http://www.photon-inc.com/support/library/pdf/nanoscan_reliability.pdf - Photon Inc - #1

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PHOTO M me 6878 Santa leresa Blvd. ban (ose, CA 95119-120:* Précision Bearn Profiling ICI: 408.226-I0O0 Fax; 408.226,1025 vvww.p ho Ion - i ne com Technical Note NanoScan and Cohérent Light When profiling a cohérent laser beam with a NanoScan with non-blackened, reflective apertures (slit or pinhole), il is possible that interférence may be observed ou the beani trace, (see Figure lb). Figure la Idéal Trace Figure 1b Typical Ripple Pattern Figure 3 Note that the lens has been displaced from the center with reflections never crossing each other. (This is a practical solution sometinics, but uot always.) The reflection can be directed out of the system by scanning the image at a slight angle (see Figure 4). One must then correct the measured beam size by multiplying the measured beam size by the cosine of the angle of tilt. If the tilt is 10°, cos 10°=0.985 actual beam size. The interférence is due to back reflections from the slit/pinhole. Hven a blackened slit/pinhole can cause tins efTect, because the air slit/pinhole edges appear as a point source Figure 2 illustrâtes the setup. Scan image at angle [see (ex: i Laser Lasor Figure 2 Slit surfaces and slit edge (5) reflects light that interfères with reflections from surfaces (2), (3), and (4). When the slit is in the exact focal plane and perfectly aligned, the configuration is like an interferoineter. The interférence can be reduced or eliminated as shown in Figure 3, Figure 4 Photon Inc. Tel; 408.226.1000 Fax: 408.226.1026 Email; beam<gphoton-in.com www.photon-lncxom NénoScàtt and Cohérent Ught B010206399