An apparatus and method for delivering excitation radiation to a sample and collecting radiation emanating from the sample. The sample is placed in a deep well which consists of a wall and a bottom end closed by a membrane to form a sample recepticle. A GRIN lens is provided that has a first surface and a second surface, the second surface being inserted into the deep well. A point source of light on the first surface of the GRIN lens is conditioned by the lens and, subsequently, emanates from the second surface of the lens towards the membrane. Reflected, luminescent of fluorescent radiation from the sample is incident on the second surface of the lens, passes through the lens to emanate from the first surface toward collection means, a detector and any desired processing.