Method and Apparatus for Detecting Changes in Direction of a Light Beam

A method of detecting changes in direction of a collimated coherent light beam, the method comprising

• splitting the light beam into at least two partial light beams,
• superimposing the at least two partial light beams on a camera such as to form an interference pattern displaying light intensity minima and light intensity maxima alternatingly following to one another in at least one transverse direction oriented transversely to an average propagation direction of the at least two partial beams,
• focusing the light beam into at least one focus located in front of the camera,
• registering pictures of at least a part of the interference pattern including a plurality of the light intensity maxima with the camera,
• determining an average shift of the plurality of light intensity maxima with regard to the camera in the at least one transverse direction from the pictures registered with the camera, and
• deducing a change in angular orientation of the collimated coherent light beam in the at least one transvers direction from the average shift of the plurality of light intensity maxima with regard to the camera in the at least one transverse direction.