LIGHT EMISSION DEVICE AND METHOD FOR OPERATION THEREOF

Abstract

A light-emitting device comprising: a display including a plurality of pixels in which a plurality of first light-emitting elements, each configured to emit a first light-emitting color, and a plurality of second light-emitting elements, each configured to emit a second light-emitting color different from the first light-emitting color, are arranged in a predetermined pattern; and a lighting control device configured to supply an operating current to each of the plurality of first light-emitting elements and each of the plurality of second light-emitting elements and to control a light-emitting period of each of the plurality of first light-emitting elements and each of the plurality of second light-emitting elements. A light-emitting color of a second light-emitting element of the plurality of second light-emitting elements is variable in accordance with an operating current supplied thereto.

Description

CROSS REFERENCE TO RELATED APPLICATIONSThis application is based on and claims priority from JP 2023-218 219 filed December 25, 2023, the entire contents of which are incorporated herein by reference.BACKGROUNDThe present disclosure relates to a light emitting device and a method of operating the light emitting device.Displays and surface light emitting devices having semiconductor light emitting elements such as LEDs and LDs are used. Here, in order to produce a full-color LED display, it is generally necessary to arrange subpixels in at least the three RGB colors for each pixel. However, this configuration is not suitable for high resolution because in such a configuration, it is necessary to provide at least three times as many of the subpixels as the pixel, and there are problems such as high cost and lower yield due to a higher number of LEDs.On the other hand, a micro LED display that causes a single LED element to emit multi-color light is known (see JP 2021-52168 A). However, with respect to a configuration of a display using such a multicolor light emitting micro LED, no actual circuit configurations and operation methods have been reported. For example, in the current technology of controlling a multicolor light emitting micro LED, it is not easy to emit light in all RGB chromaticity ranges.It is an object of the present disclosure to provide a light emitting device and a method of operating the light emitting device, with which appropriate light emitting color control can be implemented when a light emitting device such as a display is configured using multicolor semiconductor light emitting elements.SUMMARYA light emitting device according to an aspect of the present disclosure includes a display including a plurality of pixels in which a plurality of first light emitting elements each configured to emit a first light emitting color and a plurality of second light emitting elements each configured to emit a second light emitting color different from the first light emitting color are arranged in a predetermined pattern; and a lighting control device configured to supply an operating current to each of the plurality of first light emitting elements and each of the plurality of second light emitting elements and control a light emitting period. A light emission color of a second light emitting element of the plurality of second light emitting elements is variable according to an operation current supplied thereto, and the illumination control device divides a frame into a first sub-frame and a second sub-frame and operates the plurality of first light emitting elements and the plurality of second light emitting elements, the one frame being a frame for causing the plurality of first light emitting elements and the plurality of second light emitting elements to emit light, the first sub-frame being a sub-frame for causing each of the plurality of first light emitting elements to emit light, and the second sub-frame being a sub-frame for causing each of the plurality of second light emitting elements to emit light.A method of operating a light emitting device according to another aspect is a method of operating a light emitting device including a display having a plurality of pixels in which a plurality of first light emitting elements each configured to emit light of a first light emitting color and a plurality of second light emitting elements each configured to emit light of a second light emitting color different from the first light emitting color are arranged in a predetermined pattern, a light emitting color of each of the plurality of second light emitting elements being variable depending on an operation current, and an illumination control device configured to supply an operation current to each of the plurality of first light emitting elements and the plurality of second light emitting elements and control a light emitting period, the method including, by the illumination control device, controlling a light emitting period, comprising: dividing a frame into a first sub-frame and a second sub-frame, and driving the plurality of first light emitting elements and the plurality of second light emitting elements, the one frame being a frame for causing the plurality of first light emitting elements and the plurality of second light emitting elements to emit light, the first sub-frame being a sub-frame for causing each of the plurality of first light emitting elements to emit light, the second sub-frame being a sub-frame for causing each of the plurality of second light emitting elements to emit light.With the configuration described above, by combining the first light emission color and the second light emission color serving as another light emission color depending on the driving current, an advantage is obtained that multi-color light emission such as full-color emission is possible and simpler light emission control can be implemented.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a block diagram showing a light emitting device according to a first embodiment. FIG. 2 is a timing diagram for illuminating and operating a first light emitting element and a second light emitting element. FIG. 3 is a block diagram showing an example in which a first control circuit and a second control circuit are arranged in a pixel circuit. FIG. 4 is a block diagram with an enlarged view showing a display of the light emitting device according to the first embodiment. FIG. 5 is a schematic cross-sectional view showing an example of an element structure of a light emitting element. FIG. 6 is a schematic diagram of an illumination image in a first sub-frame. FIG. 7 is a schematic diagram of an illumination image in a second sub-frame. FIG. 8 is a functional block diagram illustrating a method for determining an operation current value and a PWM light emission period. FIG. 9 is a chromaticity diagram for illustrating a method for determining a light emission chromaticity in FIG. 8. FIG. 10A is a schematic diagram showing a pixel of the light emitting device according to the first embodiment, and FIG. 10B is a schematic diagram showing a pixel of a light emitting device according to a second embodiment.DETAILED DESCRIPTIONHereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, terms indicating specific directions and positions (for example, "above", "below", and other terms including these terms) are used as necessary. However, the use of these terms is intended only to facilitate understanding of the invention with reference to the drawings, and the technical scope of the present disclosure is not limited by the meaning of these terms. Parts having the same reference numerals that occur in multiple drawings denote identical or equivalent parts or elements.The following embodiments show specific examples of the technical idea of the present disclosure, and the present disclosure is not limited to the following embodiments. Unless otherwise indicated, the dimensions, materials, shapes, relative arrangements, and the like of components to be described below are not intended to limit the scope of the present disclosure to these only, but rather provide examples. The contents to be described in one embodiment and an example may be transferred to another embodiment and another example. The size, spatial relationship, and the like of the elements shown in the drawings may be exaggerated for the sake of explanation.First EmbodimentA block diagram of a light emitting device 100 according to a first embodiment is shown in FIG. 1. The light emitting device 100 shown in this drawing includes a display 10, a driver 30, lighting controllers 50, an information memory 70, a sensing circuit 20, and an operation controller 60.The display 10 includes a plurality of pixels 12 in which a plurality of first light emitting elements 11A and a plurality of second light emitting elements 11B are arranged in a predetermined pattern. Specifically, the plurality of first light emitting elements 11A and second light emitting elements 11B are arranged in a matrix. A period in which image data for one frame is displayed on a screen formed by the pixels 12 arranged in a matrix may be referred to as a vertical scanning period, and a period obtained by dividing the vertical scanning period by the number of lines of the screen may be referred to as a horizontal scanning period. For example, in the horizontal scanning period, a voltage value for controlling the current supply of the pixels 12 arranged in a row direction (X-axis direction) and a voltage value for analog image data are set. In the vertical scanning period, the scanning circuit 20 scanning the pixel 12 is sequentially shifted in a column direction (Y-axis direction). The light emitting device 100 in FIG. 1 uses an active matrix driving method as an illumination driving method for illuminating the individual pixels 12.Each pixel 12 is formed by one or more of the first light emitting elements 11A and one or more of the light emitting elements 11B. In the example shown in FIG. 1, a pixel 12 includes a first light emitting element 11A and a second light emitting element 11B. However, the present disclosure is not limited to this configuration, but a pixel may be configured to include a plurality of first light emitting elements or a plurality of second light emitting elements. By using a plurality of first light emitting elements and second light emitting elements, the light emitting luminance per pixel can be improved.The first light emitting elements 11A may emit light of a first light emitting color. The first light emission color is blue, for example.The second light emitting element 11B may emit light of a second light emitting color different from the first light emitting color. The light emission color of the second light emitting element 11B can be controlled in accordance with its driving current. As such a second light emitting element 11B, a multicolor and wavelength tunable light emitting type LED and a multicolor variable emission wavelength LED, respectively, can be suitably used. The second light emission color is tunable from green to red, for example. In the present disclosure, the first light emitting elements 11A and the second light emitting elements 11B may collectively be referred to as light emitting elements 11.Lighting Control Unit 50The lighting control device 50 supplies an operating current to each of the plurality of first light emitting elements 11A and the plurality of second light emitting elements 11B to control a light emission period. In the example shown in the enlarged view of FIG. 1, the lighting control devices 50 are connected to a power supply line 9 and a write scan line WS extending in the horizontal direction. The illumination controller 50 is driven by the power supply line 9 and receives a power supply control signal and an analog image signal via the write scan line WS. On the other hand, the illumination controller 50 is also connected to a signal line SL extending in a vertical direction and receives the power supply control signal and the analog image signal.The lighting control device 50 divides a frame to cause the plurality of first light emitting elements 11A and the plurality of second light emitting elements 11B to emit light into a first sub-frame to cause each of the plurality of first light emitting elements 11A to emit light and a second sub-frame to cause each of the plurality of second light emitting elements 11B to emit light, and drives the plurality of first light emitting elements 11A and the plurality of second light emitting elements 11B. For example, the first sub-frame is a B sub-frame for emitting blue light, and the second sub-frame is an RG sub-frame for emitting green light to red light.With such a configuration, the light emitting device 100 can be efficiently operated with a tunable light emitting color. Specifically, by limiting the light emission control of the second light emitting elements 11B that can emit light in different light emission colors depending on the driving current to a light emission control tunable only in a limited wavelength range, for example, from green light to red light, without controlling the light emission in the entire RGB range, in combination with the first light emission color of the first light emitting element 11A, full-color light emission for each pixel can be achieved and simpler light emission control can be implemented.In a multicolor light emission type LED having a tunable light emission wavelength, a light emission color is changed by an operating current. In other words, since the magnitude of the driving current varies greatly depending on the light emission color, the light emission luminance also varies greatly at the same time. For example, when a multicolor light emission type LED is used to display short wavelength light and long wavelength light on a display with the luminance and the light emission colors appropriately adjusted, a light emission period must be controlled in a range of about 3 to 30 times depending on the light emission wavelength. Therefore, in order to obtain a sufficient light emission luminance by reducing an unnecessary non-light emission period, field sequential driving is desirable to perform illumination in different subframes for each light emission color.However, in field sequential operation, color separation may occur to change the light emission color for the individual subframes, particularly in a moving image, so that the image quality may be significantly degraded. That is, in the field sequential operation, since the pixels are active matrix type, a certain light emission time must be ensured after display data is written in a row selected by scanning. Thus, a scanning period and the light emission period of each of the rows are defined independently of each other. Thus, in the field sequential method, light emission does not occur in lines but in subfields, resulting in a problem that color separation occurs as a side effect.On the other hand, in the light emitting device 100 according to the first embodiment, as described above, the light emitting elements 11 that form one pixel are formed by the first light emitting elements 11A that can emit light of the first light emitting color and the second light emitting elements 11B that can emit light of the second light emitting color, and the second light emitting color is tunable, thereby restricting the range of a necessary color change. Further, the color separation is prevented by using only blue light with low visibility to the human being as another sub frame. A detailed description is given below.First light emitting element 11A and second light emitting element 11BAs the first light emitting element 11A and the second light emitting element 11B, a semiconductor light emitting element such as a light emitting diode (LED) or a semiconductor laser (LD) may be suitably used. As the LED, an LED including one or more semiconductor laminated bodies having light emitting portions (hereinafter also referred to simply as "semiconductor laminated bodies") may be used. The semiconductor layered body is suitable for emitting light. Such a semiconductor laminated body is manufactured by laminating a plurality of semiconductor layers such as ZnS, SiC, GaN, GaP, InN, AIN, ZnSe, GaAsP, GaAlAs, InGaN, GaAlN, AlInGaP, AlInGaN, or the like on a substrate by liquid phase epitaxy such as HVPE or MOCVD and forming an active layer on one of the semiconductor layers. By selecting the semiconductor layer materials and their mixing ratios, the light emission wavelength of the active layer can be selected to be different from ultraviolet light to infrared light. Particularly in the case of a display device which can be suitably used outdoors, a semiconductor laminated body capable of emitting light with high luminance is advantageous. Therefore, it is preferable to select a nitride semiconductor as a material for a light emitting portion that emits light with high luminance. For example, In X Al Y Ga 1-X-Y N (0≤X≤1, 0≤Y≤1, and X+Y≤1), or the like may be used as the material of the light emitting portion.In the first embodiment, a semiconductor light emitting element such as a light emitting diode or a semiconductor laser is used as the first light emitting element 11A and the second light emitting element 11B. As the light emitting diode, a micro LED may also be used. The micro LED has a chip size of 5 μm to 100 μm, and suitably 10 μm to 50 μm, respectively, in consideration of light efficiency and the like.The light emission color of the first light emitting element 11A is set as a first light emission color. On the other hand, the light emission color of the second light emitting element 11B is the second light emission color that is tunable. The second light emitting element 11B emits light of a different light emitting color depending on the driving current. For example, the second light emitting element 11B, when operated at a first driving current, emits light of a first light emission wavelength, for example, red light, and when operated at a second driving current larger than the first driving current, emits light of a second light emission wavelength shorter than the first light emission wavelength, for example, green light.The first light emitting element 11A and the second light emitting element 11B are respectively connected to a plurality of common lines and a plurality of drive lines. The first light emitting element 11A and the second light emitting element 11B are respectively connected to one of the plurality of common lines and one of the plurality of drive lines and arranged in a matrix so as to form the display 10.Sampling Circuit 20The sampling circuit 20 is arranged in a column located farther leftward than the leftmost column of the pixels 12 arranged in the form of a matrix, and the sampling circuit 20 may be arranged in a column located farther rightward than the rightmost column of the pixels 12 arranged in the form of a matrix. As shown in FIG. 4, for each row of the pixels, a power supply control signal write sampling line WS1 and an analog image signal write sampling line WS2 are provided as write sampling lines WS extending from the sampling circuit 20. The power supply control signal write scan line WS1 and the analog image signal write scan line WS2 extend in the row direction.The power supply control signal writing scan line WS 1 supplies a first scan signal, which is a digital signal for selecting pixel circuits 14 (the lighting controller 50 and the light emitting elements 11 in FIG. 1 ) in the row direction, to which desired voltage values are written by the power supply control signal. A reference triangular wave signal is supplied to a selected pixel circuit 14, and the light emitting element 11 of each pixel circuit 14 emits light during an ON period based on a written analog image signal voltage. The analog image signal writing scan line WS 2 supplies a second scan signal that is a digital signal for selecting the pixel circuit 14 in the row direction when a voltage value is written by an analog image signal. When the light emitting element 11 emits light, an operation current value is set by a power supply control signal voltage (for details, see U.S. Pat. No. 10,885,834).Driver 30As shown in FIG. 4, the driver 30 includes a power supply control signal line SL 1 and an analog image signal line SL 2 extending as the signal lines SL in the vertical direction for each column of the pixels. The driver 30 supplies a power supply control signal to each pixel circuit 14 via the power supply control signal line SL 1. The driver 30 supplies an analog image signal to each pixel circuit 14 via the analog image signal line SL2. The analog image signal is also an analog signal which can take a plurality of voltage values. Each pixel circuit 14 to which the power supply control signal is supplied and the voltage value is written adjusts an operation current based on the written voltage value. Each pixel circuit 14 to which the analog image signal is supplied and the voltage value is written sets a threshold voltage to be compared with the reference triangular wave signal based on the voltage value of the analog image signal, and sets a time interval in which the pixel circuit 14 emits light (for details, see U.S. Pat. No. 10,885,834).The driver 30 may generate the reference triangular wave signal supplied to each pixel circuit 14 for each column. Alternatively, the reference triangular wave signal may be separately provided as a reference triangular wave circuit in a row below the lowermost row of the matrix of the pixel circuits 14. The driver 30 or the reference triangular wave circuit distributes, for example, a reference triangular wave supplied from the outside of these circuits to the columns of the pixel circuits 14.The driver 30 may include a storage unit. The storage unit may store luminance settings for a plurality of voltage values adopted by the power supply control signal and luminance settings for a plurality of voltage values adopted by the analog image signal. The relationship between the voltage values and the luminance settings can be set and set by visually checking the luminance of the light emitting element 11 constituting the pixel circuit 14. The γ correction can be made by appropriately setting the relationship between the voltage values and the luminance settings. While the gradation characteristics become linear in a digital PWM system, the fact that γ correction can be applied to a signal is one of the advantages of this system. The storage unit is constituted by, for example, an electrically rewritable memory circuit or the like.Operation Control Unit 60The operation controller 60 further controls the operations of the sensing circuit 20 and the driver 30. the sensing circuit 20 and the driver 30 control the illumination controller 50 of the individual pixels. As shown in FIG. 3, each lighting control device 50 may include a first control circuit 51 and a second control circuit 52. The first control circuit 51 supplies an operating current to both the first light emitting element 11A and the second light emitting element 11B. The second control circuit 52 controls the light emission periods of both the first light emitting element 11A and the second light emitting element 11B. A configuration in which the light emitting element is connected to the illumination controller 50 may be referred to as a "pixel circuit 14". The first control circuit 51 is connected between the power supply line 9 and the second control circuit 52.The pixel circuit 14 may be provided for each subpixel constituting a pixel 12. In the example of FIG. 1, the pixel circuit 14 includes a first subpixel circuit 14A and a second subpixel circuit 14B. The first subpixel circuit 14A drives the first light emitting element 11A constituting a first subpixel. On the other hand, the second subpixel circuit 14B drives the second light emitting element 11B constituting a second subpixel. In the example of FIG. 1, the first light emitting element 11A may emit blue light as a first subpixel and the second light emitting element 11B may emit green to red light as a second subpixel, such that the first subpixel and the second subpixel form a pixel 12.Information Storage 70As described above, the second light emitting element 11B is a multicolor and wavelength tunable light emitting type LED, and changes the second light emitting color according to the driving current. Therefore, an operation current value for operating the second light emitting element 11B needs to be determined in accordance with second light emitting color to be emitted by the second light emitting element 11B. Therefore, the information storage 70 stores current chromaticity information indicating the light emission color to be emitted from the second light emitting element 11B and a correspondence relationship that determines a current value for emitting this color. The lighting control device 50 accesses the information memory 70 and determines the driving current of the second light emitting element 11B corresponding to the second light emitting color. The information storage 70 may include, for example, a storage element such as a current chromaticity data storage for storing current chromaticity data of the second light emitting element 11B.The information storage 70 may store current chromaticity information based on an actually measured value of each second light emitting element 11B arranged in the display 10, and may further store current chromaticity information generated by measuring an operating current and a light emitting color of a light emitting element corresponding to each second light emitting element 11B arranged in the display 10. Alternatively, the information storage 70 may store current chromaticity information recorded by statistically determining the relationship between the driving current and the light emission color of the second light emitting element 11B. In the example of FIG. 1, the information storage 70 has a (G-R) light emission chromaticity-driving current characteristic table and a (G-R) light emission chromaticity-driving current-luminance characteristic table.The operation controller 60 controls the driver 30 to supply an operation current to the first light emitting element 11A and the second light emitting element 11B so that the first light emitting element 11A and the second light emitting element 11B emit light having a certain light emitting color and light emitting luminance, respectively. Since the first light emission color of the first light emitting element 11A is fixed, the operation controller 60 controls the operation current corresponding to the light emission luminance. On the other hand, the operation controller 60 for the second light emitting element 11B determines an operation current value for operating each second light emitting element 11B and an ON period during which each second light emitting element 11B emits light by accessing the current chromaticity information stored in the information memory 70 corresponding to a determined light emission color and gradation information for each second light emitting element 11B, and performs the lighting operation of each second light emitting element 11B using the operation current from the driver 30.The operation controller 60 also performs the gradation control of the light emission luminance. For example, the operation controller 60 determines the operation current value of the first light emitting element 11A and the second light emitting element 11B by using the current chromaticity information in accordance with the determined light emission color of the first light emitting element 11A and the second light emitting element 11B, and determines the ON period of each of the first light emitting element 11A and the second light emitting element 11B according to the determined operation current value and with the predetermined gradation information for the first light emitting element 11A and the second light emitting element 11B.The operation control device 60 may include a storage unit. The storage unit may store luminance settings for a plurality of voltage values adopted by the power supply control signal and luminance settings for a plurality of voltage values adopted by the analog image signal. The relationship between the voltage values and the luminance settings can be set and set by visually checking the luminance of the light emitting element constituting the pixel circuit 14. The γ correction can be made by appropriately setting the relationship between the voltage values and the luminance settings. While the gradation characteristics become linear in a digital PWM system, the fact that γ correction can be applied to a signal is one of the advantages of this system. The storage unit is constituted by, for example, an electrically rewritable memory circuit or the like.The operation controller 60 may further cause the driver 30 to simultaneously perform illumination control of the first light emitting element 11A and the second light emitting element 11B in a state in which ON period information respectively corresponding to a screen of the first light emitting element 11A and the second light emitting element 11B constituting the display 10 is written in the storage unit.The operation controller 60 determines an operation current value for operating each first light emitting element 11A and a light emission period during which each first light emitting element 11A emits light in accordance with a light emission color given from the outside and gradation information given from the outside for the first light emitting element 11A and the second light emitting element 11B. The operation controller 60 determines an operation current value for operating the second light emitting element 11B and a light emission period during which each second light emitting element 11B emits light by accessing the current chromaticity information stored in the information storage 70. Subsequently, the operation controller 60 causes the driver 30 to perform the lighting operation of the first light emitting element 11A and the second light emitting element 11B. With such a configuration, the lighting control of the display 10 formed by the first fixed-wavelength-type light emitting element 11A and the second multicolor light emitting element 11B can be implemented.With respect to the second light emission color of the second light emitting element 11B, the magnitude of the drive current values satisfies the condition IR<IG<IB when the drive current values for emitting the respective light emission colors red (R), green (G), and blue (B) are IR, IG, and IB, respectively. Therefore, the relationship between the lengths of the maximum light emission periods of the respective colors in white display corresponding to full irradiation satisfies the condition TR>TG>TB when the light emission periods of the maximum gradation of the respective colors are TR, TG and TB.However, when the second light emitting color is varied in the entire range of R, G, and B, because the range in which the driving current of the second light emitting element 11B is changed is increased, the control thereof is complicated. Therefore, the range of the second light emission color for which the second light emitting element 11B is responsible can be limited by making the first light emission color and the second light emission color different from each other and making the first light emitting element 11A responsible for the first light emission color, so that control can be simplified. As for the correspondence of the first light emission color and the second light emission color, preferably, the first light emission color is blue and the second light emission color is tunable from green to red, or the second light emission color is blue to green and the first light emission color is red, so that the second light emission color can be continuously changed. Since the driving current value (IB) for blue light emission is the maximum for the driving current value of the multicolor light emission type LED, the driving current value of the second light emitting element 11B can be preferably suppressed by setting the first light emission color to blue and the second light emission color to green to red.Further, the above assignment of the light emission colors can solve the problem that in the field sequential operation, color separation occurs to change the light emission color for each sub frame. That is, by causing the first light emitting element 11A to emit blue light and the second light emitting element 11B to emit green to red light z, the light emission of the first light emitting element 11A and the second light emitting element 11B can be divided into the B sub-frame and the GR sub-frame tunable between (G-R), and the first light emitting element 11A and the second light emitting element 11B can be operated. Since the color resolution of the human eye is low in blue light, despite the assignment of the blue light to another sub-frame and field sequential operation, the color separation is hardly recognized, thereby avoiding color separation, reducing an unnecessary non-light emission period when using a multi-color light emission LED, and achieving sufficient light emission luminance.Accordingly, in the light emitting device 100 according to the first embodiment, the first light emitting element 11A emits blue light of the first light emitting color and the second light emitting element 11B emits light of any color from red to green (RG) of the second light emitting color. Thus, full-color light emission can be implemented by the first light emitting element 11A and the second light emitting element 11B without causing color separation. PWM can be used for gradation control of each of the light emitting colors. Here, the product of the maximum light emission periods and the driving current values by the PWM driving is R>G>B. This is because the light emission luminance efficiency of the second light emitting element 11B is higher in the order of R<G<B.The above description assumes that the second light emission color of the second light emitting element 11B can be varied over the entire range of R, G, and B. However, by manufacturing the second light emitting element 11B such that the second light emitting color can be varied only in the range of R to G, advantages such as simplification of the manufacturing process and cost reduction are obtained. For example, the margin of the manufacturing process of the second light emitting element 11B can be made wider.Timing DiagramFIG. 2 is a timing chart showing the lighting timing of each of the RGB colors of the light emitting device 100 shown in FIG. 1. A frame period FT is divided into a first sub-frame period SF 1 in which the first light emitting element 11A emits light and a second sub-frame period SF 2 in which the second light emitting element 11B emits light. The first sub-frame period SF 1 is the B sub-frame in which blue light is emitted, and the second sub-frame period SF 2 is the GR sub-frame in which light of any color from green to red is emitted. In the B sub-frame, a current having a value corresponding to blue light, for example, 470 nm is supplied to the first light emitting element 11A. In the GR sub-frame, due to the change from green to red light, a current having a value in a range from a current value corresponding to green light, for example, 515 nm to a current value corresponding to red light, for example, 630 nm is supplied to the second light emitting element 11B. That is, a current having the maximum value that causes the first light emitting element 11A to emit light is supplied in the B sub-frame, while an operating current corresponding to the second light emitting color is supplied in the GR sub-frame. In other words, in the GR sub-frame, the light emission color is controlled by the vertical axis (driving current) in FIG. 2.In each sub-frame, the light emission luminance is controlled by PWM control. By changing an ON period ONT within a maximum light emission period LTmax, the luminance can be set to a desired value by changing an integrated current value while supplying a current having a maximum value. A maximum light emission period of blue light is referred to as LTmaxB, and the ON period of blue light is referred to as ONTB. On the other hand, in a maximum light emission period from green light to red light, the maximum light emission period from green light is denoted as LTmaxG, and the maximum light emission period from red light is denoted as LTmaxR. The ON period ONT is included in the maximum light emission period. Actually, once the driving current value (vertical axis) is determined in accordance with a desired light emission color, the horizontal axis is determined in accordance with the luminance as shown by oblique lines in FIG. 2. In this way, in each of the B sub-frame and the (G-R) sub-frame, luminance control is performed by the horizontal axis (ON period) in FIG. 2.A pixel signal writing period is provided in each subframe, and PWM control is performed after the pixel signal writing period. In the pixel signal writing period, a pixel signal for one screen of each of the first light emitting element 11A and the second light emitting element 11B is written in a pixel memory. The driver 30 controls lighting of the light emitting element 11 by accessing the pixel signal written in the pixel memory. The pixel memory is provided in the illumination controller 50 of the pixel circuit 14.As shown in FIG. 3, the lighting control device 50 includes the first control circuit 51 and the second control circuit 52. the first control circuit 51 performs the current driving in accordance with a light emission color. The second control circuit 52 performs PWM control. Specifically, in performing the PWM control, the second control circuit 52 sets a time interval for supplying a current to the light emitting element 11 based on the result of comparison between a first signal including a triangular wave signal and a first DC voltage set in a predetermined period. On the basis of a second DC voltage set in a period other than the predetermined period, the first control circuit 51 controls a current value to be supplied from the lighting controller 50.As shown in FIG. 4, the power supply control signal write scan line WS 1 and the analog image signal write scan line WS 2 are extended from the scan circuit 20 and are connected to each pixel 12. The power supply control signal line SL 1 and the analog image signal line SL 2 are output from the driver 30 and are connected to each pixel 12. The driver 30 is a driver IC that processes a power supply control signal and an analog image signal. The power supply control signal write scan line WS1 and the analog image signal write scan line WS2 are connected to a TFT circuit which is disposed on a mounting substrate together with the pixel circuit 14. The TFT is made of low temperature polycrystalline SI or an oxide semiconductor.Each pixel 12 includes multiple sub-pixels, as shown in an enlarged view of the major components of FIG. 4. The pixel 12 includes a first subpixel 12A and a second subpixel 12B. Each subpixel includes the light emitting element 11. in particular, the first subpixel 12A includes a first illumination controller 50A and the first light emitting element 11A constituting the first subpixel 12A. The second subpixel 12B includes a second illumination controller 50B and the second light emitting element 11B constituting the second subpixel 12B. Each pixel circuit 14 includes the lighting controller 50. the first lighting controller 50A includes a first control circuit 51A and a second control circuit 52A. The second lighting control device 50B includes a first control circuit 51B and a second control circuit 52B. The first control circuits 51A and 51B supply control currents to the first light emitting element 11A and the second light emitting element 11B, respectively. On the other hand, the second control circuits 52A and 52B control the light emission periods of the first light emitting element 11A and the second light emitting element 11B, respectively. The first control circuits 51A and 51B are power supply control circuits, and the second control circuits 52A and 52B are analog image PWM circuits. The first control circuits (power supply control circuits) 51A and 51B are connected to the power supply line 9 and the power supply control signal line SL 1. A power supply control signal writing timing is input from the power supply control signal writing scan line WS 1. On the other hand, the second control circuits (analog image PWM circuits) 52A and 52B are connected in series to the power supply line 9 via the first control circuits 51A and 51B, respectively. The second control circuits 52A and 52B are also connected to the analog image signal line SL2. From the analog image signal line, an analog image signal writing timing for writing the scanning line WS2 is input. In this way, each of the light emitting elements 11 is connected to the power supply line 9 via the power supply control circuit and the analog image PWM circuit. An operation current value is controlled via the power supply control circuit and a control time is controlled via the analog image PWM circuit.FIG. 4 shows an example in which the first subpixel 12A and the second subpixel 12B each include an LED. However, the present disclosure is not limited to this configuration, but each subpixel may include a plurality of light emitting elements such as LEDs. For example, two or more light emitting elements may be connected in series when a plurality of light emitting elements are used for the purpose of increasing luminance or the like.LEDFIG. 5 shows an example of an element structure when an LED is used as the light emitting element 11. the light emitting element 11 shown in FIG. 5 includes an n-type semiconductor layer 2, an active layer 3, a p-type semiconductor layer 4, an n-side electrode 5, and a p-side electrode 6. the active layer 3 may include a multiple quantum well structure (MQW) or the like. The light emitting element 11 is connected to a pixel operation circuit 8 such as a DC power supply, and emits light when receiving an operation current supplied from the power supply line 9. The light emission period of the first light emitting element 11A is controlled by a certain driving current. The light emission color of the first light emitting element 11A is set to blue. The second light emission color of the second light emitting element 11B is controlled by an operation current, and the light emission period of the second light emitting element 11B is controlled by the operation current. The second light emission color is tunable to each color from green to red.B subframesFIG. 6 shows an illumination image in the B sub-frame using such a display 10, and FIG. 7 shows an illumination image in the GR sub-frame using such a display 10. In the B sub-frame, the luminance of the pixels 12 is different, but the chromaticity is constant. Luminance gradation is controlled by PWM. The density difference of the individual pixels 12 in FIG. 6 represents the difference in the average luminance in the sub-frame.GR subframesOn the other hand, in the GR sub-frame, both the luminance and chromaticity between the pixels 12 are tunable. In the (G-R) sub-frame, a current value supplied to the second light emitting element 11B and the second light emitting color, that is, chromaticity, are controlled in the range of (G-R). Specifically, the illumination controller 50 acquires the RGB chromaticity in each pixel 12 by accessing the information storage 70. The chromaticity of B, i.e., the first light emitting color emitted from the first light emitting element 11A, is uniquely determined. On the other hand, the second light emission color of the second light emitting element 11B is to be determined. First, a light emission color at the time of (G-R) wavelength change and a luminance ratio of B to (G-R) are to be displayed from a chromaticity signal to correspond to a color at the time of B emission. Subsequently, from the chromaticity of the light emission color and the luminance ratio, a light emission intensity corresponding to a luminance signal to be displayed is determined.Method of Operating the Light Emitting Device.An example of a method of operating the light emitting device will be described below. Next, a method will be described in which the lighting control device 50 divides a frame to cause the plurality of first light emitting elements 11A and the plurality of second light emitting elements 11B to emit light into a first sub-frame and a second sub-frame, and operates the plurality of first light emitting elements 11A and the plurality of second light emitting elements 11B. In the first sub-frame, each of the plurality of first light emitting elements 11A is caused to emit light. Since blue light is emitted as the first light emission color in the first sub-frame, it is referred to as a B sub-frame. In the second sub-frame, each of the plurality of second light emitting elements 11B is caused to emit light. Since the second light emission color is emitted in the second sub-frame, it is referred to as an RG sub-frame.The lighting control device 50 is caused to supply a respective driving current to the first light emitting element 11A and the second light emitting element 11B, and causes the second control circuit 52 to control a light emitting period of the first light emitting element 11A and the second light emitting element 11B. The step of driving, by the illumination controller 50, the plurality of first light emitting elements 11A and the plurality of second light emitting elements 11B includes a step of determining the second light emitting color and a luminance ratio of the first light emitting element 11A and the second light emitting element 11B from a chromaticity signal and a luminance signal displayed by the pixel 12 to correspond to the first light emitting color, a step of determining a light emitting intensity corresponding to a luminance signal displayed based on the chromaticity of the second light emitting color and the luminance ratio, a step of supplying, by the first control circuit 51, an driving current having a value corresponding to a light emitting color, to the corresponding one of the first light emitting element 11A and the second light emitting element 11B by accessing the information memory 70 and a step of controlling, by the second control circuit 52, a light emission period of the driving current to be supplied to the first light emitting element 11A and the second light emitting element 11B in accordance with the determined light emission intensity.In the first sub-frame, the first control circuit 51 controls the driving current of each of the plurality of first light emitting elements 11A to a constant value, and the second control circuit 52 controls the light emission intensity by PWM control. The driving current of the first light emitting element 11A is set to a driving current value at which the emission of blue light is highly efficient. For example, it is a rated current value.On the other hand, in the second sub-frame, the first control circuit 51 controls a light emission color by a current value for driving each of the plurality of second light emission elements 11B. The second control circuit 52 controls the light emission period of the current value of each of the plurality of second light emitting elements 11B controlled by the first control circuit 51, thereby controlling luminance. Specifically, the second control circuit 52 determines the chromaticity of the second light emission color and the luminance ratio of the first light emission element 11A and the second light emission element 11B from the chromaticity signal and the luminance signal displayed by each pixel 12 to correspond to the first light emission color. Subsequently, the second control circuit 52 determines the light emission intensity corresponding to the luminance signal to be displayed by the second light emitting element 11B based on the chromaticity of the second light emission color and the luminance ratio. In response, referring to the information memory 70, the first control circuit 51 supplies an operating current having a value corresponding to the luminous emission color of the first luminous element 11A and the second luminous element 11B to the first luminous element 11A and the second luminous element 11B. The second control circuit 52 controls the light emission period of each of the first light emitting element 11A and the second light emitting element 11B in accordance with the determined light emission intensity.Method for Determining Driving Current Value and PWM Light Emission PeriodDetails of the method for determining the driving current value and the PWM light emission period of the first light emitting element 11A and the second light emitting element 11B will be described below with reference to the functional block diagram of FIG. 8 and the chromaticity diagram of FIG. 9.First, in step S 801, the operation controller 60 acquires image data from an external source. The input data includes R luminance, G luminance, and B luminance.Subsequently, in step S 802, a specific light emission chromaticity and luminance are determined for each pixel. Each light emission chromaticity to be emitted is represented by a point A in the chromaticity diagram of FIG. 9. In this chromaticity diagram, since the first light emitting element 11A emits blue light as the first light emitting color, it is set at a point B in the vicinity of the lower left vertex of the chromaticity diagram. On the other hand, since the second light emitting element 11B emits light of a second light emitting color between green and red, the second light emitting color is displayed on the chromaticity diagram at a point C between green near the upper vertex and red near the right vertex of the chromaticity diagram. Accordingly, the chromaticity in point A expressed by the mixed light of the first light emitting element 11A and the second light emitting element 11B can be expressed by points B and C. In other words, the light emission color of the second light emitting element 11B is set to set the point C so as to represent the chromaticity in the point A. Further, the luminance ratio of B to (G-R) is determined with respect to a predetermined point A in consideration of the balance of luminance between the first light emitting element 11A and the second light emitting element 11B. Thus, the driving current value and the light emission period of the second light emitting element 11B are determined in point C.According to the above-described idea, in consideration of the light emission chromaticity (B) of B, from the light emission chromaticity (A) of A determined in step S 802 (step S 803), the light emission chromaticity (C) of (G-R) and the luminance ratio of B to (G-R) are determined (step S 804). When the luminance ratio of B to (G-R) is determined in step S 804, the luminance of (G-R) and the luminance of B are forcibly obtained from the luminance at the light emission chromaticity (A) in step S 802 (step S 808).On the other hand, when the light emission chromaticity (C) of (G-R) is determined in step S804, the (G-R) light emission chromaticity driving current characteristic table stored in the information memory 70 is accessed (step S805) to determine the driving current value of (G-R) (step S806).When the operation current value of (G-R) is determined in step S 806, the (G-R) light emission chromaticity-operation current-luminance characteristic table stored in the information memory 70 (step S 807) and the luminance of (G-R) (step S 808) are accessed to determine the PWM light emission period of (G-R) (step S 809).On the other hand, from the luminance of B obtained in step S 808, the PWM light emission period of B is determined with reference to the luminance characteristic value (step S 810) at the operation current value corresponding to the chromaticity of B (step S 811). In this manner, the driving current values of the second light emitting element 11B and the PWM light emitting periods of the first light emitting element 11A and the second light emitting element 11B are determined. As shown in FIG. 2 and described above, the driving current value of the first light emitting element 11A is the maximum value of the driving current value for causing the first light emitting element 11A to emit light.In the light emitting device 100 according to the first embodiment described above, each pixel 12 includes the first light emitting element 11A and the second light emitting element 11B. As shown in FIG. 10A, the first light emitting element 11A is a blue light emitting element with fixed wavelength, and the second light emitting element 11B is a green to red light emitting element with tunable wavelength. In this example, a first light emitting element 11A and a second light emitting element 11B are provided in each pixel 12. However, a plurality of first light emitting elements and / or a plurality of second light emitting elements may also be provided in each pixel. This enables an increase in light emission luminance.In the first embodiment, the one frame period FT is divided into the first sub-frame period SF 1 in which the first light emitting element 11A emits light and the second sub-frame period SF 2 in which the second light emitting element 11B emits light, the first sub-frame period SF 1 being the B sub-frame in which blue light is emitted, and the second sub-frame period SF 2 being the GR sub-frame in which light of an arbitrary color from green to red is emitted, FIG. 2 showing a state in which the first sub-frame period SF 1 precedes the second sub-frame period SF 2. However, the present disclosure is not limited to this configuration. For example, the second sub-frame that is the GR sub-frame for emitting light of any color from green to red may precede the first sub-frame that is the B sub-frame for emitting blue light. As described above, the human eye is sensitive to brightness in the GR sub-frame and colors by combining the GR sub-frame and the B sub-frame, but it is the time at which brightness is perceived that determines the temporal resolution. Accordingly, the advancement of the GR sub-frame makes it possible to suppress the delay in timing experienced by a human with respect to video display data input to a display system. In this case, the previous GR subframe may be referred to as a first subframe and the B subframe may be referred to as a second subframe.Second EmbodimentThe present disclosure is not limited to the configuration in which the first light emitting element has a fixed wavelength and the second light emitting element has a tunable wavelength, but the first light emitting element may be a tunable wavelength light emitting element. Such an example is shown in FIG. 10B as a light emitting device 200 according to a second embodiment. FIGS. 10A and 10B show examples in which a fixed wavelength light emitting element is indicated by a square and tunable wavelength light emitting elements are each indicated by a square having a diagonal line. The tunable wavelength light emitting element is operated by tuning a light emitting wavelength in a range from a light emitting color in an upper left region to a light emitting color in a lower right region of the square, which are separated by a diagonal line. The reason why the square is separated by a diagonal line is merely to indicate a change in a light emission wavelength, and it is not intended that a light emitting region of the light emitting element is physically divided by a diagonal line to emit light in different light emission colors for each region.In the light emitting device according to the first embodiment shown in FIG. 10A, the first light emitting element 11A is a fixed wavelength light emitting element, and the second light emitting element 11B is a tunable wavelength light emitting element used by tuning a light emitting wavelength in the range of light emitting colors from red R to green B. On the other hand, in the second embodiment shown in Fig. 10B, a tunable wavelength light emitting element is also used as the first light emitting element 11A', but the first light emitting element 11A' is operated with its light emitting wavelength fixed to blue B.Regardless of the region of the light emission wavelength actually driven in this manner, the tunable region of the light emission wavelength of the tunable wavelength light emitting element used as the first light emitting element 11A' may be B-G, B-R, or B-Y as long as B is included in the tunable region of the light emission wavelength. In this case, when the tunable wavelength light emitting element used as the first light emitting element 11A' and the tunable wavelength light emitting element used as the second light emitting element 11B are light emitting elements in which both B-R tunable emission wavelength ranges are actually operated independently of the light emitting wavelength range, each pixel 12D can be formed using light emitting elements having only one specification, so that the manufacturing process of the pixel 12D can be simplified.Further, the information storage 70 stores current chromaticity information and the like of the first light emitting element 11A' and the second light emitting element 11B to cause the first light emitting element 11A' to emit light having the tunable wavelength at the set first light emitting color of blue. The lighting control device 50 determines an operating current of the first light emitting element 11A' corresponding to the first light emitting color by accessing the information memory 70. Further, when the first light emitting element 11A' is of the tunable wavelength type, the wavelengths of blue light can be adjusted. For example, variations in the light emission wavelength of the first light emitting element 11A' from the pixels 12D may be corrected, and the blue light wavelengths of the pixels 12D may be equalized.The above examples describe an active matrix operating method. However, the present disclosure may be applied to a passive matrix operation method.A light emitting device of the present disclosure may be suitably used for, for example, a medium-size or large-format display, an indicator, a sign, or the like.Industrial applicabilityThe light emitting device and its operation method according to the present invention can be suitably used for, for example, medium-size or large-size display, indicator, marking, or the like.Further, the disclosure includes examples according to the following points:Item 1. A light emitting device comprising:a display comprising a plurality of pixels in which a plurality of first light emitting elements each configured to emit a first light emitting color and a plurality of second light emitting elements each configured to emit a second light emitting color different from the first light emitting color are arranged in a predetermined pattern; anda lighting control device configured to supply an operating current to each of the plurality of first light emitting elements and each of the plurality of second light emitting elements and to control a light emitting period of each of the plurality of first light emitting elements and each of the plurality of second light emitting elements,wherein a light emission color of a second light emitting element of the plurality of second light emitting elements is variable according to an operating current supplied thereto, andwherein the illumination control device is configured to:a frame in which the lighting control device operates the plurality of first light emitting elements and the plurality of second light emitting elements is divided into a first sub-frame and a second sub-frame,operating the plurality of first light emitting elements in the first sub-frame; anddriving the plurality of second light emitting elements in the second sub-frame.Item 2. the light emitting device according to Item 1, further comprising:an information memory configured to store current chromaticity information for determining an operation current value to illuminate each of a first light emitting element of the plurality of first light emitting elements and the second light emitting element in accordance with a determined light emitting color of each of the plurality of pixels; andwherein the lighting control device is configured to control the plurality of first light emitting elements and the plurality of second light emitting elements so that each of the plurality of first light emitting elements and the plurality of second light emitting elements emits light of a specific light emitting color and light emitting luminance based on the current chromaticity information stored in the information storage.Item 3. The light emitting device according to Item 1 or 2, wherein:the lighting control device includes:a first control circuit configured to supply an operating current to each of the first light emitting element and the second light emitting element; anda second control circuit configured to control a light emission period of the first light emitting element and the second light emitting element.Item 4. The light emitting device according to any one of Items 1 to 3, wherein one or more illumination controllers are provided for each of the plurality of pixels.Item 5. The light emitting device according to any one of Items 1 to 4, wherein each of the plurality of pixels includes at least one of the plurality of first light emitting elements and at least one of the plurality of second light emitting elements.Item 6. The light emitting device according to any one of Items 1 to 5, wherein the first light emitting color is blue.Item 7. the light emitting device according to any one of Items 1 to 6, wherein the first light emitting color is blue.Item 8 The light emitting device according to any one of Items 1 to 7, wherein the second light emitting color is tunable between green and red according to an operating current supplied to the second light emitting element.Item 9: The light emitting device according to any one of Items 1 to 8, wherein:the first control circuit is configured to supply an operating current having a value corresponding to a light emission color of each of the first light emitting element and the second light emitting element to the corresponding one of the first light emitting element and the second light emitting element by accessing the information memory, andthe second control circuit is configured to control a light emission period of each of the first light emitting element and the second light emitting element in accordance with a light emission intensity corresponding to a luminance signal to be displayed by the second light emitting element, wherein the light emission intensity is determined based on a chromaticity of the second light emission color and a luminance ratio of the first light emitting element and the second light emitting element, wherein the chromaticity of the second light emission color and the luminance ratio are determined from a chromaticity signal and a luminance signal that are a basis of the chromaticity and the luminance to be displayed by each pixel in the second sub-frame to correspond to the first light emission color.Item 10. The light emitting device according to any one of Items 1 to 9, wherein:the lighting control device is configured to set a time interval for supplying a current to each of the first light emitting element and the second light emitting element based on a comparison between a first signal including a triangular wave signal and a first DC voltage set in a predetermined period; andthe lighting control device is configured to control a current value to be supplied based on a second DC voltage set in a period different from the predetermined period.Item 11 A method of operating a light emitting device comprising a display having a plurality of pixels in which a plurality of first light emitting elements each configured to emit a first light emitting color and a plurality of second light emitting elements each configured to emit a second light emitting color different from the first light emitting color are arranged in a predetermined pattern, a light emitting color of each of the plurality of second light emitting elements is variable according to an operation current supplied thereto, and an illumination controller configured to supply an operation current to each of the plurality of first light emitting elements and each of the plurality of second light emitting elements and controls a light emitting period of each of the plurality of first light emitting elements and each of the plurality of second light emitting elements, the method comprising:Item. The method of operating a light emitting device according to item 11, wherein:operating the plurality of first light emitting elements and the plurality of second light emitting elements with the lighting controller comprises:determining the second light emission color and a luminance ratio of a first light emission element of the plurality of first light emission elements and a second light emission element of the plurality of second light emission elements from a chromaticity signal and a luminance signal that form the basis of chromaticity and luminance to be displayed by each of the plurality of pixels to correspond to the first light emission color, respectively,determining a light emission intensity corresponding to a luminance signal to be displayed based on chromaticity of the second light emission color and the luminance ratio,supplying an operating current having a value corresponding to a light emission color of the first light emitting element and the second light emitting element to the corresponding one of the first light emitting element and the second light emitting element by accessing an information memory configured to store current chromaticity information for determining an operating current value to control the first light emitting element and the second light emitting element in accordance with a determined light emission color of each of the plurality of pixels with a first control circuit of the lighting control device, andcontrolling a light emission period of the driving current to be supplied to the first light emitting element and the second light emitting element in accordance with the determined light emission intensity with a second control circuit of the lighting control apparatus.Item 13: The method of operating a light emitting device according to Item 11 or 12, wherein:operating the plurality of first light emitting elements and the plurality of second light emitting elements with the lighting controller comprises:controlling a light emission intensity by pulse width modulation control in the first sub-frame with the second control circuit while the first control circuit keeps an operating current of each of the plurality of first light emitting elements constant,controlling, by the first control circuit, a light emitting color by a current value for driving each of the plurality of second light emitting elements; andcontrolling, by the second control circuit, luminance by a light emission period of the current value of each of the plurality of second light emitting elements controlled by the first control circuit in the second sub-frame.List of reference characters100, 200 Light emitting device 2 n-type semiconductor layer 3 Active layer 4 p-type semiconductor layer 5 n-side electrode 6 p-side electrode 8 Pixel operation circuit 9 Power supply line 10 Display 11 Light emitting element; 11A, 11A' First light emitting element; 11B Second light emitting element 12, 12B, 12D pixels; 12A First sub-pixel; 12B Second sub-pixel 14 Pixel circuit; 14A First sub-pixel circuit; 14B Second sub-pixel circuit 20 Sensing circuit 30 Driver 50, 50A, 50B Lighting controller 51, 51A, 51B First control circuit; 52, 52A, 52B Second control circuit 60 Operation controller 70 Information memory WS Write scan line WS 1 Power supply control signal write scan line; WS 2 Analog image signal write scan line SL Signal line; SL 1 Power supply control signal line; SL 2  References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2023-218 219

[0001] JP 2021-52168 A

[0004] US 10 885 834 [0027, 0028]

Claims

A light emitting device comprising: a display including a plurality of pixels in which a plurality of first light emitting elements each configured to emit a first light emitting color and a plurality of second light emitting elements each configured to emit a second light emitting color different from the first light emitting color are arranged in a predetermined pattern; An illumination control apparatus configured to supply an operation current to each of the plurality of first light emitting elements and each of the plurality of second light emitting elements and control a light emission period of each of the plurality of first light emitting elements and each of the plurality of second light emitting elements, wherein a light emission color of each of the plurality of second light emitting elements is variable according to an operation current supplied thereto, and wherein the illumination control apparatus is configured to: divide a frame in which the illumination control apparatus operates the plurality of first light emitting elements and the plurality of second light emitting elements into a first sub-frame and a second sub-frame, operate the plurality of first light emitting elements in the first sub-frame, and operate the plurality of second light emitting elements in the second sub-frame.The light emitting device according to claim 1, further comprising: an information memory configured to store current chromaticity information for determining an operation current value to illuminate each of a first light emitting element of the plurality of first light emitting elements and the second light emitting element in accordance with a determined light emission color of each of the plurality of pixels, and wherein the illumination control device is configured to control the plurality of first light emitting elements and the plurality of second light emitting elements so that each of the plurality of first light emitting elements and the plurality of second light emitting elements emits light of a determined light emission color and light emission luminance based on the current chromaticity information stored in the information memory.The light emitting device according to claim 2, wherein: the illumination control device comprises: a first control circuit configured to supply an operating current to the first light emitting element and the second light emitting element, respectively; and a second control circuit configured to control a light emitting period of the first light emitting element and the second light emitting element.The light emitting device according to claim 3, wherein one or more illumination control devices are provided for each of the plurality of pixels.The light emitting device of claim 1, wherein each of the plurality of pixels comprises at least one of the plurality of first light emitting elements and at least one of the plurality of second light emitting elements.The light emitting device according to claim 1, wherein the first light emitting color is blue.The light emitting device according to claim 6, wherein the first light emitting color has a fixed wavelength.The light emitting device according to claim 1, wherein the second light emitting color is tunable between green and red according to an operating current supplied to the second light emitting element.The light emitting device according to claim 3, wherein: the first control circuit is configured to supply an operation current having a value corresponding to a light emission color of each of the first light emitting element and the second light emitting element to the corresponding one of the first light emitting element and the second light emitting element by accessing the information memory, and the second control circuit is configured to control a light emission period of each of the first light emitting element and the second light emitting element in accordance with a light emission intensity corresponding to a luminance signal to be displayed by the second light emitting element, the light emission intensity being determined based on a chromaticity of the second light emission color and a luminance ratio of the first light emitting element and the second light emitting element, wherein the chromaticity of the second light emission color and the luminance ratio are determined from a chromaticity signal and a luminance signal that are a basis of the chromaticity and the luminance to be displayed by each pixel in the second sub-frame to correspond to the first light emission color.The light emitting device according to claim 1, wherein: the illumination controller is configured to set a time interval for supplying a current to each of the first light emitting element and the second light emitting element based on a comparison between a first signal including a triangular wave signal and a first DC voltage set in a predetermined period; and the illumination controller is configured to control a current value to be supplied based on a second DC voltage set in a period different from the predetermined period.A method of operating a light emitting device comprising a display having a plurality of pixels in which a plurality of first light emitting elements each configured to emit a first light emitting color and a plurality of second light emitting elements each configured to emit a second light emitting color different from the first light emitting color are arranged in a predetermined pattern, a light emitting color of each of the plurality of second light emitting elements is variable according to an operation current supplied thereto, and an illumination controller configured to supply an operation current to each of the plurality of first light emitting elements and each of the plurality of second light emitting elements and control a light emitting period of each of the plurality of first light emitting elements and each of the plurality of second light emitting elements, the method comprising: dividing a frame in which the illumination controller operates the plurality of first light emitting elements and the plurality of second light emitting elements, in a first sub-frame and a second sub-frame, driving the plurality of first light emitting elements in the first sub-frame, and driving the plurality of second light emitting elements in the second sub-frame.The method for driving a light emitting device according to claim 11, wherein: driving the plurality of first light emitting elements and the plurality of second light emitting elements with the lighting controller comprises: determining, from a chromaticity signal and a luminance signal that are the basis of chromaticity and luminance to be displayed by each of the plurality of pixels, the second light emitting color and a luminance ratio of a first light emitting element of the plurality of first light emitting elements and a second light emitting element of the plurality of second light emitting elements to correspond to the first light emitting color, respectively; determining, based on chromaticity of the second light emitting color and the luminance ratio, a light emitting intensity corresponding to a luminance signal to be displayed; supplying, to the corresponding one of the first light emitting element and the second light emitting element, a driving current having a value corresponding to a light emitting color of the first light emitting element and the second light emitting element, accessing an information memory configured to store current chromaticity information for determining an operation current value to control the first light emitting element and the second light emitting element in accordance with a determined light emitting color of each of the plurality of pixels with a first control circuit of the lighting control device, and controlling a light emitting period of the operation current to be supplied to the first light emitting element and the second light emitting element in accordance with the determined light emitting intensity with a second control circuit of the lighting control device.The method of driving a light emitting device according to claim 12, wherein: driving the plurality of first light emitting elements and the plurality of second light emitting elements with the lighting controller comprises: controlling a light emission intensity by pulse width modulation control in the first sub-frame with the second control circuit while the first control circuit keeps an driving current of each of the plurality of first light emitting elements constant, controlling, by the first control circuit, a light emission color by a current value for driving each of the plurality of second light emitting elements, and controlling, by the second control circuit, a luminance by a light emission period of the current value of each of the plurality of second light emitting elements controlled by the first control circuit in the second sub-frame.

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