JPH06236553A - Recording and reproducing method for optical recording medium - Google Patents

Abstract

PURPOSE:To optimize recording conditions by detecting position shifts in the binary signals of reproduced data obtained from evaluation patterns, analyzing the position shifts and detecting fluctuation in binary signals which are generated during a recording and reproducing process. CONSTITUTION:A detection window width Tw is used as a reference for a pulse width. The leading pulse width is 3/2 Tw and in order record 3Tw, a recording waveform in which Tw/2 pulses are successively connected with Tw/2 gaps is used. Moreover, in order to record 3Tw, pulses are set to the power and pulse width which are the values used record previous 2Tw, and a recording power is again irradiated with a Tw/2 width, through a preheat level with a Tw/2 width. Moreover, as a mark length is stretched for every Tw, a gap section and a pulse section are made into one combination and a recording is performed using the waveform to which one combination is added as Tw increases. Thus, how the amount of the maximum edge position shift varies against the change in fluctuation parameters which are generated during a recording and reproducing process is evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording / reproducing information on / from an optical recording medium such as an optical disk in ultra-high density optical recording using a mark length recording method, and more particularly to a method for recording / reproducing code data. The present invention relates to a recording / reproducing method suitable for analyzing an error and a change in the position of "1" of data generated in the recording / reproducing process.

[0002]

2. Description of the Related Art As the needs for high-density and large-capacity file memories have increased with the progress of the advanced information society in recent years, optical memories have been receiving attention. For optical recording,
A read-only type that only reproduces the recorded information, a write-once type that allows the user to record only once, and record / reproduce as many times as necessary.
It can be classified into three types of rewritable type that can be erased. And, it is used in applications that take advantage of the features of each type. Currently, we are conducting research and development with the aim of further increasing the recording capacity. By the way, in the write-once type and the rewritable type, one method for realizing high-density recording is to reduce the bit pitch. In that case, the thermal interference between the recording bits is to be thermally suppressed. In particular, when performing mark length recording, it is necessary to precisely control the shape of the recording bit, especially the bit length. In the write-once disc, the recording condition at the time of recording may fluctuate due to the fluctuation of the power at the time of recording and the rewritable disc due to the fluctuation of the power at recording and the fluctuation of the environmental temperature. As a result of these fluctuations, the shape of the recording domain formed on the disc changes, and in particular, when the mark length recording is performed, an edge shift occurs, which may cause an error. Also, the recording conditions may differ depending on the structure of the disc. Particularly in high density recording, a technique for removing thermal interference is important. It is necessary to detect power fluctuations during recording, fluctuations in environmental temperature, and differences in disc characteristics before recording information. As a known example in which this point is examined, there is JP-A-1-137223. In this example, a method of evaluating jitter in a write-once optical disc is described.

[0003]

In the above-mentioned prior art, the evaluation method in which the thermal or optical interference of the recording medium is taken into consideration is described, but the object of control is not described from the evaluation result. In particular, in an optical disk using a metal recording film that is susceptible to thermal interference, in order to ensure compatibility between media and devices, it has been necessary to control so that recording can always be performed under optimum conditions.

An object of the present invention is to propose an evaluation pattern for detecting the thermal or optical characteristics of a medium, reproduce the recorded pattern, and use the result to detect the optimum recording condition. The purpose of the present invention is to provide an ultra-high-density optical recording device that is compatible with each other.

[0005]

In order to achieve the above object, it is necessary to find an optimum recording condition by using a certain recording pattern before shipping an optical disk or recording data on the disk. Therefore, in optical recording for recording, reproduction, or erasing using at least a laser beam, data to be noted as recorded data of a modulated binarized signal at least at the time of shipment of the disc or immediately before recording information on the disc. "1" of the surrounding data of "
An evaluation pattern including at least a thermal / optical interference area, which is a range in which 1 "or" 0 "affects the recording / reproducing process, is recorded on an optical recording medium, and the reproduction data obtained from the evaluation pattern is binarized. Regarding the signal, the position of data "1" or "0" with respect to the reference position is obtained, and the position of data "1" or "0" with respect to the reference position and the corresponding reproduction data "1" or "0" It is sufficient to detect the positional deviation from the position and analyze the positional deviation to detect the fluctuation of the binarized signal generated in the recording / reproducing process.
By the way, the above-mentioned reference position is an absolute position built on the disk surface which is the optical recording medium. Alternatively, as the reference position, the position of at least one data “1” of the evaluation pattern may be virtually used as a reference. Further, the relative distance between adjacent data "1" may be measured as a method for detecting the positional deviation. Statistical analysis in the specified area may be performed for the positional deviation amount of "1" of the reproduction data described above. By the way, the disc 1 which is an optical recording medium is used as the prescribed area.
The circumference may be the specified area, or the area between the resynchronization areas may be the specified area, or one sector in one circumference of the disk may be the specified area. By the way, the above-described evaluation pattern may have a periodicity, and a pattern in which each data "1" included in the evaluation pattern has a different interval may be used. by the way,
An edge shift which is an average value of the positional deviation of the data "1" which is statistically analyzed is obtained, and a noise component which is symmetrically distributed with respect to the average value is removed to obtain a binarized signal in a recording / reproducing process. It is sufficient to separate the fluctuation of by the factor. Further, the edge fluctuation, which is the variance with respect to the average value, of the statistically measured relative data intervals is obtained, and the fluctuation of the binarized signal in the recording / reproducing process is caused by the change in the fluctuation parameter in the recording / reproducing process. It can be separated separately. By the way, as for the above-mentioned evaluation pattern, the occurrence frequency of each pattern in one cycle may be equal. The thermal interference region and the optical interference region may be obtained by obtaining the change in the position of "1" of the isolated data of interest. In addition, a part of the pattern length appearing in the variable length modulation method or all of the pattern length is arranged at a distance wider than the thermal interference region and the optical interference region, and the periodic evaluation pattern is used to obtain data "1" depending on the difference in mark length. You just have to find the difference in the position shift.
Specifically, 1-7 modulation method is used as a pattern to be used, T is a data period, and 2.66T-1.33T-1.33T-5.33T-4.
0T-4.0T-1.33T-1.33T-3.33T-2.66T-4.0T-1.33T-4.66T-
5.33T-5.33T-5.33T-2.66T-1.33T-1.33T-5.33T-4.0T-4.0
T-1.33T-1.33T-3.33T-2.66T-4.0T-1.33T-4.66T-5.33T-
5.33T-5.33T-5.33T-2.66T-1.33T-1.33T-5.33T-4.0T-4.0
T-1.33T-1.33T-3.33T-3.33T-4.0T-1.33T-4.66T-5.33T-
5.33T It is preferable to use an evaluation pattern with 5.33T as one cycle. As the above-mentioned evaluation pattern, the positional deviation of data due to all the factors occurring in the recording / reproducing process appears,
Furthermore, they are arranged so that the respective positional deviation factors can be separated. As the above-mentioned evaluation pattern, the worst pattern including the edge position that maximizes the positional deviation that is the combination of the data positional deviations that occur during the recording / reproducing process is used, and the error evaluation is performed by calculating the edge fluctuation amount that is the ratio to the window width You can do it. In addition to this, when T is a data period as a pattern to be used and the domain and the gap are repeated,
In this order, 1.33T-1.33T-5.33T-3.33T-4.0T-1.33T-1.33T
-6.0T-4.66T-4.66T-1.33T-4.66T-5.33T-5.33T-6.66T-3.
An evaluation pattern having 33T as one cycle may be used. In the case of this pattern, considering the case where the (1,7) method is used as the modulation method, it includes a pattern that cannot exist from the code, but this is only an evaluation pattern of the thermal characteristics of the medium. Therefore, the modulation code is ignored here because the evaluation is important. In addition to this, let T be the data cycle,
In the domain and gap repetition, in this order 5.33
T-1.33T-1.33T-1.33T-1.33T-1.33T, 5.33T-1.33T-5.33T
, 5.33T-1.33T-1.33T-1.33T-5.33T, or 1.33T-5.
Even if an evaluation pattern having 33T-1.33T-5.33T-1.33T as one cycle is used, the same effect as the pattern shown above can be obtained, and it is particularly effective for evaluating thermal interference.

[0006]

According to the present invention, attention is paid to recorded data.
Before the recording or at the time of shipment of the disc, the mark is used by using the evaluation pattern including the thermal interference area and the optical interference area, which is the range where "1" of the surrounding data influences "1" during the recording / reproducing process. Evaluate the discrepancy of the edges, evaluate the thermal characteristics of the disc and the optical resolution of the device, and then control the recording conditions using the results to record the user information. By using the evaluation pattern shown in the present invention, the edge to be noticed is shifted due to the influence of thermal interference when recording the preceding and subsequent marks in the recording process. However, in the reproduction process, the spread of the light spot, aberration (coma and astigmatism),
Alternatively, it is possible to know how the edge of the target mark shifts due to the influence of the edge of the mark recorded before and after the defocus and the influence of the reproduced waveform shape. Then, by analyzing the positional deviation, it is possible to separately detect the variation factor of the binarized signal generated in the recording / reproducing process. Using the results, it is possible to optimize the required accuracy and recording conditions when assembling the head.

As an analysis method, by setting the reference position as an absolute position formed on the disk surface, the relationship between the edge position of the recorded data and the edge position of the detected data can be known, and at least one data of the evaluation pattern " By using the position of 1 "as a virtual reference, it is possible to obtain the position shift of other data" 1 "based on this. Further, by measuring the relative interval between the adjacent data "1", each position of the reproduction data "1" with respect to the reference position can be known. An accurate data position shift can be detected by performing a statistical analysis on the detected position shift amount of the reproduction data "1" in a specified area. For example, the uniformity of the medium over the entire circumference of the disk can be evaluated by defining the circumference of the disk as the defined area. Further, by setting one sector as the defined area, the reliability in the minimum area for data management can be evaluated. Further, when the resynchronization area is defined as the prescribed area, the phase synchronization ability can be evaluated. The above evaluation pattern has periodicity,
Since the intervals of the data "1" included in the pattern are different, the data "1" can be separated even in the statistical measurement. Then, the edge shift which is the average value of the position shift of the statistically analyzed data "1" is obtained, and the noise component that is symmetrically distributed with respect to the average value is removed to obtain the binarized signal in the recording / reproducing process. It is possible to separate and detect the fluctuation of each factor. Further, regarding the statistically measured relative data interval, the edge fluctuation, which is the variance with respect to the average value, is obtained, and the fluctuation factor of the binarized signal in the recording / reproducing process is determined from the change in the fluctuation parameter in the recording / reproducing process. Can be detected separately. The occurrence of the individual patterns in one cycle has the same frequency, which makes it possible to prevent the occurrence of errors in a particular pattern having an error. Further, even if the phase-locked circuit is passed, it is not fixed to a specific frequency, so that the phase-locked circuit can be accurately evaluated. In the modulation method used, the modulation method, the recording density, or the recording medium which is characterized in that the edge position deviation in the reproducing process and the edge position deviation at the time of recording due to the difference between the shortest pattern and the longest pattern of the modulated data are equal, By combining them, an optical disk device with a low error rate can be constructed.

[0008]

EXAMPLES The details of the present invention will be described with reference to Examples 1 and 2.

(Embodiment 1) A method of analyzing characteristics when recording / reproducing code data to / from a magneto-optical disk will be described. Test recording is performed prior to recording data on the disc, and the results are used to analyze the characteristics.
The pattern used for test recording is shown in FIG. (1,7) RLL was used as the modulation method. Here, the effect of the present invention is
It goes without saying that it does not depend on the modulation method. Further, a pit corresponding to each data "1" was formed by using a recording waveform composed of an aggregate of minute pulses as shown in FIG. The power level used consists of four levels. That is, there are four types of recording levels: a first recording level, a second recording level, a preheat level, and a reading level. The first recording level is lower than the second recording level, and the ratio between them and the ratio between the preheat level and the first and second recording levels are values determined by the thermal characteristics of the medium. In order to determine these values, recording was performed using the patterns of FIGS. 1 and 2, and the results were reproduced and statistically processed for analysis.

The pattern of FIG. 2 will be described in more detail. Specifically, the shortest pit length (2T
A pulse waveform of 60 ns shorter than the actual length was used to record w). The power at this time was set to the first recording level. Here, the pulse width is a length synchronized with the write clock. That is, the leading pulse width is 3 / 2T
w, and to record 3Tw, follow this with Tw /
A recording waveform in which Tw / 2 pulses are connected with a gap of 2 is used. As an example, the first recording level was set to 5.75 mW for the disc used here. The pulse width was expressed based on the detection window width (Tw). In addition, when recording 3 Tw, after setting the pulse to the power and pulse width for recording the previous 2 Tw, Tw / 2
After the preheat level (gap part) of
A w / 2 width recording power (pulse portion) was applied. Here, the preheat level was set to 2.9 mW. Also,
The power at this time is set to the second recording level, and here, 6.
It was set to 0 mW. In addition to this, as the mark length increases by Tw, the gap portion and the pulse portion may be combined into one, and as the Tw increases, recording may be performed using a waveform in which one combination is added. Second after the recording pulse
The power was changed from the recording level to the reading level, the level at that time was held for Tw, and then raised again to the preheat level. In the recording mode, the power was kept at the preheat level except when the domain was formed.

Next, FIGS. 3 and 4 show the results of recording using the pattern shown in FIG. 1 and reproducing the recorded data. FIG. 3 is a diagram showing the results of measuring the amount of edge shift in various discs. The discs used show the difference between the recorded pulse length and the reproduced pulse length for six types of discs having different laminated structures. The original waveform slicing method was used as the reproducing method, and the so-called front and rear edge independent reproducing method was used in which the front edge and the rear edge were reproduced independently, and finally both were combined. Also,
No waveform equalization is performed. Thus, it can be seen that there are various disks such as a disk in which the shortest pulse is most affected by thermal interference and the shift amount is large, and a disk which is hardly affected by thermal interference. In addition, in recording the mark length, it goes without saying that the distance between the pulses must be controlled with the same accuracy in addition to the pulse length.
Further, FIG. 4 shows the jitter distributions of the disk with the largest shift amount and the disk with the smallest shift amount among these disks. A time interval analyzer (TIA) was used for the measurement. This figure shows the results of measuring the jitter distribution in the innermost portion of the disk.
From this figure, it is 70 for the disk with the largest shift amount.
%, And the disk with the smallest jitter distribution had a window-to-window ratio of 50%. In addition, this value decreases for discs with increased S / N, and S / N is 23.5 dB.
In the case of, it decreased to 36%. When this is multiplied by PLL, the value is further reduced to 28%. Further, with respect to the disk having a large edge shift amount in FIG. 3, it was possible to suppress it to ± 2 ns or less by controlling the pulse width and the laser power in the recording waveform. In that case,
When recording is performed using a pulse whose pulse width is synchronized with the write clock, the pulse width cannot be changed, so that the laser power must be controlled precisely.
As a result of examination, when controlling with power, power must be controlled with an accuracy of ± 0.1 mW or less. Further, even if the current value is set to a constant value, the same laser power is not always obtained. Therefore, before recording user data, test recording is performed in advance, control data such as recording power and pulse width is detected, and new recording conditions are set based on the results, so various conditions change. However, the disc can always be recorded under the optimum recording conditions. Here, changes in various conditions include laser current-laser power fluctuations (due to changes over time and changes in operating environment temperature), effective reduction in laser power due to dirt on the surface of the objective lens, and even operating environment temperature. The change in the disc sensitivity due to the fluctuation of
As described above, by using the recording pattern proposed in the present invention, not only the thermal characteristics of the disc can be evaluated, but also the optimum recording condition is selected, and the compatibility between the media for discs of different structures is ensured. it can.

(Embodiment 2) FIG. 5 is a schematic diagram showing a recording pattern used in the present invention. Here, the (1,7) RLL method is used as the modulation method, but since the purpose is to evaluate the thermal characteristics of the disk, patterns that are not included in the modulation code are also used. Further, in order to form the bit corresponding to each data "1", as in the first embodiment, the recording waveform composed of the aggregate of minute pulses as shown in FIG. 2 was used. The power levels used consisted of the same four levels used in Example 1. Then, in order to determine these values, recording was performed using the pattern shown in FIG. 5 and the pulse shown in FIG. 2, and the results were reproduced and statistically processed for analysis. First, FIG. 6 shows the result of measuring the edge shift amount with respect to the defocus using the power thus determined. The original waveform detection method was used to detect the edge position. In this figure, the horizontal axis shows the amount of defocus and the vertical axis shows the amount of edge shift. In the upper diagram, the shift amount from the front edge to the front edge is represented by ↑↑, and the shift amount from the rear edge to the rear edge is represented by ↓↓. From this figure, almost no change in the shift amount was observed for a focus shift of ± 0.1 μm as the edge shift amount, and it was a constant value. However, when the defocus increased further, the edge shift amount increased sharply. From this, it is understood that the defocus should be suppressed to ± 0.1 μm or less. Furthermore, by recording using the pattern shown in FIG. 5 and reproducing the result, it is possible to further study the influence of various aberrations. That is, various aberrations of the lens were recorded for recording, the results were reproduced, and statistical processing was performed to examine the influence of the aberration on the edge shift. The result is shown in FIG. 7. Here, the results of examining the influence on the edge shift amount when the amount of coma aberration is changed are shown. According to this, as the coma becomes larger, the edge shift amount also increases. From this result, it is necessary to reduce the edge shift amount in order to operate the device normally, and it is possible to obtain a value that must be suppressed in design. Further, by obtaining this shift amount, it is possible to control the shift amount to the minimum.

[0013]

According to the present invention, it is possible to evaluate how the maximum edge position deviation amount changes with respect to the change of the fluctuation parameter that occurs during the recording / reproducing process. Furthermore, the above-mentioned changes can be evaluated by separating them into fluctuation factors due to each recording / reproducing characteristic in the recording / reproducing process. Furthermore, by optimizing the recording conditions using this result, compatibility between devices and media can be ensured. It is possible to improve the control accuracy of the recording magnetic domain formed by performing the test recording prior to recording the user information using this pattern.

[Brief description of drawings]

FIG. 1 is a diagram showing a test recording pattern.

FIG. 2 is a waveform diagram of a recording pulse.

FIG. 3 is a diagram showing a relationship between a domain length and an edge shift amount when recorded on various discs.

FIG. 4 is a diagram showing jitter distributions of a disk having the largest edge shift amount and a disk having the smallest edge shift amount.

FIG. 5 is a diagram showing a test recording pattern.

FIG. 6 is a diagram showing a relationship between a defocus amount and an edge shift amount.

FIG. 7 is a diagram showing a relationship between a defocus amount and an edge shift amount.

FIG. 8 is a diagram showing a relationship between a coma aberration amount and an edge shift amount.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hiroshi Ide 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Takeshi Maeda 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Atsushi Saito 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Hisaki Sugiyama 1-280 Higashi Koigokubo, Kokubunji, Tokyo Hitachi Central Research Center Co., Ltd. ( 72) Inventor Fumio Kugiya 1-280, Higashi-Kengokubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (20)

[Claims] 1. In optical recording for recording, reproducing, or erasing by using a laser beam, at least at the time of shipment of the disc or immediately before recording information on the disc, the modulated light is used.
The recorded data of the binarized signal includes at least a thermal / optical interference area where "1" or "0" of surrounding data influences "1" of the focused data through the recording / reproducing process. Recording the evaluation pattern on the optical recording medium,
For the binarized signal of the reproduction data obtained from the evaluation pattern, the position of data "1" or "0" with respect to the reference position is obtained, and the position of data "1" or "0" with respect to the reference position and An optical device characterized by detecting a positional deviation of the corresponding reproduction data from the position of "1" or "0" and analyzing the positional deviation to detect a change in the binarized signal generated in the recording / reproducing process. Recording medium reproducing method. 2. The reference position is an absolute position built on the surface of the optical recording medium.
A recording / reproducing method for the optical recording medium described. 3. The recording / reproducing method for an optical recording medium according to claim 1, wherein the reference position is a position where at least one data "1" of the evaluation pattern is virtually used as a reference. 4. Adjacent data for detecting the positional deviation
The recording / reproducing method for an optical recording medium according to claim 1, which is obtained by measuring a relative distance of 1 ". 5. The recording / reproducing method for an optical recording medium according to claim 1, wherein a statistical analysis in a prescribed area is performed with respect to the positional deviation amount of "1" of the reproduction data. 6. The recording / reproducing method for an optical recording medium according to claim 5, wherein the specified area is one track of the optical recording medium. 7. The recording / reproducing method for an optical recording medium according to claim 6, wherein one sector constituting the track is used as the specified area. 8. The recording / reproducing method for an optical recording medium according to claim 5, wherein the specified area is between resynchronization areas. 9. The optical recording medium according to claim 1, wherein the evaluation pattern has a periodicity, and data "1" included in the evaluation pattern has different intervals. Recording and playback method. 10. A binarized signal in a recording / reproducing process by obtaining an average value of the positional deviation of the data "1" which is statistically analyzed and removing a component symmetrically distributed with respect to the average value. 6. The recording / reproducing method for an optical recording medium according to claim 5, wherein the fluctuation of the above is separated according to factors. 11. The variance of statistically measured relative data intervals with respect to the average value is obtained, and the variation of the binarized signal in the recording / reproducing process is separated by the factor from the variation with respect to the variation parameter in the recording / reproducing process. 6. The recording / reproducing method for an optical recording medium according to claim 5, wherein 12. The recording / reproducing method for an optical recording medium according to claim 9, wherein the occurrence frequency of the pattern of the evaluation pattern in one cycle is equal. 13. The recording / reproducing method for an optical recording medium according to claim 5, wherein the thermal interference region and the optical interference region are obtained by obtaining a change in the position of "1" of the isolated data of interest. 14. A pattern length of 1 represented by a variable length modulation method.
The feature is that the difference in the positional deviation of data "1" due to the difference in mark length is obtained by using a periodic evaluation pattern in which some or all of them are arranged apart from the heat interference area and the optical interference area. The recording / reproducing method of the optical recording medium according to claim 5 or 10. 15. A 1-7 modulation method is used, where T is a data period, and gaps and domains are repeated in this order, 2.66T-1.33T-1.33T-5.33T-4.0T-4.0T-1.33T. -1.33
T-3.33T-2.66T-4.0T-1.33T-4.66T-5.33T-5.33T-5.33T-
2.66T-1.33T-1.33T-5.33T-4.0T-4.0T-1.33T-1.33T-3.33
T-2.66T-4.0T-1.33T-4.66T-5.33T-5.33T-5.33T-5.33T-
2.66T-1.33T-1.33T-5.33T-4.0T-4.0T-1.33T-1.33T-3.33
An evaluation pattern having one cycle of T-3.33T-4.0T-1.33T-4.66T-5.33T-5.33T5.33T is used.
4. The recording / reproducing method of the optical recording medium according to 4. 16. The evaluation pattern according to claim 5, wherein data displacement due to all factors occurring in the recording / reproducing process appears, and the respective displacement factors are arranged so as to be separable. 15. The recording / reproducing method for an optical recording medium according to any one of 1 to 14. 17. The evaluation pattern is a worst pattern including an edge position that maximizes a positional deviation that is a combination of data positional deviations that occur during a recording / reproducing process, and uses this as an edge variation amount that is a ratio to a window width. 17. The recording / reproducing method for an optical recording medium according to claim 16, wherein the error evaluation is performed by the determination. 18. In the repetition of domains and gaps with T as a data period, 1.33T-1.33T-5.33T- in this order.
3.33T-4.0T-1.33T-1.33T-6.0T-4.66T-4.66T-1.33T-4.66
18. The recording / reproducing method for an optical recording medium according to claim 17, wherein an evaluation pattern having one period of T-5.33T-5.33T-6.66T-3.33T is used. 19. In the repetition of domains and gaps, where T is the data period, 5.33T-1.33T-1.33T- in this order.
1.33T-1.33T-1.33T, 5.33T-1.33T-5.33T, 5.33T-1.33T
-1.33T-1.33T-5.33T or 1.33T-5.33T-1.33T-5.33
18. The recording / reproducing method for an optical recording medium according to claim 17, wherein an evaluation pattern having T-1.33T as one cycle is used. 20. The optical recording medium according to claim 1, which is either a write-once type optical recording medium capable of recording information only once or a rewritable type optical recording medium. A recording / reproducing method for the optical recording medium described.