COMMANDE DE MISE AU POINT AUTOMATIQUE POUR APPAREIL PHOTOGRAPHIQUE

1321137 Focusing apparatus WESTERN ELECTRIC CO Inc 19 April 1971 [28 Jan 1970] 20497/71 Heading G2A Focus control apparatus for maintaining a predetermined distance between a camera lens 14 and a photographic plate 10 includes first and second force applying means between which a plate 10 is supportable, the forces being such that, in operation, they are in equilibrium when the distance between the lens and the plate is equal to the predetermined distance. The first means, preferably a first gas-thrust bearing 12 applies a first force to the plate, inversely proportional to the distance between the plate 10 and the lens 14, while the second means, preferably a second gas-thrust bearing 22 applies a second force to the plate in opposition to the first, the second force being substantially independent of the distance between the plate 10 and the lens 14. The plate 10 is held by a spring (18) Fig. 1 (not shown) and diaphragm (20) arrangement, the stiffness of which is approximately 1/100th that of the bearing 12. The bearing 22 is flexibly mounted and supported by a pneumatic drive 24. The apparatus is used in a precision camera used in e.g. the making of integrated circuit masks.