vergence
noun/ˈvɜː(ɹ)dʒəns/
Etymology From verge (“tend, incline”, from Latin vergere) + -ence, synonym of earlier (1660s) vergency (the equivalent of French vergence). Coined as a technical term in ophthalmology, as a hypernym of convergence and divergence, in 1902. The sense of the numeric quantity in geometric optics was introduced, from use of the term in physiological optics, in the 1920s.
1
Medicine, Physiology, Sciences The simultaneous turning of both eyes when focusing.
2
Engineering, Natural sciences, Optics, Physical sciences, Physics A measure of convergence or divergence of rays.
- a special vertex trial case computed for an object vergence of 4.00.1921, The Optician and Scientific Instrument Maker, volume 62, page 1
- 1947 Benjamin King Johnson, Optics and Optical Instruments: An Introduction with Special Reference to Practical Applications, Courier Corporation (1960 [1947]), p. 152. "Ample movement between the source and condenser should be available in order to allow for a variation in the vergence of the light leaving the condenser"