JPH0349049A - Laser power output device - Google Patents

Abstract

PURPOSE:To remarkably simplify adjustment for a laser power by automatically performing the adjustment for the laser power for respective level of recording, reproduction, and erasure as monitoring the laser power by using a CPU. CONSTITUTION:Two adjusting functions of the adjustment for the laser power at a stationary state by a laser output control circuit and that for a power response when a mode is switched are automatically performed by using the CPU 15. Thereby, the adjustment for the laser power can be remarkably simplified, however, the adjustment for the sensitivity of a PD 11 for monitoring should be performed necessarily. A power detection signal VPD having integral sensitivity for the laser power of an LD 10 is found with the monitor PD 11 and a monitor output amplifier 1. The signal VPD can be fetched with the CPU 15 at an appropriate timing via a sample-and-hold circuit 13 and an A/D converter 14. On the other hand, a power reference signal V1 is outputted from the CPU 15 via a latch 18 and a D/A converter 16, and the power reference signal V1 and the power detection signal VPD are inputted to a comparator 2, then, the difference of those signals V1 and VPD is found.

Description

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

The present invention relates to a laser power output device that outputs necessary laser light to an optical disk on which signals can be recorded, rewritten, and erased via a laser diode (hereinafter also abbreviated as LD), and particularly relates to a laser power control system. The present invention relates to a laser power output device that automates the means for giving a command value to simplify various adjustments, and also makes it possible to determine abnormalities in the control system in advance. Note that in the following figures, the same reference numerals indicate the same or corresponding parts.

[Conventional technology]

FIG. 6 shows an example of the circuit configuration of a conventional laser power output device. In the figure, the laser power output from the LDIO is the monitor photodiode F' (hereinafter also abbreviated as PD).
A voltage signal VP (referred to as a power detection signal) proportional to the laser power is monitored by the monitor output amplifier l.
converted to O. On the other hand, the power reference signal generation circuit 6 performs signal recording (WRITE), reproduction (READ), and erasing (
ERASE), respectively corresponding power) Jf4a signal V signal light 1. This power reference signal Vl and the power detection signal vPD are compared by a comparator 2 to obtain a difference 2a between both signals Vl and VPD, and this difference is then peak-held by a peak-hold amplification circuit lPt3. In addition, the number of hole toys will be expanded. The reason for this peak hold is that when recording a signal, the laser power is modulated by the recorded data (however, this modulation circuit is omitted in this figure), and the peak hold amplification circuit 3 is used at the point when the laser power is greatest. So, comparator 2
The differential output 2a is held and amplified. Next, the output 3a of the peak hold' amplification circuit 3 is added to an additional current command signal V2, which will be described later, via an adder 4, and then,
The current command signal 4a as this added value is input to the 11t flow control circuit 5, and the current control circuit 5 causes a current ILD proportional to the input current command signal 4a to flow through the LDIO. Figure 5 shows the current rL flowing through the laser diode (LD) 10.
The relationship between D (horizontal axis) and laser power (light output) P (vertical axis) output from this LDIO is shown using the peripheral temperature of the LDIO as a parameter. As can be seen from the figure, the laser power P changes greatly as shown in the solid line due to temperature changes (or due to deterioration), but laser output control using the power detection signal vPD as a feedbank signal as shown in Figure 6 The circuit always limits the laser power to a value proportional to the power reference signal Vl in steady state. Also, if the playback state changes to recording or erasing state,
Or conversely, when changing from the recording or erasing state to the reproducing state, in order to quickly change the laser power to the target value, the additional current command circuit 7 outputs the current to be added to the reproducing state only during recording or erasing. A corresponding current command signal (referred to as an additional current command signal) V2 is given to the laser output control circuit. In this case, the additional current command signal 2 may be added to the adder 4 as shown in FIG. 6, or the current control circuit (V/
In addition to the I conversion circuit) 8, via this current control circuit 8,
Flow additional current directly to LDIO. This allows quick laser power switching regardless of the response speed of the laser output control circuit.

[Problem to be solved by the invention]

1) Regarding the first invention: The above laser power output device has a problem in that adjusting the laser power for each mode (reproducing, recording, erasing) requires considerable effort as described below. That is, it is necessary to adjust the power reference signal 1 with a volume in order to bring the steady state laser power value to a predetermined value. Also, when switching modes (
In order to speed up the power switching response (reproduction-recording or erasing), it is necessary to adjust the additional current signal 2 with the volume. Also, since there are large variations in the characteristics of individual LDIOs,
Is it necessary to adjust the laser power output device for each LDIO? Furthermore, even after the -degree adjustment, if the LD characteristics change due to aging, the j1M alignment will deviate. Therefore, this first invention provides a laser power output device equipped with a CPU that automatically outputs the power base (1 east signal Vl and additional current command No. 18) while monitoring the laser power. 2) Regarding the second invention: The laser power control loop in FIG.
Therefore, the power detection VPD has the function of adjusting the current flowing through LDlo so that it is equal to the power reference signal 1 as a predetermined value. Therefore, if sufficient power detection signal VPD cannot be obtained due to, for example, PDII failure or monitor output amplifier I failure, the control loop will cause the
An excessive current will flow through DIO, and even LDIO will be damaged. In order to prevent this, it is possible to limit the LDIO current or add a mink circuit, but the P (power) -1 (current) characteristics of the LD have extremely large individual variations and temperature changes, so It is difficult to limit the current value.For example, an LD with the characteristics shown in Figure 5
In this case, if current is limited at L and T in consideration of temperature changes, if ILHT flows below room temperature, the laser bar will exceed its maximum rated output. Therefore, it is an object of the second invention to provide a laser power output device that can eliminate the above-mentioned problem 8.

[Means for Solving the Problems] In order to solve the above problems, the device of the present invention includes a laser diode (such as 10) capable of outputting the laser power necessary for an optical disc capable of recording, reproducing, and erasing signals; Laser power detection means (monitor photodiode 11° monitor output amplifier 1, etc.) that detects and outputs a power detection signal (VPO) proportional to the output power of the laser diode, a given power reference signal (Vl, etc.) and the A laser power control means (comparator 2, peak hold amplification circuit 3, etc.) that compares the power detection signal and outputs a command value (3a, etc.) of the current to be passed through the laser diode so that these two signals match. ), addition means (adder 4, etc.) for adding the current command value and a current command value added to the current command value (additional current command signal ■2, etc.); The current (I) corresponding to the current command value (tla, etc.)
A laser power output device comprising a current control means (current control circuit 5, etc.) for causing a current (LD, etc.) to flow through the laser diode I-P, and reads the power detection signal described in 11 during recording and reproduction. The power reference signal is output so that the power detection signal reaches a required predetermined level during erasing, and the current that should be passed through the laser diode during playback and the current that should be passed through the laser diode during recording or erasing are output. Means (sample and hold circuit I3, A/D converter 14
, CPL115, latch 18.19, D/A converter 16
．． 17, etc.), or further, a current detection means (current detection amplifier, A/D converter 2) for detecting the current of the laser diode (1, LD, etc.).
1, etc.), and the power reference signal and the additional current 1-h order value are set or varied by a predetermined value, and from the detected current of the current detection means and the power detection signal at this time, the radar diode, It is assumed that the apparatus is equipped with a means (such as a CPU 15) for detecting an abnormality in a control loop that connects a laser power detection means, a laser power control means, an addition means, and a current control means. [Function] ■) Regarding the first invention: In this invention, the following two adjustment functions are automatically performed using the CPU. (1) Laser power adjustment in a steady state using the laser output control 1211 circuit (2) Power response adjustment when switching modes Therefore, laser power adjustment is greatly simplified (however, only the sensitivity adjustment of the monitoring PD is required) need). Furthermore, data is recorded for automatic adjustment by the CPU. By appropriately performing the operation when neither reproducing nor erasing operations are being performed (for example, immediately after inserting a disk cartridge), optimal laser power adjustment can always be performed even if the LD characteristics deteriorate somewhat due to aging. 2) Regarding the second invention: In this invention, before performing the original laser power adjustment (laser power adjustment in a steady state and power response adjustment during mode switching), the LD current is gradually increased, and the LD current at that time is It is possible to judge whether the laser power control loop operates normally from the monitored value of the laser power control loop and the LD output power monitored value (power detection signal vpo). This allows P
To prevent damage to the LD when adjusting the original laser power due to a defect in the D or monitor output amplifier.

【Example】

The first invention will be described in detail below with reference to FIGS. 1 and 2. FIG. 1 is a block circuit diagram showing a configuration as an embodiment of the first invention, and corresponds to FIG. 6. Further, FIG. 2 is a time chart for explaining the adjustment operation in FIG. 1. In FIG. 1, the power reference signal generation circuit 6 of FIG.
．． In place of the additional current command circuit 7, a circuit mainly composed of CP (Ji5) is used.The power detection signal VPD is sent to the sample and hold circuit 13.A in the CPU 15.
A power reference signal V1 is inputted from the CPU 15 via the latch 1B and the D/A converter 14, and the power reference signal V1 is also inputted from the CPU 15 via the latch 19 and the D/A converter 17.
The additional current command signal V2 is outputted through the respective terminals. Next, the operation shown in FIG. 1 will be described. First, a power detection signal VPD having the same sensitivity to the laser power of the LDIO is obtained using the monitor PD 11 and the monitor output amplifier 1. This signal VPD is supplied to the sample and hold circuit 13. A
The CPU 15 can take in the data via the /D converter 14 at an appropriate timing. On the other hand, the power reference signal ■1 is C
PU15 to latch 18. It is output via the D/A converter 16. Power reference signal Vl and power detection signal VPD
is input to a comparator 2, and the difference between these two signals Vl and VPD is determined.This difference signal 2a is peak-held and amplified by a peak-hold amplification circuit 3. Additionally, the additional current command signal ■2 at the time of erasing or recording is sent to CPU1.
5 to latch 19. It is output via the D/A converter 17. Output signal 3a of the peak hold amplification circuit 3
and additional current command signal v2 are added by an adder 4. This addition signal 4a is input to the current control n circuit 5,
The circuit 5 causes current ILD to flow through LDIO with a constant V/l conversion ratio. To provide a supplementary explanation of the latches 18 and 19, the latch I8 for the power reference signal vI is used for reproduction and recording. It consists of three latches for erasing (internally abbreviated as R and WE, respectively), and data is input from CPtJ15 into each of them (and when the erase gate EC is ON, the latch 18 is connected to the E part. The stored erase latch data is output to the D/A converter 16, and when the write gate WG is ON, the recording latch data stored in the W portion is output to the D/A converter 16.
Output to A converter I6, both gates EC, WG are O
In the case of FF, the reproduction latch data stored in the R portion is output to the D/A converter 16. The latch I9 for the additional current command signal v2 consists of two latches for recording and erasing (internally abbreviated as W and E, respectively), each of which stores data from the CPL 115, and an erase gate. When EC is ON, the erase latch data stored in the E part is output to the D/'A converter 17, and when WG is ON, the recording latch data stored in the W part is D/A converted. It is assumed that the output signal is output to the device 17. In addition, power reference signal Vl, additional current command signal
Changing the erase or record latch data during the adjustment in item (2) is performed when the erase gate EC and write gate WG are both OFF. Next, referring to FIG. 2, an adjustment method for the apparatus shown in FIG. 1 will be explained. (1) Adjustment of laser power in steady state by laser output control circuit: First, the reproduction level is adjusted. Lunch from CPL115 18. While gradually increasing the power reference signal Vl given to this control circuit via the D/A converter 16, the power detection signal ■PD is sampled and held by the sample and hold circuit 13, A/
CPU], 5 via the D converter 14. Then, the power reference signal V when the power detection signal VPD matches the reproduction level predetermined as the specification value of this device.
l becomes the power reference signal during reproduction. Next, steady power adjustment is performed during erasing and recording. However, this adjustment may interfere to some extent with "power-response adjustment during mode switching," which will be described later, so it is necessary to perform the adjustment alternately to converge. For example, the erase level is adjusted as follows. The data corresponding to the power reference signal v1 during reproduction obtained by the above method is input into the R portion of the latch 18. Separately, the same data as the reproduction level Vl is initially stored in the E portion of the latch 18, which is used to store data corresponding to the erasing power reference signal 1 to be obtained. Next, by 0N10FF of the erase gate EC, the data in the playback level latch 8 part and the data in the erase level latch E part in the latch 18 are alternately (1)/A change fA2.
316, it is applied to the laser output control circuit as a power reference signal Vl. In this case, as shown in FIG. 2(A), while gradually increasing the erase level power reference signal Vl from the reproduction level, the power detection signal VPD is sent to the sample and hold circuit 13. A/
It is monitored by the CPU 15 via the D converter 14. This monitoring timing LM requires that the laser power change at the time of mode switching is sufficiently stable, so for example, the ON signal of the erase gate EG is during the second pulse (time difference between L2.t and 1 in the same figure). As, the latter half of the lIn
Implemented within 5 days. In this way, the power detection signal VPD
The power reference signal (1) when the erase level matches the erase level predetermined as a specification value of this device becomes the temporary erase power reference signal. Next, perform the power-response adjustment J when switching modes described in (2) below. The power reference signal ■1 during playback and erasing is alternately output using a continuous pulse signal of ON10F1? (about 2IIFs each) of the erase gate EG.
As shown in Figure (B), another latch 19.
An additional current command signal v2 at the time of erasing, which is a signal outputted only during the ON period of the erase gates FF and G, is gradually increased from zero via the R/A converter 17. This additional current command signal ■2 is added to the peak hold increase [↑J circuit output 3a in the laser output control circuit, and the current control circuit 5
is man-powered. The current control circuit 5 supplies a current proportional to the input voltage to the LDIO at a constant conversion ratio. When the additional current command signal V2 is zero, the power response time at the time of mode switching is determined only by the response speed of the laser output side t11 circuit, and generally takes several tens of microseconds or more (corresponding to A in the figure). The response time of the LD lightning current LD due to the additional current command signal ■2 is about 0.1 μs, which is sufficiently fast compared to the response of the laser output control circuit, so when the additional current command signal ■2 during erasing is increased, the response time shown in the figure The power response will improve as shown in →B→B. On the other hand, if it is raised too much, overshoot will occur as shown in figure 2. Therefore, the value of VPD of the power detection signal is set at the erase gate EC in addition to the monitor timing LM mentioned above.
Also check the monitor timing LMI within 10 μs immediately after turning ON (in this case, as described above, this is done by the CPU 15 via the sample and hold circuit 13 and the A/D converter 14), compare the VPD values of both, and - fail. The additional current command signal v2 (corresponding to C in the figure) is determined. With the additional current command signal 2 optimized in this way, check again to see if the power detection signal VPD in the erase steady state deviates from the erase level determined for this device.
If it is outside the target allowable value, the additional current command signal V2 is left as is, and the steady power adjustment during erasing described in the previous section (1) is performed again. If the target tolerance is reached, the adjustment at the time of erasure is completed. Power adjustment during data recording can be considered in substantially the same way as during erasing, so a description thereof will be omitted. Next, the second invention will be explained in detail using FIGS. 3 to 5. FIG. 3 is a block circuit diagram showing a configuration as an embodiment of the second invention. 3, the difference from FIG. 1 is that a current detection amplifier 20 that detects the LD current ILD, and an A/D converter 21 that converts the output from A/D and outputs it to the CPU 15 are added. Although not clearly shown in this diagram, the D/A converter 1
7 used to have unipolar (■) output, but it now has bipolar (■) output.
■The point is that it was changed to θ). Since the original laser power adjustment in FIG. 3 is exactly the same as that in FIG. 1, the explanation here will focus on the part related to the second invention. FIG. 4 shows a time chart for explaining the operation of FIG. 3. FIG. 5 shows the characteristics of the LD as described above. First, as an initial state, the power reference signal (=D/A converter 16
) output) Vl d outputs a signal corresponding to a sufficiently small power PI (FIGS. 4 and 5) for LDIO. Also, current command signal (=output of D/A converter 17) V2
In this case, an e polarity signal having a value larger than the maximum (2) side saturation output of the peak hold amplification circuit 3 is output. In this state, the peak hold amplification circuit 3 tries to output a saturated output by the power reference signal Vl and cause current to flow through the LDIO, but since the current command signal 2, which has the opposite polarity, is larger, the current control circuit 5 The human power 4a has ○ polarity, and no current flows to LDIO. Next, the current command signal v°2 is gradually decreased until it approaches zero, and when this signal 2 becomes smaller than the signal 3a which is the saturated output, the signal 4a becomes the polarity of L
Current ILD begins to flow through DIO. When the signal V2 is further reduced and the LD current ILD is increased, the LDIO starts emitting light at a certain point (<ll (FIGS. 4 and 5)). CPU 15 is A/D converter 1
By constantly taking in the signals of 4 and 21, the laser power and the LD current IL port are monitored. When the control loop is normal, when the laser power P reaches Pl (point L1 in Fig. 4), even if the current command signal v2 is reduced further, the laser power control loop operates, so the laser power P and the LD current ILD remains almost constant. The above operation is shown by the solid line in FIG. Next, consider a case where the laser power control loop does not operate normally. For example, when the power detection signal VPD cannot be obtained due to a failure or disconnection of the laser power monitor PDII or a failure of the monitor output amplifier I, the LD current ILD further increases as the current command signal 2 decreases. go. By monitoring the LD current ILD via the current detection amplifier 20, when the LD current ILD reaches a certain level (1), the current command signal (2) stops decreasing and outputs a constant value. The above operation is shown by the broken line in FIG. As shown in FIG. 5, the value of 11 is determined to be a current value that can produce at least the laser power (optical output) of Pi, taking into account the operating temperature range of the LD and individual variations (not shown). Therefore, if a current of 11 is passed through LDIO, a laser power greater than PI should be produced. The laser power at this time varies considerably depending on temperature conditions and individual variations, but it can generally be kept within the maximum rated output if Pl is set to a sufficiently small value. As described above, if the power detection signal VPD as a monitor output for laser power monitoring is not obtained when the LD current ILD is increased to 1, it can be determined that the laser power control loop is abnormal. In addition, if the power detection signal VPD is normal but the control loop does not operate normally due to a failure in the peak hold amplification circuit 3, etc., the LD current ILD
When the power detection signal VPD exceeds a value corresponding to P1 when the power detection signal VPD increases to II, it can be determined that the laser power control loop is abnormal.

【Effect of the invention】

According to the first invention, the laser power adjustment at each level of recording, reproduction, and erasing can be automatically performed while monitoring the laser power using the CPU, so that the laser power adjustment can be greatly simplified. Furthermore, since it is easy to readjust as necessary, the optimum laser power can always be obtained even if the LD characteristics deteriorate somewhat due to aging. Further, according to the second invention, a means for detecting the LD current is added, and a monitor value of the LD current rLD and a change in the power detection signal vpo correspond to a predetermined change in the power reference signal l and the current command signal V2. By examining fJI%, we were able to determine whether the laser power control loop is operating normally before making the actual laser power adjustment.
This can prevent a defective PD or circuit in the loop from damaging the LD when adjusting the laser power.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing a configuration as an embodiment of the first invention, FIG. 2 is an explanatory diagram of the adjustment method in FIG. 1, and FIG. 3 is a block circuit diagram showing a configuration as an embodiment of the second invention. Figure 4 is a time chart for explaining the operation of Figure 3, Figure 5 is a diagram showing an example of the characteristics of a laser diode, and Figure 6 is a conventional block diagram corresponding to Figures 1 and 3. . 1: Monitor output amplifier, 2: Comparator, 3: Peak hold underground circuit, 4: Adder, 5: Current control i10 circuit, lO
: Laser diode (LD), 11: Monitoring photodiode (PD), 13: Sample and hold circuit, 14.
21: A/D converter, 15: CPU, 16, 17
: D/A converter, 1B, 1. ! J: Lanochi, 20;
Current detection amplifier, VPD; power detection signal, ■1: Power
No base signal, ■2: Additional current command signal, ILD
〉Leaving bell tI 1hl? Mt=:: Old? (Self) Figure 2 Figure 4 Figure 4

Claims (1)

[Scope of Claims] 1) A laser diode capable of outputting the laser power necessary for an optical disk on which signals can be recorded, reproduced, and erased, and a laser power detection means for detecting and outputting a power detection signal proportional to the output power of the laser diode. , a laser power control means that compares a given power reference signal and the power detection signal and outputs a command value of a current to be passed through the laser diode so that these two signals match; , an addition means for adding an additional current command value to the current command value, and a current control means for causing a current corresponding to the current command value added via the addition means to flow through the laser diode. The device reads the power detection signal, outputs the power reference signal so that the power detection signal reaches a required predetermined level during recording, playback, and erasing, and sends it to the laser diode during playback. It is characterized by comprising means for outputting a current command value of the difference between a current and a current to be passed through the laser diode at the time of recording or erasing as the additional current command value at the time of recording or erasing, respectively. Laser power output device. 2) The laser power output device according to claim 1, further comprising: current detection means for detecting the current of the laser diode; and setting or varying the power reference signal and the additional current command value according to a predetermined procedure. and means for detecting an abnormality in a control loop connecting the laser diode, the laser power detection means, the laser power control means, the addition means, and the current control means from the detected current of the current detection means and the power detection signal at this time; A laser power output device characterized by comprising: