The measurements of the diameter of the field of view circle of the pyrometer, carried out using a slit diaphragm method.

The main optical characteristic of pyrometers is the dependence of the diameter of the circle of the pyrometer’s field of view on the distance between the pyrometer and the object being measured. This dependence is not possible to be calculated strictly currently, so it has to be measured experimentally. The diameter of the field of view circle can be determined using circular (iris) and slit diaphragm methods. In the first method, the results of measurements of the diameter of a variable iris diaphragm, fitted near the emitter outlet, are used, and in the second method the results of measurements of the width of a slit diaphragm, also fitted near the emitter outlet and moved in a plane which is perpendicular to the optical axis of the pyrometer, are used. The results obtained using these two methods somewhat differ from each other because of difference of areas of the iris diaphragm and in the surface cut by the slit diaphragm, the width of the slit being equal to the diameter of the iris diaphragm. The relationship has been established linking the results obtained by the mentioned methods of a circular diaphragm and a slit diaphragm. This enables to correctly measure the diameter of the field of view circle using the slit diaphragm method, which is faster and less labor-intensive than the iris diaphragm method. The obtained results are relevant for contactless temperature measurements performed in technological processes as well as in research and development work.