NL2011874C2

NL2011874C2 - Lens system.

Info

Publication number: NL2011874C2
Application number: NL2011874A
Authority: NL
Inventors: Edwin Maria Wolterink; Yelena Vladimirovna Shulepova
Original assignee: Anteryon Wafer Optics B V
Priority date: 2013-11-29
Filing date: 2013-11-29
Publication date: 2015-06-01
Also published as: WO2015080582A1

Abstract

The present invention relates to a lens system consisting of four lenses, wherein each lens comprises two lens elements, wherein said two lens elements within each lens have different optical properties. In a preferred embodiment the present lens elements have been manufactured according replication technology. The present lens system can be identified as a wafer level optics bimaterial lens system, wherein the present lens system comprises four bimaterial lenses, each lens being an assembly of at least two contiguous lens elements comprising at least two different lens materials having different optical properties.

Description

Title: Lens system

The present invention relates to a lens system.

Lens systems as such are known and widely used in, inter alia, mobile phones, tablets and compact cameras. The ppicture quality (resolution) of current cameras used in those handheld devices is relative poor, especially in the corners of images. Although the lens designs used in abovementioned cameras show that very high corner resolution should be possible to achieve in the nominal case, the actual measured resolution is usually significantly lower than the nominal design.

The present inventors found that, on a large degree, this resolution degradation is caused by production tolerances in lens manufacturing resulting in decenter deviations up to 5 micrometers, and by tilt of the lens caused by the autofocus system. In addition, it is possible to make a design that is more robust to tolerances. So given production tolerances, by making a more robust design, production tolerances such as decenter will have a limited effect on resolution degradation.

One possible solution is that in current plastic molding lens technology, a more robust design would be possible by relocation the diaphragm from the front towards the middle of the lens system. However, this would result in very thin lenses (< 200-300 urn), which cannot be manufactured by injection molding. Another disadvantage of relocation of the diaphragm is that the nominal design performance gets lower.

Nowadays the trends in cameras for hand-held devices can be identified as follows: higher resolution, higher Mpix count, smaller pixels, lower z-height and higher field of views (from 55 deg to 70 deg).

The consequences of these trends are: optics in cameras require changes in designing the optics for the cameras: low F# and more lens elements are needed, low F# and more lens elements require tighter production tolerances. Lens systems will show an increased sensitivity to manufacturing tolerances such as lens decenter, lens shape deviations and lens tilt. This will be visible in - for example - a low corner resolution, and/or non-uniformity of the resolution in the pictures taken with these cameras. In addition lens performance is highly determined by manufacturing tolerances. The main production tolerances that lead to lower image quality and/or non-uniformity are lens decenter and lens tilt. Typical manufacturing tolerances for injection molding for decenter are typically 3-5 microns. In order to keep the performance degradation to an acceptable low level, typical maximum decenter of 1 micron would be required, which is beyond current manufacturing capability.

An object of the present invention is thus to develop lens designs that more robust to tolerances.

Another object of the present invention is to develop such robust lens designs while maintaining nominal performance.

Another object of the present invention is to provide high performing lens designs showing high level of chromatic properties of the lens, allowing new ways of choosing the lens configuration.

The present invention relates thus to a lens system comprising four lenses, wherein each lens comprises two lens elements, wherein said two lens elements within each lens have different optical properties.

The present lens system can be identified as a wafer level optics bimaterial lens system, wherein the present lens system comprises four bimaterial lenses, each lens being an assembly of at least two contiguous lens elements comprising at least two different lens materials having different optical properties.

The present term “bimaterial lenses" refers to the use of to different materials in one lens, e.g.. a lens element X made of material Q and a lens element Z made of material P, wherein both lens element X and lens element Y form together a lens. The present lenses are groups of contiguous lens elements cemented together by replication technology according to W02009048320A1 and in preferred embodiments they contain additional integrated intermediate substrates, filters and diaphragms. Injection molded type lenses can be used as well. The contents of W02009048320 are considered to be incorporated here in its entirety.

The present inventors are of the opinion that better chromatic properties provide better performance with less lens groups. The present lens system also provide ultra-thin lenses (down to 50 micron, preferably 70-80 microns at the edges) that consist of two or more different materials.

According to a preferred embodiment of the present lens system the lens elements have been manufactured according replication technology.

For an optimum optical performance it is preferred that in the present lens system the range of index (n) and Abbe properties in the first lens are:

Lens element (105A): 1.45< n < 1.60, 50 < Abbe < 80

Lens element (106B): 1.55 < n < 1.75, 20 < Abbe < 40.

The specific location of the first, second, third and fourth lens will be elucidated when discussing the figures.

In addition, It is preferred that in the present lens system the range of index (n) and Abbe properties in the second lens are:

Lens element (205A): 1.45< n < 1.75, 20 < Abbe < 80

Lens element (206B): 1.45< n < 1.75, 20 < Abbe < 80.

In addition, It is preferred that in the present lens system the range of index (n) and Abbe properties in the third lens are:

Lens element (305B): 1.45< n < 1.75, 20 < Abbe < 80

Lens element (306A): 1.45< n < 1.75, 20 < Abbe < 80.

Moreover, It is preferred that in the present lens system the range of index (n) and Abbe properties in the fourth lens are:

Lens element (405C): 1.45< n < 1.75, 20 < Abbe < 80

Lens element (406B): 1.45< n < 1.75, 20 < Abbe < 80.

In addition, It is preferred that in the present lens system the range of index (n) and Abbe properties in the first lens are according to the next equation: η (106B minus 105A) = 0.05 < delta < 0.2

Abbe (105A minus 106B) = 15 < delta <40.

In addition, It is preferred that in the present lens system the range of index (n) and Abbe properties in the second lens are according to the next equation: η (206B minus 205) = 0.01 < /delta/ < 0.3

Abbe (205A minus 206) = 10 < /delta/ <40.

The indication “/delta/” as used here means (absolute delta).

In addition, It is preferred that in the present lens system the range of index (n) and Abbe properties in the third lens are according to the next equation: η (306A minus 305) = 0 < /delta/ < 0.3

Abbe (305B minus 306) = 0 < /delta/ < 40.

In addition, It is preferred that in the present lens system the range of index (n) and Abbe properties in the fourth lens are according to the next equation: η (406B minus 405C) 0 < /delta/ < 0.3

Abbe (405C minus 406B) 0 < /delta/ < 40.

According to a preferred embodiment of the lens system one or more additional layers are present in one or more of said four lenses, wherein the additional layers are chosen from the group of integrated intermediate substrates, IR filters, UV filters, apertures and diaphragms, or combinations thereof.

It is preferred that a diaphragm is positioned in the second lens, especially positioned between lens element (205A) and lens element (206B).

The materials of said lens elements are preferably chosen from the group of UV curable polymers, preferably epoxy, acrylic and nylon type polymers.

The present invention relates furthermore to a stack of a lens assembly, wherein said stack comprises the present lens system.

In such a stack the individual four lenses are preferably stacked by using spacers and/or adhesives.

The present stack further comprises one or more of an image sensor, a sensor cover plate and a cover plate.

The present inventors found that the optical performance is to a large extent determined by the material combinations in Lens 1. Lens 1 comprises material A in layer 105 and material B in layer 106. The layers 205, 206, 305, 306, 405, 406 may have any combination of (different) material types A, B, C, as indicated in the range of material properties below:

Layers 210, 220,230 provide mechanical features for alignment in the present construction. Based on simple buffer layers 111, 210, 311 or specific alignment geometries 112, 212, 312. Diaphragm is preferably between surfaces 205A and 206B but in other embodiments other positions are also possible.

The present invention will be explained by using the Figures and embodiments.

Fig 1 shows a commercially available lens system.

Fig 2 shows the nominal MTF vs. field performance (left graph) of the lens system according to Fig 1 and the performance (right graph) after application of 1.5 urn decenter (overlay) to lenses in a Monte Carlo analysis.

Fig 3 shows the MTF vs. frequency of the lens system according to Fig 1.

Fig 4 shows the field curvature and distortion of the lens system according to Fig 1.

Fig 5 shows a construction of a 5x plastic lenses mounted in barrel.

Fig 6 shows an embodiment of a lens system comprising four lenses according to the present invention.

Fig 7 shows a more detailed scheme of the lens system shown in Fig 6.

Fig 8 shows a ray tracing model for the present lens system.

Fig 9 shows the nominal performance (left graph) and the right graph shows performance after applying 1.5 urn decenter to the lenses in a Monte Carlo analysis.

Fig 10 shows MTF vs. frequency of a lens system comprising four lenses according to the present invention.

Fig 11 shows a distortion < 1.5% for a lens system comprising four lenses according to the present invention.

Fig 12 shows a relative illumination > 50% for a lens system comprising four lenses according to the present invention.

Fig 13 shows two mounting options (B and C) for a lens system comprising four lenses according to the present invention and a commercially available mounting option for a lens system (A).

Fig 1 shows a commercially available lens system, consisting of 5 plastic lenses + cover plate S + Image Sensor I, 8M 1.4 urn pix ; 5.7 mm image circle ; FOV 65 deg; EFL 4.3 mm; F# 2.4, Diaphragm D in front of Lensl, showing a high nominal performance, but low performance after tolerances (decenter, lens shape, tilt).

Fig 2 shows the nominal MTF vs. field performance (left graph) of the lens system according to Fig 1 and the performance (right graph) after application of 1.5 urn decenter (overlay) to lenses in a Monte Carlo analysis, wherein a significant MTF reduction is observed.

Fig 3 shows the MTF vs. frequency of the lens system according to Fig 1.

Fig 5 shows a construction of a 5x plastic lenses mounted in barrel.

Fig 6 shows an embodiment of a lens system comprising four lenses according to the present invention. This Fig 6 shows the present 4x bi-material lens system with diaphragm D located in Lens 2 (cover plate SCG and image sensor i not shown).

Fig 7 shows a more detailed scheme of the lens system shown in Fig 6, wherein in the present 4x bi-material lens system (cover plate, diaphragm and image sensor not shown) a diaphragm is present at location (s202). Lensl, i.e. the first lens, comprises Lens element (105A) and Lens element (106B). Lens2, i.e. the second lens, comprises Lens element (205A) and Lens element (206B). Lens3, i.e. the third lens, comprises Lens element (305B) and Lens element (306A). Lens4, i.e. the fourth lens, comprises Lens element (405C) and Lens element (406B). As recited in the appended claims, there exist preferred optical properties for the materials applied in each of the lenses 1, 2,3 and 4. The optical properties within one lens are not same, this means that for example the optical properties for Lens element (205A) differ from the one used for Lens element (206B). The same applies for Lens element (105A) and Lens element (106B), and for Lens element (305B) and Lens element (306A), and for Lens element (405C) and Lens element (406B).

Fig 8 shows a ray tracing model for the present lens system wherein diaphragm D (surface 202) is located between lens surface 201 and 203. The additional references refer to SCG = sensor cover glass, i is image sensor plane.

The present lens system is characterized by high nominal performance, high performance after tolerances.

Fig 9 shows the nominal performance (left graph) and the right graph shows performance after applying 1.5 urn decenter to the lenses in a Monte Carlo analysis. This Fig 9 shows a low MTF reduction compared to a commercially available five lens system.

Fig 13 shows two mounting options (B and C) for a lens system comprising four lenses according to the present invention and a commercially available mounting option for a lens system (A). For the present lens systems two mounting options are preferred, i.e. an: option B providing mounting the lenses in a barrel. By mounting ridges, the present lenses can be centered with respect to each other. According to option C, the present lenses are mounted by stacking, using a bonding process in in which wafer optics technology is used. The present lenses are groups of contiguous lens elements cemented together by replication technology according to W02009048320A1. The contents of W02009048320 are considered to be incorporated here in its entirety.

Optical table for Embodiment 1 (according to the invention):

Material A n=1.52 Abbe = 53.7 Material B n= 1.60 Abbe = 31 Material C n= 1.54 Abbe = 42

Surf Type Radius Thickness Material Diameter

Conic Comment OBJ STANDARD Infinity Infinity S101 EVENASPH 1.870627 0.7351413 A 2.586919 1.144467 lens 1 (105A)

5102 STANDARD Infinity 0.0875 B 5103 EVENASPH 13.81253 0.07015218 2.097756 63.81962 lensl (106B) 5201 EVENASPH 2.47591 0.2291261 A 1.604307 0.5457059 Iens2 (205A) 5202 STANDARD Infinity 0.3199788 B 1.6 D (202) 5203 EVENASPH 1.968053 0.4865585 1.58688 0.7136187 Iens2 (206B) 5301 EVENASPH -6.432559 0.7067649 B 1.946082 0.8996415 Iens3 (305B)

5302 STANDARD Infinity 1.123083 A 5303 EVENASPH -1.45851 0.5121329 3.43089 1.003002 lens 3 (306A) 5401 EVENASPH -3.962874 0.5195437 C 5.058419 0.9701412 lens 4 (405C)

5402 STANDARD Infinity 0.1773141 B 5403 EVENASPH 2.562319 0.3484415 5.39402 1.024785 Iens4 (406B) COVER PLATE Infinity 0.3125 B270 glass 14 STANDARD Infinity 0.0664165 5.640891 0 IMA STANDARD Infinity 6.6 0 SURFACE DATA DETAIL:

Surface OBJ STANDARD Surface 1 EVENASPH lensl (S101)

Coefficient on rA 2 : 0

Coefficient on rA 4 0.022652296

Coefficient on rA 6 0.018753471

Coefficient on rA 8 -0.028355933

Coefficient on rA10 0.033010866

Coefficient on rA12 -0.016648728

Coefficient on rA14 0.0024823651

Coefficient on rA16 0.00053958397

Surface 2 STANDARD (S102)

Aperture : Floating Aperture

Maximum Radius 3

Surface 3 EVENASPH Iens2 (S103) Coefficient on rA 2 : 0

Coefficient on rA 4 0.0031455283

Coefficient on rA 6 -0.032536968

Coefficient on rA 8 0.14176771

Coefficient on rA10 -0.25272211

Coefficient on rA12 0.22552228

Coefficient on rA14 -0.097422324

Coefficient on rA16 0.016434877

Surface 4 EVENASPH Iens3 (S201) Coefficient on rA 2 : 0

Coefficient on rA 4 -0.019713274

Coefficient on rA 6 0.00264897

Coefficient on rA 8 0.043876821

Coefficient on rA10 -0.05587171

Coefficient on rA12 -0.07567125

Coefficient on rA14 0.12471767

Coefficient on rA16 -0.025013124

Surface STO STANDARD (S202) Aperture : Floating Aperture

Maximum Radius 3

Surface 6 EVENASPH Iens4 (S203) Coefficient on rA 2 : 0

Coefficient on rA 4 0.018642901

Coefficient on rA 6 0.0023282314

Coefficient on rA 8 0.00041436458

Coefficient on rA10 0.074676766

Coefficient on rA12 -0.084412902

Coefficient on rA14 -0.06883524

Coefficient on rA16 0.13593759

Surface 7 EVENASPH Iens5 (S301) Coefficient on rA 2 : 0

Coefficient on rA 4 -0.052726114

Coefficient on rA 6 -0.0022331954

Coefficient on rA 8 -0.0040717168

Coefficient on rA10 -0.0011547069

Coefficient on rA12 0.002762003

Coefficient on rA14 0.0087752687

Coefficient on rA16 -0.0059529382

Surface 8 STANDARD (S302)

Aperture : Floating Aperture

Maximum Radius 3

Surface 9 EVENASPH Iens6 (S303) Coefficient on rA 2 : 0

Coefficient on rA 4 0.017936829

Coefficient on rA 6 -0.0076344231

Coefficient on rA 8 0.0004591403

Coefficient on rA10 : 0.00022137229

Coefficient on rA12 0.00054965147

Coefficient on rA14 : -0.00013451813

Coefficient on rA16 : -1,9410251e-006

Surface 10 EVENASPH Iens4 (S401) Coefficient on rA 2 : 0

Coefficient on rA 4 -0.04488157

Coefficient on rA 6 0.022367094

Coefficient on rA 8 -0.0024957924

Coefficient on rA10 : -5.1530527e-005

Coefficient on rA12 : 2.7311573e-005

Coefficient on rA14 : -1.4324951 e-006

Coefficient on rA16 8.0425754e-009

Surface 11 STANDARD (S402)

Aperture : Floating Aperture

Maximum Radius 3

Surface 12 EVENASPH Iens4 (S403) Coefficient on rA 2 : 0

Coefficient on rA 4 -0.07885175

Coefficient on rA 6 0.020435353

Coefficient on rA 8 -0.0027677544

Coefficient on rA10 : -7.548918e-005

Coefficient on rA12 5.4343155e-005

Coefficient on rA14 : -3.5119348e-006

Coefficient on rA16 : 4.6966387e-009

Claims

1. Lenssysteem omvattende vier lenzen, waarbij elke lens twee lenselementen omvat, waarbij voornoemde twee lenselementen binnen elke lens verschillende optische eigenschappen bezitten.A lens system comprising four lenses, each lens comprising two lens elements, said two lens elements having different optical properties within each lens.

2. Lenssysteem volgens conclusie 1, waarbij voornoemde lenselementen zijn vervaardigd volgens replicatietechnologie.The lens system of claim 1, wherein said lens elements are made according to replication technology.

3. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de eerste lens zijn: lenselement (105A): 1,45< n < 1,60, 50 < Abbe < 80 lenselement (106B): 1,55 < n < 1,75, 20 < Abbe < 40.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the first lens are: lens element (105A): 1.45 < n < 1.60, 50 < Abbe < 80 lens element (106B): 1.55 < n < 1.75, 20 < Abbe < 40.

4. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de tweede lens zijn: lenselement (205A): 1,45< n < 1,75, 20 < Abbe < 80 lenselement (206B): 1,45< n < 1,75, 20 < Abbe < 80.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the second lens are: lens element (205A): 1.45 < n < 1.75, 20 < Abbe < 80 lens element (206B): 1.45 < n < 1.75, 20 < Abbe < 80.

5. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de derde lens zijn: lenselement (305B): 1,45< n < 1,75, 20 < Abbe < 80 lenselement (306A): 1.45< n < 1,75, 20 < Abbe < 80.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the third lens are: lens element (305B): 1.45 < n < 1.75, 20 < Abbe < 80 lens element (306A): 1.45 < n < 1.75, 20 < Abbe < 80.

6. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de vierde lens zijn: lenselement (405C): 1,45< n < 1,75, 20 < Abbe < 80 lenselement (406B): 1,45< n < 1,75, 20 < Abbe < 80.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the fourth lens are: lens element (405C): 1.45 < n < 1.75, 20 < Abbe < 80 lens element (406B): 1.45 < n < 1.75, 20 < Abbe < 80.

7. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de eerste lens voldoen aan de volgende vergelijking: η (106B minus 105A) = 0,05 < delta < 0,2 Abbe (105A minus 106B) = 15 < delta <40.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the first lens satisfy the following equation: η (106B minus 105A) = 0.05 < delta < 0.2 Abbe (105A minus 106B) = 15 < delta < 40.

8. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de tweede lens voldoen aan de volgende vergelijking: η (206B minus 205) = 0,01 < /delta/ < 0.3 Abbe (205A minus 206) = 10 </delta/ < 40.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the second lens satisfy the following equation: η (206B minus 205) = 0.01 < / delta / < 0.3 Abbe (205A minus 206) = 10 < / delta / < 40.

9. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de derde lens voldoen aan de volgende vergelijking: η (306A minus 305) = 0 < /delta/ < 0,3 Abbe (305B minus 306) = 0 < /delta/ < 40.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the third lens satisfy the following equation: η (306A minus 305) = 0 < / delta / < 0.3 Abbe (305B minus 306) = 0 < / delta / < 40.

10. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de brekingsindex (n) en Abbe-eigenschappen in de vierde lens voldoen aan de volgende vergelijking: η (406B minus 405C) = 0 < /delta/ < 0,3 Abbe (405C minus 406B) = 0 < /delta/ < 40.Lens system according to one or more of the preceding claims, wherein the refractive index (s) and Abbe properties in the fourth lens satisfy the following equation: η (406B minus 405C) = 0 < / delta / < 0.3 Abbe (405C minus 406B) = 0 < / delta / < 40.

11. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij in een of meer van voornoemde vier lenzen een of meer aanvullende lagen aanwezig zijn, gekozen uit de groep bestaande uit geïntegreerde intermediaire substraten, IR-filters, UV-filters, apertures en diafragma’s, of combinaties hiervan.Lens system according to one or more of the preceding claims, wherein one or more of said four lenses contains one or more additional layers selected from the group consisting of integrated intermediate substrates, IR filters, UV filters, apertures and diaphragms , or combinations thereof.

12. Lenssysteem volgens conclusie 11, waarbij een diafragma is gepositioneerd in de tweede lens, in het bijzonder gepositioneerd tussen lenselement (205A) en lenselement (206B).The lens system of claim 11, wherein a diaphragm is positioned in the second lens, in particular positioned between lens element (205A) and lens element (206B).

13. Lenssysteem volgens een of meer van de voorgaande conclusies, waarbij de materialen van voornoemde lenselementen zijn gekozen uit de groep van UV-hardbare polymeren, bij voorkeur epoxy-, acryl- en nylon-type polymeren.Lens system according to one or more of the preceding claims, wherein the materials of said lens elements are selected from the group of UV-curable polymers, preferably epoxy, acrylic and nylon-type polymers.

14. Stack van een lensrangschikking, waarbij voornoemde stack het lenssysteem volgens een of meer van de voorgaande conclusies 1-13 omvat.A stack of a lens arrangement, wherein said stack comprises the lens system according to one or more of the preceding claims 1-13.

15. Stack volgens conclusie 14, waarbij de individuele vier lenzen zijn gestapeld onder toepassing van spacers en/of hechtmiddelen.The stack of claim 14, wherein the individual four lenses are stacked using spacers and / or adhesives.

16. Stack volgens een of meer van de conclusies 14 - 15, verder omvattende een of meer van een beeldsensor, een sensorafdekplaat en een afdekplaat.The stack of any one of claims 14 to 15, further comprising one or more of an image sensor, a sensor cover plate, and a cover plate.