Performance evaluation of soft copy display systems according to AAPM TG18 protocol.

The purpose of this study was to evaluate the display performance of the liquid crystal display monitors according to the American association of physicists in medicine task group 18 (AAPM TG18) protocol at prior and after new calibration. We measured minimum and maximum luminance, luminance ratio, luminance and contrast response, luminance angular and spatial dependency, resolution, veiling glare and chromaticity quantitatively for 33 medical displays. Display noise was evaluated only visually. The mean maximum luminance and luminance ratio were 386 and 273 cd m(-2), respectively. The mean deviation of measured luminance and contrast response from expected response associated with the digital imaging and communications in medicine (DICOM) grayscale standard display function (GSDF) were 9.76 and 2.35 % at prior calibration and 1.23 and 0.26 % after recalibration, respectively. In luminance uniformity test the mean maximum luminance deviation was 16 %. Luminance method was used in the spatial resolution test and the mean percent luminance difference was 12 % at the center. The mean glare ratio was 1 154. The average color uniformity parameter across the display area of each display device was 0.0093. Majority of the test results were in good agreement with the criteria recommended by AAPM TG18 report. Considerable improvement was observed in display luminance and contrast response with respect to expected response of DICOM GSDF after new calibration for some displays.

Achieving precise display timing in visual neuroscience experiments.

In experimental visual neuroscience brief presentations of visual stimuli are often required. Accurate knowledge of the durations of visual stimuli and their signal shapes is important in psychophysical experiments with humans and in neuronal recordings with animals. In this study we measure and analyze the changes in luminance of visual stimuli on standard computer monitors. Signal properties of the two most frequently used monitor technologies, cathode ray tube (CRT) and liquid crystal display (LCD) monitors, are compared, and the effects of the signal shapes on the stated durations of visual stimuli are analyzed. The fundamental differences between CRT and LCD signals require different methods for the specification of durations, especially for brief stimulus presentations. In addition, stimulus durations on LCD monitors vary over different monitor models and are not even homogeneous with respect to different luminance levels on a single monitor. The use of LCD technology for brief stimulus presentation requires extensive display measurements prior to the experiment.