Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133602—Direct backlight
  • G02F1/133604—Direct backlight with lamps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S6/00—Lighting devices intended to be free-standing
  • F21S6/004—Lighting devices intended to be free-standing with a lamp housing in direct contact with the floor or ground
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V7/00—Reflectors for light sources
  • F21V7/005—Reflectors for light sources with an elongated shape to cooperate with linear light sources
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V7/00—Reflectors for light sources
  • F21V7/0058—Reflectors for light sources adapted to cooperate with light sources of shapes different from point-like or linear, e.g. circular light sources
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133602—Direct backlight
  • G02F1/133605—Direct backlight including specially adapted reflectors

Definitions

• the invention relates to a backlight luminaire for a display device, which luminaire comprises a plurality of fluorescent lamps and a reflector which includes a plurality of sub-reflectors.
• the invention also relates to a liquid-crystal display device which includes a backlight luminaire.
• Backlight luminaires are used as a light source in flat-panel type display devices, in particular liquid-crystal display devices (LCD devices).
• LCD devices liquid-crystal display devices
• Fluorescent lamps are very suitable for use as light sources in flat-type display devices because they have a high light output and the spectral characteristic of the light emitted can be adapted in a simple manner.
• a luminaire which is arranged behind the display, is generally provided with elongated fluorescent lamps which are arranged in parallel relation to each other. It is alternatively possible to use U-shaped fluorescent lamps or so-called meander-shaped fluorescent lamps.
• a backlight luminaire of the type mentioned in the opening paragraph is disclosed in UK Patent Application GB-A 2 207 496.
• a description is given of a backlight luminaire which is used as a light source for a liquid-crystal display (LCD) device, which luminaire includes a plurality of U-shaped fluorescent lamps which are alternately arranged at the back of a liquid-crystal display device.
• a reflector including reflectors or an assembly of sub-reflectors.
• the (sub-)reflectors are concave in shape.
• one of the arm portions of one of the U-shaped fluorescent lamps is inserted between the arm portions of an adjacent lamp or lamps so as to be parallel thereto.
• the light source(s) in backlight luminaires should uniformly illuminate the active part of the display device.
• a disadvantage of the known backlight luminaire is that if one of the (U- shaped) fluorescent lamps emits less light or light having a different spectral characteristic, or if one of said fluorescent lamps fails, there is a locally non-uniform light distribution at the location of the relevant lamp.
• the backlight luminaire in accordance with the invention is characterized in that at least a number of the sub-reflectors are provided with a portion of at least two lamps, and at least a number of the lamps are situated in at least two sub-reflectors
• the inventor has recognized that by accommodating portions of the fluorescent lamps in two or more sub-reflectors and providing said sub-reflectors with a portion of at least two lamps, the adverse effect caused by the (temporary) reduction in light emission of one of the fluorescent lamps or by the fact that one of the lamps emits light having a different spectral characteristic (for example, if two lamps have a different color appearance), or by the fact that one of the lamps fails, is reduced in that the change in light distribution is distributed (spread out) over various sub-reflectors of the backlight luminaire As a result of said spread, the non-uniformity of the light distribution is spread out (averaged out) over a relatively larger area of the backlight luminaire and becomes relatively less visible by virtue of the presence of (portions of) other lamps.
• the effect of a deviation in a fluorescent lamp is limited to the sub-reflector accommodating said lamp, so that a non-uniformity of the backlight luminaire manifests itself more clearly.
• An embodiment of the backlight luminaire in accordance with the invention is characterized in that the lamps comprise at least a first arm portion and a second arm portion, which arm portions are arranged in side-by-side relation to each other and are interconnected via a connecting portion, said first arm portion being accommodated in a first sub-reflector and said second arm portion being accommodated in a second sub-reflector.
• a (fluorescent) lamp comprising two at least substantially parallel arm portions which are interconnected via a connecting portion, is referred to as a U-shaped or V-shaped lamp.
• a lamp comprising a plurality of arm portions extending one beside the other and being interconnected via a number of connecting portions, which connecting portions also extend parallel to each other, is referred to as a meander-shaped fluorescent lamp.
• An embodiment of the backlight luminaire in accordance with the invention is characterized in that the above-mentioned portions exhibit, in the longitudinal direction, a variation of the spectral characteristic, and in that the spectral characteristic of the portion of a first lamp in a sub-reflector varies in the opposite direction relative to the variation in spectral characteristic of the portion of a second lamp in said sub-reflector.
• the spectral characteristic, for example the color point, of fluorescent lamps is not uniform in the longitudinal direction of said lamps.
• a variation in the spectral characteristic of the lamp is generally caused by spreads occurring during the manufacture of fluorescent lamps, which variation occurs, for example, during filling the lamp with a phosphor mixture.
• some components of the (three-) phosphor mixture adhere more rapidly to the lamp than other components.
• the lamp is filled on one side from an end portion of the lamp, so that the spectral characteristic of the lamp changes in the longitudinal direction of the lamp, which results, for example, in a difference in color point over the length of the fluorescent lamp.
• the positioning of lamps in sub- reflectors must be taken to mean that (the portions of) the lamps are so positioned relative to each other in one sub-reflector that the spectral differences between the lamps are averaged out or leveled off.
• spectral differences in one (portion of a) lamp are compensated for by arranging said (portion of) the lamp proximate to one (portion of a) lamp whose spectral characteristic varies in the opposite direction.
• the (adjacent) (portions of the) lamps are so positioned relative to each other that the spectral characteristic of the sum of the (portions of the) lamps varies less than the spectral characteristic of the individual (portions of the) lamps.
• An embodiment of the backlight luminaire in accordance with the invention is characterized in that all portions of the lamps are so arranged that the spectral characteristics of two portions extending side by side in one sub-reflector vary in opposite directions. If the fluorescent lamps are elongated or U-shaped, and if an (arm) portion of a first lamp and an (arm) portion of a second lamp are arranged one beside the other in one sub-reflector, an effective compensation of an (at least substantially reproducible) variation in spectral characteristic in each one of said (arm) portions of the (at least two) lamps is attained by always alternately arranging the (arm) portions of the lamps having a defined variation in the sub-reflector in such a way that the spectral variation in said (arm) portion of the first lamp is compensated for by the spectral variation in said (arm) portion of the second lamp, which spectral variation changes in the opposite direction In the adjacent sub-reflectors, corresponding (arm) portions of the (at least two) elongated or U-
• a preferred embodiment of the backlight luminaire in accordance with the invention is characterized in that the lamps are alternately connected in series.
• lamps which are alternately connected in series is to be understood to mean that two (arm) portions of two lamps, which (arm) portions are arranged one beside the other in one sub-reflector, are not connected to the same power source.
• a power source having a slightly different voltage characteristic which leads to variations in the light intensity (or luminance) of (at least) one of the (fluorescent) lamps, is distributed over two (arm) portions of the lamps arranged one beside the other in one sub-reflector
• This can be brought about, for example, by groupwise (alternately) connecting the lamps in series or by alternately connecting all lamps in series. If two or more power sources are used and if the various power sources are suitably connected to the lamps, the effect of failure of one of the power sources on the light distribution can be minimized.
• Fig. 1A is a plan view of an embodiment of the backlight luminaire in accordance with the invention, which is provided with fluorescent lamps;
• Fig. IB is a cross-sectional view of the backlight luminaire, taken on the
• Fig. 2A is a perspective view of an embodiment of the backlight luminaire in accordance with the invention, which is provided with U-shaped fluorescent lamps;
• Fig. 2B is a cross-sectional view of the backlight luminaire shown in Fig.
• Fig. 3A is a plan view of an embodiment of the backlight luminaire in accordance with the invention, which is provided with meander-shaped fluorescent lamps.
• Fig. 3B is a cross-sectional view of the backlight luminaire, taken on the line IIIB-IIIB in Fig. 3A;
• Fig. 4A is a plan view of an embodiment of the backlight luminaire in accordance with the invention, which comprises two or more arm portions of fluorescent lamps per sub-reflector;
• Fig. 4B is a cross-sectional view of the backlight luminaire, taken on the line IVB-IVB in Fig. 4A, and
• Fig. 5 is an exploded view of an assembly of a liquid-crystal display device and a backlight luminaire.
• Fig. 1A is a schematic plan view of an embodiment of the backlight luminaire m accordance with the invention, which is provided with fluorescent lamps 4, 5, and Fig. IB is a schematic, cross-sectional view of the backlight luminaire 10 as shown in Fig. 1A, which luminaire is further provided with a light-scattering cover 7 (diffusor) which is supported by walls 6.
• the backlight luminaire 10 comprises a first group of sub-reflectors 2, 2' , 2", 2" ' and a second group of sub-reflectors 3, 3', 3" , 3" ' , which groups of sub-reflectors 2, 3 are arranged in a side-by-side relation.
• a luminaire is used, for example, if the display device does not have to be illuminated integrally (for example if different types of information are displayed).
• the (sub-)reflectors comprise directed reflectors which direct the direct and indirect light generated in the backlight luminaire towards the display device.
• the reflectors are concave in shape and provided, for example, with a matt, white coating which brings about a (diffuse) reflection of the light emitted by the lamps in a direction away from the display device.
• the expression "concave (sub-)reflector” must be taken to mean in this Application that the lamps are accommodated in a chamber (the sub-reflector) comprising a rear wall facing away from the display device and (oblique) vertical side walls, or a rear wall and side walls which are completely or partly pit-shaped.
• a first portion of the (linear) fluorescent lamps 4, 5 is always accommodated in the first group of sub-reflectors 2, and a second portion is always accommodated in the second group of sub-reflectors 3.
• each sub-reflector 2, 3 accommodates two portions of different fluorescent lamps 4, 5
• differences in color point (spectral characteristic) and light intensity between (at least) two lamps are not limited to one sub- reflector, but distributed (spread out) over each sub-reflector accommodating at least one (equivalent) portion of each of these (at least) two lamps.
• the lamps 4, 5 are alternately connected in series in such a manner that (portions of) lamps 4, 5 in one sub-reflector are not connected to the same power source.
• two power sources 8, 9 also referred to as inverters
• one half 4 of the fluorescent lamps being connected in series to the first power source 8 and the other half 5 of the fluorescent lamps being connected in series to the second power source 9.
• the light of each sub- reflector will be reduced by fifty percent. The same effect occurs if one of the power sources is switched off or fails.
• the quantity of light produced is halved m all (sub-)reflectors, so that the uniformity of the light output of the backlight luminaire is preserved, the only limitation being an integrally lower light intensity.
• the integral light output of the backlight luminaire is halved without the uniformity of the light distribution being seriously affected, which switching option is desirable since the display device is employed in greatly varying ambient-light conditions (for example, if it is used as a backlight luminaire of display devices in vehicles or aircraft).
• the lamps can also be connected pairwise (and alternately) to a power source. In this case, four power sources are required. Moreover, if the lamps are connected to at least two groups of power sources, (the portions of) the lamps connected to one of the groups of power sources can be so distributed over the sub-reflectors that each of the sub-reflectors has a portion of a lamp of each of the groups.
• the backlight luminaire is preferably provided with a switch (not shown in Fig. 1) by means of which one of the groups can be switched off, so that, by switching off one of the (groups of) power sources, the integral light output of the backlight luminaire is reduced without the uniformity of the light distribution being seriously affected.
• switches or other types of light regulators constitute a very desirable means for regulating the light intensity of display devices, for example in the case of substantially varying ambient-light conditions.
• Fig. 2A is a very schematic perspective view of an embodiment of the backlight luminaire in accordance with the invention, which is provided with U-shaped fluorescent lamps 14, 15, and Fig. 2B is a schematic, cross-sectional view of the backlight luminaire 20 shown in Fig. 2A, which luminaire is further provided with a light-scattering cover 17 which is supported by walls 16.
• each arm portion of the U-shaped fluorescent lamps 14, 15 is indicated by a reference numeral, i.e. 14', 14" and 14"' and 15', 15" and 15"', respectively.
• a reference numeral i.e. 14', 14" and 14"' and 15', 15" and 15"'
• two "half" sub-reflectors 12, 12', which each contain only one arm portion 14" ', 15"' of a fluorescent lamp, are provided at the two edges of the backlight luminaire 20.
• the light output and the uniformity (homogeneity) of the light distribution are further improved if the (vertical) walls of the "half" sub-reflectors 12, 12' are provided with a reflective layer 16' having a high reflection coefficient.
• the connecting portions of the U-shaped fluorescent lamps 14, 15, which connect the at least substantially parallel arm portions to each other, are situated on the outside of the backlight luminaire 20.
• these connecting portions are incorporated in a transition portion between two sub-reflectors and hence are an integral part of the backlight luminaire.
• the above-described method of distributing the lamps 14, 15 over the sub- reflectors 13, enables differences in color point (spectral characteristic) and light intensity between two lamps to be distributed (spread out) in each sub-reflector which accommodates an (equivalent) portion of each of said two lamps. This results in a substantial improvement of the uniformity of the backlight luminaire.
• the lamps 14, 15 are alternately connected in series in such a manner that (portions of) lamps 14, 15 in one sub- reflector 13 are not connected to the same power source.
• two power sources 18, 19 are employed, with the two U-shaped lamps 14 being connected in series to the first power source 18 and the other two U-shaped lamps 15 being connected in series to the second power source 19.
• the lamps 14, 15 are distributed over the sub-reflectors 13 in the above-described manner, the quantity of light produced is halved in the (sub-)reflectors comprising two arm portions, so that the uniformity of the light output of the backlight luminaire is substantially preserved.
• Fig. 3A is a schematic, plan view of an embodiment of the backlight luminaire in accordance with the invention, which is provided with two so-called meander- shaped fluorescent lamps 24, 25, and
• Fig. 3B is a schematic, cross-sectional view of the backlight luminaire 30 shown in Fig. 3 A, which luminaire is further provided with a light- scattering cover 27 which is supported by walls 26.
• a meander-shaped fluorescent lamp 24, 25 generally comprises a hermetically sealed, tubular lamp envelope having (multiple) M- shaped bends, as schematically shown in Fig. 3A.
• the meander-shaped lamp is composed of several (at least substantially parallel) arm portions which are interconnected via connecting portions.
• Fig. 3A is a schematic, plan view of an embodiment of the backlight luminaire in accordance with the invention, which is provided with two so-called meander- shaped fluorescent lamps 24, 25, and
• Fig. 3B is a schematic, cross-sectional view of the backlight luminaire 30 shown in Fig. 3 A
• the backlight luminaire 30 comprises a group of sub-reflectors 22, 22', 22", etc. which are arranged in a side-by-side relation.
• the successive arm portions of the meander-shaped fluorescent lamps 24, 25 are accommodated in successive sub-reflectors 22.
• each sub-reflector 22 accommodates two arm portions of each meander-shaped fluorescent lamp 24, 25.
• the light output and the homogeneity of the light distribution are further improved if the (vertical) portions of the walls 26 are provided with a reflective layer 26' having a high reflection coefficient.
• the lamps 24, 25 are individually connected to a voltage source 28, 29, respectively. If one of the power sources is switched off, the integral light output of the backlight luminaire is reduced by fifty percent without seriously affecting the uniformity of the light distribution.
• Fig. 4A is a schematic, plan view of an embodiment of the backlight luminaire in accordance with the invention, which comprises two or more arm portions of fluorescent lamps per sub-reflector
• Fig. 4B is a cross-sectional view of the backlight luminaire 40 corresponding to the one shown in Fig. 4A, which luminaire further comprises a light-scattering cover 37 which is supported by walls 36.
• the majority of the sub-reflectors 33, 33', 33" always comprise four arm portions of four different U-shaped lamps 34, 34', 34", 34"'; 35, 35' , 35", 35"'.
• the two edges of the backlight luminaire 40 are provided with two "half" sub-reflectors 32, 32' which each accommodate only two arm portions of two fluorescent lamps.
• the light output and the uniformity of the light distribution are further improved if the (vertical) walls of the "half" sub-reflectors 32, 32' are provided with a reflective layer 36' having a high reflection coefficient.
• Fig. 5 is a very schematic, exploded view of an assembly of a liquid- crystal display device 51 and a backlight luminaire 50.
• Fig. 5 is a very schematic, exploded view of an assembly of a liquid- crystal display device 51 and a backlight luminaire 50.
• the liquid-crystal display device 51 is accommodated in a housing 52 which is provided with mounting means (not shown in Fig. 5) and, if necessary, a support 54
• a filter 53 may be situated between the liquid-crystal display device 51 and the backlight luminaire 50.
• Said backlight luminaire 50 is provided with a light-scattering cover 47 (diffusor) which, in the assembled form, is supported by walls 46.
• the majority of the sub-reflectors 43, 43', 43", 43"' always comprise two arm portions of two different U-shaped fluorescent lamps 44, 44', 44"; 45, 45'
• the upper side and the lower side of the backlight luminaire 50 are provided, in this example, with two "half" sub- reflectors 42, 42' which each accommodate only one arm portion of a fluorescent lamp 44, 44" .
• the way in which the U-shaped fluorescent lamps 44, 45 are connected to power sources is not shown in Fig. 5.
• the connecting portions of the U-shaped fluorescent lamps 44, 45 are situated in a transition portion between two sub-reflectors and hence are an integral part of the backlight luminaire.
• the invention relates to a backlight luminaire comprising a plurality of fluorescent lamps and a plurality of sub-reflectors.
• the backlight luminaire is characterized in that the majority of the sub-reflectors are provided with a portion of more than one lamp. In addition, the majority of the lamps are distributed over more than one sub- reflector.
• the lamps are preferably U-shaped and alternately connected in series.
• the backlight luminaire is used in liquid-crystal display devices to attain a uniform light distribution.

Landscapes

• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mathematical Physics (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Liquid Crystal (AREA)
• Planar Illumination Modules (AREA)
• Non-Portable Lighting Devices Or Systems Thereof (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8224398

Family Applications (1)

Country Status (7)

Cited By (3)

Families Citing this family (20)

Citations (5)

Family Cites Families (4)

• 1997
  • 1997-02-19 TW TW086202638U patent/TW426203U/zh not_active IP Right Cessation
  • 1997-07-14 EP EP97928398A patent/EP0859934B1/en not_active Expired - Lifetime
  • 1997-07-14 JP JP51442798A patent/JP4015200B2/ja not_active Expired - Fee Related
  • 1997-07-14 DE DE69725694T patent/DE69725694T2/de not_active Expired - Fee Related
  • 1997-07-14 KR KR10-1998-0703639A patent/KR100455595B1/ko not_active Expired - Fee Related
  • 1997-07-14 WO PCT/IB1997/000866 patent/WO1998012471A1/en not_active Ceased
  • 1997-08-20 US US08/916,777 patent/US5971567A/en not_active Expired - Fee Related

Patent Citations (5)

Also Published As

Similar Documents

Legal Events