Decomposition of the OTF: Wavefront Coding as a Cornu Spiral

Recent years have witnessed the development of a new imaging technique, known as wavefront coding, that employs an aspherical phase mask and post-detection electronic processing to enable high-performance imaging with far greater tolerance to defocus aberration than traditional optical imaging [1]. Various methods have been employed for synthesizing the design of wavefront-coding phase mask [1,2]; a frequency domain analysis using the ambiguity function indicated that the ideal mask for an extended depth of field has a linearly separable cubic form. Although these techniques are efficient in synthesizing the shape of wavefront coding masks against specific criteria, the performance parameters are not amenable to simple calculation and interpretation and nor do they readily yield a physical insight into the underlying process. We describe a new insight into the fundamental physical principles of wavefront coding and show how its functioning can be reduced to a simple geometrical depiction of a spiral curve from which to obtain the performance parameters.