JP2003257043A - Optical reproducing device and optical reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical reproducing method and an optical reproducing device, by which the information is reproduced with a high S/N from an optical recording medium including a minute mark or a pit in the reproduction limit or smaller. <P>SOLUTION: In an optical reproducing device for reproducing the information from the pit or the mark formed in the track direction of a super-high resolution optical disk by detecting reflected light (or transmitted light) of the light irradiated on the super-high resolution optical disk, a 1st edge photodetector 45 and a 2nd edge photodetector 47 are furnished for detecting signals of the terminal parts in the track direction in the luminous flux of the reflected light (or transmitted light). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reproducing method and an optical reproducing apparatus for reproducing an optical recording medium, and more particularly to an optical reproducing method and an optical reproducing apparatus for a super-resolution optical disk.

[0002]

2. Description of the Related Art In recent years, in the field of optical recording, high density recording has been advanced. Along with this, there has been proposed an optical disc (super-resolution optical disc) capable of super-resolution reproduction with an improved recording density, using a recording medium that causes some structural change by condensing light.

The mark or pit pitch, which is the reproduction limit of an ordinary optical disk, is determined by the wavelength λ of the reproduction light and the numerical aperture NA of the objective lens, and the reproduction limit is λ /
2NA. On the other hand, in the super-resolution optical disc, it is possible to reproduce minute marks or pits exceeding such a reproduction limit.

Japanese Patent Laid-Open No. 6-183152 discloses a super-resolution reproduction in which a phase change material layer such as BiTe alloy is formed on a disk having pits and a partial liquid state is formed at a condensing point. It is disclosed to do.

Further, Japanese Patent Application Laid-Open No. 5-205314 discloses that a lanthanoid material layer is formed on a disc having pits formed thereon, and a change in reflectance is caused by a temperature gradient to perform super-resolution reproduction. .

Further, in Japanese Patent Laid-Open Publication No. 11-250493, a phase change recording layer made of GeSbTe is used.
An optical system having a wavelength λ of 488 nm and a numerical aperture NA of 0.6 is provided by a structure in which a super-resolution mask layer made of b is provided and an intermediate layer of SiN is formed between the mask layer and the recording layer to a thickness of 30 nm. It is disclosed that a reproduction signal from a recording mark having a mark length of 100 nm or less can be detected at (the reproduction limit mark length of 200 nm).

Further, in Japanese Patent Laid-Open No. 2001-250274, in a ROM type optical disk having minute pits formed, a structure using Ge, Si, W, etc. as a reflective film
It is shown that a signal with a pit length of 200 nm can be super-resolution-reproduced by using an optical system (wavelength: 635 nm, NA: 0.6) (reproduction limit pit length 270 nm). The above-described super-resolution optical disc can improve the recording density without making a large change in the optical system.

[0008]

Super-resolution reproduction is achieved by reproducing fine marks and pits. The spatial frequency of the signal reproduced at this time exceeds the diffraction limit of the optical system. Therefore, it is difficult to detect the reproduction light from the fine marks or pits. Therefore, by increasing the power of the reproduction light, the modulation degree of the reproduction signal can be increased. However, white noise increases because the amount of incident light increases. Due to this increase in white noise, the signal to noise ratio (CNR: Carrier to Noi) is increased.
se ratio) decreases. That is, in the above-described super-resolution reproduction, it can be pointed out that the signal-to-noise ratio is low for minute marks or pits as a problem.

Furthermore, Kikukawa et al., In a ROM type super-resolution optical disc using Ge as a reflective film, when a pit having a length equal to or shorter than the reproduction limit is sandwiched between pits longer than the reproduction limit, a signal We have found the problem of missing parts. (JJAP, No. 40, 2001, p. 1624) The present invention has been made in view of the above conventional problems.
It is an object of the present invention to provide an optical reproducing method and an optical reproducing apparatus capable of reproducing information from an optical recording medium including a minute pit or mark having a length less than a reproduction limit with a high signal-to-noise ratio.

[0010]

The optical reproducing apparatus of the present invention comprises:
In order to solve the above-mentioned problems, optical reproduction for reproducing information from pits or marks formed in the track direction of an optical recording medium by detecting reflected light or transmitted light of light irradiated on the optical recording medium. The apparatus is characterized in that it is provided with a detecting means for detecting a signal at an end of the reflected or transmitted light flux.

With the above arrangement, it is considered that the signal from the pit or mark having a short length passes around the light flux of the reproducing optical system more than the signal from the pit or mark having a long length. Therefore, with the above structure, if the end portion of the light flux of the reflected light or the transmitted light is detected, the signal from the pit or mark with a short length, and thus the pit or mark with a length less than the reproduction limit of the optical recording medium, is detected. The signal can be detected more reliably. That is, it is possible to avoid the loss of a signal that does not reach the reproduction limit.
Further, since the central portion of the light flux is reduced or removed, the amount of light to be detected is cut. Therefore, the white noise can be reduced, and the signal-to-noise ratio in the detected signal can be improved.

The optical reproducing apparatus of the present invention is characterized in that, in addition to the above-mentioned structure, it comprises a split photodetector having the above-mentioned detecting means.

According to the above arrangement, the split photodetector can detect the end portion of the light flux of the reflected light or the transmitted light, and the length is less than the reproduction limit of the optical recording medium which is considered to pass many end portions of the light flux. It is possible to more reliably detect the signal from the pit or mark.

The optical reproducing apparatus of the present invention is characterized in that, in addition to the above configuration, it is provided with a reproducing means for reproducing at least the signal detected by the detecting section.

With the above arrangement, it is possible to more reliably reproduce a signal from a pit or mark having a length less than the reproduction limit of the optical recording medium. That is, it is possible to increase and reproduce a signal from a pit or mark having a length less than the reproduction limit.

In addition to the above configuration, the optical reproducing apparatus of the present invention comprises a center detecting means for detecting at least a signal of a central portion of the reflected or transmitted light flux, and the reproducing means is the detecting means. It is characterized in that the detected signal and the signal detected by the center detecting means are combined and reproduced.

According to the above arrangement, the signal at the central portion of the light beam is detected, and the signal from the pit or mark having a length equal to or longer than the reproduction limit is detected. Then, by combining the signal of the central portion and the signal of the end portion in the light flux, both the signal from the pit or mark having a length longer than the reproduction limit and the signal from the pit or mark having a length less than the reproduction limit. Can be reliably detected. Therefore, the information recorded on the optical recording medium can be reproduced while avoiding the loss.

The optical reproducing apparatus of the present invention is characterized in that, in addition to the above configuration, it is provided with a split photodetector having the center detecting means.

According to the above arrangement, the split photodetector can separate and detect the signal at the central portion of the light beam.

In the optical reproducing apparatus of the present invention, in addition to the above structure, the reproducing means further combines the signal detected by the detecting means and the signal detected by the center detecting means to generate a servo signal. Is generated.

According to the above arrangement, the signals detected by the detecting means and the center detecting means are combined, so that the servo signal can be easily generated only by adding a circuit having a simple structure. Therefore, it is possible to provide an optical reproducing device that can perform optical reproduction more stably. Further, it is not necessary to add a device or the like for newly generating a servo signal, and space can be saved.

In order to solve the above-mentioned problems, the optical reproducing apparatus of the present invention is a reflected light of the light irradiating the optical recording medium with information from pits or marks formed in the track direction of the optical recording medium. Alternatively, in an optical reproducing device for reproducing by detecting transmitted light, a first detection unit for detecting a signal from a pit or mark longer than a reproduction limit in the reflected light or transmitted light, and reproduction in the reflected light or transmitted light A second detector for detecting a signal from a pit or mark shorter than the limit, a reproduction for reproducing information by combining the signal detected by the first detector and the signal detected by the second detector Means and are provided.

According to the above construction, the signal from the pit or mark having a length longer than the reproduction limit and the signal from the pit or mark having a length less than the reproduction limit are combined and reproduced. As a result, signals from pits or marks whose length is less than the reproduction limit are emphasized and reproduced. That is, the information recorded on the optical recording medium can be reproduced while avoiding the loss.

In addition to the above structure, the optical reproducing apparatus of the present invention is characterized in that the second detecting section is provided with a detecting means for detecting an end portion of a light beam of reflected light or transmitted light.

According to the above arrangement, since the end of the light flux of the reflected light or the transmitted light is detected, the signal from the pit or mark having a length less than the reproduction limit can be detected more reliably. .

In order to solve the above problems, the optical reproducing method of the present invention is formed in the track direction of the optical recording medium by detecting the reflected light or transmitted light of the light applied to the optical recording medium. In a light reproducing method for reproducing information by means of pits or marks, a first signal from a pit or mark having a length longer than a reproduction limit is detected from the luminous flux of reflected light or transmitted light, and the luminous flux of reflected light or transmitted light is detected. Further, it is characterized in that the second signal from the pit or mark having a length less than the reproduction limit is detected, and the information of the optical recording medium is reproduced by synthesizing the first signal and the second signal.

According to the above construction, the optical signal from the pit or mark having a length longer than the reproduction limit and the optical signal from the pit or mark having a length less than the reproduction limit are combined and reproduced. As a result, the optical signal from the pit or mark having a length less than the reproduction limit is emphasized and reproduced. That is, the information recorded on the optical recording medium can be reproduced while avoiding the loss.

In addition to the above configuration, the optical reproducing method of the present invention is characterized in that the second signal is a signal obtained by removing at least the central portion of the light flux and detecting the end portion of the light flux. .

According to the above arrangement, since the end of the light flux of the reflected light or the transmitted light is detected, it is possible to more reliably detect the signal from the pit or mark having a length less than the reproduction limit. .

The optical reproducing method of the present invention is characterized in that, in addition to the above configuration, a servo signal is generated by combining the first signal and the second signal.

According to the above configuration, the first signal and the second signal
A servo signal can be easily generated by combining the signals. As a result, more stable light reproduction can be performed.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] An embodiment of the present invention will be described with reference to FIGS. 1 to 3.
As shown in FIG. 2, the optical reproducing apparatus (the present optical reproducing apparatus) according to the present embodiment, which is as follows, includes an optical recording medium driving unit 1, a light emitting unit 2, a light detecting unit 3, and a signal processing unit. It is composed of a section (reproducing means) 4.

The present optical reproducing apparatus reproduces information recorded on the super-resolution optical disk (optical recording medium) 12 held in the optical recording medium driving section 1. When reproducing information on the super-resolution optical disk 12, the light irradiation section 2 irradiates the super-resolution optical disk 12 held by the optical recording medium driving section 1 with light. Then, the light detection unit 3 detects the reflected light of the light with which the super-resolution optical disc 12 is irradiated as a signal. Then, the signal processing section 4 processes (combines) the signals detected by the photodetection section 3 to reproduce the information recorded on the super-resolution optical disk 12.

Here, each part will be described in more detail. Although the case of detecting the reflected light will be described below, the transmitted light of the light emitted to the super-resolution optical disc 12 is not limited to the reflected light and may be detected as a signal.

The optical recording medium driving section 1 is, for example, as shown in FIG.
As shown in, a spindle motor (driving means) 11 is provided. A super-resolution optical disk 12 is held on the spindle motor 11. The spindle motor 11 drives the super-resolution optical disc 12 so as to rotate in a fixed direction at a predetermined speed.

The super-resolution optical disk 12 has, for example,
Ge reflective layer 15 nm thick on polycarbonate substrate
The thing formed (film-formed) is mentioned. A pitch composed of a pair of pits and spaces is formed on the polycarbonate substrate. This pitch is the super resolution optical disc 1
2 is formed in a fixed direction. This direction is the track direction. This track direction is equal to the rotation direction of the super-resolution optical disk 12. That is, this track direction is equal to the reproduction scan direction when reproducing information on the super-resolution optical disk 12. For example, the pit length (pit length) is 290 nm at the shortest, and the pitch is 5 at the shortest.
It is 80 nm.

The light irradiation section 2 includes a laser diode (light irradiation means) 21, a collimator lens 22, a polarization beam splitter 23, a quarter wavelength plate 24, and an objective lens 2.
It is equipped with 5. Laser light of wavelength λ is emitted from the laser diode 21. Also,
The objective lens 25 includes a drive unit 26. The drive unit 26 adjusts the focus of the light with which the super-resolution optical disk 12 is irradiated. The objective lens 25 has a numerical aperture NA. In the present embodiment, for example, the wavelength λ is 680 nm and the numerical aperture NA is 0.5.
It is set to 5. In this case, the reproduction limit (λ / 2NA) is
It is about 620 nm. The wavelength λ and the numerical aperture NA are appropriately changed according to the laser diode used, the objective lens, etc., and are not particularly limited.

The light detecting section 3 is provided with a condenser lens 36 and a split photodetector (detection means) 37.
The condenser lens 36 condenses the reflected light from the super-resolution disc 12 on the split photodetector 37. The split photo detector 37 detects the condensed reflected light as an optical signal.

The signal processing section 4 includes a signal processing circuit (reproducing means) 40, and processes the optical signal to reproduce the information recorded on the super-resolution optical disk 12.

Next, the operation of each part of the present optical reproducing device (the present optical reproducing method) when reproducing the super-resolution optical disk 12 will be described.

First, in the optical medium driving section 1, the spindle motor 11 holds the super-resolution optical disk 12.
Then, the spindle motor 11 rotates the super-resolution optical disk 12 at a predetermined speed in a certain direction.

The super-resolution optical disk 12 is irradiated with laser light from the light irradiation section 2. In this light irradiation unit 2,
Laser light of wavelength λ is generated from the laser diode 21. The laser light is, for example, linearly polarized divergent light and has a wavelength of λ = 680 nm. This laser light is converted into parallel light by the collimator lens 22. This parallel light enters the polarization beam splitter 23. At this time,
Only predetermined polarized light passes through the polarization beam splitter 23. Then, the light transmitted through the polarization beam splitter 23 is converted into circularly polarized light by the quarter-wave plate 24. This circularly polarized light is condensed on the super-resolution optical disk 12 by the objective lens 25 focused by the drive unit 26. As a result, the super-resolution optical disk 12 is irradiated with the laser light.

The laser light emitted onto the super-resolution optical disk 12 is reflected by the super-resolution optical disk 12. This reflected laser light is used as reproduction light. Also,
When the laser light applied to the super-resolution optical disk 12 is applied to the pit formed on the super-resolution optical disk 12, the laser light is modulated by the pit.

The reproduced light is collimated by the objective lens 25, passes through the quarter-wave plate 24, and becomes a linearly polarized light inclined by 90 ° from the linearly polarized light at the time of irradiation. Therefore, this reproduction light is reflected by the polarization beam splitter 23 toward the photodetector 3.

In the photodetector 3, the reproduction light is condensed by the condenser lens 36.
Thus, the light is focused on the split photodetector 37. The split photodetector 37 is arranged so as to receive a light beam in a defocused state. The reproduction light is detected as an optical signal by the split photodetector 37.
This optical signal is processed in the signal processing unit 4, and the information on the super-resolution optical disk 12 is reproduced.

The operation of the split photodetector 37 and the signal processing circuit (reproducing means) 40 of the signal processing unit 4 will be described with reference to FIG.

As shown in FIG. 1, the reproduction light is focused on the split photodetector 37 as a detection beam h (light flux) (a region surrounded by a chain line in FIG. 1). Then, in the split photodetector 37, the detection beam h is detected as an optical signal.

In the present embodiment, the split photodetector 37 includes a first end photodetector (detector, first detector) 45, a central photodetector (center detector, second detector) 46, and a second end. The photo detector (detection means, first detection unit) 47 is divided into three parts. The photodetectors 45 to 47 are arranged in the track direction of the detection beam h. That is, the first end photodetector 45 and the second end photodetector 47 detect reflected light (reproduced light) from both ends in the track direction of the light emitted on the super-resolution optical disc 12. Further, the central portion photodetector 46 is adapted to detect the reflected light (reproduced light) of the central portion in the track direction of the light emitted on the super-resolution optical disk 12.

The width of the central portion photodetector 46 in the track direction may be 1/2 to 49/50 with respect to the diameter of the detection beam h.
A ratio of 20 is preferable. The central portion photodetector 46 detects the central portion of the detection beam h. Therefore, in other words, the central portion is a portion having a ratio of 1/2 to 49/50, and preferably a portion having a ratio of 19/20 to the diameter of the detection beam h.

Further, each end photodetector 45.4
The width dimension of 7 in the track direction is not particularly limited, but according to the detection range of the central portion photodetector 46, it is 1/10 of the diameter of the detection beam h.
The detection beams having a ratio of 0 to 1/4 are detected by the end photodetectors 45 and 47, respectively. Therefore,
In other words, the edge photo detectors 45 and 47 are
May have a size that can detect a detection beam other than that detected by the central portion photodetector 46.

Further, the so-called reproduction limit (λ / 2NA) in the present optical reproduction device is 620 nm pitch. Moreover, the power of the reproduction light is, for example, 3 mW.

The optical signal a is detected at the first end photodetector 45. The central portion photodetector 46 detects the optical signal b. Further, the second end photodetector 47 detects the optical signal c. Each optical signal a,
b and c are input to the signal processing unit 4 and processed (combined) by the signal processing circuit 40 of the signal processing unit 4. Thereby, the optical reproduction signal g (information of the super-resolution optical disk 12) is generated. As a result, the information on the super-resolution optical disc 12 is reproduced.

The generation of the optical reproduction signal g will be described in more detail as follows.

The respective optical signals a, b and c are input to the signal processing circuit 40 as shown in FIG. The respective optical signals a, b, c are input to the adding amplifier 41 and added. As a result, the addition output d is generated. The signal amount of the added output d is adjusted by the volume 43 and becomes the output f. On the other hand, the optical signals a and c are added to the adding amplifier 42.
Is input to and added. As a result, the addition output e is generated. Then, the output f and the addition output e are input to the addition amplifier 44, and are added by the addition amplifier 44 to generate a reproduction signal g.

Here, the case of reproducing the super-resolution optical disk 12 using the present optical reproducing apparatus will be described more specifically with reference to FIG. At this time, the signal processing circuit 40 shown in FIG.

FIG. 3A shows the pitch formed continuously on the super-resolution optical disk 12. Here, an example in which three pitches are arranged in the order of the pitch lengths of 580 nm, 580 nm, and 2320 nm will be given. (B) is the optical signal d output from the addition amplifier 41
Shows the waveform of. (C) shows the waveform of the optical signal e output from the addition amplifier 42. Further, (d) shows the waveform of the optical reproduction signal g output from the addition amplifier 44. This optical reproduction signal g is the optical signal d whose signal amount is adjusted.
A waveform obtained by combining the (waveform of (b)) and the optical signal e (waveform of (c)) is shown.

From the waveform of the optical signal d shown in (b), from the entire luminous flux of the reproduction light detected by the split photodetector 37 (the entire region of the detection beam h shown in FIG. 1), the minimum pitch is 580 nm. It can be seen that pits (pits shorter than the reproduction limit) are hardly detected.
In other words, if all of this reproduction light is integrated, an optical signal (low frequency component) from a pit longer than the reproduction limit will be detected,
It can be seen that almost no optical signal (high frequency component) from the pit having a length less than the reproduction limit is detected. In other words, if all of the reproduction light is integrated, it can be seen that the optical signal from the pit shorter than the reproduction limit is not decomposed and is missing. This is because the optical signal from the pits shorter than the reproduction limit has a low output and is buried in the high-output optical signal from the pits exceeding the reproduction limit. The pit above the reproduction limit (or shorter than the reproduction limit) means a pit at a pitch with a length equal to or larger than the reproduction limit (or less than the reproduction limit).

On the other hand, from the waveform of the optical signal e shown in (c), the luminous flux at the end of the reproduction light detected by the split photodetector 37 (the first end photodetector 45 and the first photodetector 45 in the detection beam h shown in FIG. From the area on the two-end photodetector 47), the minimum pitch is 580.
It can be seen that the optical signal from the pit (nm shorter than the reproduction limit) in nm is detected. That is, it can be seen that the high-frequency component can be detected from the light flux at the end of the reproduction light, and the pits shorter than the reproduction limit can be decomposed and detected. Also, at this time, it can be seen that the edge of the pit can be detected by being emphasized.

Thus, by removing the central portion of the luminous flux of the reproduction light guided to the split photodetector 37, the light quantity can be cut without affecting the high-frequency component passing near the end portion of the luminous flux. it can. As a result, the white noise is reduced and the signal-to-noise ratio of the reproduced signal can be increased. Therefore, the high frequency component can be detected more clearly.

It is considered that an optical signal (high frequency component) having a high spatial frequency is likely to pass through the end of the pupil of the detection optical system, that is, the end of the light beam. Therefore, it is considered that the end photodetectors 45 and 47 can detect an optical signal having a high spatial frequency more clearly. Then, in the addition amplifier 42, these end photodetectors 45
The optical signal having a high spatial frequency detected at 47 can be emphasized. Therefore, the addition amplifier 42 can emphasize and output an optical signal from a short pit which is an optical signal with a high spatial frequency and does not reach the reproduction limit.

Further, the optical signal d in which the reproduction signal of the pit longer than the reproduction limit is detected and the optical signal e in which the reproduction signal of the short pit less than the reproduction limit is detected are combined to substantially reproduce the signal. It is possible to increase the optical signal from a short pit that is less than the limit. Since the optical signal d is reduced by the volume 43 before being combined, the optical signal e is relatively emphasized more than the optical signal d. As a result, it is possible to avoid the loss of the reproduction signal from the short pit that does not reach the reproduction limit. That is, the information actually recorded on the super-resolution optical disc 12 can be more reliably reproduced. Further, since the optical signal b from the central portion of the light flux is reduced, the total amount of light is reduced and white noise can be reduced.

[Second Embodiment] Another embodiment of the present invention will be described with reference to FIGS. For convenience of description, members having the same functions as the members shown in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted. In this embodiment, the split photodetector 37 and the signal processing circuit 40 in the first embodiment are different from each other. That is, in the present embodiment,
A split photodetector 37a is provided in place of the split photodetector 37, and a signal processing circuit (reproducing means) 40a is provided in place of the signal processing circuit 40.

In the present embodiment, the split photodetectors (photodetection means) 37a are end photodetectors (detection means, second detection portions) 51, 54, 55, 58, central photodetectors (center detection means, first detection means). Part) 52.
It is divided into eight parts 53, 56 and 57. The photodetectors 51 to 54 and the photodetectors 55 to 58 are arranged in the track direction of the detection beam h, as in the first embodiment. In addition, the central photodetector 52.5
The area composed of 3.56.57 is similar to the central portion photodetector 46 in the first embodiment, but the detection beam h
The width dimension with respect to the track direction may be 1/2 to 49/50 with respect to the diameter of the detection beam h, and is preferably 19/20. The central portion photodetector 46 detects the central portion of the detection beam h. Therefore, in other words, the central portion is 1/2 to 49/50 with respect to the diameter of the detection beam h.
The ratio is preferably 19/20, and is preferably 19/20.

Further, each end photodetector 45.4
The width dimension of 7 in the track direction is not particularly limited, but according to the detection range of the central portion photodetector 46, it is 1/10 of the diameter of the detection beam h.
The detection beams having a ratio of 0 to 1/4 are detected by the end photodetectors 45 and 47, respectively. Therefore,
In other words, the edge photo detectors 45 and 47 are
May have a size that can detect a detection beam other than that detected by the central portion photodetector 46. Other,
The reproduction limit (λ / 2NA), reproduction light power, etc. are the same as those in the first embodiment.

The photodetectors 51 to 58 sequentially detect the optical signals S1 to S8, respectively. Each optical signal S
1 to S8 are input to the signal processing unit 4 and processed by the signal processing circuit 40a of the signal processing unit 4. Thereby, the optical reproduction signal w, the focus error signal (servo signal) t for converging the light beam on the super-resolution optical disk 12, and the track error signal (for tracking the light beam to the track of the super-resolution optical medium 12 ( The servo signal u can be generated at the same time.

Now, the generation of the optical reproduction signal w, the focus error signal t, and the track error signal u from the respective optical signals S1 to S8 input to the signal processing circuit 40a will be described.

First, the generation of the optical reproduction signal w will be described.

Photodetectors 51, 54, 55 at each end
Each optical signal S1, S4, S5 detected at 58
S8 is added by the addition amplifier 60 to generate an addition output l. On the other hand, each central photodetector 52/53
Each optical signal S2, S3, detected at 56, 57
S6 and S7 are added by the addition amplifier 61, and the addition output m
Is generated.

These addition outputs l · m are added to the addition amplifier 66.
Are added to generate an addition output n. Then, the addition output n has a signal amount adjusted by the volume 70,
It becomes the output v.

The output v and the addition output l are added by the addition amplifier 67 to generate an optical reproduction signal w. As a result, a signal from a short pit that does not reach the reproduction limit is emphasized and detected.

Next, the generation of the focus error signal t will be described.

Photodetectors 51, 52, 55.5
Each optical signal S1, S2, S5, S6 detected in 6
Are added by the addition amplifier 62 to generate an addition output o. On the other hand, each photo detector 53, 54, 57, 58
Optical signals S3, S4, S7, S8 detected in
Are added by the addition amplifier 63 to generate an addition output p.

The well-known astigmatism focus error signal t is generated by inputting the addition output o and the addition output p to the subtraction amplifier 68 and subtracting them.

Next, the generation of the track error signal u will be described.

Photodetectors 51, 52, 53.5
Each optical signal S1, S2, S3, S4 detected in 4
Are added by the addition amplifier 64 to generate an addition output q. On the other hand, each photo detector 55, 56, 57, 58
Each optical signal S5, S6, S7, S8 detected in
Are added by the addition amplifier 65 to generate an addition output r.

The addition output q and the addition output r are input to the subtraction amplifier 69 and are subtracted to generate a track error signal u of the well-known push-pull method.

As described above, in the present embodiment, the split photodetector (light detecting means) 37a can simultaneously detect a signal from a short pit that does not reach the reproduction limit and detect a servo signal.

The optical reproducing method and the optical reproducing apparatus of the present invention are not limited to the above-mentioned embodiments, but can be variously modified within the scope of the gist. In particular, the super-resolution optical disc is not limited to the ROM type and can be applied to various media. Further, the detailed configurations of the light source unit and the optical system for detecting the reproduction light are arbitrary. The shape of the split photodetector is not limited to the strip shape, but can be variously changed within the scope of the gist thereof. For example, as shown in FIGS. 5A and 5C, the split photodetector includes a central portion photodetector 80 having a quadrangular shape (rectangular shape or rhombus), and the other portions of the split photodetector are defined by end photodetectors 81 to 84. You may divide equally. In addition, FIG.
The central portion photodetector 80 may be circular as shown in FIG. Also in these cases, the central portion photodetector 80 may have a width dimension in the track direction in the detection beam h of 1/2 to 49/50 with respect to the diameter of the detection beam h. 20
Is preferable.

In the first and second embodiments, the end portion of the light flux in the track direction is detected. However, the present invention is not limited to this, and the end portion of the light flux may be detected. Further, although the photo detectors are aligned in the track direction, the photo detectors are not limited to this, and may be arranged so as to be able to detect the ends of the light flux. As a result, by detecting the edge portion in the direction perpendicular to the track, not only the recording density of the above pits or marks,
It is possible to increase the track strength. That is, it is possible to more reliably detect a signal from a track having a short pitch, and further, a signal from a track pitch having a length less than the reproduction limit of the optical recording medium. That is, tracks can be separated and detected at a track pitch that is less than the reproduction limit.

Further, in the above, the signal is detected from the pit of the super-resolution disc, but not limited to the pit, a recording mark or the like on a recordable medium can be similarly detected.

In the above, the detection of the signal from the pit is described, but the information is actually reproduced (read).
In this case, the information is reproduced (read out) from the pitch formed by the pits or marks and the space formed on the optical recording medium.

Further, in the optical reproducing apparatus according to the present invention, when the wavelength λ of the reproducing light and the numerical aperture of the objective lens are NA,
In an apparatus for reproducing information from an optical recording medium containing marks or pits having a pitch of λ / 2NA or less, at least the central portion of a light beam is removed from the optical path of an optical system for detecting light from the optical recording medium, and reproduction is performed. It can be expressed as having a reproducing means for reproducing.

Further, the optical reproducing apparatus according to the present invention comprises a first detection system for reproducing an optical signal from a mark or pit having a pitch longer than approximately λ / 2NA, and approximately λ /
A second detection system for reproducing an optical signal from a mark or pit having a pitch shorter than 2NA, a signal detected by the first detection system, and a signal detected by the second detection system. A signal processing circuit that synthesizes and reproduces information can be described as being included. Further, it is preferable that the second detection system includes a reproducing means for reproducing a signal by removing at least a central portion of the light flux.

Further, in the optical reproducing method according to the present invention, when the wavelength of the reproducing light is λ and the numerical aperture of the objective lens is NA, an optical recording medium including marks or pits with a pitch of λ / 2NA or less is used. In the method of reproducing information, from all of the light flux containing information from the optical recording medium, approximately λ /
A first signal for information from a mark or pit having a pitch longer than 2NA is reproduced, at least a central portion of a light beam containing information from the optical recording medium is removed, and a light beam positioned at an end in the track direction. Is detected and roughly λ /
It can be said that a second signal containing information from a mark or pit having a pitch shorter than 2NA is reproduced, and information is reproduced from the first and second signals.

The super-resolution phenomenon occurs due to the arrangement of fine marks and pits. The spatial frequency of the reproduced signal exceeds the diffraction limit of the optical system. Increasing the power of the reproduction light increases the modulation of the reproduction signal, but also increases white noise due to an increase in the amount of incident light. In order to improve the signal-to-noise ratio, it is important to suppress the increase of white noise while increasing the modulation degree.

Therefore, in the optical reproducing apparatus and the optical reproducing method according to the present invention, since at least the central portion of the luminous flux of the reproduced light is removed, the signal component does not affect the vicinity of the luminous flux. Since the amount of light at the center of the luminous flux is reduced or cut, white noise is reduced and the signal-to-noise ratio of the reproduced signal is increased.

In the super-resolution optical disk, it is considered that the optical signal from the mark or pit having a high spatial frequency detected by the super-resolution effect is likely to pass through the end of the light flux of the detection optical system. Therefore, in order to detect optical signals from marks or pits with high spatial frequency,
By detecting only the light flux that passes through the end of the light flux, or by providing such an optical system, it is possible to emphasize and reproduce the signal below the reproduction limit. Then, by constructing this reproduction signal and a signal (a signal from a mark or pit larger than the reproduction limit) that detects the light flux including the central portion of the light flux, a plurality of lengths included in the actual recording / reproduction information can be obtained. The signal from the mark or pit can be reproduced.

In addition, the low output high frequency component from the mark or pit below the reproduction limit is buried in the high output low frequency component from the mark or pit above the reproduction limit. By blocking the passage of low frequency components, it is possible to avoid the loss of low output signals from marks or pits below the reproduction limit. Also in the same manner as described above, by detecting and combining the light fluxes passing through the end and the center of the light flux with different detection systems, a signal including a mark or a pit of a plurality of lengths can be detected without a signal below the reproduction limit. It can be avoided and its output can be increased.

[0089]

As described above, the optical reproducing apparatus of the present invention has the following features.
In an optical reproducing device for reproducing information from pits or marks formed in the track direction of an optical recording medium by detecting reflected light or transmitted light of the light irradiated on the optical recording medium, This is a configuration including a detection unit that detects a signal at an end portion of a light beam.

With the above arrangement, it is considered that the signal from the pit or mark having a short length passes around the light flux of the reproducing optical system more than the signal from the long pit or mark. Therefore, with the above configuration, if the end portion of the light flux of the reflected light or the transmitted light is detected, the signal from the pit or mark with a short length, and thus the pit or mark with a length less than the reproduction limit of the optical recording medium, is detected. The signal can be detected more reliably. That is, there is an effect that it is possible to avoid the loss of a signal that does not reach the reproduction limit. Further, since the central portion of the light flux is reduced or removed, the amount of light to be detected is cut. Therefore, the white noise can be reduced, and the signal-to-noise ratio of the detected signal can be improved.

The optical reproducing apparatus of the present invention has, in addition to the above-mentioned configuration, a split photodetector having the above-mentioned detecting means.

According to the above arrangement, the split photodetector can detect the end portion of the reflected or transmitted light flux in the track direction, and the reproduction limit of the optical recording medium, which is considered to pass many end portions of the light flux. It is possible to more reliably detect a signal from a pit or mark having a length less than that.

The optical reproducing apparatus of the present invention has, in addition to the above structure, a reproducing means for reproducing at least the signal detected by the detecting section.

According to the above configuration, it is possible to more reliably reproduce the signal from the pit or mark whose length is less than the reproduction limit from the optical recording medium. That is, there is an effect that it is possible to increase and reproduce a signal from a pit or mark having a length less than the reproduction limit.

The optical reproducing apparatus of the present invention comprises, in addition to the above configuration, a center detecting means for detecting a signal of a central portion of at least the luminous flux of the reflected light or the transmitted light, and the reproducing means is the detecting means. The configuration is such that the detected signal and the signal detected by the center detecting means are combined and reproduced.

According to the above arrangement, the signal at the central portion of the light beam is detected, and the signal from the pit or mark having a length equal to or longer than the reproduction limit is detected. Then, by combining the signal of the central portion and the signal of the end portion in the light flux, both the signal from the pit or mark having a length longer than the reproduction limit and the signal from the pit or mark having a length less than the reproduction limit. Can be reliably detected. Therefore, there is an effect that information recorded on the optical recording medium can be reproduced while avoiding loss.

The optical reproducing apparatus of the present invention has, in addition to the above configuration, a split photodetector having the center detecting means.

With the above arrangement, the split photodetector can separate and detect the signal of the central portion of the light beam.

In the optical reproducing apparatus of the present invention, in addition to the above configuration, the reproducing means further combines the signal detected by the detecting means and the signal detected by the center detecting means to generate a servo signal. Is a configuration for generating.

According to the above arrangement, the signals detected by the detecting means and the center detecting means are combined, so that the servo signal can be easily generated only by adding a circuit having a simple structure. Therefore, there is an effect that it is possible to provide an optical reproducing device that can perform optical reproduction more stably. In addition, it is not necessary to add a device or the like for newly generating a servo signal, and there is an effect that space can be saved.

As described above, the optical reproducing apparatus of the present invention converts the information from the pits or marks formed in the track direction of the optical recording medium into the reflected light or the transmitted light of the light irradiated on the optical recording medium. In an optical reproducing device that reproduces by detecting, a first detection unit that detects a signal from a pit or a mark that is longer than the reproduction limit of the reflected light or the transmitted light, and a shorter than the reproduction limit of the reflected light or the transmitted light. A second detecting unit for detecting a signal from the pit or mark; and a reproducing unit for reproducing the information by combining the signal detected by the first detecting unit and the signal detected by the second detecting unit. This is the configuration provided.

According to the above configuration, the signal from the pit or mark having a length equal to or longer than the reproduction limit and the signal from the pit or mark having a length less than the reproduction limit are combined and reproduced. As a result, signals from pits or marks whose length is less than the reproduction limit are emphasized and reproduced. That is, the information recorded on the optical recording medium can be reproduced while avoiding the loss.

In addition to the above configuration, the optical reproducing apparatus of the present invention has a configuration in which the second detecting section includes a detecting means for detecting an end of the reflected or transmitted light beam.

According to the above arrangement, since the end of the reflected or transmitted light beam is detected, it is possible to more reliably detect a signal from a pit or mark having a length less than the reproduction limit. Has the effect.

In order to solve the above-mentioned problems, the optical reproducing method of the present invention is formed in the track direction of the above-mentioned optical recording medium by detecting the reflected light or transmitted light of the light applied to the optical recording medium. In a light reproducing method for reproducing information by means of pits or marks, a first signal from a pit or mark having a length longer than a reproduction limit is detected from the luminous flux of reflected light or transmitted light, and the luminous flux of reflected light or transmitted light is detected. Thus, the second signal from the pit or mark having a length shorter than the reproduction limit is detected, and the information of the optical recording medium is reproduced by combining the first signal and the second signal.

According to the above construction, the optical signal from the pit or mark having a length longer than the reproduction limit and the optical signal from the pit or mark having a length less than the reproduction limit are combined and reproduced. As a result, the optical signal from the pit or mark having a length less than the reproduction limit is emphasized and reproduced. That is, the information recorded on the optical recording medium can be reproduced while avoiding the loss.

In addition to the above configuration, the optical reproducing method of the present invention has a configuration in which the second signal is a signal obtained by removing at least the central portion of the light flux and detecting the end portion of the light flux.

According to the above arrangement, the end portion of the reflected or transmitted light flux is detected, so that it is possible to more reliably detect the optical signal from the pit or mark having a length less than the reproduction limit. It has the effect of being able to.

The optical reproducing method of the present invention has a configuration in which, in addition to the above configuration, a servo signal is generated by combining the first signal and the second signal.

According to the above configuration, the first signal and the second signal
A servo signal can be easily generated by combining the signals. This brings about an effect that more stable light reproduction can be performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a split photodetector and a signal processing circuit used in an optical reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an optical reproducing device according to an embodiment of the present invention.

FIG. 3A is a shape of a recording pit in a super-resolution optical disc used in the above-mentioned optical reproducing device, and FIGS.
FIG. 3D is a diagram showing a waveform of a reproduction signal detected by the optical reproduction device.

FIG. 4 is a circuit diagram showing a split photodetector and a signal processing circuit used in an optical reproducing device according to another embodiment.

5A to 5C are configuration diagrams showing another configuration example of the split photodetector.

[Explanation of symbols]

12 super-resolution optical disk (optical recording medium) 21 laser diode (irradiation means) 23 polarization beam splitter 25 objective lens 37 split photodetector (light detection means) 40 signal processing circuit (reproduction means) 45 first end photodetector (detection means, 1st detection part) 46 Central part photodetector (center detection means, 2nd detection part) 47 2nd end photodetector (detection means, 1st detection part) h Detection beam (light flux)

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 000003067             TDK Corporation             1-13-1 Nihonbashi, Chuo-ku, Tokyo (72) Inventor Junji Tominaga             1-1-1 Higashi 1-1-1 Tsukuba City, Ibaraki Prefecture             Inside the Tsukuba Center, National Institute of Advanced Industrial Science and Technology (72) Inventor Takashi Nakano             1-1-1 Higashi 1-1-1 Tsukuba City, Ibaraki Prefecture             Inside the Tsukuba Center, National Institute of Advanced Industrial Science and Technology (72) Inventor Hiroshi Fuji             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company (72) Inventor Akira Sato             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture             Osaka International Building Minolta Co., Ltd. (72) Inventor Takashi Kikukawa             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F term (reference) 5D090 AA01 BB04 BB20 CC04 DD05                       EE17 EE18 FF41                 5D118 BA01 BB05 BF02 CA23 CB05                       CD01 CF04 CF06 CF10                 5D119 AA11 AA12 BA01 BB20 EA01                       KA18 KA20 KA22 KA24 KA27                 5D789 AA11 AA12 BA01 BB20 EA01                       KA18 KA20 KA22 KA24 KA27

Claims (11)

[Claims] 1. An optical reproducing apparatus for reproducing information from pits or marks formed in the track direction of an optical recording medium by detecting reflected light or transmitted light of light applied to the optical recording medium, An optical regenerator comprising a detecting means for detecting a signal at an end of the reflected or transmitted light flux. 2. The optical reproducing apparatus according to claim 1, further comprising a split photodetector including the detecting means. 3. An optical reproducing apparatus according to claim 1, further comprising reproducing means for reproducing a signal detected by at least the detecting means. 4. A center detecting means for detecting at least a signal of a central portion of the light flux of the reflected light or the transmitted light is provided, and the reproducing means is detected by the signal detected by the detecting means and the center detecting means. The optical reproduction apparatus according to claim 3, wherein the optical reproduction apparatus synthesizes the reproduced signal and the reproduced signal. 5. The optical regenerator according to claim 4, further comprising a split photodetector including the center detecting means. 6. The reproducing means further synthesizes a signal detected by the detecting means and a signal detected by the center detecting means to generate a servo signal. The optical regenerator described in. 7. An optical reproducing apparatus for reproducing information from pits or marks formed in the track direction of an optical recording medium by detecting reflected light or transmitted light of light applied to the optical recording medium, A first detection unit for detecting a signal from a pit or mark longer than the reproduction limit of the reflected light or the transmitted light; and a second detection unit for detecting a signal from a pit or mark shorter than the reproduction limit of the reflected or transmitted light. A detection unit, and reproduction means for combining the signal detected by the first detection unit and the signal detected by the second detection unit to reproduce information.
An optical regenerator comprising: 8. The optical regenerator according to claim 7, wherein the second detection unit includes a detection unit that detects an end of the reflected light beam or the transmitted light beam. 9. An optical reproducing method for reproducing information of the optical recording medium by detecting reflected light or transmitted light of light applied to the optical recording medium, wherein reproduction is performed from a light flux from the reflected light or transmitted light. A first signal from a pit or mark longer than a limit is detected, and a second signal from a pit or mark shorter than the reproduction limit is detected from the luminous flux from the reflected light or transmitted light. An optical reproducing method characterized by reproducing information of an optical recording medium by synthesizing two signals. 10. The optical reproducing method according to claim 9, wherein the second signal is a signal obtained by removing at least a central portion of the light flux and detecting an end portion of the light flux. 11. The optical reproducing method according to claim 9, wherein a servo signal is generated by combining the first signal and the second signal.