WO2004021065A1 - 光ピックアップ装置用の対物レンズ、光ピックアップ装置及び光情報記録再生装置 - Google Patents
光ピックアップ装置用の対物レンズ、光ピックアップ装置及び光情報記録再生装置 Download PDFInfo
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- WO2004021065A1 WO2004021065A1 PCT/JP2003/010994 JP0310994W WO2004021065A1 WO 2004021065 A1 WO2004021065 A1 WO 2004021065A1 JP 0310994 W JP0310994 W JP 0310994W WO 2004021065 A1 WO2004021065 A1 WO 2004021065A1
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- objective lens
- optical
- information recording
- pickup device
- wavelength
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- 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
- G11B7/1353—Diffractive elements, e.g. holograms or gratings
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- 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
- G11B7/1372—Lenses
- G11B7/1374—Objective lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
- G02B27/0037—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration with diffracting elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
- G02B27/4233—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive element [DOE] contributing to a non-imaging application
- G02B27/4238—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive element [DOE] contributing to a non-imaging application in optical recording or readout devices
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
- G02B27/4283—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive element with major temperature dependent properties
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1876—Diffractive Fresnel lenses; Zone plates; Kinoforms
- G02B5/189—Structurally combined with optical elements not having diffractive power
- G02B5/1895—Structurally combined with optical elements not having diffractive power such optical elements having dioptric power
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- 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
- G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
- G02B27/4294—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect in multispectral systems, e.g. UV and visible
Definitions
- the present invention relates to an optical pickup device, an optical information recording / reproducing device, and an objective lens used therefor, and more particularly, to an optical pickup device capable of recording or reproducing optical information at high density, an optical information recording / reproducing device, and an objective lens used therefor.
- a plastic single lens is generally used as an objective lens used in an optical pickup device or an optical information recording / reproducing device for recording or reproducing an optical information recording medium such as a CD, MO, and DVD. ing.
- the plastic lens Since the plastic lens has a smaller specific gravity than the glass lens, the burden on the actuator driving the objective lens for focusing and tracking can be reduced, and the objective lens can be followed at that time at high speed. There is an advantage.
- plastic lenses manufactured by injection molding a plastic material with a mold can be mass-produced with high precision by precisely manufacturing the desired mold, thereby improving the performance of the lens. Despite being able to perform stably, it is possible to reduce costs.
- a DVD (NA 0.6, light source wavelength 12 cm diameter optical disc of the same size as 6 50 nm, storage capacity 4, 7 GB) Can record 20 to 30 GB of information per page.
- a spherical aberration caused by a refractive index change due to a temperature change (hereinafter, this spherical aberration is referred to as This is called “temperature aberration”).
- This problem is caused by the fact that the plastic lens is about two orders of magnitude larger than the glass lens in the change in the refractive index due to the temperature change. Since this temperature aberration is proportional to the fourth power of NA, if the objective lens with NA 0.85 used for high-density DVD is a plastic lens, the usable temperature range will be very narrow. However, this is a problem in practical use.
- Japanese Patent Application Laid-Open No. 11-337818 discloses a technique for correcting the temperature aberration of such a plastic single lens by utilizing the diffraction effect of an annular structure formed on the optical surface.
- the slope of the spherical aberration curve when the wavelength changes (hereinafter, the slope of the spherical aberration curve in this specification is referred to as “color”). (Referred to as spherical aberration). Therefore, a semiconductor laser whose oscillation wavelength deviates from the reference wavelength due to a manufacturing error cannot be used, and semiconductor lasers need to be sorted, resulting in high costs.
- the objective lens whose lens data is shown in Table 1 is a plastic single lens with an incident beam diameter of 3 mm, a focal length of 2.5 mm, NA of 0.6, a design reference wavelength of 650 nm, and a design reference temperature of 25 ° C.
- the temperature aberration is corrected by the diffraction effect of the annular structure formed on the optical surface of the light source example.
- the objective lens whose lens data is shown in Table 2 is a plastic single lens with an incident light beam diameter of 3 mm, a focal length of 1.76 mm, NA of 0.85, a design reference wavelength of 405 nm, and a design reference temperature of 25 ° C.
- the temperature aberration is corrected by the diffraction operation of the annular structure formed on the first surface.
- 1 0 exponent for example, 2 ⁇ 5 X 1 0- 3
- E e.g., 2. 5 XE 3
- the aspherical surface of such an objective lens can be expressed by the following formula 1 when the optical axis direction is X axis, the height in the direction perpendicular to the optical axis is h, and the radius of curvature of the optical surface is r.
- ⁇ is a circular coefficient
- a 2 i is an aspheric coefficient.
- the orbicular structure as a diffractive structure formed on the optical surface is represented by an optical path difference added to the transmitted wavefront by the diffractive structure.
- Replacement form (Rule 26 4/1
- the value of the optical path difference function b (mm) is n times the predetermined wavelength B (however, n is a natural number.
- the diffractive structure is the wavelength lambda beta, optimized is the diffraction order ⁇ " and refers that such diffraction structure is determined, optimized wavelength or wavelengths beta, production wavelength Call.
- Table 3 shows the RMS value of the temperature aberration when the ambient temperature of the two objective lenses rises by 30 ° C, and the RMS value of the spherical aberration of the color when the incident wavelength is 5 nm longer than the design reference wavelength. Is shown.
- the objective lens with NA of 0.6 has a spherical aberration of chromaticity of only 0.003 rms even if the temperature aberration is corrected to 0. ⁇ ⁇ ⁇ ⁇ rms.
- Semiconductor lasers having different wavelengths can be used.
- NAO.85 objective lens when the temperature aberration is corrected to 0.014 rms as much as NA0.6 objective lens, the spherical aberration of chromaticity is 0.057 rms Therefore, it is impossible to use a semiconductor laser whose wavelength is shifted by 5 nm.
- the semiconductor laser used as the light source in the optical pickup device has a variation in oscillation wavelength of about ⁇ 5 nm due to manufacturing errors.Therefore, in the case of an NA 0.85 objective lens, it is necessary to select the semiconductor laser.
- the light pick 6 Increase the manufacturing cost of backup equipment.
- the rate of change of the refractive index with temperature rise is set to 9.0 x 10-5, and the rate of change of the wavelength of the incident light with temperature rise is +0. 2 nmZ ° C, +0.05 nm / ° C.
- r (mm) is the radius of curvature
- d (mm) is the spacing between surfaces
- N650 is the refractive index at a wavelength of 65 nm
- vd is the Abbe number at the d-line.
- r (mm) is the radius of curvature
- d (mm) is the surface spacing
- N 405 is the refractive index at a wavelength of 405 nm
- vd is the Abbe number at the d-line.
- Mode hopping is a wavelength change that occurs instantaneously so that the focusing mechanism of the objective lens cannot follow. If the axial chromatic aberration of the objective lens is not corrected, a defocus component corresponding to the amount of movement of the imaging position is added. This causes a problem that the focusing performance of the objective lens is deteriorated.
- the dispersion of general lens materials used for objective lenses is not so large in the wavelength range of 600 nm to 800 nm of infrared semiconductor lasers and red semiconductor lasers. Then, degradation of the focusing performance of the objective lens due to mode hopping was not a problem.
- the dispersion of the lens material becomes very large, so that even if the wavelength changes by only a few nm, the imaging position of the objective lens is greatly shifted. Therefore, in high-density DVDs, if the semiconductor laser light source undergoes mode hopping, the light-gathering performance of the objective lens will be significantly degraded, and stable recording and reproduction may not be possible.
- the present invention has been made in view of the above circumstances, and has a high NA objective lens.
- a plastic single lens that can be used as an objective lens of an optical pickup device that uses a single lens, and has a sufficiently wide usable temperature range and little deterioration in light-collecting performance due to mode hopping of the light source. It is intended to provide.
- the present invention further relates to a plastic single lens applicable as an objective lens of an optical pickup device using a high NA objective lens, wherein even if temperature aberration is corrected to widen the usable temperature range, the color is improved. It is an object of the present invention to provide a plastic single lens that does not make the spherical aberration excessively large and that does not require the selection of a semiconductor laser light source in a manufacturing process of an optical pickup device. Still another object of the present invention is to provide an optical pickup device equipped with such a plastic single lens as an objective lens, and an optical information recording / reproducing device equipped with this optical pickup device. Disclosure of the invention
- An objective lens for an optical pickup device wherein: a condensing optic comprising a light source and an objective lens for converging a light beam emitted from the light source on an information recording surface of an optical information recording medium.
- a condensing optic comprising a light source and an objective lens for converging a light beam emitted from the light source on an information recording surface of an optical information recording medium.
- a light system capable of performing information recording and Z or reproduction by condensing a light beam from the light source on an information recording surface of an optical information recording medium.
- the objective lens is a single plastic lens, and has an image-side numerical aperture of the objective lens necessary for recording and Z or reproducing information on the optical information recording medium.
- NA when the focal length of the objective lens is f (mm), the following formula is satisfied.
- the amount of change in spherical aberration (temperature aberration) due to the change in the refractive index of a plastic single lens due to temperature change increases in proportion to the focal length and the fourth power of NA. Therefore, even if the NA is increased to increase the density of the optical information recording medium, the temperature aberration can be suppressed to a relatively small value by reducing the focal length accordingly. Therefore, 8 In the objective lens described in claim 1, by setting the upper limit of the focal length as in equation (2), even if the plastic lens is a high NA plastic lens that satisfies equation (1), temperature The aberration is prevented from becoming too large.
- reducing the focal length is advantageous from the viewpoint of suppressing the amount of occurrence of temperature aberration, but if the focal length is too small, it is disadvantageous from the viewpoint of working distance and image height characteristics.
- securing the working distance is a very important issue in preventing collision with the optical information recording medium. If the focal length is too small, the working distance will be lost correspondingly. Absent. Also, if an attempt is made to obtain the same image ⁇ as an objective lens having a relatively large focal length, the angle of incidence on the objective lens having a relatively small focal length becomes large, so that astigmatism and coma aberration deteriorate.
- the objective lens described in claim 1 has secured the necessary and sufficient working distance and image height characteristics by determining the lower limit of the focal length as in equation (2).
- the focal length should not exceed the upper limit of equation (2), As a result, it is preferable to have a temperature characteristic satisfying the expression (4). As a result, information can be recorded / reproduced satisfactorily on / from the optical information recording medium using the plastic single lens within the temperature range of actual use in the optical pickup device.
- the objective lens for an optical pickup device is the invention according to claim 1 or 2, wherein the design reference wavelength L Q of the objective lens is 500 nm or less.
- ambient temperature T. 25 ° C
- the back force of the objective lens when light of wavelength ⁇ 0 (nm) is incident on the objective lens is f B (E., T 0 )
- First ambient temperature T. 25 ° C at ambient temperature, the wavelength of the objective lens.
- ⁇ f B defined by the following formula satisfies the following expression.
- Axial chromatic aberration due to mode hopping of a semiconductor laser increases in proportion to the focal length. Therefore, even when, for example, a blue-violet semiconductor laser is used as the light source, the axial chromatic aberration can be suppressed to a relatively small value by reducing the focal length accordingly. It is impossible to make the chromatic aberration completely zero with a refraction type single lens.
- the focal length is set so as to satisfy the expression (2).
- the amount of change in the pack focus when the incident wavelength increases by 5 nm is made smaller than 0.01 mm ((6 )
- the change in the wavefront aberration including the defocus component can be suppressed to less than 0.03 rms compared to the change in the wavelength due to the mode hobbing of the blue-violet semiconductor laser. Even if mode hobbing occurs when switching to the recording state, the light-collecting performance is not significantly degraded.
- the objective lens for an optical pickup device is the object lens according to any one of claims 1 to 3, wherein the divergent light beam emitted from the light source is focused on the information recording surface.
- Finite conjugate type objective lens that satisfies 10 Features.
- the objective lens described in claim 4 is preferable as an objective lens for an optical pickup device required to be miniaturized.
- it is used as an objective lens for an optical pickup device mounted on a portable optical disc player. be able to.
- a lens with a brightness (l-m) times the image-side numerical aperture of the infinite type objective lens must be used. Need to design. If the objective lens is a finite conjugate type that converges the divergent light beam emitted from the light source onto the information recording surface of the optical information recording medium, the sign of m is negative and the effective image-side numerical aperture is infinite. It becomes larger than the image-side numerical aperture of the objective lens.
- the temperature aberration is larger than that of an infinite type objective lens. Therefore, in the objective lens described in claim 4, by setting the upper limit of the focal length to be smaller than that of the expression (2) and determining it as in the expression (6A), the NA can be expressed by the expression (1). Even with a finite conjugate plastic single lens with a high NA that satisfies, the temperature aberration can be kept within the allowable range for practical use.
- the working distance of a finite conjugate type objective lens that collects divergent light beams is longer than that of an infinite type objective lens having the same focal length. Therefore, even when the upper limit of the focal length is made smaller than the expression (2) as in the objective lens described in claim 4, there is no disadvantage from the viewpoint of securing the working distance.
- An objective lens for an optical pickup device is characterized in that, in the invention according to claim 4, when the imaging magnification of the objective lens is m, the following expression is satisfied.
- the imaging magnification m is larger than the lower limit of the above equation (6B), a sufficient working distance can be secured even with an objective lens having a short focal length that satisfies the above equation (6A). Wear.
- the imaging magnification m is smaller than the upper limit of the expression (6B), the actual image-side numerical aperture does not become too large, so that the temperature aberration can be suppressed within an allowable range in practical use. .
- a focusing optical system including an objective lens for focusing the light beam emitted from the source on the information recording surface of the optical information recording medium, wherein the light collecting optical system transmits the light beam from the light source
- the objective lens includes a plurality of orbicular zones.
- a plastic single lens having, on at least one optical surface, a transport zone structure configured so that adjacent ring zones generate a predetermined optical path difference with respect to incident light,
- NA the image-side numerical aperture of the objective lens required to record and / or reproduce information on the optical information recording medium
- f focal length
- the spherical aberration (temperature aberration) generated by the refractive index change due to the temperature change is reduced by the optical aberration. If the correction is made by the action of the annular structure formed on the surface, the fall of the spherical aberration curve (chromatic spherical aberration) when the wavelength changes becomes too large, and the oscillation wavelength deviates from the reference wavelength due to manufacturing errors. Semiconductor lasers that have shifted cannot be used, and semiconductor lasers must be sorted.
- the amount of change in spherical aberration due to the change in the refractive index of the plastic objective lens increases in proportion to the focal length and the fourth power of NA. Therefore, even if the NA increases due to the high density of the optical information recording medium, the spherical aberration due to the change in the refractive index of the objective lens can be suppressed relatively small if the focal length is reduced accordingly. It becomes.
- the upper limit of the focal length is determined as in equation (8), so that the correction amount of the temperature aberration due to the action of the annular structure is suppressed to a small value. It is possible to prevent the spherical aberration of the corrected color from becoming too large. As a result, in the optical pickup device equipped with the objective lens according to the present invention, it is not necessary to sort the semiconductor lasers in the manufacturing process, so that the manufacturing cost can be reduced. On the other hand, reducing the focal length requires compensation for temperature aberration as described above. 12 Although it is advantageous from the viewpoint of positive amount, if the focal length is too small, it is disadvantageous from the viewpoint of working distance and image height characteristics. Therefore, in the objective lens according to the present invention, the necessary and sufficient working distance and image height characteristics are secured by setting the lower limit of the focal length as in equation (8).
- the objective lens is, in a narrow sense, a condensing function that is arranged to face the optical information recording medium at a position closest to the optical information recording medium when the optical recording medium is loaded in the optical pickup device.
- the numerical aperture of the objective lens on the optical information recording medium side refers to the numerical aperture of the lens surface located closest to the optical information recording medium of the objective lens.
- the necessary (predetermined) numerical aperture is the numerical aperture specified in the standard of each optical information recording medium, or the wavelength of the light source used for each optical information recording medium. It refers to the numerical aperture of an objective lens with diffraction-limited performance that can obtain the spot diameter required for recording or reproducing information according to the conditions.
- recording information means recording information on the information recording surface of the optical information recording medium as described above.
- information reproduction means reproducing information recorded on the information recording surface of the optical information recording medium as described above.
- the objective lens according to the present invention may be used for performing only recording or reproduction, or may be used for performing both recording and reproduction. Further, it may be used for performing recording on a certain optical information recording medium and reproducing on another optical information recording medium, or recording on a certain optical information recording medium. Alternatively, it may be used for performing reproduction and performing recording and reproduction on another optical information recording medium. Note that reproduction here includes simply reading information.
- the objective lens for an optical pickup device wherein the annular structure is a diffractive structure having a function of diffracting predetermined incident light,
- the lens forms a converging wavefront that converges on the information recording surface by a combined effect of the diffraction action and the refraction action, the above-described action can be effectively performed. 13 It is preferable because it can be demonstrated.
- the objective lens for an optical pickup device described in claim 8 is the invention according to claim 7, wherein when the wavelength of the incident light changes to a longer wavelength side, the spherical aberration changes in a direction where correction is insufficient. It is preferable to have such spherical aberration characteristics.
- the refractive index of a plastic single lens decreases as the temperature rises, so that the spherical aberration changes in the overcorrected direction, while the oscillation wavelength of the semiconductor laser generally tends to change in the longer direction as the temperature rises. is there. Therefore, by giving the above-mentioned spherical aberration characteristics to the objective lens by the action of the diffractive structure, the change of the spherical aberration, which is overcorrected by the change of the refractive index due to the temperature rise, is reduced by the temperature rise of the semiconductor laser. It can be canceled out by a change in spherical aberration that is insufficiently corrected due to a change in oscillation wavelength.
- an optical surface (diffractive surface) on which a diffractive structure is formed is a surface provided with a relief on a surface of an optical element, for example, a lens surface, so as to diffract an incident light beam.
- a diffraction structure or a diffraction pattern refers to a region where this diffraction occurs.
- the shape of the relief for example, it is formed as a substantially concentric annular zone around the optical axis on the surface of the optical element, and if the cross section is viewed on a plane including the optical axis, each annular zone has a sawtooth shape or a staircase. Such shapes are known, but include such shapes.
- the diffractive structure has a wavelength
- ⁇ 0 (nm) is the design reference wavelength of the objective lens
- h MAX is the maximum effective diameter height (mm) of the optical surface on which the diffraction structure is formed.
- m is the imaging magnification of the objective lens.
- the objective lens for an optical pickup device includes a fourth-order optical path difference function coefficient b 4 , an effective diameter maximum height h MAX of an optical surface on which a diffractive structure is formed, an imaging magnification m, a focal length f, and an image side.
- the numerical aperture NA is designed so as to satisfy the condition of the above-mentioned expression (8A). This condition is a condition for correcting the temperature aberration and improving the balance of the generation amount of the chromatic spherical aberration in the plastic lens on which the diffractive structure is formed.
- the correction of the temperature aberration does not become excessive, so that the generation amount of the chromatic spherical aberration does not become too large, and the oscillation wavelength relatively deviates from the reference wavelength due to a manufacturing error. It can also be used with a semiconductor laser, and can reduce the cost by relaxing the conditions for selecting the semiconductor laser.
- the spherical aberration caused by the change in the wavelength of the semiconductor laser can cancel the spherical aberration caused by the change in the refractive index of the high-NA plastic lens. Can be used in a wider temperature range.
- the objective lens for an optical pickup device is the invention according to claim 6, wherein the orbicular zone structure is formed such that adjacent orbicular zones are displaced from each other in the optical axis direction. Accordingly, the predetermined optical path difference is generated with respect to the incident light, and the objective lens forms a converging wavefront that converges on the information recording surface by refraction. 15 It is preferable because the above-mentioned effects can be effectively exerted.
- the objective lens for an optical pickup device is the invention according to claim 10, wherein the objective lens is formed by being displaced inward from an annular zone adjacent to a side closer to the optical axis.
- a band formed by displacing the belt closer to the side closer to the optical axis to the outside than the ring adjacent to the side closer to the optical axis; and a zone adjacent to the side closer to the optical axis.
- the annular zone displaced inwardly is formed closer to the optical axis than the annular zone displaced outwardly from the adjacent zone adjacent to the optical axis. In this case, it is preferable to configure the annular structure in this manner, because temperature aberration can be satisfactorily corrected.
- the objective lens for an optical pickup device according to claim 12 is the invention according to claim 10 or 11, wherein the total number of the orbicular zones is 3 or more and 20 or less.
- the objective lens for an optical pickup device is the invention according to any one of claims 10 to 12, wherein an effective diameter maximum height of the optical surface on which the annular structure is formed.
- an effective diameter maximum height of the optical surface on which the annular structure is formed In the orbicular zone structure formed in the area from 75% to 100% in height, any of the steps in the optical axis direction at the boundary between adjacent orbicular zones is different.
- the amount is ⁇ ”( ⁇ ), and the design reference wavelength ⁇ of the objective lens. Assuming that the refractive index at ( ⁇ m) is n,
- I NT (X) is an integer obtained by rounding off the X - 1) / ( ⁇ o ⁇ 1 0.)
- the total number of orbicular zones is 3 or more and 20 or less, and furthermore, 75% of the maximum effective diameter of the optical surface on which the orbicular structure is formed.
- the step amount of an arbitrary step is ⁇ ;
- the design reference wavelength ⁇ of the objective lens is 3 or more and 20 or less.
- the annular zone structure is determined so that ni j expressed by the above equation (8B) is an integer of 2 or more, and the direction perpendicular to the optical axis of the transport zone Can secure a large width of the 16
- the mold processing for molding the lens becomes easy, and the time required for the mold processing can be shortened.
- the orbicular zone structure is formed on the first surface (the optical surface on the light source side)
- “formed by being displaced inward from the orbicular zone adjacent to the side closer to the optical axis” means “light "It is formed by being displaced in the direction of the second surface (optical surface on the optical information recording medium side) rather than the ring zone adjacent to the near axis side.” Is formed by being displaced outward. ”“ It is displaced in the direction opposite to the direction of the second surface (optical surface on the optical information recording medium side) than the ring zone adjacent on the side near the optical axis. Is formed.
- the objective lens for an optical pickup device is the invention according to any one of claims 6 to 13, wherein the first ambient temperature T is satisfied.
- the wavelength which is the design reference wavelength of the objective lens At an environmental temperature of 25, the wavelength which is the design reference wavelength of the objective lens.
- the RMS value of the residual aberrations of the objective lens of the time that light was made to enter with the (nm) W ( ⁇ 0, ⁇ 0) and a first ambient temperature T. 25 ° C. at an ambient temperature of 25 ° C.
- W ( 2 , ⁇ ) an MS value of residual aberration of the objective lens when light having a wavelength of ⁇ 2 (nm) is incident on the objective lens
- AW 2 1 W U ;
- (10) satisfy the following expression.
- Equation (9) is an equation corresponding to the temperature aberration when the temperature is increased by 3 (TC rise)
- equation (10) is an equation corresponding to the color spherical aberration when the wavelength of the incident light changes by 5 nm.
- the temperature aberration, the spherical aberration of the color, and the combined aberration of the spherical aberration of the color and the temperature difference are (11), (12) and (described later), respectively. It is preferable to satisfy the expression (13).
- the design reference wavelength of the objective lens is defined as a value obtained when various wavelengths of light are incident on the objective lens under the same conditions (imaging magnification, temperature, incident light beam diameter, and the like). The wavelength at which the residual aberration of the objective lens is minimized.
- the design reference temperature of the objective lens refers to the residual aberration of the objective lens under various environmental temperatures under the same conditions (imaging magnification, wavelength, incident light beam diameter, etc.) with respect to the objective lens. Is the temperature at which the residual aberration of the objective lens is minimized when is measured. It is preferable that the objective lens for an optical pickup device described in claim 15 satisfies the following expression in the invention described in claim 14.
- the objective lens for an optical pickup device may be any one of claims 6 to 15
- the objective lens is a finite conjugate type objective lens that focuses a divergent light beam emitted from the light source on the information recording surface. Therefore, the following equation is satisfied.
- the operation and effect of the present invention are the same as those of the invention described in claim 4.
- the objective lens for an optical pickup device is the invention according to claim 16, wherein an imaging magnification of the objective lens is When m, the following equation is satisfied.
- the operation and effect of the present invention are the same as those of the invention described in claim 5.
- the objective lens for an optical pickup device is the invention according to any one of claims 1 to 17, When the lens thickness on the optical axis of the objective lens is d (mm) and the focal length is f (mm), the following formula is satisfied.
- Equation (14) shows that, for a small-diameter high NA objective lens whose focal length satisfies equations (2), (6A), (8) and (13A), good image height characteristics, This is a condition for securing a sufficient manufacturing tolerance and a sufficient working distance. If the value of d / f is larger than the lower limit of the expression (14), the third order non-uniformity when the image height characteristic is evaluated by the wavefront aberration is calculated. There is an advantage that the astigmatism component does not become too large and the fifth-order or higher-order coma aberration component does not become too large.
- the third-order spherical aberration component, the fifth-order astigmatism component, the third-order coma aberration component, and the astigmatism difference when the image height characteristic is evaluated by the wavefront aberration do not become too large.
- the gear radius of the optical surface on the light source side does not become too small, it is possible to suppress the occurrence of coma aberration due to the optical axis shift between the optical surfaces, and to secure a sufficient manufacturing tolerance.
- the edge thickness is sufficiently secured and the thickness deviation ratio does not become too small, so that the occurrence of birefringence due to injection molding can be suppressed.
- the value of d / f is less than the upper limit of the expression (14), the lens thickness does not become too large, so that the lens can be reduced in weight and can be driven by a smaller actuator. The working distance can be sufficiently secured.
- an optical pickup provided with a short-wavelength light source such as a blue-violet semiconductor laser, for example, when the design reference wavelength ⁇ 0 (nm) power of the objective lens satisfies the following expression: Can be used for equipment.
- a short-wavelength light source such as a blue-violet semiconductor laser
- An objective lens for an optical pickup device described in claim 20 is the invention according to any one of claims 1 to 19, characterized by satisfying the following expression.
- XI Optical axis between the plane perpendicular to the optical axis and in contact with the vertex of the optical surface on the light source side, and the optical surface on the light source side at the outermost periphery of the effective diameter (the position on the light source side where the marginal ray of NA is incident). The distance in the direction (mm). Positive when measured in the direction of the optical information recording medium with respect to the above tangent plane, negative when measured in the direction of the light source.
- X 2 a plane perpendicular to the optical axis and in contact with the vertex of the optical surface on the optical information recording medium side, and light at the outermost periphery of the effective diameter (the position on the optical information recording medium side on which the marginal ray of NA is incident).
- N the design reference wavelength. Refractive index of the objective lens at
- Claim 20 defines a conditional expression relating to the amount of sag between the optical surface on the light source side and the optical surface on the optical information recording medium side for favorably correcting spherical aberration.
- the effect of overcorrecting the spherical aberration of the marginal ray increases as X1 defined as described above is positive and its absolute value is small, and as 2 is negative and its absolute value is small, and X1 is positive.
- the larger the absolute value the more negative the value of X2 and the larger the absolute value, the greater the effect of undercorrecting the spherical aberration of the marginal ray. Therefore, to correct the spherical aberration, (X1-X2 ) Must be within a certain range.
- the expression (16) is satisfied.
- the spherical aberration of the marginal ray is not excessively corrected.
- the design reference wavelength In particular, the design reference wavelength.
- the optical pickup device Has a light source, and a light collecting optical system including an objective lens for condensing a light beam emitted from the light source on an information recording surface of an optical information recording medium, wherein the light collecting optical system includes: An optical pickup device capable of recording and / or reproducing information by condensing a light beam from the optical information recording medium onto an information recording surface of the optical information recording medium;
- the objective lens is a single plastic lens, and the image-side numerical aperture of the objective lens required for recording and / or reproducing information on the optical information recording medium is NA, and the focal length of the objective lens is When f is set to f (mm), the following equation is satisfied.
- W E., ⁇ ⁇
- ⁇ f B I f ⁇ ( ⁇ ⁇ T 0 )-f B (; L 0 , T 0 )
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 3.
- the optical pickup device described in claim 24 is the invention according to any one of claims 21 to 23, wherein the objective lens transmits a divergent light beam emitted from the light source on the information recording surface.
- This is a finite conjugate type objective lens that converges light at a point, and satisfies the following equation.
- the operation and effect of the present invention are the same as those of the invention described in claim 4.
- the optical pickup device described in claim 25 is the optical pickup device according to claim 24, wherein the following expression is satisfied when the imaging magnification of the objective lens is m.
- the optical pickup device is the invention according to claim 24 or 25, wherein the objective lens and the light source are at least track-driven together by an actuator. And
- the objective lens according to the present invention satisfies the above-mentioned expression (6A).
- the objective lens is eccentric with respect to the light emitting point of the light source by 0.2 to 0.3 mm due to tracking errors, large coma and astigmatism are generated, and the optical information recording medium Recording and Z playback cannot be performed satisfactorily. Therefore, in the optical pickup device described in claim 22, the objective lens and the light source are configured to be at least tracking-driven integrally by an actuator.
- the optical pickup device can solve the problem of coma and astigmatism by Toratsuki Nguera includes a light source and an optical information recording light beam emitted from the light source A focusing optical system including an objective lens for focusing on an information recording surface of the medium, wherein the focusing optical system focuses a light beam from the light source on the information recording surface of the optical information recording medium.
- a focusing optical system including an objective lens for focusing on an information recording surface of the medium, wherein the focusing optical system focuses a light beam from the light source on the information recording surface of the optical information recording medium.
- the objective lens includes a plurality of orbicular zones, and has an orbicular structure in which adjacent orbicular zones are formed so as to generate a predetermined optical path difference with respect to incident light, on at least one optical surface.
- a plastic single lens having
- the image-side numerical aperture of the objective lens required to record and / or reproduce information on the optical information recording medium is NA
- the focal length of the objective lens is f (mm)
- the operation and effect of the present invention are the same as those of the invention described in claim 6.
- the optical pickup device according to claim 28 is the optical pickup device according to claim 27, wherein the annular structure is a diffraction structure having a function of diffracting predetermined incident light, and the objective lens is A converging wavefront for converging light on the information recording surface is formed by a combined effect of a diffraction effect and a refraction effect.
- the operation and effect of the present invention are the same as those of the invention described in claim 7. 23 In the optical pickup device according to claim 29, in the invention according to claim 28, the objective lens has insufficient correction of spherical aberration when the wavelength of the incident light changes to a longer wavelength side.
- the optical pickup device according to claim 30 is the optical pickup device according to claim 28 or 29, wherein an optical path difference 4> b added to a wavefront transmitted through the diffractive structure is defined by: As a function of height h (mm),
- (Nm) is the design reference wavelength of the objective lens
- h MAX is the maximum effective diameter height (mm) of the optical surface on which the diffraction structure is formed
- m is the imaging magnification of the objective lens.
- the optical pickup device described in claim 31 is the optical pickup device according to claim 27, wherein the orbicular zone structure is formed by displacing adjacent orbicular zones in the optical axis direction. in, cause the predetermined optical path difference to an incident light, the action effect of the objective lens, c present invention and forming a converging wavefront which converges on the information recording surface by the refractive action, This is the same as the function and effect of the invention described in claim 10.
- the optical pickup device described in claim 32 is the optical pickup device according to claim 31, wherein the objective lens is formed by being displaced inward from an orbicular zone adjacent to a side closer to the optical axis.
- the annular zone formed by displacing more inward is formed closer to the optical axis than the annular zone formed displaced outside than the adjacent zone on the side closer to the optical axis. It is characterized.
- the operation and effect of the present invention are the same as those of the invention described in claim 11. 24.
- An optical pickup device is the invention according to claim 31 or 32, wherein the total number of the annular zones is 3 or more and 20 or less.
- the operation and effect of the present invention are the same as those of the invention described in claim 12.
- the optical pickup device described in claim 34 is the invention according to any one of claims 31 to 33, wherein the height of the optical surface on which the annular structure is formed is 75% of the maximum effective diameter height. at 100% of the height region formed ring-shaped structure from the out of the optical axis direction step at the boundary of zones adjacent to each other in each other physician, the step amount of any of the step and ⁇ 5 ( ⁇ ) When the refractive index at the design reference wavelength (nm) of the objective lens is n,
- Mj represented by is an integer of 2 or more.
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 13.
- the wavelength ⁇ which is the design reference wavelength. (nm)
- the RMS value of the residual aberration of the objective lens at the time of incidence of light (nm) is W ( ⁇ ⁇ 0 )
- the RMS value of the residual aberration of the objective lens when light having a wavelength of ⁇ 2 (nm) is incident on the objective lens under the second ambient temperature T i 55 ° C. Is W ( ⁇ 2 ⁇ ⁇ ),
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 14.
- the optical pickup device described in claim 36 preferably satisfies the following expression in the invention described in claim 35.
- the objective lens emits a divergent light beam emitted from the light source onto the information recording surface.
- This is a finite conjugate type objective lens that focuses light, and satisfies the following expression.
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 16.
- the optical pickup device described in claim 38 is characterized in that, in the invention described in claim 37, when the imaging magnification of the objective lens is m, the following expression is satisfied.
- the optical pickup device described in claim 39 is characterized in that, in the invention described in claim 37 or 38, at least tracking drive is performed on the objective lens and the light source integrally with an actuator. And The operation and effect of the present invention are the same as those of the invention described in claim 26.
- the optical pickup device described in claim 40 is the invention according to any one of claims 21 to 39, wherein a lens thickness on the optical axis of the objective lens is d (mm), and a focal length is When f (mm), the following equation is satisfied.
- the optical pickup device according to claim 41 is characterized in that: 26
- a design reference wavelength ⁇ of the objective lens. (Nm) characterized by satisfying the following equation.
- An optical pickup device described in claim 42 is characterized in that, in the invention described in any one of claims 21 to 41, the following expression is satisfied.
- XI Optical axis between the plane perpendicular to the optical axis and in contact with the vertex of the optical surface on the light source side, and the optical surface on the light source side at the outermost periphery of the effective diameter (the position on the light source side where the marginal ray of NA is incident).
- X 2 a plane perpendicular to the optical axis and in contact with the vertex of the optical surface on the optical information recording medium side, and light at the outermost periphery of the effective diameter (the position on the optical information recording medium side on which the marginal ray of NA is incident).
- N the design reference wavelength ⁇ . Refractive index of the objective lens at
- the optical information recording / reproducing apparatus comprising: a light source; and a light collecting optical system including an objective lens for condensing a light beam emitted from the light source on an information recording surface of an optical information recording medium.
- An optical pickup device capable of performing information recording, Z or reproduction by condensing a light beam from the light source on an information recording surface of an optical information recording medium.
- the objective lens is a plastic single lens, and an image-side numerical aperture of the objective lens required for recording and / or reproducing information on / from the optical information recording medium. NA, said pair When the focal length of the 27-object lens is f (mm), the following formula is satisfied.
- the optical information recording / reproducing apparatus is the invention according to claim 43, wherein the first ambient temperature T is set.
- the objective lens has a wavelength which is a design reference wavelength.
- the RMS value of the residual aberrations of the objective lens of the time that light was made to enter with the (nm) W ( ⁇ ., ⁇ 0) and, at ambient temperature under a second atmospheric temperature T 1 5 5 ° C, the Wavelength for objective lens.
- ⁇ f B I f ⁇ ( ⁇ ⁇ ⁇ ⁇ ) one f B (; L 0 , T 0 )
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 3. 47.
- the optical information recording / reproducing apparatus according to claim 46 wherein in the invention according to any one of claims 43 to 45, the objective lens transmits a divergent light beam emitted from the light source on the information recording surface.
- the operation and effect of the present invention are as described in claim 4 The effect is the same as that of Item 28.
- the p-optical information recording / reproducing device is characterized in that, in the invention according to claim 46, when the imaging magnification of the objective lens is m, the following expression is satisfied.
- the optical information recording / reproducing apparatus further comprising: a light source; and a light collecting optical system including an objective lens for condensing a light beam emitted from the light source on an information recording surface of the optical information recording medium.
- An optical pickup device capable of performing information recording, Z or reproduction by condensing a light beam from the light source on an information recording surface of an optical information recording medium.
- the objective lens is composed of a plurality of transmissive lenses, and adjacent ring zones are formed so as to generate a predetermined optical path difference with respect to incident light.
- NA On at least one optical surface, wherein the image-side numerical aperture of the objective lens required for recording and / or reproducing information on the optical information recording medium is NA, Of the objective lens
- the focal length is f (mm)
- the optical information recording / reproducing apparatus according to claim 50 is the invention according to claim 49, wherein the annular structure is a diffraction structure having a function of diffracting predetermined incident light, and The lens is characterized in that a converging wavefront for converging light on the information recording surface is formed by a combined effect of a diffraction effect and a refraction effect.
- the operation and effect of the present invention are the same as those of the invention described in claim 7. 29
- the optical information recording / reproducing apparatus according to claim 51 wherein in the invention according to claim 50, when the wavelength of the incident light changes to a longer wavelength side, the objective lens has a spherical aberration.
- the optical information recording / reproducing apparatus according to claim 52 is the optical information recording / reproducing apparatus according to claim 50 or 51, wherein an optical path difference b added to a wavefront transmitted through the diffractive structure is determined from an optical axis. As a function of height h (mm),
- eh. (nm) is the design reference wavelength of the objective lens
- h MAX is the maximum effective diameter height (mm) of the optical surface on which the diffraction structure is formed
- m is the imaging magnification of the objective lens.
- the optical information recording / reproducing device is the invention according to claim 49, wherein the orbicular zone structure is formed by displacing adjacent orbicular zones in the optical axis direction. in Rukoto produces said predetermined optical path difference to an incident light, the objective lens, c advantages of the present invention and forming a converging wavefront which converges on the information recording surface by the refractive action Is the same as the function and effect of the invention described in claim 10.
- the optical information recording / reproducing apparatus is the invention according to claim 53, wherein the objective lens is formed so as to be displaced inward from an annular zone adjacent to a side closer to an optical axis.
- the ring formed by being displaced inward from the band is formed closer to the optical axis than the ring formed by being displaced outside than the ring adjacent to the optical axis. It is characterized by that.
- the operation and effect of the present invention are the same as those of the invention described in claim 11. 30.
- the optical information recording / reproducing apparatus is characterized in that, in the invention according to claim 53 or 54, the total number of the orbicular zones is 3 or more and 20 or less.
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 12.
- the optical information recording / reproducing apparatus according to claim 56 is the optical information recording / reproducing apparatus according to any one of claims 53 to 55, wherein the effective diameter maximum height of the optical surface on which the annular structure is formed is determined.
- any step in the optical axis direction at the boundary between adjacent zones is the amount of any step Is ⁇ ( ⁇ ), and the design reference wavelength of the objective lens.
- Nij is an integer of 2 or more.
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 13.
- the operation and effect of the present invention are the same as the operation and effect of the invention described in claim 14.
- the optical information recording / reproducing device described in claim 58 is preferably such that the following expression is satisfied in the invention described in claim 57.
- the optical information recording / reproducing apparatus is the invention according to claim 59, wherein the imaging magnification of the objective lens is m. In this case, the following equation is satisfied.
- the optical information recording / reproducing device is the invention according to claim 59 or 60, wherein the objective lens And the light source is an actuator unit and at least is driven for tracking.
- the operation and effect of the present invention are the same as those of the invention described in claim 26.
- the optical information recording / reproducing apparatus is the invention according to any one of claims 43 to 61, wherein a lens thickness on the optical axis of the objective lens is d (mm), When the focal length is f (mm), the following formula is satisfied.
- the optical information recording / reproducing apparatus is characterized in that: 32
- a design reference wavelength of the objective lens. (Nm) characterized by satisfying the following equation.
- An optical information recording / reproducing apparatus is characterized in that, in the invention according to any one of claims 43 to 63, the following expression is satisfied.
- XI Optical axis between the plane perpendicular to the optical axis and in contact with the vertex of the optical surface on the light source side, and the optical surface on the light source side at the outermost periphery of the effective diameter (the position on the light source side where the marginal ray of NA is incident).
- X 2 a plane perpendicular to the optical axis and in contact with the vertex of the optical surface on the optical information recording medium side, and light at the outermost periphery of the effective diameter (the position on the optical information recording medium side on which the marginal ray of NA is incident).
- N refractive index of the objective lens at the design reference wavelength ⁇ 0
- FIG. 1 is a schematic diagram showing an objective lens 1 of the present embodiment
- FIG. 2 is a schematic diagram showing the objective lens 4 of the present embodiment
- Figure 3 is a diagram showing the wavefront of a biconvex plastic single lens with two aspheric optical surfaces when the temperature rises by 30 ° C from the design reference temperature.
- FIG. 4 shows the structure of the optical pickup device (optical information recording / reproducing device) according to the first embodiment.
- FIG. 5 is a diagram for explaining the pack focus fB
- FIG. 6 is a diagram schematically showing a configuration of an optical pickup device (optical information recording / reproducing device) according to the second embodiment.
- FIG. 1 is a schematic view showing an objective lens 1 according to the present embodiment, in which (A) is a front view, (B) is a side view, and (C) is a partially enlarged view of a side face.
- the objective lens 1 is applied to, for example, an optical pickup device for recording / reproducing a high-density DVD or MO using a short-wavelength light source such as a blue-violet semiconductor laser. It has the function of condensing light on the information recording surface of the laser.
- the objective lens 1 is a biconvex plastic single lens having two aspherical optical surfaces 2 and 3, and has one optical surface 2 centered on the optical axis as shown in FIG. 1 (A).
- An annular structure as a diffraction structure on the concentric circles is formed.
- this annular zone structure has a step ⁇ in the optical axis direction at the boundary of each annular zone like a Fresnel lens.
- the laser beam incident on an arbitrary zone of this zone structure has a width in the direction perpendicular to the optical axis of the zone (in this specification, the width of the zone in the direction perpendicular to the optical axis is referred to as “zone”. Diffraction in the direction determined by the pitch).
- This annular structure has spherical aberration characteristics such that when the wavelength of the incident light changes to the longer wavelength side, the spherical aberration changes in a direction in which correction is insufficient. Because the refractive index of plastic single lenses decreases as the temperature rises. The spherical aberration changes in the over-capture direction.
- the oscillation wavelength of a semiconductor laser changes in the direction in which it becomes longer due to a rise in temperature. For example, in a blue-violet semiconductor laser, the oscillation wavelength changes by +0.05 nm / ° C due to a rise in temperature, so if the temperature rises by +30 ° C, the 1.5 nm wavelength changes to the longer wavelength side. I do.
- the objective lens has a spherical aberration characteristic such that the spherical aberration changes in a direction in which the correction becomes insufficient. Changes in spherical aberration, which are overcorrected due to changes in the refractive index due to temperature rise, are insufficiently corrected due to changes in the oscillation wavelength of the semiconductor laser due to temperature rise It can be canceled by the change of the spherical aberration which becomes 34.
- the amount of chromatic spherical aberration must be set large, and the oscillation wavelength deviated from the reference wavelength due to manufacturing errors. Semiconductor lasers cannot be used. Therefore, in the objective lens 1, in order to reduce the amount of correction of the temperature aberration, the focal length is set so as to satisfy the expression (8) or the expression (13A). The balance between the two is set so that the amount of aberrations satisfy the equations (11) to (13), respectively. Even though the plastic single lens has a high NA, temperature aberration and chromatic spherical aberration Both are good lenses.
- FIG. 2 is a schematic view showing an objective lens 4 according to another embodiment, (A) is a front view, and (B) is a side view.
- the objective lens 4 is applied to an optical pickup device for recording / reproducing a high-density DVD or MO using a short-wavelength light source such as a blue-violet semiconductor laser, and emits light from the light source. It has the function of condensing the laser light on the information recording surface of the optical disk.
- a short-wavelength light source such as a blue-violet semiconductor laser
- the objective lens 4 is a biconvex plastic single lens having two aspherical optical surfaces 5 and 6, and has one optical surface 5 centered on the optical axis as shown in FIG. 2 (A).
- a concentric annular zone structure is formed.
- This annular zone structure has a step ⁇ in the optical axis direction at the boundary of each annular zone, and each step ⁇ at 25 ° C, which is the design reference temperature, causes the laser beam transmitted through the adjacent annular zone to have a wavelength
- the optical path difference is determined to be different by an integral multiple.
- this annular zone structure further includes an annular zone that is displaced in the optical axis direction so that the optical path length is shorter than that of the inner zone. And at least one annular zone formed by being displaced in the optical axis direction so that the optical path length is longer than that of the annular zone, and the optical path length is shorter than the inner annular zone.
- the annular zone formed by being displaced in the optical axis direction is closer to the optical axis than the annular zone formed by being displaced in the optical axis direction so that the optical path length is longer than the inner adjacent annular zone. It is formed on the side.
- Fig. 3 is a diagram showing the appearance of the wavefront of a biconvex plastic single lens having two aspheric optical surfaces when the temperature rises by 30 ° C from the design reference temperature, and the horizontal axis in Fig. 3 Represents the effective radius of the optical surface, and the vertical axis represents the optical path difference.
- a plastic single lens spherical aberration occurs due to the effect of a change in the refractive index due to a rise in temperature, and the wavefront changes as shown by the diagram Ag in Fig. 3.
- the diagram B g in FIG. 3 shows the optical path difference added to the transmitted wavefront by the ring zone structure determined as described above, and the diagram C g in FIG. 3 shows 30 ° from the design reference temperature.
- This figure shows the appearance of the wavefront transmitted through such a ring-shaped structure and a plastic single lens when the C temperature rises. From the diagram B g and the diagram, the wavefront transmitted through the transport zone structure and the wavefront of the plastic single lens when the temperature rises by 30 ° C from the design reference temperature cancel each other, and the information recording on the optical disk is performed.
- the wavefront of the laser light condensed on the surface becomes a good wavefront with no optical path difference macroscopically, and it can be understood that such a ring-shaped structure corrects the temperature aberration of the plastic single lens.
- the temperature is corrected. If aberrations were to be corrected completely, the amount of chromatic spherical aberration would be too large, and a semiconductor laser whose oscillation wavelength deviated from the reference wavelength could not be used due to manufacturing errors.
- the focal length is set so as to satisfy the expression (8) or (13A), and the correction of the temperature aberration and the spherical aberration of the color are further performed.
- the balance between the two is made so that the amount of generation of each lens satisfies the formulas (1 1) to (13). And a chromatic spherical aberration are both good lenses.
- FIG. 4 is a diagram schematically showing the configuration of an optical pickup device (optical information recording / reproducing device) equipped with an objective lens according to the present invention.
- the optical pickup device 7 has a semiconductor laser 8 as a light source and an objective lens 9.
- the semiconductor laser 8 is a GaN-based violet semiconductor laser that generates light having a wavelength of about 400 nm.
- a light source that emits light having a wavelength of about 400 nm is used.
- an SHG blue-violet laser may be used.
- the objective lens 9 is a plastic single lens whose focal length satisfies the expression (2). Either 1 or objective lens 4 in FIG.
- the objective lens 9 has a flange portion 9A having a surface extending perpendicularly to the optical axis. With the flange portion 9A, the objective lens 9 can be attached to the optical pickup device 7 with high accuracy.
- the numerical aperture of the objective lens 9 on the optical disk 10 side is set to 0.80 or more.
- the divergent light beam emitted from the semiconductor laser 8 passes through the polarizing beam splitter 11, passes through a collimator lens 12 and a quarter-wave plate 13, and becomes a parallel light beam of circularly polarized light.
- the light flux diameter is regulated by the above, and the objective lens 9 becomes a spot formed on the information recording surface 10B via the protective layer 10A of the optical disk 10 which is a high-density DVD.
- the objective lens 9 is subjected to focus control and tracking control by an actuator 15 arranged around the objective lens 9.
- the reflected light beam modulated by the information pit on the information recording surface 10 B again passes through the objective lens 9, the aperture 14, the 1Z4 wave plate 13, and the collimating lens 12, and then becomes a convergent light beam, and is polarized.
- the light is reflected by the beam splitter 11, passes through the cylindrical lens 16 and the concave lens 17, is given astigmatism, and converges on the photodetector 18. Then, information recorded on the optical disk 10 can be read using the output signal of the photodetector 18.
- FIG. 6 is a diagram schematically showing the configuration of another optical pickup device (optical information recording / reproducing device) equipped with the objective lens according to the present invention.
- the optical pickup device 7 ' has a semiconductor laser 8 as a light source and an objective lens 9.
- the semiconductor laser 8 is a GaN-based blue-violet semiconductor laser that generates light having a wavelength of about 400 nm. Further, in addition to the GaN blue-violet laser described above, the SHG blue-violet laser may be used as a light source that generates light having a wavelength of about 400 nm.
- the objective lens 9 has a focal length of ( 6 A) A plastic single lens which satisfies the formula, any one of the objective lens 1 and the objective lens 4 described above, and the semiconductor laser 8 This is a finite conjugate type objective lens that converges the divergent light beam emitted from 37 onto the information recording surface 10B via the protective layer 10A of the optical disk 10 which is a high-density DVD.
- the objective lens 9 has a flange portion 9A having a surface extending perpendicularly to the optical axis, and the objective lens 9 can be accurately attached to the optical pickup device 7 by the flange group 9A.
- the numerical aperture of the objective lens 9 on the optical disk 10 side is set to 0.80 or more.
- the divergent light beam emitted from the semiconductor laser 8 passes through the polarizing beam splitter 11 and becomes circularly polarized light via the quarter-wave plate 13. Then, the light beam diameter is regulated by the aperture 14, and the The lens 9 serves as a spot formed on the information recording surface 10B via the protective layer 1OA of the optical disk 10 which is a low-density DVD.
- the reflected light flux modulated by the information pit on the information recording surface 10 B again passes through the objective lens 9, the aperture 14, and the 14-wave plate 13, and is then reflected by the polarization beam splitter 11.
- the astigmatism is given by passing through the cylindrical lens 16 and the concave lens 17, and converges on the photodetector 18. Then, information recorded on the optical disk 10 can be read using the output signal of the photodetector 18.
- the optical pickup device 7 ′ includes a semiconductor laser 8, an objective lens 9, a polarizing beam splitter 11, a 1 wavelength plate 13, a cylindrical lens 16, a concave lens 17, and a photodetector 18. They are modularized on a substrate, and are driven together by an actuator 19 in tracking control. Next, six examples that are suitable for the above-described embodiment will be presented. Examples 1 to 6 are objective lenses applied to an optical pickup device for a high-density DVD having a wavelength of 405 nm used for recording / reproducing information and a protective layer having a thickness of 0.1 mm.
- Example 1 is a plastic single lens in which the amount of occurrence of temperature aberration and axial chromatic aberration is suppressed to a small value by setting the focal length so as to satisfy the expression (2).
- This is a plastic single lens whose temperature aberration has been corrected by the action of the annular structure formed on the (optical surface on the light source side).
- Example 4 is a finite conjugate type plastic single lens in which the amount of temperature aberration and axial chromatic aberration is kept small by setting the focal length so as to satisfy the expression (6A).
- 6 are finite conjugate-type positive lenses whose temperature aberration is corrected by the action of the annular structure formed on the first surface (optical surface on the light source side). 38 tick single lens.
- Table 4 shows the lens data of the objective lens of Example 1
- Table 5 shows the lens data of the objective lens of Example 2
- Table 6 shows the lens data of the objective lens of Example 3.
- r (mm) is the radius of curvature
- d (mm) is the surface spacing
- N 405 is the bending ratio at a wavelength of 405 nm
- d is the d-line. Indicates Abbe number.
- Table 7 In Table 7, when calculating the temperature aberration, the rate of change of the refractive index due to the temperature rise of the plastic lens is assumed to be 9.0 x 10 and the rate of change of the wavelength of the incident light due to the temperature rise is + 0.05 nmZ ° C, the wavefront yield when mode hopping occurs
- the amount of wavelength change due to mode hobbing of the blue-violet semiconductor laser is assumed to be +1 nm, and the focus position of the objective lens is fixed at the best image plane position of 405 nm.
- f B E., T 0
- f B ⁇ 0.0762 mm
- f B ⁇ 0.0766 mm
- ⁇ ⁇ ⁇ 0.04 mm.
- the pack focus f B is, as shown in FIG. 5, the optical axis between the optical surface S 2 of the objective lens on the optical information recording medium side and the light beam incident surface S IN of the optical information recording medium. Refers to the interval above.
- This is an objective lens suitable as the objective lens 1 in the above-described embodiment.
- the first surface of the objective lens of Example 2 has a zone structure as a diffraction structure having a step ⁇ of about 0.7 111 to 1.2 / xm in the optical axis direction at the boundary.
- the first-order diffracted light is generated so as to have the maximum amount of diffracted light (ie, this ring).
- the band structure is optimized at a wavelength of 405 nm and the diffraction order is 1), and the diffraction effect of this ring structure corrects the temperature aberration well.
- the first surface of the objective lens of Example 3 which is a suitable objective lens as the objective lens 4 in the above-described embodiment, is approximately 1.5 ⁇
- Six orbital structures having a step difference of 2.3 ⁇ m to 2.3 ⁇ m are formed within the effective diameter, and the temperature aberration is favorably corrected by the action of the orbicular structure.
- the focal length was set so as to satisfy Equation (8) in order to reduce the amount of correction of temperature aberration.
- correction of temperature aberration and spherical aberration of chromaticity were performed.
- the lens is designed with a balance between the two to satisfy the equations (11) to (13), respectively, so that the temperature aberration and the color As shown in Table 9, both lenses have good spherical aberration.
- Table 9 In Table 9, when calculating the temperature aberration, the rate of change of refractive index caused on the rise temperature of the plastic lens - 9.0 and X 1 0- 5, the wave length of the incident light with increasing temperature The rate of change is +0.05 n mZ ° C.
- Table 11 shows the lens data of the objective lens of Example 5, and Table 15 shows the lens data of Example 6. 44 Shows the night.
- r (mm) is the radius of curvature
- d (mm) is the surface spacing
- N405 is the bending ratio Vd at the wavelength of 405 nm
- Vd is the d-line Indicates Abbe number.
- Example 4 is a plastic single lens having a focal length of 0.30 mm, NA of 0.85, a design reference wavelength of 405 nm, an imaging magnification of 0, 084, and a design reference temperature of 25 ° C.
- the stop diameter is 0.532 mm. Since the focal length is set to satisfy Equation (6A), the temperature aberration and the wavefront aberration when mode hopping occurs are shown in Table 12 even though it is a finite conjugate plastic single lens with high NA. Thus, both are good lenses.
- Example 5 is a plastic single lens with a focal length of 0.40 mm, NA of 0.85, a design reference wavelength of 405 nm, an imaging magnification of 0.083, and a design reference temperature of 25 ° C. It is an objective lens suitable as the objective lens 1 in the embodiment.
- the stop diameter is 0.708 mm.
- the first surface of the objective lens of Example 5 had a diffraction structure having a step difference of about 0.7 i ⁇ m to l.l / zm in the optical axis direction at the boundary.
- Example 4 0.028 Arms 0.024Arms
- AW 1 0.01 8 rms.
- the focal length was set so as to satisfy the expression (13 A), and the correction of temperature aberration and the amount of generation of chromatic spherical aberration were performed.
- the correction of temperature aberration and the amount of generation of chromatic spherical aberration were performed.
- Example 6 is a plastic single lens having a focal length of 0.40 mm NA 0.85, a design reference wavelength of 405 nm, an imaging magnification of 0.083, and a design reference temperature of 25 ° C.
- This is an objective lens suitable as the objective lens 4 in the form (1).
- the stop diameter is 0.772 mm.
- the first side of the objective lens of Example 6 is a replacement sheet (Rule 26) 49/1
- the objective lens of the sixth embodiment has a focal length that is small in order to reduce the amount of correction for temperature aberration.
- Equation (6A) is set, and the balance between the two is set so that the correction of temperature aberration and the amount of generation of chromatic spherical aberration satisfy Equations (11) to (13), respectively.
- Equation (12) both lenses have a good temperature and chromatic spherical aberration, despite being a high NA finite conjugate type plastic single lens.
- Example 5 0 5 3 8 51
- Example 6 0.558 Industrial Applicability
- a plastic single lens applicable as an objective lens of an optical pickup device using a high NA objective lens, wherein a usable temperature range is sufficiently wide, and a mode hopping of a light source is performed. It is possible to provide a plastic single lens with small deterioration in light-collecting performance, thereby providing a high-performance optical pickup device and optical information recording / reproducing device.
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- General Physics & Mathematics (AREA)
- Lenses (AREA)
- Optical Head (AREA)
- Optical Recording Or Reproduction (AREA)
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020057003182A KR101061347B1 (ko) | 2002-08-28 | 2003-08-28 | 광픽업 장치용 대물 렌즈, 광픽업 장치 및 광정보 기록 재생 장치 |
AU2003257582A AU2003257582A1 (en) | 2002-08-28 | 2003-08-28 | Object lens for optical pickup device, optical pickup device and optical information recording/reproducing device |
US10/525,660 US7606136B2 (en) | 2002-08-28 | 2003-08-28 | Object lens for optical pickup device, optical pickup device and optical information recording/reproducing device |
EP03791401A EP1544652A4 (en) | 2002-08-28 | 2003-08-28 | OBJECTIVE LENS FOR AN OPTICAL IMAGE SENSOR, OPTICAL IMAGE SENSOR AND OPTICAL INFORMATION RECORDING / REPRODUCING DEVICE |
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002-248207 | 2002-08-28 | ||
JP2002248207 | 2002-08-28 | ||
JP2002-379657 | 2002-12-27 | ||
JP2002379657 | 2002-12-27 | ||
JP2003042269A JP2004252135A (ja) | 2002-08-28 | 2003-02-20 | 光ピックアップ装置用の対物レンズ、光ピックアップ装置及び光情報記録再生装置 |
JP2003-42269 | 2003-02-20 |
Publications (1)
Publication Number | Publication Date |
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WO2004021065A1 true WO2004021065A1 (ja) | 2004-03-11 |
Family
ID=31982122
Family Applications (1)
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PCT/JP2003/010994 WO2004021065A1 (ja) | 2002-08-28 | 2003-08-28 | 光ピックアップ装置用の対物レンズ、光ピックアップ装置及び光情報記録再生装置 |
Country Status (8)
Country | Link |
---|---|
US (2) | US7606136B2 (ja) |
EP (1) | EP1544652A4 (ja) |
JP (1) | JP2004252135A (ja) |
KR (1) | KR101061347B1 (ja) |
CN (1) | CN100357780C (ja) |
AU (1) | AU2003257582A1 (ja) |
TW (2) | TW200814036A (ja) |
WO (1) | WO2004021065A1 (ja) |
Families Citing this family (20)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2004252135A (ja) * | 2002-08-28 | 2004-09-09 | Konica Minolta Holdings Inc | 光ピックアップ装置用の対物レンズ、光ピックアップ装置及び光情報記録再生装置 |
WO2005101393A1 (ja) * | 2004-04-13 | 2005-10-27 | Konica Minolta Opto, Inc. | 光ピックアップ装置用の対物光学系、光ピックアップ装置、光情報記録媒体のドライブ装置、集光レンズ、及び光路合成素子 |
JP4529176B2 (ja) * | 2005-02-02 | 2010-08-25 | コニカミノルタオプト株式会社 | 光ピックアップ装置 |
KR100724772B1 (ko) * | 2005-09-27 | 2007-06-04 | (주)아이엠 | 하이브리드렌즈의 수차보정방법 |
US7885167B2 (en) * | 2005-11-29 | 2011-02-08 | Konica Minolta Opto, Inc. | Objective lens for optical pickup apparatus, objective lens unit for optical pickup apparatus and optical pickup apparatus using the same |
DE602007001995D1 (de) | 2006-04-06 | 2009-10-01 | Daewoo Electronics Corp | Optisches Informationswiedergabegerät und optisches Informationswiedergabeverfahren damit |
US7889220B2 (en) * | 2006-10-31 | 2011-02-15 | Hewlett-Packard Development Company, L.P. | Device and method for maintaining optical energy density on a medium |
JP2010511262A (ja) * | 2006-11-27 | 2010-04-08 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | 走査デバイス用のレンズシステム |
JP4823114B2 (ja) * | 2007-03-23 | 2011-11-24 | 三洋電機株式会社 | 光ディスク装置 |
JP4193914B1 (ja) | 2007-04-27 | 2008-12-10 | コニカミノルタオプト株式会社 | 光ピックアップ装置用の対物レンズ及び光ピックアップ装置 |
WO2009066687A1 (ja) * | 2007-11-21 | 2009-05-28 | Konica Minolta Opto, Inc. | 対物レンズ及び撮像レンズ |
JP2009217925A (ja) * | 2008-02-12 | 2009-09-24 | Hoya Corp | 光学素子および光情報記録再生装置用対物光学系 |
JP5363951B2 (ja) * | 2008-11-19 | 2013-12-11 | Hoya株式会社 | 光情報記録再生装置 |
JP2010153016A (ja) * | 2008-11-19 | 2010-07-08 | Hoya Corp | 光情報記録再生装置用対物レンズ、および光情報記録再生装置 |
US8121012B2 (en) | 2008-11-19 | 2012-02-21 | Hoya Corporation | Objective lens and optical information recording/reproducing apparatus |
JP5180138B2 (ja) * | 2009-04-13 | 2013-04-10 | 日立マクセル株式会社 | 光ピックアップレンズ |
US8786965B2 (en) | 2009-09-30 | 2014-07-22 | Konica Minolta Opto, Inc. | Die processing method, die, objective lens, and optical pick-up device |
CN102054490B (zh) * | 2009-10-29 | 2015-01-28 | Hoya株式会社 | 光学拾取头的光学系统和光学信息记录/再现装置 |
CN104880753B (zh) * | 2015-05-05 | 2018-07-20 | 清华大学深圳研究生院 | 用于制作菲涅尔光栅的优化设计方法 |
WO2020110525A1 (ja) * | 2018-11-30 | 2020-06-04 | パナソニックIpマネジメント株式会社 | 対物レンズ及び光ヘッド装置及び光情報装置と光ディスクシステム |
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2003
- 2003-02-20 JP JP2003042269A patent/JP2004252135A/ja active Pending
- 2003-08-28 TW TW096130953A patent/TW200814036A/zh not_active IP Right Cessation
- 2003-08-28 AU AU2003257582A patent/AU2003257582A1/en not_active Abandoned
- 2003-08-28 US US10/525,660 patent/US7606136B2/en not_active Expired - Fee Related
- 2003-08-28 TW TW092123779A patent/TW200411649A/zh not_active IP Right Cessation
- 2003-08-28 CN CNB038205424A patent/CN100357780C/zh not_active Expired - Fee Related
- 2003-08-28 WO PCT/JP2003/010994 patent/WO2004021065A1/ja active Application Filing
- 2003-08-28 EP EP03791401A patent/EP1544652A4/en not_active Withdrawn
- 2003-08-28 KR KR1020057003182A patent/KR101061347B1/ko active IP Right Grant
-
2009
- 2009-09-01 US US12/551,834 patent/US7920456B2/en not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
---|---|
US20050254399A1 (en) | 2005-11-17 |
KR20050058522A (ko) | 2005-06-16 |
TWI338891B (ja) | 2011-03-11 |
US7920456B2 (en) | 2011-04-05 |
TW200814036A (en) | 2008-03-16 |
JP2004252135A (ja) | 2004-09-09 |
EP1544652A4 (en) | 2009-12-02 |
TWI344645B (ja) | 2011-07-01 |
EP1544652A1 (en) | 2005-06-22 |
AU2003257582A1 (en) | 2004-03-19 |
TW200411649A (en) | 2004-07-01 |
US20100054108A1 (en) | 2010-03-04 |
US7606136B2 (en) | 2009-10-20 |
CN1678935A (zh) | 2005-10-05 |
KR101061347B1 (ko) | 2011-08-31 |
CN100357780C (zh) | 2007-12-26 |
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