Using a CCD camera in determination of the target size in radiation thermometry

The objective of this paper is to present new method for determination of the target size in radiation thermometry using a CCD camera and custom made software. The target size is one of the essential components needed for proper calibration of a radiation thermometer. In practice, most radiation thermometers have a small black ring engraved on the ocular and the interior of the ring defines the target area. The existing method was very subjective. A person determining the target size looked through the radiation thermometer and tried to read from the millimeter grid paper the target size of the thermometer. In our case, three different persons in our laboratory, using this existing method, determined different target sizes. The new method uses a predefined mask of known dimensions, printed on millimeter grid paper and positioned in front of the radiation thermometer and instead of a person looking through the ocular, a CCD camera and the image processing software is used.