CN100435006C - Backlight, display device and light source control method - Google Patents

Abstract

A backlight for illuminating a display portion includes: a plurality of light sources arranged to correspond to a display area of the display portion; a diffusion plate configured to transmit light from the light sources to the display portion; a single light source a sensor; a light guide member configured to guide light from the light source to the photosensor; and an arithmetic operation processing part configured to The luminance or chromaticity detected in the light is used to calculate the luminance or chromaticity of each of the light sources.

Description

Backlight, display device and light source control method

Cross-references to related patent applications

The present invention contains subject matter related to Japanese Patent Application JP 2005-303405 filed in Japan Patent Office on October 18, 2005 and Japanese Patent Application JP 2006-223378 filed in Japan Patent Office on August 18, 2006, which The entire content of is hereby incorporated by reference.

technical field

The present invention relates to a backlight typically applied to a liquid crystal display device, a display device including the backlight, and a light source control method for controlling illumination of the backlight.

Background technique

In a liquid crystal display device, pixels arranged on a display panel do not emit light by themselves. Therefore, the backlight should be arranged on the back of the display panel, so that the back of the display panel is illuminated by the backlight to display images and the like. As the screen size of liquid crystal display devices increases, the display area of the display panel tends to increase, and the size of the backlight itself also increases significantly.

8A and 8B show an example of a backlight arranged on the backside of a display panel of a liquid crystal display device in the past. More specifically, FIG. 8A shows the backlight seen from the front, and FIG. 8B shows the backlight seen from the side. Referring to FIGS. 8A and 8B, in the shown backlight, cold cathode fluorescent lamps (CCFLs) are used as light emitting elements. The backlight includes a light box 1 and a plurality of cold cathode fluorescent lamps 2 arranged in a vertical row in the light box 1 and extending horizontally. The reflection sheet 6 is arranged on the back of the cold cathode fluorescent lamp 2 . The diffuser plate 4 is arranged in front of the light box 1, and the cold cathode fluorescent lamps 2 are arranged in the light box. It should be noted that the side on which the display panel is arranged opposite the backlight is referred to as the front, while the other side is referred to as the rear or rear. The same applies to the instructions here and below. Specifically, on FIG. 8B, the left side is the front. The diffusion plate 4 is formed, for example, of an acrylic sheet or plate having a size substantially equal to the display area of the display panel and a predetermined thickness so that it can diffuse light. In addition, a plurality of diffusion sheets are arranged in front of the diffusion plate 4 . The diffusion sheet 3 may be formed of a thin film of a resin material having such a characteristic that, for example, it provides a certain directional characteristic.

9A and 9B show another example of the structure of a backlight in which partitions are provided between some adjacent light sources. In particular, Figure 9A shows the backlight viewed from the front, and Figure 9B shows the backlight viewed from the side. Referring to FIGS. 9A and 9B , the shown backlight has the same structure as that of the backlight of FIGS. 8A and 8B except for the spacers mentioned above. In particular, the partition 7 is arranged between some adjacent ones of the plurality of cold cathode fluorescent lamps 2 arranged in the light box 1 so that the luminous flux from the cold cathode fluorescent lamps 2 can be introduced to the diffuser plate 4 without mixing with each other.

Where the structure shown in FIGS. 9A and 9B is used, it is possible to realize the blinking, ie, turning off, of some light sources in synchronization with the displayed image. Specifically, where an image is displayed on a liquid crystal display device using a backlight, light emission control of the backlight called flicker is sometimes used to ensure moving images such as high responsiveness. More specifically, the liquid crystal display panel temporarily enters a state in which its display state is not fixed during the period in which a display signal is written to pixels arranged on the panel. This state is likely to be perceived by the user and deteriorates the image quality of a displayed image, especially the responsiveness of a moving image. Therefore, the light source of the backlight on the back side of the relevant horizontal light is turned off during the time period when the display signal is written into the panel, so that no light is reflected from the light source, thereby enhancing the responsiveness of the moving image. In the case where the partitions 7 are arranged as seen in Figs. 9A and 9B, the luminous fluxes from adjacent light sources, that is, cold cathode fluorescent lamps 2, do not mix with each other. Therefore, the blinking process can be properly implemented. Hereinafter, specific examples of light emission control involving the blinking process are described in conjunction with preferred embodiments of the present invention.

Japanese Patent Publication No. 2003-50569 discloses a liquid crystal image display device in which light emission (on/off) control of a backlight is performed in synchronization with rewriting of images in order to ensure high visibility of moving images.

Summary of the invention

Incidentally, when the luminous flux from the light source is partitioned by partitions as in the backlight of FIGS. 9A and 9B , if the illumination of the light source is not uniform, the displayed image suffers from non-uniformity in brightness, resulting in deterioration of image quality. deterioration. In particular, if the luminous flux from the cold cathode fluorescent lamp 2 has some non-uniformity in luminance or chromaticity, this causes non-uniformity in luminance as seen from the front side and improves the brightness of the displayed image. non-uniformity. This leads to deterioration of the image quality of the displayed image. This non-uniformity in luminance or chromaticity of the emitted light is caused by the scatter in luminance that the light source - (in the example described, a CCFL) - originally has. Non-uniformity in brightness or chromaticity is sometimes also caused by the degree of deterioration caused by long-term changes

One possible solution to the above-mentioned problem is to fix a light sensor near each light source arranged in the backlight so that the brightness of light from the light source is individually corrected according to the brightness or chromaticity detected by the light sensor. However, if as many photosensors as the number of light sources are provided, a large number of photosensors are required for one backlight. This causes a problem that the backlight is greatly complicated in structure.

It should be noted that although the above describes the problem in which the backlight is mainly configured for flickering, the problem of non-uniformity of the luminance of light emitted from the light source is also involved in such a structure as shown in FIGS. 8A and 8B where no spacers are provided .

Contents of the invention

Therefore, it is required to provide a backlight, a display device, and a light source control method by which light emission control without display non-uniformity can be simply performed.

According to an embodiment of the present invention, there is provided a backlight for illuminating a display section including a plurality of light sources, a diffusion member, a single photosensor, a light guide member, and an arithmetic operation processing section. A plurality of light sources are arranged corresponding to the display area of the display section. The diffusion plate is configured to send light from the light source to the display portion. The light guiding member is configured to guide light from the light source to the light sensor. The arithmetic operation processing section is configured to calculate the luminance or chromaticity of each light source from the luminance or chromaticity detected by the photo sensor from the light guided by the light guide member.

For backlighting, the brightness or chromaticity of light emitted by a plurality of light sources can be detected by using a limited number of photosensors. Therefore, the luminance or chromaticity of each prepared light source can be detected with a simple structure. Also, the control to make the light emission state of the light source uniform can be implemented with a simple structure.

Description of drawings

1 is a block diagram showing the configuration of a liquid crystal display device to which the present invention is applied;

2A to 2F are schematic diagrams showing scanning flicker of a backlight of a liquid crystal display device;

3A to 3F are schematic diagrams showing examples of light emission states of a backlight;

4A to 4D are waveform diagrams showing the output of the light sensor of the liquid crystal display device;

5 to 7 are block diagrams showing configurations of different liquid crystal display devices to which the present invention is applied;

8A and 8B are schematic diagrams showing configurations of examples of past backlights;

9A and 9B are schematic views showing the configuration of another example of the past backlight; and

FIG. 10 is a schematic diagram showing display non-uniformity occurring for the backlight of FIGS. 9A and 9B.

Detailed ways

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 4D.

In this embodiment, the present invention is applied to a liquid crystal display device. First, an example of the general configuration of a liquid crystal display device is described with reference to FIG. 1 . It should be noted that in FIG. 1 , for ease of understanding, a plan view and a vertical sectional view of the liquid crystal display device are shown in a cross-overlapping relationship with each other. A video signal or image signal input to a liquid crystal display device is supplied to a liquid crystal display image display control circuit 11, which generates a signal for driving a liquid crystal display panel 12 to perform a display action according to the video signal. The display driving signal thus generated is supplied to the liquid crystal display panel 12 on which a display signal is written to each pixel arranged on the liquid crystal display panel 12 . The writing of the display signal is performed, for example, within a period of one frame in synchronization with the frame period of the video signal supplied thereto.

The backlight 20 is arranged on the back of the liquid crystal display panel 12 . In the present embodiment, the backlight 20 includes cold cathode fluorescent lamps 21, 22, 23, 24, 25, and 26 as light sources, which are juxtaposed in vertical columns and each of which extends in the horizontal direction.

The backlight is configured such that its cold cathode fluorescent lamps 21 to 26 are arranged in vertical columns in a light box 29 , which forms the backlight 20 . The reflective sheet 28 is arranged on the back of the cold cathode fluorescent lamps 21 to 26 . The diffusion plate 14 is arranged in front of a lamp box 29 in which the cold cathode fluorescent lamps 21 to 26 are installed. The diffusion plate 14 has a size substantially equal to the display area of the liquid crystal display panel 12, and is formed of, for example, an acrylic sheet or plate so that it diffuses light. Also, partitions 31 to 35 are arranged between some adjacent ones of the cold cathode fluorescent lamps 21 to 26 in the light box 29, so that luminous flux from the cold cathode fluorescent lamps 21 to 26 can be introduced into the diffusion plate 14 and Does not mix with luminous flux from other adjacent lamps.

Lighting or on/off of the cold cathode fluorescent lamps 21 to 26 is controlled by light emission control signals supplied from the light emission control circuit 15 to the cold cathode fluorescent lamps 21 to 26 individually, respectively. The vertical synchronizing signal VS and the horizontal synchronizing signal HS of the video signal are supplied from the liquid crystal display image display control circuit 15 to the light emission control circuit 15, so that the light emission control circuit 15 successively executes the temporary shut-off process for the cold cathode fluorescent lamps 21 to 26 . A position where one of the cold-cathode fluorescent lamps 21 to 26 is turned off and no longer emits light is related to the pixel on the liquid crystal display panel 12 arranged in front of the turned-off one of the cold-cathode fluorescent lamps 21 to 26. The positions of the horizontal lines of the written one coincide with each other. Thus, the blinking process described above in the background description of the invention is achieved.

In addition, in the present embodiment, two light guide members 41 and 42 are arranged at the right end of the light box 29, so that the luminous fluxes entering the light guide members 41 and 42 from the positions of CCFLs 21 to 26 are respectively introduced into Light sensors 43 and 46 fixed on light guide members 41 and 42 . The light guiding members 41 and 42 are made of a transparent material such as, for example, an acrylic resin material.

The light guiding members 41 and 42 are described in more detail below. The positions of the fluorescent lamps 21 in the first row, the fluorescent lamps 22 in the second row, and the fluorescent lamps 23 in the third row arranged in order from above are selected so that the luminous flux from the fluorescent lamps 21, 22 and 23 Introduced to the first light guide member 41 at the right end of the light box 29 , and then introduced to the photosensor 43 provided on the board 44 at the upper end of the backlight 20 . The first light guide member 41 has such a shape that it reflects the light fluxes from the fluorescent lamps 21, 22 and 23 at mutually different angles so as to lead the light fluxes to the single photosensor 43. In this example the light paths are individually indicated by the respective arrow marks in FIG. 1 .

On the other hand, the fluorescent lamps 24 in the fourth row, the fluorescent lamps 25 in the fifth row, and the fluorescent lamps 26 in the sixth row are selected so that the luminous fluxes from the fluorescent lamps 24, 25 and 26 are introduced into the lamp box. The second light guide member 42 at the right end of the backlight 29 is then introduced to the light sensor 46 provided on the board 47 at the lower end of the backlight 20 . The second light guide member 42 has such a shape that it reflects the luminous flux from the fluorescent lamps 24, 25 and 26 at angles different from each other so as to lead the luminous flux to the single photosensor 46. In this example the light paths are individually indicated by the respective arrow marks in FIG. 1 .

The photosensors 43 and 46 are configured so as to output voltage signals corresponding to the level of light incident thereon and each output a voltage signal of a level corresponding to the total brightness of light arriving from the corresponding three fluorescent lamps. The output voltage signals are converted into digital data by analog/digital converters 45 and 48 mounted on boards 44 and 47 , respectively, and then sent to the light emission control circuit 15 . The light emission control circuit 15 sends a digital conversion trigger pulse to the analog/digital converters 45 and 48 , and the data sampled at the timing indicated by the trigger pulse is sent to the light emission control circuit 15 . An example of timing for sampling is described later.

The arithmetic operation circuit 16 is connected to the light emission control circuit 15 so that the detection level data of the photosensors 43 and 46 supplied to the light emission control circuit 15 is supplied to the arithmetic operation circuit 16 . Therefore, the arithmetic operation circuit 16 performs an arithmetic operation operation of calculating the luminance of light emitted from the six cold cathode fluorescent lamps 21 to 26 by arithmetic operation using an operation formula set in advance. These calculation formulas will be described later.

Now, an example of the corresponding relationship between the write state of the image written to the pixels arranged on the liquid crystal display panel of the display device of the present embodiment and the light emission state of the backlight will be described with reference to FIGS. 2A to 2F . In the example shown in FIGS. 2A to 2F, image writing to the liquid crystal display panel is performed in one unit of horizontal lines, and FIGS. 2A to 2F show different writing positions of images, which are sequentially changed in order. In each of FIGS. 2A to 2F , the right half shows the writing state in which an image is written to the liquid crystal display panel, and the left half shows the lighting and non-lighting positions of the backlight. In FIGS. 2A to 2F , the old image represents the image of the previous frame, and the new image represents the image of the current frame. As seen on FIGS. 2A to 2F , the two fluorescent lamps near the position where the image signal is written into the pixel of the current frame (that is, the boundary position between the old image and the new image) are turned off. The one that does not emit light, while the remaining four fluorescent lamps are turned on to emit light.

Figures 2A to 2F are studied in more detail. In FIG. 2A, the position where the image is written is located at the lower part of the screen, and the two lowermost fluorescent lamps 25 and 26 among the six fluorescent lamps are turned off and do not emit light, while the remaining four fluorescent lamps are turned on to emit light. If the writing position is moved further downward from this position, the lowermost fluorescent lamp 26 and the uppermost fluorescent lamp 21 are turned off without emitting light, as shown in FIG. 2B. Then, if the writing position comes to the top of the screen, the uppermost two fluorescent lamps 21 and 22 are turned off without emitting light, as shown in FIG. 2C. If the writing position is subsequently moved down successively from this position, the off positions of the two fluorescent lamps are moved down successively, as shown in FIGS. 2D, 2E and 2F. The transitions shown in Figs. 2A to 2F are repeated for each frame.

Now, the relationship between the light-emitting state (non-light-emitting state) in one frame and the detection timing of the two photosensors 43 and 46 will be described with reference to FIGS. 3A to 3F and 4A to 4D. 3A, 3B, 3C, 3D, 3E, and 3F, when the first to sixth light-emitting states in which combinations of two fluorescent lamps out of the six fluorescent lamps are respectively specified to be turned off are specified, in each One detection is performed by each photosensor 43 and photosensor 46 in the light-emitting state. In particular, in the case where the lighting states are specified as shown in FIGS. 3A to 3F, if the two photosensor outputs are successively detected in the first to sixth lighting states, then the results as shown in FIG. 4A are obtained. state. In FIG. 4A , the upper light sensor represents the output of light sensor 43 and the lower light sensor represents the output of light sensor 46 . Figure 4B shows the vertical sync pulses of the displayed image. As shown in Figure 4B, the pulse occurs immediately before the first light emitting state.

As shown in FIG. 4A, the outputs of the two photosensors 43 and 46 are repeatedly varied according to the position of the turned off fluorescent lamp. FIG. 4C shows a trigger pulse to be used to sample the output of light sensor 43 , while FIG. 4D shows a trigger pulse to be used to sample the output of light sensor 46 . As shown in FIGS. 4A to 4D , the output of the photosensor 43 is obtained in the first to third states, and the output of the photosensor 46 is obtained in the fourth to sixth states. In FIG. 4A , sensor outputs acquired in the first to sixth lighting states are represented as signals S1 to S6 , respectively.

Among them, the detection data S1 of the upper light sensor 43 in the first light emitting state, the detection data S2 of the upper light sensor 43 in the second light emitting state, the detection data S3 of the upper light sensor 43 in the third light emitting state, The detection data S4 of the lower photosensor 46 in the fourth light-emitting state, the detection data S5 of the lower photosensor 46 in the fifth light-emitting state, and the detection data S6 of the lower photosensor 46 in the sixth light-emitting state are expressed in this way. In the case where the two methods are specified, if the luminous quantities of 21, 22, 23, 24, 25 and 26 are respectively defined as L1, L2, L3, L4, L5 and L6 in order, then the output of the light sensor and the luminescence of the fluorescent lamp The relationship between the quantities is given as follows:

[Formula 1]

S1＝L1+L2+L3

S2=L2+L3

S3=L3

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="S"\; filenames="C20061013562200242.png,C20061013562200244.png"\; state="\{\{state\}\}">S</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 3</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="C20061013562200242.png,C20061013562200244.png"\; state="\{\{state\}\}">L</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 3</span>}\end{array}\right]$

S4＝L4+L5+L6

S5＝L5+L6

S6=L6

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 4</span>}\\ \mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 5</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="S"\; filenames="C20061013562200231.png,C20061013562200242.png"\; state="\{\{state\}\}">S</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 6</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 4</span>}\\ \mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 5</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="L"\; filenames="C20061013562200231.png,C20061013562200242.png"\; state="\{\{state\}\}">L</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 6</span>}\end{array}\right]$

By using this relational expression to solve the following matrix, the luminous quantities L1, L2, L3, L4, L5, and L6 of the six CCFLs 21, 22, 23, 24, 25, and 26 are determined as:

[Formula 2]

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="L"\; filenames="C20061013562200242.png,C20061013562200244.png"\; state="\{\{state\}\}">L</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 3</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="S"\; filenames="C20061013562200242.png,C20061013562200244.png"\; state="\{\{state\}\}">S</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 3</span>}\end{array}\right]$

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 4</span>}\\ \mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 5</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="L"\; filenames="C20061013562200231.png,C20061013562200242.png"\; state="\{\{state\}\}">L</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 6</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 4</span>}\\ \mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 5</span>}\\ \mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="S"\; filenames="C20061013562200231.png,C20061013562200242.png"\; state="\{\{state\}\}">S</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 6</span>}\end{array}\right]$

This arithmetic operation process is performed by the arithmetic operation circuit 16 shown in FIG. 1 . The data of the respective light emission luminances of the six fluorescent lamps 21 to 26 obtained by the arithmetic operation circuit 16 is sent to the light emission control circuit 15 . A process in which the light emission control circuit 15 corrects the light emission luminance of the fluorescent lamps 21 to 26 based on the light emission luminance data. Correction for each luminance of light emission is achieved, for example, by controlling the voltage applied to the corresponding fluorescent lamp. By performing correction of the emission luminance correction based on the data detected by the two photosensors 43 and 46 in this way, the emission luminances of the six fluorescent lamps 21 to 26 can always be corrected to a uniform level. For example, even if some change or long-term change in the use environment occurs, uniform lighting conditions can always be ensured, and non-uniformity in luminance of an image displayed by backlighting can be prevented.

In this case, since the liquid crystal display device of this embodiment includes only two light guide members 41 and 42 and two photosensors 43 and 46, it is better to provide one photosensor for each of the six light sources. The alternative case for has a much simpler structure. Therefore, the cost required for producing the backlight can be reduced.

A liquid crystal display device according to a second embodiment of the present invention will now be described with reference to FIG. 5. FIG. The liquid crystal display device of this embodiment is a modification of the liquid crystal display device of the first embodiment described above with reference to FIGS. 1 to 4D and it has a configuration generally similar to that of the first embodiment. Therefore, in the following description, only the differences between the liquid crystal display device of this embodiment and the first embodiment will be described. The liquid crystal display device of this embodiment is generally configured such that it includes a single photosensor, so that the brightness of all light sources is detected by the single photosensor, and the brightness of the light sources is determined according to the detection outputs of the single photosensors at different timings.

Specifically, referring to FIG. 5, a light guide member 51 for guiding light from six cold cathode fluorescent lamps 21 to 26 to a single photosensor 53 is located at the right end of the backlight 20 where the cold cathode fluorescent lamps 21 to 26 are arranged, such that , the light sensor 53 detects all outputs of the cold cathode fluorescent lamps 21 to 26 . The light guiding member 51 is made of, for example, an acrylic resin material. The liquid crystal display device also includes a mirror 52 arranged to reflect the light guided to the center by the light guide member 51 to be input to the light sensor 53 . A light sensor 53 is mounted on a board 54 and acquires a signal as digital data from an analog/digital converter 55 mounted on the board 54 . The digital data is sent to the light emission control circuit 15 .

The light emission amount data sent from the photo sensor 53 is sent to the arithmetic operation circuit 16', and the light emission amounts of the cold cathode fluorescent lamps 21 to 26 are calculated from the received light emission amount data by arithmetic operation of the arithmetic operation circuit 16'. It should be noted that since the liquid crystal display device shown in FIG. 5 includes a single photosensor, it is necessary to change the light emission mode and the operational formula of the lamp from those of the liquid crystal display devices shown in FIGS. 1 to 4D. In the case of employing the configuration shown in FIG. 5, the number of photosensors is reduced to one, and therefore, a more simplified structure can be achieved.

A liquid crystal display device according to a third embodiment of the present invention will now be described with reference to FIG. 6. FIG. The liquid crystal display device of this embodiment is a modification of the liquid crystal display device of the second embodiment described above with reference to FIG. 5 and it has a configuration generally similar to that of the second embodiment. Therefore, in the following description, only the differences between the liquid crystal display device of this embodiment and the second embodiment will be described. Referring to FIG. 6, a liquid crystal display device according to a third embodiment is shown as a whole configured so that the light guiding member has a more simplified structure. Specifically, the light guiding member in the first and second embodiments shown in FIGS. 1 and 4 is configured such that it is made of an acrylic material or the like and serves to guide light. In contrast, the light guide member in this embodiment is configured such that it has the form of a reflective sheet arranged in a light box, which is a member of the backlight and inputs light to one or two photosensors.

Specifically, the light guiding hollow part 61 is arranged at the right end of the light box 29 , and a reflective part is arranged on the inner wall of the light guiding hollow part 61 . In addition, a reflective mirror 62 is arranged at a central portion of the reflective member so that light reflected by the reflective mirror 62 is introduced to the photosensor 63 . The photosensor 63 is fixed on the board 64, and the output of the photosensor 63 is converted into digital data by the analog/digital converter 65 and supplied to the light emission control circuit 15 side.

Where the liquid crystal display device is configured as described above, the need for a light guiding member of acrylic resin material or the like is eliminated, and a simpler light guiding structure can be achieved.

A liquid crystal display device according to a fourth embodiment of the present invention will now be described with reference to FIG. 7. FIG. The liquid crystal display device of this embodiment is a modification of the liquid crystal display device of the first embodiment described above with reference to FIGS. 1 to 4D and it has a configuration generally similar to that of the first embodiment. Therefore, in the following description, only the differences between the liquid crystal display device of this embodiment and the first embodiment will be described. Specifically, the liquid crystal display device of this embodiment uses a light emitting diode as a light source. Specifically, the backlight 70 arranged on the backside of the liquid crystal display panel 12 includes red light emitting diodes 71R to 76R, green light emitting diodes 71G to 76G, and blue light emitting diodes 71B to 76B arranged in order in respective rows. The lamp box 79 is configured such that the inside of the reflection sheet 78 is divided into six divisions in the vertical direction by the partitions 31 to 35, similarly to the lamp box 29 shown in FIG. 1 . In each divided section (as shown in FIG. 7, which are rows), red light emitting diodes, green light emitting diodes, and blue light emitting diodes are arranged in order.

In the device shown in FIG. 7, a required number of red LEDs 71R, green LEDs 71G, and blue LEDs 71B are horizontally arranged in a row, ie, a first row, at the top portion of the light box 79. In the second row which is the next division, a required number of red light emitting diodes 72R, green light emitting diodes 72G, and blue light emitting diodes 72B are arranged in one row. In the third row, a required number of red light emitting diodes 73R, green light emitting diodes 73G and blue light emitting diodes 73B are arranged in a row. In the fourth row, a required number of red light emitting diodes 74R, green light emitting diodes 74G, and blue light emitting diodes 74B are arranged in a row. In the fifth row, a required number of red light emitting diodes 75R, green light emitting diodes 75G, and blue light emitting diodes 75B are arranged in a row. In the sixth row, a required number of red light emitting diodes 76R, green light emitting diodes 76G, and blue light emitting diodes 76B are arranged in a row.

The two light guide parts 41 and 42 are arranged at the right end of the light box 79, so that the light introduced into the light guide parts 41 and 42 from the position of the light emitting diode is introduced into the light guide parts fixed on the light guide parts 41 and 42 respectively. Light sensors 43 and 46. The light guiding members 41 and 42 are made of a transparent material such as, for example, an acrylic resin material.

The light guiding members 41 and 42 are described in more detail below. The light emitting diodes 71R, 71G and 71B in the first row, the light emitting diodes 72R, 72G and 72B in the second row, and the light emitting diodes 73R, 73G and 73B in the third row are placed in order from above, so that Light from them is caused to be introduced to the first light guide member 41 at the right end of the light box 79 , thereby causing the light to be introduced to the photosensor 43 fixed on the board 44 at the upper end of the backlight 70 . The first light guide member 41 has a shape that reflects the light fluxes at angles different from each other in order to introduce the light fluxes from the LEDs of the first, second and third rows to the single light sensor 43 .

Meanwhile, the light emitting diodes 74R, 74G and 74B in the fourth row, the light emitting diodes 75R, 75G and 75B in the fifth row, and the light emitting diodes 76R, 76G and 76B in the sixth row are placed such that Their light is introduced to the second light guide member 42 at the right end of the light box 79 so that the light is introduced to the light sensor 46 fixed on the board 47 at the lower end of the backlight 70 . The second light guide member 42 also has a shape that reflects the light fluxes at different angles from each other in order to introduce the light fluxes from the LEDs of the fourth, fifth and sixth rows to the single light sensor 46 .

The light sensors 43 and 46 are configured to output voltage signals corresponding to the level of light incident thereon. Specifically, each photosensor 43 and 46 outputs a voltage signal at a level corresponding to the total brightness of light fluxes coming from the corresponding three rows of light emitting diodes. The voltage signal output from the light sensor 43 or 46 is converted into digital data by the analog/digital converter 45 or 48 fixed at 44 or 47, and then sent to the light emission control circuit 15'. The light emission control circuit 15' sends a digital conversion trigger signal to the analog/digital converter 45 or 48. Therefore, data sampled at the timing indicated by the trigger pulse is sent to the light emission control circuit 15'.

The arithmetic operation circuit 16" is connected to the light emission control circuit 15', so that the detection level data of the photosensors 43 and 46 supplied to the light emission control circuit 15' is supplied to the arithmetic operation circuit 16". The arithmetic operation circuit 16" thus performs an arithmetic operation process for calculating the emitted light luminances of the light emitting diodes in the six rows by the arithmetic operation in which the operation expression group is used in advance. For the operation expression, the above in the first Those formulas given in the description of the examples.

Since the liquid crystal display device of this embodiment is configured as described above, similar brightness control of emitted light can be applied to the light source in the case of using light emitting diodes as the light source, and similar good image display can be expected. It should be noted that although the numbers of red light-emitting diodes, green light-emitting diodes, and blue light-emitting diodes are equal to each other in the device of FIG. color LEDs so that a white backlight can be obtained.

It should be noted that in the liquid crystal display device of FIG. 7, each photosensor 43 and 46 is formed as a sensor for detecting luminance, and a process of correcting the emitted light luminance of the light source is performed based on the output of the sensor. However, each photosensor 43 and 46 can additionally detect chromaticity. Where the chromaticity is detected by the photosensors 43 and 46 in this way, the light emission amounts of the colored LEDs are controlled according to the detected value of the chromaticity to perform correction of the chromaticity, that is, to correct deviation from white. Where color correction is performed in this way, better light of the backlight can be obtained. It should be noted that the control of the amount of light emitted by the light emitting diodes may be, for example, controlling the amount of current supplied to the light emitting diodes, or controlling the time period during which the current is supplied to the light emitting diodes.

Also in the case where the cathode ray fluorescent lamps are used in the first to third embodiments described above, the chromaticity of the fluorescent lamps can be determined so that the luminous color of the light source can be independently corrected according to the determination.

Also, although, in the embodiments described above, a cathode ray fluorescent lamp or a light emitting diode is used as a light source, some other light source such as a hot cathode fluorescent lamp may be used so that the brightness and chromaticity of the light source are corrected. Meanwhile, when light emitting diodes are used, for example, light emitting diodes that emit white light may also be used. In addition, the invention can also be used with many different types of light sources, for example using a combination of cold cathode fluorescent lamps and light emitting diodes.

In addition, in the above-described embodiments, the light source is divided into six light sources in the vertical direction. However, the light source can also be divided into a plurality of light sources in the horizontal direction, thus becoming a matrix. In this case, the brightness of the light source is detected and corrected by using a limited number of photosensors.

In addition, in the above-described embodiments, the present invention is applied to the backlight configured such that a partition member or spacer is arranged between adjacent light sources. However, the present invention can also be applied to another backlight device which does not include a partition member and which allows luminous fluxes from adjacent light sources to mix with each other. In this case, however, it is necessary to decide the brightness of each light source, etc., also taking into account the influence of light from adjacent light sources.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and changes may be made depending on design requirements and other factors in the scope of the appended claims or their equivalents.

Claims (13)

1. A backlight for illuminating the backside of a display portion, comprising: a plurality of light sources arranged to correspond to the display area of the display portion; a diffusion plate configured to transmit light from the light source to the display portion; single light sensor; a light guide member configured to guide light from each of the light sources to the light sensor such that the light sensor detects brightness or chromaticity of all of the light sources; and An arithmetic operation processing section configured to calculate the luminance or chromaticity of each of the light sources from the luminance or chromaticity detected by the photo sensor from the light guided by the light guide member. 2. The backlight according to claim 1, wherein said light sources are grouped into first and second groups, and said light guide member comprises a pair of light guide member units and said light sensor comprises a pair of light sensor units, The lights from the light sources in the first and second groups are each independently introduced to the light sensor unit through the light guide member unit, and the arithmetic operation processing section is guided from the light sensor by the light sensor unit. The luminance or chromaticity detected in the light guided by the light guiding member is used to calculate the luminance or chromaticity of each of the light sources. 3. The backlight according to claim 1, wherein the luminance or chromaticity of each of said light sources is calculated based on the luminance or chromaticity of each individual light source in said light sources calculated as a result of arithmetic operation processing performed by said arithmetic operation processing section. degree is corrected. 4. The backlight according to claim 1, wherein said arithmetic operation processing section performs control so that said light sources each individually blink in synchronization with a frame period of an image signal to be displayed on said display section, and decides to pass the Flicker controls which of the light sources light from is input to the light sensor in order to calculate the luminance or chromaticity of each of the light sources. 5. The backlight according to claim 1, wherein each of said light sources is a fluorescent lamp. 6. The backlight of claim 1, wherein each of said light sources is a light emitting diode. 7. A display device comprising: a display section configured to display an image corresponding to the input image signal; and a backlight for illuminating the back of the display portion; The backlight includes: a plurality of light sources arranged to correspond to the display area of the display portion; a diffusion plate configured to transmit light from the light source to the display portion; single light sensor; a light guide member configured to guide light from each of the light sources to the light sensor such that the light sensor detects brightness or chromaticity of all of the light sources; and An arithmetic operation processing section configured to calculate luminance or chromaticity of each of the light sources based on luminance or chromaticity detected by the photo sensor from light guided by the light guide member. 8. The display device according to claim 7, wherein said light sources are grouped into first and second groups, said light guide member comprises a pair of light guide member units and said light sensor comprises a pair of light sensor units, Lights from the light sources in the first and second groups are each individually introduced to the photosensor unit through the light guide member unit, and the arithmetic operation processing part The luminance or chromaticity of each of the light sources is calculated based on the detected luminance or chromaticity of the light guided by the light guiding member. 9. The display device according to claim 7, wherein said arithmetic operation processing section executes control of causing said light sources to blink individually in synchronization with a frame period of said input image signal, and decides to control one of said light sources by the blinking. Which light source's light is input to the light sensor in order to calculate the luminance or chromaticity of each of the light sources. 10. The display device according to claim 7, wherein the luminance or chromaticity of each of said light sources is calculated based on a result of arithmetic operation processing performed by said arithmetic operation processing section of each individual light source in said light sources. luminance or chromaticity are corrected. 11. The display device according to claim 7, wherein each of said light sources is a fluorescent lamp. 12. A display device according to claim 7, wherein each of said light sources is a light emitting diode. 13. A light source control method for controlling brightness and chromaticity of a light source illuminating a rear surface of a display portion, comprising the steps of: detecting brightness or chromaticity of light from a plurality of light sources arranged corresponding to a surface area of the display portion by using photosensors the number of which is less than the number of light sources; calculating the luminance or chromaticity of each of said light sources based on the luminance or chromaticity detected by said light sensor; and The light sources are individually controlled according to the calculated luminance or chromaticity of each of the light sources.

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