A Method for Removing the Effect of the Camera Radiance on the Infrared Image
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A Method for Removing the Effect of the Camera Radiance on the Infrared Image Shidu Dong & Xiaofan Yang & Wu Yang & He Yan & Yue Wang
Received: 10 August 2007 / Accepted: 25 February 2008 / Published online: 15 March 2008 # Springer Science + Business Media, LLC 2008
Abstract The radiance coming from the interior of an uncooled infrared camera has significant effect on the quality of an infrared image. The classical two-point-correction (TPC) method fails to remove this effect where no TPC data is collected. To overcome this deficit, this paper presents a three-phase scheme. First, from a set of samples and through least squares fitting, how the TPC datum varies with the interior temperature of the camera is determined. On this basis, all the necessary TPC data are calculated. Finally, the collected infrared image is corrected with the TPC method. Theoretical analysis and experimental results show that, for a proper interior temperature of the camera, the scheme can remove the effect effectively. Keywords Infrared image . Camera radiance . Two-point-correction . Least squares fitting
1 Introduction Apart from the radiance coming from the object being focused, the pixels on the focal plane array (FPA) in a camera also receive the unfocused flux from the interior of the camera (camera radiance for short), which has significant effect on the quality of infrared image [1–3]. In addition, the camera radiance varies with the interior temperature of the camera (camera temperature), resulting from the change of the ambient temperature. Where the infrared images of the appointed high-temperature and low-temperature blackbodies (twopoint-correction data or TPC data) can be acquired, the classical TPC method can effectively remove the effects of both the non-uniformity of the FPA and the camera radiance on the infrared image. Unfortunately, this method fails when the TPC data are unavailable. S. Dong (*) : X. Yang College of Computer Science, Chongqing University, Chongqing 400044, China e-mail: [email protected] S. Dong : W. Yang : H. Yan : Y. Wang Computer School, Chongqing Institute of Technology, Chongqing 400050, China
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Int J Infrared Milli Waves (2008) 29:499–507
Fig. 1 Illustration of an Infrared FPA camera.
To overcome the above mentioned deficit of the TPC method, this paper proposes a novel three-phase method, which is outlined below. First, from a set of samples and through least squares fitting, how each pixel value in the TPC data (TPC datum) varies with the camera temperature is determined. On this basis, all the necessary TPC data are calculated. Finally, the collected infrared image is corrected with the TPC method, and as a result, the effect is removed. The paper is organized as follows: Section 2 provides the background knowledge and Section 3 indicates a shortcoming of the two-point-correction method. A new method for removing the effect of the camera radiance is proposed in Section 4. Experimental results are given in Section 5 and some conclusions are drawn in Section 6.
2 Background knowl
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