Display device and luminance control method therefor

Disclosed herein is a display device having an insulating substrate, an effective pixel area formed on the insulating substrate and having at least pixels arranged in the form of a matrix, and a peripheral circuit formed on the insulating substrate so as to surround the effective pixel area, the pixels being driven by the peripheral circuit to display a desired image in the effective pixel area, the display device including an extraneous light sensor provided in the effective pixel area for detecting extraneous light to output an extraneous light quantity detection result for use in controlling the luminance of the image.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2008-005191 filed in the Japan Patent Office on Jan. 15, 2008, the entire contents of which being incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a display device and a luminance control method therefor, and it is applicable to a liquid crystal display device, for example. The present invention includes an extraneous light sensor for detecting the quantity of extraneous light, wherein the extraneous light sensor is provided in an effective pixel area and luminance control is performed according to the detection result output from the extraneous light sensor, thereby performing the luminance control easily and accurately.

DESCRIPTION OF THE RELATED ART

In various display devices such as a liquid crystal display device known in the art, luminance control is performed according to the quantity of extraneous light. Particularly in a portable liquid crystal display device such as an electronic still camera and a mobile phone, luminance control is performed by controlling the luminance of light emitted from a backlight as disclosed in Japanese Patent Laid-Open No. Hei 11-295692, for example, thereby preventing undue power consumption and improving the visibility.

In such a liquid crystal display device, the quantity of extraneous light is detected by an extraneous light sensor as a photodetector for detecting extraneous light. For example, Japanese Patent Laid-Open No. 2007-322830 discloses a method of providing such an extraneous light sensor in a liquid crystal display panel.

FIG. 17is a plan view of a liquid crystal display panel1applied to such a liquid crystal display device in the related art. The liquid crystal display panel1has an effective pixel area2in which pixels are arranged in the form of a matrix, and various images are displayed in the effective pixel area2. The liquid crystal display panel1further has a light shielding area3surrounding the effective pixel area2. The light shielding area3has a fixed width to thereby form a black frame surrounding the effective pixel area2. The light shielding area3is surrounded by an outer area4, and various drive circuits for driving the effective pixel area2are provided in the light shielding area3and the outer area4. Further, a fixed portion along a given one side of the outer area4is assigned to an area5for external terminals to which electric power is supplied.

FIG. 18Ais an enlarged plan view of a peripheral portion of the effective pixel area2shown by reference symbol A inFIG. 17, andFIG. 18Bis a cross section taken along the line B-B inFIG. 18A. As shown inFIG. 18B, a liquid crystal layer7is sandwiched between a TFT (Thin Film Transistor) substrate5and a CF substrate6. The TFT substrate5is composed of a glass substrate9as a transparent insulating substrate, a TFT (Thin Film Transistor) constituting each pixel, drive circuit, etc., an extraneous light sensor8, signal lines SIGs, an alignment layer, etc. These TFTs, the extraneous light sensor8, the signal lines SIGs, and the alignment layer are formed on the glass substrate9. On the other hand, the CF substrate6is composed of a glass substrate10as a transparent glass substrate, red color filters CFRs, green color filters CFGs, blue color filters CFBs, an alignment layer, etc. These color filters CFRs, CFGs, and CFBs and the alignment layer are formed on the glass substrate10. Further, a light shielding film11forming the light shielding area3is formed on the glass substrate10.

The liquid crystal display panel1shown inFIGS. 18A and 18Bis a semitransmissive liquid crystal display panel such that each pixel has a reflective display area12functioning as a reflective liquid crystal display panel and a transmissive display area13functioning as a transmissive liquid crystal display panel. The color filters CFRs, CFGs, and CFBs are provided in merely the transmissive display area13, and the reflective display area12is utilized merely to compensate for the luminance level in the transmissive display area13. Accordingly, the reflective display area12is smaller in size than the transmissive display area13.

The extraneous light sensor8is provided in the light shielding area3at a position close to the effective pixel area2. Further, a sensor circuit14for processing the detection result output from the extraneous light sensor8is provided in the light shielding area3at a position close to the extraneous light sensor8. Various photodetectors such as a phototransistor and a photodiode may be used as the extraneous light sensor8. A light shielding film15for shielding light from a backlight is formed on the lower surface of the extraneous light sensor8opposed to the glass substrate9. Further, the light shielding film11of the CF substrate6is formed with an opening11A for allowing the entry of extraneous light into the extraneous light sensor8.

The sensor circuit14is provided by an integrating circuit for integrating an output signal from the extraneous light sensor8at given time intervals for a given integration time in synchronism with the operation of the effective pixel area2. An output signal from the sensor circuit14is supplied to an external circuit to thereby detect the quantity of extraneous light entering the extraneous light sensor8. The backlight is controlled so that the quantity of light from the backlight is increased with an increase in quantity of extraneous light.

In contrast toFIGS. 18A and 18B,FIGS. 19A and 19Bshow another liquid crystal display panel21known in the art. The liquid crystal display panel21has a correcting sensor8A in addition to the extraneous light sensor8, wherein the detection result output from the extraneous light sensor8is corrected by using an output signal from the correcting sensor8A. The correcting sensor8A has the same configuration as that of the extraneous light sensor8except that the correcting sensor8A is prevented from detecting the light from the backlight and the extraneous light. Specifically, the correcting sensor8A is provided by a photodetector having substantially the same characteristics as those of the extraneous light sensor8. More specifically, the correcting sensor8A is provided by a photodetector having the same configuration, shape, and size as those of the extraneous light sensor8, and is located close to the extraneous light sensor8. The correcting sensor8A is configured so as not to detect the light from the backlight and the extraneous light. Accordingly, a light shielding film15A for shielding the light from the backlight is formed on the lower surface of the correcting sensor8A as in the case of the extraneous light sensor8, and a light shielding member15B for shielding the extraneous light from the opening11A is provided to fully cover the correcting sensor8A.

The liquid crystal display panel21has a sensor circuit24in place of the sensor circuit14. The sensor circuit24subtracts the output signal from the correcting sensor8A from the output signal from the extraneous light sensor8, thereby preventing variations in the detection result due to dark current in the extraneous light sensor8. This subtraction of the output signal from the correcting sensor8A may be performed before integrating the output signal from the extraneous light sensor8. Alternatively, this subtraction may be performed after integrating the output signal from the correcting sensor8A and the output signal from the extraneous light sensor8.

In contrast toFIGS. 17A and 17BandFIGS. 18A and 18B,FIGS. 20A and 20Bshow a display device31known in the art. The display device31has a case32formed with a rectangular opening32A. The liquid crystal display panel1or21is provided on the inside surface of the case32so as to close the opening32A. The size of the opening32A is set so that the effective pixel area2can be seen through the opening32A, that extraneous light can enter the extraneous light sensor8through the opening32A, and that the outer area4surrounding the light shielding area3and the area5for the external terminals can be concealed by the case32. Further, the case32is provided with a guide or the like for defining the mounting position of the liquid crystal display panel1or21.

Accordingly, the effective pixel area2is formed inside the opening32A in such a manner that an inner edge portion of the black frame formed by the light shielding area3has a fixed width D.

It is desired to reduce the size of the display device31. Accordingly, the width D of the black edge portion to be seen through the opening32A has to be reduced. Further, in the case that the width D of the black edge portion is large, the appearance of the display screen is poor. Also from this point of view, the width D of the black edge portion has to be reduced. To this end, the size of the opening32A has to be minimized.

In the display device31, however, the occurrence of mounting error of the liquid crystal display panel1or21to the case32may not be avoided, so that the reduction in size of the opening32A may cause the interference with the entrance of extraneous light into the extraneous light sensor8. Specifically, if the size of the opening32A is reduced and the mounting error of the liquid crystal display panel1or21is large, there arises a problem such that the opening11A of the light shielding film11is covered with the case32or a problem such that the extraneous light entering the extraneous light sensor8is blocked by the thickness of the case32. In these cases, the entrance of the extraneous light into the extraneous light sensor8is impaired. Further, there also arises a problem such that the extraneous light is reflected on an end surface32D of the case32defining the opening32A and then enters the extraneous light sensor8. As a result, scattered light may enter the extraneous light sensor8, causing the entrance of excess amounts of extraneous light into the extraneous light sensor8.

In such a case that the entrance of extraneous light into the extraneous light sensor8is impaired or excess amounts of extraneous light enter the extraneous light sensor8, it is difficult to accurately control the luminance in the liquid crystal display device31.

As a method of solving this problem, it is considered to improve the mounting accuracy of the liquid crystal display panel1or21. However, this method may cause a problem such that the assembly of the display device31becomes troublesome.

SUMMARY OF THE INVENTION

It is accordingly an aim of the embodiments of the present invention to provide a display device and a luminance control method therefor which can perform luminance control easily and accurately.

In accordance with a mode of the present invention, there is provided a display device having an insulating substrate, an effective pixel area formed on the insulating substrate and having at least pixels arranged in the form of a matrix, and a peripheral circuit formed on the insulating substrate so as to surround the effective pixel area, the pixels being driven by the peripheral circuit to display a desired image in the effective pixel area, the display device including an extraneous light sensor provided in the effective pixel area for detecting extraneous light to output an extraneous light quantity detection result for use in controlling the luminance of the image.

In accordance with another mode of the present invention, there is provided a luminance control method for a display device having an insulating substrate, an effective pixel area formed on the insulating substrate and having at least pixels arranged in the form of a matrix, and a peripheral circuit formed on the insulating substrate so as to surround the effective pixel area, the pixels being driven by the peripheral circuit to display a desired image in the effective pixel area, the luminance control method including the steps of detecting step of detecting extraneous light by using an extraneous light sensor provided in the effective pixel area and outputting an extraneous light quantity detection result for use in controlling the luminance of the image; and controlling the luminance of the image according to the extraneous light quantity detection result.

According to the embodiments of the invention as described above, the extraneous light sensor is provided in the effective pixel area. Accordingly, it is possible to effectively avoid the problem that the entrance of extraneous light into the extraneous light sensor is impaired by the case or the like as in the case where the extraneous light sensor is provided outside the effective pixel area. As a result, the mounting operation can be easily performed and the luminance of the image can be controlled easily and accurately.

According to the embodiments of the present invention, luminance control can be performed easily and accurately.

Other aims and features of the embodiments of the invention will be more fully understood from the following detailed description and appended claims when taken with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

(1) Constitution of the First Preferred Embodiment

FIGS. 2A and 2Bare plan views of a mobile phone41as a display device according to the first preferred embodiment of the present invention.FIG. 2Ashows an open condition of the mobile phone41, andFIG. 2Bshows a folded condition of the mobile phone41. The mobile phone41is composed of an upper body portion42, a lower body portion43, and a connecting portion44for connecting the upper body portion42and the lower body portion43so that the upper body portion42is foldable with respect to the lower body portion43. As shown inFIG. 2B, the upper body portion42of the mobile phone41is provided with an auxiliary display portion45capable of indicating various kinds of information to a user in the folded condition of the mobile phone41. Further, as shown inFIG. 2A, the upper body portion42is provided with a main display portion46capable of indicating various kinds of information to the user in the open condition of the mobile phone41. The constitution of the embodiments of the present invention is applicable to the main and auxiliary display portions46and45of the mobile phone41.

The constitution of the embodiments of the present invention is applicable widely to various electronic equipment having a display portion for displaying various images and information as well as to such a mobile phone.FIGS. 3 to 6show other examples of electronic equipment to which the constitution of the embodiments of the present invention is applied.FIG. 3is a perspective view of a television receiver51. The television receiver51is provided with a display portion52on the front side. The constitution of the embodiments of the present invention is applied to the display portion52of the television receiver51.

FIG. 4Ais a perspective view of an electronic still camera53as viewed from the front side thereof, andFIG. 4Bis a perspective view of the electronic still camera53as viewed from the rear side thereof. The front side of the electronic still camera53is provided with a lens54and a light emitting portion55for flash light emission. A shutter button56is provided on the upper end surface of the electronic still camera53. Further, the rear side of the electronic still camera53is provided with a menu switch57and a display portion58. The constitution of the embodiments of the present invention is applied to the display portion58of the electronic still camera53.

FIG. 5is a perspective view of a notebook personal computer61. The notebook personal computer61is composed of a body portion62and a cover portion for covering the body portion62. The body portion62is provided with a keyboard63, and the cover portion is provided with a display portion64. The constitution of the embodiments of the present invention is applied to the display portion64of the notebook personal computer61.

FIG. 6is a perspective view of a video camera65. The rear end surface of the video camera65is provided with a trigger switch66, and the front end surface of the video camera65is provided with a lens67. Further, the left side surface of the video camera65is provided with a pivotably movable door68. The inside surface of the pivotably movable door68is provided with a display portion69. The constitution of the embodiments of the present invention is applied to the display portion69of the video camera65.

In contrast toFIGS. 20A and 20B,FIGS. 1A and 1Bare a plan view and a sectional view, respectively, showing the constitution of a display device applied to such electronic equipment as mentioned above. InFIGS. 1A and 1B, the main display portion46of the mobile phone41as a display device shown inFIGS. 2A and 2Bis illustrated. However, the auxiliary display portion45of the mobile phone41and the display portions of the other kinds of electronic equipment are constituted like the main display portion46. Further, inFIGS. 1A and 1B, the same reference numerals as those shown inFIGS. 20A and 20Bdenote the same parts, and the description thereof will be omitted herein.

As shown inFIG. 1B, the display device41has a luminance control circuit72for controlling the luminance of light emitted from a primary light source74provided in a backlight unit73according to the light quantity detection result output from the extraneous light sensor8provided in the effective pixel area2, thereby controlling the luminance of a display screen formed in the display portion46. As shown inFIG. 1B, the backlight unit73includes a light guide plate75. The primary light source74is provided by a light emitting diode or a cold cathode fluorescent tube, for example. The illumination light emitted from the primary light source74enters the light guide plate75from an end surface thereof to propagate inside the light guide plate75and to emerge from an upper surface of the light guide plate75opposed to the liquid crystal display panel71. While the backlight unit73shown inFIG. 1Bis a so-called edge light type backlight unit, a so-called direct type backlight unit may be adopted. In the case of adopting such a direct type backlight unit using a plurality of light emitting elements as the primary light source, the extraneous light sensor may be assigned to each light emitting element or to every predetermined number of light emitting elements, thereby controlling the light quantity of each light emitting element or of every predetermined number of light emitting elements.

While one extraneous light sensor8is provided in the effective pixel area2as shown inFIG. 1A, a plurality of extraneous light sensors8are actually provided at discrete positions in the effective pixel area2of the display device41. Output signals from these plural extraneous light sensors8are added up and processed to thereby improve the SN (signal noise) ratio and signal level of the light quantity detection result. The processing of the output signals from the extraneous light sensors8may be performed by simply adding up the output signals from the extraneous light sensors8or by weighting the output signals from the extraneous light sensors8with weighting factors according to the positions of the extraneous light sensors8prior to the addition step. However, merely one extraneous light sensor8may be provided if a practically sufficient SN ratio and signal level can be ensured.

In contrast toFIGS. 18A and 18B,FIGS. 7A and 7Bshow the specific position of the extraneous light sensor8in the liquid crystal display panel71. As shown inFIGS. 7A and 7B, the extraneous light sensor8is located in a green pixel in the effective pixel area2. The wavelength band of the green pixel is the most sensitive in human visual characteristics. Accordingly, the extraneous light sensor8is located so as to detect extraneous light through the green color filter CFG located in the green pixel in the liquid crystal display panel71.

The extraneous light sensor8is provided in the transmissive display area13of the green pixel. While the extraneous light sensor8is provided in the green pixel close to the light shielding area3as shown inFIGS. 7A and 7B, the green pixel for location of the extraneous light sensor8may be suitably selected as desired. In the case that the extraneous light sensor8is provided in the green pixel close to the light shielding area3as shown, the connection line between the extraneous light sensor8and the sensor circuit14can be shortened as much as possible. Further, as shown inFIGS. 7A and 7B, a blue pixel is present outside of the green pixel in which the extraneous light sensor8is located. That is, the extraneous light sensor8is located in the green pixel adjacent to the outermost blue pixel. With this arrangement, extraneous light can be detected in the condition where the outermost pixel causing the occurrence of alignment defect most easily is avoided. Accordingly, it is possible to prevent a reduction in accuracy of measurement of an extraneous light quantity due to the alignment defect in the pixel where the extraneous light sensor8is located. Further, the extraneous light sensor8may be located inside of the outermost edge of the effective pixel area2by an amount equal to or greater than t×tan □ where t is the thickness of the glass substrate10and □ is the critical angle. In this case, even if the mounted position of the liquid crystal display panel71varies, it is possible to prevent that the extraneous light reflected on the wall surface of the case32forming the opening32A may enter the extraneous light sensor8. Further, the extraneous light sensor8may be located further inside of the outermost edge of the effective pixel area2. In this case, it is possible to prevent that the extraneous light incident on the extraneous light sensor8may be blocked by the finger of the user operating various operation parts. Further, the extraneous light sensor8may be located at the center of the screen where the human visual perception to the brightness of the screen is made most easily, thereby improving the accuracy of luminance control.

(2) Operation of the First Preferred Embodiment

In the display device41shown inFIGS. 1A and 1B, the primary light source74of the backlight unit73is driven by the luminance control circuit72, and the light emitted from the primary light source74is supplied through the light guide plate75to the liquid crystal display panel71. In the liquid crystal display panel71, the gray scale in each pixel is set according to image data or the like, and the light supplied from the backlight unit73is spatially modulated in the transmissive display area13of each pixel according to the gray scale set in each pixel, thereby displaying a desired image. In the reflective display area12of each pixel, extraneous light is spatially modulated in a similar manner to thereby display a desired image.

In the display device41, the quantity of extraneous light is detected by the extraneous light sensor8, and the detection result output from the extraneous light sensor8is processed by the sensor circuit14and input into the luminance control circuit72. When the quantity of extraneous light is increased to cause the difficulty in viewing the display screen formed in the effective pixel area2, the luminance control circuit72operates to increase the luminance of the light emitted from the primary light source74, for example, in proportion to the quantity of extraneous light according to the light quantity detection result output from the extraneous light sensor8, thereby increasing the luminance of the display screen. Accordingly, even when the quantity of extraneous light is increased, sufficient visibility can be ensured. Further, a large quantity of light is not unnecessarily emitted from the primary light source74, thereby reducing power consumption.

In the existing display device (seeFIGS. 17,20A, and20B), the extraneous light sensor8is located in the light shielding area3. In this structure, the opening32A of the case32has to be increased in size so as not to block the extraneous light sensor8. As a result, the width D of the edge portion of the black frame formed by the light shielding area3so as to surround the effective pixel area2is increased to cause a degradation in quality of the display screen. If the opening32A is reduced in size to reduce the width D of the edge portion of the black frame, the extraneous light entering the extraneous light sensor8is reduced in quantity and reflected by the case32to undesirably enter the extraneous light sensor8, so that the quantity of extraneous light may not be accurately detected. Accordingly, it is difficult to accurately control the luminance of the display screen in the display device. Further, high assembly accuracy is desired and the display device may not therefore be easily fabricated.

According to this preferred embodiment, the extraneous light sensor8is located in the effective pixel area2rather than in the light shielding area3. With this arrangement, the opening32A of the case32can be reduced in size to thereby reduce the width of the edge portion of the black frame on the display screen, thereby improving the quality of the display screen. Further, the entrance of extraneous light into the extraneous light sensor8is not hindered in spite of the reduced width of the edge portion of the black frame, so that the quantity of extraneous light can be accurately detected. Accordingly, the accuracy of luminance control can be improved without high assembly accuracy. That is, the luminance can be controlled easily and accurately according to this preferred embodiment.

Further, the extraneous light sensor8is located in a green pixel in the effective pixel area2, and extraneous light is detected through the green color filter CFG provided in the green pixel. The wavelength band of the green pixel is the most sensitive in human visual characteristics. Accordingly, the luminance can be controlled according to the human visual characteristics, so that the accuracy of luminance control can be improved.

Since the extraneous light sensor8is provided in the effective pixel area2, the flexibility of layout of the extraneous light sensor8can be greatly improved as compared with the case that the extraneous light sensor8is provided in the light shielding area3. Accordingly, various disturbances due to the location of the extraneous light sensor8such as scattered light from the case32and light shield by user operations can be avoided to reliably detect the extraneous light.

In the case that the extraneous light sensor8is provided in the effective pixel area2, there is a possibility that the extraneous light sensor8may be visually perceived. However, by providing a plurality of extraneous light sensors8and adding up the output signals from these plural extraneous light sensors8to thereby improve the SN ratio and signal level, each extraneous light sensor8can be reduced in size so that it may not be visually perceived on the display screen. Further, since the extraneous light sensor8is provided in a pixel, the extraneous light sensor8can be made inconspicuous on the display screen.

(3) Effect of the First Preferred Embodiment

According to this preferred embodiment, the extraneous light sensor is located in the effective pixel area, so that the luminance can be controlled easily and accurately.

The extraneous light sensor is located in a pixel in the effective pixel area, so that the extraneous light sensor can be made inconspicuous on the display screen.

The extraneous light sensor is located in a green pixel, the quantity of extraneous light can be accurately detected according to the human visual characteristics.

The luminance can be controlled by the luminance control circuit according to the extraneous light quantity detection result output from the extraneous light sensor, so that the visibility can be improved with a reduction in power consumption.

The luminance control circuit controls the luminance by controlling the quantity of light emitted from the primary light source of the backlight unit, so that the luminance can be controlled in a liquid crystal display device.

Second Preferred Embodiment

In contrast toFIGS. 7A and 7BandFIGS. 19A and 19B,FIGS. 8A and 8Bshow a liquid crystal display panel76applied to a display device according to a second preferred embodiment of the present invention. The display device according to the second preferred embodiment includes the liquid crystal display panel76in place of the liquid crystal display panel71shown inFIGS. 7A and 7B.

The liquid crystal display panel76according to the second preferred embodiment has the same configuration as that of the liquid crystal display panel71according to the first preferred embodiment except that a correcting sensor8A is provided in the light shielding area3and that the output signal from the extraneous light sensor8is corrected by the output signal from the correcting sensor8A prior to the luminance controlling step. The configuration of the correcting sensor8A and the configuration of a sensor circuit24for processing the output signal from the correcting sensor8A in the liquid crystal display panel76shown inFIGS. 8A and 8Bare the same as those of the liquid crystal display panel21shown inFIGS. 19A and 19B. Actually, a plurality of correcting sensors8A may be provided so as to respectively correspond to a plurality of extraneous light sensors8, and the output signal from each correcting sensor8A may be subtracted from the output signal from the corresponding extraneous light sensor8, thereby canceling the influence of dark current. Further, one correcting sensor8A may be assigned to every predetermined number of extraneous light sensors8, and the output signals from these extraneous light sensors8may be corrected by the single correcting sensor8A.

According to this preferred embodiment, dark current in the extraneous light sensor8can be corrected by using he correcting sensor8A provided in the light shielding area3, thereby improving the accuracy of luminance control as comparison with the first preferred embodiment.

Third Preferred Embodiment

In contrast toFIGS. 8A and 8B,FIGS. 9A and 9Bshow a liquid crystal display panel81applied to a display device according to a third preferred embodiment of the present invention. The display device according to the third preferred embodiment includes the liquid crystal display panel81in place of the liquid crystal display panel71shown inFIGS. 7A and 7B.

In the liquid crystal display panel81, the correcting sensor8A is located in the light shielding area3at a position close to the effective pixel area2, and the light shielding member15B shown inFIG. 8Bis omitted to allow the correcting sensor8A to detect extraneous light. Further, a part of the light shielding film11corresponding to the position of the correcting sensor8A is replaced by a filter82capable of selectively transmitting a wavelength band of infrared radiation. That is, the correcting sensor8A in the liquid crystal display panel81detects merely the wavelength band of infrared radiation included in the extraneous light. Thus, the liquid crystal display panel81according to the third preferred embodiment is different from the liquid crystal display panel76according to the second preferred embodiment in merely the configuration relating to the correcting sensor8A.

As in the second preferred embodiment, a plurality of correcting sensors8A may be provided so as to respectively correspond to a plurality of extraneous light sensors8. Further, one correcting sensor8A may be assigned to every predetermined number of extraneous light sensors8. Further, a single correcting sensor8A may be provided for all of the extraneous light sensors8.

FIG. 10is a graph showing a characteristic curve of transmittance of the green color filter CFG. As shown inFIG. 10, in the human visible region, the transmittance of the green color filter CFG is increased in merely the green wavelength band and remarkably decreased in the red and blue wavelength bands. However, in the wavelength band of infrared radiation outside the visible region, the transmittance of the green color filter CFG is increased. Further, the extraneous light sensor8has a sufficient sensitivity to the wavelength band of infrared radiation. Accordingly, in the configurations of the first and second preferred embodiments, the extraneous light sensor8also detects infrared radiation.

In the second preferred embodiment, the output signal from the extraneous light sensor8is corrected by the correcting sensor8A to correct for dark current in the extraneous light sensor8. However, the detection result of infrared radiation may not be corrected by the correcting sensor8A according to the second preferred embodiment shown inFIGS. 8A and 8B. Accordingly, the accuracy of luminance control is reduced by an amount corresponding to the infrared radiation detection result output from the extraneous light sensor8.

In contrast toFIG. 10,FIG. 11is a graph showing a characteristic curve of transmittance of the filter82. As shown inFIG. 11, merely the wavelength band of infrared radiation is detected by the correcting sensor8A by providing the filter82. Accordingly, by subtracting the output signal from the correcting sensor8A from the output signal from the extraneous light sensor8, it is possible to obtain an output signal corresponding to the green wavelength band. Accordingly, a reduction in the accuracy of luminance control due to infrared radiation can be prevented, thereby further improving the accuracy of luminance control. The filter82may be prepared by laminating green and red color filters CFG and CFR.

According to this preferred embodiment, the wavelength band of infrared radiation can be detected by the correcting sensor, thereby further improving the accuracy of luminance control.

Fourth Preferred Embodiment

In contrast toFIGS. 8A and 8B,FIGS. 12,13A, and13B show a liquid crystal display panel86applied to a display device according to a fourth preferred embodiment of the present invention.FIGS. 13A and 13Bare cross section taken along the lines C-C and B-B inFIG. 12, respectively. The display device according to the fourth preferred embodiment includes the liquid crystal display panel86in place of the liquid crystal display panel71shown inFIGS. 7A and 7B.

In the liquid crystal display panel86, the correcting sensor8A is located in the effective pixel area2at a position close to the extraneous light sensor8. More specifically, the correcting sensor8A is located in the reflective display area12of the green pixel where the extraneous light sensor8is located. As shown inFIG. 13A, a light shielding film15A is formed on the glass substrate9under the correcting sensor8A, and a light shielding member15B is provided so as to fully cover the correcting sensor8A.

In the liquid crystal display panel86, variations in characteristics between the extraneous light sensor8and the correcting sensor8A due to variations in manufacturing can be greatly reduced to thereby improve the accuracy of luminance control.

According to this preferred embodiment, the correcting sensor is located in the effective pixel area at a position close to the extraneous light sensor, thereby further improving the accuracy of luminance control.

Fifth Preferred Embodiment

In contrast toFIGS. 12,13A, and13B,FIGS. 14,15A, and15B show a liquid crystal display panel91applied to a display device according to a fifth preferred embodiment of the present invention. In the liquid crystal display panel91, the configuration relating to the correcting sensor8A is the same as that in the liquid crystal display panel81shown inFIGS. 9A and 9B. That is, the correcting sensor8A in the liquid crystal display panel91is so configured as to detect merely the wavelength band of infrared radiation. Further, the configuration of the liquid crystal display panel91is the same as that of the liquid crystal display panel86according to the fourth preferred embodiment shown inFIGS. 12,13A, and13B except that the configuration relating to the correcting sensor8A is different.

According to this preferred embodiment, the correcting sensor is located in the same pixel as that where the extraneous light sensor is located, and merely the wavelength band of infrared radiation is detected by the correcting sensor, thereby further improving the accuracy of luminance control.

Sixth Preferred Embodiment

In contrast toFIG. 12,FIG. 16shows a liquid crystal display panel96applied to a display device according to a sixth preferred embodiment of the present invention. In the liquid crystal display panel96, the correcting sensor8A is located in a pixel vertically adjacent to the pixel where the extraneous light sensor8is located. The liquid crystal display panel96has the same configuration as that of the liquid crystal display panel86except the location of the correcting sensor8A.

According to this preferred embodiment, the correcting sensor8A is located in a pixel vertically adjacent to the pixel where the extraneous light sensor8is located, so that biased wiring due to the close locations of the extraneous light sensor8and the correcting sensor8A can be reduced. Accordingly, even when the wiring space between the pixels closely arranged in the vertical direction is small, the extraneous light sensor8and the correcting sensor8A can be sufficiently wired to obtain an effect similar to that of the liquid crystal display panel86.

Seventh Preferred Embodiment

A liquid crystal display panel applied to a display device according to a seventh preferred embodiment of the present invention is similar to the liquid crystal display panel96according to the sixth preferred embodiment except that the configuration relating to the correcting sensor8A in the liquid crystal display panel91according to the fifth preferred embodiment is adopted. That is, the correcting sensor in the liquid crystal display panel according to the seventh preferred embodiment detects merely the wavelength band of infrared radiation.

According to this preferred embodiment, the correcting sensor for detecting merely infrared radiation is located in a pixel vertically adjacent to the pixel where the extraneous light sensor is located, thereby improving the accuracy of luminance control and obtaining the same effect as that of the sixth preferred embodiment.

Eighth Preferred Embodiment

In the above preferred embodiments, the extraneous light sensor is located in a green pixel or both the extraneous light sensor and the correcting sensor are located in a green pixel. However, in the above preferred embodiments, the present invention is not limited to such configurations, but the extraneous light sensor or both the extraneous light sensor and the correcting sensor may be located in another color pixel provided that a practically sufficient accuracy of luminance control can be ensured.

Further, in the above preferred embodiments, the extraneous light sensor is located in a pixel in the effective pixel area. However, in the above preferred embodiments, the present invention is not limited to this configuration, but the extraneous light sensor may be located between pixels provided that a practically sufficient space for locating the extraneous light sensor can be ensured.

Further, in the above preferred embodiments, the present invention is applied to a semitransmissive liquid crystal display panel. However, in the above preferred embodiments, the present invention is not limited to this configuration, but it may be applied to a transmissive liquid crystal display panel and a reflective liquid crystal display panel.

Further, in the above preferred embodiments, the present invention is applied to a liquid crystal display panel. However, in the above preferred embodiments, the present invention is not limited to this configuration, but it may be widely applied to various self-emission type display panels such as an organic EL (electroluminescence) display panel. In this case, the luminance of light emitted from each pixel rather than the quantity of illumination light from the backlight unit is controlled, thereby controlling the luminance of the display screen.