Light emitting apparatus, display apparatus and method for controlling light emitting apparatus
In a light emitting apparatus using LEDs, luminance and chromaticity of the LED changes largely due to a temperature change. Meanwhile, by using phosphors, it is possible to improve the stability of the luminance and chromaticity against the temperature change. However, color reproducibility of the light emitting apparatus decreases. Therefore, the light emitting apparatus includes a first LED, a second LED, a first phosphor which is excited by the second LED and emits light whose color is the same as or similar to a color of light emitted from the first LED, and a control circuit which controls a ratio between an emission intensity of the first LED and an emission intensity of the second LED.
1. A light emitting apparatus, comprising:
a first LED;
a second LED;
a first phosphor which is excited by the second LED and emits light whose color is the same as or similar to a color of light emitted from the first LED; and
a control circuit which controls a ratio between an emission intensity of the first LED and an emission intensity of the second LED.
2. The light emitting apparatus as set forth in claim 1 , further comprising:
a third LED;
a fourth LED; and
a second phosphor which is excited by the second LED or the fourth LED, and emits light whose color is the same as or similar to a color of light emitted from the third LED,
the control circuit controlling a ratio among the emission intensity of the first LED, the emission intensity of the second LED, an emission intensity of the third LED and an emission intensity of the fourth LED.
3. The light emitting apparatus as set forth in claim 1 , wherein the control circuit controls the ratio in accordance with a first emission intensity obtained by light emission of the first LED, light emission of the first phosphor, or both the light emission of the first LED and the light emission of the first phosphor.
4. The light emitting apparatus as set forth in claim 3 , wherein the control circuit increases a ratio of the emission intensity of the second LED to the emission intensity of the first LED so that the first emission intensity is increased to be equal to or more than a predetermined value.
5. The light emitting apparatus as set forth in claim 1 , wherein the control circuit controls the ratio in accordance with a temperature of the light emitting apparatus.
6. The light emitting apparatus as set forth in claim 5 , further comprising:
temperature detecting means,
the temperature detecting means detecting the temperature of the light emitting apparatus.
7. The light emitting apparatus as set forth in claim 5 , wherein the control circuit increases a ratio of the emission intensity of the second LED to the emission intensity of the first LED when the temperature of the light emitting apparatus is higher than a predetermined value.
8. The light emitting apparatus as set forth in claim 1 , wherein the control circuit controls the ratio in accordance with chromaticity of the light emitting apparatus.
9. The light emitting apparatus as set forth in claim 8 , wherein the control circuit adjusts a ratio of the emission intensity of the second LED to the emission intensity of the first LED so that the chromaticity of the light emitting apparatus becomes a predetermined value.
10. The light emitting apparatus as set forth in claim 8 , further comprising:
a color sensor,
the color sensor detecting the chromaticity of the light emitting apparatus.
11. The light emitting apparatus as set forth in claim 8 , further comprising:
temperature detecting means,
the temperature detecting means estimating the chromaticity of the light emitting apparatus.
12. The light emitting apparatus as set forth in claim 1 , wherein a half band width of an emission spectrum of the first phosphor is wider than a half band width of an emission spectrum of the first LED.
13. The light emitting apparatus as set forth in claim 1 , wherein the second LED is a blue LED.
14. The light emitting apparatus as set forth in claim 2 , wherein the fourth LED is a blue LED.
15. The light emitting apparatus as set forth in claim 1 , wherein the second LED is a purple LED or a ultraviolet LED, and
the light emitting apparatus further comprising a blue LED.
16. The light emitting apparatus as set forth in claim 2 , wherein the fourth LED is a purple LED or a ultraviolet LED, and
the light emitting apparatus further comprising a blue LED.
17. The light emitting apparatus as set forth in claim 1 , wherein the first LED is a red LED, and the first phosphor is a phosphor which emits red light.
18. The light emitting apparatus as set forth in claim 2 , wherein the first LED or the third LED is a red LED, and the first phosphor or the second phosphor is a phosphor which emits red light.
19. The light emitting apparatus as set forth in claim 17 , wherein the red LED is an AlGaInP based red LED.
20. The light emitting apparatus as set forth in claim 17 , wherein the first phosphor is CaAlSiN 3 :Eu 2+ .
21. The light emitting apparatus as set forth in claim 1 , wherein the first LED is a green LED, and the first phosphor is a phosphor which emits green light.
22. The light emitting apparatus as set forth in claim 2 , wherein the first LED or the third LED is a green LED, and the first phosphor or the second phosphor is a phosphor which emits green light.
23. The light emitting apparatus as set forth in claim 21 , wherein the second phosphor is α sialon, β sialon, Sr aluminate, (Sr,Ba) 2 SiO 4 :Eu 2+ or Ca 3 (Sc,Mg) 2 Si 3 O 12 :Ce 3+ .
24. The light emitting apparatus as set forth in claim 2 , wherein the third LED is a yellow LED, and the second phosphor is a phosphor which emits yellow light.
25. The light emitting apparatus as set forth in claim 24 , wherein the second phosphor is α sialon, (Sr,Ba) 2 SiO 4 :Eu 2+ or YAG:Ce 3+ .
26. A display apparatus, comprising:
a light emitting apparatus, comprising:
a first LED;
a second LED;
a first phosphor which is excited by the second LED, and emits light whose color is the same as or similar to a color of light emitted from the first LED; and
a control circuit which controls a ratio between an emission intensity of the first LED and an emission intensity of the second LED;
a non light emitting display panel; and
a color filter.