WO2025256869A1

WO2025256869A1 - Illumination system

Info

Publication number: WO2025256869A1
Application number: PCT/EP2025/063684
Authority: WO
Inventors: Joris Jan Vrehen
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2024-06-10
Filing date: 2025-05-19
Publication date: 2025-12-18
Anticipated expiration: 2026-12-10

Abstract

An illumination system (1) comprises a light source emitting a beam of light (105). A beam directing arrangement (102) comprises a first polygon scan unit (104, 124) configured to rotate at a constant angular speed. A free-shape surface (110, 130) is configured to reflect or refract the beam of light such that the light beam (105) is scanned at a varying angular speed to provide a required intensity at each angle of scanning. Alternatively, the beam directing arrangement (202) comprises a second scan unit (204) comprising at least one reflective surface (206) for reflecting the light beam (105). The reflective surface (206) is configured to rotate at varying angular speed such that the light beam (105) is scanned at a varying angular speed to provide a required intensity at each angle of scanning.

Description

Illumination system

FIELD OF THE INVENTION

The present invention generally relates to illumination systems. More specifically, the present invention is related to an illumination system comprising a light source that emits an angularly scanning light beam and a beam directing arrangement.

BACKGROUND OF THE INVENTION

For flood illuminating large objects such as building facades there are several approaches used in the prior art. One approach is to use multiple high flux flood lights positioned at some distance from the building facing upward on the facade. A drawback with such flood lights is a difficulty to obtain a homogeneous illumination and at the same time limit the amount of light that is missing the fapade and thereby pollutes the night sky with undesired light. A reason for this is that, in order to obtain a homogeneous illumination of the facade. the peak intensity of the light beam must be aimed at the rim of the roof, i.e. at the edge of the facade, whereby a large section of the light beam will be aimed skyward.

By configuring the flood light arrangement such that the light beam becomes asymmetric, a limited reduction of spill light may be obtained. However, in general, a limited number of beam profiles can be obtained from such flood light arrangements. Consequently, most prior art flood light installations will result in a compromise of available beam shapes, building dimensions, homogeneity of the illumination and the amount of spill light.

Another approach used in the prior art is to use many small flood lights close to the building and mounted on the facade to illuminate the building and accentuate the 3D shape of the facade. Also here it is difficult to avoid spill light missing the facade and thereby illuminating the sky.

Other drawbacks of the known building illumination approaches are that they typically also illuminate windows in the facade and that, although the light source may have a high efficacy, energy is nevertheless lost because some light does not reach the faqade, but windows or night sky.

High power video projectors such as liquid crystal display (LCD) or digital light processing (DLP) projectors can also be used to illuminate buildings. In that case spill light can be significantly reduced as each pixel in the beamer display can be controlled independently. Such devices have drawbacks in that the optical efficiency (from light source to target) of a beamer is rather low, and the light is controlled by absorbing the parts that one does not need. Leading to an even worse efficacy.

Yet another alternative is the use of a so-called gobo light spot. Here a mask with the required shape is imaged onto the object to be illuminated. Also, here the mask absorbs part of the light of the light source to create the dark parts in the illumination which limits the efficiency.

In summary, drawbacks with current illumination systems for large objects such as buildings include: spill light (which contributes to night sky pollution) of the luminaire missing the building, “trespassing” light into windows of the illuminated building or neighboring buildings, energy efficiency due to the amount of light missing the intended target, as well as, in case of the beamer or gobo illumination, an undesired amount of absorbed light.

SUMMARY OF THE INVENTION

It is of interest to provide an illumination system that is capable of overcoming the drawbacks of prior art devices.

This and other obj ects are achieved in a first aspect by providing an illumination system having the features of the appended independent claim. Preferred embodiments are defined in the appended dependent claims.

Hence, according to the present invention there is provided an illumination system for emitting at least one angularly scanning light beam. The illumination system comprises a light source configured to emit at least one narrow beam of light and a beam directing arrangement. The beam directing arrangement comprises a first polygon scan unit configured to rotate at a constant angular speed in relation to at least a first rotation axis. At least one free-shape surface is configured to reflect or refract the at least one narrow beam of light such that the at least one light beam emitted by the system is scanned at a varying angular speed to provide a required intensity at each angle of scanning.

Alternatively, the beam directing arrangement comprises a second scan unit comprising at least one reflective surface for reflecting the at least one narrow beam of light. The at least one reflective surface is configured to rotate at varying angular speed such that the at least one light beam emitted by the system is scanned at a varying angular speed to provide a required intensity at each angle of scanning.

Such a system is one wherein a narrow light beam, for example in the form of a laser light beam, is scanned over a target area. By controlling the light beam intensity depending direction of the light source, a precise light distribution can be created that only illuminates the target area which does not consume energy when no illumination is required. In other words, such an illumination system creates a non-linear scan of light beams where the angular speed of the beam is adapted as a function of the required (average) intensity in each direction such that the light beam can run at a constant output power while creating a uniform illumination of the large object such as a building facade. Furthermore, such an illumination system is capable of shaping a square angular scan field such that the scan is aimed at the building fapade for a maximum amount of time.

In various embodiments, the at least one free-shape surface forms part of an optical component separated from the first polygon scan unit. In some of these embodiments, the light source is configured to emit a plurality of narrow beams of light, each beam of light of the plurality of beams of light being emitted with an angular separation, for example in a plane parallel with the first rotation axis, from each other beam of light of the plurality of beams of light.

In some embodiments, the first polygon scan unit is configured with a plurality of surfaces, each surface being defined by a plane that is non-parallel with the first rotation axis.

An advantage that is provided by such embodiments is that a small number of light beams are needed as to create a large number of scans. For example, if the first polygon scan unit has 4 reflecting surfaces with different angles in relation to the rotation axis, each light beam will draw 4 angular spaced scan lines during one revolution.

Alternatively, in some embodiments, the first polygon scan unit is configured to perform a reciprocating tilting within a tilting angle interval around a tilting axis perpendicular to the first rotation axis during said rotation in relation to the first rotation axis.

In various embodiments, the at least one free-shape surface is a reflector or a refractor integral with the first scan unit. In some of these embodiments, the at least one free- shape surface is a 1 -dimensional free-shape surface extruded parallel with the first rotation axis and the light source configured to emit a plurality of narrow beams of light, each beam of light of the plurality of beams of light being emitted with an angular separation, for example in a plane parallel with the first rotation axis, from each other beam of light of the plurality of beams of light.

In some embodiments, the at least one free-shape surface is a 2-dimensional free-shape surface and the light source configured to emit a plurality of narrow beams of light, each beam of light of the plurality of beams of light being emitted with an angular separation, for example in a plane parallel with the first rotation axis, from each other beam of light of the plurality of beams of light.

In various embodiments, the reflective surfaces form part of at least a first mirror or secondary polygon scanner and a second mirror or secondary polygon scanner, each mirror or secondary polygon scanner being configured to be controlled by a controller to rotate at a varying angular speed around a respective first mirror or polygon rotation axis and a second mirror or polygon rotation axis.

In various embodiments, the reflective surface forms part of a first mirror or tertiary polygon scanner, said first mirror or tertiary polygon scanner being configured to be controlled by a controller to rotate at a varying angular speed around a first mirror or tertiary polygon rotation axis. The light source in such embodiments may be configured to emit a plurality of narrow beams of light, each beam of light of the plurality of beams of light being emitted with an angular separation from each other beam of light of the plurality of beams of light.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figs, la and lb schematically illustrate non-uniform illumination of a facade according to prior art.

Fig. 2 schematically illustrates a block diagram of an illumination system.

Figs. 3a to 3g schematically illustrate an illumination system.

Figs. 4a to 4c schematically illustrate an illumination system.

Figs. 5a and 5b schematically illustrate an illumination system.

Figs. 6a and 6b schematically illustrate an illumination system. DETAILED DESCRIPTION OF THE EMBODIMENTS

With reference to figures la and lb, a prior art polygon scanner 12 provides a scan where the angle 9 of an outgoing light beam 13, directed at a facade 11 of a building 10. Such a scan is linearly proportional to time and can thus be considered a linear scan:

0(t) = Ka>t where t is time, K is a proportionality constant, and w is the angular scan speed.

Such a polygon scanner with a constant angular speed produces a linear scan that is repeated from angle 9 = 0 to 6 = 9_max. If such a linear scanner in ID or 2D is used to illuminate the building 10 and the narrow beam 13 has a constant light output, the facade 11 of the building 10 will not be illuminated uniformly.

Figures la and lb show how a linear scan results in a non-uniform illumination. Figure la is a side view of the building and figure lb is a frontal view of the building 10. The linear polygon scanner 12 is placed in front of the building 10 and light beams 13 are illustrated at equal angular distance in the vertical direction and horizontal direction. The light beams 13 are in figure la illustrated as dashed lines and in figure lb as dots. It is clearly seen that the distance between beams 13 increases when moving upward and to the top comers of the facade 11 of the building 10. This causes two problems:

The facade 11 of the building 10 is not uniformly lit.

A large part of the scan misses the facade 11 of the building 10.

The prior art has addressed this uniformity problem by modulating the light output of the beam 13 as function of the scan position, e.g. as a function of the angle 9, resulting in a low output when dots are close together and high output when dots are further apart (see figure lb).

It is well known that the intensity I to illuminate a building uniformly is a proportionality:

I(0)~l/cos^A3 9 For larger angles 6 this would lead to a huge over-install of optical power, to be able to illuminate the far comers of the facade 11 of the building 10.

It is also possible according to prior art to avoid light missing the facade 11 of the building 10 and thereby avoiding spill light by switching off the beam 13 when the scan is outside the target area. This also means that during a significant part of the time the beam 13 is switched off, which also requires a higher installed output power.

Other prior art scanners such as a resonant mirror scanner produces an outgoing beam angle like:

0(t) = K’sin(u)t)

However, also such a scan configuration produces a highly non uniform illumination and leads to over-install of optical power in the beam.

With reference to figure 2 and figures 3a-d, an illumination system 1 for emitting at least one angularly scanning light beam 105 comprises a light source 100 configured to emit at least one narrow beam of light 101 and a beam directing arrangement 102. The beam directing arrangement 102 comprises, as exemplified by a respective view along a first rotation axis 150 in figures 3a, 3b and 3c, a first polygon scan unit 104, 124 configured to rotate at a constant angular speed in relation to at least the first rotation axis 150. At least one free-shape surface 110, 130 of the beam directing arrangement 102 is configured to reflect, as exemplified in figure 3a, or refract, as exemplified in figure 3b, the at least one narrow beam of light 101 such that the at least one light beam 105 emitted by the system 1 is scanned at a varying angular speed to provide a required intensity at each angle of scanning.

Alternatively, as exemplified in figure 3d, the beam directing arrangement 202 comprises a second scan unit 204 comprising at least one reflective surface 206 for reflecting the at least one narrow beam of light 101. The at least one reflective surface 206 is configured to rotate at varying angular speed such that the at least one light beam 105 emitted by the system 1 is scanned at a varying angular speed to provide a required intensity at each angle of scanning.

As indicated in figure 2, a controller may be configured to control the light source 100 and the beam directing arrangement 102. As indicated in figure 3a, the first polygon scan unit 104 may comprise reflective facets 108. As illustrated in figure 3e and figure 3f, the reflective surfaces 206 may form part of at least a first mirror 210 or secondary polygon scanner 510 and a second mirror 212 or secondary polygon scanner 512, each mirror 210, 212 or secondary polygon scanner 510, 512 being configured to be controlled by the controller 50 to rotate at a varying angular speed around a respective first mirror or polygon rotation axis 221, 521 and a second mirror or polygon rotation axis 222, 522.

Alternatively, as illustrated in figure 3g, the reflective surface 506 may form part of a first mirror 510 or tertiary polygon scanner 510, said first mirror 510 or tertiary polygon scanner 510 being configured to be controlled by the controller 50 to rotate at a varying angular speed around a first mirror or tertiary polygon rotation axis 521. In these embodiments, the light source 100 may be configured to emit a plurality of narrow beams of light 501, each beam of light of the plurality of beams of light 501 being emitted with an angular separation from each other beam of light of the plurality of beams of light 501.

The at least one free-shape surface 110 may form part of an optical component 106 separated from the first polygon scan unit 104 as illustrated in figure 3a. Moreover, as illustrated in figure 4a, in some of these embodiments, the light source 100 may be configured to emit a plurality of narrow beams of light 301, each beam of light of the plurality of beams of light 301 being emitted with an angular separation, for example in a plane parallel with the first rotation axis 150, from each other beam of light of the plurality of beams of light 301.

As illustrated in figure 4b, the first polygon scan unit 104 may be configured with a plurality of surfaces 109a, 109b, 109c each surface 109a, 109b, 109c being defined by a plane that is non-parallel with the first rotation axis 150. Alternatively, as illustrated in figure 4c, the first polygon scan unit 104 may be configured to perform a reciprocating tilting within a tilting angle interval around a tilting axis 151 perpendicular to the first rotation axis 150 during said rotation in relation to the first rotation axis 150.

Instead of forming part of an optical component 106 separated from the first polygon scan unit 104, the at least one free-shape surface 130 may be a reflector or a refractor integral with the first scan unit 124, as illustrated in figure 3b. For example, the at least one free-shape surface 130 may be a 1 -dimensional free-shape surface 131 extruded parallel with the first rotation axis 150, as illustrated in figure 5a. The light source 100 in such embodiments may be configured to emit a plurality of narrow beams of light 401, each beam of light of the plurality of beams of light 401 being emitted with an angular separation from each other beam of light of the plurality of beams of light 401. The angular separation may be in a plane parallel with the first rotation axis 150.

As illustrated in figure 5b, instead of a 1-dimentional free-shape surface, the at least one free-shape surface 130 may be a 2-dimensional free-shape surface 132. The light source 100 in such embodiments may be configured to emit a plurality of narrow beams of light 401, each beam of light of the plurality of beams of light 401 being emitted with an angular separation from each other beam of light of the plurality of beams of light 401. The angular separation may be in a plane parallel with the first rotation axis 150.

As recognized herein, there is a strong desire to limit the amount of spill light when illuminating a target area such as the facade of a building. A precise distribution of light is thus needed to only illuminate the target area. This precise distribution of light can be achieved by using a scanning system in which the light output of the beam or beams is adjusted. Such a scanning system must therefore be configured such that it generates an appropriate control signal for the light level of the narrow beam(s) during the scan. These control signals can be stored, e.g., in a lookup table in a controller linking the scan position to the beam intensity. It is however difficult to pre-program such a lookup table in the factory as it requires a detailed knowledge of the specific scenario on the actual site where the scanning luminaire will be installed, e.g. in front of a facade of a building. Small changes in direction or position have a large impact and would require a re-programming of the lookup table.

A solution to this is to arrange sensors, such as an imaging device, inside the luminaire that can support defining the required light distribution. In one such example, a camera may be integrated in the luminaire facing the scanned object, e.g. the facade of a building. Any part of the object that lights up and recorded in an image by the camera can be analyzed and used to create a mapping from image pixel to scan position on the object. The camera may be used to take a picture of the object, which can be provided to a human user or an artificial intelligence algorithm in a controller capable of indicating the areas to be illuminated. By placing the camera at some distance from the luminaire, one can also use a line scan and recover depth information using triangulation. This can help obj ect recognition. Scanning can be done with a single spot across the object and the reflection may be measured, e.g. by means of recording one or more images with the camera. A spot where reflection is high enough, may then indicate that it is a spot to illuminate. Such embodiments may be particularly useful for objects having a contrast with respect to the background, such as in the case of a building against a sky background. Retroreflectors may also be arranged on the comers of a building to facilitate recognition of the area to be illuminated. In such embodiments, a single spot may be scanned across the object, whereby the retroreflectors will create a high peak reflection that can be recognized as the comers of the area to be illuminated.

Figure 6a and figure 6b, illustrate such example embodiments. An illumination system 600 comprising a luminaire 610 is arranged in front of an object in the form of three facade areas 601, 602, 603 of a building complex. The illumination system 600 is configured to emit light beams 621 that is scanned across all of the facade areas 601, 602, 603 as indicated by scan lines 631. An imaging device 611 is configured to record one or more digital images of the facade areas 601, 602, 603 during the emission of light beams 621 creating the scan lines 631. The one or more digital images are analyzed, for example by a human user or a controller 650, in relation to a predetermined specification of a desired area 640 that is to be illuminated by the illumination system 600. The desired area 640 may be in the form of a lookup table in the controller 650. As a consequence of the analysis, information is provided to the luminaire 610 that may be used in the luminaire 610 to control the emission of one or more operational light beams 622 that is scanned across only the desired area 640 as indicated by operational scan lines 632.

The illumination system 600 and the luminaire 610 may be configured as a single beam system, i.e. wherein one narrow light beam (such as a laser beam) that is scanned over the target area. Alternatively, a plurality of beams may be scanned at the same time, where the number of beams is less than the total number of lines to be scanned. After each scan a new scan is initiated with an offset in relation to the first scan. This can for example be achieved using a polygon scanner where each facet of the polygon has a small tilt in relation the former. In case of multiple colored light beams such as laser beams to achieve white or color illumination, the beams can either be combined into a single beam using dichroic mirrors, or they can be aimed at the scanned such that the different colors follow each other on the object.

Claims

CLAIMS:

1. An illumination system (1) for emitting an angularly scanning light beam (105), wherein the illumination system (1) comprises a light source (100) for emitting a plurality of narrow beams of light (301), each narrow beam of light of the plurality of narrow beams of light (301) being emitted with an angular separation from each other narrow beam of light of the plurality of narrow beams of light (301), and wherein the illumination system (1) further comprises: a beam directing arrangement (102) comprising a first polygon scan unit (104, 124) configured to rotate at a constant angular speed in relation to a first rotation axis (150), and a free-shape surface (110, 130) configured to reflect or refract each narrow beam of light of the plurality of narrow beams of light (301) such that the light beam (105) emitted by the system (1) is scanned at a varying angular speed to provide a required intensity at each angle of scanning, the free-shape surface (110) forming part of an optical component (106) separated from the first polygon scan unit (104), or a beam directing arrangement (202) comprising a second scan unit (204) comprising a reflective surface (206) for reflecting each narrow beam of light of the plurality of narrow beams of light (301), the reflective surface (206) being configured to rotate at varying angular speed such that the light beam (105) emitted by the system (1) is scanned at a varying angular speed to provide a required intensity at each angle of scanning.

2. The illumination system (1) according to claim 1, wherein the angular separation is in a plane parallel with the first rotation axis (150).

3. The illumination system (1) according to any one of claims 1 and 2, wherein the first polygon scan unit (104) is configured with a plurality of surfaces (109a, 109b, 109c), each surface (109a, 109b, 109c) being defined by a plane that is non-parallel with the first rotation axis (150).

4. The illumination system (1) according to any one of claims 1 and 2, wherein the first polygon scan unit (104) is configured to perform a reciprocating tilting within a tilting angle interval around a tilting axis (151) perpendicular to the first rotation axis (1 0) during said rotation in relation to the first rotation axis (150).

5. The illumination system (1) according to claim 1, comprising a controller (50) and two reflective surfaces (206), wherein the reflective surfaces (206) form part of at least a first mirror (210) or secondary polygon scanner (510) and a second mirror (212) or secondary polygon scanner (512), each mirror (210, 212) or secondary polygon scanner (510, 512) being configured to be controlled by the controller (50) to rotate at a varying angular speed around a respective first mirror or polygon rotation axis (221, 521) and a second mirror or polygon rotation axis (222, 522).

6. The illumination system (1) according to claim 1, comprising a controller (50) and one reflective surface (506), wherein the reflective surface (506) forms part of a first mirror (510) or tertiary polygon scanner (510), the first mirror (510) or tertiary polygon scanner (510) being configured to be controlled by the controller (50) to rotate at a varying angular speed around a first mirror or tertiary polygon rotation axis (521).