Abstract

A multiple imaging system produces an M × N array of images from a single input image. The basic components of our system are a Fourier processor and a suitably designed diffraction grating that is placed in the frequency plane. We have previously designed a single diffractive element Fourier transform lens, corrected for coma, astigmatism, and field curvature. The lens is designed to have the proper amount of distortion to produce an optical transform. The optical processing system consists of two of these lenses spaced a distance F₁ + F₂ where F₁ is the focal length of the first lens and F₂ is the focal length of the second lens. A technique has been devised to produce the necessary phase diffraction grating that generates a multiplicity of equal energy plane waves from a single incident plane wave. The method is based on an iterative Fourier transform scheme that makes use of known constraints to synthesize the phase structure. The constraints include the known Fourier modulus (array of point sources), the phase-only requirement in the grating plane, and any fabrication requirements such as discrete phase levels. The iterative algorithm provides an efficient means to calculate grating profiles that give rise to large arrays of images. System performance over a wide field of view is characterized by calculating the modulation transfer function at various points in the image plane. Since the system is not corrected for chromatic aberrations, it must be used with narrowband illumination. However, by refocusing the system, a different wavelength can be used to produce well-corrected images of the same magnification.

© 1989 Optical Society of America