ABSTRACT
Optical metrology plays an important role in modern production. Numerically controlled (NC) machines and robots depend on encoders for length and angle that are integrated in the respective axes. Optical techniques are applied for checking and adjusting production machines. Robots and automated floor-borne vehicles are guided by optical sensors. Most NC machines depend on incremental encoders integrated in the linear and rotary axes, and in the majority of cases, these are optical encoders. Incremental encoders render a periodic output signal when the respective axis is moving at constant velocity. The distance is determined by adding the periods of this signal. Laser Doppler vibrometers in principle are two-beam laser interferometers. The vibrating surface is used as the reference mirror. If the surface is not specularly reflecting, an imaging lens with large aperture is used to gather the backscattered light.
