Triggered Image Capture for High Speed Display Characterization
John W. Roberts
¿¿¿Precision display measurements often involve the integration of light measurements over many frames. Newer display technologies with high speed light modulators such as micromirrors are able to make sophisticated use of temporal modulation. This may result in measurement errors, and in situations where temporal modulation produces visible artifacts that affect display usability, but that conventional metrology techniques do not detect. There is a need for further development of new metrology techniques that collect information on the temporal behavior of high speed displays. The emergence of multiple technologies from multiple display manufacturers has created a need for generic, non-brand-specific tools. We are working on such a technique, using the triggered capture of display images with a sub-microsecond imager, with test images and image sequences designed to evoke particular display responses, triggers that can involve keying on features designed into the test images, and subsequent processing of captured images to reconstruct the behavior of the display. In principle, such measures can be calibrated with conventional full-screen measurements so that a determination of pixel sequences can lead to an accurate determination of the effective grayscale and luminance of each pixel. Complications include the finite time required for pixel switching (so that pixel duty cycles can not be computed in unit blocks of time), and the risk that the observation method used will introduce a bias in the temporal observations.