A noncontacting optical transducer, which measures the profile of machined surfaces, was constructed and tested. The profile transducer consists of a microscope objective, a point-source illuminator, and two photodetectors. The dynamic range of the instrument is typically 500 microinches with an accuracy of better than 10 microinches. The output of this transducer is a profile signal along a line on the surface under examination. The profile of a machined surface obtained by the optical-transducer correlates very well with that obtained by a mechanical Proficorder which uses a diamond stylus. Principles of operation, results of various performance tests, and potential applications of the optical-transducer are discussed.