Gentec-EO Diffractive Optics (HBS) - Manual (Page 11)

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HBS Instruction Manual Revision 4.1 Feburary 2014
3 BEAM PROFILING
HBS for Beam Profiling Purposes
In order to use the HBS for imaging a collimated beam, a special procedure is recommended. This setup
is related to the fact that there exists a geometrical narrowing of the diffracted beam when viewed from a
right angle in relation to its propagation direction. The beam will be slightly elliptical (see Fig. 3-1a ).
The following equation should be used to correct the beam profiling:
dm = do cos Erreur ! Signet non défini.
For example, if the second order is used, the diameter measured in the diffractive plan will be
reduced to;
d2 = do x 0.94
To overcome this effect, the camera's (or profiler's) perpendicular axis should be placed (turned) parallel
to the HBS perpendicular axis (Fig. 3-1b).
Another simple method may be used to avoid elliptical narrowing: by turning the HBS 10° from the incident
beam, one of the second orders will be geometrically identical to the incident beam. First orders may still
be used for energy/power monitoring (Fig. 3-1c).
For more details, contact the nearest Gentec-EO inc agent or representative.