Next: 2.3.3 Partial Coherence and
Up: 2.3 Illuminator
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As shown in Figure 2.4 the condenser lens is set up in a way that
the position of the light source coincides with its focal plane.
Such a configuration is called Köhler
illumination [11, pp. 524-526]
and has the important property that an ideal point source contributes a plane
wave disturbance on the mask side of the condenser lens. The entire
photomask is thus uniformly illuminated. Any deviation from
the plane wave shape causes phase errors in image composition and
strongly degenerates imaging quality.
2.3.2 Condenser Lens
Heinrich Kirchauer, Institute for Microelectronics, TU Vienna