Rectification of Images Distorted by Microlens Array Errors in Plenoptic Cameras

Abstract

A plenoptic cameras is a sensor that records the 4D light-field distribution of target scenes. The surface errors of a microlens array (MLA) can cause the degradation and distortion of the raw image captured by a plenoptic camera, resulting in the confusion or loss of light-field information. To address this issue, we propose a method for the local rectification of distorted images using white light-field images. The method consists of microlens center calibration, geometric rectification, and grayscale rectification. The scope of its application to different sized errors and the rectification accuracy of three basic surface errors, including the overall accuracy and the local accuracy, are analyzed through simulation of imaging experiments. The rectified images have a significant improvement in quality, demonstrating the provision of precise light-field data for reconstruction of real objects.

High-Accuracy Correction of a Microlens Array for Plenoptic Imaging Sensors

“…In order to test the effectiveness and feasibility of the improved method proposed in this paper, we employed it to correct the microlens form errors for a direct comparison with the previous method [29]. Distorted white raw images were captured using the simulation imaging system, for which a form error model was set up.…”

“…In the ideal case, the origin o st coincides with the origin O , that is, the origin o st is at (0,0,0)T with the s -and t -axes are parallel to the X -and Y -axes and the x -and y -axes, respectively. For a planar MLA arranged in a matrix-form [29], which consists of N W × N H microlenses in a square arrangement, the length and center pitch of the microlenses are both p , the two sides of the microlenses are spherical surfaces with radius-of-curvature r , the microlens height is h , and the optical axes of the microlenses are parallel to Z -axis. The orientation of an arbitrary microlens U i,j in o st - st coordinates can be represented by its center point as (sci,tcj)T=(s0+(i−1/2)p,t0−(j−1/2)p)T, where i and j denote the microlens in the i -th row and the j -th column of the MLA, i=1,2,⋯,NH and j=1,2,⋯,NW, and false(s0,t0false)T=(−NWp/2,NHp/2)T...…”

“…In the previous work [29], a method was proposed for rectifying the image distortions caused by MLA form errors. However, it yields an undesirable effect due to insufficient precision when determining the center locations and the pixel shift of microlens subimages.…”

Depth-of-Field-Extended Plenoptic Camera Based on Tunable Multi-Focus Liquid-Crystal Microlens Array

“…Compared to the standard plenoptic camera, the focused plenoptic camera can achieve a much higher spatial resolution of the rendered images but still with a limited depth of field (DOF). Nowadays, there are three kinds of plenoptic cameras that attract a wide range of research interest: A plenoptic camera based on a microlens array (MLA) [1][2][3][4][11][12][13], a plenoptic camera based on a camera array [14], and a plenoptic camera based on a coded mask [15]. Specifically, among the three main designs, the plenoptic camera based on the MLA has a very promising development prospect due to its small size, low cost, and light-field acquisition in a single photographic exposure.…”

Resolution Improvement of Light Field Imaging via a Nematic Liquid Crystal Microlens with Added Multi-Walled Carbon Nanotubes

“…And it can effectively solve several serious issues of the conventional imaging systems, such as defocus of scene and depth loss of target object [ 2 , 3 , 4 ]. Then, it has great potential for adverse condition imaging, depth estimation, target focusing, and foreground removal [ 5 , 6 , 7 , 8 ]. In light field imaging, the extraction of view angle image is the foundation [ 9 ].…”