Photolithographic fabrication of a high-precision bar-code pattern on the surface of a sphere

Bar-code patterns were produced upon gold-coated glass spheres 8 mm in diameter with a novel projection photolithography exposure system that included a computer-controlled rotation stage-and-shutter arrangement. The patterns extended in an equatorial band about the entire 360 degrees periphery of the sphere. To obtain uniform thickness of the photoresist layer, we dip coated the spheres and removed the excess with an absorption pad. The widths of the bars in the pattern were in the range 21.85 +/- 0.6 microm at the equator, and the relative error in the angular position of the pattern features was less than 0.025 degrees. The patterned spheres are suitable for use in optically interrogated flying spot magnetic heading sensors.