Objective       To design a simple and practical system which can automatically identify and monitor the reaction of pupils of human being or animals online based on infrared video measurement technology.       Methods       The system include: ordinary CCD infrared camera

data acquisition card

physiological signal recorder and basic software for signal acquisition and analysis

synchronous measurement and analysis software of pupil video

and computer

etc. The infrared reflection from eyeball was received by CCD camera and converted to digital signals. The digital video information was acquired by the data acquisition card and then sent into the computer. The core of the system was video analysis software of pupil. By dynamically tracking and analyzing

the gray value difference between pupil and the surrounding area

the total number of pixels and the total area of the pupil were acquired. The Windows RAM transfer mechanism was used as a bridge to communicate data between the signal recording system software and the video analysis software

making the changes of pupil size as quick change digitals in the physiological signal recorder. At the same time

the time-area graph of pupil real-time response was formed.       Results        The dilation reflex was successfully measured in cats by using of this system.       Conclusion       Our system solves the challenge of pupil automatic tracking and dynamic measurement

especially the influence of pupil motion to the measurement

depending on simple devices.