Geometric calibration of focused light field camera for 3-D flame temperature measurement

Abstract

Abstract-Focused light field camera can be used to measure three-dimensional (3-D) temperature field of a flame because of its ability to record intensity and direction information of each ray from flame simultaneously. This work aims to develop a suitable geometric calibration method of focused light field camera for 3-D flame temperature measurement. A modified method based on Zhang's camera calibration is developed to calibrate the camera and the measurement system. A single focused light-field camera is used to capture images of bespoke calibration board instead of flame images in this study. Geometric parameters including intrinsic (i.e., camera parameters) and extrinsic (i.e., camera connecting with the calibration board) of the focused light field camera are calibrated to trace the ray projecting onto each pixel on CCD (chargecoupled device) sensor. Instead of using line features, corner point features are directly utilized for the calibration. The characteristics of focused light field camera including one 3-D point corresponding to several image points and matching main lens and microlens f-numbers, are used for calibration. Results with a focused light field camera are presented and discussed. Preliminary the 3-D temperature distribution of a flame is also investigated and presented.

Blur Aware Calibration of Multi-Focus Plenoptic Camera

“…To overcome this problem, several calibration methods [35,34,29,20,3,21,31] have been proposed using only raw plenoptic images. In particular, features extraction in raw micro-images has been studied in [3,21,20] achieving improved performance through automation and accurate identification of feature correspondences.…”

A novel calibration method of focused light field camera for 3-D reconstruction of flame temperature

“…It is therefore difficult to extract precise locations of the corner points from raw images captured by the lytro light field camera. To capture the positional information of the light field more densely, the microlenses are focused on the image produced by the main lens in the focused light field camera [34][35][36][37]. In the focused light field camera the corner points are imaged on virtual image plane by main lens and then re-imaged on the CCD sensor by the microlenses.…”

“…However, the relationship between the virtual image points and their projections for microlenses is not included in their calibration model. The preliminary geometric calibration of the focused light field camera using raw light field images was presented in [37]. But the method was performed very poor and the high reprojection errors was found up to 1.8%.…”