JPH07122691B2 - Optical disc lens - Google Patents
Optical disc lensInfo
- Publication number
- JPH07122691B2 JPH07122691B2 JP61153888A JP15388886A JPH07122691B2 JP H07122691 B2 JPH07122691 B2 JP H07122691B2 JP 61153888 A JP61153888 A JP 61153888A JP 15388886 A JP15388886 A JP 15388886A JP H07122691 B2 JPH07122691 B2 JP H07122691B2
- Authority
- JP
- Japan
- Prior art keywords
- lens
- semiconductor laser
- aspherical
- optical
- optical disk
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】 （産業上の利用分野） この発明は、光ディスク用レンズに関する。TECHNICAL FIELD The present invention relates to an optical disk lens.
（従来の技術） 従来、一般に光ディスク用レンズ系における対物レンズ
は、３枚ないし５枚の光学ガラスレンズで構成されてい
る。(Prior Art) Conventionally, an objective lens in a lens system for an optical disk is generally composed of three to five optical glass lenses.
（発明が解決しようとする問題点） 光ディスク用レンズ系の対物レンズが複数枚のレンズで
構成されるのは、光ディスク用レンズに要求される特性
が厳密であるためであり、光ディスク上に記録された高
密度情報を読み取るために、少くとも１μ以下の分解能
が必要である。またレーザダイオードの光軸上における
配置誤差および微細な組立調整における誤差を十分にカ
バーするために軸上収差以外に、軸外の収差をも回折限
界内に納めることが要求される。そのため設計上では、
球面収差の補正と共に、正弦条件の補正が、きわめて重
要な要素となり、従ってこの種レンズ系はその構成枚数
が増加をきたし、その結果、アクチュエータの大型化を
余儀なくされ、光ディスク用レンズ系に要求される小型
軽量化の障害となっている。(Problems to be Solved by the Invention) The objective lens of the optical disc lens system is composed of a plurality of lenses because the characteristics required for the optical disc lens are strict, and the objective lens is not recorded on the optical disc. In order to read high density information, a resolution of at least 1 μ or less is required. In addition to axial aberration, off-axis aberrations are also required to be within the diffraction limit in order to sufficiently cover placement errors on the optical axis of the laser diode and errors in fine assembly adjustment. Therefore, in terms of design,
The correction of the sine condition becomes a very important factor together with the correction of the spherical aberration. Therefore, the number of components of this kind of lens system increases, and as a result, the actuator is inevitably increased in size, which is required for the optical disk lens system. This is an obstacle to reducing the size and weight.
（問題点を解決するための手段） この発明は、小型軽量で、かつ780nmの波長光に対して
良好な収差補正を行った光ディスク用レンズを提供する
ものであって、その光ディスク用レンズは、第１面およ
び第２面が共に正のパワーを有する２枚の非球面レン
ズ、もしくはその光源側の１枚が球面レンズで構成さ
れ、これら２枚のレンズには、比較的低屈折率で軽量の
光学材料、たとえば、プラスチック材が用いられる。さ
らに具体的には、半導体レーザと光ディスクとの間にお
いて、半導体レーザ側に第１レンズを光ディスク側に第
２レンズを配置し、半導体側の開口数（NA）を0.1以
上、光ディスク側のそれを0.4以上とした２群２枚構成
の光ディスク用レンズであって、第１レンズはその物像
間距離（I/O）が実質的に無限大に設定された球面また
は非球面レンズにより、また第２レンズはその両面が正
のパワーを有する非球面によりそれぞれ構成されてお
り、第２レンズの非球面は下式で示す少なくとも入射高
の４乗に比例する項を含んでおり、次の条件（１）〜
（４）を満足するものである。(Means for Solving the Problems) The present invention provides a lens for an optical disc that is small and lightweight, and that has excellent aberration correction for light having a wavelength of 780 nm. The first surface and the second surface both consist of two aspherical lenses having positive power, or one of them on the light source side is a spherical lens. These two lenses have a relatively low refractive index and are lightweight. Optical materials such as plastic materials are used. More specifically, between the semiconductor laser and the optical disk, the first lens is arranged on the semiconductor laser side and the second lens is arranged on the optical disk side, and the numerical aperture (NA) on the semiconductor side is 0.1 or more. A lens for an optical disc having a two-group two-lens structure of 0.4 or more, wherein the first lens is a spherical or aspherical lens whose object-image distance (I / O) is set to substantially infinity, and Each of the two lenses is composed of an aspherical surface having positive power on both sides, and the aspherical surface of the second lens includes at least a term proportional to the fourth power of the incident height expressed by the following formula, and the following condition ( 1) ~
It satisfies (4).
（３）−1.0＜K5＜０ （４）K6＜０ ただし、 X :光軸からＨの高さの点における非球面頂点の接平
面からの距離 H :光軸からの高さ C :非球面の頂点の曲率（1/R） K :円錐係数 K5：第２レンズの半導体レーザ側面の円錐係数 K6：第２レンズの光ディスク側面の円錐係数 D :光軸からの高さに対する４乗に比例する項の係数 f :第１レンズ及び第２レンズの合成焦点距離 I/O:半導体レーザ発振面から光ディスクのビット面ま
での距離 n5：第２レンズの屈折率 r5：第２レンズの半導体レーザ側の曲率半径 本発明の光ディスク用レンズを用いた情報読取システム
の一例を示す第１図において、このシステムは、半導体
レーザ１、ビームスプリッタ２、両面が共に正の屈折力
を有する第１非球面レンズ３、同じく両面が正の屈折力
を有する対物レンズたる第２非球面レンズ４、光ディス
クのカバーガラス５及びディテクタ６で構成されてい
る。 (3) -1.0 <K 5 < 0 (4) K 6 <0 However, X: distance from a tangent plane at the vertex of the aspherical surface at the height point of the H from the optical axis H: height from the optical axis C: Curvature of apex of aspherical surface (1 / R) K: Cone coefficient K 5 : Cone coefficient of semiconductor laser side surface of second lens K 6 : Cone coefficient of optical disk side surface of second lens D: 4 with respect to height from optical axis Coefficient of term proportional to power f: Composite focal length of first lens and second lens I / O: Distance from semiconductor laser oscillation surface to bit surface of optical disk n 5 : Refractive index of second lens r 5 : Second Radius of curvature of lens on semiconductor laser side In FIG. 1 showing an example of an information reading system using the lens for an optical disk of the present invention, this system has a semiconductor laser 1, a beam splitter 2, and both sides have positive refractive power. The first aspherical lens 3 is an objective lens having positive refractive power on both sides. The second aspherical lens 4, and a cover glass 5 and the detector 6 of the optical disc.
第１非球面レンズ３に代えて球面レンズを用いるレンズ
系では、その前群球面レンズより生じる残存収差を含め
て、後群非球面レンズで最終的な収差補正がなされるよ
うに構成される。In a lens system using a spherical lens in place of the first aspherical lens 3, final aberration correction is performed by the rear aspherical lens, including residual aberration caused by the front spherical lens.
半導体レーザからの光はビームスプリッタ２、第１非球
面レンズ３、第３非球面レンズ４およびカバーガラス５
を通過して光ディスク上のビット面に収束し、その反射
光の一部がビームスプリッタ２で偏光されてディテクタ
６に入射する。The light from the semiconductor laser is a beam splitter 2, a first aspherical lens 3, a third aspherical lens 4 and a cover glass 5.
Of the reflected light, and a part of the reflected light is polarized by the beam splitter 2 and is incident on the detector 6.
半導体レーザの発光放射パターンとエネルギーの強度分
布を２次元的に示した第２図および半導体レーザの発光
放射パターンのうち、発光軸上のNA＝0.15に対応するエ
ネルギー強度分布を３次元的に示した第３図から推察で
きるように、半導体レーザの特性を考慮し、エネルギー
分布に歪を生ぜしめることなく、最大の効率を得るため
には、半導体レーザ側のNAは、0.1〜0.2が適当であり、
また光ディスク側のNAは、 より0.45程度が好ましい。ここで、Ｋは係数、λは波
長、NAは1/2Fナンバ、φはビームの収束径、すなわち光
ディスク面上での最小スポット径で光学式記録ディスク
では1.2μｍ程度である。Fig. 2 shows the emission radiation pattern and energy intensity distribution of the semiconductor laser in a two-dimensional manner. In the emission emission pattern of the semiconductor laser, the energy intensity distribution corresponding to NA = 0.15 on the emission axis is shown in a three-dimensional manner. As can be inferred from Fig. 3, considering the characteristics of the semiconductor laser, in order to obtain the maximum efficiency without causing distortion in the energy distribution, the NA of the semiconductor laser side is 0.1 to 0.2 is appropriate. Yes,
The NA on the optical disk side is About 0.45 is more preferable. Here, K is a coefficient, λ is a wavelength, NA is a 1 / 2F number, and φ is a beam converging diameter, that is, a minimum spot diameter on the optical disk surface, which is about 1.2 μm for an optical recording disk.
半導体レーザと光ディスクのビット面との距離I/Oは、 なる有限距離内に定められる。そのため光ディスク用レ
ンズの微細組立の誤差がI/Oと光学収差特性に強く関与
するので、本発明では、２枚のレンズのうち、半導体レ
ーザ側の第１レンズをI/Oが無限遠になるように設定し
た非球面レンズまたは球面レンズとし、光ディスク側の
レンズを非球面レンズとして、微細組立の調整を容易に
した。第１レンズに非球面レンズを用いれば、この第１
非球面レンズ自身で収束補正をすることが可能であり、
また第１レンズに球面レンズを用いれば、収差補正は先
に述べたように、第２非球面レンズにより行うことがで
きる。The distance I / O between the semiconductor laser and the bit surface of the optical disk is Is defined within a finite distance. Therefore, since the error in the fine assembly of the lens for the optical disk has a strong influence on the I / O and the optical aberration characteristic, in the present invention, the I / O of the first lens on the semiconductor laser side of the two lenses becomes infinity. The aspherical lens or the spherical lens set as described above is used, and the lens on the optical disc side is used as the aspherical lens to facilitate adjustment of fine assembly. If an aspherical lens is used as the first lens, this first
It is possible to correct the convergence with the aspherical lens itself,
If a spherical lens is used as the first lens, aberration correction can be performed by the second aspherical lens, as described above.
以下、前記の各条件（１）〜（４）について説明する。Hereinafter, each of the above conditions (1) to (4) will be described.
この条件は、装置の大きさと正弦条件に関するもので、 が下限0.1をこえると装置の小型化に障害をきたし、上
限0.2をこえると、装置そのものの小型化には有利とな
るも、必要な良像範囲で正弦条件の補正が困難となると
共に、作動距離WDが小さくなってしまう。 This condition relates to the size of the device and the sine condition, If the lower limit exceeds 0.1, it hinders the downsizing of the device, and if the upper limit exceeds 0.2, it is advantageous for downsizing the device itself, but it becomes difficult to correct the sine condition within the necessary good image range, and The distance WD becomes smaller.
この条件は、レンズの形状と、第２非球面レンズの半導
体レーザ側の面のパワーを定めるものであって、 が上限1.0をこえると、正弦条件が増大し、球面収差と
軸外収差のバランスがとれなくなり、また下限0.5をこ
えると球面収差の補正が困難となる。 This condition determines the shape of the lens and the power of the surface of the second aspherical lens on the semiconductor laser side. When exceeds the upper limit of 1.0, the sine condition increases, and the spherical aberration and the off-axis aberration cannot be balanced, and when the lower limit of 0.5 exceeds, it becomes difficult to correct the spherical aberration.
（３）−1.0＜K5＜０ この条件は、第２非球面レンズの半導体レーザ側の面
（第５面）の形状、球面収差および正弦条件に関与し、
上限０をこえると正弦条件が乱れて良好な有効像円が小
さくなり、下限−1.0をこえると、球面収差が増大す
る。(3) −1.0 <K 5 <0 This condition is related to the shape of the surface of the second aspherical lens on the semiconductor laser side (fifth surface), the spherical aberration, and the sine condition,
Above the upper limit of 0, the sine condition is disturbed and the good effective image circle becomes smaller, and above the lower limit of -1.0, spherical aberration increases.
（４）K6＜０ この条件は、第２非球面レンズの光ディスク側の面（第
６面）の円錐係数に関するもので、この条件を外れる
と、特に正弦条件が増大し、軸外収差が大きくなり、球
面収差と軸外収差のバランスがとれなくなる。(4) K 6 <0 This condition relates to the conical coefficient of the surface (sixth surface) of the second aspherical lens on the optical disk side. If this condition is not satisfied, the sine condition will increase, and the off-axis aberration will increase. It becomes large and the spherical aberration and the off-axis aberration cannot be balanced.
（実施例） 実施例１ における各非球面係数 K3＝−2.28463 K5＝−7.52179×10-1 D3＝ 5.92947×10-5 D5＝ 1.30734×10-3 E3＝ 4.13858×10-6 E5＝ 4.11629×10-5 F3＝ 4.87257×10-9 F5＝−3.77913×10-8 G3＝ 9.60618×10-11 G5＝ 5.29884×10-10 K4＝−6.41741×10-1 K6＝−2.05837×10+1 D4＝ 7.75170×10-5 D6＝ 1.63816×10-3 E4＝ 3.09961×10-6 E6＝−1.59544×10-4 F4＝ 5.36291×10-8 F6＝ 8.17867×10-8 G4＝ 1.43584×10-10 G6＝ 9.96230×10-10 実施例２ における各非球面係数 K5＝−6.467477×10-1 K6＝−2.176355×10+1 D5＝ 7.592335×10-4 D6＝ 3.245087×10-3 E5＝ 5.249270×10-5 E6＝−3.241951×10-4 F5＝−3.724719×10-8 F6＝ 8.178441×10-8 G5＝ 5.301673×10-10 G6＝ 6.782948×10-8 上記実施例1,2において、 X :光軸からＨの高さの点における非球面頂点の接平
面からの距離 H :光軸からの高さ C :非球面の頂点の曲率（1/R） K :円錐係数 D,E,F,G:各々の光軸からの高さに対する４乗,6乗,8乗,1
0乗に比例する項の係数 f :第１レンズ及び第２レンズの合成焦点距離 I/O:半導体レーザ発振面から光ディスクのビット面ま
での距離 n5：第２レンズの屈曲率 r5：第２レンズの半導体レーザ側の曲率半径 （効果） この発明によれば、光ディスク用レンズを、その性能を
損うことなく、小型軽量化することができる。(Example) Example 1 Each aspherical coefficients in K 3 = -2.28463 K 5 = -7.52179 × 10 -1 D 3 = 5.92947 × 10 -5 D 5 = 1.30734 × 10 -3 E 3 = 4.13858 × 10 -6 E 5 = 4.11629 × 10 - 5 F 3 = 4.87257 x 10 -9 F 5 = -3.77913 x 10 -8 G 3 = 9.60618 x 10 -11 G 5 = 5.29884 x 10 -10 K 4 = -6.41741 x 10 -1 K 6 = -2.05837 x 10 +1 D 4 = 7.75170 × 10 -5 D 6 = 1.63816 × 10 -3 E 4 = 3.09961 × 10 -6 E 6 = -1.59544 × 10 -4 F 4 = 5.36291 × 10 -8 F 6 = 8.17867 × 10 - 8 G 4 = 1.43584 × 10 -10 G 6 = 9.96230 × 10 -10 Example 2 Each aspherical coefficient in K 5 = −6.467477 × 10 −1 K 6 ＝ −2.176355 × 10 +1 D 5 ＝ 7.592335 × 10 -4 D 6 ＝ 3.2450 87 × 10 -3 E 5 ＝ 5.249 270 × 10 -5 E 6 ＝ −3.241951 × 10 −4 F 5 = −3.724719 × 10 −8 F 6 = 8.178441 × 10 −8 G 5 = 5.301673 × 10 −10 G 6 = 6.782 48 × 10 −8 In Examples 1 and 2 above, X: distance from the tangent plane of the aspherical vertex at the height H from the optical axis H: height from the optical axis C: curvature of the aspherical vertex (1 / R) K: Cone coefficient D, E, F, G: 4th, 6th, 8th, 1 with respect to the height from each optical axis
Coefficient of term proportional to 0th power f: Composite focal length of first lens and second lens I / O: Distance from semiconductor laser oscillation surface to bit surface of optical disc n 5 : Bending ratio of second lens r 5 : Second Radius of Curvature of Two Lenses on Semiconductor Laser Side (Effect) According to the present invention, it is possible to reduce the size and weight of the optical disc lens without impairing its performance.
第１図は本発明のレンズを用いた光ディスク用レンズシ
ステムの一例を示す断面図、第２図は、半導体レーザの
発光放射パターンとエネルギーの強度分布を２次元的に
表示した強度分布図、第３図は、半導体レーザの放射パ
ターンのうち、発光軸上のNA＝0.15に対応するエネルギ
ー強度分布の３次元図、第４図および第５図は、実施例
１および２の収差曲線図である。 １……半導体レーザ、２……ビームスプリッター、３…
…第１レンズ、４……第２レンズ。FIG. 1 is a cross-sectional view showing an example of a lens system for an optical disc using the lens of the present invention, and FIG. 2 is an intensity distribution diagram in which the emission radiation pattern and energy intensity distribution of a semiconductor laser are two-dimensionally displayed. FIG. 3 is a three-dimensional diagram of the energy intensity distribution corresponding to NA = 0.15 on the emission axis in the radiation pattern of the semiconductor laser, and FIGS. 4 and 5 are aberration curve diagrams of Examples 1 and 2. . 1 ... Semiconductor laser, 2 ... Beam splitter, 3 ...
… First lens, 4 …… Second lens.
Claims (1)
て、半導体レーザ側に第１レンズを光ディスク側に第２
レンズをそれぞれ配置し、半導体側の開口数（NA）を0.
1以上とし、光ディスク側のそれを0.4以上として２群２
枚構成の光ディスク用レンズであって、 第１レンズは上記半導体レーザからのレーザ光が当該レ
ンズによりその物像間距離（I/O）が実質的に無限大に
設定された球面または非球面レンズにより、また、第２
レンズはその両面が正のパワーを有する非球面によりそ
れぞれ構成されており、第２レンズの非球面は下式で示
す項を含んでおり、次の条件（１）〜（４）を満足する
光ディスク用レンズ。 （３）−1.0＜K5＜０ （４）K6＜０ ただし、 X :光軸からＨの高さの点における非球面頂点の接平
面からの距離 H :光軸からの高さ C :非球面の頂点の曲率（1/R） K :円錐係数 K5：第２レンズの半導体レーザ側面の円錐係数 K6：第２レンズの光ディスク側面の円錐係数 D :光軸からの高さに対する４乗に比例する項の係数 f :第１レンズ及び第２レンズの合成焦点距離 I/O:半導体レーザ発振面から光ディスクのビット面ま
での距離 n5：第２レンズの屈折率 r5：第２レンズの半導体レーザ側の曲率半径1. A first lens is provided on the semiconductor laser side and a second lens is provided on the optical disc side between the semiconductor laser and the optical disc.
Place each lens and set the numerical aperture (NA) on the semiconductor side to 0.
2 groups 2 with 1 or more and 0.4 or more on the optical disk side
A single-lens optical disc lens, wherein the first lens is a spherical or aspherical lens in which the laser light from the semiconductor laser has a substantially infinite object-image distance (I / O) set by the lens. Due to the second
The lens is composed of an aspherical surface having positive power on both sides thereof, and the aspherical surface of the second lens includes the term shown in the following expression, and an optical disk satisfying the following conditions (1) to (4). Lens for. (3) -1.0 <K 5 < 0 (4) K 6 <0 However, X: distance from a tangent plane at the vertex of the aspherical surface at the height point of the H from the optical axis H: height from the optical axis C: Curvature of apex of aspherical surface (1 / R) K: Cone coefficient K 5 : Cone coefficient of semiconductor laser side surface of second lens K 6 : Cone coefficient of optical disk side surface of second lens D: 4 with respect to height from optical axis Coefficient of term proportional to power f: Composite focal length of first lens and second lens I / O: Distance from semiconductor laser oscillation surface to bit surface of optical disk n 5 : Refractive index of second lens r 5 : Second Radius of curvature of the semiconductor laser side of the lens
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61153888A JPH07122691B2 (en) | 1986-06-30 | 1986-06-30 | Optical disc lens |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61153888A JPH07122691B2 (en) | 1986-06-30 | 1986-06-30 | Optical disc lens |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS638701A JPS638701A (en) | 1988-01-14 |
| JPH07122691B2 true JPH07122691B2 (en) | 1995-12-25 |
Family
ID=15572307
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61153888A Expired - Lifetime JPH07122691B2 (en) | 1986-06-30 | 1986-06-30 | Optical disc lens |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07122691B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100234248B1 (en) * | 1995-06-07 | 1999-12-15 | 윤종용 | Dual focusing objective lens for optical pickup |
| JPH10134400A (en) * | 1996-10-28 | 1998-05-22 | Nec Corp | Optical head |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5776512A (en) * | 1980-10-31 | 1982-05-13 | Konishiroku Photo Ind Co Ltd | Large-aperture aspheric single lens |
| JPS5868711A (en) * | 1981-10-20 | 1983-04-23 | Matsushita Electric Ind Co Ltd | Objective lens |
| JPS5926714A (en) * | 1982-08-05 | 1984-02-13 | Olympus Optical Co Ltd | Lens for optical disc |
| JPS60121412A (en) * | 1983-11-28 | 1985-06-28 | Konishiroku Photo Ind Co Ltd | Aspherical collimator lens |
| JPS61177410A (en) * | 1985-02-01 | 1986-08-09 | Konishiroku Photo Ind Co Ltd | Objective lens for recording and reproducing of optical information recording medium |
-
1986
- 1986-06-30 JP JP61153888A patent/JPH07122691B2/en not_active Expired - Lifetime
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5776512A (en) * | 1980-10-31 | 1982-05-13 | Konishiroku Photo Ind Co Ltd | Large-aperture aspheric single lens |
| JPS5868711A (en) * | 1981-10-20 | 1983-04-23 | Matsushita Electric Ind Co Ltd | Objective lens |
| JPS5926714A (en) * | 1982-08-05 | 1984-02-13 | Olympus Optical Co Ltd | Lens for optical disc |
| JPS60121412A (en) * | 1983-11-28 | 1985-06-28 | Konishiroku Photo Ind Co Ltd | Aspherical collimator lens |
| JPS61177410A (en) * | 1985-02-01 | 1986-08-09 | Konishiroku Photo Ind Co Ltd | Objective lens for recording and reproducing of optical information recording medium |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS638701A (en) | 1988-01-14 |
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