Abstract
Plenoptic cameras have received a wide range of research interest because it can record the 4D plenoptic function or radiance including the radiation power and ray direction. One of its important applications is digital refocusing, which can obtain 2D images focused at different depths. To achieve digital refocusing in a wide range, a large depth of field (DOF) is needed, but there are fundamental optical limitations to this. In this paper, we proposed a plenoptic camera with an extended DOF by integrating a main lens, a tunable multi-focus liquid-crystal microlens array (TMF-LCMLA), and a complementary metal oxide semiconductor (CMOS) sensor together. The TMF-LCMLA was fabricated by traditional photolithography and standard microelectronic techniques, and its optical characteristics including interference patterns, focal lengths, and point spread functions (PSFs) were experimentally analyzed. Experiments demonstrated that the proposed plenoptic camera has a wider range of digital refocusing compared to the plenoptic camera based on a conventional liquid-crystal microlens array (LCMLA) with only one corresponding focal length at a certain voltage, which is equivalent to the extension of DOF. In addition, it also has a 2D/3D switchable function, which is not available with conventional plenoptic cameras.
Highlights
Conventional cameras only record 2D light intensity information, not most of the information about the light distribution
We demonstrate a plenoptic camera based on the tunable multi-focus (TMF)-liquid-crystal microlens array (LCMLA)
Experiments demonstrated that the proposed plenoptic camera can acquire a much wider range of digital refocusing compared to the plenoptic camera based on a conventional LCMLA with only one corresponding focal length at a certain voltage, which is equivalent to the extension of depth of field (DOF)
Summary
Conventional cameras only record 2D light intensity information, not most of the information about the light distribution. In LCMLA-based applications, DOF extension can be acquired via patterned electrodes of multi-regions and multi-apertures [21,40]; the former obtains multi-focus function by applying different voltages at different regions, while the latter utilizes interleaved apertures to obtain multi-focus function of the entire region with only one voltage Both electrode designs provide effective approaches to further extend the range of digital refocusing, i.e., the DOF of plenoptic cameras. Experiments demonstrated that the proposed plenoptic camera can acquire a much wider range of digital refocusing compared to the plenoptic camera based on a conventional LCMLA with only one corresponding focal length at a certain voltage, which is equivalent to the extension of DOF. It has 2D/3D switchable functionality, which is not available with conventional plenoptic cameras
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