Research of signal-processing methods in four-quadrant photodetector

This paper presents a four quadrant photodetecor for photon beam position measurement. For photon beam with Gaussian distribution, difference over sum (Delta/Sigma) method and log-ratio method are introduced. Then the two methods of position signal processing are compared, we found that log-ratio method has a wider linearity range and higher sensitivity than Delta/Sigma method. On the basis of above, further research is made for curves of position signal of different sizes photon beam. Finally, a photon beam position monitor system with log-ratio method is designed.