JPH0378126A - Optical write controller - Google Patents

Abstract

PURPOSE:To form an optimum recording mark by allowing an optical output control means to control an optical output pattern for an information recording signal so that a level in a section in which a recording mark for a detected output from an optical detecting means is formed is constant. CONSTITUTION:In an optical output control circuit 16, a write strategy or the output pattern of a write light pulse is controlled according to the way that a change in the level of the part in which a recording mark (pit, etc.) for an optical detected output from an optical detector 22 is formed. The optical output pattern for the information recording signal is controlled so that the level of the section in which the recording mark for the detected output from the optical detecting means can be constant. Thus, regardless of the variance of a medium or the change with the lapse of time, an optimum recording mark, especially a recording mark of a fixed pit width, can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an optical write control device for controlling write light for recording information on an optical recording medium.

B1 Summary of the Invention The present invention provides an optical writing control device for controlling the optical output of a light source for writing recording marks of information recording signals on an optical recording medium, in which a light detecting means detects the return light of the light output from the light source by the optical recording medium. When controlling the light output of the light source based on this detection output and the information recording signal, the light output relative to the information recording signal is controlled so that the level of the detection output from the light detection means in the recording mark formation section is constant. By controlling the output pattern, it is possible to form optimal recording marks regardless of variations in the medium or changes over time.

BACKGROUND OF THE INVENTION In recent years, disk-shaped recording media such as optical disks and magneto-optical disks that utilize optical or magneto-optical signal recording and reproducing methods have been developed and are being supplied to the market.

These disc-shaped recording media include read-only memory (R), such as the so-called compact disc (CD).
OM) type recording media and the so-called write-once type (write-once type) where data can be written once by the user.
Recording media that allow data to be rewritten (so-called override), such as magneto-optical disks and other recording media, are known. /In an optical disk recording and reproducing device that performs reading, a spindle servo rotates the optical disk at a constant angular velocity or linear velocity, and a focus servo or trunking servo is applied to the optical head to change the recording track of the optical disk. It scans with a light beam. The optical head includes a built-in laser diode that is driven by a laser drive circuit to output a laser beam for recording and reproducing information, a photodetector that detects reflected light of the laser beam irradiated onto the optical disk, and the like. The focus servo and tracking servo are applied based on the detection output from the photodetector.

By the way, in an optical recording and reproducing apparatus that records and reproduces information on an optical recording medium by scanning a recording track with a light beam such as a laser, a laser diode or the like that is pulse-driven in accordance with an information recording signal in recording mode is used. Information is recorded by scanning a recording track on an optical recording medium with writing light emitted from a light source to form recording marks such as pits. In this case, due to the thermal characteristics of the optical recording medium, etc., there is a difference between the irradiation timing of the writing light and the actual recording formation timing of recording marks such as pits.
For example, as shown in FIG. 8, it takes 30 minutes from the start of irradiation of the write light pulse PIll corresponding to the information recording signal until the pit PT actually starts to be recorded and formed on the recording track.
There is a time delay τ of about 0 to 400 ns, and the detection output waveform of the reflected light (return light) of the writing light irradiated onto the recording track. , a level change occurs in accordance with the time delay τ. That is, during the delay time 10, the reflectance is high and the detected light level is high because the pit PT is not formed, but after the delay time τ has elapsed, the focus P is high.
Since T is formed and the reflectance decreases, the detection light level decreases.

Additionally, in general, the error rate during data recording in an optical disk recording/playback device depends on the power of the output light (laser light, etc.) from the data writing light source, and data writing is performed using the optimal optical output. It is known that there is a need.

That is, if the writing light output is not appropriate, for example, as shown in FIG. 9, a teardrop-shaped pit PT? D may be formed and stable recording may not be possible. This ninth
In the figure, the direction of movement due to rotation of the optical disc is indicated by arrow a.
In this case, the moving direction of the light beam or the moving direction of the photodetector (23) is relatively in the direction indicated by the arrow a, which is opposite to the arrow a.

D0 Problems to be Solved by the Invention Incidentally, the optimum power of the above-mentioned harmful light varies depending on the type of optical recording medium, and therefore, the above-mentioned information writing laser is applied to a predetermined area of a recording medium such as an optical disk. Information regarding optical power and the like is recorded in advance, and the optical output from the data writing light source is controlled based on this information. In this case, the write light output and control strategy may include changing the width of the light pulse or changing the level of the light output. For example, n times the period T of the channel clock (
A strategy that uses output light with a pulse width of nT as a light pulse to form recording marks such as pits (n is an integer), and a strategy that uses output light with a pulse width of (n-α)T (where 0<α<1)
Considering the case where a strategy using an output light with a pulse width of (n-1)T and a strategy using an output light with a pulse width of The information is written at a predetermined position on the recording medium, and when the medium is used, the information written at this predetermined position is read out and the recording strategy (write light pulse width) is selected. ).

However, the state of recording marks (bits, etc.) for the same optical output may appear differently due to variations in the characteristics of the medium or changes in characteristics over time. This requires a wide margin. Therefore, in order to secure such a wide margin, high accuracy and stability are required of electric circuits, optical systems, etc., and there are restrictions on the recording density of the medium.

By the way, the inventor of this case previously filed patent application No. 63-30154.
In the specification and drawings of No. 6, a technology is proposed in which the optical output of a light source for writing data to an optical recording medium is controlled based on the detected output of the amount of reflected light. ) Changes in the reflected light detection waveform due to PTTD are not considered.

Therefore, in view of the above-mentioned conventional situation, the present invention has been devised to provide a method with a focus width such as the above-mentioned teardrop-shaped bit, which enables optimal recording mark formation regardless of variations in the characteristics of the medium or changes over time. An object of the present invention is to provide an optical writing control device that can prevent the formation of recording marks that change.

81 Means for Solving Problems According to the optical writing control device according to the present invention, a light source that outputs writing light for writing an information recording signal onto an optical recording medium as a recording mark pattern such as a focus pattern; a light detection means for detecting return light such as reflected light by the optical recording medium of the light output from the light source; and controlling the light output of the light source based on the information recording signal and the detection output from the light detection means. and a light output control means,
This light output control means solves the above problem by controlling the light output pattern for the information recording signal so that the level of the detection output from the light detection means in the recording mark formation section is constant. It is.

Here, the control of the light output pattern includes control of the light pulse width, control of the light output level, control of the light output waveform, and the like.

A light output control means for controlling the writing light output from the light source based on the F0 action information recording signal and the detection output from the light detection means changes the light output pattern for the information recording signal to the detection output from the light detection means. By controlling the level of the recording mark forming section to be constant, it is possible to form optimal recording marks, especially recording marks with a constant bit width, etc., regardless of variations in the medium or changes over time.

G. Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a recording and reproducing system when the present invention is applied to an optical disc recording and reproducing apparatus that optically performs recording and reproducing on an optical disc as a write-once optical recording medium. That is, in this recording/reproducing system, a write-once optical disc (1) is rotated by a spindle motor (2) at a constant linear velocity, and the light source of the optical head (20) is directed to the recording track of the optical disc (1). An information recording signal in a predetermined data format is optically recorded and reproduced by scanning with light from the laser diode (21), that is, a laser beam from a laser diode (21).

In the optical disk recording and reproducing apparatus shown in FIG. 1, the optical head (20) includes a laser diode (21) that is driven by a laser drive circuit (14) and outputs a laser beam for recording and reproducing digital data. , the laser beam from the laser diode (21) is applied to the optical disc (
It is configured to include a built-in photodetector (22) for detecting the reflected light from 1). This optical head (20) scans the recording track of the optical disc (1) with a laser beam output from the laser diode (21), thereby recording and reproducing information on the recording trunk of the optical disc (1). It is designed to do this.

Next, in the recording system of the optical disc recording and reproducing apparatus, digital data DIN to be recorded is supplied from an input terminal (10) to an encoder (12) via an input/output interface (11). This encoder (12) converts the input digital data DIN into a recording data string in a predetermined data format, for example, a so-called CD format, and also converts the input digital data DIN into a recording data string in a predetermined data format, for example, a so-called CD format, and also converts the input digital data DIN into a recording data string that is actually recorded using a modulation method such as so-called EFM (8-16 modulation). The information recording signal is modulated into an information recording signal in the form of a signal. This information recording signal is transmitted to the laser diode (21) of the optical head (20) which is the light source.
) optical output control circuit section (16) for controlling the optical output of the
is being sent to. This optical output control circuit section (16) consists of a write pulse generation circuit (13) and a laser drive circuit (14) to which the write pulse from the write pulse generation circuit (13) is supplied. That is, an information recording signal is obtained by converting the digital data DIN into a data string in a predetermined format and modulating it, and the laser drive circuit (14) drives the optical head (20) with a write pulse corresponding to this information recording signal. ) by pulse-driving the radar diode (21), a recording mark pattern (bit pattern, etc.) corresponding to the information recording signal is recorded on the recording track of the optical disc (1). In addition, in order to control the power of the laser beam from the laser diode (21) that is the light source to a constant value,
A so-called APC (automatic power control) circuit (15) is provided.

These write pulse generation circuit (13), laser drive circuit (14), and APC circuit (15) are controlled by a system controller (30) according to each operation mode.

Further, in the optical output control circuit section (16), the write strategy or the output pattern of the write light pulse is adjusted to the level of the recording mark (bit, etc.) forming portion of the optical detection output from the photodetector (22) consisting of a photodetector. Control can be obtained depending on the form of change in . Specifically, for example, a write pulse generation circuit (1
3) Prepare in advance several types of correspondence between the write pulse width and the pulse width of the information recording signal, and among these multiple types of correspondence between the pulse widths, select the recording mark forming section of the photodetection output. control so that the level is constant (the waveform curve is flat),
Examples include variably controlling the level of the drive output from the laser drive circuit (14) and variably controlling the pulse output waveform itself.

Next, the reproducing system of this optical disk recording/reproducing apparatus includes a photodetector (22) such as a photodetector of the optical head (20).
The photodetection output is regenerated by R through the regenerative amplifier (31).
It is equipped with a decoder (32) and the like that are supplied as F signals. In this reproduction system, the encoder (12) of the recording system receives the photodetection output from the photodetector (22).
Reproduction data D obtained by performing decoding processing corresponding to the encoding processing at the decoder (32). u7 is output from the output terminal (33). The regenerative amplifier (31) is also controlled by the system controller (30) according to each operation mode.

Furthermore, a spindle servo circuit (40), a head servo circuit (41), etc. are provided as a so-called servo system of the optical disk recording/reproducing apparatus. These spindle servo circuits (40) and head servo circuits (41) receive the reflected light (return light) detection output from the photodetector (22) of the optical head (20), a so-called regenerative RF signal, and a regenerative amplifier. (31). The spindle servo circuit (40) detects the rotational speed of the spindle motor (2) based on the photodetection output, and feedback-controls the drive circuit (3) of the spindle motor (2), thereby controlling the optical disc (1). Spindle servo control is performed to keep the rotation of ) at a constant linear velocity, for example. Furthermore, the Herad servo circuit (41) detects focus errors and tracking errors of the laser beam based on the detection output, and drives the objective lens of the optical head (20) based on the error signal. (not shown) to perform head servo control such as focus servo and trunking servo.

Next, regarding the control of the optical writing strategy described above,
This will be explained in detail below.

First, a writing laser beam from a laser diode (21) that is a light source is applied to an optical disc (1) that is an optical recording medium.
), recording marks such as focus marks are recorded and formed, but the specific shape of these pits etc. depends on the power and duration of the laser beam (light beam) as mentioned above. (pulse width) etc. In this case, the specific pit shape is as follows:
A shape in which the pit width changes, such as the teardrop shape shown in the figure, is not preferable, and a shape in which the focus width is constant, such as an oval shape, is preferable. This is caused by a change in the level of the output from the photodetector (22) that detects the reflected light from the optical disc (1), especially in the bit forming sections R and A of the photodetection output DOF shown in FIG. You can tell by looking at it.

For this purpose, a sampling pulse generation circuit (17) is provided, and this sampling pulse generation circuit (17) determines which part of the pit formation sections R and A are to be selected according to the write pulse output PIIR from the write pulse generation circuit (13). points (for example, time points 1,, 1,..., tz
) is obtained, and this sampling pulse SP is sent to the sampling clock input terminal of the A/D converter (18). The A/D converter (18) is supplied with the photodetection output DOP from the regenerative amplifier (31). , at each point in time L L
+L 4+...+By sampling at the Lth point and A/D converting, each sampling output Xff+X4+
....xll is obtained.

The sampling output from this A/D converter (1g) is
The signal is sent to the system controller (30), where it is determined whether the level changes in the pit formation sections R and A, and in particular whether the level is stable and approximately constant. For example, each sampling output value X3+X4+..., χ from the A/D converter (18) is determined by the system controller (30) as an error X3
+Xa Xs+”+X+o Whether each absolute value of
It is determined whether or not <ε (i=3 to 10). In addition, it may be determined whether or not X3 Xll < e, and when the average value of each sampling value is xI, whether or not The decision may be made.

Here, the light detection output suitable for determining the level change due to the recording shape of the focus as described above is the following photodetector output (23A) of the photodetector (23) shown in FIG.
, (23B) is preferably used. That is, in FIG. 3, the photodetector (23) for detecting the returning laser beam is divided into four parts in the track direction and track width direction, and has letter light receiving parts (23A), (23B), (23C), (
23[1] exists. When the direction of movement due to the rotation of the optical disk is the direction of arrow a, the direction of movement of the light beam or the direction of movement of the photodetector (23) is relatively in the direction of arrow a, which is opposite to arrow a.
3^)+ (23B) is provided on the trailing side of this photodetector moving direction (arrow direction), and the light receiving part (23G)
, (23D) are provided on the leading side in the direction of the arrow. At this time, the focus PT by the writing light is recorded and formed so as to extend in the direction of arrow a from approximately the center position of the photodetector (23), and when this bit is in the shape of a teardrop, the trailing side light receiving part (23A), ( 23B) changes and appears as the output DOP in FIG. 2, whereas the outputs from the preceding light receiving sections (23C) and (23D) do not change much. Therefore, the trailing side light receiving section (23
It is preferable to use only the output from A) and (23B). Note that this photodetector (23) is provided within the photodetector (22), and the RF reproduction signal and tracking signal are transmitted to the light receiving section. (23A).

Of course, the sum or difference of each output from (23B), (23C), and (230) can be used.

Next, in the optical output control circuit section (16), a plurality of write strategies are prepared in advance, and the bit formation period F? ry
By switching and selecting the above-mentioned write strategy while determining the state of level change within the recording mark formation period, writing that satisfies the above conditions (i.e., the level of the recorded mark forming section is approximately constant and stable) is performed. strategies can be found. For example, when starting to use a recording medium such as an optical disk, the above-mentioned insertion strategies are applied to a predetermined area of the recording medium, such as a trial writing area such as the inner lead-in area of the optical disk, prior to data recording. Actual writing is performed while switching and selecting , and a writing strategy is determined such that the detected output of reflected light etc. satisfies the above conditions. From now on, data will be written to this medium under this determined writing strategy. Just do it. Alternatively, a trial writing area may be provided in the sector head portion of the disk, and each time data is written to each sector, trial writing may be performed to the sector head portion to select the optimum strategy. Furthermore, the optimum strategy may be selected and controlled in real time by continuing to judge the state of change in the level of the photodetection output even during actual data writing.

Here, as a specific example of the plurality of write strategies to be switched and selected, for example, the write pulse generation circuit (13
) A case will be described in which several types of correspondence between the write pulse width and the pulse width of the information recording signal are prepared in advance. For example, as shown in FIG. 4, for a pulse with a pulse width of nT (T is the channel clock period, n is an integer) as the information recording signal S□, for example, (m+
1) Write light pulse P h*-0 with different pulse widths,
Pwi-1, . be. These signals with various pulse widths have respective pulse widths of nT, nT-Δ,..., nT-m with respect to the pulse width nT of the information recording signal S1.
Δ, which can be easily obtained using a configuration as shown in FIG. 5, for example. That is, in FIG. 5, the above information recording signal is supplied to the input terminal 35, and this information recording signal is supplied to the delay circuit (36) and the AND gate (38). The delay circuit (36) is configured to output a plurality of delay outputs in parallel according to a plurality of delay times that differ by the above-mentioned Δ unit, and each of these delay outputs is output by switching the changeover selection switch (37). The signal is sent to the AND gate (38) via the signal. This anime game) (
38), the original information recording signal S
), one of the write light pulses shown in FIG. 4 is obtained. When controlling the selection of the optimum strategy, the light detection output is determined while switching the changeover selection switch (37) in a predetermined order, and the strategy (specifically, the switching position of the changeover selection switch (37)) that satisfies the above conditions is determined. ). In this case, the selection control of the write strategy, that is, the order of switching control of the write light pulse width, is such that, for example, starting from the maximum pulse width nT, the pulse width is sequentially decreased by the above-mentioned Δ, and It is sufficient to stop switching when the pulse width reaches a value that satisfies the following (the level within the range is approximately constant). In addition, switching control may be performed to sequentially widen the pulse width from the minimum pulse width, or the direction of increase/decrease in the pulse width may be changed depending on the level change state of the photodetection output within the pit formation section. . In this way, the switching selection switch (37
) is switched and connected, and by writing the recording data, data 1 can be written in the optimum recording state (bit formation state). However, if pulse width control is to be performed in real time at the same time as data writing, it is necessary to control the increase or decrease of the pulse width in accordance with the level change state of the photodetection output within the pit formation section.

Note that in an organic dye-based recording medium, the writing light pulse width is set to (n-1) for an information recording signal with a pulse width of nT.
The inventor of the present invention has confirmed that suitable writing can be performed when the value is set near T.

The above has been an explanation of an example in which the pulse width of the write light pulse is controlled as a write strategy. The level of the waveform can be kept constant (the waveform curve is flat).

That is, for example, as shown in FIG. 6, the output level L of the write light pulse psw. , may be increased or decreased as shown by the broken line in FIG. 6, thereby controlling the level of the recorded mark forming section to be constant. Or, as shown in FIG. 7, writing a waveform whose level changes over time, such as a writing optical pulse Psw-a whose level monotonically increases or a writing optical pulse Pg-s whose level decreases by a single IK, etc. A light pulse may be used to control the level of the recording mark forming section to be constant. Furthermore, it goes without saying that these pulse width control, optical output level control, optical pulse waveform um, etc. may be arbitrarily combined to variably control the optical output level at the same time as the pulse width.

Note that the present invention is not limited to the above-described embodiments, and can be applied not only to optical disks but also to optical cards and the like as optical recording media.

Furthermore, it goes without saying that the specific circuit B configuration for pulse width control is not limited to the example shown in FIG.

H1 Effects of the Invention According to the optical writing control device according to the present invention, the optical output control means that controls the writing light output from the light source based on the information recording signal and the detection output from the light detection means, By controlling the first cover pattern so that the level of the detection output from the optical detection means in the recording mark formation section is constant, it is possible to form optimal recording marks, especially the width, regardless of medium variations or aging. It is possible to form recording marks such as pits that are constant.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a recording and reproducing system of an optical disk recording and reproducing apparatus using an optical writing control device as an embodiment of the present invention, and FIG. 2 shows the operation of the main parts of the embodiment. FIG. 3 is a plan view schematically showing an example of a photodetector, FIG. 4 is a timing chart for explaining an example of writing light pulse width control, and FIG. 5 is a diagram showing each pulse width. A circuit diagram showing a specific configuration for forming a write light pulse, FIG. 6 is a waveform diagram for explaining an example of output level control of a write light pulse, and FIG. 7 is an example of waveform control of a write light pulse. FIG. 8 is a waveform diagram for explaining the state of bit recording formation and reflected light detection output according to the writing light pulse, and FIG. 9 is a plan view showing a specific example of a teardrop-shaped bit. be. (20) (21) (22) (23) Optical head laser diode photodetector photodetector

Claims (1)

[Scope of Claims] A light source that outputs a writing light for writing an information recording signal as a recording mark pattern on an optical recording medium, and a light source that detects the return light of the light output from the light source by the optical recording medium. and a light output control means for controlling the light output of the light source based on the information recording signal and the detection output from the light detection means, and the light output control means controls the light output in response to the information recording signal. An optical writing control device characterized in that the output pattern is controlled so that the level of the detection output from the optical detection means in the recording mark forming section is constant.