Vernier Acuity

Some articles on vernier acuity, vernier, acuity:

Vernier Scale - Vernier Acuity
... Vernier scales can be read because the human eye can detect whether two line segments are aligned or if they are slightly off alignment ... Vernier acuity is the ability by a person to detect the proper alignment of two line segments ... In most people, Vernier acuity is particularly high, allowing one to accurately differentiate between aligned and misaligned marks on a Vernier scale ...
Other Measures of Visual Acuity
... Normally visual acuity refers to the ability to resolve two separated points or lines, but there are other measures of the ability of the visual system to ... Vernier acuity measures the ability to align two line segments ... contrast, and long line segments, the limit to vernier acuity is about 8 arc seconds or 0.13 arc minutes, compared to about 0.6 arc minutes (20/12) for normal visual acuity or the 0.4 arc minute diameter of a ...