Dotsunit

Dotsunit is a proposed quantitative measure used to describe the density of dots in raster graphics, halftone screens, and dot-based display technologies. It provides a way to compare the effective resolution of dot patterns independent of device-specific claims.

Definition and calculation: A dotsunit (symbol: du) is defined as the reciprocal of the average center-to-center dot pitch squared, with the pitch p measured in millimeters. Thus du = 1 / p^2, in units of square millimeters as the inverse. For example, an average pitch of 0.1 mm yields du = 1 / (0.1^2) = 100 du.

Measurement: In practice, du is estimated from high-resolution images of test patterns. The centers of individual dots are detected, the mean spacing is computed, and the reciprocal square gives the dotsunit value. Results can vary with lighting, dye, and imaging resolution, so standard protocols are needed for comparability.

Usage and interpretation: In research and development, higher du indicates a denser dot pattern or finer effective resolution. It is used to compare screening methods, inks, substrates, or displays. Because there is no universal standard for p or imaging conditions, du values are mostly relative rather than absolute across systems.

Relation to other measures: If expressed in reciprocal square millimeters, du relates to conventional density measures such as dots per inch (dpi) through p_mm = sqrt(1/du) and dpi ≈ 25.4 / p_mm. Some studies report du alongside dpi to provide a device-independent sense of dot density.