CN102956245B

CN102956245B - Lens compatible with multiple types of optical disks

Info

Publication number: CN102956245B
Application number: CN201110251728.8A
Authority: CN
Inventors: 李荣彬; 杜雪; 李莉华; 王文奎
Original assignee: Hong Kong Polytechnic University HKPU
Current assignee: Hong Kong Polytechnic University HKPU
Priority date: 2011-08-30
Filing date: 2011-08-30
Publication date: 2015-09-30
Anticipated expiration: 2031-08-30
Also published as: CN102956245A

Abstract

The invention relates to a lens compatible with various types of optical discs, which comprises a first lens surface (1) and a second lens surface (2). The first lens surface comprises a central region (11), an intermediate region (12) and an outer axial region (13), the intermediate region (12) being distinct and adjacent to the central region (12) and the outer axial region (13), the second lens surface (2) comprising an inner region (21) and an outer region (22), the inner region (21) and the outer region (22) being distinct and adjacent. Different areas of the two lens surfaces have different optical refraction and diffraction effects, and incident laser passes through the different areas of the two lens surfaces and is focused at different positions of a focusing area to form a focusing point. The corresponding focus point is the information area of different types of optical discs, thus realizing the identification, reading and writing of different types of optical discs.

Description

A lens compatible with multiple types of optical discs

技术领域 technical field

本发明涉及一种透镜，更具体地说，涉及一种可以兼容多种类型光盘的透镜。The invention relates to a lens, more specifically, to a lens compatible with various types of optical discs.

背景技术 Background technique

目前用于读取多种格式类型光盘的透镜大多数是通过在原透镜前加入光学组件的方法来实现的，例如在透镜前加入多格式兼容板、使用透镜组代替单个透镜、加入动态数值孔径控制单元等等。这些方法使透镜结构变得复杂，制作成本高，准确性和可靠性较低，组件易磨损。At present, most of the lenses used to read optical discs of various formats are realized by adding optical components in front of the original lens, such as adding a multi-format compatible plate in front of the lens, using a lens group instead of a single lens, and adding dynamic numerical aperture control. unit etc. These methods make the lens structure complicated, the manufacturing cost is high, the accuracy and reliability are low, and the components are easy to wear.

发明内容 Contents of the invention

本发明针对上述现有技术存在的问题进行改进，即本发明要解决的问题是提供一种透镜，使得单个透镜无需通过外加的光学组件就能兼容多种类型的光盘，从而实现透镜结构的简单化，降低成本，提高系统的准确性和可靠性，使得系统更加耐用。The present invention improves on the problems existing in the above-mentioned prior art, that is, the problem to be solved by the present invention is to provide a lens, so that a single lens can be compatible with various types of optical discs without additional optical components, thereby realizing a simple lens structure , reduce costs, improve system accuracy and reliability, and make the system more durable.

本发明上述技术问题这样解决，构造一种兼容多类型光盘的透镜，包括预定形状的第一透镜面和第二透镜面，第一透镜面和第二透镜面将入射光聚焦到聚焦区，其特征在于，所述第一透镜面包括中央区、中间区和外轴区，该中间区区别并相邻中央区和外轴区，所述第二透镜面包括内层区和外层区，内层区和外层区区别并相邻，到达所述聚焦区的聚焦光至少包括分别经过中央区、中间区和外轴区的不同聚焦光。The above-mentioned technical problem of the present invention is solved like this, constructs a kind of lens that is compatible with multi-type optical disk, comprises the first lens surface and the second lens surface of predetermined shape, and the first lens surface and the second lens surface focus incident light to the focal area, its It is characterized in that the first lens surface includes a central area, a middle area and an outer axis area, the middle area distinguishes and is adjacent to the central area and the outer axis area, and the second lens surface includes an inner layer area and an outer layer area, and the inner layer area The layer area and the outer layer area are distinguished and adjacent, and the focused light reaching the focusing area at least includes different focused lights passing through the central area, the middle area and the outer axis area respectively.

在本发明提供的透镜中，所述聚焦区为记录光盘信息的光盘区域，并位于透镜光轴上。In the lens provided by the present invention, the focus area is the area of the optical disc where the information of the optical disc is recorded, and is located on the optical axis of the lens.

在本发明提供的透镜中，所述多类型光盘为BD格式或CBHD格式或DVD格式或CD格式中的一种或多种。In the lens provided by the present invention, the multi-type optical disc is one or more of BD format, CBHD format, DVD format or CD format.

在本发明提供的透镜中，所述第一透镜面的镜面形状为下述方程所描述，In the lens provided by the present invention, the mirror shape of the first lens surface is described by the following equation,

${Z Z}_{11} = = circ circle ((r r - - {r r}_{a a})) {{\frac{{c c}_{11} {r r}^{22}}{11 + + \sqrt{11 - - ((11 + + {k k}_{11})) {c c}_{11}^{22} {r r}^{22}}} + + {Σ Σ}_{i i = = 22}^{99} {a a}_{i i} {r r}^{22 i i} + +$

$\frac{{δ δ}_{a a} λ λ}{n no - - 11} [[{Σ Σ}_{j j = = 11}^{55} {A A}_{j j} {((r r / / {r r}_{a a}))}^{22 j j} - - Int Int (({Σ Σ}_{j j = = 11}^{55} {A A}_{j j} {((r r / / {r r}_{a a}))}^{22 j j}))]]}} + +$

$[[11 - - circ circle ((r r - - {r r}_{a a}))]] circ circle ((r r - - {r r}_{b b})) {{\frac{{c c}_{22} {r r}^{22}}{11 + + \sqrt{11 - - ((11 + + {k k}_{22})) {c c}_{22}^{22} {r r}^{22}}} + + {Σ Σ}_{i i = = 22}^{99} {b b}_{i i} {r r}^{22 i i} + +$

$\frac{{δ δ}_{b b} λ λ}{n no - - 11} [[{Σ Σ}_{j j = = 11}^{55} {B B}_{j j} {((r r / / {r r}_{b b}))}^{22 j j} - - Int Int (({Σ Σ}_{j j = = 11}^{55} {B B}_{j j} {((r r / / {r r}_{b b}))}^{22 j j}))]]}} + +$

$[[11 - - circ circle ((r r - - {r r}_{a a}))]] [[11 - - circ circle ((r r - - {r r}_{b b}))]] circ circle ((r r - - {r r}_{c c})) {{\frac{{c c}_{22} {r r}^{22}}{11 + + \sqrt{11 - - ((11 + + {k k}_{22})) {c c}_{22}^{22} {r r}^{22}}} + + {Σ Σ}_{i i = = 22}^{99} {b b}_{i i} {r r}^{22 i i}}}$

其中，δ_a，δ_b衍射效率系数，r为第一透镜面上的点到中央光轴的距离，r_a为第一透镜面中央区的点距离光轴的最大值，r_b为第一透镜面中间区的点距离光轴的最大值(其中r_a＜r_b)，r_c为第一透镜面外轴区的点距离光轴的最大值(其中r_b＜r_c)，c₁，c₂为曲率，k₁，k₂为圆锥系数，a_i，b_i，A_j，B_j为垂度系数，λ为入射激光的主波长，n为透镜材料对应在λ波长的折射率。Among them, δ _a , δ _b diffraction efficiency coefficient, r is the distance from the point on the first lens surface to the central optical axis, r _a is the maximum value of the distance from the point on the central area of the first lens surface to the optical axis, r _b is the first The maximum value of the distance from the point in the middle area of the lens surface to the optical axis (where r _a < r _b ), r _c is the maximum value of the distance from the point in the outer axis area of the first lens surface (where r _b < r _c ), c ₁ , c ₂ is curvature, k ₁ , k ₂ are conic coefficients, a _i , b _i , A _j , B _j are sag coefficients, λ is the main wavelength of incident laser light, n is the refractive index of lens material corresponding to wavelength λ .

在本发明提供的透镜中，所述第二透镜面的镜面形状为下述方程所描述，In the lens provided by the present invention, the mirror shape of the second lens surface is described by the following equation,

${Z Z}_{22} = = circ circle ((r r - - {r r}_{d d})) {{\frac{{c c}_{44} {r r}^{22}}{11 + + \sqrt{11 - - ((11 + + {k k}_{44})) {c c}_{44}^{22} {r r}^{22}}} + + {Σ Σ}_{i i = = 22}^{99} {d d}_{i i} {r r}^{22 i i} + +$

$\frac{{δ δ}_{d d} λ λ}{n no - - 11} [[{Σ Σ}_{j j = = 11}^{55} {D D.}_{j j} {((r r / / {r r}_{d d}))}^{22 j j} - - Int Int (({Σ Σ}_{j j = = 11}^{55} {D D.}_{j j} {((r r / / {r r}_{d d}))}^{22 j j}))]]}} + +$

$[[11 - - circ circle ((r r - - {r r}_{d d}))]] circ circle ((r r - - {r r}_{e e})) {{\frac{{c c}_{55} {r r}^{22}}{11 + + \sqrt{11 - - ((11 + + {k k}_{55})) {c c}_{55}^{22} {r r}^{22}}} + + {Σ Σ}_{i i = = 22}^{99} {e e}_{i i} {r r}^{22 i i}}}$

其中δ_d衍射效率系数，r为第二透镜面上的点到中央光轴的距离，r_d为第二透镜面内层区的点距离光轴的最大值，r_e为第二透镜面外层区的点距离光轴的最大值(r_d＜r_e)，c₄，c₅为曲率，k₄，k₅为圆锥系数，d_i，e_i，D_j为垂度系数，λ为入射激光的主波长，n为透镜材料对应在λ波长的折射率。Among them, δ _d is the coefficient of diffraction efficiency, r is the distance from the point on the second lens surface to the central optical axis, r _d is the maximum value of the distance from the point on the inner layer of the second lens surface to the optical axis, and r _e is the distance from the point outside the second lens surface The maximum value of the point distance from the optical axis in the layer area (r _d < r _e ), c ₄ and c ₅ are the curvature, k ₄ and k ₅ are the conic coefficients, d _i , e _i , D _j are the sag coefficients, and λ is The dominant wavelength of the incident laser light, n is the refractive index of the lens material corresponding to the λ wavelength.

在本发明提供的透镜中，所述透镜的数值孔径在对应光盘格式为BD、CBHD、DVD、CD时的数值分别为0.85±0.01，0.65±0.01，0.6～0.65±0.01，0.47～0.51±0.01。In the lens provided by the present invention, the numerical aperture of the lens when the corresponding disc formats are BD, CBHD, DVD, and CD are respectively 0.85±0.01, 0.65±0.01, 0.6～0.65±0.01, 0.47～0.51±0.01 .

实施本发明提供的由上述两个透镜面组成的透镜，可以将入射光聚焦在聚焦区，更具体的，由于两个透镜面的不同区域具有不同的光学折射、衍射效应，入射激光经过两个透镜面的不同区域后，会在聚焦区的不同位置聚焦，形成聚焦点。对应的聚焦点为不同类型的光盘的信息区。通过选择入射激光类型、透镜能量透射效率、衍射级数、透镜镜面参数等，使得该透镜能够识别、读取或写入不同类型的光盘。实施这种透镜的有益效果在于简化了透镜结构，降低了成本，提高系统的准确性和可靠性，使得系统更加耐用。Implementing the lens composed of the above two lens surfaces provided by the present invention can focus the incident light in the focal area. More specifically, since the different areas of the two lens surfaces have different optical refraction and diffraction effects, the incident laser light passes through two Different areas of the lens surface will focus at different positions in the focal area to form a focal point. The corresponding focus points are information areas of different types of optical discs. By selecting the incident laser type, lens energy transmission efficiency, diffraction order, lens mirror parameters, etc., the lens can identify, read or write different types of optical discs. The beneficial effect of implementing this lens is that the lens structure is simplified, the cost is reduced, the accuracy and reliability of the system are improved, and the system is more durable.

附图说明 Description of drawings

附图为本发明透镜的剖视图。The accompanying drawing is a cross-sectional view of the lens of the present invention.

图中1为透镜第一透镜面；1 in the figure is the first lens surface of the lens;

11为第一透镜面的中央区；11 is the central area of the first lens surface;

12为第一透镜面的中间区；12 is the middle area of the first lens surface;

13为第一透镜面的外轴区；13 is the outer axis area of the first lens surface;

2为透镜的第二透镜面；2 is the second lens surface of the lens;

21为第二透镜面的内层区；21 is the inner layer area of the second lens surface;

22为第二透镜面的外层区；22 is the outer zone of the second lens surface;

31为蓝光(BD)格式光盘的信息区；31 is the information area of the Blu-ray (BD) format disc;

32为中国蓝光高清(CBHD)格式光盘的信息区；32 is the information area of China Blu-ray High Definition (CBHD) format disc;

33为DVD格式光盘的信息区；33 is the information area of the DVD format disc;

34为CD格式光盘的信息区。34 is the information area of CD format disc.

具体实施方式 Detailed ways

为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用于解析本发明。并不用于限定本发明。In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for illustrating the present invention. It is not intended to limit the invention.

如附图所示的透镜，透镜由第一透镜面(1)和第二透镜面(2)组成，第一透镜面(1)包括中央区(11)、中间区(12)和外轴区(13)，该中间区(12)区别并相邻中央区(11)和外轴区(13)；第二透镜面(2)包括内层区(21)和外层区(22)，内层区(21)和外层区(22)区别并相邻。入射激光从第一透镜面(1)入射，从第二透镜面出射(2)，由于第一透镜面(1)的中央区(11)、中间区(12)和外轴区(13)以及第二透镜面(2)的内层区(21)和外层区(22)具有不同的光学折射、衍射效应，出射后的激光会在聚焦区形成不同的聚焦点。As shown in the accompanying drawings, the lens consists of a first lens surface (1) and a second lens surface (2), and the first lens surface (1) includes a central zone (11), a middle zone (12) and an outer axis zone (13), the middle zone (12) distinguishes and is adjacent to the central zone (11) and the outer axis zone (13); the second lens surface (2) includes an inner zone (21) and an outer zone (22), and the inner zone The layer area (21) and the outer layer area (22) are distinguished and adjacent. The incident laser light is incident from the first lens surface (1) and exits from the second lens surface (2), due to the central zone (11), middle zone (12) and outer axis zone (13) of the first lens surface (1) and The inner layer area (21) and the outer layer area (22) of the second lens surface (2) have different optical refraction and diffraction effects, and the emitted laser light will form different focus points in the focus area.

第一透镜面(1)的镜面形状为下述的方程所描述，The mirror shape of the first lens surface (1) is described by the following equation,

第二透镜面(2)的镜面形状为下述的方程所描述The specular shape of the second lens surface (2) is described by the following equation

入射激光经过两个透镜面的不同区域后，会在聚焦区的不同位置聚焦，形成聚焦点。本实施例的透镜能够将入射光聚焦在光盘的信息区。所述的光盘信息区为：BD光盘信息区(31)、CBHD光盘信息区(32)、DVD光盘信息区(33)、CD光盘信息区(34)。从而实现了单个透镜对多种类型光盘的识别、读取或写入。After the incident laser passes through different areas of the two lens surfaces, it will be focused at different positions in the focal area to form a focal point. The lens of this embodiment can focus the incident light on the information area of the optical disc. The optical disc information area includes: BD optical disc information area (31), CBHD optical disc information area (32), DVD optical disc information area (33), and CD optical disc information area (34). Therefore, the identification, reading or writing of multiple types of optical discs by a single lens is realized.

在本实施例中，透镜可以兼容如下四种格式光盘的一种或多种：蓝光(BD)、中国蓝光高清(CBHD)、DVD和CD。这四种光盘格式对应的能量衍射效率为：In this embodiment, the lens can be compatible with one or more of the following four formats of discs: Blu-ray (BD), China Blu-ray High Definition (CBHD), DVD and CD. The energy diffraction efficiencies corresponding to these four disc formats are:

${η η}_{i i} = = \frac{{&Integral; &Integral;}_{00}^{{r r}_{a a}} exp exp ((- - {r r}^{22} / / {ω ω}_{00})) dr dr}{{&Integral; &Integral;}_{00}^{{r r}_{c c}} exp exp ((- - {r r}^{22} / / {ω ω}_{00})) dr dr} sin sin {c c}^{22} [[\frac{λ λ (({n no}_{i i} - - 11))}{{λ λ}_{i i} ((n no - - 11))} {δ δ}_{a a} - - {m m}_{iS iS 11}]] sin sin {c c}^{22} [[\frac{λ λ (({n no}_{i i} - - 11))}{{λ λ}_{i i} ((n no - - 11))} {δ δ}_{d d} - - {m m}_{iS iS 22}]] + +$

$circ circle ((22 - - i i)) \frac{{&Integral; &Integral;}_{{r r}_{a a}}^{{r r}_{b b}} exp exp ((- - {r r}^{22} / / {ω ω}_{00})) dr dr}{{&Integral; &Integral;}_{00}^{{r r}_{c c}} exp exp ((- - {r r}^{22} / / {ω ω}_{00})) dr dr} sin sin {c c}^{22} [[\frac{λ λ (({n no}_{i i} - - 11))}{{λ λ}_{i i} ((n no - - 11))} {δ δ}_{b b} - - {m m}_{iS iS 11}]] sin sin {c c}^{22} [[\frac{λ λ (({n no}_{i i} - - 11))}{{λ λ}_{i i} ((n no - - 11))} {δ δ}_{d d} - - {m m}_{iS iS 22}]] + +$

$circ circle ((i i)) [[11 - - \frac{{&Integral; &Integral;}_{00}^{{r r}_{b b}} exp exp ((- - {r r}^{22} / / {ω ω}_{00})) dr dr}{{&Integral; &Integral;}_{00}^{{r r}_{c c}} exp exp ((- - {r r}^{22} / / {ω ω}_{00})) dr dr}]] sin sin {c c}^{22} [[\frac{λ λ (({n no}_{i i} - - 11))}{{λ λ}_{i i} ((n no - - 11))} {δ δ}_{d d} - - {m m}_{iS iS 22}]] ((i i = = 1,2,3,4 1,2,3,4))$

其中i＝1，2，3，4分别对应蓝光(BD)、中国蓝光高清(CBHD)、DVD和CD。ω₀为入射激光的角频率，δ_i为对应光盘格式的能量投射效率，为对应光盘格式所使用的激光波长，m_i为对应的衍射级数，为对应的折射率n_i。Where i=1, 2, 3, 4 respectively correspond to Blu-ray (BD), China Blu-ray High Definition (CBHD), DVD and CD. ω ₀ is the angular frequency of the incident laser, δ _i is the energy projection efficiency corresponding to the optical disc format, is the laser wavelength used in the corresponding optical disc format, m _i is the corresponding diffraction order, and is the corresponding refractive index n _i .

所述的4种格式的光盘覆盖层为BD：0.1或0.0875毫米；CBHD、DVD：0.6毫米；CD：1.2毫米。The cover layers of the four formats of discs are BD: 0.1 or 0.0875mm; CBHD, DVD: 0.6mm; CD: 1.2mm.

更具体的，当光盘能量衍射效率中的能量透射效率δ_i为特定的数值时，本实施例的透镜就能识别、读取和写入一种或以上的光盘格式，具体如下表所示：More specifically, when the energy transmission efficiency _δi in the energy diffraction efficiency of the optical disc is a specific value, the lens of this embodiment can identify, read and write one or more optical disc formats, as shown in the following table:

表1Table 1

其中M，N为自然数。Among them, M and N are natural numbers.

同样的，选用不同的主波长的激光，本实施例的透镜就能识别、读取和写入一种或以上的光盘格式，具体如下表所示：Similarly, if lasers with different dominant wavelengths are selected, the lens of this embodiment can identify, read and write one or more optical disc formats, as shown in the following table:

表2Table 2

透镜可兼容光盘格式 Lens Compatible with Disc Formats 激光主波长λ Laser dominant wavelength λ BD或CBHD BD or CBHD λ＝λ₁＝λ₂＝405±10nmλ=λ ₁ =λ ₂ =405±10nm DVD DVD λ＝λ₃＝660±10nmλ=λ ₃ =660±10nm CD CD λ＝λ₄＝780±10nmλ=λ ₄ =780±10nm BD和CBHD BD and CBHD λ＝λ₁＝λ₂＝405±10nmλ=λ ₁ =λ ₂ =405±10nm DVD和CD DVDs and CDs λ＝λ₃＝660±10nmλ=λ ₃ =660±10nm BD，DVD，CD或CBHD，DVD，CD BD, DVD, CD or CBHD, DVD, CD λ＝λ₁＝λ₂＝405±10nmλ=λ ₁ =λ ₂ =405±10nm BD，CBHD，DVD和CD BD, CBHD, DVD and CD λ＝λ₁＝λ₂＝405±10nmλ=λ ₁ =λ ₂ =405±10nm

类似的，选择不同的衍射级数会令本实施例中的透镜识别、读取和写入能力不同。具体如下述表格所示：Similarly, choosing different diffraction orders will make the recognition, reading and writing capabilities of the lens in this embodiment different. The details are shown in the table below:

表3table 3

当本实施例的透镜识别BD、CBHD、DVD、CD时，对应的透镜数值孔径NA_i为0.85±0.01，0.65±0.01，0.6～0.65±0.01，0.47～0.51±0.01。优选的，当选用本实施例同时识别BD、CBHD、DVD、CD时，透镜系统镜面特性参数A₁，D₁需要调节为：When the lens of this embodiment identifies BD, CBHD, DVD, and CD, the corresponding lens numerical aperture NA _i is 0.85±0.01, 0.65±0.01, 0.6˜0.65±0.01, 0.47˜0.51±0.01. Preferably, when this embodiment is selected to simultaneously identify BD, CBHD, DVD, and CD, the mirror surface characteristic parameters A ₁ and D ₁ of the lens system need to be adjusted as follows:

$\frac{{λ λ}_{11}}{π π} (({A A}_{11} {m m}_{11 S S 11} + + {D D.}_{11} {m m}_{11 S S 22})) = = \frac{N N {A A}_{11}}{{r r}_{c c}} - - (({n no}_{11} - - 11)) [[{c c}_{11} - - {c c}_{44} + + \frac{(({n no}_{11} - - 11)) d d {c c}_{11} {c c}_{44}}{{n no}_{11}}]]$

其中d为实施例中第一透镜面和第二透镜面在光轴方向上的距离。当本实施例的透镜不需要同时兼容BD、CBHD、DVD、CD，A₁，D₁由透镜的数值孔径，入射光波长，折射率，衍射级数所限定，同时由实际需要兼容的光盘格式，按照BD、CBHD、DVD、CD的优先次序所限定。Wherein, d is the distance between the first lens surface and the second lens surface in the direction of the optical axis in the embodiment. When the lens of this embodiment does not need to be compatible with BD, CBHD, DVD, and CD at the same time, A ₁ and D ₁ are limited by the numerical aperture of the lens, the wavelength of incident light, the refractive index, and the number of diffraction orders, and at the same time by the format of the optical disc that is actually required to be compatible , defined according to the order of priority of BD, CBHD, DVD, and CD.

如上所述，通过实际调节能量透射效率δ_i，激光主波长λ，衍射级数，透镜系统镜面特性参数，可以有选择地兼容BD、CBHD、DVD、CD中的一种或多种，以下给出一组优选参数，使得本实施例中的透镜同时兼容BD、CBHD、DVD、CD的光盘格式：As mentioned above, by actually adjusting energy transmission efficiency δ _i , laser dominant wavelength λ, diffraction order, and lens system specular characteristic parameters, one or more of BD, CBHD, DVD, and CD can be selectively compatible. The following is given A group of preferred parameters are given to make the lens in this embodiment compatible with the disc formats of BD, CBHD, DVD, and CD:

表4Table 4

本发明不局限于上述具体实施方式，实施例中的参数仅为了更加清楚、明白的描述本发明的具体运用，只要透镜的第一透镜面和第二透镜面的形貌满足镜面形状Z₁，Z₂的表达，不论如何选择兼容光盘的具体格式、所使用的入射激光类型、透镜能量透射效率、衍射级数等，均落在本发明的保护范围之内。The present invention is not limited to the specific embodiments described above, and the parameters in the examples are only to describe the specific application of the present invention more clearly and clearly, as long as the topography of the first lens surface and the second lens surface of the lens satisfies the mirror surface shape Z ₁ , The expression of Z ₂ , no matter how to choose the specific format of the compatible optical disc, the type of incident laser used, the energy transmission efficiency of the lens, the order of diffraction, etc., all fall within the protection scope of the present invention.

Claims

1. A lens compatible with multiple types of optical discs, comprising a first lens surface (1) and a second lens surface (2) of a predetermined shape, the first lens surface (1) and the second lens surface (2) focus incident light To the focus area, it is characterized in that the first lens surface (1) includes a central area (11), an intermediate area (12) and an outer axis area (13), and the intermediate area (12) is distinguished from and adjacent to the central area ( 11) and the outer shaft area (13), the second lens surface (2) includes an inner layer area (21) and an outer layer area (22), and the inner layer area (21) and the outer layer area (22) are distinguished and Adjacent, the focused light reaching the focusing area at least includes different focused lights passing through the central area (11), the middle area (12) and the outer axis area (13);

The mirror shape of the first lens surface (1) is described by the following equation,

The mirror shape of the second lens surface (2) is described by the following equation,

Among them, δ _a , δ _b , δ _d are diffraction efficiency coefficients, r ₁ is the distance from a point on the first lens surface to the central optical axis, r ₂ is the distance from a point on the second lens surface to the central optical axis, r _a is the maximum distance from the point in the central region of the first lens surface to the optical axis, r _b is the maximum distance from the point in the middle region of the first lens surface to the optical axis, r _c is the distance from the point in the outer axis region of the first lens surface to the optical axis The maximum value of , _{rd is the maximum value of the point distance from the optical axis in the inner layer area of the second lens surface, r e} _is the maximum value of the point distance from the optical axis in the outer layer area of the second lens surface, c ₁ , c ₂ , c ₄ , c ₅ is curvature, k ₁ , k ₂ , k ₄ , k ₅ are conical coefficients, a _i , b _i , A _j , B _j , d _i , e _i , D _j are sag coefficients, λ is incident laser dominant wavelength, n is the refractive index of the lens material corresponding to wavelength λ, r _a < r _b , rd _d < r _e , r _b < r _c .

2 . The lens according to claim 1 , wherein the focus area is an area of the optical disc where information of the optical disc is recorded, and is located on the optical axis of the lens.

3. The lens according to claim 1, wherein the multi-type optical disc is one or more of BD format, CBHD format, DVD format, or CD format.

4. The lens according to any one of claims 1-3, wherein the numerical aperture of the lens is 0.85±0.01, 0.65±0.01, 0.65± 0.01, 0.6～0.65±0.01, 0.47～0.51±0.01.