Research on measurement of high temperature fields with equal precision for commercial CCD cameras

Abstract

Commercial planar charge-coupled device (CCD) cameras can be used as high-temperature field measuring devices after calibration. Typically, the calibration is only for the central pixel region of the CCD at a fixed distance between a reference source and the camera, so two kinds of additional errors will result in a practical application. One is the result of the deviation of actual working distance from the calibration distance, and the other is the result of the non-uniformity of the CCD flatness response to a uniform temperature field. To quantify these two kinds of errors, a radiation temperature-measurement model for planar CCD cameras was established. Then, based on this model and geometrical optics, the error-correction algorithms were derived. In addition, the degree of influence of object temperature and optical parameters on the errors were discussed in detail. The model and the algorithms were evaluated by means of general CCD cameras, a blackbody furnace, and an integrating sphere experiment. The correction results have shown that the error resulting from the distance factor was decreased from 46.3 to 2.4 K within the range of 0.5–10 m, and the error resulting from the factor of non-uniformity of flatness response was decreased from 24.6 to 3.0 K. Thus, the commercial CCD cameras met the requirement of equal-precision measurement in high-temperature fields.