Human tracking using coded masks was demonstrated for a 2-dimensional case over a grid of sixteen cells using four sensors . However, coded masks have the limitation of having low photon collection efficiency since most of the incident light is blocked by the mask and construction of masks for complex 3-dimensional segmentation of the space is an expensive process. Here, we describe the use of Fresnel lens arrays to modulate the visibility of the sensors. Fresnel lenses can be made out of plastics with suitable transmission characteristics in IR making them inexpensive and very light. Lens arrays can easily be fabricated with each lens having an independent orientation which would help in modulating the visibility of the sensors in any desired manner.
© 2004 Optical Society of AmericaPDF Article