JP7672045B2 - Illumination system and illumination method - Google Patents

Description

The present invention relates to a lighting system and a lighting method.

Various techniques have been proposed to adjust the color of the light output from a lighting device (see, for example, Patent Document 1).

JP 2009-123429 A

The present invention provides a lighting system and lighting method that can adjust the chromaticity of output light, thereby achieving output light with a high average color rendering index Ra.

The lighting system according to one aspect of the present invention includes a control unit that controls four light sources that emit light with different chromaticity values, and a rectangular region on a chromaticity coordinate system with four vertices corresponding to the chromaticity values of the light emitted by the four light sources includes at least a part of the chromaticity range of the light source color defined in JIS Z9112. The control unit realizes output light having a chromaticity value within a first triangular region with the top three points among the four points that are closest to the blackbody locus as vertices by causing three light sources among the four light sources that correspond to the three vertices of the first region to emit light, and realizes output light having a chromaticity value within a second triangular region excluding the first region from the rectangular region by causing three light sources among the four light sources that correspond to the three vertices of the second region to emit light.

The lighting method according to one aspect of the present invention includes a control step of controlling four light sources that emit light with different chromaticity values, and a rectangular region on a chromaticity coordinate system having four vertices corresponding to the chromaticity values of the light emitted by the four light sources includes at least a part of the chromaticity range of the light source color defined in JIS Z9112, and in the control step, output light having a chromaticity value within a first region of a triangle having vertices of the top three points among the four points that are closest to the blackbody locus is realized by emitting three light sources among the four light sources that correspond to the three vertices of the first region, and output light having a chromaticity value within a second region of the triangle excluding the first region from the rectangular region is realized by emitting three light sources among the four light sources that correspond to the three vertices of the second region.

A program according to one aspect of the present invention is a program for causing a computer to execute the lighting method.

The present invention provides a lighting system and lighting method that can adjust the chromaticity of output light, thereby achieving output light with a high average color rendering index Ra.

FIG. 1 is a block diagram showing a functional configuration of a lighting system according to a first embodiment. FIG. 2 is a diagram showing chromaticity coordinates in which the chromaticity values of the four light sources included in the lighting system according to the first embodiment are plotted. FIG. 3 is a diagram showing the general color rendering index Ra of output light obtained by the chromaticity control method (control example 1) in the lighting system according to the first embodiment. FIG. 4 is a diagram showing chromaticity coordinates on which points relating to control example 2 of the lighting system according to embodiment 1 are plotted. FIG. 5 is a diagram showing a simulation result of the luminous flux of output light and the general color rendering index Ra realized by Control Example 2 of the first embodiment. FIG. 6 is a block diagram showing a functional configuration of a lighting system according to the second embodiment. FIG. 7 is a diagram showing chromaticity coordinates in which the chromaticity values of the four light sources included in the lighting system according to the second embodiment are plotted. FIG. 8 is a diagram showing the general color rendering index Ra of output light obtained by the chromaticity control method (control example 1) in the lighting system according to embodiment 2. FIG. 9 is a diagram showing chromaticity coordinates on which points relating to control example 2 of the lighting system according to embodiment 2 are plotted.

The following describes the embodiments in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in an independent claim are described as optional components.

Note that each figure is a schematic diagram and is not necessarily a precise illustration. In addition, in each figure, the same reference numerals are used for substantially the same configurations, and duplicate explanations may be omitted or simplified.

(Embodiment 1)
[composition]
First, a description will be given of the configuration of a lighting system according to embodiment 1. Fig. 1 is a block diagram showing the functional configuration of a lighting system according to embodiment 1.

The lighting system 10 is a system that can cause the lighting device 40 to emit light with a chromaticity desired by the user by independently adjusting the dimming of the blue light source 42b, the green light source 42g, the red light source 42r, and the blue-green light source 42bg included in the light source unit 42 of the lighting device 40. In other words, the lighting system 10 is a system that supports the chromaticity adjustment function of the lighting device 40. The lighting system 10 includes an input device 20, a control device 30, and a lighting device 40. Note that the lighting system 10 may include multiple lighting devices 40 for one control device 30.

The input device 20 accepts input from a user to specify chromaticity. The input device 20 is, for example, a portable information terminal such as a smartphone or a tablet terminal, but may also be a stationary information terminal that is fixedly installed on a wall or the like. The input device 20 may be realized by installing an application program corresponding to the lighting system 10 on a general-purpose device, or may be a dedicated device for the lighting system 10.

The control device 30 controls the lighting device 40 to emit light with the chromaticity input to the input device 20. The control device 30 includes a control unit 31 and a storage unit 32. The input device 20 and the control device 30 may be realized as a single integrated device.

The control unit 31 controls the light emission of the lighting device 40. Specifically, the control unit 31 can adjust the chromaticity of the light emitted by the lighting device 40 by sending a control signal to the lighting device 40. The control unit 31 sends the control signal to the lighting device 40 by, for example, wireless communication, but may also send the control signal to the lighting device 40 by wired communication. The control unit 31 is realized by, for example, a microcomputer, but may also be realized by a processor. The functions of the control unit 31 are realized by the microcomputer or processor constituting the control unit 31 executing a computer program stored in the memory unit 32.

The memory unit 32 is a storage device that stores the computer program executed by the control unit 31 and various information required to control the lighting device 40. Specifically, the memory unit 32 is realized by a semiconductor memory or the like.

The lighting device 40 is installed, for example, indoors and illuminates the indoor space. The lighting device 40 is, for example, a ceiling light, but may be other lighting devices such as a spotlight or a downlight. The lighting device 40 includes a dimming circuit 41 and a light source unit 42. The light source unit 42 includes a red light source 42r, a green light source 42g, a blue light source 42b, and a blue-green light source 42bg.

The dimming circuit 41 is a circuit that supplies power to the light source unit 42 in response to a control signal transmitted from the control device 30 (control unit 31). The dimming circuit 41 includes, for example, a chopper control circuit. The control unit 31 changes the current supplied to the light source unit 42 by switching the switching element included in the dimming circuit 41 (chopper control circuit) using a control signal. The dimming circuit 41 can supply power (current) independently to each of the blue light source 42b, green light source 42g, red light source 42r, and blue-green light source 42bg of the light source unit 42. In other words, the dimming circuit 41 can independently dim the red light source 42r, green light source 42g, blue light source 42b, and blue-green light source 42bg of the light source unit 42.

The blue light source 42b is a light source that emits blue light. For example, the blue light source 42b emits blue light (specifically, including blue and purple light) with an emission peak wavelength of 380 nm or more and 480 nm or less. Specifically, the blue light source 42b is a light-emitting module that uses a blue LED, but the specific form of the blue light source 42b is not particularly limited.

The green light source 42g is a light source that emits green light. For example, the green light source 42g emits green light (specifically, including green-blue, blue-green, green, and yellow-green light) with an emission peak wavelength of 480 nm or more and 580 nm or less. Specifically, the green light source 42g is a light-emitting module that uses a green LED, but the specific form of the green light source 42g is not particularly limited.

The red light source 42r is a light source that emits red light. For example, the red light source 42r emits red light with an emission peak wavelength of 600 nm or more and 680 nm or less. Specifically, the red light source 42r is a light-emitting module that uses a red LED, but the specific form of the red light source 42r is not particularly limited.

The blue-green light source 42bg is a light source that emits blue-green light (blue-green may also be expressed as royal blue, etc.) and is an example of another light source or another blue light source. The blue-green light source 42bg emits, for example, blue-green light with an emission peak wavelength of 465 nm or more and 490 nm or less (blue light with a longer wavelength than the blue light source 42b). Specifically, the blue-green light source 42bg is a light-emitting module that uses an LED that emits blue-green light, but the specific form of the blue-green light source 42bg is not particularly limited.

[Chromaticity Control Example 1]
The lighting system 10 can improve the color rendering of the output light by selectively emitting the blue light source 42b, the green light source 42g, the red light source 42r, and the blue-green light source 42bg when controlling the chromaticity of the output light of the lighting device 40. The output light is a light obtained by synthesizing at least one of the light emitted by the red light source 42r, the light emitted by the green light source 42g, the light emitted by the blue light source 42b, and the light emitted by the blue-green light source 42bg, and means the light finally emitted from the lighting device 40. Hereinafter, a first example of controlling the chromaticity of the lighting system 10 will be described with reference to a chromaticity diagram (chromaticity coordinates). FIG. 2 is a diagram showing chromaticity coordinates on which the chromaticity values of the red light source 42r, the green light source 42g, the blue light source 42b, and the blue-green light source 42bg are plotted. The chromaticity coordinates in FIG. 2 show a color space defined in CIE1931.

The chromaticity coordinates in FIG. 2 show point B1, which indicates the chromaticity value of the blue light emitted by blue light source 42b, point G, which indicates the chromaticity value of the green light emitted by green light source 42g, point R, which indicates the chromaticity value of the red light emitted by red light source 42r, and point B2, which indicates the fourth chromaticity value of the blue-green light emitted by blue-green light source 42bg.

On the chromaticity coordinate system, the rectangular region with vertices B1, G, R, and B2 includes at least a part of the chromaticity range of the light source color defined in JIS Z9112. Here, the light source color means five types of daylight color (D), daylight white (N), white (W), warm white (WW), and incandescent color (L), and the chromaticity range of the five types of light source colors is five approximately parallelogram regions near the blackbody locus in Figure 2. Specifically, the rectangular region with vertices B1, G, R, and B2 includes the entire chromaticity range of daylight color (D), daylight white (N), white (W), and warm white (WW), and a part of the chromaticity range of incandescent color (L). The lighting system 10 can produce output light having chromaticity values within a quadrangular area with vertices at points B1, G, R, and B2, and it can be said that the chromaticity range of the output light that the lighting system 10 can produce is relatively wide.

The lighting system 10 divides the rectangular region into a first triangular region having vertices G, R, and B2, and a second triangular region having vertices B1, R, and B2, and adjusts the chromaticity to improve the color rendering of the output light. There are two ways to divide the rectangular region into two triangular regions. In the lighting system 10, the triangular region having the top three points, B1, G, R, and B2, that are closest to the blackbody locus are set as the first region, and the triangular region excluding the first region from the rectangular region is set as the second region. The distance from point B1 to the blackbody locus means, for example, the average value of the distance from point B1 to each of the multiple points when the blackbody locus is considered to be a set of multiple points. The same applies to the distances from point G, point R, and point B2 to the blackbody locus.

For example, when a point indicating a user-desired chromaticity value input to the input device 20 is located within the first region, the control unit 31 of the control device 30 does not emit light from the blue light source 42b, but emits light from the three light sources, green light source 42g, red light source 42r, and blue-green light source 42bg, and adjusts the light intensity independently to realize output light having the user-desired chromaticity value. Similarly, when a point indicating a user-desired chromaticity value input to the input device 20 is located within the second region, the control unit 31 of the control device 30 does not emit light from the green light source 42g, but emits light from the three light sources, blue light source 42b, red light source 42r, and blue-green light source 42bg, and adjusts the light intensity independently to realize output light having the user-desired chromaticity value.

The average color rendering index Ra of the output light obtained by such a chromaticity control method will be described below while comparing it with the average color rendering index Ra of the output light obtained by a chromaticity control method according to a comparative example. Figure 3 is a diagram showing the average color rendering index Ra of the output light obtained by the chromaticity control method in lighting system 10 (hereinafter also simply referred to as control example 1).

In FIG. 3, the average color rendering index Ra of the output light obtained by the chromaticity control method according to the comparative example is also shown. The chromaticity control method according to the comparative example is a control method in which the output light having the chromaticity values located within points B1, G, and R is realized by emitting the three light sources of blue light source 42b, green light source 42g, and red light source 42r without emitting the blue-green light source 42bg, and by independently dimming them. In other words, the comparative example is different from control example 1 in the way in which the rectangle is divided into two triangular regions. In FIG. 3, the output light is white light with Duv=0. In FIG. 3, the horizontal axis indicates the color temperature (Tc) of the output light, and the vertical axis indicates the average color rendering index Ra of the output light.

As shown in FIG. 3, control example 1 can achieve output light with a higher average color rendering index Ra than the comparative example.

As described above, in the lighting system 10, the control unit 31 realizes output light having chromaticity values in a first region having vertices G, R, and B2 by emitting light from three light sources corresponding to the points G, R, and B2, and realizes output light having chromaticity values in a triangular second region having vertices B1, R, and B2 by emitting light from three light sources corresponding to the points B1, R, and B2. The first region is specifically a triangular region having vertices that are the top three points among the points B1, G, R, and B2 that are closest to the blackbody locus, and the second region is a triangular region obtained by excluding the first region from a quadrangular region having vertices B1, G, R, and B2. This allows the lighting system 10 to realize output light having a high average color rendering index Ra. The lighting system 10 can improve the general color rendering index Ra of output light having a light source color (one of five types) specified in JIS Z9112, for example, and reduce color unevenness on the surface illuminated by the light.

[Control Example 2]
Control Example 2 of the chromaticity of the lighting system 10 will be described with reference to a chromaticity diagram (chromaticity coordinates). Fig. 4 is a diagram showing chromaticity coordinates in which points related to Control Example 2 are plotted. The chromaticity coordinates in Fig. 4 indicate a color space defined in CIE1931. The chromaticity coordinates in Fig. 4 are basically the same as those in Fig. 2, except that a first point P1, a second point P2, a third point P3, a fourth point P4, and a fifth point P5 are illustrated.

The first point P1 is a point located on the line segment connecting point B2, which indicates the chromaticity value of the blue-green light source 42bg, and point G, which indicates the chromaticity value of the green light source 42g (an example of the first chromaticity value). The first point P1 is a point that indicates the chromaticity value when each of the blue-green light source 42bg and the green light source 42g is made to emit light at maximum brightness.

The second point P2 is a point located on the line segment connecting point B2, which indicates the chromaticity value of the blue-green light source 42bg, and point R, which indicates the chromaticity value (an example of the second chromaticity value) of the red light source 42r. The second point P2 is a point that indicates the chromaticity value when each of the blue-green light source 42bg and the red light source 42r is made to emit light at maximum brightness.

The third point P3 is a point located within the first region. The third point P3 is a point that indicates the chromaticity value when each of the three light sources (green light source 42g, red light source 42r, and blue-green light source 42bg) corresponding to the three vertices of the first region is made to emit light at maximum brightness.

The fourth point P4 is a point located on the line segment connecting point B2, which indicates the chromaticity value of the blue-green light source 42bg, and point B1, which indicates the chromaticity value of the blue light source 42b (an example of a third chromaticity value). The fourth point P4 is a point that indicates the chromaticity value when each of the blue-green light source 42bg and the blue light source 42b is made to emit light at maximum brightness.

The fifth point P5 is a point located within the second region. The fifth point P5 is a point that indicates the chromaticity value when each of the three light sources (blue light source 42b, red light source 42r, and blue-green light source 42bg) corresponding to the three vertices of the second region is made to emit light at maximum brightness.

In the above-mentioned control example 1, the chromaticity values in the first region of the triangle with vertices G, R, and B2 are realized by emitting light from the green light source 42g, the red light source 42r, and the blue-green light source 42bg. Here, the chromaticity values in the first target region (the hatched region in FIG. 4) in the first region can be realized by emitting light from all of the blue light source 42b, the green light source 42g, the red light source 42r, and the blue-green light source 42bg. In this way, it is possible to improve the average color rendering index Ra of the output light and increase the amount of light of the output light at the same time.

Therefore, in control example 2, the control unit 31 realizes the chromaticity values in the first target area by emitting light from all of the blue light source 42b, green light source 42g, red light source 42r, and blue-green light source 42bg and adjusting the light intensity independently. The first target area is an area where a rectangular area surrounded by point B2 indicating the chromaticity value of the blue-green light source 42bg, the first point P1, the second point P2, and the third point P3 overlaps with a triangular area surrounded by point G (point indicating the first chromaticity value), point R (point indicating the second chromaticity value), and point B1 (point indicating the third chromaticity value).

The control unit 31 realizes, for example, output light having a certain chromaticity value in the first target area as follows. The control unit 31 calculates a first dimming value of each light source when the above chromaticity value in the first target area is realized by emitting light from the green light source 42g, the red light source 42r, and the blue-green light source 42bg without emitting light from the blue-green light source 42bg. The control unit 31 also calculates a second dimming value of each light source when the above chromaticity value in the first target area is realized by emitting light from the blue light source 42b, the green light source 42g, and the red light source 42r without emitting light from the blue-green light source 42bg. The control unit 31 sets the dimming value obtained by summing the first dimming value and the second dimming value as the final dimming value. Figure 5 is a diagram showing the simulation results of the luminous flux and the general color rendering index Ra of the output light realized by the control example 2.

As shown in "Control Example 1" in the "First Target Region" column of FIG. 5, when output light having chromaticity values of x = 0.263, y = 0.284 in the first target region is realized by Control Example 1, the total luminous flux is 125 and the average color rendering index Ra is 91. Note that realizing the output light by Control Example 1 corresponds to emitting light from the green light source 42g, the red light source 42r, and the blue-green light source 42bg at the first dimming value described above.

The "additional amount" in the "first target area" column in FIG. 5 refers to the case where it is assumed that the output light is realized by emitting light from blue light source 42b, green light source 42g, and red light source 42r at the second dimming value described above. In this case, the total luminous flux is 72, and the average color rendering index Ra is 84.

As shown in "Control Example 2" in the "First Target Region" column of FIG. 5, when output light having chromaticity values of x = 0.263, y = 0.284 in the first target region is realized by Control Example 2, the total luminous flux is 197 and the average color rendering index Ra is 93. Note that realizing output light by Control Example 2 is equivalent to causing blue light source 42b, green light source 42g, red light source 42r, and blue-green light source 42bg to emit light at the final dimming value that is the sum of the first dimming value and the second dimming value described above.

In this way, according to control example 2, it is possible to improve the general color rendering index Ra and increase the amount of light of the output light having the above chromaticity values in the first target region. Note that in control example 2, when the output light having the above chromaticity values in the first target region is emitted from the lighting device 40, the blue-green light source 42bg emits light at maximum output (maximum brightness).

In the above-mentioned control example 1, the chromaticity values in the second region of the triangle with vertices B1, R, and B2 are realized by emitting light from the blue light source 42b, the red light source 42r, and the blue-green light source 42bg. Here, the chromaticity values in the second target region (the hatched region in FIG. 4) in the second region can be realized by emitting light from all of the blue light source 42b, the green light source 42g, the red light source 42r, and the blue-green light source 42bg. In this way, it is possible to improve the average color rendering index Ra of the output light and increase the amount of light of the output light at the same time.

Therefore, in control example 2, the control unit 31 realizes the chromaticity values in the second target area by emitting light from all of the blue light source 42b, green light source 42g, red light source 42r, and blue-green light source 42bg and adjusting the light intensity independently. The second target area is an area where a rectangular area surrounded by point B2, the second point P2, the fourth point P4, and the fifth point P5, which indicate the chromaticity value of the blue-green light source 42bg, overlaps with a triangular area surrounded by point G (a point indicating the first chromaticity value), point R (a point indicating the second chromaticity value), and point B1 (a point indicating the third chromaticity value).

The control unit 31 realizes output light having a certain chromaticity value in the second target area, for example, as follows. The control unit 31 calculates a third dimming value for each light source when the above chromaticity value in the second target area is realized by emitting light from the blue light source 42b, the red light source 42r, and the blue-green light source 42bg, without emitting light from the green light source 42g. The control unit 31 also calculates a fourth dimming value for each light source when the above chromaticity value in the second target area is realized by emitting light from the blue light source 42b, the green light source 42g, and the red light source 42r, without emitting light from the blue-green light source 42bg. The control unit 31 determines the dimming value obtained by summing the third dimming value and the fourth dimming value as the final dimming value.

As shown in "Control Example 1" in the "Second Target Region" column in FIG. 5 above, when output light having chromaticity values of x = 0.254, y = 0.270 in the second target region is realized by Control Example 1, the total luminous flux is 115 and the average color rendering index Ra is 92. Note that realizing output light by Control Example 1 corresponds to emitting light from blue light source 42b, red light source 42r, and blue-green light source 42bg at the third dimming value described above.

The "additional amount" in the "second target area" column in FIG. 5 refers to the case where it is assumed that the output light is realized by emitting light from blue light source 42b, green light source 42g, and red light source 42r at the fourth dimming value described above. In this case, the total luminous flux is 91, and the average color rendering index Ra is 82.

As shown in "Control Example 2" in the "Second Target Region" column of FIG. 5, when output light having chromaticity values of x = 0.254, y = 0.270 in the second target region is realized by Control Example 2, the total luminous flux is 206 and the average color rendering index Ra is 92. Note that realizing output light by Control Example 2 is equivalent to causing blue light source 42b, green light source 42g, red light source 42r, and blue-green light source 42bg to emit light at the final dimming value that is the sum of the third dimming value and the fourth dimming value described above.

In this way, according to control example 2, it is possible to improve the average color rendering index Ra and increase the amount of light of the output light having the above chromaticity values in the second target region. In control example 2, when the output light having the above chromaticity values in the second target region is emitted from the lighting device 40, the blue-green light source 42bg emits light at maximum output (maximum brightness).

In addition, in the first target region and the second target region, it may be possible to switch between applying control example 1 and applying control example 2. For example, the control unit 31 may selectively execute an operation of a color rendering emphasis mode that emphasizes the color rendering of output light having chromaticity values belonging to the first target region and the second target region, and an operation of a light intensity emphasis mode that emphasizes the light intensity of output light having chromaticity values belonging to the first target region and the second target region. In the operation of the color rendering emphasis mode, as described in control example 1, the control unit 31 realizes the chromaticity values belonging to the first target region by emitting light from three light sources corresponding to the three vertices of the first region, and the chromaticity values belonging to the second target region by emitting light from three light sources corresponding to the three vertices of the second region. In the operation of the light intensity emphasis mode, as described in control example 2, the control unit 31 realizes the chromaticity values belonging to the first target region and the second target region by emitting light from four light sources provided in the lighting system 10. The color rendering emphasis mode is an example of the first mode, and the light intensity emphasis mode is an example of the second mode. Such switching of operation modes is performed, for example, based on user input to the input device 20.

(Embodiment 2)
[composition]
First, a description will be given of the configuration of a lighting system according to embodiment 2. Fig. 6 is a block diagram showing the functional configuration of the lighting system according to embodiment 2.

The lighting system 10a according to the second embodiment is a system that can cause the lighting device 40a to emit light with a chromaticity desired by the user by independently adjusting the dimming of the blue light source 42b, the green light source 42g, the red light source 42r, and the yellow light source 42y included in the light source unit 42a of the lighting device 40a. In other words, the lighting system 10a is a system that supports the chromaticity adjustment function of the lighting device 40a. The lighting system 10a includes an input device 20, a control device 30, and a lighting device 40a. Note that the lighting system 10a may include multiple lighting devices 40a for one control device 30.

Detailed explanation of the input device 20 and the control device 30 will be omitted as they have already been mentioned.

Illumination device 40a has a configuration similar to that of illumination device 40, but differs in that it has a yellow light source 42y instead of the blue-green light source 42bg.

The yellow light source 42y is a light source that emits yellow light and is an example of another light source. For example, the yellow light source 42y emits yellow light with an emission peak wavelength of 550 nm or more and 590 nm or less. Specifically, the yellow light source 42y is a light-emitting module that uses an LED that emits yellow light, but the specific form of the yellow light source 42y is not particularly limited.

The basic configurations of the blue light source 42b, green light source 42g, and red light source 42r of the lighting device 40a are similar to those of the blue light source 42b, green light source 42g, and red light source 42r of the lighting device 40, but the chromaticity values are slightly different.

[Chromaticity Control Example 1]
The lighting system 10a can improve the color rendering of the output light by selectively emitting the blue light source 42b, the green light source 42g, the red light source 42r, and the yellow light source 42y when controlling the chromaticity of the output light of the lighting device 40a. The output light is a light obtained by synthesizing at least one of the light emitted by the red light source 42r, the light emitted by the green light source 42g, the light emitted by the blue light source 42b, and the light emitted by the yellow light source 42y, and means the light finally emitted from the lighting device 40a. Hereinafter, a first example of controlling the chromaticity of the lighting system 10a will be described with reference to a chromaticity diagram (chromaticity coordinates). FIG. 7 is a diagram showing chromaticity coordinates on which the chromaticity values of the red light source 42r, the green light source 42g, the blue light source 42b, and the yellow light source 42y are plotted. The chromaticity coordinates of FIG. 7 show a color space defined in CIE1931.

The chromaticity coordinates in FIG. 7 show point B indicating the chromaticity value of the blue light emitted by blue light source 42b, point G indicating the chromaticity value of the green light emitted by green light source 42g, point R indicating the chromaticity value of the red light emitted by red light source 42r, and point Y indicating the fourth chromaticity value of the blue-green light emitted by yellow light source 42y.

On the chromaticity coordinate system, the rectangular region with vertices B, G, R, and Y includes the chromaticity range of the light source color defined in JIS Z9112. Here, the light source color refers to five types: daylight (D), neutral white (N), white (W), warm white (WW), and incandescent (L), and the chromaticity range of the five types of light source colors is five approximately parallelogram regions near the blackbody locus in Figure 7. The lighting system 10a can realize output light having chromaticity values within the rectangular region with vertices B, G, R, and Y, and it can be said that the chromaticity range of the output light that the lighting system 10a can realize is relatively wide.

The lighting system 10a divides the rectangular region into a first triangular region with vertices B, R, and Y, and a second triangular region with vertices B, G, and Y, and adjusts the chromaticity to improve the color rendering of the output light. There are two ways to divide the rectangular region into two triangular regions. In the lighting system 10a, the triangular region with the top three points among the four points B, G, R, and Y that are closest to the blackbody locus is the first region, and the triangular region excluding the first region is the second region. The distance from point B to the blackbody locus means, for example, the average value of the distance from point B to each of the multiple points when the blackbody locus is considered to be a set of multiple points. The same applies to the distances from point G, point R, and point Y to the blackbody locus.

For example, when a point indicating a chromaticity value desired by the user input to the input device 20 is located within the first region, the control unit 31 of the control device 30 does not emit light from the green light source 42g, but emits light from the three light sources, blue light source 42b, red light source 42r, and yellow light source 42y, and adjusts the light intensity independently to realize output light having a chromaticity value desired by the user. Similarly, when a point indicating a chromaticity value desired by the input device 20 is located within the second region, the control unit 31 of the control device 30 does not emit light from the red light source 42r, but emits light from the three light sources, blue light source 42b, green light source 42g, and yellow light source 42y, and adjusts the light intensity independently to realize output light having a chromaticity value desired by the user.

The average color rendering index Ra of the output light obtained by such a chromaticity control method will be described below while comparing it with the average color rendering index Ra of the output light obtained by a chromaticity control method according to a comparative example. Figure 8 is a diagram showing the average color rendering index Ra of the output light obtained by the chromaticity control method in the lighting system 10a (hereinafter also simply referred to as control example 1).

In FIG. 8, the average color rendering index Ra of the output light obtained by the chromaticity control method according to the comparative example is also shown. The chromaticity control method according to the comparative example is a control method in which the output light having the chromaticity values located within points B, G, and R is realized by emitting the three light sources of blue light source 42b, green light source 42g, and red light source 42r without emitting the yellow light source 42y, and by independently dimming them. In other words, the comparative example is different from control example 1 in the way in which the rectangle is divided into two triangular regions. In FIG. 8, the output light is white light with Duv=0. In FIG. 8, the horizontal axis indicates the color temperature (Tc) of the output light, and the vertical axis indicates the average color rendering index Ra of the output light.

As shown in FIG. 8, control example 1 can achieve output light with a higher average color rendering index Ra than the comparative example.

As described above, in the lighting system 10a, the control unit 31 realizes output light having chromaticity values in a first region having vertices at points B, R, and Y by emitting light from three light sources corresponding to points B, R, and Y, and realizes output light having chromaticity values in a second triangular region having vertices at points B, G, and Y by emitting light from three light sources corresponding to points B, G, and Y. The first region is specifically a triangular region having vertices at the top three points B, G, R, and Y that are closest to the blackbody locus, and the second region is a triangular region obtained by excluding the first region from a quadrangular region having vertices at points B, G, R, and Y. This allows the lighting system 10a to realize output light having a high average color rendering index Ra. The lighting system 10a can improve the general color rendering index Ra of output light having a light source color (any of five types) specified in JIS Z9112, for example, and reduce color unevenness on the light irradiation surface.

[Control Example 2]
Control Example 2 of the chromaticity of the lighting system 10a will be described with reference to a chromaticity diagram (chromaticity coordinates). Fig. 9 is a diagram showing chromaticity coordinates in which points related to Control Example 2 are plotted. The chromaticity coordinates in Fig. 9 indicate a color space defined in CIE1931. The chromaticity coordinates in Fig. 9 are basically the same as those in Fig. 7, except that a first point P1, a second point P2, a third point P3, a fourth point P4, and a fifth point P5 are illustrated.

The first point P1 is a point located on the line segment connecting point Y, which indicates the chromaticity value of the yellow light source 42y, and point R, which indicates the chromaticity value of the red light source 42r (another example of the first chromaticity value). The first point P1 is a point that indicates the chromaticity value when each of the yellow light source 42y and the red light source 42r is caused to emit light at maximum brightness.

The second point P2 is a point located on the line segment connecting point Y, which indicates the chromaticity value of the yellow light source 42y, and point B, which indicates the chromaticity value of the blue light source 42b (another example of the second chromaticity value). The second point P2 is a point that indicates the chromaticity value when each of the yellow light source 42y and the blue light source 42b is caused to emit light at maximum brightness.

The third point P3 is a point located within the first region. The third point P3 is a point that indicates the chromaticity value when each of the three light sources (blue light source 42b, red light source 42r, and yellow light source 42y) corresponding to the three vertices of the first region is caused to emit light at maximum brightness.

The fourth point P4 is a point located on the line segment connecting point Y, which indicates the chromaticity value of the yellow light source 42y, and point G, which indicates the chromaticity value of the green light source 42g (another example of the third chromaticity value). The fourth point P4 is a point that indicates the chromaticity value when each of the yellow light source 42y and the green light source 42g is caused to emit light at maximum brightness.

The fifth point P5 is a point located within the second region. The fifth point P5 is a point that indicates the chromaticity value when each of the three light sources (blue light source 42b, green light source 42g, and yellow light source 42y) corresponding to the three vertices of the second region is made to emit light at maximum brightness.

In the above-mentioned control example 1, the chromaticity values in the first region of the triangle with vertices B, R, and Y are realized by emitting light from the blue light source 42b, the red light source 42r, and the yellow light source 42y. Here, the chromaticity values in the first target region (the hatched region in FIG. 9) in the first region can be realized by emitting light from all of the blue light source 42b, the green light source 42g, the red light source 42r, and the yellow light source 42y. In this way, it is possible to improve the average color rendering index Ra of the output light and increase the amount of light of the output light at the same time.

Therefore, in control example 2, the control unit 31 realizes the chromaticity values in the first target area by emitting light from all of the blue light source 42b, green light source 42g, red light source 42r, and yellow light source 42y and adjusting the light intensity independently. The first target area is an area where a rectangular area surrounded by point Y indicating the chromaticity value of the yellow light source 42y, the first point P1, the second point P2, and the third point P3 overlaps with a triangular area surrounded by point R (point indicating the first chromaticity value), point B (point indicating the second chromaticity value), and point G (point indicating the third chromaticity value).

The control unit 31 realizes, for example, output light having a certain chromaticity value in the first target region as follows. The control unit 31 calculates a fifth dimming value of each light source when the above chromaticity value in the first target region is realized by emitting light from the blue light source 42b, the red light source 42r, and the yellow light source 42y without emitting light from the green light source 42g. The control unit 31 also calculates a sixth dimming value of each light source when the above chromaticity value in the first target region is realized by emitting light from the blue light source 42b, the green light source 42g, and the red light source 42r without emitting light from the yellow light source 42y. The control unit 31 can achieve both an improvement in the average color rendering index Ra and an increase in the amount of light of the output light having the above chromaticity value in the first target region by setting the dimming value obtained by summing the fifth dimming value and the sixth dimming value as the final dimming value. In control example 2, when the lighting device 40a emits output light having the above chromaticity values within the first target region, the yellow light source 42y emits light at maximum output (maximum brightness).

In addition, in the above-mentioned control example 1, the chromaticity values in the second region of the triangle with vertices B, G, and Y were realized by emitting light from the blue light source 42b, the green light source 42g, and the yellow light source 42y. Here, the chromaticity values in the second target region (the hatched region in FIG. 9) in the second region can be realized by emitting light from all of the blue light source 42b, the green light source 42g, the red light source 42r, and the yellow light source 42y. In this way, it is possible to improve the average color rendering index Ra of the output light and increase the amount of light of the output light at the same time.

Therefore, in control example 2, the control unit 31 realizes the chromaticity values in the second target area by emitting light from all of the blue light source 42b, green light source 42g, red light source 42r, and yellow light source 42y and adjusting the light intensity independently. The second target area is an area where a rectangular area surrounded by point Y indicating the chromaticity value of the yellow light source 42y, the second point P2, the fourth point P4, and the fifth point P5 overlaps with a triangular area surrounded by point R (point indicating the first chromaticity value), point B (point indicating the second chromaticity value), and point G (point indicating the third chromaticity value).

The control unit 31 realizes, for example, output light having a certain chromaticity value in the second target area as follows. The control unit 31 calculates a seventh dimming value of each light source when the above chromaticity value in the second target area is realized by emitting light from the blue light source 42b, the green light source 42g, and the yellow light source 42y without emitting light from the red light source 42r. Also, the control unit 31 calculates an eighth dimming value of each light source when the above chromaticity value in the second target area is realized by emitting light from the blue light source 42b, the green light source 42g, and the red light source 42r without emitting light from the yellow light source 42y. The control unit 31 can achieve both an improvement in the average color rendering index Ra and an increase in the amount of light of the output light having the above chromaticity value in the second target area by setting the dimming value obtained by summing the seventh dimming value and the eighth dimming value as the final dimming value. In control example 2, when output light having the above chromaticity value in the second target area is emitted from the lighting device 40a, the yellow light source 42y emits light at maximum output (maximum brightness).

In addition, in the first target region and the second target region, it may be possible to switch between applying control example 1 and applying control example 2. For example, the control unit 31 may selectively execute an operation of a color rendering emphasis mode that emphasizes the color rendering of output light having chromaticity values belonging to the first target region and the second target region, and an operation of a light intensity emphasis mode that emphasizes the light intensity of output light having chromaticity values belonging to the first target region and the second target region. In the operation of the color rendering emphasis mode, as described in control example 1, the control unit 31 realizes the chromaticity values belonging to the first target region by emitting light from three light sources corresponding to the three vertices of the first region, and realizes the chromaticity values belonging to the second target region by emitting light from three light sources corresponding to the three vertices of the second region. In the operation of the light intensity emphasis mode, as described in control example 2, the control unit 31 realizes the chromaticity values belonging to the first target region and the second target region by emitting light from four light sources provided in the lighting system 10a. The color rendering emphasis mode is an example of the first mode, and the light intensity emphasis mode is an example of the second mode. Such switching of operation modes is performed, for example, based on user input to the input device 20.

(Modification)
In the above-mentioned first and second embodiments, the blue light emitted by the blue light source 42b, the green light emitted by the green light source 42g, the red light emitted by the red light source 42r, the blue-green light emitted by the blue-green light source 42bg, and the yellow light emitted by the yellow light source 42y are realized by the light emitted by the LEDs. Here, the green light emitted by the green light source 42g, the red light emitted by the red light source 42r, and the yellow light emitted by the yellow light source 42y may be realized by the fluorescence emitted by a phosphor.

In this case, each of the green light source 42g, the red light source 42r, and the yellow light source 42y includes an excitation light source realized by, for example, a blue LED, and a phosphor-containing resin that seals the excitation light source. The phosphor constituting the green light source _{42g is a yttrium aluminum garnet (YAG)-based green phosphor such as Y3(Al,Ga)5O12 : Ce phosphor ,} but may be a lutetium aluminum garnet (LuAG)-based green phosphor such as Lu3Al5O12: _Ce phosphor. The phosphor constituting the red light source 42r is a red phosphor such as _CaAlSiN3 :Eu phosphor or (Sr,Ca) _AlSiN3 :Eu phosphor. The phosphor constituting the yellow light source 42y is an yttrium aluminum garnet (YAG)-based yellow phosphor such as _Y3 (Al _, Ga) _{5O12 :} Ce phosphor, but may also be a lutetium aluminum garnet (LuAG)-based yellow phosphor such as _Lu3Al5O12 : _Ce phosphor.

According to control example 1 of the above-mentioned embodiments 1 and 2, even when the green light emitted by the green light source 42g, the red light emitted by the red light source 42r, and the yellow light emitted by the yellow light source 42y are each realized by fluorescence emitted by a phosphor, it is possible to improve the general color rendering index Ra of the output light.

(Effects, etc.)
As described above, the lighting system 10 or the lighting system 10a includes the control unit 31 that controls four light sources that emit light having different chromaticity values. On the chromaticity coordinates, a rectangular region having four vertices corresponding to the chromaticity values of the light emitted by the four light sources includes at least a part of the chromaticity range of the light source color defined in JIS Z9112. The control unit 31 realizes output light having a chromaticity value within a first region of a triangle having vertices of the top three points among the four points that are closest to the blackbody locus by making the three light sources corresponding to the three vertices of the first region emit light, and realizes output light having a chromaticity value within a second region of the triangle, which is the rectangular region excluding the first region, by making the three light sources corresponding to the three vertices of the second region emit light.

Such a lighting system 10 or lighting system 10a can produce output light with a high average color rendering index Ra.

For example, the four light sources include a red light source 42r, a green light source 42g, a blue light source 42b, and other light sources. The points indicating the chromaticity values of the other light sources are included in all three vertices of the first region and all three vertices of the second region.

Such a lighting system 10 or lighting system 10a can achieve output light with a high average color rendering index Ra by controlling the red light source 42r, the green light source 42g, the blue light source 42b, and other light sources.

In addition, in the lighting system 10, the other light source is another blue light source (blue-green light source 42bg). The three vertices of the first region include a point indicating the chromaticity value of the blue-green light source 42bg, a point indicating the chromaticity value of the red light source 42r, and a point indicating the chromaticity value of the green light source 42g. The three vertices of the second region include a point indicating the chromaticity value of the blue-green light source 42bg, a point indicating the chromaticity value of the red light source 42r, and a point indicating the chromaticity value of the blue light source 42b.

Such a lighting system 10 can produce output light with a high average color rendering index Ra.

In addition, in the lighting system 10a, the other light source is a yellow light source 42y. The three vertices of the first region include a point indicating the chromaticity value of the yellow light source 42y, a point indicating the chromaticity value of the blue light source 42b, and a point indicating the chromaticity value of the red light source 42r. The three vertices of the second region include a point indicating the chromaticity value of the yellow light source 42y, a point indicating the chromaticity value of the blue light source 42b, and a point indicating the chromaticity value of the green light source 42g.

Such a lighting system 10a can produce output light with a high average color rendering index Ra.

For example, the three vertices of the first region include a point indicating the chromaticity value of the other light source, a point indicating the first chromaticity value, and a point indicating the second chromaticity value. The line segment connecting the points indicating the chromaticity values of the other light source and the points indicating the first chromaticity value includes a first point P1 indicating the chromaticity value when the other light source and the light source corresponding to the points indicating the first chromaticity value are each made to emit light at maximum brightness. The line segment connecting the points indicating the chromaticity values of the other light source and the points indicating the second chromaticity value includes a second point P2 indicating the chromaticity value when the other light source and the light source corresponding to the points indicating the second chromaticity value are each made to emit light at maximum brightness. The first region includes a third point P3 indicating the chromaticity value when each of the three light sources corresponding to the three vertices of the first region is made to emit light at maximum brightness. The three vertices of the second region include a point indicating the chromaticity value of the other light source, a point indicating the second chromaticity value, and a point indicating the third chromaticity value. A fourth point P4 indicating the chromaticity value when each of the other light source and the light source corresponding to the point indicating the third chromaticity value is caused to emit light at the maximum brightness is included on the line segment connecting the point indicating the chromaticity value of the other light source and the point indicating the third chromaticity value, and a fifth point P5 indicating the chromaticity value when each of the three light sources corresponding to the three vertices of the second region is caused to emit light at the maximum brightness is included in the second region. The control unit 31 realizes output light having a chromaticity value located in the first target region and output light having a chromaticity value located in the second target region by causing the four light sources to emit light. The first target region is a region where a region surrounded by the points indicating the chromaticity values of the other light source, the first point P1, the second point P2, and the third point P3, and a region surrounded by the points indicating the first chromaticity value, the points indicating the second chromaticity value, and the points indicating the third chromaticity value overlap. The second target area is an area surrounded by points indicating the chromaticity values of the other light source, the second point P2, the fourth point P4, and the fifth point P5, and an area surrounded by points indicating the first chromaticity value, points indicating the second chromaticity value, and points indicating the third chromaticity value overlap.

Such a lighting system 10 or lighting system 10a can increase the maximum amount of output light having chromaticity values within the first target area and the second target area.

For example, the control unit 31 selectively executes a first mode control in which output light having a chromaticity value within the first target region is realized by causing three light sources corresponding to the three vertices of the first region to emit light, and output light having a chromaticity value within the second target region is realized by causing three light sources corresponding to the three vertices of the second region to emit light, and a second mode control in which output light having a chromaticity value within the first target region and the second target region is realized by causing four light sources to emit light. The first mode is, for example, the color rendering priority mode of the above embodiment, and the second mode is, for example, the light intensity priority mode of the above embodiment.

Such a lighting system 10 or lighting system 10a can switch the method of realizing chromaticity values (method of controlling chromaticity) within the first target area and the second target area.

The lighting method executed by a computer such as the lighting system 10 or the lighting system 10a includes a control step of controlling four light sources that emit light with different chromaticity values, and a rectangular region on the chromaticity coordinate system with four vertices corresponding to the chromaticity values of the light emitted by the four light sources includes at least a part of the chromaticity range of the light source color defined in JIS Z9112. In the control step, output light having a chromaticity value within a first region of a triangle with the top three points among the four points that are closest to the blackbody locus as vertices is realized by emitting three light sources among the four light sources that correspond to the three vertices of the first region, and output light having a chromaticity value within a second region of the triangle excluding the first region from the rectangular region is realized by emitting three light sources among the four light sources that correspond to the three vertices of the second region.

Such a lighting method can produce output light with a high average color rendering index Ra.

Other Embodiments
Although the embodiment has been described above, the present invention is not limited to the above embodiment.

For example, it is not essential that a blue light source, a green light source, and a red light source are used as the three light sources other than the other light sources. The three light sources may be three light sources having chromaticity values that form a triangle on the chromaticity coordinate system that includes at least a portion of the chromaticity range of the light source color. In addition, the other light sources are not limited to a blue-green light source or a yellow light source.

In addition, in the above embodiment, the light emitted by the light source is realized by the light emitted by the LED or the fluorescence emitted by the phosphor, but it may also be realized by the light emitted by a semiconductor laser (laser light), the light emitted by an organic EL element (electroluminescence), or the light emitted by an inorganic EL element.

For example, in the above embodiment, the lighting system is realized by multiple devices, but it may be realized as a single device. For example, the lighting system may be realized as a single device that corresponds to the control device in the above embodiment. When the lighting system is realized by multiple devices, the components of the lighting system described in the above embodiment may be distributed in any manner among the multiple devices.

In addition, in the above embodiment, the processing performed by a specific processing unit may be executed by another processing unit. Also, the order of multiple processes may be changed, and multiple processes may be executed in parallel.

In addition, in the above embodiment, each component may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

In addition, each component may be realized by hardware. Each component may be a circuit (or an integrated circuit). These circuits may form a single circuit as a whole, or each may be a separate circuit. In addition, each of these circuits may be a general-purpose circuit, or a dedicated circuit.

The general or specific aspects of the present invention may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM. The present invention may also be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

For example, the present invention may be realized as a lighting method executed by a computer such as a lighting system, as a program for causing a computer to execute the lighting method, or as a computer-readable non-transitory recording medium on which such a program is recorded.

In addition, the present invention also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art may conceive, or forms realized by arbitrarily combining the components and functions of each embodiment within the scope of the spirit of the present invention.

REFERENCE SIGNS LIST 10, 10a Lighting system 20 Input device 30 Control device 31 Control unit 32 Memory unit 40, 40a Lighting device 41 Light control circuit 42, 42a Light source unit 42b Blue light source 42bg Blue-green light source 42g Green light source 42r Red light source 42y Yellow light source

Claims (7)

A control unit is provided for controlling four light sources that emit light having different chromaticity values from each other,
On the chromaticity coordinate system, a quadrangular region having four vertices corresponding to the chromaticity values of the light emitted by the four light sources includes at least a part of the chromaticity range of the light source color defined in JIS Z9112,
The control unit is
output light having a chromaticity value within a first region of a triangle having vertices that are the top three points among the four points that are closest to the blackbody locus, by emitting light from three light sources among the four light sources that correspond to the three vertices of the first region;
output light having a chromaticity value within a triangular second region obtained by excluding the first region from the rectangular region is realized by emitting light from three light sources among the four light sources that correspond to three vertices of the second region;
The four light sources include a red light source, a green light source, a blue light source, and another light source;
The point indicating the chromaticity value of the other light source is included in all of the three vertices of the first region and all of the three vertices of the second region.
Lighting system. the other light source is another blue light source,
the three vertices of the first region include a point indicating a chromaticity value of the other blue light source, a point indicating a chromaticity value of the red light source, and a point indicating a chromaticity value of the green light source;
The lighting system of claim 1 , wherein the three vertices of the second region include a point indicating a chromaticity value of the other blue light source, a point indicating a chromaticity value of the red light source, and a point indicating a chromaticity value of the blue light source. the other light source is a yellow light source,
the three vertices of the first region include a point indicating a chromaticity value of the yellow light source, a point indicating a chromaticity value of the blue light source, and a point indicating a chromaticity value of the red light source;
The lighting system of claim 1 , wherein the three vertices of the second region include a point indicating a chromaticity value of the yellow light source, a point indicating a chromaticity value of the blue light source, and a point indicating a chromaticity value of the green light source. the three vertices of the first region include a point indicating a chromaticity value of the other light source, a point indicating a first chromaticity value, and a point indicating a second chromaticity value;
a first point indicating a chromaticity value when each of the other light source and the light source corresponding to the point indicating the first chromaticity value is caused to emit light at maximum brightness is included on a line segment connecting the point indicating the chromaticity value of the other light source and the point indicating the first chromaticity value;
a second point indicating a chromaticity value when each of the other light source and the light source corresponding to the point indicating the second chromaticity value is caused to emit light at maximum brightness is included on a line segment connecting the point indicating the chromaticity value of the other light source and the point indicating the second chromaticity value;
a third point is included within the first region, the third point indicating a chromaticity value when each of three light sources corresponding to three vertices of the first region is caused to emit light at maximum brightness;
the three vertices of the second region include a point indicating a chromaticity value of the other light source, a point indicating the second chromaticity value, and a point indicating a third chromaticity value;
a fourth point indicating a chromaticity value when each of the other light source and the light source corresponding to the point indicating the third chromaticity value is caused to emit light at maximum brightness is included on a line segment connecting the point indicating the chromaticity value of the other light source and the point indicating the third chromaticity value;
a fifth point is included within the second region, the fifth point indicating a chromaticity value when each of three light sources corresponding to the three vertices of the second region is caused to emit light at maximum brightness;
the control unit causes the four light sources to emit light to produce output light having a chromaticity value located within a first target region and output light having a chromaticity value located within a second target region;
the first target area is an area where an area surrounded by the points indicating the chromaticity values of the other light source, the first points, the second points, and the third points overlaps with an area surrounded by the points indicating the first chromaticity values, the points indicating the second chromaticity values, and the points indicating the third chromaticity values;
The lighting system according to any one of claims 1 to 3, wherein the second target area is an overlapping area of an area surrounded by points indicating the chromaticity values of the other light source, the second point, the fourth point, and the fifth point, and an area surrounded by points indicating the first chromaticity value, points indicating the second chromaticity value, and points indicating the third chromaticity value. 5. The lighting system according to claim 4, wherein the control unit selectively executes a first mode control in which output light having a chromaticity value within the first target area is realized by causing three light sources corresponding to three vertices of the first area to emit light and output light having a chromaticity value within the second target area is realized by causing three light sources corresponding to the three vertices of the second area to emit light, and a second mode control in which output light having chromaticity values within the first target area and the second target area is realized by causing the four light sources to emit light. A control step of controlling four light sources emitting light having different chromaticity values from each other,
On the chromaticity coordinate system, a quadrangular region having four vertices corresponding to the chromaticity values of the light emitted by the four light sources includes at least a part of the chromaticity range of the light source color defined in JIS Z9112,
In the control step,
output light having a chromaticity value within a first region of a triangle having vertices that are the top three points among the four points that are closest to the blackbody locus, by emitting light from three light sources among the four light sources that correspond to the three vertices of the first region;
output light having a chromaticity value within a triangular second region obtained by excluding the first region from the rectangular region is realized by emitting light from three light sources among the four light sources that correspond to three vertices of the second region;
The four light sources include a red light source, a green light source, a blue light source, and another light source;
The point indicating the chromaticity value of the other light source is included in all of the three vertices of the first region and all of the three vertices of the second region.
Lighting method. A program for causing a computer to execute the lighting method according to claim 6 .

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