US Patent 7428783 Testing system for flatness and parallelism

A testing system for testing flatness of a surface of a workpiece includes a testing apparatus (10) and a processor (20). The testing apparatus includes a testing box (12) and a measuring apparatus (14). The testing box includes a plurality of holders (122); the holders define a datum plane. The measuring apparatus comprises a plurality of movable testing poles (142) extending out of the testing box and a plurality of gauges (141) configured for measuring distance of the testing poles retracting into the testing box. Ends (1421) of the testing poles away from the testing box are located at the datum plane and configured for supporting the surface of the workpiece thereon to allow the gauges measuring retracting distance of the testing poles under the pressure of the workpiece. The retracting distance of the testing poles is equal to distances between testing points on the surface of the workpieces and the datum plane. The processor is connected to the testing apparatus for receiving and processing testing data that are converted from the retracting distance of the testing poles measured by the gauges.