JP2675701B2 - Optical information recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention mainly relates to EFM (Eight
The present invention relates to an improvement of an optical information recording device for an optical information recording medium such as an optical disk using a Fourteen Modulation) method.

[0002]

2. Description of the Related Art In recent years, a technique for recording large-capacity information on an optical information recording medium, for example, an optical disk such as a WO disk has become popular. When recording, for example, an audio signal on an optical disc, a method of digitizing and recording the audio signal at the time of recording is generally performed 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 audio signal (hereinafter, referred to as a reference digital signal).
With the addition of parity for error correction,
Further, by modulating this by the EFM method, the reproduction characteristics are improved.

[0003] By performing the above-mentioned EFM modulation, nine time widths of 3 to 11 times the predetermined reference time width T are given as the high-level and low-level time widths of the reference digital signal. The optical disk is irradiated with laser light based on the reference digital signal, and a pit portion is formed on the recording layer. For example, laser light having an intensity capable of forming a pit portion is irradiated during the high level period of the reference digital signal.

In addition, the width of a pit formed on an optical disk is increased or decreased, and the length of a pit and a non-pit is changed due to a difference in the intensity of light emitted from a laser. Pits composed of non-pit portions and non-pit portions may be formed. That is, if the intensity of the laser beam is set high, the heat accumulated in the recording layer of the optical disk is 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 pits become longer and wider. If the intensity of the laser light is set low, it takes time until the heat is absorbed by the recording layer when the optical disk is irradiated with the laser light, and the pit portion is formed short.

Therefore, before recording information on the optical disk, the test information is recorded on the innermost portion of the optical disk by changing the intensity of the laser light, and the optimum intensity of the laser light is obtained. At the time of recording, the intensity of the laser light is set to this optimum light intensity to record information. 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 positive voltage PWa and a negative voltage PWb are obtained from the AC reference level PWt, and the difference value (PW
a−PWb) is divided by the sum of these values (PWa + PWb) to set an optimum light intensity at which the value β becomes 0, and information is recorded. Thereby, 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 disc, and is recorded in other portions. The properties of the layers may change, forming pits that do not correspond to the reference digital signal.

Further, the optical disc may be eccentric 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 goes off-track, the distribution state of the laser light is a Gaussian distribution, so that the state becomes the same as when the light intensity decreases, The formed pits do not correspond to the reference digital signal, so that there is a problem that jitter is deteriorated and errors at the time of reproduction are increased.

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 intensity of laser light according to the state of pit formation when recording information.

[0009]

In order to achieve the above-mentioned object, the present invention provides a first method which corresponds to information to be recorded and which represents a period during which a laser beam having an intensity capable of forming a pit portion is irradiated. A signal level and a signal of a predetermined intensity lower than the above 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 laser beam having a predetermined intensity for the optical information recording medium.
In an optical information recording apparatus that forms a pit by irradiating the light, a light intensity detection unit that detects the intensity of reflected light from the optical information recording medium at least when the pit is formed, and a detection result of the light intensity detection unit On the basis of the first light intensity detecting means for detecting the reflected light intensity when the reference digital signal changes from the first signal level to the second signal level, and the detection result of the light intensity detecting means. On the basis of the second level after a predetermined time has passed from the time of the level change,
Second light intensity detecting means for detecting the intensity of reflected light at the signal level of the above, and the difference or ratio between the value detected by the first light intensity detecting means and the value detected by the second light intensity detecting means. Optimal for computing means and optical information recording medium
When the pit is formed, the detection of the first light intensity detecting means is performed.
The difference between the output value and the detection value of the second light intensity detecting means, or
A reference value setting means for presetting a ratio as a reference value;
The calculation result of the calculation means and the reference value should be almost the same.
In addition, an optical information recording device is proposed, which comprises an emitted light intensity correction means for offsetting the emitted light intensity of the laser.

[0010]

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 forming the pits, and based on the detection result, the first light intensity detecting means outputs the reference digital signal. The intensity of the reflected light at the time of the level change from the first signal level to the second signal level is detected. The light intensity detected here is the reflected light intensity at the rear end of the pit formed on the optical information recording medium, and when the reflected light intensity is high, the formation of the pit is insufficient. When the pit portion is formed, that is, when the intensity of the laser light at the first signal level is too low,
When the reflected light intensity is low, the pit portion is excessively formed, which means that the intensity of the laser light at the time of forming the pit portion is too high. Further, based on the detection result of the light detecting means, the second light intensity detecting means detects the reflected light intensity at the second signal level after a lapse of a predetermined time from the level change. The light intensity detected here is
It 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 is set to a predetermined standard. The emitted light intensity of the laser is offset by the emitted light intensity correcting means so that it substantially matches the value. This allows
Same as when optimum pits are formed on the optical recording medium
Detection value of the first light intensity detecting means and the second light intensity
Pits are formed with a difference or ratio with the detection value of the detection means
Is done.

[0011]

FIG. 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, when recording information, the optical disk 1
Is rotated by a spindle motor or the like (not shown).

The recording device 2 includes an optical pickup 21 and an RF.
A well-known EFM-modulated reference digital signal composed of an amplifier 22, a timing pulse generation circuit 23, sample-hold circuits 24 and 25, an arithmetic circuit 26, a laser output control circuit 27, and a laser drive circuit 28. A is input to emit high-intensity laser light capable of forming a pit portion when the reference digital signal A is at a high level to the optical disc 1, and a non-pit portion is formed when the reference digital signal A is at a low level. Laser light of low intensity that can be reproduced and can reproduce information is emitted to the optical disc 1.

The optical pickup 21 is a laser diode.
211, a photo detector 212, a half mirror 213, a lens 214 and the like. Laser diode 211
Emits laser light having an intensity corresponding to the current input from the laser drive circuit 28, and this laser light is half mirror 21.
The optical disk 1 is irradiated with light through the lens 3 and the lens 214.
As a result, when the intensity of the laser light is high, the optical disc 1
A pit portion is formed on the pit, and a non-pit portion is formed when the laser intensity is low. Further, the reflected light from the optical disk 1 is incident on the photodetector 212 via the lens 214 and the half mirror 213, is converted by the photodetector 212 into an electric signal B having a voltage proportional to the intensity of the reflected light, and is input to the RF amplifier 22. To be done. The signal B input to the RF amplifier is amplified by a predetermined amplification degree and input to the sample-hold circuits 24 and 25 as a signal B '. Each of the sample hold circuits 24 and 25 detects and holds the voltage level of the signal B ′ when the pulse signals C and D are input from the timing pulse generation circuit 23.

The timing pulse generating circuit 23 receives the reference digital signal A, detects a falling edge of the reference digital signal A changing from a high level to a low level, and detects a predetermined time width, for example, the reference digital signal A. A pulse signal C having a time width of about ⅕ of the reference time width T is output to the sample hold circuit 24, and this pulse signal C is delayed by a predetermined time, for example, about twice the time length of the reference time width T. Sampled pulse circuit D
5 is output.

The signals E and F output from the sample and hold circuits 24 and 25 are input to the arithmetic circuit 26. The arithmetic circuit 26 includes an operational amplifier, and has a signal G having a voltage Vc obtained by subtracting the voltage of the signal E from the voltage of the signal F.
Is output. This signal G is input to the laser output control circuit 27.

A circuit diagram of the laser output control circuit 27 and the laser drive circuit 28 is shown in FIG. As shown in the figure, the laser output control circuit 27 includes operational amplifiers 271 and 272, a switch 273 having two contacts of one circuit, resistors R1 to R8 and variable resistors VR1 and VR2.
It is constituted by. The inverting input terminal of the operational amplifier 271 is supplied with the output signal G of the arithmetic circuit 26 via the resistor R1 and is also connected to its output terminal via the resistor R2. In addition, the non-inverting input terminal of the operational amplifier 271 is connected to the connection point between the series-connected resistor R4 and the variable resistor VR1 via the resistor R3, and the series-connected resistor is connected.
Positive voltage + V1 across R4 and variable resistor VR1
And a negative voltage -V2 is applied. As a result, the voltage Vh is applied to the non-inverting input terminal of the operational amplifier 271.

The inverting input terminal of the operational amplifier 272 is a resistor.
It is connected to the contact piece 273a of the switch 273 via R5, the first contact 273b of the switch 273 is connected to the output terminal of the operational amplifier 271, and the second contact 273c is grounded. further,
The inverting input terminal of the operational amplifier 272 is connected to its output terminal via the resistor R6, and is also connected to the connection point between the series-connected resistor R8 and the variable resistor VR2 via the resistor R7. , One end of the resistor R8 and the variable resistor VR2 connected in series are grounded, and the positive voltage + V3 is applied to the other end. The non-inverting input terminal of the operational amplifier 272 is grounded.

A laser output control circuit 2 having the above-mentioned configuration.
7, the operational amplifier 271 outputs the voltage Vd obtained by subtracting the voltage of the signal G from the voltage Vh. This voltage V
d is added to the voltage Ve obtained by dividing the voltage + V3 by the resistor R8 and the variable resistor VR2, and the result is input to the inverting input terminal of the operational amplifier 272. As a result, the voltage Vg output from the operational amplifier 272 becomes a negative voltage.

The laser driving circuit 28 is composed of PNP type transistors 281-283, NPN type transistors 284, 285, resistors R9-R15 and a NOT circuit 286, and the base of the transistor 281 is connected via the resistor R9. Operational amplifier 27
Connected to 2 output terminals. Also, the transistor 28
The collector of 1 is grounded through a resistor R10, and the emitter is connected to the emitters of transistors 284 and 285.
The collector of transistor 284 is the base of transistor 282.
A positive voltage + V4 is applied to the collector via a resistor R11. The voltage + V4 is applied to the collector of the transistor 285. Further, the reference signal A is input to the base of the transistor 284, and the reference signal A inverted by the NOT circuit 286 is input to the base of the transistor 285. The collector of transistor 282 is connected to the collector of transistor 283 and is connected to the laser diode via resistor R12.
It is connected to the node of the node 211, and the cathode of the laser diode 211 is grounded. Also. Transistor 282,28
A positive voltage + V5 is applied to the emitter of 3 via a resistor R13. Further, a predetermined negative voltage -V6 is applied to the base of the transistor 283.

According to the laser drive circuit 28 having the above-described structure, the transistor 284 is turned on and the transistor 285 is turned off when the pit portion Pa is formed, that is, when the reference digital signal A is at the high level. . As a result, a current corresponding to the base voltage of the transistor 281 flows through the transistor 284, and the collector voltage of the transistor 284 is applied with a voltage determined by this current value and the resistors R10 and R11. Therefore, the current flowing through the transistor 282 changes according to the base voltage of the transistor 281. At this time, the current flowing through the laser diode 211 is the sum of the current flowing through the transistor 283 set by the voltage -V6 and the current flowing through the transistor 282.

When the non-pit portion Pb is formed, that is, when the reference digital signal A is low level, the transistor is
284 turns off and transistor 285 turns on. As a result, the voltage + V4 is applied to the base of the transistor 282, and the transistor 282 is turned off. Therefore, at this time, the current flowing through the laser diode 211 is only the current flowing through the transistor 283 set by the voltage -V6.

Next, the operation of this embodiment having the above-mentioned structure will be described based on the timing chart shown in FIG.
Before recording information on the optical disk 1, the optimum light intensity of the laser light is obtained as in the conventional case, and the reference value in this embodiment is set. The method for obtaining the optimum light intensity is the same as in the conventional method. Information is recorded in the test recording area in the inner peripheral portion of the optical disc 1, this information is reproduced, and the eye pattern at this time is observed. In this eye pattern, as shown in FIG. 2, the voltage PW in the positive direction from the AC reference level PWt.
a and the voltage PWb in the negative direction are obtained, and the difference value (PWa-PWb) is added to the sum value (PWa + PWb).
The light intensity at which the value β divided by) becomes 0 is set as the optimum light intensity, and this optimum light intensity is set as the reference value in this embodiment.

In this embodiment, the voltage PWa and the voltage PWb are set to
The sample and hold circuits 24 and 2 are used as corresponding detection values.
The voltage Va and the voltage V held by each of 5
Using b, the difference between these voltages Va and Vb is always preset.
Laser diode 21 so that it almost matches the specified reference value.
Controls the current supplied to 1 to form the optimum pit.
The laser diode 211 output light intensity.
I'm fussing.

As the reference value, the desired optimum pitch is set.
The difference between the voltages Va and Vb obtained when the
It is set by the procedure described below .

The voltage PWa and the voltage PWb are AC
It is a value based on the quasi-level PWt, and is a voltage Va and
The pressure Vb is a value based on the DC reference level (0V)
So do not treat them as equal.

Here, the reflected light intensity from the non-pit portion Pb
The voltages corresponding to are the voltage PWa and the voltage Vb, and
The voltage corresponding to the intensity of the reflected light from the contact part Pa is the voltage PW.
b and voltage Va.

That is, the voltages PWa and PWb are on the optical disk.
The laser light with the reproducing light intensity is applied to the pits formed on the
It corresponds to the intensity of the reflected light when radiated. Same as this
In this embodiment, the voltages Va and Vb are the optical disk.
A laser beam with reproducing light intensity is applied to the pit formed above.
It corresponds to the intensity of the reflected light when illuminated.

Next, the reason for this is explained in the timing chart in FIG.
It will be explained based on the following. First, the signal from the RF amplifier 22
The reason why B'is output will be described. In this embodiment
Is high when the reference digital signal A is at high level.
Of the laser beam of 100 degrees, and the pit portion Pa is formed on the optical disc 1.
Formed, and when the reference digital signal A is at low level,
Low intensity laser light is emitted to form the non-pit Pb.
You.

Here, the pit portion Pa means the optical disc 1
Holes are formed by melting the recording layer with high intensity laser light.
The non-pit portion Pb is the surface of the optical disc 1.
This is a portion in which the surface and the recording layer are maintained as they are.

The optical disc 1 has a pit portion Pa and a non-pit portion.
When Pb is formed, the pits are formed on the optical disc 1 at this time.
It becomes difficult for the portion Pa to reflect light, and the non-pit portion Pb is a mirror surface.
Reflects light as well.

In addition, a pit (pit portion P
a and the non-pit portion Pb are collectively referred to as a pit)
When it is completed, there is usually a delay.

That is, the reference digital signal A is at a high level.
Even if the optical disc 1 is irradiated with high-intensity laser light,
Sometimes the formation of the pit portion Pa is not started and the optical disc 1
Part irradiated with laser light reaches the melting temperature of the recording layer
It will take some time to get there.

Further, the reference digital signal A is high level.
From low to high level, the laser light is high intensity to low intensity
Even if it is switched to the
The formation of the pit portion Pa ends with a slight delay without lowering.

On the other hand, the signal output from the RF amplifier 22
B ′ is an optical detector received by the photodetector 212.
It has a voltage proportional to the intensity of the reflected light from the disk 1.

Here, "P1" in the pit row in FIG.
At the position of, the reference digital signal A changes from high level to low level.
-Immediately after switching to the level, on the optical disc 1
The pit portion Pa is formed with a delay.

At the position of "P1", the laser diode
The intensity of the laser light emitted from the cord 211 is low.
And the laser beam irradiation position is at the rear end of the pit portion Pa.
At some of the reflection of light is little. In addition, laser light
When the irradiation position of P moves from the pit part Pa to the non-pit part Pb
Therefore, the reflection of light gradually increases, and the irradiation range of laser light increases.
The whole area is in the non-pit part Pb (eg, "P2" position)
Then, the reflected light intensity becomes constant.

Further , the reference digital signal A is at a low level.
Immediately after switching from the
The formation of the pit part Pa does not start on the sk 1, and the non-pit part
Pb is irradiated with a high-intensity laser beam, and here it is all
Is reflected. Therefore, the reflected light intensity at this time is low
It becomes larger than when the laser light is irradiated.

After this, the temperature of the optical disk 1 rises and
When the pit portion P starts to be formed, the formed pit portion P
Reflection of part of the laser light irradiation range is lost due to the portion a.
The intensity of reflected light gradually decreases. In addition, laser light
The irradiation position of moves and is within the irradiation range of the laser light.
The ratio between the pit portion Pa and the non-pit portion Pb becomes constant.
Then, the reflected light intensity also becomes constant. Reflected light intensity at this time
Is due to the irradiation of high intensity laser light,
Reflection from the non-pit Pb during laser irradiation
Greater than light intensity. From the above, it is shown in FIG.
The signal B'is obtained.

In addition, each of "P1" and "P2"
The reflected light intensity obtained at the position is usually recorded on the optical disc.
Pit portion Pa and non-pit portion Pb obtained during information reproduction
This is comparable to the reflected light intensity from the
A voltage V corresponding to the voltage PWa and the voltage PWb of the pattern
a and the voltage Vb are obtained.

Next, the data obtained when the optimum pits were formed
The procedure for setting the difference between the measured voltages Va and Vb as a reference value
explain.

In this case, the contact piece 273a of the switch 273 is set to the second position.
Connect to contact 273c of. As a result, the voltage applied to the inverting input terminal of the operational amplifier 272 becomes the voltage Ve obtained by dividing the voltage + V3 by the resistor R7 and the variable resistor VR2. In this state, by changing the resistance value of the variable resistor VR2, the voltage applied to the inverting input terminal of the operational amplifier 272 is changed, information is experimentally recorded on the innermost peripheral portion of the optical disc 1, and the optimum optical The strength is obtained and the applied voltage Ve to the inverting input terminal of the operational amplifier 272 is set.

Next, information is tentatively recorded with this optimum light intensity, and the resistance value of the variable resistor VR1 is adjusted so that the output voltage of the operational amplifier 271 at this time becomes almost 0V. Here, the pit portion P when the pit including the pit portion Pa and the non-pit portion Pb is formed with the optimum light intensity
The difference between the reflected light intensity from a and the reflected light intensity from the non-pit portion Pb is set. That is, when the pit portion Pa is formed and the laser light intensity is set to a low level reproduction light intensity, the reflected light from the rear end portion P1 of the pit portion Pa becomes the photodetector.
It is incident on 212 and the timing pulse generation circuit 2
3, the pulse signal C is output, and the voltage Va of the output signal B ′ of the RF amplifier 22 is held in the sample-hold circuit 24. After that, when the reflected light from the central portion P2 of the non-pit portion Pb is incident on the photodetector 212 when the non-pit portion Pb is formed, the pulse signal D is output from the timing pulse generation circuit 23. R
The voltage Vb of the output signal B'of the F amplifier 22 is the sample voltage.
Hold circuit 25.

In this state, the output voltage V of the operational amplifier 271
When the pit is formed with the optimum light intensity by adjusting the resistance value of the variable resistor VR1 so that d becomes approximately 0V, that is, the high-level time width t of the reference digital signal A
1 of the pit portion Pa having the optimum width and the non-pit portion Pb having the length corresponding to the low level time width t2. Voltage V corresponding to the intensity of light reflected from the rear end P1
The voltage Vh1 (= Vb-Va) which is the difference between a and the voltage Vb corresponding to the intensity of the reflected light from the central portion P2 of the non-pit portion Pb.
Is set as a voltage applied to the non-inverting input terminal of the operational amplifier 271.

After that, the contact piece 273a of the switch 273 is connected to the first contact 273b, and information recording is started. When the formation state of the pit portion Pa changes due to the nature or eccentricity of the recording layer of the optical disc 1 during the recording of information, the optimum pit is formed correspondingly, that is, the output voltage Vd of the operational amplifier 271 is changed. The intensity of the light emitted from the laser diode 211 is offset in real time so that it becomes 0V.

That is, when the pit portion Pa is excessively formed and the length thereof is long or the width thereof is wide, the rear end portion P of the pit portion Pa at the reproducing light intensity.
The intensity of the reflected light from 1 decreases. In addition, the non-pit part P
The intensity of the reflected light from the central portion P2 of b is substantially constant over the entire surface of the optical disc 1. Therefore, in this case, the output voltage Vc of the arithmetic circuit 26 increases above the reference voltage Vh1, and the negative voltage Vd is output from the operational amplifier 271 accordingly. At this time, the voltage Vf applied to the inverting input terminal of the operational amplifier 272 decreases due to the difference between the voltage Ve and the voltage Vd, and the base voltage Vg of the transistor 281 increases. As a result, the current flowing to the laser diode 211 is reduced, the intensity of the light emitted from the laser diode 211 is offset in the negative direction and is reduced, and the pit portion Pa formed subsequently is excessively formed. Is relaxed, and a pit having an optimum shape, that is, a shape corresponding to the reference digital signal A is formed.

When the pit portion Pa is not sufficiently formed and the length thereof is short or the width thereof is narrow, the rear end portion P1 of the pit portion Pa at the reproducing light intensity is formed.
The intensity of the reflected light from increases. Therefore, in this case, the output voltage Vc of the arithmetic circuit 26 becomes lower than the reference voltage Vh1, and along with this, the positive voltage Vc from the operational amplifier 271.
d is output. At this time, the voltage Vf applied to the inverting input terminal of the operational amplifier 272 increases as the sum of the voltage Ve and the voltage Vd, and the base voltage Vg of the transistor 281 decreases. As a result, the energizing current to the laser diode 211 is increased and the intensity of the light emitted from the laser diode 211 is offset in the positive direction to be increased, and the formation state of the pit portion Pa to be formed subsequently is increased. Is proper, and a pit having a shape corresponding to the reference digital signal A is formed.

In this embodiment, the arithmetic circuit 26 calculates the voltage Vc which is the difference between the voltages Va and Vb of the signals E and F, and the laser diode 211 is set so that the voltage Vc of this difference becomes constant. The output light intensity of the laser diode 211 is controlled so that the ratio of the voltages Va and Vb is obtained and the output light intensity of the laser diode 211 is controlled so as to be constant. The same effect can be obtained.

Further, in the present embodiment, the sampling timing signals C and D in the sample hold circuits 24 and 25 are generated by the timing pulse generating circuit 23 based on the reference digital signal A, but the present invention is not limited to this. It goes without saying that the output signal B ′ from the RF amplifier 22 itself may be delayed and used as a timing signal.

[0049]

As described above, according to the present invention, the pit formation state changes during recording of information due to the nature of the recording layer of the optical information recording medium or eccentricity, and the first and second light intensity detections are performed. When the detection result of the means changes, the emitted light intensity from the laser is offset in real time by the emitted light intensity correction means so that the calculated result of the arithmetic means substantially agrees with the predetermined reference value. Information is recorded with high strength, proper pits corresponding to the reference digital signal can be formed, and the recording characteristics can be improved, which is a very excellent effect.

[Brief description of the drawings]

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

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

FIG. 3 is a circuit diagram showing a laser output control circuit and a laser drive circuit in an embodiment of the present invention.

FIG. 4 is a timing chart according to an embodiment of the present invention;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical information recording device, 21 ... Optical pickup, 211 ... Laser diode, 212 ... Photodetector, 213 ... Harm mirror, 214 ... Lens, 22 ... RF
Amplifier, 23 ... Timing pulse generation circuit, 24, 25
... Sample-hold circuit, 26 ... Arithmetic circuit, 27 ... Ray
The output control circuit, 28 ... Laser drive circuit, 271,272 ... Operational amplifier, 281-285 ... Transistor, 286 ... NOT circuit.

Claims (1)

(57) [Claims] 1. A first signal level corresponding to information to be recorded and representing a period of irradiation with laser light having an intensity capable of forming a pit portion, and a laser having 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 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 A first detecting a reflected light intensity when the reference digital signal changes in level when the reference digital signal changes from the first signal level to the second signal level;
And a second light intensity detecting means for detecting the reflected light intensity at the second signal level after a predetermined time has elapsed from the time of the level change, based on the detection result of the light intensity detecting means. Calculating means for calculating a difference or a ratio between a value detected by the first light intensity detecting means and a value detected by the second light intensity detecting means, and the calculating means for forming an optimum pit on the optical information recording medium.
The detection value of the first light intensity detection means and the second light intensity detection
The difference or ratio from the detection value of the means is preset as a reference value.
A reference value setting means, and a calculation result of the calculation means substantially coincides with the reference value
Les As - and a emitted light intensity correcting means for offsetting the emission light intensity of The optical information recording apparatus characterized by.