optical interference filters - SPOT Imaging Solutions

exposure to light, particularly short UV wavelengths, results in solarization
and reduced transmission.
Figure 7 Angle of Incidence Polarization Effects – Bandpass Filters
within the cone. At system speeds of f/2.5 and slower (full cone
angle of 23° or less), the shift in peak wavelength can be approximately
predicted from the filter’s performance in collimated light
(i.e., the peak wavelength shifts about one-half the value that it
would shift in collimated light at the cone’s most off-axis angle).
Temperature Effects the performance of an interference
filter. Wavelength will shift with temperature changes due
to the expansion and contraction of the coating materials.
Unless otherwise specified, filters are designed for an operating
temperature of 20°C. They will withstand repeated thermal cycling
assuming temperature transitions are less than 5°C per minute.
An operating temperature range between -60°C and +60°C is
recommended. For the refractory oxides temperature ranges from
-60°C to 120°C. Filters must be specifically designed for use at
temperatures above 120°C or below -100°C. Although the shift is
dependent upon the design of the coating, coefficients in Figure 8
provide a good approximation.
For applications where the change in performance divided by the
change in temperature is to be minimized, the densified refractory
oxide materials are preferred. Consideration must be given to
maximize temperature as refractory oxides, even when densified
through energetic process, will experience a one-time shift in optical
thickness. The magnitude of this is