Optical recording/reproducing method and apparatus

In an optical recording/reproducing method and apparatus of the present invention, a modulation parameter is calculated for each of reproduced data signals, each modulation parameter corresponding to one of respective recording powers. An optimum recording power is determined based on a relationship between the modulation parameters and the recording powers, wherein a sequence of pairs of the modulation parameter and the recording power is selected, a gamma, which defines a ratio of a change of the modulation parameter to a change of the recording power, is calculated for each of the selected pairs, and a target recording power corresponding to the optimum recording power is found based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero. When selecting the pairs of the modulation parameter and the recording power, a pair of the modulation parameter and the recording power is omitted if a value of the modulation parameter of the pair is not larger than a threshold value, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the threshold value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical recording/reproducing method and apparatus that records information onto or reproduces information from a storage medium, such as an optical disk, by focusing a light beam, emitted by a light source, onto a recording layer of the storage medium.

2. Description of the Related Art

Recently, there are various optical storage media that are provided for recording and reproducing of information, including CD-DA, CD-ROM, CD-R (compact disk recordable), DVD-ROM, DVD-R (digital versatile disk recordable), etc.

Japanese Laid-Open Patent Application No. 11-134691 discloses an optical recording/reproducing method which determines an optimum recording power based on a relationship between the modulation parameters and the recording powers. In this method, a test writing is first performed in which writing a pattern of marks and spaces to an optical storage medium with a recording power is repeated by sequentially changing the recording power with increments. A test reading is next performed in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium. A modulation parameter is then calculated for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers. Then, an optimum recording power is determined based on the relationship between the modulation parameters and the recording powers.

However, in the optical recording/reproducing method of the above document, the algorithm to determine the optimum recording power is inadequate for accurately checking the rising slope of the modulation parameter related to the reproduced data signal. In the optical recording/reproducing method of the above document, variations of the optimum recording power may be produced due to inaccurate checking of the rising slope of the modulation parameter.

Generally, the effective range of the write power, which is supplied to the laser diode, that the laser beam emitted by the laser diode and focused on the storage medium starts forming a mark on the storage medium is very narrow. On the other hand, the locations of the storage medium to which the test patterns are written are limited, and an increase of the amount of increments to the write power level or an increase of the number of the cycles of the test writing/reading will not be an appropriate solution to the problem of inaccurate checking of the rising slope of the modulation parameter.

For example, the recording power is sequentially changed with increments of 1.0 mW from 10.0 mW to 19.0 mW, which falls within a range of ±30% centered around 15.0 mW. In this case, the test writing is repeated ten times by sequentially changing the recording power with such increments.

In a case of CD-RW media, a phase-change recording material is used in the recording layer of the optical disk. The effective range of write power supplied to the laser diode that enables the emitted laser beam focused on the disk to form a mark on the storage medium is very narrow. If the write power is increased by 1 or 2 mW, the amplitude of the reproduced data signal becomes considerably large. Specifically, even if the reproduced signal amplitude is about 0.1 (noise level) at the write power p=14 mW, the reproduced signal amplitude abruptly rises to a high level of 0.5 to 1.4 at the write power p=15 mW that is incremented from 14 mW.

Accordingly, it is desirable that the algorithm to determine the optimum recording power includes a data selection procedure for accurately checking the rising slope of the modulation parameter related to the reproduced data signal. As described above, if the checking of the rising slope of the modulation parameter related to the reproduced data signal is inaccurate, variations of the optimum recording power may be produced.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an optical recording/reproducing method and apparatus that minimizes variations of the optimum recording power through a recording power control algorithm that accurately checks the rising slope of the modulation parameter related to the reproduced data signal.

Another object of the present invention is to provide an optical recording/reproducing method that minimizes variations of the optimum recording power through a recording power control algorithm, so that the optimum recording power is accurately determined without being affected by noise.

Another object of the present invention is to provide an optical recording/reproducing apparatus that minimizes variations of the optimum recording power through a recording power control algorithm, so that the optimum recording power is accurately determined without being affected by noise.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; performing a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and determining an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determining step comprises the steps of: selecting, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; calculating a gamma=(Δh/m)/(Δp/p) for each of the selected pairs of the modulation parameter m and the recording power p, the gamma defining a ratio of a change of the modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and finding a target recording power corresponding to the optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero, wherein, in the selecting step, a pair of the modulation parameter m and the recording power p is omitted if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; performing a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and determining an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determining step comprises the steps of: selecting, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; approximating the modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the modulation parameter m and the recording power p; and finding a target recording power corresponding to the optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value, wherein, in the selecting step, a pair of the modulation parameter m and the recording power p is omitted if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; performing an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; setting a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; performing a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; performing a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; selecting, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; calculating a gamma=(Δm/m)/(Δp/p) for each of the selected pairs of the second modulation parameter m and the recording power p, the gamma defining a ratio of a change of the second modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and finding a target recording power corresponding to an optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; performing an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; setting a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; performing a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; performing a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns bn the storage medium; calculating a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; selecting, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; approximating the second modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the second modulation parameter m and the recording power p; and finding a target recording power corresponding to an optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: a test writing unit which performs a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; a test reading unit which performs a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a calculation unit which calculates a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and a determination unit which determines an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determination unit comprises: a selection unit which selects, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; a gamma calculation unit which calculates a gamma=(Δm/m)/(Δp/p) for each of the selected pairs of the modulation parameter m and the recording power p, the gamma defining a ratio of a change of the modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and a target recording power unit which finds a target recording power corresponding to the optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero, wherein the selection unit omits a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and selects a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: test writing unit which performs a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; a test reading unit which performs a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a calculation unit which calculates a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and a determination unit which determines an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determination unit comprises: a selection unit which selects, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; an approximation unit which approximates the modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the modulation parameter m and the recording power p; and a target recording power unit which finds a target recording power corresponding to the optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value, wherein the selection unit omits a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and selects a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: a first test writing unit which performs an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; a first test reading unit which performs an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a first calculation unit which calculates a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; a recording power unit which sets a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; a second test writing unit which performs a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; a second test reading unit which performs a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a second calculation unit which calculates a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; a selection unit which selects, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; a gamma calculation unit which calculates a gamma=(Δm/m)/(Δp/p) for each of the selected pairs of the second modulation parameter m and the recording power p, the gamma defining a ratio of a change of the second modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and a target recording power unit which finds a target recording power corresponding to an optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero.

The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: a first test writing unit which performs an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; a first test reading unit which performs an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a first calculation unit which calculates a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; a recording power unit which sets a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; a second test writing unit which performs a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; a second test reading unit which performs a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a second calculation unit which calculates a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; a selection unit which selects, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; a function approximation unit which approximates the second modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the second modulation parameter m and the recording power p; and a target recording power unit which finds a target recording power corresponding to an optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value.

In the optical recording/reproducing method and apparatus of the present invention, when selecting a sequence of pairs of the modulation parameter and the recording power, a pair of the modulation parameter and the recording power is omitted if a value of the modulation parameter of that pair is not larger than a threshold value, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the threshold value.

The recording power control algorithm according to the present invention accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A description will now be provided of preferred embodiments of the present invention with reference to the accompanying drawings.

FIG. 1shows one preferred embodiment of the optical recording/reproducing apparatus of the invention. As shown inFIG. 1, an optical storage medium101in the present embodiment is an optical disk101. Alternatively, the storage medium101may be another read-write storage medium.

In the optical recording/reproducing apparatus ofFIG. 1, the optical disk101is rotated by a spindle motor102, and an optical pickup104accesses the optical disk101when it is rotated. The optical pickup104includes a light source (not shown) that emits a light beam to the optical disk101. In the present embodiment, the light source is, for example, a laser diode (called LD) that emits a laser light beam. A focusing lens103focuses the light beam, emitted by the optical pickup104, onto a recording layer of the optical disk101.

The optical recording/reproducing apparatus ofFIG. 1carries out the recording of data onto and the reproducing of data from the recording layer of the optical disk101by focusing the light beam onto the optical disk recording layer and receiving a reflected light beam from the optical disk recording layer by means of the optical pickup104.

In the optical recording/reproducing apparatus ofFIG. 1, a laser power control unit109and a controller108are provided. The controller108supplies a power signal “p” to the laser power control unit109, and the laser power control unit109controls the power supplied to the LD (the light source) of the optical pickup104based on the power signal “p” supplied by the controller108. Specifically, the laser power control unit109drives the LD of the optical pickup104with the power indicated by the received power signal “p”, such that a test writing power level of the LD of the optical pickup104is determined. In accordance with the test writing power level determined by the laser power control unit109, the optical pickup104records a pattern of marks and spaces, which corresponds to a data pattern, indicated by a pulsed signal supplied by a data modulation unit (not shown), onto the recording layer of the optical disk101by focusing the laser beam emitted by the LD of the optical pickup104(with the test writing power level) onto the recording layer of the optical disk101.

In the optical pickup104, the laser beam emitted by the LD is focused onto the recording layer of the optical disk101through the focusing lens103, and a reflected laser beam from the recording layer of the optical disk101is received through the focusing lens103by a light receiving portion (not shown) of the optical pickup104. The received laser beam is optoelectrically converted into a data signal by the light receiving portion of the optical pickup104, and then the optical pickup104derives from the received laser beam a reproduced data signal that is indicative of the data recorded on the recording layer of the optical disk101.

In the optical recording/reproducing apparatus ofFIG. 1, the reproduced data signal is supplied from the optical pickup104to a radio frequency detection unit (RF)105. This data signal is amplified at the RF105, and the amplified data signal is supplied from the RF105to a peak-level holding unit (P/H)106. The P/H106detects and holds a peak level of the amplified data signal, and outputs a peak-level signal “pk”, which is indicative of the data signal peak level, to the controller108. In parallel to the P/H106, the amplified data signal is supplied from the RF105to a bottom-level holding unit (B/H)107. The B/H107detects and holds a bottom level of the amplified data signal, and outputs a bottom-level signal “bt”, which is indicative of the data signal bottom level, to the controller108.

In the optical recording/reproducing apparatus ofFIG. 1, the controller108is formed by a microcomputer generally including a CPU (central processing unit), a program ROM (read-only memory), a data RAM (random access memory), an A/D (analog-to-digital) converter, and a D/A (digital-to-analog) converter, and others. The controller108receives both the peak-level signal “pk” output by the P/H106and the bottom-level signal “bt” output by the B/H107, and converts them into respective digital signals through the A/D converter, so that the controller108derives the peak level and the bottom level of the data signal from the resulting digital signals. The controller108converts a calculated optimum power into an analog signal through the D/A converter, and supplies the analog signal to the laser power control unit109as the power signal “p”.

FIG. 2shows a recording power control routine that is executed by the optical recording/reproducing apparatus ofFIG. 1.

Hereinafter, the following symbols are used to express calculations in the recording power control routine: “*” denotes a multiplication; “/” denotes a division; “sqrt(x)” denotes a square root of x.

In the recording power control routine ofFIG. 2, the controller108at step201performs a test writing procedure in which recording of a pattern of marks and spaces onto a power calibration area (PCA) of the optical disk101with the recording power (indicated by the power signal “p”) is repeated by sequentially changing the recording power with increments of a predetermined power. Generally, an optical disk, such as the optical disk101, is provided with a PCA that is used by a disk drive during a test writing procedure (also called a write-PCA step) to perform a power calibration of the light source or the LD of the optical pickup.

The test writing procedure of step201is repeated a given number of times by incrementing the power signal “p”, which is supplied to the laser power control unit109, for each of respective cycles of the test writing. For each of the respective cycles of the test writing, the optical pickup104records a test pattern of marks and spaces onto one of sectors of the PCA of the optical disk101by focusing the laser beam emitted by the LD of the optical pickup104onto the recording layer of the optical disk104.

Specifically, in the present embodiment, the test writing procedure of step201is repeated ten times by sequentially changing the power signal “p”, supplied to the laser power control unit109, from 9.0 mW to 18.0 mW with increments of 1.0 mW, and the corresponding test patterns of marks and spaces are respectively recorded onto the corresponding sectors of the PCA of the optical disk101by means of the optical pickup104.

However, the recording power control routine according to the present invention is not limited to this embodiment. Any variation or modification may be made to the amount of increments to the write power level, the number of the cycles of the test writing/reading, and the portions of the optical disk where the test patterns are written.

After the step201is performed, the controller108at step202performs a test reading procedure (also called a read-PCA step) in which reproducing of the pattern from the PCA of the optical disk101is repeated for all of the test patterns that have been recorded onto the PCA of the optical disk101at the step201. A data signal, reproduced from one of the test patterns in the PCA of the optical disk101, is supplied from the optical pickup104to the RF105, and the data signal is amplified at the RF105. The P/H106detects and holds a peak level of the amplified data signal and outputs a peak-level signal “pk” to the controller108. The B/H107detects and holds a bottom level of the amplified data signal and outputs a bottom-level signal “bt” to the controller108. Hence, the controller108detects the peak-level signal “pk” and the bottom-level signal “bt” for each reproduced data signal.

After the step202is performed, the controller108at step203performs a data selection procedure. In the data selection procedure, the controller108calculates a modulation parameter m(i) for each reproduced data signal in accordance with the formula: m(i)=(pk(i)−bt(i))/pk(i) where i=0 to 9. In this data selection procedure of step203, the controller108determines whether the modulation parameter of a particular one of the reproduced data signals is necessary for the recording power control, based on the value of each calculated modulation parameter m. Then, the controller108selects the necessary data for the recording power control and omits the unnecessary data from the recording power control, which will be described below in greater detail.

The difference (pk−bt) between the peak level and the bottom level of the reproduced data signal is called the reproduced signal amplitude. If the data selection procedure is performed based on the value of the reproduced signal amplitude, the influences of the reflection angles of respective optical disks will not be negligible, and the recording power control will be inaccurate. To avoid this problem, it is desired to carry out the data selection procedure based on the value of the modulation parameter.

FIG. 5shows a detailed data selection procedure in the recording power control routine ofFIG. 2. The data selection procedure ofFIG. 5corresponds to the step203of the recording power control routine ofFIG. 2.

As shown inFIG. 5, the controller108at step500resets a data counter “j” to zero and resets a flag “m_rise” to zero. The data counter “j” is incremented every time one of the reproduced data signals is processed. The flag “m_rise” is set to one when a rise of the modulation parameter m occurs (at which the calculated modulation parameter value first exceeds a threshold value), and otherwise it is reset to zero.

The controller108at step501repeats the data selection procedure for all of the respective reproduced data signals. Specifically, in the present embodiment, the test reading procedure of the step202ofFIG. 2is repeated ten times so that ten reproduced data signals are obtained through the test reading of the optical disk101, and therefore the data selection procedure ofFIG. 5is repeated ten times for all of the respective reproduced data signals.

The controller108at step502calculates the reproduced signal amplitude amp(i) for one of the reproduced data signals in accordance with the formula: amp(i)=pk(i)−bt(i) where i=0 to 9, and calculates the modulation parameter m(i) for one of the reproduced data signals in accordance with the formula: m(i)=amp(i)/pk(i) where i=0 to 9. In this manner, the controller108at step502obtains the values of m(i) and p(i) for one of the reproduced data signals, and these values will form the basis for the data selection for the recording power control.

The controller108at step503selects the values of the present modulation parameter m(i) and the present power signal p(i) for the recording power control if the value of the present modulation parameter m(i) is larger than a threshold value “th1”. The controller at step503selects the values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) for the recording power control if the value of the present modulation parameter m(i) first exceeds the threshold value “th1”. Otherwise the controller108omits the values of m(i) and p(i) from the recording power control.

Further, in the step503, the controller108assigns the selected value of m(i) and the selected value of p(i) to a variable M(j) and a variable P(j), respectively. The variables M(j) and P(j) are used to indicate the selected data [m(i), p(i)] for the recording power control. The data counter “j” is incremented (j=j+1) after the substitution of the selected data into the variables M(j) and P(j) for one of the reproduced data signals is completed.

The controller at step504increments the “i” (i=i+1). The control of the controller108is transferred to the above step501. The above steps502and503are repeated for all of the reproduced data signals. When the data selection for all of the reproduced data signals is completed, the controller108at step505assigns the value of the data counter “j” to a variable N (N=j). The data selection procedure of the step203in the recording power control routine ofFIG. 2ends, and the control of the controller108is transferred to the next step204.

FIG. 7shows an example of the selected data that are derived from the data selection procedure ofFIG. 5.

InFIG. 7, the horizontal axis indicates the recording power (or write power) “Pw” that is equivalent to the power signal “p”, and the point at100in the horizontal scale corresponds to 10.0 mW. InFIG. 7, the vertical axis (on the left side) indicates the modulation parameter “m” that corresponds to the value of the calculated modulation parameter m(i). In the example ofFIG. 7, the threshold value “th1” used in the data selection procedure ofFIG. 5is equal to 0.2 (th1=0.2). The power signal “p” (or the write power Pw) is sequentially changed from 9.0 mW to 18.0 mW with increments of 1.0 mW during the test writing procedure of the step201ofFIG. 2.

In the example ofFIG. 7, among the data for all of the ten reproduced data signals, the value of the modulation parameter m(i) for the write power Pw=120 (or 12.0 mW) first exceeds the threshold value “th1” (=0.2). Hence, the controller108selects the values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) (=11.0 mW; Pw=110) for the recording power control as in the example ofFIG. 7. The selection of this data is illustrated by the circle inFIG. 7.

Further, in the example ofFIG. 7, the vertical axis (on the right side) indicates the gamma (=(Δm/m)/(Δp/p) ) that defines the ratio of a change of the modulation parameter m, normalized by the present modulation parameter value, to a change of the power signal p, normalized by the present power signal value. In the example ofFIG. 7, a target gamma “gammaT” that is a target value of the gamma(i) is equal to 1.65. In the example ofFIG. 7, the values of the gamma with respect to the respective selected data, which are calculated by the controller108in step204, are illustrated, which will be described later.

Referring back toFIG. 2, after the step203is performed, the controller108at step204performs a gamma calculation procedure.

FIG. 6shows a detailed gamma calculation procedure in the recording power control routine ofFIG. 2. The procedure ofFIG. 6corresponds to the step204in the recording power control routine ofFIG. 2.

As shown inFIG. 6, the controller108at step601repeats the gamma calculation procedure for all of the respective selected data that are obtained in the step203ofFIG. 2. The “N” in the present embodiment is the same as the value of the variable N obtained in the step505ofFIG. 5. The variables M(j) and P(j) that are used in the step503ofFIG. 5are rewritten into the selected data [m(i), p(i)] in the gamma calculation procedure ofFIG. 6.

The controller108at step602calculates a gamma(i) for one of the selected data in accordance with the formula:
gamma(i)=(m(i+1)−m(i−1))/(p(i+1)−p(i−1))*p(i)/m(i)

where i=1 to N−1

In the present embodiment, the gamma(i) is actually calculated as in the above formula, by using the values of the preceding power signal p(i−1), the present power signal p(i) and the following power signal p(i+1) as well as the values of the preceding modulation parameter m(i−1), the present modulation parameter m(i) and the following modulation parameter m(i+1). For this reason, the gamma(i) for the selected endpoint data that corresponds to the power signal p(i)=11.0 mW (Pw=110) in the example ofFIG. 7cannot be calculated. When the value of the modulation parameter m for the write power Pw=110 (11.0 mW) is selected as in the example ofFIG. 7, the gamma(i) corresponding to the write power Pw=120 (12.0 mW) can be calculated by the above formula and obtained in the memory of the controller108.

After the step602is performed, the controller108at step603increments the “i” (i=i+1). The control of the controller108is then transferred to the above step601. The above step602is repeated for all of the selected data. When the gamma calculation for all of the selected data (i=1 to (N−1)) is completed, the gamma calculation procedure of the step204ends, and the control of the controller108is then transferred to the next step205in the recording power control routine ofFIG. 2.

As shown inFIG. 2, the controller108at step205assigns the value of p(i) to a variable x(i) and assigns the value of (gamma(i)−Gt) (where Gt denotes a known target value of the gamma(i) specific to the optical disk101and it is called the target gamma) to a variable y(p). It is supposed that the function (gamma(i)−Gt) is approximated into a continuous function y(p) of the recording power p (for example, in the quadratic form). Hence, in order to determine the optimum recording power, it is necessary to find a solution (a target value of the recording power p) when the continuous function y(p) meets the condition: gamma=Gt. This solution is called “p_target”. In order to find the solution “p_target”, it is necessary to solve the quadratic equation y(x)=a*x2+b*x+c=0 (or the continuous function y(p)=gamma(i)−Gt=0).

After the step205is performed, the controller108at step206performs a quadratic regression calculation based on the respective values of x(i) and y(i), so that the coefficients “a”, “b” and “c” of the quadratic equation: a*x2+b*x+c=0 are calculated through the quadratic regression calculation. Once the coefficients “a”, “b” and “c” are determined, it is possible to find the solutions of the quadratic equation: a*x2+b*x+c=0 (that is, the condition: gamma=Gt is met). These solutions are represented by Pp and Pm, and they are also called the roots of the quadratic equation. One of the two solutions Pp and Pm will be the p_target, or the optimum recording power.

After the step206is performed, the controller108at step207calculates the solutions Pp and Pm of the quadratic equation in accordance with the following formulas.
Pp=(−b+sqrt(b2−4*a*c))/(2*a)
Pm=(−b−sqrt(b2−4*a*c))/(2*a)

After the step207is performed, the controller108at step208finds proper one of the solutions Pp and Pm that are obtained in the step207, and assigns the value of the proper one of the solutions Pp and Pm to a variable Pt that indicates the “p_target”, or the optimum recording power.

Specifically, in the step208, if only one of the solutions Pp and Pm falls within a given range between a lower limit recording power R1and an upper limit recording power R2, then the controller108determines that the only one solution is a proper solution, and assigns the value of the solution to the variable Pt. If both the solutions Pp and Pm fall within the given range between the R1and the R2, the controller108determines that an error takes place, and the control of the controller108is transferred to an error routine (not shown). If both the solutions Pp and Pm do not fall within the given range between the R1and the R2, the controller108determines that an error takes place, and the control of the controller108is transferred to the error routine.

In the error routine, any of various conceivable measures may be taken, including the restart of the recording power control routine ofFIG. 2, the selection of a fixed recording power as the optimum recording power, and the ejection of the optical disk101out of the optical recording/reproducing apparatus ofFIG. 1.

In the step208, an error may take place due to the use of an improper optical disk, a malfunction of the hardware or the presence of a defect in the PCA of the optical disk. After the step208is performed, unless any error takes place, the controller108can provide the value of the variable Pt as the value indicating the optimum recording power.

In the above-described embodiment, the recording power control algorithm accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

FIG. 3shows a detailed test writing procedure in the recording power control routine ofFIG. 2. The procedure ofFIG. 3corresponds to the step201in the recording power control routine ofFIG. 2.

As shown inFIG. 3, in the present embodiment, the test writing procedure is repeated ten times by sequentially changing the power signal “p(i)”, supplied to the laser power control unit109, from 9.0 mW to 18.0 mW with increments of 1.0 mW, and the corresponding test patterns of marks and spaces are respectively written to the corresponding sectors (i) of the PCA of the optical disk101with the recording powers p(i), by controlling the optical pickup104.

FIG. 4shows a detailed test reading procedure in the recording power control routine ofFIG. 2. The procedure ofFIG. 4corresponds to the step202in the recording power control routine ofFIG. 2.

As shown inFIG. 4, in the present embodiment, the test reading procedure (or the seek operation) is repeated ten times by controlling the optical pickup104to read the corresponding sectors (i) of the PCA of the optical disk101where the test writing procedure is performed at the step201. The reproduced data signal, derived from each of the test patterns in the corresponding sectors (i) of the PCA of the optical disk101, is supplied from the optical pickup104to the RF105, and the data signal is amplified at the RF105. The P/H106detects and holds a peak level of the amplified data signal and outputs a peak-level signal “pk” to the controller108. The B/H107detects and holds a bottom level of the amplified data signal and outputs a bottom-level signal “bt” to the controller108. In this manner, the controller108detects the peak-level signal “pk” and the bottom-level signal “bt” for each reproduced data signal, and assigns the detected values pk and bt to the variables pk(i) and bt(i), respectively.

In the above-described embodiment, the recording power control algorithm accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present embodiment are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately determining the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present embodiment can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

FIG. 8shows an alternative data selection procedure in the recording power control routine ofFIG. 2.

In the present embodiment, the procedure (step503A) ofFIG. 8is substituted for the step503in the data selection procedure ofFIG. 5, and such alternative data selection procedure corresponds to the step203in the recording power control routine ofFIG. 2.

As shown inFIG. 8, in the present embodiment, the controller108at step503A selects the values of the present modulation parameter m(i) and the present power signal p(i) for the recording power control if the value of the present modulation parameter m(i) is larger than a threshold value “th1”. The controller at step503A selects the values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) for the recording power control if the value of the present modulation parameter m(i) first exceeds the threshold value “th1” and is larger than a second threshold vale th2(th2>th1). Otherwise the controller108omits the values of m(i) and p(i) from the recording power control.

Further, in the step503A, the controller108assigns the selected value of m(i) and the selected value of p(i) to the variable M(j) and the variable P(j), respectively. The variables M(j) and P(j) are used to indicate the selected data [m(i), p(i)] for the recording power control. The data counter “j” is incremented (j=j+1) after the substitution of the selected data into the variables M(j) and P(j) for one of the reproduced data signals is completed.

FIG. 9shows an example of selected data that are derived from the data selection procedure ofFIG. 8.

InFIG. 9, the horizontal axis indicates the recording power (or write power) “Pw” that is equivalent to the power signal “p”, and the point at100in the horizontal scale corresponds to 10.0 mW. InFIG. 9, the vertical axis (on the left side) indicates the modulation parameter “m” that corresponds to the value of the calculated modulation parameter m(i). In the example ofFIG. 9, the threshold value “th1” and “th2” used in the data selection procedure ofFIG. 8are respectively equal to 0.2 and 0.3 (th1=0.2, th2=0.3). The power signal “p” (or the write power Pw) is sequentially changed from 9.0 mW to 18.0 mW with increments of 1.0 mW during the test writing procedure of the step201ofFIG. 2.

In the example ofFIG. 9, among the data for all of the ten reproduced data signals, the value of the modulation parameter m(i) for the write power Pw=140 (or 14.0 mW) first exceeds the threshold value “th1” (=0.2) and is larger than the second threshold value “th2” (=0.3). Hence, the controller108selects the values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) (=13.0 mW; Pw=130) for the recording power control as in the example ofFIG. 9. The selection of this data is illustrated by the circle inFIG. 9.

In the previous example ofFIG. 7, the value of m(i) for the write power Pw=120 (or 12.0 mW) first exceeds the threshold value “th1” (−0.2). The values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) (=11.0 mW; Pw=110) are selected for the recording power control. However, there is the possibility that the value of m(i) is not sufficiently larger than the threshold value “th1”, and the value of m(i−1) is too small to be selected for the recording power control. In such a case, the reliability in determining the optimum recording power will be lowered.

According to the above embodiment ofFIG. 8, the recording power control algorithm more accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present embodiment are more effective in minimizing variations of the optimum recording power through the recording power control algorithm. It is possible to more accurately determine the optimum recording power without being affected by noise.

Further, in the example ofFIG. 9, the vertical axis (on the right side) indicates the gamma (=(Δm/m)/(Δp/p) ) that defines the ratio of a change of the modulation parameter m, normalized by the present modulation parameter value, to a change of the power signal p, normalized by the present power signal value. In the example ofFIG. 9, a target gamma “gammaT” that is a target value of the gamma(i) is equal to 1.65. In the example ofFIG. 9, the values of the gamma with respect to the respective selected data are calculated by the controller108in the step204, and they are illustrated inFIG. 9.

FIG. 10shows an alternative recording power control routine that is executed by the optical recording/reproducing apparatus ofFIG. 1. In this alternative embodiment, the recording power control routine ofFIG. 10is substituted for the routine ofFIG. 2.

As shown inFIG. 10, the controller108at step801performs an initial test writing in which writing of a pattern of marks and spaces to the power calibration area (PCA) of the optical disk101with the recording power (indicated by the power signal “p”) is repeated by sequentially changing the recording power with increments of a predetermined power.

The initial test writing of step801is repeated a given number of times by incrementing the power signal “p”, which is supplied to the laser power control unit109, for each of respective cycles of the test writing. For each of the respective cycles of the test writing, the optical pickup104records a test pattern of marks and spaces onto one of the sectors of the PCA of the optical disk101by focusing the laser beam emitted by the LD of the optical pickup104onto the recording layer of the optical disk104.

Specifically, in the present embodiment, the initial test writing of the step801is repeated ten times by sequentially changing the power signal “p”, supplied to the laser power control unit109, from 9.0 mW to 18.0 mW with increments of 1.0 mW, and the corresponding test patterns of marks and spaces are respectively recorded onto the corresponding sectors of the PCA of the optical disk101by means of the optical pickup104.

However, the recording power control routine according to the present invention is not limited to this embodiment. Any variation or modification may be made to the amount of increments to the write power level, the number of the cycles of the test writing/reading, and the portions of the optical disk where the test patterns are written.

After the step801is performed, the controller108at step802performs an initial test reading in which reading out the pattern from the PCA of the optical disk101is repeated for all of the test patterns that have been recorded onto the PCA of the optical disk101at the step801. A data signal, reproduced from one of the test patterns in the PCA of the optical disk101, is supplied from the optical pickup104to the RF105, and the data signal is amplified at the RF105. The P/H106detects and holds a peak level of the amplified data signal and outputs a peak-level signal “pk” to the controller108. The B/H107detects and holds a bottom level of the amplified data signal and outputs a bottom-level signal “bt” to the controller108. Hence, the controller108detects the peak-level signal “pk” and the bottom-level signal “bt” for each reproduced data signal.

In the step802, the controller108calculates a reproduced signal amplitude amp(i) for each reproduced data signal in accordance with the formula amp(i)=pk(i)−bt(i) where i=0 to 9, and calculates a modulation parameter m(i) for each reproduced data signal in accordance with the formula: m(i)=(pk(i)−bt(i))/pk(i) where i=0 to 9. The controller108sets a first recording power “pth” by finding a pair of the modulation parameter m and the recording power p, from among all of the calculated modulation parameters and the respective recording powers, a value of the modulation parameter m of that pair first exceeding a threshold value “th”. This means that the controller108initially selects a sequence of pairs of the modulation parameter m and the recording power p in which all of the calculated modulation parameters m(i) are larger than the threshold value “th”.

FIG. 11shows an example of selected data that are derived from the initial test writing procedure in the recording power control routine ofFIG. 10.

InFIG. 11, the horizontal axis indicates the recording power “Pw” that is equivalent to the power signal “p”, and the point at100in the horizontal scale corresponds to 10.0 mW. InFIG. 11, the vertical axis (on the left side) indicates the modulation parameter “m” that corresponds to the value of the calculated modulation parameter m(i). In the example ofFIG. 11, the threshold value “th” used in the procedure ofFIG. 10is equal to 0.2 (th=0.2). The power signal “p” (or the recording power Pw) is sequentially changed from 9.0 mW to 18.0 mW with increments of 1.0 mW during the initial test writing of the step801ofFIG. 10.

In the example ofFIG. 11, among the data for all of the ten reproduced data signals, the value of the modulation parameter m(i) for the recording power Pw=120 (or 12.0 mW) first exceeds the threshold value “th” (=0.2). Hence, the controller108sets the recording power p(i) (=12.0 mW, or Pw=120) as the first recording power “pth”.

Referring back toFIG. 10, the controller108at step803performs a secondary test writing in which writing of a pattern of marks and spaces to the PCA of the optical disk101with the recording power p(i), which is substantially centered on the first recording power “pth”, is repeated by sequentially changing the recording power with second, smaller increments of a predetermined power.

The secondary test writing of step803is repeated the same number of times by incrementing the power signal “p”, which is supplied to the laser power control unit109, for each of respective cycles of the test writing. For each of the respective cycles of the test writing, the optical pickup104records the test pattern of marks and spaces onto one of the sectors of the PCA of the optical disk101by focusing the laser beam emitted by the LD of the optical pickup104onto the recording layer of the optical disk104.

Specifically, in the present embodiment, the second test writing of the step803is repeated ten times by sequentially changing the power signal “p” (supplied to the laser power control unit109) from 11.0 mW to 15.5 mW with the second increments of 0.5 mW, and the corresponding test patterns of marks and spaces are respectively recorded onto the corresponding sectors of the PCA of the optical disk101by means of the optical pickup104.

After the step803is performed, the controller108at step804performs a secondary test reading in which reading out the pattern from the PCA of the optical disk101is repeated for all of the test patterns that have been recorded onto the PCA of the optical disk101at the step803. A data signal, reproduced from one of the test patterns in the PCA of the optical disk101, is supplied from the optical pickup104to the RF105, and the data signal is amplified at the RF105. The P/H106detects and holds a peak level of the amplified data signal and outputs a peak-level signal “pk” to the controller108. The B/H107detects and holds a bottom level of the amplified data signal and outputs a bottom-level signal “bt” to the controller108. Hence, the controller108detects the peak-level signal “pk” and the bottom-level signal “bt” for each reproduced data signal.

In the step804, the controller108calculates a modulation parameter m(i) for each reproduced data signal in accordance with the formula: m(i)=(pk(i)−bt(i))/pk(i) where i=0 to 9. The controller108selects, from all of the calculated modulation parameter values and the respective recording powers, a sequence of pairs of the modulation parameter m and the recording power p. The controller108calculates a gamma (=(Δm/m)/(Δp/p) ) for each of the selected pairs of the modulation parameter m and the recording power p, the gamma defining a ratio of a change of the modulation parameter m, normalized by a present modulation parameter value, to a change of the recording power p, normalized by a present recording power value. Further, the controller108finds a target recording power (p_target) corresponding to an optimum recording power based on the function (y(p)=gamma(i)−Gt; Gt: target gamma) derived from the relationship between the calculated gamma values and the respective recording powers, the target recording power causing a value of the function to be equal to zero. This means that the controller108in the step804performs procedures that are essentially the same as the steps202through208in the recording power control routine ofFIG. 2, in order to determine the optimum recording power based on the relationship between the modulation parameters and the respective recording powers.

In the selecting procedure of the step804, the controller108selects the values of the present modulation parameter m(i) and the present power signal p(i) for the recording power control if the value of the present modulation parameter m(i) is larger than a threshold value “th3”. The controller selects the values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) for the recording power control if the value of the present modulation parameter m(i) first exceeds the threshold value “th3”. Otherwise the controller108omits the values of m(i) and p(i) from the recording power control. This procedure is essentially the same as the step503ofFIG. 5in the previous embodiment.

Alternatively, in the selecting procedure of the step804, the controller108selects the values of the present modulation parameter m(i) and the present power signal p(i) for the recording power control if the value of the present modulation parameter m(i) is larger than a threshold value “th3”. The controller selects the values of the preceding modulation parameter m(i−1) and the preceding power signal p(i−1) for the recording power control if the value of the present modulation parameter m(i) first exceeds the threshold value “th3” and is larger than a second threshold value “th4” (th4>th3). Otherwise the controller108omits the values of m(i) and p(i) from the recording power control. This procedure is essentially the same as the step503A ofFIG. 8in the previous embodiment.

FIG. 12shows an example of selected data that are derived from the secondary test writing procedure in the recording power control routine ofFIG. 10.

InFIG. 12, the horizontal axis indicates the recording power “Pw” that is equivalent to the power signal “p”, and the point at100in the horizontal scale corresponds to 10.0 mW. InFIG. 12, the vertical axis (on the left side) indicates the modulation parameter “m” that corresponds to the value of the calculated modulation parameter m(i). In the example ofFIG. 12, the threshold values “th3” and “th4” used in the procedure ofFIG. 10are respectively equal to 0.2 and 0.3 (th3=0.2, th4=0.3). The power signal “p” (or the recording power Pw) is sequentially changed from 11.0 mW to 15.5 mW with the second increments of 0.5 mW during the secondary test writing of the step803ofFIG. 10.

In the example ofFIG. 12, among the data for all of the ten reproduced data signals, the value of the modulation parameter m(i) for the recording power Pw=120 (or 12.0 mW) first exceeds the threshold value “th3” (=0.2) but is not larger than the second threshold value “th4” (=0.3). In this case, the controller108selects the pair of the modulation parameter m(i) and the recording power p(i) (=12.0 mW), but does not select (or omits) the pair of the modulation parameter m(i−1) and the recording power p(i−1) (=11.5 mW).

According to the above embodiment ofFIG. 10, the recording power control algorithm more accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present embodiment are more effective in minimizing variations of the optimum recording power through the recording power control algorithm. It is possible to more accurately determine the optimum recording power without being affected by noise.

In the above-described embodiments ofFIG. 1throughFIG. 12, the gamma (=(Δm/m)/(Δp/p)) is approximated into a continuous function of the recording power p, and the target recording power (p_target), which corresponds to the optimum recording power, is determined based on the continuous function of the recording power p. Even when there are variations in the modulation parameter calculations based on the reproduced data signals, it is possible to accurately determine the optimum recording power because of the approximation using the continuous function.

Next,FIG. 13shows an alternative recording power control routine that is executed by the optical recording/reproducing apparatus ofFIG. 1.

In this alternative embodiment, the recording power control routine ofFIG. 13is substituted for the recording power control routine ofFIG. 2. As described above, in the previous embodiments, the gamma is approximated into a continuous function of the recording power p. In the present embodiment, the modulation parameter m is approximated into a continuous function of the recording power p.

As shown inFIG. 13, the controller108at steps701through703performs procedures that are essentially the same as the steps201through203in the routine ofFIG. 2, and a description thereof will be omitted for the sake of convenience.

In the routine ofFIG. 13, after the step703is performed, the controller108at step704assigns the value of p(i) to a variable x(i) and assigns the value of the modulation parameter m(i) to a variable y(p). It is supposed that the function of the modulation parameter m(i) is approximated into a continuous function y(p) of the recording power p (e.g., in the quadratic form). Hence, in order to determine the optimum recording power, it is necessary to find a solution (a target value of the recording power p) when the continuous function y(p) meets the condition: gamma=Gt. “Gt” denotes a known target value of the gamma(i) specific to the optical disk101and it is called the target gamma. This solution is called “p_target”. In order to find the solution “p_target”, it is necessary to solve the quadratic equation y(x)=a*x2+b*x+c=0.

After the step704is performed, the controller108at step705performs a quadratic regression calculation based on the respective values of x(i) and y(i), so that the coefficients “a”, “b” and “c” of the quadratic equation: a*x2+b*x+c=0 are calculated through the quadratic regression calculation. Once the coefficients “a”, “b” and “c” are determined, it is possible to find the solutions of the quadratic equation: a*x2+b*x+c=0 (that is, the condition: gamma=Gt is met). These solutions are represented by Pp and Pm, and they are also called the roots of the quadratic equation. One of the two solutions Pp and Pm will be the p_target, or the optimum recording power.

After the step705is performed, the controller108at step706calculates the solutions Pp and Pm of the quadratic equation in accordance with the following formulas.
Pp=(−b*(Gt−1)+sqrt((b*(Gt−1))2−4*a*(Gt−2)*c*Gt))/2*a*(Gt−2)  (1a)
Pm=(−b*(Gt−1)−sqrt((b*(Gt−1))2−4*a*(Gt−2)*c*Gt))/2*a*(Gt−2)  (1b)

After the step706is performed, the controller108at step707finds proper one of the solutions Pp and Pm that are obtained in the step706, and assigns the value of the proper one of the solutions Pp and Pm to the variable Pt that indicates the “p_target”, or the optimum recording power.

Specifically, in the step707, if only one of the solutions Pp and Pm falls within a given range between a lower limit recording power R1and an upper limit recording power R2, then the controller108determines that the only one solution is a proper solution, and assigns the value of the solution to the variable Pt. If both the solutions Pp and Pm fall within the given range between the R1and the R2, the controller108determines that an error takes place, and the control of the controller108is transferred to an error routine (not shown). If both the solutions Pp and Pm do not fall within the given range between the R1and the R2, the controller108determines that an error takes place, and the control of the controller108is transferred to the error routine.

In the error routine, any of various conceivable measures may be taken, including the restart of the recording power control routine ofFIG. 13, the selection of a fixed recording power as the optimum recording power, and the ejection of the optical disk101out of the optical recording/reproducing apparatus ofFIG. 1.

In the step707, an error may take place due to the use of an improper optical disk, a malfunction of the hardware or the presence of a defect in the PCA of the optical disk. After the step707is performed, unless any error takes place, the controller108can provide the value of the variable Pt as the value indicating the optimum recording power.

The above formulas (1a) and (1b), used in the step706, are derived as follows. It is supposed that the function of the modulation parameter m(i) is approximated into a continuous quadratic-form function y(p) of the recording power p. In order to determine the optimum recording power, it is necessary to find a solution (a target value of the recording power p) of the quadratic equation when the continuous function y(p) meets the condition: gamma=Gt. In order to find the solution “p_target”, it is necessary to solve the quadratic equation y(x)=a*x2+b*x+c=0.

The normalized gradient “gamma” is represented by (dm/dp)*(p/m), and when the condition: gamma=Gt is met, (dm/dp)*(p/m)=Gt. Based on the above approximation, the modulation parameter m is written into the continuous, quadratic-form function of the recording power p, namely, m=a*p2+b*p+c. As (dm/dp) is a gradient function of the modulation parameter p with respect to the recording power p, dm/dp=2*a*p+b. Therefore, the equation (dm/dp)*(p/m)=Gt is as follows,
gamma=(2*a*p+b)*(p/(a*p2+b*p+c))=Gt(2)
From the above equation, the following quadratic equation is obtained,
a*(Gt−2)*p2+b*(Gt−1)*p+c*Gt=0
The solutions of the above quadratic equation yield the above formulas (1a) and (1b).

In the above-described embodiment, the continuous function of the recording power p is derived from the approximation of the modulation parameter “m”, rather than from the approximation of the normalized gradient “gamma”. The recording power control algorithm accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

In another preferred embodiment of the present invention, the procedure (the step503A) ofFIG. 8is substituted for the step503in the data selection procedure ofFIG. 5, and such alternative data selection procedure is substituted for the step703in the recording power control routine ofFIG. 13. The steps of the recording power control routine in the present embodiment are essentially the same as the corresponding steps in the previous embodiments ofFIG. 1throughFIG. 12, and a description thereof will be omitted.

According to the above preferred embodiment, the continuous function of the recording power p is derived from the approximation of the modulation parameter “m”. The recording power control algorithm accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

In another preferred embodiment of the present invention, the modulation-parameter-based calculation procedure (the step706) in the recording power control routine ofFIG. 13is substituted for the gamma-based calculation procedure of the step804in the recording power control routine ofFIG. 10. The steps of the recording power control routine in the present embodiment are essentially the same as the corresponding steps in the above embodiments ofFIG. 10andFIG. 13, and a description thereof will be omitted.

According to the above preferred embodiment, the continuous function of the recording power p is derived from the approximation of the modulation parameter “m”. The recording power control algorithm accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected-by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

In another preferred embodiment of the present invention, the procedure (the step503A) ofFIG. 8is substituted for the step503in the data selection procedure ofFIG. 5, and such alternative data selection procedure is substituted for the data selection procedure of the step804in the recording power control routine ofFIG. 10. Further, the modulation-parameter-based calculation procedure (the step706) in the recording power control routine ofFIG. 13is substituted for the gamma-based calculation procedure of the step804in the recording power control routine ofFIG. 10. The steps of the recording power control routine in the present embodiment are essentially the same as the corresponding steps in the previous embodiments ofFIG. 1throughFIG. 13, and a description thereof will be omitted.

According to the above preferred embodiment, the continuous function of the recording power p is derived from the approximation of the modulation parameter “m”. The recording power control algorithm accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.

In the above embodiments, the value of the variable Pt obtained by the recording power control algorithm is provided as the value indicating the optimum recording power. However, in certain cases, it is preferred that the value of the variable Pt multiplied by a known constant, which is specific to the optical disk, is provided as the value indicating the optimum recording power.

In the above embodiments, any of various optical storage media that are provided for recording and reproducing of information, including CD-DA, CD-ROM, CD-R, DVD-ROM, DVD-R, etc. may be provided as the optical disk101. In addition, in order to eliminate the influences of reflected light beams, the values of (pk−bt)/((pk+bt)/2) may be provided as the reproduced signal amplitude, instead of the value of (pk−bt) used in the above embodiments.

Further, the present invention is based on Japanese priority application No. 11-366806, filed on Dec. 24, 1999, the entire contents of which are hereby incorporated by reference.