WO2007116338A2

WO2007116338A2 - Scanning laser lighting device

Info

Publication number: WO2007116338A2
Application number: PCT/IB2007/051148
Authority: WO
Inventors: Adrianus J. S. M. De Vaan
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2006-04-07
Filing date: 2007-03-30
Publication date: 2007-10-18
Also published as: CN101415990A; TW200813367A; JP2009533798A; WO2007116338A3; EP2008015A2

Abstract

A lighting device comprising at least two laser light sources (6) for emitting light of different wavelength, a scanner (8) for scanning a laser beam from said at least one laser light source (6) onto a diffusing surface (10), a driver (3) arranged to control at least one of modulation of said at least one laser light source (6) and operation of said scanner (8) so that said emitted light forms a desired light pattern, and a power supply (4) arranged to provide power to said laser light sources (6) so that the average spectral output power of the lighting device over a given time period is essentially constant. According to the invention, the average spectral output power over a given time period is held essentially constant. This enables variable scanning patterns imaged by the laser projection system, while the spectral light output of the system, and as such the light output of the device that is used to illuminate the room, remains constant.

Description

Scanning laser lighting device

The present invention relates to lighting devices, and in particular decorative lighting devices. More specifically, the present invention relates to lighting devices using scanned laser light.

In the field of artificial lighting, there is an increased need to provide variable lighting, both in terms of color and lighting patterns. Existing solutions for providing variable light patterns are typically bulky and expensive, and not suitable for lighting applications. Examples include various types of projection systems, for projecting images. Laser light has found very limited use in lighting applications. JP 09-307174 is an example of a lighting device comprising a laser light source and a diffuser, resulting in a point shaped light source.

It is an object of the present invention to provide an efficient lighting device for generating variable lighting patterns.

This and other objects are achieved by a lighting device comprising at least two laser light sources for emitting light of different wavelength, a scanner for scanning a laser beam from the laser light sources onto a diffusing surface, a driver arranged to control at least one of modulation of the laser light sources and operation of the scanner so that the emitted light forms a desired light pattern, and a power supply arranged to provide power to the laser light sources so that the average spectral output power of the lighting device over a given time period is essentially constant.

By using a scanning laser projection unit in a lighting device, it is possible to generate variable decorative patterns suitable for various lighting applications, while the light from these patterns can simultaneously be used to illuminate the room. The decorative pattern might consist of colored lines on a dark background, colored spots on a dark background, colored spots on a colored background, colored spots an a white background etc.

Scanning laser based micro-projection systems are becoming technically feasible, high efficient and low cost. The lighting device is power efficient, as laser light sources are very efficient.

By using a plurality of laser light sources with different light emission spectra, the projection unit is provided with a useful light spectrum, and can generate patterns can be varied not only in shape and size, but also in color. The number of laser light sources can be three, e.g. red, green and blue, but can also be larger, and include another colors. By including many different colored lasers, the color-rendering index of the lighting device is increased, and a wide range of color temperatures can be obtained. In one embodiment, the colors of the lasers are red, blue and green, as conventionally used in scanning laser projection units, but this is by no means limiting for the invention.

According to the invention, the average spectral output power over a given time period is held essentially constant. This enables variable scanning patterns imaged by the laser projection system, while the spectral light output of the system, and as such the light output of the device that is used to illuminate the room, remains constant. The expression "spectral output power" is here intended to include both the spectral content of the light, i.e. the emitted color spectrum, as well as the intensity of the light. By keeping these factors essentially constant, the light lighting device will not cause changing shadows or changing colors in the surroundings. Further, the emitted light will not be perceived as flickering. The time period during which the spectral output is constant is preferably shorter than the response time of a human eye. This ensures that the variations that do occur are on such a short time scale that they are not perceived by the eye. The control of spectral output power can be accomplished by a control system comprising color sensors and a feedback path arranged to provide the power supply with feedback of said spectral output power, wherein the power supply is adapted to control a spectral output power based on this feedback. This solution ensures that the spectral output power is controlled based on actual emitted light. Alternatively, the power supply controls the spectral output power based on the predicted performance of the laser light sources. Such a control system does not require any feedback, but may be vulnerable to changing conditions that affect the performance of the light sources, such as temperature. The diffusing surface can be a reflecting surface, like a wall or the ceiling, preferably coated with a suitable coating, but can also be transmissive, so that light from the laser light sources is transmitted through the surface.

According to one embodiment, the diffusing surface is an exit window of a housing in which the laser light sources are contained. Such a design ensures that the laser light is not incident directly in the eyes of a user, making a laser based lighting unit safe to use in any environment. Such a housing also protects the sensitive lasers from the environment, and also ensures that no laser light escapes from the device except when diffused by the diffusing exit window. The driver can be equipped with a memory for storing various scanning patterns. Further, it can be provided with an input for receiving a scanning pattern. The input can be a connector, such as a USB, IEE1394, serial bus or parallel bus, or can be a wireless receiver, such as an RF receiver, IR receiver, Bluetooth receiver, or Wireless LAN.

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing a currently preferred embodiment of the invention.

Fig 1 shows a schematic view of an embodiment of a lighting device according to the present invention.

Figure 1 shows a lighting device according to a first embodiment of the invention. The device comprises a housing 1, preferably of a shape and material making it attractive to use as a lighting appliance in a private or public environment.

In the housing is arranged a laser-scanning unit 2, a laser-scanning driver 3, and a power supply 4. The power supply can be provided with an internal power source such as a battery pack (not shown) or be connected to the AC mains 5.

The laser scanning unit 2 comprises one or several laser light sources 6, optical elements 7 to combine light from the laser light sources into one beam, and a scanning mirror 8 for scanning this beam over a surface. Such laser scanning units, also referred to as micro beamers, are known in the art, and described e.g. in US 6,583,912, herewith incorporated by reference. The laser-scanning unit 2 can comprise several laser light sources with different light emission spectra. For example, the laser-scanning unit 2 can comprise a red, a green and a blue laser light source, in order to enable generation of light in the entire visible spectrum. However, the number of light sources is not limited to three, but on the contrary, the lighting device may include a plurality of laser light sources with different wavelengths, thus providing an even better color rendering index.

The housing is further provided with an opening 9, in which is fitted a diffuse exit window 10, e.g. made of a transparent plastic material. The exit window is adapted to diffuse light from the laser scanning unit 2, so that light emitted from the outer side 10a of the exit window 10 is no longer harmful for a human eye, and so that the light from the lasers illuminates the entire room into all directions.

The diver 3 is connected to the laser-scanning unit 2, and adapted to provide the laser light source(s) with a control signal 12 for modulating the light from the laser light sources 6, in order to enable generation of various patterns on the diffusing exit window 10. The driver can be preprogrammed with a number of different patterns stored in a memory and selectable by a user using a selector switch 13. Alternatively, or in combination, the driver can be provided with an input 14, such as a USB terminal or a (wireless) LAN connection, through which pattern information can be loaded into the driver 3.

The power supply 4 is arranged to provide the driver 3 and laser scanning unit 2 with power. The power supply is adapted to regulate the power output so that the average light spectrum during a given period of time stays constant. This time period can be selected to be in the order of the response time of the human eye, i.e. in the order of 10 ms. By providing light with spectrum stability, i.e. where the spectral power is perceived as constant by a human, the lighting device can illuminate with a varying pattern without causing undesired color effect on the environment.

In use, the laser-scanning unit 2 will be controlled by the driver to generate light with a given pattern by scanning modulated light from the laser light source(s) 6 onto the inner surface of the exit window. The light leaving the exit window will be diffused, no longer harmful for a human eye, even when looking directly into the exit window 10, and will provide a smooth illumination of the room.

According to one embodiment, the control of light spectrum output power is provided by a control system comprising color sensors 15 arranged to receive light emitted from the laser light sources 6, and a feedback path 16 arranged to feedback information from these sensors 15 to the driver 3 and/or power supply 4. The power supply 4 and/or driver 3 is thus provided with spectral output feedback, and is adapted to control a spectral output of the lighting device based on this feedback. Such optical feedback is well known e.g. in LED lighting systems, and will not be described in detail. A purpose of such control system in relation to the lighting device according to this embodiment of the invention is that the control system can enable the driver 3 and power supply 4 to regulate the spectral light output power to remain constant over a given period of time.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the driver may be arranged to control not only the modulation of light, but also the scanning of the laser-scanning unit 2.

Further, the invention is not limited to a device having a diffusing exit window. In an alternative embodiment, the laser-scanning unit (including laser light sources, scanner and driver) is separated from the diffuser, and where the diffuser is a surface, preferably coated by a suitable coating, on the ceiling and/or a wall in a room.

Claims

CLAIMS:

1. A lighting device comprising: at least two laser light sources (6) for emitting light of different wavelength, a scanner (8) for scanning a laser beam from said laser light sources (6) onto a diffusing surface (10), a driver (3) arranged to control at least one of modulation of said laser light sources (6) and operation of said scanner (8) so that said emitted light forms a desired light pattern, and a power supply (4) arranged to provide power to said laser light sources (6) so that the average spectral output power of the lighting device over a given time period is essentially constant.

2. The lighting device in claim 1, wherein said given time period is shorter than the response time of a human eye.

3. The lighting device according to claim 1 or 2, further comprising color sensors

(15) and a feedback path (16) arranged to provide said power supply (4) with feedback of said spectral output power, wherein said power supply (4) is adapted to control the spectral output power based on said feedback.

4. The lighting device according to any one of the preceding claims, wherein the driver (3) further comprises a memory for storing at least one scanning pattern.

5. The lighting device according to any one of the preceding claims, wherein the driver (3) further comprises an input (14) for receiving a scanning pattern.

6. The lighting device according to claim 5, where the input (14) comprises an input connector.

7. The lighting device according to claim 5, where the input (14) comprises a wireless receiver.

8. The lighting device according to any one of the preceding claims, wherein said diffusing surface is formed by a transmissive surface (10), arranged to transmit light from the laser light units (6).

9. The lighting device according to claim 8, wherein said laser light sources (6) are contained in a housing (1), and said transmissive surface is formed by an exit window (10) of said housing (1), so that said lighting device is arranged to emit diffused light through said exit window (10).