JPS60143438A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To achieve an accurate recording and reproducing function, by locking the output level of a semiconductor laser at a previously set prescribed level at the time of power on and/or standby mode of an information recording and reproducing device and controlling the optical output of the laser at the time of recording and/or reproducing by using the locked level. CONSTITUTION:The level of an optical output from a semiconductor laser 21 is detected by a photodetector 22 and its detected signal is supplied to a comparator 24-2 through an amplifier 23. The detected signal is compared with a previously set reference voltage VR2 at the comparator 24-2. When the signal inputted into the comparator 24-2 exceeds the reference voltage VR2, the comparator 24-2 outputs an inverse signal and a counter 25-2 is set to the counted value at the moment by the inverse signal and, therefore, the optical output level of the semiconductor laser 21 at the high condition of a record signal (a) is set to a prescribed level. By using the output level of the semiconductor laser maintained under such a condition, recording and reproduction of information are performed.

Description

[Detailed Description of the Invention] 11L" The present invention relates to an optical information recording and reproducing device, and in particular, it uses a semiconductor laser as a light source and records information by changing its optical output, and also records information from a recording medium. The present invention relates to an optical information recording/reproducing apparatus that reproduces information recorded on a recording medium using reflected light from the recording medium.

Prior Art Conventionally, optical information recording and reproducing devices using semiconductor lasers have been used, but the current-light output characteristics of semiconductor lasers generally have different characteristics with temperature T as a parameter as shown in FIG. are doing. Therefore, when the differential quantum efficiency of a semiconductor laser changes with temperature, even if recording pulses having the same amplitude A are used, the amplitude of the obtained optical output will be at a different level depending on the temperature. Therefore, due to temperature changes, the laser light output emitted from the semiconductor laser fluctuates, and errors may occur in writing information onto and reading information from the recording medium.

Purpose The present invention has been made in view of the above points, and it is possible to eliminate the drawbacks of the prior art as described above and to accurately record information on a recording medium using light. Another object of the present invention is to provide an optical information recording and reproducing device that can accurately reproduce information recorded on a recording medium.

1-Apparatus In one configuration example of the present invention, there is provided an optical information recording and reproducing apparatus that uses a semiconductor laser to record information on an optical information recording medium and to reproduce information from the recording medium. The output level of the semiconductor laser is locked to a predetermined level when the device is powered on and/or in standby mode, and the locked level is used to control the output of the semiconductor laser during recording and/or playback. It is characterized by controlling the output and achieving accurate recording and playback functions.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows the overall configuration of an optical information recording/reproducing apparatus to which the present invention is applied. As shown in the figure, the optical information recording/reproducing apparatus has a semiconductor laser 1 as a light source, and a laser beam emitted from the laser 1 is made into parallel light by a collimator lens 2 and is incident on a deflection beam splitter 3. The parallel light polarized in the right angle direction by the polarization beam splitter 3 passes through the quarter-wave plate 4, where it is converted from linearly polarized light to circularly polarized light, and each converted circularly polarized light is converged by an objective lens 5. The light is focused onto a recording medium 6 provided on a disk 7, and information is recorded thereon. On the other hand, when performing reproduction, the optical output from the laser 1 is set to a low level, and the light is focused onto the recording medium 6 in the same manner as described above. The reflected light reflected from the recording medium 6 is 1/4
The light passes through the wavelength plate 4 in the opposite direction and becomes linearly polarized light with a phase shift of 90 degrees from the incident light, and this linearly polarized light is detected to reproduce information. On the other hand, this linearly polarized light passes through the beam splitter 3 and proceeds, and the transmitted light passes through the lens 8 and is incident on the focusing servo detector 11 by the half mirror 9, and the light transmitted through the half mirror 9 is incident on the tracking servo detector 10, and performs focusing and tracking control of the recording medium 6.

In such an optical information recording/reproducing apparatus, information recorded on the recording medium 6 is recorded in the form of a digital signal series. Therefore, the optical output of the semiconductor laser 1 changes approximately binary depending on the recording pulse 13. Furthermore, even when such a recording pulse is not applied to the semiconductor laser drive circuit 12,
In order to perform focus and track detection, it is necessary to irradiate the recording medium 6 with a low-level light beam as in the case of reproduction.

In this case, the laser beam output during recording is approximately 10 times as large as that during reproduction, and the recording medium 6 may be partially melted due to such strong laser beam output during recording. Recording is performed by removing the bits and forming uneven bits on the recording medium 6. FIG. 3 shows a state in which the recording medium 6 is partially melted and removed by the recording pulse, and information is recorded as uneven bits.

In FIG. 3, LR represents the laser light output level during reproduction or non-recording, and L represents the optical output level during recording. Therefore, L is approximately 10 times larger than LR.

FIG. 4 is a circuit diagram showing the detailed configuration of the semiconductor laser drive circuit 12. At power-on or standby mode, the controller 2 having a sequence controller etc.
The counters 25-1 and 25-2 are simultaneously reset by the semiconductor laser output control command signal from 9, and the recording signal a becomes low. The counter 25-1 then counts the clock signal from the clock generator 28,
Therefore, the counter output increases sequentially. The counter output signal is input to the digital-to-analog converter 26-1, and the output signal from the digital-to-analog converter 26-1 is supplied to the non-inverting input terminal of the operational amplifier 27, so that the voltage at the non-inverting input terminal of the operational amplifier 27 is ■1 increases sequentially. Therefore, the output level of the operational amplifier 27 increases and the on state of the transistor Q1 becomes stronger, so that the forward current 1+ (=V+ /R') flows through the transistor Q1.
+ ) increases.

The current 11 flowing through the transistor Q1 is a driving current for the semiconductor laser 21, so that the semiconductor laser 21 emits light. A portion of the emitted beam is incident on a photodetector 22 disposed close to the semiconductor laser 21 . This detection signal is amplified by the detection amplifier 23, and the amplified signal is input to comparators 24-1 and 24-2. The comparator 24-1 receives the reference voltage VRI set to the output level during reproduction, while the comparator 24-2 receives the reference voltage VR2 set to the output level of the recording pulse. .

These reference voltages can be set to appropriate levels as desired, but as described above, it is desirable to set the reference voltage VR2 during recording to about 10 times the reference voltage VRI during reproduction. Therefore, when the amplified signal from the detection amplifier 23 is input, first, the output of the comparator 24-1 is inverted, and this inverted signal causes the counter 25-1 to be inverted.
is set, thereby setting the output level of the semiconductor laser at times other than during recording pulse irradiation. Record signal a then goes high and counter 25-2 starts counting the clock signal from clock generator 28, so the output from counter 25-2 increases sequentially. The output signal from counter 25-2 is applied to the base of transistor Q2 via digital-to-analog converter 26-2. As the count of the counter 25-2 increases, the base voltage of the transistor Q2 increases sequentially,
Therefore, the collector current flowing through transistor Q2■
2 increases similarly. The current 2 flowing through the transistor Q2 flows into the collector of the transistor Q6 through the resistor R4.

The emitters of the transistors Q6 and Q5 are connected in common to the reference voltage VEE, and the bases of the transistors Q6 and Q5 are connected in common, and the collector and base of the transistor QB are connected to form a current mirror circuit. It consists of

Therefore, to the collector of transistor Q6, transistor Q
When current I2 is supplied from transistor Q2, the same current I2 is also generated at the collector of transistor Q5. Note that a differential amplifier is configured by a pair of transistors Q3 and Q4 and resistors R2 and R3.

When recording signal @a is in a high state, transistor Q4
is maintained in an off state, so the collector current wtI2 of transistor Q5 generated by the II mirror circuit flows only through transistor Q3. Therefore, when the recording signal a is in a high state, the current flowing through the semiconductor laser 21 is I++12. As the output from the counter 25-2 increases successively, the current I2 increases, so the optical output from the semiconductor laser 21 gradually increases. The optical output level from the semiconductor laser 21 is detected by the photodetector 22 as described above, and the detection signal is supplied to the comparator 24-2 via the amplifier 23 and compared with a preset reference voltage VR2. When the signal input to the comparator 24-2 exceeds the reference voltage VR2, the comparator 24-2
-2 outputs an inverted signal, and this inverted signal sets the counter 25-2 to the count value at that point,
Therefore, the optical output level of the semiconductor laser 21 when the recording signal a is in a high state is set to a predetermined level.

Through the above sequence, the upper limit and lower limit of the optical output level from the semiconductor laser 21 are set. Such a sequence may be repeated at predetermined time intervals, for example, when the present optical information recording/reproducing device is in power-up mode or standby mode, and the upper i value and lower limit value may be updated as needed. . The output level of the semiconductor laser thus maintained is used to record and reproduce information.

Effect Even if the current-light output characteristics of the semiconductor laser fluctuate due to changes in temperature, etc., it is possible to always obtain stable optical output at the recording level and playback level, and it is possible to accurately form information bits. . The output of the semiconductor laser is locked to a predetermined level during power-on and standby mode, and only that level is used during recording or playback, so the output of the semiconductor laser is always detected and controlled during recording or playback. Therefore, not only is the circuit configuration simple, but also the circuit operation does not need to be very high-speed, so it can be configured at low cost.

Although specific embodiments of the present invention have been described in detail above, the present invention should not be limited only to these specific examples, and various modifications can be made without departing from the technical scope of the present invention. Of course, it is possible.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the current (1) - optical output (L) characteristic with the temperature T of the semiconductor laser as a parameter, and Fig. 2 shows an example of an optical information recording/reproducing device to which the present invention is applied. A schematic diagram, FIG. 3 is an explanatory diagram showing a state in which a part of the recording medium 6 is melted and removed by a recording pulse and information is recorded in the form of an uneven shape, and FIG. 4 shows an embodiment of the present invention. This is the circuit diagram. (Explanation of symbols) 1.21: Semiconductor laser 12: Semiconductor laser drive circuit 22: Photodetector 23: Amplifier 24: Comparator 25: Counter 26: Digital-to-analog converter 27: Operational amplifier 28: Clock generator 29: Controller a: Recording signal Q: Transistor R: Resistance Vcc: Power supply voltage VEE: Reference voltage

Claims (1)

[Claims] 1. In an information recording and reproducing apparatus that records information on a recording medium using light and reproduces information recorded on the recording medium, a light irradiation device that irradiates the recording medium with light. means and
recording using a light output level setting means for receiving irradiated light from the light irradiation means and setting a first light output level and a second light output level; and one of the first and second light output levels. 1. An information recording/reproducing apparatus comprising: a recording/reproducing means for performing one operation and one for reproducing information using the other. 2. In claim 1, the first and second
The optical output level is set when the device is powered on and/or
Or an information recording/reproducing device characterized by being operated in standby mode. 3. In claim 1, the light irradiation means includes a semiconductor laser, and the setting means sets the drive current level supplied to the semiconductor laser to control the first and second light. An information recording/reproducing device characterized by setting an output level.