Holographic lens for optical correlator

Aberrations in holographic optics place limitations on the information capacity of the data that can be processed by holographic optical correlators. Nonetheless, the aberrations can be reduced sufficiently for an extensive class of devices such as those for real time data input using space-time light modulators and a TV channel. This paper analyzes the aberrations of holographic lenses, demonstrating the feasibility of an off-axis lens for correlation image analysis with aberrations similar to an axial lens. A requirement that the wave aberrations not exceed a quarter-wavelength was placed on the lens. Equations are solved for coma and astigmatism, and used to plot the maximum wave aberrations as a function of the spatial frequency of the proposed signal for three cases: (1) normal propagation of a diverging beam and oblique propagation of a plane beam; (2) oblique propagation of diverging and parallel beams, symmetrical with respect to the normal to the photographic plate; (3) oblique propagation of the diverging beam and normal propagation of the parallel beam. The angle between the beam axes was 45 deg in all cases, with a lens focal length of 350 mm and an operture of 32 mm.