly arranged on the signal track n. The formed sub-spot Ss1 is arranged such that the inner half is projected onto the signal track n and the outer half is projected between the signal track n and the adjacent signal track (n + 1) on the outer circumference. Sub-spots Ss2 formed on the disk by irradiation with the row sub-beams are substantially half on the outer peripheral side for signal track n, and substantially half on the inner peripheral side for signal track n and adjacent signal track (n-1 on the inner peripheral side). ) Are projected to each other.
[0014]
The optical head is provided with a photodetector that receives each reflected light from which the main beam and each sub beam are reflected by the disk. This photodetector receives each reflected light of each of the main beam and each sub beam. An area A and a pair of sub light receiving areas B and C are provided.
[0015]
The main light receiving area A is divided into four by dividing lines in directions corresponding to the signal track direction and the orthogonal direction of the disk, respectively. Each divided area corresponds to an RF signal, a focus error signal, and Each received light output used to generate a tracking error signal is generated.
[0016]
The pair of sub light receiving areas B and C are each divided into two by dividing lines in the direction corresponding to the signal track direction of the disk, and each of the divided sub light receiving areas B and C has a light receiving amount. Each received light output used to generate a tracking error signal is generated in response to.
[0017]
The various light receiving outputs of the photodetectors of the optical head 1 are supplied to a front end processing circuit 2, which generates an RF signal read from the disk and controls the gain of the RF signal to an optimum level. A focus error signal indicating equalization error with the disk signal surface of the laser beam irradiated from the optical head 1 to the disk by equalizing according to various disks, and a signal track of the laser beam on the disk A tracking error signal indicating the tracking error is generated.
[0018]
The astigmatism method is adopted for the focus servo, and the differential push-pull method is adopted for the tracking servo.
[0019]
By the way, the reflected light of the sub beam subsequent to the main beam includes a signal component related to tracking control, and also includes a recording signal component recorded by the main beam, in this case, a recording signal component of the signal track n. ing.
[0020]
Therefore, the RF signal obtained by reading the recording signal recorded on the signal track of the disk can be extracted using the reflected light of the sub beam.
[0021]
Here, in the on-track state of the main beam, the sub spot Ss2 is arranged on the signal track n at the outer peripheral side, so that the light reception output c1 in one divided region of the sub light reception region C includes an RF signal component. It will be a thing.
[0022]
The front end processing circuit 2 generates an RF signal based on the light receiving output c1 of the sub light receiving area C.
[0023]
The RF signal generated by the light receiving output c1 of the sub light receiving region C is supplied to a high pass filter (HPF) 3, and after the offset component is removed by the high pass filter 3, an auto gain control circuit (hereinafter referred to as an AGC circuit). 4 is controlled to a constant level.
[0024]
The RF signal limited to a certain level by the AGC circuit 4 is further supplied to a low-pass filter (LPF) 5, and an offset component is generated by the low-pass filter 5.
[0025]
Here, the offset component generated by the low-pass filter 5 is detected by the difference value (A−B) between the amplitude values A and B of the positive side and the negative side of the RF signal limited to a constant level by the AGC circuit 4. When the difference value (A−B) is zero, as shown in FIG. 2A, the RF signal output from the AGC circuit 4 has an offset voltage of “0”, and the difference value (A−B) 2), the RF signal output from the AGC circuit 4 becomes a positive level offset voltage “+ a”, and the difference value (A−B) is positive, as shown in FIG. As shown in FIG. 2C, the RF signal output from the AGC circuit 4 becomes a negative level offset voltage “−b”.
[0026]
The offset component generated by the low-pass filter 5 is supplied as a control signal of an auto power control circuit (hereinafter referred to as APC circuit) 6, and the APC circuit 6 drives a laser light source of the optical head 1 in accordance with the offset voltage. 7 to control the light emission output of the optical head 1 to the optimum recording level.
[0027]
By the way, when the RF signal from which the offset component is removed by the high-pass filter 3 is controlled to a constant level by the AGC circuit 4, the peak level is changed from the bottom level of the RF signal regardless of the level fluctuation of the RF signal output from the front end processing circuit 2. The amplitude value (A + B) obtained by adding the amplitude values A and B on the plus side and the minus side of the RF signal is constant.
[0028]
The offset component of the RF signal extracted by the low-pass filter 5 is the difference value (A−) between the amplitude values A and B on the plus side and minus side of the RF signal limited to a certain level obtained from the AGC circuit 4. B).
[0029]
Therefore, the offset component of the RF signal extracted by the low-pass filter 5 corresponds to β value = (A−B) / (A + B).
[0030]
Therefore, the light emission output of the optical head 1 can be set to the optimum recording level by controlling the APC circuit 6 in correspondence with the offset component of the RF signal extracted by the low-pass filter 5.
[0031]
By the way, during the recording operation in which the recording signal is recorded on the disc by the main beam, the RF signal is taken out by the sub beam which is temporally rearward.
[0032]
During the recording operation of the disc, the laser light quantity of the succeeding sub beam also changes in accordance with the recording signal level in order to change the light emission output of the optical head 1 in accordance with the recording signal level to be recorded on the disc. The RF signal read by the sub-beam is sampled during the period when the light emission output of 1 becomes one of the recording level and the reproduction level. For this reason, an RF signal corresponding to the recording signal actually recorded immediately before by the main beam is obtained by the sub beam without any level change.
[0033]
Therefore, during the recording operation of the disk, an offset voltage corresponding to the β value corresponding to the recording state of the recording signal actually recorded immediately before by the main beam is output from the low-pass filter 5, and the light emission output of the optical head 1 is the disk output. The optimum recording level that is optimum for recording is controlled.
[0034]
【The invention's effect】
As described above, according to the present invention, since a control signal for controlling the light emission output of the optical head is obtained from the RF signal read from the disk, it is not converted into a digital signal or requires a calculation by a microcomputer. Although there is a constant, it is possible to control the light emission output of the optical head to the optimum recording level by achieving higher speed than the method using the operation of the microcomputer.
[0035]
Further, since the RF signal is read from the recording signal actually recorded immediately before the recording operation of the disc, it is advantageous for use in running OPC during high-speed recording.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing an embodiment of an optical head light emission output control device of an optical disk recording apparatus according to the present invention.
FIG. 2 is a signal waveform diagram for explaining the operation of FIG. 1;
FIG. 3 is an explanatory diagram for explaining the irradiation position of each light beam on the disk in the optical head;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical head 2 Front end processing circuit 3 High pass filter 4 Auto gain control circuit 5 Low pass filter 6 Auto power control circuit

Claims (2)

An optical head light emission output control device for an optical disk recording apparatus that controls light emission output of an optical head in an optical disk recording apparatus that performs disk recording using a light beam from the optical head, and removes an offset component from an RF signal read from the disk A high pass filter, an auto gain control circuit that controls the output of the high pass filter to a constant level, and a low pass filter that generates an offset component of the output from the auto gain control circuit, according to the output of the low pass filter An optical head light emission output control device for an optical disk recording apparatus, wherein the light emission output of the optical head is controlled. A sub beam that follows the main beam that diffracts the light beam emitted from the light source of the optical head and writes the signal is formed on the disk. During the recording operation of the disk, the light emission output of the optical head is recorded and reproduced. 2. An optical head light emission output control device for an optical disk recording apparatus according to claim 1, wherein an RF signal is read from the disk by the sub beam during a period when one of the predetermined levels is reached.

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