BINARY OPTICAL GRATING AND METHOD FOR GENERATING A MOIRE PATTERN FOR 3D IMAGING

In the context of a machine-vision system for inspecting a part, a method and apparatus to provide high-speed high accuracy 3D (three-dimensional) inspection of manufactured parts by reducing vibration. The invention provides a method, a grating, and a 3D imaging system using a binary grating in the projection system to generate patterned light. The grating includes a binary grating having a cycle pattern, wherein each cycle includes a first substantially clear stripe of a first width and a first substantially opaque stripe of substantially the same first width, and between the first substantially clear stripe and the first substantially opaque stripe are a second substantially opaque stripe of a second width narrower than the first width, and a second substantially clear stripe of substantially the second width. In some embodiments, a plurality of alternating relatively narrow clear and opaque stripes are positioned between the relatively wider first substantially clear stripe and first substantially opaque stripe, in order that the optics of the projection optical system and the relative motion between the projection light pattern and the imaging time (trapezoidal integration) smooth the resulting pattern to provide a linear sine-wave-like pattern of projection light.