Screen design and visual evoked potentials.

In this paper we present a method to complement the sophisticated mathematical analyses on screen designs. The use of an objective measure of screen "goodness" is employed, namely, the Visual Evoked Potential (VEP) of the humans performing the test. After the screen is designed, the text on the screen is transformed into an intensity pattern using a recursive algorithm. This intensity pattern is used as a stimulus to obtain wave forms from the scalp of the subject, and the wave forms are analyzed as to their frequency content. A 2-D Fourier transform of the screen design is performed and the frequency components of the power spectrum are compared to the frequency components of the wave form. Our results indicate that when a "balanced" and well-designed screen is used as a stimulus, the second harmonic of the VEP wave form is always smaller than the first harmonic. The implications of such an analysis are discussed.