JPH02297731A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To make the time required for rising a high frequency superposing current within such time as of no hindrance to reading the recorded information and hence to securely perform the read-out by controlling a variation of the high frequency superposing current between its on-state and off-state to fall within a prescribed range. CONSTITUTION:When a high frequency superposing module HFM 27 is turned on/off, and a variation of DELTAIop between currents I1 and I2 to flow in a laser diode 7 at this time is calculated by a CPU 33, and then the variation DELTAIop is controlled to become a target value by controlling the high frequency superposing current in amplitude to be supplied to the laser diode 7 from the HFM 27 according to the size of this variation DELTAIop. By setting this variation DELTAIop at the target value, the rising time ton of the HFM 27 at the time of turning on from its off is set less than a prescribed value. By this method, noise can be reduced, while a read error rate can be prevented from increasing as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an optical information PiI recording and reproducing device that superimposes a high frequency signal to adjust the optical output of a semiconductor laser to υ1111.

[Prior art] In recent years, optical information recording and reproducing devices that can record information and reproduce recorded information by irradiating a focused light beam instead of using a magnetic head have been put into practical use. It was done.

This optical 8-position system uses laser light to
It has a large / 22 position that can record information with high density,
It is expected to become more popular in the future.

Laser diodes (semiconductor lasers), which can be miniaturized, are widely used as the source of the laser light.

By the way, in the device using the above-mentioned laser diode, in order to reduce the noise of the laser diode,
As disclosed in No. 6, 500MH7~1001
It is known that it is effective to modulate the excitation lJ current with a high frequency of 00O.

It is also known that this modulation is effective in reducing noise if it is modulated with an amplitude that covers the threshold of laser emission.

[Problems to be solved by the invention] Conventionally, when modulating to cover the threshold of the laser diode, the noise reduction effect increases as described above, so the amplitude of the high-frequency signal is increased and the high-frequency signal is At the time of 0N10FF, the current change period Δtop flowing through the laser diode was increased. The maximum value of this current change ■Δlop was used without any particular restriction.

By the way, since information cannot be recorded normally in the state in which the high frequency signal is superimposed, the superimposition of the high frequency signal is turned off in the recording mode, and turned on when the reproduction mode is entered.

On the other hand, in a recording medium (hereinafter referred to as a disk), each track is divided into multiple sectors, and each sector has a pre-pit section at the beginning of which the address number of that sector is stored, and information is recorded. Even in the recording mode, in order to read the address in the pre-pit portion, the mode is switched to the reproduction mode, and it is recognized whether or not this is the sector to be recorded.

For this reason, the operation of the high frequency superimposed signal Joule that generates the high frequency superimposed signal is set to 0N10FF, and the high frequency superposed signal is reduced to 0N.
I often switch to 10FF.

However, when the high-frequency m-tatami signal is 0N10FF due to the 0N10FF of the high-frequency Φ-tatami module, the current change Δlo
The magnitude of p and the ON time until the high frequency superimposed signal rises
There is an almost proportional relationship with time, and if the current change amount Δlop is too large, it will take time to start up when switching from recording mode to playback mode, and it will be difficult to read information such as addresses of bleep 1 to 1. The problem was that I couldn't do it.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an optical information recording and reproducing device that can read recorded information when switching from recording mode to reproducing mode.

[Means and effects for solving the problem] In the present invention, the amount of change in the high frequency superimposed current between when the high frequency superimposed current is turned on and when the high frequency superimposed current is turned off is controlled within a predetermined range, so that the high frequency superposed current rises. The time required to raise the record information is within the time that does not pose a problem in reading the recorded information, so that reading can be performed reliably.

[Example] Hereinafter, the present invention will be specifically described with reference to the drawings.

FIGS. 1 to 7 relate to the first embodiment of the present invention.
The figure is a block diagram of the current change control system in the first embodiment, Figure 2 is the overall block diagram of the first embodiment, and Figure 3 is a block diagram of the high-frequency superimposed current ffi! Figure 4 is a characteristic diagram showing the relationship between laser diode noise and current variation, and Figure 5 is from light emission to read emission. A waveform diagram showing how the high-frequency superimposed current rises when switching. Figure 6 is a characteristic diagram showing the relationship between the current change and the time required for the high-frequency superimposed current to rise. Figure 7 shows how the amount of current change FIG. 7 is an explanatory diagram showing that as the frequency increases, the time required for the high frequency superimposed current to rise becomes longer.

As shown in FIG. 2, in the optical information recording and reproducing apparatus 1 of the first embodiment, an optical (academic) pickup 4 is arranged opposite to an optical disk 3 that is rotationally driven by a spindle motor 2. As shown in FIG. This optical pickup 4 is attached to a movable base 5, and is moved in the radial direction R of the optical disk 3 (that is, the direction that traverses the concentric or spiral tracks of the optical disk 3) by an optical pickup moving means such as a voice coil motor 6. It's up to you.

The optical pickup 4 has a laser diode 7,
The light beam of this laser diode 7 is focused and irradiated onto the optical disc 3 so that information can be recorded or reproduced. The laser diode 7 and a monitoring photodetector such as a bin photodiode 8 are housed in the housing 9 (see FIG. 1). The front light of the laser diode 7 is used for recording or reproduction, while the back light is received by the pinned photodiode 8, and the light emission range of the laser diode 7 is controlled by this photoelectric conversion output.

-F The pickup 4 has the following configuration.

The front light of the laser diode 7 is made into a parallel beam by the collimator lens 11, and then enters the polarizing beam splitter 12 as Pla light, where almost 100% of the light is transmitted. The light beam transmitted through the polarizing beam splitter 12 is made into circularly polarized light by a quarter-wave plate 13, and then condensed by an objective lens 14 and irradiated onto the disk 3.

The return light from the disk 3 is transmitted through the objective lens 14.1/
The light passes through the four-wavelength plate 13, becomes S-polarized light, enters the polarizing beam splitter 12, and is almost 100% reflected. This reflected light is incident on a critical angle prism 15, and the light that has passed through this critical angle prism 15 is incident on a four-split photodetector 16 located at a far field position.

The output signal of this photodetector 16 is input to an addition/subtraction circuit 17, and a reproduced signal is generated by the cylinder.

In addition, a focus error signal FER is generated by a pair of differential outputs that are divided into two sides parallel to the radial direction R.
A track error signal ``R'' is generated by a pair of differential outputs divided by an in parallel to the six tangent directions of the track.

These two signals FER and R are respectively applied via drive circuits 18 and 19 to a focusing coil 21 and a tracking coil 22 which form a lens actuator to bring the objective lens 14 into a focusing state and a tracking state. A holding servo system is constructed.

Incidentally, the output of the pin photodiode 8 (see FIG. 1) which monitors the front light of the laser diode 7 is input to the recording light transmission control section 24 and the APC circuit 25 constituting the reproduction light amount υll1I1 means.

The recording start group control unit 24 is for controlling the light emission amount in the recording mode to maintain an appropriate value, and its output is used to control the recording emission M of the laser diode 7 via the laser drive circuit 26. For example, the light emission length is maintained at a preset emission length.

On the other hand, the APC circuit 25 is for controlling the reproduction light amount (read light amount) in the reproduction mode to a constant value.
The automatic light 51υ1ffII is transmitted through the laser drive circuit 26 so that the read original image of the sea 1f diode 7 becomes a constant value.
will be held.

In this reproduction mode, the laser drive circuit 26 includes:
A high frequency superimposed signal from a high frequency mi module (hereinafter abbreviated as HFM) 27 serving as a high frequency signal generating means for reducing the noise of the laser diode 7 is transmitted to the DC of the △PC circuit 25.
It is input superimposed on the component.

In this embodiment, the drive current supplied to the laser diode 7 when the HFM 27 is 0N10FF is 11.12.
A current change amount control section 28 is provided to control the difference between the two, that is, the current change "ΔIop(12-11), to be within a certain value.

This current change Iυ control unit 28 detects the current flowing from the laser drive circuit 26 to the laser diode 7, and adjusts the high frequency IH ratio output os of the HFM 27 based on the detected output.
I am trying to make c into le11h.

The specific configuration of the peripheral area of the M flow change m control group 28 is described first.
As shown in the figure.

The anode of the sea 4r diode 7 is connected to GND,
Its cathode is connected to the collector of a transistor Q1 constituting the laser drive circuit 26, its emitter is connected to the negative VCC via a resistor R1, and its base is connected to the ΔPC circuit 25. It is connected to the output terminal, and controls the drive current I flowing through the radar diode 7 based on the output level of the APC circuit 25.

The input terminal of the APC circuit 25 is connected to the 7th node of the pin photodiode 8. The cathode of this pin photodiode 8 is connected to GND, and the anode is connected to the negative power supply terminal -Vcc via a resistor R2. The anode potential of this pin photodiode 8 changes according to the light weight from the sea 11 diode 7, and this change is detected by the ΔPC circuit 25, and is output as an error output from the not-shown quasi-cell in the APC circuit 25. Laser diode 7 is driven through transistor Q1! The JI current is controlled to be constant.

The collector of the transistor Q1 has l-I F M
The output end of HFM 27 is connected, and when the HFM 27 is in operation, a high frequency superimposed signal 1 osc is supplied. this)-IFM
27 goes up l-IFM ON/CUFFN/C and is switched to an active state or a non-active state.

Further, the drive current of the radar diode 7 is detected by a differential amplifier 31 that detects the voltage across the resistor R1. This differential amplifier 31 is constituted by an OP amplifier A1, and each input terminal of this OP amplifier A1 is connected to a resistor R.
3, connected to both ends of the resistor R1 via R4. The non-inverting input terminal of this OP amplifier A1 is connected to G through a resistor R5.
ND, and the inverting input terminal is connected to the output terminal via a resistor R6. The voltage corresponding to the drive current (2) detected by the differential amplifier 31 is converted into a digital signal by the A/D converter 32 and input to the CPU 33. This CPU 33 performs the above HFM during initial diagnosis.
27 into an operating state and a non-operating state, each drive current 1 is outputted via the A/D converter 32 in each state.
1.12, and from these differences the current change amount Δlop
Detect. This current change amount Δlop is converted into an analog signal via a D/A converter 34 and applied to one input terminal of a differential amplifier 35. This differential amplifier 35
At the other input terminal of the
A reference voltage ■r is applied, and this differential amplifier 3
5 is the near i difference voltage with respect to this reference voltage Vr HF M
It is applied to the oscillation output control terminal of 27.

In other words, when the 7IS flow change amount Δlop is smaller than the target value, the amplitude of the high frequency superimposed current of HF M 27 is increased, and on the other hand, when the current change amount Δlop is larger than the target value, the amplitude of the high frequency superimposed current of HF M 27 is increased. is made small, and the current change amount Δ[op is set to match the target value. In addition, the above basic t% lightning pressure Vr is calculated by the current change ΔI
OP is set to be between 2111A and 6I11, for example.

In this way, the HFM27 is set to 0N10FF, and the CPU 33 measures and sieves the amount of change Δ1of the current 11.12 flowing through the laser diode 7 at that time.
The amplitude of the high frequency superimposed current supplied from the HFM 27 to the laser diode 7 is controlled by the magnitude of op, and the amount of change Δ
Control is performed so that lop becomes the target value.

By setting this amount of change ΔIOp as the target value, the HF
The rise time t0 of the HFM 27 when the M27 is turned from OFF to ON is set to be less than or equal to a predetermined value.

By the way, when the operation of HFM27 is 0N10FF,
In other words, FIG. 3 shows the relationship between the laser drive current (2) and the output power P of the laser diode 7 when the high frequency signal is superimposed on a 0N10FF basis.

When the l-I FM 27 is turned on with the read power being RPa, the curve shown by B is obtained, and when it is turned OFF, the curve shown by A is obtained. When the high frequency superimposed signal 1 osc shown on the lower side of FIG. 3 is added to the DC component 11 and supplied to the laser diode 7, the output power is as shown on the right side of FIG. 3.

When the above 1-IFM27 is turned off, the current is I2
The change RΔlop when HFP27 is 0N10FF is
becomes I2-11.

If the amount of change Δ101) is increased, the fourth
"rJR/N noise (laser diode noise) shown in the figure
As can be seen from the characteristics of
If it is set to 1^) or more, the R/N noise can be kept small.

On the other hand, as shown in FIG. 5(a), at the same time as changing from the write light emission (WP) state to the read light emission (RP) state,
When IFM27 is turned on by the HFMON10FF control signal as shown in Fig. 1 (b), this HF
The high-frequency superimposed current l osc of M27 exhibits a rising characteristic as shown in FIG. In other words, since HFM27 is ONL, the high frequency superimposed current of IFM27 1o
Since sc does not rise instantaneously, it takes time ton for the read power RP to reach 90% of the stable state value RPa on the bin monitor output.

From FIG. 4, it can be seen that in the high frequency type, the method of increasing the current [OSC] can reduce noise, so it is desirable to increase it by a certain amount.

On the other hand, if the high frequency superimposed current 1 osc is increased, the time ton required for rising also becomes large, and the relationship is linear as shown in FIG.

FIG. 7 shows how the time ton required for rising increases as the high frequency superimposed current 1 osc increases.

When the write power WP is turned off and the read power is set, the trajectory follows the HFM OFF curve as shown by arrow C, and drops below the read power RP, reaching the DC level set according to the magnitude of the high-frequency superimposed current. It moves from 1a, Ib, or lc toward the characteristics when 11-1F is ON as shown by arrows a, b, and c.

From the locus of this transition, it can be seen that as the current change mΔlop increases, a longer time is required to shift to a predetermined read power state in the order of Δ1opa, Δ1opb, and Δloopc.

Therefore, if the amount of current change Δtop is increased, the line l-
An error that occurs when switching from the light emitting state to the read light emitting state and attempting to read, for example, the address of a pre-pit part, and the reading fails because it takes 0.1 seconds for the b read power state to reach a predetermined value. rate increases.

Therefore, in this embodiment, as shown in FIG.
27 is controlled so that the current change amount ΔIOp between ONI and OFF is constant, and the time ton until the read power RP reaches a predetermined level is set within a time that does not affect data reading. ing.

Accordingly, by applying C1 to J: in this embodiment, noise can be reduced and it is also possible to prevent the 1-Ray-1- reading from becoming distracting.

FIG. 8 shows the main parts of an optical system according to a second embodiment of the present invention.

In this second embodiment, a neutral density filter 41 is provided between the remeter lens 11 and the polarizing beam splitter 13 in the optical system of the first embodiment, which is not shown in FIG. , the laser beam irradiated onto the disc 3 is reduced. In other words, laser diode 7
By actually using only a part of the output beam instead of the entire output beam, the actual output level can be made larger than when the neutral density filter 41 is not used, and the current change amount Δ
Use under conditions where the lop is small.

In this way, by setting the output power of the laser diode 7 to be high and reducing the amount of light irradiated to the recording medium side with the filter 411, the condition (for example, 21IA to 6I^) where the current change interval ΔIOp is small (for example, 21IA to 6I^)'C-use is achieved. do.

In this case, the oscillation current 1 os as shown in FIG.
c is not controlled.

Further, the filter 41 reduces the level at which the output power, which is set to be high, is irradiated onto the disk 3 to a level suitable for the read power.

In FIG. 8, a mirror 42 is interposed between the 1/4 wavelength plate 14 and the objective lens 14.

This second embodiment has the advantage that it is not necessary to control the current change amount Δ1011 to a constant value.

In the first embodiment, the current change peak ΔIOp is controlled to be a constant value, but υI is controlled to be within a predetermined range.
In and 6 good.

[Effects of the Invention] As described above, according to the present invention, when the high frequency 19 tatami current is switched to the operating state and the throat operating state, the I3G is
Since the flow rate is controlled to be within a predetermined range, it is possible to read the time required for the high-frequency fI'J current to rise when switching from the write light emission state to the read light emission state. Settings can be made within a reasonable amount of time.

[Brief explanation of the drawing]

FIGS. 1 to 7 relate to the first embodiment of the present invention.
The figure shows the T1 flow change ffl fi in the first embodiment and the configuration diagram of the control system. Figure 2 is the overall configuration diagram of the first embodiment.
Figure 4 is a characteristic diagram showing the relationship between drive current and output power when high-frequency superimposed current is superimposed and when it is not superimposed. Figure 4 is a characteristic diagram showing the relationship between laser diode noise and current variation. Figure 5 is a waveform diagram showing how the high frequency FIF11 current rises when switching from write light emission to read light emission, and Figure 6 shows the relationship between the amount of current change and the time required for the high frequency superimposed current to rise. A characteristic diagram, FIG. 7 is an explanatory diagram showing that the time required for the high-frequency superimposed current to rise increases as the amount of current change increases, and FIG. 8 shows a part of the optical system in the second embodiment of the present invention. FIG. 1... Optical information recording/reproducing device 3... Disk 4... Optical head 7...
・Laser diode 8... Pin photodiode 24... Recording light emitting product control unit 25... APC circuit 27... High frequency superimposition module (HFM) 28...
Current change bus control unit 31...Differential amplifier 33...CPU Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 tOn Fig. 6 tOn Fig. 7 Fig. 8

Claims (1)

[Claims] 1. A semiconductor laser used as a light source for an optical head that has the function of irradiating a recording medium with a light beam and receiving the returned light, and a high-frequency laser that supplies a high-frequency superimposed current to reduce noise. An optical information recording/reproducing device comprising an oscillator, an on/off control means for controlling on/off of the high frequency oscillator, and an output control section for controlling the output of the semiconductor laser to a constant level, comprising: 1. An optical information recording and reproducing apparatus, comprising: a control means for controlling a difference in drive current to the semiconductor laser between when the semiconductor laser is turned on and when it is on to within a predetermined range. 2. A device according to claim 1, characterized in that a means is provided for increasing the output power of the semiconductor laser to reduce the amount of laser light irradiated onto the recording medium side, thereby making the difference in the drive current relatively small. optical information recording and reproducing device.