Using a television monitor and a CCD camera, researchers at the Universidad Complutense de Madrid in Spain have developed a simple, flexible and low-cost method of analyzing the wavefront properties of lenses and other optical elements. They place the element between the monitor and camera, and display a sinusoidal line pattern on the monitor. The camera images the distortion caused by the element, which is then digitally analyzed using standard fringe pattern analysis techniques.The group described its method in the April issue of Optical Engineering. The controlled pattern displayed on the monitor offers easy manipulation of test conditions without moving parts that must be precisely aligned. Changing the period of the pattern allows researchers to tailor the measurement sensitivity as a function of the test element's phase variation. Moving the orientation of the pattern's lines allows analysis of the element's wavefront slope. The researchers predict that, with improved displays and fringe processing methods, the technique will be useful for wavefront testing in industrial settings.