Projection Apparatus (1917)

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Bausch & Lomb Optical Company the same angle to the mirror, M', which stands parallel to M and reflects the beam in a direction parallel to the axis of the projection apparatus. The mirror, M', is made of black glass and covered with two plane glass plates The light becomes polarized by reflection from this mirror and passes through a pair of quarter-wave mica plates, P, one of which may be rotated so as to rotate the plane of polarization. It is then converged by the condenser, C, on the speci- men, placed on the stage, S, so as to pass through the specimen under all angles. The interference figure, I, is formed in the focal plane of the other lens system, C' which is exactly like C and arranged symmetrically with respect to the object. The interference figure, as well as any micrometer scale, pointer, etc., which may be introduced at I, is imaged on the screen by the single achromatic lens, O e analyzer prism, A, is placed between O and the screen at the point where the pencils cross. i n' For work in parallel polarized light the two lens systems, C and b, are swung out. Petrographical For illustrating lectures on petrography, chemistry, etc., we offer for the first time a number of accessories, by means of which . oner iui me moi umv Projection with pro j ec tion microscope can be readily employed for projection Microscope ^ polarized light . Thes e accessories can be added to our Large Projection Microscope only and are described under Projection Microscopes. (See “Accessories.”) , , For all projection with polarized light we recommend strongly the use of an aluminum screen. Projection of the Spectrum For the projection of absorption spectra we place upon the optical bed an adjustable slit, upon which the condenser forms an image of the light source. he slit thus illuminated is imaged on the screen by the projection lens. 14