CA2042060C - Backlighting apparatus - Google Patents
Backlighting apparatusInfo
- Publication number
- CA2042060C CA2042060C CA002042060A CA2042060A CA2042060C CA 2042060 C CA2042060 C CA 2042060C CA 002042060 A CA002042060 A CA 002042060A CA 2042060 A CA2042060 A CA 2042060A CA 2042060 C CA2042060 C CA 2042060C
- Authority
- CA
- Canada
- Prior art keywords
- light
- distributing
- reflecting
- recess
- light pipe
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Fee Related
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
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Planar Illumination Modules (AREA)
- Liquid Crystal (AREA)
- External Artificial Organs (AREA)
- Supplying Of Containers To The Packaging Station (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Non-Portable Lighting Devices Or Systems Thereof (AREA)
- Devices For Indicating Variable Information By Combining Individual Elements (AREA)
Abstract
Improved backlighting apparatus evenly illuminates positive and negative LCDs under all ambient lighting conditions. In-candescent lamps (301-304) provide light for distribution by a light pipe (101). The bottom of the light pipe (101) is selectively painted white to reflect light to the top of the light pipe (101) while the unpainted areas reflect light internal to the light pipe (101).
controlling hot and dim spots. The corners of the light pipe (101) near the lamps (301-304) are dual angled to reflect the light into the center of the display. The burn-out of a lamp (301-304) will not substantially affect the even lighting capabilities of the appar-atus.
controlling hot and dim spots. The corners of the light pipe (101) near the lamps (301-304) are dual angled to reflect the light into the center of the display. The burn-out of a lamp (301-304) will not substantially affect the even lighting capabilities of the appar-atus.
Description
2Q4205~
2 - 1- PCI/US90tO4718 BACKLIGHTING APPARATUS
Field of the Invention This invention relates generally to b~ckli~hting.
Specifically, this invention concerns the backlighting of liquid crystal displays.
15 Back~round Art Two types of liquid crystal displays (LCD)in common use are positive and negative image displays. The positive image display allows the background to emit or reflect light 20 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 se~rnented area forms the ch~r~cters by P~nit~in~ or reflec~in~ light. The b~ck~round of 25 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 ch~snginE the color of the LED l~mps.
The LCD acts as a light shutter rather than a light emitting display requiring light behind the LCD to define 30 which se~rnents are turned on. This ligh*ng of an LCD from behind is called backlighting.
Backli~h*n~ 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
35 to be reflected back through the LCD from behin~l- T}liS iS very effective in high ambient lighting conditions such as sunlight.
WO 91/05202 - 2 - PCr/US90/04718 The brighter the ambient light, the brighter the b~ckli~hting and, therefore, the more readable the LCD. In low ambient lighting conditions, such as at night or twilight, a reflector is not effective since there is not enough light entering the top of 5 the LCD for b~ckli~htin~.
The second b~ckli~hting 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 10 light overpowers the artificial light. As a result, the LCD
segments are either dim or completely unreadable. Artificial light sources may include: incandescent bulbs, light emitting diodes (LED), electrolumuniscent p~nel~, fluorescent tubes or halogen bulbs.
Typically, 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 liehting conditions. If the b~cklighting is not bright enough, the display will loo~ poor in 20 average ambient lighting conditions. This is caused by the lack of enough ambient light to utilize the reflective properties of the diffuser and not enough artificial h~kli~hting to overcome the average ambient light.
When the b~cklighting is combined with the LCD and 25 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 b~kliehting. Some display modules also have length and width restrictions. These small, low profile display modules require that the illumination sources be on the sides 30 of a light pipe to provide the LCD b~rkli~hting.
Both negative image and positive image LCDs suffer from simil~r problems. These problems can include: uneven lighting, dim lighting and low lamp reliability. Uneven lighting is generally characterized by hot spots. The hot spot 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 2042Q~
Field of the Invention This invention relates generally to b~ckli~hting.
Specifically, this invention concerns the backlighting of liquid crystal displays.
15 Back~round Art Two types of liquid crystal displays (LCD)in common use are positive and negative image displays. The positive image display allows the background to emit or reflect light 20 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 se~rnented area forms the ch~r~cters by P~nit~in~ or reflec~in~ light. The b~ck~round of 25 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 ch~snginE the color of the LED l~mps.
The LCD acts as a light shutter rather than a light emitting display requiring light behind the LCD to define 30 which se~rnents are turned on. This ligh*ng of an LCD from behind is called backlighting.
Backli~h*n~ 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
35 to be reflected back through the LCD from behin~l- T}liS iS very effective in high ambient lighting conditions such as sunlight.
WO 91/05202 - 2 - PCr/US90/04718 The brighter the ambient light, the brighter the b~ckli~hting and, therefore, the more readable the LCD. In low ambient lighting conditions, such as at night or twilight, a reflector is not effective since there is not enough light entering the top of 5 the LCD for b~ckli~htin~.
The second b~ckli~hting 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 10 light overpowers the artificial light. As a result, the LCD
segments are either dim or completely unreadable. Artificial light sources may include: incandescent bulbs, light emitting diodes (LED), electrolumuniscent p~nel~, fluorescent tubes or halogen bulbs.
Typically, 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 liehting conditions. If the b~cklighting is not bright enough, the display will loo~ poor in 20 average ambient lighting conditions. This is caused by the lack of enough ambient light to utilize the reflective properties of the diffuser and not enough artificial h~kli~hting to overcome the average ambient light.
When the b~cklighting is combined with the LCD and 25 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 b~kliehting. Some display modules also have length and width restrictions. These small, low profile display modules require that the illumination sources be on the sides 30 of a light pipe to provide the LCD b~rkli~hting.
Both negative image and positive image LCDs suffer from simil~r problems. These problems can include: uneven lighting, dim lighting and low lamp reliability. Uneven lighting is generally characterized by hot spots. The hot spot 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 2042Q~
area surrounding the illumination source itself. For low profile dispiays with the illumin~ion sources at the edge of the light pipe, the LCD usually ha~ 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 lm~cceptable brightness. B~rklighting a negative image display is more difficult than a positive image display. For a negative 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. Because of the display module's size restrictions, typically incandescent bulbs o~r LEDs have been L5 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.
The low reliability of the incandescent bulbs usually deters their use for b~cktighting the displays. The 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 resiet~nc~ to me~h~nic~l shock and vibration.
l~rpically, therefore, a bright negative image LCD using incandescent b~cklighting has either a short life span or high power requirements and is susceptible to failure during mechanical shock and vibration.
There is therefore a need for a b~klig~lting device that ha~ even illumination, aesthetically pleasing brightness under all viewing conditions, and high reliability.
r o60 mm~ry of the Invention The present invention provides even and bright illu$nination for either a positive or negative image display.
The dim lighting problem occurs when the entire area of the display is at an lm~cceptable brightness. B~rklighting a negative image display is more difficult than a positive image display. For a negative image display, the viewer only sees the light emitting from the segmented area rather than the entire background area as in a positive image LCD. Therefore, the quantity of the backlighting illumination must be great to produce an aesthetically pleasing display in average ambient lighting conditions. Because of the display module's size restrictions, typically incandescent bulbs o~r LEDs have been L5 used. Incandescent bulbs would be the preferred choice for negative image, low profile display modules since they put out more light than LEDs. A disadvantage of incandescent bulbs is that they are inherently less reliable than LEDs.
The low reliability of the incandescent bulbs usually deters their use for b~cktighting the displays. The life expectancy of a lamp is inversely proportional to its efficiency.
In other words, increasing an incandescent lamps efficiency decreases its life span. A high rated voltage also reduces the lamp's resiet~nc~ to me~h~nic~l shock and vibration.
l~rpically, therefore, a bright negative image LCD using incandescent b~cklighting has either a short life span or high power requirements and is susceptible to failure during mechanical shock and vibration.
There is therefore a need for a b~klig~lting device that ha~ even illumination, aesthetically pleasing brightness under all viewing conditions, and high reliability.
r o60 mm~ry of the Invention The present invention provides even and bright illu$nination for either a positive or negative image display.
5 Using four incandescent lamps to provide illumination, a light pipe distributes the light by reflecting it off the side internal to the light pipe. Each comer of the light pipe is dual angled to reflect the light toward the center of the display.
Light is diffused offthe bottom of the light pipe, while 10 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 15 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 illl~minating the entire display, a lower voltage is applied to each lamp. The lower 20 voltage translates into higher reliability for the lamps.
The 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.
Brief I)escription of the DrawinFs FIG. 1 shows a block diagram of the preferred embodiment in accordance with the present invention.
30 FIG. 2 shows the preferred embo~liment 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 35 painting the bottom of the light pipe in accordance with the present invention.
20~20~0 FIG. 5 Qhows the configuration of the preferred çmbofliment of the light pipe in accordance with the present invention.
Best Mode for Carryin~ Ollt the ~nv~ntion 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 (103), and two elastomeric connect;nE strips (104). A bright, evenly lit display is achieved by coupling the light from l~mps (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 m~int~in a narrow side profile for the apparatus. The lamps (301 - 304) are placed as close to the light pipe (101) as possible to insure m~ imllm luminous flux entering the light pipe (101) from the lamps (301 - 304). The lamp (301 - 304) bottoms are positioned close enough together to minimi7e 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 E`ig. 2. Either pair of series connected la_ps (301 - 302, 303 - 304) alone can adequately illuminate the entire display. The illumination pattern of each pair is illustrated in Fig. 3. A benefit of this configuration is that if one of the lamps (301 - 304) burns o~t, 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 -?.~ 49~9~
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 con~umption.
A white diffuse reflector is placed around the three sides of the lamps which do not face the light pipe. This reflects both the light from the adjacent lamps (301-303, 302-304) into the light pipe and also light which has passed through the light pipe from the other lamps (301-303, 302-304).
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 equal~ the angle of in~ience. 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 flimming the hot spots caused by the pro~cimity of the lamps, and increasing the bri~htness in the painted area.
The inside radius of the light pipe (101) near each lamp (301 - 304) follows the outside radius of the l~mps' (301 - 304) lenses. Thi8 allows the light leanng the lamp8' (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) i~l~oves 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 signifir~nt portion of the lamps output e~its 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 ~04206G
Light is diffused offthe bottom of the light pipe, while 10 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 15 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 illl~minating the entire display, a lower voltage is applied to each lamp. The lower 20 voltage translates into higher reliability for the lamps.
The 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.
Brief I)escription of the DrawinFs FIG. 1 shows a block diagram of the preferred embodiment in accordance with the present invention.
30 FIG. 2 shows the preferred embo~liment 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 35 painting the bottom of the light pipe in accordance with the present invention.
20~20~0 FIG. 5 Qhows the configuration of the preferred çmbofliment of the light pipe in accordance with the present invention.
Best Mode for Carryin~ Ollt the ~nv~ntion 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 (103), and two elastomeric connect;nE strips (104). A bright, evenly lit display is achieved by coupling the light from l~mps (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 m~int~in a narrow side profile for the apparatus. The lamps (301 - 304) are placed as close to the light pipe (101) as possible to insure m~ imllm luminous flux entering the light pipe (101) from the lamps (301 - 304). The lamp (301 - 304) bottoms are positioned close enough together to minimi7e 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 E`ig. 2. Either pair of series connected la_ps (301 - 302, 303 - 304) alone can adequately illuminate the entire display. The illumination pattern of each pair is illustrated in Fig. 3. A benefit of this configuration is that if one of the lamps (301 - 304) burns o~t, 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 -?.~ 49~9~
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 con~umption.
A white diffuse reflector is placed around the three sides of the lamps which do not face the light pipe. This reflects both the light from the adjacent lamps (301-303, 302-304) into the light pipe and also light which has passed through the light pipe from the other lamps (301-303, 302-304).
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 equal~ the angle of in~ience. 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 flimming the hot spots caused by the pro~cimity of the lamps, and increasing the bri~htness in the painted area.
The inside radius of the light pipe (101) near each lamp (301 - 304) follows the outside radius of the l~mps' (301 - 304) lenses. Thi8 allows the light leanng the lamp8' (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) i~l~oves 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 signifir~nt portion of the lamps output e~its 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 ~04206G
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 three sides of the lamps which do not face the light pipe. This reflects both the light from the adjacent lamps (301-303, 302-304) into the light pipe and also light which has passed through the light pipe from the other lamps (301-303, 302-304).
The light pipe (101) must be alll.ro~l;ately constructed 16 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 lmps3inted. The preferred embodiment of such a pattern is illustrated in Fig. 4. The smooth unpainted surfaces of the li~ht pipe internally reflect light that has an angle of incidence greater 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 ~imming the hot spots caused by the proximity of the lamps, and increasing the brightness in the painted area.
The inside radius of the light pipe (101) near each lamp (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 strzight path for the light leaving the lamp (301 - 304) and entering the light , ~.
~042060 pipe (101) improves the evenness of the illllmination 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. In the l,lefelled embodiment, the first surface (501) is angled 18 from the side and the second surface (502) is angled 30 from the- side. Any light striking the angled surfaces (501 - 502) or ~ide (503) less than the critical angle will be r~l d~led outside the light pipe (101).
Light that is refracted outside the light pipe (101) is reflected back into it by the two white elastomeric connecting strips (104) and the two white diffusing reflectors (103). The positioning of these reflectors (103) and connectors (104) is illustrated in Fig. 1. The elastomeric connecting strips (104) also have the purpose of connecting the LCD driving circuitry to the LCD.
The top surface of the biq~kli~hting 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.
~ .
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 three sides of the lamps which do not face the light pipe. This reflects both the light from the adjacent lamps (301-303, 302-304) into the light pipe and also light which has passed through the light pipe from the other lamps (301-303, 302-304).
The light pipe (101) must be alll.ro~l;ately constructed 16 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 lmps3inted. The preferred embodiment of such a pattern is illustrated in Fig. 4. The smooth unpainted surfaces of the li~ht pipe internally reflect light that has an angle of incidence greater 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 ~imming the hot spots caused by the proximity of the lamps, and increasing the brightness in the painted area.
The inside radius of the light pipe (101) near each lamp (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 strzight path for the light leaving the lamp (301 - 304) and entering the light , ~.
~042060 pipe (101) improves the evenness of the illllmination 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. In the l,lefelled embodiment, the first surface (501) is angled 18 from the side and the second surface (502) is angled 30 from the- side. Any light striking the angled surfaces (501 - 502) or ~ide (503) less than the critical angle will be r~l d~led outside the light pipe (101).
Light that is refracted outside the light pipe (101) is reflected back into it by the two white elastomeric connecting strips (104) and the two white diffusing reflectors (103). The positioning of these reflectors (103) and connectors (104) is illustrated in Fig. 1. The elastomeric connecting strips (104) also have the purpose of connecting the LCD driving circuitry to the LCD.
The top surface of the biq~kli~hting 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.
~ .
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for backlighting a liquid crystal display, comprising:
a) substantially transparent means for distributing light having sides, a top, and a bottom, at least one side of the sides having at least one recess b) at least one light source, positioned in the at least one recess, for providing the light;
c) a diffuse reflecting material disposed upon the bottom of the means for distributing light; and d) a portion of the at least one side, between the at least one recess and a corner of the transparent means for distributing light, having a pluralityof angles for reflecting the light.
a) substantially transparent means for distributing light having sides, a top, and a bottom, at least one side of the sides having at least one recess b) at least one light source, positioned in the at least one recess, for providing the light;
c) a diffuse reflecting material disposed upon the bottom of the means for distributing light; and d) a portion of the at least one side, between the at least one recess and a corner of the transparent means for distributing light, having a pluralityof angles for reflecting the light.
2. An apparatus for backlighting a liquid crystal display according to claim 1 wherein the means for distributing light is a flat light pipe comprised of a substantially transparent material.
3. An apparatus for backlighting a liquid crystal display according to claim 1 further comprising first reflecting means for changing a path of the light exiting at least one side of the means for distributing light.
4. An apparatus for backlighting a liquid crystal display according to claim 1 further comprising second reflecting means, positioned in at least one plane around the at least one light source, for reflecting the light.
5. An apparatus for backlighting a liquid crystal display according to claim 1 wherein the diffuse reflective material is disposed such that the at least one light source provides evenly distributed light.
6. Apparatus for backlighting a liquid crystal display, comprising:
a) a flat, substantially transparent means for distributing light wherein a first and a second opposing side each have a recess, each recess having at least one light source positioned therein for providing the light, each opposing side having a plurality of angles between a corner of the means for distributing light and the recess wherein the light emitted from a light source of the at least one light source is reflected off the plurality of angles to substantially evenly distribute the light within the means for distributing light;
b) a first reflecting surface positioned on a third side of the means for distributing light and a second reflecting surface positioned on a fourth side of the means for distributing light such that the light exiting the third and fourth sides is reflected into the means for distributing light;
c) a third reflecting surface positioned in at least one plane around the at least one light source for reflecting the light; and d) a diffuse reflecting material disposed on a bottom of the means for distributing light for diffusing light striking the bottom of the means for distributing light, the reflecting material disposed in such a manner as to substantially evenly distribute the light from the at least one light source.
a) a flat, substantially transparent means for distributing light wherein a first and a second opposing side each have a recess, each recess having at least one light source positioned therein for providing the light, each opposing side having a plurality of angles between a corner of the means for distributing light and the recess wherein the light emitted from a light source of the at least one light source is reflected off the plurality of angles to substantially evenly distribute the light within the means for distributing light;
b) a first reflecting surface positioned on a third side of the means for distributing light and a second reflecting surface positioned on a fourth side of the means for distributing light such that the light exiting the third and fourth sides is reflected into the means for distributing light;
c) a third reflecting surface positioned in at least one plane around the at least one light source for reflecting the light; and d) a diffuse reflecting material disposed on a bottom of the means for distributing light for diffusing light striking the bottom of the means for distributing light, the reflecting material disposed in such a manner as to substantially evenly distribute the light from the at least one light source.
7. A communication device having transmitting means and receiving means, the communication device comprising:
a liquid crystal display (LCD) for displaying data, the LCD comprising:
substantially transparent means for distributing light having sides, a top, and a bottom, at least one side of the sides having at least one recess;
at least one light source, positioned in the at least one recess, for providing the light;
a diffuse reflecting material disposed upon the bottom of the means for distributing light; and a portion of the at least one side, between the at least one recess and a corner of the transparent means for distributing light, having a plurality of angles for reflecting the light.
a liquid crystal display (LCD) for displaying data, the LCD comprising:
substantially transparent means for distributing light having sides, a top, and a bottom, at least one side of the sides having at least one recess;
at least one light source, positioned in the at least one recess, for providing the light;
a diffuse reflecting material disposed upon the bottom of the means for distributing light; and a portion of the at least one side, between the at least one recess and a corner of the transparent means for distributing light, having a plurality of angles for reflecting the light.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/415,741 US4975808A (en) | 1989-10-02 | 1989-10-02 | Backlighting apparatus |
| US415,741 | 1989-10-02 | ||
| PCT/US1990/004718 WO1991005202A1 (en) | 1989-10-02 | 1990-08-22 | Backlighting apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2042060A1 CA2042060A1 (en) | 1991-04-03 |
| CA2042060C true CA2042060C (en) | 1994-11-01 |
Family
ID=23646995
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002042060A Expired - Fee Related CA2042060C (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) |
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-
1989
- 1989-10-02 US US07/415,741 patent/US4975808A/en not_active Expired - Lifetime
-
1990
- 1990-08-22 AU AU64136/90A patent/AU625629B2/en not_active Ceased
- 1990-08-22 CA CA002042060A patent/CA2042060C/en not_active Expired - Fee Related
- 1990-08-22 EP EP90914093A patent/EP0446324B1/en not_active Expired - Lifetime
- 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 AT AT90914093T patent/ATE145716T1/en not_active IP Right Cessation
- 1990-09-28 CN CN90108038A patent/CN1017289B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0446324A4 (en) | 1993-06-30 |
| US4975808A (en) | 1990-12-04 |
| EP0446324B1 (en) | 1996-11-27 |
| AU6413690A (en) | 1991-04-28 |
| CN1050785A (en) | 1991-04-17 |
| ATE145716T1 (en) | 1996-12-15 |
| CN1017289B (en) | 1992-07-01 |
| EP0446324A1 (en) | 1991-09-18 |
| DE69029258D1 (en) | 1997-01-09 |
| AU625629B2 (en) | 1992-07-16 |
| DE69029258T2 (en) | 1997-06-05 |
| WO1991005202A1 (en) | 1991-04-18 |
| CA2042060A1 (en) | 1991-04-03 |
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Legal Events
| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed |