JP3841287B2 - Optical pickup and optical information processing apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup that monitors light emitted from each light source in a blue wavelength band, a red wavelength band, and an infrared wavelength band by a single monitor light-receiving means, and records, reproduces, and erases an optical recording medium. The present invention relates to an optical information processing apparatus using the same.
[0002]
[Prior art]
Optical recording media such as CDs with a recording capacity of 0.65 GB and DVDs with a recording capacity of 4.7 GB are becoming popular as means for storing video information, audio information, or data processed by computers. In recent years, there has been an increasing demand for further improvement in recording density and increase in capacity. Specifically, there is a need for a capacity of 22 GB that can record HD (High Definition) -TV for 2 hours (one movie).
[0003]
As means for increasing the recording density of such an optical recording medium, in an optical pickup for writing or reading information on the optical recording medium, the numerical aperture (NA) of the objective lens is increased, or the wavelength of the light source is shortened. Thus, it is effective to reduce the diameter of the beam spot condensed by the objective lens and formed on the optical recording medium.
[0004]
Therefore, for example, in the “CD optical recording medium”, the numerical aperture of the objective lens is 0.50 and the wavelength of the light source is 780 nm, whereas the recording density is higher than that of the “CD optical recording medium”. In the “DVD-based optical recording medium” in which the objective lens is formed, the numerical aperture of the objective lens is 0.65 (more specifically, the range is 0.59 to 0.66), and the wavelength of the light source is 660 nm. . Further, as described above, further improvement in recording density and increase in capacity are desired for optical recording media.
[0005]
For this purpose, it is desired to make the numerical aperture of the objective lens larger than 0.65 or make the wavelength of the light source shorter than 660 nm. As such a large-capacity optical recording medium and optical information processing apparatus, for example, a light source in the blue wavelength region and NA 0.85 listed in ISOM2001 proceedings “Next Generation Optical Disc” Hiroshi Ogawa, p6-7, etc. There is a proposal of a system that satisfies the capacity securing equivalent to 22 GB using the objective lens.
[0006]
As described above, in order to increase the numerical aperture of the objective lens (to increase the NA), it is necessary to use a lens having a short focal length. Therefore, the working distance that means the physical distance between the objective lens and the optical recording medium is shortened. In the system listed in the ISOM2001 draft “Next Generation Optical Disc” Hiroshi Ogawa, p. 6-7, the working distance is 0.15 mm, which is about 1/10 of a conventional CD or DVD. When the working distance is shortened, there is a problem that damage due to collision between the optical recording medium and the objective lens easily occurs.
[0007]
Further, when the numerical aperture of the objective lens is increased or the wavelength of the light source is shortened, the influence of spherical aberration caused by the manufacturing error of the lens, the thickness error of the transparent substrate of the optical recording medium, etc. becomes remarkable. The spherical aberration caused by the thickness error of the transparent substrate of the optical recording medium is generally given by the following (Equation 1).
[0008]
[Expression 1]
W ₄₀ = ((N ² -1) / (8n ^Three )) X (d x NA ^Four / Λ)
Here, n is the refractive index of the transparent substrate of the optical recording medium, d is the thickness of the transparent substrate, NA is the numerical aperture of the objective lens, and λ is the wavelength of the light source.
[0009]
From this (Equation 1), it can be seen that the shorter the wavelength and the higher the NA, the larger the aberration. Similarly, the manufacturing error of the optical component in the optical pickup, particularly the objective lens used for condensing on the optical recording medium, also increases the deterioration of aberration as the wavelength is shorter and the NA is higher.
[0010]
In addition, while new standards with higher NA and shorter wavelengths have been realized in recent years, CDs and DVDs, which are conventional optical recording media, exist at the user's hand. It is desirable that both the conventional optical recording medium and the large-capacity new standard optical recording medium using the blue wavelength band described above can be handled by the same optical information processing apparatus. As the simplest method, there is a method of mounting both a conventional optical pickup and a new standard optical pickup. However, with this method, it is difficult to achieve downsizing and cost reduction.
[0011]
As described above, in the large-capacity optical information processing apparatus proposed in the ISOM2001 draft “Next Generation Optical Disc” Hiroshi Ogawa, p6-7, in order to increase the capacity (for example, 22 GB), an increase in NA or When the wavelength is shortened, the working distance is reduced, and the reliability is lowered such as aberration deterioration due to fluctuations. In addition, compatibility with conventional optical recording media is a problem. That is, there is a problem that it is necessary to perform the third generation compatibility between the large-capacity generation using the blue wavelength band and the existing DVD and CD generations.
[0012]
As a means to deal with these problems, only the wavelength is shortened compared with DVD, NA is the same as that of conventional DVD, and the information recording density multiplication factor for binary recording is 1.8 times or more. It is only necessary to realize such an optical pickup. That is, since the recording capacity to the optical recording medium is determined by the spot diameter, the spot diameter ratio (λ / NA) can be obtained by using the blue wavelength band as compared with the DVD optical recording medium (4.7 GB). ² The capacity is increased by 12GB. By applying the multi-value recording to this, a recording capacity equivalent to 22 GB can be obtained. As a result, the margin due to fluctuations can be expanded. For example, since the depth of focus of the objective lens becomes stricter in proportion to the square of NA, the lens with NA 0.65 has a 1.7 times wider margin than the objective lens with NA 0.85. Further, by using such an objective lens having a blue wavelength band and NA of 0.65, a sufficient working distance can be ensured even when conventional DVD and CD are compatible.
[0013]
Furthermore, in an optical pickup, it is important that the amount of light emitted from a light source is stable in order to stably detect various information and perform a stable recording operation. For this reason, conventionally, the amount of light emitted from the light source is monitored by a dedicated light receiving element, and the amount of light from the light source is controlled according to the amount of light received by the monitor. As a monitoring method in this case, there is also a configuration in which a monitor light receiving element for receiving backward light emitted toward the rear side is integrated in the chip of the light source, but the structure of the light source is limited and actually Proposed to provide a monitor light-receiving element that receives a part of the light beam emitted forward from the light source as described in Japanese Patent No. 2571034 because the correspondence with the front light to be used is not always accurate. Has been.
[0014]
The optical pickup described in this Japanese Patent No. 2571034 performs recording and reproduction with respect to a single type of optical recording medium, and corresponds to three types of optical recording media such as blue / DVD / CD. However, if the monitor means is disposed in each of the blue / DVD / CD optical paths, the cost and the size of the apparatus are increased. There exists an invention described in Japanese Patent Application Laid-Open No. 2002-8263 as a countermeasure to such a problem. According to this, it has been proposed to dispose a monitor unit having a plurality of wavelengths at the subsequent stage of the optical path combining unit that combines the light emitted from the plurality of light sources.
[0015]
On the other hand, in a conventional DVD or CD optical recording medium, the method of controlling the amount of light emitted from a light source during recording described in Japanese Patent Application Laid-Open No. 8-96364 uses a sample hold for the level during which space data is output. Thus, there is a method of accurately controlling the bias level and erase level during recording by a detection / control circuit having a relatively low bandwidth.
[0016]
[Problems to be solved by the invention]
However, the monitor control via the dichroic film of the optical path synthesizing means as described in Japanese Patent Application Laid-Open No. 2002-8263 deteriorates the reliability of the light amount control because the characteristic of the film varies depending on the wavelength. In the optical information processing apparatus that performs multi-value recording by the light amount control method described in JP-A-8-96364, there is a problem that level detection for a specific period cannot be performed. .
[0017]
The present invention is directed to solving the above-described problems of the prior art, and uses a light source with a blue wavelength band and NA of 0.65, and is 1.8 times more information than DVD. Record An optical pickup that performs multi-value recording with density multiplication and is compatible with DVD and CD, and can control the amount of light of three types of optical recording media with a single monitor light receiving means, as well as manufacturing variations It is an object of the present invention to provide an optical pickup capable of performing highly reliable light quantity control that is not easily affected by wavelength fluctuations, and capable of performing light quantity control during multi-value recording, and an optical information processing apparatus using the same. To do.
[0018]
[Means for Solving the Problems]
To achieve this object, the claims according to the invention 1 The optical pickup described is Multiple light sources and light emitted from each light source For optical recording media A focusing objective lens, a collimating lens arranged according to each light source between each light source and the objective lens, and a single monitor for monitoring the light emitted from each light source Light receiving means for monitoring In each of the optical pickups, each light source and each collimating lens are arranged in parallel, and a single light receiving means for monitoring is provided between each light source and each collimating lens among the light beams emitted from the light source and directed to the optical recording medium. Arranged so that each divergent light beam intersects and receives only the peripheral light that is not focused on the objective lens. Depending on the configuration Performs stable monitor control with a simple configuration using a single light receiving means for monitoring. be able to.
[0019]
Claims 2 The optical pickup described is A plurality of light sources and a dichroic prism that combines optical paths from the light sources; An objective lens for condensing the light emitted from each light source onto an optical recording medium; A single monitor that monitors the light emitted from each light source that has passed through the dichroic prism. Light receiving means for monitoring The optical pickup includes a hologram pattern or an optical element in which a hologram pattern and a grading pattern are formed between the light paths of a plurality of light sources and a dichroic prism, and a single light receiving means for monitoring is emitted from the light source. Of the light beams directed toward the optical recording medium, the light beam is diffracted in the emission direction from the light source by the optical element and does not travel toward the objective lens, and is arranged at a position where a plurality of diffracted light beams from each light source overlap. Depending on the configuration A single light-receiving means for monitoring is arranged at a position where unnecessary diffracted light emitted from each light source is detected and is monitored, and diffracted light diffracted in the light emitting direction by the hologram pattern and grating pattern is monitored. The light amount margin to the optical recording medium can be increased, and the detection levels for a plurality of optical recording media can be made substantially equal. Stable monitor control in a single light receiving means for monitoring Therefore It can be carried out.
[0020]
Claims 3 The optical pickup described in 3. The optical pickup according to claim 2, wherein the hologram pattern of the optical element is Beam-split reflected light from optical recording media And Light source Out To the shooting direction Luminous flux diffraction Do thing, The grading pattern of the optical element is almost perpendicular to the diffraction direction of the hologram pattern. Splits the light emitted from the light source into the diffracted light of the main beam and multiple sub-beams Structure As a result, the light beam diffracted by the hologram pattern and grating pattern is monitored and controlled by a single light receiving means for monitoring. Can prevent the occurrence of unnecessary offset to the light receiving means by the reflected diffracted light in the grating pattern diffracted in the light source direction be able to.
[0021]
Claims 4 The optical pickup described in 4. The optical pickup according to claim 1, wherein at least any two or more light sources are accommodated in a single package in each light source. Depending on the configuration Stable monitor control single Light reception for monitor Monitor control with simple configuration by means be able to.
[0022]
Claims 5 The optical pickup described in The optical pickup according to claim 1, wherein the plurality of light sources are Each light source of blue wavelength band, red wavelength band, infrared wavelength band Is Depending on the configuration Stable monitor control in each wavelength band Light receiving means for a single monitor With a simpler configuration be able to.
[0025]
Claims 6 Light described in Information processing device Are claims 1 to 5 An optical information processing apparatus that performs any one or more of recording, reproducing, and erasing information with respect to an optical recording medium using the optical pickup according to claim 1, wherein the optical information processing apparatus performs a blue wavelength band, a red wavelength band, At least one or more optical recording media corresponding to each light source in the infrared wavelength band In addition, An optical information processing apparatus that can control light quantity that is not easily affected by manufacturing variations and wavelength fluctuations can be provided by a configuration that performs multi-value recording by switching the light quantity or time width of a light source in multiple stages according to data to be recorded. .
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0027]
FIG. 1 shows a “blue optical recording medium having a used wavelength of 407 nm, NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm” and “used wavelength of 660 nm, NA of 0.66, light in Example 1 of Embodiment 1 of the present invention. Recording, reproduction or erasure on each optical recording medium of “DVD-type optical recording medium with irradiation side substrate thickness of 0.6 mm” and “CD-type optical recording medium with operating wavelength of 780 nm, NA 0.50, light irradiation side substrate thickness of 1.2 mm” It is explanatory drawing which shows schematic structure of the optical pick-up which can perform.
[0028]
As shown in FIG. 1, the main part of the optical pickup is a blue wavelength band composed of a blue hologram unit 101, a collimating lens 102, a dichroic prism 103, a deflection mirror 104, a quarter wavelength plate 105, and an objective lens 106. A red wavelength band composed of a blue optical system through which light passes, a DVD / CD hologram unit 201, a collimating lens 202, a dichroic prism 103, a deflection mirror 104, a quarter-wave plate 105, and an objective lens 106, and red It comprises a DVD / CD optical system through which light in the outer wavelength band passes, and a monitor light receiving means for monitoring the light emitted from each light source in the blue / DVD (red) / CD (infrared) wavelength band. Yes. That is, the dichroic prism 103, the deflection mirror 104, the quarter wavelength plate 105, and the objective lens 106 are common components.
[0029]
Next, as an operation of the optical system, a case where “a blue optical recording medium having a used wavelength of 407 nm, NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm” is recorded, reproduced or erased will be described. In the first embodiment, a hologram unit is used in which a light emitting / receiving element is installed in one can and a light beam is separated using a hologram. A blue hologram unit 101 in FIG. 1 is a hologram unit formed by integrating the semiconductor laser 101a (light source), the hologram 101b (light path separating means) and the light receiving element 101c in FIG. The optical pickup of the present embodiment may be other than a hologram as the optical path separating means for the forward path and the return path, and may be a prism, for example.
[0030]
The light in the blue wavelength band emitted from the semiconductor laser 101a of the hologram unit 101 is transmitted through the hologram 101b and converted into parallel light by the collimator lens 102, the light in the blue wavelength band is transmitted, and the light in the red and infrared wavelength bands. Is reflected in the direction of the deflecting mirror 104 by the reflecting dichroic prism 103, the optical path is deflected by 90 degrees by the deflecting mirror 104, passes through the quarter-wave plate 105, becomes circularly polarized light, and enters the objective lens 106 for optical recording. It is condensed as a minute spot on the medium 107. Information is reproduced, recorded or erased by this spot.
[0031]
The light reflected from the optical recording medium 107 is deflected by the deflecting mirror 104 and transmitted through the dichroic prism 103 to be collimated. G As shown in FIG. 2, the light is converged by the lens 102 and is diffracted by the hologram 101b in the direction of the light receiving element 101c in the same can as the semiconductor laser 101a and received by the light receiving element 101c. An information signal and a servo signal are detected from the light receiving element 101c.
[0032]
Next, “DVD-based optical recording medium with use wavelength 660 nm, NA 0.65, light irradiation side substrate thickness 0.6 mm”, “CD type optical recording with use wavelength 780 nm, NA 0.50, light irradiation side substrate thickness 1.2 mm” A case of recording, reproducing or erasing “medium” will be described. The DVD / CD optical system also includes a DVD / CD hologram unit 201 similar to the blue optical system. A difference from the blue hologram unit 101 is that two types of light sources, light receiving elements, and optical path separating means for DVD / CD are integrated into a single package as shown in FIG. Thereby, it is possible to realize an optical system of three wavelength bands with a small optical pickup.
[0033]
As the hologram 301b, a structure including a layer having a hologram surface for DVD and a layer having a hologram surface for CD may be used. The light in the red wavelength band or the infrared wavelength band emitted from the semiconductor laser 201a of the hologram unit 201 is transmitted through the hologram 301b and is converted into parallel light by the collimator lens 202, and the light in the blue wavelength band is transmitted and red / Light in the infrared wavelength band is reflected in the direction of the deflecting mirror 104 by the reflecting dichroic prism 103, the optical path is deflected by 90 degrees by the deflecting mirror 104, passes through the quarter wavelength plate 105, and is circularly polarized, and the objective lens 106 And is condensed as a minute spot on the optical recording medium 107. Information is reproduced, recorded or erased by this spot.
[0034]
The light reflected from the optical recording medium 107 is deflected by the deflecting mirror 104, reflected by the dichroic prism 103, and collimated. G The light is converged by the lens 202, and is selectively diffracted in the light receiving element 201c direction or 301c direction by the hologram 301b as shown in FIG. Information signals and servo signals are detected from each light receiving element.
[0035]
As shown in FIG. 4, the parallel light beams from the collimating lenses 102 and 202 have one of the optical paths of the light beam directed to the objective lens 105 and the other directed to the monitor light receiving means 100 by the action of the deflecting mirror 104 as the distribution means. Since it has a function, it is separated into two light beams. One of the separated luminous fluxes enters the monitoring light receiving means 100 as “monitor light” through the optical path to the monitoring light receiving means 100. The monitor light receiving means 100 emits a light reception signal corresponding to the amount of light received. This signal is input to a control means (not shown) constituted by an A / D converter and a CPU.
[0036]
This control means controls a driver circuit (not shown) for the semiconductor laser based on the input information, and performs output control so that the intensity of the emitted light emitted from the semiconductor lasers 101a, 201a, 301a becomes a predetermined value. I do.
[0037]
As the light amount distribution means for the luminous flux, as the simplest method, a distribution means in which an optical thin film is deposited is known. On the other hand, a semiconductor laser light source causes a wavelength variation with a temperature variation. In general, the permissible fluctuation width of the light amount control needs to be ± 5% or less. However, when an optical thin film that transmits and reflects is used as a distribution means, the optical thin film is affected by wavelength fluctuation. According to the measurement results of the inventors, the operating temperature range of the optical pickup: a semiconductor laser in the blue wavelength band at −10 to 70 ° C., the wavelength variation is ± 2 nm, and the semiconductor laser in the red wavelength band and the infrared wavelength band is ± The optical thin film has a fluctuation of about 10 nm, and the transmittance of the optical thin film fluctuates with an arbitrary period as the wavelength changes. Therefore, care must be taken in the case of monitor control using the distribution means on which the optical thin film is deposited as described above for an optical pickup.
[0038]
For example, when the ratio of the light traveling toward the objective lens and the light traveling toward the monitor light receiving means is 5:95, the monitor light receiving means changes the light amount by 20% when the ratio becomes 6:94 due to wavelength fluctuation. As a result, control is performed to reduce the light emitted from the light source correspondingly.
[0039]
However, in the first embodiment, since the optical thin film having the inflection point of the transmittance variation is deposited at each room temperature wavelength of the three light sources, the following state can be realized. . In the distribution means using an optical thin film in which the ratio of the light toward the objective lens and the light toward the monitor light-receiving means is 5:95,
(1) When the wavelength at the room temperature of the light source in the blue wavelength band is λ1, the transmittance variation ΔT1 of the light beam toward the monitor light-receiving means is in the range of λ1 ± 2 nm (Equation 2)
[0040]
[Expression 2]
| ΔT1 | <0.002
(2) When the wavelength at the room temperature of the light source in the red wavelength band is λ2, the transmittance variation ΔT2 of the light beam toward the monitor light receiving means is in the range of λ2 ± 10 nm (Equation 3)
[0041]
[Equation 3]
| ΔT2 | <0.002
(3) When the wavelength at room temperature of the light source in the infrared wavelength band is λ3, the transmittance variation ΔT3 of the light beam toward the monitor light-receiving means is in the range of λ3 ± 10 nm (Equation 4)
[0042]
[Expression 4]
| ΔT3 | <0.002
Can be satisfied. That is, the change in transmittance to the light receiving means for monitoring is ± 0.2% or less, and stable monitor control can be performed while ensuring the allowable fluctuation range of light amount control is ± 5% or less. Here, room temperature means a range of 20 to 30 ° C., and a blue wavelength band λ1: 397 to 417 nm, a red wavelength band λ2: 650 to 670 nm, and an infrared wavelength band λ3: 775 to 800 nm.
[0043]
Further, the recording light amount varies depending on whether the optical recording medium is a blue optical recording medium, a DVD optical recording medium, or a CD optical recording medium. Here, for the sake of simplicity, description will be made using two optical paths of CD and DVD. As an example, the amount of light necessary for recording on the recording surface of the CD optical recording medium is 20 mW, and the amount of light necessary for recording on the recording surface of the DVD optical recording medium is 10 mW. If the optical characteristic of the deflecting mirror 104 is “transmitting 50% of incident light and reflecting the remaining 50%”, when recording on a CD-based optical recording medium, the wavelength is 780 nm. It is necessary to emit a laser beam of about 40 mW to the semiconductor laser that emits the laser beam. Of the emitted laser beam, 20 mW is used for recording, and the remaining 20 mW is received by the monitor light receiving means 100 as the monitor beam. The
[0044]
When recording on a DVD optical recording medium, it is necessary to radiate a laser beam of about 20 mW to a semiconductor laser that emits a laser beam having a wavelength of 660 nm, and 10 mW of the emitted laser beam is 10 mW. The remaining 10 mW is supplied to the monitor and received by the monitor light receiving means 100 as monitor light. Therefore, the amount of monitor light incident on the monitor light receiving means 100 is approximately 2: 1 when the optical recording medium 107 is a CD optical recording medium and when the optical recording medium 107 is a DVD optical recording medium. The difference in the amount of light received by 100 is as large as 10 mW.
[0045]
Such a problem is avoided in the first embodiment as follows. That is, the spectral characteristics of the separation film of the deflection mirror 104 are, for example, as follows. Light having a wavelength of 660 nm “transmits 50% of incident light and reflects the remaining 50%”. Further, light having a wavelength of 780 nm “reflects 66% of incident light and transmits the remaining 34%”. With such spectral characteristics, when recording information on a DVD optical recording medium, if a semiconductor laser with an emission wavelength of 660 nm is emitted at 20 mW, a light spot with a light amount of 10 mW is formed on the recording surface. The amount of monitor light received by the monitor light receiving means 100 is also 10 mW. For the sake of simplicity, in this description, “kicking” of a light beam by a lens or the like and light quantity loss due to transmittance are ignored.
[0046]
When recording information on a CD-based optical recording medium, if a semiconductor laser with an emission wavelength of 780 nm is emitted at 30 mW, a light spot with a light amount of 20 mW can be formed on the recording surface, and light reception for monitoring is possible. The amount of monitor light received by the means 100 is 10 mW. Therefore, there is substantially no difference in the amount of monitor light due to the semiconductor laser (that is, the amount of light received by the monitor light receiving means is different depending on whether the information recording medium for recording is a CD disc or a DVD disc). It is substantially 1: 1), and it is not necessary to take a large light amount detection range of the monitor light receiving means 100, and gain adjustment and switching are not required.
[0047]
FIG. 5 is a diagram showing a schematic configuration of the optical pickup in Example 2 of Embodiment 1 of the present invention. As in Example 1 described above, “a blue-based optical recording medium having a use wavelength of 407 nm, NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm” and “use wavelength of 660 nm, NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm. Optical pickup capable of recording, reproducing or erasing on each of the optical recording media of “DVD optical recording medium” and “CD optical recording medium having a working wavelength of 780 nm, NA of 0.50, and a light irradiation side substrate thickness of 1.2 mm”. It is.
[0048]
The second embodiment is different from the optical pickup of the first embodiment in that the position of the monitor light receiving means 100 is different from each of the diverging light paths between the two hologram units 101 and 201 arranged in parallel to the collimating lenses 102 and 202. This is the point where the crosses. As a result, the light emitted from the light sources of the two hologram units can be monitored by the single light receiving means 100 for monitoring.
[0049]
Further, in the second embodiment, as shown in FIG. 6, only the light flux in the outer peripheral portion that is not condensed by the objective lens is monitored. Thereby, a highly efficient optical pickup can be realized. Further, in the optical pickup of the second embodiment, two hologram units are flattened as shown in FIG. Column The arrangement is not limited to the arrangement, and the arrangement may be an orthogonal arrangement or an arrangement in which the arrangement is performed with a certain angle.
[0050]
FIG. 7 is a diagram showing a schematic configuration of the optical pickup in the third embodiment of the first embodiment of the present invention. Also in the same manner as in Example 1 described above, “a blue-based optical recording medium having a use wavelength of 407 nm, NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm” and “use wavelength of 660 nm, NA of 0.66, and a light irradiation side substrate thickness of 0. .6 mm DVD optical recording medium ”and“ CD optical recording medium having a working wavelength of 780 nm, NA of 0.50, and a light irradiation side substrate thickness of 1.2 mm ”can be recorded, reproduced or erased. It is an optical pickup.
[0051]
The third embodiment is different from the optical pickup of the first embodiment in that the position of the monitor light receiving means 100 is not the light beam distributed by the deflection mirror 104, but the objective lens 106 as shown in FIG. This is the point where the diffracted light from the hologram unit which is not directed to the position is monitored. At the same position, the diffracted lights of the hologram units 101 and 201 are monitored.
[0052]
Next, a specific method for monitoring the diffracted light from the hologram unit that does not face the objective lens according to Embodiment 2 of the present invention will be described using the blue hologram unit shown in FIG.
[0053]
First, in the hologram unit 101 shown in FIG. 2, a hologram pattern is formed by forming grooves on the upper surface of the hologram 101b by etching, and a grating pattern is formed by forming grooves on the lower surface by etching. . In addition, the light receiving element 101c is, for example, an eight-divided light receiving element, and is composed of divided segments 15a to 15h.
[0054]
The light emitted from the semiconductor laser 101a of the hologram unit 101 is diffracted by the grating pattern and separated into a main light beam and two sub light beams for tracking servo, and has a beam splitting function with respect to the reflected light from the optical recording medium 107. The hologram pattern formed for generating the servo signal is also diffracted. In the second embodiment, monitor control is performed using these diffracted lights.
[0055]
Here, the hologram pattern is composed of three regions 14a to 14c as shown in FIG. 9A, and the dividing lines of the region 14b and the region 14c and the region 14a coincide with the radial direction of the optical recording medium. The dividing line 14c coincides with the jitter direction. The reflected light from the optical recording medium of the 0th order light diffracted by the grating pattern is diffracted by the hologram pattern region 14a, and is on the dividing lines of the light receiving portions 15a and 15b on the 8-divided light receiving element surface shown in FIG. In addition, the light is diffracted by the hologram pattern regions 14b and 14c incident on the other side and collected on the light receiving portions 15c and 15d.
[0056]
Reflected light from the optical recording medium of ± first-order light diffracted by the grating pattern is condensed on the light receiving portions 15e, 15f, 15g, and 15h, respectively. These collected light fluxes are Record It changes as shown in FIG. 9B according to the convergence state of the light flux on the medium. Therefore, if the output of each segment of the 8-divided light receiving element is S1 to S8, the focus error signal FE is given by (Equation 5),
[0057]
[Equation 5]
FE = S1-S2
On the other hand, the tracking error signal TE is detected by a so-called push-pull method and is given by (Equation 6).
[0058]
[Formula 6]
TE = S3-S4
The information signal Rf is given by (Expression 7).
[0059]
[Expression 7]
Rf = S1 + S2 + S3 + S4
As described above, the light emitted from the semiconductor laser 101a is diffracted by the grating pattern and separated into a main light beam (0th order light) and two sub light beams (± 1st order light) for tracking servo, and from the optical recording medium. The hologram pattern formed for generating the servo signal having the beam split function is also diffracted with respect to the reflected light. The state of these diffracted lights is shown in FIG. After being divided into three light beams by the grating pattern as shown in FIG. 11, it is further divided into three light beams of 0th order and ± 1st order in each region of the hologram pattern as shown in FIG.
[0060]
In particular, the hologram pattern of FIG. 9A is finally divided into five diffracted lights because the diffraction angle of the focus signal generating region 14a and the tracking signal generating regions 14b and 14c are different. In this way, the grating pattern is divided into three, and the hologram pattern is diffracted in five directions orthogonal to the diffracted light of the grating pattern, so that it is divided into a total of 15 light beams as shown in FIG.
[0061]
In the grating pattern, as shown in FIG. 11, light (reflected diffracted light) that is diffracted in the light source direction opposite to the optical recording medium direction is generated. When such reflected diffracted light is incident on the light receiving element for servo signal detection, an offset is generated in the signal output from the optical recording medium, which causes a problem in servo control. Therefore, in the present invention, the diffracted light in the hologram pattern and the diffracted light in the grating pattern are generated in directions orthogonal to each other. As a result, the reflected diffracted light from the grating pattern is directed in a direction orthogonal to the light receiving element for signal detection, and as a result, unnecessary offset does not occur.
[0062]
Some of the plurality of diffracted lights generated in this way do not enter the objective lens, that is, are not used for irradiation of the optical recording medium. This extra light is detected by the light receiving means for monitoring, and a detection signal proportional to the amount of light flux is output. This detection signal is compared with a predetermined reference value in an APC (automatic output control) circuit (not shown), and a drive signal corresponding to the difference between the detection signal and the reference value is generated, and the semiconductor laser 101a (see FIG. 2). ). As a result, the light amount of the light beam emitted from the semiconductor laser 101a is controlled, and feedback is performed so that the difference between the detection signal of the monitor light receiving means and the reference value approaches zero, so that the light amount of the light beam is always kept constant. Control will be performed. Among the generated diffracted lights, light that does not enter the objective lens is received for monitoring means As a specific position, for example, a region where a plurality of diffracted lights overlap as shown in FIG.
[0063]
Even if the hologram 101b is not provided with a grating pattern, monitor detection is possible as shown in FIG. Furthermore, unnecessary diffracted light from the hologram pattern can be monitored for the DVD and CD of the DVD / CD hologram unit 201 shown in FIG. 3 by the same method as in the second embodiment.
[0064]
As an optical pickup according to the third embodiment of the present invention, a multi-value recording optical pickup that performs recording by switching the light amount or time width (pulse width) of a light source in multiple stages according to data to be recorded will be described. In particular, it is a blue-based optical recording medium, and NA is equivalent to that of a conventional DVD. If multi-value recording is applied such that the information recording density multiplication factor for binary recording is 1.8 times or more, it is equivalent to 22 GB. As described above, the capacity can be obtained.
[0065]
In this third embodiment, for this type of multi-value optical recording medium, an APC section is provided in the middle of recording, and APC (automatic output control) is performed on the output value of the light source. Even if there is a fluctuation in the output value due to self-heating of the light source or the like, the high-quality recording can be performed.
[0066]
A specific procedure will be described. In order to obtain a reproduction signal having a high S / N at the start of recording or in a predetermined area, test data is recorded / reproduced to obtain the optimum output value or optimum time width of the light source. Thereafter, the output value of the light source fluctuates due to self-heating, but in the third embodiment, an APC section for performing APC (automatic output control) on the output value of the light source is provided in the middle of recording. As shown in FIG. 14, this APC section is an area that emits light at a predetermined level within a predetermined period. means Sample hold at. Control is performed by a control circuit (not shown) so as to correct the monitor result, that is, the output fluctuation accompanying the temperature fluctuation.
[0067]
In addition, the optical pickup in Example 1 of Embodiment 4 of the present invention is an optical pickup that performs crosstalk cancellation for correcting crosstalk components accompanying intersymbol interference from adjacent tracks. An optical pickup in which a circuit for canceling the crosstalk component of the Rf signal is mounted on the blue optical system on the optical pickup of Example 3 of the first embodiment will be described.
[0068]
The irradiation to the optical recording medium 107 shown in FIG. 7 is performed by irradiating the main beam Bm and the first side at a position shifted by a half of the track pitch with respect to the radial direction of the optical recording medium before and after the main beam. The beam Bs1 and the second side beam Bs2 are respectively irradiated. As shown in FIG. 15, the reflected light of the main beam Bm is received by the light receiving elements 15a, 15b, 15c and 15d shown in FIG. 9B, and the reflected light of the pair of side beams Bs1 and 2 is received by the light receiving elements 15e and 15f. , 15g, and 15h, respectively, to generate a track error signal, a focus error signal, and an Rf signal.
[0069]
Now, with multi-level recording as described above, or with an optical recording medium with a narrow track pitch, the effect of so-called crosstalk, in which the signals of adjacent tracks are reproduced together, becomes so large that recording signals cannot be reproduced. There are challenges. The optical pickup according to the fourth embodiment has the configuration shown in FIG. 15 in order to cancel the Rf component crosstalk from the adjacent track in the Rf signal as described above.
[0070]
A signal 51 obtained from the first side beam light receiving element 15e is input and an amplifier circuit 51 amplifies the signal. The obtained signal is a signal obtained from the adjacent track side portion of the first side beam. It is. Therefore, the signal obtained from the light receiving unit 15e includes the Rf component on the adjacent track. 54 and 55 are delay circuits that delay the signal that has passed through the amplifier circuit 51. The delay times are the time required for the main beam to move to the position of the first side beam, and the second time at the position of the main beam. The time required for the side beam to move is set.
[0071]
Reference numeral 52 denotes an amplification circuit for amplifying the signal obtained by inputting a signal obtained from the second side beam light receiving element 15h. The obtained signal is a signal obtained from the adjacent track side portion of the second side beam. It is. Therefore, the signal obtained from the light receiving unit 15h includes the Rf component on the adjacent track.
[0072]
An adder circuit 53 for summing signals obtained from the light receiving elements 15c and 15d for the main beam has an output signal Rf. Reference numeral 56 denotes a delay circuit that delays the Rf signal from the adder circuit 53 for a predetermined time, and the delay time is set to be a time required for the main beam to move to the position of the first side beam. In this Rf signal, the Rf component from the adjacent track is superimposed as described above.
[0073]
Reference numeral 57 denotes a signal from the light receiving unit 15e amplified by the amplifier circuit 51 and delayed by the delay circuits 54 and 55, and a signal from the light receiving unit 15h amplified by the amplifier circuit 52, respectively, to the negative terminal. The Rf signal delayed by the delay circuit 56 is input to the positive terminal.
[0074]
Then, the Rf signal (SA + SB) on which the Rf component of the adjacent track is superimposed is subtracted by k1SE and k2SH, which are output signals from the adjacent track causing the crosstalk, (Equation 8) is obtained. Become.
[0075]
[Equation 8]
Rf = (SA + SB)-(k1SE + k2SF)
This is an Rf signal from which the Rf crosstalk component from the adjacent track has been removed. Record It is possible to accurately identify and reproduce the Rf signal recorded on the medium. Further, when the above calculation is performed, the delay amount in the delay circuit is the distance between the beams of the preceding first side beam, main beam, and following second side beam at the linear velocity of the optical recording medium. Set to the divided value.
[0076]
Using the diffracted light in the optical pickup of the first embodiment in which the spot arrangement on the information recording surface, the light receiving element, and the hologram pattern are arranged so as to cancel the crosstalk component of the Rf signal as described above, You may apply the light-receiving means for a monitor demonstrated in Examples 1-3 of Embodiment 1. FIG.
[0077]
Further, in the optical pickup of Example 2 in the fourth embodiment, the optical recording medium 107 is irradiated with the main beam Bm as shown in FIG. 16 and the first side on the tracks on both sides of the main beam Bm. The configuration may be such that the beam Bs1 and the second side beam Bs2 are respectively irradiated.
[0078]
A guide groove is formed in the optical recording medium 107 for tracking control of the laser beam. A sine having a predetermined amplitude and a predetermined period is formed on the opposite end surface of the guide groove along the track as shown in FIG. It is used for system control by forming a wave shape (hereinafter referred to as a wobble) and optically detecting this wobble with a laser beam, and in particular, a rotational drive means for an optical recording medium, for example, a spindle motor Used to servo-control (not shown). The servo control here controls the rotation speed of the spindle motor so that the period of the wobble signal is constant.
[0079]
By the way, the groove with the wobble shape may not be in the same phase arrangement as the adjacent groove in general. In fact, the phase difference between two adjacent groove arrangements varies along the groove. The phase difference relationship between adjacent grooves is extreme when there is no phase difference (see FIG. 17A), and when the phase difference between adjacent grooves is shifted by 1/2 (see FIG. 17). 17 (b)). If there is a phase difference between adjacent grooves, the wobble signal when the address information is reproduced causes intersymbol interference along with the phase difference and a beat is generated. In practice, the beat increases dramatically when the readout beam spot is defocused. As a result, the wobble signal becomes small and the error rate of the address at the time of reproduction becomes high, so that accurate reading and writing cannot be performed. By using the spot arrangement on the information recording surface as shown in FIG. 16, the influence of the beat as described above can be canceled.
[0080]
Reference numeral 60 denotes a subtraction circuit that generates a push-pull signal that is a difference signal between the outputs from the first side beam light receiving elements 15e and 15f, and the obtained signal is scanned by the first side beam Bs1. This signal contains a lot of wobble signals on the track. Reference numeral 62 denotes an amplifier circuit that receives the push-pull signal and amplifies the signal. Reference numerals 65 and 66 denote delay circuits that delay the signal that has passed through the amplifier circuit 62. The delay times are the time required for the main beam Bm to move to the position of the first side beam Bs1, and the position of the main beam Bm. It is set so that the time required until the second side beam Bs2 moves is set.
[0081]
Reference numeral 61 denotes a subtraction circuit that generates a push-pull signal that is a difference signal between outputs from the second side beam light receiving elements 15g and 15h. The obtained signal is scanned by the second side beam Bs2. This signal contains a lot of wobble signals on the track. Reference numeral 63 denotes an amplifier circuit that receives this push-pull signal and amplifies this signal. Reference numeral 64 denotes a subtraction circuit that generates a push-pull signal that is a difference signal between outputs from the main beam light receiving elements 15c and 15d. 67 is a delay circuit for delaying the push-pull signal from the subtraction circuit 64 for a predetermined time, and the delay time is set to be a time required for the second side beam Bs2 to move to the position of the main beam Bm. ing. In the wobble signal obtained from this push-pull signal, the wobble component from the adjacent track is superimposed as described above.
[0082]
68, the delayed push-pull signals from the light-receiving elements 15e and 15f from the delay circuit 66 and the push-pull signals from the light-receiving elements 15g and 15h from the amplifier circuit 63 are input to the negative terminal, respectively. This is a subtraction circuit in which the push-pull signal delayed by the circuit 67 is input to the + side terminal.
[0083]
The wobble signal (SA-SB) on which the wobble component of the adjacent track is superimposed is subtracted by k1 (SE-SF) and k2 (SG-SH) which are output signals from the adjacent track that cause the beat ( Equation 9) is obtained.
[0084]
[Equation 9]
Wb = (SA-SB) -k1 (SE-SF) -k2 (SG-SH)
This is a wobble signal from which the wobble and crosstalk components from the adjacent track are removed, and the wobble signal recorded on the optical recording medium can be accurately identified and reproduced. Further, when the above calculation is performed, the delay amount in the delay circuit is the distance between beams of the first side beam Bs1, the main beam Bm, and the second side beam Bs2 that follows the optical recording medium. The value divided by the linear velocity is set.
[0085]
Using the diffracted light in the optical pickup of the second embodiment in which the spot arrangement on the information recording surface, the light receiving element, and the hologram pattern are arranged so as to cancel the crosstalk component of the wobble signal as described above, You may apply the light-receiving means for a monitor demonstrated in Examples 1-3 of Embodiment 1. FIG.
[0086]
The optical pickup according to the fourth embodiment may include a condensing lens (not shown) in the front stage of the monitor light receiving means. When this condensing lens is arranged, a sufficient amount of light can be detected by the monitor light receiving means, and as a result, high S / N monitor control is possible. Compared with the case where no condensing lens is arranged, the light receiving element surface for monitoring the same amount of received light can be made smaller and the responsiveness can be improved.
[0087]
FIG. 18 is a transparent perspective view showing a schematic configuration of an information recording / reproducing apparatus which is an optical information processing apparatus according to Embodiment 5 of the present invention. The information recording / reproducing apparatus 10 is an apparatus that performs at least one of information recording, reproduction, and erasing with respect to the optical recording medium 20 by using the optical pickup 11. In the fifth embodiment, the optical recording medium 20 has a disk shape and is stored in a cartridge 21 of a protective case. The optical recording medium 20 is inserted into the information recording / reproducing apparatus 10 from the insertion opening 12 in the direction of the arrow “disc insertion” and is rotated by the spindle motor 13, and the information is recorded, reproduced or erased by the optical pickup 11. Is done. As this optical pickup 11, the optical pickup described in the first, second, third, and fourth embodiments can be used as appropriate.
[0088]
【The invention's effect】
As described above, according to the present invention, there is provided an optical information processing apparatus for a large-capacity (blue) optical recording medium that secures a sufficient working distance and has small aberration deterioration due to fluctuations, and an optical pickup used therefor. An optical information processing apparatus compatible with three generations including a conventional DVD and CD, and an optical pickup used therefor, capable of optimal light quantity control in a plurality of optical recording media by a single light receiving means for monitoring In addition, stable light quantity control can be performed even during multi-value recording, and moreover, it is possible to realize highly reliable light quantity control that is less susceptible to manufacturing variations and wavelength fluctuations.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an optical pickup that performs recording, reproduction, or erasing on each optical recording medium of a blue optical recording medium, a DVD optical recording medium, and a CD optical recording medium in Example 1 of Embodiment 1 of the present invention; Diagram showing configuration
FIG. 2 is a diagram showing a hologram unit constructed by integrating a semiconductor laser (light source), a hologram (optical path separating means) and a light receiving element.
FIG. 3 is a diagram showing a hologram unit configured by unifying two kinds of light sources for DVD / CD, a light receiving element, and an optical path separating means.
FIG. 4 is a diagram for explaining a function of directing one of the light paths of a light beam to an objective lens and the other to a monitor light-receiving means by the action of a deflecting mirror as a distribution means;
5 is a schematic diagram of an optical pickup that performs recording, reproduction, or erasing on each of the blue optical recording medium, the DVD optical recording medium, and the CD optical recording medium in Example 2 of Embodiment 1 of the present invention. FIG. Diagram showing configuration
FIG. 6 is a diagram showing a configuration for monitoring only a light beam at an outer peripheral portion that is not condensed by the objective lens of the light receiving means for monitoring.
7 is a schematic diagram of an optical pickup that performs recording, reproduction, or erasing on each of the blue optical recording medium, the DVD optical recording medium, and the CD optical recording medium in Example 3 of Embodiment 1 of the present invention. FIG. Diagram showing configuration
[Figure 8] Monitor light reception means The figure which shows the structure arrange | positioned in the position which monitors the diffracted light from the hologram unit which does not go to the objective lens of
9A shows a hologram pattern and FIG. 9B shows a light receiving element segment in the hologram unit.
FIG. 10 is a diagram showing a state of diffracted light by a hologram
FIG. 11 is a diagram illustrating a state of diffracted light that is divided into three light beams of 0th order and ± 1st order by a grating pattern.
FIG. 12 is a diagram showing the state of diffracted light in each region of the hologram pattern
FIG. 13 shows light that is not incident on the objective lens among the generated diffracted light. means Of the position detected by
FIG. 14 is a diagram showing an APC section provided for performing APC (automatic output control) on a light source output value during recording;
FIG. 15 is a diagram illustrating a circuit that cancels a crosstalk component of an Rf signal.
FIG. 16 is a diagram illustrating a circuit that cancels a crosstalk component of a wobble signal
FIGS. 17A and 17B are diagrams for explaining a phase difference relationship when there is no phase difference in the groove, and FIG.
FIG. 18 is a transparent perspective view showing a schematic configuration of an information recording / reproducing apparatus which is an optical information processing apparatus in Embodiment 5 of the present invention.
[Explanation of symbols]
10 Information recording and playback device
11 Optical pickup
12 insertion slot
13 Spindle motor
14 Carriage
20, 107 Optical recording medium
21 cartridge
22 Shutter
51, 52, 62, 63 Amplifier circuit
53 Adder circuit
57, 60, 61, 64, 68 Subtraction circuit
54, 55, 56, 65, 66, 67 delay circuit
100 Light receiving means for monitor
101, 201 hologram unit
101a, 201a, 301a Semiconductor laser
101b, 301b hologram
101c, 201c, 301c light receiving element
102,202 Collimating lens
103 Dichroic prism
104 Deflection mirror
105 1/4 wave plate
106 Objective lens

Claims (6)

A plurality of light sources, an objective lens for focusing the optical recording medium the light emitted from the respective light sources, the a collimating lens arranged in accordance with the respective light sources between each light source and the objective lens, from said each light source In an optical pickup provided with a single monitor light receiving means for monitoring the emitted light of
The light sources and the collimating lenses are arranged in parallel, and the single light receiving means for monitoring is arranged between the light sources and the collimating lenses among the light beams emitted from the light sources and directed to the optical recording medium. An optical pickup characterized in that each divergent light beam intersects and is arranged so as to receive only outer peripheral light that is not condensed on the objective lens . A plurality of light sources, a dichroic prism that combines optical paths from the light sources, an objective lens that collects light emitted from the light sources on an optical recording medium, and light emitted from the light sources that has passed through the dichroic prism In an optical pickup provided with a single monitor light receiving means for monitoring
An optical element in which a hologram pattern or a hologram pattern and a grading pattern are formed is provided between the light paths of the plurality of light sources and the dichroic prism, and the single light receiving means for monitoring is emitted from the light source and emitted from the light source. Among the light beams directed to the recording medium, the light beam is diffracted in the emission direction from the light source by the optical element, does not go to the objective lens, and is arranged at a position where a plurality of diffracted light beams from the light sources overlap. the optical pick-up you, characterized in that. The hologram pattern of the optical element splits the reflected light from the optical recording medium and diffracts the light beam from the light source in the emission direction. The grading pattern of the optical element is substantially orthogonal to the diffraction direction of the hologram pattern. 3. The optical pickup according to claim 2 , wherein the light emitted from the light source is branched in a direction into diffracted light of a main light beam and a plurality of sub light beams. In each light source, at least one or two or more light sources the optical pickup according to any one of claims 1-3, characterized by comprising housed in a single package. The optical pickup according to any one of claims 1 to 4 , wherein the plurality of light sources are light sources of a blue wavelength band, a red wavelength band, and an infrared wavelength band . An optical information processing apparatus for performing any one or more of recording, reproducing, and erasing information on an optical recording medium using the optical pickup according to any one of claims 1 to 5, wherein the optical information processing apparatus performs blue wavelength band Multi-level recording by switching the light quantity or time width of the light source in multiple steps on at least one or more optical recording media corresponding to each light source in the red wavelength band and infrared wavelength band according to the data to be recorded An optical information processing apparatus characterized by performing:

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