Adjustable hybrid diffractive/refractive achromatic lens.
Bottom Line: Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position.Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at selected focal lengths.Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats.
Affiliation: College of Optical Sciences, University of Arizona Tucson, Arizona 85721, USA. email@example.comShow MeSH
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Mentions: It is non-trivial to place the proper fluid into the chamber when compensating for the diffractive lens. Identifying the proper fluid came from a four step process. Firstly, one must identify the membrane’s radius of curvature range. This allows for one to physically characterize the limitations of the fluidic lens. Also, by identifying the radius of curvature with a known fluid, it is possible to quantify the focal length range of any fluid by knowing the new fluid’s index of refraction. Once one knows the achievable radii of curvature and focal lengths of the fluidic lens, it is necessary to specify the focal lengths needed to compensate for the diffractive lens. For our experimental setup, we have already specified the Abbe number of the diffractive lenses and also the focal lengths achievable by our diffractive lenses. Table 1 took these values into consideration and found the focal length solutions of fluids at a wide scope of Abbe values. Therefore, we match the physical focal length range of the fluidic lens to a reasonable Abbe number so that a high percentage of achromatic doublets are achievable. The final step is to identify a fluid with the proper index of refraction and Abbe number as was previously assessed. It is also important that the fluid found is non-reactive or absorptive with the membrane that one is applying. Through this approach we satisfy the achromat equation: f1 V1 + f2 V2 = 0, where V is the Abbe number. De-ionized (DI) water was first used to characterize the fluidic lens’ radius of curvature range. DI water has an Abbe number of 55.74 and the indices of refraction are known for a wide scope of wavelength ranges . The focal lengths of the DI water fluidic lens were first measured using red (HeNe 633 nm), green (HeNe 543 nm), and blue (Argon 488 nm) lasers with the previously described pump controls. All three laser beams were aligned to the optical axis. The combination of the lasers allows to either individually test the lenses with specific wavelengths or to concurrently test multiple wavelengths as shown in Fig. 2Fig. 2
Affiliation: College of Optical Sciences, University of Arizona Tucson, Arizona 85721, USA. firstname.lastname@example.org