Active detector for determining the position of a laser beam

The detector has a photodetector (6) having several photodiodes (8) which are offset along a line in a defined manner with respect to a reference point (7). A processor (11) has a parameter set (P) of an associated line laser transmitter (2) for emitting the light beam (1). A quantity determining module (13) determines an energy quantity associated with a detected light energy (E) of a light beam. An error estimating module (14) estimates an error estimation value (F) depending upon the energy quantity. An offset display (9) displays offset of the light beam (1) with respect to the reference point (7). The detected light energy (E) is reduced by a background noise energy (R) by the quantity determining module (13). The processor has a programmable storage area (12) for storing the parameter set (P). The processor is connected to an error display (10) for digitally displaying the error estimation value. The processor compares the error estimation value (F) with a threshold error value (G), generating an error signal. A control module (16) associated with the processor (11) signals the error signal depending on the error signal. The control module is associated with the processor for actively stopping efficacious use depending upon the error signal. The control module modifies display of the offset position in an inefficacious manner.