JP2806520B2 - Level control method for optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 〔Overview〕   Optical disk device for optically writing / reading data
Laser diodes, each having its own characteristics.
The amount of laser light emitted from the load unit becomes almost constant
Automatic adjustment and laser diode unit
Control to restore fluctuations in light emission power level from
To multiple digital / analog (D / A) conversion means
Laser control circuit by automatic control based on the value
Simplification and automation of testing, reduction of test man-hours and cost
Down and setting by the above D / A conversion means
Is performed with particularly high precision. [Industrial applications]   The present invention relates to a light source for optically writing / reading data.
In the case of disk devices, in particular,
Control the amount of laser light
The present invention relates to a laser control method (laser control circuit) to be controlled.   Expected as a large-capacity external storage device for information processing equipment
The optical disk drive that is used
Capable of recording more than ten times higher density than disk devices
is there.   Recording of data on the optical disk device is performed, for example,
Light emission from laser diode on recording film on optical disk medium
Strong laser light amount, for example, with a light amount equivalent to 5 to 10 mW,
This is called the light power level, and the light beam is
And a thermal reaction causes a hole (pick) in the optical disk medium.
G) is opened. Also, the crystal of the recording film
It is also done by changing the state.   On the other hand, data written on an optical recording medium is
Weak laser light emitted from the mode, for example, about 1 mW equivalent
The amount of light, which is called the read power level, is the light beam
Read by the amount of reflected light obtained by irradiating the recording film as
Rukoto can.   The light emission of the laser diode used in this way is
Stable write power level and read power level
The amount of light emitted from the laser diode to obtain
Monitor with a photodiode and monitor the laser control circuit.
Control the emission power of the laser diode by the laser current
Like that.   Also, laser diodes have unique characteristics, and
In order to use it for disk devices,
Make the corresponding adjustments to ensure a substantially constant light power level and
It is set so that the read power level can be obtained.   Such settings and always constant write power level and reset
Control to obtain the power level
It is required that it can be realized by an easy control method. [Conventional technology]   FIG. 4 shows an example of a conventional laser control circuit (for example,
For example, Japanese Patent Application No. 60-255422). The optical disk device of FIG.
The circuit that controls the drive of the laser diode unit
Laser diode (LD) unit 1, photodiode
(PD) current / voltage converter 12, read power level detector
3, D / A converter 4, read power level current adjuster
5. Write power level current adjuster 6, D / A converter
7, write power level setting unit 8, write power level
Current subtraction setting section 17, write power level current subtraction section 10,
Level shift unit 11 and microprocessor unit
(MPU) 21.   The LD unit 1 controls the read power level by the drive current.
Light level, for example, about 1 mW
For example, a laser diode that emits light of an amount equivalent to 5 to 10 mW.
Monitors the amount of light emitted from the LD (hereinafter called LD).
A photodiode (hereinafter referred to as PD).
Read power level detector 3 is an operational amplifier
31, fixed resistors R1, R2 and feedback capacitor C1
The read power level detection unit 3 performs PD current adjustment.
Detects the PD voltage taken out of
Set the voltage to the read power level
Output to the power supply level current adjustment unit 5. D / A converter
Data 4 is a PD in which the output power of the LD indicates the read power level.
Set in advance by the microprocessor 21 so that the voltage becomes
Have been. The read power level current adjustment unit 5
It consists of a transistor TR1, a wire L, and a fixed resistor R3.
Drive current is adjusted so that light of read power level is emitted.
adjust. The coil L is not essential,
It is provided to prevent light interference. Light
The power level current adjuster 6 includes two transistors TR2,
TR3 and fixed resistor R4.
Light of the power level superimposed on the bell is emitted
Drive current is adjusted as follows. Transistors TR2 and TR3 are made
It is connected so that it can operate at high speed.
You. D / A converter 7 is the output power of LD in LD unit 1.
In advance so that the voltage becomes the PD voltage indicating the write power level.
It is set by the microprocessor 21.   The write power level setting unit 8 is a transistor TR4,
It consists of a constant resistor R5 and is set in the D / A converter 7.
LD outputs laser light according to the write power level
The write power level current adjustment unit 6
You. The write power level current subtraction setting unit 17 is a transistor.
Output from the D / A converter 7
Write the current subtraction amount according to the power
Set 10 Write power level current subtractor 10 is high
Two differentially connected transistors for fast operation
It consists of two resistors, TR6 and TR7, and a fixed resistor R6.
-The write power level current is superimposed on the level current
Subtract write power level current from PD current.   The level shift unit 11 includes an AND circuit AND and two zeners.
-Composed of diodes D1 and D2 and resistors R7 and R8
The write power level shifts according to the data
The write power level current adjuster 6 and the write power level
The transistors TR2, TR3, TR6, and TR7 of the bell current subtractor 10
Adjust ias.   The PD current / current converter 12 converts the current flowing to the PD to a predetermined value.
Convert to voltage with ratio. The analog switch 13
PD current / voltage converter 12 and read power level detector 3
And the output value of A / D converter 16 is read power
The microprocessor unit (MP
U) While the D / A converter 4 is set by 21, the PD current /
Turn off the output of the voltage converter 12 and read the power level.
The functions such as out 3 are substantially stopped. D / A converter 4
Indicates that the output value of the A / D converter 16
MPU21 determines the value to determine the PD voltage value as shown
Is set. The analog switch 15
Between the setting unit 8 and the write power level current subtraction setting unit 17
Yes, the set value of the D / A converter 14 is
While the power value indicates the PD voltage indicating the read power level,
The operation of the power level current subtraction setting unit 17 is turned on. A /
The D converter 16 converts the PD voltage at that time from A / D to MPU 21
Notify.   PD current / voltage converter 12 converts PD current to voltage at a specified ratio
Fixed resistors R9 to R13 and their fixed resistors
Switch 21 to short-circuit devices R9-R12, for example,
Switch, short bar, analog switch, etc.
Have been.   The fixed resistors R9 to R13 of the PD current / voltage converter 12
For example, it is set at the time of design at a ratio of 1,2,4,8,16. Also, Sui
The switch 21 is turned on or off when assembling or testing the equipment.
Will be In other words, due to product variation, the light emission power of LD
And PD current are different for each LD unit 1
If set, there will be too many errors to use. for that reason,
Measure the characteristic data at this time in advance, and add
The output voltage of the PD when emitting light with a certain power based on the
That is, the value set in the A / D converter 16 after A / D conversion is
A fixed value that has been weighted in advance as described above so as to be a constant value
Determine the combination of resistance values of resistors R9 to R12 with switch 21
You.   As a result, the relationship between the LD emission power and the PD voltage can be compared, for example.
For example, a PD voltage of 0.5 V is determined for an emission power of 1 mW.
You. Also, the emission power and PD current are in a 1: 1 proportional relationship
Therefore, if the light emission power changes, the PD voltage
Will be.   The above is the contents to be processed before the product is shipped. On the other hand,
The following process is used on the user side, for example, when the power is turned on
Alternatively, the processing is performed at the time of exchanging the optical disk.   For example, the current that flows to the LD when writing data is shown in Fig. 5.
The LD output is applied so as to form a pulse waveform.
You. In FIG. 5, the vertical axis indicates the light emission amount (mW) of LD, and the horizontal axis indicates LD.
Shows the applied current. Symbol CV is LD characteristic curve, symbol P_WRIs
Write power level point, code P_RDIs the read power level
Point, sign I_WRIs the level of the current flowing through the LD when writing data.
, Sign I_RDIs the current level flowing to LD when reading data
Are respectively shown.   At this time, the amount of light emitted from the LD
The applied PD voltage has the waveform shown in FIG. That is, the lead
Power level P_RDLight power level P above_WRThe amplitude of
Has a superimposed pulse waveform.   On the other hand, each LD has its own characteristics.
Output write power level and read power level
If there is a large fluctuation, data read on the optical disc,
What characteristics should be used to adversely affect light quality, etc.
Even if the LD has a constant write power level
PD current / voltage conversion to obtain read power level
Initial setting is performed in the section 12. That is, the optical head (shown
Power meter calibrated as completed
The LD emits light at a certain power with a
Switch 21 so that the PD output voltage when
Turn on / off.   (MPU) 21 is an A / D converter 16 as shown in FIG.
Input data and set to D / A converters 4, 7, 14
Give the value, activate the analog switches 13 and 15, and
Write gate W / RG, write data W / RD
give. The operation of the MPU 21 and the circuit of FIG.
This will be described with reference to a flowchart. Step 00 (S001)   The MPU 21 turns off the analog switch 13 and turns off the APC.
I do. This makes the amplifier 31 a voltage follower
And the input voltage applied to the non-inverting input terminal
Well output. Step 002 (S002)   Initialize the read output data of D / A converter 4 to 0
I do. Step 003 (S003)   Analog voltage based on output data from D / A converter 4
Is applied to the non-inverting input terminal of the amplifier 31. From amplifier 31
Is applied voltage of the polarity to the base of transistor TR1.
Applied. When the output voltage of D / A converter 4 is 0
Transistor TR1 is turned off and LD does not light.
No. However, as described later, the output voltage of the D / A converter 4
As the LD rises, the LD emits light with the amount of light corresponding to the output voltage.
You. Step 004 (S004)   The output light of the LD is detected by the PD, and this detection value is used for A / D conversion.
The data is converted into a digital value by the data 16 and given to the MPU 21. Step 005,006 (S005, S006)   The MPU21 converts the detected value of the A / D converted PD to the read power level.
To determine if the device has reached Detected value is read power
If the level has not been reached, the output data of D / A converter 4
Is incremented by 1 and the process returns to step 003 (S003). Below, P
Step until the detected value of D reaches the read power level.
Steps S003 to S006 are repeated. Step 011 (S011)   When the detected value of PD reaches the read power level, MPU2
1 is the write gate W / RG =
ON, write data W / RD = ON output is applied, and level
The write power level current adjuster 6 and the shifter 11
And energizes the write power level setting unit 10. Ie
Transistors TR2 and TR7 are turned off and transistor T
A state where the LD can emit light up to the write power level via R2
become. Step 011 (S011)   MPU21 initializes the write output data of D / A converter 7
I do. Step 012 (S012)   Based on write output data via D / A converter 7
The analog voltage is transferred to the write power level
Applied to the base of the star TR4. LD has transistor TR1
Emits light at the read power level determined as above
doing. Thereby, the write power level current adjusting unit 6
The write current flows to LD through the transistor TR2 of
Emit light above the read power level. Step 013 (S013)   The output light of the LD is detected by the PD, and this detection value is used for A / D conversion.
The data is converted into a digital value by the data 16 and given to the MPU 21. Step 014,015 (S014, S015)   MPU21 detected value of PD reached write power level
Is detected. The detected value has not reached the write power level
In this case, the output data of the D / A converter 7 is added by 1,
It returns to step S012. Below, the detected value of PD
Repeat steps S012 to S015 until the power level is reached
I do. Step 020 (S020)   When the detected value of PD reaches the write power level, MPU2
1 is the same value as the last write data of D / A converter 7
Set in converter 14. This allows data write
At this time, the writing is performed by the write pulse amplitude shown in FIG.
Write power level via the power level current subtraction setting unit 17
It is set in a state where it can be subtracted from the bell current subtractor 10. Step 021 (S021)   The MPU 21 turns on the analog switch 15 and
-Level current subtraction setting unit 17 and write power level
The flow subtraction unit 10 is activated. Step 022 (S022)   Analog voltage based on output data from D / A converter 14
The write power level current subtraction setting unit 17 transistor
Apply to TR5 and subtract the write current. D / A converter 14
The LD emits light with the current subtracted according to the output voltage.
You. Step 023 (S023)   The output light of the LD is detected by the PD, and this detection value is used for A / D conversion.
The data is converted into a digital value by the data 16 and given to the MPU 21. Step 024,025 (S024, S025)   MPU21 detected value of PD dropped to read power level
Is detected, the detected value has not reached the read power level
In the case of, the output data of the D / A converter 14 is subtracted by 1, and
Return to Step S022. Below, the detected value of PD is
-Repeat steps S022 to S025 until the
You. Step 030 (S030)   When the detected value of PD decreases to the read power level, MP
U21 is a write gate W / RG for the AND gate of the level shift unit 11.
= OFF, write data W / RD = OFF
The write power level current adjuster 6 and the
And the energization of the write power level setting unit 10 is stopped. Step 031 (S031)   With the above operations, the read power level and write power
MPU21 is automatically set
Turn on the analog switch 13 and turn on the APC.   In other words, to summarize the above operations, APC was turned off
State (S001), determine the read power level (S002-S0
06), decide the write power level (S010 ~ S015)
Target read power level and write power
-Level target value and current subtraction target value
Data 4, D / A converter 7, and D / A converter 14
It is. As described above, the target value was automatically determined
Later, turn on the APC to keep the read power level constant.
Such normal operation is possible. [Problems to be solved by the invention]   In the above, the D / A converter 4 and the D / A converter 7
From the origin of the curve in FIG._RD, Write current I_WR
The analog voltage is output so that In FIG.
It is used only on the steep part of the curve
However, the output of the above D / A converter 4 and D / A converter 7 is
Analog voltage corresponding to full span with reference to the origin
Output.   On the other hand, D / A converters have a finite
Long. For example I_O= 50mA, I_RDD / A when = 55mA
The range that should be controlled by the converter 4 is ± a number around 55 mA
mA, and it is necessary to control only ± several mA with high accuracy.
However, for example, the analog voltage in the range of full span 60 mA
Is output. In this case 2⁸= Controls 60mA with 256 counts
The resolution per count is 60mA / 25660
0.234 mA, which is coarse, and sufficient setting accuracy cannot be obtained.
No.   One way to increase the setting accuracy is to use the bit of a D / A converter.
May be longer, but it will be more expensive
Problem. [Means to solve the problem]   According to the present invention, data writing or optical
Laser that emits light in response to reading data from disk
Compatible with diode and emission power of the laser diode
And a photodiode for outputting the output value.
Detecting means for detecting the output value of the code, and the detecting means comprises
A predetermined detection value corresponding to a certain power level is detected.
Target value control means for controlling a target value in the
The target value is set so that read power
The target read power level is obtained from the control
Read power current supply for supplying read power current
Means, the read power level target value and the photo
Equilibrium that works so that the output value of Iode is in balance
Means and a target read power based on the output of the balancing means.
APC control to operate the read power current supply means
Switch means for activating / deactivating the control
The APC control is deactivated by the switch means.
In this state, lead power is applied to the laser diode.
-Light emission is performed, and the detection means reaches a predetermined power level.
The target value control procedure is performed until a corresponding predetermined detection value is detected.
Determining a target read power level for the step;
After the read power level target value is determined,
The APC control is activated by the switch means, and the
When the diode emits read power, the balance means
Is the determined read power level target value and
Works so that the output value of the
At the target read power based on the output of the balancing means.
Activating the read power current supply means, the laser
Make sure the diode emits light at the given read power level
Adjusting step and controlling by
Provided is a level control method for an optical disk device characterized by the following.
It is.   FIG. 1 shows a level control circuit of an optical disk device according to the present invention.
FIG. 2 shows a principle block configuration diagram.   The level control circuit writes data to the optical disc or
Light emission that emits light in response to reading data from an optical disk
Element LD and light detecting element for detecting output light of the light emitting element
Operatively connected to a PD to output light from the light emitting element to a predetermined
Control to the level. For this reason, the level control circuit
A read current applying means for causing an optical element to emit light at a data read level.
Step 5, the light emitting element emits light at the data write level
A current of a predetermined level is superimposed on the current of the read level.
Write current applying means 6, 8 and the output of the light emitting element
Means for setting a target value for controlling light to a predetermined readout level
4,21. Further, a level control circuit is provided for the light emitting element.
Power control means for controlling output light to the read level target value
An output detection light of a light emitting element from the light detection element
Is compared with the read level target value and
The balance circuit 50 that operates to make the output zero when
Connected via a read current applying means.
Having a control circuit 3 'for energizing an optical element,
Switch means 53, 55 for activating or deactivating the control means,
At the time of data writing, the output of the balance circuit of the power control means is
From the force corresponds to the superimposed current for writing the data
Means 10 and 17 for subtracting a value,
Subtraction target value setting means 14, 21 to be set, and the writing
Superimposition target value setting that sets the value to be superimposed on the current application means
Means 7, 21 are provided. (Operation)   According to the optical disc device of the present invention, the light emitting element is an optical disc.
Write data to disk or read data from optical disk
Emits light in response to light emission, and the light detection element emits light from the light emitting element.
The value corresponding to the word is detected. Read power control system
Emits light so that the light emitting element emits light at the data read level.
Control the power, and the write power control system
The light emission power is controlled so as to emit light at the writing level. So
Then, the subtracting means emits the light-emitting element data with the writing power.
At the time of reading from the output of the control circuit of the read power control system.
It is designed to be deducted at a fixed amount. This allows the book
According to the optical disc device of the invention, the non-use characteristic of the light emitting element
Excluding the parts corresponding to the
Target value can be set by
Setting accuracy per bit when using D / A converter
And improve the accuracy of APC
be able to.   That is, in the level control circuit of the present invention,
It is processed as follows. I. Executing the power control means via the switch means
The read level target value in a state where the operation is qualitatively disabled.
Sequentially updating the target value of the setting means and responding to the update;
Monitor the output light of the light emitting element and determine the read level target value
You. B. With the power control means substantially inactive,
For the determined read level target value, the light emitting element is turned on.
Energized and the write current applying means and the write superimposition
With the current subtracting means operating, the write current superimposed
The target value of the target value setting means is sequentially updated and responded to the update.
The output light of the light emitting element is monitored and the write current superimposed target value is calculated.
Is determined, and the determined write current superimposed target value is
Set in the flow superimposition target setting means. C. The write current superimposition target value setting means and the write weight
The tatami current subtractor is deactivated and the read level determined
The output of the balance circuit is balanced for the target value.
Thus, the read level target value setting means is operated. D. In the state where the power control means is operated,
The write current application means and the write superimposed current subtraction means.
Operate to allow the light emitting element to reach the read level
The target value of the write current subtraction target value setting means is sequentially
Update, the write current difference
And determining the target value, and setting the target value to the write current subtraction target value.
Set in the setting means.   As described above, the read level target value
Read level target value setting means for setting the write current superimposed target value
Of the setting means and the write current superimposition subtraction target value setting means.
Set the benchmark. 〔Example〕   One embodiment of the present invention will be described with reference to FIG.   The laser control circuit shown in FIG.
Analog switches 13, 15 of laser control circuit, PD current adjustment
Analog switches 53 and 55, PD current / power
A pressure converter 12 'is provided. Also, PD current / voltage converter
A resistor R5 is connected between 12 'and the read power level detector 3'.
The balance circuit 50 including the amplifiers 51 to 61 and the amplifier 51 is provided.
A / D converter 16 is not directly connected to PD, PD current / voltage
It is connected to the output of the converter 12 '. Also light power
Transistor TR7 of level current subtraction circuit 10 is also directly connected to PD
It is not connected and is connected to the input terminal of the amplifier 31. D / A
Converter 4 is a non-inverting input of amplifier 31 via resistor R62.
Connected to the output terminal, the amplifier 5 via the resistor R60
Connected to 1 inverted input terminal. Resistors R62 and R63
Same resistance value.   In FIG. 4, when a positive / negative bipolar power supply is used,
In this embodiment, a unipolar power supply is used.
Have been. The power supply voltage is, for example, V_cc= 12V, V_AA= 10V, V_CT
= 5V, V_DD= 5V, V_EE= 0V. V_CTIs the contact in FIG.
Corresponds to the ground level. Resistor network 5 due to use of unipolar power supply
9, resistor net 57 resistor R63, R64 and resistor net 50 resistor R5
9 is added. Also, since a unipolar power supply was used, the level
The internal circuit of the shift unit 11 'is different from that of FIG.
Since the principle is the same, the description is omitted.   The rest is the same as the circuit of FIG.   Hereinafter, the operation of the control circuit shown in FIG.
This will be described with reference to FIG. Step 100 (S100)   The MPU 21 turns on the analog switch 53. This
The capacitor C1 connected in parallel with the amplifier 31 is bypassed.
And the amplifier 31 becomes a voltage follower. Sand
That is, the voltage applied to the non-inverting input terminal (+) of the amplifier 31
Is then applied to the transistor TR1 via the amplifier 31.
Will be able to Step 101 (S101)   The MPU 21 turns off the analog switch 55. This
The output of the D / A converter 4 passes through a resistor R62 of a resistor network 57.
Then, it is applied to the non-inverting input terminal of the amplifier 31. Step 102 (S102)   Initialize the read output data of D / A converter 4 to 0
You. Step 103 (S103)   Analog based on read output data by D / A converter 4
The output voltage is applied to the non-inverting input terminal of the amplifier 31. A
Amp 31 is applied because it is in a voltage follower state
The analog voltage is 0V in the initial state, and the transistor TR1
Applied to the base. Therefore, from D / A converter 4
Transistor TR1 is driven by the analog output voltage of
LD is the power level light amount corresponding to the analog output voltage
Emits light. Step 104 (S104)   The output light of the LD is detected by the PD, and this detection value is used for A / D conversion.
The data is converted into a digital quantity by the data 16 and given to the MPU 21. Step 105, 106 (S105, S106)   The MPU21 converts the detected value of the A / D converted PD to the read power level.
Detects whether or not it has arrived. PD detected value is read power
If the level has not been reached, the read data of the D / A
Then, the process returns to step 103. Below, PD
Step S1 until the detected value reaches the read power level
03 to S106 are repeated.   The above operations are the same as the operations in steps S002 to S006 described above.
It is. That is, this determines the read power level.
Is determined. Step 110 (S110)   When the detected value of PD reaches the read power level, MPU2
1 indicates that write data W / RD = ON,
The gate gate W / RG = ON output is applied and the level shifter
11 ', the write power level current adjuster 6
The transistor TR2 and the write power level setting unit 10
Turn on transistor TR7. This causes the LD to transition
Can emit light up to the write power level via the star TR2
State. Step 111 (S111)   MPU 21 initializes write data of D / A converter 7
You. Step 112 (S112)   Based on write output data via D / A converter 7
Analog voltage is applied to transistor TR of power level setting section 8
4. Apply to base. Applied to the base of transistor TR4
The current corresponding to the applied voltage is LD, transistor TR2,
Flows into the transistor TR4 and resistor R5, and the LD
Flashes above Step 113 (S113)   The output light of the LD is detected by the PD, and this detection value is used for A / D conversion.
The data is converted into a digital quantity by the data 16 and given to the MPU 21. However, LA
The transistor TR7 of the power level current subtractor 10 is P
Not directly connected to D, A / D converter 16 also
D / A conversion of PD reading that is not performed. Step 114, 115 (S114, S115)   MPU21 detected value of PD reached write power level
Is detected. PD detected value becomes write power level
If not reached, the write data of the D / A converter 7 is added by one.
Then, the process returns to step S112. Below the detected value of PD is written
Repeat steps S112 to S115 until power level is reached
I do.   The operations in steps S110 to S115 are also performed in step S0 described above.
Substantially the same as 10 to S015. Therefore, this
Power level can be determined and the write power level at that time can be determined.
The bell is output from the D / A converter 7. Step 120 (S120)   MPU21 is write gate W / RG = OFF, write data W / RD
= Off, write power via level shifter 11 '
Level current adjuster 6 and write power level current subtraction
The light circuit of the circuit 10 is deactivated. As a result, LD
No light is emitted at the power level, and the D / A converter
Target power given to amplifier 31 from data 4
It emits light at the level. Steps 121 to 123 (S121 to S123)   MPU21 reads the output value of D / A converter 4
And the D / A converter 4 is driven.
Also, turn on the analog switch 55 and non-invert the amplifier 31.
Input terminal to V_CTDrop to level. Analog switch 5 on the other hand
Turn 3 off. This connects in parallel with the amplifier 31
The activated capacitor C1 becomes operable. As a result, APC times
The road becomes active.   Here, the PD current adjustment unit 1 that constitutes the APC circuit
2 ', balance circuit 50 and read power level detector 3'
Will be described.   The target value of the read power level from the D / A converter 4
Applied to the inverting input terminal of the amplifier 51 via the resistor R60.
You. On the other hand, the PD detection value is balanced through the PD current adjustment unit 12 '.
Applied to path 50. The balance circuit 50 is from the D / A converter 4.
If the target value of PD and the detection value of PD match, the output is set to zero
Work like that. Resistors R59 and R60 have the same resistance value. flat
The output from the balance circuit 50 is supplied to the read power level detector 3 '.
Is applied to the read power level current adjuster 5 via the
Is automatically adjusted at the target read power. Step 124 (S124)   The MPU 21 returns to the write system via the level shift unit 11 '.
Energize roads 6,10. This allows the LD to go to steps 112-115
Light determined by the D / A converter 7
Light is emitted for the target value of the power level.   Here, unlike the previous embodiment, the APC is functioning.
Please note that. That is, the APC circuit has read power
Since APC control is performed at the level, LD
When light is emitted at the level, it is reduced to the read power level.
Control. As a result, light mode
However, the output level of the LD decreases. Steps 130-134 (S130-S134)   The MPU 21 reads from the PD and writes
The amount by which the power level is superimposed is subtracted from the D / A converter 14.
Update sequentially via Insert the superimposed write power level
The A / D converter 16 converts the reading of the drawn PD to A / D.
Repeat until the value returns to the write power level. Rye
By detecting the return to the power level
The current subtraction target value in the D / A converter 14 is determined.
You. Step 135 (S135)   The write circuits 6, 10 are turned off via the level shift unit 11 '.
Energize.   As described above, the read power level target value and the write power
-Level target value and current subtraction target value are determined.
Values of D / A converter 4, D / A converter 7, D / A converter
Output from the data 14. All D / A converters are VEE to VAA
Output up to.   The above embodiment is referred to in the characteristic diagram of FIG.
Compare with the example.   In the embodiment of FIG. 4, the D / A converter 4
Power level detector 3 in the state of voltage follower
Used and combined with read power level current adjuster 5
Current I corresponding to the read power_RDFlow. D / A Con
The output level of the inverter is V3 of the resistor R3 and transistor TR1._beWhen
And V_{D / A}= V_be+ I_RD× Determined as R3.   If the maximum output of the D / A converter is ± 5V, I_RDIndividual differences
R3 is determined to a value operable at + 5V, including.   On the other hand, the D / A converter 4 detects the PD detection value in the APC mode.
Is the same voltage as the read power
Output to non-transfer input. PD is not only read power,
It is also necessary to detect
If the power ratio is 1:10, the input range of the A / D converter
If the power is detected at -5V when
In this embodiment, the output power is -0.5V. Therefore, D / A
1/10 setting of converter output.
Inferior to   As shown in FIG. 2, in this embodiment, a single
Source D / A converter can be used and its range is 0-10V.
If the input of the balance circuit (50) is only the read power level
The D / A converter operation
Can be used. That is, the resistors R59 and R60 are the same
So, by selecting resistors R58 and R61 arbitrarily, almost 0-10V
Can be used as a range of read power,
A significant improvement in the degree can be expected.   In the above embodiment, a laser die is used as a light emitting element.
A photodiode, using a photodiode as a photodetector,
If these are configured as an integrated LD unit
I mentioned the case. However other light emitting devices and light
The same applies to the detection element. 〔The invention's effect〕   As described above, according to the present invention, the light emitting element is not used.
Range that should be truly controlled excluding the part corresponding to the
It is possible to set a target value for
When using a D / A converter with a
Constant accuracy is improved, and the accuracy of APC is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the principle of a level control circuit according to the present invention, FIG. 2 is a level control circuit according to an embodiment of the present invention with respect to FIG. 1, and FIG. Flowchart for explaining the operation of the control circuit FIG. 4 is a conventional level control circuit, FIG. 5 is a characteristic diagram of the laser diode in FIGS. 2 and 4, and FIG. 6 is a diagram for explaining the monitor voltage in FIG. FIG. 7 is a flowchart for explaining the operation of the level control circuit of FIG. (Explanation of reference numerals) 1... LD unit 3 ′ Read power level detector 4 D / A converter 5 Read power level current adjuster 6 Write power level current adjuster 7 … D / A converter, 8… Write power level setting section, 10… Write power level current subtraction section, 11… Level shift section, 12… PD current / voltage conversion section, 14… D / A converter , 16 A / D converter, 17 Write current level current subtraction setting unit, 21 MPU, 50 balancing unit, 53, 55 switch.

Continuation of front page       (56) References JP-A-60-103529 (JP, A)                 JP-A-61-192042 (JP, A)                 JP-A-62-285231 (JP, A)                 Showa 60-35554 (JP, U)                 60-52020 (JP, U)

Claims (1)

(57) [Claims] A laser diode that emits light in response to writing data to the optical disk or reading data from the optical disk, a photodiode that outputs a value corresponding to the emission power of the laser diode, and a detecting unit that detects an output value of the photodiode A target value control unit that controls a target value so that the detection unit detects a predetermined detection value corresponding to a predetermined power level; and from the target value control unit, so that the laser diode emits read power. Read power current supply means for obtaining a read power level target value and supplying a current of a target read power; andbalance means for operating so that the read power level target value and the output value of the photodiode are in a balanced state. The read power current supply means with a target read power based on the output of the balancing means. Switch means for activating / deactivating APC control for operating the laser diode. In a state where the APC control is deactivated by the switch means, the laser diode performs read power emission, and the detection means determines a predetermined power. Determining a read power level target value of the target value control means until a predetermined detection value corresponding to the power level is detected; and, after the read power level target value is determined, controlling the APC by the switch means. In an operating state, when the laser diode emits read power, the balancing means works so that the determined read power level target value and the output value of the photodiode are in a balanced state, and based on the output of the balancing means, The read power current supply means is operated at a target read power, and the laser Ord level control method of the optical disc apparatus being characterized in that so as to control the, and adjusting to emit light at a predetermined read power level. 2. The level control method of the optical disk device further includes obtaining a write power level target value from the target value control means, and controlling a read power level current from the read power current supply means so as to perform write power emission to the laser diode. Supplying a write power level current by the write power current supply means in a superimposed manner on the output power of the photodiode at the time of light power emission and the output of the photodiode at the time of read power emission in the APC control operation state. The deduction amount corresponding to the difference from the value is
2. The level control method for an optical disk device according to claim 1, further comprising: a step of subtracting from an output value of the photodiode at the time of light power emission by a subtracting unit. 3. The level control method of the optical disc device further comprises: causing the laser diode to emit light power when the subtraction means is not operating; and setting the target until the detection means detects a predetermined detection value corresponding to the write power level. Adjusting the write power level target value of the value control means,
3. The level control method for an optical disk device according to claim 2, further comprising: determining the write power level target value. 4. The level control method of the optical disc apparatus further comprises: causing the laser diode to emit write power at the time of operation of the subtraction means, and the subtraction amount until the detection means detects a predetermined detection value corresponding to the read power level. 4. The level control method for an optical disk device according to claim 2, further comprising the step of: adjusting the target value of (i) and determining the target value of the subtraction amount.