Image reproduction quality estimation for output raster scanning devices

Abstract

Any image conversion leads to its distortion. Therefore, any playback system, providing minimal distortion should give each link in image conversion required quality. This raises the question: what should be the image represented to person, so that it estimated it as high quality?

In television, which is one way of transforming raster scanned images, integral quality criterion includes a set of parameters that characterize chromaticity, size, brightness, contrast, sharpness, uniformity and cleanliness of background and others. Each of these parameters are linked with sensory function of the visual system.

Perception of lineart information, particularly, a font picture depends on the complexity of the characters, brightness, contrast and sharpness of images, and the number of obstacles on the print of the laser printer.

Optimal conditions of perception font alphanumeric characters in a live (dark characters on a light background) and inverse (otherwise) corresponds to different contrast relative thickness of strokes. Therefore fontware symbolic image must form more thin strokes. To transfer a single signal with steep transition from dark to light, as in periodic with a period λ=2·b, twice bandwidth is required.

If a person as information consumer can work with it indefinitely long, being able to get a grasp text as necessary to return to reading, in most cases sufficient is value ν_R<1/b. In systems designed to work with operational rapidly changing information in terms of the time limit for its review and evaluation the value  ν_R<3/(2·b) should be used advisable.