Projection Apparatus (1917)

Bausch & Lomb Optical Company The path of light for this system is shown in Figure 7. To obtain this the condensing lens directly back of the lantern slide carrier, which lens is mounted in a swinging arm, is thrown out of the optical axis, and a small double convex lens, mounted in the dark chamber, is swung into position directly in front of the large rear condensers. This produces a gradually converging pencil of light, which finally forms a large image of the arc at the diaphragm plane of the substage condensers and fully fills the aperture of the high power condenser. With the improved substage condensers this arrangement is used for all the different powers of objectives that may be required. Microscopical Projection with Polarized Light For those who wish to project petrographical or chemical specimens with polarized light, we have arranged a set of accessories to be used with either of the microscopes mentioned above. (See “Accessories.”) Combined Vertical and Polariscope Attachment An attachment of this kind will be of great service in a Department of Physics, because one can demonstrate both parallel and convergent polarized light and use the attachment as well for demonstrating various physical phenomena, such as the lines of magnetic force, etc., or for projecting any transparent objects which must be held in a horizontal plane. The Combined Vertical and Polariscope Attachment, Figure 8, con- sists of a dark chamber with an adjustable interior mirror which can be set at an angle of 52° for polariscopical projection, or at an angle of 45° for vertical pro- jection. A plate which slides across the top of this dark chamber carries the re- flecting box and plates for producing polarized light and the optical system used with the vertical attachment. The change from one form of projection to the other is made by shifting the mirror in the dark chamber and sliding the plate on top of the chamber into the desired position. The light is then reflected by the mirror up through the vertical attachment or the polariscope attachment, according as one or the other has been slid into position. For projection with the vertical attachment we have mounted a 4/4-inch diameter plano-convex condensing lens in the sliding plate with a projection lens and reversing mirror carried above it on a vertical rod. This condensing lens is mounted with the plane side up to serve also as a stage. At the other end of the sliding plate is the box containing the reflectors and polarizing plates of the polari- scope. When projecting opaque objects the vertical attachment is withdrawn from the path of the large projection lens by means of the sliding plate, and the supports carrying the body tube and revolving stage of the polariscope are hinged so that they, too, can be turned away from the path of light. Some departments may have use for only the polariscope attachment on this outfit; others may wish to use only the vertical feature. For this reason we supply the attachment with the polariscope or the vertical equipment only, if desired. (See price list.) Special Vertical Attachment In order to meet the demand for some means of projecting X-ray plates, large sections, such as brain sections, and other large transparencies without reduc- ing them to ordinary lantern slides, we have devised this special attachment which 77