EP1099079A1

EP1099079A1 - Lighting device

Info

Publication number: EP1099079A1
Application number: EP00943592A
Authority: EP
Inventors: Frank Vollkommer; Lothar Hitzschke
Original assignee: Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
Current assignee: Osram GmbH
Priority date: 1999-05-20
Filing date: 2000-05-13
Publication date: 2001-05-16
Also published as: WO2000071928A1; JP2003500814A; CN1125941C; KR100730426B1; US6402343B1; KR20010053383A; CN1304484A; DE19923264A1; CA2334234A1; TW473764B

Abstract

A lighting device with an aperture lamp (1) comprising two series-connected optical means (8, 9), whereby at least the first optical means (8), when seen on a cross-sectional plane perpendicular to the longitudinal axis of said lamp, is curved. The first means (8) focuses the broad distribution of light beams which are emitted by each surface element in the region of the aperture in the direction of the normal of each respective surface element. The second means tilts at least part of the bundle of light coming from the first means at angle of inclination which can vary in size for at least one part of said bundle of light. This enables the light emitted from the curved surface of the aperture to be directed in a targeted manner, e.g. in a parallel manner.

Description

lighting device

Technical field

The invention relates to a lighting device with an electric lamp with an aperture and an optical system according to the preamble of claim 1. The invention also relates to a method for directing light rays from an aperture lamp according to the preamble of the method claim.

The lamp used for the lighting device has a tubular lamp vessel which is closed on both sides. To increase the luminance of the lamp, the inside or outside of the lamp vessel is provided with a reflector for visible light, where a defined area is left out along the longitudinal axis. In this way, an aperture is created through which the light passes the lamp reaches the outside (aperture lamp) .The reflector can also be formed by a suitably thick phosphor layer. These lamps are also known as aperture fluorescent lamps.

Because of their light control function, lighting devices of the type mentioned are suitable, inter alia, for effect lighting and workplace lighting.

In addition, such lighting devices are suitable, supplemented by a light guide plate, for example for backlighting displays, in particular of liquid crystal displays (LCD = Liquid Crystal Display) but also large-scale advertising boards. Liquid crystal displays are used in a variety of ways, for example in control rooms, cockpits of aircraft and increasingly also in motor vehicles, in entertainment and communication electronics and as screens for personal computers (PC).

In this case, the lamp, the optical system and the light guide plate are matched to one another in such a way that the light of the lamp can be coupled into the light guide plate through at least one narrow side (“edge”). Light technology "). By means of reflection on a diffuse reflection layer applied to the underside of the light guide plate, for example, this light passes out over the entire front side of the light guide plate and thus acts as a flat light source which is expanded in accordance with the dimensions of the light guide plate.

The lamp vessel can be rod-shaped, but also angled, for example L-shaped or U-shaped. In the latter case, the light from the lamp is coupled into the light guide plate via two or three of the edges thereof. Of course, two or more lamps - each including an optical system - can also be used to couple light into a light guide plate.

As already mentioned at the beginning, the lighting device under consideration is a device with a tubular aperture lamp. The cross section of the lamp is curved, in particular circular, or also elliptical, drop-shaped, etc. Each sufficiently small surface element of the aperture surface of this lamp emits light in a good approximation with a relatively wide angular distribution, in particular a Lambertian or at least Lambertian distribution. For the lighting tasks mentioned at the outset, this angular distribution must be suitably shaped, in particular narrowed, in order to to achieve luminosity and / or to improve the effective overall efficiency of the lighting device. Because of the tubular geometry of the aperture lamp, essentially only the angular distribution in a sectional plane perpendicular to the lamp longitudinal axis is decisive. In other words, the angular distribution of the radiation in the direction of the lamp longitudinal axis is at most of secondary importance. The actually cylindrical problem of light beam distribution or guidance can therefore be reduced approximately to considerations in a sectional plane perpendicular to the lamp axis.

Presentation of the invention

It is an object of the present invention to provide a lighting device according to the preamble of claim 1, which has improved guidance or focusing of the light leaving the aperture.

This object is achieved in a device with the features of the preamble of claim 1 by the features of the characterizing part of claim 1. Particularly advantageous configurations can be found in the dependent claims.

Another aspect of the invention relates to the coupling of the lamp light leaving the aperture into a light guide plate.

It is desirable that a maximum of the light leaving the aperture is appropriately coupled into the light guide with the aid of an optical system. To make matters worse, the aperture surface is curved because it is part of the tubular lamp surface.

Protection is also claimed for a method for influencing the light of a tubular aperture lamp according to the method claim. The basic idea of the invention is to provide two optical means connected in series, the first means being curved, viewed in a sectional plane perpendicular to the longitudinal axis of the lamp. This first means bundles the wide light beam distribution emitted by each surface element in the area of the aperture in the direction of the normal of the respective surface element. The second means tilts at least a part of the light beams coming from the first means by a tilt angle, the tilt angles of at least some of the light beams being of different sizes. In this way, the light emitted by the curved aperture surface can be directed in a targeted manner, for example “parallelized” or converging light beams can be generated.

The term “bundle” is to be understood here to mean that the originally wide angular distribution of the light beams is transformed into a narrower angular distribution, ie that after bundling the light beams represent large angles with a significantly lower relative weight with respect to the main emission direction of the respective surface element The main ^emission direction of a surface element is understood here to be the direction of that light beam vector of the light beam distribution of the surface element under consideration that has the greatest magnitude (= intensity).

The tilt angle is defined here as the angle between the original main emission direction and the tilted main emission direction of the respective light beam.

The curvature of the first optical means is preferably adapted to the curvature of the lamp in the area of the aperture. It is thereby achieved that a large part of the light leaving the aperture with a broad light beam distribution is coupled into the first means, leaving it in the form of numerous relatively narrow light beams which are at least partially tilted by the second means. The first is to minimize coupling losses Means also preferably arranged substantially directly on the outer surface of the aperture.

For a better understanding of the basic idea of the invention, reference is made to FIG. 1, which shows the relationships in a highly schematic and abstracted manner. Figure 1 shows schematically a cross section through a tubular lamp 1 with a circular cross section. For the sake of clarity, further details of the lamp 1 and the optical system have been omitted here. Shown are a first and second edge 2, 3 of an aperture, the central beam 4 of the aperture and in each case the vectors of the main emission direction of an edge light bundle without 5 or with 6 the optical system according to the invention (not shown). As can be clearly seen from FIG. 1, the magnitude of the projection (P2) of the light vector 6 of the tilted main emission direction onto a parallel 7 to the central beam 4 is greater than that (Pl) of the light vector 5 of the original (untilted) main direction. In an analogous manner, this applies essentially to all main emission directions of all surface elements. The central beam 4 is formed by the main emission direction of the central surface element of the aperture.

In this way, for example, a "quasi-parallel" light beam (not shown) can be generated. For this purpose, the second optical means is designed such that the tilt angle δ of the individual light bundles increases with the angular distance from the central beam 4 of the aperture.

The means according to the invention can be formed by suitable optical structures, for example microprism structures and / or holographic structures or the like. be realized.

With regard to the coupling of light into a light guide plate, the advantageous effect of the invention is particularly effective when the diameter of the tubular vessel of the lamp is relatively large, in particular the same size as or greater than the thickness of the light guide plate. Then, without any special measures, a relatively large proportion of the light emitted by the lamp aperture passes the coupling surface of the light guide plate. However, the advantageous effect of the invention is not limited to such constellations. Here, the second means can also be integrated directly into the light guide.

A preferred embodiment uses a discharge lamp suitable for a dielectric discharge with a tubular discharge vessel. The lamp has two strip-shaped electrodes which are arranged on the inner or outer wall of the discharge vessel parallel to the longitudinal axis of the tube and diametrically to one another. In this way, the large lamp diameter is used specifically for the corresponding maximum possible stroke distance of the discharge. With increasing stroke distance, the operating voltage for the dielectrically impeded discharge and consequently the active electrical power that can be coupled in also increases. With the aid of the pulsed mode of operation according to the document WO 94/22975, this leads, as desired, to the above-mentioned increase in the luminous flux of the lamp.

Since the luminous efficiency drops significantly with a decreasing ratio b / D between aperture width b and lamp diameter D, the width d of the aperture is also chosen to be as large as possible. The width b of the aperture preferably corresponds approximately to the thickness d of the light guide plate.

Further preferred ranges for the ratio of aperture width b to thickness d of the light guide plate are b / d> 0.6, 0.8 and 1. Description of the drawings

The invention will be explained in more detail below with reference to the figures using an exemplary embodiment. Show it:

FIG. 1 shows a schematic illustration to explain the basic idea of the invention,

FIG. 2 shows a cross section through a tubular lamp with an optical system in a highly schematic representation,

FIG. 3 shows an enlargement A of the optical system from FIG. 2 in the central region of the aperture,

FIG. 4 shows an enlargement B of the optical system from FIG. 2 in the edge region of the aperture,

Figure 5 shows a partial cross section of a complete lighting device with a tubular aperture fluorescent lamp with an optical system and light guide plate.

FIG. 2 shows a highly schematic illustration of a cross section through a tubular aperture fluorescent lamp 1 according to the invention (details have been omitted here for the sake of clarity) with an optical system consisting of the two optical means 8, 9.

Details of the two foils 8, 9 are disclosed in FIGS. 3, 4, where enlargements of the optical system from the central region A or the edge region B of the aperture are shown schematically and to which reference is also made below. The two optical means are transparent plastic films 8, 9 which are arranged one after the other on the surface of the vessel wall 10 of the lamp 1 in the area of the aperture. are not. Starting from the center point M of the lamp (viewed in the cross section in FIG. 2), the aperture spans an angle α.

The first film 8 has a microprism structure on its side facing away from the vessel wall 10 of the lamp aperture. The structure is designed as a multiplicity of prisms 11 in the form of isosceles triangles, the prisms 11 running parallel to the longitudinal axis of the lamp 1. The prism structure of the first film 8 transmits only those light rays that strike the side of the film 8 facing the lamp aperture within an acceptance angle. The value of the acceptance angle can be influenced, among other things, by the respective prism angle of each prism. The remaining rays are reflected back by means of total reflection on the respective prisms in the direction of the lamp aperture or vessel wall 10 and redistributed by means of scattering or reflection until they strike the first film 8 within the acceptance angle and are finally also transmitted.

Especially when the aperture is completely spared from phosphor, it can be helpful to support the redistribution to arrange an additional diffuser between the vessel wall 10 of the lamp 1 and the first film 8. This minimizes the interface losses. The diffuser can also be realized by matting the surface of the vessel wall 10 in the area of the aperture. However, these measures can also be useful if the aperture surface of the lamp is provided with phosphor.

With the exception of the central region A, the second film 9 likewise has a prism structure on its side facing the first film 8. However, the structure is designed as a multiplicity of prisms 12 in the form of isosceles triangles, the prisms 12 likewise running parallel to the longitudinal axis of the tubular lamp 1. With the help of the uneven leg triangular prisms, the light beams coming from the first film 8 are tilted away from their respective main emission direction and towards the central beam 4.

The respective prism angles γ and consequently also the width of the prism base of the different prisms 12 decrease in the direction towards the edge region B. As a result, the tilt angle δ decreases from the edge region B towards the central region A and disappears completely in the central region A, i.e. the rays in central area A are not tilted (δ = 0 °). The change in the prism angle γ is adapted to the curved geometry of the aperture or the film 9 in such a way that overall a relatively “parallel” total beam results, which can be coupled into a light guide plate with only slight losses.

FIG. 5 shows a schematic sectional illustration of a flat lighting device for the backlighting of liquid crystal displays (not shown), consisting of an aperture fluorescent lamp 19, an optical system 110, corresponding to the illustrations in FIGS. 3 and 4, and a light guide plate 111.

The fluorescent lamp 19 consists of a tubular discharge vessel 112, two electrodes 113, 114 and a functional layer system. The layer system consists of a reflection layer 115 made of TiO ₂ and a phosphor layer 116 made of a three-band phosphor. The three-band phosphor consists of a mixture of the blue component BaMgA oOiziEu, the green component LaP0: Ce, Tb and the red component (Y, Gd) B0 ₃ : Eu. The resulting color coordinates are x = 0.395 and y = 0.383, ie white light is generated. The reflection layer 115 is applied directly to the inner wall of the discharge vessel 112, an aperture 117 of width b = 8 mm being left out. The phosphor layer 116 is on the reflection layer 115 or applied directly to the inner wall of the discharge vessel 112 in the region of the aperture 117. The outer diameter of the discharge vessel 112 made of glass is approximately 14 mm with a wall thickness of approximately 0.5 mm. The length of the tubular discharge vessel 112, closed at both ends with a dome (not shown) formed from the vessel material, is approximately 27 cm. Xenon is located within the discharge vessel 112 with a filling pressure of approximately 17 kPa. The two electrodes 113, 114 are formed as metal strips which are arranged on the inner wall of the discharge vessel 112 parallel to the longitudinal axis of the tube and diametrically to one another. In this way, the maximum stroke length w possible for a tubular discharge vessel is used for the discharge and, as explained at the outset, a correspondingly high luminous flux of the lamp is achieved. Both electrodes 113, 114 are covered with a dielectric layer 100 made of glass solder.

The light guide plate 111 consists of a flat plexiglass block of thickness d = 10 mm, the width B = 27 cm in the direction of the lamp longitudinal axis and the length L = 20 cm perpendicular to the lamp longitudinal axis. A first 118 of the four narrow sides of the light guide plate 111 is arranged parallel to the longitudinal axis of the fluorescent lamp 19 and opposite its aperture 117. For the sake of simplicity, the first narrow side 118 is referred to below as the “leading edge”. In addition, the fluorescent lamp 19 and the light guide plate 111, viewed in the sectional view, are aligned centrally to one another, ie the width b is on both sides of an imaginary center line or optical axis A. the aperture 117 is only approx. 1 mm smaller than the thickness d of the light guide plate 111 ("/ b / - \ _mm y Qj _e width b of the aperture 117

thus approximately the same size as the thickness d of the light guide plate 111.

As shown in FIGS. 2 to 4, the optical system 110 consists of the two prism foils 8, 9 (not shown in detail in FIG. 5 for reasons of clarity) ) and has the function already explained in the description of FIGS. 2 to 4 of "parallelizing" the radiation emitted by the aperture 117 in such a way that an efficient coupling into the light guide plate 111 is achieved.

A variant, not shown, of the above-mentioned lighting device for illuminating objects, e.g. Work surfaces or everyday objects as well as decorations essentially correspond to those from FIG. 2. Only the variation of the prism angle of the second film 9 - and consequently the variation of the main emission directions of the light bundle - is adapted to the surface to be illuminated.

Claims

claims

1. Lighting device with

A lamp (1; 19) with a tubular lamp vessel (112) with an aperture (117),

An optical system (8, 9; HO) for influencing the light beams emitted by the lamp (1; 19) in the area of the aperture (117) during lamp operation,

characterized in that

The optical system (8, 9; 110) comprises a first curved (8) and a second optical means (9), viewed in a sectional plane perpendicular to the longitudinal axis of the lamp,

• The first means (8) bundles the light beam distribution emitted by each surface element in the area of the aperture in the direction of the normal to the respective surface element and

The second means (9) tilts at least a part of the light bundle coming from the first means by a tilt angle (δ) - defined as the angle between the original main emission direction and the tilted main emission direction of the respective light bundle -

• The tilt angles of at least some of the light beams are of different sizes.

2. Lighting device according to claim 1, wherein - viewed in a sectional plane, perpendicular to the lamp longitudinal axis, - the tilt angle (δ) of the individual light bundles increase with the angular distance from the center (4) of the aperture.

3. Lighting device according to claim 2, wherein the variation of the tilt angle is selected such that the main emission directions of the light beams leaving the second means are tilted towards the main emission direction of the central surface element of the aperture, in particular essentially parallel to the main emission direction of the central surface element are.

4. Lighting device according to one of the preceding claims, wherein the first means (8) on its side facing away from the lamp aperture has a prism structure which is designed such that the prisms (11) of the structure run parallel to the longitudinal axis of the lamp (1).

5. Lighting device according to claim 4, wherein the prism structure is designed such that only those light rays are transmitted through the first means that meet within an acceptance angle on the side facing the lamp aperture of the means and the remaining rays by means of total reflection on the respective prisms in the direction be reflected back to the lamp aperture.

6. Lighting device according to one of the preceding claims, wherein the second means (9) on its side facing the first means and - viewed in a sectional plane perpendicular to the lamp longitudinal axis - outside the central region of the aperture has a prism structure, the prisms (12) parallel to The longitudinal axis of the lamp runs and the structure is designed such that the respective prism angles (γ) of the different prisms (12) vary with the distance of the respective prism from the central area (4) of the aperture.

7. Lighting device according to one of the preceding claims, wherein a diffuser is arranged between the lamp and the first means.

8. Lighting device according to claim 7, wherein the diffuser is realized by matting the surface of the lamp in the region of the aperture.

9. Lighting device according to one of the preceding claims, wherein the first means (8) is arranged substantially directly on the outer surface of the aperture.

10. Lighting device according to one of the preceding claims, wherein the second means (9) is arranged substantially directly on the first means (8).

11. Lighting device according to one of the preceding claims, wherein at least the curvature of the first optical means (8) of the curvature of the lamp (1) is adapted in the region of the aperture.

12. Lighting device according to one of the preceding claims, with an additional light guide (111) with light entry surface (118), the lamp (19), optical means (110) and light guide (111) being arranged in relation to one another in such a way that the optical means (110) face the light entry surface (118) and consequently couple light emitted by the aperture (117) of the lamp (19) into the light guide (111) via the light entry surface (118) during lamp operation.

13. Lighting device according to claim 12, wherein the light guide is designed as a wedge-shaped or cuboid plate (111).

14. Lighting device according to one of the preceding claims, wherein the lamp for operation by means of dielectric barrier discharge is suitable and for this purpose has at least one electrode (113, 114) which is separated from the discharge by a dielectric (100).

15. Lighting device according to claim 14 - as far as dependent on claim 13 -, wherein the diameter of the tubular vessel

Lamp is equal to or greater than the thickness (d) of the light guide plate (111).

16. A method for directing light emitted from the aperture (117) of a tubular aperture lamp (19), the light initially having a broad light beam distribution, e.g. especially a Lambert

Distribution or at least lambert-like distribution, with the following method steps - viewed in a sectional plane perpendicular to the lamp longitudinal axis,

Bundling the lambert or lambert-like light beams emitted from each location in the aperture to form relatively narrow bundles of light,

• Tilting the light beams by a tilt angle - defined as the angle between the original main emission direction and the tilted main emission direction of the respective light beam - whereby the tilt angles of at least some of the light beams are chosen to be different sizes.

17. The method according to claim 16, wherein the tilt angle of the individual light bundles with the angular distance from the center of the aperture are chosen larger.

18. The method according to any one of claims 16 or 17, wherein an optical means (8) adapted to the geometric expansion and curvature of the aperture is used for the bundling.