Increasing the Number of Gray Shades in Medical Display Systems

Tuesday February 25th, 2014 at 1:53pm

It's easy to find a medical LCD that offers 8 bits/pixel, corresponding to 256 shades of gray per pixel. Now, medical displays offer gray scales of 1024 or more. But is it necessary to offer bit depth this high, especially since available bandwidth makes it hard to transmit more than 8 bits/pixel?

The widely-accepted Barten model of the human visual system is based on experimental data in which the eye is adapted to the luminance value of a uniform background. This model defines the just-noticeable difference (JND) that an average observer can perceive 50% of the time.

We at Touchstone found this fascinating article which explores the value of increasing the number of gray shades in medical display systems. It uses a mathematical formula relating luminance to the JND index, and details how a viewer's contrast threshold is affected by medical images which feature many shapes and spatial frequencies. Take a look at this well-balanced article at




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