JPS61253651A - Recording power detecting system for optical disk device - Google Patents

Abstract

PURPOSE:To perform with a high accuracy a detection of a variation of a recording power caused by deterioration of a characteristic, by a simple circuit, by generating the power of an information recording time by driving a semiconductor laser like a direct current, in a state that an optical head has stopped at other position than a recording area of an optical disk. CONSTITUTION:In case of detecting a recording power of a laser diode 4, first of all, a state of 'check mode' is set by turning on a power source. Subsequently, a transistor 23 becomes an on-state and the laser diode 4 generates a DC power. In this state, the recording power is generated by the laser diode 4, and it is detected by a monitor diode 5. In this case, when the recording power is generated pulsatively, it is difficult to execute monitoring, therefore, a transistor 26 is turned on by a LASER OK signal 66 for showing that a laser has been stabilized, and the recording power is generated like a direct current. Whether the recording power is too large or too small is checked by setting an optical head 3 to the outside of a range of a recording film 2, detecting the recording power of the laser diode 4, which has been generated like a direct current, and comparing it with a reference voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for detecting recording power in an optical disc device, and more particularly to a method for detecting changes in recording power of a semiconductor laser in an optical disc device.

[Background of the invention]

Conventionally, when the characteristics of a semiconductor laser constituting an optical head change over time or due to temperature, the characteristics of drive current versus recording power (oscillation output) in an optical disk device also change. As a method for detecting the recording power of a semiconductor laser in order to keep the recording power within a certain value, there is
- As described in the specification of No. 138582, the recording power is sampled during the peak period of the recording pulse, and the oscillation power is sampled during one of the DC bias periods, and a predetermined recording power is output based on the sampled values. There is a way to control it.

However, in this method, since the recording power is sampled during the peak period of the recording pulse, which is usually 50 to 200 nS, a switching circuit for high-speed operation is required. In addition, since the oscillation power due to the DC bias and the recording power due to the recording pulse are separately monitored and the power is controlled at the same time, there is a problem that the circuit scale becomes large. To solve these conventional problems, in an optical disk device that uses a semiconductor laser to optically record/reproduce information, we have developed a simple circuit that can detect changes in recording power due to deterioration of the characteristics of the semiconductor laser with high accuracy. <An object of the present invention is to provide a recording power detection method in an optical disc device that can be implemented.

[Summary of the invention]

In order to achieve the above object, the recording power detection method in the optical disc device of the present invention is such that an optical disc device that records/reproduces information by irradiating the optical disc with light from a semiconductor laser, uses an optical head that outputs the laser light. Head moving means (
Limit switch 6-8. actuator 10, etc.),
It is equipped with means for detecting the power of the laser beam (monitor diode 5) and means for comparing the output of the detection means with a reference voltage (comparators 32, 33), and the head moving means moves the optical head to a position other than the recording area of the optical disk. The semiconductor laser is driven with direct current to generate power for recording information while stopped at the position, and it is determined from the output of the comparing means whether the recording power is excessive or insufficient. be.

FIG. 1 is a circuit block diagram showing an embodiment of an optical head control/recording power detection section of an optical disk device according to the present invention, and FIG. 2 is an operation time chart of FIG. 1.

In FIG. 1, 1 is an optical disk having a recording film 2 of a storage medium, 3 is an optical head having a laser diode 4° monitor diode 5, etc., and an actuator 1
Moved by 0. Reference numeral 9 denotes a detection piece attached to the lower end of the optical head 3. When the optical head 3 reaches the inner and outer limit positions of the recording area of the optical disk and the recording area test position, the detection piece 9 activates the limit switch 6, respectively. Detected by .7.8. In the normal recording/reproducing mode, the optical head 3 moves between the limit switches 6 and 7 so as to be within the range of the recording film 2.

The laser diode 4 receives the APCON signal 60 during playback.
WRPtJLSE is driven by a DC current from a transistor 23 that operates at
It is driven by a current superimposed on the current generated by the transistor 26 operated by the signal 56.

To detect the recording power of the laser diode 4 when the power is turned on, the PWON R8T signal 53 and the WRPW CHK MD signal 55 are first detected by turning on the power.
111 and put it in 'check mode' 0th order,
OUT from limit switch 7 with DR signal 52
The T LIMIT SW signal 58 is disabled and the actuator 10 is driven to move the optical radar 3 to the position of the limit switch 8 located outside. When the optical head reaches the limit switch 8, the WRPW CHK SW signal 59° and the APCON signal 60 become rr l u, the transistor 23 is turned on, and the laser diode 4 generates DC power.

In the present invention, in this state, the laser diode 4 generates recording power, which is transmitted to the monitor diode 5 and detected. In this case, since it is difficult to monitor if the recording power is generated in a pulsed manner, the LAS signal indicating that the laser has stabilized is
1 with EROK signal 66. WRPOWERON signal 61
When the voltage is set to "1", the transistor 26 is turned on, and recording power is generated in a direct current manner. Note that since the laser beam having recording power output from the optical head is irradiated onto a position outside the recording area on the optical disk, there is no risk of damaging the recording area.

The recording power is detected by the monitor diode 5, converted to voltage by the resistor 30, and then amplified by the amplifier 31 to become the LAsERPOWER signal 64. This signal 64 is compared with the reference voltage vLh+ by the comparator 32, and the reference voltage vLh− by the comparator 33.
compared to Note that the LASERPOWER signal 64 has a waveform having a PR value and a pw value as shown in FIG.

The reference voltages vth'' and vth-'' are set to values that indicate the allowable range of the Pw value.

The laser abnormality detection circuit 36 receives the LSRCHK signal 67
takes in the surface outputs of the comparators 32 and 33 within the period of rr f u, and when the laser output exceeds the range of vth+ to vt, h-, that is, when there is any of the above outputs, laser abnormality detection (WRPWALARM ) signal 6
Generates 5. When there is no output from any of the above, it is determined that the recording power is normal, and the WRPW CHK MD signal 5
5 becomes J# OH and the 'check mode' state is released. This drives the actuator 10 to move the optical head 3 to the position of the inner limit switch 6, and then returns the OUT DR signal 52 to the OUT LIMIT SW from the outer limit switch 7.
7 signal is enabled and the moving range of the optical head 3 is set to the recording film 2.
It becomes the normal recording/playback mode in the range of .

In addition, when detecting the recording power of the laser diode 4 during unloading, first, after replacing the optical disk 1, the UNLOAD signal 54 and WR'PW CHK MD are detected.
The signal 55 is set to n I IP to enter the ``check mode.'' The subsequent operations are the same as those at power-on described above, so a description thereof will be omitted.

In this way, in one aspect of the present invention, instead of monitoring the recording power in real time, the optical head 3 is moved out of the range of the recording film 2 when the power is turned on or when the optical disk 1 is replaced.
By detecting the DC-generated recording power of the laser diode 4 and comparing it with a reference voltage, it is possible to check whether the recording power is excessive or insufficient.

In addition, as mentioned above, when the power is turned on or unloaded, the recording power deviation due to a change in the drive current/recording power change ratio is checked, so data is not recorded with abnormal recording power, and this optical disc The reliability of data in the device is improved.

〔Effect of the invention〕

As explained above, according to the present invention, the recording power of the DC-driven laser diode is detected by the monitor diode and compared with the reference voltage, so that the deterioration of the characteristics of the semiconductor laser can be avoided without using a complicated analog circuit. It is possible to detect changes in recording power due to this with a simple circuit and with high accuracy.

[Brief explanation of the drawing]

The circuit block diagram in FIG. 2 is an operation time chart of FIG. 1. 1: Optical disk, 2: Recording film, 3: Optical head, 4: Laser diode, 5: Monitor diode, 6 to 8: Limit switch, 9: Detection piece, 10: Actuator, 1
1: Inverter circuit, 12゜14.15, 21.28:
AND circuit, 13, 20. 29, 35: OR circuit, 16
: Switching circuit, 17; Drive circuit, 18, 19, 22, 27
．． 34: Latch circuit, 23, 26: Transistor, 24
゜25.30: Resistor, 31: Amplifier, 32.33: Comparator, 36: Laser abnormality detection circuit, 52: OUT
DR double signal 53: PW ON R3T signal. 54: UNLOAD signal, 55: WRPW CH
K MD double signal 56:WRPULSE signal, 57:I
N LIMIT SW6 signal, 58: OUTLIMI
T SW7 signal, 59: WRPW CHKSWa signal, 60: APCON signal, 61: WRPOWERON signal, 62: Vt, h+ times signal 63: Vth- signal, 64
: LASERPOWER signal, 65 : WRPW
ALARM signal, 66: LASEROK double signal 67:
LSRCHK signal.

Claims (1)

[Claims] (1) In an optical disk device that records/reproduces information by irradiating an optical disk with light from a semiconductor laser, a head moving means for moving an optical head that outputs the laser beam to a predetermined position on the optical disk; The semiconductor laser is provided with means for detecting the power of the light and means for comparing the output of the detection means with a reference voltage, and with the optical head stopped at a predetermined position other than the recording area of the optical disk by the head moving means. A recording power detection method for an optical disk device, characterized in that the power for recording information is generated by direct current driving, and it is determined from the output of the comparing means whether the recording power is excessive or insufficient.