The following is a simple example of a real fly's eye illumination system for digital projector use.

The source is an ellipsoidal volume, centered at the focus of a parabolic mirror. The resulting output from the parabolic mirror is very non-uniform:

Note that if the lamp can be modelled in more detail: but with even a simple lamp model, the scale of the problem can be clearly seen. The rays are then traced through two Lenslet Array objects, and the condensor lens, and are then analyzed on a detector object positioned at the location of the spatial light modulator in the digital projector. The following shows the results of different numbers of lenslets in the two arrays (both arrays have the same number of lenslets in all cases:

Case 1: a 6x4 array of lenslets:

Case 3: an 11x9 array of lenslets

It can be easily seen that the 11x9 case gives the best uniformity. ZEMAX makes it easy to change the number of lenslets, their radius of curvature and apsheric coefficients etc. It is also possible to optimize for uniformity using the pixel = -4 data item from the NSDD optimization operand, please see the ZEMAX manual for full details.

If we set the detector viewer to show luminous intensity (i.e. power as a function of angle) the effect of the array of the angular spectrum of the light can also be clearly seen: