Patent ID: 6073354
Filing Date: 2000-06-13
Classification: G01C

Abstract:
An instrument for producing a plumb or level laser reference beam regardless of small tilt angles of the instrument, comprising:a housing comprising a vessel containing a liquid,a laser light source projector, positioned outside the vessel so as to project a laser beam generally vertically or horizontally through a window of the vessel and into the liquid within the vessel,a compensator float positioned to float within the liquid in the vessel generally at a constant level within the liquid, the float being self-orienting so as to remain floating upright in the liquid if the vessel is tilted, the compensator float including telescope means for reducing the angle of light rays relative to an axis of the telescope means as the rays pass through the telescope means,an exit window in the housing, at a position opposite the light source projector and below the level of the liquid in the vessel, the window being positioned to transmit a light beam exiting from the compensator float and from the liquid, andthe telescope means having optical power with a magnification which, in combination with the index of refraction of the liquid, corrects for small tilt angles of the housing by maintaining the beam exiting the instrument in a plumb orientation in the case of a laser reference beam projected generally vertically, or in a level orientation in the case of a laser reference beam projected generally horizontally.