使用LCD螢幕進行偏振相機的校準

Abstract

準確校準偏振相機的偏振器角度和相機響應函數 (CRF) 對於偏振成像至關重要。 當將此偏振相機用於多視圖幾何成像時，通常也需要校准其內部和外部參數。張氏校準方法是最廣泛用於校準相機內外部參數的方法，使用一個物理棋盤格或者是螢幕上顯示的虛擬棋盤格即可完成校準。在本文中，我們提出使用在LCD螢幕上顯示的略微改進的虛擬棋盤格來同時校準偏振器角度和相機響應反函數 (ICRF)。得益於LCD螢幕的照明原理和行業標準，在根據棋盤格估計的外部參數的輔助下，此方法大大簡化了偏振器角度和相機響應函數的校準。我們的方法包含一個用於偏振器角度校準的簡單線性方法和一個用於相機響應函數校準的凸方法，這兩種方法可以在類似於bundle adjustment的過程中共同完善。通過實驗，我們驗證了所提出的校準方法的可行性和準確性。

It is crucial for polarimetric imaging to accurately calibrate the polarizer angles and the camera response function (CRF) of a polarizing camera. When this polarizing camera is used in a setting of multiview geometric imaging, it is often required to calibrate its intrinsic and extrinsic parameters as well, for which Zhang's calibration method is the most widely used with either a physical checker board, or more conveniently a virtual checker pattern displayed on a monitor. In this paper, we propose to jointly calibrate the polarizer angles and the inverse CRF (ICRF) using a slightly adapted checker pattern displayed on a liquid crystal display (LCD) monitor. Thanks to the lighting principles and the industry standards of the LCD monitors, the polarimetric and radiometric calibration can be significantly simplified, when assisted by the extrinsic parameters estimated from the checker pattern. We present a simple linear method for polarizer angle calibration and a convex method for radiometric calibration, both of which can be jointly refined in a process similar to bundle adjustment. Experiments have verified the feasibility and accuracy of the proposed calibration method.