WO1991005202A1 - Backlighting apparatus - Google Patents
Backlighting apparatus Download PDFInfo
- Publication number
- WO1991005202A1 WO1991005202A1 PCT/US1990/004718 US9004718W WO9105202A1 WO 1991005202 A1 WO1991005202 A1 WO 1991005202A1 US 9004718 W US9004718 W US 9004718W WO 9105202 A1 WO9105202 A1 WO 9105202A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- light
- reflecting
- distributing
- light source
- pipe
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
- G02B6/0015—Means for improving the coupling-in of light from the light source into the light guide provided on the surface of the light guide or in the bulk of it
- G02B6/002—Means for improving the coupling-in of light from the light source into the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
- G02B6/0021—Means for improving the coupling-in of light from the light source into the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces for housing at least a part of the light source, e.g. by forming holes or recesses
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
- G02B6/004—Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles
- G02B6/0043—Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles provided on the surface of the light guide
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
- G02B6/0045—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
- G02B6/0046—Tapered light guide, e.g. wedge-shaped light guide
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
- G02B6/0055—Reflecting element, sheet or layer
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/0058—Means for improving the coupling-out of light from the light guide varying in density, size, shape or depth along the light guide
- G02B6/0061—Means for improving the coupling-out of light from the light guide varying in density, size, shape or depth along the light guide to provide homogeneous light output intensity
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0066—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form characterised by the light source being coupled to the light guide
- G02B6/0068—Arrangements of plural sources, e.g. multi-colour light sources
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F13/00—Illuminated signs; Luminous advertising
- G09F13/18—Edge-illuminated signs
- G09F2013/1804—Achieving homogeneous illumination
- G09F2013/1831—Achieving homogeneous illumination using more than one light source
Definitions
- This invention relates generally to backlighting. Specifically, this invention concerns the backlighting of liquid crystal displays.
- the positive image display allows the background to emit or reflect light while the segment area is dark.
- the segments block the light emitted or reflected only where the segments are darkened, thus forming the characters.
- the negative image display has a dark background while the open segmented area forms the characters by emitting or reflecting light.
- the background of a positive image LCD or the segments of a negative image LCD can be colored by using a filter with the incandescent bulbs or by changing the color of the LED lamps.
- the LCD acts as a light shutter rather than a light emitting display requiring light behind the LCD to define which segments are turned on. This lighting of an LCD from behind is called backlighting.
- Backlighting can be implemented using two techniques.
- the first technique is to place a reflector behind the LCD.
- the reflector causes the ambient light entering the top of the LCD to be reflected back through the LCD from behind. This is very effective in high ambient lighting conditions such as sunlight.
- the second backlighting technique uses an artificial light source behind the LCD. This technique is effective in low ambient lighting conditions. This technique does not function in high ambient lighting conditions since the high ambient
- Artificial light sources may include: incandescent bulbs, light emitting diodes (LED), electrolumuniscent panels, fluorescent tubes or halogen bulbs.
- a negative image display uses artificial backlighting to emit light in low ambient lighting conditions and also a diffuser sheet on top of the light pipe to reflect the ambient light in high ambient lighting conditions. If the backlighting is not bright enough, the display will look poor in
- the drive circuitry it is called a display module.
- Some display modules are so thin that there is limited space behind the LCD for the backlighting. Some display modules also have length and width restrictions. These small, low profile display modules require that the illumination sources be on the sides
- the LCD 35 is a local area where the light is more intense than the other areas of the display.
- the hot spot is generally confined to the area surrounding the illumination source itself.
- the LCD usually has hot spots at its edge and is dim in its center. The dim lighting problem occurs when the entire area of the display is at an unacceptable brightness.
- Backlighting a negative image display is more difficult than a positive image display.
- the viewer only sees the light emitting from the segmented area rather than the entire background area as in a positive image LCD. Therefore, the quantity of the backlighting illumination must be great to produce an aesthetically pleasing display in average ambient lighting conditions.
- typically incandescent bulbs or LEDs have been used. Incandescent bulbs would be the preferred choice for negative image, low profile display modules since they put out more light than LEDs.
- a disadvantage of incandescent bulbs is that they are inherently less reliable than LEDs.
- incandescent bulbs usually deters their use for backlighting the displays.
- life expectancy of a lamp is inversely proportional to its efficiency. In other words, increasing an incandescent lamps efficiency decreases its life span.
- a high rated voltage also reduces the lamp's resistance to mechanical shock and vibration.
- a bright negative image LCD using incandescent backlighting has either a short life span or high power requirements and is susceptible to failure during mechanical shock and vibration.
- the present invention provides even and bright illumination for either a positive or negative image display.
- a light pipe distributes the light by reflecting it off the side internal to the light pipe.
- Each corner of the light pipe is dual angled to reflect the light toward the center of the display.
- Light is diffused off the bottom of the light pipe, while controlling hot and dim spots, by painting the bottom white except near the edges and in a pattern around the lamps.
- Light refracted out of the sides of the light pipe is reflected back in by white diffusing reflectors on two sides of the light pipe and white elastomeric reflectors, that connect the underlying circuitry to the LCD, on the other two sides.
- the lamps are wired in two pairs, each pair connected in series. Each pair of lamps can adequately illuminate the entire display. With two series pairs illuminating the entire display, a lower voltage is applied to each lamp. The lower voltage translates into higher reliability for the lamps.
- optical efficiency of this invention allows the use of incandescent lamps that have acceptable life, power consumption and heat dissipation while still providing bright backlighting.
- FIG. 1 shows a block diagram of the preferred embodiment in accordance with the present invention.
- FIG. 2 shows the preferred embodiment of lamp connection in accordance with the present invention.
- FIG. 3 shows the illumination pattern of the lamps in accordance with the present invention.
- FIG. 4 shows the preferred embodiment of a pattern for painting the bottom of the light pipe in accordance with the present invention.
- FIG. 5 shows the configuration of the preferred embodiment of the light pipe in accordance with the present invention.
- This invention provides an even distribution of bright light across a low profile liquid crystal display .
- the preferred embodiment of this invention as illustrated in Fig. 1, is comprised of an acrylic light pipe (101), four incandescent lamps (301 - 304), two diffusing reflectors Q03), and two elastomeric connecting strips (104).
- a bright, evenly lit display is achieved by coupling the light from lamps (301 - 304) into the light pipe (101). Light emitted from the end of the lamp is directed toward the center using internal reflection of the light pipe (101).
- the four lamps (301 - 304) are positioned in pairs on opposing sides of the light pipe (101) and placed on their sides to maintain a narrow side profile for the apparatus.
- the lamps (301 - 304) are placed as close to the light pipe (101) as possible to insure maximum luminous flux entering the light pipe (101) from the lamps (301 - 304).
- the lamp (301 - 304) bottoms are positioned close enough together to minimize the dim area between the lamps (301 - 304) at the edge of the light pipe (101).
- the lamps can be electrically connected in a diagonal series parallel configuration illustrated in Fig. 2. Either pair of series connected lamps (301 - 302, 303 - 304) alone can adequately illuminate the entire display.
- the iUumination pattern of each pair is illustrated in Fig. 3.
- a benefit of this configuration is that if one of the lamps (301 - 304) burns out, the other lamp (301 - 304) in series with it also goes out leaving the other two lamps (301 - 304) to adequately evenly light the display. The average brightness will only be half when operating with the two lamps (301 - 304) out, but the illumination will still be an adequately even distribution.
- Another benefit of this configuration is that each lamp (301 - 304) is operated at a lower voltage. The lower voltage makes the lamps (301 - 304) less susceptible to shock and gives them a longer life expectancy without increasing power consumption.
- a white diffuse reflector is placed around the th ee sides of the lamps which do not face the light pipe.
- the light pipe (101) must be appropriately constructed for proper operation of this invention. All sides, the top and the non-painted area of the back must be smooth, allowing internal reflection of light to occur.
- the back of the light pipe (101) is selectively painted white. A pattern in the form of a border, half-sun and ovals around each lamp is left unpainted. The preferred embodiment of such a pattern is illustrated in Fig. 4.
- the smooth unpainted surfaces of the light pipe internally reflect light that has an angle of incidence less than the critical angle, 42° for acrylic. The angle of reflection equals the angle of incidence.
- the white paint provide diffuse reflection, scattering the light. Some of this light escapes the light pipe and passes through the LCD.
- the border, ovals and half-sun pattern therefore, has the effect of dimming the hot spots caused by the proximity of the lamps, and increasing the brightness in the painted area.
- (301 - 304) follows the outside radius of the lamps' (301 - 304) lenses. This allows the light leaving the lamps' (301 - 304) lens to enter the light pipe (101) without refracting. A straight path for the light leaving the lamp (301 - 304) and entering the light pipe (101) improves the evenness of the illumination in the light pipe (101) near each lamp (301 - 304).
- the corners of the light pipe (101) near each lamp are angled as shown in Fig. 5. A significant portion of the lamps output exits from the end of the lamp. This light would not be captured, and therefore wasted, if a simple rectangular light pipe were used.
- the angled surfaces (501, 502) reflect, this light onto surface (503) of the light pipe.
- the path of the light reflecting off surfaces (501, 502, 503) is easily plotted using a graphical method. Using such a method, the angles have been determined so that this light is directed toward the center area of the light pipe, which would otherwise be dim.
- the first surface (501) is angled 18° from the side and the second surface (502) is angled 30 c from the side. Any light striking the angled surfaces (501 - 502) or side (503) that exceeds the critical angle will be refracted outside the light pipe (101).
- the elastomeric connecting strips (104) also have the purpose of connecting the LCD driving circuitry to the LCD.
- the top surface of the backlighting apparatus should not be positioned in direct contact with any other surface. An air gap should be maintained to preserve the internal reflection properties of the light pipe (101).
- a colored filter between the LCD and the light pipe (101), a typical negative image LCD application, will not degrade the operation as there is only intermittent contact between the light pipe (101) and the filter. Only a few molecules of air above the light pipe (101) are required for proper operation of this invention.
- the backlighting apparatus can evenly light both negative and positive image LCDs. The combined improvement in optical efficiency from all aspects of this invention requires less illumination to achieve a given brightness. As incandescent lamp efficiency is inversely related to its operating life, either an increase in lifetime, a decrease in power consumption and heat, an increase in overall brightness or some combination of these advantages is achieved by this invention.
- the light pipe, with angled corners to direct light toward the middle of the display provides even lighting throughout the display with no hot spots. Using the backlighting apparatus, a negative image LCD can attain the
- An alternate embodiment of this invention is to use other light sources such as LEDs. Different numbers of light sources could be used depending on the size of the display and
- the angles and size of surfaces (501, 502) as well as the selective pattern illustrated in Fig. 4 would be optimized for the emission pattern of the light source.
- the back side of the light pipe could be treated in any manner that produces diffuse reflection.
- the light pipe could be any
- the material around the light sources could be any material that provides reflection.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002042060A CA2042060C (en) | 1989-10-02 | 1990-08-22 | Backlighting apparatus |
EP90914093A EP0446324B1 (en) | 1989-10-02 | 1990-08-22 | Backlighting apparatus |
DE69029258T DE69029258T2 (en) | 1989-10-02 | 1990-08-22 | REAR LIGHTING DEVICE |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US415,741 | 1989-10-02 | ||
US07/415,741 US4975808A (en) | 1989-10-02 | 1989-10-02 | Backlighting apparatus |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1991005202A1 true WO1991005202A1 (en) | 1991-04-18 |
Family
ID=23646995
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1990/004718 WO1991005202A1 (en) | 1989-10-02 | 1990-08-22 | Backlighting apparatus |
Country Status (8)
Country | Link |
---|---|
US (1) | US4975808A (en) |
EP (1) | EP0446324B1 (en) |
CN (1) | CN1017289B (en) |
AT (1) | ATE145716T1 (en) |
AU (1) | AU625629B2 (en) |
CA (1) | CA2042060C (en) |
DE (1) | DE69029258T2 (en) |
WO (1) | WO1991005202A1 (en) |
Cited By (2)
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US5489317A (en) * | 1992-06-22 | 1996-02-06 | Turf Systems International, Inc. | Surface for sports and other uses |
US6854854B2 (en) | 2001-04-10 | 2005-02-15 | Koninklijke Philips Electronics N.V. | Illumination system and display device |
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US5528720A (en) * | 1992-03-23 | 1996-06-18 | Minnesota Mining And Manufacturing Co. | Tapered multilayer luminaire devices |
US6002829A (en) | 1992-03-23 | 1999-12-14 | Minnesota Mining And Manufacturing Company | Luminaire device |
GB2267378B (en) * | 1992-05-22 | 1996-07-10 | Nokia Mobile Phones Uk | Illuminated LCD apparatus |
CA2097109C (en) * | 1992-06-01 | 2000-01-11 | Shozo Kokawa | Liquid crystal display |
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US6712481B2 (en) * | 1995-06-27 | 2004-03-30 | Solid State Opto Limited | Light emitting panel assemblies |
US5613751A (en) * | 1995-06-27 | 1997-03-25 | Lumitex, Inc. | Light emitting panel assemblies |
US5975711A (en) * | 1995-06-27 | 1999-11-02 | Lumitex, Inc. | Integrated display panel assemblies |
US7108414B2 (en) | 1995-06-27 | 2006-09-19 | Solid State Opto Limited | Light emitting panel assemblies |
US5895115A (en) * | 1996-01-16 | 1999-04-20 | Lumitex, Inc. | Light emitting panel assemblies for use in automotive applications and the like |
US6072551A (en) * | 1996-02-14 | 2000-06-06 | Physical Optics Corporation | Backlight apparatus for illuminating a display with controlled light output characteristics |
US5838403A (en) * | 1996-02-14 | 1998-11-17 | Physical Optics Corporation | Liquid crystal display system with internally reflecting waveguide for backlighting and non-Lambertian diffusing |
JP3860249B2 (en) * | 1996-05-02 | 2006-12-20 | ローム株式会社 | Surface emitting lighting device |
JP3466817B2 (en) * | 1996-05-02 | 2003-11-17 | ローム株式会社 | LED light emitting device and manufacturing method |
US6166787A (en) * | 1998-03-17 | 2000-12-26 | Motorola, Inc. | Optical display device having prismatic film for enhanced viewing |
US6285425B1 (en) | 1998-06-29 | 2001-09-04 | Motorola, Inc. | Ridged reflector for an optical display having a curved and a planar facet for each ridge |
US6285426B1 (en) | 1998-07-06 | 2001-09-04 | Motorola, Inc. | Ridged reflector having optically transmissive properties for an optical display device |
US7364341B2 (en) * | 1999-02-23 | 2008-04-29 | Solid State Opto Limited | Light redirecting films including non-interlockable optical elements |
US6827456B2 (en) | 1999-02-23 | 2004-12-07 | Solid State Opto Limited | Transreflectors, transreflector systems and displays and methods of making transreflectors |
US6752505B2 (en) | 1999-02-23 | 2004-06-22 | Solid State Opto Limited | Light redirecting films and film systems |
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JP3670949B2 (en) * | 2000-09-27 | 2005-07-13 | 三洋電機株式会社 | Surface light source device |
KR100701014B1 (en) * | 2000-11-22 | 2007-03-29 | 삼성전자주식회사 | A light guide plate, a liquid crystal display module and a liquid crystal display device having the same |
KR20030008790A (en) * | 2001-07-20 | 2003-01-29 | 삼성전자 주식회사 | Liquid crystal display device |
US20030206256A1 (en) * | 2002-05-06 | 2003-11-06 | Drain Kieran F. | Display device with backlight |
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US7510316B2 (en) * | 2003-07-14 | 2009-03-31 | Koninklijke Philips Electronics N.V. | Ultra compact illumination system for display systems |
KR100567249B1 (en) * | 2003-09-06 | 2006-04-03 | 현대모비스 주식회사 | Light guide plate for liquid crystal display back light and liquid crystal display module of car audio in use with the light guide plate |
US7182492B1 (en) * | 2003-12-22 | 2007-02-27 | Robert Louis Walter | License plate system having enhanced illumination |
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KR100716989B1 (en) | 2004-12-23 | 2007-05-10 | 삼성전자주식회사 | Back light system and liquid crystal display apparatus employing it |
US7545569B2 (en) * | 2006-01-13 | 2009-06-09 | Avery Dennison Corporation | Optical apparatus with flipped compound prism structures |
US7866871B2 (en) | 2006-01-13 | 2011-01-11 | Avery Dennison Corporation | Light enhancing structures with a plurality of arrays of elongate features |
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US7674028B2 (en) | 2006-01-13 | 2010-03-09 | Avery Dennison Corporation | Light enhancing structures with multiple arrays of elongate features of varying characteristics |
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US8462292B2 (en) | 2008-07-31 | 2013-06-11 | Rambus Delaware Llc | Optically transmissive substrates and light emitting assemblies and methods of making same, and methods of displaying images using the optically transmissive substrates and light emitting assemblies |
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-
1989
- 1989-10-02 US US07/415,741 patent/US4975808A/en not_active Expired - Lifetime
-
1990
- 1990-08-22 DE DE69029258T patent/DE69029258T2/en not_active Expired - Fee Related
- 1990-08-22 WO PCT/US1990/004718 patent/WO1991005202A1/en active IP Right Grant
- 1990-08-22 CA CA002042060A patent/CA2042060C/en not_active Expired - Fee Related
- 1990-08-22 AT AT90914093T patent/ATE145716T1/en not_active IP Right Cessation
- 1990-08-22 EP EP90914093A patent/EP0446324B1/en not_active Expired - Lifetime
- 1990-08-22 AU AU64136/90A patent/AU625629B2/en not_active Ceased
- 1990-09-28 CN CN90108038A patent/CN1017289B/en not_active Expired
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US3450870A (en) * | 1966-09-21 | 1969-06-17 | Coastal Dynamics Corp | Miniature light structure |
US3892959A (en) * | 1973-11-02 | 1975-07-01 | Gte Automatic Electric Lab Inc | Edge-lighted panel arrangement |
US4096550A (en) * | 1976-06-24 | 1978-06-20 | Bbc Brown Boveri & Company Limited | Illuminating arrangement for a field-effect liquid-crystal display as well as fabrication and application of the illuminating arrangement |
US4573766A (en) * | 1983-12-19 | 1986-03-04 | Cordis Corporation | LED Staggered back lighting panel for LCD module |
US4729067A (en) * | 1986-09-26 | 1988-03-01 | Mitsubishi Rayon Company Ltd. | Light diffusing device |
US4909604A (en) * | 1987-08-28 | 1990-03-20 | Hitachi, Ltd. | Light source device |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5489317A (en) * | 1992-06-22 | 1996-02-06 | Turf Systems International, Inc. | Surface for sports and other uses |
US6854854B2 (en) | 2001-04-10 | 2005-02-15 | Koninklijke Philips Electronics N.V. | Illumination system and display device |
Also Published As
Publication number | Publication date |
---|---|
CN1017289B (en) | 1992-07-01 |
EP0446324A4 (en) | 1993-06-30 |
CA2042060C (en) | 1994-11-01 |
EP0446324A1 (en) | 1991-09-18 |
DE69029258T2 (en) | 1997-06-05 |
CA2042060A1 (en) | 1991-04-03 |
AU6413690A (en) | 1991-04-28 |
AU625629B2 (en) | 1992-07-16 |
EP0446324B1 (en) | 1996-11-27 |
US4975808A (en) | 1990-12-04 |
CN1050785A (en) | 1991-04-17 |
ATE145716T1 (en) | 1996-12-15 |
DE69029258D1 (en) | 1997-01-09 |
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