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WO2006118084A1 - Tete optique et processeur d’informations optiques - Google Patents

Tete optique et processeur d’informations optiques Download PDF

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Publication number
WO2006118084A1
WO2006118084A1 PCT/JP2006/308579 JP2006308579W WO2006118084A1 WO 2006118084 A1 WO2006118084 A1 WO 2006118084A1 JP 2006308579 W JP2006308579 W JP 2006308579W WO 2006118084 A1 WO2006118084 A1 WO 2006118084A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
wavelength
optical
optical head
resin
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2006/308579
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English (en)
Japanese (ja)
Inventor
Makoto Takashima
Hideki Aikoh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Publication of WO2006118084A1 publication Critical patent/WO2006118084A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1381—Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1384—Fibre optics

Definitions

  • the present invention relates to a technique for recording and reproducing information by irradiating an information recording medium such as an optical disc with light having a relatively short wavelength such as a blue-violet laser beam.
  • Patent Document 1 discloses such an optical disc apparatus.
  • FIG. 9 shows a configuration of an optical head 100 employed in a conventional optical disc apparatus.
  • FIG. 9 shows a light passage path (optical path) in the optical head 100.
  • the laser light emitted from the infrared semiconductor laser element 101 is converted into collimated light (parallel light) by the collimator lens 102 and separated into a plurality of different parallel lights by the diffraction grating 103.
  • a plurality of separated parallel lights are transmitted through the beam splitter 104a of the composite element 104, and the objective lens 105 incorporated in the objective lens driving device (not shown) is used to place the main beam having a diameter of about 1 micron on the optical disk 106. Focused as a beam.
  • a preceding beam and a following beam are formed at regular intervals as sub beams before and after the main beam on the same track as the main beam.
  • the light reflected by the beam splitter 104a of the composite element 104 is incident on a front light monitoring photodetector 107 for monitoring the light.
  • the detection result in the photodetector 107 is used to control the drive current flowing in the laser element 101.
  • the reflected light from the optical disc 106 follows the reverse path, is reflected and separated by the beam splitter 104a of the composite element 104, and enters the polarization separation element 104b.
  • the laser element 101 is installed so as to have a polarization direction parallel to the paper surface, and incident light is polarized by the polarization separation element 104b, and has three different light components having polarization components of only P-polarized light, P-polarized light + S-polarized light, and S-polarized light. And reflected by the folding mirror (reflection mirror) 104c.
  • the light reflected by the reflection mirror 104c enters the detection lens 131.
  • Detection lens 1 31 converges a plurality of lights reflected from the optical disk 106 at a plurality of different positions, respectively. Thereafter, light for generating a focus error signal is generated by the cylindrical lens 132.
  • the multi-segment photodetector 111 detects a predetermined signal from a plurality of beam spots converged by the detection lens 131.
  • the holding member 130 holds the detection lens 131 and the cylindrical lens 132.
  • FIG. 10 shows a configuration of a detection system of the conventional optical head 100.
  • the light reflected by the reflection mirror 104c is incident on the convex lens formed on the first surface of the detection lens 131, becomes converged light, and enters the concave cylindrical lens 132.
  • Astigmatism that becomes a focus error signal is added to the light that has passed through the concave cylindrical lens 132.
  • the optical path is a solid line and converges at the focal point 112 to form the front focal line 119b.
  • the optical path is indicated by a broken line and converges at the focal point 113 to form a rear focal line 119c.
  • each focal line appears as a light spot having a minute area that is not a straight line.
  • the area of the light spots of the focal lines 119b and 119c and the area of the substantially circular spot on the photodetector is approximately 1:10, and the focal line position is the most excluding the light spots converged on the optical disk. Increases power density.
  • the position of the focal line described above varies depending on the magnification of the optical system and the S-shaped interval of the focus error signal.
  • the position of the approximately circular light spot 119a on the surface of the photodetector is ⁇ 2 mm.
  • Focal lines are formed at the front and rear positions.
  • the photodetector surface of the multi-segment photodetector 111 is positioned approximately in the middle between the focal point 112 and the focal point 113.
  • a substantially circular light spot 119a is formed on the multi-segment photodetector 111.
  • the focus error signal by the so-called astigmatism method is obtained by taking the sum of diagonals of the electrical signals generated in the quadrant light receiving area (not shown) of the multi-segment photodetector 111 and subtracting them. Therefore, it can be obtained.
  • Patent Document 1 Japanese Patent Laid-Open No. 10-3683
  • the front focal line has a substantially circular shape on the surface of the photodetector. It is formed at a position of ⁇ lmm or less around the light spot position.
  • a photodetector which is a semiconductor substrate, is molded with a resin material such as epoxy resin, and its thickness is usually about 0.4 mm to lmm. It is.
  • the focal line is always present in the vicinity of the surface of the resin or in the resin while the servo control is performed.
  • the blue-violet laser light has a shorter wavelength than conventional infrared or red laser light, so if the state where the focal line is connected for a long time, such as in the resin where the energy is high, the resin at the focal line position Deterioration such as discoloration, transpiration, cracks, etc. occurs. In this case, the transmittance of the resin is reduced and abnormal refraction occurs, so that an accurate signal cannot be obtained.
  • the above-mentioned problem is a problem when the astigmatism method is used, the energy density is the highest on the detection surface of the photodetector even when using another method, for example, the knife edge method. Get higher. Therefore, the same problem occurs. Furthermore, not only the resin that molds the photodetector, but if blue-violet light is continuously irradiated at a high temperature for a long time, discoloration or the like may occur in the optical element even if it is not convergent light. This is particularly noticeable when the optical element is made of resin.
  • One of the objects of the present invention is to reduce deterioration of the resin in the resin for molding the photodetector and the resin in the resin made of the resin, and the optical element using a short wavelength light typified by blue-violet light. It is to suppress.
  • An optical head includes a light source that emits light of a first wavelength, a lens that focuses the light on an optical recording medium, and at least a part of reflected light of the first wavelength from the optical recording medium.
  • a wavelength conversion unit that converts light having a second wavelength longer than the first wavelength and a reflected light detector that detects light having the second wavelength are provided.
  • the wavelength conversion unit may be disposed at a position on an optical path connecting the lens and the reflected light detector and at a position deviating from the optical path from the light source to the lens.
  • the optical head further includes at least one optical element disposed at the position.
  • the wavelength conversion unit may be formed in contact with an end of the at least one optical element facing the optical path.
  • the reflected light detector includes a detection element that detects incident light and a resin that covers the detection element, and the detection element transmits light of the second wavelength that has passed through the resin.
  • the wavelength converter may be provided at a position substantially in contact with the resin.
  • the wavelength conversion unit is an optical fiber having a first end on which at least a part of the reflected light of the first wavelength is incident and a second end on which the light of the second wavelength is output.
  • the second end portion may be provided at a position substantially in contact with the resin.
  • the optical head includes a branching unit that branches the light of the first wavelength emitted from the light source into a plurality of parts, and the branched light of the first wavelength that has a third wavelength longer than the one wavelength.
  • a wavelength conversion unit that converts light into light and a branching light detector that detects at least part of the light with the third wavelength may further be provided.
  • the optical head may further include an optical element at a position between the branching unit and the branching light detector. At this time, the wavelength converting unit is on one surface of the optical element. May be formed.
  • the at least one optical element may include either a lens or a diffraction grating.
  • the wavelength conversion section may be formed in a layer shape.
  • the wavelength converter may further divide and output incident light.
  • the light source emits light having a first wavelength shorter than 450 nm, and the wavelength converter converts at least part of the reflected light having the first wavelength into light having a second wavelength longer than 500 nm. Good.
  • the wavelength conversion unit has at least a part of the reflected light of the first wavelength longer than 600 nm. You may convert into the light of the 2nd wavelength.
  • the wavelength converter may be formed of a material containing rare earth ions.
  • the wavelength converter may be formed of a material containing a nonlinear material capable of optical parametric oscillation.
  • the optical information processing apparatus includes an optical head that irradiates an optical recording medium with light and outputs a signal based on reflected light, and the focal point of the light and the optical recording medium based on the signal. And a signal processing circuit for generating a control signal for controlling the positional relationship between and.
  • the optical head includes: a light source that emits light of a first wavelength; a lens that focuses the light on an optical recording medium; and at least part of reflected light of the first wavelength from the optical recording medium.
  • a wavelength conversion unit that converts light having a longer second wavelength, and a reflected light detector that detects the light having the second wavelength and outputs a signal corresponding to the detected light having the second wavelength.
  • the reflected light detector has a detection element for detecting incident light and a resin covering the detection element, and the detection element receives the light of the second wavelength that has passed through the resin.
  • the wavelength converter may be provided at a position substantially in contact with the resin.
  • An optical head receives a light source that emits light, a lens that focuses the light onto an optical recording medium, and reflected light from the optical recording medium, and reduces the amount of the reflected light.
  • An optical element that can switch whether or not to output the light, and a reflected light detector that detects the light output from the optical element.
  • An optical information processing apparatus includes a light source that emits light, a lens that focuses the light onto an optical recording medium, and a circuit that outputs an instruction signal corresponding to the type of processing performed on the optical recording medium.
  • An optical element that receives reflected light from the optical recording medium and switches whether to output the reflected light by reducing the amount of the reflected light based on the instruction signal; and detects light output from the optical element And a reflected light detector.
  • the circuit may output an instruction signal according to whether information is recorded on the optical recording medium or information is reproduced from the optical recording medium.
  • an optical information processing apparatus includes a light source that emits light, a lens that focuses the light onto an optical recording medium, and a circuit that outputs an instruction signal according to the type of the optical recording medium; In response to the reflected light from the optical recording medium, the reflected light is reflected based on the instruction signal.
  • An optical element that switches whether or not to output with the light amount reduced, and a reflected light detector that detects light output from the optical element.
  • the circuit may output an instruction signal according to whether the information recording layer has several or more powers.
  • the optical information processing apparatus further includes a polarizing element that transmits only light in a predetermined polarization direction. At this time, the optical element changes the optical rotation of the light based on the instruction signal, The polarization direction of light may be adjusted.
  • the optical element may have a liquid crystal layer! /.
  • the polarizing element may be a polarizing beam splitter! /.
  • the optical head and the optical information processing apparatus of the present invention include a wavelength conversion unit that converts the wavelength of reflected light into a longer wavelength on the optical path until the reflected light from the optical information recording medium enters the reflected light detector. It has.
  • a wavelength converter By using such a wavelength converter, short wavelength light such as blue-violet light is converted into long wavelength light such as red light and green light, thereby deteriorating the resin covering the detection surface of the photodetector, For example, discoloration, transpiration, and deformation can be prevented.
  • Stable servo signals and playback signal (RF) signals can be obtained by suppressing the deterioration of the resin.
  • the optical head and the optical information processing apparatus of the present invention selectively reduce the reflected light from the optical information recording medium according to the operation.
  • the optical head and the optical information processing apparatus of the present invention selectively reduce the reflected light from the optical information recording medium according to the operation.
  • FIG. 1 is a diagram showing a hardware configuration of an optical disc device 50 according to Embodiment 1.
  • FIG. 2 is a diagram showing a configuration of an optical head 62 according to Embodiment 2.
  • FIG. 3 is a diagram showing a configuration of an optical head 63 according to Embodiment 3.
  • FIG. 4 is a diagram showing a configuration of an optical head 64 according to Embodiment 4.
  • FIG. 5 is a diagram showing a configuration of an optical head 65 according to Embodiment 5.
  • FIG. 6 is a diagram showing a configuration of an optical head 66 according to Embodiment 6.
  • FIG. 7 is a view showing a group of optical elements arranged on the optical path from the liquid crystal substrate 17 to the photodetector 8. is there.
  • FIG. 8 Relationship between the polarization direction a of the light before entering the liquid crystal substrate 17 and the polarization direction b of the light after passing through the liquid crystal substrate 17 when the lateral force on which the light is incident is also viewed in FIG. FIG.
  • FIG. 9 is a diagram showing a configuration of an optical head 100 employed in a conventional optical disc apparatus.
  • FIG. 10 is a diagram showing a configuration of a detection system of a conventional optical head 100.
  • optical information recording medium is an optical disk
  • optical information processing apparatus is an optical disk apparatus
  • FIG. 1 shows a hardware configuration of the optical disc apparatus 50 according to the present embodiment.
  • the optical disk device 50 includes, for example, an optical head 51, an optical disk controller 52, and a spindle motor 53.
  • an outline of the operation of the optical disc device 50 will be described first, and then a detailed configuration of the optical head 51 will be described.
  • FIG. 1 also shows the optical disc 10.
  • the optical disc 10 is, for example, a Blu-ray Disc (BD). Note that the optical disc 10 itself is removable from the optical disc device 50 and is not an essential component of the optical disc device 50.
  • BD Blu-ray Disc
  • the optical head 51 detects a reflected light from the optical disc 10 by irradiating the optical disc 10 with a light beam, and outputs a light amount signal corresponding to the detection position and the detected light amount of the reflected light.
  • the irradiated light beam is a blue-violet laser beam having a wavelength shorter than 450 nm, for example, a wavelength of about 405 nm.
  • the optical disk controller 52 includes a signal processing circuit 58 and a servo control circuit 59.
  • the signal processing circuit 58 generates a focus error (FE) signal indicating the focus state of the light beam on the optical disc 10 according to the light amount signal output from the optical head 51, the focus position of the light beam, the track of the optical disc 10 and Generates and outputs a tracking error (TE) signal indicating the positional relationship of
  • FE focus error
  • TE tracking error
  • the servo control circuit 59 generates a plurality of types of drive signals based on these signals. .
  • the type of drive signal differs depending on the output destination.
  • the output destination is a spindle motor 53, an actuator 54 of an optical head 51 described later, and the like.
  • the spindle motor 11 rotates the optical disc 10 at a rotation speed corresponding to the recording speed Z reproduction speed based on the drive signal.
  • the signal processing circuit 58 outputs a reproduction signal (RF signal) based on the light quantity signal.
  • the RF signal indicates data written on the optical disc 10. Thereby, reading of data from the optical disk 10 is realized. In addition, data can be written to the optical disk 10 by making the optical power of the light beam larger than that during reproduction.
  • the signal processing circuit 58 may be incorporated in the photodetector 8 described later.
  • the optical head 51 includes a light source 1, a collimating lens 2, a polarizing beam splitter 3, a 1Z4 wave plate 4, an objective lens 5, a detection lens 6, a cylindrical lens 7, a photodetector 8, A wavelength conversion element 9 and an actuator 54 are provided.
  • the light source 1 includes a semiconductor laser chip la and a back monitor photodetector lb.
  • the semiconductor laser chip la emits blue-violet laser light having a wavelength of 405 nm.
  • the semiconductor laser chip la is mounted so that the polarization direction of the emitted laser light is parallel to the paper surface.
  • the knock monitor photodetector lb is provided to monitor the light emitted from the semiconductor laser chip la.
  • the collimating lens 2 converts light emitted from the semiconductor laser chip la into substantially parallel light.
  • the polarizing beam splitter 3 branches the light 11 in a plurality of directions on the reflecting surface 3a included therein.
  • the P-polarized light transmittance of the reflecting surface 3a is 95%
  • the P-polarized light reflectance is 5%
  • the S-polarized light reflectance is 99%.
  • this is an example, and other values may be adopted.
  • the 1Z4 wavelength plate 4 converts circularly polarized light into linearly polarized light, or converts linearly polarized light into circularly polarized light.
  • the objective lens 5 focuses the light 11 on the signal surface (information recording layer) 10b of the substrate 10a of the optical disc 10.
  • the detection lens 6 focuses the light reflected by the information recording layer 1 Ob of the optical disk 10.
  • the cylindrical lens 7 adds astigmatism to the incident light. Astigmatism The purpose of adding is to generate a focus error signal.
  • the photodetector 8 has a light detection substrate 8b covered with a resin-made package 8a.
  • the light detection substrate 8b has a plurality of light receiving regions (not shown).
  • a light receiving element is arranged in each light receiving region, and a light amount signal corresponding to the light amount or energy of the received light is output. Based on this light quantity signal, the signal processing circuit 58 generates a servo signal and an RF signal.
  • the wavelength conversion element 9 converts light having a wavelength shorter than about 450 nm into light having a wavelength longer than that, and outputs the light.
  • the wavelength of the light after conversion may be 500 nm or more, or 600 nm or more.
  • the wavelength of the light after conversion is determined by the material used for the wavelength conversion element 9.
  • the wavelength conversion element 9 is manufactured using glass containing rare earth ions, that is, fluorescent glass.
  • the rare earth ions are, for example, prasedium (Pr) ions, europium (Eu) ions, and terbium (Tb) ions.
  • the wavelength conversion element 9 contains prasedium (Pr) ions and terbium (Tb) ions, the blue-violet light is converted into green light.
  • the wavelength conversion element 9 contains Eu-Pium (Eu) ions, blue-violet light is converted to red light.
  • SHG formed of a non-linear material such as LiNbO, LiTaO, KTiOPO, etc.
  • the wavelength conversion element 9 can be obtained.
  • the wavelength can be doubled by the so-called parametric oscillation principle. Therefore, blue-violet light having a wavelength of about 405 nm can be converted into red light having a wavelength of about 800 nm.
  • An optical resonator (not shown) may be provided as necessary in order to increase the gain of the light having a longer wavelength.
  • the actuator 54 supports the objective lens 5 so as to be movable, and adjusts the position of the objective lens 5 based on the drive signal of the servo control circuit 59 force.
  • the actuator 54 moves the object lens 5 in a direction perpendicular to the optical disc 10 and in a horizontal (parallel) direction.
  • the focal position force of the light beam emitted to the optical disc 10 is controlled so as not to deviate from the recording layer and the track force is not deviated.
  • Light through The path that passes is called the “light path”.
  • blue-violet laser light is emitted from the semiconductor laser chip la.
  • the blue-violet laser beam is emitted toward the collimating lens 2 and also toward the back monitor photodetector lb.
  • the light directed to the photodetector lb (back light) is detected by the back monitor photodetector lb, and a signal corresponding to the amount of light is generated.
  • This signal is used as a feedback signal to a semiconductor laser driving circuit (not shown), thereby realizing control for keeping the output of the semiconductor laser chip la constant.
  • the light emitted toward the collimating lens 2 is converted into substantially parallel light by the collimating lens 2 and then enters the polarization beam splitter 3. Since this light is P-polarized light, 95% of the light is transmitted through the reflecting surface 3a, enters the 1Z4 wave plate 4, and is converted to circularly polarized light. Circularly polarized light is applied to the optical disk 10 through the objective lens 5. At this time, the position of the objective lens 5 is adjusted, and control is performed so that the focal point of the light is positioned on the information recording layer 10b.
  • the light reflected by the information recording layer 10b passes through the objective lens 5 again and enters the 1Z4 wavelength plate 4.
  • the light is converted into linearly polarized light by the 1Z4 wavelength plate 4.
  • the polarization direction of the converted light has a relationship perpendicular to the polarization direction of the light emitted from the light source 1.
  • the linearly polarized light is incident on the polarization beam splitter 3 as S-polarized light. Due to the optical characteristics of the reflecting surface 3a, 99% of the S-polarized light is reflected on the reflecting surface 3a.
  • the light emitted from the polarization beam splitter 3 enters the wavelength conversion element 9.
  • the wavelength conversion element 9 is disposed on the optical path connecting the objective lens 5 through which the reflected light from the optical disk 10 travels to the light detection substrate 8b. More specifically, the wavelength conversion element 9 is disposed on the optical path connecting the reflecting surface 3a of the polarization beam splitter 3 and the light detection substrate 8b. This position is a position deviating from the optical path force until the light emitted from the light source 1 passes through the objective lens 5 and is irradiated onto the optical disc 10.
  • the wavelength conversion element 9 converts blue-violet light into green light having a wavelength of about 530 nm.
  • the converted light is incident on the detection lens 6 and converted into convergent light by the detection lens 6, and astigmatism is added by the cylindrical lens 7 in order to obtain a focus error signal.
  • the light passes through the resin package 8a of the light detector 8 and is incident on the light detection substrate 8b.
  • a light spot is formed on the light detection substrate 8b, and the light amount of the light spot is detected by the light receiving element.
  • the front focal line is formed in the light before entering the light detection substrate 8b, it should be noted that the resin of the resin package 8a is hardly deteriorated by the front focal line. There is nothing. The reason is that the original blue-violet light is converted to green light having a longer wavelength, so that there is not enough energy to cause degradation of the fat. As a result, even if the focal line is formed in the grease of the photodetector 8 or on the surface of the grease for a long period of time, degradation of the grease at the focal line position, such as discoloration, transpiration, cracking, etc. may occur. The property is kept low.
  • the light detection substrate 8b generates and outputs a light amount signal having a signal level corresponding to the light amount based on the light incident on the light detection substrate 8b. Based on these signals, the signal processing circuit 58 generates a servo signal and an RF signal.
  • the possibility of occurrence of anomalous refraction due to the decrease in the transmittance of the resin due to the focal line is very low, so the servo signal and RF signal with high quality are always obtained. Therefore, the reliability of the optical head 51 and the optical disk device 50 equipped with the optical head 51 is improved.
  • the wavelength conversion element 9 has been described as being disposed between the polarization beam splitter 3 and the detection lens 6. But this is just one example. As another example, the wavelength conversion element 9 may be provided at a position substantially in contact with the resin of the resin package 8a, such as the surface of the resin package 8a, or between the photodetector 8 and the cylindrical lens 7. Alternatively, it may be provided between the cylindrical lens 7 and the detection lens 6.
  • a configuration in which the wavelength conversion element 9 is provided at a position substantially in contact with the resin is effective. The reason is that the degree to which light is scattered before the light after wavelength conversion reaches the light detection substrate 8b can be suppressed low. Therefore, it is possible to surely detect the light detection board 8b and generate a high-quality servo signal and RF signal.
  • the focus error detection method using the astigmatism method has been described. Force Applicable when using other detection methods.
  • the optical head according to the present embodiment is different from the optical head 51 of Embodiment 1 in that a detector for monitoring the light of the light source 1 is provided outside the light source 1. Due to this difference, the configuration of the optical system for making the light incident on the detector is also partially different.
  • FIG. 2 shows a configuration of the optical head 62 according to the present embodiment.
  • the optical head 62 can be mounted on the optical disk device 50 in place of the optical head 51 shown in FIG.
  • FIG. 2 the same reference numerals are assigned to the components having the same configurations and functions as the components shown in FIG. 1, and the description thereof is omitted. Further, for convenience of description, the actuator 54 shown in FIG. 1 is omitted. The same applies to the description of the third and subsequent embodiments.
  • the light source according to the present embodiment is the same as the light source 1 of the first embodiment in that the light source has the semiconductor laser chip la, but does not have the knock monitor photodetector lb.
  • the optical head 62 further includes a wavelength conversion element 12, a front light collecting lens 13, and a photodetector 14.
  • the wavelength conversion element 12 converts light having a wavelength shorter than about 450 nm into light having a longer wavelength and outputs the light. Since the wavelength conversion element 12 is an optical element independent of the wavelength conversion element 9, the wavelength of the light after being converted by the wavelength conversion element 12 is the wavelength of the light after being converted by the wavelength conversion element 9. May be different or the same. For example, when the wavelength conversion element 9 converts light having a wavelength of about 405 nm into light having a wavelength of about 530 nm, the wavelength conversion element 12 may convert the same light having a wavelength of about 405 nm into light having a wavelength of about 600 nm. However, it may be converted into light having a wavelength of about 530 nm.
  • the front light collecting lens 13 for example, a lens equivalent to the objective lens 5 can be used.
  • the numerical aperture of the front light collecting lens 13 and the numerical aperture of the objective lens 5 may be set substantially the same.
  • the photodetector 14 is provided for detecting the amount of laser light from the light source 1.
  • the photodetector 14 has a photodetector substrate 14b covered with a resin package 14a.
  • the light detection substrate 14b is used to detect the amount of laser light.
  • the reason why the wavelength conversion element 12 is provided is that, even in the combination of the front light collecting lens 13 and the photodetector 14, the focal line is in the vicinity of the resin surface of the resin package 14a or in the resin. This is because there is a high possibility that a line enters. Since this focal line exists while light is emitted from the light source 1, there is a high possibility that deterioration of the grease, discoloration, cracking, etc. at the focal line position will occur. Therefore, in order to always detect the amount of laser light from the light source 1 appropriately, it is important to suppress the deterioration of the resin. Therefore, if a wavelength conversion element 12 is provided to convert the light into a light with a smaller energy.
  • the light emitted from the semiconductor laser chip 1 a is converted into substantially parallel light by the collimating lens 2 and enters the polarization beam splitter 3. Since the incident light is P-polarized light, it passes through the reflecting surface 3a of the polarizing beam splitter 3 by 95% and proceeds in the direction of the 1Z4 wavelength plate 4 and the objective lens 5.
  • the remaining 5% is reflected and incident on the wavelength conversion element 12 and converted into light having a wavelength longer than 405 nm.
  • the light whose wavelength has been converted passes through the front light condensing lens 13 and enters the resin package 14a of the light detector. Then, the light is focused on the light detection substrate 14b, and an electrical signal corresponding to the amount of light (front light signal). Is converted to
  • the wavelength conversion element 12 may be provided on the surface of the resin package 14a of the photodetector 14.
  • a modification of the optical head 51 according to the first embodiment can be similarly applied.
  • the optical head according to the present embodiment is a modification of the optical head 62 according to the second embodiment.
  • the wavelength conversion elements 9 and 12 are each 1 It was shown as a single optical element (see Figure 1 and Figure 2). However, in the present embodiment, instead of the wavelength conversion elements 9 and 12, wavelength conversion materials are provided in layers on the surfaces of the detection lens 6 and the front light collecting lens 13, respectively.
  • FIG. 3 shows a configuration of the optical head 63 according to the present embodiment.
  • the optical head 63 can be mounted on the optical disk device 50 in place of the optical head 51 shown in FIG.
  • a wavelength conversion layer 6 a is formed on the surface of the detection lens 6, and a wavelength conversion layer 6 b is formed on the surface of the front light collection lens 13. Since all the layers have the same performance as the wavelength conversion elements 9 and 12, the description thereof is omitted.
  • any one of the wavelength conversion element 9 and the wavelength conversion element 12 may be replaced with a wavelength conversion layer.
  • the position where the wavelength conversion layer is provided is not limited to the above example.
  • a wavelength conversion layer may be provided at a position substantially in contact with the resin of the resin package.
  • FIG. 4 shows a configuration of the optical head 64 according to the present embodiment.
  • the optical head 64 includes a hologram 15 and an optical fiber group 19 in addition to the configuration of the optical head 51 according to the first embodiment.
  • the optical head 64 can be mounted on the optical disk device 50 in place of the optical head 51 shown in FIG.
  • the hologram 15 is provided between the detection lens 6 and the cylindrical lens 7 and divides incident light based on the hologram pattern. How the force is split and in which direction the split light travels depend on the hologram pattern. Each of the divided lights is detected by the photodetector 8 and used in the signal processing circuit 58 to obtain a servo signal.
  • Each of the optical fiber groups 19 is provided between the cylindrical lens 7 and the photodetector 8.
  • Each optical fiber converts light with a wavelength shorter than about 450 nm into green light with a longer wavelength and outputs it.
  • each optical fiber Various specific modes of each optical fiber are conceivable depending on the material used.
  • the length of each optical fiber is arbitrary as long as the above-mentioned physical action works. For example, it may be about 25 cm.
  • a fluorescent optical fiber containing a rare earth ion (for example, at least one of Tb, Eu, and Pr) can be formed.
  • a rare earth ion for example, at least one of Tb, Eu, and Pr.
  • Reflected light having a wavelength of about 405 nm is incident on the hologram 15.
  • the light is split by the hologram 15 and then astigmatism is added by the cylindrical lens 7.
  • 0th order light and ⁇ 1st order light diffracted by the hologram 15 are output.
  • Each light is focused on each end of the optical fiber group 19 on the cylindrical lens 7 side and is incident on each optical fiber.
  • a portion of the reflected light incident on each optical fiber is converted into longer wavelength green light while passing through the inside.
  • the light is output from the end of each optical fiber on the side of the photodetector 8.
  • the light enters the light detection substrate 8b, and the amount of light is detected.
  • each optical fiber on the side of the photodetector 8 is provided at a position substantially in contact with the resin of the resin package of the photodetector 8. As a result, the degree to which the output light is scattered can be kept low, and the light can be efficiently detected by the light detection substrate 8b.
  • the position on the optical path between the objective lens 5 and the photodetector 8 of the optical head 64 more specifically, the position on the optical path between the cylindrical lens 7 and the photodetector 8.
  • the resin that constitutes the photodetector is a semiconductor laser. Since light having a longer wavelength than the light emitted from the chip la is incident, deterioration due to discoloration, transpiration, deformation, etc. of the resin constituting the photodetector is reduced, and stable servo signals and RF signals can be obtained. Can do.
  • the signal light quantity can be amplified for laser oscillation, and a signal with a good SN ratio can be obtained.
  • Degradation of the resin is caused by the presence of a high energy focal line in the vicinity of the resin surface or in the resin for a long time.
  • a wavelength conversion element (layer) that converts blue-violet light into light having a longer wavelength is provided as one method for reducing energy.
  • FIG. 5 shows a configuration of the optical head 65 according to the present embodiment.
  • the optical head 65 includes a liquid crystal substrate 16 instead of the wavelength conversion element 9 in the configuration of the optical head 51 according to the first embodiment.
  • the optical head 65 can be mounted on the optical disk device 50 in place of the optical head 51 shown in FIG. At this time, the optical disk device 50 is further provided with a liquid crystal driving circuit 20 described later.
  • the liquid crystal substrate 16 includes a substrate on which light is incident, a substrate on which light is emitted, and a liquid crystal layer sandwiched therebetween.
  • Liquid crystal molecules in the liquid crystal layer have positive dielectric anisotropy.
  • the major axis of the liquid crystal molecules is aligned approximately parallel to the substrate surface, and the alignment process is performed so that the major axis is twisted approximately 90 degrees between the two substrates along the thickness direction of the liquid crystal layer. ing.
  • the liquid crystal drive circuit 20 is provided for adjusting the light transmitted through the liquid crystal substrate 16.
  • the liquid crystal molecules rise in parallel to the electric field, and the twist alignment (twist alignment) is eliminated.
  • the amount of light transmitted through the liquid crystal substrate 16 (transmitted light amount) varies depending on the polarization plane of the polarization filter and the angle of the polarization plane after passing through the liquid crystal. In the TN mode liquid crystal substrate 16, it accompanies changes in the orientation of liquid crystal molecules due to voltage
  • the amount of transmitted light can be adjusted by utilizing the change in optical rotation. It can be said that the voltage applied to the liquid crystal substrate 16 by the liquid crystal driving circuit 20 is an instruction signal for adjusting the amount of light transmitted through the liquid crystal substrate 16.
  • the light emitted from the polarization beam splitter 3 has a polarization characteristic in a direction perpendicular to the paper surface.
  • the plane of polarization is rotated by the liquid crystal. Then, the light passes through a polarizing filter (not shown) disposed on the exit side of the liquid crystal substrate 16.
  • the rotation of the polarization plane is controlled by the level of the voltage applied to the liquid crystal by the liquid crystal driving circuit 20, and as a result, the amount of transmitted light is adjusted. For example, the amount of transmitted light is reduced during recording processing, and the amount of transmitted light is maximized during playback processing.
  • the light After passing through the liquid crystal substrate 16, the light enters the detection lens 6 and is converted into convergent light by the detection lens 6. Astigmatism is added by the cylindrical lens 7 in order to obtain a focus error signal. Thereafter, the light is transmitted through the resin package 8a of the photodetector 8 and is incident on the light detection substrate 8b. A light spot is formed on the light detection substrate 8b, and the light amount of the light spot is detected by the light receiving element.
  • the liquid crystal substrate 16 in the optical head 65 By providing the liquid crystal substrate 16 in the optical head 65 and adjusting the amount of transmitted light, the amount of light incident on the resin package 8a or the energy of the light can be reduced. As a result, even if the focal line is present in the vicinity of or within the surface of the resin surface for a long time, deterioration due to discoloration, transpiration, deformation, etc. of the resin package 8a can be suppressed, and a stable servo signal and RF signal can be obtained. Can be obtained.
  • the liquid crystal substrate 16 is disposed at the position where the reflected light becomes the thickest, that is, between the polarization beam splitter 3 and the detection lens 6. The reason is that at that position, the power density (energy) of light with a wavelength of about 405 nm is the lowest, and the liquid crystal substrate This is because the deterioration of the plate 16 itself can be suppressed.
  • the liquid crystal substrate 16 can be provided at an arbitrary position between the polarizing beam splitter 3 and the photodetector 8 in terms of suppressing the deterioration of the grease of the photodetector 8.
  • the liquid crystal drive circuit 20 can also be installed in the optical head 65.
  • an intensity filter that can be taken in and out of the optical path immediately after the light source (for example, between the light source 1 and the collimating lens 2 shown in FIG. 5) is provided.
  • the purpose of providing an intensity filter is to achieve both reduction of the quantum noise of the light source and protection of data on the optical disk.
  • the energy on the optical disk may be so large that data on the optical disk may be lost. Therefore, while radiating laser light at that intensity, an intensity filter is inserted to attenuate the power.
  • the amount of light that the optical head with the intensity filter inserted irradiates the optical disc and the amount of light that the general optical head that emits laser light with low power irradiates the optical disc. are equal. In this case, the amount of light reflected by the optical disk becomes equal, and as a result, deterioration of the grease of the photodetector cannot be suppressed. Therefore, in this embodiment, it is important to adjust the amount of reflected light.
  • FIG. 6 shows a configuration of the optical head 66 according to the present embodiment.
  • the optical head 66 is different from the optical head 65 according to the fifth embodiment in that a liquid crystal substrate 17 is provided instead of the liquid crystal substrate 16 and a polarization beam splitter 18 is provided.
  • the liquid crystal substrate 17 is connected to the liquid crystal drive circuit 20 outside the optical head 66.
  • FIG. 7 shows a group of optical elements arranged on the optical path from the liquid crystal substrate 17 to the photodetector 8.
  • FIG. 7 shows a configuration when the configuration shown in FIG. 6 is viewed along a plane parallel to the paper surface.
  • the polarizing beam splitter 18 has a reflecting surface 18a.
  • the reflecting surface 18a transmits predetermined light at a predetermined ratio and reflects the remaining light.
  • the reflecting surface 18a is configured to have a P-polarized light transmittance of 99%.
  • FIG. 8 shows the polarization direction a of the light before entering the liquid crystal substrate 17 and the polarization direction b of the light after passing through the liquid crystal substrate 17 when the lateral force on which the light enters in FIG. The relationship is shown.
  • the liquid crystal drive circuit 20 does not apply an electric field to the liquid crystal substrate 17 when reproducing information from the optical disc 10. Since the polarization direction does not change (ie, the polarization direction remains a), almost 100% of the light passes through the polarizing beam splitter 18. On the other hand, the liquid crystal driving circuit 20 applies an electric field to the liquid crystal substrate 17 when recording information on the optical disk 10. Since the polarization direction a of the light is rotated by the angle ⁇ to become the polarization direction b, the amount of light passing through the polarization beam splitter 18 is reduced.
  • the high-power light during the recording process can be used as a resin package for the photodetector 8. It is no longer incident on 8a. Therefore, deterioration due to discoloration, transpiration, deformation, etc. of the resin package 8a constituting the photodetector 8 can be suppressed, and stable servo signals and RF signals can be obtained.
  • the above reflectivity and transmissivity for the reflective surface 18a of the polarizing beam splitter 18 are examples. Other numerical values may be applied.
  • the liquid crystal drive circuit 20 can also be provided in the optical head 66.
  • the amount of transmitted light is changed according to information recording processing and reproduction processing.
  • another reference may be provided to switch between reducing the force to increase the amount of transmitted light.
  • the information recording layer provided on the optical disc 10 is one layer (that is, when the optical disc 10 is a single-layer disc)
  • the amount of transmitted light is reduced.
  • the information recording layer is multilayer (ie, when the optical disc 10 is a multilayer disc)
  • the reflected light power is 0.05 mW. It becomes.
  • the reflectivity of the multilayer disk is 0.05 and the power of light output from the objective lens 5 is 0.5 mW
  • the power of the reflected light is 0.025 mW. Therefore, the amount of reflected light (power) from the single-layer disc is larger. Therefore, when a single-layer disc is loaded, the liquid crystal substrate may be driven and adjusted so that the amount of transmitted light is low. Note that the transmittance may be changed continuously as well as simply switching.
  • the hologram described in the fourth embodiment is provided between the detection lens 6 and the cylindrical lens 7, and wavelength conversion is performed on the hologram surface on the light incident side.
  • An element or a wavelength conversion layer may be provided.
  • the wavelength of light transmitted through the hologram becomes longer, so that the groove pitch of the hologram can be widened, and the hologram can be easily manufactured.
  • the hologram itself is manufactured from the same material as the wavelength conversion layer, and the function and function of the hologram are improved. And have both functions of the wavelength conversion layer.
  • the present invention has been described as being most effective when the light detection substrate and the light detection element on the substrate are molded with resin. However, even if they are molded with a light-transmitting material different from the resin, the same effect is exhibited.
  • the wavelength of the reflected light from the optical information recording medium is converted to a longer wavelength. Since the energy of light decreases as the wavelength becomes longer, the surface of the photodetector can be molded to be closer to the photodetector and damage to the optical element can be reduced. In general, light having a longer wavelength is easier to detect, and is useful for improving the reliability of the signal detection system.
  • the amount of reflected light from the optical information recording medium reaching the detection system is controlled.
  • control so as to obtain an appropriate amount of light for each processing such as recording processing and reproduction processing.
  • the amount of light is reduced, the amount of light energy is reduced, so that the damage to the resin can be reduced by molding the surface of the photodetector.
  • it is useful for improving the reliability of the signal detection system by controlling so that the reflected light can be received stably.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)

Abstract

L’invention concerne une tête optique utilisant une lumière à longueur d’onde courte représentée par un rayon laser bleu-violet, grâce à laquelle la détérioration d’un moulage en résine d’un photodétecteur est empêchée. La tête optique comprend une source lumineuse émettant une lumière à une première longueur d’onde, une lentille condensant la lumière sur un support d’enregistrement optique, une unité de conversion de longueur d’onde pour convertir au moins une partie de la lumière de réflexion à une première longueur d’onde à partir du support d’enregistrement optique en une lumière ayant une deuxième longueur d’onde plus longue par rapport à la première longueur d’onde, ainsi qu’un photodétecteur à réflexion pour détecter la lumière à deuxième longueur d’onde. Etant donné que la lumière à deuxième longueur d’onde pénétrant dans le photodétecteur à réflexion voit son énergie se réduire ultérieurement, la détérioration de la résine, si le photodétecteur est moulé avec celle-ci, est empêchée.
PCT/JP2006/308579 2005-04-27 2006-04-24 Tete optique et processeur d’informations optiques Ceased WO2006118084A1 (fr)

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JP2005129266A JP2008176823A (ja) 2005-04-27 2005-04-27 光ディスク記録再生装置
JP2005-129266 2005-04-27

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
WO2008069193A1 (fr) * 2006-12-04 2008-06-12 Panasonic Corporation Tête optique, dispositif d'enregistrement et de lecture d'informations optiques, et système d'informations optiques

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Publication number Priority date Publication date Assignee Title
JPH03113739A (ja) * 1990-08-30 1991-05-15 Sanyo Electric Co Ltd 光学ヘッド装置
JPH0512708A (ja) * 1991-07-05 1993-01-22 Pioneer Electron Corp 光学式ピツクアツプ
JPH08227533A (ja) * 1995-02-22 1996-09-03 Pioneer Video Corp 光ディスク再生装置
JP2000123394A (ja) * 1998-10-13 2000-04-28 Sharp Corp 光記録情報再生装置
JP2000188416A (ja) * 1998-12-22 2000-07-04 Sanyo Electric Co Ltd 受光素子
JP2002279681A (ja) * 2001-03-21 2002-09-27 Olympus Optical Co Ltd 光学ユニット及びそれを具える光ヘッド
WO2004019333A1 (fr) * 2002-08-21 2004-03-04 Matsushita Electric Industrial Co., Ltd. Dispositif de traitement d'information optique et support d'enregistrement
JP2004094200A (ja) * 1995-06-02 2004-03-25 Matsushita Electric Ind Co Ltd レーザ装置

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03113739A (ja) * 1990-08-30 1991-05-15 Sanyo Electric Co Ltd 光学ヘッド装置
JPH0512708A (ja) * 1991-07-05 1993-01-22 Pioneer Electron Corp 光学式ピツクアツプ
JPH08227533A (ja) * 1995-02-22 1996-09-03 Pioneer Video Corp 光ディスク再生装置
JP2004094200A (ja) * 1995-06-02 2004-03-25 Matsushita Electric Ind Co Ltd レーザ装置
JP2000123394A (ja) * 1998-10-13 2000-04-28 Sharp Corp 光記録情報再生装置
JP2000188416A (ja) * 1998-12-22 2000-07-04 Sanyo Electric Co Ltd 受光素子
JP2002279681A (ja) * 2001-03-21 2002-09-27 Olympus Optical Co Ltd 光学ユニット及びそれを具える光ヘッド
WO2004019333A1 (fr) * 2002-08-21 2004-03-04 Matsushita Electric Industrial Co., Ltd. Dispositif de traitement d'information optique et support d'enregistrement

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008069193A1 (fr) * 2006-12-04 2008-06-12 Panasonic Corporation Tête optique, dispositif d'enregistrement et de lecture d'informations optiques, et système d'informations optiques
JPWO2008069193A1 (ja) * 2006-12-04 2010-03-18 パナソニック株式会社 光ヘッド、光情報記録再生装置および光情報システム装置
US8208359B2 (en) 2006-12-04 2012-06-26 Panasonic Corporation Optical head, optical information recording and reproducing device, and optical information system device

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