Abstract
We present an electrically controllable fast-switching virtual-moving microlens array (MLA) consisting of a stacked structure of two polarization-dependent microlens arrays (PDMLAs) with optical orthogonality, where the position of the two stacked PDMLAs is shifted by half the elemental pitch in the diagonal direction. By controlling the polarization of the incident light without the physical movement of the molecules comprising the virtual-moving MLA, the periodic sampling position of the MLA can be switched fast using a polarization-switching layer based on a fast-switching liquid crystal cell. Using the fast-switching virtual-moving MLA, the spatial-resolution-enhanced light-field (LF) imaging system was demonstrated without a decrease in the angular sampling resolution as compared to the conventional LF imaging system comprising a passive MLA; two sets of elemental image arrays were captured quickly owing to the short switching time of the virtual-moving MLA of 450 μs. From the two captured sets of the elemental array image, four-times resolution-enhanced reconstruction images of the directional-view and depth-slice images could be obtained.
Highlights
Each polarization-dependent microlens arrays (MLAs) (PDMLAs) consists of a birefringent liquid crystalline polymer (LCP) layer having a planar-convex lens shape and an isotropic polymer layer having a concave-planar shape, wherein the ordinary refractive index of the LCP layer is the same as the refractive index of the isotropic polymer layer, and the extra-ordinary refractive index of the LCP layer is larger than np
The point indicated by the green triangle can be recoded with an increased spatial resolution. In this case, the amount of information for the angular ray distribution is decreased by half that shown in Fig. 5a owing to the limited ray sampling rate of the MLA in the LF imaging system
We demonstrated a resolution-enhanced LF imaging system by introducing an electrically controllable fast-switching virtual-moving MLA
Summary
While the points indicated by the blue circle and red square are recoded with the angular distribution of the rays, the rays from the green triangle are not recoded as the sampling interval of the LF imaging system is limited by the pitch of the elemental lens. The point indicated by the green triangle can be recoded with an increased spatial resolution In this case, the amount of information for the angular ray distribution is decreased by half that shown in Fig. 5a owing to the limited ray sampling rate of the MLA in the LF imaging system. On assuming the distance between the observation point and main lens to be approximately 2 m, the sampling interval of the LF imaging system using the single PDMLA is 71.4 μm (=100 μm/1.4), whereas, using the virtual-moving MLA, it can be improved to be 35.7 μm (=100 μm/1.4/2). The details of the optical set-up showing the LF imaging system using the virtual-moving MLA are represented in Fig. S2 (See Supplementary Section 2)
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