JP7531702B2 - Display device and display method - Google Patents

Description

The present disclosure relates to a display device and a display method.

Local dimming is a technology for improving the contrast of an image display in a liquid crystal display device by dividing the backlight into multiple regions and controlling the emission brightness of the backlight for each region based on the characteristics related to the brightness of the image to be displayed. For example, Patent Document 1 describes a display device to which local dimming control is applied.

JP 2018-146750 A

Conventionally, local dimming has been implemented by a control circuit dedicated to the backlight, which is provided separately from the control circuit for the liquid crystal display. For this reason, a display device that supports local dimming has a problem in that the circuit scale is larger than that of a display device that does not support local dimming. Note that even in the conventional display device described in Patent Document 1, a control circuit dedicated to the backlight implements local dimming, and there are concerns about the increase in circuit scale.

The present disclosure is intended to solve the above-mentioned problems, and aims to provide a display device and display method capable of performing local dimming without providing a control circuit dedicated to the backlight.

The display device according to the present disclosure is a display device including a display unit, a backlight having a plurality of light sources and illuminating the display unit with light from the light sources, a display driver for driving the display unit, and a signal processing unit for displaying an image on the display unit based on input image data, the display driver including a signal line connecting the display driver and the light source of the backlight, the signal processing unit applying a lighting signal output from the display driver to the light source of the backlight through the signal line, thereby controlling lighting of the light source determined based on the input image data , the display unit including a plurality of pixels arranged in a matrix, and a voltage applying circuit provided for each pixel row of the plurality of pixels. The backlight includes a plurality of scanning lines for selecting pixel rows, and a plurality of data lines provided for each pixel column of the plurality of pixels for applying a voltage to the pixels of the selected pixel row. The display driver includes a source driver that applies a voltage to the plurality of data lines, and a gate driver that applies a voltage to the plurality of scanning lines. The signal lines connect the source driver to a light source of the backlight. The signal processing unit applies a voltage from the source driver through the signal lines to the light source of the backlight. The light source in the backlight is a light-emitting diode, the cathode terminal of which is grounded and the signal line is connected via a resistor to the anode terminal .

According to the present disclosure, the signal processing unit applies the lighting signal output from the display driver to the light source of the backlight through the signal line, thereby controlling the lighting of the light source determined based on the input image data. This allows the display device according to the present disclosure to perform local dimming without providing a control circuit dedicated to the backlight.

1 is a block diagram showing a hardware configuration of a display device according to a first embodiment; FIG. 2 is a diagram showing a partial configuration of a display unit and a display driver. 1 is a block diagram showing a functional configuration of a display device according to a first embodiment; 4 is a flowchart showing a display method according to the first embodiment. FIG. 2 is an explanatory diagram showing the relationship between a source driver and a backlight. FIG. 2 is a circuit diagram showing a light emitting diode (LED) of the backlight. 1 is a table showing the relationship between source voltage and light emission brightness of an LED. 1 is a graph showing the relationship between gray scale and source voltage. 11 is a graph showing the relationship between the gray scale and the source voltage after correction. 1 is a graph showing a gamma curve. 11A and 11B are block diagrams showing a hardware configuration of a signal processing unit included in the display device according to the first embodiment.

Embodiment 1.
Fig. 1 is a block diagram showing a hardware configuration of a display device 1 according to a first embodiment. Fig. 2 is a configuration diagram showing a partial configuration of a display unit 11 and a display driver 13. The display device 1 is a device that performs local dimming control. In Fig. 1, the display device 1 includes a display unit 11, a backlight 12, a display driver 13, a signal processing unit 14, an image output unit 15, and a signal line 16. The display unit 11 is illuminated by the backlight 12 and driven by the display driver 13.

The backlight 12 has multiple light sources, is arranged on the back of the display unit 11, and illuminates the display unit 11 with light from the light sources. In the backlight 12, the multiple light sources are arranged in a matrix. The light sources are, for example, light-emitting diodes (LEDs) that emit white light. In the following, the multiple light sources of the backlight 12 will be described as being LEDs. The display driver 13 is a driver that drives the display unit 11, and includes a source driver 13A and a gate driver 13B.

The display unit 11 includes a panel filled with a liquid crystal material and a glass substrate disposed on the rear surface of the panel. The panel has a plurality of TFTs (Thin Film Transistors) and pixels 20, as shown in FIG. 2, arranged in a matrix. The glass substrate also has a plurality of scanning lines 17 for each pixel row of the pixels 20, and a plurality of data lines 18 for each pixel column of the pixels 20. The scanning lines 17 are gate lines for selecting a pixel row to which a gate voltage of the TFTs 19 is applied. The data lines 18 are source lines for applying a source voltage to the pixels of the selected pixel row.

The TFT 19 is turned on or off depending on the gate voltage applied from the gate driver 13B to the scanning line 17. The source voltage applied from the source driver 13A to the data line 18 is held on the pixel 20 side by the TFT 19 switching from the on state to the off state. The light transmittance of the pixel 20 changes depending on the source voltage applied to the data line 18.

The source driver 13A converts the digital control signal output from the signal processing unit 14 into an analog signal to generate a source voltage corresponding to the gradation value of the image data (e.g., 0 to 255 gradations), and supplies the source voltage to the pixels 20 of the display unit 11 through the data lines 18. Furthermore, the source driver 13A converts the digital control signal output from the signal processing unit 14 into an analog signal to generate a voltage for turning on the LEDs corresponding to the gradation value of the image data, and applies the voltage to the LEDs of the backlight 12 through the signal lines 16.

The gate driver 13B generates a scanning signal for display in response to a control signal output from the signal processing unit 14, and outputs the generated scanning signal to the scanning line 17. In local dimming control, the division of the pixel block in the pixel column direction onto which light from the LEDs of the backlight 12 is irradiated is determined based on the voltage signal that the gate driver 13B applies to the scanning line 17.

The signal processing unit 14 displays an image on the display unit 11 based on image data input from the image output unit 15. The signal processing unit 14 also applies a voltage from the display driver 13 to the light source of the backlight 12 through a signal line 16, thereby controlling the lighting of the light source of the backlight 12 determined based on the input image data. The image output unit 15 outputs image data stored in a storage device (not shown) or image data from an external device (not shown) to the signal processing unit 14.

For example, the signal processing unit 14 analyzes the luminance of the image shown by the input image data for each display area of the display unit 11, and determines the area of the LEDs of the backlight 12 that illuminates the display area. The signal processing unit 14 sets the maximum gradation in the display area to the luminance of the area of the LEDs of the backlight 12 that illuminates the display area. This improves the contrast ratio of the image displayed on the display unit 11. Furthermore, when the display area contains many low-gradation pixels, the LEDs of the backlight 12 may set the luminance of the area of the LEDs of the backlight 12 that illuminates the display area low, and when the display area contains many high-gradation pixels, the luminance of the area of the LEDs of the backlight 12 that illuminates the display area high.

Figure 3 is a block diagram showing the functional configuration of the display device 1. As shown in Figure 3, the signal processing unit 14 includes an image processing unit 141 and a timing control unit 142. The image processing unit 141 performs gamma correction on the image data output from the image output unit 15, and outputs the gamma-corrected image data to the timing control unit 142. Gamma correction is a process of correcting the brightness of the image represented by the input image data so that it has a linear relationship.

The timing control unit 142 controls the timing of synchronizing the operation of displaying the gamma-corrected image data on the display unit 11 with the turning on and off of the LEDs of the backlight 12. For example, the timing control unit 142 transmits a synchronization signal to the source driver 13A and the gate driver 13B for synchronizing the timing of the display of the gamma-corrected image data with the turning on of the LEDs. The pixel column direction of a pixel block illuminated by one LED in the backlight 12 is divided by the number of scanning lines 17 to which the gate driver 13B applies a gate voltage, and the pixel row direction is divided by the number of data lines 18 to which the source driver 13A applies a source voltage.

FIG. 4 is a flowchart showing a display method according to the first embodiment.
The image processing unit 141 included in the signal processing unit 14 inputs image data from the image output unit 15 and performs gamma correction on the image represented by the input image data (step ST1). The image processing unit 141 then converts the gamma-corrected image data into analog data. The image processing unit 141 determines a display voltage for displaying the image represented by the image data after analog conversion on the display unit 11 and a voltage for lighting the LEDs of the backlight 12 for illuminating the image displayed on the display unit 11 (step ST2).

In local dimming control, the image processing unit 141 needs to change the brightness of the LEDs in each area of the backlight 12 according to the brightness of the image represented by the input image data. In conventional local dimming control, LED brightness information in an area in the backlight 12 corresponding to the image is calculated according to the brightness of the image represented by the image data after analog conversion, and a dedicated LED control circuit changes the emission brightness of the LEDs in each area in the backlight 12 according to the LED brightness information.

As such, conventional display devices that perform local dimming control have the problem of larger circuit scale compared to display devices that do not perform local dimming, since a dedicated LED control circuit is required. In contrast, display device 1 does not require a dedicated LED control circuit by lighting the LEDs of backlight 12 using the lighting voltage from display driver 13. This prevents the display device 1 from increasing the circuit scale due to performing local dimming control.

Figure 5 is an explanatory diagram showing the relationship between the source driver 13A and the backlight 12. As shown in Figure 5, the source driver 13A has a plurality of lines 18A connected to the data lines 18 of the display unit 11, as well as signal lines 16A to 16C for turning on the LEDs 121 of the backlight 12. For example, the display unit 11 is a liquid crystal display with full high-definition (FHD) resolution (1920x1080xRGB 3 colors), and the total number of LEDs 121 of the backlight 12 is 384 in total, with 12 in the vertical direction and 32 in the horizontal direction of the backlight 12.

When the display unit 11 has FHD resolution, the pixel block illuminated by light from one LED 121 of the backlight 12 has 90 pixels (=1080/12) in the pixel column direction. The image processing unit 141 calculates the pixel block size A in the pixel column direction shown in FIG. 5 by dividing the gate voltage signal output by the gate driver 13B every 90 clocks. In this way, even without providing a dedicated LED control circuit, the image processing unit 141 can determine the division in the pixel column direction of the pixel block illuminated by light from one LED 121 of the backlight 12.

In addition, when the display unit 11 has FHD resolution, the pixel block illuminated by light from one LED 121 of the backlight 12 has 180 pixels in the pixel row direction (=1920xRGB3 colors/32 pixels). The image processing unit 141 calculates the pixel block size B in the pixel row direction shown in FIG. 5 by dividing the multiple lines 18A connected to the multiple data lines 18 of the display unit 11 into 180 lines in the source driver 13A. In this way, even without providing a dedicated LED control circuit, the image processing unit 141 can determine the division in the pixel row direction of the pixel block illuminated by light from one LED 121 of the backlight 12. Note that the resolution of the display unit 11 and the total number of LEDs or the number of lights in the vertical and horizontal directions of the backlight 12 are examples.

The source driver 13A selects the maximum source voltage (peak voltage) within pixel block 131A of size A in the pixel column direction and size B in the pixel row direction among the source voltages applied to 180 data lines 18, and determines the selected source voltage as the LED lighting voltage. The LED lighting voltage is output to signal lines 16A to 16C and applied to the anode terminal of LED 121. The LED lighting voltage is determined similarly in pixel blocks 131B and 131C.

For example, the maximum source voltage in pixel block 131A is applied as a lighting voltage to LED 121A through signal line 16A. The maximum source voltage in pixel block 131B is applied as a lighting voltage to LED 121B through signal line 16B. The maximum source voltage in pixel block 131C is applied as a lighting voltage to LED 121C through signal line 16C.

In addition, in conventional local dimming, a dedicated LED control circuit controls the current i and duty ratio flowing through the LEDs of the backlight 12 to light up the LEDs. In contrast, the display device 1 lights up the LEDs by controlling only the voltage applied to the anode terminals of the LEDs. Figure 6 is a circuit diagram showing the LEDs 121 in the backlight 12. A signal line 16 from the source driver 13A is connected to the anode terminal of the LED 121 via a resistor R. A current i flows through the LED 121 due to the lighting voltage Vp applied to the signal line 16 and the resistor R, and the current i is adjusted by controlling the lighting voltage Vp.

7 is a table showing the relationship between the source voltage Vp and the light emission luminance of the LED 121. The image processing unit 141 calculates the light emission luminance of the LED 121 corresponding to the source voltage Vp for each gradation of the image represented by the input image data. Note that the relationship between the light emission luminance of the LED and the current i flowing through the LED is usually proportional, but there may be cases where a deviation in characteristics occurs. Hereinafter, it is assumed that the light emission luminance of the LED and the current i flowing through the LED are proportional, and even if a deviation occurs in the characteristics of the two, there is no effect on the image quality of the image subjected to local dimming control.
Generally, there are two types of source voltages, a positive voltage and a negative voltage with respect to the common (COM). Since the source voltage Vp must exceed the lighting voltage Vf required to light the LED 121, it must be a positive voltage.

For example, if the lighting voltage Vf required to light the LED 121 is 6.0 (V) and the maximum current i flowing through the LED 121 is 100 (mA), the image processing unit 141 subtracts the lighting voltage Vf from the source voltage Vp to calculate the subtracted value (Vp-Vf) (V). Next, the image processing unit 141 calculates the current i (mA) flowing through the LED 121 using the formula (Vp-Vf)÷resistance (Ω). Furthermore, the image processing unit 141 calculates the brightness (%) of the LED 121 using the formula: current i flowing through the LED 121÷maximum current.

When the resistance R shown in FIG. 6 is 55.0 (Ω), the relationship between the source voltage Vp and the LED emission luminance when the gradation is "white" is as shown in FIG. 7, where Vp=11.5 (V), (Vp-Vf)=5.5 (V), current i=100 (mA), and the LED emission luminance is 100 (%). When the gradation is "gray" (128/255), the relationship between the source voltage Vp and the LED emission luminance is Vp=8.5 (V), (Vp-Vf)=2.5 (V), current i=45.5 (mA), and the LED emission luminance is 45.5 (%). When the gradation is "black", the relationship between the source voltage Vp and the LED emission luminance is Vp=6.0 (V), (Vp-Vf)=0 (V), current i=0 (mA), and the LED emission luminance is 0 (%).
Note that this relationship between the source voltage Vp and the light emission brightness of the LED is just an example.

Returning to the explanation of FIG.
When the display voltage and the LED lighting voltage are determined, the image processing unit 141 judges whether the gamma curve of the image to be displayed on the display unit 11 matches the target gamma curve (ideal gamma curve) (step ST3). FIG. 8 is a graph showing the relationship between the gradation and the source voltage Vp. Up until now, it has been assumed that the source voltage Vp and the LED light emission luminance are proportional to each other, and the source voltage Vp and the LED lighting voltage are the same value. However, in reality, as is clear from the curve C1 in FIG. 8, the intermediate gradation range is proportional, but the low gradation range and the high gradation range are not proportional to each other. Therefore, if the gamma curve of the image is determined assuming that the gradation and the source voltage are proportional to each other, the gamma curve will deviate from the ideal gamma curve.

Therefore, if the gamma curve of the image does not match the target gamma curve (step ST3; NO), the image processing unit 141 returns to step ST1 and changes the voltage from the source driver 13A. For example, the image processing unit 141 performs normal gamma correction on the input image data, multiplies the gamma curve of the corrected image by a correction coefficient, and sets the gradation value multiplied by the correction coefficient as the gamma parameter. When the gamma parameter is set to "1", the correction coefficient "1" is multiplied at gradation 0 and gradation 255, and the correction coefficient is increased as the gradation becomes intermediate, and gradually decreased as the gradation moves to the high gradation range.

Figure 9 is a graph showing the relationship between the gradation and the corrected source voltage Vp. In Figure 9, when the relationship between the gradation of the image to be displayed on the display unit 11 and the source voltage Vp is shown as curve C1, multiplying the source voltage Vp by a correction coefficient for each gradation results in the relationship shown as curve C2, in which the source voltage Vp in the intermediate gradation range is higher.

Fig. 10 is a graph showing gamma curves. In Fig. 10, gamma curve D2 is a gamma curve obtained before the above-mentioned correction is performed on the image displayed on the display unit 11. The source driver 13A applies a source voltage Vp to the LEDs of the backlight 12 to light them up, performing local dimming, and the relationship between the gradation and the source voltage Vp is shown by curve C1 in Fig. 8. In curve C1, the source voltage Vp in the middle gradation range is not in a proportional relationship. For this reason, in gamma curve D2, the luminance in the middle gradation range is greatly depressed.
In an image with a gamma curve of D2, the intermediate gradations become darker than the black image definition achieved by local dimming, and the image cannot be viewed as a clear image.

Gamma curve D3 is a gamma curve that shows the ideal relationship between gradation and brightness. Gamma curve D1 is a gamma curve that corrects the relationship between the above-mentioned gradation and source voltage Vp for the image displayed on the display unit 11. As shown in FIG. 10, the correction coefficient is determined so that the ratio of brightness to each gradation is the same between gamma curve C1 and gamma curve C3. As a result, even when performing local dimming in which source voltage Vp is applied to the LEDs of the backlight 12 to light them up, an image can be displayed on the display unit 11 with the same relationship between hierarchy and brightness as the ideal gamma curve C3.

Note that the case where the relationship between the gradation and the source voltage Vp is corrected for each gradation (a process in which the source voltage Vp for each gradation is multiplied by a correction coefficient) is shown. However, it is not necessary to perform correction for all gradations; correction is performed every few gradations, and the relationship between the gradation and brightness between gradations where the source voltage Vp is not changed may be linearly interpolated. For example, it is estimated that the source voltage Vp changes linearly between gradations that are not multiplied by a correction coefficient. In this way, it is possible to correct the relationship between the gradation and the source voltage Vp.

In addition, in the above correction, the source voltage Vp applied to the LED of the backlight 12 may be multiplied by a correction coefficient, or the display source voltage applied to the data line 18 of the display unit 11 may be multiplied by a correction coefficient.

When the gamma curve of the image matches the target gamma curve (step ST3; YES), the timing control unit 142 outputs a timing control signal to the display driver 13, so that the display voltage from the source driver 13A is applied to the data line 18 and the lighting voltage is applied to the LEDs of the backlight 12 (step ST4). As a result, the operation of displaying the image represented by the corrected image data on the display unit 11 and the turning on and off of the LEDs of the backlight 12 are performed in synchronization.

The functions of the image processing unit 141 and timing control unit 142 in the signal processing unit 14 are realized by a processing circuit. That is, the signal processing unit 14 has a processing circuit for executing the processes of steps ST1 to ST4 shown in Figure 4. The processing circuit may be dedicated hardware, or may be a CPU that executes a program stored in a memory.

Figure 11A is a block diagram showing a hardware configuration that realizes the functions of the signal processing unit 14. Figure 11B is a block diagram showing a hardware configuration that executes software that realizes the functions of the signal processing unit 14. In Figures 11A and 11B, the input interface 100 is an interface that relays image data output from the image output unit 15 to the image processing unit 141. The output interface 101 is an interface that relays a control signal output from the timing control unit 142 to the display driver 13.

When the processing circuit is the dedicated hardware processing circuit 102 shown in Fig. 11A, the processing circuit 102 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination of these. The functions of the image processing unit 141 and the timing control unit 142 in the signal processing unit 14 may be realized by separate processing circuits, or these functions may be realized together by a single processing circuit.

When the processing circuit is the processor 103 shown in FIG. 11B, the functions of the image processing unit 141 and the timing control unit 142 in the signal processing unit 14 are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 104.

The processor 103 realizes the functions of the image processing unit 141 and timing control unit 142 in the signal processing unit 14 by reading and executing programs stored in the memory 104. For example, the signal processing unit 14 includes a memory 104 for storing a program that, when executed by the processor 103, results in the processing of steps ST1 to ST4 shown in FIG. 4 being executed. These programs cause the computer to execute the procedures or methods of the processing performed by the image processing unit 141 and timing control unit 142.

The memory 104 may be a computer-readable storage medium that stores a program for causing a computer to function as the image processing unit 141 and the timing control unit 142. The memory 104 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, or an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD.

Some of the functions of the image processing unit 141 and timing control unit 142 in the signal processing unit 14 may be realized by dedicated hardware, and some by software or firmware. For example, the image processing unit 141 may realize its functions by the processing circuit 102, which is dedicated hardware, and the timing control unit 142 may realize its functions by the processor 103 reading and executing a program stored in the memory 104. In this way, the processing circuit can realize the above functions by hardware, software, firmware, or a combination of these.

As described above, in the display device 1 according to the first embodiment, the signal processing unit 14 applies the lighting signal output from the display driver 13 to the LEDs 121 of the backlight 12 via the signal line 16, thereby controlling the lighting of the LEDs 121 determined based on the input image data. This allows the display device 1 to perform local dimming without providing a control circuit dedicated to the backlight.

In the display device 1 according to the first embodiment, the display unit 11 has a plurality of pixels 20 arranged in a matrix, a plurality of scanning lines 17 provided for each pixel row of the plurality of pixels 20 for selecting a pixel row to which a gate voltage is applied, and a plurality of data lines 18 provided for each pixel column of the plurality of pixels 20 for applying a source voltage to the pixels of the selected pixel row. The display driver 13 has a source driver 13A that applies a source voltage to the plurality of data lines 18, and a gate driver 13B that applies a gate voltage to the plurality of scanning lines 17. The signal line 16 connects the source driver 13A and the LED 121 of the backlight 12. The signal processing unit 14 applies the source voltage output from the source driver 13A to the LED 121 of the backlight 12 through the signal line 16. This allows the display device 1 to perform local dimming without providing a control circuit dedicated to the backlight.

In the display device 1 according to the first embodiment, the signal processing unit 14 changes the source voltage output from the source driver 13A so that the gamma curve of the image displayed on the display unit 11 matches the target gamma curve. This allows the gamma curve of the image displayed on the display unit 11 to be corrected to the target gamma curve.

In the display device 1 according to the first embodiment, the signal processing unit 14 changes the source voltage output from the source driver 13A for each gradation of the image to be displayed on the display unit 11. This allows the gamma curve of the image to be displayed on the display unit 11 to be corrected to a target gamma curve.

In the display device 1 according to the first embodiment, the signal processing unit 14 changes the source voltage output from the source driver 13A every few gradations of the image to be displayed on the display unit 11, and linearly interpolates the relationship between the gradation and brightness between gradations where the source voltage is not changed. This allows the gamma curve of the image to be displayed on the display unit 11 to be corrected to the target gamma curve.

In the display device 1 according to the first embodiment, the signal processing unit 14 determines the division of the pixel blocks in the pixel column direction to be illuminated by the light from the LEDs 121 based on the gate voltage signal applied from the gate driver 13B to the scanning line 17. This makes it possible to determine the pixel blocks to be illuminated by local dimming.

In the display device 1 according to the first embodiment, the LED 121 in the backlight 12 has a cathode terminal that is grounded, and a signal line 16 that is connected to an anode terminal via a resistor.
Even without providing a dedicated LED control circuit, the LED 121 can be turned on by the source voltage output from the source driver 13A.

In addition, any of the components of the embodiments may be modified or omitted.

The display device of the present disclosure can be used, for example, as a display device for in-vehicle equipment.

1 Display device, 11 Display section, 12 Backlight, 13 Display driver, 13A Source driver, 13B Gate driver, 14 Signal processing section, 15 Image output section, 16, 16A to 16C Signal lines, 17 Scanning lines, 18 Data lines, 18A Lines, 19 TFTs, 20 Pixels, 100 Input interface, 101 Output interface, 102 Processing circuit, 103 Processor, 104 Memory, 121, 121A to 121C LEDs, 131A to 131C Pixel blocks, 141 Image processing section, 142 Timing control section.

Claims (4)

A display unit;
a backlight having a plurality of light sources and illuminating the display unit with light from the light sources;
A display driver that drives the display unit;
a signal processing unit that displays an image on the display unit based on input image data;
A display device comprising:
a signal line connecting the display driver and the light source of the backlight;
the signal processing unit applies a voltage from the display driver through the signal line to the light source of the backlight, thereby controlling lighting of the light source determined based on input image data;
the display unit includes a plurality of pixels arranged in a matrix, a plurality of scanning lines provided for each pixel row of the plurality of pixels and for selecting a pixel row to which a voltage is applied, and a plurality of data lines provided for each pixel column of the plurality of pixels and for applying a voltage to pixels of the selected pixel row;
the display driver includes a source driver that applies a voltage to the plurality of data lines and a gate driver that applies a voltage to the plurality of scanning lines;
the signal line connects the source driver and the light source of the backlight;
the signal processing unit applies a voltage from the source driver to the light source of the backlight through the signal line;
the light source in the backlight is a light emitting diode;
The display device according to claim 1, wherein a cathode terminal of the light-emitting diode is grounded, and the signal line is connected to an anode terminal of the light-emitting diode via a resistor. 2 . The display device according to claim 1 , wherein the signal processing unit changes the voltage from the source driver so that a gamma curve of an image to be displayed on the display unit coincides with a target gamma curve. The display device according to claim 2 , wherein the signal processing unit changes the voltage from the source driver for each gradation of an image to be displayed on the display unit. 3. The display device according to claim 2, wherein the signal processing unit changes the voltage from the source driver every few gradations of the image to be displayed on the display unit, and linearly interpolates the relationship between gradations and brightness between gradations for which the voltage from the source driver is not changed .

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