In the case of an optical system using a solid lens, mechanical movement is required to vary the focus because it is focused only at a specific distance, and there are physical distance restriction when applied to various application. Liquid lens have the merit of changing the focal length because they can change the shape of the lens freely unlike the solid lens with fixed shape. But commercially available liquid lenses are basically aberrated compared to solid lens. Some attempts have been made to correct the aberration at a specific focal length by making the surface membrane of the liquid lens into a lens shape, but the aberration varies even if the focal length changes slightly. This paper proposes a system that pull the lens surface membrane vertically and horizontally by getting ideas from the lens and ciliary body of the human eye. As the ciliary body of the eye contracts and relaxes to adjust the thickness of the lens, the thickness of the lens surface film can be continuously changed while attracting the lens surface film. This allows control of aberration caused by changes in the focal length of the focus variable lens. In the proposed system, the hydraulic method is used to change the focal length of the lens. The surface of the lens is made of elastic material. Depending on the specific shape, the thickness of the lens surface can be changed and the aberration controlled.
In this paper, we present a nonmechanical three-dimensional beam steering system using electrowetting based liquid lens and liquid prism. The optical design for the radius of curvature of the liquid lens and the tilting angle of the liquid prism was modeled with Zemax and three-dimensional beam steering was simulated. The liquid lens from Corning-Varioptic was used and the focal length of the lens was varied depending on the applied voltage. Cuboid-shaped chamber of the liquid prism was fabricated with glasses and two immiscible liquids whose densities are the same were injected into the fabricated chamber. The apex angle of the liquid prism and beam steering on the x-axis, y-axis, and xy-axis were measured by changing the applied voltages on the four sidewalls of the liquid prism. The light spot passing through the liquid lens and liquid prism was measured and the calculated beam steering angle was 11.6 º to 12.0 º. The effects of gravity on the shape and apex angle of the liquid prism were also measured by rotating the sample. Nonmechanical three-dimensional beam steering control including the z-axis direction was demonstrated by combining the electrowetting based liquid lens and liquid prism.
In this paper, a surface plasmon resonance sensor for the detection of refractive index variation is presented. A novel waveguide type surface plasmon resonance sensing configuration with focal length variable liquid lens is introduced. The method of surface plasmon resonance sensor is based on the waveguide type with incident angle variation. The incident angle is varied by using an electrowetting liquid lens which is possible to actively change focal length as applying voltage. The optical system, which is adapted to electrowetting lens can continuously change the incident angle of light from 73 to 78 degrees with compact size. The surface plasmon waves are excited between metal and dielectric interface. The sensing surfaces are prepared by a coating of gold metal above high refractive index glass substrate. The incident light which is 532nm monochromatic light source passes through a noble metal coated substrate to detect intensity with incident angle variation. An analysis to distinguish the contribution of light with various incident angle is focused on the angular characteristics of the surface plasmon sensor under wavelength interrogation. The resonance angle is determined corresponding to sensing material refractive index with high sensitivity. The result suggests that the performance of surface plasmon resonance sensor can be improved by real time varying incident angle. From this presented study, it provides a different approach for angular interrogation surface plasmon resonance sensor and can be miniaturized for a portable device.
Surface plasmon resonant (SPR) phenomenon is widely researched for various purposes, among which biomedical sensing is getting more attentions as they are suitable for surface functionalization acting as a bio recognition element to detect different biological infections. The common method of surface resonant is propagating SPR such as reflection method. Another method which is widely used for SPR is localized SPR which use nanostructures in thin metal. Various structures such as slit only, slit- groove and slit-multiple groove are used for generation of SPR and obtaining the optimum optical transmittance through the structure. The number and position of slits and grooves affect transmittance through the structure. In this paper we propose a new structure of cross slit-grooves structure, which includes slit-groove structure in grid form. The slit-grooves structures are arranged in such a way that it forms symmetrical structure in two dimension with slit and groove and hence the transmittance with cross slit-grooves structure increases significantly. The cross slit-grooves structure takes the advantage of symmetrical slit and groove by using both dimensional structures for generating SPR which increases the transmittance through the structure. A comparison of proposed slit-grooves grid structure with straight slit-grooves structure is carried out to show the increase in transmittance through the cross slit-grooves grid structure. Plane wavelength of 400 nm to 900 nm is used for the analysis of transmittance through the Ag slit-grooves grid structures with glass substrate. We also measure the change in transmittance with change in refractive index, which can be helpful for measuring different chemical analytes, and hence can be used for different chemical and biosensors applications.
Conventionally, poly (dimethylsiloxane) lens array is fabricated by replica molding. In this paper, we describe simple method for fabricating lens array with expanding property of PDMS. The PDMS substrate is prepared by spin coating on cleaned glass. After spin coating PDMS, substrate is treated with O2 plasma to promote adhesion between PDMS substrate and photoresist pattern on it. Positive photoresist az-4330 and AZ 430K developer is used for patterning on PDMS. General photolithography process is used to patterning. Then patterned PDMS substrate is dipped to 1- Bromododecane bath. During this process, patterned photoresist work as a barrier and prevent blocked PDMS substrate from reaction with 1-Bromododecane. Unblocked part of PDMS directly react with 1-Bromododecane and results in expanded PDMS volume. The expansion of PDMS is depends on absorbed 1-Bromododecane volume, dipping time and ratio of block to open area. The focal length of lens array is controlled by those PDMS expansion factors. Scale of patterned photoresist determine a diameter of each lens. The expansion occurs symmetrically at center of unblocked PDMS and 1-Bromododecane interface. As a result, the PDMS lens array is achieved by this process.
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