JPH117646A - Optical information recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording device capable of stably recording information by reducing noises caused by gain switching. SOLUTION: This device is constructed in such a manner that an LD driver is composed of a current source 102 for supplying a current equivalent to first power, a current source 101 for supplying a current equivalent to second power and a current source 104 for supplying a current equivalent to third power larger than the first power and smaller than the second power, the third current source 104 is switched ON in a recording area, the second current source 101 is switched ON/OFF according to a recording signal and thereby a semiconductor laser 221 is driven. A gain switching circuit switches a gain with another according to the driving operations of the second and third current sources so as to correct it to be a signal of a roughly fixed level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording apparatus for optically recording information on an information recording medium, and more particularly to an optical information recording apparatus of a single light source system.

[0002]

2. Description of the Related Art Conventionally, various types of recording media for optically recording information or reproducing recorded information, such as a disk, a card, and a tape, are known. Among these information recording media, there are those that can be recorded and reproduced and those that can only be reproduced. In recording information on a recordable recording medium, information is recorded as an optically detectable information pit array by scanning a light beam in the form of a minute spot modulated according to the recording information on an information track. .

When information is reproduced from a recording medium, an information pit array of an information track is scanned with a light spot having a constant power enough to prevent recording on the recording medium, and reflected light or transmitted light from the recording medium is read. Is detected, and the recorded information is reproduced based on the obtained detection signal. An optical head used for recording and reproducing information on and from such a recording medium is configured to be movable relative to the recording medium in the information track direction and in the direction across the track. The spot accesses a desired information track, and the information track is scanned to record or reproduce information.

An optical head is provided with a focusing lens for narrowing a light beam, and an objective lens is used as this lens. As such an objective lens,
The optical head body is held so as to be independently movable in the optical axis direction (focus direction) and the direction (tracking direction) orthogonal to the information track of the recording medium in each direction. Such an objective lens is generally held through an elastic member, and the focus and the movement of the objective lens in the tracking direction are generally driven by an actuator utilizing magnetic interaction.

FIG. 11 is a schematic plan view of an optical card. On the information recording surface of the optical card 401, a number of information tracks 402 are arranged in parallel to the LF direction.
The information track 40 is provided on the information recording surface of the optical card 401.
Home position 40 which is a reference position for access to 2
3 are provided. The information tracks 402 are 402-1 and 402-
2,402-3...

Further, as shown in FIG. 12, 50 tracking tracks are adjacent to each of these information tracks 402.
4-1, 504-2, 504-3... These tracking tracks are used as guides for auto tracking (hereinafter abbreviated as AT) for controlling the light spot so as not to deviate from the information track during light spot scanning during information recording and reproduction.

Such an AT control detects an offset (AT error) of a light spot from an information track and uses the detected information to control a tracking actuator for driving an objective lens in a tracking direction. It is controlled by returning to. That is, the servo control circuit moves the objective lens in the tracking direction (D direction) according to the AT error, thereby controlling the light spot so as not to deviate from the target information track.

In addition, when scanning an information track with an optical spot at the time of information recording and reproduction, an auto lens with respect to an objective lens is formed in order to form (focus) a light beam on the optical card surface into a spot of an appropriate size. Focus (hereinafter, AF
Is abbreviated). Such AF control detects a deviation (AF error) of a light spot from a focused state,
The detection signal is controlled by feeding it back to an AF control circuit for controlling a focus actuator for moving the objective lens in the optical axis direction. That is, by moving the objective lens in the focus direction according to the AF error, the control is performed so that the light spot is focused on the optical card surface (recording layer).

Here, in FIG. 12, S1, S2, S
Reference numerals 3, S4, S5, S6, and S7 indicate light spots irradiated on the information tracks of the optical card. AT control is performed using the light spots S1 and S5 of which the tracking tracks 504-2 and 504-3 are partially applied. Further, the light spot S3 is used to perform AF control, create information pits during recording, and read information pits during reproduction. Further, the information pits immediately after recording are verified using the light spots S2 and S4.
The information pit is read out at the time of reproduction using steps S6 and S7. In the drawing, 505-1 and 505-2 are light spots S.
3 and the information pit 505-
Numeral 1 indicates that the recording was performed by scanning the light spot in the L direction, and information pit 505-2 was performed by scanning the light spot in the F direction.

FIG. 13 is a block diagram showing an optical information recording / reproducing apparatus using an optical card as an information recording medium. In FIG. 13, reference numeral 221 denotes a semiconductor laser as a light source, which emits a laser beam having a wavelength of 830 nm polarized in a direction perpendicular to the track, for example. Reference numeral 223 denotes a collimator lens, 250 denotes a diffraction grating having a two-dimensional grating for splitting a light beam, and 226 denotes a polarization beam splitter. 227 is a quarter-wave plate, 228 is an objective lens, 229 is a spherical lens, 230 is a cylindrical lens, and 231 is a photodetector. Photodetector 231
Are light receiving elements 231a, 231b,
231c, 231e, 231f, and 231g, and one quadrant light receiving element 231d divided into four. Each of the above optical elements is integrated as an optical head,
The optical card 401 is configured to be able to access a desired information track. Reference numeral 261 denotes a laser driver (hereinafter, referred to as an LD driver), and 262 denotes an MPU.

Here, when information is recorded on the optical card 401 by the optical head, in accordance with a recording command from the MPU 262,
A drive current at a recording level is supplied to the semiconductor laser 221 by the LD driver 261. When reproducing information, the LD driver 261 supplies a reproduction level current to the semiconductor laser 22 according to a reproduction command from the MPU 262.
1 is supplied. The semiconductor laser 221 is driven in this manner, and the light beam emitted from the semiconductor laser 221 becomes a divergent light beam and enters the collimator lens 223. After being collimated by the collimator lens 223, the light enters the two-dimensional diffraction grating 250,
, The light beam is divided into seven effective light beams (0th-order diffracted light and 1st-order diffracted light in three directions).

The seven split light beams enter the polarization beam splitter 226 as a P-polarized light beam, pass through the light beam, enter the quarter-wave plate 227, and pass through the quarter-wave plate 227. Converted to circularly polarized light. The seven luminous fluxes converted into circularly polarized light are narrowed down into minute light spots by the objective lens 228 and irradiated onto the optical card 401. As shown in FIG. 12, the radiated light forms light spots S1 and S2.
And S6 (+ 1st-order diffracted light), S3 (0th-order diffracted light), S
4, S5 and S7 (-1st order diffracted light). The light spot S3 is recorded, reproduced, AF controlled, S1 and S5 as described above.
Is used for AT control, S2 and S4 are used for verifying information pits immediately after recording, and S6 and S7 are used for reproducing information on an information track adjacent to an information track irradiated with recording light.

As shown in FIG. 12, the spot positions on the optical card 401 are such that the light spots S1 and S5 are on the adjacent tracking tracks, and the spots S2, S3 and S4 are the information tracks 402- between the tracking tracks.
2, the spot S6 is on the information track 402-1 adjacent to the information track 402-2, and the spot S7 is the information track 402-3 adjacent to the information track 402-2.
Each is located above. The light spots S2 and S4 for verification are located before and after the light spot S3.

Thus, the light spot is irradiated onto the optical card 1, and a part of the light spot is reflected on the optical card surface and enters the objective lens 228. This reflected light is again transmitted to the objective lens 22.
8, the light beam is converted into a light beam whose polarization direction is rotated by 90 ° from that at the time of incidence by passing through a quarter-wave plate 227. Then, the light enters the polarization beam splitter 226 as an S-polarized beam, is reflected toward the detection optical system by its characteristics, and is separated from the incident light beam from the semiconductor laser 221. The detection optical system is a spherical lens 22
9, a cylindrical lens 230 and a photodetector 231; a spherical lens 229 and a cylindrical lens 2;
The AF control by the astigmatism method is performed by the combination of 30.

The seven light beams reflected from the optical card 401 are used as a light detector 231 composed of a plurality of light receiving elements.
Is detected by Each light receiving signal of the plurality of light receiving elements of the photodetector 231 is sent to the recording / reproduction gain switching circuit 265.
The recording / reproducing gain switching circuit 265 is a circuit for correcting the fluctuation of the signal level of each light receiving element caused by the modulation of the recording light spot, that is, the change of the recording power and the reproducing power, and keeping it at a substantially constant signal level. . In other words, MPU
The gain for amplifying the signal is switched in accordance with the recording / reproduction gain switching signal output from the H.262, so that the signal of each light receiving element is maintained at a constant signal level.

The output signal of the recording / reproduction gain switching circuit 265 is sent to an addition / subtraction circuit 263, a subtraction circuit 264, a selection switch 266, and an MPU 262. In the addition and subtraction circuit 263, as described later in detail, an AF control signal (focus error signal) and an information reproduction signal RF
The subtraction circuit 264 generates an AT control signal (tracking error signal) and sends it to the MPU 262.
The selection switch 266 includes an MPU 262 as described later.
A verifying signal is selected in accordance with a moving direction signal (a signal indicating a scanning direction of a light spot) from the camera. MPU2
At 62, a focus actuator and a tracking actuator (not shown) are driven based on the AF control signal and the AT control signal, and the objective lens 228 is displaced in the focus direction and the tracking direction.
Performs focus control and tracking control.

When reproducing information, the MPU 26
In step 2, information reproduction signals RF and RFR and RFL are each subjected to predetermined signal processing to generate reproduction data. Further, at the time of recording information, the verifying signal selected by the selection switch 266 is binarized, and this is compared with the recording signal to perform verifying at the same time as recording, that is, direct verifying.

FIG. 15 is a schematic diagram of the diffraction grating 250.
In the drawing, reference numeral 250a denotes an AT diffraction grating forming unit for generating an AT control light beam that becomes the spots S1 and S5;
Is a DV diffraction grating forming unit for generating direct verification light fluxes to be spots S2 and S4, and 250c is an RF for generating information reproduction light fluxes to be spots S6 and S7.
An R and RFL diffraction grating forming unit 301 is an incident light beam. Incidentally, the diffraction angle θn of the diffracted light is determined by θn = n · λ / d (where n is the order) from the grating pitch d and the wavelength λ of the incident light beam. The diffraction direction is determined by the inclination δ of the grating with respect to the incident light beam, and the direction is substantially perpendicular to the grating. The diffracted luminous flux and the zero-order luminous flux are
As shown in FIG. 12, the light is radiated onto the optical card as light spots S1 to S7 via an objective lens or the like.

The light power ratio of each light spot is such that a recording spot S3 (0-order diffracted light) is emitted when the recording light is emitted.
Is a recording light power for generating a recording pit, and a light spot S3.
The light power of the other spots is determined so that the recording pit is not generated. The light power ratio of each spot can be determined by setting the diffraction efficiency of each diffraction grating. That is, the light power of the light spot S3 is the sum of the zero-order light of each diffraction grating, and the light power of the other spots is set by the diffraction efficiency of the diffraction grating that generates the spot.

FIG. 16 is a specific circuit configuration diagram of the LD driver 261. In FIG. 16, reference numeral 801 denotes a current source that outputs a driving current corresponding to recording light power, and 802 denotes a current source that outputs a driving current corresponding to reproduction light power.
A switch 803 superimposes a recording light current on a reproduction light current in accordance with a recording signal. Reference numeral 221 denotes a cathode ground semiconductor laser. At the time of reproduction, the recording signal is off, and a current corresponding to the reproduction light power is supplied to the semiconductor laser 221 from the current source 802.

On the other hand, at the time of recording, the recording signal is on, the switch 803 is turned on or off in accordance with the recording signal WD, and the semiconductor laser 221 supplies the reproduction light current with the switch 803 on and off from the current source 801. The recording light current is supplied in a superimposed state. Since the semiconductor laser 221 is driven using only the positive power supply V _CC as is apparent from FIG. 16, the switch 803 uses a PNP transistor type. In order to further stabilize the optical power for reproduction and recording, a semiconductor laser 22 is generally used.
APC (automatic power control) for monitoring a part of the light output of No. 1 and applying feedback.

FIG. 14 shows the photodetector 231 of the apparatus shown in FIG.
Recording / reproduction gain switching circuit 265, addition and subtraction circuit 2
63, the subtraction circuit 264, and the selection switch 266 are shown in detail. First, 231 is a photodetector, which is a light receiving element 231.
a, 231b, 231c, 231e, 231f, 231
g and a four-divided light receiving element 231d. The light spot on the light receiving surface of each light receiving element indicates the reflected light of the light spot applied to the information track in FIG. The reflected light from the light spots S1 and S5 for AT control is
c, 231e, the reflected light from the AF control, recording, and reproducing light spot S3 is a four-divided light receiving element 231d, and the reflected light from the verifying light spots S2, S4 is the light receiving element 231.
b, 231f, light spots S6, S for RFR, RFL
The reflected light of No. 7 is received by the light receiving elements 231a and 231g, respectively.

The light receiving element 231b of the photodetector 231
To 231f are output to a recording / reproduction gain switching circuit 26.
5 are input to the corresponding gain switching circuits 265b to 265f. That is, the output signal of the light receiving element 231b is a gain switching circuit 265b, and the output signal of the light receiving element 231c is
Each of the output signals of the four light receiving element pieces of the gain switching circuit 265c and the four divided light receiving elements 231d is output from the gain switching circuit 265.
These are input to d1 to 265d2, respectively. The output signal of the light receiving element 231e is input to the gain switching circuit 265e, and the output signal of the light receiving element 231f is input to the gain switching circuit 265f. These gain switching circuits 265b to 265f
Represents the gain for amplifying the signal as described above.
The output signal of each of the light receiving elements 231b to 231f is held at a constant signal level by the gain switching operation of each gain switching circuit. Next, the output signal of the light receiving element 231a is input to the gain circuit 265a, and the output signal of the light receiving element 231g is input to the gain circuit 265g. Since these two light receiving elements use their signals only during reproduction and are not used during recording, gain switching is not necessary and only the gain corresponding to the reproduction power is obtained.

FIG. 17 shows gain switching circuits 256b to 256b.
The configuration of f is shown. In the following description, the output voltage / input current (that is, feedback resistance) is expressed as a gain. A feedback resistor Rr for determining a gain at the time of reproduction is connected between the-input and the output of the operational amplifier 701, and an analog switch 7 which is switched in parallel with this by a recording / reproduction gain switching signal.
04 and a series circuit of the feedback resistor Rw are connected. Here, as the recording / reproduction gain switching signal, a recording signal WD that is turned on and off in accordance with a pit to be recorded is used.
When the recording / reproduction gain switching signal is turned on, the analog switch 704 is turned on, and the feedback resistor Rr and the feedback resistor R are turned on.
The parallel resistance of w is set to the gain at the time of recording. The feedback resistor Rr is determined to have an appropriate gain so that the output of the operational amplifier is not saturated by the light receiving element signal during reproduction. Further, the gain at the time of recording, that is, the parallel resistance of the feedback resistor Rr and the feedback resistor Rw is determined to be the gain at which the output of the operational amplifier becomes the same as that at the time of reproduction by the signal of the light receiving element at the time of recording. For example, when the ratio between the reproduction light and the recording light is 1: 100, the gain at the time of reproduction and the gain at the time of recording are set to 100: 1.

FIG. 18 shows the R values of the light receiving elements 231a and 231g.
The configuration of the gain switching circuits 256a and 256g for FR and RFL is shown. A negative input and an output of the operational amplifier 901 are connected to a feedback resistor Rf that determines an appropriate gain so that the output of the operational amplifier is not saturated with a light receiving element signal during reproduction. In this case, the gain switching is unnecessary as described above. Here, as shown in FIG.
The output signal of 5e is output to a subtraction circuit 264, and the subtraction circuit 264 detects the difference to generate an AT control signal. The gain switching circuits 265d1 to 265d4 correspond to the four light receiving element pieces of the four-divided light receiving element 231d.
3 and the gain switching circuits 265d2 and 265
The output signals of d4 are added by adding circuits 601 and 602, respectively. The difference between the output signals of the adders 601 and 602 is detected by the subtractor 603, and the difference is output as an AF control signal. The output signals of the adders 601 and 602 are added by the adder 604 to create a sum signal of the four-divided light receiving element 231d. The sum signal of the four divided light receiving elements is output as an information reproduction signal RF.

The output signals of the gain switching circuits 265b and 265f are output to the selection switch 266,
One of the DV (direct verify) signals is selectively output in accordance with the moving direction signal from the controller. More specifically, if the scanning direction of the light spot is the F direction as shown in FIG. 12, the selection switch 266 is connected to the F side,
The signal on the light receiving element 231b side is M as a verifying signal.
Output to PU262. On the other hand, if the scanning direction of the light spot is the L direction, the selection switch 266 is connected to the L side, and the signal on the light receiving element 231f is output to the MPU 262 as a verifying signal. That is, since the verifying light spots S2 and S4 are radiated to both sides of the recording light spot S3, when the scanning direction of the light spot changes between the forward path and the return path of the optical card, the recording light spot is correspondingly changed. After that, the verifying signal reproduced by the light spot to be scanned is selected. The MPU 262 performs verification at the same time as recording using the selected verification signal.

[0027]

In the above-mentioned conventional example, the recording / reproduction gain switching circuit 265 modulates the recording light spot, that is, the signal level of each light receiving element caused by a change in the recording light power and the reproduction light power. Is compensated for. However, depending on the characteristics of the recording medium, especially when an organic recording medium is used, the reflectance of the recording medium changes over time. That is, if the same track is scanned a plurality of times with the same optical power, the reflectance of the recording medium decreases from the solid line to the one-dot chain line as shown in FIG. This is more remarkable as the recording power is higher. Therefore, when the reproduction light deteriorates and the signal level is corrected using the recording / reproduction gain switching circuit, the ratio of the recording / reproduction light power and the ratio of the recording / reproduction gain are increased according to the decrease in the reflectance. There is a need. This ratio is between 100 and 20
It becomes 0.

However, when the recording / reproducing light power ratio is large as described above, noise is generated in the output of the gain switching circuit due to the delay of the response characteristic of the amplifier of the gain switching circuit. FIG. 20A shows a recording signal WD, FIG. 20B shows a recording light emission waveform based on a recording power Pw and a reproduction power Pr, and FIG.
0 (c) indicates a response characteristic of the gain switching circuit. Here, originally, the output signal is corrected to a constant level by the gain switching operation of the gain switching circuit.
If the response of the amplifier of the gain switching circuit is slow, a delay occurs in the gain switching operation. Therefore, the gain should be at a constant level as shown in FIG. 20D. However, a component due to the response delay remains, and this is noise. Appears at the output of the gain switching circuit. In particular, when switching from the recording light power to the reproduction light power, a large noise is generated, and there is a problem that the S / N of the AT, the AF control signal and the verifying signal is deteriorated.

Further, in the recording / reproduction gain switching circuit, FIG.
Since the feedback resistance value is switched by turning on / off the analog switch as shown in FIG. 7, there is a problem that charge injection noise from the analog switch is increased by the amplifier when the analog switch is switched, and large spike noise is generated. . FIG. 21 illustrates this problem.
This will be described with reference to FIG. 21A shows the recording signal WD, FIG. 21B shows the photocurrent of the light receiving element, FIG. 21C shows the set gain of the gain switching circuit, and FIG. 21D shows the output waveform of the gain switching circuit. I have.

First, when reproducing light is emitted, the light receiving element generates a photocurrent ir corresponding to the reproducing light as shown in FIG. In this case, the gain of the gain switching circuit is as shown in FIG.
As shown in FIG. 21C, the output of the Rr and gain switching circuit is shown in FIG.
(Ir × Rr) as in (d). When the recording light is emitted, the light receiving element generates a photocurrent ir as shown in FIG. In this case, the gain of the gain switching circuit is Rr as shown in FIG. 21C, and the output of the gain switching circuit is ir × Rr as shown in FIG. When the recording light is emitted, the light receiving element generates a photocurrent iw as shown in FIG. In this case, the gain of the gain switching circuit is Rr · Rw / (Rr + R) as shown in FIG.
w), the output of the gain switching circuit is as shown in FIG.
iw · Rr · Rw / (Rr + Rw). iw ・ Rr
Rw / (Rr + Rw) is set to be equal to ir × Rr.

Here, when the analog switch is turned on / off by a gain switching signal, charge injection noise is generated at the input / output terminal of the analog switch as shown in FIG. This noise is generated when charge is injected into the input / output terminal by capacitive coupling through the switching gate when the switch is switched. In general, the amount of noise is defined by the amount of charge. Here, the time when noise occurs is considered as a predetermined time, and is treated as spike noise. Therefore, when this noise is represented by In, FIG.
As shown in (c), in is superimposed on the photocurrent. Here, the output of the gain switching circuit when reproducing light is emitted is shown in FIG.
As shown in (d), (ir × Rr) is a signal component and (in
× Rr) is a spike noise component at the time of switching. When recording light is emitted, iw · Rw · Rr / (R
w + Rr) is a signal component, and inRwRr / (Rw + R)
r) is a noise component. The S / N, which is the ratio between the signal component and the noise component, is as follows: S / N = Rw ÷ [(Rw · Rr) / (Rw + Rr)] × (iw / in) ≒ iw / in However, Rr >> Rw.

The spike noise is generated as noise having a large peak because the gain is large even if the photocurrent is small. Also, as shown in FIG. 21D, spike noise is small when switching from reproduction to recording gain, but becomes large when switching from recording to reproduction gain. In this manner, the power modulation component is originally removed by the gain switching operation, and the signal should have a constant level. However, spike noise is generated according to the gain switching timing as shown in FIG. Such spike noise degrades the signal quality and makes the operation of the device unstable. In particular, when verification is performed simultaneously with recording using a verification signal, an erroneous verification may be performed.

FIG. 22A shows a recording light emission waveform, and FIG.
(B) is an output waveform of the gain switching circuit. The spike-like noise indicates noise due to turning on / off of the analog switch as described above. FIG. 22 (c) shows a verifying signal when there is no noise, and FIG. 22 (d) shows a binary signal thereof. However, when noise is generated as shown in FIG. 22B, the noise is superimposed on the verifying signal as shown in FIG. 22E, and when this is binarized, the noise is affected by the noise as shown in FIG. As a result, a pseudo signal as indicated by A and B is generated in addition to the original binary signal. Therefore, even when information can be correctly recorded, there is a problem that a verification error occurs due to a pseudo signal and erroneous verification is performed.

In addition, when the power of the semiconductor laser decreases, the astigmatic difference increases and the size of the light spot changes. Therefore, the light spot is modulated by the light spot during recording, that is, the light spot is changed by the change in the recording power and the reproduction power. However, there is a problem that the signal of a constant level cannot be obtained due to a change in the magnitude of the signal. Such problems can be alleviated to some extent by using an amplifier having a high response characteristic, an analog switch having a small switching noise, and a semiconductor laser having a small astigmatic difference. There was a problem of inviting high prices.

The present invention has been made in consideration of the above-described conventional problems, and has as its object to provide an optical information recording apparatus capable of reducing noise generated due to gain switching and stably recording information. And

[0036]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light source, means for driving the light source according to a recording signal,
A means for recording information by scanning an information track of an information recording medium with a light beam emitted from the light source and intensity-modulated according to a recording signal, and a light detector for detecting light passing through the recording medium, A gain switching circuit for removing a modulation component due to a recording signal from an output signal of the photodetector;
A first current source that supplies a current corresponding to the power of the first current source, a second current source that supplies a current corresponding to the second power,
And a third current source for supplying a current corresponding to a third power that is greater than the first power and less than the second power, wherein the third current source is turned on in a recording area, and a recording signal is output. The light source is driven by turning on and off a second current source in response thereto, and the gain switching circuit switches a gain corresponding to a driving operation of the second and third current sources. This is achieved by an optical information recording device.

Another object of the present invention is to provide a light source, means for driving the light source in accordance with a recording signal, and a light beam emitted from the light source and intensity-modulated in accordance with the recording signal. Means for scanning the information track to record information, a photodetector for detecting light passing through the recording medium, a current-voltage converter for converting a photocurrent of the photodetector into a voltage signal, Connected to the output of the current-to-voltage converter,
And an attenuator for switching an amount of attenuation in accordance with a recording signal.

[0038]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, a first embodiment of the present invention will be described. First, the overall configuration of the optical information recording / reproducing apparatus according to the present embodiment is the same as that shown in FIG. 13, and the optical card shown in FIG. 11 is used as a recording medium. However, in the present embodiment, FIG.
The driver circuit of FIG. 1 is used as the LD driver 261 and the circuit of FIG. 2 is used as the gain switching circuits 265b to 265f in the recording / reproduction gain switching circuit 265 of FIG.

First, the configuration of the LD driver shown in FIG. 1 will be described. In FIG. 1, reference numeral 221 denotes a semiconductor laser which is a light source for recording and reproduction, and uses a cathode ground. Reference numeral 101 denotes a current source for supplying a driving current corresponding to the recording power Pw to the semiconductor laser 221. Reference numeral 104 denotes a power Pv that is not recorded during non-recording.
Is a current source that supplies a drive current corresponding to the power to the semiconductor laser 221, and 102 is a current source that supplies a drive current corresponding to the power for reproduction Pr to the semiconductor laser 221. Also,
Reference numeral 103 denotes a switch driven according to the recording signal WD,
05 is on in response to the recording / reproduction gain switching signal SG2,
This is a switch that is driven off. The recording / reproduction gain switching signal SG2 is a signal that turns on in the recording area and turns off in other cases. Recording signal WD, recording / reproduction gain switching S
G2 is supplied from the MPU 262 to the LD driver 261.

The MPU 262 sets the recording signal WD and the recording / reproduction gain switching signal SG2 to off during the information reproducing operation, and the switches 103 and 105 are off.
Therefore, the current I of the current source 102 is supplied to the semiconductor laser 221.
Since only r is supplied, the reproducing light of the power Pr corresponding to the current Ir is emitted. The power Pr is a power at which the reflectivity does not become lower than a predetermined level even if the track of the optical card is scanned many times, that is, the reproduction light does not cause a problem.

Next, during the recording operation, the recording signal WD changes between on (high level) and off (low level), and a pit is recorded on the optical card when the recording signal WD is on. In the present embodiment, the case where the recording signal WD is off is called a non-recording mode, and the case where it is on is called a recording mode. MPU26
2 is a recording / reproduction gain switching signal S in the non-recording mode.
G2 is turned on, and the switch 105 is turned on. As a result, a current (Ir + Iv) obtained by superimposing the current Iv of the current source 104 on the current Ir of the current source 102 is supplied to the semiconductor laser 221 and the power Pv corresponding to the current (Ir + Iv) is supplied.
Emits the non-recording light. The power Pv is a power at which the reflectance does not become lower than a predetermined level even if the track on the optical card is scanned once or a few times, that is, the reproduction light is not degraded at a predetermined scanning frequency or less.
The power Pv is higher than the power Pr at which no pit is formed on the optical card.

On the other hand, in the recording mode, the MPU 262
Turns on the recording / reproduction gain switching signal SG2, turns on the recording signal WD, and supplies the semiconductor laser 221 with a current obtained by superimposing the current Iw of the current source 101 on the current Ir of the current source 102 and the current Iv of the current source 104. This current (Ir + I
v + Iw), and emits a recording light having a power Pw according to the power. The power Pw is a level at which the reflectance is sufficiently reduced when the light is irradiated onto the optical card, that is, a power at which a pit is formed on the optical card, and is higher than the power Pv. In the present embodiment, since the semiconductor laser 221 is driven using only the positive power supply V _CC , the switches 103 and 105 are PNP transistor type switches. Although not shown, in order to further stabilize the optical power for reproduction and recording, APC (auto power control) for monitoring a part of the optical output of the semiconductor laser 221 and applying feedback is performed.

Next, the configuration of the gain switching circuit of FIG. 2 will be described. In FIG. 2, first, a feedback resistor Rr is connected between the (−) input and the output of the operational amplifier 112.
An analog switch 110 driven by a recording signal WD
And a feedback resistor Rw connected in series with the analog switch 111 driven by the recording / reproduction gain switching signal SG2.
And a feedback resistor Rv connected in series with the feedback resistor Rr. Here, the recording / reproduction gain switching signal S
G1 is a signal that is turned on / off according to the recording signal.
As described with reference to FIG. 1, the recording / reproduction gain switching signal SG2 is a signal that is turned on in the recording area. These signals are supplied from the MPU 262, respectively.

Here, when the MPU 262 turns off both the recording / reproduction gain switching signals SG1 and SG2, the analog switches 110 and 111 are turned off, so that only the feedback resistor Rr contributes to the gain. The gain at this time is a gain Gr corresponding to the power at the time of reproduction, and the feedback resistance Rr is determined to an appropriate value so that the output of the operational amplifier 112 is not saturated with the light receiving element signal in the reproduction mode. Next, the MPU 26
When the recording / reproduction gain switching signal SG2 is turned on and the recording / reproduction gain switching signal SG1 is turned off, the analog switch 111 is turned on and the analog switch 110 is turned off, so that the parallel resistance of the feedback resistor Rr and the feedback resistor Rv becomes the gain. Contribute. The gain at this time is a gain Gv corresponding to the power in the non-recording mode, and the feedback resistance Rr and the feedback resistance R
The parallel resistance value with v is determined so that the output of the operational amplifier 112 is the same as that in the reproduction mode in the signal of the light receiving element in the non-recording mode.

When the recording / reproduction gain switching signal SG2 is turned on and the recording / reproduction gain switching signal SG1 is turned on, both the analog switches 110 and 111 are turned on. Contributes to the gain. The gain at this time becomes a gain Gw corresponding to the power in the recording mode, and the feedback resistance R
r, the feedback resistance Rw and the parallel resistance value of the feedback resistance Rv are:
The output of the operational amplifier 112 is determined by the signal of the light receiving element at the time of recording so as to be the same as that at the time of reproduction. For example, when a recording medium having the characteristics shown in FIG. 19 is used, if the ratio of the power Pw in the recording mode, the power Pv in the non-recording mode, and the power Pr in the reproduction mode is set to about 100: 10: 1, the power Pv The reproduction light does not deteriorate in one scan, and the ratio of the gain Gw in the recording mode, the gain Gv in the ratio recording mode, and the gain Gr in the reproduction mode at that time is 1: 1.
0: 100.

Next, a specific operation of the present embodiment will be described. First, when reproducing information on an optical card, M
The PU 262 turns off the recording signal WD, turns off the recording / reproduction switching signal SG1, turns off the recording / reproduction switching signal SG2, and supplies only the current Ir of the current source 102 to the semiconductor laser 221. Thus, the semiconductor laser 221 emits light with the reproduction light power Pr proportional to the current Ir. Further, as described above, the light beam emitted from the semiconductor laser 221 is divided into seven light spots via the optical system and is irradiated on the optical card. On the other hand, the seven light beams reflected from the optical card are detected by the respective light receiving elements of the photodetector 231 and the detected light receiving signals are respectively sent to the corresponding gain switching circuits of the recording / reproduction gain switching circuit 265. At this time, since the recording / reproduction gain switching signal SG1 is set to off and the recording / reproduction gain switching signal SG2 is set to off, the gain Gr of the gain switching circuit is determined only by the feedback resistor Rr. The signal is amplified and output, and an AT and AF control signal and an information reproduction signal are generated.

On the other hand, when recording information on an optical card,
When the recording light spot S3 reaches the recording area of the target track, the MPU 262 outputs the recording / reproduction gain switching signal SG2.
Is turned on, and the recording signal WD is turned on / off according to the recording information to start recording. This recording control will be described with reference to FIG. 3A shows the recording signal WD, and FIG. 3B shows the emission waveform of the semiconductor laser 221. The recording signal is off in the area, turned on in the area, and turned off in the area. First, when the recording signal WD is turned off in the area, that is, in the non-recording mode, the recording / reproduction gain switching signal SG2 is on as shown in FIG. 3F, so that the switch 105 is turned on and the semiconductor laser 221 is turned on. Are supplied with the current (Ir + Iv) of the current sources 102 and 104. Therefore, in the region, the semiconductor laser 221 is (Ir) as shown in FIG.
+ Iv) to emit light at the non-recording light power Pv corresponding to (+ Iv)

Since the recording / reproduction gain switching signal SG1 is turned on and off in accordance with the recording signal WD, FIG.
Is off in the region as shown in FIG. Thereby, in the gain switching circuit of FIG. 2, the analog switch 110 is turned off,
Also, since the gain switching signal SG2 is on, the other analog switch 111 is on. Therefore, in this state, the gain Gv of the gain switching circuit is determined by the parallel resistance value of the feedback resistors Rr and Rv, and Gv = Rr · Rv / (Rr + Rv) <Gr. The output Vv of the gain switching circuit at this time is as follows, where the photocurrent of the light receiving element is PIv: Vv = PIv · Rr · Rv / (Rr + Rv)

Next, as shown in FIG. 3A, when the recording signal WD is turned on and the area is reached, the switch 103 is turned on in the LD driver of FIG.
The total current of the currents Ir, Iv and Iw of 1, 103 and 104 is supplied. Accordingly, in the region, as shown in FIG. 3B, the semiconductor laser 221 supplies the current (Ir + Iv + Iw).
At the recording light power Pw corresponding to. In addition, since the recording / reproduction gain switching signals SG1 and SG2 are both on in the region as shown in FIGS. 3E and 3F, both the analog switches 110 and 111 are on in the gain switching circuit. Accordingly, in the gain switching circuit, all of the feedback resistors Rr, Rv, and Rw are in a state of being connected in parallel, and the gain Gw is given by Gw = Rr · Rv · Rw / (Rr · Rv + Rv · Rw +
Rr · Rw) <Gv <Gr

The output V of the gain switching circuit in this case is
w is the photocurrent of the light receiving element as PIw, and Vw = PIw · Rr · Rv · Rw / (Rr · Rv + Rv)
Rw + RrRw). Here, as for the output of the gain switching circuit, assuming that the output at the time of reproduction is Vr, the ratio of the optical power and the gain of the gain switching circuit are set so that Vr = Vv = Vw.

Next, as shown in FIG. 3A, when the recording signal WD is turned off and the area again enters the non-recording mode, the switch 103 of the LD driver is turned off, and the current sources 102 and 105 are connected to the semiconductor laser 221. The currents Ir and Iv are supplied. Accordingly, the semiconductor laser 221 emits light at the non-recording light power Pv as shown in FIG. In the area, the recording / reproduction gain switching signal SG1
Is off and SG2 is on, the analog switch 110 of the gain switching circuit is off and the analog switch 111
Is turned on, and the feedback resistors Rr and Rv are connected in parallel. Therefore, in the region, the gain of the gain switching circuit is Gv, which is the same as the gain of the region.

Here, noise is generated in the output of the gain switching circuit due to delay of the response characteristic of the amplifier of the gain switching circuit, or ON / OFF of an analog switch of the gain switching circuit. However, in the present embodiment, the power of the semiconductor laser 221 is increased and the gain of the gain switching circuit is decreased in the non-recording mode during information recording as described above. Can be reduced. For example, when attention is paid to noise due to a delay in the response of the amplifier of the gain switching circuit, when the recording signal WD switches from ON to OFF as shown in FIG. 3A (when switching from the area), FIG. As described above, the optical output of the semiconductor laser 221 switches from the recording light power Pw to the non-recording light power Pv.

FIG. 3C shows the delay of the response characteristic of the amplifier of the gain switching circuit in this case. The output of the gain switching circuit that amplifies the photocurrent of the light receiving element is delayed due to the delay of the response characteristic, and it takes time to change from the photocurrent PIw to PIv. Since the gain of the gain switching circuit during this delay time has already been switched to Gv, FIG.
As shown in FIG.
Noise of magnitude v occurs. However, when compared with the conventional maximum value PIw · Gr of noise (see FIG. 20), the ratio becomes PIw · Gv / PIw · Gr = Gv / Gr (Gv <Gr), and the noise is reduced as compared with the conventional case. be able to. Also, when switching from the region, FIG.
As shown in (d), the magnitude of the noise can be reduced. Further, noise caused by turning on and off the analog switch of the LD driver is also similarly Gv / G
It can be reduced by r.

As described above, in this embodiment, the non-recording light power at the time of information recording is Pv (Pr <Pv <Pw), and the gain of the gain switching circuit at that time is Gv (Gr) corresponding to the non-recording light power Pv. >Gv> Gw), L
Noise generated at the output of the gain switching circuit due to delay of the response of the D driver, delay of the response of the amplifier of the gain switching circuit, or ON / OFF of the analog switch of the LD driver can be reduced. As a result, S / S of the verify signal, AT and AF control signals during the recording operation
N can be improved. In particular, the verify signal is set to 2
Since no pseudo signal is generated when the value is converted, a verify error does not occur and the recording operation can be stabilized even though the information is correctly recorded.

Next, a second embodiment of the present invention will be described. In the first embodiment, the semiconductor laser 221 emits light at a constant power in the non-recording mode, but the present embodiment performs intermittent light emission. However, the average power in the non-recording mode is such that when the track of the optical card is scanned once or a few times, the reflectivity does not become lower than a predetermined level. Power Pv which does not become the same. Further, the frequency of the intermittent light emission is set to a frequency sufficiently higher than the band of the photodetector 231 and the gain switching circuit, and is already averaged before the gain switching circuit at the time of the intermittent light emission, or the output of the gain switching circuit is averaged. To be done.

FIG. 4 shows the configuration of the LD driver used in this embodiment. In FIG. 4, the same parts as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Note that the gain switching circuit and other configurations are the same as those of the first embodiment. In FIG. 4, first, the switch 105 is driven not by the gain switching signal SG2 but by SG3.
This SG3 is an inverter circuit 1 for inverting the recording signal WD.
The AND circuit 106 generates an output signal 07, SG2 described in the first embodiment, and a pulse signal CLK having a predetermined frequency and a duty by performing an AND operation on the AND circuit 106. Also,
Switch 10 between current source 102 and semiconductor laser 221
8 and the gain switching signal SG2 is
The switch 108 is driven by the signal inverted in 9. This prevents the current Ir of the current source 102 from flowing to the semiconductor laser 221 in the recording area. The current Ir of the current source 102 is the reproduction light power Pr, the current source 101
The current Iw light power Pw at the time of recording, the current Iv of the current source 104 respectively correspond to the maximum Pv _max of the non-recording mode.

FIG. 5 shows signals of various parts of the LD driver of FIG. FIG. 5A shows a recording / reproduction gain switching signal S.
G2, FIG. 5B shows a clock CLK having a predetermined frequency, and FIG.
(C) is the recording signal WD. The recording / reproduction gain switching signal SG2 is the same as that of the first embodiment. First,
When recording information on an optical card, the recording spot S3 starts scanning from the end of the information track outside the recording area.
When it is out of the recording area, the MPU 262 turns off SG2 as shown in FIG. 5A, and at this time, the output S of the AND circuit 106 is independent of the clock CLK and the recording signal WD.
Since G3 is off, switch 105 is off.
On the other hand, when SG2 is off, the inverter circuit 109
Is turned on and the switch 108 is turned on, so that only the current Ir of the current source 102 is supplied to the semiconductor laser 221. Therefore, the semiconductor laser 221 has the reproduction light power P
Light is emitted at r.

Next, the recording spot S3 is set in the recording area.
Upon arrival, the MPU 262 sets SG2 as shown in FIG.
Is turned on, and the recording signal WD is supplied to the switch 103.
To start the recording operation. Here, when SG2 is on and recording signal
When the signal WD is off, that is, in the non-recording mode, FIG.
The clock CLK is output from the AND circuit 106 as shown in FIG.
Switch 105 outputs clock signal SG2.
It is driven according to the clock CLK. Therefore, the semiconductor laser 2
21 from the current source 104 during the ON period of the clock CLK.
Since the current Iv is supplied, the semiconductor laser 221
Pv corresponding to v _max And emit light intermittently. This non-record
Maximum power in mode Pv_max Is the aforementioned second power P
v and the average power in non-recording mode is
-The same power as Pv.

Next, when the recording signal WD is turned on and the recording mode is set, SG3 is turned off as shown in FIG.
The switch 105 is turned off, and the current Iv of the current source 104 is not supplied to the semiconductor laser 221. On the other hand, in this case,
Since the switch 103 is turned on, the current I
w is supplied to the semiconductor laser 221, and the semiconductor laser 22
1 emits light at an optical power Pw corresponding to the current Iw. Hereinafter, similarly, the semiconductor laser 221 is driven so as to emit light intermittently by the clock CLK in the non-recording mode and emit light with the optical power Pw in the recording mode to record on the information track.

In the present embodiment, since the semiconductor laser emits light intermittently in the non-recording mode, the maximum power in the non-recording mode can be increased, and the astigmatic difference in the non-recording mode of the semiconductor laser and the non-recording in the recording mode can be increased. The difference in the point difference can be reduced. As a result, a change in the size of the light spot in the recording mode and the non-recording mode due to the astigmatic difference is reduced, so that a signal of a constant level can be obtained. Also in this embodiment, it is needless to say that the noise due to the gain switching can be reduced to Gv / Gr as compared with the related art as in the first embodiment.

Next, a third embodiment of the present invention will be described. Also in the present embodiment, the configuration of the entire apparatus is shown in FIG.
As in the case of 3, the optical card shown in FIG. 11 is used as a recording medium. However, the gain switching circuit 265b of FIG.
It is assumed that the circuit shown in FIG. FIG.
Will be described. In FIG. 6, first, a current-voltage conversion circuit that converts a photocurrent into a voltage signal by a resistor Rf and an amplifier 120 is configured. That is, the photocurrent of the light receiving element (for example, light receiving element 231b) of the photodetector 231 in FIG. 14 flows through the resistor Rf, generates a voltage drop according to the photocurrent, and is input to the + terminal of the amplifier 120. .

The amplifier 120 has a negative terminal and an output terminal connected to each other. The input signal is subjected to impedance conversion by the amplifier 120 and output as a voltage signal. Amplifier 12
The output of zero have been divided by the resistors R ₁ and R ₂ which constitutes the attenuator, the resistor R ₂ analog switches 121 which are driven in accordance with the gain switch signal are connected in series. Here, when the reproduction light is emitted, the analog switch 121 is turned off, and the output signal of the amplifier 120 is output as it is. On the other hand, when the recording light is emitted, the analog switch 121 is turned on, so that the output of the amplifier 120 is divided and output by the resistors R ₁ and R ₂ . That is, the output voltage of the amplifier 120, the voltage signal obtained by multiplying the _{R 2 / (R 1 + R} 2) is output.

Next, a specific operation of this embodiment will be described with reference to FIG. FIG. 7A shows a recording signal WD, and FIG.
FIG. 7B shows the photocurrent of the light receiving element, and FIG.
Is the output signal. First, when the semiconductor laser 221 emits reproduction light, the light receiving element generates a photocurrent ir as shown in FIG. 7B, and the output signal of the amplifier 120 at this time is ir × as shown in FIG. 7C. Rf. FIG.
FIG. 7D shows the amount of attenuation by the dividing circuit including the resistors R ₁ and R ₂ , and FIG. 7E shows the output signal of the gain switching circuit. At the time of reproduction light emission, since the analog switch 121 is off, the attenuation is 1 as shown in FIG. 7D, and the output of the gain switching circuit is ir × Rf as shown in FIG. 7E.

On the other hand, at the time of recording light emission, FIG.
As shown in FIG. 7B, a photocurrent iw is generated in the light receiving element, and the output of the amplifier 120 becomes iw × Rf as shown in FIG.
In this case, since the analog switch 121 is turned on, the amount of attenuation is R ₂ / (R ₁ + R) as shown in FIG.
₂ ) The output of the gain switching circuit is iw as shown in FIG.
・ Rf · R ₂ / (R ₁ + R ₂ ) However, the value of R ₂ / (R ₁ + R ₂ ) is set so that the output voltage of the gain switching circuit is the same at the time of reproducing light emission and at the time of recording light emitting.

Here, when the analog switch 121 is turned on / off in response to the gain switching signal, spike current noise, that is, charge injection noise is generated at the input / output terminal of the analog switch 121 as described above.
When this noise and in, the noise current in the superimposed on the resistor R _2. Note that the on resistance of the analog switch 121 is negligible compared to the resistance values of the resistors R ₁ and R ₂ , and the off resistance is infinite. More specifically, when to turn on the analog switch 121 when switching to the recording light emitting, since one end of the analog switch 121 is connected to ground, the noise component superimposed on the resistor R ₁ is no longer. For this reason, S /
N can be improved. Incidentally, the conventional S / N in this case is iw / in.

On the other hand, when the analog switch 121 is turned off when switching to the reproduction light emission, the output of the gain switching circuit becomes i
n × R ₁ noise components appear. Since the signal component in this case is ir × Rf, the S / N becomes S / N = Rf / R ₁ · ir / in. By the way, the conventional S / N in this case is ir / in
It is. Here, Rf / R 1 >> set to _1, i.e., by the resistance value of Rf is larger than the resistance value of R _1, or the resistance value of R ₁ is set smaller than the resistance value of Rf,
S / N can be improved. For example, when switching to reproduction light emission with large spike noise, ir = 10, in
= 1, S / N = ir / in = 10 in the past, whereas in the present embodiment, by setting Rf = 10 and R ₁ = 1, S / N = 100, which is Thus, the S / N can be greatly improved. In addition, even when switching to recording light emission with small spike noise, the S / N can be improved as compared with the related art.

As described above, in the present embodiment, FIG.
Of the output signals of the gain switching circuits 256b to 256f
N can be greatly improved, and the quality of AT, AF control or verify signals can be significantly improved. In particular, A
In the case of the T and AF control signals, the influence of noise is low because the signal is a difference signal. However, in the case of the verify signal, the influence of noise appears as it is not the difference signal. A pseudo signal is generated due to the influence of the spike noise component. In this embodiment,
Since the spike noise component at the time of gain switching is reduced, no verification error occurs due to the pseudo signal even though the information has been correctly recorded, and the operation of the apparatus can be stabilized.

FIG. 8 shows a gain switching circuit used in the fourth embodiment of the present invention. In the present embodiment, the configuration of the current-voltage conversion circuit is different from that of the third embodiment. That is,
Connecting a resistor Rf between the negative terminal of the amplifier 120 and the output,
The input impedance of the current-voltage conversion circuit is reduced. The input impedance in this case is Rf / (1 + A
v). Av is the open loop gain of the amplifier 120. Normally, when converting the photocurrent of the light receiving element into a voltage signal, the higher the input impedance, the worse the linearity becomes, and the waveform is distorted. In the present embodiment, in addition to the effects of the third embodiment, the input impedance is reduced, so that the linearity can be improved regardless of Rf.

FIG. 9 shows the configuration of a gain switching circuit according to a fifth embodiment of the present invention. In the embodiment of FIG.
While connecting the analog switch 121 to the resistor R ₂ in series, in this embodiment, are connected in parallel to the analog switch 121 and resistor R _1. In this embodiment, when the recording light is emitted, the analog switch 121 is off and the amplifier 1 is turned off.
The output voltage of 20 is divided and outputted by resistors R ₁ and R ₂ . On the other hand, when the reproduction light is emitted, the analog switch 121 is turned on, and the output ir × Rf of the amplifier 120 is output as it is.

Here, the spike noise becomes larger when switching to the reproduction light emission, but when the analog switch 121 is turned on when switching to the reproduction light emission, the output of the gain switching circuit becomes ir × Rf. Signal component, in × R ₂
Is a noise component at the time of switching. S / N in this case
Is S / N = (Rf / R ₂ ) × (ir / in). In the third embodiment, as described above, S /
N is (Rf / R ₁ ) × (ir / in), and when the amount of attenuation by the split resistors R ₁ and R ₂ is smaller than 時 に during recording light emission, R ₁ > R ₂ is set. Therefore, the present embodiment can further improve the S / N as compared with the third embodiment.

FIG. 10 shows a gain switching circuit according to a sixth embodiment of the present invention. In the present embodiment, an amplifier 122 and resistors R ₃ and R ₄ are connected to the output of the third embodiment in FIG.
Is connected. By connecting an amplifier (buffer) having a high input impedance in this way, even if the output of the gain switching circuit is connected to a circuit system having a low input resistance, impedance conversion is performed by the inverting amplifier 122. Stable gain switching can be performed regardless of the circuit system.

[0072]

As described above, the present invention has the following effects. (1) By increasing the power in the non-recording mode during information recording and setting the gain of the gain switching circuit accordingly, the gain ratio at the time of information recording can be reduced.
It is possible to reduce noise caused by delay of the response characteristic of the amplifier at the time of gain switching or noise caused by turning on / off an analog switch. Therefore,
Even when a recording / reproducing gain ratio is increased by using a medium such as an organic recording medium, noise can be effectively reduced. (2) In particular, by reducing the noise of the verifying signal for performing the verifying at the same time as the recording, despite the fact that the recording was correctly performed by the pseudo signal due to the noise,
No verification error occurs, and the operation of the device can be stabilized. (3) By performing intermittent light emission in the non-recording mode, the difference between the astigmatic difference of the light source in the non-recording mode and the astigmatic difference in the recording mode can be reduced, and the change in the size of the light spot is also reduced. The output of the gain switching circuit does not change, and a signal of a constant level can be obtained. (4) Since the gain is switched using the attenuator to remove the power modulation component, spike noise due to the switch gain switching can be reduced. Therefore, the S / N of the AF / AT control signal and the verifying signal can be improved, and especially in the case of the verifying signal, a verify signal does not generate a verify error and the recording operation can be stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an LD driver according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a gain switching circuit according to the first embodiment of the present invention.

FIG. 3 is a time chart for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of an LD driver according to a second embodiment of the present invention.

FIG. 5 is a time chart for explaining the operation of the embodiment of FIG. 4;

FIG. 6 is a diagram illustrating a configuration of a gain switching circuit according to a third embodiment of the present invention.

FIG. 7 is a time chart for explaining the operation of the embodiment in FIG. 6;

FIG. 8 is a diagram illustrating a configuration of a gain switching circuit according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a gain switching circuit according to a fifth embodiment of the present invention.

FIG. 10 is a diagram illustrating a configuration of a gain switching circuit according to a sixth embodiment of the present invention.

FIG. 11 is a plan view of the optical card.

FIG. 12 is an enlarged view of a part of the optical card of FIG. 11;

FIG. 13 is a diagram illustrating a configuration example of an optical card information recording / reproducing device.

FIG. 14 is a diagram showing a photodetector and a signal processing circuit of the device of FIG. 13 in detail.

FIG. 15 is a diagram showing a diffraction grating used in the apparatus of FIG.

FIG. 16 is a circuit diagram showing an LD driver used in the device of FIG.

17 is a gain switching circuit 2 used in the device of FIG.
It is a circuit diagram showing 65b-265f.

18 is a gain switching circuit 2 used in the device of FIG.
It is a circuit diagram showing 65a, 265g.

FIG. 19 is a diagram showing characteristics of reflectance of an optical information recording medium, particularly an organic recording medium, with respect to optical power.

FIG. 20 is a diagram for explaining a problem due to a delay in response characteristics of an amplifier of the gain switching circuit.

FIG. 21 shows ON / OFF of an analog switch of a gain switching circuit;
FIG. 4 is a diagram for explaining generation of noise due to turning off.

FIG. 22 is a diagram for explaining generation of a verification error due to noise.

[Explanation of symbols]

 101, 102, 104 Current source 103, 105, 108 Switch 106 AND circuit 107, 109 Inverter circuit 110, 111 Analog switch 112 Operational amplifier 120 Amplifier 121 Analog switch 221 Semiconductor laser 231 Photodetector 261 LD driver 262 MPU 265 Recording / reproduction gain Switching circuit 401 Optical card

Claims (11)

[Claims] 1. A light source, means for driving the light source according to a recording signal, and a light beam emitted from the light source and intensity-modulated according to the recording signal, is scanned on an information track of an information recording medium. Information recording device, an optical detector for detecting light passing through the recording medium, and a gain switching circuit for removing a modulation component due to a recording signal from an output signal of the photodetector. Wherein the driving means comprises a first current source for supplying a current corresponding to a predetermined first power, a second current source for supplying a current corresponding to a second power, and a first power source. A third current source which supplies a current corresponding to a third power which is larger than the second power and which is smaller than the second power.
The current source is turned on, and the light source is driven by turning on and off the second current source according to the recording signal. The gain switching circuit corresponds to the driving operation of the second and third current sources. An optical information recording apparatus characterized in that the gain is switched by performing the above operation. 2. The apparatus according to claim 1, wherein the driving unit intermittently drives the third current source to emit light intermittently in a non-recording mode when a recording signal is off. The optical information recording device as described in the above. 3. An average power of the intermittent light emission is equal to the third power.
2. The optical information recording apparatus according to claim 1, wherein the power is substantially the same as the power of the optical information recording apparatus. 4. The optical information recording apparatus according to claim 1, wherein the light source irradiates a recording light spot with a verifying light spot after the recording light spot, and performs the verifying simultaneously with the recording. apparatus. 5. A light source, means for driving the light source according to a recording signal, and a light beam emitted from the light source and intensity-modulated according to the recording signal is scanned on an information track of an information recording medium. Means for recording information, a photodetector for detecting light passing through the recording medium, a current-to-voltage converter for converting a photocurrent of the photodetector to a voltage signal, and an output of the current-to-voltage converter. And an attenuator connected to the attenuator for switching the amount of attenuation according to the recording signal. 6. The optical device according to claim 5, wherein the current-to-voltage converter comprises a resistor for converting a photocurrent of the photodetector into a voltage signal, and an amplifier for amplifying the voltage signal. Information recording device. 7. The optical information recording apparatus according to claim 5, wherein the current-voltage converter comprises an amplifier and a resistor connected between the input and output of the amplifier. 8. The attenuator operates according to a recording signal with first and second resistors for dividing an output voltage of the current-to-voltage converter, and is connected in series with the second resistor. 6. The optical information recording apparatus according to claim 5, comprising a switching element. 9. The attenuator operates in accordance with a recording signal and first and second resistors for dividing an output voltage of the current-voltage converter, and is connected in parallel with the first resistor. 6. The optical information recording apparatus according to claim 5, comprising a switching element. 10. The optical information recording apparatus according to claim 5, wherein an amplifier having a high input impedance is connected to an output of said attenuator. 11. The light source follows a recording light spot and irradiates a verifying light spot onto a recording medium. 6. The optical information recording apparatus according to claim 5, wherein a modulation component due to the recording signal is removed.