Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation Application of U.S. Application of U.S. application Ser. No. 13/081,237 filed Apr. 6, 2011 which claims priority from Korean Application No. 10-2010-0033008, filed on Apr. 10, 2010, Korean Application No. 10-2010-0033009, filed on Apr. 10, 2010, the subject matters of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     This embodiment relates to a method for controlling a lighting apparatus. 
     2. Description of the Related Art 
     Recently, more and more attention is paid to a lighting apparatus. The lighting apparatus should be disposed in a certain place and emit light for a long time. For this reason, the lighting apparatus is required by a user thereof to uniformly maintain for a long period of time its characteristic such as a visual sensation of light emitted therefrom. When the characteristic of the lighting apparatus is not uniformly maintained, a user may feel fatigue of his/her eyes or be affected in activities using the lighting apparatus. 
     In addition, when the lighting apparatus is manufactured, various domestic and international standards are taken into account. That is, the lighting apparatus is manufactured according to the various domestic and international standards. Though the lighting apparatus is manufactured according to the aforementioned various standards, light emitted from the lighting apparatus is required to be fit the standards when the lighting apparatus is operated for a long time after being disposed. 
     SUMMARY 
     One embodiment is a method for controlling a lighting apparatus including a first light source unit, a second light source unit and a third light source unit, all of which emit lights having mutually different color temperatures and mutually different color coordinates. The method includes: outputting an R component signal, a G component signal and a B component signal, each of which respectively corresponds to light quantities of an R component, a G component and a B component of lights outputted from the first light source unit, the second light source unit and the third light source unit; receiving the R component signal, the G component signal and the B component signal and generating a comparative color coordinate; and comparing the comparative color coordinate with standard color coordinates located within an area formed by the respective color coordinates of the first, the second and the third light source units, and controlling light quantities of the first, the second and the third light source units in such a manner as to reduce an error value between the standard color coordinate and the comparative color coordinate. 
     Another embodiment is a method for controlling a lighting apparatus including a light source unit and a first optical exciter, a second optical exciter and a third optical exciter, all three of which convert light emitted from the light source unit into lights having different color temperatures and different color coordinates. The method includes: outputting an R component signal, a G component signal and a B component signal, each of which respectively corresponds to light quantities of an R component, a G component and a B component of the light output from the first optical exciter, the second optical exciter and the third optical exciter; receiving the R component signal, the G component signal and the B component signal and generating a comparative color coordinate; and comparing the comparative color coordinate with a standard color coordinate located within an area formed by the respective color coordinates of the first, the second and the third optical exciters, and controlling light quantity of the light source unit in such a manner as to reduce an error value between the standard color coordinate and the comparative color coordinate. 
     Further another embodiment is a method for controlling a lighting device emitting light. The method includes: receiving an R component signal, a G component signal and a B component signal, each of which respectively corresponds to light quantities of an R component, a G component and a B component of the light; generating a comparative color coordinate corresponding to the R component signal, the G component signal and the B component signal; comparing a standard color coordinate with the comparative color coordinate, and generating an error value between the standard color coordinate and the comparative color coordinate; and controlling an intensity of the light in correspondence with the error value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a lighting apparatus according to a first embodiment of the present invention. 
         FIG. 2  shows a color coordinate system according to the first embodiment of the present invention. 
         FIG. 3A  shows transformations of a color temperature and a color coordinate when the lighting apparatus includes only a first light source unit and a second light source unit. 
         FIG. 3B  shows transformation of a color temperature and a color coordinate of the lighting apparatus according to the embodiment of the present invention. 
         FIGS. 4A and 4B  show a setting of a standard color coordinate in consideration of MacAdam curve and Ansi bin curve according to the first embodiment of the present invention and show the operation of the lighting apparatus. 
         FIG. 5  shows a lighting apparatus according to a second embodiment of the present invention. 
         FIG. 6  shows a color coordinate system according to the second embodiment of the present invention. 
         FIG. 7  shows a lighting apparatus according to a third embodiment of the present invention. 
         FIG. 8  shows a color coordinate system according to the third second embodiment of the present invention. 
         FIGS. 9A and 9B  show a setting of a standard color coordinate in consideration of MacAdam curve and Ansi bin curve according to the third embodiment of the present invention and show the operation of the lighting apparatus. 
         FIG. 10  shows a lighting apparatus according to a fourth embodiment of the present invention. 
         FIG. 11  shows a color coordinate system according to the fourth second embodiment of the present invention. 
         FIGS. 12A and 12B  show how optical exciters of the lighting apparatus according to the embodiment of the present invention are arranged. 
         FIG. 12C  shows that a second optical exciter and a third optical exciter of the lighting apparatus according to the embodiment of the present invention are arranged to face each other. 
     
    
    
     DETAILED DESCRIPTION 
     A thickness or size of each layer is magnified, omitted or schematically shown for the purpose of convenience and clearness of description. The size of each component does not necessarily mean its actual size. 
     It will be understood that when an element is referred to as being ‘on’ or “under” another element, it can be directly on/under the element, and one or more intervening elements may also be present. When an element is referred to as being ‘on’ or ‘under’, ‘under the element’ as well as ‘on the element’ can be included based on the element. 
     Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings. 
       FIG. 1  shows a lighting apparatus according to a first embodiment of the present invention. As shown in  FIG. 1 , the lighting apparatus according to the first embodiment of the present invention includes a light source unit  100  including a first light source unit  110 , a second light source unit  130  and at least one third light source unit  150 , an RGB sensor  200 , a controller  300  and a power supplier  400 . The lighting apparatus shown in  FIG. 1  includes one third light source unit  150  as well as the first light source unit  110  and the second light source unit  130 . A lighting apparatus shown in  FIG. 5  includes a plurality of third light source units  150   a  and  150   b  as well as the first light source unit  110  and the second light source unit  130 . 
     The first light source unit  110  and the second light source unit  130  emit lights having different color temperatures from each other and different color coordinates from each other. That is, the first light source unit  110  emits light having a first color temperature and a first color coordinate. The second light source unit  130  emits light having a second color temperature and a second color coordinate. Since the embodiment of the present invention relates to a lighting apparatus, the first light source unit  110  and the second light source unit  130  are able to emit white light. 
     The at least one third light source unit  150  emits light having a color temperature and a color coordinate which are different from those of the first light source unit  110  and the second light source unit  130 . The third light source unit  150  may include a light emitting diode (LED) capable of emitting light having a color temperature and a color coordinate which are different from those of the first light source unit  110  and the second light source unit  130 . 
     The RGB sensor  200  outputs an R component signal, a G component signal and a B component signal, each of which corresponds to light quantities of an R (red) component, a G (green) component and a B (blue) component, respectively, of the light output from the first light source unit  110  to the third light source unit  150 . That is, the RGB sensor  200  senses each of the light quantities of the R (red) component, G (green) component and B (blue) component of light mixed with lights emitted from a plurality of the light source units. 
     The RGB sensor  200  may include an R filter, a G filter and a B filter in order to detect the R (red) component, G (green) component and B (blue) component of light. The R filter, G filter and B filter transmit their corresponding components. That is, the R filter transmits the R (red) component. The G filter transmits the G (green) component. The B filter transmits the B (blue) component. 
     Here, the RGB sensor  200  may include an analog/digital converter (not shown) for converting an analog signal into a digital signal. When the analog/digital converter is included, a first light signal, a second light signal and a third light signal may be digital signals. 
     The controller  300  controls light quantities of the first light source unit  110 , the second light source unit  130  and the third light source unit  150  such that a color coordinate of the light emitted from the first light source unit  110 , a color coordinate of the light emitted from the second light source unit  130 , and a color coordinate of the light emitted from the at least one third light source unit  150  are placed within an area formed by the color coordinates of the first light source unit  110 , the second light source unit  130  and the at least one third light source unit  150 . The operation of the controller  300  will be described later in detail. 
     The power supplier  400  supplies voltage changing the light quantities of the first light source unit  110 , the second light source unit  130  and the third light source unit  150  under the control of the controller  300 . 
     Here, the power supplier  400  is able to supply alternating current voltage having a controlled duty ratio to the first light source unit  110  to the third light source unit  150  under the control of the controller  300 . To this end, the power supplier  400  may include a pulse width modulation (PWM) generator. The first light source unit  110 , the second light source unit  130  and the third light source unit  150  may include LEDs. The light quantity of the LED is changeable depending on the duty ratio of the alternating current voltage. 
       FIG. 2  shows a color coordinate system according to the first embodiment of the present invention. 
     The lighting apparatus according to the embodiment of the present invention is able to increase an area capable of controlling a color coordinate. That is, unlike the embodiment of the present invention, when the lighting apparatus includes only the first light source unit  110  and the second light source unit  130 , the color coordinate of the light of the lighting apparatus transforms along a straight line connecting the color coordinate of the first light source unit  110  and the color coordinate of the second light source unit  130 . 
     On the contrary, the lighting apparatus according to the embodiment of the present invention includes, as shown in  FIG. 2 , the third light source unit  150  as well as the first light source unit  110  and the second light source unit  130 . The RGB sensor  200  outputs the R component signal, G component signal and B component signal of the light output from the first light source unit  110  to the third light source unit  150 . 
     The controller  300  calculates tristimulus values of X, Y and Z by using the R component signal, G component signal and B component signal. The tristimulus values of X, Y and Z may be calculated by using a kind of light illuminated to an object, a surface defined by reflectance, and a color matching function of the R component signal, G component signal and B component signal. 
     The controller  300  calculates a color coordinate of the light from the light source units by using the tristimulus values of X, Y and Z. An X component of the color coordinate is calculated by X/(X+Y+Z). A Y component of the color coordinate is calculated by Y/(X+Y+Z). A Z component of the color coordinate is calculated by 1−(X+Y). 
     In the embodiment of the present invention, the controller  300  sequentially calculates the tristimulus values and the color coordinate. However, when the R component signal, G component signal and B component signal are input, corresponding color coordinate value thereof may be stored in advance in the controller  300 . 
     When the calculated color coordinate is out of an area formed by the color coordinates of the first light source unit  110 , the second light source unit  130  and the third light source unit  150 , the controller  300  controls the light quantities of the first, the second and the third light source units  110 ,  130  and  150  and causes the light of the lighting apparatus to be within the area. 
     As a result, the lighting apparatus according to the embodiment of the present invention is able to emit light having a color coordinate located within a triangular area formed by the color coordinate of the first light source unit  110 , the color coordinate of the second light source unit  130  and the color coordinate of the third light source unit  150 . 
     The lighting apparatus according to the embodiment of the present invention is able to control the light quantity in accordance with standard color coordinates located within an area formed by the color coordinate of the first light source unit  110 , the color coordinate of the second light source unit  130  and the color coordinate of the third light source unit  150 . 
     For this purpose, the lighting apparatus according to the embodiment of the present invention may further include a memory  500 . The memory  500  stores the standard color coordinates. 
     The standard color coordinates of the memory  500  may correspond to a color coordinate for some points on the black body locus or to a color coordinate for some points approaching the black body locus. 
     In order to obtain the standard color coordinate by using the color coordinates of the lights emitted from the first light source unit  110 , the second light source unit  130  and the third light source unit  150 , the first light source unit  110 , the second light source unit  130  and the third light source unit  150  may be controlled during the manufacturing process of the lighting apparatus such that the light quantities of the first light source unit  110 , the second light source unit  130  and the third light source unit  150  change. 
     That is, during the manufacturing process of the lighting apparatus according to the embodiment of the present invention, light quantities of the R (red) component, G (green) component and B (blue) component of light emitted from the first light source unit  110 , the second light source unit  130  and the third light source unit  150  are measured by a measuring device. 
     The tristimulus values of X, Y and Z are calculated by using the measured light quantities of the R (red) component, G (green) component and B (blue) component. Through the tristimulus values of X, Y and Z, a corresponding color coordinate can be calculated. When the corresponding color coordinate calculated through the tristimulus values of X, Y and Z are on the black body locus or approach the black body locus, the calculated color coordinate may be used as a standard color coordinate. The standard color coordinate obtained by the aforementioned method is stored in the memory  500 . Here, the standard color coordinate, as described above, is located within the area formed by the color coordinates of the light source units. 
     Meanwhile, the controller  300  receives an R component signal, a G component signal and a B component signal from the RGB sensor  200  and generates a comparative color coordinate. Then, the controller  300  compares the comparative color coordinate with the standard color coordinate read from the memory  500  and generates a duty ratio control signal for reducing an error value between the standard color coordinate and the comparative color coordinate. Here, in order to generate the comparative color coordinate, the controller  300  calculates a corresponding tristimulus values by using the R component signal, G component signal and B component signal, and calculates the comparative color coordinate by using the tristimulus values. 
     Unlike the embodiment of the present invention, when the lighting apparatus includes only the first light source unit  110  and the second light source unit  130 , it is difficult for the lighting apparatus to emit light having a color temperature approaching the black body locus. For example, when the first light source unit  110  emits light having a color temperature of 6500K and the second light source unit  130  emits light having a color temperature of 2700K, the color temperature and color coordinate of the light, as shown in  FIG. 3A , transform along a straight line in accordance with the light quantity changes of the first light source unit  110  and the second light source unit  130 . As a result, there is a big difference between the transformation of the color temperature and color coordinate of the light and the transformation of the color temperature and color coordinate of the black body locus. 
     Meanwhile, as shown in  FIG. 3B , when the lighting apparatus includes not only the first light source unit  110  and the second light source unit  130  but the third light source unit  150 , the lighting apparatus is able to emit light having a color temperature and a color coordinate similar to those of the black body locus. For example, when the first light source unit  110  emits light having a color temperature of 6500K, the second light source unit  130  emits light having a color temperature of 2700K and the third light source unit  150  emits greenish white light, the lighting apparatus according to the embodiment of the present invention is able to emit light having a color temperature and a color coordinate, each of which transforms along the black body locus in accordance with the light quantity changes of the first light source unit  110  to the third light source unit  150 . 
     In the foregoing description, the black body locus has been used as a standard for the color temperature of the lighting apparatus. However, it is possible to set a standard color coordinate of the lighting apparatus according to the embodiment of the present invention on the basis of MacAdam curve or Ansi bin curve which are other standards for the color temperature of a lighting apparatus. 
     The MacAdam curve shown in  FIG. 4A  shows a color distribution at the same color temperature. 
     Color distribution is greater at a specific color temperature toward an outer ellipse at the specific color temperature. As shown in  FIG. 4A , unlike the embodiment of the present invention, when the lighting apparatus includes only the first light source unit  110  having a color temperature of 6500K and the second light source unit  130  having a color temperature of 2700K, the color distributions are increased at the color temperatures of 5000K, 4000K and 3500K of the light emitted from the lighting apparatus. Therefore, it can be seen that the characteristic of the lighting apparatus is deteriorated. 
     On the other hand, as described in the embodiment of the present invention, when a standard color coordinate is set such that the color distribution at each color temperature is within 3-step MacAdam ellipse, the light quantity changes of the first to the third light source units  110 ,  130  and  150  are controlled in accordance with the standard color coordinate, thereby improving the characteristic of the lighting apparatus. As a result, as regards each of the lights emitted from the light source units  110 ,  130  and  150  of the lighting apparatus according to the embodiment of the present invention, the color distribution at each color temperature may be within 3-step MacAdam ellipse. 
     As shown in  FIG. 4B , unlike the embodiment of the present invention, when the lighting apparatus includes only the first light source unit  110  having a color temperature of 6500 k and the second light source unit  130  having a color temperature of 2700 k, the color temperature transformation of light emitted by the lighting apparatus may not be located at the center of the Ansi bin curve. 
     On the contrary, in the embodiment of the present invention, a standard color coordinate can be set such that the color temperature transformation of light emitted by the lighting apparatus is close to the center of the Ansi bin curve. The light quantity changes of the first to the third light source units  110 ,  130  and  150  are controlled in accordance with the standard color coordinate, thereby improving the characteristic of the lighting apparatus. 
     The lighting apparatus according to the embodiment of the present invention may include four or more light source units 
       FIG. 5  shows a lighting apparatus according to a second embodiment of the present invention. 
     While the lighting apparatus of  FIG. 5  includes four light source units, the lighting apparatus is allowed to include four or more light source units. 
     The plurality of the third light source units  150   a  and  150   b  emit light having a color temperature and a color coordinate which are different from those of the first light source unit  110  and the second light source unit  130 . The plurality of the third light source units  150   a  and  150   b  also emit lights having color temperatures different from each other and having color coordinates different from each other. In other words, the color coordinate and the color temperature of the light emitted from a third light source unit  150  are different from those of another third light source unit  150 . 
     Therefore, as shown in  FIG. 6 , light quantities of the light source units  110 ,  130 ,  150   a  and  150   b  may be controlled such that a color coordinate of the light from the lighting apparatus is placed within an area (a dotted-lined quadrangle) formed by the color coordinates of the first light source unit  110 , the second light source unit  130  and the plurality of the third light source units  150   a  and  150   b.    
     The standard color coordinates are located within the area (a dotted-lined quadrangle) formed by the color coordinates of the first, the second and a plurality of the third light source units  110 ,  130  and  150   a  and  150   b . The controller  300  controls the light quantities of the first, the second and the third light source units  110 ,  130  and  150   a  and  150   b  such that an error between the standard color coordinates and the color coordinate of light actually emitted is reduced. Accordingly, as regards the lighting apparatus according to the embodiment of the present invention, an area capable of controlling the color coordinate may be increased. 
       FIG. 7  shows a lighting apparatus according to a third embodiment of the present invention. 
       FIG. 7  shows, unlike  FIG. 1 , that optical exciters  120 ,  140  and  160  having mutually different wavelengths are added to the one or more light source units  100  having the same color temperature, so that an area in which the color coordinate can be controlled. 
     As shown in  FIG. 7 , the lighting apparatus according to an embodiment of the present invention includes a light source unit  100 , a first optical exciter  120 , a second optical exciter  140 , and at least one third optical exciter  160 , an RGB sensor  200 , a controller  300  and a power supplier  400 . 
     The lighting apparatus shown in  FIG. 7  includes one third optical exciter  160  as well as the first optical exciter  120  and the second optical exciter  140 . A lighting apparatus shown in  FIG. 10  includes a plurality of third optical exciters  160   a  and  160   b  as well as the first optical exciter  120  and the second optical exciter  140 . 
     The light source unit  100  may include a plurality of light emitting diodes (LEDs). The LEDs of the of the light source unit  100  may emit lights having the same color temperature to each other. Therefore, the structure of the light source unit  100  may become simple. 
     The first optical exciter  120 , the second optical exciter  140  and the third optical exciter  160  receive the light emitted from the light source unit  100  and emit lights having different wavelengths from each other. 
     To this end, the first optical exciter  120 , the second optical exciter  140  and the third optical exciter  160  may include a luminescent film respectively. The luminescent film includes a resin layer and a fluorescent substance. The fluorescent substance is located between the resin layers. The light emitted from the light source unit  100  excites the fluorescent substance of the luminescent film. The fluorescent substance emits light having a specific wavelength. 
     Here, the first optical exciter  120  and the second optical exciter  140  emit lights having different color temperatures from each other and different color coordinates from each other. That is, the first optical exciter  120  emits light having a first color temperature and a first color coordinate. The second optical exciter  140  emits light having a second color temperature and a second color coordinate. 
     Since the embodiment of the present invention relates to a lighting apparatus, the first optical exciter  120  and the second optical exciter  140  can emit white light. Here the first optical exciter  120  may emit light having a color temperature of 6500 k and the second optical exciter  140  may emit light having a color temperature of 2700 k. 
     The third optical exciter  160  emits light having a color temperature and a color coordinate which are different from those of the first optical exciter  120  and the second optical exciter  140 . 
     The RGB sensor  200  outputs an R component signal, a G component signal and a B component signal, each of which corresponds to light quantities of an R (red) component, a G (green) component and a B (blue) component, respectively, of the light output from the first optical exciter  120  to the third optical exciter  160 . That is, the RGB sensor  200  senses each of the light quantities of the R (red) component, G (green) component and B (blue) component of light mixed with lights emitted from a plurality of the optical exciters  120 ,  140  and  160 . 
     The RGB sensor  200  may include an R filter, a G filter and a B filter in order to detect the R (red) component, G (green) component and B (blue) component of light. The R filter, G filter and B filter transmit their corresponding components. That is, the R filter transmits the R (red) component. The G filter transmits the G (green) component. The B filter transmits the B (blue) component. 
     Here, the RGB sensor  200  may include an analog/digital converter (not shown) for converting an analog signal into a digital signal. When the analog/digital converter is included, a first light signal, a second light signal and a third light signal may be digital signals. 
     The controller  300  controls light quantities of the light source unit  100  such that a color coordinate of the light emitted from the first optical exciter  120 , a color coordinate of the light emitted from the second optical exciter  140 , and a color coordinate of the light emitted from the at least one third optical exciter  160  are placed within an area formed by the color coordinates of the first optical exciter  120 , the second optical exciter  140  and the at least one third optical exciter  160 . The operation of the controller  300  will be described later in detail. 
     The power supplier  400  supplies voltage changing the light quantities of the light source unit  100  under the control of the controller  300 . 
     Here, the power supplier  400  can supply alternating current voltage having a controlled duty ratio to the light source unit  100  under the control of the controller  300 . To this end, the power supplier  400  may include a pulse width modulation (PWM) generator. When the light source unit  100  includes light emitting diodes, the light quantity of the light emitting diode is changeable depending on the duty ratio of the alternating current voltage. 
       FIG. 8  shows a color coordinate system according to the third second embodiment of the present invention. 
     The lighting apparatus according to the embodiment of the present invention can increase an area capable of controlling a color coordinate. That is, unlike the embodiment of the present invention, when the lighting apparatus includes only the first optical exciter  120  and the second optical exciter  140 , the color coordinate of the light of the lighting apparatus transforms along a straight line connecting the color coordinate of the light emitted from the first optical exciter  120  and the color coordinate of the light emitted from the second optical exciter  140 . 
     On the contrary, the lighting apparatus according to the embodiment of the present invention includes the third optical exciter  160  as well as the first optical exciter  120  and the second optical exciter  140 . The RGB sensor  200  outputs the R component signal, G component signal and B component signal of the light output from the first optical exciter  120  to the third optical exciter  160 . 
     The controller  300  calculates tristimulus values of X, Y and Z by using the R component signal, G component signal and B component signal. The tristimulus values of X, Y and Z may be calculated by using a kind of light illuminated to an object, a surface defined by reflectance, and a color matching function of the R component signal, G component signal and B component signal. 
     The controller  300  calculates a color coordinate of the light from the optical exciters  120 ,  140  and  160  by using the tristimulus values of X, Y and Z. An X component of the color coordinate is calculated by X/(X+Y+Z). A Y component of the color coordinate is calculated by Y/(X+Y+Z). A Z component of the color coordinate is calculated by 1−(X+Y). 
     In the embodiment of the present invention, the controller  300  sequentially calculates the tristimulus values and the color coordinate. However, when the R component signal, G component signal and B component signal are input, corresponding color coordinate value thereof may be stored in advance in the controller  300 . 
     When the calculated color coordinate is out of an area formed by the color coordinates of the lights emitted from the first optical exciter  120 , the second optical exciter  140  and the at least one third optical exciter  160 , the controller  300  controls the light quantities of the light source unit  100  and causes the light of the lighting apparatus to be within the area. Here, the light of the lighting apparatus is light mixed with lights emitted from a plurality of the optical exciters  120 ,  140  and  160 . 
     As a result, the lighting apparatus according to the embodiment of the present invention is able to emit light having a color coordinate located within a triangular area formed by the color coordinate of the light emitted from the first optical exciter  120 , the color coordinate of the light emitted from the second optical exciter  140  and the color coordinate of the light emitted from the third optical exciter  160 . 
     The lighting apparatus according to the embodiment of the present invention is able to control the light quantity of the light source unit in accordance with standard color coordinates located within an area formed by the color coordinate of the light emitted the first optical exciter  120 , the color coordinate of the light emitted from the second optical exciter  140  and the color coordinate of the light emitted from the third optical exciter  160 . 
     For this purpose, the lighting apparatus according to the embodiment of the present invention may further include a memory  500 . The memory  500  stores the standard color coordinates. 
     In order to obtain the standard color coordinate by using the color coordinates of the lights emitted from the first optical exciter  120 , the second optical exciter  140  and the third optical exciter  160 , the light source unit  100  is controlled during the manufacturing process of the lighting apparatus such that the light quantity of the light source unit  100  changes. 
     During the manufacturing process of the lighting apparatus according to the embodiment of the present invention, light quantities of the R (red) component, G (green) component and B (blue) component of light, which is emitted from the first optical exciter  120 , the second optical exciter  140  and the third optical exciter  160  in accordance with the light quantity change of the light source unit  100 , are measured by a measuring device. 
     Unlike the embodiment of the present invention, when the lighting apparatus includes only the first optical exciter  120  and the second optical exciter  140 , it is difficult for the lighting apparatus to emit light having a color temperature approaching the black body locus. For example, when the first optical exciter  120  emits light having a color temperature of 6500K and the second optical exciter  140  emits light having a color temperature of 2700K, the color temperature and color coordinate of the light transform along a straight line in accordance with the light quantity changes of the lights emitted from the first optical exciter  120  and the second optical exciter  140 . As a result, there is a big difference between the transformation of the color temperature and color coordinate of the light and the transformation of the color temperature and color coordinate of the black body locus. 
     Meanwhile, when the lighting apparatus includes not only the first optical exciter  120  and the second optical exciter  140  but the third optical exciter  160 , the lighting apparatus is able to emit light having a color temperature and a color coordinate similar to those of the black body locus. For example, when the first optical exciter  120  emits light having a color temperature of 6500K, the second optical exciter  140  emits light having a color temperature of 2700K and the third optical exciter  160  emits greenish white light, the lighting apparatus according to the embodiment of the present invention is able to emit light having a color temperature and a color coordinate, each of which transforms along the black body locus in accordance with the light quantity changes of the first optical exciter  120  to the third optical exciter  160 . 
     In the foregoing description, the black body locus has been used as a standard for the color temperature of the lighting apparatus. However, it is possible to set a standard color coordinate of the lighting apparatus according to the embodiment of the present invention on the basis of MacAdam curve or Ansi bin curve which are other standards for the color temperature of a lighting apparatus. 
     The MacAdam curve shown in  FIG. 9A  shows a color distribution at the same color temperature. 
     Color distribution is greater at a specific color temperature toward an outer ellipse at the specific color temperature. As shown in  FIG. 9A , unlike the embodiment of the present invention, when the lighting apparatus includes only the first optical exciter  120  having a color temperature of 6500K and the second optical exciter  140  having a color temperature of 2700K, the color distributions are increased at the color temperatures of 5000K, 4000K and 3500K of the light emitted from the lighting apparatus. Therefore, it can be seen that the characteristic of the lighting apparatus is deteriorated. 
     On the other hand, as described in the embodiment of the present invention, when a standard color coordinate is set such that the color distribution at each color temperature is within 3-step MacAdam ellipse, in accordance with the standard color coordinate, the light quantity of the light source units  100  is controlled, and the light quantities of the first to the third optical exciters  120 ,  140  and  160  are hereby changed, thereby improving the characteristic of the lighting apparatus. As a result, as regards each of the lights emitted from the optical exciters  120 ,  140  and  160  of the lighting apparatus according to the embodiment of the present invention, the color distribution at each color temperature may be within 3-step MacAdam ellipse. 
     As shown in  FIG. 9B , unlike the embodiment of the present invention, when the lighting apparatus includes only the first optical exciter  120  having a color temperature of 6500 k and the second optical exciter  140  having a color temperature of 2700 k, the color temperature transformation of light emitted by the lighting apparatus may not be located at the center of the Ansi bin curve. 
     On the contrary, in the embodiment of the present invention, a standard color coordinate can be set such that the color temperature transformation of light emitted by the lighting apparatus is close to the center of the Ansi bin curve. The light quantity of the light source unit  100  is controlled in accordance with the standard color coordinate. As a result, the light quantities of the first to the third optical exciters  120 ,  140  and  160  are changed, thereby improving the characteristic of the lighting apparatus. 
     The lighting apparatus according to the embodiment of the present invention may include four or more optical exciters. 
       FIG. 10  shows a lighting apparatus according to a fourth embodiment of the present invention. 
       FIG. 10  shows, unlike  FIG. 5 , that optical exciters  120 ,  140 ,  160   a  and  160   b  having mutually different wavelengths are added to the one or more light source units  100  having the same color temperature, so that an area in which the color coordinate can be controlled. 
     While the lighting apparatus of  FIG. 10  includes four optical exciters, the lighting apparatus is allowed to include four or more optical exciters. 
     The plurality of the third optical exciters  160   a  and  160   b  emit light having a color temperature and a color coordinate which are different from those of the first optical exciter  120  and the second optical exciter  140 . The plurality of the third optical exciters  160   a  and  160   b  also emit lights having color temperatures different from each other and having color coordinates different from each other. In other words, the color coordinate and the color temperature of the light emitted from a third optical exciter  160   a  are different from those of another third optical exciter  160   b.    
     Accordingly, as shown in  FIG. 11 , the light quantity of the light source unit  100  is controlled such that a color coordinate of the light from the lighting apparatus is placed within an area (a dotted-lined quadrangle) formed by the color coordinates of the first optical exciter  120 , the second optical exciter  140  and the plurality of the third light source units  160   a  and  160   b.    
     The standard color coordinates are located within the area (a dotted-lined quadrangle) formed by the color coordinates of the first, the second and a plurality of the third optical exciters  120 ,  140  and  160   a  and  160   b . The controller  300  controls the light quantity of the light source unit  100  such that an error between the standard color coordinates and the color coordinate of light actually emitted is reduced. Accordingly, since the light quantities of the first, the second and a plurality of the third optical exciters  120 ,  140  and  160   a  and  160   b  are changed, as regards the lighting apparatus according to the embodiment of the present invention, an area capable of controlling the color coordinate may be increased. 
       FIG. 12A  shows how optical exciters of the lighting apparatus according to the embodiment of the present invention are arranged. As shown in the upper side of  FIG. 12A , the second optical exciter  140  and the third optical exciter  160  are arranged adjacently to the first optical exciter  120 . Here, the second optical exciter  140  and the third optical exciter  160  may be alternately arranged. The first optical exciter  120  is able to emit light having a color temperature of about 6500K. 
     As shown in the lower side of  FIG. 12A , the third optical exciter and the second optical exciter  140  are arranged in the order listed adjacently to the first optical exciter  120 . Here, the second optical exciter  140  and the third optical exciter  160  may be alternately arranged. The first optical exciter  120  is able to emit light having a color temperature of about 6500K. The second optical exciter  140  is able to emit light having a color temperature of about 2700K. 
       FIG. 12B  shows that the optical exciters  120 ,  140  and  160  shown in the upper side of  FIG. 12A  are viewed from an “A” side and a “B” side. The figure on the upper side of  FIG. 12B  shows that the optical exciters are viewed from a “B” side. The figure on the lower side of  FIG. 12B  shows that the optical exciters are viewed from an “A” side. 
     As shown in  FIG. 12B , the light source unit  100  includes a plurality of light emitting diodes (LEDs) mounted on a printed circuit board (PCB). A part of the LEDs may be located in an area of the first optical exciter  120 . The rest of the LEDs may be located in areas of the second and the third optical exciters  140  and  160 . The controller  300  is able to change the light quantity of each of the LEDs included in the light source unit  100  through a duty ratio control. 
     As described above, the second optical exciter  140  and the third optical exciter  160  may be alternately arranged and may be arranged adjacently to the first optical exciter  120 . The areas which the second optical exciter  140  and the third optical exciter  160  occupy at the time when the second optical exciter  140  and the third optical exciter  160  are alternately arranged is as shown in  FIG. 12C , smaller than the area which the second optical exciter  140  and the third optical exciter  160  occupy at the time when the second optical exciter  140  and the third optical exciter  160  are arranged facing each other. As a result, when the second optical exciter  140  and the third optical exciter  160  are alternately arranged, the volume of the lighting apparatus can be reduced. 
     While the embodiment of the present invention has been described with reference to the accompanying drawings, it can be understood by those skilled in the art that the present invention can be embodied in other specific forms without departing from its spirit or essential characteristics. Therefore, the foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the foregoing embodiments is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.

Technology Category: f