BOTH GROUND AND SPACE TELESCOPES EMPLOY ASPHERIC MIRRORS. A PARTICULAR EXAMPLE IS THE X-RAY TELESCOPE WHERE…

Public award description

BOTH GROUND AND SPACE TELESCOPES EMPLOY ASPHERIC MIRRORS. A PARTICULAR EXAMPLE IS THE X-RAY TELESCOPE WHERE PRIMARY AND SECONDARY MIRRORS HAVE NEARLY CYLINDRICAL SURFACES. COMPUTER GENERATED HOLOGRAMS (CGH), IN COMBINATION WITH COMMERCIAL INTERFEROMETERS, PROVIDE HIGH RESOLUTION AND HIGH ACCURACY MEASUREMENTS OF ASPHERIC OPTICAL SURFACES. THE CURRENT STATE OF THE ART CGHS ARE MADE ON 6" SQUARE SUBSTRATES SUCH AS THOSE FOR TESTING THE PRIMARY SEGMENTS OF JAMES WEBB SPACE TELESCOPE. HOWEVER, LARGER CGHS ARE ALWAYS DESIRED. A LARGER CGH ENABLES TESTING OF CORRESPONDINGLY LARGER CONVEX AND NEARLY CYLINDRICAL CONCAVE SURFACES IN ONE SHOT; STUDIES HAVE SHOWN THAT LARGER CGHS ALSO OFFER BETTER IMAGING OF THE SURFACE UNDER TEST, WHICH IMPROVES THE CGH NULL TEST SYSTEM'S INSTRUMENT TRANSFER FUNCTION, AN EQUIVALENT METRIC TO AN IMAGING SYSTEM'S MODULATION TRANSFER FUNCTION. FURTHERMORE, PURSUIT OF IMPROVING CGH TEST ACCURACY NEVER ENDS. THE FUNDAMENTAL LIMITING FACTOR IS QUALITY OF THE SUBSTRATE. THE CURRENT STATE OF THE ART TECHNOLOGY IS STILL UNABLE TO FABRICATE GENERAL CGHS OF ARBITRARY SYMMETRY ON HIGH QUALITY CUSTOM SUBSTRATES.