SELF-LEVELLING LEVEL Russian patent published in 1994 - IPC

FIELD: geodetic instrument engineering. SUBSTANCE: lens 1, the first prism 2 and suspended second prism 3 of 1-kind Porro erecting system, set of hairs 4 and eye-piece 5 are mounted in series in case 6, which has vertical axis of revolution. The second prism works as focusing element. Geometric length of ray path in Porro system is equal to no less 1.5 diameters of lens 1 in the direction being parallel to optical axis of the lens and no less 2,0 diameters of lens I in the direction being perpendicular to optical axis of the lens. Principal point of lens 1 is disposed onto vertical axis of revolution of case 6. EFFECT: improved precision. 2 dwg