1 Advanced Display Optics Lab Syuan Li APL 05 Variable-focus liquid lens by changing aperture Hongwen Ren and Shin-Tson Wu College of Optics and Photonics, University of Central Florida, Orlando, Florida Speaker: Syuan Li ( 李玄 ) Advisor: Prof. Yi-Pai Huang( 黃乙白 教授 ) Department of Photonics & Display Institute, Department of Photonics & Display Institute, National Chiao Tung University, Hsinchu, Taiwan October 28,

2 Advanced Display Optics Lab Syuan Li Outline  Introduction - Four type of the liquid lens  Variable-focus liquid lens by changing aperture - Structure of variable-focus liquid lens - The relationship between r and R - The corresponding focal length - Image quality - The simulated focal length and the radius of the lens aperture - The best thickness of the rotatable impellers - Discussion  Conclusions

3 Advanced Display Optics Lab Syuan Li Introduction Four type of the liquid lens First type Cons - during the distance change, lens cannot easily keep the periphery of the elastic membrane parallel to the planar substrate - the operating system for tuning the focus is complicated moving the periphery of the elastic membrane the liquid assembly is redistributed the curvature of the film is changed light to converge or diverge

4 Advanced Display Optics Lab Syuan Li Introduction Four type of the liquid lens Second type - Liquid lenses operated by pumping liquid in and out of the lens chamber to change the curvature of the elastic membrane surface Pros - high lens power (=1/f) without changing lens aperture Cons - a fluidic pumping system is needed - lens system is sensitive to vibration

5 Advanced Display Optics Lab Syuan Li Introduction Four type of the liquid lens Third type the focal length of the liquid lens is tuned by applying an external voltage Pros - has fast response time and continuous focus change Cons - making a large aperture lens is a difficult

6 Advanced Display Optics Lab Syuan Li Introduction Four type of the liquid lens Fourth type vary the focus of the liquid lens by changing its aperture size

7 Advanced Display Optics Lab Syuan Li Outline  Introduction - Four type of the liquid lens  Variable-focus liquid lens by changing aperture - Structure of variable-focus liquid lens - The relationship between r and R - The corresponding focal length - Image quality - The simulated focal length and the radius of the lens aperture - The best thickness of the rotatable impellers - Discussion  Conclusions

8 Advanced Display Optics Lab Syuan Li Structure of variable-focus liquid lens - elastic membrane - solid plate - annular sealing ring (seal is wrapped using an elastic membrane to confine the liquid) - liquid with a fixed volume stored in lens chamber The radius of the annular sealing ring is changeable the circular periphery seal is similar to an iris diaphragm with rotatable impellers Variable-focus liquid lens by changing aperture

9 Advanced Display Optics Lab Syuan Li Variable-focus liquid lens by changing aperture Structure of variable-focus liquid lens lever actuator control the movement of the rotatable impellers and impart the pressure to the fluid-filled lens the redistributed liquid will change the shape of the lens curvature change the focal length of the lens Pros - simple fabrication process -compact structure -easy operation - low cost tuning the radius of the annular sealing ring the stored liquid in the lens will be redistributed Changing the curvature of the elastic membrane

10 Advanced Display Optics Lab Syuan Li Variable-focus liquid lens by changing aperture rotating the lever actuator clockwise rotating the lever actuator counterclockwise convex concave change the aperture size can vary the focus of the liquid lens

11 Advanced Display Optics Lab Syuan Li the radius of the aperture is changed from r0 to r The volume of the redistributed liquid Variable-focus liquid lens by changing aperture The relationship between the radius of the liquid lens r and the radius of the lens curvature R (h is the effective thickness of the liquid lens)

12 Advanced Display Optics Lab Syuan Li (r0=12.5 mm and h=5.5 mm) When the radius of the lens is decreased from 12.5 to 9.5 mm, the radius of curvature R is decreased sharply Variable-focus liquid lens by changing aperture As r<9.5 mm, R decreases at a much slower rate The relationship between R and r

13 Advanced Display Optics Lab Syuan Li (n is the refractive index of the liquid) the focal length can be reduced by 1. decreasing r 2. a high refractive index liquid 3. increasing the lens thickness To increase the lens power D (=1/f) Variable-focus liquid lens by changing aperture The corresponding focal length liquid redistribution elastic membrane curvature is altered different focal length

14 Advanced Display Optics Lab Syuan Li the focal length and the radius of curvature have a similar trend Variable-focus liquid lens by changing aperture The simulated focal length and the radius of the lens aperture

15 Advanced Display Optics Lab Syuan Li Variable-focus liquid lens by changing aperture Image quality In the original state the surface of the elastic membrane of the lens was flat no lens effect the aperture of the lens became smaller the observed image is magnified The liquid lens belongs to a convex lens

16 Advanced Display Optics Lab Syuan Li the impellers screwed inward(used a thin ~0.5mm) Variable-focus liquid lens by changing aperture The best thickness of the rotatable impellers the lens aperture shrinks the volume of the redistributed liquid is halved The relationship between R and r Once the R is obtained, the lens focal lens can be calculated from Compared to the demo (5.5mm) Used a different block rotatable impellers

17 Advanced Display Optics Lab Syuan Li Variable-focus liquid lens by changing aperture In the same aperture, the focal length is halved To obtain a liquid lens with a wide tunable focal length the thickness of the rotatable impellers should be the same as the circular periphery seal The best thickness of the rotatable impellers

18 Advanced Display Optics Lab Syuan Li Discussion The actuator lever of the liquid lens can be rotated mechanically or electrically If the rotatable impellers are made of other materials (such as clear glass, plastics, or polymer) then the apparent aperture will not be noticeable even when the impellers are rotated The range of the variable focal length can be significantly widened if we use a higher index liquid, increase the effective thickness of the liquid lens, or change the radius of the lens aperture to a larger degree Variable-focus liquid lens by changing aperture

19 Advanced Display Optics Lab Syuan Li Outline  Introduction - Four type of the liquid lens  Variable-focus liquid lens by changing aperture - Structure of variable-focus liquid lens - The relationship between r and R - The corresponding focal length - Image quality - The simulated focal length and the radius of the lens aperture - The best thickness of the rotatable impellers - Discussion  Conclusions

20 Advanced Display Optics Lab Syuan Li Conclusions Advantages: - in the simple fabrication process - simple lens structure - easy operation - the relatively low cost - lightweight - very weak color dispersion The lens has a very wide range of variable focal lengths By rotating the impellers of the liquid lens in or out, we can get a convex lens and a concave lens easily

21 Advanced Display Optics Lab Syuan Li Thank you for your kind attention! Display Institute, National Chiao Tung University

22 Advanced Display Optics Lab Syuan Li