English to Greek Tech/Engineering Photography/Imaging (& Graphic Arts)

Screen Ruling - (from a scanner manual) I have found these definitions in English: "The number of lines of dots per inch, both vertically and horizontally, on a screen tint or halftone screen.//The frequency of a row of dots in a halftone image, usually expressed as lines per inch (lpi); the higher the screen ruling value, the smoother the image, depending on the print medium used".