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Method of observation in which a converging lens forms an image in the plane of the entrance pupil of the observer. If the observer's eye is focused on the lens, the lens will appear as a disc filled with light of uniform intensity. This optical arrangement makes it possible to choose the point of incidence within the pupil, to minimize the effect of the optical aberrations of the eye and to avoid the effect of pupil size on the amount of light entering the eye (Fig. M6). See conjugate distances.