JPH0664745B2 - Focus actuator heating prevention device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to recording or reproducing information in an optical device such as an optical disk device for optically recording and / or reproducing information on / from an information recording medium. For preventing overheating of a focus drive actuator (focus actuator) of the optical pickup of the above.

2. Description of the Related Art In an optical disc device, immediately after the device is activated, a focus actuator for focus drive of the optical pickup is energized, and the optical pickup is once lowered,
When the optical pickup is raised and the just focus point is detected during the ascent, the focus servo state is entered.

If the detection of the just focus point fails, the same focus servo pull-in operation is repeated a predetermined number of times.
If the just focus point cannot be detected even after repeating a predetermined number of times, an error is displayed and the drive of the focus actuator is stopped.

However, in the conventional optical disk device, due to a circuit failure of the focus servo system or a focus lock attempting to coincide with the acrylic surface instead of the recording surface of the optical disk, a large drive current is applied to the focus actuator. No special protective measures have been taken against drive abnormalities that continuously flow.

As a result, when such a drive abnormality occurs, the focus actuator overheats, causing the focus actuator to burn out due to the heat generation, or the alteration or deformation of the optical disk approaching the focus actuator may cause the recorded information. However, there is a problem that the data is destroyed or information cannot be recorded on the optical disc.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a focus actuator overheat prevention device for preventing overheating of a focus actuator in an optical disk device or a similar device.

Means for Solving the Problems In order to solve the above problems, the present invention provides a sufficient time from the start of the pull-in operation of the focus servo of the optical pickup by the actuator so that the focus of the optical pickup is aligned with the recording surface of the optical disc. After that, check whether the drive current value of the focus actuator exceeds a predetermined value,
When the drive current value exceeds the predetermined value, it is determined that the focus actuator is abnormally driven, and the drive of the focus actuator is stopped.

That is, the focus actuator overheat prevention device of the present invention responds to the start signal of the focus servo pull-in operation by the focus servo system of the optical pickup and generates a timing signal after a fixed time, as shown in the claim correspondence diagram of FIG. The first means and the timing signal and a signal proportional to the drive current value of the focus actuator of the optical pickup are input, and an abnormality is detected when the drive current value of the focus actuator is larger than a predetermined value at the time of generation of the timing signal. It is characterized by having a second means for generating a signal and a third means for stopping the drive of the focus actuator by the focus servo system in response to the abnormality detection signal.

Effect of the Invention With the above-described configuration, the present invention detects the abnormality and stops the drive of the focus actuator when the drive current continuously exceeding the predetermined value such that the focus actuator is overheated flows to the focus actuator. It is possible to prevent overheating.

Therefore, it is possible to avoid burnout of the focus actuator and deterioration or deformation of the information recording medium caused by overheating of the focus actuator.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a schematic structure of a focus actuator overheat prevention device according to an embodiment of the present invention, which is applied to an optical disk device.

In FIG. 2, reference numeral 1 is an optical pickup, and 2 is a focus actuator for focus driving of the optical pickup 1. This focus actuator 2
Is composed of, for example, a voice coil motor.

Reference numeral 3 is a focus servo system of the optical pickup 1. The focus servo system 3 detects a focus error from the output signal of the photodetector in the optical pickup 1 and controls the drive of the focus actuator 2 so as to keep the focus error to a minimum, thereby making the optical pickup 1 an optical disc. Focusing is performed on the recording layer (which is rotated above the optical pickup 1, but is omitted in the drawing). Since the focus servo system 3 has a general configuration, a detailed description of its configuration will be omitted.

Reference numeral 4 denotes a microprocessor, which includes the focus servo system 3, a tracking servo system (not shown),
It controls the operation of other parts of the optical disk device. Reference numeral 5 denotes a memory for storing a program executed by the microprocessor 4, data, etc., which is connected to the bus 6 of the microprocessor 4. Reference numeral 7 is an input / output port for interfacing the bus 6 with the focus servo system 3 and the like.

The configuration described so far is a general configuration as an optical disc device. Next, the configuration of the focus actuator overheat prevention device will be described.

Reference numeral 8 is a mono-multivibrator, which corresponds to the first means in FIG. This mono multivibrator 8
Triggered by the falling edge of the signal UPON output from the focus servo system 3, it resets when a certain metastable time T has elapsed and generates a timing signal TS. In addition, the focus servo system 3 is included in the mono multivibrator 8.
The signal FOCUSON output from is applied as a reset signal.

Reference numeral 9 is a drive abnormality detection circuit as the second means shown in FIG. The drive abnormality detection circuit 9 detects the voltage of the drive line 10 of the focus actuator 2 (voltage proportional to the drive current) and the threshold voltages TH + and TH corresponding to the predetermined value.
Analog comparator 11 and
12, D flip-flops 13 and 14 that latch the output signals of the analog comparators 11 and 12 at the rising time of the timing signal TS, and an OR gate 15 that ORs the output signals of these D flip-flops 13 and 14. ing.

The output signal FDBCK of the OR gate 15 is input to the input / output port 7 as an abnormality detection signal. I / O port 7 has
A flag is provided to display the state of this abnormality detection signal FDBCK.

Further, the D flip-flops 13 and 14 are reset by the FOCUSON signal.

In this embodiment, the third means shown in FIG. 1 is realized by the function of the microprocessor 4 under program control.

Here, the pull-in operation of the focus servo by the focus servo system 3 will be described. FIG. 3 shows an example of temporal changes in the drive current of the focus actuator 2, the signal UPON and the signal FOCUSON when the pull-in operation of the focus servo is normally performed.

When the power of the optical disk device is turned on, the microprocessor 4 activates the focus servo system 3 (at the time). The focus servo system 3 causes the focus actuator 2 to flow a drive current having a value and polarity as shown in FIG. 3 to temporarily lower the optical pickup 1 and then raise the optical pickup 1 from the point of
The substantial focus servo pull-in operation is started.
At this point, the signal UPON is set to L level.

Then, when the focus servo system 3 detects the just focus point while the optical pickup 1 is moving upward (at the time shown in FIG. 3), it shifts to the focus servo state, and at the same time sets the signal FOCUSON indicating the start of the focus servo to the L level. .

Note that FIG. 3 shows a case where the focus servo pull-in succeeds in the first pull-in operation. When the pull-in fails, the drive current of the focus actuator 2 is controlled as shown by the broken line in FIG. 3, and the same pull-in operation is repeated up to three times, for example. When the just focus point cannot be detected in the final pull-in operation, an error occurs and the focus servo system 3 stops the operation.

Next, the operation of the focus actuator overheat prevention device of this embodiment will be described. FIG. 4 is a flowchart of program control related to this operation. Also, in FIG.
FIG. 6 is a waveform diagram showing an example of a temporal change of a focus actuator drive current and a signal related to the focus actuator overheat prevention device when a drive abnormality of the focus actuator 2 occurs.

When the device is powered on, the microprocessor 44
A designated value of the number of trials for recovering the drive abnormality is set in the counter N on the memory 5 (step 1). Next, after resetting the focus servo system 3 (step 2), the focus servo system 3 is activated (step 3), and then a certain period of time is waited (step 4).

When the focus servo system 3 is activated (at the time point shown in FIG. 5), the focus servo pull-in operation is started. The mono-multi vibrator 8 is set by being triggered by the signal UPON at the substantial start of the pulling operation.

The metastable time T of the mono multivibrator 8 is (2T
It is set to be more than 3 times longer than a + Tb). Ta and T
b is the time shown in FIG. 3, respectively.

Here, when the drive current of the focus actuator 2 is fixed to a current value exceeding a predetermined value on the plus side (current value corresponding to the threshold voltage TH +) as shown in FIG. 5 due to a circuit failure of the focus servo system 3 ( The pulling of the focus servo fails), and the voltage of the drive line 10 continues to exceed the positive threshold voltage TH +, so that the output signal of the positive analog comparator 11 is held at the H level. Further, since the focus servo pull-in fails, the signal FOCUSON signal is held at the H level.

Thus, the monostable multivibrator 8 is reset and the timing signal TS is generated (changed to the H level) at the time when the metastable time T has elapsed from the time. The rising of the timing signal TS triggers the D flip-flops 13 and 14, and the plus side D flip-flop 13
Output signal becomes H level. As a result, the abnormality detection signal
FDBCK becomes H level, and the corresponding flag (specific bit of register) in the input / output port 7 is turned on.

As shown by the broken line in FIG. 5, when an abnormality occurs such that the focus actuator drive current is fixed at a current value exceeding a predetermined negative value (current value corresponding to the threshold voltage TH−), the drive line Since the voltage of 10 exceeds the threshold voltage TH-, the output signal of the comparator 12 is fixed to the H level as shown by the broken line. As a result, the output signal of the D flip-flop 14 changes to the H level at the time of,
The abnormality detection signal FDBCK becomes H level. Therefore, as in the case of drive abnormality in which the drive current is fixed to the positive side,
The abnormality detection flag is turned on.

Now, the microprocessor 4 executes step 5 after the point of and checks whether the flag of the abnormality detection signal FDBCK is in the ON state. When the above-mentioned drive abnormality occurs, the flag is in the ON state, so the microprocessor 4 decrements the value of the counter N (step 6), and the counter N
The value 0 is determined to be zero (step 7).

When the value of the counter N is larger than zero, the process returns to step 2 to try to recover the drive abnormality, the focus servo system 3 is reset to stop the drive of the focus actuator 2, and then the focus servo system 3 is restarted. (Step 3).

In this way, if the drive abnormality is not recovered and the optical focus servo pull-in is not successful even if the focus servo pull-in is attempted the number of times specified in the counter N, the value of the counter N is determined to be zero in step 7. . In this case, the microprocessor 4 resets the focus servo system 4 (step 8), further displays an error on a display device (not shown) (step 9), and ends the control. That is, it ends abnormally.

In this way, when an unrecoverable drive abnormality occurs, the focus servo system 3 is reset and the drive of the focus actuator 2 is stopped, so overheating of the focus actuator 2 is prevented.

On the other hand, if the drive abnormality does not occur at all or the drive abnormality is recovered and the focus servo pull-in succeeds,
Before the point of time, the signal FOCUSON falls and the mono-multivibrator 8 and the D flip-flops 13 and 14 are reset, so that the abnormality detection signal FDBCK becomes L level, and the corresponding flag becomes off state. In this case, the flag is determined to be in the off state in step 5, and the control ends normally.

Up to this point, the case where the drive abnormality occurs during the first ascending or descending stage of the optical pickup in the pulling operation has been described, but the same control is performed when the drive abnormality occurs during the second or third stage of raising or lowering the optical pickup. Is done.

In this embodiment, when the drive abnormality of the focus actuator 2 occurs, the focus servo system 3 is restarted a predetermined number of times to try to recover the drive abnormality. However, when the drive abnormality is detected, the drive of the focus actuator 2 may be immediately stopped and the apparatus may be abnormally terminated.

Further, in this embodiment, the third means shown in FIG. 1 is realized by program control, but it may be realized by hardware. The third means may simply be a means for transmitting the abnormality detection signal to the focus servo system 3 as a reset signal.

Further, in the present embodiment, the signal UPON output from the focus servo system 3 is used as the start signal of the focus servo pull-in operation, but a start signal or the like given to the focus servo system 3 may be used.

The first means and the second means shown in FIG. 1 are not limited to the circuit shown in this embodiment, and may be modified as appropriate.

Further, although the present embodiment is applied to the optical disk device, the present invention can be similarly applied to other similar devices.

EFFECTS OF THE INVENTION As is apparent from the above description, the present invention includes an optical disc, an optical pickup for recording / reproducing information on / from the optical disc, and a drive unit for bringing the optical pickup into contact with / separating from the optical disc. The driving means measures a sufficient time for making the focal point of the optical pickup coincide with the recording surface of the optical disc, a detecting means for detecting a driving current of the driving means after the time is finished, and the driving current is By providing the control means for stopping the drive of the drive means when the value exceeds the predetermined value, it is possible to prevent the focus actuator from being overheated. Therefore, the focus actuator is burned or the information recording medium is deteriorated due to the overheating of the focus actuator. Or deformation,
It is possible to avoid destruction of recorded information and the like, and it is possible to improve reliability and safety of an optical disk device and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing the claims of the present invention, FIG. 2 is a block diagram showing a focus actuator overheat prevention device according to an embodiment of the present invention applied to an optical disk device, and FIG. 3 is a waveform for explaining a focus servo pull-in operation. 4 and 5 are flowcharts of program control relating to the operation of the focus actuator overheat prevention device, and FIG. 5 is a waveform diagram for explaining the operation of the focus actuator overheat prevention device. 1 ... Optical pickup, 2 ... Focus actuator, 3 ... Focus servo system, 4 ... Microprocessor, 8 ... Mono multivibrator, 9 ... Drive abnormality detection circuit, 10 ... Drive line, 11, 12 ... … Analog comparator, 13,14 …… D flip-flop, 15 …… OR gate.

Claims (1)

[Claims] 1. An optical disc, an optical pickup for recording / reproducing information on / from the optical disc, driving means for bringing the optical pickup into and out of contact with the optical disc, and the driving means for focusing the optical pickup on the optical pickup. Clocking means for clocking a sufficient time to match the recording surface of the optical disc, detecting means for detecting the drive current of the drive means after the timing is finished, and drive of the drive means when the drive current exceeds a predetermined value. A focus actuator overheat prevention device comprising a control means for stopping.