Abstract

A new tunable-focus liquid lens system is proposed that consists of a liquid-filled PDMS (polydimethylsiloxane) membrane, special liquid injection mechanism based on a cam structure, antagonistic winding-type SMA(shape memory alloys) actuator for changing the surface curvature of the membrane, and liquid injection control system, including a digital signal processing board and actuator driver board. The focal length of the liquid lens is adjusted by changing the radius of the curvature of the liquid lens through redistributing the liquid using an injection mechanism. In the case of liquid lens systems using conventional injection mechanisms, the nonlinear relationship between the focal length change and the actuator displacement makes it difficult to control the focal length of the lens system, as there is only a narrow control range for adjusting the focal length over a wide range. In addition, miniaturization of the lens system is difficult due to the requirement of bulky and heavy actuators, such as an electrical motor and pump[7]. Thus, a relatively light and small SMA actuator is proposed for a compact lens system. This paper then provides a detailed description of the proposed tunable-focus liquid lens system, and an experimental system is also implemented. Finally, the focusing performance of the proposed liquid lens system is analyzed, and its usefulness and effectiveness verified through a series of experiments.

© 2009 Optical Society of America

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References

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  1. H. Ren and S. T. Wu, "Variable-focus liquid lens," Opt. Express 15, 5931-5936 (2007).
    [CrossRef] [PubMed]
  2. H. Ren, S. T. Wu, "Variable-focus liquid lens by changing aperture," Appl. Phys. Lett. 88, 21107 (2005).
  3. H. Ren, D. Fox, P. Anderson, B. Wu, and S. T. Wu, "Tunable-focus liquid lens controlled using a servo motor," Opt. Express 14, 8031-8036 (2006).
    [CrossRef] [PubMed]
  4. H. Ynag, C. Y. Yang, and M. S. Yeh, "Fabrication of miniature variable-focus using liquid technique," DTIP of Mens and Moems, Streas, Italy, Apr. (2007).
  5. J. M, Choi, H. M. Son, and Y. J. Lee, "Design of biomimetic robot-eye system with single vari-focal lens and winding-type SMA actuator," International Conference on Control, Automation and Systems 2008, 1173-1177, Seoul, Korea, (2008).
  6. S. Kuipper and B. W. Hendriks, "Variable-focus liquid for miniature camera," Appl. Phys. Lett. 85, 1128-1130, Aug. (2004).
    [CrossRef]
  7. G. C. Knollman, J. J, S. Bellind, and J. L. Weaver, "Variable-focus liquid-filled hydroacoustic lens," J. Acous. Am. 49, 253-261, (1970).
    [CrossRef]
  8. D. Reynaerts and H. V. Brussel, "Design aspects of shape memory actuators," Mechatronics, 635-656, (1998).
  9. Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).
  10. H. M. Son, J. B. Gu, T. H. Nam, and Y. J. Lee, "Dynamic gait of a quadruped robot with SMA actuator," SICE-ICASE International Joint Conference 2006, Busan, Korea, Oct. (2006).
    [CrossRef]

2007 (1)

2006 (2)

H. Ren, D. Fox, P. Anderson, B. Wu, and S. T. Wu, "Tunable-focus liquid lens controlled using a servo motor," Opt. Express 14, 8031-8036 (2006).
[CrossRef] [PubMed]

Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).

2005 (1)

H. Ren, S. T. Wu, "Variable-focus liquid lens by changing aperture," Appl. Phys. Lett. 88, 21107 (2005).

1998 (1)

D. Reynaerts and H. V. Brussel, "Design aspects of shape memory actuators," Mechatronics, 635-656, (1998).

1970 (1)

G. C. Knollman, J. J, S. Bellind, and J. L. Weaver, "Variable-focus liquid-filled hydroacoustic lens," J. Acous. Am. 49, 253-261, (1970).
[CrossRef]

Anderson, P.

Brussel, H. V.

D. Reynaerts and H. V. Brussel, "Design aspects of shape memory actuators," Mechatronics, 635-656, (1998).

Fox, D.

Gu, J. G.

Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).

Hendriks, B. W.

S. Kuipper and B. W. Hendriks, "Variable-focus liquid for miniature camera," Appl. Phys. Lett. 85, 1128-1130, Aug. (2004).
[CrossRef]

Knollman, G. C.

G. C. Knollman, J. J, S. Bellind, and J. L. Weaver, "Variable-focus liquid-filled hydroacoustic lens," J. Acous. Am. 49, 253-261, (1970).
[CrossRef]

Kuipper, S.

S. Kuipper and B. W. Hendriks, "Variable-focus liquid for miniature camera," Appl. Phys. Lett. 85, 1128-1130, Aug. (2004).
[CrossRef]

Lee, Y. J.

Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).

Nam, T. H.

Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).

Ren, H.

Reynaerts, D.

D. Reynaerts and H. V. Brussel, "Design aspects of shape memory actuators," Mechatronics, 635-656, (1998).

Son, H. M.

Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).

Wu, B.

Wu, S. T.

Appl. Phys. Lett. (1)

H. Ren, S. T. Wu, "Variable-focus liquid lens by changing aperture," Appl. Phys. Lett. 88, 21107 (2005).

Int. J. Appl. Electromag. Mech. (1)

Y. J. Lee, H. M. Son, J. G. Gu, and T. H. Nam, "Design and control of a multistep SMA actuator," Int. J. Appl. Electromag. Mech. 23, 119-124, (2006).

J. Acous. Am. (1)

G. C. Knollman, J. J, S. Bellind, and J. L. Weaver, "Variable-focus liquid-filled hydroacoustic lens," J. Acous. Am. 49, 253-261, (1970).
[CrossRef]

Mechatronics (1)

D. Reynaerts and H. V. Brussel, "Design aspects of shape memory actuators," Mechatronics, 635-656, (1998).

Opt. Express (2)

Other (4)

H. Ynag, C. Y. Yang, and M. S. Yeh, "Fabrication of miniature variable-focus using liquid technique," DTIP of Mens and Moems, Streas, Italy, Apr. (2007).

J. M, Choi, H. M. Son, and Y. J. Lee, "Design of biomimetic robot-eye system with single vari-focal lens and winding-type SMA actuator," International Conference on Control, Automation and Systems 2008, 1173-1177, Seoul, Korea, (2008).

S. Kuipper and B. W. Hendriks, "Variable-focus liquid for miniature camera," Appl. Phys. Lett. 85, 1128-1130, Aug. (2004).
[CrossRef]

H. M. Son, J. B. Gu, T. H. Nam, and Y. J. Lee, "Dynamic gait of a quadruped robot with SMA actuator," SICE-ICASE International Joint Conference 2006, Busan, Korea, Oct. (2006).
[CrossRef]

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Figures (16)

Fig. 1.
Fig. 1.

Conceptual block diagram of proposed tunable focus lens system: (a) process of focal length tuning and (b) tunable focus lens system.

Fig. 2.
Fig. 2.

Conceptual model of lens system: (a) conceptual drawing of uniconvex lens and (b) variation of radius of curvature according to injected depth of actuator.

Fig. 3.
Fig. 3.

Cylindrical cam structure.

Fig. 4.
Fig. 4.

Components of proposed liquid lens system: (a) Designed using 3-D design tool CATIA and (b) manufactured using RP(rapid prototyping) method.

Fig. 5.
Fig. 5.

Proposed tunable-focus liquid lens system: (a) Assembled system using CATIA and (b) real assembly of liquid lens system.

Fig. 6.
Fig. 6.

Basic driving principle of proposed liquid lens system: (a) injection motion and (b) ejection motion.

Fig. 7.
Fig. 7.

Simulated and measured depth of injection mechanism when varying rotational length displacement.

Fig. 8.
Fig. 8.

Conceptual drawing of antagonistic winding-type SMA actuator.

Fig. 9.
Fig. 9.

Control system boards: (a) DSP(TMS320F2812) and (b) SMA driver board.

Fig. 10.
Fig. 10.

Control block diagram.

Fig. 11.
Fig. 11.

Experimental setup for focal length measurement.

Fig. 12.
Fig. 12.

Experimental setup for focal length measurement based on Korean industrial standards [KS B 5408].

Fig. 13.
Fig. 13.

Simulated and measured focal length.

Fig. 14.
Fig. 14.

Test images: (a) defocused image at arbitrary position (initial f = 55 mm), (b) intermediate state of focused image with f = 51.5 mm, and (c) final focused image with f = 48 mm.

Fig. 15.
Fig. 15.

Multi-objects focusing test: (a) Experimental setup, (b) test image (f = 50.6 mm), and (c) test image (f = 55.1 mm).

Fig. 16.
Fig. 16.

Response time of proposed liquid lens system with SMA actuator.

Tables (1)

Tables Icon

Table 1. Detailed specifications of proposed liquid lens system.

Equations (7)

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V1=πa2H
h=RR2a2
V2=16πh(3a2+h2)
f=Rn1=kL+d,R=(kL+d)(n1)
H=16a2π((kL+d)(n1)((kL+d)(n1))2a2)
(3a2+((kL+d)(n1)((kL+d)(n1))2a2)2)
f=f0y'y

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