JP4576651B2 - Coupling lens, optical pickup device, and semiconductor laser collimating device - Google Patents

Coupling lens, optical pickup device, and semiconductor laser collimating device Download PDF

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Publication number
JP4576651B2
JP4576651B2 JP34444299A JP34444299A JP4576651B2 JP 4576651 B2 JP4576651 B2 JP 4576651B2 JP 34444299 A JP34444299 A JP 34444299A JP 34444299 A JP34444299 A JP 34444299A JP 4576651 B2 JP4576651 B2 JP 4576651B2
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Prior art keywords
coupling lens
diffractive
lens
change
optical pickup
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JP2001159731A (en
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耕平 大田
則一 荒井
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コニカミノルタホールディングス株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coupling lens for an optical pickup, an optical pickup device, and a semiconductor laser collimating device, and more particularly, to an optical pickup of an optical recording / reproducing device that records or reproduces information recording media such as magneto-optical disks and optical disks. More particularly, the present invention relates to a coupling lens that converts divergent light from a light source and converts the divergent angle to an objective lens, an optical pickup device using the coupling lens, and a semiconductor laser collimator device.
[0002]
[Prior art]
In an optical pickup device that records or reproduces information on a recording medium, a coupling lens is placed in front of an objective lens. This coupling lens converts the divergent light from a semiconductor laser, which is a light source, by converting its divergence angle. Lead to. As the coupling lens, a single aspherical lens having an NA of about 0.1 to 0.2 is generally used, and collimated light from a semiconductor laser is collimated into parallel light.
[0003]
[Problems to be solved by the invention]
If the above-described coupling lens is made of a plastic material, it can be manufactured at a low cost. However, a lens made of a plastic material causes a change in focal length due to temperature fluctuation. Therefore, the divergence angle of the light beam emitted from the coupling lens changes with temperature fluctuation. As a result, there is a problem that the object position with respect to the objective lens changes and the spherical aberration is deteriorated.
[0004]
In view of the problems of the prior art, the present invention is made of a plastic material, and the divergence angle of the emitted light beam hardly changes due to temperature fluctuation, and the emitted light beam is not limited to parallel light, even in the case of convergent light or divergent light. It is an object of the present invention to provide a coupling lens in which the degree of convergence or the degree of divergence hardly changes due to temperature fluctuations.
[0005]
Also provided are an optical pickup device in which the divergence angle of the light beam emitted from the coupling lens hardly changes due to temperature variation, and the spherical aberration of the objective lens does not deteriorate, and a semiconductor laser collimator device in which the parallel light beam does not change in parallel due to temperature variation. The purpose is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a coupling lens of the present invention is a coupling lens used for an optical pickup device for recording and / or reproducing information recording media, which is made of a plastic material and has a first surface or a first surface. It has a diffractive surface in which a step is formed in an annular shape on at least one of the two surfaces, and satisfies the following formula (A).
[0007]
| C1 + (c2-c1) · φD / φC | / fc <0.15λ (mm) (A)
−0.2 ≦ mc ≦ 0.2 (B)
2.0 ≦ fc ≦ 25 (C)
However, c1 = 1 / (n-1) ・ dn / dt + 1 / (n-1) ・ dn / dλ ・ dλ / dt-α
c2 = 1 / λ ・ dλ / dt-2α
fc: focal length of coupling lens (mm) (= 1 / φC)
λ: Wavelength (mm)
n: Refractive index of coupling lens α: Linear expansion coefficient of coupling lens φD: Power of diffractive surface (when diffractive surfaces are provided on both surfaces, the arithmetic sum of powers of diffractive surfaces is φD)
φC: power of coupling lens dn / dt: ratio of refractive index change with respect to temperature fluctuation dn / dλ: ratio of refractive index change with respect to wavelength change dλ / dt: ratio of wavelength change of light source used with respect to temperature fluctuation
According to this coupling lens, the divergence angle of the light beam emitted from the coupling lens hardly changes due to temperature fluctuation. For this reason, the emitted light beam is not limited to parallel light, and even in the case of convergent light or divergent light, the degree of convergence or the degree of divergence hardly changes due to temperature fluctuations.
[0009]
Further, when dλ / dt = 2 × 10 −7 , it is preferable to satisfy the above-described formula (A). Alternatively, when dλ / dt = 5 × 10 −8 , it is preferable to satisfy the above formula (A).
[0012]
Further, the diffractive surface is blazed with respect to diffracted light of the second order or higher, that is, so as to satisfy the above formula (A), or (B) and (C), and the second order. It is preferable that the diffractive surface blazed so as to maximize the diffraction effect of the diffracted light having the above order and the predetermined order is formed.
[0013]
Further, by configuring the optical pickup device so as to have each of the above-described coupling lenses, the divergence angle of the light beam emitted from the coupling lens hardly changes due to the temperature variation, and is stable and accurate with respect to the temperature variation. An apparatus capable of recording or reproducing can be realized.
[0014]
The optical pickup device of the present invention is configured to record or reproduce information by condensing a light beam from a light source on an information recording surface of an information recording medium by an optical system including a coupling lens and an objective lens. In this optical pickup device, the coupling lens is made of a plastic material, and at least one surface of the coupling lens is provided with a diffractive surface in which a step is formed in an annular shape, or the coupling lens An optical element having at least one diffractive surface in which a step is formed in an annular shape is provided in the vicinity, and satisfies the above-described formulas (A) , (B), and (C) .
[0015]
According to this optical pickup device, since the divergence angle of the light beam emitted from the coupling lens hardly changes due to temperature fluctuation, the spherical aberration of the objective lens does not deteriorate. As a result, it is possible to realize an apparatus capable of performing recording or reproduction that is stable and accurate with respect to temperature fluctuations.
[0016]
In the above-described optical pickup device, it is preferable that the following expression is satisfied.
(NAo · (1-mo)) 4 · (fo 2 /fc)·|c1+(c2−c1)·φD/φCl<0.019λ
Also, (NAo · (1-mo)) 4 · (fo 2 /fc)·|c1+(c2−c1)·φD/φCl<0.010λ
It is further preferable to satisfy
NAo: image side numerical aperture of objective lens mo: lateral magnification of objective lens fo: focal length of objective lens
The wavelength λ of the light source described above preferably satisfies λ <0.00068 mm, and more preferably satisfies λ <0.00045 mm.
[0020]
Further, the semiconductor laser collimating device of the present invention is a semiconductor laser collimating device comprising a semiconductor laser and a coupling lens from which a light beam from the semiconductor laser enters and emits parallel light, the coupling lens being a plastic It is made of a material, has a diffractive surface having a ring-shaped step formed on at least one of the first surface and the second surface, and satisfies the following expression.
[0021]
| C1 + (c2-c1) · φD / φC | / fc <0.15λ (mm)
−0.2 ≦ mc ≦ 0.2
2.0 ≦ fc ≦ 25
However, c1 = 1 / (n-1) ・ dn / dt + 1 / (n-1) ・ dn / dλ ・ dλ / dt-α
c2 = 1 / λ ・ dλ / dt-2α
fc: focal length of coupling lens (mm) (= 1 / φC)
λ: wavelength of semiconductor laser (mm)
n: Refractive index of coupling lens α: Linear expansion coefficient of coupling lens φD: Power of diffractive surface (when diffractive surfaces are provided on both surfaces, the arithmetic sum of powers of diffractive surfaces is φD)
φC: power of coupling lens dn / dt: ratio of refractive index change with respect to temperature change dn / dλ: ratio of refractive index change with respect to wavelength change dλ / dt: ratio of wavelength change of semiconductor laser to be used with respect to temperature change ]
According to this semiconductor laser collimating device, since the divergence angle of the light beam emitted from the coupling lens hardly changes due to temperature fluctuation, the parallel state of the parallel light flux from the coupling lens does not change due to temperature fluctuation. Therefore, the light from the semiconductor laser can be emitted as a stable parallel light beam even if the temperature fluctuates.
[0023]
The optical system in the present invention is a set of two or more optical elements including a coupling lens and an objective lens that can record or reproduce a CD or DVD, for example. It may mean a part of the optical system as well as the entire optical system for enabling recording and / or information on the information recording medium to be reproduced. Here, the coupling lens is an optical element that converts the divergence angle of the light beam from the light source and guides it to the objective lens, and includes a so-called collimating lens that converts the divergent light from the light source into a substantially parallel light beam. On the other hand, the objective lens is a lens group that is disposed opposite to the optical information recording medium at a position closest to the optical information recording medium when the optical information recording medium is loaded in the optical pickup apparatus. The lens group which has the condensing effect | action provided so that it could operate | move at least by the actuator of this optical axis direction is pointed out. In the present invention, the optical element that can be arranged in the vicinity of the coupling lens is separate from the lens group of the objective lens and can be provided in the vicinity of the coupling lens (may be integrated). An optical element includes, for example, an optical element having almost no refractive action. Of course, this optical element is not necessarily provided when the diffractive surface of the present invention is provided in a coupling lens.
[0024]
Examples of the information recording medium in the present invention include various CDs such as CD, CD-R, CD-RW, CD-Video, and CD-ROM, DVD, DVD-ROM, DVD-RAM, DVD-R, and DVD. Examples include various DVDs such as -RW, and disk-shaped information recording media such as MD.
[0025]
Further, recording or (and / or) reproduction of information with respect to an information recording medium means that information is recorded on the information recording surface of the information recording medium as described above, and information recorded on the information recording surface is reproduced. That means. The optical pickup device in the present invention may be used only for recording or reproduction, or may be used for both recording and reproduction. Further, it may be used for recording on a certain information recording medium and reproducing on another information recording medium, or may be used for recording or recording on a certain information recording medium. It may be used for performing reproduction and recording and reproduction on another information recording medium. Note that reproduction here includes simply reading information. Therefore, the optical pickup device to which the coupling lens or the semiconductor collimator device of the present invention is applied also includes the above-described optical pickup device.
[0026]
The plastic material for the coupling lens may be acrylic, polyolefin, polycarbonate, styrene, or the like, but is not limited thereto.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical pickup device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an optical pickup device.
[0028]
As shown in FIG. 1, the optical pickup device is an optical information recording unit for a semiconductor laser 1 as a light source, a coupling lens 2 for converting a divergence angle of diverging light emitted from the light source, and a light beam from the coupling lens 2. The objective lens 3 which condenses on the information recording surface 5 of the medium 11 and the photodetector 4 which receives the reflected light from the optical information recording medium 11 are provided.
[0029]
The optical pickup device further includes a beam splitter 6 that reflects and separates the reflected light from the optical information recording medium 11 toward the photodetector 4, and is disposed between the coupling lens 2 and the objective lens 3. Operates when reproducing information from the optical information recording medium 11, the four-wavelength plate 7, the diaphragm 8 placed in front of the objective lens 3, the cylindrical lens 9 disposed between the beam splitter 6 and the photodetector 4. And a focus / tracking actuator 10.
[0030]
The coupling lens 2 is formed of a resin material, and has a diffractive surface on which at least one surface is formed with a step in a ring shape. The diffraction surface is provided with a diffraction zone as a relief (surface irregularities) on the surface of a substrate lens serving as a substrate. Therefore, the substrate lens is a lens having a macro view without the relief structure for diffraction.
[0031]
The optical pickup device of the present invention compensates for a change in the focal length of the coupling lens due to a temperature variation caused by forming the coupling lens from a resin material by applying appropriate power to the diffractive surface. That is, when the temperature rises, the oscillation wavelength of the semiconductor laser becomes longer and the power of the diffractive surface becomes stronger to compensate for the power reduction due to the temperature rise of the substrate lens of the coupling lens.
[0032]
Here, the change of the wavefront aberration of the objective lens when the focal length of the coupling lens changes due to temperature fluctuation is obtained.
[0033]
First, in a system consisting of an objective lens and a coupling lens, the wavefront aberration of the objective lens caused by a change in the object magnification relative to the objective lens due to a change in the focal length of the coupling lens and a change in the imaging magnification of the objective lens. Consider the deterioration of It is assumed that the objective lens is focused at the best position.
[0034]
Deterioration ratio dWo / dmo of the wavefront aberration Wo (rms in mm) of the objective lens due to a change in the lateral magnification mo of the objective lens is expressed by NAo for the image side numerical aperture of the objective lens, fo for the focal length, and mo for the lateral magnification. The coefficient is represented by the following equation with β. The image side means the information recording medium side.
[0035]
dWo / dmo = β · (NAo · (1-mo)) 4 · fo
[0036]
Note that, when examined with a single objective lens, the value of β was about ± 0.012.
(The sign shall be selected in the direction of increasing Wo.)
[0037]
Further, when the ratio dmo / df of the change in the imaging magnification of the objective lens due to the change in the focal length of the coupling lens is obtained, the following equation is approximately obtained when the light emitted from the coupling lens is close to parallel light. .
[0038]
dmo / dfc = −fo / fc 2
[0039]
Next, changes in the focal length of the coupling lens due to temperature fluctuations will be described. First, the power of the substrate lens is φB, the power of the diffractive surface is φD, and the power of the entire coupling lens is φC = φB + φD. When diffractive surfaces are provided on both surfaces, the arithmetic sum of powers of the diffractive surfaces is φD.
[0040]
When n is the refractive index, λ is the wavelength, α is the linear expansion coefficient, t is the temperature, and fc is the focal length, the ratio dfc / dt of the change in the focal length of the coupling lens due to temperature variation is expressed by the following equation. .
[0041]
dfc / dt = −fc 2 · dφC / dt
= -Fc 2 · (c1 · φB + c2 · φD)
However, c1 = 1 / (n-1) ・ dn / dt + 1 / (n-1) ・ dn / dλ ・ dλ / dt-α
c2 = 1 / λ ・ dλ / dt-2α
[0042]
Alternatively, when φB = φC−φD is used, the following equation is obtained.
[0043]
dfc / dt = −fc · (c1 + (c2−c1) · φD / φC)
[0044]
In summary, in this system, the wavefront aberration deterioration ΔWo (rms in mm) of the objective lens with respect to the temperature fluctuation Δt is expressed by the following equation.
ΔWo = (dWo / dmo) · | (dmo / dfc) · (dfc / dt) · Δt |
[0045]
Here, numerical examples are shown. That is, assuming that the image side numerical aperture of the objective lens is NAo = 0.6, the focal length is fo = 3 mm, the lateral magnification is mo = 0, and the coefficient is β = ± 0.12, dWo / dmo = ± 0.047. (Mm)
[0046]
If the focal length of the coupling lens is fc = 20 mm,
dmo / dfc = −0.0075 (mm −1 )
[0047]
Further, the wavelength is λ = 650 nm, the refractive index of the coupling lens is n = 1.54113, the linear expansion coefficient is α = 7 × 10 −5 , and the temperature variation of the refractive index is dn / dt = −1.2 × 10 −. 4. When the temperature variation of the oscillation wavelength of the semiconductor laser is dλ / dt = 2 × 10 −7 and the refractive index change due to the wavelength change is dn / dλ = −38,
c1 = -2.97 × 10 −4 and c2 = 1.68 × 10 −4 .
[0048]
If the coupling lens does not have a diffractive surface,
If dfc / dt = 0.599 and Δt = 30 degrees,
ΔWo = 0.047 × | (−0.0075) × 0.0059 × 30 | = 0.000062 mm = 0.096λ
Thus, the deterioration is less than the Marshall discriminant value 0.07λrms. This deterioration is greater as the focal length of the coupling lens is shorter.
[0049]
According to the present invention, this deterioration can be reduced by applying an appropriate diffraction power to the coupling lens.
[0050]
That is, assuming that the wavefront aberration in the reference state of the objective lens is 0, it is necessary to suppress the deterioration of the wavefront aberration to 0.07λrms with respect to a temperature variation of 30 degrees, and the following condition is obtained.
0.07λ> (dWo / dmo) · | (dmo / dfc) · (dfc / dt) · 30 (° C.) |
When the above relationship is used for this equation, the following equation (1) is obtained.
[0051]
(NAo · (1-mo)) 4 · (fo 2 /fc)·|c1+(c2−c1)·φD/φC|<0.019λ (1)
[0052]
If the relationship of the above equation (1) is satisfied, even if the temperature changes, the positional relationship between the light emitting point of the light source and the focal position of the coupling lens hardly changes, and the divergence of the light beam emitted from the coupling lens is reduced. Since the degree hardly changes and the divergence angle hardly changes, an optical pickup device in which the wavefront aberration deterioration of the objective lens is small can be obtained. It is more desirable to satisfy the following formula (2).
[0053]
(NAo · (1-mo)) 4 · (fo 2 /fc)|c1+(c2-c1)·φD/φC|<0.010λ (2)
[0054]
Further, as a practical condition range as a coupling lens, in order to be able to correspond to an optical pickup with an image side numerical aperture NAo = 0.6, a focal length fo = 1.0 mm, and a lateral magnification mo = 0. It is necessary to satisfy the following formula (3).
[0055]
| C1 + (c2-c1) · φD / φC | / fc <0.15λ (mm) (3)
[0056]
More desirably, the following expression (4) is satisfied.
[0057]
│c1 + (c2-c1) ・ φD / φC | / fc <0.037λ (mm) (4)
[0058]
More preferably, the following expression (5) is satisfied.
[0059]
| C1 + (c2-c1) · φD / φC | / fc <0.009λ (mm) (5)
[0060]
Further, it is practical that the coupling lens magnification mc (0 when parallel light is emitted) and the focal length satisfy the ranges of the following formulas (6) and (7), respectively.
[0061]
−0.2 ≦ mc ≦ 0.2 (6)
[0062]
2.0 ≦ fc ≦ 25 (7)
[0063]
In this case, when mc is equal to or greater than the lower limit of the expression (6), the outer diameter of the coupling lens does not increase, and when it is equal to or smaller than the upper limit, the outer diameter of the objective lens does not increase, and the optical pickup device can be downsized. It becomes possible.
[0064]
Further, when fc is equal to or higher than the lower limit of the expression (7), a strong power diffractive surface is not necessary so as to obtain the above temperature compensation effect, and it becomes easy to manufacture a diffractive ring zone having high diffraction efficiency. If it is below the upper limit, the optical pickup device can be miniaturized.
[0065]
In addition, if the distance between the diffracting ring zones is too small, manufacturing becomes difficult. To avoid this problem, it is effective to provide diffractive surfaces on both sides and to blaze using high-order diffracted light. . Further, by applying the present invention to an optical pickup device using a light source having a short wavelength, an optical pickup device capable of recording or reproducing with high density can be obtained. Therefore, it is desirable that the wavelength λ of the light source satisfies λ <0.00068 mm, more preferably λ <0.00045 mm.
[0066]
【Example】
Next, Examples 1, 2, and 3 will be described for the above-described coupling lens of the present invention. Examples 1 and 2 have a reference wavelength of 650 nm, and Example 3 has a reference wavelength of 400 nm. The specification values of each example are as shown in Table 1 below. Moreover, the value of the above-mentioned formula (1) regarding the pickup device is shown at the bottom of Table 1.
[0067]
[Table 1]
[0068]
In Example 3, since a short wavelength laser having a smaller dλ / dt is used than in Examples 1 and 2, strong diffractive surface power is required.
[0069]
The diffraction surface is represented by the following optical path difference function Φ (h), and a diffraction ring zone is provided every time the value of the optical path difference function changes by mλ (m is the diffraction order).
[0070]
Φ (h) = b2 · h 2 + b4 · h 4 + b6 · h 6 +...
Where h: distance from the optical axis b2, b4, b6,...: Coefficient of optical path difference function
An aspherical surface is expressed by the following equation.
[0072]
X = (h 2 / r) / (1 + √ (1− (1 + K) h 2 / r 2 )) + A 2 · h 2 + A 4 · h 4 + A 6 · h 6 +.
Where A2, A4, A6,...: Aspheric coefficient K: conical coefficient r: paraxial radius of curvature
<Example 1>
[0074]
Table 2 shows lens data of Example 1. As shown in Table 1, when the light source wavelength is λ650 nm, the focal length is fc 14.0 mm and the light source side numerical aperture NA is 0.107.
[0075]
[Table 2]
[0076]
FIG. 2 is a lens cross-sectional view of the coupling lens of Example 1, and FIG. 3 is a spherical aberration diagram of the coupling lens of Example 1 (reference wavelength λ 650 nm, light source side numerical aperture NA 0.107). 3 that the spherical aberration is sufficiently corrected at the reference wavelength λ = 650 nm in the coupling lens of Example 1. FIG.
[0077]
<Example 2>
[0078]
Table 3 shows lens data of Example 2. As shown in Table 1, when the light source wavelength is λ650 nm, the focal length is fc 8.0 mm and the light source side numerical aperture NA is 0.188.
[0079]
[Table 3]
[0080]
4 is a lens cross-sectional view of the coupling lens of Example 2, and FIG. 5 is a spherical aberration diagram of the coupling lens of Example 2 (reference wavelength λ 650 nm, light source side numerical aperture NA 0.188). 5 that the spherical aberration is sufficiently corrected at the reference wavelength λ = 650 nm in the coupling lens of Example 2. FIG.
[0081]
<Example 3>
[0082]
Table 4 shows lens data of Example 3. As shown in Table 1, when the light source wavelength is λ400 nm, the focal length is fc 8.0 mm and the light source side numerical aperture NA is 0.188.
[0083]
[Table 4]
[0084]
FIG. 6 is a lens cross-sectional view of the coupling lens of Example 2, and FIG. 7 is a spherical aberration diagram of the coupling lens of Example 3 (reference wavelength λ400 nm, light source side numerical aperture NA0.188). It can be seen from FIG. 7 that the spherical aberration is sufficiently corrected at the reference wavelength λ = 400 nm in the coupling lens of Example 3.
[0085]
In the above embodiments, the example in which the diffractive surface of the present invention is provided in the coupling lens has been described, but instead of providing the coupling lens, an optical element in which the divergence angle of the incident light beam is not substantially converted, It may be provided in the vicinity of the coupling lens so that the diffractive surface of the present invention is provided on the optical element.
[0086]
【The invention's effect】
According to the present invention, the divergence angle of a light beam emitted from a coupling lens made of a plastic material hardly changes even if the temperature varies. Therefore, when this coupling lens light is used in a pickup device, it is possible to provide a pickup device in which the object position with respect to the objective lens does not change even when the temperature fluctuates and the spherical aberration of the objective lens does not deteriorate. In addition, it is possible to provide a semiconductor laser collimating apparatus that can emit a stable parallel light beam even when temperature fluctuation occurs.
[Brief description of the drawings]
FIG. 1 is an optical path diagram showing a configuration of an optical pickup device according to an embodiment of the present invention.
FIG. 2 is a lens cross-sectional view of a coupling lens of Example 1 according to an embodiment of the present invention.
3 is a spherical aberration diagram of the coupling lens of Example 1 with respect to a reference wavelength λ = 650 nm. FIG.
4 is a lens cross-sectional view of a coupling lens of Example 2 according to an embodiment of the present invention. FIG.
5 is a spherical aberration diagram with respect to a reference wavelength λ = 650 nm of the coupling lens of Example 2. FIG.
6 is a lens cross-sectional view of a coupling lens of Example 3 according to an embodiment of the present invention. FIG.
7 is a spherical aberration diagram of the coupling lens of Example 3 with respect to a reference wavelength λ = 400 nm. FIG.
[Explanation of symbols]
1 Semiconductor laser (light source)
2 Coupling lens 3 Objective lens 4 Optical detector 5 Information recording surface 11 Optical information recording medium

Claims (11)

  1. A coupling lens used in an optical pickup device for recording and / or reproducing information recording media,
    Made of plastic material,
    Having a diffractive surface in which a step is formed in an annular shape on at least one of the first surface or the second surface;
    A coupling lens that satisfies the following formula.
    | C1 + (c2-c1) · φD / φC | / fc <0.15λ (mm)
    −0.2 ≦ mc ≦ 0.2
    2.0 ≦ fc ≦ 25
    However, c1 = 1 / (n-1) ・ dn / dt + 1 / (n-1) ・ dn / dλ ・ dλ / dt-α
    c2 = 1 / λ ・ dλ / dt-2α
    fc: focal length of coupling lens (mm) (= 1 / φC)
    λ: Wavelength (mm)
    n: Refractive index of the coupling lens α: Coefficient of linear expansion of the coupling lens φD: Power of the diffractive surface (If diffractive surfaces are provided on both sides, calculate the power of the diffractive surface
    The art sum is assumed to be φD)
    φC: coupling lens power dn / dt: ratio of refractive index change with respect to temperature change dn / dλ: ratio of refractive index change with respect to wavelength change dλ / dt: ratio of wavelength change of light source used with respect to temperature change
  2. The coupling lens according to claim 1, wherein dλ / dt = 2 × 10 −7 .
  3. The coupling lens according to claim 1, wherein dλ / dt = 5 * 10 −8 .
  4. 4. The coupling lens according to claim 1, wherein the diffractive surface is blazed with respect to diffracted light of the second or higher order .
  5. The optical pick-up apparatus which has a coupling lens of any one of Claims 1-4 .
  6. An optical pickup device configured to condense a light beam from a light source on an information recording surface of an information recording medium by an optical system including a coupling lens and an objective lens to record or reproduce information,
    The coupling lens is made of a plastic material;
    At least one surface of the coupling lens is provided with a diffractive surface in which a step is formed in an annular shape, or a diffractive surface in which a step is formed in an annular shape is provided on at least one surface in the vicinity of the coupling lens. An optical element having
    An optical pickup device satisfying the following formula:
    | C1 + (c2-c1) · φD / φC | / fc <0.15λ (mm)
    −0.2 ≦ mc ≦ 0.2
    2.0 ≦ fc ≦ 25
    However, c1 = 1 / (n-1) ・ dn / dt + 1 / (n-1) ・ dn / dλ ・ dλ / dt-α
    c2 = 1 / λ ・ dλ / dt-2α
    fc: focal length of coupling lens (mm) (= 1 / φC)
    λ: Wavelength (mm)
    n: Refractive index of the coupling lens
    α: Coefficient of linear expansion of the coupling lens
    φD: Power of the diffractive surface (when diffractive surfaces are provided on both sides, calculate the power of the diffractive surface
    The art sum is assumed to be φD)
    φC: Power of coupling lens
    dn / dt: ratio of refractive index change to temperature fluctuation
    dn / dλ: ratio of refractive index change with respect to wavelength change
    dλ / dt: ratio of wavelength change of light source to temperature fluctuation
  7. The optical pickup device according to claim 6, wherein the following expression is satisfied.
    (NAo ・ (1-mo)) Four ・ (Fo 2 /Fc)·|c1+(c2−c1)·φD/φCl<0.019λ
    Where NAo: the image side numerical aperture of the objective lens
    mo: Horizontal magnification of objective lens
    fo: focal length of the objective lens
  8. The optical pickup device according to claim 7, wherein the following expression is satisfied.
    (NAo · (1-mo)) 4 · (fo 2 /fc)·|c1+(c2−c1)·φD/φCl<0.01 0 λ
  9. The optical pickup device according to claim 6, wherein the following expression is satisfied.
    λ <0.00068mm
  10. The optical pickup device according to claim 6, wherein the following expression is satisfied.
    λ <0.000 45 mm
  11. A semiconductor laser collimating device comprising a semiconductor laser and a coupling lens from which a light beam from the semiconductor laser is incident and from which parallel light is emitted,
    The coupling lens is
    Made of plastic material,
    Having a diffractive surface in which a step is formed in an annular shape on at least one of the first surface or the second surface;
    A semiconductor laser collimator that satisfies the following formula.
    | C1 + (c2-c1) · φD / φC | / fc <0.15λ (mm)
    −0.2 ≦ mc ≦ 0.2
    2.0 ≦ fc ≦ 25
    However, c1 = 1 / (n-1) ・ dn / dt + 1 / (n-1) ・ dn / dλ ・ dλ / dt-α
    c2 = 1 / λ ・ dλ / dt-2α
    fc: focal length of coupling lens (mm) (= 1 / φC)
    λ: wavelength of semiconductor laser (mm)
    n: Refractive index of the coupling lens
    α: Coefficient of linear expansion of the coupling lens
    φD: Power of the diffractive surface (when diffractive surfaces are provided on both sides, calculate the power of the diffractive surface
    The art sum is assumed to be φD)
    φC: Power of coupling lens
    dn / dt: ratio of refractive index change to temperature fluctuation
    dn / dλ: ratio of refractive index change with respect to wavelength change
    dλ / dt: Ratio of wavelength change of semiconductor laser to be used with respect to temperature fluctuation
JP34444299A 1999-12-03 1999-12-03 Coupling lens, optical pickup device, and semiconductor laser collimating device Expired - Fee Related JP4576651B2 (en)

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Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004005943A (en) 2002-04-26 2004-01-08 Konica Minolta Holdings Inc Registration reproduction optics, objective lens, optical element for aberation compensation, optical pickup system, and orecording/reproducing apparatus, aberration correcting optical element, optical pickup device and recording and reproducing device
JP2005084359A (en) 2003-09-09 2005-03-31 Matsushita Electric Ind Co Ltd Lens
JP2009104724A (en) 2007-10-24 2009-05-14 Hoya Corp Coupling lens and optical information recording and reproducing device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09185836A (en) * 1995-11-02 1997-07-15 Konica Corp Optical system for recording and reproducing optical information recording medium
JPH09212908A (en) * 1995-11-02 1997-08-15 Konica Corp Optical system for recording and reproducing of optical information recording medium, objective lens for recording and reproducing, coupling lens for recording and reproducing and optical pickup device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09185836A (en) * 1995-11-02 1997-07-15 Konica Corp Optical system for recording and reproducing optical information recording medium
JPH09212908A (en) * 1995-11-02 1997-08-15 Konica Corp Optical system for recording and reproducing of optical information recording medium, objective lens for recording and reproducing, coupling lens for recording and reproducing and optical pickup device

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