Abstract: A test lens and a photo-detector array are fixed in position along an optical axis a fixed distance from each other. Light is reflected by the front and rear surfaces of the test lens through an objective lens and is detected by the photo-detector array. The detected light is processed to produce a pixel count by video processing electronics. Control electronics adjusts the focusing of the objective lens by incremental displacement along the optical axis during a measurement cycle and significant focus position data is obtained from the video processing electronics to determine best focus location from which test lens data is derived.

Abstract: A velocity profile analyzing device measures the change or non-linearity in the velocity of a system under test, and digitally displays the measured variation. The principle of operation is to determine any velocity differences that occur in relation to an ideal state, and to present via a digital display the difference value. The system derives from a linear encoder a velocity representative signal, which includes a grating output coupled to a first counter, and an index output for simultaneously starting the first counter and a second counter coupled to receive a reference frequency signal. The counter outputs are fed to a digital subtractor which provides a digital difference frequency signal for digital display and recording. The digital display may be scaled to directly indicate velocity difference, which can be analyzed for various cyclic or other perturbations without accommodating the whole range of deviation.