Lock-in enhanced non-quantum ghost imaging approach for low scattering surfaces in a highly light contaminated environment

Ghost imaging (GI) as a tool for the indirect estimation of two-dimensional information by using a single detection unit is of high interest in different fields of industrial and academic applications1. One of the crucial benefits of such a technique is the flexibility of the single detection unit, which may, for example, consist of an avalanche photodiode that can provide several orders of sensitivity compared to PIN diodes. In this work, a combined technique is proposed using a high frequency (1 MHz) modulated color selective light source together with a phase sensitive amplifier for the detection of incoming light from low scattering technical surfaces. The aim of this work is the proposition of the optical metrology approach in combination with an application-optimized set of the necessary illumination patterns to reduce acquisition time. Instrumentalization of the modulation phase information of the scattered light enables estimation and visualization of the fluorescence of the surfaces e.g., organic contaminations. The target application for this technique is the estimation of typical surface properties (roughness, homogeneity) for monitoring of additive manufacturing procedures in industrial, highly light-contaminated environments. Due to the high-speed switching time between different light sources, a fast operational acquisition of the spectral image data is achieved enabling the resulting measurement approach for inline applications.