JP2018085288A - Luminaire and control method thereof, and display device using luminaire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminaire which can suppress the change in color temperature of irradiation light when the luminance of irradiation is reduced, a control method of the luminaire, and a display device using the luminaire.SOLUTION: A luminaire comprises: a plurality of LEDs; a luminance decision part 113 for deciding a light emission amount of each LED; and control means for controlling light emission of each LED based on the light emission amount of the LED decided by the luminance decision part 113. The luminance decision part 113 temporarily decides a light emission amount of each LED. When the temporarily decided light emission amounts of the plurality of LEDs are all equal to or less than a predetermined value, or all larger than the predetermined value, the luminance decision part outputs the temporarily decided light emission amount of each LED. When at least one of the temporarily decided light emission amounts of the plurality of LEDs is larger than the predetermined value, and at least one temporarily decided light emission amount is equal to or less than the predetermined value, the luminance decision part corrects the temporarily decided light emission amount of the LED which is the temporarily decided light emission amount being the predetermined value or less, so as to be larger than the predetermined value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an illumination device that emits light using a plurality of light-emitting elements corresponding to a plurality of different colors, a control method thereof, and a display device using the illumination device.

  There are display devices that display light by transmitting light emitted from a backlight. The backlight includes a light source and irradiates light emitted from the light source to a transmissive display panel such as a liquid crystal panel. In order to widen the color reproduction range of a display device, a plurality of light emitting elements corresponding to a plurality of different colors may be used as a light source of a backlight. For example, a light emitting element that emits red light, a light emitting element that emits green light, or a light emitting element that emits blue light may be used as the light source of the backlight. The backlight irradiates the display panel with white light obtained by mixing light emitted from each light emitting element.

  In the case of using a plurality of light emitting elements corresponding to a plurality of different colors, it is possible to adjust the luminance and white balance by controlling the light emission amount of each light emitting element. Patent Document 1 discloses that the light emission amount of each light-emitting element is controlled by PWM control of a lighting period and a light-off period of each light-emitting element. By changing the ratio of the light emission amount of each light emitting element, it is possible to adjust the white balance of the light emitted from the backlight. In addition, by changing the total light emission amount of each light emitting element, it is possible to adjust the luminance (irradiation luminance) of light emitted from the backlight.

  In recent years, an image (HDR image) corresponding to High Dynamic Range (HDR) in which the difference in brightness included in the image is wider than in the past may be displayed. In some cases, the expression of the HDR image is further improved by controlling the irradiation brightness close to zero.

JP 2004-29141 A

  However, in the conventional technology described above, when the light (irradiation light) emitted from the backlight is controlled to a predetermined white balance and the irradiation luminance is controlled to be low luminance, the light emission amount ratio among the plurality of light emitting elements. In some cases, the light emission amount of a light emitting element having a small value becomes zero. When the amount of light emitted from one or two light emitting elements becomes zero, the color temperature of light emitted from the backlight may change greatly.

  Accordingly, an object of the present invention is to provide a lighting device, a lighting device control method, and a display device using the lighting device capable of suppressing a change in color temperature of irradiated light when irradiation luminance is reduced. To do.

  In order to solve the above-described problem, the present invention is a backlight for a transmissive liquid crystal display provided with LEDs of a plurality of colors, and in the calculation of the backlight emission amount, the emission values of all LEDs are zero. Except for, the PWM value of the LED color whose light emission value is calculated to be zero is not set to zero.

  According to the illumination device, the control method of the illumination device, and the display device using the illumination device of the present invention, it is possible to suppress the change in the color temperature of the irradiation light when the irradiation luminance is reduced.

It is a block diagram which shows the structure of a display apparatus. It is a functional block diagram which shows the functional block of a display apparatus. It is a table | surface which shows the value of the chromaticity point of the light emitted from LED provided in the backlight unit, and standard light. It is a 1st table | surface which shows an example of the relationship between the luminance control value of each LED, and the chromaticity point of irradiated light. It is a flowchart which shows the process which determines the light emission amount of each LED. It is a 2nd table | surface which shows an example of the relationship between the luminance control value of each LED, and the chromaticity point of irradiated light.

Example 1
The illuminating device of Example 1 suppresses a change in the color temperature of light emitted from the backlight by determining the luminance control value of each light emitting element so that the luminance control value does not become a predetermined value or less.

  FIG. 1 is a device configuration diagram of a display device 100 according to the first embodiment. The display device 100 includes a backlight unit 101, a display panel 102, a memory 103, a luminance sensor 104, and a control circuit board 110.

  The backlight unit 101 includes a plurality of light emitting elements that emit light of different colors. The backlight unit 101 irradiates the display panel 102 with light. The backlight unit 101 has a plurality of light emitting areas, and can control the light emission amount and the color temperature for each light emitting area. For example, the backlight unit 101 has at least one LED (RLED) that emits red light, an LED (GLED) that emits green light, and an LED (BLED) that emits blue light for each light emitting region. . FIG. 2 is a table showing the chromaticity points of light emitted from the light emitting elements and the chromaticity points of standard light.

  Note that the backlight unit 101 may be a lighting device capable of controlling the light emission amount and the color temperature for a single light emitting region. The backlight unit 101 also includes a luminance sensor 104 that receives light emitted from each light emitting element and measures the luminance.

  The backlight unit 101 constitutes an illumination device together with a control circuit board 110 described later.

  The display panel 102 is a transmissive display panel that transmits light emitted from the backlight unit 101 and displays an image. For example, it is assumed that the display panel 102 is a liquid crystal panel that displays an image by controlling the light transmittance by controlling the orientation of the liquid crystal element.

  FIG. 3 is a block diagram illustrating functional blocks of the display device 100 according to the first embodiment. The control circuit board 110 of the display device 100 includes an input unit 111, an image signal processing unit 112, a luminance determination unit 113, a display control unit 114, and a backlight control unit 115. The functions of the image signal processing unit 112, the luminance determination unit 113, the display control unit 114, and the backlight control unit 115 are executed by a processor provided in the control circuit board 110 by reading a program stored in the memory 103. It can also be realized. Note that one or more functional blocks can exhibit their functions by an electronic circuit.

  The input unit 111 acquires an input image signal output from an image output device external to the display device 100 or the memory 103 and outputs the input image signal to the image signal processing unit 112. For example, it is assumed that the input unit 111 is an interface that can transmit one or more image signals among DisplayPort, HDMI (registered trademark), SDI, SATA, and the like.

  The image signal processing unit 112 performs image processing for converting the input image signal input from the input unit 111 into a display image signal suitable for display on the display panel 102. For example, the image processing is assumed to be IP conversion for converting an interlace signal into a progressive signal, scaling for converting the angle of view of the input image signal to match the angle of view of the display panel 102, and the like.

  Further, the image signal processing unit 112 acquires luminance information indicating the brightness of the display image signal. The luminance information is, for example, the average luminance (APL) of the display image signal. The image signal processing unit 112 outputs pixel information and luminance information of the display image signal to the display control unit 114 and the luminance determination unit 113.

  The luminance determination unit 113 determines the light emission amount of each light emitting element of the backlight unit 101 from the pixel information and luminance information of the display image signal acquired from the image signal processing unit 112 and the luminance measurement value acquired from the luminance sensor 104. To do. A method for determining the light emission amount of the backlight will be described in detail later. The luminance determination unit 113 sends the backlight emission amount calculation result to the image signal processing unit 112. The image signal processing unit 112 sends the light emission amount of the backlight unit to the backlight control unit 115.

  The display control unit 114 controls the display panel 102 based on the pixel information and luminance information of the display image signal input from the image signal processing unit 112.

  The backlight control unit 115 controls the backlight unit 101 based on the light emission amount of the backlight input from the image signal processing unit 112.

  The brightness sensor 104 measures the brightness value of the backlight unit 101 and sends the brightness measurement value to the brightness determination unit 113.

  A method of determining the light emission amount for each light emitting element of the luminance determining unit 113 will be described. The luminance determination unit 113 determines the luminance (irradiation luminance) of the light irradiated by the backlight unit 101 based on the luminance information. For example, it is assumed that the irradiation luminance is represented by a value from 0 to 255 indicated by 8-bit data.

  The luminance determining unit 113 provisionally determines the light emission amount of each LED based on the determined irradiation luminance and a preset white balance (WB) set in advance. Further, the luminance determining unit 113 determines that the temporarily determined light emission amount is equal to or less than a predetermined value when the light emission amount of one or two LEDs among the light emission amounts of the temporarily determined LEDs is equal to or less than a predetermined value. The light emission amount of one or two LEDs is adjusted to a light emission amount larger than a predetermined value.

  Specifically, the luminance determination unit 113 determines the balance of the light emission amounts of the LEDs based on the setting WB, and determines the intensity of the light emission amount of each LED based on the irradiation luminance. For example, it is assumed that the luminance determining unit 113 determines the irradiation luminance so that the higher the display image signal is, the higher the irradiation luminance is.

  The luminance determination unit 113 controls the light emission amount of each LED with a gradation value of 0 to 255 indicated by 8-bit data. For example, when all the LEDs are turned on with the maximum light emission amount, the light emission amount of each LED is expressed as (R, G, B) = (255, 255, 255). In the case of black (non-lighting), the light emission amount of each LED is represented as (R, G, B) = (0, 0, 0). The gradation value of 0 to 255 indicated by 8-bit data is a luminance control value indicating the light emission amount of each LED.

  Note that the luminance determining unit 113 takes the pixel information and luminance information acquired from the image signal processing unit 112 into luminance control values in consideration of the amount of light that is reduced by the transmittance of the liquid crystal display unit 106. Furthermore, it is assumed that the luminance determination unit 113 corrects the white balance from the luminance measurement value acquired from the luminance sensor 104 and determines the balance of the light emission amounts of the LEDs.

  FIG. 4 is a table showing the relationship between the brightness control value of each LED and the chromaticity point of the irradiated light. FIG. 4A shows the relationship between the brightness control value of each LED and the chromaticity point of the irradiated light when the control of this embodiment is not performed. FIG. 4B shows the relationship between the brightness control value of each LED and the chromaticity point of the irradiated light when the control of this embodiment is performed. FIG. 4 shows the relationship between the brightness control value of each LED and the chromaticity point of the irradiation light when the irradiation luminance is high.

  Based on the luminance measurement value of the luminance sensor 104, the ratio of the light emission amounts of the respective LEDs when irradiating light from the backlight unit 101 with a predetermined white balance (setting WB) is (R, G, B). = (A-2, a, a-2) (a is an integer of 0 or more). It is assumed that the setting WB of the backlight unit 101 is set by the user from a plurality of white balances preset at the time of manufacture stored in the memory 103. Also, the user can arbitrarily set the setting WB.

  The luminance determination unit 113 temporarily determines the light emission amount of each LED from the irradiation luminance so that the gradation value indicating the largest light emission amount among the light emission amounts of each LED is the same as the gradation value indicating the irradiation luminance. . For example, when the illumination brightness is controlled with the above-described setting WB, the light emission amount of each LED corresponding to the illumination brightness 127 is (R, G, B) = (125, 127, 125).

  When the emission luminance is made closer to black (not lit) while maintaining the setting WB, the luminance determination unit 113 sets the emission amount of each LED to (R, G, B) as shown in FIG. = (3,5,3) → (2,4,2) → (1,3,1) → (0,2,0). When the light emission amount of each LED changes from (R, G, B) = (1, 3, 1) to (R, G, B) = (0, 2, 0), LEDs other than GLED are turned off. Therefore, the deviation Δu′v ′ of the color temperature of the light emitted from the backlight unit 101 changes greatly.

  In this embodiment, the luminance determination unit 113 adjusts the light emission amount of the LED whose tentatively determined light emission amount is equal to or less than a predetermined value to a value larger than the predetermined value. For example, it is assumed that the predetermined value is 0. As a result of the adjustment, as shown in FIG. 4B, when the luminance determination unit 113 brings the emission luminance closer to black (non-lighting), (R, G, B) = (3, 5, 3) → (2, 4, 2) → (1, 3, 1) → (1, 2, 1). This makes it possible to reduce the change in Δu′v ′ even when the light emission amount is low.

  If the light emission amount of each LED that is provisionally determined is (R, G, B) = (0, 0, 0), the luminance determination unit 113 does not perform this adjustment process. When the tentatively determined light emission amount of one or two LEDs is equal to or less than a predetermined value, the above-described adjustment process is executed.

  The luminance determination unit 113 sends a luminance control value indicating the light emission amount of each LED of the backlight unit 101 to the image signal processing unit 112.

  In the image signal processing unit 112, the luminance determination unit 113 sends the acquired luminance control value indicating the light emission amount of each LED of the backlight unit 101 to the backlight control unit 115.

  The backlight control unit 115 controls the backlight unit 101 based on the luminance control value indicating the light emission amount of each LED of the backlight unit 101 input from the image signal processing unit 112. Here, the backlight control unit 115 controls the light emission amount of each LED by performing PWM control of the lighting period and extinguishing period of each LED of the backlight unit 101, and the luminance of light emitted from the backlight unit 101. And control white balance.

  FIG. 5 is a flowchart illustrating a process in which the luminance determining unit 113 determines the light emission amount of each LED.

  In step S <b> 401, the luminance determination unit 113 acquires pixel information and luminance information from the image signal processing unit 112 and acquires luminance measurement values from the luminance sensor 104. The process proceeds to step S402.

  In step S <b> 402, the luminance determination unit 113 calculates the irradiation light amount using the pixel information, the luminance information, and the luminance measurement value acquired from the image signal processing unit 112. In addition, the luminance determination unit 113 acquires the light emission amount of each LED based on the irradiation light amount and the setting WB. Specifically, the brightness determination unit 113 acquires the brightness control value of each LED. The process proceeds to step S403.

  In step S403, the luminance determination unit 113 determines the presence / absence of an LED whose light emission amount (brightness control value) is calculated to be zero based on the light emission amount (brightness control value) of each LED acquired in S402. If there is no LED whose light emission amount (luminance control value) is calculated as zero, the process proceeds to step S405. If there is an LED whose light emission amount (luminance control value) is calculated to be zero, the process proceeds to step S404.

  In step S404, the luminance determination unit 113 replaces the light emission amount (luminance control value) of the LED color for which the light emission amount (luminance control value) is calculated as zero with a value other than zero. The process proceeds to step S405.

  In step S <b> 405, the luminance determining unit 113 outputs the light emission amount (luminance control value) of each LED to the image signal processing unit 112. The process proceeds to step S406 and the flow ends.

  As described above, by determining the brightness control value of each LED, when the illumination brightness is reduced in the backlight that irradiates light using a plurality of LEDs (light emitting elements) each corresponding to a plurality of different colors. It is possible to suppress a change in the color temperature of the backlight.

(Example 2)
Hereinafter, the display device 100 according to the second embodiment of the present invention will be described with reference to FIG. Since the configuration of the display device 100 and the functional blocks included in the display device 100 are the same as those in the first embodiment, description thereof is omitted.

  In the display device 100 according to the second embodiment, the operation of the luminance determining unit 113 is different from that according to the first embodiment.

  FIG. 6 is a table showing the relationship between the luminance control value of each LED determined by the luminance determining unit 113 of Example 2 and the chromaticity point of the irradiation light. The upper side of FIG. 6 shows the relationship between the luminance control value of each LED and the chromaticity point of the irradiation light when the irradiation luminance is high.

  When there is an LED color whose light emission value is calculated to be zero, the luminance determination unit 113 in the second embodiment replaces the light emission values of all the light sources with settings that minimize the change in color temperature deviation. Specifically, as shown in FIG. 6, the luminance determining unit 113 corresponds to the temporarily determined backlight emission amount (R, G, B) = (0, 2, 0) with higher irradiation luminance. Replace with (R, G, B) = (1, 3, 1). Thereby, the change of Δu′v ′ can be reduced.

DESCRIPTION OF SYMBOLS 100 Display apparatus 101 Backlight unit 102 Display panel 110 Control circuit board 111 Input part 112 Image signal processing part 113 Brightness control value determination part 114 Display control part 115 Backlight control part 104 Brightness sensor

Claims (5)

A plurality of light emitting elements corresponding to a plurality of colors;
Determining means for determining the light emission amount of each light emitting element;
Control means for controlling the light emission of each light emitting element based on the light emission amount of each light emitting element determined by the determining means;
With
The determining means includes
Tentatively determine the amount of light emitted from each light-emitting element,
When all the light emission amounts of the light-emitting elements that are provisionally determined are less than or equal to the predetermined value, or when all light emission amounts of the light-emitting elements that are temporarily determined are greater than the predetermined value, Outputs the amount of emitted light,
Among the plurality of light emitting elements, there is at least one light emitting element whose tentatively determined amount of light emission is greater than a predetermined value, and at least one light emitting element whose tentatively determined amount of light emission is equal to or less than a predetermined value. An illumination device, wherein, when present, the provisionally determined light emission amount of a light emitting element having a temporarily determined light emission amount equal to or less than a predetermined value is corrected to be larger than a predetermined value. The determining means includes a setting means for setting the luminance of the irradiation light emitted from the illumination device and the color temperature of the irradiation light,
2. The deciding means tentatively decides a light emission amount of each light emitting element so as to emit light having a color temperature set by the setting means at a luminance of the irradiation light set by the setting means. The lighting device described in 1. The determining means includes
Among the plurality of light emitting elements, there is at least one light emitting element whose tentatively determined amount of light emission is greater than a predetermined value, and at least one light emitting element whose tentatively determined amount of light emission is equal to or less than a predetermined value. 3. The light emission amount of each light emitting element corresponding to the luminance of the irradiation light, which is higher than the luminance of the irradiation light set by the setting unit, is output to the control unit when present. The lighting device described. The lighting device according to any one of claims 1 to 3,
Display means for transmitting light emitted from the illumination device and displaying an image;
A display device comprising: A method for controlling an illumination device including a plurality of light emitting elements corresponding to a plurality of colors,
A determination step of determining the light emission amount of each light emitting element;
A control step of controlling the light emission of each light emitting element based on the light emission amount of each light emitting element determined by the determining means;
With
The determination step includes
Tentatively determine the amount of light emitted from each light-emitting element,
When all the light emission amounts of the light-emitting elements that are provisionally determined are less than or equal to the predetermined value, or when all light emission amounts of the light-emitting elements that are temporarily determined are greater than the predetermined value, Outputs the amount of emitted light,
Among the plurality of light emitting elements, there is at least one light emitting element whose tentatively determined amount of light emission is greater than a predetermined value, and at least one light emitting element whose tentatively determined amount of light emission is equal to or less than a predetermined value. A lighting device control method, comprising: correcting a provisionally determined light emission amount of a light emitting element having a provisionally determined light emission amount equal to or less than a predetermined value when it exists.

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