GB657491A - Apparatus for the illumination of objects and optical projection and viewing thereof - Google Patents

Abstract

657,491. Optical - projection apparatus. HANSEL, C. W. Nov. 5, 1947, No. 29460. [Class 97 (i)] Apparatus for illuminating an object and producing an image of it optically comprises a transparent, translucent, or opaque object stage, an objective comprising a lens or lenses, or a curved mirror, or a combination of these, part of the objective aperture being rendered ineffective by removal or by the interposition of another reflecting optical element, the hole formed by said removal, or the said other optical element, being utilized to direct on to the object an illuminating light-beam, all the rays of which are parallel, or nearly parallel, to the optical axis, an image being formed by the remainder of the objective. As shown in Fig. 1, the object 4 on a transparent stage 5 is illuminated by a lamp 7 and condenser 8 through the hole 2 in a concave mirror 1 with central stop 6. The mirror may be used to form a real or virtual image. In another arrangement a plano-convex lens is used instead of the mirror, being silvered on its convex face, apart from a central region through which the object is illuminated, the object resting on its upper, plane, face. In another arrangement akin to that of Fig. 1 the system is inverted, the object resting on a small opaque stage which forms the stop, the illuminating light beam being horizontal and being reflected on to the object by a small inclined mirror above the stage. In Fig. 3 the object 4 rests on an opaque stage 16 and is illuminated by a light-beam 3 reflected from a prism 15, an image being formed by the lens 13. In another arrangement, a lamp surmounted by a reflector is arranged immediately above a lens such as shown in Fig. 3, covering only its central part, and illuminates the subject through the lens. In Fig. 4 the subject 4 is illuminated by light from a lamp 7, passing through apertures 20 in an opaque stage 19 and reflected from a central silvered portion 18 of the projection lens 17. Instead of the holes 20 one larger hole may be covered with a transparent stage for the object. In another arrangement lamps above the background are used and light therefrom is reflected on to the subject from silvering on the peripheral portions of the projection lens, a system of shields being used to prevent light from the lamps passing directly through the central part of the lens through which projection takes place.