To enhance imaging performance of hybrid imaging systems by using two asymmetrical phase masks

We propose the use of two asymmetrical phase masks combined with the subtracted imaging method to enhance the signal-to-noise ratio in wavefront coding systems. This subtracted imaging technique is similar to the variable pinhole diameter in confocal microscopy. Two different phase modulations of same phase masks are employed to promote the magnitude of the optical transfer function (OTF). The ratio factor is used to control the phase variation between two phase masks. The noise of decoded images is suppressed owing to the higher magnitude of the OTF than the wavefront coding systems with a phase mask. A tangent phase mask as an example is used to demonstrate our concept. Simulated results show that the performance promotion controls noise amplification of decoded images while maintaining a depth-of-field extension.