Lighthouse structure and compensating lens in reference laser beam

Abstract

An apparatus for projecting a laser beam in a reference plane includes several imrovements. A generally cylindrical, one-piece molded transparent lighthouse structure overlies the rotatable pentaprism beam diverting assembly of the apparatus. The lighthouse structure is mounted on the housing so as to allow transmission therethrough of the rotating laser beam projected by the beam diverting assembly. The lighthouse structure has a tapered or conical configuration facilitating molding thereof, but which produces a divergence of the laser beam as it passes through the structure. A continuous resilient flexible ring is adapted to releasably attach to the apparatus housing and tightly fit about the lighthouse structure for removably anchoring the structure to the housing in a sealed relationship, providing a water-tight enclosure for the pentaprism beam diverting assembly and imposing a generally uniform attaching pressure about the lighthouse structure. A beam compensating lens aligned across the laser beam and coupled with the beam diverting assembly for movement therewith. The compensating lens being in the form of a positive meniscus lens is configured to correct the divergence in the laser beam which occurs when the beam passes through the one-piece molded lighthouse structure.