US849977A - Fresnel lens. - Google Patents

Description

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To (1r/ZZV whom it may concern,.-V

UNITED STATES PATENT OFFICE. l

l4v T .lwiiiIlIAMCHURCHILL, 'or coRNING, NEWLYORK, 'AssiGNoRjrro' coRNiNG GLASS WORKS, oF coRNING, NEW YYoR'K.

FssNEL LENS. I

in'va'rious other ways, and also for -signalflights upon vc lrawbridges over vnavigable rivers in conformity with the regulations of the United States lighthouse establishment. Such a lens consists of a hollow cylinder of glass or section of `a cylinder, with corrugations arrangedtransversely on the outerface,

. the cylinder'having a smooth inner face. Its

eect is-to roduce a concentration of-'the light from t e fiame into a comparatively narrowfan-like beam spreadin over the ane gle covered by the fresnel. In ship-lights such'an angle is usually ten points of the compass, or one hundred and twelve and onespecifically4 indicating the nature of my imcircle w half degrees. The mast-head light vusually covers two hundred and twenty-tive degrees.

' Such fresnels are either constructed by building up a series of se arate clit and polished segments of glass he d in place by some kind of a metal frame or the lens is pressed in one solid piece in a metal mold.

My improvementv in the construction of such lenses is seen in the accompanying draw? in s, in Whichigure 1 shows in vertical section the profileo one side of a lens; but should a threehundred-and-siXty-degree iiresnell be represented the vertical section would show a corresponding profile on the opposite side of the figure. Fig. 2 is a horizontal section more provement, as hereinafter described.

My improvement consists in causing the mnei sur ace of the lens to comprise a series ofl 'connected rectangular planes angularly disposed'with respect to each other, each of the said lanes being tangential to an inner liich is concentric with the outer bounding circle of the lens, the inner surface of the lens, in other words, producing in cross-section a polygonal figure the axis of which is the center of curvature of the bound- 4ing circle. The optical result reduced by suchimproved construction is t at the light Specification of Letters Patent. Application filed November 22, 1906. Serial No. 344 6SQ.

lof the light, for the reason that Ecircle, it is shown in each il slivht taper, this being required in the act of emanating fromthe iiame is concentrated with a higher intensity along the axial planes bisecting the said rectangular surfaces at` right angles. There .is a corresponding diniinution of intensity alon similar; axial planes proceeding through t e lines of intersection of the rectangular surfaces. Such Vatented April 9, 1907. 'A

planes of concentration are illustrated in Fig. 2 by the lines C A, C D, C F, and the lines showing the planes' of somewhat diminished intensity are those C B, C E, and C G. These linesv are, as will .be understood, cross-sectional pf thp planes mentioned above.

The main advantage gained vb my iin- .;A

proved 'lens is that owing to the hig er intensity of the beams in certain planes the ran e of the light is increased., this result,fwhich.1s, of' the highest importance in a 'signal-light.

being diminution of intensity inother lanes above y mentioned is not detrimental to t e eicieiic j sincesuch lights are on board a vessel or other movin o ject in more or less continual motion, an since the observer is usually u on a movin vessel this motion in various iiections wi -bring the regions of higher intensity within the range of an observer about as often las the achieved by a simple and ineiipensivej' change in'this general type of lens," and thi regions of diminished intensity are brou ht Within s uch range. Whenso desired, t is flashlight effect can be enhanced by increasing the vbreadth of the plain surfaces forming the polygon and decreasing their number. For general purposes it will probably'be advisable to use surfaces l not much, if any, broader than the breadth of the flame used for illumination.

While I have preferably described my'improved lens as one covering three hundred and sixty degrees, as shown more particularly in Fig. 2, it is to be understood that the invention is intended to include a lens covering any lesser numbe'r of de ees, as shown more especially in Fig. l.A ile the lens in one of its forms is herein described as cylindrical and in its other form as a section of a -re as having a mlding.

Having thus 'described my invention,` I claim* 1. An integral Fresnel lens the inner sur-1v lface of which consists of a series of connected IOO lrectangularlanes angularly placed with respect to eac other, each of the said planes being tangential vto an 'inner circle which is concentric with the outer bounding 4circle of the lens, substantially as set forth.

2. An integral Fresnel lens the inner sur faceof which consists cfa series of connected rectangular planes angularly placed with re spect to each other and producing in cross-section a polygonal figure, the axis of sucli'figure being the center of curvature ofthe outer l l boundingy circleiof the lens and each o'f'i'the said planes 'being tangential to an inner ciff" cle which is. concentric with said puter bounding circle, substantially as set forth.

In testimony whereof I aflX my signature in presence of two Witnesses.

.' WILLIAM crIURcHHiL.'

' Witnesses: A

MARION AXWH'ITLOCK, FRED. C. CAMERON

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