JP4014463B2 - Optical disc device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc apparatus that irradiates a disc as a recording medium with a laser beam from an optical head, records a signal on the disc, or reproduces a signal from the disc.
[0002]
[Prior art]
In a laser pulse magnetic field modulation type optical disk apparatus using a magneto-optical disk as a recording medium, as shown in FIG. 12, the magnet is vertically moved with a magneto-optical disk (1) rotated by a spindle motor (2) interposed therebetween. A head (3) and an optical head (5) are provided, a magnetic head drive circuit (4) is connected to the magnetic head (3), and a laser drive circuit (6) is connected to the optical head (5). .
A digital signal processor (17) is connected to the magnetic head driving circuit (4) and the laser driving circuit (6), and the signal recording / reproducing operation is controlled by the digital signal processor (17). Further, the output signal of the optical head (5) is supplied to the digital signal processor (17), subjected to processing such as amplification, detection of the reproduction signal, error correction, and the like, and then outputted to the subsequent circuit as reproduction data.
[0003]
At the time of signal reproduction, a laser beam is emitted from a semiconductor laser (not shown) built in the optical head (5) to the magneto-optical disk (1), and the reflected light is detected by the optical head (5). Recording data is read out. Further, at the time of signal recording, the magneto-optical disk (1) is irradiated with laser light from the semiconductor laser of the optical head (5), and the magneto-optical disk (1) is locally heated, and at the same time, the heating unit is magnetically Recording data is written by applying a magnetic field from the head (3).
In such an optical disc device, there is an optimum value for the laser beam power during recording (recording laser power) and the laser beam power during reproduction (reproducing laser power), and the laser power is optimum. When deviating from the value, the bit error rate of the reproduction signal increases, and when the bit error rate exceeds a certain specified value, normal recording / reproduction operation becomes difficult.
[0004]
Therefore, at the time of starting the system, for the test track provided in advance on the magneto-optical disk, the signal is reproduced while gradually changing the reproduction laser power and the error rate is calculated, or the recording laser power is gradually changed. However, a method has been proposed in which a signal is recorded and an error rate of the reproduction signal is calculated to search for an optimum reproduction laser power and recording laser power that minimizes the error rate.
At the time of signal recording and reproduction, the temperature of the magneto-optical disk gradually increases due to the irradiation of the laser beam, and the optimum laser power changes accordingly. As shown in FIG. A method is proposed in which a temperature sensor (16) is installed opposite to 1), the temperature of the disk is monitored by the temperature sensor (16), and the laser power is optimized whenever a predetermined temperature change occurs. (See JP-A-7-182721 [G11B11 / 10]).
[0005]
For example, as shown in FIG. 13, the temperature sensor (16) is formed by connecting a thermistor and a fixed resistor in series with each other. A 2.6V power source is connected to the end point on the thermistor side, and the fixed resistor side is also connected. The sensor output Vout is taken out from the connection point between the thermistor and the fixed resistor.
[0006]
[Problems to be solved by the invention]
By the way, the operating temperature range of the semiconductor laser built in the optical head (5) is set to, for example, −10 ° C. to + 70 ° C. If the semiconductor laser is used at a high temperature exceeding this temperature range, the service life is shortened. It will cause damage.
Therefore, there is a method to attach a temperature sensor to the optical head, monitor the temperature of the semiconductor laser (laser temperature), stop the laser light irradiation and set the sleep mode when the temperature exceeds the limit value. It is done.
However, the installation of the laser temperature sensor requires that the digital signal processor be additionally equipped with an input port for processing the sensor output, an A / D conversion circuit, and a control circuit, which complicates the configuration of the digital signal processor. Problem arises.
[0007]
Further, in the conventional temperature sensor (16), the relationship between the temperature and the output voltage is nonlinear as shown in FIG. 14, and the resolution in the high temperature range of 60 ° C. to 80 ° C. is as low as 8.65 mV / ° C. Even if the temperature sensor (16) is attached to the optical head, the laser temperature cannot be monitored with sufficient accuracy, and the laser may be damaged in some cases.
On the other hand, a dedicated IC with a built-in thermistor is installed, and a temperature measuring device having a linear output characteristic as shown in FIG. 15 and having a resolution of 10 mV / ° C. in a high temperature range of 60 ° C. to 80 ° C. Although it is possible to measure the laser temperature with high accuracy by attaching a temperature measuring device to the optical head, since such a temperature measuring device is expensive, there is a problem of increasing the cost of the disk device.
[0008]
An object of the present invention is to simultaneously realize laser power control based on a disk temperature and laser protection by monitoring the laser temperature with a simple configuration in an optical disk device.
[0009]
[Means for solving the problems]
An optical disk device according to the present invention includes a first temperature sensor installed opposite to a disk, a second temperature sensor attached to the optical head, a control circuit for controlling the power of laser light, and a first temperature. A change-over switch that selectively supplies one of the output of the sensor and the output of the second temperature sensor to the control circuit is provided.
The control circuit includes:
Temperature state determination means for determining whether the temperature of the disk or the optical head is a low temperature state lower than the reference temperature or a high temperature state higher than the reference temperature based on the output of any one of the temperature sensors;
A switching control means for switching the changeover switch to the first temperature sensor side in the low temperature state, and a changeover switch to the second temperature sensor side in the high temperature state;
Laser power optimization means for optimizing the laser power based on the output of one of the temperature sensors in a low temperature state and a high temperature state;
In a high temperature state, it is determined whether or not the temperature of the optical head has exceeded the dangerous temperature based on the output of the second temperature sensor, and the laser light irradiation is stopped while the temperature of the optical head exceeds the dangerous temperature. Laser stop means
And has.
[0010]
In the optical disc apparatus of the present invention, laser light is emitted from the optical head to the disc when the power is turned on, and recording / reproduction becomes possible. However, the temperature of the disc and the optical head rises with time. Will do. In the low temperature state, the changeover switch is switched to the first temperature sensor side, the disk temperature is measured by the first temperature sensor, and the laser power is optimized based on the measured value.
Thereafter, when the temperature of the optical head rises and reaches a high temperature state, the changeover switch is switched to the second temperature sensor side, and the temperature of the optical head is measured by the second temperature sensor. The laser power is optimized based on the output of the second temperature sensor on the assumption that the temperature of the optical head is correlated with the temperature of the disk.
When the temperature of the optical head further rises and exceeds a dangerous temperature at which there is a risk of laser damage, the laser light irradiation is stopped and the laser is protected.
[0011]
In the optical disc device of the present invention, since either one of the first temperature sensor and the second temperature sensor is selectively connected to the control circuit, the control circuit processes the sensor output. There is no need to provide a processing circuit such as an AD conversion circuit for each sensor individually. As a result, the configuration of the control circuit becomes simpler than when both sensors are connected to the control circuit at the same time.
[0012]
In a specific configuration, the laser power optimization means detects the temperature of the disk based on the output of the first temperature sensor in the low temperature state, optimizes the laser power based on the detected temperature, and the second temperature sensor in the high temperature state. The temperature of the disk is estimated based on the output of, and the laser power is optimized based on the estimated temperature.
According to this specific configuration, optimization of the laser power based on the disk temperature is executed not only in a low temperature state but also in a high temperature state.
[0013]
In a specific configuration, the laser power optimizing means converts a first temperature conversion table for converting the output of the first temperature sensor into the temperature of the disk, and converts the output of the second temperature sensor into the temperature of the optical head. A second temperature conversion table and table switching means for switching between both temperature conversion tables are provided.
In the specific configuration, the temperature of the disk is derived from the first temperature conversion table in the low temperature state, and the temperature of the optical head is derived from the second temperature conversion table in the high temperature state.
[0014]
Another optical disk device according to the present invention includes a first temperature sensor installed opposite to the disk, a second temperature sensor attached to the optical head, a control circuit for controlling the power of the laser beam, A comparator for comparing the output of the two temperature sensor with a predetermined reference value is provided.
The control circuit includes:
Laser power optimizing means for optimizing the laser power based on the output of the first temperature sensor;
Laser stop means for judging whether the temperature of the optical head has exceeded the dangerous temperature based on the output of the comparator, and for stopping the laser light irradiation during the period when the temperature of the optical head exceeds the dangerous temperature
And has.
[0015]
In the optical disk device of the present invention, recording / reproduction is performed while the laser power is optimized based on the output of the first temperature sensor in both the low temperature state and the high temperature state, while the second temperature sensor The output is constantly monitored by the comparator, and when the temperature of the optical head exceeds the dangerous temperature, the irradiation of the laser beam is stopped and the optical head is protected.
Here, the control circuit only needs to monitor the output (high or low) of the comparator, and it is not necessary to provide an AD conversion circuit or the like for processing the output of the second temperature sensor.
[0016]
In a specific configuration, the control circuit further comprises temperature estimating means for estimating the temperature of the optical head based on the output of the first temperature sensor, and the laser stop means is configured to detect when the estimated temperature of the optical head falls below a predetermined temperature. Then, the laser beam irradiation is resumed.
As a result, the control circuit detects the time when the temperature of the optical head has decreased to the normal temperature based on the output of the first temperature sensor without using the output of the second temperature sensor, and resumes the irradiation of the laser light. I can do it.
[0017]
In addition, another optical disk device according to the present invention includes a temperature sensor attached to the optical head and a control circuit for controlling the power of the laser beam, and the temperature sensor is supplied with a sensitivity band switching signal. Thus, it is possible to switch between a low temperature operation mode having high sensitivity in a low temperature region and a high temperature operation mode having high sensitivity in a high temperature region.
The control circuit includes:
A temperature state determination means for determining whether the temperature of the optical head is a low temperature state lower than a reference temperature or a high temperature state higher than the reference temperature based on the output of the temperature sensor;
Switching control means for switching the temperature sensor to the high temperature operation mode in the high temperature state, while switching the temperature sensor to the low temperature operation mode in the low temperature state,
Laser power optimization means for optimizing the laser power based on the output of the temperature sensor in a low temperature state and a high temperature state;
At high temperature, based on the output of the temperature sensor, determine whether the temperature of the optical head has exceeded the critical temperature, and stop the laser light irradiation while the temperature of the optical head exceeds the critical temperature means
And has.
[0018]
In the optical disc apparatus of the present invention, in the low temperature state, the operation mode of the temperature sensor is switched to the low temperature operation mode, the disc temperature is measured by the temperature sensor, and the laser power is optimized based on the measured value. Is done.
Thereafter, when the temperature of the optical head rises and reaches a high temperature state, the operation mode of the temperature sensor is switched to the high temperature operation mode, and the temperature of the optical head is measured by the temperature sensor. The laser power is optimized based on the output of the temperature sensor, assuming that the temperature of the optical head is correlated with the temperature of the disk.
Further, when the temperature of the optical head rises and exceeds a dangerous temperature at which there is a risk of laser damage, the laser light irradiation is stopped and the laser is protected.
[0019]
In the optical disk device of the present invention, a configuration is adopted in which a single temperature sensor is connected to the control circuit and the sensitivity band is switched on the temperature sensor side. A processing circuit may be provided. As a result, the configuration of the control circuit becomes simpler than when two sensors are connected to the control circuit at the same time.
[0020]
In a specific configuration, the laser power optimization unit estimates the disk temperature based on the output of the temperature sensor, and optimizes the laser power based on the estimated temperature.
According to this specific configuration, the laser power is optimized based on the disk temperature in both the low temperature state and the high temperature state.
[0021]
In a more specific configuration, the laser power optimizing means outputs a first temperature conversion table for converting the temperature sensor output in the low temperature operation mode into the temperature of the optical head, and the temperature sensor output in the high temperature operation mode. A second temperature conversion table for converting to the temperature of the optical head and table switching means for switching between both temperature conversion tables are provided.
In the specific configuration, the temperature of the optical head is derived from the first temperature conversion table in the low temperature state, and the temperature of the optical head is derived from the second temperature conversion table in the high temperature state.
[0022]
The temperature sensor attached to the optical head is constructed by connecting a thermistor and a fixed resistor in series with each other. The temperature sensor is installed in the laser mounting part, and the first power source is connected to the end point on the thermistor side and fixed. A second power source is connected to the end point on the resistance side, and the sensor output is taken out from the connection point between the thermistor and the fixed resistance.
In the sensor output, the relationship between temperature and output voltage is almost linear, and still high resolution can be obtained.
[0023]
【The invention's effect】
According to the optical disk apparatus of the present invention, it is possible to simultaneously realize laser power control based on the disk temperature and laser protection by monitoring the laser temperature by a control circuit having a simple configuration.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention applied to a laser pulse magnetic field modulation type optical disc apparatus will be described in detail below with reference to the drawings.
[0025]
First embodiment
In the optical disk apparatus of this embodiment, as shown in FIG. 1, a magnetic head (3) and an optical head (5) are vertically arranged with a magneto-optical disk (1) rotated by a spindle motor (2) interposed therebetween. The magnetic head drive circuit (4) is connected to the magnetic head (3), and the laser drive circuit (6) is connected to the optical head (5).
A digital signal processor (7) is connected to the magnetic head driving circuit (4) and the laser driving circuit (6), and signal recording / reproducing operations are controlled by the digital signal processor (7). Further, the output signal of the optical head (5) is supplied to the digital signal processor (7), subjected to processing such as amplification, detection of the reproduction signal, error correction, etc., and then outputted to the subsequent circuit as reproduction data.
[0026]
A disk temperature sensor (8) for measuring the temperature of the magneto-optical disk (1) is installed opposite to the magneto-optical disk (1), and is built in the optical head (5). A laser temperature sensor (9) for measuring the temperature of the laser is attached.
The output terminal of the disk temperature sensor (8) and the output terminal of the laser temperature sensor (9) are connected to two input terminals of the changeover switch (10), respectively. The output terminal of the changeover switch (10) is a digital signal processor. Connected to (7). The changeover of the changeover switch (10) is controlled by a changeover control signal output from the control output port (11) of the digital signal processor (7).
[0027]
As the disk temperature sensor (8), a temperature measuring device is adopted in which a linear output characteristic as shown in FIG. 15 is realized by a dedicated IC with a built-in thermistor.
On the other hand, as shown in FIG. 2, the laser temperature sensor (9) is configured by connecting a 10 kΩ thermistor and a 1.8 kΩ fixed resistor in series with each other, and a +6 V power source is connected to the end point on the thermistor side. At the same time, a −2 V power source is connected to the end point on the fixed resistance side, and the output voltage Vout is taken out from the connection point between the thermistor and the fixed resistance. In the laser temperature sensor (9), as shown in FIG. 3, the relationship between temperature and output voltage (output characteristics) is linear in the temperature range of 50 ° C. to 85 ° C., and 57 in the range of 60 ° C. to 80 ° C. A high resolution of .65 mV / ° C. can be obtained. This output characteristic is superior to the output characteristic shown in FIG. 14 and the output characteristic shown in FIG.
[0028]
The digital signal processor (7) includes a table for converting the output voltage of the disk temperature sensor into temperature based on the output characteristics shown in FIG. 15, and the output of the laser temperature sensor based on the output characteristics shown in FIG. A table for converting voltage into temperature is registered in advance.
The digital signal processor (7) switches both tables depending on which sensor is in use, and converts the sensor output voltage into temperature.
[0029]
In the optical disk device, in a low temperature state where the disk temperature is lower than a predetermined reference temperature (for example, 50 ° C.), the changeover switch (10) is switched to the disk temperature sensor (8) side, and the disk temperature sensor (8 ), The disk temperature is measured, and the laser power is optimized based on the measured value.
Thereafter, when the disk temperature reaches a high temperature state exceeding a predetermined reference temperature (for example, 50 ° C.), the changeover switch (10) is switched to the laser temperature sensor (9) side, and the laser temperature is detected by the laser temperature sensor (9). Measured. Then, on the assumption that a substantially constant temperature difference (for example, 10 ° C.) is maintained between the laser temperature and the disk temperature, the disk temperature is estimated from the measured value of the laser temperature, and the laser power is based on the estimated temperature. Is optimized.
[0030]
FIG. 4 shows a control procedure related to temperature management at the time of recording / reproducing in the optical disc apparatus of the present embodiment.
First, in step S1, it is determined whether or not a magneto-optical disk is mounted. If it is determined yes, the power is turned on in step S2. Next, in step S3, the optimum read power and write power at the current temperature are determined by test read / write, and then the recording / reproducing mode is set in step S4.
[0031]
Subsequently, in step S5, it is determined whether or not a power-off operation has been performed. If NO is determined, the process proceeds to step S7, and a predetermined temperature change (for example, a disk temperature) is performed based on the output of the disk temperature sensor. 5) is determined. If it is determined NO, the process returns to step S4 to enter the recording / playback mode, and the determination in step S5 is repeated.
Thereafter, when a predetermined temperature change occurs in the disk temperature and it is determined as YES in step S7, the process proceeds to step S8, and whether the disk temperature has exceeded a predetermined value (for example, 50 ° C.). Judge whether.
[0032]
When it is determined NO in step S8, the process proceeds to step S9, and simple test read / write is executed to obtain the optimum read power value and write power value again. In step S10, the read power and write are determined. After changing the power to the optimum value, the process returns to step S4 to enter the recording / reproducing mode, and the determination in step S5 is repeated.
Thereafter, if the laser temperature further rises for some reason and exceeds the predetermined temperature, it is determined as YES in step S8, and after performing a temperature management switching procedure described later in step S20, the process proceeds to step S9.
[0033]
Thereafter, when the power-off operation is performed and it is determined as YES in step S5, the process proceeds to step S6 to determine whether the power-on operation is performed. If it is determined NO, the determination in step S6 is repeated and the apparatus waits for a power-on operation. Thereafter, when a power-on operation is performed and it is determined as YES in step S6, the process returns to step S2, the power is turned on, and the recording / reproducing mode is entered.
[0034]
FIG. 5 shows the temperature management switching procedure in step S20.
First, in step S21, a switch switching signal for switching the changeover switch (10) from the disk temperature sensor (8) side to the laser temperature sensor (9) side is output. Thereby, the changeover switch (10) is switched to the laser temperature sensor (9) side. Thereafter, in step S22, the table for converting the output voltage of the disk temperature sensor (8) into temperature is switched to the table for converting the output voltage of the laser temperature sensor (9) into temperature.
[0035]
Next, in step S23, the laser temperature is derived by converting the output voltage of the laser temperature sensor into a temperature, and it is determined whether or not the laser temperature is higher than the dangerous temperature. If the determination is yes, the process proceeds to step S24 to display that the laser temperature has exceeded the dangerous temperature (high temperature display), and stop the laser beam irradiation to set the sleep mode.
Subsequently, in step S25, it is determined whether or not the laser temperature has decreased to a predetermined value (for example, 50 ° C.) or less. If it is determined as YES, the high temperature display is stopped and the sleep mode is canceled in step S26. In step S27, a switch switching signal for switching the changeover switch (10) from the laser temperature sensor (9) side to the disk temperature sensor (8) side is output. As a result, the changeover switch (10) is switched to the disk temperature sensor (8) side. Thereafter, in step S28, the table for converting the output voltage of the laser temperature sensor (9) into a temperature is switched to the table for converting the output voltage of the disk temperature sensor (8) into a temperature, and the procedure is completed. To do.
On the other hand, if the laser temperature is below the critical temperature and it is determined NO in step S23, the procedure is terminated.
[0036]
In the optical disk device of the present embodiment, since either one of the disk temperature sensor (8) and the laser temperature sensor (9) is selectively connected to the digital signal processor (7), the configuration is adopted. The digital signal processor (7) does not need to include a processing circuit such as an AD conversion circuit that should process the sensor output for each sensor. As a result, the configuration of the digital signal processor (7) becomes simpler than when both sensors are connected to the digital signal processor at the same time.
Further, the laser temperature sensor (9) is a simple one comprising a thermistor and a fixed resistor as shown in FIG. 2, and realizes high performance without using a dedicated IC with a built-in thermistor, thereby increasing the cost of the apparatus. High-precision laser temperature management is possible without incurring.
[0037]
Second embodiment
In the optical disk apparatus of this embodiment, as shown in FIG. 6, a disk temperature sensor (8) is installed facing the magneto-optical disk (1) and an optical head (as shown in FIG. 6). A laser temperature sensor (9) is attached to 5), and the output of the disk temperature sensor (8) is input to the digital signal processor (7). In contrast, the output terminal of the laser temperature sensor (9) is connected to one input terminal of the comparator (12), and the output terminal of the comparator (12) is connected to the control input port (13) of the digital signal processor (7). It is connected to the. A reference voltage corresponding to the output voltage of the laser temperature sensor (9) when the laser of the optical head (5) reaches a dangerous temperature is input to the other input terminal of the comparator (12).
[0038]
In the optical disk device, recording / reproduction is performed while the laser power is optimized based on the output of the disk temperature sensor (8) regardless of whether the disk temperature is low or high. At the same time, the output of the laser temperature sensor (9) is constantly monitored by the comparator (12), and when the laser temperature exceeds the dangerous temperature, the output of the comparator (12) switches from low to high (or from high to low). Accordingly, the laser beam irradiation is stopped and the sleep mode is set.
Therefore, the digital signal processor (7) only needs to monitor the output (high or low) of the comparator (12), and no equipment such as an AD conversion circuit for processing the output of the laser temperature sensor (9) is required. .
[0039]
FIG. 7 shows a control procedure related to temperature management at the time of recording / reproduction in the optical disc apparatus of the present embodiment.
First, in step S31, it is determined whether or not a magneto-optical disk is mounted. If it is determined yes, the power is turned on in step S32. Next, in step S33, the optimum read power and write power at the current temperature are determined by test read / write, and then the recording / reproducing mode is set in step S34.
[0040]
Subsequently, in step S35, it is determined whether or not a power-off operation has been performed. If NO is determined, the process proceeds to step S37, and a predetermined temperature change (for example, disk temperature) is performed based on the output of the disk temperature sensor. 5) is determined. If it is determined NO, the process returns to step S34 to enter the recording / playback mode, and the determination in step S35 is repeated.
Thereafter, when a predetermined temperature change occurs in the disk temperature and it is determined YES in step S37, the process proceeds to step S38, and whether or not a temperature increase exceeding a predetermined value (for example, 50 ° C.) has occurred in the disk temperature. If YES is determined here, the process proceeds to step S50, and laser temperature management described later is executed.
[0041]
Next, simple test read / write is executed in step S39, and the optimum read power value and write power value are obtained again. In step S40, the read power and write power are changed to optimum values, and the process returns to step S34. The recording / reproducing mode is set, and the determination in step S35 is repeated.
Thereafter, when a power-off operation is performed and it is determined as YES in step S35, the process proceeds to step S36 to determine whether or not a power-on operation is performed. If it is determined NO, the determination in step S36 is repeated and the process waits for a power-on operation. Thereafter, when a power-on operation is performed and it is determined as YES in step S36, the process returns to step S32 to turn on the power and then shift to the recording / reproducing mode.
[0042]
FIG. 8 shows the laser temperature management procedure in step S50.
First, in step S41, it is determined whether or not the output of the comparator has been switched from low to high (or from high to low). If it is determined yes, the process proceeds to step S42 to indicate that the laser temperature has exceeded the dangerous temperature. Is displayed (high temperature display), and the laser beam irradiation is stopped to set the sleep mode.
Thereafter, in step S43, on the premise that a substantially constant temperature difference (for example, 10 ° C.) is maintained between the laser temperature and the disk temperature, the laser temperature is estimated from the measured value of the disk temperature. It is determined whether or not the temperature has decreased to a predetermined value (for example, 60 ° C.) or less. If the determination is YES, the high temperature display is stopped and the sleep mode is canceled in step S44, and the procedure is terminated.
[0043]
In the optical disk apparatus of this embodiment, the digital signal processor (7) only needs to monitor the output (high or low) of the comparator (12) with respect to the laser temperature, and processes the output of the laser temperature sensor (9). Therefore, it is not necessary to provide an AD converter circuit or the like for the purpose of reducing the circuit scale and cost.
[0044]
Third embodiment
In the optical disk apparatus of this embodiment, as shown in FIG. 9, a laser temperature sensor (14) is attached to the optical head (5), and its output is supplied to the digital signal processor (7). A disk temperature sensor for measuring the temperature of the magneto-optical disk (1) is omitted.
As shown in FIG. 10, the laser temperature sensor (14) is configured by connecting a 10 kΩ thermistor and a 1.8 kΩ fixed resistor in series with each other, and a +6 V power source is connected to the end point on the thermistor side and fixed. A changeover switch (15) is connected to the end of the resistance side, a + 0.5V power supply is connected to one input terminal of the changeover switch (15), a -2V power supply is connected to the other input terminal, and the thermistor The output voltage Vout is taken out from the connection point of the fixed resistor. A switch switching signal for switching the selector switch (15) is supplied from the control output port (11) of the digital signal processor (7) as shown in FIG.
[0045]
When the changeover switch (15) is switched to the 0.5V side, the output characteristic A shown in FIG. 11 is realized, and when the changeover switch (15) is switched to the −2V side, the output characteristic B shown in FIG. 11 is realized. become. In the output characteristic A, the sensitivity is obtained mainly in the low temperature range of −20 ° C. to 50 ° C. On the other hand, in the output characteristic B, sensitivity is obtained in a high temperature range of 50 ° C. to 80 ° C., the output characteristic is linear, and a high resolution of 57.65 mV / ° C. is obtained.
[0046]
The digital signal processor (7) has a table for converting the output voltage of the laser temperature sensor into a temperature based on the output characteristic A shown in FIG. 11 and the output voltage of the laser temperature sensor based on the output characteristic B. A table for converting to temperature is registered in advance.
The digital signal processor (7) switches both tables depending on whether the laser temperature is in a high temperature state or a low temperature state, and converts the sensor output into temperature.
[0047]
In the optical disk device, in a low temperature state where the laser temperature is lower than a predetermined reference temperature (for example, 50 ° C.), the changeover switch (15) is switched to the 0.5 V side, and the laser temperature sensor (14) The temperature is measured, the disk temperature is estimated based on the measured value, and the laser power is optimized based on the estimated disk temperature.
Thereafter, when the temperature in the output characteristic A reaches 50 ° C., the changeover switch (15) is switched to the −2V side, the output characteristic B is set, the laser temperature is measured by the laser temperature sensor (14), and the measured value Is used to estimate the disk temperature, and the laser power is optimized based on the estimated temperature.
[0048]
The control procedure for temperature management during recording / reproduction in the optical disc apparatus of this embodiment is basically the same as that of the first embodiment shown in FIG. 4, but in step S8, the changeover switch (15) is turned on. In the state of switching to the 0.5 V side, it is determined whether or not a temperature rise exceeding a predetermined reference temperature (for example, 50 ° C.) has occurred in the laser temperature based on the output of the laser temperature sensor (14). Further, the disk temperature is estimated from the laser temperature measured by the laser temperature sensor (14), and the laser power is optimized based on the estimated disk temperature.
Thereafter, when a temperature rise exceeding a predetermined value (for example, 50 ° C.) occurs in the laser temperature and it is determined YES in step S8, the process proceeds to step S20, where the laser temperature is a dangerous temperature at which laser damage may occur. It is determined whether or not (for example, 70 ° C.) or higher.
[0049]
If the laser temperature exceeds the dangerous temperature for some reason, the temperature management switching procedure in step S20 is executed. The procedure is basically the same as the procedure of the first embodiment shown in FIG. 5, but in step S21, a switch switching signal for switching the changeover switch (15) from the 0.5V side to the -2V side is output. . Thereafter, in step S22, the table based on the output characteristic A is switched to the table based on the output characteristic B.
In step S27, a switch switching signal for switching the changeover switch (15) from the -2V side to the 0.5V side is output. Thereafter, in step S28, the table based on the output characteristic B is switched to the table based on the output characteristic A, and the procedure is terminated.
[0050]
In the optical disk device of this embodiment, only the output signal of the laser temperature sensor (14) is supplied to the digital signal processor (7), and the sensitivity band is switched on the laser temperature sensor (14) side. The digital signal processor (7) may comprise a single processing circuit for the laser temperature sensor (14). As a result, the configuration of the digital signal processor (7) becomes simpler than when two sensors are simultaneously connected to the digital signal processor.
[0051]
In addition, the laser temperature sensor (14) has a simple configuration in which a changeover switch is connected to a sensor section consisting of a thermistor and a fixed resistor as shown in FIG. 10, and by switching the changeover switch, both a wide sensitivity band and high resolution can be obtained. Since this is realized, highly accurate temperature management is possible without increasing the cost of the apparatus.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus according to a first embodiment.
FIG. 2 is a diagram showing a specific configuration of a laser temperature sensor provided in the optical disk device.
FIG. 3 is a graph showing output characteristics of the laser temperature sensor.
FIG. 4 is a flowchart showing a temperature management control procedure in the optical disc apparatus.
FIG. 5 is a flowchart showing a temperature management switching procedure.
FIG. 6 is a block diagram illustrating a configuration of an optical disc device according to a second embodiment.
FIG. 7 is a flowchart showing a temperature management control procedure in the optical disc device.
FIG. 8 is a flowchart showing a laser temperature management procedure.
FIG. 9 is a block diagram showing a configuration of an optical disc apparatus according to a third embodiment.
FIG. 10 is a diagram showing a specific configuration of a laser temperature sensor provided in the optical disk device.
FIG. 11 is a diagram showing output characteristics of the laser temperature sensor.
FIG. 12 is a block diagram showing a configuration of a conventional optical disk device.
FIG. 13 is a diagram showing a specific configuration of a temperature sensor provided in the optical disk device.
FIG. 14 is a diagram showing output characteristics of the temperature sensor.
FIG. 15 is a diagram illustrating output characteristics of a thermistor built-in dedicated IC.
[Explanation of symbols]
(1) Magneto-optical disk
(3) Magnetic head
(5) Optical head
(7) Digital signal processor
(8) Disc temperature sensor
(9) Laser temperature sensor
(10) Changeover switch
(11) Control output port
(12) Comparator
(13) Control input port
(14) Laser temperature sensor
(15) Changeover switch

Claims (7)

In an optical disk apparatus that irradiates a disk with laser light from an optical head, records a signal on the disk, or reproduces a signal from the disk, a first temperature sensor disposed opposite to the disk, and the optical head A second temperature sensor attached to the control circuit, a control circuit for controlling the power of the laser beam, and the output of the first temperature sensor and the output of the second temperature sensor are selectively sent to the control circuit. A switching switch to supply, the control circuit,
Temperature state determination means for determining whether the temperature of the disk or the optical head is a low temperature state lower than the reference temperature or a high temperature state higher than the reference temperature based on the output of any one of the temperature sensors;
A switching control means for switching the changeover switch to the first temperature sensor side in the low temperature state, and a changeover switch to the second temperature sensor side in the high temperature state;
Laser power optimization means for optimizing the laser power based on the output of one of the temperature sensors in a low temperature state and a high temperature state;
In a high temperature state, it is determined whether or not the temperature of the optical head has exceeded the dangerous temperature based on the output of the second temperature sensor, and the laser light irradiation is stopped while the temperature of the optical head exceeds the dangerous temperature. An optical disc device comprising laser stop means. The laser power optimization means detects the temperature of the disk based on the output of the first temperature sensor in the low temperature state, optimizes the laser power based on the detected temperature, and based on the output of the second temperature sensor in the high temperature state. 2. The optical disk device according to claim 1, wherein the temperature of the disk is estimated, and the laser power is optimized based on the estimated temperature. The laser power optimization means includes a first temperature conversion table for converting the output of the first temperature sensor into the temperature of the disk, a second temperature conversion table for converting the output of the second temperature sensor into the temperature of the optical head, The optical disk apparatus according to claim 2, further comprising table switching means for switching both temperature conversion tables. In an optical disk device that irradiates a disk with laser light from an optical head and records signals on the disk or reproduces signals from the disk, a temperature sensor attached to the optical head and control of the power of the laser light And a control circuit that performs
The temperature sensor is capable of switching between a low temperature operation mode having high sensitivity in a low temperature region and a high temperature operation mode having high sensitivity in a high temperature region upon receipt of a sensitivity band switching signal,
The control circuit, based on the output of the temperature sensor, temperature state determination means for determining whether the temperature of the optical head is a low temperature state lower than the reference temperature or a high temperature state higher than the reference temperature;
In the low temperature state, the temperature sensor is switched to the low temperature operation mode, while in the high temperature state, the switching control means for switching the temperature sensor to the high temperature operation mode and the laser power based on the output of the temperature sensor in the low temperature state and the high temperature state. Based on the laser power optimization means to optimize and the output of the temperature sensor at high temperature, determine whether the temperature of the optical head has exceeded the dangerous temperature,
An optical disk device comprising: laser stop means for stopping the irradiation of laser light during a period when the temperature of the optical head exceeds the dangerous temperature. 5. The optical disk device according to claim 4, wherein the laser power optimizing means estimates the disk temperature based on the output of the temperature sensor and optimizes the laser power based on the estimated temperature. The laser power optimizing means converts the output of the temperature sensor in the low temperature operation mode into the temperature of the optical head, and converts the output of the temperature sensor in the high temperature operation mode into the temperature of the optical head. 6. The optical disk device according to claim 5, further comprising a second temperature conversion table and table switching means for switching between both temperature conversion tables. The temperature sensor attached to the optical head is configured by connecting a thermistor and a fixed resistor in series with each other. A first power source is connected to an end point on the thermistor side, and a second power source is connected to an end point on the fixed resistor side. 7. The optical disc apparatus according to claim 1, wherein the sensor output is taken out from a connection point between the thermistor and the fixed resistor.

Images