<p>The compensator is used for an equipment which requires verticality or horizontality. The compensator comprises a sealed liquid container (4) in which transparent liquid is sealed in such a way that the liquid has a free surface (1); a light projecting system (5 and 6) for projecting a light beam to the free surface at a given angle, the beam being totally reflected at the free surface; and an optical system arranged in a required position in the optical path of the totally reflected light beam outside the sealed liquid container so that the variation of the reflection angle to the optical axis corresponding to the variation of the incident angle to the optical axis is equalized in all the directions. When the sealed liquid container is inclined and consequently the incident angle of the light beam to the free surface varies relatively, the sensitivity depending on the variation of the reflection angle is optically compensated. <IMAGE></p>
