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Patents: 246 of 530	UNITED STATES PATENT OFFICE JACOB JACOBS, OF NEW YORK, N.Y.	Jacob Jacobs 26 of 57
ILLUMINATING-TILE. SPECIFICATION forming part of Letters Patent No. 458,850, dated September 1, 1891. Application filed April 17, 1891. Serial No. 389,273. (No model.)

To all whom it may concern:     Be it known that I, JACOB JACOBS, of New York, in the county of New York, and in the State of New York, have invented certain new and useful Improvements in Illuminating-Tiles; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, in which--     Figure 1 is a perspective view of a lens constructed in accordance with my invention. Fig. 2 is a sectional view on the line x x of Fig. 1; and Fig. 3, a detail view in elevation of a portion of a lens, shown on a larger scale than the preceding figure.     Letters of like name and kind refer to like parts throughout the several figures.     The object of my invention is to provide a lens for use in illuminating-tiles or other situations where it is desirable and important that there shall be as complete collection and utilization of rays of light as is possible; and to this end said invention consists in a lens having the construction substantially as hereinafter specified.     In constructing my lens I have had in view the utilization of those rays of light which with lenses of ordinary construction are lost, owing to the law of optics that when the line of their direction has a certain angle to the plane of the surface which receives them they will not be transmitted through such surface, but will be reflected therefrom, and this I have sought to do without impairing the transmission of such rays as are ordinarily passed through the lens unaffected as are those above referred to.     My lens, as shown, consists of a plate of glass A, rectangular in outline, with a plane surface a, which is to be placed toward the source of light when in use, and a surface opposite thereto formed by a number or series of triangular projections a', which extend in parallel lines across the plate, whose bases are the sides of the plate and whose apices stand away therefrom, and preferably having their inclined sides or faces at the same angle of inclination. One face a² of each of these triangular projections is a plane surface, but the other is formed into a number of projections a³, which may be in the form of small triangular protuberances or ribs extending parallel

with each other and with the projection itself, on whose side they are formed. One side of each of the small projections is preferably parallel with the plane surface a of the plate A, while the other is at a right angle thereto.     A lens as above constructed will operate to transmit and diffuse light for illuminating purposes to excellent advantage. Such rays as fall perpendicularly to the surface a will where it is at the point opposite the plane side or face a' of one of the triangular projections pass through the plate of glass until they strike said plane surface (being of course refracted in transit) and from the same be reflected at an angle not much inclined from a horizontal plane if the lens be placed horizontal. The course of such rays is indicated by the dotted line b, Fig. 3. Similar rays which fall upon the surface of the plate opposite the small triangular projections or ribs a will pass directly therethrough in a line coincident with that of their entrance without refraction or reflection, as shown by the dotted line c, Fig. 3. The effect of these ribs a³ upon such rays as come in directions most oblique to the plane surface a of the plate A (which rays are ordinarily lost because of the law above stated) is to allow the direct transmission of some, such as those indicated by the dotted line d, which favorably strike the face of the ribs a³, which is at a right angle to the surface a and the reflected transmission of others, such as those indicated by the dotted line e, which come within the operation of the said law. Some rays, of course, will strike the the faces of the ribs a³ so as to be reflected against the plane face a² of the adjacent projection, but these in large measure will in turn be reflected by said face into the space where they are needed, and so will be utilized. Rays proceeding in a direction at right angles to the plane surface a² (indicated by the dotted line f) will pass directly through the glass without reflection, although, of course, with some refraction. It will thus be seen that provision is made for the direct transmission of rays perpendicular to the surface a of the plate A, as the rays c, for the direct transmission of the obliquely-falling rays, as the rays d and f, and for the reflected transmission of rays of both description. It will be seen, too, that the direction given the light by the lens