AUTOMATIC VERTICAL ANGLE COMPENSATOR

PURPOSE:To allow detection of the inclination of a reference surface only by a uniaxial optical system by providing a lens system for equalizing variation of the reflection angle of optical axis, corresponding to the variation of the incident angle of optical axis, in all directions and offsetting variation of angle of reflection optical axis. CONSTITUTION:Liquid encapsulated in a container 4 forms a free liquid plane 1. Luminous flux is projected from a light source 6 through a concrete lens 5 onto the liquid plane 1 at a predetermined angle causing total reflection with the optical axis of luminous flux being set in yz coordinate plane. When the container 4 inclines to cause relative variation of the incident angle of luminous flux to the liquid plane 1, sensitivity for the variation of reflection angle varies depending on the inclining direction of the liquid plane 1. The difference of sensitivity is corrected by a lens system and the relative inclination of the liquid surface 1 is optically offset by a lens system for the luminous flux reflected from a reflector 14 in the vertical direction thus keeping verticality constantly.