Abstract

A ray-tracing method with a detour phase coding scheme [e.g., 1] is developed to design on-axis and off-axis computer-generated holograms (CGHs). To date, the usual Fourier-transform approach and coding schemes published by others has been restricted to designs for the reconstruction of two-dimensional (2D) light patterns or "objects" (e.g., [1-3]). The ray-tracing method presented here is readily employed to design CGHs for both 2D and 3D reconstructions and these objects can be situated in either Fresnel or Fraunhofer regions. The ray-based approach simply calculates the optical path length from any chosen point in the object domain and computes the phase of the spherical wavefront from a coherent point source at the recording plane. This approach also conveniently permits various incident and reference beam functions to be modeled, as well as quite complex beam shapes, such as snake beams in the reconstruction regime. While sometimes computationally more intensive than a Fourier-based method, we will show how this approach is highly flexible and allows for very precise location of original object points. A further advantage is that transparent and semi-transparent objects can be easily specified [4].

© 1996 Optical Society of America