Arrangement and method for disturbance correction for imaging flow measuring processes

Abstract

A generally time-varying boundary surface between a plurality of flowing fluids having different refractive indices, e.g. the boundary surface between water and air with an open water surface, produces an optical disturbance. Optical flow measurement procedures that occur through the boundary surface are affected by this disturbance, which can lead to significant measurement deviations or can even completely prevent a measurement from being made. The invention contributes to solving this metrological problem by proposing arrangements and methods for instantaneous, hardware-based correction of optical disturbances caused by a fluctuating boundary surface. For this purpose, a wavefront modulator is introduced into the beam path of the optical measuring method, the modulator actively compensating for the optical disturbance by means of a control system. The invention makes it possible to perform optical flow measurements through a fluctuating boundary surface. It is not limited to a single flow measurement technique, but can be implemented in all known imaging methods. The invention can be used in a variety of technical applications. Some examples include: liquid-air boundary surfaces, e.g. in water channels with an open surface; film streams, e.g. in process techniques for cooling, purification or distillation; jets of fluid with surfaces fluctuating on all sides; measurements in levitated drops or drops adhering to an opaque base, or gas bubbles occurring in liquids. The invention is also suitable for the correction of disturbances caused by temperature gradients in combustion, pressure gradients, such as in pressure surges, or concentration gradients, such as in electrolysis processes.