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The determination of a motor vehicle's drag coefficient CD requires measurements of its aerodynamic resistance and its projected frontal area with high measuring accuracies. The presented paper gives an overview of optical methods for measuring projected areas, and describes a newly developed laser reflection system. It operates on a principle similar to that of a light-barrier system but in a reflection mode. With this optical device and a single numerically controlled traversing facility the outer enveloping contour of the vehicle is automatically tracked and the corresponding coordinates are recorded. The principle of the new measuring method, its advantages and results of measurements on test objects and vehicles are discussed in detail.

The newly developed optical instrument for vibration analysis is based on the laser Doppler effect that can be used to measure the vibration velocity of object surface points. The new system “SOVAS” (Scanning Optical Vibration Analysis System) analyzes the vibration amplitude of whole surface areas by means of computer controlled laser scanning and fast Fourier transform of the velocity signals derived from Doppler frequency modulation. As results frequency spectra of single points as well as vibration patterns of up to seven simultaneously measured frequency ranges can be displayed. The presented paper gives a detailed description of “SOVAS” and some typical applications in vibration analysis of car body and engine parts.