The MY34 has a spectral range of 3.43 µm. It was developed especially to take advantage of unusual absorption or transmission features of certain materials.
Among other reasons, standard quartz glasses also differ in their transmission properties within the short-wave infrared area. Some types of glass are available with high enough transmission at 3.43 µm to perform measurements but others are low enough to protect from unwanted radiation originating from warm sources. In semiconductor production one can find a wide application range for the Metis MY34 product line.
To measure temperatures on thin plastic foils using a characteristic CH absorption range, e.g., polybutylene, polystyrene, polyurethane, vinyl and nylon, this series can be delivered with a lower temperature range starting from 100°C as well, should this be required by the customer.
The infrared energy radiated by the target is centered via focusable or fixed focus lenses directly on the detector. The focusing feature allows control of the cone of vision and offers the possibility to measure either a small spot (focused) or the average of a bigger spot (out of focus). Fixed focus lenses with larger diameter collect more infrared energy and therefore result in smaller spot sizes. The lenses are made of calcium fluoride CaF2 which is highly transparent in visible and infrared regions up to 10 µm. If additional windows are necessary they must offer similar optical characteristics.
The detector is sensitive to infrared radiation in an area called the cone of vision. For the spot size diameter Ø of the cone of vision at shortest, medium and widest focal distances, please see Chart 2. For full scale temperatures up to 1300°C the cone of vision diameter in front of the lens is about 16 mm and about 9 mm for full scale temperatures above. This area has to be kept free from any intervening objects. The spot size diameter for distances not given in the chart can be calculated by interpolation.