Astigmatic defocus sensor: its performance and optimization

Astigmatic defocus sensor is a very simple and easy technique for measuring the amount of defocus (deviation from the focal plane) present in an optical beam. The approach uses a cylindrical lens to introduce astigmatism into the beam and also focus the beam. The measure of the intensity at the focal plane is then used to find out the amount of defocus present in the beam. In this paper, we provide a theoretical discussion on the astigmatic defocus sensor, which is further validated through simulation results. The performance of the astigmatic defocus sensor in terms of sensitivity, crosstalk and dynamic range is studied. Further, the process of optimization of the sensor in terms of the above parameters is also put forward.