Optical imaging system with extended depth of focus

The invention concerns an optical imaging apparatus comprising a light source, sample holding means, an interferometer, reference means, an objective which is adapted to have its sample side focal plane crossing a sample held in said sample holding means, optical or electro-optical means adapted to produce a ring shaped or multi-spot light source in the front focal plane or any conjugated plane of said objective, at least one detector. The invention also includes a method for using said apparatus where the sample is illuminated by an interference pattern and the depth information is obtained by using optical coherence tomography.