WO2011004241A1 - Projection system - Google Patents

Projection system Download PDF

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Publication number
WO2011004241A1
WO2011004241A1 PCT/IB2010/001660 IB2010001660W WO2011004241A1 WO 2011004241 A1 WO2011004241 A1 WO 2011004241A1 IB 2010001660 W IB2010001660 W IB 2010001660W WO 2011004241 A1 WO2011004241 A1 WO 2011004241A1
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WO
WIPO (PCT)
Prior art keywords
light
projection system
concentrator
upstream
ellipsoid
Prior art date
Application number
PCT/IB2010/001660
Other languages
French (fr)
Inventor
Massimo Riva
Original Assignee
Cinemeccanica S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cinemeccanica S.P.A. filed Critical Cinemeccanica S.P.A.
Publication of WO2011004241A1 publication Critical patent/WO2011004241A1/en

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Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/04Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
    • G02B6/06Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres the relative position of the fibres being the same at both ends, e.g. for transporting images
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0028Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed refractive and reflective surfaces, e.g. non-imaging catadioptric systems
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0047Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
    • G02B19/0061Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED
    • G02B19/0066Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED in the form of an LED array
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0905Dividing and/or superposing multiple light beams
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0938Using specific optical elements
    • G02B27/0977Reflective elements
    • G02B27/0983Reflective elements being curved
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0938Using specific optical elements
    • G02B27/0994Fibers, light pipes
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00Projectors or projection-type viewers; Accessories therefor

Definitions

  • the present invention relates to a light generator and a system for projecting light and/or fixed or moving images, using said light generator.
  • the teachings of the present invention can be used for example to form analogue and digital cinematographic projectors, slide projectors, projectors for projecting images stored on a computer, white or coloured light projectors for theatrical, scenographic, performance or technical lighting uses in general.
  • LEDs light emitting diodes
  • LEDS are known to be characterised by a ratio of emitted light flux to absorbed electric power which is much higher than the more traditional gas discharge, halogen or incandescent lamps.
  • a first object of the present invention is to provide a light source which represents an improvement on light sources of known type, in particular compared with gas discharge, halogen and incandescent lamps.
  • a second object of the present invention is to provide a distance projector for light and/or images, such as a floodlight for scenographic or technical lighting effects in general, or a cinematographic projector for slides or films, which represents an improvement on floodlights or projectors of known type, in particular compared with projectors the light source of which is one or more gas discharge, halogen or incandescent lamps.
  • Figure 1 is a perspective view of a light generator for a first embodiment of a projection system of the present invention
  • Figure 1A is a detailed perspective view of an elemental cell of the LED carrier support of the generator of Figure 1 ;
  • Figure 2 is a lateral view of a concentrator of the generator of Figure 1 ;
  • Figure 3 is a section through a concentrator of the generator of Figure 1 , taken on a longitudinal sectional plane;
  • Figure 4 is a section on a longitudinal sectional plane through a detail of that portion of the concentrator of Figure 3 at the interface with the LEDs which energize it, in the light generator of Figure 1 ;
  • Figure 5 is a longitudinal section through the emission head of the generator of
  • Figure 1 Figure 6 shows the operating scheme of a cinematographic film projector of known type
  • Figure 7 shows the operating scheme of a digital projector with DLP technology of known type, provided with a white light generator
  • Figure 8 shows the operating scheme of a digital projector with DLP technology in accordance with a third embodiment of a projection system of the invention, with three coloured light generators based on an RGB system;
  • Figure 9 shows a lateral view of a concentrator and the relative waveguide, of a fourth embodiment of a light generator of the present invention.
  • cross-sections are assumed to be taken on a plane perpendicular to the upstream-downstream direction along said optical path of the light emission generated overall by the light emitting diodes 3A-3D and conveyed by the waveguides 9, or via other respective optical components.
  • Figures 1-5 relate to a first embodiment of a light generator of the invention; this light generator, indicated overall by the reference numeral 1 , comprises a plurality of light emitting diodes (LEDs) 3 fixed to a suitable LED carrier support 5 such as to form a matrix, for example substantially flat.
  • LEDs light emitting diodes
  • the LEDs are disposed along mutually perpendicular rows and columns.
  • the LEDs can be disposed for example quincuncially.
  • the LEDs are grouped in elemental cells 3, each formed of three or four LEDs 3A-3D relatively very close together ( Figure 1A).
  • each elemental cell 3 is separated from the other adjacent cells by a distance greater than that which mutually separates the various LEDs 3A- 3D comprising each elemental cell.
  • the light generator 1 also comprises at least one concentrator 7 the external walls 11 of which form at least one reflecting surface arranged to reflect the light radiation emitted by the LEDs 3A-3D.
  • the concentrator 7 is optically connected to a length of optical waveguide 9 ( Figure 1).
  • the optical waveguide 9 terminates downstream with an emission end and is arranged to receive from upstream at least part of the light radiation collected by the at least one concentrator 7 and to direct it as far as the emission end.
  • the cross-sections of the at least one reflecting surface progressively enlarge to reach substantially at least one maximum, after which they progressively contract; moreover the cross-sections of the at least one optical waveguide 9 within a length thereof are substantially not greater than the cross-sections of the at least one concentrator 7.
  • the quantity of light radiation collected by the concentrator 7 and directed into the optical waveguide 9 within its acceptance angle is increased compared for example with known concentrators of parabola or more generally cup shape.
  • Each concentrator 7 is advantageously optimized to collect as much as possible of the light radiation emitted in the visible band by the LEDs of each elemental cell 3 and to direct it, by reflection from its walls 11 , into the head of the optical fibre 9.
  • the external walls 11 of the concentrator form at least one ellipsoid portion 70 ( Figures 2, 3).
  • this portion 70 begins at the level of the upstream focal point F1 ; in other words, the focal point F1 lies in that plane transverse to the major axis of the ellipsoid which bounds this portion upstream.
  • the ellipsoid portion can contain at least the upstream focal point F1 , i.e. that focal point of the ellipsoid which is closer to the individual LED or to the group of LEDs 3A-3D the light emission of which is collected by the concentrator.
  • the emission ends of the LEDs 3A-3D of the LED elemental cell are situated at or close to the focal point F1 ; preferably these emission ends lie in a plane passing through the upstream focal point F1.
  • the ellipsoidal surface portion 70 is sufficiently large and contains at least one quarter of the major axis of the ellipsoid; more preferably the ellipsoidal surface portion 70 contains at least one half of the major axis of the ellipsoid and, still more preferably, a fraction between 0.6 and 0.85 times the major half axis of the ellipsoid.
  • the ratio between the minor and major half axis of the ideal ellipsoid of which the portion 70 forms part is between 0.6 and 0.9, and more preferably between 0.7 and 0.8.
  • the external walls 11 of the concentrator define, downstream of the ellipsoid portion 70, a substantially frusto-conical portion 72.
  • this frusto-conical surface 72 has a solid opening angle at the vertex ⁇ substantially less than the acceptance angle ⁇ of the optical fibre 9 ( Figure 2).
  • the solid opening angle at the vertex ⁇ is between about one quarter and about one half of the acceptance angle ⁇ of the optical fibre 9.
  • the optical efficiency of the system is greater if at the interface between the concentrator 7 and the optical fibre 9 there is no lens or concave, convex or otherwise lenticular refracting surface, and if the concentrator 7 and optical fibre 9 are coupled together by two simple flat surfaces; in this case the acceptance angle of current optical fibres varies indicatively between 60 and 75°, and the opening angle at the vertex ⁇ of the frusto-conical portion 72 is preferably between 15° and 35°, and more preferably between 20° and 30°. In the embodiment of Figure 2 the opening angle at the vertex ⁇ is about 23-25°.
  • the frusto-conical portion 72 of the concentrator reflecting surface is able to collect the light rays emitted by the LED or group of LEDs 3A-3D and to deviate them towards the mouth of the optical fibre 9 with a particularly small number of reflections, so minimizing the quantity of light rays escaping from the concentrator by refraction.
  • the two flat interface surfaces between the concentrator 7 and optical fibre 9 can be bonded by suitable optical adhesive.
  • the ratio between the minor axis of the ideal ellipsoid of which the portion 70 forms part and the diameter Dint of the interface surface 74 downstream of the frusto-conical surface 72 varies between 5 and 10, preferably between 7 and 8.
  • second focal point or downstream focal point F2 of the ideal ellipsoid of which the portion 70 forms part means the focal point of that optical system situated more downstream, i.e. more distant from the LED or group of LEDs 3A-3D.
  • the second focal point of the ideal ellipsoid F2 is situated on the downstream interface surface 74 of the frusto-conical surface 72, or on that surface of the optical waveguide 9 situated more upstream; this positioning optimizes the system optical efficiency.
  • the second focal point F2 can also be situated within the concentrator 7, and more particularly within the frusto-conical portion 72.
  • the axis of the optical fibre, or other optical waveguide 9, immediately downstream of the concentrator 7, is parallel to and coincides with the major axis of the ideal ellipsoid of which the portion 70 forms part.
  • the efficiency of the optical system is further increased, and transmission losses reduced, if the LEDs 3A-3D have a substantially flat emission surface, and if that surface 76 of the concentrator 7 facing them is substantially concave, preferably as a hemispherical cap, as shown in Figure 4.
  • the purpose of the spherical cap 76 is to better distribute the light emission of the LEDs 3A-3D on the ellipsoidal surface 79.
  • the LEDs 3A-3D of the support 5 have a relatively large 50% viewing angle ⁇ V, for example 120°, such as the LEDs of type OSTAR LE ATB S2W produced by the company OSRAM (Germany), where a 50% viewing angle ⁇ V is the displacement from the normal of the LED with which a light of intensity 50% (-3dB) of that measurable along the axis is visible: this emission angle, at least with currently available LEDs, ensures better optical and energy efficiency of the generator 1.
  • ⁇ V for example 120°
  • a 50% viewing angle ⁇ V is the displacement from the normal of the LED with which a light of intensity 50% (-3dB) of that measurable along the axis is visible: this emission angle, at least with currently available LEDs, ensures better optical and energy efficiency of the generator 1.
  • the forms of the aforedescribed concentrators advantageously enable currently available high efficiency LEDs to be properly utilized, to collect virtually the entire light radiation emitted by them and to transfer it with very small losses - indicatively less than 50% - to the optical fibres 9.
  • Each concentrator 7 can be made for example in the form of a solid body of optically transparent material - for example plexiglass, synthetic resins in general, or glass - by injection moulding; the outer surface of the concentrator 7 can be made reflecting by polishing or by coating it with a suitable reflecting layer.
  • the concentrator 7 has the shape of an ellipsoid of rotation with the ends suitably flattened to enable it to be coupled to the LEDs 3A-3D.
  • the length LUC of the concentrator can be for example about 100 mm, and its maximum diameter LAC about 35 mm, while the diameter DF of the optical fibre 9 can be about 3-5 mm ( Figure 3).
  • the concentrators 7 can be formed as hollow bodies bounded by mirror-finished or sufficiently reflecting walls,
  • the aforedescribed concentrators 7 are able to retain in their interior and to feed into the optical fibre 9 between 50 and 70% of the light irradiated by the
  • Each of the waveguides 9 is preferably in the form of a so-called liquid waveguide, i.e. formed from a tubular casing of a suitable plastic material filled with a suitable gel or other transparent fluid and closed at its ends by quartz plugs.
  • Light guides of this type are currently marketed by the company FORT
  • each optical waveguide 9 can be formed as a solid body of a suitable transparent material such as plexiglass or other synthetic resin or glass, moulded or machined mechanically, or a bundle of smaller optical fibres, for example a bundle of synthetic resin or glass optical fibres of diameter less than one millimetre.
  • the different optical fibres 9 originating from the various concentrators 7 are brought together side by side as in a bundle or bunch ( Figures 1 , 5); preferably the various optical fibres 9 in the bundle or bunch are fixed together by a suitable fibre carrier support 15, which can be in the form for example of a block of polymer resin co-moulded directly onto the optical fibres 9, or as a clip which is not co-moulded but grips the optical fibres 9.
  • a suitable fibre carrier support 15 can be in the form for example of a block of polymer resin co-moulded directly onto the optical fibres 9, or as a clip which is not co-moulded but grips the optical fibres 9.
  • the downstream ends of the optical fibres 9, arranged to outwardly emit the light emissions conducted by them are brought to the outside of the fibre carrier support 15 and aligned in rows and columns to form a square or rectangular mesh matrix; other different arrangements are clearly also possible.
  • the cross-sections through the various optical fibres 9 within the fibre carrier support 15 are disposed parallel to each other in the direction of the thickness of the fibre carrier support 15 ( Figure 5) and are also aligned along mutually perpendicular rows and columns ( Figure 1); other arrangements are clearly also possible.
  • optical fibres 9 By virtue of the capacity of the optical fibres to conduct the light emitted by the various LEDs 3A-3D along a path including bends and curvatures with a substantially negligible light intensity loss and the fact that, as the cross-section through the various optical fibres 9, at least at the fibre carrier support 15, is smaller than the maximum cross-sections through the concentrators 7, the optical fibres 9 in approaching each other from upstream to downstream are able to concentrate within a very small area the light flux emitted by a potentially infinite number of LEDs disposed on a very much larger support 5.
  • optical fibres 9 in approaching each other to finally group into a bundle or bunch, form an optical concentrator; the optical fibre portions which approach each other and possibly group together, plus the emission head 13 when present, together form the so-called collector portion 16 ( Figure 1).
  • the ratio between a) the maximum width or length of the largest cross-section of the bundle of optical fibres or other waveguides 9, where the cross-section is perpendicular to the bundle axis, and b) the maximum width or length of the assembly of the ends of the optical fibres or waveguides 9 which project downstream of the fibre carrier support 15, is equal to or greater than four times; more preferably this ratio is equal to or greater than six times; even more preferably this ratio is equal to or greater than ten times.
  • the greater this ratio called in this description the "narrowing ratio of the collector portion 16", the greater the intensity of the light beam emitted downstream of the fibre carrier support 15.
  • the light beam emitted overall by the emission head 13 is therefore sufficiently narrow to be able to be easily reduced by a relatively simple lens system such as to illuminate an area of only 7 mm diameter, which corresponds to the target to be illuminated in digital projectors for cinematographic use or in conference halls; in cinematographic projectors for 35 mm film the target dimensions are precisely a rectangle of 22 x 16 mm.
  • LED light generators can be formed with performance comparable, in terms of emitted light flux, to gas discharge lamps of known type used up to the present time for cinematographic projectors, with a saving in absorbed electrical power indicatively of up to 80%.
  • a light generator 1 By using LEDs 1 a light generator 1 according to the invention could attain an operating life of the order of 20,000-40,000 hours of operation, and could use low voltage single phase power units instead of the three-phase units required for gas discharge lamps; as it does not contain high pressure gas in its interior, it provides a much higher level of intrinsic safety.
  • Another advantage achievable by the present invention is that in the light generator 1 the distance DM between the LEDs 3A-3D and the emission ends 9A of the optical fibres can be relatively small, indicatively about 30 cm ( Figure 1). Moreover the geometry of a generator 1 of the invention is no longer rigidly related to that of the concentrator mirror which surrounds the current gas discharge, incandescent or halogen lamps.
  • the light emission can be generated by LED assemblies each able to emit a different coloured light, for example - as already anticipated with reference to Figure 1A - by using elemental groupings or elemental cells 3 each formed for example from LEDs 3A which emit red light, LEDs 3B and 3D which emit green light, and LEDs 3C which emit blue light.
  • the colour of the light emitted downstream by the optical fibres 9 can hence be varied and regulated.
  • the light of one or more LEDs which emit light of a single colour can be collected with each concentrator 7, a plurality of LEDs able to emit light of different colours can be arranged on the LED carrier support 5, and the lights of different colours be mixed merely by spatially mixing the downstream ends of the optical fibres 9 in the emission head 13, in such a manner as to in any event vary the colour of the overall light beam emitted by the generator 1.
  • a masking cover 106 gives the light spot illuminating the film 102 a suitable rectangular shape.
  • the film 102 advances stepwise, with the rotary shutter 104 suitably obscuring the light source 100 - such as a gas discharge lamp - when the film 102 translates. Hence the film is illuminated only when at rest.
  • FIG. 7 shows the operating scheme of a so-called DLP device (digital light processing deviceTM) for white light, of known type.
  • DLP device digital light processing deviceTM
  • a suitable optical prism system 206 the so-called colour splitter 206.
  • the colours of the three rays are red, green and blue, such as to form a system of primary colours.
  • Each coloured light ray is directed onto a device comprising micromirrors 208A, 208B, 208C, currently known in the art as a DMD (digital micromirror device) acting as a light modulator; DMDs of this type are described for example in US4662746 and US5096279.
  • DMD digital micromirror device
  • Each DMD is formed substantially of a matrix of micromirrors formed on a semiconductor chip; each micromirror deflects the light independently of the other micromirrors, and corresponds to a pixel of the image to be composed.
  • a first application of the present invention to DLP projectors is the replacement of the light generator 200 of known type by one or more light generators 1 of the invention, where the generators 1 emits white light.
  • FIG. 8 A second application of the present invention to RLP projectors is shown in Figure 8: in this embodiment a plurality of light generators 1', 1" and 1"' according to the invention emit beams of coloured light towards respective micromirror modulators (DMDs) 208A, 208B 1 208C.
  • the colour of the light emitted by the light generators V 1 1" and V" is substantially uniform within space, i.e. is not spatially modulated, and can be for example red, green and blue respectively, or alternatively in the primary colours green/red/blue, in the complementary colours yellow/magenta/cyan or in still further bases of primary or complementary colours.
  • the light generators of the invention can likewise be used to form digital projectors with other types of spatial light modulation, for example with so-called LCD (Liquid Crystal Device) or LCOS (Liquid Crystal on Silicon) technologies, or floodlights for theatrical, scenographic or technical lighting applications, which produce beams or spots of white or coloured light.
  • LCD Liquid Crystal Device
  • LCOS Liquid Crystal on Silicon
  • the LEDs can be grouped into elemental cells 3' formed from six LEDs (3 x 2) or other numbers and arrangements.
  • the concentrator 7 can be without the frusto-conical portion 72 and have an ellipsoidal external surface or reflecting surface which is virtually complete or which also contains the second focal point F2 or terminates at its level.
  • the concentrator can be provided with an upstream portion formed from several ellipsoid segments or "slices" 7OA, 7OB, 7OC joined together in succession, in which each of the ellipsoids of which the various segments or “slices” form part defines two focal points, namely an upstream focal point FV, FV 1 FV" and a downstream focal point F2', F2", F2"' where the major axes of the various ellipsoids are aligned along a straight line, the upstream focal points FV, FV, FV” are aligned along the straight line of the major axes but spaced from each other in positions substantially non-coincident, whereas the downstream focal points F2', F2", F2"' substantially coincide and fall at one and the same point (Figure 9).
  • This embodiment enables account to be taken of the fact that each LED or each elemental cell of LEDs 3A-3D is not a point-like source but has a finite area.
  • the distance DM between the LEDs 3A-3D and the emission ends of the waveguides 9 is preferably equal to or less than five times the length LUC of the concentrator 7, and more preferably equal to or less than three times the length LUC.
  • the distance DM is preferably equal to or less than fifteen times the maximum diameter LAC of the concentrator 7, more preferably equal to or less than twelve times the maximum diameter LAC, and even more preferably equal to or less than nine times the maximum diameter LAC.
  • the mean diameter DF of the optical fibre or other waveguide 9 is preferably equal to or less than one third of the maximum diameter LAC of the concentrator 7; more preferably the diameter DF is equal to or less than one quarter of the maximum diameter LAC of the concentrator 7; even more preferably the diameter DF is equal to or less than one seventh of the maximum diameter LAC; still more preferably the diameter DF is equal to or less than one tenth of the maximum diameter LAC. Said dimensional relationships between the diameter DF and diameter LAC also contribute to increasing the dimensions of the LED carrier support 5, the number of LEDs 3 and the number of concentrators 7 able to collect the light emission and to concentrate it into the emission head 13.

Abstract

The projection system according to the invention comprises a light generator (1), itself comprising, in order from upstream to downstream: a) at least one light emitting diode (3A-3D); b) at least one concentrator (7) provided with at least one reflecting surface (11, 70, 72) arranged to receive from upstream at least part of the light radiation emitted by the at least one light emitting diode (3A-3D); c) at least one optical waveguide (9) terminating with an emission end and arranged to receive from upstream at least part of the light radiation collected by the at least one concentrator (7) and to direct it as far as the emission end. Proceeding from upstream to downstream the cross-sections of the at least one reflecting surface progressively enlarge, reaching substantially at least one maximum, then progressively contracting. The cross-sections of the at least one optical waveguide (9) within a length thereof are substantially not greater than the cross-sections of the at least one concentrator (7).

Description

PROJECTION SYSTEM
This application claims priority of Italian application No. Mi2009A001188, the content of which is incorporated herein by reference.
Field of the Invention
[1] The present invention relates to a light generator and a system for projecting light and/or fixed or moving images, using said light generator. The teachings of the present invention can be used for example to form analogue and digital cinematographic projectors, slide projectors, projectors for projecting images stored on a computer, white or coloured light projectors for theatrical, scenographic, performance or technical lighting uses in general.
State of the art
[2] Current projectors for cinema halls use as their light source a gas discharge or halogen or incandescent lamp. These known lamps have powers variable between 500 W - with a corresponding life of about 3000 hours - and 12000 W - with a corresponding life of about 400 hours - and are powered by three- phase or single-phase electronic power units with a weight indicatively of 30-35 kg, but up to 200 kg for linear power units.
[3] Recently, semiconductor devices have been developed - the so-called light emitting diodes (LEDs) - able to emit increasingly more intense light fluxes. LEDS are known to be characterised by a ratio of emitted light flux to absorbed electric power which is much higher than the more traditional gas discharge, halogen or incandescent lamps.
[4] Consequently a first object of the present invention is to provide a light source which represents an improvement on light sources of known type, in particular compared with gas discharge, halogen and incandescent lamps. [5] A second object of the present invention is to provide a distance projector for light and/or images, such as a floodlight for scenographic or technical lighting effects in general, or a cinematographic projector for slides or films, which represents an improvement on floodlights or projectors of known type, in particular compared with projectors the light source of which is one or more gas discharge, halogen or incandescent lamps.
Summary of the invention
[6] This object is attained, according to the invention, by a projection system having the characteristics of claim 1.
The advantages attainable by the present invention will be more apparent to the expert of the art from the ensuing detailed description of some particular embodiments thereof illustrated by way of non-limiting example with reference to the accompanying schematic figures.
List of Figures
[7] Figure 1 is a perspective view of a light generator for a first embodiment of a projection system of the present invention;
Figure 1A is a detailed perspective view of an elemental cell of the LED carrier support of the generator of Figure 1 ;
Figure 2 is a lateral view of a concentrator of the generator of Figure 1 ;
Figure 3 is a section through a concentrator of the generator of Figure 1 , taken on a longitudinal sectional plane;
Figure 4 is a section on a longitudinal sectional plane through a detail of that portion of the concentrator of Figure 3 at the interface with the LEDs which energize it, in the light generator of Figure 1 ;
Figure 5 is a longitudinal section through the emission head of the generator of
Figure 1 ; Figure 6 shows the operating scheme of a cinematographic film projector of known type;
Figure 7 shows the operating scheme of a digital projector with DLP technology of known type, provided with a white light generator;
Figure 8 shows the operating scheme of a digital projector with DLP technology in accordance with a third embodiment of a projection system of the invention, with three coloured light generators based on an RGB system;
Figure 9 shows a lateral view of a concentrator and the relative waveguide, of a fourth embodiment of a light generator of the present invention.
Detailed description
[8] In the present description the expressions "upstream", "downstream", "towards upstream", "towards downstream" refer to the optical path of the light emission generated overall by the light emitting diodes 3A-3D and conveyed by the waveguides 9;
If not otherwise specified, the cross-sections are assumed to be taken on a plane perpendicular to the upstream-downstream direction along said optical path of the light emission generated overall by the light emitting diodes 3A-3D and conveyed by the waveguides 9, or via other respective optical components.
[9] Figures 1-5 relate to a first embodiment of a light generator of the invention; this light generator, indicated overall by the reference numeral 1 , comprises a plurality of light emitting diodes (LEDs) 3 fixed to a suitable LED carrier support 5 such as to form a matrix, for example substantially flat. In the present embodiment, in said matrix the LEDs are disposed along mutually perpendicular rows and columns. In other embodiments, not shown, the LEDs can be disposed for example quincuncially.[10] More particularly, in the present embodiment, the LEDs are grouped in elemental cells 3, each formed of three or four LEDs 3A-3D relatively very close together (Figure 1A). [11] Preferably each elemental cell 3 is separated from the other adjacent cells by a distance greater than that which mutually separates the various LEDs 3A- 3D comprising each elemental cell.
The light generator 1 also comprises at least one concentrator 7 the external walls 11 of which form at least one reflecting surface arranged to reflect the light radiation emitted by the LEDs 3A-3D.
[12] According to one aspect of the invention, the concentrator 7 is optically connected to a length of optical waveguide 9 (Figure 1). The optical waveguide 9 terminates downstream with an emission end and is arranged to receive from upstream at least part of the light radiation collected by the at least one concentrator 7 and to direct it as far as the emission end.
Proceeding from upstream to downstream, the cross-sections of the at least one reflecting surface progressively enlarge to reach substantially at least one maximum, after which they progressively contract; moreover the cross-sections of the at least one optical waveguide 9 within a length thereof are substantially not greater than the cross-sections of the at least one concentrator 7.
In this manner the quantity of light radiation collected by the concentrator 7 and directed into the optical waveguide 9 within its acceptance angle is increased compared for example with known concentrators of parabola or more generally cup shape.
[13] Each concentrator 7 is advantageously optimized to collect as much as possible of the light radiation emitted in the visible band by the LEDs of each elemental cell 3 and to direct it, by reflection from its walls 11 , into the head of the optical fibre 9.
[14] For this purpose the external walls 11 of the concentrator form at least one ellipsoid portion 70 (Figures 2, 3). In the embodiment of Figures 2, 3 this portion 70 begins at the level of the upstream focal point F1 ; in other words, the focal point F1 lies in that plane transverse to the major axis of the ellipsoid which bounds this portion upstream. In other embodiments, not shown, the ellipsoid portion can contain at least the upstream focal point F1 , i.e. that focal point of the ellipsoid which is closer to the individual LED or to the group of LEDs 3A-3D the light emission of which is collected by the concentrator.
[15] Advantageously the emission ends of the LEDs 3A-3D of the LED elemental cell are situated at or close to the focal point F1 ; preferably these emission ends lie in a plane passing through the upstream focal point F1.
Advantageously the ellipsoidal surface portion 70 is sufficiently large and contains at least one quarter of the major axis of the ellipsoid; more preferably the ellipsoidal surface portion 70 contains at least one half of the major axis of the ellipsoid and, still more preferably, a fraction between 0.6 and 0.85 times the major half axis of the ellipsoid.
[16] Advantageously the ratio between the minor and major half axis of the ideal ellipsoid of which the portion 70 forms part is between 0.6 and 0.9, and more preferably between 0.7 and 0.8.
Advantageously the external walls 11 of the concentrator define, downstream of the ellipsoid portion 70, a substantially frusto-conical portion 72.
[17] Advantageously this frusto-conical surface 72 has a solid opening angle at the vertex α substantially less than the acceptance angle β of the optical fibre 9 (Figure 2). Preferably the solid opening angle at the vertex α is between about one quarter and about one half of the acceptance angle β of the optical fibre 9.
[18] It has been noted that the optical efficiency of the system is greater if at the interface between the concentrator 7 and the optical fibre 9 there is no lens or concave, convex or otherwise lenticular refracting surface, and if the concentrator 7 and optical fibre 9 are coupled together by two simple flat surfaces; in this case the acceptance angle of current optical fibres varies indicatively between 60 and 75°, and the opening angle at the vertex α of the frusto-conical portion 72 is preferably between 15° and 35°, and more preferably between 20° and 30°. In the embodiment of Figure 2 the opening angle at the vertex α is about 23-25°.
The frusto-conical portion 72 of the concentrator reflecting surface, if suitably designed, is able to collect the light rays emitted by the LED or group of LEDs 3A-3D and to deviate them towards the mouth of the optical fibre 9 with a particularly small number of reflections, so minimizing the quantity of light rays escaping from the concentrator by refraction.
[19] Consequently the combination of an ellipsoidal surface portion 70 upstream and a frusto-conical surface 72 downstream maximizes the diffraction of light emission of the LED or group of LEDs 3A-3D which effectively enters the optical fibre with an inclination not greater than the acceptance angle β of this latter; it has been found that this fraction can reach 50-70% of the total emission of the LED or group of LEDs 3A-3D.
[20] The two flat interface surfaces between the concentrator 7 and optical fibre 9 can be bonded by suitable optical adhesive.
Advantageously the ratio between the minor axis of the ideal ellipsoid of which the portion 70 forms part and the diameter Dint of the interface surface 74 downstream of the frusto-conical surface 72 varies between 5 and 10, preferably between 7 and 8.
In the present description the term "second focal point" or "downstream focal point" F2 of the ideal ellipsoid of which the portion 70 forms part means the focal point of that optical system situated more downstream, i.e. more distant from the LED or group of LEDs 3A-3D.
[21] Advantageously the second focal point of the ideal ellipsoid F2 is situated on the downstream interface surface 74 of the frusto-conical surface 72, or on that surface of the optical waveguide 9 situated more upstream; this positioning optimizes the system optical efficiency. In other embodiments not shown, the second focal point F2 can also be situated within the concentrator 7, and more particularly within the frusto-conical portion 72.
Advantageously the axis of the optical fibre, or other optical waveguide 9, immediately downstream of the concentrator 7, is parallel to and coincides with the major axis of the ideal ellipsoid of which the portion 70 forms part.
[22] These measurements and/or dimensional ratios increase the emitted light which effectively enters the optical fibre within its acceptance angle.
The efficiency of the optical system is further increased, and transmission losses reduced, if the LEDs 3A-3D have a substantially flat emission surface, and if that surface 76 of the concentrator 7 facing them is substantially concave, preferably as a hemispherical cap, as shown in Figure 4. The purpose of the spherical cap 76 is to better distribute the light emission of the LEDs 3A-3D on the ellipsoidal surface 79.
[23] Advantageously the LEDs 3A-3D of the support 5 have a relatively large 50% viewing angle ΦV, for example 120°, such as the LEDs of type OSTAR LE ATB S2W produced by the company OSRAM (Germany), where a 50% viewing angle ΦV is the displacement from the normal of the LED with which a light of intensity 50% (-3dB) of that measurable along the axis is visible: this emission angle, at least with currently available LEDs, ensures better optical and energy efficiency of the generator 1.
[24] The forms of the aforedescribed concentrators advantageously enable currently available high efficiency LEDs to be properly utilized, to collect virtually the entire light radiation emitted by them and to transfer it with very small losses - indicatively less than 50% - to the optical fibres 9.
[25] Each concentrator 7 can be made for example in the form of a solid body of optically transparent material - for example plexiglass, synthetic resins in general, or glass - by injection moulding; the outer surface of the concentrator 7 can be made reflecting by polishing or by coating it with a suitable reflecting layer.
[26] This solution is shown in Figure 3, in which the concentrator 7 has the shape of an ellipsoid of rotation with the ends suitably flattened to enable it to be coupled to the LEDs 3A-3D. The length LUC of the concentrator can be for example about 100 mm, and its maximum diameter LAC about 35 mm, while the diameter DF of the optical fibre 9 can be about 3-5 mm (Figure 3).
[27] Alternatively the concentrators 7 can be formed as hollow bodies bounded by mirror-finished or sufficiently reflecting walls,
[28] The aforedescribed concentrators 7 are able to retain in their interior and to feed into the optical fibre 9 between 50 and 70% of the light irradiated by the
LEDs 3A-3D.
[29] Each of the waveguides 9 is preferably in the form of a so-called liquid waveguide, i.e. formed from a tubular casing of a suitable plastic material filled with a suitable gel or other transparent fluid and closed at its ends by quartz plugs. Light guides of this type are currently marketed by the company FORT
(Italy), LINOS (Germany) and EDMOND (USA). Alternatively each optical waveguide 9 can be formed as a solid body of a suitable transparent material such as plexiglass or other synthetic resin or glass, moulded or machined mechanically, or a bundle of smaller optical fibres, for example a bundle of synthetic resin or glass optical fibres of diameter less than one millimetre.
[30] The different optical fibres 9 originating from the various concentrators 7 are brought together side by side as in a bundle or bunch (Figures 1 , 5); preferably the various optical fibres 9 in the bundle or bunch are fixed together by a suitable fibre carrier support 15, which can be in the form for example of a block of polymer resin co-moulded directly onto the optical fibres 9, or as a clip which is not co-moulded but grips the optical fibres 9. [31] Preferably the downstream ends of the optical fibres 9, arranged to outwardly emit the light emissions conducted by them, are brought to the outside of the fibre carrier support 15 and aligned in rows and columns to form a square or rectangular mesh matrix; other different arrangements are clearly also possible.
[32] Preferably the cross-sections through the various optical fibres 9 within the fibre carrier support 15 are disposed parallel to each other in the direction of the thickness of the fibre carrier support 15 (Figure 5) and are also aligned along mutually perpendicular rows and columns (Figure 1); other arrangements are clearly also possible.
[33] The combination of the fibre carrier support 15 and the downstream ends of the optical fibres 9 forms an example of the so-called emission head 13 of the light generator 1.
[34] By virtue of the capacity of the optical fibres to conduct the light emitted by the various LEDs 3A-3D along a path including bends and curvatures with a substantially negligible light intensity loss and the fact that, as the cross-section through the various optical fibres 9, at least at the fibre carrier support 15, is smaller than the maximum cross-sections through the concentrators 7, the optical fibres 9 in approaching each other from upstream to downstream are able to concentrate within a very small area the light flux emitted by a potentially infinite number of LEDs disposed on a very much larger support 5.
[35] For example, with reference to Figure 1 , it was possible to concentrate over a surface area of about 50 x 20 mm (LM2 = 50 mm and HM2 = 20 mm) the light flux emitted by twenty-five elemental LED cells disposed in a square mesh arrangement of 40 mm between axes, disposed on an LED carrier support 5 of dimensions HM1 = 20 cm and LM1 = 20 cm.
The optical fibres 9, in approaching each other to finally group into a bundle or bunch, form an optical concentrator; the optical fibre portions which approach each other and possibly group together, plus the emission head 13 when present, together form the so-called collector portion 16 (Figure 1).
[36] Advantageously the ratio between a) the maximum width or length of the largest cross-section of the bundle of optical fibres or other waveguides 9, where the cross-section is perpendicular to the bundle axis, and b) the maximum width or length of the assembly of the ends of the optical fibres or waveguides 9 which project downstream of the fibre carrier support 15, is equal to or greater than four times; more preferably this ratio is equal to or greater than six times; even more preferably this ratio is equal to or greater than ten times. The greater this ratio, called in this description the "narrowing ratio of the collector portion 16", the greater the intensity of the light beam emitted downstream of the fibre carrier support 15.
[37] The light beam emitted overall by the emission head 13 is therefore sufficiently narrow to be able to be easily reduced by a relatively simple lens system such as to illuminate an area of only 7 mm diameter, which corresponds to the target to be illuminated in digital projectors for cinematographic use or in conference halls; in cinematographic projectors for 35 mm film the target dimensions are precisely a rectangle of 22 x 16 mm.
[38] Using the aforesaid OSTAR LE ATB S2W LEDs or the power LEDs P4 produced by SEOUL SEMICONDUCTOR, with an LED carrier matrix 5 with 10 x 10 elemental cells 3, a light flux of about 30,000 Im can be emitted from the emission head 13.
[39] Consequently by virtue of the present invention, LED light generators can be formed with performance comparable, in terms of emitted light flux, to gas discharge lamps of known type used up to the present time for cinematographic projectors, with a saving in absorbed electrical power indicatively of up to 80%.
[40] By using LEDs1 a light generator 1 according to the invention could attain an operating life of the order of 20,000-40,000 hours of operation, and could use low voltage single phase power units instead of the three-phase units required for gas discharge lamps; as it does not contain high pressure gas in its interior, it provides a much higher level of intrinsic safety.
[41] Another advantage achievable by the present invention is that in the light generator 1 the distance DM between the LEDs 3A-3D and the emission ends 9A of the optical fibres can be relatively small, indicatively about 30 cm (Figure 1). Moreover the geometry of a generator 1 of the invention is no longer rigidly related to that of the concentrator mirror which surrounds the current gas discharge, incandescent or halogen lamps.
[42] In a light generator 1 according to the invention the light emission can be generated by LED assemblies each able to emit a different coloured light, for example - as already anticipated with reference to Figure 1A - by using elemental groupings or elemental cells 3 each formed for example from LEDs 3A which emit red light, LEDs 3B and 3D which emit green light, and LEDs 3C which emit blue light. The colour of the light emitted downstream by the optical fibres 9 can hence be varied and regulated.
[43] Alternatively the light of one or more LEDs which emit light of a single colour can be collected with each concentrator 7, a plurality of LEDs able to emit light of different colours can be arranged on the LED carrier support 5, and the lights of different colours be mixed merely by spatially mixing the downstream ends of the optical fibres 9 in the emission head 13, in such a manner as to in any event vary the colour of the overall light beam emitted by the generator 1.
[44] To mix and superimpose the light beams emitted by the ends of the various optical fibres 9, these ends could be provided with suitable refraction systems, such as lenses, arranged to emit a conical beam of sufficient opening β (Figure 5). The overall light beam is then narrowed, collimated or further diffused, depending on the application, by a suitable lens system 17 (Figure 1).
It has however been observed that optimal optical efficiency of the entire system is achieved when the ends of the various optical fibres 9 are without lenses and are simply of cylindrical form (Figure 5).
[45] Another advantage obtainable with the present invention will now be illustrated with reference to Figure 6, which shows the operating principle of a cinematographic film projector of known type.
A masking cover 106 gives the light spot illuminating the film 102 a suitable rectangular shape. During cinematographic projection the film 102 advances stepwise, with the rotary shutter 104 suitably obscuring the light source 100 - such as a gas discharge lamp - when the film 102 translates. Hence the film is illuminated only when at rest.
[47] The use of one or more light generators 1 according to the invention in a cinematographic film projector enables the rotary shutter to be eliminated together with all the mechanical components which operate it: in this respect, the generator LED needs only to be activated while the film 102 is at rest, and deactivated while the film is translating.
[48] Further advantageous applications of a light generator of the invention to digital projectors are illustrated with reference to Figures 7 and 8.
Figure 7 shows the operating scheme of a so-called DLP device (digital light processing device™) for white light, of known type.
[49] In this device, the white light generated by a light generator 200 of known type, such as a gas discharge lamp, after passing through a system of condensing lenses 202 and having been deflected by a mirror 204 is separated into three rays of different colour by a suitable optical prism system 206, the so- called colour splitter 206. Typically the colours of the three rays are red, green and blue, such as to form a system of primary colours. [50] Each coloured light ray is directed onto a device comprising micromirrors 208A, 208B, 208C, currently known in the art as a DMD (digital micromirror device) acting as a light modulator; DMDs of this type are described for example in US4662746 and US5096279. Each DMD is formed substantially of a matrix of micromirrors formed on a semiconductor chip; each micromirror deflects the light independently of the other micromirrors, and corresponds to a pixel of the image to be composed.
[51] By means of a second prism different from the colour splitter 206 the three rays of coloured light returning from the DMD are again combined into a multicolour light beam in order to form the final image with the correct colours; the multicolour beam is then focused by projection lenses 210.
[52] A first application of the present invention to DLP projectors is the replacement of the light generator 200 of known type by one or more light generators 1 of the invention, where the generators 1 emits white light.
[53] A second application of the present invention to RLP projectors is shown in Figure 8: in this embodiment a plurality of light generators 1', 1" and 1"' according to the invention emit beams of coloured light towards respective micromirror modulators (DMDs) 208A, 208B1 208C. The colour of the light emitted by the light generators V1 1" and V" is substantially uniform within space, i.e. is not spatially modulated, and can be for example red, green and blue respectively, or alternatively in the primary colours green/red/blue, in the complementary colours yellow/magenta/cyan or in still further bases of primary or complementary colours.
[54] After being space modulated by the respective micromirror modulators 208A, 208B, 208C1 the beams of coloured light are again superimposed by a second prism such as to compose the desired image in real colours. This image is projected towards the projection lens 210. [55] An advantage of the projector of Figure 8 compared with that of Figure 7 is that the colour splitter 206' and the chromatic filters usually associated with it can be eliminated, so improving the quality of the image obtained: in this respect, these filters, even though optimized, are never ideal or perfect and hence introduce inevitable distortions.
[56] The light generators of the invention can likewise be used to form digital projectors with other types of spatial light modulation, for example with so-called LCD (Liquid Crystal Device) or LCOS (Liquid Crystal on Silicon) technologies, or floodlights for theatrical, scenographic or technical lighting applications, which produce beams or spots of white or coloured light.
[57] The aforedescribed embodiments are susceptible to various modifications and variations but without leaving the scope of protection of the present invention. For example, the LEDs can be grouped into elemental cells 3' formed from six LEDs (3 x 2) or other numbers and arrangements. The concentrator 7 can be without the frusto-conical portion 72 and have an ellipsoidal external surface or reflecting surface which is virtually complete or which also contains the second focal point F2 or terminates at its level. The concentrator can be provided with an upstream portion formed from several ellipsoid segments or "slices" 7OA, 7OB, 7OC joined together in succession, in which each of the ellipsoids of which the various segments or "slices" form part defines two focal points, namely an upstream focal point FV, FV1 FV" and a downstream focal point F2', F2", F2"' where the major axes of the various ellipsoids are aligned along a straight line, the upstream focal points FV, FV, FV" are aligned along the straight line of the major axes but spaced from each other in positions substantially non-coincident, whereas the downstream focal points F2', F2", F2"' substantially coincide and fall at one and the same point (Figure 9). This embodiment enables account to be taken of the fact that each LED or each elemental cell of LEDs 3A-3D is not a point-like source but has a finite area.
[58] In embodiments, not shown, the distance DM between the LEDs 3A-3D and the emission ends of the waveguides 9 is preferably equal to or less than five times the length LUC of the concentrator 7, and more preferably equal to or less than three times the length LUC. Alternatively the distance DM is preferably equal to or less than fifteen times the maximum diameter LAC of the concentrator 7, more preferably equal to or less than twelve times the maximum diameter LAC, and even more preferably equal to or less than nine times the maximum diameter LAC. These dimensional relationships enable the number of concentrators 7 able to feed light emissions into the emission head 13 to be increased, hence increasing the intensity of the overall light beam emitted by the head 13.
[59] In embodiments, not shown, the mean diameter DF of the optical fibre or other waveguide 9 is preferably equal to or less than one third of the maximum diameter LAC of the concentrator 7; more preferably the diameter DF is equal to or less than one quarter of the maximum diameter LAC of the concentrator 7; even more preferably the diameter DF is equal to or less than one seventh of the maximum diameter LAC; still more preferably the diameter DF is equal to or less than one tenth of the maximum diameter LAC. Said dimensional relationships between the diameter DF and diameter LAC also contribute to increasing the dimensions of the LED carrier support 5, the number of LEDs 3 and the number of concentrators 7 able to collect the light emission and to concentrate it into the emission head 13.
[60] In embodiments, not shown, several generators such as that shown in Figure 1 can be disposed in parallel such as to illuminate the same target with a greater light flux. [61] The examples and lists of possible variants of the present patent application are to be considered as non-exhaustive lists.

Claims

1. A projection system comprising a light generator (1), itself comprising, in order from upstream to downstream:
a) at least one light emitting diode (3A-3D);
b) at least one optical waveguide (9) terminating with an emission end;
c) at least one concentrator (7) provided with at least one reflecting surface (11 ,
70, 72) arranged to receive from upstream at least part of the light radiation emitted by the at least one light emitting diode (3A-3D) and to deflect it into the at least one optical waveguide (9);
wherein:
- proceeding from upstream to downstream the cross-sections of the at least one reflecting surface (11 , 70, 72) progressively enlarge, reaching substantially at least one maximum, then progressively contract;
- the at least one optical waveguide is arranged to receive from upstream at least part of the light radiation collected by the at least one concentrator (7) and to direct it as far as the emission end;
- the cross-sections of the at least one optical waveguide (9) within a length thereof are substantially not greater than the cross-sections of the at least one concentrator (7).
2. A projection system as claimed in claim 1 , wherein the at least one optical waveguide (9) comprises one or more of the following elements:
- a conduit containing a substantially transparent fluid, for example liquid or gel;
- one or more optical fibres.
3. A projection system as claimed in claim 1 , wherein the at least one reflecting surface of the at least one concentrator (7) is substantially a surface of revolution.
4. A projection system as claimed in claim 1 , wherein the at least one reflecting surface of the at least one concentrator (7) forms at least one ellipsoid portion (70) which contains at least a first focal point (F1) of the ellipsoid or which commences upstream at the level of said first focal point (F1).
5. A projection system as claimed in claim 4, wherein the at least one ellipsoid portion (70) of the at least one reflecting surface contains at least one quarter of the major axis of the ellipsoid.
6. A projection system as claimed in claim 4, wherein the at least one reflecting surface of the at least one concentrator (7) defines a substantially frusto-conical portion (72) arranged to direct towards the at least one optical waveguide (9) the light radiation emitted by the at least one light emitting diode (3A-3D) and possibly reflected by the at least one ellipsoid portion (70).
7. A projection system as claimed in claim 6, wherein the substantially frusto- conical portion (72) contains the second focal point (F2) of the at least one ellipsoid portion (70) or terminates downstream at the level of said second focal point (F2), where the second focal point (F2) is situated more downstream than the first focal point (F1).
8. A projection system as claimed in claim 6, wherein the substantially frusto- conical portion (72) of the at least one reflecting portion contains at least one quarter of the major axis of the ellipsoid.
9. A projection system as claimed in claim 1 , comprising:
a) a plurality of light emitting diodes (3A-3D);
b) a plurality of concentrators (7), the at least one reflecting surface of each concentrator (7) being arranged to receive from upstream at least part of the light radiation emitted by at least one of the light emitting diodes (3A-3D);
c) a collector portion (16) comprising a plurality of optical waveguides (9), where:
- at least some of the optical waveguides (9) terminate with an emission end and are arranged to receive from upstream at least part of the light radiation collected by at least one of the concentrators (7) and to conduct it as far as the emission end;
- the collector portion (16) is arranged to collect the light radiation transmitted by the plurality of optical waveguides (9);
- the outer dimensions of the collector portion (16) in at least part of its cross- sections are substantially less than the outer dimensions of the optical waveguides (9) and/or of the concentrators (7) in those cross-sections of the projection system (1) upstream of the collector portion (16).
10. A projection system as claimed in claim 9, wherein the outer dimensions of the collector portion (16) reduce progressively from upstream to downstream.
11. A projection system as claimed in claim 9, wherein in the collector portion (16) the optical waveguides (9) are closer together than those portions more upstream of the projection system (1), and possibly form a bundle or bunch.
12. A projection system as claimed in claim 9, wherein each concentrator (7) is arranged to collect the emission of a plurality of light emitting diodes (3A-3D), at least one of these diodes being able to emit light of a colour substantially different from the colour of the light of the other diodes associated with the same concentrator (7).
13. A projection system as claimed in claim 9, comprising at least one spatial light modulator (208A, 208B, 208C) arranged to modulate in space the light emission of the at least one light generator (1) such as to form an image.
14. A projection system as claimed in claim 13, wherein the at least one spatial light modulator comprises:
- a film with one or more cinematographic frames;
- a film reproducing a slide;
- a micromirror spatial modulator (208A, 208B, 208C);
- a liquid crystal spatial modulator (318A, 318B, 318C) possibly of LCOS type.
15. A projection system as claimed in claim 13, comprising: a) one or more projection lenses arranged to focus and/or project the images modulated by the cinematographic film onto a screen external to the projection system; and
b) a control and operating system arranged to:
- switch on the at least one light generator (1) when the film with several cinematographic frames is not moving relative to the one or more projection lenses, and illuminate a single frame of said film;
- switch off the at least one light generator (1) at least when the film with several cinematographic frames is moving relative to the one or more projection lenses.
16. A projection system as claimed in claim 13, comprising a plurality of light generators (1), each arranged to emit coloured light of a colour of a base of primary colours such as red, green and blue light, or complementary colours such as magenta, cyan and yellow, each light generator (1) being arranged to project its coloured light towards a respective spatial light modulator (208A, 208B, 208C) without separating the coloured light with a colour separator.
17. A projection system as claimed in claim 13, comprising at least one colour combiner arranged to combine the images produced by each spatial light modulator (208A1 208B, 208C) in the various primary or complementary colours, to form an image in real colours.
PCT/IB2010/001660 2009-07-06 2010-07-02 Projection system WO2011004241A1 (en)

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