Method and apparatus for printing periodic patterns

An apparatus for printing a pattern of features, which includes:

• a) a substrate having a recording layer disposed thereon;
• b) a mask bearing at least one of a periodic pattern of features and a quasi-periodic pattern of features;
• c) a means for arranging the substrate substantially parallel to the mask and with a separation having an initial value;
• d) an illumination system for illuminating the mask for an exposure time with an intensity of substantially monochromatic light to generate a transmitted light-field for exposing the recording layer;
• e) a means for changing the separation over a distance having a desired value and with a rate of change of separation during the illumination of the mask;
• and
• f) a means for varying at least one of the rate of change of separation and the intensity of light so that the mask is illuminated by an energy density per incremental change of separation that varies in a substantially gradual manner over the distance;
• whereby the pattern printed in the recording layer has low sensitivities to a deviation of the distance from the desired value and to the initial value of the separation.