Optical Hartley transforms

The two-dimensional Hartley transform is of particular interest not only as a tool for analysis and processing of images and other two-dimensional functions, but because it can be implemented optically without introducing the phase ambiguities associated with intensity-only observations of Fourier transforms. The Hartley transform property of producing real transforms from real inputs means that square law detection introduces only a sign ambiguity, which can be resolved much more easily than a phase ambiguity. This suggests applications in optical signal processing, holography, and optical diffraction