WO2011065276A1 - 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 - Google Patents
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 Download PDFInfo
- Publication number
- WO2011065276A1 WO2011065276A1 PCT/JP2010/070552 JP2010070552W WO2011065276A1 WO 2011065276 A1 WO2011065276 A1 WO 2011065276A1 JP 2010070552 W JP2010070552 W JP 2010070552W WO 2011065276 A1 WO2011065276 A1 WO 2011065276A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- objective lens
- lens
- information recording
- transparent substrate
- max
- Prior art date
Links
Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
-
- 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
-
- 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
- G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
- G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
- G11B2007/0013—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage for carriers having multiple discrete layers
Definitions
- the present invention relates to an objective lens for an optical pickup device and an optical pickup device capable of recording and / or reproducing information with respect to an optical disc having three or more information recording surfaces in the thickness direction.
- a high-density optical disk system that performs information recording and / or reproduction (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm is known.
- Patent Document 1 the magnification of the objective lens is changed by moving a coupling lens arranged between the light source and the objective lens in the optical axis direction, and the selected information recording surface is tertiary.
- An optical pickup device capable of condensing a light beam with reduced spherical aberration is disclosed.
- Patent Document 2 discloses a BD plastic objective lens having two information recording surfaces. The operation of changing the information recording surface on which information is to be recorded / reproduced from one information recording surface to another information recording surface may be referred to as “focus jump” in this specification.
- the objective lens is tilted along the radial direction and / or tangential direction of the optical disc (in this specification, the lens tilt).
- the coma that occurs due to the warp or tilt of the optical disc (referred to as disc tilt in this specification) can be canceled. Therefore, if the amount of coma generated when the lens is tilted is small, the amount of lens tilt required to correct the coma due to disc tilt increases, so it is necessary to ensure a sufficiently large dynamic range of the lens tilt. As a result, problems such as an increase in the size of the optical pickup device and an increase in power consumption of the actuator occur.
- the coupling lens when recording / reproducing information on the information recording surface L0 (100 ⁇ m) having the thicker transparent substrate, the coupling lens is moved in the optical axis direction. As a result, the divergent light beam enters the objective lens, so that the coma aberration amount when the lens is tilted is smaller than when the parallel light beam is incident.
- an objective lens made of a plastic material is used to achieve a high NA, spherical aberration is generated in a beam spot due to a temperature change (referred to as temperature aberration in this specification).
- a plastic having a focal length of 1.41 mm The amount of change in spherical aberration due to a 30 ° C.
- the change in the objective lens made of material is about 100 m ⁇ rms, which exceeds the Marshall limit value of 70 m ⁇ rms.
- the conventional DVD has an NA of about 0.60 to 0.67, so that the amount of spherical aberration caused by temperature change is relatively small, and it is not necessary to correct this spherical aberration.
- the spherical aberration is proportional to the fourth power of NA, and the amount of spherical aberration generated by the temperature change becomes large. Therefore, in a BD optical pickup device equipped with a plastic objective lens, it is necessary to correct temperature aberration by moving the coupling lens in the optical axis direction.
- the optical pickup device for BD when the environmental temperature becomes high while recording / reproducing information on the information recording surface L0 using the plastic objective lens, Since the degree of divergence of incident light to the objective lens is further increased, the amount of coma aberration when the lens is tilted is further reduced, and coma aberration due to disc tilt cannot be corrected well.
- Patent Document 2 discloses a BD plastic objective lens having two information recording surfaces.
- the environmental temperature can be high (55 degrees).
- the cover glass thickness for correcting the spherical aberration to zero is made thicker than L0.
- the magnification at the time (design magnification) is negative (incident divergent light). Further, the sine condition in the design magnification is corrected in the entire region within the effective radius.
- the objective lens of Patent Document 2 is suitable for condensing a light beam on the information recording surface of a BD having three or more layers, where the maximum difference in the transparent substrate thickness of the information recording surface is larger than that of the two layers of BD.
- the objective lens of Patent Document 2 requires a large amount of movement of the coupling lens at the time of focus jump, and is therefore used for a thin optical pickup device. Not suitable for.
- the present invention has been made in consideration of the above-mentioned problems, and the amount of movement of the coupling lens can be reduced without causing high-order spherical aberration such as fifth-order spherical aberration to remain even at the time of focus jump. It is another object of the present invention to provide an objective lens for an optical pickup device and an optical pickup device capable of recording / reproducing information with respect to an optical disc having a multi-layer information recording surface at a low cost.
- the “transparent substrate thickness” is the distance from the light beam incident surface of the optical disc to the information recording surface.
- each information recording surface is transparent. The substrate thickness will be different from each other.
- the correction state of the spherical aberration is determined so that the objective lens for the optical pickup is combined with a transparent substrate having a predetermined thickness so that the spherical aberration ( ⁇ rms) is minimized.
- a transparent substrate having a predetermined thickness is referred to as a cover glass
- the thickness of the predetermined transparent substrate is referred to as a cover glass thickness or a design cover glass thickness.
- the cover glass thickness at the time of design may be the same as or different from the transparent substrate thickness of any information recording surface of the optical disc.
- cover glass when describing the characteristics of the objective lens, the term “cover glass” is used to distinguish it from the “transparent substrate” of the optical disk.
- cover glass thickness is not limited to glass but may be resin.
- the objective lens according to claim 1 includes a light source that emits a light beam having a wavelength ⁇ 1 (390 nm ⁇ 1 ⁇ 415 nm) and an objective lens, and three or more information recording surfaces having different transparent substrate thicknesses in the thickness direction. Information is recorded and / or reproduced by selecting one of the information recording surfaces of the optical disc having the optical disc and condensing the light beam having the wavelength ⁇ 1 emitted from the light source onto the selected information recording surface by the objective lens.
- An objective lens for an optical pickup device that performs The objective lens is a single lens,
- the image-side numerical aperture (NA) is 0.8 or more and 0.95 or less, Made of plastic material,
- T MAX (mm) the maximum transparent substrate thickness among the transparent substrate thicknesses
- ⁇ rms spherical aberration
- T (mm) the cover glass thickness T (mm) satisfying the expression (1).
- the formula (2) when the magnification M when the T MAX ⁇ 0.85 ⁇ T ⁇ T MAX ⁇ 1.1 (1) -0.003 ⁇ M ⁇ 0.003 (2)
- the sine condition violation amount has a positive maximum value between 70% and 90% of the effective radius.
- At least the following three characteristics are required for an objective lens suitable for a BD having three or more information recording surfaces.
- (Characteristic 2) The amount of movement of the coupling lens when performing a focus jump is small.
- (Characteristic 3) The tilt sensitivity of the objective lens when recording / reproducing information with respect to the information recording surface with the thicker transparent substrate is not too small. In particular, when a plastic objective lens is used, the lens tilt sensitivity when the environmental temperature becomes high during recording / reproduction of information on the information recording surface with the thicker transparent substrate is high. It is necessary not to become too small.
- BD having three or more information recording surfaces (hereinafter referred to as three or more layers) having all the above characteristics (characteristic 1) to (characteristic 3) at a level that can withstand practical use.
- the objective lens suitable for (referred to as BD) was found. This will be described in detail below.
- the present inventors examined a target value to be satisfied by a three-layer or more BD plastic objective lens with respect to coma generated when the lens is tilted.
- some optical pickup devices that record / reproduce information with respect to a two-layer BD have a plastic objective lens mounted on the information recording surface with the thicker transparent substrate.
- Spherical surface by combining a cover glass thickness of 87.5 ⁇ m between L0 (100 ⁇ m) and the information recording surface L1 (75 ⁇ m) of the thinner transparent substrate and zero magnification (corresponding to the case where a parallel light beam is incident). Designed to minimize aberrations.
- the amount of coma generated when the lens is tilted is minimized when information is recorded / reproduced on the information recording surface L0.
- the amount of third-order coma aberration due to the tilt of the objective lens is defined as CM (LT).
- CM LT
- a plastic objective lens for BD having three or more layers can withstand practical use if it is designed so that the minimum amount of coma generated when the lens is tilted is greater than CM (LT). It can be said.
- CM (LT) of the objective lens is about 0.02 ⁇ rms
- CM (DT) generated when the optical disk is tilted by the same amount in the same state and CM (LT) The ratio is about 0.36.
- CM (LT) is satisfied by setting the correction state of the spherical aberration so that the cover glass thickness T when the aberration is minimized is equal to or greater than the lower limit of the expression (1).
- the CM (LT) can be increased as the cover glass thickness T increases.
- the cover glass thickness T exceeds the upper limit of the formula (1), information is recorded on the information recording surface with the thinnest transparent substrate.
- the degree of convergence of the light beam incident on the objective lens becomes too large, and the lens shift characteristic (indicating the amount of aberration generated when the objective lens performs tracking in the optical pickup device) becomes poor. This is not preferable because there is a problem that the residual higher-order spherical aberration increases when the focus jumps to the information recording surface with the thinnest transparent substrate.
- the objective lens according to claim 1 has (Characteristic 1) small residual high-order spherical aberration at the time of focus jump, and (Characteristic 2) small movement amount of the coupling lens at the time of focus jump.
- (Characteristic 3) the lens tilt even when the environmental temperature becomes high during the recording / reproducing of information on the information recording surface having the larger transparent substrate thickness. It has all the characteristics that the sensitivity does not become too small at a level that can withstand practical use. Therefore, by using the objective lens of the present invention, it is possible to provide an optical pickup device for an optical disc having three or more information recording surfaces that is small, low cost, and excellent in recording / reproducing characteristics. It becomes.
- the objective lens according to claim 2 is the invention according to claim 1, wherein the cover glass thickness T (mm) satisfies the following expression (3): T MAX ⁇ 0.85 ⁇ T ⁇ T MAX ⁇ 1.0 (3) It is characterized by that.
- the invention according to the present invention can solve such a larger problem unique to the BD having three or more layers. That is, when the cover glass thickness T satisfies the upper limit of the expression (3), the degree of convergence of the light beam incident on the objective lens becomes too large when information is recorded / reproduced on the information recording surface having the thinnest transparent substrate thickness.
- the objective lens according to claim 3 includes a light source that emits a light beam having a wavelength ⁇ 1 (390 nm ⁇ 1 ⁇ 415 nm) and an objective lens, and three or more information recording surfaces having different transparent substrate thicknesses in the thickness direction. Information is recorded and / or reproduced by selecting one of the information recording surfaces of the optical disc having the optical disc and condensing the light beam having the wavelength ⁇ 1 emitted from the light source onto the selected information recording surface by the objective lens.
- An objective lens for an optical pickup device that performs The objective lens is a single lens,
- the image-side numerical aperture (NA) is 0.8 or more and 0.95 or less, Made of glass material,
- T MAX (mm) the maximum transparent substrate thickness among the transparent substrate thicknesses
- spherical aberration at normal temperature (25 ⁇ 3 ° C.) and the cover glass thickness T (mm) satisfying the expression (4)
- the magnification M when ( ⁇ rms) is minimum satisfies the formula (2), T MAX ⁇ 0.75 ⁇ T ⁇ T MAX ⁇ 1.0 (4) -0.003 ⁇ M ⁇ 0.003 (2)
- the sine condition violation amount has a positive maximum value between 70% and 90% of the effective radius.
- the present inventors set the sine condition violation amount to a positive maximum value between 70% to 90% of the effective radius at the magnification M satisfying the expression (2).
- the present inventors have found that high-order spherical aberration at the time of focus jump can be effectively suppressed.
- the present inventors as a result of the study, have a positive maximum value in which the sine condition violation amount is between 70% and 90% of the effective radius at the magnification M satisfying the expression (2). It has been found that not only can high-order spherical aberration at the time of focus jump be effectively suppressed, but also the amount of change in third-order spherical aberration with respect to the change in magnification can be increased.
- the present inventors examined a target value to be satisfied by a three-layer or more glass objective lens for BD with respect to coma generated when the lens is tilted.
- the glass objective lens since the influence of temperature change can be almost ignored, the degree of divergence of the incident light to the objective lens is not so large as compared with the case where a plastic objective lens is used. Accordingly, it has been found that the cover glass thickness becomes smaller when the spherical aberration ( ⁇ rms) is minimized at the normal temperature (25 ⁇ 3 ° C.) and the magnification satisfying (2), and as a result, the lower limit of the expression (4) is exceeded.
- the target value of the third-order coma aberration generation amount CM (LT) due to the lens tilt is satisfied by setting the correction state of the spherical aberration so that Further, by making the cover glass thickness T not exceed the upper limit of the expression (4), the degree of convergence of the light beam incident on the objective lens when information is recorded / reproduced on the information recording surface with the thinnest transparent substrate thickness. Is prevented from becoming too large, and it is possible to prevent the lens shift characteristic from being deteriorated and the increase in residual higher-order spherical aberration when the focus jump is made to the information recording surface having the thinnest transparent substrate thickness.
- the objective lens according to claim 3 has (Characteristic 1) small residual high-order spherical aberration at the time of focus jump, and (Characteristic 2) small movement amount of the coupling lens at the time of focus jump.
- (Characteristic 3) Even when information is recorded / reproduced on the information recording surface having a larger transparent substrate thickness, the lens shift tilt sensitivity does not become too small, and the lens shift characteristic is improved. It has all the characteristics that it can be kept good at a level that can withstand practical use. Therefore, by using the objective lens of the present invention, it is possible to provide an optical pickup device for an optical disc having three or more information recording surfaces that is small, low cost, and excellent in recording / reproducing characteristics. It becomes.
- the objective lens according to claim 4 is the invention according to claim 3, wherein the cover glass thickness T (mm) satisfies the following expression (5): T MAX ⁇ 0.8 ⁇ T ⁇ T MAX ⁇ 0.95 (5) It is characterized by that.
- the lens shift characteristic can be further improved, and the residual higher-order spherical aberration when the focus jump is made to the information recording surface with the smallest transparent substrate thickness can be further reduced.
- the objective lens according to claim 5 includes a light source that emits a light beam having a wavelength ⁇ 1 (390 nm ⁇ 1 ⁇ 415 nm) and an objective lens, and three or more information recording surfaces having different transparent substrate thicknesses in the thickness direction. Information is recorded and / or reproduced by selecting one of the information recording surfaces of the optical disc having the optical disc and condensing the light beam having the wavelength ⁇ 1 emitted from the light source onto the selected information recording surface by the objective lens.
- An objective lens for an optical pickup device wherein the objective lens is a single lens, the image-side numerical aperture (NA) is not less than 0.8 and not more than 0.95, and is at room temperature (25 ⁇ 3 ° C.
- the thickness of the cover glass when the spherical aberration ( ⁇ rms) is minimized is T (mm), and the focal length of the wavelength ⁇ 1 at room temperature (25 ⁇ 3 ° C.) is f (M )
- the change rate ⁇ SA3 / ( ⁇ M ⁇ f) of the third-order spherical aberration with respect to the product of the focal length f of the objective lens and the magnification change ⁇ M. ( ⁇ rms / mm) satisfies the formula (6). -0.003 ⁇ M ⁇ 0.003 (2) 21 ⁇
- the invention according to claim 5 sets conditions for achieving both suppression of residual high-order spherical aberration at the time of focus jump and suppression of the movement amount of the coupling lens from another viewpoint.
- the value By setting the value to a value larger than the lower limit of the expression (6), the amount of change in the third-order spherical aberration with respect to the change in magnification becomes sufficiently large, the amount of movement of the coupling lens can be reduced, and the higher order when the focus jump occurs. It is possible to prevent the spherical aberration from being insufficiently corrected.
- the value to be smaller than the upper limit of the expression (6), it is possible to prevent the third-order spherical aberration change amount with respect to the magnification change from being excessively large. Can be prevented. That is, by satisfying the expression (6), it is possible to achieve both the suppression of the residual high-order spherical aberration during the focus jump and the suppression of the movement amount of the coupling lens.
- the objective lens according to claim 6 includes a light source that emits a light beam having a wavelength ⁇ (390 nm ⁇ ⁇ 415 nm) and an objective lens, and three or more information recording surfaces having different transparent substrate thicknesses in the thickness direction. Information is recorded and / or reproduced by selecting one of the information recording surfaces of the optical disc having the optical disc and condensing the light beam having the wavelength ⁇ 1 emitted from the light source onto the selected information recording surface by the objective lens.
- An objective lens for an optical pickup device wherein the objective lens is a single lens, the image-side numerical aperture (NA) is not less than 0.8 and not more than 0.95, and is at room temperature (25 ⁇ 3 ° C.
- the cover glass thickness when the spherical aberration ( ⁇ rms) is minimum at the magnification M satisfying the expression (2) is T (mm), the room temperature (25 ⁇ 3 ° C.), and the cover glass Thickness T Te, meet the third-order spherical aberration generating a magnification of the objective lens when varying DerutaSA3 ([lambda] rms) and the fifth-order spherical aberration DerutaSA5 ([lambda] rms) is (7), -0.003 ⁇ M ⁇ 0.003 (2) 4.2 ⁇ SA3 / ⁇ SA5 ⁇ 5.2 (7) It is characterized by that.
- the invention according to claim 6 sets the conditions for achieving both the suppression of the residual high-order spherical aberration at the time of focus jump and the suppression of the movement amount of the coupling lens from another viewpoint.
- the ratio of the third-order spherical aberration change amount and the fifth-order spherical aberration change amount when the magnification is changed does not become too small, and the higher-order spherical aberration when the focus jump occurs. It is possible to prevent overcorrection and to reduce residual high-order spherical aberration.
- the ratio of the third-order spherical aberration change amount and the fifth-order spherical aberration change amount when the magnification is changed does not become too large, and the third-order spherical aberration change with respect to the magnification change.
- the amount does not become too small, the amount of movement of the coupling lens can be reduced, and it is possible to prevent the higher-order spherical aberration from being insufficiently corrected when the focus jump is performed. That is, by satisfying the expression (7), it is possible to achieve both suppression of the residual higher-order spherical aberration at the time of focus jump and suppression of the movement amount of the coupling lens.
- the objective lens according to claim 7 is the invention according to any one of claims 1 to 6, wherein, in the magnification M, the sine condition violation amount is a positive maximum between 70% to 90% of the effective radius.
- the sine condition violation amount does not have a negative maximum value within the effective radius.
- the objective lens according to claim 8 is the invention according to any one of claims 1 to 6, wherein the sine condition violation amount is a positive maximum value between 70% and 90% of the effective radius at the magnification M. Furthermore, the sine condition violation amount has a negative maximum value at a position closer to the optical axis than the positive maximum value.
- the objective lens according to claim 9 is the objective lens according to any one of claims 1 to 8, wherein the objective lens is at room temperature (25 ⁇ 3 ° C.), the cover glass thickness T, and the magnification M.
- the fifth-order coma aberration CM5 ( ⁇ rms) generated when an oblique light beam having a half angle of view of 1 is incident on the lens satisfies the equation (8). 0.02 ⁇
- the objective lens according to claim 10 is a half-screen for the objective lens according to the invention according to claim 9, at a normal temperature (25 ⁇ 3 ° C.), the cover glass thickness T, and the magnification M.
- Third-order coma aberration CM3 ( ⁇ rms) generated when an oblique light beam having an angle of 1 degree is incident satisfies the equation (9). 0 ⁇
- the objective lens according to claim 11 includes a light source that emits a light beam having a wavelength ⁇ (390 nm ⁇ ⁇ 415 nm) and an objective lens, and three or more information recording surfaces having different transparent substrate thicknesses in the thickness direction. Information is recorded and / or reproduced by selecting one of the information recording surfaces of the optical disc having the optical disc and condensing the light beam having the wavelength ⁇ 1 emitted from the light source onto the selected information recording surface by the objective lens.
- the objective lens used in the optical pickup device that performs the above-described objective lens is a single lens, has an image-side numerical aperture (NA) of 0.8 or more and 0.95 or less, and is at room temperature (25 ⁇ 3 ° C.), and at a magnification M satisfying the expression (2), when the cover glass thickness when the spherical aberration ( ⁇ rms) is minimum is T (mm), the cover glass is at room temperature (25 ⁇ 3 ° C.).
- NA image-side numerical aperture
- the invention according to claim 11 sets conditions for achieving both suppression of residual higher-order spherical aberration at the time of focus jump and suppression of the movement amount of the coupling lens from another viewpoint.
- the expression (8) at the magnification M satisfying the expression (2) it is possible to achieve both the suppression of the residual higher-order spherical aberration at the time of the focus jump and the suppression of the movement amount of the coupling lens.
- An objective lens according to a twelfth aspect of the invention according to the eleventh aspect of the present invention is the half-drawing of the objective lens according to the eleventh aspect of the invention at room temperature (25 ⁇ 3 ° C.), the cover glass thickness T, and the magnification M.
- Third-order coma aberration CM3 ( ⁇ rms) generated when an oblique light beam having an angle of 1 degree is incident satisfies the equation (9). 0 ⁇
- the invention according to claim 12 can prevent the lens tilt sensitivity from becoming too small even when information is recorded / reproduced on the information recording surface having the thicker transparent substrate. Further, even if the objective lens is made of plastic, the lens tilt sensitivity is small even when the environmental temperature becomes high during the recording / reproducing of information on the information recording surface having the thicker transparent substrate. Since it can prevent becoming too much, it is preferable.
- the objective lens according to a thirteenth aspect is characterized in that, in the invention according to any one of the fifth to twelfth aspects, the objective lens is made of a plastic material.
- the objective lens according to claim 14 is the invention according to claim 13, wherein when the maximum transparent substrate thickness among the transparent substrate thicknesses is T MAX (mm), the cover glass thickness T is the formula (1). It is characterized by satisfying.
- T MAX ⁇ 0.85 ⁇ T ⁇ T MAX ⁇ 1.1 The objective lens according to claim 15 is the invention according to claim 14, wherein the cover glass thickness T and the magnification M satisfy the expressions (3) and (10).
- T MAX ⁇ 0.85 ⁇ T ⁇ T MAX ⁇ 1.0 (3) M 0 (10) It is characterized by that.
- the objective lens according to claim 16 is characterized in that, in the invention according to any one of claims 5 to 12, the objective lens is made of a glass material.
- the objective lens is made of a glass material, the amount of movement of the coupling lens when the temperature changes can be reduced, so that the amount of movement of the coupling lens can be kept small. Further, (Characteristic 3) When recording / reproducing information on the information recording surface having a larger transparent substrate thickness, the lens tilt sensitivity is not easily reduced even at a high temperature, which is preferable.
- a high output laser light source is often used because there is a strong demand for higher speed. Since the glass material has high durability against blue-violet wavelengths, it is suitable as an objective lens for an optical pickup device.
- the objective lens according to claim 17 is the objective lens according to claim 16, wherein when the maximum transparent substrate thickness among the transparent substrate thicknesses is T MAX (mm), the cover glass thickness T is an expression (4). Meet, T MAX ⁇ 0.75 ⁇ T ⁇ T MAX ⁇ 1.0 (4) It is characterized by that.
- the objective lens according to claim 18 is the invention according to claim 17, wherein the cover glass thickness T and the magnification M satisfy the expressions (5) and (10).
- T MAX ⁇ 0.8 ⁇ T ⁇ T MAX ⁇ 0.95 (5) M 0 (10) It is characterized by that.
- the objective lens according to claim 19 is the invention according to any one of claims 1 to 18, wherein the positive maximum value of the sine condition violation amount is OSC MAX (mm), and is at room temperature (25 ⁇ 3 ° C.).
- the focal length of the wavelength ⁇ 1 is f (mm)
- Equation (11) is satisfied.
- 0.003 ⁇ OSC MAX / f ⁇ 0.022 (11) It is characterized by that.
- the objective lens according to claim 20 is the objective lens according to any one of claims 1 to 3, claim 5 to 17, and claim 19, and has a high temperature (55 ⁇ 3 ° C.) and the maximum transparent substrate thickness.
- the objective lens was tilted in a state where a non-parallel light beam was incident on the objective lens so that the third-order spherical aberration of the focused spot by the objective lens was corrected at a cover glass thickness equal to T MAX .
- the third-order coma aberration CM (LT) ( ⁇ rms) that occurs when the cover glass is tilted by the same amount and the third-order coma aberration CM (DT) ( ⁇ rms) that occurs when the cover glass is tilted satisfy the equation (12). 0.3 ⁇
- the lens tilt sensitivity is small even when the environmental temperature becomes high during the recording / reproducing of information on the information recording surface having the thicker transparent substrate. Since it can prevent becoming too much, it is preferable.
- the objective lens according to claim 21 is the objective lens according to any one of claims 1 to 3, claim 5 to 17, claim 19 or 20, and is at room temperature (25 ⁇ 3 ° C.) and the maximum transparency.
- a cover glass thickness equal to the substrate thickness T MAX
- a magnification M1 in a state in which a non-parallel light beam is incident on the objective lens so as to correct third-order spherical aberration of the focused spot by the objective lens, (25 ⁇ 3 ° C.) and the cover glass thickness equal to the minimum transparent substrate thickness T MIN among the transparent substrate thicknesses, the third-order spherical aberration of the focused spot by the objective lens is corrected.
- the magnification M2 in a state where a non-parallel light beam is incident on the objective lens satisfies the expression (13). 0 ⁇ M1 / M2 ⁇ 0.92 (13) It is characterized by that.
- the cover glass thickness T is between T MAX and T MIN .
- T MAX the one closer to T MAX is preferable.
- Expression (13) What defines the preferable range from the viewpoint of magnification is Expression (13).
- the objective lens according to claim 22 is the invention according to any one of claims 1 to 21, wherein the refractive index N of the objective lens with respect to the wavelength ⁇ 1 at normal temperature (25 ⁇ 3 ° C.) and the optical property on the light source side.
- the inclination angle ⁇ (degrees) in the outermost periphery of the effective diameter of the surface satisfies the equation (14). ⁇ 59.8 ⁇ N + 162 ⁇ ⁇ 59.8 ⁇ N + 166 (14) It is characterized by that.
- the refractive index N of the lens and the inclination angle ⁇ in the outermost periphery of the effective diameter of the optical surface on the object side are constant. It was found to exist within the range of conditions. From the above knowledge, the objective lens of the present invention is defined from the viewpoint of a preferable shape (14).
- the objective lens according to claim 23 is the objective lens according to any one of claims 1 to 22, wherein the minimum transparent substrate thickness among the transparent substrate thicknesses is TMIN, and the maximum transparent substrate thickness among the transparent substrate thicknesses is used.
- T MAX the substrate thickness
- the equation (15) is satisfied. 0.03 (mm) ⁇ T MAX -T MIN ⁇ 0.06 (mm) (15) It is characterized by that.
- the objective lens according to claim 24 is the objective lens according to any one of claims 1 to 23, wherein the refractive index of the objective lens for the wavelength ⁇ 1 at normal temperature (25 ⁇ 3 ° C.) is N, and When the radius height at which the one-time differential X ′ (h) of the aspherical deformation amount X (h) (mm) of the optical surface is switched from negative to positive is H (mm), the expression (16) is satisfied.
- the aspherical deformation amount X (h) is defined by the distance in the optical axis direction from the plane contacting the surface vertex of the optical surface on the optical disk side to the aspherical surface, and is negative when the surface is deformed from the plane to the light source side.
- H is a relative value when the effective radius is 1.
- the refractive index N of the lens and the aspherical deformation amount X (h) (mm) of the optical surface on the image side are 1 It has been found that the radial height H (mm) at which the rotational differential X ′ (h) is switched from negative to positive exists within a certain range of conditions. From this knowledge, the objective lens of the present invention is defined from the viewpoint of a preferable shape, which is the expression (16).
- An optical pickup device includes the objective lens according to any one of the first to twenty-fourth aspects, and a coupling lens that is movable in an optical axis direction, and the coupling lens is disposed in the optical axis direction.
- the information recording surface of the optical disc is selected by moving the optical disc.
- An optical pickup device corresponding to an optical disc having an information recording surface of three or more layers tends to have a large residual high-order spherical aberration at the time of (Problem 1) focus jump, and (Problem 2) coupling at the time of focus jump
- the amount of movement of the lens tends to be large, and (Problem 3) that the lens tilt sensitivity tends to be large when information is recorded / reproduced on the information recording surface of the thicker transparent substrate.
- (Characteristic 1) Focus Residual high-order spherical aberration at the time of jump can be reduced.
- the coupling lens is a single lens.
- the coupling lens has a two-group configuration of a positive lens group and a negative lens group, and at least one of the positive lens groups. Any information recording surface of the optical disk is selected by moving the lens.
- the moving amount of the coupling lens can be further reduced, and a more compact optical pickup device can be provided.
- the optical pickup device has at least one light source (first light source).
- first light source a plurality of types of light sources may be provided so as to support a plurality of types of optical disks.
- the optical pickup device of the present invention has a condensing optical system for condensing at least the first light flux from the first light source on the information recording surface of the first optical disc.
- the condensing optical system condenses the second light beam on the information recording surface of the second optical disk, and the third light beam on the information recording surface of the third optical disk. You may make it condense.
- the optical pickup device of the present invention includes a light receiving element that receives at least a reflected light beam from the information recording surface of the first optical disc.
- the light receiving element receives a reflected light beam from the information recording surface of the second optical disk and receives a reflected light beam from the information recording surface of the third optical disk. Also good.
- object side means the light source side
- image side means the optical disk side.
- the first optical disk has a transparent substrate having a thickness t1 and an information recording surface.
- the second optical disc has a transparent substrate having a thickness t2 (t1 ⁇ t2) and an information recording surface.
- the third optical disc has a transparent substrate having a thickness of t3 (t2 ⁇ t3) and an information recording surface.
- the first optical disc is preferably a BD
- the second optical disc is a DVD
- the third optical disc is preferably a CD, but is not limited thereto.
- the first optical disc has three or more information recording surfaces stacked in the thickness direction.
- the first optical disc has three or more information recording surfaces in the thickness direction that have different distances from the light incident surface of the optical disc to the information recording surface (this is referred to as “transparent substrate thickness” in this specification). It is. Of course, you may have four or more information recording surfaces.
- the second optical disc and the third optical disc may also have a plurality of information recording surfaces.
- the “maximum transparent substrate thickness” means the transparent substrate thickness of the information recording surface farthest from the light incident surface of the optical disc among the plurality of information recording surfaces
- the “minimum transparent substrate thickness” means the optical disc. The thickness of the transparent substrate on the information recording surface closest to the incident surface of the light beam in FIG.
- the optical pickup device selects one of the plurality of information recording surfaces of the first optical disc, and condenses the light beam emitted from the light source onto the selected information recording surface by the objective lens. By doing so, information is recorded and / or reproduced.
- BD means that information is recorded / reproduced by a light beam having a wavelength of about 390 to 415 nm and an objective lens having an NA of about 0.8 to 0.9, and the thickness of the transparent substrate is 0.05 to 0.00 mm.
- the optical pickup device of the present invention has at least three layers. It is possible to deal with a BD having the above information recording surface.
- DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.60 to 0.67 and the thickness of the transparent substrate is about 0.6 mm.
- CD is a general term for CD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.45 to 0.51 and the transparent substrate has a thickness of about 1.2 mm.
- CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like As for the recording density, the recording density of BD is the highest, followed by the order of DVD and CD.
- the present invention is not limited to this.
- the first light source, the second light source, and the third light source are preferably laser light sources.
- the laser light source a semiconductor laser, a silicon laser, or the like can be preferably used.
- the wavelength ⁇ 3 ( ⁇ 3> ⁇ 2) is defined by the following conditional expressions (20), (21), 1.5 ⁇ ⁇ 1 ⁇ 2 ⁇ 1.7 ⁇ ⁇ 1 (20) 1.8 ⁇ ⁇ 1 ⁇ 3 ⁇ 2.0 ⁇ ⁇ 1 (21) It is preferable to satisfy.
- the first wavelength ⁇ 1 of the first light source is preferably 350 nm or more and 440 nm or less, more preferably 390 nm.
- the second wavelength ⁇ 2 of the second light source is preferably 570 nm or more and 680 nm or less, more preferably 630 nm or more and 670 nm or less, and the third wavelength ⁇ 3 of the third light source is preferably 750 nm or more. It is 880 nm or less, More preferably, it is 760 nm or more and 820 nm or less.
- the first light source, the second light source, and the third light source may be unitized.
- the unitization means that the first light source and the second light source are fixedly housed in one package, for example.
- a light receiving element to be described later may be packaged.
- a photodetector such as a photodiode is preferably used.
- Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on each optical disc is obtained using the output signal. Furthermore, it detects the change in the light amount due to the spot shape change and position change on the light receiving element, performs focus detection and track detection, and based on this detection, the objective lens can be moved for focusing and tracking I can do it.
- the light receiving element may comprise a plurality of photodetectors.
- the light receiving element may have a main photodetector and a sub photodetector.
- two sub photodetectors are provided on both sides of a photodetector that receives main light used for recording and reproducing information, and the sub light for tracking adjustment is received by the two sub photodetectors. It is good also as a simple light receiving element.
- the light receiving element may have a plurality of light receiving elements corresponding to the respective light sources.
- the condensing optical system has a coupling lens and an objective lens.
- the coupling lens is a lens group that is disposed between the objective lens and the light source and changes the divergence angle of the light beam.
- the collimator is a kind of coupling lens, and is a coupling lens that emits an incident light beam as parallel light or substantially parallel light.
- the coupling lens may be composed of only a positive lens group or may have a positive lens group and a negative lens group.
- the positive lens group has at least one positive lens.
- the positive lens group may include only one positive lens or may include a plurality of lenses.
- the negative lens group includes at least one negative lens.
- the negative lens group may include only one negative lens or may include a plurality of lenses. Examples of a preferable coupling lens include only a single positive lens or a combination of a single positive lens and a single negative lens.
- a lens that is movable in the optical axis direction in the coupling lens may be referred to as a “movable lens”.
- “movement amount of the coupling lens” is used in the same meaning as “movement amount of the movable lens”.
- the power of the lens group moved in the optical axis direction is increased (that is, in the optical axis direction). It is conceivable to shorten the focal length of the lens group that is moved to (1). This is because the amount of movement of the lens group moved in the optical axis direction decreases as the power of the lens group increases (that is, as the focal length of the lens group decreases).
- the coupling lens has a group configuration
- the focal length of the lens group moved in the optical axis direction that is, equal to the focal length of the coupling lens
- the spot condensed by the objective lens becomes an ellipse.
- the recording and / or reproduction of information on the BD may be hindered. The reason for this will be described below.
- the coupling lens has a two-group configuration including a positive lens group and a negative lens group, and at least one lens in the positive lens group is moved in the optical axis direction, thereby It is preferable to select whether to collect light on the information recording surface.
- the coupling lens is a two-group thin lens system composed of a positive lens and a negative lens, and the positive lens is moved along the optical axis direction during focus jump.
- the power of the positive lens is P P
- the focal length of the positive lens is f P
- the power of the negative lens is P N
- the focal length of the negative lens is f N
- the distance between the positive lens and the negative lens is L
- the system magnification M is about -0.1. Further, in consideration of a space in which an optical element such as a polarizing beam splitter disposed between the light source and the coupling lens is considered, the focal length f C of the entire coupling lens system cannot be extremely shortened.
- the distance between the objective lens and the BD (also referred to as a working distance) is not too short, and in order to reduce the thickness of the optical pickup device, optimal range of the focal length f O of the lens naturally determined.
- the focal length range of the entire system needs to be a certain predetermined range, and the movement of the coupling lens necessary at the time of focus jump Considering only the amount, the focal length f C of the entire coupling lens system cannot be reduced unnecessarily.
- the power P P of the positive lens is increased, and further, the power P of the negative lens is set so that the focal length f C of the entire coupling lens system is not too short. It is preferable to increase the absolute value of N (see equation (22)).
- the movement amount of the positive lens group required at the time of focus jump is reduced by moving the positive lens group in the optical axis direction.
- the arrangement of the positive lens group and the negative lens group may be arranged in the order of the negative lens group and the positive lens group from the light source side, or may be arranged in the order of the positive lens group and the negative lens group from the light source side. good.
- the preferred arrangement is the former.
- the optimum example of the coupling lens in the optical pickup device is composed of a combination of one positive lens and one negative lens, and the negative lens and the positive lens from the light source side. Are arranged in this order.
- the present invention is not limited to this, and from the viewpoint of simplifying the configuration of the coupling lens as much as possible, there can be an option of a single positive lens coupling lens.
- At least one lens (preferably a positive lens) of the positive lens group is movable in the optical axis direction in order to correct spherical aberration occurring on the selected information recording surface of the first optical disk. It is preferable that For example, when recording and / or reproducing on one information recording surface of the first optical disk and then recording and / or reproducing on another information recording surface of the first optical disk, the positive lens group of the coupling lens group Spherical aberration that occurs at the time of focus jump to a different information recording surface of the first optical disk by moving at least one lens in the optical axis direction, changing the divergence of the light beam, and changing the magnification of the objective lens Correct.
- FIG. 1 is a diagram showing the results of studies conducted by the present inventors.
- the first optical disc (BD) having a surface, the maximum spherical aberration difference A ( ⁇ rms) that occurs when the optimum focused spot is formed on each of the information recording surfaces that are separated as much as possible, and the environmental temperature changes by ⁇ 30 ° C.
- the maximum spherical aberration B ( ⁇ rms) that occurs when the wavelength of the light source changes and the maximum spherical aberration C ( ⁇ rms) that occurs when the wavelength of the light source changes by ⁇ 5 nm were determined. This is represented by the bar graph of FIG.
- Such spherical aberration can be corrected by moving the coupling lens in the optical axis direction and changing the magnification of the objective lens. However, if the same coupling lens is used, the total amount of spherical aberration is the amount of movement of the coupling lens. It is equivalent to.
- the amount of spherical aberration is obtained regardless of whether the optical surface is an aspherical refractive surface or a diffractive surface. Is about 410 to 430 m ⁇ rms, and it can be said that the amount of movement of the coupling lens is relatively small.
- the total amount of spherical aberration is 680 m ⁇ rms in an objective lens having an aspherical refractive surface. The amount of movement is required to be about 1.5 times that required when an optical disc having two information recording surfaces is used. Furthermore, as shown in FIG.
- the objective lens is made of glass and the optical surface is an aspherical refracting surface
- the objective lens is made of glass and the optical surface is a diffractive surface that corrects spherical aberration that occurs when the wavelength varies, in addition to spherical aberration B caused by environmental temperature changes, spherical aberration C caused by wavelength fluctuations of the light source due to the function of the diffractive surface.
- the amount of movement of the coupling lens is smaller (corresponding to the correction amount of the spherical aberration of 500 m ⁇ rms in FIG. 1C). That is, in order to reduce the amount of movement of the coupling lens, the objective lens is preferably made of a glass material. However, even if the objective lens is improved in this way, the amount of movement of the coupling lens when the optical disk having two information recording surfaces is used is smaller than that of the coupling lens when the optical disk having four information recording surfaces is used. Since the amount of movement is still about twice, it is preferable to further devise in order to suppress the amount of movement of the coupling lens. The same applies to the amount of movement of the coupling lens when using an optical disc having three information recording surfaces or five or more information recording surfaces. Therefore, in the present invention, it is possible to further reduce the amount of movement of the coupling lens by breaking the sine condition of the objective lens.
- an optical disc having two information recording surfaces an information recording surface having a smaller distance from the light beam incident surface of the optical disc is RL1, an information recording surface having a larger distance from the light beam incident surface of the optical disc is RL2
- optical disk having four information recording surfaces (assuming that the information recording surface having the smallest distance from the light beam incident surface of the optical disk is RL1, and the information recording surface having the largest distance from the light beam incident surface of the optical disk is RL4), An optical disk was assumed in which the distance from the light beam incident surface of the optical disk to RL1 was 50 ⁇ m and the distance from the light beam incident surface of the optical disk to RL4 was 100 ⁇ m.
- the objective lens refers to an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing a light beam emitted from the light source onto the information recording surface of the optical disk.
- the objective lens is a single plastic lens or glass lens.
- the objective lens is a single convex lens.
- the objective lens may be composed of only a refractive surface or may have an optical path difference providing structure.
- the hybrid lens which provided the optical path difference providing structure with the photocurable resin, UV curable resin, or thermosetting resin etc. on the glass lens may be sufficient.
- the objective lens preferably has a refractive surface that is aspheric.
- the base surface on which the optical path difference providing structure is provided is preferably an aspherical surface.
- the optical surface on the light source side of the objective lens may be referred to as the optical surface on the object side, and the optical surface on the optical disk side may be referred to as the optical surface on the image side.
- the absolute value of the radius of curvature of the optical surface on the light source side is preferably smaller than the absolute value of the radius of curvature of the optical surface on the image side.
- the objective lens is a glass lens, as described with reference to FIG. 1, it is not necessary to move the coupling lens in order to correct the spherical aberration caused by the temperature change. This is preferable because it can be reduced and the optical pickup device can be downsized.
- the objective lens is a glass lens
- a glass material having a glass transition point Tg of 500 ° C. or lower more preferably 400 ° C. or lower.
- a glass material having a glass transition point Tg of 500 ° C. or lower molding at a relatively low temperature is possible, so that the life of the mold can be extended.
- Examples of such a glass material having a low glass transition point Tg include K-PG325 and K-PG375 (both product names) manufactured by Sumita Optical Glass Co., Ltd.
- a physical property value which is important when molding and manufacturing a glass lens is a linear expansion coefficient ⁇ . Even if a material having a Tg of 400 ° C. or lower is selected, the temperature difference from room temperature is still large compared to the resin material. When lens molding is performed using a glass material having a large linear expansion coefficient ⁇ , cracks are likely to occur when the temperature is lowered.
- the linear expansion coefficient ⁇ of the glass material is preferably 200 ( ⁇ 10 ⁇ 7 / K) or less, more preferably 120 ( ⁇ 10 ⁇ 7 / K) or less.
- the specific gravity of a glass lens is generally larger than that of a plastic lens, if the objective lens is a glass lens, the weight increases and a load is imposed on the actuator that drives the objective lens. Therefore, when the objective lens is a glass lens, it is preferable to use a glass material having a small specific gravity.
- the specific gravity is preferably 4.0 or less, more preferably the specific gravity is 3.0 or less.
- the objective lens is a plastic lens
- an alicyclic hydrocarbon polymer material such as a cyclic olefin resin material.
- the resin material has a refractive index of 1.54 to 1.60 at a temperature of 25 ° C. with respect to a wavelength of 405 nm, and a wavelength of 405 nm according to a temperature change within a temperature range of ⁇ 5 ° C. to 70 ° C.
- the refractive index change rate dN / dT (° C.
- the coupling lens is preferably a plastic lens.
- a first preferred example is a polymer block [A] containing a repeating unit [1] represented by the following formula (1), a repeating unit [1] represented by the following formula (1) and the following formula ( 2) and / or polymer block [B] containing the repeating unit [3] represented by the following formula (3), and the repeating unit in the block [A] It consists of a block copolymer in which the relationship between the molar fraction a (mol%) of [1] and the molar fraction b (mol%) of the repeating unit [1] in the block [B] is a> b. It is a resin composition.
- R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms
- R 2 to R 12 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a hydroxyl group, a carbon number of 1 ⁇ 20 alkoxy groups or halogen groups.
- R 13 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
- each of R 14 and R 15 independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
- a second preferred example is obtained by addition polymerization of a monomer composition comprising at least an ⁇ -olefin having 2 to 20 carbon atoms and a cyclic olefin represented by the following general formula (1).
- Polymer (B) obtained by addition polymerization of polymer (A) and a monomer composition comprising an ⁇ -olefin having 2 to 20 carbon atoms and a cyclic olefin represented by the following general formula (2) ).
- R 1 to R 18 , R a and R b are each independently a hydrogen atom, A halogen atom or a hydrocarbon group, R 15 to R 18 may be bonded to each other to form a monocycle or polycycle, and the monocycle or polycycle in parentheses may have a double bond Alternatively, R 15 and R 16 , or R 17 and R 18 may form an alkylidene group. ]
- R 19 to R 26 each independently represents a hydrogen atom, a halogen atom or a hydrocarbon group.
- the following additives may be added.
- Stabilizer It is preferable to add at least one stabilizer selected from a phenol stabilizer, a hindered amine stabilizer, a phosphorus stabilizer, and a sulfur stabilizer. By suitably selecting and adding these stabilizers, for example, it is possible to more highly suppress the white turbidity and the optical characteristic fluctuations such as the refractive index fluctuations when continuously irradiated with light having a short wavelength of 405 nm. .
- phenol-based stabilizer conventionally known ones can be used.
- 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate
- 2 4-di-t-amyl-6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate and the like
- JP-A Nos. 63-179953 and 1-168643 JP-A Nos. 63-179953 and 1-168643.
- Preferred hindered amine stabilizers include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis ( 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-benzyloxy-2, 2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6) -Pentamethyl-4-piperidyl) 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acryloyl-2,2, , 6-Tetramethyl-4-piperidyl) 2,2-bis (3,5-di-t-but
- the preferable phosphorus stabilizer is not particularly limited as long as it is a substance usually used in the general resin industry.
- triphenyl phosphite diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonyl).
- Phenyl) phosphite tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9 Monophosphite compounds such as 1,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) Phosphite), 4,4 'isopropylidene-bis (phenyl-di-alkyl (C12-C15)) Fight) and the like diphosphite compounds such as.
- monophosphite compounds are preferable, and tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite and the like are particularly preferable.
- Preferred sulfur stabilizers include, for example, dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3- Thiodipropionate, pentaerythritol-tetrakis- ( ⁇ -lauryl-thio) -propionate, 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane Etc.
- each of these stabilizers is appropriately selected within a range not to impair the purpose of the present invention, but is usually 0.01 to 2 parts by mass with respect to 100 parts by mass of the alicyclic hydrocarbon-based copolymer, The amount is preferably 0.01 to 1 part by mass.
- a surfactant is a compound having a hydrophilic group and a hydrophobic group in the same molecule.
- the surfactant can prevent white turbidity of the resin composition by adjusting the rate of moisture adhesion to the resin surface and the rate of moisture evaporation from the surface.
- hydrophilic group of the surfactant examples include a hydroxy group, a hydroxyalkyl group having 1 or more carbon atoms, a hydroxyl group, a carbonyl group, an ester group, an amino group, an amide group, an ammonium salt, a thiol, a sulfonate, A phosphate, a polyalkylene glycol group, etc. are mentioned.
- the amino group may be primary, secondary, or tertiary.
- the hydrophobic group of the surfactant include an alkyl group having 6 or more carbon atoms, a silyl group having an alkyl group having 6 or more carbon atoms, and a fluoroalkyl group having 6 or more carbon atoms.
- the alkyl group having 6 or more carbon atoms may have an aromatic ring as a substituent.
- Specific examples of the alkyl group include hexyl, heptyl, octyl, nonyl, decyl, undecenyl, dodecyl, tridecyl, tetradecyl, myristyl, stearyl, lauryl, palmityl, cyclohexyl and the like.
- the aromatic ring include a phenyl group.
- the surfactant only needs to have at least one hydrophilic group and hydrophobic group as described above in the same molecule, and may have two or more groups.
- examples of such a surfactant include myristyl diethanolamine, 2-hydroxyethyl-2-hydroxydodecylamine, 2-hydroxyethyl-2-hydroxytridecylamine, 2-hydroxyethyl-2- Hydroxytetradecylamine, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, di-2-hydroxyethyl-2-hydroxydodecylamine, alkyl (8-18 carbon atoms) benzyldimethylammonium chloride, ethylene
- examples thereof include bisalkyl (carbon number 8 to 18) amide, stearyl diethanolamide, lauryl diethanolamide, myristyl diethanolamide, palmityl diethanolamide, and the like.
- amine compounds or amide compounds having a hydroxyalkyl group are preferably used. In the present invention, two or more of these compounds may be used in combination.
- the surfactant is added to 100 parts by mass of the alicyclic hydrocarbon-based polymer.
- the addition amount of the surfactant is more preferably 0.05 to 5 parts by mass, still more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the alicyclic hydrocarbon-based polymer.
- Plasticizer The plasticizer is added as necessary to adjust the melt index of the copolymer.
- Plasticizers include bis (2-ethylhexyl) adipate, bis (2-butoxyethyl) adipate, bis (2-ethylhexyl) azelate, dipropylene glycol dibenzoate, tri-n-butyl citrate, tricitrate citrate -N-butylacetyl, epoxidized soybean oil, 2-ethylhexyl epoxidized tall oil, chlorinated paraffin, tri-2-ethylhexyl phosphate, tricresyl phosphate, t-butylphenyl phosphate, tri-2-ethylhexyl phosphate Diphenyl, dibutyl phthalate, diisohexyl phthalate, diheptyl phthalate, dinonyl phthalate, diundecyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisode
- cycloolefin resins are preferably used.
- ZEONEX manufactured by Nippon Zeon, APEL manufactured by Mitsui Chemicals, TOPAS ADVANCED, TOPAS manufactured by POLYMERS, and ARTON manufactured by JSR are preferable. Take as an example.
- the Abbe number of the material constituting the objective lens is preferably 50 or more.
- the maximum transparent substrate thickness (at the deepest position) among the transparent substrate thicknesses of the optical disk When the distance between a certain information recording surface and the surface of the optical disk is T MAX (mm), at normal temperature (25 ⁇ 3 ° C.) and the cover glass thickness T (mm) satisfying the following expression (1):
- the magnification M when the spherical aberration ( ⁇ rms) is minimized satisfies the expression (2).
- CM Third-order coma aberration CM (DT) generated when the optical disk is tilted when the environmental temperature becomes high during the recording / reproducing of information with respect to the information recording surface having the largest substrate thickness), and CM The ratio with (LT) was set to about 0.36. As described above, the value of this ratio is the information recording surface of the thicker transparent substrate in the optical pickup device equipped with the plastic objective lens that records / reproduces information with respect to the two-layer BD.
- the magnification satisfying the formula (2) at normal temperature 25 ⁇ 3 ° C.
- the target value of CM (LT) is satisfied by setting the correction state of the spherical aberration so that the cover glass thickness T when the spherical aberration is minimized is equal to or greater than the lower limit of the equation (1).
- the CM (LT) can be increased as the cover glass thickness T increases.
- the cover glass thickness T exceeds the upper limit of the formula (1), information is recorded on the information recording surface with the thinnest transparent substrate.
- the cover glass thickness T satisfies the upper limit of the expression (3), the degree of convergence of the light beam incident on the objective lens becomes too large when information is recorded / reproduced on the information recording surface with the thinnest transparent substrate thickness. Further suppression is preferable, and as a result, the lens shift characteristic can be further improved, and the residual higher-order spherical aberration when the focus jump is made to the information recording surface having the thinnest transparent substrate can be further reduced.
- the objective lens is a single lens made of a glass material having an image-side numerical aperture (NA) of 0.8 or more and 0.95 or less, the largest transparent substrate thickness (most of the transparent substrate thicknesses of the optical disk)
- the cover glass thickness T has a normal temperature (25 ⁇ 3 ° C.) and a thickness satisfying the following expression (4):
- the magnification M when the spherical aberration ( ⁇ rms) is minimized satisfies the expression (2).
- the cover glass thickness T becomes smaller when the spherical aberration is minimized at a magnification satisfying (2 ⁇ 3) at normal temperature (25 ⁇ 3 ° C.), and as a result, becomes equal to or more than the lower limit of the expression (4). In this way, it was found that the target value of the third-order coma aberration generation amount CM (LT) due to the lens shift tilt is satisfied by setting the correction state of the spherical aberration.
- the cover glass thickness T not exceed the upper limit of the expression (4), the degree of convergence of the light beam incident on the objective lens when information is recorded / reproduced on the information recording surface with the thinnest transparent substrate thickness. Is prevented from becoming too large, and it is possible to prevent the lens shift characteristic from being deteriorated and the increase in residual higher-order spherical aberration when the focus jump is made to the information recording surface having the thinnest transparent substrate thickness.
- the sine condition is h when a light beam having a height h 1 from the optical axis is incident on the lens parallel to the optical axis, and when the light beam is emitted from the lens at an emission angle U. 1 / sinU satisfies a certain value.
- U. 1 / sinU a constant value regardless of the height from the height h 1 from the optical axis
- the sine condition is satisfied and the lateral magnification of each light ray within the effective diameter can be regarded as constant.
- This sine condition is a calculated value on the axis, but is effective in correcting off-axis lateral magnification error (ie off-axis coma).
- FIG. 3 is a graph showing the sine condition violation amount in the objective lens on the horizontal axis and the height from the optical axis on the vertical axis.
- the graph matches the vertical axis, but in the case of an objective lens that does not satisfy the sine condition, the graph moves away from the vertical axis to the positive side and / or the negative side as shown in FIG. It becomes.
- the sine condition violation amount always has a maximum value.
- OSCmax the maximum value on the positive side of the sine condition violation amount
- OSCmin the maximum value on the negative side
- the objective lens having the characteristics shown in FIG. 3A is an example in which the sine condition violation amount has one negative maximum value OSCmin and does not have a positive maximum value OSCmax. According to such an objective lens, since the surface shift sensitivity is small and the on-axis thickness error sensitivity is small, it is easy to manufacture. On the other hand, as the coupling lens moves, the higher-order spherical aberration increases and the magnification changes. It has the characteristic that the change in spherical aberration due to is small. Therefore, when the coupling lens is moved to select an information recording surface in an optical disc having three or more layers, there is a possibility that the necessary movement amount increases.
- the objective lens having the characteristics shown in FIGS. 3B and 3C which is the objective lens of the present invention, is between 70% and 90% of the effective radius of the objective lens at the magnification M described above.
- the sine condition violation amount has at least one maximum value OSCmax on the positive side (preferably only one).
- the sine condition violation amount has a positive maximum value OSCmax between 70% and 90% of the effective radius of the objective lens. Since the higher-order spherical aberration that occurs with the movement of the ring lens is reduced and the change in spherical aberration due to the change in magnification is large, the coupling lens is moved to select the information recording surface in an optical disc with three or more layers. In this case, the necessary movement amount can be reduced.
- the sine condition violation amount has one negative maximum value on the optical axis side than the positive maximum value. Further, in the example of FIG. 3C, the sine condition violation amount has only a positive maximum value and does not have a negative maximum value. In both the example of FIG. 3B and the example of FIG. 3C, the sine condition violation amount monotonously decreases in the peripheral portion from the maximum value.
- the sine condition violation amount has a positive maximum value and the sine condition violation amount has a negative maximum value between 70% and 90% of the effective radius.
- (Characteristic 1) The residual high-order spherical aberration at the time of focus jump can be reduced, (Characteristic 2) the amount of movement of the coupling lens at the time of focus jump can be reduced, and (Characteristic 3) the transparent substrate thickness is In addition to being able to further suppress the reduction in lens tilt sensitivity even when the environmental temperature becomes high during recording / reproducing information on the thicker information recording surface, (Characteristic 4) When the two optical surfaces are shifted in the direction perpendicular to the optical axis due to manufacturing errors, the amount of aberration generated can be suppressed. (Characteristic 5) The lens thickness on the optical axis varies in the optical axis direction due to manufacturing errors. Aberration generation amount in case of deviation It becomes possible to suppress, it is possible to provide a more easily manufacturable objective lens
- the sine condition violation amount has a positive maximum value and the sine condition violation amount has a negative maximum value between 70% and 90% of the effective radius. If not, (Characteristic 1) residual high-order spherical aberration at the time of focus jump can be further reduced, (Characteristic 2) the amount of movement of the coupling lens at the time of focus jump can be further reduced, and (Characteristic 3) ) It is possible to further suppress the reduction in lens tilt sensitivity even when the environmental temperature becomes high during the recording / reproducing of information on the information recording surface having the thicker transparent substrate.
- the third-order spherical aberration that occurs in the objective lens due to the change in the divergence / convergence of incident light is the third-order spherical aberration that occurs during the focus jump.
- the objective lens may be set in a shape that violates the sine condition, giving priority to reducing the amount of movement of the coupling lens, or giving priority to minimizing residual aberration during focus jump.
- the shape of the condition violation amount may be set.
- both the suppression of the residual higher-order spherical aberration at the time of focus jump and the movement amount of the coupling lens are compatible. It becomes possible to do.
- conditional expression (6) ′ 21.5 ⁇
- the third-order spherical aberration ⁇ SA3 and the fifth-order spherical aberration ⁇ SA5 that occur when the magnification of the objective lens is changed at normal temperature (25 ⁇ 3 ° C.) and the cover glass thickness T satisfy the expression (7).
- the ratio of the change of the third-order spherical aberration and the fifth-order spherical aberration when the magnification is changed is the ratio of the third-order spherical aberration and the fifth-order spherical aberration when the cover glass thickness is changed. Therefore, it is possible to achieve both the suppression of the residual higher-order spherical aberration during the focus jump and the suppression of the movement amount of the coupling lens.
- conditional expression (7) ′, 4.3 ⁇ SA3 / ⁇ SA5 ⁇ 4.9 (7) ′ Is to satisfy.
- the fifth-order coma aberration CM5 (occurred when an oblique light beam having a half angle of view of 1 degree is incident on the objective lens at normal temperature (25 ⁇ 3 ° C.), the above-mentioned transparent substrate thickness T, and magnification M. ⁇ rms) satisfies the equation (8). 0.02 ⁇
- Conditional expression (8) is set from another viewpoint to satisfy both the suppression of the residual higher-order spherical aberration during the focus jump and the suppression of the movement amount of the coupling lens.
- conditional expression (9) it is possible to prevent the lens tilt sensitivity from becoming too small even when information is recorded / reproduced on the information recording surface having the thicker transparent substrate. Further, even if the objective lens is made of plastic, the lens tilt sensitivity is small even when the environmental temperature becomes high during the recording / reproducing of information on the information recording surface having the thicker transparent substrate. Since it can prevent becoming too much, it is preferable.
- the objective lens has the positive maximum value of the sine condition violation amount as OSC MAX (mm) and the focal length of the wavelength ⁇ 1 at room temperature (25 ⁇ 3 ° C.) as f (mm), the expression (11) Meet, 0.003 ⁇ OSC MAX / f ⁇ 0.022 (11) It is preferable.
- the higher-order spherical aberration at the time of the focus jump is not insufficiently corrected, and the sine condition violation
- the coma aberration correction state is set when the oblique light beam is incident so that the amount is smaller than the upper limit of the expression (11)
- the higher-order spherical aberration at the time of focus jump is effective because the higher-order spherical aberration is not overcorrected. Can be suppressed.
- the amount of lens tilt required to correct the coma generated by the disc tilt will increase.
- the objective lens collides with the optical disk when the lens is tilted.
- the coma generated by the lens tilt changes depending on the sine condition violation amount of the objective lens, and the sine condition violation amount depends on the magnification of the objective lens in a state where information is recorded / reproduced with respect to the optical disc. It changes depending on. Specifically, in an objective lens in which the sine condition violation amount is corrected when a parallel light beam is incident on the objective lens, the sine condition violation amount is changed to the negative side when a divergent light beam is incident on the objective lens. Therefore, the amount of coma generated by the lens tilt is reduced. The amount of coma aberration decreases as the divergence of the light beam incident on the objective lens increases.
- the divergence of the light beam incident on the objective lens is maximized when information is recorded and / or reproduced on the information recording surface having the longest distance from the light beam incident surface. Furthermore, in the case of an objective lens made of a plastic material, the degree of divergence of the light flux is further increased in order to correct the spherical aberration caused by the change in the environmental temperature.
- the cover glass thickness equal to the maximum transparent substrate thickness T MAX is non-parallel to the objective lens so that the third-order spherical aberration of the focused spot by the objective lens is corrected.
- conditional expression (12) ′ 0.35 ⁇
- ⁇ 0.8 (12) ′ Is to satisfy.
- the absolute value of the spherical aberration of the spot collected through the cover glass thickness equal to the maximum transparent substrate thickness T MAX is:
- the objective lens spherical aberration correction state is set so that the spherical aberration of the spot collected through the cover glass thickness equal to the minimum transparent substrate thickness T MIN becomes smaller.
- (24) Is synonymous with
- a non-parallel light beam is made incident on the objective lens so that the third-order spherical aberration of the focused spot by the objective lens is corrected at normal temperature (25 ⁇ 3 ° C.) and the maximum transparent substrate thickness T MAX .
- the objective lens so that the third-order spherical aberration of the focused spot by the objective lens is corrected at the magnification M1 in the above state, normal temperature (25 ⁇ 3 ° C.), and the minimum transparent substrate thickness TMIN .
- the magnification M2 in a state where a parallel light beam is incident satisfies the expression (13). 0 ⁇ M1 / M2 ⁇ 0.92 (13) It is preferable.
- T is between T MAX and T MIN .
- the one close to T MAX is preferable. What defines the preferable range from the viewpoint of magnification is Expression (13).
- the refractive index N of the objective lens with respect to the wavelength ⁇ 1 at normal temperature (25 ⁇ 3 ° C.) and the inclination angle ⁇ (degree) in the outermost effective diameter of the optical surface on the light source side (object side) are ( 14) ⁇ 59.8 ⁇ N + 162 ⁇ ⁇ 59.8 ⁇ N + 166 (14) It is preferable.
- the refractive index N of the lens and the inclination angle ⁇ in the outermost periphery of the effective diameter of the optical surface on the object side are within a certain range of conditions. It was. From the above knowledge, the objective lens of the present invention is defined from the viewpoint of a preferable shape (14).
- the horizontal axis represents the refractive index N of the wavelength ⁇ 1 at room temperature (25 ⁇ 3 ° C.), and the vertical axis represents the inclination angle ⁇ (degree) in the outermost periphery of the effective diameter of the optical surface on the object side.
- FIG. 8 is a diagram plotting a comparative example described later and Examples 1 to 16.
- the refractive index of the objective lens with respect to the wavelength ⁇ 1 at normal temperature (25 ⁇ 3 ° C.) is N
- the first derivative X ′ of the aspherical deformation amount X (h) (mm) of the optical surface on the optical disk side is satisfied.
- the aspherical deformation amount X (h) is defined by the distance in the optical axis direction from the plane contacting the surface vertex of the optical surface on the optical disk side to the aspherical surface, and negative when the plane is deformed from the plane to the light source side.
- the case of deformation from the plane to the optical disk side is positive, and H is a relative value when the effective radius is 1.
- the refractive index N of the lens and the first derivative X ′ (h) of the aspherical deformation amount X (h) (mm) of the optical surface on the image side are negative. It has been found that the radius height H (mm), which is positively switched, exists within a certain range of conditions. From this knowledge, the objective lens of the present invention is defined from the viewpoint of a preferable shape, which is the expression (16).
- the horizontal axis represents the refractive index N of the wavelength ⁇ 1 at room temperature (25 ⁇ 3 ° C.), and the vertical axis represents the first derivative X of the aspherical deformation amount X (h) of the optical surface on the image side.
- '(H) is a diagram plotting Examples 1 to 16, which will be described later, by taking a radial height H at which negative (+) is switched from negative to positive, showing the correlation of the Examples.
- NA1 The numerical aperture on the image side of the objective lens necessary for reproducing / recording information on the first optical disc is NA1, and the numerical aperture on the image side of the objective lens necessary for reproducing / recording information on the second optical disc.
- NA2 NA1> NA2
- NA3 NA2> NA3
- NA1 is preferably 0.8 or more and 0.95 or less, and more preferably 0.8 or more and 0.9 or less.
- NA1 is preferably 0.85.
- NA2 is preferably 0.55 or more and 0.7 or less.
- NA2 is preferably 0.60 or 0.65.
- NA3 is preferably 0.4 or more and 0.55 or less.
- NA3 is preferably 0.45 or 0.53.
- an objective lens satisfy
- d represents the thickness (mm) on the optical axis of the objective lens
- f represents the focal length of the objective lens in the first light flux. Note that f is preferably 1.0 mm or more and 1.8 mm or less.
- the working distance of the objective lens when using the first optical disk is preferably 0.15 mm or more and 1.0 mm or less.
- An optical information recording / reproducing apparatus includes an optical disc drive apparatus having the above-described optical pickup apparatus.
- the optical disk drive apparatus can hold an optical disk mounted from the optical information recording / reproducing apparatus main body containing the optical pickup apparatus or the like. There are a system in which only the tray is taken out, and a system in which the optical disc drive apparatus main body in which the optical pickup device is stored is taken out to the outside.
- the optical information recording / reproducing apparatus using each method described above is generally equipped with the following components, but is not limited thereto.
- An optical pickup device housed in a housing or the like, a drive source of an optical pickup device such as a seek motor that moves the optical pickup device together with the housing toward the inner periphery or outer periphery of the optical disc, and the optical pickup device housing the inner periphery or outer periphery of the optical disc include a transfer means of an optical pickup device having a guide rail or the like that guides toward the head, a spindle motor that rotates the optical disk, and the like.
- the former method is provided with a tray that can be held in a state in which an optical disk is mounted and a loading mechanism for sliding the tray, and the latter method has no tray and loading mechanism. It is preferable that each component is provided in a drawer corresponding to a chassis that can be pulled out to the outside.
- an optical pickup device capable of recording / reproducing information with respect to an optical disc having a multilayer information recording surface while being compact and low in cost.
- FIG. 4 is a graph showing the effective radius on the vertical axis and the spherical aberration and the sine condition on the horizontal axis for Example 1.
- FIG. FIG. 5 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc side of Example 1 with the effective radius on the vertical axis for Example 1.
- the effective radius is plotted on the vertical axis, and spherical aberration and sine conditions are plotted on the horizontal axis.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc side of Example 1 with the effective radius on the vertical axis for Example 2.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc side of Example 1 with the effective radius on the vertical axis for Example 2.
- Example 3 the effective radius is plotted on the vertical axis, and spherical aberration and sine conditions are plotted on the horizontal axis.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc side of Example 1 with the effective radius on the vertical axis for Example 3.
- Example 4 the effective radius is plotted on the vertical axis, and spherical aberration and sine conditions are plotted on the horizontal axis.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disk side of Example 1 with the effective radius on the vertical axis for Example 4.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disk side of Example 1 with the effective radius on the vertical axis for Example 4.
- Example 5 the effective radius is taken on the vertical axis and the spherical aberration and the sine condition are taken on the horizontal axis.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc side of Example 1 with the effective radius on the vertical axis for Example 5.
- FIG. It is a graph which takes an effective radius on a vertical axis
- FIG. 10 is a graph showing the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 with the effective radius on the vertical axis for Example 6.
- FIG. 10 is a graph showing the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 with the effective radius on the vertical axis for Example 6.
- Example 7 the effective radius is plotted on the vertical axis and the spherical aberration and sine condition are plotted on the horizontal axis.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc of Example 1 with the vertical axis representing the effective radius for Example 7.
- FIG. It is a graph which takes an effective radius on a vertical axis
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc of Example 1 with the effective radius on the vertical axis for Example 8.
- FIG. 10 is a graph showing the first-order differential X ′ (h) of the aspherical shape on the optical surface on the optical disc of Example 1 with the effective radius on the vertical axis for Example 8.
- Example 9 the effective radius is plotted on the vertical axis and the spherical aberration and sine condition are plotted on the horizontal axis.
- Example 9 the effective radius is plotted on the vertical axis, and the first-order differential X ′ (h) of the aspheric shape on the optical surface on the optical disc side in Example 1 is shown.
- Example 10 the effective radius is plotted on the vertical axis and the spherical aberration and sine condition are plotted on the horizontal axis.
- the effective radius is plotted on the vertical axis, and the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 is shown.
- Example 11 the effective radius is plotted on the vertical axis and the spherical aberration and sine condition are plotted on the horizontal axis.
- Example 11 the effective radius is plotted on the vertical axis, and the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 is shown.
- Example 12 the vertical axis represents the effective radius and the horizontal axis represents the spherical aberration and the sine condition.
- the effective radius is plotted on the vertical axis, and the first-order differential X ′ (h) of the aspheric shape on the optical surface on the optical disc side in Example 1 is shown.
- Example 13 It is a graph which takes an effective radius on a vertical axis
- the effective radius is plotted on the vertical axis, and the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 is shown.
- Example 15 the vertical axis represents the effective radius, and the horizontal axis represents the spherical aberration and the sine condition.
- the effective radius is plotted on the vertical axis, and the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 is shown.
- the effective radius is plotted on the vertical axis and the spherical aberration and sine condition are plotted on the horizontal axis.
- the effective radius is plotted on the vertical axis, and the aspherical first-order differential X ′ (h) on the optical disc side optical surface of Example 1 is shown.
- the horizontal axis represents the refractive index N of the wavelength ⁇ at room temperature (25 ⁇ 3 ° C.), and the vertical axis represents the inclination angle ⁇ (degrees) at the outermost effective diameter of the optical surface on the object side.
- FIG. 6 is a diagram in which Examples 1 to 16 are plotted.
- the horizontal axis represents the refractive index N of the wavelength ⁇ at room temperature (25 ⁇ 3 ° C.)
- the vertical axis represents the one-time differential X ′ (h) of the aspherical deformation amount X (h) of the optical surface on the image side.
- FIG. 10 is a diagram in which Examples 1 to 16 are plotted with a radial height H that is switched from negative to positive.
- FIG. 4 shows that information is appropriately recorded on a BD that is an optical disk having three information recording surfaces RL1 to RL3 (referred to as RL1, RL2, and RL3 in order of increasing distance from the light beam incident surface of the optical disk) in the thickness direction.
- FIG. 2 is a diagram schematically showing a configuration of an optical pickup device PU1 of the present embodiment that can perform reproduction. Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device.
- the present invention is not limited to the present embodiment. For example, FIG.
- the objective lens OBJ is made compatible with BD / DVD / CD, or the objective lens for DVD / CD is separately arranged, so that the BD / DVD is used.
- An optical pickup device compatible with CD can be used.
- the optical pickup device PU1 moves the objective lens OBJ, the objective lens OBJ in the focusing direction and the tracking direction, and tilts in the radial direction and / or tangential direction of the optical disc, the ⁇ / 4 wavelength plate QWP, Coupling CL having a positive lens unit L2 composed of one positive lens having a refractive power and a negative lens unit L3 composed of one negative lens having a negative refractive power, only the positive lens unit L2 in the optical axis direction.
- the coupling lens CL is disposed between the polarizing prism PBS and the ⁇ / 4 wavelength plate QWP.
- the objective lens OBJ is a single lens made of plastic or glass.
- the positive lens group L2 of the coupling lens CL is moved to the position of the solid line by the uniaxial actuator AC1.
- the lens unit L2 After passing through the lens unit L2 to be a weakly convergent light beam, it is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the light beam diameter is regulated by a diaphragm (not shown), and the first thickness is obtained by the objective lens OBJ.
- the spot is formed on the first information recording surface RL1 as shown by the solid line.
- the reflected light beam modulated by the information pits on the first information recording surface RL1 is again transmitted through the objective lens OBJ and the diaphragm, and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP.
- the information recorded on the first information recording surface RL1 can be read by focusing or tracking the objective lens OBJ by the triaxial actuator AC2.
- the positive lens group L2 of the coupling lens CL is moved to the position of the alternate long and short dash line by the uniaxial actuator AC1.
- the lens unit L2 After passing through the lens unit L2 to be a substantially parallel light beam, it is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the light beam diameter is regulated by a diaphragm (not shown), and the objective lens OBJ has the second thickness.
- This is a spot formed on the second information recording surface RL2 through the transparent substrate PL2 having a thickness (thicker than the first thickness), as indicated by a one-dot chain line.
- the reflected light beam modulated by the information pits on the second information recording surface RL2 is again transmitted through the objective lens OBJ and the aperture, and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP.
- the information recorded on the second information recording surface RL2 can be read by focusing or tracking the objective lens OBJ by the triaxial actuator AC2.
- the positive lens group L2 of the coupling lens CL is moved to the dotted line position by the uniaxial actuator AC1.
- the lens unit L2 After passing through the lens unit L2 to be a weak divergent light beam, it is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light beam is regulated by a diaphragm (not shown), and the third thickness is obtained by the objective lens OBJ. This is a spot formed on the third information recording surface RL3 through the transparent substrate PL3 (thicker than the second thickness) as shown by the dotted line.
- the reflected light beam modulated by the information pits on the third information recording surface RL3 is again transmitted through the objective lens OBJ and the diaphragm, and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP.
- the information recorded on the third information recording surface RL3 can be read by focusing or tracking the objective lens OBJ by the triaxial actuator AC2.
- the objective lens OBJ is attached by the triaxial actuator AC2. Tilt along the radial direction and / or tangential direction of the optical disc. As a result, it is possible to stably record and / or reproduce information on the warped optical disc, and to maintain a good spot quality on the information recording surface even when the optical disc is tilted during rotation.
- the design wavelength of the objective lens is 405 nm
- r in the table below is the radius of curvature
- d is the distance in the optical axis direction from the i-th surface to the (i + 1) -th surface
- Nd is the refractive index of each surface in the d-line (587.6 nm).
- N405 represents the refractive index of each surface at the design wavelength of 405 nm
- ⁇ d represents the Abbe number in the d-line.
- a power of 10 (for example, 2.5 ⁇ 10 ⁇ 3 ) is represented by using E (for example, 2.5 ⁇ E ⁇ 3).
- the optical surface of the objective lens is formed as an aspherical surface that is axisymmetric about the optical axis, each of which is defined by an equation in which the coefficient shown in Table 1 is substituted into Equation (1).
- X (h) is an axis in the optical axis direction (the light traveling direction is positive)
- ⁇ is a conical coefficient
- a 2i is an aspherical coefficient
- h is a height from the optical axis
- r is a paraxial curvature. Radius.
- Table 1 shows lens data concerning the objective lens of the comparative example.
- the temperature dependence (refractive index change with respect to temperature change) of the refractive index in the plastic materials of the comparative example and Examples 1 to 9, 14, and 16 described later was set to ⁇ 10 ⁇ 10 ⁇ 5 / ° C.
- FIG. 5 shows the spherical aberration and sine condition curve of the comparative example, and FIG.
- FIG. 6 shows an aspherical first-order differential curve on the optical surface on the optical disc side of the comparative example.
- the objective lens of the comparative example is designed such that the sine condition violation amount OSC is substantially zero, that is, the sine condition is satisfied.
- FIG. 7 shows the spherical aberration and sine condition curve of Example 1
- FIG. 8 shows an aspherical first-order differential curve on the optical disk side optical surface of Example 1.
- the sine condition violation amount OSC has a positive maximum value at a position of 80/4 of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 2 Table 3 shows lens data of Example 2.
- FIG. 9 shows the spherical aberration and sine condition curve of Example 2
- FIG. 10 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 2.
- the sine condition violation amount OSC has a positive maximum value at a position that is 80% and 5 minutes of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 3 Table 4 shows lens data of Example 3.
- FIG. 11 shows the spherical aberration and sine condition curve of Example 3
- FIG. 12 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 3.
- the sine condition violation amount OSC has a positive maximum value at a position that is 80% and 5 minutes of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 4 Table 5 shows lens data of Example 4.
- FIG. 13 shows the spherical aberration and sine condition curve of Example 4
- FIG. 14 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 4.
- the sine condition violation amount OSC has a positive maximum value at a position that is 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 5 Table 6 shows lens data of Example 5.
- FIG. 15 shows the spherical aberration and sine condition curve of Example 5
- FIG. 16 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 5.
- the sine condition violation amount OSC has a positive maximum value at a position that is 80% and 6 minutes of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 6 Table 7 shows lens data of Example 6.
- FIG. 17 shows the spherical aberration and sine condition curve of Example 6, and
- FIG. 18 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 6.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 80/3 of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 7 Table 8 shows lens data of Example 7.
- FIG. 19 shows the spherical aberration and sine condition curve of Example 7, and
- FIG. 20 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 7.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 8 Table 9 shows lens data of Example 8.
- the off-axis aberration CM3 is larger than that in the fourth embodiment.
- FIG. 21 shows the spherical aberration and sine condition curve of Example 8
- FIG. 22 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 8.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 70% and 9 minutes of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 9 Table 10 shows lens data of Example 9.
- the off-axis aberration CM3 is larger than that in the eighth embodiment.
- FIG. 23 shows the spherical aberration and sine condition curve of Example 9, and
- FIG. 24 shows an aspherical first-order differential curve on the optical disc side optical surface of Example 9.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 70/2 of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 10 Table 11 shows lens data of Example 10.
- FIG. 25 shows the spherical aberration and sine condition curve of Example 10
- FIG. 26 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 10.
- the sine condition violation amount OSC has a positive maximum value at a position of 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 11 Table 12 shows lens data of Example 11.
- FIG. 27 shows the spherical aberration and sine condition curve of Example 11, and
- FIG. 28 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 11.
- the sine condition violation amount OSC has a positive maximum value at a position of 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 12 Table 13 shows lens data of Example 12.
- FIG. 29 shows the spherical aberration and sine condition curve of Example 12, and
- FIG. 30 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 12.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 13 Table 14 shows lens data of Example 13.
- FIG. 31 shows the spherical aberration and sine condition curve of Example 13
- FIG. 32 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 13.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- FIG. 33 shows the spherical aberration and sine condition curve of Example 14, and
- FIG. 34 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 14.
- the sine condition violation amount OSC has a positive maximum value at a position corresponding to 80/5 of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Example 15 Table 16 shows lens data of Example 15.
- FIG. 35 shows the spherical aberration and sine condition curve of Example 15, and
- FIG. 36 shows the aspherical first-order differential curve on the optical disk side optical surface of Example 15.
- the objective lens of Example 15 has a positive maximum value at the position where the sine condition violation amount OSC is 80% of the effective radius, and the optical axis is more than the positive maximum value. This is an example having a negative maximum at a position close to.
- FIG. 37 shows the spherical aberration and sine condition curve of Example 16
- FIG. 38 shows the aspherical first-order differential curve on the optical disc side optical surface of Example 16.
- the sine condition violation amount OSC has a positive maximum value at a position of 80% of the effective radius.
- the sine condition violation amount OSC does not have a negative maximum value.
- Tables 18 (A) to 18 (C) show Comparative Examples and Examples 1 to 5, Tables 19 (A) to 19 (C) Examples 6 to 11, Tables 20 (A) to 20 (C) Table 6 summarizes the characteristic values of Examples 12 to 16.
- Table 21, Table 22, and Table 23 show the values of the conditional expressions described in the claims.
- the values in Tables 21 to 23 are values at room temperature (25 ⁇ 3 ° C.), the units of T, TMAX, T MAX -T MIN , H are mm, and the units of ⁇ SA3 / ⁇ M, CM3, CM5 are ⁇ rms, and the unit of ⁇ is degree (°).
- the difference in high-order spherical aberration at the time of focus jump in Patent Document 2 is 0.02 ⁇ rms or more in absolute value
- the difference in high-order spherical aberration in this example is almost 0 or 0. 001 ⁇ rms, which is about 0.01 ⁇ rms at the maximum.
- the objective lens of the present invention is superior in terms of suppressing higher-order spherical aberration at the time of focus jump.
- OBJ Objective lens PU1 Optical pickup device LD Blue-violet semiconductor laser AC1 Single-axis actuator AC2 Three-axis actuator PBS Polarizing prism CL Coupling lens L2 Positive lens group L3 Negative lens group PL1 First transparent substrate PL2 Second transparent substrate PL3 Third Transparent substrate RL1 first information recording surface RL2 second information recording surface RL3 third information recording surface QWP ⁇ / 4 wavelength plate
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- General Physics & Mathematics (AREA)
- Optical Head (AREA)
- Lenses (AREA)
Abstract
Description
(1)特許文献2の対物レンズを用いると、設計倍率における正弦条件を有効半径の全領域にて補正しているため、フォーカスジャンプ時の残留高次球面収差が大きくなる傾向がある。つまり、倍率変化した際の3次球面収差と5次球面収差の比が、カバーガラス厚が変化した際の3次球面収差と5次球面収差の比(約5:1)から大きくかけ離れてしまうので、特許文献2の対物レンズは、2層のBDよりも情報記録面の透明基板厚の最大差が大きい3層以上のBDの情報記録面に光束を集光する為に用いるのには適していない。
(2)倍率変化した際の3次球面収差の変化量が小さいので、特許文献2の対物レンズは、フォーカスジャンプ時に大きなカップリングレンズの移動量が必要となり、従って薄型の光ピックアップ装置に用いるのに適していない。
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
プラスチック材料からなり、
前記透明基板厚のうち最大の透明基板厚をTMAX(mm)としたとき、常温(25±3℃)、かつ、(1)式を満たすカバーガラス厚T(mm)において、球面収差(λrms)が最小となるときの倍率Mが(2)式を満たし、
TMAX×0.85≦T≦TMAX×1.1 (1)
-0.003≦M≦0.003 (2)
前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持つことを特徴とする。
(特性1)フォーカスジャンプ時の残留高次球面収差が小さいこと。
(特性2)フォーカスジャンプをする際のカップリングレンズの移動量が小さいこと。
(特性3)透明基板厚が厚い方の情報記録面に対して情報の記録/再生を行う際の対物レンズのチルト感度が小さくなりすぎないこと。特に、プラスチック製の対物レンズを使用する場合には、透明基板厚が厚い方の情報記録面に対して情報の記録/再生を行う最中に環境温度が高温になった場合のレンズチルト感度が小さくなり過ぎないことが必要である。
本発明者らは、対物レンズの設計において正弦条件を満たすべきとする従来の技術常識から離れ、正弦条件をあえて崩すことによって従来技術の問題を解消できないか検討した。しかしながら、特許文献2に示すように、設計倍率を負(発散光入射)とし、かつ、設計倍率における正弦条件を有効半径内の全領域において満足するようにコマ収差の補正状態を設定すると、フォーカスジャンプ時に残留高次球面収差が大きくなり過ぎ、また倍率変化した際の3次球面収差と5次球面収差の比が、カバーガラス厚が変化した際の3次球面収差と5次球面収差の比(約5:1)から大きくかけ離れてしまうことがわかった。かかる知見に基づき本発明者らは、(2)式を満たす前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持つようにすることで、フォーカスジャンプ時における高次球面収差を有効に抑制できることを見出したのである。
フォーカスジャンプをする際のカップリングレンズの移動量を小さくするためには、倍率変化に対する球面収差変化量を大きくする必要がある。本発明者らは、検討の結果、(2)式を満たす前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持つようにすることで、フォーカスジャンプ時における高次球面収差を有効に抑制できるだけでなく、倍率変化に対する3次球面収差変化量も増大させることが可能となることを見出した。
また、本発明者らは、レンズチルトした際に発生するコマ収差に関して、3層以上のBD用のプラスチック製の対物レンズが満たすべき目標値を検討した。現在、2層のBDに対して情報の記録/再生を行う光ピックアップ装置にはプラスチック製の対物レンズが搭載されているものがあり、かかる対物レンズは、透明基板厚が厚いほうの情報記録面L0(100μm)と透明基板厚が薄いほうの情報記録面L1(75μm)の中間のカバーガラス厚87.5μmと、ゼロの倍率(平行光束が入射する場合に相当する)との組み合わせにて球面収差が最小となるように設計されている。このように設計されたプラスチック製の対物レンズでは、上述したように、レンズチルトした際に発生するコマ収差量が最小となるのは、情報記録面L0に対して情報の記録/再生を実行中に環境温度が高温になる場合であり、この状態において対物レンズが傾いたこと(レンズチルト)による3次コマ収差発生量をCM(LT)とする。逆にいうと3層以上のBD用のプラスチック製の対物レンズは、レンズチルトした際に発生するコマ収差量の最小値がCM(LT)より大きくなるように設計されていれば実用に耐えうる、ということが出来る。比較例として後述するように、情報記録面L0に対して情報の記録/再生を行う場合に、高温(55度)にて0.5度のレンズチルトをした状態の2層BD用のプラスチック製の対物レンズのコマ収差発生量CM(LT)は0.02λrms程度であり、同じ状態にて光ディスクを同量傾けた際に発生する3次コマ収差CM(DT)と、CM(LT)との比は、0.36程度となる。本発明者らは、これらの値を目標値として、3層以上のBD用に好適なプラスチック製の対物レンズを検討した結果、常温(25±3℃)かつ(2)を満たす倍率において、球面収差が最小となるときのカバーガラス厚Tが(1)式の下限以上となるように球面収差の補正状態を設定することで、CM(LT)の目標値をみたすことを見出した。尚、CM(LT)は、カバーガラス厚Tが厚いほど大きくすることができるが、カバーガラス厚Tが(1)式の上限を超えると、透明基板厚が最も薄い情報記録面に情報の記録/再生を行う際に対物レンズに入射する光束の収束度合いが大きくなりすぎて、レンズシフト特性(光ピックアップ装置において、対物レンズがトラッキングを行った際の収差発生量を指す)が劣悪になったり、透明基板厚が最も薄い情報記録面へフォーカスジャンプした際の残留高次球面収差が大きくなったりするという課題が発生するので好ましくない。
TMAX×0.85≦T≦TMAX×1.0 (3)
ことを特徴とする。
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
ガラス材料からなり、
前記透明基板厚のうち最大の透明基板厚をTMAX(mm)としたとき、常温(25±3℃)、かつ、(4)式を満たす厚みのカバーガラス厚T(mm)において、球面収差(λrms)が最小となるときの倍率Mが(2)式を満たし、
TMAX×0.75≦T≦TMAX×1.0 (4)
-0.003≦M≦0.003 (2)
前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持つことを特徴とする。
TMAX×0.8≦T≦TMAX×0.95 (5)
ことを特徴とする。
-0.003≦M≦0.003 (2)
21<|ΔSA3/(ΔM×f)|<25 (6)
ことを特徴とする。
-0.003≦M≦0.003 (2)
4.2<ΔSA3/ΔSA5<5.2 (7)
ことを特徴とする。
0.02<|CM5|<0.05 (8)
ことを特徴とする。
0≦|CM3|<0.02 (9)
ことを特徴とする。
-0.003≦M≦0.003 (2)
0.02<|CM5|<0.05 (8)
ことを特徴とする。
0≦|CM3|<0.02 (9)
ことを特徴とする。
請求項15に記載の対物レンズは、請求項14に記載の発明において、前記カバーガラス厚Tと前記倍率Mが(3)式及び(10)式を満たす、
TMAX×0.85≦T≦TMAX×1.0 (3)
M=0 (10)
ことを特徴とする。
TMAX×0.75≦T≦TMAX×1.0 (4)
ことを特徴とする。
TMAX×0.8≦T≦TMAX×0.95 (5)
M=0 (10)
ことを特徴とする。
0.003<OSCMAX/f<0.022 (11)
ことを特徴とする。
0.3≦|CM(LT)/CM(DT)|≦0.8 (12)
ことを特徴とする。
0≦M1/M2<0.92 (13)
ことを特徴とする。
-59.8×N+162<θ<-59.8×N+166 (14)
ことを特徴とする。
0.03(mm)<TMAX-TMIN<0.06(mm) (15)
ことを特徴とする。
-2.8×N+5.1<H<-2.8×N+5.4 (16)
但し、非球面変形量X(h)は、前記光ディスク側の光学面の面頂点に接する平面から非球面までの光軸方向の距離で規定し、前記平面から前記光源側に変形する場合を負、前記平面から前記光ディスク側に変形する場合を正とし、Hは有効半径を1とした場合の相対値とする。
0.03(mm)<TMAX-TMIN<0.06(mm) (15)
ことが好ましい。
0.050mm≦t1≦0.125mm (17)
0.5mm≦t2≦0.7mm (18)
1.0mm≦t3≦1.3mm (19)
を満たすことが好ましいが、これに限られない。
1.5・λ1<λ2<1.7・λ1 (20)
1.8・λ1<λ3<2.0・λ1 (21)
を満たすことが好ましい。
PC=PP+PN-L・PP・PN
PC=1/fC
PC=1/fP+1/fN-L/(fP・fN) (22)
で表される。
M=-fO/fC (23)
となる。
次に、第2の好ましい例は、少なくとも炭素原子数2~20のα-オレフィンと下記一般式(1)で表される環状オレフィンからなる単量体組成物とを付加重合させることにより得られる重合体(A)と、炭素原子数2~20のα-オレフィンと下記一般式(2)で表される環状オレフィンからなる単量体組成物とを付加重合させることにより得られる重合体(B)とを含む樹脂組成物である。
樹脂材料に更なる性能を付加するために、以下のような添加剤を添加してもよい。
フェノール系安定剤、ヒンダードアミン系安定剤、リン系安定剤及びイオウ系安定剤から選ばれた少なくとも1種の安定剤を添加することが好ましい。これらの安定剤を適宜選択し添加することで、例えば、405nmといった短波長の光を継続的に照射した場合の白濁や、屈折率の変動等の光学特性変動をより高度に抑制することができる。
界面活性剤は、同一分子中に親水基と疎水基とを有する化合物である。界面活性剤は樹脂表面への水分の付着や上記表面からの水分の蒸発の速度を調節することで、樹脂組成物の白濁を防止することが可能となる。
可塑剤は共重合体のメルトインデックスを調節するため、必要に応じて添加される。
TMAX×0.85≦T≦TMAX×1.1 (1)
-0.003≦M≦0.003 (2)
ことが好ましい。
TMAX×0.85≦T≦TMAX×1.0 (3)
この時、M=0であると特に好ましい。
TMAX×0.9≦T≦TMAX×0.95 (3)′
この時、M=0であると特に好ましい。
TMAX×0.75≦T≦TMAX×1.0 (4)
-0.003≦M≦0.003 (2)
ことが好ましい。
TMAX×0.8≦T≦TMAX×0.95 (5)
この時、M=0であると特に好ましい。
常温(25±3℃)、かつ、カバーガラス厚Tにおいて、対物レンズの焦点距離fと倍率変化ΔMに対する3次球面収差の変化率ΔSA3/(ΔM×f)(λrms/mm)が(6)式を満たす、
21<|ΔSA3/(ΔM×f)|<25 (6)
ことが好ましい。
21.5<|ΔSA3/(ΔM×f)|<24.5 (6)′
を満たすことである。
4.2<ΔSA3/ΔSA5<5.2 (7)
ことが好ましい。
4.3<ΔSA3/ΔSA5<4.9 (7)′
を満たすことである。
0.02<|CM5|<0.05 (8)
ことが好ましい。
0≦|CM3|<0.02 (9)
ことが好ましい。
0.003<OSCMAX/f<0.022 (11)
ことが好ましい。
0.003<OSCMAX/f<0.015 (11)′
を満たすことである。
0.3≦|CM(LT)/CM(DT)|≦0.8 (12)
を満たすことによって、透明基板厚が厚い方の情報記録面に対して情報の記録/再生を行う場合であっても、レンズチルト感度が小さくなりすぎることを防止できる。更に、対物レンズがプラスチック製であったとしても、透明基板厚が厚い方の情報記録面に対して情報の記録/再生を行う最中に環境温度が高温になった場合でもレンズチルト感度が小さくなり過ぎることを防止できるため好ましい。
0.35≦|CM(LT)/CM(DT)|≦0.8 (12)′
を満たすことである。
|T1-T0|<|T2-T0| (24)
が成り立つことと同義である。
0≦M1/M2<0.92 (13)
ことが好ましい。
0≦M1/M2<0.8 (13)′
を満たすことである。
-59.8×N+162<θ<-59.8×N+166 (14)
ことが好ましい。
-2.8×N+5.1<H<-2.8×N+5.4 (16)
但し、非球面変形量X(h)は、光ディスク側の光学面の面頂点に接する平面から非球面までの光軸方向の距離で規定し、当該平面から光源側に変形する場合を負、当該平面から光ディスク側に変形する場合を正とし、Hは有効半径を1とした場合の相対値とする。
0.9≦d/f≦1.5 (25)
但し、dは、対物レンズの光軸上の厚さ(mm)を表し、fは、第1光束における対物レンズの焦点距離を表す。なお、fは、1.0mm以上、1.8mm以下となることが好ましい。
実施例を説明する前に、比較例について説明する。表1に比較例の対物レンズにかかるレンズデータを示す。比較例は、情報記録面を2つ有する2層BD(TMAX=0.1mm、TMIN=0.075mm)に対応するプラスチック材料からなる対物レンズである。比較例と、後述する実施例1~9、14、16のプラスチック材料における屈折率の温度依存性(温度変化に対する屈折率変化)は、-10×10-5/℃とした。図5に比較例の球面収差及び正弦条件カーブを示し、図6に、比較例の光ディスク側光学面における非球面形状の1階微分カーブを示す。図5に示すように、比較例の対物レンズにおいては、正弦条件違反量OSCがほぼゼロであり、即ち正弦条件を満たす設計がなされている。
表2に実施例1のレンズデータを示す。本実施例は3層以上の多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.075mm(基準状態のd4が対応)とした。図7に実施例1の球面収差及び正弦条件カーブを示し、図8に、実施例1の光ディスク側光学面における非球面形状の1階微分カーブを示す。図7に示すように、実施例1の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割4分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表3に実施例2のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.080mm(基準状態のd4が対応)とした。図9に実施例2の球面収差及び正弦条件カーブを示し、図10に、実施例2の光ディスク側光学面における非球面形状の1階微分カーブを示す。図9に示すように、実施例2の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表4に実施例3のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.085mm(基準状態のd4が対応)とした。図11に実施例3の球面収差及び正弦条件カーブを示し、図12に、実施例3の光ディスク側光学面における非球面形状の1階微分カーブを示す。図11に示すように、実施例3の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表5に実施例4のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.090mm(基準状態のd4が対応)とした。図13に実施例4の球面収差及び正弦条件カーブを示し、図14に、実施例4の光ディスク側光学面における非球面形状の1階微分カーブを示す。図13に示すように、実施例4の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表6に実施例5のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.095mm(基準状態のd4が対応)とした。図15に実施例5の球面収差及び正弦条件カーブを示し、図16に、実施例5の光ディスク側光学面における非球面形状の1階微分カーブを示す。図15に示すように、実施例5の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割6分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表7に実施例6のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.1mm(基準状態のd4が対応)とした。図17に実施例6の球面収差及び正弦条件カーブを示し、図18に、実施例6の光ディスク側光学面における非球面形状の1階微分カーブを示す。図17に示すように、実施例6の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割3分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表8に実施例7のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.11mm(基準状態のd4が対応)とした。図19に実施例7の球面収差及び正弦条件カーブを示し、図20に、実施例7の光ディスク側光学面における非球面形状の1階微分カーブを示す。図19に示すように、実施例7の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割4分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表9に実施例8のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.090mm(基準状態のd4が対応)とした。本実施例は、実施例4に対して軸外収差のCM3が大きめである。図21に実施例8の球面収差及び正弦条件カーブを示し、図22に、実施例8の光ディスク側光学面における非球面形状の1階微分カーブを示す。図21に示すように、実施例8の対物レンズにおいては、正弦条件違反量OSCが有効半径の7割9分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表10に実施例9のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.090mm(基準状態のd4が対応)とした。本実施例は、実施例8に対して軸外収差のCM3が大きめである。図23に実施例9の球面収差及び正弦条件カーブを示し、図24に、実施例9の光ディスク側光学面における非球面形状の1階微分カーブを示す。図23に示すように、実施例9の対物レンズにおいては、正弦条件違反量OSCが有効半径の7割2分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表11に実施例10のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したガラス製の対物レンズであり、その素材はSK5(株式会社オハラ製)であって、T=0.075mm(基準状態のd4が対応)とした。図25に実施例10の球面収差及び正弦条件カーブを示し、図26に、実施例10の光ディスク側光学面における非球面形状の1階微分カーブを示す。図25に示すように、実施例10の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表12に実施例11のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したガラス製の対物レンズであり、その素材はSK12(株式会社オハラ製)であって、T=0.08mm(基準状態のd4が対応)とした。図27に実施例11の球面収差及び正弦条件カーブを示し、図28に、実施例11の光ディスク側光学面における非球面形状の1階微分カーブを示す。図27に示すように、実施例11の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表13に実施例12のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したガラス製の対物レンズであり、その素材はLAC13(HOYA株式会社製)であって、T=0.095mm(基準状態のd4が対応)とした。図29に実施例12の球面収差及び正弦条件カーブを示し、図30に、実施例12の光ディスク側光学面における非球面形状の1階微分カーブを示す。図29に示すように、実施例12の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割7分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表14に実施例13のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したガラス製の対物レンズであり、その素材はSK5(株式会社オハラ製)であって、T=0.1mm(基準状態のd4が対応)とした。図31に実施例13の球面収差及び正弦条件カーブを示し、図32に、実施例13の光ディスク側光学面における非球面形状の1階微分カーブを示す。図31に示すように、実施例13の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表15に実施例14のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.09mm(基準状態のd4が対応)とした。図33に実施例14の球面収差及び正弦条件カーブを示し、図34に、実施例14の光ディスク側光学面における非球面形状の1階微分カーブを示す。図33に示すように、実施例14の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
表16に実施例15のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したガラス製の対物レンズであり、その素材はSK5(株式会社オハラ製)であって、T=0.08mm(基準状態のd4が対応)とした。図35に実施例15の球面収差及び正弦条件カーブを示し、図36に、実施例15の光ディスク側光学面における非球面形状の1階微分カーブを示す。図35に示すように、実施例15の対物レンズは、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っており、さらに、正の極大値よりも光軸に近い位置にて、負の極大値も持つ例である。
表17に実施例16のレンズデータを示す。本実施例は、多層BD(TMAX=0.1mm、TMIN=0.05mm)に対応したプラスチック製の対物レンズであり、T=0.09mm(基準状態のd4が対応)とした。図37に実施例16の球面収差及び正弦条件カーブを示し、図38に、実施例16の光ディスク側光学面における非球面形状の1階微分カーブを示す。図37に示すように、実施例16の対物レンズにおいては、正弦条件違反量OSCが有効半径の8割5分の位置で正の極大値を持っている。一方、正弦条件違反量OSCは負の極大値を持たない。
PU1 光ピックアップ装置
LD 青紫色半導体レーザ
AC1 1軸アクチュエータ
AC2 3軸アクチュエータ
PBS 偏光プリズム
CL カップリングレンズ
L2 正レンズ群
L3 負レンズ群
PL1 第1の透明基板
PL2 第2の透明基板
PL3 第3の透明基板
RL1 第1の情報記録面
RL2 第2の情報記録面
RL3 第3の情報記録面
QWP λ/4波長板
Claims (27)
- 波長λ1(390nm<λ1<415nm)の光束を出射する光源と対物レンズとを有し、透明基板厚が互いに異なる情報記録面を厚さ方向に3つ以上有する光ディスクにおけるいずれかの情報記録面を選択して、前記光源から出射された波長λ1の光束を前記対物レンズにより前記選択された情報記録面に集光することによって、情報の記録及び/または再生を行う光ピックアップ装置用の対物レンズであって、
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
プラスチック材料からなり、
前記透明基板厚のうち最大の透明基板厚をTMAX(mm)としたとき、常温(25±3℃)、かつ、(1)式を満たすカバーガラス厚T(mm)において、球面収差(λrms)が最小となるときの倍率Mが(2)式を満たし、
TMAX×0.85≦T≦TMAX×1.1 (1)
-0.003≦M≦0.003 (2)
前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持つことを特徴とする対物レンズ。 - 前記カバーガラス厚T(mm)が、以下の(3)式を満たすことを特徴とする請求項1に記載の対物レンズ。
TMAX×0.85≦T≦TMAX×1.0 (3) - 波長λ1(390nm<λ1<415nm)の光束を出射する光源と対物レンズとを有し、透明基板厚が互いに異なる情報記録面を厚さ方向に3つ以上有する光ディスクにおけるいずれかの情報記録面を選択して、前記光源から出射された波長λ1の光束を前記対物レンズにより前記選択された情報記録面に集光することによって、情報の記録及び/または再生を行う光ピックアップ装置用の対物レンズであって、
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
ガラス材料からなり、
前記透明基板厚のうち最大の透明基板厚をTMAX(mm)としたとき、常温(25±3℃)、かつ、(4)式を満たすカバーガラス厚T(mm)において、球面収差(λrms)が最小となるときの倍率Mが(2)式を満たし、
TMAX×0.75≦T≦TMAX×1.0 (4)
-0.003≦M≦0.003 (2)
前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持つことを特徴とする対物レンズ。 - 前記カバーガラス厚T(mm)が、以下の(5)式を満たすことを特徴とする請求項3に記載の対物レンズ。
TMAX×0.8≦T≦TMAX×0.95 (5) - 波長λ1(390nm<λ1<415nm)の光束を出射する光源と対物レンズとを有し、透明基板厚が互いに異なる情報記録面を厚さ方向に3つ以上有する光ディスクにおけるいずれかの情報記録面を選択して、前記光源から出射された波長λ1の光束を前記対物レンズにより前記選択された情報記録面に集光することによって、情報の記録及び/または再生を行う光ピックアップ装置用の対物レンズであって、
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
常温(25±3℃)、かつ、(2)式を満たす倍率Mにおいて、球面収差(λrms)が最小となるときのカバーガラス厚をT(mm)、常温(25±3℃)における前記波長λ1の焦点距離をf(mm)としたとき、
常温(25±3℃)、かつ、前記透明基板厚Tにおいて、前記対物レンズの焦点距離fと倍率変化ΔMの積に対する3次球面収差の変化率ΔSA3/(ΔM×f)(λrms/mm)が(6)式を満たすことを特徴とする対物レンズ。
-0.003≦M≦0.003 (2)
21<|ΔSA3/(ΔM×f)|<25 (6) - 波長λ1(390nm<λ1<415nm)の光束を出射する光源と対物レンズとを有し、透明基板厚が互いに異なる情報記録面を厚さ方向に3つ以上有する光ディスクにおけるいずれかの情報記録面を選択して、前記光源から出射された波長λ1の光束を前記対物レンズにより前記選択された情報記録面に集光することによって、情報の記録及び/または再生を行う光ピックアップ装置用の対物レンズであって、
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
常温(25±3℃)、かつ、(2)式を満たす倍率Mにおいて、球面収差(λrms)が最小となるときのカバーガラス厚をT(mm)としたとき、
常温(25±3℃)、かつ、前記カバーガラス厚Tにおいて、前記対物レンズの倍率を変化させた際に発生する3次球面収差ΔSA3(λrms)と5次球面収差ΔSA5(λrms)が(7)式を満たすことを特徴とする対物レンズ。
-0.003≦M≦0.003 (2)
4.2<ΔSA3/ΔSA5<5.2 (7) - 前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持ち、前記有効半径内において正弦条件違反量が負の極大値を持たないことを特徴とする請求項1から6までのいずれか一項に記載の対物レンズ。
- 前記倍率Mにおいて、有効半径の7割から9割の間で、正弦条件違反量が正の極大値を持ち、更に、前記正の極大値よりも光軸に近い位置で、正弦条件違反量が負の極大値を持つことを特徴とする請求項1から6までのいずれか一項に記載の対物レンズ。
- 常温(25±3℃)、かつ、前記カバーガラス厚T、かつ、前記倍率Mにおいて、前記対物レンズに対して半画角1度の斜め光束を入射させた場合に発生する5次コマ収差CM5(λrms)が(8)式を満たすことを特徴とする請求項1から8までのいずれか一項に記載の対物レンズ。
0.02<|CM5|<0.05 (8) - 常温(25±3℃)、かつ、前記カバーガラス厚T、かつ、前記倍率Mにおいて、前記対物レンズに対して半画角1度の斜め光束を入射させた場合に発生する3次コマ収差CM3(λrms)が(9)式を満たすことを特徴とする請求項9に記載の対物レンズ。
0≦|CM3|<0.02 (9) - 波長λ1(390nm<λ1<415nm)の光束を出射する光源と対物レンズとを有し、透明基板厚が互いに異なる情報記録面を厚さ方向に3つ以上有する光ディスクにおけるいずれかの情報記録面を選択して、前記光源から出射された波長λ1の光束を前記対物レンズにより前記選択された情報記録面に集光することによって、情報の記録及び/または再生を行う光ピックアップ装置用の対物レンズであって、
前記対物レンズは、単玉レンズであり、
像側開口数(NA)は0.8以上、0.95以下であり、
常温(25±3℃)、かつ、(2)式を満たす倍率Mにおいて、球面収差(λrms)が最小となるときのカバーガラス厚をT(mm)としたとき、
常温(25±3℃)、前記カバーガラス厚T、かつ、(2)式を満たす倍率Mにおいて、前記対物レンズに対して半画角1度の斜め光束を入射させた場合に発生する5次コマ収差CM5(λrms)が(8)式を満たすことを特徴とする対物レンズ。
-0.003≦M≦0.003 (2)
0.02<|CM5|<0.05 (8) - 常温(25±3℃)、かつ、前記カバーガラス厚T、かつ、前記倍率Mにおいて、前記対物レンズに対して半画角1度の斜め光束を入射させた場合に発生する3次コマ収差CM3(λrms)が(9)式を満たすことを特徴とする請求項11に記載の対物レンズ。
0≦|CM3|<0.02 (9) - 前記対物レンズはプラスチック材料からなることを特徴とする請求項5から12までのいずれか一項に記載の対物レンズ。
- 前記透明基板厚のうち最大の透明基板厚をTMAX(mm)としたとき、前記カバーガラス厚Tが(1)式を満たすことを特徴とする請求項13に記載の対物レンズ。
TMAX×0.85≦T≦TMAX×1.1 (1) - 前記カバーガラス厚Tと前記倍率Mが(3)式及び(10)式を満たすことを特徴とする請求項14に記載の対物レンズ。
TMAX×0.85≦T≦TMAX×1.0 (3)
M=0 (10) - 前記対物レンズはガラス材料からなることを特徴とする請求項5から12までのいずれか一項に記載の対物レンズ。
- 前記透明基板厚のうち最大の透明基板厚をTMAX(mm)としたとき、前記カバーガラス厚Tが(4)式を満たすことを特徴とする請求項16に記載の対物レンズ。
TMAX×0.75≦T≦TMAX×1.0 (4) - 前記カバーガラス厚Tと前記倍率Mが(5)式及び(10)式を満たすことを特徴とする請求項17に記載の対物レンズ。
TMAX×0.8≦T≦TMAX×0.95 (5)
M=0 (10) - 前記正弦条件違反量の正の極大値をOSCMAX(mm)とし、常温(25±3℃)における前記波長λ1の焦点距離をf(mm)としたとき、(11)式を満たすことを特徴とする請求項1から18までのいずれか一項に記載の対物レンズ。
0.003<OSCMAX/f<0.022 (11) - 高温(55±3℃)、かつ、前記最大の透明基板厚TMAXと等しいカバーガラス厚において、前記対物レンズによる集光スポットの3次球面収差が補正されるように、前記対物レンズに対して非平行光束を入射させた状態において、前記対物レンズを傾けた場合に発生する3次コマ収差CM(LT)(λrms)と、カバーガラスを同量傾けた場合に発生する3次コマ収差CM(DT)(λrms)が(12)式を満たすことを特徴とする請求項1から3、請求項5から17、請求項19のいずれか一項に記載の対物レンズ。
0.3≦|CM(LT)/CM(DT)|≦0.8 (12) - 常温(25±3℃)、かつ、前記最大の透明基板厚TMAXと等しいカバーガラス厚において、前記対物レンズによる集光スポットの3次球面収差が補正されるように、前記対物レンズに対して非平行光束を入射させた状態における倍率M1と、常温(25±3℃)、かつ、前記透明基板厚のうち最小の透明基板厚TMINと等しいカバーガラス厚において、前記対物レンズによる集光スポットの3次球面収差が補正されるように、前記対物レンズに対して非平行光束を入射させた状態における倍率M2が(13)式を満たすことを特徴とする請求項1から3、請求項5から17、請求項19又は20のいずれか一項に記載の対物レンズ。
0≦M1/M2<0.92 (13) - 常温(25±3℃)における前記波長λ1に対する前記対物レンズの屈折率Nと、前記光源側の光学面の有効径最周辺における傾斜角θ(度)が(14)式を満たすことを特徴とする請求項1から21までのいずれか一項に記載の対物レンズ。
-59.8×N+162<θ<-59.8×N+166 (14) - 前記透明基板厚のうち最小の透明基板厚をTMINとし、前記透明基板厚のうち最大の透明基板厚をTMAXとしたとき、(15)式を満たすことを特徴とする請求項1から22までのいずれか一項に記載の対物レンズ。
0.03(mm)<TMAX-TMIN<0.06(mm) (15) - 常温(25±3℃)における前記波長λ1に対する前記対物レンズの屈折率をN、前記光ディスク側の光学面の非球面変形量X(h)(mm)の1回微分X’(h)が負から正に入れ替わる半径高さをH(mm)としたとき、(16)式を満たすことを特徴とする請求項1から23までのいずれか一項に記載の対物レンズ。
-2.8×N+5.1<H<-2.8×N+5.4 (16)
但し、非球面変形量X(h)は、前記光ディスク側の光学面の面頂点に接する平面から非球面までの光軸方向の距離で規定し、前記平面から前記光源側に変形する場合を負、前記平面から前記光ディスク側に変形する場合を正とし、Hは有効半径を1とした場合の相対値とする。 - 請求項1から24までのいずれか一項に記載の対物レンズと、光軸方向に移動可能なカップリングレンズとを有し、前記カップリングレンズを光軸方向に移動させることによって、光ディスクにおけるいずれかの情報記録面を選択することを特徴とする光ピックアップ装置。
- 前記カップリングレンズは単玉レンズからなることを特徴とする請求項25に記載の光ピックアップ装置。
- 前記カップリングレンズは正のレンズ群及び負のレンズ群の2群構成からなり、前記正のレンズ群の少なくとも1枚のレンズを移動させることによって、光ディスクにおけるいずれかの情報記録面を選択することを特徴とする請求項25に記載の光ピックアップ装置。
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2011543220A JPWO2011065276A1 (ja) | 2009-11-30 | 2010-11-18 | 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 |
US13/512,273 US20120269051A1 (en) | 2009-11-30 | 2010-11-18 | Objective Lens for Optical Pickup Device and Optical Pickup Device |
CN2010800533824A CN102640218A (zh) | 2009-11-30 | 2010-11-18 | 光拾取装置用的物镜以及光拾取装置 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009272538 | 2009-11-30 | ||
JP2009-272538 | 2009-11-30 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2011065276A1 true WO2011065276A1 (ja) | 2011-06-03 |
Family
ID=44066380
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2010/070552 WO2011065276A1 (ja) | 2009-11-30 | 2010-11-18 | 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 |
Country Status (4)
Country | Link |
---|---|
US (1) | US20120269051A1 (ja) |
JP (1) | JPWO2011065276A1 (ja) |
CN (1) | CN102640218A (ja) |
WO (1) | WO2011065276A1 (ja) |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003085806A (ja) * | 2001-09-07 | 2003-03-20 | Pentax Corp | 光ヘッド用対物レンズおよびこれを用いた光ヘッド |
JP2007323793A (ja) * | 2006-06-05 | 2007-12-13 | Sanyo Electric Co Ltd | 光ピックアップ装置 |
JP2010073238A (ja) * | 2008-09-17 | 2010-04-02 | Hitachi Media Electoronics Co Ltd | 光ピックアップ、対物レンズ、球面収差補正素子及び光学的情報記録再生装置 |
JP2010113745A (ja) * | 2008-11-04 | 2010-05-20 | 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 |
JP2010231840A (ja) * | 2009-03-27 | 2010-10-14 | Hitachi Ltd | 光ディスク装置 |
JP2010238277A (ja) * | 2009-03-30 | 2010-10-21 | Konica Minolta Opto Inc | 光ピックアップ装置及び対物レンズユニット |
JP2010238276A (ja) * | 2009-03-30 | 2010-10-21 | Konica Minolta Opto Inc | 光ピックアップ装置及び対物レンズユニット |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6621742B1 (en) * | 2002-04-29 | 2003-09-16 | Fujitsu Limited | System for programming a flash memory device |
JP2008027475A (ja) * | 2006-07-18 | 2008-02-07 | Hitachi Maxell Ltd | 対物レンズ及び光ピックアップ光学系 |
JP5075681B2 (ja) * | 2008-03-05 | 2012-11-21 | 日立マクセル株式会社 | 対物レンズ |
-
2010
- 2010-11-18 JP JP2011543220A patent/JPWO2011065276A1/ja active Pending
- 2010-11-18 CN CN2010800533824A patent/CN102640218A/zh active Pending
- 2010-11-18 WO PCT/JP2010/070552 patent/WO2011065276A1/ja active Application Filing
- 2010-11-18 US US13/512,273 patent/US20120269051A1/en not_active Abandoned
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003085806A (ja) * | 2001-09-07 | 2003-03-20 | Pentax Corp | 光ヘッド用対物レンズおよびこれを用いた光ヘッド |
JP2007323793A (ja) * | 2006-06-05 | 2007-12-13 | Sanyo Electric Co Ltd | 光ピックアップ装置 |
JP2010073238A (ja) * | 2008-09-17 | 2010-04-02 | Hitachi Media Electoronics Co Ltd | 光ピックアップ、対物レンズ、球面収差補正素子及び光学的情報記録再生装置 |
JP2010113745A (ja) * | 2008-11-04 | 2010-05-20 | 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 |
JP2010231840A (ja) * | 2009-03-27 | 2010-10-14 | Hitachi Ltd | 光ディスク装置 |
JP2010238277A (ja) * | 2009-03-30 | 2010-10-21 | Konica Minolta Opto Inc | 光ピックアップ装置及び対物レンズユニット |
JP2010238276A (ja) * | 2009-03-30 | 2010-10-21 | Konica Minolta Opto Inc | 光ピックアップ装置及び対物レンズユニット |
Also Published As
Publication number | Publication date |
---|---|
JPWO2011065276A1 (ja) | 2013-04-11 |
US20120269051A1 (en) | 2012-10-25 |
CN102640218A (zh) | 2012-08-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
WO2010128654A1 (ja) | 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 | |
WO2013047202A1 (ja) | 対物レンズ及び光ピックアップ装置 | |
WO2011132691A1 (ja) | 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 | |
WO2011136096A1 (ja) | 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 | |
JP5152439B2 (ja) | 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 | |
JP5582421B2 (ja) | 光ピックアップ装置及び光情報記録再生装置 | |
WO2011065276A1 (ja) | 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 | |
WO2013005672A1 (ja) | 光ピックアップ装置 | |
WO2012036052A1 (ja) | 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 | |
WO2011078022A1 (ja) | 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 | |
WO2011099317A1 (ja) | 光ピックアップ装置 | |
WO2011052469A1 (ja) | 光ピックアップ装置 | |
JP2011198446A (ja) | 光ピックアップ装置 | |
JP5835320B2 (ja) | 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 | |
JP5585879B2 (ja) | 光ピックアップ装置及び光情報記録再生装置 | |
JP5229657B2 (ja) | 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 | |
JP5713280B2 (ja) | 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 | |
WO2013027622A1 (ja) | 対物レンズ及び光ピックアップ装置 | |
WO2013121615A1 (ja) | 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 | |
WO2013084558A1 (ja) | 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 | |
WO2013147014A1 (ja) | 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 | |
WO2012133363A1 (ja) | 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 | |
WO2013114662A1 (ja) | 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 | |
WO2012133364A1 (ja) | 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 | |
WO2012063850A1 (ja) | 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 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 201080053382.4 Country of ref document: CN |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 10833122 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2011543220 Country of ref document: JP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 13512273 Country of ref document: US |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 10833122 Country of ref document: EP Kind code of ref document: A1 |