JPH05282695A - Optical information recording device - Google Patents

Abstract

PURPOSE:To provide an optical information recording device which corrects the intensity of a laser light in accordance with the forming condition of a smallest pit during the recording of information. CONSTITUTION:The reflected light from an optical disk 1 during an information recording is received by a photodetector 21b and a signal B which has a voltage proportional to the reflected light intensity is outputted. The voltage of a signal B2 obtained from the signal B is held by in sample-and-hold circuits 25 and 26 by a pulse signal C which is generated by a timing pulse generating circuit 24 based on reference digital signals and corresponds to the end edge section of a pit section and by a pulse signal D corresponds to the center section of a non-pit section and the pulse width of the laser light irradiated from a laser diode 21a is corrected in a real time so that the differences of these voltages coincide with reference values all the time. Therefore, a pit, whose shape corresponds to a reference digital signal all the time, is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to EFM (Eight
The present invention relates to an improvement in an optical information recording device for an optical information recording medium such as an optical disc using the to fourteen modulation method.

[0002]

2. Description of the Related Art In recent years, a technique for recording a large amount of information on an optical information recording medium, for example, an optical disc such as a WO disc has become popular. In the case of recording an acoustic signal on an optical disc, for example, a method of digitizing the acoustic signal at the time of recording and recording the signal is generally used in order to eliminate distortion, noise, and the like at the time of reproduction. In addition, a CIRC (Cross Interleaved Reed-Solomon Code) is applied to a digitized acoustic signal (hereinafter referred to as a reference digital signal).
With the addition of parity for error correction,
Further, this is modulated by the EFM method to improve the reproduction characteristic.

By performing the above-mentioned EFM modulation, nine time widths, which are 3 to 11 times the predetermined reference time width T, are given as the time widths of the high level and low level of the reference digital signal. The optical disc is irradiated with laser light based on the reference digital signal to form a pit portion in the recording layer. For example, pulsed laser light having an intensity capable of forming a pit portion is irradiated during the high level period of the reference digital signal.

Further, the width of the pit portion formed on the optical disk is increased or decreased, or the lengths of the pit portion and the non-pit portion are changed depending on the intensity of the emitted light of the laser, so as to correspond to the reference digital signal. A pit composed of a pit portion and a non-pit portion may be formed. That is, if the intensity of the laser light is set to be high, the heat accumulated in the recording layer of the optical disk will be reduced when the light intensity is lowered and the formation of the non-pit portion is started after the pit portion is formed. It takes time to diverge, and the pit becomes long and wide. Further, if the intensity of the laser light is set low, it takes time for the recording layer to absorb heat when the optical disk is irradiated with the laser light, and the pit portion is formed short.

Therefore, before the information is recorded on the optical disc, the intensity of the laser light is changed to record the test information on the innermost peripheral portion of the optical disc, and the optimum intensity of the laser light is obtained to obtain the information. At the time of recording, information is recorded by setting the laser light intensity to this optimum light intensity. That is, the information recorded on the optical disk is reproduced and the eye pattern at this time is observed. In this eye pattern, as shown in FIG. 2, a voltage PWa in the positive direction and a voltage PWb in the negative direction are obtained from the AC reference level PWt, and the difference value (PW
Information is recorded by setting the optimum light intensity at which the value β obtained by dividing a−PWb) by the value of these sums (PWa + PWb) is zero. As a result, each of the pit portion and the non-pit portion can form a pit corresponding to the reference digital signal.

[0006]

However, even if the information is recorded with the optimum light intensity as described above, this optimum light intensity is measured at the innermost peripheral portion of the optical disk, and is recorded at other portions. Since the properties of the layers change and the intensity of laser light does not correspond to this change, pits that do not correspond to the reference digital signal may be formed. Further, the optical disc may have an eccentricity, and the optical pickup may be in an off-track state at the time of recording information. When the optical pickup that emits laser light follows eccentricity, or when it becomes off-track, the distribution state of laser light is a Gaussian distribution, so the same state as when the light intensity decreased, The formed pit does not correspond to the reference digital signal, and the jitter is deteriorated, and there is a problem that the error at the time of reproduction is increased.

Further, the output intensity and the oscillation wavelength of the laser change due to changes in the ambient temperature and the pits formed on the optical disc may not correspond to the reference digital signal.

As described above, when the pit does not correspond to the reference digital signal, the deviation between the pit and the reference digital signal becomes noticeable in the pit portion having a short time width.

In view of the above problems, it is an object of the present invention to provide an optical information recording apparatus capable of correcting the pulse width of laser light in accordance with the pit formation state when recording information.

[0010]

In order to achieve the above-mentioned object, the present invention corresponds to the information to be recorded and represents a period for irradiating laser light having an intensity capable of forming a pit portion. The signal level and the intensity of a predetermined intensity lower than the intensity
A second signal level representing a period for irradiating the light,
The first and second signal levels are based on a reference digital signal having a time width forming an arithmetic series that is an integral multiple of a predetermined reference time width, and a pulsed laser beam having a predetermined intensity for the optical information recording medium. In an optical information recording apparatus for forming a pit by irradiating the light, a light intensity detecting means for detecting the intensity of reflected light from the optical information recording medium at least when forming the pit, and a detection result of the light intensity detecting means High frequency component removing means for removing high frequency components of a predetermined frequency or higher in
A first detecting the reflected light intensity when the reference digital signal changes in level from the first signal level to the second signal level, based on the reflected light intensity from which the high frequency component has been removed by the high frequency component removing means. Based on the light intensity detection means and the reflected light intensity from which the high frequency component has been removed by the high frequency component removing means, a predetermined time has elapsed from the time when the level changed from the first signal level to the second signal level. A second light intensity detecting means for detecting the intensity of reflected light at the second signal level, and a difference between a value detected by the first light intensity detecting means and a value detected by the second light intensity detecting means, or The calculating means for calculating the ratio and the time width of the first and second signal levels of the reference digital signal are increased or decreased so that the calculation result of the calculating means substantially agrees with a predetermined reference value. A recording signal and forms a recording signal generating means, based on the recording signal, to propose an optical information recording apparatus and a laser driving means for driving the laser.

[0011]

According to the present invention, the light detecting means detects the light intensity of the reflected light from the optical information recording medium at the time of pit formation, and the high frequency component of a predetermined frequency or higher in the detection result is removed by the high frequency component removing means. To be done.
As a result, an erroneously detected component due to a scratch or the like formed on the optical information recording medium, that is, a noise component is removed. When the reference digital signal is changed by the first light intensity detecting means from the first signal level having the minimum time width to the second signal level based on the reflected light intensity from which the high frequency component has been removed, The reflected light intensity at is detected. For example,
The reflected light intensity detected here is the reflected light intensity at the rear end portion of the pit portion having the minimum time width formed on the optical information recording medium. When the reflected light intensity is high, the formation of the pit portion is formed. Is insufficient, and when the pit part is formed, that is, the first
The amount of heat supplied to the optical information recording medium by the laser light at the signal level is too low, that is, the pulse width of the laser light is too short, and when the reflected light intensity is low, the pit portion is excessive. It means that the amount of heat supplied by the laser light at the time of forming the pit portion is too high, that is, the pulse width of the laser light is too long. Further, based on the reflected light intensity from which the high-frequency component has been removed, the second light intensity detecting means causes a predetermined time to elapse after a time when the level changes from the first signal level to the second signal level. The reflected light intensity at the second signal level is detected. The reflected light intensity detected here is the reflected light intensity from the non-pit portion. Further, the calculation means calculates a difference or a ratio between the detection value by the first light intensity detection means and the detection value by the second light intensity detection means, and the calculation result substantially matches the predetermined reference value. As described above, the recording signal generation unit generates the recording signal in which the time width of the first and second signal levels of the reference digital signal is increased or decreased. Based on this recording signal, the laser is driven by the laser driving means, and the pulse width of the laser light is increased or decreased.

[0012]

1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is an optical disc which is an optical information recording medium, and 2 is an optical information recording device (hereinafter referred to as a recording device). As is well known, at the time of recording information, the optical disc 1
Is rotated by a spindle motor or the like (not shown).

The recording device 2 includes an optical pickup 21 and an RF.
It is composed of an amplifier 22, a low-pass filter 23, a timing pulse generating circuit 24, sample-hold circuits 25 and 26, an arithmetic circuit 27, a recording signal generating circuit 28, and a laser driving circuit 29, and is well-known EFM modulated. The reference digital signal A is input, and when the reference digital signal A is at a high level, a high-intensity laser beam capable of forming a pit portion is emitted to the optical disc 1, and the reference digital signal A is low.
When the level is reached, low intensity laser light capable of forming a non-pit portion and reproducing information is emitted to the optical disc 1.

The optical pickup 21 includes a laser diode 21a, a photodetector 21b, and a half mirror-21.
c, a lens 21d, and the like. The laser diode 21a emits laser light having an intensity corresponding to the current input from the laser drive circuit 29, and the laser light is emitted from the laser light.
Optical disk 1 through Fumira-21c and lens 21d
Is irradiated. As a result, a pit portion is formed on the optical disc 1 when the intensity of the laser light is high, and a non-pit portion is formed when the intensity of the laser light is low. Further, the reflected light from the optical disc 1 is reflected by the lens 21d and the Hafmira-21.
It is incident on the photodetector 21 b via c, is converted by the photodetector 21 b into an electric signal B having a voltage proportional to the intensity of reflected light, and is input to the RF amplifier 22. The signal B input to the RF amplifier is converted into a signal B1 amplified by a predetermined amplification degree, and then the low-pass filter 2
A signal B2 from which a high frequency component higher than a predetermined frequency has been removed by 3 is input to the sample and hold circuits 25 and 26. As a result, noise components due to scratches formed on the optical disc 1 are removed. Sample-hold circuit 2
5 and 26 are each a timing pulse generation circuit 24.
When the pulse signals C and D are input from, the voltage level of the signal B2 is detected and held, and the signals E and F having the held voltage are output.

The timing pulse generation circuit 24 receives the reference digital signal A, and the reference digital signal A has a time width three times the reference time width T (hereinafter referred to as 3T time width).
And a trailing edge that changes from a high level period to a low level period is detected, and a pulse signal C having a predetermined time width, for example, about 1/5 of the reference time width T is sampled and held in the sample-hold circuit. 25, and after detecting the falling edge where the reference digital signal A changes from the high level period to the low level period, the pulse signal C is delayed by, for example, about twice the reference time width T. The pulse signal D having an equivalent pulse width is output to the sample hold circuit 26. As a result, the sample hold circuit 2
A voltage corresponding to the reflected light intensity from the rear end portion of the pit portion Pa is held at 5, and a voltage corresponding to the reflected light intensity from the non-pit portion Pb is held at the sample hold circuit 26.

The signals E and F output from the sample hold circuits 25 and 26 are input to the arithmetic circuit 27. The arithmetic circuit 27 is composed of an operational amplifier and outputs a signal G having a voltage level obtained by subtracting the voltage of the signal E from the voltage of the signal F. This signal G is input to the recording signal generation circuit 28.

The recording signal generating circuit 28 is a reference digital signal A corresponding to the information to be recorded on the optical disc 1.
And a clock signal CP synchronized with this are input, and a signal G
A recording signal M obtained by correcting the reference digital signal A based on
To generate. This recording signal M causes the laser drive circuit 29
The laser diode 21a is driven through the recording medium to record information on the optical disc 1. Further, here, as the optical disc 1, for example, a recording layer is formed of a cyanine dye on a substrate on which a tracking groove is formed, and a gold reflection layer and a protective layer of an ultraviolet curable resin are further formed on the recording layer. The formed optical disc is used. Further, when the reference digital signal A is at a high level, the optical disc is irradiated with high-intensity laser light capable of forming a pit portion,
At the level, the optical disc is irradiated with low-intensity laser light capable of forming a non-pit portion, or the laser light irradiation is stopped to form pits on the recording medium.

As shown in FIG. 3, the recording signal generating circuit 28 includes a trailing edge pulse generating circuit 100 and a plurality of delay circuits 201 to 20.
6, charge / discharge circuit 207, voltage control circuit 300, signal synthesis circuit
It is composed of 400, a comparator 500 and a NOT circuit 600. The trailing edge pulse generation circuit 100, based on the clock signal CP, outputs the reference digital signal A at a high level and a low level.
The time width of the level is detected, and the time width of the high level is 3 to 6
When the time width is T, the positive pulse signals P3 to P6 having the reference time width T are output corresponding to each time width, and
When the level time width is 3 or 4T time width of the reference time width T, the positive pulse signals L3, L4 of the reference time width T are output corresponding to each time width.

The trailing edge pulse generation circuit 100 is composed of a shift register 111, NOT circuits 112 to 118, and 4-input AND.
The clock signal CP is input to the clock input terminal CK of the shift register 111, which is composed of the circuits 119 to 124.
The reference digital signal A is applied to the serial data input terminal AB.
Has been entered. Output terminal Qa of shift register 111
Is connected to the respective first input terminals of the AND circuits 123 and 124, and is connected via the NOT circuit 112 to the AND circuit.
119 to 122 are connected to the respective first input terminals. The output terminal Qb of the shift register 111 is an AND circuit.
A second input terminal of each of 119 to 122 and the signal synthesizing circuit 400 and A via the NOT circuit 113.
It is connected to the respective second input terminals of the ND circuits 123 and 124. The output terminal Qd of the shift register 111 is AN
It is connected to the third input terminal of the D circuit 119 and is NO
It is connected to the third input terminal of the AND circuit 123 via the T circuit 114. Output terminal Qe of shift register 111
Is the third input terminal of the AND circuit 120 and the AND circuit 12
3 is connected to the fourth input terminal of the NOT circuit 11
The fourth input terminal of the AND circuit 119 and the AND
It is connected to the third input terminal of circuit 124. The output terminal Qf of the shift register 111 is connected to the third input terminal of the AND circuit 121 and the fourth input terminal of the AND circuit 124, and is also connected to the fourth input terminal of the AND circuit 120 via the NOT circuit 116. It is connected. Shift register 111
The output terminal Qg of the AND circuit 122 is connected to the third input terminal of the AND circuit 122, and the AND circuit is connected via the NOT circuit 117.
It is connected to the 4th input terminal of 121. The output terminal Qh of the shift register 111 is connected to the AN via the NOT circuit 118.
It is connected to the fourth input terminal of the D circuit 122.

As a result, when the high-level time width of the reference digital signal A is 3 to 6T, the corresponding A
Pulse signals P3, P4 from the ND circuits 119, 120, 121, 122
P5 and P6 are output respectively. Further, when the low-level time width of the reference digital signal A is 3, 4T time width, the corresponding AND circuits 123, 124 output pulse signals L3, L3.
L4 is output respectively.

As shown in FIG. 4, each of the delay circuits 201 to 206 includes an NPN type transistor 211, 212 and a NOT circuit.
It is composed of circuits 213, 214, a diode 215, resistors R1 to R3, and a capacitor C1, and a predetermined positive voltage + V21, for example + 5V, is applied to the collector of the transistor 211. In addition, the emitter of transistor 211
A capacitor C1 is connected between the collectors, and the emitter is the collector and the diode 215 of the transistor 212.
And the input terminal of the NOT circuit 213. The anode of the diode 215 is grounded, and the output terminal of the NOT circuit 213 is connected to the input terminal of the NOT circuit 214. A resistor R2 is provided at the emitter of the transistor 212.
A predetermined negative voltage -V22, for example, -5V is applied through the base and the base is connected to one end of the resistor R3.

Further, the transistors of the delay circuits 201 to 206
The base of 211 is AND circuits 119 to 12 through a resistor R1.
The delay circuit 20 is connected to each of the 4 output terminals.
The other end of the resistor R3 in each of 1 to 206 is provided with a predetermined voltage v1 to v6 described later by the voltage control circuit 300.
Is being applied.

As a result, in the delay circuits 201 to 206, the delay circuit 201 to 206 delays from the rear end pulse generation circuit 100.
The ON / OFF state of the transistor 211 is switched by the pulse signals P3 to P6, L3 and L4 input to the pulse signal P3 to P3 from the output terminal of the NOT circuit 214.
Positive pulse signals Pd3 to Pd6, Ld3, Ld4 whose rear ends are delayed by a predetermined time t1 to t6.
Is output.

That is, as shown in FIG. 5, the pulse signal P3
~ P6, L3, L4 are input, and when the base voltage VE of the transistor 211 becomes high level, the transistor 211
Is turned on, the capacitor C1 is discharged, and
The input voltage Vin of the NOT circuit 213 becomes the voltage + V1, and N
The output voltage Vout of the OT circuit 214 becomes high level. When the base voltage VE of the transistor 211 becomes low level, the transistor 211 is turned off, and the capacitor C1 has a base voltage of the transistor 212 and a resistor R3.
A current flows based on the resistance value of the capacitor C1, and the charging of the capacitor C1 is started. As a result, the input voltage V of the NOT circuit 213
The in gradually decreases as the charging of the capacitor C1 progresses, and when the voltage becomes equal to or lower than the threshold voltage of the NOT circuit 213, NO
The output voltage Vout of the T circuit 214 becomes low level.

The charging / discharging circuit 207, as shown in FIG.
It is composed of PN type transistors 211 and 212, a diode 215, resistors R1 to R3, and a capacitor C1. The collector of the transistor 211 has a predetermined positive voltage + V21,
For example, + 5V is applied. In addition, the transistor
A capacitor C1 is connected between the emitter and collector of 211, and the emitter is connected to the collector of the transistor 212, the cathode of the diode 215 and the output terminal 216. The anode of the diode 215 is grounded, and a predetermined negative voltage -V22, for example, -5V is applied to the emitter of the transistor 212 through the resistor R2, and the base is the resistor R3. It is connected to one end.

A signal K, which will be described later, is input to the base of the transistor 211 via the resistor R1, and the resistor R3 is used.
A predetermined negative voltage −v is applied to the other end of the. As a result, in the charging / discharging circuit 207, as shown in FIG. 7, a signal K'in which the waveform of the high-level rear end of the signal K drops with a constant slope is output.

The voltage control circuit 300, as shown in FIG.
Operational amplifiers 301 to 304, one-circuit two-contact switch 305,
Resistors R11 to R24, r1 to r8 and variable resistors VR1 to VR3
It is composed by. The inverting input terminal of the operational amplifier 301 is connected to the output signal G of the operational circuit 27 via the resistor R11.
Is input and is also connected to its output terminal via resistor R12. The non-inverting input terminal of the operational amplifier 301 is connected in series via the resistor R13.
The positive voltage + V31 and the negative voltage -V32 are applied to both ends of the resistor R14 and the variable resistor VR1 which are connected to the connection point of the variable resistor VR1 and the variable resistor VR1, respectively. As a result, the voltage Vh is applied to the non-inverting input terminal of the operational amplifier 301.

The inverting input terminal of the operational amplifier 302 is a resistor.
It is connected to the contact piece 305a of the switch 305 via R15, the first contact 305b of the switch 305 is connected to the output terminal of the operational amplifier 301, and the second contact 305c is grounded. Further, the inverting input terminal of the operational amplifier 302 is connected to its output terminal via the resistor R16. Also, operational amplifier
The non-inverting input terminal of the 302 is connected to the connection point between the series-connected resistor R18 and the variable resistor VR2 via the resistor R17, and one end of the series-connected resistor R18 and the variable resistor VR2 is It is grounded and a positive voltage + V33 is applied to the other end. As a result, the voltage Ve is applied to the non-inverting input terminal of the operational amplifier 302.

The non-inverting input terminal of the operational amplifier 303 is connected to the output terminal of the operational amplifier 302 via the resistor R19 and to its output terminal via the resistor R20. Further, the non-inverting input terminal of the operational amplifier 303 is connected to the connection point between the series-connected resistor R22 and the variable resistor VR3 via the resistor R21, and the series-connected resistor is connected.
One end of R22 and the variable resistor VR3 is grounded, and the other end is applied with a negative voltage -V34. This allows the operational amplifier
The voltage Vg is applied to the non-inverting input terminal of 302.

Further, the resistors r1 to r5 are connected in series, and the resistors r6 to r8 are connected in series to form a resistor r.
One end of each of r1 and r6 is connected to the output terminal of the operational amplifier 303. The other ends of the resistors r5 and r8 are grounded.

The non-inverting input terminal of the operational amplifier 304 is grounded, and the inverting input terminal is connected through the resistor R23 to the operational amplifier 302.
It is connected to the output terminal of and also connected to that output terminal through the resistor R24.

According to the voltage control circuit 300 having the above configuration, the operational amplifier 301 outputs the voltage Vd obtained by subtracting the voltage of the signal G from the voltage Vh. This voltage Vd is
It is input to the operational amplifier 302, and by the operational amplifier 302,
A voltage Vf obtained by subtracting the voltage Vd from the voltage Ve obtained by dividing the voltage + V33 by the resistor R18 and the variable resistor VR2 is output. At this time, the constants of the respective parts are set so that the voltage Vf output from the operational amplifier 302 becomes a negative voltage. This voltage Vf is inverted by the operational amplifier 304 and input to the comparator 500 as a positive voltage v7.

Further, the output voltage Vf from the operational amplifier 302 is
Is input to the operational amplifier 303, and the operational amplifier 303 outputs the voltage Vj obtained by subtracting the voltage Vf from the voltage Vg obtained by dividing the voltage -V34 by the resistor R22 and the variable resistor VR3. At this time, the constants of the respective components are set so that the voltage Vj output from the operational amplifier 303 becomes a negative voltage.

This voltage Vj is divided by the resistors r1 to r8 to generate voltages v1 to v6 (v1 <v2 <v3 <v4,
v5 <v6) is generated. These voltages v1 to v6 are applied to the bases of the transistors 212 of the delay circuits 201 to 206 described above. That is, the other end a of the resistor r1 is connected to the other end of the resistor R3 of the delay circuit 201, and the other end b of the resistor r2 is connected to the other end of the resistor R3 of the delay circuit 202. The other end c of the resistor r3 is connected to the other end of the resistor R3 of the delay circuit 203, and the other end d of the resistor r4 is a delay circuit.
It is connected to the other end of the resistor R3 of 204. Further, the other end e of the resistor r6 is the other end of the resistor R1 of the delay circuit 205, and the other end f of the resistor r7 is the resistor R of the delay circuit 206.
1 is connected to the other end, respectively.

Therefore, as the output voltage Vj of the operational amplifier 303 changes, the respective voltages v1 to v6 change continuously,
Thereby, the delay times t1 to t6 at the rear ends of the pulse signals Pd3 to Pd6, Ld3 and Ld4 output from the delay circuits 201 to 206 can be continuously changed. Furthermore, as the output voltage v7 of the operational amplifier 304 changes,
It is possible to continuously change the delay time t7 at the rear end of the signal L output from the comparator 500, which will be described later, and the pulse-shaped recording signal M obtained by inverting the signal L.

The signal synthesizing circuit 400 is a three-input OR circuit 40.
1 to 403, 3-input AND circuits 404, 405, 3-input NA
It is composed of an ND circuit 406 and NOT circuits 407 and 408. The first input terminal of the OR circuit 401 is grounded, and each of the second and third input terminals has a corresponding delay circuit 201, 20.
2 is connected to the output terminal of the NOT circuit 214. OR
The first input terminal of the circuit 402 is grounded, and each of the second and third input terminals is NO of the corresponding delay circuit 203,204.
It is connected to the output terminal of the T circuit 214.

The first input terminal of the OR circuit 403 is
It is connected to the output terminal Qb of the shift register 111 of the rear end pulse generation circuit 100 via AND circuits 404 and 405 connected in series. That is, the three input terminals of the AND circuit 404 are both connected to the output terminal Qb of the shift register 111, the output terminal of the AND circuit 404 is connected to the three input terminals of the AND circuit 405, and the output terminal of the AND circuit 405 is It is connected to the first input terminal of the OR circuit 403.
The second and third input terminals of the OR circuit 403 are connected to the output terminals of the corresponding OR circuits 401 and 402, respectively, and the output terminal of the OR circuit 403 is connected to the first input terminal of the AND circuit 406. The second and third input terminals of the NAND circuit 406 are connected to the output terminals of the NOT circuits 214 of the corresponding delay circuits 205 and 206 via the NOT circuits 407 and 408, respectively, and the output terminal of the NAND circuit 406 is a transistor of the charge / discharge circuit 207. It is connected to the base of 211. further,
The output of the charge / discharge circuit 207 is the comparator 500 and the NOT circuit 600.
And the laser diode 21 via the laser drive circuit 29.
It is connected to a.

Further, the resistance value of the resistor in each of the delay circuits 201 to 206 and the charging / discharging circuit 207 and the capacitor C
The capacity of 1 is set to an appropriate value obtained in advance by experiments or the like.

Next, the operation of this embodiment having the above-mentioned structure will be described based on the timing charts shown in FIGS. The recording signal generation circuit 28 described above operates as follows. Each of the pulse signals P3 to P6, L3, and L4 output from the rear-end pulse generation circuit 100 is, as shown in FIGS. 9 and 10, an output terminal Q of the shift register 111.
It corresponds to the signal output from b, that is, the signal B obtained by delaying the reference digital signal A by 2 clock pulses CP, and the rear end of the pulse signals P3 to P6 has a time width of 3 to 6T in the reference digital signal A. And the trailing ends of the pulse signals L3 and L4 are output so as to match the trailing ends of the low level having the 3,4T time width in the reference digital signal A. The time width of each of these pulse signals P3 to P6, L3, and L4 is equal to the reference time width T.

Each of the pulse signals P3 to P6, L3 and L4 output from the rear end pulse generation circuit 100 has its rear end at a predetermined time t1 to t6 by the corresponding delay circuit 201 to 206 as described above. It is delayed and output.

Thereafter, the signal synthesizing circuit 400 synthesizes the pulse signals Pd3 to Pd6, Ld3, Ld4 and the signal H, and inputs them to the laser driving circuit 29 via the charging / discharging circuit 207 and the NOT circuit 600. .. That is, the signal synthesis circuit 40
At 0, the pulse signals Pd3 to Pd6 are transferred to the OR circuit 401.
.About.403, the signal is logically ORed with the signal H to obtain the signal J.
As a result, in the signal J, the time width of the high level having the time width of 3 to 6T is lengthened by the time t1 to t4, respectively, and the time width of the low level following them is shortened accordingly.

Further, the signal J is the signal Ld3 obtained by inverting the pulse signals Ld3 and Ld4 by the NAND circuit 406.
After being ANDed with −, Ld4−, it is further inverted and output as a signal K. Thus, in the signal H 3,
Each of the trailing ends of the low level having the 4T time width has a time t.
It is extended by 5, t6, and the time width of the high level following these is shortened accordingly.

Next, the signal K is input to the charging / discharging circuit 207, and is output as a signal K'in which the waveform of the high-level rear end of the signal K drops with a constant slope. This signal K ′ is input to the comparator 500, and the voltage of the signal K ′ is compared with the voltage v7 from the voltage control circuit 300 by the comparator 500, and when the voltage of the signal K ′ is equal to or higher than the voltage v7, the high level is obtained. Then, a signal L is output. This output signal L is N
It is inverted by the OT circuit 600 and recorded as a recording signal M.
It is input to the drive circuit 29. As a result, the high-level time width of the signal H is uniformly reduced by the time t7.

The laser drive circuit 29 supplies a predetermined current to the laser diode 21a when the recording signal M is at a high level, and a laser light of high light intensity capable of forming a pit portion in the recording layer of the optical disk. When the recording signal M is at a low level, a current for emitting a laser beam of low light intensity capable of forming a non-pit portion in the laser diode 21a is passed, or the laser diode 21a is emitted. -Stop the power supply to the terminal 21a.

On the other hand, when recording information on the optical disk 1, the laser power is set to a constant value (actually, the amplitude of the laser power is optimum to the conventional fixed pulse), and the recording state at the time of recording is optimized. Changes the duty of the laser pulse and the correction amount of the pulse width of the pulse signals P3 to P6, L3, L4 (that is, the variable resistor VR of the voltage control circuit 300).
2) Change the resistance value).

That is, information is recorded in the test recording area in the inner peripheral portion of the optical disc 1 and this information is reproduced, and the eye pattern at this time is observed. In this eye pattern, as shown in FIG. 2, the voltage PWa in the positive direction and the voltage PWb in the negative direction are obtained from the AC reference level PWt, and the difference value (PWa-PWb) is calculated as the sum of these values ( The light intensity at which the value β divided by PWa + PWb) becomes 0 is the optimum pulse, and the calculated value (signal G in FIG. 1) when recording with this optimum pulse is the reference value.

In this case, the contact piece 305a of the switch 305 is set to the second
Connect to contact 305c. As a result, the voltage Ve applied to the non-inverting input terminal of the operational amplifier 302 becomes a voltage obtained by dividing the voltage + V33 by the resistor R18 and the variable resistor VR2, and the voltage Vf applied to the inverting input terminal of the operational amplifier 303.
Is a voltage obtained by dividing the voltage -V34 by the resistor R22 and the variable resistor VR3. In this state, the variable resistors VR2, VR
By changing the resistance value of 3, the applied voltage to the non-inverting input terminal of the operational amplifier 302 and the applied voltage to the non-inverting input terminal of the operational amplifier 303 is set to a predetermined voltage that is obtained in advance by experiments or the like. .. As a result, the pulse widths of the pulse signals P3 to P6, L3, L4 are corrected to appropriate values, and the pulse width of the recording signal M is set to an appropriate value.

Next, when recording is performed in the recording test area, the resistance value of the variable resistor VR2 is changed and the pulse width is changed to perform recording, and the resistance value at which β of the reproduced waveform becomes zero is found.
At this time, the resistance value of the variable resistor VR1 is adjusted so that the output voltage of the operational amplifier 301 becomes approximately 0V. here,
Pit part P having a 3T time width when a pit composed of a pit part Pa and a non-pit part Pb is formed with an optimum pulse width
The intensity of the reflected light from the rear end P1 of the a and the pit portion Pa
The difference from the intensity of reflected light from the central portion P2 of the non-pit portion Pb subsequent to is set.

That is, when the pit portion Pa having a 3T time width is formed and the intensity of the laser light is set to the reproduction light intensity of a low level, the reflected light from the rear end portion P1 of the pit portion Pa is changed to the photodetector 21b. And the pulse signal C is output from the timing pulse generation circuit 24, and the voltage Va of the output signal B2 of the low pass filter 23 is sampled.
It is held in the field circuit 25. After this, this pit part Pa
The non-pit portion Pb during the formation of the non-pit portion Pb following
The reflected light from the central portion P2 of the photodetector 21b
Timing pulse generation circuit 2 when
4 outputs a pulse signal D, and the voltage Vb of the output signal B2 of the low-pass filter 23 at this time is held in the sample-hold circuit 26. At this time, in the signal B2, the noise component due to the scratches K1 and dust K2 of the optical disc 1 included in the signal B1 is removed, so that erroneous detection can be prevented.

In this state, the output voltage V of the operational amplifier 301
When a pit is formed with an optimum pulse width by adjusting the resistance value of the variable resistor VR1 so that d becomes approximately 0 V, the length corresponds to the high-level time width of the reference digital signal A, And the pit part P with the optimum width
a and a voltage corresponding to the intensity of reflected light from the rear end P1 of the pit portion Pa having a 3T time width when a pit composed of a non-pit portion Pb having a length corresponding to the low-level time width is formed. Va and the non-pit part P following this pit part Pa
The voltage Vh (= Vb-Va), which is the difference from the voltage Vb corresponding to the intensity of reflected light from the central portion P2 of b, is set as the voltage applied to the inverting input terminal of the operational amplifier 301.

After that, the contact piece 305a of the switch 305 is connected to the first contact 305b, and information recording is started. Depending on the nature of the recording layer of the optical disc 1 or eccentricity during recording of information, 3
When the formation state of the pit portion Pa having the T time width changes, the optimum pit is formed correspondingly, that is, the output voltage Vd of the operational amplifier 301 becomes 0V, so that the laser diode is real-time. -The pulse width of the laser light emitted from the terminal 21a and the pulse signals P3 to P6, L3, L4
The delay amount of is increased or decreased.

That is, when the pit portion Pa having the 3T time width is excessively formed and the length thereof is long or the width thereof is wide, from the rear end portion P1 of the pit portion Pa during reproduction. The intensity of the reflected light is reduced. The intensity of the reflected light from the central portion P2 of the non-pit portion Pb following this is substantially constant over the entire surface of the optical disc 1. Therefore, in this case, the voltage Vc of the signal G output from the arithmetic circuit 27 increases above the reference voltage Vh, and the negative voltage Vd is output from the operational amplifier 301 accordingly. At this time, the voltage applied to the inverting input terminal of the operational amplifier 302 decreases, the voltage v7 decreases, and the entire pulse width (duty) decreases. Further, the voltage Vj also decreases, and the pulse signals P3 to P6 and L corresponding to the duty are reduced.
The correction amount is 3, L4. This makes the laser diode
The pulse width of the laser pulse emitted from the beam 21a is reduced, the amount of heat supplied to the optical disc 1 by the laser pulse is reduced, and the excessive formation of the pit portion Pa that is subsequently formed is alleviated. A pit having a shape corresponding to the reference digital signal A is formed.

When the pit portion Pa having a 3T time width is not sufficiently formed and the length thereof is short or the width is narrow, the rear end portion of the pit portion Pa at the reproducing light intensity. The intensity of the reflected light from P1 increases. Therefore, in this case, the voltage of the signal G of the arithmetic circuit 27 becomes lower than the reference voltage Vh, and the positive voltage Vd is output from the operational amplifier 301 accordingly. At this time, the pulse width of the laser pulse emitted from the laser diode 21a increases, the amount of heat supplied to the optical disc 1 by the laser pulse increases, and the formation state of the pit portion Pa formed subsequently is A pit having a proper shape and having a shape corresponding to the reference digital signal A is formed.

Here, the circuit constants are set so that the increase / decrease rate of the output pulse width in the delay circuits 201 to 206 becomes a predetermined value smaller than the increase / decrease rate of the output pulse width in the charge / discharge circuit 207.

As described above, according to the present embodiment, the formation state of the pit portion Pa having the 3T time width in which the formation state changes remarkably due to the change of the properties of the recording layer of the optical disc 1, the eccentricity of the optical disc 1, and the like. Since the amount of heat supplied to the optical disk 1 is corrected by detecting the reflected light and increasing or decreasing the pulse width of the laser light, it is possible to always form a pit having a shape corresponding to the reference digital signal A. The recording characteristics can be improved.

Even when the ambient temperature changes and the intensity or oscillation wavelength of the laser light changes, the pulse width of the laser light is increased or decreased as described above, and the amount of heat supplied to the optical disc 1 is corrected. Therefore, it is possible to reduce jitter and the like, and it is possible to always form a pit having a shape corresponding to the reference digital signal A, and it is possible to improve recording characteristics.

In the present embodiment, the arithmetic circuit 27 obtains the voltage Vc which is the difference between the voltages Va and Vb of the signals E and F, and the laser diode 21a is set so that the voltage Vc becomes constant. Although the pulse width of the laser pulse emitted from is controlled, it is not limited to this and the voltage Va,
The same effect can be obtained by obtaining the ratio of Vb and controlling the pulse width of the laser pulse so that this ratio becomes constant.

In this embodiment, the sample-hold circuit 26 holds the voltage corresponding to the intensity of the reflected light from all the non-pit portions Pb. However, the non-pit portion following the pit portion Pa of 3T time width is held. You may make it hold | maintain the voltage corresponding to the reflected light intensity from the part Pb.

Further, in the present embodiment, the voltage corresponding to the intensity of the reflected light from the non-pit portion Pb is held at the position delayed from the rear end of the pit portion Pa by about twice the reference time width T. It goes without saying that this holding position may be a position that is not affected by the pit portion Pa.

[0060]

As described above, according to the present invention, the formation state of the pit portion having the minimum time width changes due to the nature of the recording layer of the optical information recording medium or the eccentricity during the recording of the information. When the detection result of the second light intensity detection means changes, the pulse width of the laser light is increased or decreased in real time so that the calculation result of the calculation means substantially matches the predetermined reference value.
Since the amount of heat supplied to the optical information recording medium is corrected, it is possible to always form an appropriate pit corresponding to the reference digital signal. Further, since the short pulse is corrected for each, the thermal interference between the pits can be reduced and the jitter can be reduced.
Further, even if the intensity of the reflected light changes temporarily due to a scratch or the like formed on the optical information recording medium, the temporary change in the light intensity is removed by the high frequency component removing means. It is possible to prevent the erroneous detection of the first and second light intensity detecting means and to improve the recording characteristics, which is a very excellent effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of setting an optimum light intensity in a conventional example.

FIG. 3 is a circuit diagram showing a recording signal generation circuit according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a delay circuit according to an embodiment.

FIG. 5 is a timing chart of a delay circuit according to an embodiment.
To

FIG. 6 is a configuration diagram of a charging / discharging circuit according to an embodiment.

FIG. 7 is a timing chart of the charging / discharging circuit in one embodiment.

FIG. 8 is a configuration diagram of a voltage control circuit according to an embodiment.

FIG. 9 is a timing chart illustrating the operation of the embodiment.

FIG. 10 is a timing chart illustrating the operation of the embodiment.

FIG. 11 is a timing chart illustrating the operation of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical information recording device, 21 ... Optical pickup, 21a ... Laser diode, 21b ... Photodetector, 21c ... Harm mirror, 21d ... Lens, 2
2 ... RF amplifier, 23 ... Low pass filter, 24 ... Timing pulse generating circuit, 25, 26 ... Sample hold circuit, 27 ... Arithmetic circuit, 28 ... Recording signal generating circuit, 29
... laser drive circuit, 100 ... rear end pulse generation circuit, 201 ...
206 ... Delay circuit, 207 ... Charge / discharge circuit, 300 ... Voltage control circuit, 400 ... Signal combining circuit, 500 ... Comparator, 600 ... NOT
circuit.

Claims (1)

[Claims] 1. A first signal level corresponding to information to be recorded and representing a period for irradiating laser light having an intensity capable of forming a pit portion and a laser having a predetermined intensity lower than said intensity.
A second signal level representing a period for irradiating the light,
The first and second signal levels are based on a reference digital signal having a time width forming an arithmetic series that is an integral multiple of a predetermined reference time width, and a pulsed laser beam having a predetermined intensity for the optical information recording medium. In an optical information recording apparatus for forming a pit by irradiating the light, at least a light intensity detecting means for detecting the intensity of reflected light from the optical information recording medium at the time of forming the pit, and a detection result of the light intensity detecting means A high frequency component removing means for removing a high frequency component of a predetermined frequency or more, and the reference digital signal from the first signal level of the minimum time width based on the reflected light intensity from which the high frequency component is removed by the high frequency component removing means. A first light intensity detecting means for detecting the intensity of reflected light when the level changes to the second signal level, and the high frequency component removing means removes the high frequency component. A second detecting a reflected light intensity at the second signal level after a lapse of a predetermined time from a level change at which the first signal level transits to the second signal level based on the reflected light intensity Light intensity detecting means, calculating means for calculating the difference or ratio between the detection value of the first light intensity detecting means and the detection value of the second light intensity detecting means, and the calculation result of the calculating means is predetermined. Of the reference digital signal so that the time width of the first and second signal levels of the reference digital signal is increased or decreased to form a recording signal, and a laser is driven based on the recording signal. An optical information recording device comprising: a laser driving unit.