The use of a computer-generated hologram (CGH) in interferometric testing provides new methods for highly accurate optical measurement. To fabricate a CGH, polygons are used to approximate the smooth CGH pattern. Because the data size supported by CGH writing machines is limited, the number of polygon vertices must be limited. Therefore, the CGH-encoding method determines the encoding accuracy. To realize a highly accurate optical measurement using CGHs, we propose a CGH-pattern-encoding method based on non-maxima suppression. A self-aligned CGH is designed to verify the accuracy. The experimental result shows that a highly accurate CGH can be fabricated using this method.