DE2537547

1520471 Overhead projectors MINNESOTA MINING & Mfg CO 20 Aug 1975 [21 Aug 1974 3 March 1975] 34651/75 HeadingG2J [Also in Division B5] An overhead projector has a light source, a lens arrangement 100, 101, 102, a support 99 for a transparency to be projected and a projection head; the lens arrangement comprising at least two surfaces 100, 101, 102 each formed with an array of straight, parallel grooves and ridges; the grooves and ridges of one array being inclined to those of the other(s). The purpose of this lens arrangement is to reduce glare. Fig. 12 shows a triplet of arrays angled at 60 degrees to each other, Figs. 13, 14 (not shown) show two such triplets relatively displaced by 10 degrees, Figs. 4 to 8 (not shown) show a pair of arrays at right angles; Figs. 9, 10, 16 (not shown) show two such pairs, relatively displaced by 30 degrees; and Fig. 15 (not shown) shows three such pairs relatively displaced by 10 to 15 degrees. Typically the arrays are plastics and the transparency support is glass and is laminated thereto (see Division B5).