Patent ID: 7826653

Claim:
A fluid measurement system comprising: an imaging means for taking images of particles contained in a fluid to be measured at small time intervals, said imaging means comprising a long focus optical system being of a long distance type that images a fluid to be measured a long distance away, and said long focus optical system being provided with a shield which shields a part including a central portion of a main mirror at an arbitrary shield rate, wherein said shield rate is set in a range of 20% to 60% when one particle image obtained by the imaging means is across two pixels or more, and is set in a range of 0% to 40% when a plurality of particle images are contained in one pixel; a control means for controlling said imaging means; and an image processing means for comparing luminance pattern distributions at a plurality of consecutive time points obtained by said imaging means to measure a moving direction and a moving amount of a particle group, and analyzing a flow field of the fluid to be measured.