This is a sample of table salt.  The out of focus areas are too close or too far from the lens to be in focus. The sample is placed on a black anodized aluminum plate. The illumination was by the red, green, and blue LEDs in the optical head.  This image is a composition from 3 monochrome images. The individual images are shown in thumbnail below. Clicking on a color name will take you to a full size view. The UV image shows thermal noise in the sensor and either some faint fluorescence or some residual visual light from the UV LEDs.. 

              Red ( Full Size View)                             Green ( Full Size View)                        Blue ( Full Size View)                            UV ( Full Size View)