5. Heat-shielding light filters
Heat protection filters transmit light in the visible spectrum and partially reflect infrared radiation.
These filters protect the objective lens and condenser from thermal shock.
Types of produced heat-shielding light filters and their characteristics
The T720-B light filter has a substrate (base) made of German borosilicate glass SCHOTT BOROFLOAT®33, withstands temperatures of 350 ° C and is used for lamps with a power of up to 400 W.
The more temperature stable T720-Q light filter possesses a quartz substrate and operates at temperatures up to 400-500° C.
The T720-GB heat protection filter has an extended stop zone and blocks 90% of the radiation from a source with a color temperature of Tcolor = 3200° K in the range of 400-4000 nm.
Fig. 1. Spectral transmission of thermal filter T720-Q
Fig. 2. The transmission spectrum of the heat-protective light filter at an angle of 0° to the normal. In the range from 300 to 1600 nm, the measurement was performed on a Shimadzu UV-VIS-NIR Spectrophotometer UV-3600, in the range from 1700 to 4000 made with an MDR-23 monochromator
Figure: 3. External view of the heat-protective light filter with an extended stop zone