JP2771411B2 - 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 in an information recording device for an optical information recording medium such as an optical disk using a Fourteen Modulation (to 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 a high level period of the reference digital signal.

When pits are formed by irradiating the optical disk with laser light based on a reference digital signal to dissolve or alter the recording layer and form pits, when the optical disk is irradiated with laser light, the pits are formed on the recording layer. It takes time until heat is absorbed, and it takes time to radiate the heat stored in the recording layer when the laser beam irradiation is stopped. For this reason,
The lengths of the pits and non-pits actually formed on the recording layer may not correspond to the time width of the high or low level of the reference digital signal described above, and there is a problem that the reproduction characteristics are deteriorated. Was.

That is, as shown in FIG. 2, at the start of laser light irradiation, it takes time for heat to be absorbed by the recording layer, so that the tip of the pit Pa is slightly smaller than the tip of the reference digital signal A. Formed late.

Further, when the laser beam irradiation is stopped, the rear end of the pit Pa is formed rearward by the amount of heat energy absorbed in the recording layer and the transmission of the heat energy. This tendency is observed when the irradiation time of laser light is long.
That is, since the temperature of the optical disk rises in proportion to time,
This is particularly noticeable when the time width is large. In this case, the shape of the pit Pa becomes a tear shape, the width of the rear portion of the pit becomes wide, the reflectance decreases, and the crosstalk between tracks deteriorates. Invite.

[0007] Since the amount of heat energy is small when the time width is the shortest, the rear end of the pit Pa is rarely stretched, but may be too short as compared with other pits. .

Accordingly, there has been a problem that the deviation of the length of the pits Pa caused by thermal interference between the pits Pa causes an increase in jitter and a deterioration in recording / reproducing characteristics.

In order to solve the above-mentioned problem, conventionally, the high-level or low-level time width of the reference digital signal A is uniformly reduced, or a high-level or low-level time of a specific time width is conventionally used. A recording signal having a changed width is generated, and the optical disk is irradiated with high-intensity laser light by the recording signal, and a pit comprising a pit portion and a non-pit portion having a length corresponding to the time width of the reference digital signal. Had formed.

That is, a delay line or a charge / discharge circuit is provided for each specific time width, a time width of a reference digital signal is detected, and then a delay line or a charge / discharge circuit corresponding to the time width is selected to select a reference digital signal. The recording signal in which the time width of the high level or the low level is changed is generated.

[0011]

However, when the above-mentioned means is used, it is necessary to provide a delay line or a charging / discharging circuit for each time width and a switching circuit for switching these circuits in accordance with the time width. There has been a problem that the circuit size increases and the cost increases. In addition, when a delay line or a charge / discharge circuit is used for each specific time width, there is a problem in that the correction time varies due to the variation in component constants and the like, and the reliability decreases.

An object of the present invention is to provide an optical information recording apparatus capable of recording information with a simple configuration in consideration of the influence of thermal interference during recording in view of the above problems.

[0013]

According to the present invention, in order to achieve the above object, according to the present invention, a period for irradiating laser light having an intensity capable of forming a pit portion while corresponding to information to be recorded is provided. A first signal level and a second signal level indicating a period during which laser light of a lower intensity is irradiated or a period during which laser light irradiation is stopped.
The signal level is based on a reference digital signal having an integer multiple of a predetermined reference time width, and the current supplied to the laser is changed to irradiate the optical information recording medium with laser light of a predetermined intensity. In the optical information recording apparatus for forming pits, the output voltage is changed from the first reference voltage with a predetermined time constant from the start of one of the first and second signal levels of the reference digital signal. A charging circuit for gradually increasing the output voltage from a second reference voltage higher than the first reference voltage at a predetermined decay rate from at least the end of the one signal level of the reference digital signal; A discharge circuit for lowering, and outputting the signal of the one signal level when an output voltage of the charging circuit is lower than an output voltage of the discharging circuit; A comparison circuit that outputs a signal at the other signal level of the first and second signal levels when the output voltage is equal to or higher than the output voltage, and a logic that outputs a signal obtained by performing an OR operation on the output signal of the comparison circuit and the reference digital signal An optical information recording apparatus is provided which includes a sum circuit and irradiates a laser beam to the optical information recording medium based on an output signal of the OR circuit.

According to a second aspect of the present invention, in the optical information recording apparatus according to the first aspect, at the end of the one signal level, the output circuit detects the output voltage of the charging circuit and holds the detected voltage for a predetermined time. And the comparison circuit compares the holding voltage of the hold circuit with the output voltage of the discharge circuit, and when the output voltage of the hold circuit is lower than the output voltage of the discharge circuit, the signal of the one signal level And an optical information recording device for outputting a signal of the other signal level when the output voltage of the hold circuit is equal to or higher than the output voltage of the discharge circuit.

[0015]

According to the first aspect of the present invention, when the level of the reference digital signal changes from the other one of the first and second signal levels to one of the first and second signal levels by the charging circuit, the output voltage of the reference digital signal changes from the first to the second. Is gradually increased from the first reference voltage by a predetermined time constant. Thereby, the output voltage of the charging circuit is increased in accordance with the time width of the one signal level. Also, at least from the end of one signal level of the reference digital signal, that is, at least from the time when the level of the reference digital signal changes from the one signal level to the other signal level, the output voltage of the discharge circuit is changed. The voltage is gradually reduced at a predetermined attenuation rate from a second reference voltage higher than the first reference voltage. An output voltage of the charging circuit and an output voltage of the discharging circuit are compared by a comparing circuit. The comparing circuit outputs the one signal level when the output voltage of the charging circuit is lower than the output voltage of the discharging circuit. And the signal of the other signal level is output when the output voltage of the charging circuit is equal to or higher than the output voltage of the discharging circuit. An output signal of the comparison circuit is ORed with the reference digital signal by an OR circuit, and the output signal of the OR circuit is corrected by extending the rear end of the one signal level of the reference digital signal. Signal. Further, the current supplied to the laser is changed based on the logical sum signal, and the optical information recording medium is irradiated with the laser light.

According to the second aspect, at the end of the one signal level, the output voltage of the charging circuit is detected by the hold circuit, the detected voltage is held for a predetermined time, and the held voltage is set to the voltage. Input to the comparison circuit. The comparison circuit compares the output voltage of the hold circuit with the output voltage of the discharge circuit, and outputs the signal of the one signal level when the output voltage of the hold circuit is lower than the output voltage of the discharge circuit. When the output voltage of the hold circuit is equal to or higher than the output voltage of the discharge circuit, the signal of the other signal level is output.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of an optical information recording apparatus according to a first embodiment of the present invention. In the figure,
10 is a discharging circuit, 20 is a charging circuit, 30 is a comparing circuit,
0 is a two-input OR circuit, and 50 is a laser drive circuit.

The discharge circuit 10 includes a Zener diode 1
1, NPN transistor 12, electronic switch 13,
Resistors 14, 15, variable resistor 16, capacitor 17,
18 and a diode 19, the anode of the Zener diode 11 is grounded, and the cathode is a resistor 1
4, a predetermined positive voltage Vcc is applied. The base of the transistor 12 is connected to the variable terminal of the variable resistor 16, and the collector is connected to the first contact 13 of the electronic switch 13.
a and the cathode of the diode 19,
A predetermined negative voltage Va is applied to the emitter via a resistor 15. One end of the variable resistor 16 is grounded, and a predetermined negative voltage VEE is applied to the other end. Further, the cathode of the Zener diode 11 is grounded via the capacitor 17 and is connected to the second contact 13b of the electronic switch 13. The contact 13c of the electronic switch 13 is grounded via the capacitor 18.
As a control signal for the electronic switch 13, a reference digital signal A is input. When the reference digital signal A is at a high level, the contact 13c
The contact 13c is connected to the first contact 13a when the reference digital signal A is at a low level.

The charging circuit 20 includes a resistor 21, a capacitor 22, and an electronic switch 23. The resistor 21 and the capacitor 22 are connected in series, one end of the capacitor is grounded, and the other end of the resistor is a Zener diode. 1
1 cathode. Electronic switch 2
The third first contact 23a is connected to a connection point between the resistor 21 and the capacitor 22. Further, the contact piece 23c of the electronic switch 23 is grounded.

The comparison circuit 30 comprises a comparator 31 composed of an operational amplifier, a resistor 32 and an electronic switch 33. The non-inverting input terminal of the comparator 31 is connected to a contact 13c of the electronic switch 13 of the discharge circuit 10. , The inverting input terminal is connected to the connection point of the resistor and the capacitor of the charging circuit 20. The output terminal of the comparator 31 is pulled up by applying a predetermined positive voltage Vb via a resistor 32 and is connected to a second contact piece 33 b of the electronic switch 33. Further, the first contact piece of the electronic switch 33 is grounded.

The reference digital signal A is input to one input terminal of the OR circuit 40, and the other input terminal is connected to the contact 33 c of the electronic switch 33 of the comparison circuit 30. As a control signal for the electronic switches 23 and 33 of the charging circuit 20 and the comparison circuit 30, an output signal of the OR circuit 40, that is, a recording signal B is input.
3 and 33, respectively, connect the contact sides 23c and 33c to the second contacts 23b and 33b when the recording signal B is at the high level, and connect the contact sides 23c and 3c when the recording signal B is at the low level.
3c is connected to the first contacts 23a and 33a.

The laser drive circuit 50 irradiates an optical disc (not shown) with a laser beam having a light intensity based on the recording signal B output from the OR circuit 40.

Next, the operation of the first embodiment having the above configuration will be described with reference to the waveform diagram shown in FIG. here,
The constants of each resistor and capacitor are determined by experiment before recording information, and each is set to this determined value. For example, the resistor 1 in the discharge circuit 10
4 and 15, the variable resistor 16 and the capacitors 17 and 18 can charge the capacitor 18 to the Zener voltage Vz within the minimum time width of the reference digital signal A, and at a predetermined decay rate after the start of discharge. Capacitor 18
Are set to decrease. Also,
Each value of the resistor 21 and the capacitor 22 in the charging circuit 20 is set so that the voltage between the terminals of the capacitor 22 gradually increases with a predetermined time constant.

Before recording of information, that is, when the reference digital signal A is not input and a low-level signal is input as a control signal of the electronic switch 13, the contact 13c of the electronic switch 13 It is connected to one contact 13a. In this state, the charge of the capacitor 18 is discharged through the transistor 12 and the resistor 15,
The capacitor 17 is sufficiently charged. Further, since the recording signal B becomes low level, the electronic switches 23 and 33
Are connected to the first contacts 23a, 33a. Thus, the capacitor 22 of the charging circuit 20 is in a completely discharged state.

When the recording of the information is started and the reference digital signal A is inputted and the level changes from the low level to the high level, the contacts 13c, 23c and 33c of the electronic switches 13, 23 and 33 become the second. Contacts 13b, 23b,
33b. As a result, charging of the capacitor 18 of the discharging circuit 10 is started, and charging of the capacitor 18 is instantaneously performed by the charge stored in the capacitor 17, and the voltage V1 applied to the non-inverting input terminal of the comparator 31
Instantaneously becomes the Zener voltage Vz. Further, the charging circuit 2
The charging of the 0 capacitor 22 is started. The capacitor 22 is charged by the resistance R of the resistor 21 and the capacitor 2
2, the voltage between the terminals of the capacitor 22, that is, the voltage V2 applied to the inverting input terminal of the comparator 31, gradually increases based on the time constant. During this time, since the voltage V1 applied to the non-inverting input terminal of the comparator 31 is higher than the voltage V2 applied to the inverting input terminal, a high-level signal D is input to the other input terminal of the OR circuit 40. Output signal, ie, recording signal B
Is at the high level.

When the level of the reference digital signal A changes from the high level to the low level, the contact 13c of the electronic switch 13 of the discharge circuit 10 is connected to the first contact 13a,
The electric charge stored in the capacitor 18 is gradually discharged via the transistor 12 and the resistor 15. Capacitor 1
When the voltage V1 between the terminals of the capacitor 18 is higher than the voltage between the terminals of the capacitor 22 in the process of discharging the capacitor 8 and charging the capacitor 22, the output signal D of the comparator 31 is maintained at the high level, , The recording signal B output from the high level also remains at the high level. When the discharge of the capacitor 18 progresses and the voltage V1 between the terminals of the capacitor 18 becomes lower than the voltage V2 between the terminals of the capacitor 22, the output signal D of the comparator 31 changes to a low level. Also changes to the low level. Further, when the recording signal B changes to the low level, the contacts 23c and 33c of the electronic switches 23 and 33 of the charging circuit 20 and the comparison circuit 30 are connected to the first contact 23a.
The electric charge stored in the capacitor 22 is discharged through the electronic switch 23, the other input terminal of the OR circuit 40 is grounded, and a stable low-level recording signal is output from the OR circuit 40. B is output.

Therefore, from the time when the level of the reference digital signal A changes from the high level to the low level, until the voltage V1 between the terminals of the capacitor 18 becomes lower than the voltage V2 between the terminals of the capacitor 22, the recording signal B The high-level time width is increased compared to the reference digital signal A,
Corrections are made. Further, this correction amount corresponds to the high-level time width of the reference digital signal A, and if the time width changes, the correction amount also changes correspondingly.

As a result, the conventional digital signal A
While a delay line or a charge / discharge circuit was provided for each time width to generate a recording signal in which each time width was corrected,
In this embodiment, it is possible to generate a recording signal in which a correction corresponding to each time width is performed by one circuit common to each time width, a simple and small-scale circuit configuration, and low cost. Thus, a pit portion and a non-pit portion having a length corresponding to the reference digital signal A can be formed on the optical disc.

Next, a second embodiment of the present invention will be described.
FIG. 4 is a circuit diagram showing a main part in the second embodiment.
In the figure, the same components as those of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted. The difference between the first embodiment and the second embodiment lies in that a hold circuit 60 is provided between the charging circuit 20 and the comparison circuit 30.

That is, the hold circuit 60 includes the capacitor 2
2, the reference digital signal A and the recording signal B are inputted, and the terminal voltage V3 of the capacitor 22 at the time when the reference digital signal A changes from the high level to the low level is held to invert the comparator 31. Output to the input terminal, and when the recording signal B changes from high level to low level, the holding voltage V3 is reset to 0V.

As a result, errors in correcting the time width can be reduced as compared with the first embodiment. That is, the terminal voltage V2 of the capacitor 22 is equal to the resistance value R of the resistor 21.
, And gradually increases in a logarithmic function based on a time constant determined by the capacitance C of the capacitor 22. Therefore, even after the reference digital signal A changes from the high level to the low level, the voltage V2 changes and an error in the correction amount occurs. Occurs. This error increases as the high-level period of the reference digital signal A increases. On the other hand, in the second embodiment, since the voltage V3 of the voltage V2 between the terminals of the capacitor 22 when the reference digital signal A changes from the high level to the low level is held, the correction corresponding to the logarithmic function is performed. The amount can be obtained, and the error of the correction amount is almost eliminated.

In the first and second embodiments, the correction is made so as to increase the time width of the high level of the reference digital signal A. However, the present invention is not limited to this, and the time width of the low level is increased. The correction may be performed so as to cause the correction. It is desirable to appropriately select this according to the difference in the light intensity of the laser or the thermal conductivity of the optical disk.

The configuration of the first and second embodiments is an example, and the present invention is not limited to this. For example, as shown in FIG. 5, an electronic switch 24 is provided in the charging circuit 20 to cut off the power supply to the capacitor 22 when the reference digital signal A falls, so that the function of the hold circuit 60 in the second embodiment is achieved. The same effect can be obtained even if the charging circuit 20 is provided.

[0034]

As described above, according to the first aspect of the present invention, the output of the charging circuit that changes according to the time width of one of the first and second signal levels of the reference digital signal. Since the rear end of the time width of the one signal level in the reference digital signal is corrected by the voltage and the output voltage of the discharge circuit, any time width can be dealt with by one set of circuits. Thus, the circuit scale can be significantly reduced, and the cost can be reduced.

According to the present invention, in addition to the above effects, at the end of the one signal level, the output voltage of the charging circuit is held by the holding circuit, and the reference digital signal is held based on the holding voltage. Is corrected, the error of the correction amount can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a main part of an optical information recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a reference digital signal and pits in a conventional example.

FIG. 3 is a waveform chart for explaining the operation of the first embodiment.

FIG. 4 is a circuit diagram showing a main part in a second embodiment.

FIG. 5 is a circuit diagram showing another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Discharge circuit, 11 ... Zener diode, 12 ... Transistor, 13 ... Electronic switch, 14, 15 ... Resistor, 16 ... Variable resistor, 17, 18 ... Capacitor, 20
... Charging circuit, 21 ... Resistor, 22 ... Capacitor, 23,
24 ... electronic switch, 30 ... comparison circuit, 31 ... comparator,
32: resistor, 33: electronic switch, 40: OR circuit, 50: laser drive circuit, 60: hold circuit.

Claims (2)

(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 laser light having an intensity lower than the first signal level. And a second signal level indicating a laser light irradiation stop period. The first and second signal levels are converted to a reference digital signal having a time width that is an integral multiple of a predetermined reference time width. An optical information recording device for irradiating an optical information recording medium with laser light of a predetermined intensity by changing a current supplied to a laser to form a pit; A charging circuit for gradually increasing the output voltage from the first reference voltage by a predetermined time constant from the start of one of the two signal levels; and at least the end of the one signal level of the reference digital signal Time Second higher than the first reference voltage
A discharge circuit that gradually lowers the output voltage at a predetermined decay rate from the reference voltage, and outputs the one signal level signal when the output voltage of the charging circuit is lower than the output voltage of the discharge circuit; A comparison circuit that outputs a signal of the other signal level of the first and second signal levels when an output voltage of the charging circuit is equal to or higher than an output voltage of the discharging circuit; and an output signal of the comparison circuit and the reference digital signal. An optical information recording device, comprising: an OR circuit that outputs a signal obtained by performing an OR operation on a signal and irradiating the optical information recording medium with laser light based on an output signal of the OR circuit. And a holding circuit for detecting an output voltage of the charging circuit at the end of the one signal level and holding the detected voltage for a predetermined time, and wherein the comparing circuit compares the holding voltage of the holding circuit with the holding voltage of the holding circuit. The output voltage of the discharge circuit is compared, and the output signal of the one signal level is output when the output voltage of the hold circuit is lower than the output voltage of the discharge circuit, and the output voltage of the hold circuit is the output voltage of the discharge circuit. 2. The optical information recording apparatus according to claim 1, wherein the signal of the other signal level is output when the voltage is equal to or higher than a voltage.