correct. Brown and Lohmann proposed turning the hologram at an angle

to the incoming waveform. Thus, along the surface of the hologram, a

phase shift occurs. This phase shift is proportional to the position

along the hologram. Using this "tilted wave" technique, a phase shift

occurs as the aperture moves up and down the hologram causing the

total path length through that aperture to change.i The further the

detour through the aperture, the larger the phase shift. Phase shift

induced by this technique is known as detour phase. Thus, in the

Brown-Lohmann hologram, an aperture is moved up and down to create the

appropriate phase shift. The size of the aperture is varied to allow

the appropriate amount of light through. To synthesize the complex

filter function F(u,v), a continuous function is sampled. The cells

of a sizeA u by Av must be sufficiently small that the function F

will be effectively constant throughout the cell.


 F(u,v) = F(nAu,mAv) = Fnm =Anmexp ienm (3.6)


 where n and m are integers


For each cell in the hologram, the amplitude and phase are determined

by the size and position of an aperture as shown in Figure 3.1. From

each cell a complex light amplitude Fnm will emerge. The tilted wave

must approach at an angle steep enough to allow for a full wavelength

of detour phase within one cell. The dynamic range of the amplitude

and phase is limited by the number of resolvable points within the

cell. If a cell has only 4 by 4 resolvable points, the dynamic range

of the amplitude or phase can be no better than 4. The granularity in

the amplitude and phase may cause distortion in the reconstructed