A modified spatial frequency domain imaging configuration with reduced speckle noise images

Spatial frequency domain imaging (SFDI) is a safe wide-field and non-contact imaging modality that has been broadly utilized in various medical applications. It has shown successful results in dermatology and photodynamic therapy preclinical and clinical studies. In SFDI system, a spatially modulated illumination is incident on the target and the diffuse reflectance is captured at different spatial frequencies. A spatial map of the tissue optical properties is then extracted analytically. The present study suggests a de-noising optical method based on modifying the common SFDI system using an interferometry configuration to reduce the possible speckle noise in the resultant images. Diffuse reflectance images of the examined samples were captured at different spatial frequencies after splitting a visible laser source into two identical beams using a beam splitter. One beam illuminates a reflecting mirror and the other strikes a spatial light modulator’s (SLM) reflecting window. The SLM displays sinusoidal patterns at various frequencies providing spatial modulation reflected beam. The two beams are combined and directed to the sample for capturing reflectance images via CCD camera. The modified SFDI system was tested on diffusers and chicken-skin samples. Speckle noise contrast was calculated before and after applying the interferometry approach revealing a decrease in the noise contrast by 17–24%. Moreover, the recorded skin’s diffuse reflectance was compared with Monte-Carlo simulation results providing 0.033 and 0.024 absolute-error before and after applying the interferometry configuration respectively. The current work revealed the efficacy of employing an interference-based technique to reduce speckle noise in SFDI-based images.