Camera-based measurement of relative image contrast in projection displays
Résumé
This research investigated the measured contrast of projection displays based on pictures taken by un-calibrated digital cameras under typical viewing conditions. A high-end radiometer was employed as a reference to the physical response of projection luminance. Checkerboard, gray scale and color complex test images with a range of the projector's brightness and contrast settings were projected. Two local and two global contrast metrics were evaluated on the acquired pictures. We used contrast surface plots and Pearson correlation to investigate the measured contrast versus the projector's brightness and contrast settings. The results suggested, as expected, the projector contrast has a more significant impact on measured contrast than projector brightness, but the measured contrast based on either camera or radiometer has a nonlinear relationship with projector settings. The results also suggested that simple statistics based metrics might produce a higher Pearson correlation value with both projector contrast and projector brightness than more complex contrast metrics. Our results demonstrated that the rank order of un-calibrated camera based measured contrast and radiometer based measured contrast is preserved for large steps of projector setting differences.
Mots clés
cameras
display devices
image processing
optical projectors
optical variables measurement
radiometers
statistical analysis
Pearson correlation
camera-based measurement
checkerboard
color complex test images
contrast surface plots
global contrast metrics
gray scale
high-end radiometer
picture acquisition
projection displays
projection luminance
projector brightness settings
projector contrast settings
relative image contrast
statistic based metrics
uncalibrated digital camera
viewing conditions
Brightness
Correlation
Digital cameras
Image color analysis
Radiometry
digital camera
measured contrast
metrics
projection display
radiometer