A conventional laser beam level instrument is quite complex for its structure or mechanism and also occupies a larger volume.
The automatic optical levelling, plumbing and verticality-determining apparatus of U.S. Pat. No. 6,035,540 also granted to the same inventor of this application includes a frame (3) for securing the illuminators (6, 7, 8) and the plumb device (4) on the frame (3) rotatably mounted on the base (1), easily causing precision problem by such a rotatable mechanism; and a longer stem (42) for mounting the plumb device (4) on the stem on the frame (3), thereby increasing the total height of the instrument and causing unstable standing and inconvenient handling of the instrument.
The present inventor has found the drawbacks of the conventional laser levelling or calibrating instrument and invented the present compact optical calibrating apparatus.
The object of the present invention is to provide a compact optical calibrating apparatus including: a housing having a base formed on a bottom of the housing, a horizontality calibrator universally pendulously mounted in the housing, a plurality of illuminators embedded or secured in a plumb pendulously secured to the horizontality calibrator, and a switch device pivotally secured in the housing for switching on or off a power source supplied to the illuminators and for braking or releasing the pendulous movement of the plumb; whereby upon embedding of the illuminators in the plumb, the height and volume of the calibrating apparatus is decreased for obtaining a compact optical calibrating instrument.