Study on depth of field of wavefront coding imaging system

摘要

The wavefront coding imaging technology is a good approach of extending DOF (depth of field) of imaging optical system with an identical exit pupil. A phase mask being introduced in the exit pupil of the optical system makes the MTF of the system to be defocus-independent. As a result, the DOF of the system is extended without a loss of resolution. How much this technique can extend the DOF of optical system? It was shown by experimental and simulation results of some papers that a wavefront coding imaging system can make the DOF raise an order of magnitude. However, there is no theoretical analysis of DOF extension of wavefront coding technique up to now. In this paper, a special condition under which MTF of wavefront coding system is defocus-independent is discovered by investigating the OTF of the wavefront coding imaging system with cubic phase mask. Based on the condition, an expression of the DOF of wavefront coding imaging system is obtained. The conclusion is verified by the simulation results.