1. A design or plan divided into squares to facilitate its proportionate enlargement or reduction; the style or pattern of such a division.
1887 GEN. WALKER in Encycl. Brit. XXII. 714/1 The graticule is sometimes rectangular, sometimes spherical, sometimes a combination of both.. Spherical graticules are constructed in various ways.
2. A transparent plate or cell bearing a grid, cross-wire, or scale, designed to be used with an optical instrument or cathode-ray oscilloscope for the purpose of positioning, measuring, or counting objects in the field of view; the scale, grid, etc., on such a plate. Hence graticuled ppl. a., fitted with a graticule.
1914 Handbk. Artill. Instrum. 42 In front of the eye-piece is fixed.. a diaphragm, with spider’s web graticules attached to it. 1919 Trans. Opt. Soc. XX. 277 Generally the graticules are on glass and it is usual to refer to the complete discs or plates with the measuring scales or marks on them, as ‘graticules’. Ibid. 286 Graticuled binoculars are not used much for peace purposes. [...] 1971 Physics Bull. July 398/2 A graduation line is centred in the microscope eyepiece graticule.
If one were to be classically accurate, it should be “craticule”; the etymology is:
a. F. graticule, ad. med.L. grâtîcula, for crâtîcula gridiron, dim. of crâtis hurdle.
For meaning 2, the word reticle is also used; the words are unconnected, this one being from a diminutive of rête ‘net.’