Multi-Functional Metasurfaces as a Platform to Realise Ultra-Compact Confocal Instrumentation for On-Machine Metrology

As manufacturing looks to employ more smart and autonomous processes to improve how items are made, reducing scrappage rates and with it the associated waste in time and energy, new ultra-compact sensors are needed that can be deployed where existing instrumentation cannot. The use of traditional methods when constructing optical sensors limits the progress that can be made in reducing their size and weight, however emerging technologies such as metasurfaces offer a platform by which these barriers can be overcome to develop the sensors needed to underpin this manufacturing transition. Here we demonstrate how a single metasurface can be used to deliver all the optical manipulations required to create a metasurface based confocal sensor with only the addition of a point source and point detector. By combining the optical functionality of both the illumination and the collection optics in this way the system is simplified and reduced in size significantly. While here we demonstrate how a metasurface can be used to reduce the number of elements needed to produce an ultra-compact confocal sensor, this approach can be used to simplify a far wider range of instrumentation to greatly reduce their size and weight.