Frequency domain velocity measurements and time domain velocity measurements are made using light from cells or other objects. An optical grating is used to modulate the light from an object so that it has a frequency proportional to the velocity of the object. Depending upon the embodiment, the pitch...http://www.google.com.tw/patents/US6507391?utm_source=gb-gplus-share專利 US6507391 - Measuring the velocity of small moving objects such as cells
