SPACE QUALIFIED, IMAGE QUALITY ULTRAVIOLET INTERFERENCE FILTERS

PRESENT UV FILTERS CAN HAVE VERY HIGH SPECTRAL PERFORMANCE, BUT THE BEST SPECTRAL PERFORMANCE GENERALLY REQUIRES USE OF MATERIALS AND FILTER CONSTRUCTION WHICH ARE NOT WELL QUALIFIED FOR USE IN SPACE AND HAVE MARGINAL IMAGE QUALITY. THE OBJECTIVE OF THIS EFFORT IS TO IMPROVE THIS SITUATION BYREDUCING TO MINIMUM, THE NUMBER OF SUBSTRATES USED AND TOTALLY ELIMINATING CEMENT AND COLOR GLASSES. IN ORDER TO DO THIS, MORE ROBUST AND SPECTRALLY STABLE FILTER COATINGS MUST BE DEVELOPED WHICH CAN BE EMPLOYED AS OPEN, UNPROTECTEDFILTER ELEMENTS. THE BULK OF THIS WORK WILL INVOLVE DEVELOPING THESE COATING MATERIALS AND DEPOSITION PROCESSES AND TO APPLY THEM TO SPACE QUALIFIED SUBSTRATES. THE PRIMARY DEPOSITION TECHNIQUES WILL BE ION ASSISTED DEPOSITION (IAD) AND REACTIVE SPUTTERING. OXIDE AND NITRIDEMATERIALS WILL BE THE PRIME COATING MATERIAL CANDIDATES, WITH FLUORIDES USED WHERE NECESSARY AT THE SHORTEST WAVELENGTHS. ALUMINUM IS EXPECTED TO BE THE PRIMARY METAL MATERIAL USED. IF INDICATED AT EARLY STAGES OF THE EFFORT, WE WILL REVERT FROM THE IDEAL SINGLE SUBSTRATE TO A DOUBLE (AIR-SPACED), SUBSTRATE APPROACH. BASED ON SIMILAR SUCCESSFUL IR & D WORK ON VISIUAL FILTER COATINGS, IT IS ANTICIPATED THAT THE TECHNIQUE CAN BE EXTENDED TO THE UV WAVELENGTH.