An ultra-compact metasurface and specklemeter based chromatic confocal sensor

The development of ultra-compact lightweight optical instrumentation that can be used on-machine and to carry out in-process measurements is vital in realizing improved manufacturing processes, increasing the quality of parts being made while saving time and energy by reducing scrappage rates. Only incremental progress is being made in developing suitable instrumentation based on conventional components such as traditional refractive elements as fundamental limits in terms of size and weight are already reached. Here we demonstrate a chromatic confocal sensor that utilizes the natural chromatic aberration found with a basic hyperbolic metalens to realize an ultra-compact and simple probe. Further, we demonstrate how this can be combined with a compact specklemeter as the detection element, thus realizing the whole sensing system in a compact manner. Even with the proof-of-principle instrument in its preliminary and unoptimised state we achieve the successful recovery of the location of a scatterer as it is scanned over a 227 μm range, with a standard deviation of error in the position of 1.37 μm. Sensors of this form can be deployed in areas where traditional instrumentation would typically impede the manufacturing processes, increasing the number of processes that can have metrology applied directly and providing real-time feedback to improve manufacturing outcomes.