JP2001331960A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device which reduces electric power consumption and can make long-time reproduction in battery driving by reducing the average drive current of a laser diode. SOLUTION: The drive current of the laser diode 3 is formed into pulses by using a clock generating circuit 29, by which the average drive current is lowered. The pulse components in reproducing waveforms are removed by using an envelope detecting circuit 15 or low-pass filters 17 and 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode for emitting laser light to an optical disk in order to detect data recorded by irradiating the optical disk with the laser light and a focus state and a tracking state of the laser light. The present invention relates to an optical disk device having a configuration for reducing the average drive current in the optical disk device.

[0002]

2. Description of the Related Art Conventionally, an optical disk apparatus for reproducing information from an optical disk such as an MD (mini disk) has been known. In this method, a disk is irradiated with laser light from a laser diode, and reflected light of the laser light modulated by data (information signal such as coded sound) recorded on the disk is received by a light receiving element. Thus, the recording data and information on the focus state and tracking state of the laser beam are detected.

[0003] Hereinafter, a conventional optical disk apparatus will be referred to as MD.
A description will be given of an optical disk device for use as an example.

FIG. 7 is a configuration diagram of a conventional optical disk apparatus. An optical pickup 81 is composed of a laser diode 82, a photodiode 83 for signal detection, and a photodiode 84 for monitoring.
2 and the anode of the photodiode 83 for signal detection are grounded, and the cathode of the photodiode 84 for monitoring is connected to the power supply. Laser diode 8
The laser light emitted from 2 is reflected by the disk 85 and received by the photodiode 83. A part of the laser light emitted from the laser diode 82 is received by a monitoring photodiode 84.

[0005] The PNP transistor 86 has an emitter connected to the power supply and a collector connected to the anode of the laser diode 82.

[0006] The first operational amplifier 87 performs current-voltage conversion, and its inverting input terminal is connected to the cathode of the photodiode 83 and its non-inverting input terminal is connected to the terminal 88. Further, the output terminal 89 and the inverting input terminal of the first operational amplifier 87 are connected by a resistor 90.
For example, a DC voltage of １ ／ of the power supply voltage is applied to the terminal 88.

The anode of the photodiode 84 has a resistor 9
1 is grounded. The non-inverting input terminal of the second operational amplifier 92 is connected to the anode of the photodiode 84, and the inverting input terminal is connected to the reference voltage source 93. The output of the second operational amplifier 92 is connected via a resistor 94 to the base of a transistor 86.

[0008] The operation of the conventional optical disk apparatus configured as described above will be described. The laser light emitted from the laser diode 82 irradiates the disk 85, and the reflected light is received by the photodiode 83 for signal detection and converted into a current. Further, the converted current is subjected to current-voltage conversion by the first operational amplifier 87 and the resistor 90 and output to the terminal 89. At this time, since the reflected light is modulated by data recorded on the disk 85, a signal voltage corresponding to the data is output to the terminal 89.

On the other hand, part of the laser light emitted from the laser diode 82 is directly received by the monitoring phototransistor 84 without irradiating the disk 85, so that both ends of the resistor 91 are connected to both ends of the resistor 91. A voltage proportional to the amount of emitted light is output. Since the second operational amplifier 92, the resistor 94, and the transistor 86 are set so that the error between the voltage across the resistor 91 and the reference voltage source 93 becomes zero, negative feedback is applied to the laser diode 82, and the operating current is reduced. It is controlled to a substantially constant value.

[0010]

However, in the above-mentioned conventional configuration, the current value required for driving the laser diode is large, so that the optical disk device driven by a battery such as a portable MD requires a battery. There is a problem that the life is short and the reproduction time that can be satisfied by the user cannot be secured.

The present invention solves the above-mentioned conventional problems, and reduces the average driving current of a laser diode,
It is an object of the present invention to provide an optical disk device that reduces power consumption of the device.

[0012]

In order to achieve the above object, an optical disk apparatus according to the present invention comprises a laser diode for irradiating a disk on which data is recorded with a laser beam for data detection, and a drive current for the laser diode. Pulse driving means for intermittently turning on and off with a clock having a frequency higher than the data, and a light receiving element group for converting reflected light emitted from the laser diode at the data, focus position, and tracking position on the disk into electric signals, respectively. A detection circuit for performing envelope detection of an output signal of the light receiving element group, or a low-pass filter for blocking a clock frequency band of the clock.

According to this configuration, since the drive current of the laser diode is pulsed, the average drive current of the laser diode is reduced, and therefore the power of the optical disk device is reduced.

Also, the optical disk apparatus of the present invention comprises a first light receiving element for converting reflected light irradiated from the laser diode and modulated with data on the disk into an electric signal, and at least a focus position based on the reflected light. A second light receiving element that detects and converts the signal into a focus control signal;
A detection circuit that performs envelope detection from an output signal of the first light receiving element, and passes a frequency band of the focus control signal from an output signal of the second light receiving element and cuts off a clock frequency band of the clock. A low-pass filter.

According to this configuration, the data recorded on the disk can be detected at a high reproduction signal level by using the detection circuit, so that the signal quality is ensured and the focus control signal having a relatively large signal level is used. Can be detected by a low-pass filter having a simpler circuit configuration.

Further, in the optical disk apparatus of the present invention, there is provided a light receiving element for detecting a monitor signal for outputting a monitor signal proportional to the amount of light emitted from the laser diode, and a difference between the level of the monitor signal and a reference signal level indicating a reference amount of light. Amplifier as an error signal, and the laser diode is driven by a current pulsed to a peak value or a pulse width corresponding to the error signal with a clock having a higher frequency than data recorded on the disk. Pulse driving means for performing negative feedback control such that a voltage proportional to the amount of emitted light is substantially equal to the reference voltage.

According to this configuration, the drive current of the laser diode can be easily controlled by the peak value of the pulsed current or the pulse width of the current.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical disk device for explaining a first embodiment of the present invention. In FIG. 1, a disk 1 has data (information signals such as coded audio) recorded in advance. Is what it is.

The optical pickup 2 comprises a laser diode 3, a photodiode for detecting data, a photodiode for detecting a focus control signal 5, a photodiode for detecting a tracking control signal, and a photodiode 7 for monitoring. The anode of the laser diode 3 and the anodes of the photodiode 4 for data detection, the photodiode 5 for focus control signal detection, and the photodiode 6 for tracking control signal detection are grounded. The cathode is connected to a power supply.

The laser beam emitted from the laser diode 3 is reflected by the disk 1 and received by the photodiode 4 for data detection, the photodiode for focus control signal detection, and the photodiode 6 for tracking control signal detection. Is done. In addition, the laser diode 3
A portion of the laser light emitted from the monitor is directly received by the monitoring photodiode 7 without irradiating the disk 1.

The operational amplifiers 8, 9 and 10 perform current-voltage conversion, and their inverting input terminals are a photodiode 4 for detecting data, a photodiode 5 for detecting a focus control signal, and a photodiode 5 for detecting a tracking control signal. The cathode of the photodiode 6 and the non-inverting input terminal are connected to a voltage source 11, respectively. First operational amplifier 8 connected to photodiode 4 for data detection
Of the envelope detection circuit 15 through the resistor 12
, And the inverting input terminal of the second operational amplifier 9 connected to the photodiode 5 for focus control signal detection is connected to the first low-pass filter 17 via the resistor 13 to detect the tracking control signal. The inverting input terminal of the third operational amplifier 10 connected to the photodiode 6 is connected via a resistor 14 to a second low-pass filter 19.
It is connected to the.

The voltage V1 of the voltage source 11 is, for example, a DC voltage which is 1/2 of the power supply voltage. Thus, for example, the product of the current value generated in the photodiode 4 for data detection and the resistor 12 becomes the output voltage of the first operational amplifier 8 with reference to the voltage V1. Also, the output voltages of the second operational amplifier 9 and the third operational amplifier 10 are the same as the output voltage of the first operational amplifier 8, and a detailed description thereof will be omitted.

The envelope detection circuit 15 envelope-detects the peak value of the output signal of the first operational amplifier 8 and outputs it to a terminal 16. The envelope detection circuit 15 can be realized by a known method using, for example, charging and discharging of a capacitor, and thus a detailed description is omitted.

The first low-pass filter 17 passes at least a signal band for focus control from the output signal of the second operational amplifier 9 and outputs it to a terminal 18. The second low-pass filter 19 passes at least a tracking control signal band from the output signal of the third operational amplifier 10 and outputs the signal to the terminal 20. A first low-pass filter 17,
The second low-pass filter 19 can be composed of, for example, a combination of a resistor and a capacitor.

The anode of the monitoring photodiode 7 is grounded via a resistor 21 and connected via a third low-pass filter 22 to an inverting input terminal of an amplifier 23 which is an error amplifier. The non-inverting input terminal of the amplifier 23 is connected to the reference voltage source 24.

The amplifier 23 amplifies the difference between the non-inverting input terminal and the inverting input terminal with high gain, sinks (sinks), and outputs a current. When the non-inverting input terminal has a higher voltage than the inverting input terminal, the sink current increases. When the non-inverting input terminal has a lower voltage than the inverting input terminal, the sink current stops. Note that the resistance value of the resistor 21 and the voltage value of the reference voltage source 24 are set in advance so that the non-inverting input terminal and the inverting input terminal are substantially equal in the normal operation.

In PNP transistors 25 and 26 having a current mirror connection relationship, both emitters are connected to the power supply, and both bases and the collector of the first transistor 26 are connected to each other. The size of the second transistor 25 is set to be larger than that of the transistor 26, and the collector current of the first transistor 26 is amplified so that the second transistor 25
Is output to the collector current of the transistor 25 of FIG. Second
Of the transistor 25 is connected to the anode of the laser diode 3.

Third transistor 2 having the same characteristics as each other
7. Both emitters of the fourth transistor 28 are connected to the amplifier 23
, The collector of the third transistor 27 is connected to the collector of the first transistor 26, and the collector of the fourth transistor 28 is connected to the power supply via the emitter of the first transistor 26. When the base voltage of the third transistor 27 is
When the voltage is equal to or higher than the base voltage, the third transistor 27 is turned on, and otherwise, it is turned off.

The clock generation circuit 29 is connected to the base of the fourth transistor 28 and
8 is turned on and off, and its frequency is set to a frequency sufficiently higher than the frequency band of the data recorded on the disk 1.

The voltage source 30 applies a DC bias voltage to the base of the third transistor 27, and is set to, for example, the midpoint voltage of the output amplitude of the clock generation circuit 29.

The operation of the optical disk apparatus thus configured will be described with reference to the signal waveform diagrams of FIGS. 2A, 2B and 2C for explaining the operation of the optical disk apparatus in the first embodiment. I do.

The waveform a in FIG.
9 is represented by a transition of time, V2 is represented by a transition of time, and an output waveform of the voltage source 30 is represented by a transition of time. FIG. 2 (b) represents a current (Iop) of the laser diode 3 at the same timing as above.
Waveforms b, c, d, and e in FIG. 2C represent the waveforms at the same reference numerals in FIG. 1 at the same timing.

The third transistor 27 and the fourth transistor 28 repeat the ON / OFF operation according to the voltage relationship between the waveform a output from the clock generation circuit 29 and the voltage V2 of the voltage source 30. As a result, FIG.
A current having a waveform Iop shown in (b) flows, and the laser diode 3 is intermittently pulsed.

A part of the laser light emitted from the laser diode 3 is directly received by the monitoring photodiode 7 without irradiating the disk 1, thereby generating a current.
The voltage is further converted by the resistor 21 into a voltage. This voltage is smoothed by the third low-pass filter 22 by removing the pulse component.

The output voltage of the third low-pass filter 22 and the voltage V3 of the voltage source 24 are compared by the amplifier 23. If an error occurs, the output current of the amplifier 23 changes, and the third transistor 27 and the first The current Iop of the laser diode 3 via the transistor 26 and the second transistor 25
To change.

For example, when the amount of light emitted from the laser diode 3 is large, the amount of light received by the monitoring photodiode 7 increases, and the output voltage of the third low-pass filter 22 becomes higher than that of the voltage source 24. Output current decreases. As a result, the current of the laser diode 3 is reduced to suppress the amount of emitted light. If the amount of light emitted from the laser diode 3 is small, the monitoring photodiode 7
And the output voltage of the third low-pass filter 22 becomes lower than that of the voltage source 24, so that the output current of the amplifier 23 increases. As a result, the current of the laser diode 3 is increased to increase the amount of emitted light.

As a result, the current I is adjusted so that the output of the third low-pass filter 22 and the voltage V3 of the voltage source 24 become the same voltage.
The peak value of op is maintained. Note that the second transistor 2
5 is larger than the first transistor 26, the output current of the amplifier 23 is smaller than the current Iop.

On the other hand, another laser beam emitted from the laser diode 3 is incident on the disk 1, and the reflected light from the disk 1 is converted into a photodiode 4 for data detection, a photodiode 5 for focus control signal detection, and a tracking control signal. And is converted into a current. Further, current-voltage conversion is performed by the first to third operational amplifiers 8 to 10 and the resistors 12 to 14, respectively. At this time, since the reflected light is modulated by the data (information signal such as encoded sound) recorded on the disk 1, the output of the first operational amplifier 8 has the waveform b in FIG. A pulse train as shown in FIG. 4 becomes a voltage modulated by data on the disk. The waveform b is peak-detected by the envelope detection circuit 15 and becomes a waveform d, which is output to the terminal 16. Obviously, the waveform d is substantially equivalent to the output waveform at the terminal 89 of the conventional optical disk device shown in FIG.

Since the reflected light for the focus control signal is received by the photodiode 5, if the output waveform of the second operational amplifier 9 is, for example, the waveform c, the output of the first low-pass filter 17 is As shown in the waveform e, the amplitude is reduced according to the pulse width and smoothed. Similarly, the reflected light for the tracking control signal is received by the photodiode 6, and the second low-pass filter 1
The output of No. 9 is smoothed by decreasing the amplitude according to the pulse width.

Here, the operation in the case of intentionally changing the emitted light amount of the laser diode will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 3A shows the voltage source 2
4 shows a temporal transition of the voltage value V3 of FIG. 4, and FIG. 3B shows a temporal transition of the current value Iop of the laser diode 3. When the voltage V3 is changed, as is apparent from the above description, the output voltage of the third low-pass filter 22 becomes
In order to follow V3, the current of the laser diode 3 changes. In other words, the peak value of the current Iop is proportional to the voltage V3.

As described above, according to the first embodiment, the average current consumption can be reduced to about こ と by pulsing the drive current of the laser diode 3, and in the data reproducing circuit system, the envelope detection is performed. The circuit 15 maintains the signal quality by maintaining the amplitude of the reproduced signal as before, and in a focus control system or a tracking control system having a relatively large signal level, low-pass filters 17 and 19 having a simpler circuit configuration are used. By using the device, the device can be optimized.

In the first embodiment, the photodiode for data detection, the photodiode for detecting a focus control signal, and the photodiode 6 for detecting a tracking control signal are each one element for easy understanding. In the example shown in FIG.
In many cases, detection is performed by a combination of photodiodes, and even in such a case, it can be easily realized only by providing a current-voltage conversion circuit and an envelope detection circuit or a low-pass filter by the number of photodiodes.

In the first embodiment, a low-pass filter is used to remove a pulse component of a signal for detecting a tracking control signal. However, a slightly higher signal quality may be required depending on specifications. Therefore, in that case, it is preferable to use an envelope detection circuit instead of the low-pass filter. Alternatively, depending on the pickup, there may be a case where a sufficient detection level cannot be ensured, such as a case where the amount of laser light emitted from the laser diode 3 is low, or the sensitivity of the photodiode is low. It is preferable to secure the signal amplitude by the envelope detection circuit in all cases. Alternatively, in the case of a device in which the detection levels of all signal systems are sufficiently high, the pulse components may be removed using a low-pass filter having a simpler circuit configuration including the data detection system. This case is advantageous in terms of cost. Note that the frequency components of all the photodiodes or the detection circuit itself may be limited to remove the pulse component. in this case,
Since it is not necessary to provide a low-pass filter independently, it is more advantageous in terms of the number of elements or cost.

By the way, even if a low-pass filter is used in place of the envelope detection circuit in all the detection circuit systems including the data detection system, if the drive current of the laser diode 3 is slightly increased, the conventional optical disk can be used. An output level equivalent to that of the device can be secured.

With respect to the compatibility between the low-pass filter and the envelope detection circuit as described above, the clock is set so that the amplitude of the output signal of the low-pass filter and the amplitude of the output signal of the detection circuit are substantially equal. The driving current of the laser diode 3 is set by pulse driving means such as the generation circuit 29.

FIG. 4 is a characteristic diagram showing the amount of emitted light of the laser diode versus the driving current. As a characteristic of the laser diode, when the threshold current (Ith) is exceeded, the amount of emitted light increases sharply. In the conventional optical disk device, assuming that the driving current for obtaining the output light amount LP1 of the target is Iop1, as described in the first embodiment, the detection level is reduced to に よ り by pulse driving the laser diode.

However, by increasing the driving current by, for example, 20% and increasing it to Iop2, it is possible to obtain a light quantity LP2 whose emission light quantity is about twice as large. In other words, it is possible to realize a current reduction of about 40% including the pulsing of the driving current, while ensuring the same reproduction signal quality as in the related art.

FIG. 5 is a block diagram of an optical disk device for explaining a second embodiment of the present invention. Data (information signal such as encoded audio) is recorded on a disk 41 in advance. The optical pickup 42 includes a laser diode 43, a photodiode 44 for detecting data, a photodiode 45 for detecting a focus control signal, a photodiode 46 for detecting a tracking control signal, and a photodiode 47 for monitoring. 1 may be regarded as the same as the optical pickup 2 and its components in FIG.

The operational amplifiers 48, 49, and 50 perform current-voltage conversion, and their inverting input terminals are a photodiode 44 for detecting data, a photodiode 45 for detecting a focus control signal, and a photodiode for detecting a tracking control signal. The cathode of the diode 46 and the non-inverting input terminal are connected to a voltage source 51. Operational amplifiers 48, 49,
The output of 50 and the inverting input terminal are resistors 52, 53, respectively.
It is connected at 54. The voltage V1 of the voltage source 51 is, for example, a DC voltage that is １ ／ of the power supply voltage. Thus, for example, the product of the current value generated in the photodiode 44 for data detection and the resistor 52 becomes the output voltage of the first operational amplifier 48 with reference to the voltage V1. The output voltages of the second operational amplifier 49 and the third operational amplifier 49 provided corresponding to the photodiode 45 for detecting the focus control signal and the photodiode 46 for detecting the tracking control signal are also used for the first operational amplifier 48. Since the output voltage is similar to the output voltage, a detailed description thereof will be omitted.

The first low-pass filter 55 passes at least the frequency band of the data on the disk 41 from the output signal of the first operational amplifier 48 and outputs it to the terminal 56. The second low-pass filter 57 passes at least a signal band for focus control from the output signal of the second operational amplifier 49 and outputs the signal to a terminal 58. The third low-pass filter 59 passes at least a tracking control signal band from the output signal of the third operational amplifier 50 and outputs the signal to the terminal 60. First to third low-pass filters 55,
57 and 59 can be realized by, for example, a combination of a resistor and a capacitor.

The anode of the monitoring photodiode 47 is grounded via a resistor 61 and is connected via a fourth low-pass filter 62 to an operational amplifier 6 serving as an error amplifier.
3 non-inverting input terminals. The inverting input terminal of the operational amplifier 63 is connected to a reference voltage source 64. Note that the resistance value of the resistor 61 and the voltage value of the reference voltage source 64 are set in advance so that the non-inverting input terminal and the inverting input terminal are substantially equal in the normal operation.

In the PNP transistors 65 and 66 having a current mirror connection relationship, both emitters are connected to a power supply, and both bases and the collector of the first transistor 66 are connected to each other. The rated size of the second transistor 65 is set larger than that of the first transistor 66, and the collector current of the first transistor 66 is amplified and output as the collector current of the second transistor 65. The collector of the second transistor 65 is connected to the anode of the laser diode 43.

Further, the emitters of the NPN transistors 67 and 68 having the same characteristics are connected to the current source 69, the collector of the third transistor 67 is connected to the collector of the first transistor 66, and the collector of the fourth transistor 68 is connected to the collector of the fourth transistor 68. Each is connected to a power supply. When the base voltage of the third transistor 67 is higher than the base voltage of the fourth transistor 68, the third transistor 67 is turned on, and the current of the current source 69 is supplied to the first transistor 66. When the base voltage of the third transistor 67 is equal to or lower than the base voltage of the fourth transistor 68, the third transistor 67 is turned off, and the current of the current source 69 becomes the first current.
Is not supplied to the transistor 66.

A pulse width modulation generation circuit (hereinafter abbreviated as a PWM generation circuit) 70 is connected to the base of the fourth transistor 68 to turn on / off the fourth transistor 68, and its frequency is set to The frequency is set to be sufficiently higher than the frequency band of the data recorded in No. 1. Further, the PWM generation circuit 70 includes the operational amplifier 6
3, the pulse width increases when the output voltage increases, and the pulse width decreases when the output voltage of the operational amplifier 63 decreases. The pulse width modulation can be easily realized by a known technique such as a method of generating a triangular wave by a combination of a capacitor charging / discharging circuit and a fixed clock, and comparing the triangular wave with an input voltage.

The voltage source 71 supplies a DC bias voltage to the base of the third transistor 67, and is set to, for example, the midpoint voltage of the output amplitude of the PWM generation circuit 70.

The operation of the optical disk apparatus configured as described above will be described. Since there are many parts in common with the first embodiment described above, description will first be made with reference to FIGS. 2 (a) to 2 (c).

The waveform a shown in FIG. 2A is output from the PWM generation circuit 70. This waveform a and the voltage of the voltage source 70
The third transistor 67 and the fourth transistor 68 repeat on / off operations due to the voltage relationship of V2. As a result, the waveform I shown in FIG.
The current indicated by op flows, and the laser diode 43 is pulsed intermittently.

A part of the laser light emitted from the laser diode 43 is directly received by the photodiode 47 without irradiating the disk 41 to generate a current, which is further converted into a voltage by the resistor 61. This voltage is smoothed by a fourth low-pass filter 62 by removing the pulse component.

The output voltage of the fourth low-pass filter 62 and the voltage (V3) of the voltage source 64 are compared by the operational amplifier 63, and when an error occurs, the output voltage of the operational amplifier 63 changes. The pulse width changes to change the on / off ratio of the laser diode 43 via the transistors 68, 67, 66, 65. For example, when the amount of light emitted from the laser diode 43 is large, the amount of light received by the monitoring photodiode 47 increases and the output voltage of the fourth low-pass filter 62 becomes higher than the voltage source 64, so that the output voltage of the operational amplifier 63 Rises, the pulse width of the PWM generation circuit 70 increases,
The ON ratio of the third transistors 66, 65, 67 is reduced, the pulse lighting ratio of the laser diode 43 is reduced, and the amount of emitted light is suppressed.

When the amount of light emitted from the laser diode 43 is small, the amount of light received by the monitoring photodiode 47 decreases, and the output voltage of the fourth low-pass filter 62 becomes lower than the voltage source 64. , The pulse width of the PWM generation circuit 70 is reduced, the ratio of turning on the transistors 67, 66, and 65 is increased, the pulse lighting ratio of the laser diode 43 is increased, and the amount of emitted light is increased. Let it.

As a result, the current I is adjusted so that the output of the fourth low-pass filter 62 and the voltage V3 of the voltage source 64 become the same voltage.
The driving pulse width of op is maintained. Since the rated size of the second transistor 65 is set to be larger than that of the first transistor 66, the current source 6 is compared with the current Iop.
9 is small.

On the other hand, the other laser light emitted from the laser diode 43 is applied to the disk 41, and the reflected light is reflected by the photodiode 44 for detecting data, the photodiode 45 for detecting a focus control signal, and the reflected light for detecting a tracking control signal. The light is received by the photodiode 46 and is converted into a current in each of the photodiodes 46.
The current and voltage are converted by 0 and the resistors 52, 53, 54. At this time, since the reflected light is modulated by the data (information signal such as coded sound) recorded on the disk 41, the output of the first operational amplifier 48 is
A pulse train as shown by a waveform b in (c) is a voltage modulated by data on the disk. Further, the output of the first low-pass filter 55 has its amplitude reduced according to the pulse width and is smoothed as shown by the waveform e. The reflected light for the focus control signal and the reflected light for the tracking control signal are received by photodiodes 45 and 46, respectively.
By the same operation as described above, the outputs of the low-pass filters 57 and 59 are also reduced in amplitude according to the pulse width and smoothed.

Here, the operation when the emitted light amount of the laser diode is arbitrarily changed will be described with reference to FIG. FIG. 6A shows a temporal transition of the voltage value V3 of the voltage source 64, and FIG. 6B shows a temporal transition of the current value Iop of the laser diode 43. By changing the voltage V3, as is apparent from the above description, the fourth
The current pulse width of the laser diode 43 changes so that the output voltage of the low-pass filter 62 follows the voltage V3. In other words, the pulse width of the current Iop is proportional to the voltage V3.

As described above, according to the second embodiment, since the drive current Iop of the laser diode 43 is a constant value, it is suitable for an apparatus in which it is difficult to freely set the peak value of Iop due to restrictions on power supply conditions, such as for portable use. Also, the laser diode 43
The average current consumption can be reduced to about に よ り by performing pulse width modulation on the driving current. Further, as described in the first embodiment, the signal quality equivalent to that of the conventional optical disk device can be maintained only by increasing the average current of the laser by, for example, about 20%.

In the second embodiment, the photodiode 44 for detecting data, the photodiode 45 for detecting a focus control signal, and the photodiode 46 for detecting a tracking control signal are each one element for easy understanding. Although it is configured, usually, it is often detected by a combination of about one or two sets of photodiodes. Even in that case, it can be easily realized only by providing the current-voltage conversion circuits and the envelope detection circuit or the low-pass filters by the number of photodiodes.

[0067]

As described above, according to the present invention,
A light receiving element group for converting reflected light emitted from a laser diode on the disk and modulated according to a focus state and a tracking state into an electric signal, and a detection circuit for performing envelope detection of an output signal of the light receiving element group, or a light receiving circuit By providing a low-pass filter group that cuts off a clock frequency band from the output signals of the element group, the difference between the monitor signal level proportional to the amount of light emitted from the laser diode and the reference signal level indicating the reference amount is an error signal. And a pulse driving means for driving the laser diode by a current pulsed to a peak value or a pulse width corresponding to the error signal with a clock having a higher frequency than the data recorded on the disk. And the voltage proportional to the amount of emitted light is substantially equal to the reference voltage. In addition to performing negative feedback control so that the drive current of the laser diode is pulsed, the average drive current of the laser diode can be reduced without deteriorating the reproduction signal quality, and the power of the optical disc device is reduced. In particular, there is an effect that the battery life of a portable optical disk device having a severe power supply condition such as being able to mount only a small-capacity battery can be extended.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical disk device for explaining a first embodiment of the present invention;

FIG. 2 is a signal waveform diagram for explaining the operation of the optical disc device according to the first embodiment of the present invention.

FIG. 3 is a signal waveform diagram for explaining the operation of the optical disc device according to the first embodiment of the present invention.

FIG. 4 is a characteristic diagram of a laser diode for explaining the operation of the optical disc device according to the first embodiment of the present invention;

FIG. 5 is a configuration diagram of an optical disc device for explaining a second embodiment of the present invention;

FIG. 6 is a signal waveform diagram for explaining the operation of the optical disc device according to the second embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional optical disk device.

[Explanation of symbols]

1,41 disk 2,42 optical pickup 3,43 laser diode 4,5,6,7,44,45,46,47 photodiode 8,9,10,23,48,49,50,63 operational amplifier 11, 24, 30, 51, 64, 71 Voltage source 12, 13, 14, 21, 52, 53, 54, 61 Resistance 15 Envelope detection circuit 16, 18, 20, 56, 58, 60 Terminal 17, 19, 22, 55, 57, 59, 62 Low-pass filter 23 Amplifier 25, 26, 27, 28, 65, 66, 67, 68 Transistor 29 Clock generator 69 Current source 70 Pulse width modulation (PWM) generator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/105 556 G11B 11/105 556B 586 586V (72) Inventor Kazuhiko Kono 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture F term (reference) in Matsushita Electric Industrial Co., Ltd. 5D075 AA03 CC24 CD11 CE03 5D090 AA01 CC04 FF05 KK03 KK20 5D118 AA08 BA01 BB06 CA11 CD02 5D119 AA37 BA01 HA54

Claims (6)

[Claims] 1. A laser diode for emitting a laser beam for information detection to a disk on which data is recorded, and a pulse for intermittently driving a drive current of the laser diode by a clock in a frequency band higher than a recording frequency of the data. A driving unit, a light receiving element group that receives the reflected light of the laser light modulated by the data recording unit on the disk, a focus state, and a tracking state, and converts the reflected light into an electric signal; An optical disk device comprising: a detection circuit group for performing envelope detection on each of the electric signals. 2. A laser diode for emitting a laser beam for information detection to a disk on which data is recorded, and a pulse for intermittently driving a drive current of the laser diode by a clock in a frequency band higher than a recording frequency of the data. A driving unit, a light receiving element group that receives the reflected light of the laser light modulated by the data recording unit on the disk, a focus state, and a tracking state, and converts the reflected light into an electric signal; An optical disk device, comprising: a low-pass filter group that blocks a clock frequency band of the clock for each of the electrical signals. 3. A laser diode for emitting a laser beam for information detection to a disk on which data is recorded, and a pulse for intermittently driving a drive current of the laser diode by a clock having a frequency band higher than a recording frequency of the data. A driving unit, a light receiving element group for receiving reflected light of the laser light modulated by a data recording unit, a focus state, and a tracking state on the disk, and converting the reflected light into an electric signal; A detection circuit connected to some of them for performing envelope detection on the output electric signal; and a detection circuit connected to another light receiving element to cut off a clock frequency band of the clock for the output electric signal. A low-pass filter, wherein the amplitude of the output signal of the low-pass filter is substantially equal to the amplitude of the output signal of the detection circuit. The optical disk apparatus characterized by setting the drive current of the laser diode by said pulse driving means. 4. A laser diode for emitting a laser beam for information detection to a disk on which data is recorded, and a pulse for intermittently driving a drive current of the laser diode by a clock having a frequency band higher than a recording frequency of the data. Driving means; a first light receiving element for receiving reflected light of the laser light modulated by a data recording unit on the disk and converting the reflected light into an electric signal; and at least the laser modulated by a focus state on the disk A second light receiving element that receives the reflected light of the light and converts it into an electric signal; a detection circuit that performs envelope detection on the electric signal output from the first light receiving element; and the second light receiving element From the electric signal output from the control signal, and passes the frequency band of the focus control signal, and cuts off the clock frequency band of the clock. Optical disk apparatus characterized by comprising: a filter, a. 5. A laser diode for emitting a laser beam for information detection to a disk on which data is recorded, and a monitor signal detector for receiving a beam emitted from the laser diode and detecting a monitor signal proportional to the amount of emitted light. A light receiving element for outputting a difference between a monitor signal level of the light receiving element and a reference signal level indicating a reference light amount as an error signal; and a higher frequency than a recording frequency of the data recorded on the disk. A pulse driving means for driving the laser diode with a clock and a pulsed current having a peak value according to the error signal, wherein a monitor signal level proportional to the emitted light amount is substantially equal to the reference signal level. An optical disc device characterized by performing negative feedback control as follows. 6. A laser diode for emitting a laser beam for information detection to a disk on which data is recorded, and a monitor signal detection for receiving a light emitted from the laser diode and detecting a monitor signal proportional to the amount of emitted light. A light receiving element for outputting a difference between a monitor signal level of the light receiving element and a reference signal level indicating a reference light amount as an error signal; and a higher frequency than a recording frequency of the data recorded on the disk. A pulse driving means for driving the laser diode by a clock and a pulsed current having a pulse width corresponding to the error signal, wherein a monitor signal level proportional to the emitted light amount is substantially equal to the reference signal level. An optical disc device characterized by performing negative feedback control as follows.