JP3463293B2 - Optical disk drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device capable of writing information on an optical disk.

[0002]

2. Description of the Related Art Today, CD (abbreviation of Compact Disc, which is an example of an optical disc) has been remarkably popular as a protagonist in the multimedia age. Also, the CD is a read-only memory ROM (Read Only Mem).
The CD-ROM applied to "ory)" reads information from the CD-ROM drive device (also called reproduction or read).
However, this CD-ROM drive device has come to be installed in a personal computer as a standard product.

The world of CD is still developing,
CD-R (CD-Recordable) in which information can be written (also referred to as recording or writing) once, and CD-RW (CD-Rewr) in which information can be written any number of times
It has been applied to "table" and its potential has continued to evolve. A CD expresses a data string on a disk substrate by the presence or absence of holes called pits, which is irradiated with laser light to read data by the change in reflected light. This data string is arranged spirally on the disk substrate like a record board. This spirally arranged line is called a track. The distance between adjacent tracks is 1.6 microns.

FIG. 13 shows the structure of a general CD-R drive device. An optical disk (CD or CD-ROM) 1 is driven to rotate by a spindle motor 2. The optical pickup 3 has a built-in laser light source including a semiconductor laser (laser diode), an optical system such as a lens, a focus servo system including a focus actuator, a track servo system including a track actuator, a light receiving element, a position sensor, and the like. Laser beam is irradiated onto the optical disc 1 through the optical system, and the reflected light is received by the light receiving element through the optical system. The output signal of the light receiving element is output via the read amplifier 4. The focus servo system drives the lens position of the optical system in a direction perpendicular to the optical disc 1 so that the laser beam is focused on the optical disc 1, and the track servo system traces the laser beam focus on the track of the optical disc 1. The lens position of the optical system is driven in the radial direction (sledge direction) of the optical disc 1.

The spindle motor 2 is driven by a motor driver 5, and the servo means 6 controls the motor driver 5 using the output signal of the read amplifier 4 to control the rotation speed of the spindle motor 2 to a constant speed. . The entire optical pickup 3 is driven in the radial direction (sledge direction) of the optical disk 1 by a seek motor (not shown), and the servo means 6 uses the output signal of the read amplifier 4 to direct the seek motor to the laser beam spot on the optical disk 1 at a desired position. Control to be located at.

When reading data from the optical disc 1, the optical pickup 3 irradiates the optical disc 1 with laser light from a semiconductor laser through an optical system, and the reflected light is received by a light receiving element through the optical system and reproduced. Get the signal. This reproduction signal is amplified by the read amplifier 4 and binarized (digitized), then input to the CD decoder 7 and EFM demodulated. EFM is Eight to Fourteen
It is an abbreviation of Modulation, and the optical disc 1 is written with data obtained by modulating 8-bit data into 14-bit data so as to facilitate optical reproduction or recording.

The data subjected to EFM demodulation by the CD decoder 7 is subjected to deinterleaving (reordering) and error correction processing by the CD-ROM decoder 8 and is temporarily stored in the buffer RAM 10 by the buffer manager 9 to be arranged as sector data. ATAPI and SCS
It is sent to the host computer at once through an interface (I / F) 11 such as I. In the case of music data, the data output from the CD decoder 7 is input to the D / A converter 12 and converted into an analog audio signal.

When writing data on the optical disk 1,
The data sent from the host computer through the I / F 11 is temporarily buffered by the buffer manager 9.
The writing of the data is started when the data is stored in the AM 10 and a certain amount of data is stored in the buffer RAM 10. Before that, the laser light spot on the optical disc 1 is positioned at the writing start point. This point is obtained from the wobble signal previously recorded on the optical disk 1 due to the meandering of the track. ATI for wobble signal
Absolute time information called P is included, and this information is obtained from the reproduction signal from the read amplifier 4 by the ATIP decoder 1
Taken out by 3.

The synchronization signal generated by the ATIP decoder 13 is input to the CD encoder 14 and the optical disc 1
It is possible to write the data at the exact position above. The data stored in the buffer RAM 10 is a CD-ROM
After the error correction code is added or interleaved (rearranged) by the encoder 15 or the CD encoder 14, EFM modulation is performed, and the optical disc 1 is passed through the laser control circuit (laser controller) 16 as the emission power control means and the optical pickup 3. Recorded in.

FIG. 14 shows the structure of the optical pickup 3.
The laser light emitted from the semiconductor laser 17 as a laser light source passes through the collimator lens 18 and the beam splitter 19, is condensed by the objective lens 20, and is irradiated onto the optical disc 1 as a light spot. The light reflected by the optical disk 1 passes through the objective lens 20 and the beam splitter 19
Then, the light is reflected toward the light receiving element 41 formed of a photodiode, and is condensed on the light receiving element 41 by the condenser lens 22. The light receiving element for monitoring the emission power of the semiconductor laser 17 is a photodiode for monitoring the laser light emitted backward from the semiconductor laser 17, or a photodiode 21 for monitoring the laser light emitted forward from the semiconductor laser 17. Is used.

The objective lens 20 is movable in a direction perpendicular to the recording surface of the optical disk 1, and a direction perpendicular to the recording surface of the optical disk 1 so that a laser beam spot is formed on the recording surface of the optical disk 1 by a focus actuator. Driven to. The objective lens 20 is movable in the radial direction of the optical disc 1, and is driven by the track actuator so as to follow the track spirally recorded on the optical disc 1.

Here, the optical output of the semiconductor laser 17 changes with temperature. Since this affects the gain characteristics of the servo system and the like, it is necessary to prevent the optical output of the semiconductor laser 17 from changing. Since the semiconductor laser 17 emits light from both sides due to its structure, the laser control circuit 16 controls the current flowing through the semiconductor laser 17 so that the light output becomes constant. This semiconductor laser 17
Control of the optical output of the APC (APC (A
uto Power Control). Also,
When the light receiving element 21 including a photodiode (hereinafter referred to as PD) receives the light emitted from the semiconductor laser 17 to the side opposite to the optical disk 1 side, this PD 21 is used as the rear PD.
Say. PD 21 from semiconductor laser 17 to optical disk 1
When a part of the light emitted to the side is received, the PD 21 is referred to as a front PD.

FIG. 15 shows the structure of a laser control circuit of an optical disk device which only controls the read power like a CD player. The output of the PD 21 is a current output, which is very small, so that it is once converted into a voltage by the amplifier 23 (may be used as it is for current control) and amplified. The output of the amplifier 23 is compared with the reference voltage by the comparator 24, and the laser driver 25 drives the semiconductor laser 17 by the output signal of the comparator 24.

If the output of the amplifier 23 is larger than the reference voltage, the output of the comparator 24 is lowered, and if the output of the amplifier 23 is smaller than the reference voltage, the output of the comparator 24 is raised. As a result, the current flowing through the semiconductor laser 17 is controlled so that the output of the amplifier 23 and the reference voltage become equal. Since the output of the PD 21 is proportional to the optical output power received by the semiconductor laser 17 from the PD 21, it is necessary to determine how much optical output power the semiconductor laser 17 emits when the reference voltage is (actually, The light output power emitted from the semiconductor laser 17 is measured by a light quantity measuring device called a power meter), and the semiconductor laser 17 can be made to emit light at an arbitrary constant light output power by adjusting the reference voltage. Generally, the reference voltage is often given by a D / A converter or the like.

FIG. 16 shows the configuration of the laser control circuit 16 of the CD-R drive device for controlling the read power and the write power. In a laser control circuit of an optical disk device that only controls the read power like a CD player, once the relationship between the emission power of the semiconductor laser 17 and the output voltage of the read amplifier 23 is obtained, the output of the PD 21 is the semiconductor laser 17. The semiconductor laser 1 so that the light emission power of
APC can be performed by adjusting the light emission power of 7.

On the other hand, in the laser control circuit 16 of the CD-R drive device for controlling the read power and the write power, the output voltage of the amplifier 23 is the voltage when the emission power of the semiconductor laser 17 is the read power. Then, since the emission power of the semiconductor laser 17 becomes a square wave of a binary voltage with the voltage at the write power, it is necessary to sample and hold the voltage at the time of reading and the voltage at the time of writing.

The sample hold (S / H) circuit 26 is
Amplifier 23 when repowered by sampling signal 1
The output voltage of is sampled and held at write power. The sample hold (S / H) circuit 27 samples the output voltage of the amplifier 23 at the write power by the sampling signal 2 and holds it at the read power. The output voltage of the sample hold circuit 26 is the comparator 28.
Is compared with the reference voltage 1 by the sample hold circuit 2
The output voltage of 7 is compared with the reference voltage 2 by the comparator 29. The laser driver 25 supplies a current proportional to the input voltage input from the comparators 28 and 29 to the semiconductor laser 17. The laser driver 25 also has a function of switching between write power emission and read power emission according to the input EFM signal.

The sample hold circuits 26 and 27 are shown in FIG.
As shown in, the analog switch 30, the capacitor 31,
It is composed of a buffer amplifier 32, and the analog switch 30 is turned on / off by a sampling signal. When the sampling signal is turned on, the analog switch 30 is turned on, and the input voltage at this time is charged in the capacitor 31. When the sampling signal is turned off, the analog switch 30 is turned off, and the capacitor 31 holds the voltage charged when the analog switch 30 is turned on.

FIG. 18 shows the emission power of the semiconductor laser 17 when writing data on the CD-R. In FIG. 18, the waveform before the time ts is the emission power waveform of the semiconductor laser 17 when reading data from the optical disc 1, and the waveform after the time ts is the emission power of the semiconductor laser 17 when writing data to the optical disc 1. It is a waveform. When reading data from the optical disk 1, the semiconductor laser 17 generally outputs 1 mW or less (specifically, 0.4 mW or less).
Light with a read power of mW) is output with a constant light amount.
The read power is maintained at a constant light quantity by the emission power of the semiconductor laser 17 being APC by the laser control circuit 16 as described above.

On the other hand, at the time of writing, the semiconductor laser 17 repeats the emission power of read power and write power. The write power is generally several mW to several tens of mW (specifically, a power of 5 mW to 20 mW with good recording characteristics for actual writing is selected). Similarly to the read power, the write power is also maintained at a constant light quantity by performing APC.
Note that the emission power waveform of the semiconductor laser 17 at the time of actual writing improves the writing characteristics to the optical disc (improves the shape of the pits written on the optical disc), so that the writing power is immediately after switching from the read power to the write power. Lift power and write.

FIG. 19 shows waveform examples of the output of the semiconductor laser (hereinafter also referred to as LD) 17, sampling signal 1 and sampling signal 2. The sample-hold circuit 26 samples the output voltage of the amplifier 23 at the time of reading with the sampling signal 1, and the sample-hold circuit 27 samples the output voltage of the amplifier 23 at the time of writing with the sampling signal 2. Sample and hold circuits 26 and 27
Is actually the case where the output voltage of the amplifier 23 is sampled for all the read pulses and the write pulses (3T to 11T), and the case where the output voltage of the amplifier 23 is sampled only for the pulses having a certain width or more. , And FIG. 19 shows the latter case.

FIG. 20 shows how a pseudo offset occurs due to the speed (hereinafter referred to as band) of the light receiving element 21 being insufficient. Semiconductor laser 1 with laser control circuit 16
If the band of the light receiving element 21 used for controlling the light emission power of 7 is insufficient, when sampling the output voltage of the amplifier 23 corresponding to the read power, the output voltage of the amplifier 23 is sampled before falling to the voltage corresponding to the read power. (Generally, when the output voltage of the amplifier 23 is sampled, a light receiving element 21 having a sufficiently fast band so that the voltage drops to a voltage corresponding to the read power sufficiently before sampling is performed. Used), the outputs of the sample and hold circuits 26, 27 appear to have an offset. This is called a pseudo offset due to insufficient band of the light receiving element. Although the optical output of the semiconductor laser 17 is constant in FIG. 20, if the optical output of the semiconductor laser 17 is actually APC, the read power is reduced due to the pseudo offset, and as shown in FIG. A control error of the light output of 17 occurs.

[0023]

Today, the read speed of a CD-ROM drive device or a CD-R drive device is 30 times faster than the standard speed for audio reproduction. Moreover, the writing speed of the CD-R drive device is lagging behind the reading speed, but is steadily increasing from 2 × speed to 4 × speed.
Due to the increase in the writing speed, the required band of the light receiving element used for controlling the emission power of the semiconductor laser is also increasing.

However, there is a technical problem in raising the required band of the light receiving element, and when the band of the light receiving element is lower than the required band, when considering the read power, the sample hold circuit 26 as shown in FIG. , 27 will cause a pseudo offset. The laser control circuit 16 thinks that the emission power of the semiconductor laser 17 has increased due to the pseudo offset, and the semiconductor laser 17
The light emission power of is controlled so that it decreases. Therefore, a control error occurs in the emission power control of the semiconductor laser 17. FIG. 21 shows the emission power of the semiconductor laser 17 in this case. Note that the write pulse is omitted in FIG.

Further, not only the read power but also the write power causes a pseudo offset in the output of the sample hold circuit 27, and the laser control circuit 16 raises the emission power of the semiconductor laser 17 above the desired power due to the pseudo offset. To control. Therefore, a control error occurs in the emission power control of the semiconductor laser 17.

Generally, in the sample hold circuit, when the analog switch is turned off, the output voltage is different from when the analog switch is turned on. This is commonly called a hold step. For example, in the circuit shown in FIG. 16, since the analog switch of the sample hold circuit 26 is turned off during reading, the voltage input to the laser driver 25 increases due to the hold step. Although the emission power of the semiconductor laser 17 has not actually increased, the laser control circuit 16 does not
I think the semiconductor laser 17
Reduces the light emission power of. In other words, the read power will change between read and write. Fluctuations in the emission power of the semiconductor laser 17 adversely affect the servo signal and the like, which is not good in terms of reliability.

Even if writing is performed on the optical disk with the same write power, the write characteristics are different for each optical disk. Therefore, in an actual CD-R drive apparatus or CD-RW drive apparatus, the write power is changed for each optical disk. . In this method, the write power is determined by actually performing trial writing on the optical disc with various write powers and reading the test write power. But,
If the write power is different, the pseudo offset voltage is changed due to the insufficient bandwidth of the light receiving element, and the emission power of the semiconductor laser fluctuates, which adversely affects the servo signal and the like, which is not good in terms of reliability. .

An actual CD-R drive device or CD-RW
In the drive device, the writing speed is not constant, and writing is possible at a plurality of writing speeds (double speed). For example, recent CD-R drive devices and CDs
-RW drive supports writing at 4x speed, 2x speed and 1x speed. This is because the writing speed is intentionally lowered depending on the quality of the optical disc or the speed of the information receiving side device is matched with that of the information transmitting side device when the optical disc is copied. The change in the writing speed changes the pseudo offset voltage component due to the shortage of the band of the light receiving element, and the emission power of the semiconductor laser fluctuates to adversely affect the servo signal and the like, which is not good in terms of reliability.

The invention according to claim 1 can realize an optical disk device having a desired writing speed without using a light receiving element having a necessary band, and can select an inexpensive light receiving element to use an inexpensive apparatus as a whole. An object is to provide an optical disk device that can be realized. The invention according to claim 2 can provide an optical disk device capable of eliminating the fluctuation of the emission power of the laser light source due to the hold step of the sample hold circuit, enabling stable servo control, and further improving the reliability of the device. The purpose is to do.

According to the third aspect of the present invention, even if the write power changes for each optical disk, it is possible to eliminate the fluctuation of the light emission power of the laser light source, stable servo control becomes possible, and the reliability of the apparatus is improved. An object of the present invention is to provide an optical disk device that can be used. The invention according to claim 4 provides an optical disk device capable of eliminating the fluctuation of the light emission power of the laser light source even if the writing speed changes, enabling stable servo control, and further improving the reliability of the device. The purpose is to It is an object of the invention according to claim 5 to provide an optical disk device capable of simplifying the optical disk device assembling equipment and reducing the number of assembling steps.

[0031]

In order to achieve the above object, the invention according to claim 1 provides a laser light source for irradiating an optical disk with light, a light receiving element for monitoring the light emission power of the laser light source, and the light receiving element. And a light emission power control means for controlling the light emission power of the laser light source using the output signal of the optical disc device, the response of the light receiving element in the optical disc device for writing information to the optical disc at a speed higher than the standard speed. When writing is performed at a writing speed that requires a response speed faster than the speed, when the emission power of the laser light source is switched, the emission of the laser light source after switching occurs due to insufficient band of the light receiving element.
Before the output signal of the light receiving element corresponding to the power is output,
Light emission power of the laser light source after switching
-Off for the output signal of the light receiving element corresponding to
The light emission power control means is provided with a correction means for correcting an error in the light emission power of the laser light source according to the set amount .

According to a second aspect of the present invention, in the optical disk device according to the first aspect, the light emission power control means has a sample hold circuit for sampling and holding the output signal of the light receiving element, and the correcting means has the light receiving element. The pseudo offset due to the shortage of the band and the error in the emission power control of the laser light source due to the hold step generated in the sample hold circuit are corrected.

According to a third aspect of the present invention, in the optical disk device according to the first aspect, there is provided means for varying the correction value of the correction means according to the writing power of the laser light source. The invention according to claim 4 is the optical disk device according to claim 1, further comprising means for varying the correction value of the correction means according to the writing speed. According to a fifth aspect of the present invention, in the optical disc device according to the third or fourth aspect, the light emission power control means monitors a sample hold circuit for sampling and holding an output signal of the light receiving element, and an output signal of the sample hold circuit. A monitor means is provided, and the coefficient of the operation for calculating the correction value is obtained from the output signal of the monitor means.

[0034]

1 shows a laser control circuit according to a first embodiment of the present invention. This first embodiment is an embodiment of the invention according to claim 1, and in the CD-R drive device shown in FIG. 13 described above, the laser shown in FIG. 1 is used instead of the laser control circuit 16 shown in FIG. A control circuit is used, and as the light receiving element 21, a light receiving element whose response speed is slower than a required response speed determined by the writing speed of the device is used. In this laser control circuit, in the laser control circuit 16 shown in FIG. 16, by correcting the pseudo offset of the outputs of the sample and hold circuits 26 and 27, the emission power control error of the semiconductor laser 17 caused by the shortage of the band of the light receiving element 21 is eliminated. Correction means is provided for correction.

The correction means is a sample hold circuit 2
Correction voltage 1 to cancel the pseudo offset in the output of 6
By adding the first correction means for canceling the pseudo offset of the output of the sample hold circuit 26 and the correction voltage 2 for canceling the pseudo offset of the output of the sample hold circuit 27 to the reference voltage 2. It comprises a second correction means for canceling the pseudo offset of the output of the sample hold circuit 27.

Assuming that the pseudo offset of the output of the sample hold circuit 26 due to the shortage of the band of the light receiving element 21 is + α, if the correction voltage 1 is −α, the pseudo offset of the output of the sample hold circuit 26 will be as shown in FIG. Can be canceled to eliminate the control error of the read power control (light emission power control of the semiconductor laser 17). Further, the pseudo offset amount of the output of the sample hold circuit 27 due to the shortage of the band of the light receiving element 21 is assumed to be -α '(in the case of write power, the output of the sample hold circuit 27 is sampled lower than the voltage corresponding to the desired power. , And a negative number), if the correction voltage 2 is set to + α ′, the pseudo offset of the output of the sample hold circuit 27 is canceled and the write power (light emission power control of the semiconductor laser 17) is performed.
The control error of can be eliminated.

As a matter of course, instead of adding the correction voltage 1 to the output of the sample hold circuit 26 to cancel the pseudo offset of the output of the sample hold circuit 26, the first correction means uses the reference voltage 1 of the sample hold circuit. Two
By increasing the pseudo offset of the output of 6 + α, the pseudo offset of the output of the sample hold circuit 26 can be canceled and the read power control error can be eliminated. The second correction means is the sample hold circuit 2
It is also possible to cancel the write power control error by canceling the pseudo offset of the output of the sample hold circuit 27 by adding -α 'as the correction voltage 2 to the output of 7.

According to the first embodiment, the light receiving element 2
It is possible to realize a CD-R drive device having a desired writing speed even if there is no light receiving element having a band required as 1. Further, a light receiving element having a speed lower than a required band can be used as the light receiving element 21, and an inexpensive light receiving element can be selected and used to realize an inexpensive device as a whole. The invention according to claim 1 is not limited to the first embodiment, and can be applied to an optical disk device such as a CD-RW drive device.

Next, a second embodiment of the present invention will be described. The second embodiment is an embodiment of the invention according to claim 2. FIG. 3 shows the output voltage waveform of the sample-hold circuit when a constant voltage is input to the sample-hold circuit. As shown in FIG. 3, the output voltage of the sample-hold circuit has an error called Hall step due to ON / OFF of the analog switch. As a result, as shown in FIG. 4, the CD shown in FIG.
In the −R drive device, in addition to the emission power control error of the semiconductor laser 17 caused by the shortage of the band of the light receiving element 21, the emission power control error of the semiconductor laser 17 due to the hold step occurs.

Therefore, in the second embodiment, in the first embodiment, as shown in FIG. 5, the first correction means uses the pseudo offset of the output of the sample hold circuit 26 due to the shortage of the band of the light receiving element 21. The correction voltage 1 (= −α−β) obtained by adding the correction voltage −α for correcting + α and the correction voltage −β for correcting the hole step + β of the output voltage of the sample hold circuit 26 to the output voltage of the sample hold circuit 26. Is added to cancel the pseudo offset of the output of the sample hold circuit 26 and the hole step of the output voltage of the sample hold circuit 26, thereby eliminating the control error of the read power control. Here, the write pulse is omitted in FIG.

As a matter of course, the first correction means adds the above-mentioned correction voltage 1 to the output of the sample-hold circuit 26 to perform the pseudo offset of the output of the sample-hold circuit 26 and the hall step of the output voltage of the sample-hold circuit 26. Instead of canceling, the sample hold circuit is increased by increasing the reference voltage 1 by a correction voltage (= + α + β) obtained by adding the pseudo offset amount + α of the output of the sample hold circuit 26 and the hole step + β of the output voltage of the sample hold circuit 26. The pseudo offset of the output of 26 and the hole step of the output voltage of the sample hold circuit 26 can be canceled to eliminate the control error of the read power control.

The second correction means includes a pseudo offset amount + α 'of the output of the sample hold circuit 27 and a hall step + β' of the output voltage of the sample hold circuit 27.
Control of write power control by increasing the reference voltage 2 by a correction voltage 2 (= + α ′ + β ′) added with and canceling the pseudo offset of the output of the sample hold circuit 27 and the hole step of the output voltage of the sample hold circuit 27. Eliminate the error.

It should be noted that the second correction means uses the correction voltage 2 (=
Instead of increasing the reference voltage 2 by + α ′ + β ′), the correction voltage − (α ′ + β ′) is added to the output of the sample hold circuit 26.
May be added to cancel the pseudo offset of the output of the sample hold circuit 27 and the hole step of the output voltage of the sample hold circuit 27 to eliminate the control error of the write power control.

According to the second embodiment, since the emission power control error of the semiconductor laser 17 due to the hole step of the output voltage of the sample hold circuits 26 and 27 is eliminated, stable servo control can be performed and the reliability of the device can be improved. You can improve your sex. The invention according to claim 2 is not limited to the second embodiment, but can be applied to an optical disk device such as a CD-RW drive device.

Next, a third embodiment of the present invention will be described. The third embodiment is an embodiment of the invention according to claim 3. In the above-described CD-R drive device, as shown in FIG. 6, when the write power is different, the pseudo offset voltage in the output voltage of the sampling and holding circuit 26 is changed due to the shortage of the band of the light receiving element 21. That is, a change in the write power causes a control error in the read power. In the third embodiment, a read power control error due to a change in write power is eliminated.

If the relationship between the pseudo offset + α and the write power is proportional as shown in FIG. 7, the pseudo offset + α due to the shortage of the band of the light receiving element 21 is expressed as + α = A × (write power) + B. . Of course, the relationship between the pseudo offset + α and the write power may have a second-order or higher relationship, but the basic idea is the same as the case of the first-order relationship, so the relationship between the pseudo offset + α and the write power is There will be described a case where there is a linear relationship.

Here, A is A = Δα, where Δα is the change in α when the write power changes by Δ power.
/ Δ power. Further, B is the value of α when the write power is 0, and basically B = 0. In the third embodiment, in the first embodiment, the first correction means uses the correction voltage 1 (= -α) in the circuit shown in FIG.
By setting x (write power) + B}, a read power control error due to a change in write power is eliminated. In the circuit shown in FIG. 8, the correction coefficients A and B are stored in the memory 30. A microcomputer (hereinafter referred to as CPU) 31 as a calculation means is
D / A from the correction factors A and B stored in the memory 30
The correction voltage to be output from the converter 32 is calculated. The calculated correction voltage is converted into an analog voltage by the D / A converter 32 to become the correction voltage 1, which is added to the output of the sample hold circuit 26. The first correction means uses the D / A converter 32 for the reference voltage 1 instead of adding the correction voltage 1 to the output of the sample hold circuit 26.
The correction voltage 1 = A × (write power) + B may be increased.

Similarly, the second correction means uses the correction voltage 2 (=
By setting α ′) to A × (read power) + B,
Eliminates write power control errors due to changes in read power. That is, the correction coefficient of a linear expression representing the relationship between the read power and the pseudo offset voltage in the output voltage of the sampling and holding circuit 27 due to the shortage of the band of the light receiving element is stored in the memory. CPU as arithmetic means
Calculates the correction voltage to be output from the D / A converter from the current read power and the correction coefficient stored in the memory. The calculated correction voltage is converted into an analog voltage by the D / A converter and becomes the correction voltage 2,
It is added to the reference voltage 2. The second correction means is
Instead of adding the correction voltage 2 to the reference voltage 2, the correction voltage 2
= − {A × (read power) + B} may be added to the output voltage of the sampling and holding circuit 27.

In the third embodiment, since the light emission power of the semiconductor laser does not change even if the write power changes, stable servo control becomes possible and the reliability of the device can be improved. The invention according to claim 3 is not limited to the third embodiment, but can be applied to an optical disk device such as a CD-RW drive device.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment is an embodiment of the invention according to claim 4. FIG. 9 shows a pseudo offset due to the shortage of the band of the light receiving element 21 when the writing speed changes in the above-mentioned CD-R drive device. As can be seen from FIG. 9, the change in the writing speed changes the pseudo offset voltage due to the shortage of the band of the light receiving element 21. That is, an emission power control error of the semiconductor laser 17 will occur due to a change in writing speed.

In the fourth embodiment, an emission power control error of the semiconductor laser 17 due to a change in writing speed is eliminated. FIG. 10 shows a circuit for generating the correction voltage 1 in the fourth embodiment. In the fourth embodiment, the correction coefficients A and B (A single speed, B single speed, A two speeds) in the third embodiment, which are different for each writing speed in the memory 33 as the calculating means in the first embodiment, are used. (Double speed, double speed B ... double speed An, double speed Bn) are stored in advance. The CPU 34 should read a correction coefficient (for example, An double speed, Bn double speed) matching the current write speed from the memory 33 from the current write speed, and output from the D / A converter 35 from this correction coefficient and the current write power. Calculate the correction voltage. This calculated correction voltage is D
The converted voltage is converted into an analog voltage by the / A converter 35 to obtain the correction voltage 1 = − {An double speed × (write power) + Bn double speed}, which is added to the output of the sample hold circuit 26. The first correction means uses the reference voltage 1 from the D / A converter 32 as the correction voltage 1 = {An double speed × (write power) + Bn double speed instead of adding the correction voltage 1 to the output of the sample hold circuit 26. } May be increased.

Similarly, in the second correcting means, the correction coefficient (the relationship between the read power and the pseudo offset voltage in the output voltage of the sampling and holding circuit 27 due to the shortage of the band of the light receiving element) in the third embodiment, which is different for each writing speed. A plurality of correction coefficients of a linear expression that expresses are stored. The CPU as the calculation means calculates the correction voltage to be output from the D / A converter from the current read power and the correction coefficient corresponding to the current writing speed stored in the memory. The calculated correction voltage is converted into an analog voltage by the D / A converter to become the correction voltage 2, which is added to the reference voltage 2. The second correction means may add the correction voltage 2 to the output voltage of the sampling and holding circuit 27 instead of adding the correction voltage 2 to the reference voltage 2.

In the fourth embodiment, since the light emission power of the semiconductor laser does not change even if the writing speed changes, stable servo control can be performed and the reliability of the device can be improved. The invention according to claim 4 is not limited to the fourth embodiment, but can be applied to an optical disk device such as a CD-RW drive device.

FIG. 11 shows a laser control circuit according to the fifth embodiment of the present invention. The fifth embodiment is an embodiment of the invention according to claim 5. In the third and fourth embodiments described above, in order to obtain the correction voltage 1 and the correction voltage 2, while monitoring the emitted light amount of the semiconductor laser 17 with a power meter or the like that can measure the emitted light amount of the semiconductor laser 17 once. It is necessary to perform the work of obtaining the correction voltage 1 and the correction voltage 2. This imposes a heavy burden on the assembly equipment of the CD-R drive device.

Therefore, the fifth embodiment is different from the fourth embodiment in that the correction coefficient A,
B is obtained, and an A / D converter 36 as a monitor means for monitoring the output voltage of the sample hold circuit 26 is arranged on the read power side. A
The / D converter 36 monitors the output voltage of the sample hold circuit 26 at the start of writing shown in FIG. 12, converts it into a digital value, and passes the digital value to the CPU 34a.

The CPU 34a first issues the read sampling signal 1 to the sample hold circuit 26 at a time interval at which the output value of the light receiving element 21 is sufficiently restored to a level corresponding to the read power. As a result, the output voltage of the sample-hold circuit 26 does not have a pseudo offset due to the shortage of the band of the light-receiving element 21, so that the CPU 34a uses the A / D for the output voltage of the sample-hold circuit 26.
From the monitoring result of the converter 36, the correction voltage β for correcting the hall step of the output voltage of the sample hold circuit 26, that is, the error due to the ON / OFF of the analog switch is obtained.

Next, the CPU 34a starts writing at a predetermined writing speed, and the A / D converter 36 monitors the output voltage of the sample hold circuit 26 at the start of writing shown in FIG. 12 and converts it into a digital value. At this time, A
The output voltage of the sample-hold circuit 26 monitored by the / D converter 36 is the pseudo-offset amount due to the hall step of the output voltage of the sample-hold circuit 26 with respect to the reference voltage 1 and the output voltage of the sample-hold circuit 26 due to the shortage of the band of the light receiving element 21. And the pseudo offset amount of.

Therefore, the CPU 34a removes the pseudo offset amount due to the hall step of the output voltage of the sample hold circuit 26 previously obtained from the monitor result of the A / D converter 36, and the sample hold circuit 26 of the sample hold circuit 26 due to the shortage of the band of the light receiving element 21. Calculate the pseudo offset of the output voltage.

Then, the CPU 34a causes the laser driver 25 to change the write power a plurality of times and start writing as described above at each write power, and causes the A / D converter 36 to perform monitoring to monitor the A / D converter 36. From the result, the pseudo offset of the output voltage of the sample hold circuit 26 due to the shortage of the band of the light receiving element 21 excluding the pseudo offset of the output voltage of the sample hold circuit 26 is calculated. From the relationship with
Ask for.

Next, the CPU 34a determines the correction coefficients A and B at each writing speed by changing the writing speed and repeating the above-mentioned operation, and stores these correction coefficients in the non-volatile memory 33. As a result, the correction coefficient can be obtained without using the power meter, and once the correction coefficient is obtained, the operation of obtaining the correction coefficient does not have to be performed each time the apparatus is started up. Note that the CPU 34a uses the current read power and the correction coefficient at the current write speed stored in the memory 33, as in the fourth embodiment, to obtain D /
A correction voltage to be output from the A converter 35 is calculated, and the calculated correction voltage is converted into an analog voltage by the D / A converter 35 to become the correction voltage 1.

The write power side is also provided with an A / D converter 37 as a monitor means for monitoring the output voltage of the sample hold circuit 27. The A / D converter 37 monitors the output voltage of the sample hold circuit 27 at the start of reading and converts it into a digital value, and passes the digital value to the CPU 38. This CPU 38
First, the sampling signal 2 for writing is issued to the sample hold circuit 27 at time intervals at which the output value of the light receiving element 21 is sufficiently restored to a level corresponding to the write power.
As a result, the output voltage of the sample hold circuit 27 does not have a pseudo offset due to the shortage of the band of the light receiving element 21. A correction voltage β for correcting an error due to the on / off of the analog switch, that is, the hole step of the voltage is obtained.

Next, the CPU 38 starts reading at a predetermined reading speed, and the A / D converter 37 monitors the output voltage of the sample hold circuit 27 at the start of reading and converts it into a digital value. At this time, the output voltage of the sample hold circuit 27 monitored by the A / D converter 37 is a pseudo offset amount due to the hall step of the output voltage of the sample hold circuit 27 with respect to the reference voltage 2 and the sample hold circuit due to the shortage of the band of the light receiving element 21. 27
It is the sum of the output voltage and the pseudo offset amount.

Therefore, the CPU 38 removes the pseudo offset due to the hall step of the output voltage of the sample hold circuit 27 previously obtained from the monitor result of the A / D converter 37, and the sample hold circuit 27 of the sample hold circuit 27 lacks the band. Calculate the pseudo offset of the output voltage.

Then, the CPU 38 controls the laser driver 2
5, while the read power is being changed a plurality of times, the read starts at each read power as described above, and the A / D converter 3
7. The light receiving element 2 in which the pseudo offset due to the hall step of the output voltage of the sample and hold circuit 27 is removed from the monitoring result of the A / D converter 37 by performing the monitoring by 7
The pseudo offsets of the output voltage of the sample and hold circuit 27 due to the shortage of the band of 1 are obtained, and the correction coefficient is obtained from the relationship between these pseudo offsets and the read powers.

Next, the CPU 38 changes the reading speed and repeats the above-mentioned operation to obtain the correction coefficient at each reading speed, and stores these correction coefficients in the non-volatile memory 39. Note that the CPU 38 calculates the correction voltage to be output from the D / A converter 40 from the current write power and the correction coefficient corresponding to the current read speed stored in the memory 39, as in the fourth embodiment. The calculated correction voltage is converted into an analog voltage by the D / A converter 40 and becomes the correction voltage 2.

According to the fifth embodiment, the correction coefficient can be obtained without using a power meter or the like, and CD-
It is possible to simplify the assembly equipment of the R drive device. Further, the write power adjustment and the read power adjustment can be automatically performed, and the man-hours for assembling the device can be reduced.
The invention according to claim 5 is not limited to the fifth embodiment, but can be applied to an optical disk device such as a CD-RW drive device.

[0067]

As described above, according to the first aspect of the present invention, with the above configuration, a CD-R drive device or the like having a desired writing speed can be provided without a light receiving element having a band required as a light receiving element. An optical disk device can be realized. Further, a light receiving element having a speed lower than a required band can be used as the light receiving element, and an inexpensive light receiving element can be selected and used to realize an inexpensive device as a whole.

According to the second aspect of the present invention, with the above configuration, it is possible to eliminate the error in the emission power control of the laser light source due to the hole step of the output voltage of the sample hold circuit, and it is possible to perform stable servo control, and thus the device. Can increase the reliability of.

According to the third aspect of the present invention, since the light emission power of the laser light source does not change even if the write power changes, stable servo control is possible and the reliability of the device is improved. it can.

According to the fourth aspect of the present invention, since the light emission power of the laser light source does not change even if the writing speed changes, stable servo control is possible and the reliability of the device is improved. it can.

According to the fifth aspect of the present invention, with the above configuration, the correction coefficient can be obtained without using a power meter or the like, and the assembling equipment of an optical disk device such as a CD-R drive device can be simplified. Become. Also, write power adjustment and read power adjustment can be performed automatically,
It is possible to reduce the man-hours for assembling the device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a laser control circuit according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the first embodiment.

FIG. 3 is a waveform diagram showing a state of an output voltage waveform of the sample hold circuit when a constant voltage is input to the sample hold circuit.

FIG. 4 is a waveform diagram showing how a read power control error occurs in a conventional CD-R drive device.

FIG. 5 is a waveform diagram for explaining the second embodiment of the present invention.

FIG. 6 is a waveform diagram showing how the pseudo offset voltage in the output voltage of the sampling and holding circuit changes due to the shortage of the band of the light receiving element due to the change of the write power in the CD-R drive device.

FIG. 7 is a characteristic diagram showing a relationship between a pseudo offset and a write power of a CD-R drive device.

FIG. 8 is a block diagram showing first correction means in a third embodiment of the present invention.

FIG. 9 is a waveform diagram showing a pseudo offset due to a band shortage of the light receiving element when the writing speed changes in the CD-R drive device.

FIG. 10 shows a correction voltage 1 in the fourth embodiment of the present invention.
FIG. 6 is a block diagram showing a circuit for generating

FIG. 11 is a block diagram showing a laser control circuit according to a fifth embodiment of the present invention.

FIG. 12 is a waveform diagram for explaining the fifth embodiment.

FIG. 13 is a block diagram showing a configuration of a general CD-R drive device.

FIG. 14 is a diagram showing a configuration of an optical pickup.

FIG. 15 is a block diagram showing a configuration of a laser control circuit of an optical disc device that only controls read power.

FIG. 16 is a diagram showing a configuration of a laser control circuit of a CD-R drive device.

FIG. 17 is a circuit diagram showing a sample hold circuit.

FIG. 18 is a waveform diagram showing the emission power of a semiconductor laser when writing data to a CD-R in a CD-R drive device.

FIG. 19 shows the output of the LD in the CD-R drive device,
It is a wave form diagram which shows the waveform example of the sampling signal 1 and the sampling signal 2.

FIG. 20 is a waveform diagram showing how a pseudo offset is generated due to a band shortage of a light receiving element in a CD-R drive device.

FIG. 21 is a diagram illustrating a CD-R drive device.

[Explanation of symbols] 17 Semiconductor laser 21 Light receiving element 23 amplifier 25 laser driver 26,27 Sample and hold circuit 28, 29 comparator 30, 33, 39 memory 31, 34, 34a, 38 CPU 32, 35, 40 D / A converter 36, 37 A / D converter

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Claims (5)

(57) [Claims] 1. A laser light source for irradiating an optical disk with light,
A light receiving element for monitoring the light emission power of this laser light source,
In the optical disc device, which has an emission power control means for controlling the emission power of the laser light source using the output signal of the light receiving element and writes information on the optical disc at a speed higher than the standard speed, the light receiving element When writing is performed at a writing speed that requires a response speed faster than that of the laser light source after switching, the light emission of the laser light source is caused by insufficient bandwidth of the light receiving element when the emission power of the laser light source is switched. Corresponding to power
Sampled before becoming the output signal of the light receiving element
Before switching to the emission power of the laser light source after switching
Depending on the amount of pseudo offset for the output signal of the light receiving element
The optical disc device is characterized in that the emission power control means is provided with a correction means for correcting an error in the emission power of the laser light source. 2. The optical disk device according to claim 1, wherein
The light emission power control means has a sample and hold circuit for sampling and holding the output signal of the light receiving element, and the correction means of the laser light source by the pseudo offset due to the shortage of the band of the light receiving element and the hold step generated by the sample and hold circuit. An optical disk device characterized by correcting a light emission power control error. 3. The optical disk device according to claim 1, wherein
An optical disk device comprising means for varying the correction value of the correction means according to the writing power of the laser light source. 4. The optical disk device according to claim 1, wherein
An optical disk device comprising means for varying a correction value of the correction means according to a writing speed. 5. The optical disk device according to claim 3 or 4, wherein said light emission power control means includes a sample hold circuit for sampling and holding an output signal of said light receiving element.
An optical disk device comprising: monitor means for monitoring the output signal of the sample-hold circuit, and obtaining a coefficient for calculation for calculating the correction value based on the output signal of the monitor means.