JP2009058678A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device wherein luminance of a backlight is controlled, detection accuracy of an optical sensor is not reduced even in low luminance operation, influence on luminance uniformity is suppressed to the minimum and a common component can be used independent of a used sensor. <P>SOLUTION: The image display device 1 includes a display part 21, lamps 221 for a backlight illuminating the display part, a reflection sheet 222 for reflecting light radiated by the lamps, the optical sensor 32 for detecting light introduced by a first aperture 224 of the sheet, a control part for controlling luminance of the lamps based on a detection result of the sensor and a sensor holder 31 disposed on the rear surface side of the reflection sheet for storing the optical sensor, wherein the holder has a second aperture 33 formed an inside region of the first aperture and having an area smaller than that of the first aperture and a reflection part provided at a part exposed from the first aperture and at a reflection sheet side surface part in the vicinity of the second aperture and light from the lamps is introduced into the optical sensor via both apertures. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display device that detects light emitted from a backlight with an optical sensor, controls the brightness of the backlight based on the detection result, and displays an image on a display unit.

  One type of image display device is a liquid crystal display device. A general liquid crystal display device uses a light emitting device using planar light emission called a backlight as a light source. The backlight reflects and diffuses the light emitted by the backlight lamp installed therein and emits light in a planar manner. A reflection sheet disposed on the back side of the backlight lamp is used for reflection.

  Cold-cathode tubes and LEDs are mainly used for the backlight lamps, but since the luminance and chromaticity of the lamps are highly temperature-dependent, the luminance and chromaticity of the lamps change due to changes in ambient temperature. . In addition, changes in the light emission luminance and chromaticity of the backlight lamp affect the output image of the liquid crystal display device.

  For this reason, a method for detecting the light emitted from the backlight lamp and controlling the amount of input to the backlight lamp based on the detection result is proposed by the techniques of Patent Documents 1 to 3 listed below. . Here, the input amount refers to a physical amount for controlling the brightness of the backlight lamp to be used. For example, when the backlight lamp is PWM control (pulse width modulation), it indicates the pulse width, and when it is DC control, it indicates the voltage.

Patent Document 1 proposes a technique of installing a light sensor via a reflection sheet and detecting light leaking from the reflection sheet. Patent Document 2 proposes a technique in which an opening is provided in a reflection sheet and light from the opening is detected by an optical sensor. Patent Document 3 proposes a technology in which a concave or convex storage portion is provided on a reflection sheet of a backlight, and light from an opening provided in the storage portion is detected by an optical sensor provided in the storage portion. ing.
JP-A-10-2222084 Japanese Utility Model Publication No. 5-8900 JP-A-2005-71702

However, Patent Documents 1 to 3 have the following problems.
That is, the technique disclosed in Patent Document 1 has a problem that the detection accuracy of the optical sensor is lowered particularly in a low luminance operation because the light transmitted through the reflection sheet is significantly attenuated and the S / N is lowered. It was.

  In the technique disclosed in Patent Document 2, since the light of the backlight is directly detected by providing an opening in the reflection sheet, the detection accuracy does not deteriorate even in the low luminance operation. However, there is a problem that the portion where the opening of the reflection sheet is provided cannot maintain the uniformity of reflection because the light is not reflected to the front surface, and the luminance uniformity of the planar light emission by the backlight is lowered. If the aperture is small, the influence on the luminance uniformity is small. However, in the technique of Patent Document 2, an opening that is so large that the influence on the luminance uniformity cannot be ignored due to the assembly tolerance of the reflection sheet must be provided. This will be described in detail below.

  FIG. 4 is a view showing the reflection sheet 603 and the sensor holder 602 when the reflection sheet 603 is combined at a regular position. The light L1 that has passed through the opening 604A of the reflection sheet 603 is detected by the optical sensor 601 provided in the sensor holder 602. However, as shown in FIG. 5, when the reflection sheet 603 is combined with a deviation from the normal position, the opening 604A is displaced to the position of the opening 604B, so that the optical sensor 601 can detect only a part of the light L2. In order to solve this problem, as shown in FIG. 6, the opening 604B must be enlarged like the opening 604C. Thereby, since the uniformity of reflection cannot be maintained, the luminance uniformity of planar light emission by the backlight is lowered.

  Even in the technique disclosed in Patent Document 3, an opening must be provided for the light detected by the optical sensor in the reflection sheet storage portion, but brightness uniformity is considered as in the technique of Patent Document 2. There was no problem. Further, since it is necessary to provide a concave or convex storage portion on the reflection sheet of the backlight to store the optical sensor, a backlight with a different specification is used for each type of optical sensor. For example, when only a luminance sensor is used for a low-priced monochrome product and a chromaticity sensor is used for a high-performance color product, both types of backlights are manufactured as necessary. As a result, it is necessary to produce a backlight for each sensor, and there is a problem that the cost is increased.

  The present invention has been made in view of the above-described circumstances. The brightness of the backlight is controlled based on the detection result of the optical sensor, and the luminance is uniform without reducing the detection accuracy of the optical sensor even in a low luminance operation. It is an object of the present invention to provide an image display apparatus that can minimize the influence on the performance and can use common components regardless of the sensor to be used.

In order to solve the above problems, the present invention proposes the following means.
The present invention provides a display unit that receives light from the back side and displays an image, a backlight lamp that is disposed on the back side facing the display unit and illuminates the display unit in a planar shape, and the backlight A reflective sheet that is disposed on the back side of the lamp and reflects light emitted from the backlight lamp to the front surface; and is disposed on the back side of the reflective sheet and is introduced from a first opening formed in the reflective sheet. In the image display device, comprising: a light sensor that detects the reflected light; and a control unit that controls the brightness of the backlight lamp based on a detection result of the light illuminated on the light sensor. A sensor holder that houses the optical sensor is disposed on the side, and a second opening having an area smaller than the area of the first opening is formed in an inner region of the first opening. , The sensor ho A reflective portion is provided on a surface portion of the reflective sheet side near the second opening and exposed from the first opening, through the first opening and the second opening. The light from the backlight lamp is introduced into the light sensor.

According to the image display device of the present invention, the light sensor detects the light that has passed through the first opening and the second opening, not the light that passes through the reflection sheet. The light detected by the optical sensor is not greatly attenuated. Therefore, the detection accuracy does not decrease even in a low luminance operation.
Moreover, since the reflection part reflects the light emitted from the backlight lamp in the same manner as the reflection sheet, the light other than the light introduced into the optical sensor is reflected to the front surface of the backlight through the second opening. Therefore, no matter how large the first opening is provided, the uniformity of reflection does not deteriorate, so that the problem of assembly tolerance of the reflection sheet is solved. In addition, since the second opening is also provided in the sensor holder that houses the photosensor, there is little misalignment due to assembly tolerances between the photosensor position and the second opening position, and the size of the second opening is made sufficiently small. Can do. As a result, the reduction in the uniformity of reflection can be minimized, and the influence on the luminance uniformity can be minimized.
Further, by providing a sensor holder in which an optical sensor is incorporated outside the backlight, the backlight can be shared even when different sensors are incorporated.

  In the invention, it is preferable that the reflecting portion is white.

  According to the image display device of the present invention, since the reflecting portion is white, it is possible to reflect any color of light emitted from the backlight lamp.

  Moreover, this invention is an image display apparatus of Claim 2, Comprising: The said reflection part and the said reflection sheet are substantially parallel, It is characterized by the above-mentioned.

Originally, the light emitted to the reflecting portion is reflected by the reflecting sheet on the front side, and the uniformity of the reflection is maintained. Therefore, it is desirable that the reflecting portion reflects light in the same direction as the reflecting sheet.
According to the image display device according to the present invention, there is no inclination of the angle between the reflecting portion and the reflecting sheet. Therefore, if it is the light radiated | emitted from the same direction, a reflection part will reflect light in the same direction as a reflective sheet. Thereby, the uniformity of reflection can be maintained, and the influence on the luminance uniformity can be suppressed.

  Moreover, this invention is an image display apparatus in any one of Claims 1-3, Comprising: A transparent protective sheet is affixed on the said 1st opening, It is characterized by the above-mentioned.

  According to the image display device of the present invention, it is possible to avoid the possibility that foreign matter enters the image display device from the first opening and affects the display.

  According to the image display device of the present invention, each of the reflection sheet and the sensor holder has an opening, and the sensor holder is provided with a reflection portion. It is possible to provide an image display device that does not deteriorate the detection accuracy of the optical sensor during operation, minimizes the influence on luminance uniformity, and can use common components regardless of the sensor to be used. It becomes.

  An embodiment of an image display device according to the present invention will be described using a liquid crystal display device as an example with reference to FIGS. FIG. 1 is a cross-sectional view illustrating a configuration example of an image display apparatus according to the present embodiment. A liquid crystal display device 1 that is an image display device in the present embodiment includes an LCD module 2 that displays a predetermined image, a sensor unit 3 fixed to the LCD module 2, and an LCD module 2 and a sensor unit 3. The transparent protective sheet 4 and the control unit 5 are attached.

  The LCD module 2 includes a display unit 21 disposed on the front surface of the LCD module 2, a backlight 22 disposed on the back surface facing the display unit 21, and a housing 23 that combines them (here In FIG. 1, the left side is called the front surface and the right side is called the back surface). The display unit 21 includes a liquid crystal material, an alignment film material, a glass substrate, a spacer, a sealing material, a polarizing plate, a color filter, and the like, and displays a predetermined image on the front surface by receiving light emitted from the backlight 22. .

  The backlight 22 includes a substantially fluorescent lamp 221 that is a backlight lamp installed therein, a reflection sheet 222 that also serves as a housing for the back and side surfaces, and a diffusion plate 223 that is disposed on the front surface. A substantially circular first opening 224 is provided in the center of the sheet 222. The input amount to the fluorescent lamp 221 is controlled by the control unit 5 described later. The reflection sheet 222 is disposed for the purpose of reflecting the light emitted from the fluorescent lamp 221 to the display unit 21 and is white to reflect each color of light uniformly and efficiently. The backlight 22 has a function of emitting light in a planar shape to the display unit 21 on the front surface. This is because the fluorescent lamp 221 emits light and the light traveling directly to the front surface and the light traveling to the front surface by being reflected by the reflection sheet 222 are diffused by the front diffusion plate 223.

  The housing 23 includes a display unit 21 and a backlight 22, and a housing opening 231 that is larger than the first opening 224 of the backlight 22 and encloses the first opening 224 is provided on the back surface. ing. The sensor unit 3 is fixed to the housing opening 231.

  The sensor unit 3 includes a sensor holder 31 that is a housing made of a white member, and an optical sensor 32 that is housed in the sensor holder 31 and detects light emitted from the fluorescent lamp 221. The sensor holder 31 includes a plate-shaped sensor support 31a to which an optical sensor 32 is attached, a convex sensor protection unit 31b that covers the optical sensor 32 and protects the optical sensor 32 from the outside, and a sensor protection unit 31b. And a plate-like holder lid 31c for sealing the back side of the plate. A substantially circular second opening 33 is provided on the front surface of the sensor protection unit 31 b so that light that has passed through the first opening 224 is introduced into the optical sensor 32. The second opening 33 is adjusted to a minimum size that allows the optical sensor 32 to detect light at the stage of designing and assembling the sensor unit 3 before the LCD module 2 and the sensor unit 3 are combined. The optical sensor 32 measures the luminance and chromaticity of the light from the fluorescent lamp 221 and outputs the detection result to the controller 5 described later.

  The protective sheet 4 is transparent and is affixed between the first opening 224 of the backlight 22 and the second opening 33 of the sensor holder 31. Here, when the vicinity of the first opening 224 is viewed from the front, it is as shown in FIG. The second opening 33 is smaller than the first opening 224, and the protective sheet 4 is attached therebetween. The outer side of the first opening 224 is a reflection sheet 222, and the outer side of the second opening 33 is a reflection part 34 inside the first opening 224. The reflection part 34 is substantially parallel to the reflection sheet 222. Since the sensor holder 31 is a white member and the protective sheet 4 is transparent, the white color of the reflecting portion 34 is not changed by the protective sheet 4.

  FIG. 3 is used for explaining the control unit 5. FIG. 3 is a diagram illustrating a method for controlling the amount of input to the backlight 22 of the image display apparatus according to the embodiment of the present invention. The control unit 5 includes a calculation unit 51 and a luminance / chromaticity control unit 52. The calculation means 51 receives the detection result of the optical sensor 32, compares the detection result with a preset target value, performs calculation so as to reduce the difference, and outputs a signal to be controlled to the luminance / chromaticity control means 52. Output to. The luminance / chromaticity control means 52 receives the control signal from the computing means 51, controls the luminance of the backlight 22 according to this, and processes the video signal to control the chromaticity. The calculation means 51 may be controlled not by comparing with a preset target value but by performing calculation so that the difference is reduced by comparing with the immediately preceding state. Further, the luminance / chromaticity control means 52 may perform luminance control by processing video signals.

  Next, the operation of the liquid crystal display device 1 of the present embodiment will be described. A part of the light emitted from the fluorescent lamp 221 is introduced into the optical sensor 32 in the sensor unit 3 through the first opening 224, the protective sheet 4, and the second opening 33 and detected. Since the protective sheet 4 is transparent, light is not attenuated. That is, since light that is not attenuated is introduced into the optical sensor 32, the luminance of the light detected by the optical sensor 32 is sufficiently maintained even in the low luminance operation.

  Further, a part of the light passing through the first opening 224 and radiated to the reflecting portion 34 outside the second opening 33 is reflected to the front surface of the backlight 22 because the reflecting portion 34 is white. The The reflecting portion 34 is substantially parallel to the reflecting sheet 222, and the second opening 33 is provided as a minimum opening that allows the optical sensor 32 to detect light. For this reason, the influence on the uniformity of reflection can be minimized.

  Further, the LCD module 2 and the sensor unit 3 are made independent, and a common LCD module and backlight can be used regardless of the optical sensor 32 to be used.

  Further, since the protective sheet 4 is provided, it is possible to avoid the possibility that foreign matter enters the LCD module 2 from the first opening 224 and affects the display.

  As described above, according to the liquid crystal display device 1 of the present embodiment, the control unit 5 controls the amount of input to the fluorescent lamp 221 of the backlight 22 based on the detection result of the optical sensor 32, and the light is emitted even in the low luminance operation. The detection accuracy of the sensor 32 is not lowered, the influence on the luminance uniformity is minimized, the common parts can be used regardless of the sensor used, and the possibility that foreign matter affects the display is reduced. Can be made.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration of the present invention is not limited to the above-described embodiments, and includes design changes and the like without departing from the scope of the present invention. It is. For example, the backlight 22 of this embodiment is a direct type, but may be a structure having a backlight lamp and a reflection sheet. For example, an edge light type may be used.

  In this embodiment, the fluorescent lamp 221 is used as the backlight lamp. However, the fluorescent lamp 221 is not limited to a cold cathode type or a hot cathode type, and is not limited to the fluorescent lamp, and other light sources such as LEDs are used. It doesn't matter.

  The LCD module 2 and the sensor unit 3 are fixed by screws. However, the present invention is not limited to this, and the housing opening 231 includes the first opening 224 and the first opening 224 is the second opening 33. As long as the positional relationship including the can be maintained, there are no restrictions on the fixing method and the fixing location.

  Moreover, although the function which reflects the light which the fluorescent lamp 221 radiates was provided in the reflection part 34 by making the member of the sensor holder 31 white, the sensor holder 31 whole does not need to be white, for example, the reflection part 34 It doesn't matter if the is painted white. Further, the surface of the reflecting portion 34 may be any surface as long as the reflection spectrum in visible light is substantially constant. For example, the surface of the reflecting portion 34 may be coated with aluminum, silver, or the like. It is preferable to do.

  In addition, it is preferable from the viewpoint of uniformity that the reflecting portion 34 is installed in the vicinity of the protective sheet 4, and it is more desirable that the reflecting portion 34 be arranged substantially in parallel with the reflecting sheet 222, but the present invention is not limited to this. Absent. Furthermore, it is desirable that the reflecting surface of the reflecting portion 34 is disposed on the inner side of the outer surface of the housing 23, that is, on the side where the protective sheet 4 is present, but the present invention is not limited thereto.

  In the present embodiment, the optical sensor 32 may be arranged at any location that does not affect the display of the image display device. However, since the average brightness of the entire image display device can be detected by the sensor, the LCD More preferably, the module 2 is arranged in the center of the back surface. Further, the number of the optical sensors 32 may be two or more. The type of the optical sensor 32 is not particularly limited, such as a luminance sensor or a chromaticity sensor.

  In the present embodiment, the first opening 224 and the second opening 33 are substantially circular, but the present invention is not limited to this, and may be rectangular or the like as necessary.

  Further, the protective sheet 4 is pasted between the first opening 224 of the backlight 22 and the second opening 33 of the sensor holder 31. However, the present invention is not limited to this, and no foreign matter enters the LCD module 2. For example, it may be attached so as to cover the first opening 224 from the inside of the backlight 22. Further, the protective sheet 4 may be omitted, but it is desirable to consider the possibility that a foreign object may affect the display.

It is sectional drawing which shows the structural example of the image display apparatus of embodiment of this invention. It is a figure for demonstrating the reflection part of the image display apparatus of embodiment of this invention. It is the figure which showed the control method of the input amount to the backlight of the image display apparatus of embodiment of this invention. It is a figure for demonstrating the positional relationship of the opening of a reflective sheet and optical sensor in a prior art. It is a figure for demonstrating the positional relationship of the opening of a reflective sheet and optical sensor in a prior art. It is a figure for demonstrating the positional relationship of the opening of a reflective sheet and optical sensor in a prior art.

Explanation of symbols

1 Liquid crystal display device (image display device)
21 Display unit 221 Fluorescent lamp (backlight lamp)
222 Reflective sheet 224 First opening 31 Sensor holder 32 Optical sensor 33 Second opening 34 Reflector 4 Protective sheet

Claims (4)

A display unit that receives light from the back and displays an image;
A backlight lamp that is disposed on the back side facing the display unit and illuminates the display unit in a planar shape, and a light that is disposed on the back side of the backlight lamp and is emitted from the backlight lamp. A reflection sheet that reflects light toward the front surface, a light sensor that is disposed on the back side of the reflection sheet and that detects light introduced from a first opening formed in the reflection sheet, and light that is illuminated by the light sensor In an image display device comprising a control unit that controls the brightness of the backlight lamp based on the detection result of
A sensor holder that houses the optical sensor is disposed on the back side of the reflective sheet,
A second opening having an area smaller than the area of the first opening is formed in an inner region of the first opening in the sensor holder,
A reflective portion is provided on the surface portion of the sensor holder near the second opening on the side of the reflective sheet that is exposed from the first opening,
An image display device, wherein light from the backlight lamp is introduced into the photosensor through the first opening and the second opening. The image display device according to claim 1,
The image display device, wherein the reflecting portion is white. The image display device according to claim 2,
The image display device, wherein the reflection portion and the reflection sheet are substantially parallel to each other. The image display device according to any one of claims 1 to 3,
An image display device, wherein a transparent protective sheet is attached to the first opening.

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