JPS58158051A - Controller for stabilizing output of semiconductor laser oscillator - Google Patents

Abstract

PURPOSE:To perform invariably accurate and stable control over an oscillation output without reference to the switching of an oscillation output level by controlling the oscillation output on the basis of a value stored and held in a temporary storing and holding circuit inserted in a stabilization control loop. CONSTITUTION:When a beam modulated signal (d) is inputted to an adder 16, the signal (d) is added to the output signal of a sample holding circuit 14 to supply the sum signal to a current supply circuit 17, performing switching to a high output level. The sample holding circuit 14, however, is in a holding state because a control level (c) is at a level 0 and stores and holds the last input voltage to supply it to the adder 16. Consequently, a large signal due to the monitor light of recording beam light is intercepted to remove the influence of the monitor light signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a semiconductor Rade oscillator output stabilization control device for stabilizing the oscillation output of a semiconductor Rade oscillator used as a light source of an optical disk device, for example.

[Technical background of the invention and its problems]

Optical disk devices optically record or reproduce information by irradiating a rotating optical disk with Ledeby light, and have recently attracted a lot of attention as an unprecedentedly large-capacity information memory. Application to large-capacity image file devices is being considered.

Recently, in such optical disk devices, semiconductor laser oscillators have been used as light sources for the purpose of improving stability and increasing access speed by downsizing the optical head. On the other hand, semiconductor laser oscillators have large fluctuations in oscillation output due to changes in ambient temperature, etc., and there is a gap in terms of low electrical power. That is, in general, the oscillation threshold current (Ith) of a semiconductor oscillator depends on the junction temperature (T
j), and has the following relationship. Furthermore, in practice, since a heat sink is attached to the semiconductor laser oscillator, the temperature becomes T3*Ta (III ambient temperature). This situation (characteristics of the MP conductor Rade oscillator) is shown in FIG. Therefore, even if the drive current of the semiconductor laser oscillator is constant, the oscillation output will vary significantly if the ambient temperature changes.

Therefore, control is normally performed to stabilize the oscillation output by detecting the oscillation monitor light from the semiconductor laser oscillator and feeding it back to the drive circuit of the semiconductor laser oscillator. There is one described in Japanese Patent No. 54-10481. However, since this conventional technology simply detects the oscillation monitor light and applies feedback, it is possible to obtain a reproduction radar result in a device dedicated to information reproduction as shown in the above-mentioned publication. In an optical disk drive using such a recording method, it is difficult to always accurately and stably control a semiconductor laser oscillator that alternately switches the oscillation output between a first output level and a second higher output level. It is possible.

In other words, recently, in order to realize high-density recording on optical discs, recording tracks are formed in advance on optical discs by grooves (or pre-pit rows) called pre-groups in a spiral shape (or concentric circles). By alternately switching the Hayabusa's laser beam to a reproduction beam and a recording beam of higher energy, the recording beam tracks data bits in the pregroup while the reproduction beam tracks the pregroup. Optical disk devices that record information by forming optical disks are being developed. An optical disk device that performs such recording normally outputs a low-level (first output level) reproduction beam light from a semiconductor radar oscillator to perform the above-mentioned tracking and recording. When a beam modulation signal ()<recording pulse with a pulse length of several thousand seconds or less) is input, the output level (energy) of the semiconductor laser oscillator is switched to a high level (second The above-mentioned recording is performed by using a recording beam light of a certain output level.

, so in this case the energy at the recording beam destination is
In order to melt and deform the metal coating on the optical disk, the light intensity is several ten times that of the reproduction beam, and a correspondingly high level of monitor light is also input to the detector, and its output signal level is equal to that of the reproduction beam. It will be more than 10 times. For this reason,
When using the conventional method of detecting the monitor light of the reproduction beam light and applying feedback at step 7, the signal due to the monitor light of the recording beam light is generated as a very large level in the output signal of the monitor light detector, and this 7 When the stabilizing control loop responds to the two-way optical signal.

It works to push down the output of the playback beam to a low level, making stable recording impossible. In this way, the signal from the monitor light of the recording beam light greatly influences the operation of the circuit, making the operation extremely unstable and causing malfunctions, making accurate and stable control impossible at all times.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to cause the oscillation to normally occur at a first output level and, if necessary, to oscillate at a second output level different from the first output level for a predetermined period of time. In a semiconductor laser oscillator that switches the oscillation output, it is possible to always accurately and stably control the stabilization of the oscillation output regardless of the switching of the oscillation output level, and the output of the semiconductor laser oscillator can be realized with a relatively simple circuit configuration. An object of the present invention is to provide a stabilization control device.

[Summary of the invention]

In the present invention, a temporary storage holding circuit is inserted in the stabilization control loop, and this temporary storage holding circuit is made conductive as a control loop when oscillating at a first output level, and is turned on as a control loop when oscillating at a first output level. At the time of oscillation, the control loop is disconnected by being in a non-conducting state, and the value just before that is memorized and retained, and the oscillation output is controlled using the memorized and retained value. That is, as shown in the characteristics of the semiconductor Rade oscillator in FIG. 1, the oscillation threshold voltage varies greatly depending on the temperature, but the change in [oscillation output/current] in the failure region is constant. Therefore, a stabilizing control loop is formed only for the oscillation output necessary for the first output level.

[Embodiments of the invention]

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

FIG. 2 mainly shows the optical system of an optical disk device according to the present invention, in which 1 is an optical die on which recording tracks are formed in advance in a spiral shape by pre-groups on the surface (lower surface); is a motor that rotates the optical disc 1, and I is an optical head for recording and reproducing. The optical head 3 is moved by a linear motor mechanism (not shown) in the radial direction of the optical dinuque 1, and includes a semiconductor laser oscillator 4 that outputs a laser beam in two directions, a collimator lens 5, and a deflected beam. splitter 6%
It is composed of a λ/4 plate 1, an objective lens 8, a condensing lens 9, a first photodetector 10, and a second photodetector 11.

That is, the laser oscillator 4 is driven and controlled by a drive circuit 15, which will be described later, and its oscillation output level is switched between two beam powers: a reproduction beam light (first output level) and a recording beam light (second output level). It looks like this. The main beam output from the front of the laser oscillator 4 is collimated by the collimator lens 5, and then passed through the beam splitter 6 and the λ/4 plate 7 to the objective lens 8.
Here, the light is focused to about 1 μmφ and irradiated onto the optical disk 1 (lower surface).

Then, the reflected light from the optical disk 1 is reflected by the objective lens 1, λ
/411i7 and beam splitter 6 to condenser lens #, where it is condensed and focused on first photodetector 10, where it is converted into an electrical signal. The output signal of the first photodetector 10 is sent to a signal processing circuit (not shown) and is used as a reproduction signal, a tracking control signal, a focus control signal, and the like. On the other hand, the output from the rear of the laser oscillator 4 is monitored by the second photodetector 11.
It is designed to be incident on the , where it is converted into an electrical signal.

Further, 12 is an integral amplifier that integrates and amplifies the output signal of the second photodetector 11, and 13 is an error amplifier that amplifies the difference between the output signal 1 of the second amplifier 12 and a preset reference signal S. Here, the reference signal S is a set voltage for setting the output level (for example, 1 mW) of the reproduction beam light. Further, numeral 14 denotes a sample and hold circuit as a temporary storage and holding circuit to which the output signal of the error amplifier IJ is supplied, and it enters either a sample state or a hold state depending on the state of the control signal C (see FIG. 3). That is, when reproducing information (when oscillating with the reproducing beam light), the control signal is in the state C)M, and the output signal of the error amplifier 13 is output as is. Then, when recording information (when oscillating with the recording beam light), the control signal C is set to logic @0 level for that period to enter a hold state (non-conducting state), and the output signal of the error amplifier 13 just before that It stores and outputs it. Further, 15 is a drive circuit for driving and controlling the laser oscillator 4, and is controlled according to the output signal of the sample and hold circuit 14 and the beam modulation signal d. The drive circuit 15 includes an adder 16 that adds the output signal of the sample and hold circuit 14 and the beam modulation signal d, and a constant current circuit that supplies the laser oscillator 4 with a drive current according to the output signal of the adder 16. It is constituted by a current supply circuit 11.

Next, the operation in such a configuration will be explained. For example, when recording information, the optical head 3 is moved to a predetermined position on the optical disk 1, the laser oscillator 4 outputs a reproduction beam, and the objective register 8 records the beam on the optical disk 1. Let the truck bind. At this time, the optical disc 1 is rotating at a predetermined speed, so the reproduction beam scans the recording track and starts tracking while detecting the track. Note that this zero tracking control is not the gist of the present invention, and various methods are already well known, so further explanation will be omitted.

Thus, the monitor light from the laser oscillator 4 is converted into an electrical signal by the second photodetector 11, amplified by the amplifier 12, becomes 8 parts of the signal shown in the stripe diagram 3, and is supplied to the error amplifier 22. The error amplifier 12 amplifies the difference between the output signal port of the amplifier 1z and the reference signal S, and supplies a signal corresponding to the difference to the sample hold circuit 14. In this case, the control signal C supplied to the sample-and-hold circuit 14 is at the 11'' level, and the sample-and-hold circuit 14 is in the sampling state. supply to

The adder and the beam modulation signal d (usually zero volts) are added together, and the addition result (in this case, the sample and hold circuit 1
4) is supplied to the current supply circuit 11. The current supply circuit 11 supplies a drive current to the Rade oscillator 4 according to the input output signal of the adder 16. Through this operation, the output level of the reproduction beam light is controlled to a constant value according to the reference signal. That is, control is performed to stabilize the output of the laser oscillator 4 during reproduction beam light.

In this state, when a beam modulation signal d (a recording pulse with a pulse width of several Zoofls or less) as shown in FIG. 3 is input to the adder 1i in order to record information, the adder 1i
# adds the beam modulation signal d to the output signal of the sample hold circuit 14 and supplies the result to the current supply circuit 17. As a result, the current supply circuit 1r supplies a current corresponding to the amplitude of the beam modulation signal d to the laser oscillator 4 for the period of the signal d, and switches the output level to a high level to produce a recording beam light, which is used to record the optical disc. Data bits are formed in b pregroups forming one recording track on the other hand.

At this time, since the monitor light of the recording beam light is input to the second photodetector 11, the output signal a of the amplifier 11 becomes a high level (part W) as shown by the broken line in FIG. This signal level is several times higher than that of the monitor light of the reproduction beam light.

However, in this case, the control body %c is at the @O'' level, and the sample and hold circuit 14 is in the Hall Y state. The output signal of the amplifier 13) is stored and supplied to the adder 16. As a result, a large signal due to the monitor light of the recording beam light can be cut off, and the influence of the monitor light (!) can be removed.

That is, during the recording period, it is equivalent to the sample-and-hold circuit 14 being in a non-conducting state, and as a result, the output signal of the error amplifier 11 at the time of the above-mentioned 72-mega optical signal is not inputted to the adder 16, but is output from the sample-and-hold circuit. The reproduction signal stored and held in 14 is input to adder 1#. As a result, even during the recording beam, the oscillation output of the Rade oscillator 4 is stabilized and controlled only for the monitor light output level of the reproduction beam without being affected by the optical signal.

As described above, according to the above-mentioned output stabilizing side device, the stabilization control of the missed output of the Rade oscillator 4 is performed only for the monitor light output level of the reproduction beam, both during the reproduction beam and the recording beam. will be held. This results in
The oscillation output during the reproduction beam period and the oscillation output during the recording beam period can be accurately and stably controlled at all times, regardless of switching between the output levels of the reproduction beam and recording beam, resulting in stable recording or reproduction. In addition, as mentioned above, the oscillation threshold current of semiconductor laser oscillation *S changes depending on the temperature, but the change in [missed output/current] in the oscillation region is constant, so The oscillation output can be stabilized at the same time, making even more stable recording possible, and the oscillation output level of the recording beam light can also be set independently of the reproduction beam light.

In the above embodiment, a sample hold circuit was used as the temporary memory holding circuit, but other memory holding circuits may be used. However, if applied to an image file device, for example, one The recording time for scratches is several seconds or less at most, and temporary storage using a simple and inexpensive sample-and-hold circuit is sufficient.

Furthermore, in the above embodiment, the oscillation output was stabilized using the monitor light of the semiconductor Rade oscillator, but it goes without saying that the oscillation output can also be similarly stabilized by using the reproduction beam light or the recording beam light. It is.

Further, in the above embodiment, a case has been described in which the present invention is applied to a semiconductor radar oscillator used as a light source of an optical denuttering device, but the present invention is not limited to this, and the present invention is applied to a semiconductor radar oscillator used as a light source of other optical devices. Any semiconductor laser oscillator that causes the oscillator to oscillate with a bell and switches the oscillation output to a second output level different from the first output level for a predetermined period as necessary can be applied.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to always perform accurate and stable stabilization control of the oscillation output regardless of switching of the oscillation output level, and moreover, the semiconductor radar oscillator can be realized with a relatively simple circuit configuration. We can provide the output stabilization control device.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram of a semiconductor laser oscillator, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 3 is a main signal waveform diagram for explaining the operation of the embodiment. ! ...Optical disker, J...Optical head, 4...Semiconductor laser oscillator, 11...Photodetector, IS...w
Am amplifier (comparison @), 14... sample hold circuit (temporary memory holding circuit), 15... drive circuit.

Claims (1)

[Claims] In a semiconductor laser oscillator, which normally oscillates at a first output level and switches the oscillation output to a second output level different from the first output level for a predetermined period of time as necessary, the oscillation light from the semiconductor laser oscillator is detected. a photodetector for converting the signal into an electrical signal; a level setting circuit for setting the first output level according to the output signal of the photodetector; a temporary memory storage path that outputs the input signal as it is when oscillating at the output level of the second output level, and stores and outputs the immediately preceding input signal, etc. when oscillating at the second output level; - A drive circuit for driving the semiconductor laser oscillator, which is controlled by an output signal of the temporary storage circuit.