JP4873773B2 - Optical pickup device, optical recording medium recording / reproducing device, and track discrimination signal detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device that writes and reads information signals to and from an optical recording medium, and an optical recording medium recording and reproducing device that includes such an optical pickup device and records and reproduces information signals to and from the optical recording medium. TECHNICAL FIELD The present invention relates to an apparatus and a track discrimination signal detection method for detecting a track discrimination signal for detecting the position of a recording track in such an optical recording medium recording / reproducing apparatus, and in particular, an optical recording medium recording / reproducing apparatus for performing land-group recording. The present invention relates to an optical pickup device and a track discrimination signal detection method used in the optical recording medium recording / reproducing apparatus.
[0002]
[Prior art]
Conventionally, an optical recording medium such as a so-called optical disk has been proposed, and an optical recording medium recording / reproducing apparatus has been proposed as an apparatus for recording and reproducing information signals using such an optical recording medium. In this optical recording medium recording / reproducing apparatus, optical disks based on various methods are used as the optical recording medium. In such an optical recording medium recording / reproducing apparatus, information signals are written to and read from the optical disk by an optical pickup device.
[0003]
This optical pickup device has a light source such as a semiconductor laser, and is configured to condense and irradiate a light beam emitted from this light source on a signal recording surface of an optical disc via an objective lens. The optical pickup device writes an information signal on the signal recording surface by a light beam irradiated on the signal recording surface, and detects a reflected light beam by the signal recording surface of the light beam irradiated on the signal recording surface. Thus, the information signal recorded on the signal recording surface is read.
[0004]
This optical pickup device writes and reads information signals along land portions or group portions formed spirally or concentrically on a signal recording surface of an optical disc.
[0005]
On the other hand, in the optical disk, the information signal to be recorded has been increased in density. For example, as a so-called “ROM disc” for reproduction only, an optical disc having a diameter of 120 mm is used as in the case of “compact disc (CD)” (trade name), and the recording capacity is about 7 of 650 MB, which is the capacity of “compact disc”. “DVD” (trade name), which is doubled to 4.7 GB, has been proposed.
[0006]
Higher recording density is also progressing in “rewritable discs” capable of recording and playing back information signals, and the so-called “DVD-RAM” discs are used for recording and playback of optical recording media in the position of “rewritable” DVDs. A device has been proposed. This "DVD-RAM" disc is not a conventional system for recording information signals only in one of the land part or group part in order to increase the density of recorded information signals. The “land groove recording method” is used to record the information signal.
[0007]
In recent years, the “DVR” format, which uses a short-wavelength light source with an emission wavelength of about 405 nm and a high NA objective lens with an NA (numerical aperture) of 0.85, has been developed as an optical disc format for further higher recording density. However, even in this format, the “land groove recording method” is adopted.
[0008]
[Problems to be solved by the invention]
By the way, as represented by the above-mentioned “DVD-RAM”, in the high-density rewritable disc using the “land-groove recording method”, the width of the land portion and the groove portion are set to be substantially equal. Causes the following problems.
[0009]
That is, when the “land recording method” in which recording is performed only on the land portion using an optical disk having a land portion wider than the groove portion, as shown in FIG. 22, the tracking error signal (TE) is returned. The sum signal (SUM) of light (main spot when using the “3-spot method”) is a relationship in which the phase is shifted by (1/4) period when one period is from the group part to the next group part. It is in.
[0010]
Therefore, when tracking control is performed so that the tracking error signal (TE) becomes zero, the tracking error signal (TE) becomes zero when the light beam is irradiated on the land portion and on the groove portion. The two cases can be distinguished by the level of the sum signal (SUM).
[0011]
Thus, the signal for distinguishing between the case where the light beam is irradiated on the land portion and the case where the light beam is irradiated on the groove portion is a “track discrimination signal” or “cross track signal ( CTS) ". As such a “track discrimination signal”, the sum signal (SUM) level is applied to the land portion and the groove portion as in the case of adopting the “land recording method”. 23, the alternating current (AC) component (AC-SUM) of the sum signal can be used as shown in FIG. 23. The alternating current component of the sum signal is shown in FIG. As shown, the track discrimination signal is 90 degrees out of phase with the tracking error signal.
[0012]
When the “land recording method” is adopted, by using two signals of such a tracking error signal and an alternating current component of the sum signal, even when a high speed seek operation is performed, a spot is recorded on the recording track. Thus, it is possible to accurately know how many tracks have moved in which direction, and it is possible to stably count the number of track crossings and to perform the tracking servo pull-in operation.
[0013]
However, when the “land / groove method” is employed, the land portion and the groove portion are generally set to have substantially the same width in order to optimize the recording / reproducing characteristics. As a result, as shown in FIG. 24, the sum signal in the above explanation becomes almost equal when the light flux is irradiated on the land portion and when the light flux is irradiated on the groove portion. A track discrimination signal cannot be generated from the sum signal.
[0014]
As a result, it becomes difficult to access a predetermined recording track at a time during high-speed seek operations that are frequently performed particularly in applications such as external storage devices, professional video recording and editing devices, and the access time becomes longer. There was a problem.
[0015]
In addition, as a format for increasing the density of information signals recorded on an optical recording medium without adopting the “land groove method”, there are so-called “DVD + RW” and the like. Although the information signal is recorded, the AC component (AC-SUM) of the sum signal is several times the direct current (DC) component because the land and group widths are set to be substantially equal to each other. In many cases, there were only%, and they had the same problem.
[0016]
Therefore, the present invention has been proposed in view of the above circumstances, and without increasing the number of components or complicating the configuration of components, for example, “land” such as “DVD-RAM” and “DVR”. Even in the case of using an optical recording medium adopting a “groove method”, a track discrimination signal can be generated, and an optical pickup device capable of high-speed access, a track discrimination signal detection method, and such an optical It is an object of the present invention to provide an optical recording medium recording / reproducing apparatus employing a pickup device and a track discrimination signal detection method.
[0017]
[Means for Solving the Problems]
  In order to solve the above-described problem, an optical pickup device according to the present invention includes a light source having at least one light emitting point that emits a light beam, and the light beam.The land part and the group part have an information signal recordable in one or both of the land part and the group part.An objective lens for focusing and irradiating the signal recording surface of the optical recording medium and a light detecting means for receiving a reflected light beam from the signal recording surface of the optical recording medium are provided.
[0018]
  And in this optical pickup device, in the forward path emitted from the light source, the light beam emitted from the light source,By astigmatism adding means that is an optical diffraction element disposed in the optical path,A main light beam for forming a main spot for recording and / or reproducing an information signal on the signal recording surface of the optical recording medium, and a position separated from the main spot on the signal recording surface of the optical recording medium A sub-light beam having astigmatism that forms a sub-spot is formed. Also, the astigmatism directions added to the pair of sub-spots by the astigmatism adding means are opposite to the tangential direction of the recording track formed on the signal recording surface of the optical recording medium. And approximately 45 degrees.The light detecting means includes a main light receiving portion for receiving a main reflected light beam, which is a light beam reflected by the signal recording surface of the optical recording medium, and a light beam in which the sub light beam is reflected by the signal recording surface. A sub-light-receiving unit that receives the sub-reflected light beam, and the sub-light-receiving unit includes a plurality of light-receiving elements that output independent light detection signals. Each of the light receiving elements outputs a plurality of light detection signals that generate a track discrimination signal for discriminating the position of the main spot by adding and subtracting.The
[0019]
Further, the optical recording medium recording / reproducing apparatus according to the present invention has a land portion and a group portion, and an optical recording medium capable of recording an information signal is detachably attached to one or both of the land portion and the group portion, An operating mechanism for operating the mounted optical recording medium, an optical pickup device for writing and reading information signals to and from the optical recording medium operated by being mounted on the operating mechanism, and an output signal from the optical pickup device And a servo circuit for controlling the position of the objective lens of the optical pickup device.
[0020]
  In this optical recording medium recording / reproducing apparatus, the optical pickup device includes a light source having at least one light emitting point that emits a light beam, an objective lens that focuses and irradiates the light beam on a signal recording surface of the optical recording medium, And a light detecting means for receiving a reflected light beam from the signal recording surface of the optical recording medium. In this optical pickup device, the light beam emitted from the light source is transmitted in the forward path emitted from the light source.By astigmatism adding means that is an optical diffraction element disposed in the optical path,A main light beam for forming a main spot for recording and / or reproducing an information signal on the signal recording surface of the optical recording medium, and a position separated from the main spot on the signal recording surface of the optical recording medium A sub-beam having astigmatism that forms a sub-spot is used. Also, the astigmatism directions added to the pair of sub-spots by the astigmatism adding means are opposite to the tangential direction of the recording track formed on the signal recording surface of the optical recording medium. And approximately 45 degrees.The light detecting means includes a main light receiving portion for receiving a main reflected light beam, which is a light beam reflected by the signal recording surface of the optical recording medium, and a light beam in which the sub light beam is reflected by the signal recording surface. A sub-light-receiving unit that receives the sub-reflected light beam, and the sub-light-receiving unit includes a plurality of light-receiving elements that output independent light detection signals. Each of the light receiving elements outputs a plurality of light detection signals that generate a track discrimination signal for discriminating the position of the main spot by adding and subtracting.The
[0021]
In the track discrimination signal detecting method according to the present invention, first, an optical recording medium having a land portion and a group portion and capable of recording an information signal on one or both of the land portion and the group portion is detachably attached. An operation mechanism for operating the mounted optical recording medium is operated by mounting the optical recording medium. Next, a light source having at least one light emitting point that emits a light beam, an objective lens that collects and irradiates the light beam on the signal recording surface of the optical recording medium, and a reflected light beam from the signal recording surface of the optical recording medium An information signal is read from an optical recording medium that is mounted on the operation mechanism and operated using an optical pickup device having a light detection means for receiving light.
[0022]
  In the optical pickup device, the light beam emitted from the light source is disposed in the optical path in the forward path emitted from the light source.Optical diffraction elementA main light beam for forming a main spot for recording and / or reproducing an information signal on the signal recording surface of the optical recording medium by the astigmatism adding means and the main spot on the signal recording surface of the optical recording medium A sub-beam having astigmatism that forms a sub-spot at a position separated from the sub-spot is used. Here, the directions of astigmatism added to the pair of sub-spots by the astigmatism adding means are opposite to the tangential direction of the recording track formed on the signal recording surface of the optical recording medium. Yes and roughly 45 °A main light receiving portion that receives a main reflected light beam that is a light beam reflected by the signal recording surface of the optical recording medium, and a sub-reflected light beam that is a light beam that is reflected by the signal recording surface. The sub reflected light beam is divided and received by a plurality of light receiving elements that output independent light detection signals constituting the sub light receiving part of the light detecting means having a sub light receiving part for receiving light. A track discrimination signal for discriminating the position of the main spot is generated based on the added / subtracted output signal.The
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0024]
In this embodiment, an optical recording medium recording / reproducing apparatus according to the present invention configured to include the optical pickup apparatus according to the present invention is selected from a plurality of types of optical disks as optical disks that are optical recording media. Information signals can be recorded and reproduced for each. Then, by operation such as mode switching, “land group recording” can be performed using an optical disk capable of performing “land group recording” such as a so-called “DVD-RAM” disk.
[0025]
As shown in FIG. 1, the optical recording medium recording / reproducing apparatus includes a spindle motor 1 serving as a rotation operation unit that rotationally drives an optical disk 101 that is an optical recording medium. In the spindle motor 1, a disk table (not shown) is attached to a drive shaft, and the optical disk 101 is rotated together with the disk table by mounting the optical disk 101 on the disk table. The spindle motor 1 is controlled by a servo control circuit 5 and a system controller 7 and is driven at a predetermined rotational speed.
[0026]
The optical pickup device 2 writes and reads information signals to and from the optical disc 101 that is rotated by the spindle motor 1. The optical pickup device 1 is moved by a feed motor 3 in the radial direction of the optical disc 101 mounted on the disc table. The optical pickup device 1 and the feed motor 3 are also controlled and driven by the servo control circuit 5.
[0027]
The optical pickup device 2 reads the information signal from the signal recording surface by irradiating the signal recording surface of the optical disc 101 with a light beam and detecting the reflected light beam of the light beam. The signal read from the optical disk 101 by the optical pickup device 2 is amplified by the preamplifier 4 and sent to the signal modulation / demodulation and ECC block 6 and the servo control circuit 5. The signal modulation / demodulation and ECC block 6 performs signal modulation, demodulation, and ECC (error correction code) addition according to the type of optical recording medium to be reproduced. The signal modulation / demodulation and ECC block 6 generates a focus error signal, a tracking error signal, a track determination signal, an RF signal, and the like based on the transmitted signal. The servo control circuit 5 controls the optical pickup device 2 based on the signal modulation / demodulation and focus error signal, tracking error signal, and track determination signal generated by the ECC block 6.
[0028]
The signal demodulated in the signal modulation / demodulation and ECC block 6 is sent to an external computer 9a or the like via the interface 8a if this signal is data for data storage of a computer, for example. In this case, the external computer 9a or the like can receive a signal recorded on the optical disc 101 as a reproduction signal.
[0029]
Further, when the information signal recorded on the optical disc 101 is a signal for so-called “audio visual” (sound reproduction and image reproduction), the signal demodulated in the signal modulation / demodulation and ECC block 6 is D / A. , A / D converter 8b performs digital / analog conversion and sends it to audio / visual processing section 9b. The signal that has been subjected to the audio / video processing in the audio / visual processing unit 9b is transmitted to an external video / projection device (not shown) via the audio / visual signal input / output unit 9c.
[0030]
Further, the optical pickup device 2 irradiates the signal recording surface of the optical disc 101 to be rotated based on the signal modulation / demodulation and the signal sent from the ECC block 6 with a light beam. Information signal writing to the signal recording surface of the optical disc 101 is performed by irradiation of such a light beam.
[0031]
As shown in FIG. 2, the optical pickup device 2 includes a light source unit 10. The light source unit 10 has at least one light emitting point that emits a light beam. In this embodiment, the light source unit 10 has one light emitting point 10a as shown in FIG. The light emitting point 10a is supported by the holding base 10d and stored in the package 10e. The light source unit 10 includes an optical diffraction element 17. As shown in FIG. 4, the light diffraction element 17 is configured as a hologram pattern (hologram element) that causes astigmatism. A light beam emitted from the light emitting point 10a and diffracted by the light diffraction element 17 is separated into zero-order light and ± first-order light. The zero-order light is equal to the main light beam emitted from the light emitting point 10a and traveling as it is. The + 1st order light is equal to the first sub-beam emitted from the first virtual light emitting point 10b that is not the light emitting point 10a but shifted from the light emitting point 10a. Also, the minus first-order light is equal to the second sub-beam emitted from the second virtual light emitting point 10c which is not the light emitting point 10a but shifted from the light emitting point 10a.
[0032]
The zero-order light in the optical diffraction element 17 becomes a main light beam that forms a main spot on the signal recording surface of the optical disc 101 for recording and reproducing information signals with respect to the optical disc 101. The + 1st order light in the optical diffraction element 17 becomes a first sub-beam that forms a first sub-spot. Further, the −1st order light in the light diffraction element 17 becomes a second sub-beam that forms a second sub-spot. Further, the main spot formed by the main light beam and each sub spot formed by each sub light beam are formed at positions separated from each other on the signal recording surface of the optical disc 101.
[0033]
The ± first-order light in the optical diffraction element 17 has astigmatism that is opposite in sign and forms an angle of approximately 45 ° with respect to the tangential direction of the recording track formed on the signal recording surface of the optical disc 101. It has been added.
[0034]
In the light source unit 10, the light diffraction element 17 is rotated around the optical axis, so that the sub-spot and the recording track on the signal recording surface of the optical disc are not changed without changing the focus position of the main spot. It is possible to change the positional relationship. Each sub-spot has an absolute value of the distance to the main spot in the normal direction of the recording track formed on the signal recording surface of the optical disk as S, the track pitch as Tp, and n as an integer.
S ≒ Tp · n / 2
Is formed at a position where is established.
[0035]
In the present invention, “track pitch (Tp)” means “land groove method”, and even when information signals are recorded on both the land portion and the group portion on the optical disk, "Distance to the next land part" (or "Distance from the group part to the next group part").
[0036]
When an information signal is read from an optical recording medium on which “land groove recording” has been performed using the optical pickup device 2, the light emitted from the virtual light emitting points 10 a, 10 b, and 10 c of the light source unit 10. As shown in FIG. 2, the light beam is incident on the polarizing beam splitter prism 11 and is substantially entirely reflected by the dielectric multilayer film by being in the S-polarized state with respect to the dielectric multilayer film included in the polarizing beam splitter prism 11. The amount of light is reflected and enters the quarter-wave plate 12. The light beam incident on the quarter-wave plate 12 is converted into a circularly polarized state by transmitting through the quarter-wave plate 12, and is converted into a parallel light beam through the collimator lens 13 and is incident on the objective lens 14. .
[0037]
The polarization beam splitter prism 11 is generally composed of a pair of triangular prisms that are bonded together to form a cube, and a dielectric multilayer film formed by vapor deposition or sputtering between the triangular prisms. ing. In the incident light beam to the polarization beam splitter prism 11, the P-polarized component with respect to the dielectric multilayer film is transmitted through the dielectric multilayer film, and the S-polarized component with respect to the dielectric multilayer film is reflected by the dielectric multilayer film.
[0038]
The objective lens 14 is supported by a biaxial actuator (not shown) so as to be movable in the focus direction indicated by arrow F in FIG. 2 and the tracking direction indicated by arrow T in FIG. Focus on the signal recording surface. At this time, the light beams emitted from the three virtual light emitting points 10a, 10b, and 10c are condensed on the signal recording surface.
[0039]
The three reflected light beams that are irradiated onto the signal recording surface of the optical disc 101 and reflected by the signal recording surface pass through the objective lens 14, the collimator lens 13, and the ¼ wavelength plate 12 to be linearly polarized and polarized. It reaches the beam splitter prism 11. In this polarization beam splitter prism 11, the reflected light beam is in a P-polarized state with respect to the dielectric multilayer film, so that almost all the amount of light passes through the dielectric multilayer film and is separated from the optical path returning to the light source unit 10. Then, the light travels through the optical branching element 22 and the multi-lens 15 to enter the light detecting element 16. The multi-lens 15 is a lens in which a concave surface and a cylindrical surface are combined. The multi-lens 15 extends the distance of the reflected light beam to the condensing point and causes astigmatism in the reflected light beam.
[0040]
In addition, each optical component which comprises the optical pick-up apparatus 2 is individually mounted and supported in the optical block part which is not shown in figure. Moreover, the light diffraction element 17 can also be comprised by a polarization hologram element. In this case, the light diffraction element 17 may be provided not between the light emitting point 10a and the polarizing beam splitter prism 11 but between the polarizing beam splitter prism 11 and the quarter wavelength plate 12 as described above. Good. This is because the polarization hologram element acts as a hologram with respect to the outward light flux toward the optical disk, but can be formed so as not to cause any optical action with respect to the return light flux returning from the optical disk.
[0041]
As shown in FIG. 5, the light detection element 16 receives a first main light receiving unit 18 that receives a main reflected light beam from the main spot, and a first main light receiving unit that receives a first sub reflected light beam from the first sub spot. The sub-light-receiving unit 19, the second sub-light-receiving unit 20 that receives the second sub-reflected light beam from the second sub-spot, and the first light beam that receives the light beam branched from the main reflected light beam from the main spot independently. It has two main light receiving parts 21. As shown in FIG. 2, the branching of the main reflected light beam to the second main light receiving unit 21 is provided with a light branching element 22 such as a Wollaston prism between the polarizing beam splitter prism 11 and the multi lens 15. Is done by being.
[0042]
The first main light receiving unit 18 includes four light receiving elements a, b, c, d in a state of being radially arranged through a central portion in order to detect a focus error signal by a so-called “astigmatism method”. Consists of. In the main light receiving unit 18, the light receiving elements a and c and the light receiving elements b and d are diagonally opposed to each other through the central portion of the main light receiving unit 18. These four light receiving elements a, b, c, and d output independent light detection signals a, b, c, and d, respectively.
[0043]
The second main light receiving unit 21 includes one light receiving element s that receives a reflected light beam from the main spot branched by the light branching element. A light detection signal s is output from the light receiving element s. This light detection signal s is a so-called RF signal read from the optical disc 101.
[0044]
In addition, each of the sub light receiving portions 19 and 20 has four light receiving elements e, f, and g that are arranged radially through the central portion in order to detect a focus error signal by a so-called “astigmatism method”. , H, i, j, k, l. In the first sub light receiving unit 19, the light receiving elements e and g and the light receiving elements f and h are diagonally opposed to each other via the central portion of the first sub light receiving unit 19. These four light receiving elements e, f, g, and h output independent light detection signals e, f, g, and h, respectively. In the second sub light receiving unit 20, the light receiving elements i and k and the light receiving elements j and l are diagonally opposed to each other through the central portion of the second sub light receiving unit 20. These four light receiving elements i, j, k, and l output independent photodetection signals i, j, k, and l, respectively.
[0045]
The photodetection signal output from the photodetection element 16 is subjected to current-voltage conversion by an amplifier (not shown) formed on the semiconductor substrate of the photodetection element 16, for example, and then an arithmetic circuit or each light receiving unit 18, Sent to arithmetic circuits outside the photodetecting elements connected to 19, 20, and 21. In this arithmetic circuit, a focus error signal FE, a tracking error signal TE, a track discrimination signal CTS, and an RF signal are calculated as follows.
[0046]
That is, the track discrimination signal CTS is generated by the following calculation.
[0047]
CTS = {(e + g)-(f + h)}-{(i + k)-(j + l)}
The focus error signal FE1, the tracking error signal TE, and the RF signal are generated by the following calculations, respectively. The focus error signal FE1 is generated by a so-called “astigmatism method”, and the tracking error signal TE is generated by a so-called “differential push-pull method”.
[0048]
FE1 = (a + c) − (b + d)
TE = {(a + d) − (b + c)} − K1 ·[{(E + h)-(f + g)} + {(i + l)-(j + k)}]
(∵K1 is a coefficient)
RF = s
  In the light detection element 16 of the optical pickup device according to the present invention, each of the sub light receiving portions 19 and 20 has a light receiving surface similar to that of the main light receiving portion 18, and is proposed in Japanese Patent Laid-Open No. 2000-82226. As described above, the focus error signal FE2 may be generated by the following calculation.
[0049]
FE2 = {(a + c)-(b + d)} + K2 ·[{(E + g)-(f + h)} + {(i + k)-(j + l)}]
(∵K2 is a coefficient)
  The tracking error signal can also be generated by a so-called differential phase difference method (differential phase detection method: DPD method) using the light detection signals a, b, c, d from the main light receiving unit 18. It is.
[0050]
Next, the principle of signal detection in the track discrimination signal detection method according to the present invention will be described.
[0051]
In the present invention, on the signal recording surface of the optical disc, a sub-spot with an astigmatism that is approximately 45 ° with respect to the tangential direction of the recording track is formed. When a hologram element is used as the astigmatism adding means and the ± first-order light is used as a sub-light beam forming a sub-spot, two sub-spots having different astigmatic directions are formed. When each spot crosses the recording track in this state, the intensity of the return light is equal in the main spot depending on whether the irradiation position is the land position or the group position, whereas in the secondary spot, the wavefront interference state is caused by astigmatism. Due to the change, a large difference occurs in the return light intensity depending on whether the irradiation position is the land position or the group position. Track discrimination can be performed based on such a difference in light intensity.
[0052]
For example, in an optical pickup device using a “DVR” disc (trade name) as an optical disc, the results of calculating the intensity distribution and phase distribution of the diffracted light on the objective lens pupil in the optical disc are shown in FIGS.
[0053]
As calculation conditions for the calculation results shown here, the wavelength of the light beam irradiated by the optical pickup device was 405 nm, and the numerical aperture (NA) of the objective lens was 0.85. The period of the recording track on the optical disc was 0.60 μm, and the reciprocal phase depth of the group portion was (λ / 6). In addition, both the land portion and the group portion are rectangular with an equal width (0.30 μm).
[0054]
FIGS. 6 to 11 show one sub-spot (FIG. 6), main spot (FIG. 7), and astigmatism difference of +0.5 μm when the main spot is on the land portion (FIGS. 6 to 8). For the other sub-spot (FIG. 8) with an astigmatic difference of −0.5 μm (for convenience, the signs of “+” and “−” are used to indicate the direction of the astigmatic difference), and the main spot. Is on the group part (FIGS. 9 to 11), one sub-spot (FIG. 9) with an astigmatic difference of +0.5 μm, the main spot (FIG. 10) and the other with an astigmatic difference of −0.5 μm The secondary spot (FIG. 11) shows the intensity distribution in the reflected light beam.
[0055]
As shown in FIGS. 7 and 10, in the state where the light beam has no astigmatism, the intensity distribution in the reflected light beam does not differ depending on whether the spot is on the land portion or the group portion. As described above, this is also the reason that the sum signal cannot be used as the track discrimination signal in the land-group recording medium. On the other hand, when astigmatism is added to the luminous flux, there is a large difference in the intensity distribution in the reflected luminous flux depending on whether the spot is on the land portion or on the group portion, and the direction of astigmatism (sign) ) Shows that the relationship between the land portion and the group portion is reversed.
[0056]
By the way, in the optical pickup device described above, the focus error signal can be detected by the method proposed in the above-mentioned Japanese Patent Laid-Open No. 2000-82226 in addition to the normal astigmatism method. As shown in FIG. 12, the luminous flux is caused to have astigmatism by a multi-lens 15 in a direction forming 45 ° with respect to the direction of the diffraction pattern by the recording track. As shown in FIG. 12, the light receiving portion of the photodetecting element 16 is not added with a focal line in the direction in which astigmatism is generated due to astigmatism and astigmatism orthogonal thereto. By placing it at a substantially intermediate position with the direction, that is, the focal line in the direction parallel to the generatrix of the cylindrical surface of the multi-lens 15, the spot of the return light is approximately circular at the time of focusing, and at both ends of the drawing range, By focusing on the optical disk, the spot on the light receiving element of the reflected light beam is substantially circular when it is focused on the optical disk. A focus error curve is obtained.
[0057]
Considering the diffraction pattern of the reflected light beam on the pupil of the objective lens and the diffraction pattern on the light receiving unit at the time of focusing on the optical spot of the main spot, out of the directions perpendicular to the direction parallel to the generatrix of the cylindrical surface, Since the pattern is reversed only in the direction of focusing in front of the light receiving unit surface, a return light spot corresponding to each light receiving unit is formed on the light receiving unit surface of the light detection element 16 as shown in FIG. The
[0058]
Accordingly, when the reflected light beam of the sub-light beam is divided and received in the light receiving unit, as shown in FIG. 16, if it is received in a state of being radially divided into four from the center of the spot, it is shown in FIGS. As described above, the track discrimination signal can be detected based on the intensity change depending on whether the irradiation position is on the land portion or the group portion.
[0059]
Here, the positional relationship between the main spot and the sub spot on the optical disk is determined so that the main spot is on the groove when the method described in Japanese Patent Laid-Open No. 2000-82226 is used as the focus error signal detection method. In some cases, it is desirable that the secondary spot is set to be on the land portion. In addition, when the calculation for obtaining the focus error signal is the normal astigmatism method, when the main spot is on the groove part, even if the secondary spot is set on the group part, It may be set to be in In these cases, the polarities of the track discrimination signals are inverted from each other.
[0060]
  In order to have such a positional relationship between the main spot and the sub spot on the optical disc, as described above, the distance from the main spot in the normal direction of the recording track formed on the signal recording surface of the optical disc is set to S, When the track pitch of the recording track is Tp and n is an integer, the following expression must be satisfied.
S ≒ Tp · n / 2
  In particular, each secondary spot is represented by the following formula (I)To (III)It is desirable to be formed at two positions where is established.
(I) S≈ + P / 2
S ≒ -P / 2
(II) S = 0
(III) S≈ + P, S≈−P
  However, each sub spot does not need to be formed at a symmetrical position with respect to the main spot.
S ≒ + nP / 2
S ≒ -mP / 2
(∵n> m, n <m, or n = m)
  In particular, when the above formula (II) is established, since the main spot and the sub spot are all formed on the same recording track, the recording track of the sub spot is always provided even for a plurality of optical disks having different track pitches. Can be in the same state.
[0061]
As shown in FIG. 17, the track discrimination signal (CTS signal) is out of phase with the tracking error signal TE by (1/4) period when the period from the group part to the next group part is one period. There is a relationship. In the state shown by (A) and (C) in FIG. 17 where the track discrimination signal is minimum, the light detection element 16 is compared with the state shown by (B) in FIG. 17 where the track discrimination signal is maximum. The light receiving surface portion has an intensity distribution in which the polarity of the track discrimination signal is reversed as shown in FIG. 19 with respect to the states shown in FIGS.
[0062]
In the above-described embodiment, two spots formed by the hologram element are used as sub-spots for obtaining the track discrimination signal. In order to reduce the influence of various disturbances, it is desirable to use two sub-spots as described above, but a track discrimination signal can be generated from one sub-spot.
[0063]
As shown in FIG. 21, the light receiving surface portion of the light detection element 16 is a light receiving surface m, n, o that receives only the central portion of each return light spot in the main light receiving portion 18 and the sub light receiving portions 19, 20. It is good also as providing. As described above, in each of the light receiving units 18, 19, and 20, the light receiving surfaces m, n, and o that receive only the central portion of the reflected light beam are provided, so that the diffracted light on the signal recording surface of the optical disk overlaps and the center of the reflected light beam. Even when spot movement occurs in a state where the light intensity of the portion is increased, fluctuations in the focus error signal due to this spot movement can be avoided.
[0064]
Also in this case, the focus error signals FE1 and FE2, the tracking error signal TE, the track determination signal CTS, and the RF signal RF can be generated by the above-described calculation methods.
[0065]
【The invention's effect】
As described above, in the optical pickup device, the optical recording medium recording / reproducing device, and the track discrimination signal detection method according to the present invention, even when “land group recording” is performed using a “land groove recording medium”, a simple operation is possible. A good track discrimination signal can be obtained by the configuration.
[0066]
For this reason, it is possible to use control methods conventionally used in “land groove recording”, such as tracking servo pull-in and counting of the number and direction of recording track crossings during seek.
[0067]
Therefore, according to the present invention, “land group recording” is performed by using, for example, “DVD-RAM”, “DVR”, etc., which have a small number of parts, have a simple configuration of parts, are low-cost, and can be accessed at high speed. It is possible to provide an optical pickup device and an optical recording medium recording / reproducing device that perform the above.
[0068]
In addition to “DVD-RAM” and “DVR”, the present invention can be generally applied to optical discs of other standards using “land groove recording”, and the number of parts is small and the structure of the parts is simple. A pickup device and an optical recording medium recording / reproducing device can be provided.
[0069]
In other words, the present invention does not increase the number of parts or complicate the structure of the parts, for example, even when using an optical recording medium adopting a “land groove system” such as “DVD-RAM” or “DVR”. , An optical pickup device capable of generating a track discrimination signal and enabling high-speed access, a track discrimination signal detection method, and an optical recording medium employing such an optical pickup device and a track discrimination signal detection method It is possible to provide a recording / reproducing apparatus.
[0070]
Note that the present invention does not use a specific phenomenon that occurs with the adoption of the “land / groove method”, so that the land portion or groove portion such as “DVD + RW” or “DVD-RW” is used. This is also effective in the case of using an optical recording medium of a system that records an information signal only on one of these.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical recording medium recording / reproducing apparatus according to the present invention.
FIG. 2 is a side view showing a configuration of an optical pickup device according to the present invention.
FIG. 3 is a side view showing a configuration of a light source unit of the optical pickup device.
FIG. 4 is a front view showing an optical diffraction element constituting the light source unit.
FIG. 5 is a front view showing a configuration of a light receiving portion of a light detection element and a state of a light spot on the light detection element of the optical pickup device according to the present invention.
FIG. 6 shows an example of the diffracted light of a sub-spot optical disc having an astigmatic difference of +0.5 μm when “DVR” is reproduced by an optical pickup device using “DVR” as an optical disc when the main spot is on a land portion. It is a graph which shows the calculation result of the intensity distribution on an objective lens pupil.
FIG. 7 shows the objective lens pupil of the diffracted light by the main spot optical disc with no astigmatic difference when the main spot is on the land when the “DVR” is reproduced by the optical pickup device using “DVR” as the optical disc. It is a graph which shows the calculation result of intensity distribution in.
FIG. 8 shows diffraction light by an optical disc of a sub-spot having an astigmatic difference of −0.5 μm when “DVR” is reproduced by an optical pickup device using “DVR” as an optical disc when the main spot is on the land portion. It is a graph which shows the calculation result of intensity distribution on the objective-lens pupil.
FIG. 9 shows a case in which diffracted light from an optical disc of a sub-spot having an astigmatic difference of +0.5 μm when a “DVR” is reproduced by an optical pickup device using “DVR” as an optical disc when the main spot is on the group portion; It is a graph which shows the calculation result of the intensity distribution on an objective lens pupil.
FIG. 10 shows the objective lens pupil of the diffracted light by the optical disc of the main spot having no astigmatic difference when “DVR” is reproduced by an optical pickup device using “DVR” as the optical disc when the main spot is on the group part. It is a graph which shows the calculation result of intensity distribution in.
FIG. 11 shows diffracted light by an optical disc of a sub-spot having an astigmatic difference of −0.5 μm when “DVR” is reproduced by an optical pickup device using “DVR” as an optical disc when the main spot is on the group portion. It is a graph which shows the calculation result of intensity distribution on the objective-lens pupil.
FIG. 12 is a perspective view showing a change in cross-sectional shape of a light beam in the “astigmatism method”.
FIG. 13 is a front view showing a state of each spot on the light detection element in a focused state in the optical pickup device.
FIG. 14 is a plan view showing a light intensity distribution of a reflected light beam in one sub light receiving unit in a focused state in the optical pickup device.
FIG. 15 is a plan view showing a light intensity distribution of a reflected light beam in the other sub light receiving unit in a focused state in the optical pickup device.
FIG. 16 is a plan view showing a light receiving state of a reflected light beam in each sub light receiving unit in the optical pickup device.
FIG. 17 is a graph showing a track discrimination signal detected by the track discrimination signal detection method according to the present invention.
FIG. 18 is a front view showing a state of a spot on the photodetecting element when the track discrimination signal takes a minimum value.
FIG. 19 is a front view showing a state of a spot on the photodetecting element when the track discrimination signal takes a maximum value.
FIG. 20 is a front view showing a state of a spot on the photodetecting element when the track discrimination signal takes the minimum value again.
FIG. 21 is a front view showing another example of the configuration of the light receiving portion of the light detection element of the optical pickup device according to the present invention and the state of the light spot on the light detection element;
FIG. 22 is a graph showing a relationship between a tracking error signal and a sum signal in the conventional “land recording method”.
FIG. 23 is a graph showing a tracking error signal and a track discrimination signal in the conventional “land recording method”.
FIG. 24 is a graph showing a sum signal in the conventional “land group recording method”.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Spindle motor, 2 Optical pick-up apparatus, 7 System controller, 10 Light source part, 10a Main light emission point, 10b, 10c Virtual light emission point, 11, Polarizing beam splitter prism, 14 Objective lens, 16 Light detection element, 17 Light diffraction element, 18 Main light receiving part, 19, 20 Sub light receiving part

Claims (7)

A light source having at least one light emitting point that emits a luminous flux;
An objective lens for condensing and irradiating the light flux on a signal recording surface of an optical recording medium having a land portion and a group portion and capable of recording an information signal on one or both of the land portion and the group portion ;
Photodetection means for receiving a reflected light beam from the signal recording surface of the optical recording medium,
The light beam emitted from the light source is mainly used for recording and / or reproducing information signals in the forward path emitted from the light source by astigmatism adding means which is an optical diffraction element disposed in the optical path. A main luminous flux that forms a spot on the signal recording surface of the optical recording medium, and an astigmatism that forms a pair of sub-spots at positions spaced from the main spot on the signal recording surface of the optical recording medium A pair of sub-beams,
The directions of astigmatism added to the pair of sub-spots by the astigmatism adding means are opposite to and substantially opposite to the tangential direction of the recording track formed on the signal recording surface of the optical recording medium. direction der of 々_45 ° is,
The light detecting means includes a main light receiving portion that receives a main reflected light beam, which is a light beam reflected by a signal recording surface of an optical recording medium, and a light beam in which the sub light beam is reflected by the signal recording surface. A sub-light-receiving unit that receives the sub-reflected light flux,
The sub light receiving unit is composed of a plurality of light receiving elements that each output an independent photodetection signal.
Each light-receiving element, by being added or subtracted, the optical pickup device according to claim also be output from a plurality of light detection signal track discrimination signal for discriminating the position of the main spot is generated. The sub-spot is defined as S, where the absolute value of the distance to the main spot in the normal direction of the recording track formed on the signal recording surface of the optical recording medium is S, the track pitch is P, and n is an integer.
S ≒ Pn / 2
The optical pickup device according to claim 1, wherein the optical pickup device is formed at a position where is established. The sub-spot is defined by assuming that the distance from the main spot in the normal direction of the recording track formed on the signal recording surface of the optical recording medium is S, the track pitch is P, and n is an integer.
S ≒ + Pn / 2
And S≈−Pn / 2
The optical pickup device according to claim 1, wherein the optical pickup device is formed at a position where is established. The sub-spot is defined as S, where the absolute value of the distance from the main spot in the normal direction of the recording track formed on the signal recording surface of the optical recording medium is S.
S = 0
The optical pickup device according to claim 1, wherein the optical pickup device is formed at a position where is established. The plurality of light receiving elements constituting each sub light receiving section, the optical pickup apparatus according to claim 1, characterized in that it is arranged substantially in parallel and substantially perpendicular to the direction in the far field pattern of recording tracks . An operation mechanism that has a land portion and a group portion, an optical recording medium capable of recording an information signal is detachably attached to one or both of the land portion and the group portion, and operates the mounted optical recording medium;
An optical pickup device that writes and reads information signals to and from an optical recording medium that is mounted on and operated by the operation mechanism;
A servo circuit that controls the position of the objective lens of the optical pickup device based on an output signal from the optical pickup device;
The optical pickup device includes a light source having at least one light emitting point that emits a light beam, an objective lens that focuses and irradiates the light beam on a signal recording surface of the optical recording medium, and a signal recording surface of the optical recording medium A light detecting means for receiving a reflected light beam from
In the optical pickup device, the light beam emitted from the light source is recorded and / or reproduced by an astigmatism adding means which is an optical diffraction element disposed in the optical path in the forward path emitted from the light source. Forming a main spot on the signal recording surface of the optical recording medium and a pair of sub-spots at positions spaced from the main spot on the signal recording surface of the optical recording medium A pair of sub-light beams having astigmatism,
The directions of astigmatism added to the pair of sub-spots by the astigmatism adding means are opposite to and substantially opposite to the tangential direction of the recording track formed on the signal recording surface of the optical recording medium. direction der of 々_45 ° is,
The light detecting means includes a main light receiving portion that receives a main reflected light beam, which is a light beam reflected by a signal recording surface of an optical recording medium, and a light beam in which the sub light beam is reflected by the signal recording surface. A sub-light-receiving unit that receives the sub-reflected light flux,
The sub light receiving unit is composed of a plurality of light receiving elements that each output an independent photodetection signal.
Each light-receiving element, by being added or subtracted, the optical recording medium recording and reproducing apparatus according to claim also be output from a plurality of light detection signal track discrimination signal for discriminating the position of the main spot is generated. An optical recording medium having a land part and a group part and capable of recording an information signal is detachably attached to one or both of the land part and the group part, and the optical mechanism is operated on the optical recording medium. Insert and operate the recording medium,
A light source having at least one light emitting point that emits a light beam, an objective lens that collects and irradiates the light beam on a signal recording surface of the optical recording medium, and receives a reflected light beam from the signal recording surface of the optical recording medium An optical pickup device having a light detecting means for reading out an information signal from an optical recording medium that is mounted on the operation mechanism and operated;
In the optical pickup device, the light beam emitted from the light source is recorded and / or recorded by an astigmatism adding means that is an optical diffraction element disposed in the optical path in the forward path emitted from the light source. Alternatively, a main light beam for forming a main spot for reproduction on the signal recording surface of the optical recording medium and a pair of sub-spots at positions separated from the main spot on the signal recording surface of the optical recording medium. To be a pair of sub-beams with astigmatism to form,
The directions of astigmatism added to the pair of sub-spots by the astigmatism adding means are opposite to and substantially opposite to the tangential direction of the recording track formed on the signal recording surface of the optical recording medium. 45 degrees direction,
A main light receiving portion that receives a main reflected light beam that is a light beam reflected by a signal recording surface of an optical recording medium, and a sub reflected light beam that is a light beam that is reflected by the signal recording surface. The sub reflected light beam is divided and received by a plurality of light receiving elements that output independent light detection signals constituting the sub light receiving unit of the light detecting means having a sub light receiving unit,
A track discrimination signal detection method for generating a track discrimination signal for discriminating the position of the main spot on the basis of output signals added and subtracted by the light receiving elements .

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