The method of generalized projections is used to design pure-amplitude diffraction holograms that generate gray-scale images. Two algorithms are presented: the direct method nonlinearly constrains the hologram transmittance to the range of real values in [0, 1]; the indirect method constrains the transmittance values to the real axis and linearly transforms the resulting values to the range [0, 1]. Digital amplitude holograms were simulated by quantizing the amplitude holograms resulting from the indirect method. Performance is demonstrated with objective measures (error, efficiency, and variance) as well as with subjective comparison of images. Test images included a photographic quality image of Lena, a uniform intensity spot array, and a binary amplitude block text image.
© 1998 Optical Society of America
(050.1970) Diffraction and gratings : Diffractive optics
(070.2580) Fourier optics and signal processing : Paraxial wave optics
(090.0090) Holography : Holography
(100.0100) Image processing : Image processing
William C. Catino, Joseph L. LoCicero, and Henry Stark, "Design of continuous and quantized amplitude holograms by generalized projections," J. Opt. Soc. Am. A 15, 68-76 (1998)