Description

The present invention relates to a method for manufacturing an optical unit for a collimator. The invention further relates to an optical unit for a collimator, a collimator and a lighting unit.

Light-emitting diodes (LEDs) are part of many modern lighting systems. However, when using a plurality of LEDs, it is still an issue that each single LED can be noticed by a person. This may not only be seen as unpleasant by some people but can also contain safety issues, since a plurality of LEDs may distract a user of a respective LED-device, for example. Therefore, it is desired to provide lighting units with a plurality of LEDs, wherein the single LEDs may not be realized as such. One way to achieve this is to cover the LEDs with a diffusor panel. However, there are many different kinds of LEDs and many different kinds of diffusor panels and sometimes the single LEDs can be noticed even though they are covered by a diffusor. Another way to achieve a homogeneous light output, a higher number of LEDs and/or bigger LEDs can be used. However, this increases the costs of the lighting unit.

A further challenge for achieving homogeneous light output is how to configure the distance from a light source to a collimating optical unit and how to construct such a system by conventional geometrical optics. This is the reason why certain optical surfaces are not capable of providing homogenous light output.

It is an object of the present invention to overcome the above mentioned disadvantages. In particular, it is an object of the present invention to provide a method for manufacturing an optical unit for a collimator with improved light output properties. Further, it is an object to provide an optical unit, a collimator as well as a collimator having such improved light output properties. Aforesaid objects are achieved by the subject-matters of the claims. In particular, the objects are achieved by a method according to claim 1 , an optical unit according to claim 4, a collimator according to claim 8 as well as a lighting unit according to claim 9 of the present application. Further features and details of the invention result from the dependent claims, the description and the figures. Features and details discussed with respect to the inventive method are also correlated with the inventive optical unit, the inventive collimator, the inventive lighting unit and the other way around.

According to the present invention, a method is provided for manufacturing an optical unit for a collimator with the optical unit having a basic body with a light ray entrance surface for receiving light rays within an initial beam from a light source and a light ray outlet surface for emitting light rays within a collimated beam, comprising the steps of: providing an imaginary reference surface inside the optical unit, calculating the curvature of the light ray entrance surface based on the imaginary reference surface such that the light rays within the initial beam will pass the imaginary reference surface in a perpendicular manner, calculating the curvature of the light ray outlet surface based on the imaginary reference surface such that light rays within the collimated beam are parallel to each other, and manufacturing the basic body based on the calculated curvature of the light ray entrance surface and the calculated curvature of the light ray outlet surface.

By means of the inventive method, an optical unit is manufactured that provides homogeneous light output. In addition, there will be good collimation for the cases where the light source is directly behind the optical unit. Moreover, the light source may thus be placed directly behind the optical unit and/or the basic body. In addition, fully rotational symmetry can be achieved while still having the desired homogeneous light output.

The curvature of the light ray entrance surface and the curvature of the light ray outlet surface can be calculated by means of computer-aided designing software, in particular 3D CAD software like Catia, preferably in combination with light simulation software and/or raytrace simulation software like Helios environment. The imaginary reference surface can be understood as a 3-dimensional surface and preferably as a 2-dimensional curve. In particular, the imaginary reference surface can be considered as a second order curve. The curvature of the light ray entrance surface may be calculated by means of, for example, the wavefront optical tool in Catia. With such a tool it is possible to calculate the shape and/or curvature of the light ray entrance surface such that light rays coming from the light source are perpendicular to the wavefront control curve. Since the problem of the respective calculation is not linear, the second order curve helps to achieve the desired result. While using Catia or any other comparable tool, the basic analysis can be done in 2D, while the end result can be checked in a 3D-simulation. Key of the invention is the idea of using the imaginary reference surface for the calculations.

According to the present invention, the imaginary reference surface can be provided as a first guess of a suitable curve and/or curved plane. Afterwards, the curvatures of the entrance surface and the outlet surface can be calculated by using said reference surface and/or curve. In other words, the curvature of the light ray entrance surface can be calculated from the light source to the imaginary reference surface as a target for a proper distribution for the collimator. The curvature of the light ray outlet surface can be calculated thereafter backwards from the collimated source and/or light rays in the collimated beam to the same imaginary reference surface as a target for a proper collimation of the light rays. That is, the curvature of the light ray entrance surface can be calculated such that a desired collimated light distribution is get to the light ray outlet surface. The source can be considered as the collimated beam with collimated, in particular parallel or essentially parallel, light rays.

The actual calculations may then vary depending on different parameters like physical sizes, focal lengths and light source sizes. With different parameters, a light intensity distribution of the collimated beam can be modified from center and/or side heavy or the opposite thereof, until the light output is as desired. The optical unit can be regarded as an optical element provided in one piece and/or in the shape of a monobloc. The imaginary reference surface is preferably located between the light ray entrance surface and the light ray outlet surface.

The optical unit can be characterized by a basic body having a first portion with the light ray entrance surface for receiving light rays within the initial beam and a second portion with the light ray outlet surface for emitting light rays within the collimated beam, wherein the first portion and/or the light ray entrance surface are domed with a curvature direction away from the light ray outlet surface and the second portion and/or the light ray outlet surface are domed with a curvature direction away from the light ray inlet surface, and wherein the height of the second portion is, regarded in a height direction from an entrance peak of the light ray entrance surface to an outlet peak of the light ray outlet surface, multiple times higher than the height of the first portion. In addition, the basic body comprises a third portion located, regarded in the height direction, between the first portion and the second portion, wherein the third portion is truncated cone shaped while a diameter of the third portion increases in the height direction. In such an embodiment it is preferred that the imaginary reference surface is provided partly in the third portion, wherein a peak of the imaginary reference surface is located in the second portion. Several experimental approaches have shown that this configuration quickly leads to the desired values for manufacturing an optical unit and/or basic body providing a highly homogeneous light output.

According to a further embodiment of the present invention a method is characterized in that the light ray entrance surface is domed with a curvature direction away from the light ray outlet surface and the light ray outlet surface is domed with a curvature direction away from the light ray inlet surface, wherein the imaginary reference surface is provided domed with a curvature direction away from the light ray entrance surface. With this orientation of the imaginary reference surface it is possible to calculate the desired curvatures in a fast manner. The domed shape can be understood as a hill shaped and/or bell-shaped 2-dimensional curve and/or a 3-dimensional bell and/or dome-shape. In a preferred embodiment, the imaginary reference surface is provided domed and/or bell-shaped as a second order curve.

It is further possible that according to the present invention a method is characterized in that the imaginary reference surface is adjusted based on the calculated curvature of the light ray entrance surface and/or the calculated curvature of the light ray outlet surface, wherein the light ray entrance surface and/or the calculated light ray outlet surface are calculated again based on the adjusted imaginary reference surface. It has been shown that the desired values for the curvature of the light ray entrance surface and the curvature of the light ray outlet surface become better the more often the following calculations are performed: adjusting the imaginary reference surface based on and/or by using the calculated curvature of the light ray entrance surface and/or the calculated curvature of the light ray outlet surface, calculating the curvature of the light ray entrance surface based on the adjusted reference surface such that the light rays within the initial beam will pass the imaginary reference surface in a perpendicular manner and/or calculating the curvature of the light ray outlet surface based on the adjusted reference surface such that light rays (13) within the collimated beam (15) are parallel to each other, further adjusting the imaginary reference surface again based on the again calculated curvature of the light ray entrance surface and/or the again calculated curvature of the light ray outlet surface, and so on.

The more loops are calculated and/or adjusted, the better the final result, i.e. , the more homogeneous the light output from the desired basic body. Consequently, there may be performed a plurality of such loops before using the calculated data for manufacturing and manufacturing the basic body and/or the optical unit, respectively.

According to another aspect of the invention, an optical unit for a collimator is provided for collimating an initial beam of light rays radiating from a light source into a collimated beam of light rays, wherein the optical unit is manufactured according to a method as described in detail above. Therefore, said optical unit brings up the same advantages that have been discussed in detail with respect to the inventive method.

Moreover, it is possible that, according to the present invention, the optical unit is characterized by a basic body having a first portion with the light ray entrance surface for receiving light rays within the initial beam and a second portion with the light ray outlet surface for emitting light rays within the collimated beam, wherein the first portion and/or the light ray entrance surface are domed with a curvature direction away from the light ray outlet surface and the second portion and/or the light ray outlet surface are domed with a curvature direction away from the light ray inlet surface, and wherein the height of the second portion is, regarded in a height direction from an entrance peak of the light ray entrance surface to an outlet peak of the light ray outlet surface, multiple times higher than the height of the first portion. With such a shape, which results from the calculations according to the inventive method, the desired homogeneous light output can be reliably achieved. In such an embodiment, the light ray outlet surface has a stronger curvature than the light ray entrance surface. It can be of further advantage in view of the desired homogeneous light output, that the second portion is more than 3 times, in particular more than 5 times, higher than the first portion. The light ray entrance surface and/or the light ray outlet surface are each preferably dome- and/or bell-shaped.

Pursuant to another embodiment of the present invention, an optical unit is characterized in that the basic body comprises a third portion located, regarded in the height direction, between the first portion and the second portion, wherein the third portion is truncated cone shaped while a diameter of the third portion increases in the height direction. It is also an advantageous possibility according to the present invention that the height of the second portion is, regarded in the height direction, higher than the height of the third portion . In accordance with another aspect of the present invention, a collimator is provided comprising at least one light source and at least one optical unit as described above. The light source is preferably positioned such that light rays from the light source pass through the first portion, then through the imaginary reference surface in a perpendicular manner and then leave the second portion parallel to each other while providing homogenous intensity over the light output area.

According to a further aspect of the present invention, a lighting unit is provided comprising a plurality of optical units as described above. The optical units can be arranged side by side to provide homogenous backlighting for example. It is preferred that at least some of the optical units are arranged in a linear manner and/or at least some of the optical units are arranged in a circular manner.

Moreover, it is possible that the optical units of an inventive lighting unit are positioned next to each other in an overlapping manner. Due to the advantageous collimated light output from the inventive optical units, overlapping optical units may provide the desired homogeneous light output within the lighting unit without specific diffusors needed. An overlapping manner means that the basic bodies of the optical units provide flat contact faces by means of which the basic bodies are positioned in contact to each other. In other words, the optical units can be in contact to each other as long as the remaining light ray outlet surface do have its counter part light ray entrance surface available and clear aperture between those two.

The present invention is discussed in more detail with respect to the accompanying drawings, in which

Fig. 1 shows a side view of an optical unit according to a preferred embodiment of the present invention,

Fig. 2 shows another side view of the optical unit according to the preferred embodiment of the present invention, Fig. 3 shows a perspective view of a lighting unit according to a first embodiment of the present invention,

Fig. 4 shows a perspective view of a lighting unit according to a second embodiment of the present invention, and

Fig. 5 shows a flow chart for explaining a method according to a preferred embodiment of the present invention.

Fig. 1 shows an optical unit 10 for a collimator 11 for collimating an initial beam 12 of light rays 13 radiating from a light source 14 into a collimated beam 15 of light rays 13. In Fig. 2, the optical unit 10 of Fig. 1 is shown in more detail. As illustrated in Fig. 2., the optical unit 10 comprises a basic body 16 having a first portion 30 with a light ray entrance surface 17 for receiving light rays 13 within the initial beam 12 and a second portion 31 with a light ray outlet surface 18 for emitting light rays 13 within the collimated beam 15. The first portion 30 and the light ray entrance surface 17, respectively, are domed with a curvature direction away from the light ray outlet surface 18. The second portion 31 and the light ray outlet surface 18, respectively, are domed with a curvature direction away from the light ray inlet surface 17. The height H2 of the second portion 30 is, regarded in a height direction D1 from an entrance peak 19 of the light ray entrance surface 17 to an outlet peak 20 of the light ray outlet surface 18, multiple times higher than the height H 1 of the first portion 31.

The basic body 16 further comprises a third portion 32 located, regarded in the height direction D1 , between the first portion 30 and the second portion 31 , wherein the third portion 32 is truncated cone shaped while a diameter of the third portion 32 increases in the height direction D1. The height H2 of the second portion 31 is, regarded in the height direction D1, higher than the height H3 of the third portion 32 and even higher than the first portion 30 and the third portion 32 together. In Fig. 3, a lighting unit 50 is shown, comprising a plurality of optical units 10 as described with reference to Fig. 1 and Fig. 2. Some of the optical units 10 are arranged in a circular manner around one centered optical unit 10. According to the embodiment of Fig. 3, the optical units 10 are positioned next to each other in an overlapping manner. Fig. 4 shows a lighting unit 50, in which a plurality of optical units 10 are arranged in a linear as well as an overlapping manner.

With reference to the flow chart of Fig. 5, a method for manufacturing an optical unit 10 for a collimator 11 with the above described optical unit 10 will be described. In a first step S1 , an imaginary reference surface 21 inside the optical unit 10 will be provided. Thereafter, in step S2, the curvature of the light ray entrance surface 17 is calculated based on the imaginary reference surface 21 such that the light rays 13 within the initial beam 12 will pass the imaginary reference surface 21 in a perpendicular manner. In step S3, the curvature of the light ray outlet surface 18 is calculated based on the imaginary reference surface 21 such that light rays 13 within the collimated beam 15 are parallel to each other. The steps S1 to S3 can be repeated as often as desired. That is, the imaginary reference surface 21 can be repeatedly adjusted based on calculated curvatures of the light ray entrance surface 17 and the light ray outlet surface 18, wherein the light ray entrance surface 17 and the calculated light ray outlet surface 18 can be repeatedly calculated based on the adjusted imaginary reference surface 21. Further, steps S2 and S3 can be performed the other way around. As soon as the calculated curvatures appear to be as desired such that the desired homogeneity of light output is reached, basic body 16 is manufactured in step S4 based on the calculated curvature of the light ray entrance surface 17 and the calculated curvature of the light ray outlet surface 18. As can be seen in Fig. 1 and Fig. 2, the imaginary reference surface 21 is provided domed in the shape of a second order curve with a curvature direction away from the light ray entrance surface 17.

The aforesaid description of the accompanying drawings is only by the way of detail and example. Specific features of each aspect of the present invention and the figures can be combined which each other if of technical sense. Reference signs

10 optical unit

11 collimator

12 initial beam

13 light ray

14 light source

15 collimated beam

16 basic body

17 light ray entrance surface

18 light ray outlet surface

19 entrance peak

20 outlet peak

21 imaginary reference surface

30 first portion

31 second portion

32 third portion

50 lighting unit