High Quality Content by WIKIPEDIA articles! Synthetic schlieren is a process that is used to visualize the flow of a fluid of variable refractive index. Named after the schlieren method of visualization, it consists of a digital camera or video camera pointing at the flow in question, with an illuminated target pattern behind. The method was first proposed in 1999.Variations in refractive index cause the light from the target to refract as it passes through the fluid, which causes a distortion of the pattern in the image seen by the camera. Pattern matching algorithms can measure this distortion and calculate a qualitative density field of the flow.