US 2229693 A
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Jam 28, 1941 F. R. Dn-:TRLcH ANTIDAZZLE HEAD LAMP Filed Feb. 17, 1938 Patented Jan. 28, 1941 UNITED STATES 2,229,693 AN'rIDAzzLE HEAnLAr/'ne Friedrich Richard Dietrich, Munich, Germany, assignor to Max Hermann Wende, Zurich,
Switzerland Application February 17, 1938, Serial No. 190,966 In Germany February 18, 1937 1 Claim.
The invention relates to antidazzle head lamps particularly yfor use in motor Vehicles.
One of the objects of the present invention is to provide a yhead lamp which produces a completely dazzle-free light.
Another object of the invention is to produce a lamp the light of which is laterally diffused while the source of light Vas well as the reilector and the diffusing element a-re completely hidden from view under a normal angle of observation behind a screen.
A -further object is to produce a head llamp yielding brightness values yon the road which -are greatest centrally infront of the lamp at a certain distance therefrom and which -diminish gradually towards the sides and towards the vehicle.
Still another object is to produce a head lamp in which the light emitted from the source, rthe reector `and the diiusing elements is invisible under a normal angle 'of observation, while the road is illuminated to a substantially uniform brightness.
The `above mentioned and lother objects, -Which will appear -as the description proceeds, are accomplished by the arrangement and combination of elements specied in the following description, set forth in the appended claim and illustratively exemplified in the accompanying drawing, in which:
Fig. 1 is a head lamp according to the invention shown in vertical section.
Fig. 2 is a horizontal section of the head lamp shown in Fig. 1.
Fig. 3 is a section through the beam produced by the lamp shown in Figs. 1 and 2.
Fig. 4 shows a second embodiment of the invention in horizontal section.
Fig. 5 is a vertical section of the head lamp shown in Fig. 4.
Figs. 6 and 7 are vertical sections of further forms of a head lamp.
According to Figs. 1 and 2, a reflector l consisting of a quarter of an ellipsoid is mounted in a housing 2. At the focal point F of the quarter ellipsoid la lamp is arranged. The point of Iconvergence of the elli-psoid is designated F1. The housing 2 has a projecting portion 3 serving as a screen or hood which covers at the front the opening Al of the quarter ellipsoid through which the light emerges, and which is approximately bounded below by a horizontal pl-ane through the optical -axis A, A1. The light outlet opening 4 is covered by a glass `disc -5 Which is therefore disposed behind the hood 3, land between the focal point F and the point of `convergence F1. Beneath the reflector I there is, inside the housing 2 a semi-spherical mirror i6, the center point of .which coincides with the focal point F of the: The housing 2 extends be-l quarter ellipsoid l. low the plane intersecting the optical axis A, A1 and that part of the housing below the axis A, A1 may be provided with `a -coVer 1. The rays `indicated pass through the glass disc 5 and emerge -through the horizontal opening 8'dis' posed 4between the lower end of the disc 5 and the foremost end of the screen 3. y
Owing to :the rays from the source of light disposed in the focal point F crossing each other in the horizontal plane through the optical axis 1'5 A, A1 they lcan emerge through the horizontal opening 8 in forwardV and downward direction,
without it being possible for an oncoming peras a plane-parallel element, the intersection of all the rays at the point of convergence F1 would produce a shadow inthe form of a ycone centrally in fron-t lof the head lamp.
In order to eliminate this lconical shadow, the glass disc 5 is provided with a plurality of adjacent cylindrical flutes 9 which are vertical to the intersecting plane A, A1 bounding the reiiector on its under side. The vertical cylindrical iiutes 9 extend the point of convergence F1 into a line of convergence F2, so .that the rays viewed in plan extend along the chain lines While if the cylindrical lenses -9 were not used they would extend as shown by the dash lines (see Fig. 2). In a side view all the rays intersect on the line of convergence F2. c
Owing to this distribution lof the light, if the beam is viewed in section, a iight image as shown in Fig. 3 results. The maximum brightness Values are disposed below the limit of darkness in part I0 and lthe diiused light in part Il. The cone of shadow is eliminated. It is impossible for an oncoming person to see the lens. The distribution of the light takes place rearwardly of the point of convergence F1 or the line of convergence F2, so that a View into the utes 9, and
shadow in front of the lamp, there is, nevertheless a lateral diiiusion, as shown by the rays in Fig. 2. As, however, the light diminishes in intensity inversely as the square of the distance from the source of light, it is essential, in order to throw the light forward as far as possible and also to ensure uniform illumination of the road surface so that the greatest brightness values are concentrated forwards and the light is caused to diminish gradually laterally and towards the vehicle.
This is specially provided for by the construction shown in Figs. 4 and 5. The glass disc 5 shown in Figs. 1 and. 2 is in this case replaced by a cylindrical lens I3, the; cylindrical axis .of which is vertical to the intersecting plane A, A1. By means of this cylindrical lens I3 the rays, considered horizontally, are parallel, though there is intersection of the rays in the line of convergence F2 (see Fig. 5). It will be seen that lateral diiusion no longer exists as compared with the construction shown in Fig. 2. The cylindrical lens I3 may, however, in order to still produce a certain slight lateral diffusion, be provided on one side with a 'plurality of cylindrical iiutes 9 of small radii, the axes of which are, of course, also vertical to the intersecting plane A, A1.
Although 'normally an ellipsoidal reflector Will be used, because the latter has by nature a focal point and a point of convergence, which are essential conditions for the invention, it is, nevertheless, possible to make use of an optical system without employing an ellipsoidal reector.
A possibility of producing points of convergence, Without the use of an ellipsoidal mirror is shown in Fig. 6 in connection with a head lamp shown in vertical section.
In this case, there is arranged in front of the aperture of a paraboloid mirror I4 a collector lens I5, which is provided Von one side with cylindrical flutes 9 in accordance WithrFig. 2. In this case, there exists a plurality of lines of convergence F3, F4, F5, and in frontof the foremost line of convergence F5 lies the screen 3. The lens I5 is of course, disposed between the focal point F and the rearmost line of convergence FB.
If the cylindrical lens I5 shown in Fig. 6 is provided with steps of different refractive power (different radius) it is possible, as shown in Fig. '7, to obtain, instead of a plurality of lines of convergence, one single line of convergence F5. Of course, in this case also, only those parts of the parabolic mirror I4 and the cylindrical lens I5 are used which lie above the intersecting plane A, A1.
What I claim is:
A headlight comprising a reector having substantially the shape of a quarter section of an ellipsoid, a lamp disposed in the inner focus of said reiiector, a curved dispersing prism disposed in the front opening of said reflector approximately halfway between the inner focus and the point of convergence thereof, the axis of said prism traversing the reiiector axis at right angles to the plane dened by the axis and the side edges of the reflector and its curvature being sucient to stretch the converging point of the reflector to a converging line extending in said plane transversely of the reflector axis and having a length approximately equal to the width of said reflector opening in said plane, and a light impervious screen for said reilector and prism, one edge of said screen being disposed adjacent said plane in front of and substantially parallel to said line of convergence and having a Width substantially equal to the length of the latter.
FRIEDRICH RICHARD DIETRICH.