Illuminators using reflective optics with recycling and color mixing

• US 20060227302A1
• Filed: 04/11/2005
• Published: 10/12/2006
• Est. Priority Date: 04/11/2005
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Harbers, Gerard, Keuper, Matthijs, Holman, Robert H., Scheffel, Laurie
• Granted Patent: US 7,234,820 B2
• Time in Patent Office: Days
• US Class Current: 353/94
• CPC Class Codes: G02B 19/0023 at least one surface having optical power
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: G02B 19/0095 for use with ultraviolet radiation
• CPC Class Codes: G02B 27/0983 being curved
• CPC Class Codes: G02B 27/1053 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G03B 21/204 using secondary light emission, e.g. luminescence or fluorescence using different colours G03B33/00; if related to video signals H04N9/3197
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

Various optical techniques are described for obtaining a specified light output from an LED source. One technique uses a parabolic reflector surrounding an LED or LED array to create a collimated beam, and the light exit opening of the parabolic reflector is defined by a reflective disc with an opening of the desired size. Any generated light that is outside of the opening is reflected back into the parabolic reflector and re-reflected until the light exits the opening. For mixing different light colors from different LEDs or energized phosphors, a mixing tunnel is used. The mixing tunnel includes angled dichroic mirrors or angled polarizer mirrors that selectively reflect and pass selected colors or polarizations of light to a single output port of the mixing tunnel. Efficient and compact ways to energize phosphors are also described. Other optical techniques are also described.

Claims

1. A light system comprising:

a light source comprising;

at least one light emitting element;

a collection optic comprising a reflector with reflective walls for receiving light from the at least one light emitting element, the walls being at an angle with respect to the at least one light emitting element to generally collimate light emitted by the at least one light emitting element, the collection optic having an end with a first cross-sectional area;

a partially reflective element at the end of the collection optic, the partially reflective element for transmitting light that meets certain criteria to an application system and for reflecting light that does not meet the certain criteria back towards the at least one light emitting element for re-reflection by the collection optic back towards the partially reflective element; and

an application system optically coupled to the light source for employing the light transmitted by the partially reflective element, the partially reflective element reflecting light that would not be effectively employed in the application system had the light not been reflected.

2. The system of claim 1 wherein the reflector is a solid formed of a transparent material, wherein the walls reflect by total internal reflection (TIR) due to a difference in refraction indices of the transparent material and air.

3. The system of claim 1 wherein the reflector has a generally parabolic shape.

4. The system of claim 1 wherein the partially reflective element for transmitting light that meets certain criteria comprises a reflective material with an opening, wherein all light from the reflector that impinges on the reflective material is reflected back into the reflector, and light that passes through the opening is transmitted to the application system.

5. The system of claim 1 wherein the first cross-sectional area is rectangular.

6. The system of claim 1 wherein the first cross-sectional area is circular.

7. The system of claim 1 wherein the at least one light emitting element comprises at least one light emitting diode (LED).

8. The system of claim 1 wherein the partially reflective element for transmitting light that meets certain criteria comprises a reflective material with an opening, wherein all light from the reflector that impinges on the reflective material is reflected back into the reflector, and light that passes through the opening is transmitted to the application system, and wherein the opening comprises a polarizing mirror that transmits only light having a certain polarization and reflects light having other than the certain polarization.

9. The system of claim 1 wherein the partially reflective element for transmitting light that meets certain criteria comprises a reflective material with an opening, wherein all light from the reflector that impinges on the reflective material is reflected back into the reflector, and light that passes through the opening is transmitted to the application system, and wherein the opening comprises a dichroic mirror that transmits only light having first wavelengths and reflects light having other than first wavelengths.

10. The system of claim 1 wherein the partially reflective element for transmitting light that meets certain criteria comprises a reflective material with an opening, wherein all light from the reflector that impinges on the reflective material is reflected back into the reflector, and light that passes through the opening is transmitted to the application system, and wherein the opening comprises a diffraction grating that transmits only light impinging within a certain angle and reflects light impinging outside the certain angle.

11. The system of claim 1 wherein the partially reflective element has an opening smaller than the first cross-sectional area through which light is transmitted, and wherein the application system has a light entrance opening approximately the same size as the opening in the partially reflective element.

12. The system of claim 1 wherein the application system comprises a light mixing tunnel having a light entrance opening smaller in cross-section than the first cross-sectional area.

13. The system of claim 12 wherein the light source comprises a first light source, wherein the partially reflective element has an opening smaller than the first cross-sectional area through which light is transmitted, and wherein the light mixing tunnel comprises:

a first opening optically coupled to the opening in the partially reflective element for receiving light from the at least one light emitting element, the at least one light emitting element emitting light of a first color;

a second opening for receiving light from a second light source emitting light of a second color;

wherein the light mixing tunnel has internally reflective walls;

the first light source supplying the first color light into the light mixing tunnel;

the second light source supplying the second color into the light mixing tunnel;

a first dichroic mirror that reflects light of the second color and passes light of the first color, the first dichroic mirror being in the mixing tunnel at a first angle to allow the light of the first color to pass through to an output port and reflect the light of the second color in the direction of the output port so as to mix the first color light and second color light at the output port.

14. The system of claim 13 further comprising at least one lens at the first opening and second opening of the light mixing tunnel.

15. The system of claim 13 wherein the mixing tunnel has a third opening for receiving light from a third light source emitting light of a third color, the mixing tunnel further comprising a second dichroic mirror that reflects light of the third color and passes light of the first color and second color, the second dichroic mirror being in the mixing tunnel at an angle to allow the light of the first color and second color to pass through to an output port and reflect the light of the third color in the direction of the output port so as to mix the first color, second color, and third color light at the output port.

16. The system of claim 1 wherein the application system comprises a light wavelength conversion system having a light entrance opening smaller in cross-section than the first cross-sectional area.

17. The system of claim 16 wherein the at least one light emitting element acts as a pump light source emitting blue or UV light in a first direction through an opening in the partially reflective element, and wherein the light wavelength conversion system comprises:

a first dichroic mirror at an oblique angle with respect to the first direction, the dichroic mirror passing the blue or UV light;

a first phosphor for converting the blue or UV light to a longer wavelength light of a first color upon being energized by the blue or UV light, the first phosphor being located to receive the blue or UV light after passing through the dichroic mirror and emitting light of the first color;

the dichroic mirror having a surface that reflects light of the first color, wherein the dichroic mirror receives the light emitted by the first phosphor and directs the light to an output port of the light wavelength conversion system.

18. The system of claim 17 wherein the application system also comprises a light mixing tunnel receiving light emitted by the first phosphor reflected off the dichroic mirror and receiving light of one or more other wavelengths, the mixing tunnel comprising:

a first opening optically receiving the first color light from the light wavelength conversion system;

a second opening for receiving light from a second light source emitting light of a second color;

wherein the light mixing tunnel has internally reflective walls;

a first dichroic mirror that reflects light of the second color and passes light of the first color, the first dichroic mirror being in the mixing tunnel at a first angle to allow the light of the first color to pass through to an output port and reflect the light of the second color in the direction of the output port so as to mix the first color light and second color light at the output port.

19. The system of claim 1 wherein the partially reflective element reflecting light that would not be effectively employed in the application system had the light not been reflected comprises the partially reflective element reflecting all light that would not be effectively employed in the application system had the light not been reflected comprises.

20. The system of claim 1 wherein the application system comprises a projection display system.