JP3552245B2 - Light amount control device and optical disk device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a light amount control device suitable for use in controlling the laser power of a laser beam, such as a CD recording device for recording data on a recordable CD (so-called CD-R) or a magneto-optical disk recording device. And an optical disk device including the light amount control device.
[0002]
[Prior art]
Today, optical disks have come to be frequently used for recording of recording data because of their large storage capacity and good preservation of recording data. A so-called CD-R is known as a typical optical disk.
[0003]
Data is recorded on the CD-R by irradiating the data recording surface of the CD-R with a laser beam and forming pits on the recording surface in accordance with the data.
[0004]
A CD recording apparatus that records data on the CD-R is configured to control the level of a laser beam applied to the CD-R by a light amount control device.
[0005]
In this light amount control device, when recording is started, data is supplied to a timing generation circuit. The timing generation circuit supplies a control signal corresponding to the data to a laser driver. The laser driver controls a laser diode so that a laser beam is turned on and off in accordance with the control signal, that is, in accordance with data.
[0006]
The level of the laser beam emitted from the laser diode is detected by a monitor circuit. The monitor circuit supplies the current laser beam level detection signal to the sample and hold circuit. The sample and hold circuit samples and holds the detection signal and supplies the sample and hold signal to the laser driver. The laser driver drives and controls the laser diode based on the sample and hold signal so that the level of the laser beam emitted from the laser diode becomes constant.
[0007]
The light quantity control device servo-controls the level of the laser beam in such a negative feedback loop. For this reason, a laser beam of a constant level can always be emitted from the laser diode according to data, and stable recording of data can be performed.
[0008]
[Problems to be solved by the invention]
However, the light quantity control device provided in the conventional CD recording apparatus preferably keeps the laser power constant by the servo control of the negative feedback loop, but starts emitting the laser beam in a closed loop. At the start of the recording, a larger voltage is required than when the laser beam is continuously emitted. However, the light amount control device cannot provide a wide loop band because the sample hold circuit is provided in the loop. For this reason, the voltage supplied to the laser diode at the start of the recording becomes low, the rise of the laser beam is poor (the laser beam does not immediately reach a sufficient level), and the laser beam is continuously supplied immediately after the previously recorded data. Even when it is desired to record the next data (when additional recording is desired), there is a problem that an unrecorded portion occurs between the last part of the previously recorded data and the head of the next data.
[0009]
The present invention has been made in view of the above-described problems, and improves the rise of a laser beam to generate an unrecorded portion between the last portion of previously recorded data and the beginning of the next data. It is an object of the present invention to provide a light quantity control device capable of performing additional writing without any trouble and an optical disc device provided with the light quantity control device.
[0010]
[Means for Solving the Problems]
A light amount control device according to the present invention includes: a level detection unit that detects a level of a laser beam from a laser beam emission unit that irradiates an optical disk; a detection output from the level detection unit; Forming a sample hold signal indicating a level, outputting a target level signal for setting the level of the laser beam to a target level, comparing the sample hold signal with the target level signal, and determining that the level of the laser beam is the target level. Until the target level signal is output, when the level of the laser beam reaches the target level, a comparison signal indicating the difference between the target level signal and the sample hold signal instead of the target level signal And the target level from the sample and hold means And having a laser driving means for driving said laser beam emitting means in accordance with the item and the comparison signal.
In the light quantity control device according to the present invention, for example, the sample and hold unit samples and holds a detection output from the level detection unit and outputs a sample and hold signal, and the sample and hold unit outputs the sample and hold signal. A target level signal output unit for outputting a target level signal for setting the level of the laser beam to a target level, and a sample hold signal from the sample hold unit and a target level signal from the target level signal output unit are compared. The first comparing means, the switching means is controlled by a comparison signal from the first comparing means, and a switch means for outputting a sample and hold signal from the sample and hold unit, and while the switch means is in an ON state, Supplied from the sample hold unit via the switch means. Comparing the target level from the sample-hold signal and the target level signal output means configured the comparison signal and a second comparison means for supplying to said laser drive means.
[0011]
Also, an optical disc apparatus according to the present invention includes a level detecting means for detecting a level of a laser beam emitted from a laser beam emitting means for irradiating an optical disc; Forming a sample hold signal indicating the level of the laser beam, outputting a target level signal for setting the level of the laser beam to a target level, comparing the sample hold signal with the target level signal, and setting the level of the laser beam to the target level. The target level signal is output until the level reaches the target level. When the laser beam level reaches the target level, a comparison indicating the difference between the target level signal and the sample hold signal is performed instead of the target level signal. A sample-and-hold means for outputting a signal; Characterized in that it comprises a light control device having a laser driving means for driving said laser beam emitting means in accordance with the level signal and the comparison signal.
[0012]
[Action]
In the light amount control device and the optical disk device according to the present invention, the sample and hold unit samples and holds the detection output from the level detection unit that detects the level of the laser beam applied to the optical disk and indicates the current laser beam level. Forming a signal, comparing the target level signal for setting the level of the laser beam to the target level and the sample hold signal, and laser driving the target level signal until the level of the laser beam reaches the target level. When the level of the laser beam reaches a target level, a comparison signal indicating a difference between the target level signal and the sample hold signal is supplied to the laser driving means instead of the target level signal. I do.
[0013]
【Example】
Hereinafter, embodiments of the light amount control device according to the present invention will be described with reference to the drawings.
[0014]
As shown in FIG. 1, a light amount control device according to an embodiment of the present invention applies a laser beam from a laser diode 3 serving as a laser beam emitting unit to a recordable CD (so-called CD-R) 1 provided as an optical disk. The present invention can be applied to a CD recording / reproducing apparatus that records data by forming a pit by irradiating a beam, and receives a signal from a monitor circuit 5 which is a level detecting means for detecting a level of a laser beam emitted from the laser diode 3. The writing sample and hold circuit 7 which is a sample and hold means for controlling the level of the laser beam based on the output has the following features.
[0015]
In the CD recording / reproducing apparatus shown in FIG. 1, when recording data, the CD-R 1 is driven to rotate at a constant linear velocity by the spindle motor 2 and the data to be recorded is transmitted to the data input terminal 9. The signal is supplied to the timing generation circuit 8 via the control circuit.
[0016]
When the data is supplied, the timing generation circuit 8 supplies a signal (data signal) indicating that the data is supplied to the write sample and hold circuit 7 and, in accordance with the data, the laser diode 3. Is supplied to a laser driver 4 which is a laser driving means.
[0017]
The write sample and hold circuit 7 is configured as shown in FIG. 2, and the data signal from the timing generation circuit 8 is supplied to a target level signal output circuit 26 as target level signal output means.
Assuming that the data signal is supplied at time t1 shown in FIG. 3A, the target level signal output circuit 26 outputs a target level on signal from this time t1. The voltage level of the target level on signal has a voltage that can immediately make the level of the laser beam emitted from the laser diode 3 suitable for recording. This target level on signal is supplied to a voltage / current (V / I) converter 29 via a first comparator 25 which is a first comparing means. Then, the current is converted into a current by the V / I converter 29 and supplied to the laser driver 4 shown in FIG.
[0019]
The laser driver 4 drives the laser diode 3 based on an on / off control signal from the timing generation circuit 8 so that a laser beam having a level corresponding to the target level on signal is emitted. Thus, the level of the laser beam emitted from the laser diode 3 at the start of recording can be immediately made suitable for recording. The laser beam is applied to the CD-R1, and data is recorded on the CD-R1 in the form of pits.
[0020]
The level of the laser beam applied to the CD-R1 is detected by the monitor circuit 5. The monitor circuit 5 receives the return light generated by irradiating the CD-R1 with the laser beam, and converts the received return light into an electric signal to form a detection signal indicating the current laser beam level. And output. The detection signal from the monitor circuit 5 is supplied to a reproduction sample-hold circuit 6 and a write sample-hold circuit 7. The reproduction sample and hold circuit 6 is used at the time of reproduction described later.
[0021]
As described above, the write sample and hold circuit 8 has a configuration as shown in FIG. 2, and the detection signal from the monitor circuit 5 is supplied to the sample and hold unit 21 via the input terminal 20. .
[0022]
The sample and hold section 21 samples and holds the detection signal indicating the current laser beam level by the sampling pulse from the timing generation circuit 8 shown in FIG. 1, and outputs the sample and hold signal via the reference signal input terminal 28b. The signal is supplied to a second comparator 28 which is a second comparing means.
[0023]
Here, the target level on signal from the target level signal output circuit 26 is supplied to a reference signal terminal 25 b of the first comparator 25 and to a voltage divider 27.
[0024]
As shown in FIG. 3B, the voltage divider 27 converts the target level on signal to a predetermined voltage division ratio (n: natural number) from time t1 when the target level on signal is supplied from the target level signal output circuit 26. ) And supplies the divided voltage to the second comparator 28 via the comparison signal input terminal 28a.
[0025]
The second comparator 28 compares the sample hold signal with the divided target level on signal. The level of the laser beam, that is, the level of the sample hold signal, gradually increases to a predetermined level from the start of recording as shown in FIG. When the level of the sample-and-hold signal becomes higher than the level of the divided target level-on signal by the above-described comparison, at the time t2 in FIG. As shown, the low-level switching signal output up to that point is output as a high-level switching signal.
[0026]
The switching signal output from the second comparator 28 is supplied to a switch 22 serving as a switch.
[0027]
The switch 22 is turned off when a low-level switching signal is supplied, and is turned on when the high-level switching signal is supplied.
[0028]
Therefore, as shown in FIG. 3E, the switch 22 is turned off until the time t2 when the low level switching signal is supplied, and from the time t2 when the high level switching signal starts to be supplied. ON controlled.
[0029]
When the switch 22 is turned on, a sample hold signal from the sample hold unit 21 is supplied to the first comparator 25 via the switch 22, the resistor 23, and the comparison signal input terminal 25a.
[0030]
As described above, the target level ON signal is supplied to the first comparator 25 via the reference signal terminal 25b. The first comparator 25 compares the target level-on signal with the sample-and-hold signal and outputs a comparison signal indicating the difference. The comparison signal output from the first comparator 25 is voltage / current converted by the V / I converter 29 and supplied to the laser driver 4 via the output terminal 30. The laser driver 4 drives the laser diode 3 so as to emit a laser beam having a level at which the difference between the target level on signal indicated by the comparison signal and the sample hold signal is zero.
[0031]
Thereby, a laser beam of a constant level can always be emitted from the laser diode 3 according to the data, and stable recording of data can be performed.
[0032]
The CD recording / reproducing apparatus according to the present embodiment servo-controls the level of the laser beam emitted from the laser diode 3 in a so-called negative feedback loop configuration. The laser diode 3 is controlled by an open-loop control by turning off the laser diode 22 and a target level-on signal having a voltage from the target level signal output circuit 26 having a voltage capable of immediately setting the level of the laser beam to a level suitable for recording. When the current level of the laser beam reaches a target level (a level suitable for recording), the switch 22 is turned on to perform closed loop control, and the laser diode 3 is turned on by the target level on signal and the sample. Drive with the difference from the hold signal.
[0033]
Thereby, the level of the laser beam emitted from the laser diode 3 at the start of recording can be immediately made suitable for recording. When data is additionally recorded, the level of the laser beam from the last part of the previously recorded data is increased. The next data can be recorded, which contributes to high-density recording of data.
[0034]
The servo control of such a negative feedback loop may be programmed and executed by a CPU (microcomputer) or the like.
[0035]
Next, the data thus recorded is reproduced at the time of reproduction. That is, at the time of this reproduction, the timing generation circuit 8 controls the laser diode 3 via the laser driver 4 so that a laser beam of a constant level weaker than at the time of recording is continuously emitted. The laser beam emitted from the laser diode 3 is applied to the CD-R1. A data detection unit (not shown) detects data based on reflected light generated by irradiating the CD-R1 with a laser beam, converts the data to analog data via a data processing circuit, and supplies the analog data to a speaker device or the like. Thereby, an acoustic output is obtained from the speaker device.
[0036]
On the other hand, the monitor circuit 5 forms a detection signal indicating the current level of the laser beam from the reflected light, and supplies this to the sample hold circuit 6 for reproduction.
[0037]
The sample hold circuit 6 for reproduction samples and holds the detection signal, compares the level of the sample hold signal with the target level of the laser beam for reproduction, and supplies the difference to the laser driver 4. . The laser driver 4 drives the laser diode 3 so as to emit a laser beam at such a level that the difference becomes zero. Thereby, the laser diode 3 can irradiate the CD-R 1 with a weak and constant level laser beam for reproduction, and stable reproduction can be performed.
[0038]
【The invention's effect】
As is clear from the above description, in the light amount control device and the optical disk device according to the present invention, the sample and hold signal indicating the current level of the laser beam, sampled and held by the sample and hold means, is set to the target level (for example, a level suitable for recording). Until the laser power reaches the target level, the laser beam emitting means can be driven by the target level signal for setting the laser power to the target level. Therefore, for example, the rise of the laser beam at the time of recording can be improved.
[0039]
Therefore, when data is additionally recorded, it is possible to record the next data from the last part of the previously recorded data.
Therefore, it is possible to contribute to high-density recording of data.
[Brief description of the drawings]
FIG. 1 is a block diagram when a light amount control device according to an embodiment of the present invention is applied to a CD recording / reproducing device.
FIG. 2 is a specific block diagram of a write sample and hold circuit provided in the CD recording / reproducing apparatus according to the embodiment.
FIG. 3 is a time chart for explaining an operation of the write sample and hold circuit.
[Explanation of symbols]
1 .... CD-R
2 ... Spindle motor 3 ... Laser diode 4 ... Laser driver 5 ... ····· Monitor circuit 6 ································ Sample Hold circuit 8 Timing generation circuit 9 Data input terminal 21 Sample Hold section 22 Switches 23, 24 Resistor 25 First comparator 26 ········· Target value output circuit 27 ··· Voltage divider 28 ··· Second comparator 29・ ・ ・ ・ ・ ・ ・ ・ ・ ・Pressure / current conversion circuit

Claims (3)

Level detecting means for detecting the level of the laser beam from the laser beam emitting means irradiated on the optical disc,
Samples and holds the detection output from said level detecting means to form a sample-and-hold signal indicating the level of current laser beam, and outputs a target level signal to the level of the laser beam and the target level, the sample hold Comparing the signal with the target level signal, outputting the target level signal until the laser beam level reaches the target level, and replacing the target level signal when the laser beam level reaches the target level. Sample and hold means for outputting a comparison signal indicating a difference between the target level signal and the sample and hold signal;
Light amount control apparatus, characterized in that it comprises a laser driving means for driving said laser beam emitting means in response to the target level signal and the comparison signal from the sample hold means. The sample and hold unit samples and holds a detection output from the level detection unit and outputs a sample and hold signal, and a level of the laser beam emitted from the laser beam emission unit as a target level. Target level signal output means for outputting a target level signal of the first, and a first comparison means for comparing a sample hold signal from the sample hold unit and a target level signal from the target level signal output means,
Switching means controlled by a comparison signal from the first comparison means to output a sample and hold signal from the sample and hold unit, and a switch from the sample and hold unit to the switch while the switch means is on. Means for comparing the sample and hold signal supplied via the means with the target level from the target level signal output means, and supplying the comparison signal to the laser driving means. 2. The light amount control device according to claim 1, wherein Level detecting means for detecting the level of the laser beam from the laser beam emitting means irradiated on the optical disc,
The detection output from the level detecting means is sampled and held to form a sample hold signal indicating the current laser beam level, and a target level signal for setting the laser beam level to a target level is output. Comparing the signal with the target level signal, outputting the target level signal until the laser beam level reaches the target level, and replacing the target level signal when the laser beam level reaches the target level. Sample and hold means for outputting a comparison signal indicating a difference between the target level signal and the sample and hold signal;
An optical disc device comprising: a light amount control device including a laser driving unit that drives the laser beam emitting unit in accordance with the target level signal and the comparison signal from the sample and hold unit.

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