JPH04157633A - Laser power generator - Google Patents

Abstract

PURPOSE:To eliminate power switching regulation at the time of switching a mode by deciding a current flowing to a laser diode (LD) according only to an LD current command value of each mode to be originally output from a CPU toward a current controller. CONSTITUTION:A conventional analog LD power control loop is eliminated, and an LD current is decided only according to an LD current command value by a CPU 15. In this case, after the command value of each mode is first temporarily set in a focusing servo off state, a head is moved to an innermost periphery (or outermost periphery) so as not to damage data on a disk by an optical spot, and the command value is further finally decided under a focusing servo on state. A power detection signal VPD is monitored in a steady state of a reproducing mode or an erasure mode. Thus, a circuit is simplified largely as compared with prior art, and a high speed amplifier necessary for a recording mode is also eliminated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a laser power generation device for an optical disk device that records, reproduces, and erases signals by outputting laser light through a laser diode (hereinafter also abbreviated as LD), and in particular, a laser power generation device with a simplified circuit configuration. Regarding. Note that in the following figures, the same reference numerals indicate the same or corresponding parts.

[Conventional technology]

The prior art closest to the present invention is Japanese Patent Application No. 1-93687 entitled "Laser Power Output Apparatus" filed by the present applicant. This device automates the means for giving command values to the laser power control system and facilitates various adjustments.The contents of this technology will be briefly explained below using FIGS. 5 to 7. Furthermore, Fig. 5 is a block diagram showing the configuration of the control circuit of this laser power output device, Fig. 6 is an explanatory diagram of the power adjustment operation of this device, and Fig. 7 is a block diagram showing the configuration of the control circuit of this laser power output device.
FIG. 3 is a characteristic diagram showing an example of the relationship between current carrying current (ILD) and output power (PLP) of D. That is, in FIG. 5, the CPU 15 reproduces (R). Laser power command values for each mode of recording (W) and erasing (E) are given to the latch 18 in advance. When the erase gate EC is active, the power command value for erasing is set, and when the write gate WG is active, the power command value for recording is set.
At other times, the reproduction and power command values are output from the latch 18 to the D/A converter 16, and converted by the D/A converter 16 into an analog power reference signal V1, which is then sent to the comparator 2. is input. On the other hand, a current proportional to the output power of the LDIO flows through the monitor photodiode (also abbreviated as PD) 11, which is converted into a voltage by the monitor output amplifier 1, becomes a power detection signal VPI), and is input to the comparator 2. - Therefore, the difference signal 2a as the output of the comparator 2 is (Vl-
VPD). The peak hold amplification circuit 3 holds the negative peak of the value of the difference signal 2a (Vl-VPD) and amplifies the held peak value with a high gain. Output 3a of this peak hold amplification circuit 3
is input to the adder 4. On the other hand, in the same way as the laser power command value, the CPU 15 provides the latch 19 with an LD current increase command during erasing and an LD current increase command during recording with respect to the reproduction time. When the erase gate EC is active, an erase current increase command is output, and when the write gate WG is active, a recording current increase command is output from the latch 19 to the D/A converter 17. The converter 17 converts the signal into an analog current command signal (2), which is input to the adder 4. As a result, the current control circuit 5 causes a current ILD proportional to the 8-power 4a of the adder 4, which is obtained by adding the current command signal 2 and the peak hold amplification circuit output 3a, to flow through the LDIO. Further, the current ILD is turned on and off according to the write data signal WD. Note that the power detection signal VPD output from the monitor output amplifier 1 is sampled and held at 13. A/
The signal is also input to the CPU 15 through the D converter 14. Next, in the initial adjustment of the LD power immediately after the power is turned on for the circuit shown in FIG. 5, the CPU 15 first sends the power reference signal
1 is gradually increased until the power detection signal VPD reaches a predetermined value. (This predetermined value is determined by the LD power PR and P shown in Fig. 7 for each mode of reproduction, recording, and erasing, respectively.
Corresponds to W and PE. ] The input data of the latch 18 at this time becomes the laser power command value in each mode. Next, as shown in FIG. 6, power switching adjustment is performed when switching the mode from the reproduction mode to the erase mode (or recording mode). In other words, neither erase gate EG (or write gate WG) is inactive (that is, in playback mode).
From the state, when the erase gate (or write gate WG) is activated, the power reference signal V1
In conjunction with this, the current command signal (2) is applied and adjusted so that the power detection signal VPD immediately after this mode switching becomes the same level as in the steady state. The input data to the latch 19 at this time becomes a current increase command in the erase mode (or recording mode). This current increase command is applied to the LD in Figure 7.
Corresponds to IEI-TRI (or l-1-IRI) of current. However, here IRI, I! il, IEI at room temperature 2
LD current IL required for LDIO to output the specified power required for playback, recording, and erasing at 5°C
It is assumed that the initial adjustment of the LD power PLD is performed at a room temperature of 25°C.

[Problem to be solved by the invention]

However, the above LD power generator has the following problems. ■The circuit is complicated. That is, two sets of D/A converters 16, 17 and latch circuits 18, 19 are required, one for power command and one for current increase command. Furthermore, a peak hold circuit 3 is required for the recording mode. ■Requires expensive parts. That is, the power detection signal VPD
The analog LD power control loop is always operating, using the feedbank signal as the feedbank signal. Even in the recording mode, it is necessary to accurately detect the peak power, and the monitor output amplifier 1 requires a high-speed amplifier (rise time: 10 ns). Therefore, the present invention provides an LD that can solve the above problems.
An object of the present invention is to provide a power generation device.

[Means for Solving the Problems] In order to solve the above problems, the apparatus of claim 1) provides r
A head (01 etc.) is moved to an optical disk (0
Head moving means (CPU 15.2, etc.) for moving the data section (03, etc.) of the CPU15.
Driver 41. head actuator 31, etc.), and focus servo means (focus actuator 32, focus error detector 33, compensation circuit 43, switching circuit 44, driver 45, search circuit 46, etc.) including an automatic gain control circuit (42, etc.). A laser diode (such as 10) capable of outputting the laser power necessary for an optical disc device that is capable of recording, reproducing, and erasing signals, and a power detection signal (such as VPD) proportional to the output power of the laser diode. Laser power detection means (PDIl, monitor output amplifier 1, etc.) that detects a Laser diode driving means (latch 21. D/A converter) which selects a current command value of a specified mode from digital current command values for each mode of the octopus, and causes a current corresponding to the current command value to flow through the laser diode. 20.
(current control circuit 5, etc.), the power setting values (PR, PW, PE) are set in advance for each mode, and the power detection signal is sent to the A/D.
The power detection signal is inputted as a digital value (via a converter 14, etc.), and this power detection signal is compared with the power setting value corresponding to the detection signal as necessary, and the current command value is set so as to set this difference to 0. Laser power control means (CPU
In the apparatus of claim 2), in the apparatus of claim 1), ``the laser power control means controls the laser power control means (for each disk rotation period, etc.) during operation in the reproduction mode or erasing mode. ) The correction of the current command value for each of the three modes is performed based on the comparison result with the power setting value, and the apparatus of claim 3) ), the laser power control means sets the focus servo means in an inoperable state based on a first initial setting command, and controls at least the current command value in the reproduction mode and erase mode in the laser diode drive means. After setting the current command value to a value lower than the level required for normal playback operation and erase operation, respectively, set the mode command signal to playback mode, and based on the correction operation, set the current command value as the current command value that allows normal playback operation. First regeneration initial current command value (LD current lR11
A corresponding command value) is temporarily set for the laser diode driving means, the mode designation signal is set to the erase mode, and based on the correction operation, the first erase is performed as the current command value that allows normal erase operation. initial current command value (LD current I El
Temporarily set a command value corresponding to l) to the laser diode driving means, then operate the head moving means and focus servo means, set the mode designation signal to the reproduction mode, and set the mode to normal based on the corrective operation. The second regeneration initial current command value (LD current I R1
A command value equivalent to 2: V'' (R)) is reset to the laser diode driving means, the mode designation signal is set to the erase mode, and the current that enables normal erase operation is set based on the corrective operation. The second initial current command value for erasing as a command value (command value equivalent to LD current I R12: V" (
E)) is reset to the laser diode driving means, and further the second initial current command value for reproduction, the second initial current command value for erasing, and the power setting values of the three modes set for itself. is used to calculate the current command value (V'' (W)) that allows normal recording operation, and set it to 1 for the laser diode driving means.

[For use]

Originally, the current flowing through the LDIO can be uniquely determined only by the LD current command value for each mode outputted from the CPU 15 to the current control circuit 5. Therefore, the LD current command value is determined by the initial adjustment of the LD power,
To eliminate the need for power switching adjustment when switching modes. However, in this case, after performing the initial adjustment of the LD power (that is, in the focus servo off state), when the focus servo is turned on, the L
The current/power characteristics of D change due to the influence of the returning light to the LD. Therefore, in the present invention, this LD power initial adjustment is performed in the focus servo off state and then in the focus servo on state.
It is divided into two steps. That is, in the first step, the LD current command value is provisionally determined in the focus servo off state as follows. That is, first, the LD current command values in the reproducing and erasing modes are determined so that the power detection signal VPD in the steady state becomes a value corresponding to a predetermined value, that is, the laser powers PR and PE in FIG. 2, respectively. Therefore, the LD current command value is IRII. The value is equivalent to IEII. Next, the head is moved to the innermost or outermost side away from the data area of the disk so as not to adversely affect the disk data area, and then the focus servo is turned on. At this time, an AGC circuit for the focus error signal is provided in the focus servo loop, and the L of the current/power characteristic of the LD is
To prevent stability from being lost even if there is a change in the intensity of detection of a focus error signal due to a change based on the return light to D. In this state, as the second step in the initial adjustment of the LD power, the LD current command for each mode is set so that the power detection signal VPD in the playback and erase modes becomes a predetermined value, that is, a value corresponding to the laser powers PR and PE in Fig. 2. Redetermine the value. Therefore, the LD current command value is l R12, I E12
equivalent value. In addition, in general, the luminous efficiency of LDIO (P LD / I LD
) Considering that the temperature dependence of the characteristics is almost constant as shown in Figure 2, the LD current command value in recording mode is calculated from the re-determined values of the LD current command values for playback and erasing. . That is, it is made unnecessary to check the output of the monitor output amplifier 1 in the recording mode, and it is no longer necessary to use a conventional high-speed amplifier as the monitor output amplifier 1. This completes the LD power initial adjustment. Regarding temperature changes during normal operation, the eight monitor output amplifiers are monitored from time to time (approximately every time the disk rotation is synchronized) in playback mode or erase mode, and if the temperature changes from a predetermined value,
By interlocking and correcting the LD current command values of all modes, the LD power is always maintained within a predetermined error range.

【Example】

Next, the present invention will be explained in detail based on FIGS. 1 to 4. FIG. 1 is a configuration diagram of a control circuit of an LD power generator as an embodiment of the present invention, and corresponds to FIG. 5. Next, FIG. 2 is a characteristic diagram in which the influence of focus servo on/off is added to the LD characteristics of FIG. 7. FIG. 3 is an explanatory diagram of the initial adjustment of the LD power in the first step according to the present invention. In FIG. 1, basically the comparator 2) peak hold amplification circuit 3, adder 4 and D/A converter 16, 17 of FIG.
, Lunch 18.19 has been deleted and a new latch 21. The LD current command (9) is given from the CPU 15 to the current control circuit 5 via the D/A converter 20. However, in FIG. 1, a drive circuit for the front actuator and a focus servo system are also shown as means for initial adjustment of the LD power with a second steering knob, which will be described later. LD for each mode (recording, playback, erasure) from the CPU 15
The electric current command value 0M is output to the trace launch 21. As a result, from launch 21, when the erase gate EG is active, the LD current command value for erase mode is set, when the write gate WG is active, the LD current command value for recording mode is set, and at other times, the LD current command value for playback mode is set to D. /A converter 20. Current control circuit 5
is the LD current command which is the output of this D/A converter 20.
A current ILD proportional to is passed through LDIO. Further, the current ILD is turned on and off in accordance with the write data signal WD. P
A current proportional to the output power of LDIO flows through DII, and monitor output amplifier 1 converts this into a voltage to generate a power detection signal VPD. This power detection signal VPD can be recognized by the CPtJ 15 through the A/D converter 14. Therefore, if the power detection signal VPD deviates from a predetermined value due to temperature changes or aging of the LDIO, since this change is slow in time, the CPtJ15 will occasionally detect this deviation as described later. LD so that it is 0
Rewrite and correct the t-flow command value CMD. When the CPU 15 receives a command to perform initial adjustment of the LD power at power-on, etc., the CPU 15 obtains a tentatively determined value CMD of the LD current command value for each mode as follows and sets it in the latch 21. That is, the CPU 15 first sets the gates 1-EC and WG to non-active (reproduction mode) with the focus servo off, and by rewriting the LD current command value 0M given to the latch 21 to gradually increase the D/A converter. The LD current command (1) output from 20 is gradually increased to bring the power detection signal VPD to a predetermined reproduction laser power level (corresponding to PR in FIG. 2). CP at this time
The manual setting data from U15 to latch 21 becomes the temporary command value CMD of the LD radio wave for playback mode (corresponding to IR11 in FIG. 2). Similarly, the CPU 15 activates the erase gate EG and gradually increases the LD current command `` in the erase mode to bring the power detection signal VPD to a predetermined erase laser power level (PH in FIG. 2 is set to 1). Time CPtJ1
The input setting data from 5 to latch 21 is L for erase mode.
Dt flow (corresponding to IEII in FIG. 2) provisional command value C?
It becomes an ID. The time chart in Figure 3 shows the LD current commands ■, °, and power detection signal VPD during the initial adjustment of the first step.
, examples of changes in the LD power PLD are shown. In the same figure, the LD power PLO immediately follows the change in the LD current command V'', but the power detection signal VPD rises slowly and follows the change due to the detection delay of the monitor output amplifier 1, etc. Therefore, CPtJ15 changes the power detection signal VPD. LD by reading the steady state value when it rises and becomes a constant value.
Detect the correct value of power PLD. Next, a method for determining the re-determined value CMD of the LD current command value in the second step of the initial adjustment of the LD power will be explained. In FIG. 1, a focus error detector 33.AGC (automatic gain control circuit) 42. Compensation circuit 43. Switching circuit 44. Driver 45. The focus actuator 32 constitutes a focus servo system. Further, when the search circuit 46 is connected by the switching circuit 44, a focus search operation is performed. Furthermore, the head 01 can be moved by passing a current through the driver 41 to the head actuator 31. Here, the possible range of the head 01 is set to sufficiently cover the outside of the data section 03 of the optical disc 02. Now, in the second step of LD power initial adjustment, the CPU 15
First, the head 01 is moved via the driver 41 and the head actuator 31 to the innermost circumferential side (or outermost circumferential side) away from the data area 03 of the disk. Next, CPU1
5 operates the switching circuit 44 to first perform the aforementioned focus search operation and then perform the aforementioned focus servo operation. In this case, the laser spot 04 is outside the data section 03 of the disk 02, so there is no need to worry about destroying the data on the disk while adjusting the LD power.
Due to C42, even if the detection value of the focus error signal output from the focus error detector 33 fluctuates due to changes in LD power, stability is not impaired. In this state, each monitor PD in playback mode and erase mode
The detected value (therefore, the power detection signal VPD) is checked and the predetermined value (
That is, if it deviates from the value corresponding to the LD power PR, PH, the LD current command value of each mode is gradually corrected to a predetermined value. LD current command value CMD at this time (I in Figure 2)
R12, I (equivalent to E12) is the final determined value. Next is the CPU! 5 is the LD current for recording mode (l- in Fig. 2).
Since the luminous efficiency (PLD/ILD) of LDIO is constant, the command value CMD corresponding to 12 is calculated by the following equation and set in the latch 21. PH-PR However, ■ “(-): LD current command value V for recording mode” (R
): LD current command value for playback mode (IR12 equivalent value) V'''(E): LD current command value for playback mode (IE12
Equivalent value) PW: Target recording laser power PR: Target reproduction laser power PE: The final initial adjustment value CMD of the LD current command value in each mode in the focus servo on state is set in the latch 21 when the target erasing laser power is greater than or equal to the target erasing laser power. At this time, since it is only necessary to know the steady level of the reproduction mode and erase mode as the power detection signal VPD, there is no need to use a particularly high-speed amplifier as the monitor output amplifier 1. In addition, the sample hold circuit 1 used in Fig. 4
There's no need for 3. By the way, in the conventional control circuit shown in FIG. 5, the LD power control loop formed by the analog circuit operates constantly to maintain a predetermined target laser power even if there is a temperature change. In contrast, in the case of the present invention, this function is performed by the CPU 15.
is executed. That is, the CPU 15 occasionally reads the PA'7-detection signal VPD in the reproduction mode or erase mode (approximately every time the disk rotation is synchronized), and if it deviates from the above-mentioned predetermined value, it changes the LD current command value CMD in all modes. Modifications allow it to respond to temperature changes. For example, if the power detection signal VPD in the regeneration mode is smaller than a predetermined value, the data of the LD current command CMD in all modes is +1, and if it is larger than the predetermined value, the L
Repeat decrementing the D current command value data by 1. This takes advantage of the fact that LD luminous efficiency is almost unaffected by temperature, and by monitoring the power detection signal only in playback mode, the optimum LD current command value CMD corresponding to temperature changes in all modes is determined, and the latch 21 Setting command (1! (J
ID can be modified. [Effects of the Invention] In the present invention, the conventional analog LD power control loop is discontinued, and the LD current command value C? The LD current is determined only by the ID, and in this case, the first
After temporarily setting the LD current command value for each mode with the focus servo off as a step knob, move the head to the innermost circumference (or outermost circumference) so as not to destroy the data on the disk with the optical spot as a second step knob. After that, the LD current command value is further determined while the focus servo is on, and the power detection signal VPD is monitored in the steady state of playback mode or erase mode, so the circuitry is significantly reduced compared to the conventional method. has been simplified. Also, the high-speed amplifier required for recording mode is no longer needed. Furthermore, even if the current/power characteristics of the LD change in the focus servo-on state compared to the servo-off state, it is now possible to obtain the optimum laser power in each mode.

[Brief explanation of the drawing]

FIG. 1 is a program circuit diagram showing a configuration as an embodiment of the present invention, and FIG. 2 is a diagram showing an example of changes in LD characteristics depending on the presence or absence of a focus servo. Figures 3 and 4 show L when the focus servo is off in Figure 1.
FIG. 5 is a conventional block circuit diagram corresponding to FIG. 1. FIG. 6 is a time chart for explaining the LD power initial adjustment operation of FIG. 5. FIG. 7 is a time chart for explaining the initial adjustment operation of the LD power. FIG. 3 is a diagram showing an example of LD characteristics using ambient temperature as a parameter. 01: Head, 02: Optical disk, 03: Data section, 0
4: Laser spot, 1: Monitor output amplifier, 5: Current control circuit, 10: Laser diode (LD), 11: Photodiode (PD), 14: A/D converter,
152 CPUs, 20: D/A converter, 21: Lunch,
CMD: LD current command value, V": LD current command, VPD
: Power detection signal, 31: Head actuator, 32
: Focus actuator, 33: Focus error detector, 41, 45: Driver, 42: AGC14
3: Compensation circuit, 44: Switching circuit, 46: Search circuit.

Claims (1)

[Claims] 1) A head moving means for moving the head to the innermost circumferential side or outermost circumferential side outside the data area of the optical disk in accordance with a predetermined command, and a focus servo means including an automatic gain control circuit. An optical disc device, comprising: a laser diode capable of outputting laser power necessary for an optical disc capable of recording, reproducing, and erasing signals; a laser power detection means for detecting and outputting a power detection signal proportional to the output power of the laser diode; Based on the designated signal for each mode of recording, playback, and erasing, the current command value of the designated mode is selected from among the digital current command values set for each mode, and the current corresponding to the current command value is selected. A laser diode driving means for causing a power to flow through the laser diode, a power setting value is set in advance for each of the modes, inputting the power detection signal as a digital value, and corresponding to the power detection signal and the detection signal as necessary. A laser power generation device characterized by comprising a laser power control means for comparing the current command value with the power setting value and correcting the current command value so as to set the difference to zero. 2) In the apparatus according to claim 1, the laser power control means sets current commands for each of the three modes based on a comparison result with the power setting value during operation in the reproduction mode or the erase mode. A laser power generation device characterized in that it performs the above-mentioned correction regarding the value. 3) In the apparatus according to claim 1 or 2, the laser power control means sets the focus servo means in an inoperable state based on a first initial setting command, and controls at least the laser diode. After setting the current command values in the regeneration mode and erase mode in the driving means to values lower than levels necessary for normal regeneration operation and erase operation, respectively, the mode command signal is set to regeneration mode, and based on the correction operation, A first regeneration initial current command value as the current command value that allows normal regeneration operation is temporarily set in the laser diode driving means, the mode designation signal is set to an erase mode, and the correction operation is performed based on the correction operation. , provisionally setting a first initial erasing current command value as the current command value that allows a normal erasing operation in the laser diode driving means, and then operating the head moving means and the focus servo means; The mode designation signal is set to the regeneration mode, and based on the correction operation, a second regeneration initial current command value as the current command value that allows normal regeneration operation is reset to the laser diode driving means, and setting the mode designation signal to an erase mode, and resetting a second initial erase current command value as the current command value that allows a normal erase operation to the laser diode driving means based on the corrective operation; Furthermore, by using the second initial current command value for reproduction, the second initial current command value for erasing, and the power setting values of the three modes set for itself, the current command that enables normal recording operation is provided. A laser power generation device characterized in that the value is calculated and set in the laser diode driving means.