Laser Levelling

The need for levelling instruments is as old as when mankind started to erect monuments which were planned to last for good. The fact that a laser beam can be formed in such a way that it travels nearly parallel over a long distance, made lasers a valuable tool for defining a straight line. In all applications, like construction of buildings, roads, railway tracks or tunnel where straightness is an important parameter, lasers proven their superiority. The construction of the railway tunnel from France across the English Channel started from France and England simultaneously and the met with an offset of a few centimetres, a brilliant performance of the engineers and the used laser for levelling. The straightness and low divergence of the laser beam are the properties which are exploited for this technique. By means of a simple laser beam, huge road construction machines are guided along a perfectly straight line and during the construction of buildings, the straightness of floors can be adjusted. By means of imaging optics the laser beam can be transformed into a line and even into a rectangular cross which, for instance, is used for positioning objects with respect to a handling facility or a machine. Light lines and even crossed lines are important in sawmills to align the saw blades with respect to the logs. Furthermore, stonemasons use light lines when cutting valuable boulders.
Within this workshop, Laser Levelling“ basic properties of a laser beam are discussed. Due to the fact that a laser beam represents a Gaussian beam, it can be manipulated in such a way that lowest beam divergence can be obtained. Classical light sources do not emit pure Gaussian beams as laser does and thus cannot be used for levelling instruments. As part of the experiment, the laser beam will be transferred from its circular shape into a line by means of a cylindrical lens. Subsequently, a second cylindrical lens and a beam splitter cube are used to generate a crossed line. The used diode-laser is mounted on a sturdy professional tripod for a variety of levelling tasks.

Principle of operation

In the example, laser spirit level is attached to the tripod. In the system is positioned in the room in such a way that the laser spot hits the reference point of the to be transferred height. The spirit level is adjusted horizontally also for the 90° rotated direction. One may now check if the craftsmen who built the object of interest did a good job.

In the next example, laser levelling as well as range finding will be applied. The room should be divided into two halfs. For this purpose the 90° beam bender must also be used.