JP2002319136A - Multivalued recording method, optical recording medium, playback method and playback unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new playback method by which high density development is realized by giving multivalued information to one recording mark and compatibility with the playback system of a conventional CD system and a conventional DVD system is maintained. SOLUTION: With respect to an optical recording medium 6 on which recording marks 10 are formed by (i×j) pieces of mark kinds based on the combination of i-piece length kinds and j-piece height kinds, the length of each recording mark 10 is discriminated by using a general photodetector 7 having light-receiving areas (a) to (d) divided into four on the basis of the addition signals a+b+c+d of all the light-receiving areas divided into four. The height of each recording mark 10 is discriminated on the basis of the subtraction signal (a+d)-(b+c) of the addition signal of the light-receiving areas (a) and (d) present in one side to a direction orthogonal to a recording mark column direction in the light-receiving areas divided into four and the addition signal of the light-receiving areas (b) and (c) present in the other side. Thereby, the compatibility with the playback system of the conventional CD system and the conventional DVD system is maintained about a discrimination method of length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilevel recording method, an optical recording medium, a reproducing method, and a reproducing apparatus intended to increase the recording density.

[0002]

2. Description of the Related Art The diameter of a light spot irradiated on an optical recording medium is proportional to the wavelength λ of the laser light to be irradiated and is inversely proportional to the numerical aperture NA of the objective lens. In general, the design of (1) is to reduce the wavelength λ or increase the numerical aperture NA.

However, there is a limit to reducing the wavelength λ of the laser light or increasing the numerical aperture NA of the objective lens due to the design of the semiconductor laser and the objective lens.

Therefore, conventionally, various methods of increasing the recording mark density have been proposed as a method of improving the recording density.

For example, Japanese Patent Application Laid-Open No. 63-302426 proposes that information is recorded by changing the area of a recording mark and multi-bit recording is performed on a recording element of a fixed size.

Japanese Patent Application Laid-Open No. 58-215735 proposes a method of recording multi-valued data by setting the pit depth in a plurality of steps. In this multi-level recording method, the reproduced RF signal level changes according to the pit depth. Japanese Patent Application Laid-Open No. 5-205276 discloses a proposal similar to the multi-value recording method. According to this publication, a method of reproducing multi-value data using a reproduced RF signal level and a reproduced push-pull signal (radial push-pull signal) level is proposed. in this way,
At the time of data reproduction, the read push-pull signal is almost zero, so that two read spots are irradiated on the disc, and the spot for obtaining the push-pull signal is shifted from the track center so that the RF signal and the push-pull signal can be obtained. I have to.

Further, according to JP-A-2000-215458, JP-A-2000-215462, etc., a pit edge multilevel recording system for modulating a pit edge position on an optical recording medium in multiple stages and recording digital data in a multilevel manner is disclosed. Proposed.

According to Japanese Patent Application Laid-Open No. Hei 8-235593, an optical recording medium in which data pits are displaced from a track center in a direction orthogonal to the track, and the pits are displaced from the track center for multi-level recording. Has been proposed.

According to Japanese Patent Application Laid-Open No. 8-124167,
A method has been proposed in which recording is performed by changing the size of a recording mark on a predetermined lattice point, an optical change caused by the information mark is detected using at least two or more light spots, and information is reproduced. I have.

[0010]

However, in this type of conventional multi-value recording system, there is no reproduction compatibility with existing CD optical discs and DVD optical discs.
A dedicated reproducing device is required for an optical recording medium on which multi-value recording is performed.

Accordingly, an object of the present invention is to provide a novel multi-level recording method, an optical recording medium, a reproducing method, and a reproducing apparatus capable of achieving high density by giving multi-level information to one recording mark. I do.

Further, the present invention provides a multi-level recording method and an optical recording medium which can be reproduced by a conventionally used reproducing apparatus for a CD optical disc or a DVD optical disc while being an optical recording medium on which multi-level recording is performed. The purpose is to:

[0013]

According to a first aspect of the present invention, there is provided a multi-value recording method, wherein a combination of i types of recording mark lengths and j types of recording mark heights is used (i × j). Recording marks are formed on the optical recording medium according to the individual mark types.

Therefore, by giving multi-value information to one recording mark and recording it by a combination of length and height,
It is possible to increase the recording density while maintaining reproduction compatibility with conventional CD-based optical recording media and DVD-based optical recording media.

According to a second aspect of the present invention, there is provided the multi-value recording method, wherein i is the length of the recording mark and k of the i types of the recording mark whose modulation factor is in the saturation region. The recording marks are formed on the optical recording medium by using {i + k (j-1)} mark types in combination with the recording mark height types j that have been allocated.

Therefore, the modulation is basically the same as that of the first aspect of the invention, except that the modulation degree is modulated by j kinds of heights only for k kinds of lengths in the saturation region. Therefore, even if the height of the recording mark is modulated within a certain range, the change of the addition signal for length discrimination is small, and the change of the subtraction signal due to the adjacent mark can be suppressed small. It is possible to provide reproduction compatibility with a system optical recording medium or a DVD system optical recording medium.

According to a third aspect of the present invention, in the multi-level recording method according to the first or second aspect, the main data is recorded by modulating the length of the recording mark, and the additional information is recorded by modulating the height of the recording mark. I made it.

Therefore, the main data is recorded by the modulation of the length of the recording mark, and the additional information is recorded by the modulation of the height of the recording mark.
It is possible to reproduce even a reproducing apparatus for a system optical recording medium or a DVD system optical recording medium, and to have practical reproduction compatibility.

According to a fourth aspect of the present invention, there is provided an optical recording medium comprising (i.times.j) mark types in which a combination of i types of lengths of the recording marks and j types of heights of the recording marks. Are formed.

Therefore, since one record mark is given multi-value information by a combination of length and height, it is recorded.
It is possible to increase the recording density while maintaining reproduction compatibility with conventional CD-based optical recording media and DVD-based optical recording media.

According to a fifth aspect of the present invention, there is provided an optical recording medium comprising: i types of recording marks, and k types of the i types of recording marks whose modulation factor is in a saturation region. The recording marks are formed by {i + k (j-1)} mark types in combination with the assigned recording mark height types j.

Therefore, basically the same as the case of the fourth aspect of the present invention, except that the modulation degree is limited to k lengths in the saturation region and modulated by j heights and recorded. Therefore, even if the height of the recording mark is modulated within a certain range, the change in the addition signal for length determination is small, and the change in the subtraction signal due to the adjacent mark can be suppressed small. Reproduction compatibility with conventional CD-based optical recording media and DVD-based optical recording media can be provided.

According to a sixth aspect of the present invention, in the optical recording medium of the fourth or fifth aspect, the main data is recorded by modulating the length of the recording mark, and the additional information is recorded by modulating the height of the recording mark. .

Therefore, the main data is recorded by the modulation of the length of the recording mark, and the additional information is recorded by the modulation of the height of the recording mark.
Even a playback device for a D-based optical recording medium or a DVD-based optical recording medium can perform playback, and can have practical playback compatibility.

According to a seventh aspect of the present invention, in the reproducing method, the recording marks are formed by (i × j) mark types based on a combination of i types of recording mark lengths and j types of recording mark heights. For the formed optical recording medium, using a photodetector having a light receiving area in which the reproduction light from the optical recording medium is divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction, The length of the recording mark is determined based on the addition signal of all the four divided light receiving regions, and the light receiving region existing on one side in the direction orthogonal to the recording mark column direction in the four divided light receiving regions The height of the recording mark is determined on the basis of a subtraction signal of the addition signal of the above and the addition signal of the light receiving area existing on the other side.

Therefore, a general four-part photodetector can be used with respect to an optical recording medium that has achieved high density by giving multi-value information to one recording mark according to a combination of length and height and recording. Since the mark type of the recording mark is determined by determining the length and height using the output signal, it has reproduction compatibility with the conventional CD-based optical recording medium and DVD-based optical recording medium. Can be played back.

According to an eighth aspect of the present invention, in the reproducing method of the seventh aspect, the height of the recording mark is determined based on the amplitude and the polarity of the subtraction signal.

Therefore, it is possible to easily determine the height of the multi-valued recording mark based on the characteristics of the signal obtained from the quadrant photodetector.

According to a ninth aspect of the present invention, in the reproducing method, a recording mark is formed by (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. For the formed optical recording medium, using a photodetector having a light receiving area in which the reproduction light from the optical recording medium is divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction, The length of the recording mark is determined based on the addition signal of all the four divided light receiving regions, and the light receiving region existing on one side in the direction orthogonal to the recording mark column direction in the four divided light receiving regions The height of the recording mark is determined based on a division signal obtained by dividing a subtraction signal of the addition signal of the light reception area existing on the other side and the addition signal of the light reception area existing on the other side by the addition signal of all the light reception areas divided into four.

Therefore, the light receiving area is basically the same as that of the seventh aspect of the present invention, except that the light receiving area existing on one side in the direction orthogonal to the recording mark row direction in the light receiving area divided into four. In some cases, the difference between the addition signal of the light receiving area and the addition signal of the light receiving area existing on the other side is small, so the height of the recording mark should be determined based on the division signal obtained by dividing the addition signal of the entire light receiving area. Thereby, the detection sensitivity can be increased, and the reliability of the determination of the height can be improved.

According to a tenth aspect of the present invention, in the reproducing method of the ninth aspect, the height of the recording mark is determined based on the maximum amplitude value and the polarity of the division signal.

Therefore, according to the division signal obtained by dividing the subtraction signal by the addition signal of the entire light receiving area, the maximum amplitude value having substantially the same polarity and substantially the same absolute value near the front and rear edges of the recording mark can be obtained. The height can be determined more simply and accurately.

In the reproducing method according to the eleventh aspect of the present invention, the recording marks are assigned to i types of recording mark lengths and k types of the i-type recording marks whose modulation factor is in a saturation region. The reproduction light from the optical recording medium is applied to an optical recording medium on which recording marks are formed by {i + k (j-1)} mark types in combination with the recording mark height types j. Using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction, an addition signal of all the light receiving areas divided into four for all i types of recording marks The length of the recording mark is determined based on, and the modulation degree exists on one side in the direction orthogonal to the recording mark row direction in the light receiving area divided into four for the k kinds of recording marks in the saturation area. Signal of the light receiving area The height of the recording mark based on the subtraction signal and the addition signal of the light receiving region existing in the other side so as to determine.

Therefore, the light is basically the same as that of the seventh aspect of the invention, except that the light modulated by the j kinds of heights is limited to k kinds of lengths in the saturation region. Since the recording medium is targeted, even if the height of the recording mark is modulated within a certain range, the change in the addition signal for length determination is small, and the change in the subtraction signal due to the adjacent mark can be suppressed small. Ensure that conventional CD-based optical recording media and DV
Reproduction compatibility with D-type optical recording media can be provided.

According to a twelfth aspect of the present invention, in the reproducing method of the eleventh aspect, the height of the recording mark is determined based on the amplitude and the polarity of the subtraction signal.

Accordingly, it is possible to easily determine the height of the multi-valued recording mark based on the characteristics of the signal obtained from the four-divided photodetector.

According to a thirteenth aspect of the present invention, there is provided a reproducing method, wherein i types of recording mark lengths and k types of lengths of the i types of recording marks whose modulation factor is in a saturation region are assigned. The reproduction light from the optical recording medium is applied to an optical recording medium on which recording marks are formed by {i + k (j-1)} mark types in combination with the recording mark height types j. Using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction, an addition signal of all the light receiving areas divided into four for all i types of recording marks The length of the recording mark is determined based on, and the modulation degree exists on one side in the direction orthogonal to the recording mark row direction in the light receiving area divided into four for the k kinds of recording marks in the saturation area. Signal of the light receiving area And to determine the height of a recording mark based on the four divided divided signal the divided by the light receiving region all addition signal of the subtraction signal and the addition signal of the light receiving region existing on the other side.

Therefore, the light receiving area is basically the same as that of the eleventh aspect of the present invention, except that the light receiving area existing on one side in the direction orthogonal to the recording mark row direction in the light receiving area divided into four. In some cases, the difference between the addition signal of the light receiving area and the addition signal of the light receiving area existing on the other side is small, so the height of the recording mark should be determined based on the division signal obtained by dividing the addition signal of the entire light receiving area. Thereby, the detection sensitivity can be increased, and the reliability of the determination of the height can be improved.

According to a fourteenth aspect of the present invention, in the reproducing method of the thirteenth aspect, the height of the recording mark is determined based on the maximum amplitude value and the polarity of the division signal.

Therefore, according to the division signal obtained by dividing the subtraction signal by the addition signal of the entire light receiving area, the maximum amplitude value having substantially the same polarity and substantially the same absolute value near the leading and trailing edges of the recording mark can be obtained. The height can be determined more simply and accurately.

According to a fifteenth aspect of the present invention, in the reproducing method according to any one of the seventh to fourteenth aspects, the light receiving area divided into four parts is located on one side with respect to a direction orthogonal to the recording mark row direction. Instead of the subtraction signal of the addition signal of the light receiving region and the addition signal of the light receiving region present on the other side,
A signal obtained by AC coupling the subtraction signal was used.

Accordingly, an offset may occur in the subtraction signal or the division signal due to a difference in sensitivity between the respective light receiving regions in the photodetector. However, by using an AC-coupled signal, the influence of the offset is eliminated and recording is performed. The reliability of the determination of the mark height can be improved.

According to a sixteenth aspect of the present invention, in the reproducing method of any one of the seventh to fifteenth aspects, the type of the recording mark is determined by determining the length of the recording mark and then determining the height of the recording mark. Was determined.

Therefore, after determining the length of the recording mark,
Since the type of the recording mark is determined by determining the height of the recording mark, it is possible to accurately determine the type of the recording mark.

According to a seventeenth aspect of the present invention, the reproducing apparatus divides the reproducing light from the optical recording medium of the recording mark length type i into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Photodetector having a divided light receiving area, mark length determining means for determining the length of a recording mark based on an addition signal of all the four divided light receiving areas, and recording of i types of recording mark length With respect to the optical recording medium on which recording marks are formed by (i × j) mark types in combination with the mark height types j, the recording mark row direction in the four divided light receiving areas Mark height determining means for determining the height of a recording mark based on a subtraction signal of an addition signal of the light receiving area present on one side and a subtraction signal of the light receiving area existing on the other side with respect to a direction orthogonal to , Is provided.

Therefore, a general four-division photodetector can be used for an optical recording medium that has achieved high density by giving multi-value information to one recording mark according to the combination of the length and the height. Since the mark type of the recording mark is determined by determining the length and height using the output signal, it has reproduction compatibility with the conventional CD-based optical recording medium and DVD-based optical recording medium. It is possible to reproduce even a conventional CD-based optical recording medium or DVD-based optical recording medium.

According to an eighteenth aspect of the present invention, in the reproducing apparatus according to the seventeenth aspect, the mark height determining means determines the height of the recording mark based on the amplitude and polarity of the subtraction signal.

Accordingly, it is possible to easily determine the height of the multi-valued recording mark based on the characteristics of the signal obtained from the quadrant photodetector.

According to a nineteenth aspect of the present invention, the reproducing apparatus divides the reproducing light from the optical recording medium of the recording mark length type i into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Photodetector having a divided light receiving area, mark length determining means for determining the length of a recording mark based on an addition signal of all the four divided light receiving areas, and recording of i types of recording mark length With respect to the optical recording medium on which recording marks are formed by (i × j) mark types in combination with the mark height types j, the recording mark row direction in the four divided light receiving areas Dividing the subtraction signal of the addition signal of the light receiving area present on one side and the addition signal of the light receiving area existing on the other side with respect to the direction orthogonal to the direction by the addition signal of all the light receiving areas divided into four Recording mark based on signal Comprising a mark height determining means for determining the height, the.

Therefore, the light receiving area is basically the same as that of the seventeenth aspect of the present invention, except that the light receiving area existing on one side in the direction orthogonal to the recording mark row direction in the four divided light receiving areas. In some cases, the difference between the addition signal of the light receiving area and the addition signal of the light receiving area existing on the other side is small, so the height of the recording mark should be determined based on the division signal obtained by dividing the addition signal of the entire light receiving area. Thereby, the detection sensitivity can be increased, and the reliability of the determination of the height can be improved.

According to a twentieth aspect of the present invention, in the reproducing apparatus according to the nineteenth aspect, the mark height determining means determines the height of the recording mark based on the maximum amplitude value and the polarity of the division signal.

Therefore, according to the division signal obtained by dividing the subtraction signal by the addition signal of the entire light receiving area, the maximum amplitude value having substantially the same polarity and substantially the same absolute value near the front and rear edges of the recording mark can be obtained. The height can be determined more simply and accurately.

According to a twenty-first aspect of the present invention, a reproducing apparatus divides reproduction light from an optical recording medium of i recording mark lengths into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Photodetector having a divided light receiving area, mark length determining means for determining the length of all of the i types of recording marks based on an addition signal of all four divided light receiving areas, and the i types of recording marks Recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to k types of lengths whose modulation factor is in the saturation region. With respect to the optical recording medium, an addition signal of the light receiving area existing on one side with respect to a direction orthogonal to the recording mark row direction in the light receiving area divided into four and the light receiving existing on the other side Subtraction with addition signal of area Modulation on the basis of the issue of and a mark height determining means for determining the height of the recording mark with respect to k types of recording marks in the saturation region.

Therefore, it is basically the same as the case of the seventeenth aspect of the present invention, except that the light modulated by the j kinds of heights is limited to k kinds of lengths in the saturation region. Since the recording medium is targeted, even if the height of the recording mark is modulated within a certain range, the change in the addition signal for length determination is small, and the change in the subtraction signal due to the adjacent mark can be suppressed small. Ensure that conventional CD-based optical recording media and DV
Reproduction compatibility with D-type optical recording media can be provided.

According to a twenty-second aspect of the present invention, in the reproducing apparatus according to the twenty-first aspect, the mark height determining means determines the height of the recording mark based on the amplitude and polarity of the subtraction signal.

Therefore, it is possible to easily determine the height of the multi-valued recording mark based on the characteristics of the signal obtained from the four-divided photodetector.

According to a twenty-third aspect of the present invention, the reproducing apparatus divides the reproducing light from the optical recording medium of the recording mark length i into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Photodetector having a divided light receiving area, mark length determining means for determining the length of all of the i types of recording marks based on an addition signal of all four divided light receiving areas, and the i types of recording marks Recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to k types of lengths whose modulation factor is in the saturation region. With respect to the optical recording medium, an addition signal of the light receiving area existing on one side with respect to a direction orthogonal to the recording mark row direction in the light receiving area divided into four and the light receiving existing on the other side Subtraction with addition signal of area Mark height discriminating means for discriminating the height of a recording mark for k types of recording marks whose modulation factor is in a saturation region based on a division signal obtained by dividing the signal by an addition signal of all the light receiving regions divided into four, Is provided.

Therefore, the light receiving area is basically the same as that of the twenty-first aspect of the present invention, except that the light receiving area existing on one side in the direction orthogonal to the recording mark row direction among the four divided light receiving areas. In some cases, the difference between the addition signal of the light receiving area and the addition signal of the light receiving area existing on the other side is small, so the height of the recording mark should be determined based on the division signal obtained by dividing the addition signal of the entire light receiving area. Thereby, the detection sensitivity can be increased, and the reliability of the determination of the height can be improved.

According to a twenty-fourth aspect of the present invention, in the reproducing apparatus according to the twenty-third aspect, the mark height determining means determines the height of the recording mark based on the maximum amplitude value and the polarity of the division signal.

Therefore, according to the division signal obtained by dividing the subtraction signal by the addition signal of the entire light receiving area, the maximum amplitude value having substantially the same polarity and substantially the same absolute value near the front and rear edges of the recording mark can be obtained. The height can be determined more simply and accurately.

According to a twenty-fifth aspect of the present invention, in the reproducing apparatus according to any one of the seventeenth to twenty-fourth aspects, the mark height determining means is orthogonal to the recording mark row direction in the four divided light receiving areas. Instead of the subtraction signal of the addition signal of the light receiving area existing on one side and the addition signal of the light receiving area existing on the other side in the direction, a signal obtained by AC coupling the subtraction signal is used.

Accordingly, an offset may occur in the subtraction signal or the division signal due to a difference in sensitivity between the respective light receiving regions in the photodetector. However, by using an AC-coupled signal, the influence of the offset is eliminated, and recording is performed. The reliability of the determination of the mark height can be improved.

According to a twenty-sixth aspect of the present invention, in the reproducing apparatus according to any one of the seventeenth to twenty-fifth aspects, the mark height determining means determines the length of the recording mark by the mark length determining means. Then, the height of the recording mark is determined.

Therefore, after determining the length of the recording mark,
Since the type of the recording mark is determined by determining the height of the recording mark, it is possible to accurately determine the type of the recording mark.

[0065]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. First, the principle of the reproducing method of the present invention will be described. The optical system of the reproducing apparatus for the optical recording medium according to the present embodiment is almost the same as the reproducing apparatus for the conventionally used CD optical recording medium or DVD optical recording medium. That is, as shown in FIG.
Light emitted from the semiconductor laser 1 is converted into parallel light by a collimating lens 2, passes through a polarizing beam splitter 3,
The light enters the wavelength plate 4. The light incident on the １ ／ wavelength plate 4 becomes circularly polarized light, and is applied to the optical recording medium 6 through the objective lens 5.

The light (reproducing light) reflected by the optical recording medium 6 becomes circularly polarized light of reverse rotation, passes through the objective lens 5, and
The light again enters the 波長 wavelength plate 4. The light incident on the １ ／ wavelength plate 4 becomes linearly polarized light whose polarization direction is shifted from the circularly polarized light by 90 ° from the outward path, and is guided to the photodetector 7 by the polarization beam splitter 3.

As shown in FIG. 2 or FIG. 3, the optical recording medium 6 of this embodiment has a lengthwise direction (track direction) which is exactly the same as a conventional CD-based optical recording medium or DVD-based optical recording medium. The recording marks 10 have recording mark rows with different lengths. The length type is, for example, i type. FIG. 2 shows an example of an optical recording medium having no pre-groove such as a so-called ROM type optical disc, and FIG. 3 shows a pre-groove (8 is used) like an optical disc having a recording layer made of a phase change material or an organic material. This is an example of a recordable optical recording medium having a groove and 9 being lands.

In the recording mark train, the reproduction light is guided to the photodetector 7 by the above-described optical system. As shown in FIG. 2, the photodetector 7 has a cross-shaped light receiving area a, b, and four divided into a recording mark row direction (track direction) and a direction orthogonal to the recording mark row direction. It has c and d. Assuming that the light receiving signals of these light receiving areas a, b, c, and d are also represented by a, b, c, and d, respectively, an added signal (= a + b + c + d = sum signal) of all the light receiving areas a, b, c, and d Thus, the length of each recording mark 10 is determined.

In addition, in the present embodiment, as shown in FIG. 4, the height h of each recording mark 10 is also modulated (even if the length of the recording mark 10 is the same, several different heights). Has the type j), and the combination with the length of the i types gives
Multi-level recording is performed on the optical recording medium 6 with (i × j) mark types. Such determination of the height h of the recording mark 10 is performed by adding the light receiving areas a and d existing on the left side (one side) with respect to the direction (radial direction) orthogonal to the recording mark row direction in the photodetector 7. Signal (a + d)
And the subtraction signal of the addition signal (b + c) of the light receiving areas b and c existing on the right side (other side), that is, (a + d) − (b +
c) or based on a tangential push-pull signal of (b + c)-(a + d). Alternatively, such a subtraction signal (tangential push-pull signal)
Is divided by the addition signals from all the four divided light receiving areas a, b, c and d, that is, ｛(a + d) − (b
+ C)｝ / (a + b + c + d) or ｛(b + c) −
This is performed based on the signal of (a + d)｝ / (a + b + c + d).

As described above, in this embodiment, the type of the length of the recording mark 10 is determined in the same manner as in the related art,
The type of the height of the recording mark 10 is also determined. That is, the length of the recording mark 10 is first determined by the addition signal (= a + b + c + d: sum signal) of all the light receiving areas a, b, c, and d by the same reproducing method as that of the related art. a + d)-(b +
c) or by a tangential push-pull signal of (b + c)-(a + d), or ｛(a + d)
− (B + c)} / (a + b + c + d) or {(b
The height of the recording mark 10 is determined based on a signal obtained by dividing a tangential push-pull signal by (+ c) − (a + d)｝ / (a + b + c + d) by a sum signal. This makes it possible to reliably determine the length and height of the recording mark 10, that is, to determine the mark type of the multi-value recorded recording mark 10. If it is reversed (that is, length determination is performed after height determination), accurate determination cannot be performed.

In the present embodiment, the height h of the recording mark 10 is determined by adding the addition signal of the light receiving areas a and d existing on the left side with respect to the direction orthogonal to the recording mark row direction and the light receiving area existing on the right side. Although a subtraction signal (tangential push-pull signal) from the addition signal of b and c can be used,
In some cases, the change of the push-pull signal is very small. In order to increase the change due to the difference in the height h of the recording mark 10 (that is, the detection sensitivity is increased and the height of the recording mark 10 is increased). In order to improve the reliability of discriminating the difference), a signal {(a + d)-(b + c)} / (a signal obtained by dividing such a tangential push-pull signal by the sum signal of all the light receiving areas a, b, c, and d). a + b + c +
d) or {(b + c)-(a + d)} / (a + b
+ C + d) is preferably used.

By the way, such (a + d)-(b +
c) Alternatively, as a method of determining the height h of the recording mark 10 based on the tangential push-pull signal of (b + c)-(a + d), the method is performed based on the maximum amplitude value of the tangential push-pull signal and its polarity. it can.

That is, the tangential push-pull signal (= Tpp) changes according to the height of the recording mark 10 as shown in the example of FIG. 5 (FIG. 5A shows the sum signal of a + b + c + d, (b) to (e) show the tangential push-pull signal Tpp, and illustrate the case where the height of the recording mark 10 increases in order from (b) to (e)). Therefore, if the tangential push-pull signal Tpp is sampled at a plurality of sampling timings and its amplitude and polarity (sign) as indicated by p1 to p6 are detected, the recording mark 1
The height of 0 can be determined.

However, in order to simplify the detection of the amplitude and the polarity (sign) by sampling and to improve the reliability thereof, as described above, the tangential push-pull signal is applied to all the light receiving areas a, b, c. , D divided by the sum signal {(a + d) − (b + c)} / (a + b + c)
+ D) or {(b + c)-(a + d)} / (a +
It is preferable to determine the height h of the recording mark 10 based on (b + c + d). The signal obtained by dividing the tangential push-pull signal by the sum signal changes according to the height of the recording mark 10, as in the example shown in FIGS. According to the division signal obtained by dividing the tangential push-pull signal by the sum signal, as shown in FIG. 6, among the plurality of extreme values (peak = maximum amplitude value),
A specific extremum near the leading and trailing edges of the recording mark 10 is amplified.

Therefore, according to the determination based on the division signal obtained by dividing the tangential push-pull signal by the sum signal, the determination can be made based on the maximum amplitude value and the polarity of the division signal. That is, as in the example shown in FIGS. 6A to 6C, the division signal obtained by dividing the tangential push-pull signal by the sum signal has signs different from each other in the vicinity of the front and rear edges of the recording mark 10, and has an absolute value. The substantially equal maximum value (| p
1 | ≒ | p2 |).

These signals change as shown in FIGS. 6A to 6C depending on the height of the recording mark 10 even if the length and width of the recording mark 10 are the same. . That is, the change in height h of the recording mark 10 causes p1
And the value of p2 and the sign relationship (polarity) between p1 and p2 change.

As described above, in the present embodiment, when a tangential push-pull signal or a division signal obtained by dividing the tangential push-pull signal by a sum signal is used, the signal sampled at a plurality of sampling timings is used. It is characterized in that the height of the recording mark 10 is determined based on the amplitude and polarity of the signal.
With this method, it is possible to reliably determine the type of the height of the recording mark 10. Thus, for example, a tangential push-pull signal or a high h ₂ of the recording mark 10, such as the amplitude division signal by dividing the tangential push-pull signal by the sum signal is minimized as a reference (Fig. 4, Fig. 6 (B)), a recording mark whose height is changed by + δ such as h ₃ = h ₂ + δ (FIGS. 4 and 6)
(C), and a recording mark (FIG. 4 and FIG. 6A) whose height is changed by -δ, such as h ₁ = h ₂ -δ, to form a recording mark of the same length. 10, these recording marks 10 have almost the same degree of modulation.
Can be clearly distinguished.

In the present embodiment, among the lengths of the recording marks 10 having the i types, only the k types of the recording marks 10 having the modulation degree in the saturation region are provided with the recording marks 10. A method of modulating the height by j types is provided as a preferable method. This is because, for a mark type in which the degree of modulation is in the saturation region, the sum signal changes little even if the height of the recording mark 10 is modulated within a certain range.
Also, it is possible to suppress a change in the tangential push-pull signal due to the adjacent mark to be small.

Here, the "modulation degree" refers to a recording contrast in an added signal (sum signal) from all four divided light receiving areas a, b, c, and d. The “saturated area” indicates an area where the change in the sum signal level at the center of the recording portion due to the change in the height of the recording mark 10 is small. Accordingly, the recording mark in which the change in the sum signal level at the center of the recording portion due to the change in the height is small, that is, the recording mark 10 having a certain length or more with respect to the reproduction beam diameter.

According to the multi-level recording method of this embodiment, even if the recording marks 10 have the same length but different heights, almost the same degree of modulation can be obtained. Signals (sum signals) from the light receiving areas a, b, c, d of
In this case, it is possible to make the mark look the same type of mark length as the conventional CD-based optical recording medium or DVD-based optical recording medium, even though the recording mark 10 is also modulated in the height direction. (If the modulation degree of the sum signal changes when the height of the recording mark is modulated, the discrimination of the recording mark length based on the sum signal in the same manner as in the past determines that the mark length differs depending on the height of the recording mark. Mark types different from the above are generated).

As a result, the main data is recorded by modulating the length of the recording mark, and the additional information is recorded by modulating the height of the recording mark, so that the main data can be reproduced from a conventional CD optical disc or DVD optical disc. Playback can also be performed by the device, and playback compatibility can be provided.

In the case of the recording mark 10 whose modulation degree does not reach the saturation area, the modulation degree changes depending on the height of the recording mark 10, and the recording degree in which the modulation degree does not reach the saturation area across the minimum space length. For example, when the marks 10 are formed continuously, the amplitude of the tangential push-pull signal becomes small and its change tends to be small, so that it may be difficult to determine the height of the recording mark 10. . Therefore, the method of the present embodiment in which the height of the recording mark 10 is modulated by j types with respect to k types of the modulation degree in the saturation region among the recording marks of which the types are the lengths is effective. Become.

However, conventional CD optical discs and DV
In the case where compatibility with a D-type optical disc reproducing apparatus is not provided, a modulation degree in the height direction may be applied to all types of lengths of the recording marks. However, in this case, the height, width, and range for changing the height of the recording mark are set so that the recording marks having different mark lengths are not determined to be the same type (the same length) by the modulation in the height direction. There is a need.

As described above, in the present embodiment, the height of the recording mark 10 is determined by the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal. An offset may occur in a tangential push-pull signal or a division signal obtained by dividing a tangential push-pull signal by a sum signal due to a difference in sensitivity between the light receiving areas a, b, c, and d. Alternatively, instead of the division signal obtained by dividing the tangential push-pull signal by the sum signal, the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is AC-coupled to generate the recording mark 10. Determining height is also effective As a result, the reliability of determining the height of the recording mark 10 is greatly improved.

As described above, the optical recording medium 6 of the present embodiment
In the related art, the main data is recorded by modulating the length of the recording mark 10 and the additional information is recorded by modulating the height of the recording mark 10 to obtain a conventional optical recording medium compatible with a CD optical recording medium or a DVD optical recording medium. The main data can also be reproduced by the reproducing device of (1). Further, by reproducing the optical recording medium 6 according to the present embodiment with the reproducing apparatus according to the present embodiment, it becomes possible to read additional information in addition to the main data.

That is, in the conventional reproducing apparatus, the main data of the conventional CD-based optical recording medium or DVD-based optical recording medium and the optical recording medium 6 according to the present embodiment can be reproduced. Since the device has the same basic configuration as a conventional reproducing device for a CD-based optical recording medium or a DVD-based optical recording medium, all the data (main data and additional information) of the optical recording medium 6 of the present embodiment are included. And conventional CD-based optical recording media and DV
Reproduction with a D-based optical recording medium becomes possible.

The “main data” in the present invention means that the optical recording medium 6 according to the present invention can be used in a conventional CD-type optical disc or DV.
When played back by a D-type optical disk playback device, there is no restriction as long as the data is meaningful (for example, it may be a part of an image). The information recorded in the height direction may be information that supplements main data, address information, servo information, manufacturing information, and the like, and various information can be recorded.

The principle of the present invention has been described above in detail.
FIG. 7 shows a specific example (optical system and signal processing system) of the configuration of the reproducing apparatus according to the present embodiment based on the above description.
That is, the sum signal detecting means 12 detects the sum of the light receiving signals of all four divided light receiving areas a, b, c, and d, and the tangential push-pull signal detecting means 16 detects the sum orthogonal to the recording mark row direction. The sum signal of the light receiving areas a and d existing on the left side with respect to the set direction and the light receiving area b existing on the right side with respect to the direction orthogonal to the recording mark row direction.
A subtraction signal from the addition signal of c or a division signal obtained by dividing this subtraction signal by addition signals from all the four divided light receiving areas a, b, c, and d is detected.

The signal obtained from the sum signal detecting means 12 is
After passing through the waveform equivalent circuit 13 and the binarization circuit 14, the mark length of the recording mark 10 is determined by the mark length detecting means 15. These sum signal detecting means 12, waveform equivalent circuit 1
3, the binarizing circuit 14 and the mark length detecting means 15
The mark length determining means 19 is configured.

On the other hand, the polarity / amplitude detecting means 17 determines the amplitude and polarity of the signal obtained by the tangential push-pull signal detecting means 16 and reproduces the signal based on the mark length discrimination result by the mark length detecting means 15. The data judging means 18 judges the type of the recording mark 10 in the height direction. The tangential push-pull signal detecting means 16, the polarity / amplitude detecting means 17, and the reproduced data determining means 18 determine the mark height
0 is configured. Through such determination processing, final determination of the mark type of the recording mark 10 (determination of the type in the length direction and the height direction) is performed.

In such a reproducing apparatus, a signal from the mark length detecting means 15 is transmitted to a conventional CD optical disk or DVD.
It is exactly the same as that of the playback device of the system optical disk.

Note that the present invention is applicable to the RO as shown in FIG.
The present invention is effective not only for the M-type optical recording medium 6 but also for the optical recording medium 6 having a recording layer made of a phase change material, an organic material, or the like as shown in FIG. When the multi-value recording of the present invention is applied to the optical recording medium 6 having a recording layer made of a phase change material, an organic material, or the like, the recording power of the semiconductor laser 1 and the recording strategy are controlled to control the recording mark. Length and height (corresponding to the size of the recording area in the recording layer thickness direction in the recording layer)
Can have information.

[0093]

EXAMPLE It was confirmed by calculation that a plurality of pieces of information could be recorded (multi-valued recording) on a recording mark 10 having almost the same reproduced RF signal waveform or degree of modulation.

The calculation conditions assume that the incident light has a Gaussian distribution, has a circular aperture with a radius of 6000λ and a radius of 3000λ where the amplitude is e− ¹ , and an objective lens NA of 0.6. Also, the optical recording medium 6 has no pre-groove in FIG.
It was assumed that the ROM type optical recording medium shown in FIG. 1 was used, the refractive index of the substrate was 1.58, and the reflectance on the flat surface was 90%.

FIGS. 8A to 8G show the case where the mark length is set to 3.
When 0λ (λ: reproduction wavelength), the height h of the recording mark
Is 0.10λ to 0.40λ (in increments of 0.05λ) (a + b + c + d in the photodetector 7 in FIG. 2)
2 shows a result of calculating a tangential push-pull signal ((a + d)-(b + c) in the photodetector 7 in FIG. 2) and a division signal obtained by dividing the tangential push-pull signal by a sum signal (when the reproduction beam is a recording mark). The change of each signal when passing through is calculated.
The horizontal axis of (g) indicates the amount of movement when the reproduction wavelength is 0.650 μm). FIG. 8A shows h = 0.10.
λ, FIG. 8B shows h = 0.15λ, and FIG.
0.20λ, FIG. 8D shows h = 0.25λ, and FIG.
8 is h = 0.30λ, FIG. 8 (f) is h = 0.35λ, FIG.
(G) Each case of h = 0.40λ is shown.

In the legend in FIG. 8, Sum is a sum signal,
Tpp is a tangential push-pull signal, Tpp /
Sum represents a division signal obtained by dividing the tangential push-pull signal by the sum signal.

Further, FIGS. 9A to 9G show that when the mark length is 2.0λ (λ: reproduction wavelength), the height h of the recording mark is 0.10λ to 0.40λ (0. 05λ increments)
, The sum signal (a + b in the photodetector 7 in FIG. 2)
+ C + d) and the tangential push-pull signal (FIG. 2)
(A + d)-(b + c)) of the photodetector 7 and the result of calculation of the division signal obtained by dividing the tangential push-pull signal by the sum signal (change of each signal when the reproduction beam passes through the recording mark). 9A to 9G, the horizontal axis represents the reproduction wavelength of 0.650 μm.
And the amount of movement is shown). FIG. 9A shows h.
= 0.10λ, FIG. 9B shows h = 0.15λ, FIG.
(C) is h = 0.20λ, and FIG. 9 (d) is h = 0.25.
λ, FIG. 9E shows h = 0.30λ, and FIG.
0.35λ, and FIG. 9 (g) shows the case where h = 0.40λ.

The legend in FIG. 9 is the same as in FIG.
Sum represents a sum signal, Tpp represents a tangential push-pull signal, and Tpp / Sum represents a signal obtained by dividing the tangential push-pull signal by the sum signal.

From this result, when the height h of the recording mark 10 is 0.20λ or more, the modulation degree hardly changes even if the height of the recording mark 10 is changed. It can be seen that the reproduced signal looks exactly the same as that of the CD optical disc and DVD optical disc.
Therefore, if significant information is recorded even in the length direction only, such as by recording main data in the length direction, the multi-level recorded optical recording medium 6 according to this embodiment can
It can be seen that the data can be reproduced by a reproducing apparatus for a D-type optical disk or a DVD-type optical disk.

For example, when the length of the recording mark 10 is 3.0λ, the height h of the recording mark 10 is changed as shown in FIG.
(D) If the three types shown in (e) are used, the modulation degree is almost the same, but the amplitude value of the tangential push-pull signal or the divided signal obtained by dividing the tangential push-pull signal by the sum signal depends on the height h. Since the polarity changes, it is possible to easily determine the difference in the height h of the recording mark 10 (when the height h of the recording mark 10 is 0.25λ, the tangential push-pull signal or the tangential push-pull signal is used. The amplitude value of the division signal divided by the sum signal is substantially the minimum, and the height h of the recording mark 10 is
Is 0.20λ, the amplitude value of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is large, and the sign of the peak value is a signal that changes from + to-. When the height h of the mark 10 is 0.30λ, the amplitude value of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is large, and the sign of the peak value changes from-to +. Signal).

Similarly, the length of the recording mark 10 is 3.0λ.
In the case of FIG. 8, the height h of the recording mark 10 is changed as shown in FIGS.
(G) can be set. In this case, the modulation degree is almost the same, but the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal depending on the height h. Since the amplitude value and the polarity of the recording mark 10 change, the difference in the height h of the recording mark 10 can be easily determined.

When the length of the recording mark 10 is 2.0λ,
Assuming that the height h of the recording mark 10 is one of the three types shown in FIGS. 9C, 9D, and 9E, the degree of modulation is almost the same, but the tangential push-pull signal or the tangential push-pull depends on the height h. Since the amplitude and the polarity of the divided signal obtained by dividing the signal by the sum signal change, the difference in the height h of the recording mark 10 can be easily determined (recording mark 1).
When the height h of 0 is 0.25λ, the amplitude value of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is substantially minimum, and the height h of the recording mark 10 is 0.20λ. In the case of, the amplitude value of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is large, the sign of the peak value is a signal that changes from + to-, and the height of the recording mark 10 When h is 0.30λ, the amplitude value of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is large, and the sign of the peak value is a signal that changes from-to +.) .

Similarly, when the length of the recording mark 10 is 2.0λ
In the case of FIG. 9, the height h of the recording mark 10 is changed as shown in FIGS.
(G) can also be set. In this case, the degree of modulation is almost the same, but the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal depending on the height h. Since the amplitude value and the polarity change, the difference in the height h of the recording mark 10 can be easily determined.

As described above, with reference to the recording mark height at which the amplitude of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is minimized (FIG. 5B), By forming a recording mark whose height is changed by + δ (FIG. 5 (c)) and a recording mark whose height is changed by −δ (FIG. 5 (a)), recording marks of the same length can be obtained. It was confirmed that these recording marks could be clearly distinguished despite having substantially the same degree of modulation.

In the present invention, however, the height j of the recording mark 10 is not limited to three types, and the amplitude of the tangential push-pull signal or the division signal obtained by dividing the tangential push-pull signal by the sum signal is not specified. More types can be provided by judging the value, polarity, and pattern.

8 and 9, the recording mark 10
Can be used to determine the height h of the tangential push-pull signal or the division of the tangential push-pull signal by the sum signal. Therefore, it has been confirmed that it is preferable to use a division signal obtained by dividing the tangential push-pull signal by the sum signal in order to increase the detection sensitivity.

[0107]

According to the multi-value recording method of the present invention, (i × j) number of combinations of the type i of the length of the recording mark and the type j of the height of the recording mark are provided. Since a recording mark is formed on an optical recording medium according to a mark type, multi-value information is given to one recording mark by a combination of a length and a height, and recording is performed. It is possible to increase the recording density while maintaining reproduction compatibility with the optical recording medium.

According to the multi-value recording method of the present invention, i kinds of recording mark lengths and k kinds of lengths of the i kinds of recording marks whose modulation degree is in the saturation region are used. The recording marks are formed on the optical recording medium by using {i + k (j−1)} mark types in combination with the recording mark height types j assigned to the recording marks. As in the case of the first aspect of the present invention, since the modulation degree is modulated by j kinds of heights only for k kinds of lengths in the saturation region, the height of the recording mark is set to a certain value. Even if the modulation is performed within the range, the change of the addition signal for length determination is small, and the change of the subtraction signal due to the adjacent mark can be suppressed small.
Reproduction compatibility with a VD optical recording medium can be provided.

According to a third aspect of the present invention, in the multi-value recording method according to the first or second aspect, the main data is recorded by modulating the length of the recording mark, and the additional information is recorded by modulating the height of the recording mark. The main data is recorded by the modulation of the length of the recording mark, and the additional information is recorded by the modulation of the height of the recording mark. Even a reproducing apparatus for an optical recording medium can reproduce, and practical reproduction compatibility can be provided.

According to the optical recording medium of the fourth aspect of the present invention, there are (i × j) mark types obtained by combining i types of recording marks and j types of recording marks in height. Since the recording marks are formed, it is possible to increase the recording density while maintaining reproduction compatibility with conventional CD-based optical recording media and DVD-based optical recording media.

According to the optical recording medium of the fifth aspect of the present invention, it is possible to reduce the number of recording mark lengths to i and the k types of modulation marks in the saturation region of the i types of recording marks. The recording marks are formed by {i + k (j-1)} mark types in combination with the assigned recording mark height types j.
As in the case of the described invention, the modulation degree is limited to k lengths in the saturation region and recorded by being modulated by j height types, so that the height of the recording mark is set to a certain value. Even if it is modulated within the range, the change of the added signal for length discrimination is small,
The change of the subtraction signal due to the adjacent mark can be suppressed small, and the reproduction compatibility with the conventional CD-based optical recording medium and DVD-based optical recording medium can be more reliably provided.

According to the sixth aspect of the present invention, in the optical recording medium of the fourth or fifth aspect, the main data is recorded by modulating the length of the recording mark, and the additional information is recorded by modulating the height of the recording mark. Therefore, the main data can be reproduced even by a conventional reproducing apparatus for a CD-based optical recording medium or a DVD-based optical recording medium, and practical reproduction compatibility can be provided.

According to the reproducing method of the invention described in claim 7,
The optical recording is performed on an optical recording medium in which recording marks are formed by (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. Using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction, the reproduction light from the medium is recorded based on an addition signal of all the four light receiving areas. The length of a mark is determined, and an addition signal of the light receiving area existing on one side and a light receiving area existing on the other side in a direction orthogonal to the recording mark row direction in the four divided light receiving areas. Since the height of the recording mark is determined based on the subtraction signal from the signal, the optical recording is realized by increasing the recording density by giving multi-value information to one recording mark according to a combination of the length and the height. For the medium, Using the output signal of the light detector, 4 divided since so as to determine the mark type of the recording mark by determining the length and the height, the conventional CD
It is possible to perform reproduction with reproduction compatibility with the system optical recording medium and DVD system optical recording medium.

According to the invention of claim 8, in the reproducing method of claim 7, the height of the recording mark is determined based on the amplitude and the polarity of the subtraction signal.
It is possible to easily determine the height of the multi-valued recording mark based on the characteristics of the signal obtained from the divided photodetector.

According to the reproducing method of the ninth aspect,
The optical recording is performed on an optical recording medium in which recording marks are formed by (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. Using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction, the reproduction light from the medium is recorded based on an addition signal of all the four light receiving areas. The length of a mark is determined, and an addition signal of the light receiving area existing on one side and a light receiving area existing on the other side in a direction orthogonal to the recording mark row direction in the four divided light receiving areas. The invention according to claim 7, wherein the height of the recording mark is determined based on a division signal obtained by dividing a subtraction signal with a signal by an addition signal of all the light receiving areas divided into four. Is the same as Since the addition signal of the light receiving area existing on one side and the addition signal of the light receiving area existing on the other side in the direction orthogonal to the recording mark row direction in the light receiving area, the change signal may be small. By judging the height of the recording mark based on the division signal obtained by dividing by the addition signal of all the light receiving areas, it is possible to increase the detection sensitivity and improve the reliability of the height judgment.

According to the tenth aspect, the ninth aspect is provided.
In the reproducing method described above, since the height of the recording mark is determined based on the maximum amplitude value and the polarity of the division signal, according to the division signal obtained by dividing the subtraction signal by the addition signal of all the light receiving regions, Since the maximum amplitude value having different polarities and substantially the same absolute value is obtained near the leading and trailing edges of the recording mark, the height of the recording mark can be determined more simply and accurately.

According to the reproduction method of the present invention, the length of the recording mark is i and the length of the k of the i types of recording marks whose modulation factor is in the saturation region is the same. An optical recording medium in which recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to the optical recording medium. Using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction perpendicular to the recording mark row direction, the light receiving area divided into four for all i types of recording marks The length of the recording mark is determined on the basis of the addition signal of the above. Side of the light receiving area Since the height of the recording mark is determined based on the subtraction signal of the sum signal and the addition signal of the light receiving area existing on the other side, it is basically the same as the invention of claim 7. Is k in which the degree of modulation is in the saturation region.
Since the length of the type is limited to the optical recording medium modulated by j kinds of heights, even if the height of the recording mark is modulated within a certain range, the change of the added signal for length discrimination is changed. And the change in the subtraction signal due to the adjacent mark can be suppressed to a small value.
Reproduction compatibility with a VD optical recording medium can be provided.

According to the twelfth aspect, according to the first aspect,
In the reproducing method according to the first aspect, since the height of the recording mark is determined based on the amplitude and the polarity of the subtraction signal, the multi-valued signal is obtained based on the characteristics of the signal obtained from the four-divided photodetector. It is possible to easily determine the height of the recording mark.

According to the reproducing method of the thirteenth aspect of the present invention, the recording mark length i and the k types in which the degree of modulation is in the saturation region among the i types of recording marks are determined. Reproduction from an optical recording medium on which recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights allocated in the above manner. Using a photodetector having a light receiving area divided into four in the recording mark row direction and a direction orthogonal to the recording mark row direction, the light is divided into four for all i kinds of recording marks. The length of the recording mark is determined based on the addition signal, and the modulation degree is one side in a direction orthogonal to the recording mark row direction in the light receiving area divided into four for k kinds of recording marks in the saturation area. Of the light receiving area Since the height of the recording mark is determined based on a division signal obtained by dividing a subtraction signal of the signal and the addition signal of the light receiving area existing on the other side by the addition signal of all the light receiving areas divided into four, Specifically, this is the same as the invention according to claim 11, except that the addition signal of the light receiving area existing on one side in the direction orthogonal to the recording mark row direction in the light receiving area divided into four and the other side Since the change of the subtraction signal from the addition signal of the light receiving area existing in the light receiving area may be small, the detection sensitivity is improved by determining the height of the recording mark based on the division signal obtained by dividing the addition signal of the entire light receiving area. In addition, the reliability of the height determination can be improved.

According to the fourteenth aspect of the present invention, the first aspect is provided.
In the reproducing method according to the third aspect, since the height of the recording mark is determined based on the maximum amplitude value and the polarity of the division signal, according to the division signal obtained by dividing the subtraction signal by the addition signal of all the light receiving areas, Since the maximum amplitude value having substantially different polarities and substantially the same absolute value is obtained in the vicinity of the leading and trailing edges of the recording mark, the height of the recording mark can be determined more simply and accurately.

According to the fifteenth aspect, the seventh aspect is provided.
15. The reproducing method according to any one of the items 14 to 14, wherein, in the light receiving area divided into four parts, an addition signal of the light receiving area existing on one side with respect to a direction orthogonal to the recording mark row direction and the addition signal existing on the other side. Instead of the subtraction signal with the addition signal of the light receiving area, a signal obtained by AC coupling the subtraction signal is used. Therefore, an offset occurs in the subtraction signal and the division signal due to a difference in sensitivity of each light receiving area in the photodetector. However, by using an AC-coupled signal,
The influence of the offset can be eliminated, and the reliability of determining the height of the recording mark can be improved.

According to the sixteenth aspect, the seventh aspect is provided.
In the reproducing method according to any one of (1) to (15), after determining the length of the recording mark, the type of the recording mark is determined by determining the height of the recording mark. Can be performed accurately.

According to the reproducing apparatus of the seventeenth aspect, the reproducing light from the optical recording medium of the recording mark length type i is transmitted in the recording mark row direction and the direction perpendicular to the recording mark row direction. A photodetector having a light receiving area divided into four, a mark length discriminating means for judging the length of a recording mark based on an addition signal of all the light dividing areas divided into four, and i kinds of recording mark lengths And the type of height of the recording mark j
For the optical recording medium on which recording marks are formed by (i × j) mark types in combination with
A recording mark is formed based on a subtraction signal of an addition signal of the light receiving area present on one side of the divided light receiving area in a direction orthogonal to a recording mark row direction and an addition signal of the light receiving area existing on the other side. And mark height determining means for determining the height of the mark, so that the mark height can be determined by a combination of the length and the height.
The length and height of an optical recording medium whose density is increased by giving multi-valued information to one recording mark and recording it is determined using the output signal of a general four-division photodetector. This makes it possible to determine the mark type of the recording mark, so that it is possible to perform reproduction while maintaining reproduction compatibility with the conventional CD-based optical recording medium and DVD-based optical recording medium. Even an optical recording medium or a DVD-based optical recording medium can be reproduced.

According to the eighteenth aspect, according to the first aspect,
7. The reproducing apparatus according to claim 7, wherein the mark height determining means determines the height of the recording mark based on the amplitude and the polarity of the subtraction signal. , It is possible to easily determine the height of the multi-valued recording mark.

According to the reproducing apparatus of the nineteenth aspect, the reproducing light from the optical recording medium of the recording mark length type i is transmitted in the recording mark row direction and the direction perpendicular to the recording mark row direction. A photodetector having a light receiving area divided into four, a mark length discriminating means for judging the length of a recording mark based on an addition signal of all the light dividing areas divided into four, and i kinds of recording mark lengths And the type of height of the recording mark j
For the optical recording medium on which recording marks are formed by (i × j) mark types in combination with
In the divided light receiving area, a subtraction signal of an addition signal of the light receiving area existing on one side and a addition signal of the light receiving area existing on the other side in a direction orthogonal to the recording mark row direction is divided into four. And a mark height discriminating means for discriminating a height of a recording mark based on a division signal obtained by dividing the sum of the light receiving areas by an addition signal.
As in the case of the described invention, the addition signal of the light receiving area existing on one side and the light receiving area existing on the other side in the direction orthogonal to the recording mark row direction in the four divided light receiving areas. Since the difference between the subtracted signal and the signal may be small, the height of the recording mark is determined based on the division signal obtained by dividing the total signal of the light-receiving area by the addition signal, so that the detection sensitivity is increased and the reliability of the determination of the height is improved. Performance can be improved.

According to the twentieth aspect, according to the first aspect,
9. In the reproducing apparatus according to Item 9, the mark height determination means determines the height of the recording mark based on the maximum amplitude value and the polarity of the division signal. According to the divided signal, the maximum amplitude value having substantially different polarities and substantially the same absolute value can be obtained in the vicinity of the leading and trailing edges of the recording mark, so that the height of the recording mark can be determined more simply and accurately. Can be.

According to the reproducing apparatus of the twenty-first aspect of the present invention, the reproducing light from the optical recording medium of the recording mark length type i is transmitted in the recording mark row direction and the direction perpendicular to the recording mark row direction. A photodetector having a light receiving area divided into four, a mark length discriminating means for judging the lengths of all the i types of recording marks based on an addition signal of all the light receiving areas divided into four, ｛I + k (j), which is a combination of k types of recording marks having a modulation degree in a saturation region and j types of allocated recording mark heights.
-1) With respect to the optical recording medium on which recording marks are formed by マ ー ク mark types, the optical recording medium is present on one side in a direction orthogonal to the recording mark row direction in the four divided light receiving areas. Mark height discrimination for judging the height of recording marks for k types of recording marks whose modulation factor is in a saturation area based on a subtraction signal of an addition signal of the light reception area and an addition signal of the light reception area existing on the other side. Means is basically the same as that of the invention according to claim 17, except that the modulation degree is modulated by j height types limited to k lengths in the saturation region. Since the optical recording medium is a target, even if the height of the recording mark is modulated within a certain range, the change of the addition signal for length determination is small, and the change of the subtraction signal due to the adjacent mark can be suppressed to be small. , More reliably, conventional CD-based optical recording It can have a reproduction compatibility with medium or DVD type optical recording medium.

According to the twenty-second aspect, the second aspect is provided.
In the reproducing apparatus according to the first aspect, the mark height determining means determines the height of the recording mark based on the amplitude and the polarity of the subtraction signal. , It is possible to easily determine the height of the multi-valued recording mark.

According to the reproducing apparatus of the twenty-third aspect of the present invention, the reproducing light from the optical recording medium of the recording mark length type i is transmitted in the recording mark row direction and the direction perpendicular to the recording mark row direction. A photodetector having a light receiving area divided into four, a mark length discriminating means for judging the lengths of all the i types of recording marks based on an addition signal of all the light receiving areas divided into four, ｛I + k (j), which is a combination of k types of recording marks having a modulation degree in a saturation region and j types of allocated recording mark heights.
-1) With respect to the optical recording medium on which recording marks are formed by マ ー ク mark types, the optical recording medium is present on one side in a direction orthogonal to the recording mark row direction in the four divided light receiving areas. Based on a division signal obtained by dividing a subtraction signal of the addition signal of the light receiving region and the addition signal of the light receiving region present on the other side by the addition signal of all the light receiving regions divided into four, k kinds of modulation degrees in the saturation region are provided. Mark height determining means for determining the height of the recording mark with respect to the recording mark, so that it is basically the same as the invention according to claim 21, except that the light receiving area divided into four is provided. In some cases, the subtraction signal of the addition signal of the light receiving area existing on one side and the addition signal of the light receiving area existing on the other side in the direction orthogonal to the recording mark row direction may have a small change. Divided by the sum signal of By determining the height of the recording mark based on the item, increasing the detection sensitivity, it is possible to improve the reliability of the height determination.

According to the invention of claim 24, claim 2
3. In the reproducing apparatus according to item 3, the mark height determination means determines the height of the recording mark based on the maximum amplitude value and the polarity of the division signal. According to the division signal obtained by the division, the maximum amplitude value having substantially different polarities and substantially the same absolute value is obtained in the vicinity of the front and rear edges of the recording mark, so that the height of the recording mark can be determined more simply and accurately. Can be.

According to the twenty-fifth aspect, the first aspect is provided.
25. The reproducing apparatus according to any one of 7 to 24, wherein the mark height determination unit is configured to detect the light receiving area existing on one side in a direction orthogonal to a recording mark row direction in the light receiving area divided into four. In place of the subtraction signal between the addition signal and the addition signal of the light receiving area existing on the other side, this subtraction signal is represented by A
Since the C-coupled signal is used, an offset may occur in the subtraction signal and the division signal due to a difference in sensitivity between the respective light receiving regions in the photodetector. However, by using the AC-coupled signal, The influence of the offset can be eliminated, and the reliability of determining the height of the recording mark can be improved.

According to the invention of claim 26, claim 1
27. In the reproducing apparatus according to any one of Items 7 to 25, the mark height determining means determines the length of the recording mark after determining the length of the recording mark by the mark length determining means. Thus, the type of the recording mark can be accurately determined.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical system portion of a reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a recording mark in the case of a ROM optical disk.

FIG. 3 is a schematic diagram showing an example of a recording mark in the case of a recording type optical disc.

FIG. 4 is a schematic sectional view showing an example in which the height of a recording mark is modulated.

FIG. 5 is a characteristic diagram of an addition signal and a tangential push-pull signal based on an output signal of a photodetector.

FIG. 6 is a characteristic diagram of a division signal obtained by dividing a tangential push-pull signal based on an output signal of a photodetector by an addition signal.

FIG. 7 is a schematic configuration diagram of a reproducing apparatus including a signal processing system.

FIG. 8 is a characteristic diagram showing an example of an embodiment of the present invention.

FIG. 9 is a characteristic diagram showing another example of the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 6 optical recording medium 7 photodetector 10 recording mark 19 mark length determining means 20 mark height determining means a to d light receiving area

Claims (26)

[Claims] 1. A recording mark is formed on an optical recording medium by using (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. Multi-value recording method. 2. A recording mark having a length i and a length i
The type j of the height of the recording mark assigned to the length of k types in which the degree of modulation is in the saturation region among the types of recording marks
A multivalued recording method in which recording marks are formed on an optical recording medium by {i + k (j-1)} mark types in combination with the recording marks. 3. The multilevel recording method according to claim 1, wherein the main data is recorded by modulating the length of the recording mark, and the additional information is recorded by modulating the height of the recording mark. 4. An optical recording medium in which recording marks are formed by (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. 5. A recording mark having a length i and a length i
The type j of the height of the recording mark assigned to the length of k types in which the degree of modulation is in the saturation region among the types of recording marks
An optical recording medium in which recording marks are formed by {i + k (j-1)} mark types in combination with the recording marks. 6. The optical recording medium according to claim 4, wherein the main data is recorded by length modulation of the recording mark, and the additional information is recorded by height modulation of the recording mark. 7. An optical recording medium in which recording marks are formed by (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. A light detector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction by using the photodetector for reproducing light from the optical recording medium; The length of the recording mark is determined based on the addition signal, and the addition signal of the light receiving area existing on one side with respect to the direction orthogonal to the recording mark row direction in the light receiving area divided into four exists on the other side. A reproducing method in which the height of a recording mark is determined based on a subtraction signal from an addition signal of the light receiving area. 8. The reproducing method according to claim 7, wherein the height of the recording mark is determined based on the amplitude and the polarity of the subtraction signal. 9. An optical recording medium in which recording marks are formed by (i × j) mark types by a combination of i types of recording mark lengths and j types of recording mark heights. A photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction by using a photodetector having four divided light receiving areas. The length of the recording mark is determined based on the addition signal, and the addition signal of the light receiving area existing on one side with respect to the direction orthogonal to the recording mark row direction in the light receiving area divided into four exists on the other side. A reproducing method in which the height of a recording mark is determined based on a division signal obtained by dividing a subtraction signal from an addition signal of the light receiving area by an addition signal of all the light receiving areas divided into four. 10. The recording mark height is determined based on a maximum amplitude value and a polarity of the division signal.
The described reproduction method. 11. A recording mark having a length of i types and k of the i types of recording marks whose modulation factor is in a saturation region.
For an optical recording medium in which recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to the lengths of the types. The reproduction light from the optical recording medium is divided into four for all the i types of recording marks by using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. The length of the recording mark is determined based on the addition signal of all the light receiving areas, and the modulation degree is orthogonal to the recording mark row direction in the light receiving area divided into four for k kinds of recording marks in the saturation area. A reproducing method in which a height of a recording mark is determined based on a subtraction signal of an addition signal of the light receiving region present on one side and a subtraction signal of the light receiving region existing on the other side with respect to a direction. 12. The reproducing method according to claim 11, wherein the height of the recording mark is determined based on the amplitude and the polarity of the subtraction signal. 13. A recording mark having i length types and k of the i types of recording marks having a modulation degree in a saturation region.
For an optical recording medium in which recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to the lengths of the types. The reproduction light from the optical recording medium is divided into four for all the i types of recording marks by using a photodetector having a light receiving area divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. The length of the recording mark is determined based on the addition signal of all the light receiving areas, and the modulation degree is orthogonal to the recording mark row direction in the light receiving area divided into four for k kinds of recording marks in the saturation area. Based on a division signal obtained by dividing a subtraction signal of the addition signal of the light receiving region existing on one side with respect to the direction and the addition signal of the light receiving region existing on the other side by the addition signal of all the light receiving regions divided into four. Recording mark height A playback method that determines the length. 14. The apparatus according to claim 1, wherein the height of the recording mark is determined based on a maximum amplitude value and a polarity of the division signal.
3. The reproduction method according to 3. 15. An addition signal of the light receiving area existing on one side with respect to a direction orthogonal to the recording mark row direction in the light receiving area divided into four and an addition signal of the light receiving area existing on the other side. 15. The reproducing method according to claim 7, wherein a signal obtained by AC coupling the subtraction signal is used instead of the subtraction signal. 16. The reproducing method according to claim 7, wherein after determining the length of the recording mark, the type of the recording mark is determined by determining the height of the recording mark. 17. A photodetector having a light receiving area obtained by dividing reproduction light from an optical recording medium of i recording mark lengths into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Mark length determining means for determining the length of a recording mark based on the addition signal of all the four divided light receiving areas; i type of recording mark length and j type of recording mark height For the optical recording medium on which recording marks are formed by (i × j) mark types by the combination of
A recording is performed based on a subtraction signal of an addition signal of the light receiving area existing on one side and a addition signal of the light receiving area existing on the other side in a direction orthogonal to the recording mark row direction in the four divided light receiving areas. A reproducing apparatus comprising: mark height determining means for determining a mark height. 18. The reproducing apparatus according to claim 17, wherein said mark height determining means determines the height of the recording mark based on the amplitude and the polarity of said subtraction signal. 19. A photodetector having a light receiving area in which reproduction light from an i recording medium of recording mark length type i is divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Mark length determining means for determining the length of a recording mark based on the addition signal of all the four divided light receiving areas; i type of recording mark length and j type of recording mark height For the optical recording medium on which recording marks are formed by (i × j) mark types by the combination of
In the four divided light receiving areas, a subtraction signal of an addition signal of the light receiving area existing on one side and a addition signal of the light receiving area existing on the other side in a direction orthogonal to the recording mark row direction is divided into four. And a mark height discriminating means for discriminating the height of the recording mark based on a division signal obtained by dividing the sum of the light receiving areas by the addition signal. 20. The reproducing apparatus according to claim 19, wherein the mark height determining means determines the height of the recording mark based on a maximum amplitude value and a polarity of the division signal. 21. A photodetector having a light-receiving area obtained by dividing reproduction light from an optical recording medium of i recording mark lengths into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Mark length determining means for determining the lengths of all of the i types of recording marks based on an addition signal of all of the four divided light receiving regions; With respect to the optical recording medium in which recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to certain k lengths. In the light receiving area divided into four, a subtraction signal of an addition signal of the light receiving area existing on one side with respect to a direction orthogonal to the recording mark row direction and an addition signal of the light receiving area existing on the other side in the direction orthogonal to the recording mark row direction. Based on the modulation depth That k type of reproduction apparatus and a mark height determining means for determining the height of the recording mark with respect to the recording mark. 22. The reproducing apparatus according to claim 21, wherein the mark height determining means determines the height of the recording mark based on the amplitude and the polarity of the subtraction signal. 23. A photodetector having a light-receiving region in which reproduction light from an optical recording medium of a recording mark length type i is divided into four in a recording mark row direction and a direction orthogonal to the recording mark row direction. Mark length determining means for determining the lengths of all of the i types of recording marks based on an addition signal of all of the four divided light receiving regions; With respect to the optical recording medium in which recording marks are formed by {i + k (j-1)} mark types in combination with j types of recording mark heights assigned to certain k lengths. In the light receiving area divided into four, a subtraction signal of an addition signal of the light receiving area existing on one side with respect to a direction orthogonal to the recording mark row direction and an addition signal of the light receiving area existing on the other side in the direction orthogonal to the recording mark row direction. The light receiving area divided into four Modulation on the basis of the division signals divided by the sum signal Te is reproducing apparatus comprising marks the height determining means, a to determine the height of the recording mark with respect to k types of recording marks in the saturation region. 24. The reproducing apparatus according to claim 23, wherein said mark height determining means determines the height of a recording mark based on a maximum amplitude value and a polarity of said division signal. 25. The mark height discriminating means exists on the other side with the addition signal of the light receiving area present on one side in a direction orthogonal to the recording mark row direction in the light receiving area divided into four. 25. The reproducing apparatus according to claim 17, wherein a signal obtained by AC coupling the subtraction signal is used instead of the subtraction signal from the addition signal of the light receiving region. 26. The mark height determining means determines the length of a recording mark by the mark length determining means,
26. The reproducing apparatus according to claim 17, wherein the height of the recording mark is determined.