Abstract
In this article, we propose a time-sequential switching light-field (LF) camera for an alternative image capture of the high-resolution two-dimensional (2-D) images and three-dimensional (3-D) LF elemental images as additional functionalities. For image data acquisitions of both the 2-D and 3-D LF imaging of moving objects at a video frame rate (or even higher frame rate up to approximately 1000 f/s), a polarization-dependent-switching microlens array (MLA) is implemented in the LF camera system instead of a conventional passive-type MLA. By controlling the incident polarization conditions using an electrically fast-switching liquid crystal layer, the imaging mode can be time-sequentially switched quite rapidly (switching times of approximately 220 and 290 μ s for the mode conversions from the 3-D LF to the 2-D mode, and the reversal mode change, respectively). Using the elemental image sets sampled from the alternating time-sequential imaging results, either the directional-view images or depth-refocused images can be reconstructed and provided at a moving picture frame rate. The depth-refocused images are possible for a wide depth range from 25 to 350 cm. Directional views of 22 × 22 and 9 × 9 in portions can be reconstructed for the single-shot image capture and the time-sequential video-rate image capture, respectively.
Highlights
L IGHT-FIELD (LF) imaging techniques acquire positional ray information from object points on directional vectors, as well as intensities utilizing periodic ray sampling, usually by the introduction of a microlens array (MLA) [1]–[5]
The 3-D LF imaging method based on the single image sensor and the singlelens unit does not lead the device or image calibration issues that originate from imaging discrepancies of imaging properties acquired at different imaging units in multiple-camera-based imaging systems and undesired packaging variation under gap conditions between each imaging module [37], [38]
In this LF imaging system, the reconstructable depth range can be extended by the DOF of the MLA, which can be increased according to the condition of separation distance between the intermediate image plane and the MLA [39], [40]
Summary
L IGHT-FIELD (LF) imaging techniques acquire positional ray information from object points on directional vectors, as well as intensities utilizing periodic ray sampling, usually by the introduction of a microlens array (MLA) [1]–[5]. We present an LF camera system which can provide both fast switching time-sequential image capture of the high-resolution 2-D images and functional 3-D LF imaging. An extremely fast-switching dynamic exists between the defocused state and the periodic ray-sampling of the focused state of the liquid crystalline reactive mesogen (RM) based MLA operated by control of an incident polarization state This rapid switching property enables the 2-D imaging and 3-D imaging used for the LF image reconstruction to be acquired time sequentially at a frame rate greater than the moving picture frame. SCHEMATICS AND OPERATIONAL PRINCIPLE OF TIME-SEQUENTIAL 2-D AND 3-D IMAGE SAMPLING LF
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