JPH07175035A - Back light device - Google Patents

Back light device

Info

Publication number
JPH07175035A
JPH07175035A JP5317219A JP31721993A JPH07175035A JP H07175035 A JPH07175035 A JP H07175035A JP 5317219 A JP5317219 A JP 5317219A JP 31721993 A JP31721993 A JP 31721993A JP H07175035 A JPH07175035 A JP H07175035A
Authority
JP
Japan
Prior art keywords
temperature
light source
peltier element
backlight device
fluorescent tube
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.)
Pending
Application number
JP5317219A
Other languages
Japanese (ja)
Inventor
Hirokazu Nakase
浩和 中瀬
Original Assignee
Sharp Corp
シャープ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sharp Corp, シャープ株式会社 filed Critical Sharp Corp
Priority to JP5317219A priority Critical patent/JPH07175035A/en
Publication of JPH07175035A publication Critical patent/JPH07175035A/en
Pending legal-status Critical Current

Links

Abstract

PURPOSE:To miniaturize a back light device which eliminates brightness change according to a temp. change of a back light device to be used for a liquid crystal display device. CONSTITUTION:A Peltier element 12 is fixed or thermally coupled to a light source 10 in contact therewith. The temp. of the light source 10 is maintained nearly constant by supplying an electric current for driving for heating or cooling according to the output of a temp. sensor 13 to this Peltier element 12. As a result, nearly specified luminance is obtd. over temps. over a wide range of -40 to +80 deg.C, and the degradation in the luminance is prevented. Since the Peltier element 12 functions for both effects of heating and cooling, the need for a heater for heating and fins for cooling is eliminated and the formation of the thin, light and compact back light device is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device having a temperature control element capable of heating and cooling in order to properly control the temperature of a light source for illuminating a liquid crystal display device.

[0002]

2. Description of the Related Art When a fluorescent tube is used as a light source for a backlight of a liquid crystal display device, a temperature increase or decrease around the display device and a change in internal temperature of the display device due to heat generation of the fluorescent tube are combined to cause a fluorescent light. The temperature of the tube may deviate from the optimum operating temperature.

FIG. 5 shows the relationship between temperature and mercury radiation intensity in a fluorescent tube. The horizontal axis represents mercury vapor pressure (Torr), and the vertical axis represents resonance line intensity (%). As is clear from this figure, the optimum operating temperature of the fluorescent tube is around 40 ° C. Then, when the temperature of the fluorescent tube deviates from the optimum operating temperature, the brightness decreases as shown in FIG. In FIG. 6, the horizontal axis represents the ambient temperature and the vertical axis represents the brightness relative value. Therefore, conventionally, in order to prevent the temperature of the fluorescent tube from deviating from the optimum operating temperature, a radiation plate, a radiation fin, or the like is provided around the fluorescent tube, or a cooling fan is used for air cooling.

In addition, a heating heater or the like is provided for heating to apply heat.

In addition, by providing a Peltier element in the fluorescent tube,
There is a method of cooling with a Peltier element.

An example thereof is shown in Japanese Patent Laid-Open No. 18857/1990. FIG. 7 shows the configuration of the fluorescent lamp 71.
The Peltier element 72 has a heat conduction compound 73 on the side of the pipe.
The Peltier element 72 has its heat absorbing side 74 connected to the heat conducting compound 73 and its heating side 75.
Is in contact with the reflection plate 76. A temperature sensor 76 is provided at the coldest point portion of the Peltier element 72, detects the temperature of the portion, and outputs it to the drive control circuit 77 as a detection voltage. The detected voltage is compared with the output voltage of the reference voltmeter 80 in the comparison circuit 79 through the amplifier circuit 78, and the output thereof controls the driving of the Peltier element 72, and the coldest point temperature is controlled to be equal to or lower than a predetermined temperature. When the temperature becomes equal to or lower than a predetermined temperature, the operation is stopped to prevent a decrease in brightness.

[0007]

The use of the Peltier element of the above-mentioned embodiment is as follows, in order to prevent the decrease in brightness under high temperature environment and supercooling, the heat absorption side of the Peltier element is in contact with the heat conduction compound, It absorbs the heat of the fluorescent lamp when the temperature is equal to or higher than the predetermined temperature, and only stops when the temperature becomes equal to or lower than the predetermined temperature. Therefore, a. In the case where a wide temperature specification such as an on-vehicle component is required, the Peltier element function is not utilized in the use in a temperature environment at a temperature lower than a predetermined temperature, which is unreasonable.

B. Further, in order to prevent a decrease in the brightness of the illumination when using the liquid crystal display device at a low temperature and prevent a shortened life,
When combined with a heater as a heating device, the product size becomes large, which is an obstacle to downsizing.

C. Further, in the case of a flat panel display, a uniform luminance distribution is required as backlight illumination, the surface temperature of the fluorescent tube is locally cooled, and a deviation in light emission / luminance distribution occurs due to a deviation in temperature distribution. The present invention is intended to eliminate the above drawbacks.

[0010]

According to the present invention, a light source such as a fluorescent tube, an EL, or a light emitting diode that illuminates from the rear or side of a liquid crystal display device is provided with a Peltier element as a temperature control element capable of heating and cooling. The temperature control element is used in contact with and fixed to the reflector side or the back side of the light source so that heat can be conducted to the entire side surface of the light source. And
A temperature sensor is installed in the light source to detect the temperature of the light source, and a drive control circuit that compares the output of the temperature sensor with the set temperature and supplies power to the temperature control element according to the ambient temperature or switches it The heat absorption, the stop, and the heat generation are performed under each environmental temperature by switching the input voltage of the temperature control element.

Further, the present invention has a control circuit for setting the light source temperature from the ambient temperature to an appropriate temperature of the light source at the same time when the main power source of the light source is turned on.

[0012]

The brightness of the fluorescent lamp changes as shown in FIG. 6 depending on the temperature of the tube wall, but the EL and the light emitting diode also have different temperature characteristics of the fluorescent lamp, but the brightness changes depending on the temperature. When the temperature of the light source is detected by the temperature sensor installed close to the light emitting diode and the temperature of the light source exceeds the set temperature upper limit under high temperature environment, the control circuit absorbs heat from the side of the Peltier element as the temperature control element on the light source side. As a result, the current driven as Peltier element flows into the Peltier element to cool the fluorescent tube, so that it is possible to prevent the brightness from decreasing at a high temperature.

When it is detected by the temperature sensor installed near the tube wall or EL or the light emitting diode that the temperature becomes lower than the set temperature upper limit value, the power supply from the control circuit is stopped and the driving of the Peltier element is stopped. This stops further cooling of the fluorescent tube.

In a low temperature environment, the pipe wall or EL,
When the temperature sensor installed close to the light emitting diode detects that the temperature is lower than the lower limit value of the set value, the control circuit causes the side of the Peltier element on the fluorescent tube side to drive as heat dissipation, that is, the current direction when absorbing heat. By flowing the opposite current to the Peltier element and heating the fluorescent tube, it is possible to prevent the discharge from starting at a low temperature and the decrease in brightness at the time of lighting.

Further, when it is detected that the temperature of the temperature sensor installed near the tube wall or EL or the light emitting diode becomes higher than the lower limit value of the set value, the power supply from the control circuit is stopped and the Peltier element is driven. It will stop and further heating of the fluorescent tube will stop.

[0016]

1 shows an embodiment of the present invention. FIG. 1 includes a fluorescent tube 10, a reflecting plate 11, a Peltier element 12, a temperature sensor 13, a drive control circuit 14, and a fluorescent tube drive circuit 15.

As shown in FIG. 2, the fluorescent tube 10 is a lamp such as a W-shaped fluorescent tube, which is driven by a lamp drive circuit. The reflector 11 is made of a material having excellent heat conduction (aluminum,
It is formed of copper or other metal material, has a function of absorbing heat and a measure against heat at the time of heat dissipation, and also functions as a shield function of electromagnetic radiation, and is arranged so as to face the fluorescent tube 10.

The Peltier element 12 is directly connected to the fluorescent tube 10.
Alternatively, the heat conductive compound 16 is bonded so as to sandwich it, and is further physically fixed by a heat resistant resin (not shown).

The drive control circuit 14 is a circuit for controlling the drive of the Peltier element 12 so that the measured temperature falls within the set temperature range based on the output of the temperature sensor 13, and the set temperature is the optimum operating temperature of the fluorescent tube, or The ambient temperature is set to, for example, 40 ° C.

The drive control circuit 14 is, for example, 15v, -1.
A DC power supply 17 capable of obtaining a DC voltage of 5v and a DC voltage from the DC power supply 17 are converted to a voltage suitable for the Peltier element 12, for example, a DC voltage of 8v or -8v,
It is composed of a drive circuit 18 which supplies the Peltier element 12, an amplifier circuit 19 which amplifies and compares the output of the temperature sensor 13, a comparison circuit 20, and a timer circuit. Details of the drive control circuit 14 are as shown in FIG. 3, and the same components as those in FIG. 1 are designated by the same reference numerals.

In the above apparatus, the temperature detected by the temperature sensor 13 is the above when the ambient temperature of the fluorescent tube 10 is low, or when the temperature of the fluorescent tube 10 is low, such as when the fluorescent tube 10 is turned on. When the temperature is within the predetermined temperature range, the detection voltage Vd becomes the reference voltage V1 or less, and the Peltier element 12
A driving voltage for heating the side surface of the fluorescent tube side to serve as a heating function is applied to, and the fluorescent tube 10 is heated by heating the Peltier element 12. When the temperature of the temperature sensor 13 reaches within a predetermined temperature range due to the heating by the Peltier element 12 and the heat generation of the fluorescent tube itself, the detection voltage Vd becomes equal to or higher than the reference voltage V1, and the power supply to the Peltier element 12 is stopped. , When the driving is stopped, heating by the Peltier element is lost. Therefore, it is possible to prevent a decrease in brightness in a low temperature environment.

When the ambient temperature of the fluorescent tube is within the predetermined temperature range, or when the fluorescent tube 10 is turned on, the heat generated by the fluorescent tube itself is low, so the temperature at the temperature sensor 13 is within the above predetermined temperature range. If the detected voltage Vd is equal to or higher than the reference voltage V1 and equal to or lower than the reference voltage Vh, no power is supplied from the drive control circuit 14 to the Peltier element 13, the Peltier element 12 is not driven, and the fluorescent tube 10 is overheated. , No cooling is done.

When the ambient temperature of the fluorescent tube is high, or when the fluorescent tube 10 is turned on, the temperature at the temperature sensor 13 exceeds the predetermined temperature range in combination with the heat generation of the fluorescent tube itself. In this case, when the detected voltage Vd exceeds the reference voltage Vh, a driving voltage is applied to the Peltier element 12 so that the side surface on the fluorescent tube side has an endothermic function, and the fluorescent tube 10 is cooled by the heat absorption of the Peltier element 12.

When the temperature at the temperature sensor 13 reaches within a predetermined temperature range due to the heat generated by the Peltier element 12 and the heat generated by the fluorescent tube itself, the detected voltage Vd becomes equal to or lower than the reference voltage Vh, and the power is supplied to the Peltier element 12. When the Peltier element 12 is stopped and the driving is stopped, cooling by the Peltier element 12 is lost.
Therefore, it is possible to prevent a decrease in brightness in a high temperature environment.

[0025]

As described above, according to the present invention, as shown in FIG. 4, the brightness relative value is kept substantially constant under high temperature environment of −40 ° C. to + 80 ° C. and low temperature environment. In addition to being able to widen the operating temperature range of the backlight device, it is possible to prevent a decrease in brightness and also prevent a decrease in brightness due to overcooling or overheating.

Further, the Peltier element has both cooling and heating functions, and does not require a large-scale device such as a heater for heating or a fan for cooling, and a backlight system having the same function can be made thinner, lighter and more compact. Becomes possible.

By disposing the Peltier element as described above, the fluorescent tube can be uniformly heated and cooled,
By keeping the temperature distribution of the fluorescent tube uniform, the emission brightness distribution of the fluorescent tube required when used as a flat light source can be made uniform.

Further, it is possible to avoid shortening the life of the fluorescent lamp due to overheating in a low temperature environment, and it is possible to increase the emission brightness and stabilize the fluorescent lamp more quickly than the start of lighting the fluorescent tube.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a backlight device according to an embodiment of the present invention.

FIG. 2 shows a relationship diagram of a fluorescent tube, a Peltier element, and a reflector in an embodiment of the present invention.

FIG. 3 is a detailed circuit diagram of a drive control circuit according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between ambient temperature and relative luminance value according to an embodiment of the present invention.

FIG. 5 shows a relationship diagram between mercury vapor pressure and resonance line intensity.

FIG. 6 is a diagram showing the relationship between the ambient temperature and the brightness relative value in the case of the characteristics shown in FIG.

FIG. 7 shows a configuration diagram of a conventional example.

[Explanation of symbols]

 10 Fluorescent Tube 11 Heat Dissipation / Shield Reflector 12 Peltier Element 13 Temperature Sensor 14 Drive Control Circuit 15 Lamp Drive Circuit 16 Heat Conductive Adhesive 17 DC Power Supply 18 Drive Circuit 19 Amplification Circuit 20 Comparison Circuit

Claims (7)

[Claims]
1. A light source such as a fluorescent tube, an EL, or a light emitting diode that illuminates from the rear or side of a liquid crystal display device, and a temperature control element capable of heating and cooling is fixed in contact with the reflector side or the back side of the light source. Alternatively, a backlight device that is thermally coupled.
2. The backlight device according to claim 1, wherein the temperature control element is a Peltier element.
3. The backlight device according to claim 1, wherein a temperature sensor is installed near the light source to detect the temperature of the light source.
4. The drive control circuit according to claim 1, further comprising: a drive control circuit that compares the output of the temperature sensor with a set temperature and supplies power to the temperature control element or switches the power supply in accordance with the ambient temperature. Backlight device.
5. The backlight device according to claim 1, wherein heat absorption, stoppage, and heat generation are performed under each environmental temperature by switching the input voltage of the temperature control element.
6. The backlight device according to claim 1, further comprising a control circuit for setting the temperature of the light source from the ambient temperature to an appropriate temperature of the light source at the same time when the main power source of the light source is turned on.
7. The backlight device according to claim 1, further comprising a reflection shield plate that radiates heat from the temperature control element.
JP5317219A 1993-12-17 1993-12-17 Back light device Pending JPH07175035A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP5317219A JPH07175035A (en) 1993-12-17 1993-12-17 Back light device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP5317219A JPH07175035A (en) 1993-12-17 1993-12-17 Back light device

Publications (1)

Publication Number Publication Date
JPH07175035A true JPH07175035A (en) 1995-07-14

Family

ID=18085809

Family Applications (1)

Application Number Title Priority Date Filing Date
JP5317219A Pending JPH07175035A (en) 1993-12-17 1993-12-17 Back light device

Country Status (1)

Country Link
JP (1) JPH07175035A (en)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003029262A (en) * 2001-07-13 2003-01-29 Matsushita Electric Ind Co Ltd Liquid crystal display device
US6636190B2 (en) 2000-10-12 2003-10-21 Hitachi, Ltd. Liquid crystal display having an improved lighting device
US6960759B2 (en) 2000-09-26 2005-11-01 Fuji Photo Film Co., Ltd. Light source device, image reading apparatus and image reading method
US7164224B2 (en) 2000-12-14 2007-01-16 Sharp Kabushiki Kaisha Backlight having discharge tube, reflector and heat conduction member contacting discharge tube
JP2009133933A (en) * 2007-11-29 2009-06-18 Kyocera Mita Corp Image reader and image forming apparatus
KR100917005B1 (en) * 2003-06-26 2009-09-10 삼성전자주식회사 Backlight assembly and liquid crystal display apparatus having the same
US7731377B2 (en) 2006-03-21 2010-06-08 Semiconductor Energy Laboratory Co., Ltd. Backlight device and display device
US8833987B2 (en) 2005-09-14 2014-09-16 Donnelly Corporation Mirror reflective element sub-assembly for exterior rearview mirror of a vehicle
US8884788B2 (en) 1998-04-08 2014-11-11 Donnelly Corporation Automotive communication system
US8908039B2 (en) 2000-03-02 2014-12-09 Donnelly Corporation Vehicular video mirror system
US9014966B2 (en) 2000-03-02 2015-04-21 Magna Electronics Inc. Driver assist system for vehicle
US9019091B2 (en) 1999-11-24 2015-04-28 Donnelly Corporation Interior rearview mirror system
US9019090B2 (en) 2000-03-02 2015-04-28 Magna Electronics Inc. Vision system for vehicle
US9073491B2 (en) 2002-09-20 2015-07-07 Donnelly Corporation Exterior rearview mirror assembly
US9090211B2 (en) 2002-09-20 2015-07-28 Donnelly Corporation Variable reflectance mirror reflective element for exterior mirror assembly
US9278654B2 (en) 1999-11-24 2016-03-08 Donnelly Corporation Interior rearview mirror system for vehicle
US9352623B2 (en) 2001-01-23 2016-05-31 Magna Electronics Inc. Trailer hitching aid system for vehicle
US10175477B2 (en) 2008-03-31 2019-01-08 Magna Mirrors Of America, Inc. Display system for vehicle

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US8884788B2 (en) 1998-04-08 2014-11-11 Donnelly Corporation Automotive communication system
US9221399B2 (en) 1998-04-08 2015-12-29 Magna Mirrors Of America, Inc. Automotive communication system
US9481306B2 (en) 1998-04-08 2016-11-01 Donnelly Corporation Automotive communication system
US9376061B2 (en) 1999-11-24 2016-06-28 Donnelly Corporation Accessory system of a vehicle
US9278654B2 (en) 1999-11-24 2016-03-08 Donnelly Corporation Interior rearview mirror system for vehicle
US10144355B2 (en) 1999-11-24 2018-12-04 Donnelly Corporation Interior rearview mirror system for vehicle
US9019091B2 (en) 1999-11-24 2015-04-28 Donnelly Corporation Interior rearview mirror system
US9014966B2 (en) 2000-03-02 2015-04-21 Magna Electronics Inc. Driver assist system for vehicle
US9019090B2 (en) 2000-03-02 2015-04-28 Magna Electronics Inc. Vision system for vehicle
US10239457B2 (en) 2000-03-02 2019-03-26 Magna Electronics Inc. Vehicular vision system
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US10179545B2 (en) 2000-03-02 2019-01-15 Magna Electronics Inc. Park-aid system for vehicle
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US9315151B2 (en) 2000-03-02 2016-04-19 Magna Electronics Inc. Driver assist system for vehicle
US9809171B2 (en) 2000-03-02 2017-11-07 Magna Electronics Inc. Vision system for vehicle
US9809168B2 (en) 2000-03-02 2017-11-07 Magna Electronics Inc. Driver assist system for vehicle
US10053013B2 (en) 2000-03-02 2018-08-21 Magna Electronics Inc. Vision system for vehicle
US6960759B2 (en) 2000-09-26 2005-11-01 Fuji Photo Film Co., Ltd. Light source device, image reading apparatus and image reading method
US7683899B2 (en) 2000-10-12 2010-03-23 Hitachi, Ltd. Liquid crystal display device having an improved lighting device
US7138974B2 (en) 2000-10-12 2006-11-21 Hitachi, Ltd. Liquid crystal display device having an improved lighting device
US6636190B2 (en) 2000-10-12 2003-10-21 Hitachi, Ltd. Liquid crystal display having an improved lighting device
US7169005B2 (en) 2000-12-14 2007-01-30 Sharp Kabushiki Kaisha Method of producing a backlight having a discharge tube containing mercury
US7164224B2 (en) 2000-12-14 2007-01-16 Sharp Kabushiki Kaisha Backlight having discharge tube, reflector and heat conduction member contacting discharge tube
US7541723B2 (en) 2000-12-14 2009-06-02 Sharp Kabushiki Kaisha Backlight having a polarization separating element
US7309146B2 (en) 2000-12-14 2007-12-18 Sharp Kabushiki Kaisha Backlight having discharge tube, reflector and heat conduction member contacting discharge tube
US9694749B2 (en) 2001-01-23 2017-07-04 Magna Electronics Inc. Trailer hitching aid system for vehicle
US10272839B2 (en) 2001-01-23 2019-04-30 Magna Electronics Inc. Rear seat occupant monitoring system for vehicle
US9352623B2 (en) 2001-01-23 2016-05-31 Magna Electronics Inc. Trailer hitching aid system for vehicle
JP2003029262A (en) * 2001-07-13 2003-01-29 Matsushita Electric Ind Co Ltd Liquid crystal display device
US9878670B2 (en) 2002-09-20 2018-01-30 Donnelly Corporation Variable reflectance mirror reflective element for exterior mirror assembly
US9090211B2 (en) 2002-09-20 2015-07-28 Donnelly Corporation Variable reflectance mirror reflective element for exterior mirror assembly
US9545883B2 (en) 2002-09-20 2017-01-17 Donnelly Corporation Exterior rearview mirror assembly
US10538202B2 (en) 2002-09-20 2020-01-21 Donnelly Corporation Method of manufacturing variable reflectance mirror reflective element for exterior mirror assembly
US9073491B2 (en) 2002-09-20 2015-07-07 Donnelly Corporation Exterior rearview mirror assembly
US10363875B2 (en) 2002-09-20 2019-07-30 Donnelly Corportion Vehicular exterior electrically variable reflectance mirror reflective element assembly
US9341914B2 (en) 2002-09-20 2016-05-17 Donnelly Corporation Variable reflectance mirror reflective element for exterior mirror assembly
US10029616B2 (en) 2002-09-20 2018-07-24 Donnelly Corporation Rearview mirror assembly for vehicle
US10661716B2 (en) 2002-09-20 2020-05-26 Donnelly Corporation Vehicular exterior electrically variable reflectance mirror reflective element assembly
KR100917005B1 (en) * 2003-06-26 2009-09-10 삼성전자주식회사 Backlight assembly and liquid crystal display apparatus having the same
US8833987B2 (en) 2005-09-14 2014-09-16 Donnelly Corporation Mirror reflective element sub-assembly for exterior rearview mirror of a vehicle
US9045091B2 (en) 2005-09-14 2015-06-02 Donnelly Corporation Mirror reflective element sub-assembly for exterior rearview mirror of a vehicle
US10308186B2 (en) 2005-09-14 2019-06-04 Magna Mirrors Of America, Inc. Vehicular exterior rearview mirror assembly with blind spot indicator
US9758102B1 (en) 2005-09-14 2017-09-12 Magna Mirrors Of America, Inc. Mirror reflective element sub-assembly for exterior rearview mirror of a vehicle
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US9694753B2 (en) 2005-09-14 2017-07-04 Magna Mirrors Of America, Inc. Mirror reflective element sub-assembly for exterior rearview mirror of a vehicle
US8733959B2 (en) 2006-03-21 2014-05-27 Semiconductor Energy Laboratory Co., Ltd. Backlight device and display device
US7731377B2 (en) 2006-03-21 2010-06-08 Semiconductor Energy Laboratory Co., Ltd. Backlight device and display device
US7950816B2 (en) 2006-03-21 2011-05-31 Semiconductor Energy Laboratory Co., Ltd. Backlight device and display device
US8132931B2 (en) 2006-03-21 2012-03-13 Semiconductor Energy Laboratory Co., Ltd. Backlight device and display device
US8277068B2 (en) 2006-03-21 2012-10-02 Semiconductor Energy Laboratory Co., Ltd. Backlight device and display device
JP2009133933A (en) * 2007-11-29 2009-06-18 Kyocera Mita Corp Image reader and image forming apparatus
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