Spiegelstand

Spiegelstand is a term used in optical engineering to describe the angular orientation of a reflective surface, typically a mirror, within an optical system. It denotes how the mirror is rotated with respect to a defined reference frame, usually expressed as tilt angles about two perpendicular axes (often called tip and tilt) and, in some cases, a rotation around the surface normal. The spiegelstand directly determines the direction of the reflected beam and thus the geometry of the optical path.

In practice, the spiegelstand is controlled and adjusted to achieve and maintain proper beam alignment. Mirrors are mounted on actuators and their position is monitored with encoders, autocollimators, or interferometric sensors. Small changes in spiegelstand can shift the beam position, alter focus, or affect interference fringes, making precise control essential in high-precision instruments.

Measurement and adjustment are typically performed with a combination of hardware and procedures. Autocollimators, laser interferometers, or beam profilers assess the current orientation, while actuators—such as piezoelectric, microstepper, or servo systems—apply corrections. Closed-loop feedback may be used to keep the spiegelstand stable against vibrations, thermal drift, or mechanical creep. Tolerances depend on the application and can range from arc minutes to micro-radians in high-precision setups.

Common applications include interferometers, spectrometers, telescopes, laser machining and marking, microscopy, and general optical alignment tasks. The term Spiegelstand is primarily used in German-language documentation and discussions, where it is understood as the mechanical orientation of a mirror within an optical arrangement.