Structured illumination has been making headway outside of medical imaging for some time (since around 2000), in areas such as 3D reconstruction / scanning, underwater imaging, super-resolution microscopy and specular/diffuse optical analysis. Consumer devices on market and near to market, such as some versions of the Xbox Kinect and Google’s project Tango, already make use of structured illumination to build up a 3D ‘image’ of the scenario in front of them. Medical applications of structured illumination have mainly found traction by using the method to differentiate reflection mechanisms and diffusion dependencies on illumination.

The advantages posed by this technique are apparent in situations where light is scattered diffusely and specularly, either by the object of interest or by the medium it resides within. By varying the spatial intensity of light in a known pattern, one can analyze how the resulting image in dark and light regions varies as a function of illumination. In the sub surface analysis case, doing this builds up mapping of the light which has ‘bounced’ directly off the surface and the light which has taken a more tortuous path through the substance. In terms of light diffusion, by changing the sizes of the dark and bright fringes of a barcode-like structure, it changes the effective depth to which the illumination penetrates. One can thus construct an image from light which has emanated from beneath the surface, giving a discernible depth greater than would be possible with simple planar illumination.

A potential application of structured light in medical applications is to image subcutaneously – this avenue of interest has been pursued by several research groups previously, one of the first being researchers at the University of California.