u03b2 2 at the mirror 3 and 2l tan u03b2 2 at the beam director 1 therefore the overall separation d between the two sub beams 14 and 15 becomes 2l tan u03b2 1 tan u03b2 2 for the aforementioned crystals u03b2 1 and u03b2 2 are functions of the wedge angle u03b1 and the incident angle u03b3 ideally u03b2 1 and u03b2 2 are equal i e u03b2 1 u2212 u03b2 2 0 resulting in the sub beams 14 and 15 exiting the beam director 1 exactly parallel however there are other factors that must be balanced including having u03b2 1 u03b2 2 large enough to enable proper beam separation while maintaining u03b2 1 u2212 u03b2 2 small enough to provide adequate parallelism of the sub beams 14 and 15 fig6 a graphically illustrates the relationship between the angle separation u03b2 1 u03b2 2 the incident angle u03b3 and the wedge angle u03b1 for a yvo 4 crystal fig6 b graphically illustrates the relationship between the angle difference u03b2 1 u2212 u03b2 2 the incident angle u03b3 and the wedge angle u03b1 for a yvo 4 crystal from these graphs it is obvious that the larger the wedge angle u03b1 the larger the angle separation u03b2 1 u03b2 2 as an example if we assume that the wedge.