High speed opto-electronic gage and method for gaging

An apparatus for determining deviation of characteristics of a sample workpiece from characteristics of a control workpiece, comprising:

• an illumination system for producing a collimated beam having substantially parallel rays;
• a positioning system for placing the sample workpiece between outer edges of said collimated beam to produce a sample image including a silhouette of the sample workpiece;
• an imaging array, normal to said collimated beam and comprising a plurality of discrete light sensing elements, for producing signals corresponding to intensities of pixels of said sample image including said silhouette;
• and
• a processor for producing pixel data corresponding to said signals and for determining dimensions of the sample workpiece comprising:
• means for detecting a diffraction band produced by edges of said sample workpiece and having an intensity of a diffraction band of a control image produced by edges of a control workpiece of the same type as the sample workpiece;
• means for determining a sample distance between points located within said diffraction band of said sample image;
• means for determining a control distance between corresponding points located within the diffraction band of the control image;
• means for determining an offset between said control distance and a known distance between corresponding points of the control workpiece;
• and
• means for applying the offset to said sample distance.