Testowe promienniki podczerwieni

Jednym z najważniejszych parametrów oceny jakości kamery termowizyjnej jest jej rozdzielczość temperaturowa. Do jej oceny wymagane są kosztowne wzorce kontrastu. W pracy omówiono zasadę działania oraz praktyczną możliwość wytworzenia wzorcowego kontrastu termicznego za pomocą promiennika monolitycznego. Różnicę kontrastu termicznego uzyskano poprzez wytworzenie struktury mikrownęk na jego powierzchni. Zmiana wartości kontrastu uzyskiwana jest poprzez dobór odpowiedniej temperatury takiego promiennika.

Comparative evaluation of the thermal resolution of infrared cameras can be performed by simultaneous observation of a precisely defined temperature difference (two standard blackbodies, each at different temperature) or thermal contrast obtained by any different method [1]. The standard testing procedure involves usually application of an expensive, precise blackbody and four-bar tests (Fig. 1) [2]. The paper deals with the possibility of obtaining the standard thermal contrast using a single monolithic IR emitter, by creating microcavity pattern on its surface. (Fig. 20 [8]. The results of numerical simulation of such an IR emitter are presented as a set of characteristics, expressing the relation between the effective emissivity and the shape coefficient (Fig. 4). The idea of creating the thermal contrast is discussed in Section 4. The possibility of achieving the thermal contrast desired value is shown on the thermal image of the proposed type of emitter (Fig. 6). The profile of the apparent temperature across the surface is shown in Fig. 7 (the emitter temperature T=75°C). On the basis of thermographic measurements the relation between effective thermal contrast and the emitter temperature was determined (Fig. 9). By choosing the emitter sectors of small differences in emissivity it is possible to observe and evaluate the response of the tested infrared device to the very subtle changes of thermal contrast. The change in thermal contrast between the adjacent sectors is achieved by proper selection of the emitter temperature.