Continuous phase and amplitude holographic elements

A method for creation of a phase hologram element with n-ary levels of phase delay assigned to pixel areas thereof, where the number of levels is greater than sixteen, using e-beam lithography for creating complex surface relief patterns in a layer of low contrast e-beam resist material on a transparent substrate, comprising the steps of

• exposing said pixel areas by a range of low doses of e-beam at n-ary levels in polymer resist material with individual dose correction for proximity effect, and
• partially developing said resist material by controlled time of development less than necessary for full development, resulting in partial removal of e-beam exposed resist material in pixel areas in proportion to said n-ary levels of e-beam doses,
• wherein exposures to said e-beam of adjacent pixels are each individually assigned a primary dose corrected for proximity effect, said proximity effect being defined as exposure dose contributed by backscattered electrons from said transparent substrate, said proximity effect being of the Gaussian form ##EQU5## where D.sub.p, which depends strongly on substrate composition and geometry and upon the electron beam voltage, is the proximity dose intensity at distance r from a primary point dose Q.sub.o delivered at r=0, .eta. is the proximity factor, and .alpha. is the range of the Gaussian, and
• said primary dose assigned to each of said adjacent pixels is corrected by having the total dose arriving at said distance r due to a spatially varying patterned primary dose D.sub.prim, expressed as a convolution of an effective point spread function, PSF, with that patterned primary dose, as:
• ##EQU6## where ##EQU7##