In Fig. 2, the 1-D diffractive phase mask was designed to project three groups of lines of varying widths and spacings onto three planes positioned at , 81, and 82 mm, respectively. The target images are summarized in Fig. 1(c). Since these patterns have no variations in the direction, they could be exposed onto a plane tilted at 45 deg, instead of three exposures at three planes. In this way, it is also possible to record all the intensity patterns along the direction. The optimized phase mask topography is plotted in Fig. 2(b). Figure 2(c) shows an optical micrograph of the fabricated mask along with an atomic-force micrograph of the region delimited by the black rectangle. The multiple height levels and the discrete pixels are clearly visible. The simulated light intensity in the plane from to is shown in Fig. 2(d). At the design planes corresponding to , 81, and 82 mm, the patterns corresponding to 9 lines (), 3 lines (), and 5 lines (), respectively, are clearly visible. The optical efficiency, in one plane, is defined as the ratio of the energy within the desired pattern to the total energy incident on the mask. The calculated optical efficiencies are denoted in the figure. The samples for lithography were silicon wafers coated with a -thick photoresist (Shipley 1813) and mounted on a holder that was placed at 45 deg to the optical axis. The illumination power density at the mask plane was and the exposure time was 90 s. The sample was developed in 352 developer for 60 s. Optical micrographs of the patterns corresponding to the regions close to the planes at , 81, and 82 mm [rectangular blocks of yellow-broken lines in Fig. 2(d)] are shown in Figs. 1(e)–1(g), respectively. Excellent agreement with the simulation results is seen. The linewidths at three positions (80, 81, and 82 mm) are 34, 100, and , respectively, which indicate the deviation of , , and . These errors, together with the undesired exposures outside the designated line regions, are partially ascribed to overexposure. The simulated light intensity at three positions is plotted as blue lines beside the micrographs in Figs. 2(e)–2(g). By applying a proper threshold, it is possible to achieve clean lines with accurate widths and suppressed noises (black lines). Subsequently, numerical analysis will show how fabrication errors affect the exposure results. Additionally, a simulated line [Fig. 2(h) representing the green box in Fig. 2(d)] was measured roughly wide by exposure [Fig. 2(i) representing the green box in Fig. 2(e)].