Calibration of Imaging Sensor and Fiber Optic Taper-Caused Distortion in an X-Ray Intensified CMOS Camera

Haoting Liu,Ming Yan,Shaohua Yang,Chang Guo,Jiacheng Li,Jinhui Lan

doi:10.1109/access.2019.2960259

Abstract

An integrated calibration method of the imaging sensor and the fiber optic taper-caused distortion in an intensified Complementary Metal-Oxide-Semiconductor (CMOS) camera for the X-ray capture application is proposed. Generally, four kinds of distortions need to be corrected in this system: the column noise, the inconsistent pixel intensity response of whole frame, the nonlinear intensity response of each pixel, and the geometry distortion of whole frame. To conquer these problems, first, the column noise is estimated and subtracted from the captured image. The multiple measurement data processing method and the strip noise estimation technique are used. Second, a kind of two-step correction technique of the pixel intensity response is proposed to solve middle two distortion problems. The first step builds the ideal intensity response line for all pixels in image; and the second step estimates and compensates the correction error for each pixel by a polynomial function. Third a polynomial fitting method is also utilized to correct the geometry distortion. The RANdom SAmple Consensus (RANSC) computation mechanism is used to improve the calibration precision further. The optic indices of fiber optic taper and camera are considered to assist the selection of key parameters of these calibration method above. Many experiment results have proved the correctness and effectiveness of proposed method.

Highlights

The X-ray imaging detection system has been widely used in the fields of medical diagnosis [1], industrial inspection [2], or nuclear security surveillance [3], etc
After a preliminary test it can be found the main error source comes from the Complementary Metal–Oxide– Semiconductor (CMOS) sensor and the fiber optic taper; the corresponding calibration methods should be developed
An integrated calibration of the imaging sensor and the fiber optic taper-caused distortion in an X-ray intensified CMOS camera is proposed in this paper

Summary

INTRODUCTION

The X-ray imaging detection system has been widely used in the fields of medical diagnosis [1], industrial inspection [2], or nuclear security surveillance [3], etc. H. Liu et al.: Calibration of Imaging Sensor and Fiber Optic Taper-Caused Distortion. After a preliminary test it can be found the main error source comes from the CMOS sensor and the fiber optic taper; the corresponding calibration methods should be developed. An integrated calibration of the imaging sensor and the fiber optic taper-caused distortion in an X-ray intensified CMOS camera is proposed in this paper. In many cases the camera user hopes the response of pixel intensity should be linear to the input illuminance some measurement tasks in scientific degree can be made. Images (d) and (e) are the example and the sketch map of geometry distortion: the shape change issue can be observed This distortion mainly comes from the quality problem of fiber optic taper

CALIBRATION EVALUATION NEEDS and CRITERIA

GEOMETRY DISTORTION CORRECTION

ALGORITHM PERFORMANCE IMPROVEMENT USING RANSAC

CONCLUSION