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Spatial optical Fourier filtering is a widespread technique for in situ image or light
field processing. However, conventional fixed absorbing patterns or mechanical irises only allow
an inflexible, very restricted control. Thus, we present two electrochromic spatial filters with
ring-shaped or directional segments, which can be individually addressed and continuously tuned
in transmission resulting in up to 512 different filtering states. For realization of the electrochromic
devices, we overcome technical obstacles to realize seamless, gap-free electrochromic segments.
We describe this novel fabrication process and demonstrate the successful application in an
optical Fourier transform set-up.
Passive graduated filters with fixed absorption profile are currently used in image recording to avoid overexposure. However, a whole set of filters with prescribed gradients is required to cope with changing illumination conditions. Furthermore, they demand mechanical adjustment during operation. To overcome these deficiencies we present a microfabricated active electrochromic graduated filter which combines multiple functionalities: The overall absorbance, the position of medium transmission as well as the magnitude of its gradient can be tuned continuously by electrical means. Live image control is possible using low operation voltages in the range of ±2 V to reach a high change in optical density ΔOD of 1.01 (400 nm to 780 nm) with a coloration and bleaching time 1.3 s and 0.2 s, respectively. Owing to their low volume and power consumption they are suitable for widespread applications like in smartphones, surveillance cameras or microscopes.