1993 年 13 巻 Supplement2 号 p. 3-8
Several image measurement methods for obtaining time-mean velocity field are investigated. The spatial filter method and the time-averaged contrast method, which have been reported already by the authors, are examined again for comparison of techniques. A new method, called zero-cross counting method here, is also proposed. Algorithm of the present technique is very simple using only difference betweeen images and its accumulation. This is effective to measure a slow velocity.