WO2000063727A1

WO2000063727A1 - Optical switch and assembly of at least two of such optical switches

Info

Publication number: WO2000063727A1
Application number: PCT/NL2000/000215
Authority: WO
Inventors: Frank Alexander Van Der Bovenkamp
Original assignee: Bovenkamp Frank Alexander V D
Priority date: 1999-04-07
Filing date: 2000-03-31
Publication date: 2000-10-26
Also published as: NL1011749C2; AU3844700A

Abstract

Optical switch comprises a light guide receiving the input light. The light guide has a light output surface and guides the received input light to this light output surface, where the light exits from the light guide. An optical element is provided having a light receiving surface and a viewing surface. The optical element is positioned such that the light receiving surface receives the light that exits from the light output surface. A reservoir is provided containing an at least partially transparent fluid, said fluid can at least partially be positioned between the light output surface and the light receiving surface. Means are provided for mutual movement of the light output surface and the light receiving surface.

Description

Optical switch and assembly of at least two of such optical switches.

The present invention relates to an optical switch with which light supplied to the optical switch can be switched. By switching is meant not only having the quantity of light changed but also having the colour of the light that is supplied changed.

In many fields of application there is a need for such an optical switch, which amongst others has a high light efficiency, shows no phantom effects as a result of unwanted internal reflections, has a very large switching range, and needs little servicing.

The present invention meets this need by providing an optical switch for switching light supplied to an optical switch, which optical switch is provided with a light conductor receiving the supplied light, which light conductor is provided with a light exit surface, the light conductor conduc- ting the supplied light received to the light exit surface where the light exits the light conductor, an optical element having a light receiving surface and a sight surface, which optical element is placed such that the light receiving surface receives the light exited from the light exit surface, the optical element being made of a material which is at least partially transparent to light, so that light from the light receiving surface is conducted to the sight surface, a reservoir containing an at least partially transparent liquid, in which at least a quantity of the liquid can be placed between the light exit surface and the light receiving surface. Switching the optical switch is realised by the liquid which can be placed between the light exit surface and the light receiving surface. By altering the characteristics of the liquid, such as transparency, density, colour and the like, the light which is led through the optical switch is influenced, in other words switched. It is therefore possible to obtain a light range between white and black, as well as for instance various "shades of grey" of red.

The invention arose as a result of a need for new possibilities for so-called Dynamic Route Information Panels (DRIPs), which ensure the display of route information, graphic pictures, such as traffic signs to road users. There is a particular need for DRIPs to display as desired certain road signs, which may include several colours. Up until now LED technology has been used to that end. LED technology however entails certain drawbacks for various uses, particularly used when in DRIPs. First of all the light efficiency of LEDs is limited. Second of all the angle at which LEDs emit light is limited. Third of all LEDs have a limited switching range (below 60%). Fourth of all LED technology is expensive. The use of an optical switch according to the invention does not entail such drawbacks. Moreover it appeared that such an optical switch can be used for many other applications, such as atmospheric lighting, billboards, car industry, print plates etcetera.

In a preferred embodiment of an optical switch according to the invention, the light exit surface and the light receiving surface can be placed at a variable distance from each other. As a result it is possible to adjust the quantity of liquid between the light exit surface and the light receiving surface, as a result of which the light going through the liquid is more or less absorbed, and thus a simple switching of the light is created. Although it is possible to vary the distance between the light exit surface and the light receiving surface by increasing the liquid pressure, as a result of which at a correct suspension of the light exit surface and the light receiving surface a variable distance between it is obtain, for reasons of reproducibility of the distance it is preferred that means are provided for moving the light exit surface and the light receiving surface with respect to each other, for placing the light exit surface and the light receiving surface at a variable distance from each other. ln a preferred embodiment of an optical switch according to the invention the means for moving the light exit surface and the light receiving surface with respect to each other, are provided with a first electromagnetic means attached to the optical element, with a second electromagnetic means cooperating therewith attached to the light conductor, and with means for exciting the first and second electromagnetic means.

Preferably the light conductor is a tubular element. In particular the tubular element is provided with a central blind cavity, which is closed near the light exit surface. Preferably the tubular element is made of an acrylic plastic.

According to a further embodiment of an optical switch according to the invention the reservoir is formed by a cylindrical element surrounding both the liquid and the light conductor. Preferably the cylindrical element is placed at least almost coaxially around the tubular light conductor. As a result a compact liquid-proof construction is possible. Preferably the cylindrical element is flexible, for instance made of a silicone material. As a result the pressure variations which might arise when increasing the dis- tance between the light exit surface and the light receiving surface are compensated and absorbed.

In an embodiment of an optical switch according to the invention the optical element is provided with a cylindrical member of which the end plane forms the light receiving surface, and in which the cylindrical element at least partially surrounds the cylindrical member. As a result a simple mechanical construction is obtained as a result of which the light exit surface and the light receiving surface are positioned with respect to each other in a defined manner.

A very compact, simple and reliably working optical switch is obtained when the second electromagnetic means is cylindrical and has a U-shaped cross-section, and in which the first electromagnetic means is placed in the space between the legs of the U of the second electromagnetic means. Preferably the optical switch according to the invention is further provided with a cover-shaped housing having a central opening for receiving and attaching the light conductor and having a cylindrical wall, in which the second electromagnetic means is arranged on the free end of the cylindrical wall.

In a preferred embodiment of the invention the optical switch is further provided with a cover of transparent material, preferably having a lens shape, amongst other in order to diffuse exiting light over a large field of vision. Preferably the cover is arranged on the second electromagnetic means, and is particularly made of an acrylic plastic.

In order to prevent that the light exit surface and the light receiving surface stick together at minimal distance, in an embodiment of an optical switch according to the invention the light exit surface is provided with a relief, preferably the light exit surface is partially spherical. Alternatively or additionally the light receiving surface is provided with a relief, preferably the light receiving surface is partially spherical.

In a preferred embodiment of an optical switch according to the invention the sight surface has a lens shape, so that certain optical characteristics can be given to the exiting light.

In order to be able to switch over a large range of colours it would be possible to use various light sources to supply light to the optical switch. However in some applications this is impossible amongst others because of lack of space. In order to be able to switch a large range of colours in one single light source the invention also provides an assembly of at least a first and a second optical switch each according to the invention, in which the light coming from the sight surface of the first optical switch is sup- plied to the light conductor of the second optical switch. Preferably the assembly is further provided with a common housing surrounding and serving for the attachment to it of ail optical switches of the assembly. Because several optical switches are placed in line it is possible by providing each of the optical switches with liquids of different colours, to switch a large range of colours.

The present invention will by way of example be described on the basis of some exemplary embodiments shown in the drawings, in which:

Figure 1 shows a schematic cross-section of an optical switch according to the invention,

Figure 2 schematically shows a part of a DRIP having switches according to the present invention, and

Figure 3 schematically and in perspective view shows an assembly according to the present invention.

In figure 1 an optical switch according to the invention is showed schematically in cross-section. The optical switch 1 is destined for switching light supplied to the optical switch 1 . Said light can be supplied by a known light source (not shown) such as for instance a light bulb, a strip light, a laser and the like. The optical switch 1 has a light conductor 2 receiving the supplied light.

The light conductor 2 may assume any known form for light conductors but preferably is a tubular element. Said tubular element may be solid, but alternatively may be provided with a central blind cavity for accom- modating for instance an optical fibre. The cavity is closed near a light exit surface 3 of the light conductor 2. Preferably the tubular element is made of an acrylic plastic, although any other at least partially transparent material is suitable.

The light conductor 2 conducts the received light supplied to the light exit surface 3 where the light exits the light conductor 2.

The optical switch 1 is further provided with an optical element 4 having a light receiving surface 5 and a sight surface 6. Said optical element 4 is placed such that the light receiving surface 5 receives the light exited from the light exit surface 3. The optical element 4 is made of a material which is at least partially transparent to light, for instance an acrylic plastic, so that light from the light receiving surface 5 is conducted to the sight surface 6.

Furthermore a reservoir 7 is provided containing an at least partially transparent liquid, such as for instance an oily emulsion, a colorant or the like. At least a quantity of the liquid can be placed between the light exit surface 3 and the light receiving surface 5.

In the exemplary embodiment shown the reservoir 7 is formed by a cylindrical element 8 surrounding both the liquid and the light conductor 2.

In order to provide a compact construction the cylindrical element 8 is placed at least almost coaxially around the tubular light conductor 2.

For obtaining a good and defined positioning of the light conductor and the optical element the optical element 4 is provided with a cylindrical member

9 of which the end plane forms the light receiving surface 5. Here the cylindrical element 8 at least partially surrounds the cylindrical member 9.

Switching supplied light is realised for instance by altering the charac- teristics of the liquid, such as transparency, density, colour and the like, so that the light which is led through the optical switch is influenced, in other words is switched. It is possible to introduce different liquids, or liquids having different characteristics into the reservoir and to remove liquids present out of there. However this requires more parts and is unwanted for some more compact applications.

In a as to design simple and compact optical switch according to the invention, the light exit surface 3 and the light receiving surface 5 can be placed at a variable distance from each other. As a result use can be made of a closed liquid revoir, and depending on the distance between the light exit surface 3 and the light receiving surface 5 the absorbtion can be more or less. It is therefore possible to obtain a light range between white (little absorbtion, little distance) and black (maximum absorbtion, large distance), as well as for instance various "shades of grey" of red, as a result of which for instance in a car the optical switch used as brake light, clearly display the differences in brake power exerted by the driver through the different shades of red.

Preferably the cylindrical element 8 is flexible. As a result the pressure variations which might occur when increasing the distance between the light exit surface 3 and the light receiving surface 5 are compensated and absorbed.

There are many means which allow to adjust the distance one to the other between the light exit surface 3 and the light receiving surface 5, in other words to cause a liquid displacement. Electro motors, piezo elements, pistons and the like can be thought of here. Moreover by exerting pressure, for instance by controlled pinching elements, on the flexible reservoir 8 and a correct suspension one to the other of the light conductor and the optical element, the distance one to the other between the light exit surface and the light receiving surface can be adjusted. The means described below are particularly suitable for use in service-low, compact and reliable constructions which for instance can be used in DRIPs. According to an embodiment of the invention the means for moving the light exit surface 3 and the light receiving surface 5 with respect to each other, are provided with a first electromagnetic means 10 attached to the optical element 4, and with a second electromagnetic means 1 1 cooperating therewith attached to the light conductor 2. Furthermore means are provided for exciting the first and second electromagnetic means. Said means are shown in figure 2 by cables 1 6, 1 7 which are able to provide the first and second electromagnetic means with an excitation voltage.

In the exemplary embodiment shown the second electromagnetic means 1 1 is cylindrical and has a U-shaped cross-section. The second electromagnetic means 1 1 may for instance be a ferrite ring. The first electromagnetic means 10, for instance a coil, is placed in the space between the legs of the U of the second electromagnetic means 1 1 . By excitation of the electromagnetic means 10, 1 1 the optical element 4 can therefore be moved with respect to the light conductor 2. The cylindrical part 9 then slides into the cylindrical reservoir 8, and more or less liquid can come between the light exit surface 3 and the light receiving surface 5.

The optical switch 1 further has a cover-shaped housing 1 2, 14 having a central opening 1 3 for receiving and attaching the light conductor 2. The housing has a cylindrical wall 14, in which the second electromagnetic means 1 1 is arranged on the free end of the cylindrical wall 14. This ensures that the supply side of light of the optical switch 1 has a closed construction, as a result of which the unwanted penetration of dust and the like is prevented.

In order to further close off the optical switch 1 from unwanted dirt, a cover 1 5 of transparent material, for instance acrylic plastic, is provided, but another transparent material used in optics is also suitable. Preferably the cover 1 5 is arranged on the second electromagnetic means 1 1 , al- though an attachment to the wall 14 of the housing is also possible.

In order to prevent that at minimal distance between the light exit surface 3 and the light receiving surface 5 these unwantedly stick together, the light exit surface 3 and/or the light receiving surface 5 is provided with a relief. For example, said relief renders the element concerned partially spherical.

In order to give the light exiting the optical switch a certain optical charac- teristic, it is preferred to provide the sight surface 6 and/or the cover 1 5 with a lens shape.

In figure 2 a cross-section is schematically shown of a part of a DRIP, in which a number of optical switches 1 according to the invention are attached next to each other (for instance like a matrix) on a front panel 22.

The cover 1 5 of the optical switch 1 for instance lies on the front panel 22. The excitation of the optical switches 1 takes place via cables 16, 17, which are shown merely for one of the optical switches. It is noted that an additional advantage of the present invention is that the cables of the existing DRIPs already present can be used for the control of the inventive optical switches and that as a result the adaptation to the invention can take place involving relatively low costs.

In order to be able to switch over a large range of colours it would be possible to use different light sources to supply light to the optical switch.

However in some applications this is impossible amongst others because of lack of space. In order to be able to switch a large range of colours with one single light source the invention also provides an assembly of at least a first 1 ' and a second 1 " optical switch (see figure 3, in which also a third optical switch V" is shown) each according to the invention. The light coming from the sight surface of the first optical switch 1 ' is supplied to the light conductor of the second optical switch 1 ". Preferably the as- sembly is further provided with a common housing 20 surrounding and serving for the attachment to it of all optical switches 1 ', 1 ", 1 '" of the assembly. Because several optical switches 1 ', 1 ", 1 '" are placed in line it is possible, by providing each of the optical switches with liquids of different colours, to switch a large range of colours. A green, a blue and a red liquid can be thought of here for the separate optical switches.

It will be clear that light in principle can be offered to the optical switch in various manners, in which for the sake of simplicity light conductor technology as present in existing DRIPs can be taken as starting point, in which from a central light source the light flow is conducted to the optical switches by means of glass fibres. Also a logo or pictogram can be integrated in each optical switch.

It will be clear that the present invention is not limited to the embodiments described above, but that many alterations within the scope of the attached claims are possible. It is possible of course to measure the distance between the light exit surface and the light receiving surface, for instance capacitive. Furthermore many drives can be used for varying the distance between the light exit surface and the light receiving surface, in particular a continuously variable drive is preferred.

(AS\NG 2992)

Claims

1 . Optical switch (1 ) for switching light supplied to the optical switch (1 ), which optical switch ( 1 ) is provided with:

- a light conductor (2) receiving the supplied light, which light conductor (2) is provided with a light exit surface (3), the light conductor (2) conducting the supplied light received to the light exit surface (3) where the light exits the light conductor (2),

- an optical element (4) having a light receiving surface (5) and a sight surface (6), which optical element (4) is placed such that the light receiving surface (5) receives the light exited from the light exit surface (3), the optical element (4) being made of a material which is at least partially transparent to light, so that light from the light receiving surface (5) is conducted to the sight surface (6),

- a reservoir (7) containing an at least partially transparent liquid, in which at least a quantity of the liquid can be placed between the light exit surface (3) and the light receiving surface (5).

2. Optical switch ( 1 ) according to claim 1 , in which the light exit surface (3) and the light receiving surface (5) can be placed at a variable distance from each other.

3. Optical switch (1 ) according to claim 2, in which means are provided for moving the light exit surface (3) and the light receiving surface (5) with respect to each other, for placing the light exit surface (3) and the light receiving surface (5) at a variable distance from each other.

4. Optical switch (1 ) according to any one of the preceding claims, in which the light conductor (2) is a tubular element.

5. Optical switch (1 ) according to claim 4, in which the tubular element is provided with a central blind cavity, which is closed near the light exit surface (3).

6. Optical switch (1 ) according to claim 4 or 5, in which the tubular element is made of an acrylic plastic.

7. Optical switch (1 ) according to any one of the preceding claims, in which the reservoir (7) is formed by a cylindrical element (8) surrounding both the liquid and the light conductor (2).

8. Optical switch (1 ) according to claim 7 referring to any one of the claims 4 -6, in which the cylindrical element (8) is placed at least almost coaxially around the tubular light conductor (2).

9. Optical switch (1 ) according to claim 7 or 8, in which the optical element (4) is provided with a cylindrical member (9) of which the end plane forms the light receiving surface (5), and in which the cylindrical element (8) at least partially surrounds the cylindrical member (9).

10. Optical switch (1 ) according to claim 7, 8 or 9, in which the cylindrical element (8) is flexible.

1 1. Optical switch (1 ) according to claim 3, in which the means for moving the light exit surface (3) and the light receiving surface (5) with respect to each other, are provided with a first electromagnetic means (10) attached to the optical element (4), with a second electromagnetic means (1 1 ) cooperating therewith connected to the light conductor (2), and with means for exciting the first and second electromagnetic means.

12. Optical switch (1 ) according to claim 1 1 , in which the second electromagnetic means (1 1 ) is cylindrical and has a U-shaped cross-sec- tion, and in which the first electromagnetic means (10) is placed in the space between the legs of the U of the second electromagnetic means (1 1 ).

1 3. Optical switch (1 ) according to claim 12, in which the optical switch

(I ) is further provided with a cover-shaped housing (12, 14) having a central opening (13) for receiving and attaching the light conductor (2) and having a cylindrical wall ( 14), in which the second electromagnetic means

(I I ) is arranged on the free end of the cylindrical wall (14).

14. Optical switch (1 ) according to any one of the preceding claims, in which the optical switch (1 ) is further provided with a cover (1 5) of transparent material.

1 5. Optical switch (1 ) according to claim 1 3 and 14, in which the cover

(1 5) is arranged on the second electromagnetic means (1 1 ).

16. Optical switch (1 ) according to claim 14 or 1 5, in which the material is an acrylic plastic.

17. Optical switch (1 ) according to any one of the preceding claims, in which the light exit surface (3) is provided with a relief.

18. Optical switch (1 ) according to claim 17, in which the light exit surface (3) is partially spherical.

1 9. Optical switch (1 ) according to any one of the preceding claims, in which the light receiving surface (5) is provided with a relief.

20. Optical switch (1 ) according to claim 1 9, in which the light receiving surface (5) is partially spherical.

21. Optical switch (1 ) according to any one of the preceding claims, in which the sight surface (6) has a lens shape.

22. Optical switch (1 ) according to claim 14, 15 or 16, in which the cover (15) has a lens shape.

23. Assembly of at least a first and a second optical switch (1 , 1 ', 1 ") each according to any one of the preceding claims, in which the light coming from the sight surface of the first optical switch is supplied to the light conductor of the second optical switch.

24. Assembly according to claim 23, in which the assembly is further provided with a common housing (20) surrounding and serving for the attachment to it of all optical switches of the assembly.