negative o

An o. in which the real image is formed somewhere between the two lenses or lens systems of the o. orthoscopic o. An o. with an eye lens like one of the combinations of an objective, and a double convex field lens in the focus of the eye lens. It gives a large, flat field, parfocal o's. Of Pennock, o's so mounted or so constructed that they may be interchanged without the microscopic image getting out of focus. periscopic o. A positive o. devised by Gundlach. It has a double convex field lens and a triplet eye lens, positive o. An o. in which the real image formed by the objective is below the o. projection O. An o. especially designed for projecting the image formed by a microscopic objective on a screen for cla demonstra- See tion under or for photography. Ramsden. searching Ramsden's o., o. seeker o. A low o., used especially with high objectives, for the purpose of finding or locating minute objects or parts for study with the working o's. solid o. A negative o. devised by Tolles, consisting of a solid piece of gla with a moderate curvature at one end for a field lens and a much greater curvature at the other for an eye lens. It is especially adapted for use when a high o. is desired. working o. An o. used for ordinary microscopical observation, in contradistinction to a searching o. (q, v.). [Lat., oculus, the eye.]