US1955597A - Headlight - Google Patents

Description

April 1934- G. A. M. LAMBLlN-PARENT 1,955,597

HEADLIGHT Qriginal Filed Dec. 17, 1929 3 Sheets-Sheet l gin/mantel AprilU, 93 -v s. A. M. LAMBLlN-PARENT HEADLIGHT Original Filed 0 90. 17, 1929 3 Sheets-Sheet 2 Q Liv p 1934= G. A. M. LAMBLlN-PARENT 1,955,597

HEADLIGHT 3 Sheets-Sheet 5 ori inal Filed Dec. 17, 1929 I I abl o'znaqa asrakfd/wAe/vazzM/hawr Patented Apr. 17, 1934 HEADLIGHT Gustave Alphonse Marie Lamblin-Parent, Lille, France, assignor, by mesne assignments, to United States Holding Corporation, a corporation of Delaware Application December 17, 1929, Serial No. 414,749

Renewed September 27, 1933 35 Claims. (or. 240-413) This application isa continuation in part of my application Serial No. 380,281, filed July 23, 1929.

In that application I have disclosed a head- 5 light for motor cars, or the like, which prevents the formation of stray, or dazzling rays in the beam of the headlight, and have shown an arrangement in which part of the rays of the issuing beam diverge below the horizontal, so as to 1 light parts of the road adjacent the vehicle, and

without producing a glaring effect upon the drivers of vehicle coming in the other direction. Such application also disclosesmeans for giving indications of the position of the vehicle to the 5 drivers of following vehicles.

My present application is directed more particularly to improvements in the optical characteristics of the headlight disclosed in my prior application, and to improvements in the construc- 39 tion, combination and arrangement of the parts of such headlight.

One of the objects of my present invention is to improve the construction of the lamp and condenser lens mounting.

Another object is to provide an improved construction of the modified Fresnel lens and the optical system, whereby the concentrated portion of the beam is brought into its most useful position therein, and whereby the divergent part of the beam is improved in intensity and uniformity of spread.

With these and other objects in view, which will become apparent as the description proceeds, the invention resides in the construction, com- 35 bination and arrangement of parts hereinafter more fully described and claimed.

In the drawings forming part of this specification,-

Figure 1 represents a vertical central sectional view taken through a headlight constructed according to my invention.

Figure 2 represents a detail horizontal sectional view on a larger scale through the lamp casing.

Figure 3 represents a front face view of the main lens.

Figure 4 represents a rear face view thereof.

Figure 5 represents a fragmentary horizontal sectional view through the lens.

. Figure 6 represents a fragmentary vertical perspective view thereof.

Figure 7 represents a vertical section through the lens, showing the construction thereof.

Figure 8 represents a similar view of a modified form.

Figure 9 represents a vertical section of the lens of Figure 7, showing the light distribution.

Figure 10 represents a similar view through the lens of Figure 8. I

Figure 11 is a view showing the use of the conto denser lens and mirror in the optical system.

Figure 12 represents a vertical section on a small scale through the'beam projected by the lens of Figure 9, taken. at a distance from the lens.

Figure 13 represents a similar View of the beam projected by the lens of Figure 10.

Figure 14 represents a top plan view of the lamp-supporting bracket, removed. Referring more particularly to Figures 1 and 2 of the drawings, the headlight includes a metallic casing A, of general ellipsoidal form, or of other form if desired, havinga forward section 5 and a rear section 6, which are seperable from each other, the forward section being shouldered l5 vertically and circumferentially of the headlight as at 7, to receive the forward edge of the rear section which fits over said shoulder. The sections are removably retained together by means of thumb screws 8, the threaded shanks of which pass through openings provided in the rear half of the casing into engagement with internally threaded sleeves 9 screwed into cars 10 which may be cast with the' forward section of the casing, the concave washers 11 being interposed between the thumb screws and casing to frictionally retain the former in positionagainst accidental unscrewing. When the thumb nuts are unscrewed and removed, the rear section of the casing may be slipped ofi of the shoulder '7 to ex-- pose the parts of the headlight contained within-the casing. Within the casing there is carried an angularly disposed bracket B, which may be a casting, hav ing a tripod support comprising three lugs 12 adapted to fit against the upper of corresponding sets of lugs 13 which may be cast upon the upper and the lower inside portion of the front. casing section, the tripod lugs being retained in place by screws and washers 14. The bracket B is shown as supported upon the upper set of lugs by its tripod connection, but, if desired, it. may be removed from the upper set, turned upsidedown, and supported. upon the lower set.

The bracket B at its lower end, is provided with a rearwardly extending centrally located ring 15, and flanking this and forward of it, a pair of rings 16, such rings being adapted to receive lamp sockets l7,\the lamp 18 mounted in the middle or centrally located socket being used for ordinary driving purposes, and the lamps 19 in the flankingsockets being used, if desired, when dim lights are wanted. Set screws 20 may be utilized to retain the sockets in position. The

side lamps need not be used unless desired, and

indeed, may, if preferred, be left out of the assembly. The connections to the lamps may be 7 other desirable manner.

23 may, if desired, not be used in the optical sysmade in any desired manner, the terminals 21 on the lamp sockets being provided for this purpose.

Forward of the lamp 18 is arranged a ring 22, in which is mounted a condensing lens 23, such ring having arms 24 which straddle the bracket 13, and which are secured thereon by means of a pin 25 extending through the side flanges of the bracket and through openings in the arms 24, and one of such arms has an extension 26 which, by means of a screw 27 prevents pivotal movement of the ring on the pin 25 and retains the ring and the condenser lens in a fixed angular position in the optical system of the headlight.

In the opening at the forward portion of the headlight casing is mounted a lens C, the outer flange of which is held in position between the lip 28 at the opening of the casing and the ring 29, at the forward face of the lens flange, and a ring 30 at the rear thereof. An arm 31' extends into a notch at the top of the le flange for properly positioning the lens in the casing, such am being retained in position beneath the forlug 13.

To the rear of the lamp 18 is. arranged a spherical reflector 32, and this reflector may be carried by a mounting secured to the central lamp supporting ring 15, or may be supported in The condensing lens tem of the headlight, and the same is true of the reflector 32, or either may be used without the other. If used, however, theyenter into the combination ofthe optical elements in projecting the desired beam, as will later appear.-

face 35, and on the upper half of its rear face ,has a series of substantially semi-circular refracting zones 36 and on the lower half another series of substantially semi-circular refracting zones 38, there being also provided a centrally located bulls eye 40. The retracting zones and the part of the bull's eye in the upper half of the lens, and the zones and the part of the bulls eye in the lower half of the lens, are separated along the line of the abrupt shoulders 41, which extend substantially horizontally and diametrically of the lens across the zones thereof and the bulls eye. The inner corners 3'; of the refracting zones of the lower half of the lens are continuous with those of the respective zones of the upper half of the lens, so that the separating shoulders merge with the surfaces at the inner corners 3'7. Beginning at the merging comers, the shoulders increase in width across the rearating the upper and lower parts merge with the surface near the center of the bulls eye and. in-

crease in width toward the outer edges, following the increase in thickness of the lower half of the bulls eye toward its outer edges.

The refracting zones and the part of the bulls eye in the upper half of the lens have a common principal focal region at X, and are of such curvatures as to project into parallel rays, light originating at such focal region, the upper portion of the bulls eye and the zones being struck from centers 0, along the optical axis OA, forward of the lens with increasing radii as the outer edge of the lens is approached. The lower zones, and the lower half of the bulls eye have a common principal focal region at Y (indicated by the focus of the parallel dotted rays K) a region disposed further from the lens than the focal region X, and are of such curvature as to project, with increasing divergence away from the axis, rays originating at the focal region Y, the lower half of the bull's eye, like'the upper half, having its inner face spherical, but being struck with a radius substantially three times as long, and the faces of the lower zones being segments of conic surfaces whose axes coincide with the optical axis of the lens. The dotted line e in Figure 7 indicates the base of the generating triangle of one of the lower zones, the line. (1 the hypotenuse, and the distance i along the optical axis indicates the altitude of the generating triangle. The angle opposite the axis in the form shown, for instance, may be approximately 5.

With this construction of the lens, and with the light source at the principal focal region of the upper zones and upper half of the bulls eye, such parts will project light originating at such source into parallel rays, as indicated at 9 (Figure 9), while the lower zones and lower half of the bull's eye will project rays of increasing divergence away from the axis as the outer edge of the lens is approached, as indicated by the rays i, the rays near the central portion of the lower half of the bulls eye being parallel to the axis as at h, and the rays projected through the outer portion of the last zone of the series on the lower half being of the greatest spread or divergence, such gradually increasing spread being accomplished, in connection with the structure of the lower half of the lens, by the location of the light source not at the principal focal region of the lower part of the lens, but

at the principal focal region of the upper part thereof. 7

On the-lower half of the lens, and on opposite sides of the central portion of the front thereof, are arranged a series .ofvertically disposed cylindrical flutes 42, to laterally spread the light rays passing through the end portions or segments of the lower refracting zones on the opposite sides'of the cental lower portion of the lens. Such flutes may be struck with equal radii upon centers equally spaced angularly about a common point on the optical axis as indicated in Figure 5.

The resultant beam projected by this optical system, as indicated in Figure 12, is of high in-- tensity in its upper section, as at Q, being composed therein of parallel rays projected through the upper half of the lens, and which reach to distant points on the roadway. In its lower sectiorr, which is abruptly widened horizontally over the upper section, as at r, the beam comprises the lateral portions composed of the wide spread rays of less and outwardly'decreasing intensity projected through the vertical flutes, and which illuminate the sides of the roads and adjacent gutters or side-walks. The central portion T of the lower section of the beam, of higher intensity than the portion s, which is projected through the lower lens section between the fluted portions thereof, illuminates the roadway with decreasing intensity as the front of the vehicle is approached. All of the upper half of the lens enters into the formation of the intense parallel rays for distant illumination and the lower half .forms the illumination of greater width, with decreasingintensity towards the vehicle and with increasing spread towards the sides of the lower portion of the lens. The spread obtained by the fluted sections, added to that obtained in the central portion of the lower lens section, may give to the lower section of the beam a total spread of as much as if desired, depending upon the curvatures used, an adequate spread for emciently lighting the roadway and bordering side-walks and gutters.

The spherical reflector, when utilized with the optical system, as indicated in Figure 11, is preferably arranged with its focus at the principal focal. region X of the zones and bulls eye of the upper half of the lens, to increase the light flux projected through the lens, and, if the condensing lens 23 is used, the latter has its optical axis 0a preferably arranged at an angle with the optical axis of the system, with the top of the condenser inclined forwardly away from the light source, to thereby condense the light passing through the Fresnel below the upper zones, to increase the in-- tensity of lower portions of the light beam, as indicated in dotted lines at I, m.

In the form of the system shown in Figure 8, the shape of the bulls eye is somewhat changed, the lower half having its principal focal region at Z, between the principal focal region X of the upper part of the lens and bulls eye and the principal focal region Y of the lower zones, and the radius of the upper part of the bulls eye is increased and is struck from a point below the optical axis, so that, as shown in Figure 10, with the light source at the principal focal region X, the upper part of the bulls eye will project rays n which, as the optical axis is approached, will converge toward and cross such axis, and the lower part of the bulls eye, will project rays which are parallel adjacent the optical axis, and which diverge as the points of projection are removed from the axis. Thus, the rays which from the upper part of the bulls eye converge and cross the axis will fall at angles below the horizontal, to thus lower the position of the socalled hot spot in the projected beam, as indicated at V in Figure 13, and in crossing the f parallel rays projected by the portion of the lower half of the bulls eye adjacent the axis, will intensify the upper central part of the lower section of the beam, as shown. I also so shape the lower zones as to cause the light rays projected through them to cross each other with equal degrees of spread for the various zones, with the light projected through one of such zones overlapping that projected through adjacent zones, as indicated by the rays b-c inFigure 10, such zones being struck from centers 17 (Figure 8), arranged at decreasing distances below the axis and with decreasing radii, as the outer edge of the lens is approached (except for the outermost zone), and with such exception being of cylindrical curvature of decreasing radii radially of the lens. The outermost zone is preferably struck with a somewhat longer radius than the next adjacent zone to bring its projected light well to the edge of and define the lower section of the beam. The rays from each of the lower zones thus crossing, and overlapping the projec.

tion from adjacent zones, the uniformity of light in the beam projected by the lower part of the lens is increased, as indicated by the cross hatching on Figure. 13, and at the same time the spread or dispersion of the lower part of the beam is retained. In this form of the invention, the upper zones merge with the respective lower zones at their outer edges, the thickness of the upper zones increasing from theirputer edges inwardly with respect to the respective lower zones, and the abrupt shoulders (see M -Figure 8) are reversed in position, being wider at the inner edges of the zones and narrowing toward their outer edges. I

Since this applicationwas filed, I have filed applications Serial Nos. 28,876, and 554,111, both of which applications disclose subject-matter common to this application and to my application, Serial No. 380,281. In this application, however, I am making the broader claims to the modified Fresnel lens disclosed in my said applications, as well as claims to various structural features thereof, and to the combination of such lens with the condenser, and also the'arrangement in which the light source is arranged at one of the focal regions of the lens, claims to other subject-matters being made in my other applications. e

The foregoing detailed description has been given for purposes of illustration of my invention, and no undue limitation should be deduced therefrom, it being understood that such variations in the construction, combination and arrangement of parts, are permissible as do not depart from the spirit of the invention and the scope of the appended claims.

I claim:

1. In a light projector, a modified Fresnel lens having a spherical front face, and on its rear face having circular stepped refracting zones, the zones on the upper half of the lens having a principal focal region, a light source substantially at said focal region, the zones on the lower half of the lens having a focal region differing from that of the zones on the upper half and being of such curvatures as to disperse light fallingon them from the light source, the angles of dis persion gradually increasing from the axis outward, a line of abrupt shoulders extending substantially horizontally and diametrically across the lens between the zones, the zones on the lower half being of longer focal length than the zones on the upper half of the lens.

2. In a light projector, a modifibd Fresnel lens having on its rear face an upper set of stepped zones of decreasing curvature outwardly and radially of the lens, such zones having a'principal focal region, andhaving a lower set of stepped zones differing in curvature from the upper zones and having a focal region displaced from that of the upper zones a d being of such curvatures as to disperse light f ling thereon from their focal region, the angles of dispersion increasing from the axis outward, and a line of abrupt shoulders extending substantially horizontally e and diametrically of the lens and separating the upper and lower zones, in combination with a light source arranged substantially at one of said focal regions. 7 l

3. In a light projector, the combination of a modified Frenel lens having a convex front face and on its rear face having circular stepped refracting zones and a centrally located bulls eye,

the zones and bulls: eye on the upper half of the lens having a principal focal region, the

zones and bulls eye on the lower half of the lens having a focal region, and being of such curvature as-to disperse light falling on them from such focal region, the angles of dispersion gradually increasing from the axis outwardly, a line of abrupt shoulders extending substantially horizontally and diametrically of the lens across the bulls eye and zones, the zones and bulls eye of the lower half being of longer focal length than the zones and bulls eye of the upper half of the lens, in combination with a light source arranged substantially at the principal focal region of the zones and bulls eye of the upper half.

4. In a light projector, the combination with a modified Fresnel lens having a convex front face, and on its rear face having circular stepped refracting zones and a centrally located bulls eye, the zones in the upper half of the lens and the upper half of the bulls eye having a principal focal region, and the zones of the lower half of the lens having a focal region displaced from that of the upper lens and being of such curvature as to disperse light falling on them from their focal region, the angles of dispersion of the lower zones gradually increasing from the axis outward, a line of substantially horizontally disposed shoulders extending substantially diametrically of the lens, such shoulders difi'ering in width between the inner and outer edges of the zones, the zones of the lower half of the lens being of longer focal length than the zones and bulls eye of the upper half, in combination with a light source arranged substantially at the principal focal region of the zones and bulls eye of the upper half of the lens.

5. In a light projector, the combination 05a modified Fresnel lens having a convex front face and having on its rear face an upper set of stepped zones of decreasing curvature outwardly and radially of the lens,and a lower set of stepped zones differing in curvature from the zones of the upper set, a line of abrupt shoulders extending substantially horizontally and diametrically of the lens separating the upper and lower zones,

a central bulls eye of different curvatures in its upper and lower portions, the upper zones having a principal focal region, and the lower zones havinga focal region displaced from the focal region of the upper zones, and a light source arranged substantially at the principal focal region of the upper zones. I o

6. In a motor vehicle headlight, the combination of a modified Fresnel lens having a spherical front face and having on its rear face an upper set of stepped zones of decreasing curvature outwardly and radially of the lens and a lower set of stepped zones of conic segmental form, a line of abrupt shoulders extending substantially horizontally and diametrically of the lens separating the upper and lower zones, a central bulls eye of different curvatures in its upper and lower portions, sets of vertical cylindrical flutes on the forward face of the lens extending not higher than the line of shoulders and disposed on opposite sides of the lower central portion of the lens, the upper zones having a principal focal region and the lower zones having a focal region displaced from the focal region of the upper zones,

' and a light source arranged at the principal focal cular stepped zones of increasing curvature outwardly and radially of the lens, the curvature of the zones of one section differing from the curvature of the zones of the other. section, the focal length of one lens section being different from the focal length of the other lens section.

8. A modified Fresnel lens having an upper set of refracting zones and a lower set of refracting zones, the zones of the lower set varying in ourvature among themselves and difiering in refractive powers from the zones of the upper set, and being struck with radii from difierent centers arranged at decreasing distances below the axis of the lens and with decreasing length of radius as the outer edge of said lens is approached.

9. A modified Fresnel lens having upper and lower sections, each formed with refracting zones of varying curvatures, the upper section having a focal region different from that of the lower section, the curvature of the zones of one section differing from the curvature of the zones of the other section and a centrallyv located bulls eye, part of said bulls eye having a focal region between the focal regions of the upper and lower sections of the said lens.

10. A modified Fresnel lens having upper and lower sections, each formed with refracting zones varying in curvature, a centrally located bulls eye divided into upper and lower parts, the up per section and the upper part of the bulls eye having a focal length different from that of the lower section and the lower part of the bulls eye, the curvature of the zones of one section diiiering from the curvature of the zones of the other section.

11. A, modified Fresnel lens having an upper section and a lower section, the upper section being formed with refracting zones difiering in ourvature with respect to each other, the lower section of the lens being formed with refracting zones differing in curvature with respect to each other and to the zones of the upper section, a centrally located bulls eye divided into upper and lower parts, the radius of the upper part of said bulls eye being struck from a point below the optical axis of the lens.

12. A modified Fresnel lens having an upper set of retracting zones and a lower set of re- Iracting zones, the zones of the lower set varying in curvature among themselves and differing in refractive powers from. the zones of the upper set, each zone being struck with a radius from a difierent center, and a centrally located bulls eye, part of said bulls eye being struck with a longer radius than the zones of the lens.

13. Ina light projector, a modified Fresnel lens having upper and lower sections each formed with retracting zones varying in curvature with respect to each other, and with respect to the zones of the other section, a light source, the upper section projecting rays from said light source into a substantially horizontal beam, and the lower section projecting rays from said light source downwardly and laterally, the zones of the lower section being struck from centers arranged at decreasing distances below the axis of the lens, and with decreasing radii whereby the light rays from the various lower zones will cross each other with substantially equal degrees of spread, and the rays projected through one zone will cross those projected through adjacent zones.

14. A modified Fresnel lens having upper and lower sections, each formed with refracting zones, the zones of the upper section being of varying curvature and differing from the zones 15 of the lower section, the rear faces of the zones of the lower section being substantially segments of conicsurfaces having axes of rotation substantially coinciding with the optional axis of the lens.

15. A modified Fresnel lens having an upper section and a lower section, thelower section being formed with refracting zones differing in curvature with respect to each other, the upper section of the lens being formed with refracting zones diifering in curvature with respect to each other and to the zones of the lower section, the zones of the upper section merging with the respective zones of the lower section at their outer edges and being increased in thickness inwardly with respect to the respective zones of thelower section and forming shoulders between the zones of the upper and lower sections.

16. A modified Fresnel lens having upper and lower sections, each formed with refracting zones, the zones of the one section being of varying curvature and differing from the zones of the other section, the inner corners of the refracting zones of the upper section merging with those of the respective zones of the lower section, and a line of abrupt shoulders separating the upper and lower sections, said shoulders beginning at the merging corners of said refracting zones and increasing in width'toward the outer edges of the zones;

17. In a light projector, in combination, a modified Fresnel lens divided into an upper section and a lower section of stepped refracting zones of varying curvature and of different power, and a centrally disposed two-halves bulls eye, the zones and the half bulls eye in the upper section of the lens having a focal region, the zones and the other half bulls eye in the lower section of the lens having a different focal region, and a light source arranged substantially at one of said focal regions.

18. In a light projector, a. unitary modified Fresnel lens having upper and lower sections, each formed with refracting zones of varying curvatures, the upper section having a focal length different from that of the lower section, the curvature of the zones of one section differing from the curvature of the zones of the other section, and a line of abrupt shoulders extending substantially horizontally and diametrically of the lens separating the upper and lower sections.

19. In a light projector, in combination, a

' modified Fresnel lens having upper and lower sections, each formed with refracting zones varying in curvature, the uppersection having a focal region difierent from that of the lower section, the curvature of the zones of one section difiering from the curvature of the zones of the source.

other section, the lens being formed with fiutings, said fiutings being struck with equal radii on centers equally spaced angularly about a cornmon point on the optical axis of said lens.

v 20. In a light projector, the combination of a modified Fresnel lens having upper and lower sections, each formed with refracting zones of varying curvatures, the upper section having a focal length difierent from that of the lower sec- I tion, the curvature of the zones of one section difi'ering from the curvature of the zones of the other section, a light source in the region of the foci of the sections, a second light source at one side of the first said light source, and a third light source at the other'side of said first light 21. In a light projector, the combination of .a modified Fresnel lens having an upper and a lower set of refracting zones, with the refracting zones of the upper set varying in curvature with respect to each other and with respect to the refracting zones of the lower set, a light source, and a condensing lens interposed between said Fresnel lens and said light source.

22. A light projector including in combination, a modified Fresnel lens having a spherical front face and having on its rear face an upper set of stepped zones of difierent curvatures outwardly and radially of the lens, and a lower set of stepped zones of difiere'nt refractive power, a bulls eye disposed centrally of the lens, a series of vertical cylindrical fiutes on the front face of the lens extending below the horizontal axis of the lens, the lower refracting zones having a common focal region diiferent from the focal region of the upper refracting zones beyond the focal region of the upper zones in a direction away from the lens, and a condenser between said source of light and said lens.

23. In a light projector, the combination of a modified Fresnel lens having upper and lower sections; each formed with refracting'zones of varying curvatures, the upper section having a focal length difierent from that of the lower section, the curvature of the zones of one section differing from the curvature of the zones of the other section, a light source, a condensing lens interposed between said Fresnel lens and said light source, and a reflector behind said light source.

24. A concavo-convex lens comprising two half Fresnel lenses in one unit, the lens halves being provided with refracting zones, the zones of the one half varying in curvature from the zones of the other half, the zones of each half varying in curvature among themselves, the focal length of one lens half being different from the focal length of the other lens half.

25. In a light projector, a modified Fresnel lens having upper and lower sections each formed with refracting zones of varying curvature, the upper section having "a focal length diifering from that of the lower section, the curvature of the zones of one section diifering from the curvature of the zones of the other section, a light source positioned in the region of the foci, and a reflector behind the light source and adapted to collect light from the source and direct it onto the lens.

26. A unitary modified Fresnel lens having upper and lower sections, each formed with refracting zones-of varying curvature, the upper sec- 27. A modified Fresnel lens divided on the 'horizontal median line into an upper half and a lower half, the upper half being formed with refracting steps differing in curvature with respect to each other, the lower half of the lens being formed with refracting steps differing in curvature with respect to each other and to the steps of the upperhalf, each step of the lens being of substantially uniform refractive power.

28. A light projector comprising a modified Fresnel lens having a plurality of sections, one .of which above the horizontal axial plane has a difierent focal region from another section below said plane, both the sections of the lens having refracting zones, the curvature of the zones of each of said sections varying relatively to each other and to the zones of the other section, and a light source in the region of the fool, the formation of the refracting zones of the sections of the lens making the projected beam from the lens as a whole relatively insensitive to limited varying relations between the light source and the foci of the lens sections.

29. In a light projector, a unitary modified Fresnel lens having upper and lower sections, each formed with refracting zones of dififerent curvatures, the upper section having a focal length difierent from that of the lower section, the curvature of the zones of one section difiering from the curvature of the zones of the other section, and a light source positioned in the region of the foci. V

30. A modified Fresnel lens having an upper section and a lower section, the lower section being formed with retracting zones differing in curvature with respect to each other, the upper section of the lens being formed with refracting zones differing in curvature with respect to each other and to the zones'of the lower section, each zone being of substantially uniform refractive power.

31. A modified Fresnel lens having an upper set of retracting zones and a lower set of curved retracting zones, the zones oi the lower set varying in curvature among themselves and differing in refractive powers from the zones of the upper set, each complete zone being struck with a radius from a different center.

32. A modified Fresnel lens having an upper and a lower set of retracting zones, the zones of the upper set varying in curvature among themselves and being struck with radii from various centers and difiering in refractive powers from the zones of the lower set, some of said centers I lying substantially on the axis of the lens and some below the axis thereof.

33. A unitary modified Fresnel lens having upper and lower sections, each section formed with refracting zones of varying curvature, the upper section having -a focal length different from that of the lower section, the curvature of the zones of the one section difiering from the curvature of the zones of the other section, the lens being formed with fiutings for lateral light diffusion.

3%. A modified Fresnel lens having an upper and a lower set of retracting zones, the zones of the upper set varying in curvature among themselves and difiering in curvature from the zones of the lower set and being strucl; with radii from various centers, the zones of the lower set being also strucl; with radii from various centers, some of the latter centers lying substantially below the axis of the lens.

35. in a light projector, a Fresnel-lens having its rear face divided into an upper set a lower set, of stepped rei'racting zones, the zones lOii from the zones of the lower set, the zones of each set difiering among themselves in curva-' ture radially of the lens.

GUSTAW AL'PHONSE RQAPUE LAMBllN-PAREEW.

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