JP5926977B2 - Image display device, brightness setting method, program, and computer-readable recording medium - Google Patents

Description

  The present invention relates to an image display device including a backlight and capable of setting the brightness of a display screen, a brightness setting method in the image display device, a program, and a computer-readable recording medium.

  FIG. 4 is a block diagram showing a configuration of a liquid crystal display device 100 according to the prior art. In the liquid crystal display device 100, when a video signal is input from the outside, predetermined processing is performed on the video signal on a main I / F board (hereinafter referred to as “main control board”) 101, and the processed video signal is An LED-TCON (Light Emitting Diode-Timing Controller) substrate 102 is input.

  The LED-TCON board 102 generates an LCD (Liquid Crystal Display) control signal and an LED control signal based on the video signal input from the main control board 101, and transmits the LCD control signal to the LCD-TCON board 103. The LED control signal is transmitted to the LED driver board 104.

  The LCD-TCON board 103 controls the LCD panel 105 based on the LCD control signal transmitted from the LED-TCON board 102, and the LED driver board 104 is based on the LED control signal transmitted from the LED-TCON board 102. Thus, the backlight 106 composed of a plurality of light emitting diodes (hereinafter referred to as “LEDs”) is controlled. As a result, an image is displayed on the display surface of the LCD panel 105.

  Conventionally, an image display device such as the liquid crystal display device 100 has a function that allows a user to freely change the setting (brightness) of the display screen. The brightness setting is divided into, for example, 32 stages, and the user can change the setting to a desired brightness by operating a remote control device (hereinafter abbreviated as “remote controller”) or the like.

  The main control board 101 includes a setting value storage area for storing information indicating the brightness setting value. As shown in FIG. 4, the brightness for notifying the brightness setting value stored in the setting value storage area. The setting notification signal is constantly transmitted to the LED-TCON substrate 102 while the liquid crystal display device 100 is in operation. The LED-TCON board 102 generates an LED control signal based on the brightness setting notification signal transmitted from the main control board 101 so that the backlight 106 is turned on with the set brightness.

  Conventionally, as the brightness setting notification signal, the PWM (Pulse Width Modulation) signal has been used for the reason that the number of signal lines can be reduced and communication is possible with a simple procedure. The board 101 generates a PWM signal having a duty ratio corresponding to the brightness setting value stored in the setting value storage area, and transmits the PWM signal to the LED-TCON board 102 as a brightness setting notification signal. The brightness setting value stored in the setting value storage area is appropriately changed by a user's remote control operation. When the setting value is changed, the main control board 101 changes the duty ratio corresponding to the changed setting value. Is transmitted to the LED-TCON board 102 as a brightness setting notification signal.

  On the other hand, in the LED-TCON board 102, the PWM signal transmitted from the main control board 101 is sampled at a predetermined number of resolutions (for example, 1024) per cycle, and brightness is increased by, for example, the number of samplings at a high (H) level. And the backlight 106 is turned on.

  5A and 5B are diagrams illustrating how the PWM signal is sampled on the LED-TCON substrate 102. FIG. 5A illustrates a state in which sampling is performed normally, and FIG. 5B illustrates the sampling timing. FIG. 5C shows the case where jitter occurs in the brightness setting notification signal.

  In the liquid crystal display device 100 according to the prior art, the main control board 101 and the LED-TCON board 102 are not configured to synchronize timing between modules, and the LED-TCON board 102 performs sampling with the internal clock of the CPU. Has been done. For this reason, as shown in FIG. 5B, a deviation occurs in the sampling timing, and an error occurs in the number of high-level samplings. Further, even when jitter occurs in the brightness setting notification signal or noise occurs, an error occurs in the number of high-level samplings as shown in FIG.

  As described above, when an error occurs in the number of samplings, the brightness setting when the backlight 106 is turned on undesirably fluctuates during operation of the liquid crystal display device 100, thereby causing the display screen to flicker. There is a problem of end up.

  As a method for solving such a problem, for example, a method of increasing the resolution per cycle when sampling the PWM signal, or a method of completely synchronizing the main control board 101 and the LED-TCON board 102 between the modules can be considered. .

  However, in the case of the method for increasing the resolution, it is necessary to improve the operation speed of a CPU (Central Processing Unit) in the LED-TCON substrate 102, which leads to an increase in cost of the entire liquid crystal display device 100. On the other hand, in the case of a method of completely synchronizing between modules, there is a problem that additional wiring and additional circuits are required separately.

  For example, Patent Document 1 discloses a technique in which a time interval during sampling is not constant when sampling an input signal input to an I / O circuit of a display unit. Periodic noise such as generated noise is effectively removed to prevent malfunction of the circuit. However, as described above, when the main control board 101 and the LED-TCON board 102 are not configured to synchronize timing between modules, the occurrence of display screen flickering due to an error in the number of samplings is prevented. The technology for doing this is not disclosed.

JP 2001-282198 A

  An object of the present invention is to provide an image display device, a brightness setting method, a program, and a computer-readable recording medium that can prevent flickering on a display screen based on an error in the number of samplings without increasing the device cost. Is to provide.

The present invention includes a display panel having a display screen capable of setting brightness,
A backlight having a light source capable of adjusting brightness and irradiating the display panel with light;
A set value storage unit for storing a set value of brightness of the display screen;
A brightness setting notification unit for generating and transmitting a pulse width modulation signal having a duty ratio corresponding to the brightness setting value stored in the setting value storage unit;
The pulse width modulation signal transmitted by the brightness setting notification unit is sampled at a predetermined resolution per cycle, and a number detection unit that detects the number of sampling times of a predetermined signal level per cycle;
A number storage unit for storing the number of samplings;
A luminance adjusting unit that adjusts the luminance of the light source based on the number of samplings stored in the number storage unit;
The number detection unit calculates a difference between the detected sampling number and the sampling number stored in the number storage unit, and when the calculated absolute value of the difference is equal to or greater than a predetermined threshold, the number storage unit The number of samplings stored in is updated to the detected number of samplings, and when the calculated absolute value of the difference is less than a predetermined threshold, the number of samplings stored in the number storage unit is maintained. An image display device.

  Further, the present invention is characterized in that the predetermined threshold is 1% of the predetermined resolution.

The present invention also relates to a brightness setting method in an image display apparatus, comprising: a display panel having a display screen capable of setting brightness; and a backlight that includes a light source capable of adjusting brightness and irradiates light on the display panel. Because
A transmission step of generating and transmitting a pulse width modulation signal having a duty ratio corresponding to a setting value of brightness of the display screen;
The pulse width modulation signal transmitted in the transmission step is sampled at a predetermined resolution per cycle, and the number of times detection step of detecting the number of sampling of a predetermined signal level per cycle;
Number of times storage step of storing the number of times of sampling in the number of times storage unit,
A luminance adjustment step of adjusting the luminance of the light source based on the number of samplings stored by the number of times storage step,
The number detection step calculates a difference between the detected sampling number and the sampling number stored in the number storage unit, and the absolute value of the calculated difference is equal to or greater than a predetermined threshold value, the number storage unit The number of samplings stored in is updated to the detected number of samplings, and when the calculated absolute value of the difference is less than a predetermined threshold, the number of samplings stored in the number storage unit is maintained. This is a brightness setting method.

  Further, the present invention is characterized in that the predetermined threshold is 1% of the predetermined resolution.

The present invention also provides a computer.
Receives a pulse width modulation signal with a duty ratio corresponding to the brightness setting value of the display screen that can set the brightness, samples the received pulse width modulation signal with a predetermined resolution per cycle, and per cycle Is a number detection procedure for detecting the number of samplings at a predetermined signal level, and calculates a difference between the number of samplings stored in a number storage unit for storing the number of samplings and the number of detected samplings, When the absolute value is greater than or equal to a predetermined threshold, the number of samplings stored in the number storage unit is updated to the detected number of samplings, and when the calculated absolute value of the difference is less than a predetermined threshold, the number of times The number detection procedure for maintaining the number of samplings stored in the storage unit ,
A program for executing a brightness adjustment procedure for adjusting the brightness of a light source based on the number of samplings stored in the number storage unit.

According to the present invention, the number detection unit calculates a difference between the detected sampling number and the sampling number stored in the number storage unit, and when the absolute value of the calculated difference is equal to or greater than a predetermined threshold value, The sampling number stored in the number storage unit is updated to the detected sampling number, and when the calculated absolute value of the difference is less than a predetermined threshold, the sampling number stored in the number storage unit is maintained. Has been.

  Therefore, the module provided with the brightness setting notification unit for transmitting the pulse width modulation signal and the module provided with the number detection unit for receiving the pulse width modulation signal are not synchronized, thereby causing a deviation in the sampling timing. If there is an error in the number of samplings, or if there is jitter in the brightness setting notification signal, the brightness setting will fluctuate even though the brightness setting change command is not issued by the user. It is possible to prevent the problem of being lost. Thereby, it is possible to prevent the brightness setting from fluctuating within a minute range, and it is possible to prevent the occurrence of flickering on the display screen due to the error in the number of samplings.

It is a block diagram which shows the structure of the liquid crystal display device 10 which concerns on one Embodiment of this invention. It is a figure which shows an example of the PWM signal produced | generated by the video signal processing board | substrate 13. FIG. It is a flowchart which shows the process sequence of the brightness setting method which concerns on this embodiment. It is a block diagram which shows the structure of the liquid crystal display device 100 which concerns on a prior art. FIG. 5A is a diagram illustrating a state of sampling of a PWM signal in the LED-TCON substrate 102, FIG. 5A illustrates a state in which sampling is normally performed, and FIG. 5B illustrates a deviation in sampling timing. FIG. 5C shows a case where jitter occurs in the brightness setting notification signal.

  FIG. 1 is a block diagram showing a configuration of a liquid crystal display device 10 according to an embodiment of the present invention. The liquid crystal display device 10 includes an LCD (Liquid Crystal Display) panel 11 having a display screen, a light source capable of adjusting brightness, a backlight 12 that irradiates light to the LCD panel 11, and an external device. A video signal processing board 13 that performs predetermined processing on the video signal, and a liquid crystal panel control board that controls driving of the LCD panel 11 and the backlight 12 so that an image based on the video signal is displayed on the display screen of the LCD panel 11. 14.

  The liquid crystal display device 10 according to the present embodiment includes a function that allows the user to freely change the setting (brightness) of the display screen. The brightness setting is divided into 32 steps in this embodiment, and the user operates a remote control device attached to the liquid crystal display device 10 (hereinafter abbreviated as “remote control”) or the like. The setting can be changed to a desired brightness. In another embodiment, the brightness setting may be a number of sections different from 32 levels, for example, 60 levels.

  The LCD panel 11 has a liquid crystal layer and two glass substrates. One glass substrate is formed by laminating a color filter, a transparent electrode, and an alignment film on the surface on one side in the thickness direction, and the other glass substrate. Is formed by laminating a transparent electrode for forming an alignment film and pixels and a thin film transistor connected thereto on the surface on one side in the thickness direction. The LCD panel 11 is configured by enclosing a liquid crystal between two glass substrates arranged so that the alignment films face each other and forming a liquid crystal layer.

  The backlight 12 is disposed so as to face the back side of the LCD panel, that is, the surface on the other side in the thickness direction of the other glass substrate, and from the back side with respect to the LCD panel 11 by light emitted from the light source. Has the function of irradiating light. In the present embodiment, the light source is configured by arranging a plurality of light emitting diodes (hereinafter referred to as “LEDs”) in a planar manner, for example, in a matrix.

  The video signal processing board 13 includes a central processing unit (hereinafter referred to as “CPU”) 21, a read only memory (hereinafter referred to as “ROM”) 22, and a random access memory (hereinafter referred to as “Random Access Memory”). (Referred to as “RAM”) 23.

  The CPU 21 executes a program stored in the ROM 22, performs predetermined processing such as gamma correction processing on the video signal input to the video signal processing board 13, and transmits the video signal to the subsequent liquid crystal panel control board 14. .

  The ROM 22 stores a program executed by the CPU 21 and information for initial setting, and is configured by a nonvolatile rewritable semiconductor memory such as a flash memory. The RAM 23 is composed of a rewritable semiconductor memory such as a static random access memory (hereinafter referred to as “SRAM”). The RAM 23 stores information necessary for the CPU 21 to execute the program.

  The video signal processing board 13 has a set value storage unit for storing the set value of the brightness of the display screen. This set value storage unit is realized by, for example, a register of the RAM 23 or the CPU 21. The ROM 22 is provided with a set value holding area for holding a set value of brightness of the display screen.

  When the liquid crystal display device 1 is activated, the CPU 21 executes a program stored in the ROM 22 to read the brightness setting value from the setting value holding area, store the read value in the setting value storage unit, and set the setting value. A pulse width modulation (hereinafter referred to as “PWM”) signal having a duty ratio D corresponding to the brightness setting value stored in the storage unit is generated and transmitted to the subsequent liquid crystal panel control board 14. . That is, the CPU 21 functions as a brightness setting notification unit. This PWM signal is constantly transmitted from the video signal processing board 13 to the liquid crystal panel control board 14 while the liquid crystal display device 1 is in operation.

  FIG. 2 is a diagram illustrating an example of a PWM signal generated by the video signal processing board 13. In the present embodiment, it is assumed that the duty ratio D indicates a ratio (%) of a period τ in which the signal level is high (H) level with respect to one period T of the PWM signal. The duty ratio D is set so as to increase or decrease in proportion to the brightness setting value stored in the setting value storage unit. For example, the brightness setting value is divided into 32 levels of 1 to 32. In this case, when the set value is 32, a PWM signal with a duty ratio D = 100% is generated, when the set value is 16, a PWM signal with a duty ratio D = 50% is generated, and when the set value is 15, the duty ratio D = about 47%. When the set value is 1, a PWM signal having a duty ratio D = 0% is generated. That is, when the brightness setting value changes by one step, the duty ratio D of the PWM signal changes by about 3%. Based on the duty ratio D of the PWM signal, the liquid crystal panel control board 14 is notified of what percentage of the maximum output the light source constituting the backlight 12 is turned on.

  Also, a change command for changing the brightness setting value is input to the video signal processing board 13 by the user operating a remote controller or the like. When the change command is input, the CPU 21 updates the brightness setting value stored in the setting value storage unit to the setting value designated by the user, and corresponds to the updated brightness setting value. The PWM signal having the duty ratio D is generated and transmitted to the liquid crystal panel control board 14. The brightness setting value stored in the setting value storage unit is stored in the holding area when the liquid crystal display device 1 is terminated, for example, and is read again when the liquid crystal display device 1 is activated.

  The liquid crystal panel control board 14 includes a sub CPU 31, a TCON (Timing Controller) 32, a ROM 33, and a RAM 34. Note that the video signal processing board 13 and the liquid crystal panel control board 14 are not configured to operate synchronously.

  The sub CPU 31 executes a program stored in the ROM 33 and cooperates with the TCON 32 to control the LCD panel 11 based on the video signal transmitted from the video signal processing board 13. A signal is generated, the LCD control signal is transmitted to the LCD panel 11, an LED control signal for controlling the driving of the backlight 12 is generated, and the LED control signal is transmitted to the backlight 12.

  The LCD panel 11 controls the light transmittance of the sub-pixels according to the image to be displayed based on the LCD control signal transmitted from the liquid crystal panel control board 14, while the backlight 12 has the liquid crystal panel control board 14. The luminance of the light source is controlled based on the LCD control signal transmitted from. As a result, an image to be displayed is displayed on the display screen of the LCD panel 11. In the present embodiment, the backlight is configured such that the brightness can be adjusted for each divided region obtained by dividing the display screen of the LCD panel 11 into a plurality of regions, that is, local dimming control is possible.

  The ROM 33 stores a program executed by the sub CPU 31 and information for initial setting, and is configured by a nonvolatile rewritable semiconductor memory such as a flash memory, for example. The RAM 34 is configured by a rewritable semiconductor memory such as an SRAM. The RAM 34 stores information necessary for the sub CPU 31 to execute the program.

  The sub CPU 31 of the liquid crystal panel control board 14 executes a program stored in the ROM 33 to sample the PWM signal transmitted from the video signal processing board 13 with a predetermined resolution per period, Detects the number of samplings at a specified signal level. That is, the sub CPU 31 functions as a number detection unit.

  Specifically, the sub CPU 31 samples the PWM signal transmitted from the video signal processing board 13 for example 1024 times per cycle of the PWM signal according to the clock signal of 20 MHz generated by the clock generation circuit, for example. It operates so as to detect the number of high-level samplings for each period of the PWM signal. The number of times of sampling, that is, the resolution is an example, and the number of times of sampling may be different from the above. The signal level to be sampled is high in the above description, but may be low (L).

  In the present embodiment, the liquid crystal panel control board 14 includes a temporary storage unit in which the number of samplings detected by sampling as described above is sequentially updated and stored for each cycle of the PWM signal, and the sub CPU 31 receives the LED control signal. A number-of-times storage unit that stores the number of times of sampling used for generation. The temporary storage unit and the number of times storage unit are realized by, for example, the RAM 34 or the register of the sub CPU 31.

  When the sub CPU 31 detects the high level sampling count in the PWM signal, the sub CPU 31 updates the sampling count stored in the temporary storage unit to the sampling count detected immediately before and stores the updated sampling count and the count storage unit in the updated sampling count. Compare the number of samplings that have been made.

  Specifically, the sub CPU 31 calculates the difference between these two sampling times, and if the absolute value of the calculated difference is equal to or greater than a predetermined threshold Th, the sampling number stored in the number storage unit is Update to the updated sampling count. On the other hand, when the absolute value of the difference between the two sampling counts is less than the predetermined threshold Th, the sampling count stored in the count storage unit is maintained without being updated.

  Here, the predetermined threshold Th is a value that is sufficiently smaller than the number of high-level samplings that fluctuates when the brightness setting value fluctuates by one step, and the video signal processing board 13 and the liquid crystal panel control board 14. A fluctuation value from the normal number of sampling times due to the fact that the sampling frequency is not synchronized with and / or a value larger than a fluctuation value from the normal number of sampling times due to noise or jitter occurring in the PWM signal Selected. The regular number is the number of times of sampling determined in advance for each set value of brightness, and is a value obtained by multiplying the number of times of sampling (resolution) per one period of the PWM signal by the duty ratio.

  For example, in this embodiment, when the set value is changed by one step, the duty ratio D of the PWM signal fluctuates by about 3%, and accordingly, the high level sampling frequency is set to the sampling frequency (1024 times) per PWM signal cycle. ), Which is about 3 times that is 3%. Also, the sampling number may vary from the regular number by about 1 to 7 times due to the error factor of the sampling number as described above.

  Therefore, in the present embodiment, the predetermined threshold Th is a value sufficiently smaller than 30 and is set to a fluctuation value of the number of samplings when the duty ratio D of the PWM signal fluctuates by 1%, that is, Th = 10. Has been.

  Then, the sub CPU 31 generates an LED control signal for adjusting the luminance of the light source so that the brightness of the display screen becomes a brightness corresponding to the number of samplings stored in the number storage unit as described above.

  FIG. 3 is a flowchart showing a processing procedure of the brightness setting method according to the present embodiment. When the liquid crystal display device 1 is activated, the process of the brightness setting method is started, and the process proceeds to step s1.

  In step s1, the sub CPU 31 stores a default value of the number of samplings stored in the ROM 33 in advance in the number storage unit, and proceeds to step s2. In step s2, the sub CPU 31 generates an LED control signal for adjusting the luminance of the light source so that the brightness corresponds to the number of samplings stored in the number storage unit, and the process proceeds to step s3.

  In this embodiment, since the number of times of sampling per PWM signal cycle is 1024 times, an LED control signal for adjusting the brightness of the light source is generated based on a value obtained by the formula of maximum output of light source × number of sampling times ÷ 1024. Is done. Thereafter, the sub CPU 31 generates an LED control signal for adjusting the luminance of the light source so that the brightness corresponds to the default value of the sampling count until the sampling count stored in the count storage unit is updated.

  In step s3, the sub CPU 31 detects the number of high-level samplings in one cycle of the PWM signal transmitted from the video signal processing board 13, and proceeds to step s4. In step s4, the sub CPU 31 stores the number of samplings detected in step s3 in the temporary storage unit, and proceeds to step s5.

  In step s5, the sub CPU 31 calculates a difference between the number of samplings stored in the temporary storage unit and the number of samplings stored in the number storage unit or a default value, and the absolute value of the calculated difference is a predetermined threshold value. It is determined whether it is less than Th. If the absolute value is less than the predetermined threshold Th, the process returns to step s3, and the number of high-level samplings in the next cycle of the PWM signal is detected. On the other hand, if the absolute value of the PWM signal is greater than or equal to the predetermined threshold Th, the process proceeds to step s6.

  In step s6, the sub CPU 31 updates the number of samplings stored in the number storage unit to the number of samplings stored in the temporary storage unit, and proceeds to step s7. In step s7, the sub CPU 31 generates an LED control signal for adjusting the luminance of the light source so that the brightness corresponds to the number of samplings stored in the number storage unit, and the process returns to step s3.

  Thereafter, the sub CPU 31 generates an LED control signal for adjusting the luminance of the light source so that the brightness corresponds to the sampling number updated in step s6 until the sampling number stored in the number storage unit is updated. To do. Note that the processing of the brightness setting method shown in FIG. 3 is continuously performed until the liquid crystal display device 1 is finished.

As described above, according to the present embodiment, the number detection unit, for each period of the PWM signal, the number of samplings stored in the number storage unit and the high-level sampling number of the PWM signal one period detected immediately before. When the absolute value of the calculated difference is equal to or greater than a predetermined threshold Th , the sampling count stored in the count storage unit is updated to the sampling count detected immediately before, and the calculated When the absolute value of the difference is less than a predetermined threshold, the number of samplings stored in the number storage unit is maintained.

  Therefore, since the video signal processing board 13 that transmits the PWM signal and the liquid crystal panel control board that receives the PWM signal are not synchronized, the sampling timing is shifted and an error occurs in the number of samplings. In this case, even when jitter or noise occurs in the PWM signal, it is possible to prevent undesired fluctuations in the number of high-level samplings for each period of the PWM signal. Can be prevented from fluctuating within a minute range. Therefore, it is possible to prevent the display screen from flickering due to the sampling frequency error. Further, by executing the process of the brightness setting method as shown in FIG. 3 in software, an increase in manufacturing cost of the image display apparatus can be prevented.

  In the above-described embodiment, the program is stored in the ROM 33 of the liquid crystal panel control board 14, but is not limited to these storage devices, and may be recorded on a computer-readable recording medium. The recording medium may be a recording medium that can be read by providing a program reading device as an external storage device (not shown) and inserting the recording medium therein, or may be a storage device of another device. .

  Any recording medium may be used as long as the program stored in the recording medium is accessed from a computer and executed. In other words, any recording medium may be used as long as the program is read from the recording medium, the read program is stored in the program storage area of the storage device, and the program is executed. Further, it may be downloaded from another device via a communication network and stored in the program storage area. The download program is stored in advance in a storage device of a computer, or installed in a program storage area from another recording medium.

  The recording medium configured to be separable from the main body is, for example, a tape recording medium such as a magnetic tape / cassette tape, a magnetic recording disk such as a floppy (registered trademark) disk, or a magnetic disk such as a flexible disk / hard disk. Disc or CD-ROM (Compact Disk Read Only Memory) / MO (Magneto Optical disk) / MD (Mini Disk) / DVD (Digital Versatile Disk) disk-type recording medium, IC (Integrated Circuit) card (memory Card-type recording media such as optical cards, etc., or fixed programs including mask ROM / EPROM (Erasable Programmable Read Only Memory) / EEPROM (Electrically Erasable Programmable Read Only Memory) / semiconductor memory such as flash ROM May be a recording medium carrying the.

  The liquid crystal display device 1 may be configured to be connectable to a communication network, and the above program may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN (Integrated Services Digital Network), CATV (Community Antenna TeleVision) communication network, virtual private network, telephone line network. Mobile communication networks, satellite communication networks, etc. can be used. Also, the transmission medium constituting the communication network is not particularly limited. For example, IEEE (Institute of Electrical and Electronic Engineers) 1394, USB (Universal Serial Bus), power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital) Subscriber Line (IR), such as IrDA (Infrared Data Association) or remote control infrared, Bluetooth (registered trademark), 802.11 wireless, HDR (High Data Rate), mobile phone network, satellite line, terrestrial digital It can also be used wirelessly such as on the network. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 LCD panel 12 Backlight 13 Video signal processing board 14 Liquid crystal panel control board

Claims (6)

A display panel having a display screen capable of setting brightness;
A backlight having a light source capable of adjusting brightness and irradiating the display panel with light;
A set value storage unit for storing a set value of brightness of the display screen;
A brightness setting notification unit for generating and transmitting a pulse width modulation signal having a duty ratio corresponding to the brightness setting value stored in the setting value storage unit;
The pulse width modulation signal transmitted by the brightness setting notification unit is sampled at a predetermined resolution per cycle, and a number detection unit that detects the number of sampling times of a predetermined signal level per cycle;
A number storage unit for storing the number of samplings;
A luminance adjusting unit that adjusts the luminance of the light source based on the number of samplings stored in the number storage unit;
The number detection unit calculates a difference between the detected sampling number and the sampling number stored in the number storage unit, and when the calculated absolute value of the difference is equal to or greater than a predetermined threshold, the number storage unit The number of samplings stored in is updated to the detected number of samplings, and when the calculated absolute value of the difference is less than a predetermined threshold, the number of samplings stored in the number storage unit is maintained. Image display device.   The image display device according to claim 1, wherein the predetermined threshold is 1% of the predetermined resolution. A brightness setting method in an image display device comprising a display panel having a display screen capable of setting brightness, a light source capable of adjusting brightness, and a backlight for irradiating light to the display panel,
A transmission step of generating and transmitting a pulse width modulation signal having a duty ratio corresponding to a setting value of brightness of the display screen;
The pulse width modulation signal transmitted in the transmission step is sampled at a predetermined resolution per cycle, and the number of times detection step of detecting the number of sampling of a predetermined signal level per cycle;
Number of times storage step of storing the number of times of sampling in the number of times storage unit,
A luminance adjustment step of adjusting the luminance of the light source based on the number of samplings stored by the number of times storage step,
The number detection step calculates a difference between the detected sampling number and the sampling number stored in the number storage unit, and the absolute value of the calculated difference is equal to or greater than a predetermined threshold value, the number storage unit The number of samplings stored in is updated to the detected number of samplings, and when the calculated absolute value of the difference is less than a predetermined threshold, the number of samplings stored in the number storage unit is maintained. Brightness setting method.   4. The brightness setting method according to claim 3, wherein the predetermined threshold is 1% of the predetermined resolution. On the computer,
Receives a pulse width modulation signal with a duty ratio corresponding to the brightness setting value of the display screen that can set the brightness, samples the received pulse width modulation signal with a predetermined resolution per cycle, and per cycle Is a number detection procedure for detecting the number of samplings at a predetermined signal level, and calculates a difference between the number of samplings stored in a number storage unit for storing the number of samplings and the number of detected samplings, When the absolute value is greater than or equal to a predetermined threshold, the number of samplings stored in the number storage unit is updated to the detected number of samplings, and when the calculated absolute value of the difference is less than a predetermined threshold, the number of times The number detection procedure for maintaining the number of samplings stored in the storage unit ,
A program for executing a brightness adjustment procedure for adjusting the brightness of a light source based on the number of samplings stored in the number storage unit.   A computer-readable recording medium on which the program according to claim 5 is recorded.

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