Roper Industries Inc. of Bogart, Ga., has approved the purchase of Eastman Kodak Co.'s Motion Analysis Systems Div. in San Diego. The company expects the $51 million acquisition to be completed by the end of 1999. It effected a $9 million purchase of Redlake Imaging Corp. of Morgan Hill, Calif., Nov. 4. With these deals, Roper will have acquired six companies in the digital imaging sector since 1996, said Derrick Key, Roper's president and CEO. The Kodak division and Redlake, which manufacture high-speed digital video cameras, will be incorporated into Roper's Analytical Instrumentation segment.