The invention relates to light directing louvers according to the preamble of the main claim.

Manufacturing light louvers with two functional sections is well known. In 212 508 B1 , Figs. 5 and 7, the functional section with light control of the interior is a concave curved mirror with the disadvantage that in order to achieve the desired anti-glare, steep light deflection inwards, a very large louver height h is required, which allows a reduced viewing of about 70% between the louvers. In the case of a ladder cord wire, the ladder cord steps do not lie in the folds, in a form-fitting manner. Forming of a small pack of louvers comprising blinds that have been moved close together is prevented with disadvantages.

This also applies to CH 694 947 A5, Figs. 1 1 and 13. Fig. 1 1 and Fig. 13 also have a reflector section 120 with a flat daylight redirecting contraption into interior. Redirect the daylight does not take place, however, for Zenith radiation. The disadvantage of the flat daylight redirecting contraption is the glare in the interior due to the flat daylight redirecting contraption of the central flat section. This can occur directly in the eye of the viewer. The louver can, therefore, be used at al all events in the upper area above the eyelevel. Another disadvantage is the requirement of 2 types of louvers in one blind.

In PCT / CN 201 1/073552 Figs. 36 to 38 show surface folds in the first part oriented for sunshine, whose folded sides that direct the daylight have an angle of 10° to the horizontal, so that the collected zenith radiation is deflected only to the underside of the upper louver, without illuminating the interior space in depth. The mutually perpendicular folded sides in the first section prevent a light deflection of flat sun in the interior, so that with these louvers that have been developed primarily for sun and light protection, lighting the room with deflected zenith light / sun is not possible. This also applies to DE 198 285 42 A1. Here a light-guiding section 97 was specified for the light-deflecting section 91 in Fig. 1 1. Vertically an incident light radiation is indeed softened, however, does not fall on the blind because of shading of the upper louvers. Even zenith radiation with angle of incidences < 90 ° is deflected primarily on the angled section and back into the outer space and though not for room illumination in the interior. PCT/IB2013/060877 describes a serrated concave-convex louver with a dual function as a reversible louver with zenith-light directing function or in reverse mounting position as solar shading with deflecting function of the high sunlight incidence angle in primary horizontal position. The background to the development of louvers is the possibility to wind up the same onto a coil. The possibility of zenith-light directing - as is desirable, especially for large buildings depths, to save artificial lighting is, however, extremely limited due to the folded structure. The high sun (see Fig. 1 .0) incident on the functional part to redirect the daylight inwards is only minimal, but directed essentially outside. Only a few inward deflected light rays actually fall between the louvers into an interior. A large part applies only to the underside of the upper louver; maximum share is retro- reflected adversely toward the sun incidence. The daylight-directing folded sides have an inclination angle of about 30°, but the angled daylight-deflecting folded sides are so large that only a minimal share of zenith radiation can be deflected inside.

The innovation has therefore set itself the task of developing a zenith daylight-directing louver, which is disposed in the skylight of a blind or window and deflects most of the zenith radiation with incidence angles between 40° and 80° in flat angles into the room and shows a deflection for high solar radiation in the lower region of the blinds hanging. The aim is to optimize the following daylight-directing functions:

As zenith light-catcher louver:

o Primary daylight-directing for incident sunlight > 60°,

o Directing the daylight of zenith radiation while largely avoiding back reflection and with a predominantly flat and horizontal directing the daylight in large interior depths,

o Avoiding light deflection on the underside of the upper louver (mono-reflectivity) o Scattering of radiation at an interior ceiling.

Sun protection louver for zenith radiation:

o Primary mono-reflective light deflection of high, overheating summer sun for zenith light- and incident sunlight of > 50°.

o Primary mono-reflective daylight directing for flat sunlight radiation, which acts on the functional part with light deflection into the interior.

Light deflection to the interior ceiling at angles > 25 °, in order to avoid dazzling near the window in the workplace. These highly complex tasks of optimizing a light directing optics for two different louvers with opposing functions and under the loading condition of utmost mono-reflectivity arise from the physical building facade optimization and the interior illumination.

At a light directing facade the following demands are set:

1 . Lighting requirements:

Ensuring daylight supply function.

2. Building technical and climatic requirements:

Minimizing external heat load.

3. Configuring the functional areas within a blind:

- Functional zone that primarily fulfils a protective function against overheating.

- Functional zone that primarily fulfils a daylight supply function.

- Further, it requires that the blind facilitates a very good view.

4. Using only one louver with two functions by rotating the louver about a vertical axis.

5. Dimming of the interior.

6. Possibility to thread the louver in the guide cord and moving the cords together to a small louvers stack.

7. Preparing the louver as a roll shaped profile made of a strip material.

The solution to these varied tasks of optics, physics and crafts is carried out by the characterizing part of the main claim.

All indicated percentages of light transmission and reflection relate to a purely geometrical determination of the louver upper side without considering the actual reflectance values of used surfaces or rounded edges that cause scattering.

The inclination of the daylight-directing folded sides b ₄ in daylight directing section 1 1 , 41 at an angle β, mainly in the figures between 0° and 30°, gradually increases from the louver-middle to the louver edge 20. The daylight-directing folded sides b ₄ in the first lamellar section are at least configured, partially twice as wide as the angled folded sides. The light-receiving folded sides bi / b ₂ in daylight-deflecting louver section 10, 40 are disposed at angles a and β. a amounts to about 40° to 60°, increasingly from the louver centre to louver edge and β amounts to approximately 30° to 60°, increasingly towards the louver centre. In the second daylight-deflecting section, the folds are configured at angles γ circa 80° to 100° and in the section directing the daylight inward γ > 100° to 160°. The angle will vary depending on the louver spacing and inclination angle of the shadow line S and are, therefore, to be understood as exemplary. Essential to the invention is the functionality.

The design features of the main claim ensure the desired physical and photometric characteristics of the light guiding blinds. The features can be represented at least for cross-section parts of the louvers as follows:

∑ b ₄ /∑ b ₃ >∑ bi /∑ b ₂ as well as∑ b ₄ /∑ b ₃ >∑ b ₂ /∑ bi

Further characteristics can be:

∑ b ₂ >∑ b ₄ as well as∑ b ₂ >∑ b ₃

These features ensure the thinness of the louvers to form smaller stacks of louvers and a good viewing and optimized lighting.

In the first daylight directing part the opening width W is at least partially three times as large as W in the second section. Due to the larger opening widths W ₁₄ , W ₁₅ , W ₁₆ in the section directing the daylight inward against the smaller opening widths W-i to W ₁₃ , W ₃₅ , W ₃₆ in daylight deflecting section and indeed in combination with at least partially larger folded sides b ₄ directing the daylight inward, the essential characteristics of the louver contour are defined. A concave shape of folded sides b ₄ directing the daylight inward provides a precise light guide. Essential for redirecting the daylight of zenith radiation of > 50% at a shadow line S of 30° is the opening angle γ in the first section. This is > 90°, preferably > 130°. To achieve the mono-reflective daylight inwardness, the angles βι of the folded sides directing the daylight inward are formed between 0° and < 30° - 45°, close to the middle axis 29 in the first section directing the daylight inward. The exact angle at the end point 20 results from the angle of the shadow line S. For a shadow line S of 30°, a tangent incline of 30° results in and for a shadow line S of 45°, there is a tangent incline of 45°. The steeper the shadow line S, the steeper is the tangent angle in louvers endpoint.

The lighting requirements in 1 are to be met by the 1 ^st section that directs daylight inwards with a contour of daylight directing surfaces 1 1.1 .2, 1 1.2.2, 1 1.3.2 ascending towards the louver edges 20, which in angle β are characterized by the secant 21 , 22, 23, 33, 36 (see also Fig. 9.1 ). In order to direct the zenith radiation inwards in zenith light catcher as flat as possible, but > 0° into the room, the angles βι to β ₃ are configured for louver edge rising upward. The folded sides 1 1 .1.2, 1 1.2.2, 1 1.3.2 are formed concave. Secants 21 , 22, 23 through these folded sides meet in a zone T. T is shown in Fig. 8, for example, in the louver edge 20.

The concave shape of the light-directing folded sides ensures the said advantage of exact, mono-reflective and anti-glare radiation guide and a nearly uniform scatter to the interior ceiling as shown in Fig. 1.0, 2.0 and 15 and in Fig. 4.1 , 8 and 14, without having to impinge the bottom side of the upper louver (mono-reflectivity) and without having to blend at very flat sun in a lower pane. This is achieved, in which foci Z and BZ are formed between two adjacent louvers, as shown in Fig. 1 .1 , 4.1 , 8, Fig. 13 and 14. The contour of the concave part surfaces 1 1 .1.2, 1 1 .2.2, 1 1 .3.2 is obtained approximately from fragmentation and a spatial displacement of a parabola-like curve as shown in Fig. 8.1.

The climate technical requirements to 2nd on the louvers' development for passive cooling are, as shown in Fig. 1 1 , achieved by the special folded in light-deflecting sections 10 by making the sunlit folded sides of individual folds in their angles β4 to β5 increase from the louver edge towards the louver centre (β ₄ < β ₅ ). Preferably, the angled folded sides decrease from the louver edge towards the louver centre in their angles of attack a ₅ to a ₄ (a ₅ < a ₄ ), in order to reflect the flatter sun back into the sky in zenith light-catcher mounting position - as far as possible mono-reflectively. The angles of inclination of individual folded sides a and β are ideally determined in Fig. 1 1 such that for a beam 80 at an angle 30° of the shadow line S in sun protection function, a focussing zone F-i is formed and for a beam 81 at an angle of the shadow line S a focussing zone F ₂ is formed, so that the sun is deflected by the light-deflecting part mono-reflectively in the direction of sunlight incidence.

Thanks to the nearly equal widths bi in the second daylight deflecting part, a particularly slim louver with a flat cross-sectional profile is achieved compared to the state of the art in Figs. 1 to 4, which optimizes the viewing D of blinds. The width variations bi are < 30%. The opening widths W of each fold W-i to W ₁₃ correspond to a maximum of twice the folded height F _h in the present example, Fig. 8. In the section where daylight is directed inwards, the opening width W is partly up to 5 times the fold height F _h and more. In Fig. 12, the ratio h/W in daylight deflecting section amounts to 1/1.6, in the section where daylight is directed inwards it is 1/9. The demand for a viewing D between the louvers and the lowest possible viewing height of the louvers h is achieved by a nearly horizontal positioning of the louvers, and a micro-fold with smaller opening widths W-i to W ₁₃ in daylight deflecting section 10 compared to the opening widths W ₁₄ to W ₁₆ in the section 1 1 , where daylight is directed inwards. A micro folded, adapted to the louvers' width, can have a folded height of F _h 0.1 to 3.0 mm. For an embossed tooth structure as shown in Fig. 16, the folded height can even be smaller than 800 nm, however, can be made larger than the wavelength of light.

The light- and climate-controlling functions in accordance with 1 and 2 are met, wherein the louvers in zenith light-catcher installation on the upper area of the curtain and the louvers in the turned louvers installation are fitted only at the bottom of a blind, so that it comes to a balance of protection and supply function within a curtain by means of only a few louvers. The louvers in the upper and lower curtain region are arranged essentially parallel to one another.

The dim setting of the closed blind in Fig. 10 is particularly well realized by the louver edge ascending toward louver section 1 1 or by the ascending connecting line 14 between folded peaks 16, 17 in Fig. 8. The inner-side louver edge inclines to the underside of the upper louver and closes the gap between the louvers. The elevator belt 30 can be laid down without obstacle between the closed louvers on the folded peaks. Also in zenith section where daylight is directed inwards in the upper area of the curtain blind in Fig. 9 shows a good sealing.

By micro folded in retro-reflective section, the curtain strung in a ladder-cord fold into a small pack of louvers, without having to insert the ladder cord webs into the folds upon moving. For the state of the art it turns out that a blind threaded in the ladder cords with large folds forms larger louvers' sets, because the ladder cord webs are not joined into the fold in a form-fit manner. Further, the ladder cord webs should be substantially wider than the louvers themselves, which leads to inaccurate positioning of the louvers in the open curtain. This problem is not there any longer due to the miniaturized fold formation at folded height < 2 mm.

Further advantages and details are explained with reference to the drawings. It shows:

Figs. 1 - 4 light directing functions of the louvers pertaining to prior art

Fig. 3.0.1 detail of the louver part directing the daylight inward from Fig. 3

Figs. 1.1-4.1 light directing functions of the said louvers with light directing part Figs. 5.0-7.0 angle-selective light transmission of the louvers pertaining to prior art from Fig. 1 - 4

Figs. 5.1 -7.1 angle-selective light transmission of the said louvers from Figs. 1.1 - 4.1 Fig. 8 four stacked louvers of Figs. 1 .1 - 4.1 , according to the invention

Fig. 8.1 detail design of the section directing daylight inward

Figs. 9 &10 said louvers in closed position

Fig. 1 1 the louver of Fig. 8 with light radiation on the light-deflecting part

Fig. 12 a greatly enlarged mini louver

Fig. 12.1 -12.3 detail design of the light-directing section of the mini-louver of Fig. 1 1 Figs. 13 & 14 light control of the section directing daylight inward in normal and turned- over louver position

Fig. 13.1 alternative, trough-shaped folds design in the section directing daylight inward

Fig. 14 light directing requirement on a blind

Fig. 15 shows the light deflection inward when arranging the first section directing the daylight outwards or inwards

Figs. 16, 17, 18 show a further embodiment of the louvers.

Fig. 1 shows a louver of the prior art with the light guide for solar incidence angle of 60°. Only 30% of the incident zenith radiation is deflected into the interior. The incident occurs at angles of 30°, without illuminating the interior throughout the room. There is a lack of horizontal light entry. Approximately 75% of the incident zenith radiation is undesirably reflected back into sky.

Fig. 1 .1 shows an embodiment of innovative, asymmetrical flat louver for a solar incidence angle of 60°. The louver shows the improved light guide on the section 1 1 directing the daylight in the interior by 65% and only a minimal light deflection. Sunlight is, according to the object, mono-reflectively redirected by the concave folded sides 1 1.1 , 1 1.2, 1 1 .3 in a scattering angle of 0° to 45° into the room. Thanks to the folded sides rising at the folded edge 1 1.1.2, 1 1.2.2, 1 1 .3.2 and the greater width b ₄ as a result of larger opening widths W ₁₄ , W ₁₅ , W ₁₆ in Figs. 8 and 12, the flat steering of daylight is allowed for illuminating the room depth.

During a light incident of 40° in prior art in Fig. 2 there is only a minimal light entry of 5% of the incident light radiation, the said louver in Fig. 2.1 , because of greater width b ₅ to b ₇ and as a result of the lamination contour ascending at the louver edge, always shows a light entry of 23%, while in the prior art in Fig. 2.0 a steering of daylight is largely prevented.

Fig. 4.1 shows the optical behaviour of the said louver of Fig. 1 .1 at a sunlight incidence angle of 30°, but in a position flipped by 180°. The section 1 1 directing the sunlight is turned inward and the light-deflecting section 10 is turned for guiding the sunlight outward. The light-deflecting section 10 mono-reflectively deflects sun up to a sunlight incidence angle corresponding to the angle of the shadow line S. The section 1 1 directing the sunlight inward steers the flat winter sun mono-reflectively and indeed at angles ≥ 30° to ensure an anti-glare for the user. Due to the larger opening widths W ₁₄ , W ₁₅ , W-I6 and the greater width b ₄ and the ascending concave louvers' contour of the daylight- directing folded sides, more flat sun is collected than in prior art and at 30° it is deflected up to 65% instead of 40%. The louver height h amounts to < 2 mm in a louver width of 60 mm. It results in a viewing up to 90%, while in the prior art in Figure 1 , the viewing is only 83% - even at steeper inclination of the shadow line of 35°.

As a result, in the diagrams in Fig. 5.0 to 7.0 in the prior art and in Fig. 5.1 to 7.1 for the innovation, the sun incident angle-dependent light transmission values of the light directing systems of Figs. 1 to 3 and Figs. 1 .1 to 3.1 are analyzed for explaining the functionality and benefits of the surface contour and fulfilling the task.

The curves a' show the light transmission between the louvers and the curves bi/b ₂ , the inwardly deflected radiation components for the zenith light-catcher position of the louvers in Fig. 5.0 and Fig. 5.1 , and for the turned louvers position in Fig. 6.0 and Fig. 6.1. Figs. 7 and 7.1 show, in the curves c', an addition of light transmission of the inwardly deflected radiation b-T + b ₂ ' from Fig. 5 and Fig. 6 or Fig. 5.1 and 6.1.

Particularly indicated by hatching is the angular range between 40° and 50° incidence of sunlight. This shows in the prior art an extremely low light transmission, which causes a temporarily strong darkening of the interior in the diurnal cycle or between seasons.

A comparison of curves c' in Figs. 5 and 5.1 shows the great advantage of the innovation: The inclination of the daylight-directing folded sides b ₄ up to 30° from the louver centre of increasingly concave shape and by the connection line 14 between folded peaks 16, 17 in Fig. 8 that was set up in angle > 0°, preferably > 9°, a 4-time larger share of zenith radiation is captured and the room depth illumination is preferred for the diffuse sky. This also shows a comparison of the shaded area below the curved sections c' in the diagrams of Fig. 7.1 and 7. The new design guidelines give rise to an approximately 3-fold higher incidence of light in a Lambertian radiation range (diffuse sky light).

Due to the innovative design of the louvers, it is also possible to redirect the flat sun in winter onto the section directing the daylight inward into the room. This is clear from a comparison of Figs. 6 and 6.1 for the incidence angle up to 15°, marked by dashed line.

Further optimization can be achieved by the percentage-wise surface coverage of the curtain with louvers in zenith light-catcher function or in turned-in louver position.

Fig. 8 shows details of the louver contour development, by means of which the above functions are achieved. The construction of the louver tops takes place according to rules, which cannot be derived from the prior art. The peaks 60, 61 in Fig. 8.1 or 50, 51 in Fig. 13.1 lie on a line at an angle of 0°, unlike the prior art in Fig. 03.1 . The section 1 1 in Fig. 9 has wider folded sides b ₄ that direct the sunlight inward. The angled folds b ₅ are at least partially narrow, so that∑b ₄ >∑b ₅ results in. In the case of the prior art in Fig. 03.1∑b ₄ is <∑b ₅ . In section 10 with light being directed back in the direction of sunlight incidence, the folded sides bi and b ₂ have, as compared to the prior art, approximately the same width and consistently smaller folded angles γ and opening widths W.

∑bi≡∑b ₂ holds good. For prior art in Fig. 1 , it is∑bi >∑b ₂ .

In section 1 1 with daylight directing inward, it results in at least partially folded angle > 130°, wherein the folded sides b ₄ are disposed at angles βι to β ₃ turning inward, which increase towards the louver edge. These angles can be between 0° and 45°. The tangent angle at the folded sides b ₄ can be near the louvers' centre 29 0° to 5°, and at the lamellar edges 20 to 25°, e.g. 45°, preferably 30°, thus corresponding to the angle of the shadow line.

Fig. 18 shows the light deflection of flat sun in reverse mounting position of the louvers with the first section oriented inward. Flat sun in incidence angles < 10° is deflected antiglare inward at angles > 20°. This is achieved, in which the angled folded sides b ₃ provide shades to the very flat inclined sections c with tangent angles < 5° of the folded sides b4, so that the light bending inward occurs at least at angles > 20°. - -

Fig. 13 shows the flat steering of daylight inward in voluminous spaces and the scattering of light at the concave folded sides that direct the daylight inward for angles of incidence of 50° and 65°. It manages a uniform light scatter, independent of the sun incidence angle, in the interior depth.

Fig. 13.1 shows an alternative to the V-shape of the folds in U-shape. b ₃ of Figs. 8 and 12 always refers to the shortest distance between the nadir and the peak of a fold, as indicated by the lines 90 to 93.

In turned-over louver position in Fig. 4.1 and 14, the folded sides that steeply steer the daylight inward serve the flat sun incidence angle on the interior ceiling so as not to dazzle the user. Here it is important to develop the light guide so that the reflected rays, as far as possible, do not hit the underside of the upper louver, but back down steeply so as to steer the light radiation in the case of progressively flatter sunlight to the interior ceiling without having to dazzle the inmate by the flat light redirection.

Fig. 1 1 shows the ideal structure for the folded angle of the daylight deflecting section of the louver. Deviations from this result in folded peaks and valleys alone by the manufacturing tolerances and fillets. Therefore, the innovation applies primarily to construction guidelines. Production-related deviations such as rounding at the edges are always negligible. Solar radiation in incidence angle greater than the angle of the shadow lines is essentially redirected mono-reflectively in the sky - a particular advantage of the design. A louver of Figs. 9 and 12 can be manufactured in widths of 2.5 cm to 10 cm.

Fig. 12 shows a greatly enlarged miniature louver of circa B = 12 mm and h 1 .4 mm. This has only two V-shaped folds in the daylight directing section 41 . b ₄ is configured wider than bi. The opening width W ₃₅ , W ₃₆ in the section deflecting the daylight are smaller than the opening widths W ₃₃ , W ₃₄ in the section directing the daylight inward. The connecting line 32 between folded peaks 39, 31 is set up strongly increasing at an angle of 10°. The folded heights F _h in daylight deflecting section are greater than the folded heights F _h in the section portion directing the daylight inward.

In the present case, the folded peaks lie on parallel lines E-i and E ₂ . As long as no single folded peak line transgresses E-i or E ₂ , the louvers can be wound up in a miniaturized version on a coil. This is also true for a broader louver in Fig. 1 1 or Fig. 16. - -

Fig. 12.2 shows the intersection point Z of the chords 33, 36 through the folded sides that direct the daylight inward or through the points 34, 39 / 35, 31 between the levels E-i and E ₂ within the cross-section height h of the louvers.

Fig. 12.3 shows a hump-shaped formation H by a folding along the fold side b ₄ . This formation H reflects light back to outside within the first louver section. The advantage is the protection of very flat oriented parts of the folded sides b ₄ in order to prevent a light redirection in very small angles < 30°. This avoids glare if looking onto the louver surface.

Louvers of Fig. 12 are preferably installed fixed in the cavity of insulating glass in facades and roofs as well as blind. Especially in pitched roofs, the louvers are installed in modified angular positions relative to the horizontal, whereby the bottom of the louver can be subjected to direct sun by rotation about a horizontal axis.

In facades the bottom sides of louvers can be white or coloured. The louvers' tops are preferably reflective or at least metallically reflective. In roofs, the louvers are used in inverse mounting position, with white top and shiny metallic back, wherein the backside can be turned to face the sunlight.

In the figures, the louvers are all optimized for horizontal viewing D without compromising the validity of the design guidelines of the innovation thereto. For a better viewing on the street level, the louvers geometries can then be constructed for inclined louvers' position, but with reduced horizontal viewing D. The construction principles are to be equally applied. Ss can be seen in Figs. 15 and 16, the louvers can also have a convex or concave or bent roof-shaped contour, wherein the mini folds are additionally introduced.

As louver material a very thin strip with thickness < 0.4 mm, preferably 0.07 mm to 0.15 mm, is used. Aluminium or steel or stainless steel with a yield strengths after processing up to about 400 - 2000 MPa is used. Such a tensile strength results in a material with high elasticity and resilience which enables to wind-up the finished moulded louvers as tapes back to a coil, without suffering deformations. However, the coiling specifies a very low fold height of < 2 mm, preferably 0.3 mm - 1 .0 mm. The blinds' manufacturer wraps the finished, micro-structured louver belt from a winch and punches and pierces the louvers to the mounting dimensions. - -

The micro-structured strips have a reflective surface either by an electrolytically coating and/or by an additional protective coating like a lacquer or PVD. Strips with qualities before processing with a tensile extension > 10 % up to 30-50 % and with a tensile strength of 300-500 MPa are used in order to avoid a splitting of the strips in the edges of the folds.

In order to avoid the risk of glare to the folded peaks, these can be online white-painted in the coil-coating process after moulding at the folded peaks.

A manufacturing advantage of the louvers as per the invention, over prior art in Figs. 1 to 4 is the better moulding ability of the first folds W-i - W ₆ , especially W-i, located at the louvers edge in daylight deflecting section, provided that the following rule is observed: The folded sides bi and b ₂ are formed with approximately the same width in individual folds, so that a more uniform stress distribution and more uniform stretching of folded sides result in the tool run. A reference value of b ₂ /bi ~ 1 to 1/2 or 2/1 is sought.

Under manufacturing aspects it holds good to form the folds b ₄ and bi very small that are located at the lamination edge, when the formed tapes must be coiled. The edge must be stabilized by means of a small fold, so as not to suffer any deformation during winding. As a reference value bi and b ₄ or b ₂ and b ₃ holds good in the louver edge < 4 mm, better < 2 mm to 0,5 mm.

Further, the dimension x-i (bi or b ₂ ) und x ₂ (b ₃ or b ₄ ) is valid in the region of louvers' edges (see Fig. 13):

x ₂ < x 2

≤ x ₂ x 2

Taking into account all design criteria of the optical system or the light guide technology to achieve the light directing function, the aforementioned reference values for louvers' rewinding under manufacturing aspects are considered a sine qua non. It reserves the right to eliminate a re-windable lamellar structure with these features as its own application. For macrostructures or rigid disk with larger folds these rules do not apply.

For louvers with smooth bottoms and embossed folded tops, either a rolling embossing procedure is applied, in which the contour in the rolling pass is pressed directly into the metallic material or the louver is coated with a lacquer, in which the contour is embossed in the run between embossing rollers. The lacquer layer may be a sol-gel coating, which - - cures after moulding by means of UV light. The louver is metallised in the terminal. Alternatively, an embossed, metallised film can be laminated on the strip material.

The following equations shall hold good, without restricting the invention thereto: to Fig.8 to Fig.12

bi = b ₂ ± b ₂ x 0.3 ∑b ₄ /∑b ₃ >∑bi/∑b ₂

F _h /Wi5 = 1/5.5 W ₃₅ /W ₃₆ < W ₃₃ /W ₃₄

a ₄ > as B/h = 9,3

β ₅ >β ₄ F _h /W ₃₃ ≡ 1/9

βι <β ₂ <β ₃ F _h /W ₃₄ = 1/2.8

a ι > a ₂ > a ₃ F _h /W ₃₅ und W ₃₆ ≡ 1/1.6

Y1, Υ2 < Υ3, Υ4 ∑b ₄ /∑b ₃ ≡ 3.6

α,4, α¾ > «2, CL3

β ₄ , β ₅ >β ₂ , β ₃