Time-resolved diffuse optical techniques reveal the integrating-sphere behavior of intact chicken eggs

Optical methods and techniques are widely used in the industrial inspection and grading of eggs. Using time-domain diffuse optical spectroscopy measurements in the near-infrared, corroborated by Monte Carlo simulations, we study the role of the eggshell as an integrating sphere that traps photons inside its enclosed volume. We demonstrate the capability of this non-invasive technique to effectively retrieve the optical properties of the eggs' contents and thereby distinguish between incubated and unincubated eggs. Extended photon migration inside the egg is further confirmed by means of time-resolved Raman and time-resolved fluorescence measurements. Our findings shed light on the optics of intact chicken eggs and may lead to novel approaches for non-invasive quality inspection as well as early sex and fertility detection.