JPH04345930A - Laser emission control method for optical disk storage devices - Google Patents

Abstract

PURPOSE:To always confirm the accurate emitted light quantity by comparing the detected quantity of light emitted from a light emitting element with the control target value given from a storage means and controlling the light emitting element to correct the deviation of the emitted light quantity and at the same time producing a timing pulse according to the change of the read/write state to update the target value at each time and synchronously with the timing pulse. CONSTITUTION:A low read state and a high write state are designated by a target value storage means 20 and a processor 50 respectively and then given to a pulse generating circuit 60. The circuit 60 produces the timing pulses in accordance and synchronously with the changes of those states and gives these pulses to an A/C converter 12 of an emitted light quantity detecting means 10, the processor 50, and a detected value storage means 70. The means 70 converts the detected value of the means 10 into the digital value by the converter 12 in response to the timing pulse and reads and stores the digital value at each time. Thus the change of the emitted light quantity is known at each time. The processor 50 reads the storage contents of the means 70 and updates the target value stored in the means 20 to always set the emitted light quantity at a reference target level even if the light emitting characteristic of a light emitting element 4 is changed by the influence of temperatures, etc.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the amount of light emitted from a light emitting element of a laser beam used for reading and writing data in an optical disk storage device using a magneto-optical or phase change optical disk as a data recording medium.

0002

BACKGROUND OF THE INVENTION As is well known, optical disk storage devices use laser light that can be easily focused into a small spot with high light intensity to write data to and read data from a recording medium. Laser diodes are mainly used as light-emitting elements. Since this laser light is used to heat the recording medium when writing data or during erasing prior to that, a much larger amount of light is required than when reading data to detect light reflected from the recording medium. Therefore, the amount of laser light emitted from the light emitting element is controlled depending on the state of reading and writing data in the optical disk storage device. Conventionally, this control has typically been performed by switching the target value of the amount of light emitted according to the data read/write state. Hereinafter, an overview of the conventional laser emission amount control method will be explained with reference to FIGS. 4 and 5.

The optical disc 1 shown in the upper part of FIG. 4 is driven at a constant speed by a spindle motor 2, and a laser beam L from a light emitting element 4 is directed from a head 3 onto a recording medium in tracks on its surface by a lens 3a. The light is focused. A photodetector element 5 such as a photodiode for monitoring the light emission state of the light emitting element 4 is usually incorporated into the head 3 as shown in the figure, and the light emission amount detection circuit 10 receives the detection signal from the photodetector element 5 through its amplifier 11. and outputs the detected value v of the amount of light emitted. The target value storage means 20 stores target values for the amount of light emitted, and is stored in the built-in processor 5 in the optical disk storage device.
It is equipped with registers 21 and 22 that store a first target value V1 at the time of reading given from 0 and a second target value V2 at the time of writing as digital values, respectively. The analog value is output via the DA converter 23.

The light emission amount control circuit 30 compares the above-mentioned detected value v of the light emission amount with the control target value and issues a control signal CS to the drive circuit 40 of the light emitting element 4 to correct the deviation. For example, in a PID control circuit represented by a deviation amplifier 31 that receives the detected value v and the analog value v1 or v2 shown in FIG. be. The element drive circuit 40, which receives the control signal CS, outputs a drive current from its output amplifier 41 to the light emitting element 4 to specify a corresponding amount of light emission.

[0005] In the conventional laser emission amount control system configured as described above, when the power is turned on to the optical disk storage device and the processor 50 starts up or starts up, the target of, for example, an 8-bit configuration stored in the ROM, for example, is sent from the processor 50. The values V1 and V2 are sequentially sent together with the latch command LS to the target value storage means 20 and stored in the registers 21 and 22, respectively. Thereafter, the digital target value V1 is stored from the target value storage means 20 in accordance with the state of the read/write command RW.
or analog target value v1 or v2 corresponding to V2
are sequentially switched and applied to the light emission amount control circuit 30 as shown in FIG.

The light emission amount control circuit 30 that receives this controls the light emission amount of the light emitting element 4 via the drive circuit 40 using the control signal CS so as to eliminate the deviation from the detected value v received from the light emission amount detection circuit 10. do. Note that if the optical disk 1 is of a magneto-optical recording type, for example, erasing is required before writing data, so the second target value V2 or the first
In reality, it is common to use two types of values as the target value V1, but since this would be unnecessarily complicated, the above explanation is based on each single target value.

[0007]

[Problems to be Solved by the Invention] Even with the conventional laser emission amount control method shown in FIG. Although accurate control is possible, there is a problem in that the control accuracy decreases if the light emitting characteristics of the light emitting element 4 change due to the influence of temperature or the like.

For example, in a laser diode normally used as the light emitting element 4, the emission threshold value with respect to its drive current is considerably affected by temperature, and the gradient of the amount of light emission with respect to the difference between the drive current and the threshold value is also a function of temperature. . Therefore,
If the temperature at the time of setting the target values V1 and V2 described above differs from the temperature during actual operation, the light emitting element The actual light emission amount of No. 4 deviates from the set value. To solve this problem, it is possible to correct the target value setting according to the temperature, but the temperature dependence of the threshold and slope of the luminescence characteristics is very complex and varies considerably depending on the light emitting element, so such temperature correction is difficult. There are many problems with practicality.

Furthermore, if the operating temperature deviates from the time when the target value was set, the control of the light emission amount control circuit 30 will no longer be performed in accordance with the light emission characteristics of the light emitting element 4. There is a problem in that the responsiveness of light emission control is degraded, resulting in an insufficient amount of writing light or an excessive amount of reading light immediately after switching, as shown in FIG.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to make it possible to accurately control the amount of light emitted even if the light emitting characteristics of a laser light emitting element for reading and writing data in an optical disk storage device changes. .

[0011]

[Means for Solving the Problems] According to the laser light emission amount control system of the present invention, this purpose is to provide a means for detecting the light emission amount of the light emitting element, and a control target value for the light emission amount of the light emitting element for each reading/writing state. a light emission amount control circuit that compares the detected value of the light emission amount with a control target value and issues a control signal to correct a control deviation; and a light emission amount control circuit that receives the control signal and drives the light emitting element with a corresponding amount of light emission. A circuit that generates a timing pulse in synchronization with a change in the read/write state, and a means for storing a detected value of the amount of light emitted in synchronization with the timing pulse are incorporated into an optical disk storage device, and each change in the read/write state is detected. This is achieved by sequentially updating the control target value in the target value storage means based on the stored contents of the detected values in the value storage means and the reference target value.

[0012] Note that the storage contents of the control target value in the target value storage means in the above configuration are updated by storing it in the detected value storage means after a predetermined number of timing pulses are generated from the pulse generation circuit after a change in the read/write state. It is most reliable to update based on a predetermined number of light emission amount detection values and a reference target value, and such updating is performed when the deviation of the light emission amount detection value from the reference target value is larger than the allowable limit. It is reasonable to do this only occasionally. When updating is necessary, it is practical to increase or decrease the stored content of the control target value in the target value storage means by a predetermined unit value depending on the sign or negative of the above-mentioned deviation, and it is usually sufficient from the point of view of control accuracy. It is.

The light emission amount detection means, the light emission amount control means, and the element drive circuit in the above-mentioned configuration of the method of the present invention perform analog operations based on the control target value by the target value storage means to control the control speed for the laser light emission amount. In order to increase the accuracy of updating the control target value, it is advantageous for the detected value storage means and the target value storage means to operate digitally based on timing pulses from a pulse generation circuit.
The combined use of such analog operation and digital operation is particularly desirable in order to advantageously exhibit the high control performance of the system of the present invention.

Furthermore, in order to improve the responsiveness of the light emission amount control after a change in the read/write state, the control target values are stored separately in the target value storage means, one for transient changes in the light emission amount and one for steady state changes. It is particularly advantageous to set these two control target values to be output to the light emission amount control circuit to be switched in the course of successive generation of timing pulses from the pulse generation circuit. Note that the simplest timing for such switching is when a predetermined number of timing pulses are generated.

Furthermore, it is most simple and advantageous for the detected value storage means and the target value storage means constituting the system of the present invention to be constructed by software loaded into the built-in processor of the optical disk storage device. Other aspects that are advantageous in implementing the system of the present invention are as described in the Examples section.

[0016]

[Operation] The method of the present invention sequentially updates the control target value, which is the basis for controlling the amount of light emitted by the laser emitting element, in accordance with the detected value of the amount of emitted light each time the read/write state of the optical disk storage device changes. The influence of changes in the light emitting characteristics of the light emitting elements during operation of the optical disk storage device is automatically compensated for. Therefore, in the method of the present invention, the amount of light emitted by the light emitting element is controlled by the light emitting amount detecting means, the light emitting amount controlling means, and the element driving circuit based on the control target value in the target value storage means, as in the conventional method. In the method of the present invention, the detection value storage means as described in the previous section is provided to store the detection value by the light emission amount detection means, and each time the read/write state changes, the light emission amount detection value stored therein and the light emission amount are stored. By sequentially updating the control target value in the target value storage means based on the reference target value, even if the light emission characteristics of the light emitting element change, the control target value can be replaced with an updated value that conforms to the change. .

However, this is not necessarily sufficient to accurately detect and store the transient state in which the amount of light emission changes after the read/write state is switched, and then update the control target value appropriately. Furthermore, a pulse generation circuit is provided to generate a timing pulse synchronized with changes in the read/write status of the optical disk storage device, and to store the detected value of the amount of light emitted in the detected value storage means in synchronization with this pulse. As a result, the amount of light emission sampled at a constant timing after a change in the read/write state is stored in the detected value storage means, so in the method of the present invention, the control target value is updated based on the content of the light emitting element. The influence of changes in light emission characteristics on the quick response of light emission amount control can be minimized.

[0018]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an optical disk storage device showing an embodiment of the laser emission amount control method of the present invention, FIG. 2 is a waveform diagram of related main signals, and FIG. 3 is a flowchart of related operations, which are explained above. Components corresponding to those in FIG. 4 are given the same reference numerals.

In FIG. 1, an optical disk 1 is rotated by a spindle motor 2, and a laser beam L from a light emitting element 4 is focused from a head 3 onto its surface by a lens 3a.
A photodetecting element 5 for monitoring the amount of light emitted from the light emitting element 4 is incorporated in the , and the detection signal is sent to the amplifier 1 of the light emitting amount detection circuit 10.
1 and output as the detected value v is the same as in the case of FIG.
An AD converter 12 is incorporated in the device to convert the analog value of the light emission amount detection value v into, for example, an 8-bit digital value in synchronization with the timing pulse TP.

Digital first target value V1 and second target value V given by processor 50 to target value storage means 20
The provision of registers 21 and 22 for storing V2, respectively, is the same as in the case of FIG. 4, but in this embodiment, DA converters 23 and 24 are provided corresponding to these registers, respectively. The analog value of the second target value V2 is outputted at all times, and the analog value of the second target value V2 is outputted only when the read/write command RW is in the write specification state, and the sum of both specifies the amount of light emitted when writing data. .

The light emission amount control circuit 30 is configured in accordance with this, and includes an operational amplifier 31 that differentially receives the light emission amount detection value v and the output of the DA converter 24, and an operational amplifier 31 that differentially receives the light emission amount detection value v and the output of the DA converter 24.
This is, for example, a PID-operated analog circuit including an operational amplifier 32 which receives the output of the latter summatively, and the output of the latter is given to the drive circuit 40 of the light emitting element 4 as a control signal CS. Therefore, when reading data, the light emission amount control circuit 30 in this embodiment operates as shown in FIG. 2(c) corresponding to the first target value V1.
When writing the analog target value v1, the control signal CS is constantly output to correct the deviation of the light emission amount detection value v from the analog target value v2 corresponding to the sum of the first target value V1 and the second target value V2. do. Note that when the optical disc 1 is of the magneto-optical recording method, two types of values are actually used for the second target value V2, including one for erasing, as described above, but in order to avoid complexity, a single target value is used here. value.

The element drive circuit 40 receives the control signal CS and applies a drive current to the light emitting element 4 from its output amplifier 41 to specify a corresponding amount of light emission, as in the conventional case.

As described above, an analog automatic control system for controlling the amount of light emitted from the light emitting element 4 based on the control target values V1 and V2 in the target value storage means 20 is constructed. A pulse generating circuit 60 and a detected value storage means 70 are provided to update the control target values V1 and V2 every time the read/write state changes during operation of the apparatus.

The pulse generating circuit 60 is connected to the target value storage means 20.
In this example, as shown in FIG. 2(a), the processor 50 receives a read/write command RW that specifies a read state when it is low and a write state when it is high. The timing pulse TP shown in FIG. Note that this timing pulse T
P may be generated continuously, but in this example,
As shown in (c), eight timing pulses TP are generated within a period T until the change in the detected value v of the light emission amount has almost stopped after the read/write state change.

The detected value storage means 70 stores the detected value v from the light emission amount detecting means 10 in response to the timing pulse TP.
The digital values converted by the AD converter 12 are read and stored each time. As a result, immediately after each read/write state change, the luminescence amount detection value v changes over time as shown in FIG. 2(c) within the period T shown in FIG. 2(b). In this example, eight digital values This detected value storage means 7
Stored within 0. The processor 50 similarly receives timing pulses TP, and immediately after receiving eight timing pulses, reads the stored contents of the detected value storage means 70, and updates the target value in the target value storage means 20 based on it as described later. do. When the reading state changes to the writing state as shown in FIG. 2, the corresponding second target value V2 is mainly updated.

As can be seen from the above explanation, the method of the present invention is advantageous in that the target value storage means 20 and the detected value storage means 70 are incorporated into the optical disc storage device in the form of software loaded in the processor 50. Storage means 20
As the DA converters 23 and 24, those attached to the processor 50 can be used as appropriate.

Now that the explanation of the configuration of the system of the present invention has been completed, its operation will now be explained with reference to the flowchart of FIG. This figure shows the operational steps of the software in the processor 50 built into the optical disk storage device. When the optical disk storage device is started after the power is turned on, that is, when the software of the processor 50 starts up the system, the illustrated flow is started.

The first step S51 is a step only at the time of startup, and the processor 50 sequentially sends the first target value V1 and the second target value V2 together with the latch command LS to the target value storage means 20 and stores them. Target value V at this time
1 and V2, those reference values stored in the ROM of the processor 50 may be used as they are, but the optical disk storage device may be operated after completing the first update based on the detection result of the amount of light emitted by the light emitting element 4. It is desirable to put it in To do this, the processor 50 sends a read/write command RW to the target value storage means 20 and the pulse generation circuit 60, as shown by the broken line in FIG. The digital value of the value v may be read into the processor 50.

The operations from step S52 onwards are constantly repeated during operation of the optical disk storage device. In step S52, the pulse generation circuit 60
This step is a wait step for the timing pulse TP generated from TP, and in response to its arrival, the operation moves to the next step S53, and after adding 1 to the variable n for pulse counting, the step S53 waits for the timing pulse TP.
54, the value of the variable n is compared with a predetermined value m, 8 in this embodiment, and as long as it is smaller than that, the operation is performed in the first step S5.
Return to 1 and repeat the same operation.

When the value of the variable n reaches m, the eight detected values v shown in FIG. Then, the process moves to step S55. This step S5
In step S5, first, the digital values of the eight light emission amount detection values v described above are read from the detection value storage means 70, and then the variable n is reset to 0, and the operation moves to the next step S56.

In this step S56, the previous step S5
The detected value v read in step 5 is compared with the reference target value, and the target value V1 or V2 is determined depending on whether the difference between the two values is greater than or equal to the allowable limit.
It is determined whether updating is necessary or not. If not, the flow returns to the first step S52, and only if necessary, the operation moves to the next step S57. This step S57 is a step of updating the control target values V1 and V2 stored in the target value storage means 20, and some examples of this updating will be explained below.

In the case of a laser diode, the light emission characteristics of the light emitting element 4 are determined approximately by the light emission threshold value with respect to the drive current and the gradient of the light emission amount with respect to the difference between the drive current and the light emission threshold. Since the first target value V1 for the reading state is small and the second target value V2 for the writing state is much larger, the first target value V1
It can be considered that this mainly corresponds to the light emission threshold, and the second target value V2 mainly corresponds to the above-mentioned gradient. Therefore, if the light emission amount detection value v deviates from its reference target value in the reading or writing state, it indicates that the light emission threshold or gradient of the light emission characteristics has changed.
The target value V1 or the second target value V2 may be updated to independently compensate for deviations from the reference target value in the reading or writing state, respectively. However, in reality, these target values V1 and V2 do not correspond purely to the emission threshold value and the gradient, but are somewhat dependent on both, so the software for updating the target values V1 and V2 in step S57 Interdependence is built in.

As can be seen from FIG. 2(c), the temporal change in the detected light emission value v is quite different between the first half and the second half of the period T, and in order to improve the control speed, it is necessary to accelerate the change in the first half. Especially desirable. For this reason, if the period T is set to, for example, a timing pulse TP, the first half T1 and the second half T2 of four pulses each.
In the example of FIG. 2, the second target value V2 is set as a transient target, which is slightly higher than the second target value V2, in order to accelerate the change in the luminescence amount based on the calculation result. Within a short period of time immediately after the value is switched from the reading state to the writing state, e.g. 3 timing pulses TP
It is advantageous to output from the setpoint value storage means 20 only during a period corresponding to .

In this case, the second target value V2 is updated based on the four light emission amount detection values v in the second half T2. Further, the updating of the transient target value is of course performed after the detected value v in the first half T1 is stored in the detected value storage means 70, and the updated transient target value is updated when the next read/write status change occurs in the same direction. used on occasion.

Since the control target value is updated in step S57 every time the read/write state changes, it is not actually necessary to completely compensate for the change in the light emission characteristics of the light emitting element 4 in one update. Even if each update is performed by increasing or decreasing the control target values V1 and V2 by a predetermined unit value, it is often sufficient in terms of control accuracy, and this so-called sequential update method simplifies the software in Figure 3. It is advantageous above. However, in this update method, the second
If the target value V2 becomes too high, there is a problem that a transient overshoot will occur in the light emission amount, so the second It is desirable to increase the target value V2 in order to prevent excessive overshoot.

As described above, after the first target value V1 and the second target value V2 are updated in step S57, the flow of operation returns to the first step S52, and from then on, similar operations are performed for the operation of the optical disk storage device. repeated throughout time. Note that FIG. 2(c) shows that the second
The progress of the light emission amount detection value v after the update time tu when the target value V2 is updated is shown.

As can be seen from the above description, the present invention is not limited to the above-described embodiments, but can be implemented in various forms. In the above, we have shown how to update the control target value by accurately compensating for changes in the light emitting characteristics of the light emitting element in one update, and by updating it little by little each time the read/write status changes. Intermediate methods may be adopted as appropriate. Even when using a transient target value, it is possible to control the amount of light emission in various ways. Further, the method of the present invention can be widely applied not only to ordinary magneto-optical type optical disk storage devices but also to phase change type optical disk storage devices in general.

[0038]

[Effects of the Invention] As described above, the laser light emission amount control method of the present invention includes means for detecting the light emission amount of the laser light emitting element;
means for storing a control target value for the amount of light emitted by the light emitting element for each read/write state; a light emitting amount control circuit that compares the detected amount of emitted light with the control target value and issues a control signal to correct a control deviation; A circuit that receives a control signal and drives the light emitting element with a corresponding amount of light emitted; a circuit that generates a timing pulse in synchronization with a change in read/write status; and a means for storing a detected value of the amount of light emitted in synchronization with the timing pulse. is incorporated into the optical disk storage device, and the control target value in the target value storage means is updated every time the read/write state changes based on the stored contents of the detected value in the detected value storage means and the reference target value. You can get the following effects.

(a) Even if the light emitting characteristics of the light emitting element change due to the influence of temperature or the like during operation of the optical disk storage device, the control target value, which is the basis for controlling the amount of light emitted, will not change due to the change in the read/write state of the optical disk storage device. It is updated according to the light emission amount detection value at each time, and the influence of changes in the light emission characteristics is automatically compensated for, so the light emission amount of the laser beam for data reading and writing is always maintained accurately at the reference target value and optical disc storage is performed. The equipment can be operated in the best possible condition.

(b) Since the detected value of the amount of light emitted is stored in the detected value storage means in accordance with the timing pulse synchronized with the change in the read/write state, transient changes in the amount of light emitted after the change in the read/write state are always recorded. To be able to accurately update a control target value based on detection at a constant timing to compensate for changes in light emission characteristics of a light emitting element, and to minimize deterioration in responsiveness of light emission amount control due to changes in light emission characteristics. Can be done.

(c) Since the light emitting amount control system based on the control target value and the control target value updating system are used together to bring out the respective features, it is possible to accurately compensate for changes in the light emission characteristics of the light emitting element. The amount of light emitted by the light emitting element can be controlled at a very high control speed based on the control target value updated in the above.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a main part of an optical disk storage device showing an embodiment of a laser emission amount control method according to the present invention.

[Fig. 2] The main signals related to the embodiment of Fig. 1 are shown in Fig. 2(a).
It is a waveform diagram shown in - (c).

FIG. 3 is a flowchart of operations associated with the embodiment of FIG. 1;

FIG. 4 is a configuration diagram of an optical disc storage device showing a conventional laser emission amount control method.

FIG. 5 is a waveform diagram of related signals showing the operation of the light emission amount control method of FIG. 4;

[Explanation of symbols]

1 Optical disk 4 Light emitting element 10 Light emission amount detection means 20 Target value storage means 30 Light emission amount control circuit 40 Element drive circuit 50 Processor 60 Pulse generation circuit 70 Detected value storage means CS Control signal L Laser light RW Read/write command TP Timing pulse V1 Control target First target value V2 for reading as a value Second target value v for writing as a control target value Light emission amount detection value

Claims (5)

[Claims] 1. A system for controlling the amount of light emitted from a light emitting element of a laser beam for reading and writing data in an optical disk storage device, comprising: means for detecting the amount of light emitted from the light emitting element; means for storing a control target value; a light emission amount control circuit that compares a detected value of light emission amount with the control target value and issues a control signal to correct a control deviation; a circuit that generates a timing pulse in synchronization with a change in read/write status, and means for storing a detected value of the amount of light emitted in synchronization with the timing pulse. 1. A laser light emission amount control method for an optical disk storage device, characterized in that a control target value in a target value storage means is updated every time a read/write state changes based on stored contents and a reference target value. 2. In the method according to claim 1, the control in the target value storage means is performed based on a predetermined number of detected values stored in the detected value storage means when a predetermined number of timing pulses are generated after a change in the read/write state. A laser emission amount control method for an optical disk storage device, characterized in that a target value is updated. Claim 3: The method according to claim 1 or 2,
When the deviation of the light emission amount detection value from the reference target value is larger than the allowable value, the control target value in the target value storage means is updated by adding or subtracting by a predetermined unit value depending on the sign or the negative of the deviation. Features a laser light emission amount control method for optical disk storage devices. 4. In the system according to claim 1, control target values for transient changes in light emission amount after a change in read/write status and for steady state are stored in the target value storage means, and the control target values are stored in a timing pulse. A laser emission amount control method for an optical disk storage device, characterized in that these control target values are switched accordingly. 5. The method according to claim 1, wherein the detected value storage means and the target value storage means are constituted by software loaded on a processor incorporated in the optical disc storage device. Laser emission control method for the device.