CN101236262B - multifocal objective lens - Google Patents

Abstract

A multi-focus objective lens comprises a first surface and a second surface. The first surface includes a first aspheric surface, a second aspheric surface, a first diffractive structure and a second diffractive structure. The first aspheric surface and the first diffraction structure are located in a first area, and the second aspheric surface and the second diffraction structure are located in a second area. The second region surrounds the first region. The second surface includes a third aspheric surface, a fourth aspheric surface, a third diffractive structure and a fourth diffractive structure. The third aspheric surface and the third diffraction structure are located in a third area, and the fourth aspheric surface and the fourth diffraction structure are located in a fourth area. The fourth region surrounds the third region. The second surface is a back surface of the first surface.

Description

Multi-focus objective lens

Technical field

The present invention is about a kind of multi-focus objective lens, especially in regard to a kind of multi-focus objective lens of easily making.

Background technology

Traditional multi-focus objective lens, disclosed as No. the 2006/0201250th, U.S. Patent Publication, it is the object lens that a kind of two lens is formed, and its object lens weight is heavier, and the cost of assembling adjustment is higher.And, owing to need to use manufacture of semiconductor to make eyeglass, so cost is higher, and be easy to generate the problem of parasitic light.

U.S. Patent Publication discloses a kind of multi-focus objective lens of single eyeglass for No. 2005/0281172, this multi-focus objective lens has a diffraction structure, a first surface and a second surface, this first surface is with respect to this second surface, and this diffraction knot is configured on this first surface.The diffraction fringe spacing of the diffraction structure that No. the 2005/0281172nd, U.S. Patent Publication needs less than 3 μ m, and the degree of depth of diffraction fringe is about 2.24 μ m, and this diffraction structure need be processed by high precision and be made, and its manufacturing cost and manufacture difficulty are all higher.

Summary of the invention

The multi-focus objective lens that solves the problem of conventional art and provide has been provided in the present invention, comprises a first surface and a second surface.First surface comprises one first aspheric surface, one second aspheric surface, one first diffraction structure and one second diffraction structure.First aspheric surface and the first diffraction structure are positioned at a first area, and second aspheric surface and the second diffraction structure are positioned at a second area.This second area is around this first area.Second surface comprises one the 3rd aspheric surface, one the 4th aspheric surface, one the 3rd diffraction structure and one the 4th diffraction structure.The 3rd aspheric surface and the 3rd diffraction structure are positioned at one the 3rd zone, and the 4th aspheric surface and the 4th diffraction structure are positioned at one the 4th zone.The 4th zone is around the 3rd zone.Second surface is the back side of this first surface.

Use multi-focus objective lens of the present invention, the diffraction exponent number collocation of each diffraction structure can compensate the aberration because of temperature variation and light source center wavelength drift generation.Simultaneously, the first surface of multi-focus objective lens of the present invention and second surface all have the diffraction structure, whereby, can strengthen the interval of diffraction fringe, and be minimized manufacture difficulty.Simultaneously, use the present invention, the diffraction efficient that can make this first light beam (HD-DVD laser), this second light beam (DVD laser) and the 3rd light beam (CD laser) is entirely greater than more than 90%, and is minimized the loss of luminous energy.

Description of drawings

Fig. 1 shows multi-focus objective lens of the present invention;

The first surface of the complete demonstration of Fig. 2 a multi-focus objective lens of the present invention;

The second surface of the complete demonstration of Fig. 2 b multi-focus objective lens of the present invention;

Fig. 3 shows another embodiment of the present invention;

Fig. 4 shows another embodiment of the present invention.

The primary clustering symbol description

11～the first aspheric surfaces

12～the second aspheric surfaces

13～the 3rd aspheric surfaces

14～the 4th aspheric surfaces

21～the first diffraction structures

22～the second diffraction structures

23～the 3rd diffraction structures

24～the 4th diffraction structures

100～multi-focus objective lens

200～disc

A1～first area

A2～second area

A3～the 3rd zone

A4～the 4th zone

S1～first surface

S2～second surface

Embodiment

With reference to Fig. 1, it shows multi-focus objective lens 100 of the present invention, and in order to read disc 200, this multi-focus objective lens 100 comprises a first surface S1 and a second surface S2.Collocation is with reference to Fig. 2 a, and first surface S1 comprises one first aspheric surface 11, one second aspheric surface 12, one first diffraction structure 21 and one second diffraction structure 22.First aspheric surface 11 and the first diffraction structure 21 are positioned at a first area A1, and second aspheric surface 12 and the second diffraction structure 22 are positioned at a second area A2.This second area A2 is around this first area A1.Collocation is with reference to Fig. 2 b, and second surface S2 comprises one the 3rd aspheric surface 13, one the 4th aspheric surface 14, one the 3rd diffraction structure 23 and one the 4th diffraction structure 24.The 3rd aspheric surface 13 and the 3rd diffraction structure 23 are positioned at one the 3rd regional A3, and the 4th aspheric surface 14 and the 4th diffraction structure 24 are positioned at one the 4th regional A4.The 4th regional A4 is around the 3rd regional A3.Second surface S2 is the back side of this first surface S1, and this first area A1 is to should the 3rd regional A3, and this second area A2 is to should the 4th regional A4.

Multi-focus objective lens of the present invention is in order to focus on one first light beam (HD-DVD laser), one second light beam (DVD laser) and one the 3rd light beam (CD laser), this first light beam comprises one first wavelength X 1, this second light beam comprises that one second wavelength X, 2, the three light beams comprise a wavelength lambda 3.

Below, the design relation between this first diffraction structure and the 3rd diffraction structure at first is described.

Design relation between the first diffraction structure and the 3rd diffraction structure

This first diffraction structure and the 3rd diffraction structure comprise one first design wavelength lambda r1, between this first design wavelength lambda r1 and this first wavelength X 1, this second wavelength X 2 and this wavelength lambda 3, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4,$ $\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_1}\right)={\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">m</figure-callout>}}_1,$ λ 1 is between 390 to 420nm;

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4,$ $\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_2}\right)=m_2,$ λ 2 is between 600 to 698nm;

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_3}\right)-\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_3}\right)|\&le;0.4,$ $\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">r</figure-callout>}1}}{{\mathrm{\&lambda;}}_3}\right)=m_3,$ λ 3 is between 700 to 890nm; And

λ _r1＝d ₁×(N-1)，

Wherein, d1 is the degree of depth between this first diffraction structure and the 3rd diffraction structure, and N is the refractive index of this first diffraction structure and the 3rd diffraction structure, and this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, the 3rd light beam comprises one the 3rd diffraction exponent number m ₃, this first, second and the 3rd diffraction exponent number (m ₁, m ₂, m ₃) be selected from by following ordered series of numbers (2,1,0), (2,1,1), (3,2,0), (3,2,2), (4,3,0), (4,3,2), (5,3,0), (5,3,3), (6,4,0), (6,4,3), (8,5,0), (8,5,4), (9,6,0), (9,6,5), (10,6,0) and (10,6,5) group of being formed.

The above ordered series of numbers that provides, but be when design convergent ordered series of numbers.

This first aspheric surface and the 3rd aspheric surface form one first focal distance f 1, and this first diffraction structure comprises one first diffraction focal distance f D1, and this first focal distance f 1 satisfies following relational expression with this first diffraction focal distance f D1:

$-0.3<\frac{f_1}{{\mathrm{<figure-callout\; id="1"\; label="f\; D"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">f</figure-callout>}}_D}<0.3$

Simultaneously, this first diffraction focal distance f D1 satisfies following relational expression:

${\mathrm{<figure-callout\; id="1"\; label="f\; D"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">f</figure-callout>}}_D=\frac{{\mathrm{\&lambda;}}_{r1}}{(-2\&times;{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">P</figure-callout>}}_1\&times;m_n\&times;{\mathrm{\&lambda;}}_n)}$

Wherein, n=1,2 or 3, P1 represent the second order phase coefficient of this first diffraction structure.

Same, the 3rd diffraction structure comprises one the 3rd diffraction focal distance f D3, this first focal distance f 1 satisfies following relational expression with the 3rd diffraction focal distance f D3:

$-0.3<\frac{f_1}{f_{D3}}<0.3$

Simultaneously, the 3rd diffraction focal distance f D3 satisfies following relational expression:

$f_{D3}=\frac{{\mathrm{\&lambda;}}_{r1}}{(-2\&times;P_3\&times;m_n\&times;{\mathrm{\&lambda;}}_n)}$

Wherein, n=1,2 or 3, P3 represent the second order phase coefficient of the 3rd diffraction structure.

The absolute value of all phase coefficients of this first diffraction structure and the 3rd diffraction structure (for example, second order phase coefficient, three rank phase coefficients) is less than 0.1.

First, second of this first diffraction structure and the 3rd diffraction structure and the 3rd diffraction exponent number (m ₁, m ₂, m ₃), can be identical or different.

The numerical value and the restriction relation that are provided more than using, by operational software (for example, the software Code V that Terasoft provided), can obtain this first diffraction structure, the 3rd diffraction structure, this first aspheric surface and the 3rd aspheric design data, wherein, this first design wavelength lambda r1 calculates in the mode of trial and error pricing and obtains, its can for, for example, 3264nm.

Below, the design relation between this second diffraction structure and the 4th diffraction structure then is described.

Design relation between the second diffraction structure and the 4th diffraction structure

This second diffraction structure and the 4th diffraction structure comprise one second design wavelength lambda r2, between this second design wavelength lambda r2 and this first wavelength X 1 and this second wavelength X 2, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4,$ $\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)={\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="H2007100077323E00031.png,H2007100077323E00041.png"\; state="\{\{state\}\}">m</figure-callout>}}_1,$ λ 1 is between 390 to 420nm;

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4,$ $\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)=m_2,$ λ 2 is between 600 to 698nm; And

λ _r2＝d ₂×(N-1)，

Wherein, d2 is the degree of depth between this second diffraction structure and the 4th diffraction structure, and N is the refractive index of this second diffraction structure and the 4th diffraction structure, and this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, this first and second diffraction exponent number (m ₁, m ₂) be selected from the group that is formed by following ordered series of numbers (2,0), (2,1), (3,0), (3,2), (4,0), (4,3), (5,0), (5,3), (6,0), (6,4), (8,0), (8,5), (9,0), (9,6), (10,0) and (10,6).

The above ordered series of numbers that provides, but be when design convergent ordered series of numbers.

This second aspheric surface and the 4th aspheric surface form one second focal distance f 2, and this second diffraction structure comprises one second diffraction focal distance f D2, and this second focal distance f 2 satisfies following relational expression with this second diffraction focal distance f D2:

$-0.3<\frac{f_2}{f_{D2}}<0.3$

Simultaneously, this second diffraction focal distance f D2 satisfies following relational expression:

$f_{D2}=\frac{{\mathrm{\&lambda;}}_{r2}}{(-2\&times;P_2\&times;m_n\&times;{\mathrm{\&lambda;}}_n)},$

Wherein, n=1,2 or 3, P2 represent the second order phase coefficient of this second diffraction structure.

The 4th diffraction structure comprises one the 4th diffraction focal distance f D4, and this second focal distance f 2 satisfies following relational expression with the 4th diffraction focal distance f D4:

$-0.3<\frac{f_2}{f_{D4}}<0.3$

Simultaneously, the 4th diffraction focal distance f D4 satisfies following relational expression:

$f_{D4}=\frac{{\mathrm{\&lambda;}}_{r2}}{(-2\&times;P_4\&times;m_n\&times;{\mathrm{\&lambda;}}_n)}$

Wherein, n=1,2 or 3, P4 represent the second order phase coefficient of the 4th diffraction structure.

The absolute value of all phase coefficients of this second diffraction structure and the 4th diffraction structure (for example, second order phase coefficient, three rank phase coefficients) is less than 0.1.

First, second of this second diffraction structure and the 4th diffraction structure and the 3rd diffraction exponent number (m ₁, m ₂, m ₃) can be identical or different.

The numerical value and the restriction relation that are provided more than using, by operational software (for example, the software Code V that Terasoft provided), can obtain this second diffraction structure, the 4th diffraction structure, this second aspheric surface and the 4th aspheric design data, wherein, this second design wavelength lambda r2 calculates in the mode of trial and error pricing and obtains, its can for, for example, 2040nm.

This multi-focus objective lens can be made by materials such as plastics or glass.

In an embodiment of the present invention, utilize aspheric surface can eliminate the spherical aberration that main aberration and temperature variation cause variations in refractive index to produce.Again, the spherical aberration that produced of utilize the diffraction structure to disappear aberration that residual aberration and temperature variation produce and the drift of light source center wavelength.Aspheric surface produces positive spherical aberration, and the diffraction structure produces negative spherical aberration, and total aberration balance mutually reaches the purpose of convergence 0 aberration.

Utilize the combination of asphericity coefficient and diffraction coefficient and diffraction exponent number the best, can reach the design of disc inclination optics Compensation Design, disc thickness error optical compensation, the design of object lens inclining optical compensation, the design of temperature variation optical compensation, the design of light source center wavelength drift optical compensation, object lens purpose in the design of assembly error optical compensation, the high diffraction efficiency optical design of diffraction structure.

Use multi-focus objective lens of the present invention, the diffraction exponent number collocation of each diffraction structure can compensate the aberration because of temperature variation and light source center wavelength drift generation.Simultaneously, the first surface of multi-focus objective lens of the present invention and second surface all have the diffraction structure, whereby, can strengthen the interval of diffraction fringe, and be minimized manufacture difficulty.Simultaneously, use the present invention, the diffraction efficient that can make this first light beam (HD-DVD laser), this second light beam (DVD laser) and the 3rd light beam (CD laser) is entirely greater than more than 90%, and is minimized the loss of luminous energy.

With reference to Fig. 3, in another embodiment of the present invention, this multi-focus objective lens comprises a first surface S1 and a second surface S2.First surface S1 comprises one first aspheric surface 11, one second aspheric surface 12, one first diffraction structure 21 and one second diffraction structure 22, this second diffraction structure 22 is around this first diffraction structure 21, this first diffraction structure 21 is formed on this first aspheric surface 11, and this second diffraction structure 22 is formed on this second aspheric surface 12.Second surface S2 is the back side of this first surface S1, this second surface S2 comprises one the 3rd aspheric surface 13 and one the 3rd diffraction structure 23, the 3rd diffraction structure 23 is formed on the 3rd aspheric surface 13, and wherein, 23 pairs on the 3rd diffraction structure should the first diffraction structure 21.

With reference to Fig. 4, in another embodiment of the present invention, this multi-focus objective lens comprises a first surface S1 and a second surface S2.First surface S1 comprises one first aspheric surface 11, one second aspheric surface 12, one first diffraction structure 21 and one second diffraction structure 22, this second diffraction structure 22 is around this first diffraction structure 21, this first diffraction structure 21 is formed on this first aspheric surface 11, and this second diffraction structure 22 is formed on this second aspheric surface 12.Second surface S2 is the back side of this first surface S1, this second surface S2 comprises one the 4th aspheric surface 14 and one the 4th diffraction structure 24, the 4th diffraction structure 24 is formed on the 4th aspheric surface 14, and wherein, 24 pairs on the 4th diffraction structure should the second diffraction structure 22.

Though the present invention with concrete preferred embodiment openly as above; right its is not in order to qualification the present invention, any insider, without departing from the spirit and scope of the present invention; still can do a little change and retouching, so protection scope of the present invention is as the criterion when looking claims person of defining.

Claims (16)

1. multi-focus objective lens comprises:

One first surface, it comprises one first diffraction structure and one second diffraction structure, this second diffraction structure is around this first diffraction structure; And

One second surface is the back side of this first surface, and this second surface comprises one the 3rd diffraction structure and one the 4th diffraction structure, and the 4th diffraction structure is around the 3rd diffraction structure,

Wherein, this multi-focus objective lens focuses on one first light beam, one second light beam and one the 3rd light beam, this first light beam comprises one first wavelength X 1, this second light beam comprises one second wavelength X 2, the 3rd light beam comprises a wavelength lambda 3, and wherein, this first diffraction structure and the 3rd diffraction structure comprise one first design wavelength lambda r1, between this first design wavelength lambda r1 and this first wavelength X 1, this second wavelength X 2 and this wavelength lambda 3, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_3}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_3}\right)|\&le;0.4;$ And

λ _r1＝d ₁×(N-1)，

Wherein, d1 is the degree of depth between this first diffraction structure and the 3rd diffraction structure, and N is the refractive index of this first diffraction structure and the 3rd diffraction structure, and wherein, this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, the 3rd light beam comprises one the 3rd diffraction exponent number m ₃, wherein,

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)=m_1,$ λ ₁Between 390 to 420nm;

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)=m_2,$ λ ₂Between 600 to 698nm;

λ ₃Between 700 to 890nm, wherein, this first, second and the 3rd diffraction exponent number (m ₁, m ₂, m ₃) be selected from by following ordered series of numbers (2,1,0), (2,1,1), (3,2,0), (3,2,2), (4,3,0), (4,3,2), (5,3,0), (5,3,3), (6,4,0), (6,4,3), (8,5,0), (8,5,4), (9,6,0), (9,6,5), (10,6,0) and (10,6,5) group of being formed.

2. multi-focus objective lens according to claim 1, wherein, this first surface also comprises one first aspheric surface, and this second surface also comprises one the 3rd aspheric surface, this first diffraction knot is configured on this first aspheric surface, and the 3rd diffraction knot is configured on the 3rd aspheric surface.

3. multi-focus objective lens according to claim 2, wherein, this first aspheric surface and the 3rd aspheric surface form one first focal distance f 1, and this first diffraction structure comprises one first diffraction focal distance f D1, and this first focal distance f 1 satisfies following relational expression with this first diffraction focal distance f D1:

$-0.3<\frac{f_1}{f_{D1}}<0.3,$ Simultaneously, this first diffraction focal distance f D1 satisfies following relational expression:

$f_{D1}=\frac{{\mathrm{\&lambda;}}_{r1}}{(-2\&times;P_1\&times;m_n\&times;{\mathrm{\&lambda;}}_n)},$

Wherein, n=1,2 or 3, P1 represent a second order phase coefficient of this first diffraction structure.

4. multi-focus objective lens according to claim 3, wherein, the absolute value of all phase coefficients of this first diffraction structure is less than 0.1.

5. multi-focus objective lens according to claim 2, wherein, this first aspheric surface and the 3rd aspheric surface form one first focal distance f, 1, the three diffraction structure and comprise one the 3rd diffraction focal distance f D3, and this first focal distance f 1 satisfies following relational expression with the 3rd diffraction focal distance f D3:

$-0.3<\frac{f_1}{f_{D3}}<0.3,$ Simultaneously, the 3rd diffraction focal distance f D3 satisfies following relational expression:

$f_{D3}=\frac{{\mathrm{\&lambda;}}_{r1}}{(-2\&times;P_3\&times;m_n\&times;{\mathrm{\&lambda;}}_n)},$

Wherein, n=1,2 or 3, P3 represent a second order phase coefficient of the 3rd diffraction structure.

6. multi-focus objective lens according to claim 5, wherein, the absolute value of all phase coefficients of the 3rd diffraction structure is less than 0.1.

7. multi-focus objective lens comprises:

One first surface, it comprises one first diffraction structure and one second diffraction structure, this second diffraction structure is around this first diffraction structure; And

One second surface is the back side of this first surface, and this second surface comprises one the 3rd diffraction structure and one the 4th diffraction structure, and the 4th diffraction structure is around the 3rd diffraction structure,

Wherein, this multi-focus objective lens focuses on one first light beam, one second light beam and one the 3rd light beam, and this first light beam comprises one first wavelength X 1, and this second light beam comprises that one second wavelength X, 2, the three light beams comprise a wavelength lambda 3,

Wherein, this second diffraction structure and the 4th diffraction structure comprise one second design wavelength lambda r2, between this second design wavelength lambda r2 and this first wavelength X 1 and this second wavelength X 2, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4;$ And

λ _r2＝d ₂×(N-1)，

Wherein, d2 is the degree of depth between this second diffraction structure and the 4th diffraction structure, and N is the refractive index of this second diffraction structure and the 4th diffraction structure, and wherein, this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, wherein,

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)=m_1,$ λ ₁Between 390 to 420nm;

λ ₂Between 600 to 698nm, wherein, this first and second diffraction exponent number (m ₁, m ₂) be selected from the group that is formed by following ordered series of numbers (2,0), (2,1), (3,0), (3,2), (4,0), (4,3), (5,0), (5,3), (6,0), (6,4), (8,0), (8,5), (9,0), (9,6), (10,0) and (10,6).

8. multi-focus objective lens according to claim 7, wherein, this first surface also comprises one second aspheric surface, and this second surface also comprises one the 4th aspheric surface, this second diffraction knot is configured on this second aspheric surface, and the 4th diffraction knot is configured on the 4th aspheric surface.

9. multi-focus objective lens according to claim 8, wherein, this second aspheric surface and the 4th aspheric surface form one second focal distance f 2, and this second diffraction structure comprises one second diffraction focal distance f D2, and this second focal distance f 2 satisfies following relational expression with this second diffraction focal distance f D2:

$-0.3<\frac{f_2}{f_{D2}}<0.3,$ Simultaneously, this second diffraction focal distance f D2 satisfies following relational expression:

$f_{D2}=\frac{{\mathrm{\&lambda;}}_{r2}}{(-2\&times;P_2\&times;m_n\&times;{\mathrm{\&lambda;}}_n)},$

Wherein, n=1,2 or 3, P2 represent a second order phase coefficient of this second diffraction structure.

10. multi-focus objective lens according to claim 9, wherein, the absolute value of all phase coefficients of this second diffraction structure is less than 0.1.

11. multi-focus objective lens according to claim 8, wherein, this second aspheric surface and the 4th aspheric surface form one second focal distance f, 2, the four diffraction structures and comprise one the 4th diffraction focal distance f D4, and this second focal distance f 2 satisfies following relational expression with the 4th diffraction focal distance f D4:

$-0.3<\frac{f_2}{f_{D4}}<0.3,$ Simultaneously, the 4th diffraction focal distance f D4 satisfies following relational expression:

$f_{D4}=\frac{{\mathrm{\&lambda;}}_{r2}}{(-2\&times;P_4\&times;m_n\&times;{\mathrm{\&lambda;}}_n)},$

Wherein, n=1,2 or 3, P4 represent a second order phase coefficient of the 4th diffraction structure.

12. multi-focus objective lens according to claim 11, wherein, the absolute value of all phase coefficients of the 4th diffraction structure is less than 0.1.

13. a multi-focus objective lens comprises:

One first surface, comprise one first aspheric surface, one second aspheric surface, one first diffraction structure and one second diffraction structure, this second diffraction structure is around this first diffraction structure, this first diffraction knot is configured on this first aspheric surface, and this second diffraction knot is configured on this second aspheric surface; And

One second surface is the back side of this first surface, and this second surface comprises one the 3rd aspheric surface and one the 3rd diffraction structure, and the 3rd diffraction knot is configured on the 3rd aspheric surface, wherein, and corresponding this first diffraction structure of the 3rd diffraction structure,

Wherein, this multi-focus objective lens focuses on one first light beam, one second light beam and one the 3rd light beam, and this first light beam comprises one first wavelength X 1, and this second light beam comprises that one second wavelength X, 2, the three light beams comprise a wavelength lambda 3,

Wherein, this first diffraction structure and the 3rd diffraction structure comprise one first design wavelength lambda r1, between this first design wavelength lambda r1 and this first wavelength X 1, this second wavelength X 2 and this wavelength lambda 3, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_3}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_3}\right)|\&le;0.4;$ And

λ _r1＝d ₁×(N-1)，

Wherein, d1 is the degree of depth between this first diffraction structure and the 3rd diffraction structure, and N is the refractive index of this first diffraction structure and the 3rd diffraction structure, and wherein, this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, the 3rd light beam comprises one the 3rd diffraction exponent number m ₃, wherein

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)=m_1,$ λ ₁Between 390 to 420nm;

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)=m_2,$ λ ₂Between 600 to 698nm; And

λ ₃Between 700 to 890nm, wherein, this first, second and the 3rd diffraction exponent number (m ₁, m ₂, m ₃) be selected from by following ordered series of numbers (2,1,0), (2,1,1), (3,2,0), (3,2,2), (4,3,0), (4,3,2), (5,3,0), (5,3,3), (6,4,0), (6,4,3), (8,5,0), (8,5,4), (9,6,0), (9,6,5), (10,6,0) and (10,6,5) group of being formed.

14. a multi-focus objective lens comprises:

One first surface, comprise one first aspheric surface, one second aspheric surface, one first diffraction structure and one second diffraction structure, this second diffraction structure is around this first diffraction structure, this first diffraction knot is configured on this first aspheric surface, and this second diffraction knot is configured on this second aspheric surface; And

One second surface is the back side of this first surface, and this second surface comprises one the 3rd aspheric surface and one the 3rd diffraction structure, and the 3rd diffraction knot is configured on the 3rd aspheric surface, wherein, and corresponding this first diffraction structure of the 3rd diffraction structure,

Wherein, this multi-focus objective lens focuses on one first light beam, one second light beam and one the 3rd light beam, and this first light beam comprises one first wavelength X 1, and this second light beam comprises that one second wavelength X, 2, the three light beams comprise a wavelength lambda 3,

Wherein, this second diffraction structure comprises one second design wavelength lambda r2, between this second design wavelength lambda r2 and this first wavelength X 1 and this second wavelength X 2, satisfies the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4;$ And

λ _r2＝d ₂×(N-1)，

Wherein, d2 is the degree of depth between this second diffraction structure and this second surface, and N is the refractive index of this second diffraction structure, and wherein, this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, wherein

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)=m_1,$ λ ₁Between 390 to 420nm;

λ ₂Between 600 to 698nm, wherein, this first and second diffraction exponent number (m ₁, m ₂) be selected from the group that is formed by following ordered series of numbers (2,0), (2,1), (3,0), (3,2), (4,0), (4,3), (5,0), (5,3), (6,0), (6,4), (8,0), (8,5), (9,0), (9,6), (10,0) and (10,6).

15. a multi-focus objective lens comprises:

One first surface, comprise one first aspheric surface, one second aspheric surface, one first diffraction structure and one second diffraction structure, this second diffraction structure is around this first diffraction structure, this first diffraction knot is configured on this first aspheric surface, and this second diffraction knot is configured on this second aspheric surface; And

One second surface is the back side of this first surface, and this second surface comprises one the 4th aspheric surface and one the 4th diffraction structure, and the 4th diffraction knot is configured on the 4th aspheric surface, wherein, and corresponding this second diffraction structure of the 4th diffraction structure,

Wherein, this multi-focus objective lens focuses on one first light beam, one second light beam and one the 3rd light beam, and this first light beam comprises one first wavelength X 1, and this second light beam comprises that one second wavelength X, 2, the three light beams comprise a wavelength lambda 3,

Wherein, this second diffraction structure and the 4th diffraction structure comprise one second design wavelength lambda r2, between this second design wavelength lambda r2 and this first wavelength X 1, this second wavelength X 2 and this wavelength lambda 3, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4;$ And

λ _r2＝d ₂×(N-1)，

Wherein, d2 is the degree of depth between this second diffraction structure and the 4th diffraction structure, and N is the refractive index of this second diffraction structure and the 4th diffraction structure, and wherein, this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, wherein

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r2}}{{\mathrm{\&lambda;}}_1}\right)=m_1,$ λ ₁Between 390 to 420nm

λ ₂Between 600 to 698nm, wherein, this first and second diffraction exponent number (m ₁, m ₂) be selected from the group that is formed by following ordered series of numbers (2,0), (2,1), (3,0), (3,2), (4,0), (4,3), (5,0), (5,3), (6,0), (6,4), (8,0), (8,5), (9,0), (9,6), (10,0) and (10,6).

16. a multi-focus objective lens comprises:

One first surface, comprise one first aspheric surface, one second aspheric surface, one first diffraction structure and one second diffraction structure, this second diffraction structure is around this first diffraction structure, this first diffraction knot is configured on this first aspheric surface, and this second diffraction knot is configured on this second aspheric surface; And

One second surface is the back side of this first surface, and this second surface comprises one the 4th aspheric surface and one the 4th diffraction structure, and the 4th diffraction knot is configured on the 4th aspheric surface, wherein, and corresponding this second diffraction structure of the 4th diffraction structure,

Wherein, this multi-focus objective lens focuses on one first light beam, one second light beam and one the 3rd light beam, this first light beam comprises one first wavelength X 1, this second light beam comprises one second wavelength X 2, the 3rd light beam comprises a wavelength lambda 3, and wherein, this first diffraction structure comprises one first design wavelength lambda r1, between this first design wavelength lambda r1 and this first wavelength X 1, this second wavelength X 2 and this wavelength lambda 3, satisfy the following relationship formula:

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)|\&le;0.4;$

$0\&le;|\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_3}\right)-\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_3}\right)|\&le;0.4;$ And

λ _r1＝d ₁×(N-1)，

Wherein, d1 is the degree of depth between this first diffraction structure and this second surface, and N is the refractive index of this first diffraction structure, and wherein, this first light beam comprises one first diffraction exponent number m ₁, this second light beam comprises one second diffraction exponent number m ₂, the 3rd light beam comprises one the 3rd diffraction exponent number m ₃, wherein

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_1}\right)=m_1,$ λ ₁Between 390 to 420nm;

$\mathrm{INT}\left(\frac{{\mathrm{\&lambda;}}_{r1}}{{\mathrm{\&lambda;}}_2}\right)=m_2,$ λ ₂Between 600 to 698nm; And

λ ₃Between 700 to 890nm, wherein, this first, second and the 3rd diffraction exponent number (m ₁, m ₂, m ₃) be selected from by following ordered series of numbers (2,1,0), (2,1,1), (3,2,0), (3,2,2), (4,3,0), (4,3,2), (5,3,0), (5,3,3), (6,4,0), (6,4,3), (8,5,0), (8,5,4), (9,6,0), (9,6,5), (10,6,0) and (10,6,5) group of being formed.

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