EP2409075A1

EP2409075A1 - Reflector, light source arrangement and projector apparatus

Info

Publication number: EP2409075A1
Application number: EP10706977A
Authority: EP
Inventors: Ulrich Hartwig; Henning Rehn
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2009-03-18
Filing date: 2010-02-23
Publication date: 2012-01-25
Also published as: WO2010105890A1; US20110317430A1; US8579474B2; DE102009013812A1

Abstract

Disclosed is a reflector (10) which receives the shape of a rotational body according to a rational square Bezier curve. Such a reflector can advantageously be used for focusing light from a high-pressure discharge lamp (116) so that the light source arrangement (110) has a specific etendue. Such a light source arrangement (110) with the reflector (10), in particular with an integrator (30) arranged downstream thereof, can advantageously be used in a projector apparatus.

Description

description

Reflector, light source arrangement and projector device

Technical area

The invention relates to a reflector with a reflective surface. It also relates to a light source arrangement in which the reflector according to the invention is used. Finally, it also relates to a projector apparatus having such a light source arrangement.

State of the art

Reflectors are always used when a light source emits light undirected or over a solid angle, which is not suitable for the intended purpose.

As is also preferred in the present case, reflectors are often produced from a stable base material onto which a reflective layer is applied. The reflective layer faces an interior intended for receiving a lamp.

The shape of conventional reflectors, in particular the contour of the reflective surface, is based on conic sections. A section through the reflector shows a conic section. As a rule, the reflector is a rotational body of a conic section. So conventional reflectors z. B. the shape of a paraboloid (rotational body of a parabola) or ellipsoid (body of revolution of an ellipse). Parabolic reflectors and Ellipsoidreflektoren are advantageously used when the Light must be strongly parallelized (parabolic reflector) or focused (ellipsoidal reflector).

However, there are applications where the light from the lamp should not be focused as much as possible but should be concentrated on a slightly larger area. This is z. As in the case of projector equipment, or when the light is to be coupled into a glass fiber. In these cases, the so-called etendue (light conductance) is used as a parameter. The etendue is a parameter for an optical system, for example a light source, wherein in the present case a lamp with a reflector located around it is regarded as a total light source. The surface onto which the reflector concentrates the light from the lamp is seen as the emitting surface of the light source. If the solid angle is included, the etendue can be calculated. The etendue is a conserved quantity (Lagrangian invariant) in all optical systems. In applications where a certain etendue is given, conical section based reflectors are not completely satisfactory.

In the field, it has begun to deviate from the conic sections. By way of example, reference is made to WO 2007/081812 A2, CA 2071635 C, EP 519112 A1, US Pat. No. 4,355,350 A, US Pat. No. 5,662,828 and US Pat. No. 6,547,416 B2.

Presentation of the invention

The object of the present invention is to provide a reflector having a reflective surface which is better suited than previous reflectors is, in a light source arrangement with a lamp (discharge lamp, incandescent lamp, based on other physical effects light generator, electrodeless lamp), as z. B. is used in a projector, for a given Etendue the light source arrangement to provide the highest possible light output at given properties of the lamp.

This object is achieved by a reflector according to claim 1. The reflector is used in a Lichtquel- len arrangement according to claim 5, and the same is used in a projector apparatus according to claim 10.

Particularly advantageous embodiments of the invention can be found in the dependent claims.

According to the invention, the contour of the reflective surface is traversed by a Bezier curve. By "passing through" is meant here that visibly a (straight) section through the reflector shows a Bezier curve, which in particular should be a longitudinal section, ie the Bezier curve should go through the contour along the reflector the light, starting from the lamp, moves toward the exit surface of the light source assembly.

It has been found that light along a Bezier curve is better imaged onto an exit surface of a light source arrangement than is the case with conic sections. Just as rotational elements are preferred in the case of conic sections, in the present case too, the contour of the reflective surface is preferably a rotational body of a Bezier curve.

In principle, Bezier curves of a high degree can also be used, but the Bezier curve is preferably a rational quadratic Bezier curve (whose special case is the quadratic Bezier curve). A quadratic Bezier curve is defined by three points, called control or Bezier points. If these points are suitably chosen, it will be possible to design an optimal reflector for the desired etendue and the desired arrangement, matching the characteristics of the lamp.

Experiments have revealed the following:

If, in a discharge lamp, the distance of the two electrodes normally present in operation is defined as d (for other lamp types d denotes the diameter of a sphere around the light source, from which 63% of the total luminous flux originates), and the Bezier curve is as follows (in accordance with FIG the general definition of a rational quadratic Bezier curve), if a point on the Bezier curve has the coordinates x (t) and z (t), where t is a curve parameter between 0 and 1:

(\ -t) ² (lw) x ₀ + 2t (lt) w- X ₁ + t ² (lw) x ₂ x (t) = (U) ² (\ -w) + 2t (\ - t) w + t ² (\ -w)

such as

(U) ² (lw) z ₀ + It (U) WZ ₁ + t ² (Vw) Z ₁ z (t) =

(U) ² (\ -w) + 2t (\ - t) w + t ² (\ -w) Bezier points (X ₁ , Z ₁ ) with i = 0, 1, 2 are used and a weighting w, whereby the following values for these quantities have been found to be preferred: w is between 0.25 and 0.5 and preferably between 0.3 and 0.43. The quantities X ₁ , Z ₁ are in the ratio d: l to corresponding quantities x _l0 , z _l0 .

For xoo it is said to be between 4 and 10 mm, and preferably between 5.5 and 8 mm, if d is given in millimeters. Similarly, for x ₁₀ , it is between 20 and 42 mm, and preferably between 27 and 34.5 mm, and for x ₂ o, it is between 12 mm and 24 mm, and preferably between 16 mm and 19.5 mm , Z ₀ O is between -0.5 and +0.5 mm, so the reflector walls start above the gap between the two electrodes. Preferably, they start exactly at the level of the midpoint between the two electrodes, so Z ₀ O is preferably = 0 mm. z ₂ o is between 30 and 112 mm and preferably between 38 and 93.5 mm. Zio scales by a factor of c with Z20, zio ⁼ CZ ₂ O, where c is between 0.22 and 0.67 and preferably between 0.30 and 0.55.

It should be noted that the above-mentioned values expressly lead to a non-monotonically increasing Bezier curve, in particular in the preferred embodiment, because x ₁₀ can be greater than X 20 and this is also the preferred values. The reflector is therefore bulged in a certain way. It is precisely such an embodiment that has proved to be advantageous, without the specificity of the values specified here being specified. The bulge is in accordance with the definition of the factor c preferably after the first third and before the last third of the course of the reflector.

The light source arrangement according to the invention has a discharge lamp and, as the first reflector, the reflector according to the invention. In addition, it has a second reflector, which is (preferably) flush with the first reflector. The reflectors enclose the discharge lamp. The second reflector terminates the light source arrangement on one side, namely on the side which is to be non-exit side for light.

The object of the second reflector is, in a manner known per se, to reflect back the light emitted by the discharge lamp in one direction, in which it does not strike the first reflector, so that it reaches the first reflector (after reflection). This can be achieved by suitable shape and arrangement of the second reflector with respect to the discharge lamp. It can be linked to forms for the so-called back reflector of the prior art. For example, its shape may be part of a spherical shell, for. B. a spherical shell half.

The lamp is preferably placed so that the origin of the coordinate system in which the Bezier curve is defined is in the range of light generation, wherein preferably the center of gravity of the luminance distribution is exactly at the origin, ie at x = 0 mm and z = 0 mm. This applies in particular in connection with the above-mentioned preferred values for the determination of the Bezier curve.

The light source arrangement may include that at an end remote from the second reflector end of the first reflector an optic is present (that is, at least one optical element), which is followed by a light guide, wherein the optics bundles light and directs it into the light guide.

Alternatively, an optical integrator may be arranged at the open end of the first reflector. Such an integrator is known per se from the prior art and z. B. often used in projector devices.

Thus, according to the invention, an application of the light source arrangement is also in a projector device.

Brief description of the drawings

In the following, the invention will be explained in more detail with reference to several embodiments. Show it:

1 shows a reflector according to the invention in longitudinal section,

Fig. 2 shows a light source arrangement according to the invention, in which a reflector according to the invention is used, according to a first embodiment and

Fig. 3 shows a light source arrangement according to the invention, in which a reflector according to the invention is used, according to a second embodiment.

Preferred embodiment of the invention

A reflector designated as a whole by 10 is designed as a rotary body, so that it has the appearance illustrated in FIG. 1 for any longitudinal sections that pass through an axis of rotation 12 of the rotary body. The reflector has, in a manner known per se, on its inner side, that is, toward the axis of rotation 12. send page, a reflective surface on. In the present case, the contour of the reflector 10 is not different from that of the surface, because the wall of the reflector 10 plays no role in the illustration.

The rotation axis 12 should be defined as a z-axis, while any direction perpendicular to it is defined as an x-direction.

The reflector 10 has the task of concentrating light from an extended light source 16 whose luminance centroid is in a plane 14 into an exit plane 18. A light beam 20 is shown by way of example.

The contour of the reflecting surface and thus the inner contour of the reflector 10 in section is exactly a rational quadratic Bezier curve, so that the reflector 10 as a whole has the shape of a body of revolution to a rational square Bezier curve.

If the reflector 10 is provided for a high-pressure discharge lamp 116 with two electrodes at a distance of 1 mm (in the operating state), the midpoint between the two electrodes lies exactly in the plane 14, ie coincides with the light source 16. In this case, the control points or Bezier points for the rational quadratic Bezier curve can be set to P ₁ = (X ₁ , Z ₁ ) with i = 0,1 or 2, where xo is between 5.5 and 8.0 mm and z ₀ = 0 mm, X2 is between 16.0 and 19.5 mm and Z2 is between 38.0 and 39.5 mm, that x \ is between 27.0 to 34.5 mm and z \ = z ^ c with c is between 0.30 and 0.55. That in a rational quadratic Table Bezier curve existing weight w is between 0, 30 and 0, 43.

If a high-pressure discharge lamp with electrode spacings other than 1 mm is provided, in the presently preferred first approximation the entire Bezier curve can be scaled accordingly. With an electrode distance of d = do • 1 mm, the above values for X ₁ and Z _{1 are} therefore multiplied by do.

The stated values imply that the location of the largest radius of the reflector 10 does not coincide with the plane 18. To produce the reflector, two partial reflectors can first be produced and then connected to one another, wherein the connection point is the point with the largest radius. Hollow bodies with monotonously increasing radii are particularly easy to produce.

In a first light source arrangement 100, which is shown in FIG. 2, as well as in a second light source arrangement 110, which is shown in FIG. 3, another reflector 22 is attached flush to the reflector 10. The second reflector 22 has the task of a back reflector. He may have the basic shape of a hemisphere shell. Likewise, it is possible to take into account the shape of the desired discharge lamp 116 used in the design of the back reflector 22: light that arises between the two electrodes, breaks at the transition from the space in which the electrodes are located to the glass and again at the transition from the glass to the outside. If the shape of the glass is precisely known inwardly and outwardly, the back reflector 22 can be appropriately shaped such that precisely light which is emitted by the one electrode tip is used for the purpose other electrode tip is reflected back and vice versa. As a result, the entire space between the two electrodes is imaged on itself.

Alternatively to the illustration in FIGS. 2 and 3, it is possible simply to mirror the bulb of the lamp itself on the back. In this case, care should then be taken that the shape of the glass body to which the sealing is applied is such that the light is reflected back as optimally as possible, in particular in the manner described above for the back reflector.

Figures 2 and 3 show an example of a light beam 24, which is reflected back from the back reflector.

In the light source arrangement 100, the plane 18 is an optical system, symbolized by a lens 26, arranged downstream, and the optics, so the lens 26, an optical waveguide 28 is arranged downstream. The lens 26 concentrates the incident light (see light beam 20a) into the optical waveguide 28. In such arrangements, the reflector 10 according to the invention proves to be particularly advantageous.

In the case of the light source arrangement 110, a so-called integrator 30 adjoins the reflector 10 directly. This is a body in which light, such as the further guided light beam 20b, is reflected on the inner walls, in such a way that light emerges particularly homogeneously in a plane 32. In the present case, the integrator 30 is funnel-shaped; it should not be rotationally symmetric, but generally has a quadrangular cross-section. Other forms of integrators 30 are conceivable. The light source assembly 110 finds favored use in a projector device.

Claims

claims

1. reflector (10) having a reflective surface, characterized in that the contour of the reflective surface is traversed by a Bezier curve.

Second reflector (10) according to claim 1, characterized in that the contour of the reflective surface is a body of revolution of a Bezier curve.

3. reflector (10) according to claim 1 or 2, characterized in that the Bezier curve is a rational quadratic Bezier curve.

4. Reflector (10) according to claim 3, which is designed for a discharge lamp (116) with two electrodes in a distance d specified in millimeters, wherein for a point on the Bezier curve with the coordinates x (t) and z (t ) z (t), where te [0,1], then:

(\ -t) ² (lw) x ₀ + It (Vt) WX ₁ + t ² (lw) x ₂ x (t) = (lt) ² (lw) + 2t (\ - t) w + t ² ( lw)

such as

(lt) ² (lw) z ₀ + It (U) WZ ₁ + t ² (XW) Z ₁ z (t) = (U) ² (lw) + 2t (\ - t) w + t ² (\ - w)

characterized, that w is between 0.25 and 0.5, and preferably Zvi ^¬'s 0.3 and 0.43, and that x ₀ = dx _00, x \ dx = ₁₀ x ₂ = dx _20, z = ₀ dz _00,

where xoo is between 4 and 10 mm and preferably between 5.5 and 8 mm, xio is between 20 and 42 mm and preferably between 27 and 34.5 mm, x ₂ o is between 12 and 24 mm and preferably between 16 and 19, 5 mm, z _O o is between -0.5 and +0.5 mm and preferably equal to 0, Z20 is between 30 and 112 and preferably between 38 and 93.5, and zio = CZ ₂ O with one between 0 , 22 and 0.67, and preferably between 0.30 and 0.55.

5. light source arrangement (100, 110) with a discharge lamp (116), a first reflector (10) according to one of claims 1 to 4 and a second reflector (22), wherein the reflectors (10, 22) the discharge lamp (116) in sections and the second reflector (22) at least partially terminates one side of the light source assembly.

A light source assembly (100, 110) according to claim 5, wherein the second reflector (22) is shaped and disposed relative to the discharge lamp (116) so as to project light (24) from the discharge lamp (116) thereto reflecting surface of the first reflector (10) reflected.

7. light source arrangement (100, 110) according to claim 5 or 6 in its back to claim 4, characterized in that two electrodes of the discharge lamp (116) paral- IeI to the x-axis and a point between the two electrodes at x = 0 mm and z = 0 mm.

8. light source arrangement (110) according to one of claims 5 to 7, wherein at an end remote from the second reflector (22) end of the first reflector (10) an optical integrator (30) is arranged.

9. light source arrangement (100) according to any one of claims 5 to 7, wherein at a second reflector (22) facing away from the end (10) of the first reflector at least one optical element (26) is arranged and further an optical waveguide (28) is arranged in which the at least one optical element (26) bundles light (20a) which passes from the first reflector (10) to the optical element (26).

10. Projector device with a light source arrangement (110) according to one of claims 5 to 8.