WO2017012828A1

WO2017012828A1 - A digital image projection device with a fiber laser

Info

Publication number: WO2017012828A1
Application number: PCT/EP2016/064838
Authority: WO
Inventors: Teunis Willem Tukker; Willem Lubertus Ijzerman
Original assignee: Philips Lighting Holding B.V.
Priority date: 2015-07-21
Filing date: 2016-06-27
Publication date: 2017-01-26

Abstract

The invention provides a digital image projection device comprising a fiber laser (2) comprising an optical fiber (3) and a laser light source being adapted to emit a white light beam (4), the white light beam comprising a visible component (41), an image producing element (6) adapted for producing an image based on the white light beam, and a projection lens element (5) adapted for projecting the image produced by the image producing element, the image producing element (6) being arranged between the fiber laser and the projection lens element, wherein the digital image projection device further comprises a beam expanding element (8) adapted for expanding the white light beam emitted by the fiber laser and arranged between the fiber laser and the image producing element and a two photon phosphor fiber (7) for removing an IR component (42) of the white light beam (4).

Description

A DIGITAL IMAGE PROJECTION DEVICE WITH A FIBER LASER

FIELD OF THE INVENTION

The invention concerns a digital image projection device comprising a fiber laser comprising an optical fiber and a laser light source being adapted to emit a light beam, an image producing element adapted for producing an image based on the light beam, and a projection lens element adapted for projecting the image produced by the image producing element, the image producing element being arranged between the laser light source and the projection lens element.

BACKGROUND OF THE INVENTION

One of the important key parameters of such a digital image projection device is its color gamut and screen brightness, for which it is desired to be as wide and high, respectively, as possible. Therefore it is of key importance to provide a laser light source that emits in a wide spectral range and with a high brightness. Therefore, in the recent years red, blue and green lasers have been applied in digital image projection devices. In other words three lasers must be provided. However, a sufficiently good green laser is still not available. Therefore further technologies, such as phosphor garnets, have been developed to supply a good green laser light source for the RGB engine. Furthermore, the light beams emitted from these three lasers must be combined.

CN 102540653 A describes a digital image projection device with three lasers, namely a red laser, a blue laser and a green laser. A base, in which an optical waveguide is formed, is provided for mixing the light emitted from the three lasers. The light beam of each laser is directed into a respective input waveguide in the base, and the thus three input waveguides are, in the base, joined and combined to one output waveguide thereby mixing the light.

However, such a digital image projection device is a rather complicated system, and it is furthermore quite expensive due to the presence of the three lasers and the associated and necessary light mixing device as well as the required relatively large optical elements, in particular lenses. A further problem related to systems using three lasers, namely a red laser, a blue laser and a green laser, is the presence of speckle, which should be avoided or reduced as much as possible.

Furthermore, there is a desire for providing a digital image projection device with a smaller etendue, and furthermore with a color gamut being even wider and a screen brightness being even higher than what is achievable with known devices of the type mentioned above.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome these problems, and to provide a digital image projection device which is structurally simpler, which is less costly to produce and acquire, with which speckle is reduced or avoided, and which has a smaller etendue and improved color gamut and screen brightness.

According to a first aspect of the invention, this and other objects are achieved by means of a digital image projection device comprising a fiber laser comprising an optical fiber and a laser light source being adapted to emit a white light beam, the white light beam comprising a visible component, an image producing element adapted for producing an image based on the white light beam, and a projection lens element adapted for projecting the image produced by the image producing element, the image producing element being arranged between the fiber laser and the projection lens element, and a beam expanding element adapted for expanding the white light beam emitted by the fiber laser and arranged between the fiber laser and the image producing element.

In recent years the developments of high power fiber lasers with non- linear optical elements has completely changed how such these lasers look and operate. The high power electronics and bulky laser systems have become obsolete. Recent developed laser systems are of the size of a shoebox and use 100 W for obtaining an output power of 2 W over a brought spectral range from 350 nm to 2200 nm. Companies offering such lasers are for example NKT and Fianium.

The white light beam comprises a visible component, i.e. the fiber laser is adapted to emit light in the visible wavelength region in a wavelength range from about 390 nm to 700 nm.

The presently achievable output of such a laser is 2 W in the visible wavelength region. The emission is from an area with a diameter of 1 mm to 2 mm and with a beam divergence of 10 mrad. This means that if we take a conversion efficiency of 200 lm/W the source has a brightness of:

(2 W * 200 lm/W) / (4xl0^~6 m² * lxlO^"4 sr) ~ lxlO¹² cd/m² = 1 Gnit (Giga nit)

This is extremely high and shows the power of such lasers. Furthermore, it is worth noting that a beam emitted by a fiber laser is highly collimated, so collimation losses are almost absent. This compensates for the lower efficacy of fiber lasers. Furthermore, because the light is generated in a fiber by a non-linear effect, the light has no coherence which makes it very suitable for the intended application.

Thus, by providing a digital image projection device with a fiber laser comprising an optical fiber and a laser light source being adapted to emit a white light beam, the white light beam comprising a visible component, a digital image projection device is provided with which it is no longer necessary to provide three lasers and a color mixing element. Such a digital image projection device is therefore structurally simpler and less costly to produce and acquire.

Furthermore, due to the high output power and wide spectral range of such fiber lasers such a digital image projection device furthermore has a smaller etendue and improved color gamut and screen brightness.

Also, by providing the digital image projection device with a fiber laser comprising an optical fiber and a laser light source being adapted to emit a white light beam, the presence of speckle is reduced or even avoided. It is noted that the longer the optical fiber, the more the presence of speckle may be reduced. Also, as an alternative, or addition to a relatively long optical fiber, other means, such as e.g. a system of mirrors, for alternating the beam path of at least a part of the white light beam may be provided for the reduction of speckle.

By providing a beam expanding element adapted for expanding the white light beam emitted by the fiber laser and arranged between the fiber laser and the image producing element, a digital image projection device is obtained with which the relatively small beam diameter inherent in the light beam emitted by fiber lasers may be expanded to a size suitable for digital image projection devices and in particular for the image producing element and projection lens devices of such digital image projection devices.

Finally, by providing a digital image projection device with a fiber laser comprising an optical fiber and a laser light source being adapted to emit a white light beam, the white light beam comprising a visible component, and a beam expanding element adapted for expanding the white light beam emitted by the fiber laser and arranged between the fiber laser and the image producing element, a digital image projection device is provided with which it becomes possible to use smaller and fewer optical components, thus further simplifying the structure of the system, in particular due to the very small etendue of the fiber laser.

In an embodiment the white light beam further comprises an IR component and the digital image projection device further comprises an optical element adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially, the optical element being arranged between the fiber laser and the image producing element.

Most fiber lasers available on the market and emitting a white light beam not only emit light in the visible wavelength region, i.e. comprising a visible component, but also light in the infrared (IR) wavelength region, the light beam thus comprising also an IR component. The IR light, however, does not contribute to the brightness of the image formed by the image producing element. Furthermore, the IR light causes heating of the elements of the digital image projection device, and therefore, the IR component is undesired. By providing an optical element adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially, these disadvantages related to the IR component are reduced or even avoided.

The optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially may be any one of an optical element adapted for converting the IR component to visible light, an optical element adapted for performing static or dynamic color selection and/or an optical element adapted for performing static or dynamic color splitting.

In an embodiment the digital image projection device further comprises a free- shape optical element adapted for converting a spatial light distribution of the white light beam emitted by the fiber laser in such a way that the converted spatial light distribution is provided with such an aspect ratio that, when the converted spatial light distribution is expanded by the beam expanding element, the resulting converted and expanded spatial light distribution is provided with an aspect ratio being equal to an aspect ratio of the image producing element. Thereby a digital image projection device is provided with which the shape of the light beam emitted by the fiber laser may be converted to a shape fitting the image producing element in a very simple manner. In an embodiment the free-shape optical element is a further optical fiber, and an end of the optical fiber of the fiber laser is coupled to a first end of the further optical fiber, the further optical fiber comprising a core having a cross section converging from being circular at the first end of the further optical fiber to rectangular at a second end opposite to the first end of the further optical fiber. Thereby a digital image projection device is provided with which the conversion of the shape of the light beam emitted by the fiber laser to a shape fitting the image producing element may take place in an optical element being particularly simple and cost efficient.

In an embodiment the further optical fiber further comprises a cladding having a cross section converging from being circular at the first end of the further optical fiber to rectangular at a second end opposite to the first end of the further optical fiber. Such an optical fiber is even simpler and cheaper to produce, and thus acquire, as compared to an optical fiber in which only the core has a converging cross section.

In an embodiment the further optical fiber is shaped such that is adapted for converting a spatial light distribution of the white light beam emitted by the fiber laser in such a way that the converted spatial light distribution is provided with such an aspect ratio that, when the converted spatial light distribution is expanded by the beam expanding element, the resulting converted and expanded spatial light distribution is provided with an aspect ratio being equal to an aspect ratio of the image producing element. Thereby a digital image projection device is provided with which the shape of the light beam emitted by the fiber laser may be converted to a shape fitting the image producing element in a particularly simple manner.

In an embodiment the further optical fiber is a two photon phosphor fiber. The use of such an optical fiber has the further advantage that the IR component of the white light beam is converted to visible light when propagating through the fiber. Thereby a digital image projection device is provided with a considerably improved efficiency and with which a higher output intensity is achieved. Thereby the free-shape optical element and the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially may be integrated in one and the same optical element, which in turn provides for a further and significant simplification of the digital image projection device.

In an embodiment the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially is a dichroic mirror element adapted for reflecting the visible component of the light beam emitted by the white fiber laser only. Thereby, the disadvantages related to the presence of an IR component in the white light beam are avoided in a simple manner by use of a simple, small and cost efficient optical element.

In an embodiment the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially is adapted for color splitting, and is any one of a beam splitter, a fiber based beam splitter and a Bragg grating based fiber splitter. In addition to obtaining the same advantages as mentioned in relation to the dichroic mirror, the use of a Bragg grating based fiber splitter enables even further miniaturization of the optical system of the digital image processing device.

In an embodiment the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially is a filtering device adapted for static or dynamic color selection. Thereby, the same advantages as mentioned in relation to the dichroic mirror may be obtained, albeit by means of an optical element potentially being even simpler and more cost efficient. The filtering device may in the simplest and most cost efficient form be an optical filter. In one alternative the filtering device may be a color wheel, whereby dynamic color selection is achieved.

In an embodiment the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially is a two photon phosphor fiber adapted for converting the IR component to visible light. Thereby, a digital image projection device is provided with which the efficiency is improved considerably, and with which higher output intensity is achieved.

The image producing element may e.g. be a Digital Micromirror Device (DMD), a Liquid Crystal Display (LCD) or a Liquid Crystal on Silicon (LCoS) device or in principle any other suitable image producing element.

In an embodiment the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially is an optical element adapted for performing static or dynamic color selection, and the image producing element is a Digital Micromirror Device (DMD). Especially preferred is in this connection an optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially in the form of a color wheel enabling dynamic color selection.

In an embodiment the optical element adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially is an optical element adapted for performing static or dynamic color splitting, and the image producing element is a Liquid Crystal Display (LCD) or a Liquid Crystal on Silicon (LCoS) device. In an embodiment the digital image projection device further comprises at least one optical modulator. In an embodiment the optical modulator is a polarizer. Thereby further modulation of the white light beam may be obtained, for instance in order to enable the image producing element to produce 3D images.

It is noted that the invention relates to all possible combinations of features recited in the claims.

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.

Fig. 1 shows a schematic illustration of a first embodiment of a digital image projection device according to the invention and employing a fiber laser adapted for emitting a white light beam as well as a beam expanding element.

Fig. 2 shows a schematic illustration of a second embodiment of a digital image projection device according to the invention and further comprising an optical element adapted for removing an IR component of the white light beam emitted by the fiber laser.

Fig. 3 shows a schematic illustration of a third embodiment of a digital image projection device according to the invention and comprising a further optical fiber in addition to the optical fiber of the fiber laser.

Fig. 4 shows one embodiment of a further optical fiber of the digital image projection device according to Fig. 3.

Fig. 5 shows another embodiment of a further optical fiber of the digital image projection device according to Fig. 3.

Fig. 6 shows a schematic illustration of a fourth embodiment of a digital image projection device according to the invention and further comprising an optical element in the form of a dichroic mirror adapted for removing an IR component of the white light beam emitted by the fiber laser.

Fig. 7 shows a schematic illustration of a fifth embodiment of a digital image projection device according to the invention and further comprising an optical element in the form of a Bragg grating based fiber adapted for removing an IR component of the white light beam emitted by the fiber laser.

Fig. 8 shows a schematic illustration of a sixth embodiment of a digital image projection device according to the invention and further comprising an optical element in the form of a filtering device adapted for removing an IR component of the white light beam emitted by the fiber laser.

As illustrated in the figures, the sizes of the various optical elements are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

Fig. 1 shows a first embodiment of a digital image projection device 1 according to the invention. The digital image projection device 1 comprises a fiber laser 2 comprising an optical fiber 3 and a laser light source being adapted to emit a white light beam 4. The white light beam 4 comprises a visible component, i.e. light with a wavelength in the visible wavelength region.

The digital image projection device 1 further comprises a projection lens element 5 and an image producing element 6. The image producing element 6 is adapted for producing an image based on the white light beam 4. The projection lens element 5 is adapted for projecting the image produced by the image producing element 6. The image produced by the image producing element 6 may be projected onto e.g. a screen, a wall or the like. The image producing element 6 is arranged between the fiber laser 4 and the projection lens element 5.

The digital image projection device 1 further comprises a beam expanding element 8 adapted for expanding the white light beam 4 emitted by the fiber laser 2. The beam expanding element 8 is arranged between the fiber laser 2 and the image producing element 5. The beam expanding element 8 may furthermore be arranged between the image producing element 6 and the fiber laser 2.

In other words, when viewed in the direction of propagation z of the white light beam 4, i.e. in a direction extending from the fiber laser 2 towards the projection lens element 5, the beam expanding element 8 is arranged upstream of the image producing element 5, and possibly also upstream of the image producing element 6.

The beam expanding element 8 generally comprises a first magnification factor in a first direction x and a second magnification factor in a second direction y, the first direction x and the second direction y being perpendicular to a direction z of propagation of the white light beam 4 and furthermore being mutual perpendicular. It is noted that the first and second magnification factor of the beam expanding element 8 may be equal, but may also be different.

Fig. 2 shows a second embodiment of a digital image projection device 100 according to the invention. The digital image projection device 100 is identical to that shown in Fig. 1 and described above, except for one aspect.

Most fiber lasers available on the market and emitting a white light beam not only emit light in the visible wavelength region but also light in the infrared (IR) wavelength region. Therefore, in this embodiment the white light beam 4 further comprises an IR component, i.e. light with a wavelength in the IR region, which is a wavelength larger than about 700nm. As a consequence of this, the digital image projection device 100 is provided with an optical element 7 adapted for removing the IR component of the white light beam 4 emitted by the fiber laser 2 at least partially, and in some embodiments even completely. Thus, wavelengths above about 700nm are removed from, or at least significantly reduced, the white light beam 4. The optical element 7 adapted for removing the IR component of the white light beam 4 emitted by the fiber laser 2 is arranged between the fiber laser 2 and the image producing element 5.

When viewed in the direction of propagation of the white light beam 4, the optical element 7 adapted for removing the IR component of the white light beam 4 emitted by the fiber laser 2 is arranged upstream of at least the image producing element 6. The optical element 7 may also be arranged upstream of the beam expanding element 8, but this need not be the case.

The optical element 7 may be adapted for removing the IR component of the light beam emitted by the white fiber laser at least partially in a static manner or alternatively in a dynamic manner. The optical element 7 may further be an optical element adapted for converting the IR component to visible light. Alternatively, the optical element 7 may be an optical element adapted for performing static or dynamic color selection. Alternatively, the optical element 7 may be an optical element adapted for performing static or dynamic color splitting. Examples of suitable optical elements 7 will be given further below. Fig. 3 shows a third embodiment of a digital image projection device 101 according to the invention. The digital image projection device 101 differs from that described above and shown in Fig. 2 in the following aspects.

The digital image projection device 101 comprises a free-shape optical element 9. The free-shape optical element 9 converts a spatial light distribution of the white light beam 4 emitted by the fiber laser 2 in such a way that the converted spatial light distribution is provided with such an aspect ratio that, when the converted spatial light distribution is expanded by the beam expanding element 8, the resulting converted and expanded spatial light distribution is provided with an aspect ratio being equal to an aspect ratio of the image producing element 6. In that way it is also possible to take into account the relative values of the first and second magnification factor of the beam expanding element 8, e.g. whether these values are equal or different. In the embodiments shown in Fig. 3 this is obtained by coupling an end 31 of the optical fiber 3 of the fiber laser 2 to a first end 91 of a free-shape optical element in the form of a further optical fiber 9.

As is illustrated for example in Fig. 4, the further optical fiber 9 comprises in an embodiment a core 93 having a cross section converging from being circular 94 at the first end 91 to rectangular 95 at a second end 92 opposite to the first end 91. The cladding 96 is circular in cross section at both the first end 91 and the opposite second end 92. The core 93 is at the second end 92 shaped in such a way that the further optical fiber 9 is adapted for converting a spatial light distribution of the white light beam 4 emitted by the fiber laser 2 in such a way that the converted spatial light distribution is provided with such an aspect ratio that when the converted spatial light distribution is expanded by the beam expanding element 8, the resulting converted and expanded spatial light distribution is provided with an aspect ratio being equal to an aspect ratio of the image producing element 6. Typical examples of aspect ratios of the image producing element are an aspect ratio of 3:4 or 9: 16.

As is illustrated in Fig. 5, it is also possible in an embodiment to provide the further optical fiber 9 with a cladding 96 that also has a cross section converging from being circular at the first end 91 to rectangular at the opposite second end 92 of the further optical fiber 9. The cladding 96 would in such an embodiment typically be shaped to have a similar shape as the core 93.

Optionally, the further optical fiber 9 may be provided as a type of fiber, which is furthermore adapted for converting the IR component of the light beam 4 emitted by the white fiber laser 2 at least partially to visible light. An example of such a type of fiber is a two photon phosphor fiber. In such an embodiment, the optical element 7 may in principle be omitted, or it may be adapted to remove a remaining part of the IR component of the light beam 4 emitted by the white fiber 2 laser at least partially.

Other types of free-shape optical elements may also be feasible, examples being a lens system with free-shape surfaces or a collimator (CPC-like, RXI, or the like) with free-shape surfaces.

Turning now to Fig. 6, a fourth embodiment of a digital image projection device 102 according to the invention is shown. The digital image projection device 102 is of the same type as that described above and shown in Fig. 2. However, in this embodiment the optical element 7 adapted for removing the IR component 42 of the white light beam 4 emitted by the fiber laser 2 at least partially is an optical element adapted for performing static color splitting. More particularly, the optical element 7 is a dichroic mirror 71 adapted for reflecting the visible component 41 of the white light beam 4 and for transmission of the IR component 42 of the white light beam 4.

Fig. 7 shows a fifth embodiment of a digital image projection device 103 according to the invention. The digital image projection device 103 is of the same type as that described above and shown in Fig. 2. However, in this embodiment the optical element 7 adapted for removing the IR component 42 of the white light beam 4 emitted by the fiber laser 2 at least partially is an optical element adapted for performing static color splitting. More particularly, the optical element 7 is a Bragg grating based fiber splitter 72. The Bragg grating is arranged within the Bragg grating based fiber splitter 72 and is on Fig. 7 symbolized by a plurality of transverse lines. In an alternative to such a fiber, the optical element 7 may also be provided as a Bragg grating or other suitable grating, which may even be adjustable such as to enable dynamic color splitting.

Optical elements 7 adapted for performing static or dynamic color splitting may be adapted for splitting the white light beam 4 into two, three or even more different colors or components or beams. In an embodiment the optical element 7 adapted for performing static or dynamic color splitting may for instance be another suitable type of fiber based splitter or beam splitter.

In a favorable embodiment a digital image projection device according to the invention is provided with an optical element 7 adapted for performing static or dynamic color splitting, particularly into three or more colors, components or beams, such as for example the optical elements 71 and 72 shown in Figs. 6 and 7, respectively, in embodiments where the image producing element 6 is a Liquid Crystal Display (LCD) or a Liquid Crystal on Silicon (LCoS) device. Fig. 8 shows a sixth embodiment of a digital image projection device 104 according to the invention. The digital image projection device 104 is of the same type as that described above and shown in Fig. 2. However, in this embodiment the optical element 7 adapted for removing the IR component 42 of the white light beam 4 emitted by the fiber laser 2 at least partially is an optical element 73 adapted for performing static or dynamic color selection. Such an optical element 73 may for example be an optical filter adapted for static color selection or a color wheel adapted for dynamic color selection.

In a favorable embodiment a digital image projection device according to the invention is provided with an optical element 7 adapted for performing static or dynamic color selection, such as for example the optical element 73 shown in Fig. 8, in embodiments where the image producing element 6 is a Digital Micromirror Device (DMD) device.

Furthermore, in this embodiment the digital image projection device 104 comprises an optional optical modulator 1 1. The optical modulator 11 may be any suitable type of optical modulator. One non-limiting example of an optical modulator 11 is a polarizer adapted for polarizing the white light beam 2.

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 different embodiments of a digital image projection device described herein may be combined according to desire and/or practical need. Thus, the digital image projection device according to any of the embodiments described herein may also be provided with e.g. one or more of a free-shape optical element 9 and an optical modulator 11.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

CLAIMS:

1. A digital image projection device comprising:

a fiber laser (2) comprising an optical fiber (3) and a laser light source being adapted to emit a white light beam (4), the white light beam comprising a visible component (41),

an image producing element (6) adapted for producing an image based on the white light beam, and

a projection lens element (5) adapted for projecting the image produced by the image producing element,

the image producing element (6) being arranged between the fiber laser and the projection lens element, wherein the digital image projection device further comprises:

a beam expanding element (8) adapted for expanding the white light beam emitted by the fiber laser and arranged between the fiber laser and the image producing element, and

wherein the white light beam (4) further comprises an IR component (42), and wherein the digital image projection device further comprises an optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially, the optical element (7) being arranged between the fiber laser (2) and the image producing element (6), and

wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is a two photon phosphor fiber adapted for converting the IR component to visible light.

2. A digital image projection device according to claim 1, and further comprising a free-shape optical element (9) adapted for converting a spatial light distribution of the white light beam (4) emitted by the fiber laser in such a way that the converted spatial light distribution is provided with such an aspect ratio that when the converted spatial light distribution is expanded by the beam expanding element (8), the resulting converted and expanded spatial light distribution is provided with an aspect ratio being equal to an aspect ratio of the image producing element (6).

3. A digital image projection device according to claim 2, wherein the free-shape optical element is a further optical fiber (9), and wherein an end (31) of the optical fiber (3) of the fiber laser (2) is coupled to a first end (91) of the further optical fiber, the further optical fiber comprising a core (93) having a cross section converging from being circular (94) at the first end of the further optical fiber to rectangular (95) at a second end (92) opposite to the first end of the further optical fiber.

4. A digital image projection device according to claim 3, wherein the further optical fiber (9) further comprises a cladding (96) having a cross section converging from being circular at the first end (91) of the further optical fiber to rectangular at a second end (92) opposite to the first end of the further optical fiber.

5. A digital image projection device according to claim 3 or 4, wherein the further optical fiber (9) is shaped such that it is adapted for converting a spatial light distribution of the white light beam (4) emitted by the fiber laser in such a way that the converted spatial light distribution is provided with such an aspect ratio that, when the converted spatial light distribution is expanded by the beam expanding element (8), the resulting converted and expanded spatial light distribution is provided with an aspect ratio being equal to an aspect ratio of the image producing element (6).

6. A digital image projection device according to any one of claims 3 to 5, wherein the further optical fiber (9) is a two photon phosphor fiber.

7. A digital image projection device according to any one claims 1 to 6, wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is any one of an optical element adapted for converting the IR component to visible light, an optical element adapted for performing static or dynamic color selection and an optical element adapted for performing static or dynamic color splitting.

8. A digital image projection device according to any one of claims 1 to 7, wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is adapted for color splitting, and is any one of a beam splitter, a fiber based beam splitter and a Bragg grating based fiber splitter (72).

9. A digital image projection device according to any one of claims 1 to 7, wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is a filtering device (73) adapted for static or dynamic color selection.

10. A digital image projection device according to claims 1 to 7, wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is a dichroic mirror element (71) adapted for reflecting the visible component of the white light beam emitted by the fiber laser only.

11. A digital image projection device according to any one of claims 1 to 9, wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is an optical element adapted for performing static or dynamic color selection, and wherein the image producing element (6) is a Digital Micromirror Device (DMD).

12. A digital image projection device according to any one of claims 1 to 8 or 10, wherein the optical element (7) adapted for removing the IR component of the white light beam emitted by the fiber laser at least partially is an optical element adapted for performing static or dynamic color splitting, and wherein the image producing element (6) is a Liquid Crystal Display (LCD) or a Liquid Crystal on Silicon (LCoS) device.

13. A digital image projection device according to any one of the above claims, and further comprising at least one optical modulator (11).