In this project, we developed more comprehensive comprehensive methods to evaluate the transfer function and to refine the existing techniques. Work was also done on quantifying the noise (including spatial and temporal components) on these displays and finding a relationship with results from the psychophysical studies. The ultimate aim is to devise a display system on which the image perception is not distorted due to the inherent properties of the display and effects from the human eye.

The following image shows LCD pixels magnified, in which the three components (subpixels) of each pixel and the spatial noise are clearly visible. Also shown is a typical transfer function (horizontal and vertical) for an LCD display.

The former mode of evaluation is the phantom technique, which is based on the use of test objects that simulate anatomical structures. A measurement of threshold modulation is done, based on standard "test patterns," and a comparison is made between various LCDs and CRTs. However, this method suffers from problems in the interpretation of the images, which depends strongly on observer subjectivity. One other measure of performance is the spatial resolution of the imaging system, which is not well evaluated in the above method. In the analytical studies, the modulation transfer function (MTF) is evaluated to provide information on the system's spatial resolution.

This work was a collaborative effort with Prof. Hans Roehrig in the Dept. of Radiology.