Four-dimensional image formation theory of high-NA full-field optical coherence tomography

We describe the 4D theory that can rigorously treat the image formation and precisely express the imaging characteristics in full-field optical coherence tomography/microscopy (FF-OCT). Our theory shows that the image of a single point object outside a depth of focus becomes a curved shape if an effective NA is large and a light-source spectrum is wide. In addition to the distorted image, the high-NA system may lose some object-structure information, which causes the imperfection of refocusing. Our theory shows that the FF-OCT with almost zero illumination NA and a large collection NA allows for a perfect refocusing with a high optical resolution maintained.