Novel reflected light confocal profilometer

We present an instrument that uses a novel technique to render topographical maps of microscopic reflecting surfaces in which depth resolution can be an order or magnitude or more better than the lateral resolution of the confocal microscope. In a confocal scanning reflected-light microscope, the illumination light coming out of the objective is a cone of light with its axis parallel to the optical axis and focused into a diffraction-limited spot. If the specimen is smooth within the size of the spot, then the laws of reflection apply. When the reflecting surface is perpendicular to the optical axis, the reflected light is a cone that coincides with the illumination light. If the reflecting surface is not perpendicular to the optical axis, the axis of the reflected cone of light is at an angle with respect to the optical axis equal to twice the tilt angle of the surface and oriented in the direction of the surface tilt. Because of this tilt, a portion of the back focal plane (BFP) of the objective does not receive any of the reflected light, while in the diametrically opposite side, the aperture stop blocks part of the reflected light. For a given illumination profile, the distribution of light on the BFP is determined by the tilt and orientation angles of the reflecting surface and thus can be used to recover these angles for each pixel in the specimen. These angles are then used to render a topographical map of the reflecting surface.