EP1232363B2 - Anti-dazzling transparent screen for illuminants - Google Patents

Abstract

An anti-dazzling transparent screen for elongate illuminant bodies which covers the illuminant body over the length thereof for the purpose of anti-dazzling of a radiating sector of the illuminant body, has a surface formed by elongate prisms extending approximately parallel to one another and aligned substantially along the illuminant body. The prisms are positioned relative to the illuminant body such that on at least one of the prism surfaces a total reflection of the light beams, having entered the respective prism and impinging on this prism surface, occurs.

Description

The invention relates to a Verblendungstransparent for elongated luminous body, which covers the illumination of the body over the length thereof for glare of a radiation sector of the filament, according to the species specified in the preamble of claim 1.

In room lighting, especially in office lighting with the usually required high luminance, the light source from the position of a workplace is so entblenden that no disturbance occurs when glancing at the working template in the field of vision of the worker. In order to obtain a comfortable room lighting, measures are necessary to change the perceived by the working, resulting from the light source luminance. In particular, in office workplaces equipped with screens, direct glare and reflected glare are to be avoided. Direct glare occurs when you look at the work surface, such as screen or paper template, in the field of high brightness is generated. Basically, a direct view of the luminous element must be excluded. For elongated luminaires are glare reduction measures in the transverse direction, in part also known in the longitudinal direction of the luminous element, in which the emission angle of the luminous element is achieved by pulled-down housing walls of a housing receiving the luminous element. These jobs are glare-free, which are outside the radiating sector of the filament.

To glare the luminous body within the Abstrahlsektors defibering are known, which consist of translucent material and cover the filament over its length. From the DE 34 20 414 C2 is a translucent light cover for glare of lights with elongated lamps and a reflector arranged above the lamp is known, which closes off the reflector opening and has on the side facing away from the lamp stretched prisms, which are to scatter the transmitted light. The elongated prisms are approximately parallel to one another and run transversely to the lamp longitudinal axis, wherein, taking into account the refractive index of the material of the Entblendungstransparentes the radiation angle of the filament along the lamp axis to be limited. The prism cross section has the shape of an isosceles triangle, wherein the shape of the prism cross section must be chosen so that a total reflection is excluded so as to influence the light distribution of the lamp transverse to the lamp axis as little as possible. In this way, the luminous body is imaged on the visible surface of the Entblendungstransparentes, the extremely bright image of the filament is often perceived as disturbing. In this case, perceived luminances of about 80% to 100% of the luminance of the light source measured in the field of view of an observer, especially in a sitting position. A glare of the filament in the transverse direction does not aim at the known arrangement.

Purpose of glare is surrounded by a prismatic film. The prisms are arranged parallel next to each other and parallel to the housing longitudinal axis. On the film arranged concentrically to the bar light source, the prisms are in the form of an isosceles triangle and arranged symmetrically, wherein a transparent protective tube is placed around the cylindrical prism body. The rays of light radiated radially from the fluorescent tube and the immediate neighboring rays enter the respective prism approximately perpendicularly through the prism base and are reflected by the prism surfaces, which are reflected by the legs of the rectangular prism cross section. In this way, the radial rays, which are most intense of all radiated light rays, thrown back into the light source and absorbed there, so that with this known arrangement glare can only be achieved with enormous light losses.

From the DE 197 45 844 A1 one knows the use of prism sheets in front of the light exit opening of a reflector. The reflector and prismatic foil surround the luminous element. The prism contour is essentially a planar surface, on one side of which the ribs of the actual prism structure are arranged. The longitudinal axis of the prisms is mounted perpendicular to the lamp axis. To a broad-beam (vehicle interior light) or a directional (vehicle signal light) To obtain light distribution, the reflector is to be dimensioned so that the reflector and the prismatic film form an integral unit.

A tubular Entblendungskörper is also from the EP 0 372 272 A1 known for a mirror grid lamp. The prism structure of a light guide body surrounding the flashlight is intended to scatter the emitted light, wherein the prism structure in a sector can be totally reflective in order to achieve an asymmetrical light distribution. The bright radial beams are subjected to total reflection and thrown back directly into the lamp so that light losses can not be avoided.

From the US 1,941,079 is an elongated luminous body with a surrounding this designed as a trough glass body with prisms known. The prisms are arranged on the surface of the glass body, partly on the inside. The prisms are used to modify the passage of light in the vertical plane.

The DE 1 935 927 describes a street lamp with a spherical lamp. This luminous body is surrounded by an annular light deflecting device which is provided with prisms on its outer periphery. The light deflector is designed so that the light rays are directed towards the ground to be illuminated.

The US 4,450,509 discloses a translucent light for street lighting, with one directly in the center the portion of the bowl lying on the emitting sector of the light source has a prismatic structure for glare reduction. In this case, in the surface alternately flat portions for direct light transmission and prisms with triangular cross-section are provided, which achieve a scattering effect by reflection on a prism surface and subsequent diffraction on the respective other surface. However, with this known prism arrangement for a street lamp, only a glare of the illuminated area, but not of a room can be achieved.

Furthermore, prism arrangements for light conduction in a pipe are known. In the light guide after the US 4,906,070 is on the outside of the light pipe, a prism structure provided with symmetrical to the tube axis aligned triangular prisms, which should reduce the loss of light on the way of total reflection.

The present invention has for its object to further develop the generic Entblendungstransparent such that a completely glare-free and uniform for the room impression room illumination with the highest possible luminous intensity.

This object is achieved with the features of claim 1.

According to the invention a uniform light emission from the Entblendungstransparent is achieved by such an arrangement of the prisms relative to the luminous element that at least one of the prism surfaces, which are totally reflected on this prism surface incident light rays. The Entblendungstransparent is thereby penetrated by a part of the entering into the prisms light rays, while the other part of the occurred radiation beam is reflected by total reflection. Thus, the light beam radially radiated from the light source to the prisms is scattered. With the orientation of the prisms along the luminous element, a complete glare reduction is achieved, and the room is evenly illuminated, especially in the lateral areas of the luminous element. The prisms are to be arranged according to their cross-sectional shape and the refractive index of the material relative to the luminous element so that partial beams of the incident light beams are prevented from direct passage of the transparency by total reflection on a prism surface. In the invention, the transparency of a prismatic film with one-sided prismatic surface, which is arranged to cover the luminous body. By arching the prismatic film around the luminous body, the prisms can be easily brought into the intended position.

Suitably, the side of the Entblendungstransparentes facing the luminous body is formed from substantially flat base surfaces of the prisms, wherein the total reflection takes place at one of the priming surfaces on the side lying beyond the luminous body of the transparency. The totally reflected light bundles are prevented from exiting the prisms beyond the luminous element. Corresponding to the cross-sectional shape of the prisms, that is, the width of the base surfaces and the angular orientation of the protruding prism surfaces on the prismatic surface, the prism sheet is to be positioned at a distance from the lamp such that the desired total reflection at the prism surfaces is achieved. Advantageously, the intended position brought brought about cross-section, wherein the prisms a triangular cross-section, wherein the base surface of the prisms of the base side of the triangular cross section corresponds and faces the filament. In this case, of the light bundle entering through the base surface, the part which impinges on one of the limb surfaces of the prism is totally reflected, while the light bundle incident on the other limb surface of the triangular prism penetrates the glare-deflecting transparent under deflection. The leg surfaces correspond to the triangle sides of the prism cross section, which are angled to the base side.

Particularly advantageously, the prisms have the shape of an isosceles triangle, wherein the radiation angle of the Entblendungstransparentes are adjusted as required by curvature of the prismatic film. It is considered advantageous if the totally reflected light bundles are reflected back next to the axis of the filament. The prisms with the cross-sectional shape of an isosceles triangle can be easily brought by appropriate curvature in the intended position, in which at one of the catheter surfaces a Total reflection results when the base areas of the individual prisms each lie at an angle other than 90 ° to the light rays striking the respective prism.

• Fig. 1 eine Ansicht einer Leuchte mit einem erfindungsgemäßen Entblendungstransparent,
• Fig. 2 einen Querschnitt einer Leuchte mit einem erfindungsgemäßen Entblendungstransparent,
• Fig. 3 bis Fig. 6 Strahlengänge an einem einzelnen Prisma in unterschiedlichen Winkellagen des Prismenquerschnittes zum Leuchtkörper,
• Fig. 7 eine Darstellung der Winkelbeziehungen der Strahlengänge,
• Fig. 8 eine Darstellung der Strahlengänge bei zwei benachbarten Prismenstrahlengängen,
• Fig. 9 und Fig. 10 schematische Darstellungen zur Bildung der Transparentgeometrie bei einer gewölbten Folie,
• Fig. 11 und Fig. 12 Querschnitte durch den Leuchtkörper und die Strahlengänge der auf die Prismenfolie auftreffenden Lichtstrahlen.

Embodiments of the invention are explained below with reference to the drawing. Show it:

• Fig. 1 a view of a lamp with a Entblendungstransparent invention,
• Fig. 2 a cross section of a lamp with a Entblendungstransparent invention,
• Fig. 3 to Fig. 6 Beam paths on a single prism in different angular positions of the prism cross section to the luminous element,
• Fig. 7 a representation of the angular relationships of the beam paths,
• Fig. 8 a representation of the beam paths at two adjacent prism beam paths,
• FIGS. 9 and 10 schematic representations for the formation of the transparent geometry in a curved foil,
• Fig. 11 and Fig. 12 Cross sections through the luminous element and the beam paths of the incident on the prismatic light rays.

Fig. 1 shows a perspective view of a lamp 7, which is preferably attached to the room lighting to the ceiling. The luminaire 7 comprises a housing 3 in which an elongate luminous element 2 is arranged is. On the illuminated space to the facing, open side of the housing 3, a prism sheet 1 a, 1 b, 1 c is arranged, which covers the luminous body 2 over its entire length. The prism sheet is made of translucent material and has on the visible, that is the side facing away from the luminous body 2 a prismatic surface. The prismatic surface is formed by approximately parallel to the longitudinal direction of the luminous body 2 adjacent, continuous prisms, which scatter the light bundle entering on the inner side of the film. The anti-glare effect of the prize foil is determined by the relative position of the respective prism cross sections, which can be varied by the dome radius of the prism foil 1a, 1b, 1c. Especially with prismatic films with symmetrical prismatic cross-sections, as in the present case triangular cross-sections with isosceles triangles, the desired deblading effect can be individually adapted to the spatial conditions of the space to be illuminated by the radius of curvature around the luminous element 2. The optical operation of the prism sheet for glare removal of the luminous element 2 will be explained in more detail below. In the Fig. 1 are different Wölbungsradien 1a, 1b and 1c shown by way of example, with expedient the curvature of the prismatic film over the entire length of the filament 2 remains the same. The prismatic film rests on a curved edge 5 of the end walls 4 of the lamp housing 3, wherein the contour of the curved edge 5 determines the intended radius of curvature of the film. The prism sheet can also be flush or sunk onto or into the respective end wall 4. The flat curvature designated 1a has a flat light distribution curve, which has a low luminous intensity approximately between 60 ° and 80 ° to the vertical of the filament. A medial curvature of the prism sheet 1b leads to a light distribution curve that emits no light between about 60 ° and 90 ° to the vertical. With the outer geometry of the prism sheet 1c turned up, the luminance in the light distribution curve is minimal in the angular range between approximately 75 ° and 90 ° to the vertical.

Fig. 2 shows a cross section of a lamp housing 3 with a prism sheet 1 for glare removal of the elongated filament 2. The prism sheet 1 covers the Abstrahlsektor of the filament 2 in the room to be illuminated over about 180 °. The prism sheet 1 is surrounded in the present embodiment of the luminaire 7 according to the invention by a housing bottom 18, which may be highly transparent or structured in order to achieve optical lighting effects. The lying parallel to the longitudinal axis of the luminous body 2 side edges of the prism sheet 1 and the housing bottom 18 are enclosed in a housing support 22. The housing support 22 comprises two profiled rails, which extend approximately parallel to each other on both sides of the luminous element 2 and receive the edges of the prism sheet 1. The prism sheet 1 is fixed in the housing supports 22 with such a width that results in a curved course of the prisms around the luminous element 2. The anti-glare effect of the curvature of the prism sheet 1 will be explained in more detail below. Suitably, the prism sheet as shown in the present example is arranged approximately mirror-symmetrical to a diameter axis of the filament 2, which is perpendicular to the transverse axis between the housing supports 22.

The housing supports 22 are on the top, d. H. opposite the prism sheet 1 side provided with spacers 20 which carry a housing roof 17. The housing roof 17 is transparent. The housing roof 17, the housing support 22 and the housing bottom 18 with the prism sheet 1 therein are arranged to each other such that between the housing roof 17 and the housing bottom 18, an air gap 19 is formed. Through the air gap 19 there is an exchange of air between the housing interior and the environment of the lamp 7, wherein the air can circulate without particles can fall from above into the housing gap 19. Over the length of the lamp 7, a plurality of spacer elements 20 are provided, on which the housing roof 17 are each secured with clamps 21 or the like. The right side of the drawing figure shows a section at the height of a spacer element 20, while on the left half a section is shown on a lying between two spacer elements 20 transverse plane of the lamp 7, wherein the air gap 19 is clear.

The FIGS. 3 to 6 show the refraction ratios of the light rays at the prisms using the example of a prism shown individually. The prism sheet is arranged such that the base surface 8 faces the base side of the triangular cross section of the luminous body 2. In the present case, the leg surfaces 11, 12 of the isosceles triangular cross-section of the prism are at an angle of 45 ° to the base surface 8, taking into account the distance of the prism 10 to the luminous element 2 in a certain range of the angle of attack of the base surface 8 to the radials of the filament. 2 the desired total reflection at one of the leg surfaces 11, 12 occurs. Each prism of the prism sheet is in such an angular position to the luminous element 2, that the light beams 13 in the Abstrahlsektor Δε of the filament 2 at an angle deviating from 90 ° through the base surface 8 enter the prism 10. At a shallow angle of the base surface 8 to the emitted light beam 13 in the radiation sector Δε according to Fig. 3 the incident on the upper leg surface 12 light beam 16 is broken at the leg surface 12 on exiting the prism and radiated into the space to be illuminated. The incident on the lower leg surface portion 11 of the radiated radially from the luminous body 2 light beams 13 is totally reflected when hitting the leg surface 11, wherein the refracted light beam 14 exits in a substantially orthogonal directions to the radiation sector Δε with refraction on the second leg surface 12. The angle of attack of the prism 10 or its base surface 8 to the luminous element 2 is in the present case about 15 °. It will be apparent that the invention allows the light beam in the prism to partially exit under diffraction and partially through Rejecting total reflection at a prism surface, even with prism cross-sections other than that of the isosceles triangle is possible. For example, a triangular cross-section with different leg angles could be selected, whereby an exactly orthogonal alignment of the base surface to the luminous element 2 would also be possible. Also, other prism cross sections are conceivable, such as trapezoidal cross sections or the like, wherein total reflection occurs at a prism surface due to the prism structure and position.

Fig. 4 shows a prism 10 of the same geometry as in Fig. 3 in a position with a larger angle of attack to the luminous element 2, in the present case about 30 °. It is clear that the light rays 16, which are refracted at the upper leg surface 12 and pierce the leg surface 12, in approximately the same direction as in the lower angular position of the prism 10 in accordance Fig. 3 be radiated. Accordingly, given the distance of the prism to the luminous element 2, the emission direction of the totally reflected light rays 14, which impinge on the lower thigh surface 11 in the prism 10, can be influenced by the angular position of the prism 10 relative to the luminous element 2. By rotation of the prism in an angular range in which occurs on the leg surface 11 total reflection, that is, the emission direction of the totally reflected light beams 14 can be varied in a larger angular range than the diffraction region of the only refracted light beams 16 upon passage of the upper leg surface 12. An enlargement The angle of attack of the prism base 8 leads up to a critical angle to a proportionately greater influence on the angular range of the total reflection than that of the refraction.

Fig. 5 shows the beam paths on a prism with triangular cross-section, which is opposite to the position of the prism in Fig. 4 relative to the horizontal reference axis 23 is rotated about the light source 2. The radiation angle Δε of the light beam impinging on the base surface corresponds to the prism arrangement according to FIG Fig. 4 , Due to the offset with respect to the horizontal axis 23, however, there is a greater average angle of incidence ε _{0 of} the beam onto the prism 10. The inclination of the base surface 8 to the vertical thus corresponds to the prism Fig. 4 and is about 30 °. As a result, the light beams refracted at the base surface 8 are refracted at the lower leg surface 11 and deflected out of the prism 10 upon exiting. The part of the beam which impinges on the upper leg surface 12 is totally reflected and then strikes the other leg surface 11. Depending on the angle of incidence, either refraction and exit of these light beams 14a from the prism 10 or further total reflection takes place Light rays 14 b exit through the base surface 8 of the prism 10. The curvature of the prismatic film around the luminous element 2 determines the position of the individual prisms relative to the luminous element 2, whereby, like the beam paths of the prisms of the same cross-section Fig. 4 and 5 show, by the relative position of the prisms, the desired glare can be achieved.

The influence of the inclination angle of the total reflection incident light beams provided leg surface relative to the base surface is described below with reference to Fig. 6 explained in more detail. The angle of the leg surface 11 relative to the base surface 8 is denoted by α, wherein the angle α 11 α ₂ , α ₃ , α ₄ , α ₅ different prism angle between leg and base correspond. If the base surface 8 is arranged at an inclination angle ε to the luminous source, total reflection takes place at the prism surface 11 if the following inequality is fulfilled: $$\mathrm{\epsilon }\le {\mathrm{\epsilon }}_{\mathrm{tg}}:=\arccos \left[\sin \left(\mathrm{\alpha }\right)\sqrt{{\mathrm{n}}^2-1}+\cos \left(\mathrm{\alpha }\right)\right]$$

In the preferred angular range of the prism cross sections 15 ° ≤α≤75 °, the equation derived therefrom applies: $$\begin{array}{||}\hline \mathrm{\epsilon }\le {\mathrm{\epsilon }}_{\mathrm{tg}}:=\frac{\mathrm{<figure-callout\; id="2"\; label="\pi "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{2}+\mathrm{n}\left[\mathrm{\alpha }-{\mathrm{<figure-callout\; id="1"\; label="\alpha \; tg"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}_{\mathrm{tg}}\right]\left\{1+\left[{\mathrm{n}}^2-1\right]\frac{{\left[\mathrm{\alpha }-{\mathrm{<figure-callout\; id="2"\; label="\alpha \; tg"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}_{\mathrm{tg}}\right]}^2}{6}\right\}\\ \hline\end{array}$$

α:

Prismawinkel zwischen (linkem) Prismaschenkel und Basis

ε:

Einfallswinkel des Lichtes bezogen auf die Basisneigung
=δ_q-δ_b, wobei
δ_q: die Neigung des einfallenden Strahls zur Horizontalen
δ_b: die Neigung der Basis zur Horizontalen

n:

Brechungsindex des Prismas

α_tg:

Brechungswinkel, genügt der Gleichung:
n sin (α_tg)=1.

With the names:

α:

Prism angle between (left) prismatic skeleton and base

ε:

Incidence angle of the light relative to the base inclination
= δ _q -δ _b , where
δ _q : the inclination of the incident beam to the horizontal
δ _b : the inclination of the base to the horizontal

n:

Refractive index of the prism

α _tg :

Angle of refraction, satisfies the equation:
n sin (α _tg ) = 1.

Fig. 6 shows the basic angular relationships of the incident light rays in the prism and the deflection angle on a prism with isosceles and right triangular cross-section, wherein the inclination of the prism base to the luminous body 2 is about 15 °. At a ratio of the distance between the luminous body 2 and the prism base 8 and the length of the prism base 8 of approximately 1, a mean angle of incidence of ε ₀ = 45 ° results for the illustrated prism. The emission sector Δε covered by this prism is approximately 40 ° between the boundary light beams respectively incident at the base surface peaks in accordance with the boundary incident angles ε ₁ and ε ₂ . The incident on the right leg surface 11 of the prism light rays are refracted for direct room illumination to the visible outside of the prisms. The light deflection takes place in the angular range between ε _g1 and ε _g2 of about 30 °. The incident on the left leg surface 12 rays are totally reflected and subsequently additionally refracted on the right leg surface 11, wherein the refraction to the base surface 8 out, so the luminous body 2 out. With a further extension of the distance of the prism of the luminous element 2, a second total reflection of the light rays already reflected on the first femoral surface can also occur, taking into account the Prismengeometrie. Due to the double total reflection of the entire angular range of the provided for total reflection first leg surface in the direction of the luminous body 2 is reflected.

In the presentation of the Fig. 7 the prism angles α ₁ to α ₅ relative to the base surface 8 are indicated. The base surface 8 is here for a better overview about horizontally. The inclination of the leg _surfaces 11 is _plotted at inclination angles Δ _lip1 to Δ _lip5 from the vertical. The _{critical angles} at which total reflections arise with prisms having the corresponding prism angles α are _denoted by ε _tg1 to ε _tg5 . As soon as the angle of incidence ε of the light _{exceeds the critical} angle ε _tgi with i = 1 to 5, that is to say in the region lying in the direction of the arrow 24, a total reflection occurs on the leg surface 11.

In the prism sheet to glare the lamp, the curvature of the film is chosen such that the individual prisms are each arranged such inclined to the luminous body that the desired glare or the desired light distribution curve of the luminous body is achieved by total reflection. The inclinations of the individual prisms can be different, but in each case, taking into account the prism length and the respective distance to the luminous element, the angles of incidence on the femoral surfaces within the prisms are in the angular range of total reflection. The angle of inclination of the prisms are increased in the circumferential direction of the prism sheet around the luminous element in each case with respect to the preceding prism. The increase in the angle of inclination between the prisms can be approximately in the angular range of 1 ° to 2 °.

Fig. 8 shows a section of a prism sheet with two illustrated, adjacent prisms 8, which are inclined by about 15 ° to each other. In this case, the inclination angle of the inclined surfaces 8 in the upper prism are approximately _Δb1 = 15 ° and at the lower prism _Δb2 = 30 °. The light rays 16 passing through the prisms in total, which are respectively refracted on the left side surface 12 of the two prisms, exit in the critical angle range between ε _g1 = 15 ° and ε _g2 = 30 °. The light beams 14, which are initially totally reflected on the right leg surface 11, then on the left leg surface 12, are deflected away from the luminous element 2 into the space to be illuminated.

An advantageous curvature contour of the prism foil, in which the refraction range of the prisms is optimal, is in Fig. 9 shown. The prism sheet 1 is in the circumferential direction around the filament 2 composed of circular segments 9 with a plurality of prisms, wherein the curvature radii of the circular sectors each lead to an optimal expansion of the beam region in which the incident light is refracted. The course of the prism foil geometry is formed by engagement of the circle segments 9, wherein a subsequent circle segment 9 to the previous circle segment by such rotation about the axis of the filament 2, that the outer boundary ray of the recessed circular segment contour with the inner boundary ray of the previous circle segment contour is as congruent. In this way one obtains adjacent circle segments, which have a common tangent at the common point of intersection. In the respective circle segment, taking into account the Prismengeometrie and the distance corresponding to the optimal radius of curvature given a refraction of light, which lead to the optimal light distribution curve and light scattering to glare the lamp 2.

Fig. 10 shows the curved arrangement of the prism sheet 1 relative to the luminous element 2, in which the curvature of the prism sheet 1 by a as above Fig. 9 described conflict of circle segments is formed. The ratio of the distance a of the luminous bodies 2 from the prism foil 1 to the respective curvature radius W is the same in each region of the prism foil 1. An optimal glare of the luminous element 2 by blanking individual beam on the way of total reflection on each leg surface of the prisms is carried out at such a curvature of the prism sheet 1, that in each region of the prism sheet 1, the distance a of the filament 2 is less than the curvature radius W of Prism sheet 1.

The beam paths at a similar Fig. 10 formed vault contour is in Fig. 11 shown. The prism sheet 1 covers in the illustrated section a radiation sector of the luminous body 2 an angle of incidence of the radially emitted light beams 13 of about ε ₂ = 60 °. The angular range of the refracted light beams, which are emitted with diffraction on the prismatic surface of the film 1 opposite the filament 2 in the space to be illuminated, lie in an approximately equal angular range as the angle of incidence ε ₂ , but the radiation of the refracted light beams in the emission ε _g1 + ε _g2 is shifted from the horizontal. The Broken beams in the emission region of the luminous element 2 from ε ₁ to ε ₂ are directed into the angular ranges of the critical angles ε _g1 and ε _g2 , in each case based on the horizontal. In the present exemplary embodiment, ε _g1 = 30 ° and ε _g2 = -30 ° and therefore | Δε | = (ε _g1 -ε _g2 ) = 60 ° = ε 2. The emission range of the luminous body 2 of ± 60 ° becomes in an angular range deflected by ± 30 °.

Due to the described curvature of the prism sheet 1, the totally reflected light rays 14 are reflected back in a lying away from the luminous body 2 space portion behind the film 1, whereby a further glare of the lamp 2 takes place. Furthermore, partial beams of the totally reflected light bundles 14 on the path of the refraction on the respectively other side surface of the prisms in an angular range ε _{trg1 can be emitted} as scattered light on the side of the prismatic film 1 lying beyond the luminous _element 2 into the space to be illuminated. In the illuminated room light beams are therefore emitted with a variety of alignments with a favorable scattering effect. Such an arrangement of the prisms can advantageously by a mirror-symmetric curvature of the prismatic film as in Fig. 2 shown to be achieved.

The luminosity of the prismatic film is homogeneous over the entire surface of the film, with similar luminances being visible from all viewing angles on the prism sheet. The scattered light is visible, but does not cause glare.

Fig. 12 shows the arrangement of a prism sheet with the already in Fig. 7 illustrated curvature contour. In this case, right-angled, isosceles prisms and a ratio of the distance between the luminous body 2 and prismatic film and the curvature radius W of about 0.33, the desired light distribution is achieved. This ratio is expediently less than three, wherein distance / bulge ratios which are smaller than 1 have been found to be particularly advantageous. As can be seen in the enlargement of the dashed rimmed area of the prism sheet, a large part of the totally reflected light rays 14 is reflected back to the filament 2 facing side of the prism sheet, but isolated light rays on the leg surfaces of the individual prisms 10 emerge such that they on the Thigh surfaces of the adjacent prism impact. These transverse beams emerge after multiple refraction at several prisms as scattered light 15, with further beam directions of the light emitted by the prism sheet 1 being formed. The light scattering with a variety of beam directions results in a uniform and pleasant to be considered brightness, which is given an increased feeling of comfort of the persons located in the lighted room.

Claims (9)

1. Elongate illuminated body with anti-dazzle transparent screen, which covers the illuminated body (2) across its length in order to prevent the dazzling effect of a radiating sector (α) of the illuminated body (2), the surface of the transparent screen being formed by elongate prisms (10) lying adjacent to one another more or less parallel and oriented essentially alongside the illuminated body (2), the transparent screen being made from a prismatic film (1) with a prismatic surface on one side and the prismatic film (1) is disposed around the illuminated body (2) in a cambered arrangement, the prisms (10) having a base surface (8) and lateral surfaces (11, 12) and, with base surfaces (8) directed towards the illuminated body (2), lie relative to the illuminated body (2) in such a way that, on at least one of the lateral surfaces (11, 12), the part of the light beams (13) entering the respective prism (10) hitting this lateral surface (11, 12) is totally reflected and, on at least one other lateral surface (11, 12), the part of the light beams (13) entering the prism (10) hitting this lateral surface (11, 12) penetrates, the prismatic film (1) being disposed in a cambered arrangement such that the distance (a) of the illuminated body (2) from the prismatic film (1) is shorter than the camber radius (W) of the prismatic film (1) in every area of the prismatic film (1).
2. Illuminated body as claimed in claim 1,
   characterised in that the ratio of the distance (a) of the illuminated body (2) from the prismatic film (1) to the respective camber radius (W) is essentially identical in every area of the prismatic film (1).
3. Illuminated body as claimed in claim 1 or 2,
   characterised in that the side of the transparent screen (1) facing the illuminated body (2) is formed by flat base surfaces (8) of the prisms (10).
4. Illuminated body as claimed in one of claims 1 to 3,
   characterised by a triangular cross-section of the prisms (10) in which the base side of the triangular cross-section corresponds to the base surface (8) of the prism (10).
5. Illuminated body as claimed in claim 4,
   characterised in that the cross-sectional shape of the prisms (10) is that of an isosceles triangle.
6. Illuminated body as claimed in one of claims 1 to 5,
   characterised in that the prismatic film (1) is disposed such that there is a total reflection on one of the respective lateral surfaces (11, 12) of the prisms (10).
7. Illuminated body as claimed in claim 5 or 6,
   characterised in that the base surfaces (8) of the prisms (10) subtend an angle with the light beams (13) hitting the respective prism (10) that is not 90°.
8. Illuminated body as claimed in one of claims 1 to 7,
   characterised by an optical path in the prism (10) which is such that the totally reflected light beams are at least partially deflected past the illuminated body (2) at a distance therefrom.
9. Illuminated body as claimed in one of claims 1 to 8,
   characterised in that the illuminated body (2) is accommodated in a housing (3), the end walls (4) of which lying opposite one another in the longitudinal direction of the housing (3) are provided with a cambered edge (5), the contour of which matches the camber of the prismatic film (1) and on which the prismatic film (1) lies.

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