Sensors & transducers


reference) can be subtracted to obtain the wavefront that carries only the aberrations of the phase plate.


Many applications make use of spatial filtering methods to reduce wave aberrations. To demonstrate the effect of spatial filtering on the transmitted wavefront, a pinhole with 100µm diameter can be inserted at the Fourier plane of the Kepler telescope, thereby low-pass filtering the wave generated by the phase plate (the pinhole must be aligned in the x-, y- and z-axis by minimising wavefront rms). The effect of this pinhole is small; the corrected wavefront rms decreases from 0.1µm to 0.09µm. So the 100µm pinhole is replaced by a 50µm pinhole. The corrected wavefront rms distinctly decreases to 0.06µm. When replacing the 50µm pinhole with a 30µm pinhole, the corrected wavefront rms decreases further to 0.02µm. The PSF shown below is calculated from the corrected wavefront with an added refractive power representing the effect of the telescope lens with 40mm focal length.


The Optocraft wavefront sensors are distinguished by their high speed,


single-shot measurements, excellent unreferenced accuracy, extreme dynamics and broad spectral ranges. They are also able to measure wavefronts with very strong higher order aberrations. They can measure large tilt angles and strongly defocused beams. They offer high intrinsic stability and reliability, powerful, customisable evaluation software and are versatile and flexible in usage. Optocraft’s systems are in operation in many demanding customer applications.


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Instrumentation Monthly May 2023


33


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