Edge enhancement by unsharp masking using liquid-crystal displays

A new method for real-time edge enhancement is presented. The method is based on the capacity of liquid-crystal displays to generate a contrast-reverted replica of the image displayed on it. When the negative replica is defocused and it is superposed to the original image (displayed in a second liquid-crystal display), one obtains an image with enhanced second derivatives. The proposed technique resembles the classical (photographic) unsharp masking method, but unlike the time-consuming photographic implementation, it can be applied in real-time. The proposed method is potentially interesting for image processing in areas such as microscopy, industrial edge inspection, etc. Validation experiments are presented.